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Biomedical subjects

R B Singh

Publications and source records attributed to R B Singh.

At least 55 records · Page 3Linked to original sources
PubMed2001

Sensitivity analysis and evaluation of microFacCO: a microscale motor vehicle emission factor model for CO emissions.

This paper presents a sensitivity analysis of a microscale emission factor model (MicroFacCO) for predicting real-time site-specific motor vehicle CO emissions to input variables, as well as a limited field study evaluation of the model. The sensitivity analysis has shown that MicroFacCO emission estimates are very sensitive to vehicle fleet composition, speed, and ambient temperature. For the present U.S. traffic fleet, the CO emission rate (g/mi) is increased by more than 500% at 5 mph in comparison with a speed greater than 40 mph and by approximately 67% at ambient temperatures of 45 degrees F and > or = 95 degrees F in comparison with an ambient temperature of 75 degrees F. The input variable "emission failure standard rate" is more sensitive to estimating emission rates in the 1990s than in the 2000s. The estimation of emission rates is not very sensitive to relative humidity. MicroFacCO can also be applied to examine the contribution of emission rates per vehicle class and model year. The model evaluation is presented for tunnel studies at five locations. In general, this evaluation study found good agreement between the measured and the modeled emissions. These analyses and evaluations have identified the need for additional studies to update the high-speed (>35 mph) air conditioning (A/C) correction factor and to add effects due to road grades. MicroFacCO emission estimates are very sensitive to the emission standard failure rate. Therefore, the model performance can be greatly improved by using a local emission standard failure rate.

Algorithms↗
PubMed2001

The influence of climate variation and change on diarrheal disease in the Pacific Islands.

Freshwater resources are a high-priority issue in the Pacific region. Water shortage is a serious problem in many small island states, and many depend heavily on rainwater as the source of their water. Lack of safe water supplies is an important factor in diarrheal illness. There have been no previous studies looking specifically at the relationship between climate variability and diarrhea in the Pacific region. We carried out two related studies to explore the potential relationship between climate variability and the incidence of diarrhea in the Pacific Islands. In the first study, we examined the average annual rates of diarrhea in adults, as well as temperature and water availability from 1986 to 1994 for 18 Pacific Island countries. There was a positive association between annual average temperature and the rate of diarrhea reports, and a negative association between water availability and diarrhea rates. In the second study, we examined diarrhea notifications in Fiji in relation to estimates of temperature and rainfall, using Poisson regression analysis of monthly data for 1978-1998. There were positive associations between diarrhea reports and temperature and between diarrhea reports and extremes of rainfall. These results are consistent with previous research and suggest that global climate change is likely to exacerbate diarrheal illness in many Pacific Island countries.

Child, Preschool↗
PubMed2000

Extra-hepatic biliary-ductal necrosis in acute pancreatitis: a rare complication.

An 8-year-old male presented with an acute abdomen. Exploration revealed bilious ascites, oedematous pancreatitis with areas of necrosis, and omentum showing patches of fat necrosis. The common bile duct and almost all of the common hepatic duct were gangrenous and had sloughed, with bile leaking from the junctional stump of the right and left hepatic ducts. The patient was managed successfully by Roux-en-Y hepaticojejunostomy. This is a rare case showing necrosis and sloughing of the extrahepatic bile ducts in acute pancreatitis.

Acute Disease↗
PubMed2000

Effect of coenzyme Q10 on experimental atherosclerosis and chemical composition and quality of atheroma in rabbits.

