Three yeast genes,PIR1, PIR2 and PIR3, containing internal tandem repeats,are related to each other,and PIR1 and PIR2 are required for tolerance to heat shock

We isolated three highly homologous genes, PIR1, PIR2 and PIR3, collectively called the PIR genes. The remarkable feature of their putative amino acid sequence is that they contain a sequence consisting of 18–19 amino acid residues repeated tandemly seven to ten times. Genes homologous to PIR were found in Kluyveromyces lactis and Zygosaccharomyces rouxii but not in Schizosaccharomyces pombe, suggesting that a set of PIR genes plays some role in budding yeast. Bias of codon usage seen in each of the PIR translation products suggests that they are expressed abundantly. The fact that disruption of each gene is viable indicates that none of them is essential. The double disruptants, pir1 pir2, were viable under various conditions, such as higher temperature (37°C) or high salt concentration, but showed a slow-growing phenotype on an agar slab. Furthermore, they were sensitive to heat shock. Addition of a pir3 disruption to the pir1 pir2 double disruptant brought about no phenotypic difference from the original double mutant. PIR1 and PIR3 are closely linked to each other and are on chromosome XI.     

Suppression of deicing salt corrosion of weathering steel bridges by washing

To elucidate the influences of deicing salts and high pressure (2-4 MPa) washing on the characteristics of the rust formed on weathering steel bridges, washing experiments have been carried out for three years. The rust was characterized by means of ion chromatography, X-ray diffraction and adsorption of N₂. The rust thickness was measured, and also the rust weight per unit area of the steel surface was measured. It was found that water-soluble chloride accelerated the rate of corrosion because the rust particles grow by the chloride ions and micro-pore structure of the rust appeared by the chloride ions. Washing with water suppressed corrosion owing to the disappearance of chloride ions.     

Active slip systems and their contribution to deformation phenomena by indentation of the cube face of face-centered cubic metals

New models are proposed for the distributions of active slip systems induced by a cone and a ball indentation on the (001) plane of f.c.c. metals. By employing modified elastic stress fields, three or four primary slip systems are predicted to be individually active in the octant bounded by the [110] and [010] axes.The observed slip traces, surface topography and the shape of dislocation clustering zones are shown to be in reasonable agreement with those expected by the activation of the predicted slip systems. It is also shown that the anisotropy of the extent of this plastic region can be related to that of the elastic stress field.     

Determining double-bond positions in monoenoic 2-hydroxy fatty acids of glucosylceramides by gas chromatography-mass spectrometry

We applied a gas chromatography-mass spectrometry (GC-MS) method using dimethyl disulfide (DMDS) adducts and were able to determine the double-bond positions in monounsaturated 2-hydroxy fatty acids (2-HFA). 2-HFA methyl esters, prepared from the hydrolysate ofArabidopsis thaliana leaf glucosylceramides, were acetylated and methylthiolated. GC-MS analysis of the resulting DMDS adducts showed simple mass spectra with recognizable molecular ions and a series of key fragment ions indicating the original double-bond positions in the aliphatic chain. Based on this GC-MS elucidation, we confirmed thatArabidopsis leaf glucosylceramides have C₂₂, C₂₃, C₂₄, C₂₅, and C₂₆ chain length 2-HFA with monounsaturation, and all their double bonds are placed at the n−9 position. This procedure is simple, time efficient, and highly sensitive.     

Effects of C60, a Fullerene, on the Activities of Glutathione S-Transferase and Glutathione-Related Enzymes in Rodent and Human Livers

