Search PubMed⌕ Search

Biomedical subjects

S Aiba

Publications and source records attributed to S Aiba.

At least 163 records · Page 9Linked to original sources
PubMed1984

[An autopsy case of primary malignant melanoma of the esophagus--appraisal of radiation therapy].

A rare case of primary malignant melanoma of the esophagus is reported. Our case is of interest because an extraordinary effect was observed early during conventional radiation therapy. The primary lesion was irradiated with 60 Gy, it almost disappeared. Metastatic lesions were irradiated with 30 Gy, their volume decreased by more than 50%. At autopsy, these lesions were more or less unchanged. Histologically, cells from the main tumor were small and round. The growth of pleomorphic cells with large amounts of melanin granules was observed in the regions of irradiation. These findings suggest that the small round cells in malignant melanoma are radiosensitive and the pleomorphic cells with abundant melanin granules are radioresistant.

Aged↗
PubMed1983

Isolation and characterization of pock-forming plasmids for Streptomyces griseus from soil actinomycetes.

Thirty independent actinomycetes strains carrying plasmids were isolated from soil. These plasmids were purified as cccDNA by CsCl-EtBr equilibrium density-gradient centrifugation. Plasmids that induce "pocks", namely formation of circular zones of sporulation-inhibition, were selected by protoplast transformation of streptomycin-producing strain, Streptomyces griseus ATCC10137. Six pock-forming plasmids, pOA7, pOA11, pOA15, pOA23, pOA29 and pOA30, were obtained, and their cleavage maps, transformation frequencies, and copy numbers, as well as their stability, are described.

Actinomycetales↗
PubMed1983

Comparative studies on extracellular penicillinases of the same structural gene, penP, expressed in Bacillus licheniformis and Bacillus subtilis.

Extracellular penicillinases produced by Bacillus licheniformis ATCC 9945A and Bacillus subtilis from the same structural gene, penP, were compared. The two strains secreted the same exo-large penicillinase (mol. wt, 305000; isoelectric point, pI = 5.00-5.04; NH2-terminal amino acid, Ser). In contrast, the exo-small enzyme from Bacillus subtilis (mol. wt, 29500; pI = 5.00-5.04; NH2-terminal amino acid, Glu or Asn) was slightly different from that of Bacillus licheniformis (mol. wt, 29500; pI = 5.13; NH2-terminal amino acid, Lys). The difference in the NH2-terminal residue is most probably due to differences in degradation by host-specific proteolytic enzymes.

Amino Acid Sequence↗
PubMed1983

Monoclonal antibodies to various morphologic components of human skin.

Somatic cell hybrids were established from the mouse myeloma, P3x63Ag8.653 cells, and the spleen cells of a mouse hyperimmune to human epidermal cells. Indirect immunofluorescence test with hybridoma culture fluids displayed that 253 out of 263 hybridoma cultures secreted antibodies reactive with the frozen sections of human skin. The hybridomas secreting unique antibodies to skin components were cloned and designated as AHS-1 to -8. Monoclonal antibodies (MoAb) from AHS-1, AHS-2, and AHS-3 hybridomas did detect cytoplasmic antigens present in the epidermal layer, eccrine ducts and glands (except MoAb AHS-1), and hair follicles. Enzyme-linked immunosorbent assay showed that the antigen recognized by either MoAb AHS-1 or MoAb AHS-2, but not by MoAb AHS-3, shares the antigenic determinant with antigen(s) present in keratin polypeptides isolated from human callus. MoAb AHS-4 to -8 distinctly stained each morphologic component of the skin tissues: cell membranes of epidermal cells by MoAb AHS-4, cytoplasms in upper layer cells of epidermis by MoAb AHS-5, dermis by MoAb AHS-6, basement membrane zone by MoAb AHS-7, and eccrine ducts by MoAb AHS-8.

Adolescent↗
PubMed1983

Cloning and Expression of Thermostable alpha-Amylase Gene from Bacillus stearothermophilus in Bacillus stearothermophilus and Bacillus subtilis.

