Correlation of sleep macrostructure parameters and idiopathic epilepsies

Sleep and epilepsy share some common mechanisms. The objective of the present investigation was to study the macrostructure of sleep in patients with idiopathic epilepsies, focal and generalized, comparing these two groups to each other and to a control group of 12 individuals without epilepsy. A total of 35 polysomnographies were performed, 12 of them in the control group, 10 in patients with idiopathic generalized epilepsies, and 13 in patients with idiopathic focal epilepsies. Antiepileptic medications were maintained for ethical reasons. The group with idiopathic focal epilepsy showed an increase in the total recording time (p = 0.04) and the group with idiopathic generalized epilepsy had a reduction of phase 4 NREM sleep. The efficiency of total sleep period and of total sleep time was also lower in the group with idiopathic generalized epilepsy (p = 0.03 in both cases). We concluded that the group with idiopathic generalized epilepsy presents sleep of poorer quality, whereas the group with idiopathic focal epilepsy presents a tendency toward an excessive somnolence.     

Evolutionary convergence and shared computational principles in the auditory system

Precise temporal coding is a hallmark of the auditory system. Selective pressures to improve accuracy or encode more rapid changes have produced a suite of convergent physiological and morphological features that contribute to temporal coding. Comparative studies of temporal coding also point to shared computational strategies, and suggest how selection acts to improve coding. Both the avian cochlear nucleus angularis and the mammalian cochlear nuclei have heterogeneous cell populations, and similar responses to sound. These shared characteristics may represent convergent responses to similar selective pressures to encode features of airborne sound.     

Guanine and adenine nucleotidase activities in rat cerebrospinal fluid

Adenine and guanine nucleotides have been shown to exert multiple roles in central and peripheral nervous systems, and the sequential breakdown of these nucleotides by enzymatic systems is an important step in the modulation of their extracellular effects. The aim of this study was to investigate whether nucleotide hydrolysis also occurs in the cerebrospinal fluid (CSF) of rats. CSF was able to hydrolyze all guanine and adenine nucleotides investigated (2.0 mM): GDPADP=ATP=GTPAMP=GMP. More detailed studies with the diphosphate nucleotides showed that the hydrolysis of ADP and GDP was linear with incubation time and protein concentration. The apparent K_M (Henry–Michaelis–Menten constant) and V (maximal velocity) values for ADP and GDP were 164.3±54.7 μM and 12.2±3.8 nmol P_i/min per mg protein, and 841.0±90.2 μM and 22.8±8.0 nmol P_i/min per mg protein. The sum of ADP, GDP and UDP hydrolysis (2.0 mM) upon individual incubations with CSF was similar to the hydrolysis observed when all three nucleotides were incubated together. This pattern of hydrolysis strongly suggests the involvement of more than one enzyme activity. The higher maximum activity for GDP and UDP compared to ADP is compatible with presence of a soluble NTDPase5.     

Laryngeal effects of stimulation of rostral and ventral pons in the anaesthetized rat

In order to study the importance of two pontine regions modulating laryngeal resistance, electrical current or microinjections of glutamate (10-30 nl, 1-3 nmol) were made into the pontine parabrachial complex and the A5 region in spontaneously breathing anaesthetized rats. Two distinct patterns of laryngeal and respiratory responses were elicited. An increase of subglottal pressure was accompanied with an expiratory facilitatory response consisted of a decrease in both respiratory rate and phrenic nerve activity. A decrease of subglottal pressure was accompanied with an inspiratory facilitatory response consisted of an increase in both respiratory rate and phrenic nerve activity. The modification of laryngeal calibre occurred during both respiratory phases in most cases. The concomitant cardiovascular changes of these responses were also analyzed. Controls using guanethidine to block autonomic responses which might interact with respiratory control were also made. Histological analysis of stimulation sites showed a topographical organization of these responses: laryngeal constriction was evoked from K?lliker-Fuse, medial parabrachial nuclei and A5 region, whilst the laryngeal dilation was evoked from the lateral parabrachial nucleus.     

