The arginase tissue distribution, the biochemical properties of the argininolytic system and the subcellular localization of the enzymes carbamoylphosphate synthetase, ornithinecarbamoyl transferase, glutamine synthetase and arginase in Antarctic fish, N. neglecta and N. rossii were the main aims of the present work. The tissue with highest argininolytic activity was the kidney distal portion amounting as much as four times the specific activity of the hepatic tissue. Arginase and ornithine carbamoyltransferase were found as mitochondrial enzymes, while glutamine synthetase and carbamoylphosphate synthetase were found as cytosolic enzymes. Argininolytic assays with isolated mitochondria gave values of Kmapp for the hydrolysis of arginine 2 to 3.5 times higher than the values found for the Km with mitochondrial extracts. The effect of Mn2+ on the argininolytic activity displayed by isolated mitochondria and mitochondrial extracts, in reaction conditions near the physiological ones showed that membranes were fundamentally involved in the control of L-arginine metabolism.

O autor relata trabalhos experimentais que o levaram a concluir pela existência da galactoquinase em tecidos animais, explicando desta maneira, que a primeira fase do metabolismo intermediário da galactose nos mesmos é a sua esterificação, em presença do ATP e da enzima em questão, ativada pelo magnésio, para galactose-1-fosfato.

The author relates experimental work which lead him to conclude for the presence of galactokinase in animal tissues, explaining in this way that the first step of the galactose intermediary metabolism is its esterification, in the presence of ATP and the enzyme in question, activated by magnesium to galactose-1-phosphate.

A fim de obter culturas celulares e monocamada de células hepáticas do peixe subtropical Metynnis roosevelti, foram comparadas três metodologias: dissociação celular enzimática com tripsina versene 0,25%; utilização do soro fetal bovino; e soro homólogo, obtido por meio da punção da veia caudal, de exemplares adultos da mesma espécie de peixe. O meio de cultura utilizado foi F10-199 acrescido de L-glutamina 2 mM, insulina 10 µg/mL, fibronectina 50 µg/mL; e antibióticos. A dissociação celular enzimática apresentou maior eficiência na adesão e confluência da monocamada celular em comparação a outras metodologias utilizadas.

In order to achieve monolayers and adhesion in cell cultures of hepatocytes from the subtropical fish Metynnis roosevelti (Pisces, Teleostei, Characidae) three different methodologies were used: enzyme cell dissociation by means of a system containing trypsin and versene 0.25%; by means of bovine fetal serum and by the use of blood serum obtained from adult specimens of M. roosevelti. The cell medium used has been a modified F10-199 by the addition of 2 mM L-glutamine, 10 µg/mL insulin, 50 µg/mL fibronectin; and antibiotics. The best results in terms of cell dissociation as well as in terms of adhesion and confluence of the cells monolayer has been achieved by means of the enzymatic cell dissociation.