两例补体第8成份β亚基缺陷家系患者的进一步分子遗传基础研究

目的　在白人群体中 ,导致人类补体第 8成份 β亚基缺陷的分子基础主要是在编码 β亚基基因的第 9外显子上发生碱基 C→ T的突变 ,从而形成终止密码 ,导致 C8β亚基不能完全合成。国外学者在两例 C8β亚基完全缺失的患者家系研究中 ,发现这两例β亚基缺失个体只是第 9外显子上碱基 C→ T突变的杂合子 ,现进一步寻找这两例 C8β亚基完全缺失的分子遗传学机理。方法　对两例 C8β亚基完全缺失患者的 C8β编码基因的全部 11个外显子的 PCR扩增产物进行 DNA测序分析并与正常人 DNA序列进行对比。结果　两例完全性 C8β亚基缺失患者的蛋白质编码基因中 ,分别在第 3外显子的 2 98和 388位置发现了 C→T突变 ,同时对这两个突变位点的家系分析也证实 ,位于第 3外显子上的这两个突变位点是独立于第 9外显子的突变而遗传。结论　所发现的两个突变位点均能形成终止密码而导致 C8β亚基合成提前终止 ,因此这两例患者 C8β亚基完全缺失的分子遗传学机理是由于编码 C8β亚基的基因在第 3和第 9外显子上同时发生了点突变 ,进而形成终止密码造成 C8β亚基合成终止所致。     

Caffeine and histamine-induced oscillations of K(Ca) current in single smooth muscle cells of rabbit cerebral artery

In the present experiment, we characterized the intracellular Ca²⁺ oscillations induced by caffeine (1 mM) or histamine (1–3 M) in voltage-clamped single smooth muscle cells of rabbit cerebral (basilar) artery. Superfusion of caffeine or histamine induced periodic oscillations of large whole-cell K⁺ current with fairly uniform amplitudes and intervals. The oscillatory K⁺ current was abolished by inclusion of ethylenebis(oxonitrilo)tetraacetate (EGTA, 5 mM) in the pipette solution. Caffeine- and histamine-induced periodic activation of the large-conductance Ca²⁺-activated K⁺ [K_(Ca)] channel was recorded in the cell-attached patch mode. These results suggest that the oscillations of K⁺ current are carried by the K_(Ca) channel and reflect the oscillations of intracellular Ca²⁺ concentration ([Ca²⁺]_i). Ryanodine (1–10 M) abolished both caffeine- and histamine-induced oscillations. Caffeine- induced oscillations were abolished by the sarcoplasmic reticulum Ca²⁺-adenosine 5-triphosphatase (Ca²⁺-ATPase) inhibitor, cyclopiazonic acid (10 M), and a high concentration of caffeine (10 mM). Inclusion of heparin (3 mg/ml) in the pipette solution blocked histamine-induced oscillations, but did not block caffeine-induced oscillations. By the removal of extracellular Ca²⁺, but not by the addition of verapamil and Cd²⁺, the caffeine-induced oscillations were abolished. Increasing Ca²⁺ influx rate increased the frequencies of caffeine-induced oscillations. Spontaneous oscillations were also observed in cells that were not superfused with agonists, and had similar characteristics to the caffeine-induced oscillations. From the above results, it is concluded, that in smooth muscle cells of the rabbit cerebral (basilar) artery, ryanodine-sensitive Ca²⁺-induced Ca²⁺ release pools play key roles in the generation of caffeine- and histamine-induced intracellular Ca²⁺ oscillations.     

极低频磁场对胞内钙振荡影响的机理分析

基于双钙库模型,本文以离子跨过细胞膜、细胞器膜迁移的几率作为细胞对电磁场的响应因子,来调制流过膜通道的离子的速率,进而影响细胞内钙离子的浓度。数值分析表明:在极低频磁场的作用下,一定能量因子下的频率条件或是一定频率因子下的能量条件可引起钙振荡形式的变化;窗效应是频率因子和能量因子共同作用的结果。     

TCRVβ基因谱系分析在AIDS疾病T细胞克隆性研究中的应用

对于T淋巴细胞TCRVB基因家族以及T细胞的克隆性的研究是近年的热点问题.通过对艾滋病人(模型)的TCRVβ基因谱系分析,测定特定CDR3长度及序列出现的频率能反映T细胞克隆扩增的程度和功能状态,进而有助于对MDS的临床诊断、免疫机制、药物或疫苗的治疗效果等的理解.     

