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H Takebe

Publications and source records attributed to H Takebe.

At least 91 records · Page 5Linked to original sources
PubMed1990

Evidence for spontaneous conversion of Mex- to Mex+ in human lymphoblastoid cells.

A series of human lymphoblastoid cell lines (LCLs) called Mex- were defined by Sklar and Strauss on the basis of their inability to remove O6-methylguanine from DNA. Instability of Mex- has previously been shown as a population phenotype of LCLs. We examined whether Mex- as a cellular phenotype is spontaneously convertible or not. At the population doubling number (PDN) 23 after recloning, two out of 15 independent subcultures derived from a Mex- LCL, AT1-1, were found to contain a small fraction of Mex+ cells after treatment with 1-(4-amino-2-methyl-5-pyrimidinyl)methyl-3-(2-chloroethyl)-3-nitrosourea (ACNU). Three Mex+ subclones were identified without exposure to ACNU among 486 subclones from replica plating of an expanded Mex- clone (PDN30). The rate of spontaneous conversion was estimated to be in the range of 10(-8)-10(-7) per cell per generation by the fluctuation analyses on two Mex- subclones. These results strongly support the hypothesis that Mex- as a cellular phenotype is spontaneously convertible to Mex+.

Cell Line↗
PubMed1990

[Light and skin].

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DNA Damage↗
PubMed1989

Tumorigenic conversion of xeroderma pigmentosum lymphoblastoid cells without karyotypic alteration.

In order to examine the process of malignant transformation of human somatic cells, we studied the tumorigenic conversion of an Epstein-Barr-virus-immortalized lymphoblastoid cell line (LCL) derived from a patient with xeroderma pigmentosum (XP) complementation group A. Repeated irradiation of the XP cells, XP7NI, with UV-light and subsequent treatment with 12-O-tetradecanoylphorbol-13-acetate (TPA) resulted in the acquisition of tumorigenicity in athymic nude mice. The tumorigenicity of XP7NI cells was also induced by TPA treatment alone. The tumors formed in athymic mice were of B-cell lymphoma with characteristic histology, cell surface immunoglobulins and an antigen as detected by a B-cell-specific monoclonal antibody (MAb), CD20. The surface immunoglobulins and the HLA type of these tumor cells were identical with those of the parental cells. These malignantly transformed cells retained the same UV sensitivity, serum requirement, colony-forming ability in soft agar, and normal human karyotype as the parental cells. Unlike other tumorigenic lymphoblastoid cell lines, this XP lymphoblastoid cell line provides a unique case in that process(es) leading to tumorigenicity may be induced by UV and TPA without apparent karyotypic changes.

Animals↗
PubMed1989

Frequency of variant erythrocytes at the glycophorin-A locus in two Bloom's syndrome patients.

Blood type MN is determined by a glycoprotein termed glycophorin A (GPA) which exists on the surface of erythrocytes, and the difference between the M and N types is derived from the presence of 2 different amino acids in the amino-terminal portion (Furthmayer, 1978). Using a pair of fluorescence-labeled monoclonal antibodies specific to each GPA, somatic mutations in erythrocytes of MN heterozygotes at the GPA-M and -N alleles can be quantitatively determined using a flow sorter (Langlois et al., 1986). Our results for 2 Bloom's syndrome (BS) patients showed that variants either lost expression of one allele (simple gene inactivation or loss) or expressed only one allele at twice the normal level (most probably somatic recombination) occurring at a frequency of about 1-3 per 10(3) erythrocytes. The flow cytometric patterns of erythrocytes from the BS patients showed a typical smear of variants bearing intermediate levels of expression of one GPA allele, indicating that the real variant frequency is even greater than that measured. On the other hand, the parents heterozygous for the BS gene showed variant frequencies (1-8 x 10(-5)) within the normal range. These data strongly support the hypothesis that the cancer proneness of BS patients is due to their increased frequency of spontaneous mutations and somatic recombination.

Alleles↗
PubMed1989

X-ray-induced G2 arrest in ataxia telangiectasia lymphoblastoid cells.

