Zeitschrift fur Naturforschung. Section C, Biosciences最新文献

Electrofusion of mesophyll cell protoplasts of Avena sativa was induced by simulated atmospheric discharges. It is shown both experimentally and theoretically that the potential differences which occur at quite long distances from the point of lightning stroke are large enough to induce fusion. Besides electromagnetic waves which are emitted during lightning (G. Küppers and U. Zimmermann, FEBS Lett. 164, 323 (1983] cell fusion may have also occurred directly by means of the voltage built-up on the earth during evolution in response to a lightning stroke.

A high performance liquid chromatography method for determining the levels of 4-pregnene-3-ones in tissue containing fat, e.g. in thymus is reported. Following the extraction with chloroform/methanol the fat has been separated from the steroidal-fraction by using disposable extraction-columns. The steroidal-fraction has been analysed in two separation systems, on a RP18-column with a methanol/water gradient and on an amino column with a isopropanol/hexane gradient. The applicability of the described method is demonstrated with calf thymus samples.

The phospholipids and glycerides composition of spheroplasts of Mycobacterium smegmatis ATCC 14468 was examined. The percent total phospholipids in total lipids as well as cardiolipin were found to be higher in spheroplasts as compared to their parent forms. Increase in cardiolipin and free fatty acids content and decrease in triglycerides levels were observed during spheroplasts formation. The results suggest that increase in cardiolipin content in spheroplasts is an adaptational change concomitant with the loss of cell walls.

Experimental data on surface pressure-surface area hysteresis of mixed serum albumin/dipalmitoyl lecithin/sphingomyelin monolayers in the Langmuir trough are presented. Several possible physicochemical mechanisms of the hysteresis are discussed: Marangoni effect, surface pressure relaxations, bulk-to-surface diffusion interchange, and collapse. Depending on the concrete conditions each of these mechanisms can be important. Possible applications of these results to the alveolar dynamics are presented and discussed on the basis of the balloon model of the alveolus. The main conclusions of biological importance are that 1) the alveolar stability depends on the DPL/SM ratio as well as on the protein content. Under normal breathing conditions the surface pressure hysteresis is small and does not play a decisive role in the alveolar dynamics. 2) At large extent of compression the collapse predominates in determining the hysteretic behavior of the alveolar surface.

Chromatin from two Syrian hamster tissues: the Kirkman-Robbins hepatoma and the liver, has been separated into soluble (S) and insoluble (P) fractions. Both fractions contain the complete set of five main histones but differ in respect of H1 subfractions. The hepatoma chromatin is known to contain an unusual H1 subfraction, H1 slow [12, 13], probably identical with a similar subfraction present in hamster testes. The content of H1 slow in total H1 histone has been estimated for total, S and P chromatin from hamster hepatoma. The values 20.9 +/- 7.2, 13.8 +/- 1.8 and 26.8 +/- 4.2%, respectively, were obtained.

Mouse lymph node lymphocytes are irradiated at different dose rates and the B-cell receptors to anti IgG are tested. The expression of receptors is inhibited by irradiation. It is shown that the effectivity of irradiation increases with decreasing dose rate suggesting that membrane damage may be important for situations of chronic irradiation or implant radiotherapy.

The glutathione reductase from Escherichia coli strain S33 was purified to homogeneity by a simple and fast procedure consisting of two affinity chromatography steps. After 40-80% ammonium sulfate fractionation, the enzyme was adsorbed to an N6-2'.5'-ADP-Sepharose affinity column from which it was specifically eluted by a 0-10 mM NADP+ linear gradient. The enzyme was finally purified to homogeneity after a second affinity chromatography step in a C8-ATPR-Sepharose column, from which it was eluted by means of the same NADP+ gradient. Starting from 182 g of E. coli cells, 6.9 mg of pure enzyme was obtained after a 2632-fold purification, with a total yield of 63%. The pure enzyme showed a specific activity of 361 U/mg, and its absorption spectrum was characteristic of a flavoprotein, with an A272/A450 of 7.84. The enzyme was a dimer with a molecular weight 109 000 and 40 A hydrodynamic radius. The optimum pH were 7.5 and 4.5 with NADPH and NADH, respectively, as reductants. Apparent K'm values of 16, 377, and 66 microM were determined at pH 7.5 for NADPH, NADH, and GSSG, respectively. Upon storage the enzyme was stable at pH values ranging from 7.5 to 9.5, being additionally stabilized by FAD, NADP+, dithiothreitol, or glycerol. The pure enzyme was quite heat stable, denaturing significantly only after 10 min at 70 degrees C. A marked activity loss was observed however, even at 0 degrees C, in the presence of 20 microM NADPH. The enzyme was inactivated by low concentrations of para-hydroximercuribenzoate; the sensitivity towards such mercurial was greatly enhanced after reduction of the enzyme by NADPH.

We established more than 200 primary cell lines of Cydia pomonella (coding moth). 81 of them were selected and screened for replication of two baculoviruses (from two different subgroups): the Choristoneura murinana NPV and the Cydia pomonella GV. Although all these cell lines had been derived from the same insect species, they varied largely in their response to challenge with the NPV. Most of them showed CPE or produced different amounts of polyhedra. Interestingly, we also found a few cell lines that were permissive for GV replication. To our knowledge this is the first time that GV replication in cell lines has been obtained. Our results show that cell line properties are most important for baculovirus in vitro replication.

Semithin and thin sections of glutaraldehyde-fixed, epoxy resin-embedded animal tissues were treated with solutions of oxidized p-phenylenediamine (PPD). This method is suitable to reveal the general morphology of tissues in light microscopy, showing a high staining degree in some polyanion containing components. Posttreatments of thin sections with gold chloride solutions give considerable electron opacity in PPD positive structures.