Mammalian Physiology II
Mammalian Physiology II BMS 501
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BS 501 Lecture Notes LECTURE 1 Go over Handout concepts outline If you do not attend class you almost certainly will get a lower grade than if you attend class conscientiously Chapters 5255 of Boron and Boulpaep 2005 cover human reproduction reasonably well However there are more than 4 000 species of mammals There is more speciestospecies variation in reproduction than with other physiological systems such as cardiovascular renal and nervous systems gastrointestinal is intermediate Huge differences in placenta litter size gestation length testis to body weight ratios sperm shape female reproductive cycles maturity at birth etc Impossible to cover all species Information very limited except human domestic animals and lab animals N dozen species Most concepts apply across species I will cover a few important exceptions Good general health and bodily function are essential for successful reproduction Suffers if illness poor nutrition environmental stress Nature follows the principle that reproduction can wait until better times For example reproduction is delayed until puberty inhibited during lactation and delayed until spring in seasonal breeding species Parturition can even be delayed in stormy weather Sex differences in mammalian reproductive participation Essentially all healthy breeding age females become pregnant during the breeding season Most males do not sire offspring in most species but most males compete for mates In humans older females do not reproduce directly but have an indirect role in care of children and grandchildren Reproductive life corresponds more closely to lifespan in most other mammals Nonreproductive organs role in reproduction Good feet and legs in bulls Good nutrition essential Information processing in the brain e g to identify sex of an individual The spinal cord is essential for ejaculation re ex release of oxytocin at suckling inducing ovulation in some species etc The pineal gland at the base of the brain has an important role in reproduction in many species Cerebrum is involved in sexual behavior Hypothalamus is so involved in reproduction that it is a sex organ e g releasing hormones and source of oxytocin for the posterior pituitary Anatomy of the reproductive system Many parts can be removed surgically with only minor effects on other bodily functions Gonads ovaries and testes primary sex organs source of the gametes sperm and eggs and steroid hormones Seconda sex structures Internal Tubular structures such as uterus and vas deferens Accessory sex glands such as seminal vesicles External Penis clitoris labia scrotum List of slides Human female reproductive tract parts 2 Human oviduct more accurate 3 Slide of ovary follicles 4 Slide of lweekold calf reproductive tract with India ink 5 Human male reproductive tract parts 6 Reproductive tract of the bull plumbing 7 Histological slide of testis interstitial seminiferous tubules Sertoli and germ cells Seconda sex characteristics Neutral same for both sexes in the late fetus and newborn Changes occur due to gonadal hormones estrogens progestins and androgens binding to receptors in the tissues List of human male secondary sex characteristics voice muscle and bone mass hair pattern including baldness sexual and other behaviors List of human female secondary sex characteristics pattern of fat deposition breasts and hips carrying patterns olfactory sensitivity changes with stage of menstrual cycle J Embrvologv of the svstem Slide 8 list ofparts of100cell embryo Gastrula stage precursors to body are forming ectoderm coverings and linings skin central nervous system endoderm digestive system some endocrine glands liver mesoderm most of the body for example muscle amp reproductive system except for the germ cells which originate in embryonic ectoderm Slide 9 Continuity of germ line 7 gametes gt zygoteearly embryo gt inner cell mass gt primordial germ cells gt precursors of gametes gt gametes Slides 10 day 40 human embryo ll migration of primordial germ cells All cells can be divided into somatic cells and germ cells or their precursors primordial germ cells are undifferentiated cells that form the ovum and the precursors to the sperm which however becomes very differentiated during the final month before their release Primordial germ cells repositories of information on how to produce a copy of the organism Divide as migrate DNA in many other cells also has sufficient information to reproduce the organism if reprogrammed for example the cloned sheep Dolly Irreversible changes occur in some cells eg lymphocytes A chicken can be de ned as an egg s way of making another egg The germ cells in the chicken connect the life cycle between the egg stages Embryos are bipotential with regard to sex They have the structures for both male and female development and both sexes are morphologically identical A few decision events determine if the indifferent structures become male or female it is easy to have errors in this process which leads to intersexes intersexes are fairly common in some species such as pigs Some bipotential remains in adults for example nipples on males Slide 12 hermaphrodyte mare Similar abnormalities in nonreproductive tissues usually lead to death before birth LECTURE 2 Sex chromosomes Fundamental differences between male and female are genetic as reflected in sex chromosomes XX female XY male Functionally the genetic information produced from two Xchromosomes is not very different from an X plus a Ychromosome Two principles make this so First there are only about 80 genes on the Ychromosome 30 of which also are on the X chromosome and second one of the Xchromosomes is inactivated in most female mammalian tissues no mRNA transcribed from approximately 95 of the genes on the inactivated Xchromosome in differentiated cells Note that X chromosomes contain about 5 of all genes about 30000 total in mammals Slides 13 female cat demonstrating chimerism 14 Lyon hypothesis 15 consequences of Lyon hypothesis Molecular Mechanism Females receive one Xchromosome from their mother and one from their father As cells differentiate either the X from the mother or the X from the father is randomly inactivated Inactivation is active expression of XIST gene Xinactive specific transcripts is nontranslated RNA that binds DNA on inactive X XIST expression is inhibited by T six expression by the active X T six is also a regulatory RNA not translated into a protein produced by the antisense strand of the XIST gene Once a decision on inactivation is made all progeny from that cell have the same X inactivated for the rest of the life of the individual females are functional chimeras identical twin females are different from each other in this inactivation pattern Define chimera Molecular mechanism 7 methylation of cytosines adjacent to a guanine maintenance methylase whenever cells divide Transcription inhibited from highly methylated DNA Slide 16 methylated DNA XXX females have 2 inactivated X chromosomes Histological evidence for random Xinactivation l Barr body seen in nuclei of spinal cord neurons 2 drumstick seen on polymorphonuclear leukocyte nuclei Exception to these principles of Xinactivation 1 both Xchromosomes are active in the ovum and early female embryo 2 the paternal X is always inactivated in the placenta so the pattern is not random 3 the Xchromosome from the father is inactivated in all cells of marsupials except for the ovum 4 about 5 of X is not inactivated including gene steroid sulfatase 7 why women have smooth silky skin 2 doses and men do not 1 dose If this gene mutated women s skin like men s and men s is scaly 7 termed ichthyosis Slide 17 karyo gram Ychromosome Smallest chromosome in most species and has very few genes probably fewer than 50 that are Yspecific Approximately 30000 genes on all of the chromosomes in mammals but depends on definition of a gene e g alternate splicing Most Ychromosome DNA is inert contains no genes therefore XY is similar to XX inactivated Genes responsible for maleness are on Ychromosome XY XYY XXY XXYY are all male XX amp XXX are all female those underlined are sterile OY are dead Super males super females Tumer s X0 and Klinefelter s syndromes XXY X inactivation in male Balr bodies aneuploids Nearly all autosomal aneuploids extra trisomy missing monosomy are lethal during embryonic development effects of sex chromosome aneuploidy are minor Tricolor male cats are XXY Principle one gene on the Ychromosome is a switch to turn on dozens of other genes on other chromosomes to make a testis and sequellae Lack of the switch leads to development in the female direction Note that thousands of structural genes for male reproductive function most are on the autosomes and Xchromosome but around 2030 are on the Y chromosome Detection of the first gene on the Ychromosome discovered by skin grafting in inbred mice Maletomale grafts accepted Femaletofemale grafts accepted Femaletomale grafts accepted Maletofemale grafts rejected Gene termed histocompatibilityY or HY antigen Gene expressed on the surface of all male cells but not in females Mistakenly thought to be the sexdetermining gene for many years Role of HY in finetuning development of parts of the testis Additional false starts in isolating the testisdetermining gene This gene was eventually definitively identified and termed SRY Sry in mice It is a DNA binding protein expressed in developing testes that bends DNA sharply where it binds Proven to be the testisdetermining gene by transgenic Transgenic make genetic change in lcell embryo that is copied into all resulting cells methods whereby female embryo develops into a male which however was sterile for reasons that will become clear later Gene discovered in individuals that are sterile and had sex chromosome mutations XY females and XX males SRY AMH expression Undifferentiated tissue gt indifferent gonad gt testis gt male structures Summary Ychromosome makes the indifferent gonad to a testis Lack of a Ychromosome causes the indifferent gonad to develop into an ovary This occurs at about 112 months of gestation in humans Differentiation of the internal reproductive system during fetal life in the male or female direction Slide 18 testis histology Testis secretes two hormones in fetal life 1 testosterone a steroid from the interstitial cells 2 antiMullerian hormone also known as Mullerian inhibiting factor from the Sertoli cells a protein hormone of the transforming growth factorB TGF B family Ovary secretes only very low levels of hormones at this stage Presence of testis leads to masculinization of the undifferentiated reproductive system Presence of an ovary or lack of a gonad results in development in the female direction See figure 524 in Boron and Boulpaep Terminology Primitive kidney mesonephric system parts of male reproductive system undifferentiated female also has all of these parts Why reproductive tract so associated with urine mesonephric Wolffian duct mesonephric tubules Mullerian duct Draw indifferent reproductive system Slides l9 indifferent human reproductive tract at 7 weeks of gestation 20 male fetus at 2 months of differentiation 21 female fetus at 2 months of differentiation 22 summary 7 both sexes The Mullerian duct develops into female reproductive tract structures and the mesonephric duct regresses in females The mesonephric Wolfflan duct leads to male reproductive tract structures and the Mullerian duct regresses in males Mechanisms of deciding which duct develops Rule 1 Wolffian duct maintained in the presence of testosterone if no testosterone degenerates Therefore if a testis is present the Wolfflan duct is maintained and if it is absent it degenerates Rule 2 The Mullerian duct remains unless Mullerianinhibiting hormone actively prevents its development