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Biomedical subjects

K Kawano

Publications and source records attributed to K Kawano.

At least 145 records · Page 8Linked to original sources
PubMed1998

Sequential hemodynamic activation of motor areas and the draining veins during finger movements revealed by cross-correlation between signals from fMRI.

Activity in the human supplementary motor area (SMA), primary motor cortex (M1), and the draining vein of the motor cortex during a visually triggered finger opposition task was measured by functional magnetic resonance imaging with a repetition time of 1 s. Sequential hemodynamic activation in these areas was revealed by cross-correlating a signal sequence in M1 directly with signal sequences from SMA and the draining vein, and applying polynomial fitting with the aid of Akaike's information criterion. We succeeded in detecting a time delay of approximately 0.5 s between the activations of SMA and M1, and a delay of nearly 1.3 s between the activations of M1 and its draining vein. The new combination of fMRI and data analysis techniques has attained a time resolution comparable to those in preceding studies that used shorter fMRI repetition times of 100-200 ms.

Adult↗
PubMed1998

Adsorption of human lysozyme onto hydroxyapatite. Identification of its adsorbing site using site-directed mutagenesis.

To elucidate hydroxyapatite-protein interaction, mutant human lysozymes in which the surface charge was modified by site-directed mutagenesis were used. Five mutant human lysozymes (K1A, K13A, K33A, R10A, R14A) were expressed in yeast. The chromatographic behavior of these lysozymes was studied with a HPLC hydroxyapatite column. Elution molarities of K1A and R14A mutants were greatly lowered. While Lys-13 and Arg-10 are located around Lys-1 and Arg-14, K13A and R10A mutants bound onto hydroxyapatite stronger than K1A and R14A mutants. In combination with an X-ray crystal structure of human lysozyme, it is concluded that the adsorbing site of human lysozyme is at the back of the active site and that Arg-14, Lys-1, Arg-10 and Lys-13 play important roles in binding.

Adsorption↗
PubMed1998

Respiratory effects of halothane and AMPA receptor antagonist synergy in rats.

The influence of N-methyl-D-aspartate (NMDA) or alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA) receptor antagonists in combination with halothane anaesthesia on the respiratory system was investigated. Under 1.5% halothane anaesthesia, respiratory parameters including respiratory rate, minute volume, tidal volume, inspiratory and expiratory duration were measured before and after drug administration in rats. The AMPA receptor antagonists, 6-(1H-imidazol-1-yl)-7-nitro-2,3-(1H,4H)-quinoxalinedione hydrochloride, YM90K (5 and 10 mg/kg) and 2,3-dihydroxy-6-nitro-7-sulfamoyl-benzo(F)quinoxaline (NBQX, 15 mg/kg), which were administered intravenously for 30 min, significantly reduced the respiratory rate (P < 0.01) and minute volume (P < 0.01) and increased the tidal volume (P < 0.05) compared with values obtained before drug administration. None of these drugs affected respiratory parameters in the absence of anaesthesia. A NMDA receptor antagonist, MK-801 (0.5 mg/kg), which was administered intravenously for 30 min, also significantly reduced respiratory rate (P < 0.01), minute volume (P < 0.01) and tidal volume (P < 0.01) and prolonged inspiratory duration (P < 0.05). These results suggest that both AMPA and NMDA receptor antagonists cause respiratory depression under halothane anaesthesia in rats, although the mechanisms may be different for the two types of antagonists.

Anesthetics, Inhalation↗
PubMed1998

Gain-of-function mutations of c-kit in human gastrointestinal stromal tumors.

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumors in the human digestive tract, but their molecular etiology and cellular origin are unknown. Sequencing of c-kit complementary DNA, which encodes a proto-oncogenic receptor tyrosine kinase (KIT), from five GISTs revealed mutations in the region between the transmembrane and tyrosine kinase domains. All of the corresponding mutant KIT proteins were constitutively activated without the KIT ligand, stem cell factor (SCF). Stable transfection of the mutant c-kit complementary DNAs induced malignant transformation of Ba/F3 murine lymphoid cells, suggesting that the mutations contribute to tumor development. GISTs may originate from the interstitial cells of Cajal (ICCs) because the development of ICCs is dependent on the SCF-KIT interaction and because, like GISTs, these cells express both KIT and CD34.

