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1.
Sci Total Environ ; 747: 141152, 2020 Jul 25.
Artigo em Inglês | MEDLINE | ID: mdl-32799018

RESUMO

By determining susceptibility to disease, environment-driven variation in immune responses can affect the health, productivity and fitness of vertebrates. Yet how the different components of the total environment control this immune variation is remarkably poorly understood. Here, through combining field observation, experimentation and modelling, we are able to quantitatively partition the key environmental drivers of constitutive immune allocation in a model wild vertebrate (three-spined stickleback, Gasterosteus aculeatus). We demonstrate that, in natural populations, thermal conditions and diet alone are sufficient (and necessary) to explain a dominant (seasonal) axis of variation in immune allocation. This dominant axis contributes to both infection resistance and tolerance and, in turn, to the vital rates of infectious agents and the progression of the disease they cause. Our results illuminate the environmental regulation of vertebrate immunity (given the evolutionary conservation of the molecular pathways involved) and they identify mechanisms through which immunocompetence and host-parasite dynamics might be impacted by changing environments. In particular, we predict a dominant sensitivity of immunocompetence and immunocompetence-driven host-pathogen dynamics to host diet shifts.

2.
Philos Trans R Soc Lond B Biol Sci ; 375(1804): 20190645, 2020 08 03.
Artigo em Inglês | MEDLINE | ID: mdl-32536309

RESUMO

By 2100, global warming is predicted to significantly reduce the capacity of marine primary producers for long-chain polyunsaturated fatty acid (LC-PUFA) synthesis. Primary consumers such as harpacticoid copepods (Crustacea) might mitigate the resulting adverse effects on the food web by increased LC-PUFA bioconversion. Here, we present a high-quality de novo transcriptome assembly of the copepod Platychelipus littoralis, exposed to changes in both temperature (+3°C) and dietary LC-PUFA availability. Using this transcriptome, we detected multiple transcripts putatively coding for LC-PUFA-bioconverting front-end fatty acid (FA) desaturases and elongases, and performed phylogenetic analyses to identify their relationship with sequences of other (crustacean) taxa. While temperature affected the absolute FA concentrations in copepods, LC-PUFA levels remained unaltered even when copepods were fed an LC-PUFA-deficient diet. While this suggests plasticity of LC-PUFA bioconversion within P. littoralis, none of the putative front-end desaturase or elongase transcripts was differentially expressed under the applied treatments. Nevertheless, the transcriptome presented here provides a sound basis for future ecophysiological research on harpacticoid copepods. This article is part of the theme issue 'The next horizons for lipids as 'trophic biomarkers': evidence and significance of consumer modification of dietary fatty acids'.

3.
Ecol Evol ; 9(21): 12089-12098, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31832146

RESUMO

Immunity is a central component of fitness in wild animals, but its determinants are poorly understood. In particular, the importance of locomotory activity as a constraint on immunity is unresolved. Using a piscine model (Gasterosteus aculeatus), we combined a 25-month observational time series for a wild lotic habitat with an open flume experiment to determine the influence of locomotor activity (countercurrent swimming) on natural variation in immune function. To maximize the detectability of effects in our flume experiment, we set flow velocity and duration (10 cm/s for 48 hr) just below the point at which exhaustion would ensue. Following this treatment, we measured expression in a set of immune-associated genes and infectious disease resistance through a standard challenge with an ecologically relevant monogenean infection (Gyrodactylus gasterostei). In the wild, there was a strong association of water flow with the expression of immune-associated genes, but this association became modest and more complex when adjusted for thermal effects. Our flume experiment, although statistically well-powered and based on a scenario near the limits of swimming performance in stickleback, detected no countercurrent swimming effect on immune-associated gene expression or infection resistance. The field association between flow rate and immune expression could thus be due to an indirect effect, and we tentatively advance hypotheses to explain this. This study clarifies the drivers of immune investment in wild vertebrates; although locomotor activity, within the normal natural range, may not directly influence immunocompetence, it may still correlate with other variables that do.

