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T Koga

Publications and source records attributed to T Koga.

At least 235 records · Page 13Linked to original sources
PubMed1997

Biological function of the dTDP-rhamnose synthesis pathway in Streptococcus mutans.

We have cloned a new gene locus that comprises three genes concerned with the biosynthesis of the serotype c-specific polysaccharide antigen in Streptococcus mutans. The genes encode proteins exhibiting significant homology to the rfbA, rfbB, and rfbD gene products that are involved in the anabolism of dTDP-L-rhamnose from D-glucose-1-phosphate. This anabolism pathway pertains to biosynthesis of the O antigen of lipopolysaccharide in gram-negative bacteria. The cell extract of Escherichia coli expressing each of the cloned genes of S. mutans exhibited enzymatic activity corresponding to the homologous counterpart of the rfb gene products. Rhamnose was not detected in the cell wall preparation purified from the mutant in which each of the three cloned genes was insertionally inactivated. Rabbit antiserum against S. mutans serotype c-specific antigen did not react with the autoclaved extracts from these mutants. These results indicate that the gene products identified in the present study are involved in the dTDP-L-rhamnose synthesis pathway and that the pathway relates to the biosynthesis of the serotype-specific polysaccharide antigen of S. mutans. Southern hybridization analysis revealed that genes homologous to the cloned genes involved in the dTDP-L-rhamnose synthesis pathway were widely distributed in a variety of streptococci. This is the first report of the biological function of the dTDP-rhamnose pathway in streptococci.

Blotting, Southern↗
PubMed1997

Sulfidoleukotriene release test (CAST) in hypersensitivity to nonsteroidal anti-inflammatory drugs.

There is a great need to develop a method for making an accurate and reliable in vitro diagnosis of adverse hypersensitivity reactions to drugs. We measured the amount of sulfidoleukotriene (sLT) released from the peripheral blood leukocytes obtained from 25 patients who developed hypersensitivity reactions following the administration of nonsteroidal anti-inflammatory drugs (NSAIDs); 12 patients demonstrated reactions to Voltaren, 8 patients to Bufferin, and 5 patients to Sedes G. The stimulation index, the ratio of the amounts of sLT (pg/ml) incubated with and without drugs, was considerably higher in the patients than in the controls, which consisted of 5 nonallergic healthy subjects. The sensitivity of the CAST (cellular antigen stimulation test) was evaluated to range from 62.5 to 80%, while the specificity was 70-100%. The CAST may thus be useful as a novel in vitro test system in order to screen for possible hypersensitive reactions to NSAIDs with both reliability and safety.

Adult↗
PubMed1997

Ambulatory blood pressure monitoring in diagnosing a pheochromocytoma of the urinary bladder. A case report.

A patient is presented in whom the preoperative diagnosis of an intravesical pheochromocytoma was facilitated by noninvasive ambulatory blood pressure monitoring. A fifty-two-year-old Japanese man suffered headache and palpitation after micturition. Cystoscopy revealed an intravesical tumor. To investigate whether his symptoms were associated with an elevation of blood pressure, the authors monitored his ambulatory blood pressure automatically for twenty-four hours. The patient was also instructed to activate the recording manually upon the onset of symptoms. As a result, elevations of blood pressure were apparent following micturition. The twenty-four-hour urinary excretion of norepinephrine was elevated on the day of the blood pressure monitoring. Pheochromocytoma was suspected and was confirmed by histopathologic studies following the operation. Thus, ambulatory blood pressure monitoring may be useful in detecting the transient hypertension induced by micturition, which can provide preoperative evidence of pheochromocytoma of the urinary bladder.

Blood Pressure Monitoring, Ambulatory↗
PubMed1997

Purification and some properties of endo-1,4-beta-D-xylanase from a fresh-water mollusc, Pomacea insularus (de Ordigny).

Endo-1,4-beta-D-xylanase (EC 3.2.1.8) was purified from viscera of a fresh-water mollusc, Pomacea insularus (de Ordigny). The purified enzyme, with a molecular weight of 47,000, gave a single protein band in sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). The amino-terminal sequence was Ala-Ala-Gly-Ala-Gly-Val-Thr-Ser-Glu-Lys-Asp-Arg-Leu-Arg-Arg-Ser-Asp-Lys -Thr-Val-His-Val-Asn-. The enzyme was stable from pH about 4.5 to 9.5 and had its maximum activity at pH about 5.5. The purified enzyme produced X2, X3, X4, and larger xylooligosaccharides from birchwood xylan. The enzyme activity was greatly inhibited by Ag+, Hg2+, Cu2+, N-bromosuccinimide, and p-chloromercuribenzoic acid. On the other hand, the enzyme activity was greatly elevated by the addition of chloride ion.

