Biomedical subjects
Publications and source records attributed to R Jáuregui.
We demonstrate the experimental generation at optical frequencies of the lowest- and first-order Bessel beams with TE and TM polarizations in free space by means of a Mach-Zehnder interferometer. The polarization and angular momentum properties of these waves are analyzed and discussed.
We have performed a computer analysis to study the prevalence of DNA static curvature in the regulatory regions of Escherichia coli, detecting a large number of operons with curved DNA fragments in their 5' upstream regions. A statistical analysis reveals that all the global transcription factors identified so far in E. coli have a tendency to regulate operons with curved DNA sequences in their upstream regions. In addition to these global regulators, we also found that the PurR, ArgR, FruR, TyrR, and CytR specific regulators present a similar propensity. Interestingly, for these cases we found no previous reference describing a possible relationship with curved DNA regions. To validate our theoretical results, we performed site-directed mutagenesis to reduce the degree of DNA curvature in the regulatory sequences of the aroG, pyrC, and argCBH operons. The effects of these changes were measured by polyacrylamide gel electrophoresis assays and further evaluated in vivo by transcriptional fusions to a reporter gene. All our results point toward a more widespread role of curved DNA in gene transcription, a fact that has previously been underestimated.
To study possible relationships between an organism's genomic DNA curvature and the aminoacid composition of its proteome, every peptidic sequence from fully determined genomes was retrotranslated using the E. coli codon preferences, and the curvature profiles of the resulting DNA sequences were calculated and compared. A clear interdependence between these two variables was observed, as each retrotranslated proteome presented a distinctive, statistically significant DNA curvature profile biased toward its natural DNA curvature profile. In addition, by comparing the profiles arising from real and randomly permuted proteomes, we also found a position-dependent contribution of the peptidic sequence to DNA curvature. The implications of these results support the idea of a possible selection toward a specific global curvature of genomes.
Static DNA curvature distributions of full-sequenced genomes and large DNA contigs from different organisms were calculated. Very distinctive differences among histogram profiles coming from archaebacteria, eubacteria, and eukaryotes were observed. Eubacterial profiles were, on average, more curved than were archaeal and eukaryotic profiles. A comparative analysis between real and randomized DNA sequences revealed that eubacterial genomes presented, overall, higher curvature values than random sequences. An opposite portrait was exhibited by archaeal and eukaryotic genomes. They displayed a lower frequency of curved regions than their corresponding randomized sequences. The contributions of coding and intergenic regions to the curvature profile were also analyzed. Intergenic regions, on average, were found to be more curved than the overall genomic sequences, especially in prokaryotic organisms. Nevertheless, because of their small size with respect to coding regions, the contribution of intergenic sequences to the overall curvature profile tended to be minor. A clear relationship between codon usage and DNA curvature was demonstrated, and a proposal of the possible coevolution of both systems is discussed. Finally, we present a procedure to quantify the deviation of a curvature profile from randomness through a formal statistical analysis.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
The risk of suddenly presenting ventricular tachyarrhythmias or death was analyzed in a prospective way in 71 patients with acute myocardial infarction and in 21 patients without any apparent cardiopathy. The average surface signal was measured when the patient was admitted in the hospital and on the following days of the acute phase of the infarction. Holter 24 hours monitoring and determination of the ejection fraction with radionuclide angiocardiography were also performed. Patients were divided into 4 groups, depending on the existence of arrhythmias and if late electric activity was recorded or not. Fifty-five patients (group I), presented an abnormal signal analysis (voltage in the 40 msec of the QRS period higher than 20 microvolts), and ventricular arrhythmias. Group II was formed by 8 patients who presented arrhythmogenic activity but did not present late electric activity. Group III was formed by 6 patients who did not present arrhythmias but presented late electric activity. Twenty-three patients who did not present late electric activity or ventricular arrhythmias formed group IV. Late electric activity that was registered at 41 +/- 1 msec with a QRS complex lasting 115 +/- 4 msec and with a voltage lower than 20 microvolts in group I showed meaningful differences with the other groups: Group II: (24 +/- 5 msec, QRS 111 +/- 4 msec, P less than 0.001); Group III: (41 +/- 2 msec, QRS 109 +/- 5 msec, P less than 0.01); Group IV: (26 +/- 5 msec, QRS 80 +/- 7 msec, P less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)