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PubMed1992

Chromaticity analysis of immunostained tumor specimens.

In order to evaluate the correlation between immunohistochemical and morphometric data on the same histological sections, we have developed a flexible color image analyzer (Microcomputer-Assisted Picture Processing System type II, MAPPS-II), and established an effective method to analyze the immunostained colorectal neoplasms based on the color recognition theory of human visual system. Colorectal adenomas and adenocarcinomas were stained with a monoclonal antibody C 12, which recognizes abnormal H antigen, using Avidin-Biotin method and diaminobenzidine (DAB, brown dye). Nuclei were stained with Hematoxylin (blue dye). Density and colorimetric analyses revealed two results: (A) Separation of immunostained brown area from blue nuclei was best performed by plotting the representative sample areas on a standard chromaticity diagram, which displays the hue and saturation of colors simulating color of human visual system. (B) After separation of immunostained areas, usual density analysis was useful for the assay of nuclear morphometric information. Using these programs, normal mucosa was negative for C 12, and showed low nuclear/cytoplasmic ratio (NCR). Adenoma was occasionally focally positive for C 12, and showed medium NCR. Carcinomas were C 12 positive, and showed high NCR. Our method permits nuclear counterstaining by hematoxylin instead of low contrast methyl green, which will widen the field of combined immunohistochemical and morphometric study.

Adenocarcinoma↗
PubMed1996

Chromatic visual phenomenon caused by a subluxed intraocular lens.

A 74-year-old man developed an unusual chromatic aberration as a complication of cataract extraction surgery with posterior chamber intraocular lens implantation. The patient could see the location and color of one of the haptics of the dislocated lens. His symptoms resolved with miotic therapy.

Aged↗
PubMed2001

Neural correlates of chromatic motion perception.

A variety of psychophysical and neurophysiological studies suggest that chromatic motion perception in the primate brain may be performed outside the classical motion processing pathway. We addressed this provocative proposal directly by assessing the sensitivity of neurons in motion area MT to moving colored stimuli while simultaneously determining perceptual sensitivity in nonhuman primate observers. The results of these studies demonstrate a strong correspondence between neuronal and perceptual measures. Our findings testify that area MT is indeed a principal component of the neuronal substrate for color-based motion processing.

Animals↗
PubMedDate not supplied

Behavioral and neural effects of chromatic isoluminance in the primate visual motion system.

We have previously reported that the responses of individual neurons in macaque visual area MT elicited by movement of contrast-reversing heterochromatic red/green borders are largest when the two hues are "balanced" or isoluminant (Dobkins & Albright, 1994). This "neural" isoluminant point was found to vary somewhat across the sample of neurons. Here, we compare the average neural isoluminant point in area MT to a behavioral measure of isoluminance, obtained using a modification of an oculomotor procedure developed by Chaudhuri and Albright (1992). These behavioral estimates of isoluminance closely parallel the neuronal data obtained from area MT. In accordance with previous evidence (e.g. Lee et al., 1988; Kaiser et al., 1990; Valberg et al., 1992), this correlation suggests that activity within the dorsal/magnocellular stream underlies behavioral expression of chromatic isoluminance.

Animals↗
PubMedDate not supplied

Effect of foveal tritanopia on reaction times to chromatic stimuli.

