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991.
992.
Coulson-Thomas VJ Coulson-Thomas YM Gesteira TF de Paula CA Mader AM Waisberg J Pinhal MA Friedl A Toma L Nader HB 《Cell and tissue research》2011,346(2):223-236
During cancer cell growth many tumors exhibit various grades of desmoplasia, unorganized production of fibrous or connective
tissue, composed mainly of collagen fibers and myofibroblasts. The accumulation of an extracellular matrix (ECM) surrounding
tumors directly affects cancer cell proliferation, migration and spread; therefore the study of desmoplasia is of vital importance.
Stromal fibroblasts surrounding tumors are activated to myofibroblasts and become the primary producers of ECM during desmoplasia.
The composition, density and organization of this ECM accumulation play a major role on the influence desmoplasia has upon
tumor cells. In this study, we analyzed desmoplasia in vivo in human colorectal carcinoma tissue, detecting an up-regulation of collagen I, collagen IV and collagen V in human colorectal
cancer desmoplastic reaction. These components were then analyzed in vitro co-cultivating colorectal cancer cells (Caco-2 and HCT116) and fibroblasts utilizing various co-culture techniques. Our findings
demonstrate that direct cell-cell contact between fibroblasts and colorectal cancer cells evokes an increase in ECM density,
composed of unorganized collagens (I, III, IV and V) and proteoglycans (biglycan, fibromodulin, perlecan and versican). The
desmoplastic collagen fibers were thick, with an altered orientation, as well as deposited as bundles. This increased ECM
density inhibited the migration and invasion of the colorectal tumor cells in both 2D and 3D co-culture systems. Therefore
this study sheds light on a possible restricting role desmoplasia could play in colorectal cancer invasion. 相似文献
993.
994.
Leffler CW Parfenova H Basuroy S Jaggar JH Umstot ES Fedinec AL 《American journal of physiology. Heart and circulatory physiology》2011,300(2):H440-H447
Hydrogen sulfide (H2S) is a gaseous signaling molecule that appears to be involved in numerous biological processes, including regulation of blood pressure and vascular tone. The present study is designed to address the hypothesis that H2S is a functionally significant, endogenous dilator in the newborn cerebrovascular circulation. In vivo experiments were conducted using newborn pigs with surgically implanted, closed, cranial windows. Topical application of H2S concentration-dependently (10(-6) to 2×10(-4) M) dilated pial arterioles. This dilation was blocked by glibenclamide (10(-6) M). L-cysteine, the substrate of the H2S-producing enzymes cystathionine γ-lyase (CSE) and cystathionine β-synthase (CBS), also dilated pial arterioles. The dilation to L-cysteine was blocked by the CSE inhibitor d,l-propargylglycine (PPG, 10 mM) but was unaffected by the CBS inhibitor amino-oxyacetate (AOA, 1 mM). Western blots detected CSE, but not CBS, in cerebral microvessels, whereas CBS is detected in brain parenchyma. Immunohistological CSE expression is predominantly vascular while CBS is expressed mainly in neurons and astrocytes. L-cysteine (5 mM) increased H2S concentration in cerebrospinal fluid (CSF), measured by GC-MS, from 561±205 to 2,783±818 nM before but not during treatment with PPG (1,030±70 to 622±78 nM). Dilation to hypercapnia was inhibited by PPG but not AOA. Hypercapnia increased CSF H2S concentration from 763±243 to 4,337±1789 nM before but not during PPG treatment (357±178 vs. 425±217 nM). These data show that H2S is a dilator of the newborn cerebral circulation and that endogenous CSE can produce sufficient H2S to decrease vascular tone. H2S appears to be a physiologically significant dilator in the cerebral circulation. 相似文献
995.
996.
Moralejo-Gárate H Mar'atusalihat E Kleerebezem R van Loosdrecht MC 《Applied microbiology and biotechnology》2011,92(3):631-639
In this work, the potential of using microbial community engineering for production of polyhydroxyalkanoates (PHA) from glycerol
was explored. Crude glycerol is a by-product of the biofuel (biodiesel and bioethanol) industry and potentially a good substrate
for bioplastic production. A PHA-producing microbial community was enriched based on cultivation in a feast–famine regime
as successfully applied before for fatty acids-based biopolymer production. A glycerol-fed sequencing batch reactor operated
at a 2-day liquid and biomass residence time and with feast–famine cycles of 24 h was used to enrich a mixed community of
PHA producers. In a subsequent fed-batch PHA production step under growth-limiting conditions, the enriched mixed community
produced PHA up to a dry weight content of 80 wt.%. The conversion efficiency of substrate to PHA on electron basis was 53%.
