Endothelin-1 and -3 induce choleresis in the rat through ETB receptors coupled to nitric oxide and vagovagal reflexes.

We have reported previously that centrally applied ET (endothelin)-1 and ET-3 induce either choleresis or cholestasis depending on the dose. In the present study, we sought to establish the role of these endothelins in the short-term peripheral regulation of bile secretion in the rat. Intravenously infused endothelins induced significant choleresis in a dose-dependent fashion, ET-1 being more potent than ET-3. Endothelins (with the exception of a higher dose of ET-1) did not affect BP (blood pressure), portal venous pressure or portal blood flow. ET-1 and ET-3 augmented the biliary excretion of bile salts, glutathione and electrolytes, suggesting enhanced bile acid-dependent and -independent bile flows. ET-induced choleresis was mediated by ET(B) receptors coupled to NO and inhibited by truncal vagotomy, atropine administration and capsaicin perivagal application, supporting the participation of vagovagal reflexes. RT (reverse transcription)-PCR and Western blot analysis revealed ETA and ET(B) receptor expression in the vagus nerve. Endothelins, through ET(B) receptors, augmented the hepatocyte plasma membrane expression of Ntcp (Na⁺/taurocholate co-transporting polypeptide; Slc10a1), Bsep (bile-salt export pump; Abcb11), Mrp2 (multidrug resistance protein-2; Abcc2) and Aqp8 (aquaporin 8). Endothelins also increased the mRNAs of these transporters. ET-1 and ET-3 induced choleresis mediated by ET(B) receptors coupled to NO release and vagovagal reflexes without involving haemodynamic changes. Endothelin-induced choleresis seems to be caused by increased plasma membrane translocation and transcriptional expression of key bile transporters. These findings indicate that endothelins are able to elicit haemodynamic-independent biological effects in the liver and suggest that these peptides may play a beneficial role in pathophysiological situations where bile secretion is impaired.

Degradation and detoxification of cresols in synthetic and industrial wastewater by an indigenous strain of Pseudomonas putida in aerobic reactors.

We studied the degradation of mixtures of o-cresol, m-cresol, and p-cresol, by Pseudomonas putida isolated from natural sources, and the application of this degradation to the depuration and detoxification of synthetic and industrial wastewater. Biodegradation assays were performed in batch and continuous-flow fixed-bed aerobic reactors. Biodegradation was evaluated by cresol determination using micellar electrokinetic capillary chromatography, UV spectrophotometry, and chemical oxygen demand (COD). Mineralization of cresols was assessed by gas chromatography performed both at the end of the batch process and in the continuous flow reactor effluent. Microbial growth was measured by the plate count method. Scanning electronic microscopy was employed to observe bacterial cells adsorbed on polyvinyl chloride cylinders in the reactor. Detoxification was evaluated by Vibrio fischeri, Pseudokirchneriella subcapitata, and Daphnia magna toxicity tests. Results obtained show that under batch conditions the strain grew exponentially with 100, 200, and 300 mg/L of each of the isomers in synthetic minimal medium within 48 h; in industrial wastewater with 540 mg/L of cresols similar results were obtained. Removal of cresols and COD was higher than 99.9% and 95.0%, respectively. When assays were performed in continuous flow reactor in synthetic wastewater under operating conditions a removal of total cresols and COD of 99.9% and 96.4%, respectively, was achieved. Results of capillary electrophoresis may suggest a concurrent isomers utilization and simultaneous growth on the substrates. Toxicity was neither detected at the end of the batch process nor in the continuous flow reactor effluent.

C-type natriuretic peptide stimulates pancreatic exocrine secretion in the rat: role of vagal afferent and efferent pathways.

