A1. Volume load and pressure load both relate to relative wall thickness in former PE.

AIMS: To study the relationship between volume and pressure load on the one hand and relative wall thickness (RWT) on the other hand in former preeclamptic women. METHODS: In 654 former PE women, blood pressure (BP) and PV (iodine 125 albumin indicator dilution technique) where measured. PV was indexed for body surface area (BSA). Echocardiography was performed to calculate RWT. The study population was divided in 4 subgroups consisting of women with either normal- or high-systolic BP (sysBP) (<140 versus ≥140mmHg, respectively) and normal- or low-PV index (>1373 versus ≤1373 ml/m2 respectively). Differences between the four subgroups where analyzed with ANOVA. Pearson's rho is calculated for the correlation between PV and sysBP on the one hand and RWT on the other hand. RESULTS: RWT was the lowest in the group with normal sysBP and normal PV and the highest in the subgroup with high sysBP and low PV subgroup (Table 1). Moreover, PVindex correlated negatively with RWT in the setting of both normal sysBP and high sysBP (Figure 1a and b) while systolic BP correlated positively with RWT in the setting of normal sysBP but not in the setting of high sysBP (Figure 1c and d). DISCUSSION: Raised RWT, as a measure for concentric remodelling, relates to both decreased volume load and increased pressure load.

Cellular and subcellular morphological localization of normal prion protein in rodent cerebellum.

Normal cellular prion protein, a necessary protagonist in fatal neurodegenerative prion diseases, was mapped in rodent cerebellum to establish its cellular and ultrastuctural localization. Existing morphological data about native prion protein distribution in brain tissues remain, indeed, contradictory and do not fit with biochemical and cell biological results. Using ultrastructural preembedding immunocytochemistry and a monoclonal anti-mouse prion protein antibody, this report shows that cellular prion protein is present in all cortico-cerebellar and deep nuclei neuronal cell types, as well as in all glial cell types. The heaviest expression appears on parallel fibres and astrocytic processes. The protein is exclusively located on the outer cell membrane and in Golgi and endosomal intracytoplasmic organelles, with no cytoplasmic or synaptic vesicle labelling. Most important, and in contrast with previous ultrastructural data, cellular prion protein is shown to be distributed on all portions of neurons, without any preferential synaptic targeting. The present morphological report shows, for the first time in vivo, that the cellular prion protein is present on the entire cell surface membrane of all neuronal and glial cell types of the rat cerebellum. This ubiquitous presence supports the notion that prion protein has a generalized cellular function in brain tissue rather than a specialized role restricted to synaptic transmission.

Reticular control of thalamic transmission during behavioral states: a study in dorsal lateral geniculate nucleus relay neurons of the cat.

In behaving cats adapted to head restraint we examined the changes of spontaneous activity of dorsal lateral geniculate relay neurons provoked by weak stimulation of mesencephalic reticular formation during different states of sleep and alertness. The neurons were classified as fast- and slow-conducting neurons depending on their optic tract latency. When the reticular stimulation was delivered during slow-wave sleep, it increased the firing rate principally in slow neurons and suppressed the burst pattern. The increases occurred on a long depolarization in intracellular recordings (n = 9). The effect resembled one that was simultaneous with pontogeniculooccipital waves. Only slow neurons showed a correlation between the relative increases and the prestimulus firing rate. The excitatory effect was reduced and less frequent during wakefulness and paradoxical sleep in both latency groups. When reticular stimulation did not influence the spontaneous activity of the activated states, it also did not modify the optic tract-elicited hyperpolarization. The data tend to demonstrate that the efficiency of the reticular stimulation depends principally on the rate and pattern of the spontaneous activity which, itself, varies largely according to the behavioral state and moderately according to the optic tract latency.

Oscillations of the spontaneous slow-wave sleep rhythm in lateral geniculate nucleus relay neurons of behaving cats.

