The Effect of Heavy Metal Stress on Avian Proximal Tubule Urate Secretion

In both humans and birds, urate is an important antioxidant when maintained at normal plasma concentrations. Though human kidneys primarily reabsorb filtered urate, while those of birds perform mostly secretion, both maintain urate levels at ~300microM. The importance of maintaining urate levels within the homeostatic range was observed when the study of several prominent diseases revealed an association with hyperuricemia. This study examined the effect of elevated zinc concentration on avian urate secretion. Here, acute exposure of chicken proximal tubule epithelial cells (cPTCs) to zinc stress had no effect on urate secretion, but prolonged zinc-induced cellular stress inhibited active transepithelial urate secretion with no change in Mrp4 expression, glucose transport, or transepithelial resistance. Moreover, zinc had no effect on urate transport by isolated brush border membrane vesicles, suggesting involvement of a more complex cellular stress adaptation. Previous work has demonstrated that AMP-activated protein kinase (AMPK), a critical metabolic regulator, conserves energy during cellular stress by shutting down ATP-utilizing processes and activating ATP-generating processes. Pharmacological activation of AMPK by AICAR produced decreased urate secretion by cPTCs similar to the effect seen with prolonged exposure to zinc, while the AMPK inhibitor Compound C prevented both AICAR and zinc inhibition of urate secretion, suggesting a stress induced mechanism of regulation. Supported by NSF. IACUC #A08-046.

Dynamic Smile Analysis : Changes with Age

Introduction: The objective of this study was to define age-related changes in the human smile. The areas of interest were: upper lip length at smile and repose, upper lip thickness at smile and repose, maxillary incisal display at smile, interlabial gap height at smile, smile index, percent buccal corridors, intercommissural width at rest, smile height, and smile arc. A secondary objective was to study the perioral changes from rest to smile and compare them on the basis of age. Materials and Method: Video equipment was used to capture video for 261 subjects. Two frames for each subject were selected; one frame representing the lips and rest and the second representing the widest smile. After excluding 40 subjects the data for the remaining 221 subjects was analyzed. Results: There was a decrease of 1.5 to 2 mm in the maxillary incisor display during smile, with increase in age. Smile index significantly increased with increase in age. Most (78%) subjects displayed an average smile height. No subjects in the 50 and over age group displayed a high smile while no subjects in the 15-19 year old age group presented with a low smile. All the dynamic measures indicated there was a pattern of decreasing change from rest to smile especially evident after the 30-39 year old age group. Conclusions: This study helps to establish age related dynamic norms. As the person ages the smile gets narrower vertically and wider transversely. The dynamic measures indicate that the muscles' ability to create a smile decreases with increasing age.

A Dynamic Stochastic Frontier Production Model with Time-Varying Efficiency

In this paper we introduce technical efficiency via the intercept that evolve over time as a AR(1) process in a stochastic frontier (SF) framework in a panel data framework. Following are the distinguishing features of the model. First, the model is dynamic in nature. Second, it can separate technical inefficiency from fixed firm-specific effects which are not part of inefficiency. Third, the model allows one to estimate technical change separate from change in technical efficiency. We propose the ML method to estimate the parameters of the model. Finally, we derive expressions to calculate/predict technical inefficiency (efficiency).