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Y. FOLMAN and D. DRORI

Summary.

Unmated male rats were raised in social isolation and grouped, and mated males were raised in cohabitation with hysterotomized females. The unmated males were raised under conditions providing different intensities of female odours.

In isolation, the penis muscles, levator ani, penis and the seminal vesicle tissue of the males exhibited a relative atrophy similar in degree to that prevalent in grouped males. Isolated males grew faster and had larger ratios of kidney to body weight and adrenal to body weight than grouped males. A correlation between these two ratios was observed.

Continuous exposure to female odours, from weaning to 136 or 240 days of age, did not affect the general atrophy of the accessory reproductive organs either in isolated or in grouped, unmated males.

Grouping and exposure to female odours reduced the amount of secretion contained in the seminal vesicles and the size of the bulbourethral glands.

It was concluded that social conditions, i.e. isolation and grouping, and continuous exposure to female odours, have only minor effects on the reproductive system of unmated males; conversely, under conditions of cohabitation, heterosexual mating is the factor responsible for preventing the atrophy of the reproductive system in males.

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D. DRORI and Y. FOLMAN

Summary.

Male rats were raised to different ages in cohabitation, i.e. with sexually receptive females, and unmated males were raised with spayed females or in all-male groups. The size of the testes, several accessory reproductive organs, kidneys and adrenals was compared. The body composition of the males was determined at 286 days of age.

At all times after puberty, the males raised with receptive females had larger accessory reproductive organs and kidneys. At 286 days of age some of the accessory reproductive organs of the unmated males were 35 to 40% smaller, a degeneration of the testes and the coagulating glands had begun and their bodies contained 72% more fat and 6% less total ash. The findings suggest that in the male rat cohabitation is necessary for the proper maintenance of testicular androgen secretion.

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D. DRORI, D. AMIR and Y. FOLMAN

Summary.

Male rats mated infrequently had consistently larger coagulating glands containing more fructose than unmated males, and the concentration of fructose in these glands was higher in four out of five experiments. However, males mated frequently had smaller glands and lower fructose content than males mated infrequently.

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Miriam Rosenberg, Z. Herz, M. Davidson and Y. Folman

Summary. Progesterone concentrations in peripheral plasma of 18 primiparous and 34 multiparous dairy cows were determined by radioimmunoassay every 4 days, from 10 days post partum until the next conception. The interval from parturition to the first progesterone peak (> 4 ng/ml plasma) was significantly longer (P < 0·01) in primiparous than in multiparous cows. The progesterone concentrations on Days 4–15 of the oestrous cycle were significantly lower (P < 0·025) during the summer than in cycles occurring in winter. The conception rate during the summer was lower than in winter. In cows inseminated in summer, conception was related to the shape of the progesterone curve in the cycle preceding insemination.

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Y. FOLMAN, MIRIAM ROSENBERG, Z. HERZ and M. DAVIDSON

Summary.

Fourteen dairy cows were maintained on high and standard (low) levels of nutrition. Plasma progesterone concentration was determined by a protein-binding method every 4 days from 10 days post partum until pregnancy. Cows that conceived after one insemination had significantly higher progesterone levels during the oestrous cycle preceding insemination than did cows that did not conceive. Correlation coefficients between the occurrence of conception after the first insemination and plasma progesterone concentration during the preceding luteal phase were statistically significant. Cows maintained on a high level of nutrition required fewer inseminations per conception, conceived earlier and had a high plasma progesterone level 23 days earlier than cows maintained on a standard level of nutrition. In cows that conceived after one insemination, level of nutrition had no effect on progesterone concentration but it had a profound effect in cows that needed more inseminations for conception. During the luteal phase preceding insemination, cows that conceived after the first insemination gained weight whereas cows that did not conceive lost weight; the difference approached significance. The correlation coefficient between body weight changes and progesterone concentration 8 to 15 days before the first insemination approached significance (r = 0·492). It is suggested that plasma progesterone concentration during the oestrous cycle preceding insemination is closely related to the occurrence of conception.

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Miriam Rosenberg, Y. Folman, Z. Herz, I. Flamenbaum, A. Berman and M. Kaim

Summary. In a subtropical climate, high milk-yielding dairy cows were kept during the summer under ventilated conditions or untreated; during the winter, cows were kept untreated. The afternoon mean rectal temperature for multiparous cows in the three groups was 39·3, 39·8 and 38·9°C, respectively. Each group was significantly different from the other two (P < 0·05). Plasma LH concentrations measured every 6 h during the oestrous period in 38 'summer' cows were not significantly different for untreated and ventilated animals. Conception rate was higher (P < 0·05) in cows that showed oestrous behaviour before the LH surge reached its peak than in cows in which oestrus coincided with or occurred later than the LH surge. Plasma progesterone levels measured in 62 cows during the oestrous cycle before the first insemination were higher in the winter than in the summer in multiparous, but not in primiparous, cows. Ventilation increased progesterone levels in multiparous and primiparous cows. Plasma oestradiol-17β levels did not differ between groups until 36 h before the onset of oestrus, when they remained at 4·75 pg/ml in winter and summer-ventilated cows but increased to 6·75 pg/ml in summer untreated cows (P < 0·01). Significant negative correlations were found between oestradiol levels observed 12 h before to 12 h after the onset of oestrus and plasma progesterone concentration during both the preceding and the subsequent oestrous cycles.

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A Shaham-Albalancy, Y Folman, M Kaim, M Rosenberg and D Wolfenson

Low progesterone concentrations during the bovine oestrous cycle induce enhanced responsiveness to oxytocin challenge late in the luteal phase of the same cycle. The delayed effect of low progesterone concentrations during one oestrous cycle on uterine PGF(2alpha) secretion after oxytocin challenge on day 15 or 16 of the subsequent cycle was studied by measuring the concentrations of the major PGF(2alpha) metabolite (13,14-dihydro-15-keto PGF(2alpha); PGFM) in plasma. Two experiments were conducted, differing in the type of progesterone treatment and in the shape of the low progesterone concentration curves. In Expt 1, progesterone supplementation with intravaginal progesterone inserts, with or without an active corpus luteum, was used to obtain high, or low and constant plasma progesterone concentrations, respectively. In Expt 2, untreated cows, representing high progesterone treatment, were compared with cows that had low but increasing plasma progesterone concentrations that were achieved by manipulating endogenous progesterone secretion of the corpus luteum. Neither experiment revealed any differences in plasma progesterone concentrations between the high and low progesterone groups in the subsequent oestrous cycle. In both experiments, both groups had similar basal concentrations of PGFM on day 15 (Expt 1) or 16 (Expt 2) of the subsequent oestrous cycle, 18 days after progesterone treatments had ended. In both experiments, the increases in PGFM concentrations in the low progesterone groups after an oxytocin challenge were markedly higher than in the high progesterone groups. These results indicate that low progesterone concentrations during an oestrous cycle have a delayed stimulatory effect on uterine responsiveness to oxytocin during the late luteal phase of the subsequent cycle. This resulting increase in PGF(2alpha) secretion may interfere with luteal maintenance during the early stages of pregnancy.