Spatial genetic structure in two congeneric epiphytes with different dispersal strategies analysed by three different methods

Three different approaches were used to assess the kinship structure of two epiphytic bryophytes, Orthotrichum speciosum and O. obtusifolium, that have different dispersal strategies. The two species were sampled in a 200 ha landscape where species occurrence and host trees had been mapped previously. Local environmental conditions at sampled trees were recorded and kinship between individuals was calculated based on amplified fragment length polymorphism (AFLP)-marker data. We did not detect any association between AFLP-markers and investigated environmental conditions. In both species, significant kinship coefficients were found between individuals up to 300-350 m apart which shows that both species have a restricted dispersal range. The spatial kinship structure was detected with both autocorrelation analysis and generalized additive models (GAMs), but linear regression failed to detect any structure in O. speciosum. Although the dioecious O. obtusifolium is currently the more common species it may, none the less, due to its restricted dispersal range and reproduction mode, become threatened in the future by current silvicultural practices which enhance the distance between host trees and decrease their life span. Finally, GAMs seem most appropriate for analysing spatial genetic structure because the effects of local environmental conditions and spatial structure can be analysed simultaneously, no assumption of a parametric form between kinship coefficient and distance is required, and spatial data resolution is not lost in the arbitrary choice of distance classes characterizing autocorrelation analysis.     

Endogenous Adenosine Modulation of 22Na Uptake by Rat Brain Synaptosomes

To evaluate if endogenous extracellular adenosine influences sodium channel activity in nerve terminals, we investigated how manipulations of extracellular adenosine levels influence ²²Na uptake by rat brain synaptosomes stimulated with veratridine (VT). To decrease extracellular adenosine levels, adenosine deaminase (ADA) that converts adenosine into an inactive metabolite was used. To increase extracellular adenosine levels, we used the adenosine deaminase inhibitor erythro-9(2-hydroxy-3-nonyl) adenine (EHNA), as well as the inhibitor of adenosine transport, nitrobenzylthioinosine (NBTI). ADA (0.1–5U/ml) caused an excitatory effect on ²²Na uptake stimulated by veratridine, which was abolished in the presence of the adenosine deaminase inhibitor erythro-9(2-hydroxy-3-nonyl) adenine (EHNA, 25M). Both the adenosine uptake inhibitor nitrobenzylthioinosine (NBTI, 1–10M) and the adenosine deaminase inhibitor EHNA (10–25M) inhibited ²²Na uptake by rat brain synaptosomes. It is suggested that adenosine is tonically inhibiting sodium uptake by rat brain synaptosomes.     

Evidence That Antioxidants Prevent the Inhibition of Na+,K+-ATPase Activity Induced by Octanoic Acid in Rat Cerebral Cortex in Vitro

The objective of the present study was to investigate the in vitro effects of octanoic acid, which accumulates in medium-chain acyl-CoA dehydrogenase (MCAD) deficiency and in Reye syndrome, on key enzyme activities of energy metabolism in the cerebral cortex of young rats. The activities of the respiratory chain complexes I–IV, creatine kinase, and Na⁺, K⁺-ATPase were evaluated. Octanoic acid did not alter the electron transport chain and creatine kinase activities, but, in contrast, significantly inhibited Na⁺, K⁺-ATPase activity both in synaptic plasma membranes and in homogenates prepared from cerebral cortex. Furthermore, decanoic acid, which is also increased in MCAD deficiency, and oleic acid strongly reduced Na⁺, K⁺-ATPase activity, whereas palmitic acid had no effect. We also examined the effects of incubating glutathione and trolox (-tocopherol) alone or with octanoic acid on Na⁺, K⁺-ATPase activity. Tested compounds did not affect Na⁺, K⁺-ATPase activity by itself, but prevented the inhibitory effect of octanoic acid. These results suggest that inhibition of Na⁺, K⁺-ATPase activity by octanoic acid is possibly mediated by oxidation of essential groups of the enzyme. Considering that Na⁺, K⁺-ATPase is critical for normal brain function, it is feasible that the significant inhibition of this enzyme activity by octanoate and also by decanoate may be related to the neurological dysfunction found in patients affected by MCAD deficiency and Reye syndrome.     

