Biomedical subjects

D T Baird

Publications and source records attributed to D T Baird.

At least 73 records · Page 4Linked to original sources

PubMed1999

Perivascular interleukin-8 messenger ribonucleic acid expression in human endometrium varies across the menstrual cycle and in early pregnancy decidua.

Human endometrium and decidua contain large numbers of different leukocyte populations, the concentration of which fluctuates during the menstrual cycle and pregnancy. There is, for example, a large influx of neutrophils into premenstrual endometrium associated with an increased expression of interleukin (IL)-8 protein, which is chemotactic for neutrophils. Our aim in this study was to localize IL-8 messenger RNA (mRNA) expression in endometrium and decidua using in situ hybridization. In situ hybridization was carried out with a 35S-uridine 5'-triphosphate-labeled riboprobe using standard procedures. Late secretory endometrial and decidual biopsies demonstrated clear perivascular localization of IL-8 mRNA, with additional expression colocalized to activated macrophages. Midluteal endometrium showed minimal IL-8 expression, whereas endometrium obtained from women administered progesterone for 4 days from (LH peak + 8 days), to simulate luteal regression, demonstrated significantly increased localization of IL-8 mRNA, 48 h after withdrawal of progesterone. In conclusion, IL-8 mRNA expression is localized to perivascular cells of late secretory endometrium and decidua.

Blood Vessels↗

PubMed1999

Regulation of bcl-2 gene family members in human endometrium by antiprogestin administration in vivo.

It is likely that the changes which occur in the endometrium throughout the menstrual cycle involve apoptosis, and that expression of associated genes, such as the bcl-2 family, are regulated by sex steroids. The aim of this study was to investigate the presence of bcl-2, Bax and oestrogen receptor proteins in secretory endometrium collected from ten patients with normal ovulatory cycles 4 or 6 days after the LH surge, and on the same days in a subsequent cycle in which the formation of secretory changes was inhibited by the administration of the antiprogestin mifepristone (RU486) 2 days after the onset of the LH surge. Since some stromal cells display positive immunoreactivity, leucocyte subpopulations of macrophages (CD68-positive) and large granular lymphocytes (CD56-positive) were identified in serial sections. After administration of mifepristone on day 2 after the LH surge, a significant increase in bcl-2 immunoreactivity was observed in glandular and surface epithelium. A positive correlation (0.874) with nuclear oestrogen receptor immunoreactivity in endometrial glands was demonstrated. Subsets of stromal cells, identified as CD68-positive macrophages and CD56-positive large granular lymphocytes displayed positive immunoreactivity for the bcl-2 epitope, which was unaffected by mifepristone administration. Bax immunostaining was similar in control and antiprogestin-treated endometrium. These data indicate that antiprogestin administration inhibits progesterone downregulation of steroid receptors in endometrial glands, resulting in persistence of a proliferative endometrium and accompanying bcl-2 secretion.

Adult↗

PubMed1999

Direct effects of ovine follicular fluid on ovarian steroid secretion and expression of markers of cellular differentiation in sheep.

