Showing papers by "University of Costa Rica published in 1971"

The extraordinary claim of praxeology

Abstract: The author states first praxeology's dilemma: if its theoremes are a priori in the unidimensional sense in which praxeology seems to be intended, then the theory as represented in the theorem is inapplicable. If it is not a priori in that sense, then praxeology is already defeated. In a concrete analysis of a part of a praxeological system the author shows that the contention which sees economic theory simply as the result of formal deduction starting from an a priori axiom is unfounded. As a language, praxeology is not ‘water-tight’; its line of reasoning must always draw from the inarticulate background of professional knowledge. Praxeology can be explained away as a process of dialectical redefinition of concepts, ultimately and inevitably dependent upon empirical hypotheses.

Immunoelectrophoretic comparison of Trypanosoma vespertilionis and Trypanosoma cruzi.

Abstract: En un estudio inmunoelectroforetico usando antigeno de T. vespertilionis y antisuero contra T. cruzi se obtuvo cinco bandas comunes de precipitacion y dos mas cuando se uso el antigeno homologo, demostrandose gran similitud entre estas dos especies. Un antigeno preparado con L. braziliensis no mostro ninguna banda de precipitacion con el mismo antisuero.

Aracnidismo por Phoneutria en Costa Rica (Araneae: Ctenidae)

Abstract: The occurrence in Costa Rica of venomous spiders affecting man has recently been established, thanks to communication with rural workers through the "Instituto Centroamericano de Extension de la Cultura" and its programs "Escuela para Todos" and "Almanaque ICECU". Several cases of people bitten by spiders identified as Phonentria were recorded from Guapiles, Pococi, Province of Limon and specimens of the species in question were obtained. Laboratory experiments with rats and mice revealed that the spiders possess a very active neurotoxic venom, which in one instance killed a mouse in six minutes. Treatment with analgesics and antihistamines proved successful in the two cases presented.

Efecto de la temperatura de la piel en la leishmaniasis cutanea experimental

Abstract: The literature on the thermosensitive properties of strains or species of Leishmania and of other miercorganisms is revised. Cutaneous or mucocutaneous strains that infect animais in the coldest areas of the skin or mucosa in general can not grow in tissue culture at 37°C or higher temperatures and their respiratory metabolism decreases at these temperatures. These facts suggest a thermosensitive event in some important metabolism phase of the organisme. The strains or species that are able to produce visceral leishmaniasis were probably originated from cutaneous strains after genetioally determined physiological adaptation, to warmer temperatures. These strains can not only visceralize in animais and man but will also grow in tissue culture at 36-37°C and the respiratory metabolism will be higher at such temperatures. There are reasons to believe that intermediate strains, i. e., with properties of both groupsi do exist. A thermosensitive physiological event is a more general phenomenon and examples of it can also be found in the fields of virology, bacteriology and mycology. It has practical applications since some of the diseases produced by these agents can be cured by treatments with heat or artificial fever. Experiments along these line were performed on hamsters with a Costa Rican strain of L. braziliensis as an experimental model. Even after intraperitoneal inoculation lesions appear in the nose, ears, paws and tail with a subcutaneous temperature bellow 33°C at 22-24°C. Healing of the lesion is accomplished by increasing room temperature. A good lesion is produced in the rump of the animal if the area is depilated (comercial cream depilatory) previously and the naked skin cooled artificially. Elevated temperature, or the growing back of the hair will tend to diminish or cure the lesion.

La investigación jurídica

Abstract: De todas las tareas que se senalan como propias de la Universidad creo que la docente es la fundamental. Por ella entiendo tanto la transmision de la cultura como la formacion de los cuadros profesionales que constituyen la dirigencia intelectual de todas las sociedades. Pero, eso si, no veo como pueda pensarse en realizar una labor docente sin que ella se fundamente en tareas de investigacion. Ambas son en verdad inseparables. La investigacion vivifica la ensenanza y la obligacion de llevar a cabo la segunda es fuerte acicate para la primera. Dada la primordialidad de la tarea del desarrollo en America Latina es indudable que la investigacion universitaria debe ser vista no solo en ocasion de la ensenanza, sino tambien como contribucion de aquella. Dos son las formas en que la investigacion universitaria ha de contribuir al desarrollo: el conocimiento de la realidad nacional y el enjuiciamiento de la forma en que se cumplen los planes nacionales por los organismos gubernamentales. Ambas son labores tipicamente universitarias. Si en la Universidad es donde se encuentran profesionales de mas alto nivel en los distintos campos del saber humano, si es en ella donde estos pueden encontrar el mejor ambiente para su actividad investigativa, dado que la pueden realizar en un plano objetivo, de estabilidad completa en sus posiciones, de continuidad en sus tareas y de medios adecuado para efectuarlas, logico que sea la Universidad el principal foco de la investigacion sobre la realidad y necesidades nacionales.