Mullerianinhibiting hormone is produced by the Sertoli cells of the testis It is a heterodimer of the transforming growth factor beta family Summary In females no androgen is present so the Wolfflan duct degenerates No Mullerianinhibiting hormone is present so the Mullerian duct remains In the male androgen is present so the Wolffian duct is maintained Mullerian inhibiting hormone is also present which regresses the Mullerian duct Experimental manipulations Remove the gonad from either sex and development is in the female direction Give androgen to females and both ducts develop If a testis is grafted to a female the system develops in the male direction If antiandrogen is given to a male no ducts form at all Summary SRY 7 indifferent gonad gt testis gt T AMH gt hormone action No SRY 7 indifferent gonad gt ovary and little hormone production Slides 23 24 25 fusion of the female reproductive tracts bovine freemartin bovine freemartin 2629 descent ofthe testis 30 temperature in different parts of the ram testis LECTURE 3 Mechanism of keeping testis and epididymis cool Blood entering the testis is cooled by blood leaving the testis and blood leaving the testis is warmed by blood entering the testis Occurs in pampiniform plexus Cooling of the testis is important in scrotal mammals Sterility at body temperature Some mammals do not have scrotal testes termed inguinal Mechanism of testicular descent Fig 528 in Boron and Boulpaep 1 Differential growth gubemaculum 2 Maintaining an open inguinal ring remains open some species Cryptorchid hidden gonad sterile Most common congenital defect in humans congenital means present at birth Insufficient testosterone at critical stage Can be corrected hormonally with hCG or surgically even age 78 External genitalia also are bipotential Penis and clitoris are homologs labia and scrotum are homologs Mechanism of differentiation of external genitalia Testosterone causes development in the male direction penis scrotum Lack of testosterone causes development in the female direction vagina clitoris labia E2 is not involved in initial differentiation of female external genitalia Steroid pathway is 39 39 39 gt pr gt J gt estradiol 176 In adrenal progesterone gt androgen gt cortisol see Fig 535 in text Mutations adrenal enzymes result in adrenal androgen s masculinizing females and causing male babies to enter precocious puberty Treatment usually cortisol Abnormality of differentiation in human babies in Central America mutation in the enzyme 50Lreductase which causes testosterone to be made to dihydrotestosterone Dihydrotestosterone is the active androgen in most cells is testosterone Wolffian duct Cells that cannot convert testosterone to dihydrotestosterone will have very little androgenic response for most tissues Describe how A ring of testosterone can be aromatized with loss of hydrogens Consequences of SOLreductase de ciency External genitalia in baby boys develop in the female direction because of not being able to mount an androgen response However at the age of puberty external genitalia become masculinized because of a great increase in testosterone production This is a weak androgen compared to dihydrotestosterone but the high concentration causes the little girls to turn into little boys and develop a penis at the age of 12 Masculinization of the brain particularly the hypothalamus Numerous examples will cover 2 l Sexually dimorphic nucleus Nucleus is a collection of cell bodies of neurons Sexually dimorphic nucleus is three times larger in males of rodent species than females Testosterone prevents degeneration of neurons Less anatomical dimorphism in human homosexual implications 2 V Sexual differentiation of preotic area of hypothalamus Preview of female reproductive endocrinology most species E2 gt GnRH release gt LH release gt ovulation of follicles that secreted E2 Give E2 to male and no GnRH release This system is very different in male than female rodents much less human This differentiation occurs in late fetal or neonatal life If testosterone is present during a critical window N7 months of gestation in humans male pattern results Lack of testosterone is female pattern Ovary results in the female pattern Testis and testosterone result in male pattern defminization Important point Female pattern is not due to estradioll7B as the ovary does not make this hormone at this stage In fact estradioll7B is about 1000 X more potent than testosterone in causing this sexual differentiation in the male brain Explanation Testosterone is converted to estradioll7B in the male brain that is aromatization chemical change of A ring to benzene ring of testosterone occurs to produce estradiol 175 Potential problem is masculinization of the brain of female fetuses from their mothers estradioll7B estrogen To cancel this effect sex steroidbinding globulin concentrations increase in maternal circulation during gestation Also in some species the molecule alpha fetoprotein is made by placenta These bind estradioll7B so that one doesn t get large amounts of estrogen into the fetal circulation to masculinize the brain inappropriately The area of the brain that is masculinized is the preoptic area 10 Experiments in this area Give testosterone to males or females male pattern results Give estmdiol to males or females male pattern results even more so than with testosterone astmtion results in female pattern unless there is replacement therapy Testosterone also affects the cerebrum in some species from a sexual differentiation standpoint setting up the potential for male sexual behavior in adult life Lack of testosterone results in potential for female sexual behavior in the adult Summary There are tWo roles for testosterone 1 an organizational role during fetal and neonatal development and 2 an operational role that only occurs a er puberty Receptors are involved with both of these roles Also estmdiol17 has a inctional role in adult female but not an organizational role in the fetal female Gender femininemasculine Gender is how one perceives oneself sexually It has hormonal and environmental components as Well as chance encounter components Summary dihydrotestosterone in external genitalia estradioI17 in central nervous system Y testis antiMullenan hormonetestosteronelt Internal genitalia This pathway affects the nature of the internal plumbing of the reproductive system hypothalamic differentiation and gender from the central nervous system The process can be demiled by environmental contaminants with estrogenic or antiandrogenic properties Superimposed on the above are descent of the testis secondary sex characteristics post puberal function Illustrative genetic defect testicular feminization For androgens to function they require a receptor in the nucleus of the cell The receptor binds testosterone or dihydrotestosterone The gene for this protein receptor is on the X chromosome Note Males get their Xchromosome from their mother In some individuals the gene for this receptor is defective so the receptor is not made or is made incorrectly An XY fetus with the testicular feminization defect differentiates a testis The testis makes testosterone but there is no effect of the testosterone since receptors are not there to use it No internal plumbing in these individuals Mullerian duct degenerates Wolffian duct is not maintained Testis does not descend scrotum does not form EXtemal genitalia are female Hypothalamus is female In these individuals puberty does not occur because they have no ovaries They look like females but have no estrogen production includes famous thin women e g movie star Kim Novak They produce huge amounts of testosterone but it has no effect Testis frequently becomes cancerous removed surgically Condition found in many species example of XY female externally wtestes CLASS 4 Recitation l Assisted Reproduction including arti cial insemination in vitro fertilization embryo transfer and cryopreservation will be discussed Quiz 4 LECTURE 4 Class 5 Male reproduction postpubertal Functions of the male reproductive system 1 produce spermatozoa 2 deliver the spermatozoa to the female reproductive tract Slide 31 plumbing of male reproductive tract Drawing of the male reproductive tract testis seminiferous tubules rete testis efferent ducts epididymis vas deferens accessory sex glands Wolffian duct derivatives Functions of the epididymis maturation transport and storage of sperm Sperm stored a week to months 3 slides efferent ducts 3234 Testicular histology Four types of cells 1 germ cells 2 Sertoli cells 3 Leydig or interstitial cells 4 infrastructure eg blood vessels nerves connecting tissue muscle These in seminiferous tubules Draw seminiferous tubule without germ cells Slides of testicular histology 35 standard histology 36 scanning EM slide 3738 diagrams of ultrastructure including the bloodtestis barrier myoid cells SertoliSertoli cell junctions basal and adluminal compartments 39 electron micrograph of interstitial tissue 40 diagram of interstitial tissueiseminiferous tubule interaction Functions of the blood testis barrier 1 keep toxins from the testis 2 protect testis from immune system Selfnonself determined fetal life sperm not made until after puberty Different mechanisms from the bloodbrain barrier which is tight junctions of capillary endothelial cells During spermatogenesis 7 Xchromosome is inactivated functional aneuploid Only one X chromosome can be inactivated which is why XXY is sterile Note rule in female is all but one X is inactivated Characteristics of sperm Smallest nucleated cell in the body and Very specialized Haploid no DNA RNA or protein synthesis r DNA i so no mRNA amp no protein synthesis 2 slides ofsperm 41 42 diagram ofa sperm head including acrosome nucleus equatorial segment neck midpiece mitochondria tail cell membrane Production of sperm 7 takes about 2 months Many kinds of cells in the seminiferous tubule Germ cells are embedded in Sertoli cells which are somatic nurse cells Slides 43 spermiogenesis and spermiation List ofgerm cells in the testis spermatogonia divide by mitosis primary spermatocytes undergo meiosis division 2 Ge d39v39s39ons but secondary spermatocytes undergo meiosis II division only 1 rgund of DNA synthess synthesis spermatids differentiate into spermatozoa All ofthe above cells are spherical except the spermatid which starts as spherical and develops into the sperm by the process spermiogenesis Spermiogenesis results in smallest nucleated cell in the body Nucleus condenses Histones change to protamines rich in lysine and arginine with lots of positive charge to neutralize negative charge on DNA 3 slides 44 acrosome formation specialized lysosome developing from juxtanuclear Golgi 45 Manchette formation amp Sertoli cell phagocytosis 46 sperm loses excess cytoplasm phagocytosed by Sertoli cells Slide 47 spermiation release of sperm from Sertoli cells protoplasmic droplet left Sertoli cell nurse cell spermatid loses ability to care for self eg inactive X chromosome Also major regulating and remodeling functions Spermatogonia Seven or eight kinds in some species We ll consider three for discussion purposes stem spermatogonia stem cell renewal system renews itself and divides into A spermatogonia other examples of stem cell systems 2 A spermatogonia divide into B spermatogonia 3 B spermatogonia divide into primary spermatocytes V Slides 48 spermatogenesis intracellular bridges and degeneration 49 ultrastructure of intracellular bridges origin and functions of intracellular bridges note half of spermatids X and half Y NOTES SPERMATOGENESIS the sum of the transformations which result in formation of spermatozoa The entire spermatogenic process is initiated in early embryonic development and continues after birth and puberty as a consequence of continual renewal of stem cells SPERMATOCYTOGENESIS mitotic divisions of