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Biomedical subjects

J J Ford

Publications and source records attributed to J J Ford.

At least 127 records · Page 7Linked to original sources
PubMed1978

Simple technique for chronic venous catheterization of swine.

Catheters were placed into the vena cava of swine via the external jugular vein. The catheters were then passed subcutaneously through a cannula to the back and exteriorized. These catheters were impregnated with heparin and were functional for more than 46 days. Length of estrous cycle and hematology traits were not affected adversely by this technique.

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↗
PubMed1977

Ovulation in light-estrous rats induced by darkness.

Adult female rats show continual vaginal cornification and cease ovulation a few weeks after they are exposed to continuous lighting (light-estrous rats). When these rats were placed in the darkness for 10 hr, 80% of the animal ovulated approximately 46 hr later. Peripheral LH increased to a small peak immediately after placing in darkness concomitant with a decrease in pituitary LH content; a large peak, 20 times higher than the basal LH level, was observed at 20 to 22 hr. Progesterone concentration in ovarian vein blood remained at extremely low levels while estrogen levels tended to rise after small LH peak. This estrogen rise appeared to play an important role in inducing the main LH peak. Simulation of the small LH peak by low doses of exogenous LH succeeded in inducing ovulation of light-estrous rats in similar fashion to the exposure of light-estrous rats to 10-hr darkness. Therefore, the small amount of LH secretion observed after the initiation of the darkness-treatment may be considered as a trigger for the whole sequence of hormonal changes leading to ovulation.

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↗
PubMed1975

Carotid endarterectomy for nonhemispheric transient ischemic attacks.

Fifty carotid endarterectomies were performed in 46 patients with nonhemispheric transient ischemic attacks. There was no mortality. Three patients had temporary strokes postoperatively. Ninety-five percent of the patients were improved and remained so at follow-up examination. Clinical improvement was not related to the presence or absence of vertebral or subclavian stenosis. In retrospect, the two patients who were unimproved had been improperly selected.

Aged↗
PubMed1975

The role of LH in the luteotrophic process of lactating rats.

The role of LH in the leuteotrophic process was examined by evaluating progesterone secretion in pregnant, lactating, and pregnant lactating rats, and the response of these rats to antisera against LH (LHAS) was observed. Ovarian venous progesterone concentration in lactating rats was elevated as litter size increased. Treatment with LHAS on day 8 postpartum of rats nursing 12 pups significantly decreased peripheral progesterone levels within 24 hr. Treatment with LHAS on days 8 and 9 of pregnancy terminated gestation in all normal pregnant animals by in similarly treated pregnant lactating rats gestation was maintained until day 14 in 4 of 10 rats. If the litter was removed from pregnant lactating dams at the time of initiation of LHAS treatment, pregnancy was interrupted in all 12 animals. Ovarian venous progesterone concentration was reduced by greater than 90% 24 hr after LHAS treatment on day 8 of normal pregnant rats and 20alpha-OH-P increased such that the concentration of total progestins remained constant. Ovarian venous progesterone concentration 24 hr after LHAS treatment of pregnant lactating rats was reduced by 50% in animals receiving daily estradiol treatment by LHAS had little effect in pregnant lactating animals which received a single injection of estradiol on day 4 postpartum. The level of 20alpha-OH-P in pregnant lactating animals was not affected by LHAS. The results of these studies demonstrate that in lactating rats nursing a large litter (12 pups) LH is part of the luteotrophic complex, and the data obtained from studies in pregnant lactating rats suggest that when pregnancy and lactation are superimposed the role of LH in the luteotrophic process on day 8 of gestation is diminished.

Animals↗
PubMed1975

The role of prolactin in the luteotrophic process of lactating rats.

Treatment of pseudopregnant rats with ergocryptine mesylate (ECR) depressed serum prolactin levels but had no apparent effect on LH secretion. Ovarian progesterone secretion was significantly, reduced 24 hr after ECR treatment on day 6 or 9 of pseudopregnancy and the secretion rate of 20alpha-OH-P remained constant. When lactating rats nursing 6 pups were treated with ECR on day 6 or 9 postpartum, progesterone secretion was significantly decreased by 48 hr after treatment and 20 alpha-OH-P secretion was not altered. Furthermore, ECR inhibited litter weight gains of these lactating dams. After treatment of normal pregnant and pregnant lactating rats with ECR on day 6 of pregnancy, gestation was terminated in all animals. If ECR was given on day 9 to normal pregnant rats, to pregnant lactating animals whose pups were removed on day 9 postpartum, or to pregnant lactating rats treated with LH, gestation was not terminated. However, treatment with ECR of day 9 pregnant lactating rats whose pups continued to suckle terminated pregnancy in 13 of 21 animals. The results of these studies suggest the elevated pituitary prolactin secretion is necessary for maintenance of luteal function in pseudopregnant and lactating rats, and in pregnant lactating rats elevated pituitary prolactin secretion is a component of the luteotrophic complex for a longer period of time than in normal pregnant rats.

Animals↗
PubMed1975

Effects of cervical stimulation and anti-LH releasing hormone serum on LH releasing hormone content in the hypothalamus.

Hypothalamic content of LHRH was radioimmunoassayed after cervical stimulation on the morning of day of estrus' LHRH content rose 3-fold by 120 min after the stimulation, reaching a level equivalent to that of day 5 of pseudopregnancy. The increase was not steady as there were two early periods when the content did not increase. Measurement of pituitary LH content revealed a marked increase followed by a sudden decrease which corresponded respectively to the two periods when LHRH levels failed ro tise. These changes in pituitary LH level suggest that both the synthesis and release of LH in the pituitary are promoted by the action of LHRH released from the hypothalamus. LH changes in the pituitary were abolished iv injection of 2 ml LHRH antiserum at the time of cervical stimulation, but pseudopregnancy was still induced and diestrus prolonged 4 days longer than in the control group. Progestin concentrations in ovarian vein blood were comparable between anti-LHRH-treated and control groups. These results suggest that the LH released by cervical stimulation is dispensable for the induction of pseudopregnancy. The marked elevation of LHRH in the hypothalamus observed immediately after cervical stimulation must be related to the regulatory mechanism of the characteristic secretory pattern of LH during the period of pseudopregnancy.

Animals↗
PubMed1975

Ergocryptine and pregnancy maintenance in hamsters.

Ergocryptine (ECR) terminated pregnancy in hamsters when administered on Day 5; when ECR was given on Day 6 the response was diminished, and pregnancy continued after ECR treatment on Day 7. The abortifacient action of ECR in Day 5 pregnant hamsters was overcome by exogenous prolactin but not FSH and LH. When sera collected from hamsters on different days of gestation were examined for their ability to neutralize the effect of ECR in Day 5 pregnant hamsters, a peak of luteotrophic activity was observed in sera collected on Days 10 and 11. The results of these studies suggest that in hamsters the role of hypophyseal prolactin in luteal support is diminished by Day 7 of pregnancy, and the appearance of luteotrophic activity in sera collected on Days 10 and 11 may be indicative of a placental luteotrophin.

Animals↗