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Biomedical subjects

C Timo-Iaria

Publications and source records attributed to C Timo-Iaria.

At least 37 records · Page 2Linked to original sources
PubMed1990

Meal-feeding and physical effort. 2. Metabolic changes induced by an acute exercise.

In this study, rats under meal-feeding up to four weeks were submitted to a sudden exercise (swimming) to evaluate the effects of a behavior that requires mobilization of a large amount of energy on some physiological parameters already changed due to the chronic food-restriction. During exercise meal-fed rats: 1) increase the rate of gastric emptying; 2) maintain glycemia more steadily than the controls even during a long-lasting exercise; 3) maintain high liver glycogen concentration and its mobilization starts later on; 4) free fatty acid mobilization is lower than in the controls but during exercise do use much more; 5) keep more glycogen in the muscles (including the heart) than the controls but during the exercise do utilize much more; 6) are slightly less stressful (mainly after a longer exercise) than the controls as suggested by the adrenal ascorbic acid content.

Animals↗
PubMed1990

Electrical activity of the posterior thalamic nucleus and the hippocampus during wakefulness and desynchronized sleep in the rat: a spectral analysis.

The electrical activity of the posterior thalamic nuclear complex was studied in rats and related to the simultaneous hippocampal electro-oscillogram. Electrocorticographic tracings and spectral analysis showed that during attentive wakefulness the electro-oscillogram peaked at 8 Hz and in desynchronized sleep it oscillated at regular frequencies between 8 and 9 Hz. In quiet wakefulness, frequency was lower (around 6 Hz) and during synchronized sleep rhythmicity disappeared. The electrophysiological patterns during wakefulness and desynchronized sleep are proposed to be linked to the retrieval and combination of information for the generation of attention and dream content.

Animals↗
PubMed1990

Stationarity and normality of distribution of rat cortical brain waves.

Establishing the stationarity and statistical distribution of potentials recorded from the nervous system is crucial for the application of frequency analysis. Both parameters were determined in the electrocorticograms of six adult Wistar rats during wakefulness and desynchronized sleep, during both of which desynchronization prevails. Stationarity of the signals was found to occur during at least 20 s in both states of the wakefulness-sleep cycle. A normal distribution was also found for at least 6.7 s. These findings provide strong support for the use of frequency analysis of brain waves as a reliable method to quantify neural electro-oscillograms.

Animals↗
PubMed1990

Rostrum movements in desynchronized sleep as a prevalent manifestation of dreaming activity in Wistar rats.

Considering that eye movements express visual dreams in humans and are prominent during desynchronized sleep in cats, monkeys and birds, rostrum movements were investigated in a macrosmatic species, the rat, to assess the hypothesis that, expressing olfactory and tactile (involving the vibrissae) dreams, they would prevail over eye movements. Desynchronized sleep episodes lasted 148.8 +/- 12.4 s, rostrum movements lasted 80.7 +/- 6.9 s and eye movements occurred during 40.4 +/- 3.9 s, all in accordance with the original hypothesis.

Animals↗
PubMed1989

Reversibility of metabolic changes induced by feeding schedule in rats.

This study aimed to investigate the effect of free-feeding on rats kept on meal-feeding schedule for a prolonged period. Thus, rats meal-fed for 4 and 20 weeks were given free access to food for subsequent 5 weeks. The metabolic adaptation of higher hepatic glycogen content, low plasma FFA values and sustained glycemia during 22-hr fast, reported for rats subjected to meal-feeding, completely disappeared after free-eating period. The rate of body weight gain increased as a consequence of the free access to food in both groups but the control values (group with food ad lib all the time) were attained only in rats previously submitted to meal-feeding for the shorter period of time (4 weeks). The findings of this study suggest that the recovery of body weight by meal-fed rats, for the control values, seems to depend on the duration of the meal-feeding schedule and the age when it is imposed.

Adaptation, Physiological↗
PubMed1989

An evoked potential mapping of transcallosal projections in the cat.

In ten adult cats anesthetized with ketamine hydrochloride the neocortex was exposed and rectangular pulses (1 msec, 0.5 Hz and variable intensity) were applied to discrete points of one side and transcallosal evoked potentials were recorded from the other. The stimulation and recording positions were determined on a cartesian map of most of the exposable neocortical areas and the potentials were analysed as to their components, voltage and latency. Passive spread and electrotonic potentials and the effects of increasing frequency were also analysed. The results showed large transcallosal potentials in some areas and an increase of potentials in the caudorostral direction, attaining the highest values in anteromedial areas of the suprasylvian gyrus. Confirming anatomical studies, a few silent spots were found in the motor and somesthetic cortex and in restricted posterior regions of the visual cortex, where small or zero voltages occurred. While causing weak contralateral potentials, stimulation of some posterior sites provoked high voltage potentials in anterior regions of the side being stimulated and in the corresponding area of the opposite site. These posterior sites are poorly interconnected by the corpus callosum. The L-shaped indirect connection described in this work may be involved in some types of epilepsy and may explain the effectiveness of partial callosotomy in their treatment.

