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Biomedical subjects

Hiroyuki Hamada

Publications and source records attributed to Hiroyuki Hamada.

12 recordsLinked to original sources
PubMed2006

Cooperative effect of two amino acid mutations in the coat protein of Pepper mild mottle virus overcomes L3-mediated resistance in Capsicum plants.

We found that an L3 resistance-breaking field isolate of Pepper mild mottle virus (PMMoV), designated PMMoV-Is, had two amino acid changes in its coat protein (CP), namely leucine to phenylalanine at position 13 (L13F) and glycine to valine at position 66 (G66V), as compared with PMMoV-J, which induces a resistance response in L3-harboring Capsicum plants. The mutations were located to a CP domain corresponding to the outer surface of PMMoV particles in computational molecular modeling. Analyses of PMMoV CP mutants containing either or both of these amino acid changes revealed that both changes were required to efficiently overcome L3-mediated resistance with systemic necrosis induction. Although CP mutants containing either L13F or G66V could not efficiently overcome L3-mediated resistance, these amino acid changes had different effects on the elicitor activity of PMMoV CP. L13F caused a slight reduction in the elicitor activity, resulting in virus restriction to necrotic local lesions that were apparently larger than those induced by wild-type PMMoV, while G66V rendered wild-type PMMoV the ability to overcome L3-mediated resistance, albeit with a lower efficiency than PMMoV with both changes. These results suggest that a cooperative effect of the L13F and G66V mutations on the elicitor activity of CP is responsible for overcoming the L3-mediated resistance.

Amino Acid Sequence↗
PubMed2006

Application of bioinformatics for DNA microarray data to bioscience, bioengineering and medical fields.

In the 1990s, DNA microarray or DNA chip as a novel biological experimental technology was developed, which enables the comprehensive measurement of the expression levels of hundreds of genes, simultaneously. Using this technique, a comprehensive understanding of the cell can be achieved. However, because even simple life forms, such as microorganisms, have more than a thousand kinds of genes, the data from a DNA chip cannot be analyzed without statistical and informational technology. Bioinformatics is the interdisciplinary research field integrating molecular biology with informatics, and it is expected to have a huge impact on the bioscientific, bioengineering and medical fields. There are many techniques in bioinformatics for the analysis of DNA microarray data; however, these are mainly divided into fold-change analysis, clustering, classification, genetic network analysis, and simulation. In this review, these techniques are briefly explained by using some examples.

Animals↗
PubMed2005

Position-specific incorporation of a highly photodurable and blue-laser excitable fluorescent amino acid into proteins for fluorescence sensing.

A new fluorescent amino acid, L-2-acridonylalanine, was incorporated into proteins at specific positions using 4-base codon/anticodon strategy. The efficiency of the incorporation was high enough to obtain enough quantities of the mutants. The acridonyl group was highly fluorescent when it was excited at the wavelengths of blue-lasers and was highly photodurable compared with conventional fluorophores often used for biological analyses. The fluorescence intensity was sensitive to small changes in the polarity of the environment. When the nonnatural amino acid was incorporated into specific positions of streptavidin, the mutant protein worked as a fluorescent sensor to biotin. Similarly, when the amino acid was incorporated into camel single-chain antibody, the mutant protein sensitively responded to the antigen molecule. The high incorporation efficiency, the high photodurability, the excitability with blue-lasers, and high sensitivity to the environment make the acridonylalanine as the promising fluorescent amino acid for sensing small molecules when incorporated into specific positions of various antibodies, receptors, and enzymes.

Acridines↗
PubMed2005

Dual effects of n-alcohols on fluid secretion from guinea pig pancreatic ducts.

