PubMed Health⌕ Search

Biomedical subjects

R Takaki

Publications and source records attributed to R Takaki.

At least 91 records · Page 5Linked to original sources
PubMed1979

Enhancement of excision-repair efficiency by conditioned medium from density-inhibited cultures in V79 Chinese hamster cells: evidence for excision repair as an error-free repair process.

Conditioned medium from density-inhibited V79 Chinese hamster cell cultures, given as a post-treatment to UV-irradiated homologous cells, was demonstrated to reduce the lethal action of ultraviolet light by temporarily blocking DNA replication. Since the increased survival was not affected by various non-toxic concentrations of caffeine, such protective effect would be attributable to the prolonged intervention of excision repair before DNA replication during the post-treatment period. The influence of conditioned medium on the UV-induced mutation at the ouabain-resistance locus was also examined and a significant decrease in mutation frequency was noted. The observed reduction in killing and mutation as a result of post-incubation in conditioned medium, which delays DNA replication, would be interpreted as evidence that conditioned medium provides a longer period of time for an error-free excision-repair process, leaving lesion in DNA available for error-prone post-replication repair.

Animals↗
PubMed1979

High incidence of rat mammary carcinoma by oral administration of ethyl methanesulphonate.

Ethyl methanesulphonate (EMS), one of the alkylating agents, is known to be a potent mutagen. We tested EMS for its carcinogenicity in female rats by oral administration. EMS was dissolved in drinking tap water at a concentration of 10(-3) M and was given for the first 12 weeks. The subcutaneous tumors were noticed as early as 16 weeks after initiating the experiment. At the 32nd week, all the surviving rats produced tumors; the majority were multiple tumors in the neck, axillar and inguinal areas corresponding to bilateral mammary glands. Histologically, the prevailing feature of the tumors was infiltrating medullary adenocarcinoma consistent with carcinoma of mammary duct origin. Neither regional lymph node involvement nor distant metastases were shown, but intraductal spread of carcinoma was a marked finding during the 32-week period.

Adenocarcinoma↗
PubMed1979

Simple method for the collection of pancreatic islets by the use of Ficoll-Conray gradient.

Simple method for the collection of large numbers of viable pancreatic islets from normal rats is described. This method involves collagenase digestion of the pancreas, followed by the use of Ficoll-Conray discontinuous gradient for the separation of isolated islets from unwanted acinal debris. Ficoll-Conray A solution was prepared by mixing undialyzed 12.5% Ficoll and 33.4% Conray in the ratio 2 : 1, to make a specific gravity of 1.095 and osmolarity of 396 mOsm/l. The solution B, C, and D, with specific gravities 1.084, 1.072, and 1.048, respectively were obtained by diluting A solution with distilled water. Using Ficoll-Conray gradient, about 200 viable islets which maintained excellently their morphology and function, were collected consistently from a young adult rat pancreas.

Animals↗
PubMed1977

Preparation of single cells from pancreatic islets of adult rat by the use of dispase.

A high yield of viable single cells was attained from isolated pancreatic islets of adult rat by the sequential treatment with EDTA and Dispase. The percentage of single cells was consistently higher with EDTA-Dispase in comparison with EDTA-trypsin treatment, being 65.8 +/- 7.9% and 36.0 +/- 5.4% respectively, when more than 90% of total islet cells were viable. Excellent preservation of free islet cells dissociated with EDTA-Dispase was demonstrated morphologically by light and electron microscopy. The secretory response of dissociated B cells to glucose was stabilized earlier with EDTA-Dispase than with EDTA-trypsin treatment. The amount of insulin released into the medium was proportional to the number of cells inoculated, thus permitting the quantitative analysis of B-cell function in vitro.

Animals↗
PubMed1976

Differential response of cultured mammalian cells to cytochalasin B in multinucleation.

Cytochalasin B (CB) was applied to 13 kinds of non-tumorigenic or tumorigenic cells in vitro to investigate whether the drug would be applicable as an indicator to identify the transformation of cells. Normal cell strains suffered from more deteriorative changes in morphology than cell lines, showing arborization of their cytoplasm at 5 mug/ml. CB at 2.5 mug/ml consistently prevented cytoplasmic cleavage without interfering with nuclear division. Multinucleation of the cells exposed to CB was not related to their generation time. The correlation between multinucleation and tumorigenicity of the cells was found with some exceptions. It appears, however, that multinucleation induced by CB would not be a reliable parameter for identifying malignant transformation of cells in vitro.

Animals↗
PubMed1975

Long-term culture of isolated pancreatic islet cells.

Successful long-term culture of isolated pancreatic islet as well as dissociated islet cells was accomplished with the use of Microtest II trays which provides the very small amount of culture medium that is easily conditioned. In the culture of isolated islet, the ultrastructure of the islet cells was completely preserved up to the 30th day and vigorous secretion of insulin was maintained even on the 75th day. While in the islet cell culture, insulin secretion gradually decreased from the 12th day. The latter procedure makes inoculation of a definite number of dissociated pure islet cells possible, thus opeing the way to the quantitative evaluation of B cell function in vitro.

Animals↗
PubMed1967

[Organ culture].

Explore the source record for details and available documents.

Animals↗