Search PubMed⌕ Search

Biomedical subjects

A Chatterjee

Publications and source records attributed to A Chatterjee.

At least 217 records · Page 12Linked to original sources
PubMed1995

DNA strand breakage is correlated with unaltered base release after gamma irradiation.

Unaltered base release is correlated with strand breakage for gamma-irradiated bacteriophage PM2 DNA in aqueous solution at pH 7.4. The yield of DNA strand breaks is determined by the agarose gel electrophoresis method. High-performance liquid chromatography (HPLC) is used to assay the release of unaltered nucleic bases. Previously reported HPLC methods have been updated. Unaltered base release is linear with dose up to 424 Gy, where up to 0.2% of all DNA bases are released. No detectable amounts of unaltered nucleosides are released and, besides unaltered bases, only one other product released from DNA is observed. Base release yields do not reflect the PM2 GC content of 43%. Only 76% of all prompt strand breaks appear to be associated with the release of an unaltered free base, whereby the guanine, cytosine, adenine and thymine yields are 9, 27, 18 and 22% of the prompt strand break yield, respectively. Postirradiation incubation at 37 degrees C for 24 h increases the strand break yield 1.38-fold and the unaltered base release yield 1.76-fold such that 97% of the final strand breaks appear to be associated with the release of an unaltered base, whereby the guanine, cytosine, adenine and thymine yields are 10, 36, 23 and 28% of the final strand break yield, respectively. These data indicate that, given proper conditions, nearly every strand break leads to a base release. The bearing of these results on OH radical attack leading to strand breakage and base release is discussed.

Bacteriophages↗
PubMed1995

Disposable soft contact lens ulcers: a study of 43 cases seen at Manchester Royal Eye Hospital.

We report an outbreak of 43 episodes of presumed microbial keratitis in 42 disposable soft contact lens wearers seen in the Accident Room of Manchester Royal Eye Hospital during a period of 20 months, and compare this with the general incidence of contact lens-related corneal infection found in a retrospective survey of 6 months' Accident Room attendances during the same period. Thirty-seven patients had worn Acuvue lenses, three had worn Nuvue, and there was no record in two cases. Corneal scrapes were taken for microbiological examination in 27 patients, and 6 of these were culture positive. Conjunctival swabs were taken from eight eyes and one was culture positive. The contact lenses of 11 patients were sent for culture and all grew pathogenic organisms. Pseudomonas spp. were the most common organisms grown, having been found in three of six corneal scrapes and six of 11 contact lens cultures. All affected eyes responded promptly to cessation of contact lens wear and topical antibiotic therapy, with none sustaining severe or permanent visual loss. Reasons for the associated high risk of microbial keratitis are discussed. Thirty-three of the 42 patients responded to a questionnaire regarding lens wear and care and their responses are reported. In consequence, we consider disposable soft contact lenses to be relatively high-risk devices for the cosmetic management of simple myopia, and their continued use must be called into question.

Adolescent↗
PubMed1995

Sarcoidosis.

Explore the source record for details and available documents.

Child↗
PubMed1994

Comparative mapping of the actin-binding protein 280 genes in human and mouse.

Two genes encode actin-binding protein 280 isoforms. ABP-280 or filamin (FLN1) is present in the cytoskeleton of many cell types, whereas expression of FLN2 is limited to skeletal muscle and heart. FLN1 maps to human chromosome Xq28, and, by physical mapping in YAC clones, we have mapped the homologous murine locus (Fln1) to mouse chromosome X, in a region of syntenic homology with human chromosome X. We mapped FLN2 to human chromosome 7q32-q35 by analysis of somatic cell hybrids containing portions of chromosome 7, and, by using a mapping panel from an interspecific murine cross, we mapped the corresponding murine locus (Fln2) to murine chromosome 6 in a region homologous to human chromosome 7.

