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Biomedical subjects

D Ballantyne

Publications and source records attributed to D Ballantyne.

At least 73 records · Page 4Linked to original sources
PubMed1985

Delay in diagnosis of right atrial myxoma.

Clinical, echocardiographic, and nuclear angiographic findings in a 51-year-old woman who presented with a history of dyspnea are discussed. Initial echocardiography revealed no abnormality. However, a subsequent radionuclide angiogram revealed a filling defect on the right side of the heart. This represented a right atrial myxoma. Radionuclide angiography can provide a useful noninvasive tool in the diagnosis of intracardiac tumors when echocardiography has not been helpful.

Diagnosis, Differential↗
PubMed1985

Systolic murmurs in pregnancy: value of echocardiographic assessment.

A systolic murmur discovered in antenatal care is the most common reason for cardiological assessment during pregnancy. We have assessed the value of clinical and echocardiographic assessment in 50 consecutive patients who were referred to our cardiac clinic following the discovery of a cardiac murmur at an antenatal clinic. Most of the murmurs occurred at 10-12 weeks gestation; 46 subjects had cardiac murmurs confirmed at the cardiac clinic, of whom 16 gave a history suggestive of a previous cardiovascular disorder. Of the 16 patients, 13 had been found to have a murmur earlier in life which was thought to be of no clinical significance. Complications during pregnancy were infrequent. The most frequent murmur discovered was a soft midsystolic murmur heard with greatest intensity at the left sternal edge. The results of electrocardiography and echocardiography were not helpful in assisting with the diagnosis or substantially altering antenatal management in these patients. We do not feel that echocardiography has an important role in the assessment of systolic murmurs in pregnancy in the absence of other clinical or ECG abnormalities.

Adolescent↗
PubMed1985

Respiratory modulation of sympathetic activity.

Sympathetic activity recorded from cardiac and renal nerves was correlated with phrenic and internal intercostal nerve activity under normocapnea and hypercapnea. Cats were anesthetized with halothane for surgery switching to chloralose for recording. Both vagal and carotid sinus nerves were cut, animals were paralyzed and artificially ventilated. We found that sympathetic activity followed the rhythmic pattern of phrenic nerve discharge fairly closely except in two important respects: first, sympathetic activity was significantly depressed during early inspiration and second, it reached a minimum during post inspiration while phrenic activity was decaying but still active. These effects were accentuated when PACO2 was raised. In one cat early inspiratory depression was the only manifestation of respiratory modulation of sympathetic activity superimposed on an otherwise tonic pattern. In 4 cats sympathetic activity increased in an augmenting fashion in parallel with the augmenting discharge of expiratory alpha motoneurones. We suggest that respiratory-related, excitatory and inhibitory inputs modulate sympathetic activity at the brainstem level. Inspiratory and possibly expiratory interneurones may be the source of activation, and inhibitory inputs may derive from early inspiratory and postinspiratory interneurones. The inhibitory effects may be the only manifestation of respiratory modulation during strong tonic drive of the sympathetic activity.

Animals↗
PubMed1985

Systolic time intervals in adolescents with insulin-dependent diabetes mellitus.

Systolic time intervals were used to evaluate left ventricular performance in 20 diabetic adolescents with a mean age of 15.2 +/- 2.2 years (range 9-17 years) and were compared with an age- and sex-matched control group. Pre-ejection period index (PEPI), left ventricular ejection time index (LVETI), total electromechanical systole index (QS2I) and the PEP to LVET ratio were calculated at rest and following sustained isometric handgrip (SIHG). None of the diabetics had demonstrable microangiopathy or autonomic neuropathy. There was no significant difference in resting or post-exercise heart rate, PEPI, LVETI or PEP/LVET ratio between the two groups. QS2I was significantly prolonged (p less than 0.05) at rest in the diabetics, but was not significantly different following SIHG. These results indicate that cardiac contractility is not detectably abnormal in young diabetics, compared to their adult counterparts who may develop impaired myocardial performance.

Adolescent↗
PubMed1985

Beta-adrenoceptor blockade and intrinsic sympathomimetic activity--relevance in the treatment of ischaemic heart disease.

Beta adrenoceptor blockade has become one of the major therapeutic interventions in the medical management of ischaemic heart disease over the last 15 years. A number of beta adrenoceptor blockers have been developed with differing pharmacological properties including cardioselectivity and intrinsic sympathomimetic activity (ISA). The relevance of this latter property has been in some doubt. A number of reports suggest that ISA confers haemodynamic benefits although there does not appear to be any clear therapeutic advantage. In addition it would appear that patients with severe or rest angina might benefit more from a pure beta antagonist rather than one with ISA when the beta blocker is used as monotherapy, but this situation rarely arises. This paper reviews and assesses the value of treatment of ischaemic heart disease with beta blockers possessing intrinsic sympathomimetic activity.

Adrenergic beta-Antagonists↗
PubMed1984

Sudden death in squash players.

