膜磷脂代谢与心肌缺血再灌注损伤

膜磷脂是维持细胞结构与功能的重要成份。心肌缺血—再灌注后导致膜磷脂降解,其含量明显减少,这是再灌注损伤的重要发病环节。用药物阻止膜磷脂降解可预防缺血心肌的再灌注损伤。     

卡托普利对短时间停灌后再灌注大鼠心肌的保护作用

短时间缺血的心肌再灌注时不会发生坏死,但往往出现较长时间的舒缩功能低下等变化,这一现象被称为心肌顿抑(myocardial stunning)。预防或减轻心肌顿抑则有利于心肌再灌注时心功能的恢复。从这一考虑出发,本实验在离体大鼠工作心脏模型上,观察了再灌注时给予卡托普利(caaptopril)对20min停灌/再灌注心脏舒缩功能恢复、心肌Ca~(2 )含量和心肌乳酸脱氢酶(LDH)释放量的影响。     

心肌缺血／再灌注损伤后血清和心肌组织Leptin水平的变能

目的：观察大鼠心肌缺血／再灌注损伤对血清和心肌组织瘦素（Leptin）表达的影响,探讨Leptin在心肌缺血／再灌注损伤中的作用。方法：建立大鼠心肌缺血／再灌注模型,检测血清乳酸脱氢酶（LDH）和Leptin浓度,并用HE染色和免疫组织化学观察心肌组织病理学及Lepfin表达水平。结果：缺血组、再灌注组血清LDH水平显著升高（P〈0．05）,表明该模型制作成功,造成心肌局部一定程度的损伤。缺血组血清Leptin含量（6．34±2．49）ng／ml显著低于对照组（7．50±2．93ng／ml,P〈0．05）;再灌注后Leptin水平缓慢恢复,于再灌注2h时Leptin达到（8．32±1．74）ng／ml,恢复到损伤前水平（8．38±2．56）ng／ml,且随再灌注时间延长有升高趋势。免疫纽化显示与假手术纽心肌Leptin蛋白表达水平相比,其他四组均有显著降低（P〈0．01）,按缺血45min后再灌注1h组、缺血45min后再灌注3h组、单纯缺血45min组、缺血45min后再灌注2h组依次递减。结论：Leptin在心肌缺血／再灌注损伤后早期45min血中有明显减少,心肌组织中也明显表达下降。心肌组织病理损伤与Leptin的改变可能有一定的关系。     

缺血预处理及低温对幼兔心肌缺血/再灌注损伤的影响

目的：探讨缺血预处理(ischemic preconditioning,IP)及低温对幼兔心脏缺血／再灌注损伤的影响。方法：采用Langendorff离体心脏灌注模型,取3～4周龄幼兔心脏,分别给予不同次数的IP后使其在20℃低温下缺血或给予同样次数的IP后使其分别在不同低温下缺血。常温再灌注30min。记录心脏缺血／再灌注前后左心室功能指标,测定再灌注末心肌组织中ATP和丙二醛(MDA)含量,超氧化物歧化酶(SOD)及Ca^2 -ATP酶的活性。结果：再灌注末,IP2组左心室各功能指标的恢复率及心肌组织的ATP含量及Ca^2 -ATP酶的活性均显著高于Con组和IP3组;SIP1、SIP2组的左心室各功能指标的恢复率及心肌组织的ATP含量均分别显著高于SConn1组和SCon2组。其心肌组织MDA含量亦分别低于SCon1组和SCon2组。结论：IP可减轻低温缺血的幼兔心肌缺血／再灌注损伤,其效应与IP的次数和低温程度有关。     

大鼠心肌线粒体缺血再灌损伤及SOD抗缺血再灌损伤作用的形态计量研究

研究了在体大鼠心肌缺血再灌模型心肌线粒体再灌损伤和SOD抗缺血再灌损伤的作用。实验分为:A组(缺血再灌组)B组(SOD组)和C组(假手术组)。电镜见A组线粒体高度肿胀、外膜缺损、嵴断裂溶解,出现无定形致密体、四膜嵴和杆状嵴等改变。B组线粒体轻度或中度肿胀、少数有轻度嵴溶解。个别线粒体内出现无定形致密体。三组线粒体超微结构立体计量数据比较,A组线粒体密度、线粒体体密度与肌原纤维体密度比率增高((P<0.01),线粒体比表面和比膜面降低(P<0.01)。自身动图像分析仪检测SDH反应灰度值A组呈强损伤反应,B组反应较轻,二者差别有显著性(P<0.05)。结果表明,心肌缺血再灌可致线粒体发生不可逆性损伤,SOD能减轻线粒体缺血再灌性损伤。     

