自体骨髓间充质干细胞移植对急性心肌梗死后心律失常影响的实验研究

目的 观察自体骨髓间充质干细胞(MSC)移植对小型猪心肌梗死后心律失常的影响,并研究其作用机制.方法 利用介入方法制作小型猪心肌梗死模型并进行自体MSC移植.MSC移植组12头和心肌梗死对照组10头,分别于移植2 h及4周后通过电生理程序刺激,观察室性心动过速(室速)的发生情况.于建模4周后,通过膜片钳技术研究移植后MSC在心肌环境下的离子通道表达和梗死区域心电异质性变化.结果 (1)建模后2 h MSC移植组9头(75%)、对照组9头(90%)诱发出室速,两组间差异无统计学意义(P=0.445).术后4周MSC移植组3头(25%)、对照组8头(80%)可诱发出持续性单形性室速(P=0.012).(2)MSC移植组的心外膜细胞(Epi)、心内膜细胞(Endo)和中层细胞(M)INa峰值电流密度分别为(-12.43±3.04)pA/pF、(-14.04±3.82)pA/pF和(-29.26±5.70)pA/pF,对照组梗死边缘区的Epi、Endo和M层INa峰值电流密度分别为(-8.47±3.34)pA/pF、(-9.71±3.38)pA/pF和(-18.98±4.05)pA/pF;MSC移植组在三层心肌的表达具有异质性,与对照组相比差异具有统计学意义(P<0.05).(3)MSC移植未室速组MSC的Epi、Endo和M层INa失活半数电压分别为(-93.1±13.8)mV、(-95.2 ±15.5)mV和(-103.4±8.7)mV,MSC移植室速组分别为(-126.2±10.9)mV、(-106.7±11.9)mV和(-105.4±11.0)mV,心肌梗死室速组分别为(-129.1±10.9)mV、(-112.2±9.9)mV和(-109.7±9.3)mV,MSC移植室速组和心肌梗死室速组相比各层差异无统计学意义(P>0.05),和MSC移植未室速组相比各层差异有统计学意义(P<0.05).(4)多元logistic回归分析表明INa失活半数电压(RR=1.449,95%CI1.276～2.079,P=0.029)、INa峰值密度(RR=1.092,95%CI1.008～1.917,P=0.012)是影响心肌梗死室性心律失常的独立危险因素.结论 自体MSC移植致心律失常可能性较小,且有抑制梗死后心律失常发生的作用.自体MSC在心肌内可分化成为具有心肌细胞离子通道特性的类心肌细胞,其离子通道分化程度可能是影响室性心律失常发生的主要机制.     

新生大鼠心肌细胞短暂外向钾电流下降与心肌肥大的相关性研究

在某些心力衰竭患者中常观察到心肌细胞短暂外向钾电流 (Ito)下降和动作电位时程 (APD)延长 ,笔者主要探讨Ito下降与心肌肥大的关系及内在机制。用Ito阻断剂 ,4 氨基吡啶 (4 AP) ,处理新生大鼠心室肌细胞 ,观察作为心肌肥大指标的细胞膜电容和3 H 亮氨酸 (3 H Leu)掺入量 ,同时测Ito振幅和APD。结果 :Ito振幅下降近 5 0 %(1 5 0 .3± 1 8.6pA ,n =7vs 74 .0± 1 1 .5pA ,n =1 1 ,P <0 .0 5 )。APD50 (5 0 %复极 )显著的延长 (75 .8± 1 4 .1ms,n =7vs2 0 1 .7± 2 3.5ms,n =1 1 ,P <0 .0 5 )。膜电容和3 H Leu掺入量分别增加 4 7%和 31 % (P均 <0 .0 5 )。L 型钙通道阻断剂维拉帕米 ,能抑制 4 AP诱导的APD延长以及膜电容和3 H 亮氨酸掺入量的增加。环孢素A(CsA)也可抑制 4 AP诱导的膜电容和3 H Leu掺入量的增加 ,但对APD影响不明显。结论 :Ito下降通过延长APD ,致细胞内钙增加 ,激活钙调神经磷酸酶反应途径 ,可能引起心肌肥大     

Regulation of protein kinase C by short term hyperglycaemia in human platelets in vivo and in vitro

