Sildenafil preserves diastolic relaxation after reduction by L-NAME and increases phosphodiesterase-5 in the intercalated discs of cardiac myocytes and arterioles

OBJECTIVES: We investigated the influence of sildenafil on cardiac contractility and diastolic relaxation and examined the distribution of phosphodiesterase-5 in the hearts of hypertensive rats that were treated with by NG-nitro-L-arginine methyl ester (L-NAME). METHODS: Male Wistar rats were treated with L-NAME and/or sildenafil for eight weeks. The Langendorff method was used to examine the effects of sildenafil on cardiac contractility and diastolic relaxation. The presence and location of phosphodiesterase-5 and phosphodiesterase-3 were assessed by immunohistochemistry, and cGMP plasma levels were measured by ELISA. RESULTS: In isolated hearts, sildenafil prevented the reduction of diastolic relaxation (dP/dt) that was induced by L-NAME. In addition, phosphodiesterase-5 immunoreactivity was localized in the intercalated discs between the myocardial cells. The staining intensity was reduced by L-NAME, and sildenafil treatment abolished this reduction. Consistent with these results, the plasma levels of cGMP were decreased in the L-NAME-treated rats but not in rats that were treated with L-NAME + sildenafil. CONCLUSION: The sildenafil-induced attenuation of the deleterious hemodynamic and cardiac morphological effects of L-NAME in cardiac myocytes is mediated (at least in part) by the inhibition of phosphodiesterase-5.

Metronidazole release using natural rubber latex as matrix

Natural Rubber Latex (NRL) can be used successfully in controlled release drug delivery due to their excellent matrix forming properties. Recently, NRL has shown to stimulate angiogenesis, cellular adhesion and the formation of extracellular matrix, promoting the replacement and regeneration of tissue. A dermatological delivery system comprising a topically acceptable, inert support impregnated with a metronidazole (MET) solution was developed. MET 2-(2- methyl- 5-nitro- 1H- imidazol- 1-yl) ethanol, has been widely used for the treatment of protozoa and anaerobic bacterial infections. MET is a nitroimidazole anti-infective medication used mainly in the treatment of infections caused by susceptible organisms, particularly anaerobic bacteria and protozoa. In a previous study, we have tested NRL as an occlusive membrane for GBR with promising results. One possible way to decrease the inflammatory process, it was incorporated the MET in NRL. MET was incorporated into the NRL, by mixing it in solution for in vitro protein delivery experiments. The solutions of latex and MET were polymerized at different temperatures, from -100 to 40 °C, in order to control the membrane morphology. SEM microscopy analysis showed that the number, size and distribution of pores in NRL membranes varied depending on polymerization temperature, as well as its overall morphology. Results demonstrated that the best drug-delivery system was the membrane polymerized at -100 °C, which does release 77,1% of its MET content for up 310 hours.

Efficient synthesis of benzothiazine and acrylamide compounds

This article describes the synthesis of the new (2Z)-2-(4-methoxybenzylidene)-6-nitro-4H -benzo[1,4]thiazin-3-one, (2Z)-2-(4-methoxybenzylidene)-4-methyl-6-nitro-4H-benzo[1,4]thiazin-3-one, (2Z)-6-amino-2-(4-methoxybenzylidene)-4H -benzo[1,4]thiazin-3-one, (2Z)-6-butylamino-2-(4-methoxybenzylidene)-4-methyl-4H-benzo[1,4]-thiazin-3-one and (2E)-N-alkyl-N-(2-hydroxy-5-nitrophenyl)-3-phenylacrylamides and the spectroscopic data. The arylidenebenzothiazine compounds were prepared using the Knoevenagel condensation with substituted benzaldehydes in the presence of sodium methoxide in DMF. The presence of a nitro substituent in the 4-position, water and a slightly acid reaction medium in this condensation caused the rupture of the benzothiazine ring and subsequent formation of the phenylacrylamide compounds. A crystallographic data was presented for (2E)-3-(4-bromophenyl)-N-dodecyl-N -(2-hydroxy-5-nitrophenyl) acrylamide.

Aspectos mecanísticos da bioatividade e toxicidade de nitrocompostos

Nitrocompounds are bioactive molecules used as antibacterial, antiparasitic and antitumoral agents. In the past of years, these molecules have been broadly studied in several fields, such as medicinal chemistry, organic chemistry, biochemical, toxicology and electrochemistry. The nitrocompounds mode of action involves the biotransformation of the nitro group, releasing intermediates in the redox process. Some of those intermediates attack enzymes, membranes and DNA, providing the basis for their biological activity and adverse effects. In this report, some aspects regarding the biological activity, mechanism of action and toxicity of nitrocompounds are explored, purposing the research of new bioactive derivatives having low toxicity.

