Biomedical subjects

J E Minton

Publications and source records attributed to J E Minton.

At least 55 records · Page 3Linked to original sources

PubMed1993

Influence of repeated restraint and isolation stress and electrolyte administration on pituitary-adrenal secretions, electrolytes, and other blood constituents of sheep.

Crossbred lambs (n = 24) were blocked by weight and assigned within blocks to four treatments applied in two replications of a 2 x 2 factorial arrangement. Main effects included no stress (NS) or three consecutive days of restraint and isolation stress (RIS) and treatment with either water (W) or an electrolyte (E) solution. Each lamb in the RIS treatment group was moved from its home stanchion to another room, isolated from visual and tactile contact with other lambs, and restrained for 6 h on three consecutive days. Lambs received either distilled W or E (320 mL) on each of the 3 d of stressor treatment. On the morning of the 3rd d of stressor treatment, blood samples were collected at 1-h intervals for 6 h for determination of concentrations of ACTH, cortisol, and lactate. Also, blood was collected at the conclusion of, and 18 h after, the termination of stressor treatment (at slaughter) to measure serum electrolyte concentrations and other blood constituents. Polynomial curves fit to plasma concentrations of ACTH, cortisol, and lactate data differed (P < .005) between RIS and NS lambs during the last 6-h stressor bout. Stressed lambs had lower (P < .05) serum calcium and alkaline phosphatase concentrations than did NS lambs. Serum glutamic oxaloacetic transaminase was increased (P < .05) 20- to 30-fold in RIS lambs. Restraint and isolation stress caused clear increases in plasma concentrations of ACTH, cortisol, lactate, and glutamic oxaloacetic transaminase but had minimal effects on serum electrolytes. Electrolyte treatment had no appreciable effect on pituitary-adrenal secretions or any other measured component of blood.

Adrenocorticotropic Hormone↗

PubMed1993

Influence of source and amount of dietary protein on performance, blood metabolites, and reproductive function of primiparous beef cows.

Forty Angus x Hereford 2-yr-old primiparous cows (358 kg) were used to determine the effects of source and amount of CP on performance, reproductive function, and metabolic status of suckled primiparous cows. A 2 x 2 factorial treatment arrangement was used; cows received either 100 or 150% of NRC recommendations for CP in diets that contained either soybean meal (low escape = L) or corn gluten meal/blood meal (high escape = H) as the principal supplemental protein source. Resulting treatments were 100-L, 100-H, 150-L, and 150-H. Cows were individually fed diets for 100 d or until they were observed to be in standing estrus. Diets were isoenergetic and limit-fed to meet NRC recommendations for NE, Ca, and P for 364-kg, 2-yr-old primiparous cows producing 4.5 kg of milk daily and gaining .23 kg/d. Increased CP tended (P = .09) to increase ADG in cows, but body condition score was unaffected. Increased CP and use of a CP source with higher potential for ruminal escape increased ADG in calves from d 0 to 97 (P = .002 and .04, respectively), which corresponded with numerical changes in milk production. Feeding high escape CP sources decreased plasma glucose and urea N (P = .04 and .0001, respectively). Increased CP tended (P = .12) to increase plasma glucose and increased (P = .0001) plasma urea N. Treatment had no effect on profiles of LH or progesterone. Although numerical differences in conception rate seemed large for 100-L compared with the remaining treatments, statistical significance was not detected.(ABSTRACT TRUNCATED AT 250 WORDS)

Animal Feed↗

PubMed1993

Adrenocorticotropic hormone and cortisol response to corticotropin-releasing factor and lysine vasopressin in pigs.

