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Biomedical subjects

D Das

Publications and source records attributed to D Das.

At least 55 records · Page 3Linked to original sources

Disseminated tuberculosis presenting as hemobilia, successfully treated by arterial embolization.

Tuberculosis, specially disseminated tuberculosis, involves the liver frequently. Focal hepatic tuberculosis with local hemorrhage has been reported. We report on a twenty-one year female with disseminated tuberculosis presenting with initially non-localisable massive upper gastrointestinal bleeding, subsequently found to have pancreatitis, right sided pleural effusion and hemobilia which was treated successfully.

Adult↗

Studies on Mg/Fe hydrotalcite-like-compound (HTlc) I. Removal of inorganic selenite (SeO3(2-)) from aqueous medium.

A Mg/Fe hydrotalcite-like-compound (HTlc) was prepared and its affinity toward the removal of SeO(3)(2-) from an aqueous medium was studied as a function of pH, time, temperature, particle dose, and SeO(3)(2-) concentration. The fraction of SeO(3)(2-) removal increases with decrease in both pH and temperature. The adsorption data are fitted to the Langmuir adsorption isotherm in the temperature range 303-333 K, and the thermodynamic parameters viz. standard Gibbs' free energy change (DeltaG degrees ), enthalpy change (DeltaH degrees ), and entropy change (DeltaS degrees ) are calculated. The negative value of DeltaH degrees indicates that the adsorption process is exothermic. The apparent equilibrium constants (K(a)) are also calculated and found to decrease with increase in temperature.

Adsorption↗

Topological jamming and the glass transition in a frustrated system.

The relationship between extended structures, glassy dynamics and an underlying critical point is examined in the context of a lattice model of fluctuating lines. Monte Carlo simulations are used to construct an effective, coarse-grained dynamics for the "order parameter" near the critical point. Analysis of the effective dynamics reveals that the critical point is associated with diverging barriers leading to the observed Vogel-Fulcher divergence of the relaxation times. A direct connection is established between the presence of extended structures and the activated dynamics.

Journal Article↗

Pharmacological studies on Myristica fragrans--antidiarrheal, hypnotic, analgesic and hemodynamic (blood pressure) parameters.

Recurrent diarrhea is prevalent in developing countries, particularly in tropical regions. A natural based antidiarrheal home remedy can serve as an ideal health tool to limit diarrhea-related morbidity and mortality. In the traditional Indian medical science of Ayurveda, nutmeg is one such plant said to possess antidiarrheal activity. A study was therefore planned to assess the various pharmacological effects (antidiarrheal, sedative, analgesic and blood pressure) of nutmeg. Both Nutmeg crude suspension (NMC) and petroleum ether (PE), but not aqueous extract (Aq), decreased the mean number of loose stools or increased the latency period. NMC increased intestinal tone while PE had no such effect. PE had no effect on guinea pig ileum, but inhibited the contraction produced by acetylcholine, histamine and prostaglandin. NMC but not PE extract showed a significant but weak analgesic effect. While PE effectively potentiated both phenobarbitone and pentobarbitone-induced sleeping time, NMC was considerably less effective. NMC administered intraduodenally did not produce much effect on blood pressure (BP), but potentiated the action of exogenously administered adrenaline and nor-adrenaline. On the other hand, PE in higher, but not lower, doses caused a precipitous fall in BP not blocked by atropine. Thus, overall extracts of nutmeg showed a good antidiarrheal effect, with a significant sedative property. The extracts possessed only a weak analgesic effect, with no harmful effects on blood pressure and ECG.

Administration, Oral↗

Surgical management of tennis elbow.

