Palladium-Catalyzed Chemoselective Protodecarboxylation of Polyenoic Acids.

Conditions for the first palladium-catalyzed chemoselective protodecarboxylation of polyenoic acids to give the desired polyenes in good yields are presented. The reactions proceed under mild conditions using either a Pd(0) or Pd(II) catalyst and tolerate a variety of aryl and aliphatic substitutions. Unique aspects of the reaction include the requirement of phosphines, water, and a polyene adjacent to the carboxylic acid.

Physico-electrochemical Characterization of Pluripotent Stem Cells during Self-Renewal or Differentiation by a Multi-modal Monitoring System.

Monitoring pluripotent stem cell behaviors (self-renewal and differentiation to specific lineages/phenotypes) is critical for a fundamental understanding of stem cell biology and their translational applications. In this study, a multi-modal stem cell monitoring system was developed to quantitatively characterize physico-electrochemical changes of the cells in real time, in relation to cellular activities during self-renewal or lineage-specific differentiation, in a non-destructive, label-free manner. The system was validated by measuring physical (mass) and electrochemical (impedance) changes in human induced pluripotent stem cells undergoing self-renewal, or subjected to mesendodermal or ectodermal differentiation, and correlating them to morphological (size, shape) and biochemical changes (gene/protein expression). An equivalent circuit model was used to further dissect the electrochemical (resistive and capacitive) contributions of distinctive cellular features. Overall, the combination of the physico-electrochemical measurements and electrical circuit modeling collectively offers a means to longitudinally quantify the states of stem cell self-renewal and differentiation.

Seasonal changes in the assembly mechanisms structuring tropical fish communities.

Despite growing interest in trait-based approaches to community assembly, little attention has been given to seasonal variation in trait distribution patterns. Mobile animals can rapidly mediate influences of environmental factors and species interactions through dispersal, suggesting that the relative importance of different assembly mechanisms can vary over short time scales. This study analyzes seasonal changes in functional trait distributions of tropical fishes in the Xingu River, a major tributary of the Amazon with large predictable temporal variation in hydrologic conditions and species density. Comparison of observed functional diversity revealed that species within wet-season assemblages were more functionally similar than those in dry-season assemblages. Further, species within wet-season assemblages were more similar than random expectations based on null model predictions. Higher functional richness within dry season communities is consistent with increased niche complementarity during the period when fish densities are highest and biotic interactions should be stronger; however, null model tests suggest that stochastic factors or a combination of assembly mechanisms influence dry-season assemblages. These results demonstrate that the relative influence of community assembly mechanisms can vary seasonally in response to changing abiotic conditions, and suggest that studies attempting to infer a single dominant mechanism from functional patterns may overlook important aspects of the assembly process. During the prolonged flood pulse of the wet season, expanded habitat and lower densities of aquatic organisms likely reduce the influence of competition and predation. This temporal shift in the influence of different assembly mechanisms, rather than any single mechanism, may play a large role in maintaining the structure and diversity of tropical rivers and perhaps other dynamic and biodiverse systems.

Oxyropsis ephippia, a New Hypoptopomatine Catfish (Siluriformes: Loricariidae) from Guyana.

Oxyropsis ephippia, a new species of loricariid catfish in the subfamily Hypoptopomatinae, is described from the Essequibo and Branco basins, Guyana. Based on the presence of a keel-like row of relatively enlarged odontodes on trunk median plates immediately above the lateral line canal, the new species is assigned to the genus Oxyropsis Eigenmann & Eigenmann 1889. It can be distinguished from its congeners by having the keel-like row on each median plate dominated by a single odontode (one closest to the posterior margin of the plate) conspicuously larger than preceding ones, and by having the sides of the trunk below the median series (approximately between median plates 7 to 12) shielded only by plates of the midventral series, with the exclusion of plates from the ventral series. The report of O. ephippia from the Essequibo is the first record of the genus in a river system that drains the north-central portion of the Guiana Shield into the Atlantic Ocean.

Palaeontological evidence for the last temporal occurrence of the ancient western Amazonian river outflow into the Caribbean.

Fossil catfishes from fluvio-lacustrine facies of late Miocene Urumaco, early Pliocene Castilletes and late Pliocene San Gregorio formations provide evidence of a hydrographic connection in what is today desert regions of northern Colombia and Venezuela. New discoveries and reevaluation of existing materials leads to the recognition of two new records of the pimelodid Brachyplatystoma cf. vaillantii, and of three distinct doradid taxa: Doraops sp., Rhinodoras sp., and an unidentified third form. The presence of fossil goliath long-whiskered catfishes and thorny catfishes are indicative of the persistence of a fluvial drainage system inflow into the South Caribbean during the Pliocene/Pleistocene boundary, complementary to the previous western Amazonian hydrographic system described from the Middle Miocene Villavieja Formation in central Colombia and Late Miocene Urumaco Formation in northwestern Venezuela. The Pliocene Castilletes and San Gregorio formations potentially represent the last lithostratigraphic units related with an ancient western Amazonian fish fauna and that drainage system in the Caribbean. Alternatively, it may preserve faunas from a smaller, peripheral river basin that was cut off earlier from the Amazon-Orinoco, today found in the Maracaibo basin and the Magdalena Rivers.

