961 resultados para Molecular Reproduction, Development
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The aflatoxin B1 (AFB1) is a mycotoxin that has been identified as the most potent hepatocarcinogen. The metabolite resulting from detoxification process of AFB1 in liver, has the ability to react with the genomic DNA, generating AFB1-DNA adducts; during DNA replication process, this adduct induced the G:CT:A transversion. Polymorphism in genes encoding for enzymes involved in the activation and detoxification of AFB1 and DNA repair enzymes has been associated with the risk of hepatocellular carcinoma (HCC) development. Additionally, in populations of high exposure to aflatoxin and high prevalence of hepatitis B virus (HBV) infection, has been demonstrated a synergism between these two risk factors for the development of HCC.
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In this paper we search the concept of nonviolent resistance inquiring a rural experience from Rio Negros steppe. The initiative highlights the need to recognize the context of the resistance exercise and the consideration of three aspects: the evaluation and interpretation of space, the dispute to public policy and the restructuring of the family order. These three elements, which overlap material and symbolic aspects, are discussed from an organization of trade domestic craft production. The notion of development is discovered on the basis of the frameworks of values from which the reproduction of subordination is associated with this idea, and even the challenge of change is the basis of the proposal which reviews that development idea, and illuminates from this complexity the notion of nonviolent resistance.
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ANTECEDENTES:El aislamiento de clulas fetales libres o ADN fetal en sangre materna abre una ventana de posibilidades diagnsticas no invasivas para patologas monognicas y cromosmicas, adems de permitir la identificacin del sexo y del RH fetal. Actualmente existen mltiples estudios que evalan la eficacia de estos mtodos, mostrando resultados costo-efectivos y de menor riesgo que el estndar de oro. Este trabajo describe la evidencia encontrada acerca del diagnstico prenatal no invasivo luego de realizar una revisinsistemtica de la literatura. OBJETIVOS:El objetivo de este estudio fuereunir la evidencia quecumplacon los criterios de bsqueda, en el tema del diagnstico fetal no invasivo por clulas fetales libres en sangre materna para determinar su utilidad diagnstica. MTODOS:Se realiz una revisinsistemtica de la literatura con el fin de determinar siel diagnstico prenatal no invasivo por clulas fetales libres en sangre materna es efectivo como mtodo de diagnstico. RESULTADOS:Se encontraron 5,893 artculos que cumplan con los criterios de bsqueda;67 cumplieron los criterios de inclusin: 49.3% (33/67) correspondieron a estudios de corte transversal, 38,8% (26/67) a estudios de cohortes y el 11.9% (8/67) a estudios casos y controles.Se obtuvieron resultados de sensibilidad, especificidad y tipo de prueba. CONCLUSIN:En la presente revisin sistemtica, se evidencia como el diagnstico prenatal no invasivo es una tcnica feasible, reproducible y sensible para el diagnstico fetal, evitando el riesgo de un diagnstico invasivo.
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Dengue and Chikungunya viruses cause the most important arthropod-borne viral infections for humans. These viruses are predominant in tropical and subtropical regions. In addition, these viruses are predominant in tropical and subtropical regions. Dengue mortality rate is around 1.2 to 3.5% and deaths due to chikungunya fever are around 1 in 1000; however, half of chikungunya-infected patients evolve into a chronic state that can persist for months up to years. There are no antiviral drugs available for DENV and CHIKV treatment and prevention. Moreover, vector control strategies have failed so far. Thus, the development of potent inhibitors for a broad spectrum of RNA viruses is urgently needed. We established and characterized a new embryonic insect cell line from Culex quinquefasciatus mosquito. Also we established the flaviviruses and alphavirus replication, both in C6/36 and Lulo insect cell lines, as well as in Vero cell line. In addition we carried out a reference compound library and reference panel of assays and data for DENV, which provides a benchmark for further studies. During this study, a panel of 9 antiviral molecules, with proven in vitro anti-dengue virus activity and that act at different stages of the DENV life cycle, was selected. Finally, Favipiravir or T-705, was identified as inhibitor in vitro and in vivo of alphaviruses and the mutation K291R in nsP4, which is responsible of the polymerase activity, was found as the mode of action in CHIKV. Interestingly, lysine in motif F1 is also highly conserved in positive-stranded RNA viruses and this might explain the broad spectrum of T-705 antiviral activity.
