In-vitro antibacterial, antifungal and cytotoxic properties of metal-based furanyl derived sulfonamides

A new series of antibacterial and antifungal furanyl-derived sulfonamides and their cobalt (II), copper (II), nickel (II) and zinc (II) metal complexes have been synthesized, characterized and screened for their in-vitro antibacterial activity against four Gram-negative (Escherichia coli, Shigella flexneri, Pseudomonas aeruginosa and Salmonella typhi) and two Gram-positive (Bacillus subtilis and Staphylococcus aureus) bacterial strains and, for in-vitro antifungal activity against Trichophyton longifusus, Candida albicans, Aspergillus flavus, Microsporum canis, Fusarium solani and Candida glaberata. The results of these studies revealed that all compounds showed significant to moderate antibacterial activity. However, the zinc (II) complexes were found to be comparatively much more active as compared to the others. For antifungal activity generally, compounds (22) and (24) showed significant activity against Escherichia coli (a), (6) against Shigella flexeneri (b), (16) and (22) against Pseudomonas aeruginosa (c), (14) and (16) against Salmonella typhi (d), (9) against Staphylococcus aureus (e) and, (14) and (16) against Bacillus subtilis (f) fungal strains. The brine shrimp (Artemia salina) bioassay was also carried out to study their in-vitro cytotoxic properties. Only three compounds, (6), (10) and (23) displayed potent cytotoxic activity with LD50 = 1.8535 x 10(-4), 1.8173 x 10(-4) and 1.9291 x 10(-4) respectively.

Nutritional enhancement of total lipid, n-3 and n-6 fatty acids in Artemia urmiana nauplii by enriching with ICES/30/4

Artemia urmiana nauplii were enriched with three different concentrations (100, 200 and 300 ppm) of commercial emulsion, ICES/30/4 during two periods (12 and 24 h) to evaluate the enhancement of its Highly Unsaturated Fatty Acids (HUFAs). This source was selected because of its high concentration of the longest chain HUFA's in the n-3 and n-6 series. When 24-h-old Artemia nauplii were enriched with 100 ppm concentration of ICES30/4 during 12 h enriching period, the docosahexanoic acid (DHA), eicosapentaenoic acid (EPA) and arachidonic acid (ARA) contents of the nauplii increased to 0.77, 1.22 and 0.34 and when enriched with 300 ppm during 24 h increased to 5.99, 4.97 and 0.73 mg g(-1) dry weight, respectively. DHA, EPA and ARA in control nauplii were 0.00, 0.82 and 0.61 mg g(-1) dryweight, respectively. Total lipid increased from 16.79% in control group to 20.87% in the treatment ICES30/4 24-300. The results suggest that high amount of emulsion and prolong the enriching period are effective in enriching Artemia nauplii in both DHA and EPA increasingly (p < 0.05) but in other fatty acids, there are differences only among period treatments (p < 0.05) and concentration are not any increasing effective. There are only differences among concentration treatments in total lipid p < 0.05) and enriching period do not show any differences.

Brine shrimp bioassay: importance of correct taxonomic identification of Artemia (Anostraca) species

Despite the common use of the brine shrimp bioassay in toxicology, there is confusion in the literature regarding citation of the correct taxonomic identity of the Artemia species used. The genus Artemia, once thought to be represented by a single species Artemia salina, is now known to be composed of several bisexual species as well as parthenogenetic populations. Artemia franciscana is the best studied of the Artemia species and is considered to represent the vast majority of studies in which Artemia is used as an experimental test organism. We found that in studies referring to the use of A. salina, the zoogeography of the cyst harvest site indicated that the species used was actually A. franciscana. Those performing bioassays with Artemia need to exercise diligence in assigning correct species identification, as the identity of the test organism is an important parameter in assuring the validity of the results of the assay.