Ethanol strongly augments secretin-stimulated, but not acetylcholine (ACh)-stimulated, fluid secretion from pancreatic duct cells. To understand its mechanism of action, we examined the effect of short-chain n-alcohols on fluid secretion and intracellular Ca(2+) concentration ([Ca(2+)](i)) in guinea pig pancreatic ducts. Fluid secretion was measured by monitoring the luminal volume of isolated interlobular ducts. [Ca(2+)](i) was estimated using fura-2 microfluorometry. Methanol and ethanol at 0.3-10 mM concentrations significantly augmented fluid secretion and induced a transient elevation of [Ca(2+)](i) in secretin- or dibutyryl adenosine 3',5'-cyclic monophosphate (DBcAMP)-stimulated ducts. However, they failed to affect fluid secretion and [Ca(2+)](i) in unstimulated and ACh-stimulated ducts. In contrast, propanol and butanol at 0.3-10 mM concentrations significantly reduced fluid secretion and decreased [Ca(2+)](i) in unstimulated ducts and in ducts stimulated with secretin, DBcAMP, or ACh. Both stimulatory and inhibitory effects of n-alcohols completely disappeared after their removal from the perfusate. Propanol and butanol inhibited the plateau phase, but not the initial peak, of [Ca(2+)](i) response to ACh as well as the [Ca(2+)](i) elevation induced by thapsigargin, suggesting that they inhibit Ca(2+) influx. Removal of extracellular Ca(2+) reduced [Ca(2+)](i) in duct cells and completely abolished secretin-stimulated fluid secretion. In conclusion, there is a distinct cutoff point between ethanol (C2) and propanol (C3) in their effects on fluid secretion and [Ca(2+)](i) in duct cells. Short-chain n-alcohols appear to affect pancreatic ductal fluid secretion by activating or inhibiting the plasma membrane Ca(2+) channel.

1-Propanol↗
PubMed2005

Left-sided acute appendicitis with intestinal malrotation.

Intestinal malrotation is a rare anomaly of rotation and fixation of the midgut. Left-sided appendicitis occurs in association with two types of congenital anomalies, situs inversus and intestinal malrotation. We describe a rare case of left-sided acute appendicitis with intestinal malrotation in a 14-year-old boy, in which computed tomography (CT) was useful for a preoperative diagnosis.

Adolescent↗
PubMed2004

Development of a computer-aided diagnosis system for a new modality of renal replacement therapy: an integrated approach combining both peritoneal dialysis and hemodialysis.

The authors developed a computer-aided diagnosis system that includes a simple clinical test for the chronic renal disease patient who needs an integrated approach that combines both peritoneal dialysis and hemodialysis (PD-HD therapy). In this case study, the system simulated and estimated the dialysis outcome, the ultrafiltration volume and nutritional analysis by employing a pharmacokinetic model, and assessed the peritoneal permeable enhancement that can be a grave complication with peritoneal dialysis. This system requires only a minimum amount of nursing time and may be able to predict the optimal treatment schedule for PD-HD therapy and provide therapeutic monitoring in long-term peritoneal dialysis.

Computer Simulation↗
PubMed2004

Dialysis dose and nutrition in Japanese peritoneal dialysis patients.

In the present study, we tried to determine the relationship between dialysis dose and nutrition in PD patients. We enrolled 100 Japanese outpatients, including 11 diabetic patients, who were on continuous ambulatory peritoneal dialysis [CAPD (n = 74)] and automated peritoneal dialysis [APD (n = 26)] at 49 local hospitals. In all patients, a peritoneal function test (PET) was performed using the PD NAVI software (JMS, Hiroshima, Japan). The PD NAVI software measured parameters of nutrition and dialysis dose; percentage creatinine generation rate (%CGR); percentage lean body mass normalized to body weight (%LBM); normalized protein nitrogen appearance (nPNA); total fluid removal (TFR), including urine; weekly total Kt/V; and creatinine clearance (CCr). The %CGR correlated linearly with %LBM and nPNA, parameters of the nutrition status of the patients. The %CGR also showed a significant linear correlation with Kt/V, CCr, and TFR. Patients with a %CGR below 100% (the "low group") numbered 37 (32 men, 5 women). The CCr and TFR values in that group were lower than the CCr and TFR values in the other patients (the "high group"). Conclusively, the dialysis dose did not reach the solute clearance values proposed by the National Kidney Foundation Dialysis Outcomes Quality Initiative. That finding may be the result of prescribing and monitoring dialysis therapy based on the PET The %CGR by PD NAVI may become an important index for clinical evaluation of PD dose and optimal dialysis prescription.

Biological Transport↗
PubMed2003

Ethanol induces fluid hypersecretion from guinea-pig pancreatic duct cells.

