Biomedical subjects

T H Elsasser

Publications and source records attributed to T H Elsasser.

At least 73 records · Page 4Linked to original sources

PubMed1996

Effects of Synovex-S and recombinant bovine growth hormone (Somavubove) on growth responses of steers: I. Performance and composition of gain.

The influence of Synovex-S (SYN) ear implant (200 mg progesterone and 20 mg estradiol benzoate) and Somavubove (SbV) recombinant bovine growth hormone (.1 mg/kg BW i.m., daily) on live animal performance, tissue growth, and the partitioning of energy gain was determined using a slaughter-balance protocol with 25 young MARC II x (Angus-Hereford crossbred) beef steers (initial BW 182 +/- 1.8 kg). Following 21 d of adjustment to individual pens and to a diet of 80% concentrate and 20% corn-grass (1:1) silages, five groups of five steers per group were assigned to initial slaughter or a 2 x 2 factorial arrangement of treatments of CTL (no implant + daily placebo i.m. injection of bicarbonate-saline), SYN (implant + placebo), SbV, or SYN + SbV and slaughtered at 56 d on treatment. Steers were fed (per kilogram BW.75 daily) 20 g of CP and 252 Kcal of ME and consumed 5.5 +/- .07 kg/d DM across treatments. Empty body and carcass gains were affected (SYN, P < .01; SbV, P < .01) by treatments (CTL, SYN, SbV, and SYN + SbV: 1.26, 1.43, 1.63, 1.78 kg/d, SEM = .05, and .78, .97, .97, 1.08 kg/d, SEM = .04, respectively). Noncarcass gain was .45, .48, .60, and .60 kg/d (SEM = .03; SbV, P < .01). For empty body, both protein and water gains were greater for SYN-implanted steers (P < .05) than for steers not implanted and for SbV-injected steers (P < .01) than for placebo-injected steers. Treatments did not influence the efficiency of energy gain. The proportional amount of energy deposited as protein was greater (P < .01) for SbV-injected steers than for placebo-injected steers. The proportional amount of protein deposited was not influenced by SYN (P > .10); however, means were numerically greater for SYN-implanted steers than for steers not implanted, the largest mean being for the SYN + SbV treatment group. Somavubove increased (P < .01) the efficiency of energy deposited as protein in both the empty body and carcass compared with steers not receiving SbV. Efficiency of energy deposited as protein in the empty body tended to be greater (P < .10) for SYN-implanted steers than for steers not implanted. The efficiency with which total feed energy was deposited as protein in empty body was 10% greater for the SYN group than for the CTL group, 21% greater for the SbV group than for the CTL group, and 37% greater for the combined SYN + SbV treatment than for the CTL group. The data from this study are interpreted to indicate that SYN and SbV act in an additive manner to improve growth and protein deposition in young growing steers.

Animals↗

PubMed1996

Effects of Synovex-S and recombinant bovine growth hormone (Somavubove) on growth responses of steers: II. Muscle morphology and proximate composition of muscles.

Twenty crossbred beef steers (initial BW 182 +/- 1.8 kg) were used in a 2 x 2 factorial to determine the effects of implantation with Synovex-S (SYN; 20 mg 17-beta estradiol benzoate + 200 mg progesterone, ear implant) and administration of recombinant bovine growth hormone (Somavubove SbV, .1 mg.kgBW-1.d-1, i.m.) on the morphology of six muscles (longissimus, psoas major, supraspinatus, triceps brachii, semitendinosus, rectus femoris) of growing steers. Implantation with SYN decreased the percentage distribution of FOG fibers and increased FG fibers in the supraspinatus and rectus femoris muscles (P < .05). Steers treated with SYN had a larger area of SO and FG fibers in the psoas major muscle (P < .05). The administration of SbV decreased the percentage distribution of FOG fibers and increased FG fibers in the rectus femoris muscle (P < .05). Steers administered SbV had larger SO, FOG, and FG fibers in the psoas major muscle and SO fibers in the supraspinatus and semitendinosus muscles (P < .05). The combined administration of SYN and SbV had minimal, if any, effect on the percentage distribution of fiber types (P > .05) but increased (P < .05) the fiber areas of all muscles (18.5 to 54.8%) except the rectus femoris (P > .05). Proximate composition of the muscles was generally not affected (P > .05) by any of the treatments. The only observations were decreases in fat content for psoas major and rectus femoris muscles as a result of the combined administration of SYN and SbV. These results indicate that both growth-promoting agents, SYN and SbV, have potential to increase muscle fiber size, but muscles respond differently to the administrations of SYN and SbV. However, when SYN and SbV are administered in combination, the combined effects result in an additive increase in muscle fiber hypertrophic response.

