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1.
Life Sci ; 232: 116621, 2019 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-31269415

RESUMO

Kainate (KA) mouse model induced by intraperitoneal injection has been widely used for epilepsy and neurodegeneration studies. KA elicits sustained epileptic activity in mouse brain revealed by recurrent behavioral seizures, deteriorative neurodegeneration and various neurological deficits. However, to date, the vast majority of the studies used male mice only, and few studies on the comparison of brain injury between male and female mice in this model were reported. Epidemiological studies indicate that sex may affect the susceptibility to seizure response and neurodegeneration process. Therefore, this study focused on the effect of sex difference on KA-induced recurrent seizures and mortality, locomotor activity and cognitive impairment, and hippocampal neurodegeneration and reactive gliosis in mice. Our results showed that, compared to females, adult male mice exhibited worse performance in mortality rate, severity of epileptic seizures, and cognitive impairment indicated by novel object recognition task. Unexpectedly, post-KA male and female mice underwent similar decline and recovery of locomotor activity. KA-induced neurodegeneration in the whole hippocampus, particularly in CA1 and CA3 subregions, along with the deteriorative reactive gliosis in astrocytes and microglia, was more severe in males than that in females. These data provided the direct in vivo evidence that indicates the key role of sex difference in studies with KA mouse model, and this could be beneficial for optimizing the design of future studies.


Assuntos
Ácido Caínico/efeitos adversos , Ácido Caínico/metabolismo , Animais , Astrócitos/efeitos dos fármacos , Disfunção Cognitiva/fisiopatologia , Modelos Animais de Doenças , Epilepsia/induzido quimicamente , Feminino , Gliose/induzido quimicamente , Hipocampo/efeitos dos fármacos , Ácido Caínico/farmacologia , Masculino , Camundongos , Microglia/efeitos dos fármacos , Neurônios/efeitos dos fármacos , Convulsões/induzido quimicamente , Convulsões/fisiopatologia , Fatores Sexuais
2.
ACS Chem Biol ; 14(5): 1002-1010, 2019 05 17.
Artigo em Inglês | MEDLINE | ID: mdl-31026143

RESUMO

Plasma-membrane glutamate transporters of the excitatory amino acid transporter (EAAT) family are important for maintaining a low glutamate concentration in the extracellular space of the mammalian brain. Glutamate is believed to be transported in its negatively charged form and energetically driven by the cotransport of three sodium ions, at least two of which are bound within the dielectric of the membrane. It was hypothesized that binding of substrates and competitive inhibitors is also electrogenic because the binding site is located near the center of the membrane. To test this hypothesis, we rapidly applied a low-affinity competitive inhibitor, kainate, to the glutamate transporter subtype EAAT2, resulting in outward transient current caused by movement of net negative charge of the inhibitor into the low dielectric of the protein/membrane. Consistent with these data, rate constants for inhibitor dissociation and binding were also voltage dependent. Our results are supported by electrostatic calculations and molecular dynamics simulations of spontaneous substrate dissociation, showing that the substrate and inhibitor binding site is located within the membrane environment of low dielectric constant. Charge movement caused by binding of negatively charged amino acid substrate is compensated by the charge of cotransported Na+ ion(s), thus preventing inhibition of substrate binding at negative membrane potentials. This charge compensation mechanism may be relevant for other Na+-driven transporters which recognize negatively charged substrates.


Assuntos
Sistema X-AG de Transporte de Aminoácidos/metabolismo , Antagonistas de Aminoácidos Excitatórios/farmacologia , Sistema X-AG de Transporte de Aminoácidos/antagonistas & inibidores , Animais , Fenômenos Biofísicos , Encéfalo/metabolismo , Ácido Caínico/metabolismo , Cinética , Mamíferos , Potenciais da Membrana , Simulação de Dinâmica Molecular , Especificidade por Substrato
3.
BMC Mol Biol ; 20(1): 7, 2019 02 26.
Artigo em Inglês | MEDLINE | ID: mdl-30808304

