Sentence:  In contrast to the nuclear changes described above , another change in muscle nuclei was seen , usually occurring in fibers that were somewhat smaller than normal but that showed distinct cross <WSD>striations</WSD> and myofibrillae . 
Meaning of the word marked with <WSD> tags:  any of a number of tiny parallel grooves such as: the scratches left by a glacier on rocks or the streaks or ridges in muscle tissue