Cytogenetical and histological studies in testis of Tayassu tajacu (Cateto), Tayassu pecari (Queixada) and a natural interspecific hybrid

The karyotype, the histological structure of the testis and the synaptonemal complex (SC) of the mammalian species Tayassu tajacu , Tayassu pecari and of an interspecific male hybrid captured in nature were analysed. The specimens of T. tajacu (2n=30) and T. pecari (2n=26) exhibited seminiferous tubules with germ cells in all spermatogenesis stages. In the SC studies both species had a regular structure, easily identified in the autosomes and in the sex chromosomes. The hybrid (2n=28) had seminiferous tubules with almost all germinal cells in the spermatogonium stage and only a few cells in the primary spermatocyte stage. Gross abnormalities in SC were observed. A few lateral elements showed regular or partially regular synapsis, other lateral elements were synapsed as multivalents, and most axial elements remained unsynapsed. The results suggest that the karyotypes of the parental species have sufficient differentiation to avoid chromosome synapsis. Alternatively, the hypothesis of the existence of genetic incompatibilities between the parental species is discussed.     

Assessment of biodegradability and oxidation stability of mineral, vegetable and synthetic oil samples

This study proposes to evaluate rapid methodologies to estimate oxidative stability and biodegradability for mineral, vegetable and synthetic oil samples, using quick and simple experiments. The synthetic oil sample was obtained from castor oil, so the vegetable oil chosen for this evaluation was a sample of the crude castor oil source. The oxidative stability tests described enabled the comparison of synthetic lubricant samples and showed that their stability was lower than that of petroleum-based oil. However, the physico-chemical properties, such pour points and viscosity index, were improved and potentially interesting for lubricant applications. The biodegradability experiments were carried out using a model of bio-kinetics. These studies proved that synthetic lubricant samples were easily degradable (similar to crude castor oil) and showed half-life significantly lower than those of the mineral oil samples.     

Antigenotoxicity and Antioxidant Activity of Acerola Fruit (Malpighia glabra L.) at Two Stages of Ripeness

Genotoxic and antigenotoxic effects of acerola fruit at two stages of ripeness were investigated using mice blood cells. The results show that no ripeness stage of acerola extracts presented any genotoxic potential to damage DNA (Comet assay) or cytotoxicity (MTT assay). When antigenotoxic activity was analyzed, unripe fruit presented higher DNA protection than ripe fruit (red color) extract. The antioxidant capacity of substances also showed that unripe samples inhibit the free radical DPPH more significantly than the ripe ones. The results about determination of compounds made using HPLC showed that unripe acerola presents higher levels of vitamin C as compared to ripe acerola. Thus, vitamin C and the complex mixture of nutrients of Malpighia glabra L., and especially its ripeness stages, influenced the interaction of the fruit extract with the DNA. Acerola is usually consumed when ripe (red fruit), although it is the green fruit (unripe) that has higher potential as beneficial to DNA, protecting it against oxidative stress.     

Natural Enemies of the Frankliniella Complex Species (Thysanoptera: Thripidae) in Ataulfo Mango Agroecosystems

A field survey was conducted in Ataulfo mango (Mangifera indica L.) orchards in Chiapas, Mexico, with the objective of determining the natural enemies of the Frankliniella complex species (Thysanoptera: Thripidae). Seven species of this genus feed and reproduce in large numbers during the mango flowering. Two representative orchards were selected: the orchard “Tres A” characterized by an intensive use of agrochemicals directed against thrips, and the orchard “La Escondida” that did not spray insecticides. During mango flowering, five inflorescences were randomly collected every 5 d in both orchards, for a total of 18 sampling dates. Results revealed the presence of 18 species of arthropods that were found predating on Frankliniella. There were 11 species in the families Aeolothripidae, Phlaeothripidae, Formicidae, Anthocoridae and Chrysopidae; and seven species of spiders in the families Araneidae, Tetragnathidae, and Uloboridae. Over 88% of predators were anthocorids, including, Paratriphleps sp. (Champion), Orius insidiosus (Say), Orius tristicolor (White), and O. perpunctatus (Reuter). The orchard that did not spray insecticides had a significantly higher number of predators suggesting a negative effect of the insecticides on the abundance of these organisms.     

Peripheral selection of the T cell repertoire

T lymphocytes undergo selection events not only in the thymus, but also after they leave the thymus and reside in the periphery. Peripheral selection was found to be dependent on T cell receptor (TCR)-ligand interactions but to differ from thymic selection with regard to specificity and mechanism. Unlike thymic selection, peripheral selection required binding of antigen to the TCR, and it induced expansion of T cell clones. Tolerance to self antigens that are restricted to the periphery occurred through the elimination of self-reactive T cells and by the clonal anergy, which was associated with down-regulation of the alpha beta TCR and CD8.     