BACKGROUND: To ascertain whether there were any differences in the outcome of release of the common extensor origin and release of the common extensor origin and drilling of the lateral epicondyle in the management of recalcitrant tennis elbow. METHODS: One hundred and eleven patients (125 elbows; 40 males, median age: 47 years; 71 females, median age: 45 years) entered the study. The minimum follow-up period was 2 years (average follow-up: 52.8 months). Patients were reviewed at 2 and 6 or 8 weeks, and 3 and 6 months after surgery. If a complication ensued, or if a patient did not report improvements, they were followed up for at least 1 year postoperatively. Two years after the recruitment period had ended, telephone interviews were performed. We used a 1 to 10 scale when enquiring about pain, both preoperative and postoperative, with 1 as the best score and 10 the worst. We also determined patient satisfaction, grip strength, and elbow function. RESULTS: Seventy-five percent of patients had excellent or good results, with 73% of them being satisfied with the results of surgery. There was no statistical significance in the outcome of the 2 procedures (chi-square, p=0.488). There were no statistically significant differences between the 2 procedures regarding pain, satisfaction, elbow function, and grip strength. CONCLUSIONS: Release of the common extensor origin at the elbow is a relatively simple operation, and produces reliable long term relief of tennis elbow pain in at least 70% of patients.

Adolescent↗

Fluctuation-dominated phase ordering driven by stochastically evolving surfaces: depth models and sliding particles.

We study an unconventional phase ordering phenomenon in coarse-grained depth models of the hill-valley profile of fluctuating surfaces with zero overall tilt, and for hard-core particles sliding on such surfaces under gravity. We find that several such systems approach an ordered state with large scale fluctuations which make them qualitatively different from conventional phase ordered states. We consider surfaces in the Edwards-Wilkinson (EW), Kardar-Parisi-Zhang (KPZ) and noisy surface-diffusion (NSD) universality classes. For EW and KPZ surfaces, coarse-grained depth models of the surface profile exhibit coarsening to an ordered steady state in which the order parameter has a broad distribution even in the thermodynamic limit, the distribution of particle cluster sizes decays as a power-law (with an exponent straight theta), and the scaled two-point spatial correlation function has a cusp (with an exponent alpha=1/2) at small values of the argument. The latter feature indicates a deviation from the Porod law which holds customarily, in coarsening with scalar order parameters. We present several numerical and exact analytical results for the coarsening process and the steady state. For linear surface models with a dynamical exponent z, we show that alpha=(z-1)/2 for z<3 and alpha=1 for z>3, and there are logarithmic corrections for z=3, implying alpha=1/2 for the EW surface and 1 for the NSD surface. Within the independent interval approximation we show that alpha+straight theta=2. We also study the dynamics of hard-core particles sliding locally downward on these fluctuating one-dimensional surfaces, and find that the surface fluctuations lead to large-scale clustering of the particles. We find a surface-fluctuation driven coarsening of initially randomly arranged particles; the coarsening length scale grows as approximately t(1/z). The scaled density-density correlation function of the sliding particles shows a cusp with exponents alpha approximately 0.5 and 0.25 for the EW and KPZ surfaces. The particles on the NSD surface show conventional coarsening (Porod) behavior with alpha approximately 1.

Journal Article↗

Weak and strong dynamic scaling in a one-dimensional driven coupled-field model: effects of kinematic waves.

We study the coupled dynamics of the displacement fields in a one-dimensional coupled-field model for drifting crystals, first proposed by Lahiri and Ramaswamy [Phys. Rev. Lett. 79, 1150 (1997)]. We present some exact results for the steady state and the current in the lattice version of the model for a special subspace in the parameter space, within the region where the model displays kinematic waves. We use these results to construct the effective continuum equations corresponding to the lattice model. These equations decouple at the linear level in terms of the eigenmodes. We examine the long-time, large-distance properties of the correlation functions of the eigenmodes by using symmetry arguments, Monte Carlo simulations, and self-consistent mode-coupling methods. For most parameter values, the scaling exponents of the Kardar-Parisi-Zhang equation are obtained. However, for certain symmetry-determined values of the coupling constants the two eigenmodes, although nonlinearly coupled, are characterized by two distinct dynamic exponents. We discuss the possible application of the dynamic renormalization group in this context.

Journal Article↗

The binding interaction of HMG-1 with the TATA-binding protein/TATA complex.

