Biomedical subjects
Publications and source records attributed to S K Sharma.
A case of poikiloderma developed polymyositis ten years after the onset of skin changes. This rare case of poikilodermatomyositis, hitherto not reported from Asian continent, is documented.
Antibody-directed enzyme prodrug therapy is a targeted therapy in which a prodrug is activated selectively at the tumour site by an enzyme, which has been targeted to the tumour by an antibody (antibody-enzyme conjugate). Previous clinical trials have shown evidence of tumour response, however, the activated drug had a long half-life, which resulted in dose-limiting myelosuppression. Also, the targeting system, although giving high tumour to blood ratios of antibody-enzyme conjugate (10 000 : 1) required administration of a clearing antibody in addition to the antibody-enzyme conjugate. The purpose of this current study therefore was to attempt tumour targeting of the antibody-enzyme conjugate without the clearing antibody, and to investigate a new prodrug (bis-iodo phenol mustard, ZD2767P) whose activated form is highly potent and has a short half-life. Twenty-seven patients were treated with antibody-directed enzyme prodrug therapy using A5CP antibody-enzyme conjugate and ZD2767P prodrug, in a dose-escalating phase I trial. The maximum tolerated dose of ZD2767P was reached at 15.5 mg m(-2)x three administrations with a serum carboxypeptidase G2 level of 0.05 U ml(-1). Myelosuppression limited dose escalation. Other toxicities were mild. Patients' quality of life was not adversely affected during the trial as assessed by the measures used. There were no clinical or radiological responses seen in the study, but three patients had stable disease at day 56. Human anti-mouse antibody and human anti-carboxypeptidase G2 antibody were produced in response to the antibody enzyme conjugate (A5CP). The antibody-enzyme conjugate localisation data (carboxypeptidase G2 enzyme levels by HPLC on tumour and normal tissue samples, and gamma camera analysis of I-131 radiolabelled conjugate) are consistent with inadequate tumour localisation (median tumour: normal tissue ratios of antibody-enzyme conjugate of less than 1). A clearance system is therefore desirable with this antibody-enzyme conjugate or a more efficient targeting system is required. ZD2767P was shown to clear rapidly from the circulation and activated drug was not measurable in the blood. ZD2767P has potential for use in future antibody-directed enzyme prodrug therapy systems.
Demonstration of Mycobacterium tuberculosis in a smear or culture is the most reliable method for diagnosing tuberculosis (TB). In the last 10 years, several enzyme-linked immunosorbent assays (ELISAs) based on mycobacterial antigens (such as antigen 60, 38 kDa antigen, and antigen Kp90) have been used for the rapid diagnosis of TB. In this study, we report the isolation of an immunodominant lipopolysaccharide (LPS) antigen from M. tuberculosis H(37)Rv, which can be used for the serodiagnosis of TB. The LPS antigen was compared with three commercially available mycobacterium-specific antigens for the detection of TB. The antigens were evaluated using serum samples obtained from 59 Indian patients (19 patients with active pulmonary TB, 20 with extrapulmonary TB, and 20 with nontuberculous pulmonary disease) and 20 healthy adults. Antigen 60 IgG (sensitivity 89%, specificity 97%) and LPS (sensitivity 84%, specificity 97%) were more sensitive and specific than 38 kDa antigen IgG (sensitivity 79%, specificity 97%) and Kp90 IgA (sensitivity 82%, specificity 40%). These results indicate that the LPS antigen can be used as a sensitive tool for the serodiagnosis of TB and could be utilized to develop an ELISA for the screening of patients for TB.
PURPOSE: We evaluated the attenuation value of renal calculi on unenhanced axial computerized tomography (CT) images as a predictor of calculous fragmentation by extracorporeal shockwave lithotripsy (ESWL) (Dornier Medical Systems, Inc., Marietta, Georgia). MATERIALS AND METHODS: We included 30 patients with renal calculi up to 20 mm. in this prospective study. Calculous attenuation value was measured in Hounsfield units on unenhanced CT sections through the calculi. Patients were subsequently treated with ESWL. RESULTS: Patients were grouped according to calculous attenuation value as groups 1-less than 500, 2-500 to 1,000 and 3-greater than 1,000 Hounsfield units. Of the 30 patients 24 (80%) underwent successful treatment. The rate of stone clearance was 100% (12 of 12 cases) in group 1, 85.7% (6 of 7) in group 2 and 54.5% (6 of 11) in group 3. The success rate for stones with an attenuation value of greater than 1,000 Hounsfield units was significantly lower than that for stones with a value of less than 1,000 Hounsfield units (6 of 11 versus 18 of 19 cases, chi-square 7.07, p <0.01). Patients in group 3 required a greater median number of shock waves for stone fragmentation than those in groups 1 and 2 (7,300, 2,500, and 3,390, respectively). The mean attenuation value and number of shock waves required for calculous fragmentation correlated significantly (r = 0.779, p <0.001). CONCLUSIONS: The CT attenuation value of renal calculi can help to differentiate stones that are likely to fragment easily on ESWL from those that would require a greater number of shock waves for fragmentation or may fail to fragment on ESWL.
