Distribution and dynamics of two species of Dinophyceae producing high biomass blooms over the French Atlantic Shelf.

The frequency and distribution of high biomass blooms produced by two dinoflagellate species were analysed along the French continental shelf from 1998 to 2012. Two species were specifically studied: Karenia mikimotoi and Lepidodinium chlorophorum. Based on remote-sensing reflectances at six channels (410, 430, 480, 530, 550 and 670nm), satellite indices were created to discriminate the species forming the blooms. A comparison with observations showed that the identification was good for both species in spite of a lower specificity for L. chlorophorum. The overall analysis of the satellite indices, in association with some monitoring data and cruise observations, highlights the regularity of these events and their extent on the continental shelf. L. chlorophorum blooms may occur all along the South Coast of Brittany. All the coastal areas under the influence of river plumes and the stratified northern shelf area of the Western English Channel appear to be areas of bloom events for both species. These two species are likely to be in competitive exclusion as they share the same spatial distribution and the timing of their bloom is very close. Finally, due to the scarcity of off-shore observations, these satellite indices provide useful information regarding HABs management and the development of a warning system along the French coast.

Role of the forebrain commissure and hemispheric independence in photosensitive response of epileptic baboon, Papio papio.

The effect of monocular intermittent light stimulation (ILS) of either hemivisual field (HVF) of the full visual field (FVF) was examined in Papio papio with or without forebrain bisection. ILS of the HVF or the FVF in non-bisected baboons produced bisymmetrical and bisynchronous spike and wave which was followed by a self-sustained seizure without EEG evidence of hemispheric independence. ILS of the FVF in bisected baboons also produced bilateral spike and wave and self-sustained seizures of a similar nature. With ILS of the HVF in bisected baboons, EEG seizures lateralized largely to the contralateral hemisphere and when the ILS of the HVF was switched to the other eye similarly lateralized spike and wave and a self-sustained seizure were produced in the other hemisphere. These findings suggest that (a) the forebrain commissure, most probably the corpus callosum (and possibly the hippocampal commissure), plays a major but not unique role in the bisynchronization and generalization of the ILS-induced spike and wave and the self-sustained seizures, and (b) each hemisphere possesses independent cerebral excitability to the ILS.

Multiunitary activity analysis of cortical and subcortical structures in paroxysmal discharges and grand mal seizures in photosensitive baboons.

Cortical and subcortical multiunitary activities (MUA) and EEG were simultaneously recorded in baboons made photosensitive by a subconvulsant dose of DL-allylglycine. Intermittent light stimulation (ILS) trains induced in these animals fronto-rolandic (FR) paroxysmal discharges (PDs, constituted as spikes and waves) and grand mal seizures. During the induction of FR PDs by ILS trains, the visual structures (occipital cortex, colliculi superioris, pulvinar) showed a significant MUA increase which was not related to the PD spike or wave but correlated with the flashes. The first structure showing bursts of MUA that frequently preceded the PD appearance was the FR cortex. When PDs appeared, the bursts were related to the spikes of PDs and were followed by an inhibition during the slow wave. The pontine and mesencephalic reticular formations and the facial nuclei were activated in bursts after the FR PDs had reached a certain amplitude. The thalamic nuclei ventralis lateralis, centrum medianum and lateralis posterior were activated only later, when the FR PDs had reached an even greater amplitude. It is suggested that the activation of visual structures is necessary for FR PD appearance. The secondary pontine and mesencephalic activation could reinforce that of the FR cortex and then the thalamus, and could determine the myoclonus observed in unparalysed animals. When the ILS is continued, grand mal seizures appear. The onset of the seizures could be linked to the loss of FR cortical control of the subcortical structures. The resulting reticular activation would be responsible for the vasomotor modifications which constitute the first clinical signs of a seizure.

[Analysis of the multi-unit activity of the cortex and subcortical structures during paroxysmal discharges and grand mal seizures in the photosensitive baboon]. / Analyse de l'activité multiunitaire du cortex et des structures sous-corticales lors des décharges paroxystiques et des crises grand mal chez le babouin photosensible.

