RESUMO
The Dynamic Energy Budget theory (DEB) enables ecotoxicologists to model the effects of chemical stressors on organism life cycles through the coupling of toxicokinetic-toxicodynamic (TK-TD) models. While good progress has been made in the application of DEB-TKTD models for aquatic organisms, applications for soil fauna are scarce, due to the lack of dedicated experimental designs suitable for collecting the required time series effect data. Enchytraeids (Annelida: Clitellata) are model organisms in soil ecology and ecotoxicology. They are recognised as indicators of biological activity in soil, and chemical stress in terrestrial ecosystems. Despite this, the application of DEB-TKTD models to investigate the impact of chemicals has not yet been tested on this family. Here we assessed the impact of the pyrethroid insecticide cypermethrin on the life cycle of Enchytraeus crypticus. We developed an original experimental design to collect the data required for the calibration of a DEB-TKTD model for this species. E. crypticus presented a slow initial growth phase that has been successfully simulated with the addition of a size-dependent food limitation for juveniles in the DEB model. The DEB-TKTD model simulations successfully agreed with the data for all endpoints and treatments over time. The highlighted physiological mode of action (pMoA) for cypermethrin was an increase of the growth energy cost. The threshold for effects on survival was estimated at 73.14 mg kg- 1, and the threshold for effects on energy budget (i.e., sublethal effects) at 19.21 mg kg- 1. This study demonstrates that DEB-TKTD models can be successfully applied to E. crypticus as a representative soil species, and may improve the ecological risk assessment for terrestrial ecosystems, and our mechanistic understanding of chemical effects on non-target species.
Assuntos
Inseticidas , Oligoquetos , Piretrinas , Animais , Inseticidas/toxicidade , Projetos de Pesquisa , Solo , Ecossistema , Piretrinas/toxicidade , Estágios do Ciclo de VidaRESUMO
Neonicotinoids are currently licensed for use in 120 countries, making accurate nontarget species sensitivity predictions critical. Unfortunately, such predictions are fraught with uncertainty, as sensitivity is extrapolated from only a few test species and neonicotinoid sensitivities can differ greatly between closely related taxa. Combining classical toxicology with de novo toxicogenomics could greatly improve sensitivity predictions and identify unexpectedly susceptible species. We show that there is a >30-fold differential species sensitivity (DSS) for the neonicotinoid imidacloprid between five earthworm species, a critical nontarget taxon. This variation could not be explained by differential toxicokinetics. Furthermore, comparing key motif expression in subunit genes of the classical nicotinic acetylcholine receptor (nAChR) target predicts only minor differences in the ligand binding domains (LBDs). In contrast, predicted dissimilarities in LBDs do occur in the highly expressed but nonclassical targets, acetylcholine binding proteins (AChBPs). Critically, the predicted AChBP divergence is capable of explaining DSS. We propose that high expression levels of putative nonsynaptic AChBPs with high imidacloprid affinities reduce imidacloprid binding to critical nAChRs involved in vital synaptic neurotransmission. This study provides a clear example of how pragmatic interrogation of key motif expression in complex multisubunit receptors can predict observed DSS, thereby informing sensitivity predictions for essential nontarget species.
Assuntos
Inseticidas , Receptores Nicotínicos , Animais , Inseticidas/toxicidade , Neonicotinoides/toxicidade , Nitrocompostos/toxicidade , Oligoquetos , Receptores Nicotínicos/genética , ToxicogenéticaRESUMO
Nostalgia, a sentimental longing for one's past, can serve as a resource for individuals coping with discomforting experiences. The experience of bereavement poses psychological and physical risks. In a longitudinal study, we examined whether dispositional nostalgia predicted reductions in distress associated with the death of a loved one. Undergraduate students (N = 133) provided information regarding their loss (time elapsed since loss, expectedness) and levels of initial grief, nostalgia, and distress (hyperarousal, intrusion, avoidance) at three time points over a one-month period (Times 2 and 3 occurred one week and one month after the initial session, respectively). Individuals experiencing higher nostalgia reported a decrease in intrusive thoughts across time, whereas those experiencing lower nostalgia reported no change in intrusive thoughts across time. Hyperarousal (physical symptoms, negative feelings) decreased across time among individuals with higher initial grief who experienced greater nostalgia, but increased across time among those with higher initial grief who experienced lesser nostalgia. No changes occurred in avoidance. Nostalgia can palliate bereavement.
