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Biomedical subjects

S K Sharma

Publications and source records attributed to S K Sharma.

At least 181 records · Page 10Linked to original sources
PubMed2000

Mechanism of biochemical action of substituted 4-methylbenzopyran-2-ones. Part 6: hydrolysis of 7,8-diacetoxy-4-methylcoumarin by a novel deacetylase in rat liver microsomes--a simple method for assay and characterisation.

The existence of a novel microsomal deacetylase in rat liver catalysing deacetylation of diacetoxy 4-methylcoumarins has been reported. A simple method is outlined for the enzyme assay based upon the quantification of the dihydroxy derivative by measuring the UV absorption of its complex with ADP and Fe3+ at 600 nm. The enzyme can be routinely assayed using 7,8-diacetoxy-4-methylcoumarin (DAMC) as the substrate and demonstrated hyperbolic kinetics and yielded Km and vmax values of 1250 microM and 500 units, respectively. The pH optima was found to be 7.5 for the enzyme. No DAMC deacetylase activity was found in hepatic cytosol and the enzyme activity was not discernible in extrahepatic tissues.

Acetylesterase↗
PubMed2000

Epidural analgesia during labor and maternal fever.

Most studies indicate that epidural analgesia during labor is associated with maternal fever, although the nature of this fever is unclear. The consequences of maternal fever may include increased neonatal evaluations for sepsis, the increased use of antibiotics, and prolonged hospital stay. However, the need for such measures after epidural analgesia during labor is controversial. This article discusses currently held views on this issue.

Journal Article↗
PubMed2000

Evaluation of myocardial viability in asymptomatic patients early after infarction with perfusion/metabolism single-photon-emission computed tomographic imaging and dobutamine echocardiography.

OBJECTIVE: To study the impact of detection of viability of myocardium in asymptomatic patients early (3-10 days) after Q-wave myocardial infarction on segmental recovery of left ventricular function after elective revascularization. METHODS: Patients were studied with low-dose dobutamine echocardiography (LDDE) and single photon-emission computed tomography with 99mTc sestamibi and [18F]-fluorodeoxyglucose (FDG) imaging. Viability of myocardium was defined as detection of improvement in segmental thickening of left ventricle by LDDE (versus baseline echocardiographic data), uptake of 99mTc sestamibi > 50% of maximum counts, uptake of [18F]-FDG > 50% of maximum normal, combined uptake of 99mTc sestamibi or [18F]-FDG > 50% of normal maximum, uptake of [18F]-FDG > 50% or mismatched pattern (uptake of [18F]-FDG greater than that of 99mTc sestamibi). Functional recovery was defined as improvement of segmental thickening of left ventricle detected at follow-up 8 weeks after infarction (versus baseline resting echocardiographic data). Interpretation of the tests was blinded with respect to the angiographic data and the results of the alternative method. RESULTS: In total 18 patients with 133 left-ventricle segments with abnormal contractile function at baseline were analysed; 29% were hypocontractile and 71% were noncontractile. Examination with LDDE showed that 18% of the segments had normal contractility and 26% were hypocontractile; the respective percentages were 29 and 28% according to follow-up resting echocardiography. Radionuclide tests for viability of myocardium gave positive results in 57% (uptake of [18F]-FDG > 50%) and 62% (uptake of 99mTc sestamibi > 50%) of cases. With respect to segmental analysis, there was a 25-27% positive concordance, a 24-27% negative concordance, and a 48-50% discordance between the LDDE and the radionuclide definitions of viability of myocardium. Additionally, there was no significant difference among sensitivities and specificities for the definitions of viability. The sensitivity was 69% for the uptake of 99mTc sestamibi > 50% criterion, and the highest specificity was 66% for the LDDE. Incorporation of imaging with [18F]-FDG into the analysis yielded a marginally higher sensitivity of 71% for the criterion of uptake of [18F]-FDG or 99mTc sestamibi > 50%, versus imaging with the 99mTc sestamibi alone. CONCLUSION: LDDE was more specific and radionuclide imaging more sensitive for detection of viability of myocardium in asymptomatic patients early after infarction. Possibly defective myocardial metabolization of glucose in the period early after infarction and the specific LDDE protocol applied account for the limited benefit of these studies in terms of facilitating prediction of segmental functional recovery after revascularization in this clinical setting.

