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901.
The location of rRNA processing was analyzed by usingin situ hybridization with ITS1 probe and immunolabeling of anti-fibrillarin mAb in pea (Pisum sativum) root pole cells. The results showed that rRNA processing sites were in dense fibrillar components (DFCs) and granular components
(GCs), but not in fibrillar centers (FCs). Low doses of actinomycin D (AMD) treatment can selectively suppress pre-rRNA synthesis
but cannot disturb the processing of preformed pre-rRNAs. With AMD treatment prolonged, the density of labeled signals gradually
decreased, indicating the preformed pre-rRNAs were gradually processed. 相似文献
902.
肾血管性高血压大鼠发病过程中心血管AT1-受体自身抗体的变化 总被引:1,自引:1,他引:0
实验观察了肾血管性高血压(RVH)大鼠血浆中抗AT1-受体自身抗体在发病过程中的作用及其变化规律。采用两肾一夹Goldblatt RVH模型,以合成的大鼠AT1-受体细胞外第二环165-191位氨基酸序列作为特慢性抗原,用SA-ELISA法检测大鼠血清中抗AT1-受体自身抗体。结果表明,RVH模型组术后2周时大鼠血清中抗AT1-受体自身抗体的阳性率和平均滴度与术前相比明显增高,较高的阳性率和平均滴度持续几周后逐渐下降,12周时下降到正常水平。结果提示,自身免疫机制参与了高血压的形成,抗AT1-受体自身抗体可能与心肌肥厚有关。 相似文献
903.
Synergetic effects of epidermal growth factor and estradiol on cytoplasmic maturation of porcine oocytes 总被引:2,自引:0,他引:2
This study was conducted to examine the effect of epidermal growth factor (EGF) and 17beta-estradiol (E2) on nuclear and cytoplasmic (male pronuclear formation and early embryo development) maturation of porcine oocytes. Oocytes were aspirated from antral follicles and cultured in modified TCM-199 medium supplemented with 0.57 mM cysteine, 10 IU/ml eCG, 10 IU/ml hCG, with or without EGF and/or E2. In vitro fertilisation of matured oocytes was performed in a modified Tris-buffered medium (mTBM) with frozen-thawed ejaculated spermatozoa. Oocytes were transferred to NCSU-23 supplemented with 0.4% bovine serum albumin at 6 h after in vitro fertilisation. Significantly higher (p < 0.05) rates of nuclear maturation, pronuclear formation and cleavage (91.7%, 65.2% and 37.3%, respectively) were observed when oocytes were cultured in the medium containing both EGF (10 ng/ml) and E2 (1 microg/ml) than in the medium supplemented with either EGF or E2 or without both. Intracellular glutathione concentration in the oocytes cultured in the medium containing both E2 and EGF was also significantly higher (12.1 pmol per oocyte) than that of oocytes cultured in the medium with E2 or EGF alone or without both. These findings suggested that EGF and E2 have a synergestic effect on both nuclear and cytoplasmic maturation of porcine oocytes. 相似文献
904.
Nuclear and cytoplasmic maturation of porcine oocytes collected from different sizes of follicles were examined. Oocyte-cumulus complexes were collected from small (1-2 mm in diameter), medium (3-6 in diameter) and large (7-8 mm in diameter) follicles and cultured in a modified tissue culture medium 199 for 44 h. Nuclear maturation was evaluated after orcein staining, and cytoplasmic maturation was evaluated by intracellular glutathione (GSH) assay. Oocyte diameter, cumulus morphology, steroid hormones and glutathione in the follicular fluid (FF), were also examined. Significantly higher proportions of oocytes collected from large and medium follicles reached metaphase II than did oocytes from small follicles. Oocytes from small follicles also had a smaller size. GSH content was significantly higher (p < 0.05) in oocytes from large (14.24 +/- 2.1 pmol/oocyte) and medium (13.69 +/- 1.5 pmol/oocyte) follicles than in oocytes from small (9.44 +/- 1.28 pmol/oocyte) follicles just after collection. After maturation, oocytes from medium follicles had a higher GSH concentration than oocytes from small follicles. It was found that between 49.7 +/- 5.18 nM and 52.25 +/- 0.78 nM GSH was present in FF but there was no statistical difference between follicle sizes. A significantly higher (p < 0.001) estradiol level was present in FF from large follicles (299.2 +/- 68.6 ng/ml) than from medium (40.0 +/- 6.4 ng/ml) and small (41.2 +/- 3.7 ng/ml) follicles. Progesterone concentrations in FF from large (281.6 +/- 45.9 ng/ml) and medium (267.5 +/- 38.6 ng/ml) follicles were significantly higher than that (174.7 +/- 22.0 ng/ml) from small follicles. These results indicate that the oocyte's ability to accumulate intracellular GSH during maturation, and extracellular steroid hormones and cumulus cells, affect the competence of porcine oocytes to undergo nuclear and cytoplasmic maturation. 相似文献
905.