Animals↗
PubMed1994

A 2.3-Mb yeast artificial chromosome contig spanning from Gabra3 to G6pd on the mouse X chromosome.

A yeast artificial chromosome (YAC) contig of approximately 2.3 Mb has been constructed for the region of the mouse X chromosome between Gabra3 and G6pd. YACs were isolated from four genomic libraries by PCR or hybridization screening for the loci Gabra3, DXHX1104, F8a, DXHX52, DXBay2, L1cam, and Rsvp. Orientation of YACs was performed by isolation of ends using several PCR-based methods, including an adaptation for mouse YAC analysis of interspersed repetitive sequence (IRS)-vector PCR. YAC ends were mapped on a panel of somatic cell hybrids, in an interspecific backcross, using pulsed-field gel (PFG) electrophoresis or by hybridization to other YACs in the contig. Overlapping YACs were further aligned by restriction mapping using rare-cutter restriction endonucleases, as well as by comparison of IRS-PCR fingerprints. This contig represents the largest one assembled to date in the mouse. It should facilitate the isolation of genes in the region and may aid in the completion of a physical contig for the homologous human region, Xq28.

Animals↗
PubMed1994

The psychophysical power law and unilateral spatial neglect.

The relationship between objective measures and subjective experiences of sensory stimuli is described by a power law, psi = K phi beta, in which psi represents the psychological value and phi the physical value. The constant (K) and the exponent (beta) are empirically derived. This relationship is often assumed to correspond to properties of peripheral receptor sensory transduction. Patients with left-sided spatial neglect tend to bisect lines to the right of the objective midline. Line bisection bias was used as the dependent variable in how a patient with neglect and five normal subjects bisected lines of varying lengths. Analyzing these data as a power function accounted for over 99% of the variance in five different experimental conditions. The normal exponent matched the value expected from traditional psychophysical experiments of line length estimation, whereas the patient's exponent was diminished. The patient's data provide evidence for central nervous system participation in computations underlying psychophysical relationships. The notion that attentional and perceptual processes are closely linked was supported by the influence of attentional cuing on the power functions obtained in normal subjects. The descriptive precision of the power function uncovered qualitative variability in how normal subjects allocate attention across different spatial reference frames and demonstrated that this patient had a quantitative defect in directing attention across an allosteric reference frame, but a qualitative defect in directing attention across a viewer/environment reference frame.

Aged↗
PubMed1994

Genetic and physical mapping of a gene encoding a methyl CpG binding protein, Mecp2, to the mouse X chromosome.

The methyl CpG binding proteins (MeCP1 and MeCP2) are a class of proteins that bind to templates containing symmetrically methylated CpGs. Using an interspecific backcross segregating a number of X-linked markers, we have localized the Mecp2 gene in mouse to the X chromosome close to the microsatellite marker DXMit1. Detailed physical mapping utilizing an available YAC contig encompassing the DXMit1 locus has localized the Mecp2 gene to a 40-kb region between the L1cam and the Rsvp loci, indicating the probable position of a homologue on the human X chromosome.

Animals↗
PubMed1994

Monte Carlo approach in assessing damage in higher order structures of DNA.

We have developed a computer monitor of nuclear DNA in the form of chromatin fibre. The fibres are modeled as a ideal solenoid consisting of twenty helical turns with six nucleosomes per turn. The chromatin model, in combination with are Monte Carlo theory of radiation damage induces by charged particles, based on general features of tack structure and stopping power theory, has been used to evaluate the influence of DNA structure on initial damage. An interesting has emerged from our calculations. Our calculated results predict the existence of strong spatial correlations in damage sites associated with the symmetries in the solenoidal model. We have calculated spectra of short fragments of double stranded DNA produced by multiple double strand breaks induced by both high and low LET radiation. The spectra exhibit peaks at multiples of approximately 85 base pairs (the nucleosome periodicity), and approximately 1000 base pairs (solenoid periodicity). Preliminary experiments to investigate the fragment distributions from irradiated DNA, made by B. Rydberg at Lawrence Berkeley Laboratory, confirm the existence of short DNA fragments and are in substantial agreement with the predictions of our theory.

