黄皮酰胺促钾通道开放

一种新发现的具有促智作用的药物——黄皮酰胺能抑制去甲肾上腺素(NE)或KCl引起的血管平滑肌收缩。本研究旨在应用膜片钳(patch clamp)技术探讨黄皮酰胺对Wistar大鼠尾动脉平滑肌细胞膜钾离子通道的作用。单个平滑肌细胞用酶法分离,以细胞封接方式记录离子通道活动。在细胞池内注入2μM黄皮酰胺后,钾离子通道活动明显增强。用本实验室开发的计算机软件(patch clamp analysis system,Version 1.0)计算分析通道活动的特征参数。     

Preferential apoptosis of CD56dim natural killer cell subset in patients with cancer

Natural killer (NK) cells (CD56(+)/CD3(-)) in the circulation of cancer patients were reported to have low NK activity and undergo spontaneous apoptosis. A possible relationship between apoptosis and impaired NK activity was studied by Annexin V-binding and NK-cell assays performed with peripheral blood mononuclear cells of patients with head and neck cancer (HNC), breast cancer (BC) and normal controls (NC). Cells stained with Annexin V (Anx) and antibodies to CD56, CD3, CD95, CD25, CD122 or CD132 were examined by flow cytometry. NK activity was tested against K562 targets in 4-h (51)Cr-release assays. The ratio of CD56(dim)/CD56(bright) NK cells was significantly different in patients vs. controls (10 vs. 16; p<0.01). A significantly greater percentage of CD56(dim) NK cells bound Anx in HNC patients (27+/-17%, median +/- SD) or BC (46+/-18%) than in NC (15+/-18%, p<0.04 and p<0.0002, respectively). CD56(dim) NK cells were preferentially targeted for apoptosis. NK activity was significantly lower in patients with HNC and BC than in NC (p<0.009). An inverse correlation between NK activity and the percent of Anx(+)CD56(dim) NK cells was observed in cancer patients (p =0.002) but not in NC. In patients, circulating CD56(dim) NK cells were targeted for apoptosis, leading to low levels of NK activity.     

Significance of fibrils in the formation of the Kimmelstiel-Wilson nodule

Summary The pathogenesis of the nodular lesion in diabetic glomerulosclerosis is described in association with fibrils. Thirteen diabetic patients with glomerular nodular lesions and 9 diabetics without the nodules were examined by electron microscopy using periodic acid-thio-carbohydrazide-silver proteinate staining. In cases of nodular glomerulosclerosis, abundant fibrillar structures mixed with electron-dense material were detected within the nodule and the mesangial matrix. They were also occasionally observed along the subendothelial space of the glomerular capillary walls. On the cross-section, these fibrils, including the lucent periphery, were 34 nm wide. Immunohistologically, collagen V and collagen VI were detected in nodular lesions. In contrast, in cases of the diffuse type of glomerulosclerosis, the widened mesangium was composed of dense material, which resembled the original mesangial matrix. The above fibrils were not detected in the mesangium. These findings suggest that the accumulation of the peculiar fibrils in the glomerular mesangium is a major pathogenic factor in the formation of Kimmelstiel-Wilson nodules.     

Expression of voltage-dependent sodium and transient potassium currents in an identified sub-population of dorsal root ganglion cells acutely isolated from 12-day-old mouse embryos

The electrophysiological properties of a subset of dorsal root ganglion (DRG) neurons microdissected from 12-day-old (E12) mouse embryos and acutely isolated were analyzed as soon as 3 after their isolation. Two classes of neurons were defined according to their mean diameter. The larger diameter class was examined in this study. They display uniform cytoskeletal properties with co-expression of vimentin and neurofilament triplet proteins. Patch-clamp methods also revealed a homogeneous and limited repertoire of ionic channels that included (1) a TTX-sensitive Na⁺ current whose properties are similar to that reported in mature mammalian neurons, and (2) two types of K⁺ currents that can be compared with the delayed rectifier (I _k ) and the transient (I _a) potassium currents found in other mammalian preparations. It may be possible to use this in vitro model to examine the development of new types of currents, such as Ca²⁺ currents during neuronal growth and differentiation.     

Excitatory amino acids and potassium release in the frog spinal cord

Synaptic release of excitatory amino acids such as L-glutamate and/or L-aspartate and subsequent activation of specific receptors by these putative transmitters appears necessary for the release of K+ by afferent stimulation in the isolated frog spinal cord. This conclusion is based on the findings that (-)baclofen, which is thought to reduce the presynaptic release of putative excitatory amino acid transmitters, and some amino dicarboxylic amino acids (D, L-alpha-aminoadipic acid, 2-amino-4-phosphonobutyric acid, and D, L-alpha, epsilon-diaminopimelic acid), which are believed to interfere with the activation of receptors by these same excitatory amino acids, significantly attenuate the increment in extracellular K+ evoked by tetanic dorsal root stimulation.     

