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Biomedical subjects

D Mendel

Publications and source records attributed to D Mendel.

27 records · Page 2Linked to original sources
PubMed1967

Some observations on 'autoregulatory escape' in cat intestine.

1. ;Autoregulatory escape' (Folkow, Lewis, Lundgren, Mellander & Wallentin, 1964a) in which intestinal blood flow escapes from the constrictor influence of splanchnic nerve stimulation, was investigated in the cat. Measurements were made of intestinal blood flow, movements and portal venous pH and oxygen content.2. ;Autoregulatory escape' was observed with sympathetic nerve stimulation and noradrenaline infusion. It did not occur during haemorrhage.3. The recovery of flow during noradrenaline infusion could not be explained by changes in intestinal motility or loss of effect of noradrenaline due to changes in portal venous hydrogen ion concentration.4. During a noradrenaline infusion there was a reduction in oxygen consumption associated with a fall in blood flow. During the period of ;autoregulatory escape', however, oxygen consumption increased. The significance of these observations is discussed.

Animals↗
PubMed1967

The effects of alteration of CO2 and pH on intestinal blood flow in the cat.

1. The effect of alteration of arterial blood pH on intestinal blood flow in the cat has been determined under conditions of constant perfusion pressure.2. Arterial blood pH was altered over the range 7.12-7.70 by infusion of acid and alkali. When end-tidal CO(2) was held constant, there was no change in intestinal blood flow.3. When arterial blood pH was altered over the range 7.19-7.55 by the administration of CO(2) at constant respiratory volume and rate, flow increased with increasing CO(2).4. The intestinal vascular bed was less responsive to noradrenaline at pH 7.2 than at pH 7.6. The change in sensitivity was evident when end-tidal CO(2) was controlled and depended therefore on a change in hydrogenion concentration.5. The dilator effect of CO(2) did not depend upon alteration of sensitivity to noradrenaline since it was seen after adrenergic blockade.

Animals↗
PubMed1966

The effects of acute haemorrhage on respiration in the cat.

1. The effect of haemorrhage on minute ventilation, arterial blood pH and end-tidal CO(2) has been investigated in cats anaesthetized with Nembutal. There was no change in minute ventilation with alteration of blood pressure above 100 mm Hg. Below this level ventilation progressively increased, the minute ventilation at 60 mm Hg being 33% above that at 100 mm Hg. The increase in minute ventilation was always associated with a fall in end-tidal CO(2) and a decrease in arterial blood hydrogen ion concentration.2. The effects were not influenced by vagotomy, but were abolished by carotid sinus denervation or carotid body destruction. After vagotomy and sinus denervation or aortic and carotid chemoreceptor destruction, haemorrhage resulted in a depression of respiration.3. The changes in arterial blood pH and end-tidal CO(2) did not occur without a change in minute ventilation.4. When the changes in arterial blood pH during haemorrhage were prevented by administration of CO(2) there was a marked increase in minute ventilation. It is concluded that the respiratory drive to respiration in the cat during haemorrhage is controlled mainly by carotid body chemoreceptors and that the resultant alkalaemia decreases the respiratory response.

Animals↗