心血管疾病患者血浆CF 6的含量变化

目的:研究常见心血管疾病中血浆内线粒体偶联因子6(mitochondrial coupling factor 6,CF6)含量的变化,以探讨CF6在其发病中的意义.方法:放射免疫分析检测血浆CF6的含量(pg/ml).结果:正常健康人群血浆CF6含量为210.5±33.7pg/ml.原发性高血压患者为307.5±95.5pg/ml,急性心肌梗塞患者为364.5±105.1,心力衰竭患者为351.2±104.6;睡眠呼吸暂停综合征患者为351.9±87.1,原发性高血压伴糖尿病患者为466.4±136.3,p＜0.01,与正常人比较均明显升高(均p＜0.01或p＜0.05);稳定性心绞痛患者为266.3±69.3,心律失常患者为258.8±80.1,有上升趋势,但无统计学明显差异(p＞0.05),肺动脉高压患者降低(159.3±122.8,p＞0.05).结论:原发性高血压、急性心肌梗塞、心力衰竭、睡眠呼吸暂停综合征患者血浆CF6含量明显升高,并与病情严重程度有关,提示CF6可能在其病理生理过程中发挥着重要的作用,对于变化的机制及其意义有待于深入研究.     

Is calmodulin involved in the regulation of gap junction permeability?

The cell-to-cell channels of gap junctions mediate the direct exchange of ions and small metabolites between neighboring cells. A number of studies have shown that these channels close when the intracellular free calcium or hydrogen concentration increases, the result being cell-to-cell uncoupling. Since most of the calcium-activated biological phenomena are mediated by calmodulin (CaM), an obvious question is whether or not CaM is involved in the mechanism of cell coupling regulation. Data from the present study, showing the inhibitory effects of a calmodulin blocker on electrical uncoupling in Xenopus embryo cells, suggest a possible CaM participation in the uncoupling mechanism.     

Fooling the brain into thinking it sees both hands moving enhances bimanual spatial coupling

This study examined the hypothesis that the mirror reflection of one hands movement directly influences motor output of the other (hidden) hand, during performance of bimanual drawing. A mirror was placed between the two hands during bimanual circle drawing, with one hand and its reflection visible and the other hand hidden. Bimanual spatial coupling was enhanced by the mirror reflection, as shown by measures of circle size. Effects of the mirror reflection differed significantly from effects of vision to one hand alone, but did not differ from a control task performed in full vision. There was no evidence of a consistent phase lead of the visible hand, which indicates that the observed effects on spatial coupling were immediate and not based on time-consuming feedback processes. We argue that visual mirror symmetry fools the brain into believing it sees both hands moving rather than one. Consequently, the spatial properties of movement of the two hands become more similar through a process that is virtually automatic.     

The time course of cross-talk during the simultaneous specification of bimanual movement amplitudes

 We investigated the time course of the amplitude specification of rapid bimanual reversal movements (lateral displacements on two digitizers). To this end we used the timed-response paradigm in which the response has to be initiated synchronously with an auditory signal. Information about the required amplitudes was presented at various times before the synchronization signal. Consistent with previous results, the progression of amplitude specification was reflected in the dependence of the amplitudes of the reversal movements on the time interval between amplitude information and synchronization signal. Same or different amplitudes for the hands were used to examine cross-talk at the programming level of the two-level model of intermanual interference. The results indicate the existence of cross-talk in particular at short intervals between information about amplitude and movement initiation. This is consistent with the notion that cross-talk between concurrent processes of amplitude specification is transient and vanishes as the time available for motor programming increases. Received: 28 August 1996 / Accepted: 10 July 1997     

The late component of L-type calcium current during guinea-pig cardiac action potentials and its contribution to contraction

 L-Type Ca²⁺ current (I _Ca,L) elicited during the action potential (AP) of guinea-pig ventricular myocytes exhibits an early and a late component. The whole-cell patch-clamp technique was used to characterize the process regulating the late I _Ca,L component and to assess its contribution to excitation-contraction coupling. A stepwise decrease in repolarization rate of AP-like voltage-clamp pulses led to an exponential increase in Ca²⁺ charge carried by I _Ca,L. This saturation behaviour was significantly reduced or absent when Ba²⁺ or monovalent cations were used as charge carriers, which suggests that the late component of I _Ca,L is controlled mainly by Ca²⁺-dependent processes. Simultaneously recording I _Ca,L and zero-load shortening or the internal Ca²⁺ concentration (fura-2) revealed that Ca²⁺ carried by the late component of I _Ca,L markedly contributes to the Ca²⁺ content of the sarcoplasmic reticulum (SR). Reducing the charge transfer by late I _Ca,L during a series of AP-like conditioning clamp pulses by 48% reduced the shortening amplitude during a subsequent test stimulation by 56%. This relationship was absent during long rectangular depolarizing conditioning clamps, during which Na⁺/Ca²⁺ exchange increased its influence on SR Ca²⁺ loading. The late component of I _Ca,L developed only a minor direct influence on the simultaneous cell shortening. Thus, the main contribution of the late I _Ca,L component is to supply Ca²⁺ for SR loading. Received: 5 November 1997 / Received after revision: 12 June 1998 / Accepted: 15 June 1998     

