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Biomedical subjects

Y Hama

Publications and source records attributed to Y Hama.

At least 19 recordsLinked to original sources
PubMed2006

Examining the necessity to include event-by-event fluctuations in experimental evaluations of elliptical flow.

Elliptic flow at BNL RHIC is computed event by event with NeXSPheRIO. We show that when symmetry of the particle distribution in relation to the reaction plane is assumed, as usually done in the experimental extraction of elliptic flow, there is a disagreement between the true and reconstructed elliptic flows (15%-30% for eta=0, 30% for p perpendicular=0.5 GeV). We suggest a possible way to take into account the asymmetry and get good agreement between these elliptic flows.

Journal Article↗
PubMed2005

Liver abscess formation after hepatic chemoembolization for metastatic pancreatic neuroendocrine tumor.

Hepatic chemoembolization is an effective treatment of unresectable hypervascular hepatic tumors, but history of bilioenteric anastomosis is a major risk factor for liver abscess due to the retrograde enteric bacterial contamination. We report a case of culture-negative liver abscess developed after hepatic chemoembolization for a metastatic pancreatic endocrine tumor, and discuss the pathogenesis of liver abscess formation. We also present a potential pitfall for the prophylactic antibiotic therapy in a patient with a history of bilioenteric anastomosis. This is the first report of a culture-negative liver abscess caused by hepatic chemoembolization for a metastatic pancreatic endocrine tumor.

Journal Article↗
PubMed2004

Fluctuations of the initial conditions and the continuous emission in the hydrodynamical description of two-pion interferometry.

Within the hydrodynamical approach, we study the Bose-Einstein correlation of identical pions by taking into account both event-by-event fluctuating initial conditions and continuous pion emission during the whole development of the hot and dense matter formed in high-energy collisions. Important deviations occur, compared to the usual hydrocalculations with smooth initial conditions and a sudden freeze-out on a well defined hypersurface. Comparison with data at the BNL Relativistic Heavy Ion Collider (RHIC) shows that, despite the rather rough approximation we used here, this description can account for the m(T) dependence of R(L) and R(s), and produces a significant improvement for R(o) with respect to the usual version.

Journal Article↗
PubMed2002

Freeze-out problem in hydrokinetic approach to A + A collisions.

A new method for evaluating spectra and correlations in the hydrodynamic approach is proposed. It is based on an analysis of the Boltzmann equations (BE) in terms of probabilities for constituent particles to escape from the interacting system. The conditions of applicability of the Cooper-Frye freeze-out prescription are considered within the method. The results are illustrated with a nonrelativistic exact solution of BE for an expanding spherical fireball as well as with approximate solutions for ellipsoidally expanding ones.

Journal Article↗
PubMed2002

Severe complications after hypofractionated high dose rate intracavitary brachytherapy following external beam irradiation for oesophageal carcinoma.

The purpose of this study was to evaluate severe complications that developed after high dose rate (HDR) intracavitary brachytherapy for oesophageal carcinoma. Six consecutive patients with oesophageal carcinoma were treated by external beam irradiation (60 Gy in 30 fractions over 6 weeks) followed by hypofractionated intracavitary HDR brachytherapy (10 Gy in 2 fractions). Two of the six patients were alive and well for more than 2-3 years following therapy, but three of the six patients developed treatment-related oesophageal fistulae and died. HDR intracavitary brachytherapy following external beam irradiation is an effective method for radical treatment of oesophageal carcinoma. However, hypofractionated HDR brachytherapy should be used with care.

Aged↗
PubMed2002

Picture archiving and communication system: prospective study.

OBJECTIVES: To evaluate the use of a picture archiving and communication system and user satisfaction in order to further improve its quality. DESIGN: Prospective study. SETTING: Medical college hospital, Japan. MATERIALS AND METHODS: An automated computerised method was used to collect the data from March 1999 to February 2000. MAIN OUTCOME MEASURES: Each workstation automatically recorded data on the rank of the user, purpose of use, use of postprocessing tools, and user satisfaction. RESULTS: The number of resident users in the radiology reading room increased and those outside the reading room decreased, but the number of staff users changed little. The purpose of use and the use of postprocessing functions in the reading room were not significantly different from those outside it (P=0.179 and P=0.269, respectively). The average numbers of images accessed to per workstation monthly in the reading room, the general practice ward, and the gastroenterology ward were 1081, 970 and 741, respectively. Only 12 images in the orthopaedic surgery out-patient clinic and 70 images in the orthopaedic surgery ward, however, were accessed per month. The percentages of satisfied users decreased both inside and outside the reading room. The degree of satisfaction of users in the reading room was significantly different from that outside it (P=0.004). The most common reason for dissatisfaction was the length of time necessary to retrieve images. CONCLUSIONS: It is necessary to shorten response times of picture archiving and communication system workstations. Repeated data collection and evaluation, however, are also important.