Amino Acid Sequence↗
PubMed1997

Isolation and characterization of the dnaKJ operon from Actinobacillus actinomycetemcomitans.

The dnaKJ operon of Actinobacillus actinomycetemcomitans Y4 was cloned by the DNA-probing method using synthetic oligonucleotides designed on the basis of two conserved regions in DnaK/hsp70 proteins and sequenced by inverse PCR. The sequenced region was shown to contain two open reading frames coding for proteins analogous to DnaK and DnaJ.

Aggregatibacter actinomycetemcomitans↗
PubMed1997

Inhibitory effect of drugs with a ketone group on reduction of acetohexamide catalyzed by carbonyl reductase from rabbit kidney.

The reduction of acetohexamide catalyzed by carbonyl reductase from rabbit kidney was inhibited by befunolol, moperone, levobunolol, daunorubicin and loxoprofen, which have a ketone group within their chemical structures and are substrates for the enzyme. A significant correlation was observed between the common logarithm of Vmax/Km values of the enzyme for befunolol, moperone, levobunolol and daunorubicin and the percentage inhibition of the enzyme, confirming that these drugs are competitive substrates of the enzyme with respect to acetohexamide. However, the plot for loxoprofen, a nonsteroidal anti-inflammatory drug with a ketone group, was apparently distant from the regression line obtained. Although nonsteroidal anti-inflammatory drugs with a ketone group such as suprofen and fenbufen were not reduced by the enzyme, they strongly inhibited the reduction of acetohexamide catalyzed by the enzyme.

Acetohexamide↗
PubMed1997

Biological activities of novel zaragozic acids, the potent inhibitors of squalene synthase, produced by the fungus, Mollisia sp. SANK 10294.

Four novel zaragozic acids, F-10863A, B, C and D, were isolated from a culture broth of the fungus Mollisia sp. SANK 10294. F-10863 compounds contain a 4,6,7-trihydroxy-2,8-dioxyobicyclo-[3.2.1]octane-3,4,5-tricarboxyl ic acid core like previously reported zaragozic acids, but the structures of the side chains are different. Recently, it was found that F-10863A is identical to zaragozic acid D3, while the other three are novel compounds. F-10863 compounds are potent inhibitors of squalene synthase like previously reported zaragozic acids, and, furthermore, they exhibit serum cholesterol-lowering activity in vivo.

Animals↗
PubMed1997

Influence of the discontinuation of a school-based, supervised fluoride mouthrinsing programme on the prevalence of dental caries.

OBJECTIVE: Since 1984 a weekly supervised fluoride mouthrinsing programme has been implemented for schoolchildren in Hisayama, Japan. Consequently, four years after the start of the programme the DMFT index for 12.5-year-old schoolchildren in Hisayama decreased to a value of less than 3.0. However, since 1992 it has increased. The purpose of this study was to investigate the causes of this increasing prevalence of dental caries since 1992. PARTICIPANTS: One hundred and one schoolchildren aged 12 years in 1994 were selected. This age group showed the highest increase in the prevalence of dental caries in that year. OUTCOME MEASURES: Children who had discontinued the use of fluoride mouthrinse for one year or more were identified by means of a confidential questionnaire. Oral examination was carried out, by three examiners, under a suitable artificial light using a mirror and an explorer. RESULTS: The DMFT and DMFS indices of the continuous mouthrinsing (CM) group were significantly lower than those of the discontinuous mouthrinsing (DM) group (P < 0.001). Significant differences between the CM and DM groups were also observed in the DMFT rates for premolars (P < 0.05) and for the first molar (P < 0.001). CONCLUSIONS: The continuation of fluoride mouthrinsing for children of school age was important in achieving the advantages of the programme in Hisayama.

Bicuspid↗
PubMed1997

Inhibitory effect of azelastine hydrochloride and suplatast tosilate on airway responses in sensitized rats following exposure to antigen.

In the present study, we examined the relationship between the increase in respiratory resistance following exposure to antigen and the IgE level in the identical rate sensitized with DNP-As. Additionally, we investigated the effects of the antiallergic drugs, suplatast tosilate and azelastine hydrochloride, which have been reported to suppress the production of IgE, on the increase in respiratory resistance in rats following exposure to antigen. The IgE antibody level rose to its highest value on day 10 during the course of sensitization with DNP-As, and decreased sharply on day 20. The changes of IgE antibody level in the azelastine hydrochloride-administered group were similar to those in the distilled water-administered group (control). In contrast, in the suplatast tosilate-administered group, the IgE antibody levels were lower than those in the control group at days 10 and 15. The ratio of increase in the respiratory resistance induced by the early and late phase responses in the control group reached its highest value on day 15, and then decreased gradually. In contrast, in both the azelastine hydrochloride and suplatast tosilate-administered groups, the ratio of increase in the respiratory resistance induced by the early and late phase responses remained almost unchanged, and was lower than that in the control group at day 15 or 20. In the present study, an increased peak of respiratory resistance was observed at 5 days after the appearance of an increased peak in the IgE level.