Sensitivity to X-ray-induced G2 arrest was compared between ataxia telangiectasia (AT) lymphoblastoid cells and normal human cells. Flow cytometrical analysis of cells following X-ray irradiation revealed that the fraction of cells with 4n DNA content was greater in AT cells than in normal cells as previously reported by other investigators. However, the other parameters for cell-cycle progression kinetics including mitotic indices, cumulative mitotic indices and cumulative labelled mitotic indices indicated that X-ray-induced G2 arrest as a function of dose in AT cells was indistinguishable from that in normal cells. Moreover, no significant difference in cell viability was noted between AT and normal cells until 48 h following X-irradiation up to 2.6 Gy, although X-irradiated AT cells, compared to normal cells, showed a significantly decreased survival in terms of cell multiplication in growth medium and colony formation in soft agar. These data collectively suggest that the greater accumulation of AT cells with 4n DNA content in flow cytometry cannot be attributed to more stringent irreversible blockage of cell-cycle progression at the G2 phase and eventual cell death there. The possible reasons for this greater accumulation are discussed.

Ataxia Telangiectasia↗
PubMed1989

5-Azacytidine-induced recovery of O6-alkylguanine--DNA alkyltransferase activity in mouse Ha821 cells.

Mouse Ha821 cells, Harvey murine sarcoma virus-transformed NIH3T3 cells, have extremely low O6-alkylguanine--DNA alkyltransferase (O6AGTase) activity and are hypersensitive to an anti-tumor chloroethylating agent 1-(4-amino-2-methyl-5-pyrimidinyl) methyl-3-(2-chloroethyl)-3-nitrosourea hydrochloride (ACNU). The treatment of Ha821 cells with a DNA demethylating agent, 5-azacytidine, resulted in an increase in the frequency of ACNU-resistant cell clones. All randomly isolated ACNU-resistant cell clones were found to have O6AGTase activity comparable to the level of the parental NIH3T3 cells. These results suggest that reversible loss of O6AGTase activity in Ha821 cells is caused at least in part by inactivation of the O6AGTase gene due to methylation of cytosine in the gene.

Animals↗
PubMed1989

Predominance of Mex+ cells in newly-established human lymphoblastoid cell lines.

Previous studies have demonstrated that approximately one-third of human lymphoblastoid cell lines (LCLs) are deficient in removing O6-methylguanine residues because of the lack of O6-alkylguanine-DNA alkyltransferase (O6-AGT) activity. Such LCLs have been designated Mex-, while the proficient LCLs are Mex+. Our determinations of O6-AGT activity as a function of cellular protein concentration on 37 previously-established LCLs disclosed that the expression of the enzyme was high in 14 (Mex+) and barely detectable in 16 (Mex-). The other seven LCLs showed intermediate activity of the enzyme. By contrast, all of the 28 LCLs that we newly established contained high enzyme activity, implying that they consisted of mainly Mex+ cells. Since the conventional O6-AGT assay on Mex+ cell populations was not capable of detecting the co-existence of Mex- cells as a minor component, we attempted to determine the proportion of Mex- phenotype in newly-immortalized lymphoblastoid cell clones which had been established directly on semisolid agar. All of the 15 independent clones derived from a single blood sample also showed high O6-AGT activity, rendering it unlikely that Epstein-Barr virus transformation per se was responsible for the generation of Mex- LCLs. These results collectively indicate that Mex+ cells predominate in LCLs shortly after establishment and also suggest that the possible growth advantage for Mex- cells should play an important role in the subsequent development of Mex- LCLs during the long-term culture in vitro.

Cell Line↗
PubMed1989

Reduced superoxide dismutase activity in xeroderma pigmentosum fibroblasts.

This study was performed in order to assess the possible protective effect of superoxide dismutase (SOD) on ultraviolet (UV) damage in xeroderma pigmentosum (XP) fibroblasts. SOD activity in fibroblasts originating from seven xeroderma pigmentosum (XP) patients was significantly lower than that in normal cells (p less than 0.005). Average SOD activity in XP cells belonging to complementation group A was 3.68 +/- 0.54 (n = 7) and that in normal human cells was 5.79 +/- 1.59 (n = 6). Addition of SOD before and during UV irradiation (UVB and UVC) to the cells caused no change in the amount of unscheduled DNA synthesis and UV survival. A possible involvement of reduced SOD in XP and a possible protective effect by SOD on UV damage is discussed.

Adolescent↗
PubMed1989

Melanoma and other skin cancers in xeroderma pigmentosum patients and mutation in their cells.

