Structural changes of isolated hepatocytes during treatment with digitonin

The structural changes accompanying digitonin-induced release of enzymes and metabolites from isolated hepatocytes have been studied by scanning and transmission electron microscopy. In the initial phase, characterized by total release of the cytosolic marker enzyme, lactate dehydrogenase, the plasma membrane was immediately damaged, rapidly followed by extensive damage to the endoplasmic reticulum. The shape of the cell, however, was maintained, and the mitochondria and nucleus remained tightly held together by the cytoskeleton. Mitochondria remained intact initially, whereas the cytosol became less electron dense and the nuclear chromatin was more dispersed. An intermediate phase was characterized by total release of adenylate kinase and most of the glucose-6-phosphatase, marker enzymes for the mitochondrial intermembrane space and the endoplasmic reticulum, respectively. The outer mitochondrial membrane was ruptured, but mitochondria maintained their normal matrix electron density. In the final phase, characterized by the beginning of citrate synthase release from the mitochondrial matrix space, the mitochondria became swollen, and only the nucleus, inner and outer mitochondrial membranes, and the cytoskeleton could be clearly distinguished. Although the plasma membrane could not be readily discerned in electron micrographs after the initial phase, the plasma membrane marker enzyme 5'-nucleotidase remained associated with digitonin-treated hepatocytes. Acetyl-CoA carboxylase was released much more slowly than lactate dehydrogenase, indicating some severe restriction on its release. The release of acetyl-CoA carboxylase closely paralleled the release of glucose-6-phosphatase. The controlled exposure of hepatocytes to digitonin, therefore, leads to the sequential release of soluble, compartmentalized cellular components and some membrane-bound components, but the mitochondrial membrane, cytoskeleton and the nucleoskeleton survive even long-term digitonin treatment.     

Unprocessed Bran in Treatment of Diverticular Disease of the Colon

Seventy patients with diverticular disease of the colon were treated with a high-residue, low-sugar diet including unprocessed bran. Follow-up for an average of 22 months showed marked relief of symptoms in 62 patients. Bowel habit was restored towards normal and abdominal discomfort relieved. Only seven patients were unable to give up the use of laxatives. Eight patients did not tolerate the bran diet, and one of these needed surgical treatment. None of the 62 patients who took the diet needed surgery.     

The role of cations and other factors on the apparent energy of activation of (Na + K)-ATPase

Data concerning the temperature dependence of ouabain-sensitive (Na⁺ + K⁺)-activated ATPase have enabled estimates of the apparent activation energies of this process to be obtained. Arrhenius plots show a point of inflection at about 20 °; at higher temperatures the activation energy is about 13.5 kcal/mole while below this temperature the value increases to 28.5 kcal/mole. Storage at −5 ° or reduction in total cation concentration without alteration of the Na⁺:K⁺ ratio causes no significant change in these values, although the specific activity is markedly reduced. Reduction in the sodium concentration alone, however, increases the apparent activation energy at lower temperatures. These results support the hypothesis that two independent processes are involved in ATP hydrolysis, one operating above the critical temperature and one operating below this temperature. Storage, or reduction in the concentrations of both sodium and potassium ions, appears to reduce the number of functional ATPase units, without significantly altering the properties of those which can still hydrolyze ATP. Reduction in the sodium concentration alone, however, may also cause some inhibition of all units. This is more marked at lower temperatures, and may arise from competition by potassium for sodium-binding sites.     

Clonal Analysis of Cell Division in the Bacillus subtilis div IV-B1 Minicell-Producing Mutant

Spores of the Bacillus subtilis minicell-producing mutant div IV-B1 were germinated and grown to microcolonies in chambers which facilitate continuous observation of the developing clones with a phase-contrast microscope. Time lapse photographs were taken of 46 clones, covering the period from the beginning of outgrowth until at least two rounds of cell division had been completed. Cell lineages were constructed from contour length measurements of the photographs. These data include cell lengths, division site locations, and cell numbers in clones of various ages. From these data we have determined that the probability of a minicell being produced at any division by the div IV-B1 mutant is 0.31. The location of the abnormal division site which generates the first minicell produced in the outgrowing clone appears to be random with respect to the existing cell poles. In contrast, the location of the second abnormal division site, and hence the second minicell, is not random but rather occurs preferentially in proximity to the first minicell. This clustering of abnormal events suggests that division site location is related to pole age (generations), although other influences on minicell clustering cannot be ruled out at present.     

Experiments on resting site selection by nocturnal moths

When different species of moths are presented with a choice between black and white resting backgrounds, there is a strong correlation between the colour selected and the reflectance of the forewings. Under more natural conditions, light-coloured moths usually rest on fresh vegetation whilst dark-winged species select tree bark or rest upon the ground, and different defensive strategies appear to have been adopted by species in these two latter situations. Studies on the mechanism of background selection, and on background selection in polymorphic species, are reviewed.     

Calcium interactions with D-glucans: crystal structure of alpha, alpha-trehalose-calcium bromide monohydrate

Three-dimensional X-ray diffraction data were used to determine the crystal structure of α,α-trehalose-calcium bromide monohydrate, a model system for investigation of factors involved in the binding of calcium ions to d-glucans of dental plaques. Crystals of C₁₂H₂₂O₁₁ ·CaBr₂·H₂O are orthorhombic, space group C222₁, with a  11.058(1) b  11.537(1), c  15.101(1) Å, and Z  4. Intensity data for 925 independent reflections were measured with an automated diffractometer. A trial structure, obtained by the heavy-atom method, was refined by least-squares to R  0.03. An outstanding feature of the crystal packing is the interaction of trehalose molecules with calcium ions. Each calcium is coordinated to hydroxyl groups from four symmetry-related d-glucose moieties, thereby cross-linking the trehalose molecules. Similar interactions between calcium ions and the d-glucose residues of extracellular d-glucans may be of importance in the agglutination processes involved in dental-plaque formation.