RESUMO

BACKGROUND: A major cause of phytoplankton mortality is predation by zooplankton. Strategies to avoid grazers have probably played a major role in the evolution of phytoplankton and impacted bloom dynamics and trophic energy transport. Certain species of the genus Pseudo-nitzschia produce the neurotoxin, domoic acid (DA), as a response to the presence of copepod grazers, suggesting that DA is a defense compound. The biosynthesis of DA comprises fusion of two precursors, a C10 isoprenoid geranyl pyrophosphate and L-glutamate. Geranyl pyrophosphate (GPP) may derive from the mevalonate isoprenoid (MEV) pathway in the cytosol or from the methyl-erythritol phosphate (MEP) pathway in the plastid. L-glutamate is suggested to derive from the citric acid cycle. Fragilariopsis, a phylogenetically related but nontoxic genus of diatoms, does not appear to possess a similar defense mechanism. We acquired information on genes involved in biosynthesis, precursor pathways and regulatory functions for DA production in the toxigenic Pseudo-nitzschia seriata, as well as genes involved in responses to grazers to resolve common responses for defense strategies in diatoms. RESULTS: Several genes are expressed in cells of Pseudo-nitzschia when these are exposed to predator cues. No genes are expressed in Fragilariopsis when treated similarly, indicating that the two taxa have evolved different strategies to avoid predation. Genes involved in signal transduction indicate that Pseudo-nitzschia cells receive signals from copepods that transduce cascading molecular precursors leading to the formation of DA. Five out of seven genes in the MEP pathway for synthesis of GPP are upregulated, but none in the conventional MEV pathway. Five genes with known or suggested functions in later steps of DA formation are upregulated. We conclude that no gene regulation supports that L-glutamate derives from the citric acid cycle, and we suggest the proline metabolism to be a downstream precursor. CONCLUSIONS: Pseudo-nitzschia cells, but not Fragilariopsis, receive and respond to copepod cues. The cellular route for the C10 isoprenoid product for biosynthesis of DA arises from the MEP metabolic pathway and we suggest proline metabolism to be a downstream precursor for L-glutamate. We suggest 13 genes with unknown function to be involved in diatom responses to grazers.


Assuntos
Diatomáceas/genética , Diatomáceas/metabolismo , Ácido Caínico/análogos & derivados , Toxinas Marinhas/genética , Toxinas Marinhas/metabolismo , Redes e Vias Metabólicas/genética , Eritritol/análogos & derivados , Eritritol/metabolismo , Herbivoria , Ácido Caínico/metabolismo , Fosfatos de Poli-Isoprenil/metabolismo , Fosfatos Açúcares/metabolismo
4.
Genome Biol Evol ; 11(3): 731-747, 2019 03 01.
Artigo em Inglês | MEDLINE | ID: mdl-30778535

RESUMO

Untangling the functional basis of divergence between closely related species is a step toward understanding species dynamics within communities at both the evolutionary and ecological scales. We investigated cellular (i.e., growth, domoic acid production, and nutrient consumption) and molecular (transcriptomic analyses) responses to varying nutrient concentrations across several strains belonging to three species of the toxic diatom genus Pseudo-nitzschia. Three main results were obtained. First, strains from the same species displayed similar transcriptomic, but not necessarily cellular, responses to the experimental conditions. It showed the importance of considering intraspecific diversity to investigate functional divergence between species. Second, a major exception to the first finding was a strain recently isolated from the natural environment and displaying contrasting gene expression patterns related to cell motility and domoic acid production. This result illustrated the profound modifications that may occur when transferring a cell from the natural to the in vitro environment and asks for future studies to better understand the influence of culture duration and life cycle on expression patterns. Third, transcriptomic responses were more similar between the two species displaying similar ecology in situ, irrespective of the genetic distance. This was especially true for molecular responses related to TCA cycle, photosynthesis, and nitrogen metabolism. However, transcripts related to phosphate uptake were variable between species. It highlighted the importance of considering both overall genetic distance and ecological divergence to explain functional divergence between species.


Assuntos
Evolução Biológica , Diatomáceas/fisiologia , Ácido Caínico/análogos & derivados , Ácido Caínico/metabolismo , Família Multigênica , Nutrientes , Fenótipo
5.
Harmful Algae ; 79: 105-114, 2018 11.
Artigo em Inglês | MEDLINE | ID: mdl-30420012

RESUMO

Blooms of Pseudo-nitzschia species are frequent, but presently unpredictable, in the Juan de Fuca Eddy region off the coasts of Washington (US) and British Columbia (Canada). This upwelling eddy region is proposed to be the bloom commencement site, before cells are entrained into the coastal surface currents. During a shipboard study, we characterized the different stages of the Pseudo-nitzschia bloom development from its initiation and intensification, to its eventual sinking and dissipation. Specifically, we followed a water mass using lagrangian ARGOS-tracked drifters released at the eddy water mass and quantified production of dissolved and particulate domoic acid, and the physiological status of the Pseudo-nitzschia cells with regards to photosynthesis, nutrient needs and sinking rates, along with its relationship with competing species - in this case, the marine euglenoid, Eutreptiella spp. The drifter study allows for an interpretation of the presence or absence of Pseudo-nitzschia and domoic acid against active environmental factors - particularly copper and iron.


