Biomedical subjects

K Okamoto

Publications and source records attributed to K Okamoto.

At least 271 records · Page 15Linked to original sources

PubMed1999

Inhibition of xanthine oxidase and xanthine dehydrogenase by nitric oxide. Nitric oxide converts reduced xanthine-oxidizing enzymes into the desulfo-type inactive form.

Xanthine oxidase (XO) and xanthine dehydrogenase (XDH) were inactivated by incubation with nitric oxide under anaerobic conditions in the presence of xanthine or allopurinol. The inactivation was not pronounced in the absence of an electron donor, indicating that only the reduced enzyme form was inactivated by nitric oxide. The second-order rate constant of the reaction between reduced XO and nitric oxide was determined to be 14.8 +/- 1.4 M-1 s-1 at 25 degrees C. The inactivated enzymes lacked xanthine-dichlorophenolindophenol activity, and the oxypurinol-bound form of XO was partly protected from the inactivation. The absorption spectrum of the inactivated enzyme was not markedly different from that of the normal enzyme. The flavin and iron-sulfur centers of inactivated XO were reduced by dithionite and reoxidized readily with oxygen, and inactivated XDH retained electron transfer activities from NADH to electron acceptors, consistent with the conclusion that the flavin and iron-sulfur centers of the inactivated enzyme both remained intact. Inactivated XO reduced with 6-methylpurine showed no "very rapid" spectra, indicating that the molybdopterin moiety was damaged. Furthermore, inactivated XO reduced by dithionite showed the same slow Mo(V) spectrum as that derived from the desulfo-type enzyme. On the other hand, inactivated XO reduced by dithionite exhibited the same signals for iron-sulfur centers as the normal enzyme. Inactivated XO recovered its activity in the presence of a sulfide-generating system. It is concluded that nitric oxide reacts with an essential sulfur of the reduced molybdenum center of XO and XDH to produce desulfo-type inactive enzymes.

Animals↗

PubMed1999

Fragmentation of the Golgi apparatus of Betz cells in patients with amyotrophic lateral sclerosis.

The Golgi apparatus (GA) of the large pyramidal motor neurons in the cerebral cortex (Betz cells), was examined in sixteen patients with sporadic amyotrophic lateral sclerosis (ALS), in one patient with familial ALS (FALS), and in ten non-ALS age matched controls including one patient with Huntington's disease and one patient with a brain infarct. The GA was immunostained with an antibody against the MG-160 protein, a conserved sialoglycoprotein of the medial cisternae of the organelle. In ALS, 13.2% of counted Betz cells had fragmented GA in contrast to 0.6% in the ten non-ALS controls. The fragmentation of the GA of Betz cells was identical to that previously reported in spinal cord motor neurons from patients with sporadic ALS and in transgenic mice expressing the G93A mutation of the gene encoding the Cu/Zn superoxide dismutase. The striking morphological similarity between the fragmentation of the GA observed in Betz cells and in spinal cord motor neurons suggests that a similar pathogenic mechanism is responsible for both, and that the fragmentation of the GA of the spinal cord motor neurons is not a consequence of deafferentation due to the degeneration of the Betz cells.

Adult↗

PubMed1999

Direct association with thioredoxin allows redox regulation of glucocorticoid receptor function.

The glucocorticoid receptor (GR) is considered to belong to a class of transcription factors, the functions of which are exposed to redox regulation. We have recently demonstrated that thioredoxin (TRX), a cellular reducing catalyst, plays an important role in restoration of GR function in vivo under oxidative conditions. Although both the ligand binding domain and other domains of the GR have been suggested to be modulated by TRX, the molecular mechanism of the interaction is largely unknown. In the present study, we hypothesized that the DNA binding domain (DBD) of the GR, which is highly conserved among the nuclear receptors, is also responsible for communication with TRX in vivo. Mammalian two-hybrid assay and glutathione S-transferase pull-down assay revealed the direct association between TRX and the GR DBD. Moreover, analysis of subcellular localization of TRX and the chimeric protein harboring herpes simplex viral protein 16 transactivation domain and the GR DBD indicated that the interaction might take place in the nucleus under oxidative conditions. Together these observations indicate that TRX, via a direct association with the conserved DBD motif, may represent a key mediator operating in interplay between cellular redox signaling and nuclear receptor-mediated signal transduction.

