The subthalamic nucleus : Part II: Modelling and simulation of activity

Part II starts with a systemic model of the basal ganglia to evaluate the position of the STN in the direct, indirect and hyperdirect pathways. A summary of in vitro studies is given, describing STN spontaneous activity as well as responses to depolarizing and hyperpolarizing inputs, and high frequency stimulation. STN bursting activity and the underlying ionic mechanisms are investigated. Deep brain stimulation used for symptomatic treatment of Parkinson's disease is discussed in terms of the elements that are influenced and its hypothesized mechanisms. This part of the monograph pays attention to the pedunculopontine-subthalamic connections and tries in cell cultures to mimic neurotransmitter actions of the pedunculopontine nucleus and high frequency stiulation on cultured dissociated rat subthalamic neurons. STN cell models: single and multi compartment, and system level models are discussed in relation to subthalamic function and dysfunction. Part I and II are mutually compared

The subthalamic nucleus : Part I: Development, cytology, topography and connections

This monograph on the subthalamic nucleus accentuates in Part I the gap between experimental animal and human information concerning subthalamic development, cytology, topography and connections. The light and electron microscopical cytology concerns the open nucleus concept and the neuronal types present in the STN. The cytochemistry encompasses: enzymes, NO, GRAP, calcium binding proteins, and receptors (dopamine, cannabinoid, piod, glutamate, GABA, serotonin, cholinergic, and calcium channels). The ontogeny of the subthalamic cell cord is reviewed. The topography concerns the rat, cat, baboon and human STN. The descriptions of the connections are also given from a historial point of view. Recent tracer studies on the rat nigro-subthalamic connection revealed contralateral projections

Evidence for the existence of homolateral and contralateral projections from the substantia nigra to the subthalamic nucleus in the rat

Hemichorea/ballism is a rare neurological disorder but the crucial involvement of the subthalamic nucleus (STN) in its pathophysiology is appreciated since decades. The idiopathic Parkinson’s disease is a common neurodegenerative disorder but the key role of the STN in the pathophysiological origin of the parkinsonian state became only recently evident. The STN was believed to exert an inhibitory, probably – GABA-mediated, effect on its projection nuclei, and this belief is one of the major reasons to overlook the involvement of the STN in the parkinsonian pathophysiology. It is now firmly established that the STN projection neurons are glutamatergic, excitatory, and heavily innervate by widely branching axons of the substantia nigra (SN), the internal pallidal segment (GPI), followed by the external pallidal segment (GPE) and the pedunculopontine tegmental nucleus (PPN)

Adsorción de bajas concentraciones de uranio en granito

Este trabajo contiene los resultados de la reelaboración de datos experimentales emergentes de la adsorción de uranio en granito. Partiendo de una isoterma de Freundlich, se consideró que ciertas hipótesis experimentales no eran enteramente correctas y se obtuvo una nueva isoterma. Puesto que ambas isotermas sugieren una adsorción de uranio mayor a lo esperable y que no son lineales, se efectuó la consideración del efecto del contenido natural de uranio del agua que albergaba el granito. Fue así posible comprobar que la adsorción no constituía un fenómeno relevante con bajas concentraciones de uranio en solución, y que era factible considerar que el modelo de adsorción era lo suficientemente lineal como para poderlo incluir en la instancia oosterior de modelación del mecanismo de flujo de agua y transporte de uranio.Publicado en Serie Correlación geológica ; no. 11

Cálculo de la recarga mediante la aplicación de la ecuación de Darcy en la zona no saturada

En este trabajo se expone la aplicación del método de cálculo del flujo al acuífero mediante la aplicación de la ecuación de Darcy a la zona no saturada, considerando un plano de flujo a los 120 cm de profundidad. La conductividad hidráulica en función de la humedad, K(9), se obtuvo mediante un ensayo de drenaje interno

Mastication and sensibility, or the five new findings in the cat mesencephalic trigeminal nucleus

