Biomedical subjects

N Hayashi

Publications and source records attributed to N Hayashi.

At least 55 records · Page 3Linked to original sources

PubMed2002

Flow measurements via two-particle azimuthal correlations in Au + Au collisions at sqrt [s(NN)]=130 GeV.

Two-particle azimuthal correlation functions are presented for charged hadrons produced in Au+Au collisions at the Relativistic Heavy Ion Collider (sqrt [s(NN)]=130 GeV). The measurements permit determination of elliptic flow without event-by-event estimation of the reaction plane. The extracted elliptic flow values (v2) show significant sensitivity to both the collision centrality and the transverse momenta of emitted hadrons, suggesting rapid thermalization and relatively strong velocity fields. When scaled by the eccentricity of the collision zone epsilon, the scaled elliptic flow shows little or no dependence on centrality for charged hadrons with relatively low p(T). A breakdown of this epsilon scaling is observed for charged hadrons with pT >1.0 GeV/c.

Journal Article↗

PubMed2002

Measurement of Lambda and Lambda(macro) particles in Au+Au collisions at the square root of S(NN) = 130 GeV.

We present results on the measurement of Lambda and Lambda(macro) production in Au+Au collisions at square root of (S (NN) = 130 GeV with the PHENIX detector at the Relativistic Heavy Ion Collider. The transverse momentum spectra were measured for minimum bias and for the 5% most central events. The Lambda;/Lambda ratios are constant as a function of p(T) and the number of participants. The measured net Lambda density is significantly larger than predicted by models based on hadronic strings (e.g., HIJING) but in approximate agreement with models which include the gluon-junction mechanism.

Journal Article↗

PubMed2002

Net charge fluctuations in Au + Au interactions at sqrt[s(NN)]=130 GeV.

Data from Au + Au interactions at sqrt[s(NN)]=130 GeV, obtained with the PHENIX detector at the Relativistic Heavy-Ion Collider, are used to investigate local net charge fluctuations among particles produced near midrapidity. According to recent suggestions, such fluctuations may carry information from the quark-gluon plasma. This analysis shows that the fluctuations are dominated by a stochastic distribution of particles, but are also sensitive to other effects, like global charge conservation and resonance decays.

Journal Article↗

PubMed2002

Polymicrogyria without porencephaly/schizencephaly. MRI analysis of the spectrum and the prevalence of macroscopic findings in the clinical population.

Although the diagnosis of polymicrogyria currently depends largely on non-invasive imaging, no large imaging-based studies of polymicrogyria have been reported. Previous anatomic studies of polymicrogyria have been based on autopsy studies and most of the cases in those series were associated with porencephaly or schizencephaly. This retrospective MRI analysis of a group of patients with polymicrogyria, without associated porencephaly or schizencephaly, was conducted to elucidate gross morphological findings of polymicrogyria in a clinical population. Seventy-one patients with polymicrogyria diagnosed by MRI were reviewed by two radiologists. The location of polymicrogyria, the associated white matter anomalies and other associated central nervous system anomalies were assessed. The polymicrogyria was unilateral in 30 (42%) patients, bilateral in 41 (58%) patients. The lobes involved in polymicrogyria were frontal 69%, parietal 63%, temporal 38%, and occipital 7%. The cortex in the Sylvian fissures was involved in 80%. The striate cortex, cingulate gyrus, hippocampus and the gyrus rectus were often spared. Diminished volume of white matter was noted in 48%, perivascular space dilatation in 27% and large cortical veins in 51%. Polymicrogyria develops in specific topological regions, the majority being centered around the Sylvian fissures, and a minority in the inferior and medial aspects of the cerebral hemispheres or the occipital lobes. Diminished volume of the white matter and dilated perivascular spaces deeply embedded close to the dysplastic cortex and abnormal cortical venous enlargement superficial to the dysplastic cortex may be useful adjuncts in making the diagnosis.

Brain↗

PubMed2002

STM1, a gene which encodes a guanine quadruplex binding protein, interacts with CDC13 in Saccharomyces cerevisiae.

