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At least 1,693 records · Page 94Linked to original sources

PubMed1988

Investigation of the bicinchoninic acid protein assay: identification of the groups responsible for color formation.

The colored complex formed between Cu+ and bicinchoninic acid is the basis of the bicinchoninic acid protein assay (P. K. Smith, R. I. Krohn, G. T. Hermanson, A. K. Mallia, F. H. Gartner, M. D. Provenzano, E. K. Fujimoto, N. M. Goeke, B.J. Olson, and D.C. Klenk (1985) Anal. Biochem. 150, 76-85). Studies show that cysteine, tryptophan, tyrosine, and the peptide bond are capable of reducing Cu2+ to Cu+. Electrochemical studies and the magnitude of the color changes observed when the reaction is carried out at 37 degrees C indicate that tryptophan, tyrosine, and the peptide bond are not completely oxidized at this temperature. When the reaction temperature is increased to 60 degrees C, significantly more color formation is observed for these three groups. Studies with di-, tri-, and tetrapeptides and with proteins indicate that the extent of color formation is not the sum of the contributions of the individual color producing functional groups. Compounds with functional groups similar to those of cysteine, cystine, tyrosine, or tryptophan are shown to react with the bicinchoninic acid reagent. The color formed by these compounds in the presence of bovine serum albumin cannot be compensated for by using a reagent blank containing an identical concentration of the interfering compound.

Color↗

PubMed1976

Intraoral infrared color photography of radiotherapy patients.

A clinical screening study was performed in which head-and-neck radiotherapy patients were photographed intraorally using infrared "false color" film and Ektachrome color film. These photographs were compared to determine if differences existed in appearance between the intraoral tissues within the field of radiation and those intraoral tissues not in the field of radiation. No differences could be detected with either the "false color" film or with Ektachrome color film. Further investigations in the use of infrared color photography as applied to the radiotherapy patient could be undertaken by using a light source that transmits infrared rays only and a lens filter that passes only infrared rays. This method would produce a film that shows only the reflected infrared rays. Both color and black-and-white film should be used in this study.

Color↗

PubMed1994

A comparison of the color stability of conventional and titanium dental porcelain.

Simulation of naturally appearing enamel in fixed prosthodontics is best achieved with porcelain. This study investigated the color stability of two different dental porcelains, Ceramco and Procera, after they were exposed to 900 hours of accelerated aging. Twenty titanium plates provided the substrate to which the Procera porcelain samples in shades A3, A3.5, C3, and D3 were fired, five in each shade. An equal number of metal-ceramic alloy (Olympia) plates were cast to the same dimensions to form the 20 substrates to which Ceramco porcelain was fired. The four shades of porcelain were again added to each of the samples. Commission International de l'Eclairage L a b readings were recorded with a Minolta Chroma Meter II before and after exposure to 900 hours of accelerated aging simulation. After the aging process the color differences between the pretest and posttest condition were calculated. Although statistical comparisons demonstrated a difference in color change (p < or = 0.05) between Ceramco and Procera porcelain in three of the shades tested, critical remarks of color refer to both types having "slight" color change. In terms of color stability, neither porcelain had "noticeable" changes after 900 hours of accelerated aging.

Color↗

PubMed1990

Polymorphism in normal human color vision and its mechanism.

Earlier we reported that Rayleigh matches made by males with normal color vision fall into distinct groups, and proposed that this behavior reflects an X-chromosome linked polymorphism in the spectral positioning of cone pigments (Neitz & Jacobs, 1986). In the present experiments two different color matches were obtained from each of 60 color normal males. Comparisons of the data from these two matches allowed variations in color matching that are produced by individual differences in the spectral positioning of middle and long wavelength cone pigments to be distinguished from color vision variations caused by other factors. Considered together with findings from molecular biology and spectral measurements of individual cone pigments, these results suggest that among color normal humans: (1) there are discrete variations in both middle and long wavelength cone pigments, and (2) most individuals have more than three different cone pigment types.

Color Perception↗

PubMed1992

A bidimensional theory of achromatic color vision.