4.
Hydrobiologia ; 832(1): 215-233, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-30880832

RESUMO

Differences in habitat and diet between species are often associated with morphological differences. Habitat and trophic adaptation have therefore been proposed as important drivers of speciation and adaptive radiation. Importantly, habitat and diet shifts likely impose changes in exposure to different parasites and infection risk. As strong selective agents influencing survival and mate choice, parasites might play an important role in host diversification. We explore this possibility for the adaptive radiation of Lake Tanganyika (LT) cichlids. We first compare metazoan macroparasites infection levels between cichlid tribes. We then describe the cichlids' genetic diversity at the major histocompatibility complex (MHC), which plays a key role in vertebrate immunity. Finally, we evaluate to what extent trophic ecology and morphology explain variation in infection levels and MHC, accounting for phylogenetic relationships. We show that different cichlid tribes in LT feature partially non-overlapping parasite communities and partially non-overlapping MHC diversity. While morphology explained 15% of the variation in mean parasite abundance, trophic ecology accounted for 16% and 22% of the MHC variation at the nucleotide and at the amino acid level, respectively. Parasitism and immunogenetic adaptation may thus add additional dimensions to the LT cichlid radiation.

5.
Front Immunol ; 9: 582, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-29623078

RESUMO

Seasonal patterns in immunity are frequently observed in vertebrates but are poorly understood. Here, we focused on a natural piscine model, the three-spined stickleback (Gasterosteus aculeatus), and asked how seasonal immune allocation is driven by physical variables (time, light, and heat). Using functionally-relevant gene expression metrics as a reporter of seasonal immune allocation, we synchronously sampled fish monthly from the wild (two habitats), and from semi-natural outdoors mesocosms (stocked from one of the wild habitats). This was repeated across two annual cycles, with continuous within-habitat monitoring of environmental temperature and implementing a manipulation of temperature in the mesocosms. We also conducted a long-term laboratory experiment, subjecting acclimated wild fish to natural and accelerated (×2) photoperiodic change at 7 and 15°C. The laboratory experiment demonstrated that immune allocation was independent of photoperiod and only a very modest effect, at most, was controlled by a tentative endogenous circannual rhythm. On the other hand, experimentally-determined thermal effects were able to quantitatively predict much of the summer-winter fluctuation observed in the field and mesocosms. Importantly, however, temperature was insufficient to fully predict, and occasionally was a poor predictor of, natural patterns. Thermal effects can thus be overridden by other (unidentified) natural environmental variation and do not take the form of an unavoidable constraint due to cold-blooded physiology. This is consistent with a context-dependent strategic control of immunity in response to temperature variation, and points to the existence of temperature-sensitive regulatory circuits that might be conserved in other vertebrates.


Assuntos
Sinais (Psicologia) , Peixes/fisiologia , Imunidade , Estações do Ano , Animais , Ritmo Circadiano , Meio Ambiente , Perfilação da Expressão Gênica , Regulação da Expressão Gênica , Interação Gene-Ambiente , Imunidade/genética , Transcriptoma
6.
Glob Chang Biol ; 24(1): 371-386, 2018 01.
Artigo em Inglês | MEDLINE | ID: mdl-28746785

RESUMO

Immune defense is temperature dependent in cold-blooded vertebrates (CBVs) and thus directly impacted by global warming. We examined whether immunity and within-host infectious disease progression are altered in CBVs under realistic climate warming in a seasonal mid-latitude setting. Going further, we also examined how large thermal effects are in relation to the effects of other environmental variation in such a setting (critical to our ability to project infectious disease dynamics from thermal relationships alone). We employed the three-spined stickleback and three ecologically relevant parasite infections as a "wild" model. To generate a realistic climatic warming scenario we used naturalistic outdoors mesocosms with precise temperature control. We also conducted laboratory experiments to estimate thermal effects on immunity and within-host infectious disease progression under controlled conditions. As experimental readouts we measured disease progression for the parasites and expression in 14 immune-associated genes (providing insight into immunophenotypic responses). Our mesocosm experiment demonstrated significant perturbation due to modest warming (+2°C), altering the magnitude and phenology of disease. Our laboratory experiments demonstrated substantial thermal effects. Prevailing thermal effects were more important than lagged thermal effects and disease progression increased or decreased in severity with increasing temperature in an infection-specific way. Combining laboratory-determined thermal effects with our mesocosm data, we used inverse modeling to partition seasonal variation in Saprolegnia disease progression into a thermal effect and a latent immunocompetence effect (driven by nonthermal environmental variation and correlating with immune gene expression). The immunocompetence effect was large, accounting for at least as much variation in Saprolegnia disease as the thermal effect. This suggests that managers of CBV populations in variable environments may not be able to reliably project infectious disease risk from thermal data alone. Nevertheless, such projections would be improved by primarily considering prevailing thermal effects in the case of within-host disease and by incorporating validated measures of immunocompetence.