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Two common methods of accounting for electric-field-induced perturbations to molecular vibration are analyzed and compared. The first method is based on a perturbation-theoretic treatment and the second on a finite-field treatment. The relationship between the two, which is not immediately apparent, is made by developing an algebraic formalism for the latter. Some of the higher-order terms in this development are documented here for the first time. As well as considering vibrational dipole polarizabilities and hyperpolarizabilities, we also make mention of the vibrational Stark effec
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La tesis tracta diferents aspectes relacionats amb el clcul de la semblana quntica, aix com la seva aplicaci en la racionalitzaci i predicci de l'activitat de frmacs. Es poden destacar dos progressos importants en el desenvolupament de noves metodologies que faciliten el clcul de les mesures de semblana quntica. En primer lloc, la descripci de les molcules mitjanant les funciones densitat aproximades PASA (Promolecular Atomic Shell Approximation) ha perms descriure amb suficient precisi la densitat electrnica dels sistemes moleculars analitzats, reduint substancialment el temps de clcul de les mesures de semblana. En segon lloc, el desenvolupament de tcniques de superposici molecular especfiques de les mesures de semblana quntica ha perms resoldre el problema de l'alineament en l'espai dels compostos comparats. El perfeccionament d'aquests nous procediments i algoritmes matemtics associats a les mesures de semblana molecular quntica, ha estat essencial per poder progressar en diferents disciplines de la qumica computacional, sobretot les relacionades amb les anlisis quantitatives entre les estructures moleculars i les seves activitats biolgiques, conegudes amb les sigles angleses QSAR (Quantitative Structure-Activity Relationships). Precisament en l'rea de les relacions estructura-activitat s'han presentat dues aproximacions fonamentades en la semblana molecular quntica que s'originen a partir de dues representacions diferents de les molcules. La primera descripci considera la densitat electrnica global de les molcules i s important, entre altres, la disposici dels objectes comparats en l'espai i la seva conformaci tridimensional. El resultat s una matriu de semblana amb les mesures de semblana de tots els parells de compostos que formen el conjunt estudiat. La segona descripci es fonamenta en la partici de la densitat global de les molcules en fragments. S'utilitzen mesures d'autosemblana per analitzar els requeriments bsics d'una determinada activitat des del punt de vista de la semblana quntica. El procs permet la detecci de les regions moleculars que sn responsables d'una alta resposta biolgica. Aix permet obtenir un patr amb les regions actives que s d'evident inters per als propsits del disseny de frmacs. En definitiva, s'ha comprovat que mitjanant la simulaci i manipulaci informtica de les molcules en tres dimensions es pot obtenir una informaci essencial en l'estudi de la interacci entre els frmacs i els seus receptors macromoleculars.
