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Biomedical subjects

K Uchikawa

Publications and source records attributed to K Uchikawa.

At least 19 recordsLinked to original sources
PubMed1997

Perceived angular and linear size: the role of binocular disparity and visual surround.

An experiment was conducted to investigate the effects of perspective cue and binocular disparity on perceived angular and linear size. Following the 'angular' and 'linear' instructions, subjects matched the size of two squares, for which the binocular disparity between the centers of the squares and the configuration of the stimulus surrounding the squares were manipulated. Results showed that angular-size matches depended on the retinal-image size and the binocular disparity, and not on the visual-surround stimulus. Linear-size matches, on the other hand, depended on the visual-surround stimulus as well as on the image size and the binocular disparity. The visual-surround stimulus also affects the perceived depth between the test squares. These findings indicate that perceived angular and linear size depend on different processes that use different cues, and suggest that there is a causal relationship between perceived depth and perceived linear size.

Adult↗
PubMed1996

Distribution of Borrelia species associated with Lyme disease in the subalpine forests of Nagano prefecture, Japan.

We surveyed the natural distribution of Borrelia species associated with Lyme disease in the subalpine forests of Nagano prefecture, Japan, during 1993-94. Tick-derived isolates (n = 112) from Ixodes persulcatus and rodent-derived isolates (n = 55) from Apodemus argenteus, Apodemus speciosus, Eothenomys andersoni, Eothenomys smithii, and Microtus montebelli were classified by rRNA gene restriction fragment length polymorphism analysis (RFLP ribotyping). Ribotype group IV (an intraspecific variant of Borrelia garinii) was predominant among the tick isolates. It was also isolated repeatedly from the rodents. Ribotype group III (Borrelia afzelii) was detected in low frequencies among the tick and rodent isolates. The data suggest that humans are likely to be exposed to the group IV when they are bitten by I. persulcatus ticks.

Animals↗
PubMed1996

Limitations of surface-color and apparent-color constancy.

Color-constancy mechanisms have been studied and discussed in a number of investigations. However, there has been little attempt to reveal how color constancy deteriorates as the conditions for it become less than optimal. We carried out a series of asymmetric color-matching experiments, using two criteria: surface-color match and apparent-color match. With brief adaptation the degree of color constancy increased as chromatic cues were added in the surround. In the condition of black surround, the test stimuli appeared self-luminous, and chromaticities of the chosen matching stimuli were the same as the physical chromaticities of the test stimulus, indicating a total deficiency of color constancy. With 15 min of preadaptation to the illuminant, the surface-color matches showed almost perfect color constancy under illuminant change. In both adaptation conditions, the chromatic-shift of matches from what would be expected for perfect color constancy increased gradually between 1,700- and 30,000-K illuminant, as chromaticity of the illuminant departed from 6,500-K illuminant. Under 1,000-K illuminant the surface-color appearance became totally achromatic, and color constancy was completely lost. Our results show that, even with brief adaptation to the illuminant, the contribution of the surrounding stimulus is large enough to achieve a fair degree of color constancy, but complete adaptation to the illuminant helps to achieve almost perfect color constancy.

Adaptation, Physiological↗
PubMed1995

Saccadic suppression of achromatic and chromatic responses measured by increment-threshold spectral sensitivity.

We measured spectral-sensitivity functions during saccadic eye movement by the increment-threshold method to test whether saccades selectively suppressed achromatic or chromatic responses. A circular monochromatic test stimulus of 12-deg diameter was presented for 10 ms on a 62 deg x 43 deg white background, and observations were made under three conditions: during fixation, during 6-deg saccades, and immediately after saccades. In two additional conditions the test stimulus was made to move during fixation and during 6-deg saccades at the same speed and in the same direction as the saccades. The during-fixation spectral-sensitivity function was found to resemble the relative luminous efficiency V (lambda) function in shape except for the case of short wavelengths, whereas the during-saccade spectral-sensitivity function showed lower sensitivity for all wavelengths and had three prominent peaks at approximately 440, 530, and 600 nm. These characteristics did not depend on whether the stimulus was stationary or moving. These results indicated that saccadic suppression was greater for achromatic than for chromatic response. A possible suppression mechanism was discussed involving the magno and parvo pathways.

