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Biomedical subjects

R S Comline

Publications and source records attributed to R S Comline.

At least 55 records · Page 3Linked to original sources
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↗
PubMed1971

Catecholamine secretion by the adrenal medulla of the foetal and new-born foal.

1. The content and output of adrenaline and noradrenaline from the equine adrenal medulla has been investigated under different conditions in foetuses, foals and adult mares.2. In the foetus only small amounts of both amines were secreted in response to stimulation of the peripheral ends of the splanchnic nerves to the gland; during anoxia the adrenal discharge was far greater and was independent of any nervous mechanism.3. Whereas in the ruminant a direct adrenal response to low P(O2) is confined to the noradrenaline cells during foetal life only, the adrenal medulla of the foetal foal secreted both adrenaline and noradrenaline during asphyxia, and the direct response persisted for some days after birth. Noradrenaline was the amine predominantly released during asphyxia in the foetus.4. Catecholamine output from the equine adrenal medulla changed with age, in that there was a gradual increase in both the absolute and relative amount of adrenaline released, irrespective of the stimulus applied, although at any given stage of development a higher proportion of adrenaline was secreted in response to stimulation of the splanchnic nerves than during anoxia.5. The relative proportions of the two amines in the effluent blood bore little resemblance to those found in the glands, removed after prolonged asphyxia, in either foetuses or foals. Preliminary observations have indicated that more noradrenaline is present in the glands when the foetus remains relatively undisturbed within the uterus.6. The possible significance of the larger adrenal response to asphyxia in the foetal foal in comparison with other species is discussed in relation to the development of the innervation and the growth of the adrenal cortex.

Adrenal Glands↗
PubMed1970

Daily changes in foetal and maternal blood of conscious pregnant ewes, with catheters in umbilical and uterine vessels.

1. Blood gas tensions, pH, packed cell volume (PCV) and the levels of glucose, fructose and lactic acid have been followed in foetal and maternal blood for periods of 3-30 days in conscious ewes between 80 days gestation and term ( approximately 147 days).2. Blood samples were withdrawn through indwelling catheters placed in one or both umbilical vessels, a uterine vein and a maternal artery.3. The success of the operation appeared to depend on the maintenance of maternal blood gas and pH levels within normal limits as well as on the final position of the tip of the catheter. The difficulties and limitations of the technique are discussed.4. Foetal blood gas tensions, pH, PCV, lactic acid and glucose levels did not change markedly during the last 50-60 days of gestation. The fructose concentration fell during this period, the greatest change was between 100 and 120 days gestation.5. Small fluctuations in P(O2), P(CO2) and pH in umbilical venous blood were associated with similar changes in the uterine vein, so that the gradients across the placenta appeared to remain constant.6. Daily changes in maternal plasma glucose levels were reflected in similar changes in foetal plasma fructose and by much smaller alterations in the foetal glucose levels. The glucose concentration in the foetal plasma was less than 25% of that in maternal plasma.7. The existence of a general relationship between maternal plasma glucose and foetal plasma fructose was masked by the independent fall in fructose levels with age. However, at any given stage of gestation, there was a significant correlation between foetal fructose and maternal glucose.8. Few changes in the umbilical blood were associated with impending abortion or birth. Blood gas tensions remained constant, but a sharp fall in fructose levels often occurred 48 hr before any changes in pH, PCV and lactate concentration.9. Present and other findings on conscious animals are compared with previous observations on acute, anaesthetized preparations.

Animals↗
PubMed1970

PO2, PCO2 and pH levels in the umbilical and uterine blood of the mare and ewe.

1. Foetal and maternal blood gas tensions and pH levels have been investigated in the mare and the ewe during late pregnancy under a number of experimental conditions.2. Observations were made on anaesthetized animals with the foetus in utero. Simultaneous blood samples were withdrawn from a maternal artery and uterine vein, and from the two umbilical vessels, through catheters inserted at the beginning of each experiment.3. At normal maternal arterial P(O2) (80-110 mm Hg) the umbilical venous P(O2) of the foal was very high (49 mm Hg) and the P(O2) in the umbilical artery (33 mm Hg) was similar to that in the umbilical vein of the lamb (34 mm Hg).4. The P(O2) difference between the umbilical and uterine venous blood was 17 mm Hg in the ewe but only 4 mm Hg in the mare. The corresponding P(CO2) gradients were about one quarter of those for oxygen in both species.5. When the maternal arterial P(O2) was raised above 100 mm Hg both uterine venous and umbilical P(O2) increased in the mare, and the gradient between the uterine vein and umbilical vein was reversed, whereas little change occurred in the corresponding vessels of the ewe.6. Alterations in maternal arterial P(CO2) were associated with concomitant changes in the blood in the other three vessels but in both species the P(CO2) difference between uterine and umbilical venous blood appeared to remain constant.7. Foetal blood pH levels followed those of the mother if the changes in the maternal blood were of respiratory origin. The effects of prolonged changes in maternal pH on foetal levels were investigated in the ewe. Foetal pH remained unchanged during maternal alkalaemia (pH 7.7) induced by Na(2)CO(3) infusions, but increased during a similar rise in maternal pH induced by hyperventilation.8. The present observations have been compared with findings on the conscious animal and possible explanations for the differences between the two species are discussed.

Animals↗