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  • 1
    ISSN: 1615-6102
    Keywords: Chloroplasts ; Epidermal cell ; Microfilament ; Orientation movement ; Phytochrome ; Vallisneria gigantea Graebner
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Using time-lapse video microscopy, we performed a semiquantitative investigation of the movement of chloroplasts on the cytoplasmic layer that faces the outer periclinal wall (P side) of epidermal cells of leaves of the aquatic angiospermVallisneria gigantea Graebner. Under continuous irradiation with red light (650 nm, 0.41 W/m2), the movement of chloroplasts on the P side was transiently accelerated within 5 min. The increased movement began to decrease at around 20 min and fell below the original level after 40 to 60 min of irradiation with red light. The acceleration and deceleration of movement of chloroplasts on the P side seemed to lead directly to the increase and the subsequent decrease in the rate of migration of chloroplasts from the P side to the anticlinal layers of cytoplasm, which are responsible for the accumulation of chloroplasts on the P side, as we demonstrated previously. In the presence of inhibitors of photosynthesis, the accelerated movement of chloroplasts was maintained for as long as the chloroplasts were irradiated with red light. The rapid acceleration and deceleration of the movement of chloroplasts could be observed repeatedly with sequential irradiation with red and then far-red light (746 nm, 0.14 W/m2). Concomitantly with the loss of motility of chloroplasts on the P side, a dynamic change in the configuration of microfilaments, from a network to a honeycomb, occurred on the P side.
    Type of Medium: Electronic Resource
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  • 2
    Publication Date: 2017-09-30
    Description: TERT promoter mutations (TPMs) are the most common noncoding mutations in cancer. The timing and consequences of TPMs have not been fully established. Here, we show that TPMs acquired at the transition from benign nevus to malignant melanoma do not support telomere maintenance. In vitro experiments revealed that TPMs do not prevent telomere attrition, resulting in cells with critically short and unprotected telomeres. Immortalization by TPMs requires a gradual up-regulation of telomerase, coinciding with telomere fusions. These data suggest that TPMs contribute to tumorigenesis by promoting immortalization and genomic instability in two phases. In an initial phase, TPMs do not prevent bulk telomere shortening but extend cellular life span by healing the shortest telomeres. In the second phase, the critically short telomeres lead to genome instability and telomerase is further up-regulated to sustain cell proliferation.
    Keywords: Genetics, Medicine, Diseases
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
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