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Biomedical subjects

K Nagakura

Publications and source records attributed to K Nagakura.

At least 55 records · Page 3Linked to original sources
PubMed1987

Inhibitory effects of tetradecanoylphorbol acetate and diacylglycerol on erythropoietin production in human renal carcinoma cell cultures.

A human renal carcinoma from a patient with an erythrocytosis, serially transplanted into athymic nude mice, was grown in primary monolayer cell cultures. After reaching confluency the cultured cells formed multicellular hemicysts (domes) which became more abundant as the cultures approached saturation density. Erythropoietin (Ep) production by this renal carcinoma in culture was only slightly increased at the time of semiconfluency but showed a marked increase in Ep levels in the culture medium after the cultures reached confluency, in parallel with an increase in dome formation. The phorbol ester tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA) showed a significant dose-related inhibitory effect on Ep production and dome formation in the renal carcinoma cell cultures, suggesting an important role of protein kinase C, the only known receptor for TPA, in inhibiting the expression of differentiated phenotypes in the renal carcinoma cells. TPA also suppressed Ep secretion over a period of 96 h, indicating a time course of suppression of this differentiated function of the renal carcinoma cells in culture. This hypothesis was further supported by the observation that diacylglycerol, the endogenous activator of protein kinase C, likewise inhibited Ep production and dome formation in the renal carcinoma cell cultures. These studies suggest a role of the inositol-lipid second messenger path and protein kinase C in the regulation of Ep production.

Carcinoma, Renal Cell↗
PubMed1987

1,25-Dihydroxyvitamin D3 receptors and their relationship to histological features in renal cell carcinoma.

The present studies were carried out in 11 human renal cell carcinomas to determine the presence of a receptor specific for an active form of vitamin D, 1,25-dihydroxyvitamin D3. Saturation and Scatchard analyses of the cytosol receptor for 1,25-dihydroxyvitamin D3 showed that nine tumors had a detectable level of the receptor (two fmol/mg. protein). The equilibrium dissociation constant of these receptors ranged between 46 and 380 pM and the binding capacity also ranged between 3.5 and 12.7 femtomol/mg. protein. Sucrose density gradient analysis of the specific binders revealed that the tumors had a receptor protein appearing as a single 3.6S peak. Two tumors which had only a trace of the receptor were high grade solid tumors consisting mainly of spindle or pleomorphic cells. Nine tumors possessing 1,25-dihydroxyvitamin D3 receptor consisted of clear and/or granular cells. Thus, the absence of the receptor was only accompanied by low differentiated sarcomatoid tumors with poor prognosis. However, so far, the amount of the receptor in the receptor-positive tumor did not relate to the other clinical and pathological features of the patients.

Aged↗
PubMed1987

Effects of low calcium levels on erythropoietin production by human renal carcinoma cells in culture.

Recent investigations have shown that calcium entry blockers enhance the effects of hypoxia on erythropoietin (Ep) production in vivo. To determine whether deprivation of calcium increases Ep production and/or release, studies were carried out to determine the effects of low levels of extracellular calcium on Ep (radioimmunoassay) secretion in human renal carcinoma cells in culture. Low extracellular calcium levels (0.3 mM) in culture medium significantly (P less than 0.01) enhanced Ep secretion (64-145% increase per day) by renal carcinoma cells in culture when compared with a concentration of 1.9 mM calcium in the control culture medium (23-68% increase per day) incubated for 24 h or more. A 53% increase per day in Ep secretion was also produced by the calmodulin inhibitor trifluoperazine. To determine whether the effects of low calcium levels on Ep production could be due to nonspecific leakage of large intracellular molecules caused by a permeabilization of the cell membrane, the effect of low calcium levels in the cultures of the renal carcinoma cells on lactate dehydrogenase release into the culture medium was studied. Low calcium concentrations failed to significantly enhance lactate dehydrogenase secretion by the renal carcinoma cells. In conclusion, our results indicate a possible involvement of the calcium ion and calmodulin in the biosynthetic pathway for Ep and that calcium may exert a suppressive effect on Ep production.

Calcium↗
PubMed1987

A case of intestinal myiasis in Japan.

A case of intestinal myiasis caused by larvae of Sarcophaga peregrina (Japanese name: senchi-nikubae) is reported. The patient passed stools containing live fly larvae for 2 days, but was otherwise asymptomatic. The patient seems to have been infested accidentally as a result of having eaten "yakitori" in which the fly had deposited its larvae. This paper is the first report of intestinal myiasis caused by the 3rd instar of this species.

