RNA-RNA in situ hybridization using DIG-labeled probes: the effect of high molecular weight polyvinyl alcohol on the alkaline phosphatase indoxyl-nitroblue tetrazolium reaction. RNA-RNA in situ hybridization protocol using alkaline phosphatase-conjugated digoxigenin-(DIG-) labeled probes is presented. The addition of polyvinyl alcohol (PVA) of high molecular weight (40 – 100 kD) to the BCIP-NBT detection system enhances the alkaline phosphatase reaction and prevents...