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Y Ejima

Publications and source records attributed to Y Ejima.

At least 37 records · Page 2Linked to original sources
PubMed2000

From image segmentation to anti-textons.

We apply the 'patchwork engine' (PE; van Tonder and Ejima, 2000 Neural Networks forthcoming) to encode spaces between textons in an attempt to find a suitable feature representation of anti-textons [Williams and Julesz, 1991, in Neural Networks for Perception volume 1: Human and Machine Perception Ed. H Wechsler (San Diego, CA: Academic Press); 1992, Proceedings of the National Academy of Sciences of the USA 89 6531-6534]. With computed anti-textons it is possible to show that tessellation and distribution of anti-textons can differ from that of textons depending on the ratio of texton size to anti-texton size. From this we hypothesise that variability of anti-textons can enhance texture segregation, and test our hypothesis in two psychophysical experiments. Texture segregation asymmetry is the topic of the first test. We found that targets on backgrounds with regular anti-textons segregate more strongly than on backgrounds with highly variable anti-textons. This neatly complements other explanations for texture segregation asymmetry (e.g. Rubenstein and Sagi, 1990 Journal of the Optical Society of America A 7 1632-1643). Second the relative significance of textons and anti-textons in human texture segregation is investigated for a limited set of texture patterns. Subjects consistently judged a combination of texton and anti-texton gradients as more conspicuous than texton-only gradients, and judged texton-only gradients as being more conspicuous than anti-texton-only gradients. In the absence of strong texton gradients the regularity versus irregularity of anti-textons agrees with perceived texture segregation. Using PE outputs as anti-texton features thus enabled the conception of various useful tests on texture segregation. The PE is originally intended as a general image segmentation method based on symmetry axes. With this paper we therefore hope to relate anti-textons with visual processing in a wider sense.

Contrast Sensitivity↗
PubMed2000

WAF1 accumulation by carbon-ion beam and alpha-particle irradiation in human glioblastoma cultured cells.

PURPOSE: There have been no reports about the effects of heavy-ion beams on the expression of the WAF1 gene, although ionizing radiation such as y-rays and X-rays is well known to induce WAF1 (p21/CIP1/sdi1) gene expression in a p53-dependent manner. In the present study, it was examined whether WAF1 accumulation was induced after carbon-ion (C-) beam or alpha-particle irradiation in four glioblastoma cell lines. MATERIALS AND METHODS: A colony assay for radiosensitivity and Western blot analysis of WAF1 were applied to two human glioblastoma cell lines, A-172 bearing wild-type p53 (wtp53) and T98G bearing mutated p53 (mp53). A-172/neo and A-172/mp53 were transfected with a control vector (containing only a neo selection marker) and a mp53 expression vector respectively. RESULTS: The amount of WAF1 increased markedly after X-ray irradiation in A-172 and A-172/neo cells but not in T98G and A-172/mp53 cells. The level of WAF1 reached a plateau at 3-10 h after X-ray irradiation at 5 Gy in A-172 and A-172/neo cells. Likewise, the levels of WAF1 in A-172 and A-172/neo cells reached a plateau at 3-10 h and 6-24 h after C-beam (3.0 Gy) and alpha-particle (4.5 Gy) irradiation respectively. The amount of WAF1 increased markedly in a dose-dependent manner 10 h after X-ray, C-beam or alpha-particle irradiation in A-172 and A-172/neo cells but not in T98G or A-172/mp53 cells. In addition, cell survival assay showed that these cell lines were most sensitive to C-beams, less sensitive to alpha-particles and least sensitive to X-rays at 10% survival. There was no difference in sensitivity among these cell lines against C-beam and alpha-particle irradiation whereas wtp53 cells (A-172 and A-172/neo) were more sensitive to X-rays than mp53 cells (A-172/mp53 and T98G). CONCLUSIONS: These results indicate that C-beams and alpha-particles induce p53-dependent WAF1 accumulation as well as is the case with X-rays, suggesting that WAF1 protein accumulation may not contribute to cell killing.

