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Biomedical subjects

S Miyachi

Publications and source records attributed to S Miyachi.

At least 73 records · Page 4Linked to original sources
PubMed1992

A gene homologous to chloroplast carbonic anhydrase (icfA) is essential to photosynthetic carbon dioxide fixation by Synechococcus PCC7942.

To understand the CO2-concentrating mechanism in cyanobacteria, a genomic DNA fragment that complements a temperature-sensitive high-CO2 (5%)-requiring mutant of Synechococcus PCC7942 has been isolated. An open reading frame (ORF272) encoding a polypeptide of 272 amino acids (Mr, 30,184) was found within the genomic region located 20 kilobases downstream from the genes for ribulose-1,5-bisphosphate carboxylase/oxygenase (rbcLS). Insertion of a kanamycin-resistance gene cartridge within the ORF272 in wild-type cells led to a high-CO2-requiring phenotype. Strains carrying a gene disabled by insertional mutagenesis accumulated inorganic carbon in the cells, but they could not fix it efficiently, even though ribulose-1,5-bisphosphate carboxylase activity was comparable to that of the wild-type strain. Therefore, the ORF272 was designated as a gene icfA, which is essential to inorganic carbon fixation. Furthermore, the predicted icfA gene product shared significant sequence similarities with plant chloroplast carbonic anhydrases (CAs) from pea (22%) and spinach (22%) and also with the Escherichia coli cynT gene product (31%), which was recently identified to be E. coli CA. These results indicate that the putative CA encoded by icfA is essential to photosynthetic carbon dioxide fixation in cyanobacteria and that plant chloroplast CAs may have evolved from a common ancestor of the prokaryotic CAs, which are distinct from mammalian CAs and Chlamydomonas periplasmic CAs.

Amino Acid Sequence↗
PubMed1992

Photochemical release of bases from nucleosides and their derivatives by water-soluble iron(III) porphyrins.

The compounds [meso-tetrakis(1-methyl-4-pyridiniumyl)porphyrinato]iron(III ) (FeIIITMPyP) and [meso-tetrakis(3,5-dichloro-1-methyl-4-pyridiniumyl)porphyrinat o]iron(III) (FeIIITCl2MPyP) photocatalysed the release of bases from nucleosides and their derivatives. The ribonucleosides, of which cytidine (C) gave the highest yield, produced much higher yields of free base than the corresponding deoxyribonucleosides. Under an argon atmosphere, virtually quantitative reduction of FeIIITMPyP into FeIITMPyP by C or 2'-deoxycytidine (dC) was observed and the reduction by C was much more effective than by dC. The increased reactivity of ribonucleosides relative to deoxyribonucleosides was ascribed to a difference in the binding properties of the porphyrin-nucleoside interactions and to base-releasing degradation of ribonucleosides from their C-2' carbon radical.

Deoxyribonucleosides↗
PubMed1992

Nonlinear pharmacokinetics of hepatobiliary transport of rose bengal in rats after i.v. bolus administration with varying doses.

To investigate the nonlinear kinetics in the hepatobiliary transport of rose bengal (RB), the time profiles of plasma concentration and biliary excretion rate after its i.v. administration at various doses were measured in rats. The total body clearance decreased remarkably with increased dose. The hepatic uptake clearance also showed a similar dose dependency, and saturation of hepatic uptake at least partly accounts for the dose-dependent change in total body clearance. The peak biliary excretion rate approached the transport maximum (approximately 150 nmol min-1 kg-1) with increased dose. To further clarify which process in RB hepatobiliary transport has nonlinearity, we analysed thus obtained data based on a three-compartment model. The hepatic uptake and sequestration rate constants decreased remarkably with increased dose. The initial hepatic uptake rates assessed from the plasma disappearance rate during the early phase fit well to the Michaelis-Menten equation with a saturable and a nonsaturable component. The maximum uptake velocity and Michaelis constant were 4.7 mumol min-1 kg-1 and 360 microM, respectively. That hepatic uptake has a much higher capacity (about 30 fold) than biliary excretion suggests that biliary excretion can be a rate-determining process in the overall hepatobiliary transport of RB. We conclude that the saturation of both hepatic uptake and biliary excretion could be the main causes for the nonlinear pharmacokinetics of hepatobiliary transport of RB.

