skip to main content

Search for: All records

Creators/Authors contains: "Spencer, B."

Note: When clicking on a Digital Object Identifier (DOI) number, you will be taken to an external site maintained by the publisher. Some full text articles may not yet be available without a charge during the embargo (administrative interval).
What is a DOI Number?

Some links on this page may take you to non-federal websites. Their policies may differ from this site.

  1. ABSTRACT There is great interspecific variation in the nutritional composition of natural diets, and the varied nutritional content is physiologically tolerated because of evolutionarily based balances between diet composition and processing ability. However, as a result of landscape change and human exposure, unnatural diets are becoming widespread among wildlife without the necessary time for evolutionary matching between the diet and its processing. We tested how a controlled, unnatural high glucose diet affects glucose tolerance using captive green iguanas, and we performed similar glucose tolerance tests on wild Northern Bahamian rock iguanas that are either frequently fed grapes by tourists or experience no such supplementation. We evaluated both short and longer-term blood glucose responses and corticosterone (CORT) concentrations as changes have been associated with altered diets. Experimental glucose supplementation in the laboratory and tourist feeding in the wild both significantly affected glucose metabolism. When iguanas received a glucose-rich diet, we found greater acute increases in blood glucose following a glucose challenge. Relative to unfed iguanas, tourist-fed iguanas had significantly lower baseline CORT, higher baseline blood glucose, and slower returns to baseline glucose levels following a glucose challenge. Therefore, unnatural consumption of high amounts of glucose alters glucose metabolism in laboratory iguanasmore »with short-term glucose treatment and free-living iguanas exposed to long-term feeding by tourists. Based on these results and the increasing prevalence of anthropogenically altered wildlife diets, the consequences of dietary changes on glucose metabolism should be further investigated across species, as such changes in glucose metabolism have health consequences in humans (e.g. diabetes).« less
    Free, publicly-accessible full text available April 15, 2023
  2. A diagnostic of thirty questions administered to incoming STEM students in Fall 2013 and Fall 2015 - Fall 2018 reflects that their spatial visualization skills (SVS) need to be improved. Previous studies in the SVS subject [1], [2], [3] report that well-developed SVS skills lead to students’ success in Engineering and Technology, Computer Science, Chemistry, Computer Aided Design and Mathematics. Authors [4], [5] mention that aptitude in spatial skills is gradually becoming a standard assessment of an individual’s likelihood to succeed as an engineer. This research reports the qualitative and quantitative results of a project designed to improve SVS’s for STEM students managed under two strategies. The first strategy utilized was a series of face-to-face (FtF), two-hour training sessions taught over six weeks to all majors in STEM. This strategy was offered in Spring 2014 and every semester from Fall 2015 - Spring 2018. The second strategy was an embedded training (ET) implemented by one faculty from Fall 2017- Fall 2018. The faculty embedded the training in the US 1100 freshman seminar and was highly motivated to increase awareness of students on the importance and applicability of SVS in their fields of study. As reported by Swail et al. [6],more »cognitive, social, and institutional factors are key elements to best support students’ persistence and achievement. Both interventions used in this project encompassed all these factors and were supported by an NSF IUSE grant (2015-2019) to improve STEM retention. The FtF training was taken by 34 students majoring in diverse STEM fields. Its effectiveness was statistically assessed through a t-test to compare the results in the Purdue Spatial Visualization Skills Test - Rotations before and after the training and through analysis of surveys. Results were very positive; 85.29% of the participants improved their scores. The average change in scores was 5.29 (from 16.85 to 22.15; 17.65% improvement) and it was statistically significant (p-value 3.9E-8). On the surveys, 90% of students answered that they were satisfied with the training. Several students reported that they appreciated a connection between SVS, Calculus II and Engineering Graphics classes while others based the satisfaction on perceiving the critical role SVS will play in their careers. Results from the ET strategy were also encouraging. Teaching methods, curriculum and results are discussed in this paper. Adjustments to the teaching methods were done over 3 semesters. In the last semester, the faculty found that covering the modules at a slower pace than in the FtF training, asking the students to complete the pre-and post-diagnostic in class, and introducing the Spatial VisTM app to provide students with additional practice were key elements to assure students success and satisfaction. In conclusion, both strategies were demonstrated to be powerful interventions to increase students’ success because they not only offer students, particularly freshman, a way to refine SVS but also increase motivation in STEM while creating a community among students and faculty. The ET is effective and apt to be institutionalized. Lastly, this experimental research strengthens the literature on SVS.« less
  3. Tyrosine kinase receptor (RTK) ligation and dimerization is a key mechanism for translating external cell stimuli into internal signaling events. This process is critical to several key cell and physiological processes, such as in angiogenesis and embryogenesis, among others. While modulating RTK activation is a promising therapeutic target, RTK signaling axes have been shown to involve complicated interactions between ligands and receptors both within and across different protein families. In angiogenesis, for example, several signaling protein families, including vascular endothelial growth factors and platelet-derived growth factors, exhibit significant cross-family interactions that can influence pathway activation. Computational approaches can provide key insight to detangle these signaling pathways but have been limited by the sparse knowledge of these cross-family interactions. Here, we present a framework for studying known and potential non-canonical interactions. We constructed generalized models of RTK ligation and dimerization for systems of two, three and four receptor types and different degrees of cross-family ligation. Across each model, we developed parameter-space maps that fully determine relative pathway activation for any set of ligand-receptor binding constants, ligand concentrations and receptor concentrations. Therefore, our generalized models serve as a powerful reference tool for predicting not only known ligand: Receptor axes but also howmore »unknown interactions could alter signaling dimerization patterns. Accordingly, it will drive the exploration of cross-family interactions and help guide therapeutic developments across processes like cancer and cardiovascular diseases, which depend on RTK-mediated signaling.« less