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At least 127 records · Page 7Linked to original sources
PubMed2000

Effects of NADH and H(2)O(2) on chromate-induced human erythrocytes hemoglobin oxidation and peroxidation.

The effects of NADH and H(2)O(2) on chromate-induced human erythrocyte hemoglobin oxidation and peroxidation were studied. It was observed that NADH decreases the levels of chromate-induced human erythrocyte hemoglobin oxidation and peroxidation. H(2)O(2) decreases the levels of chromate-induced hemoglobin oxidation, but increases the levels of chromate-induced peroxidation. The ability of H(2)O(2) to decrease the levels of chromate-induced hemoglobin oxidation is higher than that observed for NADH. Furthermore, H(2)O(2) increases the inhibitory effect of NADH on chromate-induced hemoglobin oxidation, but decreases the NADH effect on chromate-induced peroxidation. The meaning of these results is discussed in terms of involvement of reactive chromium(V) species and reactive oxygen species in the mechanism by which chromate induces its effects in human erythrocytes.

Cell Culture Techniques↗
PubMed1994

Temporal properties of the red-green chromatic mechanism.

The temporal properties of the red-green chromatic mechanism were studied with red and green equiluminant flashes of 1 deg diameter presented in the center of a bright (800-3000 td) yellow adapting field. A subthreshold 200 msec red or green flash makes an immediately subsequent, suprathreshold yellow luminance flash appear tinged with the complementary color. The chromatic flash also makes a subsequent chromatic flash of the same hue harder to detect and identify, and makes a flash of the opposite hue easier to detect and identify. These results indicate that the response of the red-green mechanism changes polarity during its time-course, suggesting that the chromatic temporal impulse-response function has a negative lobe. Pairs of chromatic pulses were used to estimate the shape of the chromatic impulse-response. The estimated impulse-response function has a zero crossing near 90 msec, followed by a long, shallow negative lobe. We also measured threshold-duration functions; the critical duration for the chromatic and luminance flashes is about 95 and 45 msec, respectively. Chromatic sensitivity (measured in cone contrast units) is 10 times greater than luminance sensitivity for long durations, and is 3 times greater for all durations less than 45 msec.

Adaptation, Ocular↗
PubMed1996

Magnetic and electrical brain responses to chromatic contrast in human.

Differences between magnetic responses to red-green chromatic gratings and yellow-black luminance gratings were: (1) response waveforms differed considerably; (2) at some recording sites the chromatic grating response was considerably greater than the sum of responses to the red and green components of the chromatic grating; (3) the latencies of the successive peaks in the response to the onset of chromatic contrast were greater than the latencies of the corresponding peaks in the response to luminance contrast onset; (4) chromatic grating responses were lowpass with respect to spatial frequency while luminance grating responses were bandpass; (5) chromatic grating responses attenuated more steeply with increasing frequency above 2 c/deg than did luminance grating responses. Items (3)-(5) above are consistent with well-known psychophysical findings that contrast sensitivity is lowpass for chromatic gratings and chromatic responses are more sluggish than luminance responses. In subsidiary experiments we found that magnetic responses to red-green and blue-yellow equiluminant gratings had similar waveforms in all six subjects tested, but the topographical distributions were different in three subjects. The results of comparing magnetic and electrical responses to the onset and offset of contrast can be understood in terms of the considerable intersubject variability in the relation between neuroanatomy and cortical function that has been demonstrated by other techniques.

Adult↗
PubMed1996

Global-motion perception: interaction of chromatic and luminance signals.

A global dot-motion stimulus was employed in order to investigate the interaction between luminance and chromatic signals in motion processing. Thresholds are determined by measuring the minimum number of dots which need to move in a coherent fashion in a field of randomly moving dots in order for the observers to be able to determine the direction of coherent motion. We found that: (1) observers could not track an achromatic signal-dot which changes its luminance polarity between frame transitions. The addition of a consistent chromatic signal allowed observers to track such a dot when the dot contained low- (8%) luminance contrast but this ability was impaired as the luminance contrast was increased; (2) the addition of chromatic contrast to a dot which contained consistent low-luminance contrast could result in threshold elevation. For fixed contrast chromatic and luminance signals, the presence and degree of threshold elevation depended upon the spatiotemporal properties of the dot motion; (3) the ability of observers to extract a global-motion signal carried by a group of dots of one colour was impaired by the addition of a number of additional-noise dots of a different colour. These results are interpreted as indicating that: (1) the motion-selective cells that are sensitive to chromatic signals are also sensitive to luminance signals; (2) the combined chromatic and luminance and purely luminance motion cells are pooled to form a single pathway prior to global-motion extraction; and (3) the negative interaction observed between the chromatic and luminance signals is likely to be due to the differences in the processing speeds of the combined luminance and chromatic and the purely luminance sensitive motion cells.