Assuntos
Diatomáceas/fisiologia , Proliferação Nociva de Algas , Ácido Caínico/análogos & derivados , Intoxicação por Frutos do Mar , Colúmbia Britânica , Diatomáceas/química , Ácido Caínico/metabolismo , Fotossíntese , Washington
6.
Harmful Algae ; 79: 44-49, 2018 11.
Artigo em Inglês | MEDLINE | ID: mdl-30420014

RESUMO

A somewhat disparate, yet temporally cohesive, set of phytoplankton abundance, microphytobenthos, including the diatom Pseudo-nitzschia, benthic infauna, and sediment toxin data were used to develop a theory for the transfer of domoic acid (DA) from the toxic diatom to the benthos in the highly productive waters of the northern Gulf of Mexico near the Mississippi River plume. Archived samples and new data were used to test the theory that DA is likely to be incorporated into benthic consumers. High spring abundances of potentially toxic Pseudo-nitzschia diatoms were simultaneously present in the surface waters, bottom waters and on the seafloor. Examination of the gut contents of a typical deposit-feeding and suspension-feeding polychaete, Paraprionospio pinnata, during similar periods of high Pseudo-nitzschia abundance in surface water indicated consumption of the diatoms. Demersal fishes, particularly Atlantic croaker, are known to consume these polychaetes, with a potential for transfer of DA to even higher trophic levels. These findings warrant a theory to be tested with further studies about the trophic linkage of a phytoplankton toxin into the benthic food web.


Assuntos
Diatomáceas/metabolismo , Cadeia Alimentar , Sedimentos Geológicos/química , Ácido Caínico/análogos & derivados , Poliquetos/metabolismo , Animais , Diatomáceas/química , Golfo do México , Ácido Caínico/metabolismo , Fitoplâncton/metabolismo , Estações do Ano
7.
Harmful Algae ; 79: 58-63, 2018 11.
Artigo em Inglês | MEDLINE | ID: mdl-30420017

RESUMO

The commercial demand for domoic acid (DA), the phycotoxin responsible for Amnesic Shellfish Poisoning, is currently met by extraction from a diminishing supply of stockpiled contaminated mussels (Mytilus edulis). As this supply becomes scarce, a more reliable source is needed. Purification of the toxin from an algal source would be easier and more economical than from shellfish tissue if algal growth and yield of toxin were maximized. This project was initiated to determine if DA could be produced using large-scale semi-continuous algal cultures, which should reduce labour and shorten the time required for biomass production. Pseudo-nitzschia multiseries was grown in 300-L fibreglass photobioreactors called a Brite-Box™. The effect of temperature and nutrient depletion on the yield of DA by P. multiseries was examined. A decline in maximum cell number without a substantial increase in cellular DA was associated with increased temperature. Maximum total cellular DA (8.8 pg cell-1) was achieved at 20 °C. Semi-continuous culture of P. multiseries is accompanied by increasing amounts of DA lost to the medium. The process was deemed to be feasible for growing P. multiseries but methods to recover this extracellular DA are necessary for this process to be economical.


Assuntos
Diatomáceas/metabolismo , Ácido Caínico/análogos & derivados , Intoxicação por Frutos do Mar , Animais , Bivalves , Estudos de Viabilidade , Ácido Caínico/metabolismo , Frutos do Mar
8.
Harmful Algae ; 79: 64-73, 2018 11.
Artigo em Inglês | MEDLINE | ID: mdl-30420018

RESUMO

Grazers can induce toxin (domoic acid, DA) production in diatoms. The toxic response has been observed in two species of Pseudo-nitzschia and was induced by Calanus copepods. In this study, interactions between diatoms and copepods were further explored using different species of diatoms and copepods. All herbivorous copepods induced toxin production, whereas exposure to carnivorous copepods did not. In line with this, increasing the number of herbivorous copepods resulted in even higher toxin production. The induced response is thus only elicited by copepods that pose a real threat to the responding cells, which supports that the induced toxin production in diatoms evolved as an inducible defense. The cellular toxin content in Pseudo-nitzschia was positively correlated to the concentration of a group of specific polar lipids called copepodamides that are excreted by the copepods. This suggests that copepodamides are the chemical cues responsible for triggering the toxin production. Carnivorous copepods were found to produce less or no copepodamides. Among the diatoms exposed to grazing herbivorous copepods, only two of six species of Pseudo-nitzschia and none of the Nitzschia or Fragilariopsis strains responded by producing DA, indicating that not all Pseudo-nitzschia species/strains are able to produce DA, and that different diatom species might have different strategies for coping with grazing pressure. Growth rate was negatively correlated to cellular domoic acid content indicating an allocation cost associated with toxin production. Long-term grazing experiments showed higher mortality rates of grazers fed toxic diatoms, supporting the hypothesis that DA production is an induced defense mechanism.