Animals↗
PubMed1992

Histopathological study of balloon embolization: silicone versus latex.

Bilateral, symmetrical, experimental aneurysms were produced with anastomosed vein flap in the carotid arteries of 24 mongrel dogs. Aneurysms were occluded with latex or silicone balloons on each side and observed angiographically from 2 weeks to 2 months. A histopathological study was performed subsequently using light and scanning electron microscopy. Rupture after balloon embolization occurred in five aneurysms; all of which were incompletely occluded by a silicone balloon. On subsequent angiograms, four silicone balloons and one latex balloon were found to have migrated into the aneurysm, resulting in aneurysmal expansion. Parent artery occlusion was more common with latex balloons than silicone balloons. Histopathologically, residual fresh thrombi, decreased proliferation of fibroblasts within the aneurysmal cavity, and poor endothelialization were present around the silicone balloon. These results suggest that the intra-aneurysmal organization, as seen in the aneurysm occluded by the silicone balloon, will be delayed because the balloon is not fixed within the aneurysm, and that this free-floating and rotating balloon causes repeated trauma to the aneurysm wall, contributing to subsequent enlargement and rupture of the aneurysm. The superior antithrombogenic nature of silicone may be responsible for the bias of such phenomena toward the silicone balloon.

Aneurysm↗
PubMed1992

Characterization of carbonic anhydrase isozyme CA2, which is the CAH2 gene product, in Chlamydomonas reinhardtii.

From high-CO2 (5% CO2) grown unicellular green alga, Chlamydomonas reinhardtii, carbonic anhydrase (CA) was isolated by affinity chromatography and characterized. Isolated CA was identified as an isozyme (CA2) which is the product from the second gene CAH2 by peptide sequencing. The CA2 was inactivated by dithiothreitol. This treatment caused dissociation of CA2 into the large (38 kDa) and small subunits (4243 Da). The molecular mass of the CA2 holoenzyme measured by low-angle laser light-scattering photometry and precision differential refractometry combined with gel-filtration HPLC was 87.9 kDa. These results and gene structure indicate that CA2 is a heterotetramer consisting of two large and two small subunits linked by disulfide bonds like CA1, which is the CAH1 gene product. The specific activity of CA2 purified by anion-exchange HPLC was 3300 units per mg protein, which was approximately 1.6 times higher than that of CA1. Therefore, it was concluded that two structurally related isozymes, CA1 and CA2, are present in the wild type cells of C. reinhardtii and differentially regulated by the atmospheric CO2 concentration.

Amino Acid Sequence↗
PubMed1992

Vascular endoscopy for intravascular surgery--an experimental study.

A combination of endoscope and high-pressure saline irrigation system was tested in the occlusion of experimental aneurysms, and angioplasty and fibrinolysis of vascular occlusive lesions in canine femoral arteries. Endoscopy provided detailed information about the aneurysmal orifice and lumen and aided balloon placement and detachment. Endoscopy visualized the dynamic changes accompanying thrombolysis and the fine intimal injury due to angioplasty invisible on angiography. Vascular endoscopy is valuable for pre-, intra-, and postoperative evaluation of intravascular interventions.

Angiography↗
PubMed1992

Giant meningioma fed by the anterior choroidal artery: successful removal following embolization--case report.

A 53-year-old female was admitted with apathy, left sensory and motor disturbance, left homonymous hemianopsia, and dressing apraxia. Computed tomography and magnetic resonance imaging showed a huge mass markedly enhanced in and around the right trigone. Cerebral angiography revealed rich vascularity of the tumor mainly fed by the right anterior choroidal artery. The feeding vessel was embolized with microfibrillar collagen after superselective catheterization. Seven days later, the tumor was totally removed with low blood loss. The histological diagnosis was fibroblastic meningioma. She was discharged without neurological deficit, except for left homonymous hemianopsia.

