Circadian and pulsatile variations in plasma levels of inhibin, FSH, LH and testosterone in adult Murrah buffalo bulls.

The present study investigated pulsatile and circadian variations in the circulatory levels of inhibin, gonadotrophins and testosterone. Six adult buffalo bulls (6 to 7 yr of age) were fitted with indwelling jugular vein catheters, and blood samples were collected at 2-h intervals for a period of 24 h and then at 15-min interval for 5 h. Plasma concentrations of inhibin, FSH, LH and testosterone were determined by specific radioimmunoassays. Plasma inhibin levels in Murrah buffalo bulls ranged between 0.201 to 0.429 ng/mL, with a mean of 0.278 +/- 0.023 ng/mL. No inhibin pulses could be detected during the 15-min sampling interval. Plasma FSH levels ranged between 0.95 to 3.61 ng/mL, the mean concentration of FSH over 24 h was 1.66 +/- 0.25 ng/mL. A single FSH pulse was detected in 2 of 6 bulls. The LH levels in peripheral circulation ranged between 0.92 to 9.91 ng/mL, with a mean concentration of 3.33 +/- 1.02 ng/mL. Pulsatility was detected in LH secretion with an average of 0.6 pulses/h. Plasma testosterone levels in 4 buffalo bulls ranged from 0.19 to 2.99 ng/mL, the mean level over 24 h were 1.34 +/- 0.52 ng/mL. Testosterone levels in peripheral circulation followed the LH secretory pattern, with an average of 0.32 pulses/h. The results indicate parallelism in inhibin, FSH and LH, and testosterone secretory pattern. Divergence in LH and FSH secretory patterns in adult buffalo bulls might be due to the presence of appreciable amounts of peripheral inhibin.

Comparison of two methods for determining in vitro intestinal absorption of nutrients using rats fed different diets.

Absorption of sucrose, glucose, leucine and aspartate was studied using intestinal everted sac of rats fed on french bean diets namely PDR-14, HUR-137 and HUR-15 using casein as a control. Absorption of nutrients was monitored spectrophotometrically and by 14C radio assay of metabolites using scientillation counting. The absorption pattern of amino acids was found to be similar but of glucose and sucrose differed. Glucose was found to be more absorbed than sucrose in spectrophotometer assay and the pattern reversed in radio assay. Absorption of sucrose and leucine were higher by rats fed on HUR-137 diet and similarly, more aspartate was absorbed when fed on HUR-15 diet as demonstrated by both the methods. Rats fed on HUR-137 diet exhibited higher glucose absorption as shown by spectrophotometric assay, but rats on HUR-15 diet by radio assay. Absorption of nutrients differed significantly between casein and french beans.

Intratesticular injection of glycerol as a model for studying the quantitative relationship between spermatogenic damage and serum FSH.

Intratesticular injection of glycerol (1,2,3-trihydroxypropane) was evaluated as an experimental approach for studying the relationship between spermatogenic activity, i.e. relative proportion of euspermatogenic and aspermatogenic tubules in the testis, and serum concentrations of FSH. Adult rats received a single intratesticular injection of either 400 microliters distilled water or five different doses of glycerol, ranging from 25 to 400 microliters, and were killed after 1 or 4 weeks respectively. Injection of glycerol caused focal destruction, so that the same testes contained intact tubules, tubules with spermatogonia and Sertoli cells only, and tubules devoid of cellular material. There was a close correlation (r = 0.896) between the frequency of intact tubules and the dose of glycerol, and a similarly strong correlation (r = 0.908) between acellular tubules and the dose of glycerol. A correlation existed between FSH and euspermatogenic tubules (r = -0.758, n = 122) and, conversely, between FSH and acellular tubules (r = 0.820, n = 122), while the correlation for tubules containing spermatogonia and Sertoli cells was only marginal (r = -0.055). The exact relationship between FSH and spermatogenic activity in the testis was used to estimate the minimal amount of spermatogenic tissue necessary for maintaining normal serum concentrations of FSH. Only the disruption of spermatogenesis in more than 30% of seminiferous tubules in each testis caused increased serum concentrations of FSH.(ABSTRACT TRUNCATED AT 250 WORDS)

Focal testicular destruction following intratesticular injection of glycerol in rats.

