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991.
J. Hřib R. Janisch B. Vooková J. Nahálková P. Gemeiner M. Hajduch 《Biologia Plantarum》2000,43(3):329-336
The megagametophytes of the European black pine (Pinus nigra Arn.) were cultured on modified MS medium. After 10 d, protein bodies showed well-marked degradation on freeze-etched replicas and in preparations observed by scanning electron microscopy. After 20 d of cultivation, the megagametophyte cells were completely empty. Proteins secreted into the agar medium were determined by electrophoresis and 15 different proteins, in the range of 6.5 to 71 kDa, were identified. 相似文献
992.
Bone morphogenetic proteins secreted by breast cancer cells upregulate bone sialoprotein expression in preosteoblast cells 总被引:3,自引:0,他引:3
It is well established that bone metastases comprise bone; however, the exact factors/mechanisms involved remain unknown. We hypothesized that tumor cells secreted factors capable of altering normal bone metabolism. The aims of the present study were to (1) determine the effects of secretory products isolated from HT-39 cells, a human breast cancer cell line, on osteoprogenitor cell (MC3T3-E1 cells) behavior, and (2) identify tumor-derived factor(s) that alters osteoblast activities. Conditioned media (CM) from HT-39 cells were collected following a 24-h serum-free culture. The ability of CM to alter gene expression in MC3T3-E1 cells was determined by Northern analysis. CM effects on cell proliferation and mineralization ability were determined using a Coulter counter and von Kossa stain, respectively. MC3T3-E1 cells were treated with CM plus noggin, a factor known to block bone morphogenic proteins (BMPs), to determine whether BMPs, shown to be present in CM, were linked with CM effects on MC3T3-E1 cell activity. In addition, inhibitors of MAP kinase kinase (MEK), protein kinase C (PKC), and protein kinase A were used to identify the intracellular signaling pathway(s) by which the active factors in CM regulated osteoblast behavior. CM treatment significantly enhanced BSP mRNA (2.5-fold over control), but had no effect on cell proliferation. Mineralization assay showed that CM enhanced mineral nodule formation compared to controls. Noggin inhibited CM-induced upregulation of BSP mRNA, suggesting that BMPs were responsible for upregulating BSP gene expression in MC3T3-E1 cells. The PKC inhibitor blocked CM-mediated upregulation of BSP, suggesting involvement of the PKC pathway in regulating BSP expression. BMPs secreted by HT-39 cells may be responsible for enhancing BSP expression in MC3T3-E1 cells. Continued studies targeted at determining the role of BMPs in regulating bone metabolism are important for understanding the pathogenesis of bone diseases. 相似文献
993.
New advances in coenzyme Q biosynthesis 总被引:2,自引:0,他引:2
Catherine F. Clarke 《Protoplasma》2000,213(3-4):134-147
Summary Coenzyme Q (or ubiquinone) is the product of two distinct biosynthetic pathways: the lipid tail of coenzyme Q is formed via the isoprene biosynthetic pathway, and the quinone ring derives from the metabolism of either shikimic acid or tyrosine. In general, eukaryotic organisms use the classical mevalonate pathway to form isopentenyl- and dimethylallyl-diphosphate, the five carbon building blocks of the polyisoprenoid tail, and prokaryotes use 1-deoxy-D-xylulose-5-phosphate, formed via the Rohmer pathway. The quinone ring precursor is 4-hydroxybenzoic acid, which is formed directly from chorismate inSaccharomyces cerevisiae andEscherichia coli, or from tyrosine in animal cells. Ring modification steps including prenylation, decarboxylation, and successive hydroxylation and methylation steps form the fully substituted benzoquinone ring of coenzyme Q. Many of the genes and polypeptides involved in coenzyme Q biosynthesis have been isolated and characterized by utilizing strains ofE. coli andS. cerevisiae with mutations in theubi andCOQ genes, respectively. This article reviews recent progress in characterizing the biosynthesis of coenzyme Q inE. coli, S. cerevisiae, and other eukaryotic organisms. 相似文献
994.
Summary Chloroplasts and pigment granules are known to be intracellularly translocated upon discrete extracellular stimuli. The machineries transducing these signals inside cells are yet not understood. In studies investigating the motility of peroxisomes, we were able to identify both extracellular and intracellular signaling steps regulating movements of these organelles. Following simultaneous stimulation of CHO cells with both extracellular ATP and lysophosphatidic acid, an arrest of peroxisomes was observed. This block of motility was shown to be dependent on signaling cascades involving heterotrimeric G proteins of the class Gi/Go, phospholipase C, calcium influx, and activation of protein kinase C as well as of mitogen-activated protein kinase. Cytosolic phospholipase A2 is a point of convergence for these pathways, resulting in the release of arachidonic acid. This signaling pathway is specific for peroxisomes and does not influence motility of mitochondria, lysosomes, or endosomes. However, since the cytoskeleton and its associated proteins including the motor proteins play an important role in mediating motility of all cell organelles, it may well be that variant signaling cascades exist ensuring specific regulation of each distinct compartment.Abbreviations AA
arachidonic acid
- ATPS
adenosine-5-O-(3-thiotriphosphate)
- cAMP
cyclic adenosine monophosphate
- CaM-PK
calmodulin-dependent protein kinase
- CLIP
cytosolic linker protein
- DAG
diacylglycerol
- DiC8
1,2-dioctanoyl-sn-glycerol
- GFP
green-fluorescent protein
- GTPS
guanosine-5-O-(3-thiotriphosphate)
- IP3
inositol trisphosphate
- LPA
lysophosphatidic acid
- MAPK
mitogen-activated protein kinase
- MEK MAPK
kinase
- PKA
protein kinase A
- PKC
protein kinase C
- cPKC
classical PKC isoforms
- PLA2
phospholipase A2
- PLAP
PLA2-activating proteinpeptide
- PLC
phospholipase C
- PP2A
protein phosphatase 2A 相似文献
995.
