Search PubMed⌕ Search

Biomedical subjects

M Otsuka

Publications and source records attributed to M Otsuka.

At least 253 records · Page 14Linked to original sources
PubMed1994

Mechanochemical synthesis of bioactive material: effect of environmental conditions on the phase transformation of calcium phosphates during grinding.

The effect of environmental conditions on the crystalline transformation of metastable calcium phosphates during grinding was investigated using X-ray diffractometry and fourier transformed infrared spectroscopy. A mixture of CoA and dicalcium phosphate anhydrate (DCPA, CaHPO4) did not transform after grinding in air. On the other hand, CaO and dicalcium phosphate dihydrate (DCPD, CaHPO4 2H2O) were converted into a noncrystalline solid. Mixtures of DCPD and Ca(OH)2 transformed into low-crystallinity hydroxyapatite after grinding in air. When ground under N2, a mixture of Ca(OH)2 and DCPD did not transform into hydroxyapatite, whereas that of DCPD: Ca(OH)2: CaCO3 = 1:0.8: 0.2 did. The results of X-ray diffraction of FT-IR spectra suggested that the presence of carbon dioxide in the grinding system was necessary for transformation from metastable calcium phosphates to hydroxyapatite.

Air↗
PubMed1994

[Efficacy of combination therapy against MRSA in Ibaraki Prefecture].

Clinical efficacies of fosfomycin (FOM) or arbekacin (ABK) plus beta-lactam combination therapies against methicillin-resistant Staphylococcus aureus (MRSA) infections were examined in 15 major hospitals in Ibaraki Prefecture. The subjects were 54 inpatients from January 1991 to April 1993, and most of them showed moderate to severe infections with underlying diseases. MRSA alone was isolated from 23 patients and the other 31 patients had polymicobes including MRSA. Pseudomonas aeruginosa was the most frequent among the co-isolated strains. The number of patients treated with FOM and cefmetazole (CMZ) was 22 (Group C) and that with FOM and flomoxef (FMOX) was 25 (Group F). CMZ or FMOX was administrated 60 minutes after FOM administration. To 8 nonresponding patients in Groups C and F and 7 nonresponders to the other therapies, ABK and ceftazidime (CAZ) or ABK and piperacillin (PIPC) were treated simultaneously (Group A). The clinical efficacies of Groups C and F were 63.6% and 64%, respectively. The bacteriological efficacies (eradication rates) of both groups including microbial substitutions were 42.9% in the former and 56.5% in the latter. No statistical differences were observed in the clinical and the bacteriological efficacies between Groups C and F. The clinical and bacteriological efficacies in Group A were 66.7% and 46.2%, respectively. No side effects were observed in any cases. Mild disturbances of hepatic functions were observed in 2 cases of Groups C and F, and there were no abnormal laboratory test results in Group A.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1994

The distribution of ascorbic acid and dehydroascorbic acid during tissue regeneration in wounded dorsal skin of guinea pigs.

The distribution of L-ascorbic acid AA and dehydroascorbic acid DHA in wounded and intact skin of guinea pig was investigated to elucidate the utilization of AA during tissue regeneration. Male guinea pigs fed an AA-free diet for 14 days were surgically injured on the dorsal skin, followed by intraperitoneal supplementation of AA (0.5, 5 and 50 mg/day/animal) for 4 days. The wounded skin, its surroundings and intact skin in each animal were removed for the determination of AA, DHA and collagen. The collagen content in wounded and intact skin increased in dose-dependent manner up to 5 mg AA/day, although neither the wounded nor the intact skin of the group supplemented with 50 mg AA had a higher content of collagen than those supplemented with 5 mg. In each group, the wounded skin had only about half the collagen of intact skin. AA content in the wounded skin of the groups supplemented with 5 and 50 mg AA were significantly lower than that in the other parts of their skin, whereas DHA content in wounded skin increased markedly. These results indicate that other factors besides collagen synthesis may enhance the oxidation of AA in the early stage of tissue regeneration.

