Detection of low iNOS mRNA levels in fetal membranes (FM) by nested RT-PCR, in serum-free cultures. Lane 1 fetal membranes immediately after collection, lane 2 control (cultured membranes without PAF), lane 3 10 nM PAF, lane 4 positive control (CHOiNOS cells), lane 5 PCR blank (no template), lane 6 empty, lanes M ΦX174 DNA/Hae III marker. The expected size of the product was 262 base pairs. The faint band below the main band at 262 base pairs was present in all gels and appeared to be an artefact of nested amplification. This is one example of four identical results with four different samples of fetal membranes.