雷米普利与BQ-123合用对大鼠在体心肌缺血／再灌注损伤的保护作用

目的：研究雷米普利与BQ-123合用对大鼠在体心肌缺血／再灌注损伤的影响。方法：健康雄性Wistar大鼠随机分为5组,制备缺血30min再灌注120min模型,采用雷米普利、BQ-123单用及两药联合应用的方式处理实验动物。观察两药合用对大鼠在体心肌缺血／再灌注损伤的保护作用。观察动物心率、血压、心电图ST-段变化,记录缺血期室性心律失常;检测血浆CK及LDH活力;心肌HE染色和TIC染色,定性和定量检测心肌梗死情况。结果：与I／R组比较,各给药组ST-段均明显降低;缺血期室性心律失常（VA）出现时间明显推迟且持续时间明显缩短,联合给药组作用更为显著;心律失常发生率明显降低;血浆CK及LDH活力显著降低且联合给药组降低更为显著;梗死面积明显缩小,心肌损伤程度明显减轻,其中联合给药组变化更为显著。结论：雷米普利、BQ-123单用及联合应用均对大鼠在体心肌缺血／再灌注损伤有保护作用,且两药合用在推迟缺血期VA的出现时间,缩短其持续时间,减少CK及LDH漏出,缩小心肌梗死面积方面优于两药各自单用。     

粉防己碱对大鼠心肌缺血再灌注时心肌ATP酶活性的影响

实验旨在观察在体大鼠短暂缺血后心肌膜ＡＴＰ酶活性的变化及粉防己碱（Ｔｅｔ）的作用。分离缺血１５ｍｉｎ、再灌注２ｈ后及在缺血再灌注前给Ｔｅｔ的大鼠心肌粗制质膜和内质网,测定质膜Ｎａ＋－Ｋ＋－ＡＴＰ酶和内质网Ｃａ２＋－ＡＴＰ酶活性。结果表明,心肌缺血１５ｍｉｎ后二酶活性均明显降低,分别为假结扎组的６３．６％和７２．６％（Ｐ＜０．０１）,再灌注后Ｎａ＋－Ｋ＋－ＡＴＰ酶活性有所恢复,再灌注３０ｍｉｎ时为假结扎组的７２．１％（Ｐ＜０．０１）,而Ｃａ２＋－ＡＴＰ酶活性则进一步下降,再灌注３０ｍｉｎ时为假结扎组的５０．４％（Ｐ＜０．０１）,再灌注后２ｈ二酶活性分别升高至假结扎组的８０．９％和６５．３％（Ｐ＜０．０１）。在缺血前２０ｍｉｎ分别给予Ｔｅｔ６４．２和９６．３μｍｏｌ／ｋｇ及硝苯啶（０．２３μｍｏｌ／ｋｇ）,能明显减少内质网Ｃａ２＋－ＡＴＰ酶活性的降低。结果提示心肌膜ＡＴＰ酶活性的降低可能参与了短暂心肌缺血所致再灌注损伤的发生机制,Ｔｅｔ可减少缺血和／或再灌注时内质网Ｃａ２＋－ＡＴＰ酶活性降低。     

莱菔硫烷通过抑制细胞凋亡改善大鼠心肌缺血再灌注损伤

目的 研究莱菔硫烷(sulforaphane,SFN)对心肌缺血再灌注(ischemia-reperfusion,I/R)后大鼠心脏的保护作用以及机制.方法 构建大鼠心肌I/R模型,通过血液动力学实验研究SFN对I/R损伤后大鼠心脏功能的影响,通过HE染色和Evans blue/TTC染色研究SFN对I/R损伤后大鼠心...     

大鼠心脏缺血-再灌注损伤对心肌L-Arg/NO途径的影响

为探讨大鼠心脏缺血-再灌注损伤(IRI)期间一氧化氮(NO)生成增加的环节和过程。本实验用离体灌流大鼠心脏,预灌流15 min,停灌45 min,取30 ml KH 液循环灌流15 min,观察冠脉流出液中细胞胞浆酶(LDH)、蛋白质、肌红蛋白漏出量和NO     

细胞因子在心肌缺血再灌注损伤中的作用机制

心肌缺血再灌注损伤(Myocardial Ischemic/Reperfusion Injury,MI/RI)已成为临床心肌梗塞病人血管再通后重要的死亡因素之一,对于这一过程中因细胞因子诱导炎症反应的的作用机制仍是目前研究的热点。本文综述了与MI/RI相关的细胞因子的作用及其机制,并就其相互作用进行探讨。     

