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Biomedical subjects

K Miyahara

Publications and source records attributed to K Miyahara.

At least 109 records · Page 6Linked to original sources
PubMed1995

Classic steroid 11 beta-hydroxylase deficiency caused by a C-->G transversion in exon 7 of CYP11B1.

Steroid 11 beta-hydroxylase deficiency (11 beta OHD) is derived from mutations in the P45011 beta gene (CYP11B1) and inherited in an autosomal recessive manner. In the present study, we have performed a molecular genetic analysis of CYP11B1 in a Japanese patient clinically diagnosed as classic 11 beta OHD. Nucleotide sequencing of the PCR-amplified exons from the patient's genomic DNA reveals a unique C-->G transversion that converts codon 384 CGA (arginine) to GGA (glycine) in exon 7. Restriction fragment length polymorphism (RFLP) data demonstrate that the patient is homozygous for this mutation. When the full-length cDNA corresponding to CYP11B1 of the patient is transfected into COS-7 cells, no steroid 11 beta-hydroxylase activity is detectable in mitochondria of the cells. These results indicate that this point mutation completely abolishes P45011 beta activity and causes the classic 11 beta OHD.

Adolescent↗
PubMed1995

A SP1 binding site in the GC-rich region is essential for a core promoter activity of the human endothelial nitric oxide synthase gene.

Endothelial nitric oxide synthase (eNOS) is an important oxygenase which catalyzes the conversion of L-arginine to L-citrulline to form nitric oxide (NO), a potent important factor for vasodilation and inhibition of platelet aggregation. We have analyzed characteristics of the promoter region of the human eNOS gene using the transient expression in human endothelial cells of CAT constructs with a series of 5'-deletion mutants. The 5'-flanking region between -116 and -98, which contains a putative consensus sequence for binding of transcription factor Sp1, is essential to direct a basal promoter activity. Gel mobility shift analysis involving anti-Sp1 antibody and competitor DNAs disrupted at the binding site for Sp1 reveals that Sp1 or its closely related protein(s) binds to the consensus sequence located between -104 and -96. These results indicate that the Sp1 site is essential for a core promoter activity of the human eNOS gene.

Base Composition↗
PubMed1995

A new device for exposing the circumflex coronary artery.

We have devised a new retractor for use in coronary artery bypass grafting that is made from three woven Teflon tapes. This method allows sufficient counterclockwise rotation of the heart, provides excellent exposure of the posterior and inferior coronary artery systems, and creates a horizontal surgical plane for the circumflex anastomosis.

Coronary Artery Bypass↗
PubMed1995

Inborn errors of aldosterone biosynthesis in humans.

Corticosterone methyl oxidase (CMO) type I and type II deficiencies are inborn errors at the penultimate and ultimate steps in the biosynthesis of aldosterone in humans. Recently, steroid 18-hydroxylase (P450C18), or aldosterone synthase (P450aldo), was shown to be a multifunctional enzyme catalyzing these two steps of aldosterone biosynthesis, i.e., the conversion of corticosterone to 18-hydroxycorticosterone and the subsequent conversion of 18-hydroxycorticosterone to aldosterone. This observation suggests that CMO I and CMO II deficiencies are derived from two different mutations in the P450C18 gene (CYP11B2). To elucidate whether or not this is the case, we performed molecular genetic studies on CYP11B2 of both types of patients. Nucleotide sequence analysis has indicated that the gene of CMO I deficient patients is completely inactivated by a frameshift to form a stop codon due to a 5-bp nucleotide deletion in exon 1. Sequence analysis of CYP11B2 of CMO II deficient patients has revealed two point mutations, CGG-->TGG (Arg181-->Trp) in exon 3 and GTG-->GCG (Val386-->Ala) in exon 7. CYP11B1, the gene for steroid 11 beta-hydroxylase (P45011 beta) which was previously postulated to be the target for CMO II deficiency, is not impaired in these two types of patients. Expression studies using the corresponding mutant cDNAs have shown that CMO I deficient patients are null mutants with a complete lack of P450C18 whereas CMO II deficient patients are leaky mutants with an altered P450C18 activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenal Hyperplasia, Congenital↗
PubMed1995

Complementary effects of paeoniflorin and glycyrrhizin on intracellular Ca2+ mobilization in the nerve-stimulated skeletal muscle of mice.

Effects of paeoniflorin (PF) and glycyrrhizin (GLR), contained in paeony and licorice roots, respectively, on contractile and non-contractile Ca2+ mobilization were examined by measuring the Ca(2+)-aequorin luminescence (Ca2+ transients) of the nerve-stimulated skeletal muscle of mice in the presence of neostigmine (0.3 microM). PF (0.1-1 mM) prolonged the duration of non-contractile Ca2+ transients, which may induce the desensitization of nicotinic acetylcholine receptor, but did not affect contractile Ca2+ transients. GLR (0.3-1 mM) depressed contractile Ca2+ transients without affecting non-contractile transients. These results suggest that PF and GLR may have complementary effects on intracellular Ca2+ mobilization to block the neuromuscular transmission.

