Biomedical subjects

Veronica Rodriguez

Publications and source records attributed to Veronica Rodriguez.

4 recordsLinked to original sources

PubMed2004

Exploratory EEG data analysis for psychophysiological experiments.

A method for the exploratory analysis of electroencephalographic (EEG) data for neurophysiological experiments is presented. It is based on a time-frequency decomposition of the EEG time series, which is measured by several electrodes in the scalp surface, and includes the computation of a statistic that measures the deviations of the log-power with respect to the pre-stimulus average; the computation of a significance index for these deviations; a new type of display (the time-frequency-topography plot) for the visualization of these indices, and the segmentation of the time-frequency plane into regions with uniform activation patterns. As a particular example, an experiment to study EEG changes during figure and word categorization is analyzed in detail.

Algorithms↗

PubMed2003

Role of helices and loops in the ability of apolipophorin-III to interact with native lipoproteins and form discoidal lipoprotein complexes.

The structure of Locusta migratoria apolipophorin-III consists of a five-helix bundle connected by four short loops. The role of the conformational flexibility of helices and loops on the lipid-binding activity of this apolipoprotein was investigated by disulfide mediated tethering experiments. One disulfide mutant tethering the second and fourth loops (L2-L4), and two disulfide mutants restricting the flexibility of the neighboring alpha-helices 3 and 4 (H3-H4) and 1 and 5 (H1-H5), were studied. The ability of the disulfide mutants to interact with phospholipid vesicles, mixed micelles of phosphatidylcholine and cholate, and in vivo with native spherical lipoprotein particles was studied. The L2-L4 mutant was active with native lipoproteins as well as being able to form discoidal lipoproteins upon incubation with either liposomes or discoidal micelles. The H3-H4 mutant was not able to interact with liposomes or native lipoproteins but interacted with discoidal micelles. The H1-H5 mutant was unable to interact with lipid in any of the three systems. Three conclusions were reached: (1) opening of the helix bundle does not require the separation of loops 2 and 4 as recently proposed by others and (2) alpha-helices 3 and/or 4 are involved in the insertion of apoLp-III in both phospholipid bilayers and monolayers. The conformational flexibility of helices 3 and 4 is required for the lipid-binding activity of apoLp-III. (3) Interaction of helices 1 and/or 5 with the lipid surface is required to the formation of stable lipoprotein complexes of any kind.

Animals↗

PubMed2003

GLUT-1 overexpression: Link between hemodynamic and metabolic factors in glomerular injury?

Mesangial matrix deposition is the hallmark of hypertensive and diabetic glomerulopathy. At similar levels of systemic hypertension, Dahl salt-sensitive but not spontaneously hypertensive rats (SHR) develop glomerular hypertension, which is accompanied by upregulation of transforming growth factor beta1 (TGF-beta1), mesangial matrix expansion, and sclerosis. GLUT-1 is ubiquitously expressed and is the predominant glucose transporter in mesangial cells. In mesangial cells in vitro, GLUT-1 overexpression increases basal glucose transport, resulting in excess fibronectin and collagen production. TGF-beta1 has been shown to upregulate GLUT-1 expression. We demonstrated that in hypertensive Dahl salt-sensitive (S) rats fed 4% NaCl (systolic blood pressure [SBP]: 236+/-9 mm Hg), but not in similarly hypertensive SHR (SBP: 230+/-10 mm Hg) or their normotensive counterparts (Dahl S fed 0.5% NaCl, SBP: 145+/-5 mm Hg; and Wistar-Kyoto, SBP: 137+/-3 mm Hg), there was an 80% upregulation of glomerular GLUT-1 protein expression (P< or =0.03). This was accompanied by a 2.7-fold upregulation of TGF-beta1 protein expression in glomeruli of DSH compared with DSN rats (P=0.02). TGF-beta1 expression was not upregulated and did not differ in the glomeruli of Wistar-Kyoto and SHR rats. As an in vitro surrogate of the in vivo hemodynamic stress imposed by glomerular hypertension, we used mechanical stretching of human and rat mesangial cells. We found that after 33 hours of stretching, mesangial cells overexpressed GLUT-1 (40%) and showed an increase in basal glucose transport of similar magnitude (both P< or =0.01), which could be blocked with an anti TGF-beta1-neutralizing antibody. These studies suggest a novel link between hemodynamic and metabolic factors that may cooperate in inducing progressive glomerular injury in conditions characterized by glomerular hypertension.

Animals↗

PubMed2002

Detection of a novel Tet M determinant in tetracycline-resistant Neisseria gonorrhoeae from Uruguay, 1996-1999.

BACKGROUND: Determination of the diversity within the tet(M) sequence from N gonorrhoeae is a useful epidemiologic tool for monitoring the movement or importation of strains within a geographic region. Only two distinct tet(M) genes in clinical gonococcal isolates have been described up to now: the Dutch and the American types. GOAL: The study involved surveillance of the tet(M) gene types in high-level-tetracycline-resistant gonococcal isolates from Uruguay during the period 1996 to 1999. STUDY DESIGN: Among 181 gonococcal isolates, those showing MICs >/=16 microg/ml to tetracycline were analyzed for detection and characterization of the tet(M) gene by a polymerase chain reaction (PCR) and further HpaII restriction fragment polymorphism methods, respectively. The plasmid content and antibiogram were determined. RESULTS: Twenty-two of 181 isolates (12%) exhibited high levels of resistance to tetracycline (MICs >/=16 microg/ml) and harbored a putative 25.2-Mda plasmid that contained the tet(M) gene. A high percentage of isolates (95%; 21/22) presented the Dutch type tet(M) gene. One isolate from 1999 revealed a new restriction pattern. Such a pattern had been previously noted in 1991. This new restriction pattern has not been described previously as occurring in isolates of N gonorrhoeae. The tet(M) amplimer sequence showed 100% identity with a previously described tet(M)-carrying plasmid from N meningitidis. CONCLUSION: A new HpaII restriction pattern of the tet(M) gene is present in low frequency. The tet(M) sequence was different from the gonococcal tet(M) sequences already known and not typable with the use of a differential PCR assay. Accordingly, with the genetic diversity already present within the tet(M) sequence of N gonorrhoeae isolates, we should be aware of the sensitivity of the PCR assays in use for tetracycline-resistant N gonorrhoeae detection.

Anti-Bacterial Agents↗