Attenuation of myocardial injury due to oxygen free radicals(OFR) by pretreatment with OFR or calcitonin gene-related peptide

目的：研究氧自由基（ＯＦＲ）及降钙素基因相关肽（ＣＧＲＰ）预处置对ＯＦＲ所致离体大鼠心脏损伤的拮抗作用．方法：Ｌａｎｇｅｎｄｏｒｆ法灌流心脏，电解ＫＨ液产生ＯＦＲ．结果：ＣＧＲＰ或ＯＦＲ预处置减轻ＯＦＲ所致心脏收缩功能下降，冠脉流量减少和肌酸激酶（ＣＫ）释放增加．蛋白激酶Ｃ（ＰＫＣ）抑制剂Ｈ７可取消ＯＦＲ预处置的心脏保护作用（对照组，ＯＦＲ损伤组，ＯＦＲ预处置组，Ｈ７加ＯＦＲ预处置组及Ｈ７组的ＣＫ释放量分别是１１０±７，２１５±２３，１６９±１４，２４０±３０，１１３±１９Ｕ·Ｌ－１）．结论：ＯＦＲ或ＣＧＲＰ预处置对ＯＦＲ所致心肌损伤具有拮抗作用，该作用与ＰＫＣ激活有关．     

实验性视网膜光化学损伤中的蛋白激酶C

目的：研究实验性视网膜光化学损伤中蛋白激酶C(protein kinase C，PKC)活性的改变；探索地塞米松(dexamethasone，DXM)对视网膜中PKC活性的影响。 方法；48只SD大鼠分为对照组和DXM组，后者于光照前3天开始，连续5天腹膜腔注射DXM 1mg/(kg·d)。经(1 900±106.9)Ix的绿色荧光灯(λ＝510nm～560nm)连续照射24小时后的6小时和1、3、7、14天，进行视网膜PKC活性检测。 结果：光化学损伤后视网膜中的PKC活性在短暂的上升后即出现持续性的下降；DXM对PKC的活性改变无明显作用。 结论：光化学损伤中的视网膜功能障碍可能与PKC活性的持续降低有关。 （中华眼底病杂志，1997，13：78-80）     

A fluorometric micromethod for estimation of carnosinase in dried blood samples

Human alkaline phosphatases extracted with butanol from liver, kidney and placenta, and from foetal and adult small intestine each contain fragments with molecular masses within the range of approximately 8 kDa to 20 kDa which can be removed by digestion with bromelain. However, in the case of adult intestine, this fragment (which is presumed to represent a membrane-binding domain) can only be demonstrated in tissue extracted immediately after removal at operation. Similar fragments are also present in foetal intestinal phosphatase in amniotic fluid, and in liver and bone alkaline phosphatases recovered from serum. Again, however, adult intestinal phosphatase from serum differs in the absence of the bromelain-sensitive fragment. These observations indicate differences in the ways in which intestinal and non-intestinal alkaline phosphatases gain access to the circulation, and also have implications for structural studies on intestinal phosphatase extracted post mortem from adult tissue.     

-2-Hydroxyglutaric acid inhibits mitochondrial creatine kinase activity from cerebellum of developing rats

L-2-Hydroxyglutaric acid (LGA) is the biochemical hallmark of patients affected by the neurometabolic disorder known as L-2-hydroxyglutaric aciduria (LHGA). Although this disorder is predominantly characterized by severe neurological findings and pronounced cerebellum atrophy, the neurotoxic mechanisms of brain injury are virtually unknown. In the present study, we investigated the effect of LGA, at 0.25-5mM concentrations, on total creatine kinase (tCK) activity from cerebellum, cerebral cortex, cardiac muscle and skeletal muscle homogenates of 30-day-old Wistar rats. CK activity was measured also in the cytosolic (Cy-CK) and mitochondrial (Mi-CK) fractions from cerebellum. We verified that tCK activity was significantly inhibited by LGA in the cerebellum, but not in cerebral cortex, cardiac muscle and skeletal muscle. Furthermore, CK activity from the mitochondrial fraction was inhibited by LGA, whereas that from the cytosolic fraction of cerebellum was not affected by the acid. Kinetic studies revealed that the inhibitory effect of LGA on Mi-CK was non-competitive in relation to phosphocreatine. Finally, we verified that the inhibitory effect of LGA on tCK was fully prevented by pre-incubation of the homogenates with reduced glutathione (GSH), suggesting that this inhibition is possibly mediated by oxidation of essential thiol groups of the enzyme. Considering the importance of creatine kinase activity for energy homeostasis, our results suggest that the selective inhibition of this enzyme activity by increased levels of LGA could be possibly related to the cerebellar degeneration characteristically found in patients affected by L-2-hydroxyglutaric aciduria.     

