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Biomedical subjects

K Iwaki

Publications and source records attributed to K Iwaki.

At least 19 recordsLinked to original sources
PubMed1992

Determination of tetracycline antibiotics by reversed-phase high-performance liquid chromatography with fluorescence detection.

A highly sensitive method for the determination of tetracycline antibiotics (TCs) using reversed-phase high-performance liquid chromatography with fluorescence detection is presented. This method was based on the use of disodium ethylenediaminetetraacetate (EDTA) and calcium chloride as fluorescence-increasing reagents in the mobile phase. The concentrations of each reagent in the mobile phase greatly influenced the fluorescence intensity of TCs. When the concentration of EDTA and calcium chloride were 25 and 35 mM, respectively, and the pH of the mobile phase was 6.5, the maximum fluorescence intensity was obtained. The column temperature hardly influenced the fluorescence intensity. At 3.75 ng of TCs injected, the precision (relative standard deviation) ranged from 1.12 to 2.20%. In the range 0.075-37.5 ng for tetracycline and oxytetracycline and 0.225-37.5 ng for chlortetracycline, a linear response was observed. The detection limits of this method were 49-190 pg for three different TCs. The proposed method was applied to the determination of one of the TCs in pharmaceuticals by the internal standard method using other TCs as internal standards and was also applied to determination of TCs added to fish tissue.

Animals↗
PubMed1992

[Concomitant graft replacement of the total aortic root and the transverse aortic arch for type A aortic dissection associated with annuloaortic ectasia].

Between April 1988 and February 1992, eight patients with type A aortic dissection associated with annuloaortic ectasia (AAE) underwent the concomitant graft replacement of the total aortic root and the transverse aortic arch at our institution. The acuity of the aortic dissection was acute stage in 3 patients and chronic stage in 5 including 3 cases of re-do operation. All operations were performed with an aid of extracorporeal circulation, blood cardioplegia, selective cerebral perfusion and open distal anastomosis. The operative techniques employed in this series consisted of total aortic root replacement using a composite graft (Bentall, Cabrol or Piehler's technique), and total arch replacement using en bloc arch reconstruction or three vessels graft replacement. One patients underwent re-do operation for coronary anastomotic false aneurysm following Bentall operation and aneurysmal dilatation of the false lumen at the aortic arch, and died of LOS because of the prolonged myocardial ischemia. Other seven patients survived the operation, and lead the normal life at the present time. The present data suggests that type A aortic dissection associated with AAE involving aortic arch could be treated by concomitant graft replacement of the total aortic root and the transverse aortic arch.

Adult↗
PubMed1990

Alpha- and beta-adrenergic stimulation induces distinct patterns of immediate early gene expression in neonatal rat myocardial cells. fos/jun expression is associated with sarcomere assembly; Egr-1 induction is primarily an alpha 1-mediated response.

The present study was designed to determine if alpha- and beta-adrenergic stimulation of neonatal rat myocardial cells might induce common and/or distinct members of the immediate early gene program and to assess whether their induction might correlate with the differential effects of these adrenergic agonists on cardiac gene expression, sarcomere assembly, and several features of myocardial cell hypertrophy. Alpha- and beta-adrenergic stimulation of neonatal rat myocardial cells both produce an increase in the assembly of an individual contractile protein (myosin light chain-2) into organized sarcomeric units and also rapidly induce mRNAs for the immediate early genes c-fos and c-jun, thereby suggesting a potential role for these protooncogenes in sarcomerogenesis. alpha-Adrenergic stimulation results in the co-induction of mRNAs encoding a zinc finger protein gene (Egr-1). However, beta-adrenergic stimulation does not produce a significant increase in the levels of Egr-1 mRNA, providing the first evidence in any cell system that c-fos and Egr-1 expression can regulated separately. Studies with norepinephrine in combination with various adrenergic receptor antagonists revealed that the induction of Egr-1 is primarily an alpha 1-mediated, pertussis toxin-insensitive response. These studies provide the first evidence for the induction of immediate early genes following adrenergic stimulation of myocardial cells and demonstrate alpha- and beta-adrenergic stimulation can rapidly activate the expression of common and distinct subsets of these transcriptional regulators. Since alpha- and beta-adrenergic agonists have differential effects on cardiac gene expression and on the acquisition of several features of myocardial cell hypertrophy, the induction of Egr-1 provides a potential mechanism for the induction of genes that are exclusively induced during alpha-adrenergic-mediated myocardial cell hypertrophy.