Amino Acid Sequence↗
PubMed1998

Gene expression of alpha1-6 fucosyltransferase in human hepatoma tissues: a possible implication for increased fucosylation of alpha-fetoprotein.

The 1-6 fucosylated -fetoprotein (AFP) present in serum of patients with hepatocellular carcinoma (HCC) has been employed for the differential clinical diagnosis of HCC from chronic liver diseases. The molecular mechanism by which this alteration occurs, however, remains largely unknown. To address this issue, we purified GDP-L-Fuc:N-acetyl-beta-D-glucosaminide 1-6 fucosyltransferase (1-6 FucT), an enzyme involved in the 1-6 fucosylation of N-glycans from porcine brain, as well as from a human gastric cancer cell line, and cloned their genes. In this study, levels of 1-6 FucT mRNA expression and the activity of this enzyme for 12 human HCC tissues were examined and compared with that in surrounding tissues and normal livers. The mean +/- SD for 1-6 FucT activity was 78 +/- 41 pmol/h/mg in normal control liver, 202 +/- 127 pmol/h/mg in adjacent uninvolved liver tissues (chronic hepatitis: 181 +/- 106 pmol/h/mg; liver cirrhosis: 233 +/- 164 pmol/h/mg), and 195 +/- 72 pmol/h/mg in HCC tissues. The mRNA expression of 1-6 FucT was also enhanced in proportion to enzymatic activity except for a few cases, suggesting that 1-6 FucT expression is increased in chronic liver diseases, especially liver cirrhosis. Transfection of 1-6 FucT gene into cultured rat hepatocytes markedly increased 1-6 FucT activity and led to an increase in lens culinaris agglutinin (LCA) binding proteins in both cell lysates and condition media. When the 1-6 FucT gene was transfected into a human HCC cell line, Hep3B, which originally showed low levels of 1-6 FucT expression, 1-6-fucosylated AFP was dramatically increased in the condition media. Collectively, these results suggest that the enhancement of 1-6 FucT expression increased the fucosylation of several proteins, including AFP, and that the level of 1-6-fucosylated AFP in patients with HCC was in part caused by up-regulation of the 1-6 FucT gene expression.

Adult↗
PubMed1998

Calcium-binding and structural stability of echidna and canine milk lysozymes.

For echidna and canine milk lysozymes, which were presumed to be the calcium-binding lysozymes by their amino acid sequences, we have quantitated their calcium-binding strength and examined their guanidine unfolding profiles. The calcium-binding constants of echidna and canine lysozymes were determined to be 8.6 x 10(6) M(-1) and 8.9 x 10(6) M(-1) in 0.1 M KCl at pH 7.1 and 20 C, respectively. The unfolding of decalcified canine lysozyme proceeds in the same manner as that of alpha-lactalbumin, through a stable molten globule intermediate. However, neither calcium-bound nor decalcified echidna lysozyme shows a stable molten globule intermediate. This unfolding profile of echidna lysozyme is identical to that of conventional lysozymes and pigeon egg-white lysozyme, avian calcium-binding lysozyme. This result supports the suggestion of Prager and Jolles (Prager EM, Jolles P. 1996. Animal lysozymes c and g: An overview. In: Jolles P, ed. Lysozymes: Model enzymes in biochemistry and biology. Basel-Boston-Berlin: Birkhauzer Verlag. pp 9-31) that the lineage of avian and echidna calcium-binding lysozymes and that of eutherian calcium-binding lysozymes diverged separately from that of conventional lysozymes.

Animals↗
PubMed1998

Dependence of short-latency ocular following and associated activity in the medial superior temporal area (MST) on ocular vergence.

