Desenvolvimento de um micro-aquecedor para sistemas de análise química em fluxo: determinação espectrofotométrica de manganês em plantas

In this work a micro-heater device to be used as an integral part of the flow analysis manifold is described. The usefulness of the device was demonstrated using it in the development of a multicommutated flow analysis procedure for the spectrophotometric determination of manganese in plant digest. The method was based on the manganese oxidation by periodate in phosphoric acid medium to form the permanganate anion. The reaction development is dependent on the temperature and it was observed that at 25 °C a time interval of ca. 15 min was necessary for the reaction to attain equilibrium. Setting the temperature to 70 ºC, this time interval could be decreased to ca. 30 s. This condition was easily attained employing the proposed micro-heater device coupled to the manifold. The procedure was applied to manganese determination in soybean digests and results compared with those obtained by inductively coupled argon plasma optical emission spectrometry (ICP-OES). No significant difference at 90% confidence level was observed. A linear response for sample concentrations ranging from 5.0 to 30.00 mg L-1 Mn2+; a relative standard deviation of 1.3% (n = 6) for a typical sample containing 6.3 mg L-1 Mn2+; a sampling rate of 22 determinations per hour; a low reagent consumption, of 12.0 mg NaIO4 per determination; and a detection limit of 1.2 mg L-1 were achieved.

Copper, zinc and manganese in soils of two watersheds in Santa Catarina with intensive use of pig slurry

Systematic pig slurry application to crop soils may lead to the accumulation of heavy metals in regions with intensive pig raising. The aim of this study was to evaluate the accumulation of Cu, Zn and Mn in soils under systematic pig slurry application. For this purpose, soil samples were collected from two of the most representative watersheds of Santa Catarina where the predominant activity is pig raising. In each watershed, 12 properties were chosen to evaluate the different systems of pig husbandry (complete cycle (CC), farrowing (FaU) and finishing units (FiU)). Based on information of the producers, soil samples were collected in areas with and without systematic manure application. To determine the total Cu, Zn and Mn content in soils and manure, a methodology proposed by the Environmental Protection Agency of the United States (USEPA), method nº 3050B, was used. For the available heavy metal content, Cu and Zn was extracted with HCl 0.1 mol L-1 and Mn with KCl 1 mol L-1. Data were subjected to multivariate analysis, using the canonical discriminant analysis to identify the metals that best differentiate the soils studied within each swine housing system. Successive pig slurry applications cause an increase in Cu, Zn and Mn availability in the soil and this indicates the need for monitoring of the metal concentrations over time. The critical values of Cu in the soil can be reached and exceeded more rapidly than Zn. The results showed that the soil type may be one of the attribute underlying the determination of public policies in pig raising and waste management because soils such as Inceptisols were shown to be more prone to possible contamination since they may more rapidly reach total critical Cu levels.

A network society communicative model for optimizing the Refugee Status Determination (RSD) procedures

This article recommends a new way to improve Refugee Status Determination (RSD) procedures by proposing a network society communicative model based on active involvement and dialogue among all implementing partners. This model, named after proposals from Castells, Habermas, Apel, Chimni, and Betts, would be mediated by the United Nations High Commissioner for Refugees (UNHCR), whose role would be modeled after that of the International Committee of the Red Cross (ICRC) practice.

Determination of reactivity rates of silicate particle-size fractions

The efficiency of sources used for soil acidity correction depends on reactivity rate (RR) and neutralization power (NP), indicated by effective calcium carbonate (ECC). Few studies establish relative efficiency of reactivity (RER) for silicate particle-size fractions, therefore, the RER applied for lime are used. This study aimed to evaluate the reactivity of silicate materials affected by particle size throughout incubation periods in comparison to lime, and to calculate the RER for silicate particle-size fractions. Six correction sources were evaluated: three slags from distinct origins, dolomitic and calcitic lime separated into four particle-size fractions (2, 0.84, 0.30 and <0.30-mm sieves), and wollastonite, as an additional treatment. The treatments were applied to three soils with different texture classes. The dose of neutralizing material (calcium and magnesium oxides) was applied at equal quantities, and the only variation was the particle-size material. After a 90-day incubation period, the RER was calculated for each particle-size fraction, as well as the RR and ECC of each source. The neutralization of soil acidity of the same particle-size fraction for different sources showed distinct solubility and a distinct reaction between silicates and lime. The RER for slag were higher than the limits established by Brazilian legislation, indicating that the method used for limes should not be used for the slags studied here.