We previously reported that C-type natriuretic peptide (CNP) increases amylase release in isolated pancreatic acini through natriuretic peptide receptor C activation and enhances pancreatic exocrine secretion via vagal pathways when applied to the brain. In the present study we sought to establish whether CNP was involved in the peripheral regulation of pancreatic secretion. Anesthetized rats were prepared with pancreatic duct cannulation, pyloric ligation and bile diversion into the duodenum. CNP dose-dependently enhanced pancreatic flow, chloride and protein excretion but did not modify bicarbonate output. A selective natriuretic peptide receptor C agonist enhanced pancreatic flow and mimicked CNP-evoked protein output but failed to modify chloride secretion. Truncal vagotomy, perivagal application of capsaicin and hexamethonium reduced CNP-evoked pancreatic flow and abolished chloride excretion but did not affect protein output. Furthermore, pre-treatment with atropine reduced both CNP-stimulated pancreatic flow and chloride excretion but failed to modify protein excretion. Partial muscarinic blockade of CNP-evoked chloride output suggested that mediators other than acetylcholine were involved. However, CNP response was unaltered by cholecystokinin and vasoactive intestinal peptide receptor blockade or by nitric oxide synthase inhibition. In conclusion, CNP-stimulated pancreatic flow through the activation of the natriuretic peptide receptor C and the vago-vagal reflex but it increased protein output only by natriuretic peptide receptor C activation and chloride excretion by vago-vagal reflexes. Present results suggest that CNP may play a role as a local regulator of the exocrine pancreas.

Endothelin-3 applied to the brain evokes opposite effects on bile secretion mediated by a central nitric oxide pathway.

We sought to establish Endothelin (ET-3) role in the central regulation of bile secretion in the rat. The intracerebroventricular (icv) injection of ET-3 evoked a cholestatic or a choleretic effect depending on the administered dose. Lower doses increased bile flow and bicarbonate excretion, whereas higher doses decreased bile flow and bile acid output. ET-3 effects were dependent on brain nitric oxide and independent of the autonomic nervous system or hemodynamic variations. A selective ETB antagonist abolished the cholestatic effect, whereas the choleretic effect was totally inhibited by either ETA or ETB selective blockade. These results show that ET-3 applied to the brain modified through a nitric oxide pathway distinct bile flow fractions depending on the administered dose and give further insights into the complexity of brain-liver interaction.

A carbon nanotube/poly [Ni-(Protoporphyrin IX)] composite for amperometric detection of long chain aliphatic amines.

Poly [Ni-Protoporphyrin] film (pNiPP), containing multiwall carbon nanotubes (MWCNT) was used to cover a glassy carbon electrode. The hybrid material (pNiPP/MWCNT) successfully combines the permselectivity of pNiPP with the high conductivity of MWCNT. The modified electrode was used to perform amperometric detection of long chain aliphatic amines (LCAA) in order to prevent the passivation effect of the aliphatic chain. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) demonstrated that the pNiPP/MWCNT facilitates the electron transfer reaction. The charge transfer resistance (Rct) values were significantly lower by up to one order of magnitude compared to the bare electrode. Differential pulse polarography (DPP) showed a marked decrease of the overpotential generated by the aliphatic chain. The calibration of the amperometric peak area vs. concentrations of derivatized LCAA exhibits a linear response within the range of 0.018 and 28 µM and correlation coefficient (R(2)) higher than 0.999 (n=5). The quantitation limit of the pNiPP/MWCNT electrode is about 400 times lower than the UV-visible detection. RSD of 7.2%, 5.8%, 2.5% and 2.3% was obtained for concentrations of 0.028, 0.28, 2.8 and 28 µM of ferrocenyl octadecylamine. A solution of sphingosine, 0.23 µM, was exclusively detected with HPLC-ECD with pNiPP/MWCNT electrode.

Optimized separation conditions of soy isoflavonoids in urine by capillary zone electrophoresis.

The last few years have seen a growing interest in the study of the sources and metabolism of isoflavones due to their potential role in the prevention and treatment of chronic disease (i.e., coronary artery disease, osteoporosis, and certain types of cancer). Furthermore, isoflavonoids have reportedly been instrumental in relieving menopausal symptoms (i.e., hot flashes, night sweats, other vasomotor symptoms, and bone loss). Isoflavonoids are compounds that occur naturally in plants and belong to the phytoestrogen family, as do coumestans and lignans. There is much to learn about the effects of isoflavonoids and their potential health benefits; thus they are researched extensively through molecular, preclinical, and clinical studies. Capillary zone electrophoresis (CZE) was explored as a new tool for characterizing the content of isoflavonoids in the urine of subjects who consume large amounts of soy and derivative products. The effect of pH, buffer concentration, and instrument parameters on the migration behavior of these products was studied. Due to the phenolic nature of isoflavonoids, alkaline pHs (8.20-9.90) were tested. The influence of electrolyte concentration in the 50-250 mM range on migration times and resolution was researched. Solid-phase extraction (SPE) was carried out for sample cleanup and preconcentration.