Effects of phorbol ester on carbachol-induced contraction in bovine ciliary muscle: possible involvement of protein kinase C

The aim of the research was to characterize muscarinic receptors of bovine ciliary muscle and to investigate the desensitization process. The role of protein kinase C was analyzed. The results show that muscarinic receptors of bovine ciliary muscle have the pharmacological characteristics of the M₃ subtype. Acute exposure to phorbol esters (1 μM phorbol 12,13-dibutyrate, PDB, or 0.1 μM phorbol 12-myristate 13-acetate, PMA, for 15 and 5 min, respectively) resulted in antagonism of muscarinic receptor-mediated contraction. Long-term pretreatment (18 h) with PMA to down-regulate protein kinase C resulted in potentiation of carbachol-induced contraction, reduction of agonist-induced desensitization and loss of phorbol ester-induced desensitization. Staurosporine (3 μM) and H₇ [1-(5-isoquinolinesulfonyl)-2-methyl-piperazine] (1 μM), protein kinase C inhibitors, produced a significant potentiation of the contractile effect of carbachol, reduced the desensitization produced by repeated addition of carbachol and suppressed that induced by phorbol esters. In vitro incubation with carbachol, PDB or PMA did not cause any modification of the binding of labeled [³H]quinuclidinyl benzilate. In vitro incubation with PDB and PMA produced, as expected, a significant translocation of protein kinase C from the cytosol to the membrane. The incubation of the ciliary muscle with carbachol, using the protocol of exposure that induced maximal desensitization of contractile responses, produced a significant redistribution of the enzyme from the cytosol to the membrane. These findings suggest that agonist-induced modulation of functional cholinergic sensitivity in ciliary muscle is correlated, at least partially, to the translocation of protein kinase C from the cytosol to the membrane. The desensitization by phorbol esters is completely due to protein kinase C activation; during the desensitization process, direct modification of the density and affinity of muscarinic receptors is not involved.     

The effect of ionic strength on the kinetics of rigor development in skinned fast-twitch skeletal muscle fibres

 Recent atomic 3-D reconstructions of the acto-myosin interface suggest that electrostatic interactions are important in the initial phase of cross-bridge formation. Earlier biochemical studies had also given strong evidence for the ionic strength dependence of this step in the cross-bridge cycle. We have probed these interactions by altering the ionic strength (Γ/2) of the medium mainly with K⁺, imidazole⁺ and EGTA^2– to vary charge shielding. We examined the effect of ionic strength on the kinetics of rigor development at low Ca²⁺ (experimental temperature 18–22°C) in chemically skinned single fast-twitch fibres of mouse extensor digitorum longus (EDL) muscle. On average the delay before rigor onset was 10 times longer, the maximum rate of rigor tension development was 10 times slower, the steady-state rigor tension was 3 times lower and the in-phase stiffness was 2 times lower at high (230 mM) compared to low (60 mM) ionic strength. These results were modelled by calculating ATP depletion in the fibre due to diffusional loss of ATP and acto-myosin Mg.ATPase activity. The difference in delay before rigor onset at low and high ionic strength could be explained in our model by assuming a 15 times higher Mg.ATPase activity and a threefold increase in K _m in relaxing conditions at low ionic strength. Activation by Ca²⁺ induced at different time points before and during onset of rigor confirmed the calculated time course of ATP depletion. We have also investigated ionic strength effects on rigor development with the activated troponin/tropomyosin complex. ATP withdrawl at maximum activation by Ca²⁺ induced force transients which led into a ”high rigor” state. The peak forces of these force transients were very similar at low and high ionic strength. The subsequent decrease in tension was only 10% slower and steady-state ”high rigor” tension was reduced by only 27% at high compared to low ionic strength. Addition of 10 mM phosphate to lower cross-bridge attachment strongly suppressed the transient increases in force at high ionic strength and reduced the steady-state rigor tension by 17%. A qualitatively similar but smaller effect of phosphate was observed at low ionic strength where steady-state rigor force was reduced by 10%. The data presented in this study show a very strong effect of ionic strength on rigor development in relaxed fibres whereas the ionic strength dependence of rigor development after thin filament activation was much less. The data confirm the importance of electrostatic interactions in cross-bridge attachment and cross-bridge-attachment-induced activation of thin filaments. Received: 3 September 1997 / Received after revision and accepted: 12 December 1997     

取代四氢异喹啉衍生物的合成及其生物活性

粉防己碱有钙拮抗作用,临床试用于治疗高血压,其裂解产物钙拮抗作用降低,但有α-肾上腺素能受体拮抗作用,本文以裂解物为先导化合物设计合成了两类取代的四氢异喹啉衍生物Ⅲ及Ⅳ。初步药理试验表明:大部分化合物有α-肾上腺素能受体拮抗作用,少数化合物钙拮抗活性有所增强,其中Ⅲ_15,19对正常麻醉大鼠有一定的降压作用、Ⅳ_17,19对实验性动物心律失常有明显的保护作用。部分化合物量化计算表明:化合物与α₁-受体作用方式可能是形成电荷转移复合物。     

Plastic surgical treatment of a chronic thoracic duct fistula using a sternocleidomastoid muscle flap — a case report

Thoracic duct fistula is a rare but potentially serious complication of head and neck surgery. Such fistulae may be difficult to treat, and several techniques, both operative and non-operative, have been advocated. A case of successful surgical treatment of a chronic thoracic duct fistula is presented. The fistula occurred in a 51-year-old female following treatment of a solitary supraclavicular breast metastasis by local excision and radiotherapy. The divided duct was ligated and the area was covered with the clavicular head of the sternocleidomastoid muscle.     