Hypoxia is known to induce oxidative stress in organisms leading to tissue injury. In the present study beta-carotene (BC) given at 10 mg/kg body weight (BW) in reducing the oxidative stress induced by hypoxia was evaluated on male albino rats. Hypoxia exposure caused an increase in malondialdehyde (MDA) levels in plasma and tissues, a concurrent decrease in blood glutathione (GSH), glutathione peroxidase (GPx), plasma protein and plasma BC content. Hemoglobin concentration, Red blood corpuscles (RBC) and White blood corpuscles (WBC) count were also increased under hypoxia. BC supplementation reversed the trend, inducing a significant decrease (P<0.05) in MDA and subsequent increase in plasma and tissue GSH levels in animals exposed to hypoxia. Blood GPx and plasma protein also increased significantly in BC supplemented animals. BC supplementation did not alter the changes in Hb concentration, RBC and WBC count. BC has potent antioxidant activities in reducing the oxidative stress induced by hypobaric hypoxia.
The fruits extracts of Emblica officinalis (Amla) has been reported to have strong anti-oxidant properties. There is a paucity of studies on the immunomodulatory properties of fruit extracts of Amla in immuno-compromised states, with the emphasis on lymphocytes. Therefore, the aim of the study was to determine the anti-oxidant and immunomodulatory properties of Amla using chromium (VI) as an immunosuppressive agent. Chromium (Cr) treatment results in enhanced cytotoxicity, free radical production, lipid peroxidation and decreased glutathione peroxidase (GPx) activity and diminished glutathione (GSH) levels. There was a significant inhibition of both lipopolysaccharide and concanavalin-A-stimulated lymphocyte proliferation. Chromium also inhibited Con A stimulated interleukin-2 and gamma-interferon production significantly. Further, there was enhanced apoptosis and DNA fragmentation in the presence of Cr. Amla significantly inhibited Cr-induced free radical production and restored the anti-oxidant status back to control level. Amla also inhibited apoptosis and DNA fragmentation induced by Cr. Interestingly, Amla relieved the immunosuppressive effects of Cr on lymphocyte proliferation and even restored the IL-2 and gamma-IFN production considerably.
At high altitudes, the reactive oxygen species are continuously generated as a consequence of low oxygen partial pressure (hypoxia), which causes tissue damage. The body's defence system to combat the oxidative stress (e.g., anti-oxidant enzymes, free radical scavengers such as vitamin C, vitamin E, beta-carotene, reduced glutathione and minerals such as selenium, etc.) may diminish. In the present study, the antioxidant effect of selenium (Se) in reducing the hypoxia-induced oxidative stress was evaluated by exposing male albino rats to hypoxic stress in a decompression chamber. Exposure to hypoxia resulted in an increase in malondialdehyde (MDA) levels in plasma and tissues and a concurrent decrease in blood glutathione (GSH), glutathione peroxidase (GPx), plasma protein and plasma selenium content when compared with controls. Haemoglobin concentration (Hb%), red blood corpuscles (RBC) and white blood corpuscles (WBC) count were also increased in the hypoxia-exposed group. Selenium supplementation to animals reversed the trend. There was a significant decrease (P < 0.001) in MDA and subsequent increase in plasma and tissue GSH levels. Similarly the blood and tissue GPx and plasma protein also increased significantly in the Se supplemented animals compared with control animals. The Hb%, RBC and WBC counts showed no significant difference between Se-fed and control rats. These results suggest that selenium may help in reducing the lipid peroxidation during hypoxia.
