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Biomedical subjects

J D Reed

Publications and source records attributed to J D Reed.

72 records · Page 4Linked to original sources
PubMed1974

Actions of prolactin and frusemide on heart rate and rhythm.

Rat hearts with coronary circulations perfused by the Langendorff technique were studied. Recordings were made of the electrical and mechanical activity. Once the rate and rhythm of each heart and stabilized it was perfused with Ringer-Locke solution for 90 minutes; frusemide (40 mug/ml) was added to the perfusate during the last 30 minutes of this period. Eighteen experiments were performed-six controls, six in which prolactin at a concentration of 50 ng/ml was added to the perfusate for the whole 90 minutes, and six in which a prolactin concentration of 200 ng/ml was used.With the controls heart rate and rhythm remained steady, but there was a slow decline in amplitude of the contraction. With a prolactin concentration of 50 ng/ml the heart rate rose to about 40% above control during the first hour and after an initial sharp increase the contraction amplitude declined more rapidly than in the controls. The prolactin concentration of 200 ng/ml produced a decline of about 25% in heart rate over the first hour and amplitude behaved much as in the controls. Frusemide had no clear effect on the rate of beating of the controls, but it tended to reverse both the acceleration produced by 50 ng/ml prolactin and the slowing produced by the higher dose. Both the doses of prolactin consistently caused disturbances of rhythm. These effects occur at concentration of prolactin found in human plasma in various pathophysiological conditions.

Animals↗
PubMed1971

The effect of splanchnic nerve stimulation on gastric acid secretion and mucosal blood flow in the anaesthetized cat.

1. Electrical stimulation of the vagus nerves produced a parallel increase in gastric acid secretion and gastric mucosal blood flow.2. Gastric acid secretion and mucosal blood flow, stimulated by pentapeptide infusions or by vagal stimulation, were markedly and equally reduced by electrical stimulation of splanchnic nerve fibres.3. The splanchnic stimulated reduction in acid and mucosal blood flow occurred only when the rise in blood pressure, normally associated with splanchnic stimulation, was prevented by inclusion of a pressure reservoir in the circulation.4. There was evidence that the effect of the splanchnic nerves was not mediated by release of adrenaline from the adrenal medulla.

Adrenal Medulla↗
PubMed1971

Pepsin secretion, gastric motility and mucosal blood flow in the anaesthetized cat.

1. There is a weak relationship between pepsin output and gastric mucosal blood flow (MBF) during vagal stimulation. When compared with the strong relationship between H(+) output and MBF, this suggests little dependence of pepsin secretion on MBF.2. Gastric MBF per unit H(+) output was significantly greater during vagal stimulation, when H(+) secretion was accompanied by pepsin secretion, than during pentapeptide stimulation when no pepsin was secreted.3. Pepsin output was not reduced during splanchnic stimulation whereas MBF and acid output were, when blood pressure was kept constant.4. Splanchnic stimulation did not produce any pepsin secretion.5. Gastric motor responses to vagal stimulation and to I.A. injections of acetylcholine were equally reduced by splanchnic stimulation.

Acetylcholine↗
PubMed1971

Splanchnic nerve inhibition of gastric acid secretion and mucosal blood flow in anaesthetized cats.

1. Efferent electrical splanchnic nerve stimulation will significantly inhibit gastric acid secretion and mucosal blood flow (MBF) stimulated by either large I.V. doses of pentapeptide or histamine, if the rise in blood pressure is prevented.2. Splanchnic stimulation will also reduce the increase in MBF in response to infusions of isopropylnoradrenaline, if the blood pressure rise is prevented.3. Evidence is presented which suggests that the splanchnic nerve inhibitory effect is not due to reducing the amount of stimulant arriving at the gastric mucosa.4. By analysing the responses to histamine, when acid secretion is accompanied by a large MBF relative to the pentapeptide responses, it is suggested that the inhibitory effect of splanchnic nerve stimulation is due to vasoconstriction.5. It remains possible that there is a direct inhibitory effect on the parietal cells.

Animals↗
PubMed1971

Mechanisms relating gastric acid secretion and mucosal blood flow during gastrin and histamine stimulation.