Spontaneous tension oscillation in skinned bovine cardiac muscle

 Skinned fibres from bovine ventricles exhibited spontaneous tension oscillations when MgADP and inorganic phosphate (Pi) were added to the solution bathing fibres in the relaxed state (ADP-SPOC). A similar type of oscillation was observed at intermediate concentrations of free Ca²⁺ in the absence of MgADP and Pi (Ca-SPOC). To investigate the correlation between ADP-SPOC and Ca-SPOC, we constructed two-dimensional state diagrams of cardiac muscle using different concentrations of Pi (0–20 mM) and free Ca²⁺ [pCa=around 5 (+Ca²⁺), pCa=5.15–6.9 and +EGTA (–Ca²⁺)], with varying concentrations of MgADP (0–10 mM), with 2 mM MgATP and 2 mM free Mg²⁺ maintaining ionic strength at 0.15±0.01 M, pH 7.0, 25 °C. The three-dimensional (pCa-Pi-MgADP) state diagram thus obtained was divided into three regions, i.e. the contraction region in which tension oscillation was undetectable, the spontaneous tension oscillation (SPOC) region and the relaxation region. We found that the regions of ADP-SPOC and Ca-SPOC were continuously connected by a single oscillation region sandwiched between the contraction and relaxation regions. The state diagram, which encompasses physiological conditions, shows that the probability of SPOC is higher in cardiac muscle than in skeletal muscle. From these results, we suggest that, despite distinct ionic conditions, the molecular state of cross-bridges during SPOC is common to both ADP-SPOC and Ca-SPOC. Received 19 February 1996 / Received after revision: 16 July 1996 / Accepted: 14 August 1996     

Slow sleep oscillation, rhythmic K-complexes, and their paroxysmal developments

This paper presents the relations between the slow (< 1 Hz) oscillation (characterizing the activity of corticothalamic networks during quiescent sleep in cats and humans), sleep K-complexes, and some paroxysmal developments of sleep patterns. At the cellular level, the slow oscillation is built up by rhythmic membrane depolarizations and hyperpolarizations of cortical neurons. The EEG expression of this activity is marked by periodic K-complexes which reflect neuronal excitation. The slow oscillation triggers, groups and synchronizes other sleep rhythms, such as thalamically generated spindles as well as thalamically and cortically generated delta oscillations. We discuss the distinctness of the slow (< 1 Hz) and delta (1–4 Hz) oscillations. We also show that the slow cortical oscillation underlies the onset of spike-wave seizures during sleep by transforming the periodic K-complexes into recurrent paroxysmal spike-wave complexes.     

Sensitivity Analysis of Respiratory Parameter Estimates in the Constant-Phase Model

The constant-phase model is increasingly used to fit low-frequency respiratory input impedance (Zrs), highlighting the need for a better understanding of the use of the model. Of particular interest is the extent to which Zrs would be affected by changes in parameters of the model, and conversely, how reliable are parameters estimated from model fits to the measured Zrs. We performed sensitivity analysis on respiratory data from 6 adult mice, at functional residual capacity (FRC), total lung capacity (TLC), and during bronchoconstriction, obtained using a 1-25 Hz oscillatory signal. The partial derivatives of Zrs with respect to each parameter were first examined. The limits of the 95% confidence intervals, 2-dimensional pairwise and p-dimensional joint confidence regions were then calculated. It was found that airway resistance was better estimated at FRC, as determined by the confidence region limits, whereas tissue damping and elastance were better estimated at TLC. Airway inertance was poorly estimated at this frequency range, as expected. During methacholine-evoked pulmonary constriction, there was an increase in the uncertainty of airway resistance and tissue damping, but this can be compensated for by using the relative (weighted residuals) in preference over the absolute (unweighted residuals) fitting criterion. These results are consistent with experimental observation and physiological understanding.     