Alpha Particles↗
PubMed2000

Method for recovery of heading from motion.

A new method for recovery of heading from motion is developed on the basis of Longuet-Higgins and Prazdny's algorithm [Proc. R. Soc. London Ser. B 208, 385 (1980)]. In the algorithm a radial virtual flow field is generated and the difference between the original velocity field and the virtual radial field is computed. The difference vectors, which are directed to the heading point in the projected plane, allow us to estimate the direction of heading. The simulations of the algorithm were performed, and it was shown that the method estimates the direction of heading accurately.

Algorithms↗
PubMed2000

[Anesthetic management of a patient with hemophilia A for left modified Blalock-Taussig shunt].

We gave anesthesia to a patient with hemophilia A for left modified Blalock-Taussig shunt. The patient was a twenty five-day-old boy with pulmonary atresia. We performed the bolus injection test of factor VIII concentrate in preoperative period. His factor VIII activity increased from 9.3 to 113.3% after a bolus injection of 165 units. To keep his factor VIII activity above 80% in perioperative period, a bolus of 125 units of recombinant factor VIII concentrate was injected at anesthesia induction, 125 units 2 hours after the start of the operation, and 125 units 6 hours after the end of the operation. Factor VIII activity 2 hours after anesthesia induction increased only 37.8%, and we had to infuse recombinant factor VIII concentrate additionally. We measured factor VIII activity during operation, and he finally received total of 415 units of factor VIII concentrate. Hydroxyethyl starch infusion, blood transfusion and bleeding in the perioperative period might have caused the factor VIII activity to decrease beyond our expectation. We should infuse factor VIII concentrate properly measuring the factor VIII activity during this operation.

Anastomosis, Surgical↗
PubMed1999

Effect of high-density extremely low frequency magnetic field on sister chromatid exchanges in mouse m5S cells.

The induction of sister chromatid exchanges (SCEs) was evaluated in the cultured mouse m5S cells after exposure to extremely low frequency magnetic field (ELFMF; 5, 50 and 400 mT). Exposure to 5 mT and 50 mT ELFMF led to a very small increase in the frequency of SCEs, but no significant difference was observed between exposed and unexposed control cells. The cells exposed to 400 mT ELFMF exhibited a significant elevation of the SCE frequencies. There was no significant difference between data from treatments with mitomycin-C (MMC) alone and from combined treatments of MMC plus ELFMF (400 mT) at any MMC concentrations from 4 to 40 nM. These results suggest that exposure to highest-density ELFMF of 400 mT may induce DNA damage, resulting in an elevation of the SCE frequencies. We suppose that there may be a threshold for the elevation of the SCE frequencies, that is at least over the magnetic density of 50 mT.

Animals↗
PubMed1999

The FANCA gene in Japanese Fanconi anemia: reports of eight novel mutations and analysis of sequence variability.

Fanconi anemia (FA), an autosomal recessive disorder characterized by a progressive pancytopenia associated with congenital anomalies and high predisposition to malignancies, is a genetically and clinically heterogeneous disease. At least eight complementation groups (FA-A to FA-H) have been identified with their relative prevalence varying among the ethnical backgrounds. Recently, responsible genes, FANCA and FANCC, have been cloned. This report describes mutations of the FANCA gene, which we studied by direct sequencing of cDNA with confirmation on genomic DNA in 15 unclassified Japanese FA patients. A total of 19 sequence alterations were identified, of which 10 (six missense and four silent alterations) were likely to be nonpathogenic polymorphism. The remaining nine alterations, of which eight were novel mutations, were assumed to be pathogenic and consisted of two missense mutations and seven mutations resulting in truncation of gene product, demonstrating a wide allelic heterogeneity. The pathogenic mutations were found in 12 patients (80%); they were either homozygous or compound heterozygous in 10 patients, apparently heterozygous in two patients and none in three patients. We conclude that the sequence variability is intrinsic to the FANCA gene and that the relative prevalence of the FA-A subtype is unusually high in Japanese FA patients.

