Cyanobacteria and Eukaryotic Microalgae as Emerging Sources of Antibacterial Peptides.

Cyanobacteria and microalgae are oxygen-producing photosynthetic unicellular organisms encompassing a great diversity of species, which are able to grow under all types of extreme environments and exposed to a wide variety of predators and microbial pathogens. The antibacterial compounds described for these organisms include alkaloids, fatty acids, indoles, macrolides, peptides, phenols, pigments and terpenes, among others. This review presents an overview of antibacterial peptides isolated from cyanobacteria and microalgae, as well as their synergism and mechanisms of action described so far. Antibacterial cyanopeptides belong to different orders, but mainly from Oscillatoriales and Nostocales. Cyanopeptides have different structures but are mainly cyclic peptides. This vast peptide repertoire includes ribosomal and abundant non-ribosomal peptides, evaluated by standard conventional methodologies against pathogenic Gram-negative and Gram-positive bacteria. The antibacterial activity described for microalgal peptides is considerably scarcer, and limited to protein hydrolysates from two Chlorella species, and few peptides from Tetraselmis suecica. Despite the promising applications of antibacterial peptides and the importance of searching for new natural sources of antibiotics, limitations still persist for their pharmaceutical applications.

Voltage vs. Ligand I: Structural basis of the intrinsic flexibility of S3 segment and its significance in ion channel activation.

We systematically predict the internal flexibility of the S3 segment, one of the most mobile elements in the voltage-sensor domain. By analyzing the primary amino acid sequences of V-sensor containing proteins, including Hv1, TPC channels and the voltage-sensing phosphatases, we established correlations between the local flexibility and modes of activation for different members of the VGIC superfamily. Taking advantage of the structural information available, we also assessed structural aspects to understand the role played by the flexibility of S3 during the gating of the pore. We found that S3 flexibility is mainly determined by two specific regions: (1) a short NxxD motif in the N-half portion of the helix (S3a), and (2) a short sequence at the beginning of the so-called paddle motif where the segment has a kink that, in some cases, divide S3 into two distinct helices (S3a and S3b). A good correlation between the flexibility of S3 and the reported sensitivity to temperature and mechanical stretch was found. Thus, if the channel exhibits high sensitivity to heat or membrane stretch, local S3 flexibility is low. On the other hand, high flexibility of S3 is preferentially associated to channels showing poor heat and mechanical sensitivities. In contrast, we did not find any apparent correlation between S3 flexibility and voltage or ligand dependence. Overall, our results provide valuable insights into the dynamics of channel-gating and its modulation.

SnoReport 2.0: new features and a refined Support Vector Machine to improve snoRNA identification.

BACKGROUND: snoReport uses RNA secondary structure prediction combined with machine learning as the basis to identify the two main classes of small nucleolar RNAs, the box H/ACA snoRNAs and the box C/D snoRNAs. Here, we present snoReport 2.0, which substantially improves and extends in the original method by: extracting new features for both box C/D and H/ACA box snoRNAs; developing a more sophisticated technique in the SVM training phase with recent data from vertebrate organisms and a careful choice of the SVM parameters C and γ; and using updated versions of tools and databases used for the construction of the original version of snoReport. To validate the new version and to demonstrate its improved performance, we tested snoReport 2.0 in different organisms. RESULTS: Results of the training and test phases of boxes H/ACA and C/D snoRNAs, in both versions of snoReport, are discussed. Validation on real data was performed to evaluate the predictions of snoReport 2.0. Our program was applied to a set of previously annotated sequences, some of them experimentally confirmed, of humans, nematodes, drosophilids, platypus, chickens and leishmania. We significantly improved the predictions for vertebrates, since the training phase used information of these organisms, but H/ACA box snoRNAs identification was improved for the other ones. CONCLUSION: We presented snoReport 2.0, to predict H/ACA box and C/D box snoRNAs, an efficient method to find true positives and avoid false positives in vertebrate organisms. H/ACA box snoRNA classifier showed an F-score of 93 % (an improvement of 10 % regarding the previous version), while C/D box snoRNA classifier, an F-Score of 94 % (improvement of 14 %). Besides, both classifiers exhibited performance measures above 90 %. These results show that snoReport 2.0 avoid false positives and false negatives, allowing to predict snoRNAs with high quality. In the validation phase, snoReport 2.0 predicted 67.43 % of vertebrate organisms for both classes. For Nematodes and Drosophilids, 69 % and 76.67 %, for H/ACA box snoRNAs were predicted, respectively, showing that snoReport 2.0 is good to identify snoRNAs in vertebrates and also H/ACA box snoRNAs in invertebrates organisms.

