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Biomedical subjects

C Ogata

Publications and source records attributed to C Ogata.

At least 19 recordsLinked to original sources
PubMed2005

Evaluation of intrarenal hemodynamics by Doppler ultrasonography for renoprotective effect of angiotensin receptor blockade.

AIMS: It has been shown that both angiotensin-converting enzyme inhibitors (ACE-I) and angiotensin II type 1 receptor blockers (ARB) have renoprotective effects via mechanisms that are independent of blood pressure reduction. The aim of this study was to evaluate the intrarenal hemodynamic change with ARB by renal Doppler ultrasonography (RDU) and to assess the mechanism of ARB in patients with hypertension. METHODS: Thirty hypertensive patients with renal insufficiency caused by glomerular diseases, diabetes and hypertensive nephrosclerosis were included in this study. RDU was performed before and one week after taking ARB. Resistance index (RI) (peak systolic velocity - end diastolic velocity/peak systolic velocity) in the intrarenal segmental artery were calculated, and the amounts of urinary protein or albumin were determined. RESULTS: We defined patients whose microalbuminuria or proteinuria was reduced by greater than 30% by ARB as responders (n = 22) and defined other patients as non-responders (n = 8). There were no significant differences between the responder and non-responder groups in baseline characteristics. RI was significantly improved by ARB in the responder group, but not in the non-responder group. The reduction of RI after ARB treatment was most prominent in patients with hypertensive nephrosclerosis. CONCLUSIONS: Improvement in intrarenal hemodynamics might play an important role in the mechanisms of the renoprotective effect of ARB in patients with hypertension.

Angiotensin II Type 1 Receptor Blockers↗
PubMed2000

Effects of cationic charge on three-dimensional structures of intercalative complexes: structure of a bis-intercalated DNA complex solved by MAD phasing.

We characterize intercalative complexes as either "high charge" and "low charge". In low charge complexes, stacking interactions appear to dominate stability and structure. The dominance of stacking is evident in structures of daunomycin, nogalamycin, ethidium, and triostin A/echinomycin. By contrast in a DNA complex with the tetracationic metalloporphyrin CuTMPyP4 [copper (II) meso-tetra(N-methyl-4-pyridyl)porphyrin], electrostatic interactions appear to draw the porphyrin into the duplex interior, extending the DNA along its axis, and unstacking the DNA. Similarly, DNA complexes of tetracationic ditercalinium and tetracationic flexi-di show significant unstacking. Here we report x-ray structures of complexes of the tetracationic bis-intercalator D232 bound to DNA fragments d(CGTACG) and d(BrCGTABrCG). D232 is analogous to ditercalinium but with three methylene groups inserted between the piperidinium groups. The extension of the D232 linker allows it to sandwich four base pairs rather than two. In comparison to CuTMPyP4, flexi-di and ditercalinium, stacking interactions of D232 are significantly improved. We conclude that it is not sufficient to characterize intercalators simply by net charge. One anticipates strong electrostatic forces when cationic charge is focused to a small volume or region near DNA and so must consider the extent to which cationic charge is focused or distributed. In sum, ditercalinium, with a relatively short linker, focuses cationic charge more narrowly than does D232. So even though the net charges are equivalent, electrostatic charges are expected to be of greater structural significance in the ditercalinium complex than in the D232 complex.

Cations↗
PubMed1998

Structure of the complex of Maclura pomifera agglutinin and the T-antigen disaccharide, Galbeta1,3GalNAc.

Maclura pomifera agglutinin is a tetrameric plant seed lectin with high affinity for the tumor-associated T-antigen disaccharide, Galbeta1,3GalNAcalpha, and hence for many O-linked glycopeptide structures. Unlike members of most lectin families, it lacks both metal ions and Cys residues. The structure of its complex with Galbeta1,3GalNAc was determined to 2.2 by first using multiwavelength anomalous diffraction with a lead derivative of the native protein, and then using molecular replacement with the unrefined structure as a model to solve the structure of the complex. The subunits share the beta-prism architecture and three-fold pseudo-symmetry of the related lectin jacalin, with the 21-residue beta-chains in the center of the tetramer. Interactions with the GalNAc predominate in the binding of the disaccharide. It forms a network of H-bonds with only one side chain, from an Asp residue, the amino group of the N-terminal Gly of the alpha-chain, and peptide backbone atoms of two aromatic residues. The Gal moiety does not H-bond directly with residues in the same monomer, i.e. there is no true subsite for it, but there are interactions through two water molecules. In the crystal, it interacts with residues in the binding site of an adjacent tetramer. The minimum energy conformation expected for the disaccharide is retained, despite its mediating the tetramer-tetramer interactions in the crystal packing. The resulting lattice is comparable to those seen for complexes of other lectins with branched glycopeptides.

Antigens, Tumor-Associated, Carbohydrate↗
PubMed1996

Crystal structure of the rat liver fructose-2,6-bisphosphatase based on selenomethionine multiwavelength anomalous dispersion phases.

