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Biomedical subjects

S Sarkar

Publications and source records attributed to S Sarkar.

At least 163 records · Page 9Linked to original sources
PubMed1997

Sestamibi scan for preoperative localization in primary hyperparathyroidism.

BACKGROUND: Various invasive and noninvasive localizing tests are available for the evaluation of primary hyperparathyroidism. The surgical success in primary intervention exceeds 90% without localization studies. However, localization tests are absolutely essential for re-exploration and in certain select circumstances, even in primary exploration. The traditional noninvasive localization studies include the sonogram, thallium-technetium scan, computed tomography (CT) scan, and magnetic resonance imaging (MRI). The purpose of this report is to review our recent experience with sestamibi scan. The sestamibi scan appears to be the most sensitive and accurate noninvasive test available today. METHODS: Technetium 99m sestamibi has recently been used for parathyroid localization, in conjunction with iodine123 subtraction. We have evaluated 24 patients with suspected primary hyperparathyroidism to study the role of technetium 99m sestamibi scan. Tc-sestamibi was used either with or without iodine123 for subtraction of thyroid activity. RESULTS: None of these patients had renal failure or secondary hyperparathyroidism. Of 24 patients, the parathyroid adenoma was localized by scintigraphy in 19 patients. Twenty patients underwent surgical exploration. In 17 patients there was a complete correlation between the imaging study and the operative findings (positive predictive value, 89%). There were no false positives in this series. The interpretation of the parathyroid images was relatively easy; however, the depth of the adenoma could not be predicted, based on the scan alone. The largest adenoma weighed 2.7 g, the smallest, 700 mg. CONCLUSION: This newer radiopharmaceutical, technetium 99m sestamibi, appears to be quite useful and accurate in the preoperative localization of patients with primary hyperparathyroidism. Parathyroid enlargement can also be studied by sestamibi imaging alone if delayed imaging is performed.

Adult↗
PubMed1997

Action of capparis decidua against alloxan-induced oxidative stress and diabetes in rat tissues.

Alloxan-induced diabetic rats were treated with insulin (i.p.) or with Capparis decidua powder as a hypoglycaemic agent mixed with diet. The effect was assessed on lipid peroxidation (LPO) and the antioxidant defense system in rat tissues. The increased levels of blood glucose in diabetes produce superoxide anions and hydroxyl radicals in the presence of transition metal ions which cause oxidative damage to cell membranes. The heart tissue showed an increased lipid peroxidation (LPO) in diabetic rats while no significant change was observed in the liver and kidney. The treatment with C. decidua lowered LPO in these tissues even more effectively than insulin-treated rats. The superoxide dismutase (SOD) activity increased in the heart and kidneys in the diabetic group of rats probably to increase dismutation of superoxide anions. However, treatment with C. decidua decreased SOD activity in the liver and kidney and was comparable to control rats. Catalase (CAT) activity was not significantly affected in any of the tissues in diabetic and insulin-treated animals, however, CAT activity markedly increased in tissues with C. decidua treatment. Total and Se-dependent glutathione peroxidase (GSH-Px) in the heart was markedly lowered in diabetic rats which recovered with insulin as well as with C. decidua treatment. The increase in GSH-Px and CAT activity with C. decidua treatment may lower H2O2 toxicity and reduce oxidative stress in diabetes. However, glutathione (GSH) content in the heart and kidney and glutathione reductase (GSH-R) activity in all the tissues studied increased in diabetic rats while treatment with insulin lowered GSH content and GSH-R activity in these tissues. The treatment with C. decidua also decreased GSH-R activity in the kidney and heart which resulted in the decrease in GSH content in these tissues. The changes such as the increase in kidney and heart SOD may be an adaptive response in order to neutralize superoxide anions. The increase in GSH content and GSH-R activity in the tissue are in response to neutralize superoxide anions and to counteract oxidative stress in diabetes. Glutathione S-transferase (GST) was not significantly affected in diabetic rat tissue, however, heart GST increased with antidiabetic treatments. The increase in glucose-6-phosphate dehydrogenase (G6PDH) in the kidney and heart of diabetic rats subsequently decreased with C. decidua treatment. The increase in G6PDH in tissues may increase NADPH generation required for GSH-R activity and GSH production. It is suggested that these changes initially counteract the oxidative stress in diabetes, however, a gradual decrease in the antioxidative process may be one of the factors which results in chronic diabetes. The data indicate that C. decidua may have potential use as an antidiabetic agent and in lowering oxidative stress in diabetes.

Alloxan↗
PubMed1997

Biochemical and immunological characterization of soluble antigens of Giardia lamblia.

