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Biomedical subjects

S Miwa

Publications and source records attributed to S Miwa.

At least 73 records · Page 4Linked to original sources
PubMed1998

Delayed onset of hemolytic anemia in CBA-Pk-1slc/Pk-1slc mice with a point mutation of the gene encoding red blood cell type pyruvate kinase.

The Pk-1slc gene encodes a mutant red blood cell (RBC) type pyruvate kinase (PK), and adult CBA-Pk-1slc/Pk-1slc mice show a severe nonspherocytic hemolytic anemia. However, the number of RBCs and the proportion of reticulocytes were comparable between neonatal CBA-Pk-1slc/Pk-1slc mice and control -+/+ mice. Since the age-dependent increase of RBCs was much greater in CBA-+/+ mice than in CBA-Pk-1slc/Pk-1slc mice, significant anemia was observed in the latter mice on day 14 after birth. The increase of RBCs in CBA-+/+ mice was due to the prolongation of their survival time. The half life of RBCs increased in CBA-+/+ mice with ages, but it decreased in CBA-Pk-1slc/Pk-1slc mice. The relatively longer half life of RBCs in neonatal CBA-Pk-1slc/Pk-1slc mice appeared to be due to the delayed switching from M2-type PK that are expressed by undifferentiated erythroid precursor cells to RBC-type PK that are expressed by mature RBCs.

Age of Onset↗
PubMed1998

Nuclear inclusions of the androgen receptor protein in spinal and bulbar muscular atrophy.

Spinal and bulbar muscular atrophy (SBMA) is an X-linked motor neuronopathy caused by the expansion of an unstable CAG repeat in the coding region of the androgen receptor (AR) gene. To study AR protein expression in normal and SBMA individuals, we used several antibodies that recognize AR protein, and analyzed neural and nonneural tissues by immunohistochemistry and western blotting. Both the normal and the mutant AR proteins were widely distributed, predominantly, but not exclusively, in the cytoplasm of neurons regardless of the pathological involvement, and predominantly in the nuclei of the nonneural tissues in both normal and SBMA individuals, with different expression levels of AR protein among different tissues. In the motor neurons of SBMA patients, there were AR-immunoreactive ubiquitinated nuclear inclusions that were detected by antibodies that recognize a small portion of the N terminus of the AR protein. Absence of other immunoreactive AR epitopes within the inclusion may be due to altered AR configuration, or masking of AR epitopes by other proteins, or proteolytic cleavage of the AR. Our data show that, in addition to the normal cellular distribution of the AR protein, mutant AR-bearing nuclear inclusions are present in SBMA.

Aged↗
PubMed1998

Expression and enzymatic characterization of human glucose phosphate isomerase (GPI) variants accounting for GPI deficiency.

To elucidate the structure-function relationships in glucose phosphate isomerase (GPI), we established an expression system for human GPI as a fusion protein with glutathione S-transferase (GST) in E. coli. The GST-GPI fusion protein showed affinities for the substrates glucose 6-phosphate (G6P) and fructose 6-phosphate (F6P) similar to those of the native enzyme purified from human red blood cells (RBC). We expressed GPI cDNAs with four distinct disease-causing mutations and examined their enzymatic characteristics. Although each mutation caused reduced thermal stability, an amino acid substitution Thr-5-->Ile (T5I) exhibited marked thermal instability, suggesting that the amino-terminal of GPI is important for enzymatic stability. Thr-224 seemed not to be an essential residue, since the amino acid substitution Thr-224-->Met (T224M) showed normal substrate affinity in spite of a slight decrease in both specific activity and thermostability. Gln-343 and Asp-539 have been shown to be in close proximity to the putative catalytic sites, and the present study showed that both Gln-343-->Arg (Q343R) and Asp-539-->Asn (D539N) caused impaired substrate affinity; Q343R showed high Km for both G6P and F6P, whereas D539N showed significantly decreased affinity only for F6P. These results suggest that not only reduced enzymatic stability but also impaired kinetics may disturb RBC metabolism of the GPI variants associated with hereditary hemolytic anemia.

Amino Acid Sequence↗
PubMed1998

Differential gene expression of thyroid hormone receptor alpha and beta in fish development.