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Luto , Transtornos Mentais , Adaptação Psicológica , Pesar , Humanos , Estudos LongitudinaisRESUMO
Changes to host behaviour induced by some trematode species, as a means of increased trophic transmission, represents one of the seminal examples of host manipulation by a parasite. The amphipod Echinogammarus marinus (Leach, 1815) is infected with a previously undescribed parasite, with infected individuals displaying positive phototaxic and negative geotaxic behaviour. This study reveals that the unknown parasite encysts in the brain, nerve cord and the body cavity of E. marinus, and belongs to the Microphallidae family. An 18 month population study revealed that host abundance significantly and negatively correlated with parasite prevalence. Investigation of the trematode's influence at the transcriptomic level revealed genes with putative neurological functions, such as serotonin receptor 1A, an inebriated-like neurotransmitter, tryptophan hydroxylase and amino acid decarboxylase, present consistent altered expression in infected animals. Therefore, this study provides one of the first transcriptomic insights into the neuronal gene pathways altered in amphipods infected with a trematode parasite associated with changes to its host's behaviour and population structure.
Assuntos
Anfípodes/parasitologia , Comportamento Animal , Regulação da Expressão Gênica , Interações Hospedeiro-Parasita , Trematódeos , Acantocéfalos/fisiologia , Anfípodes/genética , Anfípodes/crescimento & desenvolvimento , Anfípodes/fisiologia , Animais , Sequência de Bases , DNA de Helmintos/química , DNA de Helmintos/genética , DNA Ribossômico/química , DNA Ribossômico/genética , Feminino , Masculino , Dados de Sequência Molecular , Filogenia , Estações do Ano , Análise de Sequência de DNA/veterinária , Trematódeos/classificação , Trematódeos/genética , Trematódeos/isolamento & purificação , Trematódeos/fisiologiaRESUMO
First- and second-born adolescents' and their parents' perceptions of adolescents' decision-making autonomy were compared from ages 12 to 19 in a longitudinal sample of 145 predominantly White, middle class families. Utilizing a multivariate, multilevel modeling approach, differences in perceptions of adolescents' autonomy between parents and each adolescent, as well as by social-cognitive domain were examined. The present study found that when comparing parents' perceptions of their children at the same age, second-borns were granted more autonomy regarding conventional issues than first-borns during early adolescence, but by later adolescence first-borns were granted more autonomy regarding prudential issues than second-borns. However, comparisons between adolescents' and siblings' perceptions showed no differences. Potential reasons for, and implications of, differences in perceptions of adolescent autonomy are discussed.
Assuntos
Ordem de Nascimento , Tomada de Decisões , Autonomia Pessoal , Adolescente , Criança , Feminino , Humanos , Masculino , Educação Pré-Natal , Inquéritos e Questionários , Adulto JovemRESUMO
This study examined the psychometric equivalence of Forms A and B of the Multidimensional Health Locus of Control Scale in a sample of college students (N = 370; M = 19.5 yr.; 318 Caucasians; 281 women). Given the dearth of studies that address the issue of form equivalence directly, this study sought to ascertain whether these forms could be used interchangeably by researchers. Subscales on the two forms had fairly high correlations (range of r = .77-.81), and similar alpha and omega reliability coefficients. Additionally, confirmatory factor analysis revealed both forms fit a three-factor model well. However, paired-sample t tests yielded significant mean differences for all three subscales. Furthermore, the two forms yielded inconsistent associations with relevant measures. Although the observed pattern of associations with social desirability and safe swimming behaviors were similar for Forms A and B, the pattern of differences was not identical for smoking groups and bicycle helmet use groups between forms. Overall, these results suggested that Forms A and B do not meet the strict criteria for parallel forms, but instead should be considered alternative forms.