Assuntos
Copépodes/fisiologia , Diatomáceas/fisiologia , Ácido Caínico/análogos & derivados , Animais , Coevolução Biológica , Herbivoria , Ácido Caínico/metabolismo , Ácido Caínico/toxicidade
9.
Harmful Algae ; 79: 87-104, 2018 11.
Artigo em Inglês | MEDLINE | ID: mdl-30420020

RESUMO

Blooms of the marine diatom genus Pseudo-nitzschia that produce the neurotoxin domoic acid have been documented with regularity along the coast of southern California since 2003, with the occurrence of the toxin in shellfish tissue predating information on domoic acid in the particulate fraction in this region. Domoic acid concentrations in the phytoplankton inhabiting waters off southern California during 2003, 2006, 2007, 2011 and 2017 were comparable to some of the highest values that have been recorded in the literature. Blooms of Pseudo-nitzschia have exhibited strong seasonality, with toxin appearing predominantly in the spring. Year-to-year variability of particulate toxin has been considerable, and observations during 2003, 2006, 2007, 2011 and again in 2017 linked domoic acid in the diets of marine mammals and seabirds to mass mortality events among these animals. This work reviews information collected during the past 15 years documenting the phenology and magnitude of Pseudo-nitzschia abundances and domoic acid within the Southern California Bight. The general oceanographic factors leading to blooms of Pseudo-nitzschia and outbreaks of domoic acid in this region are clear, but subtle factors controlling spatial and interannual variability in bloom magnitude and toxin production remain elusive.


Assuntos
Diatomáceas/metabolismo , Proliferação Nociva de Algas , Ácido Caínico/análogos & derivados , California , Ácido Caínico/metabolismo , Fitoplâncton , Estações do Ano , Água do Mar , Frutos do Mar
10.
J Phycol ; 54(6): 918-922, 2018 12.
Artigo em Inglês | MEDLINE | ID: mdl-30270437

RESUMO

Pseudo-nitzschia nanaoensis sp. nov. is described from waters around Nan'ao Island (South China Sea), using morphological data and molecular evidence. This species is morphologically most similar to P. brasiliana, but differs by a denser arrangement of fibulae, interstriae, and poroids, as well as by the structure of the valvocopula and the narrow second band. Pseudo-nitzschia nanaoensis constitutes a monophyletic lineage and is well differentiated from other species on the LSU and ITS2 sequence-structure trees. Pseudo-nitzschia nanaoensis makes up the basal node on the LSU tree, and forms a sister clade with a group of P. pungens and P. multiseries on the ITS2 tree. The ability of cultured strains to produce domoic acid was assessed, including its possible induction by the presence of a copepod and brine shrimp, by liquid chromatography-tandem mass spectrometry. However, no strains showed detectable domoic acid.


Assuntos
Diatomáceas/classificação , Ácido Caínico/análogos & derivados , Toxinas Marinhas/metabolismo , China , DNA de Protozoário/análise , DNA Espaçador Ribossômico/análise , Diatomáceas/citologia , Diatomáceas/genética , Diatomáceas/ultraestrutura , Ácido Caínico/metabolismo , Filogenia
11.
Toxicon ; 155: 27-31, 2018 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-30312694

RESUMO

Pseudo-nitzschia multiseries is a diatom species associated with the production of domoic acid (DA), a water soluble neurotoxin that is easily transferred up in the food web, causing devastating effects on top marine organisms and humans. Despite studies on Pseudo-nitzschia are relevant to human health safety, partitioning of marine toxins between intracellular and extracellular fractions are poorly documented. This study aimed to determine the growth rates and DA content, both intracellular and extracellular, of Pseudo-nitzschia multiseries cultures at three different light settings (15, 120 and 560 µmol m-2 s-1). The optimal conditions for cell growth were observed at 120 and 560 µmol m-2 s-1, whereas DA production was observed in P. multiseries at 15 and 120 µmol m-2 s-1, ranging between 0.18-2.56 and 0.16-3.5 pg DA cell-1, respectively. Higher intracellular DA concentrations were found during the senescence phase at low light intensity and during the exponential phase at medium light intensity, while higher concentrations of dissolved DA were found at low and medium light intensities in the senescence phase reaching 3 and 10 ng DA mL-1 respectively. The amount of toxin released into the culture medium represents the most important fraction ranging between 63 and 98% during the exponential phase and nearly 99% during the senescence phase. In contrast, under low light intensity, dissolved DA was detected in the culture medium only during the senescence phase. This study confirms the importance of light intensity on DA production and clearly shows that dissolved domoic acid is an important fraction in Pseudo-nitzschia cultures, suggesting with the careful assumptions of results from static cultures extrapolated to bloom situations that waterborne exposure of marine organism should be considered during blooms of Pseudo-nitzschia multiseries.