Modulatory effect of Byrsonima basiloba extracts on the mutagenicity of certain direct and indirect-acting mutagens in Salmonella typhimurium assays

Byrsonima basiloba A. Juss. species is a native arboreal type from the Brazilian ""cerrado"" (tropical American savanna), and the local population uses it to treat diseases, such as diarrhea and gastric ulcer. It belongs to the Malpighiaceae family, and it is commonly known as ""murici."" Considering the popular use of B. basiloba derivatives and the lack of pharmacological potential studies regarding this vegetal species, the mutagenic and antimutagenic effect of methanol (MeOH) and chloroform extracts were evaluated by the Ames test, using strains TA97a, TA98, TA100, and TA102 of Salmonella typhimurium. No mutagenic activity was observed in any of the extracts. To evaluate the antimutagenic potential, direct and indirect mutagenic agents were used: 4 nitro-o-phenylenediamine, sodium azide, mitomycin C, aflatoxin B(1), benzo[a] pyrene, and hydrogen peroxide. Both the extracts evaluated showed antimutagenic activity, but the highest value of inhibition level (89%) was obtained with the MeOH extract and strain TA100 in the presence of aflatoxin B(1). Phytochemical analysis of the extracts revealed the presence of n-alkanes, lupeol, ursolic and oleanolic acid, (+)-catechin, quercetin- 3-O-alpha-L-arabinopyranoside, gallic acid, methyl gallate, amentoflavone, quercetin, quercetin-3-O-(2 ''-O-galloyl)-beta-D-galactopyranoside, and quercetin-3-O-(2 ''-O-galloyl)-alpha-L-arabinopyranoside.

Electrochemical Reduction Using Glassy Carbon Electrode in Aqueous Medium of a Potential Anti-Chagas Drug: NFOH

Nitrofurazone (NF) presents activity against Chagas' disease, yet it has a high toxicity. Its analog, hydroxymethylnitrofurazone (NFOH), is more potent against Trypanosoma cruzi and much less toxic than the parent drug, NF. The electrochemical reduction of NFOH in an aqueous medium using a glassy carbon electrode (GCE) is presented. By cyclic voltammetry in anacidic medium, one irreversible reduction peak related to hydroxylamine derivative formation was registered, being linearly pH dependent. However, from pH > 7, a reversible reduction peak at a more positive potential appears and corresponds to the formation of a nitro radical anion. The radical-anion kinetic stability was evaluated by Ip(a)/Ip(c) the current ratio of the R-NO(2)/R-NO(2)-redox couple. The nitro radical anion decays with a second-order rate constant (k(2)) of 6.07, 2.06, and 1.44(X 10(3)) L mol(-1) s(-1) corresponding to pH 8.29, 9.29, and 10.2, respectively, with a corresponding half-time life (t(1/2)) of 0.33, 0.97, and 1.4 s for each pH value. By polishing the GCE surface with diamond powder and comparing with the GCE surface polished with alumina, it is shown that the presence of alumina affects the lifetime of the nitro radical anion. (C) 2009 The Electrochemical Society. [DOI: 10.1149/1.3130082] All rights reserved.

Study of the antimicrobial peptide indolicidin and a mutant in micelle medium by molecular dynamics simulation

The antimicrobial peptide indolicidin (IND) and the mutant CP10A in hydrated micelles were studied using molecular dynamics simulations in order to observe whether the molecular dynamics and experimental data could be sufficiently correlated and a detailed description of the interaction of the antimicrobial peptides with a model of the membrane provided by a hydrated micelle system could be obtained. In agreement with the experiments, the simulations showed that the peptides are located near the surface of the micelles. Peptide insertions agree with available experimental data, showing deeper insertion of the mutant compared with the peptide IND. Major insertion into the hydrophobic core of the micelle by all tryptophan and mutated residues of CP10A in relation to IND was observed. The charged residues of the terminus regions of both peptides present similar behavior, indicating that the major differences in the interactions with the micelles of the peptides IND and CP10A occur in the case of the hydrophobic residues.

