Animal Science Department

 

First Advisor

Dustin T. Yates

Date of this Version

3-2017

Comments

A THESIS Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For the Degree of Master of Science, Major: Animal Science, Under the Supervision of Professor Dustin T. Yates. Lincoln, Nebraska: March 2017

Copyright (c) 2017 Caitlin N. Cadaret

Abstract

We sought to identify the effect of sustained maternal inflammation at mid-gestation on fetal mortality, skeletal muscle growth, and development at term. Fetal rats had reduced total mass that coincided with impaired myoblast function, as myoD was reduced and myogenin expression was increased in hindlimb muscle. Fetuses also had increased circulating TNFα at term after maternal inflammation, which decreased TNFR and IL6R mRNA in muscle, reducing sensitivity to cytokines. These findings indicate that sustained maternal inflammation at mid-gestation impairs fetal skeletal muscle growth near-term due to changes in myoblast responsiveness to inflammatory regulation.

To evaluate the acute impact of inflammatory and adrenergic factors on muscle metabolism, basil and insulin-stimulated glucose uptake and oxidation was measured in primary rat soleus muscle incubated with TNFα, IL-6, β1 adrenergic agonist, or β2 adrenergic agonist with or without insulin. Βeta 2 adrenergic agonist increased basal glucose oxidation, decreased basal glucose uptake, and synergistically increased insulin-stimulated glucose oxidation and Akt phosphorylation, but β1 agonist had no effect. Inflammatory cytokines antagonized insulin signaling but simultaneously increased glucose oxidation via MAPK. Together, our findings show acute exposure to these stress factors increases glucose oxidation independently of glucose uptake and insulin signaling.

A final study identified the effects of timing of retrieval practice on long-term information retention. Students were given online retrieval practices one or five days after introduction of material. Short-term information retention was measured at one week and long-term information retention at semester’s end. Timing of repetition had no discernable effects on short-term retention at one week. Average-performing students (B to D- overall) exhibited better long-term retention on three of four evaluated topics when retrieval practice occurred at five days. High-performing students (B+ or greater overall) exhibited better long-term retention in, one of four topics when retrieval practice occurred at five days. Increasing the interval between introduction to material and first retrieval practice enhances long-term information retention.

Advisor: Dustin T. Yates

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