Characterization of the dynamics of semiconductor lasers usingoptical modulation

An optical modulation technique for measuring the intrinsic frequency response of semiconductor lasers is described. This technique, which uses an RF-modulated pump laser to create an optical modulation signal to inject into a DC-biased probed laser, offers significant advantages over previous methods such as being affected by electrical parasitics of either the laser to be characterized or the photodetector. The method allows extremely accurate measurements of many important dynamic parameters, including the nonlinear gain coefficients, the amount of spontaneous emission into the guided modes, and the differential carrier lifetime at lasing threshold     

Efficient phosphate binding using a combination of gluconolactate and carbonate calcium salts

Although renal-failure-related hyperphosphataemia can be corrected by various phosphate binders, there remains a need for safer and more efficient formulations to precipitate phosphate. This work describes both a theoretical approach and a phosphate precipitation test in order to design efficient binding calcium salts formulations. The results show that the combination of a soluble calcium salt (the gluconolactate) and a proton-consuming calcium salt (the carbonate) can precipitate phosphate effectively. Furthermore, the theoretical computations correlate well with the ability of the salt to bind phosphate in vitro.     

Comparison of dipyridamole Tc-99m myocardial imaging with dipyridamole electrocardiogram in detecting coronary artery disease

The authors compared the results of dipyridamole myocardial-SPECT (D-ECT) with dipyridamole electrocardiogram (D-ECG) in detecting coronary artery disease (CAD). According to the result of coronary artery angiogram. We analysed the results of D-ECT and D-ECG in 62 patients. In detecting CAD, the sensitivity and specificity of D-ECT were 89%, and 92%, while those of D-ECG were 54% and 76% respectively. In detecting single double, triple vessel diseases, the sensitivity of D-ECT was 76%, 100% and 100% respectively. The sensitivity of D-ECG was 35%, 73% and 67% respectively. In identifying left anterior descending, left circumflex and right coronary artery, the sensitivity of D-ECT was 73%, 80% and 80% respectively, while that of D-ECG was 54%, 20% and 25% respectively. The results showed that D-ECT was better than D-ECG in diagnosing CAD.     

Okadaic acid inhibits alkaline phosphatase activity in MC3T3-E1 cells

Alkaline phosphatase activity is regulated by various hormones and growth factors at least in part through the phosphorylation of target proteins during the bone cell differentiation. To investigate the role of protein phosphorylation in alkaline phosphatase activity in MC3T3-E1 osteoblast, we used okadaic acid which is a potent specific inhibitor of serine/threonine protein phosphatases to type 1 and 2A. Alkaline phosphatase activity in cellular layer was measured by spectrophotometer using p-nitrophenyl phosphate as substrate and data were expressed as p-nitrophenyl of nmol/min/mg of protein. Okadaic acid (1-50 ng/ml) caused the inhibition of alkaline phosphatase activity in MC3TC-E1 cells. At 50 ng/ml of okadaic acid showed the maximal inhibitory effect on alkaline phosphatase activity. Okadaic acid (50 ng/ml) also inhibited alkaline phosphatase activity in all differentiation stages. These results indicate that okadaic acid inhibits alkaline phosphatase activity in MC3T3-E1 cells.     

The 1.7 A refined X-ray structure of the periplasmic glucose/galactose receptor from Salmonella typhimurium

Although unexplained declines in the number of bacterial sexually transmitted diseases (STDs) are currently being documented on a national level, increasing rates among minority populations and among adolescents in general, present challenges for STD prevention and control. By contrast, little evidence has been presented to suggest declines in rates of incident viral STDs in any population. Unique approaches to prevention and control based on the epidemiological heterogenicity of STDs are discussed.     

Purification and characterization of Streptococcus mutans glucosyltransferase (GtfC) expressed in Escherichia coli

Streptococcus mutans constitutively expresses three glucosyltransferases, i.e., GtfB, GtfC, and GtfD; which synthesize glucan polymers from sucrose. To obtain individual GTF without complexing with one another, a purification strategy was developed to recover recombinant GTF expressed from Escherichia coli. The recombinant GtfC was aggregated and associated with the insoluble fraction in E. coli homogenates. GtfC was solublized with the 8M urea, renatured to its biologically active form by serial dialysis against sodium phosphate buffer, and subsequently purified to homogeneity by DEAE-Sephacel and hydroxylapatite column chromatography. The GtfC enzyme preparation was purified 16.3-fold and the molecular weight was estimated to be 140 kDa. GtfC synthesized water insoluble glucan in a primer independent manner and its enzymatic activities could be enhanced by dextran. Purified GtfC had a pH optimum of 6.5, a K(m) of 9.26 mM for sucrose and a pI of 5.5. Distinct from the previous reports, results from this study offers an alternative for the purification of the recombinant GTFs free from any detergent contamination to make it more suitable for utilization in vivo.