Motion of a large-field pattern elicits short-latency ocular following responses (OFR) in the monkey, which are mediated at least in part by the medial superior temporal area of the cortex (MST). The magnitude of the OFR is known to be inversely related to viewing distance, and we investigated the dependence of OFR and the associated neuronal activity in the MST on a major cue to viewing distance, ocular vergence, in alert monkeys (Macaca fuscata). The vergence angle, expressed in terms of the apparent viewing distance, ranged from infinity to 16.6 cm (0-6 m(-1)). The magnitude of the initial OFR increased monotonically with increases in convergence at a mean (+/-SD) rate of 19.6+/-4.5%/m(-1) in four monkeys (over the range 0-4 m(-1)). In two monkeys, we recorded the single unit activity of 160 MST neurons that responded to motion of a large-field pattern with directional selectivity. The mean latency (+/-SD) of the MST discharges elicited by large-field motion was 50+/-7.5 ms (n=115), which preceded the onset of OFR by an average of 10+/-9.9 ms. The discharge modulation elicited by large-field motion showed a significant dependence on vergence in 91/160 neurons (57%), 72 of which (79%) increased their firing rate with increasing convergence ("near" neurons), and the remainder increasing their firing rate with decreasing convergence ("far" neurons). However, on average, the sensitivity of these MST neurons to vergence was only about 30% of that shown by the OFR. It could be that only those neurons that are very sensitive to vergence angle contribute to the OFR, but it is also possible that much of the modulation of OFR with vergence occurs downstream from the MST or in alternative pathways (yet to be discovered) that contribute to OFR.

Animals↗
PubMed1998

Human platelet activation by thrombolytic agents: effects of tissue-type plasminogen activator and urokinase on platelet surface P-selectin expression.

The mechanisms that underlie reocclusion during thrombolytic therapy have not yet been clarified. The purpose of this study was to investigate the activating effects of tissue-type plasminogen activator and urokinase and the inhibitory effects of acetylsalicylic acid by measuring platelet surface P-selectin as a marker of platelet activation. After addition of urokinase (final concentration 192 U/ml, 1920 U/ml, or 19,200 U/ml) or tissue-type plasminogen activator (final concentration 120 U/ml, 1200 U/ml, or 12,000 U/ml) to platelet-rich plasma from 12 healthy persons, platelet surface P-selectin expression was measured by means of flow cytometry with an anti-CD62 monoclonal antibody. The presence of urokinase and tissue-type plasminogen activator increased platelet surface P-selectin expression in a concentration-dependent manner. In the next step, either 160 mg/day (n = 6) or 660 mg/day (n = 6) acetylsalicylic acid was administered to the 12 healthy persons, and venous blood samples were collected after 7 days of treatment. Platelet surface P-selectin expression was measured with the method used earlier and after addition of tissue-type plasminogen activator or urokinase. Although the effect of acetylsalicylic acid at 160 mg/day on P-selectin expression was minimal, a dose of 660 mg/day suppressed platelet P-selectin expression and inhibited the platelet activating effects of tissue-type plasminogen activator and urokinase in a statistically significant way. Platelets were activated by tissue-type plasminogen activator or urokinase, and this platelet activation was suppressed with administration of acetylsalicylic acid at 660 mg/day.

Aspirin↗
PubMed1998

Short-latency vergence eye movements elicited by looming step in monkeys.

The looming associated with forward and backward motion of the observer has been shown to elicit vergence eye movements with short-latency (approximately 80 ms) in human subjects. We studied the vergence eye movements elicited by looming in three monkeys (Macaca fuscata). The animals faced a large tangent screen onto which a random dot pattern was back-projected. The movements of both eyes were recorded with an electromagnetic induction technique. Fifty milliseconds after a centering saccade, this first pattern was replaced with a new one that showed the same image viewed from a slightly different distance. This looming step (two-frame movie) included both radial optic flow and a size change. As expected from the optical geometry, centrifugal flow coupled with enlargement (signaling forward motion) increased the vergence angle, whereas the converse combination decreased the vergence angle. In both cases, the optimal step-change in apparent viewing distance was 2%. The latency of these vergence responses was very short and similar to those induced when disparity steps are applied to such large patterns (approximately 60 ms). We suggest that these two systems act in synergy to help maintain binocular alignment during forward and backward motion of the observer.