Animals↗
PubMed1990

Precolumn derivatization technique for high-performance liquid chromatographic determination of penicillins with fluorescence detection.

A precolumn derivatization method was developed for the high-performance liquid chromatographic (HPLC) determination of penicillins using fluorescence detection. Penicillins were derivatized by a two-step reaction, the beta-lactam ring being opened by hydrolysis in aqueous sodium carbonate solution in the first step to give a secondary amine functionality, and the secondary amino group being reacted with 7-fluoro-4-nitrobenzo-2-oxa-1,3-diazole in the second step to give a fluorescent derivative. The resulting reaction mixture was injected directly onto a reversed-phase column and analysed by HPLC. At a penicillin concentration of 10 micrograms/ml, the precision (relative standard deviation) ranged from 1.49 to 2.20%. In the concentration range 0.2-100 micrograms/ml, a linear response was observed. The detection limits of this method were 30-85 ng/ml for five different penicillins at a signal-to-noise ratio of 3:1. The proposed method was applied to the determination of penicillins added to serum following pretreatment by deproteinization and removal of compounds containing amino functionalities with a cation-exchange resin.

Chromatography, High Pressure Liquid↗
PubMed1990

Phorbol esters induce immediate-early genes and activate cardiac gene transcription in neonatal rat myocardial cells.

The mechanisms which transduce intracellular signals for the accumulation of myofibrillar protein during the onset of myocardial cell hypertrophy are unknown. Although previous studies in skeletal muscle cells have suggested that the activation of protein kinase C induces de-differentiation, including the selective disassembly of myofibrils and inhibition of myofibrillar protein synthesis, the present study demonstrates that phorbol esters which activate protein kinase C lead to the accumulation of an individual contractile protein, myosin light chain-2 (MLC-2) and produce several features of myocardial cell hypertrophy. Utilizing immunoblotting and indirect immunocytofluorescence with MLC antisera, the present study demonstrates a several-fold increase in the content of MLC-2, and a marked increase in the assembly of MLC into organized contractile units in individual neonatal rat myocardial cells following treatment with phorbol 12-myristate 13-acetate (PMA). The concentration of PMA required to elicit this response and the lack of a response with an inactive phorbol ester is consistent with the activation of a protein kinase C dependent pathway. Furthermore, PMA treatment results in the rapid induction of a program of immediate-early gene expression (including the c-fos and c-jun proto-oncogenes, and an inducible zinc finger containing gene, egr-l), and activates cardiac gene transcription as assessed by nuclear run-on analyses. The results of the present study suggest the possibility that a protein kinase C dependent pathway may be involved in the up-regulation of myofibrillar protein content and the activation of cardiac gene transcription during growth and hypertrophy of neonatal rat myocardium, and that the induction of a program of immediate-early gene expression may be linked to this response.

Animals↗
PubMed1990

Increased numbers of CD8+CD11+, CD8+CD11- and CD8+Leu7+ cells in patients with chronic graft-versus-host disease after allogeneic bone marrow transplantation.

Peripheral blood lymphocytes from 25 allogeneic bone marrow transplant recipients were studied serially using flow cytometry and two colour analysis. Fourteen patients were transplanted for haematologic malignancies, eight for aplastic anaemia, two for congenital immunodeficiencies and one for Morquio's disease. All patients were alive more than 100 days post-grafting; nine patients had chronic graft-versus-host disease (GVHD). Dual labelling with monoclonal antibodies, CD4/2H4, CD4/4B4, CD8/CD11, CD8/HLA-DR and CD8/Leu 7 was used to analyse the surface phenotypes of lymphocytes. The population of CD4+2H4+ cells was decreased, and CD8+CD11+, CD8+CD11- and CD8+Leu7+ cells were markedly increased in patients with chronic GVHD. The increase of CD8+CD11+, CD8+CD11- and CD8+Leu7+ cells closely correlated with clinical signs of chronic GVHD in each patient. These results suggest that CD8+ cells may play an important role in effector and/or suppressor mechanisms of chronic GVHD and could be used as an indicator of need for and response to treatment.

Adolescent↗
PubMed1989

Fluorescence intensity analysis through simplex optimization in flow cytometry.