Adult↗
PubMed1994

Trombiculid fauna and seasonal abundance of Leptotrombidium scutellare (Acari: Trombiculidae) in an endemic area of scrub typhus (Tsutsugamushi disease) in Yamakita Town, Kanagawa Prefecture, Japan.

Using the Tullgren funnel method, we surveyed for trombiculid larvae around dwellings and in mandarin orange groves on the slopes of Sengenyama and Maruyama, Yamakita Town, Kanagawa Prefecture, Japan, during the period between 8 October 1992 and 8 January 1993. In total, 6,690 trombiculid larvae, consisting of 6,669 Leptotrombidium scutellare (Nagayo, Mitamura, Tamiya & Tenjin), 13 L. fuji Kuwata, Berge & Philip, two L. himizu (Sasa, Kumada, Hayashi, Enomoto, Fukuzumi & Obata), two Neotrombicula japonica (Tanaka, Kaiwa, Teramura & Kagaya), one Gahrliepia saduski Womersley, and three Walchia ogatai Sasa & Teramura, were taken from 240 soil samples (40 samples, six times at intervals of 2-4 wk). From the above species composition, L. scutellare is suspected to be the sole vector of scrub typhus in the survey area, where the disease is known to be caused by two serotypic strains of Rickettsia tsutsugamushi Ogata, Kawasaki and Kuroki. L. scutellare larvae rapidly increased in number in late October to form an acuminate peak of abundance in early November, followed by a gradual wane.

Agriculture↗
PubMed1994

Infectivity and early antibody response to Borrelia burgdorferi sensu lato isolated in Japan in outbred mice.

Borrelia burgdorferi sensu lato isolated from Ixodes ovatus (B. japonica), I. persulcatus and patients with erythema migrans (EM) in Japan were determined on infectivity and arthritis induction-activity in outbred mice. Infectivity of B. japonica was weak and did not induce the development of footpad swelling by subcutaneous (s.c.) inoculation into the footpad. Challenged strain, NO129-M of B. japonica, to ddY mice were reinoculated to the mice at various cell numbers (1 x 10-1 x 10(6) cells/mouse). The strain isolated from the mouse did not reinfect ddY mice and did not induce the production of specific antibody to the homologous strain. On the other hand, strains from I. persulcatus and patients with EM in Japan infected the mice and induced a serious inflammatory response in Borrelia-inoculated footpad as well as strains belonging to the three genospecies, B. burgdorferi sensu stricto, B. garinii, and B. afzelii, related to Lyme disease, from North America and Europe. The mice were infected with 10 cells of strain HP1 isolated from I. persulcatus in Hokkaido and of strain 297 isolated from a patient in the U.S.A. by subcutaneous inoculation into the hind footpad, or by intradermal inoculation into the back. Antigens of ca. 20, 23-24 (Osp C), 29, 39, 41 (flagellin) and 45 kDa reacted with the pooled sera from mice inoculated with strains HP1 and 297, but Osp A and Osp B did not.

Animals↗
PubMed1994

Correlation of octanol-water partition coefficients with capacity factors measured by micellar electrokinetic chromatography.

Micellar electrokinetic chromatography (MEKC) was used to measure hydrophobicity of 18 aromatic compounds. The capacity factors, which are proportional to the micelle-water distribution coefficients, were closely correlated with the octanol-water partition coefficients. The addition of Brij 35 to the charged micelle was effective in improving the correlation because the surface charges of the micelle were shielded.

Chromatography↗
PubMed1994

Influence of the illuminance and spectral composition of surround fields on spatially induced blackness.

The influence of the illuminance and spectral composition of monochromatic surround fields on spatially induced blackness was investigated. The amount of induced blackness in a white 50' central field was measured as a function of the illuminance of monochromatic 64'-120' surround fields with a color-naming method. The function relating induced blackness to log surround illuminance was described by either the logistic function or the Weibull function. Action spectra for blackness were determined from those functions and were also measured directly with the method of adjustment. These action spectra indicated that blackness induction was determined only by the illuminance of the surround, regardless of the blackness level at the criteria and the wavelength of the surround. It was concluded that there is no chromatic contribution from the chromatic surround to blackness induction.

Adult↗
PubMed1993

Apparent relative size and depth of moving objects.

