Biomedical subjects

Krishna K Sharma

Publications and source records attributed to Krishna K Sharma.

6 recordsLinked to original sources

PubMed2006

Aspirin restores normal baroreflex function in hypercholesterolemic rats by its antioxidative action.

Besides its well-known effects on platelet aggregation, aspirin has been suggested to be an antioxidant and is also known to improve the lipid profile. In the present study we tested the hypothesis that aspirin by its antioxidant effect, improves haemodynamic profile and baroreflex sensitivity in rat model of hypercholesterolemia. Hypercholesterolemia was induced in Wistar rats by feeding 1% cholesterol rich diet for 10 weeks. Lipid profile, lipid peroxidation and reduced glutathione were estimated in serum. Haemodynamic changes and baroreflex were measured in anaesthetized rats. Hypercholesterolemic rats showed significant increase in total cholesterol, low-density lipoprotein-cholesterol (LDL-C), very low-density lipoprotein-cholesterol (VLDL-C) and atherogenic index and significant decrease in high-density lipoprotein-cholesterol (HDL-C). Significant rise in blood pressure, heart rate and attenuation of baroreflex sensitivity were also found in hypercholesterolemic rat. Aspirin in the dose of 100 mg/kg showed significant decrease in total cholesterol, LDL-C, VLDL-C and atherogenic index and significant increase in HDL-C. Aspirin treatment prevented the rise in blood pressure, heart rate and significantly improved baroreflex sensitivity in hypercholesterolemic rats. Hypercholesterolemic rats showed free radical generation, evident by a significant increase in serum lipid peroxidation and significant reduction in serum reduced glutathione content. Aspirin treatment significantly decreased lipid peroxidation and significantly increased reduced glutathione content. We have demonstrated that aspirin improves baroreflex response and prevents the rise in blood pressure and heart rate possibly by reducing sympathetic activity due to its antioxidant effect in experimentally induced hypercholesterolemic rats.

Animals↗

PubMed2005

Effect of oxidized betaB3-crystallin peptide (152-166) on thermal aggregation of bovine lens gamma-crystallins: identification of peptide interacting sites.

We studied the effect of oxidized betaB3-crystallin peptide (residues 152-166) on the thermal aggregation of bovine gamma-crystallin and on chaperone activity of alpha-crystallin. Thermal aggregation of gamma-crystallin was higher in the presence of oxidized betaB3-crystallin peptide than without oxidized peptide. Increased aggregation was not observed in the presence of unoxidized betaB3-crystallin peptide or a control oxidized peptide. Enhanced aggregation of gamma-crystallin by oxidized betaB3-crystallin peptide was observed even at 37 degrees C. Interaction with oxidized betaB3-peptide increased the hydrophobicity in the gamma-crystallin as shown by increased 4, 4'-dianilino-1, 1'-binaphthyl-5, 5'-disulfonic acid (bis-ANS) binding. Enhanced aggregation of gamma-crystallin was observed despite the presence of alpha-crystallin (a chaperone protein) in the system. Sulfo succinimidyl-2-[6-(biotinamido)-2-{p-azidobenzamido}-hexanoamido]ethyl-1-3 dithio propionate (Sulfo-SBED) cross-linker studies further confirmed the interaction between oxidized betaB3-crystallin peptide and gamma-crystallin. Peptide interacted sites in gamma-crystallin were identified by matrix assisted laser desorption time-of-flight mass spectrometric methods and the result suggests that oxidized betaB3-crystallin peptide interacted with amino acid residues present on the outer surface of the gamma-crystallin. These results imply that oxidized betaB3-crystallin peptide interact with gamma-crystallins and enhance their aggregation and light scattering.

Amino Acid Sequence↗

PubMed2004

Inhibition of amyloid fibrillogenesis and toxicity by a peptide chaperone.

Aggregation of proteins in tissues is associated with several diseases, including Alzheimer's disease. It is characterized by the accumulation of amyloid beta peptide (Abeta) in the extracellular spaces of the brain cells, resulting in neuronal death and other pathological changes. alpha-Crystallin, a small heat-shock protein in lens, and a peptide chaperone having the functional site sequence DFVIFLDVKHFSPEDLTVK of alphaA-crystallin may inhibit Abeta fibrillogenesis and toxicity. The peptide chaperone (mini-alphaA-crystallin), having an Abeta interacting domain and a complex solubilizing domain, was shown in previous studies to prevent aggregation of several proteins under denaturing conditions. In this in vitro study, using transmission electron microscopy and thioflavin T binding assay, we show that mini-alphaA-crystallin arrests the fibril formation of Abeta peptides. Mini-alphaA-crystallin also suppresses the toxic action of Abeta on rat pheochromocytoma (PC 12) cells. The wide chaperoning capability of the peptide and its ability to inhibit amyloid fibril formation and suppress toxicity suggest that mini-alphaA-crystallin may serve as a universal chaperone in controlling diseases of protein aggregation, including Alzheimer's disease.