Airway Resistance↗
PubMed1996

Molecular and genetic analysis of multiple changes in the levels of production of virulence factors in a subcultured variant of Streptococcus mutans.

We previously isolated a variant strain, Xc100L, which shows decreased production of a surface protein antigen with a molecular mass of 190 kDa (PAc), after repeated subculturing of Streptococcus mutans strain Xc [Koga, T. et al. (1989) J.Gen. Microbiol. 135, 3199-3202]. In the present study, the levels of expression of the gtfB, gtfC, gtfD and ftf genes coding for polysaccharide-synthesizing enzymes in strain Xc100L were compared with those in strain Xc. Western blot analysis revealed multiple differences in the levels of production of these enzymes between these two strains. The amounts of the gtfB and gtfC gene products responsible for water-insoluble glucan synthesis in strain Xc100L were lower than those in strain Xc, whereas the amounts of the gtfD and ftf gene products responsible for water soluble glucan synthesis and fructan synthesis, respectively, in strain Xc100L were higher than those in strain Xc. Northern blot analysis revealed that the amounts of the four enzymes and PAc produced by strain Xc100L reflected the relative amounts of mRNAs from the genes. The chloramphenicol acetyltransferase gene was fused with each of these five genes, and the transcriptional activity of each gene in strain Xc100L was quantitatively compared with that in strain Xc. The chloramphenicol acetyltransferase assay also indicated that the phenotypic differences between strain Xc and strain Xc100L were due to differences in the transcriptional activities of the virulence genes. No differences in the nucleotide sequences of the promoter regions of the gtfB, gtfC, gtfD, ftf and pac genes were found between strain Xc and strain Xc100L. It is possible that a factor(s) affecting the levels of transcription of the multiple virulence genes exists in S. mutans.

Antigens, Bacterial↗
PubMed1996

Rifampicin resistance and mutation of the rpoB gene in Mycobacterium tuberculosis.

Using 39 clinical isolates of Mycobacterium strains with a broad range of susceptibility to rifampicin, we examined the relationship between the degree of resistance to rifampicin and mutational sites of the rpoB gene. All rifampicin-resistant strains had missense mutations. Twenty strains (95%) had a mutation in the cluster I region, which has also been reported in Escherichia coli [Jin and Gross (1988) J. Mol. Biol. 202, 45-58], and the remaining one strain had a mutation at codon 381 [Ala-->Val] in the N-terminal region, which has not been reported in E. coli. Among 18 rifampicin-susceptible strains, two had a mutation in the cluster I region and the other three strains had a mutation in the cluster III region. The mutations at codons 513 (5%), 526 (33%) or 531 (43%) in the cluster I region led to high level resistance to rifampicin (50 micrograms ml-1 < or = MIC). The mutations at the other sites, in the cluster III region (codons 679 or 687) and even in the cluster I region (codon 514, 521, or 533), showed low level (MIC = 12.5 micrograms ml-1) or no (MIC < 0.39 microgram ml-1) resistance to rifampicin. These results suggest that mutations in the rpoB gene are, mostly, but not necessarily, associated with rifampicin resistance of M. tuberculosis, and the sites of mutations on the rpoB gene will affect the level of resistance to rifampicin.

Amino Acid Sequence↗
PubMed1996

Actions of CP-060S on veratridine-induced Ca2+ overload in cardiomyocytes and mechanical activities in vascular strips.