Two experiments were conducted to evaluate the ability of corticotropin-releasing factor (CRF) and lysine vasopressin (LVP) to stimulate the secretion of ACTH and cortisol in pigs. In Exp. 1, barrows were blocked by weight (average BW 97 +/- 1 kg) and received an i.v. bolus of 10 (n = 4), 50 (n = 4), or 100 (n = 3) micrograms of LVP. Samples of plasma were obtained at 10-min intervals for 2 h before and for 2 h after peptide treatment. The percentage of change in plasma concentration of ACTH (average of the concentration 1 h after LVP compared with the average of the 1 h before LVP) was greater (P < .001) for 100 micrograms (452.3 +/- 4.7%) than for 10 (81.5 +/- 5.7%) or 50 micrograms (233.6 +/- 11.3%). Furthermore, the ACTH response was greater (P < .001) to 50 micrograms than to 10 micrograms. The cortisol responses to treatment (average of the concentration 2 h after LVP compared to the average of the 2 h before LVP) were similar in pigs given 50 (132.8 +/- 5.3%) and 100 (123.2 +/- 2.4%) micrograms, but both were greater (P < .001) than the response to 10 micrograms (38.2 +/- 1.4%). In Exp. 2, a dose of LVP was chosen that provided a total mass of peptide similar to the lowest dose in Exp. 1, but this time the peptide was administered at .11 nmol/kg BW. This dose of LVP was chosen because it resulted in neither maximum ACTH nor cortisol secretion in Exp. 1.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenocorticotropic Hormone↗

PubMed1993

Ovarian follicular waves in dairy cows after administration of gonadotropin-releasing hormone at estrus.

A crossover design experiment was conducted to examine the effects of GnRH on hormonal concentrations and changes in ovarian structures of lactating dairy cows during the estrous cycle. Cows were assigned randomly to receive either 100 micrograms of GnRH or saline 12 h after estrus (d 0) was first observed. Ultrasonographic examinations of the ovaries performed daily throughout the estrous cycle detected either three (n = 7) or four (n = 6) follicular waves. Transient increases in FSH generally preceding the follicular wave containing the dominant (preovulatory) follicle, and the emergence of the dominant follicle before the subsequent estrus occurred later in GnRH-treated than in saline-treated cows with either three or four follicular waves. Day of emergence of dominant follicles within follicular waves was preceded 83% of the time by a transient increase in FSH and was followed consistently by increased serum estradiol-17 beta, which generally reached peak concentrations concomitant with the peak diameter of the dominant follicle. Although clearly defined pulses were detected in 19 out of 26 sampling periods in d 7 and 14, number of FSH pulses and percentage of cows with pulses of FSH were similar in GnRH-treated and saline-treated cows with three or four follicular waves. In conclusion, treatment of cows with GnRH 12 h after the onset of estrus delayed the appearance of the next ovulatory follicle in cows with either three or four follicular waves. Regardless of treatment, emergence of dominant follicles was preceded in most cases by a transient increase in FSH and followed consistently by increased estradiol-17 beta.

Animals↗

PubMed1992

Effect of light intensity on circadian profiles of melatonin, prolactin, ACTH, and cortisol in pigs.

Eleven crossbred barrows were housed in environmentally controlled rooms with an 8-h photoperiod. Pigs in one room received control illumination of 113 1x (CON; n = 6), and pigs in the other room received intense illumination of 1,783 1x (INT; n = 5) fluorescent light. Pigs were given at least 20 d of exposure to the environment before blood samples were taken every 3 h for 48 h. Data were analyzed by split-plot analysis of variance. Except for prolactin, no treatment x time interactions were noted for the hormone profiles evaluated (P greater than .10). Pigs in INT had greater (P less than .05) concentrations of prolactin in serum than pigs in CON at every sampling time. Concentrations of ACTH and cortisol in plasma were similar for INT (33.9 +/- 3.2 pg/mL of ACTH and 24.4 +/- 3.4 ng/mL of cortisol, respectively) and CON (34.9 +/- 3.0 pg/mL of ACTH and 31.3 +/- 3.1 ng/mL of cortisol, respectively). Within the INT treatment, serum melatonin concentrations were more than doubled (P less than .05) during darkness (66.8 +/- 9.3 pg/mL) compared with during light (30.4 +/- 9.3 pg/mL); however, within the CON treatment, concentrations during light and darkness did not differ (38.4 +/- 9.3 pg/mL and 42.9 +/- 9.3 pg/mL, respectively). Results indicate that light of greater intensity is required to entrain circadian rhythms of melatonin in serum of pigs. Furthermore, pigs may respond to bright light with greater secretion of prolactin, even under constant duration of photoperiod.

Adrenocorticotropic Hormone↗

PubMed1992

Repeated restraint and isolation stress alters adrenal and lymphocyte functions and some leukocyte differentiation antigens in lambs.

