Search PubMed⌕ Search

Biomedical subjects

J Chakrabarti

Publications and source records attributed to J Chakrabarti.

At least 19 recordsLinked to original sources
PubMed2006

Accuracy of mammography in predicting histological extent of ductal carcinoma in situ (DCIS).

UNLABELLED: Accuracy of mammography in predicting pathological extent of ductal carcinoma in situ (DCIS). BACKGROUND AND AIMS: Mammographic extent is the main determinant for offering wide local excision (WLE) for DCIS. It is recognized that this is not always accurate. Patients who prove to have larger lesions than predicted require further surgery. The aim of this study was to define the degree of variance between mammographic (MMG) and pathological (path) measurements of DCIS and to analyse the factors predicting a significant discrepancy. METHODS: The pathological and mammographic data for 174 cases of DCIS were reviewed. RESULTS: The mammographic size was bigger than the histological size in 97 (55.7%) and there was >10mm difference in 18 (10.3%) cases. The histological size was bigger than the mammographic size in 69 (39.7%) cases and >10mm difference was found in 30 (17.2%) cases. There was a significant relationship between larger MMG size, MMG size measured in two dimensions (MMG bi-dimensional product) and MMG-path size discrepancy (p<0.01). In addition, the larger the size discrepancy, the greater the chance of requiring more than one therapeutic procedure (p<0.01). There was no significant correlation between age, histological grade, mammographic density and shortest distance from nipple with degree of mammographic-pathological size discrepancy.

Adult↗
PubMed2006

Interval breast cancers: prognostic features and survival by subtype and time since screening.

OBJECTIVES: To investigate the hypothesis that interval cancers arising soon after the previous screen and true interval cancers are biologically aggressive and have a relatively poor prognosis compared with other interval cancers, and to assess which prognostic features are relevant to interval cancers. METHODS: Analysis of prognostic pathological features (grade, lymph node stage, size, vascular invasion, oestrogen receptor [ER] status and histological type), radiological features (comedo/non-comedo calcification and spiculation) and survival for 538 invasive interval breast cancer cases by type and time since previous screen. RESULTS: Late interval cancers were less likely to be lymph node positive (13 versus 43%, P = 0.003). Type 1 interval cancers were more likely to be histological grade 3 than type 2 (minimal signs) and type 3 (false-negative) intervals (52 versus 35%, P = 0.05). Type 3 interval cancers were more likely to have lobular features than other intervals (47 versus 20%, P < 0.0001). There was no significant survival difference by interval cancer type (P = 0.64) or interval year (P = 0.83). At univariate analysis of all interval cancers, tumour size, grade, nodal stage, ER status, vascular invasion and comedo calcification were associated with survival. On multivariate analysis of prognostic features significant at univariate analysis, nodal stage (P value = 0.009), tumour size (P = 0.001), ER status (P < 0.0001) and vascular invasion (P < 0.0001) maintained independent significance. CONCLUSIONS: Our study shows that true intervals and interval cancers arising quickly after screening do not have a worse prognosis than other interval cancers, and that interval cancers have a unique set of prognostic features.

Breast Neoplasms↗
PubMed2005

Flow-induced transverse electrical potential across an assembly of gold nanoparticles.

We report the generation of a potential difference, of the order of tens of millivolts, induced by the flow of polar liquids over an assembly of gold nanoparticles. The device consisted of two conducting glass plates, one of which contained the gold nanoparticle multilayer assembly. The potential generated is in transverse direction to the flow and is dependent on the nature of the flowing liquid. We propose a simple theoretical model to account qualitatively for the generation of the flow-induced transverse potential.

Journal Article↗
PubMed2004

Sanguinarine: an evaluation of in vivo cytogenetic activity.

