RESUMEN
Increasing data have supported the importance of divergence with gene flow (DGF) in the generation of biological diversity. In such cases, lineage divergence occurs on a shorter timescale than does the completion of reproductive isolation. Although it is critical to explore the mechanisms driving divergence and preventing homogenization by hybridization, it is equally important to document cases of DGF in nature. Here we synthesize data that have accumulated over the last dozen or so years on DGF in the chipmunk (Tamias) radiation with new data that quantify very high rates of mitochondrial DNA (mtDNA) introgression among para- and sympatric species in the T. quadrivittatus group in the central and southern Rocky Mountains. These new data (188 cytochrome b sequences) bring the total number of sequences up to 1871; roughly 16% (298) of the chipmunks we have sequenced exhibit introgressed mtDNA. This includes ongoing introgression between subspecies and between both closely related and distantly related taxa. In addition, we have identified several taxa that are apparently fixed for ancient introgressions and in which there is no evidence of ongoing introgression. A recurrent observation is that these introgressions occur between ecologically and morphologically diverged, sometimes non-sister taxa that engage in well-documented niche partitioning. Thus, the chipmunk radiation in western North America represents an excellent mammalian example of speciation in the face of recurrent gene flow among lineages and where biogeography, habitat differentiation and mating systems suggest important roles for both ecological and sexual selection.
Asunto(s)
Flujo Génico/genética , Sciuridae/genética , Animales , ADN Mitocondrial/genética , Ecología/métodos , Ecosistema , Especiación Genética , América del Norte , Filogenia , Aislamiento ReproductivoRESUMEN
We have examined the cortex of Caenorhabditis elegans eggs during pseudocleavage (PC), a period of the first cell cycle which is important for the generation of asymmetry at first cleavage (Strome, S. 1989. Int. Rev. Cytol. 114: 81-123). We have found that directed, actin dependent, cytoplasmic, and cortical flow occurs during this period coincident with a rearrangement of the cortical actin cytoskeleton (Strome, S. 1986. J. Cell Biol. 103: 2241-2252). The flow velocity (4-7 microns/min) is similar to previously determined particle movements driven by cortical actin flows in motile cells. We show that directed flows occur in one of the daughters of the first division that itself divides asymmetrically, but not in its sister that divides symmetrically. The cortical and cytoplasmic events of PC can be mimicked in other cells during cytokinesis by displacing the mitotic apparatus with the microtubule polymerization inhibitor nocodazole. In all cases, the polarity of the resulting cortical and cytoplasmic flows correlates with the position of the attenuated mitotic spindle formed. These cortical flows are also accompanied by a change in the distribution of the cortical actin network. The polarity of this redistribution is similarly correlated with the location of the attenuated spindle. These observations suggest a mechanism for generating polarized flows of cytoplasmic and cortical material during embryonic cleavages. We present a model for the events of PC and suggest how the poles of the mitotic spindle mediate the formation of the contractile ring during cytokinesis in C. elegans.
Asunto(s)
Blastómeros/citología , Caenorhabditis elegans/embriología , Corriente Citoplasmática , Citoesqueleto de Actina/fisiología , Actinas/metabolismo , Animales , División Celular , Polaridad Celular , Centrómero/ultraestructura , Fase de Segmentación del Huevo , Corriente Citoplasmática/efectos de los fármacos , Microtúbulos/efectos de los fármacos , Películas Cinematográficas , Nocodazol/farmacologíaRESUMEN
Illness and death from diseases caused by unsafe food are a constant threat to public health security as well as socio-economic development throughout the world. The full extent of the burden and cost of foodborne diseases associated with pathogenic bacterial, viral and parasitic microorganisms, and food contaminated by chemicals is still unknown but is thought to be substantial. The World Health Organization (WHO) Initiative to estimate the global burden of foodborne diseases aims to fill the current data gap and respond to the increasing global interest in health information. Collaborative efforts are required to achieve the ambitious task of assessing the foodborne disease burden from all causes worldwide. Recognising the need to join forces, the WHO Initiative has assembled an alliance of stakeholders which share and support the Initiative's vision, intended objectives and outcomes. One important collaborator is the European Centre for Disease Prevention and Control (ECDC) which has embarked on a burden of disease study covering at least 18 foodborne diseases in nearly 30 countries.
