Biomedical subjects

A Bhattacharjee

Publications and source records attributed to A Bhattacharjee.

At least 19 recordsLinked to original sources

PubMed2006

Cloning and functional expression of an acyl-ACP thioesterase FatB type from Diploknema (Madhuca) butyracea seeds in Escherichia coli.

A cDNA of fatty acyl-acyl carrier protein (ACP) thioesterase (Fat) from developing seed of Madhuca butyracea has been cloned. The deduced amino acid sequence of the cDNA corresponding to the mature polypeptide showed 30-40% and 60-75% identity to the reported FatA and FatB class of plant thioesterases, respectively. This gene, MbFatB, is present as a single copy in M. butyracea genome and the MbFatB protein was detected clearly in seed tissues of this plant but not in that of Indian mustard (Brassica juncea). Heterologous expression of the MbFatB gene driven by different promoters in E. coli wild type and fatty acid beta-oxidation mutant (fadD88) strains resulted production of the recombinant protein with various fusion tags either as biologically inactive (insoluble) or functionally active forms. Expression of functionally active recombinant MbFatB in E. coli affected bacterial growth and cell morphology as well as changed the fatty acid profiles of the membrane lipid and the culture supernatant. Alteration of the fatty acid composition was directed predominantly towards palmitate and to a lesser extent myristate and oleate due to acyl chain termination activity of plant thioesterase in bacteria. Thus, this new MbFatB gene isolated from a non-traditional oil-seed tree can be used in future for transgenic development of oil-seed Brassica, a widely cultivated crop that expresses predominantly oleoyl-ACP thioesterase (FatA) in its seed tissue and has high amount of unwanted erucic acid in edible oil in order to alter the fatty acid profile in a desirable way.

Amino Acid Sequence↗

PubMed2006

Intermediate nonlinear evolution of the Parker instability: formation of convection-induced discontinuities and absence of finite-time singularities.

Direct numerical simulations of the line-tied Parker (or magnetic Rayleigh-Taylor) instability, based on the fully compressible ideal magnetohydrodynamic equations, are presented. In the intermediate nonlinear phase, the instability continues to grow exponentially in time and the plasma tends to develop convection-induced discontinuities in the form of shocklike coherent structures. No evidence of finite-time singularities is seen.

Journal Article↗

PubMed2005

Bernstein-Greene-Kruskal modes in a three-dimensional plasma.

Bernstein-Greene-Kruskal modes in a three-dimensional (3D) unmagnetized plasma are constructed. It is shown that 3D solutions that depend only on energy do not exist. However, 3D solutions that depend on energy and additional constants of motion (such as angular momentum) do exist. Exact analytical as well as numerical solutions are constructed assuming spherical symmetry, and their properties are contrasted with those of 1D solutions. Possible extensions to solutions with cylindrical symmetry with or without a finite magnetic guide field are discussed.

Journal Article↗

PubMed2005

Collisionless reconnection in an electron-positron plasma.

Electromagnetic particle-in-cell simulations of fast collisionless reconnection in a two-dimensional electron-positron plasma (without an equilibrium guide field) are presented. A generalized Ohm's law in which the Hall current cancels out exactly is given. It is suggested that the key to fast reconnection in this plasma is the localization caused by the off-diagonal components of the pressure tensors, which produce an effect analogous to a spatially localized resistivity.

Journal Article↗

PubMed2004

Oesophageal atresia and biliary atresia: a rare association.

Oesophageal atresia is known to be associated with cardiovascular, gastrointestinal, genitourinary and skeletal anomalies. Its association with biliary atresia is very rare and only a few cases have been reported in the literature. Although biliary atresia could be part of a multiple anomaly syndrome, its isolated occurrence is even rare. We present a case of oesophageal atresia associated with biliary atresia.

Abnormalities, Multiple↗

PubMed2004

Complete spectrum of kinetic eigenmodes for plasma oscillations in a weakly collisional plasma.

Kinetic eigenmodes of plasma oscillations in a weakly collisional plasma, described by a collision operator of the Fokker-Planck type, are obtained in closed form for initial-value as well as for boundary-value problems. These eigenmodes, which are smooth and compose a complete discrete spectrum, play the same role for weakly collisional plasmas as the Case-Van Kampen modes do for collisionless plasmas.