Cortical and subcortical multiunitary activities (MUA) and EEG were simultaneously recorded in baboons rendered photosensitive by a subconvulsant dose of DL-allylglycine. Intermittent light stimulation (ILS) trains induce in those animals fronto-rolandic (FR) paroxysmal discharges (PDs, constituted as spikes and waves) and grand mal seizures. During the induction of FR PDs by ILS trains, the visual structures (occipital cortex, colliculi superioris, pulvinar) show a significant MUA increase which is not related to the PD spike or wave but is correlated to the flashes. The first structure showing bursts of MUA that frequently precede the PD appearance is the FR cortex. When PDs appear, the bursts are related to the spikes of PDs and are followed by an inhibition during the slow wave. The pontine and mesencephalic reticular formations and the facial nuclei are activated in bursts after the FR PDs have reached a certain amplitude. The thalamic nuclei ventralis lateralis, centrum medianum and lateralis posterior are activated only later, when the FR PDs have reached an even greater amplitude. It is suggested that the activation of visual structures is necessary for FR PD appearance. The secondary pontine and mesencephalic activation could reinforce that of the FR cortex and then the thalamus, and could determine the myoclonus observed in unparalyzed animals.

Convulsant effect of Ro 5-4864, a peripheral type benzodiazepine, on the baboon (Papio papio).

The effects of Ro 5-4864, a 1,4-benzodiazepine with a high affinity for the peripheral-type benzodiazepine (Bz) binding site, were investigated in the baboon (Papio papio), which is genetically predisposed to epilepsy. A proconvulsant effect of low doses (1-3 mg/kg, i.v.) of Ro 5-4864 was observed by studying its effect on the photic responses induced by intermittent light stimulation in non-photosensitive baboons. Higher doses of Ro 5-4864 (10 mg/kg, i.v.) were overtly convulsant. The Bzs clonazepam and diazepam blocked these convulsant actions of Ro 5-4864 whereas neither Ro 15-1788, an antagonist of central Bz binding sites, nor PK 11 195, an antagonist of peripheral Bz binding sites, had any effect. It thus appeared that the convulsant effect of Ro 5-4864 was not mediated by Bz binding sites of either the central or the peripheral type. It is possible that Ro 5-4864 exerts its convulsant action at the picrotoxin site of the central Bz receptor - gamma-aminobutyric acid receptor-chloride ionophore complex.

The influence of light stimulation on subcortical potentials evoked by single flashes in photosensitive Papio papio.

Visual evoked potentials (VEPs) from the frontorolandic (FR) cortex and from subcortical nuclei (colliculi superioris, pulvinar, corpori geniculati lateralis, centrum medianum, ventralis lateralis) and from pontine reticular formation were analyzed in Papio papio monkeys rendered photosensitive by a subconvulsant dose of allylglycine. The VEPs induced by single flashes were compared statistically with those induced by flashes preceded by trains of intermittent light stimulation (ILS). This latter mode of stimulation provoked the appearance of paroxysmal VEPs (PVEPs) in the FR cortex with the same morphology as the spikes and waves induced in this area by the ILS. The aim of our research was to provide evidence for the possible implication of the subcortical structures which we have studied in the elaboration of PVEPs and thus of spikes and waves. The VEPs recorded at the thalamic and pontine levels were modified when PVEPs were present. These modifications varied according to the site, but subcortical VEPs were never paroxysmal. In structures with visual functions (colliculi superioris, corpori geniculati lateralis), the VEPs were modified by the ILS, but showed more marked changes when PVEPs were present. Thus, these structures may contribute to the genesis of PVEPs. In the other structures (centrum medianum, ventralis lateralis, and pontine reticular formation), modifications of the VEPs occurred only when PVEPs were present. Thus, these structures would be only secondarily involved. We also present preliminary results concerning the effects of lesioning the pulvinar and the ventralis lateralis on the susceptibility of the FR cortex to produce spikes and waves during ILS.(ABSTRACT TRUNCATED AT 250 WORDS)

Cerebrospinal fluid amino acid and monoamine metabolite levels of Papio papio: correlation with photosensitivity.

