Don K. Nakayama

Nitric oxide is a short-lived biologic mediator for diverse cell types. Synthesis of an inducible nitric oxide synthase (NOS) in murine macrophages is stimulated by lipopolysaccharide (LPS) and interferon gamma. In human hepatocytes, NOS activity is induced by treatment with a combination of tumor necrosis factor, interleukin 1, interferon gamma, and LPS. We now report the molecular cloning and expression of an inducible human hepatocyte NOS (hep-NOS) cDNA. hep-NOS has 80% amino acid sequence homology to macrophage NOS (mac-NOS). Like other NOS isoforms, recognition sites for FMN, FAD, and NADPH are present, as well as a consensus calmodulin binding site. NOS activity in human 293 kidney cells transfected with hep-NOS cDNA is diminished by Ca2+ chelation and a calmodulin antagonist, reflecting a Ca2+ dependence not evident for mac-NOS. Northern blot analysis with hep-NOS cDNA reveals a 4.5-kb mRNA in both human hepatocytes and aortic smooth muscle cells following stimulation with LPS and cytokines. Human genomic Southern blots probed with human hep-NOS and human endothelial NOS cDNA clones display different genomic restriction enzyme fragments, suggesting distinct gene products for these NOS isoforms. hep-NOS appears to be an inducible form of NOS that is distinct from mac-NOS as well as brain and endothelial NOS isozymes.

Differences in anatomy and mechanisms of injury are believed to contribute to the unique response of children to thoracic trauma. To characterize the scope and consequences of childhood chest injury, we reviewed the records of 105 children (ages 1 month to 17 years, mean 7.6 years) with chest injuries admitted to a level I pediatric trauma center from 1981 to 1988. Nearly all injuries (97.1%) were due to blunt trauma, and more than 50% were traffic related. Rib fractures, commonly multiple, and pulmonary contusions occurred with nearly equal frequency (49.5% and 53.3%, respectively), followed by pneumothorax (37.1%) and hemothorax (13.3%). One fourth of all pneumothoraces were under tension. Significant intrathoracic injuries occurred without rib fractures in 52% of cases with blunt trauma. Associated head, abdominal, and orthopedic injuries were present in 68.6% of children reviewed. One in five received endotracheal intubation and ventilatory support for 1 to 109 days. Presence or absence of head injury neither increased the need for respiratory support (29.4% vs. 17.2%, respectively; p = 0.24) nor affected the duration of support for those who were ventilated (6.8 +/- 8.9 days vs. 3.3 +/- 2.6 days, excluding one ventilator-dependent head-injured patient and five early deaths). The presence of associated injuries, intubation, and pneumothorax or hemothorax all resulted in significantly longer hospitalizations and more severe injury as measured by Injury Severity Score (ISS). Age, rib fracture, and contusion had no effect. Rarely encountered were ruptured diaphragm (2 cases), transection of the aorta (1), major tracheobronchial tears (3), flail chest (1), and cardiac contusion (2). Only two of the three children with penetrating injuries and three of the 83 (3.6%) with blunt injuries underwent chest operations. Six children (7%) died, one from a penetrating injury and five from blunt mechanisms. Chest Abbreviated Injury Scale (AIS) and ISS correlated significantly with mortality; age and head AIS did not. Rib fractures, lung contusions, and associated head, abdominal, and skeletal injuries are common because of the predominance of blunt-injury mechanisms. Nearly one half of chest injuries occurred without rib fractures. The need for ventilatory support is uncommon; when required, its duration is generally brief. Aortic transection, flail chest, and penetrating injuries more frequently encountered in adults and are uncommon in children. Thoracotomy generally is not required.(ABSTRACT TRUNCATED AT 400 WORDS)