Cardiotonic Agents↗
PubMed2000

Comparison of in house polymerase chain reaction with conventional techniques for the detection of Mycobacterium tuberculosis DNA in granulomatous lymphadenopathy.

AIMS: To evaluate the usefulness of the devR based polymerase chain reaction (PCR) in the detection of Mycobacterium tuberculosis in lymph node aspirates and tissues of lymphadenitis and to compare PCR with conventional diagnostic techniques. SUBJECTS AND METHODS: Coded specimens of fine needle aspirates and biopsies from 22 patients with tuberculous lymphadenitis, 14 patients with non-tubercular lymphadenitis, and nine patients with granulomatous lymphadenitis were processed and subjected to analysis by PCR, smear microscopy, M tuberculosis culture, histology, and cytology. RESULTS: Tuberculous lymphadenitis was correctly diagnosed by PCR in 18 patients, by culture in five patients, by histology in 13 patients, and by cytology in seven patients. PCR gave two false positive results in 14 patients with non-tubercular lymphadenitis. The sensitivity of the conventional techniques was significantly higher with biopsies (17 of 22 specimens; 77%) than with fine needle aspirates (nine of 22 specimens; 41%). However, the sensitivity of PCR was not significantly higher with biopsies (68%) in comparison with fine needle aspirates (55%). The sensitivity of either biopsy PCR or fine needle aspirate PCR was not significantly different from that of either histology combined with culture or cytology combined with culture. The overall combined specificity of PCR was 86%. Mycobacterium tuberculosis DNA was detected in six of nine patients with granulomatous lymphadenitis. CONCLUSION: PCR is the most sensitive single technique available to date for the demonstration of M tuberculosis in specimens derived from patients with a clinical suspicion of tuberculous lymphadenitis. The value of PCR lies in its use as an adjunct test in the diagnosis of tuberculous lymphadenitis, particularly in those patients where conventional methods fail. Because fine needle aspiration is not an invasive procedure, it is the procedure of choice, and PCR should be performed initially on these samples. Excisional biopsy histology and PCR should be recommended only for patients in whom fine needle aspirate PCR is negative or when there is discrepancy with the clinical impression.

Biopsy↗
PubMed2000

Clinical applications of phage-derived sFvs and sFv fusion proteins.

Single chain Fv antibodies (sFvs) have been produced from filamentous bacteriophage libraries obtained from immunised mice. MFE-23, the most characterised of these sFvs, is reactive with carcinoembryonic antigen (CEA), a glycoprotein that is highly expressed in colorectal adenocarcinomas. MFE-23 has been expressed in bacteria and purified in our laboratory for two clinical trials; a gamma camera imaging trial using 123I-MFE-23 and a radioimmunoguided surgery trial using 125I-MFE-23, where tumour deposits are detected by a hand-held probe during surgery. Both these trials show MFE-23 is safe and effective in localising tumour deposits in patients with cancer. We are now developing fusion proteins which use MFE-23 to deliver a therapeutic moiety; MFE-23::CPG2 targets the enzyme carboxypeptidase G2 (CPG2) for use in the ADEPT (antibody directed enzyme prodrug therapy) system and MFE::TNF alpha aims to reduce sequestration and increase tumor concentrations of systemically administered TNF alpha.

Clinical Trials as Topic↗
PubMed2000

Antibody-directed enzyme prodrug therapy: efficacy and mechanism of action in colorectal carcinoma.