Influence of foliar fertilization with manganese on germination, vigor and storage time of RR soybean seeds

ABSTRACTThis study aimed to evaluate the influence of foliar fertilizer doses containing Mn of phenological stages of suggested application in RR soybeans, to recover management damages with glyphosate at postemergence application on seed vigor in post-harvest and post six months storage. The seeds originated from a field experiment conducted , which included two applications of glyphosate, concomitant with foliar fertilizer in growth stages V4 and V6, with 0.00, 113.50 and 227.00 mg ha-1doses of Mn2+. Germination, GSI (Germination Speed Index), electrical conductivity tests and the first count of seeds were conducted. The application of Mn did not affect the physiological quality of RR soy in postharvest. However, in post-storage, higher doses of Mn had a negative effect on tests of abnormal seedlings, GSI and electrical conductivity. The applications of Mn, regardless of the developmental stage, did not interfere in the germination and first count tests, with and without storage. The electrical conductivity test showed a higher correlation with the seed germination test in the post-harvest treatment.

Comparison of different methods for the determination of total organic carbon and humic substances in Brazilian soils

ABSTRACTAiming to compare three different methods for the determination of organic carbon (OC) in the soil and fractions of humic substances, seventeen Brazilian soil samples of different classes and textures were evaluated. Amounts of OC in the soil samples and the humic fractions were measured by the dichromate-oxidation method, with and without external heating in a digestion block at 130 °C for 30 min; by the loss-on-ignition method at 450 °C during 5 h and at 600 °C during 6 h; and by the dry combustion method. Dry combustion was used as reference in order to measure the efficiency of the other methods. Soil OC measured by the dichromate-oxidation method with external heating had the highest efficiency and the best results comparing to the reference method. When external heating was not used, the mean recovery efficiency dropped to 71%. The amount of OC was overestimated by the loss-on-ignition methods. Regression equations obtained between total OC contents of the reference method and those of the other methods showed relatively good adjustment, but all intercepts were different from zero (p < 0.01), which suggests that more accuracy can be obtained using not one single correction factor, but considering also the intercept. The Walkley-Black method underestimated the OC contents of the humic fractions, which was associated with the partial oxidation of the humin fraction. Better results were obtained when external heating was used. For the organic matter fractions, the OC in the humic and fulvic acid fractions can be determined without external heating if the reference method is not available, but the humin fraction requires the external heating.

Enzyme linked immunosorbent assay: determination of anti-adenovirus antibodies in an infant population

In order to define an accurate assay for anti-adenovirus antibody detection, a recently developed ELISA was compared with IFA and CF. On 58 sera, the ELISA was more sensitive than both CF and IFA, which showed relative sensitivities of 63% and 94%, respectively. It was not possible to determine the exact specificity of the tests because of the lack of a gold standard. Furthermore, the ELISA was used to define the prevalence of adenovirus antibodies in 116 infants between 1 and 24 months old (mean 7.28). The data showed that maternal antibodies waned by the age of 5 to 6 months and that more than 80% of the children had been infected by adenoviruses by the age of 10 months.

Determination du niveau d'anticorps antitetaniques en donneurs de sang au moyen du test ELISA-TÉTANOS (São Paulo, SP, Bresil)

Le test ELISA-TÉTANOS (Biosys, France) a été utilisé pour le titrage des anti-corps tétaniques (sensibilité = 0,0025 UI/ml) en sérums humains de donneurs de sang, 566 hommes et 108 femmes, âges de 18 à 58 ans, moyenne de 29 ans, provenant de São Paulo, SP, Brésil. L'OMS, acceptant seulement la séroneutralisation sur souris (NT), la méthode de référence, pour les études sur la protection contre le tétanos, préconise le titre de 0,01 UI/ml comme minimum protecteur. BOURLEAUD & HUET ont proposé la limite de 0,06 UI/ml quand s'emploie le test ELISA, en attendant à une certaine discordance inévitable entre les méthodes. Parmi les 674 sérums étudiés, 178 (26,41%) n'ont pas présenté d'anticorps (< 0,0025 UI/ml); 413 (61,28%) ont présenté des résultats égaux ou supérieurs à 0,01 UI/ml et en 232 (34,42%) les titres ont été égaux ou supérieurs à 0,06 UI/ml. Le pourcentage d'individus protégés a été inversement proportionnel à 1'âge: environ 50% dans le groupe le plus jeune (hommes de 18 à 35 ans et femmes de 18 à 23 ans) contre environ 10% dans le groupe de plus de 42 ans ont présenté des titres sûrement protecteurs (> 0,06 UI/ml).