Chromatin↗
PubMed1994

A computational approach to the relationship between radiation induced double strand breaks and translocations.

A theoretical framework is presented which provides a quantitative analysis of radiation induced translocations between the ab1 oncogene on CH9q34 and a breakpoint cluster region, bcr, on CH 22q11. Such translocations are associated frequently with chronic myelogenous leukemia. The theory is based on the assumption that incorrect or unfaithful rejoining of initial double strand breaks produced concurrently within the 200 kbp intron region upstream of the second abl exon, and the 16.5 kbp region between bcr exon 2 and exon 6 interact with each other, resulting in a fusion gene. for an x-ray dose of 100 Gy, there is good agreement between the theoretical estimate and the one available experimental result. The theory has been extended to provide dose response curves for these types of translocations. These curves are quadratic at low doses and become linear at high doses.

Animals↗
PubMed1994

Contributions of the parietal and frontal lobes to sustained attention and habituation.

The parietal cortex may be important in sustaining attention toward visual stimuli in peripheral space whereas the frontal cortex may mediate selective attention through habituation to peripheral stimuli. To test this hypothesis, patients with focal lesions of either the parietal or frontal cortex or both and normal controls were studied using a paradigm known as Troxler fading. Accordingly, if one fixates on a centrally located stimulus and attends to a stationary stimulus in peripheral vision, the peripheral stimulus quickly fades from awareness (i.e. Troxler fading: Troxler [Verschwinden, unseres, Opthal, Vol. 2, pp. 51-53. Fromann, Jena, 1804]). Movement of the peripheral stimulus on the retina normally prevents Troxler fading. Results indicated that patients with parietal lesions not only reported accelerated Troxler fading but also reported fading of moving peripheral stimuli contralateral to their brain lesion. In contrast, patients with frontal lesions rarely reported Troxler fading. In one patient with a left parietal and a right frontal lobe lesion fading was hemi-spatially dissociated, being accelerated in right hemispace but absent in left hemispace. These observations suggest that the parietal and frontal cortices play complementary roles in attentional processing.

Aged↗
PubMed1994

Back pain in ophthalmologists.

A questionnaire regarding the working practices and incidence of back pain was sent to all 498 consultant ophthalmologists in the United Kingdom. Three hundred and twenty-five (65.3%) questionnaires were analysed by time spent in speciality, and time spent operating each week. One hundred and seventy-four ophthalmologists (54%) had significant attacks of back pain, with the longest-serving consultants having an increased incidence. The number and duration of acute attacks increased with years in speciality but was unrelated to time spent operating. Treatment included analgesics in 97 (56%), physiotherapy in 40 (23%), and 'alternative' medical treatment including osteopathy and chiropraxy in 14 (8%); no treatment was needed in 56 (32%). Investigation and treatment increased with years spent in speciality, 49 (28%) seeking medical advice, usually from a specialist, and 69 (39%) requiring further investigations including plain radiographs, CT scans, myelograms and MRI scans. Nine surgeons needed surgery for back pain.

Back Pain↗
PubMed1994

A comparison of the influences of body and environment centred reference frames on neglect.

Extrapersonal space can be defined by coordinate systems, or frames of reference, that are centred on the body (viewer) or on the environment. Although these frames are identical in the upright position, when the body is placed in positions orthogonal to gravity, the frames may be dissociable. We compared the influences of environmental and body-centred frames on line bisection in two patients with neglect who, when upright, neglected opposite dimensions of space. Through certain combinations of line placement and body orientation, the body and environmental frames were brought into opposition, and each frame predicted line bisection errors in an opposite direction. When the patients were positioned so that predictions of the two frames contrasted, both bisected lines as predicted by the environmental rather than the body-centred frame.

Aged↗