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K. JANAKIRAMAN and L. E. CASIDA

Summary.

Sixty-eight oestrous New Zealand white rabbits were used in four experiments to study the pituitary lh content, ovulation time and corpus luteum development in the presence of intra-uterine devices (IUD) fitted in both horns. The results indicate that the IUD-fitted animals ovulate later and their pituitary lh content following mating is higher than in sham-operated controls. Also, such animals have lighter and less luteinized corpora lutea compared with their sham-operated controls at 24 hr after mating.

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G. L. HUNTER and L. E. CASIDA

Summary.

Six groups of rabbits were mated and used as follows: (1) embryos in one horn of the uterus, no embryos in the other; (2) pregnant, unilaterally hysterectomized; (3) pseudopregnant, unilaterally hysterectomized; (4) embryos present in both horns; (5) bilaterally pseudopregnant; and (6) bilaterally hysterectomized. At 26 days post coitum (p.c.) comparisons of the mean weights of corpora lutea in the ovaries adjacent to each horn showed no significant evidence of differences in local actions of the uterine horn on luteal growth and regression. The mean weights of corpora lutea in the two ovaries were similar in rabbits with one gravid horn and/or one non-gravid horn.

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A. C. MENGE, W. J. TYLER and L. E. CASIDA

Summary.

Rabbit and bull spermatozoa were observed undergoing phagocytosis by polymorphonuclear leucocytes after being injected into ligated uteri of oestrous and luteal phase rabbits. An interaction between the species of spermatozoa injected and the reproductive phase of the rabbit occurred in the number of recovered spermatozoa.

Killing the bull spermatozoa prior to injection decreased the recovery rate significantly while killing the rabbit spermatozoa had no significant effect.

Treating either bull or rabbit spermatozoa with uterine exudates induced by bull spermatozoa decreased significantly the recovery rates from oestrous rabbits as compared to treatment with saline solution or exudates induced by rabbit spermatozoa.

In leucopenic rabbits, differences in recovery rates due to species of spermatozoa injected and reproductive phase of the rabbit were not evident. Approximately 75 to 80% of the spermatozoa injected were recovered compared to less than 20% for the controls.

In none of the experiments did the number of recovered leucocytes vary with the different treatments, except after the induction of leucopenia.

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ANANT P. LABHSETWAR, W. E. COLLINS, W. J. TYLER and L. E. CASIDA

Summary.

An experiment involving twenty multiparous Holstein cows was designed to study the pituitary-ovarian relationship in periparturient cows. The cows were divided into four equal groups. One group was slaughtered between 260 and 265 days of gestation; the second group was slaughtered within 18 hr following parturition; the third group was slaughtered 21 days post partum and the fourth group received 100 mg of progesterone daily for 20 days starting from the day of calving and was slaughtered on Day 21. There was no detectable amount of progesterone in the corpora lutea of pregnancy on the day of calving. An average of 26 μg/g progesterone was present in the corpora lutea of ante-partum cows. The corpora lutea were significantly larger in the ante-partum group than in the day-of-calving group. A significantly higher fsh level and lower lh level was found in the pituitaries of the day-of-calving group. Follicular size was significantly lower in the ante-partum and day-of-calving group as compared to both the post-partum groups. Injection of progesterone produced no significant alterations in fsh and lh levels of the pituitary glands. Neither did it depress ovarian follicular growth.

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ANANT P. LABHSETWAR, W. E. COLLINS, W. J. TYLER and L. E. CASIDA

Summary.

The effects of oxytocin and of progesterone on the pituitaryovarian relationships were studied in sixteen non-pregnant heifers. Subcutaneous injection of 100 mg of progesterone in corn oil daily for 35 days from Day 7 of the oestrous cycle depressed both the size of the largest follicle and the total weight of follicular fluid. The fsh level was significantly raised after progesterone injections as compared to Day 1 of the cycle but not as compared to Day 7. The progesterone treatment had no significant effect on lh level. It was concluded that progesterone curtails the production, and consequently the release, of fsh and lh.

The injection of 150 U.S.P. units of oxytocin daily from the day of oestrus to Day 6 of the cycle produced a smaller corpus luteum (2·51 versus 4·40 g, P < 0·05) and a reduced concentration of progesterone (14·6 versus 29·0 μg/g, P<0·05). The oxytocin treatment had no significant effect on the hypophyseal levels of fsh and lh. It did not affect the size of the largest follicle or the total follicular fluid weight.

The corpus luteum of the previous cycle, still present on the day of oestrus, was small (1·74 g) but contained a detectable amount of progesterone (2·8 μg/g.

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O. J. GINTHER, C. O. WOODY, S. MAHAJAN, K. JANAKIRAMAN and L. E. CASIDA

Summary.

