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Biomedical subjects

T Yoshimata

Publications and source records attributed to T Yoshimata.

9 recordsLinked to original sources
PubMed1999

Effects of dehydroepiandrosterone on mitogen-activated protein kinase in human aortic smooth muscle cells.

The objective of the present study was to determine whether dehydroepiandrosterone (DHEA) modifies growth factor-induced mitogen-activated protein kinase (MAPK) activation, based on our previous study demonstrating that DHEA attenuates fetal calf serum-induced proliferation in human male aortic smooth muscle cells (human male aortic SMCs). Human male aortic SMCs were used for this study. Platelet-derived growth factor-BB (PDGF-BB), epidermal growth factor (EGF), and basic fibroblast growth factor (bFGF), but not insulin-like growth factor-1 (IGF-1), stimulated MAPK activity. Only MAPK activation induced by PDGF-BB was reduced by pretreatment with DHEA, although DHEA did not affect the MAPK activation induced by EGF or bFGF. The basal and PDGF-stimulated MAPK activity were decreased by two types of cyclic AMP (cAMP) elevating agents and increased by cAMP-dependent protein kinase (PKA) inhibitor in human male aortic SMCs, suggesting that cAMP regulates MAPK negatively. The intracellular cAMP was increased by PDGF-BB. The increase of cAMP by PDGF-BB was augmented by pretreatment with DHEA, although DHEA alone did not affect cAMP. Neither EGF nor bFGF affected cAMP with and without DHEA pretreatment. Secretion of PGE2 induced by PDGF was augmented by pretreatment with DHEA. Stimulatory effects of DHEA on the production of PGE2 and cAMP were partially canceled by aromatase inhibitor and completely canceled by indomethacin or selective inhibitor of cyclooxygenase-2. These results suggest that DHEA inhibited MAPK activation induced by PDGF-BB via PGE2 overproduction and subsequent cAMP-dependent pathway in human male aortic SMCs.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1999

Inhibition of farnesyl protein transferase and P21ras memebrane association by d-limonene in human pancreas tumor cells in vitro.

The monoterpene d-limonene inhibit the plasma-membrane associated P21ras expression and the post-translational isoprenylation of P21ras, a mechanism that may contribute to its efficacy in the chemoprevention and therapy of chemically induced rodent cancers and some human solid tumor cells. In the present study, the relative abilities of d-limonene to inhibit membrane associated P21ras expression in pancreas tumor cell (PaCa) was carried out with Western blotting, and the inhibition of farnesyl protein transferase (FTPase) activity during the Ras protein isoprenylation and cell proliferation were determined. Concomitantly, the effects of d-limonene on P21ras localization by immunohistochemistry and H-ras oncogene expression in PaCa tumor cell line by Northern blotting were observed. The results showed that d-limonene inhibited FPTase activity, thus to reduce P21H-ras isoprenylation. d-limonene could decrease P21ras membrane association and increase cytosolic accumulation of P21ras. This phenomenon was also noted when d-limonene-treated PaCa cells were stained immunohistochemically with anti-P21ras antibody. It is suggested that the inhibition of FPTase activity was closely related with the inhibiton of P21ras membrane association and the alteration of P21ras localization. Inhibition of farnesylation of P21ras altered their intracellular localization and, hence, disrupted their biological activity, but no relationship with H-ras oncogene expression was found.

Alkyl and Aryl Transferases↗
PubMed1998

Strong synergistic anti-peroxidative effects of HDL3 and ascorbic acid against copper-catalyzed LDL peroxidation.

