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S Miwa

Publications and source records attributed to S Miwa.

At least 145 records · Page 8Linked to original sources
PubMed1994

Monophasic action potentials in patients with torsades de pointes.

The initiating mechanism of torsades de pointes is still unclear, although it is believed to be related to repolarization abnormalities such as QT prolongation and abnormal U wave. Recording monophasic action potentials in vivo can provide useful information about ventricular repolarization. To investigate the mechanism of torsades de pointes, monophasic action potentials were recorded by the contact electrode method in 20 patients. The patients were classified into three groups (Group 1; 4 patients at the acute phase of torsades de pointes, Group 2; 6 patients at the improved phase of torsades de pointes, Group 3; 10 patients with bradyarrhythmias without torsades de pointes). Action potential duration 90% (duration from monophasic action potential upstroke to 90% repolarization), repolarization time (duration from QRS onset to 90% repolarization), and effective refractory period were measured at several right ventricular endocardial sites during spontaneous rhythm and right ventricular pacing at several pacing cycle lengths. Humps during the repolarization phase were observed in all of the patients in Group 1 and in 1 patient in Group 3 during spontaneous rhythm. Action potential duration 90% and repolarization time in Group 1 were significantly longer than those in Groups 2 and 3. The dispersion of action potential duration 90% and repolarization time in Group 1 were also greater than those in Groups 2 and 3. With rapid ventricular pacing, the hump observed in Group 1 either disappeared completely or the amplitude of the hump decreased, and the dispersion of the action potential duration 90% and repolarization time was also reduced. A significant correlation was observed between action potential duration 90% and effective refractory period. (r = 0.78, p < 0.001). In conclusion, these results suggest that the hump and the dispersion of repolarization play a key role in the genesis of torsades de pointes. Pacing therapy may be useful in correcting these abnormalities.

Action Potentials↗
PubMed1994

Hemolytic anemias.

Explore the source record for details and available documents.

Anemia, Hemolytic↗
PubMed1994

[JCCLS proposal for clinical allowance on values of blood cell count].

We investigated the clinically allowable error for laboratory quality control of blood cell count in Japan. We have asked 409 members of Japanese Association of Clinical Hematology for an appropriate clinical allowance on the values of red blood cell count (RBC), hemoglobin value (Hb), mean corpuscular volume (MCV), white blood cell count (WBC) and platelet count (PLT). We delivered the lists in which 5 different allowable errors (2, 3, 5, 10 and 20%) were indicated on each blood cell count so that each member could check one of them. The data were collected within a month and were analyzed with computer. The results showed that 312 (76.3%) members choose 3 or 5% as an allowable error for RBC, 393 (96.1%) selected 2, 3 or 5% for Hb, 314 (76.8%) choose 3 or 5% for MCV, 358 (77.5%) indicated 3, 5 or 10% for WBC and 294 (72.6%) selected 5 or 10% for PLT. Based on these data, we propose the following clinical allowances for the values of blood cell count; 4% for RBC, 3% for Hb, 4% for MCV, 5% for WBC and 7% for PLT.

Blood Cell Count↗
PubMed1994

[Aggressive management of prolapsed fetal membranes earlier than 26 weeks' gestation by emergent McDonald cerclage combined with amniocentesis and bladder overfilling].

During the period January, 1987-December, 1992, 32 pregnant women (33 fetuses) earlier than 26 weeks' gestation were admitted to our perinatal unit with incompetent cervix and prolapsed fetal membranes through the cervix (hourglassing). Eighteen pregnant women (19 fetuses) were managed aggressively with emergent double McDonald cerclage, which included preoperative amniocentesis and bladder overfilling to decompress and replace prolapsed fetal membranes. Fourteen pregnant women were managed conservatively with bed rest, tocolysis, and antibiotic therapy. The perinatal results of aggressive management were clearly more favorable than those of conservative management when compared: Prolongation of pregnancy 35.2 +/- 39.7 vs. 3.5 +/- 2.6 days (p < 0.01), gestational age at delivery 27.3 +/- 5.3 vs. 24.2 +/- 1.2 weeks' (p < 0.05), birth weight 1,260 +/- 909 vs. 690 +/- 124 grams (p < 0.05), and fetal salvage rates 74(14/19) vs. 7(1/14)%, respectively.

