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Biomedical subjects

S Trojan

Publications and source records attributed to S Trojan.

At least 109 records · Page 6Linked to original sources
PubMed1989

Rhythmic metrazol activity in rats as a model of human absences.

Rhythmic activity of the spike-and-wave type was induced by administration of metrazol (25 or 50 mg/kg s.c.) in male rats with implanted cortical electrodes. The animals were deprived of water and then allowed to lick water from a tube. Under control conditions they licked for 3-4 min without an interruption. Rhythmic metrazol activity deranged the licking; when this pathologic activity represented about one third of the time, the licking was fully blocked. We conclude that the impairment of highly motivated behaviour confirms the adequacy of the rhythmic metrazol activity as a model of human primary generalized seizures of the absence type.

Animals↗
PubMed1989

Hypoxia and development of interneurones of the rat hippocampus.

Interneuronal connections are an important component of the integration circuits of the hippocampus. They are formed mostly postnatally, i.e. in a phase when their development can be strongly influenced by external environmental factors. In model postnatal hypoxia, a morphometric analysis showed reduction of the number of dendritic segments (chiefly 3rd order segments) in 18-day-old rats. The total length of the dendrites was unaltered, but mean segment length increased. Interneuron density in the experimental animals was higher, especially in the stratum radiatum, but pyramidal cell density was lower than in the controls. These findings are evidence that hypoxia has a complex effect on the microstructure of the hippocampus and that, in the long run, it can lead to impairment of the balance of the elementary processes of excitation and inhibition.

Animals↗
PubMed1989

[Adaptation to low intensity positive radial acceleration during early ontogenesis].

In 5, 12, and 25 day old laboratory rats of our own breeding LD50 for positive radial acceleration of the intensity of 5 g, 7.5 g and 10 g was established. Resistance was found to decrease with age. All animals exhibited full adaptation on repeated exposure to acceleration of 5 g or 7.5 g, and even 10 g over a period corresponding to 20% duration of the lethal dose for the initial age applied 3 times a day in 3 hour intervals. The resistance of the animals to oxygen deficiency was significantly increased as demonstrated by the survival of all animals 3 hours after their exposure to 10 g acceleration in a dose lethal for the given age. Adaptation is presumed to occur at tissue level.

Acceleration↗
PubMed1989

[The development of the brain and perinatal hypoxia].

The authors describe the development of dendrite structure of pyramidal cells of the CA 1 area of the hippocampus in the laboratory rat. The postnatal dendrite growth comprises their eventual branching and increasing number of dendritic segments. The final number of segments is reached first at the terminal branching of the apical dendrite and at the proximal lateral fibres (by the 10th day). In basal dendrites the branching is terminated on the 15th day of postnatal life. On the main stem and preterminal fibres of the apical dendrite the position comparable with the adult brain is reached at the age of 25 days. Repeated hypobaric hypoxia influenced the mentioned dendrite development in a quantitative way. In particular the number of dendritic branches and the density of dendritic spikes of pyramidal cells was lower. Hypoxia influenced in a similar way also interneurones of the hippocampus even when their number increased. The authors assume therefore that exposure to intermittent hypoxia during development leads to reduced input information. Conversely interneurones of the hippocampus are more resistant to oxygen deficiency, but the thus created disbalance obviously is the basis of the unbalanced character of stimulation and inhibition phenomena.

Animals↗
PubMed1989

Hypoxanthine in diagnosis, prognosis and pathogeny of hypoxic injury.

Oxypurines (hypoxanthine + xanthine, HX) were measured polarographically in the mixed umbilical cord blood plasma, the maternal venous blood plasma and in the anterior amniotic fluid of 104 deliveries. The HX increase was found in groups with clinical signs of perinatal hypoxia. The HX concentration in the mixed umbilical plasma above 15 umol/l (i.e., means +/- 2 S.D.) should be considered as pathological. The following results of experiments on animals suggested a possible pathogenic significance of xanthine oxidase (XOD) reaction on hypoxic injury: The higher the plasma XOD activity of different species (guinea pig, hamster, rat, mouse) the shorter was the survival time of the species in the interrupted hypoxia. Administration of hypoxanthine decreased the survival time of rats in the interrupted hypoxia, while the administration of allopurinol increased it. Allopurinol suppressed the post-hypoxic autoimmune response of the rats to brain tissue.