spermatogonia after birth to give rise to other aspermatogonia and preleptotene primary spermatocytes MEIOSIS meiotic division of primary spermatocyte to form secondary spermatocytes and ultimately spermatids Cells are called primary spermatocytes or secondary spermatocytes SPERMIOGENESIS the differentiation of spermatids from round cells with considerable cytoplasm to cells with a highly condensed nucleus and scant cytoplasm with a agellum Cells are called spermatids Based on changes in the spermatid acrosome sper 39 39 can be 391 J as a consisting of four phases Golgi cap acrosome and maturation In addition to acrosomal evolution condensation of the nuclear material and formation of the agellum occur SPERMIATION release of spermatozoa from the germinal epithelium into the lumen of the seminiferous tubule Prior to release the germ cells are called spermatids and after spermiation they are called spermatozoa GERMINAL EPITHELIUM the normal cellular components within the seminiferous tubule consisting of Sertoli cells and germ cells spermatogonia primary spermatocytes secondary spermatocytes and spermatids Sertoli cells are somatic cells which are non dividing in adult animals and probably are important for metabolic exchange between the germ cells in the luminal compartment and the exterior of the bloodtestis barrier coordination of spermatogenesis and have an endocrine function BLOODTESTIS BARRIER a physiological barrier isolating the germinal epithelium from the interstitial tissue and dividing the germinal epithelium into a basal compartment and an adluminal compartment Consists of the basement membrane basal lamina plus fibers and a myoid cell layer and occluding tight junctions between adjacent Sertoli cells The SertoliSertoli cell tight junctions form the principal component of the blood testis barrier BASAL COMPARTMENT 7 contains spermatogonia ADLUMINAL COMPARTMENT 7 contains primary spermatocytes secondary spermatocytes and spermatids Sperm production One can measure sperm production rates by understanding how sperm are made Healthy bulls 107 sperm gm testis day Sperm production rates are highly dependent on testis size which in turn is dependent on the number of Sertoli cells and is related to follicle stimulating hormone secretion at puberty in these animals and their relatives including females Whole process highly heritable Female relatives of males with large testes reach puberty earlier Senescence In older mammals on the average fewer sperm are produced and numbers of morphological abnormalities increase Some 70 to 80 year old men can have reasonable fertility but some younger men have very poor semen quality and are subfertile or sterile Some problems due to endocrine disruptors contaminant in environment due to plasticizers synthetic hormones etc Some problems due to mutations Freeze semen at a young age X and Y sperm are veg similar Important consequence of the way sperm are made and connected with intracellular bridges X and Ybearing sperm are very similar Recall that the Xchromosome is inactivated during spermatogenesis draw diagram During spermiogenesis gene expression drops to very low levels making X and Y bearing sperm very similar sperm depend on Sertoli cell for care The only difference seems to be that there is more DNA in Xbearing sperm than in Y bearing sperm This is the basis of methods for separating X and Ybearing sperm LECTURE 5 Class 6 I39 1 39 Fndocrinologv of male Regulating testosterone concentrations is key Effects occur only in tissues with androgen receptors Functions of testosterone T Required for normal Sertoli cell function and spermatogenesis maintenance of accessory sex glands and secondary sex structures such as penis and epididymis Accessory sex glands shrink to 13 size if no T Secondary sex characteristics beards voice muscle mass Negative feedback to regulate gonadotropin secretion Endocrinology In most tissues the active androgen is a quot39 39 but it is for the Wolffian duct As covered earlier the active androgen in the brain and Sertoli cell sometimes is estradioll7B eg stallion testis 7 rich source of estrogen Dihydrotestosterone testosterone and estradiol17B work by classic steroid mechanisms of action covered earlier in the course including binding to receptors in the nucleus resulting in regulation of RNA synthesis Note that there are some exceptions to this mechanism in some cases steroids bind to cell surface receptors causing effects not directly related to regulating RNA synthesis Cause and effect hormone pathways GnRH gt LH gt testosterone Leydig cells gt 1 local effects on Sertoli cells 2 systemic effects and 3 feedback regulation Receptors needed Note different halflives of hormones Draw curves on board Testosterone is converted to estradioll7B in Sertoli cells of most species Testosterone and estradioll7B feedback on LH and GnRHsecreting cells Parallel GnRH gt FSH gt Sertoli cells secrete extracellular androgen binding protein and inhibin Feedback of inhibin on FSH secretion Inhibin is member of TGFB family of proteins Slide 50 male reproductive endocrinology Explain diagram of endocrine pathways in male mammal Effects of exogenous GnRH LH and androgen to test causes of infertility eg T normally suppresses LH Prolactin seems to have role in maintaining Leydig cells Testicular function Slide 51 Three methods of removing substances including hormones from the testes veins lymphatics rete testis RT uid relative volumes are l000 1001 interstitial lymphatics Concentrations of testosterone in various uids and compartments ABP amp RT uid How testosterone can function as a contraceptive Diagram of LH GnRH and testosterone secretions with time Effects of constant infusion of testosterone or release from an implant Testis starved for T normally lOlOOX peripheral concentration now is 1X Anabolic steroids are androgens suppress LH cause small testes see in some athletes Epididymis 7 Divided into head body tail caput corpus cauda Functions storage transport and maturation of sperm Takes 46 days for sperm to go from efferent duct to tail of the testis where they are stored Rate of passage independent of mating frequency Epididymis requires cooler temperature than the body in the same way that the testis does Perhaps storing sperm at a cooler temperature helps maintain their viability Slide 52 Sperm can be stored in the epididymal tail for some weeks or even months in a few species if they are not removed by ejaculation in some species sperm for dozens of ejaculates stored Once ejaculated sperm deteriorate unless frozen Testes produce sperm at a constant rate About 10 million spermgmday in the bull If no ejaculation is occurring sperm over ow out of the epididymis and are expelled in the urine If 4 to 6 ejaculates are collected per week from typical mammals only a few sperm are lost in the urine Note that more frequent mating fewer sperm ejaculate Important concept The number of sperm produced by the testis is not necessarily equal to the number of sperm that are collected with an arti cial vagina because of losses in the urine and losses in the semen collection equipment Description of arti cial vagina epididymis lumen epithelium infrastructure stereocilia Function of the head of the epididymis absorbs 99 of rete testis uid secreted molecules cause maturation of sperm as they traverse the epididymis and facilitate concentrated storage in the tail Epididymal function depends on androgens specifically dihydrotestosterone Androgenbinding protein is absorbed in the head of the epididymis from rete testis uid and delivers testosterone directly to the epididymis Changes in sperm Infertile to fertile nonmotile to motile whimpy motility to progressive motility sperm tail is stiffened by disulfide bond formation in the outer dense fibers a non stiff agellum is like using a rope for a paddle parenthetically disulfide bonds also increase between protamines in the nucleus of the sperm forward motility protein is secreted into epididymal uid which when combined with ATP equals motility 2 Known functions of secreted proteins 1 forward motility protein 2 acrosomal stabilizing factor functions to prevent premature acrosome reaction Gross morphological changes Main one is migration of protoplasmic droplet from neck to partway down tail 20 Male reproductive function Slide 53 Erection of penis engorgement of erectile tissue in penis with blood more in ow than out ow human penis Prostaglandin E2 relaxes arterioles so more blood ow Viagra Ejaculation re ex centered in spinal cord traumatic neck injury induces ejaculation at that time Input from cerebrum and tactile stimuli penis both erection and ejaculation Ej aculate seminal plasma nutrients and regulatory molecules for sperm e g fructose prostaglandins antibacterial properties gels and vaginal plugs human semen coagulates liquefies Site of semen deposition species speci c vaginal or uterine LECTURE 6 Class 7 Starts female reproduction 3rd part of course Dr Winger will teach Microanatomy of the ovary Slides 54 55 56 57 ovary point out germinal epithelium parenchyma how the mare differs from other species SEM offollicle ovary follicles basement membrane capillaries theca interna theca extema corpus luteum corpus hemorrhagicum blood vessels follicle cell granulosa cell major hormones female reproductive system also relaxin oxytocin others Theca interna is homologous with Leydig cells has LH receptors produces testosterone or other androgens These transported across to granulosa cells Circulating levels of androgens in the female blood system are about onetenth those of males and likely have a function in sexual behavior Granulosa cells are homologs of Sertoli cells They have FSH receptors and an enzyme aromatase that converts testosterone to estradioll7B This is the same aromatase that is found in cells in the hypothalamus and in Sertoli cells Hypothalamopituitaryovarian axis Slide 5 8 Quite homologous to the male can exchange ovary for testis in male diagram same embryological origins Estradiol 176 feeds back on the hypothalamus and the anterior pituitary under some circumstances regulating GnRH and LH secretion This is a negative feedback system except for the preovulatory surge when it is a positive feedback system in females Recall sexual differentiation of the hypothalamus Positive feedback systems unstable Growing follicle produces estradioll7B and has FSH receptors As it grows more FSH receptors are made and in final stages of follicular growth LH receptors appear on granulosa cells in addition to thecal cells This sets up the system for the LH surge and ovulation major event mittelschmertz pain felt at ovulation in some women Large follicles produce the molecule inhibin from the granulosa cells Another homology with the male reproductive system This regulates litter size Many follicles grow simultaneously in the ovary Once a follicle becomes dominant and secretes inhibin this turns off FSH secretion so other follicles will not grow starved Dominant follicle no longer needs large amounts of FSH In the case of litterbearing species the inhibin from for example 10 follicles is required to shut off FSH secretion and thereby regulate litter size activins and inhibins 7 TGFB family both from granulosa cells Activins stimulate follicular growth by increasing FSH secretion by the anterior pituitary FSH secretion is regulated by GnRH positively Activin positively inhibin negatively Further complication follistatin is secreted by the follicle and is an activinbinding protein thereby negating the effects of activin Molecules secreted by granulosa cell autoregulatory and autocrine function too GnRH Inhibin FSH 39 Activin Follistatin 2 Shdes binds activin 5960 Superovulation Superovulation is accomplished by administration of exogenous FSH Even though inhibin concentrations become very high due to many follicles growing the