The effects of the administration of coenzyme Q10 (3 mg/kg per day) (group A, n=10) and placebo (aluminum hydroxide, 3 mg/kg per day) (group B, n=10) were compared over 24 weeks in a randomized, single-blind, controlled trial. There were two groups of rabbits receiving a trans fatty acid (TFA)-rich diet (5-8 g/day) for 36 weeks. Oxidized rabbit chow with vitamin C plus ferric chloride was administered for 4 weeks in all rabbits. Intervention with coenzyme Q10 after feeding of TFA-rich diet was associated with a significant decline in thiobarbituric acid reactive substances (TBARS), diene conjugates and malondialdehyde, and an increase in plasma levels of vitamin E in the coenzyme Q group compared to placebo group. These changes, which were indicators of a decrease in oxidative damage, were independent of lipid lowering. The aortic and coronary artery plaque sizes, coronary atherosclerosis index, aortic and coronary atherosclerosis scores were significantly lower in the coenzyme Q group than placebo group. Aortic and coronary plaque frequencies, as well as frequencies of ulceration, thrombosis or hemorrhage, and cracks and fissures, were also significantly lower in the coenzyme Q group, indicating a better quality of atheroma compared to those in the control group. Aortic cholesterol, triglycerides and sudanophilia were significantly lower and vitamin E significantly higher in the coenzyme Q group in comparison to the placebo group indicating that coenzyme Q10 can have beneficial effect on the chemical composition of atheroma. The findings suggest that antioxidant therapy with coenzyme Q10 may be used as an adjunct to lipid lowering for additional beneficial effects related to chemical composition and quality of atheroma independent of hypolipidemic agents.

Animals↗
PubMed2000

Fourier transform infrared spectra and normal mode analysis of 1-[(3-methylphenyl)piperazin-1-yl]-3-[thio(4-acetamido-phenyl]pro pane: a potent 5-HT2 and D2 receptor ligand.

1-[(3-methylphenyl)piperazin-1-yl]-3-[thio(4-acetamidophenyl]propa ne and its analogs have shown good hypotensive activity and the title compound has shown a profile of centrally acting anti-hypertensive agent. It also binds with the 5-HT2 receptors. The conformation of the title compound was determined by X-ray diffraction but this is not possible for its analogs because of the difficulty in preparing their single crystals. A novel and easy approach is envisaged to determine the conformation in such cases by the application of semi-empirical molecular orbital calculations, Fourier transform infra red (FTIR) spectroscopy and normal mode analysis. As a first step in this direction the FTIR spectrum of the title compound has been recorded and its normal mode analysis carried out. The assignments of the frequencies are based on the concept of group frequencies and band intensities. The spectrally observed frequencies have been tabulated along with the theoretically calculated ones and their assignments. Good agreement has been obtained between them and a set of 101 force field constants is established.

Antihypertensive Agents↗
PubMed2000

Development of a microscale emission factor model for CO for predicting real-time motor vehicle emissions.

The U.S. Environmental Protection Agency's (EPA) National Exposure Research Laboratory has initiated a project to improve the methodology for modeling human exposure to motor vehicle emissions. The overall project goal is to develop improved methods for modeling the source through the air pathway to human exposure in significant microenvironments of exposure. This paper presents the technical description of a newly developed model for CO emissions. The sensitivity analysis and evaluation of this emission model is presented in a companion paper titled "Sensitivity Analysis and Evaluation of MicroFacCO: A Microscale Motor Vehicle Emission Factor Model for CO Emissions." The MOBILE models (used in the United States, except California) and EMFAC models (used in California only) used to estimate emissions are suitable for supporting mostly regional (county)-scale modeling and emission inventory because of their dependence on vehicle-miles-traveled aggregate data. These emission models are not designed to estimate real-time emissions needed for human exposure studies near roadways. A number of independent studies have found that current mobile source emission factor models are not very reliable at estimating microscale emissions and are, therefore, inappropriate for use with microscale modeling necessary to estimate human exposures near roadways. A microscale emission factor model for predicting real-world real-time motor vehicle CO emissions (MicroFacCO) has been developed. It uses available information on the vehicle fleet composition. The algorithm used to calculate emission factors in MicroFacCO is disaggregated based on the on-road vehicle fleet. The emission factors are calculated from a real-time fleet rather than from a fleet-wide average estimated by a vehicle-miles-traveled weighting of the emission factors for different vehicle classes. MicroFacCO uses the same database used to develop the MOBILE6 model. As compared with MOBILE emission models, MicroFacCO requires only a few input variables, which are necessary to characterize the real-time fleet being modeled. The main input variables required are on-road vehicle fleet, time and day of year, ambient temperature, and relative humidity.

Carbon Monoxide↗
PubMed2000

Development and preliminary evaluation of a particulate matter emission factor model for European motor vehicles.

