Egginton S
Department of Physiology, University of Birmingham Medical School, UK.
J Anat. 1990 Feb;168:73-80.
The composition of a mixed fast skeletal muscle (rat extensor digitorum longus) was examined to quantify the difference between the relative number of the three major fibre types in a representative muscle and their relative contribution to muscle cross-section, i.e. numerical (NN) and areal (AA) densities, respectively. These two indices clearly differ in their physiological relevance. While the former may be useful in describing hyperplasia, the latter allows for differences in size among fibre types. When estimated as NN, over 20% of fields contained 5-10% SO fibres and less than 5% had 75-80% FG fibres. In contrast, only 2% of fields had an AA of 5-10% for SO fibres while around 30% contained 75-80% FG fibres. The importance of a direct method for estimating AA is emphasised, as an indirect approach may have an error of 20-30% when used for oxidative fibre types. The use of an unbiased sampling regime to minimise error in determining both numerical and areal densities of different fibre types is illustrated.
对混合性快收缩骨骼肌（大鼠趾长伸肌）的组成进行了检测，以量化代表性肌肉中三种主要纤维类型的相对数量差异，以及它们对肌肉横截面积的相对贡献，即分别为数字密度（NN）和面密度（AA）。这两个指标在生理相关性上明显不同。前者可能有助于描述增生情况，而后者则考虑了纤维类型之间的大小差异。当以NN估计时，超过20%的视野含有5 - 10%的慢氧化纤维（SO），不到5%的视野含有75 - 80%的快糖酵解纤维（FG）。相比之下，只有2%的视野中SO纤维的AA为5 - 10%，而约30%的视野含有75 - 80%的FG纤维。强调了直接估计AA方法的重要性，因为间接方法用于氧化纤维类型时可能有20 - 30%的误差。说明了使用无偏抽样方案以尽量减少确定不同纤维类型的数字密度和面密度时的误差。
