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K Mukherjee

Publications and source records attributed to K Mukherjee.

At least 37 records · Page 2Linked to original sources
PubMed1999

Surface Enhanced Raman Spectroscopic Study of Isomeric Methylthiophenes in Silver Colloid.

Surface Enhanced Raman Spectra (SERS) of 2-methylthiophene (2-MT) and 3-methylthiophene (3-MT) in silver colloid are compared with their normal Raman spectra in the bulk and in acetonitrile solution. Experimental results indicate that both the methylthiophene molecules are adsorbed on a metal surface through the sulfur atom. Assuming the image dipole theory to be valid, the observed surface enhancement factor of the C-H stretching mode in 2-MT indicates that the C-H bond of this isomer makes an angle of 51 degrees with the surface normal. The experimental results further suggest that the 3-MT molecule is adsorbed with its ring plane almost vertical to the metal surface; the 2-MT molecule, on the other hand, is tilted more than 45 degrees to the surface normal. The concentration dependence of the relative enhancement factor indicates that a monomolecular layer is formed on the metal surface at a specific concentration of the methylthiophenes in silver sol. No oligomerization of the two methylthiophenes on the silver surface is observed. Copyright 1999 Academic Press.

Journal Article↗
PubMed1999

Diabetes-induced vascular dysfunction in the retina: role of endothelins.

AIMS/HYPOTHESIS: Vasoactive factors like endothelins, by virtue of the microvascular regulation as well as by other effects, possibly play important parts in the pathogenesis of diabetic retinal microangiopathy. We investigated retinal vascular dysfunction in streptozotocin-induced diabetes and its relation with endothelins in short- and long-term diabetes. METHODS: Diabetic rats with or without an endothelin receptor antagonist (bosentan) treatment were investigated after 1 month and 6 months of follow-up. Retinal blood flow was measured and compared with age- and sex-matched non-diabetic control animals. Retinal tissues were analysed for endothelin-1, endothelin-3, endothelin A and endothelin B mRNA. Distribution of endothelin-1 and endothelin-3 was investigated by immunocytochemistry and that for endothelin receptors by ligand binding and autoradiography. RESULTS: Diabetic animals showed hyperglycaemia, glycosuria, elevated glycated haemoglobin values and reduced body weight gain. Retinal blood flow showed an increased resistivity index, an indicator of vasoconstriction, after 1 month of diabetes which was prevented by treatment with bosentan. This functional change in diabetes was eliminated after 6 months of follow-up. The retina from the diabetic animals showed increased mRNA expression for endothelin-1, endothelin-3 and endothelin A after one month. In addition, endothelin B mRNA expression was increased after 6 months. Furthermore, endothelin-1 and endothelin-3 immunoreactivity and endothelin receptor concentrations were increased in the retina of diabetic rats. CONCLUSION/INTERPRETATION: The results from this study indicate that the endothelin system is of importance in mediating retinal changes in diabetes although mechanisms of the endothelin system alteration as well as their effects might vary depending on the duration of diabetes. [Diabetologia (1999) 42: 1228-1234]

Animals↗
PubMed1999

Evaluation of hepatoprotective activity of Cassia fistula leaf extract.

Hepatoprotective activity of the n-heptane extract of Cassia fistula leaves was investigated in rats by inducing hepatotoxicity with carbon tetrachloride:liquid paraffin (1:1). The extract has been shown to possess significant protective effect by lowering the serum levels of transminases (SGOT and SGPT), bilirubin and alkaline phosphatase (ALP). The extract of C. fistula at a dose of 400 mg/kg showed significant hepatoprotective activity which was comparable to that of a standard hepatoprotective agent.

Alanine Transaminase↗
PubMed1999

GroEL is involved in activation of Escherichia coli RNA polymerase devoid of the omega subunit in vivo.