脑型肌酸激酶同功酶在脑血管病中的意义 Ⅱ.急性脑血管病患者血清和脑脊液中CKBB变化及与CT片上病损大小的关系

用改良的ELISA检测25例正常对照组和32例急性脑血管病患者的血清和脑脊液(CSF)中的脑型肌酸激酶同功酶BB(creatine kinase isoenzyme BB)浓度。32例急性脑血管病患者CSF CKBB平均水平为16.62±8.3ng/ml,明显高于对照组(7.5—4.8ng/ml)。发病24h内CSFCKBB轻微增高,24～48h达高峰,以后下降,7天左右尚未恢复正常。病初CSF CKBB水平明显高于恢复期。9例高血压性脑出血的血肿出血量(按CT片上血肿大小计算)与患者CSF CKBB有密切关系(r=0.8127,P<0.01)。血肿体积(X)与CSF CKBB浓度(y)的回归方程y—7.945±0.872X。     

Activation of guinea pig eosinophil respiratory burst by leukotriene B4: role of protein kinase C

Leukotriene B4 (LTB4) and the protein kinase C activator, 4-beta-phorbol dibutyrate (PDBu), both induced a pronounced and concentration-dependent stimulation of hydrogen peroxide (H2O2) generation by purified guinea pig peritoneal eosinophils in the concentration range 1 nM-1 microM. The LTB4 response was inhibited competitively by the specific LTB4 receptor antagonist, U-75302, with a KB of 25 nM, while the concentration-response curves for both stimuli were shifted rightwards (3.8-fold and 2.8-fold for LTB4 and PDBu, respectively) by the competitive protein kinase C inhibitor, 1-O-hexadecyl-2-O-methylglycerol at a concentration of 300 microM. LTB4 appears, therefore, to induce respiratory burst in eosinophils via a receptor-mediated mechanism involving protein kinase C.     

KN-93抑制脊髓背角C-纤维诱发电位LTP的诱导和早期维持

[目的]探讨钙-钙调蛋白依赖性蛋白激酶Ⅱ(CaMKⅡ)在脊髓背角C-纤维诱发电位长时程增强(LTP)的诱导和维持中的作用。[方法]用钨丝微电极在脊髓腰膨大部背角浅层神经元细胞外记录C-纤维诱发电位,强直刺激坐骨神经诱导背角C-纤维诱发电位的LTP。在LTP诱导前后,在暴露的脊髓表面局部给予CaMKⅡ的选择性抑制剂KN-93,观察C-纤维诱发电位的变化。[结果]50μmol/L的KN-93不影响脊髓背角C-纤维诱发电位的幅度,但可完全阻断脊髓背角LTP的诱导(n=6)。KN-93呈时间依赖性翻转脊髓背角LTP。在LTP诱导后30min,50μmol/L的KN-93对LTP的早期表达无影响(n=4),而100μmol/L的KN-93在用药后,LTP逐渐降低,于3h降至对照水平(n=6);在LTP诱导后1h脊髓局部给予100μmol/L的KN-93,7例动物中有5例LTP被抑制;但同样浓度的KN-93,在LTP诱导后3h,不能翻转业已建立的LTP(n=5),且增加KN-93的浓度至200μmol/L也不能抑制脊髓背角LTP。[结论]CaMKⅡ参与脊髓背角C纤维诱发电位LTP的诱导和早期维持,但KN-93对晚期LTP无抑制作用。     

Role of tyrosine kinase activity in cardiac slow delayed rectifier channel modulation by cell swelling

 We studied the effects of cell swelling on membrane currents of canine ventricular myocytes using the whole-cell patch-clamp method. Cell swelling was induced by lowering the osmolarity of the bath solution to 60% of control. Cell width and currents were measured simultaneously. Cell swelling induced little or no change in the L-type Ca, the inward rectifier, and the transient outward currents, but a marked increase in the slow delayed rectifier current (I _Ks) was seen. We further examined the role of protein kinase activities in I _Ks modulation by cell swelling. This modulation was not affected by inhibiting serine/threonine kinases using H-8. On the other hand, the modulation was inhibited by genistein (a protein tyrosine kinase inhibitor) although not by daidzein (an inactive analogue of genistein). Our data suggest that in canine ventricle cell swelling can increase protein tyrosine kinase activity, which can augment I _Ks and contribute to changes in membrane electrical activity observed under these conditions. Received: 20 September 1996 / Received after revision and accepted: 5 December 1996