Purification of Tissue Forms (Amastigotes) of Trypanosoma cruzi by Immunoaffinity Chromatography1

A rapid and simple method for the purification of amastigotes of Trypanosoma cruzi from spleens of infected mice is described. A protein A-Scpharose 4B immunoadsorbent column bound with antisera to epimastigotes of T. cruzi was used to purify the tissue forms of this parasite. Host cells and debris are not retained, and parasites can be eluted in high yields and purity. Studies of surface glycoproteins and glycolipids of the purified amastigotes with 18 lectins of various specificities revealed the presence on the parasites of receptors for N-acetylglucosamine, N-acetylgalactosamine, D-galactose, and D-mannose binding lectins.     

Chemical composition and larvicidal activity of essential oils of three Artemisia species

Aedes aegypti L. (Diptera: Culicidae) is a vector for serious diseases in tropical regions. This pest is mainly controlled by commercial larvicides but the application of such products has led to environmental problems. Essential oils (EO) have been consistently reported as molecules with insecticidal activity and can be used to produce more environmentally friendly larvicides in the control of A. aegypti. In this study, the larvicidal effect of essential oils (EO) from the leaves of three Artemisia species was evaluated against A. aegypti. The oils were obtained from steam distillation and their chemical composition was determined by gas chromatography–mass spectrometry. The EO of Artemisia camphorata was the most active in the screening bioassay and presented LC₅₀ and LC₉₅ of 64.95 and 74.18 μg ml⁻¹, respectively. In addition, we found that germacrene D-4-ol was the constituent responsible for the toxicity of this EO. Artemisia camphorata EO and its major constituent, germacrene D-4-ol, are promising for the development of natural larvicides against A. aegypti.     

The legacy of forest logging on organic matter inputs and storage in tropical streams

Riparian forests play an important role in stream ecosystems, as they support biodiversity, reduce water erosion, and provide litter that fuels aquatic biota. However, they are affected by great array of anthropogenic threats (e.g., fire, logging, and organic pollution), which alter species composition and their physical structure. Although forest recovery after disturbance such as logging can take decades, the legacy of forest clear-cut logging on key processes in tropical riparian ecosystems is mostly unknown. Here, we investigated how litter inputs (leaves, twigs, and reproductive parts) and storage, key processes for carbon and nutrient recycling and for forest and stream biota, are influenced by riparian vegetation undergoing succession (after 28 years from logging) through the comparison of reference and logged forest sites in the Cerrado biome. Litterfall was overall similar between forest types, but litterfall of twigs was twofold higher at logged than reference sites. Similarly, litter inputs from the bank to the stream (i.e., lateral inputs) and streambed storage were 50–60% higher at logged than reference sites. The higher litterfall observed in logged forests could be related to higher proportion of tree species that are characteristic of primary and secondary successional stages, including fast-growing and liana species, which often are more productive and common in anthropogenic areas. Our results showed that the legacy impact of clear-cut logging, even if residual woody vegetation is maintained in riparian buffers, can shift the type, quantity, and seasonality of litter subsidies to tropical streams. This knowledge should be considered within the context of management and conservation of communities and ecosystem processes in the forest-stream interfaces.     

Evaluation of Probiotic Properties of Novel Brazilian Lactiplantibacillus plantarum Strains

Probiotics and Antimicrobial Proteins - Beneficial effects of Lactiplantibacillus plantarum strains have been widely reported. Knowing that the effects of probiotic bacteria are strain-dependent,...     

A new survey of Brazilian marine algae for agglutinins

Aqueous protein extracts from 30 Brazilian marine algae were examined for haemagglutinating activity using native and enzyme-treated rabbit, chicken, sheep and human erythrocytes. Most extracts agglutinated at least one of the blood cells used. Sheep and rabbit erythrocytes were more suitable for detection of the agglutinating activity. The minimum protein concentration necessary to produce positive agglutination was usually lower with enzyme-treated erythrocytes than native ones. The five algal protein extracts showing the greatest haemagglutination titre were tested for sugar-binding specificity. Only the activity present in the green alga Cauler pacupressoides was inhibited by simple sugars and not by the glycoproteins tested. The activity of the other four extracts was inhibited by at least one of the glycoproteins utilised. This revised version was published online in August 2006 with corrections to the Cover Date.     