Animals↗

PubMed1999

Developmental expression and co-localization of cyclin G1 and the B' subunits of protein phosphatase 2a in neurons.

Cyclin G1 is a recently cloned transcriptional target of p53, it is located in neurons and ventricular ependymal cells and is elevated in neurons after axotomy and cerebral ischemia. The biological function for cyclin G1 in differentiated neurons has thus far not been elucidated. Recently, cyclin G1 has been shown to interact with the B' subunits of serine/threonine protein phosphatase 2A (PP2A) in a rat fibroblast cell line [K. Okamoto, C., Kamibayashi, M. Serrano, C. Prives, M.C. Mumby, D. Beach, p53-dependent association between cyclin G and the B' subunit of protein phosphatase 2A, Mol. Cell. Biol. 16 (1996) 6593-6602]. To further explore whether a similar interaction between cyclin G1 and PP2A B' subunits exists in the central nervous system, the present study compared the regional and developmental expression pattern, subcellular distribution and complex formation between cyclin G1 and the PP2A B' regulatory subunits in the rat brain. In situ hybridization of cyclin G1 and the B'alpha and B'beta subunits of PP2A showed an overlapping distribution in neurons of the cerebral cortex, hippocampus and thalamus at embryonic and early postnatal ages, but their developmental regulation differed. Whereas mRNA and protein levels of PP2A B' subunits were high in the cortical plate, subiculum, hippocampal areas and thalamus at E20 and decreased with age, those of cyclin G1 increased with age and were maximal in the adult cortex and hippocampus. In rat 14-day-old embryonic cortical cultures, cyclin G1 and PP2A B'alpha protein co-localized in nuclear and perinuclear areas of neurons, and both proteins were highly expressed in nuclei of cortical and hippocampal pyramidal cells and the mitral cell layer of the neonatal olfactory bulb. Both cyclin G1 and the PP2A regulatory B'alpha subunits were specifically expressed in neurons and not in glial cells. Antibodies raised against the B'alpha subunits of PP2A immunoprecipitated cyclin G1 in adult cortical lysates, indicating the presence of a complex involving cyclin G1 and the B'alpha subunits of PP2A. This study shows that the regional and subcellular localization of PP2A B' regulatory subunits and cyclin G1 are very similar at early postnatal stages. We discuss the possible functions of a cyclin G1-PP2A B'alpha complex in neurons.

Animals↗

PubMed1999

Pseudomonas aeruginosa alginate is a potent secretagogue in the isolated ferret trachea.

Airway mucus hypersecretion is in part a response to infection and inflammation. Pseudomonas aeruginosa infection is nearly universal in advanced cystic fibrosis (CF) lung disease. Mucoid strains of P. aeruginosa produce an exopolysaccharide product called alginate. The purpose of this study was to determine whether P. aeruginosa alginate stimulates secretion from mucous or serous cells in the ferret trachea exposed to alginate at concentrations reported to be present in the CF airway. We used a sandwich enzyme-linked lectin assay (ELLA) to measure mucin secretion and spectrophotometry to measure lysozyme secretion from isolated ferret tracheal segments. Purified Pseudomonas aeruginosa alginate stimulated mucin and lysozyme secretion in a dose-dependent fashion (mucin = +111%: P = 0.003; lysozyme = +20%: P = 0.024 at 200 microg/mL). This stimulated secretion was not due to proteolytic activity, and alginate exposure did not produce ultrastructural damage to the trachea. We conclude that alginate may contribute to mucus hypersecretion and respiratory morbidity associated with P. aeruginosa infection in patients with CF.

Alginates↗

PubMed1999

Tumor necrosis factor alpha regulation of the FAS-mediated apoptosis-signaling pathway in synovial cells.