Color↗
PubMed1997

Infant color vision: temporal contrast sensitivity functions for chromatic (red/green) stimuli in 3-month-olds.

In order to investigate the development of temporal contrast sensitivity functions (tCSFs) for chromatic (red/green) stimuli, we obtained chromatic contrast thresholds from 3-month-old infants and adults using behavioral techniques. Stimuli were moving or counterphase-reversing sinusoidal gratings of 0.25 c/deg. Five temporal frequencies were used: 0.7, 2.1, 5.6, 11 and 17 Hz (corresponding speeds = 2.8, 8.4, 22, 44 and 67 deg/sec). In order to compare chromatic results with those obtained under luminance-defined conditions, luminance tCSFs were also obtained from adults, and previously obtained infant luminance tCSFs were used (from Dobkins & Teller, 1996a). In accordance with previous studies, adults exhibited bandpass luminance tCSFs with peaks near 5 Hz and lowpass chromatic tCSFs that declined rapidly at temporal frequencies greater than 2 Hz, and the two curves crossed one another near 4 Hz. By contrast, infants exhibited bandpass rather than lowpass chromatic tCSFs with peaks near 5 Hz. These chromatic curves were quite similar in peak frequency and general shape to previously obtained infant tCSFs for luminance stimuli. Moreover, both chromatic and luminance tCSFs in infants were found to be quite similar in peak and shape to luminance tCSFs observed in adults. These findings point to the possibility that, for 3-month-old infants, both chromatic and luminance stimuli are detected by the same underlying mechanism under these conditions. We propose that such a mechanism is probably a physiological pathway dominated by magnocellular input. Earlier studies of infant color vision are discussed in this context.

Adult↗
PubMed1998

Modulation of chromatic difference in receptive field size of H1 horizontal cells in carp retina: dopamine- and APB-sensitive mechanisms.

Chromatic aspects of receptive field size in the H1 horizontal cell syncytium of the carp retina were investigated using spectral photostimuli (blue or red) presented in the form of either a pair of a small spot and annulus, or a narrow moving slit. In the light-adapted retina, the receptive field for the blue stimulus was found to be significantly smaller than that for the red, i.e. there was a chromatic difference in the receptive field size. During the course of dark adaptation, the overall receptive field size increased, but the chromatic difference decreased. Immediately after adaptation to bright light, the receptive field sizes were reduced significantly, but the chromatic difference increased, mainly due to a greater reduction in the receptive field for the blue stimulus. Application of dopamine (5 microM) to a dark-adapted retina gradually decreased the receptive field size for both colours, but the chromatic difference became larger, again due to a greater reduction in the receptive field size for the blue stimulus. 2-Amino-4-phosphonobutyrate (APB) applied to light-adapted retinae at a working concentration of 1 mM, greatly expanded the receptive field size and suppressed the chromatic difference due to the effect being greater for the receptive field for the blue stimulus. The effect of APB was slow and cumulative. On the other hand, intracellular injection of cGMP or dibutyryl-cGMP increased the chromatic difference in the receptive field size. It is suggested (i) that the chromatic difference in the receptive field size could be due to a cGMP-coupled, conductance-decreasing receptor mechanism activated by APB; and (ii) that the mechanism is associated with short-wavelength sensitive cone input to the H1 cells and operates in the light-adapted state of the retina.

Adaptation, Ocular↗
PubMed2002

Scalp VEPs and intra-cortical responses to chromatic and achromatic stimuli in primates.

