Yerba Mate (Ilex paraguariensis) Aqueous Extract Decreases Intestinal SGLT1 Gene Expression but Does Not Affect Other Biochemical Parameters in Alloxan-Diabetic Wistar Rats

Yerba mate (Ilex paraguariensis) is rich in polyphenols, especially chlorogenic acids. Evidence suggests that dietary polyphenols could play a role in glucose absorption and metabolism. The aim of this study was to evaluate the antidiabetic properties of yerba mate extract in alloxan-induced diabetic Wistar rats. Animals (n = 41) were divided in four groups: nondiabetic control (NDC, n = 10), nondiabetic yerba mate (NDY, n = 10), diabetic control (DC, n = 11), and diabetic yerba mate (NDY, n = 10). The intervention consisted in the administration of yerba mate extract in a 1 g extract/kg body weight dose for 28 days; controls received saline solution only. There were no significant differences in serum glucose, insulin, and hepatic glucose-6-phosphatase activity between the groups that ingested yerba mate extract (NDY and DY) and the controls (NDC and DC). However, the intestinal SGLT1 gene expression was significantly lower in animals that received yerba mate both in upper (p = 0.007) and middle (p < 0.001) small intestine. These results indicate that bioactive compounds present in yerba mate might be capable of interfering in glucose absorption, by decreasing SGLT1 expression.

Investigation of some dielectric properties of phosphate glasses doped with iron oxides, by a microwave technique

The effects of iron ions on dielectric properties of lithium sodium phosphate glasses were studied by non-usual, fast and non-destructive microwave techniques. The dielectric constant (epsilon`). insertion loss (L) and microwave absorption spectra (microwave response) of the selected glass system xFe(2)O(3)center dot(1 - x)(50P(2)O5 center dot 25Li(2)O center dot 25Na(2)O), being x = 0, 3, 6, ....,15 expressed in mol.%, were investigated. The dielectric constant of the samples was investigated at 9.00 GHz using the shorted-line method (SLM) giving the minimum value of epsilon` = 2.10 +/- 0.02 at room temperature, and increasing further with x, following a given law. It was observed a gradual increasing slope Of E in the temperature range of 25 <= t <= 330 degrees C, at the frequency of 9.00 GHz. Insertion loss (measured at 9.00 GHz) and measurements of microwave energy attenuation, at frequencies ranging from 8.00 to 12.00 GHz were also studied as a function of iron content in the glass samples. (C) 2009 Elsevier Ltd. All rights reserved.

Dielectric properties and physical features of phosphate glasses containing iron oxide

Microwave techniques were applied to the study of dielectric properties of phosphate glasses on the basis of contributions from permanent and induced dipolar polarization of local structural units interacting with the electrical component of the electromagnetic radiation. The dielectric constant of the selected glass system (100-x)(50P(2)O(5)center dot 25Li(2)O center dot 25Na(2)O)center dot xFe(2)O(3), where 0 <= x <= 21 is in mol%, was measured using a microwave setup assembled to measure the phase shift of the standing wave pattern produced by the insertion of the sample. It is shown that the Fe2+ ions contribute effectively to the dielectric constant, as expected from the interactions of the dipoles of the local charge compensation pairs with the microwave radiation. However, there is the possibility of occurrence of some ions Fe3+, in general, at low iron content, which reinforces the glass structure and, therefore, decreases the dielectric constant. There is a gradual conversion from Fe3+ to Fe2+ as the iron ions increases. This is possibly the reason of the anomaly in the dielectric constant values observed in the results. These assumptions can be checked by results of electronic paramagnetic resonance (EPR) and optical absorption (OA). The dielectric constant of the glasses studied in this work was found to increase with the temperature in the range of 25-330 degrees C. (C) 2007 Elsevier B.V. All rights reserved.

Augmentation of insulin secretion by leucine supplementation in malnourished rats: possible involvement of the phosphatidylinositol 3-phosphate kinase/mammalian target protein of rapamycin pathway

