Platelet function and the von Willebrand factor antigen in the hepatosplenic form of schistosomiasis mansoni.

Forty-five individuals with hepatosplenic schistosomiasis mansoni were studied with the aim of measuring levels of von Willebrand factor antigen (vWF:Ag), detecting abnormalities in platelet morphology and aggregation, and identifying changes to surface antigens. Haemograms, platelet aggregation tests, flow cytometry investigations of CD41/CD42b antibody and vWF:Ag assays were performed. Mean platelet counts were low (77,522/mm3) and 82.2% of patients presented thrombocytopenia. An inverse relationship between spleen size and platelet count was seen. Macroplatelets were found in 57.1% of patients, indicating good bone-marrow response, but were insufficient to compensate for the decrease in platelets due to splenomegaly. Decreased or absent platelet aggregation was seen in 50% of patients, probably due to low platelet counts. Markers for GPIIb/IIIa were normal in more than 90% of patients, not supporting the increased capture and destruction of platelets in the spleen that is hypothesized to occur with cirrhosis. Similar to cirrhosis, vWF:Ag levels were high or very high in 70.5% of patients. High levels of vWF:Ag were associated with platelet counts <100,000/mm3, larger spleen diameter and oesophageal varices. In conclusion, hepatosplenic schistosomiasis leads to a lower platelet count due to pooling in the spleen and, consequently, impaired aggregation, but not to increased capture and destruction of platelets in the spleen. High vWF:Ag levels probably promote stabilization of platelet microaggregates and prevent minor manifestations of thrombocytopenia such as petechiae, ecchymosis and gingival bleeding.

Retail survey of Brazilian milk and Minas frescal cheese and a contaminated dairy plant to establish prevalence, relatedness, and sources of Listeria monocytogenes isolates.

A study was designed to recover Listeria monocytogenes from pasteurized milk and Minas frescal cheese (MFC) sampled at retail establishments (REs) and to identify the contamination source(s) of these products in the corresponding dairy processing plant. Fifty milk samples (9 brands) and 55 MFC samples (10 brands) were tested from REs located in Juiz de Fora, Minas Gerais, Brazil. All milk samples and 45 samples from 9 of 10 MFC brands tested negative for L. monocytogenes; however, "brand F" of MFC obtained from REs 119 and 159 tested positive. Thus, the farm/plant that produced brand F MFC was sampled; all samples from the milking parlor tested negative for L. monocytogenes, whereas several sites within the processing plant and the MFC samples tested positive. All 344 isolates recovered from retail MFC, plant F MFC, and plant F environmental samples were serotype 1/2a and displayed the same AscI or ApaI fingerprints. Since these results established that the storage coolers served as the contamination source of the MFC, plant F was closed so that corrective renovations could be made. Following renovation, samples from sites that previously tested positive for the pathogen were collected from the processing environment and from MFC on multiple visits; all tested negative for L. monocytogenes. In addition, on subsequent visits to REs 159 and 119, all MFC samples tested negative for the pathogen. Studies are ongoing to quantify the prevalence, levels, and types of L. monocytogenes in MFC and associated processing plants to lessen the likelihood of listeriosis in Brazil.

Potentiometric behaviour of ion selective electrodes based on iron porphyrins: the influence of porphyrin substituents on the response properties and analytical determination of diclofenac in pharmaceutical formulations.

The potentiometric response characteristics of diclofenac selective electrodes based on Fe(III) tetraphenylporphyrin-chloride (Fe(III)TPP-Cl) and Fe(III) tetrakis(pentafluorophenyl)porphyrin-chloride (Fe(III)TPFPP-Cl) in different mediator solvents and ionic additives are compared. The sensitivity, working range, detection limit, response mechanism, and selectivity of the membrane sensor show a significant dependence on the type of carrier substituent and on the pH value of the sample solution. Studies performed with different amounts of cationic additive (tetra-n-octylammoniumbromide (TOABr)) and anionic additive (sodium tetraphenylborate (NaTPB)) in the membranes allowed the determination of the potentiometric mechanism of action of the used metalloporphyrins. For the analysis of real samples, Fe(III)TPFPP-Cl (type G), prepared in o-NPOE, incorporating 10 mol% of TOABr, was used. This potentiometric unit presented a linear response towards diclofenac concentrations between 10(-5) and 10(-2)mol l(-1) ( I=0.1 mol l(-1)) and slopes of about -59 mV dec(-1), exhibiting a response time of 10s in a buffered solution of ammonia-ammonium sulphate with pH 9.9. The potentiometric analysis of sodium diclofenac in pharmaceutical formulations was carried out by direct potentiometry and the obtained results were compared to those provided by HPLC, presenting relative errors inferior to 1.0%.

Construction and evaluation of PVC and sol-gel sensor membranes based on Mn(III)TPP-Cl. Application to valproate determination in pharmaceutical preparations.

