Biomedical subjects

H G Burger

Publications and source records attributed to H G Burger.

At least 163 records · Page 9Linked to original sources

PubMed1987

Circulating immunoactive inhibin in the luteal phase and early gestation of women undergoing ovulation induction.

Serum inhibin was measured by radioimmunoassay in 19 women undergoing ovulation induction within an in vitro fertilization program. In 16 nonpregnant subjects, inhibin rose during the luteal phase to reach a peak (2.5 U/ml) 6 days after oocyte retrieval; it then fell to undetectable levels by day 14 (less than 0.37 U/ml). Serum inhibin was significantly correlated (P less than 0.001) with both serum progesterone and estradiol concentrations and inversely correlated with serum follicle-stimulating hormone (FSH) (P less than 0.001). In the pregnant group (n = 3), inhibin levels reached an initial peak (3.7 U/ml) on day 6, then declined to a nadir (1.5 U/ml) on day 8 after oocyte retrieval and subsequently rose to 3.4 U/ml on day 14. These data suggest (1) an inverse relationship between inhibin and FSH, which is in support of the inhibin hypothesis; (2) that the human corpus luteum secretes inhibin; and (3) a trophoblastic/placental origin of inhibin during gestation.

Estradiol↗

PubMed1987

Inhibin--a non-steroidal regulator of pituitary follicle stimulating hormone.

Inhibin is a gonadal glycoprotein produced by the granulosa and Sertoli cell under the influence of FSH and acts to specifically suppress pituitary FSH secretion. Recently, ovarian inhibin has been purified from several species and its amino acid sequence deduced using cloning techniques. Inhibin consists of two disulphide-linked heterologous subunits of which the smaller may exist in two different forms accounting for two different forms of inhibin in humans and pigs. Heterogeneity of inhibin also exists as a result of proteolytic processing of the molecule during its passage into the circulation. Significant homology exists between the subunits of inhibin and the dimeric peptides TGF-beta and Mullerian inhibitory substance (MIS), suggesting they are all derived from a common ancestral gene. Furthermore, dimers of the smaller subunit of inhibin (FSH-releasing protein (FRP) or activin) have now been found in follicular fluid (FF) and, along with TGF-beta, shown to be potent and specific stimulators of FSH secretion. These proteins may be involved in controlling FSH by another as yet unknown pathway and may prove to be the FSH-releasing factor, analogous to LHRH, which has been postulated to exist for some years. Inhibin can no longer be simply considered as an isolated FSH-suppressing protein. The physiological significance and relationship between inhibin and its related proteins represent one of the most challenging and interesting areas in reproductive endocrinology. Further studies, particularly with the development and use of sensitive assays for both the FSH releasing hormone and inhibin will clarify their role in reproduction and their usefulness in monitoring or treating fertility.

Animals↗

PubMed1987

The maternal ovary is not the source of circulating inhibin levels during human pregnancy.

The concentration of immunoreactive inhibin in serum was measured in three pregnant women with premature ovarian failure involved in a donor oocyte in-vitro fertilization programme. Inhibin was not detectable in peripheral serum prior to conception but rose within 2-4 weeks of embryo transfer, whereafter levels rose gradually during pregnancy (less than 20 weeks 1.22 U/ml (0.85-1.76) versus greater than 20 weeks 2.28 U/ml (1.42-3.67), P less than 0.01; geometric mean +/- 67% confidence interval) and were similar to those observed in 24 normal pregnant women. hCG rose in parallel with inhibin during early gestation, but declined after 3 months. FSH levels were elevated before conception and were suppressed during pregnancy. In conclusion (i) immunoreactive inhibin is detectable from early gestation in women with no endogenous ovarian function indicating that the maternal ovary does not contribute significantly to inhibin secretion during pregnancy; (ii) the trophoblast is the likely source of inhibin during pregnancy; (iii) the regulation of hCG and inhibin secretion differs throughout gestation; and (iv) inhibin may have a role in FSH regulation during pregnancy and/or a local role within the feto-placental unit.

Chorionic Gonadotropin↗

PubMed1987

The treatment of infertility.