Animals↗

PubMed1996

Effects of supplemental chromium on production of cytokines by mitogen-stimulated bovine peripheral blood mononuclear cells.

This study determined whether supplementing the diets of dairy cows during the peripartum period with organic trivalent Cr influenced the capacity of their peripheral blood mononuclear cells to produce activation cytokines in response to stimulation with mitogens in vitro. Nine cows were fed 0.5 ppm of Cr/d per cow from 6 wk prepartum to 16 wk postpartum; 10 other periparturient cows served as unsupplemented controls. Mononuclear leukocytes, enriched from peripheral blood during wk 0, 2, 4, and 6 of lactation, were cultured with or without the T-lymphocyte mitogen, concanavalin A. Culture supernatants, harvested at 24, 48, or 72 h, were assayed for interleukin-2, interferon-gamma, and tumor necrosis factor-alpha. The cytokines were barely detectable in the supernatants from the unstimulated cultures, but supernatants from mitogen-stimulated cultures contained higher concentrations of each cytokine. For cows fed Cr, concentrations of all three cytokines in the culture supernatants of the mitogen-stimulated mononuclear cells decreased significantly relative to values for unsupplemented cows, particularly around peak lactation for the 24- and 48-h cultures. Theses results extended our previous observations and supported the hypothesis that organic Cr is immunomodulatory in high producing cows.

Animals↗

PubMed1995

Endotoxin infusion in anesthetized sheep is associated with intrapulmonary sequestration of leukocytes that immunohistochemically express tumor necrosis factor-alpha.

Plasma levels of tumor necrosis factor-alpha (TNF-alpha) peak between 2 and 4 h during a 12-h continuous infusion of endotoxin in awake sheep. We hypothesized that a source of this TNF-alpha is the pool of leukocytes that accumulate in the pulmonary circulation. To test this hypothesis, we physiologically monitored six anesthetized sheep during baseline and 4-h endotoxin infusion periods (10 ng/kg x min). We obtained open-lung biopsies at baseline and at 20 min and 2 and 4 h during the endotoxin infusion period for immunohistochemical localization of TNF-alpha. The plasma concentration of TNF-alpha increased from an average baseline concentration of 0.06 +/- 0.03 ng/ml (mean +/- SD) to a peak of 1.40 +/- 0.28 ng/ml at 2 h of the endotoxin infusion. We observed increased cytoplasmic TNF-alpha immunoreactivity in situ among neutrophils and intravascular mononuclear phagocytes during the endotoxin infusion compared with baseline. Also, the number of immunopositive leukocytes increased in the pulmonary circulation during the continuous infusion of endotoxin. We conclude that TNF-alpha-producing leukocytes accumulate in the pulmonary circulation during endotoxemia. These cells probably contribute to both the rise in the circulating levels of TNF-alpha and the development of acute lung injury.

Anesthesia↗

PubMed1995

Immunomodulatory activity of blood serum from chromium-supplemented periparturient dairy cows.

