Follicle Stimulating Hormone
Sperm migration into and through the oviduct following artificial insemination at different stages of the estrous cycle in the rat. (1/45)In order to examine whether sperm migration into and through the oviduct follows an invariable pattern or is subject to regulation, rats in proestrus, estrus, metestrus, or diestrus were inseminated in the upper third of each uterine horn with 10-20 million epididymal spermatozoa. Three or eight hours later, the numbers of spermatozoa free and adhering to the epithelium in the ampullary and isthmic segments were determined. A significantly higher number of spermatozoa were recovered in estrus than in other stages, at 3 h than at 8 h, and at all stages from the isthmus than from the ampulla. Spermatozoa adhering to the epithelium were observed only in proestrus and estrus and in the isthmus. The effect of exogenous estradiol-17beta (E2) and progesterone (P4) on sperm migration was investigated in rats in which the estrous cycle was inhibited pharmacologically. E2 facilitated sperm migration into the oviduct and P4 antagonized this effect, whereas P4 alone had no effect. Concomitant treatment with E2+P4 induced adhesion of spermatozoa to the oviductal epithelium. In conclusion, the pattern of sperm migration into and through the rat oviduct varies with the stage of the cycle, being dependent on E2 and P4. The adhesion of spermatozoa to the rat oviductal epithelium is stage- and segment-specific and requires the combined action of both hormones. (+info)
Retention of a functional corpus luteum and peripheral concentrations of 13,14-dihydro-15-keto-prostaglandin F2alpha following metestrus administration of Syncro-Mate-B. (2/45)This study was conducted to examine the effects of metestrus administration of SyncroMate-B (SMB) on PGF2alpha secretion and corpus luteum (CL) development. In a study replicated over 2 yr, cows were observed for spontaneous estrus in yr 1, and cows received an injection of 25 mg of PGF2alpha and were observed for subsequent estrus in yr 2. At standing estrus (estrus = d 1), cows were randomly allotted to receive either the standard SMB regimen (n = 40) on d 3 of the estrous cycle or no treatment (n = 8). Fifty percent (n = 20) of SMB-treated cows were administered PGF2alpha on d 10 of the estrous cycle 48 h prior to implant removal. Twice-daily blood samples were collected in the morning (AM) and evening (PM) from d 2 AM through d 14 AM of the treated estrous cycle and subsequently analyzed for progesterone (P4) and PGF2alpha metabolite (PGFM). Prior to statistical analysis, SMB- and SMB/PGF2alpha-treated cows were sorted according to P4 concentration at d 10 of the treated estrous cycle to either a CL functional group (P4 > or = 1 ng/mL; n = 20) or a CL nonfunctional group (P4 < 1 ng/mL; n = 17). Following d 10 AM administration of PGF2alpha, functional and nonfunctional groups were further subdivided based on treatment. The groups were as follows: untreated control cows (n = 8); SMB-treated cows retaining a functional CL (SMB-F; n = 8); SMB-treated cows with a nonfunctional CL (SMB-N; n = 11); SMB/PGF2alpha-treated cows retaining a functional CL (SMB/PG-F; n = 12); and SMB/PGF2alpha-treated cows with a nonfunctional CL (SMB/PG-N; n = 6). Of all SMB-treated cows, 54% retained a functional CL through d 10 AM of the treated estrous cycle. Mean serum P4 concentrations increased for cows in all groups until d 7, after which P4 concentrations increased for cows in SMB/PG-F, SMB-F, and control groups and decreased for cows in SMB/PG-N and SMB-N groups. Following PGF2alpha administration on d 10, mean serum P4 concentrations remained < 1 ng/mL for cows in SMB/PG-N and SMB-N groups, decreased to < 1 ng/mL for cows in the SMB/ PG-F group, and remained > 1 ng/mL for cows in SMB-F and control groups. Mean serum PGFM concentrations tended (P = .06) to increase in cows with nonfunctional CL compared with control cows on d 8 AM and were greater (P < .05) in cows with functional CL on d 8 PM through d 9 PM. These results indicate that retention of a functional rather than a nonfunctional CL following metestrus administration of SMB is dependent on a premature release of uterine PGF2alpha. (+info)
Progesterone receptor A and B messenger ribonucleic acid levels in the anterior pituitary of rats are regulated by estrogen. (3/45)In target tissues of most mammalian and avian species, progesterone receptors (PR) are expressed as structurally related, but functionally distinct, isoforms A and B, and they are regulated by estrogen (E) as well as by their cognate ligand, progesterone (P(4)). The objectives of the present work were to identify mRNA expression for the A and B isoforms of PR in the anterior pituitary of the rat, to examine its regulation by gonadal steroids, and to compare this regulation with that in the primary target organ, the uterus. Messenger RNAs for the PR isoforms, determined by two separate reverse transcription-polymerase chain reaction protocols, one that detects PR A and PR B equally and the other specific for PR B, were identified in anterior pituitary of female and male rats. In anterior pituitary