Two residues that may ligate Ca2+ in transmembrane domain six of the plasma membrane Ca(2+)-ATPase

In order to identify Ca2+ ligands in the putative transmembrane domain 6 of the plasma membrane Ca2+ pump, amino acids Asn879, Met882, Asp883, and Ser887 were singly altered. Asn879, Met882, and Asp883 were chosen because the corresponding amino acids have been proposed as Ca2+ ligands in the sarcoplasmic reticulum Ca2+ pump (Clarke, D. M., Loo, T. W., and MacLennan, D. H. (1990) J. Biol. Chem. 265, 6262-6267). For the alterations, a fully active truncated version of the pump was used, because the interaction of Ca2+ with the pump could be studied without interference from calmodulin binding. The mutants at Asn and Asp did not carry out ATP-supported Ca2+ uptake and formed no acylphosphate from [gamma-32P]ATP, suggesting that, like the corresponding amino acids in the sarcoplasmic reticulum Ca2+ pump, these two are Ca2+ ligands. However, all the mutants at the position of Met882 showed some activity. Indeed, the Met882--> Ile mutant was fully active at a saturating Ca2+ concentration and only the K1/2 for Ca2+ activation was shifted slightly upward. Converting the Met to Thr (which is the corresponding residue in the sarcoplasmic reticulum Ca2+ pump) reduced the activity to 20% of the wild type, further emphasizing the differences between the two Ca2+ pumps. The mutant Ser887--> Ala was expressed in greater amounts than, and had a specific activity about 50% higher than, the wild type, indicating that this serine also could not be a Ca2+ ligand and could not replace the missing Thr at position Met882.     

Theoretical foundation of the 80/20 rule

A rigorous analysis of the 80/20 rule is made using an index for the observed values of the variables. Three important findings are identified. First, a sufficient condition is provided for Burrell's inverse relationship between minimum holdings and average circulation rate. Second, an indexed version of Lotka's law is used to derive a sufficient condition for Egghe's finding on the 80/20 rule. Third, through the computer simulations of the Simon-Yule model of Lotka's law, we identify the entry rate of new holdings as well as the number of circulations when the entry rate is a decreasing function to be crucial factors for the pattern of the 80/20-type curve.     

Mobility modeling, location tracking, and trajectory prediction inwireless ATM networks

Wireless ATM networks require efficient mobility management to cope with frequent mobile handoff and rerouting of connections. Although much attention has been given in the literature to network architecture design to support wide-area mobility in public ATM networks, little has been done to the important issue of user mobility estimation and prediction to improve the connection reliability and bandwidth efficiency of the underlying system architecture. This paper treats the problem by developing a hierarchical user mobility model that closely represents the movement behavior of a mobile user, and that, when used with appropriate pattern matching and Kalman filtering techniques, yields an accurate location prediction algorithm, HLP, or hierarchical location prediction, which provides necessary information for advance resource reservation and advance optimal route establishment in wireless ATM networks     

安居水电厂灯泡贯流式水轮发电机组的试运行

本文对安居水电厂2台灯泡贯流式水轮发电机组自投入试运行以来,出现的受油器壳体开裂、导叶接力器缸体和活塞拉伤、转轮桨叶传动拐臂连接销脱落、导叶外轴承座漏水、主轴工作密封漏水侵入水导轴承、锁锭装置固定螺钉剪断等故障的经过、原因分析及其处理办法进行了叙述。     

Some pharmacologic and toxicologic studies on Rhazya stricta decne in rats, mice and rabbits

