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Biomedical subjects

S Tandon

Publications and source records attributed to S Tandon.

At least 73 records · Page 4Linked to original sources
PubMed1993

Effect of sanguinarine on the transport of essential nutrients in an everted gut sac model: role of Na+,K(+)-ATPase.

The effect of the argemone alkaloid, sanguinarine, was studied on the active transport of D-glucose and some of the L-amino acids in everted sacs of the small intestine of rats. Sanguinarine (1.0 mumole) was found to inhibit (61%) the transport of D-glucose, while an alkaloid concentration of 0.1 mumole was ineffective. Both 0.1 and 1.0 mumole of sanguinarine had no effect on the transport of the L-amino acids including aspartic acid, lysine, and tyrosine. Sanguinarine showed a dose dependent inhibition of intestinal and hepatic Na+,K(+)-ATPase in a non-competitive manner. The inhibition of Na+,K(+)-ATPase by sanguinarine may in turn inhibit the active transport of D-glucose which requires a sodium pump.

Alkaloids↗
PubMed1993

Perinatal mortality in rural India with special reference to high risk pregnancies.

One-thousand-and-sixty-five pregnant mothers among a rural population of 30,000 in Uttar Pradesh were followed for 1 year. A still birth rate of 26.1 and perinatal mortality rate of 121.1 per thousand births were registered. Early neonatal mortality rate was found to be 97.4 per thousand live births. Twenty per cent of the women were identified with high risk factors. Inadequate or no antenatal care, bad obstetric history, and prolonged labour attributed to 13, 20, and 27 per cent of the risk, respectively, with a respective relative risk of 2.23, 3.1, and 4.09 times. These three factors were found to be the major and significant contributors to high perinatal mortality amongst the 'high risk' group. Selective extension of comprehensive M.C.H. Care to this group using the high risk approach is expected to lower perinatal mortality in rural community where M.C.H. services are far from optimum.

Female↗
PubMed1993

Immunocytochemical detection of prolactin binding sites in fine needle aspiration smears of breast lesions.

Specific prolactin (PRL) binding sites were demonstrated in the fine needle aspiration cytology (FNAC) specimens from 68 patients with benign and malignant diseases of the breast using highly sensitive technique of DNP hapten sandwich staining procedure and antibody against human PRL. In 16 patients, immunocytochemical staining was also carried out on paraffin embedded sections of corresponding lesions. FNAC specimens included 52 neoplasms and 16 non-proliferative and proliferative benign breast disease. The reaction varied in different lesions, being maximum (72%) in malignant tumours and 60 per cent in benign tumours. However, benign breast disease showed a reaction that varied with the lesion. The technique was found to be simple, sensitive and economical for demonstrating specific PRL binding sites in cytology specimens of breast lesions.

Binding Sites↗
PubMed1992

Microleakage of composite-ionomer laminate restorations: an in vitro evaluation.

The in-vitro study undertaken on sixty teeth, 30 each of second primary molars and first premolars to evaluate the effectiveness of sealing property of composite-ionomer laminate restorations given on buccal aspects of these teeth after either Dycal base, ionomer base not etched and ionomer base etched indicated significantly more microleakage in dycal base composite resin restorations than composite ionomer. No difference in microleakage was seen in etched and unetched composite ionomer laminate restorations. Though microleakage was observed more in primary teeth than permanent teeth it was not found to be statistically significant.

Child↗
PubMed1991

In vitro evaluation of tensile bond strength of composite to glass ionomer cement.

An in vitro study conducted on 30 primary second deciduous molars and 30 second premolars to evaluate the tensile bond strength of composite ionomer restorations revealed that (i) glass ionomer cement base was superior than Dycal under composite restorations; (ii) etched glass ionomer base provided optimal bond strength in both primary and permanent teeth; (iii) tensile bond strength was high in permanent than in the primary teeth; and (iv) composite ionomer laminate can be considered as a material of choice for restoration of primary teeth.

Adolescent↗
PubMed1990

The detection of kinetic intermediate(s) during refolding of rhodanese.

