Cloning, characterization, and expression of cadmium-induced metallothionein-2 gene from earthworm Pheretima aspergillum (E. Perrier).

Metallothioneins (MTs) are ubiquitous metal-binding, cysteine-rich proteins, associated with metal accumulation and thus providing protection against toxic heavy metals such as cadmium (Cd). To investigate the mechanisms of enrichment of Cd in the earthworm Pheretima aspergillum, we isolated and cloned metallothionein-2 (MT-2) cDNA (538 bp) from P. aspergillum, analyzed its sequence, and examined MT-2 transcription levels by relative quantitative real-time PCR under different concentrations of Cd. The sequence of P. aspergillum MT-2 cDNA and its putative amino acid sequence were highly similar to sequences from other earthworms. The induction with Cd increased the MT-2 gene transcription level in a dose-dependent manner. In addition, earthworm recombinant MT-2 exhibited high Cd bioaccumulation ability in vitro. These results suggested that MT-2 plays an important role in tolerance and accumulation of Cd in P. aspergillum.

Evaluation of erectile dysfunction and associated cardiovascular risk using structured questionnaires in Chinese type 2 diabetic men.

Erectile dysfunction (ED) is not uncommon, but frequently underdiagnosed in type 2 diabetic men. In this study, we aimed to explore the frequency and severity of ED in Chinese type 2 diabetic men using a structured questionnaire. We furthermore sought to investigate the associations of ED with diabetes-related complications and metabolic indices. A consecutive cohort of 313 Chinese type 2 diabetic men aged between 25 and 76 years attending a diabetic centre were recruited between October 2006 and June 2007. Of the study population, the frequency of ED was 39.3% according to the National Institutes of Health (NIH) Consensus Conference criteria, compared with 84.3% (41.7% of them having moderate to severe ED) as diagnosed by International Index of Erectile Function (IIEF-5) questionnaire. After adjusting for potential confounding factors by multivariable logistic regression, ED defined by NIH criterion was associated with advanced age [OR = 1.05 (95% CI 1.01-1.09), p = 0.012], the presence of diabetic retinopathy [OR = 2.43 (95% CI 1.27-4.66), p = 0.008] and coronary heart disease [OR = 2.63 (95% CI 1.21-5.70), p = 0.015]. ED defined by IIEF-5 was associated with advanced age [OR = 1.12 (95% CI 1.06-1.17), p < 0.0001], use of insulin therapy [OR = 2.94 (95% CI 1.12-7.73), p = 0.029] and urinary albumin-creatinine ratio [OR = 2.29 (95% CI 1.05-5.01), p = 0.037]. In conclusion, ED was highly prevalent in Chinese type 2 diabetic men and was associated with multiple cardiovascular risk factors and complications. Advanced age, use of insulin therapy, the existence of microvascular complications such as retinopathy, albuminuria and coronary heart disease were associated with ED. NIH criteria diagnosed a much lower rate of ED compared with IIEF-5. Overall, structured questionnaires are useful and objective tools to detect ED, which should prompt a comprehensive risk assessment in these subjects.

New self-limiting assembly model for Si quantum rings on Si(100).

We propose a new self-limiting assembly model for Si quantum rings on Si(100) where the ring's formation and evolution are driven by a growth-etching competition mechanism. The as-grown ring structure in a plasma enhanced chemical vapor deposition system has excellent rotational symmetry and superior morphology with a typical diameter, edge width, and height of 150-300, 10, and 5 nm, respectively. Based on this model, the size and morphology can be controlled well by simply tuning the timing procedure. We suggest that this growth model is not limited to certain material system, but provides a general scheme to control and tailor the self-assembly nanostructures into the desired size, shape, and complexity.

14-3-3 proteins are required for maintenance of Raf-1 phosphorylation and kinase activity.

