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排序方式: 共有166条查询结果,搜索用时 15 毫秒
1.
Differentiation of placental trophoblast stem (TS) cells to trophoblast giant (TG) cells is accompanied by transition from a mitotic cell cycle to an endocycle. Here, we report that Cdh1, a regulator of the anaphase-promoting complex/cyclosome (APC/C), negatively regulates mitotic entry upon the mitotic/endocycle transition. TS cells derived from homozygous Cdh1 gene-trapped (Cdh1GT/GT) murine embryos accumulated mitotic cyclins and precociously entered mitosis after induction of TS cell differentiation, indicating that Cdh1 is required for the switch from mitosis to the endocycle. Furthermore, the Cdh1GT/GT TS cells and placenta showed aberrant expression of placental differentiation markers. These data highlight an important role of Cdh1 in the G2/M transition during placental differentiation.  相似文献   
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Putative E2/NS1 sequence of hepatitis C virus was expressed in E. coli as a fusion protein with maltose binding protein. Approximately 80 kDa protein was obtained containing 38 kDa E2/NS1 protein. The antibody to this protein was detectable in the same serum from which the sequence was amplified. It was also detectable in none of 7 acute hepatitis, in 2 of 12 chronic persistent hepatitis, in 3 of 25 chronic active hepatitis, and in 2 of 4 cirrhosis. It was detectable in none of 10 normal subjects. In 3 cases who were positive for the antibody before the interferon treatment, it became undetectable after the treatment. Thus, it seems that the antibody is not a neutralizing antibody and is related to active viral replication.  相似文献   
4.
The cDNA clones encoding ARE(Na,K-ATPase alpha1 subunit gene regulatory element) binding protein AREC3 were isolated from myoblast C2C12 cells and mouse skeletal muscle cDNA library. At least four alternatively spliced forms of AREC3 cDNA were identified. Sequence analysis indicates that AREC3 has an extensive homology with the Drosophila sine oculis gene product required for development of the entire visual system [Cheyette et al.(1994) Neuron 12, 977-996]. The homologous region including a homeodomain is required for specific DNA binding to ARE. A transactivation domain was identified in the C-terminal part of the AREC3 by reporter gene assays using GAL4-AREC3 fusion protein constructs. Immunohistochemistry revealed that AREC3 localized to the nucleus and cytoplasm of myoblast C2C12 cells, and the production of AREC3 is augmented during muscle differentiation. Western blot analysis indicated that the 115 kDa form of AREC3 protein is increased in the cytoplasmic extract, and the 67kDa form is increased both in nuclear and cytoplasmic extracts of C2C12 cells during muscle differentiation.  相似文献   
5.
Vertebrate lens tissues contain several species of acidic andneutral glycosphingolipids in relatively high amounts. However,the epithelia with capsule from dog and rhesus monkey lenseshad a simpler composition and lower content of glycosphingolipidsthan whole lenses. Gangliosides and neutral glycosphingolipidsin monolayer cultures of lens epithelial cells were also differentfrom those in whole lenses. Although -galactosyl (Gal1-3Ga1-R)or Lewisx (Galß1-4[Fuc1-3]GlcNAc-R) epitopes werefound in glycosphingolipids from whole lenses, they were notdetected in those from monolayer cultures of dog and rhesusmonkey lens cells. In addition, significant changes in ganglio-seriesgangliosides were induced in monolayer cultures of both cells,where GM3 and GD3 were predominant. Immunofluorescence studyrevealed a characteristic distribution of cell surface gangliosidesin confluent monolayers. These findings suggest that glycosphingolipidsynthesis in lens epithelia is intrinsically different fromthat in cortical and nuclear fibres, and that the expressionof Lewisx and -galactosyl epitopes in glycosphingolipids appearsto be associated with the differentiation of epithelial cellsto fibres. gangliosides glycosphingolipids lens epithelial cells Lewisx rhesus monkey.  相似文献   
6.
The roles of the Na+/H+ exchange system in the development and cessation of reperfusion induced ventricular arrhythmias were studied in the isolated perfused rat heart. The hearts were perfused in the working heart mode with modified Krebs Henseleit bicarbonate (KHB) buffer and whole heart ischemia was induced by a one-way ball valve with 330 beat/min pacing. Ischemia was continued for 15 min followed by 20 min of aerobic reperfusion (control). Amiloride (1.0mM), an inhibitor of the Na+/H+ exchange system, was added to the KHB buffer only during reperfusion (group B) or only during ischemic periods (group C). Electrocardiographic and hemodynamic parameters were monitored throughout the perfusion. Coronary effluent was collected through pulmonary artery cannulation and PO2, PCO2, HCO 3 and pH were measured by blood-gas analyzer.The incidence of reperfusion induced ventricular arrhythmias was 100%, 100% and 0% in control, group B and group C, respectively. The mean onset time of termination of reperfusion arrhythmias was significantly shorter in group B than in control. PCO2 increased from 39.0±0.9 to 89.3±6.0 mmHg at the end of ischemia in control and from 40.6±0.4 to 60.5±5.8 in group C, the difference between groups was statistically significant. HCO 3 level decreased from 21.8±0.1 to 18.3±0.5 mmol/l in control, however, this decrease was significantly inhibited in group C (from 22.0±0.5 to 20.3±0.2). The increase in PCO2 and the decrease in HCO 3 in group B were similar over time to those observed in control. The decrease in pH produced by ischemia was marked in control (from 7.35±0.01 to 6.92±0.04) and group B (from 7.34±0.01 to 6.94±0.02), whereas a decrease in pH was significantly prevented in group C (from 7.34±0.01 to 7.15±0.04). There were no significant differences in PCO2, HCO 3 or pH among the three groups during reperfusion.These experiments provide evidence that amiloride significantly prevented the incidence of reperfusion arrhythmias when added only during ischemia and significantly terminated reperfusion arrhythmias when added only during reperfusion. Amiloride may prevent a decrease in pH, due to alterations in PCO2 and/or HCO 3 . These changes in PCO2 and HCO 3 might be indirectly influenced by inhibition of the Na+/H+ exchange system via Cl/HCO 3 exchange. The mechanism by which amiloride terminates reperfusion arrhythmias seems to involve electrophysiological effects which were not directly addressed in this experiment.  相似文献   
7.
Ohto M  Nakamura K 《Plant physiology》1995,109(3):973-981
The sugar-inducible expression of genes for sporamin and [beta]-amylase in leaf explants of sweet potato (Ipomoea batatas) and that of a [beta]-glucuronidase-fusion gene, with the promoter of the gene for [beta]-amylase in leaves of tobacco (Nicotiana tabacum), requires Ca2+ signaling (M. Ohto, K. Hayashi, M. Isobe, K. Nakamura [1995] Plant J 7: 297-307), and it was inhibited by staurosporin and K252a, inhibitors of protein kinases. Autophosphorylation activities of several potential protein kinases in leaves of tobacco were significantly higher in younger leaves than in mature leaves. However, the autophosphorylation activities of these proteins in mature leaves, especially those of the major autophosphorylatable proteins with apparent molecular masses of 56 and 54 kD, increased upon treatment of leaf discs with a 0.3 M solution of sucrose, glucose, or fructose, did not increase with sorbitol or mannitol treatments, and the increase by sucrose was inhibited by cycloheximide. Autophosphorylation of the 56- and 54-kD protein in vitro was dependent on Ca2+ and inhibited by staurosporine, K-252a, and by W-7. These results suggest that they belong to the family of calcium-dependent protein kinases. They were concentrated in the plasma membrane fraction and were released from membrane vesicles by high salt or with sodium carbonate. The possible functions of these sugar-inducible calcium-dependent protein kinases associated with the plasma membrane are discussed.  相似文献   
8.
Genes coding for sporamin and β-amylase of sweet potato are inducible not only by high levels of metabolizable sugars, such as sucrose, but also by a low concentration of polygalacturonic acid (PGA). Calmodulin inhibitors and EGTA inhibited both the PGA-inducible and the sucrose-inducible accumulation of mRNAs for sporamin and β-amylase in sweet potato. Calmodulin inhibitors, EGTA and La3+, also inhibited the sucrose-inducible expression, in leaves of transgenic tobacco, of a fusion gene, β-Amy:GUS, which consists of the promoter of the β-amylase gene and the coding sequence for β-glucuronidase. The sucrose-inducible expression of the β-Amy:GUS fusion gene was also inhibited by two inhibitors of Ca2+ channels, diltiazem and nicardipine. These results suggest that the sugar-inducible expression of genes for sporamin and β-amylase involves, at least in part, Ca2+-mediated signalling, and that the cytosolic free Ca2+ may mediate cross-talk between signals related to carbohydrate metabolism and other stimuli. Treatment of coelenterazine-loaded leaf discs of tobacco expressing a Ca2+-binding photoprotein, aequorin, with 0.2 M sucrose for 24 h significantly reduced the level of luminescence that could be induced by cold shock, as compared to cold shock-induced luminescence in coelenterazine-loaded leaf discs treated with water. Repression of cold shock-induced luminescence was due to the conversion of holoaequorin to apoaequorin during the treatment with sucrose. Treatment of coelenterazine-loaded leaf discs with a 0.2 M solution of glucose or fructose, but not of mannitol or sorbitol, also reduced the cold shock-induced luminescence. It is suggested that non-synchronous increases in cytosolic level of free Ca2+ occur in leaf discs during treatment with high levels of metabolizable sugars.  相似文献   
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10.