Since glycerol is entering the metabolic pathways of the cell in the glycolytic pathway, it was anticipated that besides PHA,
polyglucose could be formed as storage polymer as well. Indeed, polyglucose was produced in low amounts (∼10 wt.%). The results
indicated that the feast–famine-based enrichment strategy was comparably successful to obtain a microbial community compared
to fatty acids-based enrichment described before. 相似文献
997.
998.
Efficient H2 production via Chlamydomonas reinhardtii 总被引:2,自引:0,他引:2
Molecular hydrogen (H(2)) obtained from biological sources provides an alternative to bulk chemical processes that is moving towards large-scale, economical generation of clean fuel for automotive engines. This opinion article examines recent improvements in H(2) production by wild and mutant strains of Chlamydomonas reinhardtii - the green microalga currently considered the best eukaryotic H(2) producer. Here, we review various aspects of genetic and metabolic engineering of C. reinhardtii, as well as of process engineering. Additionally, we lay out possible scenarios that would lead to more efficient research approaches in the near future, as part of a consistent strategy for sustainable biohydrogen supply. 相似文献
999.
Over two hundred samples were collected in tropical headwater forested catchments in the lowland Amazon basin near Juruena, Mato Grosso Brazil. These were analyzed for fluorescence characteristics and DOC concentrations, and represented a range of terrestrial hydrologic flowpaths and first-order streams during baseflow and stormflow conditions. The fluorescence index (FI) of McKnight et al. (2001) was found to have a significant relationship with DOC concentrations for stream water at baseflow conditions, but FI values within individual terrestrial flowpaths and stormflow varied little for the range of DOC concentrations observed. FI values were seen to increase for increasing residence time of water within the terrestrial ecosystem, while DOC concentration decreased for increasing hydrologic residence time. The FI of terrestrial flow paths indicated that DOC became increasingly characterized by microbially derived carbon for flow paths with longer residence times, on the order through fall and overland flow < percolating soil water < groundwater. Base flow samples of stream water had a mean FI value of 1.78, compared with 1.51 and 1.44 for through fall and overland flow, respectively, and 1.65 for percolating soil water. The FI values for stream water at base flow were also seen to vary seasonally, and were inversely proportional to DOC concentrations over time. 相似文献
1000.
Zargar S Moreira TS Samimi-Seisan H Jeganathan S Kakade D Islam N Campbell J Adegoke OA 《American journal of physiology. Endocrinology and metabolism》2011,300(6):E986-E992
Optimal skeletal muscle mass is vital to human health, because defects in muscle protein metabolism underlie or exacerbate human diseases. The mammalian target of rapamycin complex 1 is critical in the regulation of mRNA translation and protein synthesis. These functions are mediated in part by the ribosomal protein S6 kinase 1 (S6K1) through mechanisms that are poorly understood. The tumor suppressor programmed cell death 4 (PDCD4) has been identified as a novel substrate of S6K1. Here, we examined 1) the expression of PDCD4 in skeletal muscle and 2) its regulation by feed deprivation (FD) and refeeding. Male rats (~100 g; n = 6) were subjected to FD for 48 h; some rats were refed for 2 h. FD suppressed muscle fractional rates of protein synthesis and Ser(67) phosphorylation of PDCD4 (-50%) but increased PDCD4 abundance (P < 0.05); refeeding reversed these changes (P < 0.05). Consistent with these effects being regulated by S6K1, activation of this kinase was suppressed by FD (-91%, P < 0.05) but was increased by refeeding. Gavaging rats subjected to FD with a mixture of amino acids partially restored muscle fractional rates of protein synthesis and reduced PDCD4 abundance relative to FD. Finally, when myoblasts were grown in amino acid- and serum-free medium, phenylalanine incorporation into proteins in cells depleted of PDCD4 more than doubled the values in cells with a normal level of PDCD4 (P < 0.0001). Thus feeding stimulates fractional protein synthesis in skeletal muscle in parallel with the reduction of the abundance of this mRNA translation inhibitor. 相似文献