Search PubMed⌕ Search

Biomedical subjects

R S Comline

Publications and source records attributed to R S Comline.

64 records · Page 4Linked to original sources
PubMed1968

The effects of bradykinin, angiotensin and acetylcholine on the bovine adrenal medulla.

1. The response of the adrenal medulla to the intra-arterial injection of angiotensin, bradykinin and acetylcholine and to splanchnic nerve stimulation has been investigated in day-old and 3- to 18-month-old calves and in adult cats.2. Bradykinin and angiotensin had no appreciable effect on catecholamine release in the day-old calf nor did these peptides potentiate the response of the gland to acetylcholine.3. In older calves the response of the gland to bradykinin and angiotensin was marginally above the control output, whereas acetylcholine and splanchnic nerve stimulation caused a 10-100 fold increase in the rate of secretion. The response to acetylcholine but not to the peptides was related to the dose administered.4. The adrenal medulla of the cat was stimulated by angiotensin and bradykinin but the maximum amounts released by the peptides were much smaller than the discharge elicited either by splanchnic nerve stimulation or by acetylcholine. No dose-response relationship could be found for either adrenaline or noradrenaline released by angiotensin, or for noradrenaline released by bradykinin. The slight increase in adrenaline output which followed the injection of bradykinin was dependent on the dose but the slope of the curve (b = 0.161) was much less than that for acetylcholine (b = 0.636).

Acetylcholine↗
PubMed1968

The effects of insulin of the new-born calf.

1. The normal variations in the concentrations of glucose, fructose and lactic acid in the blood of the calf which occur during the first few weeks after birth have been examined.2. The responses of calves of different ages to intravenous injections of insulin have been examined by recording both the incidence of convulsions and the changes in the concentration of glucose, fructose and lactic acid in the blood.3. New-born calves rarely convulsed during prolonged and severe hypoglycaemia and, if convulsions occurred, the onset was delayed by 6-8 hr. At 7 days of age convulsions usually followed the injection of insulin within 1(1/2)-2 hr.4. No relationship could be found between the duration of hypoglycaemia and the incidence of convulsions at different ages. Hypoglycaemia was most prolonged in new-born calves which rarely convulsed.5. Insulin hypoglycaemia during the first 24 hr after birth was associated with a rise in the concentration of lactate in the blood. Similar changes did not occur in calves at 7 days of age, in which the incidence of convulsions was much higher, or in weaned animals.6. After both splanchnic nerves had been cut, insulin always caused convulsions in 24-hr-old calves. There was no rise in the blood lactate concentration in these animals.7. Intravenous infusions of adrenaline but not noradrenaline in amounts similar to those known to be released from the adrenal medulla of the calf of this age prevented convulsions in 24-hr-old calves after section of the splanchnic nerves. These infusions had little effect on the blood glucose concentration but caused a similar rise in the lactic acid concentration to that found in normal animals at this age during hypoglycaemia.8. At 7 days of age convulsions could only be prevented during hypoglycaemia by infusing larger doses of adrenaline which significantly raised the blood glucose concentration. The increase in the blood lactate concentration was less than that in the new-born animals.9. The resistance to insulin hypoglycaemia which occurs immediately after birth is transient; it depends upon the release of adrenaline from the adrenal medulla and is associated with high concentrations of lactate in the blood during hypoglycaemia.

Age Factors↗
PubMed1966

The development of the adrenal medulla of the foetal and new-born calf.

1. The output of adrenaline and noradrenaline from the adrenal medulla during asphyxia, stimulation of the splanchnic nerves or the intra-arterial injection of acetylcholine, has been investigated in foetal and new-born calves up to 3 weeks of age.2. Between 180 days' gestation and term ( approximately 281 days) the response of the foetal adrenal gland of the calf to asphyxia appeared to be independent of its nerve supply and the discharge consisted largely of noradrenaline. A similar type of discharge was obtained after the intra-arterial injection of acetylcholine, but stimulation of the splanchnic nerves resulted in only a small discharge of both adrenaline and noradrenaline.3. Rapid changes occurred in the response of the adrenal medulla to all forms of stimulation during the first 24 hr after birth. For the first 4-6 hr the adrenal medulla was hypersensitive; thereafter the response rapidly declined and a variable period of depressed excitability followed. The changes affected the output of noradrenaline rather than that of adrenaline and were more pronounced during asphyxia or after the intraarterial injection of acetylcholine. Within 24 hr of birth the amount of noradrenaline released in response to either form of stimulation was less than 25% of that found immediately after birth.4. During the hypersensitive phase immediately after birth splanchnic nerve activity appeared to potentiate the direct effect of asphyxia on the noradrenaline cells since the maximum output of noradrenaline was attained more rapidly and at a higher P(O2) if the splanchnic nerves were intact.5. The non-nervous direct response of the adrenal medulla to asphyxia decreased rapidly after birth and disappeared within 24 hr. It did not reappear at any age and was a feature of foetal life.6. The recovery of the response to acetylcholine occurred between 3 and 8 days after birth with a return of the high level of noradrenaline secretion; no similar increase in the output of adrenaline occurred at this stage.7. The response to asphyxia was not restored to the level found in the new-born calf until 2-3 weeks after birth. At this time the effect on the adrenal medulla appeared to be mediated almost entirely by the splanchnic nerves.8. The effects of chloralose and pentobarbitone anaesthesia on the changes in the nervous response to asphyxia after birth were compared. Essentially the same pattern of changes was found with both anaesthetics although the absolute level of discharge under chloralose was greater and a considerably larger amount of adrenaline was secreted at 3 weeks of age.9. At certain ages stimulation of the splanchnic nerves enhanced the response of the adrenal medulla to subsequent injections of acetylcholine. The noradrenaline output was only significantly increased by this procedure during the period of depressed excitability whereas the adrenaline discharge was always increased throughout the first 3 weeks of life.10. The changes in adrenaline and noradrenaline content of the adrenal glands during the 3-week period after birth were investigated. The noradrenaline concentration was low immediately after birth during the hypersensitive phase and increased during the period of reduced sensitivity. The output of this amine was thus inversely related to its content in the adrenal gland. A similar relation did not occur with adrenaline, the concentration of which remained relatively constant during the first 3 weeks of life.

Acetylcholine↗