The objective of this study was to assess the effect of ovine follicular fluid (FF) treatment (with or without FSH replacement) during the late follicular phase on plasma concentrations of gonadotrophins and the development of the ovulatory follicle. Ovarian steroid secretion and expression of mRNA encoding inhibin alpha and beta A, beta B subunits, P450 aromatase and P450 17 alpha-hydroxylase were used as endpoints. After induction of luteolysis by injection of 100 micrograms cloprostenol on days 10-12, Scottish Blackface ewes were allocated to one of three groups: (1) control (n = 7): no further treatment; (2) FF (n = 9): subcutaneous injections of 3 ml steroid-free ovine follicular fluid at 9 h intervals, 18 and 27 h after cloprostenol injection; (3) FF + FSH (n = 8): injections of follicular fluid as above plus subcutaneous injections of 0.36 iu ovine FSH at 6 h intervals, 18, 24, and 30 h after cloprostenol injection. Jugular venous blood samples were obtained via indwelling cannulae at 6 h intervals from 0 to 36 h after cloprostenol injection, and at 10 min intervals from 12 to 18 h (control phase) and from 30 to 36 h after cloprostenol injection (treatment phase). At laparotomy, 36 h after cloprostenol injection, ovarian venous blood was collected and ovaries were removed and processed for in situ hybridization. Plasma concentrations of FSH, luteinizing hormone (LH) and oestradiol were determined by radioimmunoassay. Follicular fluid treatment resulted in a decrease (P < 0.001) in FSH concentrations associated with an acute decrease in ovarian steroid secretion (P < 0.01) and a specific depression in P450 aromatase, (P < 0.001), inhibin-activin beta B subunit (P < 0.05) and thecal LH receptor (P < 0.001) expression. Follicular fluid treatment had no effect on inhibin-activin alpha and beta A, subunit or P450 17 alpha-hydroxylase expression. FSH co-treatment with follicular fluid restored circulating FSH concentrations to normal values and reversed some of the effects of follicular fluid (androstenedione, testosterone and progesterone secretion, and inhibin beta B and thecal LH receptor expression) but not oestradiol secretion or P450 aromatase expression. It was concluded that the actions of follicular fluid are mediated via both central effects on pituitary FSH secretion and by direct ovarian effects on granulosa cell aromatase activity. The results indicate that follicular fluid contains a factor that inhibits aromatase activity of granulosa cells directly and may play a role in the selection of the dominant follicle.

Analysis of Variance↗

PubMed1999

Examination of the relative role of FSH and LH in the mechanism of ovulatory follicle selection in sheep.

The GnRH-antagonist suppression-ovarian autotransplant model (n = 18) was used to examine the relative roles of temporal changes in FSH and LH stimulation on follicle development and selection. Follicle development was stimulated by infusion with oFSH for 3 days and treatments applied for 60 h after progestagen sponge withdrawal and before delivery of an ovulatory stimulus. In Expt 1, there was continuous infusion of FSH with or without small amplitude high frequency LH pulses, or withdrawal of FSH with or without pulsatile LH. In Expt 2, there was acute or gradual withdrawal of FSH at sponge withdrawal with pulsatile LH. The patterns of follicle development and basal and pulsatile ovarian hormone secretion were determined. The maintenance of FSH throughout the artificial follicular phase resulted in multiple follicle development and ovulation (3.3 +/- 0.3). Pulsatile LH stimulated steroid secretion (P < 0.001) but had little effect on ovulation rates (3.8 +/- 0.8) when FSH was maintained. However, withdrawal of FSH in the absence of LH resulted in atresia of the ovulatory follicles and anovulation whereas, when FSH was withdrawn in the presence of LH, preovulatory follicle development was maintained in some animals (3/6 and 5/9 in Expts 1 and 2, respectively) and these ewes had lower (P < 0.05) ovulation rates (1-2 ovulations per ewe). When FSH was withdrawn gradually in the presence of pulsatile LH, 9/9 animals ovulated with ovulation rates in the normal range. These results indicate that ovulatory follicles can transfer their gonadotrophic dependence from FSH to LH. It is hypothesized that the ability of a follicle to respond to this switch in gonadotrophic support is central to the mechanism of follicle selection.

Analysis of Variance↗

PubMed1998

Follicle selection in sheep with breed differences in ovulation rate.

Genetic variations in ovulation rates which occur in different breeds of sheep provide useful models to explore the mechanisms underlying the antral of follicle development. Two principal strategies have evolved which enable these high fecundity breeds to over-ride the mechanisms which drastically restrict the number of ovulatory follicles. Firstly, Finnish Landrace involves reducing the sensitivity of the hypothalamic-pituitary unit to the feedback effects of ovarian hormones (inhibin and/or oestradiol) which normally suppress FSH. Treatment with oestrogens or immunisation against oestradiol or inhibin are pharmacological methods of manipulating the feedback system. The second mechanism as exemplified by the FecB gene results in an increased ovulation rate associated with the 'precocious' development of a large number of small antral follicles. The gene mutation responsible for this effect has not yet been identified. It is likely that the product will be a factor which enhances follicular development as well as affecting gonadotrophic function. Identification of the gene product should permit further research into the factors which regulate the orderly development of follicles within the ovary.

