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排序方式: 共有102条查询结果,搜索用时 15 毫秒
1.
2.
A pathway for oxidative degradation of phytanic acid in mammals 总被引:6,自引:0,他引:6
3.
Glucocorticoids or the glucocorticoid analog dexamethasone (DEX) enhances the differentiation of preadipocytes in the presence of insulin and influences preadipocyte proliferation. The purpose of the present study was to determine if DEX can induce the recruitment of preadipocytes. Using monoclonal antibodies for complement-mediated cytotoxicity, preadipocytes were removed from porcine stromal vascular (S-V) cell cultures. Our experiments demonstrated for the first time that after removal of preadipocytes by cytotoxicity, preadipocytes or fat cells could be induced by DEX or DEX plus insulin but not by insulin alone. However, many more fat cells were induced (258 ± 15/unit area) when DEX was added with fetal bovine serum (FBS) followed with insulin treatment, compared to DEX with insulin (21.3 ± 5.1/ unit area) after removal of preadipocytes. Immunocyto-chemistry with AD-3, a preadipocyte marker, showed that DEX with FBS for 3 days after seeding (i.e., the proliferation phase) produced many more preadipocytes (AD-3 positive, 223 ± 45/unit area) than FBS alone (10.5 ± 1.4/unit area). Bromodeoxyuridine (BrdU) incorporation assays demonstrated that the efficiency of DEX with FBS (i.e., during proliferation) was mitosis dependent. Accordingly, we conclude that: porcine S-V cultures contain preadipocytes at different stages of differentiation and that DEX induced early preadipocyte differentiation depends on mitosis. 相似文献
4.
K Boekelheide D G Graham P D Mize C W Anderson P W Jeffs 《The Journal of biological chemistry》1979,254(23):12185-12191
gamma-L-Glutaminyl-[3,5-3H]4-hydroxybenzene was synthesized in order to study the kinetics of its hydroxylation by tyrosinase purified from Agaricus bisporus and to explore its role in the induction of the dormant state in the spores of this species. It was found to be unique among the monophenolic substrates for tyrosinase in that the lag period for the hydroxylation reaction decreased with increasing substrate concentration. Unlike previously studied compounds, this phenol appeared to function as an electron donor, allowing it to act as its own co-substrate in the hydroxylation reaction. Its catechol product, gamma-L-glutaminyl-3,4-dihydroxybenzene, was found to be a superior co-substrate, yielding its electrons more readily (oxidation peak potential +0.18 V as compared with +0.65 V for the phenol). In situ periodate oxidation of gamma-L-glutaminyl-3,4-dihydroxybenzene to gamma-L-glutaminyl-3,4-benzoquinone confirmed the co-substrate role of the catechol in the hydroxylation reaction. The tyrosinase-mediated oxidation of gamma-L-glutaminyl-3,4-dihydroxybenzene to gamma-L-glutaminyl-3,4-benzoquinone occurred with an apparent Km = 1.54 mM and Vmax = 0.36 mmol/min/mg of enzyme. gamma-L-Glutaminyl-4-hydroxybenzene acted as an inhibitor of the oxidation reaction. 相似文献
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Expression, localization, and functional activity of TL1A, a novel Th1-polarizing cytokine in inflammatory bowel disease 总被引:9,自引:0,他引:9
Bamias G Martin C Marini M Hoang S Mishina M Ross WG Sachedina MA Friel CM Mize J Bickston SJ Pizarro TT Wei P Cominelli F 《Journal of immunology (Baltimore, Md. : 1950)》2003,171(9):4868-4874
TL1A is a novel TNF-like factor that acts as a costimulator of IFN-gamma secretion through binding to the death domain-containing receptor, DR3. The aim of this study was to test the hypothesis that TL1A may play an important role in inflammatory bowel disease (IBD) by functioning as a Th1-polarizing cytokine. The expression, cellular localization, and functional activity of TL1A and DR3 were studied in intestinal tissue specimens as well as isolated lamina propria mononuclear cells from IBD patients and controls. TL1A mRNA and protein expression was up-regulated in IBD, particularly in involved areas of Crohn's disease (CD; p < 0.03 vs control). TL1A production was localized to the intestinal lamina propria in macrophages and CD4(+) and CD8(+) lymphocytes from CD patients as well as in plasma cells from ulcerative colitis patients. The amount of TL1A protein and the number of TL1A-positive cells correlated with the severity of inflammation, most significantly in CD. Increased numbers of immunoreactive DR3-positive T lymphocytes were detected in the intestinal lamina propria from IBD patients. Addition of recombinant human TL1A to cultures of PHA-stimulated lamina propria mononuclear from CD patients significantly augmented IFN-gamma production by 4-fold, whereas a minimal effect was observed in control patients. Our study provides evidence for the first time that the novel cytokine TL1A may play an important role in a Th1-mediated disease such as CD. 相似文献
8.