Dipalmitoylphosphatidylcholine liposomes reduce [3H]acetylcholine levels in an eserine-sensitive manner in rat cerebral cortical synaptosomes

We investigated the effects of various phospholipids on the presynaptic levels of newly synthesized [³H]acetylcholine (ACh) in rat cerebral cortical synaptosomes. When administered as small unilamellar vesicles (200–500 Å diameters) dipalmitoylphosphatidylcholine (DPPC) reduced [³H]ACh levels in concentration and time-related manners, while increasing the efflux of labelled choline to a similar extent. The reductions in synaptosomal [³H]-ACh levels induced by DPPC (3 mg/ml) were found in the cytosolic S₃ but not microsomal P₃ fraction, arguing for a cytoplasmic, nonvesicular site of action. DPPC-induced reductions in [³H]ACh levels were blocked by 100 M eserine, a tertiary amine cholinesterase inhibitor, but not with 100 M neostigmine, a quaternary ammonium inhibitor. Large unilamellar vesicles (2000–5000 Å diameters) consisting of soybean-phosphatidylcholine reduced [³H]ACh levels to the same extent that small vesicles did at the same concentration (3 mg/ml). Taken together, these results suggest that DPPC can fuse with membranes to increase the hydrolysis of cytoplasmic ACh via a small intra-terminal subpopulation of cholinesterases.     

The relation between membrane lipid phase separation and frost tolerance of cereals and other cool climate plant species

Abstract. The temperatures at which liposomes prepared from membrane phospholipids begin to phase separate were compared to the temperatures at which intact plants were damaged. Woody perennials tolerated temperatures below which their membrane phospholipids began to phase separate. By contrast, rye and wheat seedlings were damaged about 25°C above their phase separation temperature. Differences in tolerance among cultivars pre-hardened to frost were reflected by changes of the phase separation temperature. The results support the notion that alterations in membrane lipid composition are associated with frost hardening. A correlation between the temperature of phase separation and frost tolerance suggests that lipid properties may influence freezing tolerance of cereals; however, the lethal event is apparently not phase separation of the membrane phospholipids.     

A model for the asymmetric lipid distribution in the human erythrocyte membrane

The asymmetric transverse distribution of phospholipids in the human erythrocyte membrane can be explained by differences between the rate constants of flip and flop motion of the lipids. A selective interaction between aminophospholipids and spectrin does not need to be assumed for creating and maintaining the asymmetric localization of these lipids. Shape transformation of red cells could be caused by alterations of the flip-flop rate constants leading to a change of the lipid distribution and, consequently, to a differential area expansion of the outer and inner membrane leaflet.     

Localisation of DivIVA by targeting to negatively curved membranes

DivIVA is a conserved protein in Gram-positive bacteria and involved in various processes related to cell growth, cell division and spore formation. DivIVA is specifically targeted to cell division sites and cell poles. In Bacillus subtilis, DivIVA helps to localise other proteins, such as the conserved cell division inhibitor proteins, MinC/MinD, and the chromosome segregation protein, RacA. Little is known about the mechanism that localises DivIVA. Here we show that DivIVA binds to liposomes, and that the N terminus harbours the membrane targeting sequence. The purified protein can stimulate binding of RacA to membranes. In mutants with aberrant cell shapes, DivIVA accumulates where the cell membrane is most strongly curved. On the basis of electron microscopic studies and other data, we propose that this is due to molecular bridging of the curvature by DivIVA multimers. This model may explain why DivIVA localises at cell division sites. A Monte-Carlo simulation study showed that molecular bridging can be a general mechanism for binding of proteins to negatively curved membranes.     

The Effects of N-Terminal Fragments of Immunophilin on Phospholipid Composition of Rat Brain and Human Erythrocyte Membranes

Rat brain slices and human erythrocyte membranes have been incubated in the presence of water-soluble synthetic peptide fragments corresponding to residues 1–9 and 1–15 of the N-terminus of immunophilin and the effects on the phospholipid composition examined. During a 2 h incubation in the presence of 1 nM, 0.1 M, and 10 M concentrations of the peptides there were observed significant and dose-dependent decreases in the amounts of phosphatidylcholine and phosphatidylethanolamine, as well as increases in the amounts of phosphatidylserine and, to a less extent, phosphatidylinositol, cardiolipin and lysophosphatidylcholine. The overall decrease in the neutral phospholipids of rat brain, and no changes in human erythrocyte membranes with the simultaneous increase in the acidic phospholipids, both in brain and erythrocyte membranes, tended to counteract any changes in the phospholipid composition of the material studied. The results are discussed in terms of the possible effects of immunophilin on modulating phospholipid turnover in brain cell erythrocyte membranes.     

