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Biomedical subjects

S Sridhar

Publications and source records attributed to S Sridhar.

At least 37 records · Page 2Linked to original sources

Automatic segmentation of medical images for renal calculi and analysis.

Development of an automated system to identify renal calculi based on its physical characteristics is proposed. Calculi are due to abnormal collection of certain chemicals like oxalate, phosphate and uric arid. Renal calculi may be present in kidney, ureter or in urinary bladder. An algorithm is proposed to detect calculus using its shadow. The system also extracts the properties of calculi such as size, shape and location, which are vital for reliable diagnosis. This method has been implemented in the MATLAB/IDL platform and a considerable success rate is obtained.

Algorithms↗

Use of heparin in the investigation of obscure gastrointestinal bleeding.

OBJECTIVE: To determine if the administration of heparin improves the predictive value of angiography in the investigation of obscure gastrointestinal (GI) bleeding. METHODS: 18 patients with a history of chronic GI bleeding were investigated with angiography. For 6 patients, the cause of GI bleeding was established with angiography; the 12 patients who had negative results were given heparin for 24 h and were reassessed with angiography. RESULTS: After heparin administration, the source of GI bleeding was determined with angiography for 6 of the remaining 12 patients. Thus, heparinization increased diagnostic yield from 33% (6 of 18) to 67% (12 of 18). No significant complications, such as uncontrolled GI bleeding, occurred. CONCLUSION: Heparinization improves the diagnostic yield of angiography when obscure GI bleeding is being investigated.

Angiography↗

Quantum fingerprints of classical ruelle-pollicott resonances

Quantum and classical correlations are studied experimentally in model n-disk microwave billiards. The wave vector kappa autocorrelation C(kappa) of the quantum spectrum displays nonuniversal oscillations for large kappa, comparable to the universal random matrix theory behavior observed for small kappa. The nonuniversal behavior is shown to be completely determined by the classical Ruelle-Pollicott resonances, arising from the complex eigenvalues of the Perron-Frobenius operator, and calculated using periodic orbit theory. This work establishes a fundamental connection between the quantum and classical correlations of an open system.

Journal Article↗

Correlations due to localization in quantum eigenfunctions of disordered microwave cavities

Statistical properties of experimental eigenfunctions of quantum chaotic and disordered microwave cavities are shown to demonstrate nonuniversal correlations due to localization. Varying energy E and mean free path l enable us to experimentally tune from localized to delocalized states. Large level-to-level inverse participation ratio ( I2) fluctuations are observed for the disordered billiards, whose distribution is strongly asymmetric about . The spatial density autocorrelations of eigenfunctions are shown to spatially decay exponentially and the decay lengths are experimentally determined. All the results are quantitatively consistent with calculations based upon nonlinear sigma models.

Journal Article↗

Solitary pulmonary nodule due to dirofilariasis.

Pulmonary dirofilariasis can produce a noncalcified solitary nodule and therefore be mistaken for a lung cancer. Careful analysis of the imaging findings in this disease can suggest the proper evaluation and management in affected patients.

Adult↗

Microwave study of quantum n-disk scattering

We describe a wave-mechanical implementation of classically chaotic n-disk scattering based on thin two-dimensional microwave cavities. Two-, three-, and four-disk scatterings are investigated in detail. The experiments, which are able to probe the stationary Green's function of the system, yield both frequencies and widths of the low-lying quantum resonances. The observed spectra are found to be in good agreement with calculations based on semiclassical periodic orbit theory. Wave-vector autocorrelation functions are analyzed for various scattering geometries, the small wave-vector behavior allowing one to extract the escape rate from the quantum repeller. Quantitative agreement is found with the value predicted from classical scattering theory. For intermediate energies, nonuniversal oscillations are detected in the autocorrelation function, reflecting the presence of periodic orbits.

Journal Article↗

Characterization of an anticryptococcal protein isolated from human serum.

Human serum at low concentrations inhibits the growth of Cryptococcus neoformans in vitro. Fractionation of serum yielded a purified inhibitory protein with a molecular mass of approximately 81.8 kDa, a pI of approximately 6.2, and an amino acid sequence that matched that of human transferrin. The inhibitory activity and that of apotransferrin and 5% human serum were reversed by 10 microM freshly prepared FeCl(3).

Antifungal Agents↗

Gastrointestinal safety profile of nabumetone: a meta-analysis.

Individual comparative studies suggest that nabumetone has a gastrointestinal (GI) safety profile superior to comparator NSAIDs but lack power to show a statistical difference. The aim of this study was to evaluate systematically the difference in GI adverse events--especially the rate of perforations, ulcers, and bleeds (PUBs)-- between studies, meta-analyses of comparative trials of nabumetone and conventional NSAIDs, and postmarketing, open-label studies of nabumetone meeting predefined inclusion and exclusion criteria. A fully recursive literature search identified 13 studies consisting of 29 treatment arms and 49,501 patients that met the predefined criteria. Tests for heterogeneity found no significant difference between studies of each subgroup. Overall, the dyspeptic symptoms flatulence, constipation, and diarrhea were the most commonly reported adverse events accounting for 98.6% of the total GI adverse events. Significantly more patients treated with a comparator NSAID experienced GI adverse events than did those taking nabumetone (P = 0.007). After adjustment for patient-exposure years, PUBs were 10 to 36 times more likely to develop in patients treated with a comparator NSAID than with nabumetone. This was consistently seen in patients in nonendoscopic (n = 7,468) and endoscopic studies (n = 244). In the analysis of postmarketing or open-label studies of nabumetone, only one PUB was reported per 500 patient-exposure years over 17,502 treatment years (n = 39,389). GI adverse event-related dropouts and hospitalizations were increased by 1.3- and 3.7-fold if patients were treated with a comparator NSAID than with nabumetone. Significantly fewer treatment-related GI adverse events, especially PUBs, are seen in patients treated with nabumetone than with a comparator NSAID. Nabumetone is very safe for the GI tract.