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Síndrome de Creutzfeldt-Jakob/epidemiología , Brotes de Enfermedades/estadística & datos numéricos , Enfermedades Transmitidas por los Alimentos/epidemiología , Cooperación Internacional , Vigilancia de la Población/métodos , Organización Mundial de la Salud/organización & administración , Incidencia , Medición de Riesgo/métodos , Factores de RiesgoAsunto(s)
Parche de Sangre Epidural , Cefalea Pospunción de la Duramadre , Femenino , Humanos , EmbarazoRESUMEN
A method was developed for the simultaneous determination of residues of pirimicarb (I) and its desmethylformamido (II) and desmethyl (III) metabolites in plums, peas, green beans, broad beans, carrots, and swedes. The compounds were extracted with ethyl acetate and determined, without cleanup, by reversed-phase liquid chromatography and electrospray mass spectrometry (MS). MS and MS/MS were used concurrently to monitor the protonated molecules and their common collision-induced dissociation product. The limit of detection (signal-to-noise ratio of >3) was 1 ng/mL, corresponding to crop concentrations of <0.0015 mg/kg. All 3 compounds were determined in plums, broad beans, and green beans by MS without interference. Interferences which affected the determination of desmethylformamido-pirimicarb in peas, and to a lesser extent in carrots and swedes, were eliminated by MS/ MS. Recoveries for all 3 compounds, at 0.05 mg/kg for plums and 0.005 mg/kg for other commodities, were in the range 83-124%. No interconversion of I, II and III, occurred during extraction, and the compounds were stable in extracts for > or = 7 days under appropriate conditions.
Asunto(s)
Carbamatos/análisis , Cromatografía Liquida/métodos , Contaminación de Alimentos/análisis , Frutas/química , Insecticidas/análisis , Espectrometría de Masas/métodos , Pirimidinas , Verduras/química , Modelos QuímicosRESUMEN
Ehrlichia canis, the causative agent of canine ehrlichiosis or tropical canine pancytopaenia (TCP) has been identified in Kenya. Transmission studies to two dogs resulted in signs of ehrlichiosis including marked thrombocytopaenia, pyrexia, reduction in the packed cell volume and the presence of E canis in peripheral blood mononuclear cells.
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Enfermedades de los Perros/microbiología , Ehrlichia/aislamiento & purificación , Infecciones por Rickettsiaceae/veterinaria , Rickettsiaceae/aislamiento & purificación , Animales , Recuento de Células Sanguíneas , Plaquetas , Perros , Fiebre/veterinaria , Kenia , Masculino , Monocitos/microbiología , Infecciones por Rickettsiaceae/microbiologíaRESUMEN
The analysis of 252 food samples (UK-produced and imported) purchased from a variety of retail outlets in the UK was undertaken for the presence of perfluorooctanesulphonic acid (PFOS), perfluorooctanoic acid (PFOA) and nine other perfluorocompounds (PFCs). A limit of quantification (LOQ) of 1 microg/kg was achieved for all target analytes, in all samples. Standard addition was used for quantification of PFC levels. All 11 of the targeted PFCs were detected in 75 individual food items. In 70% of the samples, including all meat other than offal, none of the analytes were present above the LOD. The highest levels found were 59 microg/kg perfluorooctanesulphonic acid (PFOS) and 63 microg/kg total PFCs (SigmaPFCs) in an eel sample, and 40 microg/kg PFOS (62 microg/kg SigmaPFCs) in a whitebait sample. The highest level in an offal sample was 10 microg/kg, in a wild roe deer liver. There were six samples with SigmaPFCs >15 microg/kg (fish, shellfish, crustaceans), a further seven samples with SigmaPFCs ranging 11-15 microg/kg (including a liver), nine with SigmaPFCs ranging 6-10 microg/kg (fish and livers), 31 with SigmaPFCs in the range 2-5 microg/kg (including kidneys, popcorn and processed peas) and a further 22 with SigmaPFCs close to the LOD of 1 microg/kg (including eggs and potatoes). These concentrations indicate that UK consumers are being exposed to a low level of PFC contamination from food. The estimated upper bound dietary intake of 10 ng/kg bodyweight (bw)/day of PFOS for average adult consumers is well below the 0.15 microg (150 ng)/kg bw tolerable daily intake (TDI) set by the European Food Safety Authority. The lower bound adult dietary intake estimate of 1 ng/kg bw/day is similar to estimates undertaken and reported in countries such as Canada, Germany and Spain.