Tissue expression of PPAR-alpha isoforms in Scophthalmus maximus and transcriptional response of target genes in the heart after exposure to WY-14643

Peroxisome proliferator-activated receptors (PPARs) are involved in the regulation of lipid and carbohydrate metabolism and can be activated either by natural ligands as fatty acids or by synthetic ligands including several environmental chemicals. In this study, two PPARα isoforms (α1 and α2) were analyzed in turbot (Scophthalmus maximus) for a different tissue distribution. PPARα1 was ubiquitously expressed, while the PPARα2 was predominantly expressed in the heart. Following this result, turbot juveniles were exposed by injection to a synthetic selective PPARα agonist, WY-14643, for 14 days. Suppression subtractive hybridization (SSH) was performed with pools of heart samples of control and exposed fish to get insights into PPARα-regulated genes in the heart of juvenile turbot. Four genes were positively identified in the forward-subtracted and 12 genes in the reverse-subtracted cDNA SSH library, corresponding to the down-regulated and up-regulated genes in response to the WY-14643 treatment, respectively. The confirmation of these results in individual samples of juvenile turbot exposed to WY-14643 revealed a statistically significant mRNA induction of two cardiac muscle proteins (myosin light chain 2 and tropomyosin 4), which were shown to be involved in heart contraction and heartbeat regulation in other teleost species. Herewith, we showed for the first time that PPARα2 is predominantly expressed in the heart and that a PPARα agonist can induce the mRNA expression of cardiac muscle proteins in teleosts.     

Amazon forests green-up during 2005 drought

Coupled climate-carbon cycle models suggest that Amazon forests are vulnerable to both long- and short-term droughts, but satellite observations showed a large-scale photosynthetic green-up in intact evergreen forests of the Amazon in response to a short, intense drought in 2005. These findings suggest that Amazon forests, although threatened by human-caused deforestation and fire and possibly by more severe long-term droughts, may be more resilient to climate changes than ecosystem models assume.     

Seroprevalence and risk factors for Neospora caninum in sheep in the state Minas Gerais, southeastern Brazil

The aim of this study was to determine the prevalence and risk factors associated with infection due to Neospora caninum in serum samples from 488 sheep originating from 63 farms in 63 municipalities distributed across eight of the twelve mesoregions of the state Minas Gerais, southeastern Brazil. For detection of N. caninum the sheep serum samples were subjected to the indirect fluorescence antibody test (IFAT ≥ 50). To identify the risk factors associated with infection due to N. caninum a questionnaire was filled out for each herd by interviewing, the individual responsible for the herd, demanding information on the general characteristics of the property. Sixty-four sheep sera (13.1%; 95% CI=10.3-16.4) presented IgG-specific anti-N. caninum antibodies with the following titers: 50 (49; 76.6%), 100 (7; 10.9%), 200 (4; 6.2%), 400 (3; 4.7%) and 800 (1; 1.6%). The prevalence of infected sheep per mesoregion ranged from 0 to 28.1%. Out of the 63 farms sampled, 31 (49.2%; 95% CI=36.4-62.1) presented at least one seropositive sheep. No significant association was found between the presence of anti-N. caninum antibodies and the risk factors evaluated on the farms, except for the mesoregion variable (p=0.004; OR=0.429; CI95%=0.182-1.008). These results indicate that there is a need for additional research to define the epidemiological importance of this parasite as a cause of reproductive problems in sheep herds in Minas Gerais.     

Quantification of yield loss due to coffee leaf scorch

Coffee leaf scorch caused by Xylella fastidiosa is widespread in major coffee-growing regions of Brazil. This study was done to quantify the yield loss caused by this disease. The severity data of the disease were collected during the 2006, 2007 and 2008 seasons at commercial plantations growing Coffea arabica ‘Catuaí’ in São Gotardo-MG in 250 plants of three blocks of 7000 coffee plants each. Fifty selected plants per block with different disease severities were determined. The linear regression showed a significant relationship (P < 0.01) between disease severity and bean yield and between disease severity and grain size in all years. The relationship between yield and the disease severity was significant (P < 0.01). For each 1% increase in the disease severity, there was a decrease of 1.22, 1.34 and 2.02 bags of bean yield/ha in 2006, 2007 and 2008, respectively, thus showing the importance of the disease in reducing coffee bean yields.