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Biomedical subjects

G M Clarke

Publications and source records attributed to G M Clarke.

At least 37 records · Page 2Linked to original sources
PubMed1990

The use of irradiated embryos of Chrysomya bezziana for the detection of the Old World screw-worm fly.

Irradiation of Chrysomya bezziana embryos 1 h before hatching with doses less than or equal to 7 kilorad (kr) had a significant effect on percentage egg hatch, weights and survival of larvae. Doses greater than or equal to 1 kr allowed larval development to the end of the 3rd instar stage in vitro, but prevented normal pupal development. Cattle with wounds infested with 1st instar larvae derived from irradiated embryos had 3rd instar larvae present after 3 d but these failed to pupate. Thus it would be feasible to use such larvae for wound infestation for the enhanced detection of screw-worm fly in areas where the release of fertile flies is undesirable.

Animals↗
PubMed1989

Plasma levels of the lyso-derivative of platelet-activating factor in acute severe systemic illness.

1. Evidence suggests that activation of phospholipase A2 and production of eicosanoids and platelet-activating factor (PAF) are involved in various responses associated with severe tissue damage and shock. It was postulated that the plasma level of the precursor and degradation product of PAF, lyso-platelet-activating factor (lyso-PAF), might be increased in acute severe illness. 2. After plasma extraction, lyso-PAF was acetylated in vitro to PAF, which was measured by bioassay using 5-[14C]hydroxytryptamine-labelled rabbit platelets. Measurements were made in 18 severely ill patients (five with cardiogenic shock; five with severe infection, five after repair of abdominal aortic aneurysm, two with acute pancreatitis; 13 males, five females). Plasma lyso-PAF in these patients was 33 +/- 15 (SD)ng/ml (range 5-111 ng/ml), whereas values in normal males (40-65 years) ranged from 102 to 253 ng/ml (n = 15) and in females from 74 to 174 ng/ml (n = 10). Depression of plasma lyso-PAF did not relate closely to the patient group nor to specific therapy, but repeated measurements in each of 10 patients showed an increase in plasma lyso-PAF (P less than 0.002), associated with clinical improvement. 3. Evidence was obtained indicating that neither the presence of an inhibitor in the assay system nor reconversion of PAF to lyso-PAF in vitro produced the unexpected depression of plasma lyso-PAF. 4. The mechanisms responsible, which may have therapeutic implications, remain to be elucidated.

Acute Disease↗
PubMed1987

Genetic architecture and adaptation: quantitative analysis of sheep and refuse tip populations of the Australian sheep blowfly, Lucilia cuprina.

Phenotypic differentiation between geographic areas and between sheep and adjacent refuse tip populations was assessed by quantitative analysis of population samples of L. cuprina from New South Wales (Lismore) and Victoria (Mansfield). In addition the genetic structure of populations has been defined and compared by biometrical analysis techniques. For all morphological and fitness characters examined significant phenotypic differentiation was observed both between geographic localities and between sheep and non-sheep populations of each locality. Diallel analysis of the populations revealed architectural differences between sheep and non-sheep populations for both fecundity and egg hatchability. Sheep populations only, regardless of locality, displayed dominant gene effects on these fitness traits. The results suggest that refuse tip populations may be other than transients and that the differentiation may reflect differing patterns of adaptation and history of selection of the populations. The relevance of such differentiation to the successful establishment of a chemical and/or autocidal control zone is considered.

Adaptation, Physiological↗
PubMed1986

Venous thromboembolism to the heart. A case report and review of treatment.

Venous thromboembolism to the heart is a rare and often fatal condition that is now being recognized more frequently owing to the widespread use of two-dimensional echocardiography. Death may be due to embolic obstruction of the tricuspid or the pulmonary valves, or to further migration of the embolus to the pulmonary arteries. The incidence of early recurrent pulmonary embolism is high. When used as primary treatment, medical treatment (anticoagulation or fibrinolytic therapy) failed in eight of 13 reported cases. Only one of eight patients died when surgical embolectomy was undertaken. We believe that an echocardiographic diagnosis of venous thromboembolism to the heart is sufficient evidence to warrant urgent surgical embolectomy. An undue delay in definitive treatment is often fatal.

