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Biomedical subjects

T Bennett

Publications and source records attributed to T Bennett.

At least 361 records · Page 20Linked to original sources
PubMed1976

The involvement of noradrenergic nerves in the cardiovascular reflex responses to lower body negative pressure in the anaesthetised rabbit.

1. Resting cardiovascular status and the reflex responses to lower body negative pressure (LBNP) were examined in control rabbits and in rabbits sympathectomised with 6-hydroxydopamine (6-OHDA). 2. Resting systemic arterial pressure and total peripheral resistance were significantly higher in control than in 6-OHDA treated animals. 3. Control animals responded to LBNP at -25 mm Hg with a peripheral vasoconstriction and tachycardia. These responses were absent in 6-OHDA-treated animals. 4. Control animals responded to LBNP at -70 mm Hg with a peripheral vasoconstriction and a bradycardia followed by a tachycardia. There was no significant change in heart rate in response to this stimulus in 6-OHDA-treated animals, although a slight vasoconstriction was seen. 5. Bethanidine blocked the tachycardia and vasoconstriction seen in response to LBNP in control and 6-OHDA-treated rabbits. Under these conditions there was no significant difference between the total peripheral resistance of the control and treated animals. 6. The results indicated that neither the maintenance of the resting systemic arterial pressure nor the reflexes elicited by LBNP in control or in chronically sympathectomised rabbits involved hormonal mechanisms, but LBNP was maintained for 1 min only. These findings are discussed in the context of previous observations.

Animals↗
PubMed1976

Twenty-four hour monitoring of heart rate and activity in patients with diabetes mellitus: a comparison with clinic investigations.

Heart rate and activity were recorded continuously in 11 selected diabetics during a normal day, and the observations were compared with results obtained in the same patients in the diabetic outpatient clinic 10 months earlier. Both sets of findings agreed well in heart rate variability and postural tachycardia. In patients with well-controlled diabetes simple tests of reflex cardiovascular control produce results that may be useful in following the course of diabetic autonomic neuropathy.

Arrhythmia, Sinus↗
PubMed1976

An ultrastructural examination of the action of vinblastine on microtubules, neurofilaments and muscle filaments in vitro.

In vitro incubation of autonomic nerves with vinblastine sulphate (1 times 10(-4) M) caused a disappearance of microtubules within 15 min; during the following 15 min paracrystalline arrays appeared within the axons. An increase in the abundance of microfilaments was also observed, but these did not appear to arise from disaggregated microtubules since the increase in microfilament numbers was noted at an incubation time when crystal formation was extensive. Pretreatment of autonomic nerves with colchicine (2.5 times 10(-4) M) caused a reduction of approximately 80% in the numbers of microtubules, but did not prevent the formation of crystals on subsequent exposure to vinblastine. No ultrastru"tural changes were observed in myofilaments on incubation with vinblastine.

Animals↗
PubMed1976

Selective noradrenergic denervation of the heart following intravenous injections of vinblastine or vincristine.

1. The progressive effects of a single injection (3mg/kg i.v.) of either vinblastine or vincristine on the innervation of the rat atria have been examined. 2. Functional studies were performed by stimulating electrically the noradrenergic or cholinergic nerve fibres within isolated left atria from treated and control rats. In addition, the effects of the drugs on the ultrastructure of both types of nerve fibre were examined. The noradrenergic innervation was further examined by fluorescence histochemistry and measurement of the noradrenaline content of the atria. 3. On the basis of these studies it appeared that both drugs caused degeneration of noradrenergic nerves; cholinergic nerves seemed to be unaffected. Marked effects were seen 48 h after vinblastine treatment or 30 h after vincristine treatment. 4. Evidence is presented and discussed as to whether or not this action of the vinca alkaloids can be ascribed to their well-established effects on microtubules and intra-axonal transport processes.

Animals↗
PubMed1976

Cardiovascular reflex responses to apnoeic face immersion and mental stress in diabetic subjects.

