RESUMO
Stress can have a significant impact on many aspects of an organism's physiology and behavior. However, the relationship between stress and regeneration, and how this relationship changes with age remains poorly understood. Here, we subjected young and old zebrafish to a chronic stress protocol and evaluated the impact of stress exposure on multiple measures of zebrafish behavior, specifically thigmotaxis (open field test) and scototaxis (light/dark preference test), and on regeneration ability after partial tail amputation. We found evidence that young and older adult fish are differentially impacted by stress. Only young fish showed a significant change in anxiety-like behaviors after being exposed to chronic stress, while their regeneration ability was not affected by the stress protocol. On the other hand, older fish regenerated their caudal fin significantly slower compared to young fish, but their behavior remained unaffected after being exposed to stress. We further investigated the expression of two candidate genes (nlgn1 and sam2) expressed in the central nervous system, and known to be associated with stress and anxiety-like behavior. The expression of stress-related gene candidate sam2 increased in the brain of older individuals exposed to stress. Our results suggest there is a close relationship between chronic stress, regeneration, and behavior in zebrafish (Danio rerio), and that the impact of stress is age-dependent.
RESUMO
OBJECTIVES: To determine the impact of rhinoplasty on the objective measurement and subjective appreciation of facial symmetry and to investigate whether perceptual shifts are correlated with objective changes in facial proportions. DESIGN: Frontal view photographs were used to measure bilateral symmetry ratios of the medial and lateral canthi, tragus, ala, and oral commissure in 100 patients before and 6 months after rhinoplasty. Gestalt dichotomous impressions of facial symmetry were also obtained in all cases. Paired t tests and chi(2) tests were used to compare facial proportions and the proportion of faces perceived as symmetrical, respectively, before and after surgery. The receiver operating characteristic and analysis of variance were used to assess whether perceptual shifts in symmetry could be correlated with objectively measurable changes in facial proportion. RESULTS: The number of faces perceived as symmetrical increased from 42 to 62 after rhinoplasty (P < .001, chi(2) test). Objectively, midline-to-ala symmetry increased from an average of 91.1% (5.5%) (mean [SD]) to 93.8% (4.5%) after rhinoplasty (P < .001, paired t test). Other facial proportions did not change significantly (P > .10). The degree of change in midline-to-ala symmetry was the only objective measure that was significantly associated with the subjective perception of the face as symmetrical or asymmetrical (P < .01, 1-way analysis of variance). Most positive perceptual shifts were associated with an objective improvement in nasal symmetry that was greater than 2%. Conversely, most negative perceptual shifts were associated with minimal postoperative improvement or loss of nasal symmetry. CONCLUSION: Rhinoplasty leads to objectively measurable changes in nasal symmetry that correspond with psychophysical modifications in the perception of a face as symmetrical or asymmetrical.