The effects of C₆₀, a fullerene, on the activities of glutathione 5-transferase (GST), glutathione peroxidase (GSH-Px) and glutathione reductase (GR) in rodent and human livers were investigated. the GST activity in rat liver towards frans-4-phenyl-3-buten-2-one and that in mouse liver towards ethacrynic acid were inhibited by C₆₀- the GST activity towards 1,2-dichloro-4-nitrobenzene, isomerase activity of GST towards androst-5-ene-3,17-dione, GSH-Px activity and GR activity were not affected by C₆₀ a kinetic study using purified mouse GST-π with ethacrynic acid (25-100 μM) as the substrate revealed that C₆₀ was a non-competitive inhibitor of the enzyme with a K_i = 48.8 ± 0.25 μM and a K_i = 47.9 ±0.18 μM. However, C₆₀ did not inhibit the activity of purified mouse GST-π towards l-chloro-2,4-dinitrobenzene. Thus, the inhibition by C₆₀ appears to be substrate-specific. In human liver, C₆₀ inhibited the GST activity towards ethacrynic acid, and moderately inhibited GSH-Px and GR activities.     

Mechanism of the paradoxical, inhibitory effect of phenobarbital on hepatocarcinogenesis initiated in infant B6C3F1 mice with diethylnitrosamine

Phenobarbital (PB), a classical rodent hepatopromoter, remarkably enhances hepatocarcinogenesis initiated by diethylnitrosamine (DEN) in adult B6C3F1 mice. However, it is also known to strongly inhibit liver tumor development in the B6C3F1 mice initiated with DEN in their infancy. The present study aimed to elucidate the unknown biological mechanisms for this paradoxical, inhibitory effect of PB on B6C3F1 mouse hepatocarcinogenesis. Male 12-day-old infant B6C3F1 mice were injected i.p. with DEN and, at 6 weeks of age, divided into PB-treated (PB+ group) and untreated (PB- group) animals. At 24 weeks, PB treatment was ceased for half of the PB+ animals (PB+/- group) and started for half of the PB- animals (PB-/+ group). Finally, all mice were sacrificed at 36 weeks and examined for the development of liver tumors. The mean multiplicity of gross tumors in the PB+ group was only one-fifteenth of that for the PB- group. PB-/+ animals developed fewer than half of the tumors found in PB- mice, indicating that the PB effect depends solely on the treatment duration, rather than the animal age. The effect was proven to be reversible, because the mean tumor multiplicity for the PB+/- group was seven times larger than that for the PB+ group. Stereological analysis revealed the mean volume of hepatocellular proliferative lesions in the PB- animals to be 7.7- and 4.1-fold the values for the PB+ and PB-/+ groups, respectively. The mean proliferating cell nuclear antigen-labeling indices for hepatocellular adenomas in PB+ and PB-/+ animals were also one-third of that for tumors in PB- animals, whereas no significant differences were observed with regard to the mean apoptotic index. In conclusion, the inhibitory effect of PB seemed to be primarily caused by the suppression of tumor cell proliferation. Irrespective of the group, most lesions observed were basophilic hepatocellular adenomas or foci, positive for Bcl-2 oncoprotein. They were thus distinct from the eosinophilic Bcl-2- lesions that predominate with PB promotion after the initiation of adult B6C3F1 mice. This age-dependent nature of initiation, together with the differential responses of Bcl-2+ and Bcl-2- lesions, may be responsible for the apparently contradictory outcomes of PB treatment in infant and adult B6C3F1 mice.     

An efficient method for reconstructing protein backbones from alpha-carbon coordinates

We present an approach for building protein backbones from alpha-carbon (Calpha) coordinates. The approach is analytical and based on the information of favored regions in the Ramachandran map. The backbone construction consists of three parts: prediction of (phi, psi) angle pairs from the Calpha trace, generation of atomic coordinates with these (phi, psi) angles, and refinement by subsequent energy minimization. Tests on several known protein structures show that the root mean square deviations in reconstructed backbones are 0.25-0.48 A for coordinates and 14-34 degrees for phi and psi angles. The results indicate that our method is one of the best methods proposed in terms of accuracy. It has also been revealed that the approach is not only robust against errors in Calpha coordinates but is also capable of providing equivalent or more reasonable models compared to other known methods. Furthermore, backbone structures were found to be built accurately by using the (phi, psi) angles from a different structure of the same protein. This suggests that the approach could be effective and useful in homology modeling studies.