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Biomedical subjects

N Kato

Publications and source records attributed to N Kato.

At least 559 records · Page 31Linked to original sources
PubMed1994

Murine experimental autoimmune uveoretinitis induced by interphotoreceptor retinoid-binding protein and Klebsiella pneumoniae 03 lipopolysaccharide (K03-LPS): a relation between H-2 haplotype and EAU induction.

The pathogenicity of interphotoreceptor retinoid-binding protein (IRBP) in the mouse and H-2 restriction of IRBP-induced experimental autoimmune uveoretinitis (EAU) was tested by repeated immunization using Klebsiella pneumoniae 03 lipopolysaccharide (K03-LPS) as an adjuvant. It was shown that IRBP had a greater capacity to induce EAU than S-antigen. Based on the incidence of EAU induction using B10 congenic mice and other strains, the susceptibility to EAU was, at least in part, controlled by the I-Ak haplotype of the H-2 subregion. The results also indicated that non-major histocompatibility complex (MHC) genes play some role in disease susceptibility.

Animals↗
PubMed1994

Genetic linkage analyses of Romano-Ward syndrome (RWS) in 13 Japanese families.

Romano-Ward syndrome (RWS) is an autosomal dominant disorder characterized by prolongation of the electrocardiographic QT interval, with clinical manifestations that include recurrent syncope and sudden death from ventricular arrhythmias. Presymptomatic diagnosis is difficult because of the variability in these signs among carriers, but it is important for clinical management to prevent sudden cardiac death. To find an LQT (long QT) locus in Japanese patients and to identify DNA markers useful for presymptomatic diagnosis, linkage analyses were undertaken in 13 Japanese families with RWS patients by means of two DNA markers located on 11p15.5. One of these marker loci, HRAS, was previously reported to be tightly linked to the LQT locus in another ethnic group. Our analyses of homogeneity suggest evidence for genetic heterogeneity of RWS within the Japanese population.

Adult↗
PubMed1994

Specific detection of positive and negative stranded hepatitis C viral RNA using chemical RNA modification.

Since hepatitis C virus (HCV), a major causative agent of posttransfusional non-A, non-B hepatitis, is a positive stranded RNA virus, it is supposed to replicate via a negative RNA strand. Although strand specific reverse transcription-polymerase chain reaction (RT-PCR) method was recently developed to detect each strand of HCV RNA, the specificity of the strategy has remained to be determined. In this study, using in vitro transcribed positive and negative stranded HCV RNAs mixed with hepatic cellular RNA from normal liver, we found that this strategy did not distinguish between the two RNA strands, but that chemical modification of RNA samples at the 3' end followed by strand specific RT-PCR made specific detection possible. Liver tissues, sera and peripheral blood mononuclear cells (PBMC) from ten patients with chronic HCV infection were analyzed with the novel strategy of RT-PCR combined with RNA modification. Positive and negative strands of HCV RNA were detected in liver tissues of ten (100%) and nine (90%) cases, respectively. Negative RNA strand was detected also in sera of five cases (50%), positive strand being detected in nine cases (90%). In PBMC, positive strand of HCV RNA was detected in eight cases (80%), whereas negative strand in only one case (10%), suggesting that HCV has much less cellular tropism to PBMC than to hepatocytes.

Adult↗
PubMed1994

Prostaglandin E2/parathyroid hormone-induced suppression of alkaline phosphatase activity is mediated by protein kinase C.

1. Bone resorptive factors, prostaglandin E2 and parathyroid hormone are shown to suppress alkaline phosphatase activity in a rat osteoblastic cell line. 2. Phorbol myristate acetate, but not dibutyryl cAMP or calcium ionophore can suppress alkaline phosphatase activity. 3. The protein kinase C inhibitors (H89, staurosporine) are able to block the suppression of alkaline phosphatase activity induced by prostaglandin E2 and parathyroid hormone. 4. These data suggest that protein kinase C is involved in the inhibition of alkaline phosphatase activity induced by prostaglandin E2 and parathyroid hormone.

Alkaline Phosphatase↗
PubMed1994

The role of insulin in coronary atherosclerosis.