of cycling female rats, steady-state mRNA levels for both PR A+B and PR B were highest at 0900 h on proestrus, declined rapidly to nadir values at 0900 h on metestrus (PR A+B) or 0900 h on estrus (PR B), and remained below proestrous values through 2100 h on diestrus. Administration of E to intact proestrous female rats caused significant increases in mRNA for both PR A+B and PR B on estrus and metestrus. Blockade of P(4) action by administration of the antiprogestins RU-486 and ZK-98299 on proestrus had no effect on PR mRNA levels on the morning of estrus. Ovariectomy two and ten days after surgery markedly reduced mRNA levels for both PR A+B and PR B. Whereas treatment of 10-day-ovariectomized rats with E led to marked induction of mRNA for PR A+B and PR B two days later, treatment with P(4) one day after treatment had no effect on basal or E-stimulated PR mRNA. Regulation of PR mRNA expression in the pituitary differed from that in the uterus, in which P(4) treatment of ovariectomized rats antagonized the E-induced rise in mRNA for PR B, and antiprogestins increased mRNA for both isoforms. In addition to induction of PR mRNA in the pituitary of female rats by E in vivo, we also demonstrated induction by E in primary culture of anterior pituitary cells in vitro. We conclude that in the anterior pituitary of female rats, both the A and B isoforms of PR are expressed and regulated by E. (+info)
Estrogen status affects sensitivity to focal cerebral ischemia in stroke-prone spontaneously hypertensive rats. (4/45)Estrogen treatment has been shown to reduce ischemic brain damage. Because endogenous estrogen levels fluctuate markedly during the estrous cycle, we investigated the effect of stage of estrous cycle on ischemic brain damage. Halothane anesthetized 3- to 5-mo-old female Wistar-Kyoto rats (WKY) and stroke-prone spontaneously hypertensive rats (SHRSP) in proestrus (high estradiol levels) or metestrus (low estradiol levels) underwent permanent middle cerebral artery occlusion. In SHRSP, infarct volume at 24 h postocclusion was 24% smaller in proestrus compared with metestrus [208.6 +/- 9.5 mm(3) (n = 7) vs. 272.7 +/- 23.8 mm(3) (n = 7), respectively, means +/- SE; P = 0.0278, unpaired t-test]. In WKY, infarct volumes were similar in proestrus and metestrus [157.0 +/- 5.4 mm(3) (n = 5) and 131.5 +/- 16.5 mm(3) (n = 8), respectively; P = not significant (NS)]. Brain swelling (ipsilateral minus contralateral hemispheric volumes) was similar in proestrus and metestrus for SHRSP [138 +/- 9 mm(3) (n = 6) and 136 +/- 10 mm(3) (n = 7), respectively] and for WKY [103 +/- 15 mm(3) (n = 5) and 90 +/- 11 mm(3) (n = 8), respectively]. Thus the reduction in infarct size in SHRSP is caused by a true attenuation of the infarct volume and not simply by a reduction in brain edema. (+info)
Sensitivity of myometrium to CGRP varies during mouse estrous cycle and in response to progesterone. (5/45)Calcitonin gene-related peptide (CGRP) inhibits contractions of the myometrium. Isometric force measurements on myometrial strips were carried out to monitor the inhibitory capacity of CGRP in the myometrium during the estrous cycle and in response to estrogen and progesterone in ovariectomized mice. CGRP inhibition of KCl-induced contractions was lowest at estrus and significantly increased during metestrus and diestrus. Progesterone treatment of ovariectomized mice resulted in a significant increase in the responsiveness of the myometrium to CGRP. Expression of CGRP-receptor component protein (CGRP-RCP), a marker of CGRP-receptor expression, was quantitated by Western and Northern blot analyses. The levels of inhibition exerted by CGRP during the various stages of the estrous cycle and in response to steroid hormone treatment correlated with the protein levels of CGRP-RCP. The mRNA levels did not change significantly during the estrous cycle or in response to hormone treatment, indicating that the regulation of CGRP-RCP protein does not occur at the transcriptional level. CGRP had an inhibitory effect both when applied before the stimulus for contraction and when applied during a sustained contracture induced by KCl. This suggests that CGRP-induced generation of second messengers can influence late events in electro-/chemomechanical coupling and/or the contractile machinery directly. (+info)
Hormonal variation of rat uterine contractile responsiveness to selective neurokinin receptor agonists. (6/45)Regulated uterine contractions are important in many reproductive functions such as sperm transport and embryo positioning during implantation. The role of classical neurotransmitters including acetylcholine and norepinephrine in regulating myometrial contractility has been well studied; however, the peripheral role of sensory neurotransmitters such as the neurokinins is less clear. The major neurokinins are substance P, neurokinin A, and neurokinin B, which predominantly activate neurokinin receptors (NK-Rs) 1, 2, and 3, respectively. This study utilized selective receptor agonists to examine the role of NK-Rs in uterine contractility. Uterine tissues, obtained from the major stages of the rat estrous cycle, were stimulated with selective NK-R agonists. Addition of each agonist resulted in a significant contractile response. However, the magnitude and nature of the response were dependent upon the stage of the estrous cycle, with responses to all agonists being significantly decreased in tissue from proestrus and estrus. Furthermore, the nature of NK3-R-mediated contraction was different in tissue from proestrus and estrus compared to metestrus and diestrus. The hormonal dependence of NK-R-mediated contractility was then examined in the ovariectomized estrogen-supplemented rat model. These studies confirmed that the magnitude and nature of uterine contractility in response to NK-R activation depend upon the hormonal environment. (+info)
