AV3V LESION SUPPRESSES THE PRESSOR, DIPSOGENIC AND NATRIURETIC RESPONSES TO CHOLINERGIC ACTIVATION OF THE SEPTAL AREA IN RATS

In the present study we investigated the effect of anteroventral third ventricle (AV3V) lesion on pressor, dipsogenic, natriuretic and kaliuretic responses induced by the injection of carbachol (a cholinergic agonist) into the medial septal area (MSA) of rats. Male rats with sham or AV3V lesion and a stainless-steel cannula implanted into the MSA were used. Carbachol (2 nmol) injected into the MSA in sham lesion rats produced pressor (43 +/- 2 mmHg), dipsogenic (9.6 +/- 1.2 ml/h), natriuretic (531 +/- 82-mu-Eq/120 min) and kaliuretic (164 +/- 14-mu-Eq/120 min) responses. In AV3V-lesioned rats (1-5 days and 14-18 days), the pressor (11 +/- 2 mmHg, respectively), dipsogenic (1.9 +/- 0.7 and 1.4 +/- 0.6 ml/h), natriuretic (21 +/- 5 and 159 +/- 44-mu-Eq/120 min) and kaliuretic (124 +/- 14 and 86 +/- 13-mu-Eq/120 min) responses induced by carbachol injection into the MSA were reduced. These results show that the AV3V region is essential for the pressor, dipsogenic, natriuretic and kaliuretic responses induced by cholinergic activation of the MSA in rats.

Voltammetric determination of persulfate anions using an electrode modified with a Prussian blue film

Prussian blue [PB, iron(III) hexacyanoferrate(II)] films are effective for the electrocatalysis of the persulfate (peroxodisulfate)/sulfate redox system. This has been exploited in the voltammetric determination of persulfate anions using a PB-modified platinum disc electrode. A linear correlation between electrocatalytic current and persulfate concentration was found for the range 5 x 10(-5) to 3 x 10(-3) mol dm(-3), using 0.100 mol dm(-3) potassium chloride as supporting electrolyte at pH 4. This analytical method has the advantages of speed and ease of operation in relation to traditional titrimetric methods for persulfate determination. The applicability of the method to the determination of persulfate in a commercial hair bleaching 'booster' product is demonstrated. (C) 2000 Elsevier B.V. B.V. All rights reserved.

The lateral preoptic area plays a dual role in the regulation of thirst in the rat

Electrolyte lesion and ibotenic acid lesion of the lateral preoptic area (LPO) of the rat were used to study the participation of this area in drinking behavior. Drinking was induced by cellular dehydration, hypovolemia, hypotension, and water deprivation. The animals with electrolytic lesion of the LPO showed a significant reduction in water intake in response to cellular dehydration, hypotension, and deprivation. The animals with ibotenic acid lesion of the LPO increased the water consumption produced by subcutaneous (SC) injection of hypertonic saline. The amount of water intake after SC injection of polyethyleneglycol (PEG) or isoprenaline was similar in control and ibotenic acid-lesioned animals. The rats with ibotenic acid lesion of the LPO drank significantly more water than control animals. Fibers of passage may also influence the drinking response, and the LPO may have osmosensitive receptors that facilitate water intake in connection with other areas of the central nervous system (CNS) that are implicated in drinking behavior.

Losartan (DUP-753) blocks the natriuretic, kaliuretic and antidiuretic effect of intracerebroventricular injection of carbachol in water-loaded rats

We determined the effect of intracerebroventricular (icv) administration of losartan, an angiotensin II (ANG II) subtype 1 receptor (AT1) antagonist, on icv carbachol-induced natriuresis, kaliuresis and antidiuresis in water-loaded male Holtzman rats (250-300 g) with a cannula implanted into the lateral ventricle (LV). The rats were water loaded with 5% of their body weight by gavage twice, with the second gavage one hour after the first. Carbachol (2 nmol in 1 mu l) was injected icv immediately after the second load. When losartan (DUP-753, 50 nmol in 1 mu l) was administered icv, it was given 3 min before carbachol. Previous icv treatment with losartan significantly reduced the icv carbachol-induced natriuresis (324 +/- 17 mu Eq/120 min), kaliuresis (103 +/- 15 mu Eq/120 min) and antidiuresis (13.5 +/- 2.1 ml/120 min) compared to the effects of previous icv injection of saline (Nai excretion = 498 +/- 22 mu Eq/120 min; K+ excretion = 167 +/- 20 mu Eq/120 min; urine volume = 5.2 +/- 1.2 ml/120 min). These results, reported as means +/- SEM for 12 rats in each group, are consistent with the hypothesis that AT1 subtype receptors participate in the regulation of body electrolyte balance.

