Quantitation of expressed message for inducible nitric oxide synthase

Methodology for the analysis of expressed message has evolved rather rapidly since the early 1990s and will undoubtedly continue to evolve with new technology. cRNA standards are a useful tool, which allow for absolute rather than relative quantification of an expressed message. Selecting an appropriate sequence(s) for analysis has become even more important as techniques have evolved from Northern hybridization where possible multiple hybridization bands can be observed to real-time Rt-PCR approaches where only a signal is recorded. NOS2 presents a particular problem in this regard because of the high conservation of sequence with NOS1 and NOS3, as well as the existence of both multiple genes and splice variants, which may be of experimental importance.