Intracellular recordings of 31 lateral geniculate nucleus relay neurons were performed in darkness in behaving cats in order to analyse electrical postsynaptic events which appeared during slow-wave sleep. A specific pattern characterized slow-wave sleep: a rapid depolarizing potential arising from baseline initiated a slow depolarization lasting for 40-60 ms which in turn most often elicited delayed fast spikes. This pattern recurred at a frequency of 6-12/s. The slow depolarizations were voltage dependent, usually not separated by any obvious phasic hyperpolarization and showed refractoriness. Other rapid depolarizing potentials occurring during the time course or at the end of a slow depolarization could have generated spike(s) but were followed by a rapid decay. Slow depolarizations were not observed during arousal or paradoxical sleep when the neurons tonically depolarized and displayed either rapid depolarizing potentials with a fast decay or repetitive firing and long high frequency bursts. In five of the studied neurons, decreases in frequency of the spontaneous rapid depolarizing potentials occurred during slow-wave sleep for 3-30 s oscillatory periods without any change in the behavioural state. During these periods all of the few remaining rapid depolarizing potentials arose from a flat baseline, had a higher amplitude and initiated a slow depolarization which always elicited a spike or burst of spikes after a brief delay. The slow-wave sleep rhythm decreased to 1-5/s. Simultaneously the baseline membrane potential hyperpolarized by a few millivolts and reached a level for reversal of inhibitory postsynaptic potentials. Imposed hyperpolarization of the membrane during wakefulness did not reveal any slow depolarization. But strong synaptic excitatory inputs and direct excitation (a break of the current pulse) from a hyperpolarized membrane did evoke the slow depolarization and eventually the fast spike(s) in both control and oscillatory neurons. A rhythm similar to that of slow-wave sleep was elicited during wakefulness by optic tract stimulation and was enhanced by membrane hyperpolarization. But under these conditions the rhythm was initiated by a phasic hyperpolarization and was composed of an alternating hyperpolarization-depolarization. Spontaneously and synaptically evoked rapid depolarizing potentials arising from baseline had a similar rising slope. The spontaneous ones initiated a slow depolarization leading to fast spike(s) during slow-wave sleep and could directly generate fast spike(s) during wakefulness.(ABSTRACT TRUNCATED AT 400 WORDS)

[Cerebellar cortex: simulation of recurrent collateral inhibition with the aid of a set of neuronal automata. I. Model and global results]. / Cortex cérébelleux: simulation de l'inhibition par collatérales récurrentes à l'aide d'un ensemble d'automates neuronaux. I. Modèle et résultats globaux.

In view of a study on the transfer function of the cerebellar cortex a modelization of each of the various subsystems was undertaken. The recurrent collateral inhibition existing between Purkinje cells was mimicked by means of an assembly of neuronal automata (NA) temporally evolving at random through three states ("silent", "tonic" and "phasic" and interacting with simple rules. In such an assembly--by comparison with a control group of independent NA--a drastic modulation of activity appears. First the total of the mean number of state shifts is increased by more than 10%. This increase is clearly hierarchical with a maximal effect for the "silent" state. Second the average duration of each state also varies, although in a contrasted manner. Third, and moreover, a clear spatial cooperativity emerges. Indeed all the individually coupled NA are in the same "silent" state at identical moments for more than 5.5% of the total running time. A cyclic repetition of this spatiotemporal cooperativity is apparent. The emergence of these collective properties--which can not be deduced linearly from the unitary elements--introduces a parameter of order leading to a coherent functioning of the system.

Modulation of postsynaptic activities of thalamic lateral geniculate neurons by spontaneous changes in number of retinal inputs in chronic cats. 1. Input-output relations.

The experiments were designed to explore the role of retinal inputs compared with that of the behavioral state in the modulation of the output of thalamic lateral geniculate neurons during sleep and wakefulness in cats with intact visual pathways. We made the following assumptions: the retinal dark discharge, while showing spontaneous pauses in activity, does not vary with the behavioral state; the optic tract inputs postsynaptically elicit subthreshold activities called S-potentials which in turn generate spikes, the degree of transformation being dependent on the level of alertness. On the basis of these assumptions, it could be expected that changes in retinal input frequency would modify the rate of the S-potentials. Therefore the effect of spontaneous decreases in frequency of S-potentials on the spike rate and pattern was examined in juxta- and intracellular recordings from chronically implanted cats during natural sleep and wakefulness. During quiet wakefulness and light slow-wave sleep, lateral geniculate relay neurons normally displayed numerous S-potentials associated with a moderate firing rate. Many neurons occasionally showed transient reductions in frequency of the S-potentials and an oversimplification of the discharges which combined a decreased rate with a prevalent rhythmical burst pattern. Antidromic responsiveness remained unchanged. The oscillatory periods recurred two to six times without any alteration in the control state level. They were not observed throughout wakefulness and paradoxical sleep, during which neuronal activity combined a high spike rate with a low S-potential rate. The modifications were confirmed by computation of the mean rates and of the inter-event intervals. The transfer ratio (spikes/S-potentials + spikes) significantly increased both during the oscillatory periods poor in S-potentials of quiet wakefulness and during active wakefulness. But the correlation between the transfer ratio and the spike frequency, which was high throughout the control behavioral states, faded during the periods poor in S-potentials. Thus the transient falls in the frequency of S-potentials which occurred spontaneously during quiet wakefulness caused burst discharges in lateral geniculate relay neurons, which resembled a sleep deepening, but also paralleled the effect of experimental deafferentation. The data indicate that the iterative spikes grouped in well spaced bursts which persisted during decreases in subthreshold postsynaptic activities result in an enhanced signal-to-noise ratio.(ABSTRACT TRUNCATED AT 400 WORDS)

