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Biomedical subjects

J Lefaivre

Publications and source records attributed to J Lefaivre.

34 records · Page 2Linked to original sources
PubMed1981

Plasma levels of vitamin D metabolites in the bovine species during the perinatal period.

Plasma vitamin D metabolites (25-OH D; 24,25-(OH)2D and 1,25-(OH)2D) were measured simultaneously in the blood plasma samples of young cows and their calves. Four of the calves were chronically catheterized in utero at least 2 weeks before the expected time of parturition. No significant hypocalcaemia occurred in the dams at calving. Plasma vitamin D metabolites showed no significant variations for 2 weeks before and 4 days after calving. But rapid changes in plasma 1,25-(OH)2D concentrations were observed in one calf during the first 48 postnatal hours. Before birth, the maternal and foetal concentrations of either 1,25-(OH)2D or 24,25-(OH)2D were positively correlated. 25-(OH) D (13 ng/ml), 24,25-(OH)2D (1 ng/ml) and 1,25-(OH)2D (76 pg/ml) were detected in one foetal plasma collected 35 days before term.

24,25-Dihydroxyvitamin D 3↗
PubMed1980

Aldosterone metabolism in pregnant ewes and fetal and newborn lambs.

Twenty primiparous Limousine ewes whose fetuses had been chronically catheterized in utero on day 120 of gestation were used. Plasma aldosterone levels were measured by radioimmunoassay during the last 15 days of gestation both in dams and fetuses, and during the first neonatal week in lambs. Aldosterone metabolic clearance rates in dams, fetuses and newborns were determined by continuous infusion of [1, 2, 6, 7-3H]-aldosterone. The highest plasma aldosterone levels were observed in dams on days 130 and 142 of gestation, and in fetuses on days 135 and 140. No correlation was observed between plasma aldosterone and electrolyte levels in the mother, fetus or newborn. Aldosterone metabolic clearance rate decreased between days 142 and 145 in dams and at birth in fetuses of both sexes. No aldosterone transfer could be demonstrated either from dam to fetus or vice-versa.

Aldosterone↗
PubMed1980

The endocrine regulation of exocrine pancreas in preruminant milk-fed calves.

Fifteen male Holstein X Frisian calves, weighing 65 +/- 3 kg and fed a milk replacer twice daily were fitted with a return cannula loop, chronically implanted at 10 days of age in the pancreatic duct, were used. In six successive experiments we have observed the influence of an intravenous infusion of secretin, cholecystokinin pancreozymin (CCK-PZ), vasoactive intestinal peptide (VIP), glucagon, gastrin and somatostatin on pancreatic juice flow rate, and on the excretion of proteins, calcium, inorganic phosphorus, zinc and amylase activity of pancreatic juice. In two other experiments, we have studied the interaction of secretin (or CCK-PZ) with somatostatin (SRIF). Each experiment was performed 5 h after calves feeding and no milk was given to the animals during the time of sampling. Our results indicate that the endocrine regulation of the exocrine pancreas in young calves is similar to that described in other mammals. Secretin and CCK-PZ increased significantly excretion of water, calcium, magnesium, inorganic phosphorus, zinc, proteins and amylase activity. Somatostatin and glucagon inhibited effects observed with two precedent hormones. Gastrin increased pancreatic juice flow rate but excretion of protein and amylase activity do not varied significantly. VIP showed no significant effect on pancreatic excretion of water, minerals, proteins and amylase activity. However, our animals seem to be characterized by a more intense excretion of proteins and amylase in the pancreatic juice following secretin than after CCK-PZ infusion.

Animals↗
PubMed1979

Foetal plasma magnesium levels during maternal hypo- or hypermagnesaemia in ewes.

1. The influence of maternal hypo- or hypermagnesaemia of foetal plasma magnesium levels was studied in pregnant ewes between the 120th and the 145th day of gestation using a permanent catheter inserted in utero into the left aorta of the foetus on the 115th day of gestation. 2. In seven ewes, carrying eleven foetuses, the injection of 1 alpha-hydroxycholecalciferol induced a hypomagnesaemia which lasted 72 h. This had no significant effect on foetal plasma Mg levels. 3. In five ewes, carrying six foetuses, hypermagnesaemia induced by a 2 h magnesium chloride infusion had no significant effect on foetal plasma Mg levels. 4. These results provide evidence that in sheep during the last 20 d of gestation the foetal regulation of plasma Mg is independent of the maternal plasma Mg levels.