Assuntos
Doenças dos Peixes/parasitologia , Saprolegnia/fisiologia , Smegmamorpha/parasitologia , Animais , Doenças dos Peixes/imunologia , Aquecimento Global , Estações do Ano , Temperatura
7.
Nat Commun ; 8(1): 267, 2017 08 16.
Artigo em Inglês | MEDLINE | ID: mdl-28814718

RESUMO

Species in a common landscape often face similar selective environments. The capacity of organisms to adapt to these environments may be largely species specific. Quantifying shared and unique adaptive responses across species within landscapes may thus improve our understanding of landscape-moderated biodiversity patterns. Here we test to what extent populations of two coexisting and phylogenetically related fishes-three-spined and nine-spined stickleback-differ in the strength and nature of neutral and adaptive divergence along a salinity gradient. Phenotypic differentiation, neutral genetic differentiation and genomic signatures of adaptation are stronger in the three-spined stickleback. Yet, both species show substantial phenotypic parallelism. In contrast, genomic signatures of adaptation involve different genomic regions, and are thus non-parallel. The relative contribution of spatial and environmental drivers of population divergence in each species reflects different strategies for persistence in the same landscape. These results provide insight in the mechanisms underlying variation in evolutionary versatility and ecological success among species within landscapes.The three-spined stickleback is a model species for the study of adaptive divergence. Here, Raeymaekers et al. compare how the three-spined stickleback and its relative the nine-spined stickleback vary at the phenotypic and genomic levels in response to the same spatial and environmental drivers.


Assuntos
Evolução Biológica , Meio Ambiente , Smegmamorpha/genética , Animais , Biodiversidade , Genoma , Fenótipo , Polimorfismo de Nucleotídeo Único , Salinidade , Especificidade da Espécie
8.
BMC Evol Biol ; 16: 175, 2016 09 01.
Artigo em Inglês | MEDLINE | ID: mdl-27586387

RESUMO

BACKGROUND: The effect of anthropogenic environments on the function of the vertebrate immune system is a problem of general importance. For example, it relates to the increasing rates of immunologically-based disease in modern human populations and to the desirability of identifying optimal immune function in domesticated animals. Despite this importance, our present understanding is compromised by a deficit of experimental studies that make adequately matched comparisons between wild and captive vertebrates. RESULTS: We transferred post-larval fishes (three-spined sticklebacks), collected in the wild, to an anthropogenic (captive) environment. We then monitored, over 11 months, how the systemic expression of immunity genes changed in comparison to cohort-matched wild individuals in the originator population (total n = 299). We found that a range of innate (lyz, defbl2, il1r-like, tbk1) and adaptive (cd8a, igmh) immunity genes were up-regulated in captivity, accompanied by an increase in expression of the antioxidant enzyme, gpx4a. For some genes previously known to show seasonality in the wild, this appeared to be reduced in captive fishes. Captive fishes tended to express immunity genes, including igzh, foxp3b, lyz, defbl2, and il1r-like, more variably. Furthermore, although gene co-expression patterns (analyzed through gene-by-gene correlations and mutual information theory based networks) shared common structure in wild and captive fishes, there was also significant divergence. For one gene in particular, defbl2, high expression was associated with adverse health outcomes in captive fishes. CONCLUSION: Taken together, these results demonstrate widespread regulatory changes in the immune system in captive populations, and that the expression of immunity genes is more constrained in the wild. An increase in constitutive systemic immune activity, such as we observed here, may alter the risk of immunopathology and contribute to variance in health in vertebrate populations exposed to anthropogenic environments.