Animals↗

PubMed1998

A pilot study of the effect of methotrexate or combined oral contraceptive on bleeding patterns after induction of abortion with mifepristone and a prostaglandin pessary.

Although a combination of mifepristone and a prostaglandin is a safe, acceptable alternative to vacuum aspiration for inducing abortion in early pregnancy, the longer period of vaginal bleeding after medical abortion is a disadvantage. The present study investigated whether administration of the combined oral contraceptive pill (COC) or the injection of methotrexate at the time of abortion would shorten the period of vaginal bleeding after medical abortion. After having a medical abortion induced with mifepristone (200 mg) and 0.5 mg gemeprost pessary, 80 women were randomized to four groups of 20 women each; Group A, COC; Group B, control; Group C, 50 mg/m2 methotrexate; and Group D, placebo injection. There was no significant difference in the duration of bleeding between Groups A and B (median 14 and 17 days) or between Groups C and D (18 and 15 days), or in the amount of bleeding (4 days of heavy bleeding in each group). The first period occurred sooner in Group A who took the COC (median/range: 25/15-54 control group versus 32/16-46 days, p < 0.04). The administration of methotrexate was associated with a temporary elevation in liver enzyme concentration in one woman. It is concluded that women who wish to use COC can start immediately after medical abortion. Addition of methotrexate after abortion has no significant beneficial effect on patterns of bleeding and cannot be recommended.

Abortifacient Agents↗

PubMed1998

Inhibin A and inhibin B in women with polycystic ovarian syndrome during treatment with FSH to induce mono-ovulation.

OBJECTIVE: Polycystic ovary syndrome (PCOS) is characterized by the presence of numerous small antral follicles arrested at a diameter of less than 10 mm. As development of large antral follicle(s) can be stimulated by the administration of FSH, it has been suggested that the arrest of follicle development is due to a relative lack of or resistance to FSH. We have measured the concentration of FSH and LH and the ovarian hormones oestradiol, inhibin A and B, in relation to the dynamics of follicular development in women with PCOS under basal conditions and during treatment with FSH. DESIGN: The concentrations of FSH, LH, oestradiol, inhibin A and B were measured in women with PCOS who were untreated (n = 9) or following progesterone-induced menses (10 cycles in six women) and control women on day 3 of a normal cycle (n = 10). Serial measurements of the same hormones were made during induction of ovulation with low dose of exogenous FSH in the women with PCOS who had been treated with progesterone. The dynamics of follicle development were measured by serial pelvic ultrasound examinations during treatment with FSH in PCOS and in the follicular phase of control cycles. PATIENTS: Nine anovulatory untreated women with PCOS were compared with 10 normal women and six women with PCOS undergoing FSH treatment. RESULTS: The concentrations of inhibin B and LH were higher in both groups of women with PCOS than in normal control women on day 3. In untreated women with PCOS the concentration of inhibin A was also significantly elevated compared to control women (P < 0.01) but not in women pretreated with progesterone. Basal concentrations of oestradiol were also significantly higher in women with PCOS than in the early follicular phase of the normal cycle. There were no significant differences in the concentration of FSH between the groups. Treatment of women with PCOS with low doses of FSH stimulated the development of a single dominant follicle which had an identical rate of growth and secretion of oestradiol and inhibin A to that observed in spontaneous cycles in normal women. In contrast to normal women, the concentration of inhibin B rose 7-fold following FSH treatment and remained elevated until the luteal phase. CONCLUSIONS: The raised concentrations of inhibin A and B in women with PCOS probably reflects the increased number of small antral follicles characteristically present in that condition. The striking similarity in the dynamics of growth of the dominant follicle and the pattern in concentration of oestradiol and inhibin A in normal women and in women with PCOS treated with modest amounts of FSH, suggests that the arrest of follicle development in PCOS may be due to a relative deficiency of FSH which may in turn be secondary to increased secretion of either or both inhibin forms.