The theory is based on a perceptive color system where the achromatic colors are specified by their degree of similarity to the three qualities white, black and luminous. Black and luminous are treated as opponent variables. It is assumed that white and luminous/black are determined by different kinds of visual processes termed the w- and the b-process. The relationship between these processes and luminance parameters in a simple disc/ring configuration is derived from available data. The b-process is related to stimulus contrast in a simple manner. It is assumed to involve cells with antagonistic center/surround organization of the receptive field. The w-process is primarily determined by the local luminance, and it is assumed to involve cells that lack a center/surround organization of the receptive field. The w-process has properties similar to the processes involved in chromatic color vision. The theory can account for different kinds of psychophysical data on achromatic colors like data on simultaneous contrast, color scaling, and color constancy.

Color Perception↗

PubMed1992

Color fusion and flicker fusion frequencies using tritanopic pairs.

We determined color fusion and flicker fusion frequencies for tritanopic color pairs, so that only short wavelength sensitive cones were modulated. The minimally distinct border (MDB) technique was used to determine tritanopic pairs for each observer. If S-cones do not contribute to the luminance channel, color fusion and flicker fusion frequencies should be equal, because the achromatic flicker perceived beyond color fusion frequency is supposed to be elicited just by the luminance channel. The results show a significant difference between color fusion and flicker fusion frequencies for all pairs and for all subjects, which suggests a contribution of S-cones to the luminance channel. However, the results also showed that the residual achromatic flicker can not be eliminated by adjusting relative luminance of two colors flickering in counter-phase. The relative luminance stayed the same as the MDB setting when residual flicker was minimized. This means that minimum flicker was obtained when L- and M-cones are temporally silenced, and suggests little or no contribution of S-cones to luminance channel. These conflicting results might be explained by phase shift between responses of S-cones and other longer-wavelength-sensitive cones.

Adult↗

PubMed1993

More than three different cone pigments among people with normal color vision.

A fundamental feature of normal color vision is that red and green lights can be mixed to appear identical with a monochromatic yellow light. Another characteristic of normal color vision is that people often disagree on the amounts of red and green needed in the mixture to exactly match the yellow. Comparison of such color vision differences with photopigment gene differences reveals that a serine/alanine polymorphism at amino acid position 180 of X-encoded pigments can account for this type of color vision variation. This amino acid change shifts the spectrum of the pigment produced by about 6 nm, a value that would predict a larger minimum color vision difference between individuals than is actually observed. This discrepancy can be explained if, counter to the Young-Helmholtz theory as the explanation of trichromacy, many people with normal color vision have more than three spectrally different cone pigments.

Base Sequence↗

PubMed1996

Color, orientation and cytochrome oxidase reactivity in areas V1, V2 and V4 of macaque monkey visual cortex.

Color and orientation processing in the macaque monkey first segregates into cytochrome oxidase (CO)-rich blobs and -poor interblobs of area V1, from where the two streams flow through areas V2 and V4. This parallel representation is believed to enhance processing speed by compartmentalizing tasks of similar kinds, though our knowledge of the mechanisms is still elementary. We have examined the interaction and separation of color and orientation processing in neurons (n = 569) of the macaque visual cortex (V1, V2, V4) on the basis of microelectrode recordings. In all three areas, neurons selective for midspectral (MS) colors (e.g., yellow, green) were also found to be more orientation selective than those preferring endspectral (ES) colors (e.g., blue, red). The majority of achromatic (AC) cells responsive to bright stimuli were also orientation selective. When locations of cells and penetration columns were correlated with cytochrome oxidase (CO) landmarks in V1 and V2, V1 interblob and V2 interstripe cells were found to be predominantly midspectral and oriented, while V1 blob and V2 thin stripe cells were found to be predominantly endspectral and non-oriented. Cells preferring dark colors were found to cluster in thick stripes in V2, and in columns in V4. Separate clustering of midspectral (MS) and endspectral (ES) systems in V4 was also noted. With the results shown in a companion paper (Behav. Brain Res., 76 (1996) 51-70), the present data indicate that the visual system appears to optimize color and spatial acuity by separating chromatic information into non-oriented endspectral and oriented midspectral components.