Journal Article↗

PubMed2003

Nonlinear theory of void formation in colloidal plasmas.

A nonlinear time-dependent model for void formation in colloidal plasmas is proposed. For experimentally relevant initial conditions, the model describes the nonlinear evolution of a zero-frequency linear instability that grows rapidly in the nonlinear regime and subsequently saturates to form a void. A number of features of the model are consistent with experimental observations under laboratory and microgravity conditions.

Journal Article↗

PubMed2002

Evolution of a dust void in a radio-frequency plasma sheath.

The onset and growth of a dust void are investigated in a radio-frequency (rf) sheath of a capacitively coupled argon plasma. A circularly symmetric void emerges and grows with increasing rf power and pressure in the central region of the dust cloud levitating in the sheath. Experimental measurements of the void diameter are compared with the predictions of a simple phenomenological theory, based on a balance of forces on dust grains.

Journal Article↗

PubMed2002

Phonon spectrum in a plasma crystal.

The Fourier spectra of longitudinal and transverse waves corresponding to random particle motion were measured in a two-dimensional plasma crystal. The crystal was composed of negatively charged microspheres immersed in a plasma at a low gas pressure. The phonons were found to obey a dispersion relation that assumes a Yukawa interparticle potential. The crystal was in a nonthermal equilibrium, nevertheless phonon energies were almost equally distributed with respect to wave number over the entire first Brillouin zone.

Journal Article↗

PubMed2002

Dispersion relations of longitudinal and transverse waves in two-dimensional screened Coulomb crystals.

Dispersion relations of longitudinal and transverse waves in two-dimensional (2D) screened-Coulomb crystals were investigated. The waves were excited in 2D crystals made from complex plasmas, i.e., dusty plasmas, by applying radiation pressure of laser light. The dependencies of the dispersion relation on the shielding parameter, the damping rate, and the wave propagation direction were experimentally measured. The measured dispersion relations agree reasonably with a recently developed theory, and the comparison yields the shielding parameter and the charge on particles.

Journal Article↗

PubMed2001

Magnetic-field-dependent heat capacity of the single-molecule magnet [Mn(12)O(12)(O(2)CEt)(16)(H(2)O)(3)].

Accurate heat capacities of the single-molecule magnet [Mn(12)O(12)(O(2)CEt)(16)(H(2)O)(3)] were measured from 0.3 to 311 K by adiabatic calorimetry without an external magnetic field. Heat-capacity anomalies were separated by assuming several contributions including lattice vibration, magnetic anisotropy, and hyperfine splitting. Among them, a tiny thermal anomaly between 1 and 2 K is attributable to the presence of Jahn-Teller isomers. The heat capacities of the polycrystalline sample were also measured with applied magnetic fields from 0 to 9 T in the 2-20 K temperature region by the relaxation method. With an applied magnetic field of up to 2 T, a steplike heat-capacity anomaly was observed around the blocking temperature T(B) approximately 3.5 K. The magnitude of the anomaly reached a maximum at 0.7 T. With a further increase in the magnetic field, the step was decreasing, and finally it disappeared above 3 T. The step at T(B) under 0.7 T can be roughly accounted for by assuming that a conversion between the up-spin and down-spin states is allowed above T(B) by phonon-assisted quantum tunneling, while it is less effective below T(B). Excess heat capacity under a magnetic field revealed a large heat-capacity hump around 14 K and 2 T, which would be attributed to a thermal excitation from the S = 9 ground state to the spin manifold with different S values, where S is the total spin quantum number.

Journal Article↗

PubMed2001

Scaling of collisionless forced reconnection.

The scaling of the reconnection electric field in a collisionless plasma is determined analytically for a model of forced reconnection. In particular, the dependence of the length of the reconnection layer on the ion skin depth and the boundary conditions is calculated explicitly. Analytical results are tested by Hall magnetohydrodynamics simulations.

Journal Article↗

PubMed2001

Classification of human lung carcinomas by mRNA expression profiling reveals distinct adenocarcinoma subclasses.

