NMDA receptor mediated dendritic plasticity in cortical cultures after oxygen-glucose deprivation

Dendrites and spines undergo dynamic changes in physiological and pathological conditions. Dendritic outgrowth has been observed in surviving neurons months after ischemia, which is associated with the functional compensation. It remains unclear how dendrites in surviving neurons are altered shortly after ischemia, which might reveal the mechanisms underlying neuronal survival. Using primary cortical cultures, we monitored the dendritic changes in individual neurons after oxygen-glucose deprivation (OGD). Two to four hours of OGD induced approximately 30–50% cell death in 24 h. However, the total dendritic length in surviving neurons was significantly increased after OGD with a peak at 6 h after re-oxygenation. The increase of dendritic length after OGD was mainly due to the sprouting rather than the extension of the dendrites. The dendritic outgrowth after 2 h of OGD was greater than that after 4 h of OGD. Application of NMDA receptor blocker MK-801 abolished OGD-induced dendritic outgrowth, whereas application of AMPA receptor antagonist CNQX had no significant effects. These results demonstrate a NMDA receptor-dependent dendritic plasticity shortly after OGD, which provides insights into the early response of surviving neurons after ischemia.     

Different effects of depolarization and muscarinic stimulation on the Ca2+/force relationship during the contraction-relaxation cycle in the guinea pig ileum

The effects of K⁺ depolarization and of the muscarinic agonist carbachol on [Ca²⁺]_i and force were investigated in smooth muscle sheets of the longitudinal layer of the ileum loaded with Fura-2. K⁺ -rich solutions increased [Ca²⁺]_i and force to an initial peak value, which was determined by the concentration of [K⁺]_o. Thereafter, [Ca²⁺]_i and force declined to a lower maintained level. The Ca²⁺/force relationship observed during this contraction-relaxation cycle is represented by a clockwise hysteresis loop. At 140 mM [K⁺]_o, this loop consisted of three components while at lower [K⁺]_o a two-component loop was observed. The stimulation with 0.1 mM carbachol resulted in a transient increase of [Ca²⁺]_i and force followed by a continuous decline of these parameters despite the presence of the drug. Its EC₅₀ of relaxation was around 270 nM [Ca²⁺]_i. The Ca²⁺/force relationship proceeded along a counterclockwise hysteresis loop during the contraction-relaxation cycle. The extent of this loop decreased but remained unaltered in its direction during repeated stimulation with carbachol. These results suggest that (a) both agonists increase force and [Ca²⁺]_i during stimulation; (b) during depolarization with K⁺, desensitization to Ca²⁺ occurs resulting in a clockwise hysteresis loop; (c) during carbachol stimulation, a counterclockwise hysteresis is observed. This could be due to an increased sensitivity to Ca²⁺ mainly in tonic smooth muscle. These observations might be explained by a modulation of the Ca²⁺ sensitivity by sensitizing and desensitizing mechanisms. These modulations during different stimuli could be due to different myosin light-chain kinase/myosin light-chain phosphatase ratios.     

Changes in extracellular potassium concentration in cat spinal cord in response to innocuous and noxious stimulation of legs with healthy and inflamed knee joints

Summary In 20 cats anaesthetized with alpha-chloralose and spinalized at the thoracolumbar junction we investigated the role of stimulation induced accumulation of extracellular potassium in the spinal cord in the processing of nociceptive discharges from the knee joint. For that we electrically stimulated the posterior articular nerve of the knee. We further performed innocuous and noxious stimulation of the knee and of other parts of the leg and studied the effect of an acute inflammation of the knee on [K⁺]₀ in the spinal cord. Innocuous stimulation of the skin (brushing or touching) and innocuous movements in the knee joint all induced rises in [K⁺]₀ which were maximal at recording depths of 1500 to 2200 m below the surface of the cord dorsum. Peak increases were 0.4 mM for touching the leg and 1.7 mM during rhythmic flexion/ extension of the knee joint. Noxious stimulation of the skin, the paw, the tendon and noxious movements of the knee joint also produced rises in [K⁺]₀, which were somewhat larger for the individual types of stimuli than those produced by innocuous intensities. Electrical stimulation of the posterior articular nerve induced rises in [K⁺]₀ by up to 0.6 mM. Stimulus intensities sufficient to activate unmyelinated group IV fibers were only slightly effective in raising [K⁺]₀ above the levels reached during stimulation of myelinated group II and III fibers. During development of an acute inflammation of the knee joint (induced by kaolin and carrageenan), increases in [K⁺]₀ and associated field potentials became larger by about 25%. We assume that this reflects an increase in neuronal responses. In conclusion, changes in [K⁺]₀ in the spinal cord are some-what larger during noxious stimulation than during innocuous stimulation. The absolute level reached depended more on the site and type of stimulation than on the actual stimulus intensity itself. Hence a critical role of spinal K⁺ accumulation for nociception is unlikely.     