Amniotic Fluid↗
PubMed1989

Changes of the neuronal structure produced by prolonged hypobaric hypoxia in infant rats.

Structural parameters of neuronal circuits were studied in rats exposed to aerogenic hypoxia during the postnatal development. In 18-day-old experimental animals pyramidal cells of the hippocampal CA1 area had less branches of the apical dendrites. These branches were shorter with lower dendritic spine density. Myelinated axons in the corpus callosum were less frequent. In electron-microscopic picture the mean section area of myelinated axons was lower, the myelin sheets were thinner and consisted of less myelin layers. Synapses in the II. layer of the somatosensoric cortex had more often flat pre-synaptic dense projections, smaller width between pre- and post-synaptic densities and thinner post-synaptic densities.

Altitude↗
PubMed1989

[Response of the immature brain to changes in the internal and external environment. (30 years' neuro-ontology research at the Physiology Institute)].

The authors summarize some original results obtained in long-term neuroontogenetic research. Substrate variability of immature CNS tissue, its capacity of ketone bodies utilization are described and basic developmental changes in the composition of amino acids, fatty acids and key enzymes in brain are established. Analysis of immature CNS adaptability and plasticity, especially in relation to hypoxic load is presented. On the contrary the results indicating very low resistance of newborn mammal to insufficient nutrition and its far-reaching consequences concerning regulations and functional capacities are presented.

Adaptation, Physiological↗
PubMed1989

Ontogenetic development of ketamine-induced sleeping time and electrocorticographic changes in rats.

Latency to the loss of righting reflex and sleeping time after ketamine were measured in 261 rats aged 7, 12, 18, 25 and 90 days. The sensitivity to ketamine was highest in 7-day-old animals and decreased with age. In the youngest group rats slept after the 20-mg/kg dose whereas not all adult animals lost their righting ability after a dose of 160 mg/kg. Electrocorticographic (ECoG) study demonstrated an age dependence of changes induced by ketamine. The youngest group exhibited only suppression of the originally discontinuous ECoG whereas signs of slow-wave sleep or depression appeared in older rats.

Aging↗
PubMed1989

[The effect of acute and chronic hypoxia on ascorbic acid levels in various areas of the brain, liver, adrenal glands and in biological fluids in 18-day-old rats].

The influence of acute and chronic hypoxia on the ascorbic acid content in liver, adrenal, plasma, cerebrospinal fluid and brain in 18-day-old rats was studied. Due to acute hypoxia a significant decrease in ascorbic acid concentration in the adrenal occurred. Its levels in plasma and cerebrospinal fluid increased significantly compared with controls. Chronic hypoxia caused a significant ascorbic acid concentration increase in all samples studied with the exception of olfactory lobe and vermis cerebelli.

Acute Disease↗
PubMed1988

Action of clonazepam and clorazepate on cortical self-sustained after-discharges in the rat.

Self-sustained after-discharges (SSADs) induced by electric stimulation of the sensorimotor cortex in rats exhibited under control conditions a significant progressive prolongation with repeated stimulations. Clonazepam not only blocked this increase in duration but it suppressed and/or abolished SSADs in a dose-dependent manner. Clorazepate in the lowest dose used (10 mg/kg) did not change SSADs. The two higher doses (25 and 50 mg/kg) blocked the prolongation of the 4th SSAD, i.e. this effect had a relatively long latency.

Animals↗
PubMed1988

Plasma xanthine oxidase activity correlates with the resistance to severe hypoxia in different species.