Shear Stress Induces Nitric Oxide-Mediated Vascular Endothelial Growth Factor Production in Human Adipose Tissue Mesenchymal Stem Cells

It has been demonstrated that human adipose tissue-derived mesenchymal stem cells (hASCs) enhance vascular density in ischemic tissues, suggesting that they can differentiate into vascular cells or release angiogenic factors that may stimulate neoangiogenesis. Moreover, there is evidence that shear stress (SS) may activate proliferation and differentiation of embryonic and endothelial precursor stem cells into endothelial cells (ECs). In this work, we investigated the effect of laminar SS in promoting differentiation of hASCs into ECs. SS (10 dyn/cm(2) up to 96 h), produced by a cone plate system, failed to induce EC markers (CD31, vWF, Flk-1) on hASC assayed by RT-PCR and flow cytometry. In contrast, there was a cumulative production of nitric oxide (determined by Griess Reaction) and vascular endothelial growth factor (VEGF; by ELISA) up to 96 h of SS stimulation ( NO(2)(-) in nmol/10(4) cells: static: 0.20 +/- 0.03; SS: 1.78 +/- 0.38, n = 6; VEGF in pg/10(4) cells: static: 191.31 +/- v35.29; SS: 372.80 +/- 46.74, n = 6, P < 0.05). Interestingly, the VEGF production was abrogated by 5 mM N(G)-L-nitro-arginine methyl ester (L-NAME) treatment (VEGF in pg/10(4) cells: SS: 378.80 +/- 46.74, n = 6; SS + L-NAME: 205.84 +/- 91.66, n = 4, P < 0.05). The results indicate that even though SS failed to induce EC surface markers in hASC under the tested conditions, it stimulated NO-dependent VEGF production.

Central nitrergic system regulation of neuroendocrine secretion, fluid intake and blood pressure induced by angiotensin-II

Background: Nitric oxide (NO) synthesis has been described in several circumventricular and hypothalamic structures in the central nervous system that are implicated in mediating central angiotensin-II (ANG-II) actions during water deprivation and hypovolemia. Neuroendocrine and cardiovascular responses, drinking behavior, and urinary excretions were examined following central angiotensinergic stimulation in awake freely-moving rats pretreated with intracerebroventricular injections of N omega-nitro-L-arginine methyl ester (L-NAME, 40 mu g), an inhibitor of NO synthase, and L-arginine (20 ug), a precursor of NO. Results: Injections of L-NAME or ANG-II produced an increase in plasma vasopressin (VP), oxytocin (OT) and atrial natriuretic peptide (ANP) levels, an increase in water and sodium intake, mean arterial blood pressure and sodium excretion, and a reduction of urinary volume. L-NAME pretreatment enhanced the ANG-II response, while L-arginine attenuated VP and OT release, thirst, appetite for sodium, antidiuresis, and natriuresis, as well as pressor responses induced by ANG-II. Discussion and conclusion: Thus, the central nitrergic system participates in the angiotensinergic responses evoked by water deprivation and hypovolemia to refrain neurohypophysial secretion, hydromineral balance, and blood pressure homeostasis.

Experimental and theoretical study of two-photon absorption in nitrofuran derivatives: Promising compounds for photochemotherapy

We report experimental and theoretical studies of the two-photon absorption spectrum of two nitrofuran derivatives: nitrofurantoine, (1-(5-nitro-2-furfurilideneamine)-hidantoine) and quinifuryl, 2-(5`-nitro-2`-furanyl) ethenyl-4-{N-[4`-(N,N-diethylamino)-1`-methylbutyl]carbamoyl} quinoline. Both molecules are representative of a family of 5-nitrofuran-ethenyl-quinoline drugs that have been demonstrated to display high toxicity to various species of transformed cells in the dark. We determine the two-photon absorption cross-section for both compounds, from 560 to 880 nm, which present peak values of 64 GM for quinifuryl and 20 GM for nitrofurantoine (1 GM = 1 x 10(-50) cm(4).s.photon(-1)). Besides, theoretical calculations employing the linear and quadratic response functions were carried out at the density functional theory level to aid the interpretations of the experimental results. The theoretical results yielded oscillator strengths, two-photon transition probabilities, and transition energies, which are in good agreement with the experimental data. A higher number of allowed electronic transitions was identified for quinifuryl in comparison to nitrofurantoine by the theoretical calculations. Due to the planar structure of both compounds, the differences in the two-photon absorption cross-section values are a consequence of their distinct conjugation lengths. (c) 2011 American Institute of Physics. [doi:10.1063/1.3514911]