Stochastic and Coherence Resonance in an In Silico Neural Model

We show that it is possible for chaotic systems to display the main features of stochastic and coherence resonance. In particular, a model of coupled nonlinear oscillators which emulates the transmembrane voltage activities in CA3 neurons, operating in a chaotic regime and in the presence of noise, can exhibit coherence resonance and stochastic resonance. Certain firing frequencies become more "rhythmic" for some optimal values of noise intensity. The effect of noise in different coupling pathways is investigated. We found that the effect of coherence resonance and stochastic resonance are more prominent if noise is presented in either electric field or gap junction coupling pathways. Frequency sensitivity of the model is investigated as a preliminary step in illustrating the principles of possible epileptic seizure control strategies using "chaos control" concepts. Significant effects of stochastic resonance are observed in the 4-8 Hz range. Weaker effects can be found in the 1-4 Hz and 8-10 Hz ranges whereas 0.5 Hz does not exhibit any resonance phenomenon. Our results suggest that: (a) Stochastic resonance could enhance the intrinsic 4-8 Hz rhythms in CA3 neurons more prominently via field coupling pathways. It could also help explain why some reported seizure control strategies using pulse-trains would only be effective at 0.5 Hz. (b) Stochastic resonance-like behavior can occur in the gamma range only if noise is presented via chemical synaptic pathways.     

Voluntary Heart Rate Control During Static Muscular Effort

To test the hypothesis that voluntary heart rate (HR) control is possible with simultaneous muscular effort, 8 male subjects were trained in feedback assisted bidirectional HR control, and also practiced hand grip exercises requiring different levels of effort for 3 consecutive daily sessions. In a fourth session subjects were required to increase and decrease HR while simultaneously performing muscle contractions of 0%, 10%, 30% and 50% of maximum voluntary contractions. Substantial and reliable variations in HR were produced by instructions and by muscular effort during the first 3 sessions; and in the fourth session bidirectional HR control continued even with the relatively elevated baselines induced by muscular effort. Concomitant chin EMG levels did not vary with degree of muscular effort nor with instructions to increase or decrease HR, but increased over the course of any type of trial. Discussion suggests the use of artificially elevated baselines as a strategy for studying HR deceleration and concludes that the present study provides strong evidence of subjects' abilities to voluntarily control HR during muscular effort. This conclusion lends support to the notion that biofeedback therapies may be of clinical utility in real life by modulating the eliciting effects of stressors.     

Ionophore A23187 can mimick the changes in membrane permeability that occur during acetylcholine-stimulation of pancreatic acinar secretion

Acetylcholine (ACh) released from vagal terminals increases the permeability of the pancreatic acinar membrane to Na⁺ and Ca²⁺ ions. In this report, we compare the induced changes in intracellular Na⁺ and Ca²⁺ electrode potentials (E_Na and E_Ca) due to ACh-stimulation of acini with those observed during stimulation with the calcium ionophore, A23187, which mimicks the action of ACh on pancreatic secretion. Stimulation with ACh concentrations varying from 10^–8 to 10^–5 M and with A23187 concentrations of 10^–6 and 10^–5 M caused parallel increases in cytosolic Ca²⁺ and Na⁺ ([Ca]_i, [Na]_i). The magnitude of the increases in [Ca]_i and [Na]_i due to A23187-stimulation further indicate that when presented with a calcium challenge the acinar cells continue to regulate [Ca]_i close to physiological levels and suggest that the observed increases in ionized calcium could reflect much larger increases in complexed Ca²⁺. ACh-stimulation following removal of either extracellular Na⁺ or Ca²⁺ ions, eliminated the intracellular increases found when the removed ions is present, but did not affect the increases usually found with the other ion. The independence of the permeability changes to either the presence of Ca²⁺ or Na⁺ indicates the ACh-induced currents carried by Na⁺ and Ca²⁺ are also independent. The selective translocation of Na⁺ and Ca²⁺ during acetylcholine-stimulation in a manner analogous to the changes observed when ionophore A23187 was used as stimulus, indicates the ability of the activated acinar membrane to function as an ionophore.