Assuntos
Diatomáceas/crescimento & desenvolvimento , Diatomáceas/efeitos da radiação , Ácido Caínico/análogos & derivados , Toxinas Marinhas/análise , Células Cultivadas , Diatomáceas/metabolismo , Relação Dose-Resposta à Radiação , Ácido Caínico/análise , Ácido Caínico/isolamento & purificação , Ácido Caínico/metabolismo , Luz , Toxinas Marinhas/isolamento & purificação
12.
Brain Res Bull ; 143: 106-115, 2018 10.
Artigo em Inglês | MEDLINE | ID: mdl-30347263

RESUMO

Effects of kainate or 6-hydroxidopamine (6-OHDA) lesions in the ventromedial prefrontal cortex (vmPFC) on taste-related learning and memory processes were examined. Neurotoxins were applied by iontophoretic method to minimize the extent of lesion and the side effects. Acquisition and retention of conditioned taste avoidance (CTA) was tested to different taste stimuli (0.05 M NaCl, 0.01 M saccharin, 0.01 M citrate and 0.00025 M quinine). In the first experiment, palatability index of taste solutions with these concentrations has been determined as strongly palatable (NaCl, saccharin), weakly palatable (citrate) and weakly unpalatable (quinine) taste stimuli. In two other experiments vmPFC lesions were performed before CTA (acquisition) or after CTA (retrieval). Our results showed that both kainate and 6-OHDA microlesions of vmPFC resulted in deficit of CTA acquisition (to NaCl, saccharin and citrate) and retrieval (to NaCl and saccharin). Deficits were specific to palatable tastants, particularly those that are strongly palatable, and did not occur for unpalatable stimulus. The present data provide evidence for the important role of vmPFC neurons and catecholaminergic innervation of the vmPFC in taste related learning and memory processes.


Assuntos
Ácido Caínico/farmacologia , Oxidopamina/farmacologia , Córtex Pré-Frontal/efeitos dos fármacos , Animais , Aprendizagem da Esquiva/efeitos dos fármacos , Condicionamento Clássico/efeitos dos fármacos , Ácido Caínico/metabolismo , Masculino , Memória , Oxidopamina/metabolismo , Ratos , Ratos Wistar , Sacarina , Paladar/fisiologia
13.
Science ; 361(6409): 1356-1358, 2018 09 28.
Artigo em Inglês | MEDLINE | ID: mdl-30262498

RESUMO

Oceanic harmful algal blooms of Pseudo-nitzschia diatoms produce the potent mammalian neurotoxin domoic acid (DA). Despite decades of research, the molecular basis for its biosynthesis is not known. By using growth conditions known to induce DA production in Pseudo-nitzschia multiseries, we implemented transcriptome sequencing in order to identify DA biosynthesis genes that colocalize in a genomic four-gene cluster. We biochemically investigated the recombinant DA biosynthetic enzymes and linked their mechanisms to the construction of DA's diagnostic pyrrolidine skeleton, establishing a model for DA biosynthesis. Knowledge of the genetic basis for toxin production provides an orthogonal approach to bloom monitoring and enables study of environmental factors that drive oceanic DA production.


Assuntos
Diatomáceas/metabolismo , Eutrofização , Ácido Caínico/análogos & derivados , Neurotoxinas/biossíntese , Diatomáceas/genética , Ácido Caínico/química , Ácido Caínico/metabolismo , Família Multigênica , Neurotoxinas/genética , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo
14.
Sci Rep ; 8(1): 8858, 2018 06 11.
Artigo em Inglês | MEDLINE | ID: mdl-29891970

RESUMO

Corticofugal fibers target the subthalamic nucleus (STN), a component nucleus of the basal ganglia, in addition to the striatum, their main input. The cortico-subthalamic, or hyperdirect, pathway, is thought to supplement the cortico-striatal pathways in order to interrupt/change planned actions. To explore the previously unknown properties of the neurons that project to the STN, retrograde and anterograde tools were used to specifically identify them in the motor cortex and selectively stimulate their synapses in the STN. The cortico-subthalamic neurons exhibited very little sag and fired an initial doublet followed by non-adapting action potentials. In the STN, AMPA/kainate synaptic currents had a voltage-dependent conductance, indicative of GluA2-lacking receptors and were partly inhibited by Naspm. AMPA transmission displayed short-term depression, with the exception of a limited bandpass in the 5 to 15 Hz range. AMPA synaptic currents were negatively controlled by dopamine D5 receptors. The reduction in synaptic strength was due to postsynaptic D5 receptors, mediated by a PKA-dependent pathway, but did not involve a modified rectification index. Our data indicated that dopamine, through post-synaptic D5 receptors, limited the cortical drive onto STN neurons in the normal brain.


