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1.
BMC Genomics ; 22(1): 639, 2021 Sep 04.
Artigo em Inglês | MEDLINE | ID: mdl-34479486

RESUMO

BACKGROUND: Resistance of pest insect species to insecticides, including B. thuringiensis (Bt) pesticidal proteins expressed by transgenic plants, is a threat to global food security. Despite the western corn rootworm, Diabrotica virgifera virgifera, being a major pest of maize and having populations showing increasing levels of resistance to hybrids expressing Bt pesticidal proteins, the cell mechanisms leading to mortality are not fully understood. RESULTS: Twenty unique RNA-seq libraries from the Bt susceptible D. v. virgifera inbred line Ped12, representing all growth stages and a range of different adult and larval exposures, were assembled into a reference transcriptome. Ten-day exposures of Ped12 larvae to transgenic Bt Cry3Bb1 and Gpp34/Tpp35Ab1 maize roots showed significant differential expression of 1055 and 1374 transcripts, respectively, compared to cohorts on non-Bt maize. Among these, 696 were differentially expressed in both Cry3Bb1 and Gpp34/Tpp35Ab1 maize exposures. Differentially-expressed transcripts encoded protein domains putatively involved in detoxification, metabolism, binding, and transport, were, in part, shared among transcripts that changed significantly following exposures to the entomopathogens Heterorhabditis bacteriophora and Metarhizium anisopliae. Differentially expressed transcripts in common between Bt and entomopathogen treatments encode proteins in general stress response pathways, including putative Bt binding receptors from the ATP binding cassette transporter superfamily. Putative caspases, pro- and anti-apoptotic factors, as well as endoplasmic reticulum (ER) stress-response factors were identified among transcripts uniquely up-regulated following exposure to either Bt protein. CONCLUSIONS: Our study suggests that the up-regulation of genes involved in ER stress management and apoptotic progression may be important in determining cell fate following exposure of susceptible D. v. virgifera larvae to Bt maize roots. This study provides novel insights into insect response to Bt intoxication, and a possible framework for future investigations of resistance mechanisms.


Assuntos
Bacillus thuringiensis , Besouros , Praguicidas , Animais , Bacillus thuringiensis/genética , Sobrevivência Celular , Besouros/genética , Endotoxinas/toxicidade , Resistência a Inseticidas , Larva/genética , Controle Biológico de Vetores , Plantas Geneticamente Modificadas/genética , Regulação para Cima , Zea mays/genética
2.
Ann Plast Surg ; 86(4): 421-423, 2021 04 01.
Artigo em Inglês | MEDLINE | ID: mdl-32881751

RESUMO

ABSTRACT: The authors present 3 unique cases of complex fistula formations because of orbital fracture repair with a Teflon (polytetrafluroethylene) implant. A 26-year-old man presented with dacryocystitis and a cutaneous fistula 8 years after left orbital floor and medial wall fracture repair with a Teflon implant. A 46-year-old woman suffered orbital trauma after a motor vehicle accident as a teenager and the fracture was repaired with Teflon implant. Thirty-two years later, she presented with lower eyelid fistula, ectropion, and retraction. A 65-year-old woman also previously had Teflon implants for the repair of her left inferior and lateral orbital rim after a motor vehicle accident. Twenty-five years later, she presented with chronic infections involving the repaired areas, as well as left lower lid ectropion and fistula formation. The woven material nature of Teflon acted as a nidus for infection, inflammation, and led to complex cutaneous fistula formations in these patients.


Assuntos
Doenças Orbitárias , Fraturas Orbitárias , Adolescente , Adulto , Idoso , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Órbita , Fraturas Orbitárias/etiologia , Fraturas Orbitárias/cirurgia , Politetrafluoretileno/efeitos adversos , Próteses e Implantes
3.
Pest Manag Sci ; 77(2): 860-868, 2021 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-32946636