Mirnacle: machine learning with SMOTE and random forest for improving selectivity in pre-miRNA ab initio prediction.

BACKGROUND: MicroRNAs (miRNAs) are key gene expression regulators in plants and animals. Therefore, miRNAs are involved in several biological processes, making the study of these molecules one of the most relevant topics of molecular biology nowadays. However, characterizing miRNAs in vivo is still a complex task. As a consequence, in silico methods have been developed to predict miRNA loci. A common ab initio strategy to find miRNAs in genomic data is to search for sequences that can fold into the typical hairpin structure of miRNA precursors (pre-miRNAs). The current ab initio approaches, however, have selectivity issues, i.e., a high number of false positives is reported, which can lead to laborious and costly attempts to provide biological validation. This study presents an extension of the ab initio method miRNAFold, with the aim of improving selectivity through machine learning techniques, namely, random forest combined with the SMOTE procedure that copes with imbalance datasets. RESULTS: By comparing our method, termed Mirnacle, with other important approaches in the literature, we demonstrate that Mirnacle substantially improves selectivity without compromising sensitivity. For the three datasets used in our experiments, our method achieved at least 97% of sensitivity and could deliver a two-fold, 20-fold, and 6-fold increase in selectivity, respectively, compared with the best results of current computational tools. CONCLUSIONS: The extension of miRNAFold by the introduction of machine learning techniques, significantly increases selectivity in pre-miRNA ab initio prediction, which optimally contributes to advanced studies on miRNAs, as the need of biological validations is diminished. Hopefully, new research, such as studies of severe diseases caused by miRNA malfunction, will benefit from the proposed computational tool.

Phosphatidylglycerol-derived phospholipids have a universal, domain-crossing role in stress responses.

Phosphatidylglycerol and phospholipids derived from it are widely distributed throughout the three domains of life. Cardiolipin is the best characterized of these phospholipids, and plays a key role in the response to environmental variations. Phosphatidylglycerol-derived phospholipids confer cell membranes with a wide range of responses, including changes in surface charge, fluidity, flexibility, morphology, biosynthesis and remodeling, that adapt the cell to these situations. Furthermore, the synthesis and remodeling of these phospholipids is finely regulated, highlighting the importance of these lipids in cell homeostasis and responses during stressful situations. In this article, we review the most important roles of these anionic phospholipids across domains, focusing on the biophysical basis by which these phospholipids are used in stress responses.

Regulation of nitrogenase by reversible mono-ADP-ribosylation.

Posttranslational modification of proteins plays a key role in the regulation of a plethora of metabolic functions. Protein modification by mono-ADP-ribosylation was first described as a mechanism of action of bacterial toxins. Since these pioneering studies, the number of pathways regulated by ADP-ribosylation in organisms from all domains of life expanded significantly. However, in only a few cases the full regulatory ADP-ribosylation circuit is known. Here, we review the system where mono-ADP-ribosylation regulates the activity of an enzyme: the regulation of nitrogenase in bacteria. When the nitrogenase product, ammonium, becomes available, the ADP-ribosyltransferase (DraT) covalently links an ADP-ribose moiety to a specific arginine residue on nitrogenase switching-off nitrogenase activity. After ammonium exhaustion, the ADP-ribosylhydrolase (DraG) removes the modifying group, restoring nitrogenase activity. DraT and DraG activities are reversibly regulated through interaction with PII signaling proteins . Bioinformatics analysis showed that DraT homologs are restricted to a few nitrogen-fixing bacteria while DraG homologs are widespread in Nature. Structural comparisons indicated that bacterial DraG is closely related to Archaea and mammalian ADP-ribosylhydrolases (ARH). In all available structures, the ARH active site consists of a hydrophilic cleft carrying a binuclear Mg(2+) or Mn(2+) cluster, which is critical for catalysis.

