Biomedical subjects

J E Minton

Publications and source records attributed to J E Minton.

At least 37 records · Page 2Linked to original sources

PubMed1998

GBV-C/HGV coinfection in HIV-1-positive men: frequent detection of viral RNA in blood plasma but absence from seminal fluid plasma.

Sequential paired samples of blood and seminal fluid were obtained from a cohort of 54 HIV-1-infected homosexual males. The prevalence of GBV-C/HGV RNA in the cell-free fractions of some of these patients was determined using reverse-transcription polymerase chain reaction (RT-PCR). To assess the effects of HIV-1 and HCV infection upon GBV-C/HGV RNA status, blood CD4 cell counts, HCV RNA status, and HIV-1 proviral DNA and viral RNA titres were also determined. GBV-C/HGV RNA was detected in 8/30 (27%) of the blood plasma samples obtained at the start of the study, and was present at a frequency of 14/64 (22%) in all the blood plasma samples tested. By contrast, GBV-C/HGV RNA was not detected in the 26 seminal fluid samples obtained at the start of the study, including 8 samples obtained from patients for which GBV-C/HGV RNA was detected in the corresponding blood sample. Of the samples tested for the presence of both GBV-C/HGV and HCV RNA, there was no evidence of coinfection. Although GBV-C/HGV RNA detection rates were significantly higher in individuals with blood CD4 cell counts greater than 200 cells per microlitre, there were no significant differences in the median blood CD4 cell counts or HIV-1 proviral DNA or viral RNA titres observed between the GBV-C/HGV-positive and -negative individuals. The failure to detect GBV-C/HGV RNA in seminal fluid samples obtained from this cohort would suggest that further studies need to be carried out to determine the roles of sexual transmission and of seminal fluid in GBV-C/HGV infection.

CD4 Lymphocyte Count↗

PubMed1998

Pituitary function in the acute phase response in domestic farm animals: cytokines, prostaglandins, and secretion of ACTH.

Contained in this report is a review of available data on pituitary cytokines in domestic species of agricultural importance. The concept is advanced that the pituitary gland is essential to appropriate generation of host defense mechanisms and thus should be considered among other tissues contributing to innate immunity. The functions of these intrapituitary cytokines, principally IL-6, are discussed in the context of potential regulation of the pituitary-adrenal axis (ACTH secretion) via intrapituitary PGE2 generation during the acute-phase response to infectious/inflammatory stimuli. Data from other species are cited as appropriate for comparative purposes and elaboration of proposed mechanisms. However, the scope of the review is not intended to comprehensively cover the vast literature on proinflammatory cytokines and prostaglandins generated peripherally and centrally during host responses to inflammatory stimuli.

Acute-Phase Reaction↗

PubMed1997

GnRH antagonist inhibition of luteinizing hormone secretion and ovulation in the pig.

A GnRH antagonist, Ac-D-p-Cl-Phe1,2, D-Trp3, D-Arg6, D-Ala10 GnRHb (Organon), was utilized to determine the effective dosage and duration to inhibit LH secretion in the pig. In a preliminary trial, barrows received either 10, 50, or 250 micrograms/kg BW of the GnRH antagonist. Secretion of LH was inhibited within 30 min for a duration of 12 h with the 100 micrograms/kg dose but persisted for greater than 48 h with the 250 micrograms/kg treatment. A second study determined effectiveness of the antagonist for inhibiting ovulation in cyclic gilts. At first detection of standing estrus, cyclic gilts were treated with either saline (control), 100, or 200 micrograms/kg BW of the GnRH antagonist (GnRH1). A second group of GnRH antagonist gilts received 200 micrograms/kg BW of the GnRH antagonist approximately 8 h prior to standing estrus (GnRH2). The GnRH1-treatment failed to inhibit or delay ovulation. Ovulation was inhibited and estrous cycles lengthened in GnRH2-treated gilts. These preliminary results suggest that ovulation in the gilt can be inhibited if the GnRH antagonist is administered prior to the LH surge.

