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Biomedical subjects

F Velasco

Publications and source records attributed to F Velasco.

At least 91 records · Page 5Linked to original sources
PubMed1987

Kindling-like convulsive activities in the isolated ileum of the guinea pig. I. Electrical stimulation.

A kindling-like convulsive activity model produced by subthreshold, iterative electrical stimulation of the isolated male guinea pig ileum is described. In this model, the mechanical activity of the longitudinal muscular fibers of the ileum was systematically quantified in terms of the basic frequency, tonus, amplitude, and transient amplitude increments (A, n spikes/20 min) of "normal" contractions and presence of high-amplitude, paroxysmal, "epileptiform" contractures (B, n spikes/20 min). Changes in these parameters were statistically compared through consecutive stages of the same stimulated male ileum (I = initial activation, II = initial inhibition. IIIA = late activation, and IV = late inhibition) and equivalent stages of stimulated female and nonstimulated male ilea where "kindling-like" activities were only occasionally observed. Basic tonus, amplitude, and number of A spikes showed significant changes through consecutive stimulated male ileum "kindling" stages: increased from baseline to stage I, decreased from I to II, increased from II to III and from III to IIIA, and decreased from IIIA to IV. The number of B spikes significantly increased from II to III, III to IIIA, and IIIA to IV. No significant changes in baseline frequency were found through all stages nor in tonus, amplitude, A and B spikes between stage IV and the self-sustained activity observed 120 min after stimulation. In addition, there were significant correlations between B spikes vs. basic tonus and amplitude and A spikes when the stimulated male ileum shifted from stage II to IIIA (positive correlations) and from IIIA to IV (negative correlations). Basic tonus during stage I, basic amplitude during IIIA, A spikes during self-sustained activity and B spikes during III, IIIA, IV, and self-sustained activity were in the stimulated male ileum larger than those in both the stimulated female and the nonstimulated male ilea. Tonus and A spikes during III and IIIA in the stimulated male ileum were larger than in the nonstimulated, whereas tonus during IV and self-sustaining activity and amplitude during II in the stimulated male ileum were smaller than in the female stimulated ileum.

Animals↗
PubMed1986

Behaviour of the contact phase of blood coagulation in the adult respiratory distress syndrome (ARDS).

In order to assess the role of the kallikrein-kinin (K-K) system in the pathogenesis of the adult respiratory distress syndrome (ARDS) we have prospectively determined coagulation contact phase, blood gas and hemodynamic parameters in patients with ARDS at 0, 36 and 72 h from diagnosis. Compared to normal values, significantly lower mean levels of factor XII (71.4 +/- 9.8%, p less than 0.0005), prekallikrein (PPK) (52 +/- 5.7%, p less than 0.0005), high molecular weight kininogen (HMWK) (73 +/- 2%, p less than 0.0005) and alpha 2-macroglobulin (alpha 2-M) (51 +/- 7.1%, p less than 0.0005) were found in ARDS patients. The functional kallikrein inhibitory activity (KKI) and C1-esterase inhibitor antigenic (CIINH) were significantly higher in these patients (113.2 +/- 5, p less than 0.005 and 124.7 +/- 7.6, p less than 0.0005 respectively) compared with normal values during the entire study period. The KKI/CIINH ratio decreased significantly in our ARDS patients at 0, 36 and 72 h (p less than 0.025; p less than 0.05 and p less than 0.005 respectively). We found a significant correlation between PPK levels and oxygenation index (r = 0.69, p less than 0.001), PPK and the static thoracic compliance values (r = 0.64, p less than 0.001). There was also a significant correlation between PPK levels and Qs/Qt (r = -0.89, p less than 0.001). ARDS patients that survived presented a stability in the PPK values in successive tests. Nevertheless non-survivors showed a progressive decrease in PPK levels during the follow-up period.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1986

Subcortical correlates of the somatic, auditory and visual vertex activities. II. Referential EEG responses.