DNA Mutational Analysis↗
PubMed1999

A new method for magnetoencephalography: a three-dimensional magnetometer-spatial filter system.

A novel three-dimensional magnetometer-spatial filter system was developed to study human brain activity with high spatiotemporal resolution. The system combines the high temporal resolution of magnetoencephalography with the high spatial resolution achieved by using three-dimensional magnetometers and spatial filters to measure the direction and intensity of magnetic fields generated during brain activity. Simulation and phantom studies indicate that the system is capable of mapping current sources of magnetic fields with a spatial resolution comparable to that of any other brain functional imaging technique while maintaining millisecond temporal resolution. Application of this system to the human brain resolved magnetoencephalographic responses evoked by motion stimuli on a millisecond scale into responses occurring in visual cortical areas V1, V2/3 and V5. It also revealed signals related to contextual modulation in V1 and V2/3. This system provides a new way of studying the dynamics of human brain function.

Brain↗
PubMed1999

Determination of the genotype of a panel of human tumor cell lines for the human homologues of yeast cell cycle checkpoint control genes: identification of cell lines carrying homoallelic missense base substitutions.

A number of human homologues of yeast cell cycle checkpoint control genes have been identified recently. In this study, the sequence alterations in six of such novel human genes (hRAD1, hRAD9, hRAD17, hHUS1, CHK1 and CHES1) were analyzed by PCR-single-strand conformational polymorphism (PCR-SSCP) method on a panel of 25 human tumor cell lines in an attempt to search for possible in vivo cases where any of the checkpoint-related genes are altered in human systems. For hRAD9, hHUS1 or CHK1, no SSCP variant was detected in any of the cell lines tested, indicating a high stability of these genes in human cancer. Most of the SSCP variants found in the other three genes were due to single nucleotide base substitutions. Two cell lines were found to be homozygous for missense-type base substitutions, i.e., Saos-2 was homoallelic for 1637T-->G in hRAD17; and COLO320DM for 1189G-->A in CHES1, indicating a possible use of these cell lines for further study. The former nucleotide change in hRAD17, which causes a change of amino acid from arginine to lysine at codon 546, was supposed to be polymorphic. Considering that lysine, but not arginine, is the amino acid that is well conserved among fission yeast, mouse and monkey at the corresponding position, coexistence of both alleles in human may have a functional or selectional implication.

Alleles↗
PubMed1999

Low-dose-rate radiation attenuates the response of the tumor suppressor TP53.

Acute low-dose irradiation (0.1-1 Gy, 1.33 Gy/min) of cells of a human glioblastoma cell line, A-172, induced a dose-dependent monophasic accumulation of TP53 (formerly known as p53) and CDKN1A (formerly known as WAF1). In contrast, chronic gamma irradiation (0.001 Gy/min) produced a clear biphasic response of accumulation TP53 with the first peak at 1.5 h (0.09 Gy) and the second peak at 10 h (0.54 Gy). Significantly, when the cells were preirradiated with a chronic dose of gamma irradiation for 24 h (1.44 Gy) or 50 h (3 Gy), they no longer responded to an acute challenging dose to produce a dose-dependent response of the TP53 pathway. These findings suggest that chronic irradiation at low dose rate alters the TP53-dependent signal transduction pathway. Wearing away of the TP53 pathway by chronic exposure to radiation may have important implications for radiation protection.

Adaptation, Physiological↗
PubMed1999

[Evaluation of left ventricular diastolic function during coronary artery bypass grafting by color M-mode Doppler echocardiography].

