The Pf332 gene codes for a megadalton protein of Plasmodium falciparum asexual blood stages

We characterized the Plasmodium falciparum antigen 332 (Ag332) which is specifically expressed during the asexual intraerythrocytic cycle of the parasite. The corresponding Pf332 gene has been located in the subtelomeric region of chromosome 11. Furthermore, it is present in all strais so far analyzed and shows marked restriction length fragment polymorphism. Partial sequence and restriction endonuclease digestion of cloned fragments revealed that the Pf332 gene is composed of highly degenerated repeats rich is glutamic acid. Mung been nuclease digestion and Northern blot analysis suggested that Pf332 gene codes for a protein of about 700 kDa. These data were further confirmed by Western blot and immunoprecipitation of parasites extracts with an antiserum raised against a recombinant clone expressing part of the Ag332. Confocal immunofluorescence showed that Ag332 is translocated from the parasite to the surface of infected red blood cells within vesicle-like structures. In addition, Ag332 was detected on the surface of monkey erythrocytes infected with Plasmodium falciparum.

Gundlachia dutrae: n. sp. from northwest Brazil (Mollusca: Basommatophora: Ancylidae)

A new species of Gundlachia, Gundlachia dutrae is described from northwest Brazil. It is distinguishable from other congenerie species by characteristics of the shell, radula and internal organs. Shell relatively high. Aperture near-circular; periostracum dark brown without periostracal hairs. Apex slightly inclined to the right, projected but not hooked, with an apical depression surrounted by a sculpture of well-marked irregular punctations. Shell surface with prominent radial sculpture. No septate specimens were observed. Ratios (n= 59): shell width/shell lenght = 0,66- 0,79 (mean 0,73); shell height/shell length = 0,32- 0,45 ( mean 0,37); shell height/shell width = 0,43- 0,63 (mean 0,51). Body of normal ancylid type; mantle pigmentation dark brown or black, concentrated along the mantle collar. The dorsal surface of the right anterior muscle is elongated and medially constricted. The left anterior and the posterior muscles are almost elliptical. Adhesive area is V-shaped. Pseudobranch unpigmented bearing a very small and thin dorsal lobe. Ovotestis with more than 25 unbranched diverticula. Ovispermiduct with seminal vesicle rather developed. Elongated nidamental gland continous with the glandular wall of the uterus. Nidamental gland appendix ending into a bulbous swelling Spermathecal body almost rounded. Well-developed prostate with five long diverticula. Ejaculatory complex with long glandular flagellum, without a penis or true ultra-penis. "Penis sheath" developed. "Ultra-penis" projected as a tube inside the lumem of prepuce, with a slit between "ultra-penis" and "penis sheath". Rachidian tooth tetracuspid, with two median cusps assymmetrical and aculeated. Lateral teeth tricuspid, with a reduced endocon and a prominent mesocon. A well marked gap occurs between meso and ectocon. Marginal teeth similar to lateral ones. Jaw T-shaped, with about 28 dorsal plates.

Life history of Pygidiopsis crassus n. sp. (Trematoda, Digenea, Heterophyidae) in the neotropical region

The life cycle of Pygidiopsis crassus n. sp. was experimentally reproduced, starting from cercariae from naturally infected Littoridina parchappei collected from Lujan River and different ponds in Buenos Aires Province, Argentina. Metacercariae were found encysted in the body cavity of experimentally and naturally infected fishes Cnesterodon decemmaculatus and naturally infected Jenynsia lineata. Adults were obtained experimentally in chicks and mice. The natural host is unknown. The new species is compared with Pygidiopsis macrostomum Travassos 1928, from Rattus norvegicus and from Noctilio leporinus mastivus, differing in body and egg sizes, in the size relation of oral and ventral sucker and the shape of excretory vesicle.

