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Biomedical subjects

M Yoshikawa

Publications and source records attributed to M Yoshikawa.

At least 19 recordsLinked to original sources
PubMed1995

Survival of neurons containing the enzyme nicotinamide adenine dinucleotide phosphate (NADPH) diaphorase in static slice cultures of adult rat striatum.

The present study concerns the survival potential of mature neurons containing the enzyme nicotinamide adenine dinucleotide phosphate (NADPH) diaphorase in the static slice culture of adult rat striatum. In the striatal tissues immediately after slicing, there was a scattered distribution of NADPH-diaphorase neurons stained in a Golgi-like manner, and the cell density of those neurons was 53 +/- 5 (mean +/- SEM; n = 10) cells per mm2. The time-sequential cell density analysis disclosed that the number of striatal NADPH-diaphorase neurons surviving after 1, 2, 4 and 6 day in culture were 26 +/- 5, 8 +/- 2, 5 +/- 2, and 3 +/- 2 (means +/- SEM; n = 10) cells per mm2, respectively. Thus, approximately 50% of striatal NADPH-diaphorase neurons survived for 1 day and a significant proportion of these neurons, although their number gradually decreased, were maintained in culture for at least several days. The conspicuous survival of the striatal NADPH-diaphorase neurons in slice culture is thought to reflect the damage-resistant natures of these cells.

Animals↗
PubMed1995

Contact of Shigella with host cells triggers release of Ipa invasins and is an essential function of invasiveness.

The invasion of colonic epithelial cells by Shigella, an early essential step for causing bacillary dysentery, is mediated by the IpaB, IpaC and IpaD proteins. Secretion of the Ipa proteins from Shigella requires functions encoded by the mxi and spa loci. In this study, we show that contact between the bacteria and epithelial cell triggers release of the Ipa proteins into the external medium, which results in a rapid decrease in levels of Ipa proteins presented on the cell surface. When the bacteria were used to infect polarized Caco-2 cells, release of Ipa proteins occurred efficiently from bacteria interacting with the basolateral surface rather than with the apical surface. Moreover, the interaction of bacteria with components of the extracellular matrix, such as fibronectin, laminin or collagen type IV, also stimulates the release of Ipa proteins. The release of Ipa proteins from Shigella required the surface-located Spa32 protein encoded by one of the spa genes on the large plasmid.

Adhesins, Bacterial↗
PubMed1995

Disulfide oxidoreductase activity of Shigella flexneri is required for release of Ipa proteins and invasion of epithelial cells.

Secretion of IpaB, IpaC, and IpaD proteins of Shigella flexneri, essential for the invasion of epithelial cells, requires a number of proteins encoded by the spa and mxi loci on the large plasmid. Introduction of dsbA::Tn5 into S.flexneri from Escherichia coli K-12 reduced invasiveness, which resulted from a decrease in the capacity to release IpaB, IpaC, and IpaD proteins into the external medium. Examination of the surface-presented Ipa proteins of the dsbA mutant, however, revealed Ipa proteins at levels similar to those on wild-type cells. Since the defective phenotype was similar to that of the spa32 mutant of S. flexneri and the Spa32 sequence possessed two Cys residues, the effect of dsbA mutation of the folding structure of Spa32 under reducing conditions and on the surface expression of Spa32 was investigated. The results indicated that Spa32 was a disulfide-containing protein whose correctly folded structure was required for its presentation on the outer membrane. Indeed, replacing either one of the two Cys residues in Spa32 with Ser by site-directed mutagenesis reduced its capacity to release Ipa proteins into the external medium and led to the accumulation of Spa32 protein in the periplasm. These results indicated that the DsbA protein performs an essential function during the invasion of mammalian cells, by facilitating transport of the Spa32 protein across the outer membrane.

Animals↗
PubMed1995

Biological monitoring of occupational exposure to methyl ethyl ketone in Japanese workers.

