Polyamine-like immunoreactivity in rat neurons

The localization of polyamine (PA) pools in motor, sensory, and autonomic neurons and in the nerve cells of the hypothalamo-hypophysial system of rats was examined by immunocytochemical method using the monoclonal antibody ASPM-29 specific to spermine (Spm) and spermidine (Spd) fixed in situ. Strong PA immunoreactivity was found in the cytoplasm and dendrites of the large perikaryon of motor neurons in the anterior spinal column, in the Purkinje cells of the cerebellum, in the pyramidal cells of the cerebrum, in the nerve cells of the paraventricular and supraoptic nuclei in the hypothalamus, and in the nerve cells of the spinal and autonomic ganglions. No PA immunoreactivity was seen in the nucleus and nerve terminals of the neurons. The PA immunoreactivities in the motor and sensory neurons were characterized by clustered masses and blocks of immunoreactive cells. Irrespective of location, small and medium-sized neurons were weakly PA-positive. The glia cells, some stellite cells, and Schwann cells were almost completely PA-negative. These results may suggest that in neurons PAs are not transported axonally, but are located in conjunction with Nissl bodies (the rough endoplasmic reticulum), specified as sites for protein synthesis within cells.     

精胺对放射损伤防护作用的实验研究

目的 探讨精胺对放射损伤的保护机制及可能的治疗效果。方法 昆明种雄性小鼠随机分烃和组,放射前注入精胺组,放射后注入精胺组。经６Ｇｙ一次性全身＾６０Ｃｏｒ射线照射后,在１５ｄ内观察各组小鼠体重,存活率,以及外周血和骨髓细胞数量的变化;用ＥＬＩＳＡ和放免的方法分别检测血清ＴＧＦ－β１和ＴＮＦ－α的含量;用免疫组化法检测骨髓组织ＴＮＦ－α和ＴＧＦ－β１的表达。     

Connexin40 and connexin43 determine gating properties of atrial gap junction channels

While ventricular gap junctions contain only Cx43, atrial gap junctions contain both Cx40 and Cx43; yet the functional consequences of this co-expression remain poorly understood. We quantitated the expression of Cx40 and Cx43 and their contributions to atrial gap junctional conductance (g_j). Neonatal murine atrial myocytes showed similar abundances of Cx40 and Cx43 proteins, while ventricular myocytes contained at least 20 times more Cx43 than Cx40. Since Cx40 gap junction channels are blocked by 2 mM spermine while Cx43 channels are unaffected, we used spermine block as a functional dual whole cell patch clamp assay to determine Cx40 contributions to cardiac g_j. Slightly more than half of atrial g_j and ≤ 20% of ventricular g_j were inhibited. In myocytes from Cx40 null mice, the inhibition of ventricular g_j was completely abolished, and the block of atrial g_j was reduced to < 20%. Compared to ventricular gap junctions, the transjunctional voltage (V_j)-dependent inactivation of atrial g_j was reduced and kinetically slowed, while the V_j-dependence of fast and slow inactivation was unchanged. We conclude that Cx40 and Cx43 are equally abundant in atrium and make similar contributions to atrial g_j. Co-expression of Cx40 accounts for most, but not all, of the differences in the V_j-dependent gating properties between atrium and ventricle that may play a role in the genesis of slow myocardial conduction and arrhythmias.     

The effects of some polyamines on putative behavioural indices of mesolimbic versus striatal dopaminergic function

The presence of polyamines in the brain, together with the previous reports of a structural similarity with neuroleptics, has led to the hypothesis that polyamines may have a modulatory role in the control of cerebral dopamine function. In this study, the effects of two polyamines, spermine and spermidine, were therefore tested on indices of dopamine-mediated behaviour in rats and mice. Spermine and spermidine caused a dose-dependent inhibition of mouse spontaneous climbing behaviour and wheel running at doses between 5 and 40 mg/kg IP but failed to cause catalepsy in the rat or to antagonise the stereotyped behaviour induced by apomorphine. When polyamines were given by intracerebral injection a similar regional selectivity was seen. Both spermine and spermidine (5–20 μg) when given bilaterally into the nucleus accumbens inhibited the hyperactivity caused by amphetamine injected into the same nucleus. However, when injected into the rat corpus striatum, neither polyamine was able to initiate any asymmetry or circling either spontaneously or after apomorphine injection IP. These results indicated a selective action of polyamines on mesolimbic dopamine behaviour. Possible implications for the understanding of psychosis and future work are suggested.     

