Physiological sleep myoclonus in baboons

Physiological sleep myoclonus (sleep onset myoclonus and myoclonus during paradoxical sleep) was recorded from the tails of 6 baboons (2 Papio hamadryas and 4 Papio papio) and its relationship with spontaneously occurring EEG paroxysmal discharges was studied. It was observed that during light slow wave sleep tail myoclonus (sleep onset myoclonus) was almost always associated with EEG paroxysmal discharges predominating in the fronto-rolandic cortex. During deep slow wave sleep the number of EEG paroxysmal discharges decreased and tail myoclonus disappeared. In contrast, during paradoxical sleep tail myoclonus became more frequent even in the absence of cortical paroxysmal discharges. Though at present we do not know whether sleep onset myoclonus is triggered or not by cortical paroxysmal discharges, we propose that sleep myoclonus (sleep onset myoclonus and myoclonus of paradoxical sleep) is independent of these discharges but that, at a given moment, the two phenomena may be coupled by a hypothetical subcortical pacemaker.     

Development of Epileptic Activity in Embryos and Newly Hatched Chicks of the Fayoumi Mutant Chicken

Summary: The homozygous Fayoumi strain of epileptic chickens (Fepi) is affected by generalized convulsions consistently induced by intermittent light stimulation (ILS) and by intense sound. Although interictal EEG recordings show continuous spikes and spike and wave activity, desynchronization and flattening (DF) of the EEG are observed during seizures. We have studied development of the epileptic phenotype in embryonic (E) and posthatching (P) Fepi. As compared with those of chicken embryos of a normal strain, no differences were observed in the EEG before embryonic day (E) 16. Clearly differentiated spikes and spike and waves appeared at E17 in Fepi. Metrazol-induced EEG seizures were observed at E16 in normal embryos and at E17 in Fepi. The Fepi showed some characteristics: Spontaneous EEG seizure-like discharges also appeared at E17 but decreased to-ward hatching; visual or acoustic hyperexcitability developed at E20 together with evoked responses in normal chickens; desynchronization of the EEG, typical of the epileptic seizure of the adult, could be induced by ILS at E20, but ILS- or sound-induced generalized motor seizures appeared at P1, a few hours after hatching. Results show that Fepi phenotype reaches full expression at P1, but the electric paroxysms are expressed earlier, paralleling synaptic maturation.     

Intercellular MHC transfer between thymic epithelial and dendritic cells

Thymic dendritic cells (DC) and epithelial cells play a major role in central tolerance but their respective roles are still controversial. Epithelial cells have the unique ability to ectopically express peripheral tissue-restricted antigens conferring self-tolerance to tissues. Paradoxically, while negative selection seems to occur for some of these antigens, epithelial cells, contrary to DC, are poor negative selectors. Using a thymic epithelial cell line, we show the functional intercellular transfer of membrane material, including MHC molecules, occurring between epithelial cells. Using somatic and bone marrow chimeras, we show that this transfer occurs efficiently in vivo between epithelial cells and, in a polarized fashion, from epithelial to DC. This novel mode of transfer of MHC-associated, epithelial cell-derived self-antigens onto DC might participate to the process of negative selection in the thymic medulla.     

Sleep disturbances in man during different compression profiles up to 62 bars in helium-oxygen mixture

Studies of sleep organization of 8 subjects were performed during 4 dives between 500 and 610 msw (51 and 62 bar) in a helium-oxygen mixture. The results of the 156 sleep records showed that sleep was disrupted from 30 bar: awake periods and stages I and II increased, stages III and IV and REM periods decreased. These disturbances, which were more intense with fast compression and recovered during decompression, can be considered as further symptoms of the high pressure nervous syndrome (HPNS).     