Assuntos
Meio Ambiente , Regulação da Expressão Gênica , Imunidade/genética , Vertebrados/genética , Vertebrados/imunologia , Imunidade Adaptativa/genética , Animais , Ecossistema , Humanos , Imunidade Inata/genética , Larva/genética , Larva/imunologia , Reação em Cadeia da Polimerase em Tempo Real , Estações do Ano , Smegmamorpha/genética , Smegmamorpha/imunologia , Regulação para Cima/genética
9.
Trends Parasitol ; 32(10): 820-832, 2016 10.
Artigo em Inglês | MEDLINE | ID: mdl-27595383

RESUMO

Thanks to high species diversity and a broad range of speciation mechanisms, cichlid fishes represent a textbook model in evolutionary biology. They are also of substantial economic value. Despite this importance, cichlid parasites remain understudied, although some are more diverse than their hosts. They may offer important insights into cichlid evolution and the evolution of host-parasite interactions. We review five major lines of research conducted on cichlid parasites so far: the study of parasite diversity and speciation; the role of parasites in cichlid diversification; the evolutionary ecology of host specificity; historical biogeography; and biological invasions. We call for more research in these areas and suggest approaches to valorise the potential that cichlid parasites hold for the study of evolutionary parasitology.


Assuntos
Evolução Biológica , Ciclídeos/parasitologia , Interações Hospedeiro-Parasita , Animais , Biodiversidade , Especiação Genética , Modelos Animais , Pesquisa/tendências
10.
Sci Rep ; 5: 13669, 2015 Sep 03.
Artigo em Inglês | MEDLINE | ID: mdl-26335652

RESUMO

The stunning diversity of cichlid fishes has greatly enhanced our understanding of speciation and radiation. Little is known about the evolution of cichlid parasites. Parasites are abundant components of biodiversity, whose diversity typically exceeds that of their hosts. In the first comprehensive phylogenetic parasitological analysis of a vertebrate radiation, we study monogenean parasites infecting tropheine cichlids from Lake Tanganyika. Monogeneans are flatworms usually infecting the body surface and gills of fishes. In contrast to many other parasites, they depend only on a single host species to complete their lifecycle. Our spatially comprehensive combined nuclear-mitochondrial DNA dataset of the parasites covering almost all tropheine host species (N = 18), reveals species-rich parasite assemblages and shows consistent host-specificity. Statistical comparisons of host and parasite phylogenies based on distance and topology-based tests demonstrate significant congruence and suggest that host-switching is rare. Molecular rate evaluation indicates that species of Cichlidogyrus probably diverged synchronically with the initial radiation of the tropheines. They further diversified through within-host speciation into an overlooked species radiation. The unique life history and specialisation of certain parasite groups has profound evolutionary consequences. Hence, evolutionary parasitology adds a new dimension to the study of biodiversity hotspots like Lake Tanganyika.


Assuntos
Evolução Biológica , Ciclídeos/genética , Ciclídeos/parasitologia , Brânquias/parasitologia , Interações Hospedeiro-Parasita/genética , Platelmintos/genética , Animais , Biodiversidade , Lagos , Filogenia
11.
Immunogenetics ; 65(11): 795-809, 2013 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-23989891

RESUMO

Cichlid fishes are emblematic models for the study of adaptive radiation, driven by natural and sexual selection. Parasite mediated selection is an important component in these processes, and the evolution of their immune system therefore merits special attention. In this study, light is shed on the phylogeny of the b family of cichlid major histocompatibility complex (MHC) class IIB genes. Full-length coding sequences were used to reconstruct phylogenies using criteria of maximum parsimony, maximum likelihood and Bayesian inference. All analyses suggest monophyly of the b family of cichlid MHC class IIB genes, although sequences of the cichlid sister taxa are currently not available. Two evolutionary lineages of these genes, respectively encompassing the recently defined genomic regions DBB-DEB-DFB and DCB-DDB, show highly contrasting levels of differentiation. To explore putative causes for these differences, exon 2 sequences were screened for variation in recombination rate and strength of selection. The more diversified lineage of cichlid MHC class IIB b genes was found to have higher levels of both recombination and selection. This is consistent with the observation in other taxa that recombination facilitates the horizontal spread of positively selected sites across MHC loci and hence contributes to fast sequence evolution. In contrast, the lineage that showed low diversification might either be under stabilizing selection or is evolutionary constrained by its low recombination rate. We speculate whether this lineage might include MHC genes with non-classical functions.


