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Biomedical subjects

R Lara

Publications and source records attributed to R Lara.

At least 19 recordsLinked to original sources
PubMed1994

[Tenosynovitis caused by ciprofloxacin. Clinical case].

We report a 67 years old diabetic female that received ciprofloxacin for an acute pyelonephritis. Twelve days after starting this treatment, a hand and forearm tenosynovitis appeared, that subsided after the discontinuation of ciprofloxacin. Literature review disclosed other reports of tenosynovitis associated with the use of this antimicrobial.

Aged↗
PubMed1993

Surgery for PD.

Explore the source record for details and available documents.

Adrenal Medulla↗
PubMed1989

[Application of intrauterine device through the incision of the cesarean section].

Intrauterine devices (IUDs) were applied in 554 women during cesarean sections and the results were compared with the event rates presented in 804 women who received the IUD vaginally immediately postpartum. The expulsion rates at one month were 4.1 for the IUD inserted during the cesarean section and 7.5 for the post partum IUD. The expulsion rates at three months were 10.9 and 16.4 respectively. In a third group of 240 women who had cesarean sections but did not accept the IUD for contraception, the rate of endometritis at one month resulted in 0.8 compared with 1.1 for the group of cesarean section with IUD. Almost two thirds of the cesarean sections in both groups were performed on emergency bases. The application of the transcesarean IUD is considered to be safe procedure for fertility control.

Adult↗
PubMed1985

A neural model of interactions subserving prey-predator discrimination and size preference in anuran amphibia.

The model described is an extension of a previous model of the optic tectum (Arbib & Lara, 1982; Lara, Arbib & Cromarty, 1982; Lara & Arbib, 1982) and takes into consideration anatomical, physiological and behavioral studies in anurans, as well as earlier modelling efforts (Ewert & Von Seelen, 1974; Didday, 1976). Computer simulations were conducted to analyze how interactions among retina, optic tectum and pretectum may give frogs and toads the ability to discriminate between prey and predator stimuli. Results from simulations have allowed us to reproduce empirical observations, to suggest new experiments, and to postulate what neural mechanisms might be involved in some phenomena related to prey-catching orienting behavior, with direction invariance of prey-predator recognition being a consequence of tectal architecture, and size preference and response latency depending on the motivational state of the animal.

Animals↗
PubMed1985

A model of the neural mechanisms responsible for pattern recognition and stimulus specific habituation in toads.

A neural model of the mechanisms possibly responsible for stimulus-specific habituation in toads is proposed. The model follows the hypothesis that prey-predator recognition is performed by command units as a result of retina-tectum-pretectum interaction. The model allow us to study the possible coding that the nervous system of toads uses for different prey stimuli, the neural mechanisms of habituation and dishabituation, and the dynamic changes that the command units may have during these processes. The model proposes specific hypothesis and experiments to clarify the nature of these processes and to test the validity of the command unit hypothesis.

Animals↗
PubMed1984

A global model of the neural mechanisms responsible for visuomotor coordination in toads.

A model of how the nervous system of toads processes visual information to control motor behaviour is proposed. The problem of visuomotor coordination in toads is studied through the integration of two different approaches: a top-down approach through schema theory developed in the studies of cognitive psychology, artificial intelligence and brain theory; and a bottom-up approach through the integration of physiological, anatomical, ethological, and neural modelling. The model proposes that visual information is processed in a parallel distributed way through different brain layers whose interaction defines the proper motor response for that specific situation. It is postulated that visual processing of information is organized into main schemata, which set the goal to be attained and, depending on the specific circumstances of the animal, activates different brain layers; the main schemata may use other schemata to solve a specific subproblem to reach the schemata, and a programme of schema co-ordination. With this model we have simulated how toads plan their route to reach a prey or the route to go away form a predator, depending on the state of their three-dimensional world. The model postulates specific hypotheses that could be tested experimentally on the processing of information in the toad's nervous system.

Animals↗
PubMed1983

Synaptic competition in developmental binocular plasticity.

