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931.
Jun-Feng Li 《Carbohydrate research》2009,344(5):599-4211
Oleanolic acid, a natural product, possesses an anti-osteoclast formation activity. Targeting at discovery of novel and potent anti-bone resorption agents, 22 glycosides of oleanolic acid derivatives (including d-galactopyranosides, d-glucopyranosides, d-xylopyranoses, d-arabopyranoses and d-glycuronic acids) were synthesized at phase-transfer-catalyzed conditions (K2CO3, Bu4NBr, CH2Cl2-H2O) and their inhibitory activity on the formation of osteoclast-like multinucleated cells (OCLs) induced by 1α, 25-dihydroxy vitamin D3 was evaluated in a co-culture assay system. The structure-activity relationships of these compounds were also discussed. 相似文献
932.
J.G.M. Leung 《生物化学与生物物理学报:生物膜》1980,597(2):427-432
Liposomes containing the fluorescent dye 6-carboxyfluorescein were made from dipalmitoyl phosphatidylcholine and stearylamine. At 4°C the liposomes are adsorbed on the fiber surface and when the temperature is raised to 21°C, their contents are transferred directly into the fibers at a linear rate. Liposomes had little effect on the time course of the maximal twitch tension. 相似文献
933.
Susan Mopper Michael Beck Daniel Simberloff Peter Stiling 《Evolution; international journal of organic evolution》1995,49(5):810-815
The deme-formation hypothesis states that selection can produce adaptive genetic variation within and among phytophagous insect populations. We conducted three field experiments and tested this prediction by transferring eggs and measuring performance of a mobile leafmining insect, Stilbosis quadricustatella. In Experiment 1, we compared the rate of mine initiation of leafminers transferred to natal and novel sites. In Experiment 2, we compared mine-initiation rate of leafminers transferred to natal and novel host-plant species. In Experiment 3, we compared the mine-initiation rate, mine-completion rate, and sources of mortality of miners transferred to neighboring natal and novel Quercus geminata trees. In the first, second, and third experiments, leafminer larvae initiated significantly more mines at the natal site, on the natal plant species, and on the natal Q. geminata tree, evidence for adaptive differentiation. Furthermore, plant-mediated mortality was significantly lower among miners transferred to natal Q. geminata trees. This result supports a key assumption of the deme-formation hypothesis: insects adapt to the defensive phenotypes of individual trees. However, natural-enemy mortality was significantly higher among miners transferred to natal trees, essentially reversing the plant effect. Therefore, rates of successful mine completion were similar on natal (19%) and novel (17%) trees. This experiment suggests that host plants and natural enemies may represent opposing forces of selection. Leafminers adapted to individual trees may realize a selective advantage only when natural-enemy densities are low. 相似文献
934.
Louis Van Liere 《Aquatic Ecology》1986,20(1-2):9-15
The Loosdrecht Lakes area is briefly described, light has been shed on its morphology, history, the process of eutrophication with its concomitant phenomena, as well as the planned restoration and research programme. 相似文献
935.
936.
Heterodimerization is mainly responsible for the dominant negative activity of amino-terminally truncated rat androgen receptor forms 总被引:1,自引:0,他引:1
Rat androgen receptor (rAR) mutants devoid of the amino-terminal transactivation domain are able to behave as dominant negative regulators of wild-type rAR. To address the underlying mechanisms of the trans-dominant negative action, we have examined the roles of the DNA-binding domain (DBD) and the ligand-binding domain (LBD) in this process. Transactivation experiments in CV-1 cells complemented by electrophoretic mobility shift assays revealed that the dominant negative receptor forms repress the function of wild-type rAR mainly through heterodimer formation, rather than through competition for binding to cognate DNA elements. Heterodimerization of receptor forms containing LBDs may take place even in the absence of specific DNA binding. 相似文献
937.
Lothar Geitler 《Plant Systematics and Evolution》1980,136(1-2):53-62
The morphology and life history ofChroococcopsis epiphytica nova spec. is described, a German and Latin diagnosis is added. Cultivated plants display some differences in comparison with plants in their natural habitat: calcification occurs only in the natural medium, endosporangia are developed only by cultivated plants. At the basis, where single cells and thalli are attached, a special sort of jelly is produced; it is discernible only by elective staining with methylene blue. The systematic position of the new species is discussed. 相似文献
938.
The effects of variation of intramuscular temperature (T) on conduction velocity (CV) of the action potential along single human muscle fibers of the biceps brachii was studied in situ in 15 normal volunteers (mean age 39 years, range 21–62 years). Cooling was obtained by direct application of ice over a rectangular skin region including the stimulating and recording area. The intramuscular T was monitored by a needle thermocouple (copperconstantane). In all the 24 muscle fibers studied, a linear relationship was observed between CV and T. The slopes of the regression lines, ranging between 0.190 and 0.079 m/s, were positively correlated with the starting CV at 36°C ranging between 2.2 and 5.2 m/s. If conduction changes are expressed as a percentage of the basal CV at 36°C, the CV/T coefficient is the same for all the fibers and independent of the individual CV: 3.4% of CV/°C. 相似文献
939.
. We introduce some special chiasma formation processes. First a family of discrete chiasma formation processes is introduced
and we determine the nature of higher order interference associated with those processes. Secondly we consider a two-stage
chiasma formation process, where the associated recombination frequency between two markers depends not only on their map
distance but also on their location along the chromosomes. We characterise under this process, in some cases, the nature of
interference between two segments.
Received: 22 January 1996 / Revised version: 17 September 1997 相似文献
940.
ABSTRACT. The effect of dichloroisoproterenol on macrostomal cell formation in Tetrahymena vorax was examined and the drug was found to be 50% inhibitory at a concentration of 88 μM. Cellular uptake and incorporation of a variety of radiolabelled precursors was monitored in the presence of dichloroisoproterenol. The results demonstrate a strong, concentration-dependent inhibitory effect on RNA and protein biosynthesis, with a lesser inhibition observed for lipid biosynthesis. These data indicate that dichloroisoproterenol's reported effects on vacuole formation and processing in Tetrahymena are nonspecific with regard to phagocytic processes, but result from a general suppression of macromolecular synthesis. 相似文献