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Biomedical subjects

R Sato

Publications and source records attributed to R Sato.

At least 253 records · Page 14Linked to original sources
PubMed1991

Expression and characterization of a rabbit liver cytochrome P450 belonging to P450IIB subfamily with the aid of the baculovirus expression vector system.

Using baculovirus a cDNA for cytochrome P450 (P450F1) belonging to rabbit P450IIB subfamily was expressed in Spodoptera frugiperda cells, where P450F1 was located on electron-dense structures (derived from the endoplasmic reticulum) present in both the cytoplasm and nucleus. Partially purified P450F1 exhibited absorption spectra similar to those of P450(1), the major phenobarbital-inducible form in rabbit liver. Like P450(1), P450F1 could oxidize aminopyrine, benzphetamine, 7-ethoxycoumarin, 1-nitropropane, and 2-nitropropane, though its activities toward benzphetamine and 7-ethoxycoumarin were about 50 and 5%, respectively, of those of P450(1). It is concluded that the members of P450IIB subfamily can act on a variety of xenobiotics, although substrate preferences are different among them.

Animals↗
PubMed1991

Aprindine blocks the sodium current in guinea-pig ventricular myocytes.

Aprindine is a class Ib antiarrhythmic agent. We studied effects of aprindine (3 mumol/l) on the Na+ current using whole cell voltage clamp (tip resistance = 0.5 M omega, [Na]i ando = 10 mmol/l at 18 degrees C). Aprindine revealed tonic block (Kdrest = 37.7 mumol/l, Kdi = 0.74 mumol/l; n = 4). Aprindine, shifted inactivation curve to hyperpolarizing direction by 11.4 +/- 3.5 mV (n = 4) without changes in slope factor. In the presence of 3 mumol/l aprindine, aprindine showed phasic block, i.e., duration-dependent block at 2 Hz (64% +/- 3% at 1.5 ms, 82% +/- 6% at 20 ms, 93% +/- 7% at 200 ms; n = 4). Short single prepulse also produced aprindine-induced phasic block (12% at 1.5 ms, 22% at 100 ms; n = 2). After removal of fast inactivation of Na+ current by 3 mmol/l tosylchloramide sodium, aprindine revealed phasic block, independent of holding potential. The recovery time constant from aprindine-induced phasic block was 4.8 s at holding potential = -100 mV and 5.0 s at holding potential = -140 mV. This use-dependent block of aprindine had pH dependency. Under acidic condition (pH 6.0), 3 mumol/l aprindine showed smaller use-dependent block (14% +/- 7% at 2 Hz; n = 4) comparing with either at pH 7.4 (68% +/- 13%; n = 4) or at pH 8.0 (90% +/- 12%; n = 4). The results suggest that aprindine could bind to the receptor via activation process through channel pore, resulting in decrease of Na+ current, and egress from the receptor through the lipid bilayer. These effects might be attenuated under acidic condition due to changes in intracellular ratio of charged to neutralized form of drug molecule.

Action Potentials↗
PubMed1991

Glucose overload and hepatic energy metabolism after resection of the cirrhotic liver in rats.

The effect of glucose hyperalimentation on energy metabolism in the cirrhotic rat liver after 70% hepatectomy was studied. After resection, rats received either 30 kcal/kg per day (group I) or 200 kcal/kg per day (group II) of glucose for 48 h. In both groups, hepatic mitochondrial ATP synthesis was accelerated when palmitic acid was used as substrate and suppressed when pyruvate was used. This suggests that the energy substrate of the remnant liver was principally fatty acids rather than glucose. Hepatic energy charge was within normal limits in group I, but decreased significantly in group II after hepatectomy. An abundance of glucose in the early postoperative period, therefore, caused a hepatic energy derangement by suppressing fatty acids utilization; this suppression was corroborated by the findings of lower immunoreactive glucagon and non-esterified fatty-acid concentrations in group II. To determine optimal glucose administration, the predicted value of glucose disposal rate (GDR) was calculated after an intravenous glucose tolerance test. GDR decreased significantly after hepatectomy and did not increase appreciably even with a large dose of insulin administration. These results suggest that glucose administration should be tailored to the GDR values after resection of the cirrhotic liver.

Adenosine Triphosphate↗
PubMed1991

Quinidine blocks cardiac sodium current after removal of the fast inactivation process with chloramine-T.