A mathematical model of the possible physiological and biochemical mechanisms responsible for the changes occurring during binocular development is proposed. The model is based on the mechanisms postulated for the occurrence of well known plastic processes, such as post-tetanic potentiation, sensitization and heterosynaptic inhibition. Because all these processes are of presynaptic nature, we have postulated that the plastic processes occurring during development are of the same nature. The factors we have considered in our model are: the transmitter pool size, the mobilization or synthesis of the transmitter, the transmitter release by the physiological stimulus, the neuroendocrine and genetic activity. With this model we have simulated the following phenomena during ocular development: (1) normal binocular development; (2) monocular deprivation, including the effects of reversing the occluded eye; (3) binocular deprivation and recovery; and (4) effects of alternating deprivation on mature binocularity. The model also allows us to explain in a natural way the possible changes occurring during denervation or disuse.

Animals↗
PubMed1982

A neural model of the interaction of tectal columns in prey-catching behavior.

Building on a simple model of a tectal column as the unit of processing in the amphibian tectum, we conduct a computer analysis of the interaction of a linear array of such columns. The model suggests that the inhibitory and excitatory activity in the tectum may have three functions: 1) spatio-temporal facilitation of column activity to a moving stimulus; 2) preference for the head of the stimulus, probably to avoid possible defensive reactions of the prey; and 3) modulating the state of excitation of the column once it has produced a response. The model also shows that the spatio-temporal effects of excitation and inhibition increases the acuity of the animal to the direction of the prey, through processes similar to lateral inhibition.

Animals↗
PubMed1982

The role of the tectal column in facilitation of amphibian prey-catching behavior: a neural model.

We used computer analysis of differential equations to study the properties of a family of models of a unit of neural circuitry in the amphibian tectum, the tectal column. Computer experiments were used to discriminate among various hypotheses and to suggest new experiments. Particular attention was paid to physiological data on facilitation of amphibian prey-catching behavior which led us to model the facilitation in terms of dynamic activity in the tectal column rather than in terms of synaptic modification.

Action Potentials↗
PubMed1980

Mathematical models of synaptic plasticity: I. Posttetanic potentiation.

A mathematical model of post-tetanic potentiation is proposed. The model uses differential equations and is based upon physiological postulates of the electrical, metabolic, and neuroendocrine activities that are related to synaptic connectivity. These activities may modify some important parameters in synaptic function. In the proposed model these parameters are restricted to the presynapse in view of the physiological evidence indicating that posttetanic potentiation is probably due to presynaptic mechanisms. The model takes into consideration the size of the transmitter pool available for release, the mobilization of transmitter from and to this pool, and the fraction of transmitter released. Based upon the above postulates, we have simulated different phases of the phenomenon of posttetanic potentiation, and we have presented the results of several preparations in which this event has been studied. This work represents a successful attempt to reproduce the dynamics of posttetanic potentiation based upon physiological results with a mathematical model.

Calcium↗
PubMed1980

Mathematical model of synaptic plasticity: II. Habituation.

A mathematical model of the phenomenon of habituation as a homosynaptic depression of the amount of transmitter release is proposed. The model is based on the physiological studies of habituation in invertebrates and in the spinal cord of vertebrates, where a single synapse has been isolated and some of the physiological mechanisms of this process have been elucidated. The model simulates the following properties of habituation: (1) reduced amount of transmitter release attributed to a repetitive stimulus through changes in the membrane permeability to Ca2+ ions; (2) spontaneous recovery by rest; (3) the amplitude and frequency dependence of habituation; (4) modulation of habituation: sensitization, through an increase in membrane Ca2+ permeability, and presynaptic inhibition, through a reduced depolarization of the physiological stimulus; (5) long-term habituation attributed to repetitive trials of habituation and spontaneous recovery.

Animals↗
PubMed1980

Mathematical model of synaptic plasticity: III. Heterosynaptic changes.

A mathematical model, using differential equations, of heterosynaptic plasticity is proposed. The model is based on physiological studies of invertebrates in which nonspecific conditioning, such as sensitization and heterosynaptic inhibition, starts to be elucidated and behavioral studies of classical and instrumental conditioning, which we postulate to have the same mechanisms as those found in nonspecific conditioning. The model permits us to simulate the following heterosynaptic changes: sensitization, heterosynaptic inhibition, classical and instrumental conditioning--including short- and long-term memory--extinction and recuperation--spontaneously and by stimulation.

Animals↗