Fluorescence intensity analysis in flow cytometric surface immunophenotyping has recently been appreciated in clinical applications. A curve fitting method to estimate the mean and SD values of fluorescence intensity is described in this report. A Gaussian distribution is aimed to be adapted for a specified distribution in logarithmically scaled histogram data through the simplex optimization, one of the non-linear least squares methods. In comparison with the conventional methods which include the detection of peak point and the direct calculation, this fitting method has demonstrated exceeding precisions in the estimation of both parameters with limited involved cell counts in typical lymphocytic phenotyping. The actual estimation for a precise SD value will develop the quality control approaches based on the fluorescence intensity analysis. While this method is not suitable for distributions that involve extremely small cell counts or that deviate markedly from a symmetric Gaussian, it has additional advantages of loose requirements, namely, narrow fitting regions, ordinarily small cell counts, practical computational periods and a simple programming.

Antigens, Surface↗
PubMed1988

Effect of 711389-S, a new antiarrhythmic agent, on myocardial energy metabolism in guinea-pigs and rats.

The effect of 711389-S, a new antiarrhythmic agent, on myocardial energy metabolism was investigated using anaesthetized guinea-pigs and rats. 711389-S elevated the adenylate energy charge and phosphorylation potential in normal guinea-pig myocardium. Large doses also increased the myocardial lactate content with ECG abnormalities. The close relationship between rate-pressure product and the myocardial energy state under 711389-S treatments showed the suppression of energy consumption due to a decrease of work output. In guinea-pigs with arrhythmic myocardia induced by intravenous infusion of ouabain, 711389-S prevented the loss of high-energy phosphate compounds and the acceleration of anaerobic glycolysis concomitant with the effective antiarrhythmic property. In ischaemic myocardium produced by ligation of the coronary artery in rats, 711389-S suppressed the decreases of creatine phosphate, NAD+ and adenylate energy charge. Moreover, this agent effectively blocked the incidence of ventricular arrhythmias at an early stage following the ligation. In all of these actions, 711389-S was more effective than disopyramide, which is in the same class of antiarrhythmics. 711389-S was concluded to be a favourable antiarrhythmic agent offering beneficial action against arrhythmic and ischaemic metabolic changes in the myocardium.

Animals↗
PubMed1987

Amino acid analysis by reversed-phase high-performance liquid chromatography. Automatic pre-column derivatization with activated carbamate reagent.

Succinimido alpha-naphthylcarbamate, an activated carbamate reagent, facilitated the simple and rapid pre-column derivatization of amino acids for fluorimetric detection. The method is based on the formation of naphthylcarbamyl derivatives of amino acids. The carbamylation of amino acids is completed within 1 min at room temperature, and the reaction mixture can be injected directly into a liquid chromatograph equipped with an octadecylsilyl reversed-phase column. The effluent stream is monitored fluorimetrically at 370 nm excited at 290 nm at the sub-picomole level. Naphthylcarbamyl derivatives of common protein amino acids were separated within 30 min by gradient elution with aqueous sodium acetate and acetonitrile. Excess of the reagent does not interfere with the analysis of amino acids, because it is hydrolysed in 2-3 min to give naphthylamine, which is more strongly retained than any amino acid derivatives.

Amino Acids↗
PubMed1987

Optical resolution of enantiomeric amino acid derivatives on a naphthylethylurea multiple-bonded chiral stationary phase prepared via an activated carbamate intermediate.

A new chiral stationary phase (CSP) was developed for the direct optical resolution of enantiomeric amino acid derivatives. The CSP was readily prepared by a three-step reaction carried out in a pre-packed aminopropylsilyl silica gel column. In the first step, a solution of disuccinimido carbonate (DSC) was delivered through the pre-packed column to give a succinimido carbamyl aminopropylsilyl-bonded, activated-carbamate type silica gel (ACsil) column. Through the column was then delivered a solution of pentaethylenehexamine to afford a polyamine-bonded column. Finally, a solution of optically active succinimido (S)- or (R)-naphthylethyl carbamate was delivered through the polyamine column, to give a naphthylethylurea multiple-bonded CSP. p-Bromophenylcarbamyl derivatives of enantiomeric protein amino acids were resolved on these CSPs by elution with an aqueous mobile phase. Simultaneous analysis of these amino acid enantiomers by means of gradient elution was also accomplished.

Amino Acids↗
PubMed1987

The binding rate of sialic acid to serum alpha 1-acid glycoprotein in patients with chronic hepatic injury.

