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Biomedical subjects

M Velasco

Publications and source records attributed to M Velasco.

At least 217 records · Page 12Linked to original sources
PubMed1982

Subcortical correlates of the auditory brain stem potentials in man: bipolar EEG and multiple unit activity and electrical stimulation.

Bipolar EEG and multiple unit activity (MUA) responses related to the vertex auditory brain stem potentials (ABSP) were studied in different subcortical loci in parkinsonian and epileptic patients with implanted electrodes used as an electrophysiological procedure for surgical treatment. In addition, the subjective responses of patients to the electrical stimulation of these subcortical loci were studied for their possible auditory sensations. (1) Two types of bipolar EEG responses to monoaural stimulation were recorded from a limited number of subcortical loci: type A responses were formed by two consecutive components of opposite polarity peaking at 5.2 and 8.5 msec post-stimulus in 3 different loci contra- and ipsilateral to the stimulated ear: mesencephalic reticular formation (MRF), medial geniculate (MG) and lateral geniculate (LG) nuclei thalami. The polarity of the first component was everted while the second component was inverted between MRF and MG. Type B responses were formed by one component mainly peaking at 15.5 msec post-stimulus with no polarity reversal in either side within the ventral portion of the hippocampus bilaterally (CnA). (2) MUA responses were recorded only within the basal portion of MG bilaterally. Contralateral MUA responses consisted of 3 consecutive activation bursts peaking at 5.5, 7.2 and 9.0 msec post-stimulus and correlated in latency with waves IV-V, VI and VII of ABSP respectively. Ipsilateral MUA responses consisted of two consecutive activation bursts peaking at 14.0 and 16.0 msec post-stimulus and correlating with SN following ABSP. (3) Threshold electrical stimulation of the MG elicited subjective auditory responses referred to the contralateral ear.

Auditory Pathways↗
PubMed1982

Specific and non-specific multiple unit activities during pentylenetetrazol seizures in animals with mesencephalic transections.

A group of cats with brain stem transection at the mesencephalic level was studied during the administration of convulsive doses of pentylenetetrazol in regard to changes in EMG multiple unit activity (MUA), as a method to determine the course of muscular convulsions and their relation with EEG and MUA changes in the motor cortex, pyramidal tract and mesencephalic and pontine reticular formations. PTZ induced significant increase in the duration of EMG tonic convulsions, lasting 3-100 times longer than the entire tonic-clonic seizure seen in intact animals after similar doses of PTZ and not accompanied by EEG or pyramidal tract "seizures", but by an equally long-lasting increase in MUA of mesencephalic and pontine reticular formations. Comparing present results with those seen in intact, "encéphale isolé" and "pretrigeminal" preparations, it is concluded that the mesencephalon is important for both: activating tonic phase of the convulsions and the EEG changes seen in PTZ-induced seizures. It also suggests that termination of seizures is due to inhibitory influences of supramesencephalic structures.

Animals↗
PubMed1982

Effect of indoramin and propranolol on cardiovascular response to cold in hypertensive patients.

Immersion of the hand into ice water (cold-pressor test) in nine hypertensive subjects induced elevation of mean blood pressure, increase of vascular resistance in the extremities, decrease of blood flow in the extremities, and increase in heart rate. The preejection phase of systole was not altered. Indoramin and propranolol, each alone and together, attenuated the pressor and other cardiovascular responses. Submaximal exercise increased heart rate during placebo treatment, a response only partially attenuated by indoramin, propranolol, and their combination, but it did not induce changes in mean blood pressure during any of the treatments.

Adult↗
PubMed1982

Subcortical correlates of the auditory brainstem potentials in the monkey: referential responses.