High mobility protein-1 (HMG-1) has been shown to regulate transcription by RNA polymerase II. In the context that it acts as a transcriptional repressor, it binds to the TATA-binding protein (TBP) to form the HMG-1/TBP/TATA complex, which is proposed to inhibit the assembly of the preinitiation complex. By using electrophoretic mobility shift assays, we show that the acidic C-terminal domain of HMG-1 and the N terminus of human TBP are the domains that are essential for the formation of a stable HMG-1/TBP/TATA complex. HMG-1 binding increases the affinity of TBP for the TATA element by 20-fold, which is reflected in a significant stimulation of the rate of TBP binding, with little effect on the dissociation rate constant. In support of the binding target of HMG-1 being the N terminus of hTBP, the N-terminal polypeptide of human TBP competes with and inhibits HMG-1/TBP/TATA complex formation. Deletion of segments of the N terminus of human TBP was used to map the region(s) where HMG-1 binds. These findings indicate that interaction of HMG-1 with the Q-tract (amino acids 55-95) in hTBP is primarily responsible for stable complex formation. In addition, HMG-1 and the monoclonal antibody, 1C2, specific to the Q-tract, compete for the same site. Furthermore, calf thymus HMG-1 forms a stable complex with the TBP/TATA complex that contains TBP from either human or Drosophila but not yeast. This is again consistent with the importance of the Q-tract for this stable interaction and shows that the interaction extends over many species but does not include yeast TBP.

Amino Acid Sequence↗

Mathematical model for evaluation of mass transfer limitations in phenol biodegradation by immobilized Pseudomonas putida.

A mathematical model is proposed to analyze the mass transfer limitations in phenol biodegradation using Pseudomonas putida immobilized in calcium alginate. The model takes into account internal and external mass transfer limitations, substrate inhibition kinetics and the dependence of the effective diffusivity of phenol in alginate gel on cell concentration. The model is validated with the experimental data from batch fermentation. The effect of various operating conditions such as initial phenol concentration, initial cell loading, alginate gel loading on the biodegradation of phenol is experimentally demonstrated. Phenol degradation time is found to decrease initially and reach stationary value with increase in cell loading as well as gel loading. The model predicts these trends reasonably well and shows the presence of external mass transfer limitations. A new concept of effectiveness factor is introduced to analyze the overall performance of batch fermentation.

Biodegradation, Environmental↗

A novel method for eliminating the melanin pigments from melanoma cells undergoing cytogenetic analysis in cases of uveal melanoma.

A method has been developed to eliminate melanin pigments from chromosomal plates of uveal melanoma tumors. On preparing the chromosomal plates of tumor masses of posterior uveal melanoma for cytogenetic analysis in intermediate pigmented population, it was found that the melanin pigments obscured the cells and thereby the chromosomes. Thus, cytogenetic analysis could not be carried out. Hence, a method was developed in our laboratory to eliminate these obscuring pigments. Several different attempts were made to eliminate the melanin pigments. Finally, washing the cells with phosphate buffered saline before the harvesting stage served the purpose. After harvesting and preparing the chromosomal plates, the cells were found to be devoid of melanin pigments. The protocol would help researchers trying to carry out cytogenetic analysis on melanoma tumor masses in populations with intermediate to dark pigmentation.

Cytogenetics↗

A directed approach to improving the solubility of Moloney murine leukemia virus reverse transcriptase.

One of the difficulties that can impede structural work on a molecule of interest is limited solubility. Although functionally similar to the human immunodeficiency virus type-1 reverse transcriptase (HIV-1 RT), the Moloney murine leukemia virus reverse transcriptase (MMLV RT) differs both in architecture and solubility properties. Reverse transcriptase is an essential retroviral enzyme that replicates the single-stranded RNA genome of the retrovirus producing a double-stranded DNA copy, which is subsequently integrated into the host's genome. We have introduced a single amino acid substitution in the connection domain of an N-terminally truncated MMLV RT (L435K) that significantly improves the solubility of the enzyme eliminating the need for nonionic detergents in buffering storage solutions. The substituted enzyme retains near wild-type polymerase activity. An important consequence of the improved solubility of the L435K MMLV RT has been the ability to obtain diffraction quality crystals.