Estrous changes in responses of rat gracile nucleus neurons to stimulation of skin and pelvic viscera. (7/45)Multi- and single-unit recording was performed in the gracile nucleus in urethane-anesthetized rats to examine estrous variations in responses of its neurons to brushing the hindquarters and mechanical stimulation of the uterus, vaginal canal, cervix, and colon. Six rats each were studied in each of the four estrous stages: proestrus (P), estrus (E), metestrus (M), and diestrus (D). The magnitude of multi-unit responses to gentle brushing of the perineum, hip, and tail, but not the foot and leg, was significantly greater during proestrus than during other stages. Of 70 single units responsive to brush, 56 (80%) responded to stimulation of at least one viscus. Although this percentage did not change with estrous stage, the direction and latency of some responses did. Pressure on the cervix evoked significantly more inhibitory (vs excitatory) responses in P than in E and M, and the response latency was significantly longer in D and P than in E and M. The direction of response to vaginal distention did not change with estrous stage, but response latency was significantly longer in D than in P and E. Uterine distention evoked significantly more inhibitory responses in D than in P, with no estrous changes in latency. Responses to colon distention did not change. These variations in both magnitude of response to tactile stimulation and characteristics of response to stimulation of reproductive organs, but not the colon, correlate with changes in mating behaviors of the female rat, suggesting that the gracile nucleus is a component of neural systems that control reproductive behaviors. (+info)
Cyclic changes in the responsiveness of regressing corpora lutea to the luteolytic effects of prolactin in rats. (8/45)In cyclic rats, apoptosis of luteal cells during structural luteolysis occurs cyclically at the transition from pro-oestrus to oestrus in response to the preovulatory prolactin surge. This finding indicates that cyclic changes in apoptosis during luteolysis are dependent on prolactin surge cyclicity. In this study, the effects of prolactin on structural luteolysis were studied under different experimental conditions in relation to the phase of the oestrous cycle. In rats treated with prolactin at metoestrus and dioestrus, apoptosis did not occur in regressing corpora lutea, whereas in rats treated with prolactin on the morning of pro-oestrus, a 12.3-fold and 3.4-fold increase were observed in the number of apoptotic cells in regressing corpora lutea of the current and previous oestrous cycles, respectively. However, when the preovulatory prolactin surge and hence the subsequent apoptotic burst were blocked, prolactin treatment at the dioestrus phase induced a 13-fold increase in the number of apoptotic cells and significant changes in the volume of the corpus luteum (38% decrease) and the number of steroidogenic cells per corpus luteum (70% decrease). The results of this study indicate that the responsiveness of the regressing corpus luteum to the pro-apoptotic effects of prolactin are dependent on the phase of the oestrous cycle and on the presence or absence of an apoptotic burst in response to the preovulatory prolactin surge on the evening of pro-oestrus. Steroidogenic cells surviving to the apoptotic burst during the transition from pro-oestrus to oestrus became refractory to the lytic effect of prolactin. Furthermore, these cells also responded to the luteotrophic effects of prolactin, reaching full morphological luteinization, as indicated by the rescue of regressing cyclic corpora lutea during pregnancy. (+info)
Metestrus is the second phase of the estrous cycle in animals, specifically referring to the period of sexual receptivity and ovulation. In humans, this phase corresponds to the luteal phase of the menstrual cycle. During metestrus, the corpus luteum, a temporary endocrine structure formed from the remains of the ovarian follicle after ovulation, produces progesterone, which prepares the uterus for potential implantation of a fertilized egg. The duration of metestrus varies among species and can last several days to a few weeks. It is followed by diestrus, the final phase of the estrous cycle, during which the corpus luteum regresses, and hormone levels drop, leading to the shedding of the uterine lining in non-pregnant individuals.
