Mating-Type Differentiation by Transposition of Controlling Elements in SACCHAROMYCES CEREVISIAE

The nonfunctional mutation of the homothallic gene HML alpha, designated hml alpha, produced two mutant alleles, hml alpha-1 and hml alpha-2. Both mutant clones were mixed cultures consisting of a mating-type cells and nonmating haploid cells. The frequencies of the two cell types were different, and a few diploid cells able to sporulate were found in the hml alpha-2 mutant. Conversions of an a mating-type cell to nonmater, and vice versa, were observed in both mutants. The conversion of an a mating phenotype to nonmating is postulated to occur by alteration of the a mating type to the sterile mating-type allele in the hml alpha-1 mutant. In tetrad dissection of prototrophic diploids that were obtained by rare mating of hml alpha-1 mutants with a heterothallic strain having the MATa ho HMRa HMLa genotype, many mating-deficient haploid segregants were found, while alpha mating-type segregants were observed in a similar diploid using an hml alpha-2 mutant. The mating-type-deficient haploid segregants were supposed to have the sterile alpha mating-type allele because the nonmating genetic trait always segregated with the mating-type locus. Sporogenous diploid cells obtained in the hml alpha-2 mutant clone had the MATa/MAT alpha HO/HO HMRa/HMRa hml alpha-2/hml alpha-2 genotype. These observations suggested that the hml alpha-1 allele produces a transposable element that gives rise to the sterile alpha mating type by transposition into the mating-type locus, and that the hml alpha-2 allele produces an element that provides alpha mating-type information, but is defective in the structure for transposition.     

Immobilized mitochondrial electron transport particle for NADH determination

Nonphosphorylating electron transport particles (ETP) prepared from beef heart mitochondrion were immobilized in agar gel. The immobilized ETP showed an oxidase activity to both NADH and succinate. The immobilized ETP was reusable. An electrochemical device for the determination of either NADH or succinate was assembled consisting of the membrane-bound ETP and an oxygen probe. The response to succinate was specifically inhibited by the addition of malonate.     

Mutation induced by drying of Escherichia coli on a hydrophobic filter membrane.

Drying of Escherichia coli to a required cellular water level was conducted on a hydrophobic membrane at the corresponding relative humidity. Mutation from an arginine auxotroph to the prototroph was induced by drying to a water activity (aw) of 0.53 and below, but not to an aw of 0.75 and above. The critical aw below which mutation occurred in the course of drying was similar to that for induction of deoxyribonucleic acid (DNA) strand breakage in the bacteria. Some ultraviolet or gamma-irradiation-sensitive strains, e.g., strains of carrying recA, recB, and uvrA recA were more sensitive to drying than the wild-type strains or strains carrying uvrA and polA. The DNA strand breakage of every strain was observed to be to a similar extent after drying to an aw of less than 0.53. The drying-resistant strains repaired the damaged DNA partially during postdrying incubation in a growth medium but not in phosphate buffer solution, while the drying-sensitive strains could not at all. Significant mutation on drying occurred in the wild-type strains, strains carrying uvrA and polA, but not in strains carrying recA. It is, therefore, concluded that the mutation is caused by errors in rec-dependent repair of the drying-induced breakage in DNA.     

Evidence of the Insensitivity of the alpha-inc Allele to the Function of the Homothallic Genes in Saccharomyces Yeasts

The possible function of the α-inc allele (an α mating-type allele that is insensitive to the function of the homothallic gene system) was investigated by means of protoplast fusion. The fusion of protoplasts prepared from haploid strains of α-inc HO HMα HMa and α ho hmα HMa gave rise mainly to nonmating clones (58 of 64 isolates) and a few clones (six of 64 isolates) showing α mating type. Thirty of the 58 nonmating clones showed the diploid cell size and 28 clones had a larger cell size. Tetrad analysis of the nonmating clones with diploid cell size indicated that they were a/α-inc diploid; the normal α allele in α/α-inc cells was preferentially switched to an a allele. This observation further indicated that the HO/ho HMα/hmα HMa/HMa genotype is effective for the conversion of the α to a and that the inconvertibility of the α-inc allele is due to the insensitivity of the mating-type allele to the functional combination of the homothallic genes. It was suspected that fusion products larger than diploid cells might have been caused by multiple fusion of protoplasts.     