Adult↗
PubMed1986

Localization of the Trypanosoma cruzi-specific Mr 25,000 antigen by immune electron microscopy using monoclonal antibodies.

Two monoclonal antibodies reacted with the Trypanosoma cruzi-specific antigen of an apparent Mr 25,000 from all developmental forms (Tachibana et al. 1986). This T. cruzi-specific antigen was found at the plasma membrane by immunoperoxidase electron microscopy using the monoclonal antibodies TCF48 and TCF87. The TCF48 and TCF87-treated cells showed stain deposits at the plasma membrane clearly distinguishable from those in cells treated with a monoclonal antibody against a surface antigen. This suggests that the epitope(s) of the Mr 25,000 antigen is located on the inner surface or in the matrix of the plasma membrane. TCF48 and TCF87 also reacted with an antigen on the microtubules of the axoneme, but not with the subpellicular microtubules. These results suggest that the T. cruzi-specific Mr 25,000 antigen is common to both the plasma membrane and axoneme but it is not located at the subpellicular microtubules. Its identity and that of the surface antigen, Gp25 (Scharfstein et al. 1983) as well as its role in the pathogenicity of the parasite are discussed.

Animals↗
PubMed1986

Species-specific monoclonal antibodies for a membrane antigen(s) in all developmental forms of Trypanosoma cruzi.

Two monoclonal antibodies (designated as TCF48 and TCF87 were raised against Trypanosoma cruzi, strain Tulahuen, Both antibodies reacted with all developmental forms of several different strains of Trypanosoma cruzi. The antibodies showed no detectable cross-reactivity with other species of Trypanosomatidae, so far examined. TCF48 and TCF87 were classified as immunoglobulin subclasses IgG1 and IgG2b, respectively. Apparent molecular weight of the corresponding antigen(s) to these monoclonal antibodies was 25,000 in amastigotes and epimastigotes, and 25,000 and 24,000 in trypomastigotes, as determined by the Western immunoblotting analysis. This antigen appeared to be located at the plasma membrane and the flagellum ofT. cruzi. However, no evidence supported the localization of the epitope(s) at the external surface of the live cell. Since this antigen reacted with the sera from the chronically infected mice, these monoclonal antibodies may be useful in the study of Chagas' disease.

Animals↗
PubMed1986

Leishmania braziliensis: localization of glycoproteins in promastigotes.

Two species of glycoproteins from Leishmania braziliensis promastigotes of apparent molecular weights of 53,000 (glycoprotein 53) and 47,000 (glycoprotein 47) were localized. Four lectins with different sugar specificities bound to the blotting sheet to which the electrophoretically separated materials were transferred. Concanavalin A and Ricinus communis agglutinin bound to the band of glycoprotein 53 and the lectin from Dolichos biflorus bound to the band of glycoprotein 47. Wheat germ agglutinin bound to the bands of both glycoproteins. Histochemical examinations using fluorescence labeled lectins demonstrated that the glycoproteins 53 and 47 were located on the cell surface and in the cytoplasm of promastigotes, respectively. The results are consistent with the result of agglutination test.

Agglutination Tests↗
PubMed1986

Lipid composition of three morphological stages of Trypanosoma cruzi.

The neutral and phospholipid content at each of the three morphological stages of the parasite, Trypanosoma cruzi, was analyzed by thin-layer chromatography. Total lipid fatty acid composition at each stage was analyzed by gas-liquid chromatography and the results were compared. Change in lipid composition at each stage was observed.

Animals↗
PubMed1986

A case of simultaneous bilateral germ cell tumors arising from cryptorchid testes.

We report a rare case of simultaneous bilateral testicular germ cell tumors arising from uncorrected cryptorchid testes. Each side had a different histological type, which consisted of pure high grade seminoma on the left side, and teratocarcinoma with choriocarcinoma and yolk sac tumor elements in addition to seminoma on the right side. Patients with cryptorchidism are known to have a higher risk of germ cell tumors. Genetic factors also may have a role in the oncogenesis in our patient, since his older brother had had a seminoma in the left cryptorchid testis previously. Both patients had the HLA-Aw24 antigen. The characteristics of familial testicular tumors are discussed.

Cryptorchidism↗
PubMed1986

Mucinous adenocarcinoma of prostate: a case report and review of the literature.