A regimen of low-protein diet induces a reduction of pancreatic islet function that is associated with development of metabolic disorders including diabetes and obesity afterward. In the present study, the influence of leucine supplementation on metabolic parameters, insulin secretion to glucose and to amino acids, as well as the levels of proteins that participate in the phosphatidylinositol 3-phosphate kinase (PI3K) pathway was investigated in malnourished rats. Four groups were fed with different diets for 12 weeks: a normal protein diet (17%) without (NP) or with leucine supplementation (NPL) or a low (6%)-protein diet without (LP) or with leucine supplementation (LPL). Leucine was given in the drinking water during the last 4 weeks. As indicated by the intraperitoneal glucose tolerance test, LPL rats exhibited increased glucose tolerance as compared with NPL group. Both NPL and LPL rats had higher circulating insulin levels than controls. The LPL rats also showed increased insulin secretion by pancreatic islets in response to glucose or arginine compared with those observed in islets from LP animals. Glucose oxidation was significantly reduced in NPL, LP, and LPL isolated islets as compared with NP; but no alteration was observed for leucine and glutamate oxidation among the 4 groups. Western blotting analysis demonstrated increased PI3K and mammalian target protein of rapamycin protein contents in LPL compared with LP islets. A significant increase in insulin-induced insulin receptor substrate I associated PI3K activation was also observed in LPL compared with LP islets. These findings indicate that leucine supplementation can augment islet function in malnourished rats and that activation of the PI3K/maminalian target protein of rapamycin pathway may play a role in this process. (C) 2010 Elsevier Inc. All rights reserved.

Posttranscriptional regulation of sodium-iodide symporter mRNA expression in the rat thyroid gland by acute iodide administration

Serrano-Nascimento C, Calil-Silveira J, Nunes MT. Posttranscriptional regulation of sodium-iodide symporter mRNA expression in the rat thyroid gland by acute iodide administration. Am J Physiol Cell Physiol 298: C893-C899, 2010. First published January 27, 2010; doi:10.1152/ajpcell.00224.2009.-Iodide is an important regulator of thyroid activity. Its excess elicits the Wolff-Chaikoff effect, characterized by an acute suppression of thyroid hormone synthesis, which has been ascribed to serum TSH reduction or TGF-beta increase and production of iodolipids in the thyroid. These alterations take hours/days to occur, contrasting with the promptness of Wolff-Chaikoff effect. We investigated whether acute iodide administration could trigger events that precede those changes, such as reduction of sodium-iodide symporter (NIS) mRNA abundance and adenylation, and if perchlorate treatment could counteract them. Rats subjected or not to methylmercaptoimidazole treatment (0.03%) received NaI (2,000 mu g/0.5 ml saline) or saline intraperitoneally and were killed 30 min up to 24 h later. Another set of animals was treated with iodide and perchlorate, in equimolar doses. NIS mRNA content was evaluated by Northern blotting and real-time PCR, and NIS mRNA poly(A) tail length by rapid amplification of cDNA ends-poly(A) test (RACE-PAT). We observed that NIS mRNA abundance and poly(A) tail length were significantly reduced in all periods of iodide treatment. Perchlorate reversed these effects, indicating that iodide was the agent that triggered the modifications observed. Since the poly(A) tail length of mRNAs is directly associated with their stability and translation efficiency, we can assume that the rapid decay of NIS mRNA abundance observed was due to a reduction of its stability, a condition in which its translation could be impaired. Our data show for the first time that iodide regulates NIS mRNA expression at posttranscriptional level, providing a new mechanism by which iodide exerts its autoregulatory effect on thyroid.

Divergence Involving Global Regulatory Gene Mutations in an Escherichia coli Population Evolving under Phosphate Limitation

Many of the important changes in evolution are regulatory in nature. Sequenced bacterial genomes point to flexibility in regulatory circuits but we do not know how regulation is remodeled in evolving bacteria. Here, we study the regulatory changes that emerge in populations evolving under controlled conditions during experimental evolution of Escherichia coli in a phosphate-limited chemostat culture. Genomes were sequenced from five clones with different combinations of phenotypic properties that coexisted in a population after 37 days. Each of the distinct isolates contained a different mutation in 1 of 3 highly pleiotropic regulatory genes (hfq, spoT, or rpoS). The mutations resulted in dissimilar proteomic changes, consistent with the documented effects of hfq, spoT, and rpoS mutations. The different mutations do share a common benefit, however, in that the mutations each redirect cellular resources away from stress responses that are redundant in a constant selection environment. The hfq mutation lowers several individual stress responses as well the small RNA-dependent activation of rpoS translation and hence general stress resistance. The spoT mutation reduces ppGpp levels, decreasing the stringent response as well as rpoS expression. The mutations in and upstream of rpoS resulted in partial or complete loss of general stress resistance. Our observations suggest that the degeneracy at the core of bacterial stress regulation provides alternative solutions to a common evolutionary challenge. These results can explain phenotypic divergence in a constant environment and also how evolutionary jumps and adaptive radiations involve altered gene regulation.

