Search PubMed⌕ Search

Biomedical subjects

H Yaguchi

Publications and source records attributed to H Yaguchi.

87 records · Page 5Linked to original sources
PubMed1987

Heterochromatic brightness matching with checkerboard patterns.

Heterochromatic brightness matches with checkerboard patterns made up of a white reference and a chromatic test element for various element sizes from 3' to 2 degrees 30' square and with a 5 degrees bipartite field were carried out with a color cathode-ray tube. The brightness-to-luminance (B/L) ratios of six chromatic stimuli were obtained, and the brightness additivity for the mixture of red and green was tested. When the reference and test elements were juxtaposed without a gap, the B/L ratio of the test chromatic stimulus decreased with decreasing element size. Brightness additivity failed for an element size of 30' and a 5 degrees bipartite field. Brightness additivity held for a small element size of 3'. When the reference and test elements were separated by a gap 3' in width, the B/L ratios were generally greater than unity regardless of element size. Under these conditions, the brightness additivity also failed for the smallest, that is, the 3' element size.

Adult↗
PubMed1984

Mesopic luminous-efficiency functions for various adapting levels.

The luminous-efficiency functions for a centrally viewed 10 degrees field were measured by heterochromatic brightness matching for various retinal illuminance levels of a reference field at various adapting levels. The subject was always presented with a 45 degrees white adapting light except when the test field for brightness matching was substituted for the adapting field for 500 msec. In order to investigate the contributions of rods and cones to the brightness sensation, the luminous-efficiency curves obtained from two subjects were analyzed with the Ikeda-Shimozono formula. When the subject was presented with an adapting light above about 100 trolands (Td), the luminous-efficiency function became photopic at any luminance level of the test field; similarly, when the test field was at 100 Td, the luminous-efficiency function was photopic at any adapting level.

Adaptation, Ocular↗
PubMed1983

Subadditivity and superadditivity in heterochromatic brightness matching.

Heterochromatic brightness matches were carried out between bichromatic mixtures of lambda 1 and lambda 2, and a 100 td white reference light of 2 degrees arc. Two characteristic properties of additivity failure were observed. One is the asymmetrical property of additivity failure, that is a remarkable brightness reduction at the luminance ratio where the hue cancellation occurred. The other is the superadditivity for a mixture of a violet and a white or a middle-wave light. These properties were accounted for by a nonlinear vector model on the assumption that the opponent-color channels outputs were nonlinearly transferred to the brightness perception.

Adult↗
PubMed1982

Luminous-efficiency functions for point sources.

Luminous-efficiency functions for small fields were measured with flicker photometry and heterochromatic brightness-matching methods for the same two subjects. For the larger stimuli (22.9 and 11.5'), the luminous-efficiency functions differed between the two methods. Those obtained by flicker photometry showed a simple narrow shape, whereas those obtained by heterochromatic brightness matching showed increased sensitivity at short and long wavelengths. The difference however, decreased as the stimulus was reduced to 2.3', and the luminous-efficiency functions converged to curves that resemble the CIE V (lambda ) or Judd's modification. It seems unnecessary to introduce a new luminous-efficiency function for point sources, which is fortunate for practical purposes.

Adult↗
PubMed1982

Brightness luminous-efficiency functions for 2 degrees and 10 degrees fields.

CIE V lambda is not representative of luminous-efficiency function based on heterochromatic brightness matching. CIE Technical Committee 1.4 Vision (TC 1.4) presented a 2 degrees brightness-matching luminous-efficiency function based on studies of a total of 31 observers to supplement the V lambda. In view of their importance to illuminating engineering and physiological optics, we analyzed the various conditions under which these seven studies were conducted. Data from three of the groups are considered inappropriate, and we revised the TC 1.4 brightness luminous-efficiency function based on the remaining 19 subjects. Data from 18 Japanese subjects, coming from five research groups, are added to the above subjects, and an averaged luminous-efficiency function is derived. The result does not appreciably differ from the revised TC 1.4 function and is considered to represent a brightness-matching standard luminous-efficiency function for a 2 degrees field. A brightness luminous-efficiency function for a 10 degrees field based on nine Japanese subjects is presented. It differs from the 2 degrees function only at short wavelengths when the functions are normalized at 570 nm. A theoretical approach for using the brightness-matching luminous-efficiency function to assess the brightness of 2 degrees broadband sources is introduced, and some numerical examples are given.

