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Biomedical subjects

P Benna

Publications and source records attributed to P Benna.

At least 19 recordsLinked to original sources
PubMed2004

A novel epilepsy mutation in the sodium channel SCN1A identifies a cytoplasmic domain for beta subunit interaction.

A mutation in the sodium channel SCN1A was identified in a small Italian family with dominantly inherited generalized epilepsy with febrile seizures plus (GEFS+). The mutation, D1866Y, alters an evolutionarily conserved aspartate residue in the C-terminal cytoplasmic domain of the sodium channel alpha subunit. The mutation decreased modulation of the alpha subunit by beta1, which normally causes a negative shift in the voltage dependence of inactivation in oocytes. There was less of a shift with the mutant channel, resulting in a 10 mV difference between the wild-type and mutant channels in the presence of beta1. This shift increased the magnitude of the window current, which resulted in more persistent current during a voltage ramp. Computational analysis suggests that neurons expressing the mutant channels will fire an action potential with a shorter onset delay in response to a threshold current injection, and that they will fire multiple action potentials with a shorter interspike interval at a higher input stimulus. These results suggest a causal relationship between a positive shift in the voltage dependence of sodium channel inactivation and spontaneous seizure activity. Direct interaction between the cytoplasmic C-terminal domain of the wild-type alpha subunit with the beta1 or beta3 subunit was first demonstrated by yeast two-hybrid analysis. The SCN1A peptide K1846-R1886 is sufficient for beta subunit interaction. Coimmunoprecipitation from transfected mammalian cells confirmed the interaction between the C-terminal domains of the alpha and beta1 subunits. The D1866Y mutation weakens this interaction, demonstrating a novel molecular mechanism leading to seizure susceptibility.

Action Potentials↗
PubMed2001

Clinical features, EEG findings and diagnostic pitfalls in juvenile myoclonic epilepsy: a series of 63 patients.

Juvenile myoclonic epilepsy (JME) is a common idiopathic generalized epileptic syndrome distinctively characterized by myoclonic jerks often associated to generalized tonic-clonic seizures (GTCS) and typical absence seizures. In spite of typical clinical and EEG profiles, JME is widely underdiagnosed. In the present study we retrospectively revised clinical and EEG data of JME patients referring to our Epilepsy Service. A diagnosis of JME could be made in 63 patients, that is 5.7% of all the epileptic patients referring to our Service and 25.9% of those suffering from an idiopathic generalized epilepsy. General features as well as modality of onset and course of the syndrome of our JME subjects were in accordance with literature. Regarding EEG findings, asymmetries were detected in 38.1% of cases. At referral to our Service only 31.7% of JME patients were correctly diagnosed. Main factors responsible for misdiagnosis were failure in eliciting a history of myoclonic jerks and misinterpretation of myoclonic jerks as simple partial seizures. EEG asymmetries were misleading in 13 patients. In conclusion, a correct JME diagnosis is strictly dependent on the knowledge of the syndrome leading the interviewer to look for and correctly interpret myoclonic jerks whereas EEG is just an ancillary diagnostic tool.

Adolescent↗
PubMed1995

Propofol analgesia in central pain: preliminary clinical observations.

Propofol, an intravenous general anaesthetic, has been reported to relieve some forms of pruritus at subhypnotic doses. We assessed its effectiveness in 32 patients with several kinds of non-malignant chronic pain, in a placebo-controlled, double-blind study. We found that central pain, but not neuropathic pain, is at least partially controlled by propofol at subhypnotic doses, without major side-effects. In particular, allodynia associated with central, but no neuropathic, pain has been completely controlled. Propofol analgesia leads to renormalization of brain metabolism as seen on single photon emission computed tomography. We conclude that propofol may help in the diagnosis of central pain, particularly in unclear cases, and also in treatment. Possible mechanisms of action are discussed.

Adult↗
PubMed1994

Peripheral-type benzodiazepine receptors on human blood mononuclear cells are not regulated by ovarian steroids.