The CDC13 gene encodes a protein that binds to the G-rich single-strand at yeast telomeres, and serves as a regulator of telomere replication. Cdc13 interacts with Est1 and DNA polymerase alpha, and cells carrying the temperature-sensitive allele cdc13-1 cannot complete telomere replication at the restrictive temperature and possess long telomeres. We attempted to isolate and characterize genes that interact with CDC13, in order to clarify the molecular mechanisms of telomere replication. A STM1 cDNA was isolated in a two-hybrid screen using CDC13 as a bait. The temperature-sensitive growth phenotype and the alteration in telomere size in cdc13-1 cells were corrected by introduction of the STM1 gene on a multicopy vector, but the extended G-rich single-strand overhangs which are also characteristic in the cdc13-1 mutant were not affected. Furthermore, we found that multiple copies of SGS1, a gene encoding a helicase that can unwind guanine quadruplexes, inhibited suppression of the cdc13-1 phenotype by STM1. We also demonstrate that a fusion protein consisting of the N-terminal region of Cdc13 and the C-terminal region of Stm1 (which shows similarity to the beta-subunit of the telomere binding complex in Oxytricha) could complement a cdc13 disruptant. Although STM1 itself is not essential for telomere replication, our findings suggest that STM1 genetically interacts with CDC13 to maintain telomere structure.

Amino Acid Sequence↗

PubMed2002

Centrality dependence of pi(+/-), K(+/-), p, and (-)p production from sqrt[s(NN)] = 130 GeV Au + Au collisions at RHIC.

Identified pi(+/-), K(+/-), p, and (-)p transverse momentum spectra at midrapidity in sqrt[s(NN)] = 130 GeV Au+Au collisions were measured by the PHENIX experiment at RHIC as a function of collision centrality. Average transverse momenta increase with the number of participating nucleons in a similar way for all particle species. Within errors, all midrapidity particle yields per participant are found to be increasing with the number of participating nucleons. There is an indication that K(+/-), p, and (-)p yields per participant increase faster than the pi(+/-) yields. In central collisions at high transverse momenta (p(T) > or =2 GeV/c), (-)p and p yields are comparable to the pi(+/-) yields.

Journal Article↗

PubMed2002

Transverse-mass dependence of two-pion correlations in Au+Au collisions at square root[s(NN)] = 130 GeV.

Two-pion correlations in square root[s(NN)] = 130 GeV Au+Au collisions at RHIC have been measured over a broad range of pair transverse momentum k(T) by the PHENIX experiment at RHIC. The k(T) dependent transverse radii are similar to results from heavy-ion collisions at square root[s(NN)] = 4.1, 4.9, and 17.3 GeV, whereas the longitudinal radius increases monotonically with beam energy. The ratio of the outwards to sidewards transverse radii (R(out)/R(side)) is consistent with unity and independent of k(T).

Journal Article↗

PubMed2002

Measurement of single electrons and implications for charm production in Au+Au collisions at square root[s(NN)] = 130 GeV.

Transverse momentum spectra of electrons from Au+Au collisions at square root[s(NN)] = 130 GeV have been measured at midrapidity by the PHENIX experiment at the Relativistic Heavy Ion Collider. The spectra show an excess above the background from photon conversions and light hadron decays. The electron signal is consistent with that expected from semileptonic decays of charm. The yield of the electron signal dN(e)/dy for p(T) > 0.8 GeV/c is 0.025+/-0.004(stat)+/-0.010(syst) in central collisions, and the corresponding charm cross section is 380+/-60(stat)+/-200(syst) microb per binary nucleon-nucleon collision.

Journal Article↗

PubMed2002

Diffusion-weighted magnetic resonance imaging of dural sinus thrombosis.

