RESUMEN
Hemolytic uremic syndrome is the clinical triad of thrombocytopenia, microangiopathic hemolytic anaemia and acute renal failure. Cases not associated with a preceding Shiga-like toxin producing Escherichia coli are described as atypical HUS (aHUS). Approximately 50% of patients with aHUS have mutations in one of three complement regulatory proteins, Factor H (CFH), membrane cofactor protein (MCP;CD46) or factor I (IF). A common feature of these three proteins is that they regulate complement by cofactor activity. Decay accelerating factor (DAF; CD55) regulates the complement system by disassociating the alternative and classical pathway convertases. Like CFH and MCP, the gene for DAF lies within the regulators of complement activation (RCA) gene cluster at 1q32. In 1998, we described linkage to this region in families with aHUS which led to the discovery of mutations in CFH and MCP. We therefore genotyped DAF in a panel of 46 aHUS patients including families with linkage to the RCA cluster. A mutation, I197V, was identified in one patient with familial HUS which was not found in 100 healthy controls. Molecular modelling of this mutation shows that the I197V mutation does not reside in an area which would be predicted to be important in decay accelerating activity. The expression of I197V on EBV-transformed B lymphocytes was equivalent to that of wild type controls. There was no significant decrease in decay acceleration activity of the recombinantly produced I197V mutant compared with wild type, as measured by a complement-mediated lytic assay. In conclusion, this study, identifies only one mutation in DAF in 46 patients with aHUS. This mutation, I197V, does not impair complement regulation and cannot be implicated in the pathogenesis of aHUS in this patient. This suggests that the complement regulatory abnormality in aHUS is principally one of deficient cofactor activity rather than of decay acceleration activity.
Asunto(s)
Antígenos CD55/genética , Proteínas del Sistema Complemento/genética , Síndrome Hemolítico-Urémico/genética , Mutación Missense , Factor H de Complemento/genética , Análisis Mutacional de ADN , Salud de la Familia , Fibrinógeno , Síndrome Hemolítico-Urémico/etiología , Humanos , Proteína Cofactora de Membrana/genética , Modelos Moleculares , MutaciónAsunto(s)
Dolor en el Pecho/etiología , Enfisema Mediastínico/diagnóstico , Adolescente , Humanos , MasculinoRESUMEN
We determined the prevalence of erythromycin-resistant bacteria in the oral cavity and identified mef and erm(B) as the most common resistance determinants. In addition, we demonstrate the genetic linkage, on various Tn1545-like conjugative transposons, between erythromycin and tetracycline resistance in a number of isolates.
Asunto(s)
Antibacterianos/farmacología , Bacterias/efectos de los fármacos , Eritromicina/farmacología , Boca/microbiología , Bacterias/genética , Bacterias/crecimiento & desarrollo , Southern Blotting , Elementos Transponibles de ADN/genética , Proteínas de Unión al ADN/genética , Farmacorresistencia Bacteriana , Humanos , Pruebas de Sensibilidad Microbiana , Plásmidos/genética , Proteína Metiltransferasas/genética , Resistencia a la Tetraciclina , Factores de Transcripción/genéticaRESUMEN
A major drawback of most studies on how bacteria become resistant to antibiotics is that they concentrate mainly on bacteria that can be cultivated in the laboratory. In the present study, we cloned part of the oral metagenome and isolated a novel tetracycline resistance gene, tet(37), which inactivates tetracycline.
