Quantification of normal dystrophin mRNA following myoblast transplantation in mdx mice

A mutagenesis RT-PCR method was used to detect normal dystrophin mRNA following the injection of normal myoblasts in mdx mice using two immunosuppressors. A specific sequence of the dystrophin mRNA (257 bp) was amplified by RT-PCR from the muscle total RNA. Maell digestion of the amplified products allowed us to distinguish the normal messenger of dystrophin from the dystrophic one and to establish the percentage of normal and of dystrophic (mdx) dystrophin mRNA. Normal dystrophin mRNA was detected using this technique in mdx muscles transplanted with histocompatible normal myoblasts. For this type of transplantation, no significant difference in the percentage of normal dystrophin mRNA was observed between immunosuppressed mice and those not immunosuppressed. No normal dystrophin mRNA was, however, observed in mdx mice following histoincompatible normal myoblast transplantation without immunosuppression. When such transplantations were done in mice immunosuppressed with cyclosporine or FK-506, normal dystrophin mRNA accounted for 31% and 36% of the total dystrophin mRNA, respectively. In fact, one animal immunosuppressed with FK-506 expressed as much as 57% of normal dystrophin mRNA. These results thus show that FK-506 makes it possible to restore dystrophin expression to a level comparable to that observed in DMD carriers that are usually asymptomatic. © 1995 John Wiley & Sons, Inc.     

Alterations in membrane electrical properties during long-term denervation of rat skeletal muscle

Some membrane electrical properties of the extensor digitorum longus muscle of the rat were examined up to 21 days after denervation. The resting potential was significantly more depolarized at 3 days after denervation than it was at later times. The rate of rise (dV/dt) of the action potential decreased throughout the time course of the study but approached a steady value between 14 and 21 days after denervation. In addition, the dV/dt of tetrodotoxin (TTX)-resistant action potentials increased up to and including 7 days after nerve section, but declined thereafter. When expressed as % of control, the dose-response to TTX was similar throughout denervation. It is suggested that the large depolarization observed early in denervation may be related to the turnover of membrane constituents occurring at this time. The results also suggest that denervation produces a reduction in the number of fast TTX-sensitive Na⁺ channels with the appearance of a new population of slow TTX-resistant channels. However, long term denervation results in a reduction in the density of both types of channels.     

Transport ATPases of cardiac sarcolemma in 20,25-diazacholesterol induced myopathy.

20,25-Diazacholesterol, known to induce myotonia in skeletal muscle, also affects cardiac muscle as can be concluded from the development of cardiomegaly. At the same time (Na+, K+) ATPase of cardiac sarcolemmal membranes of the 20,25-diazacholesterol treated rats showed an increased activity as compared with control animals (91 percent and 46 percent stimulation respectively). The Ca++ stimulated ATPase showed the same tendency (96 percent and 64 percent stimulation). In the plasma of the treated rats creatine phosphokinase activity was found to be elevated whereas the amount of protein-bound iodine was decreased, a finding that is common in myotonic dystrophy.     

The Control of Muscle Contracture by the Action of Dantrolene on the Sarcolemma

Although dantrolene reverses the muscle contracture seen during a malignant hyperpyrexia (MH) crisis, its site of action is not known. It has been inferred from previous work that the major abnormality in MH is in the sarcoplasmic reticulum, and that dantrolene must act on this organelle. In the present study the ability of dantrolene to control drug-induced muscle contraction was tested. The drugs were chosen because their sites of action were known for inducing contracture. Dantrolene had no effect on contractures induced by 2:4 dinitrophenol, exerted only a minor effect on caffeine contractions, but reduced significantly the contracture produced by K⁺. It is postulated that the major action of dantrolene is on the sarcolemma, which may be the site of the MH abnormality.     

Na+-K+-ATPase is not involved in the warming-up phenomenon in generalized myotonia

The initial temporary weakness that occurs in autosomal-recessive generalized myotonia diminishes with repetitive contractions. Physiological understanding of this phenomenon is incomplete. The underlying hypothesis of our study was that the "warming-up" phenomenon relates to the exercise-related activation of Na(+)-K(+)-ATPase. Three patients performed isometric exercise of the brachioradialis muscle on two separate days. Randomly, on one of these days the contraction was preceded by a 30-min infusion of the Na(+)-K(+)-ATPase inhibitor ouabain into the brachial artery of the exercising arm (0.4 mug.min(-1).dl(-1)). Force was measured simultaneously with electrical muscle activity using high-density surface electromyography (HD-sEMG). A transient rapid decline in force occurred after initiation of exercise, accompanied by electrophysiological changes indicating sarcolemmal conduction block. Ouabain infusion did not affect the recovery from transient paresis or the accompanying electromyographic changes, indicating that the warming-up phenomenon in generalized myotonia is not mediated by Na(+)-K(+)-ATPase.     