Assuntos
Dopamina/metabolismo , Córtex Motor/metabolismo , Neurônios/metabolismo , Receptores de Dopamina D5/fisiologia , Núcleo Subtalâmico/metabolismo , Ácido alfa-Amino-3-hidroxi-5-metil-4-isoxazol Propiônico/metabolismo , Animais , Corpo Estriado/metabolismo , Ácido Caínico/metabolismo , Camundongos Endogâmicos C57BL , Vias Neurais , Neurônios/citologia , Sinapses/metabolismo , Transmissão Sináptica
15.
Harmful Algae ; 73: 12-29, 2018 03.
Artigo em Inglês | MEDLINE | ID: mdl-29602500

RESUMO

The toxigenic diatom Pseudo-nitzschia multiseries Hasle, isolated from the U.S. Pacific Northwest, was examined in unialgal laboratory cultures and in natural assemblages during shipboard experiments, to examine cellular growth and domoic acid (DA) production as a function of nitrogen (N) substrate and availability expected during bloom development and decline. Laboratory experiments utilizing batch cultures conducted at saturating (120 µmol photons m-2 s-1) photosynthetic photon flux density (PPFD), demonstrated that P. multiseries (strain NWFSC-245) grows equally well on the three N substrates tested (nitrate [NO3-], ammonium [NH4+] and urea), and achieved an average specific growth rate of 0.83 d-1. Despite equivalent growth rates, cellular toxicity (particulate DA concentration normalized to cell abundance) varied as a function of N substrate, with urea-grown cells demonstrating 1.3- and 3.4-fold more toxicity than both NH4+- and NO3--grown cells. Cellular toxicity of the N-limited chemostat cultures, grown at a dilution rate of 0.48 d-1, were less than the cellular toxicity measured for the N-replete batch cultures for all three N substrates, but again cellular toxicity varied as a function of N substrate and the urea-supported cells were 3.5- and 4.3-fold more toxic than the respective NH4+- and NO3--supported cells. Starved cultures of P. multiseries showed no decline in cellular toxicity or change in the order of toxicity as a function of N substrate, and cells previously supported by urea were 13- and 5-fold more toxic than NH4+- and NO3--supported cells. At all three levels of N-sufficiency, the urea-grown cells consistently produced the highest concentration of particulate DA per cell compared to cells grown on either NO3- or NH4+. Shipboard N enrichment experiments using natural phytoplankton assemblages were conducted off the west coast of Washington in an area characterized by elevated concentrations of macronutrients and iron. All N (NO3-, NH4+ and urea) treatments showed significant increases in biomass (as measured by total and size-fractionated chlorophyll a) and the abundance of Pseudo-nitzschia species over the 6-d experiment. As with the unialgal laboratory experiments, cellular toxicity varied as a function of the N source supporting growth, and the planktonic assemblages enriched with either NH4+ or urea demonstrated greater cellular toxicity than the assemblages supported solely by NO3-. These laboratory and field results demonstrate that N substrate can regulate the toxicity of Pseudo-nitzschia species, and that N source should be considered when evaluating the potential effects of cultural eutrophication on the growth of toxigenic diatoms.


Assuntos
Técnicas de Cultura de Células/métodos , Diatomáceas/fisiologia , Nitrogênio/metabolismo , Clorofila , Ácido Caínico/análogos & derivados , Ácido Caínico/metabolismo , Toxinas Marinhas/metabolismo
16.
Br J Pharmacol ; 175(11): 2097-2115, 2018 06.
Artigo em Inglês | MEDLINE | ID: mdl-29574880

