Characteristics of pacemaker current in aged rat atrial myocytes

AIM: To investigate the characteristics of pacemker current (I_f) of atrium myocytes in aged rats. METHODS: Aged SD rats (22-24 months) were used in the study. The single atrium myocytes were isolated. I_f current was recorded by the technique of whole-cell patch clamp. RESULTS: The densities of I_f increased markedly in aged rat atrium myocytes compared with that in the cells of young rats. At the test potential of-150 mV, the average amplitude of I_f was (382±23)pA and the current density was (3.2±0.4)pA/pF, while the average amplitude of I_f in control group was (86.9±8.4)pA and the current density was (0.9±0.1)pA/pF,P<0.01. I_f current was augmented at negative hyperpolarzing test potential. Time constants of activation in aged and control cells were (230.2±14.4)ms and (670.5±23.6)ms, respectively. Furthermore, steady state curves in the elder cells was shifted to positive potentials and the voltages for half maximal activation were (-87.2±2.3)mV (aged cells) and (-104.4±6.3)mV (control cells). In contrast, the slope of activation curves and reversed potential of I_f were slightly different between aged cells and control cells. CONCLUSION: The amplitude and densities of I_f in atrium cells of aged rats were larger than that of control rats.     

Testing a low-quality urban compost as a fertilizer for arable farming

Abstract. A coarse urban compost, low in organic matter but mature, was tested for agricultural use. The response of Tewera ryegrass to this compost (applied at 12 and 48 t/ha) was evaluated in a field trial over two years. For a satisfactory yield the larger dose was necessary. This dose also gave greater values for the apparent recovery of N in both years. However, the N concentration in ryegrass was always below the sufficiency ranges proposed for N. The values of the potentially mineralizable N of the compost showed that the applied N at the greater rate of compost application was not sufficient to cover crop removal of N. In contrast, concentrations of P, S, K, Mn and Zn were within their corresponding sufficiency ranges. The dose of 48 t/ha did not increase Cu, Ni, Pb and Cd concentrations in the ryegrass.     

KNO3和抗坏血酸对老化草地早熟禾种子活力的影响

试验以贮藏5年自然老化的草地早熟禾(Poa p ratensis)'午夜'种子为材料,采用不同浓度的KNO3(0％,1.0％,2.0％ 和4.0％)和抗坏血酸(0,0.5,1.0和1.5mmol·L-1)引发0,1和2d后,回干进行发芽试验,测定发芽率、活力指数、平均发芽天数、芽长、芽鲜重、根长和根鲜重等指标,探究其对...     

村镇垃圾混合生物质衍生燃料(RDF)燃烧性能及氯化氢排放特性研究

村镇垃圾中不可降解物、可燃物所占的比例迅速增加,村镇生活垃圾问题已经成为村镇最急需解决的环境问题。试验将村镇垃圾与秸秆、稻壳等生物质按一定比例混合制成垃圾衍生燃料(RDF),利用热分析法研究燃烧特性,通过FTIR-IC法观测氯化氢的释放行为,结果表明村镇垃圾中所含有机氯基本上以氯化氢形式释放,HCl的释放量随温度上升而急剧增加,到550～650℃达到极值。     

Role of the molar ratio of kaliuretic peptide/atrial natriuretic peptide in elderly essential hypertension

AIM: To investigate the role of the molar ratio of kaliuretic peptide/atrial natriuretic peptide in elderly essential hypertension(EH). METHODS: The levels of plasma kaliuretic peptide (KP) and atrial natriuretic peptide (ANP) in 46 elderly patients with essential hypertension (EH) and 11 spontaneuos hypertension rats (SHR) were determined by radioimmunoassay. Meanwhile, the concentation of KP and ANP in myocardium of rats were observed as well. RESULTS: Compared with control group, the plasma levels of KP and ANP in EH group were no significantly different, but the molar ratio of KP/ANP were lowered significantly (P＜0.05). The levels of plasma KP and ANP in SHR were significantly higher than those in Wistar-Kyoto rats (WKY)(P＜0.01 and P＜0.05 respectively). However, the molar ratio of KP/ANP were markedly lower(P＜0.01). The concentration of KP in atrium was significantly higher than that in ventricle in SHR(P＜0.01). Moreover, there are no significantly different between SHR and SKY in atrium concentration of KP. CONCLUSION: KP and the molar ratio of KP/ANP maybe play an important role in pathogenesis of elderly essential hypertension.     

Effects of reafforestation techniques on the nutrient content,photosynthetic rate and stomatal conductance of Pinus Halepensis seedlings under semiarid conditions

A field experiment was carried out to evaluate the effect of different soil preparation techniques for Pinus halepensis afforestation on physiological parameters in Mediterranean summer conditions. The soil preparation treatments consisted of terracing (mechanical and manual) and the addition of an organic amendment (urban solid refuse). The mycorrhizal treatments consisted of nursery inoculation with Pisolithus arhizus and the addition of forest soil to the planting holes. Six years after planting the study revealed significant differences in heights and basal diameters, phosphorus and potassium concentrations in the leaves and photosynthetic rate and stomatal conductance. The pines grown in the manually prepared terraces were subjected to strong water stress, as reflected by the high A:g_s ratios and highest levels of phosphorus and potassium in leaves. Mechanical terracing and the addition of urban solid refuse produced a higher photosynthetic rate, and a combination of these treatments was particularly effective. Copyright © 2000 John Wiley & Sons, Ltd.     

青岛市城郊农村生活垃圾处理现状与对策

在对青岛市城阳区农村生活垃圾处理现状调查分析的基础上,提出了农村生活垃圾污染防治的对策及建议。主要包括：加强环保宣传教育,建立健全农村垃圾管理体系,推动垃圾分类,加强资源回收等。     

白色污染

随着世界经济的快速发展,白色污染的问题日益严重,引起了全球的关注.简述了白色污染的危害、现状以及防治的措施.