Universidade Federal Rural do Rio de Janeiro

About: Universidade Federal Rural do Rio de Janeiro is a education organization based out in Seropédica, Brazil. It is known for research contribution in the topics: Population & Species richness. The organization has 6405 authors who have published 9852 publications receiving 105911 citations.

Do techniques based on 15N enrichment and 15N natural abundance give consistent estimates of the symbiotic dependence of N2-fixing plants?

Abstract: The primary aim of this review is to determine if methods based on 15N enrichment (E) and 15N natural abundance (NA) give consistent estimates of the proportional dependence of N2-fixing species on biological N2 fixation (P atm), and secondly to attempt to explain any inconsistencies that may be found. Published estimates of the symbiotic dependence of N2-fixing plants based on E and NA techniques applied in the same experiment were compared across scales from glasshouse pots to field plots to landscapes in agricultural and forest ecosystems, which included grain legumes, pasture and forage legumes, and woody perennials. A meta-analysis of the published data was based on correlation coefficients, box-plots and confidence intervals of means. In some studies, estimates were reference plant dependent for both E and NA techniques, indicating temporal and/or spatial variations in the natural and artificial distribution of 15N, which can sometimes result in erroneous negative estimates of symbiotic dependence. While significant correlations were obtained between E and NA estimates of P atm for each of the three groups of N2-fixing species, the probability that the methods provided estimates of P atm within −5 to +5 % of each other was 0.29 or was 0.54 within −10 to +10 % of each other. We have identified a number of interacting factors that may contribute to the inconsistent agreement between estimates of P atm by E and NA techniques, which underlines the need for a re-examination of the fundamental assumptions on which each method is based, and whether those assumptions are valid in any given situation.

APORTE E DECOMPOSIÇÃO DE SERAPILHEIRA EM ÁREAS DE FLORESTA SECUNDÁRIA, PLANTIO DE SABIÁ (Mimosa caesalpiniaefolia Benth.) E ANDIROBA (Carapa guianensis Aubl.) NA FLONA MÁRIO XAVIER, RJ

Abstract: This study evaluated litter production and decomposition in areas of spontaneous secondary forest, sabia ( Mimosa caesalpiniaefolia Benth.) and andiroba ( Carapa guianensis Aubl.) plantation. For litter contribution evaluation, 10 conical collectors were installed, and the contribution was evaluated from October, 2003 to September, 2004. N, P and K contents were quantified in litter. To evaluate decomposition, rate litter bags method was used. In the andiroba plantation area, it was observed the higher litter amount 9,20 Mg ha -1 , followed by the sabia plantation with 9,06 Mg ha -1 and spontaneous secondary forest 7,63 Mg ha -1 . Sabia and andiroba litter presented larger nitrogen and phosphorus values in relation to the secondary forest area. Litter decomposition rate was faster in sabia and andiroba areas. This behavior might be influenced by larger nitrogen content in the litter. Phosphorus was the nutrient that presented the higher liberation rate.

Effect of the antitumoral alkylating agent 3-bromopyruvate on mitochondrial respiration: role of mitochondrially bound hexokinase.

Abstract: The alkylating agent 3-Bromopyruvate (3-BrPA) has been used as an anti-tumoral drug due to its anti-proliferative property in hepatomas cells. This propriety is believed to disturb glycolysis and respiration, which leads to a decreased rate of ATP synthesis. In this study, we evaluated the effects of the alkylating agent 3-BrPA on the respiratory states and the metabolic steps of the mitochondria of mice liver, brain and in human hepatocarcinoma cell line HepG2. The mitochondrial membrane potential (ΔΨm), O2 consumption and dehydrogenase activities were rapidly dissipated/or inhibited by 3-BrPA in respiration medium containing ADP and succinate as respiratory substrate. 3-BrPA inhibition was reverted by reduced glutathione (GSH). Respiration induced by yeast soluble hexokinase (HK) was rapidly inhibited by 3-BrPA. Similar results were observed using mice brain mitochondria that present HK naturally bound to the outer mitochondrial membrane. When the adenine nucleotide transporter (ANT) was blocked by the carboxyatractiloside, the 3-BrPA effect was significantly delayed. In permeabilized human hepatoma HepG2 cells that present HK type II bound to mitochondria (mt-HK II), the inhibiting effect occurred faster when the endogenous HK activity was activated by 2-deoxyglucose (2-DOG). Inhibition of mt-HK II by glucose-6-phosphate retards the mitochondria to react with 3-BrPA. The HK activities recovered in HepG2 cells treated or not with 3-BrPA were practically the same. These results suggest that mitochondrially bound HK supporting the ADP/ATP exchange activity levels facilitates the 3-BrPA inhibition reaction in tumors mitochondria by a proton motive force-dependent dynamic equilibrium between sensitive and less sensitive SDH in the electron transport system.

Community ecology of the metazoan parasites of namorado sandperches, Pseudopercis numida Miranda-Ribeiro, 1903 and P. semifasciata Cuvier, 1829 (Perciformes: Pinguipedidae), from the coastal zone of the State of Rio de Janeiro, Brazil.

Abstract: One hundred and twenty-eight specimens of namorado sandperches, 62 P. numida and 66 P. semifasciata, collected between October 2002 and June 2003 off the Cabo Frio, Rio de Janeiro, Brazil (Lat 23 degrees S and Long 42 degrees W), were examined to study their metazoan parasites. Parasite communities of these fish were composed basically of endoparasites, mainly digenean and cestodes species, with low prevalence and abundance but having high parasite species richness values (at the component community level). Among these values, that found for P. numida is the highest so far recorded for marine fishes from the Neotropical Region. Thirty-nine species of metazoan parasites were collected: 36 from P. numida and 28 from P. semifasciata. Twenty-five parasite species were common to both species of namorado sandperches. Pseudopercis numida and P. semifasciata are new host records for all parasite species collected, with the exception of Microcotyle pseudopercis. Choanodera sp., Leurodera decora, Neolebouria georgenascimentoi, and Proctoeces sp. which were recorded for the first time in the South American Atlantic Ocean. Gnathia sp. from P. numida and Scolex pleuronectis from P. semifasciata were the species having the greatest dominance frequency. Parasite abundance in P. numida and P. semifasciata were positively correlated with the host total length. Only in P. numida was parasite species richness correlated positively with the host total length. No significant differences between endoparasite infracommunities of P. numida and P. semifasciata were detected. The ectoparasites of P. numida had higher values for parasite abundance, parasite richness, Brillouin index, evenness index, and Berger-Parker index than those of the ectoparasites of P. semifasciata. Comparisons among all ecto- and endoparasites showed the ectoparasites of P. numida as the most heterogeneous group. Low similarity values were observed among the three types of parasite infracommunities of the two hosts.