Typing and susceptibility to penicillin of Neisseria meningitidis isolated from patients in Cuba (1993-1999)

The susceptibility to penicillin of 111 Neisseria meningitidis strains was assessed by the agar-dilution procedure and serosubtypes were determined by a whole-cell enzyme-linked immunoassay using monoclonal antibodies reagents. Thirty-five isolates showed reduced sensitivity to penicillin (MIC > or = 0.1 mg/l and <= 1 mg/l) and no resistant strains were detected. The most common phenotype was B:4:P1.15 (77.5%) and a rising trend of non-typeable and non-subtypeable strains was detected. The increase in levels of minimal inhibitory concentrations of meningococci to penicillin gives cause for concern and the increase in non-typeable and non-subtypeable isolation demand the use of molecular biology techniques for their typing.

The identification and characterization of new immunogenic egg components: implications for evaluation and control of the immunopathogenic T cell response in schistosomiasis

In schistosomiasis, granuloma formation to parasite eggs signals the beginning of a chronic and potentially life-threatening disease. Granulomas are strictly mediated by CD4+ T helper (Th) cells specific for egg antigens; however, the number and identity of these T cell-sensitizing molecules are largely unknown. We have used monoclonal T cell reagents derived from egg-sensitized individuals as probes to track down, isolate and positively identify several egg antigens; this approach implicitly assures that the molecules of interest are T cell immunogens and, hence, potentially pathogenic. The best studied and most abundant egg component is the Sm-p40 antigen. Sm-p40 and its peptide 234-246 elicit a strikingly immunodominant Th-1-polarized response in C3H and CBA mice, which are H-2k strains characterized by severe egg-induced immunopathology. Two additional recently described T cell-sensitizing egg antigens are Schistosoma mansoni phosphoenolpyruvate carboxykinase (Sm-PEPCK) and thioredoxin peroxidase-1 (Sm-TPx-1). In contrast to Sm-p40, both of these molecules induce a more balanced Th-1/Th-2 response, and are relatively stronger antigens in C57BL/6 mice, which develop smaller egg granulomas. Importantly, Sm-p40 and Sm-PEPCK have demonstrated immunogenicity in humans. The findings in the murine model introduce the important notion that egg antigens can vary significantly in immunogenicity according to the host's genetic background. A better knowledge of the principal immunogenic egg components is necessary to determine whether the immune responses to certain antigens can serve as indicators or predictors of the form and severity of clinical disease, and to ascertain whether such responses can be manipulated for the purpose of reducing pathology.

Epidemiological and Serological Aspects in Canine Toxoplasmosis in Animals with Nervous Symptoms

The presence of anti-Toxoplasma gondii IgM and IgG antibodies was studied in samples of blood serum taken from eighty dogs with nervous symptoms at the Serviço de Enfermidades Infecciosas dos Animais, Faculdade de Medicina Veterinária e Zootecnia, Unesp, Botucatu, São Paulo, Brazil. The frequency of IgG titers were 16 (13.7%), 64 (13.7%), and 256 (5%), and for IgM titers were 16 (7.5%), 64 (15%), and 256 (8.7%). Positive reactions were more frequent in the older animals, males, from a rural environment, in constant contact with small animals, principally birds and rodents. There was a higher frequency of a positive reaction in dogs fed with kitchen food, especially in those fed with raw ingredients. The most common neurological pictures were alterations in consciousness, in movement, and in the hand-cart test. The percentage of reagents with specific IgM antibodies was high, indicating active infections, but the possibility of co-infection with the distemper virus can not be discarded, and this may be a predisposing factor for toxoplasmosis infection, once the distemper virus has a potent immunosupressive action.

HIV-1 Polymorphism: a Challenge for Vaccine Development - A Review

The perspective for the development of anti-HIV/AIDS vaccines became a target sought by several research groups and pharmaceutical companies. However, the complex virus biology in addition to a striking genetic variability and the limited understanding of the immunological correlates of protection have made this an enormous scientific challenge not overcome so far. In this review we presented an updating of HIV-1 subtypes and recombinant viruses circulating in South American countries, focusing mainly on Brazil, as one of the challenges for HIV vaccine development. Moreover, we discussed the importance of stimulating developing countries to participate in the process of vaccine evaluation, not only testing vaccines according to already defined protocols, but also working together with them, in order to take into consideration their local information on virus diversity and host genetic background relevant for the vaccine development and testing, as well as including local virus based reagents to evaluate the immunogenicity of the candidate vaccines.

