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Biomedical subjects

M Silver

Publications and source records attributed to M Silver.

At least 235 records · Page 13Linked to original sources
PubMed1975

Transfer of gases and metabolites in the equine placenta: a comparison with other species.

Mares and fetuses with indwelling catheters in the umbilical and uterine vessels have been used to monitor transplacental blood gas tensions, pH, O2 affinities and the concentration of various metabolites in fetal and maternal blood during late gestation. Measurements of umbilical and uterine blood flows and arterio-venous differences enabled the uptake of O2 and glucose by the fetus and the uterus to be estimated. The present findings are compared with those from other species in comparable conditions.

Animals↗
PubMed1975

[Ferrous ion oxidation and uranium solubilization from a lowgrade ore by "Thiobacillus ferrooxidans" (author's transl)].

The microbiological oxidation of ferrous ion and the extraction of uranium from a low-grade ore has been studied using an adapted strain of Thiobacillus ferrooxidans. The effect of temperature, pH, volumetric oxygen transfer coefficient, K1a, and aeration number, Ia, on the activity of the microorganism has been determined. The activation energy for ferrous iron oxidation was calculated to be - 13.9 +/- 0.1 kcal/mole and inactivation (thermal death of bacteria) 53.3 +/- 0.2 kcal/mole. Temperature coefficient, Q10, was estimated to be 1.8. Uranium extraction varied between 80 and 100%.

Hydrogen-Ion Concentration↗
PubMed1974

A comparative study of blood gas tensions, oxygen affinity and red cell 2,3 DPG concentrations in foetal and maternal blood in the mare, cow and sow.

1. Blood gas tensions, pH, PCV, O(2) affinity and red cell 2,3-diphosphoglycerate (DPG) levels have been measured in uterine and umbilical blood in conscious cows and mares with indwelling vascular catheters and in sows under sodium pentobarbitone anaesthesia.2. Large P(O2) gradients (20-24 mmHg) were observed between the uterine and umbilical venous blood in the cow and pig, while in the mare the corresponding P(O2) difference was only 2.7 +/- 1.7 mmHg. Alterations in maternal arterial P(O2) did not affect the large vein-to-vein P(O2) difference in either ruminant or pig.3. In the cow the presence of different haemoglobin types in the adult (A, AB or B) did not appear to affect the O(2) affinity. In six animals the mean P(50) of the foetal blood (24.8 mmHg) was considerably lower than that of the mother (35.5 mmHg); no changes in P(50) were observed during the last month of gestation. Red cell 2,3-DPG levels were higher in the calf foetus than in the mother, but in the ruminant 2,3-DPG has no effect on the affinity of haemoglobin for O(2) and the differences in P(50) between foetus and mother could be ascribed to the presence of a foetal haemoglobin.4. In the sow large differences in O(2) affinity between foetal and maternal blood were observed, which were related to red cell 2,3-DPG concentration. A rise in foetal blood P(50) during the last half of gestation was associated with increased foetal weight and a rise in red cell 2,3-DPG.5. In the mare the P(50) of the foetal blood was 2-5 mmHg below that of the mother. This difference appeared to be due to the lower 2,3-DPG concentration in the foetal red cells as in the sow; in both species the haemoglobin of the foetus is similar to that of the mother.6. The differences in foetal and maternal O(2) affinity found in the various species and the changes which may occur during gestation or in the perinatal period are discussed in relation to the observed transplacental P(O) (2) gradients and the O(2) requirements of the foetus and neonate.

Animals↗
PubMed1972

The composition of foetal and maternal blood during parturition in the ewe.

1. Changes in the composition of foetal and maternal blood have been followed during the last 5-10 days of gestation and throughout parturition in the conscious sheep.2. Catheters were placed in the foetal inferior vena cava through a tarsal vein and in a maternal uterine vein in ten ewes under sodium pentobarbitone anaesthesia. In four of the foetuses blood pressure and heart rates were recorded before and during parturition from an arterial catheter.3. Foetal blood gas tensions, pH and PCV remained stable during the latter part of gestation and throughout labour until 15 min before delivery, when P(O) (2) and pH fell while PCV and P(CO) (2) rose in about 50% of the foetuses examined.4. Metabolite levels were also relatively stable at the end of gestation. Plasma glucose in both maternal and foetal blood rose during the hour before birth, while foetal plasma lactate was elevated as early as 4 hr before birth and was unrelated to any maternal changes. Foetal fructose levels were maintained until after delivery.5. Rises in foetal blood pressure before birth were associated with uterine contractions. Foetal heart rate changes during labour varied in different individuals. The heart rate either fell gradually before birth or there was little change until a sudden drop at delivery.6. The most striking changes in the lamb occurred at, or a few minutes after, birth; pH and P(O) (2) fell, P(CO) (2) and PCV rose, and bradycardia at delivery was succeeded by prolonged tachycardia. There were marked increases in plasma glucose and lactic acid at this time.7. P(O) (2) rose rapidly once respiration was established, while pH and P(CO) (2) levels were restored within (1/2)-1 hr. Plasma FFA levels rose rapidly in the lambs 10-30 min after birth and remained high, while plasma glucose, lactate and fructose concentrations declined slowly in the 1-2 hr after birth, although suckling raised the plasma glucose levels. Considerable individual variation in the metabolite levels was found in both ewes and lambs.8. In the majority of ewes delivery was associated with an abrupt maternal hyperglycaemia, with a much smaller rise in lactate and virtually no change in maternal blood gases or pH.9. These findings are discussed in relation to existing information on new-born lambs and the human infant during birth.

Animals↗