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Biomedical subjects

S Franceschetti

Publications and source records attributed to S Franceschetti.

At least 55 records · Page 3Linked to original sources
PubMed1994

Neurons dissociated from neocortex fire with 'burst' and 'regular' trains of spikes.

Neurons acutely dissociated from neocortex slices of 14-16-day-old rats were patch-clamped in physiological conditions. Different pyramidal cells, spontaneously or in response to current steps, generate regular spiking and intrinsically bursting behaviour during long periods of time. We show that typical firing properties recorded in somatosensory neocortex slices are preserved in dissociated pyramidal neurons originating from the slices themselves, thus, providing a way for the related characterization of biophysical properties of currents in identified subtypes of pyramidal neurons.

Action Potentials↗
PubMed1994

PME of Unverricht-Lundborg type in the Mediterranean region: linkage and linkage disequilibrium confirm the assignment to the EPM1 locus.

Seven phenotypically homogeneous Mediterranean myoclonus families were studied using DNA markers from the genetically defined EPM1 region on chromosome 21. No recombinations between the disease phenotype and the markers studied were detected. Within the EPM1 region, the highest lod score value of 5.07 (at theta = 0.00) was reached at locus PFKL. Significant allelic association (P = 0.02) between the disease mutation and PFKL was detected suggesting a founder effect in Mediterranean myoclonus. However, haplotype data using four marker loci residing within 300 kb of each other and of EPM1 suggest the occurrence of more than one mutation. The data are compatible with Mediterranean myoclonus being caused by mutations in the EPM1 gene and strengthen the concept that a large subset of progressive myoclonus epilepsies conforms with Unverricht-Lundborg disease and that this subset is an etiologically homogeneous entity.

Adolescent↗
PubMed1994

Double cortex syndrome: electroclinical study of three cases.

We describe three female patients (aged 10, 11 and 21 years) with a Magnetic Resonance appearance of band heterotopia, a diffuse neuronal migration disorder, also known as double cortex syndrome. The clinical picture was characterized by the association of epilepsy and mental retardation in all three cases, as has been previously described in patients with double cortex syndrome. The epileptic syndrome (Lennox-Gastaut syndrome in one case, and symptomatic partial epilepsy in the other two), the response to medical treatment, and the severity of mental retardation were markedly different in the three patients. No clear-cut relationship was found between the clinical picture and the severity of the neuronal migration disorder, as revealed by magnetic resonance imaging. In the three cases, EEG shares some common features: multifocal epileptic activity with frequent bilateral diffusion, and high-amplitude anterior fast activity, intermingled in two patients with bursts of repetitive spikes.

Adult↗
PubMed1993

Expression of intrinsic bursting properties in neurons of maturing sensorimotor cortex.

Intrinsically bursting (IB) neurons, responding with a burst of action potentials to just threshold intracellular depolarizing current pulses, are encountered in layer V of mature rodent sensorimotor cortex. We report the results of intracellular recordings performed on neocortical slices obtained from immature rats between postnatal day (P) 7 and P21, as compared to adult animals (above P60). The bursting properties are here reported to mature abruptly around P14. After this time a subpopulation of IB neurons was recognizable on the basis of both physiological and morphological characteristics (i.e. extensive apical and basal dendrites arborization, axon collaterals limited to layers V-VI). Maturational changes in number and distribution of Ca2+/K+ channels may account for this developmental step. The immaturity of IB neurons may be correlated with the poorly synchronized character of cortical activities in the very young animals.

Action Potentials↗
PubMed1993

Progressive myoclonus epilepsies: an electroclinical, biochemical, morphological and molecular genetic study of 17 cases.

Electroclinical, morphological, biochemical and molecular genetic data from 17 patients affected by progressive myoclonus epilepsies (PME) are reported. Twelve patients were characterized by prominent action myoclonus, sporadic seizures, mild ataxia, lack of dementia and persistence of normal EEG background activity; three patients showed a more rapid worsening of symptomatology, characterized by early mental impairment, massive and action myoclonus, cerebellar signs and tonic clonic seizures; in these patients EEG background activity was slow, even in early stages of the disease. In two patients, previously classified as cryptogenetic PME, a mitochondrial aetiology was recognized by the presence of ragged red fibers in muscle biopsy and by a reduction of the respiratory chains enzymes. Molecular genetical investigation of mtDNA demonstrated the reported heteroplasmic point mutation at nt 8344 of mtDNA in the two MERRF patients, while it was negative in all of the others.

Adolescent↗
PubMed1991

Desferrioxamine infusion can modify EEG tracing in haemodialysed patients.