Although modeling of gaseous emissions from motor vehicles is now quite advanced, prediction of particulate emissions is still at an unsophisticated stage. Emission factors for gasoline vehicles are not reliably available, since gasoline vehicles are not included in the European Union (EU) emission test procedure. Regarding diesel vehicles, emission factors are available for different driving cycles but give little information about change of emissions with speed or engine load. We have developed size-specific speed-dependent emission factors for gasoline and diesel vehicles. Other vehicle-generated emission factors are also considered and the empirical equation for re-entrained road dust is modified to include humidity effects. A methodology is proposed to calculate modal (accelerating, cruising, or idling) emission factors. The emission factors cover particle size ranges up to 10 microns, either from published data or from user-defined size distributions. A particulate matter emission factor model (PMFAC), which incorporates virtually all the available information on particulate emissions for European motor vehicles, has been developed. PMFAC calculates the emission factors for five particle size ranges [i.e., total suspended particulates (TSP), PM10, PM5, PM2.5, and PM1] from both vehicle exhaust and nonexhaust emissions, such as tire wear, brake wear, and re-entrained road dust. The model can be used for an unlimited number of roads and lanes, and to calculate emission factors near an intersection in user-defined elements of the lane. PMFAC can be used for a variety of fleet structures. Hot emission factors at the user-defined speed can be calculated for individual vehicles, along with relative cold-to-hot emission factors. The model accounts for the proportions of distance driven with cold engines as a function of ambient temperature and road type (i.e., urban, rural, or motorway). A preliminary evaluation of PMFAC with an available dispersion model to predict the airborne concentration in the urban environment is presented. The trial was on the A6 trunk road where it passes through Loughborough, a medium-size town in the English East Midlands. This evaluation for TSP and PM10 was carried out for a range of traffic fleet compositions, speeds, and meteorological conditions. Given the limited basis of the evaluation, encouraging agreement was shown between predicted and measured concentrations.

Air Pollution↗
PubMed1999

Social class, coronary risk factors and undernutrition, a double burden of diseases, in women during transition, in five Indian cities.

OBJECTIVE: To find out the association between social class and coronary risk factors in women. DESIGN AND SETTING: Cross-sectional surveys were conducted in six-twelve urban streets in each of five cities from various regions of India following a common study protocol and criteria of diagnosis. SUBJECTS AND METHODS: We randomly selected 3257 women, aged 25-64 years inclusive, from the cities of Moradabad (n=902), Trivandrum (n=760) Calcutta (n=410), Nagpur (n=405) and Bombay (n=780). Evaluation was by questionnaires validated at Moradabad. All subjects, after pooling of data, were divided into social class 1 (n=985), social class 2 (n=790), social class 3 (n=674), social class 4 (n=602) and social class 5 (n=206), based on various attributes of socioeconomic status. RESULTS: The prevalence of hypertension, diabetes mellitus, family history of coronary disease, obesity, central obesity and sedentary lifestyle were significantly associated with higher social classes and tobacco consumption was not associated with social class. Oral contraceptive intake and postmenopausal status were also more common among higher social classes, which may be due to more education and a longer lifespan among the higher social classes, respectively. Mean total cholesterol, high density lipoprotein cholesterol, systolic and diastolic blood pressure, mean body mass index and waist-hip ratio showed significant association with higher social classes. Mean age, body weight, body mass index, waist-hip ratio, systolic and diastolic blood pressure, total cholesterol and 2-h blood glucose were significantly positively correlated with social class, as assessed by Spearman's rank correlation. Higher social classes 1-3 were more common in Trivandrum and Bombay than in Moradabad. The prevalence of hypertension, diabetes mellitus and being overweight (body mass index >25 kg/m2) were also more common in Trivandrum and Bombay compared to Moradabad. Undernutrition was negatively associated with higher social classes and was more common in Moradabad and Nagpur than Trivandrum. CONCLUSIONS: Higher social classes among Indian urban women have a higher prevalence of coronary risk factors, hypertension, diabetes mellitus, being overweight, central obesity, sedentary lifestyle, family history of coronary disease, oral contraceptive intake and postmenopausal status. Mean concentrations of total and high density lipoprotein cholesterol were also significantly associated with higher social classes.

