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S Ruiz

Publications and source records attributed to S Ruiz.

At least 109 records · Page 6Linked to original sources
PubMed1986

Prefrontal cortex excitability in early postnatally malnourished rats.

The effect of early postnatal malnutrition on the responsiveness of the rat prefrontal cortex was studied by determining excitability thresholds and fatigability to direct cortical stimulation. Malnutrition imposed during the period of rapid brain growth caused a significant increase of cortical chronaxie values as well as increased fatigability of direct cortical responses, indicating a detrimental effect on the axodendritic synapses. Since the prefrontal cortex plays an important role in the temporal organization of behavior, a dysfunction of this cortical area could be a causal link between nutritional and behavioral deficits.

Animal Population Groups↗
PubMed1985

Effect of early malnutrition on dynamic properties of axodendritic synapses in the rat prefrontal cortex.

The influence of early protein-calorie malnutrition on synaptic transmission in the rat prefrontal cortex was studied by evoking direct cortical responses with different trains of threshold electrical pulses. Malnutrition resulted in a requirement for increased pulse train stimulating current, reflecting a diminished release of neurotransmitter from the preterminal endings. In addition there was an increase in the time constant of pyramidal cells, indicating that axodendritic synapses have a disability for integrating high frequency inputs at the post synaptic level. It is concluded that early malnutrition alters dynamic properties of axodentritic synapses at both the pre- and the postsynaptic levels.

Age Factors↗
PubMed1985

Malnutrition-induced changes of responses evoked in the rat prefrontal cortex as revealed by sensitivity to strychnine.

Susceptibility to strychnine of somatosensory responses evoked in the prefrontal cortex was studied in normal and protein-malnourished rats in three groups. (a) The normal group was from mothers fed a 21% casein diet. (b) The prenatally malnourished group was from mothers fed a 6% casein diet during 5 weeks prior to mating and throughout gestation. (c) The postnatally malnourished group born from dams fed a 6% casein diet throughout the nursing period. At 45 days of age, sensitivity of the responses to 0.5% strychnine sulfate solution was tested by measuring changes in peak-to-peak amplitude. The results showed that cortical neurons of the postnatally protein-restricted group had decreased susceptibility to strychnine, indicating functional disturbances of glycinergic synapses.

Animals↗
PubMed1984

Long-term effects of early undernutrition on reactivity of the rat parietal association cortex.

Cortical reactivity of the parietal association area was studied in undernourished rats after short and long rehabilitation periods. Undernutrition was induced during lactation by increasing litter size from 8 to 18 pups per nurse. At either 40 or 100 days of age, cortical chronaxie, and both fatigability and latencies of direct cortical evoked responses were determined. At the two ages, results showed that early postnatal malnutrition induced higher chronaxies, greater fatigability and longer latencies of the responses compared with normal animals, indicating the existence of long-term functional alterations of that cortical area.

Animals↗
PubMed1984

Effect of early iron deficiency on reactivity of the rat parietal association cortex.

The effect of early iron deficiency on the reactivity of the rat parietal association cortex was studied by determining excitability thresholds, fatigability and extension of the responsive field to direct cortical stimulation. Iron deficiency during the period of rapid brain growth caused a significant increase of cortical chronaxie values as well as increased fatigability of direct cortical responses, indicating a detrimental effect on the axodendritic synapses. Since the parietal association area plays an important role in brain association processes, a dysfunction of this cortical area could be a causal link between early iron deficiency and behavioral or learning deficits.

Anemia↗
PubMed1983

Temporal summation in rat prefrontal pyramidal cells. Differential effects of pre- and postsynaptic neurochemical manipulations.

The influence of both reserpine-induced depletion of catecholamines and chlorpromazine-induced blockade of dopamine receptors on integrative properties of rats prefrontal pyramidal cells was studied by evocating threshold direct cortical responses with different trains of electrical pulses. Catecholamine depletion results in increased pulse train stimulating currents for eliciting threshold cortical responses, whereas chlorpromazine blockade of dopamine receptors results in higher time constants characterizing postsynaptic temporal summation. It is suggested that the leaky-integrator neuron model may be a discriminating paradigm for detecting electrophysiologically the pre- or postsynaptic level of occurrence of some synaptic disorders.

Animals↗
PubMed1981

Effect of prenatal malnutrition on cortical reactivity of the rat parietal association area.

The influence of prenatal malnutrition on the reactivity of the rat parietal association cortex was studied by testing thresholds of direct cortical responses. Chronic and acute prenatal starvation caused a significant increase of cortical chronaxy values, indicating a detrimental effect on the axodendritic synapses. Since these synapses subserve cortico-cortical influxes underlying association processes, this detrimental effect could be correlated with behavioral and learning deficits found in malnutrition.

Animals↗
PubMed1980

Cortical facilitatory effect of mefenamic acid.

Mefenamic acid intravenously injected or locally applied upon the cerebral cortex increases the amplitude of the evoked responses recorded in the somatosensory S1 cortex. This facilitatory effect supports previous EEG studies showing that this drug also has central actions. In light of the present result it is suggested that the central action induced by mefenamic acid occurs at the cortical level.

Animals↗
PubMed1978

Differential effect of pentazocine on primary cortical evoked potentials elicited by stimulation of the trigeminal tract and spinal cord pathways.