Arteries↗
PubMed1991

Identification of a genomic region that complements a temperature-sensitive, high CO2-requiring mutant of the cyanobacterium, Synechococcus sp. PCC7942.

In a temperature-sensitive, high CO2-requiring mutant of Synechococcus sp. PCC7942, the ability to fix intracellularly accumulated inorganic carbon was severely impaired at non-permissive temperature (41 degrees C). In contrast, inorganic carbon uptake and ribulose-1.5-bisphosphate carboxylase activity in the mutant were comparable to the respective values obtained with the wild-type strain. The mutant was transformed to the wild-type phenotype (ability to form colonies at non-permissive temperature under ordinary air) with the genomic DNA of the wild-type strain. A clone containing a 36 kb genomic DNA fragment of the wild-type strain complemented the mutant phenotype. The complementing activity region was associated with internal 17 kb SmaI, 15 kb HindIII, 3.8 kb BamHI and 0.87 kb PstI fragments. These 4 fragments overlapped only in a 0.4 kb HindIII-PstI region. In the transformants obtained with total genomic DNA or a plasmid containing the 3.8 kb BamHI fragment, the ability to fix intracellular inorganic carbon was restored. Southern hybridization and partial nucleotide sequence analysis indicated that the cloned genomic region was located approximately 20 kb downstream from the structural genes for subunits of ribulose-1.5-bisphosphate carboxylase/oxygenase. The cloned region was transcribed into a 0.5 kb mRNA. These results indicate that the cloned genomic region of Synechococcus sp. PCC7942 is involved in the efficient utilization of intracellular inorganic carbon for photosynthesis.

Blotting, Northern↗
PubMed1991

[A case of systemic xanthogranulomatosis with an intracranial lesion: immunohistochemical study].

The authors describe a case of a 42-year-old woman with systemic xanthogranulomatosis who primarily manifested bilateral intraorbital tumors, generally effecting many regions. These included the intracranial dura mater, the spinal cord, the retroperitoneum, the pericardium, and the mediastinum. This disorder is basically similar to systemic Weber-Christian disease except for the absence of subcutaneous panniculitis. Immunohistochemical study reveals that this clinical entity is different from histiocytosis X because the origin of the foamy cells is not the T-zone histiocyte but the macrophage. The treatment of this disease is also discussed.

Adult↗
PubMed1990

Subunit constitution of carbonic anhydrase from Chlamydomonas reinhardtii.

Carbonic anhydrase purified from the cell surface of Chlamydomonas reinhardtii was inactivated by treatment with dithiothreitol. This treatment caused dissociation of the holoenzyme into 35-kDa (A) and 4-kDa (B) subunits as revealed by SDS/PAGE. The 35-kDa subunit was further separated into two components A1 (35 kDa) and A2 (36.5 kDa) by SDS/PAGE using a gradient gel. These two components have the same amino acid sequence up to at least the 10th amino acid from the N-terminus. The molecular masses were estimated at 76 kDa and 35 kDa for the holoenzyme and the large subunit, respectively, and the molar ratio of the former to the latter at 1:2, by using the techniques of low-angle laser light-scattering photometry and precision differential refractometry combined with gel-filtration HPLC. The molar ratio of the 35-kDa/4-kDa subunits was estimated at 1:1 the gel-filtration HPLC monitored with precision differential refractometry. Atomic-absorption spectrophotometry revealed that the holoenzyme contains two atoms of zinc. These results suggest that the holoenzyme is a heterotetramer composed of two large subunits (A1 and A2) and two small subunits (B).

