A comprehensive analysis of the structure of neuronal nitric oxide synthase (nNOS; EC 1.14.13.39) mRNA species revealed NOS1 to be the most structurally diverse human gene described to date in terms of promoter usage. Nine unique exon 1 variants are variously used for transcript initiation in diverse tissues, and each is expressed from a unique 5-flanking region. The dependence on unique genomic regions to control transcription initiation in a cell-specific fashion burdens the transcripts with complex 5-mRNA leader sequences. Elaborate splicing patterns that involve alternatively spliced leader exons and exon skipping have been superimposed on this diversity. Highly structured nNOS mRNA 5-untranslated regions, which have profound effects on translation both in vitro and in cells, contain cis RNA elements that modulate translational efficiency in response to changes in cellular phenotype.

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Aims-To determine the sensitivity and specificity of 99m Tc-Infecton (Infecton), a novel ciprofloxacin based imaging agent, in detecting sites of infection. Methods-Ninety patients thought to be suVering from a variety of infections were administered 300-400 MBq of Infecton intravenously. Whole body images were taken one and four hours later. Appropriate specimens were taken for microbiological investigations. Statistical analysis was performed using a computer statistical package. Results-Ninety eight Infecton images were produced. Forty one of these were positive, including three false positives, where the patients had non-infective conditions. Fifty seven negative images were obtained, of which 41 were true negatives and 16 were false negatives, having definite evidence of infection. Thus, Infecton imaging has a sensitivity of 70.3% and a specificity of 93.1% for detecting infective foci. The positive and negative predictive values were 92.6% and 71.9%, respectively. Conclusion-Infecton imaging is a new diagnostic tool that is specific for detecting sites of bacterial infection in the body. The high positive predictive value displayed by the technique is clinically important because a positive image strongly supports a diagnosis of bacterial infection. A negative result does not rule out an infection, and may be a result of previous or current antibiotic treatment and/or infection with organisms that do not take up Infecton. Infecton imaging has major advantages over well established imaging techniques, including radiolabelled leucocytes, and may prove to be a superior method for localising bacterial infections. (J Clin Pathol 1998;51:215-219)