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Hiroyuki Matsuda

Publications and source records attributed to Hiroyuki Matsuda.

33 records · Page 2Linked to original sources
PubMed2003

Experimental evaluation of validity of simplified Monte Carlo method in proton dose calculations.

It is important for proton therapy to calculate dose distributions accurately in treatment planning. Dose calculations in the body for treatment planning are converted to dose distributions in water, and the converted calculations are then generally evaluated by the dose measurements in water. In this paper, proton dose calculations were realized for a phantom simulating a clinical heterogeneity. Both dose calculations in the phantom calculated by two dose calculation methods, the range-modulated pencil beam algorithm (RMPBA) and the simplified Monte Carlo (SMC) method, and dose calculations converted to dose distributions in water by the same two methods were verified experimentally through comparison with measured distributions, respectively. For the RMPBA, though the converted calculations in water agreed moderately well with the measured ones, the calculated results in the actual phantom produced large errors. This meant that dose calculations in treatment planning should be evaluated by the dose measurements not in water but in the body with heterogeneity. On the other hand, the results calculated in the phantom, even by the less rigorous SMC method, reproduced the experimental ones well. This finding showed that actual dose distributions in the body should be predicted by the SMC method.

Algorithms↗
PubMed2003

Assessing the impact of the Japanese 2005 World Exposition Project on vascular plants' risk of extinction.

The Red Data Book of Japanese Vascular Plants is based on their risk of extinction. In order to construct the list, 2000 taxa were evaluated using population data and rates of decline for approximately 4400 grids, each of approximately 100 km(2). This database can be used to estimate the impact of human activity on a threatened plant's risk of extinction. In order to evaluate extinction risks and apply the evaluation to conservation actions, the discount mean time to extinction is defined as a measure of extinction risk, where the present value of a species' persistence in the future decreases exponentially. The rate of decrease has to be much less than the rate of economic discounting, in order to realize intergenerational sustainability. Increases of the inverse, and logarithm, of the discount mean time to extinction are considered measures of the extinction risk. We applied these measures to an environmental impact assessment for the Japanese World Exposition that is to be held in 2005. Development will have a greater impact on threatened Salvia species than it will on star magnolia, Magnolia tomentosa, which has been conserved by changing the site plan.

Conservation of Natural Resources↗
PubMed2003

Osmosensitive properties of rapid and slow delayed rectifier K+ currents in guinea-pig heart cells.

1. Changes in cell volume affect a variety of sarcolemmal transport processes in the heart. To study whether osmotically induced cell volume shrinkage has functional consequences for K+ channel activity, guinea-pig cardiac preparations were superfused with hyperosmotic Tyrode's solution (1.2-2-fold normal osmolality). Membrane currents and cell surface dimensions were measured from whole-cell patch-clamped ventricular myocytes and membrane potentials were recorded from isolated ventricular muscles and non-patched myocytes. 2. Hyperosmotic treatment of myocytes quickly (< 3 min to steady state) shrank cell volume (approximately 20% reduction in 1.5-fold hyperosmotic solution) and depressed the delayed rectifier K+ current (IK). Analysis using different activation protocols and a selective inhibitor (5 micro mol/L E4031) indicated that the IK inhibition was due to osmolality and cell volume-dependent changes in the two subtypes of the classical cardiac IK (rapidly activating IKr and slowly activating IKs); 1.5-fold hyperosmotic treatment depressed the amplitudes of IKr and IKs by approximately 30 and 50%, respectively. 3. Superfusion of muscles and myocytes with 1.5-fold hyperosmotic solution lengthened the action potentials by 14-17%. Hyperosmotic treatment also caused 6-7 mV hyperpolarization that is most likely due to a concentrating of intracellular K+. 4. The inhibition of IK helps explain the lengthening of action potentials observed in osmotically stressed heart cells. These results, together with the reported IK stimulation by hyposmotic cell swelling, provide further support for cell volume-sensitive properties of cardiac electrical activity.

Action Potentials↗
PubMed2003

Effects of antisense peptide nucleic acid to platelet-derived growth factor A-chain on growth of vascular smooth muscle cells.

To investigate antisense peptide nucleic acid (PNA) as a gene therapy for the arterial proliferative diseases, the authors designed and examined the effects of an antisense PNA targeting platelet-derived growth factor (PDGF) A-chain on expression of PDGF A-chain and growth of vascular smooth muscle cells (VSMCs) from spontaneously hypertensive rats. A 15-mer antisense PNA complementary to the initiation codon of rat and human PDGF A-chain mRNA was synthesized and purified by high-performance liquid chromatography. Gel-shift assay and biomolecular interaction analysis (BIAcore) revealed that the antisense PNA bound weakly to the target RNA, whereas it bound strongly to the target DNA. Fluorescein-isothiocyanate-labeled antisense PNA to PDGF A-chain was taken up slowly and maintained in VSMCs for a prolonged period of time. Antisense PNA inhibited expression of PDGF A-chain mRNA and protein as well as DNA synthesis in VSMCs in a dose-independent manner. Inhibition of DNA synthesis by the antisense PNA was greater than that by the antisense DNA at a low concentration (0.5 micromol/L). These results suggest that antisense PNA to PDGF A-chain will be used as a gene therapy for vascular proliferative diseases such as hypertensive vascular diseases, restenosis of coronary arteries after angioplasty, and atherosclerosis.