The encysted dormant embryo proteome of Artemia sinica

The possibility of the brine shrimp Artemia to produce dormant embryo (cysts) in diapause is a key feature in its life history. In the present study, we obtained a proteomic reference map for the diapause embryo of Artemia sinica using two-dimensional gel electrophoresis with a pH range of 4-7 and a molecular weight range of 10-100 kDa. Approximately 233 proteins were detected, and 60 of them were analyzed by capillary liquid chromatography tandem mass spectrometry (LC-MS/MS). Of these, 39 spots representing 33 unique proteins were identified, which are categorized into functional groups, including cell defense, cell structure, metabolism, protein synthesis, proteolysis, and other processes. This reference map will contribute toward understanding the state of the diapause embryo and lay the basis and serve as a useful tool for further profound studies in the proteomics of Artemia at different developmental stages and physiological conditions.

Identification, cloning and tissue localization of a rainbow trout (Oncorhynchus mykiss) intelectin-like protein that binds bacteria and chitin

Intelectins are a recently identified group of animal lectins involved in innate immune surveillance. This paper describes the primary structure, expression and immunohistochemical localization of a rainbow trout plasma intelectin (RTInt). RTInt exhibited calcium-dependent binding to N-acetylglucosamine (GlcNAc) and mannose conjugated Toyopearl Amino 650 M matrices. When GlcNAc eluates from chromatography matrices were analyzed by reducing 1D PAGE and Western blots, the lectin appeared as approximately 37 kDa and approximately 72 kDa bands. Similar analysis of plasma revealed a single 72 kDa band under reducing conditions. MALDI-TOF MS demonstrated five, approximately 37 kDa isoforms (pI 5.3-6.1) separated by 2D-PAGE. A 975 bp cDNA sequence obtained by RT-PCR from liver and spleen tissue encoded a 325 amino acid secretory protein with homology to human and murine intelectins, which bind bacterial components and are induced during parasitic infections. Gene expression and immunohistochemistry detected RTInt in gill, spleen, hepatic sinusoid, renal interstitium, intestine, skin, swim bladder and within leukocytes. Direct binding assays demonstrated the ability of RTInt to bind relevant bacterial and chitinous targets. These findings suggest that RTInt plays a role in innate immune defense against bacterial and chitinous microbial organisms.

Effects of sonication and advanced chemical oxidants on the unicellular green alga Dunaliella tertiolecta and cysts, larvae and adults of the brine shrimp Artemia salina: a prospective treatment to eradicate invasive organisms from ballast water

Uptake and release of ship-borne ballast water is a major factor contributing to introductions of aquatic phytoplankton and invasive macroinvertebrates. Some invasive unicellular algae can cause harmful algal blooms and produce toxins that build up in food chains. Moreover, to date, few studies have compared the efficacy of ballast water treatments against different life history phases of aquatic macroinvertebrates. In the present study, the unicellular green alga Dunaliella tertiolecta, and three discrete life history phases of the brine shrimp Artemia salina, were independently used as model organisms to study the efficacy of sonication as well as the advanced oxidants, hydrogen peroxide and ozone, as potential ballast water treatments. Algal cells and brine shrimp cysts, nauplii, and adults were subjected to individual and combined treatments of sonication and advanced oxidants. Combined rather than individual treatments consistently yielded the highest levels of mortality in algal cells (100% over a 2 min exposure) and in brine shrimp (100% and 95% for larvae and adults, respectively, over a 2 min exposure). In contrast, mortality levels in brine shrimp cysts (66% over 2 min; increased to 92% over a 20 min exposure) were moderately high but consistently lower than that detected for larval or adult shrimp. Our results indicate that a combination of sonication and advanced chemical oxidants may be a promising method to eradicate aquatic unicellular algae and macroinvertebrates in ballast water.

Developmentally regulated synthesis of p8, a stress-associated transcription cofactor, in diapause-destined embryos of Artemia franciscana

