Faculty Bibliography

This study presents the in-vivo evaluation of Ti-13Nb-13Zr alloy implants obtained by the hydride route via powder metallurgy. The cylindrical implants were processed at different sintering and holding times. The implants' were characterized for density, microstructure (SEM), crystalline phases (XRD), and bulk (EDS) and surface composition (XPS). The implants were then sterilized and surgically placed in the central region of the rabbit's tibiae. Two double fluorescent markers were applied at 2 and 3 weeks, and 6 and 7 weeks after implantation. After an 8-week healing period, the implants were retrieved, non-decalcified section processed, and evaluated by electron, UV light (fluorescent labeling), and light microscopy (toluidine blue). BSE-SEM showed close contact between bone and implants. Fluorescent labeling assessment showed high bone activity levels at regions close to the implant surface. Toluidine blue staining revealed regions comprising osteoblasts at regions of newly forming/formed bone close to the implant surface. The results obtained in this study support biocompatible and osseoconductive properties of Ti-13Nb-13Zr processed through the hydride powder route. © 2007.

Previous neurophysiological studies of the frontal eye field (FEF) in monkeys have focused on its role in saccade target selection and gaze shift control. It has been argued that FEF neurons indicate the locations of behaviorally significant visual stimuli and are not inherently sensitive to specific features of the visual stimuli per se. Here, for the first time, we directly examined single cell responses to simple, two-dimensional shapes and found that shape selectivity exists in a substantial number of FEF cells during a passive fixation task or during the sample, delay (memory), and eye movement periods in a delayed match to sample (DMTS) task. Our data demonstrate that FEF neurons show sensory and mnemonic selectivity for stimulus shape features whether or not they are behaviorally significant for the task at hand. We also investigated the extent and localization of activation in the FEF using a variety of shape stimuli defined by static or dynamic cues employing functional magentic resonance imaging (fMRI) in anesthetized and paralyzed monkeys. Our fMRI results support the electrophysiological findings by showing significant FEF activation for a variety of shape stimuli and cues in the absence of attentional and motor processing. This shape selectivity in FEF is comparable to previous reports in the ventral pathway, inviting a reconsideration of the functional organization of the visual system.

In the mouse, germ cells that do not reach the genital ridges rapidly die by a wave of apoptosis that requires the pro-apoptotic protein Bax. In Bax-null embryos, large numbers of ectopic (extragonadal) germ cells fail to die. We have studied the fates of these, in an effort to understand the etiology of human extragonadal germ cell tumors, which are thought to arise from ectopic germ cells. We find that ectopic germ cells in which apoptosis is blocked form a heterogeneous population, which partially differentiates along the gonocyte pathway to different extents in different regions of the embryo, and in the two genders. In particular, a previously undescribed population of ectopic germ cells was identified in the tail. These germ cells retained primitive markers for longer than ectopic germ cells in other regions, and represent a possible origin for sacrococcygeal type I extragonadal germ cell tumors found in neonates and infants. This hypothesis is supported, but not proved, by the finding of cells expressing the germ cell marker Oct4 associated with a coccygeal germ cell tumor in a human infant.

BACKGROUND: Weight loss can be achieved through gastric bypass surgery or diet. Surgery has been reported to be more effective in achieving long-term weight loss. The authors aimed to determine whether massive weight loss is maintained or improved after body contouring. METHODS: Seventy patients underwent body contouring surgery after massive weight loss from January of 2001 to January of 2005. Data collected included age; gender; mode of massive weight loss; body mass index before massive weight loss, at contour surgery, and at follow-up; and weight of skin excised. RESULTS: Weight loss was achieved by open (n = 57) or laparoscopic gastric bypass surgery (n = 7), or by diet (n = 6). Average weight loss at contour surgery was 152 lb for open gastric bypass, 139 lb for laparoscopic gastric bypass, and 140 lb for the diet group. Mean weight of excised skin was 12.8 lb. Gastric bypass patients on average gained 2.3 lb, whereas nonsurgical patients gained 22 lb after body contouring, netting out skin excised. On multivariate analysis, weight loss did not differ between laparoscopic and open gastric bypass (p = 0.9); however, surgery led to a 27-lb greater weight loss compared with diet (p = 0.03). This effect was more remarkable with follow-up less than or equal to 18 months compared with more prolonged follow-up. Every year increase in age was associated with an 0.8-lb weight gain (p = 0.03). CONCLUSIONS: Gastric bypass surgery patients maintain massive weight loss better than "diet" patients. Weight loss tapers over time for gastric bypass surgery patients, with ultimate weight gain, comparable to that seen in the general population as it ages.