Cloning of human immunoglobulin mu gene and comparison with mouse mu gene

We have cloned a 12 kb DNA segment containing human mu gene and its flanking sequence from human fetal liver DNA library using mouse mu gene as a probe. Partial nucleotide sequence determination shows that the cloned DNA contains the sequence encoding human mu chain. This is the first constant region gene of the human heavy chain that is cloned. We have compared human and mouse mu genes by heteroduplex analysis and Southern blot hybridization. The results clearly show that not only the sequence encoding the CH4 domain but also the 5'-flanking (S mu) sequence is conserved between human and mouse mu genes, suggesting that the nucleotide sequence in the S mu region has an important biological function, presumably a recognition signal for the class switch recombinant as proposed previously.

Genetic control of diploid recovery after gamma-irradiation in the yeast Saccharomyces cerevisiae

Genetic mechanisms(s) of gamma-ray resistance of the diploid and budding haploid cells of S. cerevisiae were investigated, with special reference to mitotic recombination, by examining 11 rad mutant strains. The radiosensitivity of the diploid was markedly enhanced in certain gamma-ray-sensitive rad mutants, whereas the sensitivity of the haploid was not so enhanced in these rad mutants. These enhanced sensitivities of diploids were irrespective of their own haploid sensitivities. From these results, the existence of a mechanism of diploid-specific recovery was postulated. The magnitude of diploid radioresistance in rad mutants was positively correlated with the ability for the induction of mitotic recombinational events which were controlled by RAD genes belonging to the RAD-51 genetic pathway. The genetic mechanism(s) of the diploid recovery after gamma-irradiation are probably related to recombinational processes between the homologous chromosomes leading to reciprocal recombination or non-reciprocal gene conversion. Furthermore, the higher radioresistance of budding cells in comparison with the non-budding cells was also correlated to the diploid radioresistance with a few exceptions. Consequently, the mechanism(s) of budding radioresistance similar to the diploid recovery seems to be related to mitotic recombinational processes.

Differential effect of UV irradiation on induction of intragenic and intergenic recombination during commitment to meiosis in Saccharomyces cerevisiae

A comparison was made between the induction of intragenic and intergenic recombinations during meiosis in a wild-type diploid of Saccharomyces cerevisiae. Under non-irradiated normal conditions, production of both intragenic and intergenic recombinants greatly increased in the cells with commitment to meiosis. The susceptibility of cells to the induction of both the spontaneous intra- and intergenic recombinations in meiotic cells was similar. However, under condition of UV irradiation, there were striking differences between intra- and intergenic recombinations. Susceptibility to induction of intragenic recombination by UV irradiation was not enhanced at meiosis compared with mitosis, and was not altered through commitment to meiotic processes. In contrast, however, susceptibility to the induction of intergenic recombination by UV irradiation was enhanced markedly during commitment to meiosis compared with mitosis. Genetic analysis suggested that the enhanced susceptibility to recombination during meiosis is specifically concerned with reciprocal-type recombination (crossing-over) but not non-reciprocal-type recombination (gene conversion). Hence it is concluded that the meiotic process appears to be intimately concerned with the mechanism(s) of induction of recombination, especially reciprocal-type recombination.

Induction of spontaneous and UV-induced mutations during commitment to meiosis in Saccharomyces cerevisiae

Inductions of reversions of nonsense, missense and frameshift-type mutations were investigated in a diploid cell population of Saccharomyces cerevisiae during commitment to meiosis, by using the medium-transfer technique from sporulation medium to vegetative medium. The yields of spontaneous reverse mutations obtained from the cells that were committed to different stages during meiosis were rather constant irrespective of the alleles tested, although the yields of both intergenic and intragenic recombinations markedly increased. The susceptibilities to UV-induced reverse mutations examined during commitment to meiosis were not changed appreciably. It is concluded that induction of base-change-type mutations in meiosis is not essentially different from that in mitosis.

Analysis of the dynamic characteristics of parasitic oscillation

An analysis of the dynamic characteristics of parasitic oscillation between target and pinhole of a beam expander was carried out using a simplified rate equation model. Suppression of parasitic oscillation was also investigated in view of the oscillation dynamics. Useful results were obtained quantitatively concerning the rise time of the amplifier gain and the distance between the target and the final amplifier of the laser fusion system.

Inverted terminal repeat sequence in the macronuclear DNA of Stylonychia pustulata

The structure of macronuclear DNA of a hypotrichous ciliate, Stylonychia pustulata, was examined by both electron microscopy and nucleotide sequence analysis. The DNA in the macronucleus consists of small linear molecules with average length of about 3400 base pairs (bp). Most, if not all, of these DNA molecules have identical inverted terminal repeat sequence of 20 nucleotide residues. This sequence is 5'-CCCCAAAACCCC-AAAACCCC.

