Biomedical subjects

A Sharma

Publications and source records attributed to A Sharma.

At least 433 records · Page 24Linked to original sources

PubMed1998

Activity of bacterial phosphomonoesterases in batch culture.

The phosphomonoesterases catalyse the hydrolysis of primary esters of phosphoric acid which help the bacteria to survive in phosphate stressed environment. Ninety-five bacterial isolates were obtained from domestic sewage and industrial effluents of gelatine and soap factories at Jabalpur on a medium enriched with phosphate and were screened for phosphatase production. The phosphatase producers were tentatively identified as Escherichia coli, Vibrio vulnificus, Aeromonas hydrophila, Staphylococcus aureus, Pseudomonas maltophilia and Micrococcus varians. The in vitro studies on the production of phosphomonoesterases by bacteria was conducted. The maximum alkaline phosphatase production was recorded on 8th day of incubation by E.coli and P.maltophilia, on 10th day of incubation by V.vulnificus while M.varians and P.maltophilia produced higher acid phosphatase on 4th and 10th day of incubation respectively. The detailed investigations were done to find out the effect of various physical and chemical factors on phosphomonoesterases activity and the optimum conditions required for enzyme activity.

Acid Phosphatase↗

PubMed1998

Comparison between adjustable and non-adjustable hang-back muscle recession for concomitant exotropia.

We compared the results of strabismus surgery using adjustable and non-adjustable hang-back muscle recessions in 38 patients having concomitant exotropia. The two groups were matched for age of the patient, type of concomitant exotropia, amount of deviation, and type and amount of muscle surgery. At 6 months follow-up, 18 of the 19 patients (95%) in the adjustable hang-back recession group and 17 of the 19 patients (90%) in the non-adjustable hang-back recession group had ocular alignment within 10 prism diopters (PD) of orthophoria. At the most recent follow-up (mean 3.4 years), 12 of the 13 patients (92%) in adjustable hang-back recession group and 12 of the 14 patients (86%) in non-adjustable hang-back recession group had ocular alignment within 10 PD of orthophoria. There was no statistically significant difference in success rates between the two groups at 6 months postoperatively and at the most recent follow-up. This preliminary study suggests that non-adjustable hang-back muscle recession can be considered for routine concomitant exotropia.

Adolescent↗

PubMed1998

Antitumour and radioprotective action of Podophyllum hexandrum.

A significant antitumour effect of P. hexandrum, a herb thriving at Himalayas (2500-4000 m), was observed in strain 'A' mice carrying solid tumours developed by transplanting Ehrlich ascites tumour (EAT). Subtoxic well tolerated sequential doses of aqueous extract of P. hexandrum (a daily dose of 34.5 mg/kg b.w. for 15 days) enhanced tumour doubling time (TDT) from 1.94 +/- 0.26 days to 19.1 +/- 2.5 days. However, no synergism was revealed between radiation and P. hexandrum, though both independently manifested antitumour effects. In normal mice, pre-irradiation administration of extract of P. hexandrum protected mice in a dose dependent manner (optimal dose being 34.5 mg/kg body.wt. rendering 72% survival for 30 days) against whole body lethal irradiation of 10 Gy. Radioprotective properties of P. hexandrum were found to be comparable to synthetic radioprotectors like diltiazem etc.

Animals↗

PubMed1998

Use of different concentrations of carbamide peroxide for bleaching teeth: an in vitro study.

OBJECTIVE: This in vitro study compared the shade changes in extracted teeth during 2 weeks' whitening with 5%, 10%, or 16% carbamide peroxide. METHOD AND MATERIALS: After color calibration, the sole examiner selected 110 extracted unrestored, noncarious teeth, shade A3 or darker on a value-oriented guide. The teeth were randomly distributed into equal color groups. The control group (11 teeth) was treated with 0.9% saline, while the experimental groups (33 teeth each) were treated with 5%, 10%, or 16% carbamide peroxide. The solutions remained on the teeth for 8 hours. The teeth and tray were rinsed with tap water for 2 minutes, then rehydrated in 0.9% saline for 16 hours in the humidifier. The shade was assessed, and the process was repeated daily for 2 weeks. RESULTS: Repeated-measures analysis of variance indicated a significant difference in overall shade values between the control and all carbamide peroxide-treated groups at days 8 and 15. A Kaplan-Meier Survival Analysis indicated a quicker two-tab color change for the 10% and 16% groups than the 5% group. However, continuation of the 5% treatment to 3 weeks resulted in shades that approached the 2-week 10% and 16% values. CONCLUSION: Lower concentrations of carbamide peroxide take longer to whitening teeth but eventually achieve the same result as higher concentrations. Higher concentrations may cause increased sensitivity.