A series of thirty sudden deaths (twenty-nine men, one woman) associated with squash playing is described. The subjects' mean age was 46.7 +/- SD 9.58 years (range 22-66). Necropsy results were available for twenty-seven subjects. Significant coronary heart disease (CHD) was found in twenty-three, valvular heart disease in three, and hypertrophic obstructive cardiomyopathy in one, and cardiac arrhythmia, in the absence of other pathology, was thought to have preceded death in two. One subject died from intracerebral haemorrhage. Twenty-two had reported prodromal symptoms, and of those with CHD, sixteen had had at least one identifiable CHD risk factor. Twelve subjects had been known by their family physician to have a medical disorder related to the cardiovascular system.

Adult↗
PubMed1984

Evidence for a monosynaptic connection between slowly adapting pulmonary stretch receptor afferents and inspiratory beta neurones.

The synaptic connection between slowly adapting pulmonary stretch receptor afferents and inspiratory neurones within a region ventral to the tractus solitarius was determined using intracellular recording and spike triggered averaging techniques. When the vagus nerve was stimulated at intensities eliciting a Hering-Breuer reflex, the difference in mean latency between centrally recorded action potentials of slowly adapting pulmonary stretch receptor afferents and e.p.s.p.s of inspiratory beta neurones was 0.2 ms. This difference is indicative of a monosynaptic connection. Extracellular single unit spikes of slowly adapting pulmonary stretch receptors recorded from the nodose ganglion were used to trigger the averaging of synaptic noise recorded from inspiratory neurones. A prominent wave of synaptic depolarization was observed in all inspiratory beta neurones even when a small number of sweeps were averaged. This depolarization was absent from inspiratory alpha neurones. The shape indices of these depolarizations are consistent with a monosynaptic connection between slowly adapting pulmonary stretch receptor afferents and inspiratory beta neurones. In addition, the data raise the possibility that this connection is multiple and distributed.

Animals↗
PubMed1984

Post-synaptic inhibition of bulbar inspiratory neurones in the cat.

Stable intracellular recordings from thirty-six bulbar inspiratory neurones revealed three centrally originating, rhythmic patterns of synaptic inhibition (i.p.s.p.s). (i) A declining pattern of i.p.s.p.s accompanying the early stages of inspiration (early inspiratory inhibition) was identified in a total of twenty neurones representing examples of each of the functional classes of bulbar neurones examined, i.e. six R alpha- and two R beta-neurones of the dorsal respiratory group and twelve R alpha-neurones of the ventral respiratory group. (ii) A transient pattern of i.p.s.p.s just preceding or coinciding with the cessation of inspiration (late inspiratory inhibition) was present in the remaining sixteen neurones which were tested, representing six R alpha-neurones and three R beta-neurones of the dorsal respiratory group and seven R alpha-neurones of the ventral respiratory group. (iii) An augmenting pattern of expiratory i.p.s.p.s was present in all thirty-six neurones. Late inspiratory and expiratory i.p.s.p.s in the same neurones showed a similar time course of reversal when chloride was injected or allowed to diffuse into the cells and were associated with similar increases in input conductance. Both patterns of i.p.s.p.s appear to arise at or close to the cell soma. Early inspiratory i.p.s.p.s required a relatively longer period of chloride injection for reversal to be accomplished. Input conductance changes were either absent or smaller than those associated with late inspiratory or expiratory inhibition. These i.p.s.p.s appear to arise at more distal dendritic sites. These patterns of i.p.s.p.s are discussed in relation to the mechanisms shaping the growth of central inspiratory activity, bringing this activity to an end, and suppressing its redevelopment during expiration.

Animals↗
PubMed1984

Apolipoprotein A and B (Sf 100-400) metabolism during bezafibrate therapy in hypertriglyceridemic subjects.

This study describes the effects of bezafibrate, an analogue of clofibrate, on the plasma lipid and lipoprotein profiles of 11 hypertriglyceridemic subjects and on their metabolism of apolipoproteins A-I, A-II, and B. The major action of the drug was to lower plasma triglyceride (by 58%; P less than 0.01). This was accompanied by a reduction in the level of very low density lipoprotein apoprotein B (Svedberg units of flotation [Sf] 60-400), whose mean residence time in the plasma fell threefold (from 3.4 to 1.0 h). Synthesis of the B protein in this fraction was not significantly altered, so the drug acts to accelerate the transit of very low density lipoprotein particles down the delipidation cascade. The metabolism of very low density lipoprotein remnant apoprotein B (Sf 12-100) changed little in response to treatment, although we detected a 30% increment (P less than 0.05) in the plasma concentration of this fraction. The mean residence time of these remnant particles in the plasma did not correlate with that of Sf 100-400 very low density lipoprotein apoprotein B, nor was this parameter altered by the drug. The most consistent and significant perturbation seen in the Sf 0-12 fraction (low density lipoprotein) was a reduction in the fractional catabolism of its apoprotein B moiety (26%; P less than 0.05). In those subjects who were grossly hypertriglyceridemic and who responded well to treatment, the level of this protein rose substantially owing to a combined increase in its synthesis and a reduction in its catabolism. In the group as a whole, high density lipoprotein cholesterol rose 13% (P less than 0.02), and detailed examination showed that this was associated with a small but significant increment in the plasma concentration of the high density lipoprotein subfraction 2. High density lipoprotein subfraction 3 also rose on the average, but this was not a consistent feature in all patients. The plasma concentrations and turnovers of the A proteins (A-I and A-II) were not significantly altered by bezafibrate therapy.

Apolipoproteins A↗