Macromolecular synthesis in human diploid fibroblasts. A viral probe examining the effect of in vivo aging.

The replication of vesicular stomatitis virus was examined in early-passage skin fibroblast cultures from old and young human donors. The production of virus was analysed by measuring synthesis of viral RNA in actinomycin D-treated cells, and by determining the yield of biologically-active viral progeny by plaque assay. Although no statistically significant differences (P < 0.05) were observed between old and young cultures, our assays were shown to be capable of detecting impaired macromolecular synthesis induced by incorporation of amino acid analogues. These results indicate that macromolecular synthesis does not appear to be significantly altered in cells from older donors.     

Secretion of granule enzymes from alveolar macrophages : Regulation by intracellular Ca-buffering capacity

Rabbit alveolar macrophages exposed to the ionophore A23187 in the presence of extracellular Ca²⁺ take up about 12 nmoles of Ca²⁺/1 × 10⁶ cells. This uptake induces a slight, but significant, extracellular release of granule enzymes, β-glucuronidase and lysozyme, but not of the cytoplasmic marker, lactate dehydrogenase. If either EGTA is added to the medium or Mg²⁺ replaces Ca²⁺ no stimulation of secretion is observed. If the energy supply is decreased by treating the macrophages with mitochondrial inhibitors such as oligomycin, cyanide, or rotenone and antimycin, Ca²⁺-dependent secretion is potentiated several fold. Selective release of granule enzymes from macrophages exposed to A23187 and Ca²⁺ is also stimulated by cytochalasin B (CB).     

Morphometric studies of the density and diameter of capillaries in supraoptic and paraventricular nuclei of unmilked and milked cows]

With mathematical-statistical methods the density and the diameter of the capillaries of the NSO and NPV were investigated by unmilked and milked cows. After the milking the diameter of the capillaries is significantly expanded in both nuclei districts. The density of the capillaries measured through the length of the capillaries pro mm3 tissue, were not significantly enlarged after the milking stimulus. The adaptation on the changed functionstate of the neurosecreoty cells arrive at a maximum 15 min after the milking, to go back afterwards, by 60 min after the milking studied cows, to the values of the beginning. It is discussed, that the intensified blood maintenance of the activated neurosecretory cells of the NSO and NPV is of a higher oxygen consumption.     

Purification and properties of soluble hydrogenase from Alcaligenes eutrophus H 16.

The soluble hydrogenase (hydrogen: NAD+ oxidoreductase, EC 1.12.1.2) from Alcaligenes eutrophus H 16 was purified 68-fold with a yield of 20% and a final specific activity (NAD reduction) of about 54 mumol H2 oxidized/min per mg protein. The enzyme was shown to be homogenous by polyacrylamide gel electrophoresis. Its molecular weight and isoelectric point were determined to be 205 000 and 4.85 respectively. The oxidized hydrogenase, as purified under aerobic conditions, was of high stability but not reactive. Reductive activation of the enzyme by H2, in the presence of catalytic amounts of NADH, or by reducing agents caused the hydrogenase to become unstable. The purified enzyme, in its active state, was able to reduce NAD, FMN, FAD, menaquinone, ubiquinone, cytochrome c, methylene blue, methyl viologen, benzyl viologen, phenazine methosulfate, janus green, 2,6-dichlorophenoloindophenol, ferricyanide and even oxygen. In addition to hydrogenase activitiy, the enzyme exhibited also diaphorase and NAD(P)H oxidase activity. The reversibility of hydrogenase function (i.e. H2 evolution from NADH, methyl viologen and benzyl viologen) was demonstrated. With respect to H2 as substrate, hydrogenase showed negative cooperativity; the Hill coefficient was n = 0.4. The apparent Km value for H2 was found to be 0.037 mM. The absorption spectrum of hydrogenase was typical for non-heme iron proteins, showing maxima (shoulders) at 380 and 420 nm. A flavin component could be extracted from native hydrogenase characterized by its absorption bands at 375 and 447 nm and a strong fluorescense at 526 nm.     

Partial purification and properties of diglyceride kinase from Escherichia coli.