Use of alternative media and different types of recipients in alaboratory culture of Ankistrodesmus gracilis ( Reinsch ) Korshikov( Chlorophyceae ) / Utilização de meios alternativos e diferentes tipos de recipientes no cultivo de Ankistrodesmus gracilis (Reinsch) Korshikov (Chlorophyceae) em laboratório

A laboratory culture of Ankistrodesmus gracilis algae was evaluated by studyingthe biology of the species and its chemical composition in a traditional medium (CHU12)and in two alternative culture media, NPK (20-5-20) and macrophyte (Eichhornia crassipes)+ NPK, in three different types of recipients (fiberglass, carboy and plastic bag). First peakin the growth curve of Ankistrodesmus gracilis occurred on the ninth day in macrophyte+ NPK medium (74.16 x 105 cells mL-1) in a fiberglass recipient. However, highest density(p < 0.01) was reported in medium CHU12 (122.87 x 105 cells mL-1) in a plastic bag on thetwelfth day. Cell density was over 70 x 105 cells mL-1 starting on the twelfth day. Growthrate of A. gracilis was similar (p > 0.05) in culture media in the three recipients. Protein andfiber were similar (p > 0.05) in the treatments, but lipids were higher (p < 0.05) in NPK.Nitrate, ammonia, total phosphorus and orthophosphate contents were over 1 mg L-1 inNPK (p < 0.01). Results show that alternative media, such as NPK and macrophyte+ NPK, are possible for large-scale culture of A. gracilis cultured in three types of recipients.Costs are low, occupying less space when cultured in plastic bags and in the laboratory. (AU)

O objetivo do estudo foi avaliar os aspectos biológicos e a composição químicada alga Ankistrodesmus gracilis em laboratório utilizando um meio tradicional (CHU12) e doismeios alternativos, NPK (20-5-20) e macrófita (Eichhornia crassipes) + NPK em trêsdiferentes tipos de recipientes (cuba de fibra de vidro translúcido, garrafões e saco plástico).O primeiro pico de densidade celular de Ankistrodesmus gracilis ocorreu no nono dia da curvade crescimento em meio macrófita+NPK (74,16 x 105 células mL-1) no recipiente de fibrade vidro, porém a maior densidade (p < 0,01) foi observada no meio CHU12 (122,87 x 105células mL-1) em saco plástico no décimo segundo dia, a partir do qual a densidade celularpermaneceu acima de 70 x 105 células mL-1. A taxa de crescimento de A. gracilis foi similar(p > 0,05) nos três recipientes e meios de cultivo. Os teores de proteína e fibra foramsimilares (p > 0,05) nos tratamentos utilizados, já os de lipídios foram mais elevados (p < 0,05)no meio NPK. Os teores médios de nitrato, amônia, fósforo total e ortofosfato estiveramacima de 1 mg L-1 no meio NPK (p < 0,01). Os resultados obtidos neste estudo indicam apossibilidade do uso de meios alternativos como o NPK e macrophyte +NPK para o cultivode A. gracilis em larga escala cultivados nos três tipos de recipientes, porém, em saco plásticoo custo é baixo e ocupa menos espaço em cultivo de laboratório.(AU)

O-Methylated mannogalactan from the microalga Coccomyxa mucigena, symbiotic partner of the lichenized fungus Peltigera aphthosa.

A structural study of the carbohydrates from Coccomyxa mucigena, the symbiotic algal partner of the lichenized fungus Peltigera aphthosa, was carried out. It produced an O-methylated mannogalactan, with a (1-->6)-linked beta-galactopyranose main-chain partially substituted at O-3 by beta-Galp, 3-OMe-alpha-Manp or alpha-Manp units. There were no similarities with polysaccharides previously found in the lichen thallus of P. aphthosa. Moreover, the influence of lichenization in polysaccharide production by symbiotic microalgae and the nature of the photobiont in carbohydrate production in lichen symbiosis are also discussed.