We have generated a molecular taxonomy of lung carcinoma, the leading cause of cancer death in the United States and worldwide. Using oligonucleotide microarrays, we analyzed mRNA expression levels corresponding to 12,600 transcript sequences in 186 lung tumor samples, including 139 adenocarcinomas resected from the lung. Hierarchical and probabilistic clustering of expression data defined distinct subclasses of lung adenocarcinoma. Among these were tumors with high relative expression of neuroendocrine genes and of type II pneumocyte genes, respectively. Retrospective analysis revealed a less favorable outcome for the adenocarcinomas with neuroendocrine gene expression. The diagnostic potential of expression profiling is emphasized by its ability to discriminate primary lung adenocarcinomas from metastases of extra-pulmonary origin. These results suggest that integration of expression profile data with clinical parameters could aid in diagnosis of lung cancer patients.

Adenocarcinoma↗

PubMed2001

Dynamics of electric-field-induced molecular reorientation of a surface-stabilized antiferroelectric liquid crystal in the smectic-C* phase probed by time-resolved infrared spectroscopy.

Polarization dependent and time-resolved Fourier transform infrared studies have been carried out on the electric-field-induced ferroelectric phase (Sm-C*) of a chiral, antiferroelectric liquid crystal at different temperatures. Polarization dependent infrared spectra under dc electric field reveal that the average alkyl chain axis does not coincide with the mesogen axis and is less tilted with respect to the layer normal than the mesogen. The analysis of the various absorbance profiles obtained from temporal response of absorption changes of infrared bands at different time delays provides clear evidence for biased orientation and hindered rotation of almost all the molecular segments around the average molecular long axis and the rotation of the whole molecule around its axis is also hindered. It is further inferred that the mesogen, the chiral segment, and the alkyl chains reach their equilibrium orientations at nearly the same time on switching the polarity of the ac electric field but the different molecular segments reorient through different angles.

Journal Article↗

PubMed2001

Longitudinal and transverse waves in Yukawa crystals.

A unified theoretical treatment is given of longitudinal (or compressional) and transverse modes in Yukawa crystals, including the effects of damping. Dispersion relations are obtained for hexagonal lattices in two dimensions and bcc and fcc lattices in three dimensions. Theoretical predictions are compared with two recent experiments.

Journal Article↗

PubMed2001

Natural-resistance-associated macrophage protein 1 is an H+/bivalent cation antiporter.

In mammals, natural-resistance-associated macrophage protein 1 (Nramp1) regulates macrophage activation and is associated with infectious and autoimmune diseases. Nramp2 is associated with anaemia. Both belong to a highly conserved eukaryote/prokaryote protein family. We used Xenopus oocytes to demonstrate that, like Nramp2, Nramp1 is a bivalent cation (Fe2+, Zn2+ and Mn2+) transporter. Strikingly, however, where Nramp2 is a symporter of H+ and metal ions, Nramp1 is a highly pH-dependent antiporter that fluxes metal ions in either direction against a proton gradient. At pH 9.0, oocytes injected with cRNA from wild-type murine Nramp1 with a glycine residue at position 169 (Nramp1(G169); P=3.22x10(-6)) and human NRAMP1 (P=3.87x10(-5)) showed significantly enhanced uptake of radiolabelled Zn2+ compared with water-injected controls. At pH 5.5, Nramp1(G169) (P=1.34x10(-13)) and NRAMP1 (P=1.09x10(-6)) oocytes showed significant efflux of Zn2+. Zn2+ transport was abolished when the proton gradient was dissipated using carbonyl cyanide p-trifluoromethoxyphenylhydrazone. Using pre-acidified oocytes, currents of 130+/-57 nA were evoked by 100 microM Zn2+ at pH 7.5, and 139+/-47 nA by 100 microM Fe2+ at pH 7.0, in Nramp1(G169) oocytes; currents of 254+/-49 nA and 242+/-26 nA were evoked, respectively, in NRAMP1 oocytes. Steady-state currents evoked by increasing concentrations of Zn2+ were saturable, with apparent affinity constants of approx. 614 nM for Nramp1(G169) and approx. 562 nM for NRAMP1 oocytes, and a curvilinear voltage dependence of transporter activity (i.e. the data points approximate to a curve that approaches a linear asymptote). In the present study we propose a new model for metal ion homoeostasis in macrophages. Under normal physiological conditions, Nramp2, localized to early endosomal membranes, delivers extracellularly acquired bivalent cations into the cytosol. Nramp1, localized to late endosomal/lysosomal membranes, delivers bivalent cations from the cytosol into this acidic compartment where they may directly affect antimicrobial activity.

