Summary. Red‐cell glutathione peroxidase (GSH‐Px) activity has been assayed in 62 normal subjects and in 163 patients with various diseases. In nine cases of iron deficiency anaemia, the mean GSH‐Px activity per cell or per volume of cells was low; during the first 2–4 weeks of treatment with iron, red‐cell GSH‐Px increased in parallel with haemoglobin. High enzyme activities, above the normal range, were found in 11 cases of megaloblastic anaemia due to deficiency of vitamin B12; rapid and marked fall in GSH‐Px activity followed the start of vitamin B12 therapy. Abnormally high values for red‐cell GSH‐Px were found in acute myeloblastic leukaemia and in myelofibrosis whereas the enzyme activity tended to be low in chronic lymphocytic and in chronic myeloid leukaemia. In two cases of chronic myeloid leukaemia, red‐cell GSH‐Px increased to normal during the early stage of remission produced by cytotoxic therapy. Normal red‐cell GSH‐Px was found in six cases of polycythaemia vera. In patients with carcinoma, there was a wide variation in red‐cell GSH‐Px but the mean value was significantly less than normal.

1The relationship between mechanical fragility, glutathione peroxidase inhibition and Heinz body formation, in erythrocytes exposed to oxidant drugs in vitro, has been investigated. All drugs tested caused Heinz body formation, and with the exception of acetyl salicylic acid and salicylic acid, also caused increased erythrocyte mechanical fragility. 2 There was a direct relationship between mechanical fragility and drug concentration. Mechanical fragility increased in parallel with Heinz body formation, with primaquine, gentisic acid, ascorbic acid and potassium chlorate. In contrast Heinz body formation occurred at drug concentrations which did not cause a marked increase in mechanical fragility in the case of menadione, acetyl phenylhydrazine and phenylhydrazine. 3 The degree of inhibition of glutathione peroxidase was directly related to increased mechanical fragility with menadione, gentisic acid and potassium chlorate. However other substances causing increased mechanical fragility resulted in little or no loss of glutathione peroxidase activity. 4 The results show that there is no constant relationship between mechanical fragility caused by drugs, the formation of Heinz bodies and the inhibition of glutathione peroxidase. The factors contributing to oxidant drug-induced haemolysis appear to be variable and depend upon the drug concerned.

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with the acute inflammatory process, sometimes associated with a chronic process, and sometimes present without any demon¬ strable microscopic evidence of inflammation. It led me to consider whether the so-called harmless type of protozoan occa¬ 2. McLaughlin,