Aims/hypothesis. Postprandial hyperglycaemia carries an increased risk of macrovascular disease even without Type II (non-insulin-dependent) diabetes mellitus. Chronic hyperglycaemia activates protein kinase C (PKC) in vitro and in vivo but it is not known whether PKC is regulated by short-term postprandial hyperglycaemia in vivo in humans. We investigated whether PKC is regulated in vivo in hyperglycaemic and hyperinsulinaemic infusion tests and correlated the results to stimulations in vitro. Methods. Protein kinase C regulation was measured in platelets obtained from 8 healthy subjects who were infused with glucose and insulin for 2 h attaining peak concentrations of 16 mmol/l glucose and in platelets from 8 healthy young subjects, 8 older subjects without diabetes, and 10 older subjects with Type II diabetes after incubation in vitro with 16 mmol/l glucose or glucose and insulin. For precise quantification, a shortened PKC β1 standard protein was generated by bacterial expression and PKC α, β1, β2 and δ isoenzyme values were measured by immunoblot analyses. Results. Hyperglycaemic and hyperinsulinaemic in vivo tests increased the amounts of PKC α, β1 and β2 in the membrane fraction of platelets to 225 ± 87 %, 164 ± 22 % and 302 ± 135 %, respectively, when compared with the baseline values in young healthy volunteers (n = 8, p < 0.05). The expression of PKC δ did not change. In comparison to the recombinant PKC β1 standard protein, 5 ng PKC β1/μg protein was measured before the test and 2 ng/μg were translocated to the membrane fraction after the infusion. No change in the absolute amount of PKC β1 was detected. In contrast, after incubation in vitro PKC was not regulated by glucose or glucose and insulin in 8 young healthy subjects (age 26 ± 0.7 years) and in 8 older, healthy subjects (age 64,8 ± 4 years) although 100 nmol/l 12-O-tetradecanoylphorbol 13-acetate caused maximal activation. In marked contrast, PKC β1 and PKC β2, but not PKC α or PKC δ, were increased in vitro in the membrane fraction by 292 ± 61 % and 432 ± 88 % (p < 0.05) in 10 subjects with Type II diabetes mellitus matched for age, sex and BMI. Conclusion/interpretation. We found that short-term hyperglycaemia activates PKC α, β1 and β2 in platelets of healthy persons making them potential candidates for mediating the increased cardiovascular risk of postprandial hyperglycaemia. Hyperglycaemia and hyperinsulinaemia did not cause short-term activation of PKC in platelets in vitro suggesting the existence of additional stimuli. Subjects with Type II diabetes showed a markedly altered reactivity of platelet PKC β in vitro indicating some diabetes-related regulation. [Diabetologia (2001) 44: 188–195] Received: 15 May 2000 and in revised form: 19 September 2000     

兔急性心肌梗死后梗死周边带心肌细胞L-型钙通道的变化

探讨L型钙通道在急性心肌梗死 (AMI)后室性心律失常发生中的作用及其机制。方法 :以开胸冠状动脉结扎法制备兔AMI模型 ,1周后处死动物分离心室肌细胞 ,采用全细胞膜片钳记录技术观察梗死周边缺血带心外膜心室肌细胞L型钙通道电流 (ICa L)的变化 ,以正常心肌ICa L为对照。结果 :AMI 1周时兔梗死周边区心室肌细胞L型钙电流受到抑制 ,其电流峰值由正常状态下的 - 5 .58± 1 .53pA/pF(对照组 ,n =1 0 )降至 - 3 .52± 0 .93pA/pF(AMI组 ,n=6) ,最大峰电流下降 2 9.1 % ,P <0 .0 5 ,I V曲线上移 ;其失活曲线左移 ,半数最大失活电位由 - 1 3 .1± 4 .2mV左移至 - 2 5 .9± 7.0mV ,P <0 .0 5 ,失活速度加快。结论 :AMI后 1周梗死周边带心外膜心室肌细胞L型钙通道受抑制 ,可能为AMI后室性心律失常发生的机制之一。     