The influence of pentazocine on primary cortical evoked potentials was studied in guinea pigs under pentobarbital anesthesia. Pentazocine (10 mg/kg, i.v.) increased the latency time of evoked responses to posterior limb stimulation, more than that of response to lip stimulation. This result suggests that pentazocine decreases the velocity of nervous conduction.

Animals↗
PubMed1977

Effects of electrical stimulation of periaqueductal gray matter on evoked potentials recorded in the primary somesthetic cortical areas of the rat.

The influence of focal electrical stimulation of PGM on primary cortical evoked potentials elicted by nociceptive peripheral stimulation was studied in anaesthetized and conscious rats. This analgesic electrical stimulation produces an abolition of cortical responses during its application and a significant decrease of the positive and negative amplitude waves after interruption of PGM electrical stimulation. Since these effects were observed in animals under barbiturate anesthesia and in conscious rats, they are interpreted as a supraspinal action on the primary pain pathway.

Animals↗
PubMed1975

Effect of pentazocine on the evoked potentials recorded in the primary somesthetic cortical areas of guinea pigs.

The influence of pentazocine on the evoked potentials registered in the primary somesthetic cortical area in guinea pigs under pentobarbital anesthesia was studied. The stimulation was applied in the contralateral lip and the evoked cortical responses from different zones on the cortex stereotaxically localized were registered. Pentazocine (5-10 mg/kg i.v.) induced a significant increase in the latency of the evoked potentials as compared with controls. Since morphine does not modify these potentials, the effect of pentazocine is interpreted as being a direct one on the primary pain pathway.

Animals↗
PubMedDate not supplied

Application of inducible and targeted gene strategies to produce transgenic fish: a review.

Compared to mammals, fishes offer easier transgenic technology because each female produces hundreds of eggs, the manipulated embryos do not need to be incubated inside the mother, and the probability of their harboring human-related pathogens is lower. In the last 15 years, traditional methods using injections of fertilized fish eggs and strong viral promoters have resulted in the generation of many transgenic fish species; however, they showed random genome integration with some mosaicism and episomic expression. The use of inducible gene systems that control temporal and tissue expression and of gene-targeting methodologies based on homologous recombination is desirable to control the expression, efficiency of insertion, and locus of incorporation of transgenes into fish genomes. A variety of systems developed for mammals are now available to be tested in fishes. The use of such systems would require further development of stem cell or nuclear transplant technologies in fish. Most of that work remains to be explored.

Animals↗
PubMedDate not supplied

Intracanalicular arachnoid cyst mimicking acoustic neuroma: CT and MRI.

A patient with a surgically proven intracanalicular arachnoid cyst was studied using computed tomography, magnetic resonance imaging, and air CT cisternography. The lesion had a similar radiographic appearance to acoustic neuroma and therefore, although rare, must be considered in the differential diagnosis of intracanalicular mass lesions. We report a case in which examination was performed, in evaluating the lesion, utilizing high-resolution air CT cisternography and magnetic resonance imaging (MRI).

Adult↗
PubMedDate not supplied

MRI diagnosis of biceps tendon rupture.

Distal biceps tendon rupture is a rare injury. While plain radiographs are usually not helpful in visualizing the defect, evaluation of the tendon with MRI has proven to be useful as it depicts complete anatomic detail of the tendon and associated structures. Its multiplanar imaging capability and superior soft tissue contrast resolution makes MRI a prime diagnostic tool in the diagnosis of tendon disorders. We report a case of complete rupture of the biceps tendon diagnosed by MRI.

Adult↗
PubMedDate not supplied

[Radiofrequency ablation of hepatic tumors].

This article aims to review the state of the art in ablation techniques for hepatic lesions. In addition to discussing the indications, outcomes, and potential complications of the technique, we illustrate the spectrum of imaging findings after treatment. Recent years have seen the development of a wide variety of minimally invasive techniques to treat liver cancer. These include ethanol injection, and thermal ablation using radiofrequency, laser, microwaves, or cryosurgery. Percutaneous radiofrequency ablation is one of the most promising non-surgical treatments for hepatic neoplasms. The results of several studies show that radiofrequency ablation enables adequate local control of tumors with few complications, achieving acceptable survival rates. Radiofrequency ablation can be performed using any imaging technique, although it is most commonly performed under ultrasound guidance. CT and MRI show the degree of tumor necrosis better and are more frequently employed in follow up. This article reviews the indications and contraindications for the procedure, potential complications, long-term outcome, and imaging findings for percutaneous radiofrequency ablation of hepatic tumors.

Carcinoma, Hepatocellular↗
PubMedDate not supplied

Reaction engineering for consecutive enzymatic reactions in peptide synthesis: application to the synthesis of a pentapeptide.

A single-pot enzymatic synthesis of Z-CCK5 (4-8) is presented in this work, employing Z-Gly-Trp-OBzl as acyl donor, under kinetic control. The first goal of the work is the development of a synthetic strategy allowing the use of the same medium for two reactions catalyzed by immobilized alpha-chymotrypsin, discriminating between simultaneous and consecutive addition systems. The second goal is the maximization of the pentapeptide yield as a function of the molar excess of both nucleophiles employed. A maximum yield of 36% was obtained, and the addition strategy as well as the optimal initial concentrations of substrates have been determined.

Acetonitriles↗