Developmental changes in functional expression and beta-adrenergic regulation of I(f) in the heart of mouse embryo 总被引:1,自引:0,他引:1
Song GL Tang M Liu CJ Luo HY Liang HM Hu XW Xi JY Gao LL Fleischmann B Hescheler J 《Cell research》2002,12(5-6):385-394
The hyperpolarization-activated current (I(f)) plays an important role in determining the spontaneous rate of cardiac pacemaker cells. The automatic rhythmicity also exists in working cells of embryonic heart, therefore we studied developmental changes in functional expression and beta-adrenergic regulation of I(f) in embryonic mouse heart. The expression of I(f) is high in early developmental stage (EDS) (10.5 d after coitus) ventricular myocytes, low in intermediate developmental stage (IDS) (13.5 d) atrial or ventricular myocytes and even lower in late developmental stage (LDS) (16.5 d) atrial or ventricular myocytes, indicating that these cells of the EDS embryonic heart have some properties of pacemaker cells. Beta-adrenergic agonist isoproterenol (ISO) stimulates I(f) in LDS but not in EDS cardiomyocytes, indicating that the beta-adrenergic regulation of I(f) is not mature in EDS embryonic heart. But forskolin (a direct activator of adenylate cyclase) and 8-Br-cAMP (a membrane-permeable analogue of cAMP) increase the amplitude of I(f) in EDS cells, indicating that adenylate cyclase and cAMP function fairly well at early stage of development. Furthermore, the results demonstrate that I(f) is modulated by phosphorylation via cAMP dependent PKA both in EDS and LDS cells. 相似文献
906.
Efficient isolation of total RNA from antibiotic-producing bacterium Amycolatopsis mediterranei 总被引:4,自引:0,他引:4
RNA extraction from antibiotic-producing actinomycetes can be a difficult and time-consuming process due to their special peptidoglycans cell wall composition and the short life of RNA. Hence, the rapidity of cellular lysis and complete inhibition of RNase are of particular importance for isolating intact RNA of high quality. The genus of Amycolatopsis mediterranei produces many clinically important antibiotics, such as rifamycin and vancomycin; however, the available methods for bacterial RNA isolation did not work very well with this genus. In this report, we described a new method for RNA isolation using the combination of LiCl, urea and guanidinium thiocyanate to disrupt the cell wall of Amycolatopsis. Compared with earlier published RNA isolation methods, the method gave higher yields of pure and intact RNA. About 1 microg total RNA free of DNA contamination can be obtained from 1 mg wet weight of A. mediterranei. The integrity of the RNA was demonstrated by formaldehyde agarose gel electrophoresis and Northern blot analyses. 相似文献
907.
Schistosoma japonicum: effect of artemether on glutathione S-transferase and superoxide dismutase 总被引:7,自引:0,他引:7
Xiao SH You JQ Gao HF Mei JY Jiao PY Chollet J Tanner M Utzinger J 《Experimental parasitology》2002,102(1):38-45
Glutathione S-transferase (GST) and superoxide dismutase (SOD) are major antioxidant enzymes of schistosomes that are involved in detoxification processes. To study the effect of artemether on these enzymes, mice infected with adult Schistosoma japonicum, were treated with artemether either at a subcurative (100 mg/kg) or a curative dose (300 mg/kg). Schistosomes were recovered 24-72 h post-treatment separated by sex and used for GST and SOD activity measurements. Female worms showed consistently higher GST inhibitions than males. For instance, 24 h after administration of 100 mg/kg artemether, GST activities of female worms were inhibited by 23.3%, as compared to 12.7% in males. Both activities were significantly lower when compared to worms recovered from untreated mice. Slightly higher inhibitions were observed at the higher dose of artemether, which gradually increased to levels of 52.5-55.1%, 72 h post-treatment. GST inhibitions could be reversed by application of 1,4-dithiothreitol at a concentration of 10 mmol/L. Adding L-cysteine also reduced GST inhibitions, but in female worms, GST activities remained significantly higher than in worms from untreated animals. Administration of 300 mg/kg artemether resulted in significant reductions of SOD activities in both sexes. In conclusion, these results suggest that the inhibition of GST and, to a lesser extent also SOD enzymes, could lead to increased schistosome susceptibility to oxidant attacks and might be linked with the antischistosomal action of artemether. 相似文献
908.