Highly purified Escherichia coli RNA polymerase contains a small subunit termed omega that has a molecular mass of 10 105 Da and is comprised of 91 amino acids. E. coli strains lacking omega (omega-less) are viable, but exhibit a slow-growth phenotype. Renaturation of RNA polymerase isolated from an omega-less mutant, in the presence of omega, resulted in maximum recovery of activity. The omega-less RNA polymerase from omega-less strains recruits the chaperonin, GroEL (unlike the wild-type enzyme), suggesting a structural deformity of the mutant enzyme. The GroEL-containing core RNA polymerase interacts efficiently with sigma70 to generate the fully functional holoenzyme. However, when GroEL was removed, the enzyme was irreversibly nonfunctional and was unable to bind to sigma70. The damaged enzyme regained activity after going through a cycle of denaturation and reconstitution in the presence of omega or GroEL. GroES was found to have an inhibitory effect on the core-sigma70 association unlike the omega subunit. The omega subunit may therefore be needed for stabilization of the structure of RNA polymerase.

Bacterial Proteins↗
PubMed1997

Surface-Enhanced Raman Spectroscopic Study of Isomeric Formylthiophenes in Silver Colloid

Surface enhanced Raman (SER) spectra of 2- and 3-formylthiophenes (2FT and 3FT) in silver colloids are compared with their normal Raman spectra in bulk and in acetonitrile solution. Experimental results indicate adsorption of 2FT on metal surface through the sulfur and the oxygen atoms with the ring plane vertical to the metal surface, whereas the ring plane of the 3FT molecule is inclined to the surface. Moreover, the SER spectrum of 2FT molecule predicts the existence of syn-form of this molecule in the adsorbed state because of large enhancement of the carbonyl stretching mode. Concentration dependence of relative enhancement infers the monolayer formation on metal surface at a specific concentration, implying strong evidence of chemisorption of the adsorbates. The excitation profile of C identical withC symmetric stretching mode of 2FT suggests classical plasmon resonance as the main contributor to surface enhancement. Copyright 1997 Academic Press. Copyright 1997Academic Press

Journal Article↗
PubMed1997

Studies on the omega subunit of Escherichia coli RNA polymerase--its role in the recovery of denatured enzyme activity.

Highly purified Escherichia coli RNA polymerase contains a small subunit termed omega that has a molecular mass of 10,105 Da and is comprised of 91 amino acids. To elucidate the function of omega, whose role is as yet undefined, the subunit was purified to over 95% purity from an overproducing strain [BL21 (pGP1-2, pE3C-2)]. Purified omega was then reconstituted with RNA polymerase isolated from an omega-less mutant. Externally added omega inhibited promoter-specific transcriptional activity at all promoters tested. Renaturation of fully denatured omega-less RNA polymerase in the presence of excess omega yielded maximum recovery of activity suggesting a structural rather than functional role for omega.

DNA-Directed RNA Polymerases↗
PubMed1997

Thermodynamics of Microemulsion Formation

Outlines of complex ternary phase diagrams of cetyltrimethyl ammonium bromide/water/CHCl3, cetylpyridinium chloride/water/CHCl3, sodium bisethylhexyl sulfosuccinate/water/CHCl3, and octylphenoxy polyoxyethylene ether/water/CHCl3 systems have been presented. Enthalpies of solution of water-in-oil + amphiphile and oil-in-water + amphiphile media have been calorimetrically determined. Except for cetyltrimethylammonium bromide/water/CHCl3 system, all the systems have exhibited thermal inversion for water and oil dispersion near the phase separation point. The surfactant concentration at the inversion point bears a linear correlation with the concentration of the dispersed solvent. The thermodynamics of solubilization of the solvents in the form of microdroplets are presented. The measured heat capacities of all the systems agree very reasonably with the calculated values assuming ideal mixing behavior of the components.

Journal Article↗
PubMed1997

Animal experimentation with tooth derived calcium hydroxyapatite based composites as bone-graft substitute biomaterials.

Calcium Hydroxyapatite (HA) has now been clinically accepted as one of the most important alloplastic bonegraft substitute in the management of oral surgical procedures including periodontal bony defects. HA can be synthetically prepared or derived from natural sources. Among the natural sources bovine bone is common but human source is also used. Of late Calcium Hydroxyapatite has been derived from extracted human tooth source. The present study involves the experiments using different varieties of HA in conjunction with chitosan, a binder, to know it's unique biological behaviour of bone bonding. The experiment was designed using 12(Twelve) New Zealand white rabbits on transcortical drilled hole tibial model and the observation was made under optical and scanning electron microscope. Result showed the osteoconductive and bioactive nature of tooth derived HA and biocompatibility of chitosan. The clinical problem of handling the particulate form of HA can be overcome by using chitosan which when mix with HA can stabilize the particle in surgical sites. This has tremendous clinical applications in dental regenerative surgery.

