Production and properties of adhesin-free gingipain proteinase RgpA.

The Arg-specific gingipains of Porphyromonas gingivalis RgpA and RgpB have 97% identical sequences in their catalytic domains yet their propeptides are only 76% identical. RgpA isolates as a proteinase-adhesin complex (HRgpA) which hinders direct kinetic comparison of RgpAcat as a monomer with monomeric RgpB. We tested modifications of rgpA identifying a variant that enabled us to isolate histidine-tagged monomeric RgpA (rRgpAH). Kinetic comparisons between rRgpAH and RgpB used benzoyl-L-Arg-4-nitroanilide with and without cysteine and glycylglycine acceptor molecules. With no glycylglycine, values of Km, Vmax, kcat and kcat/Km for each enzyme were similar, but with glycylglycine Km decreased, Vmax increased and kcat increased ~ twofold for RgpB but ~ sixfold for rRgpAH. The kcat/Km for rRgpAH was unchanged whereas that of RgpB more than halved. Recombinant RgpA propeptide inhibited rRgpAH and RgpB with Ki 13 nM and 15 nM Ki respectively slightly more effectively than RgpB propeptide which inhibited rRgpAH and RgpB with Ki 22 nM and 29 nM respectively (p < 0.0001); a result that may be attributable to the divergent propeptide sequences. Overall, the data for rRgpAH reflected observations previously made by others using HRgpA, indicating rRgpAH fidelity and confirming the first production and isolation of functional affinity tagged RgpA.

Prevalence of diabetes and hypertension in a rural population of Bangladesh.

OBJECTIVE--To determine the prevalence of non-insulin-dependent diabetes mellitus (NIDDM), impaired glucose tolerance (IGT), and hypertension in a rural community of Bangladesh. RESEARCH DESIGN AND METHODS--A cluster sampling of 1,005 subjects > 15 years of age in the rural community of Dohar was investigated. Capillary blood glucose of fasting and 2 h after 75 g oral glucose (2hBG) were estimated. World Health Organization criteria were used for diagnosis of NIDDM and IGT. Blood pressure, height, and weight were also measured. RESULTS--The crude prevalence of NIDDM was 2.1% (men 3.1, women 1.3%) and IGT was 13.3% (men 14.4, women 12.4%). Age-adjusted (30-64 years of age) prevalence was 2.23% (95% confidence interval [CI] 1.01-3.45) for NIDDM and 15.67% (95% CI 12.59-18.75) for IGT. Prevalence of hypertension with systolic blood pressure (sBP) > or = 140 mmHg was 10.5% and with diastolic blood pressure (dBP) > 90 mmHg was 9.0%. Increased age was the risk factor for NIDDM, IGT, and hypertension; whereas increased BMI showed inconsistent association with them. Relative risk for sBP with higher BMI ( < 22.0 vs. > or = 22.1) was 1.94 with CI 1.55-2.43 and for dBP it was 2.2 with CI 1.40-3.46. Correlation of sBP was significant with age, BMI, and 2hBG. Similar correlation was also observed with dBP. CONCLUSIONS--High prevalences of NIDDM, IGT, and hypertension were observed among rural subjects. Increased age was shown to be an important risk factor for all these disorders, whereas BMI-associated risk was significant with NIDDM and hypertension but not with IGT.

Diabetes and impaired fasting glycemia in the tribes of Khagrachari hill tracts of Bangladesh.

OBJECTIVE: To determine the prevalence of type 2 diabetes and impaired fasting glycemia (IFG) in a tribal population of Bangladesh. RESEARCH DESIGN AND METHODS: A cluster sampling of 1,287 tribal subjects of age > or =20 years was investigated. They live in a hilly area of Khagrachari in the far northeast of Bangladesh. Fasting plasma glucose, blood pressure, height, weight, waist girth, and hip girth were measured. Lipid fractions were also estimated. We used the 1997 American Diabetes Association diagnostic criteria. RESULTS: The crude prevalence of type 2 diabetes was 6.6% and IFG was 8.5%. The age-standardized (20-70 years) prevalence of type 2 diabetes (95% CI) was 6.4% (4.96-7.87) and of IFG was 8.4% (6.48-10.37). Both tribesmen and women had equal risk for diabetes and IFG. Compared with the lower-income group, the participants with higher income had a significantly higher prevalence of type 2 diabetes (18.8 vs. 3.1%, P < 0.001) and IFG (17.2 vs. 4.3%, P < 0.001). Using logistic regression, we found that increased age, high-income group, and increased central obesity were the important risk factors of diabetes. CONCLUSIONS: The prevalence of diabetes in the tribal population was higher than that of the nontribal population of Bangladesh. Older age, higher central obesity, and higher income were proven significant risk factors of diabetes. High prevalence of diabetes among these tribes indicates that the prevalence of diabetes and its complications will continue to increase. Evidently, health professionals and planners should initiate diabetes care in these tribal communities.

