Electrophysiological and arrhythmogenic effects of intramyocardial bone marrow cell injection in patients with chronic ischemic heart disease

BACKGROUND: Bone marrow cell injection has been introduced to treat patients with ischemic heart disease. However, focal application of bone marrow cells may generate an arrhythmogenic substrate. OBJECTIVES: To assess the electrophysiological and arrhythmogenic effects of intramyocardial bone marrow cell injection in patients with chronic myocardial ischemia. METHODS: Bone marrow was aspirated in 20 patients (65+/-11 years, 19 male) with drug-refractory angina and myocardial ischemia. Electroanatomical mapping (NOGA, Biosense-Webster, Waterloo, Belgium) was performed during mononuclear cell isolation. Areas for cell injection were selected based on the localization of ischemia on SPECT. These areas were mapped in detail to evaluate local bipolar electrogram duration, amplitude and fragmentation. Mononuclear cells were injected in the ischemic area with the NOGA system. SPECT and electroanatomical mapping were repeated at 3 months. Holter monitoring was repeated at 3 and 6 months. RESULTS: SPECT revealed a decrease in the number of segments with ischemia (3.5+/-2.5 vs. 1.1+/-1.0 at 3 months; P<0.01) and an increased left ventricular ejection fraction (44+/-13% vs. 49+/-17% at 3 months; P=0.02). The number of ventricular premature beats remained unchanged (10+/-24x10(2)/24h vs. 8+/-23x10(2)/24h at 3 months (P=NS) and 12+/-30x10(2)/24h at 6 months (P=NS)). At 3 months follow-up, bone marrow cell injection did not prolong electrogram duration (15.9+/-4.6 ms vs. 15.6+/-4.0 ms; P=NS), decrease electrogram amplitude (3.8+/-1.5 mV vs. 3.8+/-1.5 mV; P=NS), or increase fragmentation (2.0+/-0.5 vs. 1.9+/-0.4; P=NS). CONCLUSION: Intramyocardial bone marrow cell injection does not increase the incidence of ventricular arrhythmias and does not alter the electrophysiological properties of the injected myocardium.     

Regulation of spontaneous activity and oscillatory spike firing in rat midbrain dopamine neurons recorded in vitro

Intracellular recordings were obtained from identified dopamine (DA) neurons in rat midbrain slices maintained in vitro. DA neuron membranes exhibited pronounced instantaneous and time-dependent anomalous rectification that showed evidence of maximal activation at average membrane potentials of -63 and -78 mV, respectively. Action potentials were followed by prominent afterhyperpolarizations (AHP) that consisted of two components. The fast component showed evidence of inactivation at -63 mV independent of the initial membrane potential, whereas the longer-duration, later component increased in amplitude at hyperpolarized potentials. Unlike DA neurons recorded in vivo, there was no evidence of spike frequency adaptation or summation of AHPs with prolonged depolarization-induced spike trains. Spontaneous spike discharge occurred via an endogenous pacemaker potential that was dependent on both TTX-sensitive and cobalt-sensitive processes. Hyperpolarizing prepulses could activate rebound pacemaker discharge, but this rebound activity was progressively blocked with larger-amplitude hyperpolarizing prepulses. DA neurons recorded in the anesthetized animal, freely moving animal, and in vitro preparations have been shown to exist in two states of activity: 1) spontaneously discharging action potentials or 2) hyperpolarized, quiescent, and nonfiring. Furthermore, although it is rare to find DA neurons in the untreated animal in transitional states of activity, quiescent neurons can be activated by stimuli that place a demand on the DA system. The evidence presented here is consistent with the hypothesis that the special combination of membrane properties of DA neurons contribute to the segregation of their activity into active or inactive states.     

心脏传导的变异性裂隙现象

在连续３６１例患者心内电生理检查中，发现４例有心脏传导的裂隙现象。其特点表现为激动传导方向上远端平面相对不应期（ＲＲＰ）长，程序刺激中先出现传导延缓，随后近端平面也进入ＲＲＰ使传导变为延缓，激动经过近端平面延缓传导后，到达远端平面时其已脱离了ＲＲＰ，使已经在远端传导延缓的情况变为传导正常，与经典的裂隙现象相比，这种裂隙现象的发生机制，与心内电图的表现均有不同，暂定名为变异性裂隙现象。     

Modulation of Rat Striatal Glutamatergic Response in Search for New Neuroprotective Agents: Evaluation of Melatonin and Some Kynurenine Derivatives

