The effect of serum on lipid synthesis and on the expression of oligodendrocyte marker-enzymes in oligodendrocyte-enriched glial cells in culture

Glial cells were isolated from the cerebra of 7-day old rats and the effect of serum on the development of these cells in culture was studied. The activities of the oligodendrocyte marker-enzymes, 2′3′-cyclic nucleotide 3′-phosphodiesterase and glycerol 3-phosphate dehydrogenase and the synthesis of the myelin-associated sulpholipid, sulphatide, were used to monitor the differentiation of these cells in vitro. The results indicate that serum: (i) represses lipogenesis, cholesterogenesis and sulphatide synthesis, (ii) lowers the expression of 2′3′-cyclic nucleotide 3′ phosphodiesterase and glycerol 3-phosphate dehydrogenase but not of lactate dehydrogenase and (iii) thus impairs the differentiation of oligodendrocytes.     

Ultrastructural changes of the renal cortex after septic shock in rats

The purpose of this study was to observe the ultrastructural changes of the renal cortex that occur in septic shock. Twenty male Wistar rats were used. They were divided into 4 groups of five animals each one. A septic shock was caused by intraperitoneal injection of 5 x 10(6) living E. Coli, in a dose of 2ml/100gr B. W., in four rats of each group. The fifth rat of each group was used as control, and was injected by an equal volume of normal saline. A small segment from the right kidney was excised from every rat of each group, respectively 1, 2, 4 and 6 hours after the onset of the shock. Morphologically, alterations of the endothelium of the peritubular and glomerular capillaries were found. The endothelial layer was thick with many cytoplasmic folds. In the glomeruli, the basal lamina as well as the overlying epithelial podocytes and their foot processes were swollen. The urinary space contained erythrocytes and cell debris. Lesions of the proximal and distal tubule epithelium were also observed. The basal infoldings of the cell membrane disappeared in many epithelial cells of the proximal tubule and the brush border showed varying degrees of disruption. Within the tubular lumen much cellular debris was found. The epithelium of the distal tubule was thinner in some portions and in others it was swollen. The lesions were focal during the first hour after the onset of shock, while at the fourth and sixth hours they were most extensive. In conclusion, the ultrastructural findings after septic shock were non-specific and indicated cellular injury.     

Dependence of Ca outflow and depression of frog myocardium contraction on ryodipine concentration

The effect of ryodipine on calcium outflow from tissues, on contraction force, the duration of action potentials and the relaxation phase time-constant in the contraction cycles of myocardial strips was studied using frog heart preparations. It was found that calcium outflow (delta Ca) as a function on ryodipine concentration can be represented as: (formula; see text) A linear correlation exists between Ca2+, contraction blocking and the shortening of the action potential in the presence of various ryodipine concentrations. Ryodipine (10(-5) mol/l) decreased the relaxation time-constant by about 20% as compared to controls. It was concluded that calcium outflow from myocardial tissues in response to ryodipine is due to blockade of calcium entry into the cells and their output through the Na+--Ca2+ exchange system. Frog heart myocardial contractions are essentially under the control of calcium entry through sarcolemmal calcium channels.     

Indirect immunofluorescent detection of oocysts of Cryptosporidium parvum in the feces of naturally infected raccoons (Procyon lotor)

Fecal samples from 100 wild raccoons were examined for the presence of oocysts of Cryptosporidium parvum using a commercially available indirect immunofluorescent detection procedure. Thirteen (13%) of the samples were positive for oocysts. All positive samples were from juvenile raccoons. Over 61% of the infected samples contained moderate to large numbers of oocysts. Raccoons may serve as potential reservoirs for transmission of C. parvum.     

Genetic characterization and use of a restriction fragment length variant in the hypotrichous ciliate Euplotes crassus

Two forms of a macronuclear DNA molecule differing in the presence or absence of a restriction endonuclease recognition site have been detected in the hypotrichous ciliate Euplotes crassus. Through a series of genetic crosses the two forms were shown to be allelic, being derived from a single micronuclear genetic locus. This restriction fragment length variant (RFLV) was used as a genetic marker to determine that the migratory and stationary pronuclei generated during mating can be genetically non-identical. In addition, the RFLV was used to investigate the efficiency of processing of the alternate alleles during macronuclear development and their subsequent transmission during vegetative growth. Little or no bias in the processing and/or amplification of the two alleles was observed during macronuclear development. During vegetative growth, however, changes in the relative amounts of the two alleles were observed.     

Inhalation exposure-rate of ethylene oxide affects the level of DNA breakage and unscheduled DNA synthesis in spermiogenic stages of the mouse

The effect of ethylene oxide (EtO) inhalation-exposure rate on the induction of DNA breakage in late spermatids and on unscheduled DNA synthesis (UDS) in early spermatids was studied. The exposures were 450 parts per million (ppm) for 4 h, 900 ppm for 2 h, and 1800 ppm for 1 h. Thus, the total exposure was always 1800 ppm-h. Both DNA breakage and UDS were found to increase by a factor of approximately 3 in going from the low to high EtO concentration, suggesting that the molecular dose of EtO to the testis had increased by a similar factor. Our results are consistent with the EtO exposure-rate effect found by Generoso et al. (1986) for induction of dominant-lethal mutations in late spermatids and early spermatozoa.     

Killing of Escherichia coli cells modulated by components of the stability system ParD of plasmid R1

Summary The proteins P10 and P12 have been shown to be gene products of a new stability system, ParD, of plasmid R1. It is now shown that an R1 miniplasmid, pAB112, carrying a trans-complementable amber mutation in the gene of the P10 protein, is lethal for the host in the absence of suppression. This lethal effect is suppressed in a supF background and also by deletions in pAB112 that affect the gene of the P12 protein. These data indicate that the P12 protein has a lethal effect on the host and that this effect is neutralized by the P10 protein. The possibility that the stabilization conferred by the ParD system could be due to a counterselection, mediated by P12, of cells that lose the plasmid at cell division, is discussed.     

The physiologic role of pyocyanine synthesized by Pseudomonas aeruginosa

The physiological role of pyocyanine for Pseudomonas aeruginosa was studied. Its synthesis was shown to commence at the retardation growth phase. Pyocyanine was accumulated only in the growth medium. The addition of 2,6-dichlorophenolindophenol accepting the reducing equivalents from coenzyme Q and transferring them to cytochrome c inhibited the pigment accumulation. This was indicative of the connection between pyocyanine synthesis and the level of the reducing equivalents in the cells. Pyocyanine did not accept the reducing equivalents from coenzyme Q in the respiratory chain of P. aeruginosa. Only reduced pyridine nucleotides served as substrates for pyocyanine in the reaction of autooxidation. The kinetic parameters of this reaction and the affinity of NADH dehydrogenase for the substrate were measured. The kinetic data were analysed to show that, under the physiological conditions, pyocyanine could not apparently compete with the respiratory chain for the reducing equivalents and hence directly regulate the level of NAD(P)H in P. aeruginosa cells. In order to keep the oxidising activity at a level necessary for the cells, the latter decreased the content of the reducing equivalents either by synthesizing pyocyanine or owing to the activity of cyanide-resistant oxidase. These processes of releasing the reducing equivalents are in a reciprocal relationship.