Effect of socioeconomic risk factors on the difference in prevalence of diabetes between rural and urban populations in Bangladesh.

OBJECTIVE: To compare the prevalence of diabetes between the poor and rich of rural and urban populations in Bangladesh. RESEARCH DESIGN AND METHODS: A total of 1,052 subjects from urban and 1,319 from rural communities (age > or = 20 years) of different socioeconomic classes were investigated. Capillary blood glucose levels, fasting and 2 h after a 75-g glucose drink (2-h blood glucose [BG]), were measured. Height, weight, waist, hips, and blood pressure were also measured. RESULTS: Age-adjusted (30-64 years) prevalence of NIDDM was higher in urban (7.97% with 95% CI 6.17-9.77) than in rural subjects (3.84%, CI 2.61-5.07), whereas impaired glucose tolerance (IGT) prevalence was higher in rural subjects. In either urban or rural areas, the highest prevalence of NIDDM was observed among the rich, and the lowest prevalence was observed among the poor socioeconomic classes. The rural rich had much higher prevalence of IGT than their urban counterpart (16.5 vs. 4.4%, CI 6.8-17.4). Increased age was an important risk factor for IGT and NIDDM in both rural and urban subjects, whereas the risk related to higher BMI and waist-to-hip ratio (WHR) was less significant in rural than urban subjects. Using logistic regression and adjusting for age, sex, and social class, the urban subjects had no excess risk for NIDDM. In contrast, an excess risk for glucose intolerance (2-h BG > or = 7.8 mmol/l) was observed in the rural subjects. CONCLUSIONS: Adjusting for age, sex, and social class, the prevalence of NIDDM among urban subjects did not differ significantly from that among rural subjects. Increased age, higher socioeconomic class, and higher WHR were proven to be independent risk factors for glucose intolerance in either area.

Sulfated Titania-Silica Reinforced Nafion Nanocomposite Membranes for Proton Exchange Membrane Fuel Cells.

Sulfated titania-silica (SO4(2-)-/TiO2-SiO2) composites were prepared by a sol-gel method with sulfate reaction and characterized by X-ray diffraction (XRD) and energy-dispersive X-ray spectroscopy (EDS). The nanometric diameter and geometry of the sulfated titania-silica (STS) was investigated by transmission electron microscopy (TEM). A small amount of the STS composite in the range of 0.5-3 wt% was then added as reinforcing into the Nafion membrane by water-assisted solution casting method to prepare STS reinforced Nafion nanocomposite membranes (STS-Nafion nanocomposite membranes). The additional functional groups, sulfate groups, of the nanocomposite membrane having more surface oxygenated groups enhanced the fuel cell membrane properties. The STS-Nafion nanocomposite membranes exhibited improved water uptake compared to that of neat Nafion membranes, whereas methanol uptake values were decreased dramatically improved thermal property of the prepared nanocomposite membranes were measured by thermogravimetric analysis (TGA). Furthermore, increased ion exchange capacity values were obtained by thermoacidic pretreatment of the nanocomposite membranes.

Passive approach for the improved dispersion of polyvinyl alcohol-based functionalized multi-walled carbon nanotubes/Nafion membranes for polymer electrolyte membrane fuel cells.

Multi-walled carbon nanotubes (MWCNTs) are regarded as ideal fillers for Nafion polymer electrolyte membranes (PEMs) for fuel cell applications. The highly aggregated properties of MWCNTs can be overcome by the successful cross-linking with polyvinyl alcohol (PVA) into the MWCNTs/Nafion membrane. In this study, a series of nanocomposite membranes were fabricated with the PVA-influenced functionalized MWCNTs reinforced into the Nafion polymer matrix by a solution casting method. Several different PVA contents were blended to f-MWCNTs/Nafion nanocomposite membranes followed by successful cross-linking by annealing. The surface morphologies and the inner structures of the resulting PVA-MWCNTs/Nafion nanocomposite membranes were then observed by optical microscopy and scanning electron microscopy (SEM) to investigate the dispersion of MWCNTs into the PVA/Nafion composite membranes. After that, the nanocomposite membranes were characterized by thermo-gravimetric analysis (TGA) to observe the thermal enhancement caused by effective cross-linking between the f-MWCNTs with the composite polymer matrixes. Improved water uptake with reduced methanol uptake revealed the successful fabrication of PVA-blended f-MWCNTs/Nafion membranes. In addition, the ion exchange capacity (IEC) was evaluated for PEM fuel cell (PEMFC) applications.