Amino Acid Sequence↗
PubMed1990

cDNA cloning, sequence, and expression of carbonic anhydrase in Chlamydomonas reinhardtii: regulation by environmental CO2 concentration.

cDNA clones for the periplasmic carbonic anhydrase (CA; carbonate hydro-lyase, EC 4.2.1.1) of Chlamydomonas reinhardtii cells were isolated and characterized. The fact that the cloned cDNA fragments encoded a 377-amino acid polypeptide (41,626 Da) consisting of an NH2-terminal hydrophobic signal peptide of 20 amino acids, a large (35,603 Da) subunit polypeptide, and a small (4144 Da) subunit polypeptide indicates that the two subunits are cotranslated as a precursor polypeptide. The amino acid sequence of mature subunits deduced from the nucleotide sequence showed 20-22% homology with human CA isozymes (CAI, CAII, and CAIII). Three zinc-liganded histidine residues and those forming a hydrogen-bond network to zinc-bound solvent molecules were highly conserved in the plant and animal enzymes. Three possible asparagine-linked glycosylation sites were found in the large subunit. Northern blot analysis was carried out using the cDNA fragment as a probe. The level of 2.0-kilobase CA mRNA increased within 1 hr when CO2 concentration of the bubbling gas was changed from 5% to 0.04% (air level) in the presence of light. On the other hand, CA mRNA did not accumulate when CO2 concentration was lowered in the dark. Experiments using 3-(3,4-dichlorophenyl)-1,1-dimethylurea showed that photosynthesis is absolutely required for the accumulation of CA mRNA. These results indicate that CA biosynthesis is regulated by changes in environmental CO2 concentration as well as light at the level of mRNA abundance.

Amino Acid Sequence↗
PubMed1990

Structure and differential expression of two genes encoding carbonic anhydrase in Chlamydomonas reinhardtii.

Two copies of structurally related genes (CAH1 and CAH2) for carbonic anhydrase (EC 4.2.1.1) were found to be tandemly clustered on the Chlamydomonas reinhardtii genome. The previously isolated cDNA clones for carbonic anhydrase polypeptides were derived from the upstream gene, CAH1, which has 10 introns in its coding region. The downstream gene, CAH2, also has 10 introns, at positions identical to those of CAH1. Although amino acid sequences deduced from the two genes showed 91.8% identity, partial sequences of the authentic enzyme isolated from air-induced cells were identical only to those of the CAH1 product. Northern hybridization using gene-specific probes showed that the level of 2.0-kilobase CAH1 mRNA increased in response to a decrease in CO2 concentration in the presence of light. The CAH1 mRNA did not accumulate when CO2 was lowered in the dark. In contrast, the level of 2.0-kilobase CAH2 mRNA decreased in response to lowering of CO2 and increased upon transfer to the high-CO2 condition in light. The decrease of CAH2 mRNA under the low-CO2 condition was not observed in the dark. The fully induced mRNA level was much higher for CAH1 than for CAH2. These results indicate that CAH1 is a gene coding for the major periplasmic carbonic anhydrase whose level of transcript is rapidly induced under the low-CO2 condition in the presence of light, and that CAH2 may encode another periplasmic isozyme, which is made under the high-CO2 condition.

Amino Acid Sequence↗
PubMed1990

An intracranial mass lesion in systemic xanthogranulomatosis: case report.

The authors describe a 42-year-old woman with systemic xanthogranulomatosis and bilateral intraorbital tumors, who subsequently developed multiple lesions of the intracranial dura mater, spinal cord, retroperitoneum, pericardium, and mediastinum. Systemic xanthogranulomatosis is histologically similar to systemic Weber-Christian disease, except for the absence of subcutaneous panniculitis. Immunohistochemical studies suggest that this clinical entity can be differentiated from histiocytosis X, because foamy cells in systemic xanthogranulomatosis demonstrate macrophages but not T-zone histiocyte markers. Differentiation of this disease from other intracranial xanthogranulomas and treatment are discussed.

Adult↗
PubMed1990

Myeloma manifesting as a large jugular tumor: case report.