Malignant melanomas were found in 15.8% of xeroderma pigmentosum (XP) patients with skin cancer in Japan. When multiple cancers were scored separately depending on the histopathologic types, 12.1% of the skin cancers in XP patients was malignant malignant melanoma. The relative incidence of malignant melanoma in skin cancer in XP patients is similar to that in skin cancer in general (12.6%), reported previously. Most of the malignant melanoma in XP patients developed in skin exposed to sunlight, in contrast to the high incidence of malignant melanoma in general in the unexposed skin of Japanese people. A DNA repair defect of UV damage is strongly suggested to be responsible for the high incidence of skin cancer in XP patients. The onset of malignant melanoma in XP patients was about ten years old, and was as early as those of basal cell carcinoma and squamous cell carcinoma in the patients with very low DNA repair capacities. Among nine genetic complementation groups and a variant type, group A XP cells were found to be extremely hypermutable by ultraviolet light, while group C XP cells were also hypermutable, but at the same level as normal cells when adjusted for survival. Mutagenesis as a possible mechanism of carcinogenesis in XP is supported by these results, but evidence in other cancer-prone hereditary diseases is yet to be obtained.

Adolescent↗
PubMed1989

Similarity in the effect of caffeine on DNA synthesis after UV irradiation between xeroderma pigmentosum variant cells and mouse cells.

The effect of UV irradiation on the rate of DNA synthesis was compared among normal human, xeroderma pigmentosum (XP, group A and variant) and mouse cells with and without caffeine in the culture medium after UV irradiation. At the same levels of survival, approximately 37%, all cells showed reduction in the rate of synthesis 0-3 h after UV irradiation followed by a recovery to normal or near-normal level 12 h later. In the presence of caffeine, no change in the recovery patterns was observed in normal human and XP A cells. XP variant cells and mouse cells showed little or no recovery in the presence of caffeine even after 12 h, when full recovery was obtained without caffeine. XP variant and mouse cells appear to have a common response in that post-irradiation treatment with caffeine inhibits reinitiation of UV-reduced DNA replication. Enhancement by caffeine of UV-killing in XP variant and mouse cells may be due to the retarded resumption of DNA replication.

Animals↗
PubMed1989

Bloom's syndrome. XIV. The disorder in Japan.

Fourteen persons have been diagnosed Bloom's syndrome in Japan, with cytological verification in 11. Widely separated birthplaces throughout Honshu, Shikoku, and Kyushu and a parental consanguinity incidence greater than in the general population suggest that the Bloom's syndrome mutation, although very rare, is distributed widely throughout the Japanese population. The locus mutated is the same as in Jews and persons of Western European extraction. The phenotype differs somewhat from most cases recognized elsewhere, in that dolichocephaly is a less constant feature, the facial skin lesion is less prominent, and life-threatening infections are less common. The characteristic predisposition to neoplasia exists, however, as probably does that to diabetes mellitus.

Adolescent↗
PubMed1988

Instability of Mex- phenotype in human lymphoblastoid cell lines.

Three lymphoblastoid cell lines (LCLs) had extremely low activities of O6-alkylguanine-DNA alkyltransferase (O6-AGT), and were classified as Mex-. They were highly sensitive to cell killing by 1-(4-amino-2-methyl-5-pyrimidinyl)-methyl-3-(2-chloroethyl)-3-nitrosoure a hydrochloride (ACNU), whereas NMO2, a Mex+ LCL with a high O6-AGT activity, was resistant to the agent. Small fractions of these Mex- LCLs survived the treatment with 10 micrograms/ml of ACNU for 24 h, and the surviving cells were found to be resistant to subsequent treatments with the agent. In addition, they contained O6-AGT activities comparable to that of NMO2 and were therefore regarded as Mex+. These results suggest that the Mex- phenotype in LCLs is unstable.

Cell Division↗
PubMed1987

Radiation sensitivity of T-lymphocytes grown with recombinant human interleukin-2.

gamma-Ray and UV sensitivities of phytohemagglutinin (PHA)-stimulated T-lymphocytes were examined in the presence of the recombinant human interleukin-2 (IL-2). D0 values for the survival curves after gamma-irradiation varied from 0.90 to 1.25 Gy, and were comparable to those reported for human fibroblast cells. By fractionated exposure of gamma-rays, T-lymphocytes were shown to have the repair capacity for the sublethal damage. UV-survival curves yielded D0 of 6.5 J/m2 for T-lymphocytes from normal donors. T-Lymphocytes from a xeroderma pigmentosum patient with extremely low excision repair were markedly hypersensitive to UV (D0, 1.4 J/m2). T-Lymphocytes may be used to detect individuals who are sensitive to radiation or chemicals, and this method takes less time than that using fibroblast cells.