Data entry on a computer terminal: repetitive work strains on the oculomotor and central nervous systems.

Continuous telemetric recordings including E.K.G., E.O.G., and E.E.G. were carried out on two subjects during 4 working days: 1 day of "reference work" or classical clerical activities, 3 days of "data entry work". Although the time allowed for the task was not limited, the performance assessed from oculomotor patterns remained stable throughout the day, from one day to the next and from one subject to another. This stability was reflected on the stereotyped E.E.G. patterns recorded during the work period, the differences occurring between reading and typing were more acute in the left cortical hemisphere than in the right. As a result of these stable patterns, the ultradian oscillations of the behavioural and physiological parameters were less during data entry than during work reference. The only possible time adjustments were the interruptions or breaks between two document pages and their variations could be considered as indicators of work load.

Sleep-related variations of membrane potential in the lateral geniculate body relay neurons of the cat.

Membrane potential of lateral geniculate body relay neurons was monitored in chronic cats during the sleep-waking cycle. Neurons were tonically depolarized throughout paradoxical (P) sleep and the maximal level of polarization occurred during slow (S) sleep (mean difference of membrane potential between S and P sleep: + 10.2 +/- 1.3 mV, n = 6, range: 8-12 mV). Some features of the spontaneous activity of S and P sleep are briefly discussed in relation to the level of membrane potential. In particular it is suggested that the phasic depolarizations underlying the bursts of action potentials during S sleep, and which are reproduced retinal cell axons impinging upon the hyperpolarized membrane.

[Electroencephalographic rhythms during psychometric tests at 50 and 70 years of age]. / Rythmes électroencéphalographiques au cours de tests psychométriques à 50 et 70 ans.

The experiments were conducted to investigate changes occurring between maturity and old age in variations of the EEG when performing a series of mental tasks. Forty three normal male volunteers, divided in two age groups separated by 2 decades (52.9 +/- 0.2 yr, N = 22; 72.2 +/- 0.2 yr, N = 21), were continuously recorded by telemetry in 3 conditions: control, tests, questionnaires. Beta, alpha and theta rhythms and the number of slow waves were measured after visual EEG interpretation. The study showed that: (1) theta rhythms and slow waves were in higher proportions in men in their 70s; (2) variations induced by the various mental tasks were very similar at ages 50 and 70; (3) the two groups differed mostly in theta rhythm responses during tests with a coding task; (4) test performances and EEG indices were correlated only in the older group for theta rhythms.

[Effects of a cortical after-discharge on lateral geniculate neurones. Electrophysiological study in the chronic cat (author's transl)]. / Effets d'une post-decharge corticale sur les neurones du corps genouille lateral. Etude electrophysiologique chez le chat chronique.

(1) A chronic preparation is described in which it is possible to record juxtacellularly from identified thalamo-cortical relay (TCR) neurones in lateral geniculate body (LGB) of normally respiring, nonanaesthetized cats during natural sleep. (2) Cellular events were analyzed during and after focal electrical stimulation of homotopic visual cortex. (3) Projection of cortical epileptiform after-discharge (EAD) was strictly limited to functionally related areas of LGB. Of the 47 neurones tested only 30% were activated. (4) During the 2 sec, 50 c/sec tetanus the cortically evoked IPSPs in TCR cells were replaced by facilitation of cortico-thalamic transmission as demonstrated by the occurrence of a burst of action potentials (AP) following the antidromic AP. (5) During the ensuing EAD, high frequency AP discharges occurred in the cortico-thalamic axons during each cortical wave. This period was accompanied by prolonged (50-300 msec) low amplitude rhythmic depolarisations leading to temporary spike inactivation of TCR neurones. Comparable inactivating responses were recorded during paradoxical sleep. (6) Between paroxysmal bursts facilitation of synaptic transmission to the optic tract stimulation was observed. (7) Persistence of a positive collision test after a spontaneous AP indicates that AP are orthodromically propagated during the EAD.