The value of adenosine deaminase (ADA) determination in the diagnosis of tuberculous ascites

In order to evaluate the role of the determination of adenosine deaminase activity (ADA) in ascitic fluid for the diagnosis of tuberculosis, 44 patients were studied. Based on biochemical, cytological, histopathological and microbiological tests, the patients were divided into 5 groups: G1 - tuberculous ascites (n = 8); G2 - malignant ascites (n = 13); G3 - spontaneous bacterial peritonitis (n = 6); G4 - pancreatic ascites (n = 2); G5 - miscelaneous ascites (n = 15). ADA concentration were significantly higher in G1 (133.50 ± 24.74 U/l) compared to the other groups (G2 = 41.85 ± 52.07 U/l; G3 = 10.63 ± 5.87 U/l; G4 = 18.00 ± 7.07 U/l; G5 = 11.23 ± 7.66 U/l). At a cut-off value of >31 U/l, the sensitivity, specificity and positive and negative preditive values were 100%, 92%, 72% and 100%, respectively. ADA concentrations as high as in tuberculous ascites were only found in two malignant ascites caused by lymphoma. We conclude that ADA determination in ascitic fluid is a useful and reliable screening test for diagnosing tuberculous ascites. Values of ADA higher than 31 U/l indicate more invasive methods to confirm the diagnosis of tuberculosis.

Sex Determination and Female Reproductive Development in the Genus Schistosoma: A Review

Parasites of the genus Schistosoma were among the first metazoans to develop separate sexes, which is chromosomally determined in the fertilized egg. Despite the occurrence of specific sex chromosomes, the females of most Schistosomatidae species do not complete their somatic development and reach no sexual maturity without the presence of males. Indeed, the most controversial and at the same time most fascinating aspect about the sexual development of Schistosoma females lies on discover the nature of the stimulus produced by males that triggers and controls this process. Although the nature of the stimulus (physical or chemical) is a source of controversy, there is agreement that mating is a necessary requirement for maturation to occur and for migration of the female to a definitive final site of residence in the vascular system of the vertebrate host. It has also been proposed that the stimulus is not species-specific and, in some cases, not even genus-specific. Despite a vast literature on the subject, the process or processes underlying the meeting of males and females in the circulatory system have not been determined and as yet no consensus exists about the nature of the stimulus that triggers and maintains female development. In the studies about their role, Schistosoma males have been considered, at times pejoratively, the brother, the muscles or even the liver of females. Indeed, it still remains to be determined whether the stimulus responsible for female maturation involves the transfer of hormones, nutrients, neuromediators, mere tactile stimulation or a combination of chemotactic and thigmotactic factors

ANTI M. leprae IgM ANTIBODY DETERMINATION BY ULTRAMICROIMMUNOENZYMATIC (UMELISA HANSEN) FOR THE DIAGNOSIS AND MONITORING LEPROSY

The relationship between the IgM antibody response, antigenic load as well as the clinical improvement after chemotherapy was studied in order to obtain useful data for the early diagnosis and monitoring leprosy. A level of 82% (94/115) agreement was obtained between IgM UMELISA HANSEN and slitskin smear examination. Discrepant results were observed in 16 patients who showed positive IgM response despite negative by the skin smear examination. In these patients, the IgM response was seen to be associated to the early signal for bacilli recurrence in the skin. In one of these patients the presence of bacilli was demonstrated in the skin, two months after IgM antibodies being detected by UMELISA HANSEN. Also in one of the treated patients positive by both diagnostic techniques, a remarkable decrease in the IgM antibody levels was seen, correlating with a significant clinical improvement. Moreover it was found a direct relationship between the IgM antibody response and bacterial antigenic load, regardless the time elapsed in the disease's evolution.