The effect of oxytocin administration on the oestrous cycle was studied in sixteen uterine-intact and thirty-two surgically prepared unicornual heifers. Unilateral hysterectomy was performed on Day 3 of the oestrous cycle and oxytocin or an equivalent volume of physiological saline was administered daily from Day 3 to Day 7 or 8. Oxytocin produced significantly shorter oestrous cycles in the intact heifers and in the unicornual heifers with the retained uterine horn adjacent to the cl, but not in the unicornual heifers with the retained horn opposite to the cl. These results strongly suggest that at least part of the effect of oxytocin is exerted through local, utero-ovarian channels. A unilateral effect of the uterus on the cl was demonstrated in unicornual heifers that did not receive oxytocin. The oestrous cycles were extended and the cl persisted when the retained horn was opposite to the cl, but not when the retained horn was adjacent to the cl.

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A. C. MENGE, C. A. KIDDY, W. H. STONE and L. E. CASIDA

Summary.

Rabbit embryos were treated at 1 or at 9 days of age with cattle immune sera produced against rabbit semen and rabbit erythrocytes. Immune sera against semen did not produce a consistent effect on the survival rates of 1-day-old embryos, but did produce a significant increase in death rate among embryos that were treated at 9 days of age. No significant differences were observed in the survival rates of embryos treated at either stage of development with normal sera and immune sera produced against rabbit erythrocytes.

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O. J. GINTHER, C. O. WOODY, K. JANAKIRAMAN and L. E. CASIDA

Summary.

A plastic coil was inserted surgically on Day 3 of an oestrous cycle into one uterine horn of each of ten heifers. Sham-operations were performed on five additional heifers. The oestrous cycles in which the cl was on the operative side were significantly shorter than the cycles in which the cl was on the non-operative side or the cycles of the sham-operated controls. The average cycle length when the cl was on the non-operative side was not significantly different from the cycle length of the sham-operated controls. These results indicate that a plastic coil in the cranial portion of one uterine horn of the heifer results in a unilateral `inhibitory' influence on the cl.

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A. C. MENGE, W. H. STONE, W. J. TYLER and L. E. CASIDA

Summary.

Immune sera produced against bull semen in cattle and against washed bull spermatozoa in rabbits caused an antifertility effect (fertilization failure or possibly early embryonic death), when used to treat the bull semen prior to insemination of heifers. Fertilization was prevented in rabbits inseminated with semen treated with cattle antirabbit semen serum. Normal fertility occurred in both species when the semen was treated with normal sera. Fertilization was prevented in rabbits inseminated with semen treated with the gamma-globulin fraction of the immune serum, but not with the gamma-globulin fraction of the normal serum.

Absorption of the rabbit anti-bull-sperm sera and the cattle antirabbit-semen sera with the erythrocytes of bulls and male rabbits, respectively, failed to remove the sperm agglutinins or the antifertility effect of these antisera. Absorption of these sera with the appropriate washed spermatozoa removed the agglutinins and the antifertility effect. Antisera to erythrocytes did not possess either sperm agglutinins or the antifertility effect when used to treat bull or rabbit semen. Similarly, antisera to semen or washed spermatozoa had little or no specific agglutinins against erythrocytes. These results indicate that antibodies against semen or washed spermatozoa can prevent fertilization, or may cause embryonic death. Further, they indicate the absence of cross-reactivity between the antigens of either seminal plasma or spermatozoa and erythrocytes.

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K. JANAKIRAMAN, C. O. WOODY, S. P. AGARWAL, R. C. BHALLA, K. P. SHUKLA, B. A. GADGIL, N. C. BUCH and L. E. CASIDA

Summary.

The effects of IUDs on the occurrence of ovulation and the pituitary gonadotrophin content was studied in water buffalo heifers of the Surti breed. Thirty-six of these heifers were divided into four equal groups. Group 1 received sham operations, while Groups 2, 3 and 4 were fitted with plastic IUDs in the cranial region of the uterus either ipsilaterally or contralaterally (in relation to the side on which ovulation occurred) or bilaterally, 72 hr after the exhibition of heat. Treated heifers showed significantly shorter cycles than the controls (P<0·01). There was no difference between Groups 2, 3 and 4. Heifers were slaughtered after the onset of heat in post-IUD-insertion cycles. Eight of the nine heifers ovulated in the control group, but only three in the group fitted with bilateral IUDs and one each in the groups fitted with ipsilateral and contralateral IUDs. The other ovarian characters studied did not show any significant differences among the four groups.

The anterior pituitaries from these heifers in different groups were freeze-dried and assayed for lh and fsh. Neither lh nor fsh activity was statistically different among treatment groups.

The results of this experiment suggested that an IUD, when present in one horn, also affects the adjacent ovary of the opposite horn to induce shorter cycles. This contralateral effect may be mediated systemically either at the level of the pituitary, the hypothalamus, or both. It is not possible to rule out transmission of a uterine factor from the IUD-horn to the non-IUD horn.