Sanguinarine (SG), a benzophenanthridine alkaloid, has been shown to possess anti-microbial, anti-inflammatory and antioxidant properties. In the UK and USA its salts has been in use in mouthwashes and toothpastes to inhibit dental plaque and improve gingival health. In India and Nepal consumption of mustard oil contaminated with argemone seeds containing sanguinarine, was associated with "dropsy" syndrome. In the present study, SG was evaluated in vivo in mouse bone marrow cells for its ability to induce clastogenicity and DNA damage in terms of increased sister chromatid exchange (SCE) frequencies. Doses of 5, 10, and 15 mg/kg body weight of SG given intra peritoneally induced a positive dose-dependent significant clastogenicity and SCE frequency increases (trend test alpha < or = 0.05). The minimum effective concentration to induce clastogenic and DNA damage was 10mg of SG/kg body weight. In addition to examining SCEs, the BrdUrd-differential technique was utilized to assess the effect of SG on cell replication. The analysis revealed that SG treatment did not significantly affect the distribution of cells among the different phases of the cell cycle. The proliferation rate index and average generation time data were statistically non-significant. This indicated that the alkaloid was not cytotoxic to the bone marrow cells at the doses tested. Based on the results of the present findings, the use of this alkaloid should be restricted.

Alkaloids↗
PubMed2004

The transcription factor DEC1 (stra13, SHARP2) is associated with the hypoxic response and high tumour grade in human breast cancers.

DEC1, also known as SHARP-2 or Stra13, plays important roles in embryonic development, proliferation, apoptosis and cell differentiation in the mouse. DEC1 was recently identified as hypoxically induced in cDNA microarray studies of the human renal carcinoma cell line RCC4, to be regulated through hypoxia-inducible factor (HIF)-1alpha and via HIF-1alpha, able to block adipocyte differentiation. Nevertheless, its distribution and role in hypoxia and differentiation in human breast cancer are unknown. We therefore examined the pattern and level of expression of DEC1 using immunohistochemistry in whole tissue sections in normal, in situ and invasive breast carcinomas, and correlated the level of expression of DEC1 and clinicopathological factors and hypoxic tumour markers in 253 invasive carcinomas on tissue microarrays. We observed an increase in DEC1 expression during progression from normal to in situ and invasive carcinoma. Expression was not restricted to the tumour cell element but was also observed in endothelial, fibroblasts and inflammatory cells. There was a significant positive correlation between DEC1 and tumour grade (P=0.01), HIF-1alpha (P=0.04) and the hypoxically regulated gene angiogenin (P<0.0001), but no significant associations were observed with patient age (P=0.15), lymph node status (P=0.8), tumour size (P=0.3), oestrogen receptor (P=0.45), epidermal growth factor receptor (P=0.27) or Chalkley vessel count (P=0.45). There was no difference in relapse-free (P=0.84) or overall (P=0.78) survival. These findings suggest that DEC1 plays an important role in the progression to invasive breast cancer and that it may provide a mechanism by which hypoxia blocks tumour differentiation, and may contribute to a more aggressive phenotype. Reversing this phenotype may alter the biological behaviour of individual tumours.

Adult↗
PubMed2004

Reentrance effect in the lane formation of driven colloids.

Recently it has been shown that a strongly interacting colloidal mixture consisting of oppositely driven particles undergoes a nonequilibrium transition towards lane formation provided the driving strength exceeds a threshold value. We predict here a reentrance effect in lane formation: for fixed high driving force and increasing particle densities, there is first a transition towards lane formation which is followed by another transition back to a state with no lanes. Our result is obtained both by Brownian dynamics computer simulations and by a phenomenological dynamical density functional theory.

Journal Article↗
PubMed2004

Simulation of the kinetics of a sphere attached to a fluctuating polymer: Implications for target search by DNA-binding proteins.

We simulate the dynamics of a sphere, bound with a certain probability onto the beads of a harmonic bead-spring polymer in a confined geometry. The sphere hops from ith to the spatially closest i+/-kth bead. There is a crossover between kinetics dominated by different mechanisms with increasing binding probability. We relate these observations to the context of a biologically important problem of target location by DNA-binding proteins within a genome.

Binding Sites↗
PubMed2003

Coding DNA sequences: statistical distributions.