Hospital Departments↗
PubMed2001

Computed tomography-guided frameless stereotactic radiotherapy for stage I non-small cell lung cancer: a 5-year experience.

PURPOSE: Stereotactic radiotherapy (SRT) is highly effective for brain metastases from non-small-cell lung cancers (NSCLCs). As such, primary lesions of NSCLC may also be treated effectively by similar focal high-dose SRT. METHODS AND MATERIALS: Between October 1994 and June 1999, 50 patients with pathologically proven T1-2N0 M0 NSCLC were treated by CT-guided frameless SRT. Of these, 21 patients were medically inoperable and the remainder were medically operable but refused surgery. In most patients, SRT was 50-60 Gy in 5-10 fractions for 1-2 weeks. Eighteen patients also received conventional radiotherapy of 40-60 Gy in 20-33 fractions before SRT. RESULTS: With a median follow-up period of 36 months (range 22-66), 30 patients were alive and disease free, 3 were alive with disease, 6 had died of disease, and 11 had died intercurrently. Local progression was not observed on follow-up CT scans in 47 (94%) of 50 patients. The 3-year overall survival rate was 66% in all 50 patients and 86% in the 29 medically operable patients. The 3-year cause-specific survival rate of all 50 patients was 88%. No definite adverse effects related to SRT were noted, except for 2 patients with a minor bone fracture and 6 patients with temporary pleural pain. CONCLUSIONS: SRT is a very safe and effective treatment for Stage I NSCLC. Additional studies involving a larger patient population and longer follow-up periods are warranted to assess this new treatment for early-stage lung cancer.

Adenocarcinoma↗
PubMed2001

KDN-containing glycoprotein from loach skin mucus.

It has been widely recognized that the mucus coat of fish plays a variety of important physical, chemical, and physiological functions. One of the major constituents of the mucus coat is mucus glycoprotein. We found that sialic acids in the skin mucus of the loach, Misgurnus anguillicaudatus, consisted predominantly of KDN. Subsequently, we isolated KDN-containing glycoprotein from loach skin mucus and characterized its chemical nature and structure. Loach mucus glycoprotein was purified from the Tris-HCl buffer extract of loach skin mucus by DEAE-cellulose chromatography, Nuclease P1 treatment, and Sepharose CL-6B gel filtration. The purified mucus glycoprotein was found to contain 38.5 KDN, 0.5% NeuAc, 25.0% GalNAc, 3.5% Gal, 0.5% GlcNAc and 28% amino acids. Exhaustive Actinase digestion of the glycoprotein yielded a glycopeptide with a higher sugar content and higher Thr and Ser contents. The molecular size of this glycopeptide was approximately 1/12 of the intact glycoprotein. These results suggest that approximately 11 highly glycosylated polypeptide units are linked in tandem through nonglycosylated peptides to form the glycoporotein molecule. The oligosaccharide alditols liberated from the loach mucus glycoprotein by alkaline borohydride treatment were separated by Sephadex G-25 gel filtration and HPLC. The purified sugar chains were analyzed b --> 6GalNAc-ol, KDNalpha2 --> 3(GalNAcbeta1 --> 14)GalNAc-ol, KDNalpha2 --> 6(GalNAcalpha1 --> 3)GalNAc-ol, KDNalpha2 --> 6(Gal3alpha1--> 3)GalNAc-ol, and NeuAcalpha2 --> 6Gal NAc-ol. It is estimated that one loach mucus glycoprotein molecule contains more than 500 KDN-containing sugar chains that are linked to Thr and Ser residues of the protein core through GalNAc.

Amino Acids↗
PubMed2001

Interaction of GM2 activator protein with glycosphingolipids.

GM2 activator protein is a protein cofactor that stimulates the hydrolysis of the GalNAc and the NeuAc in GM2 by beta-hexosaminidase A and sialidase, respectively. To understand the mechanism of action of GM2 activator, the interaction of this protein with GM2 and/or beta-hexosaminidase A has been the subject of interest since the purified GM2 activator became available. Numerous techniques including ultracentrifugation, isoelectric a focusing, polyacrylamide gel electrophoresis, gel filtration, thin layer chromatogram overlay, and fluorescence dequenching assay have been used to investigate the binding and the affinity of GM2 activator to various glycosphingolipids. It has been generally accepted that GM2 activator must have a very weak binding with the enzyme, because they can be easily separated from each other by gel filtration. Therefore, the interaction of GM2 and GM2 activator has been the focus for most of he study. Although preferential association of GM2 activator with GM2 was detected by some methods, GM2 activator was found also to bind other glycosphingolipids. Isolation of the specific complex that consists of only GM2 activator and GM2 from incubation mixture containing the activator protein and mixed glycosphingolipids has not been successfully carried out. Ultracentrifugation and gel-filtration are the mildest methods for the isolation of the complexes. However, these methods do not separate the complexes formed by specific interaction from that formed by non-specific association. In fluorescence dequenching assay, the attempt to isolate the complex of R18 lipid probe with GM2 activator was also not successful. Since GM2 activator and glycosphingolipids contain hydrophobic domains in their molecules, the non-specific hydrophobic interactions between the two components can greatly interfere with the isolation of true functional complexes. Among the reported methods, thin layer chromatography overlay and the assay based on the inhibition of fluorescence dequenching by various glycosphingolipids are more informative than the others on the binding between GM2 activator and the carbohydrate head groups of glycosphingolipids.