Histological and ultrastructural characterization of interfascicular neurons in the rat anterior commissure

The histological, connectional, and ultrastructural characteristics of a peculiar neuron type in the rat anterior commissure (AC) are described. Since these cells are located among the axonal fascicles of the rostral and caudal parts of the AC, they are termed interfascicular neurons (IFN). In rapid-Golgi sections IFNs appeared in two forms: internuncial (i.e., short axon) and projection neurons (i.e., long axon). The axon of the internuncial neurons terminates upon neighboring IFNs. The projection neurons give rise to an axon which is either incorporated into commissural fibers or ramifies into 12-26 collaterals running laterally in opposite directions along commissural axons. Immunohistochemistry to microtubule-associated protein 2 combined with confocal microscopy showed that IFNs display short varicose dendrites which remain confined to the domain of the AC. The neuronal nature of IFNs was confirmed with the electron microscope on the basis of distinctive organelles and the presence of synaptic inputs. Small areas of neuropil surround some IFNs. These areas are composed of proximal dendrites, terminal axons, axo-shaft and axo-spinous synapses. Because IFNs with their afferents and efferents constitute sufficient elements to integrate neural inputs, it is proposed that they may be involved in processing nerve impulses proceeding from the bilateral cerebral structures connected by the AC.     

Whole-body (67)Ga scintigraphy in a patient with thymus carcinoma

We report a case of a 50 year old man referred to our department with a history of mild cough, dyspnea and dysphagia. The thoracic CT scan showed a large solid mass in the anterior mediastinum, corresponding to the findings in the chest radiographs.A 67Ga scintigraphy was performed and showed high pathological accumulation in the anterior mediastinum. A subsequent fine needle aspiration biopsy (FNAB) showed the presence of malignant cells, suggesting thymic carcinoma. Although this type of tumour is uncommon, it should be taken into account in order to establish the differential diagnosis of gallium-avid mediastinal masses.     

Caffeine modulates P50 auditory sensory gating in healthy subjects.

The P50 suppression paradigm is an index of sensory gating assumed to reflect an inhibitory process. Adenosine is a neuromodulator with mostly inhibitory activity that is released by physiological stimuli and can be blocked by non-selective adenosine receptor antagonists such as theophylline and caffeine. A previous study showed that a single dose of theophylline decreased P50 suppression in healthy volunteers. Here we investigated the effect of caffeine (0, 100, 200 and 400 mg p.o.) on P50 sensory gating in 24 healthy volunteers (15 habitual caffeine high-users and 9 low-users). The 200 and 400 mg doses reduced P50 gating, whereas 100 mg produced a non-significant effect. The effect of caffeine was independent of gender and habitual caffeine intake. High caffeine users also showed baseline differences, with lower S(2) amplitudes compared to low-users. These results reinforce the participation of adenosine in the modulation of P50 sensory gating and suggest that caffeine ingestion should be controlled for in the P50 sensory gating paradigm.     

Elevated impulsivity and impaired decision-making in abstinent Ecstasy (MDMA) users compared to polydrug and drug-na?ve controls.

Ecstasy (MDMA; 3,4-methylenedioxymethamphetamine) has a well-recognized neurotoxic effect on central serotonergic (5-HT) systems in animals, and there is some evidence of persistent serotonergic dysregulation in human ecstasy users. Serotonin is believed to mediate impulsive behavior and effective decision-making. Thus, the aim of the present study was to investigate impulsive behavior and decision-making in abstinent regular ecstasy users. Three groups were compared: 'ecstasy users' (recreational ecstasy users who reported modest use of illicit drugs other than cannabis), 'polydrug controls' (ecstasy na?ve illicit drug users), and 'drug-na?ve controls'. All participants completed personal details and general drug history questionnaires, the National Adult Reading Test, Matching Familiar Figures Test (MFF20), a risky decision-making task (RDMT), and the Card Arranging Reward Responsivity Objective Test (CARROT). The groups did not differ on the CARROT measure of responsiveness to financial incentive; however, the ecstasy group displayed significantly elevated MFF20 impulsivity, and showed reduced discrimination between magnitudes of prospective gains and losses when making risky decisions, compared to the 'polydrug' and 'drug-na?ve' control groups. These findings may reflect a vulnerability of 5-HT systems in the orbital prefrontal cortex and interconnected corticolimbic circuitry to the cumulative neurotoxic effects of ecstasy and have clinical significance for regular ecstasy users. The combination of elevated impulsivity and impaired use of reinforcement cues in uncertain decision-making may comprise risk factors for continued drug abuse and everyday functioning.