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Biomedical subjects

H Perez

Publications and source records attributed to H Perez.

At least 37 records · Page 2Linked to original sources
PubMed1989

Effect of clonidine early in life on brain morphofunctional deficits induced by neonatal malnutrition in the rat.

A great body of evidence indicates that malnutrition early in life induces central noradrenergic hyperactivity (CNH). On the other hand, it is known that noradrenaline (NA) is an important regulator of the regressive processes occurring during synaptogenesis such as cell death, axonal pruning and synaptic elimination. This leads to the hypothesis that some of the morphofunctional modifications induced by malnutrition on the brain could be due, at least in part, to an increase of NA activity during the period of accelerated brain growth. This study evaluates whether early reduction of CNH by the alpha-2 presynaptic adrenoreceptor agonist clonidine, prevents long-term morphofunctional deficits induced by protein-energy malnutrition in the rat. Results of experiments performed on 45 day-old malnourished animals that received clonidine during the suckling period, show that the pharmacological treatment prevented: (i) deficits in both NA levels and NA release in the visual cortex; (ii) deficit in brain weight but not in body weight; and (iii) reduction of the normal brain interhemispheric asymmetry of visual cortical evoked potentials. It is suggested that administration of clonidine early in life prevents brain morphofunctional deficits by malnutrition, by restoring the normal tropic role of NA during synaptogenesis.

Animals↗
PubMed1987

Locus coeruleus stimulation modulates olfactory bulb evoked potentials.

Field-evoked potentials from the main olfactory bulb in response to stimulation of the olfactory nerve and lateral olfactory tract were measured without and with conditioning stimulation of the locus coeruleus noradrenergic system. The locus coeruleus conditioning stimulus suppressed or inhibited the late components of the olfactory bulb potential evoked by orthodromic olfactory nerve stimulation; this inhibitory effect was suppressed by the microinjection of the alpha-adrenergic blocker prazosin into the olfactory bulb. Results indicate that noradrenergic fibers projecting from the locus coeruleus exert modulatory influences on neuronal networks underlying orthodromic evoked responses in the main olfactory bulb.

Adrenergic Fibers↗
PubMed1987

Early malnutrition and changes in the induced release of noradrenaline in the prefrontal cortex of adult rats.

The influence of early protein-energy malnutrition on the induced release of noradrenaline in the rat prefrontal cortex was studied: (i) by evaluating in vivo the release of the neurotransmitter as revealed by changes in the ability of pyramidal cells to integrate transient transmembrane currents generated by discrete packets of noradrenaline released by repetitive electrical stimulation of the locus coeruleus; and (ii) by measuring in vitro the potassium-induced release of 3H-noradrenaline in slices obtained from the brain frontal pole. Both electrophysiological and neurochemical data show that, in malnourished rats, weak stimulation produces an increased release, whereas strong stimulation results in a decreased release of the neurotransmitter. The results provide direct evidence that malnutrition alters the release of noradrenaline at the cortical level. Since the prefrontal cortex is involved in cognitive processing, the present results could provide functional evidence linking nutritional and behavioral deficits.

Age Factors↗
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

Myoepithelioma of the head and neck: case report and review.

The clinical, light, and ultrastructure features of a myoepithelioma occurring on the hard palate of a 24-year-old woman are presented and compared with 41 myoepithelioma of the head and neck described in the English literature. These 42 tumors (39 benign and 3 malignant) occurred in individuals from 14 to 81 years of age, affected both sexes about equally, and most often presented as a slowly enlarging, asymptomatic mass. The parotid gland and palate were the most common sites of occurrence. The tumors are typically circumscribed and encapsulated, vary from 1 to 5 cm in the greatest dimension, and are composed of spindled and/or plasmacytoid myoepithelial cells. Prognosis correlates with histologic appearance and parallels that of the pleomorphic adenoma. Conservative excision with a margin of uninvolved tissue is curative. The differential diagnosis and histogenic relationship with other closely related neoplasms are discussed.

Adenoma, Pleomorphic↗
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↗
PubMed1982

Ischemic necrosis of both lower extremities as a result of the microembolism syndrome complicating the adult respiratory distress syndrome caused by Escherichia coli pneumonia and septicemia.

Extensive gangrene of both lower extremities necessitating bilateral above-the-knee amputations complicated the adult respiratory distress syndrome (ARDS) caused by Escherichia coli pneumonia and septicemia in a 52-yr-old man. Concurrent with the evolution of tissue necrosis, peripheral blood leukocyte and platelet counts fell, and pulmonary vascular resistance increased. Adequacy of the cardiac output was confirmed by repeated thermodilution cardiac output measurements, and major vascular occlusion was excluded surgically. Fibrin degradation products and thrombocytopenia were present, but the other usual criteria for disseminated intravascular coagulation were absent. Small vessel thrombosis by fibrin and leukocytes was observed histologically in the amputated extremities. These findings suggest that gangrene was due to the "microembolism syndrome"--diffuse small vessel occlusion by fibrin thrombi complicating ARDS. This unusual complication of ARDS may occur without abnormalities suggestive of diffuse intravascular coagulation in routine laboratory tests of blood coagulation. It should be suspected and treated promptly to avoid severe disability in survivors.

Escherichia coli Infections↗
PubMed1981

The strength-duration function in the evocation of direct cortical responses.

The strength-duration function of single rectangular electrical stimuli which are required for eliciting threshold direct cortical responses in the primary somatosensory area was studied in rats anesthetized with 20 and 60 mg/kg of sodium pentobarbitone. The high linear correlation of the charge-duration data indicated that the strength-duration curve for threshold cortical activation closely resembles a hyperbolic function. Cortical chronaxie obtained from deeply anesthetized rats was higher than that obtained from slightly anesthetized ones. It is concluded that the chronaxie appears to be a significant discriminative intrinsic parameter for the quantitative characterization of excitation resulting from electrical stimulation of the cerebral cortex.

Anesthesia, General↗
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↗