Analysis of Variance↗

PubMed1998

Enantioselective synthesis of (11E, 13S)-13-hydroxy-10-oxooctadecenoic acid, the cytotoxic principle of corn.

A brief and practical enantiomeric synthesis of the title compound has been developed. The salient features of the synthesis were: (i) preparation of the required chiron, 3-octyn-1-ol via a Candida rugosa lipasecatalyzed trans-acylation, (ii) use of easily accessible and inexpensive materials viz. 10-undecenoic acid and (iii) use of a simple reaction protocol.

Magnetic Resonance Spectroscopy↗

PubMed1998

Comparative evaluation of computed tomography and cerebral angiography in the management of subarachnoid haemorrhage.

Plain and contrast enhanced computed tomography (CT) scan of brain and cerebral angiography were done in 20 subjects of subarachnoid haemorrhage (SAH), diagnosed on the basis of clinical parameters and proved by cerebrospinal fluid (CSF) examination. Plain CT scan of brain confirmed the diagnosis of SAH in all the 20 (100%) cases, but was able to demonstrate the cause of SAH in 11(55%) cases only. Contrast CT scan provided additional information in 7 more cases. CT was also able to demonstrate the site and extent of bleeding, evidence of intraventricular bleeding and hydrocephalus. Cerebral angiography done in all the cases, confirmed the diagnosis in 14 (70%) cases diagnosed on CT and was able to give additional information in 4 more cases. It also showed excellent vascular details which were not possible with CT scan. It is concluded that enhanced CT scan should be done first in all the cases of SAH for preliminary scouting and angiography should be done where CT scan gives incomplete information or where surgical management is contemplated. Both the investigations were found to be complementary to each other.

Adolescent↗

PubMed1997

Mustard oil and garlic extract as inhibitors of sodium arsenite-induced chromosomal breaks in vivo.

Arsenic, a well-known human carcinogen present as a contaminant in ground water poses a serious threat to public health in various countries. The anticlastogenic properties of two dietary supplements, garlic and mustard oil, were screened against the clastogenic activity of sodium arsenite, since diet may contain factors which affect the process of mutagenesis and carcinogenesis. Aqueous extract of garlic (100 mg/kg b.w.) and mustard oil (0.643 mg/kg b.w.) were fed to Mus musculus for 30 consecutive days either singly or simultaneously. Sodium arsenite (0.1 mg/kg b.w.) was injected subcutaneously on days 7, 14, 21 and 30 of the experiment, singly and together with the dietary supplements. The animals were sacrificed 24 h after the last exposure to sodium arsenite and clastogenic effects were observed in the bone marrow cells. The degree of modulation of sodium arsenite-induced chromosomal aberrations was more pronounced in mustard oil than in garlic extract and simultaneous administration of both the dietary supplements reduced the clastogenic effects of sodium arsenite closer to the level of the negative control. The greater efficacy could be due to the interaction of the two dietary supplements and its radical scavenging property.

Animals↗

PubMed1997

Specific interactions between human integrin alpha v beta 3 and chimeric hepatitis B virus core particles bearing the receptor-binding epitope of foot-and-mouth disease virus.

Purified integrin alpha v beta 3 was used in solid-phase binding studies with chimeric hepatitis B cores which carry the RGD-containing loop of VP1 protein of the foot-and-mouth disease virus (FMDV). High levels of specific binding between the integrin and the particles were detected by enzyme-linked immunosorbent assays. The binding was Mn2+ cation dependent and could be competed with fibronectin, vitronectin, and the peptide GRGDSPK. Particles in which the RGD motif had been mutated to RGE failed to bind, indicating that the chimeric cores bound specifically to the ligand binding site of integrin alpha v beta 3. Electron micrographs showed several individual alpha v beta 3 molecules bound to the surface of each chimeric particle. Collectively, these data constitute firm evidence that the RGD-containing loop of FMDV is critical for binding to alpha v beta 3 and provide support for identification of alpha v beta 3 as a potential cellular receptor for FMDV.