Assuntos
Conhecimentos, Atitudes e Prática em Saúde , Controle Interno-Externo , Psicometria/instrumentação , Inquéritos e Questionários/normas , Adolescente , Adulto , Feminino , Humanos , Masculino , Adulto JovemRESUMO
The dysfunction associated with intersexuality in vertebrates and molluscs is often a serious threat to ecosystems. Although poorly understood, crustacean intersexuality is associated with contamination and includes forms linked to increased sex-ratio distorting parasites at polluted sites. Despite the importance of crustaceans for monitoring vulnerable aquatic habitats, little is known about the molecular basis of this abnormal sexual differentiation and any associated sexual dysfunction. To increase the relevance of crustaceans to environmental toxicologists, we comprehensively analyzed gene expression in amphipods presenting parasite- and nonparasite-associated intersexuality. Our findings reveal existing vertebrate biomarkers of feminization should not be applied to crustaceans, as orthologous genes are not induced in feminized amphipods. Furthermore, in contrast to vertebrates, where feminization and intersexuality is often associated with deleterious demasculinization, we find males maintain masculinity even when unambiguously feminized. This reveals a considerable regulatory separation of the gene pathways responsible for male and female characteristics and demonstrates that evidence of feminization (even if detected with appropriate biomarkers) is not a proxy for demasculinization in crustaceans. This study has also produced a comprehensive spectrum of potential molecular biomarkers that, when combined with our new molecular understanding, will greatly facilitate the use of crustaceans to monitor aquatic habitats.
Assuntos
Crustáceos/efeitos dos fármacos , Transtornos do Desenvolvimento Sexual/complicações , Ecotoxicologia , Disruptores Endócrinos/toxicidade , Caracteres Sexuais , Processos de Determinação Sexual , Diferenciação Sexual/efeitos dos fármacos , Anfípodes , Animais , Biomarcadores , Feminino , Feminização , Masculino , Ovariectomia , Diferenciação Sexual/fisiologia , Razão de Masculinidade , Especificidade da EspécieRESUMO
We present a genome assembly from an individual Lumbricus rubellus (the red compost earthworm; Annelida; Clitellata; Haplotaxida; Lumbricidae). The genome sequence is 787.5 megabases in span. Most of the assembly is scaffolded into 18 chromosomal pseudomolecules. The mitochondrial genome has also been assembled and is 15.81 kilobases in length. Gene annotation of this assembly on Ensembl identified 33,426 protein coding genes.
RESUMO
Pax genes encode highly conserved transcription factors vital for metazoan development. Pax transcripts, particularly those in Group II (Pax2/5/8), are extensively alternatively spliced. This study compares the transcriptional activation capacity and developmental stage-specific expression of major isoforms of Group II Pax proteins in amphioxus (Branchiostoma floridae) and in Xenopus laevis. The comparison reveals considerable divergence of splice forms between the lineages, with the X. laevis Group II Pax genes (Pax2, Pax5, and Pax8) possessing a greater repertoire of regulated and functionally distinct splice forms than the single amphioxus gene (Pax2/5/8). Surprisingly, some apparently conserved splice forms are expressed at quite different levels during development in the two organisms and present different capacities to activate transcription. However, despite this divergence, the combinatorial transcriptional activation capacity of the isoforms present in early X. laevis and amphioxus development are broadly similar. This suggests that the some of the conserved functional roles, implied by the expression of Group II Pax genes in homologous tissues of amphioxus and X. laevis embryos, may depend upon the combination of isoforms expressed in a particular tissue at a particular time in development. Thus, during early development, the evolutionary constraint on the net effect of several isoforms co-expressed in a given tissue may be more strict than that on specific isoforms. This flexibility may facilitate the appearance of new exons and splicing patterns in the vertebrate duplicates, leading to isoforms with subtly distinct functions critical to the subsequent development of vertebrate-specific cell types and structures.