Animals↗
PubMed1995

Functional analysis of the promoter of the Saccharomyces cerevisiae multidrug resistance gene YDR1, which encodes a member of the ATP binding cassette (ABC) superfamily.

The Saccharomyces cerevisiae gene YDR1/PDR5/STS1, which encodes a member of the ATP binding cassette (ABC) superfamily, is important for cross-resistance to apparently unrelated drugs. The expression of YDR1 is induced by various drugs and heat shock [Hirata et al., Curr. Genet., 26, 285-294 (1994)]. By deletion analysis of the 5'-noncoding region of the YDR1 gene, two drug responsive regions (-604 to -485 and -335 to -275) were identified with fluphenazine and cycloheximide. Three conserved palindrome sequences were found in these regions.

ATP-Binding Cassette Transporters↗
PubMed1995

Magnetic resonance imaging of the central nervous system in the kitten.

The optimum technical conditions for magnetic resonance imaging (MRI) of the central nervous system (CNS) in the 3-week-old kitten were investigated with a low (0.2 T) magnetic field MRI unit equipped with a custom-made solenoid radio frequency (RF) coil. In the brain, T1 weighted images (TR/TE = 500/38 msec) and T2 weighted images (TR/TE = 1,800/110 msec) clearly delineated each anatomical portion of the brain. In the spinal cord, T2 weighted images (TR/TE = 1,500/110 msec) demonstrated structures distinctly. These results suggest that even low magnetic field MRI can be used for noninvasive scanning of small animals including new born animals.

Animals↗
PubMed1995

[Pulmonary embolectomy for massive pulmonary embolism].

Surgical cases of massive pulmonary embolism remain rare in Japan. To discuss the surgical problems, clinical courses of 4 patients who underwent pulmonary embolectomy under cardiopulmonary bypass at our hospital for the last six years were reviewed. There were 2 men and 2 women; ranging from 41 to 72 years (mean age, 63 years), 1 of whom had deep venous thrombosis of the lower extremity as a predisposing factor. The initial disease recurred in 2 patients. Shock occurred in 3 patients preoperatively, 2 of whom had sudden syncope. Cardiac arrest occurred before and during pulmonary arteriography (PAG) in 1 patient. The systolic pulmonary arterial pressure rose to between 60 and 80 mmHg in all patients except for 1 of whom it was not measured. The diagnosis was established in 3 patients by PAG and clinically in the remaining recurrent patient. Thrombolysis was not effective in all patients, then pulmonary embolectomy was performed between four hours and five days after the onset of the disease. One patient with preoperative cardiac arrest died of low output syndrome and severe respiratory failure, but 3 survived with clinical improvement. Development of the prompt and noninvasive diagnostic procedure, rapid cardiopulmonary support in severe cases and an early decision to operate are required to improve the operative results. Partial resection of the lung was obliged due to massive endobronchial hemorrhage after embolectomy in 1 recurred patient. Compression of the lungs and embolectomy using a balloon catheter should be performed carefully to prevent injuring pulmonary arteries. Implantation of an inferior vena cava filter may be beneficial for the selected patient to prevent recurrence of the disease.

Adult↗
PubMed1994

Cloning and structural characterization of the human endothelial nitric-oxide-synthase gene.

Nitric oxide accounts for the activity of endothelium-derived relaxing factor, which seems to have an important role in vasodilation and inhibition of platelet aggregation. In endothelial cells, one isoform of nitric-oxide synthase is constitutively expressed. Analysis of the cDNA encoding the human endothelial nitric-oxide synthase revealed that the mRNA is 4.1 kb in size and that the translated protein consists of 1203 amino acids. We have cloned a genomic DNA encoding the human endothelial nitric-oxide synthase and analyzed the entire nucleotide sequence of the gene. The gene consists of 26 exons with a total size of 21 kb. The 5' flanking region of the gene lacks TATA boxes, but it contains putative Sp1-binding sites in (G+C)-rich regions. Of particular interest is the fact that a shear-stress-responsive element is located at position -985, which probably regulates the nitric-oxide-synthase gene in response to fluid mechanical forces at the transcriptional level in the vascular endothelium. Two minisatellite sequences are detectable in introns 2 and 8; a 32-bp consensus sequence repeats 38 times and a 57-bp consensus sequence repeats ten times. We found polymorphisms of the BamHI fragment containing the former minisatellite sequence in genomic DNA from pedigree family members. Furthermore, five tandem repeats of a 27-bp core consensus sequence and 35 repeats of a dinucleotide (CA) are located in introns 4 and 13, respectively. These repeat sequences will probably provide genetic markers for gene mapping and linkage analysis of inherited diseases including cardiovascular diseases.

Amino Acid Oxidoreductases↗
PubMed1994

Saccharomyces cerevisiae YDR1, which encodes a member of the ATP-binding cassette (ABC) superfamily, is required for multidrug resistance.

