The influence of ethanol on the conversion of pregnenolone to progesterone by human placental microsomes

The effects of ethanol on kinetic parameters of placental Δ5-3β-hydroxysteroid dehydrogenase were studied. In the presence of high pregnenolone concentrations (50 μm, [S] > Km) the microsomal enzyme preparation exhibited an almost linear increase in activity as the ethanol concentration in the medium was raised from 2.5 to 15 % (v/v). At lower substrate concentrations ([S] << Km) ethanol caused inhibition. Other effects of ethanol were: linearity of product formation with time was prolonged; the maximal velocity was markedly increased; the Km for pregnenolone slightly decreased with increasing ethanol concentrations (2.5 to 10 %, v/v) whereas the Km for NAD remained the same. The pH and temperature optima of the reaction were unaffected by ethanol. Other organic solvents caused similar effects.

[Treatment of aneurysms of the anterior cerebral artery]

Os autores analisam a evolução do tratamento cirúrgico de aneurismas do sistema da artéria cerebral anterior no Instituto de Neurocirurgia de Porto Alegre, de 1960 a junho de 1972. Foram operados 63 pacientes, dos quais 41 por ataque direto. Consideram que o estudo angiográfico só deve ser feito em pacientes em condições clínicas satisfatórias ou estabilizadas. Descrevem pormenorisadamente a técnica cirúrgica preconisada em 1967 por um dos autores e o método de tratar tais aneurismas desde então. Apresentam quadros demonstrativos dos resultados obtidos em épocas sucessivas e os resultados globais alcançados. Acreditam que as técnicas atuais de tratamento serão favorecidas pela microcirurgia, mas uma via de acesso simples será sempre um fator favorável.

Endocytosis in Chang liver cells. Quantitation by sucrose- 3 H uptake and inhibition by cytochalasin B

The addition of 0.08 M sucrose to a culture medium containing Chang-strain human liver cells causes intense cytoplasmic vacuolation. Electron microscopy of these cells grown inferritin, time-lapse cinematography, and radioautography reveal that the vacuoles arise by endocytosis and that the sucrose is taken into the cell and localized in the vacuoles. Tracer studies demonstrate that sucrose-(3)H provides a marker for quantitation of endocytosis and that it neither induces nor stimulates endocytosis. Electron micrographs of vacuolated liver cells show microfilaments in close proximity to the inside of the plasma membrane, in the pseudopodia, and to the cytoplasmic side of the membrane surrounding endocytosis vacuoles. Cytochalasin B (CB), a mold metabolite that inhibits various types of cell motility, has a dose-dependent inhibitory effect on the uptake of sucrose-(3)H by these cells. This inhibition is accompanied by a cessation of the movement of ruffles and pseudopodia on the surface of the cells and the formation of blebs which arise from the cell's surface. These morphological changes are quickly reversible upon removal of CB. Alterations in the appearance and location of microfilaments are also observed in CB-treated cells.

Die Aktivität der Folatreduktase in Rattenleber während der Hepatocarcinogenese mit Diäthylnitrosamin

Während der Fütterung von Diäthylnitrosamin kommt es zu Beginn in der Leber zu einem Anstieg der Folatreduktaseaktivität, der nach Absetzen des Carcinogens reversibel ist. Nach dem Auftreten sog. kleinzelliger Nester sinkt die Aktivität ständig und erreicht im Carcinomgewebe Werte, die deutlich unter den Normalwerten liegen.