Diestrus is a stage in the estrous cycle of animals, which is similar to the menstrual cycle in humans. It follows the phase of estrus (or heat), during which the animal is receptive to mating. Diestrus is the period of relative sexual quiescence and hormonal stability between cycles. In this phase, the corpus luteum in the ovary produces progesterone, preparing the uterus for potential pregnancy. If fertilization does not occur, the corpus luteum will degenerate, leading to a drop in progesterone levels and the onset of the next estrous cycle. The duration of diestrus varies among species.
In humans, this phase is analogous to the luteal phase of the menstrual cycle. However, since humans do not exhibit estrous behavior, the term 'diestrus' is typically not used in human reproductive physiology discussions.
The estrous cycle is the reproductive cycle in certain mammals, characterized by regular changes in the reproductive tract and behavior, which are regulated by hormonal fluctuations. It is most commonly observed in non-primate mammals such as dogs, cats, cows, pigs, and horses.
The estrous cycle consists of several stages:
1. Proestrus: This stage lasts for a few days and is characterized by the development of follicles in the ovaries and an increase in estrogen levels. During this time, the female may show signs of sexual receptivity, but will not allow mating to occur.
2. Estrus: This is the period of sexual receptivity, during which the female allows mating to take place. It typically lasts for a few days and is marked by a surge in luteinizing hormone (LH) and follicle-stimulating hormone (FSH), which triggers ovulation.
3. Metestrus: This stage follows ovulation and is characterized by the formation of a corpus luteum, a structure that produces progesterone to support pregnancy. If fertilization does not occur, the corpus luteum will eventually regress, leading to the next phase.
4. Diestrus: This is the final stage of the estrous cycle and can last for several weeks or months. During this time, the female's reproductive tract returns to its resting state, and she is not sexually receptive. If pregnancy has occurred, the corpus luteum will continue to produce progesterone until the placenta takes over this function later in pregnancy.
It's important to note that the human menstrual cycle is different from the estrous cycle. While both cycles involve hormonal fluctuations and changes in the reproductive tract, the menstrual cycle includes a shedding of the uterine lining (menstruation) if fertilization does not occur, which is not a feature of the estrous cycle.
Progesterone is a steroid hormone that is primarily produced in the ovaries during the menstrual cycle and in pregnancy. It plays an essential role in preparing the uterus for implantation of a fertilized egg and maintaining the early stages of pregnancy. Progesterone works to thicken the lining of the uterus, creating a nurturing environment for the developing embryo.
During the menstrual cycle, progesterone is produced by the corpus luteum, a temporary structure formed in the ovary after an egg has been released from a follicle during ovulation. If pregnancy does not occur, the levels of progesterone will decrease, leading to the shedding of the uterine lining and menstruation.
In addition to its reproductive functions, progesterone also has various other effects on the body, such as helping to regulate the immune system, supporting bone health, and potentially influencing mood and cognition. Progesterone can be administered medically in the form of oral pills, intramuscular injections, or vaginal suppositories for various purposes, including hormone replacement therapy, contraception, and managing certain gynecological conditions.
