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排序方式: 共有253条查询结果,搜索用时 31 毫秒
71.
Brenda H Welter Elizabeth L Hansen Karla J Saner Yangzhan Wei Thomas M Price 《The journal of histochemistry and cytochemistry》2003,51(8):1049-1055
Observational studies demonstrate that estradiol and progesterone affect vasoreactivity. In animal studies, progesterone treatment causes immediate relaxation of precontracted arteries with inhibition of calcium influx in vascular endothelial and smooth muscle cells, suggesting a non-genomic mechanism of action. In this study we investigated the presence of novel membrane-bound progesterone receptors in human aortic endothelial cells and correlated the expression with cell-cycle stage. Western blotting analysis with an antibody directed to the hormone-binding domain of the classic progesterone receptors shows predominant bands at 100 and 60 kD, whereas analysis with an antibody to the DNA-binding region shows only the 100-kD band. In contrast, classic nuclear progesterone receptors B and A are identified at 116 and 94 kD in similarly processed T47D cells. Both novel bands localize to the membrane fraction after differential centrifugation. Plasma membrane-bound progesterone receptor was further shown with immunofluorescent antibody and ligand-binding studies in a small percentage of human aortic endothelial cells. Fluorescent activated cell sorting demonstrated that approximately 8% of the human aortic endothelial cells expressed a plasma membrane progesterone receptor and that a greater percentage of the expressing cells were in the G2/M-phase of the cell cycle. Treatment with progesterone conjugated to BSA did not show any significant cell-cycle changes. Plasma membrane-bound progesterone receptor in vascular endothelial cells may regulate the non-genomic actions of progesterone, and expression of the receptor appears to vary with cell cycle stage. 相似文献
72.
Bone marrow nuclei fixed with modified Carnoy's, then stained with gallocyanin-chromalum followed by air drying showed no difference in morphology when compared by means of scanning electron microscopy with similar nuclei prepared by critical point drying. Glutaraldehyde at pH 4.0 and 7.1, mercury-containing Zenker's fluid, and chromalum alone, all of which are considered to be nuclear protein cross-linking fixatives, failed to preserve the nuclear morphology as well as gallocyanin-chromalum or critical point prepared bone marrow nuclei. 相似文献
73.
74.
Osteoclast cell-surface changes during the egg-laying cycle in Japanese quail 总被引:2,自引:1,他引:1
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SC Miller 《The Journal of cell biology》1977,75(1):104-118
The medullary bone serves as a source of labile calcium mobilized during calcification of the egg shell in birds. Quantitative histological methods demonstrate that the numbers of medullary bone osteoclasts and nuclei per osteoclast remain unchanged during the egg cycle in the Japanese quail (Coturnix). Therefore, cyclic changes in bone resorption cannot be explained by modulations of osteoclasts from and into other bone cells, a mechanism previously suggested for certain species of birds. Rather, dramatic changes in osteoclast cell-surface features occur during the egg cycle, which might account for cyclic variations in resorptive activity. During egg shell calcification, osteoclasts with ruffled borders are closely apposed to bone surfaces; the cytoplasm is rich in vacuoles that contain mineral crystals and seem to derive from the ruffled border. At the completion of egg shell calcification, the ruffled borders and vacuoles move away from the bone surface, although the osteoclast remains attached to the bone along the filamentous or "clear" zone. Associated with the disappearance of the ruffled borders is the appearance of extensive interdigitated cell processes along the peripheral surface of the osteoclast away from the bone. These unusual structures, which may serve as a reservoir of membrane, largely disappear when ruffled borders and associated structures reappear. Therefore, in these hens, the osteoclasts modulate their cell surface rather than their population during the egg cycle. 相似文献
75.
G Mouton F E Sluse A Bertrand A Welter J L Cabay G Camus 《Archives internationales de physiologie et de biochimie》1990,98(1):103-109
The blood iron status of 44 male runners of various running specialties (18 sprinters, 13 middle- and 13 long-distance runners) is evaluated by measuring serum ferritin (SF), serum iron (Si), hemoglobin concentration (Hb), hematocrit (Ht), red blood cells content (RBC) and haptoglobin concentration (Hp). The results of these analyses (except Hp) are compared to those obtained in sedentary male subjects (control group) of the same mean age. Mean SF, SI, Hb and Ht measured in athletes are significantly lower than in control group. The remarkably low Hp values obtained in athletes suggests the occurrence of hemolysis. Using unpaired t test, it appears that the blood iron status of these runners does not depend on their running specialty. 相似文献
76.
A short synthetic MAR positively affects transgene expression in rice and Arabidopsis 总被引:1,自引:0,他引:1
Van der Geest AH Welter ME Woosley AT Pareddy DR Pavelko SE Skokut M Ainley WM 《Plant biotechnology journal》2004,2(1):13-26
Matrix Attachment Regions (MARs) are DNA elements that are thought to influence gene expression by anchoring active chromatin domains to the nuclear matrix. When flanking a construct in transgenic plants, MARs could be useful for enhancing transgene expression. Naturally occurring MARs have a number of sequence features and DNA elements in common, and using different subsets of these sequence elements, three independent synthetic MARs were created. Although short, these MARs were able to bind nuclear scaffold preparations with an affinity equal to or greater than naturally occurring plant MARs. One synthetic MAR was extensively tested for its effect on transgene expression, using different MAR orientations, plant promoters, transformation methods and plant species. This MAR was able to increase average transgene expression and produced integration patterns of lower complexity. These data show the potential of making well defined synthetic MARs and using them to improve transgene expression. 相似文献
77.