exogenous FSH continues to have an effect Human IVF programs cattle ET programs Luteinization The process of changing a follicle to a corpus luteum Steroid synthetic pathways cholesterol gt pregnenolone gt progesterone gt testosterone gt estradioll73 Different sets of enzymes are involved Are parallel pathways In the luteinized cell the enzymatic pathways stop at progesterone Corpus luteum Three types of cells large luteal cells small luteal cells and infrastructural cells Slide 61 CL At ovulation and luteinization blood vessels invade the follicle This is known as a corpus hemorrhagicum Angiogenesis occurs Characteristics of large luteal cells 1 2040 H in diameter 43 HR3 14000 03 2 few LH receptors no LH regulation 3 baseline progesterone production 4 prostaglandin F20t receptors 5 oxytocin and relaXin granules 23 Small luteal cells 10 20 p in diameter 1700 3 many LH receptors LH regulation essential to maintain CL regulated progesterone production no prostaglandin qu receptors no protein peptide granules large numbers of lipid droplets containing cholesterol esters storage for rapid LH response Regression of the corpus luteum with prostaglandin qu secretion from endometrium and ovary from ovary only in primates 1 2 Vasoconstriction In ux of calcium into large luteal cells and sequellae resulting in apoptosis and demise of the entire corpus luteum Functions of progesterone in cells with P4 receptors 1 2 3 Synergistic with E2 for sexual behavior Sets up cyclicity in the hypothalamus and ovary after anestrus whether prepuberal lactational or seasonal oral progestins fed to cattle for management Stimulates the epithelium of the oviduct uterus and cervix causing growth and secretions particularly effective if E first Maintenance of pregnancy by relaxing the myometrium that is preventing contractions most important function Negative feedback inhibiting final follicular growth and therefore ovulation contraceptive aspects estrus synchronization Increases body temperature 7 pyrogenic Basal body temperature shift in women Behavioral contributes to premenstrual syndrome Lactation mammary epithelium Embryo transport from the oviduct to the uterus Inhibition of progesterone receptor RU486 binds to progesterone receptor so that progesterone cannot have any effect Used as an orally active molecule to result in sloughing of the endometrium and early abortion if pregnant Orally active progestins a number of them used clinically and agriculturally for example melengesterol acetate MGA and oral contraceptives Functions of estradioll7B cells with E2 receptors Note hundreds of compounds have various degrees of estrogenic activity because they bind estrogen receptors including some environmental toxins Sexual behavior striking in most species 10 mg estradioll7B in 500 kg cow Increase in physical activity Use pedometer in cattle Stimulation of the epithelium of the oviduct uterus vulva cervical mucus further stimulation P4 Regression to 13 height with no hormones Causes cervical mucus to be less viscous Mammary gland receptors Positive and negative feedback regulation of GnRH Fat cells in breasts hips at puberty in women Metabolicanabolic function in longbone growth epiphyseal plate closure at puberty Androgens more anabolic less plate closure effects in human but there are androgen effects For example human castrates have the eunuch phenotype Note that there are several estrogen receptor types or B y and these vary from tissue to tissue Orally active estrogens Are hundreds potency varies many occur in plants eaten regularly e g soybeans Some synthetic pesticides and or their metabolites are estrogenic The most famous 7 diethylstilbesterol DES 7 used for anabolic properties agriculturally in the past and therapeutically in women An example of an antiestrogen 7 clomiphene citrate which may stimulate GnRH secretion in some species e g human and cause superovulation Functions and characteristics of relaxin source larger luteal cells and placenta gene is derived from 2 insulin genes in tandem 2 Other examples of insulin 7 gene family insulinlike growth factors 3 Relaxes the pubic ligaments at parturition 4 Relaxes cervical infrastructure 5 Possibly breakdown of collagen for widening cervix for parturition 6 Possible effects on mammary system 7 Source 7 large luteal cells and placenta 7 species differences 8 Receptor very different from that of insulin IGFl Functions of oxytocin l Stimulate myoepithelial cells in the mammary gland 2 Stimulate the myometrial cells in the uterus for sperm transport and expulsion of fetus 3 Stimulate endometrial cells to produce prostaglandin Hot in some species CLASS 8 Recitation 2 Cloning mammals will be discussed Quiz 5 LECTURE 7 Class 9 Reproductive steroids and cancer Cancers of the reproductive system are fairly common 7 1015 of women higher men but death due to other causes masks Can affect any reproductive tissues The most common human cancers are breast cancer in women and prostate cancer in males most males benign prostate tumor hypertrophy with age 1015 inherited 7 e g mutation in tumor suppressor genes rest spontaneous mutations Estrogens and androgens drive cells to undergo mitosis Billions Most cancers of reproductive tract are steroid responsive but some are not Many genes have steroid response elements in their regulatory regions If these regulatory elements mutated drive cell division inappropriately get cancer Solution Get rid of E2 or testosterone i 95 not 100 Down regulate GnRH The antiestrogen tamoxifen i familial cancers Protective effects pregnancy oral contraceptives E2 less in uence takes years for cancers to develop Being pregnant before age 20 decreases chances of breast cancer by half relative to never pregnant Mechanism is regression of mammary tissue when lactation ceases gets rid of precancerous cells BRCA mutation 7 causes the inactive X chromosome to secrete a growth factor that can stimulate breast cancer cells Female reproductive cycles Most species seasonal young born at the optimal time of the year usually in the spring Short season breeders become pregnant with decreasing daylight for example sheep have a 5 month gestation so young are born in the spring Long season breeders have reproductive cycles with lengthening daylight and either have very long gestations 11 months in the horse or quite short gestations lt1 month in rodents Nonseasonal breeders humans and domestic animals such as cattle and pigs these species have been selected for nonseasonality Note Males also are seasonal corresponding to female reproductive function Regulated hypothalamus In some species testis regress during the nonbreeding season and sperm are produced only during the breeding season Regulation of seasonality due to pineal gland regulating GnRH secretion which regulates pituitary and ovarian function testicular function in males Pineal gland Anatomy small bulbous gland at the base of the brain has nervous system input Main cell type is pinealcyte Function of the pineal gland is a light to chemical transducer Dark melatonin secretion light no melatonin secretion input from optic tract eye There is even a special pigment in the retina melanopsin that is in this signaling pathway Concentration changes in the blood are dramatic 3 to 4fold increase in concentration in melatonin in dark over light happens to each of us within a few minutes in the dark Nomenclature melatonin regulates melanin granules in amphibia and reptiles causing the skin to be light or dark depending on the lightdark status Melatonin function in short day breeders results in GnRH pulses Lack of melatonin results in limited GnRH pulses In longday breeders melatonin prevents GnRH pulses GnRH pulses occur in absence of melatonin 16 h1ight8 h dark ovine reproduction inhibited equine and rodent reproduction stimulated 8 h 1i tl6 h dark ovine reproduction stimulated equine and rodent reproduction inhibited Chemical darkness melatonin can be taken orally either by humans or fed to laboratory and farm animals and has same physiological effects as being in the dark feed to sheep at 4 pm equals short day Melatonin effects on nonseasonal breeders diurnal rhythms For example women have spontaneous LH surges for the most part between 5 and 7 am men have more testosterone secretion in the late afternoon Jet lag effects can be minimized by taking melatonin Chemistry of melatonin derivative of the amino acid tryptophan Four enzymatic steps to melatonin that are regulated by light n J cycles of females within the breeding season Slide 62 Regulation of reproductive hormones Fig 544 in text Due to changes in hormones date by outward signs such as estrus menstruation Cause amp Effect Follicle grows secretes E2 in absence ofhigh P4 GnRHLH FSH surge Ovulation CL formationfertilization P4 secretion Demise of CL if nonpregnant maintained if pregnant Some species differences Hormones secreted in pulses 7 not smooth curves QMerNH Can date cycles by epithelial cell changes by biopsying vaginal tissue for example or in the case of rodents by lavage of the vaginal cavity and cytology Reproductive cycles can be divided up in several different ways One is follicular or proliferative phase under estradioll7B domination vs the luteal or secretory phase under progesterone domination Another way of dividing up the cycle is into estrus metestrus diestrus proestrus and back to estrus Estrus is de ned as when the female permits the male to mate her Diestrus is de ned as the period during which progesterone is high Proestrus and metestrus are between these two Note estrous is adj ectival form of estrus same for proestrous etc Anestrus is de ned as periods when there is no reproductive cycle due to season lactation prepuberty nutrition stress oral contraceptives various species and so on Concentrations of reproductive hormones are often drawn as smooth curves when in reality nearly all reproductive hormones pulse to some extent Illustrate with protein and steroid hormones Reproductive cycle in season Species Some features 1 Induced ovulators rabbits cats Preovulatory LH surge from skunks euroendocrine re ex 2 Induced CL formers rodents 2X daily prolactin surges set up by neuroendocrine re ex 3 Spontaneous ovulators amp CL cattle sheep Conceptus regulatory mole formers 36 day follicular pigs horses cules cancel PC1an phase effects 4 Spontaneous ovulators amp CL human some Chorionic gonadotropin to formers 1014 day follicular other primates maintain CL phase 5 Sporadic cycles dogs 2 month luteal phases 6 Others mole rats marsupials Very varied Category 1 Induced ovulators no cycles without mating Examples rabbits cats Mating causes ovulation of follicles and starts reproductive cycle via neuroendocrine re ex Spines on penis to stimulate cervix Follicle to corpus hemorrhagicum to corpus luteum Diagram of E2 GnRH LH and progesterone GnRH secretion neuroendocrine re ex High E2 necessary but not sufficient also need mating Main function of progesterone Maintain pregnancy by inhibiting uterine smooth muscles myometrium If pregnant progesterone stays high until just before birth If pseudopregnant mating is sterile progesterone drops due to CL lysis twothirds of the way through the normal pregnancy After pregnancy or pseudopregnancy cycle starts over with follicles producing high concentrations of estradioll7B Mating and follicular growth E2 is required for starting the cycle of events over Category 2 Induced corpus luteum formers cycles are short without mating Examples are rats mice and hamsters Who cares about rodents Models If mating occurs corpus luteum forms due to prolactin secretion In absence of mating no corpus luteum forms and a short cycle ensues Diagram of E2 GnRH LH and prolactin neuroendocrine re ex Note Designate when estrus occurs prolactin luteotropic 4 to 5day cycles if no mating Prolactin secreted anterior pituitary 2Xday later from the