Amino Acid Substitution↗

Genetic profile of 81 retinoblastoma patients from a referral hospital in southern India.

PURPOSE: To determine chromosomal abnormalities and inheritance pattern in patients with retinoblastoma from a referral hospital in southern India. MATERIALS AND METHODS: Eighty-one retinoblastoma patients from 78 families were included in this study. Peripheral venous blood was taken for chromosomal analysis and pedigree was ascertained for segregation analysis. RESULTS: Male to female ratio was 1.7:1, 55.56% were bilateral retinoblastoma, the mean age of onset was 12.37 months in bilateral and 33.07 months in unilateral cases (p=0.048). Majority (90.12%) had sporadic inheritance and 6.17% had autosomal dominant inheritance. In chromosomal abnormalities, 8.33% had 13q14 deletion, three cases had de novo balanced translocations. CONCLUSION: The age of onset of the disease was much earlier in the bilateral cases compared to unilateral cases. Sporadic inheritance was predominant while only a small percentage of patients had autosomal dominant inheritance. The percentage of patients with 13q14 deletion was higher than reported in the literature and three novel chromosomal translocations were observed. This is one of the largest series of cases reported from India.

Adolescent↗

Antioxidant properties of colchicine in acute carbon tetrachloride induced rat liver injury and its role in the resolution of established cirrhosis.

Antioxidant and antifibrotic properties of colchicine were investigated in the carbon tetrachloride (CCl(4)) rat model. (1) The protective effect of colchicine pretreatment on CCl(4) induced oxidant stress was examined in rats subsequently receiving a single lethal dose of CCl(4). Urinary 8-isoprostane, kidney and liver malondialdehyde and kidney glutathione levels increased following CCl(4) treatment, but only the rise in kidney malondialdehyde was significantly inhibited by colchicine pretreatment. Serum total antioxidant levels were significantly higher in the colchicine pretreatment group. (2) The long term effects of colchicine treatment on CCl(4) induced liver damage were investigated using liver histology and biochemical markers (hydroxyproline and type III procollagen peptide). Co-administration of colchicine with sub-lethal doses of CCl(4) over 10 weeks did not prevent progression to cirrhosis. However, rats made cirrhotic with repeated CCl(4) challenge and subsequently treated with colchicine for 12 months, all showed histological regression of cirrhosis. (3) The antioxidant effect of colchicine in vitro was evident only at very high concentrations compared to other plasma antioxidants. In summary, colchicine has only weak antioxidant properties, but does afford some protection against oxidative stress; more importantly, long term treatment with this drug may be of value in producing regression of established cirrhosis.

Animals↗

Particles sliding on a fluctuating surface: phase separation and power laws

We study a system of hard-core particles sliding locally downwards on a fluctuating one-dimensional surface characterized by a dynamical exponent z and no overall tilt. In numerical simulations, an initially random particle density is found to coarsen and obey scaling with a growing length scale approximately t(1/z). The structure factor deviates from the Porod law for the models studied. The steady state is unusual in that the density-segregation order parameter shows strong fluctuations. The two-point correlation function has a scaling form with a cusp at small argument which we relate to a power law distribution of particle cluster sizes. Exact results on a related model of surface depths provide insight into this behavior.

Journal Article↗

MAPK-dependent expression of p21(WAF) and p27(kip1) in PMA-induced differentiation of HL60 cells.

Treatment of HL60 cells with phorbol 12-myristate 13-acetate (PMA) results in growth arrest and differentiation towards the macrophage lineage. PMA-induced changes are easily monitored by morphological changes while cells in suspension start adhering onto substrate. PMA induces rapid activation of the extracellular signal-regulated kinases (ERKs). Activation of the ERK pathway is essential to PMA-induced differentiation of HL60 cells. PMA also induces the expression of the cyclin-dependent kinase inhibitors p21(WAF) and p27(kip1), which is modulated by the use of an inhibitor of the ERK cascade. This implies that a link exists between ERK activation and p21(WAF) and p27(kip1) induction in the process of terminal differentiation.

Cell Cycle Proteins↗