Assuntos
Processamento Alternativo/genética , Cordados não Vertebrados/genética , Evolução Molecular , Regulação da Expressão Gênica no Desenvolvimento/genética , Variação Genética , Fatores de Transcrição Box Pareados/genética , Xenopus laevis/genética , Animais , Cordados não Vertebrados/metabolismo , Clonagem Molecular , Primers do DNA/genética , Embrião não Mamífero/metabolismo , Florida , Células HEK293 , Humanos , Fatores de Transcrição Box Pareados/metabolismo , Isoformas de Proteínas/genética , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Xenopus laevis/metabolismoRESUMO
Here, we explore the high-altitude adaptions and acclimatisation of Aporrectodea caliginosa Population diversity is assessed through mitochondrial barcoding, identifying closely related populations across the island of Pico (Azores). We present the first megabase N50 assembly size (1.2 Mbp) genome for A. caliginosa High- and low-altitude populations were exposed experimentally to a range of oxygen and temperature conditions, simulating altitudinal conditions, and the transcriptomic responses explored. SNP densities are assessed to identify signatures of selective pressure and their link to differentially expressed genes. The high-altitude A. caliginosa population had lower differential expression and fewer co-expressed genes between conditions, indicating a more condition-refined epigenetic response. Genes identified as under adaptive pressure through Fst and nucleotide diversity in the high-altitude population clustered around the differentially expressed an upstream environmental response control gene, HMGB1. The high-altitude population of A. caliginosa indicated adaption and acclimatisation to high-altitude conditions and suggested resilience to extreme weather events. This mechanistic understanding could help offer a strategy in further identifying other species capable of maintaining soil fertility in extreme environments.
Assuntos
Altitude , Oligoquetos , Adaptação Fisiológica/genética , Animais , GenomaRESUMO
The assessment of chemical mixture toxicity is one of the major challenges in ecotoxicology. Chemicals can interact, leading to more or less effects than expected, commonly named synergism and antagonism respectively. The classic ad hoc approach for the assessment of mixture effects is based on dose-response curves at a single time point, and is limited to identifying a mixture interaction but cannot provide predictions for untested exposure durations, nor for scenarios where exposure varies in time. We here propose a new approach using toxicokinetic-toxicodynamic modelling: The General Unified Threshold model of Survival (GUTS) framework, recently extended for mixture toxicity assessment. We designed a dedicated mechanistic interaction module coupled with the GUTS mixture model to i) identify interactions, ii) test hypotheses to identify which chemical is likely responsible for the interaction, and finally iii) simulate and predict the effect of synergistic and antagonistic mixtures. We tested the modelling approach experimentally with two species (Enchytraeus crypticus and Mamestra brassicae) exposed to different potentially synergistic mixtures (composed of: prochloraz, imidacloprid, cypermethrin, azoxystrobin, chlorothalonil, and chlorpyrifos). Furthermore, we also tested the model with previously published experimental data on two other species (Bombus terrestris and Daphnia magna) exposed to pesticide mixtures (clothianidin, propiconazole, dimethoate, imidacloprid and thiacloprid) found to be synergistic or antagonistic with the classic approach. The results showed an accurate simulation of synergistic and antagonistic effects for the different tested species and mixtures. This modelling approach can identify interactions accounting for the entire time of exposure, and not only at one time point as in the classic approach, and provides predictions of the mixture effect for untested mixture exposure scenarios, including those with time-variable mixture composition.
