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21.
Long-term exposure to cocaine can cause persistent behavioral changes and alterations in neuronal function. One cocaine-regulated mRNA in the rat brain is the beta-1 subunit of the Na+/K(+)-ATPase pump. We examined both Na+/K(+)-ATPase function and expression after cocaine treatment of pheochromocytoma cells. One-hour exposure to cocaine did not alter Na+/K(+)-ATPase activity, as measured by the ouabain-sensitive component of rubidium uptake. Four days of cocaine resulted in an approximately 30% decrease in Na+/K(+)-ATPase activity. Western blot analyses demonstrated an approximately 25% decrease in levels of the beta-1 isoform, without changes in pump total alpha subunit levels. Treatment with dopamine type 1 or type 2 receptor agonists for the same period did not affect Na+/K(+)-ATPase activity. The serotonin-selective reuptake inhibitor paroxetine caused an approximately 45% decrease in rubidium uptake after 4 days, whereas pump function was not altered after treatment with either the dopamine-selective reuptake blocker nomifensine or the norepinephrine-selective reuptake blocker desipramine. Chronic treatment with both cocaine and LY 278,584, a serotonin type 3 receptor antagonist, did not replicate the cocaine-associated decrease in pump function. Long-term cocaine exposure regulates expression and function of the Na+/K(+)-ATPase pump in neuronal-like cells; this regulation is mediated in part via the serotonin type 3 receptor. Similar Na+/K(+)-ATPase pump regulation in vivo may selectively alter neuronal function in the mammalian brain. 相似文献
22.
MCS接枝共聚物的结构和形态 总被引:4,自引:0,他引:4
将甲基丙烯酸甲酯(MMA)、苯乙烯(S)在氯化聚乙烯(CPE)存在下进行悬浮接枝共聚,获得MCS树脂。本文着重考察了MCS树脂的化学结构及胶粒形态。结果表明,确实发生了接枝共聚。CPE用量、RSH含量、引发剂浓度、反应温度、溶胀时间及聚合转化率对MCS树脂的接枝率、接枝效率均有影响。MCS树脂是接枝共聚物、MMA/S共聚物与MMA均聚物的混合物,橡胶相CPE在MCS树脂中的分散情况为“海岛结构”, 相似文献
23.
电力滤波装置调谐,调试与测试方法的优化 总被引:3,自引:0,他引:3
本文通过对滤波器调谐、调试和测试实践中发现的问题,作了剖析.主要针对方法上的原因.作了具体的阐述,并通过对方法的优化,节省现场工作时间20%,滤波装置的调试精确度也提高达15%左右,取得的效果比效明显。 相似文献
24.
BACKGROUND: Deaths exhibit a seasonal pattern in most parts of the world. Analyses of deaths for the years 1972-1974 from the vital registration system of Matlab, Bangladesh, published in this journal 17 years ago, showed sinusoidal seasonal patterns. As death rates have declined in other nations, the seasonal pattern is attenuated. Death rates have declined substantially in Bangladesh in the past two decades. Thus, the present study examines monthly counts of deaths from Matlab data for a period 15 years later and tests the hypothesis of a decrease or shift in seasonality over time. METHODS: Trigonometric regression models were fit to monthly data by age and cause of death from the Matlab vital registration system for the years 1982-1990. A total of 20,328 death records were available for analyses. RESULTS: In the recent period significant sinusoidal seasonal patterns are found in all but one of the age and cause of death groups. Total deaths peak in the winter as do neonatal deaths but post-neonatal and child deaths are maximum in April and July respectively. Among cause groups, injury deaths (mostly attributed to drowning) show the greatest seasonal swing. The time of peak has only shifted for one age group--neonates--since the 1972-1974 period. The magnitude of the seasonal swing has declined significantly only for the neonatal age group and injury cause of death group. CONCLUSION: Marked seasonal patterns of deaths persist in the Matlab area of Bangladesh even as the level of mortality has declined. 相似文献
25.
