Late EEG after-effects in humans following hyperventilation. I. A comparison between intero- and exteroceptive influences.

Using a modification of the computer period analysis of the EEG (Aladjov and Daskalova 1987) we studied the late after-effects (until the 30th min) in human EEG (monopolar leads at F1, C3, P3 and 01) following two kinds of influences: a) short interoceptive one: 3 min hyperventilation (HV) and b) a series of 5 trains of visual light flashes (VS), presented in 5-7 min intervals. The changes in the ongoing EEG in the 2nd min after each VS and in intervals of 5 min after HV were compared with the values before the stimulation. VS did not elicit long-lasting EEG after-effects, which characterized the single interoceptive influence (HV) and consisted mainly of beta-2 (24-36 Hz) EEG activity increase in all studied cortical regions (Nikolov and Kisselkova 1988). Moreover, the exteroceptive stimulation (VS) had no essential influence on the late EEG after-effects after HV, when both kinds of stimulation were applied in the same experiment.

Late EEG after-effects in humans following hyperventilation. II. A comparison between subjects with different level of adaptation to hypoxia.

The late EEG after-effects following application of a short-lasting ventilatory interoceptive influence (3 min hyperventilation-HV) were studied in humans with three degrees of adaptation: students (ST) with a lower degree of training, professional alpine climbers with a high level of training (AL1) and the same subjects (AL2) in a middle position of adaptation i.e. 6 months after an expedition. ST developed late EEG after-effects, consisting mainly in an increase of the beta-2 EEG activity; AL1 showed very slight changes, while in AL2 the EEG after-effects were intermediate. It is suggested, that a lower level of adaptation facilitates the triggering through HV of processes in the cortical EEG which accompany an improvement of the brain tone.

Changes in the spatial synchronization of the cortical electrical activity under extreme (hyperbaric) conditions.

Spectral correlation methods of EED-analysis were used to study the local synchronization (by power spectra--FFT) and the spatial synchronization (by assessing the coherence functions) of the cortical electrical activity of persons subjected to prolonged (one-month) extreme impact--hyperbaric conditions. Two neurophysiological mechanisms of system functional organization of the electrical activity of the central nervous system are described, through which the brain compensates its reduced functional capacities under the extreme conditions studied (including boundary physiological states). These mechanisms: (a) act in almost all situations of the extreme impact, irrespective of the scope of the remaining varied transient or lasting readjustments in the EEG, and (b) guarantee spatial interactions in the electrical activity in the brain in frequency ranges which are essential for its functions: alpha (8-12 Hz) and beta-2 (24-36 Hz).

Ovariectomy- and sex hormone-induced changes in the excitability of the CNS: an assessment by EEG paroxysmal activity and behaviour.

The changes in the excitability of the CNS were investigated in female rats after ovariectomy and subsequent substitution with ovarial hormones (estradiol, progesterone and combination of both steroids). The excitability of the CNS was evaluated by the spontaneous EEG paroxysmal activity and by some behavioural features (alertness, exploration and quiet wakefulness). The experimental results showed that the removal of the sex hormone secretion for a long-term period causes a discrepancy between the decrease of behavioral patterns and increased excitability in CNS. The substitution with physiological doses of estradiol and progesterone elicits further increase of the sensitivity of the CNS. The latter was demonstrated by an increase of the excitability both in quiet wakefulness and alertness.

Long-term locomotion regimens affect EEG paroxysmal activity, behaviour and sex hormone secretion in female rats.

The study deals with the changes of the excitability of CNS in the course of the ovarial cycle under the influence of long-term locomotion regimens. The excitability of the CNS was evaluated by the spontaneous EEG paroxysmal activity and by the changes in certain behavioural states (alertness, exploration and quiet wakefulness). The changes of the excitability (as assessed by EEG and behavioural features) were correlated with the effects of the locomotor regimens on the serum levels of ovarial hormones. The results suggest that long-term locomotion regimens alter the excitability of the CNS during the ovarial cycle. Running exercise was found to ameliorate the functional state of the nervous system by increasing the activation threshold, whereas restricted locomotion increases the sensitivity of the CNS.

Spontaneous EEG paroxysmal activity, behavioural and endocrine changes in male rats subjected to different regimens of locomotion.

The changes in the excitability of the GNS of male rats were investigated following the influence of long-term (6 months) regimens of locomotion: running exercise and relative immobilization. The excitability was evaluated by the changes in EEG paroxysmal activity and in some behavioural states (alertness, exploration and quiet wakefulness). The quantitative alterations of the features mentioned were correlated with the serum levels of several hormones (LH, testosterone, ACTH, non-specific glucocorticoids) in terms to provide a complete assessment of the functional state of the CNS. The inference was drawn, that long-term exercise elicits adaptive changes resulting in an increase of the activation threshold of the CNS. Long-term restriction of the locomotion leads to an increase of the sensitivity of the nervous system, i.e. the activation threshold of the CNS was found to be lowered.

Late EEG after-effects following short-lasting ventilatory interoceptive influences (hyperventilation and breath holding) in man.

The application of two kinds of ventilatory interoceptive influences with opposite effects on the acid-base balance (hyperventilation and breath holding) results in appearance of late nonspecific after-effects in human EEG, which do not disappear until the 30th min after the stimulation. They consist in local and spatial synchronizing processes in the alpha and beta EEG spectrum, being most pronounced in the beta-2 range (23-36 Hz). These changes are considered as a sign of a development of readjustment in the functional state of the central nervous system in the direction of its improvement. The triggering of this readjustment is largely determined by the considerable changes in the internal medium, leading to intensified interoceptive signalization (mechanical, chemical and proprioceptive), as well as to the development of a brief cerebral hypoxy, followed by improved brain blood flow.