Post-resistance exercise hypotension in spontaneously hypertensive rats is mediated by nitric oxide

1. Postexercise hypotension (PEH) plays an important role in the non-pharmacological treatment of hypertension. It is characterized by a decrease in blood pressure (BP) after a single bout of exercise in relation to pre-exercise levels. 2. The present study investigated the effect of a single session of resistance exercise, as well as the effect of nitric oxide (NO) and the autonomic nervous system (ANS), in PEH in spontaneously hypertensive rats (SHR). 3. Catheters were inserted into the left carotid artery and left jugular vein of male SHR (n = 37) for the purpose of measuring BP or heart rate (HR) and drug or vehicle administration, respectively. Haemodynamic measurements were made before and after acute resistance exercise. The roles of NO and the ANS were investigated by using N(G)-nitro-L-arginine methyl ester (L-NAME; 15 mg/kg, i.v.) and hexamethonium (20 mg/kg, i.v.) after a session of acute resistance exercise. 4. Acute resistance exercise promoted a pronounced reduction in systolic and diastolic BP (-37 +/- 1 and -8 +/- 1 mmHg, respectively; P < 0.05), which was suppressed after treatment with L-NAME. The reduction in systolic BP caused by exercise (-37 +/- 1 mmHg) was not altered by the administration of hexamethonium (-38 +/- 2 mmHg; P > 0.05). After exercise, the decrease in diastolic BP was greater with hexamethonium (-26 +/- 1 mmHg; P < 0.05) compared with the decrease caused by exercise alone. 5. The results suggest that acute resistance exercise has an important hypotensive effect on SHR and that NO plays a crucial role in this response.

Ethanol-induced vasoconstriction is mediated via redox-sensitive cyclo-oxygenase-dependent mechanisms

The present study investigated the role of ROS (reactive oxygen species) and COX (cyclooxygenase) in ethanol-induced contraction and elevation of [Ca(2+)](i) (intracellular [Ca(2+)]). Vascular reactivity experiments, using standard muscle bath procedures, showed that ethanol (1-800 mmol/l) induced contraction in endothelium-intact (EC(50): 306 +/- 34 mmol/l) and endothelium-denuded (EC(50): 180 +/- 40 mmol/l) rat aortic rings. Endothelial removal enhanced ethanol-induced contraction. Preincubation of intact rings with L-NAME [N(G)-nitro-L-arginine methyl ester; non-selective NOS (NO synthase) inhibitor, 100 mu mol/l], 7-nitroindazole [selective nNOS (neuronal NOS) inhibitor, 100 mu mol/l], oxyhaemoglobin (NO scavenger, 10 mu mol/l) and ODQ (selective inhibitor of guanylate cyclase enzyme, 1 mu mol/l) increased ethanol-induced contraction. Tiron [O(2)(-) (superoxide anion) scavenger, 1 mmol/l] and catalase (H(2)O(2) scavenger, 300 units/ml) reduced ethanol-induced contraction to a similar extent in both endothelium-intact and denuded rings. Similarly, indomethacin (non-selective COX inhibitor, 10 mu mol/l), SC560 (selective COX- I inhibitor, 1 mu mol/l), AH6809 [PGF(2 alpha) (prostaglandin F(2 alpha))] receptor antagonist, 10 mu mol/l] or SQ29584 [PGH(2)(prostaglandin H(2))/TXA(2) (thromboxane A(2)) receptor antagonist, 3 mu mol/l] inhibited ethanol-induced contraction in aortic rings with and without intact endothelium. In cultured aortic VSMCs (vascular smooth muscle cells), ethanol stimulated generation of O(2)(-) and H(2)O(2). Ethanol induced a transient increase in [Ca(2+)](i), which was significantly inhibited in VSMCs pre-exposed to tiron or indomethacin. Our data suggest that ethanol induces vasoconstriction via redox-sensitive and COX-dependent pathways, probably through direct effects on ROS production and Ca(2+) signalling. These findings identify putative molecular mechanisms whereby ethanol, at high concentrations, influences vascular reactivity. Whether similar phenomena occur in vivo at lower concentrations of ethanol remains unclear.