Melatonin attenuates the excitatory response of striatal neurons to sensorimotor cortex (SMCx) stimulation, which may be the basis for its neuroprotective role. Searching for new compounds with melatonin-like properties, the effects of several kynurenine derivatives in the response of the rat striatum to SMCx stimulation were studied using electrophysiological and microiontophoretical techniques. Melatonin iontophoresis (−100 nA) significantly attenuated the striatal excitatory response in 89.4% of the recorded neurons, showing excitatory properties in the other 10.6%. Compound A [2-acetamide-4-(3-methoxyphenyl)-4-oxobutyric acid] (−100 nA) displayed similar attenuating effects (86.7% of neurons inhibited vs. 13.3% excited). Compound B [2-acetamide-4-(2-amine-5-methoxyphenyl)-4-oxobutyric acid] (−100 nA) was more potent than melatonin itself to attenuate the excitatory response in 100% of the recorded neurons. Compound C [2-butyramide-4-(3-methoxyphenyl)-4-oxobutyric acid] (−100 nA) significantly increased the excitatory response in 84.2% of the recorded neurons, showing attenuating effects on the other 15.8% of the neurons. Interestingly, compound C iontophoresis excited the neurons in which melatonin had attenuating properties, whereas it inhibited the neurons showing excitatory responses to melatonin. These data suggest melatonin inverse agonist properties for compound C. Also, the effects of compounds B and C appeared immediately after they were iontophoretized, whereas both melatonin and compound A onset latencies were longer (2–4 min). The lack of latency shown by these melatonin analogs points to the possibility that melatonin itself was metabolized before producing its effects on striatal neurons. The results show a family of structurally-related melatonin analogs that may open new perspectives in search for new neuroprotective agents, including its clinical potentiality.     

Isochronic transplantation of neonatal grafts in the visual cortex of cats: responsiveness,ocular dominance and specificity of cortical cells to visual stimulation

Summary The visual cortex of adult cats was studied physiologically following neonatal isochronic transplantation of grafts from areas 17,18, which were placed homotopically, in order to reveal their functional integration and thus possible repairing of damaged cortical neuronal circuits. Three homograft cats, in which transplantation was carried out between siblings (228 cortical cells) were compared to 4 animals receiving reimplanted autografts of the equivalent size (131 cells) as well as 3 animals with analogous sectioning of the visual cortex (162 cells) (pseudograft controls). The location of the boundaries between the transplant region and the host were determined using the Nissl's method for staining histological cross sections. Extracellular unit recording revealed typical waveform of the action potentials in the transplanted region and in the surrounding host tissue of all groups of cats. Visual responsiveness in the homograft cats was 17.5% in the transplanted region and 80.4% in the unoperated hemisphere; the corresponding results were 40.3% for the transplanted region and 82.2% for the unoperated hemisphere in the autografts and 23.1% and 73.4% in the pseudografts. The specificity of the cells to visual stimulation as expressed by their orientation and direction specificity, indicated preservation of these properties in the transplanted cats. While all responsive cells in the transplanted region of the homografts were orientation specific, their proportion was 60% in the autografts and 55.5% in the analogous region in the pseudograft controls. As to the direction specific cells, their performance in the grafted region of the grafted cats was even much higher than that of the pseudograft controls. The ocular dominance distribution of the cells showed preservation of binocularity in the transplanted region (90.0% binocular cells) of the homografts; it was however smaller in the equivalent region of the autografts (65.0%) and remarkably reduced (20.0%) in the pseudografts. It was concluded that despite the deafferentation induced during the transplantation procedure, a remarkable visual responsiveness was found in the transplanted region, indicating postoperative recovery. However, the cells there were mainly affected in their activity and less in their specificity to visual stimulation.     

术中电生理检测在肘管综合征的应用

目的 :探讨术中电生理监测在肘管综合征手术中的临床应用价值。方法 :对25例肘管综合征手术患者进行尺神经松解前后的电生理术中监测。结果 :术中尺神经肘管松解前后 ,传导速度提高50% ,潜伏期缩短30%,其中传导速度的改善有显著意义(P<0.05)。结论 :传导速度是较敏感的术中监测参数。肘管综合征术中应用电生理检测有一定临床意义。     

Passive electrical properties of motoneurons in aged cats following axotomy

The objective of this study was to determine whether the aging process influences the changes in the electrophysiological properties of motoneurons that occur as a consequence of axotomy. Accordingly, using intracellular recording and stimulating techniques, the basic electrical properties of control (unaxotomized) and axotomized spinal cord motoneurons of aged cats were determined. Compared with control motoneurons, axotomized motoneurons exhibited increases in input resistance (R_in), membrane time constant (τ_b) and the equalizing time constant (τ_c). While the electrotonic length (L) remained unchanged, axotomy induced a decrease in the total cell capacitance (C_cell. The post-axotomy reduction of C_cell indicates that the motoneuron surface area was reduced and the increased membrane time constant indicates that there was an increase in membrane resistivity (R_m). The post-axotomy conservation of L accompanied by an increase in R_m suggests that aged axotomized motoneurons undergo geometrical changes. Furthermore, calculations based on cable theory suggest that the diameter of the equivalent cylinder (d) decreased following axotomy, whereas the equivalent cylinder length (l) remained unaffected. It is concluded that axotomy produces significant alterations in the soma-dendritic portion of aged spinal motoneurons, as indicated by the changes found in their passive electrophysiological properties, and that the pattern of the response that occurs in axotomized motoneurons of adult cats is also present in axotomized motoneurons of aged animals.     