Adult↗

PubMed1998

Incipient ovarian failure associated with raised levels of follicle stimulating hormone and reduced levels of inhibin A in older sheep.

In women there is a gradual rise in the basal level of follicle stimulating hormone (FSH) in the years prior to the menopause (pre-menopause) which is thought to be due to a relative lack of ovarian factors reflecting the number of antral follicles present in the ovaries. Experimental animal models for this phenomenon, particularly in mono-ovulatory species, have been lacking due to most animals' relatively short life span. We have available a group of experimental ewes in which the right ovary was removed and the left ovary was autotransplanted to the neck at least 10 years previously, which have been maintained in good health until an age of 12-13 years. Two experiments were conducted with these animals to determine the endocrine and follicular effects of age: a retrospective experiment in the same Finn-Merino ewes (n = 5) when the animals were 6-7 or 12-13 years of age; and a cohort experiment in old (12-13 years, n = 6) and young (2 years, n = 5) ewes of the same breed. In both retrospective and cohort experiments, the concentrations of FSH were significantly higher (P < 0.05) in older animals during the luteal phase when oestradiol secretion was low. This increase in FSH was associated with a decrease in the concentration of inhibin A (P < 0.05) in older animals in both the follicular and luteal stages of the cycle but the concentrations of oestradiol were similar between ages. Although there were significantly fewer antral follicles (P < 0.05) available for development in older ewes during the early luteal phase of the cycle, the ovulation rate was similar to that observed in younger animals (2.0+/-0 vs 2.0+/-4; P > 0.05) but the interval from luteal regression to the onset of the LH surge was longer (P < 0.05) in older animals. In conclusion, the endocrine changes associated with increasing reproductive age in sheep are therefore similar to those observed in women, suggesting that the sheep could be a useful animal model to study the effect of age on human fertility.

Aging↗

PubMed1998

Progesterone receptor subtype B is differentially regulated in human endometrial stroma.

Two anti-progesterone receptor (PgR) antibodies, a new one specific to PgRB, the other to PgR subtypes A + B, have been used to examine the cellular location of PgR subtypes A and B in normal endometrium throughout the menstrual cycle and in early human decidua by standard immunohistochemical techniques. PgR(A+B) is the receptor detected by the antibody recognizing both isoforms of the receptor. PgRB is the receptor detected by the new antibody specific to the B isoform. Since it is not possible to raise antibody specific to PgR subtype A, all immunohistochemical analysis of the PgRA subtype is by subtractive inference. Thus we refer to PgRA as the subtype responsible for positive immunoreactivity when the PgRB subtype cannot be specifically detected. Endometrial biopsies were collected from 40 women with regular menses (n = 5 each stage of cycle: menstrual; early, mid and late proliferative; ovulatory; early, mid, and late secretory). Decidual tissue was obtained from 10 women undergoing first trimester surgical termination of pregnancy. As previously reported, the PgR(A+B) antibody stained glandular and stromal nuclei during the proliferative phase but only stromal nuclei during the secretory phase and early pregnancy. The new PgRB antibody also stained both cell types intensely during the proliferative phase, but failed to stain either stromal or glandular nuclei strongly during the secretory phase and early pregnancy. We concluded that, while both PgR subtypes were present in glands and stroma in the proliferative phase, and both subtypes were dramatically reduced in the glands during the secretory phase, PgRA remained as the predominant type in the stroma during the secretory phase and early pregnancy. The profound effects of progesterone on endometrium during the secretory phase and early pregnancy appear to be mediated primarily by PgRA in the stroma.