The effects of the relative velocities of moving objects on their apparent relative size and depth were investigated with the aid of square patterns generated on a CRT display by a microcomputer. The observer matched the apparent sizes of squares, arranged in two or more rows that moved with different velocities, and made judgments of the apparent relative depth of the rows. In many conditions, squares moving more slowly were perceived as larger in size than those moving faster, regardless of the kind of depth responses, but in some conditions which contained strong depth cues the size responses seemed to be affected by perceived depth. The size-change effect of moving objects is discussed from the viewpoint of size-depth relationship.

Acceleration↗
PubMed1992

Prevalence of Lyme borreliosis spirochetes in ixodid ticks of Japan, with special reference to a new potential vector, Ixodes ovatus (Acari: Ixodidae).

To determine the vectors of Lyme borreliosis in Japan, the ixodid ticks taken in Hokkaido, Fukushima, Nagano, Ehime, and Kochi Prefectures were examined individually for spirochetal infections by culturing their midgut tissues in BSK medium. The cultivable spirochetes identified as Borrelia burgdorferi were detected in Ixodes persulcatus Schulze adults (15.5% of 634), nymph (6.7% of 15) and Ixodes ovatus Neumann adult (9.6% of 188) from Hokkaido, I. ovatus adults (25.5% of 47) from Fukushima, and I. persulcatus adults (21.7% of 143) and I. ovatus adults (27.1% of 85) from Nagano. However, 72 Haemaphysalis spp. from Ehime and Kochi were free from spirochetal infection. I. persulcatus is a vector of Lyme borreliosis in the Far East, but in Japan, I. ovatus may also transmit the spirochetes to human and feral animals.

Animals↗
PubMed1992

Epidemiology of Tsutsugamushi disease in relation to the serotypes of Rickettsia tsutsugamushi isolated from patients, field mice, and unfed chiggers on the eastern slope of Mount Fuji, Shizuoka Prefecture, Japan.

A total of 59 strains of Rickettsia tsutsugamushi were isolated from patients (24 isolates), Apodemus speciosus mice (30 isolates), and unfed larvae of Leptotrombidium scutellare (2 isolates) and Leptotrombidium pallidum (3 isolates) in the Gotenba-Oyama District, Shizuoka Prefecture, Japan. All these isolates were classified into the three serotypes Karp, Kawasaki, and Kuroki based on reactivity with strain-specific monoclonal antibodies. Kawasaki- and Karp-type rickettsiae were isolated from L. scutellare and L. pallidum, respectively, and the geographic distribution of patients and rodents infected with these two types of rickettsiae coincided with the areas densely populated by the respective chiggers. From these results, we conclude that Kawasaki-type rickettsiae are transmitted by L. scutellare and Karp-type ones are transmitted by L. pallidum. Kawasaki-type rickettsial infections were prevalent in early autumn, and Karp-type infections showed a peak of occurrence in the late autumn, reflecting the seasonal fluctuations of L. scutellare and L. pallidum. Isolates of Kuroki-type rickettsiae were obtained only from four patients in October and November, and the relationship between this type of rickettsia and its vector species could not be fully defined.

Animals↗
PubMed1992

Characterization of Borrelia burgdorferi isolated from Ixodes persulcatus and Ixodes ovatus ticks in Japan.

The Lyme disease spirochete Borrelia burgdorferi was detected in the adult stage of the ixodid ticks Ixodes persulcatus and I. ovatus collected in various localities in Japan. The total prevalence values were 16.6% of 777 I. persulcatus and 23.6% of 687 I. ovatus. Sixty-two (63.9%) of 97 isolates from I. persulcatus contained the 30-34-kD heterogeneous outer surface protein A (OspA) that reacted with monoclonal antibody H5332. In contrast, all 128 isolates from I. ovatus were homogeneous with regard to the type of 30-kD OspA protein, and were different from the I. persulcatus isolates in their protein composition. These data suggest that the transmission cycle of B. burgdorferi in I. ovatus is not related to that in I. persulcatus. No cases of Lyme disease transmitted by I. ovatus have been confirmed in Japan, in spite of the abundance of human tick bites by this species. Accordingly, the spirochetes of I. ovatus are thought to be a variant of B. burgdorferi with low virulence.

Animals↗
PubMed1990

[Solid-state stability and preformulation study of a new parenteral cephalosporin antibiotics (E1040)].