To determine if the fast sodium current inactivation process is necessary for sodium current (INa) blockade by quinidine, we studied the effects of quinidine on INa in guinea-pig ventricular myocytes treated with chloramine-T, which removes the fast inactivation process of INa. Following exposure to chloramine-T (2 mM), INa amplitude was reduced at all voltages and INa decay was irreversibly prevented. Quinidine (10 microM) produced resting block of INa of 36 +/- 2% (n = 5) at the peak potential of -30 mV in chloramine-T treated myocytes. Quinidine decreased INa in a dose-dependent manner. The half-blocking concentration (KD) was 1.9 +/- 0.2 x 10(-5) M (n = 4). The steady-state inactivation curve (hx) was shifted in the negative potential direction (-5.2 +/- 0.4 mV, n = 4). Even after removal of the fast inactivation process of INa, use-dependent block was observed in the presence of quinidine when various depolarizing pulse durations (5 ms approximately 200 ms) were applied repetitively at intervals of 300 ms approximately 2 s. Longer depolarizing pulses and higher frequency pulse trains produced greater use-dependent block. Use-dependent block was also enhanced at more positive holding potentials. These results suggest that quinidine produces both resting block and use-dependent block of sodium channels in the absence of the fast INa inactivation process.

Animals↗
PubMed1991

Specific Binding of Protoporphyrin IX to a Membrane-Bound 63 Kilodalton Polypeptide in Cucumber Cotyledons Treated with Diphenyl Ether-Type Herbicides.

Porphyrin accumulation in excised cucumber cotyledons (Cucumis sativus L.) treated with a N-phenylimide S-23142 (N-[4-chloro-2-fluoro-5-propargyloxyphenyl]-3,4,5,6- tetrahydrophthalimide) and a diphenylether acifluorfen-ethyl (ethyl-5-[2-chloro-4-(trifluoromethyl)phenoxy]-2-nitro benzoic acid) was studied. Most of the accumulated porphyrins were found in the membrane fractions of 6,000g and 30,000g pellets, forming a complex with a membrane polypeptide. The complex was solubilized with 1% n-dodecyl beta-d-maltoside and its molecular mass was estimated to be 63,000 and 66,000 daltons by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and gel permeation high performance liquid chromatography (HPLC), respectively. The polypeptide also existed in untreated cotyledons but had little protoporphyrin IX. The complex was also formed in vitro by mixing the 30,000g pellets from untreated cotyledons and authentic protoporphyrin IX. However, protoporphyrin IX formed the complex specifically with the 63,000 dalton polypeptide and not with the other proteins both in vivo and in vitro. At least four fluorescent porphyrins, including protoporphyrin IX, were found in the acetone extract of the cotyledons by HPLC using a reversed phase column. Protoporphyrin IX was one of the two porphyrins that formed the complex. These results suggest that S-23142 and acifluorfenethyl enhance the accumulation of protoporphyrin IX, which forms the complex with the membrane protein.

Journal Article↗
PubMed1991

The effect of TYB-3823, a new antiarrhythmic drug, on sodium current in isolated cardiac cells.

1. Sodium current (INa) blockade by TYB-3823, a newly synthesized antiarrhythmic agent, was investigated in isolated single ventricular myocytes by use of the whole cell patch-clamp technique. 2. TYB-3823 blocked INa under steady-state conditions (Kd,rest = 500 microM, Kd,i = 4.9 microM), findings consistent with a shift in the steady state INa availability curve to more negative potentials. 3. TYB-3823 produced use-dependent block at 2 Hz in conjunction with increase in pulse duration (5-300 ms), that was markedly enhanced at less negative holding potentials. 4. The time course of the onset of block was accelerated and the degree of use-dependent block was decreased at more negative holding potential. The time course of the onset of block was accentuated with enhancing block at more positive holding potentials. 5. The time course of recovery from use-dependent block was accelerated at more negative holding potentials but was accentuated at more positive holding potentials. 6. These results suggest that both tonic block and use-dependent block of sodium channels in cardiac tissue might result from an interaction of TYB-3832 with sodium channels mainly in the inactivated channel states and the kinetics of the interaction between drug and receptor may be modulated by the inactivation gate.

Animals↗
PubMed1991

Comparative studies on the validity of renal function tests in the experimentally-induced bovine glomerulonephritis.

To establish the usefulness of the bovine clinical renal function tests, experimental glomerulonephritis was experimentally induced in calves and some renal clearance tests were performed. Two (No. 1, 2) of three calves were injected intravenously with anti-bovine kidney rabbit serum (antiserum) and the other (No. 3) with normal rabbit serum (control serum). The early stage of proliferative glomerulonephritis was observed in the kidneys of Nos. 1 and 2. The degree of lesions in No. 1 was severer than that in No. 2. No remarkable change was observed in the kidneys of No. 3. Endogenous creatinine clearance value (CCRE), thiosulfate clearance value (CTHIO) and maximal tubular secretion of para-amino hippuric acid (TmPAH) of all calves did not show remarkable changes after the injection of antiserum or control serum. In the phenolsulfonphthalein (PSP) test, PSP excretion of Nos. 1 and 2 was disposed to delay after the injection, and in No. 3 there was no significant change after the injection. PAH clearance value (CPAH) of No. 1 decreased from 10.24 to 6.96 ml/min/kg (-32%). A small change was noted in the CPAH of Nos. 2 and 3. These results suggest that the simplified method for measuring CPAH performed in this study could assess the lesions formed in No. 1, which was pathologically diagnosed as the early stage of proliferative glomerulonephritis.

