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Biomedical subjects

K Shimono

Publications and source records attributed to K Shimono.

At least 55 records · Page 3Linked to original sources
PubMed1997

High body temperature induces micronuclei in mouse bone marrow.

The mouse micronucleus test was conducted to investigate the effect of high body temperature on micronucleus induction. Group of 10 male ddY mice were exposed to 30 degrees C for 1, 3 or 6 h, 37 degrees C for 0.5, 1, 2, 3 or 4 h, and 40 degrees C for 1 or 2 h. Bone marrow cells were sampled 24 h after heat exposure. Exposure of mice to 37 degrees C for 3 or 4 h and 40 degrees C for 1 or 2 h raised body temperature to approximately 40.5 degrees C and produced statistically significant increases in micronucleated polychromatic erythrocyte frequencies (8.1 +/- 4.5, 6.0 +/- 2.1, 5.3 +/- 3.3, 7.5 +/- 2.9%, respectively; control frequencies, 2.0 +/- 1.1%). In addition, about 25% of the induced micronuclei were relatively large (diameter of micronucleus > or = 1/4 diameter of cytoplasm). These results suggest that body temperatures of 39.5 degrees C or higher for more than 30 min induce micronuclei in bone marrow cells, and one possible mechanism is disturbance of the mitotic apparatus.

Animals↗
PubMed1995

The suitability of rat peripheral blood in subchronic studies for the micronucleus assay.

To examine the suitability of using rat peripheral blood from animals used in subchronic toxicity studies for micronucleus analysis, we orally administered phenacetin or 6-mercaptopurine for 14 days to groups of six rats and compared their micronucleus frequencies to the bone marrow micronucleus frequencies of rats similarly treated for only 2 days. In the 14-day test, phenacetin significantly increased the frequency of micronucleated reticulocytes in peripheral blood at 500 mg/kg starting from day 9, and at 750 and 1500 mg/kg starting from day 6; 6-mercaptopurine gave a positive response at 20 mg/kg starting from day 6. Positive responses in the bone marrow assay were obtained at the same dose levels. In the 2-day test, micronucleated polychromatic erythrocyte frequencies increased significantly at 1000 and 2000 mg/kg for phenacetin, and at 50, 100, and 200 mg/kg for 6-mercaptopurine. These results suggest that micronucleus assays using peripheral blood from rats in subchronic animal studies of phenacetin and 6-mercaptopurine are feasible and at least as sensitive for the assessment of micronuclei as an acute bone marrow micronucleus test.

Animals↗
PubMed1995

[Macroscopic characteristics of depressed type early gastric cancer special reference to their mucosal localizations].

Macroscopic characteristics of 143 lesions from 138 cases of depressed type early gastric cancer less than 2.0cm in the major axis (74 lesions of undifferentiated cancer, 69 lesions of differentiated cancer) were studied with respect to the localization in the gastric mucosa divided into 3 areas (area F: fundic gland region, 36 lesions, area I :intermediate gland regions, 29 lesions, area P :pyloric gland region, 79 lesions). (1) All 36 lesions in the area F were of the undifferentiated type. Narrowing and/or interruption of the folds were found in 83%. The abnormal folds were found in 97% of the lesions found in the area where the mucosal folds were present. (2) 72% lesions in the area I were determined to be undifferentiated cancers. Uneven depressed surface was observed in 95% of the undifferentiated cancer. Steep depressed margine was found in their 86%. Narrowing and/or interruption of the folds were detected in their 81%. In cases of differentiated cancer, the findings of folds both on the depressed surface and margin were scarcely observed. (3) The undifferentiated cancer was diagnosed in 22% of the lesion in the area P. In 18% and 76% of them, uneven depressed surface and steep depressed margin were observed respectively. Narrowing and/or interruption of the folds were recognized in only 6%. Although these abnormal macroscopic findings were less in this area, the marginal elevation was found in 59%. In differentiated cancer of this area, the presence of marginal elevation was the highest up to 72% compared with cancers in the other areas.

Carcinoma↗
PubMed1994

Visual directions of two stimuli in Panum's limiting case.

Visual directions of the two stimuli in Panum's limiting case with different interstimulus and convergence distances confirmed the predictions from the reformulated Wells-Hering's laws of visual direction. In experiment 1, six observers each converged on the midpoint of the interstimulus axis at 30, 60, and 90 cm from the eyes and adjusted a probe on the fixation plane to be in the same visual direction as that of each stimulus. Visual direction of the far stimulus was always nonveridical whereas that of the near stimulus was veridical only when its retinal disparity was small. In experiment 2, three observers each converged on the intersection of mid-sagittal plane and (a) the frontoparallel plane of the near stimulus, (b) that of the midpoint between the two stimuli, or (c) that of the far stimulus. The midpoint of the interstimulus axis was 60 cm from the eyes. Visual direction of the far stimulus was veridical only with convergence at the far plane. Visual direction of the near stimulus was veridical with convergence at the near plane, and also, only when its retinal disparity was small, with convergence at the two other planes.

