The induction of recessive mutations in mouse primordial germ cells with N-ethyl-N-nitrosourea

A specific-locus test was carried out to examine the mutagenic activity of N-ethyl-N-nitrosourea (ENU) on mouse primordial germ cells (PGC). Embryos of C3H/He mice were treated transplacentally with 30 or 50 mg ENU per kg of maternal body weight on day 8.5, 10.5, or 13.5 of gestation (G8.5 day, G10.5 day, or G13.5 day). Male and female mice that had been treated with ENU in embryonic stages were mated with female or male tester PW mice to detect recessive mutations induced in PGC.

ENU induced recessive mutations at a relatively high rate in PGC at these developmental stages. The most sensitive stage was G10.5 day. On G8.5 day, the induced mutation rate in males and females was not significantly different. Cluster mutations, which originate from the limited number of PGC and cell killing, were more frequently induced at an earlier developmental stage. The induced mutation rate per unit dose of ENU (1 mg/kg) was higher in G8.5 and G10.5 day PGC than in stem-cell spermatogonia. It can be concluded that mouse PGC are more sensitive than stem-cell spermatogonia to the induction of recessive mutations by ENU.     

Effects of hydrostatic pressure on the ultrastructure and leakage of internal substances in the yeast Saccharomyces cerevisiae

The structural damage to and leakage of internal substances from Saccharomyces cerevisiae 0–39 cells induced by hydrostatic pressure were investigated. By scanning electron microscopy, yeast cells treated at room temperature with pressuresbellw 400 MPa for 10 min showed a slight alteration in outer shape. Transmission electron microscopy, however, showed that the inner structure of the cell began to be affected, especially the nuclear membrane, when treated with hydrostatic pressure around 100 MPa at room temperature for 10 min; at more than 400–600 MPa, further alterations appeared in the mitochondria and cytoplasm. Furthermore, when high pressure treatment was carried out at — 20° C, the inner structure of the cells was severely damaged even at 200 MPa, and almost all of the nuclear membrane disappeared, although the fluorescent nucleus in the cytoplasm was visible by 4,6-diamidino-2-phenylindole (DAPI) staining. The structural damage of pressure-treated cells was accompanied by the leakage of internal substances. The efflux of UV-absorbing substances including amino acid pools, peptides, and metal ions increased with increase in pressure up to 600 MPa. In particular, amounts of individual metal ion release varied with the magnitude of hydrostatic pressures over 300 MPa, which suggests that the ions can be removed from the yeast cells separately by hydrostatic pressure treatment. Correspondence to: S. Shimada     

A protein fraction from aged garlic extract enhances cytotoxicity and proliferation of human lymphocytes mediated by interleukin-2 and concanavalin A

Fraction 4 (F4), a protein fraction isolated from aged garlic extract, enhanced cytotoxicity of human peripheral blood lymphocytes (PBL) against both naturalkiller (NK)-sensitive K562 and NK-resistant M14 cell lines. Although F4 treatment alone increased cytotoxicity, the effect was more remarkable when F4 was administered together with suboptimal doses of interleukin-2 (IL-2); combination treatment of 5 g/ml F4 plus 10 U/ml IL-2 for 72 h generated lymphokine-activated killer activity equivalent to that produced by 100 U/ml IL-2 alone against M14. F4 enhanced IL-2-induced proliferation and IL-2 receptor (Tac) expression of PBL without significant increase of IL-2 production. The enhancement of cytotoxicity both by F4 alone and by F4 plus IL-2 was abolished by anti-IL-2 antibody. F4 also enhanced concanavalin-A(ConA)-induced proliferation of PBL. Radiolabeled-ConA binding assays revealed that F4 treatment greatly augmented the affinity and slightly increased the number of ConA binding sites in PBL. F4 also enhanced ConA-induced IL-2 receptor (Tac) expression and IL-2 production of PBL. Anti-IL-2 antibody inhibited the effect of F4 on ConA-induced proliferation. These data suggest that IL-2 is involved in augmentative effects of F4. Our results indicate that F4 is a very efficient immunopotentiator and may be used for immunotherapy.     

Detection and production condition of acetylxylan esterase from a wood-rotting fungus,Coriolus versicolor

Acetyl esterase production was detected in a wood-rotting fungus,Coriolus versicolor, by the formation of a clear zone on a double layer agar plate containing glucose β-d-pentaacetate. Two polysaccharide acetates, carboxymethyl cellulose acetate and xylan acetate, also served as detectable substrates in place of glucose acetate to form clear zone. In an esterase assay, this fungal esterase showed a higher specificity to acetylxylan than did porcine liver esterase, indicating that it is an acetylxylan esterase.     

