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Biomedical subjects

M de la Peña

Publications and source records attributed to M de la Peña.

9 recordsLinked to original sources
PubMed2006

Antioxidant status in patients with sleep apnoea and impact of continuous positive airway pressure treatment.

The episodes of hypoxia/re-oxygenation associated with the respiratory disturbances observed in patients with obstructive sleep apnoea syndrome (OSAS) may induce the generation of oxygen free radicals. Indeed, several studies suggest that OSAS is associated with oxidative stress. The present study tested the hypothesis that patients with OSAS have an alteration in antioxidant defences. The plasma levels of total antioxidant status (TAS), glutathione peroxidase (GPX), gamma-glutamyltransferase (GGT), vitamins A, E, B12 and folate, and homocysteine were determined in 47 patients with OSAS and 37 healthy subjects. Of these, 27 patients who used continuous positive airway pressure (CPAP) for >4 h.night-1 were re-examined 12 months later. Patients with OSAS had lower TAS (1.4+/-0.16 versus 1.50+/-0.10 mmol.L-1), vitamin A (64+/-19 versus 74+/-17 microg.dL-1) and vitamin E levels (1,525+/-499 versus 1,774+/-503 microg.dL-1), and increased values of GGT (42+/-22 versus 32+/-16 U.L-1) than controls. There was no difference between groups in GPX, homocysteine, vitamin B12 and folate plasma levels. CPAP treatment normalised the levels of TAS (1.50+/-0.13 mmol.L-1) and the activity of GGT (30+/-14 U.L-1) without any influence on vitamins levels. In conclusion, the results indicate that patients with obstructive sleep apnoea syndrome have a decreased antioxidant capacity that is partially reversed by continuous positive airway pressure treatment.

Adult↗
PubMed2001

Phylogenetic analysis of viroid and viroid-like satellite RNAs from plants: a reassessment.

The proposed monophyletic origin of a group of subviral plant pathogens (viroids and viroid-like satellite RNAs), as well as the phylogenetic relationships and the resulting taxonomy of these entities, has been recently questioned. The criticism comes from the (apparent) lack of sequence similarity among these RNAs necessary to reliably infer a phylogeny. Here we show that, despite their low overall sequence similarity, a sequence alignment manually adjusted to take into account all the local similarities and the insertions/deletions and duplications/rearrangements described in the literature for viroids and viroid-like satellite RNA, along with the use of an appropriate estimator of genetic distances, constitutes a data set suitable for a phylogenetic reconstruction. When the likelihood-mapping method was applied to this data set, the tree-likeness obtained was higher than that corresponding to a sequence alignment that does not take into consideration the local similarities. In addition, bootstrap analysis also supports the major groups previously proposed and the reconstruction is consistent with the biological properties of this RNAs.

Evolution, Molecular↗
PubMed2000

An improved configuration of a moving wire transport detector.

An improved design of the transport detector is described that uses a pre-oxidized titanium ribbon as the transport medium. The titanium ribbon has a high loading capacity that permits a large proportion of the total column eluent to be taken into the sensing system. The solute is sensed by pyrolysis and the subsequent detection of pyrolysis products by a miniature argon detector. The pyrolyzer and sensor system is designed to ensure that all the pyrolysis products enter the detector with minimum dilution and band dispersion. As a result, the sensitivity of the detector (or minimum detectable concentration) has been reduced by approximately two orders of magnitude compared with the original design. The sensitivity of the system described to sucrose is 8 x 10(-8) g/mL, which is similar to the sensitivity of the fixed-wavelength UV detector to benzene (approximately 5 x 10(-8) g/mL). It would appear that the new design has potentially a sensitivity at least an order of magnitude lower than that reported here.

Journal Article↗
PubMed2000

Effect of deleterious mutation-accumulation on the fitness of RNA bacteriophage MS2.