Neurological derangement has been reported in haemodialysed patients receiving intravenous desferrioxamine (DFO) for aluminium-related disorders. The possible direct effects of desferrioxamine on EEG recordings were investigated in ten haemodialysed patients who underwent a DFO test 2 h after the end of dialysis. According to a commonly accepted protocol, 40 mg/kg body-weight of desferrioxamine was infused in 60 min. EEG recording was continuously performed, starting 30 min before and stopping 30 min after the desferrioxamine infusion. Besides visual inspection, EEG records were digitised, tapered, and spectrally analysed with Digital PDP 11/73 microcomputer. Basal EEG recording was normal in all patients. In three patients a progressive EEG slowing was detected by visual inspection during desferrioxamine infusion; in these cases automatic analysis revealed a 50% increase in power of slower frequencies 30 min after starting the infusion, when no changes in plasma aluminium concentrations are detected; a complete recovery was observed 30 min after desferrioxamine withdrawal. In one patient bilateral paroxysms of slow waves appeared, so we stopped desferrioxamine infusion. Two of the three patients who developed EEG abnormalities also had an increased aluminium body burden (positive DFO test). Results indicated that desferrioxamine per se can modify EEG in haemodialysis patients and that its effect is not mediated by acute increases of plasma aluminium concentrations. The finding of a positive DFO test in two of three patients with EEG changes may suggest that an aluminium-induced blood-brain barrier derangement could have played a role. However, prompt recovery after ceasing desferrioxamine infusion strongly suggests a direct role of desferrioxamine in the induction of EEG changes.(ABSTRACT TRUNCATED AT 250 WORDS)

Aluminum↗
PubMed1990

Influence of surgery and antiepileptic drugs on seizures symptomatic of cerebral tumours.

One hundred and twenty-eight adult patients presenting with and operated on for supratentorial neoplasms were studied. Sixty-five had preoperative seizures and were treated with antiepileptic drugs (AEDs). Among the 63 patients without preoperative epileptic fits, 41 were given AEDs (either phenobarbital or phenytoin) as prophylactic treatment and 22 were not treated. The preoperative epilepsy course was considered with respect to tumour site and histological type. Early and late postoperative seizure occurrence was considered in the different groups of patients. The results suggest the usefulness of a short term preventive treatment with AEDs after surgery in patients without preoperative seizures. In patients with preoperative epilepsy, AEDs should be continued after surgery. However long-term AEDs treatment should not be recommended in patients without preoperative epilepsy. In fact, no significant difference in late seizure occurrence was found between preventively treated and untreated patients.

Adult↗
PubMed1986

The action of valproate on spontaneous epileptiform activity in the absence of synaptic transmission and on evoked changes in [Ca2+]o and [K+]o in the hippocampal slice.

The effects of valproate (VPA) on neuronal excitability and on changes in extracellular potassium ([K+]o) and calcium ([Ca2+]o) were investigated with ion selective-reference electrode pairs in area CA1 of rat hippocampal slices. Field potential responses to single ortho- and antidromic stimuli were unaltered by VPA (1-5 mM). The afferent volley evoked in the Schaffer-commissural fibers was also unaffected. In contrast, VPA (1 mM) depressed frequency potentiation and paired pulse facilitation markedly. Decreases in [Ca2+]o induced either by repetitive stimulation or by application of the excitatory amino acids N-methyl-D-aspartate and quisqualate were reduced, and the latter results suggest that VPA interferes with postsynaptic Ca2+ entry. When synaptic transmission was blocked by lowering [Ca2+]o (0.2 mM) and elevating [Mg2+]o (7 mM), prolonged afterdischarges elicited by antidromic stimulation were blocked by VPA. VPA also suppressed the spontaneous epileptiform activity seen when [Ca2+]o was lowered to 0.2 mM, without elevating [Mg2+]o. The amplitudes of the rises in [K+]o induced by repetitive orthodromic stimulation were only slightly depressed and those elicited by antidromic stimulation were generally unaltered by VPA, as were laminar profiles of stimulus-evoked [K+]o signals. These results indicate that VPA has membrane actions in addition to known effects on excitatory and inhibitory transmitter pools.

Animals↗
PubMed1986

Classification of the EEG during neurosurgery. Parametric identification and Kalman filtering compared.

A procedure is described which aims to classify an EEG recorded during neurosurgery, for example intracerebral aneurysm clipping. A parametric approach is used; it employs auto-regressive (AR) modelling and Kalman filtering to quantify directly the dynamics of the EEG generating mechanism, supposing it to be a linear, time-invariant system driven by white noise. The results of this EEG processing are analysed together with simultaneous values of arterial blood pressure (ABP) as surgery of this kind is carried out under conditions of controlled hypotension. The object is to compare the sensitivity of ABP data with that obtained from the EEG and so provide an early warning of a potentially dangerous non-physiological state induced by the hypotensive drug (in this case sodium nitroprusside). Some methodological comments on the correct implementation of these algorithms are given and the procedure is compared with similar approaches which have appeared in the literature during the last few years. Particular emphasis is placed on the power spectral analysis of the signal by pointing out a method for spectral decomposition, related to AR power density estimation, which permits the separation of single spectral components in terms of central frequencies and their associated power. Other potential applications of this method are in long term EEG monitoring for the detection of changes due for example to drug infusion, to fast transient events, or to changes in the stationary condition.