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La present tesi, tot i que emmarcada dins de la teoria de les Mesures Semblana Molecular Quntica (MQSM), es deriva en tres mbits clarament definits: - La creaci de Contorns Moleculars de IsoDensitat Electrnica (MIDCOs, de l'angls Molecular IsoDensity COntours) a partir de densitats electrniques ajustades. - El desenvolupament d'un mtode de sobreposici molecular, alternatiu a la regla de la mxima semblana. - Relacions Quantitatives Estructura-Activitat (QSAR, de l'angls Quantitative Structure-Activity Relationships). L'objectiu en el camp dels MIDCOs s l'aplicaci de funcions densitat ajustades, ideades inicialment per a abaratir els clculs de MQSM, per a l'obtenci de MIDCOs. Aix, es realitza un estudi grfic comparatiu entre diferents funcions densitat ajustades a diferents bases amb densitats obtingudes de clculs duts a terme a nivells ab initio. D'aquesta manera, l'analogia visual entre les funcions ajustades i les ab initio obtinguda en el ventall de representacions de densitat obtingudes, i juntament amb els valors de les mesures de semblana obtinguts prviament, totalment comparables, fonamenta l's d'aquestes funcions ajustades. Ms enll del propsit inicial, es van realitzar dos estudis complementaris a la simple representaci de densitats, i sn l'anlisi de curvatura i l'extensi a macromolcules. La primera observaci correspon a comprovar no noms la semblana dels MIDCOs, sin la coherncia del seu comportament a nivell de curvatura, podent-se aix observar punts d'inflexi en la representaci de densitats i veure grficament aquelles zones on la densitat s cncava o convexa. Aquest primer estudi revela que tant les densitats ajustades com les calculades a nivell ab initio es comporten de manera totalment anloga. En la segona part d'aquest treball es va poder estendre el mtode a molcules ms grans, de fins uns 2500 toms. Finalment, s'aplica part de la filosofia del MEDLA. Sabent que la densitat electrnica decau rpidament al allunyar-se dels nuclis, el clcul d'aquesta pot ser obviat a distncies grans d'aquests. D'aquesta manera es va proposar particionar l'espai, i calcular tan sols les funcions ajustades de cada tom tan sols en una regi petita, envoltant l'tom en qesti. Duent a terme aquest procs, es disminueix el temps de clcul i el procs esdev lineal amb nombre d'toms presents en la molcula tractada. En el tema dedicat a la sobreposici molecular es tracta la creaci d'un algorisme, aix com la seva implementaci en forma de programa, batejat Topo-Geometrical Superposition Algorithm (TGSA), d'un mtode que proporcions aquells alineaments que coincideixen amb la intuci qumica. El resultat s un programa informtic, codificat en Fortran 90, el qual alinea les molcules per parelles considerant tan sols nombres i distncies atmiques. La total absncia de parmetres terics permet desenvolupar un mtode de sobreposici molecular general, que proporcioni una sobreposici intutiva, i tamb de forma rellevant, de manera rpida i amb poca intervenci de l'usuari. L's mxim del TGSA s'ha dedicat a calcular semblances per al seu s posterior en QSAR, les quals majoritriament no corresponen al valor que s'obtindria d'emprar la regla de la mxima semblana, sobretot si hi ha toms pesats en joc. Finalment, en l'ltim tema, dedicat a la Semblana Quntica en el marc del QSAR, es tracten tres aspectes diferents: - s de matrius de semblana. Aqu interv l'anomenada matriu de semblana, calculada a partir de les semblances per parelles d'entre un conjunt de molcules. Aquesta matriu s emprada posteriorment, degudament tractada, com a font de descriptors moleculars per a estudis QSAR. Dins d'aquest mbit s'han fet diversos estudis de correlaci d'inters farmacolgic, toxicolgic, aix com de diverses propietats fsiques. - Aplicaci de l'energia d'interacci electr-electr, assimilat com a una forma d'autosemblana. Aquesta modesta contribuci consisteix breument en prendre el valor d'aquesta magnitud, i per analogia amb la notaci de l'autosemblana molecular quntica, assimilar-la com a cas particular de d'aquesta mesura. Aquesta energia d'interacci s'obt fcilment a partir de programari mecanoquntic, i esdev ideal per a fer un primer estudi preliminar de correlaci, on s'utilitza aquesta magnitud com a nic descriptor. - Clcul d'autosemblances, on la densitat ha estat modificada per a augmentar el paper d'un substituent. Treballs previs amb densitats de fragments, tot i donar molt bons