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Showing papers by "University of Costa Rica published in 1981"


Journal ArticleDOI
TL;DR: The reassociation kinetics of DNA fragments obtained from the major components of the mouse and human genomes lead to the general conclusion that the sequence organization of mammalian genomes is not uniform in different chromosomal regions and that it exhibits remarkable variations in different mammals.
Abstract: Main-band DNA from mammals and birds can be resolved by density gradient centrifugation techniques into three or four families of fragments of different dG + dC contents. These major DNA components are similar in their buoyant densities and relative amounts in all species tested and are observed in DNA preparations ranging in Mr from 2 × 106 to over 200 × 106. In the present work, the four major components of mouse and human DNAs were prepared and characterized in several basic properties: relative amounts, dG + dC contents, buoyant densities and compositional heterogeneity. The results obtained lead to the following conclusions: (a) the major DNA components of mouse and man form at least 85% and possibly the totality of the main bands of these DNAs; (b) they have very low compositional heterogeneities over a wide molecular weight range; (c) they derive from very large chromosomal DNA segments of fairly homogeneous base composition, for which the name ‘isochores’ is proposed. A comparison of the compositional heterogeneity of main-band DNAs from warm-blooded and cold-blooded vertebrates confirms our previous conclusion that these DNAs are characterized by a different sequence organization.

148 citations


Journal ArticleDOI
01 Jan 1981-Toxicon
TL;DR: The ineffectiveness of antivenom in neutralizing edema and myonecrosis could be partially explained by the rapid development of these effects, and the time interval between envenomation and antivenum administration and the route of serum administration both play an important role in the neutralization of local effects.

106 citations


Journal ArticleDOI
TL;DR: Irregularly scheduled restraint resulted in post-trial alterations in plasma levels of corticosterone, glucose, and free fatty acids of greater magnitude and longer duration than did regularly scheduled trials, confirming a more pronounced effect for the unpredictable stress.

43 citations


Journal ArticleDOI
TL;DR: In this paper, an improved treatment of the reaction π − d → γnn, extending the validity of the calculation to lower photon energies, permit a new analysis of a high statistics photon spectrum, and a precise value of the effective range parameter γ nn = 283 ± 011 fm has been obtained The theoretical uncertainty is 1 1 fm.

27 citations


Journal Article
TL;DR: According to these results, age and macrophage activity are very important factors in the natural adaptability of the white rat to Toxoplasma gondii.
Abstract: White rats were found to be resistant to 3 x 10(7) Toxoplasma gondii organisms (RH strain) inoculated either sc or ip. That resistance was age-dependent since survival time of 1- or 5-day-old rats inoculated with 10(4) or 10(6) tachyzoites was lower as compared with those 10 or 15 days old. Organisms kept in contact with a lysate of white rat complete peritoneal exudate showed reduced capacity to infect mice. Peritoneal exudate of 5-day-old rats showed a stronger effect than that of 1, 2, 3, or 4 day-infected animals. After 10 days the anti-toxoplasma effect diminished and it almost disappeared after 15 days of infection. Apparently age and macrophage activity are very important factors in the natural adaptability of the white rat to Toxoplasma gondii.

17 citations


Mata L1
01 Apr 1981
TL;DR: It is shown that mortality due to diarrheal diseases in Costa Rica began to decline in the 1940's and reached a low of 12 deaths per 100,000 population in 1977, the recent rapid decline was coincidential with an overall improvement of health services, income and the quality of life.
Abstract: articulo -- Universidad de Costa Rica, Instituto de Investigaciones en Salud (INISA), 1981.

13 citations


Journal ArticleDOI
01 Jan 1981-Toxicon
TL;DR: It is proposed that the ultrastructural basis of the muscular necrosis induced by terciopelo venom is the disruption and severe alteration of the myofibril architecture.

10 citations


Journal Article
TL;DR: The Laguna Grande de Chirripo, a small high mountain lake of glacial origin located in the Cordillera de Talamanca of Costa Rica as mentioned in this paper, has a water temperature oscillating around 10 C, a very low concentration of dissolved solids and a gross primary productivity of 0.15 g C m-2 d-1.
Abstract: Morphometric data together with some selected physical, chemical and biological features of the Laguna Grande de Chirripo, a small high mountain lake of glacial origin located in the Cordillera de Talamanca of Costa Rica, are discussed. The lake has a water temperature oscillating around 10 C, a very low concentration of dissolved solids and a gross primary productivity of 0. 15 g C m-2 d-1. The maximum productivity value recorded was found at a depth of 5 m. Levels above this are probably subjected to strong light inhibition.