A multidrug resistance gene, YDR1, of Saccharomyces cerevisiae, which encodes a 170-kDa protein of a member of the ABC superfamily, was identified. Disruption of YDR1 resulted in hypersensitivity to cycloheximide, cerulenin, compactin, staurosporine and fluphenazine, indicating that YDR1 is an important determinant of cross resistance to apparently-unrelated drugs. The Ydr1 protein bears the highest similarity to the S. cerevisiae Snq2 protein required for resistance to the mutagen 4-NQO. The drug-specificity analysis of YDR1 and SNQ2 by gene disruption, and its phenotypic suppression by the overexpressed genes, revealed overlapping, yet distinct, specificities. YDR1 was responsible for cycloheximide, cerulenin and compactin resistance, whereas, SNQ2 was responsible for 4-NQO resistance. The two genes had overlapping specificities toward staurosporine and fluphenazine. The transcription of YDR1 and SNQ2 was induced by various drugs, both relevant and irrelevant to the resistance caused by the gene, suggesting that drug specificity can be mainly attributed to the functional difference of the putative transporters. The transcription of these genes was also increased by heat shock. The yeast drug-resistance system provides a novel model for mammalian multidrug resistance.

ATP-Binding Cassette Transporters↗
PubMed1994

Gene ecology: a cis-acting gene-to-gene interaction due to the spatial arrangement of genes in chromosomes affects neighbouring transfected c-H-ras expression.

A cis-acting interference between gene activities, which occurs when two genes lie on the same DNA strand and have an intergenic distance less than a defined length, was previously deduced when chromosomal organizations of various higher eukaryote nuclear genes in clusters were compared. In order to investigate such an interference due to arrangement of genes along chromosomes, we have isolated a few cell lines which possessed (i) human mutated c-H-ras fused with the mouse mammary tumour virus long terminal repeat and (ii) the E. coli xanthine-guanine phosphoribosyltransferase (gpt) gene with the SV40 promoter, on the same or on different DNA strands, separated by a short intergenic distance or unlinked. Since the cancerous phenotype of a cell can be readily identified due to c-H-ras expression, we examined in these cell lines whether continuous c-H-ras expression, induced by dexamethasone, is disturbed through a cis-acting gene-to-gene interaction when the expression of the neighbouring gpt gene is enforced and as a result, the cancerous state of a cell is converted to the 'normal' state. The enforced expression of the neighbouring gpt gene was shown to alter c-H-ras expression, and thus reversible conversion of a cell between cancerous and normal states occurred only when the cell possessed an optimum number of the gene pair, in which both c-H-ras and the gpt gene were on the same DNA strand. This implies that the spatial arrangement of genes in chromosomes plays an important role in the regulation of gene expression in a cluster.

Animals↗
PubMed1994

The effects of using a leukocyte removal filter during cold blood cardioplegia.

During myocardial ischemia, neutrophils and platelets exert negative effects on the myocardium. In this study, we used a leukocyte removal filter during cardioplegia, and investigated its effect on myocardial damage during reperfusion by measuring the plasma levels of granulocyte components, platelet components, and cardiac enzymes [creatinine phosphokinase (CK) and creatinine phosphokinase myocardial band (CK-MB)] in 24 patients who underwent cardiopulmonary bypass. The patients were divided into two groups of 12 according to whether or not a filter was placed in the cardioplegic route. Blood samples were drawn directly from the coronary sinus before aortic cross clamping, and at 1, 5, and 15 min after declamping. Group F, which had the filter, showed better cardiac enzyme and lipid peroxidation results than group N, which did not. The results of this study suggest that the application of a filter during cold blood cardioplegia may reduce myocardial damage.

6-Ketoprostaglandin F1 alpha↗
PubMed1994

Structure and function of nitric oxide synthases.

Nitric oxide (NO), which accounts for the biological activity of endothelium-derived relaxing factor, is now thought to play a variety of roles in the nervous system and in immunologic reactions. NO is synthesized from L-arginine by nitric oxide synthase (NOS). There are three isoforms of NOS; type I (neuronal), type II (inducible), and type III (endothelial). The fundamental structure of the three isoforms, which contain calmodulin-, FMN-, FAD-, and NADPH-binding domains, is the same. Calmodulin is already bound to inducible NOS without requiring Ca2+, while the others are Ca2+/calmodulin-dependent. Endothelial NOS is bound to membranes by N-myristoylation, while the other isoforms are soluble. The human endothelial NOS gene has been cloned. It has several highly repetitive regions which could provide potential sites for DNA polymorphism. It might be of interest to examine the relationship between such polymorphism and cardiovascular disorders.

Amino Acid Oxidoreductases↗
PubMed1994

A simple surgical atrial septectomy for complex congenital heart disease.

A simple method of surgical atrial septectomy using a rongeur (Kerrison bone-cutting forceps), which is used in neurosurgery, is described. The closed rongeur is inserted into the left atrium through the right atrial appendage and the atrial septum. Then it is opened and the edge of the atrial septal defect and/or patent foramen ovale can be hooked by pulling slowly. The rongeur is then tightly closed again and pulled out together with the resected atrial specimen. This technique is safer and simpler than the Blalock-Hanlon technique or atrial septectomy with extra-corporeal circulation for older infants in whom balloon atrial septostomy is difficult.

Heart Defects, Congenital↗