1. Gastric mucosal blood flow (MBF) and gastric acid secretion have been compared and related during the infusion of a wide dose range of gastrin extracts, pentapeptide (Peptavlon, I.C.I. 50123) and histamine.2. Constancy of increase in mucosal blood flow relative to H(+) secretion was obtained with gastrin stimulation, whereas histamine stimulation produced higher ratios of mucosal blood flow to H(+) secretion, and these ratios declined as each experiment continued.3. The importance of considering only the increase in mucosal blood flow in relation to acid secreted is demonstrated.4. It is concluded that the differences shown in the DeltaMBF/DeltaH(+) with histamine and gastrin stimulation provide further evidence that the amidopyrine clearance technique measures gastric mucosal blood flow.

Aminopyrine↗
PubMed1970

Effects of intragastric hyperosmolal solutions on gastric function.

1. The effects of intragastric hyperosmolal solutions on resting and secreting stomachs of anaesthetized cats have been studied.2. Hyperosmolal solutions reduced acid secretion in response to histamine and gastrin. There was a significant correlation between increase in osmolality and decrease in acid response to small doses of gastrin. A continuous acid secretion produced by large doses of gastrin was not significantly reduced.3. The loss of H(+) from resting stomachs is related to the pH and osmolality of the instilled fluid. The loss was greatest at low pH and high osmolality, but was insufficient to account for the H(+) loss from secreting stomachs at similar pH and osmolality.4. The Na(+) output into resting stomachs was increased by hyperosmolal solutions, the increase being related only to the osmolality of the solutions. For the same degree of hyperosmolality there was no difference between the sodium output into resting and secreting stomachs.5. The H(+) deficit associated with intragastric hyperosmolal conditions does not seem to depend upon a neural mechanism, a blood-borne hormone, or a reduction in gastric blood flow. Evidence is presented that diffusion, exchange or neutralizing mechanisms are unlikely to be responsible for the H(+) deficit. It is suggested that inhibition of oxyntic cell activity by release of a chemical agent from the surface cells of the mucosa is the most likely explanation of the results observed.6. The possible physiological significance of intragastric hyperosmolal inhibition of acid secretion is discussed.

Animals↗
PubMed1968

Gastric blood flow in anaesthetized cats.

1. The gastric mucosal blood flow has been measured by the amidopyrine clearance technique in anaesthetized cats. The total gastric blood flow has been (a) measured directly and (b) calculated by the Fick principle from the amidopyrine concentrations in gastric arterial and venous blood and the gastric output of amidopyrine.2. Observations on the recovery of added amidopyrine from arterial and venous blood and plasma, and on the rate of transfer of amidopyrine from corpuscles to plasma, support the underlying assumptions of the amidopyrine method of measuring mucosal blood flow.3. If acid solutions are instilled into the stomach the mucosal blood flow of the non-secreting stomach may be measured by the amidopyrine technique.4. Total gastric and mucosal blood flow increased linearly with increase in H(+) secretion, stimulated by histamine or gastrin. The increase in total flow was entirely due to the increase in mucosal flow.5. The relationship between mucosal blood flow and H(+) secretion was the same for histamine and gastrin responses, and was unaffected by maintaining the total flow at a constant level, or by reduction of the circulating blood volume. Increase in blood volume altered the relationship so that there was a greater increment in mucosal blood flow for any increase in H(+) secretion.6. It is concluded that valid observations may be made on secretion and blood flow relationships in acute anaesthetized preparations.

Aminopyrine↗
PubMed1968

Assay of gastrin by means of its gastric acid stimulating activity.

1. A method is described for the bio-assay of gastrin activity in the anaesthetized cat, based on the acid stimulating activity of gastrin.2. A ;gastrin' of unknown potency can be assayed in terms of a stable Standard Gastrin Extract or of Synthetic Human Gastrin I.3. The sensitivity of the method is such that it will detect quantities of Synthetic Human Gastrin I at least as small as those at present described as detectable by radioimmunological techniques.4. The precision of the assay is such that it falls in the category that has been described as very precise and well suited to clinical studies.

Animals↗