Animals↗

PubMed1997

Cytokines in the hypophysis: a comparative look at interleukin-6 in the porcine anterior pituitary gland.

Interleukin-6 (IL-6) is a multifunctional cytokine produced by a variety of cell types in tissues of both the immune and endocrine systems. Among the major functions described for IL-6 are its role in the maturation of B cells to high-output antibody-producing cells and its contribution to the acute physiological responses to infection and inflammation, notably production of hepatic acute phase proteins and activation of the hypothalamic-pituitary-adrenal axis. In addition to these better known functions, IL-6 recently has been found within the pituitary of laboratory rats and also in the human pituitary. In rats, pituitary IL-6 mRNA is upregulated by peripheral exposure to bacterial endotoxin. However, the role of anterior pituitary IL-6 in host responses to infection and inflammation remains uncertain, although it may regulate pituitary hormone secretion. The following brief review summarizes the information available concerning cytokine production within the anterior pituitary of species of domestic livestock. To our knowledge, experiments conducted in our laboratory evaluating regulation of IL-6 mRNA expression and secretion from the porcine anterior pituitary provide most of the data in domestic species confirming the presence of IL-6 in the pituitary. Our data indicate that IL-6 mRNA is present in cultured porcine anterior pituitary cells and that the pituitary directly responds to stimulation with bacterial endotoxin by increasing secretion of IL-6. Furthermore, endotoxin-induced upregulation of IL-6 mRNA expression and secretion appears to be dependent upon production of cyclooxygenase products of arachidonic acid metabolism.

Adrenocorticotropic Hormone↗

PubMed1997

Ad libitum suckling by an unrelated calf in the presence or absence of a cow's own calf prolongs postpartum anovulation.

Our objective was to determine whether onset of first postpartum ovulation would be altered in suckled cows nursing an unrelated calf in the presence or absence of their own nonsuckling calf. In a 2-yr study, Angus x Hereford cows were assigned randomly to five treatments between d 13 and 18 postpartum for 4 wk: 1) own calf was weaned (OCW, n = 9); 2) own calf was present continuously (OCP, n = 12); 3) own calf was present continuously but restricted from udder contact (OCR, n = 9); 4) unrelated calf was present continuously after own calf was removed (UCP, n = 10); and 5) unrelated calf was present continuously and own calf was present but restricted as in the OCR treatment (OCR + UCP, n = 10). Interval to the first increase in progesterone (ovulation) was less (P < .05) in OCW (14.7 +/- 3.4 d) and OCR (19.9 +/- 3.4 d) than in the OCP (35.0 +/- 2.9 d), UCP (38.0 +/- 3.4 d), and OCR + UCP (37.6 +/- 3.4 d) treatments. The OCW cows showed no maternal bond with their own calves after 4 wk of treatment, whereas OCR, OCP, and OCR + UCP cows were bonded to their own natural calves. Cows in the UCP treatment, suckled by unrelated calves, formed new maternal bonds with those calves, resulting in prolonged anovulation. Further, OCR + UCP cows had prolonged anovulation because maternal bonds were maintained with their own restricted calves while milk was removed by unrelated calves. We conclude that milk removal preceded by a continuously reinforced cow-calf bond (original or reestablished) is essential to prolong anovulation in beef cows.

Analysis of Variance↗

PubMed1997

Supplemental dietary chromium does not influence ACTH, cortisol, or immune responses in young calves inoculated with bovine herpesvirus-1.

