Synchronicity of nociceptive and non-nociceptive adjacent neurons in the spinal dorsal horn of the rat: stimulus-induced plasticity

Current knowledge of spinal processing of sensory information is largely based on single-cell recordings; however, temporal correlation of multiple cell discharges may play an important role in sensory encoding, and single electrode recordings of several neurons may provide insights into the functions of a neuronal network. The technique was applied to the lumbar spinal dorsal horn of pentobarbital-anaesthetized rats during background activity, steady-state noxious heat stimulation (48 degrees C, 100 s), cold block spinalization or radiant heat-induced inflammation of the skin, and the recordings were evaluated by means of auto-correlation, autospectral and cross-correlation analysis. Background patterns obtained by these three methods were extremely stable in time. Autocorrelation with short lag peaks was observed in 72.2% of neurons (n = 223). Background correlated discharges were found in 83.6% of the neuron pairs (n = 134). Cross-correlation with a central peak, suggestive of common input to the recorded cells, was the most common pattern observed in almost all laminae and was associated with high incidence (91.8%) of overlapping receptive fields and with neurons with initial peak autocorrelation pattern. Cross-correlations with central trough were associated with increase autocorrelation patterns. Bilateral peaks in cross-correlation, suggestive of reverberating circuitry, were observed only for pairs of neurons located in laminae IV and V and were associated with rhythmic discharges in one or in both simultaneously-recorded neurons. Lagged peaks or troughs were observed in 4.6% and 2.2% of neuronal pairs, respectively. Long-lasting skin heating induced qualitative changes (pattern changes) in the cross-correlation of 21.6% of the neuron pairs and quantitative changes in 85.7% of them. During skin inflammation qualitative changes in the cross-correlation pattern were observed in 30.8% of the neuron pairs, and quantitative changes (strength and/or synchronization time) in about 57.7% of them. Spinalization induced quantitative changes in cross-correlation in the vast majority of neuron pairs. The results of the present study suggest that discharges of neighbouring spinal dorsal horn neurons are strongly synchronized probably by propriospinal and primary afferent sources. The existence of functional reverberating circuitry was also evidenced. Finally, the functional synchronicity in the spinal dorsal horn presents stimulus-induced plasticity which consists mainly of changes on the strength and/or time of the synchronization and rarely of activation of new connectivities.     

Long-term mechanical circulatory support system reliability recommendation: American Society for Artificial Internal Organs and The Society of Thoracic Surgeons: long-term mechanical circulatory support system reliability recommendation

Jointly developed by members of the American Society for Artificial Internal Organs and the Society of Thoracic Surgeons along with staff from the Food and Drug Administration, the National Heart, Lung and Blood Institute and other experts, this recommendation describes the reliability considerations and goals for Investigational Device Exemption and Premarket Approval submissions for long-term, mechanical circulatory support systems. The recommendation includes a definition of system failure, a discussion of an appropriate reliability model, a suggested in vitro reliability test plan, reliability considerations for animal implantation tests, in vitro and animal in vivo performance goals, the qualification of design changes during the Investigational Device Exemption clinical trial, the development of a Failure Modes Effects and Criticality Analysis, and the reliability information for surgeons and patient candidates. The document will be periodically reviewed to assess its timeliness and appropriateness within five years.     

Intrachromosomal triplication of 15q11-q13

A 7 year old girl with intrachromosomal triplication 46,XX,-15,+der(15)(pter-->q13::q13-->q11::q11-->qter) resulting in tetrasomy of 15q11-q13 is reported. Fluorescence in situ hybridisation confirmed that the tetrasomic region included the entire segment normally deleted in Prader-Willi and Angelman syndrome patients, and breakpoints were similar to those reported in two tandem duplications of 15q11-q13. The middle repeat was inverted, suggesting a possible origin through an inverted duplication intermediate. Microsatellite analysis showed that the rearrangement was of maternal origin and involved both maternal homologues. Clinical findings included multiple minor anomalies (a fistula over the glabella, epicanthic folds, downward slanting palpebral fissures, ptosis of the upper lids, strabismus, a broad and bulbous tip of the nose, and small hands and feet), motor and mental retardation, a seizure disorder, and limited verbal abilities. In addition, immunological examination disclosed a selective immunodeficiency. The overall phenotype did not clearly resemble that of cases with tetrasomy 15pter-q13 associated with an extra inv dup(15)(pter-->q13:q13-->pter) chromosome. The latter aberration causes more severe mental deficit and intractable seizures, but less marked phenotypic alterations, although some overlap in mild facial dysmorphic features is present. A number of features common to Angelman syndrome were also observed in the patient.     

Gonadal function abnormalities in sickle cell anemia. Studies in adult male patients

Thirty-two adult patients with sickle cell anemia were evaluated endocrinologically. Secondary sex characteristics were abnormal in 29, and eunuchoidal skeletal proportions were present in all except one. The age at which different stages of pubic hair growth were attained in these patients was delayed in comparison to normals (P less than 0.005). Hormonal assays were carried out in 14 patients. Basal serum testosterone, dihydrotestosterone, and androstenedione values were lower (P less than 0.02) in patients than controls. Serum LH and FSH levels before and after stimulation with gonadotropin-releasing hormone were consistent with primary testicular failure. Erythrocyte and hair zinc concentrations were significantly decreased, and there was positive correlation between erythrocyte zinc and serum testosterone (r = 0.61, P less than 0.01) in sickle cell anemia. Our study shows that androgen deficiency in this disease is a result of primary rather than secondary hypogondadism. Further studies are required to establish the role of zinc in the pathogenesis of testicular failure in sickle cell anemia.