Assuntos
Ciclídeos/genética , Evolução Molecular , Genes MHC da Classe II , Recombinação Genética/genética , Seleção Genética , Animais , Teorema de Bayes , Duplicação Gênica , Genoma , Filogenia
12.
BMC Evol Biol ; 13: 41, 2013 Feb 14.
Artigo em Inglês | MEDLINE | ID: mdl-23409983

RESUMO

BACKGROUND: Adaptation to different ecological environments is thought to drive ecological speciation. This phenomenon culminates in the radiations of cichlid fishes in the African Great Lakes. Multiple characteristic traits of cichlids, targeted by natural or sexual selection, are considered among the driving factors of these radiations. Parasites and pathogens have been suggested to initiate or accelerate speciation by triggering both natural and sexual selection. Three prerequisites for parasite-driven speciation can be inferred from ecological speciation theory. The first prerequisite is that different populations experience divergent infection levels. The second prerequisite is that these infection levels cause divergent selection and facilitate adaptive divergence. The third prerequisite is that parasite-driven adaptive divergence facilitates the evolution of reproductive isolation. Here we investigate the first and the second prerequisite in allopatric chromatically differentiated lineages of the rock-dwelling cichlid Tropheus spp. from southern Lake Tanganyika (Central Africa). Macroparasite communities were screened in eight populations belonging to five different colour morphs. RESULTS: Parasite communities were mainly composed of acanthocephalans, nematodes, monogeneans, copepods, branchiurans, and digeneans. In two consecutive years (2011 and 2012), we observed significant variation across populations for infection with acanthocephalans, nematodes, monogeneans of the genera Gyrodactylus and Cichlidogyrus, and the copepod Ergasilus spp. Overall, parasite community composition differed significantly between populations of different colour morphs. Differences in parasite community composition were stable in time. The genetic structure of Tropheus populations was strong and showed a significant isolation-by-distance pattern, confirming that spatial isolation is limiting host dispersal. Correlations between parasite community composition and Tropheus genetic differentiation were not significant, suggesting that host dispersal does not influence parasite community diversification. CONCLUSIONS: Subject to alternating episodes of isolation and secondary contact because of lake level fluctuations, Tropheus colour morphs are believed to accumulate and maintain genetic differentiation through a combination of vicariance, philopatric behaviour and mate discrimination. Provided that the observed contrasts in parasitism facilitate adaptive divergence among populations in allopatry (which is the current situation), and promote the evolution of reproductive isolation during episodes of sympatry, parasites might facilitate speciation in this genus.


Assuntos
Ciclídeos/genética , Ciclídeos/parasitologia , Especiação Genética , Genética Populacional , África Central , Animais , Lagos , Repetições de Microssatélites , Análise de Sequência de DNA
13.
Dalton Trans ; (15): 2777-87, 2009 Apr 21.
Artigo em Inglês | MEDLINE | ID: mdl-19333501

