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LR White: Adding Catalyst To LR White

LR White user note covering the addition of a catalyst and using LR White for EM, hard tissue, immunohistochemistry, and light microscopy.

Adding catalyst to LR White

Our LR White is supplied uncatalysed with the catalyst (Benzoyl Peroxide) supplied separately in a tube. The advantage is that after catalysing our LR White has the greatest shelf life - about one year when refrigerated.

Adding all the supplied catalyst to a whole bottle of LR White is simple, but something can go wrong when its not done properly. It must be understood that much of the catalyst will dissolve within an hour, but if after initial shaking the bottle is left without occasional inverting, then the remaining catalyst settles and initiates an exothermic reaction. The heat further accelerates the reaction and an hour later the whole bottle may be very hot and solid. This is entirely avoidable.

After adding catalyst, shake the bottle vigorously for a couple of minutes and then use a means of reliably keeping the partially dissolved catalyst suspended. Either commit to frequent inverting of the bottle (first every couple of minutes, then increasing to every 10 minutes. Refrigerate the bottle after about three hours. Using a magnetic stirrer may be convenient, but never use heat and ensure that the magnet is stirring and not just sitting at the edge of the bottle. Slow stirring for 2 hours should mostly dissolve the catalyst and the bottle could then be refrigerated overnight before use. If a slow rotator or shaker (not in a hot-room) is available then the bottle with catalyst could be rotated for a couple of hours prior to refrigeration. Simple. Forgetting about a bottle that had catalyst just added is an expensive mistake.

Using L.R. White for Electron Microscopy

When using 'L.R. White' embedding resin for dedicated electron microscopy, very few changes need to be made to the regime used for epoxy resin embedding. Every laboratory has its own individual embedding schedule but we have laid out here a 'typical ' schedule for L.R. White as guidance for its use.

Using L.R. White for Hard Tissue

L.R. White can be used for the microtomy of decalcified bone and teeth and also for microtomy or "sawing and grinding" of undecalcified tissues.

Using LR White for Immunohistochemistry

Sections from L.R. White embedded tissue have been used successfully for immunocytochemistry at both the light microscope and electron microscope levels. This demonstrates quite clearly that the visualisation steps of the immunocytochemical procedure will penetrate the resin and react with the tissue antigens if they have been preserved in the tissue.

Using L.R. White for Light Microscopy

Resin embedding for light microscopy provides greatly improved cellular definition compared to paraffin embedding, and for this reason it is now widely used, particularly in diagnoses of Renal disease, Lymphomas and bone marrow trephines, as well as research.

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