The structural gene for a thermostable alpha-amylase from Bacillus stearothermophilus was cloned in plasmids pTB90 and pTB53. It was expressed in both B. stearothermophilus and Bacillus subtilis. B. stearothermophilus carrying the recombinant plasmid produced about fivefold more alpha-amylase (20.9 U/mg of dry cells) than did the wild-type strain of B. stearothermophilus. Some properties of the alpha-amylases that were purified from the transformants of B. stearothermophilus and B. subtilis were examined. No significant differences were observed among the enzyme properties despite the difference in host cells. It was found that the alpha-amylase, with a molecular weight of 53,000, retained about 60% of its activity even after treatment at 80 degrees C for 60 min.

Journal Article↗
PubMed1983

Molecular cloning of a thermostable neutral protease gene from Bacillus stearothermophilus in a vector plasmid and its expression in Bacillus stearothermophilus and Bacillus subtilis.

The structural gene for a thermostable protease from Bacillus stearothermophilus was cloned in plasmid pTB90. It is expressed in both B. stearothermophilus and Bacillus subtilis. B. stearothermophilus carrying the recombinant plasmid produced about 15-fold more protease (310 U/mg of cell dry weight) than did the wild-type strain of B. stearothermophilus. Some properties of the proteases that have been purified from the transformants of B. stearothermophilus and B. subtilis were examined. No significant difference was observed among the enzyme properties studied here despite the difference in host cells. We found that the protease, neutral in pH characteristics and with a molecular weight of 36,000, retained about 80% of its activity even after treatment of 65 degrees C for 30 min.

Bacillus subtilis↗
PubMed1982

The effect of oxidation of copoly (L-alanine, L-methionine) membranes on oxygen permeability and tensile properties.

This study pertains to the development of poly (alpha-amino acid) membranes which have potential as biomaterials. Copoly (L-alanine, L-methionine) membranes have been subjected to oxidation which produced a hydrophilic structure allowing the improvement of oxygen permeability. L-Methionine residues in the copolymers were converted to methionine sulfoxide and/or sulfone groups by action of hydrogen peroxide in various reaction compositions. Water absorption, permeability to oxygen dissolved in water, and tensile strength of the modified membranes were changed with the extent of oxidation. The water absorption was found to increase with oxidation time from 10 to 300%. The oxidation time dependency on the oxygen permeability coincided with the increase in the water absorption. The permeability coefficients of oxidized membranes were of the order of 10(-9) cm3 (STP) cm/cm2 s cm Hg, while those of unoxidized membranes were approximately 10(-11). As expected, the tensile strengths of oxidized membranes were smaller than those of unoxidized ones. In addition, the effect of L-alanine and L-methionine residue composition on the membrane properties is discussed.

Absorption↗
PubMed1982

Phenotypic variations in re-lysogenization of Bacillus licheniformis with temperate phage.

A bacitracin-producing strain Bacillus licheniformis ATCC 10716 harbors two types of inducible phages (LP52 and DLP 10716). 156 strains re-lysogenized with phage LP52 were independently isolated from a cured strain UM12 of B. licheniformis. Those strains were divided into 12 groups based on colony morphology and pigment production. Some of the re-lysogenized strains grew faster than UM12 and others produced more bacitracin than the cured strain. For example, the production of bacitracin by one of the re-lysogenized strains, L89, was enhanced by about 70% in comparison with UM12. The phenotypic variations observed with re-lysogenized strains might be due to the re-insertion of the phage genome at different sites of the chromosome in addition to the pleiotropic effect assumed.

Bacillus↗
PubMed1982

New approach to tryptophan production by Escherichia coli: genetic manipulation of composite plasmids in vitro.

For the purpose of studying the production of L-tryptophan by Escherichia coli, the deletion mutants of the trp operon (trpAE1) were transformed with mutant plasmids carrying the trp operon whose anthranilate synthase and phosphoribosyl anthranilate transferase (anthranilate aggregate), respectively, had been desensitized to tryptophan inhibition. In addition to release of the anthranilate aggregate from the feedback inhibition required for plasmids such as pSC101 trp.I15, the properties of trp repression (trpR) and tryptophanase deficiency (tnaA) were both indispensable for host strains such as strain Tna (trpAE1 trpR tnaA). The gene dosage effects on tryptophan synthase activities and on production of tryptophan were assessed. A moderate plasmid copy number, approximately five per chromosome, was optimal for tryptophan production. Similarly, an appropriate release of the anthranilate aggregate from feedback inhibition was also a necessary step to ward off the metabolic anomaly. If the mutant plasmid pSC101 trp-I15 was further mutagenized (pSC101 trp.I15.14) and then transferred to Tna cells, an effective enhancement of tryptophan production was achieved. Although further improvement of the host-plasmid system is needed before commercial production of tryptophan can be realized by this means, a promising step toward this goal has been established.

