Ultrasound imaging in an experimental model of fatty liver disease and cirrhosis in rats

Background

Atypical scrapie was first identified in Norwegian sheep in 1998 and has subsequently been identified in many countries. Retrospective studies have identified cases predating the initial identification of this form of scrapie, and epidemiological studies have indicated that it does not conform to the behaviour of an infectious disease, giving rise to the hypothesis that it represents spontaneous disease. However, atypical scrapie isolates have been shown to be infectious experimentally, through intracerebral inoculation in transgenic mice and sheep. The first successful challenge of a sheep with 'field' atypical scrapie from an homologous donor sheep was reported in 2007.

Results

This study demonstrates that atypical scrapie has distinct clinical, pathological and biochemical characteristics which are maintained on transmission and sub-passage, and which are distinct from other strains of transmissible spongiform encephalopathies in the same host genotype.

Conclusions

Atypical scrapie is consistently transmissible within AHQ homozygous sheep, and the disease phenotype is preserved on sub-passage.     

T-cell responses associated with resistance to Leishmania infection in individuals from endemic areas for Leishmania (Viannia) braziliensis

Subclinical or asymptomatic infection is documented in individuals living in endemic areas for leishmaniasis suggesting that the development of an appropriate immune response can control parasite replication and maintain tissue integrity. A low morbidity indicates that intrinsic factors could favor resistance to Leishmania infection. Herein, leishmanial T-cell responses induced in subjects with low susceptibility to leishmaniasis as asymptomatic subjects were compared to those observed in cured cutaneous leishmaniasis (CCL) patients, who controlled the disease after antimonial therapy. All of them have shown maintenance of specific long-term immune responses characterized by expansion of higher proportions of CD4+ as compared to CD8+ Leishmania reactive T-lymphocytes. Asymptomatic subjects had lower indexes of in vitro Leishmania induced lymphoproliferative responses and interferon-gamma (IFN-gamma) production in comparison to CCL patients. On the other hand, interleukin (IL-10) production was much higher in asymptomatics than in CCL, while no differences in IL-5 levels were found. In conclusion, long lived T-cell responses achieved by asymptomatic individuals differed from those who had developed symptomatic leishmaniasis in terms of intensity of lymphocyte activation (proliferation or IFN-gamma) and regulatory mechanisms (IL-10). The absence of the disease in asymptomatics could be explained by their intrinsic ability to create a balance between immunoregulatory (IL-10) and effector cytokines (IFN-gamma), leading to parasite destruction without producing skin tissue damage. The establishment of profiles of cell-mediated immune responses associated with resistance against Leishmania infection is likely to make new inroads into understanding the long-lived immune protection against the disease.     

Transformation efficiency of RasQ61 mutants linked to structural features of the switch regions in the presence of Raf

Transformation efficiencies of Ras mutants at residue 61 range over three orders of magnitude, but the in vitro GTPase activity decreases 10-fold for all mutants. We show that Raf impairs the GTPase activity of RasQ61L, suggesting that the Ras/Raf complex differentially modulates transformation. Our crystal structures show that, in transforming mutants, switch II takes part in a network of hydrophobic interactions burying the nucleotide and precatalytic water molecule. Our results suggest that Y32 and a water molecule bridging it to the gamma-phosphate in the wild-type structure play a role in GTP hydrolysis in lieu of the Arg finger in the absence of GAP. The bridging water molecule is absent in the transforming mutants, contributing to the burying of the nucleotide. We propose a mechanism for intrinsic hydrolysis in Raf-bound Ras and elucidate structural features in the Q61 mutants that correlate with their potency to transform cells.     

Masticatory muscular activation in elderly individuals during chewing

Background: Old‐age is the last stage of human evolution and, unfortunately, the ageing of the oral cavity and masticatory system seems accelerated. As a consequence, there is a reduction in the amount of food ingested, which can lead to an imbalance in nutrition. Objective: The purpose of this study was to investigate the levels of muscular activation of elderly individuals, during chewing, and to compare with young individuals. Materials and Methods: An electromyographical analysis of the masticatory system in 10 individuals aged between 60 and 75 years (elderly group) and a similar number between 23–30 years old (young group ‐ control) was carried out. The analysis was performed using a MyoSystem‐Br1 electromyographer with differential active electrodes. The test was recorded during functional conditions, and the muscles assessed were the temporalis and masseter. Data were normalised by maximum voluntary contraction (MVC), and the results were analysed using an independent t‐test for comparison between the groups. Results: The normalised electromyographic data obtained showed significant differences in both groups. Comparing the normalised values obtained for MVC, the mean values for the masseter and temporalis muscles of elderly group were statistically lower (p ≤ 0.05) than control group for harder foods, but there were no significant differences for food with the lowest consistency. Conclusion: It can be concluded that elderly individuals show slight hypoactivity of their masticatory musculature during chewing when compared to young individuals.     

Spatio-temporal variation of photosynthetic pigments in the CAM tree <Emphasis Type="Italic">Clusia hilariana</Emphasis> Schlechtendal associated with dry spells during the rainy season in southeastern Brazil

In this work we assessed spatial and temporal variation of leaf pigment content of Clusia hilariana, a dominant CAM tree on the sandy coastal plains of SE Brazil. Chlorophyll a + b concentration, chlorophyll a/b ratio, and total carotenoid concentration were measured three times during the wet season. Chlorophyll a + b and total carotenoids decreased while the chlorophyll a/b ratio increased after a series of dry spells. We discuss our results in the context of Clusia literature, and argue that leaf-level pigmentation changes are an important source of phenotypic flexibility during acclimation to fluctuating light levels and groundwater availability.     