Land-based nutrient enrichment of the Buccoo Reef Complex and fringing coral reefs of Tobago, West Indies.

Tobago's fringing coral reefs (FR) and Buccoo Reef Complex (BRC) can be affected locally by wastewater and stormwater, and regionally by the Orinoco River. In 2001, seasonal effects of these inputs on water-column nutrients and phytoplankton (Chl a), macroalgal C:N:P and delta(15)N values, and biocover at FR and BRC sites were examined. Dissolved inorganic nitrogen (DIN, particularly ammonium) increased and soluble reactive phosphorus (SRP) decreased from the dry to wet season. Wet season satellite and Chl a data showed that Orinoco runoff reaching Tobago contained chromophoric dissolved organic matter (CDOM) but little Chl a, suggesting minimal riverine nutrient transport to Tobago. C:N ratios were lower (16 vs. 21) and macroalgal delta(15)N values higher (6.6 per thousand vs. 5.5 per thousand) in the BRC vs. FR, indicating relatively more wastewater N in the BRC. High macroalgae and low coral cover in the BRC further indicated that better wastewater treatment could improve the health of Tobago's coral reefs.

The effect of organic ligands exuded by intertidal seaweeds on copper complexation.

Copper complexation in marine systems is mainly controlled by organic matter, partially produced by micro- and macroalgae that release exudates with the capacity to bind metals. This feature is important as it influences bioavailability, bioaccumulation, toxicity, and transport of copper through biological membranes. The release of Cu-complexing ligands by seaweeds cultured under copper excess was studied in the laboratory. Five macroalgae belonging to different functional groups were used, including the filamentous Chaetomorphafirma (Chlorophyta), the foliose Ulvalactuca (Chlorophyta) and Porphyra columbina (Rhodophyta), the corticated Gelidium lingulatum (Rhodophyta), and the leathery Lessonia nigrescens (Phaeophyceae). The concentration of ligands and their copper-binding strength (logK') of exudates released by each species was determined by anodic stripping voltammetry (ASV). The selected algae released exudates in a wide range of concentration (42-117 nM) after 48h of culture, and addition of 157nM copper increased the production of ligands up to 8 times. A relationship between structural complexity or thallus thickness and the amount of ligands released was not observed. The binding strength (logK') varied among species from 7.6 to 8.9, a response that was not modified by exposure to sub-lethal copper excess. The kelp L. nigrescens showed a fast response to copper excess, releasing ligands that reduced toxicity of the metal in hours. Results suggest that intertidal and shallow subtidal macroalgae might have been overlooked regarding their role as producers of organic ligands and, therefore, as modulators of metal complexing capacity in coastal waters.

Macroalgae blooms and delta 15N in subtropical coastal lagoons from the Southeastern Gulf of California: discrimination among agricultural, shrimp farm and sewage effluents.

Macroalgae blooms of Gracilaria vermiculophylla, Hypnea spinella and Spyridia filamentosa have been found in coastal lagoons in the SE Gulf of California. Agriculture, livestock, shrimp and poultry farms and sewage contribute anthropogenic nitrogen to the systems. The delta(15)N of these sources, water column and macroalgae were studied in order to identify the N supply for macroalgae blooms. delta(15)N of three species of macroalgae (4.3-13.6 per thousand) were enriched compared to the water column (delta(15)N-NO(3)(-) 3.7-6.8 per thousand), probably because of fractioning from the macroalgae. delta(15)N of POM (1.4-10.3 per thousand) was similar to the water column but the relationship was unclear. Depending on the site, macroalgae showed different delta(15)N values since some sites receive more or less influence from one given source of the associated watershed, which is reflected in the different delta(15)N values of the macroalgae of the same system and in the relative contributions of the sources.

The hard choice for alternative biofuels to diesel in Brazil.

