Preferential localization of varying forms of photoactive 1, 8-naphthalimide compounds within the atheromatous arterial wall.

BACKGROUND AND OBJECTIVE: We are currently working with a novel class of photoactivated 4-amino substituted 1,8-naphthalimide compounds for tissue bonding. With promising results in other tissues, we are pursuing potential vascular applications. This study focused on determining the appropriate compound formulation(s), concentration, and exposure times to optimize penetration of the heterogeneous arterial wall. STUDY DESIGN/MATERIALS AND METHODS: Segments of atheromatous rabbit carotid artery were immersed in hydrophilic or lipophilic forms of the compound, then frozen, cryosectioned, and examined by confocal microscopy. RESULTS: The hydrophilic compound exhibited preferential localization within the intima and media and limited presence in the adventitia. Conversely, the lipophilic compound concentrated in the intima and adventitia with virtual exclusion from the media. Exposure to both forms resulted in complete penetration of the arterial wall. CONCLUSION: These results extend our knowledge and permit a more practical approach to potential vascular applications using these photoactivated compounds for tissue bonding.

Low power, type II errors, and other statistical problems in recent cardiovascular research.

Frequently in biomedical literature, measurements are considered "not statistically different" if a statistical test fails to achieve a P value that is < or = 0.05. This conclusion may be misleading because the size of each group is too small or the variability is large, and a type II error (false negative) is committed. In this study, we examined the probabilities of detecting a real difference (power) and type II errors in unpaired t-tests in Volumes 246 and 266 of the American Journal of Physiology: Heart and Circulatory Physiology. In addition, we examined all articles for other statistical errors. The median power of the t-tests was similar in these volumes (approximately 0.55 and approximately 0.92 to detect a 20% and a 50% change, respectively). In both volumes, approximately 80% of the studies with nonsignificant unpaired t-tests contained at least one t-test with a type II error probability > 0.30. Our findings suggest that low power and a high incidence of type II errors are common problems in this journal. In addition, the presentation of statistics was often vague, t-tests were misused frequently, and assumptions for inferential statistics usually were not mentioned or examined.