An ovary is a part of the female reproductive system in which ova or eggs are produced through the process of oogenesis. They are a pair of solid, almond-shaped structures located one on each side of the uterus within the pelvic cavity. Each ovary measures about 3 to 5 centimeters in length and weighs around 14 grams.
The ovaries have two main functions: endocrine (hormonal) function and reproductive function. They produce and release eggs (ovulation) responsible for potential fertilization and development of an embryo/fetus during pregnancy. Additionally, they are essential in the production of female sex hormones, primarily estrogen and progesterone, which regulate menstrual cycles, sexual development, and reproduction.
During each menstrual cycle, a mature egg is released from one of the ovaries into the fallopian tube, where it may be fertilized by sperm. If not fertilized, the egg, along with the uterine lining, will be shed, leading to menstruation.
Estradiol is a type of estrogen, which is a female sex hormone. It is the most potent and dominant form of estrogen in humans. Estradiol plays a crucial role in the development and maintenance of secondary sexual characteristics in women, such as breast development and regulation of the menstrual cycle. It also helps maintain bone density, protect the lining of the uterus, and is involved in cognition and mood regulation.
Estradiol is produced primarily by the ovaries, but it can also be synthesized in smaller amounts by the adrenal glands and fat cells. In men, estradiol is produced from testosterone through a process called aromatization. Abnormal levels of estradiol can contribute to various health issues, such as hormonal imbalances, infertility, osteoporosis, and certain types of cancer.
The vagina is the canal that joins the cervix (the lower part of the uterus) to the outside of the body. It also is known as the birth canal because babies pass through it during childbirth. The vagina is where sexual intercourse occurs and where menstrual blood exits the body. It has a flexible wall that can expand and retract. During sexual arousal, the vaginal walls swell with blood to become more elastic in order to accommodate penetration.
It's important to note that sometimes people use the term "vagina" to refer to the entire female genital area, including the external structures like the labia and clitoris. But technically, these are considered part of the vulva, not the vagina.
The uterus, also known as the womb, is a hollow, muscular organ located in the female pelvic cavity, between the bladder and the rectum. It has a thick, middle layer called the myometrium, which is composed of smooth muscle tissue, and an inner lining called the endometrium, which provides a nurturing environment for the fertilized egg to develop into a fetus during pregnancy.
The uterus is where the baby grows and develops until it is ready for birth through the cervix, which is the lower, narrow part of the uterus that opens into the vagina. The uterus plays a critical role in the menstrual cycle as well, by shedding its lining each month if pregnancy does not occur.
Mifepristone is a synthetic steroid that is used in the medical termination of pregnancy (also known as medication abortion or RU-486). It works by blocking the action of progesterone, a hormone necessary for maintaining pregnancy. Mifepristone is often used in combination with misoprostol to cause uterine contractions and expel the products of conception from the uterus.
It's also known as an antiprogestin or progesterone receptor modulator, which means it can bind to progesterone receptors in the body and block their activity. In addition to its use in pregnancy termination, mifepristone has been studied for its potential therapeutic uses in conditions such as Cushing's syndrome, endometriosis, uterine fibroids, and hormone-dependent cancers.
It is important to note that Mifepristone should be administered under the supervision of a licensed healthcare professional and it is not available over the counter. Also, it has some contraindications and potential side effects, so it's essential to have a consultation with a doctor before taking this medication.
Castration is a surgical procedure to remove the testicles in males or ovaries in females. In males, it is also known as orchiectomy. This procedure results in the inability to produce sex hormones and gametes (sperm in men and eggs in women), and can be done for various reasons such as medical treatment for certain types of cancer, to reduce sexual urges in individuals with criminal tendencies, or as a form of birth control in animals.
Ovariectomy is a surgical procedure in which one or both ovaries are removed. It is also known as "ovary removal" or "oophorectomy." This procedure is often performed as a treatment for various medical conditions, including ovarian cancer, endometriosis, uterine fibroids, and pelvic pain. Ovariectomy can also be part of a larger surgical procedure called an hysterectomy, in which the uterus is also removed.
In some cases, an ovariectomy may be performed as a preventative measure for individuals at high risk of developing ovarian cancer. This is known as a prophylactic ovariectomy. After an ovariectomy, a person will no longer have menstrual periods and will be unable to become pregnant naturally. Hormone replacement therapy may be recommended in some cases to help manage symptoms associated with the loss of hormones produced by the ovaries.