Assuntos
Clorpirifos , Inseticidas , Oligoquetos , Animais , Clorpirifos/toxicidade , Daphnia , Inseticidas/química , ToxicocinéticaRESUMO
OBJECTIVE: Meta-analyses assessing the efficacy of expressive writing (EW) interventions have produced mixed results. The current study aimed to assess the efficacy of an EW intervention in the reduction of anxiety symptoms in first-year college students. In an effort to understand more about moderating variables that influence EW outcomes, the current study also assessed the role of linguistic features in symptom reduction. DESIGN AND MEASURES: Ninety participants were assigned to complete either an EW intervention or a non-emotional writing intervention. Participants completed 3 consecutive days of writing and two follow-up visits. Anxiety was measured at each study visit with the Beck Anxiety Inventory, and linguistic features were assessed with the LIWC software program. RESULTS: Results indicated that all participants demonstrated significant decreases in anxiety over time. Participants in the EW group who demonstrated the greatest decreases in anxiety utilized more first-person singular pronouns and fewer affect words. CONCLUSIONS: Results are explained in the context of two prominent theories regarding the therapeutic mechanisms of EW: cognitive processing theory and exposure theory. Exposure theory received more support than cognitive processing theory.
Assuntos
Ansiedade , Redação , Ansiedade/terapia , Transtornos de Ansiedade , Humanos , Linguística , EstudantesRESUMO
Polychaetes are vital for evaluating the effects of toxic metals in marine systems, and sensitive molecular biomarkers should be integral to monitoring efforts. However, the few polychaete markers that exist are inconsistent, even within the same species, failing to identify gene expression changes in metal-exposed animals incurring clear metabolic costs. Comparing previously characterised polychaete metal-responsive genes with those of another carefully selected species could identify biomarkers applicable across polychaetes. The ragworm Alitta virens (Sars, 1835) is particularly suited for such comparisons due to its dominance of fully saline coastal areas, widespread distribution, large biomass, and its phylogenetic position relative to other polychaete 'omic' resources. A transcriptome atlas for A. virens was generated and an RNASeq-qPCR screening approach was used to characterise the response to chronic exposures of environmentally relevant concentrations of copper and zinc in controlled mesocosms. Genes presenting dramatic expression changes in A. virens were compared with known metal-responsive genes in other polychaetes to identify new possible biomarkers and assess those currently used. This revealed some current markers should probably be abandoned (e.g. Atox1), while others, such as GST-Omega, should be used with caution, as different polychaete species appear to upregulate distinct GST-Omega orthologues. In addition, the comparisons give some indication of genes that are induced by metal exposure across phylogenetically divergent polychaetes, including a suite of haemoglobin subunits and linker chains that could play conserved roles in metal-stress response. Although such newly identified markers need further characterisation, they offer alternatives to current markers that are plainly insufficient.
Assuntos
Anelídeos/genética , Biomarcadores/análise , Metais/toxicidade , Poliquetos/genética , Transcriptoma/efeitos dos fármacos , Animais , Cobre/toxicidade , Perfilação da Expressão Gênica/métodos , Ontologia Genética , Poliquetos/classificação , RNA-Seq/métodos , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Especificidade da Espécie , Poluentes Químicos da Água/toxicidade , Zinco/toxicidadeRESUMO
The scale of variation in species sensitivity to toxicants has been theoretically linked to mode of action. Specifically, it has been proposed there will be greater variations for chemicals with a putative specific biological target than for toxicants with a non-specific narcotic mechanism. Here we test the hypothesis that mode of action is related to variation in sensitivity in a specifically designed experiment for species from a single ecologically important terrestrial taxa, namely earthworms. Earthworm toxicity tests were conducted with five species for four chemicals, providing a series of increasingly complex modes of action: a putative narcotic polycyclic aromatic hydrocarbon (fluoranthene), and three insecticides (chlorpyrifos, cypermethrin, imidacloprid) with known neuronal receptor targets. Across all the chemicals, the standard epigeic test species Eisenia fetida and Lumbricus rubellus, were generally among the two least sensitive, while the endogenic Aporrectodea caliginosa and Megascolecidae Amynthas gracilis were generally more sensitive (never being among the two least sensitive species). This indicates a potential for bias in the earthworm ecotoxicology literature, which is dominated by studies in epigeic Lumbricidae, but contains few endogeic or Megascolecidae data. Results confirmed the lowest range of variation in sensitivities for effects on reproduction was for fluoranthene (2.5 fold). All insecticides showed greater variation for species sensitivity (cypermethrin: 7.5 fold, chlorpyrifos: 10.3 fold, imidacloprid: 31.5 fold) consistent with the specific mechanisms of the pesticides. Difference in toxicodynamics, based on mode of action specificity and receptor complexity was reflected in the magnitude of sensitivity variation. However, measurements of tissue concentrations also indicated the potential importance of toxicokinetics in explaining species sensitivity variations for chlorpyrifos and cypermethrin.