RESUMO

BACKGROUND: Western corn rootworm (WCR) pyrethroid resistance has been confirmed in the western US Corn Belt. Toxicological and biochemical studies indicated that multiple mechanisms of resistance might be involved in the resistance trait, such as enhanced metabolism and/or kdr target-site mutation(s) in the voltage-gated sodium channels. To characterize the mechanisms of WCR pyrethroid resistance at the molecular level, pairwise comparisons were made between RNA-Seq data collected from pyrethroid-resistant and -susceptible WCR populations. Gene expression levels and sodium channel sequences were evaluated. RESULTS: Seven transcripts exhibited significantly different expression (q ≤ 0.05) when comparing field-collected pyrethroid-resistant (R-Field) and -susceptible (S-Field) WCR populations. Three of the differentially expressed transcripts were P450s overexpressed in R-Field (9.2-26.2-fold). A higher number (99) of differentially expressed transcripts was found when comparing laboratory-derived pyrethroid-resistant (R-Lab) and -susceptible (S-Lab) WCR populations. Eight of the significant transcripts were P450s overexpressed in R-Lab (2.7-39.8-fold). This study did not detect kdr mutations in pyrethroid-resistant WCR populations. Other differentially expressed transcripts that may play a role in WCR pyrethroid resistance are discussed. CONCLUSION: This study revealed that P450-mediated metabolism is likely to be a major mechanism of WCR pyrethroid resistance, which could affect the efficacy of other insecticides sharing similar metabolic pathways. Additionally, results suggested that although laboratory selection of a pyrethroid-resistant WCR population may help to characterize resistance mechanisms, a field-selected population provided rare and perhaps major variants corresponding to the resistance trait.


Assuntos
Besouros , Inseticidas , Piretrinas , Animais , Besouros/genética , Resistência a Inseticidas/genética , Inseticidas/farmacologia , Piretrinas/farmacologia , Zea mays/genética
4.
Pestic Biochem Physiol ; 164: 165-172, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-32284123

RESUMO

Western corn rootworm (WCR) pyrethroid resistance has been previously reported in the United States (US) western Corn Belt, and cross-resistance and synergism studies suggested that both target site insensitivity and enhanced metabolism may be conferring WCR resistance to pyrethroids. The present study aimed to investigate the potential mechanisms of WCR pyrethroid resistance and to estimate the heritability of the resistance trait. Biochemical assays using model substrates and spectrophotometry revealed 2-4-fold higher activity of P450s and esterases in pyrethroid-resistant WCR populations, whereas the biological activity of glutathione S-transferase was similar between populations tested. No mutation in the voltage-gated sodium channel was detected in pyrethroid-resistant WCR individuals by sequencing PCR products containing the para-homologous L1014, T929, and M918 amino acid positions that are commonly associated with target site mutations in other pyrethroid-resistant insects. A pilot estimation of pyrethroid resistance heritability obtained during laboratory selection of a WCR population suggested a major genetic component of the resistance trait and predicted a 10-fold increase in WCR bifenthrin resistance within ~7 generations of insecticide lethal exposure. Results support earlier indirect evidence that enhanced metabolism may be contributing to WCR resistance to pyrethroids and illustrates the potential of WCR pyrethroid resistance evolution.


Assuntos
Besouros , Inseticidas , Piretrinas , Animais , Resistência a Inseticidas , Larva , Zea mays
5.
Insect Biochem Mol Biol ; 118: 103285, 2020 03.
Artigo em Inglês | MEDLINE | ID: mdl-31760137

RESUMO

Insecticides are a key tool in the management of many insect pests of agriculture, including soybean aphids. The selection imposed by insecticide use has often lead to the evolution of resistance by the target pest through enhanced detoxification mechanisms. We hypothesised that exposure of insecticide-susceptible aphids to sublethal doses of insecticides would result in the up-regulation of genes involved in detoxification of insecticides, revealing the genes upon which selection might act in the field. We used the soybean aphid biotype 1 reference genome, version 6.0 as a reference to analyze RNA-Seq data. We identified multiple genes with potential detoxification roles that were up-regulated 12 h after sublethal exposure to esfenvalerate or thiamethoxam. However, these genes were part of a dramatic burst of differential gene expression in which thousands of genes were up- or down-regulated, rather than a defined response to insecticides. Interestingly, the transcriptional burst observed at 12 h s declined dramatically by 24-hrs post-exposure, suggesting a general stress response that may become fine-tuned over time.