Adult↗
PubMed1999

Serum concentration of lipoprotein(a) decreases on treatment with hydrosoluble coenzyme Q10 in patients with coronary artery disease: discovery of a new role.

OBJECTIVE: To examine the effect of coenzyme Q10 supplementation on serum lipoprotein(a) in patients with acute coronary disease. STUDY DESIGN: Randomized double blind placebo controlled trial. SUBJECTS AND METHODS: Subjects with clinical diagnosis of acute myocardial infarction, unstable angina, angina pectoris (based on WHO criteria) with moderately raised lipoprotein(a) were randomized to either coenzyme Q10 as Q-Gel (60 mg twice daily) (coenzyme Q10 group, n=25) or placebo (placebo group, n=22) for a period of 28 days. RESULTS: Serum lipoprotein(a) showed significant reduction in the coenzyme Q10 group compared with the placebo group (31.0% vs 8.2% P<0.001) with a net reduction of 22.6% attributed to coenzyme Q10. HDL cholesterol showed a significant increase in the intervention group without affecting total cholesterol, LDL cholesterol, and blood glucose showed a significant reduction in the coenzyme Q10 group. Coenzyme Q10 supplementation was also associated with significant reductions in thiobarbituric acid reactive substances, malon/dialdehyde and diene conjugates, indicating an overall decrease in oxidative stress. CONCLUSION: Supplementation with hydrosoluble coenzyme Q10 (Q-Gel) decreases lipoprotein(a) concentration in patients with acute coronary disease.

Analysis of Variance↗
PubMed1999

Effect of hydrosoluble coenzyme Q10 on blood pressures and insulin resistance in hypertensive patients with coronary artery disease.

In a randomised, double-blind trial among patients receiving antihypertensive medication, the effects of the oral treatment with coenzyme Q10 (60 mg twice daily) were compared for 8 weeks in 30 (coenzyme Q10: group A) and 29 (B vitamin complex: group B) patients known to have essential hypertension and presenting with coronary artery disease (CAD). After 8 weeks of follow-up, the following indices were reduced in the coenzyme Q10 group: systolic and diastolic blood pressure, fasting and 2-h plasma insulin, glucose, triglycerides, lipid peroxides, malondialdehyde and diene conjugates. The following indices were increased: HDL-cholesterol, vitamins A, C, E and beta-carotene (all changes P<0.05). The only changes in the group taking the B vitamin complex were increases in vitamin C and beta-carotene (P<0.05). These findings indicate that treatment with coenzyme Q10 decreases blood pressure possibly by decreasing oxidative stress and insulin response in patients with known hypertension receiving conventional antihypertensive drugs.

Administration, Oral↗
PubMed1999

Body fat percent by bioelectrical impedance analysis and risk of coronary artery disease among urban men with low rates of obesity: the Indian paradox.

OBJECTIVE: To determine the association between body fat percent and prevalence of coronary artery disease (CAD) and coronary risk factors in subjects with low rates of obesity. SUBJECTS AND METHODS: We randomly selected 850 men, aged 25 to 64 years. The survey methods were questionnaire and bioelectrical impedance analysis for body composition. Subjects were divided into high-fat (n = 357), over-fat (n = 230), normal-fat (n = 200) and under-fat (n = 63) based on criteria of body-fat percent analysis. RESULTS: The prevalence of CAD and the coronary-risk factors hypercholesterolemia, hypertension, diabetes, mellitus and sedentary lifestyle were significantly associated with high and moderate body fat percent despite low body-mass index (23.6+/-4.1 kg/m2). Mean total cholesterol, triglycerides and blood pressure were significantly associated with high and moderate body fat percent. The prevalence of smoking was weakly but inversely associated with high body-fat percent. Mean HDL cholesterol was positively associated with high body-fat percent. Body mass index was positively associated with high body-fat percent. CONCLUSIONS: High and moderate body-fat-percent subjects were associated with high prevalence of CAD and the coronary-risk factors hypertension, diabetes mellitus, higher body-mass index and sedentary lifestyle.

Adipose Tissue↗
PubMed1999

Modulation of free radical stress in human red blood cell membrane by forskolin and the prospects for treatment of cardiovascular disease and diabetes.