Magnetic resonance imaging (MRI) is useful to diagnose dural sinus thrombosis. However, the representative appearance of dural sinus thrombosis on diffusion-weighted MRI has not been established. This study was aimed at determining whether cytotoxic or vasogenic edema is more predominant in the affected cerebral parenchyma and assessing the time courses and prognosis of dural sinus thrombosis lesion. The studies on sixteen patients with dural sinus thrombosis who underwent diffusion-weighted MRI were retrospectively reviewed. The diagnosis was confirmed by digital subtraction angiography in 11 patients and magnetic resonance angiography in five patients. Diffusion-weighted images with echo-planar imaging were obtained using two or three b values, with the highest b value of up to 1,000 s/mm(2). A region of interest was placed on an area of abnormal signal intensity to calculate apparent diffusion coefficients (ADCs). Nine of the 16 patients had lesions with an increased ADC, whereas, three of these nine patients also had lesions with a decreased ADC. Among 11 patients who underwent initial MRI within 7 days of their last episode, eight had lesions with an increased ADC, of whom three had lesions mixed with both decreased and increased ADC areas. Follow-up studies of these three patients revealed the development of hemorrhagic infarction in two and subcortical hemorrhage in one. Vasogenic edema develops more predominantly and earlier in dural sinus thrombosis, though cytotoxic edema was also associated with the pathological changes in the early phase. Decrease of ADC value is presumed to reflect severe pathological conditions and indicate possible future development of infarction or hemorrhage.

Adult↗

PubMed2002

Down-regulation of Lsm1 is involved in human prostate cancer progression.

Elucidation of genetic alterations is an approach to understanding the underlying molecular mechanisms of progression of human prostate cancers. We have searched for genes differentially expressed in advanced prostate cancers using cDNA-representational difference analysis, and thereby isolated the Lsm1 as one of down-regulated gene. An Lsm1 expression vector was transfected into PC3 cells, normally featuring down-regulated Lsm1, and four transfectants were established. No differences in morphology or cell proliferation were evident in comparison with parent PC3 or PC3/mock-transfectants. In contrast, significant suppression of invasive potential or metastatic ability of Lsm1 transfectants was observed in the Matrigel chemoinvasion assay and in nude mice, respectively. With human prostate cancers, almost all of informative prostatectomised cases without neoadjuvant therapy showed allelic retention in the Lsm1 region, whereas refractory cancers frequently showed allelic loss in this region. No critical gene mutations were found in open reading frame of Lsm1 in prostate cancers examined by PCR-SSCP analysis, including localised and refractory cancers. These results suggest that Lsm1 is deeply involved in prostate cancer progression through its down-regulation, independent of any gene mutation.

Animals↗

PubMed2002

Morphological features and associated anomalies of schizencephaly in the clinical population: detailed analysis of MR images.

Although they are well documented in autopsy series, the macroscopic features and associated anomalies of schizencephalies have not been described in detail in a large clinical population. To assess the macroscopic findings of schizencephaly and the prevalence of associated findings, we conducted a retrospective MR analysis of a group of patients with schizencephaly. The MR studies of 35 patients with schizencephaly were retrospectively reviewed. The images were examined for the location and size of the schizencephalic cleft, the presence and location of associated polymicrogyria, and the presence, location, and severity of other brain anomalies. A total of 54 schizencephalic clefts were seen in the 35 patients. These clefts were unilateral in 18 (51%) patients and bilateral in 17 (49%) patients; three clefts were identified in two patients. Nine clefts (17%) had fused lips and 45 had separated-lip clefts (83%). Polymicrogyria was present inside 23 clefts (43%), while subependymal heterotopias were present at the cleft orifice in 27 clefts (50%). Polymicrogyria was identified outside the cleft, both adjacent to and remote from the cleft, in 23 patients (66%). Abnormal cerebral white-matter signal intensity was present in seven patients (20%), while white-matter volume diminution was noted in all patients. Ventricular diverticula with mass effect, roofing membranes, remnant floors, and cord-like remnants were present in 12, 1, 11, and 3 patients, respectively. Our results show that the spectrum of macroscopic findings in schizencephaly includes fused-lip and separated-lip clefts, polymicrogyric and non-polymicrogyric cleft linings, cyst-like diverticula and membranous structures, and subependymal heterotopia at the cleft. Concomitant anomalies are polymicrogyria outside the cleft, white-matter diminution, septal and optic pathway anomalies, callosal anomalies and hippocampal anomalies. Unilateral and bilateral clefts occur in a nearly equal frequency in the clinical population, in contrast to the high incidence of bilateral schizencephaly reported in the pathological literature.