Assuntos
Clorpirifos , Oligoquetos , Praguicidas , Poluentes do Solo , Animais , Ecotoxicologia , Poluentes do Solo/toxicidadeRESUMO
Phospholipase D2 (PLD2) overexpression in mammalian cells results in cell transformation. We have hypothesized that this is due to an increase of de novo DNA synthesis. We show here that overexpression of PLD2-WT leads to an increased DNA synthesis, as measured by the expression levels of the proliferation markers PCNA, p27(KIP1) and phospho-histone-3. The enhancing effect was even higher with phosphorylation-deficient PLD2-Y179F and PLD2-Y511F mutants. The mechanism for this did not involve the enzymatic activity of the lipase, but, rather, the presence of the protein tyrosine phosphatase CD45, as silencing with siRNA for CD45 abrogated the effect. The two Y-->F mutants had in common a YxN consensus site that, in the phosphorylated counterparts, could be recognized by SH2-bearing proteins, such as Grb2. Even though Y179F and Y511F cannot bind Grb2, they could still find other protein partners, one of which, we have reasoned, could be CD45 itself. Affinity purified PLD2 is indeed activated by Grb2 and deactivated by CD45 in vitro. We concluded that phosphorylated PLD2, aided by Grb2, mediates lipase activity, whereas dephosphorylated PLD2 mediates an induction of cell proliferation, and the specific residues involved in this newly discovered regulation of PLD2 are Y(179) and Y(511).
Assuntos
Proliferação de Células , Transformação Celular Neoplásica/metabolismo , DNA/biossíntese , Fosfolipase D/metabolismo , Animais , Células COS , Linhagem Celular Tumoral , Transformação Celular Neoplásica/genética , Chlorocebus aethiops , Humanos , Dados de Sequência Molecular , Fosfolipase D/genética , FosforilaçãoRESUMO
Signalling by small molecules, such as retinoic acid, is mediated by heterodimers comprising a class II nuclear receptor and an RXR (retinoid X receptor) subunit. The receptors bind to DNA response elements and act as ligand-dependent transcription factors, but, in the absence of signal, the receptors bind the co-repressors SMRT [silencing mediator for RAR (retinoic acid receptor) and TR (thyroid hormone receptor)] and NCoR (nuclear receptor co-repressor) and repress gene expression. Alternative splicing of the SMRT transcript in mammals generates six isoforms containing 1, 2 or 3 CoRNR (co-repressor for nuclear receptor) box motifs which are responsible for the interactions with nuclear receptors. We show that human cell lines express all six SMRT isoforms and then determine the binding affinity of mouse SMRT isoforms for RAR/RXR and three additional class II nuclear receptor-DNA complexes. This approach demonstrates the importance of the full complement of CoRNR boxes within each SMRT protein, rather than the identity of individual CoRNR boxes, in directing the interaction of SMRT with nuclear receptors. Each class of SMRT isoform displays a distinct feature, as the 1-box isoform discriminates between DNA response elements, the 2-box isoforms promote high-affinity binding to TR complexes and the 3-box isoforms show differential binding to nuclear receptors. Consequently, the differential deployment of SMRT isoforms observed in vivo could significantly expand the regulatory capacity of nuclear receptor signalling.
