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Biomedical subjects

K Uchikawa

Publications and source records attributed to K Uchikawa.

At least 37 records · Page 2Linked to original sources
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↗
PubMed1988

Polymorphic differences in alpha- and beta-form crystals of 2R, 4S, 6-fluoro-2-methyl-spiro[chroman-4,4'-imidazoline]-2',5-dione (M79175) as determined by X-ray diffraction, infrared spectroscopy, and differential scanning calorimetry.

Polymorphic differences in alpha- and beta-form crystals of 2R, 4S, 6-fluoro-2-methyl-spiro[chroman-4,4'-imidazoline]-2',5-dione (M79175; 1) were studied by X-ray diffractometry, infrared spectroscopy, and differential scanning calorimetry. X-ray powder diffraction indicated the longest spacing of the unit cells to be 14.9 and 12.4 A for the alpha- and beta-form crystals, respectively. The infrared spectra showed the absorption band assigned to NH streching vibration for the alpha-form crystals to be centered at 3250 cm-1 and that for the beta-form crystals to split into two peaks, at 3150 and 3425 cm-1. The enthalpies of fusion were 26.3 kJ/mol at 517.5 K and 31.3 kJ/mol at 501.0 K, respectively. Transformation from the beta- to alpha-form was observed at various heating rates, which were enhanced by the presence of a small amount of alpha-form crystals previously added to the beta-form. The former appeared to serve as a source of nuclei for the growth of both forms. These results confirm that the alpha-form crystal is more stable than the beta-form.

Calorimetry, Differential Scanning↗
PubMed1988

Myobiidae (Acarina, Trombidiformes) associated with minor families of Chiroptera (Mammalia) and a discussion of phylogeny of chiropteran myobiid genera.

Three new genera, Natalimyobia n. gen., Furipterobia n. gen., and Mizopodobia n. gen., are erected for the myobiid mites associated with the chiropteran families Natalidae, Furipteridae, and Myzopodidae, respectively. The definitions for the genera Nycterimyobia, Thyromyobia, and Mystacobia, previously known only from one sex, are refined with the description of the opposite sex. Two different types of myobiid genera, one being represented by larger elongate forms and the other by smaller rounded forms, often share hosts within a chiropteran family. A larger elongate myobiid genus is associated exclusively with each chiropteran family. Phylogenetic relationships among 16 larger-sized myobiid genera, including the 3 new ones, are deduced based primarily on the structure of female genitalia and secondarily on the formation of legs and chaetotaxy of idiosoma and legs. These relationships are regarded as being parallel to those of the chiropteran host families.

Animals↗
PubMed1987

Categorical color perception of Japanese observers: comparison with that of Americans.

Ten native Japanese observers named 424 colors of the OSA Uniform Color Scales set using monolexemic color terms of their choice. The results are compared with those from seven American subjects previously studied by Boynton and Olson. It is concluded, in full agreement with the original thesis of Berlin and Kay, that there are eleven basic color terms in each language, each of which describes a fundamental color sensation dependent upon an underlying physiology that does not differ between the two groups.

Adult↗
PubMed1987

Color discrimination and appearance of short-duration, equal-luminance monochromatic lights.

Wavelength-discrimination thresholds were measured with stimulus durations of 8, 500, and 2000 msec for test wavelengths of 420 to 630 nm at equal luminance of 100 Td. With the short duration of 8 msec, the discrimination thresholds increased for most wavelengths, but they decreased for the wavelengths near 460 nm. This short-duration wavelength-discrimination function was found to be quite different in shape from that at 2000 msec but similar to one at a low-luminance level of 2.5 Td at 500 msec. Hue, saturation, and brightness of short-duration monochromatic stimuli were also estimated by a color-naming procedure. Changes in color appearance produced by a short stimulus duration were consistent with the tendency that was characterized as tritanopic in previous studies. However, the present results on color discrimination do not necessarily support this tritanopic effect. A possible explanation is discussed.

Adult↗
PubMed1987

Myobiid mites (Trombidiformes: Myobiidae) associated with the vampire bats (Chiroptera: Phyllostomatidae) and information on host taxonomy deduced from them.

Eudusbabekia diphyllis n. sp. and Eudusbabekia diaemis n. sp., parasitic on Diphylla ecaudata and Diaemus youngi, respectively, are described, and measurements for Eudusbabekia arganoi (Vomero) are presented. The vampire bats are here treated as representatives of the family Phyllostomatidae on the basis of the occurrence of these mites on them. These 3 mites are closest to those parasitic on bats of the genus Phyllostomus, among all the known mites of the genus Eudusbabekia, suggesting a phylogenetic affinity between vampire bats and Phyllostomus. Asymmetry of different levels of legs I is observed in adults of E. arganoi and E. diaemis, whereas E. diphyllis bears bilaterally symmetrical legs I. From this, the phylogenetic line, E. diphyllis-E. arganoi-E. diaemis, is proposed on the premise that asymmetry of any part of the external body has been fostered and preserved in the parasites.