Recent studies showed that the enzyme rhodanese could be reversibly unfolded in guanidinium chloride (GdmCl) if aggregation and oxidation were minimized. Further, these equilibrium studies suggested the presence of intermediate(s) during refolding (Tandon, S., and Horowitz, P. (1989) J. Biol. Chem. 264, 9859-9866). The present work shows that native and refolded enzymes are very similar in structural and functional characteristics. Kinetics of denaturation/renaturation were used to detect the folding intermediate(s). The shift in fluorescence wavelength maximum was used to monitor the structural changes during the process. First order plots of the structural changes during unfolding and refolding show nonlinear curves. The refolding occurs in at least two phases. The first phase is very fast (t1/2 much less than 30 s) and accounts for the partial regain in the structure but not in the activity. The second phase is slow (t1/2 = 2.9 h) during which the enzyme fully regains its structure along with the activity. The fractional renaturation of rhodanese due to the fast phase, monitored in various concentrations of GdmCl, describes a transition centered at 3.5 M GdmCl which is very similar to the higher of the two transitions observed in the reversible refolding. All of these findings support the presence of detectable intermediate(s) during folding of rhodanese.

Animals↗
PubMed1989

Reversible folding of rhodanese. Presence of intermediate(s) at equilibrium.

For the first time completely reversible unfolding was achieved for guanidinium chloride-denatured rhodanese using a systematically defined protocol. These conditions included beta-mercaptoethanol, lauryl maltoside, and sodium thiosulfate. All components were required to get more than the previous best reactivation with lauryl maltoside of 17% (Tandon, S., and Horowitz, P. (1986) J. Biol. Chem. 261, 15615-15681). Non-coincidental transition curves were obtained by monitoring different parameters including: (i) variation in the activity, (ii) shifts of the fluorescence wavelength maximum, and (iii) variation in ellipticity at 220 nm. The transition followed by the fluorescence wavelength maximum was asymmetric and resolvable into two separate transitions. A thermodynamic analysis was used to define the energetics of the two processes. Studies with the fluorescent "apolar" probe 1,8ANS are consistent with the appearance of organized hydrophobic surfaces following the first transition. Near UV CD measurements indicated that the first transition is associated with a loss of dyssymmetry around at least some of the tryptophans. Thus, the unfolding of rhodanese is complex, and there are detectable intermediate(s) during the process. These results suggest that reversible unfolding occurs in two discrete stages: 1) loss of tertiary interactions and activity, with retention of secondary structure, and 2) loss of secondary structure. The available x-ray structure suggests that the first transition can be associated with changes in the domain interactions, which may modulate the effectiveness of helix dipoles in lowering the pKa of the active site sulfhydryl.

Dithiothreitol↗
PubMed1989

Highly specific sites of prolactin binding in benign and malignant breast tissue.

An immunocytochemical method involving the application of polyclonal antisera to human prolactin (PRL) followed by a highly sensitive and a modified version of dinitrophenyl (DNP) hapten sandwich staining procedure using anti-DNP IgM monoclonal antibody has been used to detect PRL binding in benign and malignant breast tissue. The technique was applied to 5 microns thick sections of paraffin embedded formalin fixed tissue. Out of 107 breast biopsies 40 were carcinomas, 41 were fibroadenomas, 18 were benign cystic disease and 8 were gynaecomastia. In cases of carcinoma positive staining was observed in 82.5% cases whereas in fibroadenoma the positivity was in 57% cases only. The positive reaction in fibroadenoma was mainly due to the presence of apocrine metaplasia associated with the tumour. Also PRL was present in greater proportion in post menopausal patients as compared to premenopausal cancer patients. These findings suggest the presence of specific PRL binding sites in breast tissue. The staining was restricted to epithelial cells and background staining of the stroma was minimally seen in these cases. Positively stained breast carcinoma may represent an apocrine subset of the carcinoma.

Binding Sites↗
PubMed1988

The effects of lauryl maltoside on the reactivation of several enzymes after treatment with guanidinium chloride.