Action Potentials↗

PubMedDate not supplied

Age, color processing and meaningfulness: an event-related potential study.

The effects of aging on event-related potentials (ERPs) and reaction time (RT) performance were investigated in a task that combined color discrimination and lexical decision. The stimuli were either words or non-words, presented either in the relevant or in the irrelevant color. RT responses were required to words in the relevant color. Stimuli appeared in the relevant color elicited attention-related ERP components (anterior positivity, selection negativity and N2b). The latency values of the attention-related ERP components and the RT were longer in the older group, indicating the slowing down of attentional processes in the elderly. In the older group the late positivity to stimuli in the relevant color was absent over the posterior locations. Unlike in the older group, in the younger subjects the words appeared in the irrelevant color elicited a central negative wave in the 400 ms range. These results are considered as a capacity limitation in the elderly in processing of the stimulus characteristics beyond to the actual stimulus-response contingencies.

Adult↗

PubMed1995

Event-related potential correlates of transient attention shifts to color and location.

Effects of selectively attending to specific combinations of stimulus location and color were measured by means of event-related brain potentials in a trial-by-trial cueing paradigm. A symbolic precue was presented at the beginning of each trial indicating the response-relevant position and color of an upcoming imperative stimulus. Responses were required to infrequent target stimuli of the relevant color appearing at the cued location. Stimuli at attended locations elicited enhanced posterior N1/components as well as enhanced negativities at midline electrodes. No P1 enhancement was found for stimuli at the attended location. Attended color stimuli elicited a broad negativity starting about 220 ms that tended to be larger for stimuli presented at attended locations. These results show that transient attention shifts to non-spatial features like color are reflected by event-related potential (ERP) effects comparable to the effects measured under sustained attention conditions. Transient spatial attention yields earlier and larger ERP effects than transient attention to color and may modulate the ERP effects of non-spatial attention.

Adult↗

PubMed1995

Quantification of color Doppler for the evaluation of tissue vascularization.

Assessment of tissue vascularization with color Doppler (CD) can improve differential diagnosis of tumors. Until now, measurement of flow velocities is restricted to conventional duplex ultrasound of single vessels or semiquantitative scoring of the vessel distribution in CD. We developed a new method for quantification of CD data in organs or tumors by statistical image analysis. Based on standardized image recording, data is acquired from the video output of any ultrasound scanner using a 24-bit color framegrabber in a personal computer. The digitized colors are recognized according to their position in the CD palette bar resulting in an 8-bit color image (number of identified pixels > 99.9%). Within the region of interest, statistics of the detected flow patterns are calculated. The color pixel density and the mean color value varies between recordings of the same image during subsequent systolic peaks with a SD of 10% and 2%, respectively, and within different sections of the same organ or tumor with 25% and 10-50%. This analysis can be used for comparative or longitudinal studies and an objective evaluation of CD in complex vascular formations such as tumors. Its diagnostic impact has already been demonstrated in clinical studies.

Blood Flow Velocity↗

PubMed1988

Hepatotoxicity of gardenia yellow color in rats.

Acute toxicity by gardenia yellow color was studied in rats. Oral administration of the colorant at doses of 800 mg/kg up to 5000 mg/kg caused diarrhea and increases in serum alanine aminotransferase and aspartate aminotransferase activities in a dose-dependent manner. After 24 h of oral treatment with 2000 mg/kg of the colorant, liver showed partially hemorrhagic changes and the intestinal tract, especially the duodenum, appeared blue. The toxicity induced by the colorant was stronger by oral administration than by intraperitoneal administration. The content of geniposide, an iridoid compound, was estimated to be 28% of the colorant, and this iridoid accounted for almost all the hepatotoxic activity of the colorant.

Administration, Oral↗

PubMed1994

Diagnostic utility of color Doppler ultrasound in lower limb deep vein thrombosis in patients with clinical suspicion of pulmonary thromboembolism.