Cloning, Molecular↗
PubMed1982

Transformation of Bacillus stearothermophilus with plasmid DNA and characterization of shuttle vector plasmids between Bacillus stearothermophilus and Bacillus subtilis.

A thermophilic bacterium Bacillus stearothermophilus IFO 12550 (ATCC 12980) was transformed with each of the following plasmids, pUB110 (kanamycin resistance, Kmr), pTB19 (Kmr and tetracycline resistance [Tcr]), and its derivative pTB90 (Kmr Tcr), by the protoplast procedure in the presence of polyethylene glycol at 48 degrees C. The transformation frequencies per regenerant for pUB110, pTB19, and pTB90 were 5.9 x 10(-3), 5.5 x 10(-3), and 2.0 x 10(-1), respectively. Among these plasmids, pTB90 was newly derived, and the restriction endonuclease cleavage map was constructed. When tetracycline (5 micrograms/ml) was added into the culture medium, the copy number of pTB90 in B. stearothermophilus was about fourfold higher than that when kanamycin (5 micrograms/ml) was added instead of tetracycline. Bacillus subtilis could also be transformed with the plasmids extracted from B. stearothermophilus and vice versa. Accordingly, pUB110, pTB19, and pTB90 served as shuttle vectors between B. stearothermophilus and B. subtilis. The requirements for replication of pTB19 in B. subtilis and B. stearothermophilus appear to be different, because some deletion plasmids (pTB51, pTB52, and pTB53) derived from pTB19 could replicate only in B. subtilis, whereas another deletion plasmid pTB92 could replicate solely in B. stearothermophilus. Plasmids pTB19 and pTB90 could be maintained and expressed in B. stearothermophilus up to 65 degrees C, whereas the expression of pUB110 in the same strain was up to 55 degrees C.

Bacillus subtilis↗
PubMed1982

Cytoplasmic transfer of oligomycin resistance during protoplast fusion of Saccharomycopsis lipolytica.

Mitotic segregation of oligomycin resistance and oligomycin sensitivity was observed among the prototrophic progeny of protoplast fusion between drug-resistant and drug-sensitive complementary auxotrophs of Saccharomycopsis lipolytica. The transfer of oligomycin resistance by protoplast fusion without karyogamy suggests a cytoplasmic inheritance of this drug resistance determinant.

Ascomycota↗
PubMed1981

TnA-directed deletion of the trp operon from RSF2124-trp in Escherichia coli.

Plasmid pMT-trp was constructed by digestion of RSF2124-trp with restriction endonuclease PstI and ligation with T4 ligase. In pMT-trp about 78% of the DNA of transposon TnA from RSF2124-trp was deleted, and hence the gene for ampicillin resistance was lost. All Trp- segregants from pMT-trp carriers in Escherichia coli W3110 and its derivatives were found to have lost the entire plasmid. On the other hand, deletion plasmids which had lost the trp operon were found among Trp- segregants from RSF2124-trp carriers, particularly from the mutant strain trpAE1 trpR tnaA. The experimental fact that deletion occurred exclusively in RSF2124-trp suggests that the presence of TnA in the plasmid (RSF2124-trp) was responsible for the deletion.

Ampicillin↗
PubMed1981

Isolation and characterization of antibiotic resistance plasmids from thermophilic bacilli and construction of deletion plasmids.

Ten plasmids were isolated as covalently closed circular deoxyribonucleic acid from antibiotic-resistant thermophilic bacteria. Of the 10 plasmids tested, 2 could transform Bacillus subtilis, yielding resistance to specific antibiotics. Plasmid pTB20 (2.8 X 10(6) daltons, approximately 24 copies per chromosome) specifies resistance to tetracycline (Tcr), whereas pTB19 (17.2 X 10(6) daltons, approximately 1 copy per chromosome) renders the host resistant to both kanamycin and tetracycline (KMrTcr). Three plasmids were not self-transmissible. The restriction endonuclease cleavage maps of the two plasmids, pTB19 and pTB20, were constructed. pTB19 and pTB20, both of which were originally isolated from thermophilic bacilli, were tested for stability in B. subtilis. Digestion of pTB19 followed by ligation yielded deletion plasmids pTB512 (Kmr), pTB52 (Tcr), and pTB53 (KmrTcr). Determinants of Kmr, Tcr, and DNA replication were associated with EcoRI fragments R1b (4.2 X 10(6) daltons), R3 (2.8 X 10(6) daltons), and R1a (4.2 X 10(6) daltons), respectively. Restriction endonuclease cleavage maps of pTB51, pTB52, and pTB53 were constructed. Tetracycline resistance of pTB20 was confirmed to be in the EcoRI fragment (1.85 X 10(6) daltons).