In designing the dosage form, one major factor controlling their physicochemical properties is solid forms of the drug powder. The method for improving the physicochemical stability of unstable beta-lactam antibiotics is very important. E1040 is a novel parenteral 3-betaine type cephalosporin which has a broad antibacterial spectrum and potent activities against Citrobacter, freundii, Enterobacter cloacase, and glucose-non-fermentative bacteria, including P. aeruginosa. The present study was intended to provide the solid-state chemical stability of perenteral steril dry dosage form of E1040. The chemical stability differences among the various solid forms, dry amorphous, additive freeze dried amorphous solid and crystalline powder, were evaluated as a function of temperature by thermo stress tests. Freeze dried anhydrous amorphous form was the first steril dry dosage form investigated during the preformulation study. However, this compound is chemically unstable, in the titer of them, reduction are observed in the freeze dried amorphous solid. In order to select the most suitable solid form of E1040, two methods were used. One was crystalline solid and the other was NaCl additive freeze-dried formulation. Through our experiments, the solid-state chemical stabilization can be achieved by these two methods (effect of crystal structure and effect of NaCl additive).

Adjuvants, Pharmaceutic↗
PubMed1989

Pseudopolymorphism and phase stability in four solid forms of (6R,7R)-7-[2-(5-amino-1,2,4-thiadiazol-3-yl)-(Z)-2-methoxy- iminoacetamid]-3- [(4-carbamoyl-1-quinuclidinio)methyl]-8-oxo-5-thia-1-azabicyclo - [4,2,0]oct-2-ene-2-carboxylate (E1040).

(6R,7R)-7-[2-(5-Amino-1,2,4-thiadiazol-3-yl)-(Z)-2-methoxy- iminoacetamid]-3- [(4-carbamoyl-1-quinuclidinio)methyl]-8-oxo-5-thia-1-azabicyclo [4,2,0]oct-2-ene-2-carboxylate (1; E1040) was isolated as alpha-(decahydrate), beta-(pentahydrate), and gamma-form (anhydrate) crystals and the X-ray amorphous form. The relationship between the pseudopolymorphic crystal forms of this compound and water content was studied by X-ray diffractometry, coulometric moisture analysis, thermal analysis, and hygroscopic and vacuum-freeze-drying experiments. The phase transition of crystalline 1 clearly indicated the effect of water content on dehydration. During dehydration, hydrated alpha-form (decahydrate) crystals and beta-form (pentahydrate) crystals became anhydrate gamma-form crystals, with the diffraction angle shifting toward shorter spacing accompanied by line broadening. These results indicate conversion of hydrate 1 crystals to the anhydrous form and contraction of the crystal lattice. It was estimated that the decahydrate (alpha-form) crystals contain 8 mol/mol crystal water and 2 mol/mol adhesion water, and that the pentahydrate (beta-form) crystals contain 4 mol/mol crystal water and 1 mol/mol adhesion water. These estimates were made by comparing the data from equilibrium hydration experiments and vacuum-freeze-drying experiments. It thus follows that gamma-form crystals are anhydrate and the X-ray amorphous form exists in either the hydrous or anhydrous form.

Adhesiveness↗
PubMed1989

Influence of achromatic surrounds on categorical perception of surface colors.

Color samples selected from the OSA Uniform Color Scales set were seen isolated in a dark field, illuminated by hidden projectors. These appeared as self-luminous aperture colors when thus isolated. We employed a categorical color-naming procedure to assess color appearance. Achromatic surrounds of 33 min width, if adjacent to samples subtending about 2.2 deg, were sufficient to render normal categorical surface-color perception. As the size of surrounds decreased, color naming shifted from that normally observed in the surface-color mode to that appropriate to the aperture-color mode. For isolated samples, brown was almost never seen, being most often replaced by orange; a white border less than one-sixtieth the width of the color samples was sufficient to restore its perception in an otherwise dark field. The reflectance of the surround and the gap between test and surround stimuli were also examined and found to be important factors in surface color perception, whereas the overall luminance level was not.

Adult↗
PubMed1989

Partial color constancy of isolated surface colors examined by a color-naming method.

Color samples selected from the OSA Uniform Color Scales set were viewed without any surround. Separate light sources were used to illuminate the samples and to control the state of adaptation of the subject, thereby separating two factors that are normally confounded. A color-naming procedure was used to assess shifts in color appearance produced by altering the spectral distributions of one or both light sources. The results confirm that chromatic adaptation, when it is the only factor operating, can mediate partial color constancy.

Color Perception↗