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Ácidos Alcanesulfónicos/análisis , Cromatografía Líquida de Alta Presión/métodos , Dieta , Fluorocarburos/análisis , Contaminación de Alimentos/análisis , Espectrometría de Masas en Tándem/métodos , Adolescente , Adulto , Anciano , Ácidos Alcanesulfónicos/administración & dosificación , Ácidos Alcanesulfónicos/toxicidad , Animales , Niño , Preescolar , Peces , Fluorocarburos/administración & dosificación , Fluorocarburos/toxicidad , Humanos , Lactante , Recién Nacido , Riñón/química , Hígado/química , Concentración Máxima Admisible , Carne/análisis , Alimentos Marinos/análisis , Mariscos/análisis , Reino UnidoAsunto(s)
Antipsicóticos/efectos adversos , Trastorno Bipolar/tratamiento farmacológico , Alucinaciones/inducido químicamente , Risperidona/efectos adversos , Trastornos Relacionados con Sustancias/tratamiento farmacológico , Adolescente , Antimaníacos/uso terapéutico , Benzodiazepinas , Trastorno Bipolar/complicaciones , Diagnóstico Dual (Psiquiatría) , Quimioterapia Combinada , Femenino , Humanos , Olanzapina , Pirenzepina/análogos & derivados , Pirenzepina/uso terapéutico , Resultado del Tratamiento , Ácido Valproico/uso terapéuticoRESUMEN
OBJECTIVES: To review the evidence on the clinical effectiveness and cost-effectiveness of non-occupational postexposure prophylaxis (PEP) for HIV. DATA SOURCES: Eleven electronic databases were searched from inception to December 2007. REVIEW METHODS: Selected studies were assessed, subjected to data extraction using a standard template and quality assessment using published criteria. Studies were synthesised using a narrative approach with full tabulation of results from all included studies. RESULTS: One clinical effectiveness study meeting the inclusion criteria was identified, a cohort study of PEP in a high-risk HIV-negative homosexual male cohort in Brazil. The quality of the study was generally weak. Seroincidence in the cohort as a whole (2.9 per 100 person-years) was very similar to that expected in this population (3.1 per 100 person-years, p > 0.97), despite the seroconversion to HIV being 1/68 in the PEP group and 10/132 in the group not receiving PEP. High-risk sexual activities declined over time for both PEP and non-PEP users. Four economic evaluations met the inclusion criteria of the review. The methodological quality of the studies was mixed. The studies are constrained by a lack of published data on the clinical effectiveness of PEP after non-occupational exposure, with effectiveness data derived from one study of occupational PEP. Their generalisability to the UK is not clear. Results suggest that PEP following non-occupational exposure to HIV was cost saving for men who have unprotected receptive anal intercourse with men, whether the source partner is known to be HIV positive or not; heterosexuals after unprotected receptive anal intercourse; and intravenous drug users sharing needles with a known HIV-positive person. PEP following non-occupational exposure to HIV was cost-effective for all male-male intercourse (unprotected receptive and insertive anal intercourse, unprotected receptive oral sex, and 'other') and was possibly cost-effective for intravenous drug users and high-risk women. Four additional studies were identified giving further information about adverse events associated with PEP after non-occupational exposure to HIV. The majority of participants experienced adverse events with the most common being nausea and fatigue. Rates were generally higher in participants receiving triple therapy than in participants receiving dual therapy. Completion of PEP therapy was variable, ranging from 24% to 78% of participants depending on type of therapy. Toxicity was the main reason for discontinuation of treatment. CONCLUSIONS: It is not possible to draw conclusions on the clinical effectiveness of non-occupational PEP for HIV because of the limited evidence available. The review of cost-effectiveness suggests that non-occupational PEP may be cost-effective, especially in certain population subgroups; however, the assumptions made and data sources used in the cost-effectiveness studies mean that their results should be used with caution.