This paper selects biofuel scenarios to substitute diesel in Brazil based on oil reserves increase, diesel imports, CO(2) emissions, crops agronomic yields, byproducts marketing and social impacts. This hard task still considers that agricultural practices in developing countries have large social impacts. Brazil presents high consumption of diesel oil in transport; low agronomic yield of traditional vegetable oil crops, which demand large cultivation areas contrasting with microalgae and palm oils which present high productivity. Concerning technologies, thermal cracking and transesterification of vegetable oils present a difficult economic situation related to vegetable oils price, food competition and glycerin market; BTL technology, meaning thermal gasification of biomass to liquids, faces problems related to low density of biomaterials and low viscosity of synthetic biodiesel produced. Biorefinery algal integrated systems and co-solvent technology to introduce up to 8% of ethanol into diesel seem to be feasible routes to reduce diesel consumption.

Evaluation onto life cycle parameters of Ceriodaphnia silvestrii submitted to 36 days dietary copper exposure.

The present study aimed to investigate the response of several life history parameters (body length and age of primipara, duration of embryonic development, maximum body length, reproduction and survival) of the zooplankton Ceriodaphnia silvestrii while exposed to copper contaminated algae Pseudokirchneriella subcapitata. In order to evaluate chronic exposure on the animal's life history, long-term experimental design was used. Cladocerans were fed with a dietary copper concentration ranging from 3 to 68 fg Cu cell(-1). Low waterborne copper exposure (around 10(-10)molL(-1) free Cu(2+) ions) was kept in the experiments. The results showed that by exposure of cladocerans during 7 days to contaminated food with 68 fg Cu cell(-1), a significant reduction in neonate production, survival and body size were obtained. Inhibition on egg production of zooplankton at 38 fg Cu cell(-1) were observed in 36 days chronic dietary copper exposure. The importance of entire life cycle study to better evaluate cladoceran responses to chronic dietary metal exposure was demonstrated.

Antioxidant capacity, polyphenol content and iron bioavailability from algae (Ulva sp., Sargassum sp. and Porphyra sp.) in human subjects.

Marine algae are easily produced and are good sources of Fe. If this Fe is bioavailable, algae consumption could help to combat Fe deficiency and anaemia worldwide. The objective of the present study was to evaluate Fe bioavailability, polyphenol content and antioxidant capacity from three species of marine algae distributed worldwide. A total of eighty-three subjects received maize- or wheat-based meals containing marine algae (Ulva sp., Sargassum sp. and Porphyra sp.) in different proportions (2.5, 5.0 and 7.5 g) added to the water to prepare the dough. All meals administered contained radioactive Fe. Absorption was evaluated calculating radioactive Fe incorporation in subjects' blood. The three species of marine algae were analysed for polyphenol content and reducing power. Algae significantly increased Fe absorption in maize- or wheat-based meals, especially Sargassum sp., due to its high Fe content. Increases in absorption were dose-dependent and higher in wheat- than in maize-based meals. Total polyphenol content was 10.84, 18.43 and 80.39 gallic acid equivalents/g for Ulva sp., Porphyra sp. and Sargassum sp., respectively. The antioxidant capacity was also significantly higher in Sargassum sp. compared with the other two species analysed. Ulva sp., Sargassum sp. and Porphyra sp. are good sources of bioavailable Fe. Sargassum sp. resulted in the highest Fe intake due to its high Fe content, and a bread containing 7.5 g Sargassum sp. covers daily Fe needs. The high polyphenol content found in Sargassum sp. could be partly responsible for the antioxidant power reported here, and apparently did not affect Fe absorption.

Lead pollution in subtropical ecosystems on the SE Gulf of California Coast: a study of concentrations and isotopic composition.