Diglyceride kinase (diacylglycerol kinase, E.C. 2.7.1.-), an enzyme localized in the inner membrane of Escherichia coli, has been purified about 600-fold. The purified enzyme exhibits an absolute requirement for magnesium ion; its activity toward both lipid and nucleotide substrates is stimulated by diphosphatidylglycerol or other phospholipids. Adenine nucleotides are much better substrates for the enzyme than are other purine or pyrimidine nucleotides. The purified enzyme preparation catalyzes the phosphorylation of a number of lipids, including ceramide and several ceramide and diacylglycerol-like analogs. The broad lipid substrate specificity of diglyceride kinase suggests that this enzyme may function in vivo for the phosphorylation of an acceptor other than diacylglycerol.     

Possible mechanisms of normal amylase activity in hyperlipemic pancreatitis.

Lipemic serum from three patients with acute pancreatitis and type IV hyperlipemia was fractionated into very-low-density lipoproteins and clear serum. Amylase activity (determined by the Phadebas method) in the component fractions did not exceed that in the original lipemic serum. Addition of these fractions or VLDL and chylomicrons from asymptomatic patients with hyperlipemia to nonlipemic serum from patients with "routine acute pancreatitis" did not inhibit amylase activity or alter the electrophoretic mobility of amylase isoenzymes. Therefore the normal amylase activity often observed in hyperlipemic pancreatitis does not result from an inhibition of amylase activity by serum lipoproteins.     

Die Bedeutung der Elytren bei Vertretern desMelolontha-Flugtyps (Coleoptera)

The function of the flapping elytra was investigated in garden shafers (Melolontha melolontha L.) and rhinoceros beetles (Oryctes boas Fabr.).

Cytoplasmic DNA in rat corpora lutein cells : Effect of prolactin on [H]thymidine incorporation

Biochemical fractionation studies of homogenates of massively luteinized ovaries showed that DNA could be isolated from mitochondrial and microsomal fractions of this tissue and that prolactin administration enhanced [³H]thymidine incorporation into mitochondrial DNA in vivo. These findings were confirmed by autoradiographic analysis of tissue sections at the light and electron microscopic levels. Further support for the existence of microsomal DNA in situ was provided by the autoradiographic detection of acid-insoluble grains from [³H]thymidine over the cytoplasm of differentiating corpora lutein cells in the control and experimental groups. A significant effect on [³H]thymidine incorporation into microsomal DNA by prolactin could not be demonstrated in this experimental system.     

Mobility of water bound to biological membranes: A proton NMR relaxation study

Water proton nuclear magnetic resonance relaxation measurements have been obtained for aqueous suspensions of red cell membranes. These data support a model in which water molecules are exchanging rapidly between a bound phase with restricted motions and a free phase with dynamic properties similar to liquid water. From this model and these data, estimates are obtained for the relaxation time for bound phase water. Possible relaxation mechanisms for bound phase water are discussed and some support is found for an intermolecular interaction modulated by translational motions characterized by a diffusion constant of 10^?9 cm²/s.     

Recruitment in networks of pulmonary capillaries.

To improve our understanding of the pressure-flow characteristics of pulmonary capillaries, we analyzed by means of computer stimulation a theoretical model composed of 50 interconnected nonlinear elements. Each element required a critical pressure across it before flow occurred and there was a subsequent linear pressure-flow region whose slope, or resistance, could be related to the transmural pressure of the element ("distensibility"). The critical pressures and resistances of each element of the network were randomly chosen from distributions. We found that recruitment (i.e., onset of flow) occurred over a large range of network upstream or "arterial" pressures, and that relatively high arterial pressures were required before all elements had no distensibility. Intermittent and reverse flow were commonly seen in some elements as the arterial pressure was raised in steps. These flow reversals were particularly common when the critical pressures and resistances of the elements were inversely related. The critical pressures required for such behavior in the capillary segments of the pulmonary microcirculation were calculated to be extremely small, of the order of 0.02 cmH2O. Pressures of this magnitude might result from sticking of red cells to capillary walls or to each other. The properties of such a network may explain the patchiness of flow in the pulmonary microcirculation and the large range of arterial pressures over which recruitment is observed to occur.