N-terminal amino acid sequences of the major outer membrane proteins from a Neisseria meningitidis group B strain isolated in Brazil

The four dominant outer membrane proteins (46, 38, 33 and 28 kDa) were detected by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) in a semi-purified preparation of vesicle membranes of a Neisseria meningitidis (N44/89, B:4:P1.15:P5.5,7) strain isolated in Brazil. The N-terminal amino acid sequence for the 46 kDa and 28 kDa proteins matched that reported by others for class 1 and 5 proteins respectively, whereas the sequence (25 amino acids) for the 38 kDa (class 3) protein was similar to class 1 meningococcal proteins. The sequence for the 33 kDa (class 4) was unique and not homologous to any known protein.

Oswaldotrema nacinovici gen. nov. sp. nov. (Digenea: Philophthalmidae) from Numenius phaeopus (Aves: Scolopacidae) in Brazil

A new genus, Oswaldotrema gen. nov. is proposed. Oswaldotrema nacinovici sp. nov. is descibed from Numenius phaeopus Latham, 1790. Differentiation from the other related genera, namely Philophthalmus, Pygorchis, Proctobium, Parorchis, Echinostephila, Cloacitrema, Pittacium, Ophthalmotrema, Skrjabinovermis and Paratrema, was based on morphological characters, mainly on those referring to the body surface, body shape, head, esophagus, pharynx, acetabulum, vitellaria, vitelline reservoir and seminal vesicle.

Antigen incorporation on Cryptosporidium parvum oocyst walls

Cryptosporidium parvum oocysts are the infective stages responsible for transmission and survival of the organism in the environment. In the present work we show that the oocyst wall, far from being a static structure, is able to incorporate antigens by a mechanism involving vesicle fusion with the wall, and the incorporation of the antigen to the outer oocyst wall. Using immunoelectron microscopy we show that the antigen recognized by a monoclonal antibody used for diagnosis of cryptosporidiosis (Merifluor®, Meridian Diagnostic Inc.) could be found associated with vesicles in the space between the sporozoites and the oocysts wall, and incorporated to the outer oocyst wall by an unknown mechanism.

Genitourinary changes in hamsters infected and reinfected with Trypanosoma cruzi

Authors describe genitourinary changes in male hamsters infected and reinfected with Trypanosoma cruzi. Changes in genital organs have been described in human and in experimental chagasic infection. Genital dysfunctions in chronic chagasic patients affect ejaculation, libido and sexual potency, and testis biopsies may show arrested maturation of germ cells, oligozoospermia and azoospermia. Sixty-five male hamsters were inoculated and reinoculated with 2x10³ trypomastigotes of T. cruzi VIC strain, and 22 non-infected animals constituted the control group. Animals were necropsied and fragments from testis, epididymis, seminal vesicle and bladder were collected and stained with hematoxylin-eosin. Peroxidase anti-peroxidase procedure was utilized to detect tissue parasitism. T. cruzi nests were found in testis, epididymis and seminal vesicle of these hamsters. Such parasitism plays a role in the origin of genital lesions observed in humans and laboratory animals during chronic chagasic infection.

The effects of drugs, ions, and poly-l-lysine on the excretory system of Schistosoma mansoni

We have been able to label the excretory system of cercariae and all forms of schistosomula, immature and adult worms with the highly fluorescent dye resorufin. We have shown that the accumulation of the resorufin into the excretory tubules and collecting ducts of the male adult worm depends on the presence of extracellular calcium and phosphate ions. In the adult male worms, praziquantel (PZQ) prevents this accumulation in RPMI medium and disperses resorufin from tubules which have been prelabelled. Female worms and all other developmental stages are much less affected either by the presence of calcium and phosphate ions, or the disruption caused by PZQ. The male can inhibit the excretory system in paired female. Fluorescent PZQ localises in the posterior gut (intestine) region of the male adult worm, but not in the excretory system, except for the anionic carboxy fluorescein derivative of PZQ, which may be excreted by this route. All stages of the parasite can recover from damage by PZQ treatment in vitro. The excretory system is highly sensitive to damage to the surface membrane and may be involved in vesicle movement and damage repair processes. In vivo the adult parasite does not recover from PZQ treatment, but what is inhibiting recovery is unknown, but likely to be related to immune effector molecules.