placentachoriosomatomammotropin Regulation of prolactin secretion shut off PIF dopamine If mating is sterile pseudopregnancy occurs ends twothirds of the way through a normal gestation length Category 3 Spontaneous ovulators spontaneous CL formers no effect of sterile mating Short follicular phase Examples horse ewe cow pig Reproductive cycles are about 20 days in length but species variation Draw diagram of progesterone estradiol GnRH LH Slides 63 64 Follicular phase 3 to 6 days In nonpregnant animal prostaglandin Flor is secreted by the uterus causes progesterone to drop due to apoptosis of luteal cells in corpus luteum positive feedback loop of oxytocin and prostaglandin ont Oxytocin initiated from CL or posterior pituitary The same happens at parturition Whether parturition or nonpregnant cycle system starts cycling again with follicular growth Prevention of prostaglandin effects in pregnant animal Conceptus secretes molecules that prevent prostaglandin actions In ruminants interferon tau secreted by conceptus inhibits the actions of prostaglandin Flor In pigs estradiol uteroovarian vasculature and anastomoses in ewe local transport PGFZOL slide bovine tract with one uterine horn LECTURE 8 Class 10 Category 4 Spontaneous ovulators spontaneous CL formers long follicular phases Slide 65 Species are primates including human Blood levels of reproductive hormones Fig 543 in text Endocrinological changes same as in previous category with these exceptions l prostaglandin anis not secreted by the endometrium to destroy the corpus luteum rather the corpus luteum ceases function spontaneously via ovarian PGde unless it is stimulated by human chorionic gonadotropin 2 follicular phase is about 10 to 14 days long instead of 3 to 6 days resulting in 25 30 day reproductive cycles hCG secreted by the conceptus very LHlike 0L amp B subunits Extremely long halflife due to heavy glycosylation 24 hours secretes its own weight of hCG each day Conceptus maintains the CL to prolong its life by preventing expulsion from the uterus One other characteristic of this category is menstruation Loss of lining of the uterus when progesterone concentration drops Slides 66 amp 67 human female reproductive tract and endometrium same changes other species but less dramatic Menstrual cycles and estrous cycles are similar but dated differently Dated on overt signs blood in case of menstrual cycle estrus behavior that is standing for being mated in estrous cycles In menstrual cycles ovulation occurs in the middle relative to dating In estrous cycle ovulation occurs toward the beginning relative to dating Note Not all blood discharge from reproductive tract is due to menstruation For example in proestrus dogs estrogen secretion causes discharge of blood and mucus In cattle withdrawal of estradiol176 at metestrus causes bleeding Discharge of Blood from Female Reproductive Tract Species Description Cause Human menstruation decrease progesterone Canine proestrous discharge increase estradiol Bovine metestrous bleeding decreased estradiol Equine conceptus also secretes chorionic gonadotropin LH gene but different glycosylation secreted days 40100 of pregnancy and binds to FSH receptors accessory CLs Category 5 Dogs Cycle every 6 to 9 months Have long periods of anestrus but grow follicles and ovulate at irregular intervals Pregnancy lasts about 60 days in dogs and progesterone stays high for 60 days no matter if dogs are pregnant mated and nonpregnant or not mated Category 6 Others mole rats marsupials mink Continuum of spontaneousinduced ovulators Males speed up ovulation to some extent in most species including the human Under constant lighting conditions rats become induced ovulators Women can be induced ovulators under certain stress conditions and intense sexual activity for example when partner has been away for prolonged periods of time Factors affecting puberty Puberty occurs when follicles grow sufficiently to initiate an ovulation and therefore ovum production In women puberty is noted outwardly by menarche the first menstrual bleeding The age of menarche has been decreasing over the years in 1860 it was 17 in this country in 1960 it averaged 13 This was probably due to much better health and nutrition in 1960 than in 1860 Nutrition and age interactions occur in other species as well One question is how the hypothalamus knows it is time for puberty to occur There seems to be a relationship with body fat content and reproductive cycling Evidence for that includes correlating body fat content with age at menarche that thin women athletes reach puberty at a later age or even become amenorrheic after puberty when they get below 20 body fat content Although women seem to require 25 body fat for normal menarche it is likely that it is a correlated response to some other factors in the system rather than just body fat A recent theory concerns the molecule leptin derived from a gene expressed in adipose tissue Leptin decreases appetite and in laboratory animals exogenous leptin decreases appetite It is not clear that this occurs in the human however Leptin may facilitate triggering of puberty possibly via GnRH secretion Molecular mechanism puberty 7 i receptors for E2 in hypothalamus so E2 less inhibitory to GnRH Result is more E2 in body Oo genesis Terminology of germ cells in mammalian ovary primordial germ cells diagram oogonia primary oocytes in prophase of meiosis I from fetal life to LH surge if LH receptors in follicle secondary oocytes induced by the LH surge and release of a polar body ootid induced by fertilization The ovary fills with primordial germ cells in fetal life and they increase in number by mitosis and are termed oogonia They have intercellular bridges like spermatogonia and divide to form primary oocytes and start meiosis but arrest in prophase of meiosis I This occurs about the sixth fetal month in humans and is similar in other species that is about twothirds through the end of gestation oocytes reach meiotic arrest In the case of women no more primary oocytes are made after the seventh fetal month so all women have all the oocytes they will ever have before they are born There are greater than a half million ooc es per ova at that time and they are enclosed in follicles This results in a rather profound situation Women pregnant with a baby girl draw it actually also have within the baby girl the oocytes that will become the grandchildren of the pregnant woman Therefore the way one treats the fetus during pregnancy with nutrition drugs smoking alcohol and so on affects not only the little girl that s born but also the grandchildren because the oocytes that will form the grandchildren are being formed Some years ago one of my postdoctoral students proved that damaging drugs given to pregnant mice in fact affected the grandmice Mammalian follicular nomenclature Slide 68 ovarian follicles Fig 5411 in text Primordial follicles Primary follicles cells become cuboidal increase in number Secondary follicles zona pellucida gelatinlike capsule around the oocytes formed and oocytes grow 34X diameter follicle has multiple layers of granulosa cells but no antrum Slides 69 amp 70 Waves Slide 71 zona pellucida Tertiary Graaflan follicles presence of antrum uid lled cavity Ovulation Not 1 cycle takes N4 months All follicle types contain primary oocytes Description of mature follicle antrum stratum granulosum cumulus oophorus corona radiata specialized follicle cells Three phases of follicular growth preantral antral large antral Preantral see above list cell numbers increase of antral follicle growth LH and other factors needed to stimulate follicular growth after antrum forms FSH 7 inhibin system superimposed Occurs between the slow growth preantral phase and the preovulatory follicles follicular growth waves in cattle other species too Intermediate waves of follicular growth occur on a recurring basis averaging two or three waves per cycle Not understood before ultrasonography Waves continue into pregnancy and also occur prepuberally Characterized by cohort of follicles starting to grow regulated by FSH Repeats every 6 to 8 days 7 FSH driven One follicle becomes dominant and represses growth of other follicles In presence of high concentrations of progesterone the dominant follicle regresses loses its repressive effect and a new wave of follicles grows Progesterone must decline for the last spurt of follicular growth high E2 and frequent GnRHLH pulses Dominant follicle makes inhibin regulates litter size FSH concentrations increase when dominant follicle loses its dominance starting new wave of follicular growth Estrus synchronization decrease P4 Follicle Timin preantral 3 months antral 68 days preovulatory 36 or 1014 days Granulosa Cell few to 100039s 1000 s to 100000 s millions Gonadotropin None LH amp FSH LH LECTURE 9 Class 11 Atresia degeneration of follicle including oocyte 999 of follicles degenerate Only those that are at the right stage when P4 falls go on to ovulate In the case of women usually only one ovulation per reproductive cycle Considering pregnancy contraception etc only several dozen to a few hundred follicles mature to ovulate in a normal lifetime Millions degenerate Atresia at any stage of follicular growth Apoptosis 50 of follicles degenerate by birth 90 degenerate by puberty Degeneration continues until from a functional standpoint too few follicles resulting in menopause At menopause ovary still has a few follicles but not sufficient numbers for reproductive cycles and the system is nonfunctional Menopause generally occurs in late 40s and early 50s although can be much earlier in some pathologies Reproductive function in women declines markedly before menopause Fairly normal until age 35 At age 35 incidence of chromosomal abnormalities in oocyte and therefore children increases markedly and becomes especially high after age 40 Down s syndrome Draw graph Not surprising oocyte actually 40 years old Fertility declines clearly by age 35 and markedly by age 40 Assisted reproductive techniques Mutations accumulate in sperm of older men Regulation of initiation of follicular growth Mechanism unknown GDF9 gene has a role in primary follicle In older women ovary runs out of primordial follicles so fewer start developing each day All oocytes are primary oocytes until LH surge reemphasize point Menopause rare in nonhuman 2 year old mice 15 year old cows 25 year old mares In mice oocytesfollicles may continue to be made into young adulthood research controversial Slides 72 Meiosis relative to ovulation etc 73 nuclear state of oocytes Nucleus in primary oocyte is termed germinal vesicle Regulation of meiotic maturation when LH surge occurs in addition to ovulation stimulates germinal vesicle nucleus breakdown which must occur for any cell division chromosome condensation and extrusion of the first polar body This is an unequal cytokinesis there are no centrioles in oocytes Therefore a secondary oocyte is ovulated Remains as a secondary oocyte until fertilization when it becomes an ootid If not fertilized oocyte dies as secondary oocyte Oocyte is prevented from maturing by inhibitors in follicular uid LH surge overcomes those inhibitors via epidermal growth factor 7 like molecules FSH surge occurs the same time as the LH surge causes hyaluronic acid secretion and cumulus cell expansion draw Slides 74 amp 75 Cumulus compaction and expansion Ovulation Physical description The preovulatory follicle on the ovary extrudes from the surface like a blister diagram Small protrusion occurs on the follicle termed the stigma That region becomes avascular no blood ow Like an in ammatory response Ovulation does mt occur due to increasing pressure follicle so it s not an explosive event rather it is breakdown of the collagen in the follicle wall graph In some species there is smooth muscular contraction that actually squeezes