PubMed Health⌕ Search

Biomedical subjects

M Higashida

Publications and source records attributed to M Higashida.

12 recordsLinked to original sources
PubMed2006

Cellular thiol status-dependent inhibition of tumor cell growth via modulation of p27(kip1) translocation and retinoblastoma protein phosphorylation by 1'-acetoxychavicol acetate.

1'-Acetoxychavicol acetate (ACA) has been shown to inhibit tumor cell growth, but there is limited information on its effects on cell signaling and the cell cycle control pathway. In this study, we sought to determine how ACA alters cell cycle and its related control factors in its growth inhibitory effect in Ehrlich ascites tumor cells (EATC). ACA caused an accumulation of cells in the G1 phase and an inhibition of DNA synthesis, which were reversed by supplementation with N-acetylcysteine (NAC) or glutathione ethyl ester (GEE). Furthermore, ACA decreased hyperphosphorylated Rb levels and increased hypophosphorylated Rb levels. NAC and GEE also abolished the decease in Rb phosphorylation by ACA. As Rb phosphorylation is regulated by G1 cyclin dependent kinase and CDK inhibitor p27(kip1), which is an important regulator of the mammalian cell cycle, we estimated the amount of p27(kip1) levels by western blotting. Treatment with ACA had virtually no effect on the amount of p27(kip1) levels, but caused a decrease in phosphorylated p27(kip1) and an increase in unphosphorylated p27(kip1) as well as an increase in the nuclear localization of p27(kip1). These events were abolished in the presence of NAC or GEE. These results suggest that in EATC, cell growth inhibition elicited by ACA involves decreases in Rb and p27(kip1) phosphorylation and an increase in nuclear localization of p27(kip1), and these events are dependent on the cellular thiol status.

Acetylcysteine↗
PubMed2001

Estimation of rhG-CSF absorption kinetics after subcutaneous administration using a modified Wagner-Nelson method with a nonlinear elimination model.

The clearance of recombinant human granulocyte-colony stimulating factor (rhG-CSF) is known to decrease with dose increase, and to be saturable. The average clearance after intravenous administration will be lower than that after subcutaneous administration. Therefore, the apparent absolute bioavailability with subcutaneous administration calculated from the AUC ratio is expected to be an underestimate. The absorption pharmacokinetics after subcutaneous administration was examined using the results of the bioequivalency study between two rhG-CSF formulations with a dose of 2 microg/kg. The analysis was performed using a modified Wagner-Nelson method with the nonlinear elimination model. The apparent absolute bioavailability for subcutaneous administration was 56.9 and 67.5% for each formulation, and the ratio between them was approximately 120%. The true absolute bioavailability was, however, estimated to be 89.8 and 96.9%, respectively, and the ratio was approximately 108%. The absorption pattern was applied to other doses, and the predicted clearance values for subcutaneous and intravenous administrations were then similar to the values for several doses reported in the literature. The underestimation of bioavailability was around 30%, and the amplification of difference was 2.5 times, from 8 to 20%, because of the nonlinear pharmacokinetics. The neutrophil increases for each formulation were identical, despite the different bioavailabilities. The reason for this is probably that the amount eliminated through the saturable process, which might indicate the amount consumed by the G-CSF receptor, was identical for each formulation.

Absorption↗
PubMed2000

Proton MR spectroscopy of the brain in patients treated with TIPS.

PURPOSE: To evaluate the utility of proton MR spectroscopy (MRS) for the early detection of hepatic encephalopathy (HE) after transjugular intrahepatic portosystemic shunting (TIPS). MATERIAL AND METHODS: Six patients, who underwent TIPS for treatment of portal hypertension, were examined by MRS I week before and 1 week after TIPS. They were simultaneously clinically examined for number connection test, blood NH3 level, liver function test and the Fischer ratio. RESULT: Three of 6 patients showed overt HE 1 to 5 weeks after TIPS and the other 3 patients did not show overt HE. The overt HE group showed the larger ratio of the amounts of glutamine and glutamate/myo-inositol (Glx/MI) than that of non-overt HE group (p<0.05). CONCLUSION: The Glx/MI ratio estimated by MRS was useful for early detection of HE after TIPS.