Twelve Holstein bull calves (6 to 8 wk of age) were used to determine the influence of supplemental dietary Cr on ACTH, cortisol, and immune responses of calves experimentally inoculated with bovine herpesvirus-1 (BHV-1). Calves supplemented with Cr received 3 mg Cr/d (Chromium, n = 6) of a high-Cr-yeast product. Following 53 d of treatment, all calves were fitted with jugular catheters, and blood samples were collected every 4 h into tubes containing ETDA. Twenty-four hours later, all calves were inoculated intranasally with BHV-1 (1 x 10(7) plaque-forming units in each naris). Serial blood collection continued at 4-h intervals for 6 d. Plasma was harvested, immediately frozen in liquid nitrogen, and stored at -20 degrees C. Individual rectal temperatures and urine samples were collected at the same time each day. Rectal temperatures were elevated (P < .05) on d 2, 3, 4, and 5 but were not affected by Cr treatment. Treatment with Cr did not affect secretion of ACTH, cortisol, or plasma tumor necrosis factor-alpha, although clear circadian variation in ACTH and cortisol occurred. No differences were detected in the concentrations of trace minerals excreted daily in the urine, lymphocyte proliferative response to mitogen stimulation, and neutrophil bactericidal function. The acute phase proteins, ceruloplasmin and fibrinogen, also were not affected by treatment or viral challenge. These data suggest the Cr supplementation using high-Cr yeast (3 mg/d) did not alter stress responses of calves experimentally inoculated with BHV-1.

Adrenocorticotropic Hormone↗

PubMed1997

Influence of timing of gain on growth and reproductive performance of beef replacement heifers.

Our objective was to determine whether beef heifers could be developed by delaying the majority of weight gain until the last third of the developmental period before the onset of the breeding season. Spring-born Angus x Hereford heifers were used in each of two consecutive years and were allotted at weaning to gain either .45 kg/d for the entire developmental period (yr 1 = 159 d, n = 40; yr 2 = 168 d, n = 40; EVENGAIN) or to gain .11 kg/d from d 0 to 112, followed by .91 kg/d from d 112 to 159 (yr 1, n = 40) or d 168 (yr 2, n = 40; LATEGAIN). Body weights and condition scores were determined at d 0, 112, and 159 (yr 1) or d 0, 112, and 168 (yr 2). Heifers were subjected to a 60-d breeding season. Frame scores and pelvic areas were determined at the conclusion of the breeding season. Actual daily gains for EVENGAIN heifers for yr 1 and yr 2 were .60 and .51 kg/d, respectively. LATEGAIN heifers gained .25 and .05 kg/d during the restricted phases from d 0 to 112, followed by 1.14 and 1.32 kg/d during the accelerated growth phases for yr 1 and 2, respectively. Body weight at the onset of the breeding season and weight at puberty were not different between treatments in either year. Age at puberty did not differ in yr 1, but, age at puberty in yr 2 was delayed (P < .01) in LATEGAIN (406.9 d) compared to EVENGAIN (386.3 d) heifers. The LATEGAIN and EVENGAIN heifers had similar pelvic areas, frame scores, and body condition scores in each year. First-service conception rates of both groups were similar in yr 1 (55.5 vs 55.3%). In yr 2, LATEGAIN heifers tended (P = .18) to have an increase in first-service conception rate compared to EVENGAIN heifers (71.1 vs 56.4%). No treatment differences occurred in either average age of conception or overall pregnancy rates at the conclusion of the breeding season for either year. The LATEGAIN heifers were developed to a similar BW on 12 (P < .01) and 2.5% (not statistically significant) less feed for yr 1 and 2, respectively, compared to EVENGAIN heifers. We interpret these data to indicate that delaying the majority of weight gain until late in heifer development may decrease costs without detrimental effects on reproductive performance.

Analysis of Variance↗

PubMed1996

Effects of corticotropin-releasing hormone, lysine vasopressin, oxytocin, and angiotensin II on adrenocorticotropin secretion from porcine anterior pituitary cells.