Phylogenetic Analyses Based on Small Subunit rRNA and Glycosomal Glyceraldehyde-3-Phosphate Dehydrogenase Genes and Ultrastructural Characterization of Two Snake Trypanosomes: Trypanosoma serpentis n. sp from Pseudoboa nigra and Trypanosoma cascavelli from Crotalus durissus terrificus

We sequenced the small subunit (SSU) rRNA and glycosomal glyceraldehyde-3-phosphate dehydrogenase (gGAPDH) genes of two trypanosomes isolated from the Brazilian snakes Pseudoboa nigra and Crotalus durissus terrificus. Trypanosomes were cultured and their morphometrical and ultrastructural features were characterized by light microscopy and scanning and transmission electron microscopy. Phylogenetic trees inferred using independent or combined SSU rRNA and gGAPDH data sets always clustered the snake trypanosomes together in a clade closest to lizard trypanosomes, forming a strongly supported monophyletic assemblage (i.e. lizard-snake clade). The positioning in the phylogenetic trees and the barcoding based on the variable V7-V8 region of the SSU rRNA, which showed high sequence divergences, allowed us to classify the isolates from distinct snake species as separate species. The isolate from P. nigra is described as a new species, Trypanosoma serpentis n. sp., whereas the isolate from C. d. terrificus is redescribed here as Trypanosoma cascavelli.

A real-time polymerase chain reaction assay for the identification and quantification of American Leishmania species on the basis of glucose-6-phosphate dehydrogenase

A real-time polymerase chain reaction (PCR) test was developed on the basis of the Leishmania glucose-6-phosphate dehydrogenase locus that enables identification and quantification of parasites. Using two independent pairs of primers in SYBR-Green assays, the test identified etiologic agents of cutaneous leishmaniasis belonging to both subgenera, Leishmania (Viannia) and Leishmania (Leishmania) in the Americas. Furthermore, use of TaqMan probes enables distinction between L. (V.) braziliensis or L. (V.) peruviania from the other L. (Viannia) species. All assays were negative with DNA of related trypanosomatids, humans, and mice. The parasite burden was estimated by normalizing the number of organisms per total amount of DNA in the sample or per host glyceraldehyde-3-phosphate dehydrogenase copies. The real-time PCR assay for L. (Leishmania) subgenus showed a good linear correlation with quantification on the basis of a limiting dilution assay in experimentally infected mice. The test successfully identifies and quantifies Leishmania in human biopsy specimens and represents a new tool to study leishmaniasis.

Glucocorticoids in Vivo Induce Both Insulin Hypersecretion and Enhanced Glucose Sensitivity of Stimulus-Secretion Coupling in Isolated Rat Islets

Although glucocorticoids are widely used as antiinflammatory agents in clinical therapies, they may cause serious side effects that include insulin resistance and hyperinsulinemia. To study the potential functional adaptations of the islet of Langerhans to in vivo glucocorticoid treatment, adult Wistar rats received dexamethasone (DEX) for 5 consecutive days, whereas controls (CTL) received only saline. The analysis of insulin release in freshly isolated islets showed an enhanced secretion in response to glucose in DEX-treated rats. The study of Ca(2+) signals by fluorescence microscopy also demonstrated a higher response to glucose in islets from DEX-treated animals. However, no differences in Ca(2+) signals were found between both groups with tolbutamide or KCl, indicating that the alterations were probably related to metabolism. Thus, mitochondrial function was explored by monitoring oxidation of nicotinamide dinucleotide phosphate autofluorescence and mitochondrial membrane potential. Both parameters revealed a higher response to glucose in islets from DEX-treated rats. The mRNA and protein content of glucose transporter-2, glucokinase, and pyruvate kinase was similar in both groups, indicating that changes in these proteins were probably not involved in the increased mitochondrial function. Additionally, we explored the status of Ca(2+)-dependent signaling kinases. Unlike calmodulin kinase II, we found an augmented phosphorylation level of protein kinase C alpha as well as an increased response of the phospholipase C/inositol 1,4,5-triphosphate pathway in DEX-treated rats. Finally, an increased number of docked secretory granules were observed in the beta-cells of DEX animals using transmission electron microscopy. Thus, these results demonstrate that islets from glucocorticoid-treated rats develop several adaptations that lead to an enhanced stimulus-secretion coupling and secretory capacity. (Endocrinology 151: 85-95, 2010)

Catalytic hydrodechlorination of chlorobenzene over supported palladium catalyst in buffered medium

The catalytic hydrodechlorination (HDC) reaction, which is an attractive abatement process for chlorinated organic wastes, was studied over a magnetically recoverable supported Pd(0) catalyst. We investigated the most favorable reaction conditions under which to obtain the highest substrate conversion rates while preserving the catalyst properties and morphology. Sodium hydroxide, triethylamine and buffered solutions were used as proton scavengers in the HDC of chlorobenzene under mild conditions. It was observed that sodium hydroxide caused corrosion of the silica support, triethylamine in 2-propanol preserved the morphology of the catalyst which could be recycled for up to five successive H DC reactions, and aqueous buffer solutions preserved the catalyst morphology and the catalytic activity for up to four successive HDC reactions. The use of buffer solutions to neutralize the HCl formed during the HDC reaction is an interesting, less aggressive, alternative approach to HDC reactions. (C) 2010 Elsevier B.V. All rights reserved.