Combined management of infertile couples is optimal. The most common problems in men are low sperm concentration and motility of unknown cause. Although there are no specific effective treatments, factors correlated with subsequent fertility are emerging that should be useful for advising couples of their chances. In the woman, disorders of ovulation can usually be treated successfully, but results of tubal surgery for past inflammatory damage remain poor. In vitro fertilization may be useful for idiopathic infertility and semen disorders of mild to moderate severity, as well as for tubal obstruction.

Female↗

PubMed1987

Follicle-stimulating hormone and somatomedin-C stimulate inhibin production by rat granulosa cells in vitro.

The direct effect of somatomedin-C (Sm-C) and FSH on inhibin production by rat granulosa cells in vitro has been examined. FSH stimulated accumulation of inhibin in culture media in a dose-dependent manner with maximal stimulation (6-fold) being observed at a dose of 300 ng FSH/ml. Addition of Sm-C (30 ng/ml) either alone or in the presence of FSH (3-300 ng/ml) increased inhibin production (up to 5-fold). Sm-C alone was effective over the physiological dose range of 3-100 ng/ml. Concomitant addition of FSH (100 ng/ml) and Sm-C (3-100 ng/ml) resulted in a significant increase in inhibin production at all doses of Sm-C. The dose-dependent effects of FSH and Sm-C were also time dependent with a synergistic effect apparent after 48 h of culture. The Sm-C induced FSH inhibitory activity of granulosa cell culture media was confirmed as authentic inhibin by the demonstration of a dose-dependent neutralization of this activity by a monoclonal antibody raised against purified bovine inhibin. The data indicate a direct role for both FSH and Sm-C in ovarian inhibin production and provide additional evidence for an autocrine-paracrine role for Sm-C in granulosa cell differentiation.

Animals↗

PubMed1987

Variable androgen receptor levels in infertile men.

Labeled methyltrienelone was used to determine androgen receptor (AR) levels in cultured pubic skin fibroblasts in 40 infertile men with primary seminiferous tubule disorders and 18 normal men. LH pulse patterns and mean serum LH levels were also determined by blood sampling at 10-min intervals for 6 h. The infertile men and the normal men had similar mean receptor levels [mean, 28.1 +/- 2.0 (+/- SEM) and 24.8 +/- 1.8 fmol/mg protein, respectively]. However, 5 men with chromosomal disorders had a higher mean AR level (41.3 +/- 6.2 fmol/mg protein) than the normal men, and 5 of the remaining infertile men (14.2%) had receptor levels that were less than the minimum value in normal men. In men with idiopathic oligospermia, 19.0% had low receptor levels. Although mean serum FSH and testosterone levels were similar in the infertile men with low AR levels and in the normal men, mean LH levels were significantly elevated in this group (7.1 vs. 3.6 IU/L), the higher values being a result of increased LH pulse amplitude (mean, 5.6 vs. 2.8 IU/L). The LH-testosterone product (an index of androgen resistance) was also elevated in these men. When infertile men with low AR levels were matched with infertile men with normal receptor levels, the mean LH values were significantly elevated in the former, as was the LH-testosterone product. Testosterone values were similar in the two groups of men. After excluding subjects with chromosomal disorders, there were no significant correlations between AR levels and other indices of androgen action, such as semen volume, seminal fructose, or sex hormone-binding globulin levels. We conclude that AR levels are higher in patients with severe testicular failure associated with X-chromosome disorders. Also, AR defects were found in 19.0% of infertile men with idiopathic oligospermia. Finally, elevation of mean LH levels in men with seminiferous tubule disorders may reflect resistance to androgen action.

Adult↗

PubMed1987

Subcutaneous administration of gonadotropin-releasing hormone: absorption kinetics and gonadotropin responses.