On the effects of human galanin in man

Summary Human galanin was recently isolated and sequenced and was found to differ from porcine galanin, hitherto used for studies in humans, in several important respects. We therefore synthesized and purified human galanin and infused it i.v. at a rate of 74 pmol · kg^–1· min^–1 into six healthy volunteers for 60 min during a hyperglycaemic clamp. The clamp was achieved by i. v. infusion of glucose at a rate which in a control experiment had been demonstrated to maintain the plasma glucose level at 12–13 mmol/l for 90 min. Galanin concentrations reached a plateau of approximately 1500 pmol/l throughout the infusion as opposed to pre-infusion and control levels of 20–30 pmol/l. The glucose levels obtained in the two experiments were indistinguishable. Plasma levels of C-peptide and insulin increased significantly in both experiments and the dynamic concentration curves were almost identical. Glucagon concentrations in plasma decreased significantly and similarly. Growth hormone levels, however, increased eight-fold during galanin infusions. Galanin was eliminated from plasma with a half-life of 3.7±0.4 min, similar to that of porcine galanin. It is concluded that human galanin powerfully stimulates growth hormone secretion in man, but has no effect on pancreatic endocrine secretion or glucose metabolism in the concentrations obtained in this study.     

Dynamic assessment of parathyroid function in acute malaria

Davis TME, Singh B, Choo KE, Ibrahim J, Sulaiman SA, Kadir ZA, Ismail R (University of Western Australia, Fremantle Hospital, Fremantle, Western Australia, Australia. Universiti Sains Malaysia, Kubang Kerian, Kota Bharu; General Hospital, Kota Bharu, Kuala Krai Hospital, Kuala Krai; Kelantan, Malaysia) Dynamic assessment of parathyroid function in acute malaria. J Intern Med 1998; 243 : 349–54.

Objectives

To investigate the dynamic parathyroid response to rapidly induced, sustained hypocalcaemia in patients with acute malaria and in healthy volunteers.

Design

Serum intact parathormone (PTH) concentrations were measured on samples taken before and during a variable-rate tri-sodium citrate infusion designed to ‘clamp’ the whole blood ionised calcium concentration 0.20 mmol L^?1 below baseline for 120 min.

Subjects

Six Malaysian patients aged 17–42 years with acute malaria, four of whom were restudied in convalescence, and 12 healthy controls aged 19–36 years.

Main outcome measures

Whole-blood ionised calcium and serum intact PTH concentrations.

Results

The mean (SD baseline ionised calcium was lower in the malaria patients than in controls (1.09 ± 0.06 vs. 1.18 ± 0.03 mmol L^?1, respectively; P= 0.01) but PTH concentrations were similar (3.0 ± 1.8 vs. 3.3 ± 1.3 pmol L^?1; P= 0.33). Target whole-blood ionised calcium concentrations were achieved more rapidly in the controls than the patients (within 15 vs. 30 min) despite significantly more citrate being required in the patients (area under the citrate infusion-time curve 0.95 (0.25 vs. 0.57 ± 0.09 mmol kg^?1; P < 0.01). The ratio of the change in serum PTH to that in ionised calcium (δPTH/δCa²⁺), calculated to adjust for differences in initial rate of fall of ionised calcium, was similar during the first 5 min of the clamp (132 ± 75 × 10^?6 vs. 131 ± 43 × 10^?6 in patients and controls, respectively, P > 0.05), as were steady-state serum PTH levels during the second hour (7.0 ± 2.2 pmol L^?1 in each case). Convalescent patients had normal basal ionised calcium levels but the lowest serum intact PTH levels before and during the clamp, consistent with an increase in skeletal PTH sensitivity after treatment.

Conclusions

There is a decreased ionised calcium ‘set point’ for basal PTH secretion but a normal PTH response to acute hypocalcaemia in malaria. Skeletal resistance may attenuate the effects of the PTH response but patients with malaria appear relatively resistant to the calcium chelating effects of citrated blood products.