Synthesis and characterization of phosphate glass microspheres for radiotherapy applications

Class microspheres containing the radioisotope (32)P, a beta(-) particle emitter, and half-life of 14.3 days, can be easily introduced in specific human organs such as liver, pancreas. and uterus to kill cancer cells. In the present work phosphate glass microspheres were produced with different compositions and particle size distribution in the range of 20- 30 mu m. Two different thermal processes were used to spherodize glass particles originally with irregular shapes. Samples were characterized by X-rays diffraction to check the amorphous structure, energy dispersive X-rays fluorescence spectroscopy to determine the final glass composition, and Fourier transformed infrared spectroscopy to determine the structural groups in the glass structure. The dissolution rate of glass samples in water was determined at 90 degrees C, and in simulated body fluid (SBF) at 37 degrees C. Classes with dissolution rates close to 10(-5) g/(cm(2) day) were obtained, which make them suitable for the present application. Scanning electron microscopy was used to evaluate the shape of the microspheres before and after the dissolution tests. The cytotoxicity tests showed that these microspheres can be used for biological applications. (C) 2008 Elsevier B.V. All rights reserved.

Magnetic and optical characterization of Mn-doped PbS nanocrystals supported in oxide glass matrix

The evidence of successful growth of Mn-doped PbS (Pb(1-x)Mn(x)S) nanocrystals (NCs) in SiO(2)-Na(2)CO(3)-Al(2)O(3)-PbO(2)-B(2)O(3) template, using the fusion method, is reported on in this study. The as-grown Pb(1-x)Mn(x)S NC is characterized using optical absorption, electron paramagnetic resonance, and atomic force microscopy. The data are discussed in terms of two distinct scenarios, namely a core-doped and a shell-doped nanostructure. (C) 2008 Elsevier B.V. All rights reserved.

Third-order nonlinearity of Er(3+)-doped lead phosphate glass

The third-order optical susceptibility and dispersion of the linear refractive index of Er(3+)-doped lead phosphate glass were measured in the wavelength range between 400 and 1940 nm by using the spectrally resolved femtosecond Maker fringes technique. The nonlinear refractive index obtained from the third-order susceptibility was found to be five times higher than that of silica, indicating that Er(3+)-doped lead phosphate glass is a potential candidate to be used as the base component for the fabrication of photonic devices. For comparison purposes, the Z-scan technique was also employed to obtain the values of the nonlinear refractive index of Er(3+)-doped lead phosphate glass at several wavelengths, and the values obtained using the two techniques agree to within 15%.

Kinetic and Crystallographic Studies on Glyceraldehyde-3-Phosphate Dehydrogenase from Trypanosoma cruzi in Complex with Iodoacetate

Kinetic and crystallographic studies on the formation of the complex between iodoacetate and the enzyme glyceraldehyde-3-phosphate dehydrogenase from Trypanosoma cruzi were conducted in order to investigate the mechanistic and structural basis underlying enzyme inactivation. The crystallographic complex reveal important structural features useful for the design of novel inhibitors.

Discovery of novel Trypanosoma cruzi glyceraldehyde-3-phosphate dehydrogenase inhibitors

Based on its essential role in the life cycle of Trypanosoma cruzi, the glycolytic enzyme glyceraldehyde 3-phosphate dehydrogenase (GAPDH) has been considered a promising target for the development of novel chemotherapeutic agents for the treatment of Chagas` disease. In the course of our research program to discover novel inhibitors of this trypanosomatid enzyme, we have explored a combination of structure and ligand-based virtual screening techniques as a complementary approach to a biochemical screening of natural products using a standard biochemical assay. Seven natural products, including anacardic acids,. avonoid derivatives, and one glucosylxanthone were identified as novel inhibitors of T. cruzi GAPDH. Promiscuous inhibition induced by nonspecific aggregation has been discarded as specific inhibition was not reversed or affected in all cases in the presence of Triton X-100, demonstrating the ability of the assay to find authentic inhibitors of the enzyme. The structural diversity of this series of promising natural products is of special interest in drug design, and should therefore be useful in future medicinal chemistry efforts aimed at the development of new GAPDH inhibitors having increased potency. (C) 2009 Elsevier Ltd. All rights reserved.