The aim of this study was to determine the ability of corticotropin-releasing hormone (CRH), lysine vasopressin (LVP), oxytocin (OT), and angiotensin II (AII) to stimulate adrenocorticotropin (ACTH) secretion from porcine anterior pituitary (AP) cells in vitro and to evaluate the role of protein kinase C (PKC) in the interaction between CRH and LVP. In this study, porcine AP cells were enzymatically and mechanically dispersed, cultured (150,000 cells/well) for 4 d, and then challenged with doses of various neuropeptides for 3 hr. CRH (10(-7)-10(-10) M) was the most potent of the peptides tested in stimulating ACTH release from porcine AP cells. In fact, none of the other peptides consistently affected ACTH concentrations relative to basal levels. However, LVP potentiated CRH action, even though by itself, it failed to stimulate ACTH production. Neither OT or AII potentiated CRH-stimulated ACTH release from porcine AP cells. To determine whether the inter-action between CRH and LVP was regulated partially by the protein Kinase C (PKC) pathway, we challenged AP cells in a 30-min incubation with 10(-7) M staurosporine (ST), a treatment predicted to decrease PKC activity. Then, cells were washed and challenged with 10(-9) M LVP, 10(-9) M CRH, and 10(-9) M CRH + LVP. Treatment with ST decreased (P < 0.05) CRH + LVP-stimulated ACTH release. To further demonstrate an interaction between protein kinase A (PKA) and PKC transduction pathways in the observed synergism between CRH and LVP to enhance ACTH secretion, we also challenged AP cells with 10(-7) M phorbol 12, 13-myristate acetate (PMA) and 5 microM forskolin (FOR) for 3 hr. This treatment was predicted to enhance PKA and PKC activities, respectively, and thereby enhance ACTH concentrations. Challenging cells with FOR + PMA enhanced (P < 0.001) ACTH release above basal concentrations, but more important, it increased (P < 0.001) ACTH concentration above that elicited by either drug given alone. Taken together, our in vitro studies support the conclusion that CRH is the principal regulator of ACTH secretion in the pig. In contrast to the results in most other species evaluated, vasopressin alone did not affect ACTH release. However, LVP can enhance the effectiveness of CRH in releasing ACTH, and this enhancement appears to rely, at least in part, on the activation of the PKC signal transduction pathway.

Adrenocorticotropic Hormone↗

PubMed1996

Effect of endotoxin on interleukin-6 secretion and messenger ribonucleic acid in porcine anterior pituitary cells.

The pleiotropic cytokine interleukin-6 (IL-6) is produced in and secreted from anterior pituitary (AP) cells of a number of species. Bacterial endotoxin (END) may enhance the transcription of IL-6 and its secretion from the AP. In the studies presented here, we evaluated pig AP cells for the presence of IL-6 mRNA. In addition, because we had observed previously that END stimulated the secretion of prostaglandin E2 from cultured porcine AP cells, the effects of the inhibition of END-stimulated cyclooxygenase products on IL-6 mRNA abundance and the secretion of IL-6 were evaluated. In the first experiment, RNA was extracted from cultured pig AP cells that had been treated with END for 0.5 or 1 hr and subjected to reverse transcription followed by polymerase chain reaction and hybridization after Southern transfer. Bands of expected amplified product size, corresponding to IL-6, were observed only from cells treated with END, although specific hybridization was observed from both control and END-treated wells. In the next experiment, RNA was extracted from cultured AP cells treated with END or END in the presence of the cyclooxygenase inhibitor indomethacin (IND). Amplification of the expected product could be observed from all cultured cells except those treated with IND. However, hybridization data indicated that IND did not eliminate IL-6 mRNA entirely. Next, we measured IL-6 secretion from cultured AP cells exposed to END or END and IND. Treatment with END stimulated IL-6 secretion (P < 0.001) above controls, whereas IND blocked END stimulation of IL-6 secretion (P < 0.001). Finally, using immunostaining, we confirmed the presence of CD14, an END receptor, in cultured pig AP cells. These studies clearly establish the presence of IL-6 mRNA and secretion of the cytokine from cultured porcine AP cells. In addition, END stimulates the secretion of IL-6, perhaps through cells expressing CD14, and END-stimulated IL-6 secretion appears to be mediated by products of the cyclooxygenase pathway.

Animals↗

PubMed1996

Restricting calf presence without suckling compared with weaning prolongs postpartum anovulation in beef cattle.

