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排序方式: 共有182条查询结果,搜索用时 15 毫秒
1.
BZ Packard 《Canadian Metallurgical Quarterly》1994,1222(2):159-163
Previously, it was shown that Oncoimmunin-M (OI-M), a recently identified tumor cell-derived 36 kDa protein, is able both to inhibit the proliferation of the human promyelocytic leukemic cell line HL-60 while maintaining viability in culture and to induce a bimodal distribution of CD11b, the alpha chain of the integrin MAC-1, on the cell surface (Packard, B.Z. and Komoriya, A. (1993) J. Biol. Chem. 268, 6356-6363). Now, data which reveal that exposure of HL-60 cells to this factor also brings about an increase in the mean level of surface expression of CD11c, the alpha chain of another leukocyte integrin (p150,95), but leaves CD11a, the alpha chain of the third leukointegrin (LFA-1), virtually unchanged (< 10%) are presented. Comparison of motility studies of OI-M-treated HL-60 bulk populations with control bulk populations demonstrates coinduction of CD11b and CD11c surface upregulation with chemotactic responsiveness to a gradient of the chemoattractant human C5a. Separation of motile from nonmotile cell subpopulations after exposure to C5a further reveals that individual cells which respond to this chemoattractant express increased levels of both CD11b and CD11c relative to unresponsive cells. These data correlate the upregulation of leukointegrins MAC-1 and p150,95 by a tumor cell-derived protein on a preterminally differentiated myeloid cell with chemotactic responsiveness to human C5a. 相似文献
2.
Examined the effect of lesions of the caudate nucleus or fimbria-fornix on the acquisition of 2 water maze tasks. In both tasks, 2 rubber balls with different visual patterns were used as cues. The correct cue was attached to a submerged rectangular platform and could be mounted by an animal to escape the water. The incorrect cue was attached to a thin round pedestal and could not be mounted. In a spatial version of the task, the correct cue was located in the same quadrant of the maze on all trials, whereas the visual pattern on the cue was varied from trial to trial. Lesions of the fornix, but not the caudate nucleus, impaired acquisition of this spatial task in relation to control animals. In a simultaneous visual discrimination version of the task, the correct cue on all trials was one with a specific visual pattern, and the spatial location of the correct cue was varied from trial to trial. Lesions of the caudate nucleus, but not the fornix, impaired acquisition of this visual discrimination task in relation to control animals. The double dissociation observed supports the hypothesis that the hippocampus and caudate nucleus are parts of systems that differ in the type of memory they mediate. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
3.
Alexander Gerianne M.; Packard Mark G.; Hines Melissa 《Canadian Metallurgical Quarterly》1994,108(2):424
Evidence from mammalian species, including humans, suggests that testosterone (TST) enhances motivational aspects of sexual behavior, although the mechanism by which TST exerts this effect is unknown. The hypothesis that increases in plasma TST have rewarding affective properties was examined. Acute elevations of plasma TST were induced in intact male rats by systemic administration of a recently developed testosterone-hydroxypropyl-β-cyclodextrin inclusion complex that mimics pulsatile release of the hormone. In a conditioned-place-preference paradigm, rats displayed a preference for an environment previously paired with TST administration (800 μg/kg and 1,200 μg/kg) as opposed to an environment paired with saline administration, indicating that TST has rewarding affective properties. The findings suggest that TST may enhance motivational aspects of mammalian sexual behavior by facilitating acquisition or expression of learned associations between environmental stimuli and sexual activity. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
4.
Prostaglandins act through specific receptors to stimulate cyclic AMP formation which inhibits platelet activation and relaxes vascular smooth muscle. We have used RT-PCR combined with Southern blot analysis to determine the subtypes of prostaglandin receptor on platelets. Platelets expressed the EP4 rather than the EP2 prostaglandin EP receptor subtype, whereas vascular smooth muscle cells predominantly expressed the EP2 receptor. The IP receptor, which binds prostacyclin and couples to stimulation of adenylyl cyclase, and three isoforms of the inhibitory EP3 receptor were equally expressed in platelets, HEL cells and umbilical artery smooth muscle cells. The EP3-II isoform showed variation in level of expression among the three cell types. As a positive control for the presence of platelet RNA, PCR was performed using primers specific for the alpha chain of the platelet membrane glycoprotein Ib. As a negative control for the absence of T and B cell contamination in the platelet RNA, PCR was performed using primers specific for the cell specific cluster determinants CD2 (a T-cell marker) and CD20 (a B-cell marker). The finding that platelets express both stimulatory and inhibitory prostaglandin receptors provides confirmation of a homeostatic model of regulation of platelet adenylyl cyclase previously proposed. 相似文献
5.