Evaluation of the direct agglutination test and the rK39 dipstick test for the sero-diagnosis of visceral leishmaniasis

The direct agglutination test (DAT) based on a freeze-dried antigen and the rK39 dipstick test were evaluated for the sero-diagnosis of visceral leishmaniasis (VL). The sensitivity and specificity of both tests were determined using sera from confirmed VL patients (n = 21), healthy controls (n = 19) and from patients with other confirmed infectious diseases (n = 42). The DAT had a sensitivity and a specificity of 100%. The rK39 had a sensitivity of 85.7% and a specificity of 82%. Both tests were also used to screen blood samples of confirmed VL patients (n = 15) and serum samples of VL suspects (n = 61). The DAT found all blood samples of confirmed VL patients positive and tested 98.4% of the serum samples of the VL suspects positive. In contrast, rK39 detected in 9/15 blood samples (60%) antibodies against Leishmania chagasi and found 85.3% of the serum samples of the suspected patients positive. Although the rK39 dipstick is more rapid and user friendlier than the DAT, the latter has a superior sensitivity and specificity. Furthermore, the reagents used for DAT do not require cold storage, whereas the buffer of the rK39 must be stored at 4ºC. Therefore, the DAT is the most suitable test for the sero-diagnosis of VL under field conditions.

Proteomic analysis of the shistosome tegument and its surface membranes

The tegument surface of the adult schistosome, bounded by a normal plasma membrane overlain by a secreted membranocalyx, holds the key to understanding how schistosomes evade host immune responses. Recent advances in mass spectrometry (MS), and the sequencing of the Schistosoma mansoni transcriptome/genome, have facilitated schistosome proteomics. We detached the tegument from the worm body and enriched its surface membranes by differential extraction, before subjecting the preparation to liquid chromatography-based proteomics to identify its constituents. The most exposed proteins on live worms were labelled with impearmeant biotinylation reagents, and we also developed methods to isolate the membranocalyx for analysis. We identified transporters for sugars, amino acids, inorganic ions and water, which confirm the importance of the tegument plasma membrane in nutrient acquisition and solute balance. Enzymes, including phosphohydrolases, esterases and carbonic anhydrase were located with their catalytic domains external to the plasma membrane, while five tetraspanins, annexin and dysferlin were implicated in membrane architecture. In contrast, few parasite proteins could be assigned to the membranocalyx but mouse immune response proteins, including three immunoglobulins and two complement factors, were detected, plus host membrane proteins such as CD44, integrin and a complement regulatory protein, testifying to the acquisitive properties of the secreted bilayer.

Advances in understanding immunity to Toxoplasma gondii

Toxoplasma gondii is an important cause of clinical disease in fetuses, infants and immunocompromised patients. Since the discovery of T. gondii 100 years ago, this pathogen and the host's immune response to toxoplasmosis have been studied intensely. This has led to the development of a working model of immunity to T. gondii, and has also resulted in fundamental new insights into the role of various cytokines in resistance to infection. By examining this organism, researchers have identified many of the requirements for resistance to intracellular pathogens and characterized numerous regulatory factors, including interleukin-10 (IL-10) and IL-27, which control inflammatory processes. In the next 100 years of T. gondii immunobiology, researchers will have the opportunity to answer some of the long-standing questions in the field using new techniques and reagents. These future studies will be vital in building a more comprehensive model of immunity to this pathogen and in advancing our understanding of immunoregulation, particularly in humans. Ultimately, the challenge will be to use this information to develop new vaccines and therapies to manage disease in affected patients.

Oocyst wall formation and composition in coccidian parasites

The oocyst wall of coccidian parasites is a robust structure that is resistant to a variety of environmental and chemical insults. This resilience allows oocysts to survive for long periods, facilitating transmission from host to host. The wall is bilayered and is formed by the sequential release of the contents of two specialized organelles - wall forming body 1 and wall forming body 2 - found in the macrogametocyte stage of Coccidia. The oocyst wall is over 90% protein but few of these proteins have been studied. One group is cysteine-rich and may be presumed to crosslink via disulphide bridges, though this is yet to be investigated. Another group of wall proteins is rich in tyrosine. These proteins, which range in size from 8-31 kDa, are derived from larger precursors of 56 and 82 kDa found in the wall forming bodies. Proteases may catalyze processing of the precursors into tyrosine-rich peptides, which are then oxidatively crosslinked in a reaction catalyzed by peroxidases. In support of this hypothesis, the oocyst wall has high levels of dityrosine bonds. These dityrosine crosslinked proteins may provide a structural matrix for assembly of the oocyst wall and contribute to its resilience.

