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At least 19 recordsLinked to original sources
PubMed1977

The significance of chromate ingestion in patients allergic to chromate.

A double-blind study was carried out to demonstrate the significance of chromate ingestion in the persistence of chromic chromate dermatitis. Each of 31 chromate-allergic patients was given one tablet containing 7.1 mg potassium dichromate, plus a placebo tablet. The dermatitis of 11 of the 31 patients flared after the ingestion of chromate, but not after placebo. 3 patients had equivocal reactions to both tablets; the dermatitis worsened in 2 patients following ingestion of the placebo but not after the chromate tablet. No statistically significant difference could be found between reactivity to chromate and eczema of dyshidrotic morphology. Nor was it possible to correlate the degree of patch test reactivity to the reaction following chromate ingestion. It is concluded that a low-chromate diet is of value in the management of patients with chronic chromate dermatitis.

Administration, Oral↗
PubMed1979

Detection of the mutagenic activity of lead chromate using a battery of microbial tests.

The potential mutagenicity of the carcinogen lead chromate was tested by the following battery of microbial tests: the Escherichia coli PolA+/PolA- survival test; the Salmonella/microsome His+ reversion assay; the E. coli Trp+ reversion test as a plate assay; the E. coli Gal+ forward mutation test; and the Saccharomyces cerevisiae assay for mitotic recombination. Lead chromate is mutagenic in Salmonella and in Saccharomyces and is thus identified as a microbial mutagen by this battery. Metabolic activation by rat liver homogenate (S9) is not required for the mutagenic activity of lead chromate. The most statistically significant, positive result is found with a supplementary assay, the E. coli fluctuation test. To determine whether the lead ion and/or the chromate ion were responsible for the mutagenicity observed, lead chloride and chromium trioxide (chromic acid) were also tested. In E. coli fluctuation test, the ranges of maximal mutagenicity for chromium trioxide and lead chromate overlap at the concentration 10(-5)M, whereas lead chloride shows no mutagenicity and little lethality at concentrations up to 10(-3)M. Thus, it appears that the chromate ion is responsible for the mutagenicity of lead chromate.

Chromates↗
PubMed1975

A cohort study of bronchial carcinomas in workers producing chromate pigments.

A cohort study of the incidence of bronchial cancer in male workers in a small company producing chromate pigments is presented. Altogether 133 workers had been employed by the company from the time production was started in 1948 until the end of 1972. Workers with more than three years employment were included in the study, and three cases of bronchial carcinoma were found among the 24 workers who fulfilled this requirement. Based on the data of the Cancer Registry of Norway the risk of bronchial cancer for a corresponding group of the general population was found to be 0.079, which gives a risk ratio for exposed workers of approximately 38. The average age of the cancer patients was as low as 50 years at the time of diagnosis. All workers in the company had been exposed mainly to zinc chromate dust, and the exposure levels of the workers developing bronchial cancers had probably been from 0-5 to 1-5 mg Cr/m-3 for six to nine years. Two of the three patients were smokers. It is assumed that exposure to chromate pigments, and probably to zinc chromate, may be related to the increased incidence of bronchial cancer in this group of workers. The possibility of a contributing effect of tobacco smoking in at least two of the three cases cannot be ruled out.

Adult↗
PubMed1979

Chromatic induction effects in the Hermann grid illusion.

The chromatic Hermann grid illusion was investigated in sixteen subjects, with variation of the lightness contrast between the chromatic inducing squares and the background, and the saturation and hue of the inducing squares. Subjects made magnitude estimates of the sharpness and clarity of perceived dots at the intersections of the grid, and matched the appearances of the dots with Munsell chips. A chromatic induction effect was found to occur in the absence of lightness contrast, but the sharpness of the illusory dots increased with increasing lightness contrast (p less than 0.001). The saturation of the perceived dots increased with increases in the saturation of the inducing squares (p less than 0.05), and was higher for the longer wavelengths than for the shorter wavelengths (p less than 0.005). Neural units with center-surround arrangements responding differentially to light of the same color in the center and the surround, e.g. red off-centers and red on-surrounds, could account for the chromatic induction effect.

Color Perception↗
PubMed1979

Reduction of chromate in cement by iron sulfate.