Diapause-destined embryos of the crustacean Artemia franciscana arrest as gastrulae, acquire extreme stress tolerance, and enter profound metabolic dormancy. Among genes upregulated at 2 days postfertilization in these embryos is a homologue of p8, a stress-inducible transcription cofactor. Artemia p8 is smaller than vertebrate homologues but shares a basic helix-loop-helix domain and a bipartite nuclear localization signal. Probing of restriction digested DNA on Southern blots indicated a single Artemia p8 gene and 5'-RACE specified 2 transcription start sites. Several putative cis-acting regulatory sequences, including two heat shock elements, appeared upstream of the p8 transcription start site. Artemia p8 mRNA increased sharply at 1 day postfertilization in diapause-destined embryos and then declined, whereas p8 protein appeared 2 days postfertilization and remained relatively constant throughout development, indicating a stable protein. p8 was not detectable in nauplius-destined (nondiapause) Artemia embryos. Immunofluorescent staining revealed p8 within Artemia nuclei. The results support the idea that p8, a known stressresponsive transcription cofactor, mediates gene expression in diapause-destined Artemia embryos. p8 is the first diapause-related transcription factor identified in crustaceans and 1 of only a small number of such proteins identified in any organism undergoing diapause.

Life without water: expression of plant LEA genes by an anhydrobiotic arthropod

Anhydrobiotic animals protect cellular architecture and metabolic machinery in the dry state, yet the molecular repertoire supporting this profound dehydration tolerance is not fully understood. For the desiccation-tolerant crustacean, Artemia franciscana, we report differential expression of two distinct mRNAs encoding for proteins that share sequence similarities and structural features with late-embryogenesis abundant (LEA) proteins originally discovered in plants. Bioinformatic analyses support assignment of the LEA proteins from A. franciscana to group 3. This eucoelomate species is the most highly evolved animal for which LEA gene expression has been reported. It is becoming clear that an ensemble of micromolecules and macromolecules is important for establishing the physical conditions required for cellular stabilization during drying in nature.

Energizing an Invertebrate Embryo: Bafilomycin‐Dependent Respiration and the Metabolic Cost of Proton Pumping by the V‐ATPase

We examine herein the contribution of V-ATPase activity to the energy budget of aerobically developing embryos of Artemia franciscana and discuss the results in the context of quiescence under anoxia. (31)P-NMR analysis indicates that intracellular pH and NTP levels are unaffected by acute incubation of dechorionated embryos with the V-ATPase inhibitor, bafilomycin A(1). Bafilomycin A(1) also has no significant effect on oxygen consumption by isolated mitochondria. Taken together, these data indicate that bafilomycin does not affect energy-producing pathways in the developing embryo. However, the V-ATPase inhibitor exhibits a concentration-dependent inhibition of oxygen consumption in aerobic embryos. A conservative analysis of respirometric data indicates that proton pumping by the V-ATPase, and processes immediately dependent on this activity, constitutes approximately 31% of the aerobic energy budget of the preemergent embryo. Given the complete absence of detectable Na(+)K(+)-ATPase activity during the first hours of aerobic development, it is plausible that the V-ATPase is performing a role in both the acidification of intracellular compartments and the energization of plasma membranes. Importantly, the high metabolic cost associated with maintaining these diverse proton gradients requires that V-ATPase activity be downregulated under anoxia in order to attain the almost complete metabolic depression observed in the quiescent embryo.

Nonylphenol algal bioaccumulation and its effect through the trophic chain

Nonylphenol is a metabolic intermediate from the microbial transformation of detergents used worldwide. While nonylphenol shows some acute toxicity, it is also able to mimic important hormones resulting in the disruption of several processes by interfering with the signals that control the overall physiology of the organism. The effect of the pollutant nonylphenol (NP) through the trophic chain was studied. Microalgae Isochrysis galbana was able to bioconcentrate NP 6940 times, where 77% of initial NP (100microgl(-1)) is accumulated intracellularly after 1-h incubation. Crustacean Artemia fransiscana showed 25% higher growth when fed with NP-rich algae. However, Artemia metabolized almost all NP ingested and only traces of NP could be found in the organism, eliminating future NP effects. Zebrafish (Brachydanio rerio) were affected by the presence of 171microgg(-1) of NP in the diet, showing higher levels of the hormone vitellogenin and lower levels of cytochrome P450 activity. These results showed that organisms placed in the first level of trophic chain are able to significantly bioconcentrate the pollutant and endocrine disruptor NP. These grassed organisms affect the growth of crustacean. Moreover, the organisms placed on the top of some trophic chains, such as fish, could be affected by the presence of NP in their food, in both the hormone levels and metabolic enzymes. This work shows that the environmental presence of NP should be considered as a risk for the organisms living in an ecosystem.