A systematic analysis of polarity, amplitude and latency of the referential EEG responses correlated to surface somatic (SVA), auditory (AVA) and visual (VVA) vertex activities (VA) was done in various subcortical structures of a non-specific system of the same group of patients with electrodes implanted and reported in a previous work. These structures included the caudal and rostral mesencephalic reticular formations (cttc and rttc), the subthalamic region (Sth), the centro-median (Ce), parafascicular (Pf), ventrolateral (VL), dorsolateral (DL) and reticularis (Rt) thalamic nuclei; the orbito-frontal cortex (GO), the anterior commissure (Acm), the pallidum medialis and lateralis (Pm and Pl), the putamen (Pt) and the amygdala (Am). Subcortical SVA, AVA and VVA were formed by 4 consecutive components O, A, B and C correlated to components P1, N1, P2 and N2 of the surface VA. Components A and B of the subcortical SVA reversed polarity 4 times when recorded in structures arranged in a caudo-rostral order: between rttc-Ce and VL, between Rt and GO, between GO and Acm and between Acm and Am. Components A and B of subcortical AVA and VVA reversed polarity two times each: AVA between cttc and rttc and between GO and Acm; while VVA between GO and Acm and between Acm and Pm. Components A and B of SVA and VVA attained maximal amplitudes and minimal latencies at GO. From here, their amplitude decreased and latency increased with distance along other structures rostrally and caudally located. Components A and B of AVA attained maximal amplitudes and minimal latencies at cttc.(ABSTRACT TRUNCATED AT 250 WORDS)

Brain↗
PubMed1986

Subcortical correlates of the P300 potential complex in man to auditory stimuli.

Bipolar and referential responses correlated to the surface P300 auditory potential complex (components N2, P3 and N4) were studied in different subcortical structures of parkinsonian and epileptic patients with implanted electrodes used as an electrophysiological procedure for surgical treatment. Bipolar and referential subcortical responses were recorded from a wide subcortical region which included subthalamo-thalamic (Sth-Th), dorsothalamic (DTh), orbitofronto-hippocampal (OFH) and striatal (STR) structures. They were formed by 3 consecutive components C, D and E correlated to components N2, P3 and N4 of the surface responses. Component D correlated to surface P3 was either absent or very small in all subcortical bipolar responses and in referential responses recorded from OFH structures. Polarity of bipolar component C was inverted between DTh and OFH while that of bipolar component E was inverted between Sth-Th and DTh, between OFH and STR and between Sth-Th and STR. Polarity of the referential component C was inverted between STh-Th and DTh and between OFH and STR while that of referential components D and E remained unchanged along all subcortical structures. Referential components C-E and D attained maximal amplitudes and minimal latencies at the subthalamic and at the medial geniculate thalamic nucleus regions respectively. From here, their amplitudes decreased and latencies increased with distance in other structures rostrally and caudally located, with the exception of those at the orbitofrontal (components C-E) and dorsal thalamic and striatal regions (component D) where no amplitude-latency gradients were observed.

Electroencephalography↗
PubMed1986

Alumina cream-induced focal motor seizures in cats: bilateral lesions of the mesencephalic reticular formation.

The effect of bilateral lesions of the mesencephalic reticular formation on the EEG-EMG patterns of types B and C alumina cream-induced focal motor seizures was studied in cats with chronically implanted electrode and cannula lesion systems. EEG patterns included number, amplitude, and contralateral propagation of type B spikes and occurrence and duration of type C tonic-clonic discharges. EMG patterns included changes in muscular multiple-unit activity time locked to the onset of type B spikes and to the onset and end of type C tonic-clonic EEG paroxysmal discharges. The lesions persistently blocked the orienting response to visual, auditory, and tactile stimuli to both sides in all cats and produced other neurologic symptoms partially or totally recovered in some cats. The lesions significantly increased the number, amplitude, and contralateral propagation of type B EEG spikes and the occurrence, but not the duration, of type C EEG tonic-clonic discharges. Ipsi- and contralateral adversion of the tonic phase were completely blocked and the muscular contractions of the clonic phase were reduced and delayed. These facts suggest that in intact epileptic cats, the mesencephalic reticular formation has an ascending suppressive influence on the mechanism related to EEG spike generation and precipitation of seizures but also a descending facilitatory control on the corticospinal epileptic impulses mediated through pyramidal and extrapyramidal pathways.

Aluminum Oxide↗
PubMed1986

Anaphylatoxin C5a generation and dialysis-induced leukopenia with different hemodialyzer membranes.