[Inactivating depolarization of relay neurons in the lateral geniculate body during paradoxical sleep in the cat]. / Dépolarisations inactivantes des neurones relais du corps genouillé latéral au cours du sommeil paradoxal chez le chat.

In relay neurons of the lateral geniculate body, burst discharges that occur during paradoxical sleep in the cat are accompanied by depolarizations. Some of these depolarizations reached threshold for spike inactivation. The possible mechanism of these depolarizations is briefly discussed.

[Intra-sleep awakenings in relation to habitual sleep length and modifications of the sleep-wake rhythms (author's transl)]. / Durée habituelle de sommeil, modifications du rythme veille-sommeil et éveils nocturnes.

The number of episodes of intervening wakefulness, their duration and their sleep stage occurrence were analyzed in the sleep recordings of 19 young (19-23 years), good sleepers. There were 5 long sleepers (LS), 5 short sleepers (SS) and 9 regular sleepers (RS). The experimental protocol included 2 reference nights, a night sleep recovery (after 36 h of wakefulness) and a day sleep recovery (after 24 h). The night following the day sleep recovery was also recorded. The duration of waking episodes was very stable and was independent both of type of sleeper and of situation. The histogram of these durations seemed to follow an exponential law. The number of awakenings varied according to the individual, the habitual sleep length (SS had very few) and the situation (such as length of prior wakefulness or circadian factors).

Habitual sleep length and patterns of recovery sleep after 24 hour and 36 hour sleep deprivation.

Five long sleepers (LS) and 5 short sleepers (SS) were selected from 310 medical students. Nine regular sleepers (RS) were used as a control. The sleep was recorded during 3 reference nights, one recovery night after a 36 h sleep deprivation (R2), one morning sleep after a 24 h sleep deprivation (D1) and the night following D1(R1). According to previous data slow wave sleep (SWS) amounts were the same in the 3 groups while stage 2 and paradoxical sleep (PS) amounts increased with the sleep duration. The hourly distribution of intervening wakefulness and SWS were similar for all groups. When compared to RS or SS the hourly distribution in LS of PS was lower until the sixth hour. As a function of experimental conditions, sleep patterns of LS were the most affected. In R2 the sleep of LS more closely resembled that of RS or SS than in reference nights, while in R1 LS' sleep was the most disturbed. Morning sleep durations were very similar for all groups, but in LS intervening wakefulness was increased and PS was decreased when compared to RS and SS. Negative correlations (Spearman rank test) were found between the morning increase of body temperature after a sleep-deprived night and both TST and PS durations. In all recorded sleep periods, SWS amounts were positively correlated with prior wakefulness duration and the PS amount with TST.

[Sleep in children with episodic sleep phenomena: a comparison with the normal child]. / Sommeil de l'enfant présentant des manifestations episodiques du sommeil: comparaison avec l'enfant normal.

(1) The sleep pattern of 23 children, aged 5-12 years, with episodic nocturnal phenomena (night-terrors, somnambulism, rhythmic movements) was recorded during two successive nights. It was compared with that of a group of 21 normal children of the same age. (2) In the pathological group, slow wave sleep (SLP, stages 3 and 4) was significantly shortened during the 2 nights. This deficit mainly involved the first 3h of sleep. (3) As for the slow wave sleep, REM sleep (SP) modifications prevailed during the first hours of sleep. The first REM period was delayed and preceded by more numerous and atypical partial REM periods. The duration of the first REM period increased faster as a function of its latency than in the normal child. (4) In contrast with this difficulty for REM sleep to occur during the first part of the night, the subsequent REM sleep pattern was similar in the 2 groups (total REM sleep duration, mean REM period duration, mean REM cycle duration). For equal latencies, REM periods had similar duration. Finally, the total REM sleep amount was a linear function of the total sleep time, with more or less identical coefficients for the two groups. (5) The part played by these modifications during the first hours of sleep in the occurrence of night terrors and somnambulism is discussed.