Cultivation and transformation of hemoflagellates. A review

Abstract: The author reviews the literature on cultivation of several of the family Trypanosomatidae and other biological aspects of these flagellates in relation to external influences. Although very few species have been cultnred successfully in defined media, the known nutritional requirements establish a gradation that ranges from the more simple monogenetic forms (invertebrate parasites) to those of the Salivaria trypanosomes, whose nutritional requirement are more complex and demanding. In view of the transformations of these flagellates during their life cycle, the lack of knowledge on their culture, especially in relation to the characteristics of the vertebrate host becomes more evident. Gaps also exist in our knowledge of nutritional and other factors that influence this transformation. However, physiological and structural changes in certain forms confirm the complexity of this phenomenon. In the few cases in which presumably vertebrate forms have been reproduced in vitro, as in certain of the Leishmanias, the identity of the replicates with the original forms must be definitively established. A more complete biochemical and physiological understanding of thc: transmitting insects would greatly contribute to the knowledge of the transo formation process of the flagellates. Environmental morphological and physiological influences apparent1y explain the ability or inability of some polymorphic trypanosomes to infect a new host. Also environmental, and possibly nutritional factors may play an important role in restoring infectivity to certain forms maintained in culture. Finally, the specificity of certain flagellates for a determined vertebrate host can be explained by the possible influence of immunological factors on those of nutrition.

Triatoma dispar Lent, 1950 in Costa Rica (Hemiptera, Reduviidae).

Abstract: The non-domiciliary species of Triatominae of Costa Rica that have been reported in the literature include Panstrongyhis geniculatus, Belminus costaricensis, Triatoma venosa (Usinger, 1944, U.S. Pub. Hlth. Serv. Bull. 288, 81 p.), Panstrongylus rufotuberculatus (Zeledon & Vargas, 1955, Rev. Biol. Trop. 3 (2): 179–82) and Triatoma nitida (Vieto, 1961, II Congreso Latinoamericano y I Nacional de Microbiologia, San Jose, Costa Rica, XVIII, p. 1–156). We now report the finding of an adult male of Triatoma dispar Lent, 1950. The specimen comes from “Finca Las Brumas” situated in Sucre, 9 km south of Ciudad Quesada, Province of Alajuela. It was captured at night, apparently after ingestion of human blood, in one room of a house located in the finca mentioned above.

Effects of glucose, time and temperature on bacterial growth in urine.

Abstract: Sterile urine and buffer samples of pH 6.5, with or without glucose, were inoculated with either 10 4 or 10 6 organims (two strains of Escherichia coli and two of Protetis vulgaris ) per ml and incubated at -10, 4, and 25 C. The subsequent growth was determined at 0, 2, 4 and 8 hours. In the absence of glucose, bacterial populations of these organisms never reached 105 bacteria per ml whell the initial inoculum was 104 organisms, regardless of time and temperature of incubation. In presence of glucose, populations higher than 10 5 were observed in all of the specimens at room temperature.

Weight losses and urine osmolarity in the hypophysectomized-adrenalectomized albino rat.

Abstract: Body weight los s in doubly endocrinectomized albino rats was higher than in adrenalectomized or hypophysectomized rats alone. Frequent body weight checks to adjust the dosages on a per weight basis for chronic experiments are suggested. The urine osmolarity in these rats was hypertonic, 965.33 mOsm/1, and close to that of normal rats: 1.119 mOsm/l. This finding is explained by reorganization of the neurohypophysis following hypophysectomy and ADH release into the blood stream directly from hypothalamic nuclei stimulated by a slightly hypertonic plasma.

Studies on the pulmonary surface-active lipoprotein. II. Biophysical characterization of its peptide moiety.

Abstract: 5tudies on the lung surface-active lipoprotein complex were carried out in order to establish, primarily, the physicoehemieal eharaeteristies of its peptide moiety. It has been undertaken in the hope that new findings may extend present knowledge on the nature of the surfactant agent and of lipoproteins in general. After removal of lipids from the SA-lipoprotein, the peptide moiety of the cow lung SA-lipoprotein was subjeeted to an exhaustive characterization study. It was observed that the lipid-free materials are insoluble in distilled water, in acid, and in neutral physiological saline solutions. They are slightly soluble in 0.1 molar sodium ehloride solutions at pH 1 0.0, and soluble in 0.1 normal sodium hydroxide solutions. The delipidized 5A-peptide is not dialyzable. The soluble lipid-free materials were eoncentrated by ultrafiltration through Diaflo Membranes and purified by gel filtration in columns of Sephadex. It was observed that the properties of the purified SA-peptide material were markedly influenced by solvent pH. In the pH range 4-6, where the peptide was nearly isoelectric, it formed a gel, which could be dispersed by 6 molar urea. At pH values higher than 7.0 or less than 4.0, traces of insoluble, perhaps aggregated material were observed in the solutions. It is apparent that the solution properties of this peptide material are controlled, at least in part, by its net charge. Ultracentrifugal and electrophoretical data indicate that the SA-peptide preparations are heterogeneous. Two bands appeared after electrophoresis of SA-peptide on ceHulose acetate strips: one major fast-moving component; and a minor one, close to the origin, which constituted about 5 per cent of the total peptide. Sedimentation patterns in the analytical ultracentrifuge showed two main components, with sedimentation constants (S20 W ) of 1.53S and 3.10S, with minimal anhydrous molecular weights of 8,600 and 24,800 (assummg spherical shape), respectively. Calculations have shown that the SA-peptide contains more negative than positive groups, in accord with its acidic properties. Molecular weight determinations with SA-peptide materials have led to values of 100,000 and 230,000, on the basis of chemical composition and sedimentation equlibrium data, respectively. The discrepancy between these two values may be explained by assuming that polymerization of SA-peptide occurs in solution, leading to a high value for the weight-average molecular weight determined by sedimentation equilibrium.