The crude soluble antigens (CSA) of Giardia lamblia trophozoites and their analytically purified fractions were characterized biochemically and immunologically to determine the most immunogenic fraction and its localization on the parasite. Both Sephacryl S-300 column chromatography and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) revealed the highly complex and heterogeneous nature of CSA. Gel filtration of CSA showed four fractions (FI-FIV) with molecular masses of 250, 150, 110, and 10 kDa for fractions I-IV, respectively. Protein profiles of CSA demonstrated 28 Coomassie-blue bands in the range of 200-14 kDa. Similar banding patterns with fewer polypeptides were observed in the FI fraction. However, fractions II and III showed polypeptide bands in the region of 97-14 kDa. The glycoprotein nature of CSA and its-fractions were demonstrated in physicochemical analysis. In antigenic activity analysis the high-molecular-weight FI antigen was found to be 8 times more immunogenic than CSA as well as the other fractions. Major differences in the immunoreactivity of CSA and FI antigens were noted at 220, 30, and 22 kDa for the FI antigen and at 205, 84, 55, 43, and 20 kDa for CSA. Some of these FI polypeptides were found to be surface-associated as revealed by immunofluorescence and immunoblot assay. These results suggest the future use of the FI antigen in the serodiagnosis of and immunoprophylaxis against giardiasis.

Animals↗
PubMed1997

DNA sequencing and comparative sequence analysis reveal that the Escherichia coli genomic DNA may replace the target DNA during molecular cloning: evidence for the erroneous assembly of E. coli DNA into database sequences.

DNA sequencing and similarity search of databases provide experimental evidence that portions of the host Escherichia coli genome may get ligated into the cloning vector, resulting in clones containing nontargeted inserts. Several lines of evidence suggest that this non-targeted ligation, as observed by us while subcloning troponin I cDNA, is presumably due to a recombination-mediated mechanism by which host DNA replaces the target DNA in the cloning vector. The E. coli genome mapping to 64-65 min and 92.8-00.1 min, the latter containing insertion sequences, appears to be the hotspot regions involved in this process. We examined the possibility that some sequences reported in the databases may also contain genomic sequences of E. coli. A search of current databases revealed that a rat hepatic glutathione transporter cDNA contains a 2.2-kb-long portion of the E. coli genome that has been wrongly assembled into its 5' untranslated and coding regions. In addition, about 30 sequences in databases, including a Yersinia pestis toxin gene, showed relatively high sequence identity with those portions of the E. coli genome that were present in the nonauthentic clones.

Animals↗
PubMed1997

Cadmium-induced lipid peroxidation and the antioxidant system in rat erythrocytes: the role of antioxidants.

Cadmium (Cd)-induced oxidative damage in erythrocytes causes loss of membrane function by enhancing lipid peroxidation (LPO) and altering the erythrocyte antioxidant system. Vitamin E and/or selenium (Se) was administered to rats, prior to Cd intoxication, in order to prepare the animals to withstand oxidative assault. The treatment with Cd increased LPO in erythrocytes while animals pretreated with vitamin E and/or Se prior to Cd treatment showed decreased LPO as compared with animals given Cd alone. The erythrocyte SOD and CAT activities decreased significantly with Cd treatment. The pretreatment with vitamin E and/or Se prior to Cd administration partially reversed such changes. The erythrocytes showed a marked depletion in glutathione (GSH) content with Cd treatment. The antioxidant treatments before Cd administration helped to maintain the erythrocyte GSH content. The erythrocyte glutathione reductase (GSH-R) activity increased markedly when treatments with vitamin E and Se were applied. The GSH-R activity was not observed to decrease in animals treated with antioxidant prior to Cd intoxication, which may mean that the replenishment of erythrocyte GSH content is via GSH-R. The glutathione-S-transferase (GST) activity increased significantly with Cd intoxication; however, treatment with antioxidants prior to Cd treatment decreased erythrocyte GST activity. The results show that Cd-induced LPO decreased the antioxidant capability of the erythrocytes, causing erythrocyte membrane damage.

Analysis of Variance↗
PubMed1997

Injection drug use in Calcutta: a potential focus for an explosive HIV epidemic.

