Day: July 1, 2013

Monday, 1 July 2013

10:06 – Thanks to everyone who recommended add-ons to make Windows 8 usable. When I have a spare moment, I’ll install Classic Shell on Frances’ system. If that works as expected, I probably won’t have to install the Windows 8.1 fix once it becomes available.

One of the items on my to-do list is making up solutions for more biology and life science kits. One of those is eosin Y stain, and I’m debating with myself about what to do. Until now, we’ve been supplying a 1% aqueous solution made up with Winston-Salem tap water, which is very soft but does have some calcium ions. We use tap water because eosin Y actually works better when some calcium ions are present. We also add a tiny percentage (~ 0.05%) of glacial acetic acid, again because eosin works better in the presence of very dilute acetic acid.

By “works better” I mean “stains more intensely”, and that’s the problem. Eosin Y is a very subtle stain. When used properly, Eosin differentiates structure types by the intensity of the staining: eosinophilic structures are stained intensely red-orange; erythrocytes a bright pink-orange; muscle tissues a paler pink-orange; and collagen a light pinkish-orange. There are two ways to get this differentiation. First, by progressively staining with a dilute (0.1% to 0.5%) eosin solution. Second, by overstaining with a stronger (1% or greater) eosin solution followed by decolorizing in alcohol or another destaining agent.

The problem is that most (I am tempted to say “all”) beginners are prone to overstaining. They’ll add a drop of stain to the fixed slide, wait 30 seconds, and then decide they’d better wait a bit longer, just in case. After all, too much is always better than not enough, right? And they almost never decolorize. After all, again, why remove the stain you just added, right?

The formulation we’ve been supplying–1% eosin with both calcium ions and acetic acid–has a big advantage: it guarantees results, in the sense that the specimen will indeed be stained. But this concentrated formulation is what I’d use myself, and I’d decolorize after staining. So I’m thinking about changing to a 0.5% concentration in DI water. The downside to this is that it may not stain intensely enough to suit an experienced user, unless they stain for longer than they’re used to doing. The upside is that a typical beginner who uses this concentration will probably “overstain”, as usual, and as a result see some actual differentiation.

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