out the follicular contents including follicular uid the ovum and the cumulus or nurse cells around the ovum Some bleeding occurs with ovulation and the corpus hemorrhagicum becomes vascularized for corpus luteum formation In addition to ovum and nurse cells follicular uid is also released at ovulation and that may signal the oviduct to stimulate sperm transport Endocrinology of ovulation LHFSH surge cumulus expansion cyclic AMP T follicle cells protein kinase A system protein phosphorylation etc Estrogen secreting system to 38 progesterone secreting system Paracrine events prostaglandin onr increases hundreds of times in concentration of follicular uid prostaglandin E2 increases there is an in ammatory response Indomethacin or aspirin which prevents prostaglandin synthesis will delay ovulation Theca interna cells form small luteal cells of CL with receptors for LH Granulosa cells form large luteal cells of CL 7 no LH receptor Pregnancy 4th and nal major part of course Sperm and egg transport in the oviduct early stages under estrogen domination list sperm goes up the oviduct oocytes go down the oviduct meet and fertilize in the ampullary region of the oviduct after 23 days the embryo goes to uterus when progesterone concentration increases Slides 76 fimbria ampulla isthmus uterotubal junction 77 human fallopian tube 78 inter circular and outer longitudinal musculature 79 crosssection of different regions of the oviduct 80 amp 81 uterotubal junction 82 2 cell types cells secretions Slides 83 84 Sperm movement up the oviduct two mechanisms 1 the sperm s motility minor relative to the distance needing to be covered 2 contractions of the reproductive tract Barriers to sperm transport cervix and uterotubal junction Cervix minor if uterine insemination sperm in cervix important storage human sperm numbers in tract For egg transport two mechanisms 1 ciliary movement cilia beat very rapidly from the ovarian end of the oviduct toward the middle of the oviduct 2 peristaltic contractions that move in that direction These mechanisms have some redundancy Kartegner s syndrome lack of functional cilia Such women remain fertile Important point Sperm are rapidly transported to the fimbria in mammals after they reach the uterus by peristaltic contractions However most of those sperm transported within the rst ve minutes are dead and are not the sperm that fertilize the egg Misleading LECTURE 10 Class 12 Slides 85 86 87 88 89 Diagram of process of fertilization largest 150 u 1200 inch and smallest nucleated cells in body sperm in zona accessory sperm SEM sperm oocyte arti cial zona removed arti cially compact cumulus expanded cumulus PV space Events that occur in the sperm Capacitation hyperactivated motility penetration of cumulus binding to zona pellucida acrosome reaction zona pellucida penetration fusion ofthe sperm and oocyte De nition of capacitation ability to fertilize an oocyte Evidence for capacitation Ejaculated sperm are infertile in in vitro fertilization systems without special 39 39 quot Jquot Sperm v d from the female reproductive tract are fertile immediately Capacitation times vary according to species One to two hours in the human and rodent 10 to 12 hours in rabbits and cows most species within this range Chemical mechanisms of capacitation 1 Removal of acrosome stabilizing factor This protein is added in the epididymis and accessory sex glands Idea is to keep the acrosome intact until just at the time of fertilization when it needs to go from a very stable system to an unstable system to fuse with oocyte Deplete sperm cell membrane of cholesterol Cholesterol is a rigid stiff molecule intercalated in cell membrane Serum albumin binds cholesterol and remove it from the membrane in a spongelike way Result more uid membrane Increased cAMP in sperm stimulates protein kinase A phosphorylated proteins 2 3 In vitro capacitation of sperm for in vitro fertilization emove seminal plasma which is loaded with acrosome stabilizing factor for example centrifuge through dense layer of albumin add heparin or fusogenic phospholipids and albumin andor m 25 mM HC0339 important Hyperactivated motility only capacitated sperm Different from progressive motility net forward motion in that it is violent with very strong power strokes of the swimming sperm Undesirable if premature 41 Penetration of the cumulus oophorus Need to break down hyaluronic acid Hyaluronidase from the acrosome thought to be important in this respect Leaks out before acrosome reaction Recent finding that a sperm membranebound protein PH20 has a hyaluronidase functional domain PH20 found over the posterior part of the sperm head and inner acrosomal membrane May function in penetration of the cumulus Acrosome reaction 7 only occurs capacitated sperm Slides 90 91 92 9394 95 Acrosome is specialized lysosome filled with enzymes 2 main ones are hyaluronidase and acrosin Physical description Fusion of outer acrosome and sperm cell membranes release of enzymes including hyaluronidase breaks down hyaluronic acid Acrosin is a proteolytic enzyme of the t psin family bound to inner acrosome membrane will digest path through zona pellucida Acrosome reaction is induced when sperm binds to the zona pellucida j Cai LM and SEM zona pellucida LM and SEM zona pellucida sperm penetrating zona pellucida acrosome reaction zona pellucida structure and chemistry Zona pellucida chemistry three glycoproteins ZPl is a structural protein that connects the other two ZP2 secondary sperm receptor ZP3 primary sperm receptor and inducer of the acrosome reaction Penetration of the zona pellucida A molecule in the sperm plasma membrane binds to ZP3 Molecule on the sperm that binds initially is unclear One possibility is galactosyl transferase an enzyme acting as a physical receptor Thousands Next zonaddhisin in the acrosomal matrix maintains binding to zona proteins Secondary binding to the zona pellucida Needed because entire outer surface of sperm disintegrates ZP2 binds to a binding domain of PH20 as the sperm penetrates the zona pellucida by digesting zona proteins with acrosin PH20 found on posterior sperm head d inner acrosomal membrane 2 functions see below Slide 96 Slides 97 98 Activat Slide 99 process of penetration Sperm fusion with a secondary oocyte The equatorial segment is very fusogenic on the sperm and microvilli of the oocyte are fusogenic At the time of fusion motility of the sperm stops spermoocyte fusion spermoocyte fusion Molecules involved turn out to be fertilin on the sperm which has a disintegrin domain that binds the integrin on oocyte microvilli Snake venom also disintegrin Summary of molecular aspects of fertilization Sperm hyaluronidase PH20 Galactosyltransferase zonadhesin Fertilin disinte grin amp acrosomal matrix posterior sperm head sperm plasma membrane acrosomal matrix inner acrosome membrane inner acrosomal membrane equatorial segment ion of the oocyte second sperm function secondary oocyte activation Ooc e hyaluronic acid in cumulus hyaluronic acid in cumulus ZP3 zona pellucida proteins all zona pellucida proteins ZP2 integrin Prefertilization situation with cortical granules Homology with acrosome Steps of activation Sperm adds phospholipase C zeta oscillin 7 causes phosphatidyl inositol to split to diacyl glycerol and inositol triphosphate 2 oocyte T Cai caused by oscillin in sperm 3 Electrical fertilization potential a depolarization that spreads across the Phsopholipase C zeta breaks down phosphotidylinositol into inositol triphosphate and diacyl glycerol which affect Ca concentrations and stimulate protein kinase 4 Cortical granule exocytosis by fusion with cell membrane homologous to acrosome reaction Cortical granules filled with proteolytic and hydrolytic enzymes pellucida zona block except in the rabbit 43 Proteolytic inactivation of ZP3 prevents additional sperm from binding to zona Vitelline block to polyspermy make sure character of oocyte membrane has changed so no longer fusogenic Cortical granule membranes have been incorporated 7 Enzyme activation due to increasing Cai but evidence unclear 8 Completion of meiosis II by polar body extrusion ootid stage 9 Retraction of corona processes 10 Continuing spikes of intracellularfree Ca due to oscillin from sperm every 30 min 11 Contraction of the oocyte Third sperm function add centrosome except rodents CLASS 13 Recitation 3 Movies on fertilization and embryo technology Quiz 6 LECTURE 11 Class 14 Integrating themes Two blocks to polyspermy in most species vitellinezona pellucida Few sperm are at the site of fertilization at any given time Three fusion events the acrosome reaction sperm oocyte membranes cortical granules Three distinct concepts 1 Get the genome of the sperm into the oocyte 2 Activate the oocyte otherwise dies 3 In some species add nongenetic components from the sperm for example centrosome from sperm midpiece First cell cycle Slide 100 dehiscence breakdown of disulfide bonds of the sperm nucleus by enzymes in oocyte cytoplasm opposite of what happens during spermiogenesis DNA repair Pronucleus formation Sphase synthesis of DNA for the first cell cycle Breakdown of nuclear pronuclear membranes no fusion in mammalian species Shdes 101 102 103 104 There is no moment of fertilization it is a process Syngamy fusion of pronuclei does not exist in mammals Twocell embryo Note No centrioles for the first cell division but is a centrosome pronuclei non syngamy timing of fertilization Mechanisms of Fertilization in Mammals Maternal inheritance Slide 105 Slide 106 Shdes 107 108 109 110 111 112 113 mitochondria About 100000 mitochondria per oocyte About 100 in the sperm Both types specialized in different ways Sperm mitochondria degenerate Even if they didn t they would become diluted out as only a few cells of the early embryo develop into the fetus Mitochondria have their own DNA about 16000 base pairs Genes for about 110th of the parts of proteins in mitochondria come from the mitochondrial genome in addition to tRNA ribosomal RNA for mitochondrial function mulehinny Cloning by nuclear transplantation consequences Preimplantation embryological development 1 Cleavage when cells get smaller and smaller without an increase in mass of the embryo terminology go over definitions stages of development in rabbit embryos ICM stages of development in cattle embryos site in bovine reproductive tract compaction compaction compaction 1 14 compaction 1 15 hatching embryo 116 ZP functions Terminology including morula blastocyst blastocoele hatching inner cell mass trophoblast Slide 117 Activation of the embryonic genome prior to the 8cell stage in human embryos mRNA that was inherited via the cytoplasm of the oocyte drives most protein synthesis New mRNA synthesis occurs at the 8cell stage Infertility Many causes Sperm and egg need to get together Sperm need to be motile to pass barriers and zona pellucida Slide 118 causes of fertilization failure Examples of problems 1 wrong timing 2 anatomical blocks 3 infections 4 antibodies to sperm or the zona pellucida Human infertility frequently circumvented by IVF GIFT gamete intra fallopiantube transfer and ICSI intracytoplasmic sperm injection Pregnancy rates are on the order of 20 per embryo usually 2 or 3 embryos are transferred There is excess of twins over 10 of pregnancies is gt2 embryos transferred Can sort out abnormal embryos by biopsy and molecular techniques Termed preimplantation genetic diagnosis PGD Slide 119 biotechnology involving fertilization unfertilize triploid when block to polyspermy fails Biotechnology applications for embryos Freezing sexing transferring culturing splitting adding genes Embryonic mortality Greater than 50 in women Can be studied by measuring hCG in sexually active women Embryonic mortality is 2030 in most farm animals Slides 120121 shapes of advanced preimplantation equine and bovine embryos 122 optimal