Animals↗
PubMed1979

Fetal blood calcium response to maternal hypercalcemia induced in the cow by calcium infusion or by solanum glaucophyllum ingestion.

Bovine fetuses chronically catheterized in utero during the last month of gestation were used to study the relationships of maternal-fetal calcium and phosphate levels. Calcium infusion into the pregnant cows induced a rapid and marked increase in maternal plasma calcium but no change in fetal plasma calcium concentrations. Oral administration of Solanum glaucophyllum to the mother for 6 days raised the plasma concentrations of calcium and phosphate in both the mother and the fetus.

Animals↗
PubMedDate not supplied

Acute versus chronic conditions for studies of fetal nutrient requirements: applicability to the human.

In order to validate results obtained in 'acute' versus 'chronic' experimental conditions, two fetal sheep nutrients, lactate and glucose, have been determined in 'acute' conditions and compared with the 'chronic' data in the literature. Maternal and fetal blood glucose in 'acute' conditions was in the range of published 'chronic' data. Fetal blood lactate was similar in 'acute' and during 'chronic' conditions. Maternal and fetal veno-arterial (VA) differences were in the same direction in 'acute' and in 'chronic' conditions for both lactate and glucose and of the same magnitude for lactate. For glucose, a good relationship was observed between umbilical VA differences and maternal arterial concentrations for all 'acute' and 'chronic' values. Thus no fundamental differences appear in the results obtained in 'acute' or during 'chronic' conditions. The applicability of such animal results to the human and the use of acute conditions to study fetal nutrition in the human are discussed.

Animals↗
PubMedDate not supplied

The effect of seprafilm and interceed on capsule formation around silicone discs in a rat model.

The insertion of a foreign substance, such as a breast implant into mammalian soft tissues, evokes a wound healing response that culminates in a dense connective-tissue envelope or capsule surrounding the implant. Several biodegradable products, such as Seprafilm (carboxymethylcellulose and hyaluronic acid) and Interceed (oxidized regenerated cellulose), have been demonstrated to inhibit adhesions in abdominal and gynecologic surgery. The ability of these cellulose compounds to inhibit capsule formation was addressed in this investigation. Twenty-eight rats were implanted intermuscularly with either plain silicone discs (10 animals), discs wrapped in Seprafilm (10 animals), or discs covered with Interceed (8 animals). Additional control animals (6 animals) consisted of two that had sham operations, two animals implanted with Seprafilm only, and two more implanted with Interceed only. Animals were sacrificed in pairs at varying time intervals after implantation (2, 4, 8, 12, and 16 wk), and the tissues around the silicone discs were analyzed with light microscopy. Control animals were sacrificed at 8 wk. Both Interceed and Seprafilm slowed the formation of a capsule around the implanted silicone discs as both products were degraded. Evidence of residual material, presumably Seprafilm and Interceed, was seen intracellularly in animals 3 to 4 mo, respectively, after implantation. However, neither material prevented the eventual formation of a fibrous capsule around the silicone discs. The results of this study suggest that encapsulating foreign substances with these types of biodegradable materials will not significantly hinder capsule formation. A more direct attack on the wound healing mechanism may provide a definitive solution for capsule problems with implanted materials.

Animals↗
PubMedDate not supplied

The influence of parathyroid hormone and calcitonin on urinary excretion of calcium, magnesium and inorganic phosphorus in chronically catheterized foetal lambs in utero.

Nine single foetal lambs with catheters chronically implanted in utero on day 122 of gestation into the left carotid artery, the right external jugular vein and the bladder were used. In these foetuses, between days 130 and 142 of gestation, urine flow rate was 0.48 +/- 0.09 ml X min-1. In the same time, an intravenous infusion of bovine parathyroid hormone (150 U per foetus in 30 min) induced hypercalcaemia and hypophosphataemia, associated with an increase in urinary flow rate and urinary phosphate concentration. Although urinary calcium concentration was unchanged, the urinary excretion of both calcium and phosphate increased. An intravenous infusion of salmon calcitonin (200 MRC mU per foetus in 30 min) induced hypocalcaemia and hypophosphataemia, associated with an increased urinary phosphate concentration. Urinary flow rate and urinary calcium concentration were not modified by the calcitonin which increased only urinary excretion of phosphate. Thus the high plasma phosphate levels measured in lambs during the perinatal period do not seem to be related to a previous unresponsiveness (just before birth) to the hormones regulating phosphate urinary excretion.

Animals↗