RESUMO

A new [ONO] tridentate phenolate ligand (H2LI) containing an aliphatic alcohol as a side arm has been synthesized, deprotonated and attached to lanthanide(II) and (III) ions, which are employed as catalysts for ring-opening polymerization of cyclic esters. In contrast to many other mono-phenolate lanthanide compounds, these have been found to be inert to polymer incorporation during the polymerization reactions. Three new divalent ytterbium compounds have been synthesized in high yield containing ancillary ligands; two via a transamination reaction between [Yb(N(SiMe3)2)2(THF)2] and one equivalent of the phenols, HOC6H2-(2,4-tBu)-6-CH2N(Me)CH2CH2OH (H2LI) or HOC6H2-(2,4-tBu)-6-CH2N(Me)CH2CH2N(Me)CH2-6-(2,4-tBu)-C6H2OH (H2LII) in hexanes to yield [Yb(LI)]2 () and [Yb(LII)]2 (), respectively. The third divalent ytterbium compound [Yb(L2)] () was prepared by treatment of [Yb(N(SiMe3)2)2(THF)2] with two equivalents of a related monoanionic ancillary phenol, HOC6H2-(2,4-tBu)-6-CH2N(Me)CH2CH2NMe2 (HL) in hexanes. Additionally, the oxidation chemistry of these divalent systems was explored where compound was treated with silver triflate and phenol to form corresponding heteroleptic trivalent ytterbium phenolate complexes [Yb(LI)(O3SCF3)(THF)] () and [Yb(LI)(OPh)] (), respectively. Finally, three new heteroleptic trivalent lanthanide silylamido compounds were synthesized via a ligand exchange transamination reaction between the homoleptic trivalent [Ln(N(SiMe3)2)3] compound and one equivalent of the new dianionic ligand (H2LI) in THF {[La(LI)(N(SiMe3)2)(THF)2] (); [Sm(LI)(N(SiMe3)2)(THF)] (); [Yb(LI)(N(SiMe3)2)(THF)] ()}. These lanthanide(II) and (III) compounds were assessed as catalyst precursors towards the ring-opening polymerization of both l-lactide and epsilon-caprolactone. End-group analyses and detailed kinetics studies {rate law: -d[LA]/dt=k[LA]1[catalyst]1} of the most efficacious lanthanum compound () further corroborated the substitutionally inert characteristics of the new stationary ancillary [ONO] tridentate dianionic ligand.


Assuntos
Ésteres/química , Elementos da Série dos Lantanídeos/química , Compostos Organometálicos/química , Fenóis/química , Polímeros/química , Caproatos/química , Catálise , Cristalografia por Raios X , Dioxanos/química , Desenho de Fármacos , Cinética , Lactonas/química , Ligantes , Compostos Organometálicos/síntese química , Oxirredução , Itérbio/química
14.
Eur Arch Otorhinolaryngol ; 265(1): 31-3, 2008 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-17978829

RESUMO

In a prospective study involving 16 patients over a 12 month period, we determined whether tonsillectomy à chaud is an acceptable alternative to interval tonsillectomy for patients with quinsy. Guidelines for the acute surgical management of quinsy (or peritonsillar abscess) were established following a departmental audit. Sixteen patients were admitted with a quinsy plus an indication for tonsillectomy; 12 were evaluated prospectively. Each was treated either by incision and drainage or needle aspiration, rehydration, analgesia and intravenous antibiotic therapy, followed by a tonsillectomy à chaud (immediate tonsillectomy) within 30 h of the acute admission. Despite initial drainage, a high incidence of pus was detected intra-operatively. A much larger group of patients had peritonsillitis rather than peritonsillar abscess. Of the 16 patients admitted with a quinsy and indication for tonsillectomy over a 12 month period, 12 consented to tonsillectomy à chaud. Aspiration was used to confirm the presence of a quinsy in seven patients (58%), and incision and drainage in the remaining five. There were no complications, and further hospitalisations were avoided thus reducing patient morbidity and costs. We propose that tonsillectomy à chaud remains a justifiable alternative to interval tonsillectomy for such patients when personnel and theatre facilities permit.


Assuntos
Abscesso Peritonsilar/cirurgia , Tonsilectomia , Adulto , Criança , Feminino , Humanos , Masculino , Adulto Jovem
15.
An Sist Sanit Navar ; 30 Suppl 2: 49-65, 2007.
Artigo em Espanhol | MEDLINE | ID: mdl-17898828

RESUMO

The prevalence of tuberculosis infection varies between countries, with an estimate in adults in Spain of 25%. The technique for its diagnosis, in spite of its antiquity, is tuberculin. Even today, this test continues to be in use in the majority of countries. In recent years two methods of immunodiagnosis based on detection of IFN-g released by T cells in response to M. tuberculosis-specific antigens, enables us to diagnose the infection in a laboratory without all of the problems deriving from the administration of tuberculin. From the contact studies made it has been shown that these techniques correlate better with the degree and duration of exposure to Mycobacterium tuberculosis and that prior vaccination with BCG does not interfere with their results, which without doubt will result in a reduction in the number of unnecessary chemoprofilaxis.


