RESUMEN
The origin of giant, sedimentary rock-hosted copper-cobalt (Cu-Co) provinces remains contentious, in part due to the lack of precise and reliable ages for mineralisation. As such, no consensus has been reached on the genetic model for ore formation, and the relationships between tectonism, palaeo-fluid circulation and mineralisation. Here, we link the timing of Cu-Co mineralisation in the Central African Copperbelt to compressional tectonics during the Lufilian Orogeny by using new ca. 609-473 Ma ages given by rhenium-osmium (Re-Os) isotope data for individual Cu-Co sulphides (carrolite and bornite) from the Cu-Co Kamoto deposit. The initial Os isotope composition of carrolite is compatible with the leaching of Os and Cu(-Co) from Mesoproterozoic Cu sulphide deposits hosted in fertile basement. In contrast, the ca. 473 Ma Cu-Au mineralisation stage, which is coeval with late- to post-compressional deformation, may be a distal expression of fluid flow and heat transfer caused by magmatic intrusions in the core of the collisional orogen. The Re-Os ages support a model for mineralisation driven by evaporite dissolution and percolation of large volumes of dense brines in the Katangan Basin during the Lufilian Orogeny.
RESUMEN
AIM: To assess the long-term incidence and predictive factors for recurrence after laparoscopic ventral hernia repair using a bridging technique. METHODS: The study group consisted of 213 consecutive patients operated by laparoscopy for primary ventral (n = 158) or incisional hernia (n = 55) between 2001 and 2014. Patients had a repair without fascia closure by intra-peritoneal onlay placement of a Parietex® composite mesh centred on the defect with an overlap of at least 3 cm. Clinical outcome was assessed by a combination of office consultation, patient's electronic medical file review and telephone interview. RESULTS: There were 144 men and 69 women with a mean age of 55 ± 12 years and a BMI of 32 ± 6. With a mean follow-up of 69 ± 44 months, a recurrent hernia was noted in 16 patients (7.5%). Univariate analysis showed a statistically significant higher recurrence rate in the following conditions: incisional hernia (15%), BMI ≥ 35 (21%), defect width >4 cm (27%), defect area >20 cm2 (27%), mesh overlap <5 cm (32%) and ratio of mesh area to defect area (M/D ratio) ≤12 (48%). Multivariate logistic analysis revealed that M/D ratio was the only independent predictive factor for recurrence (coefficient -0.79, OR 0.46, p < 0.002). With a M/D ratio ≤8, between 9 and 12, between 13 and 16, and ≥17, the recurrence rate was, respectively, 70, 35, 9 and 0% (p < 0.001). CONCLUSIONS: In laparoscopic repair of ventral hernia using a bridging technique, an overlap of at least 5 cm is not all that is required to prevent hernia recurrence. The M/D ratio is the most important predictive factor for recurrence. A ratio of 13 appears as the threshold under which that technique cannot be recommended and 16 as the threshold over which the risk of recurrence is virtually nil. If a satisfactory M/D ratio cannot be achieved, other surgical repair should be proposed to the patient.
Asunto(s)
Hernia Ventral/cirugía , Herniorrafia/métodos , Hernia Incisional/cirugía , Laparoscopía/métodos , Adulto , Anciano , Femenino , Estudios de Seguimiento , Herniorrafia/instrumentación , Humanos , Laparoscopía/instrumentación , Modelos Logísticos , Masculino , Persona de Mediana Edad , Análisis Multivariante , Recurrencia , Estudios Retrospectivos , Factores de Riesgo , Mallas Quirúrgicas , Resultado del TratamientoRESUMEN
Converting the complete genome sequence of Candida albicans into meaningful biological information will require comprehensive screens for identifying functional classes of genes. Most systems described so far are not applicable to C. albicans because of its difficulty with mating, its diploid nature, and the lack of functional random insertional mutagenesis methods. We examined artificial gene suppression as a means to identify gene products critical for growth of this pathogen; these represent new antifungal drug targets. To achieve gene suppression we combined antisense RNA inhibition and promoter interference. After cloning antisense complementary DNA (cDNA) fragments under control of an inducible GAL1 promoter, we transferred the resulting libraries to C. albicans. Over 2,000 transformant colonies were screened for a promoter-induced diminished-growth phenotype. After recovery of the plasmids, sequence determination of their inserts revealed the messenger RNA (mRNA) they inhibited or the gene they disrupted. Eighty-six genes critical for growth were identified, 45 with unknown function. When used in high-throughput screening for antifungals, the crippled C. albicans strains generated in this study showed enhanced sensitivity to specific drugs.