Bacillus subtilis↗
PubMed1981

Cloning of the genes for penicillinase, penP and penI, of Bacillus licheniformis in some vector plasmids and their expression in Escherichia coli, Bacillus subtilis, and Bacillus licheniformis.

By using plasmid pMB9, penicillinase genes (penP and penI) from both the wild-type and constitutive strains of Bacillus licheniformis 9945A were cloned in EScherichia coli. When a low-copy-number plasmid was used, both wild-type and constitutive penicillinase genes could be transferred into Bacillus subtilis. However, when a high-copy-number plasmid was used, only the genes of the wild type could be transferred. These recombinant plasmids in B. subtilis could all be transferred by the protoplast transformation procedure into B. licheniformis. Transformants of E. coli were resistant to ampicillin (20 micrograms/ml) in spite of the low penicillinase activities (7 U/mg of cells). However, transformants of B. subtilis and B. licheniformis were sensitive to ampicillin (20 micrograms/ml) even in high penicillinase activities (more than 10,000 U/mg of cells). The secretion of penicillinase was rarely observed in E. coli. In contrast, penicillinases secreted from transformants of B. subtilis and B. licheniformis were around 30 and 60% of the total activities, respectively. We took advantage of the plasmids to permit the construction of hetero- and mero-polyploid structures in host cells, and we discuss a regulatory mechanism of penicillinase synthesis in B. licheniformis.

Bacillus↗
PubMed1980

Phenotypic stability of trp operon recombinant plasmids in Escherichia coli.

The recombinant plasmids RSF2124-trp and pSC101-trp were examined for their phenotypic stability in Escherichia coli W3110 and its derivatives under various culture conditions. RSF2124-trp and pSC101-trp were stable in a trpAE1 strain. In an amber mutant of the tryptophan repressor gene, RSF2124-trp was fairly stable, whereas pSC101-trp was unstable. All Trp- segregants from the pSC101-trp carrier had lost the entire plasmid. In a mutant carrying the tnaA mutation, RSF2124-trp was unstable in rich media. Most Trp- segregants that appeared under these conditions were deleted in trp genes as well as in the cI gene on the recombinant plasmid. pSC101-trp in this tnaA mutant was also unstable. All Trp- segregants had lost the plasmid. Studies of enzyme activities revealed that the greater the activity of anthranilate synthase and tryptophan synthase in bacteria, the more segregants tended to appear in the stability test. RSF2124 and pSC101 without the trp gene were completely stable in the same bacteria. The apparent instability of bacteria carrying the recombinant plasmid could be explained by the lower growth rate compared with bacteria carrying only the vector plasmid, resulting in the enrichment of Trp- bacteria during culture.

Anthranilate Synthase↗
PubMed1980

Role and control of isocitrate lyase in Candida lipolytica.

Mutants of Candida lipolytica that were unable to grow on acetate but able to utilize succinate or glycerol as a sole carbon source were isolated. Amongst the mutants isolated, one strain (Icl-) was specifically deficient in isocitrate lyase activity, whereas another strain (Acos-) was deficient in acetyl coenzyme A synthetase activity. Since the Icl- mutant could not grow either on n-alkane or its derivatives, such as fatty acid and long-chain dicarboxylic acid, any anaplerotic route other than the glyoxylate pathway was inconceivable as far as growth on these carbon sources was concerned. Acetyl coenzyme A is most likely a metabolic inducer of isocitrate lyase and malate synthase, because the Acos- mutant was characterized by the least susceptibility to induction of these enzymes by acetate. The structural gene for isocitrate lyase was most probably impaired in the Icl- mutant, since revertants (Icl-) produced thermolabile isocitrate lyase. The production of isocitrate from n-alkane by the revertants was enhanced in comparison with the parental strain.

Acetyl Coenzyme A↗