resultats, manquen de cert rigor conceptual en allar un fragment, suposadament responsable de l'activitat molecular, de la totalitat de l'estructura molecular, tot i que les densitats associades a aquest fragment ja difereixen degut a pertnyer a esquelets amb diferents substitucions. Un procediment per a omplir aquest buit que deixa la simple separaci del fragment, considerant aix la totalitat de la molcula (calcular-ne l'autosemblana), per evitant al mateix temps valors d'autosemblana no desitjats provocats per toms pesats, s l's de densitats de Forats de fermi, els quals es troben definits al voltant del fragment d'inters. Aquest procediment modifica la densitat de manera que es troba majoritriament concentrada a la regi d'inters, per alhora permet obtenir una funci densitat, la qual es comporta matemticament igual que la densitat electrnica regular, podent-se aix incorporar dins del marc de la semblana molecular. Les autosemblances calculades amb aquesta metodologia han portat a bones correlacions amb cids aromtics substituts, podent aix donar una explicaci al seu comportament. Des d'un altre punt de vista, tamb s'han fet contribucions conceptuals. S'ha implementat una nova mesura de semblana, la d'energia cintica, la qual consisteix en prendre la recentment desenvolupada funci densitat d'energia cintica, la qual al comportar-se matemticament igual a les densitats electrniques regulars, s'ha incorporat en el marc de la semblana. A partir d'aquesta mesura s'han obtingut models QSAR satisfactoris per diferents conjunts moleculars. Dins de l'aspecte del tractament de les matrius de semblana s'ha implementat l'anomenada transformaci estocstica com a alternativa a l's de l'ndex Carb. Aquesta transformaci de la matriu de semblana permet obtenir una nova matriu no simtrica, la qual pot ser posteriorment tractada per a construir models QSAR.
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La present Tesi Doctoral, titulada desenvolupament computacional de la semblana molecular quntica, tracta, fonamentalment, els aspectes de clcul de mesures de semblana basades en la comparaci de funcions de densitat electrnica.El primer captol, Semblana quntica, s introductori. S'hi descriuen les funcions de densitat de probabilitat electrnica i llur significana en el marc de la mecnica quntica. Se n'expliciten els aspectes essencials i les condicions matemtiques a satisfer, cara a una millor comprensi dels models de densitat electrnica que es proposen. Hom presenta les densitats electrniques, mencionant els teoremes de Hohenberg i Kohn i esquematitzant la teoria de Bader, com magnituds fonamentals en la descripci de les molcules i en la comprensi de llurs propietats.En el captol Models de densitats electrniques moleculars es presenten procediments computacionals originals per l'ajust de funcions densitat a models expandits en termes de gaussianes 1s centrades en els nuclis. Les restriccions fsico-matemtiques associades a les distribucions de probabilitat s'introdueixen de manera rigorosa, en el procediment anomenat Atomic Shell Approximation (ASA). Aquest procediment, implementat en el programa ASAC, parteix d'un espai funcional quasi complert, d'on se seleccionen variacionalment les funcions o capes de l'expansi, d'acord als requisits de no negativitat. La qualitat d'aquestes densitats i de les mesures de semblana derivades es verifica abastament. Aquest model ASA s'estn a representacions dinmiques, fsicament ms acurades, en quant que afectades per les vibracions nuclears, cara a una exploraci de l'efecte de l'esmortement dels pics nuclears en les mesures de semblana molecular. La comparaci de les densitats dinmiques respecte les esttiques evidencia un reordenament en les densitats dinmiques, d'acord al que constituiria una manifestaci del Principi quntic de Le Chatelier. El procediment ASA, explcitament consistent amb les condicions de N-representabilitat, s'aplica tamb a la determinaci directe de densitats electrniques hidrogenoides, en un context de teoria del funcional de la densitat.El captol Maximitzaci global de la funci de semblana presenta algorismes originals per la determinaci de la mxima sobreposici de les densitats electrniques moleculars. Les mesures de semblana molecular quntica s'identifiquen amb el mxim solapament, de manera es mesuri la distncia entre les molcules, independentment dels sistemes de referncia on es defineixen les densitats electrniques. Partint de la soluci