Assuntos
Afídeos/efeitos dos fármacos , Expressão Gênica/efeitos dos fármacos , Genes de Insetos/efeitos dos fármacos , Inseticidas/metabolismo , Nitrilas/metabolismo , Piretrinas/metabolismo , Tiametoxam/metabolismo , Animais , Afídeos/genética , Regulação para Baixo/efeitos dos fármacos , Regulação para Cima/efeitos dos fármacos
6.
Insect Biochem Mol Biol ; 105: 69-78, 2019 02.
Artigo em Inglês | MEDLINE | ID: mdl-30654011

RESUMO

We examined the genome of the soybean aphid, Aphis glycines, and an updated genome assembly of the pea aphid, Acyrthosiphon pisum, for members of the three major families of chemoreceptors, the Odorant Receptors (ORs), Gustatory Receptors (GRs) and Ionotropic Receptors (IRs), as well as the Odorant Binding Proteins (OBPs). The soybean aphid has 47 ORs, 61 GRs, 19 IRs, and 10 OBPs, compared with 87 ORs, 78 Grs, 19 IRs, and 18 OBPs in the pea aphid, with variable numbers of pseudogenes in the OR and GR families. Phylogenetic analysis reveals that while all of the IRs are simple orthologs between these two species, the OR, GR, and OBP families in the pea aphid have experienced major expansions of particular gene lineages and fewer losses of gene lineages. This imbalance in birth-and-death of chemosensory genes has led to the larger pea aphid gene repertoire, which might be related to the broader host range of pea aphids versus the specialization of soybean aphids on a single summer host plant. Examination of the expression levels of these chemosensory genes in parthenogenetic and sexual females and males of pea aphids revealed multiple genes that are differentially expressed in sexual females or males and might be involved in reproductive biology. Examination of the soybean aphid genes in parthenogenetic females under multiple stressors revealed multiple genes whose expression levels changed with heat or starvation stress, the latter potentially important in finding new food sources.


Assuntos
Afídeos/metabolismo , Receptores Ionotrópicos de Glutamato/metabolismo , Receptores Odorantes/metabolismo , Animais , Afídeos/genética , Ervilhas , Receptores Ionotrópicos de Glutamato/genética , Receptores Odorantes/genética , Soja
7.
Sci Rep ; 8(1): 1931, 2018 01 31.
Artigo em Inglês | MEDLINE | ID: mdl-29386578

RESUMO

The Colorado potato beetle is one of the most challenging agricultural pests to manage. It has shown a spectacular ability to adapt to a variety of solanaceaeous plants and variable climates during its global invasion, and, notably, to rapidly evolve insecticide resistance. To examine evidence of rapid evolutionary change, and to understand the genetic basis of herbivory and insecticide resistance, we tested for structural and functional genomic changes relative to other arthropod species using genome sequencing, transcriptomics, and community annotation. Two factors that might facilitate rapid evolutionary change include transposable elements, which comprise at least 17% of the genome and are rapidly evolving compared to other Coleoptera, and high levels of nucleotide diversity in rapidly growing pest populations. Adaptations to plant feeding are evident in gene expansions and differential expression of digestive enzymes in gut tissues, as well as expansions of gustatory receptors for bitter tasting. Surprisingly, the suite of genes involved in insecticide resistance is similar to other beetles. Finally, duplications in the RNAi pathway might explain why Leptinotarsa decemlineata has high sensitivity to dsRNA. The L. decemlineata genome provides opportunities to investigate a broad range of phenotypes and to develop sustainable methods to control this widely successful pest.


Assuntos
Agricultura , Besouros/genética , Genoma de Inseto , Genômica , Solanum tuberosum/parasitologia , Animais , Elementos de DNA Transponíveis/genética , Evolução Molecular , Feminino , Regulação da Expressão Gênica , Variação Genética , Genética Populacional , Interações Hospedeiro-Parasita/genética , Proteínas de Insetos/genética , Proteínas de Insetos/metabolismo , Resistência a Inseticidas/genética , Masculino , Anotação de Sequência Molecular , Família Multigênica , Controle Biológico de Vetores , Filogenia , Interferência de RNA , Fatores de Transcrição/metabolismo
8.
Curr Opin Insect Sci ; 21: 68-74, 2017 06.
Artigo em Inglês | MEDLINE | ID: mdl-28822491

RESUMO

Gene flow via immigration affects rate of evolution of resistance to a pest management tactic, while emigration from a resistant population can spread resistance alleles spatially. Whether resistance detected across the landscape reflects ongoing de novo evolution in different hotspots or spread from a single focal population can determine the most effective mitigation strategy. Pest dispersal dynamics determine the spatio-temporal scale at which mitigation tactics must be applied to contain or reverse resistance in an area. Independent evolution of resistance in different populations appears common but not universal. Conversely, spatial spread appears to be almost inevitable. However, rate and scale of spread depends largely on dispersal dynamics and interplay with factors such as fitness costs, spatially variable selection pressure and whether resistance alleles are spreading through an established population or being carried by populations colonizing new territory.


