(Georgia Institute of Technology, 2023-01-18)
Cutter, Catarina Santos
Ryanodine receptors (RyRs) are a class of mammalian ion channels which are the primary efflux pathways for the release of Ca2+ from the sarcoplasmic reticulum. They play a critical role in muscle excitation-contraction coupling (ECC). Because it is the largest known ion channel, the mechanisms for its activation are not fully understood. ATP is a well characterized channel activator. However, its mechanism of activation has not been determined and the importance of ATP regulation of RyRs in vivo is not clear. In 2016, des George, et al. published a structure of RyR1 with ATP bound. The adenosine group of ATP is contained within a hydrophobic cleft while the triphosphate tail is extended and interacts with positively charged residues. The goal of this study was to identify residues important for ATP binding to the channel. Site-directed mutagenesis of the receptor was used to substitute specific residues in order to change their size and or charge. After transfection with recombinant DNA, HEK293 cells were harvested for isolation of microsomal membranes. Two of the largest hydrophobic residues of the cleft were replaced with alanine with the goal of drastically reducing or abolishing ATP binding to RyR1. The selected mutations F4960A and L4985A were expected to impair channel activation by both ATP and adenosine. After initial verification of wild type channel expression in HEK293 cells, later transfections with wild type and mutant RyR1 DNA failed to produce detectable amounts of protein. Low DNA transfection efficiency combined with the low yield of microsomal membrane likely contributed to the inability to detect channels in these preparations. Optimizing DNA transfections and scaling up the cell culture may increase the likelihood of successful protein production.
(Georgia Institute of Technology, 2022-05)
Ciaccia, Julia
In the United States, less than half of college students who enroll in a STEM program will graduate
with a STEM degree (Chen 2013). Attrition rates are disproportionately high for marginalized
students, leading to a homogenous STEM workforce (Simon et al. 2021). This study, completed
at an R1 midsized southeastern university, investigates course registration patterns and student
opinions to determine what factors contribute to students leaving STEM majors through the lens
of the Deep Teaching model (Dewsbury 2019). Through survey and course enrollment data, we
determined that 1) students feel overwhelmingly negative about textbook costs, 2) financially
insecure students are significantly more likely to consider course material costs when registering
for courses and 3) students add and drop courses for a wide variety of personal, course, and
university level reasons. These results indicate that implementing Deep Teaching in the classroom,
specifically focused on self-awareness and empathy, can increase retention in STEM and reduce
attrition rates.
(Georgia Institute of Technology, 2022-05)
Jones, Tamia M.
The accuracy of control and strength of contraction for muscles of the trunk, the muscles between our neck and groin, can vary significantly with conditions like hemiparesis, multiple sclerosis, or low back pain. Such medical conditions can contribute to an inability of our trunk muscles to perform at full capacity. A typical normalization method for applied physiologists includes finding a given muscle’s maximum voluntary isometric contraction (MVIC), and many individuals with muscle weakness or control-limiting conditions are unable to efficiently participate in this method. To properly assess the severity of muscle weakness or loss of control, there is a need for research on normalizing EMG signals produced from contractions in trunk muscles at a fraction of an individual’s MVIC. In order to contribute to this normalization, healthy participants in this study performed a muscle contraction task based on a submaximal MVIC. Participants attempted to reach and hold a contraction for a specific muscle group (i.e., deltoids, pectoralis major, external obliques, and latissimus dorsi) at a target contraction level defined as 25%, 12%, and 6% of their MVIC. The objective of this study was to characterize normalization of EMG signals from trunk muscle contractions with variability and offset error. The standardized measures supported the use of the 25% and 12% contraction levels as submaximal EMG signal normalization. In future studies, the 6% contraction level and the external obliques potentially require refinement in contraction maneuvers for a more accurate normalization. Nevertheless, future experiments may use the results of this study as a submaximal reference point within healthy populations acting as a measure of comparison for patients demonstrating muscle weakness.