The objective of the present study was to evaluate the effects of the coronary artery bypass graft surgery (CABG) and cardioplegic arrest on left ventricular diastolic function. Ten patients with coronary artery disease were studied by transesophageal Doppler echocardiography. Doppler measurements included peak velocity during early filling (peak E velocity), peak velocity during atrial contraction (peak A velocity), and the ratio of peak E velocity to peak A velocity (E/A). The rate of propagation of peak early filling flow velocity (FPV) was also measured using color M-mode Doppler echocardiography. Hemodynamic and Doppler-derived variables were measured before and after sternotomy, after the end of cardiopulmonary bypass (CPB) and after closure of the sternum. E/A showed a significant decrease after sternotomy and did not return to the pre CPB level. FPV increased after CPB. FPV was correlated with E/A (r = 0.54, P = 0.013 pre-CPB; r = 0.54, P = 0.014 post-CPB). E/A showed a significant correlation with heart rate. After the influence of heart rate had been eliminated by the analysis of covariance, corrected E/A value showed a significant increase post-CPB compared to that in pre-CPB (0.68 +/- 0.29 to 1.10 +/- 0.29, P < 0.05). In conclusion, FPV and heart-rate-corrected E/A increased after CPB. This suggests improvement of diastolic function during CABG.

Aged↗
PubMed1998

Mutations of the ATM gene detected in Japanese ataxia-telangiectasia patients: possible preponderance of the two founder mutations 4612del165 and 7883del5.

The ATM (A-T, mutated) gene on human chromosome 11q22.3 has recently been identified as the gene responsible for the human recessive disease ataxia-telangiectasia (A-T). In order to define the types of disease-causing ATM mutations in Japanese A-T patients as well as to look for possible mutational hotspots, reverse-transcribed RNA derived from ten patients belonging to eight unrelated Japanese A-T families was analyzed for mutations by the restriction endonuclease fingerprinting method. As has been reported by others, mutations that lead to exon skipping or premature protein truncation were also predominant in our mutants. Six different mutations were identified on 12 of the 16 alleles examined. Four were deletions involving a loss of a single exon: exon 7, exon 16, exon 33 or exon 35. The others were minute deletions, 4649delA in exon 33 and 7883del5 in exon 55. The mutations 4612del165 and 7883del5 were found in more than two unrelated families; 44% (7 of 16) of the mutant alleles had one of the two mutations. The 4612del165 mutations in three different families were all ascribed to the same T-->A substitution at the splice donor site in intron 33. Microsatellite genotyping around the ATM locus also indicated that a common haplotype was shared by the mutant alleles in both mutations. This suggests that these two founder mutations may be predominant among Japanese ATM mutant alleles.

Ataxia Telangiectasia↗
PubMed1998

Motion assimilation for expansion/contraction and rotation and its spatial properties.

In a two-frame apparent motion display, a test grating was displaced horizontally or vertically in the presence of an inducer of which component gratings made up expanding/contracting or rotational motion as a whole. In the first experiment, we demonstrated that motion assimilation did occur for the test accompanied by the two-dimensional motion of the inducer. In the second experiment, we showed that the spatial limit of motion assimilation for expansion/contraction or rotation was large, extending over at least a visual angle of 14-21 deg in diameter, but spatial summation did not occur within the limit. The results were discussed in terms of the interaction between local motion detectors and higher-order detectors which monitor global motion of the whole stimulus pattern.

Humans↗
PubMed1998

The effects of static magnetic fields and X-rays on instability of microsatellite repetitive sequences.

To determine the genetic effect of static magnetic fields (SMF), which are not supposed to produce any significant DNA damage, we took advantage of DNA mismatch repair (MMR) deficient cells, in which all the errors produced during DNA replication are left uncorrected. We first established a simple and less labor-intensive method to analyze genetic changes in microsatellite repetitive sequences in the MMR-deficient cells. After exposure to a strong SMF (6.34T) for 24 h, both MMR deficient HCT116 cells and proficient HeLa S3 cells did not exhibit any significant effect on microsatellite changes. Moreover, when HCT116 cells were synchronized at the G1/S boundary by aphidicolin and exposed to SMF during the whole S-phase, no increase in microsatellite changes was either observed. In contrast, irradiation by a low dose X-ray (2Gy) significantly increased microsatellite changes in HCT116 cells. This suggested that exposure to strong SMF may not induce any significant level of genetic changes in microsatellite sequences.