The relationship between occupational exposure to methyl ethyl ketone (MEK) and its concentration in urine and blood was studied in a group of 72 workers in a printing factory. Personal exposure monitoring was carried out with passive samplers during the workshifts. The time weighted average (TWA) concentration of MEK ranged from 1.3 to 223.7 ppm, with a mean concentration of 47.6 ppm. In addition to MEK, toluene, xylene, isopropyl alcohol, and ethyl acetate were detected as the main contaminants in all samples. At the end of the workshift, urine samples were collected to determine the urinary MEK, hippuric acid (HA), and creatinine, and blood samples were also collected at the same time for determination of MEK. The concentrations of urinary MEK ranged from 0.20 to 8.08 mg/L with a mean of 1.19 mg/L and significantly correlated with TWA concentrations of MEK in the air with a correlation coefficient of 0.889 for uncorrected urine samples. The concentration of MEK in the blood was also significantly correlated with the TWA concentration of MEK with a correlation coefficient of 0.820. From these relationships, MEK concentrations in urine and blood corresponding to the threshold limit value-TWA (200 ppm; ACGIH 1992) were calculated to be 5.1 mg/L and 3.8 mg/L as a biological exposure index (BEI), respectively. Although the BEI for urinary MEK obtained from the present study was higher than that of previous reports and ACGIH's recommendation (2.0 mg/L), the BEI agreed well with a previous study in Japan.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

Striatal cells containing the Ca(2+)-binding protein calretinin (protein 10) in ischemia-induced neuronal injury.

The present study concerns the vulnerability of striatal interneurons immunopositive for the Ca(2+)-binding protein calretinin to ischemic neuronal injury. An immunohistochemical study was carried out on the striata of rats which had undergone transient middle cerebral artery occlusion. Two weeks after the ischemia, there was a marked reduction in the number of calretinin-positive neurons in the ipsilateral ischemic lesion, although the striatal interneurons positive for parvalbumin, which are a neuronal population distinct from the calretinin-immunoreactive cells in the striatum, were spared in the insulted areas. The present data indicate that the striatal calretinin-positive neurons are less resistant to transient ischemia, suggesting that there may exist vulnerability differences among the striatal interneurons in ischemia-induced neuronal injury.

Animals↗
PubMed1995

Study of repeated arterial infusion chemotherapy with a subcutaneously implanted reservoir for advanced hepatocellular carcinoma.

We performed repeated arterial infusion chemotherapy (RAIC) in 114 advanced hepatocellular carcinoma (HCC) patients, using a subcutaneous reservoir implanted under ultrasonic guidance. In 60 patients, this was the initial therapy for the primary tumor and the other 54 patients being treated for recurrent tumor. One hundred and seventy-one patients with advanced HCC who had been treated by transcatheter arterial embolization (TAE) or single bolus arterial infusion chemotherapy before RAIC was available served as historical controls. In 97 patients, anticancer agents (4'-epidoxorubicin or acurarubicin) and Lipiodol emulsion were used, and in 17, anticancer agents alone were given. The response rates were 39.2% in the Lipiodol group and 17.6% in the non-Lipiodol group. The dose of Lipiodol and the degree of liver invasion were the most important factors influencing the response rate. The 1-, 2-, and 3-year survival rates were 55.0%, 30.9%, and 21.2%, respectively. The long-termsurvival was compared in relation to Child's classification and the presence or absence of portal vein tumor thrombosis (PVTT). In non-PVTT patients, the results of initial therapy and therapy for recurrence were similar, but recurrent Child's C patients showed a poorer prognosis. In PVTT patients, initial therapy had a better prognosis than treatment for recurrence, but initial Child's C patients had a poor long-termprognosis. During the observation period, no severe complications were encountered, but in Child's C patients, hepatic function sometimes deteriorated. Compared with the results in the 171 controls, RAIC was more useful for advanced HCC as initial therapy, and it was also beneficial for the treatment of recurrence after TAE.

Aged↗
PubMed1995

Interferon treatment of chronic hepatitis C in patients with hemophilia or von Willebrand's disease in Japan.

Seven patients with chronic hepatitis C, six hemophiliacs and a patient with von Willebrand's disease, were treated with interferon-alpha (IFN-alpha). Either 9 MU of recombinant IFN-alpha 2a or 3 MU of lymphoblastoid alpha-IFN was administered daily for 2 weeks and then three times a week for 22 weeks. Liver histology, hepatitis C virus (HCV) genotypes, and HCV-RNA levels in sera were investigated in all of the patients before IFN therapy was instituted. Liver histology was classified by the European classification. HCV genotyping conformed to the so-called Okamoto's classification. HCV-RNA levels in sera were quantitated by competitive polymerase chain reaction, using mutant RNA. Liver histology, HCV genotype, and serum HCV-RNA level (copies/ml) in each patient were: patient 1, chronic persistent hepatitis, type II, 3 x 10(3) respectively; patient 2, chronic active hepatitis (CAH) 2a, type III, 6 x 10(4); patient 3, CAH2a, type IV, 2 x 10(5); patient 4, CAH2b, type I, 2 x 10(7); patient 5, CAH2b, type II, 8 x 10(4); patient 6, CAH2b, type III, 7 x 10(6); and patient 7, CAH2b, type IV, 1 x 10(7). Sustained elimination of HCV was achieved in patient 3 and temporary elimination was achieved in patients 1 and 2. The other patients showed persistent HCV-RNA positivity in sera both during and after IFN treatment. Poor responsiveness to IFN was observed in patients with relatively progressive liver histology and high levels of HCV viremia.

