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Biomedical subjects

M Kataoka

Publications and source records attributed to M Kataoka.

At least 271 records · Page 15Linked to original sources
PubMed1993

Ammonia potentiates GABAA response in dissociated rat cortical neurons.

The ammonium ion (NH4+) evoked no response itself but facilitated the GABA-induced Cl- current (ICl) in dissociated rat cortical neurons. The GABA concentration-response curve shifted parallely to the left without changing the maximum response. Reversal potential of GABA response did not change in the presence of NH4+ at the concentration range between 0.1 and 1 mM. Ro 15-1788, a selective benzodiazepine receptor antagonist, did not affect the facilitatory action of NH4+ on GABAA receptor. The results suggest that NH4+ modifies the affinity of GABAA receptor for GABA, without the involvement of benzodiazepine receptors.

Ammonia↗
PubMed1993

Purification of a fibroblast-inhibitory factor from Actinobacillus actinomycetemcomitans Y4.

A factor showing inhibitory activity against human gingival fibroblasts was extracted from the cytosol fraction of Actinobacillus actinomycetemocimitans Y4. The activity markedly inhibited the proliferation of human gingival fibroblasts, but had no effect on cell viability or gross morphology. No such activity was found in cytosol fractions from either Porphyromonas gingivalis 381 or Escherichia coli HB101. The extract from A. actinomycetemocomitans Y4 was then purified by anion-exchange chromatography, hydroxyapatite chromatography and gel-filtration chromatography to give a single band on SDS-PAGE with an apparent molecular mass of 65 kDa. The purification ratio was 183-fold with a recovery rate of 5% compared with the crude extract (starting material) when the activity was assessed by direct cell counts.

Actinobacillus↗
PubMed1993

Molten globule of cytochrome c studied by small angle X-ray scattering.

Recent advances in the small angle X-ray scattering technique have made it possible to obtain information on the spatial distribution of protein structure in solution, such as the radius of gyration and shape of the molecule, in a relatively short time. We have studied the various conformational states of horse ferricytochrome c by small angle X-ray scattering. Whereas Guinier plots showed that the radius of gyration of the molten globule state is slightly larger than that of the native state, Kratky plots indicated that their shape is globular. To clarify the mechanism of the formation of the molten globule state, we measured, by the small angle X-ray scattering, the equilibrium transition at pH 2 from the acid-unfolded state to the molten globule state, which was induced either by the addition of NaCl or the acetylation of lysyl amino groups. The Kratky plots at various stages of folding showed an isoscattering point, strongly suggesting a two-state mechanism. For both the NaCl and acetylation-induced transitions, the transition curve determined from Kratky plots agreed well with the transition curves from far-ultraviolet circular dichroism, tryptophan fluorescence, and Soret absorption, further supporting the two-state mechanism.

Acetylation↗
PubMed1993

Mediastinal abscess caused by a pyriform sinus fistula: report of a case.

A 13-year-old boy who originally presented with a left neck abscess rapidly developed a mediastinal abscess and empyema. Repetitive esophagography for the persistent mediastinal abscess revealed the existence of a pyriform sinus fistula. It was thought that infection of the pyriform sinus fistula precipitated a retropharyngeal abscess which continuously extended to the mediastinum. To our knowledge, no other such case has ever been reported and we present this unusual case herein, followed by a short review of the related literature.

Abscess↗
PubMed1993

Esophageal schwannoma.

A 56-year-old woman was seen with an abnormal shadow on chest radiogram. Evaluation revealed an esophageal tumor, which was resected. The tumor was found in the muscular layers of the esophagus; esophageal schwannoma was diagnosed by light microscopic and immunohistochemical studies. There was no relationship between the tumor and vagus nerve. The tumor demonstrated partially invasive growth, and mitotic figures were occasionally observed.

Esophageal Neoplasms↗
PubMed1993

Recoverin alters its surface properties depending on both calcium-binding and N-terminal myristoylation.