Antigens, Viral↗

PubMed1997

Dissociation of cytokine signals for proliferation and apoptosis.

Cytokines such as IL-2 or IL-3 prevent cell death through apoptosis, either by preventing apoptosis directly or by sensitizing cells to survival factors present in serum. We demonstrate herein that BAF-B03 cells transfected with the wild-type IL-2R beta-chain undergo apoptosis when stimulated with IL-2 or IL-3 in the absence of serum. IL-2 also induced apoptosis in normal IL-2-responsive human T cell blasts in the absence of serum, and furthermore, epidermal growth factor and fibroblast growth factor induced increased rates of apoptosis in fibroblasts in the absence of serum, suggesting that cytokine-induced apoptosis in the absence of serum survival factors might represent an important biologic phenomenon. In the presence or the absence of serum, IL-2 and IL-3 induced expression of both c-Myc and Bax. In contrast, optimal cytokine-induced expression of Bcl-2 requires serum. Constitutive expression of Bcl-2 prevented cytokine-induced apoptosis. Transferrin mimicked serum by inducing an increase in Bcl-2 expression levels and concurrently prevented apoptosis. These results suggest that the balance between cytokine- and serum-induced Bcl-2 expression and cytokine-induced Bax expression may determine whether a cell undergoes cytokine-induced apoptosis. In BAF/BO3 cells expressing a mutant IL-2Rbeta with a deletion of the acidic domain, IL-2 did not induce either Bax expression or apoptosis. This suggests that the acidic domain of the IL-2R beta-chain plays an essential role in regulating IL-2-mediated Bax expression and apoptosis. Cytokine-induced apoptosis and its counterbalance by survival factors present in serum may play an important role in the regulation of cellular homeostasis during pathophysiologic processes.

Animals↗

PubMed1997

Pattern Formation in Spontaneous Dewetting of Thin Apolar Films

Various stages of evolution of surface instability leading to dewetting are investigated for thin (<100 nm) fluid films subjected to the long range van der Waals interactions on a nonwettable solid. The problems of pattern selection and complete three-dimensional morphology are resolved based on numerical solutions of the nonlinear two-dimensional thin film equation. The initial small scale random nonhomogeneities are quickly reorganized into a large scale coherent bicontinuous structure consisting of "hills" and "valleys," which is reminiscent of the classical picture of the spinodal decomposition in the linear approximation. On the level of a "unit-cell," the bicontinuous structure slowly evolves into an increasingly axisymmetric circular pattern, and eventually a growing circular hole (dry spot) is formed. Scaling arguments, as well as the simulations give the characteristic mean area of a unit-cell containing a single hole to be proportional to (h04gamma/|S|), where h0 is mean thickness, gamma is surface tension, and S is the spreading coefficient. Copyright 1997 Academic Press. Copyright 1997Academic Press

Journal Article↗

PubMed1997

Trapping of mammalian topoisomerase I and recombinations induced by damaged DNA containing nicks or gaps. Importance of DNA end phosphorylation and camptothecin effects.

