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S J Semple

Publications and source records attributed to S J Semple.

At least 91 records · Page 5Linked to original sources
PubMed1973

Effect on respiration of changes in the form of the naturally occurring oscillation in arterial pH.

We have previously shorn that the respiratory control system in the cat has the requisite sensitivity and speed to respond to changes in arterial pH which are equal to, or smaller than, the normal fluctuations in pH with respiration. A respiratory response was only observed when the changes in pH were produced by alterations in PCO2 and not when they were induced by non-gaseous acids. We describe now the respiratory effect produced by various procedures which modify or abolish the naturally occurring arterial pH oscillations before they reach the peripheral chemoreceptors. The pH oscillations were abolished by a mixing chamber, whilst their phase relationship to respiration was altered by delay coils; by presenting a moving plastic surface to the arterial blood stream it was possible to distort the shape of the oscillations without increasing the transport lag between lung and peripheral chemoreceptors. All manoeuvres produced a brief period of respiratory stimulation which was greater than could occur by chance. We were particularly concerned in these experiments with the possibility of artefacts in our experimental design. We feel that we have excluded respiratory effects due to changes in arterial pressure, blood temperature and mean pH. We are less confident that we have excluded changes in ventilation resulting from the release of a substance (or substances) from the contact of blood with plastic or glass surfaces. This problem is discussed in relation to experiments on the control of breathing where blood, which is perfusing the chemoreceptors, has been in contact with artificial surfaces.

Animals↗
PubMed1970

The effect on respiration of abrupt changes in carotid artery pH and PCO2 in the cat.

1. An in vivo pH monitoring technique was used to assess changes in pH, and by inference changes in P(CO2), in the carotid artery of anaesthetized cats. The changes in carotid artery pH and respiration following abrupt injections of various acids into the carotid artery or aorta were investigated.2. Injections of saline equilibrated with 100% CO(2), timed to produce changes at the carotid body chemoreceptors during early inspiration caused an increase in the tidal volume of that breath. The amplitude and rate of change of the pH changes so produced were comparable with those of the oscillations in pH produced by respiration itself.3. The respiratory responses to injection of saline equilibrated with 100% CO(2) occurred whether the animal was breathing air or 100% O(2).4. Injections of lactic or hydrochloric acid were without an effect on respiration, except when pH changes larger than 0.1 pH unit were produced. A NaHCO(3) solution equilibrated with 30% CO(2) stimulated respiration, even though the solution was alkaline to the cat's arterial blood and induced an alkaline change in arterial pH.5. Infiltration of the carotid sinus nerve area with procaine temporarily abolished the respiratory response to injections of saline equilibrated with 100% CO(2).

Animals↗