Assuntos
Tuberculose/diagnóstico , Antígenos de Bactérias/imunologia , Humanos , Interferon gama/sangue , Sensibilidade e Especificidade , Testes Sorológicos/métodos , Teste Tuberculínico/métodos
16.
Dalton Trans ; (41): 4685-92, 2007 Nov 07.
Artigo em Inglês | MEDLINE | ID: mdl-17940650

RESUMO

Five new heteroleptic lanthanide(III) phenolate compounds have been synthesised in high yield, four via a transamination reaction between Ln(N(SiMe(3))2)3 and two equivalents of the phenol, HOC(6)H(2)(2,4-Bu(t))-6-CH(2)N(Me)CH(2)CH(2)NMe(2) [corrected] (LH) in thf {L(2)LnN(SiMe(3))2 where Ln = La (1); Nd (2); Sm (3); Yb (4)}. The fifth compound, [L(2)La][BPh(4)] 5 was formed by conversion of 1 by treatment with one equivalent of [Et(3)NH][BPh(4)] in toluene. Compound 3 was subjected to a single-crystal X-ray analysis and revealed a five-coordinate, distorted trigonal bipyramidal samarium(III) metal centre where each phenolate ligand is bidentate coordinating through the phenolate oxygen and nitrogen yielding six-membered chelate rings. Compound 1 exhibited fluxional behaviour in C(4)D(8)O solution which was temperature dependent. All five compounds were assessed as catalyst precursors towards the ring-opening polymerisation of both L-lactide and epsilon-caprolactone. These polymerisation studies revealed that catalysts containing larger lanthanide metals were more efficacious than those with smaller lanthanide metals. Furthermore, replacement of the [N(SiMe(3))2] initiating group in 1 with [BPh(4)] in 5 reduced catalytic activity by this compound. Detailed kinetics analysis of the ring-opening polymerisation of L-lactide by compound 1, the most efficacious catalyst precursor analysed in this study, revealed the following rate law: -d[LA]/dt = k[LA](2)[1](1) which is second order in lactide and first order in catalyst. End-group analysis by ESI mass spectrometry revealed the presence of phenolate end-groups and lactide cycles, the latter formed by intra-molecular, intrachain transesterification.


Assuntos
Ésteres/síntese química , Elementos da Série dos Lantanídeos/química , Compostos Organometálicos , Fenóis/química , Catálise , Cristalografia por Raios X , Ciclização , Ésteres/química , Ligantes , Espectroscopia de Ressonância Magnética , Modelos Moleculares , Estrutura Molecular , Compostos Organometálicos/síntese química , Compostos Organometálicos/química , Fatores de Tempo
17.
An. sist. sanit. Navar ; 30(supl.2): 49-65, 2007. ilus, tab
Artigo em Espanhol | IBECS | ID: ibc-056272

RESUMO

La prevalencia de infección tuberculosa varía de unos países a otros, siendo la estimada en adultos en España del 25%. La técnica habitual para su diagnóstico, pese a su antigüedad, es la tuberculina. Todavía hoy, esta prueba continúa estando vigente en la mayoría de los países. En los últimos años se han desarrollado dos métodos de inmunodiagnóstico que, a través de la cuantificación in vitro del interferón-γ liberado por los linfocitos T sensibilizados, nos permiten diagnosticar en un laboratorio la infección obviando todos los problemas derivados de la administración de la tuberculina. En los estudios de contactos realizados se ha visto que estas técnicas se correlacionan mejor con el grado y duración de la exposición a Mycobacterium tuberculosis y que la vacunación previa con BCG no interfiere en sus resultados lo que sin duda alguna redundará en una reducción del número de quimioprofilaxis innecesarias