Structural design and biomechanics of friction-based releasable attachment devices in insects 总被引:4,自引:1,他引:3
Gorb SN Beutel RG Gorb EV Jiao Y Kastner V Niederegger S Popov VL Scherge M Schwarz U Vötsch W 《Integrative and comparative biology》2002,42(6):1127-1139
Design of attachment devices in insects varies enormously inrelation to different functional loads. Many systems, locatedon different parts of the body, involve surfaces with particularfrictional properties. Such systems evolved to attach partsof the body to each other, or to attach an insect to the substratumby providing fast and reversible attachment/detachment. Amongthese systems, there are some that deal with predefined surfaces,and others, in which one surface remains unpredictable. Thefirst type of system occurs, for example, in wing-locking devicesand head-arresting systems and is called probabilistic fasteners.The second type is mainly represented by insect attachment padsof two alternative designs: hairy and smooth. The relationshipbetween surface patterns and/or mechanical properties of materialsof contact pairs results in two main working principles of thefrictional devices: mechanical interlocking, or maximizationof the contact area. We give an overview of the functional designof two main groups of friction-based attachment devices in insects:probabilistic fasteners and attachment pads. 相似文献
909.
角倍由角倍蚜Schlechtendaliachinensis(Bell)寄生在盐肤木RhuschinensisMill和滨盐肤木R.chinensisvar.raxburghii(DC)Rehd.叶上致瘿而形成,约占五倍子总产量的80%。藓圃上越冬若蚜和盐肤木林中角倍的分布均属聚集分布。影响越冬若蚜和角倍聚集度的主要生态因子分别为藓长势、湿度、光照和树与藓的距离、风向、风速。于母和雏倍分布在盐肤木和滨肤木的第5~11片叶上,其中7~9片叶上干母数和雏倍数超过50%。干母数与雏倍数存在着显著的线性关系。盐肤木上:y1=3.3394+0.7662x1,r1=0.9994**滨盐肤木上:y2=3.6707+0.7431x2,r2=0.9894** 相似文献
910.
Estimating Photosynthesis and Concurrent Export Rates in
C3 and C4 Species at Ambient and Elevated
CO2 总被引:2,自引:0,他引:2
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The ability of 21 C3 and C4 monocot and dicot species to rapidly export newly fixed C in the light at both ambient and enriched CO2 levels was compared. Photosynthesis and concurrent export rates were estimated during isotopic equilibrium of the transport sugars using a steady-state 14CO2-labeling procedure. At ambient CO2 photosynthesis and export rates for C3 species were 5 to 15 and 1 to 10 μmol C m−2 s−1, respectively, and 20 to 30 and 15 to 22 μmol C m−2 s−1, respectively, for C4 species. A linear regression plot of export on photosynthesis rate of all species had a correlation coefficient of 0.87. When concurrent export was expressed as a percentage of photosynthesis, several C3 dicots that produced transport sugars other than Suc had high efflux rates relative to photosynthesis, comparable to those of C4 species. At high CO2 photosynthetic and export rates were only slightly altered in C4 species, and photosynthesis increased but export rates did not in all C3 species. The C3 species that had high efflux rates relative to photosynthesis at ambient CO2 exported at rates comparable to those of C4 species on both an absolute basis and as a percentage of photosynthesis. At ambient CO2 there were strong linear relationships between photosynthesis, sugar synthesis, and concurrent export. However, at high CO2 the relationships between photosynthesis and export rate and between sugar synthesis and export rate were not as strong because sugars and starch were accumulated. 相似文献