global en el lmit de densitats infinitament compactades en els nuclis, es proposen tres nivells de aproximaci per l'exploraci sistemtica, no estocstica, de la funci de semblana, possibilitant la identificaci eficient del mxim global, aix com tamb dels diferents mxims locals. Es proposa tamb una parametritzaci original de les integrals de recobriment a travs d'ajustos a funcions lorentzianes, en quant que tcnica d'acceleraci computacional. En la prctica de les relacions estructura-activitat, aquests avenos possibiliten la implementaci eficient de mesures de semblana quantitatives, i, parallelament, proporcionen una metodologia totalment automtica d'alineaci molecular. El captol Semblances d'toms en molcules descriu un algorisme de comparaci dels toms de Bader, o regions tridimensionals delimitades per superfcies de flux zero de la funci de densitat electrnica. El carcter quantitatiu d'aquestes semblances possibilita la mesura rigorosa de la noci qumica de transferibilitat d'toms i grups funcionals. Les superfcies de flux zero i els algorismes d'integraci usats han estat publicats recentment i constitueixen l'aproximaci ms acurada pel clcul de les propietats atmiques. Finalment, en el captol Semblances en estructures cristallines hom proposa una definici original de semblana, especfica per la comparaci dels conceptes de suavitat o softness en la distribuci de fonons associats a l'estructura cristallina. Aquests conceptes apareixen en estudis de superconductivitat a causa de la influncia de les interaccions electr-fon en les temperatures de transici a l'estat superconductor. En aplicar-se aquesta metodologia a l'anlisi de sals de BEDT-TTF, s'evidencien correlacions estructurals entre sals superconductores i no superconductores, en consonncia amb les hiptesis apuntades a la literatura sobre la rellevncia de determinades interaccions.Conclouen aquesta tesi un apndix que cont el programa ASAC, implementaci de l'algorisme ASA, i un captol final amb referncies bibliogrfiques.
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En la literatura sobre mecnica quntica s freqent trobar descriptors basats en la densitat de parells o la densitat electrnica, amb un xit divers segons les aplicacions que atenyin. Per tal de que tingui sentit qumic un descriptor ha de donar la definici d'un tom en una molcula, o sser capa d'identificar regions de l'espai molecular associades amb algun concepte qumic (com pot ser un parell solitari o zona d'enlla, entre d'altres). En aquesta lnia, s'han proposat diversos esquemes de partici: la teoria d'toms en molcules (AIM), la funci de localitzaci electrnica (ELF), les celles de Voroni, els toms de Hirshfeld, els toms difusos, etc. L'objectiu d'aquesta tesi s explorar descriptors de la densitat basats en particions de l'espai molecular del tipus AIM, ELF o toms difusos, analitzar els descriptors existents amb diferents nivells de teoria, proposar nous descriptors d'aromaticitat, aix com estudiar l'habilitat de totes aquestes eines per discernir entre diferents mecanismes de reacci.
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Germin is a homopentameric glycoprotein, the synthesis of which coincides with the onset of growth in germinating wheat embryos. There have been detailed studies of germin structure, biosynthesis, homology with other proteins, and of its value as a marker of wheat development. Germin isoforms associated with the apoplast have been speculated to have a role in embryo hydration during maturation and germination. Antigenically related isoforms of germin are present during germination in all of the economically important cereals studied, and the amounts of germin-like proteins and coding elements have been found to undergo conspicuous change when salt-tolerant higher plants are subjected to salt stress. In this report, we describe how circumstantial evidence arising from unrelated studies of barley oxalate oxidase and its coding elements have led to definitive evidence that the germin isoform made during wheat germination is an oxalate oxidase. Establishment of links between oxalate degradation, cereal germination, and salt tolerance has significant implications for a broad range of studies related to development and adaptation in higher plants. Roles for germin in cell wall biochemistry and tissue remodeling are discussed, with special emphasis on the generation of hydrogen peroxide during germin-induced oxidation of oxalate.