Amniocentesis↗
PubMed1994

Benign stricture of the intrahepatic bile duct with arterial involvement.

The absence of arterial change is one of the definitive findings of benign bile duct stricture. Here we report on a patient with a stricture of the intrahepatic bile duct with arterial involvement. Histological examination of the resected specimen revealed fibrous replacement of arterial media, with no evidence of malignancy.

Bile Duct Diseases↗
PubMed1993

G6PD Nara: a new class 1 glucose-6-phosphate dehydrogenase variant with an eight amino acid deletion.

In the course of molecular studies on Japanese glucose-6-phosphate dehydrogenase (G6PD) variants using single-strand conformation polymorphisms (SSCP) analysis, we found an unusual class 1 G6PD variant that had nucleotide deletion in exon 9. The patient showed chronic nonspherocytic hemolytic anemia associated with frequent episodes of severe hemolytic attack. The hemolysate exhibited no measurable activity. Although the partially purified enzyme had detectable activity, we could not perform kinetic studies because of its extreme instability. Nucleotide sequencing showed a unique 24 bp deletion at nucleotide 953-976 that predicts an eight amino acid deletion of TKGYLDDP at residue 319-326. While this is one of the most drastic structural alterations found in G6PD variants, the region with the amino acid deletion was distant from both the G6P and NADP+ binding sites and was located in a domain with low sequence homology among species. The comparatively low functional importance of the deleted region may have saved the patient from lethal tissue dysfunction.

Amino Acid Sequence↗
PubMed1993

Low substrate affinity of pyruvate kinase variant (PK Sapporo) caused by a single amino acid substitution (426 Arg-->Gln) associated with hereditary hemolytic anemia.

A point mutation (1277 CGG to CAG) was identified in the R-type pyruvate kinase (PK) cDNA of a PK variant, PK Sapporo, associated with hereditary non-spherocytic hemolytic anemia. The mutation causes a single amino acid substitution from Arg to Gln at the 426th amino acid residue of human R-type PK; consequently, the hydrophobicity around the mutated site is drastically decreased. The amino acid change occurred in the eighth alpha helix of A domain (A alpha 8) of PK, and it has been proposed that this region as well as A alpha 7, A beta 7, and A beta 8 is a potassium (K+) binding site. Because K+ binding to the PK subunit is considered to be essential for substrate binding, the mutation might account for the decreased affinity for phosphoenolpyruvate (PEP). This is compatible with the fact that all the reported PK variants carrying point mutations in those area have a high Michaelis constant (Km) for PEP.

Amino Acid Sequence↗
PubMed1993

Molecular basis of impaired pyruvate kinase isozyme conversion in erythroid cells: a single amino acid substitution near the active site and decreased mRNA content of the R-type PK.

Conversion of pyruvate kinase (PK) isozymes from M2- to R-PK has been observed during erythroid cell maturation. To understand this mechanism, we analyzed the PK gene of a R-PK deficient patient, in whose erythrocytes the M2-PK was persistently expressed. A point mutation, 1102 GTC-->TTC was identified in the R-PK cDNA, and it caused a single amino acid substitution from 368Val-->Phe. The residue is very close to the 372nd Gln, the putative binding site of the monovalent cation (K+). The impaired K+ binding would cause the decreased affinity for phosphoenolpyruvate, consequently the variant PK may be extremely unstable. Although the proband's other PK allele did not have any structural change, the R-PK mRNA level in reticulocytes was decreased. These findings suggested that both the structural mutation near the active site and the decreased mRNA level of the R-PK were responsible for the disorder.

Amino Acid Sequence↗
PubMed1993

Enhancement of acetylcholine release in the hippocampus by 6R-L-erythro-5,6,7,8-tetrahydrobiopterin is mediated by 5-hydroxytryptamine.

