Glycine release in the substantia nigra: Interaction with glutamate and GABA.

Previous studies have reported a high number of glycine (GLY) receptors in the substantia nigra (SN) but a low number of GLY-neurons, suggesting that taurine, a partial agonist of GLY-receptors, is the natural substrate for SN GLY-receptors. By using microdialysis to quantify amino acids in the extracellular space of the SN, we observed an extracellular pool of GLY in the rat that increased after depolarizing with high-K+ in a Ca2+-dependent manner and that diffuses through the extracellular space. GLY markedly increased after blocking either the tricarboxylic cycle with fluorocitrate or the glutamine synthetase activity with MSO. Because these products act selectively on glial cells, their effects show glia as a key cell in maintaining the extracellular pool of GLY in the SN. Extracellular GLY was modified by glutamate and glutamate receptor agonists. The local administration of GLY modified the extracellular concentration of GABA. Taken together, the complex regulation of the extracellular level of GLY, its possible glial origin and interaction with glutamate and GABA suggest a volume transmitter role for GLY in the SN, a possibility which also agrees with the recent finding of GLY-transporters in this centre.

Striatal expression of GDNF and differential vulnerability of midbrain dopaminergic cells.

Glial cell line-derived neurotrophic factor (GDNF) is a member of the transforming growth factor-beta superfamily that when exogenously administrated exerts a potent trophic action on dopaminergic (DA) cells. Although we know a lot about its signalling mechanisms and pharmacological effects, physiological actions of GDNF on the adult brain remain unclear. Here, we have used morphological and molecular techniques, and an experimental model of Parkinson's disease in rats, to investigate whether GDNF constitutively expressed in the adult mesostriatal system plays a neuroprotective role on midbrain DA cells. We found that although all midbrain DA cells express both receptor components of GDNF (GFRalpha1 and Ret), those in the ventral tegmental area (VTA) and rostromedial substantia nigra (SNrm) also contain GDNF but not GDNFmRNA. The levels of GDNFmRNA are significantly higher in the ventral striatum (vSt), the target region of VTA and SNrm cells, than in the dorsal striatum (dSt), the target region of DA cells in the caudoventral substantia nigra (SNcv). After fluoro-gold injection in striatum, VTA and SNrm DA cells show triple labelling for tyrosine hydroxylase, GDNF and fluoro-gold, and after colchicine injection in the lateral ventricle, they become GDNF-immunonegative, suggesting that GDNF in DA somata comes from their striatal target. As DA cells in VTA and SNrm are more resistant than those in SNcv to intracerebroventricular injection of 6-OHDA, as occurs in Parkinson's disease, we can suggest that the fact that they project to vSt, where GDNF expression is significantly higher than in the dSt, is a neuroprotective factor involved in the differential vulnerability of midbrain DA neurons.

Glial regulation of nonsynaptic extracellular glutamate in the substantia nigra.

GLU is the main neurotransmitter in the brain, where it induces a synaptic excitatory action. There is recent evidence for an extracellular nonsynaptic GLU (EnS-GLU) pool in different brain nuclei that, released from glial cells, may act on extrasynaptic GLU receptors of cells located far from the position in which it was released. In the present work, the EnS-GLU pool was studied with microdialysis in the rat substantia nigra (SN). We observed an EnS-GLU pool that increased in a Ca2+-dependent manner during cell depolarization. The selective alteration of with methionine sulfoximide (MSO) and fluorocitrate induced marked modifications in EnS-GLU suggesting that EnS-GLU is dependent on glial cells. Glutamine administration increased GLU, suggesting that neurons are also involved in EnS-GLU modulation. GLU administered in the rostral SN showed a long-distance diffusion to the caudal SN. The ionotropic GLU receptors agonist N-methyl-D-aspartate and kainate and the metabotropic GLU receptors agonist ACPD increased EnS-GLU and decreased extracellular glutamine. Taken together, these data indicate that nigral glia releases GLU, which probably performs a volume transmitter role.

Extracellular taurine in the substantia nigra: taurine-glutamate interaction.

Taurine has been proposed as an inhibitory transmitter in the substantia nigra (SN), but the mechanisms involved in its release and uptake remain practically unexplored. We studied the extracellular pool of taurine in the rat's SN by using microdialysis methods, paying particular attention to the taurine-glutamate (GLU) interaction. Extracellular taurine increased after cell depolarization with high-K(+) in a Ca(2+)-dependent manner, being modified by the local perfusion of GLU, GLU receptor agonists, and zinc. Nigral administration of taurine increased the extracellular concentration of gamma-aminobutyric acid (GABA) and GLU, the transmitters of the two main inputs of the SN. The modification of the glial metabolism with fluocitrate and L-methionine sulfoximine also changed the extracellular concentration of taurine. The complex regulation of the extracellular pool of taurine, its interaction with GABA and GLU, and the involvement of glial cells in its regulation suggest a volume transmission role for taurine in the SN.