Adult↗

PubMed1998

Progesterone induces calcitonin gene expression in human endometrium within the putative window of implantation.

The human endometrium acquires the ability to implant the developing embryo within a specific time window that is thought to open between days 19-24 of the secretory phase of the menstrual cycle. During this period the endometrium undergoes pronounced structural and functional changes induced by the ovarian steroids, estrogen and progesterone, that prepare it to be receptive to invasion by the embryo. The identification of reliable biochemical markers to assess this critical receptive phase in the context of the natural cycle remains one of the major challenges in the study of human reproduction. Our previous studies in a rat model system demonstrated that the expression of calcitonin, a peptide hormone involved in calcium homeostasis, is transiently induced by progesterone in the glandular epithelium at the onset of implantation. Attenuation of calcitonin synthesis in the uterus during the preimplantation phase by administration of calcitonin antisense oligodeoxynucleotides severely impairs implantation of rat embryos, suggesting that this peptide hormone plays a critical role in uterine receptivity. To investigate whether calcitonin is also expressed in the human endometrium during implantation, we monitored the spatio-temporal expression of calcitonin on various days of the menstrual cycle. Our studies employing RT-PCR showed that calcitonin messenger ribonucleic acid is expressed in human endometrium during the postovulatory midsecretory phase (days 17-25) of the menstrual cycle, with maximal expression occurring between days 19-21. Very little calcitonin expression was detected in the endometrium in either the preovulatory proliferative (days 5-14) or the late secretory (days 26-28) phase. In situ hybridization and immunocytochemical analyses localized the calcitonin expression predominantly in the glandular epithelial cells of the endometrium. Our studies further showed that calcitonin expression in the human endometrium is under progesterone regulation. Treatment of women with an antiprogestin, mifepristone (RU-486), drastically reduced calcitonin expression in the endometrium. Collectively, these findings reveal that progesterone-induced expression of calcitonin in the secretory endometrium temporally coincides with the putative window of implantation in the human.

Adult↗

PubMed1998

Effects of dose of LH on androgen production and luteinization of ovine theca cells cultured in a serum-free system.

The study reports the development of a serum-free culture system for sheep thecal cells that overcomes the problem of spontaneous luteinization and the use of this system to study the control of proliferation and differentiation. Theca cells were isolated by enzymatic dispersion from small follicles (< 3.5 mm) and the effect of plating densities (25-100 x 10(3) cells per well), LH (0.001-100 micrograms l-1), insulin (1-5000 micrograms l-1), insulin-like growth factor I (IGF-I) analogue (1-100 micrograms LR3-IGF-I l-1) and epidermal growth factor (EGF) (0.005-50 micrograms l-1) on the number of cells and androstenedione and progesterone production were determined. Plating density had a marked effect on the pattern of hormone secretion with densities between 50 and 75 x 10(3) cells per well resulting in a high androstenedione: progesterone ratio at optimum doses of LH (0.1 micrograms l-1: P < 0.001). In the first 48 h, the production of both androstenedione and progesterone was stimulated in a dose-dependent manner by LH (P < 0.001). However, the production of androstenedione was ten times higher than that of progesterone and was more sensitive to LH (ED50 value 0.08 micrograms l-1 for androstenedione and 1 microgram l-1 for progesterone). From 48-144 h of culture higher doses of LH (> 1 ng ml-1) inhibited androstenedione (P < 0.001) and stimulated progesterone (P < 0.001) and resulted in a marked change in cell morphology, thus reflecting both functional and morphological luteinization. At optimum doses of LH, both insulin and IGF stimulated cell proliferation (P < 0.001) and androstenedione production (P < 0.001) in a dose responsive manner and there was a significant (P < 0.001) interaction between them. In contrast, both insulin and IGF-I inhibited (P < 0.001) progesterone production in a dose responsive manner. EGF stimulated cell proliferation (P < 0.001) and progesterone production (P < 0.001), but inhibited androstenedione production (P < 0.001), in a dose responsive manner. In conclusion, this culture system exhibits physiologically relevant responses to known in vivo modulators of follicle development. The biphasic nature of the theca cell response to LH emphasises the exquisite sensitivity of theca cells to LH stimulation and highlights the importance of dose-response relationships in the gonadotrophic control of ovarian function.