Diet crude protein reduction on follicular fluid and cumulus-oocyte complexes of mid-lactating Girolando cows

This study evaluated the effect of crude protein (CP) reduction in four diets (156, 139, 132, and 127 g Kg^-1 DM) maintaining constant metabolizable protein (188 g/day) on the follicular fluid and cumulus-oocyte complexes of mid-lactating Girolando cows. Twenty-two Girolando cows with average of 21.55 ±3.19 L daily milk yield, 105.30 ±22.62 days in lactation and 3.22 ±0.03 body condition score were selected. To reduce CP in diets and maintain constant metabolizable protein, urea and soybean meal were gradually replaced by lignosulfonate-treated soybean meal (SoyPass^®, Cargill), resulting in an increase in rumen-undegradable protein and a reduction in rumen degradable protein. A linear and quadratic reduction was observed in the plasma and follicular fluid urea nitrogen concentration following CP reduction, with the most intense reduction occurring in the 127 g Kg^-1 DM group (p<0.001). As CP reduced, there was a tendency for a linear increase in the follicular growth rate (P=0.0696), on the number and proportion of viable oocytes (P<0.09), and also a linear increase for the number (P=0.0397) and proportion (P<0.09) of grade I viable oocytes. Plus, there was a linear effect for the number of cumulus oophorus cells. Cows fed with the lowest amount of CP had cumulus-oocyte complexes with higher numbers of cumulus oophorus cells (P=0.0238). Also, the reduction of diet crude protein was followed by a decrease in the probability of oocytes’ DNA degradation. In conclusion, the reduction of CP in the diet of mid-lactating Girolando cows, reduces urea nitrogen concentration in both blood plasma and follicular fluid, and, as a consequence, increases the viability of oocytes and the number of cumulus oophorus cells while reducing oocytes’ DNA degradation of follicular included cumulus-oocyte complex. The reduction on dietary CP may improve in vivo oocytes’ embryo development impacting fertility of lactating dairy cows.     

Reduced plasma angiotensin II levels are reversed by hydroxyurea treatment in mice with sickle cell disease

Aims

Sickle cell disease (SCD) pathogenesis leads to recurrent vaso-occlusive and hemolytic processes, causing numerous clinical complications including renal damage. As vasoconstrictive mechanisms may be enhanced in SCD, due to endothelial dysfunction and vasoactive protein production, we aimed to determine whether the expression of proteins of the renin–angiotensin system (RAS) may be altered in an animal model of SCD.

Main methods

Plasma angiotensin II (Ang II) was measured in C57BL/6 (WT) mice and mice with SCD by ELISA, while quantitative PCR was used to compare the expressions of the genes encoding the angiotensin-II-receptors 1 and 2 (AT1R and AT2R) and the angiotensin-converting enzymes (ACE1 and ACE2) in the kidneys, hearts, livers and brains of mice. The effects of hydroxyurea (HU; 50–75 mg/kg/day, 4 weeks) treatment on these parameters were also determined.

Key findings

Plasma Ang II was significantly diminished in SCD mice, compared with WT mice, in association with decreased AT1R and ACE1 expressions in SCD mice kidneys. Treatment of SCD mice with HU reduced leukocyte and platelet counts and increased plasma Ang II to levels similar to those of WT mice. HU also increased AT1R and ACE2 gene expression in the kidney and heart.

Significance

Results indicate an imbalanced RAS in an SCD mouse model; HU therapy may be able to restore some RAS parameters in these mice. Further investigations regarding Ang II production and the RAS in human SCD may be warranted, as such changes may reflect or contribute to renal damage and alterations in blood pressure.     

Distribution dynamics of South American savanna birds in response to Quaternary climate change

Several lines of evidence suggest that savannas currently distributed disjointedly in the southern and northern portions of South America might have been connected and disconnected many times during the Quaternary climatic fluctuations. Here, we investigated how climate change since the Last Interglacial may have modified the distribution of bird species associated with South American savannas. We evaluated the connections between South America's savannas using 10 broadly distributed species and the impact of climate changes in community composition using 18 species endemic to Cerrado. We fit ecological niche models to each of the 28 bird species to compare the potential distribution patterns for the Last Interglacial (120 kyr BP), the Last Glacial Maximum (21 kyr BP) and the present. Our results corroborated hypotheses of past connections between northern and southern blocks of savannas through three hypothetical corridors that existed along the Andes, Atlantic Coast and through central Amazonia. In addition, our results also suggested the existence of a fourth plausible corridor located along the Madeira River, crossing Amazonia from the southwest to the northeast. Finally, our analysis showed significant changes in the community composition dynamics of endemic Cerrado species. Our results further reinforce the notion that climate change has major impacts on the distribution of savanna species.