In antibody-directed enzyme prodrug therapy, an enzyme conjugated to an antitumor antibody is given i.v. and localizes in the tumor. A prodrug is then given, which is converted to a cytotoxic drug selectively in the tumor. Ten patients with colorectal carcinoma expressing carcinoembryonic antigen received antibody-directed enzyme prodrug therapy with A5B7 F(ab')2 antibody to carcinoembryonic antigen conjugated to carboxypeptidase G2 (CPG2). A galactosylated antibody directed against the active site of CPG2 (SB43-gal) was given to clear and inactivate circulating enzyme. A benzoic acid mustard-glutamate prodrug was given when plasma enzyme levels had fallen to a predetermined safe level, and this was converted by CPG2 in the tumor into a cytotoxic form. Enzyme levels derived from quantitative gamma camera imaging and from direct measurements in plasma and tumor biopsies showed that the median tumor:plasma ratio of enzyme exceeded 10000:1 at the time of prodrug administration. Enzyme concentrations in the tumor (median, 0.47 units g(-1)) were sufficient to generate cytotoxic levels of active drug. The concentration of prodrug needed for optimal conversion (Km) of 3 microM was achieved. Prodrug conversion to drug was shown by finding detectable levels of drug in plasma. There was evidence of tumor response; one patient had a partial response, and six patients had stable disease for a median of 4 months after previous tumor progression (one of these six had a tumor marker response). Manageable neutropenia and thrombocytopenia occurred. Conditions for effective antitumor therapy were met, and there was evidence of tumor response in colorectal cancer.

Adult↗
PubMed2000

Insecticide susceptibility status of Culex tritaeniorhynchus giles, vector of Japanese encephalitis in Delhi.

Laboratory studies were carried out to ascertain the current susceptibility status of adult and larval stages of the Culex tritaeniorhynchus mosquito, vector of Japanese encephalitis, to various insecticides used under public health programs in India. The present study revealed that exposure of adult mosquitoes to diagnostic concentrations of DDT - 4.0%, malathion - 5.0%, fenitrothion - 1.0%, and propoxur - 0.1% could induce only 50.0, 10. 0, 15.0, and 5.0% mortality, respectively, indicating that the species was resistant to all of these insecticides. The LT50 and LT95 values calculated using diagnostic concentrations of DDT, malathion, fenitrothion, and propoxur were found to be 56.4 and 136, 138 and 272, 185 and 258, and 187 and 249 min, respectively. However, when adult mosquitoes were exposed to the diagnostic concentration of synthetic pyrethroids, viz., deltamethrin - 0.025%, permethrin - 0.25%, and lambdacyhalothrin - 0.1%, 100.0% mortality was observed, indicating that the species was highly susceptible to these adulticides. Larval susceptibility tests carried out using diagnostic dosages of DDT- 0.008, temephos- 0.02, fenthion- 0.008, fenitrothion- 0.125, and malathion- 0.005 mg/l failed to induce any mortality, indicating that larvae were resistant to these larvicides. The LC50 and LC90 values calculated for commonly used larvicides, viz., temephos and fenthion, were 0.1511 and 1.9098, and 0.6151 and 2.395 mg/l, respectively. Increase in tolerance level were estimated at 95.5- and 299.4-fold when these LC90 values were compared with diagnostic dosages of temephos and fenthion, respectively.

Animals↗
PubMed2000

Immunological properties of Hn-33 purified from type A Clostridium botulinum.

Type A botulinum neurotoxin is produced along with 6-7 neurotoxin associated proteins to form a complex in addition to the neurotoxin. Immunological reactivity of type A botulinum complex and purified hemagglutinin (Fu et al., 1998) to polyclonal antibody raised against the complex have been investigated using ELISA. In competitive ELISA, 50% inhibition of the binding of IgG antibody against complex A is observed at 78 ng/ml of complex and hemagglutinin-33, suggesting that the hemagglutinin-33 accounts for most of the immunogenic response of the complex. Considering the fact that the complex consists of a group of proteins with a cumulative molecular weight of 900 kDa, hemagglutinin-33 may be one of the major immunoreactive proteins present in the type A neurotoxin complex.

Antibodies↗
PubMed2000

Seizures in patients with human immunodeficiency virus infection.