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Fármacos Anti-VIH/uso terapéutico , Infecciones por VIH/tratamiento farmacológico , Infecciones por VIH/prevención & control , Fármacos Anti-VIH/administración & dosificación , Fármacos Anti-VIH/efectos adversos , Análisis Costo-Beneficio , Bases de Datos Bibliográficas , Combinación de Medicamentos , Quimioterapia Combinada , Infecciones por VIH/economía , Infecciones por VIH/transmisión , Seropositividad para VIH/tratamiento farmacológico , Seropositividad para VIH/economía , Humanos , Lamivudine/economía , Lamivudine/farmacología , Lamivudine/uso terapéutico , Lopinavir , Premedicación , Pirimidinonas/economía , Pirimidinonas/farmacología , Pirimidinonas/uso terapéutico , Ritonavir/economía , Ritonavir/farmacología , Ritonavir/uso terapéutico , Abuso de Sustancias por Vía Intravenosa , Factores de Tiempo , Resultado del Tratamiento , Sexo Inseguro , Zidovudina/economía , Zidovudina/farmacología , Zidovudina/uso terapéuticoRESUMEN
This paper describes an analytical method for four phenolic and salicylanilide anthelmintics authorised for use within the EU (nitroxinil, oxyclozanide, rafoxanide and closantel) in bovine kidney, and the extension of this procedure to include a number of related compounds; ioxynil, niclosamide, salicylanide and 3-trifluoromethyl-4-nitrophenol (TFM). The method comprises a solvent extraction with 1% acetic acid in acetone and clean-up using a mixed-mode anion-exchange solid phase extraction column. Determination is by reversed phase LC-MS/MS. The method was validated to the latest EU requirements (Commission Decision 2002/657/EC) using both spiked and incurred tissues and was subject to second laboratory evaluation.
Asunto(s)
Antihelmínticos/análisis , Cromatografía Liquida/métodos , Residuos de Medicamentos/análisis , Riñón/química , Fenoles/análisis , Salicilanilidas/análisis , Espectrometría de Masas en Tándem/métodos , Animales , BovinosRESUMEN
The first division of the Caenorhabditis elegans embryo is unequal, generating daughter cells with distinct fates. The differences between the cells are believed to result from the partitioning of cytoplasmic determinants during the first cell cycle. Actin microfilaments play a critical, but poorly defined, role in this event. In this paper, the actin cortex in live embryos is studied during cytoplasmic localisation by fluorescently labelling microfilaments in oocytes and then using in vivo fluorescence microscopy to observe their behaviour. This reveals that there is a concerted movement of cortical actin to the anterior of the embryo at the time cytoplasmic localisation takes place. Furthermore, it is demonstrated that endogenous foci of F-actin are asymmetrically distributed following this event; these structures have previously been seen in fixed cortices. A model for the participation of the actin cytoskeleton in cytoplasmic localisation is presented based on these results.
Asunto(s)
Actinas/metabolismo , Caenorhabditis elegans/metabolismo , Citoesqueleto/metabolismo , Animales , Ciclo Celular/fisiología , División Celular , Colorantes Fluorescentes/metabolismo , Músculo Esquelético/química , Oocitos , Faloidina/metabolismo , Conejos , Rodaminas/metabolismoRESUMEN
A method was developed for the determination of the herbicide isoproturon in wheat, maize, oats and pasta, with a limit of determination of 0.05 mg kg(-1). Isoproturon was extracted from moistened samples using a mixture of acetone, hexane and dichloromethane. The resulting extract was cleaned-up by solid-phase extraction using aminopropyl-bonded silica cartridges and analysed by reversed-phase liquid chromatography with photodiode array detection. Confirmation was by electrospray liquid chromatography-mass spectrometry. Recoveries from seven samples of each of the four matrices spiked with isoproturon at 0.05 and 0.5 mg kg(-1) were in the range 88-104%. The method was used to monitor cereal grains and pasta as part of the UK food monitoring programme.