OBJECTIVE: Fas-mediated apoptosis is observed in synoviocytes of patients with rheumatoid arthritis (RA), but not in those of patients with osteoarthritis (OA). The present study was conducted to elucidate the mechanisms that initiate induction of Fas-mediated apoptosis in RA synoviocytes. METHODS: Cultured OA synoviocytes, which are insensitive to Fas-mediated apoptosis in spite of Fas antigen expression, were used in these experiments. Synovial cell proliferation and cytotoxicity studies were performed using MTS and lactate dehydrogenase release assays. Surface expression of Fas antigen was analyzed by flow cytometry. The expression and function of apoptosis-signaling molecules, such as caspase 8 and caspase 3, were examined by immunoblot analysis. RESULTS: Tumor necrosis factor alpha (TNFalpha) induced proliferation of cultured OA synoviocytes. Fas ligation with anti-Fas monoclonal antibody (mAb) resulted in cytotoxic activity against cultured OA synoviocytes that had been pretreated with TNFalpha for 5 days, but not those pretreated for 2 days. In contrast, anti-Fas mAb did not show a cytotoxic effect against untreated cultured OA synoviocytes. A gradual up-regulation of caspase 8 and caspase 3, which played a role in the caspase cascade for Fas-mediated apoptosis, was observed in TNFalpha-treated cultured OA synoviocytes. In addition, Fas ligation to TNFalpha-treated cultured OA synoviocytes induced activation of caspase 8 and caspase 3, with subsequent cleavage of poly(ADP-ribose) polymerase (PARP), a substrate of activated caspase 3. More importantly, Z-IETD-FMK, a caspase 8 inhibitor, and Ac-DEVD-CHO, a caspase 3 inhibitor, almost completely inhibited Fas-mediated apoptosis of TNFalpha-treated cultured OA synoviocytes, whereas Ac-YVAD-CHO, a caspase 1 inhibitor, did not. CONCLUSION: Our results clearly demonstrate that TNFalpha stimulates synovial cells to proliferate as well as sensitizes the cells for Fas-mediated apoptosis, at least in part by up-regulation and activation of caspase 8 and caspase 3. These findings suggest that TNFalpha may be one of the factors providing sensitization of synovial cells to Fas-mediated apoptosis in RA.

Apoptosis↗

PubMed1999

Identification and characterization of the Aeromonas sobria hemolysin glycoprotein receptor on intestine 407 cells.

Aeromonas sobria hemolysin is important in the pathogenesis of diarrhoea caused by this enteropathogenic bacterium. By immunoprecipitation analysis using hemolysin and anti-hemolysin antibody, a 66 kDa protein (p66) was identified as a receptor for A. sobria hemolysin on Intestine 407 cells. Treatment of p66 with N-glycosidase F reduced the apparent sized of p66 to 60 kDa on SDS-polyacrylamide gels. p66, released from Intestine 407 cells following incubation with phosphatidylinositol-specific phospholipase C (PI-PLC) treatment, bound A. sobria hemolysin. Thus treatment of Intestine 407 cells with PI-PLC resulted in the remarkable decrease of the sensitivity to A. sobria hemolysin. These results are consistent with the hypothesis that p66, the binding protein for A. sobria hemolysin, is a glycosylphosphatidylinositol-anchored glycoprotein expressed on the surface of Intestine 407 cells and probably plays a role as a receptor for A. sobria hemolysin on the intestinal cells.

Aeromonas↗

PubMed1999

Iodine-131 human-mouse chimeric Fab monoclonal antibody A7 guided surgery for colorectal cancer patients: a pilot study.

This study was conducted to determine the clinical usefulness of radioimmunoguided surgery (RIGS) using human-mouse chimeric Fab monoclonal antibody A7 (ch-Fab-A7) for colorectal cancer patients. Ten colorectal cancer patients were given iodine-131-labeled ch-Fab-A7 intravenously (i.v.) 2 to 7 days prior to RIGS. The RIGS was carried out using a portable gamma detecting probe (GDP). Tumor localization was identified by GDP intraoperatively in 4 of the ten patients, while liver metastasis and lymph node metastasis were identified in 2 patients and 1 patient, respectively. The GDP revealed tumor/surrounding tissue radio(gamma)count ratios of 1.5 or greater in 8 of the ten resected tumors. Although RIGS using ch-Fab-A7 is a promising tool for intraoperatively identifying the tumor localization of colorectal cancer, 125I, rather than 131I, should be used as a tracer for RIGS to enhance the accuracy of ch-Fab-A7.

