Sudip Ghosh - Academia.edu (original) (raw)

Papers by Sudip Ghosh

We investigated the effects of ischemic preconditioning (PC) on diabetic and failing human myocar... more We investigated the effects of ischemic preconditioning (PC) on diabetic and failing human myocardium and the role of mitochondrial K ATP channels on the response in these diseased tissues. BACKGROUND There is conflicting evidence to suggest that PC is a healthy heart phenomenon.

There are data supporting the existence of ischemic preconditioning in man. This study investigat... more There are data supporting the existence of ischemic preconditioning in man. This study investigated the most effective preconditioning protocol for the human myocardium and whether the second window of ischemic preconditioning (24 h) is as protective as the first window (#2 h). Methods and results: Right atrial appendages (n56 / group) obtained during coronary bypass surgery were prepared and superfused with normoxic and normothermic Krebs-Henseleit solution. After 30 min stabilisation, muscles were subjected to various preconditioning protocols followed by 90 min ischemia and 120 min reperfusion. At the end of each protocol, the leakage of creatinine kinase (CK, U / g wet wt) and the reduction of MTT to insoluble formazan dye (OD/ mg wet wt), an index of cell viability, were measured. In study 1, preconditioning was induced by 2, 3, 5 and 10 min of ischemia followed by 5 min reperfusion. In study 2, 1-4 cycles of 2 or 5 min ischemia-5 min reperfusion were applied. In study 3, preconditioning was induced by 5 min ischemia-5 min reperfusion followed by 1, 2, 3 or 4 h reperfusion before the subsequent 90 min ischemia. In study 4, preconditioning with 5 min ischemia followed by 5 min reperfusion either immediately preceded 30 or 90 min ischemia / 120 min reperfusion or was applied 24 h before. In study 1 and 2, optimal protection was achieved with 5 min or two cycles of 2 min preconditioning ischemia (CK53.0660.31 and 2.8960.02; MTT50.5660.05 and 0.4760.09, respectively vs. CK55.5660.52 and MTT50.1860.04 in ischemia alone group; P,0.05). In study 3, protection was observed 2 h after preconditioning (CK53.4360.22 and MTT50.4660.09; P,0.01 vs. ischemia alone group) but it was lost beyond 2 h (CK56.3060.56 and MTT50.1660.02 after 3 h; P5NS vs. ischemia alone group). In study 4, protection was observed 24 h following preconditioning when the atrial specimens were exposed to 30 min ischemia (CK52.9660.38 and MTT5 0.6160.01 vs. CK54.5660.26 and MTT50.4360.02 in ischemia alone group, P,0.05); however, when the period of ischemia was extended to 90 min the beneficial effect of preconditioning was lost (CK510.2860.5 and MTT50.1160.05 vs. CK59.5660.62 and MTT50.10460.05 in ischemia alone group, P5NS). Conclusions: In the isolated human myocardium maximal protection induced by preconditioning is achieved by a total 4-5 min ischemic stimulus, an effect that is lost beyond 2 h of its application. Two windows of protection were identified, the first (#2 h) being more potent than the second (24 h).

Journal of The American College of Cardiology, 2001

India. Entamoeba dispar is morphologically identical but is not associated with disease. Here we ... more India. Entamoeba dispar is morphologically identical but is not associated with disease. Here we determined the ploidy of E. histolytica and developed PCR-based methods for distinguishing field isolates of E. histolytica or E. dispar. Fluorescence in situ hybridization showed that E. histolytica trophozoites are diploid for five "singlecopy" probes tested. Intergenic sequences between superoxide dismutase and actin 3 genes of clinical isolates of E. histolytica from the New and Old Worlds were identical, as were those of E. dispar. These results suggest a bottleneck or demographic sweep in entamoebae which infect humans. In contrast, E. histolytica and E. dispar genes encoding repeat antigens on the surface of trophozoites (Ser-rich protein) or encysting parasites (chitinase) were highly polymorphic. chitinase alleles suggested that the early axenized strains of E. histolytica, HM-1 from Mexico City, Mexico, and NIH-200 from Calcutta, India, are still present and that similar E. dispar parasites can be identified in both the New and Old Worlds. Ser-rich protein alleles, which suggested the presence of the HM-1 strain in Mexico City, included some E. histolytica genes that predicted Ser-rich proteins with very few repeats. These results, which suggest diversifying selection at chitinase and Ser-rich protein loci, demonstrate the usefulness of these alleles for distinguishing clinical isolates of E. histolytica and E. dispar.

