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Biomedical subjects

Y Koga

Publications and source records attributed to Y Koga.

At least 55 records · Page 3Linked to original sources
PubMed2001

In vivo determination of the centres of resistance of maxillary anterior teeth subjected to retraction forces.

This study was designed to locate the centres of resistance of consolidated units of two, four, and six anterior teeth during retraction in two human subjects. Initial displacements of these units were separately measured when retraction forces were applied at different levels by means of a device for displacement measurement using magnetic sensors and magnets. By calculating the angle of rotation from the displacements measured, the location of the centre of resistance was determined for each unit. The results showed that the centres of resistance of the two- and four-incisor units were approximately at the same position, whilst that of the six-tooth unit was observed to be more incisal. Clinically, this finding indicates that translation can be achieved with a smaller amount of moment-to-force ratio in en masse retraction than in two- or four-incisor retraction. The results also indicate that the location of the centre of resistance of the anterior segment during retraction may depend on the palatal alveolar bone height, rather than on the labial alveolar bone height.

Adult↗
PubMed2001

Suppressive effect of Lactobacillus gasseri OLL 2716 (LG21) on Helicobacter pylori infection in humans.

To examine the efficacy of Lactobacillus gasseri OLL2716 (LG21) as a probiotic for Helicobacter pylori in humans, 31 subjects infected with the bacterium ingested yogurt containing LG21 daily for an 8 week period. The [(13)C]urea breath test and assays of serum pepsinogens revealed a significant improvement following LG21 treatment. LG21 was thus determined to be effective in both suppressing H. pylori and reducing gastric mucosal inflammation.

Female↗
PubMed2001

Development of a magnetic sensing device for tooth displacement under orthodontic forces.

We have developed a system for measuring tooth displacement from orthodontic force. Eight small magnetic sensors and a magnet are combined to measure three-dimensional displacement. Sensors, arranged cubically in the three planes of space, are placed in the mouth and fixed to the posterior teeth by a splint. A magnet is placed in the center of the eight sensors and attached to a front tooth that is subjected to orthodontic force. Sensors detect the magnet's movement as target tooth displacement. The system was designed to achieve displacement resolution of 1 microm. The mean percentage of measurement errors was determined to be less than 1% in a 600-cubic-microm volume from calibration. The system was tested clinically on human teeth. Although the oral environment, with high temperature and humidity, was not agreeable with the sensors, this system was stable and accurate enough for quantitative measurement of tooth displacement. The advantage of this system is the ability to detect tooth trajectories by decomposing displacement into translation and rotation and to determine the position of the center of rotation from these parameters.

Calibration↗
PubMed2001

A microwave exciter for Cs frequency standards based on a sapphire-loaded cavity oscillator.

A low noise and highly stable microwave exciter system has been built for Cs atomic frequency standards using a tunable sapphire-loaded cavity oscillator (SLCO), which works at room temperature. This paper discusses the successful implementation of a control system for locking the SLCO to a long-term reference signal and reports an upper limit of the achieved frequency tracking error 6 x 10(-15) at tau = 1 s.

Journal Article↗
PubMed2001

Active subtilisin-like protease from a hyperthermophilic archaeon in a form with a putative prosequence.

The gene encoding subtilisin-like protease T. kodakaraensis subtilisin was cloned from a hyperthermophilic archaeon Thermococcus kodakaraensis KOD1. T. kodakaraensis subtilisin is a member of the subtilisin family and composed of 422 amino acid residues with a molecular weight of 43,783. It consists of a putative presequence, prosequence, and catalytic domain. Like bacterial subtilisins, T. kodakaraensis subtilisin was overproduced in Escherichia coli in a form with a putative prosequence in inclusion bodies, solubilized in the presence of 8 M urea, and refolded and converted to an active molecule. However, unlike bacterial subtilisins, in which the prosequence was removed from the catalytic domain by autoprocessing upon refolding, T. kodakaraensis subtilisin was refolded in a form with a putative prosequence. This refolded protein of recombinant T. kodakaraensis subtilisin which is composed of 398 amino acid residues (Gly(-82) to Gly(316)), was purified to give a single band on a sodium dodecyl sulfate (SDS)-polyacrylamide gel and characterized for biochemical and enzymatic properties. The good agreement of the molecular weights estimated by SDS-polyacrylamide gel electrophoresis (44,000) and gel filtration (40,000) suggests that T. kodakaraensis subtilisin exists in a monomeric form. T. kodakaraensis subtilisin hydrolyzed the synthetic substrate N-succinyl-Ala-Ala-Pro-Phe-p-nitroanilide only in the presence of the Ca(2+) ion with an optimal pH and temperature of pH 9.5 and 80 degrees C. Like bacterial subtilisins, it showed a broad substrate specificity, with a preference for aromatic or large nonpolar P1 substrate residues. However, it was much more stable than bacterial subtilisins against heat inactivation and lost activity with half-lives of >60 min at 80 degrees C, 20 min at 90 degrees C, and 7 min at 100 degrees C.