To investigate the effect of foveal inhomogeneities on sensitivity to chromatic stimuli, we measured simple reaction times (RTs) and detection thresholds to temporally and spatially blurred isoluminant stimuli at retinal eccentricities from 0 deg to 8 deg. Three color-normal subjects participated. Contrast gain was derived from the slope of the RT versus contrast function. With a Gaussian spatial distribution (S.D. = 0.5 deg) and modulation between white (CIE x, y, L = 0.31, 0.316, 12.5 cd x m(-2)) and blue (MBDKL 90 deg), gain was maximal at about 2-deg eccentricity and declined by approximately 1 log unit towards the center and the periphery. The red (0 deg) and green (180 deg) cardinal axes showed maximum gain in the center, whilst the yellow (270 deg) data were intermediate. Although the spatial extent of the Gaussian spot was much larger than the S-cone free zone, we wished to determine whether foveal tritanopia was responsible for the marked drop in sensitivity to the 90-deg stimulus. To align the color vector along a tritan line, we used a smaller disk (0.3 deg) with a blurred edge and measured detection threshold, rotating the vector until minimum central sensitivity was obtained. Other workers have used transient tritanopia or minimally distinct border to similar effect. By repeating this at different locations in color space, a group of vectors were obtained. These converged near to the S-cone co-punctal point, evidence that they lay along tritan confusion lines. These threshold findings were then confirmed using the RT-derived contrast gain function. The tritan vectors were less pronounced as stimulus size increased. With the vector optimized to produce foveal tritanopia, the RT gain versus eccentricity functions for the 90-deg and 270-deg stimuli both fell markedly in the center and periphery, and sensitivity peaked at about 3-deg eccentricity. There are some similarities between these findings and the underlying photoreceptor distributions. As a result, there is a greater difference in gain between red-green and blue-yellow systems in the center than in the near periphery. We conclude that the RT versus contrast function is a sensitive index of foveal opponency.

Color Perception↗
PubMed2006

Chemical speciation and bioaccessibility of arsenic and chromium in chromated copper arsenate-treated wood and soils.

This research compares the As and Cr chemistry of dislodgeable residues from chromated copper arsenate (CCA)-treated wood collected by two different techniques (directly from the board surface either by rubbing with a soft bristle brush or by rinsing from human hands after contact with CCA-treated wood) and demonstrates that these materials are equivalent in terms of both the chemical form and bonding of As and Cr and in terms of the As leaching behavior. This finding links the extensive chemical characterization and bioavailability testing that has been done previously on the brush-removed residue to a material that is derived from human skin contact with CCA-treated wood. Additionally, this research characterizes the arsenic present in biological fluids (sweat and simulated gastric fluid) following contact with these residues. The data demonstrate that in biological fluids the arsenic is present primarily as free arsenate ions. Arsenic-containing soils were also extracted into human sweat to evaluate the potential for arsenic dissolution from soils at the skin surface. For soils from field sites, only a small fraction of the total arsenic is soluble in sweat. Based on comparisons to reference materials that have been used for in vivo dermal absorption studies, these findings suggest that the actual relative bioavailability via dermal absorption of As from CCA residues and soil may be well below the current default value of 3% used by U.S. EPA.

Arsenates↗
PubMed2000

Anomalous stereochemistry of pyrazolato-3,5-dicarboxylato-bridged dinuclear chromate(III) complexes containing ethylenediamine-N,N'-dicarboxylates with entrapped unstable conformations: X-ray structure of Na[Cr2(eddp)(mu-pzdc)].6H2O.

Several new pyrazolato-3,5-dicarboxylato (pzdc) bridged dinuclear chromate(III) complexes containing linear tetradentate O-N-N-O type ligands were synthesized and structurally characterized. Among them, the X-ray structure of the eddp complex Na[Cr2(eddp)(mu-pzdc)].6H2O (eddp = ethylenediamine-N,N'-dipropionate) was determined to have a (sym-cis)-(unsym-cis) geometrical configuration with intramolecular three-center hydrogen bonds, entrapping the unfavored sym-cis configuration for the Cr(eddp) moiety as well as the favored unsym-cis one. As a pair of positional disorders, there were also found to be two conformational isomers with respect to the absolute configurations of the coordinated asymmetric nitrogen atom at the G (in-plane) ring for the unsym-cis moiety. Moreover, chiral pzdc-bridged dinuclear complexes with another type of O-N-N-O ligand, 1,2-cyclohexanediamine-N,N'-diacetate (cdda), were successfully synthesized, isolated, and characterized by column chromatographic behavior, elemental analysis, and chiroptical spectra. There were two diastereomers for Na[(R,R-cdda)Cr(mu-pzdc)Cr(S,S-cdda)] and only one isomer for Na[(R,R-cdda)Cr(mu-pzdc)Cr(R,S-cdda)] and Na[(R,R-cdda)Cr(mu-pzdc)Cr(edda)] (R,R- or S,S- and R,S-cdda = R,R-trans- or S,S-trans- and R,S-cis-1,2-cyclohexanediamine-N,N'-diacetate, and edda = ethylenediamine-N,N'-diacetate). From their circular dichroism (CD) spectra, these complexes could exhibit the delta-delta absolute configuration with ((sym-cis-R,R-cdda)-(unsym-cis-edda or S,S- or R,S-cdda)) geometrical configuration, indicating the abnormal eq-eq (N-Ceq) configuration for the R,R-cdda. The comparison among the CD spectra of the ((cdda)-(cdda)) complexes revealed that two diastereomers of the ((R,R-cdda)-(S,S-cdda)) complex correspond to the conformational isomers resulting from the difference in geometrical orientations of the secondary amine protons on two coordinated asymmetric nitrogen atoms with the opposite absolute configuration in the unsym-cis-S,S-cdda moiety. In a series of the pzdc-bridged Cr(III) complexes the anomalous conformations in two different geometrical configurations could be entrapped probably owing to stereognostic coordination through the intramolecular N-H...O hydrogen bond interaction.