Lambs were used to evaluate the effect of repeated restraint and isolation stress (RIS) on secretion of cortisol, lymphocyte proliferative responses to mitogens, production of interleukin-2, and expression of leukocyte differentiation antigens. Differentiation antigens evaluated included cluster of differentiation antigens 2, 4, and 8 (CD2, CD4, and CD8, respectively); B cells; and major histocompatibility complex (MHC) class II, DQ, and DR. Lambs were assigned to either control (CON; n = 12) or to RIS treatment (n = 12) then were stanchioned in environmentally controlled rooms at 18 degrees C and constant light for 11 d before jugular vein catheters were inserted on d 0 of the experiment. On d 12, 13, and 14, lambs in the RIS treatment were removed to another location, restrained, and isolated from visual and tactile contact with other lambs for 6 h on each day. Following the 6-h stress treatment, lambs were returned to their home stanchions. The CON lambs remained in their stanchions. Samples of serum were obtained from all lambs, beginning before RIS (0 h) and at .5-h intervals until the completion of stress (6 h) on d 12 and 14. In addition, samples of whole blood were obtained at 0 and 6 h on d 12, 13, and 14 for evaluation of immune function characteristics. Fitted polynomial curves describing the cortisol response in RIS and CON lambs differed (P less than .005) on both d 12 and 14, reflecting the unmistakable increase in cortisol in response to the stressor.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1992

Effect of zeranol implants in ram and wether lambs on performance traits, carcass characteristics, and subprimal cut yields and distribution.

In two separate 2 x 2 factorial arrangements, 69 male, crossbred lambs were allotted randomly to the following treatments: 1) nonimplanted (NI) rams, 2) implanted (I) rams, 3) NI wethers, and 4) I wethers. In Trial 1, 36 lambs were allotted to treatment groups at birth (n = 9) and I lambs were implanted with 12 mg of zeranol between 1 and 3 d of age and again at weaning (average age of 62 d). Lambs were slaughtered at three time-constant end points of 78, 93, and 107 d on feed postweaning (average age of 155 d). Rams grew faster postweaning, were more efficient in their feed conversion, were heavier at slaughter, and had lower numerical yield grades than did wethers (P less than .05). Implanted lambs tended (P = .08) to grow faster and were (P less than .05) more efficient in their feed conversion than NI lambs. Rams produced heavier (P less than .05) trimmed subprimal shoulders, loins, and legs and had (P less than .05) a higher percentage of their carcass weight in the subprimal shoulder than did wethers. During Trial 2, NI rams (n = 8), I rams (n = 8), NI wethers (n = 8), and I wethers (n = 9) were allotted to treatment groups, and I lambs were implanted at average ages of 14, 55, and 98 d. After weaning, lambs were weighed every 14 d and were slaughtered 7 d after reaching a minimum weight of 50 kg (average age of 148 d).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1991

Free-running rhythms of adrenocorticotropic hormone (ACTH), cortisol and melatonin in pigs.

In the domestic pig, a circadian rhythm of plasma cortisol occurs, with greatest concentrations in the morning and lowest concentrations in the afternoon. However, photic entrainment of the rhythms of ACTH and melatonin in pigs have not been defined clearly. This experiment was designed to evaluate free-running rhythms of ACTH, cortisol and melatonin in pigs housed in constant light (LL) and constant darkness (DD). Twelve crossbred barrows, maintained under ambient photoperiod, were catheterized and tethered individually in two environmentally controlled rooms, one with LL and the other with DD. For animals in LL, fluorescent lights provided 202 +/- 15 (mean +/- standard deviation) lux of light at 65 cm above the floors. Incandescent nightlights equipped with 7 watt red bulbs provided 7 +/- 2 lux and were illuminated continuously in both rooms. Pigs were given at least 14 d exposure to LL and DD, then samples of plasma and serum were obtained at hourly intervals for 48 hr. Plasma was assayed for ACTH, and serum for cortisol and melatonin. Periodograms were constructed to analyze the data. For this type of analysis, a statistic, Qp, is calculated, and circadian periodicity is suggested if maximum Qp (Qp max) occurs at or near 24 hr. The period of the free-running rhythms (tau) at Qp max for ACTH, cortisol and melatonin for pigs in LL (23.80 +/- .01, 23.78 +/- .01, and 23.21 +/- .02 hr, respectively) did not differ significantly from those for pigs in DD (23.39 +/- .01, 23.20 +/- .01, and 22.55 +/- .02 hr, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenocorticotropic Hormone↗

PubMed1991

Removal of nocturnal secretion of melatonin fails to reduce antibody synthesis and interleukin-2 production of lambs.