Cement dermatitis is connected with chromate sensitivity. It can therefore be expected that "elimination" of chromate in cement would decrease the number of cases of cement dermatitis. Iron sulfate added to cement reduces the chromate completely and the 3-valent chromium is precipitated. An amount of 0.35% (w/w) iron sulfate, FeSO4 . 7H2O, is enough to reduce 20 microgram Cr6+/g cement. There is no technical side effect to the concrete. The iron sulfate is preferably added to cement when there is an intimate contact with skin, e.g. at floor laying, repairs and hand-made casting.

Chemical Phenomena↗
PubMed1977

Relapse of chromate dermatitis from sheet metal.

Galvanised sheet metal has previously been described as a source of chromate dermatitis (Fregert et al. 1970). We report a patient who appears to have been sensitised many years previously by an entirely different source of chromate, but whose resulting hand eczema has relapsed while handling galvanised sheet metal at work.

Adult↗
PubMed1977

Chromate dermatitis from a boiler lining.

Chromate dermatitis is described in a mechanical fitter working inside boiler combustion chambers. A source of hexavalent chromate is traced to the action of the heat and alkaline fuel ash on trivalent chrome ore in parts of the refractory lining. Removal of the patient from this contact has resulted in almost complete clearing of his dermatitis, without any relapse, during a 9-month follow-up period.

Chromates↗
PubMed1979

[The persistence of chromate allergy in cement eczema].

93 patients with contact allergy to chromates were followed up for 15 years during which time they were examined clinically and patch tested quantitatively at regular intervals. Results demonstrate that contact allergy to chromates and cement eczema differ from other occupational dermatoses mainly because of their persistence after a change of exposure and occupation. Explanations for this observation are offered.

Adult↗
PubMed1978

[Spectral sensitivity of off-response in human VECP during selective chromatic adaptation (author's transl)].

The spectral sensitivity of the visual system of man during selective chromatic adaptation was determined. The criterion was an off-response of constant amplitude in the evoked cortical potential. Criterion of height of response differed among the subjects investigated. Generally, a pupillary radiant intensity between 0.4 and 1.0 lg unit above the sensory threshold was used. With stimulation of both the green- and the red-sensitive mechanism, the sensitivity of the off-response was low. It was high if either the green or the red mechanism were suppressed by selective chromatic adaptation. Demonstration of an opponent color mechanism in the visual system was easier with recording of the off-response in the VECP than with determination of the sensory threshold. The presence of the blue-sensitive mechanism as revealed by the VECP off-response was shown for light stimuli near the sensory threshold during adaptation which orange and red light for a late response of low amplitude.

Adaptation, Physiological↗
PubMed1977

Chemical stabilization of Golgi silver chromate impregnations.

Blocks of neural tissue were processed by a modified Golgi-Kopsch procedure and by the rapid Golgi method. Following the impregnation, the blocks were embedded in celloidin, sectioned at 100 micrometer, and collected in 70% alcohol. The sections were then processed as follows: 1) rinsed in distilled water; 2) substituted with 0.4M sodium bromide for five minutes; 3) reduced in Kodak D-19 developer; and 4) treated in 0.5M sodium thiosulfate. The silver chromate deposits within the impregnated cells are converted successively to silver bromide and to reduced silver by this procedure. Sections so treated resist decomposition of the Golgi impregnation, and they may be counterstained with conventional aqueous cresyl violet to demonstrate the cytoarchitecture of the Golgi-impregnated tissue.

Animals↗
PubMed1979

A quantitative study of chromatic organisation and receptive fields of cells in the lateral geniculate body of the rhesus monkey.

The responses of neurones in the lateral geniculate nucleus (LGN) were investigated in anaesthetised rhesus monkeys. A new classification for cells in the parvocellular layers (PCL) is proposed, based on their spectral response curve and their response to white stimuli: (A) narrow-band, short wavelength (NS) excited cells, activity suppressed by white stimuli; (B) wide-band, short-wavelength (WS) excited cells, excited by white stimuli; (C) wide-band, long-wavelength (WL) excited cells, (D) narrow-band, long-wavelength (NL) excited cells, activity suppressed by white stimuli; (E) light suppressed (LI) cells, activity suppressed by all wavelengths, usually with some concealed excitatory input at extreme short or long wavelengths. Responses to moving bars and to spots of various diameters (area response curves) were determined for various wavelengths. It was found that the receptive fields from which wavelength-dependent excitatory or suppressive effects could be elicited are concentrically superimposed. The spectral responsiveness of the excitatory inputs to individual cell types corresponds to the absorption curves of single cones (S-, M- or L-cone for NS, WS and WL cells respectively), the spectral distribution of the suppressive mechanisms of all cells was panchromatic and approximately fitted to a sum of all cones. The excitatory input to NL-cells cannot be related to any of the known cone absorption curves, and a simple (L-M) subtraction model is questioned. Neurones in the magnocellular layers (MCL) can be divided into on- and off-centre cells as in the cat's LGN and give qualitatively similar responses over the whole spectrum. In contrast to the tonic responses of PCL cells, MCL cells respond phasically to chromatic and white flashed spots, even with the smallest stimuli. Implications of these findings for colour processing in the LGN are discussed.

