Role of cysteine in regulating morphogenesis and mitochondrial activity in the dimorphic fungus Histoplasma capsulatum.

Three stages can be distinguished in the temperature-induced mycelial-to-yeast phase transition of Histoplasma capsulatum. Stage one is characterized by a progressive decrease in the respiration rate and in the intracellular concentrations of cysteine and other amino acids. By stage two, respiration has ceased completely and free cysteine has fallen to low levels. Exogenous cysteine is required during the second stage for activation of mitochondrial respiration (stage three) and completion of the morphological transition. Mitochondria isolated from cells in the second stage show no respiration with NADH, succinate, or other substrates unless they are first incubated with cysteine. In addition, a novel, cytosolic cysteine oxidase appears during the latter part of the second stage. In stage three, the respiration rate rises, intracellular concentrations of free cysteine and other amino acids increase to levels characteristic of yeast, and the morphological transition is completed. The results support the idea that alterations in cysteine metabolism play a key role in this differentiation process.     

What do family physicians see in practice?

Health care problems dealt with in their practices were recorded by seven family physicians over a period of 1 year (two others recorded for 3 months), each diagnosis being coded according to the Canuck Disease Classification Index. Problems were classified into four types: physical, psychosocial, diseases of choice (or lifestyle) and diseases of social impact. More than 85% of the 23 108 problems recorded were physical in origin and had physical manifestations. More time was spent on routine checkups and treatment of respiratory disease than on any other activity. Venereal disease and alcoholism were infrequent problems. The family physician is in a favourable position to act as health educator and counsellor and must be throughly trained in the physical aspects of disease.     

Preoperative balloon occlusion: “the intravascular ligature”

The resection of cerebral arteriovenous malformations may be difficult or very hazardous when access to the feeding arteries is limited by overlying large draining veins. Properative occlusion of feeding arteries can be performed using detachable flow-directed balloons.     

Some effects of disopyramide and its N-dealkylated metabolite on isolated nerve and cardiac muscle

In animals and man the antidysrhythmic agent disopyramide in primarily metabolised by mono-N-dealkylation. The effects of disopyramide and its N-dealkylated metabolite (MIP) have been investigated using isolated cardiac and nervous tissue, and their effects have been compared with the effects of other antidysrhythmic agents. Disopyramide, d,l-propranolol and quinidine all decreased both maximum driving frequency and developed tension in electrically driven guinea pit atria. MIP and procaine amide also decreased maximum driving frequency, but had a positive intropic effect. MIP was only 4 times less active than disopyramide in decreasing maximum driving frequency. There was no evidence that either disopyramide or MIP possessed beta-adrenoceptor antagonist properties. In superfused rat sciatic nerves, it has been shown that neither disopyramide nor MIP possesses significant local anaesthetic properties. Procaine amide and lignocaine were highly active in this test. The possible contribution of MIP to the actions of disopyramide in vivo is discussed.