Assuntos
Proteínas de Ligação a DNA/metabolismo , DNA/metabolismo , Complexos Multiproteicos/metabolismo , Receptores Citoplasmáticos e Nucleares/metabolismo , Proteínas Repressoras/metabolismo , Elementos de Resposta/fisiologia , Transdução de Sinais/fisiologia , Animais , DNA/genética , Proteínas de Ligação a DNA/genética , Camundongos , Complexos Multiproteicos/genética , Correpressor 2 de Receptor Nuclear , Isoformas de Proteínas/genética , Isoformas de Proteínas/metabolismo , Receptores Citoplasmáticos e Nucleares/genética , Proteínas Repressoras/genéticaRESUMO
The brain of the basal chordate amphioxus has been compared to the vertebrate diencephalic forebrain, midbrain, hindbrain and spinal cord on the basis of the cell architecture from serial electron micrographs and patterns of developmental gene expression. In addition, genes specifying the neural plate and neural plate border as well as Gbx and Otx, that position the midbrain/hindbrain boundary (MHB), are expressed in comparable patterns in amphioxus and vertebrates. However, migratory neural crest is lacking in amphioxus, and although it has homologs of the genes that specify neural crest, they are not expressed at the edges of the amphioxus neural plate. Similarly, amphioxus has the genes that specify organizer properties of the MHB, but they are not expressed at the Gbx/Otx boundary as in vertebrates. Thus, the genetic machinery that created migratory neural crest and an MHB organizer was present in the ancestral chordate, but only co-opted for these new roles in vertebrates. Analyses with the amphioxus genome project strongly support the idea of two rounds of whole genome duplication with subsequent gene losses in the vertebrate lineage. Duplicates of developmental genes were preferentially retained. Although some genes apparently acquired roles in neural crest prior to these genome duplications, other key genes (e.g., FoxD3 in neural crest and Wnt1 at the MHB) were recruited into the respective gene networks after one or both genome duplications, suggesting that such an expansion of the genetic toolkit was critical for the evolution of these structures. The toolkit has also increased by alternative splicing. Contrary to the general rule, for at least one gene family with key roles in neural crest and the MHB, namely Pax genes, alternative splicing has not decreased subsequent to gene duplication. Thus, vertebrates have a much larger number of proteins available for mediating new functions in these tissues. The creation of new splice forms typically changes protein structure more than evolution of the protein after gene duplication. The functions of particular isoforms of key proteins expressed at the MHB and in neural crest have only just begun to be studied. Their roles in modulating gene networks may turn out to rival gene duplication for facilitating the evolution of structures such as neural crest and the MHB.