In-vivo quantification of myocardial Na-K pump rate during β-adrenergic stimulation of intact pig hearts

Maintenance of adequate electrical activity of the heart depends critically on the ability of the Na-K pump to compensate for normal passive sodium and potassium fluxes. Using sudden injections of [³H]ouabain into the left coronary artery in anaesthetized open-chest pigs, we monitored transient changes in myocardial potassium balance by PVC-valinomycin mini-electrodes. When related to the number of pumps blocked and fractional inhibition, these data provided estimates of total Na-K pump capacity as well as actual pump rate and perturbations of the Na-K balance. Experiments were performed in hearts with and without intracoronary isoprenaline infusion (2.5 nmol min^-1). After injection of 120 nmol [³H]ouabain into the left coronary artery, myocardial [³H]ouabain concentrations were 118 (74–178) and 103 (76–145) pmol g^-1 and total concentrations of [³H]oubain binding sites were 893 (752–1076) and 785 (691–877) pmol g^-1 (median, 95% confidence interval) in isoprenaline-treated and control hearts respectively (differences not significant). The [³H]ouabain injection caused a net potassium release of 81 (56–132) and 43 (23–75) μcool 100 g^-1 (median, 95% confidence interval) in isoprenaline-treated and control hearts respectively (n= 6–8; significance of difference, P= 0.03). Na–K pump rate estimated from mono-exponential release curves was 6363 (3942–10,858) K⁺ ions min^-1 site^-1 during β-adrenoceptor stimulation and 2514 (1380–4322) in control (significance of difference, P= 0.03). This corresponds to 40 and 16%, respectively, of the maximum possible pump rate determined from ATP hydrolysis. Comparison of accumulated potassium release and relative Na-K pump rate indicates that catecholamines enhance the sensitivity of the Na-K pump for intracellular sodium.     

Priming B cell-mediated anti-HIV envelope responses by vaccination allows for the long-term control of infection in macaques exposed to a R5-tropic SHIV

The potential of vaccine-elicited anti-HIV envelope antibodies to control HIV-infection was evaluated by immunizing macaques with the HIV envelope protein and transiently depleting them of their CD8+ cells before intravenous challenge with the pathogenic CCR5-tropic SIV/HIV chimeric virus, SHIV(SF162P4). Although sterilizing immunity was not achieved, all vaccinated animals effectively controlled infection and remained free of disease for the duration of observation (over 3 years). In contrast, during the same period, the control animals progressed to disease. Both the vaccinees and the controls developed robust cell-mediated antiviral and neutralizing antibody responses following infection. A comparative analysis of these responses suggests that the more effective long-term control of infection by the vaccinated animals is due to the more rapid development of anti-HIV envelope antibodies. These studies suggest that priming by vaccination of B cell anti-HIV envelope responses maybe crucial for the long-term control of HIV infection.     

Characteristics of the delayed rectifier K current compared in myocytes isolated from the atrioventricular node and ventricle of the rabbit heart

The delayed rectifier potassium current (I _K) is known to be important in action potential repolarisation and may contribute to the diastolic pacemaker depolarisation in pacemaker cells from the heart. In this study, using whole-cell patch clamp, we investigated the characteristics of I _K in morphologically normal cells from the atrioventricular node (AVN) and ventricle of the rabbit heart. Cells were held at −40 mV and 5 μM external nifedipine was used to block L-type calcium current (I _Ca,L). Significant I _K was observed with pulses to potentials more positive than −30 mV. The steady-state activation curve in both cell types showed maximal activation at between + 10 and + 20 mV. Half-maximal activation of I _K occurred at −4.9 and −4.1 mV with slope factors of 8.3 and 12.4 mV in ventricular and AVN cells, respectively. Using pulses of increasing duration, significant I _K tails after repolarisation from + 40 mV were observed with pulses of 20 ms and increased with pulses up to 100–120 ms in both cell types. Pulses of longer duration did not activate further I _K and this suggested that only the rapid component of I _K, called I _Kr, was present in either cell type. Moreover, I _K tails after pulses to all potentials were blocked completely by E-4031, a selective blocker of I _Kr. The reversal potential of I _K varied with the concentration of external K. Superfusion of AVN cells with medium containing 4, 15 and 40 mM [K⁺]_o resulted in reversal potentials of −81, −56 and −32 mV, respectively, which are close to values predicted if the I _K channel were highly selective for K. The time constants for deactivation of I _K in ventricle and AVN on return to −40 mV after a 500-ms activating pulse to + 60 mV were 480 ms and 230 ms, respectively. The faster deactivation of I _K in AVN cells was a distinguishing feature and suggests that there may be differences in the I _Kr channel protein between ventricular and AVN cells. Received: 24 July 1995 /Received after revision: 20 October 1995 /Accepted: 23 October 1995