Our previous research showed enhanced immune responses, including mitogen-induced blastogenesis of peripheral blood mononuclear cells from feedlot calves and periparturient dairy cows supplemented with dietary chromium (Cr). The objective of the present study were to test whether blood sera from Cr-supplemented periparturient cows contained immunomodulatory activity for mitogen-stimulated peripheral blood mononuclear cells and, if so, to determine if this activity was explicable by differences in blood profiles of some glucose-regulating hormones (insulin, cortisol, growth hormone, insulin-like growth factor I, and tumor necrosis factor-alpha) between Cr-supplemented and unsupplemented (control) animals. Blood sera from ten unsupplemented cows and nine Cr-supplemented cows (0.5 ppm day-1) were collected weekly from 2 weeks before to 6 weeks after parturition, and were used to supplement (1, 10, and 20% vol/vol) culture medium supporting concanavalin A (Con A) stimulated mononuclear cells enriched from blood of four nulliparous donor cows. Hormone concentrations were determined using radioimmunoassays. Con A-induced blastogenesis was enhanced when 1, 10, and 20% sera from Cr-supplemented cows was added to the mononuclear cell cultures, and this was particularly evident around parturition. Conversely, peripartum sera from unsupplemented cows depressed Con A-induced blastogenesis. Except for a marginal rise in blood cortisol 2-4 weeks after parturition, no significant effects of Cr supplementation on other hormones (insulin, growth hormone, insulin-like growth factor I, tumor necrosis factor-alpha) were observed. These observations suggest that factors in peripheral blood serum from Cr-supplemented cows, other than absolute concentrations of the glucose-regulating hormones studied, modulate Con A-induced blastogenesis of mononuclear leukocytes.

Adjuvants, Immunologic↗

PubMed1995

Endotoxin administration decreases plasma insulin-like growth factor (IGF)-I and IGF-binding protein-2 in Angus x Hereford steers independent of changes in nutritional intake.

Endotoxemia and sepsis cause severe shifts in metabolism towards catabolic events. The objective of the research was to determine whether endotoxin administration changes plasma concentrations of IGF-I and IGF-binding protein-2 (IGFBP-2) in Angus x Hereford steers. In Experiment 1, mean feed intake in endotoxin-treated steers (n = 6) decreased 60% within the first 24 h after endotoxin and averaged, for the duration of the 96 h test period, an intake 35.5% lower than the mean ad libitum intake recorded prior to endotoxin. Plasma concentrations of IGF-I averaged 182 ng/ml in steers before endotoxin (E. coli, 055:B5, 0.2 micrograms/kg, i.v. bolus) and decreased an average of 24.2% at 24 to 96 h after endotoxin. In Experiment 2, a paired feeding strategy was used to determine whether the reduced feed intake was a significant factor in changing plasma concentrations of IGF-I and IGFBP-2 after endotoxin challenge. Steers were divided into endotoxin (0.2 micrograms/kg, i.v., n = 6) or control (saline, i.v., n = 3) treatments. Each of three endotoxin-treated steers was paired to a specific control. In this fashion, the adjusted feed intake of each endotoxin-treated steer was fed to it's paired control every 24 h through 96 h after endotoxin.(ABSTRACT TRUNCATED AT 250 WORDS)

Animal Nutritional Physiological Phenomena↗

PubMed1995

Adrenal responses of Angus x Hereford cattle to the stress of weaning.

To test adrenal responsiveness of beef cattle to stress, plasma norepinephrine, epinephrine, and cortisol responses of Angus x Hereford cattle to weaning were measured in blood samples taken from 1) eight cows and their 4- to 6-mo-old calves before and after separation and, the following day, before and after being reunited and 2) an equal number of control animals. After separation and before they were reunited, dams were returned to their original pen and calves to an adjacent pen. Experimental trials were conducted every 2 wk and included two cow/calf pairs per trial. Norepinephrine concentrations tended to increase in calves after separation, were increased (+82 pg/mL, P < .01) on the 2nd d before animals were reunited, and decreased (-88 pg/mL, P < .01) after animals were reunited. Epinephrine concentrations tended to increase in calves after separation, were increased in calves (+128 pg/mL, P < .001) and dams (+104 pg/mL, P < .001) on the 2nd d before animals were reunited, and decreased after calves (-162 pg/mL, P < .001) and dams (-101 pg/ml, P < .001) were reunited. There were no significant effects of time on catecholamine concentrations for control animals. Cortisol concentrations for treated and control animals tended to increase in sequential samples each day; however, the increases were small (approximately 1 ng/mL) and concentrations remained low (> 5 ng/mL). In conclusion, peripheral catecholamine concentrations in beef calves and epinephrine concentrations in dams increased in response to stress associated with weaning and separation.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenal Glands↗