Assuntos
Distribuição Animal , Insetos/genética , Resistência a Inseticidas/genética , Animais , Evolução Biológica , Fluxo Gênico , Insetos/fisiologia , Controle Biológico de Vetores
10.
Ecol Evol ; 6(3): 818-29, 2016 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-26865969

RESUMO

Bacterial endosymbionts can drive evolutionary novelty by conferring adaptive benefits under adverse environmental conditions. Among aphid species there is growing evidence that symbionts influence tolerance to various forms of stress. However, the extent to which stress inflicted on the aphid host has cascading effects on symbiont community dynamics remains poorly understood. Here we simultaneously quantified the effect of host-plant induced and xenobiotic stress on soybean aphid (Aphis glycines) fitness and relative abundance of its three bacterial symbionts. Exposure to soybean defensive stress (Rag1 gene) and a neurotoxic insecticide (thiamethoxam) substantially reduced aphid composite fitness (survival × reproduction) by 74 ± 10% and 92 ± 2%, respectively, which in turn induced distinctive changes in the endosymbiont microbiota. When challenged by host-plant defenses a 1.4-fold reduction in abundance of the obligate symbiont Buchnera was observed across four aphid clonal lines. Among facultative symbionts of Rag1-stressed aphids, Wolbachia abundance increased twofold and Arsenophonus decreased 1.5-fold. A similar pattern was observed under xenobiotic stress, with Buchnera and Arsenophonus titers decreasing (1.3-fold) and Wolbachia increasing (1.5-fold). Furthermore, variation in aphid virulence to Rag1 was positively correlated with changes in Arsenophonus titers, but not Wolbachia or Buchnera. A single Arsenophonus multi-locus genotype was found among aphid clonal lines, indicating strain diversity is not primarily responsible for correlated host-symbiont stress levels. Overall, our results demonstrate the nature of aphid symbioses can significantly affect the outcome of interactions under stress and suggests general changes in the microbiome can occur across multiple stress types.

11.
J Cell Biochem ; 117(3): 612-20, 2016 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-26264132

RESUMO

TCERG1 was characterized previously as a repressor of the transcription factor C/EBPα through a mechanism that involved relocalization of TCERG1 from nuclear speckles to pericentromeric regions. The inhibitory activity as well as the relocalization activity has been demonstrated to lie in the amino terminal half of the protein, which contains several discrete motifs including an imperfect glutamine-alanine (QA) repeat. In the present study, we showed that deletion of this domain completely abrogated the ability of TCERG1 to inhibit the growth arrest activity of C/EBPα. Moreover, the QA repeat deletion mutant of TCERG1 lost the ability to be relocalized from nuclear speckles to pericentromeric regions, and caused an increase in the average size of individual speckles. We also showed that deletion of the QA repeat abrogated the complex formation between TCERG1 and C/EBPα. Examination of mutants with varying numbers of QA repeats indicated that a minimal number of repeats are required for inhibitory activity as well as relocalization ability. These data contribute to our overall understanding of how TCERG1 can have gene-specific effects in addition to its more general roles in coordinating transcription elongation and splicing.


Assuntos
Proteínas Estimuladoras de Ligação a CCAAT/fisiologia , Fatores de Elongação da Transcrição/química , Animais , Células COS , Pontos de Checagem do Ciclo Celular , Proliferação de Células , Chlorocebus aethiops , Células HEK293 , Humanos , Domínios e Motivos de Interação entre Proteínas , Transporte Proteico , Fatores de Elongação da Transcrição/fisiologia
12.
BMC Genomics ; 16: 558, 2015 Jul 29.
Artigo em Inglês | MEDLINE | ID: mdl-26220297