Alzheimer Disease↗

PubMed2003

Involvement of GABA-A receptor chloride channel complex in isolation stress-induced free choice ethanol consumption in rats.

The present study revealed the effect of diazepam, a benzodiazepine, and progesterone, a pregnane precursor of neurosteroids, which act via modulating GABA-A chloride channel complex on the isolation stress-induced free choice ethanol consumption in adult rats. Isolation stress for 24 hr over a period of 6 days produced a significant increase in ethanol consumption, which persisted during the 6-day recovery period. Pretreating the animals with diazepam (5 mg/kg, i.p.), or progesterone (5 mg/kg, i.p.), blocked the isolation stress-induced increase in ethanol consumption. Bicuculline (2 mg/kg, i.p.), a GABA-A receptor antagonist significantly attenuated the effect of both diazepam and progesterone on stress-induced modulation of ethanol consumption. Isolation stress also caused an increase in total fluid consumption, which was antagonised by both diazepam and progesterone. Like ethanol consumption, this effect of diazepam and progesterone on isolation stress-induced increase in total fluid consumption was attenuated by bicuculline. Neither diazepam nor progesterone produced an increase in ethanol consumption in non-stressed rats. However, unlike diazepam, progesterone administration to non-stressed rats caused a significant increase in total fluid consumption. Results of the present study thus show that GABAergic mechanisms may be playing an important role in isolation stress-induced increase in ethanol consumption.

Animals↗

PubMed2002

Identification of a region in alcohol dehydrogenase that binds to alpha-crystallin during chaperone action.

alpha-Crystallin, the major eye lens protein and a member of the small heat-shock protein family, has been shown to protect the aggregation of several proteins and enzymes under denaturing conditions. The region(s) in the denaturing proteins that interact with alpha-crystallin during chaperone action has not been identified. Determination of these sites would explain the wide chaperoning action (promiscuity) of alpha-crystallin. In the present study, using two different methods, we have identified a sequence in yeast alcohol dehydrogenase (ADH) that binds to alpha-crystallin during chaperone-like action. The first method involved the incubation of alpha-crystallin with ADH peptides at 48 degrees C for 1 h followed by separation and analysis of bound peptides. In the second method, alpha-crystallin was first derivatized with a photoactive trifunctional cross-linker, sulfosuccinimidyl-2[6-(biotinamido)-2-(p-azidobenzamido)-hexanoamido]ethyl-1,3di-thiopropionate (sulfo-SBED), and then complexed with ADH at 48 degrees C for 1 h in the dark. The complex was photolyzed and digested with protease, and the biotinylated peptide fragments were isolated using an avidin column and then analyzed. The amino acid sequencing and mass spectral analysis revealed the sequence YSGVCHTDLHAWHGDWPLPVK (yeast ADH(40-60)) as the alpha-crystallin binding site in ADH. The interaction was further confirmed by demonstrating complex formation between alpha-crystallin and a synthetic peptide representing the binding site of ADH.

Alcohol Dehydrogenase↗

PubMed2002

Redo mitral valve surgery using the port-access system.

Redo mitral valve surgery is hazardous, hence we explored an alternative approach using a port-access system that avoids reentry. Between October 1997 and December 2000, 32 patients underwent mitral reoperation using the system. All patients had previous cardiac operations. This procedure consisted of a right anterolateral minithoracotomy and femorofemoral cannulation using special port-access instruments and endoaortic clamping in 24 patients or direct transthoracic sliding-rod aortic clamping in 8. The valve disease was of rheumatic etiology in 28 patients and degenerative in 4. The valve was replaced in 31 cases and a paravalvular leak after mitral valve replacement was closed in 1. In 2 cases, the tricuspid valve was repaired along with mitral valve replacement. Mean total operating time was 4.5 +/- 1.2 hours, cardiopulmonary bypass time 162 +/- 72 minutes, and aortic crossclamp time 62 +/- 21 minutes. There was no mortality, and mean stay in the intensive care unit was 22 +/- 7 hours and hospital stay 6.4 +/- 1.2 days. Postoperative blood transfusion was required in 12 patients. In view of the favorable results, we recommend using the port-access system as a standard approach for mitral reoperation.

Adult↗