Ethanol is the leading cause of pancreatitis; however, its cellular effects are poorly understood. We examined the direct effects of ethanol in the concentration range 0.1-30 mM, i.e. relevant to usual levels of drinking, on fluid secretion from guinea-pig pancreatic duct cells. Fluid secretion was continuously measured by monitoring the luminal volume of interlobular duct segments isolated from the guinea-pig pancreas. [Ca2+]i was estimated by microfluorometry in duct cells loaded with fura-2. Ethanol at 0.3-30 mM significantly augmented fluid secretion stimulated by physiological (1 pM) or pharmacological (1 nM) concentrations of secretin. It augmented dibutyryl cAMP-stimulated fluid secretion but failed to affect spontaneous or acethylcholine-stimulated secretion. Ethanol at 1 mM shifted the secretin concentration-fluid secretion response curve upwards and raised the maximal secretory response significantly by 41%. In secretin-stimulated ducts, 1 mM ethanol induced a transient increase in [Ca2+]i that was dependent on the presence of extracellular Ca2+. Ethanol failed to augment secretin-stimulated secretion from ducts pretreated with an intracellular Ca2+ buffer (BAPTA) or a protein kinase A inhibitor (H89). In conclusion, low concentrations of ethanol directly augment pancreatic ductal fluid secretion stimulated by physiological and pharmacological concentrations of secretin, and this appears to be mediated by the activation of both the intracellular cAMP pathway and Ca2+ mobilization.

Animals↗
PubMed2003

Scintigraphic progress of the liver in a patient with Alagille syndrome (arteriohepatic dysplasia).

We encountered a 9-year-old Japanese girl with Alagille syndrome. Her scintigraphic examinations of the liver were performed at the ages of 16 months and 9 years. 99mTc-PMT, a hepatobiliary imaging agent, was distributed homogeneously in the liver at the younger age, but unevenly produced an area of focally increased uptake in the medial segment of the liver surrounded by peripheral atrophy at the older age. 99mTc-GSA, a hepatoreceptor binding agent, was highly accumulated in the area, corresponding to the focally increased uptake of 99mTc-PMT. These imaging findings suggest that the pathophysiological and morphological changes of the liver occurred in our patient during the clinical course.

Alagille Syndrome↗
PubMed2003

Induction of resistance and expression of defense-related genes in tobacco leaves infiltrated with Ralstonia solanacearum.

Ralstonia solanacearum 8107 (8107) is non-pathogenic to tobacco and elicits the hypersensitive response (HR). In Nicotiana tabacum cv. Samsun NN leaves infiltrated with 8107, acquired resistance to challenging tobacco mosaic virus (TMV) was induced 2-6 d after 8107-infiltration. hsr203J and hin1 genes were expressed only in the 8107-infiltrated area. On the other hand, the expression of PR-1a and PR-1b genes was not detected in the 8107-infiltrated area, but in areas other than that developing the HR. Expression of these PR-1 genes was regulated simultaneously and the kinetics of the expression was dependent on the distance from the infiltration area. Therefore, diffusible signal(s) might be produced in HR-causing cells and transmitted to peripheral cells resulting in expression of PR genes. In NahG10 tobacco infiltrated with 8107, the HR was induced but resistance to TMV was not. Analysis using NahG10 tobacco also showed that the salicylic acid (SA)-dependent signal regulated the expression of hsr203J and PR-1a, but not that of hin1 and PR-1b. These results suggest that resistance of tobacco to 8107 is SA-independent and involves a quite different mechanism from acquired resistance to TMV induced by 8107-infiltration which is SA-dependent.

Amino Acid Sequence↗
PubMed2003

Re-evaluation of adequate dose in Japanese peritoneal dialysis patients.

Our objective in the present study was to evaluate the dialysis dose required to maintain Japanese peritoneal dialysis (PD) patients in good condition. From 32 local hospitals, we selected 100 stable patients without diabetes mellitus who were on continuous ambulatory peritoneal dialysis (CAPD) or automated peritoneal dialysis (APD), and we performed the peritoneal function test using the newly developed PD NAVI software (JMS, Hiroshima, Japan). Weekly total Kt/V and creatinine clearance (CCr) were calculated and plotted against body weight (BW) to evaluate the PD dose. In CAPD patients (n = 58), we found an inverse linear correlation between total Kt/V and BW (r = -0.576). In the same patients, total Kt remained essentially constant (60 L/week). Those results imply that most patients were being treated with the same PD regimen (2 L, 4 times daily), and that smaller patients were generally receiving a greater PD dose relative to body size than were the larger patients. In APD patients (n = 21), total Kt/V and total CCr normalized to 1.73 m2 did not change with BW. Total Kt and non normalized CCr gradually increased with BW, although the correlation was not significant. Those findings suggest that most APD patients received prescriptions that were more closely based on body size. In conclusion, smaller patients generally receive a greater PD dose than do larger patients, and targeting a single value of Kt/V or CCr may not always be relevant for adequate dialysis.

Body Weight↗