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A Hakura

Publications and source records attributed to A Hakura.

124 records · Page 7Linked to original sources
PubMed1982

New human papilloma virus isolated from epidermodysplasia verruciformis lesions.

Human papilloma virus (HPV) was isolated from red plaques of a patient (N. F.) with epidermodysplasia verruciformis. Electron microscopic examination showed characteristic particles of papilloma virus as icosahedrons about 45 nm in diameter. DNA was extracted from these particles, and closed-circular DNA (Form I) was purified by centrifugation in CsCl containing ethidium bromide. The molecular weight of the DNA was about 5.0 x 10(6). A physical map of the HPV DNA was constructed using several restriction enzymes. The restriction endonuclease cleavage pattern of the HPV DNA was different from those of other types of HPV reported thus far, suggesting that the isolate was a new, as yet unclassified, HPV.

Adult↗
PubMed1979

Cell cycle dependence of transformation expression in mouse cells transformed by a thermosensitive mutant (Ts-121) of polyoma virus.

Change in division capability as a phenotypic expression of cellular transformation was investigated by using one of the temperature-sensitive (ts) mutants of the polyoma virus-transformed cell line, the 121-6-5 cells of BALB/3T3. When contact -inhibited cells were treated with hyaluronidase at 39 degrees C, a single round of cell division was induced after which cell growth was inhibited by cell density. However, if the cells were incubated at 35 degrees C, after the enzyme treatment, density-inhibition block disappeared and the cells entered a second division. This indicates that the release of cells from density-inhibition depends on the low temperature incubation. The ability of cells to complete a second division was examined by shifting the cells from 39 degrees C to 35 degrees C during different phases of the first division cycle after the enzyme-treatment. A 6-hour incubation of S phase cells at 35 degrees C resulted in a second cycle of division, while the 24-hour incubation of G1 cells at 35 degrees C did not induce a second round of division. These results suggest that expression of the transformed phenotype in 121-6-5 cells is clearly dependent upon both the temperature and the phase of the division cycle.

Animals↗
PubMed1979

Selective replication of transformation-defective avian sarcoma virus mutants in duck embryo fibroblasts.

When an avian sarcoma virus (ASV), subgroup C Bratislava 77 (B77-C) was inoculated into duck embryo fibroblast cultures (DEF) at a m.o.i. of 0.02, its replication was retarded by about 3 days compared with that in chick embryo fibroblast cultures (CEF). A transformation-defective (td) mutant was isolated during this period of retardation. Unlike the sarcoma virus, this td mutant replicated in both DEF and CEF with no retardation, even at a low m.o.i. The subgroup C Prague strain of Rous sarcoma virus (PR-C), which can infect DEF, also replicated in DEF slower than its td mutant, tdPR-C, at a m.o.i. of 0.02.

Animals↗
PubMed1976

Different cation requirements for aggregation of BHK cells and their transformed derivatives.

BHK21 cells singly dissociated by trypsin aggregate in medium with calcium ions, but not in medium with magnesium ions. Their malignant derivatives (pyBHK) induced by polyoma virus, after dissociation with trypsin, aggregate equally well in medium with either calcium or magnesium ions. When EDTA is used for dissociation of cells from culture on a substrate, neither BHK21 nor pyBHK cells require addition to the medium of divalent cations for rapid aggregation. Trypsin-dissociated BHK21 cells become aggregative in medium without divalent cations, when they are incubated for 60 min in dispersion with medium containing calcium ions before aggregation. In the case of pyBHK cells, incubation in dispersion in the medium with calcium or magnesium ions is effective in this respect. Calcium and magnesium ions are equally effective for adhesion of both BHK21 and pyBHK cells to non-cellular substrate or to a cell monolayer. We discuss the different cation requirements for aggregation of BHK21 and their transformed derivatives in relation to the recovery process of cell surfaces after exposure to trypsin.

Calcium↗
PubMed1975

Temperature-dependent properties of cells transformed by a thermosensitive mutant (TS-121) of polyoma virus. II. Characterization of 121-6 cells.

The properties of 121-6 cells were characterized. This cell line is transformed by ts-121, a temperature-sensitive mutant of polyoma virus. Both the morphology and saturation density of the 121-6 cells were affected by temperature; i.e. at 39 degrees C, the cells grew to monolayer sheets and remained contact inhibitied for a long time (at least 25 days), while at 35 degrees C, they grew beyond the monolayer density, like cells transformed by wild-type polyoma virus. These phenotypic changes were reversible, but increased agglutinability by Concanavalin A, which was another phenotype of these transformed cells, was not temperature-sensitive, and even at high temperature, 121-6 cells, like transformed cells, showed high agglutinability.

