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21.
Cell type-specific expression of the IkappaB kinases determines the significance of phosphatidylinositol 3-kinase/Akt signaling to NF-kappa B activation 总被引:12,自引:0,他引:12
Gustin JA Ozes ON Akca H Pincheira R Mayo LD Li Q Guzman JR Korgaonkar CK Donner DB 《The Journal of biological chemistry》2004,279(3):1615-1620
Phosphatidylinositol (PI) 3-kinase/Akt signaling activates NF-kappa B through pleiotropic, cell type-specific mechanisms. This study investigated the significance of PI 3-kinase/Akt signaling to tumor necrosis factor (TNF)-induced NF-kappa B activation in transformed, immortalized, and primary cells. Pharmacological inhibition of PI 3-kinase blocked TNF-induced NF-kappa B DNA binding in the 293 line of embryonic kidney cells, partially affected binding in MCF-7 breast cancer cells, HeLa and ME-180 cervical carcinoma cells, and NIH 3T3 cells but was without significant effect in H1299 and human umbilical vein endothelial cells, cell types in which TNF activated Akt. NF-kappa B is retained in the cytoplasm by inhibitory proteins, I kappa Bs, which are phosphorylated and targeted for degradation by I kappa B kinases (IKK alpha and IKK beta). Expression and the ratios of IKK alpha and IKK beta, which homo- and heterodimerize, varied among cell types. Cells with a high proportion of IKK alpha (the IKK kinase activated by Akt) to IKK beta were most sensitive to PI 3-kinase inhibitors. Consequently, transient expression of IKK beta diminished the capacity of the inhibitors to block NF-kappa B DNA binding in 293 cells. Also, inhibitors of PI 3-kinase blocked NF-kappa B DNA binding in Ikk beta-/- but not Ikk alpha-/- or wild-type cells in which the ratio of IKK alpha to IKK beta is low. Thus, noncoordinate expression of I kappa B kinases plays a role in determining the cell type-specific role of Akt in NF-kappa B activation. 相似文献
22.
Zhao L Samuels T Winckler S Korgaonkar C Tompkins V Horne MC Quelle DE 《Molecular cancer research : MCR》2003,1(3):195-206
Cyclin G1 is a p53-responsive gene that is induced in alternative reading frame (ARF)-arrested cells, yet its role in growth control is unclear. We tested its effects on growth and involvement in the ARF-Mdm2-p53 tumor suppressor pathway. We show that cyclin G1 interacts with ARF, Mdm2, and p53 in vitro and in vivo. At high levels, cyclin G1 induces a G(1)-phase arrest in mammalian cells that coincides with p53 activation. Conversely, lower levels of cyclin G1 lack intrinsic growth inhibitory effects yet potentiate ARF-mediated growth arrest. Notably, cyclin G1 is down-regulated by Mdm2 through proteasome-mediated degradation. These data suggest that cyclin G1 is a positive feedback regulator of p53 whose expression is restrained by Mdm2. Interestingly, growth inhibition by cyclin G1 does not require p53 but instead exhibits partial retinoblastoma protein (pRb) dependence. These findings reveal that cyclin G1 has growth inhibitory activity that is mechanistically linked to ARF-p53 and pRb tumor suppressor pathways. 相似文献
23.
Winter herbivory by voles during a population peak: the relative importance of local factors and landscape pattern 总被引:4,自引:0,他引:4
PETER A. HAMBÄCK MICHAEL SCHNEIDER & TARJA OKSANEN 《The Journal of animal ecology》1998,67(4):544-553
1. We studied the relative role of local habitat variables and landscape pattern on vole–plant interactions in a system with grey-sided voles ( Clethrionomys rufocanus (Sund.)) and their favourite winter food plant, bilberry ( Vaccinium myrtillus L.). The study was conducted during a vole peak year (1992–93) in a tundra area in northern Norway.
2. Using Mantel statistics we were able to separate the direct effects of the spatial patterning of habitats and the indirect effects due to spatial aggregations of similar habitats.
3. Results indicate that knowledge about the explicit spatial patterning of patches does not improve our understanding of the system. Instead, two local factors, vegetation height and bilberry biomass, explained more than 50% of the variation in cutting intensity in winter (defined as the proportion of above-ground shoots cut). Increasing vegetation height increased, and increasing bilberry biomass decreased, the cutting intensity.
4. The conclusion that grey-sided voles are able to distribute themselves relative to habitat quality was also partially supported by our estimated over-winter persistence by voles in the various habitats. Vole persistence was uncorrelated with vegetation height, the important predictor of autumn vole density, but tended to correlate with the deviation from the relation between vegetation height and autumn vole density. This conforms to the expectations from the theory of ideal-free habitat distribution.
5. The cue for vole habitat choice, i.e. vegetation height, indicates that either predation or freezing risk is important for voles when selecting over-wintering habitat. 相似文献
2. Using Mantel statistics we were able to separate the direct effects of the spatial patterning of habitats and the indirect effects due to spatial aggregations of similar habitats.