Asunto(s)
Bacterias/efectos de los fármacos , Placa Dental/microbiología , Genoma Bacteriano , Saliva/microbiología , Resistencia a la Tetraciclina/genética , Adulto , Secuencia de Aminoácidos , Bacterias/genética , Humanos , Datos de Secuencia MolecularRESUMEN
Tetracycline is a broad-spectrum antibiotic used in humans, animals, and aquaculture; therefore, many bacteria from different ecosystems are exposed to this antibiotic. In order to determine the genetic basis for resistance to tetracycline in bacteria from the oral cavity, saliva and dental plaque samples were obtained from 20 healthy adults who had not taken antibiotics during the previous 3 months. The samples were screened for the presence of bacteria resistant to tetracycline, and the tetracycline resistance genes in these isolates were identified by multiplex PCR and DNA sequencing. Tetracycline-resistant bacteria constituted an average of 11% of the total cultivable oral microflora. A representative 105 tetracycline-resistant isolates from the 20 samples were investigated; most of the isolates carried tetracycline resistance genes encoding a ribosomal protection protein. The most common tet gene identified was tet(M), which was found in 79% of all the isolates. The second most common gene identified was tet(W), which was found in 21% of all the isolates, followed by tet(O) and tet(Q) (10.5 and 9.5% of the isolates, respectively) and then tet(S) (2.8% of the isolates). Tetracycline resistance genes encoding an efflux protein were detected in 4.8% of all the tetracycline-resistant isolates; 2.8% of the isolates had tet(L) and 1% carried tet(A) and tet(K) each. The results have shown that a variety of tetracycline resistance genes are present in the oral microflora of healthy adults. This is the first report of tet(W) in oral bacteria and the first report to show that tet(O), tet(Q), tet(A), and tet(S) can be found in some oral species.
Asunto(s)
Boca/microbiología , Resistencia a la Tetraciclina/genética , Adulto , Bacterias/efectos de los fármacos , Placa Dental/microbiología , Humanos , Pruebas de Sensibilidad Microbiana , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Saliva/microbiología , Tetraciclinas/farmacologíaRESUMEN
A homologue of the HtrA family of stress-response proteases was detected by analysis of the Streptococcus mutans genome sequence. Disabling of the S. mutans htrA gene by insertional inactivation resulted in bacterial clumping in liquid medium, altered colony morphology and a reduced ability to withstand high temperature, extremes of pH or oxidative stress. Seven different extracellular or wall-associated proteins that are known to be subject to post-translational proteolysis were examined in cultures of wild-type S. mutans and an htrA mutant. Inactivation of the htrA protease had no effect on degradation of the proteins.
Asunto(s)
Proteínas Bacterianas/metabolismo , Proteínas de Choque Térmico , Respuesta al Choque Térmico , Proteínas Periplasmáticas , Serina Endopeptidasas/metabolismo , Streptococcus mutans/enzimología , Streptococcus mutans/fisiología , Secuencia de Aminoácidos , Animales , Proteínas Bacterianas/química , Clonación Molecular , Medios de Cultivo , Eliminación de Gen , Humanos , Datos de Secuencia Molecular , Conejos , Serina Endopeptidasas/química , Serina Endopeptidasas/genética , Streptococcus mutans/genéticaAsunto(s)
Bacillus subtilis/fisiología , Biopelículas/crecimiento & desarrollo , Modelos Biológicos , Proteoma/análisis , Bacillus subtilis/genética , Técnicas Bacteriológicas , Medios de Cultivo , Electroforesis en Gel Bidimensional , Estudios de Evaluación como Asunto , Mutación , Proteoma/genéticaRESUMEN
OBJECTIVE: The aim of this study was to evaluate ribavirin therapy for acute bronchiolitis caused by viral syncytial respiratory infection. PATIENTS AND METHODS: Ninety-seven patients with acute bronchiolitis in which respiratory syncytial virus was identified by direct immunofluorescence and admitted to the hospital between October 1990 and May 1995 were studied. Data pertaining to age, sex, weight, respiratory frequency at admission, respiratory frequency on the fourth day, day in which respiratory ausculation was normal, day in which there were no thoracic retractions, number of days that the infants needed oxygen, duration of hospital stay, and whether or not they were treated with ribavirin were collected retrospectively. RESULTS: At admission there were no statistically significant differences in patients treated or not with ribavirin or in age, sex or weight, but the respiratory frequency was higher in those patients treated with ribavirin than in those who were not. The number of days of oxygen therapy was statistically different between these groups, with infants treated with ribavirin requiring oxygen for 2.7 days and the nontreated group requiring 1.7 days. However, we think that this difference is not clinically relevant. CONCLUSIONS: We did not find any difference of clinical relevance between patients treated or not with ribavirin.