In 197 patients with coronary artery disease (CAD) who underwent coronary angiography, 75 g oral glucose tolerance test (OGTT) was performed, measuring plasma glucose(PG) and plasma insulin (IRI) at 4 time points (0, 30, 60 and 120 min). Subjects were separated into two groups by their insulinogenic index (I.I. = delta IRI/delta PG from 0 up to 30 min), 99 cases with good insulin response (I.I. > or = 0.4) and 98 cases with poor insulin response (I.I. < 0.4). Only two subjects were diabetic in good insulin response, while 37 were diabetic in poor insulin response. The severity of coronary atherosclerosis was expressed as a coronary index (CI), calculated according to Balcon's method. Fasting PG and the sum of PG were significantly higher in the latter group, while the sum of IRI was significantly lower. CI was not significantly different, however. In the group with good insulin response, the severity of CAD was significantly correlated to fasting IRI (n = 99, r = -0.387, P < 0.02), but, there was no such relationship in the other group. We conclude that hyperinsulinemia might be a risk factor for ischemic heart disease, but in diabetics it is difficult to link the relationship between fasting IRI and CI.

Adult↗
PubMed1994

The effect of delta sleep-inducing peptide (DSIP) on the changes of body (core) temperature induced by serotonergic agonists in rats.

Hyperthermia induced by high doses of 5-methoxy-N,N-dimethyl-tryptamine (5-MeODMT) was diminished and hypothermia induced by low doses of 5-MeODMT was enhanced by pretreatment with delta sleep-inducing peptide (DSIP). Delta sleep-inducing peptide had an enhancing effect of hypothermia induced by 8-hydroxy-2-(di-n-propylamino) tetralin (8-OH-DPAT). This action of DSIP was completely inhibited by ICV injection of anti-DSIP. Pindolol prevented the enhancing action of DSIP on both 8-OH-DPAT- and apomorphine-induced hypothermia. It is suggested that the thermoregulatory action of DSIP is primarily exerted by a 5-HT1A mechanism in the rat.

Animals↗
PubMed1994

Characterization of the 5' noncoding and structural region of the hepatitis C virus genome from patients with non-A, non-B hepatitis responding differently to interferon treatment.

We examined 14 patients with hepatitis C caused by infection with the hepatitis C virus-II genotype to understand differences in responsiveness to interferon. The patients were classified into two groups according to their response to interferon: eight responding and six non-responding patients. The 5' noncoding and structural regions of the hepatitis C virus-II genome from each patient specimen were amplified by reverse transcription followed by the polymerase chain reaction. The nucleotide sequences of these amplified DNAs were then determined. By comparing the nucleotide sequences and the deduced amino acid sequences of samples from both groups, no group-specific sequence was observed in the analyzed regions despite the presence of considerable sequence diversity. However, additional cysteine residues were observed in half the responding group. The degree of micro-heterogeneity in hypervariable region 1 of the hepatitis C virus in relation to the sensitivity to interferon treatment was also examined; however, no significant correlation was observed. In addition, frequent alterations in the amino acid sequences were observed in hypervariable region 1 during the course of interferon treatment.

Adolescent↗
PubMed1994

High-level ATP production by a genetically-engineered Candida yeast.

Previous studies of ATP production with the methylotrophic yeast, Candida boidinii, suggested that the phosphorylation of AMP catalyzed by adenylate kinase (ADK) was rate-limiting. To investigate whether the enhancement of ADK activity in C. boidinii cells would improve ATP productivity, the Saccharomyces cerevisiae ADK1 gene encoding ADK was expressed in C. boidinii under the C. boidinii AOD1 promoter. Methanol-induced transformants had 10,000-fold enhanced levels of ADK activity and produced 23-fold more ATP from adenosine when compared to the control, parent strain. In a pH-controlled reaction system with successive adenosine-feeding, the ATP concentration in the reaction mixture reached 230 mM (117 g/l) over 45 hours, and was easily purified with an overall yield of 78 percent.

Adenosine Kinase↗
PubMed1994

Genetic analysis of Escherichia coli O9 rfb: identification and DNA sequence of phosphomannomutase and GDP-mannose pyrophosphorylase genes.