Um fotômetro de fluxo para análises clínicas a base de um diodo emissor de luz bicolor

The construction and evaluation of an inexpensive flow photometer for clinical analysis, using a bicolour LED and a phototransistor adapted for tubular flow cell, are described. The instrument presents some new features such as: automatic zero, electronic calibration and peak-hold signal. When compared with a classical photometer, it is simpler and has the advantages of a flow analysis system: lower volumes of reagents and samples, lower levels of contamination, shorter time for analysis and lower analysis costs. The instrument was used in the determination of the constituents in blood samples. The results obtained agree with those obtained by a classical photometer and the precision was better.

Multicomutação e amostragem binária em análise química em fluxo: determinação espectrofotométrica de ortofosfato em águas naturais

A flow system based on multicommutation and binary sampling process was developed to implement the sample zone trapping technique in order to increase the spectrophotometric analytical range and to improve sensitivity. The flow network was designed with active devices in order to provide facilities to determine sequentialy analyte with a wide concentration range, employing a single pumping channel to propel sample and reagents solutions. The procedure was employed to determine ortophosphate ions in water samples of river and waste. Profitable features such as an analytical throughput of 60 samples determination per hour, relative standard deviation (r.s.d.) of 2% (n = 6) for a typical sample with concentration of 2.78 mg/L were achieved. By applying the paired t-test no significant difference at 95% confidence level was observed between the results obtained with the proposed system and those of the usual flow injection system.

Análise de extratos de plantas por CCD: uma metodologia aplicada à disciplina "química orgânica"

extracts of the regional plants Annona squamosa and Annona muricata were analysed by silica gel thin-layer chromatography using adequate systems of solvents and spray reagents. Carbohydrates, amino acids, alkaloids, flavonoids and terpenoids were detected in both species. These data agree with those on the literature about phytochemistry of the Annonaceae.

Determinação simultânea de cobalto e níquel

The simultaneous determination of cobalt and nickel is a classical analytical problem. A great number of reagents associated with several techniques of analysis have been applied to achieve this determination. In this review 117 references, which appeared between 1996-1980, are described and classified according to the technique applied.

Abordagens em síntese assimétrica

The approaches in asymmetric synthesis as the chiron approach, chiral auxiliaries, chiral reagents and asymmetric catalysis are described in a simplified way.

Titulador potenciométrico automatizado baseado em sistema de fluxo monossegmentado

A new automated system for acid-base flow titrations is proposed. In the operation mode, several sample to titrant volumetric ratios are injected in an air segmented plug. Five three way solenoid valves and three acrilic junctions, assembled in a hidrodynamic injection system, were accountable for the monosegmented reagents plug formation. A turbulent flow reactor was used for a perfect mix of reagents in the plug. The detector system employed a glass combined electrode fitted in an acrilic holder. Titrations of hydrochloric, nitric and acetic acids, in several concentrations, were performed with standard sodium hidroxide, for evaluation of the efficiency of the system. The relative standard deviation of the determinations was about ±0,5% and each titration was carried out in 3-4 minutes. A Quick BASIC 4.5® program was developed for the titrator control.

Estudo comparativo da seletividade de um método cinético-catalítico: a determinação de Cr(VI) pela oxidação da o-dianisidina pelo peróxido de hidrogênio

Selectivity studies for the determination of Cr(VI) using the catalytic oxidation of the o-dianisidine by hydrogen peroxide showed two distincts situations. In the first, when interferents were studied by a univariate procedure, Cr(III) and Cu(II) cause serious interferences even at the 2:1 proportion, relative to Cr(VI), while Fe(III) interfered at the 15:1 ratio and EDTA at the 10:1 ratio. On the other hand, when a multivariate investigation was performed, Cr(III) did not present any significant principal effects and its significant interaction effects were negative, in contrast to EDTA, that presented positive interaction effects although, like Cr(III), did not show significant interaction effects. In view of the interferent's action it become necessary to separate Cr(VI) by extraction with methylisobutylketone in a chloridric acid medium before its determination in vegetals and in wastewater from a cellulose industry samples. Using this procedure, the method precision is ±0,5% at the 10 ng/mL Cr(VI) concentration level. The detection and quantification limits, calculated by means of absorbance measurements of ten replicates of blank reagents were 1,1 and 3,2 ng/mL, respectively. The results obtained with real samples showed a relative standard deviation between 1,2% and 3,0% relative to their reference values.