conditions differ for natural vs assisted reproduction 123 maltiming of ovulation leads to infertility Implantation Slides 124 endometrium of mare 125 apposition of human embryo to endometrium 126 nidation of human embryo De nition depends on the species In rabbits rodents and the human embryo nidates digests a path into the endometrium In many species implantation implies the embryo s becoming fixed in place There are different degrees of attachment that depend on the species will cover next time Timing of implantation day 5 to day 35 depending on the species Rodents 5 to 6 huma 7 to 8 cattle 20 to 25 horses about 35 days after fertilization LECTURE 12 Class 15 If strong intermixing of tissues during implantation then more damage to uterus at birth when the placenta is released If attachment is more superficial then less damage at birth For example in the m there is relatively little damage when the placenta is released so the uterus is reasonably fertile a few days after birth Conversely takes a month to repair uterus of cow after birth Horses sometimes show estrus after giving birth known as foal heat It can be fertile because there is little repair needed to the uterus One other term specific to rodents and humans decidualization Uterine response to implantation by a thickening increase in the cell number at implantation site The placenta is embryonic not maternal tissue derived partly from inner cell mass partly from trophoblast Very important species differences Disaster occurs if there is inappropriate extrapolation from one species to the other Slide 127 drawing of placental morphology illustrating amnion allantois chorion yolk sac Slide 128 placental structure there are 6 potential barriers between fetal blood and maternal blood 1 fetal capillary endothelium 2 fetal connective tissue 3 fetal placental chorion epithelium 4 maternal endometrium epithelial lining of uterus 5 maternal connective tissue 6 maternal capillary endothelium Slide 129 Grosser classification 4 broad types of placenta M Maternal erosion Form Species 1 epithelialchorial none diffuse pig mare 2 syndesmochorial endometrium cotyledonary ruminants 3 endothelialchorial 2 layers zonary carnivores 4 hemochorial all layers discoid primates rodents Ruminants mother s part of placentome is termed caruncle fetal part is cotyledon No blood vessels huma pools ofblood in hemochorial Due to erosion of the human maternal tissues there are relatively stagnant pools of blood no capillaries are in the region so the arterials release jets of fluid that mix the pools of blood so that nutrient and oxygen exchange can occur Slides 130132 cotyledonary placentas 7 anastomosis freemartin 133134 zonary placentas 135 discoid placenta Transfer of passive immunity from mother to offspring Real practical physiology Mother has made antibodies to most of the disease organisms in the environment These premade antibodies are transferred to the fetus to protect it until its own immune system can make appropriate antibodies Antibodies are transferred three different ways depending on the amount of erosion of maternal tissue in the placenta In the mouse and human much erosion antibodies transferred directly to the fetal blood prior to giving birth Camivores have intermediate erosion of maternal tissue some antibodies are transferred via the blood but additional antibodies are transferred in the first milk colostrum The third category pigs horses ruminants little erosion no antibody is transferred between the mother and the fetus via the blood because the tissue is relatively intact so all passive immunity must go to the offspring via the first milk colostrum Colostrum is extremely rich in IgM and IgG immunoglobulins mother s blood to milk via mammary gland receptors and then taken from the stomach and small intestine directly into the circulation of the newborn That is the stomach and intestines do not digest the immunoglobulins and they are taken up wholesale into the blood probably receptormediated system Big problem mechanism only functions during the first 24 hours after birth and only functions well during the first 12 hours after birth because the gut epithelium closes up and immunoglobulins digested after that Thus extremely important to get colostrum to newborns to transfer the passive immunity If this is not done ruminants horses swine death rates exceed 50 This mechanism is not operating in human babies because they receive the passive immunity directly from the mother before birth Exception to the above for humans IgA a class of antibodies that act in the mouth and stomach are in the first milk as well and confer a passive immunity to the individual without having to enter the blood This protects against microorganisms in the mouth throat esophagus stomach and so on Thus even though nursing babies do not obtain circulating immunoglobulins via the milk have a slight health advantage because of the IgAs Practical point Antibodies in mother re ect environmen Sweden Iran study Placental function Slide 136 functions as lung liver exchange of nutrients removal of waste products storage of energy in the form of glycogen has many endocrine functions speci c to human Slide 137 embryonic signals Oxygen exchange is quite efficient because fetal hemoglobin different gene carries more oxygen per molecule under given conditions than does adult hemoglobin Also fetal blood has more hemoglobin molecules per unit volume than adult blood Circulating hormones in the blood during pregnancy Sources of progesterone depend on species primary corpus luteum accessory corpora lutea placenta Human placenta as an endocrine organ human chorionic gonadotropin 2 progesterone no need for the human ovary or pituitary after 6 weeks post fertilization 3 choriosomatomammotropin 4 estradiol 1 7B and numerous other minor hormones Slide 138 graph of blood levels progesterone hCG human chorionic somatomammotropin estradiol Slides 139 140 endometrial cups of mare Invasion of trophoblast cells into endometrium produces eCG equine LH glycosylated differently destroyed by immune system eventually Functions of placental hormones I maintain pregnancy 2 adjust homeostatic mechanisms of the mother 3 setup the system for birth or parturition 4 setup the mammary gland for lactation Functional changes at birth Changes in respiration lungs function circulation excretory function baby s kidney starts to function nutrition has to get nutrients via the mouth rather than the umbilical cord Changes in fetal circulation at biIth Figs 562 and 564 in text 1 2 3 Slide 141 No more placental circulation the umbilical veins and arteries are closed Circulation to the lungs goes from about 10 of cardiac output to 100 that is the circulatory system goes from pumping in parallel to pumping in series change due to closing of foramen ovale and ductus a1teriosis Circulation to the liver is greater after birth than before birth fetal circulation simplified version of text Fig 564A Ductus venosus 7 bypasses fetal liver Why the fetus is not rejected by the mother Slide 142 4 Fetus is foreign to the mother Causes immune response Fetal tissue is rejected if grafted to the mother There are a number of mechanisms some redundancy mechanisms Progesterone is immunosuppressive weakly but measurably More infections occur during the luteal phase in female mammals including women than the follicular phase Immunosuppression by specific lymphocytes Antigens on the outer part of the fetalplacental unit are masked and internalized For example the zona pellucida is a physical barrier to cellular contact with the early embryo and after that MHC major histocompatibility antigens are not present on the outside of the conceptus Acellular barriers of ground substance are secreted by the chorion to further mask antigens 6 7 8 9 The immune system in the uterus is a local circulation Lymphocytes do not seem to get back to the main circulation from uterine lymph but are destroyed Local immunosuppressive factors may be secreted by the fetalplacental unit that inhibits cell division of lymphocytes The immune system participates directly in fooling itself HLAG is expressed in placental tissue Acts like a universal acceptor transplantation antigen of MHC Immune system does not recognize as foreign Placenta also secretes interleukinlOanti in ammatory balance of immune response Immune system cytokines stimulate the placenta Not all mechanisms function in all species LECTURE 13 Class 16 Quiz at end of lecture Maternal physiology of gestation Great species differences will concentrate on the human Fetus is a parasite relies on the mother for growth and maintenance Receives nutrients uses oxygen mother removes waste products Homeostatic mechanisms of the mother are reset to deal with the extra load on the system traumatic disruption at the time of birth Resetting mechanisms is done by regulatory molecules primarily placental hormones including progesterone estradioll7B chorionic somatomammotropin They also affect other hormonal loops in the mother Water and electrolyte balance Great increase in water during gestation 4 to 6 liters l conceptus 2 extracellular space of the mother especially lower extremities 3 blood volume Concomitant increase in sodium and potassium About 900 milliequivalents in a typical gestation but not enough compensation in sodium and potassium to maintain non pregnant concentrations Therefore blood is slightly more dilute during pregnancy Renin and aldosterone concentrations increase in attempt to correct this and they are partially successful in retaining sodium Normally at birth in the human about 500 ml of blood is lost All the extra blood and water volume in the mother acts as a safety factor in case more is lost Placenta squeezes out the blood volume during birth back into the mother Much excess uid right after birth in normal parturition the excess uid is gotten rid of over the next month via adjusted kidney function Red blood cells and 0 transport Pregnancy requires more oxygen transport therefore more red blood cells are made for the blood The regulatory molecule erythropoietin stimulates extra red blood cell formation However this doesn t completely compensate for the need especially because blood volume has increased 40 result is known as a pregnancy anemia at about 30 weeks of gestation Red blood cell production decreases after birth Fetus makes fetal hemoglobin 7 different gene 7 fetal hemoglobin carries more oxygen than adult hemoglobin under most conditions Hemodynamics Cardiac output increases 40 during pregnancy from 5 to 7 liters per minute leveling off by 20 weeks of gestation Upright posture problem Upright posture of the human poses special problems because of need to pump uid out of the bottom of the body with the fetus restricting return Draw picture Intraabdominal pressure plus gravity keep extra blood uids in the lower extremities In late pregnancy even though there is increasing uid volume in the mother there is less venous return so cardiac output plateaus Can result in hypotension that is low blood pressure because cardiac output is insufficient to keep blood pressure up Heart can only pump the blood that is available 53 Cardiac output CO made up of 2 factors heart rate and stroke volume Heart rate increases about 10 by 4 weeks of gestation 25 by term Stroke volume increases up to 30 above prepregnancy values by midpregnancy Stroke volume less in later pregnancy During labor cardiac output increases markedly blood squeezed out of uterus so even more available for rest of body after birth At term 17 CO to uterus nonpregnant 23 Cardiac output increases markedly postlabor because fetus no longer occludes venous return from lower body Safety mechanism blood clots more easily during pregnancy to minimize blood loss during the birth process However this also results in greater tendency for blood clots to form in