Subcloning, transposon insertion, and deletion analysis revealed that the Escherichia coli O9 rfb region is about 12 kb in size. The region encodes at least seven polypeptides of 89, 74, 55, 50, 44, 41 and 39.5 kDa. Southern hybridization analysis of rfb regions of E. coli O8 and O9, and Klebsiella O3 and O5 serotypes (all of these O polysaccharides are mannose homopolymers and the structures of the repeating unit of E. coli O9 and Klebsiella O3 are identical) showed that a central region specific for E. coli O9 and Klebsiella O3 is flanked by two regions common to all four. Complementation experiments using strains with known defects and specific tests for the enzymic activity showed that the 50 and 55 kDa polypeptides, encoded by the common region, are phosphomannomutase (PMM) and GDP-mannose pyrophosphorylase (GMP), respectively. Nucleotide sequencing of the region revealed the presence of two genes, rfbK and rfbM, analogous to the corresponding genes of Salmonella typhimurium. In E. coli O9, rfbK and rfbM encode proteins of 460 amino acids (50,809 Da) and 471 amino acids (52,789 Da). The amino acid sequence of GMP was conserved in RfbMs of E. coli O7 and Salmonella groups B, C1 and C2, CpsB of S. typhimurium, AlgA of Pseudomonas aeruginosa, and XanB of Xanthomonas campestris. The phylogenetic trees of PMM and GMP were different in topology and in the evolutionary distances from ancestors.

Amino Acid Sequence↗
PubMed1994

Effect of Escherichia coli lipopolysaccharide on Bacteroides fragilis abscess formation and mortality in mice.

To study the mechanism of synergism between Bacteroides fragilis and Escherichia coli, the effect of sublethal dose of E. coli lipopolysaccharide (LPS) (25 micrograms/mouse) was checked on B. fragilis abscess formation. LPS was administered prior or after inoculum injection. No significant difference in the abscess size was observed at necropsy on day 6. However, all the groups receiving LPS showed higher incidence of recovery of additional intestinal bacteria (23.5-45.5%) from the abscess pus. When LPS was given 4 hr prior to inoculum administration, 83-100% mortality was observed. Detailed investigation showed autoclaved cecal contents alone could also cause similar mortality. Studies with stimulation of endogenous cytokines by E. coli LPS demonstrated induction of all of them within 3 hr in the blood stream with TNF-alpha demonstrating peak at 1 hr, IL-1 alpha and IL-6 at 4 hr and IFN-gamma between 6-9 hr with moderately high levels at 4 hr. This E. coli LPS-triggered cytokine cascade possibly gets further stimulated by injection of autoclaved cecal contents containing high concentration of endotoxins (1.6 x 10(5) EU/ml) contributed by dead bacteria and lead to the mortality of animals.

Abscess↗
PubMed1994

Lidocaine hydrochloride and acetylsalicylate kill bacteria by disrupting the bacterial membrane potential in different ways.

Lidocaine hydrochloride (LH), a local anesthetic, and acetylsalicylate (AcSAL), show antibacterial activity for both gram-negative and gram-positive bacteria. Kinetic studies indicated that antibacterial activity of LH was different from that of AcSAL. A subinhibitory concentration of LH and AcSAL enhanced the sensitivity of Escherichia coli, Salmonella typhimurium, and Pseudomonas aeruginosa to novobiocin and nalidixic acid. The synergistic effect of AcSAL with novobiocin and nalidixic acid was higher than that of LH. The effect of both drugs on the membrane potential of inner membrane was also studied using inverted membrane vesicles of bacteria. Both LH and AcSAL depolarized the membrane potential after the vesicles were energized with nicotinamide adenine dinucleotide. However, unlike AcSAL, pre-treatment of vesicles with LH had no effect on the generation of membrane potential. These results suggest that depolarization of the cytoplasmic membrane, preceded by the permeabilization of the outer membrane for gram-negative bacteria, is associated with antibacterial activity of LH and AcSAL. The difference in actions of LH and AcSAL was discussed.

Anti-Bacterial Agents↗
PubMed1994

Crystallization and analyses of crystals of various chemotypes of R-form lipopolysaccharides from Salmonella spp.

Various chemotypes (Re, Rd2, Rd1P-, Rd1, RcP-, Rc, Rb3, Rb2, Rb1, and Ra) of R-form lipopolysaccharides (LPSs) of Salmonella spp. were crystallized by treatment with 70% ethanol containing 250 mM MgCl2, and crystals of the LPSs were observed electron microscopically and analyzed by electron diffraction and synchrotron X-ray diffraction. All the LPSs tested formed three-dimensional crystals showing very similar shapes; hexagonal plate, solid column, discoid, square or rectangular plate, lozenge plate and truncated hexangular or rectangular pyramid forms. Electron diffraction patterns from the hexagonal plate crystals of all these LPSs obtained by electron irradiation from the direction perpendicular to the basal plane showed that they consist of hexagonal lattices with the lattice constant of 4.62 A. The crystals of all the LPSs thus formed gave ring-like X-ray diffraction patterns because of their small sizes. The long-axis values were calculated from the X-ray diffraction patterns from crystals of all the LPSs in the low-angle region and they corresponded roughly to the length of the proposed primary chemical structures of the R cores of the LPSs. The volume occupied by a single molecule of all the LPSs were calculated from the molecular weights based on the proposed structures and the crystallographic data obtained by electron diffraction, X-ray diffraction, and density determination.