The diagnosis of pulmonary thromboembolism is frequently based on ventilation-perfusion scintigraphy and ascending lower limb venography when pulmonary angiography is not available. The aim of this study is to compare color Doppler ultrasound against ascending venography in the evaluation of the lower limb deep vein system in patients with clinical suspicion of pulmonary embolism, with special attention to calf veins. We prospectively studied 30 patients with clinical suspicion of pulmonary embolism in whom a color Doppler ultrasound and venogram were performed with no more than a 3-h interval between both procedures. The diagnostic criteria was that of loss of venous compressibility. The 'color' ability was used to identify artery from vein. Out of 15 patients in whom a venogram proved positive (50%), 9 had isolated calf vein thrombosis (60%). In 5 patients, the color Doppler ultrasound of the calf was considered inconclusive. Overall sensitivity was 53%, specificity 100%, positive predictive value 100%, and negative predictive value 68%. In the femoropopliteal system, sensitivity was 83% and specificity 100%. Considering all patients, sensitivity in the calf system was 40%. Excluding the 5 patients who were difficult to assess, sensitivity increased to 60%. In conclusion, color Doppler ultrasound is not as sensitive as venography in dealing with patients with clinical suspicion of pulmonary embolism, due to its low sensitivity in the calf system when distal thrombi need to be excluded. However, a reasonable alternative is to begin by performing a compression ultrasonography of the femoropopliteal system. Color Doppler ultrasonography of the calf system represents a rarely sensitive and arduous task and does not seem justifiable in this type of patient.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1996

A new Doppler method for quantification of volumetric flow: in vivo validation using color Doppler.

OBJECTIVES: This study was designed to assess the accuracy of a new Doppler method for quantification of volumetric flow in vivo. BACKGROUND: Noninvasive assessment of volumetric flow through heart valves and the great vessels remains a clinical goal. We present a new method for quantification of volumetric flow based on color Doppler mapping that computes velocity vectors over a surface normal to the point of scanning. This Doppler technique assumes only the incompressibility of the fluid. The method is basically independent of the angle of incidence between the ultrasound beam and the direction of blood flow and includes variations of flow area. METHODS: The color Doppler method was tested in seven anesthetized pigs by measuring pulmonary volumetric flows using multiplane Doppler echocardiography. The results were compared with those obtained by the thermodilution technique. In addition, volumetric flows across the mitral valve were determined in 10 normal volunteers by transthoracic Doppler echocardiography and compared with flows obtained with velocity-encoded magnetic resonance imaging (MRI). RESULTS: The mean value of the differences between the thermodilution technique and color Doppler were -0.16 +/- 0.94 liter/min for pulmonary volumetric flows (mean value of differences for [Thermodilution-Color Doppler] +/- 2 SD of differences). The mean value of the differences between MRI and color Doppler were 0.21 +/- 0.83 liter/min for mitral valvular volumetric flows (mean value of differences for [MRI-Color Doppler] +/- 2 SD of differences). CONCLUSIONS: The method showed close agreement with thermodilution and MRI for assessment of volumetric flow in vivo. It is therefore a noninvasive method with potential applications for cardiac output measurement and for quantification of volumetric flow of valvular insufficiency and restrictive lesions.

Adult↗

PubMed2026

Comparative transcriptome analysis provides insights into dorso-ventral color pattern formation of Holothuria edulis.