Assessing protein stability of the dimeric DNA-binding domain of E2 human papillomavirus 18 with molecular dynamics

The objective of this study is to understand the structural flexibility and curvature of the E2 protein of human papillomavirus type 18 using molecular dynamics (6 ns). E2 is required for viral DNA replication and its disruption could be an anti-viral strategy. E2 is a dimer, with each monomer folding into a stable open-faced β-sandwich. We calculated the mobility of the E2 dimer and found that it was asymmetric. These different mobilities of E2 monomers suggest that drugs or vaccines could be targeted to the interface between the two monomers.

Prokaryotic cells: structural organisation of the cytoskeleton and organelles

For many years, prokaryotic cells were distinguished from eukaryotic cells based on the simplicity of their cytoplasm, in which the presence of organelles and cytoskeletal structures had not been discovered. Based on current knowledge, this review describes the complex components of the prokaryotic cell cytoskeleton, including (i) tubulin homologues composed of FtsZ, BtuA, BtuB and several associated proteins, which play a fundamental role in cell division, (ii) actin-like homologues, such as MreB and Mb1, which are involved in controlling cell width and cell length, and (iii) intermediate filament homologues, including crescentin and CfpA, which localise on the concave side of a bacterium and along its inner curvature and associate with its membrane. Some prokaryotes exhibit specialised membrane-bound organelles in the cytoplasm, such as magnetosomes and acidocalcisomes, as well as protein complexes, such as carboxysomes. This review also examines recent data on the presence of nanotubes, which are structures that are well characterised in mammalian cells that allow direct contact and communication between cells.

Chemical changes in argisols under irrigated grape production in the central São Francisco river valley, Brazil

This study compares the chemical composition of the solution and exchange complex of soil in a 3-year-old irrigated vineyard (Vitis vinifera L., Red Globe cultivar) with that of adjacent clearing in the native hyperxerophyllic 'caatinga' vegetation. The soils are classified as Plinthic Eutrophic Red-Yellow Argisol; according to Soil Taxonomy they are isohyperthermic Plinthustalfs. Detailed physiographic characterization revealed an impermeable gravel and cobble covering the crystalline rocks; the relief of this layer was more undulating than the level surface. Significant higher concentrations of extractable Na, K, Mg and Ca were observed within the vineyard. Lower soil acidity, higher Ca/Mg ratios, as well as lower sodium adsorption and Na/K ratios reflected additions of dolomitic lime, superphosphate and K-bearing fertilizers. As the water of the São Francisco River is of good quality for irrigation (C1S1), the increases in Na were primarily attributed to capillary rise from the saline groundwater table. None of the soil in the study area was found to be sodic. About 62% of the vineyard had an Ap horizon with salinity levels above 1.5dSm-1 (considered detrimental for grape production); according to average values for this horizon, a potential 13% reduction in grape production was predicted. Differences in chemical composition in function of distance to the collector canals were observed in the clearing, but not in the vineyard. The influence of differences in the elevations of the surface and impermeable layers, as well as pediment thickness, was generally weaker under irrigation. Under irrigation, soil moisture was greater in points of convergent surface waterflow; the effect of surface curvature on chemical properties, though less consistent, was also stronger in the vineyard.

Computer-assisted cartography using topographic properties: precision and accuracy of local soil maps in central Mexico

Map units directly related to properties of soil-landscape are generated by local soil classes. Therefore to take into consideration the knowledge of farmers is essential to automate the procedure. The aim of this study was to map local soil classes by computer-assisted cartography (CAC), using several combinations of topographic properties produced by GIS (digital elevation model, aspect, slope, and profile curvature). A decision tree was used to find the number of topographic properties required for digital cartography of the local soil classes. The maps produced were evaluated based on the attributes of map quality defined as precision and accuracy of the CAC-based maps. The evaluation was carried out in Central Mexico using three maps of local soil classes with contrasting landscape and climatic conditions (desert, temperate, and tropical). In the three areas the precision (56 %) of the CAC maps based on elevation as topographical feature was higher than when based on slope, aspect and profile curvature. The accuracy of the maps (boundary locations) was however low (33 %), in other words, further research is required to improve this indicator.