Animals↗
PubMed1998

Increased serum levels of advanced glycation end-products and diabetic complications.

We determined serum advanced glycation end-products (AGE) levels in patients with NIDDM and evaluated the relationship between these levels and diabetic complications. The subjects consisted of 125 patients (mean age, 59.2 +/- 11.1 years, duration of diabetes 11.6 +/- 8.9 years, mean HbA1c, 6.8 +/- 1.0%) with stable blood sugar control. Sixty-three healthy volunteers (mean age, 58.3 +/- 12.7 years) served as controls. Serum AGE were measured by a newly developed ELISA method. Serum AGE levels were significantly higher in the diabetic group compared with the normal control group (7.2 +/- 14.6 vs. 3.3 +/- 1.0 mU/ml, P < 0.05). Significant correlations were seen between serum AGE and the degree of diabetic nephropathy. Serum AGE levels of diabetic patients with proliferative retinopathy were significantly higher than those of patients without proliferative retinopathy (5.7 +/- 1.8 vs. 3.1 +/- 1.0 mU/ml, P < 0.025) in the patient groups whose serum creatinine levels were between 2.0 and 3.9 mg/dl, although serum creatinine levels of both groups were not significantly different. Serum AGE levels reflected the severity of diabetic complications, including nephropathy and retinopathy.

Aged↗
PubMed1998

Inter-ethnic comparisons of the pharmacokinetics of the HMG-CoA reductase inhibitor cerivastatin.

AIMS: During the world-wide clinical development of the HMG-CoA reductase inhibitor cerivastatin, pharmacokinetic data have been collected from studies performed in Europe, North America and Japan, covering different ethnic groups, mainly Caucasians and Japanese subjects, but also Black and Hispanics. The aim of the present investigation was to search for any inter-ethnic differences in cerivastatin pharmacokinetics. METHODS: All concentration data were assessed by fully validated specific h.p.l.c. assays employing post-column photochemical derivatization with ultra-violet light and subsequent fluorescence detection. The comparability of analytical results was guaranteed by cross-validations between all analytical laboratories. The inter-ethnic comparison was based on retrospective analysis of the overall pharmacokinetic data pool (n = 340 complete profiles) in the key parameters AUC, Cmax, tmax and t1/2, assessed via non-compartmental methods. RESULTS: Based on the comparison of selected individual single- and multiple-dose escalation studies in healthy young males, performed when starting the clinical development, exposure and disposition of the parent compound and its cytochrome P450-mediated biotransformation products M-1 and M-23, and amounts of metabolites M-1, M-23 and M-24 excreted in urine were comparable for US Americans, mainly Caucasians, and Japanese. Retrospective analysis of the complete pharmacokinetic data pool revealed that there are no statistically significant differences in dose-normalized AUC- and Cmax-values. The respective ratios of weight-adjusted geometric least-squares (LS) means (95% confidence intervals) between Japanese and Caucasians were: for AUCdose-norm 0.96 (0.86-1.08) for single dose, and 1.04 (0.86-1.24) for multiple dose; for Cmax,dose-norm 0.93 (0.83-1.05) for single dose, and 1.01 (0.82-1.25) for multiple dose. Half-life was slightly, but statistically significantly shorter in Japanese than in Caucasian subjects following single dose: ratios (95% CI) were 0.68 (0.61-0.77) for single dose, and 1.00 (0.79-1.26) for multiple dose. Times to peak tended to be slightly greater in Japanese: differences of weight-adjusted LS means (95% CI) were 0.60 h (0.28 h-0.92 h) for single dose, and 1.15 h (0.48 h-1.81 h) for multiple dose. Black and Hispanics did not differ in their pharmacokinetic characteristics from Caucasians. CONCLUSIONS: Based on inter-study comparisons and a retrospective analysis of the complete PK data pool there is no evidence for any clinically relevant inter-ethnic differences in cerivastatin pharmacokinetics in Caucasians, Black and Japanese subjects after oral therapeutic doses.