RESUMO

BACKGROUND AND PURPOSE: A non-psychoactive phytocannabinoid, cannabidiol (CBD), shows promising results as an effective potential antiepileptic drug in some forms of refractory epilepsy. To elucidate the mechanisms by which CBD exerts its anti-seizure effects, we investigated its effects at synaptic connections and on the intrinsic membrane properties of hippocampal CA1 pyramidal cells and two major inhibitory interneurons: fast spiking, parvalbumin (PV)-expressing and adapting, cholecystokinin (CCK)-expressing interneurons. We also investigated whether in vivo treatment with CBD altered the fate of CCK and PV interneurons using immunohistochemistry. EXPERIMENTAL APPROACH: Electrophysiological intracellular whole-cell recordings combined with neuroanatomy were performed in acute brain slices of rat temporal lobe epilepsy in in vivo (induced by kainic acid) and in vitro (induced by Mg2+ -free solution) epileptic seizure models. For immunohistochemistry experiments, CBD was administered in vivo (100 mg·kg-1 ) at zero time and 90 min post status epilepticus, induced with kainic acid. KEY RESULTS: Bath application of CBD (10 µM) dampened excitability at unitary synapses between pyramidal cells but enhanced inhibitory synaptic potentials elicited by fast spiking and adapting interneurons at postsynaptic pyramidal cells. Furthermore, CBD restored impaired membrane excitability of PV, CCK and pyramidal cells in a cell type-specific manner. These neuroprotective effects of CBD were corroborated by immunohistochemistry experiments that revealed a significant reduction in atrophy and death of PV- and CCK-expressing interneurons after CBD treatment. CONCLUSIONS AND IMPLICATIONS: Our data suggest that CBD restores excitability and morphological impairments in epileptic models to pre-epilepsy control levels through multiple mechanisms to reinstate normal network function.


Assuntos
Anticonvulsivantes/farmacologia , Canabidiol/farmacologia , Modelos Animais de Doenças , Epilepsia do Lobo Temporal/tratamento farmacológico , Hipocampo/citologia , Hipocampo/efeitos dos fármacos , Interneurônios/efeitos dos fármacos , Administração Oral , Animais , Anticonvulsivantes/administração & dosagem , Canabidiol/administração & dosagem , Epilepsia do Lobo Temporal/induzido quimicamente , Epilepsia do Lobo Temporal/metabolismo , Hipocampo/metabolismo , Interneurônios/fisiologia , Ácido Caínico/metabolismo , Masculino , Ratos , Ratos Sprague-Dawley
17.
Epilepsy Behav ; 79: 154-161, 2018 02.
Artigo em Inglês | MEDLINE | ID: mdl-29289903

RESUMO

Tobacco smoking is considered the greatest risk factor for early death caused by noncommunicable diseases. Currently, there are more than one billion tobacco smokers in the world predisposed to many diseases including heart attack, stroke, cancer, and premature birth or birth defects related to the consumption of cigarettes. However, studies on the association between tobacco smoking and seizures or epilepsy are insufficient and not well documented. In the present study, the authors examined the convulsive effects of the intracerebroventricular administration of cigarette smoke condensate (CSC, 2µl/Rat) in rats and compared it with the intensity of seizures in the kainic acid (KA)-induced seizure model of epilepsy. The role of the cholinergic system was also investigated by testing the effect of the muscarinic acetylcholine receptors (mAChRs) antagonist atropine (2ml/kg) on CSC-induced seizures. The results indicate that a central injection of CSC produces an epileptic behavior similar to that induced by KA, the similarities include the following parameters: time latency of seizures, latency and duration of tonic-clonic seizures, duration of seizures, survival, and tonic-clonic rate. However, a pretreatment with atropine reduced seizures and all their parameters.


Assuntos
Convulsivantes , Epilepsia/induzido quimicamente , Antagonistas Muscarínicos/farmacologia , Convulsões/induzido quimicamente , Fumar/efeitos adversos , Animais , Atropina/farmacologia , Feminino , Ácido Caínico/efeitos adversos , Ácido Caínico/metabolismo , Ácido Caínico/farmacologia , Masculino , Gravidez , Ratos , Receptores Muscarínicos , Convulsões/epidemiologia
18.
Sci Rep ; 8(1): 356, 2018 01 10.
Artigo em Inglês | MEDLINE | ID: mdl-29321590

RESUMO

Domoic acid (DA, 1), a potent neurotoxin that causes amnesic shellfish poisoning, has been found in diatoms and red algae. While biosynthetic pathway towards DA from geranyl diphosphate and L-glutamate has been previously proposed, its late stage is still unclear. Here, six novel DA related compounds, 7'-methyl-isodomoic acid A (2) and B (3), N-geranyl-L-glutamic acid (4), 7'-hydroxymethyl-isodomoic acid A (5) and B (6), and N-geranyl-3(R)-hydroxy-L-glutamic acid (7), were isolated from the red alga, Chondria armata, and their structures were determined. The compounds 4 and 7, linear compounds, are predictable as the precursors to form the DA pyrrolidine ring. The compounds 2 and 3 are thought as the cyclized products of 7; therefore, dehydration and electron transfer from the internal olefin of 7 is a possible mechanism for the pyrrolidine ring formation. One terminal methyl group of the side chain of 2 and 3 is predicted to be oxidized to hydroxymethyl (5, 6), and then to carboxylic acids, forming isodomoic acids A and B. Finally, the terminal olefin of isodomoic acid A would be isomerized to form DA. In addition, [15N, D]-labeled 4 was incorporated into DA using the diatom, Pseudo-nitzschia multiseries, demonstrating that 4 is the genuine precursor of DA.