Animals↗
PubMed1989

Electrophysiological evidence for an L-shaped interhemispheric connection in the cat.

Transcallosal potentials evoked by electrical stimulation with rectangular pulses of 1 ms, 5 c/s and variable intensity were recorded from the cortical surface in cats anesthetized with ketamine hydrochloride. Sites of stimulation and recording were selected by means of a cartesian map of most of the neocortex. In addition to the well known transcallosal projection pattern it was found that stimulation of a restricted posterior area evokes low voltage potentials over the contralateral symmetric area while high voltage potentials are recorded from a few sites located at the ipsilateral anterior cortex and from the area symmetric as to the latter. This L-shaped transcallosal connection may be involved in complex cortical processes and is compatible with effective results of partial anterior callosotomies in patients with multifocal epilepsy and frontal bisynchronism.

Animals↗
PubMed1987

Time course of insulin, corticosterone and metabolic changes caused by lesion of the ventromedial hypothalamus in the rat.

The time course of changes in glycemia, insulinemia, corticosteronemia, liver glycogen, food intake, body and stomach's fresh weight were studied in rats subjected to electrolytic bilateral destruction of the ventromedial hypothalamus (VMH) and in a sham-operated (SO) group. Some of these parameters were determined during the first four hours after lesioning and all were measured also up to two weeks. Glycemia increased steadily, attaining 37.1% 120 min post-lesioning, and a parallel decrease (51.3%) in hepatic glycogen was observed. Twenty minutes after VMH destruction the insulin levels were 215.8% higher than in the SO group, a difference that was reversed 220 min later. At the first day post-lesioning the insulin levels increased 348%. It is suggested that the release was stimulated by the early reflex insulin secretion elicited by food ingestion. During the first hours after VMH lesioning corticosteronemia was elevated to 253.9% of the corresponding parameter in the SO group. When the effects of the lesion were followed up during fifteen days it was found that glycemia and hepatic glycogen returned to normal levels but insulinemia went up again. Plasma insulin increased 325.9% by the end of the observation period while corticosteronemia was 404.5% higher as compared with the SO animals. Food intake increased 63.5% on the day after lesioning and continued to rise, attaining 106% by the fifteenth day, which paralleled the weight gain (31%). A close topographic correlation was found in this study between the precise lesioning of the ventromedial nuclei of the hypothalamus and the changes herein described.

Adrenal Cortex↗
PubMed1985

Increase of food intake induced by glucagon in the rat.

The effect of intraperitoneal administration of saline, glucose (25 mg/100 g b.w.), insulin (0.025 U/100 g b.w.) and glucagon (50 micrograms/kg b.w.) on glycemia, liver glycogen concentration and food intake was studied on 104 male adult Wistar rats. When saline was injected the amount of food ingested was similar to that expected at the metabolic moment selected for the tests. Glucose administration did not reduce food intake but both insulin and glucagon provoked a threefold increase during the 60 minutes ensuing the injection. The overall ingestion of food during the 24 hours after the injection of the hormones was significantly higher (about 10%) than the control values during the preceding or the succeeding 24 hours. A hyperphagic, rather than a hypophagic effect of glucagon administration is possibly related to the small dose used in the experiments. The mechanisms involved in the increase of food intake due to glucagon are discussed in terms of acceleration of the metabolic reactions that normally prevent large drops of glycemia as glucose utilization proceeds during the inter-meal periods and that in physiological conditions build up until the need for food arises.

Animals↗
PubMed1985

Carbohydrate metabolism and food intake in food-restricted rats. Relationship between the metabolic events during the meal and the degree of food intake.

To study some metabolic features during feeding in food-restricted rats two groups of animals were maintained on a 2 hr feeding/22 hr fast schedule. Group D (n = 38) received a meal every day from 8:00 to 10:00 a.m. Group N (n = 34) was given the meal from 8:00 to 10:00 p.m. The average total amount of food ingested by rats of group N in the two hour period was 6.3 +/- 0.4 whereas Group D ingested 4.8 +/- 0.3 g/100 g b.w. The metabolic pattern also was different in one group as to the other. The basal liver glycogen content when feeding started was considerably lower in the nocturnal group (0.14 +/- 0.02 mg/100 mg of liver tissue) than in the diurnal group (0.44 +/- 0.10 mg/100 mg). Afterwards glycogen increased in both groups but more steeply and intensely in group N. Glycemia increased in group D and was almost invariant in group N. Insulinemia went up in both groups but in group D its peak was higher and occurred 60 minutes after the onset of feeding whereas the peak in group N was much lower and occurred at 90 minutes. There was a clear dissociation between the time courses of insulinemia and glycemia in both groups, especially in group N, which suggests a central control of insulin secretion during feeding that partially unlocks it from blood glucose concentration. The hepatic glycogen content was partially linked to the amount of food ingested but again there was a dissociation between these two variables, inasmuch as a higher glycogen replenishment in the nocturnal group corresponded to a larger food intake.