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Ovarian follicle development continues in a wave-like manner during the bovine oestrous cycle giving rise to variation in the duration of ovulatory follicle development. The objectives of the present study were to determine whether a relationship exists between the duration of ovulatory follicle development and pregnancy rates following artificial insemination (AI) in dairy cows undergoing spontaneous oestrous cycles, and to identify factors influencing follicle turnover and pregnancy rate and the relationship between these two variables. Follicle development was monitored by daily transrectal ultrasonography from 10 days after oestrus until the subsequent oestrus in 158 lactating dairy cows. The cows were artificially inseminated following the second observed oestrus and pregnancy was diagnosed 35 days later. The predominant pattern of follicle development was two follicle waves (74.7%) with three follicle waves in 22.1% of oestrous cycles and four or more follicle waves in 3.2% of oestrous cycles. The interval from ovulatory follicle emergence to oestrus (EOI) was 3 days longer (P < 0.0001) in cows with two follicle waves than in those with three waves. Ovulatory follicles from two-wave oestrous cycles grew more slowly but were approximately 2 mm larger (P < 0.0001) on the day of oestrus. Twin ovulations were observed in 14.2% of oestrous cycles and occurred more frequently (P < 0.001) in three-wave oestrous cycles; consequently EOI was shorter in cows with twin ovulations. Overall, 57.0% of the cows were diagnosed pregnant 35 days after AI. Linear logistic regression analysis revealed an inverse relationship between EOI and the proportion of cows diagnosed pregnant, among all cows (n = 158; P < 0.01) and amongst those with single ovulations (n = 145; P < 0.05). Mean EOI was approximately I day shorter (P < 0.01) in cows that became pregnant than in non-pregnant cows; however, pregnancy rates did not differ significantly among cows with different patterns of follicle development. These findings confirm and extend previous observations in pharmacologically manipulated cattle and show, for the first time, that in dairy cows undergoing spontaneous oestrous cycles, natural variation in the duration of post-emergence ovulatory follicle development has a significant effect on pregnancy rate, presumably reflecting variation in oocyte developmental competence.
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Antral follicle growth in cattle occurs in two distinct phases; the first 'slow' growth phase spans the time from antrum acquisition to a size of approximately 3 mm detectable by transrectal ultrasound, and the second 'fast' phase is gondadotrophin-dependent and includes cohort growth, dominant follicle (DF) selection, and DF growth. This review summarises current concepts of the relative roles FSH and LH, ovarian and metabolic hormones play mainly in the second phase of antral follicle growth in animals of different reproductive and nutritional states. It is proposed that differential FSH response may enable one cohort follicle to become selected, and that follicular secretions, particularly inhibin, suppress FSH and thus are responsible for DF selection and dominance. Acute dependence of the DF on LH pulses will determine DF lifespan, and the LH pulse profile can be influenced by metabolic hormones such as leptin, providing one possible link for nutritional state and reproduction. Direct ovarian effects of acute and chronic changes in growth hormone, insulin and insulin-like growth factor (IGF)-I have been described on cohort follicles, DF oestrogen activity and on DF growth. Influences of metabolic hormones on early antral follicles undergoing their first 'slow' growth phase are less well described, yet metabolic hormones appear to enhance growth into the cohort available for FSH-induced emergence, and may influence subsequent developmental competence of oocytes. (C) 2003 Elsevier Science B.V. All rights reserved.