Biochemical responses of glyphosate resistant and susceptible soybean plants exposed to glyphosate

Glyphosate is a wide spectrum, non-selective, post-emergence herbicide. It acts on the shikimic acid pathway inhibiting 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS), thus obstructing the synthesis of tryptophan, phenylalanine, tyrosine and other secondary products, leading to plant death. Transgenic glyphosate-resistant (GR) soybean [Glycine max (L.)] expressing an glyphosate-insensitive EPSPS enzyme has provided new opportunities for weed control in soybean production. The effect of glyphosate application on chlorophyll level, lipid peroxidation, catalase (CAT), ascorbate peroxidase (APX), guaiacol peroxidase (GOPX) and superoxide dismutase (SOD) activities, soluble amino acid levels and protein profile, in leaves and roots, was examined in two conventional (non-GR) and two transgenic (GR) soybean. Glyphosate treatment had no significant impact on lipid peroxidation, whilst the chlorophyll content decreased in only one non-GR cultivar. However, there was a significant increase in the levels of soluble amino acid in roots and leaves, more so in non-GR than in GR soybean cultivars. Root CAT activity increased in non-GR cultivars and was not altered in GR cultivars. In leaves, CAT activity was inhibited in one non-GR and one GR cultivar. GOPX activity increased in one GR cultivar and in both non-GR cultivars. Root APX activity increased in one GR cultivar. The soluble protein profiles as assessed by 1-D gel electrophoresis of selected non-GR and GR soybean lines were unaffected by glyphosate treatment. Neither was formation of new isoenzymes of SOD and CAT observed when these lines were treated by glyphosate. The slight oxidative stress generated by glyphosate has no relevance to plant mortality. The potential antioxidant action of soluble amino acids may be responsible for the lack of lipid peroxidation observed. CAT activity in the roots and soluble amino acids in the leaves can be used as indicators of glyphosate resistance.

Genomics of pyrrolnitrin biosynthetic loci: evidence for conservation and whole-operon mobility within Gram-negative bacteria

Pyrrolnitrin (PRN) is a tryptophan-derived secondary metabolite produced by a narrow range of Gram-negative bacteria. The PRN biosynthesis by rhizobacteria presumably has a key role in their life strategies and in the biocontrol of plant diseases. The biosynthetic operon that encodes the pathway that converts tryptophan to PRN is composed of four genes, prnA through D, whose diversity, genomic context and spread over bacterial genomes are poorly understood. Therefore, we launched an endeavour aimed at retrieving, by in vitro and in silico means, diverse bacteria carrying the prnABCD biosynthetic loci in their genomes. Analysis of polymorphisms of the prnD gene sequences revealed a high level of conservation between Burkholderia, Pseudomonas and Serratia spp. derived sequences. Whole-operon- and prnD-based phylogeny resulted in tree topologies that are incongruent with the taxonomic status of the evaluated strains as predicted by 16S rRNA gene phylogeny. The genomic composition of c. 20 kb DNA fragments containg the PRN operon varied in different strains. Highly conserved and distinct transposase-encoding genes surrounding the PRN biosynthetic operons of Burkholderia pseudomallei strains were found. A prnABCD-deprived genomic region in B. pseudomallei strain K96243 contained the same gene composition as, and shared high homology with, the flanking regions of the PRN operon in B. pseudomallei strains 668, 1106a and 1710b. Our results strongly suggest that the PRN biosynthetic operon is mobile. The extent, frequency and promiscuity of this mobility remain to be understood.

Response of watermelon cultivated under different levels of water and nitrogen

The effect of four irrigation levels (50; 75; 100 and 150% of the evaporation in the class A pan) and four levels of N (0,075; 0, 150; 0,225 and 0,300 kg(-1)), were evaluated on productivity and components of production of the watermelon `Charleston Gray`. The experiment was conducted under field conditions, from October/2003 to January/2004, using a randomized split-plot design, with the factor depths in plot and depths of N in split-plot. It was verified that the factors water and nitrogen presented a highly significant effect in the yield of watermelon, while the interaction among the factors was not significant. The maximum productivity of the watermelon (68.59 Mg ha(-1)) was obtained with 421 mm of water and 267 kg ha(-1) of N. The water was more efficiently used with increments in dosage of N, being the maximum value observed of 279.54 kg ha(-1) mm(-1), obtained with a depth of water of 205 mm and a depths of N of 225 kg ha(-1). The maximum efficiency of the use of the water for the nitro en was 221 kg ha(-1) mm(-1), for 249 kg ha(-1) of N. The sugar content of the watermelon, measured in degrees Brix, was affected by the depths of irrigation, depths of N and by its interactions.