Adenocarcinoma↗

PubMed1999

The effects of cardiopulmonary bypass on postoperative oxygen metabolism.

The relationships between oxygen delivery (DO2), oxygen consumption (VO2), and the extraction rate (ER = VO2/DO2 x 100) in patients undergoing cardiopulmonary bypass (CPB) may differ from the normal physiologic state due to the oxygen debt acquired during CPB. Blood gas analysis and hemodynamic parameters were repeatedly measured for the determination of DO2 and VO2 in 40 patients undergoing CPB, every 8 h during the first 48 h postoperatively. As a control, 20 patients who had suffered acute myocardial infarction (AMI) were also studied using the same protocol. In the CPB group, a regression analysis showed that VO2 was significantly dependent on DO2, even within the physiologic range of DO2 (>500 ml/min per m2); VO2 = 121.4 + 0.0844 x DO2 (r = 0.254, P = 0.023). Conversely, in the AMI group, no such supply-dependent consumption was observed within the same range of DO2. At an ER of 30%, which is the optimal value in general, the DO2 of the CPB group was 575 ml/min per m2 and that of the AMI group was 493 ml/min per m2. All these results suggest that patients undergoing CPB need a much higher oxygen supply to recover from the oxygen debt acquired during open heart surgery.

Aged↗

PubMed1999

The molecular mechanism of inhibition of interleukin-1beta-induced cyclooxygenase-2 expression in human synovial cells by Tripterygium wilfordii Hook F extract.

OBJECTIVE: Several extracts of Tripterygium wilfordii Hook F (TWHF) have been reported to be effective in patients with rheumatoid arthritis. We investigated the effect of multi-glycosides ofTWHF (GTW), a TWHF extract, on interleukin (IL)-1beta stimulated human rheumatoid synovial cells. MATERIALS AND METHODS: IL-1beta-stimulated synovial cells were used to detect the effects of GTW on cyclooxygenase (COX)-1 and COX-2 activities, expression of COX protein and mRNA, and nuclear transcription factors in experiments using respective reporter plasmids. RESULTS: GTW inhibited prostaglandin E2 production by IL-1beta-stimulated synovial cells in a concentration-dependent manner, and also inhibited COX-2 protein and mRNA expression in a similar fashion to dexamethasone. However, GTW did not act as a glucocorticoid agonist. GTW repressed IL-1beta-induced nuclear factor-kappaB activity, but did not have a significant influence on activating protein-1 activity. CONCLUSION: The anti-rheumatic effect of GTW or TWHF may be partly mediated through the inhibition of prostaglandin E2 production in human synovial cells due to suppression of COX-2 mRNA, possibly via inhibition of nuclear factor-kappaB activity.

Animals↗

PubMed1999

Imaging of calvarial eosinophil granuloma.

We reviewed the imaging of four pathologically proven calvarial eosinophil granulomas. The diameter of the lesions ranged from 13 to 40 mm; three were biconvex, but the other had a collar-stud appearance. Two lesions were in the frontal and two in the parietal bone. On bone-window CT, a bevelled edge was seen in three cases and button sequestration in one, but no sclerotic rim was shown. Although one lesion had a low-density area, the lesions were slightly denser than grey matter. They were isointense with grey or white matter on T1-weighted MRI and gave heterogeneous high signal on proton-density and T2-weighted images. All enhanced markedly, with a less strongly enhancing portion within them. A tail of dural enhancement and reactive change in the overlying galea or temporal muscle were seen in all cases.

Bone Diseases↗

PubMed1999

Cloning of the transketolase gene and the effect of its dosage on aromatic amino acid production in Corynebacterium glutamicum.