Localization of [F]fluorodeoxyglucose in mouse brain neurons with micro-autoradiography

This is the first study of micro-autoradiography (micro-ARG) for [¹⁸F]2-fluoro-2-deoxy- -glucose ([¹⁸F]FDG). The localization of [¹⁸F]FDG was demonstrated in dendrites of neuron and also in the myelinated axon in mouse normal brain in vivo. The nucleolus was relatively free of label. The counted silver grain numbers in autoradiogram were linearly correlated to the ¹⁸F radioactivities in the specimen. The micro-ARG using positron emitting ¹⁸F is a very time-saving technique with 4 hours exposure compared with the conventional method using ³H- or ¹⁴C-labeled tracers.     

三取代型钛钨硅酸盐体内抑瘤效应的免疫机制探讨

目的:探讨三取代型钛钨硅酸盐(WT)体内抑瘤效应的免疫机制。方法:建立荷H22肝癌小鼠模型,WT连续灌胃10d,取出肿瘤称重测定抑瘤率。用MTT比色法测定荷H22肝癌小鼠淋巴细胞转化的活性及NK细胞的杀伤活性。通过形态学观察和流式细胞仪检测WT诱导BEL-7402细胞的凋亡。结果:WT可显著抑制荷瘤小鼠肿瘤生长(P<0.05),提高荷瘤小鼠淋巴细胞转化的活性及NK细胞的杀伤活性(P<0.05),并诱导肿瘤细胞发生凋亡。结论:WT的抑瘤作用与机体免疫功能的增强有关。     

Agonist-mediated conformational changes of β-adrenoceptors could occur independent of functional coupling to Ns

Summary Agonist and antagonist binding characteristics of -adrenoceptors in turkey erythrocyte ghosts were determined at different temperatures ranging between 7°C and 42°C. [³H]-DHA saturation binding experiments revealed that the antagonist-receptor interaction is entropy-driven with a small enthalpic contribution. Isoproterenol/[³H]-DHA competition binding followed the law of mass action at all the investigated temperatures. The agonist-receptor interaction is enthalpy driven with a small unfavorable decrease in entropy. This is consistent with the agonist's ability to favor an endoenergetic transconformation of the receptors.Only part of the agonist-bound receptors can undergo functional coupling to the stimulatory component of the adenylate cyclase system (Ns). This coupling process is associated with locking-in of the agonist and becomes persistent in the presence of the alkylating reagent N-ethylmaleimide. The number of agonist/N-ethylmaleimide-sensitive sites (i.e. coupling-prone receptors) increases with the temperature until it reaches a plateau value of 50% between 27–32°C. Qualitatively similar data were obtained for rat lung and turkey erythrocyte membranes. These observations suggest that the whole receptor population can undergo agonist-mediated conformational changes but that only part of them can couple to Ns.     

胫骨交锁髓内钉术后感染分析

目的：探讨胫腌骨骨折交锁髓内钉术后感染的预防与治疗方法。方法;对12例术后感染的病例进行回顾性分析。3例经过抗菌素治疗,9例经过闭式滴不引流加抗菌素治疗,结果;全部病例获随访,随访时间10个月－2年,感染控制,骨折愈合,结论：对胫骨交锁髓内钉术后感染的病人,不必急于取出内固定,采用闭式滴注引流加抗菌素治疗可获得满意效果。     