Animals↗
PubMed1977

[Chromatic adaptation produces opposite effects on the on and off responses of the photopic electroretinogram (author's transl)].

The electrical response of the light adapted human eye to onset (a-wave) and offset (d1-wave of the positive off-effect) of monochromatic test stimuli between 448 and 654 nm (Ganzfeld stimulation, duration of test flash 0.3 s) was recorded by means of the electroretinogram in 10 normal observers during steady illumination of various wavelengths of 2.2 log Troland. During exposure to white light the spectral sensitivity of the a-wave and off-effect as determined by a criterion amplitude of 25 micronV were similar, the sensitivity of the off-effect being 0.4 log units lower as compared to the a-wave. Blue adaptation (467 nm) decreased the sensitivity of the a-wave and increased the sensitivity of the off-effect within the short wavelengths region of the spectrum. Red adaptation (630 nm) decreased the sensitivity of the a-wave and increased the sensitivity of the off-effect within longer wavelengths. Green adaptation (530 nm) produced only a small decrease of sensitivity of the a-wave for green test light, the sensitivity of the off-effect remained constant. The opposite changes of the a-wave and off-effect during chromatic adaptation demonstrate different participation of these components in the generation of color mechanisms in the human retina.

Adaptation, Ocular↗
PubMed1979

Receptoral and postreceptoral visual processes in recovery from chromatic adaptation.

The time course of recovery from chromatic adaptation in human vision was tracked by determining the wavelength of light that appears uniquely yellow (neither red nor green) both before and after exposure to yellowish green and yellowish red adapting lights. Recovery is complete within 5 min after steady light exposure. After exposure to the alternating repeated sequence 10-sec light/10-sec dark, the initial magnitude of the aftereffect is reduced but recovery is retarded. The results are interpreted in terms of two processes located at different levels in the hierarchical organization of the visual system. One is a change in the balance of cone receptor sensitivities; the second is a shift in the equilibrium baseline between opposite-signed responses of the red/green channel at the opponent-process neural level. The baseline-shift mechanism is effective in the condition in which repeated input signals originating at the receptors are of sufficient strength to activate the system effectively. Hence, this process is revealed in the alternating adaptation condition when the receptors undergo partial recovery after each light exposure, but receptor adaptation during continued steady light exposure effectively protects the subsequent neural systems from continued strong activation.

Color↗
PubMed1978

Further observations on the extramacular chromatic mechanisms.

Monochromatic targets presented at 30 degrees excentricity on orange, magenta and blue backgrouds are used. A small monochromatic light, 476 nm on orange, 551 nm on magenta and 621 nm on blue, is flashed at 3 cps-1 on the centre of the targets. The size of the targets is varied and their luminance adjusted using neutral filters until the flashing light is just not visible. This method allows the study of chromatic mechanism sensitivity and of retinal interactions (summation and inhibition). Some observations in normal as well as in pathological conditions are presented.

Adult↗
PubMedDate not supplied

[Modelling the effect of photosynthetic enhancement and chromatic transitions].

A simple method is proposed and analysed which explains characteristic manifestation of the enchancement effect (2nd Emerson effect) and of chromatic transients effect (Blinks effect). The model is based on the hypothesis concerning the ATP/NADP concentrations ratio with a change of falling light wavelength. The model is suggested to reflect the behaviour of the reduction pentosophosphate cycle (Calvin cycle) under low illumination intensity, when the photosynthesis rate is determined only by ATP and NADP.H concentrations formed in the course of different photochemical reactions.

Adenosine Triphosphate↗