Our objective was to assess HIV risk perceptions, risk behaviours and factors that may facilitate an increase in injection drug use in Calcutta. Focus group discussions and in-depth interviews were conducted with a selected group of drug users to delineate drug use patterns, languages used to express addictive and related experiences and acceptance of harm minimization messages. Results from these were used to develop a semi-structured interview instrument which was used to interview 111 drug users (76 IDUs and 35 non-IDUs) recruited from jails and detoxification centres. Secondary data of narcotic seizures for the last 5 years were collected from the Calcutta police department. Data on percentage of IDUs admitted to large detox facility in the city was also collected. Findings show that HIV/AIDS knowledge and risk perceptions were low; sharing of injection equipment was reported by 66% of the injectors; and condom use was insignificant. Non-availability, rising cost and increasing tolerance to heroin were cited as factors contributing to switch to injection. Ecological association was found between intensified police activity and an increase in: the amount of smokable heroin seized; increased injection of buprenorphine; and admission to detoxification centres. In addition to HIV, IDUs were also found to be prone to hepatitis B and C. The findings suggest an urgent need for developing and implementing community-based HIV prevention interventions targeting drug users in Calcutta.

Journal Article↗
PubMed1997

Chemical analysis of sound and carious enamel of permanent tooth.

Enamel consists mainly of inorganic material (96%) and only a small amount of organic substance and water (4%). The inorganic material is similar to apatite. The originally found apatite mineral remains basically unchanged except at the surface in contact with the oral tissues, where diffusion processes operate. Enamel reflects the trace element environment present in the tissue fluids at the time of tissue development. These are variations of types and concentration of inorganic elements found in permanent and deciduous enamel. Variations are also seen in sound and carious enamel.

Dental Caries↗
PubMed1997

Reaching out beyond the hills: HIV prevention among injecting drug users in Manipur, India.

Outreach interventions using ex-IDUs to inform and educate their peers about HIV/AIDS prevention measures have been found to be effective in the United States and other developed countries. While HIV/AIDS prevention programmes targeting IDUs have also been implemented in a number of developing countries, very little information is available on the process of implementation of these programmes. This paper attempts to document some of this knowledge by describing the implementation process of an outreach intervention targeting IDUs in a small town--Churachandpur--with high injection drug use and high HIV infection rates, in the north-eastern state of Manipur. The paper describes the barriers encountered in implementing the outreach and how these barriers were minimized. In conclusion, the paper makes the case for targeting outreach to the larger community before targeting the IDUs.

Developing Countries↗
PubMed1997

Lipid peroxidation and antioxidant enzymes in erythrocytes and tissues in aged diabetic rats.

Antidiabetic treatment with powdered fruit of Capparis decidua decreased alloxan induced lipid peroxidation (LPO) significantly in erythrocytes, kidney and heart. Erythrocyte superoxide dismutase (SOD) activity decreased while the kidney and heart SOD increased in diabetic animals. These alterations in SOD were counteracted by insulin as well as with powdered fruit of C. decidua. Increased catalase (CAT) activity in erythrocytes, liver, kidney and heart with C. decidua treatment indicate that the treatment may neutralize H2O2 toxicity by its increased decomposition by CAT. Result shows that treatment with C. decidua lowers alloxan induced LPO and alters SOD and CAT enzymes to reduce oxidative stress.

Aging↗
PubMed1997

Melatonin action on thyroid activity in the soft-shelled turtle, Lissemys punctata punctata.

Adult female turtles (Lissemys punctata punctata) were treated with pineal indoleamine melatonin (100 micrograms/100 g) or the antithyroid agent, methylthiouracil (100 micrograms/100 g) or melatonin together with methylthiouracil (100 micrograms of each drug/100 g) for 12 days. Melatonin alone inhibited thyroid activity as evidenced by reduction in the gland weight, follicular epithelial cell height, thyroid peroxidase, and plasma thyroxine levels. Methylthiouracil caused hyperplasia of the gland, although it inhibited thyroid activity and reduced thyroid peroxidase and plasma thyroxine levels. Melatonin together with methylthiouracil produced changes similar to those obtained with melatonin alone. The results indicate that melatonin probably exerts inhibitory effects influences on both thyrotropin release from the pituitary and the activity of the thyroid itself in turtles.

Animals↗
PubMed1996

Interaction of deletion mutants of troponins I and T: COOH-terminal truncation of troponin T abolishes troponin I binding and reduces Ca2+ sensitivity of the reconstituted regulatory system.