To evaluate the suitability of the sc route for the pulsatile delivery of GnRH, plasma GnRH, LH, and FSH levels were measured by RIA in five women with hypothalamic amenorrhea after sc injection of single doses of 2.5, 5, and 10 micrograms GnRH. The results were compared with those obtained after bolus iv injection of 10 micrograms GnRH. After sc injection, plasma GnRH levels rose to a dose-related maximum after 5-10 min and fell to less than 10% of the peak value by 90 min. The mean plasma disappearance half-time was 24 min (range, 18-30 min). After bolus iv injection, an initial rapid phase of disappearance (t1/2, 2.8 min) was followed by a slower phase (t1/2, 33 min), falling within the 95% confidence intervals for the disappearance half-time after sc administration (12-36 min). The patterns of LH response to sc and iv GnRH were similar, with maximum levels reached between 20 and 30 min after injection, then declining to 50-69% of the peak value by 90 min after sc injection and 61% of the peak value 90 min after iv injection. There was no significant difference between peak LH responses to 10 micrograms iv and sc doses of GnRH [15.2 +/- 2.5 (+/- SEM) vs. 13.2 +/- 2.2 IU/L]. Subcutaneous administration of three consecutive GnRH pulses at 90-min intervals to four women resulted in gonadotropin responses to each GnRH pulse. We conclude that sc GnRH administration results in pulsatile plasma GnRH and gonadotropin responses, the latter resembling those seen after iv GnRH. These results confirm the suitability of the sc route for pulsatile GnRH delivery.

Absorption↗

PubMed1987

Circulating immunoreactive inhibin levels during the normal human menstrual cycle.

Serum inhibin concentrations were measured daily by RIA in six normal women throughout one menstrual cycle. The RIA was specific for inhibin, and inhibin subunits and related proteins cross-reacted minimally in it. In the early to midfollicular phase, inhibin levels changed little, while in the late follicular phase, inhibin levels rose, in parallel with estradiol (r = 0.43; P less than 0.05; n = 22), to a peak level of 714 (407-1267) U/L (geometric mean +/- 67% confidence limits) coincident with the midcycle LH and FSH surges. An inverse relationship was found between serum inhibin and FSH during the mid- to late follicular phase (r = 0.42; P less than 0.01; n = 45). Inhibin levels rose further during the luteal phase to a peak level of 1490 (1086-2028) U/L 7-8 days after the LH surge, and they correlated positively with serum progesterone (r = 0.76; P less than 0.001; n = 49) and inversely with serum FSH (r = 0.43; P less than 0.01; n = 49) throughout the luteal phase. We conclude that 1) circulating inhibin is detectable throughout the normal menstrual cycle; 2) in the late follicular phase, inhibin levels rise in parallel with estradiol, consistent with the concept that both are products of the maturing follicle; 3) in the luteal phase, the profile of inhibin suggests that it is a secretory product of the corpus luteum; and 4) the inverse relationship between inhibin and FSH in the follicular phase is consistent with the inhibin hypothesis, while at midcycle there is loss of the inhibitory effect of inhibin on FSH secretion. The inverse relationship between FSH and inhibin during the luteal phase suggests a hitherto unsuspected role for inhibin in the feedback regulation of FSH secretion.

Adult↗

PubMed1987

Isolation of inhibin from ovine follicular fluid.

Two forms of inhibin with molecular weights of 65,000 and 30,000 (65 and 30 kD) were isolated from ovine follicular fluid using a combination of gel permeation chromatography, reversed-phase high-performance liquid chromatography and preparative polyacrylamide gel electrophoresis. The 65 kD form was partially purified approximately 315-fold whilst the 30 kD form was isolated as two isoforms (29 and 30 kD) of similar biological activity and in greater than 95% purity (1210-fold purification and 4.2% recoveries). On reduction the 30 kD form resolved into four components of 36, 31, 20-21 and 16 kD of which the 20-21 and 16 kD components were similar to the corresponding inhibin subunits isolated from porcine and bovine follicular fluid. The 36 kD component was established as a non-reducible inhibin-like material, based on its binding to antiserum raised against bovine 58 kD inhibin. The nature of the remaining non-reducible 31 kD component is unknown. Two NH2-terminal amino acid sequences (first 13 amino acids) identified in purified 30 kD inhibin were identical to the corresponding subunit amino acid sequences of bovine 31 kD inhibin.

Animals↗

PubMed1987

Inhibin gene expression in the human corpus luteum.

We report inhibin alpha- and beta A-subunit gene expression in the human corpus luteum and placenta using human alpha-subunit and bovine beta A-subunit nucleic acid probes. In addition, we have demonstrated the presence of immunoreactive and bioactive inhibin in human corpora lutea. Our findings suggest that this tissue is a significant source of inhibin during the luteal phase of the normal human menstrual cycle.

