S. Singh

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Phytolectins: natural molecules with immense biotechnological potential

Indian journal of experimental biology, 1997

Lectins are structurally diverse, carbohydrate binding proteins that bind reversibly to specific ... more Lectins are structurally diverse, carbohydrate binding proteins that bind reversibly to specific mono- or oligosaccharides. Their abundance in the plant kingdom suggest that they have diverse roles to perform. They serve as recognition factor between symbiotic nitrogen fixing bacteria and host plants, as a deterrent to phytopathogens like fungi, insects, and animals, as storage protein and as an aid in sexual reproduction in Chlamydomonas, amongst others. The possible application of lectins as a factor in increasing soil fertility and as a biopesticide by genetically engineered organisms is yet to be fully explored by the biotechnologists. However, they are being used by the biomedical scientists and biochemists in blood typing and stimulation of cells for chromosome analysis and gene mapping, in cell separation, identification of complex glycoproteins and typing of bacteria. Cell targeting by lectins in cancer therapy is still in its infancy. This review gives an insight into the p...

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Current status of groundwater arsenic and its impacts on health and mitigation measures in the Terai basin of Nepal: An overview

Environmental Reviews, 2011

Nepal is located in the vicinity of Himalayas. Nearly 47% (11 million) of the total Nepalese popu... more Nepal is located in the vicinity of Himalayas. Nearly 47% (11 million) of the total Nepalese population lives on the flat lands located in the southern part of the country, the Terai region. The majority (90%) of people living in the Terai region of Nepal depends on groundwater as their primary source of potable water. Out of 24 674 tested wells in the Nawalparasi district approximately 7896 wells (32%) had As concentrations greater than 10 mgÁL -1 (safe-water limit set by WHO). In addition, 3676 wells (14.9%) had As concentrations greater than 50 mgÁL -1 (standard permissible limit proposed by Nepal). However, at present, none of the wells in the Terai districts of Nepal are free from As. Based on sedimentaquifer studies, the Siwalik Hills and the higher Himalayas are assumed to be the possible sources of As in the Terai region. Leaching of As from natural rocks has been the main source of groundwater contamination in Nepal. However, little is known about the mechanism of As release in the Terai groundwater. High levels of As contamination in the drinking water poses a serious risk to the health of resident living in the Terai plain regions. In the region, 23% (2.53 million, based on WHO guideline of 10 mgÁL -1 ) and 5% (0.5 million, Nepal's standard of >50 mgÁL -1 ) of population are at the risk of As exposure. Chronic exposure to As imparts characteristic skin manifestations (pigment change), melanosis and keratosis. The prevalence of arsenicosis was found to be 3.6%, 0.9%, and 0.7% in Nawalparasi, Rupandehi, and Kapilavastu districts, respectively. Arsenicosis is most prevalent among the male population, especially those in their late 50s. The most promising approach for the removal of As to acceptable levels include the use of Gagri filters and iron-assisted bio-sand filters. Here, we review the current status of groundwater arsenic and its impacts on health and mitigation measures in the Terai region of Nepal.

format_quote14% of wells in Nepal exceed safe arsenic limit, posing significant public health threat to ~11 million people exposed to contamination.format_quote

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Physiological and Biochemical Alterations in a Diazotrophic Cyanobacterium Anabaena cylindrica Under NaCl Stress

Current Microbiology, 2007

Growth, morphological variation, and liquid chromatography-photodiode array detection-mass spectr... more Growth, morphological variation, and liquid chromatography-photodiode array detection-mass spectrometric analysis of pigments have been studied in a diazotrophic cyanobacterium Anabaena cylindrica in response to NaCl stress. The chlorophyll and cellular protein contents increased initially in response to 50 mM NaCl. Further increment in NaCl concentration, however, resulted in a significant decrease in both chlorophyll and cellular protein.

format_quoteAt 50 mM NaCl, growth of A. cylindrica increased, but higher concentrations caused a significant reduction, indicating cytotoxic effects.format_quote

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Nitrosyl cytochrome c oxidase. Formation and properties of mixed valence enzyme

Journal of Biological …, 1988

... FORMATION AND PROPERTIES OF MIXED VALENCE ENZYME* (Received for publication, August 25, 1987)... more

Heterocysts: Current status and future prospects

Immobilization caused physiological and biochemical changes in NaCl-resistant (NaClr) mutant strain of diazotrophic cyanobacterium Anabaena variabilis