The base distributions in coding DNA sequences (CDS) are investigated. We explore the scaling properties of the 4-dimensional directed random walk and compare them with that for the DNA sequences. Inference from these observation are, however, contradicted by alternate analysis using factorial moments. To resolve this conflict we look directly at the nucleotide base distributions. In all the cases the base distributions change from gaussian to non-gaussian as the scale size is increased. The CDS, therefore, have nucleotide distributions different from the random.

Animals↗
PubMed2003

Prenatal exposure to high galactose adversely affects initial gonadal pool of germ cells in rats.

BACKGROUND: In rats, prenatal exposure to high concentrations of galactose may contribute to a condition that is equivalent to the premature ovarian failure (POF) component of human galactosaemia. We investigated if development of POF under experimental galactosaemia-like conditions was attributed to impaired germ cell migration. METHODS: Pregnant rats were fed pellets supplemented with, or without, 35% galactose from day 3 of conception continuing through parturition. Between days 12-15, embryos from one uterine horn were dissected out. Primordial germ cells (PGC) were histochemically localized and counted on the basis of binding of Dolichos biflorus agglutinin, a lectin specific for terminal N-acetylgalactosamine (GalNAc), to the surface glycoconjugate of the germ cells. The embryos from the other uterine horn were maintained until parturition. Liver activity of uridine diphosphate galactose 4-epimerase, the enzyme involved at multiple steps in the process of synthesis of GalNAc, was assayed in 1-2 day old female pups. RESULTS: The numbers of PGC at the day-specific sites on all days of examination were significantly lower (P </= 0.0003), and liver epimerase activity was significantly (P = 0.000001) reduced in the galactose-exposed group. CONCLUSION: Impaired germ cell migration leading to the development of gonads with deficient initial pools of germ cells may form the causal link between galactosaemia and POF.

Animals↗
PubMed2003

Galactose toxicity in the rat as a model for premature ovarian failure: an experimental approach readdressed.

BACKGROUND: The pathophysiological mechanisms underlying premature ovarian failure (POF) are largely unknown. Our objective was to develop a working animal model to explore the pathogenesis of POF. Since galactosaemic women eventually develop POF, we evaluated the potential of experimental galactose toxicity as the proposed model. METHODS: Pregnant rats were fed pellets supplemented with or without 35% galactose from day 3 of conception continuing through weaning of the litters. Female offspring were evaluated for serum levels of galactose and galactose-1-phosphate, growth rate, onset of puberty, reproductive cyclicity, ovarian complement of follicles, hypothalamo-pituitary-ovarian function and follicular response to gonadotrophins. RESULTS: Galactose toxicity delayed the onset of puberty and developed a state of hypergonadotrophic hypoestrogenism. The characteristic low FSH levels at weaning followed by pubertal spurts of gonadotrophins and estradiol (E(2)) secretion of the controls was replaced by a sustained high level of FSH and a low level of E(2) under galactose toxicity. The ovary developed with apparently normal or deficient complement of follicles. Ovarian response to exogenous gonadotrophin stimulation was blunted, but the response improved significantly when the stimulation was preceded by pituitary desensitization. CONCLUSION: Experimental galactose toxicity may serve as a model for exploring some of the basic tenets of POF.

Aging↗
PubMed2001

Codon distributions in DNA.

The codons, 64 in number, are distributed over the coding parts of DNA sequences. The distribution function is the plot of frequency versus rank of the codons. These distributions are characterized by parameters that are almost universal, i.e., gene independent. There is but a small part that depends on the gene. We present the theory to calculate the universal (gene-independent) part. The part that is gene-specific, however, has undetermined overlaps and fluctuations.

Animals↗
PubMed2001

Cytogenetical effects of sonication in mice and their modulations by actinomycin D and a homeopathic drug, Arnica 30.

