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排序方式: 共有176条查询结果,搜索用时 15 毫秒
1.
Administration of oestradiol to ovariectomized baboons caused the epithelium of the cervix to differentiate into tall columnar cells that were ciliated or secretory. Administration of progesterone in the presence or absence of oestradiol altered the appearance of the lining epithelium, suggesting a decrease in secretory activity. Fluorographs of media from cultures of tissue from steroid-treated animals reflected changes in polypeptide biosynthesis which correlated with the morphological observations: 6 polypeptides (Mr 88,000-37,000; pI 5.5-6.0) were observed in all treatment groups and, except for relative changes in intensity, these polypeptides were electrophoretically similar to those synthesized by the endometrium. A new group of low molecular weight polypeptides (Mr 23,000-20,000, pI greater than 8.0-5.5) and a basic protein (Mr 160,000) were synthesized and released in the oestradiol-dominated animal. These polypeptides were distinct to the cervical mucosa since they were not observed in the endometrium or oviduct. Progesterone suppressed the synthesis of the low molecular weight acidic polypeptides (Mr 23,000-20,000; pI 6.1-5.5) but maintained the synthesis of the basic polypeptides (Mr 23,000-20,000; pI greater than 8). Treatment with progesterone +/- oestradiol did not appear to induce the synthesis of any new major polypeptides in the cervical epithelium. These results suggest that oestradiol induces the synthesis of a group of cervix-specific polypeptides and progesterone antagonizes the action of oestradiol in the baboon cervix. 相似文献
2.
Isolation and characterization of plasma membrane-associated cortical granules from sea urchin eggs 总被引:9,自引:6,他引:3
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Cortical granules, which are specialized secretory organelles found in ova of many organisms, have been isolated from the eggs of the sea urchins Arbacia punctulata and Strongylocentrtus pupuratus by a simple, rapid procedure. Electron micropscope examination of cortical granules prepared by this procedure reveals that they are tightly attached to large segments of the plasma membrane and its associated vitelline layer. Further evidence that he cortical granules were associated with these cell surface layers was obtained by (125)I-labeling techniques. The cortical granule preparations were found to be rich in proteoesterase, which was purified 32-fold over that detected in a crude homogenate. Similarly, the specific radioactivity of a (125)I-labeled, surface glycoprotein was increased 40-fold. These facts, coupled with electron microscope observations, indicate the isolation procedure yields a preparation in which both the cortical granules and the plasma membrane-vitelline layer are purified to the same extent. Gel electrophoresis of the membrane-associated cortical granule preparation reveals the presence of at least eight polypeptides. The major polypeptide, which is a glycotprotein of apparent mol wt of 100,000, contains most of the radioactivity introduced by (125)I-labeling of the intact eggs. Lysis of the cortical granules is observed under hypotonic conditions, or under isotonic conditions if Ca(2+) ion is present. When lysis is under isotonic conditions is induced by addition of Ca(2+) ion, the electron-dense contents of the granules remain insoluble. In contrast, hypotonic lysis results in release of the contents of the granule in a soluble form. However, in both cases the (125)I-labeled glycoprotein remains insoluble, presumably because it is a component of either the plasma membrane or the vitelline layer. All these findings indicate that, using this purified preparation, it should be possible to carry out in vitro studies to better define some of the initial, surface-related events observed in vivo upon fertilization. 相似文献
3.
Aggregation-dependent turnover of flagellar adhesion molecules in chlamydomonas gametes 总被引:8,自引:7,他引:1
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Previous studies on flagellar adhesion in chlamydomonas (Snell, W. and S. Roseman. 1979. J. Biol. Chem. 254:10820-10829.) have shown that as gametes adhere to flagella isolated from gametes of the opposite mating type, the adhsiveness of the added flagella but not of the gametes is lost. The studies reported here show that the addition of protein synthesis inhibitors (cycloheximide [CH] or anisomycin) to the medium of such cell- flagella mixtures causes the cells to lose their adhesiveness. This loss, however, occurs only after the cells have interacted with 4-8 flagella/cell and does not occur if the cells are kept in CH (7 h) without aggregating. The availability of an impotent (imp) mating type plus (MT(+)) mutant (provided by U.W. Goodenough), which adheres but is unable to undergo the fusion that normally follows adhesion, made it possible to determine whether a similar loss of adhesiveness occurs in mixtures of matting type minus (mt(-)) and imp mt(+) gametes. In the absence of inhibitor, mt(-) and imp mt(+) gametes adhered to each other (without fusing) for several hours; however, in the presence of CH or anisomycin, the gametes began to de-adhere 35 min after mixing, and, by 90 min, 100 percent of the cells were single again. This effect was reversible, and the rapid turnover of cells were single again. This effect was reversible, and the rapid turnover of molecules involved in adhesion occurred only during adhesion inasmuch as gametes pretreated for 4 h with CH were able to aggregate in CH for the same length of time as nonpretreated cells aggregated in CH. By the addition of CH at various times after the mt(-) and imp mt(+) gametes were mixed, measurements were made of the “pool size” of the molecules involved in adhesion. The pool reached a minimum after 25 min of aggregation, rapidly increased for the next 25 min, and then leveled off at the premixing level. These results suggest that flagellar adhesion in chlamydomonas causes modification of surface molecules (receptors, ligands), which brings about their inactivation and stimulates their replacement. 相似文献
4.