To understand the mechanisms of flounder metamorphosis, which is controlled by thyroid hormone, gene expression of the thyroid hormone receptors (TR alpha A, TR alpha B, TR beta 1, and TR beta 2) was studied in developing flounder larvae, using quantitative reverse-transcriptase polymerase chain reaction and in situ hybridization. TR gene transcripts were found at very low levels in fertilized flounder eggs. Substantial amounts of TR mRNAs were present in premetamorphic larvae, except for TR alpha B mRNA, which was low throughout larval development. TR alpha A gene transcripts increased rapidly in metamorphic climax and decreased rapidly postclimax. The expression level of TR beta s increased in climax, reached its peak postclimax, and remained high in metamorphosed juveniles. In situ hybridization confirmed the decrease in TR alpha transcripts in most tissues postclimax and further revealed the ubiquitous expression of TR genes and distinct tissue specificity of alpha and beta subtypes in the overall fish body. These results suggest that thyroid hormone exerts effects directly on each tissue during fish metamorphosis and that gene expression of TR subtypes is differentially regulated both temporally and regionally. Thus, the results suggest that the development of each tissue of the flounder by thyroid hormone is further controlled at the receptor level by the differential expression of TRs.

Animals↗
PubMed1998

Mycotic aneurysm of the left coronary artery.

We report a 24-year-old man with mitral valve endocarditis complicated by acute myocardial infarction due to coronary embolism. Percutaneous transluminal coronary angioplasty and subsequent mitral valve replacement were performed. Postoperative coronary angiography revealed formation of a mycotic aneurysm of the left anterior descending coronary artery at the site of balloon inflation. The patient then underwent successful resection of the aneurysm with coronary artery bypass grafting.

Adult↗
PubMed1998

Red blood cell enzymes and their clinical application.

Red blood cell enzyme activities are measured mainly to diagnose hereditary nonspherocytic hemolytic anemia associated with enzyme anomalies. At least 15 enzyme anomalies associated with hereditary hemolytic anemia have been reported. Some nonhematologic disease can also be diagnosed by the measurement of red blood cell enzyme activities in the case in which enzymes of red blood cells and the other organs are under the same genetic control. Progress in molecular biology has provided a new perspective. Techniques such as the polymerase chain reaction and single-strand conformation polymorphism analysis have greatly facilitated the molecular analysis of erythroenzymopathies. These studies have clarified the correlation between the functional and structural abnormalities of the variant enzymes. In general, the mutations that induce an alteration of substrate binding site and/or enzyme instability might result in markedly altered enzyme properties and severe clinical symptoms.

Anemia↗
PubMed1998

Activation of two types of Ca2+-permeable nonselective cation channel by endothelin-1 in A7r5 cells.

1. In A7r5 cells loaded with the Ca2+ indicator fura-2, we examined the effect of a Ca2+ channel blocker SK&F 96365 on increases in intracellular free Ca2+ concentrations ([Ca2+]i) and Mn2+ quenching of fura-2 fluorescence by endothelin-1 (ET-1). Whole-cell patch-clamp was also performed. 2. Higher concentrations (> or = 10 nM) of ET-1 (higher [ET-1]) evoked a transient peak and a subsequent sustained elevation in [Ca2+]i: removal of extracellular Ca2+ abolished only the latter. A blocker of L-type voltage-operated Ca2+ channel (VOC) nifedipine at 1 microM reduced the sustained phase to about 50%, which was partially sensitive to SK&F 96365 (30 microM). 3. Lower [ET-1] (< or = 1 nM) evoked only a sustained elevation in [Ca2+]i which depends on extracellular Ca2+. The elevation was partly sensitive to nifedipine but not SK&F 96365. 4. In the presence of 1 microM nifedipine, higher [ET-1] increased the rate of Mn2+ quenching but lower [ET-1] had little effect. 5. In whole-cell recordings, both lower and higher [ET-1] induced inward currents at a holding potential of -60 mV with linear I-V relationships and reversal potentials close to 0 mV. The current at lower [ET-1] was resistant to SK&F 96365 but was abolished by replacement of Ca2+ in the bath solution with Mn2+. The current at higher [ET-1] was abolished by the replacement plus SK&F 96365. 6. In a bath solution containing only Ca2+ as a movable cation, ET-1 evoked currents: the current at lower [ET-1] was sensitive to Mn2+, whereas that at higher [ET-1] was partly sensitive to SK&F 96365. 7. These results indicate that in addition to VOC, ET-1 activates two types of Ca2+-permeable nonselective cation channel depending on its concentrations which differ in terms of sensitivity to SK&F 96365 and permeability to Mn2+.

Animals↗
PubMed1998

p53 gene mutation in 150 dissected lymph nodes in a patient with esophageal cancer.

