Capillary supply of skeletal muscle fibers in untrained and endurance-trained women

Summary Muscle fiber diameters and number of capillaries per fiber, per mm² and around each fiber were determined in needle biopsies from the lateral part of the quadriceps muscle of 11 young women. Six subjects were untrained (UT) and five were endurance-trained athletes (ET). Average values for maximal oxygen uptake were 43.9 (UT) and 62.1 ml/kg×min (ET). Mean fiber diameter was somewhat smaller in the UT than in the ET group (39.1 and 42.7 m), but the difference was not statistically significant. Fibers with the highest content of mitochondria were on the average 9 m thicker than those with the lowest content.The capillary per fiber ratios were 1.11±0.07 (mean±S.E.) and 1.69±0.13 in the UT and ET groups, respectively. The number of capillaries around each fiber was 3.04±0.17 (UT) and 4.42±0.31 (ET). After correction for shrinkage the number of capillaries per mm² was 301 (UT) and 404 (ET). The capillary per fiber ratio increased with increasing fiber diameter and with the content of mitochondria.     

Assessment of skeletal muscle damage in successive biopsies from strength-trained and untrained men and women

Summary The effects of repeated biopsy sampling on muscle morphology was qualitatively and quantitatively assessed in strength-trained and untrained men and women. College-age men (13) and women (8) resistance trained twice a week for 8 weeks. A progressive resistance-training program was performed consisting of squats, leg presses, and leg extensions. Nontraining men (7) and women (5) served as controls. Muscle biopsy specimens and fasting bloods were obtained at the beginning and every 2 weeks and histochemical, biochemical, and ultrastructural methods were employed to assess the type and amount of damage. Except for a few scattered atrophic fibers in 2 of the 33 biopsy samples, all initial specimens were normal. In contrast, many of the subsequent biopsy samples from both untrained and resistance-trained men and women contained evidence of damage. Ultrastructural analysis confirmed that degenerative-regenerative processes were occurring in both groups. However, training subjects had a four-fold greater number of damaged fibers than nontraining subjects (8.53% vs 2.08%). In addition, only biopsy samples from training individuals contained fibers with internal disorganization (e.g., Z-line streaming, myofibrillar disruption). Calpain II levels in the biopsy samples and serum creatine kinase activity were not significantly affected supporting the light and electron microscopic observations that most of the damaged fibers were normal in appearance except for their small diameter. In summary, focal damage induced by the biopsy procedure is not completely repaired after 2 weeks and could affect the results, particularly cross-sectional area measurements. Moreover, resistance training appears to cause additional damage to the muscle and may delay repair of the biopsied region.     

Influences of endurance training on the ultrastructural composition of the different muscle fiber types in humans

To investigate changes in the ultrastructure of the different muscle fiber types induced by endurance training ten sedentary subjects (five women and five men) were exercised on bicycle ergometers 5 times a week for 30 min. After 6 weeks of training there were significant changes in (+14%), in the percentage of type I (+12%) and type IIB fibers (–24%) as well as in the volume densities of mitochondria. The latter increased 35% in type I, 55% in type IIA and 35% in type IIB fibers. The relative increase in subsarcolemmal mitochondria was larger than in interfibrillar mitochondria in all fiber types. There was also a significant increase in the volume density of intracellular lipid in type II fibres. It is concluded that high intensity endurance training leads to an enhancement of the oxidative capacity in all muscle fiber types.     

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     

Pigmented granules in functional black adenoma of the adrenal gland: A histochemical and ultrastructural study

A black adenoma of the adrenal gland was laparoscopically removed from an 61-yr-old Japanese female who had clinical and laboratory findings characteristic of Cushing’s syndrome. The tumor consisted of polygonal cells that contained numerous brown pigmented granules of various sizes by routine hematoxylin-eosin staining. The histochemical study showed that the pigment had the characteristics of lipofuscin, not of melanin or neuromelanin. Electron microscopic study revealed tumor cells with two types of pigmented granules. These results show that there might be differences in the lipid metabolism of individual tumor cells in black adenomas of adrenal; which suggests an interesting histogenesis for these granules.