Experiments were designed to examine if Actinomycin D, an antibiotic, and Amica 30, a homeopathic drug used against shock and injury, can ameliorate cytogenetic damage induced by single or multiple exposures to ultrasonication. Separate sets of healthy mice were directly exposed to sonication for two minutes either once or they received multiple exposures at an interval of 20 days. The mice were then assessed at different intervals, against suitable controls, using parameters like chromosome aberrations (CA), mitotic index (MI), sperm head anomaly (SHA) and micronucleated erythrocytes (MNE). Separate groups of sonicated mice were either orally administered with Arnica 30 (alcohol 30 in control) or injected intramuscularly with Actinomycin-D (AMD). Elevated frequencies of CA, MI, MNE and SHA were noted in sonicated series. AMD had genotoxic effects of its own and also had additive effects on sonication induced genotoxicity. Sonicated mice fed with Arnica 30 showed appreciably reduced genotoxicity as against alcohol 30 and distilled water fed controls, thereby showing ameliorating effect which may have human application.

Administration, Oral↗
PubMed2000

Gas-liquid transition in a two-dimensional system of millimeter-sized like-charged metal balls

Metal balls with a diameter of 1.59 mm, gently rubbed against a dielectric surface using a shaker, are seen to spontaneously exhibit a two-dimensional liquidlike order with macroscopic dimensions, viz., interball distances of several millimeters. This liquidlike order transforms to a gaslike order through coexistence upon decreasing the area fraction of the balls. The measured pair interaction of like-charged balls surprisingly exhibits a long-range attractive term analogous to that in charged colloids.

Journal Article↗
PubMed2000

In vivo cytogenetic studies on blends of aspartame and acesulfame-K.

Aspartame and acesulfame-K, non-nutritive sweeteners, are permitted individually in diets and beverages. These sweeteners of different classes, used in combination, have been found to possess a synergistic sweetening effect. Whether they also have a synergistic genotoxic effect is unknown. Swiss Albino male mice were exposed to blends of aspartame (3.5, 35, 350mg/kg body weight) and acesulfame-K (1.5, 15 and 150mg/kg body weight) by gavage. Bone marrow cells isolated from femora were analysed for chromosome aberrations. Statistical analysis of the results show that aspartame in combination with acesulfame-K is not significantly genotoxic.

Animals↗
PubMed2000

Effect of wall deformations on a confined fluid

We investigate the effect of wall deformations on a fluid confined in a slit of deformable walls. Monte Carlo (MC) simulations show that the fluid undergoes rarefaction or condensation depending on the wall rigidity for a small wall separation. The slope of the mean squared displacement as a function of MC steps has an algebraic dependence on the wall rigidity. The simulated density profile is qualitatively accounted for by means of a mean-field theory.

Journal Article↗
PubMed2000

Chromosome banding studies in an Indian mullet: evidence of structural rearrangements from NOR locations.

C-, G- and NOR bands have been studied in the female sex of Rhinomugil corsula. (Mugilidae, Pisces) by deploying the conventional methodologies with suitable modifications of minor nature. The diploid metaphase complements contained 48 acrocentric chromosomes. The localization of C-band heterochromatin was found to be mostly at or near the centromeric regions of the acrocentric chromosomes. The G-type bands were not so well defined, but some of the G-banded chromosomes also contained C-bands. Interestingly, silver-positive NORs were found at the telomeric ends of five acrocentric chromosomes, including one homologous pair having NORs in both chromatids, while one chromosome showed NORs in both of its chromatids and the other two had only one NOR localized at one of its chromatids. This would suggest that one homologue of the second pair of NOR-bearing chromosomes possibly underwent a chromatid exchange with a non-NOR bearing chromosome. This is quite a unique situation not reported earlier in any species of fish., though some other form of NOR-polymorphism/heteromorphism has rarely been reported. Therefore, further exploration in natural populations of this species to examine the other sex and to verify if there also exists other chromosomally polymorphic races (in respect of NOR-polymorphism) of this species, would be rewarding.

Animals↗
PubMed1999

Surface-induced ordering of a molecular fluid of flat hexagonal structure in a narrow graphite slit.

We systematically investigate by Monte Carlo simulations the role of the wall structure on a fluid of flat hexagonal molecules confined between two graphite walls. Our simulations show that the centers of mass of the molecules in different layers undergo an order-disorder transition as the wall separation increases, irrespective of the details of the wall structure. The wall structure thus becomes insignificant for the intervening fluid even down to a surprisingly low wall separation.

Journal Article↗