Showing papers by "University of Los Andes published in 1969"

Diversidad de hormigas (hymenoptera: formicidae) en un gradiente sucesional del bosque nublado (narino, colombia)

Abstract: We evaluate the potential use of ants as indicator taxa of cloud forest recovery in La Planada Reserve, at southwestern Andine slope in Narino, Colombia. The ants were sampled from February through August 1995, using pitfall traps, tuna baits and manual collection, in seven localities representing forest successional stages: cattle ground, grassland (three year old), two ten year old forests and 20 year old, exploit and primary forests. We found 63 species (29 genera) with a 20-26 species richness per locality, with the exception of the ten year old forest (12 species). There were no any statistical differences in species richness and diversity among sam- ples and study sites. Nevertheless taxonomic composition was associated with the successional stage (Simple Matching Coefficient). Ants can be used as indicators of forest recovery at La Planada.

Reabsorción de nitrógeno y fósforo foliar en árboles de bosques montanos en los Andes centrales de Colombia

Abstract: Se determinaron las concentraciones y los porcentajes de reabsorcion de nitrogeno y fosforo foliar en cinco especies de arboles de un bosque montano bajo (BMB) a 1850 m.s.n.m. y en cinco de un bosque montano alto (BMA) a 2800 m.s.n.m en la Cordillera Central colombiana, asi como la disponibilidad de nitrogeno y fosforo del suelo. Los porcentajes de reabsorcion de N y P no fueron significativamente diferentes entre las especies de estos dos bosques. Apesar de esto, se observo que la reabsorcion de P foliar tendio a ser mayor en las especies del BMB donde la concentracion de P en el suelo fue significativamente mas baja (3.2 ppm vs. 9.0 ppm). Cuando la reabsorcion de P foliar se expreso como funcion de la concentracion en hojas maduras en 12 tipos de bosques montanos tropicales, se encontro una correlacion negativa y estadisticamente significativa. Estos resultados sugieren que los porcentajes de reabsorcion de P foliar en bosques montanos estarian controlados parcialmente por la disponibilidad del elemento.

Population genetics in the American tropics. II. The comparative genetics ofDrosophila in european and neo-tropical environments

Abstract: We have attempted to make quantitative comparisons between the genetic systems provoked by some neo-tropical environments and a European one. These comparisons permit certain clarifications regarding the comprehension of the genetic load and of the genetic “norm” in reference to particular ecological characteristics.

Population genetics in the American tropics. IV. Temporal changes effected in natural populations ofDrosophila melanogaster from Colombia

Abstract: Samples ofDrosophila melanogaster were taken each month over several years from a locality in Fusagasuga, Colombia. Temporal shifts in gene frequencies were found. These reflect important adaptive changes in the populations, and the kind of gene pool modifications that are necessary for the better occupation of local temporal niches.

Population genetics in the American tropics. V. The sterility content in the second chromosomes of Drosophila melanogaster from Fusagasugá, Colombia.

Abstract: Samples ofD. melanogaster have revealed fluctuations in sterility genes in Fusagasuga, Colombia, over a period of seven months covering a wet and a dry season. These samples were taken from a single locality in a circle of 10 m diameter within 20 min of collecting. The temporal shiftsin, gene frequencies found in male carriers fit the weather changes in that local niche. Our observations suggest that sterility genes may be part of an adaptive system which controls and modifies the effective population size.

Abortos de semillas de Enterolobium cyclocarpum (Mimosoideae): efecto de la posición relativa dentro del fruto

Abstract: We examined if seed abortion in Guanacaste free fruits (Enterolobium cyclocarpum) is related to position within fruits, by establishing the abortion ratio in 150 fruits from 10 trees, collected in Santa Rosa National Park (Guanacaste, Costa Rica). Fruits were divided in basal, central and distal sections. We found marginal differences in abortion ratio between these sections (Anova, p = 0.058), and also among trees (p = 0.01). In general, the distal section had the greatest abortion ratio in relation to other sections. This abortion pattern could be caused by resource competition within siblings and not by genetic differences among them.

Efecto de la aplicación aguda de fluoxetina sobre una tarea de miedo condicionado al contexto en ratas sometidas a restricción comportamental

Abstract: In order to study the effect of behavioral or pharmacologically enhanced anxiety on the acquisition of contextual fear conditioning, thirty two Wistar rats (275±25gm) were divided in two groups (behavioral restriction and control). Half of each group received saline solution (ig.; 0.9%) or fluoxetine (ig.; 4mg/Kg) before the fear conditioning procedure. The two way ANOVA showed significant differences for treatment (F[1,28]=25.261; P<0.001). Student Newman-Keuls showed that subjects treated with fluoxetine had lower freezing times. There were no significant differences nor for restriction neither for the interaction between the factors (F[1,28]=0.115; P=0.737 y F[1,28]=0.016; P=0.899). Thus, the restriction procedure used did not modify the acquisition of the conditioned fear response suggesting that the putative 5-HT enhancement induced is not comparable to that induced by fluoxetine. Acute fluoxetine disrupted the acquisition of the conditioned fear response, suggesting that the mechanism by means of which anxiety disrupts learning could be serotonergic in nature

Instrumento de Responsabilidad social corporativa e el grupo Zeltia

Abstract: Este trabajo analiza las practicas de responsabilidad social en el grupo farmaceutico espanol Zeltia. A traves de un proceso de recoleccion de informacion proveniente de diversas fuentes, se han clasificado las actuaciones de RSC de la empresa. Dicho analisis revela que Zeltia es un claro ejemplo de que actuar como empresa responsable no es incompatible con obtener buenos resultados economicos. A pesar de ser una empresa comprometida en los diferentes instrumentos de RSC, este estudio detecta ciertas carencias y propone algunas lineas de mejora

Estado del Arte en el Diseño de Lagunas de Potabilización

Abstract: El autor muestra el tratamiento de aguas residuales municipales y de industrias en lagunas de potabilizacion como una alternativa viable y economica. Hace ademas una completa descripcion de los tipos de lagunas y modelos existentes. Nos presenta tambien el proceso de diseno de las estructuras y su operacion y mantenimiento, finalizando con un ejercicio practico.