RESUMO
El progreso del conocimiento en medicina, tiene e influye en la medicina interna en dos vertientes; una dirigida al estudio integral del paciente en todo su aspecto humanístico y clínico y la otra asimilando y aplicando la investigación científica proporcionada por otras especialidades y que le han servido para la solución de muchos problemas de los pacientes; pero la medicina interna con una tecnología y metodología propia, producida por sus protagonistas, ha podido hacer posible aparición y aceptación de la investigación clínica, como un modo muy justificable de germinar ciencia y conocimientos. La presente publicación, como libro, por su contenido y fundamentos fue escrita para que sirva de guía y orientación, a las nuevas generaciones de médicos internistas y no ha sido concebido sólo para facilitar el desarrollo de los trabajos especiales de grado (TEI, como anterior denominación), de los cursantes de la residencias, sino que sirva también para estimular en forma permanente a todos los internistas egresados de los cursos, y en forma más ambiciosa hacer extensión de esta edición para aquellos médicos de la especialidad que se interesen en continuar y permanecer con esta actividad.
Assuntos
Pesquisa Biomédica , Prontuários Médicos , Medicina Interna , Consentimento Livre e Esclarecido , Projetos de PesquisaRESUMO
We investigated local adaptation in the spatially structured natural Biomphalaria glabrata/Schistosoma mansoni host-parasite system in the marshy forest focus of Guadeloupe using cross-transplantation experiments. We demonstrated strong and highly significant variations in susceptibility/infectivity of host and parasite populations, respectively, but found no evidence of local adaptation neither for S. mansoni nor for B. glabrata. Environmental as well as genetic factors are discussed to explain susceptibility/infectivity variations between both host and parasite populations. The absence of local adaptation is discussed in relation to the metapopulation dynamics of both host and parasite, in particular their relative rates of dispersal at the scale under scrutiny. Our study constitutes the first cross-transplantation experiment concerning this host-parasite system of which both hosts and parasites came directly from the wild, excluding laboratory generations and experimental host passages.
Assuntos
Adaptação Biológica/fisiologia , Biomphalaria/parasitologia , Interações Hospedeiro-Parasita/fisiologia , Schistosoma mansoni/patogenicidade , Animais , Biomphalaria/imunologia , Biomphalaria/fisiologia , Tamanho Corporal/fisiologia , Geografia , Guadalupe , Schistosoma mansoni/imunologiaRESUMO
We investigated the genotypic composition of the digenetic parasite Schistosoma mansoni for its adult stages within the definitive host (the wild rat, Rattus rattus) and for the larval stages within the intermediate host (the snail, Biomphalaria glabrata) both collected at the same transmission site. Our analyses are based upon the recognition and distribution of 200 different multilocus genotypes generated by RAPD markers. While intramolluscan larval infrapopulations are characterized by a low infection rate (0.6 % on average) and low intra-host genetic diversity (1.1 genotype on average per infected snail), adult infrapopulations within rats showed a high infection rate (94%) and a substantial intra-host genetic diversity (34 genotypes on average) linked to high intensities (160 worms per host on average). A single definitive host bearing 105 different genotypes harboured 52 % of the total genetic diversity detected within the whole parasite population. Analysis of the genetic data allowed the identification of various ecological, behavioural and immunological factors which are likely to enhance transmission of multiple parasite genotypes towards the vertebrate hosts. From the distribution of repeated identical multilocus genotypes within the parasite population and among the hosts, we have inferred different parameters of the cercarial transmission efficiency as well as patterns and processes by which vertebrate hosts acquire infection in the field.
Assuntos
Biomphalaria/parasitologia , Variação Genética , Muridae/parasitologia , Doenças dos Roedores/transmissão , Schistosoma mansoni/genética , Esquistossomose mansoni/transmissão , Animais , DNA de Helmintos/análise , Feminino , Genótipo , Guadalupe , Interações Hospedeiro-Parasita , Larva/classificação , Larva/genética , Estágios do Ciclo de Vida , Masculino , Técnica de Amplificação ao Acaso de DNA Polimórfico , Ratos , Doenças dos Roedores/parasitologia , Schistosoma mansoni/classificação , Esquistossomose mansoni/parasitologiaRESUMO
The delimitation of cryptic species within the genus Lymnaea, which are the main vectors of fascioliasis, remains a topic of controversy. An analysis of genetic variability based on 12 enzyme loci revealed different fixed alleles at 9 loci between two sympatric samples of Lymnaea viatrix at the type locality in Lima, Peru. The absence of heterozygotes within this locality indicates the presence of isolated populations or cryptic species within L. viatrix. Significant genetic differences were also found between these two L. viatrix samples from Lima and other populations of L. viatrix in South America and in addition to species such as L. truncatula, L. cubensis and L. columella. Moreover, the lack of variability within each Lymnaea samples studied indicates the existence of a high selfing rate in each species.
