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  • 1
    Digitale Medien
    Digitale Medien
    Springer
    Molecular and cellular biochemistry 189 (1998), S. 107-111 
    ISSN: 1573-4919
    Schlagwort(e): gene expression ; electromagnetic fields ; superinduction ; anisomycin ; immediate early gene
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie , Medizin
    Notizen: Abstract Rat pheochromocytoma PC12 cells have been treated with nerve growth factor (NGF) at final concentrations of 2, 4, 8, and 16 ng/ml, and then were exposed to 60-Hz, sinusoidal magnetic fields (MF) of 12.5, 25, 50, and 100 μT (rms) for 30 min. Transcript levels for both c-fos and glyceraldehyde-3 -phosphate dehydrogenase were determined by Northern blot analysis using 32P-labeled cDNA probes. No change in c-fos expression was measured at any condition employed. Treatment of PC12 cells with a combination of agents (NGF, forskolin, and tetradecanoylphorbol acetate [TPA]) increased c-fos expression over that detected with NGF alone. MF exposure of cells treated with the three-agent regimen produced two outcomes, either no change or a doubling of c-fos expression. In subsequent experiments, cells were treated with NGF, NGF + forskolin + TPA, or pre-treated with anisomycin and then treated with NGF + forskolin + TPA. It was determined that MF exposure, like superinduction with anisomycin, increased c-fos expression only in cultures which were not yet exhibiting maximal c-fos expression. It is hypothesized that MF exposure, like anisomycin, may alter the activity of key intracellular protein kinases.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Plant molecular biology 32 (1996), S. 745-749 
    ISSN: 1573-5028
    Schlagwort(e): circadian rhythm ; CO2 fixation ; gene expression ; green alga
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract We have investigated whether the expression of carbonic anhydrase genes (Cah1 and Cah2) is regulated by a circadian clock in Chlamydomonas. When cells were grown in ordinary air under 12 h light/12 h dark (LD) cycles, the levels of the Cah2 mRNA hardly altered during the cycles, while the Cah1 mRNA showed a strong diurnal rhythm. The rhythm of about 24 h continued at least 3 days even under continuous light. Temperature compensation of the rhythm was demonstrated, using cultures maintained at 16, 22, and 28°C. These results indicate that the abundance of the Cah1 transcript is controlled by a circadian clock.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Plant molecular biology 36 (1998), S. 733-739 
    ISSN: 1573-5028
    Schlagwort(e): AGAMOUS ; tomato ; ripening ; calyx ; gene expression ; sepals ; in vitro
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract In vitro culture of VFNT Cherry tomato sepals (calyx) at 16–21 °C results in developmental changes that are similar to those that occur in fruit tissue [10]. Sepals become swollen, red, and succulent, produce ethylene, and have increased levels of polygalacturonase RNA. They also produce many flavor volatiles characteristic of ripe tomato fruit and undergo similar changes in sugar content [11]. We examined the expression of the tomato AGAMOUS gene, TAG1, in ripening, in vitro sepal cultures and other tissues from the plant and found that TAG1 RNA accumulates to higher levels than expected from data from other plants. Contrary to reports on the absence of AGAMOUS in sepals, TAG1 RNA levels in green sepals from greenhouse-grown plants is detectable, its concentration increasing with in vitro ripening to levels that were even higher than in red, ripe fruit. Sepals of fruit on transgenic tomato plants that expressed TAG1 ectopically were induced by low temperature to ripen in vivo, producing lycopene and undergoing cell wall softening as is characteristic of pericarpic tissue. We therefore propose that the induction of elevated TAG1 gene expression plays a key role in developmental changes that result in sepal ripening.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 4
    ISSN: 1573-5028
    Schlagwort(e): C4 photosynthesis ; maize ; phosphoenolpyruvate carboxylase ; transgenic plant ; transcription ; gene expression
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract C4-type phosphenolpyruvate carboxylase (C4PEPC) acts as a primary carbon assimilatory enzyme in the C4 photosynthetic pathway. The maize C4PEPC gene (C4Ppc1) is specifically expressed in mesophyll cells (MC) of light-grown leaves, but the molecular mechanism responsible for its cell type-specific expression has not been characterized. In this study, we introduced a chimeric maize C4Ppc1 5′-flanking region/β-glucuronidase (GUS) gene into maize plants by Agrobacterium-mediated transformation. Activity assay and histochemical staining showed that GUS is almost exclusively localized in leaf MC of transgenic maize plants. This observation suggests that the introduced 5′ region of maize C4Ppc1 contains the necessary cis element(s) for its specific expression in MC. Next, we investigated whether the 5′ region of the maize gene interacts with nuclear proteins in a cell type-specific manner. By gel shift assays with nuclear extracts prepared from MC or bundle sheath cells (BSC), cell type-specific DNA-protein interactions were detected: nuclear factors PEPIb and PEPIc are specific to MC whereas PEPIa and PEPIIa are specific to BSC. Light alters the binding activity of these factors. These interactions were not detected in the assay with nuclear extract prepared from root, or competed out by oligonucleotides corresponding to the binding sites for the maize nuclear protein, PEP-I, which is known to bind specifically to the promoter region of C4Ppc1. The results suggest that novel cell type-specific positive and negative nuclear factors bind to the maize C4Ppc1 5′-flanking region and regulate its differential transcription in MC in a light-dependent manner.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 5
    ISSN: 0197-8462
    Schlagwort(e): electromagnetic fields ; gene expression ; transcription factors ; Life and Medical Sciences ; Occupational Health and Environmental Toxicology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Physik
    Notizen: Rat PC12 pheochromocytoma cells have been treated with nerve growth factor and then exposed to athermal levels of a packet-modulated radiofrequency field at 836.55 MHz. This signal was produced by a prototype time-domain multiple-access (TDMA) transmitter that conforms to the North American digital cellular telephone standard. Three slot average power densities were used: 0.09, 0.9, and 9 mW/cm2. Exposures were for 20, 40, and 60 min and included an intermittent exposure regimen (20 min on/20 min off), resulting in total incubation times of 20, 60, and 100 min, respectively. Concurrent controls were sham exposed. After extracting total cellular RNA, Northern blot analysis was used to assess the expression of the immediate early genes, c-fos and c-jun, in all cell populations. No change in c-fos transcript levels were detected after 20 min exposure at each field intensity (20 min was the only time period at which c-fos message could be detected consistently). Transcript levels for c-jun were altered only after 20 min exposure to 9 mW/cm2 (average 38% decrease). Bioelectromagnetics 18:223-229, 1997. © 1997 Wiley-Liss, Inc. This article is a US Government work and, as such, is in the public domain in the United States of America.
    Zusätzliches Material: 2 Tab.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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