P>胰岛素样生长因子-1抑制β淀粉样蛋白25～35诱导的神经干细胞凋亡/P>

目的 观察β-淀粉样蛋白(Aβ)对神经干细胞(NSCs)增殖和凋亡的影响,探讨胰岛素样生长因子-1(IGF-1)对Aβ介导的NSCs毒性作用的保护机制.方法 从E14 SD大鼠大脑中分离神经干细胞,分别用Aβ、IGF-1和Aβ加IGF-1处理,锥虫蓝(trypan blue)染色确定细胞死亡数量和细胞死亡率,BrdU标记并分析细胞增殖能力,免疫细胞化学法鉴定神经干细胞和新生细胞,TUNEL技术检测凋亡细胞.结果 IGF-1处理时细胞死亡率低下,有大量BrdU阳性细胞生成,但无TUNEL阳性细胞.Aβ处理组细胞死亡率在6～48 h快速上升,并形成大量TUNEL阳性细胞.而IGF-1加Aβ处理时,细胞死亡率较Aβ组显著下降.TUNEL阳性细胞显著减少.结论 Aβ促进神经干细胞死亡和凋亡;而IGF-1促进神经干细胞增殖并抑制由Aβ诱导的神经干细胞凋亡.     

Tissue temperature oscillations in an isolated pig kidney during surface heating

In the present study, an isolated pig kidney was used to study tissue temperature oscillations due to vascular thermoregulation, frequently observed during hyperthermia treatments. The kidney was perfused with the distilled water pumped through the renal artery to simulate blood flow. When the local perfusion rate was increased with a time delay, temperature oscillations were observed in the kidney as its surface temperature raised linearly with time in a water bath. The magnitude of tissue temperature decreased as the flow rate increased during the surface heating. A 3D transient model was developed to predict the temperature oscillations, which was validated by the measurements. Using the model, relationships of the changes in perfusion rate and heating rate with temperature oscillations were investigated. It was found that the heating rate, and the magnitude and time delay of the flow response to the temperature elevation, each significantly affected tissue temperature oscillations. The magnitude of oscillation was primarily determined by the spatial gradient of temperature, while the oscillation type depended on the change of flow rate and the time delay. In conclusion, to accurately predict and control the tissue temperature distribution during hyperthermia treatment, understanding of the local perfusion change with respect to tissue temperature is essential. © 2002 Biomedical Engineering Society. PAC2002: 8719Pp, 8754Br, 8719Uv, 8710+e     

Caffeine induces periodic oscillations of Ca2+-activated K+ current in pulmonary arterial smooth muscle cells

The periodic oscillations of outward currents were studied in smooth muscle cells of the rabbit pulmonary artery. The combined stimuli of superfusion with 1 mM caffeine and depolarization of the membrane potential to 0 mV evoked periodic oscillations of outward currents with fairly uniform amplitudes and intervals. The oscillating outward currents induced by caffeine were dependent on intracellular Ca²⁺ concentration ([Ca²⁺]_i) and had a reversal potential near to the equilibrium potential for K⁺. So the oscillating outward currents are carried by K⁺ through Ca²⁺-dependent K⁺ channels (I _K(Ca)), and may reflect the oscillations of [Ca²⁺]_i. The oscillating outward currents were abolished, or their frequency reduced, by lowering external [Ca²⁺], Ca²⁺ channel blockers, or by 1 M ryanodine, indicating that: (1) there is a continuous influx of Ca²⁺ through the plasma membrane at a holding potential of 0 mV; (2) the periodic transient increases of [Ca²⁺]_i are ascribed to the rhythmic release of Ca²⁺ from ryanodinesensitive intracellular store by the mechanism of Ca²⁺-induced Ca²⁺ release (CICR). On the basis of the above results, we simulated the oscillation of [Ca²⁺]_i induced by caffeine, which is known to lower the threshold of CICR. The patterns of peak amplitude histograms of spontaneous transient outward currents (STOC) in the oscillating cells were different from those in non-oscillating cells. The amplitudes of STOC in the latter were more variable than those in the former. The oscillating outward currents were modulated by 1 M forskolin and 1 M sodium nitroprusside, but STOC were little affected. The above differences between STOC and oscillating outward currents suggest that the two currents are activated by the Ca²⁺ originating from different intracellular Ca²⁺ stores which are functionally heterogeneous.