Search Results

You are looking at 1 - 5 of 5 items for :

  • Author or Editor: R. Filho x
  • Biology and Life Sciences x
  • All content x
Clear All Modify Search

Among other objectives, forest inventories are aimed to identify ecological communities and to correlate community composition with environmental variables. The identification of different communities would require several forest inventories, each covering small sampling areas with relatively homogeneous environmental conditions. The multiple plot sampling method, traditionally used in local inventories of tropical forests, cannot assure such homogeneity, since even small sampling areas would show environmental heterogeneity influencing vegetation. In this paper we assessed the consequences of this heterogeneity for sampling by quantifying the variability of species abundance ranks for species sampled with 10 or more individuals in a set of plots covering a small sampling area. The species reference abundance ranks were obtained from a sample of 100 plots of 10 m × 10 m each randomly set in a sampling area of 6.5 ha in a tropical forest fragment (Southeastern Brazil). For each species we used resamplings (30 trials) to obtain the species abundance ranks in sub-samples, considering different sampling intensities (n = 25, 50 and 75 plots), and compared these ranks with the species reference rank (n = 100 plots). Then, we compared the species ranks in sub-samples of 50 plots (10.000 trials) with the reference rank and assessed the frequency and extent of rank displacements. Species rank was highly variable across resampling trials for the sampling intensities of n = 25 and n = 50, but decreased considerable with a sampling intensity of n = 75 plots. The mean rank variability and especially the maximum displacement raised significantly from the seventh most abundant species on, and some species occupied quite discrepant abundance ranks in up to 10% of the 10.000 resampling trials. This high internal variability of forest samples may impair the search for floristic patterns as scale lessens, say, to the meso-scale (1–100 km2). We discussed some possible ways to increase internal homogeneity of tropical forest samples with the multiple plot sampling method. Among these, objective entitation, based on an ancient phytosociological procedure, is suggested as the most appropriate for use on the hilly relieves of the Atlantic forest biome.

Restricted access

The species abundance distribution of ecological communities has been represented through several mathematical models, of which the most common are: geometric series, logseries, lognormal, and a type of broken stick, this latter found only in animal communities. There is no consensus on the underlying biological processes, but initial observations on plant communities related these models to equilibrium and high richness (lognormal), stress or disturbance and low richness (logseries and geometric series). Recently the value of these relationships was challenged, and other descriptors were considered better predictors of richness, disturbance and stress. We aimed at investigating how these models and their parameters, as well as dominance and evenness are related with species richness, stress and disturbance in six tropical forest communities, SE Brazil: two well-conserved fragments, two disturbed by fire, and two swampy forests (anoxic stress). The models did not show consistent relationships with richness, disturbance or stress. The parameters and indices of diversity a (logseries) and l (lognormal) varied closely with richness, and the dominance was larger in the communities submitted to stress or disturbance. Our results indicate the need of further studies in order to validate (or refute) the use of abundance distribution models for detection of patterns related to richness, stress or disturbance in tropical arboreal communities. On the other hand, richness and dominance did respond to disturbance and stress.

Restricted access

Acetaminophen (AAP), acetylsalicylic acid (ASA) and dipyrone (DIP) are antipyretic and analgesics drugs that have wide use in health sciences. Some drugs can modify the labeling of blood elements with technetium-99m (99mTc). This work has evaluated the effect of AAP, ASA and DIP on the labeling of the blood elements with 99mTc. Blood was incubated with different concentrations of the drugs before the 99mTc-labeled process. Plasma (P), blood cells (BC), insoluble (IF-P, IF-BC) and soluble (SF-P, SF-BC) fractions were separated and percentage of radioactivity (%ATI) in each fraction was determined. Data have shown that the antipyretic drugs used in this study did not significantly modify the fixation of 99mTc on the blood elements when the experiments were carried out with the doses usually used in human beings. Although the experiments were carried out with rats, it is possible to suggest that AAP, ASA or DIP should not interfere with the procedures in nuclear medicine involving the labeling of blood elements with 99mTc

Restricted access
Acta Biologica Hungarica
Authors: Carla Sayago, Vanessa Camargo, F. Barbosa, Cláudia Gularte, Geovana Pereira, Silvia Miotto, V. Cechinel Filho, R. Luiz Puntel, V. Folmer, and A. Mendez

Bauhinia species are known to have hypoglycemiant and antioxidant activities. Here, hydro-ethanolic leaf extracts from Bauhinia forficata subsp. pruinosa and Bauhinia variegata, collected in a Pampa biome region of Brazil, were investigated to characterize their chromatographic profile, flavonoid content and in vitro antioxidant activity (TBARS and DPH assays). The extracts were obtained from dried and fresh leaves. The total flavonoid content was assessed by spectrophotometric determination, and the results ranged between 572.08 and 1,102.99 μg mL−1. Moreover, flavonoids were more predominant in B. variegata than in B. forficata subsp. pruinosa. HPLC analysis detected a complex profile of phenolic compounds, being the flavonoid kaempferitrin founded B. forficata subsp. pruinosa; in addition, other kaempferol and quercetin derivatives were present. In vitro antioxidant assays demonstrated a different behavior depending on the species, leaf treatment and extract concentration. In general, B. variegata extracts obtained from fresh material presented higher antioxidant potential, which can be attributed to the predominance of flavonoids in their chemical composition.

Restricted access
Acta Biologica Hungarica
Authors: L. M. Jesus, P. R. C. Abreu, Marcela C. Almeida, Lavínia C. Brito, Sheila F. Soares, D. E. De Souza, Luciana C. Bernardo, A. S. Fonseca, and M. Bernardo-Filho

Since ancient times propolis has been employed for many human purposes because to their favourable properties. Blood constituents labeled with technetium-99m (99mTc) have been used in nuclear medicine procedures. Some authors have reported that synthetic or natural drugs can interfere with the labeling of blood constituents with 99mTc. The aim of this work was to evaluate the action of a propolis extract on the labeling of blood elements with 99mTc. Samples of whole blood of male Wistar rats were incubated in sequence with an aqueous propolis extract at different concentrations, stannous chloride and 99mTc, as sodium pertechnetate. Blood samples were centrifuged to separate plasma and blood cells, soluble and insoluble fractions of plasma and blood cells were also separated after precipitation in trichloroacetic acid solution and centrifugation. The radioactivity was counted and the percentage of incorporated radioactivity (%ATI) for each fraction was calculated. The data obtained showed that the aqueous propolis extract used decreased significantly the %ATI in plasma proteins at higher concentration studied. Results suggest that at high concentration the constituents of this extract could alter the labeling of plasma proteins competing with same binding sites of the 99mTc on the plasma proteins or acting as antioxidant compounds.

Restricted access