The aim of this study was to investigate the effects of high density lipoprotein 3 (HDL3) and ascorbic acid (AsA) in combination on copper-catalyzed low density lipoprotein (LDL) peroxidation. LDL and HDL3 were isolated from sera of healthy volunteers. LDL protein, 200 microg/ml, was incubated in phosphate-buffered saline (PBS) containing 2.5 microM CuSO4 in the absence or presence of AsA, with HDL3 protein alone, or with coincubation of HDL3, 200 microg/ml, and AsA, 20 microg/ml, at 37 degrees C for up to 24 h. As a control, the same amount of control LDL protein was added to PBS. The protective effects of the HDL3 and AsA were examined by both electrophoresis and determination of the lipid hydroperoxide (LPO) level in each sample. The concentration of AsA was also measured in samples containing AsA. The coincubation of HDL3 and AsA exerts more powerful anti-peroxidative effects against copper-catalyzed LDL peroxidation, than either of these agents alone. In addition, AsA was retained in the media by the addition of HDL3. The findings suggest that there are strong synergistic anti-peroxidative effects of HDL3 and AsA and these two may act in concert in vivo to inhibit LDL peroxidation and thus exert an anti-atherosclerotic effect.

Antioxidants↗
PubMed1998

Platelet epidermal growth factor in thyroid disorders.

We evaluated the concentration of epidermal growth factor (EGF) in platelets, serum and plasma obtained from 47 patients with Graves' disease, 7 with hypothyroidism and 20 healthy subjects. The platelets of the subjects were collected from platelet rich plasma and lysed by freezing and thawing. Subsequently the platelet debris was treated with Triton X-100. The EGF concentration was determined by homologous radioimmunoassay. The concentration of EGF in the platelets in 14 patients with untreated Graves' disease was significantly higher than that in the healthy controls. After treating these 14 patients with antithyroid agents, the EGF concentration in the platelets decreased to the level of the healthy controls. The EGF concentration in the platelets in the 7 untreated hypothyroid patients decreased after replacement therapy with thyroxine. The mean volume of the platelets in the 14 patients with untreated Graves' disease was significantly larger than in the control and decreased after treatment with antithyroid agents. The serum and plasma levels of EGF in the 7 untreated hypothyroid increased after replacement therapy. In conclusion, thyroid function affected the concentration of EGF in the platelets of patients with thyroid disorders.

Adult↗
PubMed1998

alpha-tocopherol protects the peroxidative modification of LDL to be recognized by LDL receptors.

BACKGROUND: Peroxidatively modified low-density lipoprotein (LDL) may contribute to the atherosclerotic process; therefore, protecting LDL against peroxidation may reduce or retard the progression of atherosclerosis. We evaluated the effect of alpha-tocopherol on copper-catalyzed LDL peroxidative modification. METHODS: The protective effects of alpha-tocopherol on copper-catalyzed LDL peroxidative modification were examined by measurement of the concentration of lipid hydroperoxides in LDL and by the provision of LDL cholesterol to lymphocytes via the LDL receptor-mediated pathway. RESULTS: The measurement of concentration of lipid hydroperoxides in LDL showed that alpha-tocopherol inhibited the peroxidative modification of LDL. Also, alpha-tocopherol preserved the ability of LDL to be recognized by LDL receptors in peripheral blood lymphocytes to the same extent as native LDL. CONCLUSION: These findings indicate that alpha-tocopherol may protect LDL against peroxidative modification, maintaining its ability to act as a ligand for LDL receptors in vivo.

Adult↗
PubMed1992

[Case report of Farmer's lung disease in siblings in Kagoshima Prefecture].

Two cases of farmer's lung disease in siblings are reported. A 54-year-old male farmer, who had been engaged in stock work for 20 years, presented to our clinic for the second episode of fever, productive cough and shortness of breath. Chest roentgenogram revealed diffuse micronodular pattern, and mild hypoxemia was recognized on arterial blood gas analysis. Cytology obtained from BALF showed lymphocytosis, with especially increased OKT3, OKT4 positive cells and OKT4/8 ratio. The diagnosis was confirmed by highly positive reaction of precipitins to Thermoactinomyces vulgaris and granulomatous interstitial pneumonitis on histopathological examination. The second case was a 51-year-old female patient, the sister of the first case, who also worked as a stock farmer of another farm for 20 years. She presented with an episode of similar symptoms to the first case, one and a half years after the onset of her brother's symptoms. The findings of roentgenogram, BALF analysis, precipitins to T. Vulgaris and pathology were similar to those of the first case. The finding of high OKT4/8 ratio on BALF analysis in both cases is characteristic of formers lung disease, in contrast to the summer-type hypersensitivity pneumonitis which usually shows low OKT4/8 ratio in BALF. To our knowledge, this is the first report of farmer's lung disease in an area other than the northern part of Japan. Thus we conclude that farmer's lung disease may occur in Japan under any environmental conditions, and that some genetic factor may take part in the onset of this disease.