Androstenedione↗

PubMed1998

Follicular waves and concentrations of steroids and inhibin A in ovarian venous blood during the luteal phase of the oestrous cycle in ewes with an ovarian autotransplant.

The dynamics of ovarian follicular development and the pattern of pituitary and ovarian hormone concentration were investigated during the luteal phase in ewes with autotransplanted ovaries. The follicles were measured by ultrasound and samples of ovarian and jugular venous blood were collected at intervals of 12 h. Blood samples were collected before and after a GnRH challenge (250 ng GnRH, i.v.) to allow the determination of basal and LH-stimulated concentration of ovarian steroids. Throughout the luteal phase, large antral follicles developed in three waves, each of which was preceded by a rise in the concentration of FSH (P < 0.05). The concentrations of oestradiol and androstenedione in the unstimulated and LH-stimulated samples were similar (P > 0.05) during the first 3 days of the luteal phase but differed thereafter, with the LH-stimulated being significantly higher than the basal concentrations (P < 0.05). In the first wave of follicular development the changes in follicular size were accompanied by an increase in the concentration of ovarian steroids and inhibin A. During the second follicular wave, although changes in follicle diameter were similar to the first wave (P > 0.05), the basal concentration of ovarian steroids and inhibin A remained unchanged throughout the period of emergence and demise of the large follicles. These results confirm that the development of large antral follicles during the luteal phase of the sheep occurs in successive waves that are associated with fluctuations in FSH secretion. However while the results strongly suggest that fluctuations in both inhibin A and oestradiol secretion control FSH during the first follicular wave, the cause of the FSH fluctuations associated with waves two and three is unclear. Final resolution of this issue may need to await the development of a specific assay for dimeric inhibin B.

Analysis of Variance↗

PubMed1997

Amenorrhoea.

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Amenorrhea↗

PubMed1997

Effect of two antiprogestins (mifepristone and onapristone) on endometrial factors of potential importance for implantation.

OBJECTIVE: To investigate the effects of postovulatory administration of antiprogestins on endometrial factors that may be of importance for successful implantation. DESIGN: Ten women were given 200 mg mifepristone and an additional 10 women 400 mg of onapristone 48 hours after the LH surge in urine (LH + 2). MAIN OUTCOME MEASURE(S): Biopsies were assessed for histologic dating and the immunolocalization of [1] leukemia inhibitory factor, [2] 15-hydroxyprostaglandin dehydrogenase, and [3] the cell proliferation marker Ki 67. Hormonal measurements in blood and urine were used to monitor the effects on the ovarian cycle. Glycodelin (placental protein 14) concentrations were measured in blood taken on LH + 12. RESULT(S): Treatment with antiprogestins retarded the development of secretory changes without affecting the length of the luteal phase. In addition, there was reduced immunostaining for 15-hydroxyprostaglandin dehydrogenase within glands and a significant reduction in serum levels of glycodelin. Reduced immunostaining for leukemia inhibitory factor also was apparent within glands in biopsies taken on LH + 6 of the treatment cycle. Increased Ki 67 immunostaining was observed on both cycle days after treatment, consistent with P antagonism. CONCLUSION(S): Administration of mifepristone and onapristone adversely affects uterine receptivity. This adds further evidence to support their potential as a method of postovulatory fertility control.

Abortifacient Agents, Steroidal↗

PubMed1997

Studies on the role of LH in the maturation of the pre-ovulatory follicle in a sheep using a GnRH-antagonist.