Adult↗
PubMed1997

Muscarinic receptor-mediated dual regulation of ADP-ribosyl cyclase in NG108-15 neuronal cell membranes.

Cyclic ADP-ribose (cADP-ribose) is an endogenous modulator of ryanodine-sensitive Ca2+ release channels. An unsolved question is whether or not cADP-ribose mediates intracellular signals from hormone or neurotransmitter receptors. The first step in this study was to develop a TLC method to measure ADP-ribosyl cyclase, by which conversion of [3H]NAD+ to [3H]cADP-ribose was confirmed in COS-7 cells overexpressing human CD38. A membrane fraction of NG108-15 neuroblastoma x glioma hybrid cells possessed ADP-ribosyl cyclase activity measured by TLC. Carbamylcholine increased this activity by 2.6-fold in NG108-15 cells overexpressing m1 or m3 muscarinic acetylcholine receptors (mAChRs), but inhibited it by 30-52% in cells expressing m2 and/or m4 mAChRs. Both of these effects were mimicked by GTP. Pretreatment of cells with cholera toxin blocked the activation, whereas pertussis toxin blocked the inhibition. Application of carbamylcholine caused significant decreases in NAD+ concentrations in untreated m1-transformed NG108-15 cells, but an increase in cholera toxin-treated cells. These results suggest that mAChRs couple to ADP-ribosyl cyclase within cell membranes via trimeric G proteins and can thereby control cellular function by regulating cADP-ribose formation.

ADP-ribosyl Cyclase↗
PubMed1987

Plasma-gelsolin-binding sites on the actin sequence.

Plasma gelsolin was cross-linked to fluorescently labeled actin in order to identify plasma-gelsolin-binding sites on the primary sequence of actin. Plasma gelsolin can be cross-linked to actin with 1-ethyl-3-[3-(dimethyl-amino)propyl]carbodiimide (EDC), resulting in the formation of 1:1 and 1:2 plasma gelsolin:actin cross-linked complexes with apparent molecular masses of 130 kDa and 180 kDa respectively. The cross-linked complexes were isolated separately, partially digested with cyanogen bromide and subjected to sodium dodecyl sulfate gel electrophoresis to analyze fluorescent fragments. The electrophoretic pattern showed that fluorescent CNBr fragments obtained from a free actin molecule were all found in those obtained from both the complexes. Since the fluorescent probe was attached to an actin molecule through the penultimate cysteine residue (Cys-374), the agreement in the fluorescent patterns indicated that the NH2-terminal CNBr fragments of both the actin molecules were involved in cross-linking with plasma gelsolin. This was also suggested by hydroxylamine cleavage of the two complexes as the cleavage gave the fluorescent 41-kDa fragment which could not be produced unless plasma gelsolin was cross-linked at the NH2-terminal segment comprising 12 amino acids. Since EDC cross-links an amino group with a carboxyl group only when they are direct contact, the characteristic acidic amino acid residues at the NH2 terminus of actin are suggested to participate in binding plasma gelsolin.

Actins↗
PubMed1976

Magnesium ion-induced changes in the binding mode of adenylates to chloroplast coupling factor 1.

The effect of Mg2+ on the binding of adenylates to isolated chloroplast coupling factor 1 (CF1) was studied using CD spectrometry and ultrafiltration. At adenylate concentrations smaller than 100 muM, one mole of CF1 binds three moles of ATP (or ADP) regardless of the presence of Mg2+. In the presence of Mg2+, the first two ATP's bind to CF1 independently with the same binding constant of 2.5 X 10(-1) muM-1, then the third ATP binds with a much higher affinity of 10 muM-1. In the absence of Mg2+, the first ATP binds to CF1 with a binding constant of 2.5 X 10(-1) muM-1 then the other two ATP's bind less easily with the same binding constant of 4.0 X 10(-2) muM-1. The binding mode of ADP to CF1 is quite similar to that of ATP. In the presence of Mg2+, the binding constants of the first two ADP's are both 7.6 X 10(-2) muM-1, that of the third ADP being 4.0 muM-1. In the absence of Mg2+, the binding constant of the first ADP is 7.6 X 10(-2) muM-1, the constants of the other two ADP's both being 4.0 X 10(-2) muM-1. AMP caused a negligible change in CD.

Adenosine Diphosphate↗