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Biomedical subjects

G B Rampacek

Publications and source records attributed to G B Rampacek.

At least 91 records · Page 5Linked to original sources
PubMed1982

Inhibition of ovulation and LH secretion in the gilt after treatment with ACTH or hydrocortisone.

Treatment with ACTH (100 i.u.) or hydrocortisone acetate (250 mg) twice daily for 12 days to increase cortisol concentrations blocked ovulation in all gilts. The preovulatory surge of LH was also blocked in the treated gilts. Oestrous cycle length and number of days in oestrus were similar for all treatments except that in one of the 2 experiments ACTH suppressed oestrus in 4 of the 5 gilts treated.

Adrenocorticotropic Hormone↗
PubMed1982

Prolactin and luteinizing hormone secretion after bromocryptine (CB-154) treatment in lactating sows and ovariectomized gilts.

The effects of bromocryptine (CB-154) on prolactin (PRL) and luteinizing hormone (LH) secretion were studied in lactating sows and ovariectomized (OVX) gilts. In Exp]. 1, the litters of four sows were standardized to four pigs each at 20 to 30 d of lactation and a cannula was placed nonsurgically into the jugular vein of each sow. Twenty-four hours later (0800 h) blood samples were taken and two sows each were injected subcutaneously with 120 mg CB-154 or vehicle. Blood samples were then taken every 30 min for the next 23.5 h. An additional six sows whose litters were standardized to six pigs each at 28 to 30 d of lactation comprised EXp. 2. In Exp. 3, five puberal gilts were OVX. Forty-eight hours after OVX a cannula was placed into the jugular vein. The day after cannulation blood samples were drawn every 30 min from 0800 to 2400 h. Immediately after the sampling at 1200 h, two gilts were injected subcutaneously with 120 mg CB-154 and three were injected subcutaneously with vehicle. Exp. 4 was a repetition of Exp. 3 except that six gilts were OVX 10 d before the experiment and three each were treated with CB-154 of vehicle. Serum PRL concentrations were consistently depressed after CB-154 treatment in both the lactating sows (Exp. 1, from 35 to 5 ng/ml, and Exp. 2, from 45 to 7 ng/ml) and the OVX gilts (Exp. 3, from 20 to 13 ng/ml, and ?Exp. 4, from 9 to 2 ng/ml), but changes in serum LH concentrations after CB-154 treatment were not consistent among the four experimental groups. Therefore, we conclude that CB-154 depressed PRL secretion in the lactating sows and OVX gilts. In addition, CB-154 depressed LH secretion in the lactating sows, but the data are inconclusive as to whether or not BC-154 influenced LH secretion in the OVX gilts.

Animals↗
PubMed1981

Serum luteinizing hormone, testosterone, prolactin and cortisol concentrations after PGF2 alpha in the boar.

The effect of prostaglandin F2 alpha (PGF2 alpha) on serum luteinizing hormone (LH), testosterone (T), prolactin (PRL) and cortisol (CS) was studied in the boar. Indwelling cannulae were placed nonsurgically in the jugular vein of six 8 to 9 month-old boars weighing 130 to 160 kilograms. Twenty-four hr after cannulation, blood samples were collected every 30 min from 0630 to 1830 hours. Immediately after the second blood sample (0700 hr) three boars were injected intramuscularly (IM) with 20 mg PGF2 alpha and three boars were injected IM with saline (C). Serum concentrations of LH, T, PRL and CS were quantitated by radioimmunoassay. Serum LH and T concentrations were similar for the PGF2 alpha and C boars throughout the sampling period. In contrast, PRL and CS increased from basal concentrations (mean +/- SE) of 2.1 +/- .1 ng/ml and 24.0 +/- .9 ng/ml to 11.6 +/- .3 ng/ml and 86.9 +/- 9.8 ng/ml, respectively, within 30 min after PGF2 alpha injections and then decreased to control levels over the next 2.0 to 2.5 hours.

Animals↗
PubMed1981

Delayed puberty in gilts in total confinement.