Asunto(s)
Candida albicans/crecimiento & desarrollo , Candida albicans/genética , Genes Fúngicos/genética , Genoma Fúngico , Genómica/métodos , ARN sin Sentido/genética , Antifúngicos/farmacología , Candida albicans/efectos de los fármacos , Clonación Molecular/métodos , ADN sin Sentido/genética , Evaluación Preclínica de Medicamentos , Proteínas Fúngicas/genética , Proteínas Fúngicas/metabolismo , Regulación Fúngica de la Expresión Génica , Biblioteca de Genes , Genes Esenciales/genética , Heterocigoto , Pruebas de Sensibilidad Microbiana , Mutagénesis Insercional/genética , Fenotipo , Regiones Promotoras Genéticas/genética , ARN de Hongos/análisis , ARN de Hongos/genética , ARN Mensajero/análisis , ARN Mensajero/genética , Transformación GenéticaRESUMEN
To develop better molecular genetic tools for the diploid yeast Candida albicans, the suitability of the MET15 gene as a visual selection marker was studied. Both MET15 alleles of C. albicans CAI-4 were isolated by functional complementation of a Saccharomyces cerevisiae strain lacking the MET15 gene. Growth of this complemented strain on Pb(2+)-containing medium was associated with a colour shift of brown into white colonies. The MET15 alleles of C. albicans were located on chromosome 4 by pulsed-field gel electrophoresis and Southern blotting. A met15-deficient strain of C. albicans CAI-4 was generated using the ura blaster technique. This strain showed a brown colony colour on Pb(2+)-containing medium, which corresponded with the colony colour of a S. cerevisiae strain lacking the MET15 gene. Unexpectedly, the met15-deficient strain of C. albicans still grew on methionine-depleted medium. However, this growth was severely delayed. In addition, complementation of this strain with an integrative or replicative plasmid containing either of the MET15 alleles resulted in the formation of white transformants on Pb(2+)-containing medium. These transformants grew very well on methionine-depleted medium. Colony sectoring was obtained with the replicative plasmid and not with the integrative one. This study demonstrates that the MET15 gene of C. albicans is suitable as a visual marker and therefore can be used to identify transformants and study plasmid stability. GenBank Accession Nos for MET15 nucleotide sequences are AF188273, AF188274 and AF188275.
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Candida albicans/genética , Proteínas Fúngicas/genética , Complejos Multienzimáticos , Proteínas de Saccharomyces cerevisiae , Secuencia de Aminoácidos , Secuencia de Bases , Biomarcadores , Candida albicans/enzimología , Candida albicans/crecimiento & desarrollo , Cisteína Sintasa , ADN Complementario/química , ADN Complementario/genética , ADN de Hongos/química , ADN de Hongos/genética , ADN de Hongos/aislamiento & purificación , Proteínas Fúngicas/metabolismo , Genes Fúngicos/genética , Prueba de Complementación Genética , Datos de Secuencia Molecular , Mutación , Análisis de Secuencia de ADNRESUMEN
A cDNA encoding 1,2-alpha-D-mannosidase mds 1 from Trichoderma reesei was cloned. The largest open reading frame occupied 1571 bp. The predicted sequence contains 523 amino acid residues for a calculated molecular mass of 56,266 Da and shows high similarity to the amino acid sequences of 1,2-alpha-D-mannosidases from Aspergillus saitoi and Penicillium citrinum (51.6 and 51.0% identity, respectively). T. reesei mannosidase was produced as a recombinant enzyme in the yeast Pichia pastoris. Replacement of the N-terminal part with the prepro-signal peptide of the Saccharomyces cerevisiae alpha-mating factor resulted in high amounts of secreted enzyme. A three-step purification protocol was designed and the enzymatic properties were analyzed. The enzyme was characterized as a class-I mannosidase.
Asunto(s)
Clonación Molecular , Manosidasas/genética , Manosidasas/metabolismo , Trichoderma/enzimología , Secuencia de Aminoácidos , Aspergillus/enzimología , ADN Complementario , Manosidasas/química , Factor de Apareamiento , Datos de Secuencia Molecular , Penicillium/enzimología , Péptidos/genética , Pichia/enzimología , Pichia/genética , Señales de Clasificación de Proteína/genética , Proteínas Recombinantes de Fusión , Proteínas Recombinantes , Saccharomyces cerevisiae/química , Saccharomyces cerevisiae/genética , Alineación de SecuenciaRESUMEN
The Trichoderma harzianum imidazoleglycerolphosphate dehydratase gene (igh) has been isolated by complementation of a Saccharomyces cerevisiae his3 mutant using a direct expression vector. This Escherichia coli-yeast shuttle vector was developed to allow efficient cloning and expression of cDNA libraries. The cDNA is 627 nucleotides long and codes for a protein of 209 amino acids with an apparent molecular mass of 22,466 daltons. The predicted protein sequence showed 63.6%, 58.7%, and 38.4% identity respectively to the corresponding enzymes from S. cerevisiae, Pichia pastoris and E. coli. Northern analysis showed that the expression of the igh gene in T. harzianum is not inhibited by external histidine and the level of igh mRNA was about threefold higher in cells starved of histidine.