A rapid polarographic method of measuring the O-form of xanthine oxidase (XOD) is described. Activities of this enzyme and oxypurine concentrations were measured in the plasma and cerebrospinal fluid (CSF) of 1, 12, 25 and 60-day-old rats. In the CSF, the highest oxypurine concentration was found in the group of 12-day-old rats (34.07 +/- 12.37 mumol.l-1), and it remained nearly at the same level in groups of older animals. Oxypurines in the plasma, on the contrary, are polarographically measurable on the first day of life; in groups of older rats their concentration is below the sensitivity of the method (5 mumol.l-1). This was explained by the development of XOD activity in the plasma, which increased from 8.17 +/- 2.80 to 99.46 +/- 13.85 nkat.l-1 during the first 60 days of postnatal life. The higher the normal plasma XOD activity, the shorter was the survival time of the species during interrupted hypobaric hypoxia. Adult guinea-pigs and hamsters have no measurable XOD activity in the plasma; adult rats and mice have 99.46 +/- 13.85 and 259.69 +/- 58.23 nkat.l-1, respectively. The survival time of these animals at 10,500 m was measured following exposure to an altitude of 8,000 m for 30 min and 15 minute normoxia. Guinea-pigs survived 100.8 +/- 13.84 min, hamsters 54.25 +/- 11.33, rats 25.2 +/- 5.37 and mice 3.33 +/- 1.00 min.

Animals↗
PubMed1988

Ontogenetic development of etomidate action in rats.

Action of etomidate was studied in 219 albino rats 7, 12, 18, 25 days old and adult. Etomidate at the dose of 20 mg/kg i.p. led to a loss of the righting reflex in all age groups. Sleeping time increased with decreasing age up to the 12th day. Seven-day-old rat pups exhibited short sleeping time, approximately at the level of adult animals. Etomidate can be used for general anaesthesia even in young animals but the quantitative differences in its efficacy have to be taken into account.

Analysis of Variance↗
PubMed1987

Cluster analysis of antibiotic susceptibility patterns of clinical isolates as a tool in nosocomial infection surveillance.

Hospital infections represent a major epidemiological problem. The first step in the detection of nosocomial infections consists in assessing the probability that two or more isolates from different patients are similar or different. Many methods are available for typing purposes. Among these, antibiotic susceptibility patterns do not need extra cost or extra work and are available "on line" every moment they are needed. A mathematical technique of elaboration is proposed for disk zone sizes, in order to assess the probability of two or more clinical isolates to be the same strain. Antibiograms performed according to Kirby-Bauer are evaluated detecting zone sizes by a computer controlled device and then submitted to cluster analysis. Similarity of strains is reported in a dendrogram, in which strains are successively fused. Strains that share a common susceptibility pattern are considered a "cluster". At last, epidemiological maps are constructed for each group of strains, in which all the isolates are reported, ordered for patients, plotted on the day the specimen was collected, drawn in a different shape according to the source of specimen, and shadowed by the pattern of its cluster. This method of reporting data directly allows to detect cross infections among patients and can be used as a first typing step before other more expensive procedures.

Anti-Bacterial Agents↗
PubMed1987

Effect of short-term or intermittent hypobaric hypoxia on plasma lipids in young rats.

Changes in the level of plasma lipids (cholesterol, fatty acids and lipoproteins) were followed in young rats exposed once or repeatedly to hypobaric hypoxia. A single exposure to hypoxia increased the level of LDL lipoproteins but did not influence the concentration of cholesterol and fatty acids in 18-day-old rats. Repeated exposure to hypobaric hypoxia caused a statistically significant increase in the concentration of cholesterol, fatty acids, chylomicra, low density beta-lipoproteins (LDL) and very-low-density beta-lipoproteins (VLDL) in 18-day-old rats, while the level of high-density alpha-lipoproteins (HDL) decreased. In animals that had been repeatedly exposed to hypoxia in their youth, a significant decrease of the LDL lipoprotein fraction was observed at the age of 108 days.

Aging↗