Adolescent↗

PubMed2002

A single nucleotide polymorphism of the low molecular mass polypeptide 7 gene influences the interferon response in patients with chronic hepatitis C.

Transporter associated with antigen processing (TAP) and low molecular mass polypeptides (LMP) play crucial roles in the human leukocyte antigen (HLA) class I-restricted antigen presenting systems. This study was performed to elucidate whether these antigen-presenting gene polymorphisms could influence the response to interferon (IFN) treatment in patients with chronic hepatitis C. Polymorphisms of TAP and LMP genes in 175 hepatitis C virus (HCV) patients were determined by polymerase chain reaction-restriction fragment length polymorphism. The frequencies of these genes were compared between sustained-responders (n=49) and nonresponders (n=126), classified by biochemical and virological responses to IFN. The distributions of TAP1*, TAP2*, and LMP2 genes between sustained-responders and nonresponders did not differ. However, LMP7-K gene frequency in sustained-responders was higher than that in nonresponders [odds ratio 2.3 (95% confidence interval 1.1-4.6); 16%vs 7.9%]. Multivariate analysis revealed that LMP7-K and HCV-RNA quantity were independent factors influencing the outcome of IFN therapy [4.5 (1.4-14); P=0.011, 0.40 (0.24-0.65); P=0.0003, respectively]. Furthermore, among patients with a low viral load (< or = 2.0 Meq/mL), the LMP7-K positive patients had an even higher ratio of sustained response compared to those without LMP7-K [5.9 (1.6-22); 82%vs 44%; P=0.0062]. These findings suggest that a single nucleotide polymorphism of LMP7 gene is one of the important host factors which independently influence the response to IFN in patients with chronic hepatitis C.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed2002

Endoscope-assisted far-lateral transcondylar approach to the skull base.

The far-lateral transcondylar approach was used in this cadaveric study in an attempt to evaluate the usefulness of endoscope-assisted microsurgery in this region of the skull base. The study was carried out using 4 latex-injected, formalin-fixed cadaver heads. After initial examination of intradural structures under an operating microscope, a zero degree 4 mm diameter solid-rod endoscope lens was introduced and guided into position under the direction of the operating microscope. Photographs of the regional anatomy were taken through this lens and through a 30 degree angled lens and compared to photographs of the anatomy taken through the microscope. Clear close-up views of the dural portals and intradural course of the cranial nerves were obtained using the endoscope. The endoscope was introduced through three corridors enclosed with cranial nerves, providing the surgeon with panoramic views of the vertebrobasilar arteries and anterior brainstem surface. The endoscope can be guided through narrow corridors and placed immediately adjacent to a region of interest at the skull base. It enables the surgeon to look around blind corners and work behind structures that are hidden from microscopic view.

Endoscopy↗

PubMed2002

Clinical and colonoscopic investigation of skipped periappendiceal lesions in ulcerative colitis.

BACKGROUND: Ulcerative colitis (UC) is typically a continuous and diffuse inflammation extending proximally from the rectum. However, skipped lesion in the appendiceal region has been reported recently. Although appendectomy has been shown to reduce the risk of UC, the clinical significance of skipped periappendiceal lesion remains unclear. The present study examined the relationship between the continuous distal lesion of UC and the skipped periappendiceal lesion by observing colonoscopic changes in both lesions. METHODS: Among 279 patients with UC who underwent total colonoscopy from January 1994 to December 2000, 54 patients (19.4%) had skipped periappendiceal lesions. Serial colonoscopic examinations were performed in 35 of the 54 patients to determine the activities in the distal UC lesion and skipped periappendiceal lesion during the course of disease. RESULTS: Patients with skipped periappendiceal lesions were younger and had a longer history of UC than those without them, but no differences in sex ratio and treatment modality were observed between the two groups. In 28 of 35 patients (80%), the activity in the distal lesion correlated well with that in the skipped periappendiceal lesion. Both lesions were improved in 17 patients, unchanged in 5 patients and worsened in 6 patients. Linear regression analysis showed a significant correlation between the changes in colonoscopic activity index in the two lesions. CONCLUSION: A close association is found between disease activity in the skipped periappendiceal lesion and that in the distal lesion of UC.

