Date of Graduation

2013

Document Type

Dissertation

Degree Type

PhD

College

Davis College of Agriculture, Natural Resources and Design

Department

Agricultural & Extension Education

Committee Chair

Jorge A Flores

Committee Co-Chair

E Keith Inskeep

Committee Member

Amy L Way

Committee Member

Michelle D Withers

Committee Member

Jianbo Yao

Abstract

Although it is generally accepted that calcium is an intracellular mediator of prostaglandin F2 alpha (PGF2alpha) actions on luteal cells, studies attempting to define the mechanisms of calcium homeostasis in bovine corpora lutea (CL) are lacking. The increase in intracellular calcium concentration ([Ca2+]i) induced by PGF2alpha in steroidogenic cells from mature CL is greater than in those isolated from developing CL. Our long-term hypothesis is that differences in signal transduction associated with developing and mature CL contribute to the increased efficacy of PGF2alpha to induce a calcium signal capable of mediating luteal regression in mature CL. Specifically, these studies were designed to define the major mechanisms of calcium homeostasis operational in bovine CL and, to evaluate their potential regulation at two developmental stages, PGF2alpha-sensitive (day 10) and insensitive (day 4) CL. In developing CL, the combined effect of 1) lower concentrations of inositol 1,4,5-trisphosphate, IP3, due to reduced phospholipase C beta, PLCbeta, activity; 2) lower expression in the calcium release component ryanodine receptor, RYR2; 3) increased expression of sorcin, SRI, that can prevent RYR2 from opening; and 4) greater expression of ATP2A2, the ATPase pump that causes calcium re-uptake into the ER, are major differences in mechanisms of calcium homeostasis that could account for the lesser increase in [Ca2+]i in response to PGF2alpha than in mature CL. It follows that in mature CL, the cellular mechanisms that allow PGF2alpha to induce a calcium signal of greater magnitude are the combined contribution of 1) an increase in IP3 due to a greater activity of PLCbeta, 2) a greater Ca2+ release from the ER via increased RYR2 expression, 3) a decrease in SRI expression, and 4) a reduction in calcium re-uptake to the ER due to lower expression of ATP2A2. These findings could be significant physiologically, as it was demonstrated previously that the ability of PGF2alpha to induce a decrease in LH-stimulated progesterone in the mature bovine CL was associated closely with its ability to induce an increase in [Ca2+]i. Further studies are needed to demonstrate the importance of these differences in calcium homeostasis in relation to progesterone production by bovine CL. Promoting scientific literacy continues to be a challenge for many science educators. Yet, many science educators are attempting to make the connections between learning science, critically thinking about science, and understanding its application in research in the classroom. The hypothesis of this study was that the use of primary scientific literature in an introductory biology course will improve overall student quiz scores and scores of questions rated in the mid to upper levels of Bloom's taxonomy of learning. Students' attitudes and appreciation towards science were also assessed. Comparisons were conducted amongst 1) all students, 2) biology majors only, and 3) non-biology majors. Two introductory biology course sections per semester per year were randomly assigned as control and experimental groups. Pre- and post-quiz learning gains were assessed and surveys were administered before and after the study. Overall quiz learning gains were not significantly different. Average learning gains significantly increased for evaluation/synthesis questions: 1) all majors: control, 26.9 + 8.9, experimental, 43.9 + 8.1; p = 0.004, and 2) nonbiology majors: control, 25.0 + 9.9, experimental, 57.1 + 11.1; p = 0.04. There was an increasing trend between control, 33.3 + 21.1, and experimental, 73.3 + 11.8 groups of all biology majors for quiz 3, evaluation/synthesis question, p = 0.09. Based on survey responses, the students in the experimental group recognized that they indeed read scientific journals and were able to distinguish this type of literature from other sources, such as science news articles. Most importantly, students in the experimental group were more confident in summarizing information from news articles compared to the control group, and several individual groups were confident in summarizing information from primary literature in their own words. In addition, students' interests in applying and connecting what they've learned in the biology course to other courses or research increased after the study. The outcomes of this study clearly demonstrated that the use of primary literature in an introductory biology course had a positive impact on student learning gains, particularly in the highest levels of Bloom's taxonomy, and towards student appreciation of science and scientific literacy.

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