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Biomedical subjects

J Chakrabarti

Publications and source records attributed to J Chakrabarti.

At least 19 recordsLinked to original sources
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↗
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↗
PubMed1997

In vivo cytogenetic studies on mice exposed to acesulfame-K--a non-nutritive sweetener.

Acesulfame-K, a sweetening agent, was evaluated in vivo for its genotoxic and clastogenic potentials. Swiss albino male mice were exposed to the compound by gavage. Bone marrow cells isolated from femora were analysed for chromosome aberrations. Doses of 15, 30, 60, 450, 1500 and 2250 mg of acesulfame-K/kg body weight induced a positive dose-dependent significant clastogenicity (trend test alpha < 0.05). These doses were within the no-toxic-effect levels (1.5-3 g/kg body weight in rats) reported by the Joint Expert Committee for Food Additives of the World Health Organization and the Food and Agriculture Organization of the United Nations. In view of the present significant in vivo mammalian genotoxicity data, acesulfame-K should be used with caution.

Administration, Oral↗
PubMed1995

Diagnostic evaluation of myocardial abscesses. A new look at an old problem.

A myocardial abscess is a life threatening complication of infective endocarditis that necessitates early diagnosis in order to identify the need for emergent surgical intervention and improved prognosis. This review discusses the relevant historical aspects, clinical features suggestive of the diagnosis, associated conditions and various appropriate imaging modalities--in particular, trans-thoracic and trans-esophageal echocardiography, Indium-111 radionucleide scintigraphy, and computerized tomographic scanning. Specific clinical and echocardiographic criteria for identifying a myocardial abscess are discussed and comparative data presented from published studies in the literature.

Abscess↗
PubMed1994

In vivo cytogenetic studies on mice exposed to natural food colourings.

Safflower Yellow and Kokum Red, two food colourings developed from natural plant products, were assessed in vivo for their clastogenic potential. Swiss albino male mice were exposed to the compounds through ip injections. Bone marrow cells isolated from femora were analysed for chromosome aberrations. The results show that the two food colourings were weakly clastogenic.

Animals↗