Cell Line↗
PubMed1998

The F value cannot be ruled out as a chromosomal fingerprint of radiation quality.

The F value, the ratio of inter- to intrachromosomal interchanges, as a biomarker for densely ionizing radiation which was proposed by Brenner and Sachs (Radiat. Res. 140, 134-142, 1994) has been a matter of repeated discussion. We examined our experimental data on radiation-induced chromosome aberrations in human peripheral blood lymphocytes for the F value as measured by the ratio of dicentrics to centric rings. Because of the rarity of aberrations, the F value showed a considerable variability, with a large error range particularly in the low-dose range of low-LET radiation. However, the data showed a general trend that the F value tended to be lower for high-LET than low-LET radiations. The differential F value was more pronounced at low doses and diminished with increasing dose; the F values of all radiations tended to converge toward a similar value at high doses. The limiting F value at the lowest doses, or the F0 value, was dependent on LET for high-energy radiations that can produce an array of DNA double-strand breaks along the track of the charged particle. However, LET and dose dependence were not seen for the low-energy photons, where spatially uncorrelated random breaks were produced by independent photoabsorption events.

Biomarkers↗
PubMed1997

Phenotypic correction of ataxia-telangiectasia cellular defect by exogenously introduced human or mouse subchromosomal fragments.

A human-mouse hybrid containing a human 11q22-23 fragment including the ATM locus was used to examine its capability to correct the cellular defect of ataxia-telangiectasia (A-T). Examination of 21 A-T-derived hybrids indicated that the acquired radioresistance was observed in the clones where the 11q22-23 fragment was transferred intact, but not in those where donor-derived 11q segment was lost. In one exceptional clone, the ATM locus was deleted from the transferred fragment, while it was still partially radioresistant. This partially radioresistant clone was found to include the mouse-derived fragment containing the Atm gene, the mouse homologue of human ATM gene. Similar association of partial radioresistance with the presence of mouse Atm gene was observed in three additional hybrids. The results indicate that the cellular A-T defect can be corrected by the mouse subchromosomal fragment containing the Atm gene as well as by the human 11q22-23 fragment containing the ATM gene, but apparently to a lesser extent in the former.

Animals↗
PubMed1997

Additive effect of luminance and color cues in generation of neon color spreading.

A series of experiments were designed to examine how luminance and color cues influence the occurrence of neon color spreading for the Ehrenstein pattern plus the cross pattern. The proportion of "see" responses for color spreading was obtained for different combinations of the luminance and color of the pattern components. The following were obtained. (1) Increase in the luminance of the inducing pattern and/or the color difference between the cross and the inducing pattern raised the proportion of "see" responses for color spreading. This implies that luminance and color signals additively contribute to the generation of the color spreading, but in different ways. (2) The "iso-spreading contours" for the generation of color spreading were determined on the two-dimensional isoluminant plane composed of the L-M and S-(L+M) axes. The contours were approximately described by rotated quadratic or ellipse functions. The additive interaction within the chromatic systems [the L-M system and the S-(L+M) system] was less significant than that across the luminance and chromatic systems. (3) The pattern of the experimental results could not be explained straightforwardly by existing models.

Color Perception↗
PubMed1997

Anisotropy for direction discrimination in a two-frame apparent motion display.

Direction discrimination (upward/downward or left/right) for a Gabor patch in a two-frame motion display was measured as a function of the inter-frame displacement size of the component grating with the stimulus position (center, left, right, upper and lower visual fields) as a parameter. The results showed that, for vertical motion in the center, left, right and lower visual fields, the observers saw downward motion more frequently than upward motion, whereas for vertical motion in the upper field and for horizontal motion, no preference for one of the two opposite directions was obtained. Human motion vision is anisotropic in the lower half of the visual field.

Discrimination, Psychological↗