RESUMO

BACKGROUND: Despite a number of recent reports of insect resistance to transgenic crops expressing insecticidal toxins from Bacillus thuringiensis (Bt), little is known about the mechanism of resistance to these toxins. The purpose of this study is to identify genes associated with the mechanism of Cry1F toxin resistance in European corn borer (Ostrinia nubilalis Hübner). For this, we compared the global transcriptomic response of laboratory selected resistant and susceptible O. nubilalis strain to Cry1F toxin. We further identified constitutive transcriptional differences between the two strains. RESULTS: An O. nubilalis midgut transcriptome of 36,125 transcripts was assembled de novo from 106 million Illumina HiSeq and Roche 454 reads and used as a reference for estimation of differential gene expression analysis. Evaluation of gene expression profiles of midgut tissues from the Cry1F susceptible and resistant strains after toxin exposure identified a suite of genes that responded to the toxin in the susceptible strain (n = 1,654), but almost 20-fold fewer in the resistant strain (n = 84). A total of 5,455 midgut transcripts showed significant constitutive expression differences between Cry1F susceptible and resistant strains. Transcripts coding for previously identified Cry toxin receptors, cadherin and alkaline phosphatase and proteases were also differentially expressed in the midgut of the susceptible and resistant strains. CONCLUSIONS: Our current study provides a valuable resource for further molecular characterization of Bt resistance and insect response to Cry1F toxin in O. nubilalis and other pest species.


Assuntos
Toxinas Bacterianas/toxicidade , Mariposas/genética , Precursores de Proteínas/toxicidade , Transcriptoma/efeitos dos fármacos , Animais , Bacillus thuringiensis/metabolismo , Toxinas Bacterianas/genética , Toxinas Bacterianas/metabolismo , Sequenciamento de Nucleotídeos em Larga Escala , Proteínas de Insetos/genética , Proteínas de Insetos/metabolismo , Resistência a Inseticidas/genética , Mucosa Intestinal/metabolismo , Mariposas/efeitos dos fármacos , Mariposas/metabolismo , Plantas Geneticamente Modificadas/metabolismo , Precursores de Proteínas/genética , Precursores de Proteínas/metabolismo , RNA/análise , RNA/isolamento & purificação , Reação em Cadeia da Polimerase em Tempo Real , Análise de Sequência de RNA , Zea mays/genética , Zea mays/metabolismo
13.
G3 (Bethesda) ; 5(2): 261-70, 2014 Dec 23.
Artigo em Inglês | MEDLINE | ID: mdl-25538100

RESUMO

Environmental stress affects basic organismal functioning and can cause physiological, developmental, and reproductive impairment. However, in many nonmodel organisms, the core molecular stress response remains poorly characterized and the extent to which stress-induced transcriptional changes differ across qualitatively different stress types is largely unexplored. The current study examines the molecular stress response of the soybean aphid (Aphis glycines) using RNA sequencing and compares transcriptional responses to multiple stressors (heat, starvation, and plant defenses) at a standardized stress level (27% adult mortality). Stress-induced transcriptional changes showed remarkable variation, with starvation, heat, and plant defensive stress altering the expression of 3985, 510, and 12 genes, respectively. Molecular responses showed little overlap across all three stressors. However, a common transcriptional stress response was identified under heat and starvation, involved with up-regulation of glycogen biosynthesis and molecular chaperones and down-regulation of bacterial endosymbiont cellular and insect cuticular components. Stressor-specific responses indicated heat affected expression of heat shock proteins and cuticular components, whereas starvation altered a diverse set of genes involved in primary metabolism, oxidative reductive processes, nucleosome and histone assembly, and the regulation of DNA repair and replication. Exposure to host plant defenses elicited the weakest response, of which half of the genes were of unknown function. This study highlights the need for standardizing stress levels when comparing across stress types and provides a basis for understanding the role of general vs. stressor specific molecular responses in aphids.


Assuntos
Afídeos/genética , Estresse Fisiológico/genética , Animais , Genes de Insetos , Análise de Sequência de RNA , Transcriptoma
14.
J Diet Suppl ; 10(3): 241-51, 2013 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-23957855