For thoracic esophageal cancer, we perform extended three field lymph node dissection, and have achieved nearly 50% of overall 5-year survival. However, patients sometimes develop lymph node recurrences in spite of having no lymph node metastases found by conventional histopathologic examination. In a patient with esophageal squamous cell carcinoma, we sequenced all the p53 cDNA translated regions (exon 2-10) of primary carcinoma, and confirmed one p53 nonsense mutation in exon 10. Then we extracted genomic DNA from 150 surgically dissected lymph nodes from that patient, and performed polymerase chain reaction analysis (PCR-RFLP) to detect the same p53 mutation in the lymph nodes. PCR-RFLP analysis showed the same p53 mutation in six lymph nodes. One node was located along the right recurrent laryngeal nerve, where no positive nodes was identified by conventional histopathologic examination. The p53 mutational diagnosis of metastatic cancer may be useful in detecting minimal residual disease.

Carcinoma, Squamous Cell↗
PubMed1998

Cysteine residues in the carboxyl terminal domain of the endothelin-B receptor are required for coupling with G-proteins.

We demonstrate that the human endothelin-B (ETB) receptor incorporates [3H]palmitic acid. Mutation of three putative palmitoylated cysteine residues (amino acids 402, 403 and 405) in the carboxyl terminus into serine residues (C2/3/5S) completely prevented palmitoylation of ETB. When expressed in CHO cells, C2/3/5S was localized on the cell surface, retained high affinity for ET-1 and ET-3, and was rapidly internalized when bound to the ligand. However, unlike the wild-type ETB, C2/3/5S transmitted neither an inhibitory effect on adenylate cyclase nor a stimulatory effect on phospholipase C, indicating a critical role of palmitoylation in the coupling with G-proteins, regardless of the G-protein subtype. Truncation of the carboxyl terminus, including all or a part of the three cysteine residues, gave palmitoylation-negative and -positive deletion mutants, delta 402 and delta 403. Despite the absence of the cytoplasmic tail, both delta 402 and delta 403 showed essentially the same features as C2/3/5S, except that delta 403 did transmit a stimulatory effect on phospholipase C via a pertussis toxin-insensitive G-protein, most likely a member(s) of the Gq family. These results indicated a differential requirement for the carboxyl terminus downstream from the palmitoylation site in the coupling with G-protein subtypes, i.e., it is required for the coupling with Gi but not for that with Gq.

Animals↗
PubMed1998

Surgical treatment for Scheie's syndrome (mucopolysaccharidosis type I-S): report of two cases.

Scheie's syndrome (mucopolysaccharidosis type I-S) is a rare genetic lysosomal storage disease affecting mucopolysaccharide metabolism, and is known to include cardiovascular disease. Surgical treatment was carried out in 2 patients with Scheie's syndrome. Patient 1 was a 56-year-old man with triple-vessel coronary artery disease, who successfully underwent coronary artery bypass grafting. Patient 2 was a 52-year-old man with aortic and mitral valve stenosis, who successfully underwent combined aortic and mitral valve replacement. The literature on Scheie's syndrome associated with valvular and coronary artery disease is also reviewed.

Aortic Valve Stenosis↗
PubMed1998

[Clinico-MRI study of hemispheric disorder in long-term follow-up cases of multiple system atrophy].

Twelve cases of multiple system atrophy (MSA) were studied for clinical and MRI findings of the cerebral hemispheric involvement. The subjects consisted of five olivopontocerebellar atrophy (OPCA) type and seven striatonigral degeneration (SND) type. The age at onset was 56.7 +/- 8.0 (M +/- SD) years, duration of illness at the first MRI study 3.2 +/- 1.1 years, duration of illness at the last study 8.1 +/- 2.2 years, and the following up duration 4.9 +/- 2.0 years. The grasping phenomenon was observed in 70% of the cases examined, snout reflex in 80%, slowness of verbal response in 88%, and decrease of spontaneous speech in 100%. Three cases finally fell into the state of mutism. Three out of ten cases were categorized as dementia by HDS-R (Hasegawa Dementia Scale-Revised) test. Besides the progression of the pontocerebellar atrophy and putaminal changes, MRI study revealed progressive frontal lobe atrophy in most cases. At six years after the onset, SND type showed significantly higher incidence of conspicuous frontal lobe atrophy and dilatatation of the Sylvian fissure than OPCA type. Cerebral ventricular dilatation was common feature, and atrophy of the temporal and occipital lobes were observed in several cases. We indicated the possible involvement of the cerebral hemisphere, especially the frontal lobe, and higher nervous function in MSA.

Adult↗
PubMed1998

[Treatment of subacute cardiac rupture after myocardial infarction].