By binding to serine-phosphorylated proteins, 14-3-3 proteins function as effectors of serine phosphorylation. The exact mechanism of their action is, however, still largely unknown. Here we demonstrate a requirement for 14-3-3 for Raf-1 kinase activity and phosphorylation. Expression of dominant negative forms of 14-3-3 resulted in the loss of a critical Raf-1 phosphorylation, while overexpression of 14-3-3 resulted in enhanced phosphorylation of this site. 14-3-3 levels, therefore, regulate the stoichiometry of Raf-1 phosphorylation and its potential activity in the cell. Phosphorylation of Raf-1, however, was insufficient by itself for kinase activity. Removal of 14-3-3 from phosphorylated Raf abrogated kinase activity, whereas addition of 14-3-3 restored it. This supports a paradigm in which the effects of phosphorylation on serine as well as tyrosine residues are mediated by inducible protein-protein interactions.

High-performance liquid chromatography analysis of the thiobarbituric acid adducts of malonaldehyde and trans,trans-muconaldehyde.

A reversed-phase HPLC method is described for the separation and analysis of the thiobarbituric acid (TBA) adducts of the reactive aldehydes muconaldehyde (MUC) and malonaldehyde (MDA). The TBA adduct of malonaldehyde was synthesized, purified, and its structure elucidated, for use as standard in quantitative HPLC studies. A detection limit of 1 X 10(-14) mol was achieved for the MUC:TBA and MDA:TBA adducts using the double monochromator fluorometric detector, 7 X 10(-13) mol was the detection limit using a variable wavelength uv-visible detector. Direct on-line identification of the eluting aldehyde:TBA adducts was achieved by the use of a diode-array uv-visible detector. The chromatographic behavior of the adducts under different mobile phase conditions was also examined. This HPLC methodology was used for the identification of muconaldehyde as a product of benzene oxidation in a hydroxyl radical generating system.

The synthesis and characterization of chemically bonded silica-based zwitterion-exchangers for HPLC.

The synthesis and characterization of a zwitterionic stationary phase bonded onto microparticulate silica is described. The bonded zwitterionic phase was characterized by elemental analysis, diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), and quantitative analysis of the ligands by high performance liquid chromatography (HPLC) following chemical cleavage from the silica backbone. Chromatographic evaluation of this novel bonded phase indicates that it functions as a weak cation exchanger at pH values above 4.5, an anion exchanger at pH values below 7, and as a zwitterionic phase between these two values. The simultaneous separation of a mixture of cationic, anionic and zwitterionic solutes with this novel bonded phase is shown. Using nucleotides as model compounds, a correlation was developed between maximum solute retention and the pH values corresponding to maximum solute/stationary phase zwitterion overlap. The possibility for a quadrupolar retention mechanism of the bonded zwitterionic phase for zwitterionic solutes is explored.

Localization and properties of bovine photoreceptor 5'-nucleotidase.

The main light-activated enzyme of the vertebrate photoreceptor is cGMP phosphodiesterase, whose product is GMP. GMP would be broken down to guanosine by the enzyme 5'-nucleotidase on the cytoplasmic (extradiscal) surface of the disks. The presence of 5'-nucleotidase on the cytoplasmic surface was verified by using sucrose continuous gradients to show its association with the photoreceptors and by using disk preparation and concanavalin A binding to demonstrate its presence on the extradiscal surface. Further studies using detergents and freeze-thaw showed that an even higher 5'-nucleotidase activity is present on the intradiscal surface; however, it is the smaller cytoplasmic surface activity that is potentially relevant to the physiology. The 5'-nucleotidase on the extradiscal surface is light insensitive, has a broad optimal pH range, shows a divalent cation dependence, and is competitively inhibited by nucleoside di- and triphosphates. When the data determined experimentally were extrapolated to physiological conditions, we obtained a decay time constant for GMP breakdown by 5'-nucleotidase in the range of 0.4 to 1.06 s. This time constant is in the range of the time constants of the fall of rod cell receptor potential, suggesting a possible role for GMP level in visual transduction.