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Biomedical subjects

M Velasco

Publications and source records attributed to M Velasco.

At least 289 records · Page 16Linked to original sources
PubMed1976

Alumina cream-induced focal motor epilepsy in cats. Part 3. Ultrastructure of the epileptogenic focus.

In this study the ultrastructure of motor cortex adjacent to alumina cream (AC) deposits was studied during the latent, convulsive and remission stages of an experimental model of epilepsy in cats. Findings were compared with those observed in sham-operated animals. Where AC was injected, amorphous material surrounded by macrophages containing phagocytic vacuoles was observed. At the edge of these areas, neither fibrous capsule, nor other inflammatory elements were seen. Changes in size and number of fibrous astrocytic processes and morphological signs of progressive degeneration of neuronal elements at the perilesional cortex were found through the latent, convulsive and remission stages. These findings support the idea that presence of clinical and EEG seizures in AC lesioned animals is independent of scar formation and other inflammatory elements. On the other hand, the significance of increased astrocytic processes and progressive degeneration signs of the perilesional cortex in the physiopathogenesis of convulsive activity requires further investigation. (Arch. Invest. Méd. (Méx) 7:157, 1976).

Aluminum↗
PubMed1975

Decreased plasma protein binding of diazoxide in uremia.

The effect of uremia on the binding of diazoxide to plasma proteins was studied. An equilibrium dialysis technique, using diazoxide-minus14C at approximately 30 and 300 mug/ml in the plasma phase, was used to measure diazoxide binding to plasma. Serum albumin concentration (Alb) and serum creatinine (Cr) or blood urea nitrogen (BUN) were negatively correlated. By single regression analysis, per cent free diazoxide (%FD) correlated negatively with Alb and positively with Cr or BUN. When %FD was regressed simultaneously against Alb and Cr or BUN, Alb emerged as the sole determinant of %FD (p less than 0.001), indicating that creatinine or BUN correlated with %FD by their inverse correlation to Alb rather than by an effect on drug protein binding. At the levels of Alb studied, %FD varied over a 2-fold range. In a retrospective study of the influence of uremia on diazoxide effect in hypertensive patients, a relatively low correlation (r, 0.59) was found between BUN and hypotensive effect. Prospective studies involving correlations of drug effect with renal function and %FD are required to assess the clinical importance of decreased binding of diazoxide to uremic plasma.

Adult↗
PubMed1975

Antihypertensive effect of a dopamine beta hydroxylase inhibitor, bupicomide: a comparison with hydralazine.

The cardiovascular effects of a new antihypertensive drug, bupicomide, were compared with those of hydralazine in 6 patients with mild to moderate hypertension. The mean supine arterial pressure of patients was reduced 15.2 mm Hg by bupicomide (900 to 2,000 mg/day) and 15.7 mm Hg by hydralazine (300 to 600 mg/day). Heart rate increased an average of 11.3 bpm during bupicomide and 14.5 bpm by hydralazine. Neither drug was associated with a postural decrease in mean arterial pressure. The heart rate response during maximum tolerated treadmill exercise was not diminished by either drug. Cardiac index was increased during administration of both drugs. Bupicomide and hydralazine reduced forearm vascular resistance, while renal blood flow and renal vascular resistance were not significantly modified. Evidence of equivalent augmentation of sympathetic nervous activity during administration of both drugs consisted of equal and significant increases in heart rate and urinary norepinephrine excretion, and decreases in duration of the pre-ejection period. The absolute values of these parameters were correlated with mean arterial pressure, which may indicate that the increase in sympathetic nervous activity was mediated by baroreceptor reflexes. Although bupicomide inhibits dopamine beta-hydroxylase, our results suggest that it is acting as a direct vasodilator.

Adult↗
PubMed1975

Somatic evoked response components and recovery functions in subjects with mu and alpha rhythms.

Subjects with prominent rolandic mu and alpha rhythms showed similar late somatic evoked response (SER) components but different SER recovery functions. A late P5x component was present when SER were superimposed on mu and alpha rhythms spontaneously recorded from the rolandic region of inattentive individuals. Since P5x was not present in other inattentive subjects unless SER were superimposed on a rhythmic rolandic activity evoked by an attentive situation, it seems reasonable to assume that the P5x component is partially due to spontaneous or evoked rolandic EEG rhythmicity. In addition, single propioceptive stimuli produced blocking of mu rhythm and a flat recovery function of the P5a component. In contrast, similar stimuli produced an enhancement of alpha rhythm and a periodic amplitude modulation curve of the P5a component. These results suggest that the P5a component is mediated by the same neurophysiological mechanisms which block or modulate the spontaneous rolandic EEG rhythms.