Comparison between artificial neural networks and maximum likelihood classification in digital soil mapping

Soil surveys are the main source of spatial information on soils and have a range of different applications, mainly in agriculture. The continuity of this activity has however been severely compromised, mainly due to a lack of governmental funding. The purpose of this study was to evaluate the feasibility of two different classifiers (artificial neural networks and a maximum likelihood algorithm) in the prediction of soil classes in the northwest of the state of Rio de Janeiro. Terrain attributes such as elevation, slope, aspect, plan curvature and compound topographic index (CTI) and indices of clay minerals, iron oxide and Normalized Difference Vegetation Index (NDVI), derived from Landsat 7 ETM+ sensor imagery, were used as discriminating variables. The two classifiers were trained and validated for each soil class using 300 and 150 samples respectively, representing the characteristics of these classes in terms of the discriminating variables. According to the statistical tests, the accuracy of the classifier based on artificial neural networks (ANNs) was greater than of the classic Maximum Likelihood Classifier (MLC). Comparing the results with 126 points of reference showed that the resulting ANN map (73.81 %) was superior to the MLC map (57.94 %). The main errors when using the two classifiers were caused by: a) the geological heterogeneity of the area coupled with problems related to the geological map; b) the depth of lithic contact and/or rock exposure, and c) problems with the environmental correlation model used due to the polygenetic nature of the soils. This study confirms that the use of terrain attributes together with remote sensing data by an ANN approach can be a tool to facilitate soil mapping in Brazil, primarily due to the availability of low-cost remote sensing data and the ease by which terrain attributes can be obtained.

Artificial neural networks applied for soil class prediction in mountainous landscape of the Serra do Mar¹

Soil information is needed for managing the agricultural environment. The aim of this study was to apply artificial neural networks (ANNs) for the prediction of soil classes using orbital remote sensing products, terrain attributes derived from a digital elevation model and local geology information as data sources. This approach to digital soil mapping was evaluated in an area with a high degree of lithologic diversity in the Serra do Mar. The neural network simulator used in this study was JavaNNS and the backpropagation learning algorithm. For soil class prediction, different combinations of the selected discriminant variables were tested: elevation, declivity, aspect, curvature, curvature plan, curvature profile, topographic index, solar radiation, LS topographic factor, local geology information, and clay mineral indices, iron oxides and the normalized difference vegetation index (NDVI) derived from an image of a Landsat-7 Enhanced Thematic Mapper Plus (ETM+) sensor. With the tested sets, best results were obtained when all discriminant variables were associated with geological information (overall accuracy 93.2 - 95.6 %, Kappa index 0.924 - 0.951, for set 13). Excluding the variable profile curvature (set 12), overall accuracy ranged from 93.9 to 95.4 % and the Kappa index from 0.932 to 0.948. The maps based on the neural network classifier were consistent and similar to conventional soil maps drawn for the study area, although with more spatial details. The results show the potential of ANNs for soil class prediction in mountainous areas with lithological diversity.

Lipossomas: a bala mágica acertou?

Efficient drug delivery systems are as important as drug themselves. A powerful drug unable to reach the target cell is useless in practice. Ehrlich's Magic Bullet was the first carrier system to be proposed. The evolution in this domain has been quite slow as the natural mechanisms of mammals against foreign products are hard to overcome. However, lipid-based systems (liposomes and related vesicles) have attained reasonable success. The basic preparations and structural features of liposomes and related vesicles as well as their applications are addressed from the chemist's and biochemist's point of view.