内毒素所致DIC时血小板胞浆Ca^2＋浓度变化的研究

本实验观察内毒素在体外对兔血小板胞浆游离钙浓度[Ca~(2+)]i的作用以及用二次注射内毒素法复制DIC模型时对[Ca~(2+)]i的影响。结果表明静息血小板[Ca~(2+)]i为112±24 nM,内毒素可直接作用于血小板,使[Ca~(2+)]i呈剂量依赖性升高。内毒素致DIG时(Ca~(2+)]i可升高三倍。结果提示内毒素可能是通过升高血小板[Ca~(2+)]i而激活血小板。血小板的激活可能是导致DIC的重要发病机制之一。     

Extracellular K+ accumulations and synchronous GABA-mediated potentials evoked by 4-aminopyridine in the adult rat hippocampus

Transient changes in extracellular potassium concentration ([K⁺]₀) and field potentials were evoked by 4-aminopyridine (4-AP; 50–100 M) and recorded with ion-selective microelectrodes in CA1b, CA3b and dentate sectors of adult rat hippocampal slices. Long-lasting field potentials recurred at a frequency of 1/60 s (0.016±0.003 Hz) in association with increases in [K⁺]₀ which were largest and most sustained in the dendritic regions where afferent fibers terminate (dentate>CAl>CA3) and in the hilus. In stratum radiatum of CA1 or stratum moleculare of the dentate these fields had a peak amplitude of 1.4±0.29 mV, duration 8.3±1.6 s, and were accompanied by increases in [K⁺]₀ of 1.8±0.22 mM that lasted 32±5.5 s (n = 17 slices). Interictal epileptiform potentials, which were brief (<0.2 s) and more frequent at 1/3 s (0.30±0.02 Hz) were also present in CA1, CA3 and the hilus and associated with small increases in [K⁺]₀ (0.5 mM, duration 2 s). Interictal activity was blocked by 6-cyano-7-nitroquinoxalone-2,3-dione (CNQX; 5–20 M); the slow, less frequent potentials were resistant to both CNQX and dl-2amino-5-phosphonovaleric acid (APV; 50 M) and reversibly blocked (or attenuated by 80%) by bicuculline methiodide (BMI) (25–100 M). The BMI-sensitive potentials were also abolished by baclofen (100 M), an effect which was reversed by 2-OH-saclofen (100 M). Focal application of KCl or GABA in the absence of 4-AP evoked long-lasting field and [K⁺]₀ potentials which were similar to those evoked by 4-AP but more sustained. The proportional relationship between the amplitudes of field and K⁺ potentials with GABA closely resembled that observed for 4-AP; in contrast the slope of KCl-evoked responses was lower. Our results demonstrate that in the adult rat hippocampus 4-AP induces in many different regions accumulations of [K⁺]₀ in synchrony with the long-lasting field potentials, which are known to correspond to an intracellular long-lasting depolarization of the pyramidal cells. These changes are smaller than those which occur in the immature rat hippocampus — which may be related to differences in Na-K-ATPase and susceptibility to seizures. These events involve the activation of GABA_A receptors, are under the modulatory control of GABA_B receptors, and likely arise from the activity of GABAergic interneurons and/or afferent terminals. The long-lasting field potentials appear to reflect mainly the direct depolarizing actions of GABA and to a much more limited extent the associated accumulation of [K⁺]₀.     

血栓闭塞性脉管炎患者血栓素、前列环素及血液流变学指标的检测分析

目的 :探讨血栓闭塞性脉管炎患者血栓素B2 、前列环素与血液流变学指标的变化及其与发病机制的关系。方法 :用放射免疫法测定TXA2 和PGI2 的代谢产物血栓素B2 (TXB2 )、6 酮 前列腺素F1α( 6 K PGF1α) ,LBY N6A自清洗旋转式粘度计测定血液流变学指标 ,并与对照组对比分析。结果 :血栓闭塞性脉管炎患者TXB2 ( 53.59± 83.2 1ng/L)、6 K PGF1α( 14 .50± 3.4 5ng/L) ,与对照组相比差异显著 ;全血高切粘度、低切粘度、血浆粘度及纤维蛋白原疾病组均高于对照组 ,差异具有统计学意义。结论 :血栓闭塞性脉管炎患者存在TXA2 /PGI2失衡 ,并与血液流变学的改变有密切关系