Anti-Inflammatory Agents, Non-Steroidal↗

Meta-analysis of the relationship between Helicobacter pylori seropositivity and gastric cancer.

BACKGROUND & AIMS: Reports in the literature regarding the relationship of Helicobacter pylori infection to gastric cancer are conflicting. The aim of this study was to identify the source of heterogeneity between studies. METHODS: Meta-analysis of cohort or case-control studies with age- and/or sex-matched controls, providing raw data on H. pylori infection detected by serology, was used. RESULTS: A fully recursive literature search identified 19 qualified studies with 2491 patients and 3959 controls. Test for homogeneity found a significant difference in odds ratio between patients with early and advanced gastric cancer (6.35 vs. 2.13; P = 0.01), patients with cardiac and noncardiac gastric cancer (1.23 vs. 3.08; P = 0.003), and population- and hospital-based controls (2.11 vs. 1.49; P < 0.001). The summary odds ratio for gastric cancer in H. pylori-infected patients is 1.92 (95% confidence interval [CI], 1.32-2.78), 2.24 (95% CI, 1.15-4.4), and 1.81 (95% CI, 1.16-2.84) for all studies, cohort, and case-control studies, respectively. H. pylori-infected younger patients have a higher relative risk for gastric cancer than older patients with odds ratios decreasing from 9.29 at age < or = 29 years to 1.05 at age > or = 70 years. H. pylori infection is equally associated with the intestinal or diffuse type of gastric cancer. CONCLUSIONS: H. pylori infection is a risk factor for gastric cancer. The heterogeneity of reported results is caused by differences in the selection of controls, patient age, and the site and stage of gastric cancer.

Aging↗

Embigin, a developmentally expressed member of the immunoglobulin super family, is also expressed during regression of prostate and mammary gland.

Cell adhesion molecules (CAMs) are intimately involved in a variety of cellular processes, including development, cell growth, apoptosis, and differentiation. Interaction of CAMs with components of the extracellular matrix (ECM) growth factors, and other CAMs provides an intricate regulatory mechanism for a diverse range of cellular responses. Embigin is a developmentally expressed protein that is a member of the immunoglobulin superfamily (IgSF) class of CAMs. We have identified embigin as a gene expressed during tissue regression in rat prostate and lactating mammary gland following hormonal ablation. In the absence of the appropriate hormone, the secretory epithelial cells of these two tissues undergo successive waves of apoptotic cell death co-incident with extensive reorganization of the surviving tissue. Using Northern analysis, in situ hybridization analysis, RT-PCR, and Western analysis we have characterized the expression of embigin mRNA and protein in both regressing prostate and mammary gland. During development of the prostate gland, increased expression of embigin is correlated with the appearance of highly organized lumenal and ductal structures. Embigin is also expressed in a variety of adult tissues including heart, liver, lung, and brain Zoo-blot analysis with the rat embigin cDNA indicates that embigin homologs exist in species as diverse as Homo sapiens and Drosophila melanogaster, suggesting that it has been highly conserved during evolution. Embigin protein is expressed at readily detectable levels in a variety of prostate and mammary cancer cell lines, and in some cell lines the expression of embigin appears to be down-regulated in the presence of ECM. Our data have led us to propose a model in which embigin functions as a regulator of cell/ECM interactions during development and in the homeostasis of normal adult tissues.

Amino Acid Sequence↗

Immunization of male bonnet monkeys (M. radiata) with a recombinant FSH receptor preparation affects testicular function and fertility.

Immunization of proven fertile adult male monkeys (n=3) with a recombinant FSH receptor protein preparation (oFSHR-P) (representing amino acids 1-134 of the extracellular domain of the receptor Mr approximately 15KDa) resulted in production of receptor blocking antibodies. The ability of the antibody to bind a particulate FSH receptor preparation and receptors in intact granulosa cells was markedly (by 30-80%) inhibited by FSH. Serum T levels and LH receptor function following immunization remained unchanged. The immunized monkeys showed a 50% reduction (p<0.001) in transformation of spermatogonia(2C) to primary spermatocytes (4C) as determined by flow cytometry and the 4C:2C ratio showed a correlative change (R 0.81, p<0.0007) with reduction in fertility index (sperm counts X motility score). Breeding studies indicated that monkeys became infertile between 242-368 days of immunization when the fertility index was in the range of 123+/-76 to 354+/-42 (compared to a value of 1602+/-384 on day 0). As the effects observed are near identical to that seen following immunization with FSH it is suggestive that oFSHR-P can substitute for FSH in the development of a contraceptive vaccine.

Animals↗

Clinical economics review: cost-effectiveness of treatment alternatives for gastro-oesophageal reflux disease.

Gastro-oesophageal reflux disease is a chronic recurring disorder, which is widespread, especially in Western societies. Faced with increasing health costs and finite resources, an increasingly important part of evaluating new treatments is economic appraisal. In this paper, we review critically the published economic studies of the cost-effectiveness of treatments for gastro-oesophageal reflux disease. Proton pump inhibitors are considered the best choice for the management of grades II-IV oesophagitis and are more cost-effective than H2-receptor antagonists because of their fast healing of oesophagitis, early relief of symptoms, and prevention of recurrent oesophagitis and development of complications.

Cost-Benefit Analysis↗