Stimulation by calcium and carbamoylcholine of the ouabain-sensitive uptake of 86Rb+ in isolated rat pancreatic acinar cells

The uptake of 86Rb+ was assayed in isolated rat pancreatic acinar cells to determine the effect of calcium and carbamoylcholine on the ouabain-sensitive and ouabain-insensitive components. The presence of calcium in the medium bathing the cells during the preincubation and the main incubation periods was needed to preserve in optimum conditions the uptake of 86Rb+, the stimulation by carbamoylcholine and the sensitivity to ouabain. In the presence of calcium, the ouabain-sensitive component of 86Rb+ uptake was higher than the ouabain-insensitive. The ouabain-sensitive component was 3-times lower in cells incubated in a medium lacking calcium and containing 1 mM EGTA, as compared to cells incubated in the presence of calcium. Carbamoylcholine, at 5 X 10(-4) M, stimulated the uptake of 86Rb+ and this effect depended on the presence of calcium in the bathing medium. Maximal stimulation by carbamoylcholine was reached at 0.2 mM calcium. The nett stimulation by carbamoylcholine was inhibited up to 85% by 1 mM ouabain. As judged by digitonin-disruption of plasma membrane, the above-indicated effects were limited to a cytoplasmic pool of 86Rb+ and a leaky plasma membrane could be ruled out. The results suggest that in rat pancreatic acinar cells, carbamoylcholine stimulated the ouabain-sensitive uptake of 86Rb+ and required the presence of calcium in the bathing medium.     

Nitrogenase activity in the non-heterocystous cyanobacterium Oscillatoria sp. grown under alternating light-dark cycles

The non-heterocystous cyanobacterium Oscillatoria sp. strain 23 fixes nitrogen under aerobic conditions. If nitrate-grown cultures were transferred to a medium free of combined nitrogen, nitrogenase was induced within about 1 day. The acetylene reduction showed a diurnal variation under conditions of continuous light. Maximum rates of acetylene reduction steadily increased during 8 successive days. When grown under alternating light-dark cycles, Oscillatoria sp. fixes nitrogen preferably in the dark period. For dark periods longer than 8 h, nitrogenase activity is only present during the dark period. For dark periods of 8 h and less, however, nitrogenase activity appears before the beginning of the dark period. This is most pronounced in cultures grown in a 20 h light – 4 h dark cycle. In that case, nitrogenase activity appears 3–4 h before the beginning of the dark period. According to the light-dark regime applied, nitrogenase activity was observed during 8–11 h. Oscillatoria sp. grown under 16 h light and 8 h dark cycle, also induced nitrogenase at the usual point of time, when suddenly transferred to conditions of continuous light. The activity appeared exactly at the point of time where the dark period used to begin. No nitrogenase activity was observed when chloramphenicol was added to the cultures 3 h before the onset of the dark period. This observation indicated that for each cycle, de novo nitrogenase synthesis is necessary.     

Genetic aspects of ethanol tolerance and production bySaccharomyces cerevisiae

We developed a method of hybrid selection between homothallic wild-type and heterothallic strains. The hybrids obtained were used to study the heredity of ethanol tolerance and production. Both characters segregated independently, but no ethanol-sensitive strains were able to produce high levels of ethanol. At least four genes are implicated in ethanol tolerance.     

Influence of culture medium pH on charasome development and chloride transport inChara corallina

Summary Internodal cells ofChara, grown in culture either at pH 5.7, 6.5 or 7.5, were studied to determine their chloride influx capability, the quantitative aspects of charasome morphology and the degree to which these two parameters could be correlated. In cells grown at pH 5.7 the charasomes were relatively small, were widely spaced on the plasma membrane, and contributed only a 0.6% increase to the surface area of the plasma membrane in the acid region of the cell. In contrast, the charasome membrane surface area of cells grown at pH 7.5 had increased × 19, the density of charasomes on the cell surface increased × 42, thus producing a × 3.57 increase in the acid region plasma membrane surface area. Chloride influx in cells grown at pH 7.5 was × 8.7–12.7 greater than in cells grown at pH 5.7. Cells that had been starved of chloride exhibited a × 2.4 average increase in the rate of chloride influx. Our observations establish the existence of a positive correlation between the rate of chloride influx and the increase in membrane surface area due to charasomes, although other factors, such as the effect of pH on transport-related enzymes, and the effect of charasome structure on chemical equilibria, may also be of importance.     

Selection of Wine Yeasts for Growth and Fermentation in the Presence of Ethanol and Sucrose

To optimize the conversion of carbohydrates to ethanol, strains of several Saccharomyces species were examined for the ability to grow and ferment in a range of sucrose and ethanol concentrations. A total of 632 wine yeasts, most of them isolated from wineries in Andalusia and Extremadura, southwestern Spain, were subjected to screening and selection. Growth and fermentative capacity in different ethanol and sucrose concentrations varied from one strain to another. There was no correlation between growth and fermentative capacity. The best 35 strains grew in 15% ethanol and fermented in 18% ethanol. Ethanol accumulated, although at a reduced rate, after the cells stopped growing. Most yeast strains were highly fermentative in 50% sucrose. Some of them effectively utilized the carbohydrates of the culture, yielding final ethanol concentrations of > 14%. Of the 35 selected strains, 16 were promising for genetic analysis and breeding because of their capacity to sporulate. These strains were homothallic, and their spores were viable. The meiotic products analyzed so far were also homothallic.     

Generation of an internal matrix in mature avian erythrocyte nuclei during reactivation in cytoplasts

When fused with mouse L-cell cytoplasts, chick erythrocyte nuclei enlarge, take up proteins from the host cytoplasm, and recommence RNA synthesis. We found that during this transition the erythrocyte nuclei gain an internal nuclear matrix, thus providing a novel approach to questions concerning the nature of the salt-resistant intranuclear skeleton. A new method for preparation and examination of the nuclear matrix in situ is also described.     

Study of Chromosomes in the Newborn after Ultrasonic Fetal Heart Monitoring in Labour

The effect of continuous-wave ultrasound on the chromosomes of newborn infants has been investigated. Twenty-four women were studied during labour. The fetal heart was monitored by a Sonicaid FM2 monitor applied to the abdomen, and continuous monitoring undertaken for intervals varying from 1 hour 5 minutes to 9 hours 25 minutes. There was no increase in the number of chromosome aberrations in cultures of blood taken from the insonated babies when compared with controls.     

Persistent ultrastructural changes in pancreatic acinar cells induced by 4-acetylaminofluorene

Male Leeds rats were fed a diet containing 0.05% of the non-carcinogen 4-acetylaminofluorene (4-AAF) for 8–10 months. They were then returned to a normal diet and their pancreatic tissues examined by electron microscopy at intervals between 2 and 12 months after the end of 4-AAF treatment. 4-AAF was found to induce a persistent alteration in the morphology of the granular endoplasmic reticulum, involving distortion and dilatation of the cisternae. In some respects this lesion resembles that which is induced by the carcinogenic isomer, 2-acetylaminofluorene (2-AAF).