The construction and general performance of new valproate-selective electrodes based on manganese(III) tetraphenylporphyrin [Mn(III)TPP-Cl], as an ionophore, are presented. The ionophore was incorporated into PVC and ceramic membranes (sol-gel) based on methyltriethoxysilane. The influence of membrane composition and pH and the effect of lipophilic cationic and anionic additives in PVC membranes were investigated concerning their influence on the slope, response time, selectivity and lifetime of the electrodes. The PVC membrane without additive and the sol-gel membrane presented slopes and practical limits of detection of -60.8 mV dec(-1) and 5x10(-6) mol l(-1) and -60.3 mV dec(-1) and 1x10(-4) mol l(-1), respectively. The sol-gel membranes displayed higher selectivity for valproate when compared with PVC membranes. These two types of electrodes were coupled to a sequential-injection analysis (SIA) system for the direct determination of valproate in pharmaceutical formulations. The association of Mn(III)TPP-Cl with the sol-gel support inserted in a SIA system provided potentiometric sensors with an analytical range of 1x10(-3)-5x10(-2) mol l(-1), with a sample rate of 55 samples per hour and a sample and carrier consumption of 140 and 2,500 microl per determination, respectively.

Ion selective electrodes for penicillin-G based on Mn(III)TPP-Cl and their application in pharmaceutical formulations control by sequential injection analysis.

The work describes the construction, evaluation and analytical application of ion selective electrodes sensitive to penicillin-G antibiotics for pharmaceutical products analysis. Different types of polymeric membranes based on PVC (poly(vinyl chloride)) and EVA (ethyl-vinyl-acetate), without internal reference solution, were prepared using 5,10,15,20-tetraphenylporphyrinate (TPP) manganese(III) (Mn(III)TPP-Cl) as electroactive material. Different additives such as tetra-n-octylammoniumbromide (cationic additive) and sodium tetraphenylborate (anionic additive) were incorporated into the membranes to evaluate their influence on electrodes performance. The comparison of the developed detectors was based on general analytical characteristics, selectivity and lifetime. To accomplish the analysis of real samples, two selective membranes composed of 33.0% (w/w) of PVC, 66.0% (w/w) of o-NPOE and 1.0% (w/w) of Mn(III)TPP-Cl (type A) and 33.0% (w/w) of PVC, 66.0% (w/w) of o-NPOE, 1.0% (w/w) of Mn(III)TPP-Cl and 10% mol (relative to the molar concentration of Mn(III)TPP-Cl) of sodium tetraphenylborate (type B) were used. Type A electrode presented a linear response between 2 x 10(-5) and 10(-1) moll(-1) for penicillin-G, a slope of about -59 mVdec(-1) and a reproducibility of about +/-0.5 mVday(-1), while type B exhibited a linear response between 5 x 10(-5) and 10(-1) moll(-1) for penicillin-G, a slope of about -61 mVdec(-1) and a reproducibility of about +/-0.3 mV day(-1). The potentiometric analysis of penicillin-G in pharmaceutical products was carried out by direct potentiometry and the results obtained were compared with those provided by the HPLC reference method. These membranes (type A and type B) were used to prepare tubular electrodes that were coupled to a sequential injection system (SIA) and presented a linear range between 2 x 10(-4) and 1 x 10(-2) moll(-1) and slopes of -59.3 +/- 0.8 and -57.3 +/- 1.2 mVdec(-1), respectively. The tubular electrode constructed using type B membrane (type TB) was used to carry out the potentiometric analysis of penicillin-G in pharmaceutical formulations. The proposed procedure enabled relative errors between 0.1% and 1.2% (n = 4) and a sampling-rate of about 25 samples per h.

Ion-selective electrodes based on metalloporphyrins for gibberellic acid determination in agricultural products.

This work describes the construction, evaluation and analytical application of electrodes selective to the gibberellate anion for the determination of gibberellic acid in agricultural products. Several types of PVC membrane electrodes without internal reference solution were prepared using the manganese(III) complex of meso-tetraphenylporphyrin (TPP) as ionophore and dibutyl phthalate (DBP), as plasticizer. The incorporation of lipophilic chemical species as additives, was also carried out aiming the evaluation of the response characteristics of the electrodes. To accomplish the analysis of commercial agricultural products a selective membrane composed of 28.0% (w/w) of PVC, 66.0% (w/w) of plasticizer and 6% (w/w) of ionophore was used, with no additive. This potentiometric unit presented a linear response between 10(-4) and 10(-1) mol L(-1) in gibberellate, a slope of about -69 mV dec(-1) and a reproducibility of about +/-1 mV day(-1). The potentiometric analysis of gibberellic acid in commercial products was carried out by direct potentiometry and the results obtained were compared with those provided by HPLC.