CP-060S, (-)-(S)-2-[3,5-bis(1, 1-dimethylethyl)-4-hydroxyphenyl]-3-[3-[N-methyl-N-[2-(3, 4-methylenedioxyphenoxy)ethyl]amino]propyl]-1,3-thiazolidin- 4-one hydrogen fumarate, is a novel cardioprotective drug which is designed to prevent Ca2+ overload and cause vasorelaxation. The effects of this compound were evaluated and compared with those of CP-060R (enantiomer of CP-060S,) and diltiazem (Ca2+ channel antagonist) in a veratridine-induced model of Ca2+ overload and vasorelaxation. After 5-min superfusion of veratridine (74 microM), intracellular free calcium concentrations ([Ca2+]i) of rat single cardiomyocytes, as measured with the fura-2 procedure, were greatly elevated, from 44 +/- 5 nM to 3705 +/- 942 nM, and subsequently generated cell contracture. Pretreatment of cardiomyocytes with more than 300 nM of CP-060S or CP-060R for 30 min provided almost complete protection against the veratridine-induced cell contracture; in CP-060S(1 microM)-treated myocytes, [Ca2+]i were minimal and partially elevated from 42 +/- 5 nM to 72 +/- 14 nM after 5 min of veratridine superfusion. In comparison, diltiazem showed no protection below 1 microM and only partial protection at 10 microM. CP-060S, CP-060R and diltiazem all shifted the concentration-response curve for CaCl2 to the right in a competitive manner in depolarized rat thoracic aorta. The pA2 values of CP-060S, CP-060R and diltiazem were 9.16 +/- 0.18, 8.24 +/- 0.14 and 7.66 +/- 0.09, respectively. Our results indicate that CP-060 behaves stereoselectively as a Ca2+ channel antagonist and non-stereo-selectively to protect against veratridine-induced contracture. The latter effect suggests that Ca2+ entry blockade is not the mechanism by which CP-060S exerts cardioprotection.

Animals↗
PubMed1996

Isolation and characterization of vascular smooth muscle inositol 1,4,5-trisphosphate receptor.

myo-Inositol 1,4,5-trisphosphate (InsP3) receptor of porcine aorta was purified to near homogeneity and its biochemical properties were compared with those of cerebellar InsP3 receptor of the same animal species. The aortic InsP3 receptor consisted of equal amounts of two polypeptides with slightly differing molecular masses of around 240 kDa and was found to possess a single population of InsP3-binding site (Kd of 1.2 nM). The InsP3 receptor purified from porcine cerebellum was also comprised of two polypeptides. However, the molecular mass was slightly but definitely larger, being 250 kDa, and the amounts of the two polypeptides were not equal. The aortic InsP3 receptor cross-reacted with polyclonal antibody specific to type 1 InsP3 receptor as did the cerebellar InsP3 receptor. The aortic InsP3 receptor bound to calmodulin-Sepharose in a Ca(2+)-dependent manner, while the cerebellar InsP3 receptor did not. Reverse transcriptase-PCR analysis revealed two splicing variants of the type 1 InsP3 receptor in porcine aortic smooth muscle distinct from those of the type 1 InsP3 receptor of porcine cerebellum. The possible relevance of this difference to difference in calmodulin-binding property was discussed.

Amino Acid Sequence↗
PubMed1996

Interleukin-1 alpha activates an NF-kappaB-like factor in osteoclast-like cells.

We investigated the NF-kappaB transcription factor in osteoclast-like cells. Osteoclast-like cells were differentiated from mouse bone marrow cells in co-culture with mouse calvaria-derived primary osteoblasts in the presence of 1alpha,25-dihydroxyvitamin D3 and prostaglandin E2 in collagen gel-coated dishes. We enriched osteoclast-like cells from the co-cultures by Pronase treatment. When the enriched osteoclast-like cells were treated with phorbol 12-myristate 13-acetate, interleukin-1 (IL-1), calcitonin, or macrophage colony-stimulating factor, only IL-1 activated an NF-kappaB-like factor, which specifically bound to a kappaB motif DNA sequence, as detected by an electrophoretic mobility shift assay. IL-1 also activated NF-kappaB induction in osteoblasts. However, the NF-kappaB-like factor induced by IL-1-stimulated osteoclast-like cells is of smaller molecular size than the factor in osteoblasts, as shown by an electrophoretic mobility shift assay. The NF-kappaB activity of osteoclast-like cells was recognized completely by antibodies against the p50 subunit, and only partially by antibodies against the p65 subunit of NF-++kappaB. Antibodies against c-Rel, Rel B, and p52 did not recognize the NF-kappaB-like factor. These results suggest that IL-1 activates an NF-kappaB-like factor in osteoclast-like cells, which contains p50 and p65-related proteins.

Animals↗
PubMed1996

New shuttle vectors for Actinobacillus actinomycetemcomitans and Escherichia coli.

A series of shuttle vectors for Actinobacillus actinomycetemcomitans (Aa) and Escherichia coli (Ec) was developed. These vectors carry a multiple cloning site, the lacZalpha reporter gene, the replication origin for Aa derived from pVT736-1 and a replicon for Ec originated from pUC, P15A or pSC101. With these vectors, cloning and expression can be effectively performed in Aa and Ec.

Actinobacillus↗