The course of resin canals in the shoots of conifers

The course of resin canals in stem cortex and the continuity between resin canals in leaves and those in stem cortex were investigated. The present paper is the first of three parts of the investigation. In this paper, fundamental features of resin canals and actual resin canal patterns in the Taxaceae, Cephalotaxaceae and Podocarpaceae are reported. From the observation of serial transections of shoots, composite diagrams and three-dimensional models of resin canal patterns are drawn. Central canals, if present, run vertically in stem cortex and sometimes divide, end blindly or unite each other. The distance between two adjacent central canals fluctuates rhythmically in connection with the vascular supply from the stem to leaves. The resin canal patterns of the families are classified into four types. Those ofTaxus, Nothotaxus and three species ofDacrydium belong to the Taxus type, those ofTorreya andCephalotaxus to the Torreya type, those ofDacrydium elatum, Podocarpus alpinus, P. elatus, P. elongatus andP. neriifolius to the Dacrydium type, those ofP. macrophyllus, P. nagi andP. koordersii to the Podocarpus type.     

Radiation effects of poly(l-glutamic acid) and poly(l-lysine) in the helix-coil transitional state

Summary The degradation of poly(l-glutamic acid) and poly(l-lysine) by X-rays and ultraviolet radiation has been studied at variouspH values, including the helix-coil transition region. It was found that X-rays cause maximum degradation in the transition region for both polypeptides, indicating that the efficiency of degradation is affected not only by the secondary structure but also by some other factors related to the transition. On the contrary, the degradation by monochromatic ultraviolet 2537 radiation showed a strong dependence on helix content of PLGA, suggesting that degradation occurs more effectively in the helical form than in the coil form. Theoretical calculations were made to approximate thepH dependence of degradation, assuming different cross sections for the peptide bonds in helix, coil, and junctions between helical and coil regions.     

Two-nucleotide codon change in a hemoglobin polymorphism of the Celebes black ape (Macaca nigra)

A hemoglobin polymorphism involving variant -chains was demonstrated in the Celebes black ape, Macaca nigra. Fingerprinting and amino acid analysis of the tryptic peptides from the two chain types have shown that they differ by a single amino acid substitution, between lysine and aspartic acid, which requires a two-nucleotide change in the corresponding codon. Another substitution in the same codon is found as a species difference between the black ape -chain and that of other macaques.     

Identification of asymptomatic Entamoeba histolytica infection by a serological screening test: A cross-sectional study of an HIV-negative men who have sex with men cohort in Japan

BackgroundAmebiasis, caused by Entamoeba histolytica, is spreading in developing countries and in many developed countries as a sexually transmitted infection. Here, we evaluated the efficacy of serological screening to identify asymptomatic E. histolytica infection as a potential epidemiological control measure to limit its spread.Methodology/Principal findingsThis cross-sectional study was carried out between January and March 2021 in an HIV-negative men who have sex with men (MSM) cohort at the National Center for Global Health and Medicine. Serological screening was performed using a commercially available ELISA kit. For seropositive individuals, we performed stool polymerase chain reaction (PCR) to determine current E. histolytica infection. We performed E. histolytica serological screening of 312 participants. None had a history of E. histolytica infection prior to the study. The overall E. histolytica seropositivity was 6.7% (21/312), which was similar to that found by the rapid plasma reagin test (17/312). We identified current infection in 8 of 20 seropositive participants (40.0%) by stool PCR.Conclusions/SignificanceOur serological screening approach constitutes a potentially practical epidemiological strategy. Active epidemiological surveys, in combination with an effective screening strategy for asymptomatically infected individuals, should be applied to help reduce sexually transmitted E. histolytica infections.     

Expression in Escherichia coli of chemically synthesized gene for a novel opiate peptide alpha-neo-endorphin

Chemically synthesized alpha-neo-endorphin gene was fused to the Escherichia coli beta-galactosidase gene on the plasmid pKO13. The resulting recombinant DNA was used to transform E. coli cells. Radioimmunoassay for alpha-neo-endorphin in CNBr-treated bacterial cells showed that alpha-neo-endorphin was synthesized at approximately 5 x 10(5) molecules per single E. coli cell. One of the transformants, WA802/p alpha NE2, was used for alpha-neo-endorphin purification. From 10.9 g of wet cells, we isolated 4 mg of chemically pure and biologically active alpha-neo-endorphin.