Biomedical subjects

V Coxam

Publications and source records attributed to V Coxam.

62 records · Page 4Linked to original sources

PubMed1989

Effect of triglycerides on growth hormone (GH)-releasing factor-mediated GH secretion in newborn calves.

The effect of triglycerides (Tg) on GRF-mediated GH secretion was examined in 2 groups of twelve ten-day old male calves. Twelve calves were intravenously infused with a lipid-heparin solution (5 mg Tg and 0.3 IU heparin/kg body wt/min for 90 min). The twelve control calves received in the same way, the same volume of saline. Thirty minutes after the start of infusion, GRF 1-29 (human amide, 0.16 micrograms/kg body wt) was intravenously injected in six animals of each group. Mean plasma GH levels reached peak concentrations in the 2 groups 5 min after GRF injection. However the area under the GH response curve, when lipid-heparin was given, was significantly diminished compared to the response when saline was given. In the same time, lipid-heparin treatment increased plasma SRIF concentration. These data suggest that an increase in plasma Tg concentration, induced by lipid-heparin infusion, inhibits GRF-mediated GH secretion, possibly through stimulation of SRIF secretion.

Animals↗

PubMed1989

Nutrient effects on the hepatic production of somatomedin C (IGF1) in the milk-fed calf.

The present study was aimed at determining the influence of nutrients supplied by a milk diet (glucose, amino acids, triglycerides) on hepatic somatomedin C (IGFi) production in vivo in four 30-d-old milk-fed calves fitted with chronically indwelling catheters in hepatic (HV), portal (PV) and mesenteric veins and in the hepatic artery (HA), and with electromagnetic flow-meters on HA and PV. Fasting for 16 h induced a decrease (P less than 0.01) in hepatic IGF1 production (nmol/kg body-weight (BW) for 6 h) (1.1 (SE 0.2) v. 6.6 (SE 0.7) in control animals). Infusion of glucose (1.8 g/kg BW for 4 h) or a mixture of amino acids (Azonutril; R. Bellon, Neuilly sur Seine; 62.5 mg nitrogen/kg BW for 3 h) in a mesenteric vein led to no significant effect on hepatic IGF1 production for 6 h (1.2 (SE 0.3) and 0.7 (SE 0.3) nmol/kg BW respectively) compared with fasted calves. Infusion of chylomicrons purified from milk-fed calves (10.5 mg/h per kg BW, i.e. 0.16 mg triglycerides/kg BW per min) enhanced significantly (P less than 0.01) the hepatic production of IGF1 (mean value for 6 h: 5.3 (SE 0.8) nmol/kg BW). Infusion of Intralipid (7 mg triglycerides/kg BW per min) induced a slight but significant hepatic IGF1 production which amounted to 3.5 (SE 0.4) nmol/kg BW (P less than 0.1 compared with chylomicron treatment) and it began only 5 h after starting the infusion. Neither triglyceride nor chylomicron infusion significantly modified hepatic blood flow. Thus, these results demonstrate for the first time the role of lipids in the regulation of hepatic IGF1 production in vivo.

Amino Acids↗

PubMed1988

Regulation of growth hormone release in fetal calves.

Plasma GH and IGF1 concentrations were measured during the last 2 months of gestation in 9 chronically catheterized fetal calves under basal conditions or following growth-hormone-releasing factor (GRF), thyrotropin-releasing hormone (TRH) or SRIF intravenous cotyledonnary injections. Plasma GH concentrations were higher in fetuses (1.40 +/- 0.10 nmol/l) than in dams (0.14 +/- 0.01 nmol/l). Plasma GH secretory profile was pulsatile. The number of secretory pulses, as well as their magnitude and mean baseline values decreased from 220 to 270 days of gestation. Synthetic 1-29 GRF or TRH increased fetal plasma GH concentration at 250 and 270 days of gestation but was devoid of any significant effect at 220 days. SRIF injection decreased plasma GH concentration in 270-day-old fetuses. Plasma IGF1 concentrations were lower in fetuses than in dams. No treatment had a significant effect on fetal and maternal IGF1 levels.

Animals↗

PubMed1988

Systemic bone growth factors concentrations in calves during the perinatal period.

Plasma somatostatin (SRIF), growth hormone (GH), somatomedin C (IGF1), osteocalcin (BGP), 1,25-dihydroxyvitamin D (1,25-(OH)2D), calcium and inorganic phosphorus were measured in 10 chronically-catheterized fetal calves and in their dams during the two last months of gestation. Thus fetal life is associated with high levels of GH (1.53 +/- 0.14 nmol.l-1), BGP (64 +/- 4 nmol), Ca (2.90 +/- 0.06 nmol.l-1) compared to the results obtained in the pregnant cows. The first week of postnatal life was associated with a tremendous increase in plasma SRIF concentration (from 36 +/- 5 to 106 +/- 15 pmol.l-1; P less than 0.01). These results agree with an intense bone growth during the end of fetal life in the bovine species. However, IG 1 might not play a major role in the regulation of fetal skeletal growth during this period.