Adolescent↗
PubMed1998

Intrahepatic peripheral cholangiocarcinoma: mode of spread and choice of surgical treatment.

BACKGROUND: Classification of macroscopic appearance and standard operative procedures for intrahepatic cholangiocarcinoma (ICC) are still controversial. METHODS: The mode of spread of 12 resected ICCs was examined by light microscopy, and the appropriate operative procedures for the various tumours were considered. RESULTS: Macroscopically, nine tumours were classified as mass-forming type and three as periductal infiltrating type. All patients were treated by major hepatectomy; resection of the extrahepatic bile duct was included in two cases of the periductal infiltrating type. Microscopically, invasion into the portal vein, intrahepatic metastasis and perineural or lymphatic vessel invasion occurred in none, one and all of three tumours of the periductal infiltrating type and in eight, six and six of nine tumours of the mass-forming type. CONCLUSION: ICC of the periductal infiltrating type has a tendency to spread along Glisson's sheath via lymphatic vessels. By contrast, ICC of the mass-forming type tends to invade the liver via the portal vein system; such tumours begin to invade Glisson's sheath through the lymphatic vessels when the tumour has increased in size. Therefore, major hepatectomy with combined resection of the extrahepatic bile duct should be performed for all ICCs of the periductal infiltrating type and for those of the mass-forming type with invasion of Glisson's sheath.

Adult↗
PubMed1998

Genetic polymorphisms and risk of coronary artery disease.

The fact that certain ethnic groups and specific populations residing in certain geographic areas carry an increased risk for thrombosis and that thrombosis occurs in young patients without established risk factors indicates the presence of new, previously unrecognized inherited conditions predisposing to thrombosis. We are now aware that interindividual variations within the loci coding for proteins relevant to lipid and vascular metabolisms as well as blood coagulation are universally found. Platelets play central roles in cerebrovascular diseases and acute coronary syndromes, as demonstrated by histopathological findings and clinical observations showing the efficacy of antiplatelet therapies for these disorders. In this article, we show our recent findings on the association between coronary artery disease (CAD) and polymorphisms in platelet membrane glycoproteins. The glycoprotein (GP) Ib/IX complex is a receptor for von Willebrand factor, which mediates shear stress-dependent platelet activation. It has recently been implicated in the pathogenesis of acute coronary syndromes. We have determined genotypes of the "size-polymorphism" of GPIb alpha--i.e., the variable number (1-4) of a 13 amino acid sequence (399-411)--in angiographically proven Japanese CAD patients with myocardial infarction or angina pectoris as well as in individuals from the general population with no history of angina or other heart diseases and normal resting electrocardiograms (ECG). We have found that the genotypes having at least one 4-repeat allele (4R) are more frequently found in patients than in controls. Logistic regression analyses for the adjustment of age, sex, and other acquired coronary risk factors provided an odds ratio of 7.94 (p=0.0043) for those with 4R vs. those without 4R, suggesting that the presence of 4R is an independent risk factor for CAD. The molecular mechanisms underlying this association are currently under investigation. Relationships between arterial thrombosis and polymorphisms in other platelet GPs (collagen receptor and fibrinogen receptor), blood coagulation factors, fibrinolytic factors, vasoactive substances, and factors relevant for lipid metabolisms are also discussed.

Adult↗
PubMed1998

Detection of a local interaction of hen lysozyme under highly denaturing conditions using chemically 13C-enriched methionine resonance.