Assuntos
Lymnaea/genética , Animais , Vetores de Doenças , Fasciolíase/transmissão , Genótipo , América do Sul , Especificidade da EspécieRESUMO
We studied the population genetic structure of 360 and 1247 adult Schistosoma mansoni using seven microsatellite and seven random amplified polymorphic DNA (RAPD) markers, respectively. Parasites were collected from their natural definitive host Rattus rattus in Guadeloupe (West Indies). We found a sex-specific genetic structure, a pattern never before reported in a parasitic organism. Male genotypes were more randomly distributed among rats than female genotypes. This interpretation was consistent with a lower differentiation between hosts for males relative to females, the higher genetic similarity between females in the same host and the observed local (i.e. within-individual-host) differences in allele frequencies between the two sexes. We discuss our results using ecological and immunological perspectives on host-parasite relationships. These results change our view on the epidemiology of schistosomiasis, a serious disease affecting humans in African and American intertropical zones.
Assuntos
DNA de Protozoário/genética , Schistosoma mansoni/genética , Esquistossomose mansoni/epidemiologia , Animais , Sequência de Bases , DNA de Protozoário/química , Evolução Molecular , Feminino , Variação Genética , Genética Populacional , Guadalupe , Interações Hospedeiro-Parasita/genética , Masculino , Repetições de Microssatélites/genética , Dados de Sequência Molecular , Técnica de Amplificação ao Acaso de DNA Polimórfico , Ratos , Schistosoma mansoni/crescimento & desenvolvimentoRESUMO
Clinical charts of 80 infants younger than 1 year who presented over a 14-year period (1986 to 2000) with acute liver failure (ALF), defined as prolonged prothrombin time greater than 17 seconds and decrease of clotting factor V plasma level below 50% of normal, were reviewed retrospectively. The main causes of ALF were inherited metabolic disorders in 42.5% of cases, including mitochondrial respiratory chain disorders in 17, type I hereditary tyrosinemia in 12, and urea cycle disorders in 2; neonatal hemochromatosis in 16% of cases; and acute viral hepatitis in 15% of cases (hepatitis B in 6, herpes virus type 6 in 4, and herpes simplex virus type 1 in 2). The cause of ALF remained undetermined in 16% of cases. A total of 19 (24%) infants survived without orthotopic liver transplantation; 38 (47%) infants died from sepsis, multiple organ failure, or because the underlying disease contraindicated orthotopic liver transplantation (12 [15%] infants), and 23 (29%) infants underwent orthotopic liver transplantation within 12 months from onset, 12 of whom are alive with a mean follow-up period of 5.2 years from orthotopic liver transplantation. We conclude that ALF during the first year of life is a severe condition with poor prognosis, despite the advent of liver transplantation.
Assuntos
Hospitais Pediátricos , Falência Hepática Aguda/mortalidade , Falência Hepática Aguda/cirurgia , Transplante de Fígado , Humanos , Lactente , Recém-Nascido , Falência Hepática Aguda/fisiopatologia , Prognóstico , Estudos Retrospectivos , Taxa de Sobrevida , Fatores de Tempo , Resultado do TratamentoRESUMO
The distribution of genetic diversity in a local population of the trematode Schistosoma mansoni was determined within and between individual wild rats at a microspatial geographic scale of a standing water transmission site. Using RAPD markers, molecular variance and canonical correspondence analysis were performed to test the significance of genetic differentiation between infrapopulations. Of total gene diversity, 8 and 11% was partitioned between hosts trapped at few metres distance from each other. Significant temporal differentiation (2%) was also detected among schistosomes sampled at 6 month intervals with more infrapopulation pairs differentiated during the dry season of parasite transmission than during the rainy season (45 and 12%, respectively). A combination of factors such as restricted displacement of rats, patchy spatial aggregation of infected snails and limited cercarial dispersion in standing water are likely to promote the genetic differentiation observed between infrapopulations at this microgeographic scale.