Environmental coordination chemistry: Binary systems comprising some bivalent cations and monocarboxylates in aqueous solution. Ionic medium effects on equilibrium constants

The molar single activity coefficients associated with propionate ion (Pr) have been determined at 25 degrees C and ionic strengths comprised between 0.300 and 3.00 M, adjusted with NaClO4, as background electrolyte. The investigation was carried out potentiometrically by using a second class Hg/Hg2Pr2 electrode. It was found that the dependence of propionate activity coefficients as a function of ionic strength (I) can be assessed through the following empirical equation: log y(Pr) = -0.185 I-3/2 + 0.104 I-2. Next, simple equations relating stoichiometric protonation constants of several monocarboxylates and formation constants associated with 1:1 complexes involving some bivalent cations and selected monocarboxylates, in aqueous solution, at 25 degrees C, as a function of ionic strength were derived, allowing the interconversion of parameters from one ionic strength to another, up to I = 3.00 M. In addition, thermodynamic formation constants as well as parameters associated with activity coefficients of the complex species in the equilibria are estimated. The body of results shows that the proposed calculation procedure is very consistent with critically selected experimental data.

Indirect determination of chloride and sulfate ions in alcohol fuel by capillary electrophoresis

A capillary zone electrophoresis method using indirect UV detection for the analysis of chloride and sulfate in alcohol fuel samples was developed. The anions were analyzed in less than 3 min using an electrolyte containing 10 mmol 1(-1) chromate and 0.75 mmol 1(-1) hexamethonium bromide (HMB) as electroosmotic flow modifier. Coefficients of variation were better than 0.6% for migration time (n = 10) and between 2.05 and 2.82% for peak area repeatabilities. Analytical curves of peak area versus concentration in the range of 0.065-0.65 mg kg(-1) for chloride and 0.25-4.0 mg kg(-1) for sulfate were linear with coefficients of correlation higher than 0.9996. The limits of detection for sulfate and chloride were 0.033 and 0.041 mg kg(-1), respectively. Recovery values ranged from 85 to 103%. The method was successfully applied for the quantification of sulfate and chloride in five alcohol fuel samples. The concentration of sulfate varied from 0.45 to 3.12 mg kg(-1). Chloride concentrations were below the method's LOD.

ROLE OF ADRENERGIC PATHWAYS OF THE MEDIAL PREOPTIC AREA IN ANGII-INDUCED WATER-INTAKE AND RENAL EXCRETION IN RATS

In this study, we investigated the participation of adrenergic neurotransmission in angiotensin II- (ANGII)-induced water intake and urinary electrolyte excretion by means of injection of the alpha(1)-, alpha(2)-, and beta-adrenoceptor antagonists and ANGII into the medial preoptic area (MPOA) in rats. Prazosin (an alpha(1)-adrenergic antagonist) antagonized the water ingestion, Na+, K+ and urine excretion induced by ANGII, whereas yohimbine (an alpha(2)-adrenergic antagonist) enhanced the Na+, K+ and urine excretion induced by ANGII. Propranolol (a nonselective beta-adrenoceptor blocker) antagonized the water ingestion and enhanced the Na+ and urine excretion induced by ANGII. Previous treatment with prazosin reduced the presser responses to ANGII, whereas yohimbine had opposite effects. Previous injection of propranolol produced no effects in the presser responses to ANGII. These results suggest that the adrenergic neurotransmission in the MPOA may actively participate in ANGII-induced dipsogenesis, natriuresis, kaliuresis and diuresis in a process that involves alpha(1)-, alpha(2)-, and beta-adrenoceptors.

Determination of olive oil acidity by CE

In this work, a CE method for the determination of olive oil acidity was proposed. The method was based on an ethanolic extraction (at 60 degrees C) of the oil long-chain free fatty acids (LC-FFAs) components followed by CE determination in pH 6.86 phosphate buffer at 15 mmol/L concentration containing 4 mmol/L sodium dodecylbenzenesulfonate (SDBS), 10 mmol/L polyoxyethylene 23 lauryl ether (Brij 35((R))), 2% v/v 1-octanol and 45% v/v ACN under indirect UV detection at 224 nm. Although this electrolyte promoted baseline separation of myristic acid (C14:0) (internal standard (IS)) and olive oil major components (palmitic acid (C16:0), oleic acid (C18:1c) and linoleic acid (C18:2cc)) in less than 8 min, after a few injections, the electropherogram profiles were severely altered (peak broadening, migration time shifts, etc.) and the current increased substantially. An adsorption study was conducted revealing that the dissolution of the capillary external polyimide coating during the electrophoretic run caused the detrimental effect. After removal of the capillary tip coating, ten consecutive injections could be performed without any disturbances and this simple procedure was, therefore, implemented during quantitative purposes. The reliability of the proposed method was further investigated by the determination of acidity of an extra virgin olive oil sample in comparison to the established methodology (AOCS method Ca 5a40, alkaline volumetric titration (AVT)). No statistical differences were found within 95% confidence level. A % acidity of 0.39 +/- 0.02 was found for the olive oil sample under consideration.