Adolescent↗
PubMed1975

Differential effect of thalamic and subthalamic lesions on early and late components of the somatic evoked potentials in man.

The effect of thalamic (Vo), subthalamic (Raprl) and combined (Vo-Raprl) unilateral lesions on early and late components of the somatic evoked potentials (SEPs) was investigated in a group of 16 cases operated on for the treatment of contralateral dyskinetic movements. In these cases, SEPs were independently produced by stimulation of the left and right median nerves and recorded at the corresponding somatosensory scalp regions. In addition, EEG frequencies and reaction time (RT) were independently and bilaterally determined. These tests were performed before and after operation and changes in SEP, EEG and RT were quantitatively evaluated in relation to both ipsilateral preoperative and contralateral postoperative controls. 1. All cases with either thalamic or combined lesions involving Vo nucleus showed an ipsilateral reduction in amplitude of late SEP components and EEG frequency and a contralateral increase RT. A peculiar form of "inattention" to the contralateral hand was also found. Quantitative evaluation of the total group showed significant amplitude reduction in late SEP components in relation to both ipsilateral preoperative and contralateral postoperative controls. Changes in EEG and RT were only significant in relation to their preoperative ipsilateral controls. 2. Two cases with subthalamic lesions and quick postoperative recovery showed no apparent change in SEP, EEG and RT. Three cases with similar lesions and slow postoperative recovery showed bilateral decrease in amplitude of late SEP components, EEG frequency and increase in RT. Clinical inattention to contralateral hand was also found in all these cases. Quantitative evaluation of the total group showed no significant changes in these parameters in relation to preoperative controls. 3. None of these lesions produced changes in early SEP components or somatosensory deficits at the contralateral hand.

Attention↗
PubMed1975

Differential effect of task relevance on early and late components of cortical and subcortical somatic evoked potentials in man.

The effect of "task relevance" on early and late components of cortical and subcortical somatic evoked potentials (SEPs) was studied in a group of Parkinsonian patients operated on under local anesthesia for treatment of prominent unilateral tremor. 1. SEPs produced by median nerve stimulation were found at contralateral cortical (ss), thalamic (vcpci, vcai), lemniscal (Lm), postilemniscal (PoLm), prelemniscal (Raprl) and reticular (Ttc) regions. No SEPs were found in other contiguous thalamic (M,Pf, ce) and subthalamic (Q) regions. 2. Subcortical early SEP components consisted of two monophasic positive potentials distributed within a circumscribed thalamo-lemniscal region where electrical stimulation elicited consistent sensory responses circumscribed to contralateral hand and face. In contrast, subcortical late SEP components consisted of monophasic or polyphasic, positive or negative potentials distributed in a widespread, thalamic, lemniscal, prelemniscal and reticular region where elecrical stimulation elecited sensory or motor responses of various types. Subcortical early and late SEP components appeared together in lemniscal, thalamic and cortical regions but they wers separated at postlemniscal (only early) and prelemniscal and reticular ones (only late). 3. Significant amplitude changes in cortical and subcortical late SEP componets were found concomitant to variations in "task relevance": they decreased when patients shifted from novelty to habituation, they increased when patients shifted from habituation to attention and they decreased when patients shifted from attention to distraction. In contrast, no significant ampiltude changes in cortical and subcortical early components were found when patients shifted through these various "task relevance" conditions.

Adult↗
PubMed1975

Specific and nonspecific multiple unit activities during the onset of pentylentetrazol seizures. I. Intact animals.

A quantitative evaluation of specific and nonspecific multiple unit activity (MUA) before and during pentylenetetrazol-induced EEG tonic-clonic discharges (OTCD) was made at four levels of the CNS: cortical, thalamic, mesencephalic, and pontine. In addition, MUA of sciatic nerve was recorded to detect possible spinal cord efferent discharges. At all levels, sustained increase in specific and nonspecific multiple unit activity preceded EEG and sciatic nerve discharges induced by pentylenetetrazol. Increments in nonspecific MUA occurred sooner and were larger than those of specific MUA, and increments in mesencephalic nonspecific MUA occurred sooner and were larger than those of other cortical, thalamic, and pontine nonspecific MUAs. This sequence of neuronal activation suggests that pentylenetetrazol seizures are initiated in nonspecific structures at the mesencephalic level.

Animals↗
PubMed1975

A statisticl outline of the subthalamic target for the arrest of tremor.

In 60 cases operated on for the treatment of tremor, the insertion of an electrode that measured 1 mm in diameter produced complete arrest (40 cases) or significant decrease (20 cases) of the tremor on the contralateral side. The area where such effect was obtained was studied in AP and lateral radiograms. Using a method of standardization of the size of the thalamus and subthalamus, based on a proportional reucction of the length of the AC-PC line, the cases were found to cover a small area in the subthalamus. A statistical analysis of the position of the electrode tips at the moment the tremor was arrested was carried out in order to determine, with a high degree of probability, the area that includes the mean value of the target for the general population. This work allowed us to outline a small zone in the subthalamus as the target to be destroyed in future cases. The practical implications of the method are discussed and the possibility of reducing the size of the lesion is pointed out.