The brain even of small animals, like the rat, is complicated in its structure and its function. The hardware of the smartest personal computer is difficult to unravel. Those studying the brain know, that those brain structures that left the common evolutionary path are even harder to study. Such a structure is the mesencephalic nucleus of the trigeminal system, responsible for the sensibility of the jaw-closing muscles and the periodontium. The mesencephalic trigeminal nucleus (MTN) is a drop-like nucleus with an enormous thin tail, extending from the rostral pons along the entire caudo-rostral length of the midbrain. While all sensory ganglia of the spinal and cranial nerves are placed outside the central nervous system, the MTN, that exists of the same primary afferent neurons, is placed in the brainstem. As a consequence, this nucleus receives projections from other brain parts, projects to non-primary afferent target areas, contains a different topography and neurochemistry, in which it distinguishes itself from other primary afferent sensory ganglia of the spinal and cranial nerves. In this volume of Biomedical Reviews, the first neurochemical update on the cat MTN appears. Moreover, it stems from the Department of Anatomy, Thracian University Medical Faculty in Stara Zagora by Nikolai Lazarov and Christo Chouchkov known for their skin receptor studies and their connectivity to and in the MTN. They earned the First Dimitri Kadanoff Memorial Award truly.Biomedical Reviews 1997; 8: 21-22

The milky spots of the peritoneum and pleura: structure, development and pathology

The milky spots (MS), originally described by Ranvier as taches laiteuses, are found on the greater omentum but also in other peritoneal regions, as well as on the pleura and pericardium. They represent aggregations of mesenchymal tissue surrounding blood vessels. These small whitish regions are covered by mesothelium, and within the mesothelial layer are scattered macrophage-like cells. The blood supply of MS is provided by arterioles that give rise to capillary network formed by fenestrated or continuous endothelial cells. Most MS possess also lymphatic vessels, with extremely thin endothelial cells. The most frequent cells in MS are the macrophages, followed by lymphocytes and mast cells. Typically, the macrophages are located in the periphery, while the lymphocytes - in the center of MS. Additional structural elements are plasmocytes, adipocytes, fibroblasts, roundedfibroblast-likecells (undifferentiated mesenchymal cells), as well as collagen, reticular and elastic fibers. The nerve fibers innervating MS are located under the mesothelium and among the free cells. Despite their small size, the MS are a significantorgan, functioning at both normal and pathological conditions. Under inflammatory conditions (peritonitis), MSact as the first line of defense, and dramatically change their number, size and structure. MS are also involved in extramedullary hemopoiesis. They are the first target of intraperitoneal (intrapleural) metastases, and appear an important target in the development of immunotherapeutic strategies against malignant diseases.Biomedical Reviews 2004; 15: 47-66

Análisis de la propuesta de regulación de los recursos hídricos en la provincia de Buenos Aires, Argentina

Following concepts of general nature about the environmentally- sustainable development, this paper tests to which extent such aspects are properly addressed in the Buenos Aires Province Water Law, which is currently being discussed in the province’s legislative domain. The main conclusions about such a law are that: (a) it centralizes the water resources administration by creating the Water Authority, although it also allows for certain aspects being managed by Basin Committees and Water-Users Groups, (b) it clearly spells out the rights and dutties of those directly benefited by water usage, (c) it does not foresee a great deal of involvement of the community as such, (d) it reinforces the role of the technical sector, and (e) it may prove to be very difficult to be ruled out.Luego de consideraciones de tipo general con respecto al desarrollo ambientalmente sustentable, este trabajo trata de comprobar hasta qué punto sus aspectos esenciales están contemplados en la Ley de Aguas de la Provincia de Buenos Aires, que se encuentra en discusión en ámbitos legislativos provinciales. Se concluye que la normativa en discusión: (a) centraliza administrativamente los diversos aspectos del manejo de los recursos hídricos en la Autoridad del Agua, aunque descentraliza ciertas funciones en los Comités de Cuenca y las Comunidades de Usuarios, (b) desglosa adecuadamente los derechos y obligaciones del sector privado que se beneficia con el uso del agua, (c) no prevee un grado importante de participación de la comunidad no productora de bienes o servicios, (d) revitaliza el rol de los estamentos técnicos, y (e) puede revelar severas dificultades a la hora de proceder a su reglamentación