We propose asimple method of monitoring separate visual pathways inlightly sedated monkeys using chromatic and achromatic gratings of low contrast, which are known to activate predominantly either parvo- or magno-systems. The scalp Visual Evoked Potentials (VEPs) are compared with simultaneously recorded intra-cortical VEPs which in turn are compared with multi-unit and single-unit responses. At isoluminance, the onset of low contrast, coarse chromatic square wave spatial profile gratings generates negative scalp VEPs which exhibit properties consistent with the activation of sustained, parvocellular-chromatic mechanisms (e.g. low-pass spatio-temporal characteristics). In monkeys, most components of chromatic onset VEPs have latencies comparable to neuronal activity within the supragranular layers of V1. Corresponding coarse achromatic gratings elicit positive VEPs which exhibit properties consistent with the activation of transient-type magnocellular mechanisms (e.g. temporal tuning to higher temporal frequencies) and which have a more complex morphology. Achromatic onset VEPs may contain early components of similar timing to activity recorded in monkey V1, but later components cannot be related to V1 generators; other sources are not known. Achromatic reversal VEPs are similar to achromatic onset, chromatic reversal and both chromatic and achromatic offset VEPs and all differ from chromatic onset VEPs. It is observed that early components of scalp-recorded chromatic-onset VEPs are related in time to some intra-cortical potentials. These VEPs are generated by low spatial frequencies and have low pass temporal characteristics. Other scalp potentials, apparently unrelated to V1 field potential activity must be generated by other sources such as extra-striate areas.

Animals↗
PubMed1997

Chromatic-contrast threshold impairment in diabetes.

A prospective study was carried out to investigate acquired colour-vision deficits in diabetics using an automated, computer-controlled, cathode-ray-tube based test of chromatic contrast. Chromatic-contrast thresholds estimates were measured along both a red/ green (constant S-cone) confusion axis and a tritan (constant M/L-cone) confusion axis for 305 eyes of 305 diabetics. The diabetic data were partitioned into groups based on a clinical categorisation of retinopathy. The diabetic data were compared with both age-matched and 'lens-equated' control data obtained from a bank of 347 normal subjects. Further analysis of differences between diabetic-status groups was performed. Associations between chromatic contrast threshold estimates and age, duration of disease, and severity of both macular oedema and ischaemia were investigated. The diabetic group was found to have significantly reduced chromatic-contrast threshold estimates when compared with normal controls, even in the absence of retinopathy. This reduction in chromatic contrast was predominantly tritanopic in nature. Interestingly, no reduction in red/green chromatic-contrast threshold estimate was found in diabetics without retinopathy. The tritan deficit seen in diabetics without retinopathy was strongly correlated with duration of disease, but when adjustments were made to account for the effects of duration-dependent lens yellowing, the tritan deficit was no longer apparent. A correlation between both the severity of macular oedema and severity of ischaemia with chromatic-contrast loss was established. Acquired reductions in both red/green and tritan chromatic-contrast threshold estimates seen in diabetics are strongly correlated with the severity of retinopathy. The results provide evidence that the specific tritan deficits seen in diabetics can be explained by the effects of lens yellowing rather than by selective damage of the blue cone system as has been hypothesised by other groups. The results provide support for the potential use of automated CRT-based tests of colour vision in diabetic retinopathy screening protocols.

Adolescent↗
PubMed1999

The mechanism of isoluminant chromatic motion perception.

An isoluminant chromatic display is a color display in which the component colors have been so carefully equated in luminance that they stimulate only color-sensitive perceptual mechanisms and not luminance-sensitive mechanisms. The nature of the mechanism by which isoluminant chromatic motion is perceived is an important issue because color and motion processing historically have been associated with different neural pathways. Here we show that isoluminant chromatic motion (i) fails a pedestal test, (ii) has a temporal tuning function that declines to half-amplitude at 3-6 Hz, and (iii) is perceived equally well when the entire motion sequence is presented monocularly (entire motion sequence to one eye) versus interocularly (the frames of motion sequence alternate between eyes so that neither eye individually could perceive motion). These three characteristics indicate that chromatic motion is detected by the third-order motion system. Based on this theory, it was possible to take a moving isoluminant red-green grating and, by simply increasing the chromatic contrast of the green component, to generate the full gamut of motion percepts, from compelling smooth motion to motion standstill. The perception of motion standstill when the third-order mechanism is nullified indicates that there is no other motion computation available for purely chromatic motion. It follows that isoluminant chromatic motion is not computed by specialized chromatic motion mechanisms within a color pathway but by the third-order motion system at a brain level where binocular inputs of form, color, depth, and texture are simultaneously available and where selective attention can exert a major influence.