The binding ability of cross-linked thiazolated polyamides (containing the base sequence-reading elements thiazole(Th)-pyrrole(Py)-pyr-role(Py) and thiazole(Th)-imidazole(Im)-pyrrol(Py) to various DNA dodecamers has been investigated. CD titration experiments at high salt concentration demonstrate that the dimers with a heptanediyl linker (C7 dimer) show a significantly higher sequence specificity than their corresponding monomers. The dimer of Th-Py-Py primarily prefers binding to pure AT sequences and that of Th-Im-Py to the dodecamer sequences containing a GC pair within the central sequence (e.g. AACGTT). Surprisingly, the sequence binding ability is strongly influenced by the presence of a T-A step: e.g. Th-Py-Py has a similar affinity to the sequences TTTAAA and ATCGTA; likewise Th-Im-Py shows a preference for these sequences. The CD results correlate with footprinting data. Related biochemical studies on the effect of polyamides on DNA gyrase activity in vitro show that the C7 dimers most effectively inhibit the enzyme activity compared with the monomers and the natural reference minor groove binder distamycin. The highest inhibitory potency is observed for the Th-Py-Py-dimer. The role of the T-A step in binding of the cross-linked dimer to the minor groove is discussed in light of the sequence recognition of the TATA box binding protein.
The World Health Organization has identified India as a major hot-spot region for Mycobacterium tuberculosis infection. We have characterized the sequences of the loci associated with multidrug resistance in 126 clinical isolates of M. tuberculosis from India to identify the respective mutations. The loci selected were rpoB (rifampin), katG and the ribosomal binding site of inhA (isoniazid), gyrA and gyrB (ofloxacin), and rpsL and rrs (streptomycin). We found known as well as novel mutations at these loci. Few of the mutations at the rpoB locus could be correlated with the drug resistance levels exhibited by the M. tuberculosis isolates and occurred with frequencies different from those reported earlier. Missense mutations at codons 526 to 531 seemed to be crucial in conferring a high degree of resistance to rifampin. We identified a common Arg463Leu substitution in the katG locus and certain novel insertions and deletions. Mutations were also mapped in the ribosomal binding site of the inhA gene. A Ser95Thr substitution in the gyrA locus was the most common mutation observed in ofloxacin-resistant isolates. A few isolates showed other mutations in this locus. Seven streptomycin-resistant isolates had a silent mutation at the lysine residue at position 121. While certain mutations are widely present, pointing to the magnitude of the polymorphisms at these loci, others are not common, suggesting diversity in the multidrug-resistant M. tuberculosis strains prevalent in this region. Our results additionally have implications for the development of methods for multidrug resistance detection and are also relevant in the shaping of future clinical treatment regimens and drug design strategies.
Protein-Protein (P-P) interactions play a pivotal role in determining cellular structure and in all cellular processes. The nature of P-P interactions is complex, and despite the large amount of research that has occurred in the field, is still poorly understood. Abnormal P-P interactions are particularly important because of their association with a variety of diseases, including cancer. This review examines P-P interactions with particular emphasis on the discovery of new anti-tumor drugs, including underlying physical forces that determine affinity and specificity and discusses classical and newer strategies used to discover inhibitors of P-P interactions, providing a number of recent cancer-related case studies and commentary.
A strain of Clostridium botulinum type E has been isolated from soil samples of Gwalior, India. The isolated strain shows curved vegetative cells with oval, bulging, and terminal spores. The production of toxin was detected by immunodiffusion test, symptomatic death of mice and mouse protection assay with trivalent antitoxin (A+B+E). The culture supernatant gave 10(3) MLD (minimum lethal dose) per ml without any protease treatment. Group specific and serotype specific primers amplified the DNA fragments of 260 bp and 445 bp, respectively, indicating Clostridium botulinum type 'E.'
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Sarcoidosis is now recognised as a member of a large family of granulomatous disorders and has been reported from all parts of the world. Current evidence points to genetic predisposition and exposure to yet unknown transmissible agent(s) and/or environmental factors as etiological agents. Depending on the organ systems involved, patients with sarcoidosis present themselves to various specialities; pulmonary involvement is by far the commonest and occurs in about 90 per cent of the patients. The diagnosis is based on a compatible clinical and/or radiological picture, histopathological evidence of non-caseating granulomas in tissue biopsy specimens and exclusion of other diseases capable of producing similar clinical or histopathological appearances. Sarcoidosis is an underdiagnosed disease in India. However, owing to the increasing awareness, it is being diagnosed more frequently than a few decades ago. Most Indian patients with sarcoidosis are males and present in the fourth or fifth decade of life. The disease runs a benign course with spontaneous remission of the activity though some degree of residual pulmonary function abnormality persists. Only a minority of the patients develop complicated disease. Corticosteroids remain the mainstay of treatment. For asymptomatic patients with pulmonary sarcoidosis, no therapy is required. Corticosteroid treatment should be considered in symptomatic patients with evidence of radiological or pulmonary function deterioration. Treatment under close clinical monitoring should be tailored to suit the needs of the individual patient. Sometimes steroid-sparing alternative treatments may be beneficial. In this review, the current understanding of the global scenario and Indian perspective of sarcoidosis are critically reviewed.