Two hundred fourteen crossbred gilts, born in January through March and June through July of two different years, were raised in total confinement until 100 to 120 days of age and then moved to an outside dirt lot (non-confined) or to a single pen in a confinement, finishing building (confined). Beginning at 150 days of age, estrus was checked daily with a boar to determine percentage of gilts that attained puberty and age at first estrus, and weekly blood samples were collected and analyzed for progesterone by radioimmunoassay to determine age at first ovulation. In the Jan.-Mar. born gilts, 75.4% of the non-confined gilts and 37.4% of the confined gilts attained puberty by 270 days of age (P<.001). Although differences were not significant in the gilts born in June-July, more non-confined gilts (62.6%) than confined gilts (50.9%) attained puberty. Of the 121 gilts that ovulated, only 1 non-confined and 3 confined gilts did not exhibit estrus. Average age at first estrus or at first ovulation were similar for confined and non-confined gilts. Adrenal gland weights at 250 to 270 days of age were similar also for confined and non-confined gilts. Based on the results of this study, we conclude that total confinement housing can reduce, by as much as 50%, the proportion of gilts that attain puberty by 8 to 9 months of age and that time of year may influence the extent of delayed puberty.

Journal Article↗
PubMed1981

Effect of suckling on cortisol, progesterone and luteinizing hormone in postpartum beef cows.

Five primiparous, 3-year-old Hereford cows suckled ad libitum , were cannulated via the jugular vein and stanchioned for 2-day sampling periods, every 14 days starting 14 days after the mean calving date. On the second day of each period, calves were removed to a pen away from the cows, for 9 hours. Blood was sampled 5 min before calves were returned to their dams, as soon as possible after initiation of suckling (IOS), and at 15-min intervals for 45 min, thereafter. Cortisol, progesterone and luteinizing hormone (LH) concentrations in the serum were quantitated by radioimmunoassay. Mean serum cortisol concentrations were 7.3 +/- .7, 9.4 +/- .7, 12.1 +/- .9, 7.5 +/- .5 and 5.7 +/- .4 ng/ml (mean +/- S.E.) at -5, 0, 15, 30 and 45 min after IOS, respectively, for all cows across all periods. Cortisol concentrations, during and after suckling, tended (P<.06) to differ among sampling periods, during the postpartum interval. Serum progesterone concentrations were .28 +/- .02, .28 +/- .02, .32 +/- .05 and .24 +/- .03 ng/ml at 0, 15, 30 and 45 min after IOS, respectively, for all cows across all period, indicating that suckling had no effect on serum progesterone, and were similar at all sampling periods during the postpartum interval. Serum LH concentrations were .81 +/- .07, .77 +/- .06, .71 +/- .04, and .72 +/- .04 ng/ml at 0, 15, 30 and 45 min after IOS, respectively. During the postpartum interval, serum LH concentrations were greater (P<.01) at 71 and 85 days postpartum than at any other time.

Journal Article↗
PubMed1981

Serum testosterone response in Holstein bulls after administration of luteinizing hormone.

Seven yearling Holstein bulls were given 0, 20, 40, 60, 80, 100 and 200 micrograms NIH-LH-B9 during a 7-day complete Latin square design experiment. Treatments were administered via jugular cannulas at 0900 hr, and blood was collected at 60, 30 and 0 min before treatment, at 15-min intervals for 3 hr after treatment and at 30-min intervals from 3 to 7 hr after treatment. Luteinizing hormone (LH) and testosterone concentrations wer measured in serum by radioimmunoassay. Area under the LH and testosterone response curves, expressed as nanograms per milliliter x hours, increased (P less than .001) with increasing amounts of exogenous LH. Basal LH in serum averaged 1.4 +/- .1 ng/ml, and peaks ranged from 3.8 +/- .4 to 13.3 +/- .4 ng/ml after 40 and 200 micrograms of exogenous LH, respectively. Basal testosterone in serum of bulls given saline was 1.8 +/- .2 ng/ml, and peak responses ranged from 4.1 +/- .3 ng/ml to 5.9 +/- .5 ng/ml after 40 and 200 micrograms exogenous LH, respectively. The LH area response to exogenous LH was linear (Y = .4717 + .0352X; P less than .001), with testosterone concentration reaching maximum level in response to 100 micrograms LH (Y = 1.0279 + .1041X + .0001X(2); P less than .001). On the basis of these data, we suggest that the magnitude of the pulsatile release of LH quantitatively controls the secretion of testosterone from the testes of yearling bulls.