Luteinizing Hormone (LH) is a glycoprotein hormone, which is primarily produced and released by the anterior pituitary gland. In women, a surge of LH triggers ovulation, the release of an egg from the ovaries during the menstrual cycle. During pregnancy, LH stimulates the corpus luteum to produce progesterone. In men, LH stimulates the testes to produce testosterone. It plays a crucial role in sexual development, reproduction, and maintaining the reproductive system.
Ovulation is the medical term for the release of a mature egg from an ovary during a woman's menstrual cycle. The released egg travels through the fallopian tube where it may be fertilized by sperm if sexual intercourse has occurred recently. If the egg is not fertilized, it will break down and leave the body along with the uterine lining during menstruation. Ovulation typically occurs around day 14 of a 28-day menstrual cycle, but the timing can vary widely from woman to woman and even from cycle to cycle in the same woman.
During ovulation, there are several physical changes that may occur in a woman's body, such as an increase in basal body temperature, changes in cervical mucus, and mild cramping or discomfort on one side of the lower abdomen (known as mittelschmerz). These symptoms can be used to help predict ovulation and improve the chances of conception.
It's worth noting that some medical conditions, such as polycystic ovary syndrome (PCOS) or premature ovarian failure, may affect ovulation and make it difficult for a woman to become pregnant. In these cases, medical intervention may be necessary to help promote ovulation and increase the chances of conception.
The corpus luteum is a temporary endocrine structure that forms in the ovary after an oocyte (egg) has been released from a follicle during ovulation. It's formed by the remaining cells of the ruptured follicle, which transform into large, hormone-secreting cells.
The primary function of the corpus luteum is to produce progesterone and, to a lesser extent, estrogen during the menstrual cycle or pregnancy. Progesterone plays a crucial role in preparing the uterus for potential implantation of a fertilized egg and maintaining the early stages of pregnancy. If pregnancy does not occur, the corpus luteum will typically degenerate and stop producing hormones after approximately 10-14 days, leading to menstruation.
However, if pregnancy occurs, the developing embryo starts to produce human chorionic gonadotropin (hCG), which signals the corpus luteum to continue secreting progesterone and estrogen until the placenta takes over hormonal production, usually around the end of the first trimester.
Follicle-Stimulating Hormone (FSH) is a glycoprotein hormone secreted and released by the anterior pituitary gland. In females, it promotes the growth and development of ovarian follicles in the ovary, which ultimately leads to the maturation and release of an egg (ovulation). In males, FSH stimulates the testes to produce sperm. It works in conjunction with luteinizing hormone (LH) to regulate reproductive processes. The secretion of FSH is controlled by the hypothalamic-pituitary-gonadal axis and its release is influenced by the levels of gonadotropin-releasing hormone (GnRH), estrogen, inhibin, and androgens.
An ovarian follicle is a fluid-filled sac in the ovary that contains an immature egg or ovum (oocyte). It's a part of the female reproductive system and plays a crucial role in the process of ovulation.
Ovarian follicles start developing in the ovaries during fetal development, but only a small number of them will mature and release an egg during a woman's reproductive years. The maturation process is stimulated by hormones like follicle-stimulating hormone (FSH) and luteinizing hormone (LH).
There are different types of ovarian follicles, including primordial, primary, secondary, and tertiary or Graafian follicles. The Graafian follicle is the mature follicle that ruptures during ovulation to release the egg into the fallopian tube, where it may be fertilized by sperm.
It's important to note that abnormal growth or development of ovarian follicles can lead to conditions like polycystic ovary syndrome (PCOS) and ovarian cancer.
Gonadotropin-Releasing Hormone (GnRH), also known as Luteinizing Hormone-Releasing Hormone (LHRH), is a hormonal peptide consisting of 10 amino acids. It is produced and released by the hypothalamus, an area in the brain that links the nervous system to the endocrine system via the pituitary gland.
GnRH plays a crucial role in regulating reproduction and sexual development through its control of two gonadotropins: follicle-stimulating hormone (FSH) and luteinizing hormone (LH). These gonadotropins, in turn, stimulate the gonads (ovaries or testes) to produce sex steroids and eggs or sperm.
GnRH acts on the anterior pituitary gland by binding to its specific receptors, leading to the release of FSH and LH. The hypothalamic-pituitary-gonadal axis is under negative feedback control, meaning that when sex steroid levels are high, they inhibit the release of GnRH, which subsequently decreases FSH and LH secretion.