Assuntos
Encéfalo/metabolismo , Cordados não Vertebrados/genética , Duplicação Gênica , Vertebrados/genética , Animais , Padronização Corporal/genética , Padronização Corporal/fisiologia , Encéfalo/crescimento & desenvolvimento , Cordados não Vertebrados/crescimento & desenvolvimento , Evolução Molecular , Regulação da Expressão Gênica no Desenvolvimento , Humanos , Vertebrados/crescimento & desenvolvimentoRESUMO
In multigroup factor analysis, different levels of measurement invariance are accepted as tenable when researchers observe a nonsignificant (Δ)χ2 test after imposing certain equality constraints across groups. Large samples yield high power to detect negligible misspecifications, so many researchers prefer alternative fit indices (AFIs). Fixed cutoffs have been proposed for evaluating the effect of invariance constraints on change in AFIs (e.g., Chen, 2007; Cheung & Rensvold, 2002; Meade, Johnson, & Braddy, 2008). We demonstrate that all of these cutoffs have inconsistent Type I error rates. As a solution, we propose replacing χ2 and fixed AFI cutoffs with permutation tests. Randomly permuting group assignment results in average between-groups differences of zero, so iterative permutation yields an empirical distribution of any fit measure under the null hypothesis of invariance across groups. Our simulations show that the permutation test of configural invariance controls Type I error rates better than χ2 or AFIs when the model contains parsimony error (i.e., negligible misspecification) but the factor structure is equivalent across groups (i.e., the null hypothesis is true). For testing metric and scalar invariance, Δχ2 and permutation yield similar power and nominal Type I error rates, whereas ΔAFIs yield inflated errors in smaller samples. Permuting the maximum modification index among equality constraints control familywise Type I error rates when testing multiple indicators for lack of invariance, but provide similar power as using a Bonferroni adjustment. An applied example and syntax for software are provided. (PsycINFO Database Record (c) 2018 APA, all rights reserved).
Assuntos
Interpretação Estatística de Dados , Análise Fatorial , Modelos Estatísticos , Psicologia/métodos , Projetos de Pesquisa , HumanosRESUMO
Phylogenetically distant parasites often infect the same host. Indeed, co-infections can occur at levels greater than expected by chance and are sometimes hyperparasitic. The amphipod Echinogammarus marinus presents high levels of co-infection by two intracellular and vertically transmitted parasites, a paramyxid (Paramarteilia sp. Em) and a microsporidian strain (Dictyocoela duebenum Em). This co-infection may be hyperparasitic and result from an exploitative 'hitchhiking' or a symbiotic relationship between the parasites. However, the best-studied amphipod species are often collected from contaminated environments and may be immune-compromised. Immune-challenged animals frequently present co-infections and contaminant-exposed amphipods present significantly higher levels of microsporidian infection. This suggests the co-infections in E. marinus may result from contaminant-associated compromised immunity. Inconsistent with hyperparasitism, we find that artificial infections transmit Paramarteilia without microsporidian. Our population surveys reveal the co-infection relationship is geographically widespread but find only chance co-infection between the Paramarteilia and another species of microsporidian, Dictyocoela berillonum. Furthermore, we identify a haplotype of the Paramarteilia that presents no co-infection, even in populations with otherwise high co-infection levels. Overall, our results do not support the compromised-immunity hypothesis but rather that the co-infection of E. marinus, although non-hyperparasitic, results from a relationship between specific Paramarteilia and Dictyocoela duebenum strains.
Assuntos
Anfípodes/microbiologia , Anfípodes/parasitologia , Microsporidiose/diagnóstico , Infecções Protozoárias em Animais/diagnóstico , Animais , Coinfecção , DNA Fúngico/genética , DNA de Protozoário , Feminino , Interações Hospedeiro-Parasita , Masculino , Programas de Rastreamento/veterinária , Microsporídios/genética , Microsporídios/isolamento & purificação , Microsporidiose/transmissão , Microsporidiose/veterinária , Filogenia , Infecções Protozoárias em Animais/transmissãoRESUMO
Sexuality researchers frequently use exploratory factor analysis (EFA) to illuminate the distinguishable theoretical constructs assessed by a set of variables. EFA entails a substantive number of analytic decisions to be made with respect to sample size determination, and how factors are extracted, rotated, and retained. The available analytic options, however, are not all equally empirically rigorous. We discuss the commonly available options for conducting EFA and which options constitute best practices for EFA. We also present the results of a methodological review of the analytic options for EFA used by sexuality researchers in more than 200 EFAs, published in more than 160 articles and chapters from 1974 to 2014, in a sample of sexuality research journals. Our review reveals that best practices for EFA are actually those least frequently used by sexuality researchers. We introduce freely available analytic resources to help make it easier for sexuality researchers to adhere to best practices when conducting EFAs in their own research.