Weed dynamics during the change of a degraded pasture to agroforestry system

This study evaluates weed dynamics during the first 4 years (2008–2011) of the implementation of an agroforestry system in the municipality of Tomé-açu in the state of Pará, Brazil. The study was conducted in a degraded pasture of Brachiaria humidicola, and treatments (T) included mixed plantations of oil palm with short-cycle leguminous species (T1) with the inclusion of manioc in T2 and forest species and palm trees in T3. In 2008, a floristic survey was conducted in 12 plots of 2 × 2 m per treatment. In 2009, herbicide was applied to one half of the area in each treatment. A total of 19,367 individuals of height <1.5 m were surveyed, of which 51 % were B. humidicola and 21 % were leguminous species that had been planted. Overall, an increase in plant density was observed between 2009 and 2010, followed by a decrease over the following year in areas without herbicide and a tendency for high densities to persist in areas with herbicide. Species richness increased over the study period in all areas (with or without herbicide), which might be related to habitat availability resulting from the reduced density of B. humidicola due to the effects of the herbicide, the leguminous species planted and the development of the agroforestry system. The association of short-cycle leguminous plants with afforestation appears to be an effective method for controlling weeds in the absence of herbicides.     

Inhibition of gastric acid secretion in rats by intracerebral injection of corticotropin-releasing factor

Intracisternal injection of ovine corticotropin-releasing factor (CRF) into the pylorus-ligated rat or the rat with gastric fistula resulted in a dose-dependent inhibition of gastric secretion stimulated with pentagastrin or thyrotropin-releasing hormone. When injected into the lateral hypothalamus--but not when injected into the cerebral cortex--CRF suppressed pentagastrin-stimulated acid secretion. The inhibitory effect of CRF was blocked by vagotomy and adrenalectomy but not by hypophysectomy or naloxone treatment. These results indicate that CRF acts within the brain to inhibit gastric acid secretion through vagal and adrenal mechanisms and not through hypophysiotropic effects.     

AMMONIUM AND NITRATE IN SOIL AND RATOON SUGARCANE GROWN IN FUNCTION OF NITROGEN ON OXISOL

After harvest, sugarcane residues left on the soil surface can alter nitrogen (N) dynamics in the plant-soil system. In Oxisols, the nitrogen fertilizer applied had its effects on the levels of ammonium and nitrate in the soil, N concentration in the plant leaves, and on the growth and productivity of second ratoon plants. The N rates tested were of 0, 60, 120, 180, and 240 kg ha^?1. Each treatment was replicated four times. Four months after the experiment was started, ammonium and nitrate concentration in the soil, N levels in plant leaves, and plant growth were evaluated. Productivity was evaluated 11 months after the experiment was set. By increasing the content of mineral N in soil, plant growth variables reflected differences in the production of stems; however, it did not affect foliar N. The use of leaf analysis was not important to assess the nutritional status of nitrogen in the ratoon sugarcane. Nitrogen concentration in soil was affected by nitrogen fertilization, but not the N content in leaves. The rate of 138 kg N ha^?1enabled greater production of sugarcane stalks (140 t ha^?1).     

Corticotropin-releasing factor receptors in rat forebrain: autoradiographic identification

Corticotropin-releasing factor (CRF) receptors were identified in rat forebrain by autoradiography with an iodine-125-labeled analog of ovine CRF substituted with norleucine and tyrosine at amino acid residues 21 and 32, respectively. High-affinity receptors for CRF were found in discrete areas of rat forebrain, including laminae I and IV of the neocortex, the external layer of the medium eminence, the lateral nucleus of the amygdala, and the striatum. These results are consistent with earlier findings on the immunohistochemical distribution of CRF and suggest that endogenous CRF has a physiological role in regulating activity of the central nervous system.     

Plasma membrane compartmentalization in yeast by messenger RNA transport and a septin diffusion barrier

Asymmetric localization of proteins plays a key role in many cellular processes, including cell polarity and cell fate determination. Using DNA microarray analysis, we identified a plasma membrane protein-encoding mRNA (IST2) that is transported to the bud tip by an actomyosin-based process. mRNA localization created a higher concentration of IST2 protein in the bud compared with that of the mother cell, and this asymmetry was maintained by a septin-mediated membrane diffusion barrier at the mother-bud neck. These results indicate that yeast creates distinct plasma membrane compartments, as has been described in neurons and epithelial cells.     

Kinesin walks hand-over-hand

Kinesin is a processive motor that takes 8.3-nm center-of-mass steps along microtubules for each adenosine triphosphate hydrolyzed. Whether kinesin moves by a "hand-over-hand" or an "inchworm" model has been controversial. We have labeled a single head of the kinesin dimer with a Cy3 fluorophore and localized the position of the dye to within 2 nm before and after a step. We observed that single kinesin heads take steps of 17.3 +/- 3.3 nm. A kinetic analysis of the dwell times between steps shows that the 17-nm steps alternate with 0-nm steps. These results strongly support a hand-over-hand mechanism, and not an inchworm mechanism. In addition, our results suggest that kinesin is bound by both heads to the microtubule while it waits for adenosine triphosphate in between steps.     