MG Packard 《Canadian Metallurgical Quarterly》1998,34(2):126-139
The present paper provides a review of recent research carried out in this laboratory investigating the effects of posttraining peripheral and intrahippocampal injection of estradiol on memory in rats, and estradiol-acetylcholine interactions in memory modulation. Ovariectomized rats received an eight-trial training session in a hippocampal-dependent hidden platform water maze task. Immediately following training, rats received a posttraining peripheral or intrahippocampal injection of estradiol-cyclodextrin complex or vehicle. Twenty-four hours later rats were returned to the maze for a retention test session, and latency to escape was used as a measure of memory for the previous day's training. Peripheral posttraining injection of estradiol enhances memory relative to vehicle-treated rats. Injections of estradiol given 2 h posttraining has no effect on retention, indicating a time-dependent effect of estradiol on memory storage processes. A time-dependent memory enhancing effect of posttraining intrahippocampal injections of estradiol has also been observed in both male and ovariectomized female rats. The memory enhancing effect of peripheral posttraining injection of estradiol in ovariectomized rats is blocked by a subeffective dose of the acetylcholine muscarinic receptor antagonist scopolamine, suggesting that estradiol interacts with cholinergic systems in memory modulation. Concurrent peripheral posttraining injection of a subeffective dose of estradiol and a subeffective dose of the cholinergic agonist oxotremorine produces a synergistic memory enhancing effect. The findings suggest that: (1) estradiol selectively influences memory storage independent of an effect on nonmnemonic processes, (2) the hippocampus is a potential neuroanatomical site of action mediating estrogenic effects on memory, and (3) estradiol interacts with cholinergic systems in memory modulation. 相似文献
6.
Seiler P. Topcu U. Packard A. Balas G. 《Automatic Control, IEEE Transactions on》2009,54(10):2410-2416
Robust stability of linear time-invariant systems with respect to structured uncertainties is considered. The small gain condition is sufficient to prove robust stability and scalings are typically used to reduce the conservatism of this condition. It is known that if the small gain condition is satisfied with constant scalings then there is a single quadratic Lyapunov function which proves robust stability with respect to all allowable time-varying perturbations. In this technical note we show that if the small gain condition is satisfied with frequency-varying scalings then an explicit parameter dependent Lyapunov function can be constructed to prove robust stability with respect to constant uncertainties. This Lyapunov function has a rational quadratic dependence on the uncertainties. 相似文献
7.
We extend the traditional notion of passivity to a forced system whose equilibrium is dependent on the control input by defining equilibrium-independent passivity, a system property characterized by a dissipation inequality centered at an arbitrary equilibrium point. We provide a necessary input/output condition which can be tested for systems of arbitrary dimension and sufficient conditions to certify this property for scalar systems. An example from network stability analysis is presented which demonstrates the utility of this new definition. We then proceed to numerical certification of equilibrium-independent passivity using sum-of-squares programming. Finally, through numerical examples we show that equilibrium-independent passivity is less restrictive than incremental passivity. 相似文献
8.
Many mothers with children under age 6 are employed and it is not usually feasible for a parent to stay home with a child who is mildly ill. Such ill children likely remain in child day care programs. The extent to which this occurs and the management of these children in family day care was studied. Over the course of a year, 1 to 3 visits were made to 714 family day care homes in order to survey providers. With enrollments ranging between 0 and 18 children per day care home at the time of each visit, information on 3,630 "child enrollment days" was collected. The median age of children in care was 2 years. An average of 16% of all children were ill on any one day (with seasonal variation); 1% were injured. Of ill children, 82% attended day care that day, 49% had contacted a physician about that illness, and 28% were administered a medication at the day care setting. Twenty-one percent of children receiving medication in day care had no contact with a physician for that illness. These data show that mild childhood illnesses are routinely managed by child day care providers. Physicians who traditionally limit their illness-management education to parents need to recognize the health education and consultation needs of day care providers. 相似文献
9.
J. A. Hoffmann K. Penanen J. C. Davis R. E. Packard 《Journal of Low Temperature Physics》2004,135(3-4):177-202
We present results of a study of third sound in thick 4He films in circular resonator geometry. Frequency and line shapes of third sound resonances are measured for temperatures between 0.3 and 2.1 K in saturated films approximately 30 nm thick. From these measurements we calculate the attenuation of the sound. We find that the attenuation at a given temperature is a function of history of the film, strongly affected by such events as large, sudden (more than milli-Kelvin per second) temperature spikes. We also observe variable frequency splitting of resonances, indicating trapped circulation. Our measurements, taken together with other reported attenuation experiments, are incompatible with dissipation mechanisms dependent on thermodynamic properties alone. Measurements indicate a linear dissipation mechanism, inconsistent with vortex drag and re-connection models. We conclude that high attenuation values, evidence of trapped circulation, and variation in attenuation values support the hypothesis that thick films of 4He contain high densities of remnant quantized vortices. The vortex populations suggested by trapped circulation are consistent with proposed linear dissipation mechanisms due to vortex-normal fluid interactions and vortex dimple drag. 相似文献
10.
We develop analytical and numerical conditions to determine whether limit cycle oscillations synchronize in diffusively coupled systems. We examine two classes of systems: reaction–diffusion PDEs with Neumann boundary conditions, and compartmental ODEs, where compartments are interconnected through diffusion terms with adjacent compartments. In both cases the uncoupled dynamics are governed by a nonlinear system that admits an asymptotically stable limit cycle. We provide two-time scale averaging methods for certifying stability of spatially homogeneous time-periodic trajectories in the presence of sufficiently small or large diffusion and develop methods using the structured singular value for the case of intermediate diffusion. We highlight cases where diffusion stabilizes or destabilizes such trajectories. 相似文献