Journal Article↗
PubMed2002

One-dimensional assembling of diiodo[phthalocyaninato(1-)] chromate(III) molecules through neutral I(2) molecules. Alternating ferro- and antiferromagnetic interactions in the metal-radical system.

Crystals of diiodo[phthalocyaninato(1-)] chromate(III) diiodine, CrPcI(2).I(2), were grown directly in the reaction of chromium powder with 1,2-dicyanobenzene under a stream of iodine at about 250 degrees C. The CrPcI(2).I(2) complex crystallizes in the centrosymmetric space group of the triclinic system with one molecule per unit cell, with the cell dimensions a = 7.851(2) A, b = 8.402(2) A, c = 12.668(3) A, alpha = 80.32(3)(o), beta = 74.06(3)(o), gamma = 82.33(3)(o), and V = 788.7(3) A(3). The X-ray single-crystal analysis shows that each of the centrosymmetric CrPcI(2) molecules is bridged by a neutral I(2) molecule (detected also by Raman spectroscopy) and develops a polymeric one-dimensional structure. The magnetic measurements have been carried out in the temperature range 300-2 K. Temperature dependence of the effective magnetic moment, mu(eff), shows the ferro- and antiferromagnetic interactions in the system of the paramagnetic central Cr(3+) ion and surrounding pi-conjugated radical ligand Pc(1-). The conductivity measurement on a polycrystalline sample exhibits weak temperature dependence (dsigma/dT < 0). The UV-vis spectrum exhibits, besides the B- and Q-bands, one additional band assigned to the electronic transition from a deeper level to the half-occupied HOMO level in the one-electron oxidized phthalocyaninato(1-) radical ligand.

Journal Article↗
PubMed2002

Kinetics and mechanism of chromate reduction with hydrogen peroxide in base.

[Cr(VI)O(4)](2)(-) is reduced to [Cr(V)(O(2))(4)](3)(-) by hydrogen peroxide in strongly basic media where the acid dissociation of H(2)O(2) (pK(a) = 11.65) is appreciable. The reaction is first order in chromium(VI) and inhibited by hydroxide. The hydrogen peroxide dependence is defined by the form of the effective pseudo-first-order rate constant: k(eff) = [H(2)O(2)](3)/(K(1) + K(2)[H(2)O(2)] + K(3)[HO(2)(-)]) with K(1) = 175(43) s x M(3), K(2) = 403(18) s x M(2), and K(3) = 1422(34) s x M(2). Hydrogen peroxide anion initially attacks chromate, and subsequent equilibrium steps that exchange oxo groups for three peroxo groups precede a rate-determining, one-electron, intramolecular reduction step.

Journal Article↗
PubMed2005

Selective detection of catecholamines by synthetic receptors embedded in chromatic polydiacetylene vesicles.

A new detection scheme for catecholamines was constructed through embedding synthetic receptors within vesicles comprising phospholipids and polydiacetylene. Fluorescence emission of the polydiacetylene was induced through specific interactions between the soluble ligands and the vesicle-incorporated hosts. The system demonstrated remarkable selectivity among structurally similar ligands and achieved much lower detection thresholds compared to that of other reported catecholamine sensors. The chromatic assembly provides a generic route for high sensitivity detection of ligand-receptor interactions.