Using hen lysozyme in which the epsilon-carbons of two methionine residues are enriched with 13C nuclei, we found that there is a subtle difference in the chemical shift of the epsilon-carbon resonances between Met 12 and Met 105 in thermally denatured lysozyme without any reduction of disulfide bonds at pD 3.8, and also in reduced S-alkylated lysozyme at pD 3.8 and 35 degrees C. The difference in the chemical shift was abolished on digestion with TPCK-trypsin and the chemical shifts of both resonances converged to that of Met 12, whose chemical shift is identical to that in the randomly coiled state. Therefore, it is suggested that the chemical shift in the epsilon-carbon resonance of Met 105 is different from that in the randomly coiled state due to an interaction involving Met 105. In order to locate the interaction involving Met 105, fragmentation of the reduced S-alkylated lysozyme into the peptides was carried out by means of chemical cleavage or specific endoprotease digestion. As a result, the local interaction of Met 105 or the residues around Met 105 with eleven residues at the C-terminus of lysozyme is suggested to occur.

Alkylation↗
PubMed1998

Calorimetric study of mutant human lysozymes with partially introduced Ca2+ binding sites and its efficient refolding system from inclusion bodies.

During the process of evolution, ancestral lysozymes evolved into calcium-binding lysozymes by acquiring three critical aspartate residues at positions 86, 91 and 92. To investigate the process of the acquisition of calcium-binding ability, two of the aspartates were partially introduced into human lysozyme at positions 86, 91 and 92. These mutants (HLQ86D, HLA92D and HLQ86D/D91Q/A92D), having two critical aspartates in calcium-binding sites, were expressed in Escherichia coli as non-active inclusion bodies. For the preparation of lysozyme samples, a refolding system using thioredoxin was established. This system allowed for effective refolding of wild-type and mutant lysozymes, and 100% of activity was recovered within 4 days. The calcium ion dependence of the melting temperature (Tm) of wild-type and mutant lysozymes was investigated by differential scanning calorimetry at pH 4.5. The Tm values of wild-type, HLQ86D and HLA92D mutants were not dependent on calcium ion concentration. However, the Tm of HLQ86D/D91Q/A92D was 4 degrees higher in the presence of 50 mM CaCl2 than in its absence, and the calcium-binding constant of this mutant was estimated to be 2.25(+/-0.25)x10(2) M(-1) at pH 4.5. Moreover, the calcium-binding ability of this mutant was confirmed by the result using Sephadex G-25 gel chromatography. These results indicate that it is indispensable to have at least two aspartates at positions 86 and 92 for acquisition of calcium-binding ability. The process of the acquisition of calcium-binding site during evolution of calcium-binding lysozyme is discussed.

Aspartic Acid↗
PubMed1998

Drill-hole guide for internal fixation of fractures of the mandibular condyle.

We have developed a drill-hole guide valuable in accurately positioning the fracture of the mandibular ramus. It operates by introducing a Kirschner wire through the fracture stump from the mandibular angle to the condyle. A 2.0- to 2.4-mm-diameter Kirschner wire is drilled into the ramus from below and proceeds up to the condylar fragment through the stump of the fracture. With this guide, 15 patients with 23 subcondylar fractures underwent open reduction with Kirschner wire fixation. In each case, wire, by means of a pinning technique, was inserted accurately from the mandibular angle to the repositioned condyle.

Adult↗
PubMed1998

The analysis of mRNA expression of cytokines from skin lesions in Churg-Strauss syndrome.

We report our recent clinical experience with a patient suffering from Churg-Strauss syndrome and the results of our investigation into the mRNA expression of cytokines in the patient's lesions as well as in the frozen sections from a previous patient. In both cases, blood IgG was at a high level. Cytokine mRNA expression differed according to the degree of cellular infiltration. In the presence of marked infiltration, counteracting Th1 and Th2 cytokines were simultaneously detected; the former included IL-12 and IFN-gamma, and the latter, IL-6 and IL-10. The concurrence of both types of cytokine could be attributed to several factors. For example, IL-6 is involved through some mechanism in the formation of immune complexes by IgG, and IL-12 and IFN-gamma appeared to participate in the development of granuloma. These suppositions support the suggested immunological etiology of the disease. It is also inferred that the dominance of one of the two types of cytokines depends on the clinical phase of the disease.

Biomarkers↗