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Background: Hexaploid wheat is one of the most important cereal crops for human nutrition. Molecular understanding of the biology of the developing grain will assist the improvement of yield and quality traits for different environments. High quality transcriptomics is a powerful method to increase this understanding. Results: The transcriptome of developing caryopses from hexaploid wheat ( Triticum aestivum, cv. Hereward) was determined using Affymetrix wheat GeneChip (R) oligonucleotide arrays which have probes for 55,052 transcripts. Of these, 14,550 showed significant differential regulation in the period between 6 and 42 days after anthesis ( daa). Large changes in transcript abundance were observed which were categorised into distinct phases of differentiation ( 6 - 10 daa), grain fill ( 12 - 21 daa) and desiccation/maturation ( 28 - 42 daa) and were associated with specific tissues and processes. A similar experiment on developing caryopses grown with dry and/or hot environmental treatments was also analysed, using the profiles established in the first experiment to show that most environmental treatment effects on transcription were due to acceleration of development, but that a few transcripts were specifically affected. Transcript abundance profiles in both experiments for nine selected known and putative wheat transcription factors were independently confirmed by real time RT-PCR. These expression profiles confirm or extend our knowledge of the roles of the known transcription factors and suggest roles for the unknown ones. Conclusion: This transcriptome data will provide a valuable resource for molecular studies on wheat grain. It has been demonstrated how it can be used to distinguish general developmental shifts from specific effects of treatments on gene expression and to diagnose the probable tissue specificity and role of transcription factors.
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Tick-borne encephalitis virus (TBEV) causes human epidemics across Eurasia. Clinical manifestations range from inapparent infections and fevers to fatal encephalitis but the factors that determine disease severity are currently undefined. TBEV is characteristically a hemagglutinating (HA) virus; the ability to agglutinate erythrocytes tentatively reflects virion receptor/fusion activity. However, for the past few years many atypical HA-deficient strains have been isolated from patients and also from the natural European host tick, Ixodes persulcatus. By analysing the sequences of HA-deficient strains we have identified 3 unique amino acid substitutions (D67G, E122G or D277A) in the envelope protein, each of which increases the net charge and hydrophobicity of the virion surface. Therefore, we genetically engineered virus mutants each containing one of these 3 substitutions; they all exhibited HA-deficiency. Unexpectedly, each genetically modified non-HA virus demonstrated increased TBEV reproduction in feeding Ixodes ricinus, not the recognised tick host for these strains. Moreover, virus transmission efficiency between infected and uninfected ticks co-feeding on mice was also intensified by each substitution. Retrospectively, the mutation D67G was identified in viruses isolated from patients with encephalitis. We propose that the emergence of atypical Siberian HA-deficient TBEV strains in Europe is linked to their molecular adaptation to local ticks. This process appears to be driven by the selection of single mutations that change the virion surface thus enhancing receptor/fusion function essential for TBEV entry into the unfamiliar tick species. As the consequence of this adaptive mutagenesis, some of these mutations also appear to enhance the ability of TBEV to cross the human blood-brain barrier, a likely explanation for fatal encephalitis. Future research will reveal if these emerging Siberian TBEV strains continue to disperse westwards across Europe by adaptation to the indigenous tick species and if they are associated with severe forms of TBE.
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Figs and fig-pollinating wasps are obligate mutualists that have coevolved for over 60 million years. But when and where did pollinating fig wasps (Agaonidae) originate? Some studies suggest that agaonids arose in the Late Cretaceous and the current distribution of fig-wasp faunas can be explained by the break-up of the Gondwanan landmass. However, recent molecular-dating studies suggest divergence time estimates that are inconsistent with the Gondwanan vicariance hypothesis and imply that long distance oceanic dispersal could have been an important process for explaining the current distribution of both figs and fig wasps. Here, we use a combination of phylogenetic and biogeographical data to infer the age, the major period of diversification, and the geographic origin of pollinating fig wasps. Age estimates ranged widely depending on the molecular-dating method used and even when using the same method but with slightly different constraints, making it difficult to assess with certainty a Gondwanan origin of agaonids. The reconstruction of ancestral areas suggests that the most recent common ancestor of all extant fig-pollinating wasps was most likely Asian, although a southern Gondwana origin cannot be rejected. Our analysis also suggests that dispersal has played a more important role in the development of the fig-wasp biota than previously assumed. (C) 2009 Elsevier Inc. All rights reserved.
