Browsing by Author "Winger, Quinton A., committee member"

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Investigating the ramifications of placental SLC2A3 (GLUT3) glucose transport deficiency in sheep
(Colorado State University. Libraries, 2024) Kennedy, Victoria C., author; Anthony, Russell V., advisor; Winger, Quinton A., committee member; Rozance, Paul J., committee member; Engle, Terry E., committee member
Glucose, the primary energy substrate for fetal oxidative processes and growth, is transferred from maternal to fetal circulation down a concentration gradient by placental facilitative glucose transporters. In sheep, SLC2A1 and SLC2A3 are the primary transporters available in the placental epithelium, with SLC2A3 located on the maternal-facing apical trophoblast membrane and SLC2A1 located on the fetal-facing basolateral trophoblast membrane. We have previously reported that impaired placental SLC2A3 glucose transport resulted in smaller, hypoglycemic fetuses with reduced umbilical artery insulin and glucagon concentrations, in addition to diminished pancreas weights. These findings led us to subject RNA derived from SLC2A3-RNAi (RNA interference) and NTS-RNAi (non-targeting sequence) fetal pancreases to qPCR followed by transcriptomic analysis. We identified a total of 771 differentially expressed genes (DEGs). Upregulated pathways were associated with fat digestion and absorption, particularly fatty acid transport, lipid metabolism, and cholesterol biosynthesis, suggesting a potential switch in energetic substrates due to hypoglycemia. Pathways related to molecular transport and cell signaling in addition to pathways influencing growth and metabolism of the developing pancreas were also impacted. A few genes directly related to gluconeogenesis were also differentially expressed. Our results suggest that fetal hypoglycemia during the first half of gestation impacts fetal pancreas development and function that is not limited to  cell activity. Our results at mid-gestation led us to hypothesize that the placenta could compensate for a deficiency in SLC2A3 during the second half of gestation to maintain or recover fetal growth and development. To investigate this, we repeated the same experimental paradigm by carrying out SLC2A3-RNAi pregnancies and NTS-RNAi controls to near-term. Our objective was to assess fetal growth, uterine nutrient uptake, placental utilization and transfer to the fetus, as well as assess the responsiveness of the fetal pancreas to glucose and arginine challenges in vivo to determine the long-term impact of fetal hypoglycemia during the first-half of gestation. Pregnant ewes underwent surgical catheterization followed by a metabolic study at 133 ± 2 dGA. We observed rescued fetal and pancreatic growth. There was also significantly reduced uterine glucose uptake and placental glucose utilization, along with a tendency for increased uteroplacental amino acid carbon utilization. At baseline, ewes with SLC2A3-RNAi pregnancies had significantly reduced uterine arterial IGF1 concentrations, but no differences in glucagon or insulin concentrations. During the metabolic study, umbilical artery insulin concentrations were significantly greater in the SLC2A3-RNAi pregnancies during early GSIS, tended to be greater during late GSIS, and were significantly greater again during ASIS. These data demonstrate that the global effect on pancreatic growth and development observed at 75dGA continued into late gestation as altered pancreatic glucose and arginine sensitivity, despite rescued fetal growth. Placental compensatory mechanisms appeared to also rescue fetal growth and umbilical glucose concentrations. The decrease in uteroplacental glucose utilization while increasing amino acid utilization appears to be one major compensatory mechanism aiding in recovering glucose transfer to the fetus. In conclusion, microvillous glucose uptake to the placenta appears to be rate-limiting to fetal growth and development early in gestation, but when SLC2A3-RNAi is carried out to near-term, despite rescued fetal growth, the physiology of the entire maternal-placental-fetal unit is still impacted.
