Paula C. Dabas

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.

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.

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.

CAPILLARY ION ELECTROPHORESIS OF INORGANIC CATIONS IN STANDARD REFERENCE MATERIALS FROM VEGETABLE SOURCE

Taking into account the growing interest in applying capillary ion electrophoresis (CIE) for the determination of inorganic ions in real samples, this work focuses on CIE analysis of K+, Na+, Ca2+, Mg2+, and Mn2+ in botanical and food reference materials. Microwave-Assisted Digestion for sample preparation has been chosen ensuring a rapid, accurate, and reproducible treatment. A fused-silica capillary, 75 μm × 60 cm, a background electrolyte consisting of 6 mM imidazole and 10 mM α-hydroxy-isobutyric acid (HIBA). and indirect UV detection at 214 nm were used. Certified reference materials as Apple leaves SRM 1515 (NIST, USA), Beech leaves CRM 100, Rye flour CRM 381, Haricot beans CRM 383, and the green algae Ulva lactuca CRM 279 (BCR, Belgium) were selected. The optimal experimental conditions for microwave digestion and operational parameters in the electrophoresis system were studied. The calibration curves for K, Ca, Mg, and Mn ions were linear over the range of 0.6 ppm to 120 ppm and the detection lim...

Stability Study of Lorazepam in Solid Dosage form by High Performance Liquid Chromatography

AbstractA reverse phase column with MeOH-H20 as mobile phase and detection at 230 nm was employed for the determination of lorazepam and degradation products in tablet formulation. The mean coeficient variation (n=6) for the entire analytical method was 1.15%. A working calibration curve over a concentration range of 5 to 250 ng of lorazepam was obtained and the recovery (n=3) was 100.5%. Limits of detection varied from 1.6 to 3.2 ng according to the compounds. Natural and thermal stability of the drug and tablets were carried out since the method was suitable for stability indicating studies. A comparative TLC method was also performed. The effect of the type and concentration of acid and the content of methanol in reaction medium of hydrolysis of lorazepam were also investigated. Degradation products were characterized by HPLC and TLC by comparing them to authentic samples. The first degradation product that appeared was the quinazoline-carboxaldehide and 2-amino-2′,5-dichlorobenzophenone was not detect...