The authors report a case of cranial plasmacytoma with multiple myelomas and palsy of the lower cranial nerves. The osteolytic lesion adjacent to the jugular foramen was demonstrated by an angiogram to be exceedingly hypervascular, with arteriovenous shunting resembling that seen in paragangliomas. Forty-five cases of cranial and intracranial plasmacytoma from the literature were reviewed. The findings indicate that a cranial plasmacytoma commonly appears to be a hypervascular tumor, whereas most dural tumors or intraparenchymal tumors have poor vascularity.

Diagnosis, Differential↗
PubMed1990

Light-Induced Carbonic Anhydrase Expression in Chlamydomonas reinhardtii.

The effect of external inorganic carbon concentration and light on carbonic anhydrase (CA) protein accumulation and steady-state mRNA levels were examined in Chlamydomonas reinhardtii. When photoautotrophically grown high-CO(2) cells were transferred to low-CO(2) conditions, they exhibited a significant accumulation of the 2.0-kilobase CA transcript after 1 hour with the maximum level reached after 2 hours. An increase in the accumulation of the 37-kilodalton CA monomer was observed after 2-hour exposure to air. Cells allowed to adapt to air levels of CO(2) in the dark showed neither an increase in CA mRNA abundance nor in the accumulation of the enzyme. Similarly, addition of 10 micromole 3-(3,4-dichlorophenyl)-1, 1-dimethylurea immediately after transferring high-CO(2) cells to low-CO(2) condition did not cause an increase in CA transcript abundance and enzyme accumulation, suggesting that photosynthesis is absolutely required in the regulation of CA transcript abundance. In addition to the photosynthesis-dependent process, a blue light stimulated mechanism is also involved in CA transcript regulation. Experiments with transcription inhibitors confirmed the notion that the gene for carbonic anhydrase enzyme is encoded by the nuclear genome and that the induction of the enzyme depends heavily on the transcription of the CA gene.

Journal Article↗
PubMed1989

The occipital-vertebral anastomosis as a collateral pathway: hemodynamic patterns--case report.

The authors describe the case of a 67-year-old man with acquired obstruction of the common carotid artery and a large, direct occipital-vertebral artery anastomosis bridging the vertebral and carotid artery systems. They discuss the hemodynamics within this type of anastomosis in the context of cerebrovascular occlusive disease and outline their classification of the hemodynamic patterns that have been observed. Surgical procedures for occlusive disease in the presence of such anastomoses are also addressed.

Aged↗
PubMed1988

Photosynthetic characteristics of an amphibious plant, Eleocharis vivipara: Expression of C(4) and C(3) modes in contrasting environments.

Eleocharis vivipara Link, a freshwater amphibious leafless plant belonging to the Cyperaceae can grow in both terrestrial and submersed aquatic conditions. Two forms of E. vivipara obtained from these contrasting environments were examined for the characteristics associated with C(4) and C(3) photosynthesis. In the terrestrial form (delta (13)C values = -13.5 to -15.4 per thousand, where per thousand is parts per thousand), the culms, which are photosynthetic organs, possess a Kranz-type anatomy typical of C(4) plants, and well-developed bundle-sheath cells contain numerous large chloroplasts. In the submersed form (delta (13)C value = -25.9 per thousand), the culms possess anatomical features characteristic of submersed aquatic plants, and the reduced bundle-sheath cells contain only a few small chloroplasts. (14)C pulse-(12)C chase experiments showed that the terrestrial form and the submersed form fix carbon by way of the C(4) pathway, with aspartate (40%) and malate (35%) as the main primary products, and by way of the C(3) pathway, with 3-phosphoglyceric acid (53%) and sugar phosphates (14%) as the main primary products, respectively. The terrestrial form showed photosynthetic enzyme activities typical of the NAD-malic enzyme-C(4) subtype, whereas the submersed form showed decreased activities of key C(4) enzymes and an increased ribulose 1,5-bisphosphate carboxylase (EC 4.1.1.39) activity. These data suggest that this species can differentiate into the C(4) mode under terrestrial conditions and into the C(3) mode under submersed conditions.

Journal Article↗