To determine how continued presence of a calf affected duration of postpartum anovulation, 23 udder-intact cows and their calves were assigned to three treatments on d 4 to 9 postpartum (experimental d 0). The treatments were 1) calf present with unlimited contact with its dam (n = 8), 2) calf restricted to noninguinal contact with its dam (n = 8), and 3) calf weaned from its dam (n = 7). Calves in the calf-present and calf-restricted treatments were weaned after 5 wk. Based on daily measurements of blood progesterone, days to first ovulation after onset of treatments were 35.4 +/- 2.2, 22.5 +/- 2.2, and 14.3 +/- 2.2 for the calf-present, calf-restricted, and calf-weaned treatments, respectively; each one differed (P < .01) from the others. Mean concentrations of LH were greater (P < .05) in the calf-restricted treatment and tended (P = .13) to be greater in the calf-weaned treatment than in the calf-present treatment on d 7 after the onset of treatments. On d 7 and 21, calves in the calf-present and calf-restricted (calves could not suckle) treatments were returned to their dams after overnight separation. Blood samples were collected to assess changes in cortisol, ACTH, prolactin, and oxytocin. No treatment effects were detected on d 7, but on d 21, the calf-present and calf-restricted cows had a greater (P < .05) increase in cortisol after calf return than the calf-weaned cows (calves were not returned), whereas prolactin was increased (P < .05) after calf return in the calf-present cows only. We conclude that calf presence is associated with an increase in cortisol and calf presence without suckling is one factor that delays the onset of first postpartum ovulation in beef cows.

Adrenocorticotropic Hormone↗

PubMed1995

Stress-associated concentrations of plasma cortisol cannot account for reduced lymphocyte function and changes in serum enzymes in lambs exposed to restraint and isolation stress.

Lambs were used to evaluate the effect of stress-associated plasma concentrations of cortisol on measures of immune function. Lambs given restraint and isolation stress (RIS) were isolated from visual and tactile contact with other lambs for 6 h on three consecutive days. Additional lambs were infused with cortisol (CORT) to increase plasma concentrations similar to those in lambs subjected to RIS. Control lambs (CON) were undisturbed. On the 1st and 3rd d of the experiment, plasma was obtained hourly during treatment for quantification of cortisol and ACTH. Blood mononuclear cells were obtained 24 h before the 1st d of treatment and daily at the conclusion of treatment for responses to phytohemagglutinin (PHA), concanavalin A (Con A), and pokeweed mitogen (PWM); for production of interleukin 2 (IL2); and for identification of cells expressing major histocompatibility complex class II antigens (MHCII). Combined fitted profiles of cortisol in RIS and CORT lambs differed (P < .005) from those in CON on both days evaluated. Fitted profiles of cortisol were similar between RIS and CORT lambs on the 1st d of treatment but differed (P < .005) on the 3rd d. Combined fitted profiles of ACTH from CON and CORT lambs differed from those of RIS lambs on both days of treatment (P < .005). Lymphocyte responses to PHA (P < .01), Con A (P < .01), and PWM (P < .07) were less in RIS than in CON but did not differ between CON and CORT. Treatment did not affect IL2 or MHCII. Increased plasma cortisol measured during RIS cannot alone account for reduced lymphocyte proliferative responses.

Adrenocorticotropic Hormone↗

PubMed1995

Effects of restraint and isolation stress and epidural blockade on endocrine and blood metabolite status, muscle glycogen metabolism, and incidence of dark-cutting longissimus muscle of sheep.