PubMed1994

Recombinant bovine somatotropin blunts plasma tumor necrosis factor-alpha, cortisol, and thromboxane-B2 responses to endotoxin in vivo.

In vivo studies determined the effects of recombinant bovine somatotropin (bST; sometribove) administration (0.1 mg/kg.day, im) to calves on the increases in plasma immunoreactive tumor necrosis factor-alpha (TNF alpha), prostacyclin [6-keto-prostaglandin F1 alpha (6KP)], thromboxane-B2 (TXB), and cortisol (C) that occurred after endotoxin challenge (ET). Two ETs were administered 5 days apart to test the effect of bST on the natural attenuation of hormone and cytokine responses that occurs after repeated challenge with endotoxin. Calves (n = 6) were treated with bST for 5 days. On day 6, the first ET was administered (Escherichia coli; 055:B5; 0.2 microgram/kg, i.v.). Blood was sampled before and hourly after ET through 6 h. For the next 4 days, bST injections continued, and ET was repeated 1 day later. Six additional calves were treated with bicarbonate buffer as contemporary controls for the bST and were similarly challenged with endotoxin. Plasma TNF alpha, C, 6KP, and TXB were significantly increased after each ET. The increases in TNF alpha, C, and TXB were blunted after the second Et compared to those after the first in both untreated and bST-treated animals. The increases in plasma TNF alpha and C and peak plasma TXB and TXB/6KP ratios were smaller in bST-treated than in untreated after the first ET. TNF alpha receptor binding was studied in hepatic microsomal fractions from three bST-treated and three untreated calves. Microsomal fractions from bST-treated calves bound 40% less TNF alpha (5.97 vs. 9.96 pmol/mg) than similar fractions from controls. The data indicate that bST decreases TNF alpha, TXB, and C responses to ET and reduces the TNF alpha-binding capacity of hepatic membranes, suggesting a multiplicity of sites where bST might affect the physiological response to endotoxin.

6-Ketoprostaglandin F1 alpha↗

PubMed1993

Endotoxemia in pregnant cows: Comparisons of maternal and fetal effects utilizing the chronically catheterized fetus.

We utilized the chronically catheterized bovine fetus to compare maternal and fetal responses to maternal lipopolysaccharide (LPS) infusion. Our hypothesis was that LPS-induced abortion was primarily a maternal luteolytic event with minimal transplacental fetal exposure. Fetal tibial arteries, amniotic, allantoic cavities and maternal carotid arteries were catheterized. Three cows had patent catheters with viable fetuses (190 to 200 days of gestation) 1 week after operation and were included in the study. Following a 2-day maternal and fetal baseline, 0.5 mug Salmonella typhimurium LPS/kg was infused into a maternal jugular vein over a 2-hour period. Maternal and fetal responses were monitored clinically, biochemically and hormonally. The maternal response consisted of marked increases in plasma prostaglandin F(2alpha) metabolite (PGFM), tumor necrosis factor (TNF), ACTH and cortisol with a dramatic maternal leucopenia within 2 hours. Progesterone concentrations decreased within 7 hours (P<0.05). The LPS was rapidly cleared from maternal circulation and no transplacental exposure was detected in the fetuses. Fetal responses to maternal endotoxemia consisted of increased ACTH and cortisol concentrations with delayed increases in PGE(2); TNF did not change in fetal fluids following maternal endotoxemia. There was a fetal leucocytosis within 2 hours. The results indicate that the fetus does not appear to play a major role in the pathogenesis of LPS-induced abortions. However, the role of maternal TNF in endotoxin abortion requires further study.