Leukocyte counts and plasma C5a anaphylatoxin levels were studied during hemodialysis in patients using Cuprophan, polycarbonate and polyacrylonitrile membrane dialyzers. Cuprophan induced a marked leukopenia with significant plasma C5a generation. Polycarbonate promoted the same trend of changes in both parameters but significantly less pronounced, while polyacrylonitrile did not affect leukocyte counts nor plasma C5a levels. These data suggest that complement-derived C5a generation may be an important factor in the mechanism of hemodialysis-induced leukopenia.

Acrylic Resins↗
PubMed1986

Neglect induced by thalamotomy in humans: a quantitative appraisal of the sensory and motor deficits.

Stereotactic lesions for the treatment of tremor and rigidity in patients with Parkinson's disease are occasionally followed by neglect of the use of contralateral extremities for spontaneous movement when there are no specific sensory or motor deficits. A group of patients with neglected extremities was compared with a group of patients in which thalamotomy did not produce neglect. Neglect was shown by changes in motor performance, somatosensory evoked potentials (SEP) and electroencephalographic frequency induced by the lesion, as well as radiological evidence of brain atrophy and place and extension of lesions. Reaction time to both auditory and somatosensory stimuli was significantly increased only in the extremities contralateral to the lesion of patients with neglect; tremor decreased equally in both groups, and other motor abilities remained unchanged. P-200 component of SEP decreased in amplitude and increased in latency only in cases with neglect, particularly ipsilateral to the lesion; early components and mean electroencephalographic frequency remained unchanged. Brain atrophy was significant in patients with neglect, particularly for the posterior portion of the 3rd ventricle. No differences in size and location of the lesions were found between the groups. Results indicate that this type of neglect is not secondary to lesions in specific sensory of motor pathways, but to lesions of structures coupling sensorimotor functions and the process of attention and that midline thalamic nuclei atrophy precipitates the neglect, perhaps by critically decreasing the amount of reticulothalamocortical projections engaged in selective attention.

Adult↗
PubMed1985

Subcortical correlates of the somatic, auditory and visual vertex activities in man. I. Bipolar EEG responses and electrical stimulation.

Bipolar responses correlated to somatic, auditory and visual vertex activities were studied in different subcortical structures of patients with implanted electrodes used as an electrophysiological procedure for surgical treatment. In addition, we studied the subjective responses of patients to electrical stimulation of subcortical structures where vertex-like activities (VA) were recorded, in order to determine their possible role in somatic, auditory and visual sensations. Typical subcortical VA evoked by somatic, auditory and visual stimuli, were recorded together from a single structure of a non-specific system including: reticulo-, medial dorsal-thalamic, orbito-frontal, limbic and striatal structures. Typical subcortical VA were formed by 4 consecutive components: O, A, B and C correlated to P1, N1, P2 and N2 of the surface VA. Polarity of component A was inverted between reticulo- and medial-thalamic structures while that of component B was inverted between medial thalamic and dorsal thalamic and between fronto-limbic and striatal structures. Typical subcortical VA were absent within specific thalamic nuclei and pathways in presence or absence of short latency responses evoked by specific sensory stimuli. Atypical subcortical VA of 1, 2 and 3 sensory modalities with inconsistent amplitudes, latencies and polarities were recorded from an intermediate zone surrounding and between specific and non-specific structures. Electrical stimulation of the non-specific structures at the reticulo- and medial thalamic levels elicited sensation of falling down and increase tension and tremor of the contralateral hand while no subjective responses were elicited by the stimulation at the dorsal thalamic, fronto-limbic and striatal levels. Stimulation of the specific structures and the intermediate zone elicited somatic, auditory and visual sensations with and without and apparent topographical organization, respectively.

Cerebral Cortex↗
PubMed1985

Alumina cream induced focal motor epilepsy in cats. VI. Excision of the perilesional cortex.

