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Biomedical subjects

J M Foy

Publications and source records attributed to J M Foy.

At least 19 recordsLinked to original sources
PubMed1988

Inhibitors of folic acid synthesis in the treatment of experimental Pneumocystis carinii pneumonia.

Inhibitors of folic acid synthesis were compared alone and in different combinations in the therapy of pneumocystosis in immunosuppressed rats. Sulfonamides (sulfamethoxazole, sulfadiazine, and sulfadoxine) and sulfones (dapsone) used alone were very active against Pneumocystis carinii, as judged by histologic examination of the lungs and by organism quantitation. Improved efficacy could not be demonstrated by the addition of an inhibitor of dihydrofolate reductase to the regimen. Dihydrofolate reductase inhibitors (trimethoprim, diaveridine, and pyrimethamine) used alone were ineffective against P. carinii. All drugs were well tolerated except pyrimethamine, which caused bone marrow depression; folinic acid ameliorated this adverse reaction but did not interfere with P. carinii treatment. These data have potential clinical implications but need to be interpreted with caution and in light of other systems of P. carinii drug evaluation.

Animals↗
PubMed1987

Comparison of histologic and quantitative techniques in evaluation of therapy for experimental Pneumocystis carinii pneumonia.

Pneumocystis carinii pneumonia was induced in rats by the administration of corticosteroids, and histologic and quantitative techniques were compared in the evaluation of the severity of the disease and response to therapy. A highly significant correlation was found between the histologic score of the extent of alveolar involvement (the standard method of assessment) and the number of P. carinii cysts and nuclei in lung homogenates, lung weight, and lung weight/body weight ratio. Clear differences were noted between rats which responded well and rats which responded poorly to therapy by all techniques. Quantitation of P. carinii cysts and nuclei revealed a 10(4)-fold reduction in organism burden with successful treatment. Thus, these techniques should be helpful in the development of testing of new antimicrobial agents in the rat model of pneumocystosis.

Animals↗
PubMed1985

Effect of three loop diuretics and prostaglandins E2 & I2 on the isolated perfused rat mesenteric vasculature.

Rat superior mesenteric vascular bed was isolated, perfused by the artery with Krebs solution and the perfusion pressure monitored. Dose-response curves to noradrenaline and KCl administered as bolus doses were obtained. A 1 hr continuous infusion of either piretanide (10 micrograms ml-1) frusemide (40 micrograms ml-1) or bumetanide (2 micrograms ml-1) decreased the sensitivity of the preparation to noradrenaline but not to KCl. This effect was antagonized by flurbiprofen (12 micrograms ml-1) pretreatment. A 1 hr continuous infusion of prostaglandin (PG)E2 increased the sensitivity of the preparation to both noradrenaline and KCl. PGI2 (5 ng bolus) or diuretic perfusion antagonized the responses to noradrenaline but not those to KCl. PGI2 and diuretics in combination further decreased the responsiveness of the preparation to noradrenaline. KCl responses were unaffected by either PGI2 or diuretics, alone or combined. The results suggest that the loop diuretics decrease the responsiveness of the isolated rat superior mesenteric vascular bed preparation to noradrenaline, possibly by increasing the level of PGI2, an effect which may be an important factor in the cardiovascular activity of the diuretics.

Animals↗
PubMed1984

Effect of bumetanide, frusemide and prostaglandin E2 on the isolated perfused kidney of rat and rabbit.

Rat and rabbit kidneys were isolated, perfused via the renal artery with Krebs solution and perfusion pressure monitored. Dose-response curves to noradrenaline administered as bolus doses or frequency-response curves from transmural arterial electrical stimulation were obtained. A 1 h continuous infusion of bumetanide (0.1 micrograms ml-1) increased the sensitivity of rat kidney vessels to noradrenaline, an effect also seen when bumetanide and flurbiprofen (6 micrograms ml-1) were simultaneously perfused. In the rabbit there was a decreased sensitivity to both electrical stimulation and noradrenaline. A 1 h continuous infusion of frusemide (6 micrograms ml-1) only altered the effects of electrical stimulation. An increased sensitivity in the rat (abolished by flurbiprofen) and a decreased sensitivity in the rabbit kidney was observed. A 1 h continuous infusion of prostaglandin (PG)E2 (2 ng ml-1) increased the sensitivity of rat kidney to both types of stimuli but caused a reduction in the responsiveness of the rabbit kidney to electrical stimuli only. Addition of flurbiprofen only slightly modified these results. The results emphasize and confirm the fundamental difference in reactivity of the rat and rabbit kidney. Bumetanide and frusemide, two ostensibly similar loop diuretics, show significantly different effects on these preparations suggesting that any modification by non-steroidal anti-inflammatory drugs cannot wholly be explained by similar PGE2 induced haemodynamic changes.