The cardiovascular reflex responses to apnoea accompanied by immersion of the face in water and to mental stress, have been investigated in 21 diabetic subjects. Apnoeic face immersion caused bradycardia and forearm vasoconstriction (in seven subjects), bradycardia and forearm vasodilation (three subjects), tachycardia and forearm vasoconstriction (three subjects), or tachycardia and forearm vasodilatation (eight subjects). Mental stress evoked a tachycardia and forearm vasodilatation in all subjects. The abnormalities in the responses to apnoeic face immersion are most readily accounted for by loss of vagal and/or vasoconstrictor function.

Adult↗
PubMed1976

Baroreflex sensitivity and responses to the Valsalva manoeuvre in subjects with diabetes mellitus.

Baroreflex sensitivity was measured in a group of diabetic patients from the slope of the regression of pulse interval on systolic arterial pressure, during elevation of pressure induced by phenylephrine. The response to Valsalva's manoeuvre was assessed in the same subjects. There was a good correlation between the two tests in the identification of patients with a parasympathetic autonomic disturbance, but measurements of baroreflex sensitivity were more readily quantifiable than were the responses to Valsalva's manoeuvre. Furthermore, baroreflex sensitivity could be measured in patients with sympathetic nervous dysfunction in whom vagal function could not be assessed by means of the Valsalva manoeuvre. Measurement of baroreflex sensitivity is likely to be suitable for longitudinal studies of the progress of diabetic autonomic neuropathy.

Adult↗
PubMed1976

The in vitro and in vivo effects of vinca alkaloids on the noradrenergic innervation of the vas deferens.

The effects of Vinca alkaloids on the vas deferens have been examined after in vitro and in vivo administration. In the organ bath, vinblastine (1 X 10-4M for 4 hr) caused an increase in sensitivity to noradrenaline and biochemical, histochemical and ulstrastructural signs of noradrenaline depletion from the nerves supplying the outer longitudinal muscle layer. After intravenous injection of Vinca alkaloids the nerve fibres seemed less affected. It is concluded that the apparent resistance to the drugs in vivo is largely due to low tissue perfusion.

Animals↗
PubMed1975

Cardiovascular control in diabetes mellitus.

Heart rate variability and the changes in heart rate and blood pressure which occur on standing were measured in 21 diabetics. These simple measures distinguished four groups of patients, with loss of parasympathetic activity being commoner than loss of sympathetic activity.

Adolescent↗
PubMed1975

The in vitro effects of vinblastine and vincristine on the responses of the guinea-pig vas deferens to nerve stimulation.

1. Neither vinblastine nor vincristine (1x10-4M) appeared to cause a specific blockade of transmission through the guinea-pig hypogastric ganglion, since responses to preganglionic nerve trunk stimulation were lost no sooner than responses to postganglionic nerve trunk stimulation. 2. The responses to postganglionic nerve trunk stimulation were blocked by vinblastine or vincristine at a time when responses to stimulation of intramural nerve fibres were little affected. 3. The results do not support the suggestion that inhibition of the exocytotic release of transmitter is responsible for the early in vitro effects of these drugs.

Animals↗
PubMed1974

Regeneration of the noradrenergic innervation of the cardiovascular system of the chick following treatment with 6-hydroxydopamine.

1. Fluorescence histochemical and pharmacological studies were made of the noradrenergic innervation of inferior venae cavae and left atria from 2- and 6-week-old chicks before, and following, treatment with 6-hydroxydopamine.2. Noradrenergic nerves in the younger animals appeared to be relatively resistant to the toxic effects of 6-hydroxydopamine.3. In the older animals, the time course of recovery from the effects of 6-hydroxydopamine appeared to reflect the rate of regeneration of destroyed noradrenergic nerves.4. Marked presynaptic supersensitivity to adrenaline and noradrenaline was observed in left atria and inferior venae cavae following treatment with 6-hydroxydopamine.

Action Potentials↗