Na+ currents near and away from endplates on human fast and slow twitch muscle fibers

Fast and slow twitch muscle fibers have distinct contractile properties. Here we determined that membrane excitability also varies with fiber type. Na⁺ currents (I_NA) were studied with the loose-patch voltage clamp technique on 29 histochemically classified human intercostal skeletal muscle fibers at the endplate border and <200 μm from the endplate (extrajunctional). Fast and slow twitch fibers showed slow inactivation of endplate border and extrajunctional I_NA and had increased I_NA at the endplate border compared to extrajunctional membrane. The voltage dependencies of I_NA were similar on the endplate border and extrajunctional membrane, which suggests thatboth regions have physiclogically similar channels. Fast twitch fibers had larger I_NA on the endplate border and extrajunctional membrane and manifest fast and slow inactivation of I_NA at more negative potentials than slow twitch fibers. For normal muscle, the differences between I_NA on fast and slow twitch fibers might: (1) enable fast twitch fibers to operate at high firing frequencies for brief periods; and (2) enable slow twitch fibers to operate at low firing frequencies for prolonged times. Disorders of skeletal membrane excitability, such as the periodic paralyses and myotonias, may impact fast and slow twitch fibers differently due to the distinctive Na⁺ channel properties of each fiber type. © 1993 John Wiley & Sons, Inc.     

Neuroleptic malignant syndrome in the intensive therapy unit

A case of the neuroleptic malignant syndrome occurred in a 40-year-old male after administration of chlorpromazine while on an Intensive Therapy Unit. Treatment with dantrolene sodium was successful, and a muscle biopsy was examined in the recovery phase of the illness. The importance of this condition and the difficulties in establishing a diagnosis at an early stage in patients on an Intensive Therapy Unit are discussed, along with implications for treatment.     

Decreased expression of DMPK: correlation with CTG repeat expansion and fibre type composition in myotonic dystrophy type 1

Abstract Myotonic dystrophy type 1 (DM1) is an autosomal dominant disease caused by a trinucleotide repeatexpansion, cytosine-thymine-guanine (CTG)_n, in the 3′ untranslated region of a gene encoding the myotonic dystrophy protein kinase (DMPK). To correlate CTG expansion and protein expression, we studied muscle specimens from 16 adult DM1 patients using three anti-DMPK antibodies for immunoblotting. We estimated the amount of the full-length DMPK (85 kDa) in muscle biopsies from normal controls and from DM1 patients carrying different (CTG)_n expansions. We found that DMPK concentration was decreased to about 50% in DM patients’ muscles; the protein decrease did not seem correlated with the CTG repeat length. However, the fibre type composition in skeletal muscle seemed somehow to affect DMPK decrease, as the lowest level of the enzyme was found in patients with the lowest content of type 1 fibre.     

用Alabama分析法比较安氏Ⅰ类错中国人与美国白人颅颌面结构差异

目的:研究中国安氏Ⅰ类错成人与美国安氏Ⅰ类错白人牙颌颅面形态结构的差异。方法:从西安市11所大学2098名新生中选取符合标准的101名(男53名、女48名)安氏Ⅰ类错样本。拍摄头颅定位X线片,用第四军医大学口腔医学院头影测量软件测量,用Alabama分析法与美国安氏Ⅰ类错白人颅颌面测量结果进行比较分析。结果:中国西安地区安氏Ⅰ类错成人上下颌突度大,面型较突;平面倾斜度、上下中切牙倾斜度及下中切牙至NB线距均较大;Y轴相对SN平面夹角增大,生长方向为后下。结论:与美国安氏Ⅰ类错白人比较,中国西安地区安氏Ⅰ类错成人颅面结构呈现颌骨突度大、下切牙唇倾及下颌趋向后下等特征。     

安氏Ⅱ类错(牙合)畸形对青春期面部骨轮廓发育的影响

目的:研究安氏II类错畸形对青春期面部骨轮廓发育的影响。方法:收集安氏II类错畸形的成人患者和青少年患者共362例。摄取头颅定位侧位片及头颅定位正位片。对面高、面宽等19项测量项目做比较分析及t检验。结果:①安氏II类青少年患者与正常青少年相比,下颌基骨长度、下颌长度较小,但无统计学差异。②安氏II类成年患者与正常成年人相比,下颌基骨长度、下颌长度有显著性差异。③安氏II类患者下颌骨在青春发育期有向前、向上旋转的趋势。结论:安氏II类错畸形患者经过青春期发育,使面部畸形程度更加严重。本研究得出安氏II类错畸形对青春期面部骨轮廓发育的影响,对正颌外科和正畸治疗具有参考意义。     

心理干预对错[牙合]畸形治疗中合作行为及结果的影响

目的：观察心理干预对错[牙合]畸形患者正畸治疗中合作行为及结果的影响。方法：对门诊口腔科60例青少年[牙合]畸形患者随机分为干预组和对照组各30例。两组均由从事正畸工作5年以上的主治医师采用标准方丝弓技术进行矫正治疗，干预组同时实施心理干预等心理治疗。将两组治疗中的合作行为和结果进行比较分析。结果：心理干预组自律性、主动性、自觉性、矫治时间、满意度等均明显优于对照组，差异有显著性（P〈0．01）。结论：心理干预对青少年正畸患者治疗中合作行为和结果有明显影响，通过心理干预能提高矫治的效果，保证治疗的顺利完成。     

Newer aspects of antiarrhythmic drug development: Introduction

Although cardiac arrhythmias remain a serious clinical problem in many patients with heart disease, the exact role of antiarrhythmic drug therapy is currently under intense evaluation. Within the last several years it has become clear that there are significant risks as well as potential benefits associated with existing agents. Ongoing studies in large patient populations should help determine the benefit/risk ratio of traditional therapy. Regardless of the outcome of these trials, current electrophysiological dogma will have to be re-evaluated and newer concepts evolve for drug development to make further progress. The goal of this symposium is to exchange information among basic and clinical investigators so as to facilitate the emergence of novel electrophysiological concepts that will form the basis for future generations of antiarrhythmic drugs.     

断腕再植术后手内在肌挛缩

探讨断腕再植术后手内在肌挛缩的发生率、治疗方法及预防。方法:作者总结了近24年内进行断腕再植并得到随访的63例资料,对其中发生手内在肌挛缩41例的发病机理、治疗结果及预防进行了分析和讨论。结果:63例断腕再植术后有41例发生手内在肌挛缩,发生率为65％。缺血时间超过16小时与16小时内的断腕再植术后手内在肌挛缩的发生率,两者差异有显著性意义(t=3.81,p<0.05)。二期行手内在肌手术矫正者效果不理想。结论:断腕再植术后手内在肌挛缩的处理关键在于预防。清创后用肝素化全血对离断手进行灌注,早期行手内在肌筋膜间区减压,将会取得较好的效果。     

贵阳市婴幼儿和青少年发育调查研究 Ⅰ．骨龄研究

对贵阳市１５００名健康婴幼儿童和青少年进行骨发育的调查，根据手腕部骨Ｘ线解剖变化规律，观察每块骨从出现至成熟的过程中，骨化点的出现顺序、数量、形态和密度的改变等指标的系列变化，提出了骨发育评价标准。可供我省运动员选材、儿童少年发育咨询和临床治疗参考。