Animals↗
PubMed1981

On the pharmacological actions of a diuretic, fenquizone, with particular reference to its site of action.

The pharmacological actions of a diuretic drug, fenquizone have been investigated and its effects compared with well characterized diuretics in rats, mice and rabbits. Changes in sodium and potassium excretion and urine volume were similar in magnitude and duration to those of the thiazide diuretics over dose range 0.05-100 mg kg-1. Free water clearance in rabbits was decreased indicating an action at the cortical diluting site in the nephron and since free water reabsorption was relatively unaffected it appears unlikely to have actions at other sites. Calcium and phosphate excretion studies also suggested that the predominant effects are those occurring at the cortical diluting segment of the nephron. Additional parameters not affected by the drug were blood flow to the cortex and medulla of the kidney (and other major organs), plasma glucose concentration and plasma urate concentration.

Animals↗
PubMed1978

Comparison between spontaneously beating atria from control and streptozocin-diabetic rats.

Isolated spontaneously beating atria from streptozocin diabetic rats were compared with those from controls. Diabetic atria were found to have reduced rates, increased forces of contraction and reduced sensitivity to the inotropic effects of noradrenaline, isoprenaline, tyramine and calcium. Positive chronotropic responses to tyramine were also reduced but those to noradrenaline and isoprenaline were increased suggesting that tyramine releasable stores of noradrenaline were reduced. Elevation of glucose concentration in the medium from 5.6 to 27 mM resulted in decrease of inotropic sensitivity to the agents used in both control and diabetic rat atria. Resting contractile force of control rat atria was reduced by the inclusion of either 22 mM 2-deoxyglucose, 10(-3) i.u. insulin ml-1 or 5 mM acetate in the medium. The rate was also reduced by medium containing 2-deoxyglucose but increased by insulin. 2-Deoxyglucose also reduced inotropic but increased chronotropic sensitivity to isoprenaline. Possible mechanisms responsible for the changes observed are discussed.

Acetates↗
PubMed1977

Effects of experimental diabetes and genetic obesity on regional blood flow in the rat.

Blood flow through various tissues of streptozotocin- and alloxan-diabetic and genetically obese rats was compared with that of controls by a radioisotopically labeled microsphere technique. Total cardiac output per unit body weight was unchanged in the diabetic group but decreased in the obese animals. The proportion of cardiac output received by the kidney and organs of the gastrointestinal tract was increased in the diabetic animals. Tissue hyperplasia appeared to be largely responsible. Blood flow per unit weight was markedly increased in the fat tissue of diabetic rats but was reduced in that of the obese rats, indicating a positive relationship between fat mobilization and blood flow. Blood flow in the hindlimbs, tail, skin, and spleen were all reduced in at least one diabetic group. Most of the changes observed appeared to progress with the duration of diabetes. Possible hormonal and metabolic causes are discussed. Some of the experimental changes observed may form useful models for diabetic vasculopathy.

Adrenal Glands↗
PubMed1976

Effect of experimental diabetes, food deprivation and genetic obesity on the sensitivity of pithed rats to autonomic agents.

1 The sensitivities of alloxan and streptozotocin diabetic and hereditary obese pithed rats to acetylcholine, isoprenaline and noradrenaline were compared to those of controls. 2 Blood pressure and heart rate recordings made before dosing was started showed the streptozotocin-treated animals to have a significantly reduced heart rate and increased pulse pressure as compared with controls. 3 Both diabetic groups were found to have reduced sensitivities to the pressor effect of noradrenaline, the depressor effect of acetylcholine, the positive chronotropic and inotropic effect of isoprenaline and the reduction in diastolic pressure induced by isoprenaline. The reduction in sensitivity was generally much greater in the streptozotocin diabetic animals. 4 The genetically obese rats were found to have similar sensitivities to all three agents as did their non-obese litter mates. 5 When either diabetic group was deprived of food for 24 h preceding the tests the sensitivities were found to be raised significantly towards normal in almost all cases. 6 The results are contrasted with previous in vitro results and possible causative metabolic factors discussed. It is suggested that sensitivity changes are unevenly distributed within the cardiovascular system.

Acetylcholine↗