Overview of drugs in arterial thrombosis

The recent history of randomized controlled trails in the prevention of ischaemic heart disease (i.h.d.) is considered. In 1970, it seemed that little could be done to prevent recurrent of the disease and there was almost no information on the potential for preventing its onset. Over the past decade, this rather pessimistic view has changed to one of guarded optimism. Yet there are still no drug régimes that command general support. One reason for the inconclusive results of recent trails may have been the assumption that myocardial infraction and sudden death share the same pathology. Another reason is the diversity of pathogenetic mechanisms and prognoses in i.h.d. Many patients probably stand little chance of benefiting from a particular drug either because it affects mechanisms other than those responsible for their disease or because their prognosis, excellent or hopeless, is unlikely to be influenced whatever treatment they receive. It is consequently difficult to ensure reasonable chances of demonstrating benefits in those who may really stand to gain. A tendency of pharmacological information to become available during or after a large trial, rather than beforehand, has added to the difficulties. Despite all their problems, randomized controlled trials remained the only way of testing drugs for the prevention of arterial disease. Suggestions are made for increasing the chances of clear results in future trails and of reaching the stage of benefit demonstrated sufficiently convincingly to form a basis for clinical practice. These suggestions include the use of factorial designs enabling the evaluation of more than one drug in a particular trial and the development of methods for selecting homogeneous groups of patients.     

Enzymes of carbohydrate metabolism in Leishmania donovani amastigotes

A method for the isolation of Leishmania donovani amastigotes from infected hamster spleen and liver tissues is described. Over 85% of the isolated amastigotes were viable as judged by acridine orange-ethidium bromide staining and in vitro transformation to the promastigote form. A comprehensive survey of the enzymes of carbohydrate metabolism in L. donovani amastigotes and promastigotes was conducted. Amastigotes and promastigotes possess all of the enzymes of the Embden-Meyerhof pathway, hexose monophosphate shunt, and tricarboxylic acid cycle. Cell-free extracts of both forms demonstrate an active glutamate dehydrogenase, thus linking activity which permits entry of pyruvate into the tricarboxylic acid cycle. Both forms demonstrate an active glutamate dehydrogenase, thus linking amino acid metabolism with carbohydrate metabolism. Pyruvate carboxylase, the enzyme responsible for replenishment of C4 acids by heterotrophic CO2 fixation into pyruvate, was also demonstrable in the tissue and insect forms. In general, activities of promastigote enzymes are higher than the amastigote enzymes. Differences between the vertebrate (amastigote) and invertebrate (promastigote) forms in their potential to utilize carbohydrates as substrates would appear to be quantitative rather than qualitative.     

Highly viscous polysaccharide produced by an Enterobacter isolate on a hemicellulose hydrolysate

Summary A new anionic extracellular polysaccharide (AEPS) with high molecular mass (1700 kD) was produced by an isolate tentatively identified as Enterobacter cloacae isolated from an acid hydrolysate of wood. The sugar composition of this AEPS is glucose, galactose, glucuronic acid, and fucose (5:4:4:11). Under specified conditions this AEPS is rheologically comparable to xanthan.