Adult↗
PubMed1987

Differential hypersensitivity of xeroderma pigmentosum lymphoblastoid cell lines to ultraviolet light mutagenesis.

Survival and mutation after u.v. light irradiation were examined in four human lymphoblastoid cell lines; one cell line with normal excision-repair capacity (HH4), two excision-repair-deficient xeroderma pigmentosum (XP) cell lines from patient XP3BE (complementation group C) and XP7NI (group A), and one cell line from an XP heterozygote (XPF7NI, father of XP7NI). Relative to HH4 and XPF7NI, both XP3BE and XP7NI were more sensitive to the cytotoxic effect of u.v. by virtue of a diminished shoulder and a steeper slope in the survival curve determined by growth curve extrapolations. The mutagenesis for 6-thioguanine resistance (TGr) was measured by the limiting dilution technique using 96 well microtiter plates. Even at non-cytotoxic fluences, u.v. light induced TGr mutations in HH4 and XPF7NI with no apparent threshold, and the mutagenic response of XPF7NI was no different than that of HH4. Both XP cell lines were more sensitive than normal cells to u.v.-induced mutation. However, XP7NI cells were extremely hypermutable by u.v.; i.e. 3.3 J/m2 induced an approximately 500-fold increase of mutant fraction with the background of 2 X 10(-6). XP7NI cells remained much more mutable by u.v. even when plotted against survival, whereas the mutant fractions for XP3BE and HH4 followed the same line. These results imply that the mechanism of u.v.-induced mutation in XP7NI cells may intrinsically be different from that in XP3BE, XP heterozygote or normal cells, or that potentially mutagenic lesions are repaired much less efficiently in XP7NI cells than are potentially lethal lesions, as compared with XP3BE, XPF7NI and HH4 cells.

Cell Line↗
PubMed1987

Sodium butyrate stimulates cellular recovery from UV damage in xeroderma pigmentosum cells belonging to complementation group F.

Possible stimulation of the DNA repair capacity by sodium butyrate in normal and xeroderma pigmentosum (XP) cells was investigated. XP cells belonging to the complementation group F showed considerable stimulation of DNA repair by sodium butyrate in terms of both the amount of unscheduled DNA synthesis (UDS) and the colony-forming ability after UV irradiation. UDS in XP cells belonging to the complementation group A was not enhanced, while normal cells showed slight enhancement, but less than that of XP F cells. In XP A, XP C, and normal cells, sodium butyrate treatment enhanced the killing effect of UV irradiation. The residual repair capacity in XP F cells appeared to be stimulated by sodium butyrate.

Butyrates↗
PubMed1986

Neurological manifestations in xeroderma pigmentosum.

Xeroderma pigmentosum is an unusual neurocutaneous disorder. Recent studies have classified patients with xeroderma pigmentosum into 10 groups by somatic cell hybridization methods. In this report we describe 32 patients with Group A xeroderma pigmentosum, including 1 patient with an atypical case, who were assessed for neurological complications. Of these patients, 17 had microcephaly, 13 short stature, and 21 mental retardation. In patients over 7 years of age, sensorineural deafness and spinocerebellar signs such as nystagmus, dysarthria, tremor, and ataxia were frequently observed; no patients below 7 years of age had such neurological complications. Electroencephalographic studies revealed abnormal slow and low voltage background activity. Two patients had focal abnormal discharges, one of whom developed versive seizures. Cranial computed tomographic scans revealed abnormalities, including ventricular dilatation, cerebral atrophy, cerebellar and brainstem atrophy, and cranial bone thickening. A patient with an atypical case of Group A xeroderma pigmentosum had less skin and neurological involvement, and higher levels of postultraviolet colony-forming ability and host cell reactivation than did a typical Group A case. It is possible that these less severe cytological findings are responsible for the less severe skin lesions and neurological complications noted clinically.

Adolescent↗