Cloning and expression analysis of p26 gene in Artemia sinica

The protein p26 is a small heat shock protein that functions as a molecular chaperone to protect embryos by preventing irreversible protein damage during embryonic development. A 542 bp fragment of the p26 gene was cloned and sequenced. The fragment encoded 174 amino acid residues and the amino acid sequence contained the alpha-crystallin domain. Phylogenetic analysis showed that eight Artemia populations were divided into four major groups. Artemia sinica (YC) belonged to the East Asia bisexual group. Expression of the p26 gene at different developmental stages of A. sinica was quantified using real-time quantitative polymerase chain reaction followed by cloning and sequencing. The relationship between the quantity of p26 gene expression and embryonic development was analyzed. The results indicated that massive amounts of p26 were expressed during the development of A. sinica. At the developmental stage of 0 h, A. sinica expressed the highest level of p26. As development proceeded, expression levels of the p26 gene reduced significantly. There was a small quantity of p26 gene expression at the developmental stages of 16 h and 24 h. We concluded that p26 might be involved in protecting the embryo from physiological stress during embryonic development.

Protein stability in Artemia embryos during prolonged anoxia

Encysted embryos (cysts) of the brine shrimp, Artemia franciscana, are arguably the most stress-resistant of all animal life-history stages. One of their many adaptations is the ability to tolerate anoxia for periods of years, while fully hydrated and at physiological temperatures. Previous work indicated that the overall metabolism of anoxic embryos is brought to a reversible standstill, including the transduction of free energy and the turnover of macromolecules. But the issue of protein stability at the level of tertiary and quaternary structure was not examined. Here I provide evidence that the great majority of proteins do not irreversibly lose their native conformation during years of anoxia, despite the absence of detectable protein turnover. Although a modest degree of protein denaturation and aggregation occurs, that is quickly reversed by a brief post-anoxic aerobic incubation. I consider how such extraordinary stability is achieved and suggest that at least part of the answer involves massive amounts of a small heat shock protein (p26) that acts as a molecular chaperone, the function of which does not appear to require ribonucleoside di- or tri-phosphates.

Functional characterization of artemin, a ferritin homolog synthesized in Artemia embryos during encystment and diapause

Oviparously developing embryos of the crustacean Artemia franciscana encyst and enter diapause, exhibiting a level of stress tolerance seldom seen in metazoans. The extraordinary stress resistance of encysted Artemia embryos is thought to depend in part on the regulated synthesis of artemin, a ferritin superfamily member. The objective of this study was to better understand artemin function, and to this end the protein was synthesized in Escherichia coli and purified to apparent homogeneity. Purified artemin consisted of oligomers approximately 700 kDa in molecular mass that dissociated into monomers and a small number of dimers upon SDS/PAGE. Artemin inhibited heat-induced aggregation of citrate synthase in vitro, an activity characteristic of molecular chaperones and shown here to be shared by apoferritin and ferritin. This is the first report that apoferritin/ferritin may protect cells from stress other than by iron sequestration. Stably transfected mammalian cells synthesizing artemin were more resistant to heat and H(2)O(2) than were cells transfected with vector only, actions also shared by molecular chaperones such as the small heat shock proteins. The data indicate that artemin is a structurally modified ferritin arising either from a common ancestor gene or by duplication of the ferritin gene. Divergence, including acquisition of a C-terminal peptide extension and ferroxidase center modification, eliminated iron sequestration, but chaperone activity was retained. Therefore, because artemin accumulates abundantly during development, it has the potential to protect embryos from stress during encystment and diapause without adversely affecting iron metabolism.