Journal Article↗

PubMed1993

Immune responses of growing beef steers treated with estrogen/progesterone implants or insulin injections.

Five Angus x Hereford steers were assigned to each of three 77-d treatments, controls (daily placebo injections), daily insulin injections (0.45 mg kg-1 BW.75), or single Synovex-S ear implant (20 mg 17 beta-estradiol benzoate, 200 mg progesterone), to determine whether these hormonal manipulations were immunomodulatory. All steers were immunized with ovalbumin (OVA) on days 18 and 46 of the treatment period. Immune responses monitored were in vitro blastogenic responses of peripheral blood mononuclear cells (PBMC) to mitogens (con A and PHA) and antigen (OVA), in vivo antibody responses to OVA, flow cytometric analysis of percentages of CD2+, CD4+, and CD8+ PBMC, and blood leukocyte counts. Insulin treatment caused elevations (P < .05) in PHA-stimulated responses of PBMC, in the magnitude of peak blastogenic response to OVA immunization, and in total leukocyte counts and the ratio of CD4+/CD8+ cells in peripheral blood. However, insulin treatment was also associated with slightly decreased (P < .05) anti-OVA antibody responses. Synovex-S increased (P < .05) spontaneous blastogenic activity of cultured PBMC, but lacked consistent effects on mitogen-stimulated activity, on leukocyte counts, and on the ratio of CD4+/CD8+ cells in peripheral blood. Augmenting (P < .05) effects of Synovex-S on OVA-specific blastogenesis and on antibody responses were, however, consistent. Percentages of CD2+ and CD4+ PBMC, and responsiveness of PBMC to con A were not affected by treatments. In summary, this study showed statistically-significant specific immunomodulatory effects of insulin and Synovex-S in growing beef steers, but mechanisms of action and practical implications of these effects with respect to disease resistance required clarification.

Analysis of Variance↗

PubMed1993

Relationships between the thyroid and somatotropic axes in steers. II: Effects of thyroid status on plasma concentrations of insulin-like growth factor I (IGF-I) and the IGF-I response to growth hormone.

Three studies assessed the effect of thyroid status on regulation of plasma IGF-I in cattle. First, four Angus-Hereford steers (av wt 345 kg) were fed 4 mg/d propylthiouracil daily for 35 d. With continued feeding of PTU steers were sequentially injected with thyroxine (T4, 5 mg/d, IM for 5 d) followed by triiodothyronine (T3, 2 mg/d, IM for 5 d). An injection of bovine pituitary growth hormone (GH, 0.1 mg/kg, IM) was given to each steer on day 35 of PTU, day 5 of T4 and again on day 5 of T3. PTU alone increased plasma thyroid stimulating hormone (TSH), decreased plasma T4 and T3 but had no influence on IGF-I. T3, but not T4, lowered plasma TSH, IGF-I and the IGF-I response to GH (P < .05). Next, twelve bull calves (av wht 167 kg) were divided equally into two groups. A control group was injected daily for five d with buffered saline; the experimental group was concurrently treated with T3 (5 mg/d, sc) for five d. Beginning the sixth day, all calves were injected with GH (0.1 mg/kg, IM daily) for three d with the respective buffer or T3 treatments continuing. Plasma IGF-I was depressed 29% by T3. The incremental area under the three-d response curve was less (P < .03) in T3 cattle. A growth trial was conducted in which twenty-four Angus x Hereford steers were injected daily with T3 (2 mg/kg, bi-daily x 56 d) or implanted with Synovex-S (S) in a 2 x 2 factorial arrangement. Synovex increased empty body protein gain (EBPG) and plasma IGF-I 15.5 and 27.9% (P < .01), respectively; T3 decreased EBPG and plasma IGF-I 13.9 and 15.1% (P < .07), respectively, in steers which maintained suppression in plasma TSH. The data support the conclusion that elevated T3 decreases plasma IGF-I, in part, through a diminished GH-responsiveness and anabolic treatments such as S can reverse the effects of excess T3.