Single intratesticular injections of glycerol have been reported to block spermatogenesis in rats without a concomitant change in the serum levels of testosterone and gonadotrophins (Wiebe & Barr 1983, 1984). The present studies were designed in order to confirm these effects and to cast light on the mechanism of action of glycerol. Groups of adult rats received intratesticular injections of either 200 microliter distilled water, glycerol or NaCl-solution. Following the injection of distilled water testicular histology appeared unaltered except for a few empty tubules around the injection site, which probably resulted from injection trauma. Injection of glycerol solution (greater than 3500 mosmol) caused partial tubule destruction. The most severely affected tubules were devoid of cells and filled with amorphous material. Serum FSH concentrations increased sharply in the first week and remained elevated during the entire study period of 8 weeks. Injection of an equi-osmolar NaCl-solution had very similar effects to glycerol on the testes and on hormone levels, suggesting that hyperosmolarity of the injected solutions rather than a specific action of the compounds caused the testicular damage. It is concluded that a single intratesticular injection of glycerol causes severe testicular damage and, in contrast to previous suggestions, appears unsuitable for male fertility regulation.

Serum prolactin levels of non-cycling murrah buffaloes (Bubalus bubalis ).

Prolactin levels were quantified by double antibody radio-immunoassay in the blood sampled daily for 24 days, from 9 non-cyclic Murrah buffaloes during hot months (ambient temp.41 to 43 degrees C). All buffaloes were kept in open loose housing. Three buffaloes were sprinkled with water for half an hour twice daily between 1200 and 1430 h to overcome partly the effect of heat during the period of investigation. Mean prolactin levels of 6 unsprinkled buffaloes ranged on different days from 249 to 739 ng/ml serum. The range of averages in case of 3 sprinkled animals was from 152 to 342 ng/ml serum. Buffaloes subjected to sprinkling had significantly (P / 0.01) lower prolactin levels than control buffalo.

Serum FSH levels during estrus and a 4-week period following mating in Murrah buffaloes (Bubalus bubalis ).

Circulating FSH levels of 13 Murrah buffaloes were investigated by a double-antibody radioimmunoassay using a homologous bovine system. The mean (+/- s.e.m.) peak FSH level on the day of estrus was if57.94 +/- 12.84 ng/ml of blood serum during hotter months (June-August) and 65.23+/-10.54 ng/ml during cooler months (October-December). These were much higher than the FSH concentrations recorded during the rest of the cycle post-mating. There were sizable fluctuations in FSH levels on different days of the estrous cycle within animals. However, the mean values did not exhibit much variation. The occurrence of the FSH peak and the LH peak coincided during the cycle.

Serum LH levels during pre- and post-puberty, pregnancy and lactation in Murrah buffaloes.

The concentration of luteinizing hormone (LH) was measured in the serum of pre- and post-pubertal Murrah buffaloes, in addition to during pregnancy and lactation. The mean values varied between 0.6 +/- 0.11 (S.E.) and 1.4 +/- 0.18 ng/ml, but the differences observed were not significant (P>0.05).

Serum LH concentrations in cyclic buffalo (Bubalus bubalis).

Circulating LH levels of 14 Murrah buffaloes were determined by a double-antibody radioimmunoassay using an homologous bovine system. At the onset of oestrus, the mean peak circulating LH level was 20.80 +/- 3.43 (s.e.m.) ng/ml in the hotter months (June-August) and 21.24 +/- 0.98 ng/ml during the cooler months (October-December), values remaining high for about 4 h. Basal levels throughout the rest of the cycle averaged 1-2 ng/ml. Conception occurred in 7 of the animals showing LH peaks (2/8 in June-August, 5/6 in October-December).

In vitro effect of human placental lactogen on steroidogenesis in human placental tissue from early pregnancy.

Studies were carried out with human placental lactogen (hPL) to elucidate its role in regulation of steroidogenesis (progesterone and estrogens) during early pregnancy in humans. Our in vitro studies with early pregnancy placenta under different doses of hPL demonstrated that this hormone could stimulate the synthesis of progesterone as well as estrogens (estrone and estradiol) from their respective precursors.