Animals↗

PubMed1987

Plasma somatotropin and somatomedin C concentrations following GRF or TRH injections in newborn calves.

Plasma somatotropin (GH) and somatomedin C (IGF1) concentrations were measured by radioimmunoassay in 3-dy old and 10-day old calves intravenously injected with growth hormone releasing factor (GRF) 1-44, GRF 1-29 or thyrotropin-releasing hormone (TRH). In 3 day old animals the increase in plasma GH concentration was GRF 1-44 dose-related (50, 100, 200 pmoles . kg(-1) of body wt). In four 10-day old calves injected with the lowest dose, the increase in plasma GH concentration was not different from that observed in four 3-day old animals treated with 200 pmoles . kg-1 of body weight. However, the response observed in four 3-day old calves injected with GRF 1-29 (50 pmoles . kg-1 of body wt) was not different from that observed following the same treatment in four 10-day old calves. In four 3-day old calves TRH (10 nmoles . kg-1 of body wt) induced a significant rise in plasma GH, prolactin (Prl), thyroxine (T4) and triiodothyronine (T3) concentrations. The same dose of TRH injected into four 10-day old calves elicited a similar rise in plasma T3 and T4 concentrations, but plasma GH and Prl increased less than in 3-day old animals. In three 3-day old or 10-day old calves born spontaneously before term (258-260 days of gestation), the increase in plasma Prl and GH concentrations following TRH was not different from that observed in mature calves of the same postnatal age. Neither GRF 1-44, GR 1-29 nor TRH elicited any significant change in plasma IGF1, insulin or glucose concentration in any group of calves.

Animals↗

PubMed1987

Growth hormone secretory pattern and somatomedin C plasma concentrations in newborn calves.

Plasma growth hormone (GH) and somatomedin-C (IGF-1) concentrations were measured by radioimmunoassay in 16 dairy calves during the first 20 days of postnatal life. The lowest plasma GH concentration (0.07 +/- 0.01 nmols . l-1) occurred 4 h after birth. It increased gradually until the 3rd day, to reach values similar to those measured in adult males (0.15 +/- 0.05 nmoles . l-1) and remained stable until 20 days. The lowest plasma IGF-1 concentration (3.1 +/- 0.5 nmol . l-1) was measured at 3 days, then increased at 4 days (7.6 +/- 0.6 nmol . l-1) and remained stable until 20 days of age. In nine 2-10 days-old calves, the GH secretory profile observed in blood samples collected every 30 min over a 24-h period showed 8-13 secretory spikes, without periodicity. No relationship could be demonstrated between plasma GH and IGF1 concentrations. A marked increase in plasma GH concentrations followed every morning milk feeding.

Age Factors↗

PubMedDate not supplied

Availability of calcium from skim milk, calcium sulfate and calcium carbonate for bone mineralization in pigs.

Dairy products provide abundant, accessible calcium for humans, while some calcium sulfate-rich mineral waters could provide appreciable amounts of calcium. But there is little evidence that this calcium is as available as milk calcium for making bone. The availability of calcium was studied by monitoring bone parameters in 2-month-old pigs fed restricted amounts of calcium (70% RDA) for 2.5 months. The 3 main (> or = 50% Ca intake) Ca sources were either CaCO3 or CaSO4 or skim milk powder (29% of the diet). The bones of the pigs fed the "milk" diet had higher (P < 0.01) ash contents, breaking strength and density (DEXA) than those of the two others groups, in which the bone values were similar. Thus, the calcium provided by a diet containing milk appears to ensure better bone mineralization than do calcium salts included in a non-milk diet. The calcium restriction may have enhanced some milk properties to stimulate calcium absorption in these young, rapidly growing pigs.

Alkaline Phosphatase↗

PubMedDate not supplied

Systemic bone growth factors in light breed mares and their foals.

There is a high incidence of bony pathology in race horses. Thus, plasma GH, IGF-1, osteocalcin (OC), calcium (Ca) and inorganic phosphorus (P) concentrations were measured in 12 healthy Selle Français foals and their dams during the first five months after birth. Plasma IGF-1 and OC concentrations were higher in foals than in mares (336 +/- 25 vs 230 +/- 18 ng/ml, P < 0.05; 52.5 +/- 3.2 vs 4.9 +/- 0.1 ng/mg, P < 0.01, respectively). A significant positive linear relationship could be established between these two parameters in foals (IGF-1 = 19 + 0.619 OC; P < 0.05). Another striking evidence was the increase in plasma IGF-1, OC and P concentrations observed during the first week of postnatal life. IGF-1, OC, P and Ca concentrations remained elevated during the experimental period, indicating an intense skeletal growth (confirmed by growth curve) in these animals.

Aging↗