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Biomedical subjects

Alok Singh

Publications and source records attributed to Alok Singh.

7 recordsLinked to original sources
PubMed2026

PIK3CA Polymorphisms in Cervical Cancer: Differential Impact of rs6443624 and rs141178472.

BACKGROUND: Cervical cancer remains a major cause of mortality in low- and middle-income settings. We assessed whether two PIK3CA single-nucleotide polymorphisms (SNPs) rs6443624 (A/C) and rs141178472 (C/T) are associated with disease risk, clinicopathological features, and survival. MATERIALS AND METHODS: In a prospective case control study at a tertiary center, 154 participants were enrolled (77 cases, 77 controls). Genomic DNA was isolated from FFPE cervical tumors (QIAamp DNA FFPE Tissue Kit) and genotyped using TaqMan allelic discrimination. Clinicopathological variables (FIGO stage, histology, grade, treatment, tumor-infiltrating lymphocytes [TILs]) were abstracted from records. Genotype distributions were compared by Pearson chi-square. Associations with clinicopathological features used chi-square/Fisher's exact as appropriate; ANOVA compared age across genotypes. Overall survival (OS) was estimated by Kaplan-Meier and compared with the log-rank test; mean OS with SE and 95% CI is reported. RESULTS: Cases were predominantly locally advanced at presentation and squamous histology; most were moderately differentiated. rs6443624 differed significantly between cases and controls (&#x3c7;&#xb2;=21.1, p<0.001), with CC over-represented in cases and CA less frequent. rs141178472 showed no significant case control difference (&#x3c7;&#xb2;=2.9, p=0.086). For OS, rs6443624 showed a significant genotype effect (log-rank &#x3c7;&#xb2;=23.45, p=0.001): AA had the poorest survival, CA the longest, CC intermediate. rs141178472 was not associated with OS (&#x3c7;&#xb2;=1.06, p=0.588). Genotype clinicopathological correlations for stage group, grade, TILs, and treatment were non-significant or inconsistent, with some comparisons limited by small sample sizes. CONCLUSION: The PIK3CA rs6443624 variant appears to influence both susceptibility and prognosis in cervical cancer, highlighting its potential as a biomarker for molecular risk stratification. Validation in larger, multi-center cohorts incorporating HPV/p16 assessment and extended follow-up is warranted to confirm its clinical relevance.

Humans↗
PubMed2007

Facilitated stent delivery using applied topical lubrication.

OBJECTIVES: The goal of this study was to assess the utility of topical lubrication to aid stent delivery in challenging anatomy and its effects on long-term clinical outcome. BACKGROUND: Failed stent delivery is encountered in up to 5% of percutaneous coronary interventions (PCI). METHODS: The effectiveness of topically applied lubrication to facilitate stent delivery after failed stent placement was evaluated in 20 (2.5%) out of 813 consecutive patients undergoing PCI. Initial attempts at stent delivery failed despite balloon predilatation and use of moderate-to-stiff guidewires in all patients. The lubricious solution used was Rotaglide, a phospholipid emulsion originally designed to reduce catheter friction during rotational atherectomy. Following unsuccessful delivery, stents were removed from the guiding catheters, topically saturated with Rotaglide, and deployment immediately reattempted. Procedural efficacy and long-term clinical outcomes were assessed. RESULTS: The study population included 20 patients aged 69 +/- 10 years, all of whom had complex lesions (ACC/AHA Class B(2) or C). Rotaglide lubricated stents were successfully deployed at the target lesions in 17 of the 20 patients (85%). Patients were followed 19.5 +/- 3.2 months after their index procedure. There were no periprocedural complications or subacute stent thromboses. Of the 14 patients with drug-eluting stents, none had clinical restenosis or target vessel revascularization. Target lesion revascularization secondary to restenosis was required in 1 of 3 patients treated with bare-metal stents. CONCLUSIONS: Topical lubrication is a simple and effective aid for stent delivery in complex lesions. Rotaglide appears safe and biocompatible with drug-eluting stents.

Aged↗
PubMed2006

A symmetrical indexing scheme for decagonal quasicrystals analogous to Miller-Bravais indexing of hexagonal crystals.

