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Biomedical subjects

R Low

Publications and source records attributed to R Low.

26 records · Page 2Linked to original sources
PubMed1981

Intra-aortic balloon counterpulsation: rationale, application and results.

Intra-aortic balloon counterpulsation is an effective means of reducing myocardial ischemia and supporting the failing circulation. Its therapeutic benefits are the direct result of distolic augmentation and systolic unloading, the former increasing myocardial perfusion and the latter enhancing cardiac performance. Indirect effect include diminution of ischemia by decrease in the determinants of myocardial oxygen demand and improved ventricular function secondary to the decreased ischemia. Intra-aortic balloon counterpulsation is indicated in clinical syndromes related to intractable cardiac ischemia, including myocardial infarction shock and severe left ventricular failure, refractory ischemic pains, and ventricular arrhythmias unresponsive to medical management. It is also of importance in other situations associated with low cardiac output. This therapeutic modality has recently been considered for early use in extensive myocardial infarction to limit cardiac damage and avert complications. Recent technical advances have facilitated the ease and safety of application of intra-aorta balloon counterpulsation. Complication are of low frequency but can be serious and employment of the method is predicated upon consideration of both potential benefits and risks.

Acute Disease↗
PubMed1980

Effects of oral pentaerythritol tetranitrate in cardiac failure and angina pectoris. Assessment by hemodynamic measurement and exercise capacity.

Oral pentaerythritol tetranitrate produces sustained beneficial hemodynamic effects in patients with cardiac failure of varied etiology. The principle action is a reduction of elevated left ventricular filling pressure. In a small group of angina patients, the oral nitrate in high dosage resulted in considerable increase in angina-limited exercise capacity compared to placebo for four hours following drug administration. No side effects were associated with ingestion of pentaerythritol tetranitrate in these investigations.

Administration, Oral↗
PubMed1980

Heterogeneous catalysis by phospholipase A2: mechanism of hydrolysis of gel phase phosphatidylcholine.

Hydrolysis of gel phase dipalmitoylphosphatidylcholine (DPPC) at 37 degrees C catalysed by Crotalus atrox phospholipase A2 (PLA) is described extremely well by the "path 1" kinetic mechanism of Tinker and Wei (1979) (Can. J. Biochem. 57, 97-106), if reversible adsorption is allowed as a side reaction. Progress curves show an initial rapid phase, the initial velocity being a Michaelis-Menten function dependent on the catalytic properties of the enzyme (kcat approximately equal to 9200 min-1, Km approximately equal to 0.12 mM), then level off to a slower rate determined by the desorption equilibrium constant (KD approximately equal to 0.01 mM) and desorption rate constant (kD approximately equal to 0.15 min-1). The relaxation time, tau, for the transition to the desorption-limited reaction is approximately 0.5 min; this large value of tau probably arises from a slow conversion of active, dimeric enzyme to an inactive protein species adsorbed to the lipid surface. At later times in the reaction there is an increase in the rate of hydrolysis, attributed to a stimulation of desorption by the products. The desorption equilibrium constant KD is a quadratic function of the surface concentration of products and increases 20- to 30-fold when all accessible substrate is hydrolysed. Both lysophosphatidylcholine (lyso-PC) and fatty acid were found to stimulate the desorption, but lyso-PC was also found to be a competitive inhibitor of the catalysis. Adsorption of PLA to DPPC and egg PC vesicles was directly measured using a gel partition technique. Strong binding to egg PC was observed, which was not dependent on the presence of calcium ion (essential for catalysis); PLA inhibited by acylation of up to four lysine residues per mole of monomeric enzyme with ethoxyformic anhydride was equally strongly adsorbed, indicating that lipid binding is not dependent on catalytic activity. Reaction products greatly weakened the binding of PLA to the lipid surface as expected. Cholesterol had two effects on the hydrolytic reaction: there was a striking decrease in the rate of the slower, desorption-limited phase, the rate of which decrease to almost zero at 15 mol% cholesterol, but there was also evidence for the formation of a complex with stoichiometry 1 cholesterol: 2 DPPC in which DPPC is no longer a substrate for the enzyme. Implications of the proposed mechanism for specificity and control of surface catalysis by PLA are discussed.

Crotalid Venoms↗
PubMed1979

Giant adrenal myelolipoma and testicular interstitial cell tumor in a man with congenital 21-hydroxylase deficiency.

The occurrence of a giant myelolipoma of the adrenal gland reported in a patient with congenital adrenal hyperplasia (21-hydroxylase deficiency). Associated significant findings include a massive proliferation of adrenocortical cells as an integral part of the myelolipoma and coincidental tumor of the interstitial cells of the testis. The clinical, radiologic, endocrinologic, and pathologic features of this case are correlated with a review of the literature. The additional myelolipomas are also reported here for the first time. Similar lesions have been induced experimentally in rats and provide further evidence suggesting a hyperplastic rather than a neoplastic nature for this complex lesion, at least in its earlier stages.

17-Ketosteroids↗
PubMedDate not supplied

CT findings in acute renal cortical necrosis.

Acute renal cortical necrosis has three characteristic findings on contrast enhanced CT: (a) lack of enhancement of the renal cortex, (b) enhancement of the renal medulla, and (c) absent renal excretion.

Adult↗