RNA viruses show the highest mutation rate in nature. It has been extensively demonstrated that, in the absence of purifying selection, RNA viruses accumulate deleterious mutations at a high rate. However, the parameters describing this accumulation are, in general, poorly understood. The present study reports evidences for fitness declines by the accumulation of deleterious mutations in the bacteriophage MS2. We estimated the rate of fitness decline to be as high as 16% per bottleneck transfer. In addition, our results agree with an additive model of fitness effects.

Base Sequence↗
PubMed1999

Mapping the molecular determinant of pathogenicity in a hammerhead viroid: a tetraloop within the in vivo branched RNA conformation.

Chrysanthemum chlorotic mottle viroid (CChMVd) is an RNA of 398-399 nt that can adopt hammerhead structures in both polarity strands. We have identified by Northern-blot hybridization a nonsymptomatic strain (CChMVd-NS) that protects against challenge inoculation with the symptomatic strain (CChMVd-S). Analysis of CChMVd-NS cDNA clones has revealed a size and sequence very similar to those of the CChMVd-S strain. Some of the mutations observed in CChMVd-NS molecular variants were previously identified in CChMVd-S RNA, but others were never found in this RNA. When bioassayed in chrysanthemum, cDNA clones containing the CChMVd-NS specific mutations were infectious but nonsymptomatic. Site-directed mutagenesis showed that one of the CChMVd-NS-specific mutations, a UUUC --> GAAA substitution, was sufficient to change the symptomatic phenotype into the nonsymptomatic one without altering the final accumulation level of the viroid RNA. The pathogenicity determinant-to our knowledge, a determinant of this class has not been described previously in hammerhead viroids-is located in a tetraloop of the computer-predicted branched conformation for CChMVd RNA. Analysis of the sequence heterogeneity found in CChMVd-S and -NS variants strongly supports the existence of such a conformation in vivo, showing that the rod-like or quasi-rod-like secondary structure is not a universal paradigm for viroids.

Asteraceae↗
PubMed1996

Factors influencing physicians' prescribing behaviour in the treatment of childhood diarrhoea: knowledge may not be the clue.

Proper diarrhoea treatment has received greater attention during the last 10 years. However, the unjustified use of medicines to treat simple episodes of acute diarrhoea continues to divert attention and available resources away from appropriate treatment. A study to identify the factors determining prescribing practices for diarrhoea treatment was carried out in a peri-urban part of Lima, Peru in 1991. Physicians were interviewed, and then their practice was assessed by visits of confederates with healthy children described as ill, by interviews with mothers of sick children leaving the clinic, or by both of these methods. Physicians' reported practices in treating diarrhoea cases were compared to their actual practices. Although physicians' knowledge of drug management seemed to influence the low frequency of prescription of antidiarrhoeal drugs, it did not have the same influence on prescription of antimicrobials. Our results suggest that the diagnostic process and consequently the treatment decision do not follow a scientific rationale for this illness. The physicians' prescribing practices seemed to be more related to agreement with social expectations and the caretakers' perception of the physicians' role than they were to the standard biomedical rules of diarrhoea management.

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PubMedDate not supplied

Viroids with hammerhead ribozymes: some unique structural and functional aspects with respect to other members of the group.

Viroids, subviral pathogens of plants, are composed of a single-stranded circular RNA of 246-399 nucleotides. Within the 27 viroids sequenced, avocado sunblotch, peach latent mosaic and chrysanthemum chlorotic mottle viroids (ASBVd, PLMVd and CChMVd, respectively) can form hammerhead structures in both of their polarity strands. These ribozymes mediate self-cleavage of the oligomeric RNAs generated in the replication through a rolling circle mechanism, whose two other steps are catalyzed by an RNA polymerase and an RNA ligase. ASBVd, and presumably PLMVd and CChMVd, replicate and accumulate in the chloroplast, whereas typical viroids replicate and accumulate in the nucleus. PLMVd and CChMVd do not adopt a rod-like or quasi rod-like secondary structure as typical viroids do but have a highly branched conformation. A pathogenicity determinant has been mapped in a defined region of the CChMVd molecule.

Base Sequence↗