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Biomedical subjects

B D Schanbacher

Publications and source records attributed to B D Schanbacher.

18 recordsLinked to original sources
PubMed1992

Bovine luteinizing hormone (LH) isoforms and amounts of messenger ribonucleic acid for alpha- and LH beta-subunits in pituitaries of cows immunized against LH-releasing hormone.

Ovariectomized beef cows were actively immunized against LHRH to test the hypothesis that decreased stimulation of gonadotropes would alter the distribution of LH isoforms and amounts of mRNA for subunits of LH in the pituitary. Eight long-term (3 yr) ovariectomized beef cows were randomly assigned to one of two treatments: immunization against LHRH conjugated to human serum globulin (n = 4) and nonimmunization (control, n = 4). Mean concentration of serum LH in cows immunized against LHRH (1.0 +/- .83 ng/ml) was less (p = 0.01) than in control cows (5.0 +/- 0.83 ng/ml). Amounts of alpha- (p = 0.13) and LH beta-subunit (p = 0.10) mRNA tended to be reduced in cows immunized against LHRH compared to control cows. However, weight of the anterior pituitary and concentrations of LH in this gland did not differ (p = 0.90) among cows from the two groups. Pituitary extracts were chromatofocused on pH 10.5-7.0 gradients, and concentrations of LH in eluent fractions were determined by RIA. Extracts of all pituitaries resolved into nine isoforms (designated A through H and Z beginning with the most basic form). Only isoform F (mid-alkaline elution, pH = 8.8) was influenced by treatment (p = 0.05). Cows immunized against LHRH had a greater relative amount of isoform F (42.1 +/- 1.4%) than controls (37.2 +/- 1.4%). In summary, immunization of cows against LHRH altered 1) circulating concentrations of LH, 2) amounts of mRNA for the subunits of LH, and 3) distribution of intrapituitary LH isoforms without changing the concentrations of LH in the anterior pituitary.

Animals↗
PubMed1992

Effect of implanting bull calves with testosterone propionate, dihydrotestosterone propionate or oestradiol-17 beta prepubertally on the pituitary-testicular axis and on postpubertal social and sexual behaviour.

Twelve non-implanted crossbred bull calves served as controls and 30 crossbred bull calves (10/treatment) were implanted for 82 days, beginning at 34 days of age, to determine the influence of testosterone propionate (TP), dihydrotestosterone propionate (DHTP) and oestradiol-17 beta (E2) on prepubertal and pubertal pituitary-testicular function and on postpubertal social and sexual behaviour. Compared with control bulls, concentrations of serum luteinizing hormone (LH), follicle-stimulating hormone (FSH) and inhibin concentrations were suppressed (P less than 0.01) in all implanted bulls. Testosterone (T) concentration increased (P less than 0.001) in TP-implanted, but decreased (P less than 0.01) in DHTP and E2 bulls during the implant period. LH response to gonadotrophin-releasing hormone (GnRH) challenge during the implant period (2.5 months of age) was less (P less than 0.01) in TP, E2 and DHTP bulls than in controls. A small but significant T response to GnRH occurred in control bulls at 2.5 months of age. LH and T responses to GnRH challenge at 7 months of age (100 days after implant removal) was similar (P greater than 0.20) in control and implanted bulls. Steroid implants administered prepubertally had no effect (P greater than 0.10) on postpubertal social and sexual behaviours, including number of flehmen responses, abortive mounts, services and competitive order score. Body weight did not differ (P greater than 0.10) between treatment groups, but testis size was reduced (P less than 0.01) during the implant period and up to 10 months of age in treated bulls compared with controls. Testes remained smaller in E2-treated bulls up to the end of the study (23 months of age), but daily sperm production and epididymal weight did not differ (P greater than 0.10) between treatment groups at slaughter. Control bulls reached puberty earlier (P less than 0.01; 270 +/- 11 days of age) than did TP (302 +/- 11 days), DHTP (309 +/- 11 days) or E2 (327 +/- 11 days) bulls. Although puberty was delayed in all implant groups, there was no difference in scrotal circumference at puberty (average 28.4 +/- 0.4 cm) between treatment groups. Our findings indicate that TP, DHTP and E2 implants administered prepubertally result in acute suppression of serum LH, FSH and inhibin during the implant period and in post-implant suppression of testis size and delayed puberty in bulls. The lack of treatment effect on behaviour suggests that steroidal programming of sexual behaviour occurs before 1 month of age in bulls.

Animals↗
PubMed1992

Effects of weaning on concentrations of inhibin in follicular fluid and plasma of sows.