Five successfully treated cases of subacute cardiac rupture after myocardial infarction are described. There were 4 men and 1 woman, ranging in age from 51 to 71 years. Two patients had systemic hypertension. Rupture occurred during the first myocardial infarction in all patients. The interval from the onset of myocardial infarction to cardiac rupture ranged from 1 to 6 days (mean 4 days). In one patient, the rupture was repaired under cardiopulmonary bypass using an autologous pericardial patch over the infarcted myocardium. Two patients underwent sutureless repair with fibrin glue; one of them developed a left ventricular pseudoaneurysm 2 years after the operation, requiring resection. These three patients were operated on through a median sternotomy. The remaining two patients were treated for cardiac tamponade by pericardial drainage through a subxiphoid incision; one died 38 days after the operation due to congestive heart failure. The four surviving patients are currently well 22, 39, 41 and 60 months after surgery. In summary, a conservative approach may be effective for treatment of subacute cardiac rupture.

Aged↗
PubMed1998

Dihydropyridine type calcium channel blocker-induced turbid dialysate in patients undergoing peritoneal dialysis.

We previously reported that manidipine, a new dihydropyridine type calcium channel blocker, produced chylous peritoneal dialysate being visually indistinguishable from infective peritonitis in 5 patients undergoing continuous ambulatory peritoneal dialysis (CAPD) [Yoshimoto et al. 1993]. To study whether such an adverse drug reaction would also be elicited by other commonly prescribed calcium channel blockers in CAPD patients, we have conducted postal inquiry to 15 collaborating hospitals and an institutional survey in International Medical Center of Japan as to the possible occurrence of calcium channel blocker-associated non-infective, turbid peritoneal dialysate in CAPD patients. Our diagnostic criteria for drug-induced turbidity of dialysate as a) it developed within 48 h after the administration of a newly introduced calcium channel blocker to the therapeutic regimen, b) absence of clinical symptoms of peritoneal inflammation (i.e., pyrexia, abdominal pain, nausea or vomiting), c) the fluid containing normal leukocyte counts and being negative for bacterial and fungal culture of the fluid, and d) it disappeared shortly after the withdrawal of the assumed causative agent. Results showed that 19 out of 251 CAPD patients given one of the calcium channel blockers developed non-infective turbid peritoneal dialysis that fulfilled all the above criteria. Four calcium channel blockers were suspected to be associated with the events: benidipine [2 out of 2 (100%) patients given the drug], manidipine [15 out of 36 (42%) patients], nisoldipine [1 out of 11 (9%) patients] and nifedipine [1 out of 159 (0.6%)] in descending order of frequency. None of the patients who received nicardipine, nilvadipine, nitrendipine, barnidipine and diltiazem (25, 7, 2, 1 and 8 patients, respectively) exhibited turbid dialysate. In conclusion, we consider that certain dihydropyridine type calcium channel blockers would cause turbid peritoneal dialysate being similar to that observed in patients developing infective peritonitis. To avoid unnecessary antibiotic therapy the possibility of this adverse reaction should be ruled out whenever a CAPD patient receiving a dihydropyridine type calcium channel blocker develops turbid dialysate.

Calcium Channel Blockers↗
PubMed1997

Palmitoylation of human endothelinB. Its critical role in G protein coupling and a differential requirement for the cytoplasmic tail by G protein subtypes.

By site-directed mutagenesis, three cysteine residues (amino acids 402, 403, and 405) in the carboxyl terminus of human endothelinB (ETB) were identified as potential palmitoylation sites. Substitutions of all of the three cysteine residues with serine gave an unpalmitoylated mutant, C2S/C3S/C5S. When expressed in Chinese hamster ovary cells, C2S/C3S/C5S was localized on the cell surface, retained high affinities to ET-1 and ET-3, and was rapidly internalized when bound to the ligand. However, unlike the wild-type ETB, C2S/C3S/C5S transmitted neither an inhibitory effect on adenylate cyclase nor a stimulatory effect on phospholipase C, indicating a critical role of palmitoylation in the coupling with G proteins, regardless of the G protein subtypes. Truncation of the carboxyl terminus including Cys403/Cys405 gave a deletion mutant Delta403 that was palmitoylated on Cys402 and lacked the carboxyl terminus downstream to the palmitoylation site. Delta403 did transmit a stimulatory effect on phospholipase C via a pertussis toxin-insensitive G protein but it failed to transmit an inhibitory effect on adenylate cyclase. These results indicated a differential requirement for the carboxyl terminus downstream to the palmitoylation site in the coupling with G protein subtypes, i.e. it is required for the coupling with Gi but not for that with Gq.

Amino Acid Sequence↗
PubMed1997

Molecular analysis of eight biochemically unique glucose-6-phosphate dehydrogenase variants found in Japan.