Referential responses correlated with the vertex auditory brain-stem potentials (ABSP) were recorded from different brainstem and diencephalic structures of large monkeys under barbiturate anesthesia. Polarity, latency, and amplitude of various response components were determined from structures located 2 mm apart along five different vertical trajectories aiming at the trapezoid body (TB), superior olivary complex (SOC), mesencephalic reticular formation (MRF), medial geniculate nucleus thalami (MG), and inferior colliculus (IC). Latency correlations, amplitude differences, voltage profiles, current-source-density-distribution, and current flows of the various response components were subsequently calculated. Subcortical referential responses were formed by seven initial fast positive components (I, II, A, B, C, D and E) and one late slow negative component (F) correlated to waves I to VII and SP3 of the vertex ABSP respectively. Positive components C and D' also correlated to SP1 and SN1 of ABSP respectively. Amplitude of component B at contralateral SOC and C, D' and F at contralateral MRF was significantly larger than those of other subcortical responses and vertex ABSP. A single component of the subcortical referential responses accompanied changes in voltage, CSD, and current flows of various brainstem structures. However, considering only major changes in these parameters, component B accompanied a voltage positive and a CSD positive-negative peak and an ascending current flow at the SOC; component C accompanied similar changes at MRF, and components D' and F accompanied voltage negative and CSD negative-positive-negative peaks and ascending and descending current flows at MRF. In contrast, no systematic changes in voltage, CSD and current flows accompanied components I, II, A, D and E.

Animals↗
PubMed1982

Effect of dextro-amphetamine on reticulo-preoptic interactions in "encéphale isolé" cats.

Intravenous administration of a single dose of dextro-amphetamine (1 mg/kg) in the "encéphale isolé" cat significantly increased amplitude of the P50 and N110 components of the preoptic potential evoked by the stimulation of the mesencephalic reticular formation and decreased all components of the mesencephalic reticular formation potential evoked by preoptic stimulation. Concomitantly, a state of increased and persistent arousal response was found. These findings support the idea that during wakefulness there is a reticular facilitation and a preoptic inhibition.

Animals↗
PubMed1982

Effect of prazosin on blood lipids and on thyroid function in hypertensive patients.

Nineteen patients with essential hypertension (EH) were studied as outpatients. After administration of chlorthalidone, 50 mg/day for 4 weeks, prazosin 1-4 mg/day (1.82 +/- 0.33 mg/day) was added for a period of 12 weeks. Prazosin lowered supine blood pressure from 149.7 +/- 2.85/102.0 +/- 2.75 mm Hg to 128.2 +/- 3.0/86.1 +/- 1.04 mm Hg (p less than 0.001). Prazosin did not alter heart rate significantly. Prazosin increased the thyroid stimulating hormone (TSH) from 3.63 +/- 0.33 microunits/ml to 4.83 +/- 0.45 microunits/ml (p less than 0.025), thyroxine (T4) from 10.03 +/- 0.29 micrograms/ml to 10.85 +/- 0.42 micrograms/ml (p less than 0.005), and decreased triiodothyronine (T3) from 36.65 +/- 0.62% to 35.42 +/- 0.56%, which was not significant. The free thyroxine index (FTI) increased slightly from 3.67 +/- 0.12 to 3.83 +/- 0.14 (p less than 0.025). However, all values remained within the normal range for the laboratory. Serum cholesterol increased insignificantly. Triglycerides decreased significantly from 223.4 +/- 50.6 mg/dl to 161.7 +/- 29.0 mg/dl (p less than 0.05). High density lipoproteins (HDL) increased significantly from 30.1 +/- 2.1% to 36.0 +/- 3.06 (p less than 0.025). Low density lipoproteins (LDL) decreased insignificantly and very low density lipoproteins (VLDL) decreased from 20.9 +/- 3.44 to 16.3 +/- 2.85 (p less than 0.005). The cholesterol ratio increased from 45.51 +/- 4.3 to 64.71 +/- 10.7 (+42.1%). These results indicate that, in patients with essential hypertension, prazosin is an effective antihypertensive agent and that it significantly increases HDL, decreases VLDL, and improves the cholesterol ratio.

Adult↗
PubMed1982

Introduction to chemotherapy and antineoplastic pharmacology in breast cancer.

Tumor cell biology and growth-kinetics of human breast cancer are reviewed with reference to the different action mechanisms of main antitumor drugs. Particular emphasis is given to pharmacokinetics, dosage, mode of administration, effectiveness and side-effects of drugs most commonly used in breast cancer. The importance of tumor Estrogen and Progesterone Receptor assay for the therapy planning is considered and a short review of estrogens, androgens, progestins, antiestrogens, corticoids and aminogluthetimide is presented. The rationale for combined chemotherapy and/or hormonotherapy in breast cancer is finally discussed.

Antineoplastic Agents↗