We examined the methylation status of the transcribed domain of ribosomal DNA (rDNA) in 58 patients with breast cancer. The mean percent of methylation was significantly higher in breast tumours than that of normal control samples (P< 0.0001). This increased rDNA methylation was associated with oestrogen receptor non-expression (P< 0.0273) and with moderately or poorly differentiated tumours as compared to well differentiated tumours (P< 0.0475). Our results suggest that rDNA can be a useful marker for monitoring aberrant methylation during breast tumour progression. © 2000 Cancer Research Campaign

Although the first inhabitants of western Amazonia domesticated pejibaye (Bactris gasipaes Kunth, Palmae) or peach palm for its fruits, today it is widely planted for its heart-of-palm. Like other domesticates, pejibaye presents a complex hierarchy of landraces developed before the conquest of the Americas. The existence of three landraces (Pará, Solimões, Putumayo) was proposed along the Amazonas and Solimões Rivers, Brazil, based on morphological characteristics. There are some questions remaining about the intermediate landrace being an artifact of the morphometric analysis. AFLPs were used to evaluate the relationships among samples of these putative landraces. DNA was extracted from 99 plants representing 13 populations maintained in the Pejibaye Germplasm Bank, Manaus, AM; six primer combinations generated 245 markers via PCR, which were scored in an ABI Prism 310 sequencer and analyzed with GeneScan Software; Jaccard similarities were estimated and a dendrogram was generated with UPGMA. Two groups of plants were observed in the dendrogram instead of three, and were similar at 0.795. Each group contained two subgroups, similar at 0.815. One group (n=41) contained 73% Pará landrace plants, with one subgroup (n=22) containing 91% Pará, and the other (n=19) containing 53% Pará. The other group (n=58) contained 53% Solimões and 40% Putumayo landrace plants, with one subgroup (n=21) containing 52% Solimões and 43% Putumayo, and the other (n=35) containing 57% Solimões and 37% Putumayo. The first group confirmed the Pará landrace. The second group suggested that the Solimões landrace does not exist, but that the Putumayo landrace extends along the Solimões River to Central Amazonia. Key words: molecular markers, population differentiation, genetic resources, genetic analysis USO DE AFLPS PARA DISCRIMINAR RAÇAS PRIMITIVAS DE PUPUNHA(Bactris gasipaes) NA AMAZÔNIA BRASILEIRA RESUMO: Os primeiros povos da Amazônia ocidental domesticaram a pupunha (Bactris gasipaes Kunth, Palmae) por seu fruto, embora hoje seja muito plantada por seu palmito. Como outros cultivos domesticados, a pupunha apresenta uma hierarquia complexa de raças primitivas criadas antes da conquista das Américas. A existência de três raças (Pará, Solimões, Putumayo) foi proposta ao longo dos rios Amazonas e Solimões, Brasil, com base em características morfológicas. Algumas dúvidas existem sobre a raça intermediária, pois podia ser um artefato da análise morfométrica. AFLPs foram usados para avaliar as relações entre amostras destas raças hipotéticas. DNA foi extraido de 99 plantas representando 13 populações mantidas no Banco de Germoplasma de Pupunha, Manaus, AM; seis combinações de 'primers' geraram 245 marcadores via PCR, que foram codificados num sequenciador ABI Prism 310 e analisados com o programa GeneScan; similaridades de Jaccard foram estimadas e um dendrograma foi criado com UPGMA. Dois grupos de plantas foram observados no dendrograma, em lugar de três, com similaridade de 0,795. Cada grupo continha dois subgrupos, similares a ...

Wood constitutes the unique source of DNA in dead trees, but extraction of adequate quality DNA from dry wood is usually challenging. However, many different molecular studies require the use of such DNA. We have standardized and validated a modified CTAB protocol to isolate DNA from dry wood from Abies pinsapo and Cedrus atlantica species. Due to the degradation and very little DNA that is normally present in the wood from dead trees we have developed a PCR based test to certify the quality of the extracted samples. In the present study, we have proved too the effectiveness of this methodology to isolate DNA from conifer dry wood samples of sufficient quality to perform further molecular genetic experiments.

Resumen Se comparan los diagramas Temperatura-Tiempo-Sensibilización TTS, obtenidos mediante los ensayos normalizados de coiTosión intergranular Huey y Strauss modificado, que, respectivamente, utilizan electrólitos fuerte y suavemente oxidantes, mostrándose que los diagramas obtenidos son diferentes. Si una muestra evaluada mediante el ensayo Strauss modificado se encuentra sensibilizada, entonces lo estará también en el ensayo Huey, pero no necesariamente ocunirá lo contrario; esta diferencia se asocia a la necesidad de la existencia de una zona continua empobrecida en cromo a lo largo del límite de grano para que el material se sensibilice con respecto al ensayo Strauss modificado, condición innecesaria para el caso del ensayo Huey. Hasta el momento no existe ninguna teoría que explique, para todos los medios agresivos, el fenó-meno de la CI (1), existiendo diversas hipótesis que justifican el fenómeno en cada caso y para los diversos medios agresivos (2-4). Levin (5), tras estudiar distintas hipótesis, menciona que solamente tres de las teorías expuestas son las fundamentales para explicar los fenómenos de la CI (empobrecimiento en cromo, disolución de fases precipitadas y elevados esfuerzos en límite de grano por la precipitación de fases). Hanninen (6) sugirió, tras una revisión de artículos relacionados con la CI, que en medios suavemente oxidantes, como el ensayo Strauss, el empobrecimiento en cromo es el mecanismo predominante, mientras que en medios