We analyzed the molecular mutations of eight known Japanese glucose-6-phosphate dehydrogenase (G6PD) variants with unique biochemical properties. Three of them were caused by novel missense mutations: G6PD Musashino by 185 C-->T, G6PD Asahikawa by 695 G-->A, and G6PD Kamiube by 1387 C-->T. Predicted amino acid substitutions causing asymptomatic variants G6PD Musashino (62 Pro-->Phe) and G6PD Kamiube (463 Arg-->Cys) were located in regions near the amino or carboxyl end of the polypeptide chain, whereas an amino acid change 232 Cys-->Tyr causing a class 1 variant G6PD Asahikawa was located in the region where amino acid alterations in some class 1 variants were clustered. The other five variants had known missense mutations, namely, G6PD Fukushima, 1246 G-->A, G6PD Morioka, 1339 G-->A, and G6PD Iwate, G6PD Niigata and G6PD Yamaguchi, 1160 G-->A, which cause variants, G6PD Tokyo, G6PD Santiago de Cuba, and G6PD Beverly Hills, respectively.

Anemia, Hemolytic, Congenital Nonspherocytic↗
PubMed1997

Frame shift mutation, exon skipping, and a two-codon deletion caused by splice site mutations account for pyruvate kinase deficiency.

Three novel splice site mutations and two novel missense mutations were identified by molecular analysis of pyruvate kinase (PK) deficiency associated with hereditary nonspherocytic hemolytic anemia. A Nepalese PK variant, PK Kowloon, was found to have a homozygous transversion at the 5'-splice site of the seventh intervening sequence (IVS) of the L-type PK gene (Ivs7[+1]gt --> tt). Using a reverse transcription polymerase chain reaction (RT-PCR) assay, we showed that the R-type PK mRNA in the proband's reticulocytes included the seventh IVS between the seventh and eighth exon, introducing a stop codon 3 nucleotides downstream of the mutated site. Consequently, the translational product may lack 44% of the R-PK polypeptide. A transition at the last nucleotide of exon 9 (1269GCG --> GCA) was found in a Japanese PK variant, PK 'Kamata.' The mutation did not alter the amino acid sequence, but caused skipping of the ninth exonic sequence in the R-PK transcripts. As a result, the affected R-type PK lost 51 amino acid residues (373Met-423Ala del). A transversion at the splice acceptor site of the third IVS (Ivs 3[-2]ag --> tg) was identified in PK 'Aomori.' The mutation resulted in aberrant splicing at a cryptic splice site within exon 4, causing deletion of two codons in the aberrant R-PK transcript (95 Gly-96 Pro --> del). Both PK 'Kamata' and PK 'Aomori' had a missense mutation on the other allele, 1044AAG --> AAT (348Lys --> Asn) and 1075CGC --> TGC (359Arg --> Cys), respectively. Although both 348Lys and 359Arg were located in the sixth loop of A domain (beta/alpha)8 barrel, which has been shown to contain the substrate and cation binding sites, the degree of anemia was much more severe in PK 'Kamata' than PK 'Aomori,' possibly because the 51 amino acid deletion of PK 'Kamata' but the 2 amino-acid deletion of PK 'Aomori' may abolish PK catalytic activity.

Anemia, Hemolytic, Congenital Nonspherocytic↗
PubMed1997

Cloning and characterization of a brain-specific cationic amino acid transporter.

rCAT3 (rat cationic amino acid transporter 3), a cDNA that encodes a novel member of the murine CAT family was isolated. The protein encoded by rCAT3 contained 619 amino acids, 53-58% of which were identical with those of the murine CAT family proteins previously described (mouse CAT1, CAT2a, CAT2b, and rat CAT1). Transient expression of rCAT3 and L-[14C]arginine incorporation experiments in COS7 cells verified a high affinity system y+ transporter activity of rCAT3. First, rCAT3-mediated L-[14C]arginine incorporation was time-dependent and saturable with half-saturation constant (Km) values of 103 +/- 12 microM (mean +/- S.E., n = 3). Second, the incorporation was specific for cationic amino acids as evidenced from the inhibition by L-arginine, L-lysine, and L-ornithine. Third, neither sodium nor chloride ions in the extracellular medium were required for the activity. Fourth, the incorporation was inhibited by high potassium-induced membrane depolarization. On Northern blot using RNAs from various rat tissues, the expression of rCAT3 mRNA was restricted to the brain. These results indicated a role of rCAT3 in the system y+ transporter activity in the nervous tissue.

Amino Acid Sequence↗