RESUMO

Creatine ethyl ester hydrochloride (CEE) was synthesized as a prodrug of creatine (CRT) to improve aqueous solubility, gastrointestinal permeability, and ultimately the pharmacodynamics of CRT. We used high-performance liquid chromatography (HPLC) and proton nuclear magnetic resonance (NMR) to characterize the pH-dependent stability of CEE in aqueous solution and compared the permeability of CEE to CRT and creatinine (CRN) across Caco-2 human epithelial cell monolayers and transdermal permeability across porcine skin. CEE was most stable in a strongly acidic condition (half-life = 570 hours at pH 1.0) where it undergoes ester hydrolysis to CRT and ethanol. At pH ≥ 1.0, CEE cyclizes to CRN with the logarithm of the first order rate constant increasing linearly with pH. Above pH 8.0 (half-life = 23 sec) the rate of degradation was too rapid to be determined. The rate of degradation of CEE in cell culture media and simulated intestinal fluid (SIF) was a function of pH and correlated well with the stability in aqueous buffered solutions. The permeability of CEE across Caco-2 monolayers and porcine skin was significantly greater than that of CRT or CRN. The stability of CEE in acidic media together with its improved permeability suggests that CEE has potential for improved oral absorption compared to CRT.


Assuntos
Creatina/análogos & derivados , Creatina/metabolismo , Ácido Gástrico , Mucosa Intestinal/metabolismo , Pró-Fármacos/metabolismo , Pele/metabolismo , Administração Oral , Animais , Células CACO-2 , Química Farmacêutica , Creatina/administração & dosagem , Creatinina/metabolismo , Estabilidade de Medicamentos , Humanos , Concentração de Íons de Hidrogênio , Pró-Fármacos/administração & dosagem , Suínos
15.
J Biomed Biotechnol ; 2012: 604076, 2012.
Artigo em Inglês | MEDLINE | ID: mdl-22919272

RESUMO

Feeding damage caused by the western corn rootworm, Diabrotica virgifera virgifera, is destructive to corn plants in North America and Europe where control remains challenging due to evolution of resistance to chemical and transgenic toxins. A BAC library, DvvBAC1, containing 109,486 clones with 104 ± 34.5 kb inserts was created, which has an ~4.56X genome coverage based upon a 2.58 Gb (2.80 pg) flow cytometry-estimated haploid genome size. Paired end sequencing of 1037 BAC inserts produced 1.17 Mb of data (~0.05% genome coverage) and indicated ~9.4 and 16.0% of reads encode, respectively, endogenous genes and transposable elements (TEs). Sequencing genes within BAC full inserts demonstrated that TE densities are high within intergenic and intron regions and contribute to the increased gene size. Comparison of homologous genome regions cloned within different BAC clones indicated that TE movement may cause haplotype variation within the inbred strain. The data presented here indicate that the D. virgifera virgifera genome is large in size and contains a high proportion of repetitive sequence. These BAC sequencing methods that are applicable for characterization of genomes prior to sequencing may likely be valuable resources for genome annotation as well as scaffolding.


Assuntos
Cromossomos Artificiais Bacterianos/genética , Besouros/genética , Genes de Insetos/genética , Sequências Repetitivas de Ácido Nucleico/genética , Análise de Sequência de DNA/métodos , Animais , Elementos de DNA Transponíveis/genética , Eletroforese em Gel de Ágar , Citometria de Fluxo , Biblioteca Gênica , Tamanho do Genoma , Genômica , Haplótipos/genética , Anotação de Sequência Molecular
16.
Phys Rev E Stat Nonlin Soft Matter Phys ; 85(4 Pt 2): 046202, 2012 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-22680551

RESUMO

We consider the dynamics of systems undergoing parameter sweeps through bifurcation points in the presence of noise. Of interest here are local codimension-one bifurcations that result in large excursions away from an operating point that is transitioning from stable to unstable during the sweep, since information about these "escape events" can be used for system identification, sensing, and other applications. The analysis is based on stochastic normal forms for the dynamic saddle-node and subcritical pitchfork bifurcations with a time-varying bifurcation parameter and additive noise. The results include formulation and numerical solution for the distribution of escape events in the general case and analytical approximations for delayed bifurcations for which escape occurs well beyond the corresponding quasistatic bifurcation points. These bifurcations result in amplitude jumps encountered during parameter sweeps and are particularly relevant to nano- and microelectromechanical systems, for which noise can play a significant role.

17.
Opt Express ; 20(11): 11796-805, 2012 May 21.
Artigo em Inglês | MEDLINE | ID: mdl-22714167

RESUMO

The resolution of a diffraction-limited imaging system is inversely proportional to the aperture size. Instead of using a single large aperture, multiple small apertures are used to synthesize a large aperture. Such a multi-aperture system is modular, typically more reliable and less costly. On the other hand, a multi-aperture system requires phasing sub-apertures to within a fraction of a wavelength. So far in the literature, only the piston, tip, and tilt type of inter-aperture errors have been addressed. In this paper, we present an approach to correct for rotational and translational errors as well.