Inhibition of rat hippocampal excitability by the plant alkaloid 3-acetylaconitine mediated by interaction with voltage-dependent sodium channels

The effects of the Aconitum alkaloid 3-acetylaconitine on neuronal activity were investigated in the slice preparation and on cultivated neurons of rat hippocampus by extracellular and patch-clamp recordings, respectively. 3-Acetylaconitine (0.01–1 μM) diminished the orthodromic and antidromic population spike in a concentration-dependent manner. The inhibitory action of the drug was preceded by a transiently enhanced excitability. The latency of onset of the inhibition was accelerated by increased stimulation frequency, whereas recovery during washout of the alkaloid was accelerated by decreased stimulation frequency. Moreover, the inhibitory effect of 3-acetylaconitine was evaluated in two different models of epileptiform activity induced either by blockade of GABA receptors by bicuculline (10 μM) or by a nominal Mg²⁺-free bathing medium. In accordance with the activity-dependent mode of action, this compound abolished the synaptically evoked population spikes in the presence of bicuculline or nominal Mg²⁺-free bathing medium, respectively. Whole-cell patch-clamp recordings revealed an interaction of 3-acetylaconitine with the voltage-dependent sodium channel. At a concentration of 1 μM, 3-acetylaconitine did not affect the peak amplitude of the sodium current, but shifted the current-voltage relationship in the hyperpolarized direction such that sodium currents were already activated at the resting potential. Received: 22 July 1996 / Accepted: 14 October 1996     

不同浓度的金属硫蛋白对离体豚鼠乳头肌缺氧、复氧电生理特性的影响

为探讨金属硫蛋白（MT）对豚鼠乳头肌缺血再灌注损伤所致心律失常的影响，利用标准玻璃微电极技术，采用缺氧及复氧豚鼠乳头肌模型，模拟体内缺血再灌注损伤，观察不同浓度MT对豚鼠乳头肌电生理特性的影响。结果显示低浓度的MT（0．002mmol／L）对正常及缺氧和复氧豚鼠乳头肌的动作电位（AP）有关参数及自律性均无影响；中等浓度的MT（0．02mmol／L）仅使正常乳头肌的AP复极达50％时程（APD50）缩短24％（P＜0．05），但使缺氧乳头肌的AP复极达20％时程（APD20）、APD50和AP复极达90％时程（APD90）分别缩短68％、56％和43％（P均＜0．01），并使静息电位（RP）、AP幅值（APA）和0相最大上升速率（Vmax）分别增加30％、30％和45％（P均＜0．01）；高浓度的MT（0．1mmol／L）使正常豚鼠乳头肌的APD20、APD50和APD90分别缩短57％、54％和50％（P均＜0．01），并且RP、APA及Vmax分别下降22％（P＜0．05）、28％（P＜0．01）和29％（P＜0．05），而使缺氧豚鼠乳头肌的APD20、APD50和APD90分别延长92％、78％和50％（P均＜0．01），对RP、APA及Vmax无明显影响。在复氧期间，0．02mmol／L的MT可使自律性的发生率从77．8％降至55．6％（P＜0．05）；而0．1mmol／L的MT则使自律性的发生率从77.8％降至22．2％（P     

New insights on P2X purinoceptors

Significant advances in understanding of P_2X purinoceptor pharmacology have been made in the last few years. The limitations of nucleotide agonists as drug tools have now been amply demonstrated. Fortunately, inhibitors of the degrading ecto-ATPase enzymes are becoming available and it has become apparent that the complete removal of all divalent cations can be used experimentally in some systems to prevent nucleotide breakdown. Despite these issues, convincing evidence for P_2X receptor heterogeneity, from data with agonists, has recently been reported.A number of new antagonists at P_2X purinoceptors have also recently been described which to some degree appear to be more specific and useful than earlier antagonists like suramin. It is now apparent that suramin is a poor antagonist of ATP in many tissues because it potently inhibits ATPase activity at similar concentrations to those at which it blocks the P_2X purinoceptor.Advances in the use of radiolabelled nucleotides as radioligands for binding studies has allowed the demonstration of P_2X purinoceptors in a variety of tissues throughout the body including the brain. These studies have also provided evidence for receptor heterogeneity. Excitingly, two P_2X purinoceptor genes have been cloned but operational studies suggest that more than two types exist. The cloning studies have also demonstrated a unique structure for the P_2X purinoceptor which differentiates it from all other ligand-gated ion channel receptors. Further studies on P_2X purinoceptor operation and structure are needed to help resolve controversies alluded to regarding the characterization and classification of nucleotide receptors. Hopefully such studies will also lead to a better understanding of the physiological and pathological importance of ATP and its activation of P_2X purinoceptors. This will require the identification of better drug tools, in particular antagonists which may also provide the basis for novel therapeutic agents.