Animals↗
PubMed1993

Pharmacological characteristics of tachykinin receptors mediating acetylcholine release from neonatal rat spinal cord.

The pharmacological profiles of tachykinin receptors mediating the release of acetylcholine were examined in the isolated spinal cord of the neonatal rat. The acetylcholine release evoked by neurokinin A or acetyl-[Arg6,Pro9]substance P-(6-11) was depressed by the tachykinin antagonists, spantide and GR71251 at 10 microM, whereas the release evoked by substance P (0.3 microM) or neurokinin B (0.3 microM) was not affected by these tachykinin antagonists. Polymerase chain reaction amplification of rat spinal cord cDNA and sequence analysis revealed the presence of a substantial amount of fragments having sequences identical to that of the NK1 or NK3 receptor, but only a few having a sequence identical to that of the NK2 receptor. These results suggest that in the neonatal rat spinal cord a novel subtype of tachykinin receptor similar but not identical to the classical NK1 receptor is involved in tachykinin-evoked acetylcholine release.

Acetylcholine↗
PubMed1993

Cleavage of yeast tRNA(phe) with Ni(III) and Co(III) complexes of bleomycin.

The BLM-Ni(III) complex preferentially cleaves guanine residues at D loop and anticodon loop of yeast tRNA(phe) by aniline treatment, whereas the BLM-Co(III) complex degrades certain 5'-AN sites of the minor groove region after irradiation of UV light. These cleavage features are clearly different from that of the BLM-Fe(II) complex.

Base Sequence↗
PubMed1993

DNA binding and cleavage of a novel antitumor antibiotic dynemicin A: detection of binding and cleavage sites by exonuclease III digestion and alkali-induced cutting reactions.

We found here that dynemicin A effectively breaks DNA strands under alkaline pH condition. Binding of dynemicin A to double-stranded DNA clearly interrupts the digestion reaction of exonuclease III. The DNA association sites of dynemicin A correspond considerably well to its cleavage sites. Dynemicin A seems to intercalate preferentially into the relaxed region of the DNA double helix. On the other hand, the alkali-product of dynemicin A was chromatographically identified with dynemicin N, suggesting a DNA cleavage mechanism similar to the reductant- and light-induced activation systems of dynemicin A. In order to detect drug binding to the relaxation structure in the DNA duplex, the present exonuclease III-digestion-stop-sequence method is useful.

Anthraquinones↗
PubMed1993

Hygroscopic stability and dissolution properties of spray-dried solid dispersions of furosemide with Eudragit.

Spray-dried solid dispersions of furosemide-Eudragit RS100 and RL100 (ethyl methacrylate chlorotrimethylammoniumethyl methacrylate copolymer) were studied to determine their stability at 45 degrees C and 0, 44, and 75% relative humidity and their dissolution characteristics. The crystallization rates of the solid dispersions were measured by X-ray powder diffractometry and calculated on the basis of the Jander equation to estimate physicochemical stability in the presence of water vapor. The stability of the solid dispersion depended on the kind of acrylic resins and the drug content. The solid dispersion with a drug: Eudragit RL100 ratio of 1:3 was the most stable at 75% relative humidity. The dissolution profiles of the solid dispersions were measured in a pH 6.8 buffer at 37 degrees C. The equilibrium drug concentration of the solid dispersions were estimated from the dissolution profiles after 24 h. The equilibrium drug concentration decreased with an increasing Eudragit quaternary ammonium group: furosemide molar ratio. The equilibrium drug concentrations of the solid dispersions with > 0.3 mol of the quaternary ammonium group were approximately 0. Thus, the drug was completely adsorbed on Eudragit.

Acrylic Resins↗
PubMed1993

Effects of temperature and relative humidity on the solid-state chemical stability of ranitidine hydrochloride.

