Cell proliferation in the subependymal layer of the adult mouse in vivo and in vitro

Pulse labelling experiments with [³H] thymidine (dT) and double labelling experiments with [³H]dT and bromodeoxyuridine (BrdUrd) were carried out on cells of the subependymal layer in the brain of adult normal mice in vivo, in vivo/in vitro and in vitro. The results should (i) lead to information about cell cycle parameters of these cells in the brain of adult mice, since these cells have been studied mostly in the rat brain up to now and (ii) answer the question whether results concerning cell proliferation obtained in vivo correspond with those from brain slices incubated in vitro with or without prelabelling in vivo. In vivo an LI of 20.2 ± 2.7% (x?± SEM) and T_s= 7.2 ± 0.7h were found. Furthermore, grain count halving experiments led to a surprisingly short cycle time (T_c) of 11.2–14.2 h. The longer T_c values (18–20 h) reported in the literature for subependymal cells in the rat brain seem to be due to evaluations of different areas around the lateral ventricle without considering the migrating behaviour of these cells which is quite different regionally. The in vitro studies (with or without prelabelling in vivo) showed a significantly reduced LI due to the fact that about 20% of the S phase cells, possibly lying in the middle of S, stopped further DNA synthesis after transfer to culture. This was shown by comparing the cell fluxes at the G₁/S and S/G₂ borders of in vivo vs. in vitro studies.     

Cloning and sequencing of the pheU gene for tRNAPhe of Thermus thermophilus HB8, and genomic mapping of the pheU and pheST genes

Abstract The effect of the iron content of the medium on the yield of the peptide antibiotic microcin 25 was examined; synthesis was optimal in minimal media and was reduced by adding iron. Escherichia coli AY25, the wild-type producer of the antibiotic, showed a 95% decrease in microcin yield when grown in minimal medium containing 10 μM iron (high iron) as compared to 0.2 μM (low iron). Addition of chelators to Luria broth elicited microcin production, and there was a complete reversal of the effect of the chelators by adding iron. Studies with Escherichia coli mutants deficient in iron-regulated proteins ( fur ) suggested that factors other than Fur could mediate iron regulation of microsin synthesis.     

High-pressure freezing of soybean nodules leads to an improved preservation of ultrastructure

High-pressure freezing of chemically untreated nodules of soybean (Glycine max (L.) Merr.), in sharp contrast to chemical fixation and prefixation, appears to preserve the ultrastructure close to the native state. This is supported by the observation that the peribacteroid membrane of high-pressure-frozen samples is tightly wrapped around the bacteroids, a finding that is fully consistent with the current views on the physiology of oxygen and metabolite transport between plant cytosol and bacteroids. In soybean root nodules, the plant tissue and the enclosed bacteria are so dissimilar that conventional aldehyde-fixation procedures are unable to preserve the overall native ultrastructure. This was demonstrated by high-pressure freezing of nodules that had been pre-fixed in glutaraldehyde at various buffer molalities: no buffer strength tested preserved all ultrastructural aspects that could be seen after high-pressure freezing of chemically untreated nodules.     

Characterization of three soluble c-type cytochromes isolated from soybean root nodule bacteroids of Bradyrhizobium japonicum strain CC705

Three soluble, low molecular mass cytochromes c (Mr 8000-15,000) were isolated and purified from soybean root nodule bacteroids of Bradyrhizobium japonicum strain CC705. On the basis of their alpha: absorbance peaks in the reduced forms, they were named cytochromes c550, c552 and c555. Cytochrome c552 reacted very fast, c555 very slowly and c550 not at all with carbon monoxide. The complete amino acid sequence (73 residues) of cytochrome c552 was established which identifies it as a monoheme, class I cytochrome c with some remote similarity to the cytochrome c6 family.     

Cell wall polysaccharides in black currants and bilberries—characterisation in berries, juice, and press cake

Cell wall polysaccharides from black currants and bilberries were characterised in three approaches. First, compositions of skin, pulp, and seeds show the distribution of polysaccharides over these tissues. A sequential extraction of cell wall material with different aqueous extractants informs about the extractability of the different polysaccharides, viz. pectins, hemicellulose, and cellulose. Finally, by isolation of cell wall polysaccharides from juice and press cakes obtained by the conventional juice manufacturing. The polysaccharide distribution was followed during juice processing. The main difference between bilberries and black currants is the dominant sugar residue in seeds: mannose for black currants and xylose for bilberries. Most of the hemicellulolytic sugars and cellulose can be found back in the press cake. The sugar composition of the press cake is similar to the composition of the residue after sequential extraction. Black currants contain more pectic sugars than bilberries. Consequently, a commercial enzyme used during processing releases more pectic material into the juice.