Hydrophobicity determined by a fluorescence probe method and its correlation with surface properties of proteins

The fluorescence method of Sklar et al. (Sklar, L.A., Hudson, B.S. and Simoni, R.D. (1977) Biochemistry 16, 5100-5108) using cis-parinaric acid as a probe was applied to determine the effective hydrophobicity of proteins. The initial slope (S0) of fluorescence intensity vs. protein concentration plot was used as an index of the protein hydrophobicity. A good correlation was observed for S0 of native proteins, denatured proteins and surfactant-bound proteins with an effective hydrophobicity determined by the hydrophobic partition method. The effective hydrophobicity determined fluorometrically showed significant correlations with interfacial tension and emulsifying activity of the proteins studied. The fluorescence technique using cis-parinaric acid is useful for determination of the effective hydrophobicity, as the procedure is much simpler and quicker than hydrophobic chromatography and hydrophobic partition.

Occurrence of bile alcohols in the bile of a patient with cholestasis

Considerable amounts (6.0 mumol/ml of bile) of bile alcohols were found in the bile of a patient with cholestasis due to gallstones in a common bile duct. Acid hydrolysis of the bile salts followed by chromatographic separation yielded three bile alcohols, which were identified as 26,27-dinor-5 beta-cholestane-3 alpha,7 alpha,12 alpha,24,25-pentol, 24-methyl-26,-27-dinor-5 beta-cholestane-3 alpha,7 alpha, 24-tetrol, and 3 alpha,7 alpha, 12 alpha-trihydroxy-26,27-dinor-5 beta-cholestan-24-one by comparison with synthetic reference standards.

Dose-response relations for dicentric yields in GO lymphocytes of man and crab-eating monkey following acute and chronic gamma-irradiations

A comparison has been made of dicentric yields in GO lymphocytes between man and crab-eating monkey, Macaca fascicularis, after acute and chronic gamma-irradiations. With acute irradiation (49.6 rad/min) there was no significant difference between them, but for the chronic irradiation (17.1 rad/h) a significant difference was observed between the species. When the dose-response relations were fitted to the linear-quadratic model (Y = alpha D + beta D2), the species-difference observed for chronic irradiation was almost entirely due to change in the value of beta. In addition, after chronic irradiation the beta-value for monkey was almost negligible, but that for man was significant. Post-irradiation incubation experiment showed that cells with dicentrics were partly eliminated during the course of chronic irradiation, because there were appreciable reductions of dicentric yields (ca. 25% for both man and monkey at 400 rad) together with mitotic indices (ca. 30% and 60% for man and monkey, respectively, at 400 rad). Accordingly, it would be reasonable to postulate that GO repair for dicentrics other than selection mechanism must play a major role in the effects of low dose rate. It can be further suggested that GO-repair capacity for chromosal damages leading to dicentrics may be different among different primate species.

The relationship between hydrophobicity and interfacial tension of proteins

Charge-free hydrophobic gels of Hjerten et al. (Hjerten, S., Rosengren, J. and Pahlman, S. (1974) J. Chromatogr. 101, 281--288) were used for hydrophobic affinity chromatography. The effective hydrophobicity of proteins was expressed as their retention volumes from columns of butylepoxy- and hexylepoxy-Sepharose 4B. The effective hydrophobicity was also estimated by a partition method of Shanbhag and Axelsson ((1975) Eur. J. Biochem. 60, 17--22) from the partition coefficients of proteins between two phases, poly (ethylene glycol) and dextran. The former contained a hydrophobic ligand, palmitate. A close correlation was observed between the hydrophobicities determined by the two methods. However, no significant relationship was observed between these effective hydrophobicities and the average hydrophobicity of Bigelow ((1967) J. Theoret. Biol. 16, 187--211) that was calculated from the total amino acid composition of each protein. The interfacial tensions at the 0.2% protein/corn oil interface revealed negative correlations with the effective hydrophobicities determined by both methods indicating lower interfacial tensions with more hydrophobic proteins.

Laser pumping by PFN power source

The use of a pulse forming network (PEN) as a main discharge power supply was tested in a electron-beam-controlled CO(2) laser amplifier in order to improve the utility efficiency of the energy in storage capacitors. The impedance of the pumping discharge through the laser gas was controlled by the accelerating voltage of the electron beam to match the PFN line impedance. In the matched condition all of the stored energy in the PFN was transffered to the laser gas at a constant electric field strength which was optimum for laser pumping.

Unusual dose--response of chromosome abberrations induced in human lymphocytes by very low dose exposures to tritium

Leukocyte cultures of human peripheral blood were chronically exposed for 48 h to tritiated water and [3H]thymidine using a wide range of tritium doses, and aberrations in lymphocyte chromosomes at the first metaphases were examined. In the experimental conditions, the types of aberrations induced by radiation emitted from both tritiated water and [3H]thymidine were mostly chromatid types, such as chromatid gaps and deletions. The dose--response relations for chromatid breaks per cell exhibited unusual dose-dependency in both cases. It was demonstrated that at higher dose range the yields of chromatid breaks increased linearly with dose, while those at lower dose range were significantly higher than would be expected by a downward extrapolation from the linear relation. Partial-hit or partial-target kinetic events appears at very low dose exposure.