OBJECTIVE: To study the significance of new onset seizure in patient with human immunodeficiency virus (HIV) infection. METHODS: Patients infected with HIV with the new onset seizure were enrolled in the study. Seizure type was classified. Adequate work up was done to search for a cause of their initial seizure. All patients were administered antiepileptic drugs in addition those detected to have treatable opportunistic infection were treated for the same. RESULTS: A total of 455 patients of HIV infection were admitted to this centre during study period, of these twenty three patients had new onset seizures. Seizures were generalized tonic-clonic in fifteen patients (65.21%), partial motor in six patients (26.08%) and partial motor with secondary generalization in two patients (8.69%). Recurrence of seizures was observed in 69.56% patients. Identified causes included cerebral toxoplasmosis in seven patients (30.43%), cryptococcal meningitis in four (17.39%), tuberculoma in three (13.04%), AIDS dementia complex in one (4.34%) and progressive multifocal leucoencephalopathy in one (4.34%). In seven patients (30.43%) seizures were not associated with any identifiable cause. Phenytoin was used for control of seizures and no side effects to the drug were noted during the brief period of follow up. CONCLUSION: Majority of patients with HIV infection and new onset seizures have secondary brain lesion as the cause of seizure. High rate of seizure recurrence mandates therapy of solitary seizure in patients with HIV infection.

AIDS Dementia Complex↗
PubMed1999

Picroliv modulates the expression of insulin-like growth factor (IGF)-I, IGF-II and IGF-I receptor during hypoxia in rats.

The insulin-like growth factors (IGFs), IGF-I and IGF-II, play important roles in normal growth and differentiation. In recent studies, IGFs have been implicated in tissue repair and regeneration after hypoxicischemic injury. The growth effects of these genes are exerted primarily through IGF-I receptor (IGF-IR). We have earlier shown that picroliv, obtained from the roots of Picrorhiza kurrooa, reduces cellular damage caused by hypoxia in vitro. We have now studied the modulation of IGF-I, IGF-II and IGF-IR in hypoxia and the ability of picroliv to modify their expression in vivo. Male Sprague-Dawley rats, placed in 10% oxygen for 4 days, were sacrificed, and the expression of IGF-I, IGF-II and IGF-IR was determined by immunohistochemistry, in situ hybridization and reverse transcriptase polymerase chain reaction (RT-PCR) in brain, liver and lung. One group of animals was pretreated with picroliv and the other served as control. IGF-I and IGF-IR were expressed in distinct regions of the brain but not in liver or lung. IGF-I was mainly expressed in the hippocampus and cerebellum, whereas IGF-IR expression was also observed in the cortex. A significant reduction in the messenger RNA (mRNA) level of these genes was observed in response to hypoxia. Pretreatment with picroliv not only prevented such downregulation but more importantly resulted in increased levels of IGF-I and IGF-IR. These observations correlated with reduced neuronal cell death observed in these animals. The mRNA of IGF-II was constitutively expressed and was not altered by hypoxia. Modulation of IGF-I and IGF-II expression by picroliv, a novel pharmacological agent, could benefit in similar clinical settings such as myocardial ischemia and certain cerebral injuries.

Animals↗
PubMed1999

Enhancement of antibody-directed enzyme prodrug therapy in colorectal xenografts by an antivascular agent.

The irregular nature of solid tumor vasculature produces a heterogeneous distribution of antibody-targeted therapies within the tumor mass, which frequently results in reduced therapeutic efficacy. We have, therefore, combined two complementary therapies: Antibody-directed Enzyme Prodrug Therapy (ADEPT), which targets tumor cells, and an agent that selectively destroys tumor vasculature. A single i.p. dose (27.5 mg/kg) of the drug 5,6-dimethylxanthenone-4-acetic acid (DMXAA), given to nude mice bearing the LS174T colorectal xenograft, destroyed all but a peripheral rim of tumor cells, without enhancing survival. The ADEPT system, in which a pretargeted enzyme activates a prodrug, consisted of the F(ab')2 fragment of anti-carcinoembryonic antigen antibody A5B7 conjugated to the bacterial enzyme carboxypeptidase G2 and the prodrug 4-[(2-chloroethyl)(2-mesyloxyethyl)amino]benzoyl-L-glutamic acid, which was given i.p. in three doses of 500 mg/kg at 72, 84, and 96 h post-conjugate administration (25 units of carboxypeptidase G2). The antibody-enzyme conjugate could be selectively retained at approximately twice the control levels by administration of the antivascular agent at the time of optimal conjugate localization within the tumor (20 h post-conjugate administration), as demonstrated by gamma counting, phosphor plate image analysis, and active enzyme measurement. This resulted in significantly enhanced tumor growth inhibition in groups of six mice, compared to conventional ADEPT therapy, with no concomitant increase in systemic toxicity. In a separate experiment, aimed at trapping the prodrug within the tumor, a 16-fold increase over control values was produced (means, 44.8 versus 2.8 microg/g tumor) when DMXAA was given 4 h prior to 4-[(2-chloroethyl)(2-mesyloxyethyl)amino]benzoyl-L-glutamic acid. The therapeutic window was small, with no significant enhancement of prodrug retention when DMXAA was given at either earlier or later time points. This correlated with the time of vascular shut-down induced by the antivascular agent. We are currently investigating whether it is more advantageous to trap increased levels of conjugate or prodrug within the tumor for maximal enhancement of conventional ADEPT. These studies demonstrate that combined use of antibody-directed and antivascular therapies can significantly benefit the therapeutic outcome of either strategy alone.