Animals↗

PubMed1993

Effect of endotoxin on pituitary hormone secretion in sheep.

Endotoxin, a potent stimulator of the immune system and an important mediator in the pathophysiology of septic shock, has been shown to alter the release of certain hormones following its systemic administration. The purpose of this study was to determine the effects of endotoxin on pituitary hormone secretion both in vivo and in vitro in sheep, with emphasis placed on its effects on growth hormone (GH) release. Endotoxin (400 ng/kg i.v.) increased plasma GH, adrenocorticotropic hormone (ACTH), cortisol and prolactin, while it decreased luteinizing hormone (LH) pulse frequency (p < 0.05). Plasma levels of tumor necrosis factor, a major mediator of endotoxin effects, also increased following endotoxin administration. Endotoxin did not affect the GH response to human GH-releasing hormone. In vitro studies evaluated the effect of endotoxin to alter GH secretion from dispersed sheep anterior pituitary cells at dosages of 1, 10 and 50 micrograms/ml, with samples collected at 4, 8 and 24 h. Endotoxin increased pituitary GH secretion at 24 h for 1 microgram/ml (p < 0.05) and at all time periods for 10 and 50 micrograms/ml (p < 0.05). It also led to an increased release of ACTH and LH in vitro. The results of this study demonstrate the ability of endotoxin to alter pituitary hormone secretion both in vivo and in vitro in sheep, suggesting a direct effect of endotoxin on the pituitary gland.

Adrenocorticotropic Hormone↗

PubMed1992

Relationships between the thyroid and somatotropic axes in steers. I: Effects of propylthiouracil-induced hypothyroidism on growth hormone, thyroid stimulating hormone and insulin-like growth factor I.

The effects of propylthiouracil (PTU)-induced thyroid hormone imbalance on GH, TSH and IGF-I status in cattle were examined. In the first study, four crossbred steers (avg wt 350 kg) were fed a diet dressed with PTU (0, 1, 2 or 4 mg/kg/d BW) in a Latin square design with four 35-d periods. On day 29 in each period, steers were challenged with an intrajugular bolus of thyrotropin releasing hormone (TRH, 1.0 microgram/kg). Blood samples were obtained to assess the change in plasma GH and TSH as affected by PTU. Plasma IGF-I was measured from blood samples obtained before and after (every 6 hr for 24 hr) intramuscular injection of bovine GH (0.1 mg/kg, day 31). Doses of 1 and 2 mg/kg PTU increased plasma T4 (P < .01). At 4 mg/kg, PTU depressed T4 concentrations to 30% of control (P < .01). Plasma T3 linearly decreased with increasing doses of PTU (P < .01). Plasma TSH increased when PTU was fed at 4 mg/kg (P < .05) while the TSH response to TRH declined with increasing PTU (P < .02). Neither basal nor TRH-stimulated plasma concentration of GH was affected by PTU; the IGF-I response to GH tended to increase at the 1 and 2 mg/kg PTU (P < .01). In a second study 24 crossbred steers were fed PTU (1.5 mg/kg) for 119 d in a 2 x 2 factorial design with implantation of the steroid growth effector, Synovex-S (200 mg progesterone + 20 mg estradiol), as the other main effect. Basal plasma GH and IGF-I were not affected by PTU treatment. Synovex increased plasma concentration (P < .01) of IGF-I without an effect on plasma GH. The data suggest that mild changes in thyroid status associated with PTU affects regulation of T3, T4 and TSH more than GH or IGF-I in steers.

Animals↗

PubMed1992

Influence of thyroid status regulation and Synovex-S implants on growth performance and tissue gain in beef steers.