3. Results indicate that knowledge about the explicit spatial patterning of patches does not improve our understanding of the system. Instead, two local factors, vegetation height and bilberry biomass, explained more than 50% of the variation in cutting intensity in winter (defined as the proportion of above-ground shoots cut). Increasing vegetation height increased, and increasing bilberry biomass decreased, the cutting intensity.
4. The conclusion that grey-sided voles are able to distribute themselves relative to habitat quality was also partially supported by our estimated over-winter persistence by voles in the various habitats. Vole persistence was uncorrelated with vegetation height, the important predictor of autumn vole density, but tended to correlate with the deviation from the relation between vegetation height and autumn vole density. This conforms to the expectations from the theory of ideal-free habitat distribution.
5. The cue for vole habitat choice, i.e. vegetation height, indicates that either predation or freezing risk is important for voles when selecting over-wintering habitat. 相似文献
24.
Proliferating cell nuclear antigen (PCNA) as a proliferative marker during embryonic and adult zebrafish hematopoiesis 总被引:4,自引:1,他引:3
Leung AY Leung JC Chan LY Ma ES Kwan TT Lai KN Meng A Liang R 《Histochemistry and cell biology》2005,124(2):105-111
We investigated the expression of proliferative cell nuclear antigen (PCNA) in zebrafish to delineate the proliferative hematopoietic
component during adult and embryonic hematopoiesis. Immunostaining for PCNA and enhanced green fluorescence protein (eGFP)
was performed in wild-type and fli1-eGFP (endothelial marker) and gata1-eGFP (erythroid cell marker) transgenic fish. Expression
of PCNA mRNA was examined in wild-type and chordin morphant embryos. In adult zebrafish kidney, the renal tubules are surrounded
by endothelial cells and it is separated into hematopoietic and excretory compartments. PCNA was expressed in hematopoietic
progenitor cells but not in mature neutrophils, eosinophils or erythroid cells. Some PCNA+ cells are scattered in the hematopoietic
compartment of the kidney while others are closely associated with renal tubular cells. PCNA was also expressed in spermatogonial
stem cells and intestine crypts, consistent with its role in cell proliferation and DNA synthesis. In embryos, PCNA is expressed
in the brain, spinal cord and intermediate cell mass (ICM) at 24 h-post fertilization. In chordin morphants, PCNA is significantly
upregulated in the expanded ICM. Therefore, PCNA can be used to mark cell proliferation in zebrafish hematopoietic tissues
and to identify a population of progenitor cells whose significance would have to be further investigated. 相似文献
25.
26.
Tsung-Ming Tsao Ming-Jer Tsai Ya-Nan Wang Heng-Lun Lin Chang-Fu Wu Jing-Shiang Hwang Sandy-H.J. Hsu Hsing Chao Kai-Jen Chuang Charles- CK. Chou Ta-Chen Su 《PloS one》2014,9(7)
Background
Assessment of health effects of a forest environment is an important emerging area of public health and environmental sciences.Purpose
To demonstrate the long-term health effects of living in a forest environment on subclinical cardiovascular diseases (CVDs) and health-related quality of life (HRQOL) compared with that in an urban environment.Materials and Methods
This study included the detailed health examination and questionnaire assessment of 107 forest staff members (FSM) and 114 urban staff members (USM) to investigate the long-term health effects of a forest environment. Air quality monitoring between the forest and urban environments was compared. In addition, work-related factors and HRQOL were evaluated.Results
Levels of total cholesterol, low-density lipoprotein cholesterol, and fasting glucose in the USM group were significantly higher than those in the FSM group. Furthermore, a significantly higher intima-media thickness of the internal carotid artery was found in the USM group compared with that in the FSM group. Concentrations of air pollutants, such as NO, NO2, NOx, SO2, CO, PM2.5, and PM10 in the forest environment were significantly lower compared with those in the outdoor urban environment. Working hours were longer in the FSM group; however, the work stress evaluation as assessed by the job content questionnaire revealed no significant differences between FSM and USM. HRQOL evaluated by the World Health Organization Quality of Life-BREF questionnaire showed FSM had better HRQOL scores in the physical health domain.Conclusions
This study provides evidence of the potential beneficial effects of forest environments on CVDs and HRQOL. 相似文献27.
28.
Photoreceptors for biosynthesis, energy storage and vision 总被引:3,自引:1,他引:3
Abstract Living organisms use light as a source of energy and as a means of obtaining information about their environment. Photoreactivating enzyme, provitamins D, retinal (rhodopsins and bacteriorhodopsin), porphyrins (chlorophyll, protochlorophyll and heme), photosynthetic accessory pigments (carotenoids and bilins), phytochrome and riboflavin: these are the molecules which life has settled upon to play the role of light receptor. For some of these photoreceptor molecules a great deal is now known about the chemistry which they perform upon absorbing light; for others virtually nothing is known. Riboflavin, the molecule believed to be functioning in a variety of organisms as the receptor for physiological responses to blue light, is an especially interesting case. Its widespread occurrence in cellular roles other than photoreception make it difficult to separate out the particular flavin which functions as the photoreceptor. It represents a case of a photoreceptor which is at once ubiquitous and elusive. 相似文献
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