Effect of hypo- and hyperthyroid states on phospholipid composition in developing rat heart

The aim of this study was to examine the effect of hypo- and hyperthyroidism on the phospholipid composition in developing rat heart. The hypothyroid state (PTU) was induced by 0.05% 6-n-propyl-2-thiouracil in drinking water given to nursing mothers from the postnatal day 2–21. The hyperthyroidism (T₃) was made by daily injection of 3,3,5-triiodo-L-thyronine (10 g/100 g body wt) to newborns in the same time period. Age matched intact littermates were taken as euthyroid controls. PTU decreased the concentration of total phospholipids (PL), choline phosphoglycerides (PC), ethanolamine phosphoglycerides (PE) and diphosphatidylglycerol (DPG) and increased the proportion of plasmalogen component of PE (PLPE). T₃ increased the concentration of PL, PC, PE, DPG and decreased PLPE in comparison with euthyroid controls. The ratio of saturated/unsaturated fatty acids (FA) in PE was decreased in PTU and increased in T₃ group. The ratio of n-6/n-3 polyunsaturated FA in PC, PE and phosphatidylinositol (PI) was increased in PTU due to increase of 18:2n-6 and decrease of 22:6n-3 proportion. T₃ decreased this ratio because of decline in 20:4n-6 and rise in 22:6n-3 proportion. Both hypo- and hyperthyroidism decreased the ratio of 20:4n-6/18:2n-6 in the majority of phospholipids. PTU decreased the unsaturation index in PC, PI and phosphatidylserine. It is concluded that thyroid state plays an essential role in the development of membrane phospholipid components in cardiac membranes during the early postnatal period.     

Brain cell membrane motion-restricted phospholipids: a cerebral 31-phosphorus magnetic resonance spectroscopy study of patients with schizophrenia

This study directly assessed, for the first time, whether there was a change in brain cell motion-restricted membrane phospholipids in vivo in patients with schizophrenia with mild to moderate negative symptoms, by quantification of the underlying broad resonance signal of cerebral 31-phosphorus magnetic resonance scans. Cerebral 31-phosphorus magnetic resonance spectroscopy was carried out in 16 schizophrenia patients and 16 age- and gender-matched normal controls. Spectra were obtained from 70x70x70 mm3 voxels using an image-selected in vivo spectroscopy pulse sequence. There was no significant difference in the broad resonances between the two groups, with the mean (S.E.) percentage signal being 59.4 (5.6) for the patients and 53.5 (5.9) for the controls. The phosphomonoesters and phosphodiesters narrow signals also did not differ significantly, their ratio being 0.26 (0.01) in the patients and 0.25 (0.01) in the controls. These results appear to be at variance with the changes expected under the membrane phospholipid hypothesis of schizophrenia.     

Differential desiccation sensitivity of corn and Pennisetum pollen linked to their sucrose contents

Abstract. Two pollen species from the Gramineae family were investigated as to their differential sensitivity to desiccation. Germination in vivo ceased to occur after previous drying to 7–8% moisture content in Zea mays and 3% in Pennisetum typhoides. The reduced vitality coincided with extensive membrane damage, as evidenced by the considerable leakage of fluorescein and K⁺ from the prehumidified grains into liquid media. Further experiments were undertaken to investigate the basis for this interspecific difference: (1) phospholipid analyses revealed little difference in composition and content both before and after drying; (2) free fatty acid contents increased in both species upon drying but levels were generally low; and (3) sucrose was the sole soluble carbohydrate found in both species. Fresh maize pollen contained 5% sucrose, as compared to 14% in Pennisetum pollen. During slow drying (8h) this level went up to 12% and 17%, respectively. Drying corn pollen in the cold (2°C), or at high rate, limited sucrose levels and affected the resistance to drying. The authors conclude that survival of dehydration is correlated with the presence of sucrose. Finally, they tested the ability of sucrose to preserve dry liposomes prepared from phospholipids purified from the two species. When liposomes were dried in the presence of sucrose, fusion and leakage could largely be prevented at mass ratio's of sugar to lipid of > 4. Trehalose was also effective but myo-inositol was not. No species differences were observed. The authors suggest that the presence of sucrose is a key factor in preserving membranes in dry pollen.