Corpus Luteum↗

PubMed1987

A rapid, sensitive and reliable assay for inhibin bioactivity.

A rapid 2-day quantitative assay for inhibin bioactivity based on FSH secretion from pituitary cells of immature female rats is described. The bioassay exhibited steeper slopes, improved precision and greater (fourfold) sensitivity compared with a previously established pituitary FSH cell content assay. Whole pituitary glands were used for the preparation of pituitary cells and the method for cell dispersion required a single enzymatic treatment with trypsin. Cells (180,000 viable cells per well) were dispensed into culture media containing inhibin and incubated for 48 h. Media were removed and assayed for FSH by radioimmunoassay. Using a ram rete testis fluid preparation as standard the inhibin dose-response curves of 25 consecutive experiments showed indices of precision of -0.08(mean)[range -0.04 to -0.17] and Finney's G values of 0.017[0.003-0.06]. The mean ED40 was 0.17 units of inhibin activity per well with interassay variation of 16.2% at this point of the dose-response curve. The assay had a practical capacity of 400 wells, permitting the measurement of dose-response curves of at least 40 unknowns with three dose points and triplicate wells per dose. The assay is specific for inhibin-containing preparations from several animal species. Overall, the assay is simple, precise, and sensitive, indicative of its applicability to the measurement of inhibin samples with low inhibin bioactivity and to the screening of large numbers of fractions during inhibin purification.

Animals↗

PubMed1986

The human placenta: a novel source of inhibin.

Human placental extracts contain inhibin bioactivity and immunoactivity giving dose response curves parallel to a human follicular fluid inhibin standard. Inhibin bioactivity in vitro was neutralised by preincubation of extracts with antisera raised to pure bovine inhibin. Umbilical cord blood from term infants contained immunoactivity. Human placental inhibin differs from human ovarian inhibin in terms of its biological: immunological ratio.

Animals↗

PubMed1986

Inhibin A-subunit gene expression in the ovaries of immature female rats is stimulated by pregnant mare serum gonadotrophin.

We have used a bovine cDNA probe for the A-subunit of inhibin to demonstrate the presence of inhibin in the ovaries of immature female rats: the levels of mRNA were increased following treatment of the rats with pregnant mare serum gonadotrophin (PMSG), suggesting modulation by PMSG of ovarian inhibin synthesis at least at the level of transcription. Furthermore, we report the unexpected finding of significant levels of inhibin mRNA in the corpora lutea of mature female rats. No inhibin mRNA was demonstrable in the uterus or placenta.

Age Factors↗

PubMed1986

Plasma inhibin levels during gonadotropin-induced ovarian hyperstimulation for IVF: a new index of follicular function?

Human plasma inhibin was measured by radioimmunoassay in 26 women undergoing ovarian hyperstimulation for in-vitro fertilisation. Plasma inhibin rose in parallel with oestradiol during gonadotropin therapy (r = 0.79, p less than 0.001). Peak plasma inhibin levels correlated with follicle number as determined by ultrasonography (p less than 0.001) and with the number of oocytes recovered at laparoscopy (p less than 0.05). The increase in production of human ovarian inhibin by exogenous follicle stimulating hormone (FSH) is thus consistent with its proposed role in FSH regulation. Human plasma inhibin may be useful as a circulating protein marker of granulosa-cell function and may have therapeutic implications in human ovulation-induction programmes.

Chorionic Gonadotropin↗

PubMed1986

The radioimmunoassay of bovine and human follicular fluid and serum inhibin.