Animals↗

PubMed2000

Interactive model of women's stressors, personality traits and health problems.

Theories have linked various stressors with health problems, and some studies have identified personality traits that enhance health. However, few studies have examined the interaction among women's stressors, personality traits and their health. This retrospective study (1996-1997) analysed the effects of women's major stressors and personality traits on symptoms of health problems, and developed a model of women's health based on the interaction among these factors. A convenience sample of 300 women aged between 18 and 66 years completed a questionnaire that measured three types of stressors, eight personality traits and 40 symptoms of health problems. Principle components and factor analyses identified the best items to measure the stressors, traits and problems. New reduced data subsets were constructed for classification tree analyses to identify the effects of stressors and personality traits on women's health. Women with medium or high stressors and low assertiveness, low hardiness, or the inability to express their feelings, were more likely to report physical symptoms than women who were stronger in these personality traits. Also, women with medium or high stressors and low to medium trust or love relationships were very likely to report high emotional symptoms, as were women with high trust or love, who did not express their feelings. An interactive model of women's health was supported. The amount of women's stressors and their personality traits may increase or diminish their stress response and affect their health. Nurses can identify women with high stressors and unhealthy personality traits that increase their risk for stress-related illnesses, and assist these women to modify their stressors or personality traits to enhance their health.

Adolescent↗

PubMed2000

ATP in human skin elicits a dose-related pain response which is potentiated under conditions of hyperalgesia.

Despite the considerable interest in the possibility that ATP may function as a peripheral pain mediator, there has been little quantitative study of the pain-producing effects of ATP in humans. Here we have used iontophoresis to deliver ATP to the forearm skin of volunteers who rated the magnitude of the evoked pain on a visual analogue scale. ATP consistently produced a modest burning pain, which began within 20 s of starting iontophoresis and was maintained for several minutes. Persistent iontophoresis of ATP led to desensitization within 12 min but recovery from this was almost complete 1 h later. Different doses of ATP were delivered using different iontophoretic driving currents. Iontophoresis of ATP produced a higher pain rating than saline, indicating that the pain was specifically caused by ATP. The average pain rating for ATP, but not saline, increased with increasing current. Using an 0.8 mA current, subjects reported pain averaging 27.7 +/- 2.8 (maximum possible = 100). Iontophoresis of ATP caused an increase in blood flow, as assessed using a laser Doppler flow meter. The increase in blood flow was significantly greater using ATP than saline in both the iontophoresed skin (P < 0.01) and in the surrounding skin, 3 mm outside the iontophoresed area (P < 0.05). The pain produced by ATP was dependent on capsaicin-sensitive sensory neurons, since in skin treated repeatedly with topical capsaicin pain was reduced to less than 25% of that elicited on normal skin (2.1 +/- 0.4 compared with 9.3 +/- 1.5 on normal skin). Conversely, the pain-producing effects of ATP were greatly potentiated in several models of hyperalgesia. Thus, with acute capsaicin treatment when subjects exhibited touch-evoked hyperalgesia but no ongoing pain, there was a threefold increase in the average pain rating during ATP iontophoresis (22.7 +/- 3.1) compared with pre-capsaicin treatment (7.8 +/- 2.6). Moreover, ATP iontophoresed into skin 24 h after solar simulated radiation (2 x minimal erythymic dose) resulted in double the pain rating of normal skin, increasing from 15.3 +/- 4.1 to 32.7 +/- 4.1. The pain response to saline was not significantly altered after UV irradiation at any time-point studied. We conclude that ATP produces pain by activating capsaicin-sensitive nociceptive afferents when applied to skin. The possibility that ATP activates nociceptors indirectly via its degradation products cannot be ruled out. The effects of ATP are dose-dependent and responses desensitize only slowly. In inflammatory conditions, ATP may be a potent activator of nociceptors and an endogenous mediator of pain.

Adenosine Triphosphate↗