This study has examined the effect of oxidants and elevated levels of glucose on membrane lipid peroxidation of human red blood calls (RBC). Washed RBC incubated with varying concentrations of glucose at 37 degrees C for 24 hrs. showed a significant increased membrane lipid peroxidation when compared with control RBC. Addition of ferrous sulphate and ascorbic acid which are known oxidants caused greater rise in lipid peroxides compared to elevated level of glucose alone. Pre-treatment of RBC with varying doses of forskolin (4-70 microg) was associated with significantly smaller rise in lipid peroxides in a dose dependent manner. Forskolin effect was comparable with the antioxidant effect of other drugs such as vitamin E, trimetazidine, ginkocer, probucol. It is possible that forskolin at higher concentrations may have a greater antioxidant effect than other antioxidant drug. However more studies, especially animal experiments, and trials in human would be necessary to confirm our findings.

Antioxidants↗
PubMed1999

Genetic variation and nutrition in relation to coronary artery disease.

There is evidence that coronary artery disease (CAD), hypertension, diabetes mellitus (DM) and hyperlipidemia develop due to interaction of genetic and environmental factors during transition from poverty to affluence. Rapid transition in diet and lifestyle factors may influence heritability of the variant phenotypes that are dependent on the nutrient environment for their expression. We are beginning to recognize the interaction of specific nutrients with the genetic code possessed by all nucleated cells. In the next millennium, the physician may be able to make nutrient intake recommendations not on physical characteristics but on the basis of the individual's phenotypic expression for health while suppressing his phenotypic expression for disease. We have demonstrated an increased susceptibility to CAD, diabetes, central obesity, hyperinsulinemia and lipoprotein(a) excess in Indians in younger age groups indicating a genetic predisposition to these problems due to interaction of gene and environment. Lipoprotein(a) is a genetic risk factor for CAD, diabetes and stroke and it is higher in South Indians than North Indians. Antioxidant vitamins, coenzyme Q10 and n-3 fatty acids may have a beneficial influence whereas linoleic acid, saturated fat and sugars may have adverse effects on phenotypic expression. There is significant evidence that genes are involved in determining enzymes, receptors, cofactors, structural components involved in regulation of blood pressure, the metabolism of lipids, lipoproteins and inflammatory and coagulation factors that are involved in determining an individual's risk. Majority of these genes are polymorphic. While some genes respond to nutritional modulation, others may not indicate any response.

Antioxidants↗
PubMed1998

Prevalence of type 2 diabetes mellitus and risk of hypertension and coronary artery disease in rural and urban population with low rates of obesity.

OBJECTIVE: To compare the prevalence of type 2 diabetes mellitus (DM) and coronary artery disease (CAD) and hypertension in DM in the rural and urban populations of north India. DESIGN AND METHODS: Two populations of the same ethnic background were randomly selected for this cross sectional survey. There were 1769 rural (894 men, 875 women) and 1806 urban subjects (904 men, 902 women) between 25-64 years of age. The survey methods included fasting and 2 h blood glucose and electro-cardiogram and blood pressure measurement of all subjects. RESULTS: Using the criteria of World Health Organization, the prevalence of diabetes mellitus (6.0 vs 2.8%) hypertension (24.0 vs 17.0%) and CAD (9.0 vs 3.2%) was significantly (P<0.001) higher in urban compared to rural subjects. Hypertension and CAD were significantly more frequent among subjects with diabetes compared to nondiabetes. The association of CAD and hypertension with diabetes was greater in urban than rural subjects. Excess body weight and obesity, central obesity, sedentary lifestyle, higher visible fat intake (>25 g/day), and social class 1-3 (higher and middle) were significantly associated with diabetes. Multivariate logistic regression analysis showed that after adjustment of age and sex, body mass index, central obesity, sedentary lifestyle and higher visible fat intake and alcohol intake in men were significant risk factors of diabetes among all the sub-groups. CONCLUSIONS: The study showed a high prevalence of diabetes in urban north Indian population compared to rural subjects in the same ethnic group. CAD and hypertension were significantly associated with diabetes more in urban than rural subjects. The findings suggest that higher body mass index, waist-hip ratio and visible fat intake and sedentary lifestyle were risk factors of diabetes.

Adult↗