Bronchoalveolar Lavage Fluid↗
PubMedDate not supplied

Abnormal cell morphology and cytotoxic effect are induced by 6-0-palmitol-ascorbate-2-0-phosphate, but not by ascorbic acid or hyperthermia alone.

A new derivative of ascorbic acid (AsA), 6-0-palmitoyl-ascorbate 2-0-phosphate (Asc2P6Pal) was developed to enhance the antitumor activity of AsA. When Ehrlich ascites tumor cells were treated with 50 microM Asc2P6Pal at 37 degrees C or 42 degrees C for 1 h and then cultured for 20 h, most of cells exhibited some morphological abnormalities, including exudation of intracellular granules together with other contents on the cell membrane surface, resulting in cell fragmentation. The abnormal features were further enhanced by a long term culture for 96 h and heat treatment at 42 degrees C. In contrast, no abnormality was detected for untreated cells or cells treated with AsA (free acid) at 37 degrees C or 42 degrees C. Cells cultured for 96 h after the treatment suffered from inhibition of DNA synthesis and proliferation. This inhibition was markedly enhanced by combination with the hyperthermic treatment at 42 degrees C, but not for a short-term culture of 20 h after the treatment. No effects were seen upon similar treatment with AsA. The abnormal cells produced during culture for 20 h after the treatment were evaluated to be viable, because they failed to be stained with trypan blue and retained most of the DNA synthesizing ability of Asc2P6Pal-untreated cells. However, they appeared and died after a continuous 76 h of culture (96 h).

Animals↗
PubMedDate not supplied

Inhibition of farnesyl protein transferase by monoterpene, curcumin derivatives and gallotannin.

Ras proteins must be isoprenylated at a conserved cysteine residue near the carboxyl terminus (Cys-186 in mammalian Ras p21 proteins) in order to extend their biological activity. Previous studies have indicate an intermediate in the mevalonate pathway, most likely farnesyl pyrophosphate, is the donor of this isoprenyl group, and that using inhibitors of the mevalonate pathway could block the transforming properties of ras oncogene. Unfortunately, mevalonate is a precursor of various end products essential to mammalian cells, such as dolichols, ubiquinones, heme A, and cholesterol. In this study, we partially purified farnesyl protein transferase (FPTase) capable of catalyzing the farnesylation of unprocessed Ras p21 proteins in vitro from porcine kidney epithelial-like LLC-PK 1 cells, human lung adenocarcinoma A549 cells and human pancreatic cancer MIA PaCa-2 cells. This FPTase activity requires a divalent cation, such as Mg2+ or Zn2+ ions, sulfhydryl protecting agent, DTT, as well as certain pH which is linear with time and with enzyme concentration, and is present in many mammalian normal cell and tumor cell lines. Sequentially, we observed the effects of the monoterpene compound, d-limonene; curcumin derivatives, CD-I and CD-II; polyphenol compound, gallotannin; Salvia miltiorrhiza derivative, SMD; and retinoid acid derivative, RAD on FPTase activity. We found that curcumin derivatives and gallotannin had a strong inhibition on FPTase besides d-limonene, while gallotannin was the strongest among synthetic and natural compounds tested. Salivia miltiorrhiza and retinoid acid derivatives had no influence on FPTase activity. Our results suggest that compounds containing polyphenol hydroxyl may be a new source of FPTase inhibitors. The experiment also showed that availability of an in vitro farnesyl protein transferase assay could be useful in screening for potential inhibitors of ras oncogene function that will not interfere with other aspects of the mevalonate pathway.

Alkyl and Aryl Transferases↗