Paolo Maiuri Emmanuel Terriac Perrine Paul-Gilloteaux Timothée Vignaud Krista McNally James Onuffer Kurt Thorn Phuong A. Nguyen Nefeli Georgoulia Daniel Soong Asier Jayo Nina Beil Jürgen Beneke Joleen Chooi Hong Lim Chloe Pei-Ying Sim Yeh-Shiu Chu Andrea Jiménez-Dalmaroni Manuel Théry 《Current biology : CB》2013,23(1):97
5.
6.
Diederik WJ Dippel Eric J van Breda H Bart van der Worp H Maarten A van Gemert Ron J Meijer L Jaap Kappelle Peter J Koudstaal 《BMC cardiovascular disorders》2003,3(1):1-8
Background
Body temperature is a strong predictor of outcome in acute stroke. In a previous randomized trial we observed that treatment with high-dose acetaminophen (paracetamol) led to a reduction of body temperature in patients with acute ischemic stroke, even when they had no fever. The purpose of the present trial was to study whether this effect of acetaminophen could be reproduced, and whether ibuprofen would have a similar, or even stronger effect.Methods
Seventy-five patients with acute ischemic stroke confined to the anterior circulation were randomized to treatment with either 1000 mg acetaminophen, 400 mg ibuprofen, or placebo, given 6 times daily during 5 days. Treatment was started within 24 hours from the onset of symptoms. Body temperatures were measured at 2-hour intervals during the first 24 hours, and at 6-hour intervals thereafter.Results
No difference in body temperature at 24 hours was observed between the three treatment groups. However, treatment with high-dose acetaminophen resulted in a 0.3°C larger reduction in body temperature from baseline than placebo treatment (95% CI: 0.0 to 0.6 °C). Acetaminophen had no significant effect on body temperature during the subsequent four days compared to placebo, and ibuprofen had no statistically significant effect on body temperature during the entire study period.Conclusions
Treatment with a daily dose of 6000 mg acetaminophen results in a small, but potentially worthwhile decrease in body temperature after acute ischemic stroke, even in normothermic and subfebrile patients. Further large randomized clinical trials are needed to study whether early reduction of body temperature leads to improved outcome. 相似文献7.
Evolutionary distances for protein-coding sequences: modeling site- specific residue frequencies 总被引:13,自引:8,他引:5
Estimation of evolutionary distances from coding sequences must take into
account protein-level selection to avoid relative underestimation of longer
evolutionary distances. Current modeling of selection via site-to-site rate
heterogeneity generally neglects another aspect of selection, namely
position-specific amino acid frequencies. These frequencies determine the
maximum dissimilarity expected for highly diverged but functionally and
structurally conserved sequences, and hence are crucial for estimating long
distances. We introduce a codon- level model of coding sequence evolution
in which position-specific amino acid frequencies are free parameters. In
our implementation, these are estimated from an alignment using methods
described previously. We use simulations to demonstrate the importance and
feasibility of modeling such behavior; our model produces linear distance
estimates over a wide range of distances, while several alternative models
underestimate long distances relative to short distances. Site-to-site
differences in rates, as well as synonymous/nonsynonymous and
first/second/third-codon-position differences, arise as a natural
consequence of the site-to-site differences in amino acid frequencies.
相似文献
8.
9.
Kathleen Börner Johannes Hermle Christoph Sommer Nigel P. Brown Bettina Knapp Bärbel Glass Julian Kunkel Gloria Torralba Jürgen Reymann Nina Beil Jürgen Beneke Rainer Pepperkok Reinhard Schneider Thomas Ludwig Michael Hausmann Fred Hamprecht Holger Erfle Lars Kaderali Hans-Georg Kräusslich Maik J. Lehmann Dr. 《Biotechnology journal》2010,5(1):39-49
10.
Jessica AB van Nies Rute B Marques Stella Trompet Zuzana de Jong Fina AS Kurreeman Rene EM Toes J Wouter Jukema Tom WJ Huizinga Annette HM van der Helm-van Mil 《Arthritis research & therapy》2010,12(2):R38