The crystal structure of the recombinant fructose-2,6-bisphosphatase domain, which covers the residues between 251 and 440 of the rat liver bifunctional enzyme, 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase, was determined by multiwavelength anomalous dispersion phasing and refined at 2.5 A resolution. The selenomethionine-substituted protein was induced in the methionine auxotroph, Escherichia coli DL41DE3, purified, and crystallized in a manner similar to that of the native protein. Phase information was calculated using the multiwavelength anomalous dispersion data collected at the X-ray wavelengths near the absorption edge of the K-shell alpha electrons of selenium. The fructose-2,6-bisphosphatase domain has a core alpha/beta structure which consists of six stacked beta-strands, four parallel and two antiparallel. The core beta-sheet is surrounded by nine alpha-helices. The catalytic site, as defined by a bound phosphate ion, is positioned near the C-terminal end of the beta-sheet and close to the N-terminal end of an alpha-helix. The active site pocket is funnel-shaped. The narrow opening of the funnel is wide enough for a water molecule to pass. The key catalytic residues, including His7, His141, and Glu76, are near each other at the active site and probably function as general acids and/or bases during a catalytic cycle. The inorganic phosphate molecule is bound to an anion trap formed by Arg6, His7, Arg56, and His141. The core structure of the Fru-2,6-P2ase is similar to that of the yeast phosphoglycerate mutase and the rat prostatic acid phosphatase. However, the structure of one of the loops near the active site is completely different from the other family members, perhaps reflecting functional differences and the nanomolar range affinity of Fru-2,6-P2ase for its substrate. The imidazole rings of the two key catalytic residues, His7 and His141, are not parallel as in the yeast phosphoglycerate mutase. The crystal structure is used to interpret the existing chemical data already available for the bisphosphatase domain. In addition, the crystal structure is compared with two other proteins that belong to the histidine phosphatase family.

Acid Phosphatase↗
PubMed1990

[A study of ultrasonic scaling in combination with povidone-iodine solution. (1)].

The effects of ultrasonic scaling in combination with povidone-iodine solution were examined clinically. The results obtained were as follows: 1. Three days after instrumentation, significant improvement was found in all experimental groups. Thereafter the improvement was at the same level and backing in each group. 2. Clinical findings, with exception of plaque index, showed improvement with ultrasonic scaling in combination with povidone-iodine solution in comparison with ultrasonic scaling alone and root planing.

Combined Modality Therapy↗
PubMed1989

[Effectiveness of local delivery of ofloxacin using controlled-release strips (PT-01) in periodontal patients. Part 2. Successive delivery system and combination with scaling].

Four different sites were randomly selected in each periodontal patient and divided into four group: PT-01-treated site (A), PT-01 treatment combined with scaling (S + A), placebo-treated site (P) and placebo treatment combined with scaling (S + P). PT-01 and the placebo were applied to the periodontal pocket weekly on days 0 to 28, and clinical and microbiological evaluations were made. The results obtained were as follows: 1. Weekly changes in plaque index, plus discharge and mobility of the tooth were not observed in any group. 2. In gingival index, bleeding on probing, pocket depth and gingival crevicular fluid, significant improvement was found in A in comparison with P and in S + A in comparison with S + P. 3. In total number of subgingival bacteria and in the ratio of motile rods and spirochetes to the total number of bacteria, significant reduction was found in A in comparison with P and in S + A in comparison with S + P.

Delayed-Action Preparations↗
PubMed1984

Acute and chronic complications of laser angioplasty: vascular wall damage and formation of aneurysms in the atherosclerotic rabbit.

Acute and chronic vascular responses to laser exposure in atherosclerotic rabbits were studied. In 7 rabbits fed an atherogenic diet for 3 to 5 months before the study to induce aortic atherosclerosis, a flexible quartz fiber, 400 micron core diameter, attached to an argon ion laser was passed anterogradely or retrogradely to the atherosclerotic ascending aorta. The laser was turned on using power intensities of 1 to 2 W for 3 seconds. After laser treatment, the aortas were studied acutely in 3 rabbits and chronically in 4 rabbits after recovery for 1 to 14 days. In 2 rabbits studied acutely, the argon laser produced a vaporized crater within the atherosclerotic plaque at the endothelial surface; however, in 1 there was also vascular damage extending deep into the medial layer. In addition, aortic aneurysm with muscular wall damage occurred in 2 of the 4 animals studied chronically. Thus, vascular complications may arise when catheter laser angioplasty is randomly applied without visualizing specific plaque targets or without using safe dose increments of power intensities and durations of exposure. This study suggests caution in the clinical use of intensive phototherapy to cardiovascular lesions and stresses the need for further understanding of laser vascular consequences before application of laser angioplasty in patients.

Animals↗
PubMed1984

Intraoperative use of dual fiberoptic catheter for simultaneous in vivo visualization and laser vaporization of peripheral atherosclerotic obstructive disease.