Electrocoagulation↗
PubMed1975

Control plasma renin activity and changes in sympathetic tone as determinants of minoxidil-induced increase in plasma renin activity.

A study was made of the possible mechanism(s) underlying minoxidil-induced increase in plasma renin activity (PRA). 10 patients with essential hypertension were treated with minoxidil and subsequently with a combination of minoxidil plus propranolol. Minoxidil lowered mean arterial pressure 31.6 plus or minus 3.3 mm Hg, mean plus or minus SEM. There was an associated increase in both PRA, 6.26 plus or minus 2.43 NG/ML/H, and heart rate, 21.4 plus or minus 2.7 beats/min. The changes in PRA and heart rate were positively correlated, r, 0.79. Addition of propranolol reduced mean arterial pressure by a further 10.1 plus or minus 1.5 mm Hg and returned heart rate to control levels. Propranolol reduced PRA significantly but not to control levels. Control PRA positively correlated with PRA on minoxidil, r, 0.97, and with PRA on minoxidil plus propranolol, r, 0.98. We conclude that control PRA is a major determinant of change in PRA with minoxidil. Minoxidil increased PRA by at least two mechanisms: (a) an adrenergic mechanism closely related to change in heart rate and blocked by propranolol, and (b) a mechanism(s) not sensitive to propranolol and possibly related to decrease in renal perfusion pressure.

Adult↗
PubMed1975

Thalamo-cortical systems regulating spindle bursts and recruiting responses. II. Effect of thalamic lesions.

The effects of thalamic lesions on recruiting responses and spindle bursts have been studied in 12 cats immobilized with gallamine. Recruiting responses were elicited by stimulation of the midline thalamic nuclear complex. Spindle bursts were produced by lesions in the mesencephalic tegmentum. Recruiting responses and spindle bursts were recorded from the cortex and thalamus. The effect of thalamic lesions on such spontaneous and induced potentials was evaluated by making lesions anteriorly in the rostral pole of the thalamus, medially in the midline thalamic nuclear group, and laterally in the primary and association nuclei of the thalamus. 1. Small, anterior, thalamic lesions blocked spindle bursts and recruiting responses both at the cortex and in the thalamus. 2. Massive, medial, thalamic lesions blocked spindle bursts in the suprasylvian cortex, but did not affect either frontal cortex spindle bursts or frontal and thalamic recruiting responses induced by stimulation of N. ventralis anterior. 3. Massive, lateral, thalamic lesions including specific relay and association nuclei, failed to block spontaneous spindles and recruiting responses in frontal cortex and midline thalamic nuclei. It has been postulated that the rostral pole of the thalamus constitutes an important part of the thalamic portion of a thalamo-orbitocortical system which mediates and regulates electrocortical synchronization as manifested in spindle bursts, recruiting responses and synchronized wave-like potentials.

Animals↗
PubMed1975

[Effect of chlormandinone acetate upon seizures in epileptic children with latent signs of hyperandrogenism].

The effect of chlormadinone acetate (24 mg/day) upon the plasma levels of pituitary gonadotropins and gonadal hormones on the number of generalized convulsions and spike EEG density was investigated in a group of epileptic children with intractable seizures and with clinical signs suggestive of hyperandrogenism. In each case, the effect of chlormadinone was evaluated in relation to hormonal levels and seizures observed during a control period and under the effect of placebo as follows: Control (PC)-Chlormadinone acetate (PCL1)-Placebo (PP)-Chlormadinone acetate (PCL2). In a male child (4MS), the number of convulsive attacks observed in the control period (26/month) was reduced during PCL1 (2/month) increased during PP (12/month) and was reduced again during PCL2 (0/month). Spike EEG density showed a parallel course to the clinical attacks. In this case, control levels of testosterone were markedly elevated (40 ng/ml) and were decreased during PCL1 to 4.0 increased again during PP to 34.0 and decreased again during PCL2 to 1.2 ng/ml. Plasma levels of pituitary gonadotropins were unchanged throughout the entire period of study. In other cases, neither the number of epileptic attacks nor spike EEG density were apparently affected by this regime and plasma levels of pituitary gonadotropins and gonadal hormones were also unmodified. These results suggest that a latent state of hyperandrogenism may be detected in some epileptic patients with intractable seizures and that chlormadinone may reduce convulsive attacks in these patients, probably by decreasing testosterone plasma levels.

Androstenedione↗