[Crisis and blood coagulation in chickens with experimental spirochetosis]. / Krizis i kruvosusirvane pri pileta s eksperimentalna spirokhetoza.

Studied was the process of blood clotting in normal bursectomized and entire young birds, as well as in the conditions of experimentally induced spirochaetal infection. Use was made of 10 bursectomized and 10 nonbursectomized month-old birds. It was found that blood clotting with the uninfected bursectomized birds was more strongly manifested as compared to the entire ones. At the 120th hour following infection of the bursectomized birds the clotting of blood was comparatively more weakly expressed than it was in the nonbursectomized ones.

[Effect of ultrasound-disintegrated spirochetes on blood coagulation and hemodynamics in chickens]. / Vliianie na dezintegriranite s ultrazvuk spirokheti vurkhu kruvosusirvaneto i khemodinamikata pri pileta.

Blood coagulation tests and histopathologic investigations of birds were carried out following the injection of a suspension of spirochaetes destroyed with ultrasound. It was found that the suspension acted as thromboplastin, causing disseminated intravascular clotting of blood after intravenous injection.

Spatio-temporal organization of bioelectrical processes in the nervous-system--its functional significance and complex quantitative estimation by means of spectral and coherent analyses.

The review of our research and the data in the literature shows that application of the systems approach and the complex quantitative analysis of local processes and spatio-temporal organization of bioelectrical activity in the nervous system provides better possibilities for the discovery and investigation of functionally significant changes, often discrete, appearing in the course of investigations performed under normal physiological conditions in man and in freely moving animals, as well as for the estimation of changes beyond the limits of homeostasis.

[Effect of environmental factors on the body response reactions in newborn calves]. / Vliianie na niakoi faktori na vunshnata sreda vurkhu otvetnite reaktsii na organizma na novorodenite teleta.

Studied was the role of the general state and the adaptability of newborn calves under the effect of some environmental factors (temperature and relative humidity) that had no optimal values in the onset of diseases caused by occasionally pathogenic agents. It was found that under conditions that were one and the same for all calves the metabolic and functional responses were varying. Those of the animals with which the nervous-and-hormonal system was more unstable manifested a specific biochemical-and-functional response through which no'equilibration' was achieved with the environment, and they got sick. Others, exhibiting metabolic processes that were stronger and more stable as the result of the involvement of more powerful regulatory mechanisms inherent to a 'neuro-functional' animal organism could adapt successfully to the nonoptimal factors of the environment. Such animals were not shown to be susceptible to the effects of conditionally pathogenic agents.

[Virological and bacteriological research on the etiology of gastroenteritis in newborn calves]. / Virusologichni i bakteriologichni prouchvaniia vurkhu etiologiiata na gastroenteritite po novorodenite teleta.

Virologic and bacteriologic studies were carried out of samples taken from calves with clinical gastroenteritis and from calves that died at the age of 2 to 10 days. A total of 199 samples were investigated of calves on 48 cattle-breeding farms. In 69 of the cases (34.2 per cent) strains of Escherichia coli were isolated, prevailing being those of the O8, O9, O15, O21, O26, O55, and O78 serogroups. Three of the strains isolated from fecal samples of clinically affected calves possessed the K99 antigen. The indirect immunosorbent method was employed, with 113 samples (56.8 per cent) identifying rotaviruses, and via the indirect immunofluorescence method in 26.6 per cent of the post mortem samples the virus of the mucosal disease was identified. On individual farms with records of the disease most often mixed infections of E. coli and rotaviruses were found. In order to organize effective prophylaxis and control complex bacteriologic and virologic investigations should be carried out with higher number of clinical and post mortem samples.

[Resistance of different breeds of laying poultry to Marek's disease virus]. / Ustoichivost na razlichni linii ptitsi iaitsenosno napravlenie kum virusa na bolestta na Marek.

Investigated were a total of 447 two-day-old chicks of lines 5-A, ia-73' ll and lS of the Leghorn breed divided into 2 groups: controls--99 males and females, and test ones--348 infected at the age of 2 days via intraabdominal injection with 0.4 cm3 heparinized blood each, containing 5000 PFU per dose of the Marek's disease virus (CT-1 isolate). Both linear and sexual variations were found in the resistance of the birds. Most resistant proved to be the 5-A chicks of both sexes, and most susceptible--those of the lS line. No essential differences were observed in the response of the initial lines of broiler birds and the lines of laying birds raised in this country at the intraabdominal infection with the same virus. It was established that the birds of lines 5-A and 6-E of the Canadian Leghorn breed were close in terms of resistance with the birds of lines 66 and 77 of the Cornish breed, while those of the Leghorn lines ll and lS were resembling by resistance the birds of lines 88 and 89 of the White Plymouth Rock broilers which were more susceptible to Marek's disease. It is stated that the cockerels and poults of the ia-73 synthetic line, newly developed in this country, show essentially varying resistance most probably associated with insufficient consolidation.

Equalization of the coherence of rhythms in the EEG and its significance.

The article treats problems related to the application of coherent analysis in studying the spatial synchronization of rhythms in the EEG. The significance of comparing the changes in the coherent functions (CF) of more combinations of cerebral structures, i.e. of intercoherent relations, is pointed out. Evidence is given that the observed equalization of the coherence according to different frequency ranges has a definite physiological significance, connected with the readjustment of the functional state of the nervous system on the basis of changes in the organization of the spatial rhythmic interrelations in it. Tests are made of several parameters for quantitative estimation of the changes in the intercoherent relations, which may be applicable to studying the organization of rhythms in the bioelectrical activity of the nervous system in different functional states in norm and pathology.