Adult↗
PubMed1995

A case of early gastric malignant lymphoma diagnosed and completely resected by strip biopsy.

A case of early gastric malignant lymphoma definitively diagnosed by strip biopsy is reported. The subsequent operation revealed that the strip biopsy had resulted in radical resection. A 55-year-old woman visited our hospital for detailed examination of a small gastric lesion. Histologic findings of the specimens obtained by conventional forceps biopsy indicated reactive lymphoid hyperplasia, although the possibility of malignant lymphoma was not completely ruled out. Strip biopsy was, therefore, performed to establish a definitive diagnosis. Histopathological examinations of the strip biopsy specimen revealed definitive findings of malignant lymphoma, which was B-cell phenotype immunocytochemically. The margin of the resected specimen was free of invasion by malignant lymphoma and no lymph node involvement was suggested by endoscopic ultrasonography, computed tomography, and gallium scintigram. Subtotal gastrectomy was subsequently performed to rule out the possibility of remaining malignant lymphoma cells. It was proven that the strip biopsy removed the lesion completely and no perigastric lymph nodes were involved. While is still controversial as to whether strip biopsy should be adopted for the radical resection of early gastric lymphoma, this procedure can definitely provide excellent specimens for the accurate diagnosis of gastric malignant lymphoma and probably for group III lesions in the stomach.

Biopsy↗
PubMed1995

Effect of gluten exorphins A5 and B5 on the postprandial plasma insulin level in conscious rats.

The effect of exogenous opioid peptides, gluten exorphins A5 and B5, which were isolated from the enzymatic digest of wheat gluten, on the postprandial insulin level were examined in rats. The oral administration of gluten exorphin A5 at a dose of 30 mg/kg w. potentiated the postprandial plasma insulin level and the effect was reversed by naloxone. The administration of gluten exorphin B5 showed a similar effect at a higher dose (300 mg/kg w). Furthermore, intravenous administration of gluten exorphin A5 at a dose of 30 mg/kg w. also stimulated the postprandial insulin release. The fact that orally and intravenously administered gluten exorphin A5 stimulates insulin release suggests that it modulates pancreatic endocrine function by the action after the absorption rather than within the the gastrointestinal tract.

Administration, Oral↗
PubMed1995

Isolation and characterization of ovokinin, a bradykinin B1 agonist peptide derived from ovalbumin.

A vasorelaxing peptide was purified from a peptic digest of ovalbumin, after three steps of reverse-phase HPLC. The structure of the peptide was Phe-Arg-Ala-Asp-His-Pro-Phe-Leu, which corresponded to residues 358-365 of ovalbumin. The peptide was named ovokinin. Ovokinin showed relaxing activity for a canine mesenteric artery (EC50 = 6.3 microM). The relaxing activity was blocked by the bradykinin B1 antagonist [des-Arg9] [Leu8]bradykinin, but not by the B2 antagonist Hoe 140. Ovokinin binds to B1 receptors (IC50 = 64 microM). Prostaglandin I2 was released from the artery after ovokinin stimulation as a relaxing factor. Thus, ovokinin is a weak bradykinin B1 agonist peptide derived from food proteins.

1-Methyl-3-isobutylxanthine↗
PubMed1995

Characteristics of choledochal cysts in neonates and early infants.

Thirty-six infants with choledochal cyst consisting of 28 babies less than 12 months of age and 8 between 13 and 24 months of age, were analyzed. Characteristics of cases were as follows: (1) they were usually of the cystic type, (2) a huge abdominal mass and jaundice with alcoholic stool were typically found, (3) no symptom suggesting acute pancreatitis was observed, (4) amylase levels in bile were usually low, despite the presence of pancreatobiliary malunion, while other pancreatic enzymes in bile commonly showed a high concentration, and (5) primary cyst excision and biliary reconstruction was the treatment of choice, and could be safely performed with favorable outcomes even in babies less than 1 year of age.