The effect of surgical excision of dorsolateral, ventromedial and combined (dorsolateral-ventromedial) perilesional cortices on EMG-EEG patterns of alumina cream induced focal motor seizures was studied in cats with chronically implanted electrodes. EMG patterns included clinical convulsions and related EMG-multiple unit activity. EEG patterns included number, amplitude, polarity and contralateral propagation of type B isolated spikes and type C tonic-clonic paroxysmal discharges. (1) Dorsolateral decortications abolished isolated jerks and related EMG-multiple unit activity and blocked propagation with no effect on number, amplitude and polarity of EEG spikes of type B seizures (epilepsia partialis continua). Dorsolateral decortications reduced contraversion and repetitive jerks and related EMG-multiple unit activity with no changes in number, amplitude, polarity and propagation of EEG tonic-clonic paroxysmal discharges of type C seizures (adversive epilepsy). (2) Ventromedial decortications decreased the number but neither changed jerks and related EMG-multiple unit activity nor amplitude, polarity, propagation of EEG spikes of type B seizures. Ventromedial decortications abolished contraversion and jerks and related EMG-multiple unit activity and reduced number, amplitude and duration with no changes in polarity and propagation of EEG paroxysmal discharges of type C seizures. (3) Combined decortications abolished jerks, contraversion and related EMG-multiple unit activity with a variable effect on EEG patterns of type B and C seizures. In 4 cats, combined decortications abolished while in other 2 cats decreased the amplitude and reversed the polarity of type B spikes and reversed the polarity and blocked the propagation of type C paroxysmal discharges.

Aluminum Oxide↗
PubMed1985

Comparative effects of topical perfusions of pentylenetetrazol in the mesencephalon and cerebral cortex of cats.

Push-pull perfusions of pentylenetetrazol (PTZ) were carried out in the mesencephalon and cerebral cortex (orbitofrontal, motor, and suprasylvian) of "encéphale isolé" cats, while EEG recordings from motor cortices and EMG of facial muscles were obtained. There were significant differences between perfusions in the mesencephalic reticular formation (MRF) and in the cerebral cortex: (i) EEG spikes not accompanied by muscular contractions occurred during perfusion of cerebral cortex (motor cortex included), but never with perfusions in MRF. (ii) In some instances muscular tonic and clonic contractions occurred in the absence of EEG spikes when perfusing the mesencephalon, but never with cortical perfusions. (iii) Both MRF and cortical perfusions induced EEG spikes accompanied by myoclonic seizures; however, muscular seizures were practically of the same amplitude in both sides after perfusion of the MRF and were predominant in the contralateral side after cortical perfusions. In addition, significantly less perfusion time (total dose) of PTZ was needed to induce such events in the MRF than in the cerebral cortex. (iv) Generalized seizures induced by cortical perfusions showed a clear predominance of contractions in the muscles contralateral to the perfusion site, whereas perfusions in the MRF induced generalized seizures indistinguishable from those produced by i.v. administration of PTZ. Results suggest that PTZ generalized seizures, closely resembling the so called "primary generalized seizures," result from activation of the MRF, whereas PTZ acting in the cerebral cortex produces a model of focal convulsions that may become secondarily generalized.

Administration, Topical↗
PubMed1985

Dysfunction of dopaminergic regulation of prolactin in patients with functioning and nonfunctioning pituitary adenomas and craniopharyngiomas.

The response to domperidone (a dopamine blocking agent) of serum prolactin (PRL) levels was compared in 3 patients with amenorrhea-galactorrhea without evidence of a pituitary tumor, 23 patients with prolactinomas (10 cases with histologic confirmation), 7 patients with histologically verified large nonfunctioning pituitary adenomas with normal or moderately elevated basal PRL levels, and 6 patients with histologically verified craniopharyngiomas (3 with normal basal PRL levels and 3 with elevated PRL levels). The response was compared with that of 10 patients with postpartum hyperprolactinemia and 14 normal women. Ten milligrams of intravenous domperidone induced a rapid rise in PRL that was maximal at 30 to 45 minutes in normal, postpartum, and amenorrhea-galactorrhea patients who had no sign of tumor. In contrast, domperidone failed to induce significant changes in PRL in cases of prolactinoma, nonfunctioning pituitary adenomas, and craniopharyngioma with or without elevated basal PRL levels. The results suggest that dopaminergic control on PRL secretion was impaired in all tumor cases. The mechanisms of this abnormal dopaminergic control, however, may be different. Whereas dopamine control in cases of prolactinoma is altered at the level of pituitary dopamine receptors, alternative explanations must be found for those tumors with normal basal PRL levels and lack of response to domperidone.

Adenoma↗