The interaction between troponin I (TnI) and troponin T (TnT) remains the least understood binary interaction among the regulatory proteins of vertebrate striated muscle. To identify the specific binding domains of TnI and TnT and to evaluate the interactions of TnT with troponin C and tropomyosin (Tm), we generated an NH2-terminal fragment of human fast skeletal beta TnT (TnT1-201; residues 1-201) using site-directed mutagenesis. The mutant protein failed to bind to rabbit skeletal muscle TnI as judged by HPLC, showed reduced TnC binding and reduced ternary troponin (Tn) complex formation, and exhibited a much reduced Ca2+ sensitivity in the reconstituted regulatory system. It is shown that the amount of Tn complex formed by TnT1-201 rather than the activity of the mutant Tn complex affected this Ca2+ sensitivity. Binding of the mutant to Tm was similar to that of intact TnT. These results support the view that the COOH-terminal segment of TnT is necessary for binding to TnI and TnC and Ca2+ sensitivity in the thin filament, whereas its NH2-terminus strongly binds to Tm. To identify the regions of TnI which bind to muscle TnT, we used four recombinant fragments of fast skeletal muscle TnI containing amino acid residues 1-94 (TnI1-94), 1-120 (TnI1-120), 96-181 (TnI96-181), and 122-181 (TnI122-181) and a synthetic peptide, TnI98-114, containing residues 98-114 corresponding to the inhibitory region. Only TnI1-120 showed weak binding to TnT but not to TnT1-201. These results suggest that (i) a region within the NH2-terminal 120 residues of TnI interacts with TnT and (ii) the COOH-terminal residues 202-258 of TnT contain the interaction site of TnI. Overall, our results also imply that residues 159-201 constitute the smallest region of TnT which contributes to the Ca2+ sensitivity of actoS1 ATPase in a reconstituted regulatory system.

Animals↗
PubMed1996

Inhibition patterns of a model complex mimicking the reductive half-reaction of sulphite oxidase.

Different inhibition types of the saturation kinetics involving a synthesized model complex, [Bu4N]3[MoVIO2(mnt)2] (E) (where mnt2- = 1,2-dicyanoethylenedithiolate), and HSO3- as the substrate (S) by structurally similar anions SO4(2-), H2PO4- and H2PO3- have been shown for the first time in relevance to the reductive half reaction of the native enzyme sulphite oxidase. SO4(2-) acts as a competitive inhibitor. The mixed-type non-competitive inhibition by H2PO4- and the sigmoidal-type inhibition by H2PO3- are explained by a diamond-configuration random-order model. This involves a random binding sequence of the substrate and the inhibitor, and forms, in addition to two binary complexes [enzyme-substrate (ES) and enzyme-inhibitor (EI)], one enzyme-substrate-inhibitor-type ternary complex (ESI) by participation of at least one more binding site in addition to the catalytic site. This is possible in the present case only by co-ordination enhancement of molybdenum in E. This co-ordination expansion is brought about by nucleophilic attack of the substrate or the inhibitor at the molybdenum, forming a hepta-coordinated binary complex with the generation of an oxoanionic functional site, called the allosteric site. Analysis of the experimental data suggests that the inhibition by H2PO4- is due to the mechanism following either equilibrium conditions or a combination of steady-state and equilibrium conditions. With H2PO3-, the inhibition is due to the mechanism following the steady-state conditions. It is also shown that the ternary complex involving the enzyme, substrate and H2PO4- or H2PO3- is productive, but at a lower rate than that of the enzyme-substrate binary complex. Mixed-type inhibition with H2PO4- is actually of the type called "partially mixed competitive and non-competitive' as the inhibitor binds both to the catalytic site and to the allosteric site. The sigmoidal-type inhibition by H2PO3- is similar to heterotropic allosteric effect of mixed V,K type with the distinction, however, that the significance of co-operativity in this case is of kinetic importance only.

Anaerobiosis↗
PubMed1996

B cell responses to a peptide epitope. I. The cellular basis for restricted recognition.

Primary humoral responses in BALB/c mice to a variety of peptide constructs containing a common 15-amino acid residue antigenic determinant (PS1) in conjunction with one or more Th cell epitopes were examined. In all cases, the mature IgG response was found to focus primarily on a tetrapeptide sequence, Asp-Pro-Ala-Phe. The dominance of this segment was independent of the position of the PS1 determinant in the peptide sequence and was also observed in constructs with a random secondary structure. In contrast to the mature IgG response, the early primary IgM response was constituted by multiple specificities that collectively spanned a major proportion of the PS1 sequence. However, subsequent progression of this response entailed a strict selection for only those Abs directed against the Asp-Pro-Ala-Phe segment and apparently occurred at or around the time of the IgM to IgG class switch. Studies of murine responses to peptide analogs containing single amino acid substitutions within the Asp-Pro-Ala-Phe sequence revealed that emergence of this segment as the dominant epitope was a consequence of active suppression of B cells directed against alternate determinants. Positive selection of this subset of Abs correlated with overall higher avidity for epitope binding and was the outcome of a competitive process enforced by the limiting amounts of Th cell help available in the early stages of the primary response.

Amino Acid Sequence↗