Ketogenic Diet Increases Glutathione Peroxidase Activity in Rat Hippocampus

Ketogenic diets have been used in the treatment of refractory childhood epilepsy for almost 80 years; however, we know little about the underlying biochemical basis of their action. In this study, we evaluate oxidative stress in different brain regions from Wistar rats fed a ketogenic diet. Cerebral cortex appears to have not been affected by this diet, and cerebellum presented a decrease in antioxidant capacity measured by a luminol oxidation assay without changes in antioxidant enzyme activities—glutathione peroxidase, catalase, and superoxide dismutase. In the hippocampus, however, we observed an increase in antioxidant activity accompanied by an increase of glutathione peroxidase (about 4 times) and no changes in lipoperoxidation levels. We suggest that the higher activity of this enzyme induced by ketogenic diet in hippocampus might contribute to protect this structure from neurodegenerative sequelae of convulsive disorders.     

The hemicholinium-3 sensitive high affinity choline transporter is internalized by clathrin-mediated endocytosis and is present in endosomes and synaptic vesicles

Synthesis of acetylcholine depends on the plasma membrane uptake of choline by a high affinity choline transporter (CHT1). Choline uptake is regulated by nerve impulses and trafficking of an intracellular pool of CHT1 to the plasma membrane may be important for this regulation. We have generated a hemagglutinin (HA) epitope tagged CHT1 to investigate the organelles involved with intracellular trafficking of this protein. Expression of CHT1-HA in HEK 293 cells establishes Na+-dependent, hemicholinium-3 sensitive high-affinity choline transport activity. Confocal microscopy reveals that CHT1-HA is found predominantly in intracellular organelles in three different cell lines. Importantly, CHT1-HA seems to be continuously cycling between the plasma membrane and endocytic organelles via a constitutive clathrin-mediated endocytic pathway. In a neuronal cell line, CHT1-HA colocalizes with the early endocytic marker green fluorescent protein (GFP)-Rab 5 and with two markers of synaptic-like vesicles, VAMP-myc and GFP-VAChT, suggesting that in cultured cells CHT1 is present mainly in organelles of endocytic origin. Subcellular fractionation and immunoisolation of organelles from rat brain indicate that CHT1 is present in synaptic vesicles. We propose that intracellular CHT1 can be recruited during stimulation to increase choline uptake in nerve terminals.     

Sesquiterpene lactone from Wunderlichia crulsiana inhibits the respiratory burst of leukocytes triggered by distinct biochemical pathways

The sesquiterpene lactone tubiferin was chemically purified from the brazilian native plant Wunderlichia crulsiana and identified by NMR and GC/MS data. Its ability to inhibit the respiratory burst of peritoneal inflammatory polymorphonuclear leukocytes (PMN) stimulated upon addition of phorbol miristate acetate (PMA), opsonized zymosan (OZ), and N-formyl-methionyl-leucyl-phenylalanine (fMLP) was evaluated. The tubiferin inhibition was more pronounced when PMN were stimulated through the protein kinase C pathway (PMA) compared to the alternative complement pathway (OZ). The inhibition when PMN were triggered by a chemoattractant stimulus (fMLP) was similar to that achieved with OZ-stimulated phagocytes. Tubiferin showed dose-dependent effects on the PMN respiratory burst triggered by the three different substances, and also decreased substantially the carrageenan-induced mice paw edema.     

Dietary components may prevent mutation-related diseases in humans

Since it is not always possible to reduce human exposure to mutagens, attempts have been directed to identify potential antimutagens and anticarcinogens for use in protecting the population against environmental disease. The purpose of this paper is to provide the reader with information about the antimutagenic and anticarcinogenic potentials of some dietary constituents and foods widely consumed in Brazil, and to reinforce diet as a key factor in determining genomic stability and preventing human diseases. In this report, we have summarized data that show interactive effects between some dietary components and specific chemical mutagens or carcinogens using in vitro and in vivo short- or medium-term assays. The summary indicates that certain dietary compounds may be useful agents for disease prevention.     

Mechanism of anticlastogenicity of Agaricus blazei Murill mushroom organic extracts in wild type CHO (K(1)) and repair deficient (xrs5) cells by chromosome aberration and sister chromatid exchange assays

Agaricus blazei Murill is a medicinal mushroom native to Brazil. The present work assessed the clastogenic and anticlastogenic potential of organic extracts (ethanol and chloroform/methanol) from the lineage AB97/11 in chinese hamster CHO-K(1) (wild type) and CHO-xrs5 (repair deficient) cells using the chromosome aberration (CA) and sister chromatid exchange (SCE) assays. In these experimental conditions were observed: (a) anticlastogenic effect at concentrations of 0.06 and 0.09% of the EtOH extract and at the 0.03 and 0.06% concentrations of the C/MetOH extract in CHO-K(1); (b) absence of protector effect on CHO-xrs5 cells; and (c) absence of protector effect in the SCE assay. These results indicate that organic extracts of A. blazei lineage AB97/11 present bio-antimutagenic type protective activity.