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Biomedical subjects

M Ohsawa

Publications and source records attributed to M Ohsawa.

At least 253 records · Page 14Linked to original sources
PubMed1983

Induction of 6-thioguanine-resistant mutants and single-strand scission of DNA by cadmium chloride in cultured Chinese hamster cells.

Inducibility of 6-thioguanine-resistant (6TGr) mutants and single-strand scission of DNA by cadmium chloride (CdCl2) was investigated in cultured Chinese hamster V79 cells. Frequency of 6TGr mutants increased concentration dependently by 24-h treatment with CdCl2 up to 3 X 10(-6) M but decreased beyond 3 X 10(-6) M. Mutagenic potency of cadmium in the absence of S9 was about half that of benzo[a]pyrene in the presence of S9 at equitoxic concentrations. Treatment of the cultured cells with cadmium after benzo[a]pyrene treatment was not synergistic but additive to the mutagenicity of benzo[a]pyrene. Single-strand scission of DNA by alkaline elution techniques was observed in the cells treated with CdCl2 for 2 h in a concentration-dependent manner. The single-strand scission by cadmium was detected only in combination with proteinase K digestion of the cell lysates, indicating formation of DNA--protein cross-linking by the metal. These biological and biochemical findings indicate that cadmium is mutagenic in mammalian cells, and its mutagenic effect seems to be accompanied by single-strand scission of DNA.

Animals↗
PubMed1983

Mutagenicity in Salmonella typhimurium mutants of serum extracts from airborne particulates.

Airborne particulates collected from urban and non-urban air were extracted with calf serum or benzene, and their mutagenic potencies were evaluated in the Salmonella reversion assay. The serum extracts were mutagenic to strains TA98 and TA100 and contained both direct- and indirect-acting mutagens. Mutagenic activities for TA98 recovered from the particulates by serum or benzene extraction were much less in the serum extracts than in the benzene extracts. There was no significant difference in mutagenic potencies of the extracts between the urban and non-urban particulates, irrespective of the presence of S9 mix. The calculated mutagenic activities per m3 of air, however, were greater for urban air than for non-urban air, because of higher concentration of particulates in urban air than in non-urban air. Serum effectively reduced both direct and indirect mutagenic activities of the benzene extracts except for an insufficient reduction in direct mutagenicity at a high dose of benzene extracts. These findings suggest that serum could contribute greatly to decrease the mutagenicity of airborne particulates by mechanisms such as less efficient solubilization of mutagenic components and inactivation by protein binding. Biological availability of mutagens, therefore, should be considered for evaluation of actual mutagenic hazard by airborne particulates.

Air Pollutants↗
PubMed1983

Participation of active oxygen species in the induction of DNA single-strand scissions by cadmium chloride in cultured Chinese hamster cells.

A mechanism for the induction of DNA single-strand scissions in cultured Chinese hamster cells by cadmium chloride (CdCl2) was investigated by use of the technique of alkaline elution. Inducibility of DNA single-strand scissions by cadmium was examined under an aerobic or anaerobic culture condition. About 62% of the total cellular DNA was eluted throughout the filter within 10 h of elution time by treatment with 4 X 10(-5) M CdCl2 for 2 h in our usual aerobic medium. In contrast, no difference in elution profiles of DNA was observed between untreated control cells and the cells treated with CdCl2 in the anaerobic medium which was prepared by N2 gas bubbling of aerobic medium for 60 min. Furthermore, elution of DNA from cells treated with cadmium decreased markedly in the presence of superoxide dismutase (SOD) when compared with that in the absence of SOD. Inhibition of the cell growth by cadmium was significantly protected by the presence of SOD in the medium although the cell growth was not restored to the control level. These results indicate that active oxygen species participate in Cd-induced DNA single-strand scissions and also in the growth inhibition of the cells by the metal.

Animals↗
PubMed1983

Cadmium-induced DNA single-strand scissions and their repair in cultured Chinese hamster cells.