Animals↗
PubMed1986

Structural studies on the minor teichoic acid of Bacillus coagulans AHU 1631.

The minor teichoic acid linked to glycopeptide was isolated from lysozyme digests of Bacillus coagulans AHU 1631 cell walls, and the structure of the teichoic acid moiety and its junction with the peptidoglycan were studied. Hydrolysis of the teichoic-acid--glycopeptide complex with hydrogen fluoride gave a nonreducing oligosaccharide composed of glucose, galactose and glycerol in a molar ratio of 3:1:1 which was presumed to be dephosphorylated repeating units of the polymer chain. From the results of structural analysis involving NaIO4 oxidation, methylation and acetolysis, the above fragment was characterized as glucosyl(beta 1----3)glucosyl(beta 1----6)galactosyl(beta 1----6)glucosyl(alpha 1----1/3)glycerol. In addition, the Smith degradation of the complex yielded a phosphorus-containing fragment identified as glycerol-P-6-glucosyl(beta 1----1/3)glycerol. These results led to the most likely structure for the repeating units of the teichoic acid, -6[glucosyl(beta 1----3)]glucosyl(beta 1----6)galactosyl(beta 1----6)glucosyl(alpha 1----1/3)glycerol-P-. The minor teichoic acid, just like the major teichoic acid bound to the linkage unit, was released by heating the cell walls at pH 2.5. The mild alkaline hydrolysis of the minor teichoic acid after reduction with NaB3H4 gave labeled saccharides characterized as glucosyl(beta 1----6)galactitol and glucosyl(beta 1----3)glucosyl(beta 1----6)galactitol, together with a large amount of the unlabeled repeating units of the teichoic acid chain. Thus, the minor teichoic acid chain is believed to be directly linked to peptidoglycan at the galactose residue of the terminal repeating unit without a special linkage sugar unit.

Acetone↗
PubMed1986

Structural studies on teichoic acids in cell walls of several serotypes of Listeria monocytogenes.

Structural studies were carried out on the teichoic acids in cell walls of Listeria monocytogenes serotypes 3a, 4b, 4f, 6, and 7. The structure of the dephosphorylated repeating units, obtained by treatment with 46% hydrogen fluoride or alkaline hydrolysis, was examined by methylation analysis, acetolysis, and 1H-NMR spectroscopy. The results of Smith degradation of the teichoic acids and 13C-NMR spectroscopy led to the following most likely structures of the repeating units of the teichoic acids:----1-[N-acetylglucosaminyl(alpha 1----4)]ribitol-5-phosphate----for serotype 3a,----4-[galactosyl(alpha 1----6)][glucosyl(beta 1----3)]N -acetylglucosaminyl(beta 1----2)ribitol-5-phosphate----for serotype 4b,----4-[galactosyl(alpha 1----6)][N -acetylglucosaminyl(alpha 1----3)]N-acetylglucosaminyl(beta 1----2)ribitol -5-phosphate----for serotype 4f,----4-N-acetylglucosaminyl(beta 1----4)ribitol -5-phosphate----for serotype 6, and----1-ribitol-5-phosphate----for serotype 7. About 40% of the repeating units of the teichoic acid from serotype 4f were not substituted at C-3 of beta-N-acetylglucosaminyl residues.

Carbohydrate Conformation↗
PubMed1986

Structural studies on lipoteichoic acids from four Listeria strains.

The lipoteichoic acids were isolated from phenol extracts of four Listeria strains representing serotypes 4a, 4b, 6a, and 6 to compare the differences in structure of amphiphilic polysaccharides from various serotypes of Listeria spp. The lipoteichoic acids from the four strains examined had the same structure in both hydrophilic chains and lipid portions. On the basis of the results of nuclear magnetic resonance spectroscopy and Smith degradation, the hydrophilic chains were shown to be 1,3-linked poly(glycerol phosphate) in which some of the glycerol residues had alpha-galactosyl substituents. The lipid portions were released by treatment with 46% hydrogen fluoride or 98% acetic acid. They were determined to be 3(1)-(2'-O-alpha-D-galactopyranosyl-alpha-D-glucopyranosyl)-1(3), 2-diacylglycerol and 3(1)-[6'-phosphatidyl-2'-O-(alpha-D-galactopyranosyl)-alpha- D-glucopyranosyl]-1(3),2-diacylglycerol. The degrees of glycosyl substitution and proportions of the two lipids varied to some extent among these four strains.

Acetates↗