Molecular phylogeny of thorny catfishes (Siluriformes: Doradidae).

Doradidae is a monophyletic catfish family endemic to continental South America, and composed of 93 valid species here placed in 31 genera. Existing phylogenetic hypotheses for Doradidae are derived from comprehensive analyses of morphological data, and a single molecular-based study on a limited subset of taxa. To provide a robust molecular phylogeny commensurate with those based on morphology, we gathered original and published sequence data for 86 species-level taxa (at least 70 valid species plus 16 new or questionably nominal species) and all genera of Doradidae, as well as 10 species (nine genera) of Auchenipteridae and three species and genera of Aspredinidae as outgroups. 3011 base pairs were aligned for two mitochondrial genes (cytochrome c oxidase subunit 1, and 16S ribosomal RNA) and one nuclear gene (recombination activating gene 1), and analyzed for a total of 143 specimens (130 doradids, 10 auchenipterids and three aspredinids). Tree topologies generated by Maximum Parsimony, Maximum Likelihood, and Bayesian analyses were largely congruent, and are compared to existing phylogenies based on morphology and molecules. Although many of the relationships supported by our molecular analyses corroborated those based on morphology, others are newly hypothesized or remain in conflict. The monotypic Wertheimeria, Franciscodoras and Kalyptodoras, for example, form a newly proposed clade, and the subfamily Astrodoradinae is placed at the base of the doradid tree. The monotypic Doraops and Centrochir, endemic to Caribbean drainages north and west of the Andes, are sister to Pterodoras and Platydoras, respectively, two genera that are widely distributed in Atlantic drainages. Additional biogeographic implications are discussed for hypothesized relationships among doradids. Molecular evidence strongly supports synonymization of monotypic Merodoras with Amblydoras, and transfer of Amblydoras bolivarensis to genus Scorpiodoras. Furthermore, we consider Opsodoras ternetzi to be more properly placed in the genus Nemadoras. The genus Opsodoras may warrant synonymization with Hemidoras, and the monophyly of genus Ossancora is not supported; however, we refrain from taxonomic decisions regarding those taxa until a broader spectrum of doradids can be submitted to further morphological and molecular phylogenetic analyses.

New species of thorny catfish, genus Leptodoras Boulenger (Siluriformes: Doradidae), from Tapajós and Xingu basins, Brazil

A new species of thorny catfish (family Doradidae) is described as a member of genus Leptodoras Boulenger by having a modified oral hood and first gill arch with enlarged accessory lamellae extending well onto medial face of gill filaments. The new species is distinguished by three characteristics unique within Leptodoras: gas bladder moderately sized (not reduced) with simple walls (diverticula absent), and paired bony capsules on anteriormost vertebrae reduced to paired cup-like laminar ossifications separated by triangular septum. The new species was discovered from material recently collected in the Tapajós basin at Serra do Cachimbo and in the headwaters of rio Xingu. The species description is supplemented by a detailed osteological description, discussion on its placement among congeners, and a re-evaluation of the diagnosis of Leptodoras and its relationships with sister taxon Anduzedoras oxyrhynchus. In addition, the distributions of several species of Leptodoras are expanded based on recent collecting efforts and identification of museum specimens not previously studied.

Uma nova espécie de botoado da família Doradidae é descrita. A nova espécie é incluída no gênero Leptodoras Boulenger por possuir capuz oral modificado e primeiro arco branquial com lamelas acessórias bem desenvolvidas estendidas sobre a face medial dos filamentos branquiais. A nova espécie distingue-se dentre Leptodoras por três características únicas: bexiga natatória de tamanho moderado (não reduzida), com paredes simples (sem divertículos), e cápsulas ósseas pares sobre as vértebras anteriores reduzidas a um par de ossificações laminares em formato de cuia separadas por septo triangular. A nova espécie foi descoberta a partir do material coletado na bacia do rio Tapajós na Serra do Cachimbo e nas cabeceiras do rio Xingu. A descrição da espécie é suplementada por uma descrição osteológica detalhada, discussão sobre o seu posicionamento dentre os congêneres, re-avaliação da diagnose de Leptodoras e sua relação com o táxon irmão Anduzedoras oxyrhynchus. Além disso, a distribuição de diversas espécies de Leptodoras é revisada com base nos recentes esforços de coleta e na identificação de espécimes de museus não previamente estudados.