Amylases↗
PubMed1995

Tapetum-specific expression of the gene for an endo-beta-1,3-glucanase causes male sterility in transgenic tobacco.

A cDNA for a pathogenesis-related endo-beta-1,3-glucanase isolated from soybean, was fused to an anther tapetum-specific promoter (Osg6B promoter) isolated from rice and the resulting chimeric gene was introduced into tobacco. The Osg6B promoter became active in the anther tapetum during formation of tetrads and the tapetal glucanase activity in the transgenic plants caused in a significant reduction in the number of fertile pollen grains. Most of the pollen grains were aberrant in shape, lacked germinal apertures and aggregate of the pollen grains. Granules of beta-1,3-glucan, which have not previously been reported, were often observed to adhere to the surface of the pollen grains. Further observations revealed that the callose wall was almost absent in the pollen tetrads of transgenic plants. In wild-type plants, by contrast, the tetrads were surrounded by callose that was degraded soon after the tetrad stage to release free microspores. Thus, the introduced gene for endo-beta-1,3-endoglucanase under the control of the Osg6B promoter caused digestion of the callose wall at the beginning of the tetrad stage, a time that was just a little earlier than the time at which endogenous glucanase activity normal appears. These results demonstrate that premature dissolution of the callose wall in pollen tetrads causes male sterility and suggest that the time at which tapetally produced glucanase is activate is critical for the normal development of microspores.

Base Sequence↗
PubMed1995

Identification of a novel virulence gene, virA, on the large plasmid of Shigella, involved in invasion and intercellular spreading.

A novel virulence gene (virA) was identified upstream of the virG gene on the large plasmid of Shigella flexneri 2a YSH6000. Characterization of virA mutants infecting MK2 epithelial cell monolayers revealed that their invasive capacity was decreased to less than one fifth of the wild-type level. Nevertheless, the bacteria were capable of expressing and secreting IpaB, IpaC and IpaD proteins. The virA mutants were also impaired in their ability to spread intercellularly, since the bacteria gave rise to a small number of foci in a focus-plaque-forming test with MK2 cells. Although virG expression was slightly decreased in the virA mutants, introduction of a cloned virG gene into a virA mutant, N1945, failed to restore spreading ability. Although, introduction of a cloned virA gene into N1945 restored invasiveness and spreading ability, the reduced virG transcription level was not affected, indicating that the reduced virG expression in virA mutants does not play a major role in defective intercellular spreading. The nucleotide sequence of the virA region revealed that the virA gene was located 528 bp upstream of the virG gene, in the opposite orientation. The deduced amino acid sequence of the VirA protein indicated a 44.7 kDa protein with no homology to known proteins. The VirA protein was secreted into the culture supernatant, a process that required the Mxi and Spa loci. The expression of virA was under the control of the virB gene, the positive regulator of the ipa, mxi and spa operons. These results indicate that virA is a new member of the invasion regulon directed by virB and that the VirA function is involved in invasion and intercellular spreading.

Amino Acid Sequence↗
PubMed1995

Thermoregulation of virB transcription in Shigella flexneri by sensing of changes in local DNA superhelicity.

Transcription of the virB gene, a transcriptional regulator of invasion genes on the large plasmid of Shigella flexneri, is strictly regulated by growth temperature; when bacteria are grown at 37 degrees C, virB transcription is highly activated, while at 30 degrees C the level of virB transcription decreases to less than 5% of that at 37 degrees C. Transcription from the virB promoter is activated by VirF, which is encoded on the same plasmid, in a DNA superhelicity-dependent manner (T. Tobe, M. Yoshikawa, T. Mizuno, and C. Sasakawa, J. Bacteriol. 175:6142-6149, 1993). Here we provide evidence supporting the involvement of negative superhelicity in the thermoregulation of virB transcription. A local negatively supercoiled domain in the virB promoter region was created by activating a divergent transcription from the T7 RNA polymerase-dependent promoter, phi 10, which was placed upstream of the virB promoter in the opposite orientation. Transcription from the virB promoter was activated even at 30 degrees C by induction of divergent transcription. Levels of virB transcription correlated with levels of expressed T7 RNA polymerase. Transcriptional activation of virB by the system depended completely upon VirF function. The level of virB transcription achieved by introducing a negatively supercoiled domain was enough to give rise to expression of invasion capacity at 30 degrees C. These results indicated that the repression of virB transcription at 30 degrees C was caused by a reduction in negative superhelicity around the virB promoter region at 30 degrees C.