固尔苏治疗NRDS前后血管内皮分泌功能的改变

目的 :研究肺表面活性物质 (PS)治疗新生儿呼吸窘迫综合征 (NRDS)前后血管内皮分泌功能变化及可能的治疗机理。方法 :用PS制剂固尔苏治疗 18例NRDS患儿 ,于治疗前 3 0min ,治疗后 1、 6、 12、 2 4h ,用硝酸还原酶法测定NO (一氧化氮 )、放射免疫法测定ET (内皮素 )、 6 K PGF1α (6 酮前列环素 )。结果 :固尔苏治疗后患儿NO、 6 K PGF1α明显升高 ,ET明显下降 ,与治疗前比较有显著性差异 (P <0 0 1)。治疗后 1、 6、 12、 2 4hNO、6 k PGF1α、ET各组间两两比较无明显差异 (P >0 0 5 )。结论 :PS治疗NRDS的机理可能是通过改善血管内皮功能发挥作用 ,为用外源性NO吸入和静注前列环素辅助治疗NRDS提供可能的实验依据。     

胎肌条件培养液对白血病细胞的体外效应

以髓系(HL-60)与淋系(Molt-4)细胞为观察对象,用细胞计数、细胞集落培养、台酚蓝拒染及溴化二甲噻唑二苯四唑试验为观察手段,研究胎肌条件培养液(FMCM)对白血病细胞的影响.实验标本分为4组:①对照组.②20%FMCM处理组.③阿糖胞苷(Ara-C,1×10~(-7)M/L)处理组.④混合处理组(经FMCM与Ara-C二者的处理).发现:①FMCM对两个细胞株均无明显的直接作用.②当HL-60细胞经FMCM预处理或在用Ara-C处理同时加入FMCM,Ara-C对其抑制作用可为FMCM加强,已受Ara-C抑制的HL-60细胞则无此现象.③Ara-C对Molt-4的抑制作用不受FMCM的影响.由此而初步认为:①FMCM对白血病细胞似无明显直接作用.②某些(非全部)白血病细胞对Ara-C的敏感性可为FMCM加强.③在己受抑制的细胞中不呈现这种致敏现象.①提示FMCM有可能用于白血病临床治疗.     

Can a Single Muscle Fiber Model the Features of Myocardial Stunning?

The exact mechanisms that cause myocardial stunning are still unclear. We previously utilized a computer model of the ventricle that was effective in modeling the dominant observable features of stunning, but it was not simple to implement. This led to the design of a single muscle fiber model. The mathematical model of a muscle fiber consisted of three elements: a contractile element, a series elastic element, and a parallel elastic element. The model created length waveforms based on time-dependent force and contractile stiffness functions. This model was initially evaluated by entering the same regional parameter values used in the global dual region ventricular model. First a reduction of the contractile stiffness function was applied by reducing the peak stiffness by 30%, and then the rates of activation and deactivation were reduced by 20% while maintaining the peak values constant. The three-element model produced results very similar to the canine and ventricular model. Thus, it is concluded that the simpler three-element model provides an accurate model of the myocardial tissue and its deficiencies during stunning.     

Chest Wall Implants: Their Use for Pectus Excavatum,Pectoralis Muscle Tears,Poland's Syndrome,and Muscular Insufficiency

Solid customized and prefabricated silicone implants have been used by the author for 15 years in a wide range of chest wall deformities. Chest wall implants are often used in males seeking to augment a muscularly deficient or underdeveloped chest; however, their greatest use has come in a variety of deformities both congenital and acquired, such as pectus excavatum, Poland's Syndrome, and pectoralis muscle tears. The implants can be either customized using a moulage technique or are prefabricated, manufactured implants which can be modified on the operating table to repair the contour deformity. The immediate postoperative problem of seroma and subcutaneous implant ``show' has been minimized by careful planning, gentle technique, deep insertion, improved patient positioning on the operating room table, and the use of oral anti-inflammatory medications. The long-term results of these implants seem very satisfactory. The patients are usualy physically active, and the implants show no long-term sequelae such as seroma, infection, displacement, or rupture.     

胎肌条件培养液抗损伤效应的观察

胎肌条件培养液（ＦＭＣＭ）可在ＣＦＵ－ＧＭ体外培养中提供集落刺激活性。研究发现它还能在体外培养中保护ＣＦＵ－ＧＭ，减轻理化损伤因素对其生长的抑制效应。所用化学损伤因素为５×１０－７Ｍ的阿糖胞苷与９×１０－９Ｍ的三尖杉酯碱，物理损伤因素为放射（３．５Ｇｙ），热（４４℃，６０分钟）与冷（—２０℃，１６分钟）。在损伤因素作用下，ＣＦＵ－ＧＭ的集落产率受到明显抑制，用２０％ＦＭＣＭ处理后，抑制现象可以减轻。ＦＭＣＭ可以对抗多种因素对ＣＦＵ－ＧＭ的抑制作用，没有特异性。用胰蛋白酶或热（８５℃，３０分钟）处理后的ＦＭＣＭ不具上述保护效应，用酸（ＰＨ＝２），碱（ＰＨ＝１０），ＤＮＡ酶与透析处理则无明显影响。提示ＦＭＣＭ中起保护作用的活性物质可能为分子量大于１００００的蛋白质。