10 citations


Journal ArticleDOI
TL;DR: In this article, the adsorption of Zn by soil and subsoil samples from the slopes of the Irazu and Poas volcanoes in Costa Rica was correlated with soil properties and represented by Langmuir isotherms.
Abstract: The adsorption of Zn by soil and subsoil samples from the slopes of the Irazu and Poas volcanoes in Costa Rica was correlated with soil properties and represented by Langmuir isotherms. Soil pH, texture and free aluminum and sesquioxide content correlated significantly with Zn adsorption. No correlation with organic matter content was found probably due to the variable nature and properties of its compounds. The adsorption maxima ("b”; values) calculated by the Langmuir equation are higher for the soils developed on the more weathered Poas than for the more recent Irazu ash. The bonding energy constants ("K") followed a similar trend.

8 citations


Journal ArticleDOI
TL;DR: In this paper, a conservative dilation for the 1/2-spin was constructed directly from the Bloch equation, thus yielding an example of a dilation scheme for an evolution which is not quasifree.
Abstract: A semigroup evolution for the 1/2-spin which admits a conservative dilation is known to be governed by a Bloch equation in a standard form. Here we construct a conservative dilation directly from the Bloch equation, thus yielding an example of a dilation scheme for an evolution which is not quasifree. Moreover, we show that this conservative evolution is never ergodic in the non-quasifree case.

8 citations


Journal Article
TL;DR: Clear structural differences were observed in each part of the digestive tracts in the two genera, and the epithelial cell structure of Schistocerca is much more convex.
Abstract: Surface ultrastructures of the digestive tracts of Taeniopoda and Schistocerca were studied by scanning electron microscopy and the surface of the pharynx, esophagus, crop, cardiac valve, stomach, ileum, colon and rectum are described. Clear structural differences were observed in each part of the digestive tracts in the two genera. The epithelial cell of the pharynx and esophagus showed well developed infolding and conical projections in both genera, however, the epithelial cell structure of Schistocerca is much more convex. In Schistocerca the overall structure is more mosaic-like, with three conical projections for each unit. In both genera the transitional zone between the crop and the stomach is formed by well developed triangles and the stomach and caecum have abundant infoldings and microvilli. The ileum shows abundant cone-shaped projections; the colon and rectal sac are smooth.

Journal ArticleDOI
TL;DR: It is confirmed that the intraspecific chromosomal polimorphism characteristic of this species is the same as that of other coral snakes of Costa Rica.
Abstract: Two principal karyological patterns were observed in 59 coral snakes ( Micrurus nigrocinctus ) from Costa Rica: I, "nigrocinctus" (2n = 26) and II "mosquitensis '" (2n =30), which correspond to the subspecies M. n. nigrocinctus and M. n. mosquitensis , respectively. These chromosomal patterns differ in the number of microchromosomes and in the position of the centromere in the eighth pair of macrochromosomes. In the M. n. nigrocinctus group we found three specimens with an additional microchromosome (2n =27) and one with two more (2n = 28). Among the M. n. mosquitensis we saw two individuals with a variation in the position of the centromere in the W chromosome. This study confirm s the intraspecific chromosomal polimorphism characteristic of this species.

Journal Article
TL;DR: The four species of eastern Pacific Pomadasys belonging to the subgenus Haemulopsis are analized and a description based on meristic and morphologic characteristics is given for each of the four species: P. leuciscus, P. elongatus, P axillaris and P. nitidus.
Abstract: The four species of eastern Pacific Pomadasys belonging to the subgenus Haemulopsis are analized and a description based on meristic and morphologic characteristics is given for each of the four species: P. leuciscus, P. elongatus, P. axillaris and P. nitidus . Juvenile as well as adult characters are included and species comparisons are made. P. corvinaeformis , the only Atlantic representative of the subgenus, is considered a cognate of the Pacific P. leuciscus . A key to Pacific Haemulopsis is included.



Journal Article
TL;DR: A new seven-spined goby, Elacatinus janssi, is described from 203 specimens collected at thirteen localities along the Pacific coast of Costa Rica and compared to a similar western Atlantic species.
Abstract: A new seven-spined goby, Elacatinus janssi, is described from 203 specimens collected at thirteen localities along the Pacific coast of Costa Rica. It is distinguished from its congeners and compared to a similar western Atlantic species.

