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Biomedical subjects

A García-Tejedor

Publications and source records attributed to A García-Tejedor.

5 recordsLinked to original sources

Intrapartum fetal invasive procedures and perinatal transmission of HIV.

OBJECTIVE: To study the effect of intrapartum use of fetal invasive procedures (scalp electrodes or scalp pH sampling) on perinatal transmission rate of HIV. STUDY DESIGN: We compared the perinatal transmission of 57 HIV pregnancies in which invasive procedures (IP) were performed with a control group of 214 pregnancies without IP. We controlled for potentially risk factors (maternal CD4 level, gestational age, antiretroviral therapy use, duration of rupture of membranes (ROM), length of labor and mode of delivery) by stratification and logistic regression. RESULTS: Transmission rate in the group with IP was 26.3% (15/57) versus 13.6% (29/214) in the control group, relative risk (RR) 1.9, 95% CI (1.1-3.4). By logistic regression we observed three significant factors involved in transmission of HIV: low maternal CD4 level (odds ratio (OR)=3.3, 95% CI=1.2-9.4), duration of ROM (OR=2.9, 95% CI=1.1-7.9) and IP use (OR=3.5, CI 95%=1.2-9.6). Interaction between duration of ROM and IP are also significant (OR=5.1, CI 95%=1.5-17.5). CONCLUSIONS: Intrapartum use of fetal scalp electrodes or fetal scalp pH sampling increases the perinatal transmission of HIV and should therefore be avoided in HIV patients.

CD4 Lymphocyte Count↗

Influence of the hypercycle on the error threshold: a stochastic approach.

The role of fluctuations on the error threshold of the hypercycle has been studied by a stochastic approach on a very simplified model. For this model, the master equation was derived and its unique steady state calculated. This state implies the extinction of the system. But the actual time necessary to reach the steady state may be astronomically long whereas for times of experimental interest the system could be near some quasi-stationary states. In order to explore this possibility a Gillespie simulation of the stochastic process has been carried out. These quasi-stationary states correspond to the deterministic steady states of the system. The error threshold shifts towards higher values of the quality factor Q. Moreover, information about the fluctuations around the quasi-stationary states is obtained. The results are discussed in relation to the deterministic states.

Animals↗

A BASIC microcomputer program to calculate the secondary structure of proteins from their circular dichroism spectrum.

A BASIC program (CDPROT) has been developed to calculate the secondary structure of proteins from their far UV circular dichroism spectrum. This implementation can use different reference spectra, calculated either from model polypeptides or proteins of known tertiary structure. Apart from obtaining the alpha-helical, beta-structure, beta-turns or random percentages which would generate the spectrum of best fit with respect to the experimental measures, CDPROT represents on screen both theoretical and experimental spectra indicating the root-mean-square error. The provision of additional reference spectra by the user is also considered, and another program (STOREREF) performs the editing in an adequate format for CDPROT.

Algorithms↗

Studies on evolutionary and selective properties of hypercycles using a Monte Carlo method.

The most relevant properties of hypercycles were previously studied mainly from a theoretical point of view. We have developed a Monte Carlo method simulating hypercyclic organization to obtain information about the dynamics of this prebiotic organization. Nucleation, growth, and selective properties have been tested and the results obtained are in good agreement with those of the theoretical predictions. The influence of hypercyclic organization on the "error threshold" has also been studied. As a consequence of the emergence of a hypercycle, the value of this threshold decreases. The amount of this decrease depends on the population size. Moreover, for some interval of quality factor values, either the hypercycle organization or an error catastrophe can be produced, depending on the initial conditions. The influence of these phenomena on both the dynamic behavior and evolutionary advantages of the hypercycle, as well as their decisive roles on genome size, are discussed.

Biological Evolution↗