The solution structure and calcium-dependent structural changes of recoverin, a 23 kDa calcium binding protein of vertebrate photoreceptors, have been studied by small-angle X-ray scattering and CD, as well as the effect of N-terminal myristoylation. The CD spectrum is not affected by N-terminal myristoylation, but strongly affected by Ca2+, indicating that N-terminal myristoylation alone does not cause a conformational change. The major conformational change in recoverin induced by Ca2+ is characterized as a decrease in the alpha-helical content of the protein and an increase in global size upon removal of Ca2+. In the presence of Ca2+, unmyristoylated recoverin is monomeric and globular in solution, while N-terminal myristoylation brings about aggregation. In the absence of Ca2+, unmyristoylated recoverin tends to aggregate, while myristoylated recoverin becomes monomeric and globular. These observations indicate that recoverin changes its surface properties depending on both calcium binding and N-terminal myristoylation. Melittin interacts non-specifically only with the myristoylated recoverin in the absence of Ca2+. This may be indicative of the properties of the interaction between recoverin and its normal physiological target enzyme.

Calcium↗
PubMed1993

An approach for assaying benzodiazepine receptor binding with radioiodinated ligand: 125I-labeled diazepam derivative.

[125I]2'-Iododiazepam (IDZ) was prepared and its application in a benzodiazepine receptor binding assay was studied. [125I]2'-IDZ binds to the rat cortical membrane with a high affinity (Kd, 0.66 nM). Various benzodiazepines showed competition with [125I]2'-IDZ for the binding sites in the rat cortical membrane, and the specificity of its binding correlated well with that of [3H]diazepam (r = 0.992, p < 0.001). These findings suggested that [125I]2'-IDZ binds to the same sites as [3H]diazepam and indicated that [125I]2'-IDZ can be used in a benzodiazepine receptor assay.

Animals↗
PubMed1993

[Study on the experimental ulcerative colitis model induced by dextran sulfate sodium in rats: estimation of mucosal erosions by the alcian blue-staining method].

We have developed a new method that is applicable for a macroscopic and objective evaluation of erosion in the large intestine in the experimental ulcerative colitis model induced by dextran sulfate sodium (DSS) in rats. The large intestine (without cecum) fixed in 10% neutral buffered formalin solution for more than one week was opened and stained with 1% alcian blue solution. The mucosal surface was stained in light and shade-blue. Histopathological examination revealed that the dark blue area on the mucosal surface had no epithelia and that the connective tissues in the lamina propria were stained with alcian blue. Salazosulfapyridine at 15 and 50 mg/kg twice a day inhibited the erosion area (dark blue area) by 29.6% and 50.2%, respectively. Also, prednisolone at 0.5 mg/kg, twice a day inhibited the erosion by 53.3%. Thus, by measuring the dark blue area stained with 1% alcian blue solution, we could estimate macroscopically and objectively the area of erosions. This method seems to be a useful index for assessing the damages produced in the experimental ulcerative colitis model in rats.

Alcian Blue↗
PubMed1993

[Effect of MHS-G, an amino acids granule, on hepatic encephalopathy in portacaval anastomosis rats].

Using portacaval anastomosis (PCA) rats as a model with or without injection of ammonium acetate, we investigated the effects of MHS-G on the abnormalities of electroencephalogram (EEG) and brain amines metabolism in comparison with those of SF-1008C, a commercial nutritional preparation for hepatic failure. MHS-G (0.68 g/kg, p.o.) clearly improved both the abnormalities of EEG (such as reduction of amplitude, increasing delta wave distribution and decreasing beta wave distribution) and brain amines metabolism (such as increasing of Trp and DOPAC content) after injection of ammonium acetate. Moreover, MHS-G significantly increased branched chain amino acid concentrations and decreased aromatic amino acid concentrations in plasma and brain in comparison with water, and it significantly decreased the ammonia level in plasma in comparison with water and SF-1008C. These results suggest that MHS-G has a positive effect on abnormalities of EEG and amino acids metabolism in the plasma and brain of PCA rats.