Several putative neurotransmitter amino acids and monoamine metabolites were measured in the cerebrospinal fluid of spontaneously photosensitive baboons (Papio papio) at different periods with varying degrees of photosensitivity in the same animals. At maximum photosensitivity the inhibitory amino acids gamma-aminobutyric acid and taurine were lower, and those of asparagine (metabolite of the excitatory amino acid aspartate) were higher, than when the animals were not photosensitive. Thus a decreased inhibition and perhaps increased excitation correlates with the level of photosensitivity.

Stimulus-sensitive myoclonus of the baboon Papio papio: pharmacological studies reveal interactions between benzodiazepines and the central cholinergic system.

The baboon Papio papio develops a nonepileptic myoclonus 20 to 30 min after i.m. benzodiazepine injection. It is characterized by bilateral jerks involving mainly the neck and the trunk, by the absence of any correlative EEG paroxysmal discharge, and by its facilitation during movement or agitation. This myoclonus resembles the intention myoclonus of human patients as seen, for example, after anoxia. We found in experiments on 10 adolescent baboons that atropine alone induced the myoclonus for several hours, that physostigmine completely antagonized the benzodiazepine-induced as well as the atropine-induced myoclonus, and that the peripherally acting cholinergic antagonist, methyl-QNB, and agonist prostigmine had no action on the myoclonus, suggesting that the benzodiazepine-induced myoclonus in this species depends on a strong depression of the central cholinergic system by benzodiazepine. The benzodiazepine-induced myoclonus was mediated by benzodiazepine receptors as it was blocked by the specific benzodiazepine receptor antagonist, Ro 15-1788, which did not block atropine-induced myoclonus; latency to myoclonus after benzodiazepine was longer than after atropine. These facts suggest that benzodiazepines, by an as yet unknown mechanism, induce a depression of the cholinergic system which in turn leads to the development of myoclonus. Finally, the benzodiazepine-induced myoclonus of the baboon can be considered as a good model for testing drugs that act on the muscarinic cholinergic system and also for testing benzodiazepine-acetylcholine interactions.

Physostigmine antagonizes benzodiazepine-induced myoclonus in the baboon, Papio papio.

The antagonism of some benzodiazepine (Bz) actions by physostigmine was investigated in 4 Papio papio baboons. As a model of these actions, the myoclonus induced in this species by clonazepam i.m. administration was used. The baboon develops, 20-30 min after Bz i.m. injection, a non-epileptic myoclonus characterized by clinical symptomatology (jerks involving mainly the neck and the trunk bilaterally), by the absence of any correlative EEG discharge, and by its facilitation during movement. This Bz-induced myoclonus resembles the intention myoclonus of human patients, as seen for example after anoxia. In the present series, the effect of physostigmine i.v. injection on the frequency of clonazepam-induced myoclonus was tested. Physostigmine produces a rapid and total abolition of the myoclonus, and this effect lasts for a period which corresponds to the pharmacological activity of physostigmine. On the contrary, atropine i.v. injection considerably increases the amount of Bz-induced myoclonus. These results allow the existence of an anticholinergic action of benzodiazepines, reversed by physostigmine, and the theory that the myoclonus would be the consequence of a cholinergic system depression to be hypothesized.

Differential effects of the benzodiazepine antagonist Ro 15-1788 on two types of myoclonus in baboon Papio papio.

Certain benzodiazepines (BZs) like lorazepam, diazepam or clonazepam induce myoclonus jerks in photosensitive and non-photosensitive baboons. Papio papio, which are not accompanied by EEG paroxysmal discharges (type B). The effect of the selective BZ antagonist R0 15-1788 was evaluated in this myoclonus. Ro 15-1788 completely blocked type B myoclonus without decreasing the level of vigilance in the two types of baboons, and reversed the antiepileptic action of the BZs in the photosensitive ones, permitting the reappearance of myoclonus following EEG paroxysmal discharges (type A). L-5-hydroxytryptophan and progabide also blocked type B myoclonus, but the blockade was only transiently effective and was always accompanied by slight drowsiness.