Crossbred lambs (47.3 kg BW) were used to study the effects of restraint and isolation stress on endocrine status and blood metabolites, antemortem glycogenolysis, and incidence of the dark-cutting condition (DCC) in the longissimus muscle (LM) and to determine the role of muscle contraction in the formation of the DCC in sheep. Lambs were assigned randomly to three treatments: unstressed controls (C); a single 6-h period of restraint and isolation stress (RIS); and a single 6-h period of RIS following epidural blockade (RISEB) with lidocaine. Blood was collected immediately before lambs were subjected to RIS and RISEB and at 12-min intervals during the 6-h period. Serum concentrations of glucose, lactate, and insulin were higher (P < .01) in RIS and RISEB lambs than in C lambs. Serum free fatty acid concentrations were higher (P < .01) in stressed lambs only during the first 4 h of stress. Plasma epinephrine and cortisol concentrations also were higher (P < .01) in RIS and RISEB lambs than in C lambs. Lambs were slaughtered within 30 min after completion of stress. Immediately after stunning and at .75, 3, 6, 12, and 24 h postmortem, samples were removed from the LM in the hindsaddle and foresaddle for glycogen, lactate, and pH determinations. Muscle pH was elevated (P < .01) by RIS and RISEB; ultimate pH exceeded 6.0. The LM from carcasses of RIS and RISEB lambs had lower (P < .01) glycogen and lactate concentrations in both regions than the LM of C lambs. Subjecting sheep to a single 6-h period of RIS was an effective animal model to induce the DCC. Failure of the epidural blockade to inhibit antemortem glycogen metabolism and formation of the DCC indicates that muscle contraction was not requisite to those processes in sheep.

Anesthesia, Epidural↗

PubMed1994

Serum hormones during the estrous cycle and estrous behavior in heifers after administration of propylthiouracil and thyroxine.

Two experiments were conducted to assess the characteristics of thyroid-stimulating hormone (TSH) during the estrous cycle and to examine the effects of experimentally altered thyroid status on estrous behavior and hormonal concentrations in heifers. In Exp. 1, normal profiles of luteinizing hormone (LH), follicle-stimulating hormone (FSH), and TSH were examined on days 2, 12, and 19 of the estrous cycle (day 0 = estrus) in six Holstein heifers. Baseline concentrations of LH were 1.5- to 2.1-fold higher on day 2 (P = .07) and day 19 (P < .01) than on day 12. Pulse frequency of LH was higher (P < .05) on days 12 and 19 than on day 2. For FSH, baseline concentrations were similar on all 3 d, but pulse frequency was higher (P < .05) on day 19 than on day 2 or day 12. Overall and baseline concentrations of TSH were similar on all 3 d. Pulse frequency of TSH was higher (P < .05) on day 12 than on day 19, but both were similar to that on day 2. In Exp. 2, secretion of TSH in Holstein heifers was altered by administering (i.v.; one-half of the daily dose given twice daily) either phosphate-buffered saline (SAL; n = 6), propylthiouracil (PTU; 20 mg/100 kg body weight [BW]; n = 6), or T4 (1 mg/100 kg BW; n = 5) from day 4 until the next estrus. Duration of estrous cycles during and after treatments, percentages of heifers exhibiting estrus, BW, and average daily gain were unaffected by treatment. Concentrations of TSH were higher (P < .05) in the afternoon than in the morning and higher (P = .06) in PTU heifers than in T4 heifers. Treatment with T4 during the treatment estrous cycle and for up to 6 d into the next estrous cycle increased (P < .01) concentrations of T4 and T3 compared to SAL and PTU. Treatment with PTU during the treatment cycle increased concentrations of T4 (P < .05) and TSH (P = .06) compared to SAL. We conclude that TSH secretion was pulsatile, demonstrated a diurnal change, and varied inconsistently during the estrous cycle. Altering thyroid hormones and TSH secretion in heifers seemed to have no effect on estrous behavior or estrous cycles.

Animals↗

PubMed1994

Serum hormones in response to estradiol and (or) progesterone in ovariectomized cows after thyroidectomy.