Muscle development in dendrobranchiate shrimp, with comparison with Artemia

The muscle pattern of malacostracan and entomostracan crustacean nauplius larvae was compared using fluorescent phallotoxins. In the dendrobranchiate malacostracan Sicyonia ingentis, F-actin staining was first detected in limb setae at 12 h, likely within sensory nerves. Staining of F-actin was detected in the trunk at 15 h and grew into the naupliar limbs. Sarcomeres were detected at 19 h, identifying the structures as extrinsic limb muscles. The extrinsic limb muscles enlarged but retained their general pattern during the later nauplius stages. Longitudinal trunk muscles and circumferential visceral muscle (VM) developed in the post-naupliar region during nauplius instars 4 and 5, at the time when the gut also formed. In the anostracan branchiopod Artemia salina, the newly hatched nauplius contained an extensive system of extrinsic and intrinsic limb muscles. The gut was almost complete at hatching, along with its associated circumferential VM. Muscles similar in position and structure could be identified in nauplii from the two taxa, but different anatomical origins of extrinsic muscles were evident. Whether the naupliar limb muscles are homologous in malacostracans and branchiopods remains an open question. The strong musculature of the dendrobranchiate naupliar limbs correlates with the use of all three pairs of limbs for swimming.

Using an integrated approach to link biomarker responses and physiological stress to growth impairment of cadmium-exposed larval topsmelt

In this study, we used an integrated approach to determine whether key biochemical, cellular, and physiological responses were related to growth impairment of cadmium (Cd)-exposed larval topsmelt (Atherinops affinis). Food intake (Artemia franciscana nauplii), oxygen consumption rates, apoptotic DNA fragmentation (TUNEL assay), and metallothionein (MT)-like protein levels, were separately measured in relation to growth of larval topsmelt aqueously exposed to sublethal doses of Cd for 14 days. Cadmium accumulation and concentrations of abundant metals were also evaluated in a subset of fish. Fish in the highest Cd treatments (50 and 100 ppb Cd) were smaller in final mean weight and length, and consumed fewer A. franciscana nauplii than control fish. Food intake was positively correlated with final weight of larval topsmelt in Cd and control treatments; food intake increased as final weight of the fish increased. Oxygen consumption rates were positively correlated with Cd concentration and mean oxygen consumption rates were inversely correlated with final mean weight of topsmelt; the smallest fish were found in the highest Cd treatment and were respiring at higher rates than control fish. Apoptotic DNA fragmentation was concentration-dependent and was associated with diminished growth. Apoptotic DNA fragmentation was elevated in the gill of fish exposed to 50 ppb Cd, and in the gut, gill, and liver of fish exposed to 100 ppb Cd. Metallothionein (MT)-like protein levels in fish from 100 ppb Cd treatments were significantly higher than those in other treatments. Oxygen consumption rates may have increased as a compensatory response to Cd exposure. However, it is likely that the energy produced was allocated to an increased metabolic demand due to apoptosis, MT synthesis, and changes in ion regulation. This diversion of energy expenditures could contribute to growth impairment of Cd-exposed fish.

Knockdown of spalt function by RNAi causes de-repression of Hox genes and homeotic transformations in the crustacean Artemia franciscana

Hox genes play a central role in the specification of distinct segmental identities in the body of arthropods. The specificity of Hox genes depends on their restricted expression domains, their interaction with specific cofactors and selectivity for particular target genes. spalt genes are associated with the function of Hox genes in diverse species, but the nature of this association varies: in some cases, spalt collaborates with Hox genes to specify segmental identities, in others, it regulates Hox gene expression or acts as their target. Here we study the role of spalt in the branchiopod crustacean Artemia franciscana. We find that Artemia spalt is expressed in the pre-segmental 'growth zone' and in stripes in each of the trunk (thoracic, genital and post-genital) segments that emerge from this zone. Using RNA interference (RNAi), we show that knocking down the expression of spalt has pleiotropic effects, which include thoracic to genital (T-->G), genital to thoracic (G-->T) and post-genital to thoracic (PG-->T) homeotic transformations. These transformations are associated with a stochastic de-repression of Hox genes in the corresponding segments of RNAi-treated animals (AbdB for T-->G and Ubx/AbdA for G-->T and PG-->T transformations). We discuss a possible role of spalt in the maintenance of Hox gene repression in Artemia and in other animals.