Water diffusion and measurement of cerebral blood flow by C15O2 inhalation

Measurement of local Cerebral Blood Flow (CBF) using the C15O2 continuous inhalation technique coupled with Position Emission Tomography (PET) rests on the assumption that the in vivo labelled water (H215O) of blood diffuses freely within the brain water pool. This requirement however, may be disputed: in the rhesus monkey, Eichling et al (1974) showed a linear relationship between the single-pass extraction of water (E) and CBF after intra-carotid H215O injection, such that E decreases as CBF increases. Such a limitation in water transport across the blood brain barrier has also been suggested to exist in man (Paulson, 1977). In order to verify its possible effects on measured CBF in baboons, simple computer analysis was performed comparing the data obtained with CBF values reported in similar experiments, but using a freely diffusible inert gas (133Xe). This allowed calculation of a water extraction index (IE), which was shown to decline as CBF increased. This result may be considered as a presumption of the part played by the limited water diffusibility on the final CBF values, but other factors must also be considered, such as the inescapable admixture of grey and white matter (partial volume effect), a limitation of present day PET technology.     

Potent convulsant effects of a benzodiazepine inverse agonist, methyl beta-carboline-3-carboxylate in cats

The convulsant properties of methyl beta-carboline-3-carboxylate (beta-CCM), which is a homologue of a putative benzodiazepine receptor ligand in the mammalian central nervous system, were examined in cats. Subcutaneous injection of 0.5 mg/kg of the beta-CCM produced various degrees of myoclonic jerks always accompanied by cortical spike burst. Some autonomic symptoms such as tachypnea, hypersecretion of thick mucous saliva, vomiting and mydriasis were also presented. Subcutaneous injection of 1.0 mg/kg of the compound induced a generalized tonic-clonic convulsion. Injection of the same amount of the drug 1 hour later in the same cats failed to provoke a generalized seizure. Repeated injection of the same dose 3 hours later provoked a generalized seizure, but with a longer latency. However, repetition of the experiments 24 hours after or 10 days after the first injection consistently induced the same type of generalized seizure with the same latency as the first injections. These results support the suggestion that the pharmacological effect, especially the convulsive effect, of beta-CCM is dose-related, reversible and reproducible in the same cats and among different cats. Moreover, the postictal refractory period in this model of epilepsy may continue about for 3 hours.     

Évolution des réponses évoquées le long de la voie visuelle au cours du sommeil nocturne chez Papio papio

Averaged evoked responses (AER) to light flashes were recorded in baboons (Papio papio) during wakefulness, slow-wave sleep and rapid eye movement (REM) periods, at the visual cortex, retrocalcarine sulcus, optic tract (OT), lateral geniculate (LG) and pulvinar.Waking AERs were composed: in the OT, of a negative, low amplitude wave at 13.3 msec (I), a high amplitude wave at 34.8 msec (II), a negative wave at 72 msec (III) and a late component at 151 msec; in the LG, a small positive wave (II) with a peak latency of 40 msec, a high amplitude negative wave (III) with a latency of 70 msec and a late component; in the pulvinar of two low amplitude short latency waves (I and II), respectively negative and positive at 25 msec and 40 msec, then a high amplitude negative wave (III) at 75 msec and a late component; in the retrocalcarine sulcus 3 positive waves (I, II and III) were recorded at 25, 45 and 100 msec and a late component; in the visual cortex, 3 low amplitude negative waves (II, III and IV) at 40, 50 and 54 msec, then a positive wave at 80 msec and some late components.In slow-wave sleep, AERs did not change in the OT, but in the LG and pulvinar, they showed an increase in the amplitude of wave II from stage 1 to stage 3. At the cortical level, early waves (II for the retrocalcarine sulcus, II and IV for the visual cortex) presented a marked increase in amplitude during stages 2 and 3, but only a slight increase for stage 1. Peak latency increase of each wave in cortical and subcortical AERs was seen during slow-wave sleep.REM AERs resembled, in amplitude and peak latency, those recorded in the LG and pulvinar during wakefulness; in the visual cortex and retrocalcarine sulcus, they were similar to those obtained during wakefulness and stage 1.In conclusion, a different evoked response was found between visual cortex and deep structures (except for the OT): firstly, during slow-wave sleep (the AERs showed a difference for stage 1 between the visual cortex or the retrocalcarine sulcus and the LG or the pulvinar), secondly, in REM (on the cortex, REM AERs looked like wakefulness and stage 1 responses); on the contrary, in the LG and pulvinar, REM AERs were similar only to those recorded during waking. Finally, it can be said that for Papio papio the differentiation and structural responses between the various stages of sleep (particularly light sleep and REM) were greater in the cortex than in the thalamic structures.