Anesthesia↗
PubMed1985

Effects of anticonvulsants on spontaneous epileptiform activity which develops in the absence of chemical synaptic transmission in hippocampal slices.

Spontaneous epileptiform activity (SEA) develops in area CA1 of hippocampal slices, when the Ca2+ concentration in the perfusate is lowered to 0.2 mM, at which level evoked chemical synaptic transmission is blocked. We investigated the effects of different anticonvulsants on this autonomous activity, in order to determine whether the antiepileptic effect can be ascribed to an influence on neuronal excitability. Carbamazepine was the most effective to block SEA at concentrations of 1-15 microM. Phenobarbital and phenytoin depressed SEA at concentrations of 25 microM. Valproate was effective at concentrations of 2-5 mM. Midazolam, a water-soluble benzo-diazepine agonist and the N-methyl-D-aspartate antagonists, DL-alpha-aminoadipic acid and 2-amino-7-phosphonoheptanoic acid were ineffective in blocking SEA suggesting that they exert their antiepileptic action by interference with synaptic mechanisms.

Animals↗
PubMed1980

Brain stem projections in the pulvinar-lateralis posterior complex of the cat.

The present experiments were undertaken to define the areas of projection of pretectum and superior colliculus to the pulvinar and n. lateralis posterior, respectively, and to define other brain stem structures projecting to these thalamic nuclei in cats. For this purpose of technique of retrograde transport of horseradish peroxidase (HRP) has been used. After injection of the enzyme in the pulvinar, neurons were labeled in all subdivisions of the pretectal area. The majority of the labeled cells were located in the n pretectalis anterior pars compacta and area pretectalis medialis. Neurons projecting to the pulvinar were also found in the periaqueductal gray, reticular formation and locus coeruleus. When HRP was injected in the n. lateralis posterior, labeled neurons were present in the II and III subdivisions of the second layer of the superior colliculus. The location of these cells shifted from medial to lateral as the injections were shifted from posterior to anterior within the lateralis posterior. Neurons projecting to this nucleus were also present in the intermediate layers of the superior colliculus, lateral hypothalamus and parabigeminal nucleus. The possible role of the pretectal area and superior colliculus in mediating somesthetic input to the pulvinar and lateralis posterior, respectively, and the role of these structures in the control of ocular movements, are discussed.

Animals↗
PubMed1980

Segmental action and stimuli-sensitive myoclonus with acute onset. A case report.

A 23-year old man developed action and stimulus-sensitive myoclonus involving neck and proximal arm muscles. The finding of abnormally long and tortuous vertebral and carotid arteries and the abrupt onset of symptomatology suggest a possible hemodynamic mechanism. The electrophysiological characters and the sensitivity to serotonin precursors are consistent with the definition of "reticular reflex myoclonus".

5-Hydroxytryptophan↗
PubMed1980

Multisensory convergence and interaction in the pulvinar-lateralis posterior complex of the cat's thalamus.

Responsiveness to visual, acoustic and somesthesic stimuli was studied in 260 units recorded within the associative thalamic nuclei of the cat (pulvinar-lateralis posterior complex and posterior group). Of the 123 units responding to one or more stimuli 41 (corresponding to 15% of the total) showed multisensory convergence. Bimodal, visual-somesthesic convergence was the most common finding, occurring in 33 units. Visual-somesthesic inhibitory interaction was observed only in the pulvinar nucleus, suggesting a peculiar synaptic organization of multisensory input to this nucleus.

Animals↗
PubMed1980

Cherry-red spot myoclonus syndrome and alpha-neuraminidase deficiency: neurophysiological, pharmacological and biochemical study in an adult.

A 22 year old patient with non-familial progressive myoclonus, macular cherry-red spot, moderate cerebellar syndrome and normal intelligence is described. The myoclonus began at the age of 18 years. Focal myoclonus could easily be elicited by voluntary and passive movements, and by touch and electrical stimulation of median nerve. Somatosensory evoked potentials showed a high voltage early component. Jerk-locked averaging of the EEG preceding action myoclonus detected an otherwise hidden, time-related, EEG spike. The myoclonus responded partially but clearly to L-5 hydroxytryptophan plus carbidopa treatment. Biochemical study showed an alpha-neuraminidase deficiency in cultured fibroblasts: the decrease in this enzyme activity was compared to that found in a patient affected by mucolipidosis III.

Adult↗