JF Richmond S Lu JC Santoro J Weng SL Hu DC Montefiori HL Robinson 《Canadian Metallurgical Quarterly》1998,72(11):9092-9100
DNA vaccination is an effective means of eliciting strong antibody responses to a number of viral antigens. However, DNA immunization alone has not generated persistent, high-titer antibody and neutralizing antibody responses to human immunodeficiency virus type 1 (HIV-1) envelope glycoprotein (Env). We have previously reported that DNA-primed anti-Env antibody responses can be augmented by boosting with Env-expressing recombinant vaccinia viruses. We report here that recombinant Env protein provides a more effective boost of DNA-initiated antibody responses. In rabbits primed with Env-expressing plasmids, protein boosting increased titer, persistence, neutralizing activity, and avidity of anti-Env responses. While titers increased rapidly after boosting, avidity and neutralizing activity matured more slowly over a 6-month period following protein boosting. DNA priming and protein immunization with HIV-1 HXB-2 Env elicited neutralizing antibody for T cell line-adapted, but not primary isolate, viruses. The most effective neutralizing antibody responses were observed after priming with plasmids which expressed noninfectious virus-like particles. In contrast to immunizations with HIV-1 Env, DNA immunizations with the influenza virus hemagglutinin glycoprotein did not require a protein boost to achieve high-titer antibody with good avidity and persistence. 相似文献
26.
介绍了间断式半热滑轨的研制和应用过程,以及经过节能技术改造,用新型半热滑轨代替老式滑轨的使用。实践表明,不但解决了以往的水梁漏水的问题,而且使线C级品率提高了3.39%,每年可增产3500t线材,吨钢热涌单耗降低0.14GJ,年创经济效益239万元。 相似文献
27.
Six compounds were isolated from the fruits of Luffa cylindrica. They were identified as lucyosides C, E, F, H, a mixture of alpha-spinasterol and stigmasta-7,22,25-trien-3 beta-OH and a mixture of alpha-spinasteryl glucoside and delta 7,22,25-stigmasteryl-beta-D-glucoside by means of chemical evidence and spectral analysis. 相似文献
28.
Most algorithms of smoothing schedule compute the required bit rate of video transmission to satisfy all the transmitted data.
In this paper, our proposed tolerable data dropping algorithm can adjust transmitting data to fit available bit rate. MPEG-4
with fine grained scalability (FGS) can support partial data dropping to adapt to available bandwidth network. The algorithm
is based on the minimum variance bandwidth allocation (MVBA) algorithm proposed by Salehi et al. to compute the bit rate such
that still ensuring that the buffer never underflows and overflows for MPEG-4 FGS streams under the limited bandwidth resource.
We prove that our proposed algorithm, named MVBADP, is smoother than the MVBA algorithm. The experimental results show the
peak rate, the number of rate changes, and the ratio of total dropping data, and the PSNR for four test sequences with different
content characteristics. They are varied by buffer sizes and tolerable dropping ratios. We found that the MVBADP algorithm
can reduce the peak rate and the number of changes when the transmitted data are dropped by tolerable dropping ratio, especially
on the video sequences with the high motion and complex texture characteristic and larger size change of the consecutive frame. 相似文献
29.
“绕射积分偏移”的过程一直都是用绕射波收敛理论来描述的.但是这个理论不能解释为什么经过“绕射积分偏移”的剖面会有信噪比降低和弧形干扰的现象.在这时,我们用一个简单的数学模型,并理想化了一些条件,弄清了“绕射积分偏移”成像的真正原理.我们发现在任一CDP点下面的反射界面点的位置应与某一双曲线的顶点时间相当,这个双曲线正好处在与相应的反射t_0剖面上各道波至所形成的直线相切的位置上.在此结果的基础上,本文提出了减少干扰和改善剖面质量的有效措施.我们希望它能尽早为实际工作所采用.另外,本文也对目前流行的几种类型的所谓“克希霍夫积分偏移”进行评述并指出它们的缺点. 相似文献
30.