In the mid-1970s, information technology and recombinant DNA technology were considered as the breakthrough technologies of the final quarter of the 20th century. Now, about 25 years later, information technology has penetrated deeply into our society and nearly everyone uses this technology. Compared to the formidable success of information technology, the progress in the commercialization of recombinant DNA technology is moderate, even when taking into account that all that is related to the technological application of biological sciences needs extensive safety testing. However, there are signs that the speed of this commercialization will increase in the first decade of the 21st century. Moreover, new breakthroughs in our understanding of the complete genetic make up of eukaryotes will contribute to this increase in speed. An important aspect of the commercialization of this technology is the development of cells as factories for the production of valuable and/or useful molecules. Lower eukaryotes, such as yeasts and molds, are the most promising candidates to become the factories of the future, but at present these factories still contains a lot of process lines that may be superfluous under the well controlled conditions in fermentors. On the other hand, the speed and yield of these cellular production lines can be increased by eliminating the rate-determining steps of these process lines. In this contribution to the European Union symposium from Cell to Factory, some steps in the improvement of S. cerevisiae as cell factories for (heterologous) hydrophobic molecules are presented. 相似文献
996.
The microtubular element of the plant cytoskeleton undergoes dramatic architectural changes in the course of the cell cycle, specifically at the entry into and exit from mitosis. These changes underlie the acquisition of specialized properties and functions involved, for example, in the equal segregation of chromosomes and the correct positioning and formation of the new cell wall. Here we review some of the molecular mechanisms by which the dynamics and the organization of microtubules are regulated and suggest how these mechanisms may be under the control of cell cycle events. 相似文献
997.
998.
We have expressed the gene (PAB1) encoding the yeast polyadenylate-binding protein (Pab1p) in tobacco. Plants that accumulate the Pab1p display a range of abnormalities, ranging from a characteristic chlorosis in leaves to a necrosis and large inhibition of growth. The severity of these abnormalities reflects the levels of yeast Pab1p expression in the transgenic plants. In contrast, no obvious differences could be seen in callus cultures between the transgene and vector control. Plants that display PAB-associated abnormalities were resistant to a range of plant pathogens, and had elevated levels of expression of a pathogenesis-related gene. These two properties – impairment of growth and induction of defense responses – indicate that the yeast PAB1 gene can act as a disease lesion mimic gene in plants. 相似文献
999.
Growth and Na+, K+, Cl-, proteins, sugars and proline concentrations were measured in three triticale genotypes M2A, DF99 and Asseret grown on nutrient
solution with or without 75 mM NaCl. In saline conditions, leaf area of the three triticales was reduced by 50 % and dry to
fresh mass ratio increased. Total protein concentration was diminished by 10 %. K+ concentration decreased whereas Na+ and Cl- accumulated in roots and shoots of salt-stressed plants. This ion accumulation was greater in roots of Asseret than in roots
of the other triticales. Soluble sugar concentration increased in M2A and Asseret and decreased in DF99. Proline concentration
increased in M2A and DF99 and decreased in Asseret. Osmotic adjustment was essentially realized by Na+ and Cl- uptake. Non-reducing sugars and proline contributed too, but to a lesser extent.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
1000.
May Penrad-Mobayed Nicole Moreau Nicole Angelier 《Development, growth & differentiation》1998,40(2):147-156
Pleurodeles exhibits a ZZ/ZW system of GSD (genotype sex determination). However, the Z and W sex chromosomes appear to be morphologically identical. A short RNA sequence is described that was specifically bound to lampbrush loops in the differential segment of the sexual bivalent IV. The distribution of these labeled loops in experimentally produced ZZ and WW females enabled us to demonstrate that such labeled loops were perfectly correlated with the W chromosome. Therefore, this RNA sequence constitutes an excellent marker for the W differential segment. Furthermore, analysis of the labeled loops under various experimental conditions suggested that their labeling is caused by specific interactions between this RNA sequence and lampbrush loop-associated proteins (RNA/protein interactions). North-western assays revealed that nuclear polypeptide(s) of 65 kDa could be responsible for such binding. 相似文献