The separate and combined effects of Synovex-S (SYN) ear implants and thyroxine (T4)-5'-monodeiodinase inhibition (Trial 1) and T3 injection to create a mild elevation in circulating T3 concentrations (Trial 2) on BW gain and composition of gain were studied. Trial 1 used 24, 285-kg Angus steers in two experimental phases. Low-level feeding of propylthiouracil (PTU, 1.5 mg/kg BW daily) was used to achieve inhibition of T4-5'-monodeiodinase activity (TMA). Twelve steers received neither treatment (control) and 12 received SYN+PTU (hypothesized to maximize weight gain) from 0 to 56 d (phase 1) in a single factor treatment comparison. Subsequently, PTU was fed to six control steers and not fed to six of the original SYN+PTU steers from 56 to 175 d (phase 2) in a 2 x 2 arrangement of treatments. Trial 2 used 24, 302-kg Angus-Hereford steers. Treatments were without or with SYN and without or with sc injections of T3 in polyethylene glycol (2 micrograms/kg BW every 48 hr) in a 2 x 2 factorial arrangement of treatments. In both trials, all steers were individually fed a diet of a corn-based concentrate and silage mixture at an equal metabolizable energy intakes per unit of metabolic body weight (.25 Mcal/kg BW.75). Measurements of daily dry matter intakes, weekly BW, 28-d estimates of empty body components (measured by urea dilution), final TMA (trial 1) and plasma thyroid hormone concentrations were obtained. In both trials, SYN increased BW gain and protein accretion.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1992

Plasma tumor necrosis factor-alpha during long-term endotoxemia in awake sheep.

We used a continuous 12-h infusion of Escherichia coli endotoxin (10 ng.min-1.kg-1) in 10 awake sheep equipped with a lung lymph fistula and vascular catheters to determine the time course of increased plasma tumor necrosis factor-alpha (TNF-alpha) during the infusion and a 12-h postinfusion period. Lung lymph flow increased progressively during the infusion to a peak value averaging 8.6 +/- 2.0 times the baseline flow of 6.3 +/- 1.3 g/h. During the postinfusion period, lung lymph flow remained elevated at three to four times baseline. The lymph-to-plasma protein concentration ratio was unchanged from baseline over 24 h, indicating a dramatic increase in net protein flux across pulmonary microvessels. The TNF-alpha concentration peaked early in the infusion and then declined, despite the continuing presence of endotoxin. Plasma TNF-alpha concentration increased 10-fold (0.33 +/- 0.05 ng/ml at baseline to 3.89 +/- 0.78 ng/ml peak) 2 h into the endotoxin infusion. At the end of the endotoxin infusion, plasma TNF-alpha had decreased to 1.16 +/- 0.19 ng/ml. The circulating TNF-alpha concentration did not correlate with pathophysiology or outcome in these sheep.

Animals↗

PubMed1992

Plasma concentrations of thyroid hormone in steers treated with Synovex-S and 3,5,3'-triiodothyronine.

This experiment examined the effect of daily administration of 3,5,3'-triiodothyronine (T3) on plasma profiles of T3, thyroxine (T4), 3,3',5'-triiodothyronine (reverse T3; rT3) and thyrotropin (TSH) in beef steers in which protein accretion was increased by using implants of Synovex-S (SYN). Twenty-four Angus-Hereford steers (302 +/- 16 kg) were individually fed a diet of a corn-based concentrate and silage mixture for 56 d at equal energy intake per steer (ME/unit BW.75). A 2 x 2 factorial arrangement of treatments was used in which treatments were SYN ear implants (200 mg of progesterone and 20 mg of estradiol benzoate) or no implants and s.c. injections of T3 in polyethylene glycol (2 micrograms of T3/kg BW every 48 h) or no injections of T3. Blood samples were collected every 2 wk. Plasma T3 concentration during the experimental period was increased in T3-treated steers (3.0 +/- .1 vs 2.2 +/- .1 ng/mL, P < .01) and was decreased in SYN-implanted steers (2.4 +/- .1 vs 2.7 +/- .1 ng/mL, P < .01). Plasma T4 and rT3 concentrations were reduced (22 +/- 4 vs 75 +/- 2 and .04 +/- .01 vs .12 +/- .01 ng/mL, respectively, P < .01) in T3-treated steers. Concurrently, plasma TSH concentration was decreased in T3-treated steers (.37 +/- .01 vs .51 +/- .02 ng/mL, P < .02). Synovex-S increased BW gain (21.0%, P < .01) and protein gain (35.6%, P < .01) compared with that of nonimplanted steers. Body weight gain and protein gain were not affected by treatment with T3.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1992

Effects of growth hormone-releasing factor and feed intake on energy metabolism in growing beef steers: net hormone metabolism by portal-drained viscera and liver.

