Random walks for spike-timing-dependent plasticity.

Random walk methods are used to calculate the moments of negative image equilibrium distributions in synaptic weight dynamics governed by spike-timing-dependent plasticity. The neural architecture of the model is based on the electrosensory lateral line lobe of mormyrid electric fish, which forms a negative image of the reafferent signal from the fish's own electric discharge to optimize detection of sensory electric fields. Of particular behavioral importance to the fish is the variance of the equilibrium postsynaptic potential in the presence of noise, which is determined by the variance of the equilibrium weight distribution. Recurrence relations are derived for the moments of the equilibrium weight distribution, for arbitrary postsynaptic potential functions and arbitrary learning rules. For the case of homogeneous network parameters, explicit closed form solutions are developed for the covariances of the synaptic weight and postsynaptic potential distributions.

Updated results on intestinal neuronal dysplasia (IND B).

BACKGROUND: Intestinal neuronal dysplasia (IND B) is still a subject of controversy. The aim of this paper is to review the present state of knowledge on IND B. A summary is given of the technical and diagnostic criteria which have to be considered in order to arrive at a reliable diagnosis. In addition, the available therapeutic interventions are discussed. METHODS: Between 1992 and 2001, 3984 colonic mucosal biopsies from 1328 children were investigated. Nerve cell staining was performed on native tissue sections: 15 microm thick cryostat sections, which, after spreading and drying on a microscopic slide, have a final thickness of 4-5 microm, with dehydrogenase reactions (lactic dehydrogenase, nitroxide synthase, succinic dehydrogenase). The biopsies were taken 8-10 cm above the dentate line (proximal to the ampulla recti, because of the caudo-cranial increase of giant ganglia proximal to the 4 cm biopsy) with a sufficient amount of submucosa. The criteria for IND is 15-20 % submucosal giant ganglia with more than eight nerve cells in 30 sections of a single biopsy (i.e. four to seven giant ganglia). RESULTS: The diagnosis of IND B is quantitative. A diagnosis of IND B was made over the past 10 years in 51 Hirschsprung resections (about 5 per year; 6 % of all Hirschsprung cases), and in 92 children with chronic constipation (about 9 children per year; 2.3 % incidence). Up to their fourth year of life, most children with isolated IND can be treated conservatively. This is due to the delayed maturation of the enteric nervous system which is characteristic of IND B. Only children who showed an additional hypoplastic hypoganglionosis were treated surgically. Children with Hirschsprung's disease (HD) and IND B proximal to the aganglionosis often showed, in those cases with a disseminated IND, postoperative disturbances in intestinal motility. CONCLUSION: The diagnosis of IND B requires that biopsies are taken proximal to the ampulla recti (about 8-10 cm above the dentate line) with a sufficient amount of submucosa. The biopsies must be cut rectangular to the surface of the mucosa. A diagnosis of IND B can be made only if, in the submucosa of 30 serial sections, 15-20 % of all ganglia are giant ganglia with more than eight nerve cells. Ganglioneuromatosis (MEN2B) must be clearly differentiated from IND. The clinical course of IND B depends on the extent of disturbed bowel innervation, the severity of motility failure, and the coexistence of MH. The conservative management of isolated IND is possible in most children. In individual cases, however, a transient enterostomy or a segmental resection is unavoidable.

Importancia de la correlación clínico patológica para el pronóstico y tratamiento de la tuberculosis ganglionar de evolución prolongada / Importance of clinico*pathological correlation for the prognosis and treatment of the tuberculosis of lymph nodes of prolonged evolution

Se revisó 125 casos de tuberculosis ganglionar atendidos en el Hospital Nacional `Guillermo Almenara Irigoyen', Instituto Peruano de Seguridad Social, entre 1976 y 1985; el 16.8 por ciento reactivó la enfermedad. Se analizó estas historias clínicas con evolución hasta 1990. En cada biopsia de ganglio se estudió: registro cuantitativo y cualitativo de los componentes del granuloma y elementos celulares de las áreas cortical y paracortical no afectadas por la lesión. Se clasificó los casos según el estado de reacción del paciente en el espectro de tuberculosis humana propuesto por Lenzini. Se concluye que 16.8 por ciento de pacientes tuvo características de NO REACTIVO INTERMEDIO (UI), 50 por ciento de ellos abandonó el tratamiento. Al diagnosticar la enfermedad, debe evaluarse el estado de reacción del paciente por correlación clínico patológica. El informe anátomo patológico debe incluir: diagnóstico de la lesión y características de las áreas cortical y paracortical no afectadas por la lesión. Los pacientes clasificados como UI, deben recibir el tratamiento indicado para casos con reactivación de la enfermedad, aún cuando sea su primer estudio biópsico