Journal Article
TL;DR: In this paper, an analisis de the estructura de edades (age structure) of una poblacion amerindia guaymi de Limoncito, Coto Brus, Costa Rica mostro que un 47% de la población oscila entre 0 and 14 anos and un 35% entre 15 and 44 anos.
Abstract: El analisis de la estructura de edades (age structure) de una poblacion amerindia guaymi de Limoncito, Coto Brus, Costa Rica mostro que un 47% de la poblacion oscila entre 0 y 14 anos y un 35% entre 15 y 44 anos. La proporcion sexual (sex ratio) tiene un valor de 91, lo que indica un exceso de mujeres. El 40% de los padres proviene de Panama pero la generacion filial es, en su mayoria, de origen local. La emigracion es minima.El potencial selectivo (selective potential) es relativamente alto (0,94), con predominio del componente de mortalidad (0,52). La endogamia y el coeficiente de endocruzamiento tienen valores altos y el cruzamiento poligamo es frecuente. El tamano efectivo y reproductivo (effective and reproductive size) de la poblacion es bajo. La proyeccion futura de la poblacion implica el crecimiento demografico, la emigracion, el aumento del componente selectivo de la fertilidad y variaciones en el tamano reproductivo y el tamano efectivo del grupo guaymi estudiado. Se discuten las posibles implicaciones evolutivas de los resultados obtenidos.




Journal Article
TL;DR: Post mortem ultrastructural alterations of surface epithelial tissues were studied by scanning electron microscopy and alveolal epithelial cells showed the beginning of edema.
Abstract: Post mortem ultrastructural alterations of surface epithelial tissues were studied by scanning electron microscopy. Ten male albino mice were sacrificed, and the duodenum, ileum arid lung excised and fixed immediately, at 20, 40, 60 and 120 minutes post mortem. The intestinal villi and mierovilli tended to flatten and to lose rigidity of cellular architecture. Alveolal epithelial cells showed the beginning of edema. Ultrastructural changes in epithelial cells were noticed as early as 20 minutes after death.






01 Jan 1981
TL;DR: The politica economica fundamental del Estado Nacional costarricense a lo largo del siglo XIX, with variantes segun las etapas de its desarrollo, was marcadamente liberal in el sentido de permitir un "aperturismo" of la naciente economia that garantizara su anclaje ventajoso in las movedizas arenas del emergente mercado capitalista worldial as discussed by the authors.
Abstract: Este articulo aborda como la politica economica fundamental del Estado Nacional costarricense a lo largo del siglo XIX, fue, con variantes segun las etapas de su desarrollo, marcadamente liberal en el sentido de permitir un "aperturismo" de la naciente economia que garantizara su anclaje ventajoso en las movedizas arenas del emergente mercado capitalista mundial. Las medidas protectoras fueron siempre timidas, aplicadas casuisticamente frente a la constante estrategia de la liberalizacion domestica que permitio, entre otras cosas, la entrada casi irrestricta de productos manufacturados de las economias centrales, asi como de capitales y otros estimulos.


Journal Article
TL;DR: In this paper, commercial samples of mabi, mabi bark and refined sugar were obtained from various sources and examined for the types of microorganisms in them and concluded that mabi fermentation is a natural fermentation carried out mainly by bacteria 1 and 2, the yeast Saccharomyces cerevisiae, and possibly by Citrobacter intermedius.
Abstract: Commercial samples of mabi, mabi bark and refined sugar were obtained from various sources and examined for the types of microorganisms in them. The principal microorganisms found in commercial mabi were: Enterobacter aerogenes (1 ); Enterobacter cloacae (2); Citrobacter intermedius (3); and the yeast Saccharomyces cerevisiae (4). Escherichia coli (5) was isolated from one sample only. Mabi bark contained 2 and 3, while sugar samples contained 1, 3, and 4. An Asperigillus species and a Penicillium species were found in the sugar samples. Mabi prepared in the laboratory with pure cultures of (1 + 2 +3 +4), or (1 + 4) tasted like commercial mabi, according to 78% of the members of a taste panel. It is concluded that mabi fermentation is a natural fermentation carried out mainly by bacteria 1 and 2, the yeast Saccharomyces cerevisiae , and possibly by Citrobacter intermedius . E. coli does not seem to be involved, unless unsanitary conditions prevail during the preparation of the drink.

01 Jan 1981
TL;DR: The toxina tennoldbil (TL) de Escherichia coil in 29 cepas (5.32%) and the inmunohemolisis pasiva (MP) in 27 (4.95%), una diferencia significativa (P < 0.001).
Abstract: RESUME': Se estudiO la toxina tennoldbil (TL) de Escherichia coil en cepas aisladas de las heces de 545 Ilihos menores de dos aims, con y sin diarrea. El ensayo inmunosorbente enzima conjugada (ELISA) revehi la TL en 29 cepas (5.32%) y la inmunohemolisis pasiva (MP) en 27 (4.95%), una diferencia significativa (P < 0.001). El ELISA triostrO una sensibilidad de 500 a 1000 veces mayor que la IHP. y se presenta como is prueha de eleccidn para el manejo de gran cantidad de tnuestras.