Background

Klotho was originally identified in a mutant mouse strain unable to express the gene that consequently showed shortened life spans. In humans, low serum Klotho levels are related to the prevalence of cardiovascular diseases in community-dwelling adults. However, it is unclear whether the serum Klotho levels are associated with signs of vascular dysfunction such as arterial stiffness, a major determinant of prognosis, in human subjects with chronic kidney disease (CKD).

Methods

We determined the levels of serum soluble Klotho in 114 patients with CKD using ELISA and investigated the relationship between the level of Klotho and markers of CKD-mineral and bone disorder (CKD-MBD) and various types of vascular dysfunction, including flow-mediated dilatation, a marker of endothelial dysfunction, ankle-brachial pulse wave velocity (baPWV), a marker of arterial stiffness, intima-media thickness (IMT), a marker of atherosclerosis, and the aortic calcification index (ACI), a marker of vascular calcification.

Results

The serum Klotho level significantly correlated with the 1,25-dihydroxyvitamin D level and inversely correlated with the parathyroid hormone level and the fractional excretion of phosphate. There were significant decreases in serum Klotho in patients with arterial stiffness defined as baPWV≥1400 cm/sec, atherosclerosis defined as maximum IMT≥1.1 mm and vascular calcification scores of ACI>0%. The serum Klotho level was a significant determinant of arterial stiffness, but not endothelial dysfunction, atherosclerosis or vascular calcification, in the multivariate analysis in either metabolic model, the CKD model or the CKD-MBD model. The adjusted odds ratio of serum Klotho for the baPWV was 0.60 (p = 0.0075).

Conclusions

Decreases in the serum soluble Klotho levels are independently associated with signs of vascular dysfunction such as arterial stiffness in patients with CKD. Further research exploring whether therapeutic approaches to maintain or elevate the Klotho level could improve arterial stiffness in CKD patients is warranted.  相似文献   
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