Crossbred ewe and wether lambs were used to evaluate the effects of a normal, nocturnal elevation in the concentration of melatonin in the serum on immunological functions. The nocturnal elevation in melatonin was eliminated by exposing half the lambs to constant light (LL), whereas the remainder received a 12-h light, 12-h dark cycle (LD). Immune function was challenged by treating half the lambs in LL and half of the lambs in LD with dexamethasone (DEX; .04 mg/kg); the remainder of the lambs received only a saline vehicle (SAL). The resulting treatment combinations were designated LD+SAL (n = 5), LD+DEX (n = 5), LL+SAL (n = 5), and LL+DEX (n = 5). Lambs were stanchioned individually in environmental rooms; photoperiod treatments commenced on that day (d -14). Also on d -14, lambs were given 1 mg ovalbumin/lamb in adjuvant. Lambs were given a booster injection of .5 mg ovalbumin/lamb on d 0. Treatments with DEX and SAL also began on d 0 and were repeated every 48 h through d 14. Catheters were placed in the jugular vein of all lambs on d 12; samples of plasma and serum were collected hourly from 0800 on d 14 to 0800 on d 15; plasma was assayed for adrenocorticotropic hormone (ACTH) and serum was assayed for cortisol and melatonin. In addition, samples of serum obtained at 0800 on d 15 were used to evaluate antibody titers to ovalbumin. Samples of whole blood also were obtained at 0800 on d 15, and total and differential leukocyte numbers and production of interleukin-2 (IL-2) by lymphocytes were determined.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenocorticotropic Hormone↗

PubMed1991

Repeated restraint and isolation stress in lambs increases pituitary-adrenal secretions and reduces cell-mediated immunity.

Rambouillet crossbred ewe lambs were used to evaluate the effect of repeated restraint and isolation stress (RIS) on endocrinological and immunological functions. Lambs were blocked by weight and assigned to either RIS (n = 6) or to control (CON; n = 6) treatments. All lambs were tethered in environmentally controlled rooms at 22 degrees C with constant light and, at this time (d 0), were given 1 mg of ovalbumin in adjuvant. On d 12, catheters were placed nonsurgically into the jugular vein of all lambs, and they were reimmunized with .5 mg of ovalbumin in incomplete adjuvant. Each lamb in the RIS treatment group was removed from its home stanchion, isolated from visual and tactile (but not auditory and olfactory) contact with other lambs, and restrained for 6 h on d 14, 15, and 16. Lambs in CON treatment remained undisturbed in their home stanchions. Lymphocyte blastogenic function and production of interleukin-2 (IL-2) were assessed in samples of blood collected before and at the conclusion (0 and 6 h) of each of the three stress bouts. In addition, ACTH and cortisol secretion in response to RIS was evaluated in samples of plasma and serum collected at .5-h intervals on the first and last days of stress (d 14 and 16). Finally, antibody production in response to immunization against ovalbumin was assessed in samples of serum obtained 14 d after reimmunization on d 12 of the study. Polynomial curves fit to the ACTH and cortisol data differed (P less than .005) on both d 14 and 16 between RIS and CON treatments.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenocorticotropic Hormone↗

PubMed1991

Cell-mediated immune function in lambs chronically treated with dexamethasone.

