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Biomedical subjects

R Huerta

Publications and source records attributed to R Huerta.

At least 55 records · Page 3Linked to original sources
PubMed1991

[Complex I (NADH coenzyme-Q-reductase) deficiency, MELAS syndrome and hypertrophic cardiomyopathy].

A 24-year-old male had a deficiency of the complex I (NADH coenzyme-Q-reductase) of the mitochondrial respiratory chain, which clinically presented as a mitochondrial encephalomyopathy, with lactic acidosis and stroke-like episodes (MELAS syndrome). The encephalopathic episodes were preceded by migraine and were characterized by focal deficit signs, motor partial seizures and hypodense areas in the CT scan. An echocardiographic diagnosis of hypertrophic cardiomyopathy without intracavitary thrombi was made. It is suggested that hypertrophic cardiomyopathy is caused by the mitochondrial abnormalities that have been reported in the myocardium, and that migraine and cerebral infarctions are associated with abnormalities in the mitochondria from the endothelium and smooth muscle fibres of the cerebral small arteries and arterioles.

Acidosis, Lactic↗
PubMedDate not supplied

Adherence to treatment and social support in patients with non-insulin dependent diabetes mellitus.

We carried out a cross-sectional study to investigate factors associated with adherence to diet and medication in non-insulin-dependent diabetes mellitus (NIDDM) patients. A total of 200 patients not seeking treatment from clubs for diabetics from two hospitals in León, Mexico, accepted inclusion. Patients interviewed had a mean age of 58.8 (53.3-56.4, 95% C.I.) years. We evaluated adherence to diet and medication, knowledge on diabetes, social support, family's structure and functioning (with a modified McMaster model), metabolic control, and complications. Stepwise multiple regression procedure showed that adherence to diet was associated with years since diagnosis (p = 0.003) and with social support (p = 0.007). Adherence to medication was associated with social support (p = 0.002), and the age of the spouse (p = 0.016). Adherence to medication was lower in patients from families with rigid control than in the group with Laissez-faire type of control (p = 0.010) or the group with flexible control (p = 0.002). Social support was lower in the group with chaotic control than that in the group with flexible control (p < 0.001). Compliance to diet was associated with peripheral neuropathy and plasma creatinine, and adherence to medication with plasma glucose and peripheral neuropathy. We concluded that (1) adherence to treatment in NIDDM patients is associated with social support; (2) some aspects related to the family, such as the age of the spouse and the control of behavior, were also associated with compliance to treatment; and (3) it is important for the practicing physicians, and for institutional programs, to consider factors associated with adherence to treatment.

Adult↗
PubMedDate not supplied

Connection topology dependence of synchronization of neural assemblies on class 1 and 2 excitability.

Two main classes of excitable neurons are analyzed in terms of connection topology and strength of the coupling in a network of neurons. In both cases, we measure the degree of synchronization and responsiveness of the neural assembly. Class 2 excitability presents a fast wave-like propagation of the activity pattern, strong frequency dependence on the connection topology and a good level of synchronization regardless of the topology. On the other hand, class 1 excitability shows a strong dependence of the wave propagation speed and the synchronization degree on the connection topology, in addition no frequency adaptation is observed. We conclude that both types of neural excitability endow the neural assembly with very different dynamical properties. Although, for simplicity reasons, no inhibition has been included in our study, the emergent properties described in this paper may help to determine the class of excitability underlying a neural assembly.

Action Potentials↗
PubMedDate not supplied

Regularization mechanisms of spiking-bursting neurons.

An essential question raised after the observation of highly variable bursting activity in individual neurons of Central Pattern Generators (CPGs) is how an assembly of such cells can cooperatively act to produce regular signals to motor systems. It is well known that some neurons in the lobster stomatogastric ganglion have a highly irregular spiking-bursting behavior when they are synaptically isolated from any connection in the CPG. Experimental recordings show that periodic stimuli on a single neuron can regulate its firing activity. Other evidence demonstrates that specific chemical and/or electrical synapses among neurons also induce the regularization of the rhythms. In this paper we present a modeling study in which a slow subcellular dynamics, the exchange of calcium between an intracellular store and the cytoplasm, is responsible for the origin and control of the irregular spiking-bursting activity. We show this in simulations of single cells under periodic driving and in minimal networks where the cooperative activity can induce regularization. While often neglected in the description of realistic neuron models, subcellular processes with slow dynamics may play an important role in information processing and short-term memory of spiking-bursting neurons.

Action Potentials↗
PubMedDate not supplied

Dynamical coding of sensory information with competitive networks.

Based on experiments with the locust olfactory system, we demonstrate that model sensory neural networks with lateral inhibition can generate stimulus specific identity-temporal patterns in the form of stimulus-dependent switching among small and dynamically changing neural ensembles (each ensemble being a group of synchronized projection neurons). Networks produce this switching mode of dynamical activity when lateral inhibitory connections are strongly non-symmetric. Such coding uses 'winner-less competitive' (WLC) dynamics. In contrast to the well known winner-take-all competitive (WTA) networks and Hopfield nets, winner-less competition represents sensory information dynamically. Such dynamics are reproducible, robust against intrinsic noise and sensitive to changes in the sensory input. We demonstrate the validity of sensory coding with WLC networks using two different formulations of the dynamics, namely the average and spiking dynamics of projection neurons (PN).

Animals↗
PubMedDate not supplied

Reliable circuits from irregular neurons: a dynamical approach to understanding central pattern generators.

Central pattern generating neurons from the lobster stomatogastric ganglion were analyzed using new nonlinear methods. The LP neuron was found to have only four or five degrees of freedom in the isolated condition and displayed chaotic behavior. We show that this chaotic behavior could be regularized by periodic pulses of negative current injected into the neuron or by coupling it to another neuron via inhibitory connections. We used both a modified Hindmarsh-Rose model to simulate the neurons behavior phenomenologically and a more realistic conductance-based model so that the modeling could be linked to the experimental observations. Both models were able to capture the dynamics of the neuron behavior better than previous models. We used the Hindmarsh-Rose model as the basis for building electronic neurons which could then be integrated into the biological circuitry. Such neurons were able to rescue patterns which had been disabled by removing key biological neurons from the circuit.

Animals↗