RESUMO
At the time of writing, Afghanistan is the pre-eminent theatre of operations for UK military forces, which form a lead element in the International Security Assistance Force. Many junior medical officers (MOs) can expect to see service on Operation HERRICK in the south of the country, in support of deployed battlegroup formations. MO's will often find themselves supporting Company Group formations, either within the Company Aid Post, or on dismounted/vehicle borne operations. This article presents some of the challenges faced by those deployed in such circumstances, and proposes possible strategies to address them.
Assuntos
Medicina Militar/organização & administração , Militares , Afeganistão , Comunicação , Humanos , Reino Unido , Guerra , Ferimentos e Lesões/terapiaRESUMO
Abalone sperm lysin is a nonenzymatic, 16-kDa protein that creates a hole in the egg vitelline envelope (VE) through which the sperm swims to fuse with the egg. The dissolution of isolated VE by lysin is species specific. Interspecies comparisons show that the most divergent region of lysin is the N-terminal segment of residues 1-12 which is always species-unique. The C-terminus and three internal segments are moderately variable between species, but not species unique. Analysis of nucleotide substitutions shows that lysin evolves rapidly by positive Darwinian selection, suggesting that there is adaptive value in altering its amino acid sequence. The results reported here, in which segments of lysin were exchanged between two species, prove by direct experimentation that the interspecies variable termini play major roles in the species-specific recognition between sperm lysin and the egg VE.
Assuntos
Acrossomo/fisiologia , Moluscos/fisiologia , Mucoproteínas/genética , Mucoproteínas/metabolismo , Interações Espermatozoide-Óvulo/fisiologia , Sequência de Aminoácidos , Animais , Clonagem Molecular , Feminino , Cinética , Masculino , Dados de Sequência Molecular , Mucoproteínas/química , Mutagênese Sítio-Dirigida , Estrutura Secundária de Proteína , Proteínas Recombinantes de Fusão/metabolismo , Alinhamento de Sequência , Homologia de Sequência de Aminoácidos , Especificidade da Espécie , Membrana Vitelina/fisiologiaAssuntos
Manipulação de Alimentos/legislação & jurisprudência , Abastecimento de Alimentos , Responsabilidade Legal , Manipulação de Alimentos/economia , Manipulação de Alimentos/história , Abastecimento de Alimentos/economia , Abastecimento de Alimentos/legislação & jurisprudência , Doenças Transmitidas por Alimentos , História do Século XV , História do Século XVI , História do Século XVII , História do Século XVIII , História do Século XIX , História do Século XX , História Antiga , História Medieval , História Moderna 1601- , Humanos , Modelos Teóricos , Estados UnidosRESUMO
The pyrogenic toxin (PT) family is composed of the staphylococcal enterotoxins (SE), the toxic shock syndrome toxin, and the streptococcal pyrogenic exotoxins (SPE). Whereas considerable effort has focused on characterization of PTs due to their unique biological properties, our understanding of the evolution of this gene family is incomplete. Phylogenetic relationships for members of the PT family were estimated by examining the previously reported nucleotide sequences of the genes encoding SPEA, SPEC, SEA, SEB, SEC1, SEC2, SEC3, SED, and SEE. Additionally, we present and analyze sequence data on seven previously unreported sec genes. Within the PT family, sequence divergence was partitioned in a hierarchical fashion such that mean sequence divergence ranged from 1.179 among all 16 toxin genes, 0.443 among those restricted to Staphylococcus, and 0.028 among the genes encoding 10 variants of Type C SE. Results of this study are interpreted as suggesting that the PT family consists of two large clades. One clade consists of the staphylococcal toxins SEA, SEE, and SED, being closely related to the streptococcal toxin SPEC, whereas the other clade depicts close relationships of the staphylococcal toxins SEC and SEB with the streptococcal toxin SPEA.
Assuntos
Toxinas Bacterianas/genética , Evolução Biológica , Genes Bacterianos , Staphylococcus aureus/genética , Streptococcus pyogenes/genética , Sequência de Aminoácidos , Sequência de Bases , Primers do DNA/genética , DNA Bacteriano/genética , Enterotoxinas/genética , Exotoxinas/genética , Dados de Sequência Molecular , Família Multigênica , Homologia de Sequência de Aminoácidos , Homologia de Sequência do Ácido NucleicoRESUMO
The type C staphylococcal enterotoxins (SEC) are a group of highly conserved proteins with significant immunological cross-reactivity. Although three antigenically distinct SEC subtypes (SEC1, SEC2, and SEC3) have been reported in the literature, we observed that the isoelectric points of SEC from several Staphylococcus aureus isolates are different from those of any of these three subtypes. This observation led us to propose that additional SEC molecular variants exist. For assessment of this possibility, the sec genes from representative human, animal, and food isolates were cloned and sequenced. The toxins encoded by the 18 isolates used in this study included five unique SEC proteins in addition to SEC1, SEC2, and SEC3. Six of the SEC proteins (including SEC1, SEC2, and SEC3) were produced by human and food isolates. Analysis of seven bovine and ovine isolates showed that isolates from each animal species produced a unique host-specific SEC. All of the SEC caused lymphocyte proliferation, although some of the toxins differed in their ability to stimulate cells from several animal species. An explanation for these results, which is supported by our phenotypic analysis of Sec+ staphylococcal isolates, is that toxin heterogeneity is due to selection for modified SEC sequences that facilitate the survival of S. aureus isolates in their respective hosts.
