[mRNA breakdown in tumor cells in vivo under cycloheximide protein synthesis inhibition]. / Razrushenie mRNK v opukholevykh kletkakh in vivo pri ingibirovanii belkovogo sinteza tsiklogeksimidom.

Amoung of prelabelled mRNA was unaltered in Zajhdel ascites hepatoma of rat cells within 3.5-4 hrs under conditions of treatment with actinomycin D. Due to combined effect of actinomycin D and cycloheximide the content of mRNA in the hepatoma cells was rapidly decreased. Degradation of mRNA occurred in membrane-bound polyribosomes, free polyribosomes and in cytoplasmic mRNP-particles /informosomes/ as a result of the effect of cycloheximide. Simultaneously with these phenomena, distinct increase in activity of acid and alkaline RNAases was observed in cytoplasma of the hepatoma cells; activity of endoRNAase from membrane-bound and free polyribosomes of the hepatoma was also markedly increased. Cycloheximide did not affect the activity of polynucleotide phosphorylase in polyribosomes of the hepatoma cells. Labile proteins, responsible for inhibition of RNAses appeart to participate in regulation of mRNA stability in malignant cells.

[Mechanism of hypoglycemia in insulinoma]. / K voprosu o mekhanizme gipoglikemii pri insulinome.

A study was made of the capacity of insulinoma to catalyze the splitting of hippuryl-L-arginine (HA) and the contents of proinsulin-like component in the tissues of the tumours and in the blood serum of the patients. As revealed, in the absence of HA splitting by the tumour cytoplasmic fraction in the neutral pH zone there was noted a higher proinsulin-like component both in the tumour tissue and in the blood serum. An increase amount of proinsulin-like component in the blood serum stipulates possibly a more prolonged period of starvation before the occurrence of hypoglycemia, and a less pronounced picture of hypoglycemia in such patients in comparison with the patients whose tumours were capable of splitting HA similarly to the normal islands of Langerhans.

[Nature of the enzymes participating in the transformation of proinsulin into insulin]. / O prirode fermentov, uchastvuiushchikh v prevrashchenii proinsulina v insulin

A study was made of the enzymes of the islands of Langerhans which could participate in the transformation of proinsulin into insulin. The homogenate of the islands of Langerhans of rat and man catalized the hyppuril-L-arginine splitting at pH 5.4-5.8 and 6.8-7.2 which was completely blocked with N-ethyl maleimide. The enzyme of the islands with the optimum action pH of 5.4-5.8 was similar to the enzyme of the exocrine tissue and was possibly a catheptic carboxypeptidase. The second enzyme of the islands differing from the exocrine carboxypeptidase could apparently participate in the insulin formation from the intermediate forms of proinsulin. In the formation of these proinsulin fomrs the participation of the enzyme of the endopeptidase character with a more acid optimum of the action pH is supposed.

[Conversion of proinsulin into insulin in insulin producing tumors in man]. / O prevrashchenii proinsulina v insulin v insulinoprodutsiruiushchikh opukholiakh cheloveka

The enzymatic activity of tissues of insulomas and also the proinsulin and insulin content in them was studied. As revealed, insulomas contained an increased amount of proinsulin in comparison with the unaffected islands of Langerhans. The tumours under study also differed by the capacity to catalyze the splitting of hippuryl-L-arginine, synthetic substrate of carboxypeptidase B. Proinsulin content in the tumours of the islar tissue depended on the presence in them of an enzyme catalyzing the splitting of the substrate at pH 6.8--7.2, this pointing to its participation in the conversion of proinsulin into insulin.

[Isolation of the islands of Langerhans from rat pancreas and determination of proteolytic activity in them]. / Vydelenie ostrovkov Langergansa iz podzheludochnoi zhelezy krys i opredelenie v nikh proteoliticheskoi aktivnosti

A modified method for isolation of Langerhans islands from rat pancreas is described. The islands obtained were free from acinous tissue as shown by means of an amylase test and by microscopy. In homogenates of the islands proteolytic activities were observed (pH optimum at 5.3--5.5 and 6.9--7.2).