Possible basis for membrane changes in nonparasitized erythrocytes of malaria-infected animals

Previous studies (Gupta et al. (1982) Nature 299, 259-261) have shown that nonparasitized erythrocytes of Plasmodium knowlesi-infected monkeys contain the procoagulant phospholipid phosphatidylserine (PS) in the outer-half of their membrane bilayer. A reinvestigation of this problem has now revealed that in acute P. knowlesi infection, at least 30% of the infected animals do not have this abnormality. However, PS externalization was a consistent feature in the uninfected red cells of chronically infected animals. Also, a similar membrane change was observed in the red cells of uninfected splenectomized monkeys. These results strongly suggest that spleen plays an important role in maintaining the exclusive inner distribution of PS in the normal erythrocyte membrane, and that partial migration of this lipid to the outer monolayer in nonparasitized erythrocytes could be attributed to an abnormal physiology of this organ in malarial infection.

Orotic acid, a promoter of liver carcinogenesis induces DNA damage in rat liver

Orotic acid, a precursor of pyrimidine nucleotide biosynthesis and a promoter for liver carcinogenesis, when fed at 1% level in a diet for 5 weeks resulted in liver DNA damage. The damage can be monitored as alkali-labile lesions using alkaline sucrose gradients as well as alkaline elution technique. Furthermore, the induced DNA damage persists for up to three weeks after withdrawal of the orotic acid diet. The fact that several skin-tumour promoters also induce DNA damage raises the question whether DNA damage is a component in tumour promotion.

Characterization of subspecies from a fungal fatty acid synthetase

Fatty acid synthetase from the filamentous fungus, Aspergillus fumigatus dissociates during gel filtration on Sepharose 6B into two differently sized subspecies with mol. wt. approx. 1.5 x 10(6) and 8 x 10(5). After elution, they readily reform intact molecules, as determined by their enzymic activity (overall synthetase and 3-oxoreductase activities were measured), sedimentation coefficient and appearance in the electron microscope. Synthetase was cross-linked with dimethyl suberimidate and the resultant protein did not dissociate on Sepharose 6B. The two smaller species which were eluted after chromatography of untreated enzyme were also fixed by reaction with this reagent. They did not reform intact molecules of synthetase and were characterized by electron microscopy as large and small circular aggregates; the low molecular weight form also contained tetrameric structures which exhibited cyclic symmetry. The composition of the two species derived during dissociation was, therefore, confirmed as eight and four polypeptides, respectively; each contained polypeptides A and B. It is proposed that the intact fungal synthetase of composition A6B6 comprises three equivalent loops of protein, each of which contain four polypeptides, presumably with composition A2B2; the molecular weights of A and B are 207 000 and 201 000, respectively. During filtration on Sepharose 6B, two such loops remain associated to form a large circle, leaving the other four polypeptides ro rearrange themselves into a small circle or tetramer.

Pregnancy complicated by pelvic abscess

Tuboovarian abscess in pregnancy is a rare occurrence. The case presented and discussed is one in which a tuboovarian abscess was diagnosed and managed conservatively, with subsequent delivery of a viable infant.

Renal retention of sodium in cirrhosis and fulminant hepatic failure

Abnormal renal retention of sodium is a characteristic finding in both cirrhosis and fulminant hepatic failure. In cirrhosis the pathogenesis varies according to the level of renal perfusion. When this is normal, hyperaldosteronism is probably the most important factor and this results from an increased release of renin by the kidney. The stimulus to the latter may be a shunting of blood from the outer cortical to juxtamedullary nephrons, although there is no direct relationship between the changes in intrarenal blood flow distribution and sodium excretion. The patients with hyperaldosteronism fail to escape from its sodium retaining effects because of impaired production of natriuretic hormone, which in turn is the result of a failure to expand the ‘effective’ extracellular fluid volume, because of ascites formation.

In fulminant hepatic failure the site in the nephron of abnormal sodium retention appears to be predominantly the proximal tubule, but its cause is obscure.