Acetates↗
PubMed1993

Interactions of hydroxyl radicals with tris (hydroxymethyl) aminomethane and Good's buffers containing hydroxymethyl or hydroxyethyl residues produce formaldehyde.

The production of formaldehyde from tris(hydroxymethyl) aminomethane(Tris) by interaction with hydroxyl radicals(.OH) was studied, since the reaction mixture from the Fenton reaction performed in Tris/HCl buffer was found to be color-developed by colorimetric determination of formaldehyde. The absorption spectrum of chromogens was identical to that of authentic formaldehyde. Color development, which required the presence of Tris, hydrogen peroxide and cupric ions in the Fenton reaction mixture, was inhibited by the addition of hydroxyl radical scavengers such as glucose or hyaluronic acid. These results indicated that formaldehyde was produced when Tris interacted with .OH. With structures similar to Tris, Good's buffers were also found to produce formaldehyde by interaction with .OH. Analysis of formaldehyde derived from these buffers may provide a simple and convenient assay for detecting .OH generation. In evaluating effects of .OH on the biological system in Tris/HCl buffer or certain Good's Buffers, .OH loss may be due to interactions of .OH with these buffers. The formaldehyde produced as a result of such interactions may affect biological systems.

Buffers↗
PubMed1993

[Long-term results of transscleral retinal detachment surgery with special reference to visual function].

We studied visual acuity and visual field of 44 eyes in 42 patients who had undergone transscleral retinal detachment surgery, they were classified into a preoperative group, a postoperative group, and a group ten years after surgery. With regard to visual acuity, the postoperative group showed a significant increase compared with the preoperative group (p < 0.001), and there was no significance between the postoperative group and the group ten years after surgery. In order to quantify the visual field obtained by Goldmann perimeter, the areal size of V-4 isopter, the areal size of I-4 isopter and the volume of the visual field were adopted in the present study. Each of the three mean values was high in the following order: the group ten years after surgery, the postoperative group, and the preoperative group. The mean value of the group ten years after surgery was respectively equivalent to 80.6%, 65.5%, and 71.1% of that of normal control in the order: the areal size of V-4 isopter, the areal size of I-4 isopter, and the volume of the visual field. Our results support the conclusion that the visual acuity acquired postoperatively can be maintained for ten years after surgery. The visual field acquired postoperatively also seems to be retained ten years after surgery.

Adolescent↗
PubMed1993

[Effects of MRX-III on chronic renal failure in rats].

The effects of MRX-III, a new amino acid solution for renal failure, on survival, progression of renal insufficiency, metabolism of calcium and phosphorous, and nutritional status were studied in rats with chronic renal failure induced by 7/8 renal ablation. These rats were injected intraperitoneally with MRX-III, an essential amino acid solution for renal failure (Amiyu; Sol. A) or a general amino acid solution (Moripron-F; Sol. M) for 12 weeks under the condition of a 3.5% protein diet, and these effects were compared with those in control rats infused with Sol. M under a 22% protein diet.1) Infusion of MRX-III or the other solutions under a low protein diet prolonged survival time and improved the uremic status indicated by azotemia, polyuria, albuminuria, hypocalcemia and hypertension. 2) Increase in body weight and tissue weight of rats treated with MRX-III or Sol. A was better than those in rats treated with Sol. M. MRX-III as well as Sol. A showed a tendency to provide a better nutritional effect in comparison with Sol. M.

Amino Acids, Essential↗
PubMed1993

[Analysis of MDR1 (multidrug resistance) gene expression by RT-PCR].