Adult↗

PubMed2002

Hemorrhagic brain metastases with high signal intensity on diffusion-weighted MR images. A case report.

Diffusion-weighted MR imaging has been applicable to the differential diagnosis of abscesses and necrotic or cystic brain tumors. However, restricted water diffusion is not necessarily specific for brain abscess. We describe ring-enhancing metastases of lung carcinoma characterized by high signal intensity on diffusion-weighted MR images. The signal pattern probably reflected intralesional hemorrhage. The present report adds to the growing literature regarding the differential diagnosis of ring-enhancing brain lesions.

Brain Abscess↗

PubMed2002

Early faecal excretion of inhaled plutonium.

Special individual monitoring has been performed for suspected cases of inhalation of plutonium at the Tokai Works of the Japan Nuclear Cycle Development Institute (JNC). Some experimental data obtained from this special individual monitoring during the past 20 years are presented and discussed in this paper. Our experience suggests the following conclusions. The daily plutonium excretion rate, normalised to the total excretion for the first 5 days after inhalation, was approximately in agreement with the latest ICRP 78 dosimetric model. Maximum faccal excretion is observed on the second day after inhalation of plutonium compounds. On the other hand, the activity ratio for total alpha activity observed in early faeces to that detected in nasal swabs showed a wide distribution range, and it was proven that variations in this ratio followed a log-normal distribution. The logarithmic mean probability is about 2.1 for PuO2 and about 15.7 for Pu(NO3)4. In practice, a conservative dose assessment from nasal swabs can be performed on the basis of these experimental ratios.

Feces↗

PubMed2002

An immunohistochemical study of cyclooxygenase (COX)-2 expression in endocrine tumors of the pancreas.

Cyclooxygenase (COX) is a key rate-limiting enzyme in prostaglandin biosynthesis. There are two isoforms of COX, referred to as COX-1 and COX-2. COX-2, an inducible form of COX, is found to be overexpressed in various neoplasms and is believed to play an important role in tumorigenesis and tumor development. In this study, we investigated expression of the COX-2 protein in human endocrine tumors of the pancreas (N=23; 6 insulinomas, one glucagnoma, 2 gastrinomas, and 14 non-functioning tumors) using immunohistochemistry. Strong COX-2 expression was confirmed in normal islet tissue as previously reported. COX-2 immunoreactivity was detected in 65% (15 out of 23) of these tumors with a moderate to strong intensity. In all nine functioning tumors, COX-2 expressions were preserved with the weak or strong intensity. In contrast, COX-2 was present in 6 out of 14 nonfunctioning tumors. The correlation between COX-2 expression and their function was significant (p<0.05). We found that expression of this enzyme was detected in 11 out of 15 benign tumors and in 4 out of 8 malignant tumors, respectively. Our results suggest that COX-2 may play an important role in the endocrine function of islet tumors. Additionally, malignancy was not related to COX-2 expression.

Adult↗

PubMed2001

Suppression of hadrons with large transverse momentum in central Au+Au collisions at root square[s(NN)] = 130 GeV.

Transverse momentum spectra for charged hadrons and for neutral pions in the range 1 GeV/c<p(T)<5 GeV/c have been measured by the PHENIX experiment at RHIC in Au+Au collisions at root square[s(NN)] = 130 GeV. At high p(T) the spectra from peripheral nuclear collisions are consistent with scaling the spectra from p+p collisions by the average number of binary nucleon-nucleon collisions. The spectra from central collisions are significantly suppressed when compared to the binary-scaled p+p expectation, and also when compared to similarly binary-scaled peripheral collisions, indicating a novel nuclear-medium effect in central nuclear collisions at RHIC energies.

Journal Article↗