Crossbred ewe and wether lambs were individually stanchioned in environmentally controlled rooms at 20 degrees C. On d 0, lambs were treated with .04 mg of dexamethasone (DEX; n = 10)/kg of BW or given an equal volume of saline vehicle (SAL; n = 10). Treatment was repeated every 48 h for 14 d. Samples of blood were obtained by puncture of the jugular vein on d 0 (before treatment), 2, 4, 7, 10, and 14. Total and differential leukocyte numbers, lymphocyte blastogenic responses to mitogens, and in vitro production of interleukin-2 (IL-2) were determined. No treatment x day interaction was noted for any of the experimental end points (P greater than .10); therefore, within-day comparisons between DEX- and SAL-treated lambs were not made. However, over all 14 d, DEX-treated lambs had increased (P less than .05) numbers of lymphocytes (6.5 +/- .4 vs 5.1 +/- .4 x 10(3) cells/microliters for SAL) and monocytes (.8 +/- .1 vs .6 +/- .1 x 10(3) cells/microliters for SAL), and these increases contributed to an increase (P less than .01) in total leukocytes (11.2 +/- .5 vs 9.1 +/- .5 x 10(3) cells/microliters for SAL). Lymphocyte blastogenic responses to mitogens were not affected by DEX treatment. Production of IL-2 was reduced (P less than .05) for DEX- (.90 +/- .12 units/ml) compared with SAL-treated lambs (1.27 +/- .13 units/ml). The data suggest that continued treatment of lambs with DEX may result in a modest reduction in production of IL-2, but mitogen-stimulated blastogenic responses of lymphocytes are not reduced by DEX treatment.

Animals↗

PubMed1991

Poor reproductive response of anestrous Suffolk ewes to ram exposure is not due to failure to secrete luteinizing hormone acutely.

Twenty Polypay-sired ewes (Group P) and 14 Suffolk ewes (Group S) were bled at 48-h intervals for 10 d beginning on April 6, 1989, and the serum was assayed for progesterone to determine which ewes were anestrous; 9/20 Group P ewes were anestrous, compared with 14/14 Group S ewes (P less than .001). Catheters were placed into the jugular vein of anestrous ewes from both breed groups (eight of Group P, seven of Group S), and samples of serum were collected at 12-min intervals for 4 h. Then, the ewes were exposed to mature, intact rams, and additional samples were taken at 12-min intervals for 4 h after ram exposure. The serum was later analyzed to determine the secretion of LH in response to ram introduction. After the acute bleeding period, all Group P and Group S ewes were commingled and exposed to a ram continuously for 42 d. Samples of serum were collected thrice weekly and analyzed for progesterone to monitor ovulatory response to ram introduction through the 42-d period. In addition, breeding activity and lambing data were recorded. When all Group P ewes were compared to Group S ewes, a greater proportion (P less than .001) of Group P ewes were mated (20/20 vs 3/13; one Group S ewe died during the 42-d mating period) by the end of the 42-d period and more (P less than .001) ewes lambed in the fall (17/20 Group P vs 2/13 Group S).(ABSTRACT TRUNCATED AT 250 WORDS)

Anestrus↗

PubMed1991

Influence of dietary energy on follicular development, serum gonadotropins, and first postpartum ovulation in suckled beef cows.

Twenty-eight Hereford x Angus cows (4 yr of age) were used to determine the effects of pre- and postpartum dietary energy on performance and reproductive function in suckled beef cows. The experiment was designed as a 2 x 2 factorial with cows receiving either 70 (L) or 150% (H) of NRC recommended level of dietary energy before and(or) after parturition, resulting in four treatment combinations (L-L, L-H, H-L, H-H). Prepartum diets were fed for approximately 110 d, and postpartum diets were fed until either 10 d after the second postpartum ovulation or 150 d postpartum for those cows that failed to ovulate. Cows receiving low compared with high levels of energy before calving lost more (P less than .01) weight, body condition, subcutaneous fat, and longissimus muscle area before parturition and had calves with lighter (P less than .01) birth weights. Cows receiving low compared with high levels of energy postpartum lost more (P less than .01) weight, body condition, and longissimus muscle area after parturition. Low levels of energy before and after parturition decreased (P less than .01) milk production and calf weight at 70 d of age. Rates of cervical and uterine involution were unaffected by dietary energy treatments. Cows receiving high levels of energy prepartum had increased (P less than .01) mean concentrations and pulse frequency of LH in serum after parturition, and cows receiving high levels of energy postpartum had increased (P less than .05) pulse frequency of LH. Low levels of energy postpartum decreased (P less than .01) appearance rate of small (5.0 to 7.9 mm) and large (greater than or equal to 10 mm) follicles, and low levels of energy prepartum decreased (P less than .02) appearance rate of large follicles based on transrectal ultrasonography. Cows receiving high levels of energy prepartum had shorter (P less than .02) intervals from parturition to ovulation, and a higher (P less than .01) percentage of the cows that received high levels of energy postpartum ovulated by 150 d postpartum. In summary, prepartum level of dietary energy influenced birth weight and weight gain of calves, milk production, concentrations and pulse frequency of LH in serum, appearance rate of large follicles, and the interval to first ovulation. Postpartum level of dietary energy influenced milk production, weight gain of calves, pulse frequency of LH, appearance rate of small and large follicles, and the percentage of cows that ovulated after parturition.