To evaluate the effect of gonadal steroid treatment and thyroidectomy on concentrations of gonadotropins and thyroid-stimulating hormone in the bovine, nonlactating Holstein cows were either thyroidectomized and ovariectomized (THYOVEX; n = 6) or ovariectomized only (OVEX; n = 4), and subsequently treated with no gonadal steroids (control), estradiol-17 beta (E2), progesterone (P4), or P4+E2 in a 2 x 4 factorial experiment. Averaged across steroid treatments, baseline concentrations of luteinizing hormone (LH; P < .05) and follicle-stimulating hormone (FSH; P < .10) were higher in THYOVEX cows than in OVEX cows. Pulse frequencies and amplitudes of LH and FSH did not differ between THYOVEX and OVEX cows. Secretion of TSH was pulsatile and all concentrations and pulsatile characteristics of TSH were increased (P < .05) in THYOVEX compared to OVEX cows. Treatment with E2 and P4 decreased (P < .05) baseline concentrations and magnitude of LH pulses, whereas P4+E2 increased (P < .01) pulse frequency of LH and FSH. Amplitude of LH and FSH pulses were not affected by treatment with either steroid. Treatment with P4+E2 decreased (P < .05) baseline concentrations of TSH, whereas pulse frequency, and magnitude and amplitude of TSH pulses were not altered by treatment with steroids. Mean concentrations of LH and FSH were similar during 48 hr after termination of E2 and P4+E2 treatments, but concentrations of TSH were higher (P = .06) after P4+E2 than after E2. Secretion of TSH showed a diurnal variation, with the lowest concentrations in the morning and highest in the afternoon. These results indicate that thyroidectomy influenced secretion of gonadotropins in OVEX cows.

Animals↗

PubMed1994

Peri-oestrous hormone profiles, embryonic survival and variation in embryonic development in gilts and primiparous sows.

The primary objective of this study was to determine whether embryo survival in gilts and primiparous sows is related to variations in the peri-oestrous profiles of oestradiol, progesterone and LH. A secondary objective of the present work was to compare embryo development and certain endocrine characteristics in gilts and primiparous sows. Sows (n = 6) and gilts (n = 6) were catheterized in the jugular vein on the day after weaning or on day 14 of the oestrous cycle, respectively. Additional females (one gilt and seven sows) were examined only for characteristics of embryonic development. Embryos were recovered on day 11.5-11.75 of gestation, and size and volume of individual embryos were recorded. Minimal differences were observed between sows and gilts for endocrine and embryo data. Embryo recovery was 71.38 +/- 4.77% based on the number of corpora lutea. However, endocrine differences were noted for pigs with high embryo survival (> 71% recovery) compared with those with low survival. Peak oestradiol concentration occurred closer (P < 0.05) to the onset of oestrus in pigs with high embryo survival than in pigs with low embryo survival (3.3 +/- 4.6 h after oestrus versus 13.0 +/- 5.5 h before oestrus) and peak LH concentration occurred later (P < 0.05) after the onset of oestrus for pigs with high embryo survival. Peak oestradiol concentration tended (P = 0.07) to be higher in pigs with low embryo survival (35.21 +/- 2.56 pg ml-1) compared with pigs with high embryo survival (28.17 +/- 2.14 pg ml-1).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1994

Estrus, ovulation, luteinizing hormone, and suckling-induced hormones in mastectomized cows with and without unrestricted presence of the calf.

Angus x Hereford multiparous cows were assigned to four treatments: 1) mastectomized+calf weaned at birth (MCW; n = 7); 2) mastectomized+calf presence restricted to noninguinal contact (MCR; n = 7); 3) mastectomized+unrestricted calf presence (MCP; n = 7); and 4) udder-intact cows+unrestricted calf presence (UICP; n = 8). Except for MCW cows, cow-calf pairs were penned together individually from parturition (d 0) until d 35 when calves were weaned. On d 7, calves in MCP and UICP treatments were separated overnight from their dams, and before and upon reunion, blood samples were collected from the cows to assess changes in oxytocin, cortisol, and prolactin. Calves in the MCP and UICP treatments attempted to or suckled their dams for a similar duration upon reunion, respectively. Concentrations of cortisol and percentage of change in oxytoxin and prolactin were increased (P < .05) for up to 12 min in MCP cows after reunion with their calves. Average concentrations of serum LH in samples collected on d 14, 21, 28, and 35 did not differ in noncyclic cows among treatments within day postpartum (except for greater [P < .05] LH in MCW cows on d 21). However, MCP cows had more (P < .05) LH pulses (d 21), greater (P < .05) variability in LH pulses (d 21), greater (P < .05) variability in LH concentrations, and greater (P < .05) average maximum concentrations of LH than UICP cows after d 14. Intervals to first ovulation were similar in MCW and MCR cows but shorter (P < .01) than those in MCP and UICP cows. Attempted suckling of mastectomized dams by their calves was associated with increased serum cortisol and percentage of increase in serum oxytocin and prolactin. Despite increased LH in MCP cows, intervals to first ovulation did not differ from those of UICP cows.