Serological diagnosis of toxoplasmosis: usefulness of IgA detection and IgG avidity determination in a patient with a persistent IgM antibody response to Toxoplasma gondii

We report the detection of specific IgA antibodies and the determination of IgG avidity in sequential serum samples from a patient exhibiting significant levels of Toxoplasma-specific IgM antibodies for seven years after the onset of the clinical symptoms of toxoplasmosis. IgM antibodies were detected by an indirect immunofluorescence test and by three commercial enzyme-linked immunosorbent assays (ELISA). Anti-T. gondii IgA was quantified by the a-capture ELISA technique using a commercial kit. As defined by the manufacturer of the IgA ELISA test used, most patients with acute toxoplasmosis have antibody levels > 40 arbitrary units per ml (AU/mL). At this cut-off level, the patient still had a positive ELISA result (45 AU/mL) in a serum sample taken one year after the beginning of clinical manifestations. The IgG avidity-ELISA test was performed with the Falcon assay screening test (F.A.S.T.®) - ELISA system. Avidity indices compatible with a recent Toxoplasma infection were found only in serum samples taken during the first 5 months after the onset of the clinical symptoms of toxoplasmosis. These results show that the interpretation of positive IgM results as indicative of recently acquired toxoplasmosis requires additional laboratory confirmation either by other tests or by the demonstration of a significant rise in the antibody titers in sequential serum samples.

Anti-phenolic glycolipid-I (PGL-I) determination using blood collection on filter paper in leprosy patients

The authors studied 70 leprosy patients and 20 normal individuals, comparing the traditional sera collection method and the finger prick blood with the conservation on filter paper for specific antibodies against the native phenolic glycolipid-I (PGL-I) from Mycobacterium leprae. The finger prick blood dried on filter paper was eluated in phosphate buffer saline (PBS) containing 0.5% gelatin. The classical method for native PGL-I was performed for these eluates, and compared with the antibody determination for sera. It was observed that there is a straight correlation comparing these two methods; although the titles found for the eluates were lower than those obtained for serology. This blood collection method could be useful for investigation of new leprosy cases in field, specially in contacts individuals.

Seroprevalence of hepatitis B virus infection in individuals with clinical evidence of hepatitis in Goiânia, Goiás: detection of viral DNA and determination of subtypes

The presence of serological markers for hepatitis B virus (HBsAg, anti-HBc IgM and Anti-HBc total) was investigated in the serum of 1,396 individuals who had clinical suspect of hepatitis. It was observed that 50.7% of the individuals were positive and, from the total of the studied individuals, 14.5% were positive for HBsAg. From these, 8.5% were also positive for anti-HBc IgM. The analysis in relation to gender showed a higher seroprevalence index among male individuals (p < 0.0001). It was observed the occurrence of subtypes adw2 (62.7%), ayw3 (23.5%), ayw2 (9.8%) and adw4 (3.9%). The viral DNA was detected in 61 (33.9%) HBsAg positive samples and in one sample positive only for anti-HBc total. These results indicate an important incidence of the HBV infection in this population, and reinforce previous studies regarding this virus in the central west region of Brazil.

Determination of human cytomegalovirus genetic diversity in different patient populations in Costa Rica

Seroprevalence of HCMV in Costa Rica is greater than 95% in adults; primary infections occur early in life and is the most frequent congenital infection in newborns. The objectives of this study were to determine the genetic variability and genotypes of HCMV gB gene in Costa Rica. Samples were collected from alcoholics, pregnant women, blood donors, AIDS patients, hematology-oncology (HO) children and HCMV isolates from neonates with cytomegalic inclusion disease. A semi-nested PCR system was used to obtain a product of 293-296 bp of the gB gene to be analyzed by Single Stranded Conformational Polymorphism (SSCP) and sequencing to determine the genetic polymorphic pattern and genotypes, respectively. AIDS patients showed the highest polymorphic diversity with 14 different patterns while fifty-six percent of HO children samples showed the same polymorphic pattern, suggesting in this group a possible nosocomial infection. In neonates three genotypes (gB1, gB2 and gB3), were determined while AIDS patients and blood donors only showed one (gB2). Of all samples analyzed only genotypes gB1, 2 and 3 were determined, genotype gB2 was the most frequent (73%) and mixed infections were not detected. The results of the study indicate that SSCP could be an important tool to detect HCMV intra-hospital infections and suggests a need to include additional study populations to better determine the genotype diversity and prevalence.