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Grano Comestible/química , Herbicidas/análisis , Compuestos de Metilurea/análisis , Compuestos de Fenilurea , Avena/química , Cromatografía Líquida de Alta Presión/métodos , Cromatografía Liquida/métodos , Espectrometría de Masas/métodos , Reproducibilidad de los Resultados , Espectrometría de Masa por Ionización de Electrospray/métodos , Triticum/química , Zea mays/químicaRESUMEN
Anteroposterior asymmetries are apparent in C elegans development before the first cell division. Here we identify the cue that specifies the anteroposterior axis, and investigate how this cue is interpreted to generate initial asymmetry. In C. elegans, the sperm normally enters the egg in an invariant position. We have found that causing fertilisation to occur in the abnormal end of the egg completely reverses the orientation of the anteroposterior axis, but gives otherwise normal development. This result suggests that a component of the sperm normally specifies the anteroposterior axis. We have found that a cytoplasmic rearrangement in the uncleaved zygote is directed by the sperm, suggesting a mechanism by which the sperm may specify the axis. The results additionally reveal that the C elegans oocyte is constructed with no axis prespecified in the form of asymmetrically localised cytoplasmic determinants.
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Caenorhabditis elegans/embriología , Polaridad Celular , Fertilización/fisiología , Espermatozoides/fisiología , Cigoto/fisiología , Animales , Caenorhabditis elegans/citología , Citoplasma/fisiología , Citoplasma/ultraestructura , Gránulos Citoplasmáticos/ultraestructura , Femenino , Masculino , Modelos Biológicos , Especificidad de la Especie , Espermatozoides/citología , Cigoto/citologíaRESUMEN
The polarization of the embryonic axes is a key event in embryogenesis, being one of the earliest manifestations of the shape and form of the organism. The acquisition of polarity by individual blastomeres is one of the earliest indicators of commitment to a particular pathway of differentiation. These phenomena have been studied in the development of C. elegans both at the cellular and organismal level. This review summarizes what is known about how polarity is established in the blastomeres of this organism, how the division axes of polarized cells are determined, and how the embryonic axes are set up.
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Blastocisto/fisiología , Caenorhabditis elegans/embriología , Polaridad Celular/fisiología , Animales , Cigoto/fisiologíaRESUMEN
Germ granules are ribonucleoprotein particles that are thought to function in germline specification in invertebrates and possibly in vertebrates. In Caenorhabditis elegans, these structures, termed P granules, are partitioned to the germline P cells during the early embryonic divisions. By injecting a fluorescently labelled anti-P-granule antibody into the C. elegans germline syncitium, we followed P-granule segregation in live embryos using laser-scanning confocal microscopy. We show that, in early P cells (P0 and P1), P-granule partitioning is achieved primarily by their migration through the cytoplasm towards the site of formation of the germline daughter cell. A different mechanism appears to operate in later P cells (P2 and P3): P granules associate with the nucleus and move with it toward the site of formation of the germline daughter cell, where they are then deposited. At each division, there is also disassembly or degradation of those P granules that remain in the cytoplasm destined for the somatic daughter cell. Microfilaments, microtubules and the product of the gene mes-1 are required for the normal pattern of P-granule segregation in P2.
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Caenorhabditis elegans/embriología , Gránulos Citoplasmáticos/metabolismo , Células Germinativas/citología , Ribonucleoproteínas/metabolismo , Citoesqueleto de Actina/fisiología , Animales , Núcleo Celular/metabolismo , Citoplasma/metabolismo , Trastornos del Desarrollo Sexual , Genes de Helminto , Proteínas del Helminto/fisiología , Microtúbulos/fisiología , MutaciónRESUMEN
A simple, sensitive and reliable liquid chromatography-mass spectrometry method with direct injection of diluted samples is reported for the determination of propamocarb residues in wine. Red and white wines were diluted 40- and 20-fold, respectively, using water. Liquid chromatography was performed with a mobile-phase gradient and detection was by electrospray mass spectrometry in a positive ionization mode. Propamocarb was detected as the protonated molecular species at m/z 189. Using matrix-matched calibrant solutions, a calibrated range equivalent to 0.05-2.0 mg kg(-1) in red and white wines and limits of detection of 0.025 mg kg(-1) for white wine and of 0.05 mg kg(-1) for red wine (0.00125 microg ml(-1) of sample solution injected) were readily achievable. Recovery of propamocarb hydrochloride from wine spiked before dilution was in the range 91-115%. The chromatograms were free of isobaric interferences. In a small wine survey (72 samples), no residues of propamocarb were detected above 0.1 mg kg(-1).