Changes in plasma and follicular fluid concentrations of inhibin were examined in sows after weaning at 28-32 days post partum. From 0 to 48 h after weaning, inhibin concentrations were 200-300 times higher in follicular fluid from small (less than 4 mm) and medium-large (greater than or equal to 4 mm) follicles than in ovarian venous plasma. Inhibin concentrations increased in follicular fluid from medium-large follicles at 24 and 48 h after weaning; concentrations in ovarian venous plasma were positively correlated with the number of medium-large follicles (r = 0.40) and with ovarian venous plasma concentrations of oestradiol (r = 0.61). Blood samples were collected for 30 days from sows (n = 6) that exhibited oestrus within 5 days after weaning and from sows (n = 5) that remained anoestrous for 11 days after weaning. Plasma inhibin concentrations rose in oestrous and anoestrous sows by 12 h and continued to rise for 60 h after weaning. Plasma inhibin concentrations rose further and were higher at 3.5-4.5 days after weaning in oestrous sows than in sows that remained anoestrous. After oestrus, plasma inhibin concentrations declined. At weaning, plasma concentrations of follicle-stimulating hormone (FSH) were higher in sows that subsequently exhibited oestrus than in sows that remained anoestrous. After weaning, plasma concentrations of FSH declined in both groups, reached a nadir at 2.5 days, and increased gradually in anoestrous sows; oestrous sows exhibited an FSH surge at oestrus. Plasma FSH returned to preweaning concentrations in both groups of sows at Days 7-8.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1979

Radioimmunoassay of ovine and bovine serum progesterone without extraction and chromatography.

A procedure for the radioimmunoassay of ovine and bovine serum progesterone is described which does not require extraction and chromatography. Serum samples are assayed directly, and a highly specific antiserum that was prepared in rabbits against 11 alpha-hydroxyprogesterone conjugated to bovine serum albumin is used. Interference from serum binding proteins is alleviated by use of a phosphate buffer containing 5% BSA and separation of bound and free tritiated progesterone by a double antibody procedure. Serum samples are assayed in a mini-vial, the bound fraction (double antibody precipitate) is mixed with scintillation solution and the radioactivity is counted in the same vial. The assay procedure is sensitive (10 pg, 100 pg/ml) and has acceptable accuracy and precision. Because there is no extraction or chromatography, serum progesterone is not lost. Most important, the procedure is specific for progesterone and measures serum progesterone concentrations in the ewe and cow which are comparable with those obtained with conventional assay techniques. The progesterone assay described herein provides a rapid, economical procedure that can facilitate the study of ovarian cyclicity and aid in the early diagnosis of pregnancy.

Animals↗
PubMed1977

Gonadotropin secretion in cryptorchid and castrate rams and the acute effects of exogenous steroid treatment.

Gonadotropin secretion in cryptorchid and castrate rams and the acutve been determined. Rams made cryptorchid at 6 weeks of age had increased serum levels of luteinizing hormone (LH) and follicle stimulating hormone (FSH) when determined at 9 months of age. These levels approached those of the castrate animal; and yet serum levels of testosterone (T) were unchanged. Even though mean serum LH concentrations were elevated sixfold to eightfold over those of intact ram levels, a temporal relationship between this hormone and T was observed similar to that reported in the intact ram. Intramuscular injections of dihydrotestosterone had no effect on circulating levels of LH or FSH in either cryptorchid or castrate rams, whereas T effectively reduced these gonadotropins in castrate but not in cryptorchid rams. Only estradiol-17beta (E2) was effective in both cryptorchid and castrate rams. Estradiol was a potent inhibitor of LH secretion; however, its effect on FSH levels was less dramatic. This suggests that testicular products other than E2 may be important in the regulation of FSH production and/or release. Importantly, the inhibition of LH secretion lasted less than 12 h; whereas, the negative effects of E2 on FSH secretion lasted 72 to 144 h. In conclusion, results from this study show that T is not the single factor responsible for regulation of LH and FSH secretion in male sheep. Estradiol may be an important regulator of gonadotropin secretion, but 5alpha-reduction plays no apparent role in this process.

Animals↗
PubMed1977

Luteinizing hormone secretion and female lordosis behavior in male pigs.