Spermine increases paired-pulse facilitation in area CA1 of hippocampus in a calcium-dependent manner

The effect of spermine on neurotransmission was studied in area CA1 of the hippocampal slice preparation. Paired-pulse stimulation (20 ms interpulse interval) was delivered to stratum radiatum; the evoked field potential responses were recorded simultaneously from stratum radiatum and from stratum pyramidale. At mM and sub-mM concentrations, spermine decreased the slope of pEPSP in stratum radiatum and the area of the conditioning population spike in stratum pyramidale. Short-latency paired-pulse inhibition of the population spike was converted to facilitation by spermine. These effects of spermine resembled those observed at low calcium concentration. In addition, dose-response and input-output curves determined at various Ca²⁺ concentrations demonstrated that the depressant effects of spermine were larger at low Ca²⁺ levels. The results support the notion that spermine competitively blocks presynaptic voltage-sensitive Ca²⁺ channels, thus causing a decreased release of neurotransmitter. Since spermine is present in brain, it is likely that it is a natural modulator of Ca²⁺ channels.     

Macrophage mannose receptor-specific gene delivery vehicle for macrophage engineering

Macrophages are the most plastic cells in the hematopoietic system and they exhibit great functional diversity. They have been extensively applied in anti-inflammatory, anti-fibrotic and anti-cancer therapies. However, the application of macrophages is limited by the efficiency of their engineering. The macrophage mannose receptor (MMR, CD206), a C-type lectin receptor, is ubiquitously expressed on macrophages and has a high affinity for mannose oligosaccharides. In the present study, we developed a novel non-viral vehicle with specific affinity for MMR. Mannan was cationized with spermine at a grafted ratio of ∼12% to deliver DNA and was characterized as a stable system for delivery. This spermine–mannan (SM)-based delivery system was evaluated as a biocompatible vehicle with superior transfection efficiency on murine macrophages, up to 28.5-fold higher than spermine–pullulan, 11.5-fold higher than polyethylenimine and 3.0-fold higher than Lipofectamine™ 2000. We confirmed that the SM-based delivery system for macrophages transfection was MMR-specific and we described the intracellular transport of the delivery system. To our knowledge, this is the first study using SM to demonstrate a mannose receptor-specific gene delivery system, thereby highlighting the potential of a novel specific non-viral delivery vehicle for macrophage engineering.     

精胺对急性脑缺血再灌注损伤大鼠的保护作用

目的: 观察外源性精胺对急性脑缺血-再灌注损伤大鼠的作用,并初步探讨其可能机制。方法: 采用线栓法复制大鼠大脑中动脉缺血(2 h)-再灌注(2 h)模型。SD大鼠随机分为5组:假手术组、模型组和低、中、高剂量精胺组。检测指标有神经病学评分、脑梗死面积、皮层脑组织HE染色、电镜超微结构观察、超氧化物歧化酶活性(SOD)及丙二醛(MDA)含量。结果: 与模型组相比,不同浓度精胺均能降低大鼠急性脑缺血-再灌注后神经功能学评分、梗死面积、缺血脑组织MDA含量,减轻脑组织形态学和超微结构损伤,增加缺血区SOD活性。结论: 外源性精胺对大鼠局灶性急性脑缺血-再灌注损伤有保护作用,其机制可能与清除氧自由基有关。     

癫痫患儿多胺水平的变化及其意义

目的 :探讨癫痫患儿的血、尿多胺水平变化及其意义。方法 :用高效液相色谱分析法 ,测定 3 2例癫痫患儿在癫痫发作后 48小时内的空腹血腐胺 (PUT)、精脒 (SPD)、精胺 (SPM)和晨尿PUT、SPD、SPM浓度 ,并选择 2 0例正常儿童作为对照。结果 :癫痫患儿血、尿PUT、SPD、SPM平均浓度高于正常儿童 (P <0 .0 5 )。但部分性发作与全身性发作、原发性癫痫与继发性癫痫患儿之间 ,血、尿多胺浓度的升高无统计学意义 (P >0 .0 5 )。结论 :癫痫患儿体内多胺代谢紊乱