veins particularly legs which is exacerbated by the extra uid in the legs Rarely clots lodge in the brain resulting in stroke Estradiol 176 and progesterone regulate increased blood clotting in complicated ways Oral contraceptives mimic this to some extent When placenta is expelled clotting mechanisms return to normal within weeks Excretory system Renal blood ow increases 40 by peak of pregnancy Kidneys work hard to retain sodium due to increased aldosterone to compensate for increased blood volume Respiration Both increase in the rate of breathing and the tidal volume in the lungs Carbon dioxide is lower and oxygen higher in the pregnant than nonpregnant woman to improve gas exchange at the placental level Metabolism Many nutrients used in larger quantities during pregnancy 1 calcium 2 iron 3 vitamins 4 minerals 5 protein Mechanisms are in place to enhance uptake of these molecules Will concentrate on energy Energy is required for fetal growth Fetus uses huge quantities of glucose Energy is stored in the fetus and in the mother for lactation Energy costs of standard human pregnancy 80000 kilocalories about 280 calories per day for 280 days Not constant over gestation Standard 56 kilogram woman accretion of energy during pregnancy Nutrient Fetus Mother 925 gm protein 4 Calgm 59 41 3825 gm fat 9 Calgm 12 88 7300 calories 34200 calories sum4l500 Accretion of the above takes an additional 38500 calories to move and synthesize these nutrients and maintain the tissues The fat accreted in the mother is needed for energy for lactation Weight increases 5 kg water 4 kg fat 1 kg protein Oxygen consumption Increases 20 by term Most to uterus heart lungs kidney mammary glands Actual basal metabolic rate decreases during the first twothirds of pregnancies with some diets One method of compensating for nutrient requirements Basal metabolic rate increases during last third of pregnancy Significant energy cost is carrying the excess weight of pregnancy Behavioral adjustment to less physical activity the last onethird of gestation Where does the extra energy for pregnancy come from 1 Increased food intake about 20000 calories norm ally 2 Decreased metabolic rate sparing effect 3 20000 calories 3 39 r u vary 4 Decreased physical activity culturally determined 5 39 g than 90 ef cient without pregnancy so little room for improvement However only 3 increase in improvement 20000 calories per gestation In pregnant Woman there are lnctional and morphological changes in the small intestine Food stays in the gut longer for more efficient nutrient extraction First twothirds of gestation nutrients are stored anabolic phase Fat accumulation adipocytes in the hips and thighs particularly Last third ofgestation opposite catabolic phase Glucose is shunted to the uterus mother uses fat and lactate spares glucose insulin increases Mother is insulin resistant glucose stays in the blood for the fetus rather than being driven into cells and insulin less effective in inhibiting gluconeogenesis Gluconeogenesis synthesis of glucose from nonglucose sources like fatty acids Diabetic mother too much glucose Baby s pancreas T insulin secretion little effect Get macrosomic b y Get hypoglycemic crisis in baby at birth LECTURE 14 Class 17 Parturition The signal for parturition comes from the fetus not from the mother There is a certain amount of genetic control There are considerable species differences but also a lot of similarities Human parturition regulation is poorly understood Sheep and goats are used as models for human parturition Common themes 1 Need to open ripen the cervix Occurs from prostaglandin E2 relaxin and estrogen Net result loss of collagen elastin 2 Myometrial contractions These can be very powerful under some circumstances Result in coordinated waves of peristaltic contractions Regulating molecules include prostaglandin Flor omocin estradioll7 i facilitates contractions progesterone inhibits the contractions 3 Initiation of parturition a common denominator among species is decrease in progesterone and increase in estradiol except human in which progesterone decreases gradually at the end of pregnancy rather than dramatically Progesterone at the end of pregnancy can come from the corpus luteum the corpus luteum and the placenta or the placenta only depending on the species Therefore mechanisms to decrease progesterone depend on the species Steps in endocrinology of parturition in the goa placenta makes no progesterone l Sufficiently stressed fetus Twins more stress amp birth sooner 2 Corticotropin releasing factor from the fetal hypothalamus can t happen until sufficient maturity 3 ACTH release from fetal anterior pituitary 4 Cortisol production fetal adrenal 5 Increase in estradioll7B production by the placenta 6 Causes prostaglandin onr to be secreted by the placenta 7 This causes regression of the corpus luteum high Ez P4 ratios 8 PGan synthesized in the uterus Oxytocin receptors synthesized in uterus due to E2 as occurs in nonpregnant reproductive cycles 9 Contractions of the myometrium 10 Re ex from the cervix fetus pushes against cervix causes signal to the posterior pituitary and results in release of oxytocin which causes uterine contractions and even more pushing against the cervix l l Stronger contractions Can shortcircuit this process by giving exogenous ACTH cortisol or an analog prostaglandin onr These are used clinically Oxytocin can be used as well but it is dangerous because it can rupture the uterus if the cervix is not ready Oxytocin should be used as an aid not as an initiator Parturition in the sheep Different from goat because placenta makes lots of progesterone In the sheep placental progesterone is metabolized to estradioll7B due to cortisol production and then similar things happen as in the goat In the human instead of cortisol dehydroepiandrosterone sulfate is secreted by the fetal adrenal Otherwise pathways are similar Clinical problems Most species if no anterior pituitary in the fetus birth is not initiated due to lack of CRF resulting in a very prolonged gestation This does not however occur in the human In human some question as to whether oxytocin participates in the normal parturition process It is very useful clinically as a drug however and has role in expulsion of placenta Typical labor in women Stage I system is set up for parturition one gets contractions of the uterus generally lasts about 10 hours but can be much longer or shorter Stage II expulsion of the fetus usually takes less than 1 hour Stage III expulsion of the placenta less than 10 minutes During contractions the uterus actually gets shorter The smooth muscle cells when they contract do not regain their original length Pathology in some species retain the placenta This is rare in human Vaginal stretching induces maternal behavior Very dramatically illustrated in the ewe by putting balloon in vagina of a ewe a week or 10 days before parturition Ewe tries to steal lambs from other ewes Birth process in women may also induce maternal behavior Rh disease mother father 7 OK 7 mother 7 father 7 OK mother 7 father 7 OK 7 mother father 7 can be problem No problem first pregnancy Lactation Requires huge amount of nutrients including energy much more than pregnancy During nonlactation mammary system consists of nipple and rudimentary duct system Duct system morphology varies markedly among species Ducts grow under the in uence of estradioll7B and progesterone especially with high concentrations during pregnancy Slide 143 Pregnancy stimulates further differentiation of the ducts to form alveoli at the end of the ducts Alveoli consist of a globe of epithelial cells surrounded by myoepithelial cells and a rich capillary bed Draw mammary alveolus Milk is secreted into the alveolus and is expelled by contraction of the myoepithelial cells by oxytocin Lactation could be thought of as occurring in three steps 1 Developing the system during late pregnancy 2 Milk secretion during lactation 3 Milk expulsion by oxytocin Many hormones participate in setting up the mammary system and causing lactation to occur including prolactin placental somatomammotropin estradioll7B progesterone thyroidstimulating hormone adrenal corticotropic hormone and others Important point in setting up lactogenesis for lactation 7 You want to set up the system but do not want it to make milk until birth Progesterone and estradioll7B are needed to set up the system but progesterone functions as a brake to actual lactation Because progesterone decreases at parturition it is a perfect system for releasing the lactating tissue to make milk Key hormone of milk secretion is prolactin Prolactin is released primarily due to nipple stimulation Neuroendocrine re ex to the hypothalamus J 39 J J 39 PIF 39 39 thyroidreleasing hormone both of which result in increased prolactin secretion by anterior pituitary lactotrophs There are prolactin receptors in the alveoli Prolactin also is released by stimulating nipples when there is no lactation Even for example injogging women Little consequence because there are no alveolar cells no prolactin receptors and little effects on the breasts May however result in increased growth hormone actions because prolactin binds growth hormone receptors to some extent 59 Milk the perfect food for young of given species Milk is 5090 water Especially low in water in marine mammals Lactose 37 Humans have quite high lactose 7 fortify cow s milk Fat 340 Marine mammals have highest fat Protein is 36 Milk also is loaded with vitamins amino acids minerals etc39 Ca 7 proteinbound It is especially draining on the lactating mother of calcium and energy Colostrum the first milk is higher than normal in protein especially immunoglobulins Also higher in fat Loaded with growth factors such as epidermal growth factor EGF PDGF etc During lactation great increase in blood ow to mammary glands to transport nutrients Glucose is precursor to lactose Lipid precursors are transported for milk fat synthesis Mammary gland is a champion protein synthesizing system Requires huge amounts of amino acids and energy to make the protein Milk ejection re ex via oxytocin Acute neuroendocrine re ex about 60 seconds after stimulating the teat posterior pituitary releases oxytocin and 30 seconds later it is at the alveolus causing myoepithelial cells to squeeze milk into the milk duct and available for suckling Milk ejection evolves to a conditioned re ex Women hear a baby cry oxytocin is released before the baby even suckles In dairy cows milk starts leaking from the teats when people come into the dairy barn in the morning Can be conditioned to some extent by massaging the cow s udder and training the system so that the milking machine is placed on about 90 seconds after stimulating the teats This re ex is prone to inhibition Stress including epinephrine or norepinephrine inhibits oxytocin release in all species Four effects suckling on brain 1 sensory 2 prolactin 3 oxytocin 4 inhibit GnRh Stopping lactation 7 Stopping nursing stops lactation but sometimes this is painful One can give bromocriptine a dopamine agonist that shuts off prolactin secretion 7 is used clinically One can diminish lactation with progesterone but generally just ceasing nursing stops the prolactin stimulus When lactation ceases prolactinsecreting cells in the anterior pituitary are actively destroyed Lysosomes destroy the prolactincontaining granules and the system shuts down in a few days One can initiate lactation in the absence of pregnancy 7 E2 P4 TRH STH Nutrients gt maintenance growth when growing lactation when lactating fat storage Role of growth hormone in milk production as partitioning agent Causes nutrients to be used for growth in young animals and lactation in older females in the absence of growth hormone excess nutrients go to fat deposition
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