C-terminal deletion of AID uncouples class switch recombination from somatic hypermutation and gene conversion

Class-switch recombination (CSR), somatic hypermutation (SHM), and antibody gene conversion are distinct DNA modification reactions, but all are initiated by activation-induced cytidine deaminase (AID), an enzyme that deaminates cytidine residues in single-stranded DNA. Here we describe a mutant form of AID that catalyzes SHM and gene conversion but not CSR. When expressed in E. coli, AID(delta189-198) is more active in catalyzing cytidine deamination than wild-type AID. AID(delta189-198) also promotes high levels of gene conversion and SHM when expressed in eukaryotic cells, but fails to induce CSR. These results underscore an essential role for the C-terminal domain of AID in CSR that is independent of its cytidine deaminase activity and that is not required for either gene conversion or SHM.     

Control metabólico y de factores de riesgo cardiovascular en una cohorte de pacientes con diabetes mellitus. Resultados a los 4 años

ObjectivesTo assess control of blood glucose and other cardiovascular risk factors in diabetic patients monitored at an outpatient endocrinology clinic. To ascertain treatment used and its changes over time.Patients and methodsA cohort of 424 randomly selected diabetic patients (both type 1 and type 2) was monitored from 2004 to 2008. Final cohort size was 343 patients. Data were collected about epidemiological characteristics, cardiovascular risk factors, chronic complications, glycemic, lipid and blood pressure control, and treatment at baseline and 4 years.ResultsAfter 4 years, the proportion of patients achieving glycosylated hemoglobin levels less than 7% remained stable (type 1: 18.5% in 2004 vs 21.7% in 2008, type 2: 26.6% vs 26.5%). The degree of achievement of lipid and blood pressure (BP) control levels increased in both groups. The complexity of treatment schemes used to achieve these results significantly increased.ConclusionsStabilization of glycemic control after 4 years of follow-up was a positive result, considering the long course of diabetes, progressive pancreatic function impairment, and complexity of our cohort. Treatment optimization significantly improved BP and lipid control in the study group.     

Traditional microbiological diagnosis for invasive candidiasis in critical non-neutropenic patients

Invasive candidiasis is the most prevalent fungal infection in the critical non neutropenic patient (80%) and is associated with high morbidity-mortality. Microbiological diagnosis is difficult and the positivity of traditional tests appears late in the course of infection. We herein discuss the utility of direct examination and cultures from different sites and the value of surveillance cultures for establishing the likelihood of invasive candidiasis.     

Selection and Characterization of Biofuel-Producing Environmental Bacteria Isolated from Vegetable Oil-Rich Wastes

Fossil fuels are consumed so rapidly that it is expected that the planet resources will be soon exhausted. Therefore, it is imperative to develop alternative and inexpensive new technologies to produce sustainable fuels, for example biodiesel. In addition to hydrolytic and esterification reactions, lipases are capable of performing transesterification reactions useful for the production of biodiesel. However selection of the lipases capable of performing transesterification reactions is not easy and consequently very few biodiesel producing lipases are currently available. In this work we first isolated 1,016 lipolytic microorganisms by a qualitative plate assay. In a second step, lipolytic bacteria were analyzed using a colorimetric assay to detect the transesterification activity. Thirty of the initial lipolytic strains were selected for further characterization. Phylogenetic analysis revealed that 23 of the bacterial isolates were Gram negative and 7 were Gram positive, belonging to different clades. Biofuel production was analyzed and quantified by gas chromatography and revealed that 5 of the isolates produced biofuel with yields higher than 80% at benchtop scale. Chemical and viscosity analysis of the produced biofuel revealed that it differed from biodiesel. This bacterial-derived biofuel does not require any further downstream processing and it can be used directly in engines. The freeze-dried bacterial culture supernatants could be used at least five times for biofuel production without diminishing their activity. Therefore, these 5 isolates represent excellent candidates for testing biofuel production at industrial scale.     

C3G down-regulates p38 MAPK activity in response to stress by Rap-1 independent mechanisms: Involvement in cell death

We present here evidences supporting a negative regulation of p38α MAPK activity by C3G in MEFs triggered by stress, which can mediate cell death or survival depending on the stimuli. Upon serum deprivation, C3G induces survival through inhibition of p38α activation, which mediates apoptosis. In contrast, in response to H₂O₂, C3G behaves as a pro-apoptotic molecule, as its knock-down or knock-out enhances survival through up-regulation of p38α activation, which plays an anti-apoptotic role under these conditions. Moreover, the C3G target, Rap-1, plays an opposite role, also through regulation of p38α MAPK activity.Our data also suggest that changes in the protein levels of some members of the Bcl-2 family could account for the regulation of cell death by C3G and/or Rap-1 through p38α MAPK. Bim/Bcl-x_L ratio appears to be important in the regulation of cell survival, both upon serum deprivation and in response to H₂O₂. In addition, the increase in BNIP-3 levels induced by C3G knock-down in wt cells treated with H₂O₂ might play a role preventing cell death.Therefore, we can conclude that C3G is a negative regulator of p38α MAPK in MEFs, while Rap-1 is a positive regulator, but both, through the regulation of p38α activity, can promote cell survival or cell death depending on the stimuli.     

Ciliate contributions to bioaggregation: laboratory assays with axenic cultures of Tetrahymena thermophila.

Protists, mainly ciliates, play several essential roles in biological wastewater treatment, such as the transfer of matter and energy, bacterial predation, and the removal of organic material. Moreover, during the treatment process, the formation of bioaggregates-flocs and biofilms-is essential to obtaining high-quality effluents. In the present study, Tetrahymena thermophila was used as a model organism to demonstrate the contribution of ciliates to bioflocculation. Axenic cultures of this species were exposed to chemical and mechanical stimuli that promote bioaggregation. In either case, the secretion of a capsulate mucous material by the ciliates or by particle aggregation was detected. Numerous, small, loosely compacted flocs were observed under shaking conditions and in the presence of latex beads. The composition of the exopolymeric material secreted by ciliates was analyzed by a series of fluorochromes and colorimetric methods, which showed that carbohydrates and nucleic acids were the main components involved in matrix formation and particle adhesion.