Transketolase is a key enzyme of the non-oxidative pentose phosphate pathway. The effect of its overexpression on aromatic amino acid production was investigated in Corynebacterium glutamicum, a typical amino-acid-producing organism. For this purpose, the transketolase gene of the organism was cloned on the basis of its ability to complement a C. glutamicum transketolase mutant with pleiotropically shikimic-acid-requiring, ribose- and gluconic-acid-negative phenotype. The gene was shown by deletion mapping and complementation analysis to be located in a 3.2-kb XhoI-SalI fragment of the genome. Amplification of the gene by use of low-, middle-, and high-copy-number vectors in a C. glutamicum strain resulted in overexpression of transketolase activities as well as a protein of approximately 83kDa in proportion to the copy numbers. Introduction of the plasmids into a tryptophan and lysine co-producer resulted in copy-dependent increases in tryptophan production along with concomitant decreases in lysine production. Furthermore, the presence of the gene in high copy numbers enabled tyrosine, phenylalanine and tryptophan producers to accumulate 5%-20% more aromatic amino acids. These results indicate that overexpressed transketolase activity operates to redirect the glycolytic intermediates toward the nonoxidative pentose phosphate pathway in vivo, thereby increasing the intracellular level of erythrose 4-phosphate, a precursor of aromatic biosynthesis, in the aromatic-amino-acid-producing C. glutamicum strains.

Amino Acids↗

PubMed1999

Bilateral optic neuritis in a child diagnosed with Gd-enhanced MR imaging using fat-suppression technique.

A 4-year-old boy developed bilateral optic neuritis. Although precise neuro-ophthalmological evaluation was difficult, the diagnosis was made with gadolinium-enhanced MR imaging using fat-suppression technique in the initial stage of the disease. Enhancement and enlargement of the intraorbital and intracanalicular optic nerve were demonstrated bilaterally as well as protrusion of the optic nerve head. The disease responded dramatically to intravenous steroid therapy. The etiologies in children usually differ from those in adolescent and adult patients.

Adipose Tissue↗

PubMed1999

Proportion of reflux esophagitis in 6010 Japanese adults: prospective evaluation by endoscopy.

Compared with findings in Western countries, the prevalence of reflux esophagitis in Oriental countries is estimated to be low. In this prospective study, we aimed to examine the proportion of reflux esophagitis in Japanese adults, as evaluated by endoscopy. Endoscopists were prospectively directed to grade esophageal mucosal breaks with esophagitis according to the Los Angeles Classification of Esophagitis in all subjects that underwent endoscopic examination. In total, 6010 subjects underwent endoscopic examination for evaluation of esophagitis grading from December 1996 to February 1998. The subjects included 4394 outpatients who were not receiving medication for gastrointestinal disease and 1616 subjects who visited the hospital for routine physical examinations. The overall proportion of esophagitis was 16.3%. Most of the subjects with esophagitis were classified as having grade A or B (proportion of grades A and B, 9.6% and 4.6%, respectively). The age-related proportion of esophagitis and of severe esophagitis (i.e., grades C and D) increased in females aged over 70 and in males aged over 80. Increased body mass index (partly due to decreased height caused by osteoporosis), and/or hiatal herniation, were related to the proportion of esophagitis in females aged over 70. These data indicated that reflux esophagitis is a common disease in Japan. However, severe esophagitis (grades C and D) is not common.

Adult↗

PubMed1999

Thioredoxin in the endocrine response to stress.

Adaptation to stress evokes a variety of biological responses, including activation of the hypothalamic--pituitary--adrenal (HPA) axis and synthesis of a panel of stress-response proteins at cellular levels: for example, expression of thioredoxin (TRX) is significantly induced under oxidative conditions. Glucocorticoids, as a peripheral effector of the HPA axis, exert their action via interaction with a ligand-inducible transcription factor glucocorticoid receptor (GR). However, how these stress responses coordinately regulate cellular metabolism is still unknown. We demonstrate that either antisense TRX expression or cellular treatment with H2O2 negatively modulates GR function and decreases glucocorticoid-inducible gene expression. Impaired cellular response to glucocorticoids is rescued by overexpression of TRX, most probably through the functional replenishment of the GR. Moreover, not only the ligand binding domain but the DNA binding domain of the GR is also suggested to be a direct target of TRX. Together, we propose that cellular glucocorticoid responsiveness is coordinately modulated by redox state and TRX level, suggesting that cross-talk between neuro-endocrine control of stress responses and cellular antioxidant systems may be essential for mammalian adaptation processes.

