Upregulation of inducible nitric oxide synthase (iNOS) expression in faster-healing chronic leg ulcers.

OBJECTIVE: Chronic leg ulcers represent a growing clinical problem in the light of today's ageing population. Nitric oxide (NO), which is mostly produced by inducible nitric oxide synthase (iNOS) in healing wounds, exerts beneficial effects on many processes of healing, including bactericidal effects, angiogenesis, epithelialisation and ECM formation. This study sought to investigate whether iNOS expression in chronic leg ulcers can be correlated with the healing process. METHOD: Sixteen patients with chronic leg ulcers were recruited and attempts were made to take punch biopsies at two separate time points (however, a second biopsy could not be obtained on seven patients). A linear healing rate was derived using the obtained ulcer area and perimeter. The iNOS levels in the biopsy samples were assessed using immunoblotting. RESULTS: The mean linear healing rate of patients with high iNOS levels was significantly higher (p < 0.01) than that of patients with low iNOS levels. An incidental finding was that the linear healing rate was significantly higher (p < 0.05) post-biopsy than before biopsy in the same patients. CONCLUSION: This study therefore shows for the first time that high iNOS levels are associated with higher healing rates and have the potential to be used in prognostication. This also opens the possibility of augmentation of ulcer healing through the manipulation of wound NO levels.

Localization of phosphodiesterase-4 isoforms in the medulla and nodose ganglion of the squirrel monkey.

Pre-clinical and clinical studies are currently underway to evaluate the potential of phosphodiesterase-4 (PDE4) inhibitors for the treatment of chronic obstructive pulmonary disease and other inflammatory conditions of the airways. The most common side effect associated with this class of compounds is emesis. The squirrel monkey provides a model for evaluating the efficacy of PDE4 inhibitors and their emetic potential. The distribution of three PDE4 isoforms (A, C and D) has been investigated in the squirrel monkey medulla and nodose ganglion to determine which isoform(s) could be responsible for the emetic adverse effects. The distribution of PDE4 isoforms was delineated using immunohistochemistry with antibodies specific for PDE4A, PDE4C and PDE4D and by in situ hybridization with isoform-selective riboprobes. PDE4A was present in the medulla where expression was mostly restricted to glial cells and the vasculature. PDE4C was not detected in either the medulla or nodose ganglion. Finally, the PDE4D isoform was localized to neurons in the nodose ganglion and found through many structures of medulla including the area postrema, neurons of the nucleus tractus solitarius and locus coeruleus. These data are consistent with a role for PDE4D in the emetic response.

Chemoprevention of intestinal polyposis in the Apcdelta716 mouse by rofecoxib, a specific cyclooxygenase-2 inhibitor.

Mutations in the human adenomatous polyposis (APC) gene are causative for familial adenomatous polyposis (FAP), a rare condition in which numerous colonic polyps arise during puberty and, if left untreated, lead to colon cancer. The APC gene is a tumor suppressor that has been termed the "gatekeeper gene" for colon cancer. In addition to the 100% mutation rate in FAP patients, the APC gene is mutated in >80% of sporadic colon and intestinal cancers. The Apc gene in mice has been mutated either by chemical carcinogenesis, resulting in the Min mouse Apcdelta850, or by heterologous recombination, resulting in the Apcdelta716 or Apedelta1368 mice (M. Oshima et al., Proc. Natl. Acad. Sci. USA, 92: 4482-4486, 1995). Although homozygote Apc-/- mice are embryonically lethal, the heterozygotes are viable but develop numerous intestinal polyps with loss of Apc heterozygosity within the polyps (M. Oshima et al., Proc. Natl. Acad. Sci. USA, 92: 4482-4486, 1995). The proinflammatory, prooncogenic protein cyclooxygenase (COX)-2 has been shown to be markedly induced in the Apcdelta716 polyps at an early stage of polyp development (M. Oshima et al., Cell, 87: 803-809, 1996). We demonstrate here that treatment with the specific COX-2 inhibitor rofecoxib results in a dose-dependent reduction in the number and size of intestinal and colonic polyps in the Apcdelta716 mouse. The plasma concentration of rofecoxib that resulted in a 55% inhibition of polyp number and an 80% inhibition of polyps > 1 mm in size is comparable with the human clinical steady-state concentration of 25 mg rofecoxib (Vioxx) taken once daily (A. Porras et al., Clin. Pharm. Ther., 67: 137, 2000). Polyps from both untreated and rofecoxib- or sulindac-treated Apcdelta716 mice expressed COX-1 and -2, whereas normal epithelium from all mice expressed COX-1 but minimal amounts of COX-2. Polyps from either rofecoxib- or sulindac-treated mice had lower rates of DNA replication, expressed less proangiogenic vascular endothelial-derived growth factor and more membrane-bound beta-catenin, but showed unchanged nuclear localization of this transcription factor. This study showing the inhibition of polyposis in the Apcdelta716 mouse suggests that the specific COX-2 inhibitor rofecoxib (Vioxx) has potential as a chemopreventive agent in human intestinal and colon cancer.

ECAT ART - a continuously rotating PET camera: performance characteristics, initial clinical studies, and installation considerations in a nuclear medicine department.

Advances in fully three-dimensional (3D) image reconstruction techniques have permitted the development of a commercial, rotating, partial ring, fully 3D positron emission tomographic (PET) scanner, the ECAT ART. The system has less than one-half the number of bismuth germanate detectors compared with a full ring scanner with the equivalent field of view, resulting in reduced capital cost. The performance characteristics, implications for installation in a nuclear medicine department, and clinical utility of the scanner are presented in this report. The sensitivity (20 cm diameterx20 cm long cylindrical phantom, no scatter correction) is 11400 cps.kBq-1.ml-1. This compares with 5800 and 40500 cps.kBq-1.ml-1 in 2D and 3D respectively for the equivalent full ring scanner (ECAT EXACT). With an energy window of 350-650 keV the maximum noise equivalent count (NEC) rate was 27 kcps at a radioactivity concentration of approximately 15 kBq.ml-1 in the cylinder. Spatial resolution is approximately 6 mm full width at half maximum on axis degrading to just under 8 mm at a distance of 20 cm off axis. Installation and use within the nuclear medicine department does not appreciably increase background levels of radiation on gamma cameras in adjacent rooms and the dose rate to an operator in the same room is 2 microSv. h-1 for a typical fluorine-18 fluorodeoxyglucose (18F-FDG) study with an initial injected activity of 370 MBq. The scanner has been used for clinical imaging with18F-FDG for neurological and oncological applications. Its novel use for imaging iron-52 transferrin for localising erythropoietic activity demonstrates its sensitivity and resolution advantages over a conventional dual-headed gamma camera. The ECAT ART provides a viable alternative to conventional full ring PET scanners without compromising the performance required for clinical PET imaging.