Mucinous adenocarcinoma of the prostate is rare and its biological behavior is not well known. We report a case of mucinous adenocarcinoma of the prostate, which was treated successfully with castration. Positivity for prostatic specific antigen by immunohistochemistry confirmed the prostatic origin of this tumor. A review of the literature revealed 30 authentic cases. Prostatic mucinous adenocarcinoma has been said to be different clinically from ordinary prostatic adenocarcinoma. It is insensitive to hormonal therapy, rarely produces acid phosphatase and rarely metastasizes to the bone. However, our case, together with the frequent presence of coexisting acinar elements in mucinous adenocarcinoma, indicates no significant difference in the clinical behavior between mucinous and ordinary acinar carcinomas.

Adenocarcinoma, Mucinous↗
PubMed1986

Inhibitory effect of 1 alpha,25-dihydroxyvitamin D3 on the growth of the renal carcinoma cell line.

We studied the effect of vitamin D compounds on the growth of the human renal carcinoma cell line (KU-2) and discovered a receptor protein specific for the active form of vitamin D3, 1 alpha,25-dihydroxyvitamin D3. The KU-2 cell line was established from a pulmonary metastasis of renal cell carcinoma in a patient with hyperhemoglobinemia. The cells were tumorigenic in nude mice and clonogenic in a soft agar culture. Vitamin D3 derivatives suppressed proliferation of KU-2 cells in a monolayer culture and also clonogenicity in a soft agar culture dose-dependently. Of the vitamin D3 derivatives tested, 1 alpha,25-dihydroxyvitamin D3 was the most potent in inhibiting cell growth, followed successively by 1 alpha,24R,25-trihydroxyvitamin D3, 25-hydroxyvitamin D3, 1 alpha-hydroxyvitamin D3 and 24R,25-dihydroxyvitamin D3 in that order. Analysis of the cell cycle phase of treated and non-treated KU-2 cells revealed that the action of 1 alpha,25-dihydroxyvitamin D3 was not phase-specific but simply extended the doubling time of the cells. Radioreceptor assay and sucrose density gradient analysis of the cytosol showed that KU-2 cells contained a 3.2S receptor protein to which 1 alpha,25-dihydroxyvitamin D3 was specifically bound (Kd = 20.8 +/- 4.8 pM, Nmax = 87 +/- 24 fmole/mg protein, 4000 molecules/cell). On the other hand, the equilibrium dissociation constant of internalization of 1 alpha,25-dihydroxyvitamin D3 (Kint) by intact KU-2 cells was 1.2 nM and the internalizing capacity was 33 fmole/8 X 10(6) cells (2500 molecules/cell) in the 10% serum medium, which was the same as that used in the growth study.(ABSTRACT TRUNCATED AT 250 WORDS)

Calcitriol↗
PubMed1986

Subcellular fractionation of Trypanosoma cruzi; isolation and characterization of plasma membranes from epimastigotes.

A procedure is described for the isolation of subcellular fractions from epimastigotes of Trypanosoma cruzi. The method could separate most of the nuclei, mitochondria and microsomes. The plasma membranes were purified by discontinuous density gradient centrifugation in alkaline buffer containing sucrose and magnesium. The yield of plasma membrane was 3.7 mg of protein per 10(9) epimastigotes, accounting for approximately 4.2% of the total cell proteins. The plasma membrane obtained from the 34-50% interface of sucrose density gradients was shown, by electron microscopy, to be completely free of other organella and was homogeneous according to enzymatic marker criteria. The specific activity of the 5'-nucleotidase and acid phosphatase were 96- and 5.5-fold, respectively, higher than that in the total cells, suggesting that the enzymes can be considered as good plasma membrane markers for T. cruzi. The results confirmed the possibility of the presence of membrane-bound acid phosphatase of T. cruzi.

Acid Phosphatase↗
PubMed1985

Alteration of the cell surface acid phosphatase concomitant with the morphological transformation in Trypanosoma cruzi.

Acid phosphatase activity in Trypanosoma cruzi was found to be located on the external surface of the plasma membranes. Both specific activity and activity per cell of this bound enzyme were significantly higher in the cells of amastigote (an intracellular form) than that of trypomastigote (a bloodstream form) and epimastigote (culture form). During the transformation of epimastigotes to amastigotes in vitro the activity of surface acid phosphatase was elevated concomitant with the increase in population of amastigotes. These results were interpreted as that the elevated enzyme activity is required for the intracellular parasitization of this organism or is a consequence of the morphological transformation.

Acid Phosphatase↗