The problems of redundancy and superfluous indices in indexing the planes and axes in a decagonal quasicrystal are considered, using a scheme of five coplanar vectors in the quasiperiodic plane and one perpendicular vector. Of all the indexing schemes in use, this scheme offers the maximum advantage. An analogy is drawn to the hexagonal system using Miller-Bravais indices. Based on this, a symmetry-based indexing system for decagonal phases is devised that follows a simplified approximate zone law analogous to the exact zone law for the hexagonal case. The indices based on this scheme will be designated as ;Frank indices'. High-symmetry electron diffraction zone-axis patterns as well as powder X-ray diffraction patterns are indexed using Frank indices and compared with those of other indexing schemes.

Alloys↗
PubMed2005

Effect of organic additives on the mitigation of volatility of 1-nitro-3,3'-dinitroazetidine (TNAZ): next generation powerful melt cast able high energy material.

1-Nitro-3,3'-dinitroazetidine (TNAZ) was synthesized based on the lines of reported method. Thermolysis studies on synthesized and characterized TNAZ using differential scanning calorimetry (DSC) and hyphenated TG-FT-IR techniques were undertaken to generate data on decomposition pattern. FT-IR of decomposition products of TNAZ revealed the evolution of oxides of nitrogen and HCN containing species suggesting the cleavage of C/N-NO(2) bond accompanied with the collapse of ring structure. The effect of incorporation of 15% additives namely, 3-amino-1,2,4-triazole (AT), 3,5-diamino-1,2,4-triazole (DAT), carbohydrazide (CHZ), 5,7-dinitrobenzofuroxan (DNBF), bis (2,2-dinitropropyl) succinate (BNPS), triaminoguanidinium nitrate (TAGN), 2,4,6-trinitrobenzoic acid (TNBA) and nitroguanidine (NQ) on the volatility of TNAZ was investigated by undertaking thermogravimetric analysis. The TG pattern brings out the potential of BNPS and TAGN as additives to mitigate the volatility of TNAZ. The influence of additives on thermal decomposition of pattern of TNAZ was also investigated by DSC. The DSC results indicated that the additives did not have appreciable effect on the melting point of TNAZ. Scanning electron microscopic (SEM) studies were carried out to investigate the effect of additives on morphology of TNAZ. This paper also discusses the possible mechanism involved in between the TNAZ and TAGN and BNPS. It appears that the formation of charge transfer complex formation between the TNAZ and TAGN/BNPS. The effect of addition of high explosives such as CL-20, HMX and RDX on thermo-physical characteristics of TNAZ is also reported in this paper.

Azetidines↗
PubMed2005

Functional reconstitution of protein ion channels into planar polymerizable phospholipid membranes.

We demonstrate that polymerizable planar membranes permit reconstitution of protein ion channels formed by the bacterial toxins Staphylococcus aureus alpha-hemolysin (alphaHL) and Bacillus anthracis protective antigen 63. The alphaHL channel remained functional even after membrane polymerization. Surface pressure measurements suggest that the ease of forming membranes depends on membrane surface elasticity estimated from Langmuir-Blodgett monolayer pressure-area isotherms. The ability to stabilize nanoscale pores in robust ultrathin films may prove useful in single molecule sensing applications.

Antigens, Bacterial↗
PubMed2003

Fabrication of nanoscale metallic spirals using phospholipid microtubule organizational templates.

We describe the fabrication of metallic Cu spiral/helical nanostructures prepared via selective electroless metallization of a phospholipid microtubule template. The metallization template is created through selective, sequential adsorption of the oppositely charged polyelectrolytes, sodium poly(styrenesulfonate) (PSS) and poly(ethyleneimine) (PEI), onto nanoscale seams naturally occurring on the microtubule surface. A negatively charged Pd(II) nanoparticle catalyst is bound to the terminal cationic PEI layer of the multilayer film and initiates selective template metallization to form the helical Cu nanostructures. Details of the process are presented, and a mechanism and factors affecting the control of the feature critical dimensions are discussed.

Journal Article↗