Animals↗
PubMed1996

[3H]adenosine transport in DDT1 MF-2 smooth muscle cells: inhibition by metabolites of propentofylline.

Adenosine receptor signal transduction mechanisms have previously been characterized in Syrian hamster smooth muscle DDT1 MF-2 cells but adenosine transport in these cells has not. DDT1 MF-2 cells possess a high density (370,000 sites/cell) of high affinity (Kd value of 0.26 nM) binding sites for [3H]nitrobenzylthioinosine, a marker for the equilibrative and inhibitor-sensitive subtype of nucleoside transporters. Transport of [3H]adenosine was insensitive to Na+ and was inhibited by the nucleoside transport inhibitors nitrobenzylthioinosine, dilazep and dipyridamole with IC50 values of 1, 13 and 270 nM, respectively. Propentofylline, a neuroprotective compound that can inhibit nucleoside transporters, is rapidly metabolized in vivo to the racemate (+/-)-A720287. Based on recent findings that some transport inhibitors exhibit marked stereoselectivity, we tested the degree to which individual stereoisomers of (+/-)-A720287 affect adenosine transport. Propentofylline inhibited [3H]adenosine transport in DDT1 MF-2 cells with an IC50 value of 24 microM. (+/-)-A720287 and the individual stereoisomers (+)-833791 and (-)-844261 had similar potency to propentofylline for inhibition of [3H]adenosine transport in DDT1 MF-2 cells as well as in clonal mouse leukemia L1210/B23.1 cells, cells which possess only the equilibrative and inhibitor-sensitive subtype of nucleoside transporters. Thus, the neuroprotective effects of propentofylline may be due, in part, to the primary metabolites of propentofylline.

Adenosine↗
PubMed1996

Giant cell tumour of the lower end of the radius--a new treatment modality.

Excision of the lower end of the radius with centralisation of ulna was done in 3 patients with histology proved diagnosis of giant cell tumour, as secondary procedure in 2 cases following recurrence of tumour in the fibular graft, and as a primary procedure in one, where the segment of fibula required was more than 15.2 cm. After an average follow-up of 2.3 years, the results were assessed both subjectively and objectively. The patients were happy with their hand functions and were able to have more than 80% of the grip strength. They could return to their former occupation. There was no recurrence of tumour and no pain at the wrist.

Adult↗
PubMed1996

HLA phenotype frequencies in pulmonary tuberculosis.

Susceptibility and/or immune response to tuberculosis may or may not be associated with particular histocompatibility leucocyte antigen (HLA) phenotype frequencies. The present study was undertaken to north eastern Indian population to verify any association between HLA phenotypes and immune response to mycobacterial antigen. HLA-typing was done in 60 well Tarasaki trays and T-cell subsets in each group were measured using Ficoll-hypaque nylon wool columns and dynabeads (M-450). No universal association with particular HLA-type and pulmonary tuberculosis has been confirmed.

Adolescent↗
PubMed1996

A study of inferior vena cava obstruction.

Inferior Vena Cava obstruction as a major cause of hepatic venous outflow block is not so common. A prospective study of 20 cases gave us an opportunity to device a management protocol for this disorder. Out of 20 cases we had studied, 12 had only inferior Vena Cava obstruction while rest of the 8 cases had both hepatic vein and IVC blockade. However, balloon cavoplasty showed remarkable results with substantial clinical and haemodynamic improvement in cases with isolated IVC obstruction. Therefore, we suggest that patients with IVC obstruction should be actively managed with Vena-cavography followed by cavoplasty. Treatment of Hepatic venous obstruction along with IVC obstruction is controversial; bypass shunt is usually required and long term follow-up studies are required to establish safety and efficacy.

Adolescent↗