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Biomedical subjects

S M Lopez

Publications and source records attributed to S M Lopez.

6 recordsLinked to original sources
PubMed1999

Relationship between EABR thresholds and levels used to program the CLARION speech processor.

The purpose of this study was 1) to describe the relationship between electrically evoked auditory brain stem response (EABR) thresholds and the behavioral measures needed to program the speech processor of the CLARION Multi-Strategy Cochlear Implant, and 2) to determine whether the relationship between EABR threshold and the behavioral levels used to program the Clarion device was correlated with the temporal integration abilities of these subjects. The EABR thresholds, psychophysical thresholds, and the Clarion speech processor programming levels were recorded from 29 postlingually deafened adults. The mean EABR thresholds approximated most comfortable levels (M levels) for the programming stimulus. However, intrasubject variability was substantial. Significant intrasubject variability in temporal integration also was observed. Correlations were found between the ability of a cochlear implant user to perform temporal integration and the relationship between his or her EABR threshold and the threshold for the programming stimulus.

Adult↗
PubMed1996

Innovative techniques in pediatric liver transplantation: reduced-, split- and living-donor related liver transplantation.

In spite of the increased number of organ donations, the amount of livers available for pediatric patients does not meet requirements. In an attempt to expand the pool of grafts, several techniques of size reduction (RST) have been developed: reduced-liver transplantation (RLT), liver segment transplantation (LST), "split" liver transplantation (SLT) and living-donor liver transplantation (LDLT). The aim of this work is to study the contribution of these techniques to reduction of mortality in the waiting list and the increased risks that we inflict to our patients by using these procedures. We report our experience on RST in the last nine years (23 RLT, 5 LST, 2 SLT and 3 LDLT). More than a half of them were performed in an emergency. Overall survival in children with RST (67%) is similar to that of patients receiving a "whole graft" (74%). We did not find significant differences in the incidence of graft-related complications, only reintervention for abdominal bleeding was needed more often in the RST group (30%) than in whole graft group (24%). Our data confirm the safety of the RST procedures in the pediatric liver transplantation programs and they decrease the waiting-list mortality (2.5%) among the pediatric patients.

Adolescent↗
PubMed1995

Brain large neutral amino acids and catecholamines in parenterally nourished preterm rabbits.

Total parenteral nutrition (TPN) has been adapted as a standard for providing nutrition to ill term and preterm infants. The availability of tyrosine in amino acid preparations utilized for TPN is limited and may potentiate a tyrosine-deficient state. Phenlyalanine hydroxylase activity, responsible for catalyzing tyrosine synthesis, has been suggested to be decreased in fetal and neonatal animals. Parenterally nourished premature rabbits (n = 16) and suckled rabbits (n = 19) were studied in order to compare growth parameters and amino acids in the plasma and brain, as well as whole brain catecholamine concentrations. Influx velocities into the brain of amino acids were also determined in these two groups. The preterm rabbit's average birth weight (42.6 +/- 6.0) was less than that of term rabbits (56.7 +/- 8.7, P < 0.005). Significantly lower concentrations of the catecholamine precursor tyrosine were found in both the plasma and brain of the parenterally nourished animals compared to the suckled animals. Tyrosine is reduced in the brain in TPN-supported animals reflecting both low tyrosine intake and increased plasma concentrations of large neutral amino acids that compete for uptake at the blood-brain barrier. However, no difference was observed between the two groups in their brain catecholamine concentrations. The seven-day parenterally nourished rabbit appears to be tyrosine-deficient but no evident effects on brain catecholamine concentrations were seen. The effects and impact of a tyrosine-deficient state might better be evaluated by regional evaluation of catecholaminergic areas of the brain or over a longer period of parenteral nutrition.

Amino Acids↗