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M Seki

Publications and source records attributed to M Seki.

At least 451 records · Page 25Linked to original sources
PubMed1980

[The maintenance of insulin secretory response of long-term cultured pancreatic islets to glucose, acetylcholine and epinephrine (author's transl)].

The present study was performed to investigate whether long-term cultured rat pancreatic islets possess a postcultural insulin secretory response to hormones and neurotransmitters in spite of their lack of stimulation during the culture period. We also investigated the method of maintaining the insulin secretory response of islets cultured in a physiological concentration of glucose. The tissue culture media were TCM 199 supplemented with 5.5 mM glucose (A medium), 5.5 mM glucose plus 1 mM adenosine (B medium), 16.7 mM glucose (C medium), and 16.7 mM glucose plus 1 mM adenosine (D medium). Short-term incubation after the culture period of 14 days showed that the islets cultured in B, C and D media maintained the same insulin secretory responsiveness to 8.3 mM glucose and/or 5 microM acetylcholine and also to 1 microM epinephrine as did non-cultured islets. A similar response was found among the islets maintained in B, C and D media. An insulin secretory response to epinephrine and phentolamine was deficient in islets cultured in A medium, whereas it was maintained in those cultured in C medium. The responsiveness of the islets cultured in C medium to the concomitant stimulation by epinephrine and phentolamine was not different from that of the non-cultured islets. It was thus concluded that the addition of adenosine in the culture medium containing the physiological concentration of glucose was as effective in amintaining the insulin secretory ability of the islets as was the culture medium containing a high concentration of glucose, and it was suggested that even the pancreatic islets cultured in these media, though separated from the innervation might preserve acetylcholine and adrenergic receptors similar to freshly isolated islets. Considering the action of adenosine, the necessity of enhancing ATP and C-AMP concentrations in B cells was also suggested in order to maintain the insulin secretory ability of cultured pancreatic islets.

Acetylcholine↗
PubMed1980

An experimental study on carcinogenesis related to localized fibrosis in the lung.

The present series of experiments was carried out in order to see what role pre-existing localized fibrosis plays in carcinogenesis of the lung. Hemorrhagic infarction was produced in the lung of 180 male Wistar rats by injecting 0.05 ml of hexachlorotetrafluorobutane into the tail vein. This resulted in localized fibrosis in the lung 3 months later. One hundred and fiften rats were alive 3 months after administration of the chemical. Of these animals, 30 were given no further treatment (control). The remaining 85 rats were given intratracheal instillation of 0.2 microCi of polonium-210 once a week, a total of 15 times. It was subsequently found that lung carcinoma was induced in close proximity to the localized pulmonary fibrosis in 3 of 26 rats (11.5%) during the period from completion of the 15 weekly administrations of polonium-210 until the end of this experiment (21 months after the 1st instillation of polonium-210). Polonium-210 was found to be deposited in the fibrous thickening of the alveolus around the subpleural fibrotic lesion, bronchial epithelium, and peribronchial lymph apparati at the initial period of administration of polonium-210, but during the period of pulmonary carcinogenesis, it was deposited in the localized fibrotic lesion in the lung and in a few cancer cells. This suggests that polonium-210 deposited in the pulmonary fibrotic lesion remains there over a long period of time, indicating a reduced clearance ability at this site.

Adenocarcinoma↗
PubMed1979

Distribution of mast-cell precursors in hematopoeitic and lymphopoietic tissues of mice.

Two experimental systems were used to investigate the origin of precursor cells which differentiate into tissue mast cells in vivo. (a) Increase of mast cell number was examined in the skin, stomach, cecum, and mesentery of genetically mast cell-depleted WBB6F1 (WB X C57BL/6)-W/WV mice after the injection of various hematolymphoid cells of congenic +/+ mice. (b) Appearance of mast cells with giant granules was studied in irradiated C57BL/6-+/+ mice after the injection of lymphoid cells of C57BL/6-bgJ/bgJ (beige, Chediak-Higashi syndrome) mice. Concentrations of mast cell precursors in the thymus, lymph node and Peyer's patch were less than 0.1% of the concentration in the bone marrow. Neither treatment of donor bone marrow cells with anti-Thy-1.2 serum and complement nor thymectomy of the recipient mice affects the development of mast cells in the skin, stomach, cecum, and mesentery. Moreover, the number of mast cells increased to normal level when the skin of WBB6F1-W/WV mice was grafted on the back of nude athymic (BALB/c-nu/nu) mice. These results indicate that mast cell precursors are derived from hematopoietic tissues rather than lymphopoetic ones and that the differentiation of the precursor cells does not depend on T lymphocytes or the thymus.

Animals↗
PubMed1979

High concentration of gamma-aminobutyric acid in pancreatic beta cells.

The gamma-aminobutyric acid (GABA) concentration of pancreatic islets in rats treated with streptozotocin (STZ) and of human insulinoma tissue was studied. Seven hours after the administration of 65 mg/kg body weight of STZ, a distinct increase in serum insulin concentration and at the same time a decrease in blood glucose level were seen. Twenty-four hours after the injection of STZ, however, the level of serum insulin decreased much, whereas that of blood glucose increased considerably. On the other hand, the GABA concentration of the islet was reduced dramatically to about one-tenth the control level after both 7 and 24 h. The histologic investigations of the islets revealed the destruction of B cells but no changes in A and D cells 7 and 24 h after the treatment of STZ. Nerve fibers and nerve endings in the islets were preserved intact all through the study. The GABA and insulin contents of the two cases of human insulinoma were determined. One insulinoma, which was compactly occupied with B cells according to its histologic features, contained a high concentration of GABA. The other tumor, having a rather sparse distribution of B cells in it as compared with the former case, possessed a lower concentration of GABA, but it was still high compared with that of its surrounding tissues. The present observations indicate that a large amount of GABA is available in the B cells of the pancreatic islets.

Adenoma, Islet Cell↗
PubMed1979

Evaluation of a commercial enzyme immunoassay for insulin in human serum, and its clinical application.

We applied a "sandwich" method, with use of beads coated with anti-insulin serum and of peroxidase-labeled anti-insulin serum, to an enzyme immunoassay of insulin in human serum. 5-Aminosalicylic acid was used as the substrate for the enzymic reaction. As little as 5 milli-int. units of insulin per liter of serum insulin was detectable. Reproducibility was satisfactory, but extraordinarily high concentrations of proinsulin and of hydrogen donors such as reduced glutathione affect results of the assay. Values determined by our enzyme immunoassay and by double-antibody radioimmunoassay correlated highly (r = 0.938, p less than 0.001, n = 216). We recommend this method for use in the clinical laboratory.

C-Peptide↗