ESR studies on the membrane properties of a moderately halophilic bacterium. I. Physical properties of lipid bilayers in whole cells

The lipid membrane properties of a moderately halophilic gram-negative bacterium, Pseudomonas halosaccharolytica ATCC 29423, were studied by the use of stearate spin labels, 5NS, 12NS, and 16NS, changing the temperature of ESR measurement from 15 to 50 degrees C. The order parameter and the rotational correlation time of the spin labels incorporated into intact cell membranes of this bacterium grown at various temperatures in media containing different NaCl concentrations were calculated. The activation energy of rotational microviscosity was obtained from Andrade plots. At low growth temperature and low NaCl concentration in the medium, extractable lipids of this bacterium contained comparatively large amounts of unsaturated fatty acids, but as the growth temperature and NaCl concentration in the medium increased, the contents of saturated and cyclopropanoic fatty acids increased to more than half of the total fatty acids. 5NS gave the highest order parameters for the intact cells of this bacterium, while 12NS gave lower and 16NS gave the lowest results. The order parameters of 5NS, 12NS, and 16NS were completely separated, and all order parameters decreased gradually as the measuring temperature was increased. In contrast, the rotational correlation times of the intact cells with 12NS were as large as those with 5NS, while those with 16NS were distinctly smaller. Increasing NaCl concentrations in the growth medium caused an increase of the rotational correlation times, that is, stiffened the lipid bilayers. The Andrade plot for 16NS was approximately a straight line, whereas 5NS and 12NS gave two straight lines crossing at a temperature near the growth temperature, indicating phase transition from solid to liquid. The microviscosity activation energies were 5--10 kcal/mol in the liquid phase and 15--25 kcal/mol in the solid phase.     

The amino acid sequences of two 13 kDa polypeptides and partial amino acid sequence of 30 kDa polypeptide of complex I from bovine heart mitochondria: possible location of iron-sulfur clusters

Mitochondrial NADH:ubiquinone oxidoreductase (complex I) is the most complicated system in the respiratory chain. It consists of many subunits, some of which hold iron-sulfur clusters, but structural information is still limited. The amino acid sequences of two 13 kDa polypeptides, 13 kDa-A and 13 kDa-B polypeptides, of iron-sulfur protein fraction (IP) of bovine heart mitochondrial complex I were determined by a combination of protease digestion, Edman degradation, and carboxypeptidase digestion. The 13 kDa-A polypeptide was composed of 96 amino acids with a molecular weight of 10,536. The 13 kDa-B polypeptide consisted of 114 amino acids and had an acetylated amino terminus. The molecular weight of this protein was calculated to be 13,130 including the acetyl group. These proteins had no obvious sequence similarity to other known proteins. The partial amino acid sequence of 30 kDa-B polypeptide of IP was also determined to reveal a characteristic arrangement of cysteine residues that could be involved in iron-sulfur cluster formation.     

Accidental importation of a Japanese bat into New Zealand

Abstract

A juvenile female Japanese pipistrelle (Pipistrellus javanicus abramus) wap found dead on 9 December 1981 in Hamilton, New Zealand, in a package of car parts from Japan. This is apparently the first accidental importation of an exotic bat to New Zealand.     

Studies of electric capacitance of membranes

Summary The electric capacitance and conductance of a model membrane composed of a hydrophobic filter paper and a synthetic lipid analogue, i.e., dioleylphosphate, immersed in an electrolyte solution were observed with various frequencies ranging from 20 to 3×10⁶ Hz. With successive increase of salt concentration in the external solution, the capacitance and conductance of the membrane increased discontinuously at a certain critical value of the external salt concentration. This variation of the capacitance and conductance of the membrane with the salt concentration was found to be reversible, and the critical value of salt concentration was independent of the adsorbed quantity of the lipid, and of the pore size of the filter paper as far as the adsorbed quantity of the dioleylphosphate was large.A theoretical analysis based on the membrane model for the filter paper-phospholipid system proposed in Part I of this series revealed that the dioleylphosphate impregnated in the filter paper changed its conformation from oil droplets or globular micelles to a number of bilayer membranes when the salt concentration reached the critical value for a given pair of electrolyte species and the membrane. The conformational change of the lipid analogue in the filter paper is discussed in connection with the ability of formation and stability of a black bilayer membrane of the dioleylphosphate.     

A Rapid Method for Whole Mount Preparations of Mammalian Oocytes and Early Embryos

Whole mounts of mouse oocytes and embryos are useful for observing intracellular structures while preserving morphological integrity. This method is inconvenient for rapid processing of a large number of specimens because washing each specimen in a protein-free solution is required prior to transfer into the fixative. We have developed a new fixative which does not cause protein precipitation which can be added directly to the culture medium. Specimens can be preserved in culture dishes for at least one month, and processed for cytological observation at a convenient time. When stained with hematoxylin, details of cellular structures such as nuclei, nucleoli, chromosomes and spindle microtubules can be observed while maintaining the organization of the organelles.     

The activities of mycotoxins derived from Fusarium and related substances in a short-term transformation assay using v-Ha-ras-transfected BALB/3T3 cells (Bhas 42 cells)

Cell transformation assays using BALB/3T3 cells can mimic the two-stage process of chemical carcinogenesis in experimental animals. A short-term transformation assay using v-Ha-ras-transfected BALB/3T3 cells (Bhas 42 cells), which was developed by Ohmori et al. and modified by Asada et al., has been reported to detect both tumor initiators and promoters as transformation initiators and promoters, respectively, with their differences based on their protocols. In this new short-term assay, we examined mycotoxins derived from Fusarium and related substances for the initiation and promotion activities of the transformation. The tested substances included deoxynivalenol, nivalenol, fusarenon-X, T-2 toxin, fumonisin B₁, fumonisin B₂, zearalenone, α-zearalanol, β-zearalanol, α-zearalenol and β-zearalenol. Fumonisin B₁ and T-2 toxin were positive for promoting activity in the assay. Especially, T-2 toxin was active at concentrations as low as 0.001–0.002 μg/mL in the culture medium. From a comparison between the results of this study and published carcinogenicity assay data, it was expected that the Bhas 42 cell transformation assay had a good correlation with the two-stage carcinogenicity tests using experimental animals for estimation of the tumor-promoting activity.