Animals↗
PubMed1985

Signs of synchronized sleep elicited by local application of leptazol to a circumscribed area of the ventral surface of medulla oblongata in the cat.

Topical application of some drugs to the ventral surface of medulla oblongata has been found to cause changes in blood pressure and respiration and release of vasopressin. In the present investigation, electrophysiological changes induced in the electrocorticogram of cats by drugs applied to this area of the central nervous system were studied. In eight animals kept anesthetized with sodium pentobarbiturate, leptazol (200 mg/ml) was applied bilaterally (20 microliter on each side) to a small area of the rostral portion of medulla oblongata while blood pressure, respiration, the electrocorticogram from the sigmoid gyri, the nictitating membrane and the pupil width were monitored. In some preparations sodium pentobarbiturate was also applied to the same area after leptazol. Within 30 s of leptazol application to the surface, active spindling started in the sigmoid gyri, simultaneously with myosis, relaxation of the nictitating membrane and inhibition of the limb retraction in response to noxious stimulation. All these changes characterize the state of synchronized sleep. Topical application of pentobarbital to the same area suppressed spindling and reversed the other signs of synchronized sleep. The possible intervention of some known hodological systems or of the sleeping factors described by some authors in the genesis of the above phenomena is discussed.

Animals↗
PubMed1984

Metabolic performance of free fed rats subjected to prolonged fast as compared to the metabolic pattern in rats under long term food restriction.

Glycemia, free fatty acids, insulinemia, hepatic glycogen, adrenal ascorbic acid, the amount of food ingested and of feces eliminated, gastric emptying and body weight were measured in two groups of rats of the same age. The F, free fed group was subjected to fast during 22 hours and then had a final meal for two hours. The R rats, subjected to food restriction from one to four weeks, had also a final two hour meal after the regular period of 22 hours with no access to food, and then both groups were treated equally. Coincidently, gastric emptying was more delayed, liver glycogen concentration was highest and glycemia was better maintained in the R than the F rats, particularly after three and four weeks of training. Probably due to their greater dependence upon the more frequent supply of nutrients, the F group had a larger free fatty acids mobilization during fast. Adrenal hyperactivity was induced in both groups and the amount of food ingested progressively increased in the R group and decreased in the F group. In general the metabolic efficiency tended to converge to a similar order of magnitude in both groups of animals by the end of the third week. A delayed gastric emptying seems to be a major factor in the adaptations to food restriction.

Adrenal Glands↗
PubMed1983

Neural mechanisms involved in the recovery from insulin hypoglycemia in dogs.

The contribution of the central nervous system to recovery from insulin hypoglycemia was studied in dogs. Animals with spinal transection just above the sympathetic outflow (to isolate it from encephalic influences), bilateral vagotomy or both types of lesion received an i.v. insulin injection. Also dogs in which the entire central nervous system had been inactivated by osmotic shock were submitted to this test. The results, compared to those obtained from control groups, showed that either spinal transection or severance of the vagi alone did not prevent full recovery from hypoglycemia. When both surgical procedures were combined or the entire central nervous system had been functionally destroyed normal blood glucose concentration was not regained.

Animals↗
PubMed1981

Suppression of the late component of the carotid occlusion reflex by lesion of the medial forebrain bundle in the rat.

1. The pressor response to a prolonged carotid occlusion in the rat has two components: an early, fast increase in blood pressure, and a late, slow and sustained hypertension. Since the second component can be blocked by a disconnecting lesion near the medial side of the medial forebrain bundle, the hypothesis that this complex structure is involved in the integration of the late pressor reflex was tested. 2. The medial forebrain bundle was partially or completely destroyed, or a disconnecting lesion was made to interrupt some of its medially running afferents and/or efferents. Incomplete lesion caused a transient suppression of the second component in 4 rats, whereas complete lesion in 5 rats or probable interruption of the medial efferent pathways in 3 rats led to suppression of the late component when the one-minute occlusion was performed within one hour after the lesion. 3. The data show that the medial forebrain bundle plays an important role in the integration of the late component of the pressor response to prolonged carotid occlusion.

Animals↗