GnRH agonists and antagonists have clinical applications in various medical conditions, such as infertility treatments, precocious puberty, endometriosis, uterine fibroids, prostate cancer, and hormone-responsive breast cancer.
Pregnancy is a physiological state or condition where a fertilized egg (zygote) successfully implants and grows in the uterus of a woman, leading to the development of an embryo and finally a fetus. This process typically spans approximately 40 weeks, divided into three trimesters, and culminates in childbirth. Throughout this period, numerous hormonal and physical changes occur to support the growing offspring, including uterine enlargement, breast development, and various maternal adaptations to ensure the fetus's optimal growth and well-being.
Estrogens are a group of steroid hormones that are primarily responsible for the development and regulation of female sexual characteristics and reproductive functions. They are also present in lower levels in males. The main estrogen hormone is estradiol, which plays a key role in promoting the growth and development of the female reproductive system, including the uterus, fallopian tubes, and breasts. Estrogens also help regulate the menstrual cycle, maintain bone density, and have important effects on the cardiovascular system, skin, hair, and cognitive function.
Estrogens are produced primarily by the ovaries in women, but they can also be produced in smaller amounts by the adrenal glands and fat cells. In men, estrogens are produced from the conversion of testosterone, the primary male sex hormone, through a process called aromatization.
Estrogen levels vary throughout a woman's life, with higher levels during reproductive years and lower levels after menopause. Estrogen therapy is sometimes used to treat symptoms of menopause, such as hot flashes and vaginal dryness, or to prevent osteoporosis in postmenopausal women. However, estrogen therapy also carries risks, including an increased risk of certain cancers, blood clots, and stroke, so it is typically recommended only for women who have a high risk of these conditions.
"Wistar rats" are a strain of albino rats that are widely used in laboratory research. They were developed at the Wistar Institute in Philadelphia, USA, and were first introduced in 1906. Wistar rats are outbred, which means that they are genetically diverse and do not have a fixed set of genetic characteristics like inbred strains.
Wistar rats are commonly used as animal models in biomedical research because of their size, ease of handling, and relatively low cost. They are used in a wide range of research areas, including toxicology, pharmacology, nutrition, cancer, cardiovascular disease, and behavioral studies. Wistar rats are also used in safety testing of drugs, medical devices, and other products.
Wistar rats are typically larger than many other rat strains, with males weighing between 500-700 grams and females weighing between 250-350 grams. They have a lifespan of approximately 2-3 years. Wistar rats are also known for their docile and friendly nature, making them easy to handle and work with in the laboratory setting.
The endometrium is the innermost layer of the uterus, which lines the uterine cavity and has a critical role in the menstrual cycle and pregnancy. It is composed of glands and blood vessels that undergo cyclic changes under the influence of hormones, primarily estrogen and progesterone. During the menstrual cycle, the endometrium thickens in preparation for a potential pregnancy. If fertilization does not occur, it will break down and be shed, resulting in menstruation. In contrast, if implantation takes place, the endometrium provides essential nutrients to support the developing embryo and placenta throughout pregnancy.
Furan fatty acids
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- The rodent estrous cycle lasts 4 days and consists of 4 phases: proestrus, estrus, metestrus (diestrus I), and diestrus (II). (deubiquitinaseinhibitor.com)
- Small icons indicate the proestrus, estrus, and metestrus of the dog after you have independently entered this information the first time. (eys-apps.de)
- PER2 expression peaked at different times on metestrus, and diestrus than the other two days of the cycle. (elsevierpure.com)
- In many cases, two days later a normal metoestrus can be observed. (vin.com)
- Miller explained the three stages of a heat cycle - metestrus, diestrus and proestrus. (wylr.net)
- During a cat's gestation period, she goes through four stages of heat production known as anestrus through metestrus. (thecatshub.com)
- 5. Ovariectomy had little effect on the ADH-induced renin release and the response was similar at oestrus, metoestrus and dioestrus. (portlandpress.com)
- Histological determination of the number of follicles present in various volume-classes, showed an increase in antral follicles on days 1 and 2, comparable to the increase observed during metoestrus and dioestrus 1 of the normal cycle. (nih.gov)
- Metestrus starts the cycle by releasing an egg. (wylr.net)
- Metestrus: The metestrus stage occurs if the female cat does not become pregnant. (pethomeguide.com)