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Biomedical subjects

C Menini

Publications and source records attributed to C Menini.

At least 109 records · Page 6Linked to original sources
PubMedDate not supplied

Reflex epilepsy in the Papio-papio baboon, particularly photosensitive epilepsy.

Papio-papio baboons may present two types of reflex paroxysmal manifestations: --Myoclonia and generalized seizures are induced by intermittent light stimulation in predisposed animals; this photosensitive epilepsy resembles that observed in some human patients; it involves mainly the cerebral cortex during myoclonia which are accompanied by EEG paroxysmal discharges, and the mesencephalic reticular formation during seizures; --Myoclonia of a different type, never accompanied by EEG paroxysmal discharged and never evolving into seizures, may occur during movement or agitation of predisposed animals; these myoclonia are considered "non-epileptic" since they do not involve the cerebral cortex but probably the lower brain stem; they resemble that observed in startle disease or in some human degenerative disorders. The paper demonstrates that these manifestations constitute two different entities with clinical and electrophysiological characteristics as well as pharmacological reactivities completely different one from the other. Their "epileptic" or "non-epileptic" nature is discussed.

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[The induction of seizures in "Papio papio" following allylglycine alone or in combination with intermittent photic stimulation (author's transl)].

Allylglycine, an inhibitor of GABA synthesis, produces increased sensitivity to photic stimulation and in convulsant doses spontaneous seizures arising occipitally in the baboon (Horton and Meldrum, 1973). In this study, convulsant doses of allylglycine induced either sharp wave and polyspike frontorolandic discharges (FR) or critical posterior discharges which then reinforce the fronto-rolandic spikes. A seizure may then arise from the fronto-rolandic region and secondarily spread to the rest of the cerebral cortex. Intermittent photic stimulation produces a reinforcement of the fronto-rolandic sharp waves and can also induce self-maintaining mechanisms similar to those just described. In this situation, however, and with the animals paralysed with Flaxedil no seizures arising occipitally have been observed. The role of the occipital cortex as the sensory visual and somatic afferent in photosensitive epilepsy in the baboon is discussed in the light of these results.

Allyl Compounds↗
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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)

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PubMedDate not supplied

Effect of macular and peripheral retina coagulation on photosensitive epilepsy in the forebrain bisected baboon, Papio papio.

The effects of macular and peripheral retina coagulation were examined in photosensitive baboons, Papio papio (PP), with or without forebrain bisection. The temporal part of the macula and surrounding retina of the left eye were coagulated with an Argon laser and later confirmed histologically. In forebrain nonbisected baboons, intermittent light stimulation of the operated eye produced bisymmetrical and bisynchronous spikes and waves and self-sustained seizures. In forebrain-bisected baboons intermittent light stimulation of the operated eye produced spikes and waves and self-sustained seizures localized to the contralateral hemisphere. Subsequent stimulation of the nonoperated eye in the same animal produced spikes and waves and seizures either bilaterally or only in the opposite hemisphere when stimulation took place during the postictal silent period in the first hemisphere. In both cases, the tonic phase of the seizure was always bilateral but asymmetrical as shown by electromyographic recordings. Based on these data, it has been hypothesized that the tonic phase is mediated, in part, through crossed interreticular pathways, by one or both cerebral hemispheres. However, data are also compatible with a possible origin of the tonic phase of the seizure being partly localized in the medial frontal cortex. Results demonstrated (1) the usefulness of laser coagulation of the temporal portion of the macula and retina for the study of the functional independence between two cerebral hemispheres, (2) the critical role of the corpus callosum (CC) in bisynchronization and generalization of the intermittent light stimulation (ILS)-induced seizure, (3) independent excitability of each cerebral hemisphere by the ILS, and (4) the critical role of cortical visual afferents for inducing epileptic phenomena in this species.

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PubMedDate not supplied

Electroencephalographic study of the GABA-withdrawal syndrome in rats.

The spatial and temporal EEG features of the epileptogenic syndrome induced by cessation of chronic intracortical GABA infusion in normal rats are described. In the initial stages, the paroxysmal discharges (PDs) induced by withdrawal from unilateral GABA application may appear either unilaterally or bilaterally, although with greater amplitude on the infused side. PDs are transitorily accompanied by behavioral signs of distal myoclonus of the body territory corresponding to the infused area (contralateral hindlimb). Later, the paroxysmal activity becomes more localized, circumscribed to the cannula-infused site and with ipsilateral propagation to anterior cortical areas. The amplitude of PDs decreases progressively while their frequency increases, reaching its maximal value at about 4 h after the first PDs have appeared. In the final stages of the syndrome, which may last several days, clinical manifestations are absent and PDs are activated by slow-wave sleep and reduced during REM sleep and waking. Chronic intracortical applications of taurine failed to induce any electroclinical changes on withdrawal and were unable to inhibit the focus elicited by GABA withdrawal, whereas reinstatement of GABA infusion into the epileptogenic area was effective in blocking the paroxysmal activity. Intracortical infusion of baclofen induced the appearance of an epileptogenic focus that waned on withdrawal. The GABA-withdrawal syndrome appears to be a new model of focal status epilepticus; it may be useful as an experimental model of human partial epilepsy to investigate the role of GABAergic neurotransmission.

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[Not Available].

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Favism↗
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[Not Available].

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Anemia↗
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Prevention of non-hemolytic transfusion reactions with leucocyte-poor blood: a prospective study.

Twenty-five patients with homozygous beta-thalassemia, who complained of occasional nonhemolytic transfusion reactions (NHTR), were alternately transfused eight times with normal packed red cells (PRC) and leucocyte-poor blood prepared by three methods: cotton wool filtration (CWF), buffy coat removal after dilution with saline and upright spin (BCR), and microaggregate filtration (MAF). On overall, CWF-treated RBC concentrates (CWF-RBC) contained 0.02 x 10(9) leucocytes; BCR-RBC contained 0.4 x 10(9), MAF-RBC 1.3 x 10(9) and PRC 1.7 x 10(9). The frequencies of NHTR were: CWF, 0.02; BCR, 0.04; MAF, 0.20; PRC, 0.28. Compared to PRC, both CWF and BCR significantly reduced the frequency of NHTR (p less than 0.01), whilst MAF did not (p greater than 0.1). On the other hand, in one patient CWF caused the two most severe NHTR recorded in this study, both of which were characterized by anaphylaxis.

Adolescent↗