Assuntos
Lentes , Fotografação/instrumentação , Tomografia de Coerência Óptica/instrumentação , Desenho de Equipamento , Análise de Falha de Equipamento
18.
J Orthop Trauma ; 24(10): 653-5, 2010 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-20871254

RESUMO

Salvage total hip arthroplasty for failed Dynamic hip screw fixation has widely been advocated as a viable treatment option with successful functional outcomes. However, when revising a dynamic hip screw, removal of the lag screw can pose problems in terms of difficulty and risk of iatrogenic fractures. This is because the lag screw is not reverse-cutting and therefore a large torque is generated which can lead to such fractures. We report on a series of eight cases in which we excised the femoral head with the lag screw in situ. We recommend this technique as a safe and effective method to reduce the risk of iatrogenic fractures.


Assuntos
Artroplastia de Quadril/métodos , Parafusos Ósseos , Falha de Prótese , Reoperação/métodos , Artroplastia de Quadril/instrumentação , Fraturas do Fêmur/cirurgia , Cabeça do Fêmur/cirurgia , Colo do Fêmur/cirurgia , Fixação Interna de Fraturas/instrumentação , Prótese de Quadril , Humanos , Fixadores Internos
19.
J Diet Suppl ; 7(3): 240-52, 2010 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-22432515

RESUMO

Creatine is widely used as a dietary supplement for body builders to enhance athletic performance. As the monohydrate, its low solubility in water and high dose lead to water retention and gastrointestinal discomfort. Hence, alternative creatine derivatives with enhanced water solubility and potential therapeutic advantages have been synthesized. As a zwitterionic compound, creatine can form salts at the N-methyl guanidinium or carboxylic acid functional groups. In this study, we determined the aqueous solubilities and partition coefficients of six N-methyl guanidinium salts of creatine compared to those of creatine monohydrate; two of these were new salts, namely, creatine mesylate and creatine hydrogen maleate. The aqueous solubilities of the salts were significantly more than that of creatine monohydrate with the hydrochloride and mesylate being 38 and 30 times more soluble, respectively. The partition coefficients of the creatine salts were very low indicating their relatively high polarity. Permeabilities of creatine pyruvate, citrate, and hydrochloride in Caco-2 monolayers were compared to that of creatine monohydrate. Aside from the creatine citrate salt form that had reduced permeability, there were no significant differences in permeability characteristics in Caco-2 monolayers. Typical of an amphoteric compound, creatine is least soluble in the pH region near the isoelectric point.


Assuntos
Creatina/química , Suplementos Nutricionais , Desempenho Atlético , Células CACO-2 , Guanidina , Humanos , Concentração de Íons de Hidrogênio , Permeabilidade , Sais/química , Solubilidade
20.
Environ Entomol ; 38(1): 274-80, 2009 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-19791624

RESUMO

The western bean cutworm, Striacosta albicosta (Smith) (Lepidoptera: Noctuidae), is a pest of both corn and dry bean crops. At the beginning of the 21st century, the species began to extend its range out of the Great Plains, eastward through the Corn Belt. This rapid range expansion is remarkable because the species distribution had been stable for at least the previous half century, despite the apparent abundance of suitable habitat (i.e., cornfields) immediately to the east. We hypothesized that if the western bean cutworm had to overcome a stable barrier to movement before starting the current range expansion, it probably experienced a genetic bottleneck in doing so. To test this hypothesis, variation in the mitochondrial NADH dehydrogenase one (ND1) gene was studied in populations from Wyoming, Nebraska, and Iowa. No differences in overall genetic diversity or haplotype frequencies indicative of a bottleneck were observed between the recently founded populations in Iowa and the established populations in Wyoming and Nebraska. This result suggests that the sudden loss of an ecological exclusion mechanism, allowing the species to move east in appreciable numbers, is more likely to have triggered the range expansion than the surmounting of an extrinsic barrier to movement. The nature of this mechanism is unknown but might be related to recent changes in corn farming practices and technology.


Assuntos
DNA Mitocondrial/genética , Variação Genética , Mariposas/genética , Mariposas/fisiologia , Animais , Demografia , Iowa , Nebraska , Estados Unidos , Wyoming
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