Amino Acid Sequence↗
PubMed2001

Ammonia as an accelerator of tumor necrosis factor alpha-induced apoptosis of gastric epithelial cells in Helicobacter pylori infection.

The mechanism by which Helicobacter pylori induces apoptosis remains unclear. In a previous study using biopsy samples, we found a significant correlation between the urease activity of an H. pylori strain and the apoptosis level induced by this strain. Therefore, in this study, we investigated whether urease and/or the ammonia generated by urease can induce apoptosis. Human gastric epithelial cell lines were cocultured with H. pylori, and the levels of apoptosis and ammonia production were measured. The medium was supplemented (or not supplemented) with urea and cytokines. While a large amount of ammonia (>30 mM) accumulated in the coculture containing urease-positive H. pylori and urea, no significant degree of apoptosis occurred. In the presence of tumor necrosis factor alpha (TNF-alpha), however, a marked acceleration of apoptosis was found in this coculture. Such enhancement of apoptosis was also induced by the addition of 4 to 8 mM ammonia to the cell culture without either H. pylori or urea but containing TNF-alpha. These results suggested that ammonia accelerates cytokine-induced apoptosis in gastric epithelial cells, while ammonia or urease molecules alone are unable to induce a significant degree of apoptosis.

Ammonia↗
PubMed2001

Involvement of potassium channels in spinal antinociceptions induced by fentanyl, clonidine and bethanechol in rats.

In the central nervous systems, intracellular and extracellular movement of potassium ions plays an important role in regulating neuronal excitability and the release of neurotransmitters. The purpose of our study was to determine whether nicorandil (adenosine triphosphate-sensitive K+ channel opener) exerts antinociceptive effects by itself or in combination with fentanyl, clonidine and bethanechol and whether glibenclamide (adenosine triphosphate-sensitive K+ channel blocker) and charybdotoxin (Ca2+-activated K+ channel blocker) may antagonize the antinociceptive action of fentanyl, clonidine and bethanechol. Antinociceptive effects were assessed using the tail-flick test in rats. Nicorandil (100 microg) and antinociceptively ineffective doses of fentanyl (1 microg), clonidine (2.5 microg) or bethanechol (10,ug) were coadministered intrathecally (i.t.). Glibenclamide (100 microg) or charybdotoxin (2.5 ng) were administered i.t. at 5 min before each effective dose of fentanyl (2.5 microg), clonidine (10 microg) or bethanechol (40 microg). The present findings demonstrated that i.t. administration of nicorandil alone exerted no influence on the tail-flick latency. However, concomitant administrations of antinociceptively inactive doses of fentanyl, clonidine or bethanechol with nicorandil elicited significant suppression of the thermonociceptive response. Also, each antinociception induced by fentanyl, clonidine or bethanechol was partially antagonized by both glibenclamide and charybdotoxin. These findings showed that activation of the K+ channel might enhance the antinociceptive effects of fentanyl, clonidine and bethanechol.

Adenosine Triphosphatases↗
PubMed2001

Stabilities of chimeras of hyperthermophilic and mesophilic glycerol kinases constructed by DNA shuffling.

Glycerol kinases from Thermococcus kodakaraensis KOD1 (Tk-GK) and Escherichia coli (Ec-GK) greatly differ in thermostability. The temperature (T(1/2)) at which the enzymes lose half of their activity upon incubation for 20 min is 50-55 degrees C for Ec-GK and approximately 95 degrees C for Tk-GK. To examine whether the amino acid substitutions that make Tk-GK more stable than Ec-GK are localized in a limited region, the chimeras of two parental genes encoding Tk-GK and Ec-GK were constructed by DNA shuffling. E. coli cells were transformed with a plasmid library harboring these chimeras and screened for those tht produce chimeric enzymes which are more stable than Ec-GK. Four chimeric enzymes were isolated and purified, and their biochemical properties characterized. Replacement of 83 or 93 residues in the C-terminus of Ec-GK with the corresponding ones of Tk-GK increased the T(1/2) value of Ec-GK by 25-30 degrees C. In contrast, replacement of 85 residues in the N-terminus of Ec-GK with the corresponding ones of Tk-GK reduced the T(1/2) value by 5-10 degrees C. In addition, replacement of 10 residues in the C-terminus of Tk-GK with the corresponding ones of Ec-GK reduced the T(1/2) value ot Tk-GK by approximately 15 degrees C. Measurement of the far-UV CD spectra indicates that the three-dimensional structures of the chimeric enzymes, as well as those of the parent enzymes, are similar to one another. These results suggest that the amino acid substitutions responsible for the high stability of Tk-GK are largely localized in the C-terminal region.