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Carbamatos/análisis , Contaminación de Alimentos/análisis , Fungicidas Industriales/análisis , Residuos de Plaguicidas/análisis , Vino/análisis , Cromatografía Liquida/métodos , Análisis de los Alimentos/métodos , Humanos , Espectrometría de Masa por Ionización de Electrospray/métodosRESUMEN
The first cleavage of the Caenorhabditis elegans embryo is asymmetrical, producing daughters with different cell fates. During the first cell cycle, P granules, cytoplasmic components that are segregated to the germ-line, are localized to the posterior of the embryo. It has been hypothesized that the asymmetrical behavior of the daughters of the first division results from a similar localization of developmental determinants. A process called pseudocleavage also occurs during the first cell cycle: Anterior cortical contractions culminate in a single partial constriction of the embryo called the pseudocleavage furrow. Coincident with pseudocleavage, there is an anteriorly directed flow of cortical cytoplasm and a posteriorly directed flow of internal cytoplasm. Foci of filamentous cortical actin become asymmetrically distributed into an anterior cap. Roles for these various first cell cycle events in cytoplasmic localization and development have been suggested but remain unclear. We have isolated a maternal effect mutation, nop-1(it142), which abolishes the anterior cortical contractions and the pseudocleavage furrow. In addition, cortical actin foci remain uniformly distributed in most embryos. Despite these defects, cytoplasmic and cortical streaming is present and P granules are localized to the posterior of early embryos. In most embryos from mutant mothers, development proceeds normally and the embryos hatch and grow into fertile adults. We conclude that the pseudocleavage contractions and furrow are dispensable for the development of C. elegans.
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Caenorhabditis elegans/embriología , Animales , Caenorhabditis elegans/genética , Ciclo Celular , Polaridad Celular , Embrión no Mamífero/fisiología , MutaciónRESUMEN
The nucleotide sequence of a region of wheat chloroplast DNA containing the psbB gene for the 47 kDa chlorophyll a-binding protein of photosystem II has been determined. The gene encodes a polypeptide of 508 amino acid residues which is predicted to contain six hydrophobic membrane-spanning regions. The psbB gene is located 562 bp upstream of the psbH gene for the 10 kDa phosphoprotein of photosystem II. A small open reading frame of 38 codons is located between psbB and psbH, and on the opposite strand the psbN gene, encoding a photosystem II polypeptide of 43 amino acid residues, is located between orf38 and psbH. S1 nuclease mapping indicated that the 5' ends of transcripts were located 371 and 183 bp upstream of the psbB translation initiation codon. Predominant transcripts of 2.1 kb and 1.8 kb for psbB and 0.4 kb for psbH were present in RNA isolated from etiolated and greening wheat seedlings. Immunodecoration of Western blots indicated that the 47 kDa polypeptide was absent, or present in very low amounts, in dark-grown tissue and accumulated on greening, whereas the 10 kDa polypeptide was present in similar amounts in both dark-grown and greening seedlings. The 10 kDa polypeptide was phosphorylated in vitro by incubating wheat etioplast membranes with [gamma 32P] ATP.
Asunto(s)
Cloroplastos/fisiología , Genes de Plantas , Fosfoproteínas/genética , Proteínas del Complejo del Centro de Reacción Fotosintética/genética , Triticum/genética , Secuencia de Aminoácidos , Secuencia de Bases , Membrana Celular/fisiología , ADN/genética , Complejos de Proteína Captadores de Luz , Datos de Secuencia Molecular , Peso Molecular , Complejo de Proteína del Fotosistema II , Conformación Proteica , ARN/genética , ARN/aislamiento & purificación , Mapeo Restrictivo , Homología de Secuencia de Ácido Nucleico , Transcripción Genética , Triticum/fisiologíaRESUMEN
The N-terminal amino acid sequence of a 3.2 kDa photosystem II polypeptide is shown to be identical to that of a polypeptide encoded by an open reading frame of 38 codons (orf38) in wheat chloroplast DNA. Orf38 is located just downstream of the psbE and psbF genes for the polypeptides of cytochrome b-559. Analysis of the transcription of this region of chloroplast DNA shows that psbE, psbF and orf38 are co-transcribed to give a 1.1 kb polycistronic transcript which also contains another open reading frame of 40 codons. The orf38 and orf40 products are hydrophobic polypeptides which are both predicted to span the thylakoid membrane once. Orf38 and orf40 are highly conserved, and map to similar locations adjacent to psbE and psbF, in all organisms from which this region of DNA has been sequenced. We propose that orf38 is named psbL.