Animals↗
PubMed1999

On-resin macrocyclization of peptides via intramolecular SnAr reactions.

On-resin macrocyclization via an SNAr reaction is employed in the synthesis of tocinoic acid analogs. Specifically, an N-terminal nitrofluorobenzene is attacked by a nucleophilic C-terminal sidechain. The remaining nitro group can be reduced and acylated. NMR is used to compare the conformation of the new macrocyclic peptides to tocinoic acid.

Cyclization↗
PubMed1999

Monoclonal antibody to the delta opioid receptor acts as an agonist in dual regulation of adenylate cyclase in NG108-15 cells.

Monoclonal antibodies generated against multiple antigenic peptides of the N-terminal sequence (3LVPSARAELQSSPLV17) of the cloned delta opioid receptor immunoprecipitated a 58 kDa protein from CHAPS-solubilized NG108-15 membranes. The immunoprecipitates bound [3H]DPDPE--but not [3H]DAMGO--with a Kd of 6.4 nM and a Bmax of 75 pM. Western blot analysis revealed a distinct band of 58 kDa. The antibodies inhibited basal and PGE1-stimulated cAMP levels, and mimicked the effect of agonists manifest in a compensatory increase in cAMP formation. The antibody will be potentially useful in the analysis of functional epitopes on the delta opioid receptor.

Adenylyl Cyclases↗
PubMed1999

Selective killing of transformed cells by cyclin/cyclin-dependent kinase 2 antagonists.

Recent studies identified a short peptide motif that serves as a docking site for cyclin/cyclin-dependent kinase (cdk) 2 complexes. Peptides containing this motif block the phosphorylation of substrates by cyclin A/cdk2 or cyclin E/cdk2. Here we report that cell membrane-permeable forms of such peptides preferentially induced transformed cells to undergo apoptosis relative to nontransformed cells. Deregulation of E2F family transcription factors is a common event during transformation and was sufficient to sensitize cells to the cyclin/cdk2 inhibitory peptides. These results suggest that deregulation of E2F and inhibition of cdk2 are synthetically lethal and provide a rationale for the development of cdk2 antagonists as antineoplastic agents.

Amino Acid Sequence↗
PubMed1999

Rotational atherectomy: improved procedural outcome with evolution of technique and equipment. Single-center results of first 1,000 patients.

We present our single-center experience of rotational atherectomy (RA) in the first 1,000 consecutive patients divided arbitrarily into three different time periods corresponding to significant changes in technique or equipment for RA. Period I (August 1994 to April 1995; 172 cases) is characterized by early experience, longer ablation, and frequent use of intra-aortic balloon pump; period II (May 1995 to January 1996; 254 cases) is characterized by short ablation runs (20-30 sec) and use of rotaflush; period III (February 1996 to February 1997; 574 cases) is characterized by ReoPro use, neosynephrine boluses to avoid hypotension, and rota floppy wire and flexible shaft burrs. The procedural success rate has improved and complication rates have progressively declined over these three time periods. The incidence of lesion complexity (long and type C lesions) and patients with unstable rest angina have increased over these time periods of RA. Therefore, modification in procedural techniques and equipment over time have made RA a safe technique despite its use in very complex lesion subsets.

Aged↗