Peripheral-type benzodiazepine receptors (pBZr) have been shown to be sensitive to hormonal perturbations, including changes in ovarian steroids. This study examines whether estradiol and progesterone modulate pBZr binding in membranes of human blood mononuclear cells, as measured by binding of both 3H-PK 11195 and 3H-Ro 5-4864. Our findings were negative. There was no steroidal modulation of pBZr binding to these membrane preparations in vivo in normal women studied at different sex-steroid phases of the menstrual cycle, or during 8-30 weeks of pregnancy. There was also no effect of hormones on the binding sites in cultures of mononuclear cells treated with estradiol or progesterone (up to 10(-5) M) over a period between 2 and 72 h. Further, we performed in vitro competition experiments, which showed that both steroids are not active at the pBZr. Our data suggest that pBZr located in human blood mononuclear cells are insensitive to the physiological variations of circulating female hormones.

Benzodiazepinones↗
PubMed1992

An analysis of peripheral type benzodiazepine receptors on blood mononuclear cells during high dose steroid treatment of multiple sclerosis.

We report here a study of peripheral type benzodiazepine receptors (pBZr) in mononuclear cells (MNC) from blood of patients with multiple sclerosis (MS) during periods of stable and active disease and from normal controls. Most active MS patients were retested in a longitudinal study, both during a treatment with high dose steroids and while medication free. Active MS produces a significant decrease of receptor density compared with the controls whereas remission of the disease shows no effect. Four weeks of steroid treatment restore binding density to normal levels, and two weeks of drug withdrawal result in a small, but significant increase in number of the binding sites compared with the control value. We suggest that the number of pBZr in blood MNC might change during the clinical course and steroid therapy of MS.

Adult↗
PubMed1991

A study of 3H-PK 11,195 binding to "peripheral-type" benzodiazepine receptors on human lymphocytes. Evidence of decreased binding in hepatic encephalopathy.

In an attempt to assess the involvement of the "peripheral-type" benzodiazepine receptors (pBDZR) in hepatic encephalopathy (HE), we examined the binding of the isoquinoline carboxamide derivative 3H-PK 11,195 to lymphocyte membranes from a group of patients with liver cirrhosis with or without clinical signs of HE and normal controls. Lymphocyte 3H-PK 11,195 binding is saturable, with high affinity and presents the pharmacological specificity corresponding to pBDZR. A significant 40% decrease in the number of 3H-PK 11,195 binding sites, without a concomitant change in the apparent affinity, is observed in the group with HE as compared to the controls, but not in that with liver diseases without HE. The decrease in binding capacity correlates significantly with the clinical grading of HE, but not with age, sex, aetiology of cirrhosis or presence of surgical shunt. In contrast to the reduction of pBDZR, 3H-N-methylscopolamine binding to lymphocyte muscarinic receptors is not affected in HE. These findings are consistent with a role for pBDZR in HE and may stimulate studies of endogenous modulators and pharmacological agents for these receptors in the disease.

Adult↗
PubMed1991

An analysis of lymphocyte 3H-N-methyl-scopolamine binding in neurological patients. Evidence of altered binding in Alzheimer's disease.

Muscarinic cholinergic receptors were analysed in lymphocyte membranes from 35 patients with early (n = 20) and late onset (n = 15) Alzheimer's disease (AD), 86 patients with other neurological disorders and 60 normal controls by the specific binding of 3H-N-methyl-scopolamine (3H-NMS). The number of binding sites of 3H-NMS (Bmax) was significantly decreased both in early and late onset AD groups as compared with age-matched controls, by 54% and 40%, respectively, whereas the apparent binding affinity (Kd) was the same in all disease and control groups. In addition, the average Bmax in early AD was significantly lower than in late AD. The density of the binding of 3H-NMS was also significantly lower in a subgroup of old subjects with Down's syndrome (DS), whereas no changes were found in younger individuals with DS or in patients with Parkinson's disease, whether they were demented or not, multi-infarct dementia, myasthenia gravis or epilepsy. In the AD group, the difference in binding sites was unrelated either to the severity of dementia or disease duration. Treatment of the patients with cholinergic agents did not alter the binding values in any of the examined group. We conclude that the alteration of lymphocyte muscarinic receptors is highly associated with AD, but whether this reflects the central cholinergic deficit in these patients is uncertain.

Adolescent↗
PubMed1990

Long-term bromocriptine treatment of de novo patients with Parkinson's disease. A seven-year follow-up.

Thirty-nine de novo patients with Parkinson's disease were treated with bromocriptine alone and followed on average for 5.9 years. Fifteen of the 39 patients did not complete the first year of observation, 12 of them because of drug intolerance. The symptomatology was tolerated well by other 24 for the first 2 years treatment. During the third year of follow-up levodopa treatment had to be instituted because of loss of response to bromocriptine. The number of fluctuations in disability was smaller in the patients whose symptomatology was controlled by bromocriptine monotherapy than in those requiring levodopa, either alone or combined with bromocriptine.