Multidrug resistance to anticancer drugs proved to be related to the MDR1 gene which encodes the P-glycoprotein, an energy-dependent drug-efflux pump for lipophilic drugs. We investigated the expression of the MDR1 gene in clinical samples by RT-PCR. The subjects were all resected cases of 14 colorectal cancers, five gastric cancers, two esophageal cancers, two gallbladder cancers and 20 lung cancers. Adrenal gland was used as a positive control. Total RNA was extracted from a fresh tissue sample. The cDNA was synthesized from 1 microgram of total RNA using reverse transcriptase. With the above cDNA as the template, amplification of the 157-bp fragment of the MDR1 gene was performed using PCR. The PCR product was polyacrylamide gel-electrophoresed and ethidium bromide-stained. In addition, a dot blot analysis was performed to quantify the amount of PCR product. Since PCR was performed simultaneously under the same conditions, the PCR product was quantified at four stages, from (3+) to (-), to indicate the degree of expression of MDR1 mRNA. Adrenal gland showed (3+)-(2+) and colorectal cancer exhibited mostly (2+)-(1+). Both cancerous and non-cancerous areas evidenced a similar degree of expression in the cases of colorectal cancer. The MDR1 gene was expressed at low levels in other digestive tract cancers and in lung cancer. The levels of MDR1 expression revealed no correlation to either histological type or clinical stage. The present method may contribute to designing anti-cancer protocols.

Antineoplastic Agents↗
PubMed1993

Radioiodinated 2'-iododiazepam: a potential imaging agent for SPECT investigations of benzodiazepine receptors.

2'-Iododiazepam (2'-IDZ) is the diazepam analogue iodinated at the 2'-position of C-5 phenyl ring which was synthesized and evaluated as a potential radiopharmaceutical for investigating brain benzodiazepine receptors by SPECT. The 125I-2'-iododiazepam was synthesized by halogen exchange reaction and purified by HPLC. In vitro competitive binding studies with 3H-diazepam, using rat cortical synaptosomal membranes, showed that the affinity of 2'-IDZ for benzodiazepam receptors was higher than that in diazepam and flumazenil (RO15-1788). Biodistribution studies in mice showed that the brain uptake of 2'-iododiazepam was rapid and profound, and in the brain higher accumulation was found in the cortex than in other regions. Furthermore, the cortical uptake was displaced by benzodiazepinergic compounds. In vivo uptake was assessed by autoradiographic studies. Thus, 2'-iododiazepam bound to benzodiazepine receptors in vivo and therefore holds great potential for in vivo benzodiazepine receptor studies.

Animals↗
PubMed1992

Effects of Ca2+ antagonists and antiepileptics on tetrodotoxin-sensitive Ca(2+)-conducting channels in isolated rat hippocampal CA1 neurons.

All Ca2+ antagonists blocked tetrodotoxin-sensitive Ca2+ current (TTX-ICa) more potently than Na+ current (INa). Phenytoin and MK-801, at concentrations which had no effect on INa, could block TTX-ICa concentration-dependently. Valproic acid and phenobarbital had no effect on both TTX-ICa and INa. In particular, flunarizine and phenytoin have more potent inhibitory effects on TTX-ICa than other test drugs. These results suggest that the abnormal excess-excitation of TTX-sensitive Ca(2+)-conducting channels may be one of the trigger factors generating epilepsy.

Animals↗
PubMed1992

Charge repulsion in the conformational stability of melittin.

Electrostatic repulsion between positively charged groups has been suggested to be critical in determining the conformation of melittin. To clarify the role of repulsive forces, we prepared a series of succinylated melittins, an acetylated melittin, and a synthetic melittin mutant, with various degrees of charge repulsion. The conformation of the melittin derivatives was examined by far-UV circular dichroism under various conditions of pH and salt at 20 degrees C. The stability of the tetrameric helical state was found to be dependent on the net charge of the peptides. The charge repulsive forces destabilized the helical state of intact melittin by 600 cal/(charge.mol of tetramer). This value was close to the corresponding one (450 cal/(charge.mol)) obtained for the acidic molten globule of horse cytochrome c [Goto, Y., & Nishikiori, S. (1991) J. Mol. Biol. 222, 679-686], which has a molecular weight and a net charge comparable to those of the tetrameric melittin. Small-angle X-ray scattering of the tetrameric melittin and the molten globule of cytochrome c showed that the two states are also comparable to each other in the radius of gyration. These results suggest that the contribution of electrostatic repulsion to the conformational stability of melittin is similar to that of the molten globule.

Amino Acid Sequence↗