Animals↗
PubMedDate not supplied

Establishment of an epidermal growth factor-dependent, multipotent neural precursor cell line.

We have established a multipotent clonal cell line, named MEB5, from embryonic mouse forebrains after the infection of a retrovirus carrying E7 oncogene of human papillomavirus type 16. MEB5 cells proliferated in serum-free, epidermal growth factor (EGF)-supplemented medium. They expressed markers for neural precursor cells (nestin, A2B5, and RC1) and did not express markers for neurons (class III beta-tubulin), astrocytes (glial fibrillary acidic protein), and oligodendrocytes (galactocerebroside). MEB5 cells were stably maintained in an undifferentiated state with a diploid karyotype in the presence of EGF. When they were deprived of EGF, about 50% of the cells died due to apoptosis within 24 h. The remaining cells differentiated into neurons, astrocytes, or oligodendrocytes within 2 wk. The newly developed cells with neuronal morphology were immunoreactive for gamma-aminobutyric acid and exhibited neuronal electrophysiological properties. When MEB5 cells were treated with leukemia inhibitory factor for 7 d, they were induced to differentiate exclusively into astrocytes. These results indicate that MEB5 is a cell line with characteristics of EGF-dependent, multipotent neural precursor cells. This cell line should provide a good model system to study the mechanisms of survival, proliferation, and differentiation of the multipotent precursor cells in the central nervous system.

Animals↗
PubMedDate not supplied

An improvement of the Ames test using a modified human liver S9 preparation.

INTRODUCTION: In preliminary studies on the Ames test using human liver S9 fractions, we found that the crude human S9 fractions, obtained following centrifugation of the tissue homogenate for 20 min at 9000 x g, were not always sterile. When this was the case, the S9 fractions were often accompanied by an increased number of colonies above the normal range on plates in the solvent control used in the Ames test. In addition, we also sometimes identified the incorporation of a small amount of fat in the crude human liver S9 fractions. We have therefore obtained a purified fat-free S9 fraction by a simple modification to the crude S9 preparation; fat was completely removed by centrifugation of the crude S9 fraction. METHODS: Using the purified and crude human S9 fractions (two lots each), both the sterility and the number of bacterial colonies produced on a plate with five bacterial tester strains by solvent controls (purified water and dimethyl sulfoxide) were examined. The findings were then compared to those observed with phosphate buffer or S9 fraction from rats pretreated with phenobarbital/5,6-benzoflavone. RESULTS: The data show that each of the crude human S9 fractions was not sterile and produced an increasing number of colonies with each solvent control, almost equal to the sum of the numbers of contaminating bacterial colonies and spontaneous revertant colonies observed with phosphate buffer or the rat S9 fraction. On the other hand, both the purified human S9 fractions were sterile, and the number of colonies that appeared in each solvent control was similar to that of spontaneous revertant colonies observed with phosphate buffer or the rat S9 fraction. DISCUSSION: These results indicate that this new procedure of S9 preparation, modified with an additional recentrifugation step, may provide a high quality of purified fat- and bacteria-free S9 fraction for use in the Ames test.

Biotransformation↗
PubMedDate not supplied

Mutagenicity and cytotoxicity of naphthoquinones for Ames Salmonella tester strains.

The molecular mechanisms involved in quinone cytotoxicity, especially mutagenicity, are still largely unknown. In order to better understand the molecular aspects of the mechanisms of quinone mutagenicity and cytotoxicity, we examined them by using a series of 13 simple structural naphthoquinone (NQ) derivatives for 9 Ames Salmonella mutagenicity tester strains in the presence of absence of liver homogenate S9 mix from rats induced with phenobarbital and 5,6-benzoflavone. Most NQs used in this study showed mutagenicity with and/or without S9 mix. The most potent mutagenic NQ was 2,3-dichloro-1,4-NQ, with mutagenicity of 18 induced revertants/nmol/plate for strain TA104 without S9 mix. Among the strains used, TA104, which is sensitive to oxidative mutagens, was the most sensitive to the NQs, and the second most sensitive strain was TA2637, which detects bulky DNA adducts. The relationship of mutagenic potency to the one-electron reduction potential with TA104 suggested that the higher redox potential NQs were more mutagenic than the lower redox potential NQs. Significant reduction of the mutagenicity of 1,4-naphthoquinone without S9 mix was observed in the presence of catalase. Enhancement of the mutagenic potential of the NQs by the pKM101 plasmid implicated in error-prone repair was also observed. The most cytotoxic NQ was 2,3-dichloro-5,8-dihydroxy-1,4-NQ, and the least cytotoxic NQ was beta-NQ-4-sulfonic acid potassium salt, a 700-fold range in potency. The cytotoxic effect of the NQs was largely dependent on the structures of their substituents.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