Colecistectomía laparoscópica sin gas / Laparoscopic cholecystectomy without the use of gas

El objetivo de este trabajo fue evaluar en forma prospectiva, longitudinal y no comparativa, la seguridad y eficacia de la colecistectomía laparoscópica sin gas. Entre marzo de 1994 y agosto de 1996, fueron efectuadas 60 colecistectomías laparoscópicas sin neumoperitoneo utilizando el endorretractor de Speranza en el Hospital Español de la Ciudad de México. Fueron 20 pacientes masculinos y 40 femeninos, con una edad promedio de 42 años (límites de 17 y 79 alos). Hubo dos complicaciones en relación al uso del endorretractor y no hubo mortalidad. La colecistectomía laparoscópica sin gas, con el uso del aparato del Dr. Speranza y en pacientes sin obesidad es posible, segura, eficaz y ofrece las ventajas de la técnica miniinvasiva, excepto menor dolor; pero a cambio elimina las complicaciones de la insuflación con CO2

Tratamiento laparoscópico de pancreatitis aguda grave. Reporte de un caso / Laparoscopic treatment of severe acute pancreatitis. A case report

Objetivo. Reportar el tratamiento laparoscópico de un paciente con pancreatitis aguda grave. Antecedentes. La eficacia y ventajas de la cirugía laparoscópica en el tratamiento de enfermedades intraabdominales agudas ha sido demostrado previamente. La vía laparoscópica ya ha sido reportada para el diagnóstico y tratamiento de diversas enfermedades pancreáticas, incluyendo formas severas de pancreatitis y sus complicaciones. Material y métodos. Paciente masculino de 70 años de edad con cuadro de abdomen agudo al que se le realizó laparoscopia diagnóstica encontrándose colecistitis aguda y pancreatitis grave. Siete días después debido a curso tórpido requirió de reintervención para realizar necrosectomía por vía laparoscópica. Conclusión. El tratamiento laparoscópico de la pancreatitis grave es factible en casos seleccionados y brinda grandes ventajas sobre el procedimiento tradicional. Son necesarios estudios y protocolos prospectivos para validar el abordaje laparoscópico en el diagnóstico y tratamiento de la pancreatitis grave

Coledocoscopia transoperatoria. Experiencia con 42 casos / Intraoperative choledochoscopy. Experience with 42 cases

Antecedentes: La coledocoscopia es una técnica de exploración bajo visión directa de las vías biliares que disminuye la incidencia de litiasis residual. Objetivo: Determinar la eficacia de la coledocoscopia transoperatoria en la detección de cálculos de las vías biliares y en la disminución de litiasis residual. Diseño: Estudio prospectivo, longitudinal, observacional, no aleatorio y no comparativo. Material y métodos: Entre enero de 1987 y enero de 1990, 42 pacientes fueron sometidos a coledocoscopia transoperatoria. Fueron incluidos pacientes con diagnóstico de colecistitis litiásica aguda o crónica sometidos a colecistectomía tradicional, que presentaban datos clínicos o de gabinete de sospecha o de confirmación de coledocolitiasis. Resultados: Se obtuvo el 100 por ciento de éxito técnico y el 88 por ciento en la detección de cálculos. Hubo un caso de litiasis residual. No hubo mortalidad. Conclusión: La coledocoscopia transoperatoria es un procedimiento útil en el diagnóstico y tratamiento de la coledocolitiasis y disminuye la litiasis residual

Control Manométrico en la cirugía laparoscópica antirreflujo gastroesofágico / Manometric control in the laparoscopic gastroesophageal antireflux surgery

El propósito de este estudio es el de valuar la seguridad, utilidad y eficacia del control manométrico pre y transoperatorio en la cirugía laparoscópica antirreflujo gastroesofágico. Fue un estudio prospectivo, aleatorizado, longitudinal, observacional y comparativo de 35 pacientes, que fueron sometidos a cirugía laparoscópica antirreflujo en los Hospitales ABC y Español de de la Ciudad de México, entre mayo 93 y octubre 95; fueron 19 hombres y 16 mujeres con un promedio de edad de 27 años. Se distribuyeron en dos grupos: El grupo 1 incluyó 20 pacientes con control manométrico pre y transoperatorio. EL grupo 2 estuvo integrado por 15 pacientes que fueron sometidos a cirugía laparoscópica antirreflujo sin estudio manométrico. El periodo de seguimiento varió entre dos semanas y 30 meses. En el grupo 1, ninguno de los pacientes presentó disfagia postoperatoria. En el grupo 2, cuatro sujetos tuvieron disfagia postoperatoria; de éstos, dos requirieron dilataciones esofágicas. El control manométrico en la cirugía laparoscópica antirreflujo es un método útil, seguro y eficaz que aumenta el índice terapéutico, reduce las complicaciones postoperatorias, la incidencia de disfagia y la tasa de recurrencia