Mature ferredoxin-NADP reductase with a glutaminyl residue at N-terminus from spinach chloroplasts

When 35%-acetone extract of spinach chloroplasts was separated by SDS-PAGE, ferredoxin-NADP reductase (FNR) appeared as a single band at a molecular mass of 35 kDa. After the polypeptides on the SDS-PAGE plate were electroblotted onto PVDF membrane, the FNR band was cut out and analyzed for N-terminal structure in a gas-phase protein sequencer. Two different FNR peptides were identified: one with glutamine at its N-terminus (Gln-FNR) and the other with -pyroglutamic acid (tFNR) fraction was extracted from chloroplasts with their loosely bound FNR (lFNR) fraction removed in advance. The tFNR fraction contained Gln-FNR only. The Gln-FNR could be highly purified by affinity chromatography using a ferredoxin column. The purified Gln-FNR was digested with arginyl endopeptidase for peptide mapping and partial sequence analysis. Primary structure of Gln-FNR differed from that of lFNR loosely bound FNR - tFNR tightly bound FNR - -pyroglutamic acid at N-terminus     

Hamster pulmonary endocrine cells with positive immunostaining for calbindin-D28K

 We have examined the distribution of calcium-binding proteins (CaBPs) in adult and fetal lungs of Syrian golden hamsters (Mesocricetus auratus) using immunostaining with confocal laser microscopy and electron microscopy. Single and grouped (neuroepithelial body; NEB) endocrine cells were distributed from bronchi to alveolar ducts in the adult lung. Serial frozen sections immunostained for CaBPs in combination with immunostaining for endocrine markers such as calcitonin gene-related peptide, serotonin, PGP9.5, and synaptophysin revealed that positive immunostaining for calbindin-D_28K (CB-D28K) was seen in single endocrine cells and NEBs. However, other so-called EF-hand family CaBPs, parvalbumin and calretinin, were not detected. Electron microscopically, positive immunoreaction for CB-D28K was mainly in the organelle-free cytoplasmic matrix of endocrine cells, and partly in nuclei and associated with secretory granules and endoplasmic reticulum. In fetal developing lungs, endocrine cells appeared first on gestational day 13, and they were positive for all the endocrine markers used. However, pulmonary endocrine cells were positively immunostained for CB-D28K from gestational days 15 and 16 onward. In summary, our observations suggest that CB-D28K is a useful marker for endocrine cells of the lung, and CB-D28K could function as a mediator of endocrine stimulation or calcium homeostasis in pulmonary endocrine cells. Accepted: 17 June 1997     

Immunological characterization of a 36 kDa Fe deficiency specific peptide in barley roots

In a previous paper we reported that an acidic 36 kDa peptide is the most strongly induced peptide among several peptides induced by Fe deficiency in barley roots. In this paper, polyclonal antibodies were raised against the 36 kDa peptide. This peptide appeared in the roots of all the graminaceous species tested (barley, rye, wheat, oat, maize, sorghum and rice) in response to Fe deficiency. More of the peptide was found in the roots of graminaceous species which secrete higher amounts of mugineic acids (MAs) under Fe deficient nutrition status. Induction of the 36 kDa peptide was first observed on the third day of Fe deficiency, rising to a maximum value on the seventh day. The trend has a positive correlation with secretion of MAs during Fe deficiency. Further, resupply of Fe resulted in a decrease in peptide production on the second day, reaching a control level on the seventh day. The rate of decrease in peptide production was observed to be slower than that of MA secretion. Other nutrient stresses such as B excess, B deficiency, Cu excess, Cu deficiency, Mn excess, Mn deficiency, Zn excess and Zn deficiency induced far less of the peptide. The specific expression of the 36 kDa peptide in roots of graminaceous species under Fe deficiency suggested the positive association of the peptide with a specific Fe deficiency tolerance mechanism in graminaceous plants.     

Analysis of the NH2-Terminal 83rd Amino Acid of Escherichia coli GyrA in Quinolone-Resistance

Artificial mutations of Gyrase A protein (GyrA) in Escherichia coli by site-directed mutagenesis were generated to analyze quinolone-resistant mechanisms. By genetic analysis of gyrA genes in a gyrA temperature sensitive (Ts) background, exchange of Ser at the NH₂-terminal 83rd position of GyrA to Trp, Leu, Phe, Tyr, Ala, Val, and Ile caused bacterial resistance to the quinolones, while exchange to Gly, Asn, Lys, Arg and Asp did not confer resistance. These results indicate that it is the most important for the 83rd amino acid residue to be hydrophobic in expressing the phenotype of resistance to the quinolones. These findings also suggest that the hydroxyl group of Ser would not play a major role in the quinolone-gyrase interaction and Ser83 would not interact directly with other amino acid residues.     

Novel mutation at the initiation codon in the Norrie disease gene in two Japanese families

We have identified a new mutation of Norrie disease (ND) gene in two Japanese males from unrelated families; they showed typical ocular features of ND but no mental retardation or hearing impairment. A mutation was found in both patients at the initation codon of exon 2 of the ND gene (ATG to GTG), with otherwise normal nucleotide sequences. Their mothers had the normal and mutant types of the gene, which was expected for heterozygotes of the disease. The mutation of the initiation codon would cause the failure of ND gene expression or a defect in translation thereby truncating the amino terminus of ND protein. In view of the rarity and marked heterogeneity of mutations in the ND gene, the present apparently unrelated Japanese families who have lived in the same area for over two centuries presumably share the origin of the mutation.