Assuntos
Diatomáceas/metabolismo , Ácido Caínico/análogos & derivados , Rodófitas/química , Vias Biossintéticas , Cromatografia Líquida , Ácido Caínico/química , Ácido Caínico/metabolismo , Espectroscopia de Ressonância Magnética , Espectrometria de Massas , Estrutura Molecular
19.
Life Sci ; 193: 40-46, 2018 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-29223539

RESUMO

AIMS: Experimental and clinical studies have demonstrated that components of renin-angiotensin system are elevated in the hippocampus in epileptogenic conditions. In the present work, we explored the changes in the expression of angiotensin II receptor, type 1 (AT1 receptor) in limbic structures, as well as the effect of the AT1 receptor antagonist losartan in a model of comorbid hypertension and epilepsy. MAIN METHODS: The expression of AT1 receptors was compared between spontaneously hypertensive rats (SHRs) and Wistar rats by using immunohistochemistry in the kainate (KA) model of temporal lobe epilepsy (TLE). The effect of losartan was studied on AT1 receptor expression in epileptic rats that were treated for a period of 4weeks after status epilepticus. KEY FINDINGS: The naive and epileptic SHRs were characterized by stronger protein expression of AT1 receptor than normotensive Wistar rats in the CA1, CA3a, CA3b, CA3c field and the hilus of the dentate gyrus of the dorsal hippocampus but fewer cells were immunostained in the piriform cortex. Increased AT1 immunostaining was observed in the basolateral amygdala of epileptic SHRs but not of epileptic Wistar rats. Losartan exerted stronger and structure-dependent suppression of AT1 receptor expression in SHRs compared to Wistar rats. SIGNIFICANCE: Our results confirm the important role of AT1 receptor in epilepsy and suggest that the AT1receptor antagonists could be used as a therapeutic strategy for treatment of comorbid hypertension and epilepsy.


Assuntos
Losartan/farmacologia , Receptor Tipo 1 de Angiotensina/efeitos dos fármacos , Angiotensina II/farmacologia , Bloqueadores do Receptor Tipo 1 de Angiotensina II/farmacologia , Angiotensinas , Animais , Pressão Sanguínea/efeitos dos fármacos , Comorbidade , Modelos Animais de Doenças , Epilepsia/tratamento farmacológico , Expressão Gênica/efeitos dos fármacos , Hipocampo/metabolismo , Hipertensão/tratamento farmacológico , Ácido Caínico/efeitos adversos , Ácido Caínico/metabolismo , Sistema Límbico/patologia , Losartan/metabolismo , Losartan/uso terapêutico , Masculino , Ratos , Ratos Endogâmicos SHR , Ratos Wistar , Sistema Renina-Angiotensina/efeitos dos fármacos
20.
Mar Environ Res ; 133: 45-48, 2018 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-29223596

RESUMO

Domoic acid (DA) is a neurotoxin that causes degenerative damage to brain cells and induces permanent short-term memory loss in mammals. In cephalopod mollusks, although DA is known to accumulate primarily in the digestive gland, there is no knowledge whether DA reaches their central nervous system. Here we report, for the first time, the presence of DA in brain tissue of the common octopus (Octopus vulgaris) and the European cuttlefish (Sepia officinalis), and its absence in the brains of several squid species (Loligo vulgaris, L. forbesi and Todarodes sagittatus). We argue that such species-specific differences are related to their different life strategies (benthic/nektobenthic vs pelagic) and feeding ecologies, as squids mainly feed on pelagic fish, which are less prone to accumulate phycotoxins. Additionally, the temporal persistence of DA in octopus' brain reinforces the notion that these invertebrates can selectively retain this phycotoxin. This study shows that two highly-developed invertebrate species, with a complex central nervous system, where glutamatergic transmission is involved in vertebrate-like long-term potentiation (LTP), have the ability of retaining and possibly tolerating chronic exposure to DA, a potent neurotoxin usually acting at AMPA/kainate-like receptors. Here, we filled a gap of information on whether cephalopods accumulated this neurotoxin in brain tissue, however, further studies are needed to determine if these organisms are neurally or behaviourally impaired by DA.


Assuntos
Encéfalo/metabolismo , Decapodiformes/metabolismo , Ácido Caínico/análogos & derivados , Toxinas Marinhas/metabolismo , Octopodiformes/metabolismo , Animais , Monitoramento Ambiental , Ácido Caínico/metabolismo , Intoxicação por Frutos do Mar
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