Phytotoxic effect of Sesbania virgata (Cav.) Pers. On seeds of agronomic and forestry species

Sesbania virgata(Cav.) Pers.is a pioneer species native to South America able to release allelochemicals that affect germination and development of other plant species.The aim of this work was to evaluate the allelopathic effect of S.virgata on the germination and development of co-occurring species from gallery forest and on agronomic species.Two forest native species,Enterolobium contortisiliquum(Vell.) Morong and Sapindus saponaria L.,and two agronomic species(these as control),Oryza sativa L.and Solanum lycopersicum L.were used in the lab and greenhouse assays with seeds and leaf extracts of S.virgata.Agronomic species were more affected than native species when co-germinated with seeds of S.virgata.The germination percentage and speed germination index of the agronomic species were reduced in both in vitro and greenhouse assays.In the same assays,the seeds of native species showed no significant differences in the parameters mentioned.However,the initial growth of the four species assayed was affected,with reduction in plant length and shoot diameter followed by significant reduction in plantlet shoot and root weights.In the assays with irrigation of S.virgata leaf extracts,no significant inhibitory effects on germination were observed for all species.Height and shoot diameter of the native species were not affected by the leaf extracts,nor were fresh and dry weights.However,these parameters increased in the agronomic species as they were irrigated with leaf extracts.Based on our data we conclude that seed leachates of S.virgata affect germination and seedling development of other species,suggesting that its invasive behavior is due mainly to seed allelochemicals.Although with less pronounced effects on native species,allelopathy of S.virgata might also influence Interspecific competition in its natural environment.     

Persistent efficacy of abamectin and doramectin against gastrointestinal nematodes of cattle

Objective To assess the persistent activity of injectable formulations of abamectin and doramectin against gastrointestinal nematodes of cattle.
Design Controlled slaughter study assessing residual efficacy.
Procedure Nematode-free calves were treated with abamectin or doramectin (each at a dose of 200 μg/kg) and infections then induced with repeated doses of infective larvae of Trichostrongylus axei, Haemonchus placei, Ostertagia ostertagi and Cooperia species. The duration of challenge ranged from 14 to 28 days. The calves were slaughtered at either 38/39 or 45/46 days after the treatments and nematodes recovered from the gastro-intestinal tract.
Results Significant reductions in numbers of O ostertagi occurred for both abamectin and doramectin treatments (> 93%) relative to counts in untreated calves, when challenge was administered up to 21 days after treatment. For T axei and Cooperia spp significant reductions occurred when the challenge occurred for 14 days after treatment (99%). Although differences from untreated animals were not significant, the results for H placei suggested high efficacy (> 85%) for up to 21 days for doramectin and up to 28 days for abamectin.
Conclusion There was no significant difference between abamectin and doramectin for any parasite at any challenge point, indicating that there is equivalent persistent activity of doramectin and abamectin against important gastrointestinal nematodes of cattle.     

Isotype patterns of immunoglobulins: hallmarks for clinical status and tissue parasite density in Brazilian dogs naturally infected by Leishmania (Leishmania) chagasi

The role of anti-leishmanial immune response underlying the susceptibility/resistance during canine visceral leishmaniasis (CVL) has been recognized throughout ex vivo and in vitro investigations. Recently, we demonstrated that immunoglobulin levels (Igs), as well as the parasite load are relevant hallmarks of distinct clinical status of CVL. To further characterize and upgrade the background on this issue, herein, we have evaluated, in Leishmania (Leishmania) chagasi naturally infected dogs, the relationship between tissue parasitism (skin, bone marrow, spleen, liver and lymph node), the CVL clinical status (asymptomatic (AD), with no suggestive signs of the disease; oligosymptomatic (OD), with maximum three clinical signs-opaque bristles; localized alopecia and moderate loss of weight; symptomatic (SD), serologically positive with severe clinical signs of visceral leishmaniasis), and the humoral immunological profile of anti-Leishmania immunoglobulins (IgG, IgG1, IgG2, IgM, IgA and IgE). Our major statistically significant findings revealed distinct patterns of tissue parasite density within L. chagasi-infected dogs despite their clinical status, pointing out the spleen and skin as the most relevant sites of high parasitism during ongoing CVL. Parasite density of bone marrow and spleen were the most reliable parasitological markers to decode the clinical status of CVL. Moreover, the parasite density of bone marrow better correlates with most anti-Leishmania Igs reactivity. Additionally, a prognostic hallmark for canine visceral leishmaniasis was found, highlighting strong correlation between IgG1 and asymptomatic disease, but with IgA, IgE and IgG2 displaying better association with symptomatic disease. The new aspects of this study highlighted pioneer findings that correlated the degree of tissue parasite density (low (LP), medium (MP) and high (HP) parasitism) with distinct patterns of anti-Leishmania Igs reactivity. In this scope, our data re-enforce the anti-Leishmania IgG but with IgA reactivity as the better marker for overall tissue parasitism. The association between clinical status, Ig profile and the tissue parasitism support a novel investigation on the impact of humoral immune response and susceptibility/resistance mechanism during ongoing CVL.