Animals↗

PubMed1999

ALL- and CML-type BCR/ABL mRNA transcripts in chronic myelogenous leukemia and related disorders.

Using the reverse transcription polymerase chain reaction, we investigated acute lymphoid leukemia (ALL)-type, and chronic myelogenous leukemia (CML)-type BCR/ABL mRNA expression in a total of 66 patients with chronic myeloproliferative disorder (CMPD). Thirty-six of 37 patients with CML were positive for CML-type mRNA. Thirteen of the 25 CML had ALL-type mRNA expression. The patients with ET, PV, MF, and CMML did not have any detectable BCR/ABL expression. The most remarkable finding was that two patients, a Ph1-positive CML patient and a patient with a presumptive diagnosis of essential thrombocythemia (ET), showed only ALL-type chimeric mRNA expression.

Adult↗

PubMed1999

Serum matrix metalloproteinase-3 (stromelysin-1) concentration in patients with chronic liver disease.

BACKGROUND/AIMS: Matrix metalloproteinase (MMP)-3 plays an important role in extracellular matrix degradation, because of its broad substrate specificity and its activation of other proMMPs. Our aims in the present study were to determine whether the measurement of serum MMP-3 is clinically useful for assessing ongoing liver fibrolysis in patients with chronic liver disease. METHODS: We measured the serum MMP-3 concentrations with a sandwich enzyme immunoassay in 58 patients with chronic hepatitis, 22 patients with liver cirrhosis, 45 patients with hepatocellular carcinoma and 124 healthy individuals. The liver MMP-3 content was also measured in autopsied livers. RESULTS: Among the healthy controls, the serum levels of MMP-3 were about 2-fold higher in the males than in the females. In this study, the serum MMP-3 results of mainly the male group were analyzed because of the large number of male subjects. Compared to the control level, the mean serum MMP-3 concentration was 55% lower in chronic hepatitis, 53% lower in liver cirrhosis and 46% lower in hepatocellular carcinoma. There was no significant difference in the serum MMP-3 levels among the chronic hepatitis, liver cirrhosis and hepatocellular carcinoma groups. The serum MMP-3 levels were not related to the histological degree of necroinflammation or of liver fibrosis in the patients with chronic hepatitis. No significant difference in serum MMP-3 levels was observed among three Child's subgroups in the group of cirrhotic patients. In the group of patients with hepatocellular carcinoma, the serum MMP-3 levels were not related to the severity of liver function, the HCC tumor size, or the histological differentiation. The serum MMP-3 level was not correlated with serum markers for connective tissue turnover, i.e. procollagen type III peptide, 7S fragment of type IV collagen, hyaluronan and tissue inhibitor of metalloproteinase-1 in the patients with chronic liver disease or hepatocellular carcinoma. CONCLUSIONS: The measurement of serum MMP-3 is of little use for assessing fibrolysis in chronically diseased livers.

Carcinoma, Hepatocellular↗

PubMed1999

Communication between the axillary and radial nerves in the human upper arm.

The communication between the axillary (Ax) and the radial (R) nerves, which was observed in eight upper arms from 602 arms of 301 Japanese cadavers, was studied to determine its origin and distribution. The brachial plexus and spinal segments contributing to the Ax and R in all cases where communication occurred had no distinct differences from those in cases having no communication. According to the direction, the communication is divided into two groups: the communication from the Ax to R (7 cases) and vice versa (2 cases). One specimen had both groups of communication. The origin of communicating branches in these groups extended into the overlapping area (C5 + 6) of the origin of the Ax with that of the R, mainly from the ventral layer of the posterior cord from C6. The distribution of the communicating branch varied in development according to specimens. The communication from the Ax to R has a tendency to invade, from proximally to distally, the distribution of the muscular branches of the R to the radial extensor muscles of the forearm including the supinator muscle. However, the development into the cutaneous branches has no distinct inclination. These findings in humans and some other comparative anatomical descriptions show that in phylogeny the radial extensor muscles of the forearm have a different origin from other extensor muscles of the forearm and have a close relationship with the Ax. Therefore, the communication between the Ax and R holds an important clue in clarifying the morphological significance of the extensor nerves and muscles of the forearm.

Arm↗