Serum concentrations of luteinizing hormone (LH) and testosterone were monitored during the first 9 weeks of life in male pigs. In boars, testosterone was constant during this period, and LH was elevated from birth through day 21 and declined between days 21 and 28 to levels observed in adult boars. Castration on day 3 reduced testosterone concentrations without having an immediate effect on LH, but after day 21, LH was consistently greater in castrated males than in boars. Responsiveness of the early postnatal testes to LH was shown by reduced testosterone concentrations after treatment with LH-antiserum on day 2. Norethindrone had no effect on LH or testosterone when given on day 2 but decreased the concentrations of these hormones in 5-month-old boars. Similarly, estrogen had no effect on LH secretion in 4-day-old boars. In 9-month-old castrated males, estrogen decreased LH concentrations during the first 48 h of daily treatment, but after this, LH increased and returned to pretreatment levels by 88 h. Also, daily estrogen treatment of castrated males induced female lordosis behavior. From these observations we conclude that negative feedback control of LH secretion is inoperative in neonatal male pigs and that exogenous estrogen can induce responses characteristic of females in castrated postpubertal males.

Animals↗
PubMed1976

Seasonal profiles of plasma luteinizing hormone, testosterone and estradiol in the ram.

Plasma profiles of luteinizing hormone (LH), testosterone (T), and estradiol (E2) have been determined in five mature rams during the primary breeding season (September) and again when breeding activity was low (May). Blood samples collected every half h for 24 h during September or May showed that LH was released into the general circulation as distinct peaks. Although this secretory pattern was not the same for all rams and seasonal differences were noted in certain individuals, it is suggested that an inherent rhythm persists within each ram. With the exception of one ram in September, obvious T peaks were preceded by LH peaks greater than 2 ng/ml (LH-T interval less than 60 min). Season had no effect on the number and magnitude of LH peaks or on the mean concentrations; however, basal levels of LH were higher (P less than 0.01) in September than in May. Seasonal differences in peripheral T levels were more dramatic with mean, baseline, and peak concentrations elevated (p less than 0.01) during the fall. The number of T peaks, like those of LH, was not affected by season. Large variations in circulating levels of E2 made any possible relationship between this hormone and LH or T difficult to identify. Furthermore, a diurnal or seasonal rhythm could not be established for E2 in this study. It is concluded that seasonal differences occur in secretory patterns of LH and T and that a cause and effect relationship between these two hormones exists. Under conditions of this study, neither a consistent relationship between E2 and LH or T, nor a seasonal difference in mean E2 levels, was apparent.

Animals↗
PubMed1976

Rapid chromatography for quantitation of radioimmunoassayable 5alpha-androstane-17beta-ol-3-one and testesterone in ram, bull and boar serum.

A rapid technique for the simultaneous determination of serum 5alpha-androstane-17beta-0l-3-one (DHT) and testosterone (T) was developed and validated. The procedure incorporates a chromatographic step prior to binding with a T-3BSA antiserum. Anakrom columns used to separate DHT from T also isolate other steroids quickly and efficiently. Utilizing this procedure, levels of both androgens have been measured in the intact ram, bull and boar. Concentrations of DHT and T expressed as mean +/- SE in ng/ml were respectively: ram, 0.14 +/- 0.03 and 4.96 +/- 0.80; bull, 0.10 +/- 0.01 and 3.92 +/- 0.80; boar, 0.71 +/- 0.11 and 5.58 +/- 0.64. Whether these minute quantities of serum DHT play important physiological roles, particularly in the boar, is unresolved. Monitoring DHT under varying experimental or pathological conditions may allude to its importance in the domestic male.

Animals↗
PubMed1975

Simultaneous determination of testosterone, 5alpha-androstan-17beta-ol-3-one, 5alpha-androstane-3alpha,17beta-diol and 5alpha-androstane-3beta,17beta-diol in plasma of adult male rabbits by radioimmunoassay(1).

A simultaneous radioimmunoassay procedure for plasma testosterone (T), 5alpha-androstan-17beta-ol-3-one (DHT), 5alpha-androstane-3alpha,17beta-diol (3alphaol), and 5alpha-androstan-3beta,17beta-diol (3betaol) is described in this report. Peripheral plasma concentrations of T, DHT, 3alphaol, and 3betaol were 1.16 +/- 0.26, 0.49 +/- 0.15, 0.17 +/- 0.03, and 0.24 +/- 0.04 ng/ml, respectively, in adult male rabbits. In contrast, T, DHT, 3alphaol, and 3betaol peripheral plasma concentrations in dexamethasone-treated castrate rabbits were 0.07 +/- 0.01, 0.02 +/- 0.01, 0.07 +/- 0.01, and 0.05 +/- 0.01 ng/ml, respectively. These results represent the first simultaneous measurement of T, DHT, 3alphaol, and 3betaol in peripheral plasma of any male vertebrate. Moreover, we suggest that DHT, 3alphaol, and 3betaol represent the unidentified immunoreactive material found in peripheral plasma of male rabbits by Falvo and Nalbandov (1).

Androstane-3,17-diol↗