Calibration↗
PubMed1996

Retinal and cortical evoked responses to chromatic contrast stimuli. Specific losses in both eyes of patients with multiple sclerosis and unilateral optic neuritis.

It is known that colour vision may be altered in optic neuritis. Our aim was to establish whether chromatic and achromatic vision are differentially impaired using stimuli designed to favour the activity of either the magnocellular or the parvocellular stream of the visual pathway. Fourteen patients with a past history of unilateral optic neuritis in the course of multiple sclerosis and 10 age-matched control subjects were included in the study. Patients had relatively good visual acuity in the affected eyes and no gross colour deficits (Ishihara). Stimuli were alternating gratings of low spatial frequency and of different chromaticity along the red-green axis. The psychophysical contrast sensitivity (CS) was measured at 5 Hz as a function of colour ratio [red/(red + green)] to evaluate both the equiluminant point (the colour ratio corresponding to the lowest CS) and the CS for isochromatic, luminance gratings (red-black and green-black). Steady-state (2-24 Hz) and transient pattern electroretinograms (PERGs) and visually evoked potentials (VEPs) were recorded in response to high contrast (90%) stimuli of low spatial frequency (0.3 cycles deg-1) modulated in either pure chromatic contrast (equiluminant red-green) or pure luminance contrast (yellow-black). On average, CSs were reduced (10 dB) in optic neuritis eyes compared with controls for both luminance and chromatic gratings. In the VEPs (both transient and steady-state) amplitude losses and latency delays were far larger for the chromatic VEPs than for the luminance VEPs. Chromatic VEP latency delays were remarkable also in the fellow, clinically normal, eyes. Significant losses were apparent in both the luminance and chromatic PERG. However, the chromatic PERG was comparatively more altered. In agreement with previous reports, selective losses were not apparent at threshold. By contrast, suprathreshold electrophysiological responses displayed a clear dissociation between luminance and colour, suggesting that the parvocellular stream, compared with the magnocellular stream is more impaired in optic neuritis.

Adult↗
PubMed1991

Human peripheral spatial resolution for achromatic and chromatic stimuli: limits imposed by optical and retinal factors.

1. The aim of this study was to determine whether optical, receptoral or higher-order neural properties limit spatial resolution (acuity) in human vision, especially in the peripheral regions of the visual field. 2. Both achromatic and chromatic stimuli were used, and measures were taken to ensure that the resolution estimates were not contaminated by the detection of spatial sampling artifacts. Spatial contrast sensitivity functions were measured at retinal locations from 0 to 55 deg along the naso-temporal meridian for: (i) discriminating the direction of drift of luminance-modulated (black-white) sinusoidal stimuli drifting at 8 Hz (achromatic task); and (ii) for detecting isoluminant red-green sinusoidal stimuli drifting at 0.4 Hz (chromatic task). Achromatic contrast sensitivity functions were also measured along the vertical meridian for eccentricities of 8 and 40 deg. Each achromatic function was extrapolated to a contrast sensitivity of one (100% contrast) to estimate achromatic acuity. Chromatic acuities were obtained by expressing chromatic contrast in terms of cone contrasts and using the same method of extrapolation. We compared the results with recent data on human optical properties and retinal anatomy. 3. Both achromatic and chromatic acuity decline with distance from the fovea, but at a faster rate than that dictated by the known optical and/or receptoral properties of the human eye. We conclude that, for stimuli of either achromatic or chromatic contrast, peripheral spatial resolution is limited by post-receptoral mechanisms. Also, chromatic acuity declines more steeply than luminance acuity with eccentricity suggesting that there are additional post-receptoral limitations on colour resolution in the periphery. 4. A clear naso-temporal asymmetry is seen in the resolution whose dependence is qualitatively, but not quantitatively, similar to the Nyquist limits imposed by the asymmetric density of human retinal ganglion cells. We discuss the possibility that in peripheral vision (beyond the optic nerve head) the spacing of ganglion cells may pose a fundamental limit on the resolution of achromatic stimuli, but not chromatic stimuli.