Adipose Tissue↗

PubMed1991

First postpartum luteal function in dairy cows after ovulation induced by progestogen and gonadotropin-releasing hormone.

The objective was to determine the effects of progestogen treatment on the lifespan of the first corpus luteum induced by GnRH in periparturient-milked cows. Dairy cows (n = 55) were assigned randomly following normal parturitions to receive either a progestogen implant (6 mg of norgestomet) or a blank implant (control) for 6 d beginning 2 to 5 d after calving. Fifty micrograms of GnRH were administered i.m. 72 h after implant removal to induce ovulation. Concentrations of LH and FSH in serum from 24 to 30 h and from 66 to 72 h after implant removal were similar among treatments. The magnitude of LH released after GnRH injection was higher in progestogen-treated cows (7.6 +/- .9 ng/ml) than in controls (5.3 +/- .9 ng/ml). Concentrations of estradiol in serum from the beginning of the implant period until 3 d after GnRH injection were higher in cows receiving progestogen (9.1 +/- 1.7 pg/ml) than in controls (5.6 +/- 1.7 pg/ml). The proportion of cows that responded to GnRH (elevated concentrations of progesterone in serum greater than .5 ng/ml within 3 to 5 d after injection) tended to be higher in cows receiving progestogen (24 of 28) than in control cows (19 of 27). By definition, interval to first ovulation after GnRH injection was shorter in cows responding to GnRH (3.8 +/- .5 d) than in those failing to respond (20.2 +/- .9 d).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1990

Role of photorefractoriness in onset of anoestrus in Rambouillet x Dorset ewes.

An experiment was conducted to determine the extent to which refractoriness to short daylength is involved in the onset of anoestrus in Rambouillet x Dorset ewes. Ovary-intact ewes (N = 36) were exposed to ambient photoperiod (C) or to a photoperiod equal to the winter solstice (S) beginning on 21 December 1986 and continuing until 21 April 1987. Samples of serum were obtained at weekly intervals and assayed for progesterone to assess ovarian activity, and for prolactin to assess response to photoperiod treatment. In addition, ovariectomized (ovx) ewes with implants containing oestradiol were housed with C(Covx) and S (Sovx) ewes (N = 4 per treatment). The concentration of LH was determined in serum collected biweekly from all ovariectomized ewes throughout the treatment period as an index of reproductive status. Time-trends for concentrations of LH differed (P less than 0.005) for ewes in Groups Covx and Sovx with LH decreasing on the order of about 8-fold in Group Covx through the treatment period, while not changing appreciably in Group Sovx. Intact ewes in both treatments began to become anoestrous by the 9th week of treatment (about the last week in February). However, fewer Group S than Group C ewes were anoestrous at 13 and 14 weeks of treatment (P = 0.09). Time-trends for concentrations of prolactin also differed for the Group C and S ewes (P less than 0.005), probably reflecting the divergence in duration of photoperiod between the two treatments by the end of the study.(ABSTRACT TRUNCATED AT 250 WORDS)

Anestrus↗

PubMed1990

Effect of acute stressors on endocrinological and immunological functions in lambs.