Bacterial Outer Membrane Proteins↗
PubMed1995

Cleavage of Shigella surface protein VirG occurs at a specific site, but the secretion is not essential for intracellular spreading.

The large plasmid-encoded outer membrane protein VirG (IcsA) of Shigella flexneri is essential for bacterial spreading by eliciting polar deposition of filamentous actin (F-actin) in the cytoplasm of epithelial cells. Recent studies have indicated that VirG is located at one pole on the surface of the bacterium and secreted into the culture supernatant and that in host cells it is localized along the length of the F-actin tail. The roles of these VirG phenotypes in bacterial spreading still remain to be elucidated. In this study, we examined the surface-exposed portion of the VirG protein by limited trypsin digestion of S. flexneri YSH6000 and determined the sites for VirG processing during secretion into the culture supernatant. Our results indicated that the 85-kDa amino-terminal portion of VirG is located on the external side of the outer membrane, while the 37-kDa carboxy-terminal portion is embedded in it. The VirG cleavage required for release of the 85-kDa protein into the culture supernatant occurred at the Arg-Arg bond at positions 758 to 759. VirG-specific cleavage was observed in Shigella species and enteroinvasive Escherichia coli, which requires an as yet unidentified protease activity governed by the virB gene on the large plasmid. To investigate whether the VirG-specific cleavage occurring in extracellular and intracellular bacteria is essential for VirG function in bacterial spreading, the Arg-Arg cleavage site was modified to an Arg-Asp or Asp-Asp bond. The virG mutants thus constructed were capable of unipolar deposition of VirG on the bacterial surface but were unable to cleave VirG under in vitro or in vivo conditions. However, these mutants were still capable of eliciting aggregation of F-actin at one pole, spreading into adjacent cells, and giving rise to a positive Sereny test. Therefore, the ability to cleave and secrete VirG in Shigella species is not a prerequisite for intracellular spreading.

Amino Acid Sequence↗
PubMed1995

Therapeutic effect of percutaneous ethanol injection on small hepatocellular carcinoma: evaluation with CT.

PURPOSE: To evaluate the therapeutic effect of percutaneous ethanol injection (PEI) on small hepatocellular carcinoma (HCC) with computed tomography (CT). MATERIALS AND METHODS: Sixty-seven patients with histologically proved HCC 3 cm or less in diameter underwent PEI. The patients were regularly followed up with sonography and contrast material-enhanced CT for more than 1 year (range, 12-96 months). The CT findings were evaluated for three tumor types distinguished on the basis of their appearance relative to that of the surrounding liver parenchyma: type 1 = hyperattenuating at the early phase (n = 39), type 2 = iso- or hypoattenuating at the early phase and hypoattenuating at the late phase (n = 18), and type 3 = isoattenuating (not detected) at both the early and late phases (n = 10). RESULTS: After PEI, a necrotic area of HCC and the surrounding liver parenchyma was characterized as hypoattenuating at both early and late phases of contrast-enhanced CT, regardless of the type. When an HCC appeared to be completely necrotic within 3 months after PEI, this status was retained until the latest observation in all but three cases. CONCLUSION: Contrast-enhanced CT can correctly depict PEI-induced necrosis in HCC and is reliable for evaluating the therapeutic effect of PEI.

Carcinoma, Hepatocellular↗
PubMed1995

Rhodiocyanosides A and B, new antiallergic cyanoglycosides from Chinese natural medicine "si lie hong jing tian", the underground part of Rhodiola quadrifida (Pall.) Fisch. et Mey.

Two new antiallergic cyanoglycosides named rhodiocyanosides A and B were isolated from the Chinese natural medicine "Si Lie Hong Jing Tian" (Shiretsukoukeiten in Japanese), the underground part of Rhodiola quadrifida (Pall.) Fisch. et Mey., together with two new glycosides, octyl alpha-L-arabinopyranosyl(1-6)-beta-D-glucopyranoside and gossypetin 7-O-beta-D-glucopyranosyl(1-3)-alpha-L-rhamnopyranoside. Their chemical structures were determined on the basis of chemical and physicochemical evidence. Rhodiocyanosides A and B exhibited inhibitory activity on the histamine release from rat peritoneal exudate cells sensitized with anti-DNP IgE. In addition, rhodiocyanoside A was found to inhibit the PCA reaction in rats.

Animals↗