A model designed to mimic the action of LH in preovulatory follicle development was evaluated. The model involved treatment of ewes with GnRHa (50 micrograms kg-1 24 h-1; GnRHa) at the time of luteal regression followed by exogenous LH administered as a series of bolus injections of varying frequency and amplitude. Ovarian responses to this regimen were compared to data derived from the same animals during a normal follicular phase. In experiment 1 four ewes with an autotransplanted ovary were treated with GnRHa followed by hourly LH (2.5 micrograms NIH-oLH-S25 i.v.) for 60 h at which time a further bolus of LH (25 micrograms i.v.) was given to mimic the LH surge. Plasma FSH profiles and the pattern and rate of secretion of oestradiol, inhibin, androstenedione and testosterone by the ovary in normal and GnRHa treated ewes were similar, but ovulation did not occur following the induced follicular phase. Experiment 2 examined the ability of a revised LH regimen to induce ovulation in normal intact ewes. Ewes (n = 11) were treated with GnRHa at the time of luteal regression followed by LH injections (1.25 micrograms i.v.) administered every 3 h for 12 h, every 2 h for the next 12 h and every hour for the following 36 h (3,2,1 regimen). After 60 h of LH injections the animals received an 8 h infusion of oLH (25 micrograms min-1) designed to mimic the pre-ovulatory LH surge. This treatment resulted in normal follicular phase patterns of LH and FSH and had no effect on the incidence (100%) or number (1.6 +/- 0.1) of ovulations when compared to a normal cycle (100% and 1.8 +/- 0.2). Experiment 3 examined the pattern of ovarian follicular development and hormone secretion stimulated by the 3,2,1 LH regimen in ewes with autotransplanted ovaries (n = 8). The LH regimen stimulated normal pre-ovulatory follicular development (normal 1.4 +/- 0.2; induced 1.6 +/- 0.2) and a normal pattern of ovarian oestradiol and androstenedione secretion. Pulse analysis showed, however, that baseline steroid secretion was lower in induced animals during the late follicular phase reflecting lower baseline LH at this stage. We conclude that administration of a GnRHa at the time of luteal regression in conjunction with frequent low amplitude pulses of exogenous LH induce follicular and hormonal patterns that closely mimic those observed following normal luteal regression and that this regimen represents a useful model to study the role of LH in the control of follicular selection.

Androstenedione↗

PubMed1997

Follicular dynamics and ovarian steroid secretion in sheep during the follicular and early luteal phases of the estrous cycle.

In this study, we investigated follicular dynamics and ovarian steroid secretion during the follicular and early luteal phases of the estrous cycle in sheep. Six Finn-Merino ewes with ovarian autotransplanted ovaries were monitored for 10 days during the follicular phase and subsequent early luteal phase after luteal regression was induced with cloprostenol (a potent analogue of prostaglandin F2alpha). Over this period, follicular diameter was measured by serial ultrasound scans, and the concentration of gonadotropins and steroids in ovarian venous blood was measured at intervals of 6-12 h. All animals had an LH surge (Day 0) 59 +/- 4.7 h after injection of cloprostenol. The ovulatory follicles were derived mainly from large antral follicles present at the time of injection of cloprostenol (5.1 +/- 0.4 mm; mean +/- SEM, n = 6), although in some animals recruitment of additional small follicles was observed after luteolysis. The concentration of FSH decreased during the follicular phase and peaked synchronously with the LH surge, while estradiol and androstenedione concentrations in ovarian venous plasma increased progressively from luteal regression to a maximum at the LH surge. The rise in concentration of FSH on Day 1 was followed by the growth of a new cohort of follicles. Follicular size and ovarian steroid secretion increased in a linear fashion from Day 1 to Day 3, with ovarian steroid secretion reaching a maximum when the first wave of luteal phase follicles achieved a diameter of 5 mm or more. On Day 4, steroid secretion began to decline without significant changes in follicular diameter, and a second wave of follicles emerged. We conclude that 1) the preovulatory follicles are usually derived from the large follicle population present at the time of luteal regression, but the sheep has the ability to promote smaller follicles if required; and 2) the second peak of FSH stimulates the development of large estrogenic follicles during the early luteal phase, but the period of functional dominance is shorter than the period of morphological dominance.

