Individual differences in sensitivity to nicotine: implications for genetic research on nicotine dependence

Recent evidence suggests that cigarette smoking has a heritability index around 53%. While related research on underlying mechanisms also supports the idea that genetic factors contribute to nicotine dependence--as well as to cofactors such as substance use and mood disorders--the nature of the behavioral traits and biological capacity for reinforcement that constitutes vulnerability to nicotine dependence is not well understood. The present review explores the problem of why some people become highly nicotine dependent, others develop a pattern of occasional use, and still others avoid the drug entirely despite extensive exposure and widespread experimentation with tobacco in the population. Recent research--both infrahuman and human--suggests that vulnerability to nicotine dependence is related to high initial sensitivity to nicotine and that the development of tolerance is more rapid and self-administration more extensive in such individuals. Relevant findings from neuroscience and biobehavioral research are reviewed in order to identify variables and methodologies that might improve the reliability and validity of behavioral and molecular genetic studies on cigarette smoking. The integration of research in these areas may lead to new insights in the understanding of nicotine dependence as well as to improved techniques for prevention and treatment.     

N—80油井套管的生产工艺及发展

介绍了N-80油井套管目前的生产状况,采用的钢种及有关生产工艺,以及今后的发展方向.     

卫星通信高速数据传输纠错技术新进展

本文扼要介绍最近卫星通信高速数据传输中采用纠错编译码技术的新进展,说明120Mb/s TDMA/DSI系统中BCH(128,112)码,45Mb/s IDR R3/4 Viterbi译码,以及70Mb/s卷积码与Reed-Soloman码级联等三种典型纠错的生成多项式,并行编译码技术及性能。它们对于卫星通信传输高速数字图像信号是非常有用的。     

Colocalization of NADPH-diaphorase staining and VIP immunoreactivity in neurons in opossum internal anal sphincter

Nitric oxide and vasoactive intestinal polypeptide (VIP) are important inhibitory neurotransmitters mediating relaxation of the internal anal sphincter. The location and coexistence of these two neurotransmitters in the internal anal sphincter has not been examined. We performed a double-labeling study to examine the coexistence of nitric oxide synthase and VIP in the opossum internal anal sphincter using the NADPH-diaphorase technique which is a histochemical stain for nitric oxide synthase. In perfusion-fixed, frozen-sectioned tissue, VIP-immunoreactive neurons were labeled using immunofluorescence histochemistry. After photographing the VIP-immunoreactive neurons, nitric oxide synthase was labeled using the NADPH-diaphorase technique. Ganglia containing neuronal cell bodies were present in the myenteric plexus for the entire extent of the internal anal sphincter. VIP-immunoreactive and NADPH-diaphorase-positive neurons were present in ganglia in the myenteric as well as the submucosal plexuses. Most of the VIP-immunoreactive neurons were also NADPH-diaphorase positive. VIP and nitric oxide synthase are present and frequently coexist in neurons in the internal anal sphincter of the opossum. These neurons may be an important source of inhibitory innervation mediating the rectoanal reflex-induced relaxation of the sphincter. The demonstration of the coexistence of these two neurotransmitters will be of fundamental importance in unraveling their relationship and interaction in the internal anal sphincter as well as other systems.     

Effect of sample storage on quantitation of lipoprotein(a) by an enzyme-linked immunosorbent assay

This study evaluated the effect of storage on the quantitation of lipoprotein (Lp)(a) in 25 serum samples. Aliquots of serum were stored for up to three years at either -20 degrees C or -70 degrees C and Lp(a) subsequently analyzed using an enzyme-linked immunosorbent assay kit. Concentrations of Lp(a) declined during storage, and the temperatures employed elicited significantly different (P < 0.05) values within 12 mon which further diverged during three years of storage. Compared to baseline values, significant decreases (P < 0.05) in Lp(a) levels were evident after six months of storage at -20 degrees C with apparent losses (geometric mean) reaching 36.9% (95% confidence interval: 30.9%, 42.9%) after three years. Similarly, significantly lower (P < 0.05) Lp(a) values were recorded after six months of storage at -70 degrees C and at three years the decrease (geometric mean) was 19.1% (95% confidence interval: 14.3%, 24.0%). The losses, after three years, in terms of the arithmetic mean were 53.5 and 26.2% at -20 and -70 degrees C, respectively. Phenotype analysis suggested that large isoforms are more susceptible to degradation than smaller moieties. This may be related to the observation that apparent losses are reduced in samples containing over 8 mg/dL Lp(a). Nevertheless, Lp(a) levels in stored samples retained a strong correlation with the baseline values. These results must be considered specific for the storage conditions and analytical procedures employed.     

GSM风靡全球

GSM是欧洲开发的数字蜂窝移动电话标准。现已扩展到欧洲以外的亚洲、非洲、南美、中东以及澳大利亚等地区。有关专家预测,到2000年,欧洲的GSM移动电话用户将达到190O万甚至可达2300万。其发展前景甚为乐观。本文主要介绍当前GSM在世界各地的发展,并以表格的形式展示各地区的经营现状。     

纤维光学技术及其军事应用(待续)

本文介绍了纤维光学技术的研究进展及其在各类军事装备和军事环境中的应用。本文分四部分:1.纤维光学技术的研究进展;2.纤维光学技术在陆军各领域的应用;3.舰船上的光纤通信和水下光纤通信;4.空军和机载光纤通信及光纤雷达。     

In vitro study of the early membrane effects of C27-steroid hormone ecdysterone, immobilized on the nanodispersed magnetite surface]

The object of the study was to reveal the existence of receptor interactions of C27-steroid hormone ecdysterone with the surface of various cells (liver and spleen macrophages, thymus and spleen lymphocytes, erythrocytes and hepatocytes from rat organs) in experiments in vitro using ecdysterone immobilized on the nanodispersed iron surface (which did not penetrate the cell during observation) and the model of fast (during 15 s) activation of phospholipid signal system with ecdysterone. The parameters, which are characteristic of cell phospholipid signal system activation, were evaluated (the concentrations of free arachidonic acid, diene conjugates, tromboxane B2 and leukotriene C4) and its alteration in response to free and immobilized ecdysterone introduction in suspensins of intact cells and cells with the surface modified in vivo by pre-injection of antigen (human erythrocytes). Concurrent binding of immbilized ecdysterone with intact rat cells in the presence of free ecdysterone was also investigated. It was established that there are high-affinity ecdysterone-specific binding sites on the plasma membranes of all cells investigated, Kd estimated according to two different methods varied in the region of 10(-8)-10(-7) M. The characteristic features of the changes in parameters characteristic of phospholipid system activation were revealed to be queite similar in intact cells, as well as in cells with modified surfaces, under introduction of free ecdysterone and immobilized ecdysterone, which did not penetrate into cytosole. The data obtained point to the existence of ecdysterone receptors on the surface of cells plasma membranes and are indicative of the membrane effects as mechanisms of the early pregenomic phase of cells activation by ecdysterone.