Animals↗

PubMed1994

Influence of treadmill exercise on pituitary-adrenal secretions, other blood constituents, and meat quality of sheep.

Whether lambs were used to evaluate the influence of treadmill exercise (TME) on physiological responses and meat quality. Lambs were exercised at either 5.6, 7.2, or 8.8 km/h on a 9 degrees incline for 10 min, followed by a 10-min walk at 4.0 km/h and 0 degrees incline, or were unexercised controls (C; n = 3/treatment). Heart rates were determined at -15, 1, 3, 6, 10, and 15 min relative to the onset of exercise. Blood was collected at 2.5-min intervals during and after exercise for determination of plasma concentrations of ACTH, cortisol, and lactate. In addition, blood collected during exercise was evaluated for hematocrit and for concentrations of glucose, hemoglobin, and total protein. Exercised lambs had greater (P < .01) heart rates than C lambs during and after exercise. Blood from TME lambs also had greater (P < .001) hematocrit percentages, total protein, and hemoglobin concentrations. Areas under the ACTH and cortisol response curves were greater (P < .001) for TME than for C lambs. Areas under glucose response curves were greater for all TME treatments (P < .001) than for C and greater (P < .001) for lambs exercised at 8.8 km/h than for lambs exercised at 5.6 km/h. Areas beneath lactate response curves were greater (P < .001) for lambs exercised at 8.8 km/h than for lambs exercised at 7.2 km/h and C lambs. Carcasses from lambs exercised at 5.6 km/h had lesser (P < .05) longissimus muscle (LM) glycogen concentrations at slaughter than carcasses from lambs exercised at either 7.2 or 8.8 km/h and C lambs.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenocorticotropic Hormone↗

PubMed1994

Function of the hypothalamic-pituitary-adrenal axis and the sympathetic nervous system in models of acute stress in domestic farm animals.

In response to stressors, the central nervous system of livestock (and other mammalian species) evokes physiological responses that ultimately result in activation of the hypothalamo-pituitary-adrenocortical (HPA) axis and the sympatho-adrenal axis. The responses of these major systems are presumed to have adaptive and homeostatic value during periods of stress. The major hormone regulating the synthesis and secretion of adrenal glucocorticoids is ACTH. In sheep, cattle, and pigs, both corticotropin-releasing hormone (CRH) and vasopressin (VP) participate in the regulation of secretion of ACTH, and the two peptides seem to interact to enhance that secretion. In cattle and pigs, CRH is the more potent peptide, whereas VP is the more potent in sheep. In addition to its better-known role in regulating pituitary function, CRH also may participate as a neurotransmitter acting centrally to enhance sympathetic activation of the adrenal medulla. Many experimental models of stress have been evaluated that reliably activate the HPA axis and the sympatho-adrenal medullary axis, and some of these model systems also reduce functions of cells of the immune system. Recent data support an important role of stressor-activation of the sympathetics rather than increased glucocorticoids per se in modulating some measures of immune function in response to stress. Thus, current dogma of glucocorticoids as the primary mediator of stressor-associated alteration in immune function of domestic livestock may require reevaluation.

Acute Disease↗