利多卡因、异丙酚对缺血再灌注心肌细胞膜Na^＋—K^＋—ATP酶、肌浆网Ca^2＋—ATP酶活性的影响

目的观察利多卡因、异丙酚对缺血再灌注心肌细胞膜Na _K _ATP酶、肌浆网Ca2 _ATP酶活性的影响。方法SD大鼠48只 ,随机均分为6组。假手术组 ;生理盐水组 ;利多卡因5mg·kg-1 组 ;利多卡因10mg·kg-1 组 ;异丙酚300μg·kg-1·min-1 组 ;异丙酚1000μg·kg-1·min-1 组。于缺血前5min ,生理盐水及利多卡因经股静脉注射给药(30s内注射完) ;异丙酚持续输注至缺血开始时为止。结扎冠脉左前降支 ,造成左室前壁相应心肌组织缺血15min ,然后松开结扎线再灌注10min ,应用分光光度法测定心肌细胞膜Na _K _ATP酶、肌浆网Ca2 _ATP酶活性。结果利多卡因可明显地促进肌浆网Ca2 _ATP酶活性的恢复(P<0.05) ,大剂量时还促进心肌细胞膜Na _K _ATP酶活性的恢复(P<0.05)。异丙酚可显著地促进心肌细胞膜Na _K _ATP酶活性的恢复(P<0.05 ,P<0.001),大剂量时促进肌浆网Ca2 _ATP酶活性的恢复(P<0.05)。结论利多卡因、异丙酚可促进再灌注期间心肌细胞膜Na _K _ATP和肌浆网Ca2 _ATP酶活性的恢复 ,从而抑制钙超载而减轻心肌缺血再灌注损伤。     

胸肌肌膜瓣包裹法乳房悬吊术

目的探索一种持久有效的乳房松弛悬吊术式。方法对于乳头位置低于乳房下皱襞的乳房下垂患者,采用乳晕周边"双环"切口加垂直切口,胸肌肌膜瓣包裹乳腺的方法进行校正。结果自2008年9月—2011年4月,共16例乳头位置低于下皱襞水平乳房松弛患者采用该法手术,术后均无皮瓣血运障碍,切口愈合良好,乳头乳晕无坏死、感觉障碍等并发症。1例患者术后并发血肿,清除后预后良好。随访6个月到2年,效果良好,乳头乳晕复合体位于乳房最高点,两侧乳房位置对称。患者均满意。结论乳晕周边"双环"切口加垂直切口,胸肌肌膜瓣包裹法矫正乳房松弛下垂为一种持久有效的乳房松弛悬吊术式。     

Mechanisms of Ca2+ overload induced by extracellular H2O2 in quiescent isolated rat cardiomyocytes

Rat cardiomyocytes were exposed to H₂O₂ (1–100 μmol/L) for 10 min with washout for 10 min. Intracellular Ca²⁺ concentration ([Ca²⁺]_i) was measured using fluo-3. [Ca²⁺]_i increased with 100 μmol/L H₂O₂ and further increased during washout, causing irreversible contracture in one-half of the cells. The increase in [Ca²⁺]_i with 10 μmol/L H₂O₂ was modest with few cells showing irreversible contracture and attenuated by caffeine, and [Ca²⁺]_i gradually decreased during washout and this decrease was accelerated by a calcium-free solution, while 1 μmol/L H₂O₂ did not have any effects on [Ca²⁺]_i or cell viability. Ca²⁺ overload caused during exposure to 100 μmol/L H₂O₂ was attenuated by caffeine with improved cellular viability but not by chelerythrine, KB-R7943 or nifedipine. With 100 μmol/L H₂O₂ calcium-free solution attenuated the increase during exposure and washout while KB-R7943 or chelerythrine partly attenuated further increase during washout but not improved cell viability, but chelerythrine did not have additional effect on calcium-free treatment. Catalase abolished the effects of H₂O₂. We concluded that the increased [Ca²⁺]_i during exposure to 100 μmol/L H₂O₂ was caused both by release of Ca²⁺ from the intracellular store sites including the sarcoplasmic reticulum and by influx through route(s) other than the voltage-dependent Ca²⁺ channels or Na⁺/Ca²⁺ exchanger, although the Na⁺/Ca²⁺ exchanger or protein kinase C-mediated mechanism was partly responsible for a further increase during washout. Received: 1 February 2001, Returned for revision: 19 February 2001, Revision received: 11 April 2001, Accepted: 11 April 2001     

Dystrophin–glycoprotein complex: Its role in the molecular pathogenesis of muscular dystrophies

Dystrophin, the protein product of the Duchenne muscular dystrophy (DMD) gene, is associated with a large oligomeric complex of sarcolemmal glycoproteins, including dystroglycan which provides a linkage to the extracellular matrix component, laminin. In patients with DMD, the absence of dystrophin leads to the loss in all of the dystrophin-associated proteins, causing the disruption of the linkage between the subsarcolemmal cytoskeleton and the extracellular matrix. This may render the sarcolemma vulnerable to physical stress. These recent developments in the research concerning the function of the dystrophin–glycoprotein complex pave a way for the better understanding of the pathogenesis of muscular dystrophies. © 1994 John Wiley & Sons, Inc.