Posttranslational modification of proteins by arginine and lysine has been demonstrated in crude extracts of vertebrate nerves and brain but not in intact cells. In the present experiments we have exploited the fact that Arg is added posttranslationally only at the N-terminus of target proteins, to demonstrate these reactions in intact cells of sciatic nerves and embryonic brains of rats. Sciatic nerves were crushed in anaesthesized rats and 2 hrs later segments of nerve, including the site of the crush, were removed and incubated in media containing [3H]Arg. Incorporation of [3H]Arg into total proteins was analyzed by acid precipitation and the presence of label at the N-terminus was determined by a modification of the Edman degradation procedure. Approximately 25% of protein bound [3H]Arg was released from the N-terminus by the Edman reaction indicating that it was added posttranslationally rather than through protein synthesis. N-terminal labeling was not detectable in nerves not crushed prior to explant and incubation. Slices of embryonic day 20 visual cortex, when incubated under similar conditions as injured sciatic nerves, also showed approximately 25% of the protein incorporated [3H]Arg at the N-terminus, while arginylation was not detectable in adult rat brain slices. Since Lys is not added posttranslationally to the N-terminus, we have attempted to observe lysylation of proteins in intact cells by using cycloheximide (Cx) to block protein synthesis without interfering with protein modification. The posttranslational incorporation of Arg/Lys into proteins was found to be insensitive to up to 2.0 mM Cx in tissue extracts (in vitro). However, in intact cells, doses as low as 10 uM Cx completely inhibited the incorporation of [3H]Arg/Lys into proteins. One uM Cx allowed for some incorporation of [3H]Arg/Lys into protein and approximately 40% of the Cx insensitive Arg was incorporated into the N-terminal. These results show that in vivo but not in vitro, Cx can block protein modification, suggesting that either in intact cells protein modification requires protein synthesis, or that Cx has effects other than as an inhibitor of protein synthesis on cells in culture, effects that it does not have on the partially purified components of the reaction. 相似文献
Ecosystems - The relationship between species diversity and ecosystem functioning is one of central topics in modern ecology, but variable and controversial patterns have been found depending on... 相似文献
Clinically, it is common for Class III patients with maxillary skeletal deficiency, which may result in a variety of
adverse consequences. Protraction headgear and rapid maxillary expansion (PE) is an effective treatment, but its
effect on upper airway hydrodynamics has not been reported. The main purpose of this study was to evaluate the
changes of the flow in the upper airway after PE by computational fluid dynamics (CFD). The sample includes
fifteen patients (6 males, 9 females, age 11.00 ± 1.00) and the paired T-test was used to analyze the differences
between the measured data before and after treatment. The maximum flow velocity decreased from 8.42 ±
0.16 m/s to 6.98 ± 0.36 m/s (p < 0.05), and the maximum shear force decreased from 3.72 ± 1.48 Pa to 2.13 ±
0.18 Pa. The maximum negative pressure decreased from −101.78 ± 33.60 Pa to 58.15 ± 9.16 Pa, only the changes
of velopharynx and glossopharynx were statistically significant; while the maximum resistance decreased from
140.88 ± 68.68 Pa/mL/s to 45.95 ± 22.96 Pa/mL/s. PE can effectively reduce the airflow resistance of the upper
airway and the probability of airway collapse, thus improving the patient’s ventilation function. 相似文献
RNF7 has been reported to play critical roles in various cancers. However, the underlying mechanisms of RNF7 in glioma development remain largely unknown. Herein, the expression level of RNF7 was examined in tissues by quantitative real-time PCR, Western blotting and immunohistochemistry. The effect of RNF7 on glioma progression was measured by performing CCK-8 and apoptosis assays, cell cycle-related experiments and animal experiments. The effect of RNF7 on PI3K/AKT signalling pathway was tested by Western blotting. First, we found that RNF7 was upregulated in tumour tissue compared with normal brain tissue, especially in high-grade glioma, and the high expression of RNF7 was significantly related to tumour size, Karnofsky Performance Scale score and a poor prognosis. Second, RNF7 overexpression facilitated tumour cell cycle progression and cell proliferation and suppressed apoptosis. Conversely, RNF7 knockdown suppressed tumour cell cycle progression and cell proliferation and facilitated apoptosis. Furthermore, follow-up mechanistic studies indicated that RNF7 could facilitate glioma cell proliferation and cell cycle progression and inhibit apoptosis by activating the PI3K/AKT signalling pathway. This study shows that RNF7 can clearly promote glioma cell proliferation by facilitating cell cycle progression and inhibiting apoptosis by activating the PI3K/AKT signalling pathway. Targeting the RNF7/PI3K/AKT axis may provide a new perspective on the prevention or treatment of glioma. 相似文献
Summary The effect of ancymidol concentration on the development of haploid asparagus embryos was determined. Liquid cultures from anther-derived calli were grown for three weeks in MS medium plus 1.0 mg l–1 2,4-D, 0.1 mg l–1 NAA, 0.2 mg l–1 kinetin, 800 mg l–1 glutamine, 500 mg l–1 casein hydrolysate, 2% sucrose and 0.0–1.0 mg l–1 ancymidol. Cell clumps (224–500 m) were plated on solid embryo maturation medium (MS medium plus 3% sucrose, 0.1 mg l–1 NAA, 0.5 mg l–1 kinetin and 0.0–1.0 mg l–1 ancymidol) and grown for eight weeks. Ancymidol enhanced embryo maturation and germination and was more critical in the solid than liquid medium. Total embryo number did not vary among most treatments. The best response was observed when ancymidol concentrations were 0.1 and 0.5 mg l–1 in the liquid and solid media, respectively; two-thirds of the embryos produced were bipolar and 35% of bipolar embryos germinated. Seven to 82% of plants recovered from different ancymidol treatments were haploid; the others were diploid, triploid or chimeric for ploidy level.Abbreviations NAA
naphthaleneacetic acid
- 2,4-D
2,4-dichlorophenoxyacetic acid
- GA3
gibberellic acid
- MS
Murashige and Skoog (1962) 相似文献
It is critical for spring wheat (Triticum aestivum L.) production in the semi-arid Loess Plateau to understand the impact of nitrogen (N) fertilizer on changes in N metabolism, photosynthetic parameters, and their relationship with grain yield and quality. The photosynthetic capacity of flag leaves, dry matter accumulation, and N metabolite enzyme activities from anthesis to maturity were studied on a long-term fertilization trial under different N rates [0 kg ha?1(N1), 52.5 kg ha?1 (N2), 105 kg ha?1 (N3), 157.5 kg ha?1 (N4), and 210 kg ha?1 (N5)]. It was observed that N3 produced optimum total dry matter (5407 kg ha?1), 1000 grain weight (39.7 g), grain yield (2.64 t ha?1), and protein content (13.97%). Our results showed that N fertilization significantly increased photosynthetic parameters and N metabolite enzymes at all growth stages. Nitrogen harvest index, partial productivity factor, agronomic recovery efficiency, and nitrogen agronomic efficiency were decreased with increased N. Higher N rates (N3–N5) maintained higher photosynthetic capacity and dry matter accumulation and lower intercellular CO2 content. The N supply influenced NUE by improving photosynthetic properties. The N3 produced highest chlorophyll content, photosynthetic rate, stomatal conductance and transpiration rate, grain yield, grain protein, dry matter, grains weight, and N metabolite enzyme activities compared to the other rates (N1, N2, N4, and N5). Therefore, increasing N rates beyond the optimum quantity only promotes vegetative development and results in lower yields.