Aged↗
PubMed1990

Aging effects on brainstem auditory evoked potentials.

Since age effects on central conduction time in the acoustic pathway are still debated, we recorded brainstem auditory evoked potentials in 154 normoacoustic subjects, with no history of neurologic or otologic pathology. Linear regression has been used for statistical analysis. Data obtained show an age-related prolongation of latency values which is particularly marked for wave I, while other waves (particularly wave III) do not show a significant change. Thus, interpeak latency (IPL) values do not increase with increasing age: in particular IPLs I-II and I-III decrease, showing a negative "r" value, and IPLs I-V and II-V (which is to be considered the true "central conduction time" through the acoustic pathway) do not show a significant change. Our data seem to demonstrate that the aging process is essentially a peripheral phenomenon which does not involve the central part of the acoustic pathway.

Acoustic Stimulation↗
PubMed1988

Diazepam binding inhibitor-like immunoreactivity (DBI-LI) in human CSF. Correlations with neurological disorders.

Cerebrospinal fluid (CSF) levels of the anxiogenic neuropeptide diazepam binding inhibitor (DBI) were determined by radioimmunoassay in 281 patients who underwent evaluation for neurological problems. Serial dilution curves and reverse-phase high pressure liquid chromatography showed that the immunoreactive material in CSF behaved just as authentic DBI extracted from human brain. Furthermore in the assay there was no evidence of interference from CSF samples deprived of DBI by immunoaffinity. In 82 patients with no evidence of major lesions in the central nervous system, who acted as controls, the CSF DBI content was shown to be age- and sex-related. No correlation was observed with the CSF protein concentration. In patients with different types of dementia, the levels of CSF DBI were significantly increased in a group with normal pressure hydrocephalus. No significant differences were found between Alzheimer's disease, multi-infarct dementia, or dementia with Parkinson's disease and controls. In non-demented patients with Parkinson's disease the levels of DBI were increased in a subgroup with depressive disturbances whereas no differences was observed in the non-depressed cases. The content of DBI was markedly reduced in 5 cases with olivopontocerebellar atrophy and in 4 with spinocerebellar ataxia. In all the other disorders studied the levels of DBI were similar to or slightly lower (multiple sclerosis) than those of the controls. The origin of DBI in cerebrospinal fluid is uncertain; a number of various possibilities are discussed concerning the proposed role of DBI as modulator of brain GABAergic transmission.

Adolescent↗
PubMed1985

Visual evoked potentials and brainstem auditory evoked potentials in migraine and transient ischemic attacks.

A study of brainstem auditory evoked potentials (BAEPs) and pattern reversal visual evoked potentials (VEPs), recorded in intercritical phase, was carried out in 20 subjects (10 suffering from common migraine and 10 suffering from vertebrobasilar TIA) in order to obtain a comparative evaluation of cortical-subcortical functions. The data we obtained demonstrate the presence of BAEPs alterations in patients with previous vertebrobasilar TIA: no abnormalities were found in the migraine group. VEPs parameters are normal in both groups. Our data show that the study of the so-called "stimulus-related" potentials, such as BAEPs and pattern reversal VEPs, is useful in evaluating the damage produced by any noxa, while it cannot clearly emphasize individual factors predisposing to a specific pathology, as the absence of specific alterations in migraine patients demonstrates.

Adult↗
PubMed1984

Neonatal hypoxia and epileptic risk: a clinical prospective study.

A historical cohort study was undertaken to determine the risk of epilepsy in a population of 371 newborns with an acute neurological disorder related to fetal and/or neonatal hypoxia compared with a control population of 362 normal newborns. The results showed that the risk of epilepsy was 5.1 times higher in the group of subjects affected at birth by a hypoxia-related acute neurological syndrome than in the control group. (Although the incidence of epilepsy is higher in the first year of life, epileptic seizures connected to perinatal hypoxia may occur in early childhood or later on.) Also, there were frequently persistent neuropsychiatric disorders in children with perinatal hypoxia (5.4%). There was no difference in the two groups regarding the incidence of febrile convulsions. The data show that perinatal hypoxia plays a role in the etiology of epilepsy, although at birth the hypoxia might result in only a modest and oftentimes completely reversible neurological syndrome.

Asphyxia Neonatorum↗