Animals↗
PubMed1981

Cortisol and luteinizing hormone after adrenocorticotropic hormone administration to postpartum beef cows.

Cortisol and luteinizing hormone (LH) were measured in serum after the administration of adrenocorticotropic hormone (ACTH) to suckled (S) and nonsuckled (NS) beef cows. Blood was sampled on 2 consecutive days every 2 weeks for four bleeding periods starting 14 days after calving. Cows were injected with 200 IU ACTH or saline in a 2-day switchback design. Serum was collected before ACTH or saline injection and at 30-min intervals thereafter for 8 hours. Average cortisol concentrations in serum were similar in S and NS cows (6.4 +/- .6 and 6.1 +/- .8 ng/ml, respectively) after saline. Average cortisol concentrations in serum collected during an 8-hr period after ACTH on days 14, 28, 42 and 56 postpartum were 24.7 +/- 2.4, 31.8 +/- 3.5, 36.4 +/- 4.2 and 40.7 +/- .5 ng/ml, respectively, for S cows, and 31.1 +/- 2.9, 44.7 +/- 5.2, 45.0 +/- 5.7 and 46.0 +/- 5.4 ng/ml, respectively, for NS cows. Cortisol response to ACTH, measured as area under the response curve, was greater (P less than .05) in NS than in S cows. Amount of cortisol released by 200 IU ACTH was maximal by days 28 to 29 postpartum in NS cows, but the response increased gradually between days 14 to 15 and days 56 to 57 in S cows. overall, LH in serum averaged .55 +/- .08 ng/ml for S cows and .92 +/- .06 ng/ml for NS cows after saline, and .49 +/- .07 ng/ml for S cows and .94 +/- .06 ng/ml for NS cows after ACth. Although mean and peak serum LH concentrations did not differ between cows given ACTH and those given saline, the number of LH peaks and the number of cows having LH after saline. Mean serum LH concentrations were lower (P less than. 05) in S than in NS cows at 28 days postpartum. The number of LH peaks was lower (P less than .05) and the magnitude of the largest LH peak tended to be lower (P less than .06) in S cows at all sampling periods.

Adrenocorticotropic Hormone↗
PubMed1981

Clearance of serum cortisol in suckled and nonsuckled postpartum beef cows.

Clearance of cortisol from the sera of suckled (S) and nonsuckled (NS) beef cows was studied on days 14 +/- 1 and 28 +/- 1 (mean +/- SE) postpartum (periods 1 and 2, respectively). Eight multiparous Angus cows (325 kg to 445 kg) were assigned at calving to S (n = 4) and NS (n = 4) treatments. Basal cortisol concentrations tended to be higher (p less than .10) in S (19.0 +/- 1.3 ng/Ml) than in NS (12.9 +/- .9 ng/ml) cows across both periods. After administration of 20 mg of cortisol, serum cortisol concentrations increased (p less than .01) similarly in S and NS cows to 122.1 +/- 6.4 and 165.6 +/- 11.5 ng/Ml at 2 min postinjection at periods 1 and 2, respectively. Clearance of cortisol from the body was evaluated by biological half-life (t 1/2), volume of distribution (Vd) and total body clearance (TBC) of cortisol. Serum cortisol had a similar t 1/2 in S (32.5 +/- 2.3 min) and NS (29.2 +/- 3.2 min) cows and did not not differ between sampling periods. Vd did not differ (p greater than .3) between S (248 +/- 29 liters) and NS (199 +/- 14 liters) cows across both periods, but was greater (p less than .05) at period 1 than at period 2 for both S and NS cows. Total body clearance was similar in S (5.2 +/- .4 liters/min) and NS (5.0 +/- .6 liters/min) cows and was similar at both sampling periods. On the basis of these results, we conclude that clearance of cortisol from the serum was not affected by lactational status or by postpartum interval, but that the volume of distribution of cortisol in the body decreased during the postpartum period studied.

Animals↗
PubMed1981

Luteinizing hormone secretion before and after ovariectomy in prepubertal and pubertal beef heifers.