Assuntos
DNA de Helmintos/genética , Schistosoma mansoni/genética , Esquistossomose mansoni/epidemiologia , Animais , DNA de Helmintos/química , DNA de Helmintos/isolamento & purificação , Feminino , Variação Genética , Guadalupe/epidemiologia , Desequilíbrio de Ligação/genética , Masculino , Ratos , Schistosoma mansoni/química , Estações do AnoRESUMO
Fatal cerebral hemorrhage involving the left thalamus in a neonate was attributed to deep cerebral vein thrombosis. Although antithrombin levels were at the lower end of the normal range, family and genetic studies showed constitutional type I antithrombin deficiency related to a novel missense mutation in the antithrombin gene.
Assuntos
Antitrombinas/deficiência , Hemorragia Cerebral/genética , Mutação Puntual , Antitrombinas/genética , Evolução Fatal , Humanos , Recém-Nascido , Masculino , Trombose Venosa/complicaçõesRESUMO
Schistosoma intercalatum, which causes human rectal schistosomiasis in Africa, still presents a great interest for its imprecise taxonomic status and its puzzling distribution in Africa. Two geographically isolated strains of S. intercalatum are recognized, the Lower Guinea strain and the Congo strain, which differ from each other in a number of morphological, biological and biochemical characteristics. Recent molecular data using RAPD markers indicate high divergence between the two strains, with values of Nei and Li's similarity index allowing recognition of two genetically distinct taxa: experiments on pre- and post-isolating mechanisms are in progress in order to re-evaluate the taxonomic status of this polytypic species. With regard to its geographical distribution, S. intercalatum is characterized by the existence of two stable endemic areas (localized in Lower Guinea and North East of Democratic Republic of Congo) which correspond to the historical areas of species discovery, and the emergence during the last 15 years of new foci of the Lower Guinea strain outside previously known endemic areas. The absence of local adaptation of the Lower Guinea strain to its intermediate host, supported by experimental studies, may help to facilitate the spread of this strain. Nevertheless, the present restricted distribution of this species remains puzzling, because its potential snail hosts (bulinids) are widely distributed throughout much of Africa. Recent experimental and epidemiological studies suggest that interspecific sexual interactions between human schistosomes could have a role in limiting the distribution of S. intercalatum: the competitive sexual processes acting among human schistosomes show that S. haematobium and S. mansoni are always competitively dominant over S. intercalatum. These epidemiological observations lead the authors to distinguish three kinds of transmission foci for S. intercalatum.
Assuntos
Doenças Retais/etiologia , Schistosoma/classificação , Esquistossomose/transmissão , África/epidemiologia , Animais , Doenças Endêmicas , Feminino , Humanos , Masculino , Densidade Demográfica , Doenças Retais/epidemiologia , Reprodução , Schistosoma/genética , Schistosoma/fisiologia , Schistosoma haematobium/classificação , Schistosoma haematobium/genética , Schistosoma haematobium/fisiologia , Schistosoma mansoni/classificação , Schistosoma mansoni/genética , Schistosoma mansoni/fisiologia , Esquistossomose/epidemiologiaRESUMO
Fasciolosis is a re-emerging parasitic disease that affects an increasing number of people in developing countries. The most severe endemic affects the Bolivian Altiplano, where the liver fluke (Fasciola hepatica) and its hermaphroditic snail host, Lymnaea truncatula, have been introduced from Europe. To achieve a better understanding of the epidemiological situation and the consequences of the colonization event of this invasive species, genetic analysis of Bolivian snail populations was needed. Here we compare the genetic diversity and population structure of snail samples from the Bolivian Altiplano with samples from the Old World at six polymorphic microsatellite loci. Whereas some variability exists in the snail populations from the Old World, we observe only a single genotype of L. truncatula in the Bolivian Altiplano. We discuss the possible explanations for such a reduction in genetic variability, and, given the high natural parasitism pressures exerted on the snail populations, we discuss the relevance of this result for host-parasite interactions.