The Chicago Manual of Style has some excellent tips in its recent 16th edition Questions and Answers (http://bit.ly/iKD21w).
You might, for instance, find their take interesting on repetition of molecules with several variants, or repetition of any entity with numbered variants. The specific example they deal with – interleukin – comes from their questioner. There are, in fact, seventeen variants given in the Wikipedia entry, and the abbreviations conform to the following rule: IL-1, IL-2 and so on. Obviously, too many abbreviations can be confusing. What rule should the copy editor follow? The Chicago Manual team suggest the eminently practical rule of giving the full name in any sentence dealing with several variants, following this by the corresponding abbreviation, and using abbreviations only for the rest of the series. This gives, for example, "interleukin 1 (IL-1), IL-5, and IL-7".
As publications manager, you could make the decision whether to allow this rule to apply to larger units such as a paragraph or even a short document. Whatever you decide, you should publish it in your organization style guide.
Dare I correct the manual? Only in the most collaborative spirit. In this issue, one questioner asks about the recurrent headache of whether to repeat units of measurement or percentage signs in expressions like "60 to 65% of subjects ..." Or should it be "60% to 65% of subjects ..." instead? The first form is the correct one according to the Chicago team, except if the abbreviation or symbol is "closed up to the number", i.e. 25%–41%. I presume they meant, "close up to the number" as in, "adjacent with no space in between". It's reassuring that we can all slip up occasionally, isn't it?
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