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Biomedical subjects

P Mares

Publications and source records attributed to P Mares.

At least 343 records · Page 19Linked to original sources
PubMed1978

Triggering of discharges from an epileptogenic focus in the rat by stimulation of the contralateral hemisphere. an ontogenetic study.

Fifty-two male albino rats aged 7, 9, 12 and 18 days and adult, immobilized with d-turbocurarine, were studied. Discharges were triggered from a penicillin focus with electrical pulses of double the threshold intensity needed to evoke an interhemispheric response (IHR). Developmental changes in the IHR and in spontaneous interictal discharges did not differ from the results described in earlier studies. Practically no discharges could be triggered in 7-day old animals (only a few at a very low stimulation frequency). In the other age groups, discharges were triggered at two optimal frequencies, of which the lower one rose from 0.1 to 0.6 c/s during development, while the higher one was relatively stable (about 1 c/s). With higher frequency triggering, marked signs of fatigue of the focus (intermittent triggering, loss of the main negative wave) appeared, especially in young animals. The averaged shape of triggered discharges was similar in 9- and 12-day-old rats. It consisted of a first IHR positivity which triggered the first positive wave of the focal discharge, followed by a high negative wave. In the 18-day-old and adult group, both initial positive waves merged to form a single wave. The duration of the individual waves of the triggered discharge was not significantly shorter than the duration of the corresponding waves of spontaneous discharge.

Animals↗
PubMed1978

Na-G-penicillin penetration into rat cerebral cortex and formation of an epileptic focus.

Fluorescein isothiocyanate-labelled Na-G-penicillin was applied to the intact dura of 11 rats and the cortical layers were determined to which this epileptogenic substance must penetrate for electrophysiologically demonstrable focal activity to be induced. In 10 animals labelled penicillin was demonstrated in cortical layers I--III and in one animal in layers I and II. This concurs with the results obtained in 12 other animals in which activity was recorded from three depths of the cerebral cortex with semimicroelectrodes.

Animals↗
PubMed1978

The role of the corpus callosum in the interhemispheric transmission of epileptic electrical activity.

In acute experiments on 49 curarized adult rats without general anaesthesia, we studied the transmission of discharges of cortical penicillin foci between the two hemispheres after transecting the corpus callosum. Projected discharges of the cortical penicillin focus appeared in the contralateral hemisphere later than in the controls and had a very different shape. The interhemispheric response of the experimental rats consisted of a small positive and a small negative deflection with long latent periods. Focal discharges could be triggered by electrical stimulat;on of the contralateral hemisphere only irregularly and for short periods of time. In rats with a transected corpus callosum, two symmetrical cortical foci at first behaved independently of each other; their synchronization then slowly improved, but never attained 100 per cent. The corpus callosum is the preferential pathway for interhemispheric transmission of focal activity. Transection of this pathway makes the transmission conditions much worse, but further connections, with a longer conduction time and lower efficacy, gradually come into action.

Animals↗
PubMed1978

Gas chromatographic study of cholesterol esterification during postheparin lipolysis in vitro in hypertriglyceridemia.

Direct gas chromatographic method for quantitative determination of plasma neutral lipids was used for the study of cholesterol esterification in vitro. Fully automated computerized method permits the determination of lipid classes (free cholesterol, cholesteryl esters, and triglycerides), as well as their fractions according to the molecular weight, without previous derivatization. All components are determined from one analysis. The method is highly precise and accurate. The coefficient of variation for free and esterified cholesterol is 1.21 and 1.11% in the concentration range 30--430 and 75--545 mg/dl, respectively. The LCAT activity was determined as a decrease in the free cholesterol concentration after one hour's incubation; from the same analysis, the recovery control as an increase in the esterified cholesterol concentration was calculated. The mean difference was 1.06%, maximum difference did not exceed 4%. The LCAT activity in the reference group was 97.2 +/- 28.2 mumol/l/h and was significantly lower than that in hyperlipdemic one. Intravenous administration of heparin had an inhibition effect in subjects with hyperlipidemia of type IV, while only slight changes in the reference group and an increase in hyperlipidemia of type III were observed.

Cholesterol↗
PubMed1977

Decomposition of molecular types of triglycerides by lipoprotein lipase in man.

1. The lipoprotein triglycerides of human plasma can be separated by gas chromatography according to their carbon number into four main groups: C48, C50, C52 and C54. We studied the decomposition of molecular types of triglycerides by posttheparin lipoprotein lipase in vitro. 2. Decomposition of the molecular type C52 does not depend on its concentration. Decomposition of the molecular types C48, C50 and C54 is in a direct correlation to their concentration. 3. The above mechanism assures stability of the triglyceride profile of human plasma, which is species specific and is expressed by the figures: C48--9%, C50--20%, C52--43%, C54--20%, remainder 8%. 4. The plasma triglyceride profile can be altered by dietetic factors. After drinking cream, the triglyceride composition is: C48--12%, C50--22%, C52--37%, C54--14%, remainder 15%. Selective decomposition of molecular types of triglycerides ensures that the profile, after a given time, returns to the original state.

Dietary Fats↗
PubMed1977

The influence of pentobarbital upon a cortical epileptogenic focus in rats.

Three subsequent doses of pentobarbital (5, 15, and 40 mg/kg) were applied intraperitoneally in acute experiments in rats with a cortical epileptogenic focus. Histograms of intervals between individual focal discharges were shifted towards longer intervals even after the smallest dose of pentobarbital; the prolongation of intervals was clearly visible after the third dose also in the EEG recording. Shape of primary as well as projected cortical focal discharges after pentobarbital resembled that seen after local application of GABA. Barbiturate spindles which were present after the first and second dose of pentobarbital were regularly triggered by focal discharges. The mechanism of this triggering was probably a thalamocortical one, because marked projected discharges were recorded from various thalamic nuclei from the very beginning of focal activity.

Animals↗