Effects of growth hormone-releasing factor (GRF) and intake on arterial concentrations and net visceral metabolism of hormones were measured in six growing Hereford x Angus steers using a split-plot design with 4-wk injection periods within 8-wk intake periods. Steers were fed a 75% concentrate diet at two intakes and were injected s.c. twice daily with saline or GRF (10 micrograms/kg of BW). Arterial concentrations of growth hormone (GH) were measured on d 1 and d 8 to 10 of injections. Eleven measurements, obtained at 30-min intervals, of arterial concentration and net flux of hormones across portal-drained viscera (PDV) and liver were obtained on d 8 to 10 of injections (six hourly measurements were used for insulin-like growth factor-I [IGF-I] and somatostatin). The area under the GH curve and average and peak GH concentrations were increased (P less than .01) by GRF and were greater (P less than .10) at low than at high intake. Liver removal of GH was not affected by GRF or intake. Arterial IGF-I concentration was increased (P less than .05) by GRF and not affected by intake. Treatments did not affect IGF-I flux across the liver. Arterial insulin concentration was greater (P less than .05) at high than at low intake, in part because of greater (P less than .01) PDV release. Increased (P less than .10) arterial insulin concentration in GRF-treated steers was not attributable to significant changes in PDV or liver net flux. Arterial glucagon concentration was greater (P less than .01) at high than at low intake, in part because of greater (P less than .05) PDV glucagon release and decreased (P less than .10) liver extraction ratio. Effects of intake on arterial concentration of insulin and glucagon were in part due to changes in visceral metabolism, but GRF did not affect PDV or liver hormone metabolism.

Animals↗

PubMed1992

Effects of growth hormone-releasing factor and feed intake on energy metabolism in growing beef steers: net nutrient metabolism by portal-drained viscera and liver.

Effects of growth hormone-releasing factor (GRF) and intake on net nutrient metabolism by portal-drained viscera (PDV) and liver were measured in six growing Hereford x Angus steers fed a 75% concentrate diet at two intakes in a split-plot design with 4-wk saline or GRF injection periods within 8-wk intake periods. Daily rations were fed as 12 equal meals delivered every 2 h. Steers were injected s.c. for 21 d with either saline or 10 micrograms/kg of (1-29)NH2 human GRF at 12-h intervals. Six hourly measurements of net nutrient flux (venous-arterial concentration different [VA] x blood flow) across PDV and liver were obtained 8 to 10 d after injections began. Energy and N balances were measured using respiration calorimetry during the last week of injections. Greater intake increased blood flow (P less than .01) and net visceral release or removal of most nutrients (P less than .10). Exceptions included a decrease (P less than .10) in net PDV glucose release with greater intake in saline-treated steers and a decrease (P less than .01) in net liver removal of lactate with greater intake. Treatment of steers with GRF decreased net liver removal of alpha-amino N (AAN; P less than .05) and ammonia N (NH3N; P less than .10) and release of urea N (UN; P less than .05), increased liver release of glutamate (P less than .05), and decreased net PDV release of NH3 N (P less than .10). Decreased liver extraction ratio for AAN in GRF-treated steers (P less than .01) implies a direct effect of GRF treatment on liver metabolism separate from changes in liver AAN supply. Proportions of body N retention not accounted for by net total splanchnic AAN release increased with GRF treatment. This suggests a change in peripheral utilization of dietary AAN supply or an increase in total splanchnic N retention.

Amino Acids↗