Aged↗
PubMed1986

Phenelzine poisoning.

A 46-year-old female with severe phenelzine poisoning was managed successfully by alpha blockade and fluid loading, with the aid of invasive haemodynamic monitoring. The pathophysiology was documented, showing elevated plasma and urinary catecholamines, cardiovascular abnormalities and a contracted blood volume. Most of these changes were reversed following treatment.

Adrenergic alpha-Antagonists↗
PubMed1981

Randomized controlled trial of vasodilator therapy after myocardial infarction.

Hemodynamic changes and mortality and morbidity were compared in a randomized controlled trial of sodium nitroprusside after acute myocardial infarction. Fifty patients with a mean pulmonary capillary wedge pressure of more than 20 mm Hg within 24 hours of acute infarction were randomly assigned to one of two groups: 25 patients treated with nitroprusside and 25 treated with furosemide. Nitroprusside rapidly produced a sustained decrease in systemic vascular resistance and increase in cardiac index (thermodilution). After 1 hour the cardiac index had increased 16 +/- 3 (mean +/- standard error of the mean) percent (p less than 0.001) compared with a decrease of 7 +/- 3 percent with administration of furosemide (p less than 0.01). Differences in systemic vascular resistance and cardiac index in the two groups persisted throughout the 48 hour treatment period (p less than 0.001). Pulmonary capillary wedge pressure decreased rapidly with nitroprusside and slowly with furosemide so that, although it was significantly lower in the former group overall (p less than 0.001), by 48 hours the values were not different. Although beneficial acute hemodynamic effects of nitroprusside were demonstrated, there was no difference in mortality or in morbidity assessed clinically, by chest X-ray film, echocardiogram or graded treadmill stress testing after 6 months or 1 year.

Acute Disease↗
PubMed1980

Prazosin in the treatment of severe chronic congestive cardiac failure.

The acute haemodynamic effects of prazosin 5 mg were investigated in 11 patients with severe chronic congestive cardiac failure. Six patients had their antifailure therapy discontinued while five continued on their usual medication. Two patients were exercised before and after prozosin. Following the drug, pulmonary capilary wedge pressure diminished 7 +/- 2(SE) mmHg (P < 0.005) and cardiac index increased 17 +/- 6% (P < 0.02). Mean arterial pressure fell in all subjects (- 9 +/- 2 mmHg; P < 0.001) and systemic vascular resistance was reduced in all but one (- 19 +/- 5%; P < 0.005). There was no significant change in heart rate. Four of the five subjects whose regular medications were continued were evaluated by clinical examination, chest X-ray, echocardiogram and treadmill stress test, before and after four weeks of prazosin therapy, one subject having died in this time. Two improved, one deteriorated and one remained unchanged. Thus, chronic prazosin therapy benefited individual patients but did not consistently provide long term improvement.

Adult↗
PubMed1980

Comparison of vasodilator drug prazosin with digoxin in aortic regurgitation.

Intravenous administration of the vasodilator sodium nitroprusside has beneficial haemodynamic effects in subjects with severe aortic regurgitation while acute digitalisation can produce unwanted effects associated with an increase in systemic vascular resistance. This study compares the haemodynamic effects of the vasodilator prazosin and digoxin in eight patients with isolated severe aortic regurgitation. Prazosin 5 mg orally resulted in a 12 +/- 3 (SE) per cent increase in cardiac index (thermodilution), maintained over four to six hours, while digoxin 0.75 mg intravenously did not change the cardiac index. Prazosin reduced mean arterial pressure by 9 +/- 3 mmHg and systemic vascular resistance by 18 +/- 4 per cent while digoxin resulted in a 6 +/- 2 per cent increase in the latter. Mean pulmonary capillary wedge pressure fell 3 mmHg with prazosin. In this group of patients with severe aortic regurgitation but without severe cardiac failure, the changes with either drug, studied in doses conventionally used, were small but those with prazosin were directionally more desirable than those resulting from digoxin.

Adult↗
PubMed1975

Autonomic manifestations of tetanus.

Two patients with tetanus are reported to illustrate the involvement of the sympathetic and parasympathetic nervous system respectively. Aspects of the autonomic manifestations of tetanus are illustrated and discussed.

Adult↗