Further evidence that "malignant angioendotheliomatosis" is an angiotropic large-cell lymphoma.

Malignant angioendotheliomatosis is a rare, generally fatal disease characterized by a multifocal proliferation of neoplastic mononuclear cells within the lumens of small blood vessels. Although the disease primarily involves the vasculature of the skin and central nervous system, vascular involvement of other organs may occur and may produce a variety of clinical findings. Some early investigators concluded that malignant angioendotheliomatosis was a neoplasm of endothelial cells, but recently others have suggested that it is of hematopoietic origin. We have studied three patients with the disease and have characterized the immunophenotype of the neoplasm on cryostat-cut fresh-frozen tissues. A detailed antigenic phenotyping of neoplastic lymphoid cells showed that one patient had the immunophenotype T11+, Leu-1+, Leu-3+, Leu-2+, B1-, B2-, SIg-, LN1-, LN2-, the predominant phenotype for peripheral T-cell lymphoma; the others had T11-, Leu-1-, Leu-3-, Leu-2-, B1+, B2+, SIg+, LN1+, LN2+, consistent with a B-cell-derived lymphoma. On the basis of our results, we suggest that angiotropic (intravascular) large-cell lymphoma would be more appropriate than malignant angioendotheliomatosis as a name for this disease.

A chemical approach to the nutritional availability of methionine in food proteins.

The background to earlier experiments that were designed to evaluate the nutritional availability of peptide-bound methionine sulphoxide is described. After mild acid hydrogen peroxide treatment of casein, NPU had fallen from 71 to 58. A gas-chromatographic analysis for intact methionine residues that has been developed since then has shown that in the oxidised casein all methionine residues had been oxidised to the sulphoxide, whereas in several foods only moderate levels of sulphoxide were found. The methionine potency of sulphoxide residues is considered to be less a function of digestion and absorption than of the body's capacity to reduce it to methionine. Evidence is given that hydrogen peroxide also modified cystine residues in casein to be rendered nutritionally unavailable. On a molar basis, half the sulphur amino acids in most foods is furnished by cystine which therefore plays a more important role in protein nutrition than is generally recognised.

The determination of methionine in proteins by gas-liquid chromatography.

Intact methionine residues in proteins were rapidly and precisely determined by measuring methyl thiocyanate released during the reaction with CNBr and separated by g.l.c. Conditions for the reaction and for chromatography on columns of Porapak P-S are described. The recovery of methyl thiocyanate from several methionine derivatives and analogues were examined. Carbamoylmethionine was adopted as a stable primary standard and ethyl thiocyanate as internal standard. The measured methionine content of several isolated proteins was close to the theoretical value indicated by previous work and the results for these and a range of food proteins agreed well with results obtained by ion-exchange chromatography after performic acid oxidation. Since CNBr does not react with methionine sulphoxide and a preliminary hydrolysis is not required, the method discriminates between methionine and any methionine sulphoxide that may be present. It could be useful in studies on the nutritional availability of methionine in processed foods.