Journal Article↗
PubMed2001

[Appearance of angry backfiring C-nociceptor (ABC) syndrome-like pain disorder in cross-side of one-side spinal anesthesia].

ABC (angry backfiring C-nociceptor) syndrome-like pain disorder categorized in sympathetic independent pain appeared after amputation during spinal anesthesia. A 69-year-old female who had undergone amputation of the right leg below knee 5 months before, received amputation of the left leg below knee this time because of diabetic neuropathy and gangrene of her both legs. There were no complications in her right leg after the former amputation. Spinal anesthesia was maintained in the left one-side by hyperbaric local anesthetic. After changing the body position from left lateral to supine, the left leg was completely anesthetized and the right leg was incompletely anesthetized with only loss of cold sensation. In this state, she had pain in her right leg, and this pain was relieved by intravenous lidocaine administration. It was indicated that this type of pain was caused by the presence of ABC syndrome probably after right leg amputation.

Aged↗
PubMed2001

Natural history of hypertrophic cardiomyopathy: Japanese experience.

BACKGROUND AND OBJECTIVES: Most patients with hypertrophic cardiomyopathy (HCM) remain clinically stable for long periods of time, whereas some patients progress to severe systolic dysfunction. Therefore, the natural history of HCM is largely unknown. METHODS: The present study followed up 59 patients with HCM (32 males, 27 females, mean age 38.6 +/- 13.6 years) for 10 years or more (mean 16.0 +/- 4.7 years) after the initial diagnosis. RESULTS: Eight of 17 patients who showed abnormal Q-waves at the initial examination had lost Q-waves, suggesting remodeling from asymmetric to generalized hypertrophy. The thickness of the interventricular septum showed remarkable changes, increasing by > or = 5 mm in 7 patients and decreasing by > or = 5 mm in 21. These observations indicate that ventricular remodeling occurs in patients with HCM. Follow-up electrocardiography demonstrated new Q-waves in 10 patients and bundle branch blocks or intraventricular conduction disturbances in 13. Left ventricular end-diastolic diameter increased from 41.6 to 48.1 mm, associated with a decrease in fractional shortening from 40.6% to 34.0%. Left ventricular systolic dysfunction, defined as left ventricular end-diastolic diameter > 55 mm or fractional shortening < 25%, developed in 13 patients. These observations indicate that myocardial disease including the conduction system is progressive in patients with HCM and finally deteriorates to systolic dysfunction. Left ventricular outflow obstruction also presented evolutional changes. At the initial study, 23 patients showed systolic anterior motion of the mitral valves. Systolic anterior motion disappeared in 13 patients, reduced in 2, increased in 2, and remained stable in only 6. One patient without systolic anterior motion at the initial study developed new systolic anterior motion. Impaired left ventricular filling increased left atrial diameter from 35.5 to 46.9 mm and atrial fibrillation frequently developed (24 patients). CONCLUSIONS: These findings suggest that HCM is a slowly progressive disease which develops evolutional remodeling of left ventricular hypertrophy and outflow obstruction, eventually progressing to systolic dysfunction with cavity dilation and wall thinning.

Adult↗
PubMed2001

[Good response in case of hepatocellular carcinoma with portal tumor thrombs--a case report of interdisciplinary local therapy].

A 56-year-old male patient with chronic C type hepatitis had HCC which invaded right portal vein trunk (Vp3). In August 2000, we performed intrahepatic artery infusion chemotherapy with CDDP and 5-FU under subcutaneous interferon alpha treatment. In addition, we used chemoradiation therapy for portal tumor thrombus in HCC. As the result of such therapy, the size of HCC and portal tumor thrombus reduced and the level of PIVKA-II decreased. There were no side effects except fever due to interferon alpha treatment. In February 2001, we performed devascularization and RFA therapy for HCC in S7 of liver under laparoscope. The level of PIVKA-II was within the normal range. It is important to perform interdisciplinary therapy appropriate for the HCC status.

Antineoplastic Agents↗
PubMed2000

CTP:2,3-di-O-geranylgeranyl-sn-glycero-1-phosphate cytidyltransferase in the methanogenic archaeon Methanothermobacter thermoautotrophicus.