Crystallization↗
PubMed1994

Comparison of cytokine induction by lipopolysaccharide of Bacteroides fragilis with Salmonella typhimurium in mice.

Comparison of cytokine stimulation by lipopolysaccharide (LPS) of Bacteroides fragilis and Salmonella typhimurium was done to study the early events occurring in vivo. Mice injected intraperitoneally with either LPS demonstrated endogenous production of all the cytokines studied (tumor necrosis factor-alpha, interferon-gamma and interleukin-6) within 6 hr in the bloodstream. However induction of all the cytokines by B. fragilis LPS (50 micrograms/mouse) was much weaker compared with S. typhimurium LPS (50 micrograms/mouse). Even a dose of S. typhimurium LPS 40 times smaller (1.2 micrograms/mouse) induced cytokines more strongly compared with B. fragilis LPS. Thus, a weak biological response to B. fragilis LPS as evidenced by chick embryo lethality, limulus lysate gelation, LD50 for mice and rabbit pyrogenicity could be due to weak induction of bioactive mediators by LPS.

Animals↗
PubMed1994

Virus isolate-specific antibodies against hypervariable region 1 of the hepatitis C virus second envelope protein, gp70.

Hypervariable region 1 (HVR1), located in the N-terminal region of a putative second envelope glycoprotein (gp70) of hepatitis C virus (HCV), contains immunological B-cell epitopes which might be neutralizing epitopes. To clarify whether B-cell epitopes within HVR1 are common among virus isolates or specific for the homologous virus isolate, we examined the reactivities of sera from 53 patients with chronic hepatitis or hepatocellular carcinoma/liver cirrhosis against two different HVR1 peptides (HVR1 I-1 and HVR1 Y-1) derived from patient I with sporadic acute hepatitis and an asymptomatic carrier Y, respectively, using our original assay system for the detection of anti-HVR1 antibody. All patients examined had a history of blood transfusion. Most sera showed no reactivity with either HVR1 I-1 or HVR1 Y-1 peptide. Only seven and fourteen serum samples reacted significantly, although weakly, with HVR1 I-1 and HVR1 Y-1 peptides, respectively, compared with the serum from patient I or asymptomatic carrier Y. The blood transfusions of most reactive cases had occurred more than thirty years earlier. Six cases reacted with both HVR1 I-1 and HVR1 Y-1 peptides, but further analysis revealed that only three cases reacted weakly with the peptide for either epitope I or II, identified within HVR1 I-1. These results indicate that the B-cell epitopes within HVR1 are fairly specific for the homologous virus isolate, and this may represent a serious difficulty in the development of a vaccine against HCV.

Amino Acid Sequence↗
PubMed1994

Bactericidal action of tachyplesin I against oral streptococci.

Tachyplesin I, a polycationic antimicrobial peptide isolated from hemocytes of horseshoe crabs, kills bacteria by disrupting the membrane potential of the cytoplasmic membrane. The present study shows that, among 36 oral streptococcal strains, 12 of 21 Streptococcus sanguis, 3 Streptococcus mutans, 9 Streptococcus salivarius and 3 Streptococcus milleri strains were susceptible to tachyplesin I, whereas 9 S. sanguis strains were resistant. Interestingly, these resistant strains include the clinical isolates from both Kawasaki disease and Behçet patients. According to the time-kill study, tachyplesin I inhibited irreversibly the growth of S. sanguis, S. mutans and S. salivarius strains within 20 min and an S. milleri strain within 80 min. Although it has been suggested that Escherichia coli cultured in rich media were more susceptible to tachyplesin I, the present results show that only 3 S. milleri strains were more sensitized to tachyplesin I in a glucose-supplemented medium, and other tested strains were not. Similarly, only 4 strains were more resistant to tachyplesin I in saline than these were in a rich medium.

Anti-Bacterial Agents↗