Lead pollution was investigated in environmental matrices and biological indicators collected from two typical subtropical coastal ecosystems in the southeast Gulf of California, Mexico. Lead concentrations and isotopic compositions ((206)Pb/(207)Pb and (208)Pb/(207)Pb) were measured using high resolution inductively-coupled plasma-mass spectrometry (HR-ICP-MS) and thermal ionization mass spectrometry (TIMS), respectively. Lead in surface estuary sediments (10.0-34.2microgg(-1)) and particulate Pb (25.0-128.7microgg(-1), >98% of total Pb) in the water column were significantly higher than levels in natural bedrock soils (15.1+/-8.3microgg(-1)) and river runoff (1.9+/-1.4microgg(-1)). Aquatic plants had Pb concentrations between 2.5 and 7.2microgg(-1), while those in macroalgae ranged from 3 to 5microgg(-1). The ranges of mean Pb concentrations in the aquatic animals studied (ranges in microgg(-1)) were as follows: zooplankton 32+/-3, mussels 2.3-3.9, oysters 1.9-7.9, snail 2.0-7.7, barnacles 0.1-18.5, fish 1.4-8.9, crab 6.3-40.2 and polychaetae 8.5-16.7. Pb values in 20-40% of oyster and fish samples and in all samples of crab exceeded acceptable levels for a food source for human consumption. Pb isotope ratios (206)Pb/(207)Pb, (208)Pb/(207)Pb in biota ranged from 1.188 to 1.206 and 2.448 to 2.470, respectively. A plot of (206)Pb/(207)Pb versus (208)Pb/(207)Pb for the environmental and biological samples collected from two study areas indicates that they contain lead from ores mined in Mexico and used in the past to produce leaded gasoline in use until 1997, natural Pb weathered from the Sierra Madre Occidental mother rock, and the later influence of inputs from a more radiogenic source related to industrial activity in the United States. Statistical software IsoSource results revealed that the Pb contained in environmental matrices and biomonitors is mostly derived from gasoline (20-90%) and US emissions (10-40%).

Change in life cycle parameters and feeding rate of Ceriodaphnia silvestrii Daday (Crustacea, Cladocera) exposure to dietary copper.

Changes in life cycle parameters (survival, growth, reproduction) and feeding rate of the tropical cladoceran Ceriodaphnia silvestrii as affected by Cu contaminated algae Pseudokirchneriella subcapitata were investigated. The dietary copper exposure ranged from 3 x 10(-15) to 68 x 10(-15) g Cu algal cell(-1). Low waterborne copper exposure (around 10(-10) mol l(-1) free Cu2+ ions) was kept in the experiments. The results show an increasing toxic effect on C. silvestrii with copper increase in algal cells; at the highest copper exposure, all life cycle parameters were significantly affected. A concentration of 38 x 10(-15) g Cu algal cell(-1) reduced egg hatching percentile and the number of neonates produced per female, but did not cause any statistically significant effect on animals survival nor to the number of eggs produced per female. The following sequence of events was observed from the lowest to the highest copper contamination: reproduction, feeding rate, body length and, at last, survival was affected. We conclude that algal cells are an important route of copper exposure and toxicity to cladocerans.

Heavy metals in benthic organisms from Todos os Santos Bay, Brazil.

The marine ecosystems of Todos os Santos Bay (TSB, The State of Bahia, Brazil) have been impacted by the presence on its coast of a large metropolitan area as well as of chemical and petrochemical activities. Despite its ecological importance, there is a lack of scientific information concerning metal contamination in TSB marine biota. Thus, we analyzed concentrations of metals in four species of marine benthic organisms (two seaweeds, Padina gymnospora and Sargassum sp. one seagrass, Halodule wrightii and one oyster, Crassostrea rhizophorae) in three sites from the TSB region that have been most affected by industrial activities. The concentrations of Al, Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn were determined by Atomic Absorption Spectrophometry. The obtained data indicates that cadmium and copper in seaweeds, oysters and seagrass, as well as Ni concentrations in oysters, were in range of contaminated coastal areas. Cadmium and copper are available to organisms through suspended particles, dissolved fraction of water column and bottom sediment interstitial water. As oysters and other mollusks are used as food sources by the local population, the metal levels found in oysters in TSB may constitute a health risk for this population. Our results suggest implanting a heavy metals biomonitoring program in the TSB marine ecosystems.

Antileishmanial properties of tropical marine algae extracts.