Since laser energy has been shown to produce controlled thermal injury to atherosclerotic plaques from postmortem human hearts, a 3-mm diameter fiberoptic catheter was devised and tested for use in peripheral vessels. The catheter has channels for viewing, laser delivery, and suction/flushing. In five femoral or carotid arteries from three dogs implanted with near-total human atherosclerotic obstructions, the fiberoptic catheter was capable of viewing and targeting the atherosclerotic plaque for laser irradiation. The plaque was vaporized using 5 watts with time exposures lasting from 2 to 5 sec from an argon-ion laser. In three other animals each implanted with a 3- to 4-cm long segment of human cadaver atherosclerotic vessel, the fiberoptic catheter clearly visualized the internal diseased vascular wall. Thus, this investigation provides the initial demonstration and practicality of applying a flexible dual fiberoptic catheter for simultaneous in vivo visualization and laser vaporization of peripheral atherosclerotic disease.

Animals↗
PubMed1983

Effects of laser irradiation on human thrombus: demonstration of a linear dissolution-dose relation between clot length and energy density.

Because vascular thrombosis often accompanies arteriosclerotic disease in occluding blood vessels, the dissolution properties of laser irradiation were investigated and the energies needed to penetrate different lengths of thrombus were quantitated. Spectrophotometric studies show that the blood clot due to the presence of hemoglobin is well absorbed by argon laser energies, which emit blue-green wavelengths between 454 and 514 nm. Thus, laser energies transmitted directly from an argon-ion source produced vaporization and penetration of human thrombus in a linear dose-response fashion; the longer the thrombus, the greater the power intensity or time exposure necessary to penetrate the clot.

Dose-Response Relationship, Radiation↗
PubMed1983

Effects of laser irradiation on human erythrocytes: considerations concerning clinical laser angioplasty.

Recent studies demonstrate the potential use of laser to vaporize human coronary atherosclerotic plaques. The laser energy is transmitted through flexible quartz fiber and discharged intravascularly. Since red blood cells could be exposed to intense heat, we examined effects of laser irradiation on human erythrocytes. Blood was obtained and placed in 5 ethylene diaminetetracidic acid (EDTA) vials for each normal donor. A flexible 400 microns diameter core quartz fiber coupled to an argon-ion laser source was positioned 1 cm above the surface of 1.5 ml blood. Four vials were exposed to 5 W laser beam for 5, 10, 15, or 20 s; the remaining vial was left untreated. Packed cell volume fell primarily during the first 5 s of laser exposure (p less than 0.01) and plateaued beyond 5 s. Plasma hemoglobin (Hgb) rose progressively with each increased duration of exposure (p less than 0.01). This study indicates that lysis of erythrocytes occurs in cells exposed directly to the laser beam. However, beyond the direct beam, damage to red cell membrane took place as evident by progressive Hgb leakage into plasma despite no further cell lysis. These observations require consideration during clinical laser angioplasty.

Erythrocyte Indices↗
PubMed1983

Laser irradiation of congenital heart disease: potential for palliation and correction of intracardiac and intravascular defects.

We examined the potential for laser irradiation of congenital heart defects, with the use of postmortem hearts and an argon ion laser with a flexible quartz fiber. Atrial septectomy was performed in five newborn hearts. Obstructive lesions were relieved by laser irradiation in valvular pulmonic and aortic stenosis, dysplastic pulmonary valve, pulmonary atresia, and coarctation of the aorta. To demonstrate the efficacy of in vivo cardiac laser surgery, atrial septectomy was also performed in an anesthetized dog model, under echocardiographic visualization, without change in heart rate or blood pressure. Our results demonstrate the feasibility of intracardiac and intravascular laser irradiation for palliation and repair of selected congenital heart diseases.

Animals↗
PubMed1966

Episome-mediated transfer of drug resistance in Enterobacteriaceae. IX. Recombination of an R factor with F.

Watanabe, Tsutomu (Keio University, Tokyo, Japan), and Chizuko Ogata. Episome-mediated transfer of drug resistance in Enterobacteriaceae. IX. Recombination of an R factor with F. J. Bacteriol. 91:43-50. 1966.-R factors can be transduced in Salmonella typhimurium with phage P-22, and a majority of the drug-resistant transductants are unable to transfer their drug resistance by cell-to-cell contact, as we have previously reported. Several exceptional types of transductants of S. typhimurium, with the markers of resistance to sulfonamide, streptomycin, and chloramphenicol, were recently obtained by transduction with phage P-22 of a four-drug-resistance R factor carrying the markers of resistance to sulfonamide, streptomycin, chloramphenicol, and tetracycline. They were exceptional in that they had low conjugal transferability of their drug resistance. When one of these exceptional transductants (38R) was transferred to an F(+) strain of Escherichia coli K-12, 38R acquired high transferability in its further transfer. This high transferability was found to be due to the recombination of 38R with F. Transductant 38R was of the fi(+) (fi = fertility inhibition) type, and did not show superinfection immunity against fi(+) and fi(-) R factors. The recombinant 38R.F was genetically very stable and resistant to elimination with acridines. It did not show superinfection immunity against fi(+) and fi(-) R factors, but did show superinfection immunity against F. Further, 38R.F did not restrict a female-specific phage (W-31), unlike wild-type F. F(-) and R(-) segregants were isolated from this recombinant 38R.F, and these segregants exhibited genetic characteristics different from the original R, its transductant 38R, and wild-type F.

Coliphages↗