Asunto(s)
Antivirales/uso terapéutico , Bronquiolitis/tratamiento farmacológico , Bronquiolitis/virología , Infecciones por Virus Sincitial Respiratorio/tratamiento farmacológico , Virus Sincitial Respiratorio Humano , Ribavirina/uso terapéutico , Enfermedad Aguda , Femenino , Humanos , Lactante , Recién Nacido , Masculino , Estudios RetrospectivosAsunto(s)
Bacillus subtilis/genética , Proteínas Bacterianas/química , Medios de Cultivo , Electroforesis en Gel Bidimensional/métodos , Marcaje Isotópico/métodos , Bacillus subtilis/química , Bacillus subtilis/crecimiento & desarrollo , Proteínas Bacterianas/biosíntesis , Proteínas Bacterianas/genética , Mutación , Radioisótopos de AzufreRESUMEN
Aspergillus niger var. awamori contains multiple copies of a transposable element, Vader. This element was detected as a 437-bp insertion in four independently isolated spontaneous mutants of the niaD (nitrate reductase) gene. The Vader element is present in approximately 15 copies in both A. niger var. awamori and A. niger. A single copy of Vader was detected from only one of the two laboratory strains of A. nidulans which were also examined. Insertion of the Vader element into the niaD gene of A. niger var. awamori caused a 2-bp duplication (TA) of the target sequence. The Vader element is flanked by a 44-bp inverted repeat. The genetic stabilities of the inserted Vader elements at niaD were examined by studying reversion frequencies resulting in colonies able to grow on nitrate as a sole nitrogen source. Mutants niaD392 and niaD436 reverted at a frequency of 9x10(-3) and 4x10(-2), respectively. Two of the mutants, niaD587 and niaD410, reverted at a lower frequency of 6x10(-4).
Asunto(s)
Aspergillus niger/genética , Elementos Transponibles de ADN , Secuencia de Bases , Southern Blotting , Dosificación de Gen , Datos de Secuencia Molecular , Mutagénesis , Nitrato-Reductasa , Nitrato Reductasas/análisis , Nitrato Reductasas/genética , Reacción en Cadena de la Polimerasa , Selección Genética , Análisis de Secuencia de ADN , Especificidad de la EspecieRESUMEN
Escherichia coli strains carrying the protease III structural gene (ptr) on a plasmid secreted the protein into the growth medium. Plasmid-encoded beta-lactamase and chloramphenicol acetyl transferase, which served as periplasmic and cytoplasmic markers during cell fractionation, were not released into the growth medium. There appeared to be some strain dependence on the proficiency of the secretion system. Protease III was not detectably processed upon export through the outer cell membrane.
Asunto(s)
Endopeptidasas/metabolismo , Escherichia coli/enzimología , Metaloendopeptidasas , Western Blotting , Cloranfenicol O-Acetiltransferasa/genética , Cloranfenicol O-Acetiltransferasa/metabolismo , Endopeptidasas/genética , Escherichia coli/genética , Escherichia coli/crecimiento & desarrollo , Genes Bacterianos , Plásmidos/genética , Señales de Clasificación de Proteína/genética , beta-Lactamasas/genética , beta-Lactamasas/metabolismoRESUMEN
The technological advance and the development of the odontologic profession, requires the gradual incorporation of more accurate psycho-motrice methods. The aim of this report is the presentation of the systems elaborated for the development of the students' and odontologists' psycho-motive skill. This report describes the method known as "reflection box", for the learning of indirect vision. In order to achieve a training, for the correct odontologic practice, in ergonomic positions that prevent skeleton-muscle disorders resulted from inadequate professional practices, exercises in two and three dimensions should be carried out with said box.