Humans↗
PubMed1979

Relationship between the intestinal permeability to macromolecules and invasion of septicemia-inducing Escherichia coli in neonatal piglets.

The influence of age and diet on the invasion of septicemia-inducing Escherichia coli and the endocytotic activity of the small intestinal epithelium were examined in colostrum-deprived conventional and gnotobiotic piglets orally infected with E. coli 078. The piglets infected at birth and the animals fed glucose-amino acids solution and infected at 3 days after birth soon suffered from septicemia caused by the invasion of E. coli 378. The piglets fed artifical milk and infected at 3 days after birth, however, showed resistance to the invasion of E. coli in the absence of passively acquired serum gamma globulin. The endocytotic activity of the small intestinal epithelium was more intense in the former than in the latter piglets. Some of the ileal epithelial cells of the piglets infected at birth contained organisms, although these cells were morphologically intact and showed intense endocytosis. The present results suggest that the intestinal permeability to macromolecules, which depends on the endocytotic activity of the small intestinal epithelium, might predispose neonatal piglets to colisepticemia.

Animals↗
PubMedDate not supplied

Dynamics of cell wall formation in fission yeast, Schizosaccharomyces pombe.

Studies on the dynamics of surface and intracellular structures during cell wall formation from the reverting protoplast of Schizosaccharomyces pombe were reviewed, and the correlation between cell wall formation and actin cytoskeleton, which is the most important conductor of the mechanism, is described in this paper. A close spatial and temporal relationship between actin cytoskeleton and cell wall formation was found by using wild type and actin point-mutant cps8 of S. pombe. Concomitant with the cell wall formation, dynamic behavior of the intracellular secretion machinery, especially the Golgi apparatus and secretory vesicles, was analyzed by three-dimensional reconstruction of 40 to 80 serial sections at five reverting stages. Total reverting protoplast volume increased by 3.8 and 4.3 times at 3 and 5 h, respectively, and the volume of the Golgi apparatus in the corresponding stages increased 2.3- and 2. 5-fold over the same periods. The number of secretory vesicles also markedly increased by 3.4 and 5.8 times over that of the corresponding reverting protoplasts. Actin point-mutant cps8 cells have abnormal structure in the cell wall and septum, and the distribution pattern of the actin cytoskeleton during the reversion process was different from wild-type protoplasts. The profiles of actin showed one or two thick cables and patches in the cytoplasm which remained throughout reversion. The development of crosslinkage of the glucan fibrils which are beta-1,3-glucan in nature on the reverting protoplast surface was defective; the glucan networks consisted of thin, rope-shaped fibrils up to 30 nm in width which formed a ribbon-shape 200 nm wide in wild-type reverting protoplasts. The intrafibrillar space is not filled with amorphous particles of alpha-galactomannan in nature. The secretion machinery was seen to have a similar profile as the wild type. The above results suggest that actin cytoskeleton may control secretion of beta-1,6-glucan and other cell wall substances such as alpha-glucan and alpha-galactomannan rather than beta-1,3-glucan. Study of the role of actin cytoskeleton in the cell wall formation is contributing to the development of antifungal agents together with basic cell biology.

Actins↗
PubMedDate not supplied

Transferrin concentration in seminal plasma with special reference to serum hormone levels in infertile men.

The concentration of transferrin in seminal plasma and serum levels of LH, FSH, testosterone, and prolactin were measured in 94 male patients attending our infertility clinic. The concentration of transferrin in patients with azoospermia was lowest among azoospermia, oligozoospermia, and normozoospermia groups. There was significant positive correlation between the concentration of transferrin in seminal plasma and sperm density. However, seminal plasma transferrin was inversely correlated with serum levels of LH, FSH, and prolactin, respectively. It is suggested that transferrin in seminal plasma contributes to the activation of seminiferous tubules and can be used as a reliable index of Sertoli cell function.

Adult↗