Growth (i n term of ~ and G), heterocyst differentiation, nitrogenase activity, ammonia productio... more Growth (i n term of ~ and G), heterocyst differentiation, nitrogenase activity, ammonia production, ammonia uptake, glutamine synthetase (GS) activity, 14C02 -fixation and Hill activity have been studied in the wild-type Anabaena variabilis and its NaCI-resistant (NaCl') mutant strain immobilized in calcium alginate gel. NaCl' mutant strain grew well both in the presence as well as absence of NaCI (300 mM) at a rate similar to ·its wild-type strain in NaCI-free medium. 'Further, NaCl' mutant strain had generation time of 33 .3 and 71.4 hr, respectively in its free-living and immobilized conditions. Immobilization of the cells in calcium alginate gel increased heterocyst differentiation and nitrogenase activity in both wildtype and its NaCl' strain . GS activity in NaCl' mutant strain was altered by mutati on causing liberation of ammonia in the ex tern a l medium. No detectable ammonia was however, liberated by the free-livin g and immobilized wild-type strain . NaCI (300 mM) significantly inhibited the growth, heterocyst differentiation, nitrogenase activity, ammonia uptake, GS activity, carbon-fixation and Hill activity in the wild-type strain, whereas these activities were stimulated in NaCl' mutant strain. Further immobilization of NaCl' mutant strain whereas caused decrease in ammonium uptake and GS acti vity, it stimulated carbon-fixation and Hill activity in this strain . Thus it is suggested that increased ammonium photoproduction by immobilized aCI' mutant strain was due to decrease in ammonium uptak e, GS activity and susceptibility of nitrogenase to repression by ammonia and subsequent increase in heterocyst differentiation, nitrogenase activity, carbon-fixation and Hill activity.

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Providing antiretroviral care in conflict settings

Current HIV/AIDS Reports, 2009

There has been an historic expectation that delivering combination antiretroviral therapy (cART) ... more There has been an historic expectation that delivering combination antiretroviral therapy (cART) to populations affected by violent confl ict is untenable due to population movement and separation of drug supplies. There is now emerging evidence that cART provision can be successful in these populations. Using examples from Médecins Sans Frontières experience in a variety of African settings and also local nongovernmental organizations' experiences in northern Uganda, we examine novel approaches that have ensured retention in programs and adequate adherence. Emerging guidelines from United Nations bodies now support the expansion of cART in settings of confl ict.

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$Research paper thumbnail of Risk of fractures with inhaled corticosteroids in COPD: systematic review and meta-analysis of randomised controlled trials and observational studies$

Risk of fractures with inhaled corticosteroids in COPD: systematic review and meta-analysis of randomised controlled trials and observational studies

Thorax, 2011

Background The effect of inhaled corticosteroids (ICS) on fracture risk in patients with chronic ... more Background The effect of inhaled corticosteroids (ICS) on fracture risk in patients with chronic obstructive pulmonary disease (COPD) remains uncertain. The aim of this study was to evaluate the association between ICS and fractures in COPD. Methods MEDLINE, EMBASE, regulatory documents and company registries were searched up to August 2010. Randomised controlled trials (RCTs) of budesonide or fluticasone versus control treatment for COPD ($24 weeks duration) and controlled observational studies reporting on fracture risk with ICS exposure vs no exposure in COPD were included. Peto OR meta-analysis was used for fracture risk from RCTs while ORs from observational studies were pooled using the fixed effect inverse variance method. Doseeresponse analysis was conducted using varianceweighted least squares regression in the observational studies. Heterogeneity was assessed using the I 2 statistic. Results Sixteen RCTs (14 fluticasone, 2 budesonide) with 17 513 participants, and seven observational studies (n¼69 000 participants) were included in the meta-analysis. ICSs were associated with a significantly increased risk of fractures (Peto OR 1.27; 95% CI 1.01 to 1.58; p¼0.04; I 2 ¼0%) in the RCTs. In the observational studies, ICS exposure was associated with a significantly increased risk of fractures (OR 1.21; 95% CI 1.12 to 1.32; p<0.001; I 2 ¼37%), with each 500 mg increase in beclomethasone dose equivalents associated with a 9% increased risk of fractures, OR 1.09 (95% CI 1.06 to 1.12; p<0.001). Conclusion Among patients with COPD, long-term exposure to fluticasone and budesonide is consistently associated with a modest but statistically significant increased likelihood of fractures.