Lambs were used to evaluate the effect of acute heat stress (HS) or restraint and isolation stress (RIS) on endocrinological and immunological functions. In Exp. 1, lambs were exposed to HS (35 degrees C) and control lambs (CN) were exposed to 21 degrees C for 24 h in two replicates (n = 8 lambs total per treatment). Samples of serum were obtained at frequent intervals for evaluation of cortisol; whole blood was obtained for total and differential leukocyte numbers and lymphocyte blastogenic function. The time-trends for cortisol between HS and CN lambs were different following treatment (P less than .005), but neither leukocyte numbers nor lymphocyte blastogenesis in response to mitogens were affected by acute exposure to the elevated ambient temperature. In Exp. 2, lambs (n = 6 per treatment) were given a 6-h RIS treatment and control lambs remained in their home stanchions (CON). Plasma and serum were obtained frequently during treatment and continued until 24 h after the onset of treatment. Plasma was evaluated for adrenocorticotropic hormone (ACTH) and serum was assayed for cortisol. Samples of whole blood also were obtained before and at 6, 12 and 24 h after the onset of treatment for determination of total and differential leukocyte numbers and lymphocyte blastogenic responses to mitogens. Both ACTH and cortisol were elevated in response to RIS; the profiles of these hormones over the 24-h bleeding period differed for RIS and CON lambs (P less than .001).(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenocorticotropic Hormone↗

PubMed1990

Effect of cranial sympathectomy on circadian rhythms of cortisol, adrenocorticotropic hormone and melatonin in boars.

Following weaning at 24 +/- 1 d of age, crossbred boars were subjected to removal of the cranial cervical ganglia (GX, n = 8) or sham surgery (SHAM, n = 8). At 213 +/- 1 d of age, a catheter was inserted into a jugular vein or vena cava, and all boars were housed in environmentally controlled rooms at 22 degrees C with an equatorial photoperiod. After 2 wk of exposure to this photic environment, samples of plasma and serum were collected at hourly intervals for 24 h. The plasma was assayed for adrenocorticotropic hormone (ACTH) and the serum was assayed for cortisol and melatonin by RIA. The time-trends for all three hormones were described by regression models, which were tested for heterogeneity of regression between SHAM and GX treatments. The circadian rhythm of cortisol in serum was similar for SHAM and GX treatments. The profiles of ACTH were also similar between the two treatments, but circadian changes in concentrations of ACTH paralleling those of cortisol were not evident in either treatment. Overall, concentrations of ACTH were reduced (P = .06) for GX boars compared to SHAM boars. The time-trends of melatonin in serum differed (P less than .001) for GX and SHAM treatments, with a nocturnal rise in melatonin evident in some SHAM boars but not in GX animals. Four SHAM boars had profiles of melatonin that obviously entrained to the light-dark cycle. None of the boars in GX treatment had elevated concentrations of melatonin in serum during the dark period, relative to concentrations during the light.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenocorticotropic Hormone↗

PubMed1990

Effects of isoenergetic infusions of propionate and glucose on portal-drained visceral nutrient flux and concentrations of hormones in lambs maintained by total intragastric infusion.

Three lambs were used in a repeated Latin square design to determine the influence of isoenergetic infusions of propionate or glucose on portal-drained visceral flux (PDV) of nutrients and concentrations of insulin, glucagon, growth hormone and prolactin. Lambs were fitted with appropriate catheters for blood sampling and maintained on total intragastric infusion of nutrients. Basal VFA, casein, mineral and vitamin infusions (isocaloric and isonitrogenous) were supplemented with an additional 22 +/- .5 kcal/h from propionate, glucose or a combination of propionate plus glucose. Ruminal fluid proportion and arterial blood concentration and PDV flux of propionate increased (P less than .10) by 17 mol/100 mol, .02 mM and 40 mmol/h, respectively, with infusion of an additional 61 mmol/h of propionate. Regression equations predicted that, on a net basis, 67% of ruminally infused propionate and 43% of abomasally infused glucose appeared in portal blood. Arterial L-lactate, beta-hydroxybutyrate and acetate concentrations, and beta-hydroxybutyrate flux were increased (P less than .10) by .34 mM, .20 mM, .50 mM and 4.2 mmol/h, respectively, with infusion of 33 mmol/h of added glucose. Net utilization of glucose by the PDV was approximately 4.4 mmol/h when no glucose was infused. Increased infusion of propionate resulted in a 22.2-micrograms/h increase in PDV flux of insulin (P less than .08) but had no effect on arterial insulin, glucagon and prolactin concentrations (P greater than .10). Arterial growth hormone increased by 3.8 ng/ml with increasing glucose infusion (P less than .08).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