Color Perception↗
PubMed1993

Spectral-luminosity functions, scalar linearity, and chromatic adaptation.

We report data for three experiments that assess the effect on the luminosity function of chromatic adaptation arising from the measurement stimuli. First, we report spectral-sensitivity functions (wavelength range, 510-640 nm) measured by heterochromatic flicker photometry for a luminance range of 25-5000 Td. The data were fitted to a linear combination of cone fundamentals. The data narrowed and the fits deteriorated with an increase in luminance level, which indicates that at high luminances chromatic adaptation that is dependent on the spectral composition of the standard and test lights is a factor in spectral-luminosity determination. Second, we report heterochromatic modulation photometry as measured with two spectral lights at constant time-averaged chromaticity and luminance for luminances from 1.6 to 1300 Td. For a time-averaged chromaticity of 570 nm, the red-green ratio of the photometric match was invariant with luminance. For a time-averaged chromaticity of 605 nm, the red-green ratio increased by almost 0.3 log unit for a 2-log-unit increase in luminance, which is indicative of chromatic adaptation to the 605-nm chromaticity. Third, we measured flicker increment detection (wavelength range, 510-640 nm) on 570- and 605-nm backgrounds of 25-5000 Td. The data were fitted to a linear combination of cone fundamentals and showed good fits at all luminances. Fits to the 570-nm-background data set showed little variation in the proportions of the cone fundamentals with luminance. Fits to the 605-nm-background data set required an increased weighting of the middle-wavelength-sensitive cone with luminance. These three experiments indicate that luminance-dependent variation in the spectral-luminosity function as assessed by flicker techniques is caused primarily by chromatic adaptation to the measurement stimuli.

Adaptation, Ocular↗
PubMed2000

The achromatic mechanism and mechanisms tuned to chromaticity and luminance in visual search.

The purpose of the study was to determine whether visual search can be mediated by an achromatic, or luminance, mechanism in which signals are independent of the chromaticity of the stimuli. Experiments were designed to determine whether variability in the chromaticity of distractor stimuli made it more difficult to search for a target that differed from the distractor stimuli in luminance. Variability in the chromaticity of the distractors had little or no effect on search times when the target stimulus was white. Variability in the chromaticity of the distractors increased search times when the target was a reddish or bluish chromaticity. Results obtained with white targets suggest that these searches are mediated by an achromatic mechanism in which the signals are independent of the chromaticity of the stimuli. Results obtained with reddish and bluish targets suggest that searches for those targets may be mediated by mechanisms tuned to both chromaticity and luminance. Further experiments in which observers searched for targets that differed from distractors in both chromaticity and luminance provided additional support for the second conclusion.

Attention↗
PubMed1989

Chromatic and achromatic vision of macaques: role of the P pathway.

Chromatic and achromatic contrast sensitivity were measured in a human observer, 2 normal macaque monkeys, and 3 monkeys with severe toxicant-induced damage to the parvocellular projecting retinogeniculate pathway (P cell-deficient monkeys). Damage to the P pathway was produced by the oral administration of acrylamide monomer (Eskin and Merigan, 1986). Contrast sensitivity was measured in all subjects with isochromatic luminance gratings, as well as isoluminant chromatic gratings, modulated along several directions of a color space that represents color-opponent and luminance contrast (Krauskopf et al., 1986). The chromatic and achromatic sensitivity of the control monkeys was virtually identical to that of the human observer. Chromatic sensitivity of the P cell-deficient monkeys, measured at a low spatial frequency (0.3 c/deg), along a constant-blue color axis, was 0.9-1.5 log units lower than that of controls. Similar losses were seen along a tritanopic confusion axis and along 2 intermediate axes of color direction. Chromatic thresholds measured at higher spatial frequency (2.0 c/deg) were similarly reduced. Counterphase-modulated chromatic gratings were used to test color sensitivity over a range of temporal frequencies up to 15 Hz, and the loss of color vision was substantial over the entire range of frequencies. The luminance contrast sensitivity of the P cell-deficient monkeys for stationary gratings decreased after exposure by 0.5-0.8 log units. These results indicate that the chromatic and achromatic spatial vision of macaques is very similar to that of humans. They also suggest that the P pathway plays an important role in macaque chromatic sensitivity at all spatial frequencies, as well as achromatic sensitivity at high spatial and lower temporal frequencies.

