Rat model of influenza-associated encephalopathy (IAE): studies of electroencephalogram (EEG) in vivo.

Influenza-associated encephalopathy (IAE) is characterized by severe neurological complications during high-grade fever with high morbidity and mortality in children. The major neurological complications during high-grade fever include convulsive seizures, loss of consciousness, neuropsychiatric behavior (hallucination, meaningless speech, disorientation, laughing alone); high voltage amplitude slow waves and the occurrence of theta oscillation are depicted on the electroencephalogram (EEG) in the IAE patients. At the early phase of the disease, the cytokines levels increase in severe cases. To understand the neuronal properties in the CNS leading to these neurological complications in IAE patients, we recorded EEG signals from the hippocampus and cortex of rats infected with influenza A/WSN/33 H1N1 virus (IAV) strain. Abnormal EEG activities were observed in all infected rats under anesthesia, including high voltage EEG burst amplitude and increased EEG spikes in the early phase (8 h-day 2) of infection, and these increases at the early phase were in parallel with a significant increase level of interleukin-6 (IL-6) in the serum. When the infected rats were heat-stressed by elevating the rat body core temperature to 39-41 degrees C, these abnormal EEG activities were enhanced, and the oscillation pattern shifted in most of rats from slow bursting waves (<1 Hz) to theta oscillation (3-6 Hz). These results indicate that the abnormal EEG activities in IAE patients could be well reproduced in anesthetized IAV infected rats under hyperthermia, hence this animal model will be useful for further understandings the mechanism of neuronal complications in IAE patient during high-grade fever.

Callosal responses of fast-rhythmic-bursting neurons during slow oscillation in cats.

The cortically generated slow oscillation consists of long-lasting hyperpolarizations associated with depth-positive electroencephalogram (EEG) waves and neuronal depolarizations accompanied by firing during the depth-negative EEG waves. It has previously been shown that, during the prolonged hyperpolarizations, the transfer of information from prethalamic pathways to neocortex is impaired, whereas the intracortical dialogue is maintained. To study some of the factors that may account for the maintenance of the intracortical information transfer during the hyperpolarization, intracellular recordings from association areas 5 and 7 were performed in anesthetized cats, and the synaptic responsiveness of fast-rhythmic-bursting, regular-spiking and fast-spiking neurons was tested using single pulses to the homotopic sites in the contralateral areas. During the long-lasting hyperpolarizations callosal volleys elicited in fast-rhythmic-bursting neurons, but not in regular-spiking or fast-spiking neurons, large-amplitude excitatory post-synaptic potentials crowned by single action potentials or spike clusters. Our data show that callosal volleys excite and lead to spiking in fast-rhythmic-bursting neurons during prolonged hyperpolarizations, thus enabling them to transmit information within intracortical networks during slow-wave sleep.

[Seroprevalence of hepatitis C virus (HCV) in Senegalease blood donors]. / Seroprevalence du virus de l'hepatite C (VHC) chez les donneurs de sang au Senegal.

INTRODUCTION: Hepatitis C virus (HCV) is an important problem of public health in the world according to its transmission mode and its pathogenesis. The risk of blood transmission has led to be the systematic screening of blood donors in the world. In Senegal no study about HCV prevalence on the general population and also has been done. The aim of our study was to determine HCV prevalence in blood donors and the rate of co-infection with hepatitis B (HCV/HBV) or with HIV infection (HCV/HIV). MATERIALS AND METHODS: This study had been done in the National Blood Transfusion Centre (CNTS) in Dakar. Two different techniques has been used for the assessment HCV: 1/ ELISA technique and 2/ Immunoblot RIBA as confirmation test. RESULTS: Our study relates to 1565 blood donors recruited in CNTS during 2002. 369 of them were new blood donors with 365 females and 1200 males. The mean average was 30.5 +/- 9.5 years, ranged from 18 to 59 years. HCV ELISA test were positive in 22 plasma samples and one of them were co-infected with hepatitis B (HCV/HBV). Four out of these 22 samples have been confirmed positive to RIBA test and three of them were not determined. HCV seroprevalence were 1.4% after ELISA and 0.25% after RIBA testing. This seroprevalence were similar in male and in female and higher in new blood donors than in regular blood donors. CONCLUSION: Our results reinforce the necessity to screen hepatitis C virus in all Senegalese blood transfusion centres.

Synaptic responsiveness of neocortical neurons to callosal volleys during paroxysmal depolarizing shifts.

Based on intracellular recordings in vivo, we investigated the responsiveness of cat neocortical neurons to callosal volleys during different phases of spontaneously occurring or electrically induced electrographic seizures, compared with control periods of slow sleep-like oscillations. Overt seizures, with spiking, triggered by pulse-trains to the callosal pathway, started with a latency of approximately 20 s after cessation of stimulation, thus contrasting with paroxysmal activity elicited by ipsilateral cortical or thalamic stimulation that is initiated immediately after electrical stimulation. During the rather long preparatory period to callosally triggered seizures, cortical neurons displayed subthreshold depolarizing runs at 4-7 Hz, associated with increased amplitudes of excitatory postsynaptic potentials. The sequential analysis of neuronal responsiveness during different components of spike-wave complexes revealed progressively increased amplitudes of callosally evoked postsynaptic excitatory responses in regular-spiking and fast-rhythmic-bursting neurons, over a period of approximately 20 ms prior to the generation of paroxysmal depolarizing shifts. These data support the concept that seizures consisting of spike-wave complexes originate within the neocortex through a progressive synaptic buildup and that their synchronization is achieved, at least partially, by cortical commissural synaptic linkages.