Binding Sites↗
PubMed2001

Gastrointestinal stromal tumor of the rectum.

Gastrointestinal stromal tumors (GISTs) are characterized by remarkable variability in their differentiation potential, but most of these lesions do not display convincing smooth muscle or neuronal differentiation. The GISTs arising from the rectum or anal canal are extremely uncommon. We present a case of immunohistochemically proven GIST of the rectum, which was characterized by homogenous isointensity mass without necrosis or hemorrhage on T2-weighted image and by enhancement on gadolinium-enhanced study.

Carcinoma↗
PubMed2001

Sex ratio in the offspring of male radiologists.

RATIONALE AND OBJECTIVES: The purpose of this study was to determine if male radiologists predominantly father daughters and, if so, to investigate the association between this skewed sex ratio of offspring and radiation exposure. MATERIALS AND METHODS: Questionnaires completed by 586 male radiologists in Japan provided data regarding the radiologist's age, length of employment in radiology, if he had ever received radiation doses higher than that recommended by the International Commission on Radiological Protection, the sex of each child fathered, and the birth date of each child. RESULTS: As a group, male radiologists tended to father a lower proportion of boys (48.47%) compared with the control group (51.46%), and the relative risk was 1.13 (95% confidence interval [CI]: 1.00, 1.27). Offspring of highly irradiated radiologists, however, had a reduced proportion of males (34.48%), with a significantly (P = .002) increased relative risk of 2.01 (95% CI: 1.29, 3.13). CONCLUSION: X-ray exposure may explain the reduced percentage of sons in the offspring of male radiologists.

Adult↗
PubMed2001

The rate of tumour growth does not distinguish between malignant and benign thyroid nodules.

OBJECTIVE: To clarify whether or not the rate of tumour growth is a useful measure for distinguishing papillary thyroid cancer from benign nodules. DESIGN: Retrospective study. SETTING: Teaching hospital, Japan. SUBJECTS: Fourteen patients with 27 nodules (<20 mm) followed up for 20 months or more. INTERVENTIONS: High resolution ultrasonography (US). MAIN OUTCOME MEASURE: Growth rate. RESULTS: There were 15 papillary thyroid cancers and 12 benign nodules. The median tumour diameters at the first and the last US examination were 9.0 mm (range 6-19) and 9.0 mm (range 5-21) in papillary thyroid cancers followed up for 37 months (range 21-85), and 11.5 mm (range 4-19) and 11.5 mm (range 5-23) in benign nodules followed up for 38 months (range 20-84), respectively. CONCLUSION: The rate of growth of thyroid nodules as documented by ultrasound did not prove to be useful in distinguishing between malignancy and benign disease of small thyroid nodules (<20 mm).

Adult↗
PubMed2001

Carcinoma of the uterine cervix: twice- versus once-weekly high-dose-rate brachytherapy.

PURPOSE: To compare the effectiveness and safety of once- versus twice-weekly high-dose-rate (HDR) brachytherapy for cervical cancer. MATERIALS AND METHODS: From 1980 to 1997, 124 consecutive previously untreated patients with cervical cancer were treated with external-beam irradiation (50 Gy) and HDR brachytherapy. Clinical stages were I, 4 (3%) patients; II, 51 (41%); III, 64 (52%); and IV, 5 (4%). From 1980 to 1992, 74 patients (group A) were treated with HDR brachytherapy once weekly (about three fractions of 7 Gy each to point A [2 cm superior and 2 cm lateral to the inferior end of the intrauterine radioactive source]), while from 1992 to 1997, 50 patients (group B) were treated twice weekly (about six fractions of 4.5 Gy each to point A). RESULTS: Overall survival rate at 5 years was 65.2% in group A and 65.3% in group B (P=.96). Local recurrence-free survival rate at 5 years was 69% (51 of 74 patients) in group A and 90% (45 of 50 patients) in group B (P<.001). The rate of grade 2 (moderate) and grade 3 (severe) complications was significantly lower in group B (6% vs. 32% in group A, P<.001). At multivariate analysis, the variables significantly associated with increased local-regional recurrence rates were having stage III-IV lesions (P=.04) and with fewer than six sessions of HDR brachytherapy (P=.02). CONCLUSION: The twice-weekly HDR regimen may improve the local control rate with fewer complications.

Adenocarcinoma↗