A mammalian sequence-dependent upstream open reading frame mediates polyamine-regulated translation in yeast 下载免费PDF全文
In mammals, control of S-adenosylmethionine decarboxylase (AdoMetDC) translation is one component of a feedback network that regulates intracellular levels of the polyamines, spermidine, and spermine. AdoMetDC mRNA from mammals contains a highly conserved upstream open reading frame (uORF) within its leader sequence that confers polyamine-regulated suppression of translation on the associated downstream cistron. This regulation is mediated through an interaction that depends on the amino acid sequence of the uORF-encoded hexapeptide. It remains to be shown whether polyamines participate directly in this interaction or indirectly through a specialized signal transduction pathway. We show that Saccharomyces cerevisiae does not have a uORF associated with its AdoMetDC gene (SPE2) and that ribosome loading on the SPE2 mRNA is not positively influenced by polyamine depletion, as it is in mammalian cells. Nevertheless, the mammalian AdoMetDC uORF, when introduced into a polyamine auxotroph of yeast, conferred polyamine regulation of both translational efficiency and ribosome loading on the associated mRNA. This regulatory activity depended on the amino acid sequence encoded by the fourth and fifth codons of the uORF, as in mammalian cells. The fact that the regulatory properties of this mammalian translational control element are quite similar in both mammalian and yeast cells suggests that a specialized signal transduction pathway is not required. Rather, it seems likely that polyamines may be directly participating in an interaction between the uORF-encoded peptide and a constitutive component of the translation machinery, which leads to inhibition of ribosome activity. 相似文献
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A survey was conducted to determine the levels of fumonisins B1 and B2 in corn and corn-based products available in Colombia
for human and animal consumption. A total of 120 samples were analyzed by acetonitrile-water extraction, cleanup with a strong-anion-exchange
column, and liquid chromatography with o-phthaldialdehyde-2-mercaptoethanol derivatization and fluorescence detection. The
samples of corn and corn-based products for animal intake were taken at different feed manufacturing plants, whereas the samples
used for human foods where purchased from local retail stores. The number of positive samples for fumonisin B1 was 20.0% higher
in corn and corn-based products for animal intake (75.0%) than in corn and corn-based products for human consumption (55.0%).
The levels of fumonisin B1 were also higher in corn and corn-based products for animal intake (mean = 694 μg/kg; range = 32–2964
μg/kg), than in corn and corn-based products for human intake (mean = 218 μg/kg; range = 24–2170 μg/ kg). The incidence and
levels of fumonisin B2 were lower than those for fumonisin B1. Corn and corn-based products for animal consumption had an
incidence of fumonisin B2 of 58.3%, with a mean value of 283 μg/kg, and a range of 44–987 μg/kg. The incidence of fumonisin
B2 in corn-based products for human intake was 35.0%, with a mean value of 118 μg/kg and a range of 21–833 μg/kg. The highest
incidence and levels of fumonisins were found in samples of hominy feed, with concentrations ranging from 86 to 2964 μg/kg
fumonisin B1 and 57 to 987 μg/kg fumonisin B2. 相似文献