Acetylene↗
PubMed1987

Effects of flicker-induced depth on chromatic subjective contours.

Two experiments examined the dependence of illusory colors on boundary salience and depth stratification by using flicker-induced depth. The first used a subjective-contour stimulus that appeared as a translucent colored rectangle covering a set of inducing circles and a dark background. The circles were then flickered so as to be perceived as background, and the previously dark background moved forward and appeared as foreground. Simultaneously, the chromatic subjective contour was eliminated. In the second experiment, a subjective-contour (faces/vase-concentric squares) figure was tinted with the McCollough effect, which produced a strong subjective color edge. This edge was visible only with the faces/vase percept and not in the squares percept. Flickering the target locked it into the square configuration because in this case the flicker held the entire pattern in the same depth plane. This eliminated the subjective color edge. Depth stratification and subjective color blockage were maximal at a flicker rate of 6 Hz.

Color Perception↗
PubMed2001

Self-assembly of mesoscopically ordered chromatic polydiacetylene/silica nanocomposites.

Nature abounds with intricate composite architectures composed of hard and soft materials synergistically intertwined to provide both useful functionality and mechanical integrity. Recent synthetic efforts to mimic such natural designs have focused on nanocomposites, prepared mainly by slow procedures like monomer or polymer infiltration of inorganic nanostructures or sequential deposition. Here we report the self-assembly of conjugated polymer/silica nanocomposite films with hexagonal, cubic or lamellar mesoscopic order using polymerizable amphiphilic diacetylene molecules as both structure-directing agents and monomers. The self-assembly procedure is rapid and incorporates the organic monomers uniformly within a highly ordered, inorganic environment. Polymerization results in polydiacetylene/silica nanocomposites that are optically transparent and mechanically robust. Compared to ordered diacetylene-containing films prepared as Langmuir monolayers or by Langmuir-Blodgett deposition, the nanostructured inorganic host alters the diacetylene polymerization behaviour, and the resulting nanocomposite exhibits unusual chromatic changes in response to thermal, mechanical and chemical stimuli. The inorganic framework serves to protect, stabilize, and orient the polymer, and to mediate its function. The nanocomposite architecture also provides sufficient mechanical integrity to enable integration into devices and microsystems.

Acetylene↗
PubMed2001

Chromatic sensitivity of ganglion cells in the peripheral primate retina.

Visual abilities change over the visual field. For example, our ability to detect movement is better in peripheral vision than in foveal vision, but colour discrimination is markedly worse. The deterioration of colour vision has been attributed to reduced colour specificity in cells of the midget, parvocellular (PC) visual pathway in the peripheral retina. We have measured the colour specificity (red-green chromatic modulation sensitivity) of PC cells at eccentricities between 20 and 50 degrees in the macaque retina. Here we show that most peripheral PC cells have red-green modulation sensitivity close to that of foveal PC cells. This result is incompatible with the view that PC pathway cells in peripheral retina make indiscriminate connections ('random wiring') with retinal circuits devoted to different spectral types of cone photoreceptors. We show that selective cone connections can be maintained by dendritic field anisotropy, consistent with the morphology of PC cell dendritic fields in peripheral retina. Our results also imply that postretinal mechanisms contribute to the psychophysically demonstrated deterioration of colour discrimination in the peripheral visual field.

Animals↗
PubMed2002

Imperfect optics may be the eye's defence against chromatic blur.

The optics of the eye cause different wavelengths of light to be differentially focused at the retina. This phenomenon is due to longitudinal chromatic aberration, a wavelength-dependent change in refractive power. Retinal image quality may consequently vary for the different classes of cone photoreceptors, cells tuned to absorb bands of different wavelengths. For instance, it has been assumed that when the eye is focused for mid-spectral wavelengths near the peak sensitivities of long- (L) and middle- (M) wavelength-sensitive cones, short-wavelength (bluish) light is so blurred that it cannot contribute to and may even impair spatial vision. These optical effects have been proposed to explain the function of the macular pigment, which selectively absorbs short-wavelength light, and the sparsity of short-wavelength-sensitive (S) cones. However, such explanations have ignored the effect of monochromatic wave aberrations present in real eyes. Here we show that, when these effects are taken into account, short wavelengths are not as blurred as previously thought, that the potential image quality for S cones is comparable to that for L and M cones, and that macular pigment has no significant function in improving the retinal image.

