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

Comline, R. S.; Silver, M.

doi:10.1113/jphysiol.1970.sp009181

Cited by 43 publications

(37 citation statements)

References 28 publications

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“…The maternal arterial blood acid base characteristics were similar to those found COMLINE and SILVER [2,3] under nembutal anaesthesia and in chronic preparations; the fetal pH and PO 2 values were a little lower, suggesting some inpairment of the placental circulations due to the spinal anesthesia which was found by LUCAS et al [24]. The plasma amino acid values in the pregnant ewe were lower than in the non pregnant sheep (LEIBHOLZ [20]) s might be expected from the fall in total <%-amino nitrogen observed by CURET et al [4] during gestation in the ewe.…”

Section: Discussionsupporting

confidence: 67%

Placental transfer and fetal uptake of amino acids in the pregnant ewe

Young¹,

Fadyen²

1973

Journal of Perinatal Medicine

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Section: Discussionsupporting

confidence: 67%

Placental transfer and fetal uptake of amino acids in the pregnant ewe

Young¹,

Fadyen²

1973

Journal of Perinatal Medicine

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“…Data were published by Downing [1960] Comline and Silver, 1970b] yield values that are no higher than those calculated from the previous work of Downing [1960] and Brinkman et al [1969]. It is likely that the presence of a large, relatively unresponsive vascular bed, the placenta, is in part responsible for these low values.…”

Section: Discussionmentioning

confidence: 70%

Arterial Blood Pressure in the Unanaesthetized Fetal Lamb After Changes in Fetal Blood Volume and Haematocrit

1974

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Fourteen sheep fetuses in the third trimester of gestation were surgically prepared with intravascular catheters and five were nephrectomized. All experiments were done on unanaesthetized fetuses in utero, 3 to 9 days after surgery. Mean arterial blood pressure was recorded while fetal blood volume was changed by injection or withdrawal of blood, or infusion of Ringer's or dextran solutions. Fetal arterial blood gases and pH changed little during the experiments and were shown not to have affected the results. Arterial blood pressure was strongly influenced by changes in fetal blood volume and was also found to depend on haematocrit. There were no detectable differences between the responses of normal and nephrectomized fetuses or between normal fetuses and fetuses treated with hexamethonium. In all preparations central venous pressure depended on blood volume. Heart rate did not depend on blood volume in normal fetuses, but an increase in heart rate with an increase in blood volume was seen after hexamethonium. The open loop gain of baroceptor control of arterial blood pressure could not be proved to differ significantly from zero. Venoconstrictor responses and heart rate responses of reflex origin did not occur when arterial blood pressure was changed. The absence of detectable baroceptor control appears to explain the great sensitivity of arterial blood pressure to blood volume in the unanaesthetized fetal lamb. Previously we found that fetal placental blood flow is almost proportional to fetal blood volume [Faber, Gault, Green and Thornburg, 1973]. Since placental resistance to flow is not known to be under fetal control, changes in placental blood flow were thought to be secondary to changes in arterial blood pressure, an explanation which would require that arterial blood pressure itself is also proportional to blood volume. Studies that demonstrate some control of arterial blood pressure by the baroceptors of the fetus [Brinkman, Ladner, Weston and Assali, 1969] and the neonate [Downing, 1960; Downing, Gardner and Rocamora, 1969] seem to argue against this supposition and we therefore investigated the relationship between arterial blood pressure and blood volume in unanaesthetized fetal lambs under near normal conditions. The contributions of the baroceptors, and of renal mechanisms, to the regulation of arterial blood pressure were assessed by experiments on fetuses with blocked ganglionic transmission or previous bilateral nephrectomy. Recordings of the pH, P02, and PCO2 of fetal arterial blood were made to monitor the condition of the preparations and to eliminate the possibility that the chemo-ceptors affected arterial blood pressure in these experiments. METHODS Animals Pregnant western mixed breed and Dorset ewes were starved for 24 hr prior to surgery and operated on under nitrous oxide-halothane anaesthesia, after induction 241

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“…First, the greater efficiency of its placenta, particularly for gaseous exchange, means that the foetus develops at a higher overall Po2 (Comline & Silver, 1970) and secondly, the umbilical cord remains patent throughout parturition, thereby allowing transfer of placental blood to the new-born foal (Rossdale, 1967). Under these conditions it seemed possible that the adrenal medulla might be even more sensitive than those of the foetal ruminants to changes in Po2,…”

Section: Introductionmentioning

confidence: 99%

“…This property is retained, with some regression, for several days after birth. METHODS Many of the procedures and techniques were developed for the study of the adrenal in the foetal lamb and calf (Comline & Silver, 1961, 1966Comline, Silver & Silver, 1965) and the investigation of the equine placenta (Comline & Silver, 1970): only essential information, modifications and additional procedures are described in detail below.…”

Section: Introductionmentioning

confidence: 99%

“…Details of the effects of these two anaesthetics on blood gas tensions and pH in the mare are given elsewhere (Comline & Silver, 1970). Operative procedureM. In the majority of experiments, after exposure and catheterization of uterine and umbilical vessels, blood samples were taken at intervals (Comline & Silver, 1970), beginning 2J-3 hr after the induction of anaesthesia, to 660 ADRENAL MEDULLARY OUTPUT IN FOALS follow conditions in both mother and foetus during subsequent preparation. When necessary, supplementary 02 or positive pressure ventilation was given to the mare.…”

Section: Introductionmentioning

confidence: 99%

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

Comline¹,

Silver²

1971

The Journal of Physiology

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SUMMARY1. 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 Po2 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.

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

Cited by 43 publications

References 28 publications

Placental transfer and fetal uptake of amino acids in the pregnant ewe

Placental transfer and fetal uptake of amino acids in the pregnant ewe

Arterial Blood Pressure in the Unanaesthetized Fetal Lamb After Changes in Fetal Blood Volume and Haematocrit

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

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