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A new class of 5-(1-cyanamido-2-haloethyl)-2'-deoxyuridines (4-6) and arabinouridines (7, 8) were synthesized by the regiospecific addition of halogenocyanamides (X-NHCN) to the 5-vinyl substituent of the respective 5-vinyl-2'-deoxyuridine (2) and 2'-arabinouridine (3). Reaction of 2 with sodium azide, ceric ammonium nitrate, and acetonitrile-methanol or water afforded the 5-(1-hydroxy-2-azidoethyl)-(10) and 5-(1-methoxy-2-azidoethyl)-2'-deoxyuridines (11). In vitro antiviral activities against HSV-1-TK(+) (KOS and E-377), HSV-1-TK(-), HSV-2, VZV, HCMV, and DHBV were determined. Of the newly synthesized compounds, 5-(1-cyanamido-2-iodoethyl)-2'-deoxyuridine (6) exhibited the most potent anti-HSV-1 activity, which was equipotent to acyclovir and superior to 5-ethyl-2'-deoxyuridine (EDU). In addition, it was significantly inhibitory for thymidine kinase deficient strain of HSV-1 (EC(50) = 2.3-15.3 microM). The 5-(1-cyanamido-2-haloethyl)-2'-deoxyuridines (4-6) all were approximately equipotent against HSV-2 and were approximately 1.5- and 15-fold less inhibitory for HSV-2 than EDU and acyclovir, respectively. Compounds 4-6 were all inactive against HCMV but exhibited appreciable antiviral activity against VZV. Their anti-VZV activity was similar or higher to that of EDU and approximately 5-12-fold lower than that of acyclovir. The 5-(1-cyanamido-2-haloethyl)-(7,8) analogues of arabinouridine were moderately inhibitory for VZV and HSV-1 (strain KOS), whereas compounds 10 and 11 were inactive against herpes viruses. Compounds 5 and 6 also demonstrated modest anti-hepatitis B virus activity against DHBV (EC(50) = 19.9-23.6 microM). Interestingly, the related 5-(1-azido-2-bromoethyl)-2'-deoxyuridine (1n) analogue proved to be markedly inhibitory to DHBV replication (EC(50) = 2.6-6.6 microM). All compounds investigated exhibited low host cell toxicity to several stationary and proliferating host cell lines as well as mitogen-stimulated proliferating human T lymphocytes.
A simple method for the synthesis of a rationally designed (S,S)-[Pro-Leu]-spirolactam scaffold is described. This was expanded to a small biased library of compounds mimicking the 'ZRXL' motif in order to identify E2F-1/Cyclin A antagonists. The synthesized compounds were evaluated in an E2F-1/Cyclin A binding assay and moderately active analogues were identified. In addition, the critical roles of Phe, Leu, Lys, and Arg residues of the identified motif were determined.
Filamentous tau pathology is central to a large number of dementing disorders, including Alzheimer's disease in which polymerized tau is hyperphosphorylated. Previous studies on heparin-dependent tau polymerization, using recombinant tau isoforms lacking Cys-291, suggest that tau dimerization via Cys-322 is critical for initiation of assembly of soluble tau into filaments. We report heparin-dependent in vitro polymerization of human recombinant tau (1-383 isoform), containing both Cys-291 and Cys-322, into paired helical filaments as characterized by electron microscopy. Tau polymerization, under physiological tau concentrations in the presence of dithiothreitol (DTT), was followed by a Thioflavine S fluorescence assay. To understand the molecular basis for heparin-induced tau polymerization, we expressed and purified C291A, C322A, and C291A/C322A tau mutants. The DTT requirement for tau polymerization was abolished using either the C291A or C322A tau mutant and polymerization was not observed with the C291A/C322A tau double mutant. Analysis by sodium dodecyl sulfate gel electrophoresis showed that, unlike wild type tau, a significant amount of the C291A mutant and the C322A mutant is present as a disulfide bonded dimer. Taken together these results suggest that, in isoforms containing both Cys-291 and Cys-322, a dimeric tau with an intermolecular disulfide bond through either Cys-291 or Cys-322 is presumably acting as a seed for initiation of tau polymerization.