     

抗心律失常药物靶点——IKr/HERG通道的调控机制研究

目的探讨快速延迟整流钾电流（IKr／HERG）在缺血性心律失常发生过程中的调控作用及机制。方法新西兰兔12只，随机分为对照组和缺血组，采用酶解法分离单个心室肌细胞，应用全细胞膜片钳技术记录心室肌细胞IKr／HERG变化趋势；应用Western blot技术，检测转染小RNA（miRNA）后人乳腺癌（SKBr3）细胞IKr／HERG通道蛋白表达量的改变。结果IKr／HERG在实验电压＋60mV下，缺血组（2．25±0．31）pA／pF明显低于对照组（3．81±0．64）pA／pF；miRNA转染进入SKBr3细胞后，细胞膜IKr／HERG通道蛋白表达量降低，仅是对照组的10％。结论miRNA调控IKr／HERG通道蛋白的表达，进而抑制IKr／HERG，参与缺血性心律失常的发生与发展。     

Absorption kinetics and action profiles of mixtures of short-and intermediate-acting insulins

Summary The effects of mixing short- and intermediate-acting insulins (lente and NPH) on plasma insulin levels and action profiles, assessed by the euglycaemic clamp technique, were studied in 10 volunteers. Four protocols were used: (1) comparison between two semi-synthetic human soluble insulins in seven subjects (0.22 IU/kg); (2) assessment of insulin levels and action profiles of lente insulin in six subjects and of NPH insulin in five subjects (0.33 IU/kg); (3) comparison between mixtures of soluble with lente insulin and soluble with NPH insulin, administered immediately after mixing, in eight subjects (0.55IU/kg, 40% short-acting); (4) same mixtures, administered 2 days after preparation, in seven subjects. No differences in insulin levels and action profiles during the first 4 h after injection were found between both short-acting insulins and the soluble + NPH insulin mixtures. After the administration of NPH insulin, plasma insulin levels rose slightly faster in comparison with lente insulin, with no significant differences between the action profiles for either insulin. Onset of action was delayed after soluble + lente insulin, both when administered immediately after mixing and to a greater extent when stored for 2 days before administration. After the latter procedure, the onset of action was markedly retarded and only slightly faster than after lente insulin alone.We conclude, therefore, that mixing soluble with NPH insulin in a ratio of 2:3 does not affect the absorption kinetics of soluble insulin, whereas the onset of action is delayed when soluble is combined in the syringe with lente insulin, even when administered immediately after mixing.     

三种简易胰岛素敏感性指数在糖耐量异常时的可靠性

目的　探讨在糖耐量异常的情况下 ,三种简易胰岛素敏感性指数 (HOMA IR、ISI composite和ISI cederholm)的适用性。方法　对 13例空腹血糖正常 ,而糖耐量异常的高血压病患者 ,分别以葡萄糖钳夹试验中的稳态葡萄糖利用率 (M值 )及三种简易指数评估胰岛素敏感性。结果　ISI composite和ISI cederholm与M值的相关性 (r分别为 0 687,0 5 94,P <0 0 5 )优于HOMA IR(r =-0 3 73 ,P >0 0 5 ) ,校正 β细胞功能指数后 ,ISI composite和ISI cederholm与钳夹结果的相关性更加显著 (r分别为 0 63 2 ,0 64 0 ,P <0 0 5 ) ,HOMA IR与钳夹仍未显示相关性 (r =-0 3 5 3 ,P >0 0 5 )。结论　对糖耐量异常的高血压病患者进行小样本的临床研究 ,不宜选用HOMA IR评价胰岛素敏感性 ,而ISI composite和ISI ceder holm则是可取的 ,且宜首先校正 β细胞功能指数     

血管紧张素Ⅱ对人心房肌细胞膜钾钙离子电流的作用

观察血管紧张素Ⅱ对人心房肌细胞膜主要离子流的作用,揭示其参与房性心律失常的细胞电生理机制。急性分离单个人心房肌细胞,采用全细胞膜片钳方法记录细胞膜短暂外向钾电流(Ito)、内向整流钾电流(Ik1)和L型钙电流(ICaL)。结果:0.1μmol/LAngⅡ使人心房肌细胞膜Ito峰值电流密度明显下降6.54±0.49pA/pFvs12.65±0.86pA/pF(P<0.05),在-100mV电压下使IK1峰值电流密度显著升高-8.93±1.12pA/pFvs-5.23±0.95pA/pF,(P<0.05),并明显促进人心房肌细胞膜ICaL-12.72±1.69pA/pFvs-5.79±0.84pA/pF(P<0.05)。结论:AngⅡ可促进人心房肌细胞膜IK1及ICaL,抑制人心房肌细胞膜Ito。