The prevalence of tuberculosis infection varies between countries, with an estimate in adults in Spain of 25%. The technique for its diagnosis, in spite of its antiquity, is tuberculin. Even today, this test continues to be in use in the majority of countries. In recent years two methods of immunodiagnosis based on detection of IFN-γ released by T cells in response to M. tuberculosis–specific antigens, enables us to diagnose the infection in a laboratory without all of the problems deriving from the administration of tuberculin. From the contact studies made it has been shown that these techniques correlate better with the degree and duration of exposure to Mycobacterium tuberculosis and that prior vaccination with BCG does not interfere with their results, which without doubt will result in a reduction in the number of unnecessary chemoprofilaxis


Assuntos
Masculino , Feminino , Adulto , Pessoa de Meia-Idade , Idoso , Humanos , Mycobacterium tuberculosis/patogenicidade , Tuberculose/diagnóstico , Tuberculose/epidemiologia , Tuberculina , Hipersensibilidade Tardia/complicações , Hipersensibilidade Tardia/diagnóstico , Sensibilidade e Especificidade , Análise Custo-Benefício , Testes Imunológicos/métodos , Espanha/epidemiologia , Leucócitos Mononucleares/patologia , Análise Custo-Benefício/métodos
18.
An Sist Sanit Navar ; 28 Suppl 1: 7-11, 2005.
Artigo em Espanhol | MEDLINE | ID: mdl-15915166

RESUMO

Asbestos is a fibrous mineral that has been known since ancient times. It is widely used in industry due to its physical and chemical properties which make it highly suitable for this end. Asbestos is classified in two groups--serpentine and amphibole--depending on the curved or straight configuration of their fibres. Outstanding amongst its properties are its resistance to heat, wear, alkalis and acids, and its flexibility, amongst other characteristics, which make it a suitable material for use as insulation, in industrial textiles and in many other fields. The pathogenic risk of asbestos remaining for a long time in the pulmonary tissue has been known for many years; studies attribute it with alteration of the mucociliary activity of the host, macrophage activation and the freeing of inflammatory mediators as well as an increase in their oncogenic strength on association with tobacco and even some viruses.


Assuntos
Asbestose , Asbestose/epidemiologia , Asbestose/etiologia , Asbestose/fisiopatologia , Humanos , Pulmão/fisiopatologia , Macrófagos/fisiologia , Depuração Mucociliar/fisiologia , Doenças Profissionais/epidemiologia , Exposição Ocupacional/efeitos adversos , Fatores de Risco , Fumar/epidemiologia
19.
An Sist Sanit Navar ; 28 Suppl 1: 45-9, 2005.
Artigo em Espanhol | MEDLINE | ID: mdl-15915171

RESUMO

Exposure to asbestos is associated with the development of benign and malign pleuropulmonary pathology. In recent years a broad set of regulations has been set in place, from the establishment of conditions in work involving exposure to asbestos to successive prohibitions on its use. Periodical medical checkups have been designed to detect these pathologies in exposed workers and, considering the long period of latency, they should also be carried out on retired workers or on those who in the past have suffered such exposure.


Assuntos
Asbestos/efeitos adversos , Doenças Profissionais/epidemiologia , Doenças Profissionais/etiologia , Exposição Ocupacional/efeitos adversos , Seguimentos , Humanos , Doenças Profissionais/diagnóstico
20.
An Sist Sanit Navar ; 28 Suppl 1: 117-21, 2005.
Artigo em Espanhol | MEDLINE | ID: mdl-15915179

RESUMO

Following the changes carried out in recent years in buildings, such as ventilation systems, computers, etc., a series of diseases, that are related to this, have been described. This paper concentrates on the syndrome of the sick building, which is formed by a group of symptoms normally suffered by workers in the same "sick" building. This syndrome is related to its interior ambience, since the clinical manifestations appear some hours after entering the building and improves a few minutes after leaving this ambience. The origin is probably multifactorial: volatile airborne pollutants, the ventilation system, factors related to work organisation, or even dependent on the host. Since there is no single cause, we enumerate the risk factors in developing this syndrome as well as the steps for reaching a diagnosis and useful measures for preventing the sick building.


Assuntos
Síndrome do Edifício Doente/etiologia , Síndrome do Edifício Doente/fisiopatologia , Humanos , Fatores de Risco
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