Towards soil management with Zn and Mn: estimates of fertilisation efficacy of Citrus trees

Nutrient management recommendations for fruit crops lack the understanding of the efficiency of soil fertilisation with manganese (Mn) and zinc (Zn), which could substitute, in part, the traditional foliar applications. Fruit yield of trees in response to Zn and Mn supply via soil may be limited either by sorption reactions with soil colloids or low solubility of fertilisers. We investigated the effects of fertiliser sources and rates of Mn and Zn applied to soils with different sorption capacities on nutrient uptake, biochemical responses and biomass of Citrus. Two experiments were carried out with 2‐year‐old sweet orange trees that received applications of Mn or Zn. The first experiment evaluated the application of Mn fertilisers (MnCO₃ and MnSO₄) at three levels of the nutrient (0, 0.7 and 3.5 g plant^?1 of Mn) in two types of soil (18.1% and 64.4% of clay, referred to as sandy loam and clay soils, respectively). The second experiment, likewise, evaluated Zn fertilisers (ZnO and ZnSO₄) and nutrient levels (0, 1.0 and 5.0 g plant^?1 of Zn). Application of Mn and Zn increased nutrient availability in the soils as well as leaf nutrient concentrations in the trees. The lowest rates, 0.7 g plant^?1 of Mn and 1.0 g plant^?1 of Zn, both as sulphate, were sufficient to supply these micronutrients to sufficient levels in leaves, flowers and fruits. Metal toxicity to plants occurred with higher doses of both nutrients and to a large extent in the sandy soil. In this case, protein bands lower than 25 kDa were observed as well a decrease on leaf chlorophyll content. In the clay soil, despite increased micronutrient concentrations in the plant, responses were less pronounced because of higher adsorption of metals in the soil. Superoxide dismutase (SOD, EC 1.15.1.1) isoenzyme activity was determined by non‐denaturing polyacrylamide gel electrophoresis (PAGE). The Cu/Zn‐SOD isoenzymes increased with increased Zn rates, but in contrast, when Mn was applied at the highest rate, the activity of Cu/Zn‐SODs decreased. The SOD activity pattern observed indicated increased production of superoxide and consequently an oxidative stress condition at the highest rates of Zn and Mn applied. The results demonstrated that the soil application of Mn and Zn can supply nutrient demands of orange trees, however the low solubility of fertilisers and the high sorption capacity of soils limit fertilisation efficiency. On the contrary, application of sulphate source in sandy soils may cause excess uptake of Mn and Zn and oxidative stress, which impairs the photosynthetic apparatus and consequently tree growth.     

Molecular characterization of Mycobacterium tuberculosis isolates in a region of Brazil with a high incidence of tuberculosis

One hundred and seventy Mycobacterium tuberculosis clinical isolates were characterized by spoligotyping to evaluate the biodiversity of tubercle bacilli in a region of Brazil with a high incidence of tuberculosis (Pelotas and Rio Grande cities - Rio Grande do Sul State). The spoligotyping results were compared to the World Spoligotyping Database (Institut Pasteur de Guadeloupe), which contains data from >14,000 worldwide isolates of M. tuberculosis. The isolates clustered by spoligotyping were further characterized by IS6110-RFLP to confirm the clonal relationship. Sixty-six different spoligotypes were identified, grouping 125 of the isolates (74%). Approximately half of the isolates belonged to seven of the most frequently occurring spoligotypes in the database. Three shared types (with two or more isolates) not previously identified were given the type numbers 826, 827 and 863. An additional 45 spoligotypes were identified that did not match any existing database pattern. RFLP characterization reduced the number of isolates in most of the clusters, thereby showing a higher differentiation capacity than spoligotyping. These results highlight the importance of molecular epidemiology studies of tuberculosis in insufficiently studied regions with a high TB burden, in order to uncover the true extent of genetic diversity of the pathogen.     

Structural mechanism of oxidative regulation of the phosphatase Cdc25B via an intramolecular disulfide bond

Cdc25B phosphatase, an important regulator of the cell cycle, forms an intramolecular disulfide bond in response to oxidation leading to reversible inactivation of phosphatase activity. We have obtained a crystallographic time course revealing the structural rearrangements that occur in the P-loop as the enzyme goes from its apo state, through the sulfenic (Cys-SO(-)) intermediate, to the stable disulfide. We have also obtained the structures of the irreversibly oxidized sulfinic (Cys-SO(2)(-)) and sulfonic (Cys-SO(3)(-)) Cdc25B. The active site P-loop is found in three conformations. In the apoenzyme, the P-loop is in the active conformation. In the sulfenic intermediate, the P-loop partially obstructs the active site cysteine, poised to undergo the conformational changes that accompany disulfide bond formation. In the disulfide form, the P-loop is closed over the active site cysteine, resulting in an enzyme that is unable to bind substrate. The structural changes that occur in the sulfenic intermediate of Cdc25B are distinctly different from those seen in protein tyrosine phosphatase 1B where a five-membered sulfenyl amide ring is generated as the stable end product. This work elucidates the mechanism by which chemistry and structure are coupled in the regulation of Cdc25B by reactive oxygen species.     

Molecular docking analysis of stevioside with Akt and PPARγ

Stevioside is a diterpenoid glycoside consisting of an aglycone (steviol) and three glucose molecules. It is commonly used as an anti-hyperglycemic food because of its non-caloric property. Therefore, it is of interest to document the interactions of stevioside with AKT & PPAR-γ proteins using Autodock Vina PyRx docking techniques. Results of the docking studies indicate that stevioside had more than two hydrogen bond interactions with the AKT and PPAR γ protein for further consideration.