Formacao da base genetica e manejo dos recursos geneticos de mandioca: O caso do Brasil

The concept of genetic erosion is discussed, with particular reference to cassava in Brazil. National germplasm collections are listed with the corresponding no. of accessions; information is also provided on the plant breeding activities carried out. The potential of interspecific crossbreeding in cassava with wild Manihot species is discussed. In Brazil, wild Manihot species, particularly in the form of seed, are collected by the Centro Nacional de Recursos Geneticos (CENARGEN); both a small seed stock (15 species) and a small live collection (20 species) are maintained. The collection of woody wild species is considered prioritary. The interactions of CENARGEN with active germplasm collections in the country are indicated regarding collection, internal exchange, and germplasm introduction. A tentative organizational chart of a cassava germplasm collection is included. General indications are also provided on the handling of genetic resources. (CIAT)Se discute el concepto de la erosion genetica, con particular referencia a la yuca en Brasil. Se enumeran las colecciones nacionales de germoplasma con el no. correspondiente de accesiones; tambien se proporciona informacion sobre las actividades de fitomejoramiento desarrolladas. Se discute el potencial del cruzamiento interespecifico en yuca con especies silvestres de Manihot. En Brasil, el Centro Nacional de Recursos Geneticos (CENARGEN) recolecta las especies silvestes de Manihot, particularmente en forma de semilla; tambien mantiene una limitada reserva de semilla (15 especies) y una pequena coleccion viva (20 especies). La recoleccion de especies silvestres lenosas se considera prioritaria. Se indican las interacciones de CENARGEN con las colecciones de germoplasma activa en el pais en cuanto a recoleccion, intercambio interno e introduccion de germoplasma. Se incluye un organigrama tentativo de una coleccion de germoplasma de yuca. Tambien se proporcionan indicaciones generales sobre el manejo de recursos geneticos. (CIAT

Effect of 30 mCi radioiodine on multinodular goiter previously treated with recombinant human thyroid-stimulating hormone

Recombinant human thyroid-stimulating hormone (rhTSH) enhances 131I uptake, permitting a decrease in radiation for the treatment of multinodular goiter (MNG). Our objective was to evaluate the safety and efficacy of a single 0.1-mg dose of rhTSH, followed by 30 mCi 131I, in patients with MNG. Seventeen patients (15 females, 59.0 ± 13.1 years), who had never been submitted to 131I therapy, received a single 0.1-mg injection of rhTSH followed by 30 mCi 131I on the next day. Mean basal thyroid volume measured by computed tomography was 106.1 ± 64.4 mL. 131I 24-h uptake, TSH, free-T4, T3, thyroglobulin, anti-thyroid antibodies, and thyroid volume were evaluated at regular intervals of 12 months. Mean 131I 24-h uptake increased from 18.1 ± 9.7 to 49.6 ± 13.4% (P < 0.001), a median 2.6-fold increase (1.2 to 9.2). Peak hormonal levels were 10.86 ± 5.44 mU/L for TSH (a median 15.5-fold increase), 1.80 ± 0.48 ng/dL for free-T4, 204.61 ± 58.37 ng/dL for T3, and a median of 557.0 ng/mL for thyroglobulin. The adverse effects observed were hyperthyroidism (17.6%), painful thyroiditis (29.4%) and hypothyroidism (52.9%). Thyroid volume was reduced by 34.3 ± 14.3% after 6 months (P < 0.001) and by 46.0 ± 14.6% after 1 year (P < 0.001). Treatment of MNG with a single 0.1-mg dose of rhTSH, followed by a fixed amount of radioactivity of 131I, leads to an efficacious decrease in thyroid volume for the majority of the patients, with a moderate incidence of non-serious and readily treatable adverse effects