We used purified mammalian topoisomerases I (top1) and oligonucleotides containing a unique top1 cleavage site to study top1-mediated cleavage and recombination in the presence of nicks and short gaps mimicking DNA damage. In general, top1 cleavage was not induced opposite to the nicks, and nicks upstream from the top1 cleavage site suppressed top1 activity. Irreversible top1 cleavage complexes ("suicide products" or "aborted complexes") were produced in DNA containing nicks or short gaps just opposite to the normal top1 cleavage site. Camptothecin enhanced the formation of the aborted top1 complexes only for nicks downstream from the cleavage site. These aborted (suicide) complexes can mediate DNA recombination and promote illegitimate recombination by catalyzing the ligation of nonhomologous DNA fragments (acceptors). We report for the first time that top1-mediated recombination is greatly enhanced by the presence of a phosphate at the 5' terminus of the top1 aborted complex (donor DNA). By contrast, phosphorylation of the 3' terminus of the gap did not affect recombination. At concentrations that strongly enhanced inhibition of intramolecular religation, resulting in an increase of top1 cleavable complexes, camptothecin did not reduce recombination (intermolecular religation). Nicks or gaps with 5'-phosphate termini would be expected to be produced directly by ionizing radiations or by processing of abasic sites and DNA lesions induced by carcinogens or drugs used in cancer chemotherapy. Thus, these results further demonstrate that DNA damage can efficiently trap top1-cleavable complexes and enhance top1-mediated DNA recombination.

Camptothecin↗

PubMed1997

Management of a congenitally shortened soft palate in a dog.

An 8-week-old puppy that was examined because of a nasal discharge was found to have a congenitally shortened soft palate. The palate was partially rebuilt with pharyngeal flaps constructed from the tonsillar crypts. The reconstructed soft palate extended approximately 40% of the distance between the caudal aspect of the hard palate and rostral tip of the epiglottis. During the first 18 months after surgery, the dog had 3 episodes of halitosis, sneezing, and mucopurulent nasal discharge but responded to antimicrobial treatment. The dog was fed dry dog food and drank water from an elevated bowl. Water would flow from the dog's nose if it drank water with its head lowered. Compensatory mechanisms likely play an important role in the outcome of animals with this condition.

Animals↗

PubMed1997

Secretion of Porphyromonas gingivalis fimbrillin polypeptides by recombinant Streptococcus gordonii.

The fimbriae of Porphyromonas gingivalis plays an important role in the pathogenesis of periodontal disease. A structural subunit of the P. gingivalis fimbriae, fimbrillin, has been shown to promote adherence of the bacteria to host surfaces and also induce an immune response. Biologically active domains of fimbrillin responsible for adherence or eliciting immune responses have been determined. In a previous study, we engineered the human oral commensal organism Streptococcus gordonii to express such biologically active domains on the surface of the bacteria as a vaccine delivery system. In this study we report an alternative approach of secreting fimbrillin polypeptide domains into the medium by modification of the surface-expression system described earlier. Such recombinant S. gordonii, in addition to being a source for antigen presentation to trigger a protective immune response, may have the added advantage of directly blocking the fimbriae-mediated adherence of P. gingivalis to the oral cavity following implantation. This approach can also be utilized for secreting other biologically important therapeutic molecules on mucosal surfaces for modulating local microenvironments.

Bacterial Proteins↗

PubMed1997

An in vivo quantitative structure-activity relationship for a congeneric series of pyropheophorbide derivatives as photosensitizers for photodynamic therapy.

An in vivo quantitative structure-activity relationship (QSAR) study was carried out on a congeneric series of pyropheophorbide photosensitizers to identify structural features critical for their antitumor activity in photodynamic therapy (PDT). The structural elements evaluated in this study include the length and shape (alkyl, alkenyl, cyclic, and secondary analogs) of the ether side chain. C3H mice, harboring the radiation-induced fibrosarcoma tumor model, were used to study three biological response endpoints: tumor growth delay, tumor cell lethality, and vascular perfusion. All three endpoints revealed highly similar QSAR patterns that constituted a function of the alkyl ether chain length and drug lipophilicity, which is defined as the log of the octanol:water partition coefficient (log P). When the illumination of tumor, tumor cells, or cutaneous vasculature occurred 24 h after sensitizer administration, activities were minimal with analogs of log P < or = 5, increased dramatically between log P of 5-6, and peaked between log P of 5.6-6.6. Activities declined gradually with higher log P. The lack of activity of the least-lipophilic analogs was explained in large part by their poor biodistribution characteristics, which yielded negligible tumor and plasma drug levels at the time of treatment with light. The progressively lower potencies of the most lipophilic analogs cannot be explained through the overall tumor and plasma pharmacokinetics of photosensitizer because tumor and plasma concentrations progressively increased with lipophilicity. When compensated for differences in tumor photosensitizer concentration, the 1-hexyl derivative (optimal lipophilicity) was 5-fold more potent than the 1-dodecyl derivative (more lipophilic) and 3-fold more potent than the 1-pentyl analog (less lipophilic), indicating that, in addition to the overall tumor pharmacokinetics, pharmacodynamic factors may influence PDT activity. Drug lipophilicity was highly predictive for photodynamic activity. QSAR modeling revealed that direct antitumor effects and vascular PDT effects may be governed by common mechanisms, and that the mere association of high levels of photosensitizer in the tumor tissue is not sufficient for optimal PDT efficiency.