Animals↗
PubMed1990

Monoclonal antibody EMR1a/212D recognizing site of deposition of extracellular lipid in atherosclerosis. Isolation and characterization of a cDNA clone for the antigen.

We have isolated from a rabbit liver cDNA library, clones coding for the 66-kDa glycoprotein (GP66) characterized previously by EMR1a/212D monoclonal antibody (Nakagami, K., Shimasaki, O., Sato, R., Komine, Y., Ohkuma, S. and Takano, T. (1989) Am. J. Pathol. 135, 93-100), which recognizes the extracellular regions of atherosclerotic arterial wall. The clone spans the sequence coding for the entire GP66 (456 amino acids) and 19 amino acids of signal peptide. GP66 deduced from nucleotide sequence contained an Arg-Gly-Asp cell attachment sequence and had a 76% amino acid sequence homology with human vitronectin. Furthermore, EMR1a/212D recognized rabbit vitronectin purified by heparin-affinity chromatography. RNA blot hybridization detected one transcript of the same size in normal and Watanabe-heritable hyperlipidemic rabbit liver. The levels of plasma GP66 and liver GP66 mRNA were not altered, whereas 9-fold greater accumulation of GP66 was observed in thoracic aorta of Watanabe-heritable hyperlipidemic rabbit. These results suggest that GP66 is rabbit vitronectin and that it is vitronectin which selectively accumulates in thoracic aorta with the development of atherosclerosis.

Amino Acid Sequence↗
PubMed1990

[The significance of serum fructosamine measurement in patients with thyroid diseases].

Serum fructosamine was measured in patients with Graves' disease and primary hypothyroidism. Fructosamine levels and fructosamine per albumin ratio were significantly lower in patients with Graves' disease than in normal subjects, while they were significantly higher in patients with primary hypothyroidism. Fructosamine levels were normalized by treatment in the euthyroid state in patients with Graves' disease. Along with the normalization of thyroid stimulating hormone levels, fructosamine levels returned to the normal range in patients with primary hypothyroidism with treatment. There were significant correlations between fructosamine levels and free triiodothyronine levels, free thyroxine levels, thyroid stimulating hormone levels, hemoglobin A1C levels, albumin levels, and creatine phosphokinase levels. We concluded that it was useful to measure serum fructosamine as an indicator of peripheral metabolic function in patients with thyroid diseases.

Creatine Kinase↗
PubMed1990

Paracrine growth stimulation of androgen-responsive Shionogi Carcinoma 115 by its autonomous subline (Chiba Subline 2).

Shionogi Carcinoma 115 cells (SC 115 cells) and Chiba Subline 2 cells (CS 2 cells) are clones of an androgen-responsive mouse tumor cell line and its autonomous subline, respectively. Since it was reported that the growth of cells from SC 115 was regulated by an androgen-induced fibroblast growth factor (FGF)-like peptide (1), the present study was aimed at examining whether a similar growth factor was secreted by CS 2 cells in the absence of testosterone. Although SC 115 cells did not grow in the serum-free medium without androgens, SC 115 cells could proliferate in mixed culture with CS 2 cells, suggesting stimulation of SC 115 cells by CS 2 cells. It was shown that CS 2 cells secreted a growth factor without the influence of testosterone, and this factor promoted the growth of SC 115 and CS 2 cells, as well as that of BALB/3T3 cells. The factor was partially purified from serum-free conditioned medium obtained from cultures of CS 2 cells. It showed an affinity for heparin, stability to heat and acid treatments, a decrease in activity when anti-basic FGF antibody was added to cultures, and an estimated molecular weight of approximately 50,000. Therefore, the factor seemed to have the nature of an FGF-like peptide. It was concluded that, in the absence of testosterone, CS 2 cells produced an FGF-like growth factor which controlled the growth of both CS 2 cells and parent SC 115 cells, in autocrine and paracrine manners, respectively.

Animals↗
PubMed1990

Degradation of newly synthesized apolipoprotein B-100 in a pre-Golgi compartment.

