Muscle hypertrophy in bodybuilders

Summary Muscle biopsy samples were obtained from m. vastus lateralis and m. deltoideus of three high caliber bodybuilders. Tissue specimens were analysed with respect to relative distribution of fast twitch (FT) and slow twitch (ST) fiber types and different indices of fiber area. In comparison to a reference group of competitive power/weight-lifters the following tendencies were observed: the percentage of FT fibers was less, mean fiber area was smaller and selective FT fiber hypertrophy was not evident. Values for fiber type composition and fiber size were more similar to values reported for physical education students and non-strength trained individuals. The results suggest that weight training induced muscle hypertrophy may be regulated by different mechanisms depending upon the volume and intensity of exercise.     

The I allele of the angiotensin-converting enzyme gene is associated with an increased percentage of slow-twitch type I fibers in human skeletal muscle

The insertion (I) allele of the human angiotensin-converting enzyme (ACE) gene is associated with lower serum and tissue ACE activity, and with greater endurance performance and enhanced mechanical efficiency of trained muscle. We tested the hypothesis that the ACE-I allele may be associated with increased slow-twitch fiber, which is more efficient than fast-twitch fiber in low-velocity contraction, by examining the association between the ACE genotype and skeletal muscle fiber (SMF) types in 41 untrained healthy young volunteer subjects (31 males, 10 females, age 24 +/- 3 years). Skeletal muscle samples were taken from the left vastus lateralis using the needle-biopsy method. Slow-twitch type I fibers and fast-twitch type IIa and IIb fibers were classified histochemically based on staining for myosin adenosine triphosphatase (ATPase) activity at different pH values. Amylase-periodic acid-Schiff staining was used to visualize capillaries around fibers. ACE-II subjects had significantly (p < 0.01) higher percentages of type I fibers (50.1 +/- 13.9%vs 30.5 +/- 13.3%) and lower percentages of type IIb fibers (16.2 +/- 6.6%vs 32.9 +/- 7.4%) than ACE-DD subjects. The linear trends for decreases in type I fibers and increases in type IIb fibers from ACE-II --> ID --> DD genotypes were significant as assessed by an analysis of variance. The ratio of type I:II fibers also differed according to the ACE genotype. A multivariate logistic regression analysis showed that the ACE-I allele had significant additive and recessive (codominant) effects on the increased type I fibers and the ratio of type I:II fibers. No specific pattern of capillarization was observed among the three ACE genotypes. In conclusion, the ACE-I allele was associated with increased type I SMF, which may be a mechanism for the association between the ACE genotype and endurance performance.     

Muscle electric activity I: A model study on the effect of needle electrodes on single fiber action potentials

Needle recorded electromyographic signals can be expected to be influenced by the presence of the needle, the electrical double layer at the metal-electrolyte interface, and by an edematous layer around the needle electrode. The magnitude of each of these effects is derived from a cylinder symmetrical volume conductor model. Analytical solutions of Laplace's equation have been derived. These are used for simulating single muscle fiber action potentials (SFAPs) recorded by a typical single fiber electrode. The results indicate that there is no short-circuiting effect, in spite of the presence of a highly conducting needle shaft, which is due to the high impedance of the electrical double layer. The insulating properties of the double layer cause the SFAP amplitudes to increase, when the muscle fiber passes the electrode at the side of the leading-off point. The edematous layer counteracts this increase depending on the thickness and the conductivity of this layer. Only slight SFAP waveform changes are found.     

慢性低频电刺激对背阔肌纤维类型、组织化学特性及血供的影响

目的：为探讨慢性低频电刺激影响骨骼肌耐疲劳性的机理。方法：用频率为２Ｈｚ的电脉冲刺激家兔背阔肌４周，采用组织化学和血管灌注组织切片、图像分析方法，观测背阔肌纤维类型及能量代谢、血供等方面的变化。结果：背阔肌经慢性低频电刺激，其Ⅰ型纤维所占比例由１８．４±２．２％增加至２９．３±３．４％。琥珀酸脱氢酶的活性、肌糖原含量及毛细血管密度均明显增加。结论：２Ｈｚ的电刺激可以使背阔肌耐疲劳性增强，为背阔肌动力型心肌成形术提供了实验形态学依据     

Fiber differentiation of the human laryngeal muscles using the inhibition reactivation myofibrillar ATPase technique