Acrylamide↗
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↗
PubMed2006

Competitive sorption and diffusion of chromate and sulphate in a flow system with goethite in gel beads.

Column experiments and model simulations were employed to evaluate the processes involved in multicomponent solute transport in a system with heterogeneous flow. Column experiments were performed with goethite embedded in polyacrylamide gel beads. The gel forms an immobile water region that can be accessed by diffusion. A two-region transport model with diffusion into spheres was combined with a surface complexation model to predict reactive transport in the goethite-gel bead system. Chromate and sulphate breakthrough curves were measured in a set of transport experiments, along with corresponding changes in the pH of the effluent. Sorption and transport of sulphate and chromate in separate columns were predicted from independently measured sorption parameters. The model overestimated the pH changes in the effluent, possibly because of proton buffering by the polyacrylamide gel. The effect of competitive sorption on transport was examined in experiments with both anions present. The model predicted the effect of competition very well in a system initially equilibrated with sulphate, followed by infiltration with chromate. However, when sulphate was infiltrated after equilibration with chromate, chromate desorption and sulphate adsorption were clearly overestimated by the transport model. The exchange between the more strongly bound chromate and the sulphate added subsequently may be too slow to cause a substantial chromate peak in the effluent. This suggests that the local equilibrium assumption was not applicable in this case.

Adsorption↗
PubMed2005

Adsorption of chromate by clinoptilolite exchanged with various metal cations.

Unmodified zeolite surfaces show no affinity for anions, due to the fact that zeolites are negatively charged. Thus, adsorption of anions by zeolites has not been given much attention. In this work, after modification of clinoptilolite by different cations, the mineral was found to adsorb a considerable amount of the divalent anion chromate. Chromate adsorption was proportional to the K(sp) of the chromate precipitate and the amount of the exchangeable cation. The amount of chromate adsorbed was maximized when the Pb-exchanged form was used. Chromate desorption in deionized water indicated that between 2.50% and 18.60% of the adsorbed chromate was released depending upon the exchangeable cation. Some of the exchanged forms are candidate materials for adsorption and immobilization of chromate.

Adsorption↗
PubMed2000

Analysis of chromate-induced DNA-protein crosslinks with the comet assay.

Modifications of the comet assay have been introduced to measure crosslinks by determining the reduction of induced DNA migration. Our previous results indicated that the modified protocol of the alkaline comet assay is a sensitive tool for the detection of formaldehyde-induced DNA-protein crosslinks. But results for mitomycin C and cisplatin suggested that the modified protocol is not well suited for the evaluation of DNA-DNA crosslinkers. We now used the comet assay to investigate in V79 cells the effect of potassium chromate (K(2)CrO(4)), another DNA-protein crosslinker, to see whether the results obtained for formaldehyde can be generalized. However, chromate did not reduce spontaneous or radiation-induced DNA migration in the alkaline (pH 13) comet assay but led to a small but significant induction of DNA migration. A crosslinking effect of chromate could also not be detected with the alkaline comet assay after postincubation of cells in normal medium after chromate treatment to enable repair of other (migration-inducing) lesions that might mask the crosslinking effect. Exposure of slides to proteinase K further increased DNA migration of chromate-treated cells, thus indicating the presence of DNA-protein crosslinks. In contrast to the alkaline comet assay, a "neutral" version at pH 9 was suited to demonstrate reduced induction of DNA migration after gamma-irradiation of chromate-treated cells. The crosslinking effect was seen immediately at the end of the chromate treatment as well as after a 3h postincubation period. Using the "neutral" protocol in combination with proteinase K, we were able to demonstrate the presence of DNA-protein crosslinks as the probable cause for the migration-reducing effect. Further investigations will have to show whether this protocol can be recommended as a universal approach for the detection of DNA-protein crosslinks and also of DNA-DNA crosslinks with the comet assay.

Animals↗