AV3V LESION REDUCES THE PRESSOR, DIPSOGENIC, AND NATRIURETIC RESPONSES TO VENTROMEDIAL HYPOTHALAMUS ACTIVATION

In the present study, we investigated the effect of anteroventral third ventricle (AV3V) lesion on pressor, tachycardic, dipsogenic, natriuretic, and kaliuretic responses induced by the injection of the cholinergic agonist carbachol into the ventromedial hypothalamic nucleus (VMH) of rats. Male rats with sham or AV3V lesion and a stainless steel cannula implanted into the VMH were used. Carbachol (2 nmol) injected into the VMH of sham rats produced pressor (32 +/- 4 mmHg). tachycardic (83 +/- 14 bpm), dipsogenic (8.2 +/- 1.1 ml/h). natriuretic (320 +/- 46-mu-Eq/120 min), and kaliuretic (155 +/- 20-mu-Eq/120 min) responses. In AV3V-lesioned rats (2 and 15 days), the pressor (4 +/- 2 and 15 +/- 2 mmHg. respectively), dipsogenic (0.3 +/-0.2 and 1.4 +/- 0.7 ml/h), natriuretic (17 +/- 7 and 99 +/- 21-mu-Eq/120 min), and kaliuretic (76 +/- 14 and 79 +/- 7-mu-Eq/120 min) responses induced by carbachol injection into the VMH were reduced. The tachycardia was also abolished (27 +/- 15 and -23 +/-29 bpm, respectively). These results show that the AV3V region is essential for the pressor, tachycardic, dipsogenic, natriuretic. and kaliuretic responses induced hy cholinergic activation of the VMH in rats.

Characterization of an all sol-gel electrochromic device WO3/Ormolyte/CeO2-TiO2

Electrochemical lithium intercalation in thin films of CeO2-TiO2 and WO3, prepared by the sol-gel technique was investigated with cyclic voltammetry and spectroelectrochemical techniques in propylene carbonate solutions. A solid state system having the configuration WO3/Ormolyte/CeO2-TiO2 has been assembled. The solid electrolyte, an organically modified electrolyte (ormolyte), was prepared with different [O]/[Li] ratios. The transmittance variation of this system during a potentiostatic step from -0.7 V to 0.8 V was about 35% at 550 nm.

Ionic medium effects on equilibrium constants .1. Proton, copper(II), cadmium(II), lead(II) and acetate activity coefficients in aqueous solution

The molar single ion activity coefficients associated with hydrogen, copper(II), cadmium(II) and lead(II) ions were determined at 25 degrees C and ionic strengths between 0.100 and 3.00 M (NaClO4), whereas for acetate the ionic strengths were fixed between 0.300 and 2.00 M, held with the same inert electrolyte. The investigation was carried out potentiometrically by using proton-sensitive glass, copper, cadmium and lead ion-selective electrodes and a second-class Hg\Hg-2(CH3COO)(2) electrode. It was found that the activity coefficients of these ions (y(i)) can be assessed through the following empirical equations:log y(H) = -0.542I(0.5) + 0.451I; log y(Cu) = -1.249I(0.5) + 0.912I; log y(Cd) = -0.829I(0.5) + 0.448I(1.5);log y(Pb) = -0.404I(0.5) + 0.117I(2); and log y(Ac) = 0.0370I .

Temperature and concentration dependence of density of model liquid foods

Density of binary solutions and combinations of sucrose, glucose, fructose, citric acid, malic acid, pectin, and inorganic salts were measured with an oscillating tube density meter in the temperature range from 10degrees to 60degreesC, at varying concentrations. Density can be predicted with accuracy better than 5 x 10(-5) g cm(-3) using predictive equations obtained by fitting the experimental data. Available literature values agreed well with experimental data. Relations for the excess molar volume of these solutions were derived in terms of mole fraction and temperature. A thermodynamic model for the volumetric analysis of multicomponent aqueous solutions containing electrolyte and non-electrolyte compounds was also proposed. These models can be used for prediction of density of liquid food systems, specially fruit juices and beverages, based on composition and temperature, with high accuracy and without elaborate experimental work.

Influence of membrane-solution interface on the selectivity of SnO2 ultrafiltration membranes

SnO2 supported membranes, presenting 3.0 nm average pore size, have been produced by sol casting on alumina tubular substrate using aqueous colloidal suspensions prepared by sol-gel route. The selectivity and flux throughout SnO2 membrane were analyzed by permeation experiments, using a laboratory tangential filtration pilot equipped with a monotubular membrane. To evaluate the effect of the surface charge at the membrane-solution interface, aqueous salt solutions (NaCl, Na2SO4, CaCl, and CaSO4) of different ionic strength have been filtered and the results correlated with the values of zeta potential measured at several pH. The results show that the retention coefficient is dependent on the electrolyte present in aqueous solution decreasing as: (dication, monoanion) > (monocation, monoanion) approximate to (monocation, dianion) > (dication, dianion). The surface charge and the cation adsorption capacity play a determinant role in these selectivity sequences. (C) 2001 Elsevier B.V. B.V. All rights reserved.

Electrocatalytic study of an electrode modified with Reactive Blue 4 dye covalently immobilized on amine-functionalized silica

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Efficacy of florfenicol and intravenous fluid therapy for treatment of experimental salmonellosis in newborn calves

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)