Platydoras brachylecis, a new species of thorny catfish (Siluriformes: Doradidae) from northeastern Brazil

Platydoras brachylecis, new species, is described from coastal drainages of northeastern Brazil (Pindaré to Parnaíba rivers), and diagnosed from congeners by the unique combination of: pale yellow to white stripe beginning above orbits, continuing midlaterally on body and onto middle rays of caudal fin; skin in axil of each midlateral thorn without concentration of pigment forming small dark spot, midlateral scutes shallow (depth of 10th scute 8.8-11.9 percent of SL), and midlateral scutes on caudal peduncle distinctly separated by strip of skin from middorsal and midventral caudal-peduncle plates. Three additional species of Platydoras are recognized as valid: P. armatulus (lower Orinoco, Amazon and Paraguay-Paraná drainages), P. costatus (coastal drainages of Suriname and French Guiana), and P. hancockii (upper Orinoco, Negro, Essequibo and Demerara drainages). The nominal species P. dentatus and P. helicophilus are tentatively treated as junior synonyms of P. costatus. A key to species of Platydoras is provided.

Platydoras brachylecis, espécie nova, é descrita para as drenagens costeiras do nordeste do Brasil (rios Pindaré a Parnaíba) e diagnosticada de suas congêneres pela exclusiva combinação dos seguintes caracteres: faixa amarelo-pálida a branco iniciando acima das órbitas, continuando médio-lateralmente sobre o corpo e atingindo os raios medianos da nadadeira caudal; pele das axilas dos espinhos médio-laterais sem concentração de pequenas pintas negras; escudos médio-laterais baixos (altura do décimo escudo 8.8-11.9 por cento do comprimento padrão) e escudos médio-laterais do pedúnculo caudal distintamente separados das placas médio-dorsais e médio-ventrais da mesma região por uma faixa de pele. Mais três espécies de Platydoras são reconhecidas como válidas: P. armatulus (distribuída pelas drenagens do baixo Orinoco, Amazônia e Paraguai-Paraná), P. costatus (drenagens costeiras do Suriname e Guiana Francesa) e P. hancockii (drenagens do Negro, Essequibo, Demerara e alto Orinoco). As espécies nominais P. dentatus e P. helicophilus são provisoriamente consideradas sinônimos juniores de P. costatus. Uma chave de identificação para as espécies do gênero Platydoras é apresentada.

Dietary docosahexaenoic acid alters pregnant rat reproductive tissue prostaglandin and matrix metalloproteinase production.

Shortened gestation is a major cause of infant mortality and morbidity. Evidence from both human and animal studies suggests that essential fatty acids of the n-6 and n-3 series play important and modifiable roles in gestational duration. We examined the influence of linolenic acid (LnA) vs. docosahexaenoic acid (DHA) on rat reproductive tissue prostaglandin (PG) and matrix metalloproteinase (MMP) indices of gestational duration. By varying the oil source of the diet, AIN-93G diets were constructed to provide either 0.7 energy % (en%) LnA, the current US intake of n-3 fatty acids, or 0.7 en% DHA. In addition, enhanced levels of 2.0 en% LnA or 2.0 e% DHA diets were also constructed. All diets contained approximately 6.0 en% linoleic acid (LA), the current US intake of LA. Four groups of 10 female rats were time-mated and fed the respective diets from conception through Day 20 of gestation. Day 20 uterus and placenta DHA were significantly increased by 160-180% by the 0.7 en% DHA diet, and by 250-350% by the 2.0 en% DHA diets in comparison to 0.7 en% LnA diet. DHA diets also significantly reduced uterus and placenta arachidonic acid content. Day 20 placenta and uterus PGE(2) and placenta PGF(2alpha) production rates were significantly reduced by 27-47% in the 0.7 en% DHA group in comparison to 0.7 en% LnA. Increasing LnA to 2.0 en% was without effect. Providing DHA at the enhanced 2.0 en% did not significantly enhance the suppression of PG production. Placenta active MMP-2 and active MMP-9 (gelatinase) production was suppressed significantly by 30-43% in the 0.7 en% DHA group in comparison to the 0.7 en% LnA group, and 2.0 en% DHA did not enhance this suppression. Placenta collagenase activity comprising the sum of MMP-1, MMP-8 and MMP-13 was also suppressed by 60% in the 0.7 en% DHA diet group with no additional effect with 2.0 en% DHA provision. These results suggest that substituting DHA for LnA even at the current US n-3 fatty acid intake of 0.7 en% is effective in suppressing indices of premature delivery and shortened gestation. Increasing LnA intake by 3-fold to 2.0 en% is not effective. The form of dietary n-3 fatty acid, DHA vs. LnA, appears to be more important than the amount.