Animals↗

PubMed1997

Inhibition of clastogenic effects of arsenic through continued oral administration of garlic extract in mice in vivo.

Crude aqueous extract of garlic bulbs (Allium sativum L. single clove variety) was administered by gavage to mice of both sexes daily for up to 30 and 60 days, in doses corresponding to 6 g for a 60 kg human body. Sodium arsenite (at 1/50 of LD50 dose) was injected subcutaneously to mice on every 7th day of the experiment. Chromosome preparations made from bone marrow following flame drying Giemsa schedule were screened for chromosomal aberrations. The clastogenic affects of prolonged exposure to sodium arsenite --a strong clastogen-- was reduced by a highly significant amount when crude garlic extract, in the dose used, was given daily to the mice by intubation for the same period.

Administration, Oral↗

PubMed1997

Effect of Nonadsorbing Polyelectrolytes on Colloidal Interactions in Aqueous Mixtures

The effect of adding a nonadsorbing charged polymer, sodium polystyrene sulfonate (SPSS), on the interaction energy profile between a 15 &mgr;m diameter polystyrene particle and a glass plate was measured using the optical technique of total internal reflection microscopy. A typical profile consisted of a repulsive barrier at large separations followed by a secondary well. Evidence of a longer-range tertiary well was also observed in salt-free solutions where the polymer molecules are rod-like. Addition of electrolyte causes a reduction in the depth of the tertiary well and produces oscillations at large separations. In addition, the stability of a solution of charged polystyrene particles in the presence of SPSS was measured using optical light scattering. Because of the electrostatic repulsion between the particles, the solution was stable against primary flocculation with no added polymer. However, because of long range attractive depletion forces, reversible secondary flocculation occurred into a local potential energy minimum at low SPSS concentrations (order 0.2 wt%). The polymer caused flocculation at a critical flocculation concentration (v *) which was found to decrease with increasing particle size. No restabilization of the latex dispersions was observed.

Journal Article↗

PubMed1997

Measurement of Colloidal Stability in Solutions of Simple, Nonadsorbing Polyelectrolytes

The stability of a solution of charged polystyrene particles in the presence of nonadsorbing polyelectrolyte macromolecules is measured using optical light scattering. The particles were negatively charged polystyrene latex spheres (0.5-1 &mgr;m diameter) while the macromolecules were simulated using negatively charged colloidal silica spheres (5-7 nm diameter). Because of the electrostatic repulsion between the particles, the solution is found to be stable against primary flocculation (irreversible flocculation into a primary energy minima). However, because of long-range attractive depletion forces, reversible secondary flocculation of the particles occurs into a local potential energy minimum. As observed with uncharged macromolecules, the polyelectrolyte first induces flocculation at a critical flocculation concentration (v *), but later restabilizes the system at a critical restabilization concentration (v **). These critical concentrations are found to decrease with decreasing macromolecule size and increasing particle size. The restabilized solutions are found to remain suspended for periods greater than 20 days. Comparison of the measured flocculation and restabilization results to predictions made using a recently developed force-balance model show qualitative agreement.

Journal Article↗

PubMed1997

Selenium salts and chromosome damage.

Sodium selenite and sodium selenate, fed by gavaging to age-matched male Swiss albino mice and observed after 24 h following a colchicine-fixative-air drying-Giemsa schedule, were found to induce chromosome breaks and spindle disturbances in bone marrow cells. The four concentrations used were fractions of LD50 and the effects were directly proportionate to the concentration of the chemical. Sodium selenite induced a slightly higher frequency of chromosomal aberrations than sodium selenate.

Animals↗