Androstenedione↗

PubMed1997

Continuous transdermal oestrogen and interrupted progestogen as a novel bleed-free regimen of hormone replacement therapy for postmenopausal women.

OBJECTIVE: To investigate the effects of a hormone replacement therapy regime of continuous oestrogen and interrupted progestogen, administered transdermally, on the endometrium of postmenopausal women, the pattern of bleeding and relief of menopausal symptoms. DESIGN: Volunteer pilot study of up to six months duration involving weekly application of an oestrogen-only skin patch releasing 50 microg oestradiol per day interspersed with a combined oestrogen and progestogen patch releasing 50 microg oestradiol and 250 microg norethisterone acetate per day for three days. Transvaginal ultrasound measurements of endometrial thickness and endometrial biopsies were performed in the third month of treatment at the end of both an oestrogen-only phase of treatment and a combined oestrogen-progestogen phase. SETTING: Specialist community menopause clinic, Dean Terrace Centre, Edinburgh. PARTICIPANTS: Fifteen healthy postmenopausal women. MAIN OUTCOME MEASURES: Effect of treatment on endometrial histology, the immunolocalisation of oestrogen and progesterone receptors and the cell proliferation marker Ki 67 after three months of treatment and the proportion of women without bleeding at six months. RESULTS: Treatment provided relief of hot flushes and by the sixth month of study 10 of the 14 women who completed treatment had no vaginal bleeding (71%). No endometrial hyperplasia or atypical changes were observed in biopsies and ultrasound measurements of endometrial thickness demonstrated a thin endometrium. Reduced immunostaining for Ki 67 was observed in endometrium from the combined phase of treatment compared with the oestrogen-only phase, consistent with a progestogenic-antagonism of proliferation. Exposure to progestogen did not suppress steroid receptors as similar immunostaining was observed in both treatment phases. CONCLUSIONS: Continuous oestrogen and interrupted progestogen administered transdermally offers promise as a novel bleed-free hormone replacement therapy for postmenopausal women.

Administration, Cutaneous↗

PubMed1997

Secretion of inhibin A and follicular dynamics throughout the estrous cycle in the sheep with and without the Booroola gene (FecB).

The identification of a single gene (Booroola FecB) associated with a significant increase in the ovulation rate in sheep provides a powerful tool for the study of factors regulating the selection of preovulatory follicles. The ovarian secretion of dimeric inhibin A was investigated and related to the secretion of ovarian steroids, the concentration of gonadotropins, and the pattern of ovarian follicular development during the follicular and early luteal phases in ewes with an ovarian autotransplant with or without the FecB gene. The secretion of inhibin A was related to the presence of large estrogenic follicles, being high during the follicular phase and falling after the LH surge (P < 0.05) before increasing during the early luteal phase (P < 0.05). There were no differences in the timing of the onset of the LH surge, the concentrations of FSH and progesterone, or the rates of inhibin A, estradiol, and androstenedione secretion during the follicular or luteal phase between ewes with and without the Booroola gene. Although the overall pattern of follicular development was similar between the genotypes, the ovulation rate was higher (P < 0.05) in the gene carrier ewes, and the ovulatory follicles and corpora lutea were significantly smaller (P < 0.05) than those in noncarrier animals. During the luteal phase, the diameter of the large follicles from the first wave was smaller (P < 0.05) in the gene carrier than in noncarrier ewes. Because there are no qualitative or quantitative differences in the pattern of secretion of pituitary gonadotropins or ovarian hormones between the two genotypes, we conclude that is likely that the FecB gene exerts its action at the level of ovary.

Animals↗