Cullen M J, Hollingworth S, Marshall M W
J Anat. 1984 Mar;138 ( Pt 2)(Pt 2):297-308.
An ultrastructural comparison was made between the transverse tubular systems of the extensor digitorum longus (fast twitch) and the soleus (slow twitch) muscles in the rat. Quantitative measurements were made of the volume fraction, surface to volume ratio, surface density and foot density of the T system membrane. The values for the volume fraction and surface density were approximately 50% higher in the fast twitch (extensor digitorum longus) than the slow twitch (soleus) muscle. The dimensions of the tubules and hence the surface to volume ratio was the same in the two muscles. There was no difference in the spacing of the feet, so the reported three to fivefold difference in charge movement cannot be associated with a difference in foot density. Material lying within the lumen of the T tubules was observed in the majority of tubule profiles. This material, not hitherto described, was particulate or, more commonly, laminar in form.
对大鼠趾长伸肌（快肌）和比目鱼肌（慢肌）的横小管系统进行了超微结构比较。对T系统膜的体积分数、表面积与体积比、表面密度和足突密度进行了定量测量。快肌（趾长伸肌）的体积分数和表面密度值比慢肌（比目鱼肌）高约50%。两种肌肉中小管的尺寸以及表面积与体积比相同。足突间距没有差异，因此报道的电荷移动三到五倍的差异与足突密度的差异无关。在大多数小管断面中观察到T小管腔内存在物质。这种物质此前未被描述过，呈颗粒状，更常见的是呈层状。
