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111.
Bryan Lo Geraldine Strasser Meredith Sagolla Cary D. Austin Melissa Junttila Ira Mellman 《The Journal of cell biology》2012,199(7):1117-1130
The tumor suppressor Lkb1/STK11/Par-4 is a key regulator of cellular energy, proliferation, and polarity, yet its mechanisms of action remain poorly defined. We generated mice harboring a mutant Lkb1 knockin allele that allows for rapid inhibition of Lkb1 kinase. Culturing embryonic tissues, we show that acute loss of kinase activity perturbs epithelial morphogenesis without affecting cell polarity. In pancreas, cystic structures developed rapidly after Lkb1 inhibition. In lung, inhibition resulted in cell-autonomous branching defects. Although the lung phenotype was rescued by an activator of the Lkb1 target adenosine monophosphate–activated kinase (AMPK), pancreatic cyst development was independent of AMPK signaling. Remarkably, the pancreatic phenotype evolved to resemble precancerous lesions, demonstrating that loss of Lkb1 was sufficient to drive the initial steps of carcinogenesis ex vivo. A similar phenotype was induced by expression of mutant K-Ras with p16/p19 deletion. Combining culture of embryonic tissues with genetic manipulation and chemical genetics thus provides a powerful approach to unraveling developmental programs and understanding cancer initiation. 相似文献
112.
Experiments were carried out with three seed lots of Betula nana collected in 1967 from different localities in Norway. Seeds were stratified for 0-20 days in dark at +2-+3 °C on filter papers moistened with distilled water, or treated with solution of GA3 for 24 h at room temperature, and then moved into special germination boxes that were placed in different temperature conditions. All the seed lots had conditional dormancy. Quantitatively, the dormancy was different in the different seed lots (pronenances), but there were no qualitative difference in the reaction to stratification gibberellic acid and to germination temperature. Differences between seed lots may have been due to different stage of seed development. The dormancy was deepest at low temperatures(12 and 15°C) decreasing gradually with increasing temperature (to 24 °C). The dormancy was effectively broken by a short stratification (from 5 to 15 days), and by treatment with gibberellic acid. The deeper the dormancy and the lower the germination temperature the longer the stratification that was needed for maximum germination. Similarly, the concentration of GA3 needed for maximum germination increased with decreasing temperature and with increasing dormancy. 相似文献
113.
The aim of this study was to investigate the role of plant hormones, particularly the gibberellins (GAs), in the thermoperiodic regulation of stem elongation in the short day plant (SDP) Begonia x hiemalis. Effects of GAs and some GA precursors were tested on plants grown under alternating day/night temperatures (DT/NT; 12/12 h), and the effects of these temperature regimes on endogenous plant hormones were analyzed using combined gas chromatography and mass spectrometry (GC-MS).Compared with constant temperatures (19/19 °C; 21/21 °C), stem elongation was significantly inhibited by low DT/high NT (14/24 °C; 18/24 °C) and enhanced by the opposite treatments (24/14 °C; 26/17 °C). GA1 stimulated elongation of internodes and petioles while ent-kaurene, kaurenoic acid, GA12, GA19, GA20 had no significant effect. The effect of GA1 was enhanced by a simultaneous application of calcium 3,5-dioxo-4-propionylcyclohexanecarboxylate (BX-112). BX-112 inhibited internode elongation at high DT/low NT (24/14 °C) but not at the reverse temperature regime.Gibberellins A53, A19, A20, A1, A4, A9, and indoleacetic acid (IAA), were identified by GC-MS from both leaves, including the petioles, and stems of B. x hiemalis. There were no apparent relationships between elongation of internodes and petioles and endogenous contents of gibberellins A53, A19, A20, and A1. Recoveries of deuterated GA4 and GA9 were generally too low for estimation of endogenous levels of these GAs.Constant temperature resulted in more open flowers and flower buds compared to alternating DT and NT. BX-112 decreased the time to anthesis. 相似文献
114.
Olfactory memory: the long and short of it 总被引:2,自引:2,他引:0
It has been proposed that memory for odors does not have a short-term (or
working) memory system. The distinction between short- and long- term
memory in other sensory modalities has been generally supported by three
main lines of evidence: capacity differences between the proposed systems,
evidence of differential coding, and differential memory losses in
neuropsychological patients. The present paper examines these issues in an
effort to establish a similar distinction for the memory of olfactory
stimuli. Each of these lines of evidence is examined in relation to the
literature on olfactory memory. Based on this examination, it seems that
there is at least preliminary support from each of these lines of evidence
to advocate a distinction between a long- and short-term memory for
olfactory stimuli. Emphasis is placed upon the qualitative similarity of
olfactory memory to other memory systems. This similarity is further
highlighted through an examination of the literature pertinent to serial
position effects in memory for olfactory stimuli.
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