The effects of sham ovariectomy (SOVX) or ovariectomy (OVX) on (1) basal luteinizing hormone (LH) concentrations, (2) number of LH peaks per hour and (3) magnitude of LH peaks were determined in prepubertal and pubertal beef heifers. Basal LH concentrations were not influenced by SOVX of prepubertal or pubertal heifers. However, after OVX, basal LH concentrations increased between 168 and 192 hr in prepubertal heifers and between 72 and 80 hr in pubertal heifers. The number of LH peaks per hour was not influenced by SOVX but OVX caused an increase in the number in both prepubertal and pubertal heifers, and the increase occurred sooner after OVX in pubertal than in prepubertal heifers. The magnitude of LH peaks was similar for both prepubertal and pubertal heifers prior to SOVX and OVX. Magnitude of LH peaks was unchanged after SOVX in prepubertal and pubertal heifers, but increased within the first 24 hr after OVX in pubertal heifers and within 168 to 192 hr after OVX in prepubertal heifers. These data indicate that inhibition of LH secretion by ovaries occurred in both prepubertal and pubertal beef heifers. The time-related differences between prepubertal and pubertal heifers in basal LH concentrations, number of LH peaks per hour and magnitude of the LH peaks after OVX may reflect a difference in endocrine environment in these two reproductive states. However, this hypothesis was not tested in this experiment.

Aging↗
PubMed1979

Corpus luteum susceptibility to prostaglandin F2 alpha (PGF2 alpha) luteolysis in hysterectomized prepuberal and mature gilts.

The susceptibility of induced corpora lutea (CL) of prepuberal gilts and spontaneously formed CL of mature gilts to prostaglandin F2 alpha (PGF2 alpha) luteolysis was studied. Prepuberal gilts (120 to 130 days of age) were induced to ovulate with Pregnant Mare Serum Gonadotropin and Human Chorionic Gonadotropin (HCG). The day following HCG was designated as Day 0. Mature gilts which had displayed two or more estrous cycles of 18 to 22 days were used (onset of estrus = Day 0). Gilts were laparotomized on Day 6 to 9, their CL marked with sterile charcoal and totally hysterectomized. On Day 20, gilts were injected IM with either distilled water (DW), 2.5 mg PGF2 alpha or 5.0 mg PGF2 alpha. An additional group of prepuberal gilts was injected with 1.25 mg PGF2 alpha, a dose of PGF2 alpha equivalent, on a per kilogram body weight basis, to the 2.5 mg PGF2 alpha dose given to the mature gilts. The percentages of luteal regression on Day 27 to 30 for mature and prepuberal gilts given DW, 2.5 mg PGF2 alpha and 5.0 mg PGF2 alpha were 0.0 vs 4.4, 43.5 vs 96.8 and 47.7 vs 91.6, respectively; the percentage of luteal regression for the prepuberal gilts given 1.25 mg PGF2 alpha was 75.1. These results indicate that induced CL of the prepuberal gilt were more susceptible to PGF2 alpha luteolysis than spontaneously formed CL of the mature gilt and that pregnancy failure in the prepuberal gilt could be due to increased susceptibility of induced CL to the natural luteolysin.

Animals↗
PubMed1978

Longissimus muscle and plasma enzymes and metabolites in fetally decapitated pigs.

Fetuses of nine gilts were decapitated (D) in utero and fetuses of eight gilts were sham operated (C) at 43 to 47 days of pregnancy. At 110 days, one fetus from each gilt was studied. Heart, liver, kidney, thyroid and body weights were recorded. Thyroids were evaluated for the degree of colloid accumulation and height of the follicular epithelium. Blood glucose, lactate, triglycerides and creatine phosphokinase activity were determined. Longissimus muscle glycogen was evaluated histochemically. Longissimus muscle total phosphorylase, phosphorylase a, G-6-PDH and SDH activity and glycogen were determined biochemically. The D fetuses were hairless, edematous, devoid of adrenal glands and unaffected by maternal anesthesia. Results indicate that the fetal pig pituitary gland is not required for continued fetal growth, but is necessary for normal organ and endocrine gland development. Fetal decapitation caused delayed maturation of the longissimus muscle with little change in anaerobic glycolytic capacity but decreased aerobic glycolytic capacity accompanied by increased activity of the pentose shunt.

Animals↗