Search PubMed⌕ Search

Biomedical subjects

K Murakami

Publications and source records attributed to K Murakami.

At least 1,009 records · Page 56Linked to original sources
PubMed1987

Erythrocyte insulin receptor in insulin autoimmune syndrome: effects of corticosteroid therapy.

Changes in the erythrocyte insulin receptors were studied in a patient with insulin autoimmune syndrome before and after corticosteroid therapy. In this case, despite a quite low fasting plasma glucose value (29 mg/100 ml), a 75 g oral glucose tolerance test (OGTT) showed a diabetic curve and extremely high immunoreactive insulin (IRI) levels were observed. After 6 months duration of the disease, corticosteroid was given to the patient and hypoglycemic attacks disappeared with an improvement of the levels of plasma glucose. The number of insulin receptors decreased from 58 to 29 sites/erythrocyte and an increase in binding affinity or maximal binding ability were observed after the treatment with corticosteroid. These receptor changes, for the most part, might be derived from the steroid effects, since there were similar results when we administered steroid for a long term to a certain disease. There was a 20% reduction in the amount of insulin binding IgG purified from the serum one month after treatment with corticosteroid as compared with that purified from the serum before the treatment. The results suggest the usefulness of corticosteroid therapy in treatment of the insulin autoimmune syndrome.

Aged↗
PubMed1987

[Modification of the cytotoxic effect of peplomycin by cepharanthine].

The cytotoxicity of peplomycin modified by cepharanthine, was studied on in vitro cultured Chinese Hamster V-79 cells. Cepharanthine alone showed almost no cytotoxicity on this tumor system. It was revealed that cepharanthine enhanced the cell killing action of peplomycin and also promoted the recovering process from the effects of peplomycin. The enhancing effect increased with an increase of the concentration at the lower concentrations but there were limitations at the higher concentrations. The bi-phasic properties specific to peplomycin on the dose-survival curves were unchanged even in combination with cepharanthine was observed in the recovering process from the effects of peplomycin. From these results, cepharanthine seemed not to affect on the mechanism of action of peplomycin.

Alkaloids↗
PubMed1987

Enhancement of long-term potentiation by cis-unsaturated fatty acid: relation to protein kinase C and phospholipase A2.

Previous correlative and interventive work from this laboratory has suggested that activation of protein kinase C (PKC) is important for the maintenance of the hippocampal long-term potentiation (LTP) response. One such study demonstrated that application of the cis-unsaturated fatty acid, oleate, a newly discovered PKC activator, could prolong the time course of LTP. The present study explored the mechanism of cis-unsaturated fatty acid action on LTP produced by perforant path stimulation. First, neither oleate application nor high-frequency stimulation alone produced a persistent change in synaptic transmission, while the 2 in conjunction did so. This suggests that oleate acts synergistically with the consequences of this stimulation to produce an enhancement of the LTP response. Second, oleate enhancement of LTP was more potent when applied in the perforant path synaptic terminal zone than in the dentate hilus, implying that the site of oleate action is at the synapse (where PKC is reported to be enriched). Third, translocation of PKC activity to the membrane was significantly increased after oleate-enhanced LTP relative to vehicle controls. PKC translocation was found to be unaltered by oleate application alone. Fourth, mepacrine blockade of the Ca2+-dependent enzyme phospholipase A2, which releases endogenous oleate from membrane phospholipids, inhibited the time-course of a persistent LTP response. This inhibition was shown to be reversible with oleate application. We propose that high-frequency stimulation produces an elevation of intracellular Ca2+, which then triggers phospholipase A2-mediated oleate release. This free oleate then could act in synergy with processes that render PKC oleate-sensitive to produce a persistent activation of PKC, which is critical for and leads to the persistence of the LTP response.

Animals↗
PubMed1987

Transforming growth factor activity in pleural and peritoneal effusions from cancer and non-cancer patients.

Tests were performed to study the transforming growth factor (TGF) activity in samples of pleural fluid and ascites in patients with solid tumors and non-neoplastic diseases such as congestive heart failure and liver cirrhosis. The measurement of the activity was carried out in terms of colony formation in soft agar with NRK cells as indicator cells. When the fluid samples were directly assayed, 24% (4/17) of the cancer cases and 1 of the 4 control cases were positive. The eluate of Bio-Gel P-60 gel filtration was positive in all cases. beta-Type as well as alpha-type TGF activity was found in pleural and peritoneal effusions not only from cancer patients, but also from patients with non-malignant diseases.

Adult↗
PubMed1986

Protein kinase C activation by cis-fatty acid in the absence of Ca2+ and phospholipids.

Protein kinase C has been shown to be a phospholipid/Ca2+-dependent enzyme activated by diacylglycerol (Nishizuka, Y. (1984) Nature 308, 693-697; Nishizuka, Y. (1984) Science 225, 1365-1370). We have reported that unsaturated fatty acids (oleic acid and arachidonic acid) can activate protein kinase C independently of Ca2+ and phospholipid (Murakami, K., and Routtenberg, A. (1985) FEBS Lett. 192, 189-193). This study shows that other cis-fatty acids such as linoleic acid also fully activate protein kinase C in the same manner. None of the saturated fatty acids (C:4 to C:18) nor the detergents (sodium dodecyl sulfate and Triton X-100) tested here were as effective as oleic acid. Unlike oleic acid, these detergents strongly inhibited protein kinase C activity induced by Ca2+/phosphatidylserine (PS) and diacylglycerol. Lowering the critical micelle concentration of oleic acid by increasing ionic strength also strongly inhibited oleic acid activation of protein kinase C activity. Dioleoylphosphatidylserine activated protein kinase C effectively (Ka = 7.2 microM). On the other hand, dimyristoylphosphatidylserine, which contains saturated fatty acids at both acyl positions, failed to activate protein kinase C even in the presence of Ca2+. These observations suggest that: protein kinase C activation by free fatty acid is specific to the cis-form and is not due to their detergent-like action, cis-fatty acid activation is due to the direct interaction of protein kinase C with the monomeric form of cis-fatty acids and not with the micelles of fatty acids, and cis-fatty acids at acyl positions in PS are also important for Ca2+/PS activation of protein kinase C.

Animals↗
PubMed1986

A newly discovered protein kinase C activator (oleic acid) enhances long-term potentiation in the intact hippocampus.

Protein kinase C can be activated by oleate, an unsaturated fatty acid. Since protein kinase C is activated by long-term potentiation, we wished to determine whether iontophoretic ejection of oleate into the intact hippocampal dentate gyrus of urethane-anesthetized rats would cause an enhancement of the response potentiated by high frequency stimulation of the perforant path. Oleate ejection did significantly enhance the persistence of the potentiated response. Moreover, a growth of the response beyond the initial potentiation was seen. Arachidonate, which stimulates protein kinase C to a lesser degree, had a significant preservation effect, but no effect on growth of the response. After vehicle and elaidate (trans-stereoisomer of oleate) ejections, the potentiated response decayed to baseline values. In addition, the persistence of the potentiated response observed two hours after its induction was positively correlated with the ability of an unsaturated fatty acid to activate protein kinase C in vitro. The present results support the proposal that protein kinase C activation enhances synaptic strength. It is suggested that one mechanism for this activation may be PLA2-mediated release of oleate.

Animals↗