Analysis of Variance↗
PubMed1994

How accurate is size and distance perception for very far terrestrial objects? Function and causality.

This study investigated absolute estimation of size and distance for natural and artificial objects at viewing distances of 1.1-15.3 km (Experiments 1 and 2) and 0.4-5.0 m (Experiment 3). The main results were that, regardless of distance range, size and distance estimates (S' and D') were related to objective size and distance (S and D), respectively, by a power function with an exponent of unity, but great individual differences in exponent were obtained for the far objects. The ratio S'/D' was reasonably represented by S'/D' = K theta n and S'/D' = tan(a theta +b), rather than S'/D' = tan theta, where theta is the visual angle. Partial correlations were obtained to examine whether (1) apparent size is determined by taking apparent distance into account or (2) both apparent size and apparent distance are determined directly by external stimuli. The combined data for the far objects and the data for the close objects showed that there were high correlations between S and S' and between D and D' and a low correlation between D' and S'. The data of Experiment 2 showed that both D' and S' were highly correlated with S, D, and theta, and there was a high positive correlation between D' and S'. It was suggested that the direct-perception model is valid under some situations, but the taking-into-account model is not supported in any set of data.

Distance Perception↗
PubMed1993

The efficacy of extracorporeal shock wave lithotripsy on single dense calcified gallstones according to computed tomography.

The efficacy and complications of extracorporeal shock wave lithotripsy (ESWL) for single gallstones were compared between 15 patients with a CT-lucent stone and 18 patients with a dense calcified stone. In all of five patients with a stone smaller than 10 mm in diameter, complete or sufficient clearance was observed, regardless of calcification. However, in 28 patients with a stone larger than 11 mm in diameter, the rates of complete or sufficient clearance were lower in those with a dense calcified stone (64%) than in those with a computed tomography (CT) lucent stone (93%). There was no difference in the rate of complications between patients with a CT-lucent stone and those with a dense calcified stone. These results thus suggest that extracorporeal shock wave lithotripsy may be safely employed for patients with a single calcified gallstone.

Adult↗
PubMed1992

Developing corticorubral axons of the cat form synapses on filopodial dendritic protrusions.

Developing neurons transiently grow numerous spine- or filopodium-like dendritic protrusions (SLDPs). Electron microscopy on identified input and intracellular staining of postsynaptic cells were performed to gain insight into their significance. Newborn kitten-corticorubral axons, labelled with biocytin, commonly made synapses on SLDP, often multiply invaginated by the SLDPs. Correspondingly, intracellularly labelled kitten rubrospinal cells had numerous SLDPs. Taking into account that corticorubral synapses are largely formed on dendritic shafts in adult cats, it is likely that the SLDPs play some important role in the development of corticorubral synapses. We hypothesize that rubrospinal cells elongate SLDPs searching for corticorubral axons to form synapses.

Aging↗
PubMed1992

Occlusion as a depth cue in the Wheatstone-Panum limiting case.

We examined the hypothesis (Ono & Wade, 1985) that occlusion of far stimuli by a near one on the same visual line can operate as a depth cue in stereograms containing different numbers of targets in the two eyes. By controlling eye positions, we created conditions in which the visual system could interpret the retinal images as originating from stimuli on the visual axis of one eye and also created other conditions in which the origin of the retinal images was ambiguous. In Experiment 1, we presented two lines to one eye and a single line to the other eye. When the image of the line on the temporal side of the line pair on one retina fused with the image of the single line on the other retina, the nonfused line appeared farther away more often than it did when the image on the nasal side fused. In Experiment 2, we used two differently shaped stimuli. In the condition in which the nonfused stimulus represented an object being occluded, it appeared farther away more often than in the four conditions in which it did not. In Experiment 3, we extended the idea to three different objects. When the middle of the three images fused with the single image, the nonfused stimulus appeared farther when it could be interpreted as being occluded than when it could not. In the condition in which the most temporal image fused with the single image, the nonfused stimuli appeared farther than in the condition in which the most nasal one fused. The results supported the hypothesis that occlusion plays a role in depth perception in the Wheatstone-Panum limiting case.

Adult↗
PubMed1992

[Apparent depth by the stereograms without binocular retinal disparity: is Lau effect artifact?].

We examined the idea that, when the Zöllner figure in one eye and the principal lines in the figure in the other eye were presented, the perceived depth is due to "phenomenal" disparity. The phenomenal disparity is defined as apparent displacement between two illusory "oblique" principal lines in one eye and two "parallel" principal lines in the other. Observes were asked whether depth was seen or not at upper or lower part of the two perceived lines and, if seen, which line was closer. Seventeen observers showed that only 9% of their responses was consistent with the idea, although they reported depths for disparity stimuli. This suggests that the dichoptic presentation of such figures should not be considered as that requires the processing of binocular disparity.

Adult↗
PubMed1991

[Is the "false projection phenomenon" (Jampolsky, 1970, 1978) an artefact?].