CDP-2,3-di-O-geranylgeranyl-sn-glycerol synthase (CDP-archaeol synthase) activity was discovered in the membrane fraction of the methanoarchaeon Methanothermobacter thermoautotrophicus cells. It catalyzed the formation of CDP-2,3-di-O-geranylgeranyl-sn-glycerol from CTP and 2,3-di-O-geranylgeranyl-sn-glycero-1-phosphate (unsaturated archaetidic acid). The identity of the reaction product was confirmed by thin layer chromatography, fast atom bombardment-mass spectroscopy, chemical analysis, and by UV spectroscopy. One mole of the product was formed from approximately 1 mol of each of the reactants. The enzyme showed maximal activity at pH 8.5 and 55 degrees C in the presence of Mg(2+) and K(+) ions. By in vivo pulse labeling of phospholipids with (32)P(i), CDP-archaeol was found to be an intracellular intermediate. A cell-free homogenate of M. thermoautotrophicus, when incubated with l-serine, converted the product of CDP-archaeol synthase reaction to a product with the same chromatographic mobility as archaetidylserine. It was concluded from these results that both CDP-archaeol and CDP-archaeol synthase were involved in cellular phospholipid biosynthesis. Among various synthetic substrate analogs, both enantiomers of unsaturated archaetidic acid possessing geranylgeranyl chains showed similar levels of activity, while archaetidic acid with saturated or monounsaturated isoprenoid or straight chains was a poor substrate, despite having the same stereostructure as the fully active substrate. The ester analogs with geranylgeranioyl chains showed significant activities. These results suggest that the enzyme dose not recognize ether or ester bonds between glycerophosphate and hydrocarbon chains nor the stereostructure of the glycerophosphate backbone but mainly targets substrates with geranylgeranyl chains.

Catalysis↗
PubMed2000

Primary LAMP-2 deficiency causes X-linked vacuolar cardiomyopathy and myopathy (Danon disease).

"Lysosomal glycogen storage disease with normal acid maltase" which was originally described by Danon et al., is characterized clinically by cardiomyopathy, myopathy and variable mental retardation. The pathological hallmark of the disease is intracytoplasmic vacuoles containing autophagic material and glycogen in skeletal and cardiac muscle cells. Sarcolemmal proteins and basal lamina are associated with the vacuolar membranes. Here we report ten unrelated patients, including one of the patients from the original case report, who have primary deficiencies of LAMP-2, a principal lysosomal membrane protein. From these results and the finding that LAMP-2-deficient mice manifest a similar vacuolar cardioskeletal myopathy, we conclude that primary LAMP-2 deficiency is the cause of Danon disease. To our knowledge this is the first example of human cardiopathy-myopathy that is caused by mutations in a lysosomal structural protein rather than an enzymatic protein.

Antigens, CD↗
PubMed2000

Reaction of selenobenzophenones with olefins. Formation of 1H-2-benzoselenopyrans. Reaction of 1H-2-benzoselenopyrans with diazoalkanes

Selenobenzophenone reacts as a diene with dimethyl acetylenedicarboxylate (DMAD) to lead to dimethyl 1H-1-diphenylmethyl-1-phenyl-2-benzoselenopyran-3,4-dicarboxylate (5c) in moderate yield; the initial [4 + 2] cycloaddition is followed by the addition of another 1 mol equiv of selenobenzophenone. The reaction might proceed through carbene insertion of the primary cycloadduct. On the other hand, 4,4'-dimethoxyselenobenzophenone combines as a diene with DMAD furnishing dimethyl 1H-1-p-methoxyphenyl-6-methoxy-2-benzoselenopyran-3,4-dicarboxylate (4a). The reaction of benzoselenopyran derivative (4) with diaryldiazomethanes afforded another type of carbene insertion product.

Journal Article↗
PubMed2000

Enzymatic determination of sn-glycerol-1-phosphate.

A sensitive and positive colorimetric method for quantification of sn-glycerol-1-phosphate (G-1-P) is described. The use of G-1-P-specific dehydrogenase from Methanobacterium thermoautotrophicum and a tetrazolium salt (an NAD-recycling system) allowed a positive measurement of G-1-P, and caused an increase in sensitivity. Because G-1-P is not only the backbone of the ether glycerolipids in Archaea (formerly archaebacteria) but also the component of lipoteichoic acid polymers from some Gram-positive bacteria, membrane-derived oligosaccharide from Escherichia coli, unacylated moiety of phosphatidylglycerol from bacteria and mitochondria, and some phosphoglycolipids of lactic acid bacteria, this method may be useful in the structural and metabolic studies of these materials.

Archaea↗