The level of serum orosomucoid, the amount of sialic acid binding to it, and the binding rate of sialic acid to orosomucoid in normal individuals and in patients with chronic hepatitis and liver cirrhosis were determined by affinity column chromatography, SDS electrophoresis and the method of Warren. Although no apparent changes in the level of serum orosomucoid or the amount of sialic acid binding to it in each group were seen, the binding rate of sialic acid to orosomucoid in chronic persistent hepatitis and chronic active hepatitis showed a remarkable increase, compared with normal individuals and patients with liver cirrhosis. Furthermore, the binding rate of sialic acid in liver cirrhosis was the lowest in each group.

Adult↗
PubMed1987

Adherence of Fusobacterium necrophorum to bovine ruminal cells.

The adherence of Fusobacterium necrophorum to the surface of bovine ruminal epithelial cells was paralleled by the organism's haemagglutinating ability. Treatment of the bacterial cells with haemagglutinin antiserum caused a reduction in the degree of attachment. The purified haemagglutinin became bound to the membranes of ruminal epithelial cells but lost its adherence when pre-incubated with haemagglutinin antiserum. These findings suggest that the adherence of F. necrophorum to the membrane of the ruminal cells is mediated by haemagglutinin.

Animals↗
PubMed1987

A new uricosuric diuretic, S-8666, in rats and chimpanzees.

5-Dimethylsulfamoyl-6,7-dichloro-2,3-dihydrobenzofuran-2-carboxyli c acid (S-8666) was studied as a possible new uricosuric diuretic agent using rats and chimpanzees. Various new compounds belonging to the 5-sulfamoyl-6,7-dichloro-2,3-dihydrobenzofuran-2-carboxylic acids were clearly diuretic with uricosuric activity in intraperitoneally oxonate-treated rats. S-8666 was chosen as a favorable candidate because its uricosuric activity due to the effects of tubular transport of uric acid were apparently more marked than those of known uricosuric agents such as probenecid, benzbromarone, tienilic acid and indacrinone in oxonate-treated rats. S-8666 was also uricosuric in rats not given urate oxidase inhibitor. The diuretic effect of S-8666 in oxonate-treated rats was as high-ceilinged as that of furosemide, while those of tienilic acid, indacrinone and a known compound of a 5-carbonyl-6,7-dichloro-2,3-dihydrobenzofuran-2-carboxylic acid were rather low-ceilinged. These uricosuric and diuretic activities of S-8666 were manifested by two enantiomers, of which the (+)-enantiomer displayed predominantly uricosuric activity and the (-)-enantiomer, diuretic activity like furosemide. The new compound was also uricosuric and diuretic in chimpanzees, although the potency of the uricosuric activity was similar to that of probenecid and less than that of indacrinone. Thus, it seems that S-8666 is a different type of uricosuric diuretic from known agents which have already been tried in humans.

Animals↗
PubMed1987

A new diuretic that does not reduce renal handling of uric acid in rats, S-8666.

The uric acid-retaining effects of diuretics were studied using sodium-restricted spontaneously hypertensive rats. Test agents were administered orally once a day for two weeks. Diuretic thiazides such as trichlormethiazide and hydrochlorothiazide and loop diuretics such as furosemide and indacrinone clearly reduced the renal function for uric acid excretion in treatment which produced major effects such as diuresis, saluresis and hypotension. However, a new diuretic with uricosuric activity, S-8666, developed in our laboratories, had no effect on the renal handling of uric acid at doses which showed major effects similar to those of other diuretics. The results should aid the understanding of the utility of S-8666 as a new diuretic antihypertensive which does not cause hyperuricemia during therapy.

Animals↗
PubMed1987

Decreasing effect of allantoxanamide, a hyperuricemic agent on renal functions in rats.

Both potassium oxonate and allantoxanamide have been reported as useful reagents for inhibiting urate oxidase, with the hyperuricemic effect of allantoxanamide being longer-lasting than that of oxonate in rats. The present study was done to evaluate the utility of allantoxanamide for investigating problems concerning hyperuricemia using rats. A single intraperitoneal administration of 150 mg/kg allantoxanamide elevated the plasma uric acid level progressively during the experiment for 6 hr, resulting in a much higher level than that maintained by means of repeated dosing with 250 mg/kg potassium oxonate, i.p., at 2-hr intervals. Such a severe and long-lasting hyperuricemia caused by allantoxanamide was due to decreased renal function of uric acid excretion according to its nephrotoxicity in addition to the inhibition of urate oxidase like that by oxonate. Thus, we concluded that allantoxanamide might be a useful reagent for investigating the causes of hyperuricemia with renal failure, but was not a practical agent like oxonate in order to evaluate the response to uricosuric agents.

Animals↗