1. This work examines some in vivo and in vitro pharmacologic and toxicologic effects of extracts of Rhazya stricta, a medicinal plant in the United Arab Emirates. 2. R. stricta extracts at doses of 0.1-10 mg reduced the mean arterial blood pressure (MBP) of anesthetized rats in a dose-dependent manner. The depressor effect was partially sensitive to atropine (5 microM). Although the MBP was reduced by 50% by both doses of extracts, the normal electrocardiogram pattern and the heart rate remained unaltered. 3. Acute treatment of rats with the lyophilized extract at doses of 4 g/kg produced a significant rise in insulin concentration. In streptozotocin-diabetic rats loaded orally with glucose (1 g/kg), R. stricta at doses of 8 g/kg produced significant decreases in plasma glucose concentration at 0.5 and 1 h after treatment. 4. Chronic treatment of rats and mice for 28 days with the lyophilized extract of R. stricta did not affect the plasma glucose or insulin concentration or any of the hematological or biochemical indices measured. 5. The extracts of R. stricta (0.5-4 g/kg) dose-dependently decreased the gastrointestinal transit time in mice by 4-50%. 6. The butanolic extract of R. stricta (1 and 2 g/kg) significantly reduced the carrageenan-induced increase in raw paw edema 3 and 4 h after the extract administration. 7. The rectal temperatures of normothermic and pyrexic rats were reduced significantly 0.5 and 1 h after administration of butanolic R. stricta at doses of 1 and 2 g/kg. 8. The butanolic extract of R. stricta at doses of 1 and 2 g/kg significantly increased the reaction time on the hot plate 30 and 60 min after administration to rats. 9. At concentration < 0.05 mg/ml (bath concentration), lyophilized water and butanol extracts of R. stricta potentiated the twitch responses induced by indirect electrical stimulation in the rat phrenic nerve diaphragm preparation. The responses were inhibited by concentrations > 0.05 mg/ml. Neostigmine (2 x 10(-4)M) did not alter these effects of the extracts. 10. R. stricta extracts dose-dependently decreased the force of contraction and heart rate of the isolated rabbit heart. Atropine (1 x 10(-5)M) had no effect on the inhibitory activity of these extracts. The lyophilized water extract (> 10 mg) and butanol extract (> 5 mg) produced irreversible inhibition and disturbances in the force of contraction and heart rate.     

Analysis of adhesive bonded composite lap joints with transverse stitching

The effect of transverse stitching on the stresses in the adhesive is investigated using an adhesive sandwich model with nonlinear adhesive properties and a transverse stitching model for adhesive bonded composite single-lap and double-lap joints. Numerical results indicate that, among all stitching parameters, thread pretension and stitch density have significant effect on the peel stresses in the adhesive; increase in the thread pretension and the stitch density leads to a decrease in peel stress in the adhesive, while an increase in other parameters generally results in a negligible reduction in peel stress. The effect of stitching was found to be negligible on the shear stresses in the adhesive. Thus it is concluded that stitching is effective for the joints where peel stresses are critical and ineffective for those where shear stresses are critical.     

数字程控交换机与专网中的多媒体通信

本文以一个多媒体通信应用VISIT为实例,介绍了多媒体通信在数字程控交换机及专网中的应用情况。     

Angiotensin II regulates the expression of plasminogen activator inhibitor-1 in cultured endothelial cells. A potential link between the renin-angiotensin system and thrombosis

Plasminogen activator-inhibitor C-1 (PAI-1) plays a critical role in the regulation of fibrinolysis, serving as the primary inhibitor of tissue-type plasminogen activator. Elevated levels of PAI-1 are a risk factor for recurrent myocardial infarction, and locally increased PAI-1 expression has been described in atherosclerotic human arteries. Recent studies have shown that the administration of angiotensin converting enzyme inhibitors reduces the risk of recurrent myocardial infarction in selected patients. Since angiotensin II (Ang II) has been reported to induce PAI-1 production in cultured astrocytes, we have hypothesized that one mechanism that may contribute to the beneficial effect of angiotensin converting enzyme inhibitors is an effect on fibrinolytic balance. In the present study, we examined the interaction of Ang II with cultured bovine aortic endothelial cells (BAECs) and the effects of this peptide on the production of PAI-1. 125I-Ang II was found to bind to BAECs in a saturable and specific manner, with an apparent Kd of 1.4 nM and Bmax of 74 fmol per mg of protein. Exposure of BAECs to Ang II induced dose-dependent increases in PAI-1 antigen in the media and in PAI-1 mRNA levels. Induction of PAI-1 mRNA expression by Ang II was not inhibited by pretreating BAECs with either Dup 753 or [Sar1, Ile8]-Ang II, agents that are known to compete effectively for binding to the two major angiotensin receptor subtypes. These data indicate that Ang II regulates the expression of PAI-1 in cultured endothelial cells and that this response is mediated via a pharmacologically distinct form of the angiotensin receptor.