The chemical stability of ranitidine HCl in solution and in the solid state at various temperatures was investigated by high-performance liquid chromatography. Ranitidine HCl was unstable in lower pH buffer solutions, and the percent degradation after 72 h increased as the pH of the buffer solution was reduced. The percent degradation in the unbuffered solution increased dose dependently. The critical relative humidity (CRH) of the ranitidine HCl bulk powder was approximately 67% relative humidity (RH). The amount of water adsorbed onto the sample above the CRH was proportional to the RH level. The percent degradation of the powder below 50% RH was almost negligible because, at this level, it was a solid. The percent degradation at 60-70% RH was higher than that above 70% RH. Ranitidine HCl powder was unstable around the CRH.

Biological Availability↗
PubMed1993

Discordance between thallium-201 scintigraphy and coronary angiography in patients with Kawasaki disease: myocardial ischemia with normal coronary angiogram.

To assess the usefulness of radionuclide tests in detecting coronary occlusive lesions in children with Kawasaki disease, we compared the results of stress thallium-201 myocardial single photon emission computed tomography with dipyridamole infusion and coronary angiography in 34 patients (19 males and 15 females). Perfusion defects on the stress image only were categorized as transient and were attributed to coronary vascular disease in the presence of redistribution on the delayed image. Others were classified as persistent, due to myocardial damage. Five of the seven children (71%) with severe stenosis on coronary angiography showed persistent and/or transient perfusion defects. However, six of the 11 children (55%) with aneurysms but no obvious stenosis, and four of the 16 children (25%) with normal angiography, showed persistent and/or transient defects. After analyzing 20 individual segments of perfusion defects in the 15 children, six segments (30%) were attributed to the stenosis of supplying coronary arteries, six segments (30%) were related to the coronary aneurysms, and eight segments (40%) were unrelated to any abnormalities on angiography. Thus, significant discordance between the radionuclide and angiographic studies was demonstrated. These results suggest that coronary lesions, as conventionally defined by angiography and supplemented by echocardiography, may not completely identify all Kawasaki patients who may develop myocardial ischemia in the future or who had ischemia in the past.

Adolescent↗
PubMed1993

Age-related accumulation of phosphatidylcholine hydroperoxide in cultured human diploid cells and its prevention by alpha-tocopherol.

The levels of phosphatidylcholine hydroperoxide in serially cultured human fetal diploid fibroblasts at various population doubling levels were determined by high-performance liquid chromatography combined with chemiluminescence detection. This methodology utilizes a mixture of cytochrome c and luminol as post-column hydroperoxide group specific luminescent reagents. The cellular hydroperoxide content increased with age from 0.34 to 27.72 pmol/10(6) cells. At the end of the cells' in vitro lifespan (51st population doubling level), the hydroperoxide content per 10(6) cells reached about 80 times the level found in cells of the 20th population doubling level. Supplementation of exogenous alpha-tocopherol to the culture medium prevented hydroperoxide accumulation, but did not extend the lifespan in vitro. The results indicate that substantial intracellular phospholipid hydroperoxide accumulation occurred in the course of aging of human fetal diploid fibroblasts.

Cell Line↗
PubMed1993

Positron emission tomographic (PET) studies in dementia.

Positron emission tomographic (PET) studies of regional cerebral glucose metabolism were performed in patients with various types of dementia, patients with Parkinson's disease but without dementia, and healthy normal controls. Patients with Alzheimer-type dementia showed significant decreases in glucose metabolism in frontal, temporal, parietal, sensory-motor and striatal regions. Patients with Pick's disease revealed decreased glucose metabolism in frontal and temporal regions. Parkinsonian patients with dementia had significant reductions of glucose metabolism in frontal, temporal, parietal, occipital, sensory-motor and striatal regions. Patients with Huntington's disease revealed decreased glucose metabolism in frontal, parietal and striatal regions. Patients with Creutzfeldt-Jakob's disease showed marked decreases in glucose metabolism throughout all brain regions. On the other hand, patients with Parkinson's disease but without dementia exhibited no reductions of cerebral glucose metabolism. Cerebral glucose hypometabolism in these various types of dementia might reflect neuronal dysfunction and cell death.

Adult↗