Summary The aim of the present study was to further subdivide the type II fibers of the human thyroarytenoid and posterior cricoarytenoid muscles by means of a modified myosin ATPase reaction. In order to understand the functioning of these highly strained muscles better, it is important to know the respective percentage of fatigue-resistant type IIA fibers and fatigable type IIB fibers. The material comprised the larynges of seven laryngectomized males aged between 45 and 70 years and four laryngectomized females aged between 39 and 72 years. After having been frozen in nitrogen, 10-m-thick sections were cut from the laryngeal muscles in a cryostat. The pH-lability of the enzyme that can be utilized in a classical myosin ATPase reaction permits a differentiation between fiber types I, IIA and IIB. Evidently, this is not possible with every human muscle. The fiber types IIA and IIB of the thyroarytenoid and the posterior cricoarytenoid muscles could be clearly distinguished by means of the inhibition reactivation myofibrillar ATPase technique. Using this method, the myosin ATPase enzyme was initially inhibited by hydroxymer curibenzoate and subsequently reactivated by cysteine. Regarding the incidence of type I and IIA fibers, there was a statistically significant difference between the thyroarytenoid and the posterior cricoarytenoid muscles. The type IIA fiber content was statistically significantly higher in the arytenoid muscle than in the posterior cricoarytenoid muscle. The percentage of type IIB fibers was low, not only in the thyroarytenoid muscle and the posterior cricoarytenoid muscle but also in the other laryngeal muscles. The share of fiber types I, IIA and IIB in the thyroarytenoid muscles varied greatly from one patient to another. This was also true for the other laryngeal muscles. This aspect may be especially significant with regard to an individual's vocal character and vocal fatigability under stress.     

Quantitative Analysis of Fiber Disarray Developing in Papillary Muscles Unloaded after Mitral Valve Replacement

Muscle fiber disarray which developed in the papillary muscle released from its chordal attachment after mitral valve replacement (MVR) was analysed histometrically in 23 hearts. The degree of disarray, or how far the fiber arrangement deviated from an ideal condition in which the fibers are considered to be aligned in parallel, was evaluated in terms of the "disarray index". This index corresponds to the ratio of the minor to major axes of a regression ellipse which can be obtained histometrically by plotting the reciprocal of the number of muscle fibers intersected by a test line of equal length in every direction on a polar coordinate system. The index can vary continuously in a range from 0.00 for a completely parallel fiber alignment to 1.00 for a completely random distribution. The estimated index showed a gradual increase from 0.05 to 0.68 according to the postoperative survival period after MVR with a significant positive correlation (r=0.793, p< 0.01). The index was inversely correlated with the mean muscle fiber diameter (r=-0.433, p<0.05). These results indicate that the disarray which develops in the papillary muscle after MVR is a deformation of the normally parallel arrangement of fibers toward an isotropic texture under focal disruption of the normally longitudinally oriented tensile force. Acta Pathol Jpn 39: 779-785, 1989.     

人工组织神经移植物辅加神经再生素修复大鼠周围神经缺损的实验研究

目的　用人工组织神经移植物辅加神经再生素 (NRF)桥接修复大鼠周围神经缺损。　方法　用壳聚糖套管和聚乙醇酸纤维制成人工组织神经移植物 ,辅加促神经生长的中药有效组分NRF ,桥接大鼠坐骨神经缺损10mm。术后作足迹试验 ;2 4周时对再生神经进行电生理学测试、形态学观察和计量学统计。　结果　术后 2 4周内 ,动物未见炎症及排斥反应。实验组的再生神经在足迹试验、电生理学、形态学及计量学上优于硅胶管桥接组。结论　人工组织神经移植物辅加NRF与周围神经组织具有良好的生物相容性 ;它对缺损的神经修复有较好的桥梁和促进作用     

皮质脑干纤维终末的超微结构——溃变电镜法研究

用溃变电镜法观察了１２只大鼠的中缝大核，蓝斑，旁正中网状核，巨细胞状核，桥核，外侧网状核和下橄榄主核中皮质下行纤维终末的溃变型，超微结构及突触联系。结果如下：（１）皮质纤维有三种溃变型，即电子致密型，微丝增生型和电子透明型。以电子致突型为主。（２）三种溃变型在各核中出现的数量和种类不同。（３）电子致密型溃变终扣有含圆形清亮型小泡，多形清亮型小泡和混合型小泡三种终扣。各核中，三种不同小泡终扣的出现种