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Wernicke Encephalopathy After Obesity Surgery: A Systematic Review

Neurology, 2007

To characterize the clinical features, risk factors, radiographic findings, and prognosis of Wern... more To characterize the clinical features, risk factors, radiographic findings, and prognosis of Wernicke encephalopathy after bariatric surgery. We performed a systematic review of MEDLINE, Embase, Ovid, ISI (Science Citation Index), and Google Scholar for case reports, case series, or cohort studies of Wernicke encephalopathy after bariatric surgery. We found 32 cases (27 of whom were women) reported, from 2 weeks to 18 months after the procedure. Most patients had vomiting as a risk factor (n = 25) and presented with the triad of Wernicke encephalopathy (confusion, ataxia, and nystagmus; n = 21). Optic neuropathy, papilledema, deafness, seizures, asterixis, weakness, and sensory and motor neuropathy were also reported. Characteristic radiographic findings were hyperintense signals in the periaqueductal gray area and dorsal medial nucleus of the thalamus; radiographs were normal in 15 patients. One series from Brazil reported 4 patients (among 50 patients) with Wernicke encephalopathy; all presented with vomiting and concomitant peripheral neuropathy at a median of 2.5 months (1.5 to 3 months) after bariatric surgery. Another series identified 2 of 23 patients (both women) with Wernicke encephalopathy after bariatric surgery. Wernicke encephalopathy after bariatric surgery usually occurs between 4 and 12 weeks postoperatively, especially in young women with vomiting. Atypical neurologic features are common. The diagnosis is mainly clinical, because radiographic findings are normal in some patients. Prospective studies to determine the prevalence of this problem and protocols for preventive thiamine supplementation need evaluation.

Chapter 7: Grading a Body of Evidence on Diagnostic Tests

Journal of General Internal Medicine, 2012

INTRODUCTION: Grading the strength of a body of diagnostic test evidence involves challenges over... more INTRODUCTION: Grading the strength of a body of diagnostic test evidence involves challenges over and above those related to grading the evidence from health care intervention studies. This chapter identifies challenges and outlines principles for grading the body of evidence related to diagnostic test performance. CHALLENGES: Diagnostic test evidence is challenging to grade because standard tools for grading evidence were designed for questions about treatment rather than diagnostic testing; and the clinical usefulness of a diagnostic test depends on multiple links in a chain of evidence connecting the performance of a test to changes in clinical outcomes. PRINCIPLES: Reviewers grading the strength of a body of evidence on diagnostic tests should consider the principle domains of risk of bias, directness, consistency, and precision, as well as publication bias, dose response association, plausible unmeasured confounders that would decrease an effect, and strength of association, similar to what is done to grade evidence on treatment interventions. Given that most evidence regarding the clinical value of diagnostic tests is indirect, an analytic framework must be developed to clarify the key questions, and strength of evidence for each link in that framework should be graded separately. However if reviewers choose to combine domains into a single grade of evidence, they should explain their rationale for a particular summary grade and the relevant domains that were weighed in assigning the summary grade.

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Inhaled Anticholinergics and Risk of Major Adverse Cardiovascular Events in Patients With Chronic Obstructive Pulmonary Disease

JAMA, 2008

Context Inhaled anticholinergics (ipratropium bromide or tiotropium bromide) are widely used in p... more

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Risk of serious adverse cardiovascular events associated with varenicline: a systematic review and meta-analysis

Canadian Medical Association Journal, 2011

format_quoteVarenicline significantly increased serious cardiovascular events risk (1.06% vs. 0.82% in placebo); Peto OR 1.72 (95% CI 1.09-2.71).format_quote

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Effectiveness of a Web-Based Colorectal Cancer Screening Patient Decision Aid

American Journal of Preventive Medicine, 2011

Background-Colorectal cancer (CRC) screening reduces mortality yet remains underutilized. Low hea... more

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International Journal for Equity in Health

International Journal for Equity in Health, 2009

Background Diabetes and its associated complications are part of a chronic disease global epidemi... more Background Diabetes and its associated complications are part of a chronic disease global epidemic that presents a public health challenge. Epidemiologists examining health differences between men and women are being challenged to recognise the biological and social constructions behind the terms' sex'and/or'gender', together with social epidemiology principles and the life course approach. This paper examines the epidemiology of a population with diabetes from the north-west metropolitan region of South Australia.

format_quotePHI-holders wait 1.6 days (18.9%) less for appointments than SHI-holders; 28% of SHI-holders get appointments within one week.format_quote

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Atypical profiles and modulations of heme-enzymes catalyzed outcomes by low amounts of diverse additives suggest diffusible radicals' obligatory involvement in such redox reactions

by Daniel A Gideon and S. Singh

,Atypical profiles and modulations of heme-enzymes catalyzed outcomes by low amounts of diverse a... more

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