Animal body color patterns are highly diverse and play critical roles in camouflage, intraspecific communication, and environmental adaptation. Holothuria edulis, an important echinoderm inhabiting tropical waters, exhibits a typical dorsoventral dichromatism. This unique body color difference represents a key phenotypic trait for its habitat adaptation; however, the core differential genes regulating this trait remain to be elucidated. In this study, comparative transcriptome sequencing was performed on the dorsal and ventral body wall tissues of H. edulis, leading to the identification of a number of differentially expressed genes (DEGs), followed by GO functional annotation and KEGG pathway enrichment analysis. GO enrichment analysis indicated that the DEGs were significantly enriched in functional categories such as extracellular region, peptidase inhibitor activity, and tetrapyrrole binding. KEGG pathway analysis further revealed significant enrichment of protein digestion and absorption, the TNF signaling pathway, and cholesterol metabolism. Notably, the pigmentation-related gene FMO2 was highly expressed in the dorsal body wall tissue, whereas cyp1a1, ZIC1, Slc7a11, WNT-1, and ADAMTS20 were highly expressed in the ventral body wall tissue. This study identified DEGs and enriched pathways associated with dorsoventral body color differences in H. edulis, providing new insights into the molecular regulatory mechanisms underlying body color pattern formation. From the perspective of aquaculture applications, body color is one of the important traits affecting the quality and market value of sea cucumber products. Elucidating the molecular mechanisms of body color variation can provide a scientific basis for molecular marker-assisted breeding of superior sea cucumber variety.

Animals↗

PubMed2005

Spatio-temporal dynamics of top-down control: directing attention to location and/or color as revealed by ERPs and source modeling.

This study investigated the nature and dynamics of the top-down control mechanisms that afford attentional selection using event-related potentials (ERPs) and dipole-source modeling. Subjects performed a task in which they were cued to direct attention to color, location, a conjunction of color and location or no specific feature on a trial-by-trial basis. Overall, similar ERP patterns were observed for directing attention to color and location, suggesting that spatial and non-spatial attention rely to a great extent on similar control mechanisms. The earliest attention-directing effect, at 340 ms, was localized to ventral posterior cortex and may reflect processes by which the cue is linked to its associated feature. Only late in the cue-target interval, differences in ERP were observed between directing attention to color and location. These originated from anterior and ventral posterior areas and may represent differences in, respectively, maintenance and perceptual biasing processes. The ventral posterior sources estimated for these late effects of directing attention to location and color were located posterior to those estimated for the modulatory effects of, respectively, spatial and non-spatial attention. This suggests that the precise neural populations involved in perceptual biasing and attentional modulation may differ. Conjunction cues initially elicited less posterior positivity than color and location cues, but evoked greater central positivity from 540 ms on. This central effect may reflect feature integration or ongoing processes related to cue-symbol translation. These results extend our understanding of the spatio-temporal dynamics of top-down attentional control.

Adult↗

PubMed2004

Unconscious priming by color and form: different processes and levels.

Using a metacontrast masking paradigm, prior studies have shown (a) that a target's color information and form information, can be processed without awareness and (b) that unconscious color processing occurs at early, wavelength-dependent levels in the cortical information processing hierarchy. Here we used a combination of paracontrast and metacontrast masking techniques to explore unconscious color and form priming effects produced by blue, green, and neutral stimuli. We found that color priming in normal observers is significantly reduced when an additional paracontrast mask precedes the target at optimal masking SOAs. However, no reduction of form-priming effects was obtained at similar optimal paracontrast SOAs. We conclude that unconscious color priming depends on an early, wavelength- or stimulus-dependent response of color neurons located at early cortical levels whereas unconscious form priming occurs at later levels.

Adult↗

PubMed2005

Exploring fungal biodiversity for the production of water-soluble pigments as potential natural food colorants.

The production of many currently authorized natural food colorants has a number of disadvantages, including a dependence on the supply of raw materials and variations in pigment extraction. Fungi provide a readily available alternative source of naturally derived food colorants that could easily be produced in high yields. The recent authorization of a fungal food colorant has fuelled research to explore the extraordinary chemical diversity and biodiversity of fungi for the biotechnological production of pigments as natural food colorants. These studies require an appropriate use of chemotaxonomic tools and a priori knowledge of fungal metabolites to carry out intelligent screening for known or novel colorants as lead compounds. Such screening would result in the preselection of some potential pigment producers and the deselection of pathogenic strains and toxin producers. With advances in gene technology, in the future it should be possible to employ metabolic engineering to create microbial cell factories for the production of food colorants.

Biodiversity↗