Animals↗
PubMed2002

Alteration of balance between myeloid dendritic cells and plasmacytoid dendritic cells in peripheral blood of patients with asthma.

Asthma, a well-known helper T cell Type 2 (Th2)-mediated disease, has a polarized immune response toward a Th2 phenotype. However, the factors causing the Th2 polarization remain to be fully determined in this disease. Dendritic cells (DCs) are the most potent antigen-presenting cells that play a central role in initiating the primary immune response. In human blood, two functional distinct subsets of DCs, myeloid DCs and plasmacytoid DCs, have been identified. Myeloid DCs (mDCs) and plasmacytoid DCs (pDCs) are also called Type 1 DCs (DC1) and Type 2 DCs (DC2), respectively, because mDCs and pDCs were shown to preferentially differentiate naive T cells into Th1 and Th2 cells, respectively. In asthma, it can thus be speculated that an altered balance of mDCs to pDCs toward pDCs may contribute to the Th2 polarization. To clarify this, we examined the numbers of mDCs and pDCs in the peripheral blood of 44 patients with asthma and 38 normal subjects, using multicolor flow cytometry. We found that the patients with asthma had a significantly higher number of pDCs, resulting in a significant decrease in the ratio of mDCs to pDCs compared with normal subjects. These data indicate that the patients with asthma had a polarization of the mDC:pDC balance toward pDCs, which may be involved in producing the Th2-dominant immune phenotype in asthma.

Adult↗
PubMed2002

Sarcolemmal hydraulic conductivity of guinea-pig and rat ventricular myocytes.

OBJECTIVE: Osmotic gradient-induced volume change and sarcolemmal water permeability of cardiac myocytes were evaluated to characterize the mechanism of water flux across the plasma membranes. METHODS: Cell surface dimensions were measured from isolated guinea-pig and rat ventricular myocytes by digital videomicroscopy, and membrane hydraulic conductivity (L(p)) was obtained by analyzing the time course of cell swelling and shrinkage in response to osmotic gradients. RESULTS: Superfusion with anisosmotic solution (0.5-4 times normal osmolality) caused a rapid (<3 min to steady states) and reversible myocyte swelling or shrinkage. L(p) was approximately 1.9 x 10(-10) l N(-1) s(-1) for guinea-pig myocytes and approximately 1.7 x 10(-10) l N(-1) s(-1) for rat myocytes at 35 degrees C. Arrhenius activation energy (E(a)), a measure of the energy barrier to water flux, was approximately 3.7 (guinea-pig) and approximately 3.6 kcal mol(-1) (rat) between 11 and 35 degrees C; these values are equivalent to E(a) of self-diffusion of water in bulk solution ( approximately 4 kcal mol(-1)). Treatment with 0.1 mM Hg(2+), a sulfhydryl-oxidizing reagent that blocks membrane water channels, reduced L(p) by approximately 80%, and the sulfhydryl-reducing reagent dithiothreitol (10 mM) antagonized the inhibitory action of Hg(2+). Inhibition of the volume-sensitive cation (30 microM Gd3+) and anion (1 mM 4,4'-diisothiocyanostilbene-2,2'-disulfonate) channels and Na+-K+ pump (10 microM ouabain) modified the size of osmotic swelling but had little effect on L(p). CONCLUSIONS: Although the observed L(p) is relatively small in magnitude, the low E(a) and the sulfhydryl reagent-induced modification of L(p) are characteristic of channel-mediated water transport. These data suggest that water flux across the sarcolemma of guinea-pig and rat heart cells occurs through parallel pathways, i.e., the majority passing through water channels and the remainder penetrating the lipid bilayers.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed2002

[Recurrence of inflammatory pseudotumor of the lung with endobronchial lesion after resection].

A 74-year-old man was admitted to our hospital because of an abnormal shadow in the left middle lung field on chest radiography. Since a transbronchial biopsy was not diagnostic, a left lower lobectomy was performed. Histopathologically, the patient was diagnosed as having an inflammatory pseudotumor of the lung. Four months after the surgery, the patient was readmitted with hemosputum. Bronchoscopically, an endobronchial lesion was found in the left main bronchus. Transbronchial biopsy of the lesion showed proliferation of inflammatory cells compatible with inflammatory pseudotumor. Therefore, a recurrent inflammatory pseudotumor was diagnosed. Treatment with corticosteroid resulted in the disappearance of the endobronchial lesion and the erythrocyte sedimentation rate (ESR) returned to normal. The patient showed a prolonged elevation of ESR even after the resection, suggesting that the ESR may be a good indicator of the activity of this disease.