Jampolsky (1970, 1978) found that the light from the nasal visual field seen through the eyelid of one eye is seen in the direction of the temporal visual field when the other eye is occluded. We examined whether the "false projection" is an artefact of the light "leaking" into the occluded eye. Completely occluding one eye did not eliminated the "false projection": four observers saw the light in the nasal field as coming from the temporal field in 89.4% of the trials whereas the light in the temporal field as coming from the temporal field in 95.6% of the trials. The phenomenon still needs an explanation.

Adult↗
PubMed1990

[Perceived depth produced by luminance differences in the two eyes with zero disparity].

We examined Kaufman, Bacon, and Barroso's (1973) finding that perceived depth covaries with relative luminance of the two half-fields of the stereogram. Five subjects were shown two sets of stereograms: one with three lines and another with random dots. In each trial, they reported the apparent depth plane produced by one of 15 different relative luminances of the lines or the mid portions of the random dots. The direction and the magnitude of perceived depth as a function of the relative luminance varied across subjects. It is argued that the stimulus should be considered as being Wheatstone-Panum's Limiting Case rather than that requires processing of binocular retinal disparity.

Adult↗
PubMed1989

Fecal immunoglobulin A (IgA) antibodies to Yersinia enterocolitica in mice orally vaccinated and infected.

Fecal immunoglobulin-A (IgA) antibodies to Yersinia enterocolitica serovar O3 strain were detected in the mice orally immunized with formalin-killed organisms. Y. enterocolitica O3 organisms were inhibited to colonize in the intestines of the mice producing fecal IgA. The fecal IgA antibodies were detected in the mice orally infected with the bacteria. When IgA was produced in the mice infected, they ceased shedding the organisms in their feces.

Animals↗
PubMed1989

[An experimental study on mesenteritis and deformities of the intestinal canal; with special reference to the changes with time of deformities (angulation, distortion, coil-like appearance)].

1. The relationship of the mesenteric inflammation with intestinal loop deformities was made clear and changes of these deformities were examined with time, using experimental model rabbits. 2. The above rabbit was laparotomized and was caused to develop mesenteritis by applying acetic acid onto sigmoid mesentery and descending colic mesentery, then the abdomen was closed. Subjects were divided into 2 groups (A and B); A group and B group were re-laparotomized 3-7 and 21 days later, respectively and were observed for mesentery and loop appearance, then were extirpated for sigmoid colon and descending colon with mesenterium attached thereto. Roentgenograms were taken first with attachment of mesentery, secondly there-without. Then, the intestinal canal was opened and the mucosal surface was observed, together with bleeding and blood flow disturbance in the depth of the wall in transmitted light. 3. As a result, the following conclusions were obtained: 1) Macroscopically, mesentery was marked with redness for A group and with thickening and twitch due to cicatricial contraction for B group. 2) A group near to the third day showed remarkable shortening, narrowing and marginal irregularity of the loop, which disappeared with time and were scarcely observed for B group; these deformities were considered to involve mesenteric inflammations and ischemia caused by secondary blood flow disturbance. 3) A group near to the 7th day and B group showed remarkable angulation, distortion and coil-like appearance; these deformities are considered to have been caused by thickening (stiffness) of the mesentery and its attachment and twitch-distortion due to cicatricial contraction. 4) Coil-like appearance disappeared upon cutting off the mesentery from the loop.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

A rapid in vitro assay system using anti-bromodeoxyuridine for drug susceptibility of Plasmodium falciparum.

Drug effects were monitored by the measurement of bromodeoxyuridine (BrdU) incorporation into parasite deoxyribonucleic acid (DNA). Cells are pulse-labelled with BrdU and those which are synthesizing DNA incorporate BrdU into their DNA. Anti-BrdU is used to identify cells undergoing DNA synthesis at the time of the pulse. Concentration-effect curves were determined for chloroquine, pyrimethamine and quinine in culture for only 3 h in RPMI 1640 medium supplemented with BrdU. Different strains of Plasmodium falciparum could be distinguished when BrdU uptake was monitored by the ELISA. This assay offers a fast and accurate method of monitoring the effects of a variety of antimalarial drugs.

Animals↗
PubMed1982

[Psychophysical and vergence responses of normal and stereoanomalous observers to pulse-disparity stimulus].

The relations between psychophysical and oculo-motor responses to retinal disparity were examined in two experiments. Experiment I examined the subject's discriminability of the depth produced by 2 degrees crossed, 2 degrees uncrossed, and zero disparities with the durations of 100 and 1000 ms. As a result, six stereonormal, one crossed stereoanomalous, and one stereoblind observers were identified. In Experiment II, eye movement responses of three subjects with the different types of stereoscopic vision to the disparity pulses were monitored by the photo-electric method. The results of Experiment II indicated that the normal observer showed normal vergence, the crossed stereoanomalous observer showed anomalous convergence, and the stereoblind observer did not show any vergences but saccadic movements. Several theoretical implications of the results are discussed.

Adult↗