Adult↗
PubMed2001

Detection and discrimination of chromatic targets in hemianopic macaque monkeys and humans.

We measured the ability of three macaque monkeys with unilateral removal of primary visual cortex to detect 9 degrees, 200-ms targets presented at random in the upper or lower quadrants of the normal and hemianopic visual fields. The white or variously coloured target could differ from the background in both colour and luminance, or in either of them. Blue and red targets were detectable at any luminance contrast, but green and white targets were barely or not at all detectable at and near isoluminance in the hemianopic field. Blue and red targets were better detected than white targets at the same luminance difference. However, when both the target and the background were dynamically luminance-masked, detection in the hemianopic field failed at isoluminance whatever the colour. In addition, the monkeys were unable to discriminate between simultaneously presented red and green or blue and green targets in the hemianopic field when both targets had similar luminance contrast with the background. Two hemianopic patients tested on a subset of the tasks performed similarly to the monkeys. Together, the results indicate that the residual colour-opponent system that survives damage to V1 is involved in the detection of chromatic changes but cannot sustain simultaneous discrimination between pairs of colours.

Animals↗
PubMed2003

CotB is essential for complete activation of green light-induced genes during complementary chromatic adaptation in Fremyella diplosiphon.

The dramatic modifications of photosynthetic light harvesting antennae called phycobilisomes that occur during complementary chromatic adaptation in cyanobacteria are controlled by two separate photosensory systems. The first system involves the signal transduction components RcaE, RcaF and RcaC, which appear to make up a complex multistep phosphorelay. This system controls the light responsive expression of the cpcB2A2H2I2D2, cpeBA and cpeCDE operons, which encode phycobilisome proteins. The second system, which is not yet characterized, acts in concert with the first but only regulates the light responses of cpeBA and cpeCDE. We have generated and characterized a new mutant class, named the Tan mutants. In at least one member of this class, light-regulated RNA accumulation patterns are altered for cpeBA and cpeCDE, but not for cpcB2A2H2I2D2. Thus this mutant contains a lesion that may impair the operation of the second system. We demonstrate that several Tan mutants are the result of improper expression of the gene cotB. CotB has limited similarity to lyase class proteins, particularly those related to NblB, which is required for degradation of phycobilisomes in other cyanobacteria. Possible roles of CotB in the biogenesis of phycobilisomes are discussed.

Adaptation, Physiological↗
PubMed2000

Isolation and characterization of a chromium-reducing bacterium from a chromated copper arsenate-contaminated site.

A Gram-negative bacterium (CRB5) was isolated from a chromium-contaminated site that was capable of reducing hexavalent chromium to an insoluble precipitate, thereby removing this toxic chromium species from solution. Analysis of the 16S rRNA from the isolate revealed that it was a pseudomonad with high similarity to Pseudomaonas synxantha. CRB5 was tolerant to high concentrations of chromate (500 mg l(-1)) and can reduce Cr(VI) under aerobic and anaerobic conditions. It also exhibited a broad range of reduction efficiencies under minimal nutrient conditions at temperatures between 4 degrees C and 37 degrees C and at pH levels from 4 to 9. As reduction increased, so did total cellular protein, indicating that cell growth was a requirement for reduction. Under low nutrient conditions with CRB5 or when using non-sterile contaminated groundwater from the site, reduction of Cr(VI) was followed by a increase in solution turbidity as a result of the formation of fine-grained Cr(III) precipitates, most probably chromium hydroxide mineral phases such as Cr(OH)3. Chromium adsorption and precipitation, as observed by transmission electron microscopy coupled with energy dispersive X-ray spectroscopy (TEM/EDS), revealed that the surfaces of the cells were uniformly stained with bound Cr(III) and amorphous precipitates (as determined by selected area electron diffraction; SAED). A mass balance of chromium in a batch bioreactor revealed that up to 30% of the total Cr was as settable precipitates or bound to cells.

Arsenates↗