Recently, we reported that 6R-L-erythro-tetrahydrobiopterin (6R-BH4), a natural cofactor for L-aromatic amino acid hydroxylases, enhances in vivo release of acetylcholine (ACh) in the rat hippocampus: the enhancement was abolished after depletion of brain catecholamines and 5-hydroxytryptamine (5-HT) by pretreatment with reserpine. In the present study, we have used in vivo brain microdialysis to clarify the neuronal mechanism involved in the enhancement of ACh release by 6R-BH4. After depletion of catecholamines by pretreatment of rats with alpha-methyl-p-tyrosine, 6R-BH4 added to the perfusion fluid still induced an increase in extracellular ACh levels monitored by microdialysis as an index of ACh release. In contrast, after depletion of 5-HT by pretreatment with p-chlorophenylalanine, most of the 6R-BH4-induced enhancement was eliminated. Exogenous 5-HT and dopamine (DA) but not noradrenaline added to the perfusion fluid stimulated ACh release with 5-HT being far more potent. Intraperitoneal administration of 5-hydroxytryptophan and L-DOPA also enhanced ACh release, presumably by their conversion to 5-HT and catecholamines, respectively. Administration of 6R-BH4 increased hippocampal 5-HT release, as indicated by increased extracellular levels of the major 5-HT metabolite, 5-hydroxyindoleacetic acid. These results suggest that 6R-BH4 stimulates ACh release in the hippocampus, mainly by augmenting release of 5-HT, a potent stimulator of ACh release, and partly by augmenting release of DA.

5-Hydroxytryptophan↗
PubMed1993

Hereditary triosephosphate isomerase (TPI) deficiency: two severely affected brothers one with and one without neurological symptoms.

A 13-year-old Hungarian boy (B.J.Jr.) with congenital haemolytic anaemia (CHA) and hyperkinetic torsion dyskinesia was found to have severe triose-phosphate isomerase (TPI) deficiency. One of his two brothers (A.J.), a 23-year-old amateur wrestler, has CHA as well, but no neurological symptoms. Both have less than 10% TPI activity and a highly increased dihydroxyacetone phosphate (DHAP) level in their red blood cells. Their TPI had a slow electrophoretic mobility and was heat unstable. Both parents and a third brother are healthy heterozygous carriers of the defect. A.J. represents a unique phenotype from the point of view that all published "homozygotes" had severe neurological alterations from infancy or early childhood except one infant who died at 11 months, probably too young for neurological symptoms to be noted. In contrast to the two affected Hungarian brothers all but one "homozygote" has died before the age of 6 years. The striking difference in the clinical course of the defect between the two brothers with the same severe red blood cell enzyme deficiency may originate from unusual differences between two double heterozygous brothers resulting inter alia in different levels of TPI expression in various tissues. Significantly lower TPI activities were found in both the T- and B-cells of the propositus as compared to the respective cells of the neurologically symptom-free brother.

Adult↗
PubMed1993

Molecular abnormality of G6PD Konan and G6PD Ube, the most common glucose-6-phosphate dehydrogenase variants in Japan.

G6PD Konan and G6PD Ube are the most common glucose-6-phosphate dehydrogenase (G6PD) variants found in Japan. To clarify the molecular abnormality of these two variants, the entire coding region was amplified by polymerase chain reaction from genomic DNA (G6PD Konan) or cDNA (G6PD Ube). Direct sequencing revealed that both variants have the same nucleotide substitution (241 C to T) in exon 4, which predicts an Arg to Cys substitution at amino acid 81.

Arginine↗
PubMed1993

Effect of granulocyte-macrophage colony-stimulating factor on chemotherapy-induced granulocytopenia in patients with malignancies.

To investigate the effect of recombinant human granulocyte-macrophage colony-stimulating factor (rhGM-CSF) on cytotoxic chemotherapy-induced granulocytopenia, we performed an open nonrandomized clinical trial in 46 patients with malignancies receiving cytotoxic chemotherapy regimen. Twenty-six patients who received two cycles of the identical chemotherapy regimen and had granulocytopenia less than 1 x 10(9) cells/l after the first cycle of chemotherapy were eligible for this study. They received 60, 125 or 250 micrograms/m2/day of rhGM-CSF randomly. The nadirs of peripheral granulocytes demonstrated significantly much higher levels in all dosages studied than those of control cycles. The duration of granulocytopenia was shortened with rhGM-CSF support. Such granulocyte recovery appeared in parallel with increasing dosages of GM-CSF, thus, infections with febrile episodes were reduced. Toxicity of rhGM-CSF was generally well tolerated.

Adult↗