DNA lesions induced by cadmium chloride (CdCl2) were characterized using the technique of alkaline or neutral elution for cell-DNA in cultured V79 cells. A marked increase in elution of the DNA was observed on elution of the proteinase-K-digested cell lysates with alkaline eluting solution (pH 12.2) after treatment with 5 X 10(-5) M CdCl2 for 2 h. In contrast, no increase in elution of the DNA was observed when the same cell lysates were eluted with an eluting solution of pH 9.6. These findings indicate that the DNA lesions induced by cadmium were DNA single-strand but not double-strand scissions. The DNA single-strand scissions by cadmium were partly rejoined after 4 h of repair incubation. However, the DNA lesions were not rejoined up to the control level in the technique of alkaline elution, even after 20 h of repair incubation. On the other hand, an apparent increase in elution of the DNA was observed by combined treatment with cadmium and inhibitors of repair DNA synthesis, hydroxyurea (HU) and 1-beta-D-arabinofuranosylcytosine (ara-C), for 4 h when compared to elution of the DNA from the cells treated with cadmium alone or HU and ara-C. These results indicate that cadmium-induced DNA single-strand scissions accumulated as a result of inhibition of repair DNA replication by HU and ara-C. Thus, it is concluded that cadmium-induced DNA single-strand scissions were repairable and their repair might be dependent upon the excision repair mechanism.

Animals↗
PubMed1983

Suppression of the proliferative response of human lymphocytes to cultured allogeneic HeLa cells by zinc.

Zinc added to the culture medium caused a dose-related suppression of the proliferative response of human lymphocytes to cultured allogeneic HeLa cells without any significant decrease in cell viability. In contrast to the response to HeLa cells, this metal ion moderately enhanced T lymphocyte response to mitogens such as phytohemagglutinin (PHA), concanavalin A (ConA) and 12-O-tetradecanoylphorbol-13-acetate (TPA). These findings seem to indicate that zinc may be a crucial factor for the modulation of the T lymphocyte function. It can also be considered that the different effect of zinc on the proliferative responses of lymphocytes to allogeneic HeLa cells and to some soluble mitogens might reflect a difference in mechanisms between the two proliferative responses.

HeLa Cells↗
PubMed1983

Malignant chemodectoma (paraganglioma) of the larynx. A case report with electron microscopy and biochemical assay.

This reports presents a case of malignant chemodectoma in the epiglottic region of a 47-year-old man. His initial complaint was laryngeal discomfort and he expired from generalized metastases of the tumor about one year after operation. The tumor was detected by laryngoscopy and laryngogram. The yellow parenchymatous tumor, 2.8 x 2.5 x 1.5 cm in size, was resected together with two enlarged regional lymph nodes. The mass was subjected to a histopathological study and biochemical assay. Microscopically, the tumor was located in the submucosa of the epiglottis and showed an alveolar growth pattern of comparatively uniform tumor cells. Neurosecretory granules were clearly demonstrated by Grimelius' method and by electron microscopy. The biochemical assay revealed that the tumor contained small amounts of serotonin, epinephrine, norepinephrine, and dopamine. The distribution of paraganglia as the source of these tumors, the clinicopathological review of the previous reports and significance of neurosecretory granules are discussed.

Cytoplasmic Granules↗
PubMed1983

Curing contraction of addition-type silicone impression materials.

The curing contraction of addition-type silicone impression materials was measured by the mercury bath method. The results point to a classification of this group of materials into the following two types: 1: materials with maximum 0.08% polymerization contraction at 22 degrees C 15 min after mixing and maximum 0.03% contraction at 22 degrees C during storage from 15 min to 24 h (Permagum, President, Reflect and Reprosil). 2: materials with more than 0.08% polymerization contraction at 22 degrees C 15 min after mixing and significantly more than 0.03% contraction during storage at 22 degrees C from 15 min to 24 h (Exaflex, Xantogum).

Chemical Phenomena↗
PubMed1983

Accuracy of stone-casts produced from selected addition-type silicone impressions.