Asunto(s)
Operatoria Dental/educación , Educación en Odontología , Desempeño Psicomotor , Visión Ocular , Humanos , Enfermedades Profesionales/prevención & control , Postura , Materiales de EnseñanzaRESUMEN
The product of the altered mRNA stability (ams) gene of Escherichia coli is involved in decay of mRNA. The complete nucleotide sequence of a 4-kilobase BamHI restriction fragment containing the ams coding sequence was determined. Transcription of the ams gene was analyzed by high resolution S1 mapping. A promoter was found with a homology score of 58% 361 nucleotides upstream from the start codon of ams. The ams structural gene consists of an open reading frame of 2,445 nucleotides. The protein predicted from this open reading frame has a molecular mass of 91,327 Da, which is significantly smaller than that determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis. Confirmation of the ams coding sequence was obtained by comparing the predicted amino acid sequence with that derived by amino-terminal analysis of gel-purified Ams protein. The predicted protein sequence of the ams gene was screened against translations of the GenBank DNA sequence data base. A homology of 18% over a region of 315 amino acids of the carboxyl terminus of the Ams product was found to MRP3, a mitochondrial ribosomal protein from Neurospora crassa. A smaller region of homology (29% in 86 residues) was found to the human U1 small nuclear ribonucleoparticle 70,000-Da protein.
Asunto(s)
Escherichia coli/genética , Proteínas Fúngicas/genética , Complejo Piruvato Deshidrogenasa , ARN Bacteriano/genética , ARN Mensajero/genética , Proteínas Ribosómicas/genética , Homología de Secuencia de Ácido Nucleico , Transcripción Genética , Secuencia de Aminoácidos , Clonación Molecular , Codón , Acetiltransferasa de Residuos Dihidrolipoil-Lisina , Genes Bacterianos , Datos de Secuencia Molecular , Neurospora crassa , Conformación de Ácido Nucleico , Mapeo RestrictivoRESUMEN
Regulation of bgl operon expression in E. coli occurs by a mechanism involving antitermination of transcription at two termination sites within the operon. The bglG gene product is absolutely required for this process. Here we provide evidence that BglG is an RNA binding protein that recognizes a specific sequence located just upstream of each of the terminators. The sequence was delimited using a series of specific oligonucleotide probes. Mutational analysis of this sequence indicates that the protein requires a specific RNA secondary structure for recognition. We propose that BglG prevents transcription termination by binding to nascent RNA and blocking formation of the terminator structure.
Asunto(s)
Proteínas Bacterianas/genética , Proteínas Portadoras/genética , Escherichia coli/genética , Genes Reguladores , Operón , Regiones Terminadoras Genéticas , Transcripción Genética , Proteínas Bacterianas/metabolismo , Composición de Base , Secuencia de Bases , Sitios de Unión , Proteínas Portadoras/metabolismo , Escherichia coli/metabolismo , Vectores Genéticos , Datos de Secuencia Molecular , Conformación de Ácido Nucleico , Sondas de Oligonucleótidos , Plásmidos , Señales de Clasificación de Proteína/genética , ARN Bacteriano/genética , ARN Bacteriano/metabolismo , Proteínas de Unión al ARNRESUMEN
A temperature-sensitive mutation in the ams gene of Escherichia coli causes an increase in the chemical half-life of pulse-labeled RNA at the nonpermissive temperature. Using lambda clones containing DNA fragments from the 23- to 24-min region on the E. coli chromosome, we have isolated a 5.8-kilobase DNA fragment which, when present in a low-copy-number plasmid, complements the conditional lethality and increased mRNA stability associated with the ams-1 mutation. The approximate initiation site and the direction of transcription of the ams gene were determined from the size of truncated polypeptides produced by Tn1000 insertions and Bal 31 deletions. Overexpression of the ams locus by using a T7 RNA polymerase-promoter system permitted the identification of an ams-encoded polypeptide of 110 kilodaltons.