Aged↗
PubMed2002

[Eosinophilic pleural effusion associated with dantrolene administration].

A 42-year old man was admitted to our hospital for evaluation of pleural effusion in the right hemithorax. He had been treated for spastic paraplegia with dantrolene sodium for 28 months. The pleural fluid consisted of sterile exudates with a very high eosinophil count, and peripheral blood eosinophilia was noted. Thoracoscopy revealed no apparent abnormalities and a pleural biopsy specimen showed only non-specific inflammation. Two weeks after discontinuing dantrolene therapy, the pleural effusion disappeared. The toxicity of dantrolene in patients with pleural effusion must be taken into consideration when long-term dantrolene therapy is given.

Adult↗
PubMed2002

[Secondary pulmonary alveolar proteinosis associated with myelodysplastic syndrome].

A 51-year-old man with myelodysplastic syndrome (MDS) was admitted to our hospital because of dyspnea on exertion in December 1999. Chest radiography showed ground-glass shadows in the middle and lower fields of both lungs, and chest computed tomography revealed a typical "crazy paving appearance". The bronchoalveolar lavage fluid was milky in appearance, and so secondary pulmonary alveolar proteinosis associated with MDS was diagnosed. Because there was no need to treat his MDS, we twice performed whole-lung lavage under general anesthesia in January and February 2000. The treatments were effective, and his abnormal chest radiography findings, laboratory data and pulmonary function were normalized. This was a rare case of secondary pulmonary alveolar proteinosis associated with MDS successfully treated with whole-lung lavage.

Bronchoalveolar Lavage↗
PubMed2002

[Clinical analysis of chronic hypersensitivity pneumonitis].

Chronic hypersensitivity pneumonitis (CHP) has a poor prognosis because of the difficulties in its diagnosis and treatment. Recently, we have encountered six cases of CHP (4 patients with the home-related type, a patient with bird fancier's lung, and one with flour-induced CHP), and we examined the clinical characteristics of these cases. Environmental provocation testing has been considered useful for diagnosing HP, but all patients gave negative results in short-term environmental exposure tests performed routinely for the diagnosis of HP. However, 5 patients had a positive response in long-term environmental exposure tests. Two patients died of respiratory failure after ten years' observation despite improvement of the causative environment, and were given steroid therapy. Radiographically and pathologically, the process of progressive and irreversible lesions were recognized in our series of CHP patients. The diagnosis of CHP should be carried out on the basis of the comprehensive findings including the detailed history, clinical course, radiography, and histology.

Alveolitis, Extrinsic Allergic↗
PubMed2002

[An autopsy case of cor pulmonale due to a pulmonary tumor embolism as the first clinical manifestation of occult gastric cancer].

A 47-year-old man was admitted to our hospital because of progressive dyspnea and cough. Physical examination and chest radiographs showed the signs of cor pulmonale. A lung scan using perfused radionuclide revealed multiple peripheral perfusion defects and catheterization of the right heart showed severe pulmonary hypertension. A diagnosis of severe pulmonary embolism was made. Despite intensive care with anti-coagulation therapy, the patient died on the third-hospital day. Autopsy disclosed gastric cancer in the pylorus with metastases to the regional lymph nodes. There were no macroscopic pulmonary artery emboli or parenchymal lesions, but more than 60% of the small arteries and arterioles were occluded by casts of tumor cells. Cor pulmonale due to a pulmonary tumor embolism is a rare complication of cancer. This case is particularly unusual because the embolus-caused cor pulmonale was the initial manifestation of clinically occult, but pathologically advanced, gastric cancer.

Adenocarcinoma↗
PubMedDate not supplied

Self-expandable metallic stents as palliative treatment for malignant colorectal obstruction.

BACKGROUND: In recent years, stent placement for malignant colorectal obstruction has become an accepted alternative to surgery. The purpose of this study was to evaluate the usefulness of self-expandable metallic stents (SEMS) as palliative management for patients with unresectable malignant colorectal obstruction. METHODS: Twelve patients with unresectable malignant colorectal obstruction were treated with SEMS as palliative therapy. The sites of obstruction were located in the rectum (n = 9), the descending colon (n = 1), and the transverse colon (n = 2). All procedures were performed with combined endoscopic and fluoroscopic guidance. We analyzed the technical and clinical success rates of stent placement and the complications associated with the procedure. RESULTS: The stents were successfully implanted and bowel obstruction was relieved in all cases; the technical and clinical success rates were 100%. Two complications occurred, including stent migration. There was no case requiring reintervention. All patients died of initial disease or another coexisting disease between 9 and 534 days (mean 133 +/- 148 days) after stent placement. None of the patients with stent in position at death had clinical or radiologic signs of bowel obstruction. CONCLUSIONS: SEMS placement in patients with malignant colorectal obstruction is technically feasible and safe, making it useful as a palliative treatment.

Adult↗