The present study confirms the previous reports that detergents can facilitate the reactivation of guanidinium chloride (GdmCl) denatured rhodanese (Tandon, S. and Horowitz, P. (1986) J. Biol. Chem. 261, 15615-15618; Tandon, S. and Horowitz, P. (1987) J. Biol. Chem. 262, 4486-4491). Here, we report the effect of the detergent, lauryl maltoside, on the reactivation of several enzymes other than rhodanese. For this study we used five different enzymes each having a single polypeptide chain, namely: adenosine deaminase; 3-phosphoglyceric phosphokinase; myokinase; 3 alpha-hydroxysteroid dehydrogenase; and phosphoglucomutase. The regain of enzyme activity was used to monitor refolding. Like rhodanese, these enzymes were denatured in 6 M GdmCl and diluted into a buffer containing various concentrations of lauryl maltoside. The effect of lauryl maltoside on reactivating these proteins depended on the specific enzyme used. For example, in the presence of lauryl maltoside, reactivation of adenosine deaminase increased to 98%, while phosphoglucomutase could not be reactivated significantly. The critical micelle concentration (CMC) of lauryl maltoside was measured under the present experimental conditions using 2-(p-toluidinyl)naphthalene 6-sulfonate (TNS) as an apolar fluorescent probe, and gave a value of 0.085 mg.ml-1 in 10 mM sodium phosphate (pH 7.4). The reactivating effect of lauryl maltoside was not generally related to its CMC. In some cases an induction period was observed before the enzyme attained its steady-state velocity. This might suggest the presence of intermediate(s) in the refolding pathway that could have been stabilized by the detergent. These findings indicate that 'non-denaturing' detergents may be useful for assisting reactivation of enzymes, although the optimum conditions will have to be determined for each individual case.

Enzyme Inhibitors↗
PubMed1987

Detergent-assisted refolding of guanidinium chloride-denatured rhodanese. The effects of the concentration and type of detergent.

We have established the generality of using detergents for facilitating the reactivation of 6 M guanidinium chloride-denatured rhodanese that was recently described for the nonionic detergent lauryl maltoside (LM) (Tandon, S., and Horowitz, P. (1986) J. Biol. Chem. 261, 15615-15618). We report here that not only LM but other nonionic as well as ionic and zwitterionic detergents also have favorable effects in reactivating the denatured enzyme. Not all detergents are useful, and the favorable effects occur over a limited concentration range. Above and below that range there is little or no effect. Zwittergents, which represent a homologous series with varying critical micelle concentrations (CMCs) are effective only above their CMCs. Induction phases occur in the progress curves of rhodanese refolded in the presence of the effective detergents, suggesting the presence of refolding intermediates that are apparently stabilized by detergent interactions. Gel filtration chromatography of rhodanese with and without LM suggests that even though the renaturation of the denatured enzyme requires detergent at concentrations above its CMC, the enzyme does not bind an amount of detergent equivalent to a micelle. It is suggested that renaturation of other proteins might also be assisted by inclusion of "nondenaturing" detergents, although the optimal conditions will have to be determined for each individual case.

Detergents↗
PubMed1986

Detergent-assisted refolding of guanidinium chloride-denatured rhodanese. The effect of lauryl maltoside.

For the first time, the enzyme rhodanese (thiosulfate:cyanide sulfurtransferase; EC 2.8.1.1) has been renatured from 6 M guanidinium chloride (GdmCl) by direct dilution of the denaturant at relatively high protein concentrations. This has been made possible by using the nonionic detergent dodecyl-beta-D-maltoside (lauryl maltoside). Lauryl maltoside concentration dependence of the renaturation and reactivation time courses were studied using 50 micrograms/ml rhodanese. There was no renaturation at lauryl maltoside (less than 0.1 mg/ml), and the renaturability increased, apparently cooperatively, up to 5 mg/ml detergent. This may reflect weak binding of lauryl maltoside to intermediate rhodanese conformers. The renaturability began to decrease above 5 mg/ml lauryl maltoside and was significantly reduced at 20 mg/ml. Individual progress curves of product formation, for rhodanese diluted into lauryl maltoside 90 min before assay, showed induction phases as long as 7 min before an apparently linear steady state. The induction phase increased with lauryl maltoside concentration and could even be observed in native controls above 1 mg/ml detergent. These results are consistent with suggestions that refolding of GdmCl-denatured rhodanese involves an intermediate with exposed hydrophobic surfaces that can partition into active and inactive species. Further, lauryl maltoside can stabilize those surfaces and prevent aggregation and other hydrophobic interaction-dependent events that reduce the yield of active protein. The rhodanese-lauryl maltoside complex could also form with native enzyme, thus explaining the induction phase with this species. Finally, it is suggested that renaturation of many proteins might be assisted by lauryl maltoside or other "nondenaturing" detergents.

Dose-Response Relationship, Drug↗