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The activity of MAO has been determined in the brain and liver of 36 male guinea-pigs. The animals have been exposed to electric fields of 50 Hz and 100 kV/m frequency. The guinea-pigs have been divided into the following groups (12 animals each): group I--every day 4 hrs' exposure to electric fields (total dose--100 hours), group II--4 hrs' exposure every other day (total dose--100 hours), group III--4 hrs' exposure every third day (total dose--100 hours). The control group consisted of 8 animals. Enzymatic determinations of MAO have been performed by McEven and Cohen's technique, using benzylamine as substrate. A statistically significant increase of MAO activity in brain homogenates of group I and slow decrease in groups II and III, to the control value, has been shown. No changes of the test enzyme have been found in the liver tissue.

The biological tolerance of chambers with membranes of regenerated cellulose and the influence of the implantation of isolated islets of Langerhans in these chambers on the blood sugar level of rats with experimental diabetes was investigated. It was concluded that retroperitoneal space offers the best conditions for the implantation of such chambers. The technique of implantation and the preparation of the chambers are the critical factors for the degree of foreign body reaction. The implantation normalized the blood sugar level in rats with an experimental diabetes of a slight degree for a duration of 3 weeks and the glycemia in severe diabetes was soothed for the period of 11 days.

The paper presents the behaviour of DNA, RNA and soluble proteins in whole homogenate as well as the nuclear, mitochondrial and postmitochondrial liver fractions in guinea pigs exposed to combustion exhaust gases and the products of their reaction with ammonia. A decrease of RNA level was found in the liver of animals exposed to combustion exhaust gases together with a decrease of soluble proteins in all the studied fractions. On the other hand, in the group of animals subjected to the action of neutralization products of combustion gases by ammonia, the studied components were increased. This increase may be the result of the simultaneous action of industrial noise.

The possibility for the use of membranes of regenerated cellulose was tested for constructing semipermeable chambers for the cultivation and implantation of the isolated islets of Langerhans. The membranes of regenerated cellulose was well-permeable for insulin. An implantation for one month had no influence at the rate of diffusion of insulin. This shows that the pores of the membrane were not occluded by protein. The occlusion of the pores was one of the greatest hindrances for the use hitherto. The islets of Langerhans in semipermeable chambers with membranes of regenerated cellulose showed a sufficient glucose utilization and lactate production during the whole investigation period within 37 days. A considerable decrease of the insulin secretion of the islets in the chambers was to be observed especially in the first 14 days of the experimental period.

Aspartate carbamoyltransferase (ACTase) activity has been measured in rat livers at different stages of their development and in intact and regenerating livers. The level of enzyme activity was found to be the highest in the earliest fetal livers (about 7 times higher than in the adult rat liver). Deproteinized by heating, supernatants of sheep liver homogenates were purified on a Sephadex G-25 column. The influence of deproteinized supernatant on ACTase activity in rat liver was measured. This influence depended on the amount of activating factor added to fresh homogenates. A different scope of activation of enzyme activity in rat liver caused by deproteinized supernatant was noticed. The greatest increase of enzyme activity under the influence of activating factor was obtained in the liver of young animals, mothers and old female rats, the smallest in fetuses and very young animals. A relatively smaller increase of enzyme activity was observed in regenerating livers under the same experimental conditions. In this article the role of natural ACTase activator is discussed.

The behaviour of aspartate aminotransferase (AspAT) an alanine aminotransferase (AIAT) in the whole homogenate and subcellular liver fractions of guinea pigs exposed to combustion exhaust gases and the neutralization products of these gases is presented in this paper. In the liver of animals exposed to the chronic action of combustion exhaust gases a decrease of both enzyme activities in the whole homogenate as well as in the subcellular fractions could be noted. Statistically significant changes are shown by AspAT. In the group of animals subjected to the action of neutralization products an increase of AIAT activity was observed. The activity of AspAT still shows a decrease, but less distinct in comparison with group I. An exception here is the mitochondrial fraction in which the AspAT activity is distinctly increased.

Putrescine (PU), spermidine (SPD) and spermine (SPM) levels in blood serum of MC Sa 1828 P-bearing rats have been studied in relation to tumour weight and the histological picture. A statistically significant increase of PU and SPD was found in the course of tumour development. Decrease in the level of polyamines in the necrosis stage was also found. Only increased SPD level appeared in the period of intensified necrosis, accompanied by lymphocyte infiltration.