Comparisons of stress proteins and soluble carbohydrate in encysted embryos of Artemia franciscana and two species of Parartemia

We compared stress proteins (p26, artemin, hsp70) and alcohol-soluble carbohydrates (ASC) in cysts of Artemia franciscana and two as yet un-named species populations of Parartemia, the brine shrimp endemic to Australia. The small stress proteins and molecular chaperones, p26 and artemin, previously thought to be restricted to Artemia, and present in very large amounts in its encysted embryos (cysts), were also detected by western blotting in Parartemia cysts, even though roughly 85-100 million years have passed since these genera diverged. We interpret this finding as further evidence for the adaptive importance of these proteins in coping with the severe stresses these encysted embryos endure. As expected, hsp70 was present in all three groups of cysts, but apparently at somewhat lower concentrations in those of Parartemia. Based on measurements of ASC we propose that the disaccharide trehalose, critical for desiccation tolerance in many animal cells, has probably also been maintained in the metabolic repertoire of Parartemia whose cysts have well developed tolerance to severe desiccation.

Characterization of the microtubule proteome during post-diapause development of Artemia franciscana

The microtubule proteome encompasses tubulin and a diverse group of proteins which associate with tubulin upon microtubule formation. These proteins either determine microtubule organization and function or their activity is influenced by microtubule association. To characterize the microtubule proteome in Artemia franciscana, tubulin assembly was induced with taxol in vitro after 0 and 12 h of post-diapause development. Proteins obtained by extraction of microtubules with 0.5 M NaCl were electrophoresed in two-dimensional gels and analyzed by mass spectrometry. Fifty-five proteins were identified with 10 of these occurring at both developmental stages, and multiple isoforms were observed for some proteins of the Artemia proteome. Their functions include roles in membrane transport, metabolism, chaperoning and protein synthesis, thus reflecting physiological properties of encysted Artemia such as stress resistance and the ability to rapidly initiate post-diapause development. For example, chaperones may protect tubulin during encystment and facilitate folding in metabolically active embryos. Additionally, the interaction of metabolic enzymes with microtubules funnels reaction intermediates, potentially enhancing efficiency within biochemical processes. This study represents the first systematic characterization of a crustacean microtubule proteome. Although it is difficult to be certain that all protein associations documented herein occur in vivo, the results suggest how protein-protein interactions contribute to cytoplasmic organization while implying how Artemia embryos resist stress and remain capable of development once diapause terminates.

Microcystin production in benthic mats of cyanobacteria in the Nile River and irrigation canals, Egypt

The present study describes for the first time the species composition and toxicity of benthic cyanobacteria forming mats on the Nile River and irrigation canal sediments in Egypt. A total of 19 species of cyanobacteria were isolated from these mats during this study. The toxicity of the extracts of these species was investigated using Artemia salina assay, mouse bioassay and enzyme linked immunosorbent assay (ELISA). The results showed that all the 19 benthic species isolated from cyanobacterial mats, were toxic to A. salina. Two of these species, namely Calothrix parietina and Phormidium tenue, caused toxicity to mice with neurotoxic signs appeared within 12 h after injection. Whereas, five species showed hepatotoxic effects to mice within 6 h after injection. The results of ELISA showed that all the extracts which had hepatotoxic effects to mice, contained high levels of microcystins with concentrations ranging from 1.6 to 4.1 mg g(-1) dry weight. HPLC analysis for heptotoxic extracts revealed that these extracts contained two peaks corresponding to microcystin-YR and -LR with different proportions. This study suggests that benthic species should be considered along with planktonic species during monitoring of toxic cyanobacteria in water sources, particularly the Nile river which is the main source of drinking water in Egypt.

Structural and functional roles for beta-strand 7 in the alpha-crystallin domain of p26, a polydisperse small heat shock protein from Artemia franciscana