Large efforts have been made in classifying residues as binding sites in proteins using machine learning methods. The prediction task can be translated into the computational challenge of assigning each residue the label binding site or non‐binding site. Observational data comes from various possibly highly correlated sources. It includes the structure of the protein but not the structure of the complex. The model class of conditional random fields (CRFs) has previously successfully been used for protein binding site prediction. Here, a new CRF‐approach is presented that models the dependencies of residues using a general graphical structure defined as a neighborhood graph and thus our model makes fewer independence assumptions on the labels than sequential labeling approaches. A novel node feature “change in free energy” is introduced into the model, which is then denoted by ΔF‐CRF. Parameters are trained with an online large‐margin algorithm. Using the standard feature class relative accessible surface area alone, the general graph‐structure CRF already achieves higher prediction accuracy than the linear chain CRF of Li et al. ΔF‐CRF performs significantly better on a large range of false positive rates than the support‐vector‐machine‐based program PresCont of Zellner et al. on a homodimer set containing 128 chains. ΔF‐CRF has a broader scope than PresCont since it is not constrained to protein subgroups and requires no multiple sequence alignment. The improvement is attributed to the advantageous combination of the novel node feature with the standard feature and to the adopted parameter training method. Proteins 2015; 83:844–852. © 2015 Wiley Periodicals, Inc. 相似文献
78.
Kelsey Augustin Robert S Bayne Katherine S Booker Jose R Botella Nicholas C Carpita Tyrell Carr Jin‐Gui Chen Thomas Ryan Cooke Arwen Frick‐Cheng Erin J Friedman Brandon Fulk Michael G Hahn Kun Jiang Lucia Jorda Lydia Kruppe Chenggang Liu Justine Lorek Maureen C McCann Antonio Molina Etsuko N Moriyama Sivakumar Pattathil John Schwarz Steven Seta Matthew Tan Ulrike Temp Yuri Trusov Daisuke Urano Bastian Welter Jing Yang Ralph Panstruga Joachim F Uhrig Alan M Jones 《Molecular systems biology》2011,7(1)
The heterotrimeric G‐protein complex is minimally composed of Gα, Gβ, and Gγ subunits. In the classic scenario, the G‐protein complex is the nexus in signaling from the plasma membrane, where the heterotrimeric G‐protein associates with heptahelical G‐protein‐coupled receptors (GPCRs), to cytoplasmic target proteins called effectors. Although a number of effectors are known in metazoans and fungi, none of these are predicted to exist in their canonical forms in plants. To identify ab initio plant G‐protein effectors and scaffold proteins, we screened a set of proteins from the G‐protein complex using two‐hybrid complementation in yeast. After deep and exhaustive interrogation, we detected 544 interactions between 434 proteins, of which 68 highly interconnected proteins form the core G‐protein interactome. Within this core, over half of the interactions comprising two‐thirds of the nodes were retested and validated as genuine in planta. Co‐expression analysis in combination with phenotyping of loss‐of‐function mutations in a set of core interactome genes revealed a novel role for G‐proteins in regulating cell wall modification. 相似文献
79.
Véronique Welter Maurice Charlet Michel Reuland Ferdinand Sauber Jules A. Hoffmann 《Invertebrate reproduction & development.》2013,57(3):321-331
Summary In earlier studies, we demonstrated that leeches contain ecdysone and 20-hy- droxyecdysone. The titre of these molecules was found to fluctuate during the moult/intermoult cycle which is suggestive of a role of ecdysteroids in the control of cuticulogenesis in Hirudinea similar to that observed in Arthropods. We have now extended our investigations to embryonic development in the leech Hirudo medicinalis. During this period of development, which lasts some 30 days, 5–25 embryos grow inside a large cocoon at the expense of a proteolipidic gel (‘albumen’) synthesized by clitellian glandular cells of the parent leech. We have found that the albumen already contains ecdysteroids before the onset of embryogenesis (‘parental ecdysteroids’). At this time, and during the early stages of embryogenesis, several as yet unidentified low polar ecdysteroids predominate in the albumen; the titre of these molecules shows a dramatic decrease in the albumen at mid-embryogenesis which is concomitant with a marked rise in the concentration of free ecdysone and 20-hydroxyecdysone. In the embryos, this stage coincides with a remarkable transformation of the first structures (‘the cryptolarval metamorphosis’). At all stages investigated the albumen contains significant amounts of Helix hydrolysable conjugates. At least in early stages, the hydrolysis of these conjugates yields free ecdysone and a low polarity ecdysteroid. We suggest that in Hirudo the ecdysteroids synthesized before egg-laying by the adult leech play a role in the control of embryonic development and possibly also in the as yet not understood cycle(s) of embryonic cuticulogenesis. 相似文献
80.