The synthesis and secretion of apolipoprotein (apo) B-100 have been studied in a human hepatoblastoma cell line, the Hep G2 cells. Pulse-chase analysis showed that apoB-100 was not quantitatively recovered in the culture medium. To reveal the intracellular degradation of apoB-100 prior to secretion, cells were incubated with 1 microgram/ml Brefeldin A (BFA) which impeded protein transport from the endoplasmic reticulum (ER) to the Golgi apparatus and the fate of apoB-100 retained in the cells was traced at 37 degrees C. A significant amount of intracellular apoB-100 (40-60%/h) was degraded during the chase period, whereas apoA-1 remained intact. ApoB-100 degradation was temperature dependent, no degradation was observed below 20 degrees C. This degradation process was not inhibited by chloroquine, leupeptin, pepstatin, and chymostatin, suggesting that lysosomal proteases were not involved and that apoB-100 was degraded in a pre-Golgi compartment which is either part of, or closely related to, the ER. Preincubation of cells with low density lipoproteins (LDL) induced a 22-32% increase in the degradation of apoB-100. This result raised the possibility that secretion of apoB-100 might be regulated through the intracellular degradation of apoB-100. These results suggest the existence of the degradation pathway for apoB-100 in a pre-Golgi compartment and an unique regulatory mechanism for apoB-100 secretion.

Anti-Bacterial Agents↗
PubMed1990

Blocking effect of 1389-S on the sodium current in isolated guinea-pig ventricular myocytes.

Under whole cell patch conditions, 1389-S blocked the INa in guinea-pig ventricular myocytes under steady state conditions (Kdrest = 30 microM, Kdi = 2.4 microM) with a shift of the inactivation curve to the hyperpolarizing direction. Both brief and long conditioning pulses could produce a use-dependent block of 1389-S. These results suggest that 1389-S had a higher affinity to the inactivated than to the rested state under steady state conditions and had a higher affinity to the activated state during train pulses as well as to the inactivated state, making channels unavailable for conduction upon activation.

Animals↗
PubMed1990

The effect of HMG-CoA reductase inhibitor (CS-514) on the synthesis and secretion of apolipoproteins B and A-1 in the human hepatoblastoma Hep G2.

Human hepaotoblastoma cells (Hep G2) were cultured with a competitive inhibitor of HMG-CoA reductase, CS-514. The synthesis of cholesterol was markedly inhibited after 1 h preincubation with CS-514. The synthesis and secretion of apolipoprotein (apo) B and A-1, however, were not affected. A long-term incubation (21-24 h) of cells with CS-514 did not change apo B synthesis and secretion, although a slight depression of apo A-1 synthesis was observed. Hep G2 cells were found to secrete LDL- and HDL-like lipoproteins which were poor in cholesterol when cells were incubated with the drug. These results suggest that the modulation of cholesterol synthesis affects neither the synthesis and secretion of apo B and A-1 nor the formation of lipoproteins.

Apolipoprotein A-I↗
PubMed1990

Human scalp hair as evidence of individual dosage history of haloperidol: a possible linkage of haloperidol excretion into hair with hair pigment.

We report a method for determining haloperidol concentration in human scalp hair and discuss a possible linkage of haloperidol excretion into hair with the hair pigment melanin. First, an animal study was conducted to support the idea that hair contains amounts of haloperidol corresponding to the doses given and pigmented hair contains much more drug than does unpigmented hair. The haloperidol concentration was measured using a radioimmunoassay technique after hairs were dissolved in 2.5 N NaOH solution and the drug extracted. Pigmented and albino rats, whose hair from an area on the back had been removed beforehand by plucking, were administered either 1, 3, or 10 mg of haloperidol (i.p.) per kg body weight every day for 3 weeks. At the end of the administration period hair which had newly grown on the denuded area was plucked and collected. In each of the two groups classified by hair color the drug levels in the hair correlated with the doses given; however, the concentrations in the hair from the albino rats were much lower than those in the hair from the pigmented rats (which was less than 8.5%). Second, black and white hair was collected from each of seven human subjects with grizzled hair, who were receiving or had been administered haloperidol at fixed daily doses for more than 1 month, and the concentration of haloperidol in each type of hair was measured. In the same subject the concentration in the white hair was found to be much lower than that in the black (less than 10%).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

Human scalp hair as evidence of individual dosage history of haloperidol: longer-term follow-up study.

The patients reported in our previous paper were followed further, by analyzing hair samples collected monthly for 4 or 5 months, while growing hair continues to reflect the individual dosage history of haloperidol. In patients in whom the drug had been discontinued, the portion of hair that reflected the change of dose continued to move upward. In hair of patients in whom the dosage was decreased by one-half, the portion of change was also shown to move upward. These results indicate the potential usefulness of hair for assessing the individual past dosage history of haloperidol.

Adolescent↗