The present study has shown that there is no correlation between the free curing contraction of three selected addition-type silicone impression materials and the effective contraction determined as the accuracy of stone dies produced in dental impressions of these materials. Depending on specific rheologic properties, the free curing contraction of an impression material can be partly compensated for by flow.

Calcium Sulfate↗
PubMed1983

A mechanism for the stimulation by inorganic mercury of [3H] thymidine incorporation into DNA in cultured Molt-4F cells.

Mercuric chloride at a narrow range of concentration (2 to 2.5 X 10(-5)M) facilitated [3H]thymidine incorporation into acid-insoluble material (DNA fraction) of cultured human T lymphoid cells, Molt-4F, after 72-hr culture with the metal. This effect by mercury was observed in spite of the decrease in growth rate and DNA contents of the cells. Thymidine kinase activity in Molt-4F cells treated with 2 X 10(-5)M mercury decreased to 50 to 60% of the control activity. The stimulation of [3H]thymidine incorporation into the cells by mercury, therefore, might be independent of the increase in thymidine kinase activity. 3H-Thymidine incorporation by the control cells decreased as culture time passed. In contrast to the control, [3H]thymidine incorporation by mercury-treated cells increased until 72-hr culture. [3H]Thymidine uptake by the control cells after 24, 48, or 72-hr culture increased until 20 min of incubation period, but thereafter no increase in the uptake was observed until 60 min. On the other hand, [3H]thymidine uptake by the cells treated with mercury for 24 to 72 hr increased linearly until 60 min of incubation period. These results seemed to indicate that the mercury stimulation of [3H]thymidine incorporation might be attributable not to the actual increase of DNA synthesis but to the suppression of the culture time-dependent decrease in the incorporation by the control cells.

Cell Line↗
PubMed1982

Effect of mercuric chloride on the proliferative response of human lymphocytes to cultured HeLa cells or a lectin.

Proliferative responses of human lymphocytes to cultured allogeneic HeLa cells and to PHA were employed as in vitro cellular immune systems to investigate effects of mercuric chloride on the both proliferative responses. When stimulator HeLa cells were pretreated with mercury, proliferative response of lymphocytes to HeLa cells in the mixed cell culture was suppressed dose-dependently. The response of lymphocytes treated with mercury to HeLa cells was suppressed markedly, even at 15-min exposure to 1 X 10(-5) M HgCl2. The response of lymphocytes to PHA as well as that to HeLa cells was suppressed by mercury treatment, even at 15-min exposure. A possible mechanism for the suppressive effect of mercury on the mixed cell reaction was discussed; mercury modification of molecules at the cell surface of the stimulator cells or responder cells and effects of mercury on macrophages.

Cell Division↗
PubMed1981

Percutaneous needle muscle biopsy in the diagnosis of neuromuscular disorders in children. Histological, histochemical and electron microscopic studies.

Percutaneous needle biopsy was carried out in 75 patients with various neurological and muscle diseases (myopathies in 7, lower motor neuron diseases in 22, upper motor neuron diseases in 6, and unlocalized or miscellaneous diseases in 13) and its usefulness as a diagnostic procedure was evaluated. The ages of the subjects ranged from 2 months to 35 years, 77% were younger than 6 years. The materials were examined histologically, histochemically and electron microscopically with the following results. 1. The muscle volume obtained by needle biopsy was sufficient for studies in 64 cases (85%), insufficient in 8 (11%), while in 3 cases no muscle tissue was obtained. 2. Histological staining properties were excellent in all samples examined. In histochemical preparations, staining was judged as good in 61 cases, but poor in 11 due to an inappropriate freezing procedure. 3. In 33 cases, both needle and open biopsies were carried out simultaneously, and the morphological findings of the specimens were compared. There were no significant differences between them histologically as well as histochemically. Electron microscopic examinations also provided identical information in the seven cases studied so far. 4. The method of needle biopsy has many advantages over open biopsy as a routine diagnostic procedure for neuromuscular disorders in infants and young children, but there are a few disadvantages such as the requirement of technical skill and the inappropriateness for histogram construction in some cases.

Adolescent↗