A radioimmunoassay for inhibin in bovine and human follicular fluid (bFF, hFF) and serum from both species was developed based on an antiserum raised in a rabbit to purified bovine 58 kDa inhibin. Following immunization, parallel changes in plasma FSH and inhibin antibody titre were observed suggesting inhibin neutralization in vivo. The antiserum neutralized bFF, hFF and purified 31 kDa and 58 kDa inhibin activity in an in vitro bioassay system. Purified 58 kDa and 31 kDa inhibin were iodinated using a chloramine-T procedure and the 125I-inhibin purified by elution from Matrex Red A, with the iodinated molecules showing similar physicochemical properties to non-iodinated inhibin. Both tracers were stable in bFF but only 125I-31 kDa inhibin was stable in serum. A second antibody RIA system using either tracer yielded a parallel displacement between purified 31 kDa and 58 kDa inhibin. The cross-reaction in the RIA of inhibin from different species when expressed in terms of their bioactivity was bFF 100%, hFF 30%, ovine FF less than 1% and rat ovarian extract non-detectable. Rat LH and FSH, ovine LH and FSH, hCG, bovine TSH, LHRH, ovalbumin and bovine serum albumin showed less than 0.5% cross-reactivity using either tracer. Similar profiles of both bio- and immunoactive inhibin were observed at each stage of the inhibin purification procedure. The in vitro biological to immunological ratios for a number of purified 31 kDa and 58 kDa inhibin preparations using both tracers in the RIA, ranged from 0.30 to 0.43. The RIA was modified for serum by using 125I-31 kDa inhibin as tracer and an elevated temperature (30 degrees C) to minimize non-specific effects. No detectable activity was determined in steer or human post-menopausal serum whilst bull and human female serum showed parallel dose-response curves to their respective follicular fluid standards with circulating levels of 0.9 and 1.1 ng/ml respectively.

Animals↗

PubMed1986

Isolation of a 31 kDa form of inhibin from bovine follicular fluid.

The introduction of a pH 4.75 precipitation step to a previously described purification procedure from bovine follicular fluid (bFF) resulted in the isolation of a 31 kDa form of inhibin, in addition to 58 kDa inhibin. The procedure was monitored by an in vitro bioassay based on the suppression of the FSH cell content by pituitary cells in culture. The 31 kDa form was purified 5550-fold with approximately 5% recovery. On SDS-polyacrylamide gel electrophoresis a single band was detected with a molecular weight of 31 000 +/- 1500 (mean +/- SD) which upon reduction gave 2 subunits of 20 200 +/- 300 and 14 800 +/- 600. The biological activity expressed on mg protein basis was similar for both 31 kDa and 58 kDa inhibin although on a molar basis the 58 kDa inhibin was 2-3 times higher. A high degree of cross-reaction was observed between both forms in a radioimmunoassay of bovine inhibin using an antiserum raised against the larger form with either iodinated 31 kDa or 58 kDa inhibin as tracer. Based on the subunit composition of the 31 kDa and 58 kDa inhibin, their similar cross-reaction in a radioimmunoassay system and the apparent generation of the 31 kDa inhibin following a pH precipitation step, it is concluded that 31 kDa inhibin is a smaller form of the 58 kDa inhibin resulting from a shortening of the 43 kDa subunit to a 20 kDa subunit.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1986

Plasma progesterone and prolactin changes in superovulated women before, during, and immediately after laparoscopy for in vitro fertilization and their relation to pregnancy.

To define changes in peripheral plasma progesterone (P) and prolactin (PRL) levels in relation to oocyte recovery for in vitro fertilization (IVF), the authors studied these hormones in 20 women before, during, and after oocyte recovery for IVF. The patients were superovulated with clomiphene citrate and human menopausal gonadotropin and underwent general anesthesia (19 women) or epidural anesthesia (1 woman) and laparoscopy for follicular aspiration. One half of the women were given bromocriptine to control PRL levels during anesthesia. There was a marked drop in P levels (mean decrease of 76%) within the 2 hours after induction of anesthesia and follicular aspiration. PRL levels rapidly rose in patients not treated with bromocriptine. Four of the 20 patients became pregnant after embryo transfer, and in these women P levels were significantly higher than in nonpregnant patients before and during oocyte recovery. Changes in PRL levels and P levels during oocyte retrieval were not related to the occurrence of pregnancy.

Anesthesia, Epidural↗

PubMed1986

Timing of ovulation by determination of the urinary luteinizing hormone surge with an enzyme-linked monoclonal antibody dipstick (OvuStick).

An enzyme-linked double monoclonal antibody dipstick for measuring luteinizing hormone in urine was tested for timing ovulation in thrice daily urine samples collected for several days around mid-cycle in 24 women undergoing artificial insemination. The assay produced information comparable to single daily serum LH measurements. The dipsticks could be used by untrained people to test their own urine as an aid to the detection of ovulation for the timing of artificial insemination or of sexual intercourse to promote or avoid conception.

Antibodies, Monoclonal↗