Entamoeba histolytica is a microaerophilic protozoan parasite in which neither mitochondria nor m... more Entamoeba histolytica is a microaerophilic protozoan parasite in which neither mitochondria nor mitochondrion-derived organelles have been previously observed. Recently, a segment of an E. histolytica gene was identified that encoded a protein similar to the mitochondrial 60-kDa heat shock protein (Hsp60 or chaperonin 60), which refolds nuclear-encoded proteins after passage through organellar membranes. The possible function and localization of the amebic Hsp60 were explored here. Like Hsp60 of mitochondria, amebic Hsp60 RNA and protein were both strongly induced by incubating parasites at 42°C. 5 and 3 rapid amplifications of cDNA ends were used to obtain the entire E. histolytica hsp60 coding region, which predicted a 536-aminoacid Hsp60. The E. histolytica hsp60 gene protected from heat shock Escherichia coli groEL mutants, demonstrating the chaperonin function of the amebic Hsp60. The E. histolytica Hsp60, which lacked characteristic carboxy-terminal Gly-Met repeats, had a 21-amino-acid amino-terminal, organelle-targeting presequence that was cleaved in vivo. This presequence was necessary to target Hsp60 to one (and occasionally two or three) short, cylindrical organelle(s). In contrast, amebic alcohol dehydrogenase 1 and ferredoxin, which are bacterialike enzymes, were diffusely distributed throughout the cytosol. We suggest that the Hsp60-associated, mitochondrion-derived organelle identified here be named "crypton," as its structure was previously hidden and its function is still cryptic.

Infection and Immunity, 2001

To determine how binuclear giardia swim, we used video microscopy to observe trophozoites of Giar... more To determine how binuclear giardia swim, we used video microscopy to observe trophozoites of Giardia intestinalis, which were labeled with an amino-specific Alexa Fluor dye that highlighted the flagella and adherence disc. Giardia swam forward by means of the synchronous beating of anterior, posterolateral, and ventral flagella in the plane of the ventral disc, while caudal flagella swam in a plane perpendicular to the disc. Giardia turned in the plane of the disc by means of a rudder-like motion of its tail, which was constant rather than beating. To determine how giardia divide, we used three-dimensional confocal microscopy, the same surface label, nuclear stains, and antitubulin antibodies. Giardia divided with mirror-image symmetry in the plane of the adherence disc, so that the right nucleus of the mother became the left nucleus of the daughter. Pairs of nuclei were tethered together by microtubules which surrounded nuclei and prevented mother or daughter giardia from receiving two copies of the same nucleus. New adherence discs formed upon a spiral backbone of microtubules, which had a clockwise rotation when viewed from the ventral surface. These dynamic observations of the parasite begin to reveal how giardia swim and divide.

Molecular and Biochemical Parasitology, 1997

Entamoeba histolytica (Eh) and Entamoeba dispar (Ed) are protozoan parasites that infect hundreds... more Entamoeba histolytica (Eh) and Entamoeba dispar (Ed) are protozoan parasites that infect hundreds of millions of persons. In the colonic lumen, amebae form chitin-walled cysts, the infectious stage of the parasite. Entamoeba invadens (Ei), which infects reptiles and is a model for amebic encystation, produces chitin synthase and chitinase during encystation. Ei cyst formation is blocked by the chitinase-inhibitor allosamidin. Here molecular cloning techniques were used to identify homologous genes of Eh, Ed, and Ei that encode chitinases (EC 3.2.1.14). The Eh gene (Eh chtl) predicts a 507-amino acid (aa) enzyme, which has 93 and 74°/,, positional identities with Ed and Ei chitinases, respectively. The Entamoeba chitinases have signal sequences, followed by acidic and hydrophilic sequences composed of multiple tandemly arranged 7-aa repeats (Eh and Ed) or repeats varying in length (Ei). The aa compositions of the chitinase repeats are similar to those of the repeats of the Eh and Ed Ser-rich proteins. The COOH-terminus of each chitinase has a catalytic domain, which resembles those of Brugia malayi (33% positional identity) and Munduca sexta (29%). Recombinant Entamoeba chitinases are precipitated by chitin and show chitinase activity with chitooligosacharide substrates. Consistent with previous biochemical data, chitinase mRNAs are absent in Ei trophozoites and accumulate to maximal levels in Ei encysting for 48 h. © 1997 Elsevier Science B.V.

Journal of The American College of Cardiology, 2001

Infection and Immunity, 2001

Molecular and Biochemical Parasitology, 1997