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Se ha estudiado en una dehesa en el NO de la provincia de Toledo durante 4 años consecutivos, la influencia de la fertilización fosfórica, sobre diferentes aspectos de la producción animal, en un experimento de transformación a pastos de un cultivo de avena abandonado. Se compararon los índices de fertilidad y prolificidad, así como otros indicadores productivos (producción de carne, evolución del peso vivo del rebaño, carga ganadera mantenida, etc.), en rebaños de ovino sobre un cultivo abandonado con o sin fertilización o sobre un pasto seminatural. Los índices reproductivos fueron similares entre tratamientos para el conjunto de años analizados. La influencia de los años, sobre la producción pascícola, se reflejó en la evolución del peso vivo y la condición corporal entre los diferentes tratamientos, siendo superiores los valores registrados en el tratamiento con fertilización en los años buenos. Aunque la carga ganadera mantenida fue superior en el pasto fertilizado frente al natural, no tuvo efectos significativos sobre la producción de kg de cordero/ha. A juzgar por los resultados de producción pascícola y los valores de peso vivo y condición corporal, habría sido posible mantener cargas ganaderas superiores y con ello aumentar la producción de carne/ha, pero el bajo número de corderos finalizados por oveja a cubrición y la dificultad de ajustar las cargas por la irregularidad de las primaveras, limitó los efectos positivos de la fertilización

The frequency of the Beijing genotype of Mycobacterium tuberculosis as a cause of tuberculosis (TB) in South America was determined by analyzing genotypes of strains isolated from patients that had been diagnosed with the disease between 1997 and 2003 in seven countries of the subcontinent. In total, 19 of the 1,202 (1.6%) TB cases carried Beijing isolates, including 11 of the 185 patients from Peru (5.9%), five of the 512 patients from Argentina (1.0%), two of the 252 Brazilian cases (0.8%), one of the 166 patients from Paraguay (0.6%) and none of the samples obtained from Chile (35), Colombia (36) and Ecuador (16). Except for two patients that were East Asian immigrants, all cases with Beijing strains were native South Americans. No association was found between carrying a strain with the Beijing genotype and having drug or multi-drug resistant disease. Our data show that presently transmission of M. tuberculosis strains of the Beijing genotype is not frequent in Latin America. In addition, the lack of association of drug resistant TB and infection with M. tuberculosis of the Beijing genotype observed presently demands efforts to define better the contribution of the virulence and lack of response to treatment to the growing spread of Beijing strains observed in other parts of the world.

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The development of nucleic acid-based technologies has improved the sensitivity, specificity and speed of detection of Mycobacterium tuberculosis in clinical samples. Both commercially available and ´in-house´ polymerase chain reaction (PCR) systems are in use, and a significant number of reports compare such systems with more traditional diagnostic tools for tuberculosis. Few studies, however, have focused on the reproducibility of the results when submitting a sample batch to PCR in different laboratories, especially in developing countries. Consequently, PCR results obtained from six laboratories in six different Latin American countries for samples reconstituted with defined amounts of M. tuberculosis cells were evaluated. Each laboratory used specific conditions of sample processing, nucleic acid amplification and amplicon detection. Analysis of results allowed large differences in sensitivity and specificity to be observed. We conclude that in its present setting, in-house PCR cannot be used as a single diagnostic tool for tuberculosis, and that special care needs to be taken upon interpretation of results by inclusion of a proper number of positive and negative controls. Fil: Suffys, P.. Fundación Oswaldo Cruz; Brasil Fil: Palomino, J. C.. Universidad Peruana Cayetano Heredia; Perú Fil: Cardoso Leão, S.. Universidade Federal de São Paulo; Brasil Fil: Espitia Cogollo, Edeimis. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional Autónoma de México; México Fil: Cataldi, Ángel Adrián. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigación en Ciencias Veterinarias y Agronómicas. Instituto de Biotecnología; Argentina Fil: Alito, A.. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigación en Ciencias Veterinarias y Agronómicas. Instituto de Biotecnología; Argentina Fil: Velasco, M.. Instituto de Salud Pública de Chile. Seccion Micobacterias y Unidad de Biología Molecular; Chile Fil: Robledo, J,. Corporación para Investigaciones Biológicas; Colombia Fil: Fernandez, J.. Corporación para Investigaciones Biológicas; Colombia Fil: Rosa, P. da Silva. Fundación Oswaldo Cruz; Brasil Fil: Romano, Maria Isabel. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigación en Ciencias Veterinarias y Agronómicas. Instituto de Biotecnología; Argentina

A study of the distraction callus in the femur of the growing rabbit was performed. Thirty animals separated into 10 groups were used. Distraction between both ends of a femoral osteotomy induced the formation of a connective callus which subsequently ossified. This callus disappeared between the fourth and the eighth week after the lengthening was completed. The osteogenesis model was of a mixed type, intramembranous and endochondral, with a predominance of the former. The bone healing and the initial signs of remodeling in the newly formed bony tissue were seen at the end of the first week of distraction. The original cortex was resorbed during the lengthening and was progressively substituted by a new cortex, whose formation and remodeling was not finished 24 weeks after the completion of the distraction. Experimental conditions could explain some of the findings.

Resumen de la comunicación presentada en el XIII Congreso de Estudiantes de Medicina, Alicante, 19-21 octubre 1995.