Oviparous development in the extremophile crustacean, Artemia franciscana, generates encysted embryos which enter a profound state of dormancy, termed diapause. Encystment is marked by the synthesis of p26, a polydisperse small heat shock protein thought to protect embryos from stress. In order to elucidate structural/functional relationships within p26 and other polydisperse small heat shock proteins, and to better define the protein's role during diapause, amino acid substitutions R110G, F112R, R114A and Y116D were generated within the p26 alpha-crystallin domain by site-directed mutagenesis. These residues were chosen because they are highly conserved across species boundaries, and molecular modelling indicates that they are part of a key structural interface between dimers. The F112R mutation, which had the greatest impact on oligomerization, placed two charged residues at the p26 dimer-dimer interface, demonstrating the importance of beta-strand 7 in tetramer formation. All mutated versions of p26 were less able than wild-type p26 to confer thermotolerance on transformed bacteria and they exhibited diminished chaperone action in three in vitro assays; however, all variants retained protective activity. This apparent stability of p26 may, by prolonging effective chaperone life in vivo, enhance embryo stress resistance. All substitutions modified p26 intrinsic fluorescence, surface hydrophobicity and secondary structure, and the pronounced changes in variant R114A, as indicated by these physical measurements, correlated with the greatest loss of function. Although mutation R114A had the greatest effect on p26 chaperoning, it had the least on oligomerization. These results demonstrate that in contrast to many other small heat shock proteins, p26 effectiveness as a chaperone is independent of oligomerization. The results also reinforce the idea, occasioned by modelling, that R114 is removed slightly from dimer-dimer interfaces. Moreover, beta-strand 7 is shown to have an important role in oligomerization of p26, a function first proposed for this structural element upon crystallization of wheat Hsp16.9, a small heat shock protein with different quaternary structure.

Comparative toxicokinetics of cadmium in Artemia

The toxicokinetics of cadmium was determined for five populations belonging to four species of Artemia (A. salina, A. parthenogenetica, A. franciscana, and A. persimilis) using a bicompartmental model. The effects of sublethal cadmium concentration on the kinetic parameters in A. parthenogenetica were determined. The BCF values are inversely related to the concentration, as is the uptake rate (ku), whilst the elimination rate (ke) constant seems to be directly related to the exposure concentration. Values corresponding to the rate of metal influx (I) remain relatively constant (0.2477 to 0.4455 microg/g.h) in the concentration range from 0.1 to 1 mg Cd/L, and are higher (1.098 microg/g.h) at an exposure to 10 mg Cd/L. The cadmium accumulation pattern seems well conserved in the genus and is characterized by a fast elimination of the metal with Ke ranging from 0.0050 to 0.0231 h(-1). A. persimilis displays a different model to that corresponding to the other studied species exposed to the same cadmium concentration, presenting a low uptake rate constant (1.0564 mL/g. h) and a low BCF (211.3 mL/g).

Effects of widely used pharmaceuticals and a detergent on oxidative stress biomarkers of the crustacean Artemia parthenogenetica

Pharmaceuticals are continuously dispersed into the environment as a result of human and veterinary use, posing relevant environmental concerns. The present paper reports the acute toxic effects of three therapeutic agents (diazepam, clofibrate and clofibric acid) and a detergent, sodium dodecylsulphate (SDS), to the hypersaline crustacean Artemia parthenogenetica. This study specially focused on oxidative stress parameters, namely (1) total and selenium-dependent glutathione-peroxidase (GPx), (2) glutathione reductase (GRed), (3) total superoxide dismutase (SOD), and (4) glutathione-S-transferases (GSTs). The effects of tested substances on lipid peroxidation (thiobarbituric acid reactive substances, TBARS), and soluble cholinesterases (ChE) were also investigated. Diazepam caused a significant inhibition of ChE (LOEC = 7.04 mg/l) and total GPx activities. SDS was responsible for a decrease in the activity of both ChE (LOEC = 8.46 mg/l) and GRed (LOEC = 4.08 mg/l). Both fibrates (clofibrate and clofibric acid) were responsible for significant decreases in Se-dependent GPx, with LOEC values of 176.34 and 3.09 mg/l, respectively. Clofibrate also caused a slight increase of TBARS content of A. parthenogenetica homogenates. These results indicate that the exposure to all the tested compounds induced alterations on the cellular redox status in A. parthenogenetica. In addition, diazepam was shown to have the capability of interfering with A. parthenogenetica neurotransmission, through the inhibition of ChE.

