We conducted a study of the cell cycle of coconut palm tissues cultured in vitro in order to regulate regeneration. Coconut palm is a plant for which it is difficult to monitor the ability of the meristematic cells to actively divide. Cell nuclei were isolated from various types of coconut palm tissues with and without in vitro culture. After the nuclei were stained with propidium iodide, relative fluorescence intensity was estimated by flow cytometry. Characterization of the cell cycle reinforced the hypothesis of a block in the G(0)/G(1) and G(1)/S phases of the coconut cells. A time-course study carried out on immature leaves revealed that this block takes place gradually, following the introduction of the material in vitro. Synchronization of in vitro-cultured leaves cells using 60 micro M aphidicholin revealed an increase in the number of nuclei in the S phase after 108 h of treatment. The significance of these results is discussed in relation with the ability of coconut tissue cultured in vitro to divide.
Schenck's knee dislocation (KD) I is a very uncommon pattern of KD, where the knee presents with clinical or radiographic evidence of a KD with one of the ligaments of the central pivot preserved. The correlation between imaging and physical examination is of the highest importance to correctly classify this injury. Recently, there have been reports in the literature with large numbers of Schenk's KD I, however this is due to classifying multiligament knee injuries as if they all were KDs rather to an increase of the pattern. In this report the case of an 18-year old patient that sustained a KD with a preserved posterior cruciate ligament is presented.
El cultivo de maíz en México es el más importante debido a la superficie sembrada, valor de la producción, por ser el alimento principal de la población y por ocupar el 20% de la población económicamente activa. Durante 1998, se sembraron a nivel nacional 7,9 millones de hectáreas con un rendimiento medio de 2,3 t/ha y una
Previous reports have demonstrated that gibberellins promote seed germination, including in vitro germination of zygotic embryos of coconut. Genes that control the cell cycle seem to play important roles during germination. In this study, complete full-length sequences of two E2F-like genes, CnE2F1 and CnE2F2, were obtained. Deduced amino acid sequences of both genes showed conserved domains characteristic of E2F genes. Both genes showed high homology with Arabidopsis thaliana E2Fa and E2Fb, which are transcriptional activators. The expression profiles of CnE2F genes were evaluated in in vitro zygotic embryos with or without gibberellic acid. In control embryos, expression of CnE2F1 showed a peak at day 2, and, gradually this dropped to similar levels as those at day 0. Gibberellic acid (GA3) treatment promoted expression at day 2, higher than that of the control. For CnE2F2, peak expression was detected at day 8 of culture. However, with GA treatment, CnE2F2 expression profile increased by day 2. The expression profile of a cyclin-dependent kinase (CnCDKA), another gene related to the cell cycle control, was also studied. In control embryos, expression of this gene showed two peaks at days 2 and 8, compared with day 0. A different profile was shown with GA treatment. In general, major changes in expression profiles were observed from days 2-8 when morphological changes in zygotic embryos were not yet observed.
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