Aqueous and organic extracts of twenty-seven species of marine algae (14 species of Rhodophyta, 5 species of Phaeophyta and 8 species of Chlorophyta) collected from the Gulf of Mexico and Caribbean coast of the Yucatan Peninsula (Mexico) were evaluated for their antileishmanial in vitro activity against Leishmania mexicana promastigote forms. The cytotoxicity of these extracts was also assessed using brine shrimp. Organic extracts from Laurencia microcladia (Rhodophyta), Dictyota caribaea, Turbinaria turbinata and Lobophora variegata (Phaeophyta) possessed promising in vitro activity against L. mexicana promastigotes (LC(50) values ranging from 10.9 to 49.9 microg/ml). No toxicity of algal extracts against Artemia salina was observed with LC50 ranging from 119 to >or=1000 microg/ml. Further studies on bio-guided fractionation, isolation and characterization of pure compounds from these species as well as in vivo experiments are needed and are already in progress.

Intracellular increase of glutamate in neuroblatoma cells induced by polar substances of Galaxaura marginata (Rhodophyta, Nemaliales) / Aumento do glutamato intracelular induzido por substâncias polares de Galaxaura marginata (Rhodophyta, Nemaliales) em células de neuroblastoma

Four substances purified by HPLC from red seaweed Galaxaura marginata (Ellis & Solander) Lamouroux showed neuroprotective and mitochondria regulatory properties in neuroblastoma NEURO-2A cells line. Under oxidative basal conditions, each substance is capable of modifying the glutamate, glutamine and alanine intracellular concentrations, without to alter the oxidative equilibrium of these cells. These substances, also, produced a biphasic activity in the mitochondrial metabolism, inhibiting, in lower concentrations and stimulating, in higher concentrations the mechanism of cellular 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) reduction, that indicates the mitochondrial activity. These data suggest that the intracellular increase of glutamate can be related to the glutamate/glutamine cycle alterations induced by the blockade of intracellular glutamate transport. Moreover, we suggested that there are substances, exhibiting neuroprotective activity in neuroblastoma cells, protecting them from oxidative stress produced by the inhibition of the glutamate transporters.

Quatro substâncias purificadas da alga vermelha Galaxaura marginata (Ellis & Solander) Lamouroux, mediante HPLC, apresentaram propriedades neuroprotetoras e reguladoras da atividade mitocondrial quando testadas em células de neuroblastomas da cepa NEURO-2. Sob condições oxidativas basais, cada substância é capaz de modificar as concentrações intracelulares de glutamato, glutamina e alanina, sem alterar o equilíbrio oxidativo das células. Essas substâncias também produziram uma atividade bifásica no metabolismo mitocondrial, inibindo em baixas concentrações e estimulando em altas concentrações o mecanismo celular de redução do 3-(4,5-dimetiltiazol-2-il)-2,5-difeniltetrazol brometo (MTT), que indica atividade mitocondrial. Esses dados sugerem que o aumento do glutamato pode estar relacionado com a alteração do ciclo glutamato/glutamina induzido pelo bloqueio do transporte intracelular de glutamato. Além disso, nós sugerimos que essas substâncias exibem atividade neuroprotetora nas células de neuroblastoma, as protegendo do estresse oxidativo, produzido pela inibição dos transportadores de glutamato.

Trophic distribution of Cd, Pb, and Zn in a food web from Altata-Ensenada del Pabellón Subtropical Lagoon, SE Gulf of California.

The aim of the work was to obtain a comparative view of the trophic distribution of Cd, Pb, and Zn in different organisms of the food web (from primary producers to top predators), considering representative species in Altata-Ensenada del Pabellón subtropical lagoon (SE Gulf of California). The study provides the first quantitative information on the biotransference of Cd, Pb, and Zn in a moderately contaminated lagoon ecosystem. After examination of 31 trophic interactions, 20 cases resulted in transference factors (TF) > 1.0 for Cd, 14 cases for Pb, and 18 cases for Zn. For Cd, most of the TF > 1 were found mainly among the low trophic levels (15 of 20 links); for Pb, most of the TF > 1 were found mainly among the high trophic levels (11 of 14 links), and for Zn, most of the TF > 1 were found mainly among the low trophic levels (14 of 18 links). This can be interpreted as partial evidence of biomagnification of Cd, Pb, and Zn for the species involved.