V-ATPase expression during development of Artemia franciscana embryos: potential role for proton gradients in anoxia signaling

Under anoxia, Artemia franciscana embryos downregulate metabolic processes and approach an ametabolic state. Entrance into this quiescent state is accompanied by a profound acidification of the intracellular space, and more than two decades of research now clearly demonstrates that this acidification is critical to metabolic downregulation in anoxic embryos. However, the proximal mechanisms responsible for the pH shift remain largely unidentified. Here, we report evidence demonstrating expression of the V-ATPase in encysted embryos and present an argument for its involvement in the intracellular acidification induced by anoxia. We identified a single B-subunit cDNA sharing the greatest degree of sequence similarity with ;generalist-type' homologues from mammals (brain-type) and invertebrates. Quantitative analysis of B-subunit mRNA demonstrates differential expression throughout early development, and western blot analyses confirm the expression of at least six V-ATPase subunits in both heavy membranes and microsomal vesicles. The critical need for proton pumping during the anoxia-tolerant stage of development is demonstrated by incubation with the V-ATPase inhibitor bafilomycin A1, which halts embryonic development. Importantly, net proton flux from V-ATPase-acidified compartments to the surrounding cytoplasm is likely under anoxia and may significantly contribute to the enigmatic acidification critical to quiescence.

Dietary protein:lipid ratio and lipid nature affects fatty acid absorption and metabolism in a teleost larva

Studies with teleost larvae have reported poor performance associated with quantitative lipid imbalances in the diet. The present study examined the effect of dietary protein:neutral lipid ratio on fatty acid (FA) absorption efficiency and metabolism in larval Senegalese sole. In addition, the effect of lipid class (triolein (TRI) and l-3-phosphatidylcholine-1,2-di-oleoyl (PC)), carbon number and degree of saturation of the labelled NEFA, stearic acid (SA), oleic acid (OA) and DHA) was tested. FA absorption was determined by tube feeding [1-14C]-labelled lipids and NEFA after a single meal of either non-enriched Artemia (NEA) or Artemia enriched on a soyabean oil emulsion (EA), or after feeding these diets over an extended period of time (18 d). The tested dietary protein:lipid ratios had no short-term influence but long-term feeding of a diet higher in neutral lipid (EA) increased lipid accumulation within the gut epithelium and resulted in lower FA absorption (higher label evacuation and lower retention of dietary FA), which may partially explain the trend for lower growth observed with this diet. The lipids and NEFA, showed different digestive and metabolic properties, independent of feeding regime. FA absorption increased with unsaturation, being lowest for SA, followed by OA, and highest for DHA. In addition, sole larvae had a lower capacity to digest and absorb FA esterified to TRI, compared with PC, with the order of decreasing absorption being NEFA>PC>>TRI. Moreover, larvae appeared to discriminate between the source of OA, as this FA in the free form or esterified to PC was catabolised less than TRI.

Toxicity of algal-derived aldehydes to two invertebrate species: do heavy metal pollutants have a synergistic effect?

The recent discovery of the production of anti-proliferative aldehydes in a variety of microalgal species has lead to considerable investigation into the effects of these toxins on aquatic invertebrates. Studies have, however, rarely considered the impact pollutants may have on grazer responses to algal toxins. In this study, the acute toxicities of five aldehydes to the rotifer Brachionus plicatilis and nauplii of the brine shrimp Artemia salina are examined using immersion assays. In addition, the effect of a representative of these aldehydes in the presence of sub-lethal levels of heavy metals was examined. B. plicatilis generally showed greater sensitivity to the aldehydes than A. salina. The polyunsaturated 2-trans,4-trans-decadienal was the most toxic to both species having 24h LD(50) values of 7 and 20 microM for B. plicatilis and A. salina, respectively. The remaining aldehydes had different orders of toxicity for the two species with a stronger relationship observed between mortality and aldehyde carbon-chain length for A. salina whereas B. plicatilis mortality showed a stronger dependence on the presence of carbon-carbon double bonds in the aldehydes. The presence of 1 microM of copper sulphate in solutions of decadienal resulted in the reduction of the 24h LD(50) of decadienal by approximately a third for both species. 1 microM of copper chloride in solutions of decadienal reduced the 24h LD(50) of decadienal to A. salina nauplii by approximately 11% and 1 microM zinc sulphate caused a reduction of only 3%. Pre-exposure of the organisms to 1 microM copper sulphate had no significant impact on their subsequent mortality in decadienal. The ecological implications and the possible mechanisms for the action of copper sulphate on the response of organisms to decadienal are discussed.