Open Access
Pre-weaning performance in lambs after nutrient specific restriction in gestation and training cognitive skills to improve integration and application of knowledge in animal physiology
(Colorado State University. Libraries, 2024) Stucke, Rachael, author; Cadaret, Caitlin N., advisor; Ahola, Jason K., committee member; Winger, Quinton A., committee member
Due to seasonal availability and quality of range forage, extensively managed ewes often experience nutrient restriction during gestation. Neonatal lamb performance after severe experimental nutrient restriction during gestation has been well studied; however, there is a gap in understanding of how practical nutrient restriction experienced over the course of a production cycle impacts lamb success. Therefore, the objective of the first study was to investigate early life performance in lambs from ewes fed a diet from 30-125 days of gestation (dGA) that simulates winter forage or one that meets all nutritional requirements for gestation. Maternal BCS and weight losses were evident prior to the standard supplementation period suggesting impacts on the fetus could be happening due to nutrient restriction earlier in gestation. Lambs from dams who received the lower quality diet did not differ by bodyweight but were not able to thermoregulate as well as lambs whose dams had their requirements met during the first week and on specific weeks thereafter. Beginning at six weeks of life through weaning lambs from restricted dams had lower body weights compared to lambs from fully nourished dams. This data demonstrates that nutrient challenge during gestation, even when re-alimented in late gestation, decreases performance. The lamb data showed that while there are no apparent differences in growth during the first week of life, NR animals start to diverge later in life even when provided high quality nutrition. This coupled with reduced thermoregulatory ability suggests tissue specific differences may underlie animal variation and warrants further investigation. Case-based learning immerses students in real-world scenarios, prompting observation, action, and reflection to enhance cognitive skills. The open-ended nature of such learning can challenge students to reach higher levels of critical thinking, however, we have noticed that without guidance, students often do not know how to approach these types of questions. Therefore, the objective of study 2 was to investigate how two low-input interventions strategies may help train cognitive skills and improve student performance. Three semesters of an undergraduate physiology course employed a case-based assessment strategy. Semester 1 (S1) represented no intervention, Semester 2 (S2) included two dedicated class periods of instructor-led guidance on approaching case studies, and Semester 3 (S3) utilized an online peer evaluation platform, where students evaluated and provided feedback to each other. In S2 and S3 pre-surveys were administered to understand changes in students' perceptions of their own cognitive skills. The average grade on case studies after intervention was the highest in S3 where peer intervention was employed. When comparing changes in perceptions, student confidence in their cognitive skills generally increased in S2 and S3. Interestingly, while peer evaluation improved student performance, free response questions indicated that students did not enjoy peer evaluation and felt that it was not beneficial to their learning. Peer evaluation provides a unique opportunity for students to actively engage in the learning process and to practice cognitive skills. This process holds dual benefit as reviewing peers requires students to reflect, analyze, and evaluate, which are cognitive skills also needed to solve the case studies.
Open Access
The development of ovine placental lactogen deficient pregnancies
(Colorado State University. Libraries, 2014) Baker, Callie M., author; Anthony, Russell V., advisor; Winger, Quinton A., committee member; Curthoys, Norman, committee member
Intrauterine growth restriction (IUGR) results in significant fetal and neonatal mortalities and morbidities. Additionally, infants surviving IUGR experience increased incidence of heart disease, diabetes, hypertension and stroke during adulthood. A major placental secretory product, placental lactogen (PL), is found at high levels in maternal and fetal circulation, and is significantly reduced in both human and sheep IUGR pregnancies. While the exact function of PL has not been defined for any species, it is thought to modulate the mobilization of maternal nutrients to the fetus. Recently, the development of lentiviral-mediated expression of short hairpin RNA (shRNA) within sheep conceptuses has provided a means of examining placental gene function in sheep. The objective of this research was to generate ovine PL (oPL) deficient sheep pregnancies using lentivirus targeting the degradation of oPL mRNA, in order to assess the function of PL during pregnancy. We hypothesize that oPL deficiency during pregnancy will lead to IUGR near term. To test our hypothesis a preliminary study was conducted to evaluate the in vivo efficacy of lentiviral-oPL targeting vectors in the sheep placenta at 55 days gestational age (dGA). Efficiency of oPLmRNA degradation was first measured in vitro using twelve promoter-targeting sequence combinations, tested in three cell lines overexpressing oPL. Two oPL target sequences (tg2 and tg6) were used, as either shRNA or shRNAmiR (microRNA mimic) sequences. Subsequently, three lentiviral constructs; hLL3.7 tg6 (human U6 promoter expressing oPL tg6 shRNA), hEF-1 tg2 (human elongation factor-1α promoter expressing oPL tg 2 shRNAmiR) and oPGK tg6 (ovine phosphoglycerate kinase-1 promoter expressing oPL tg 6 shRNAmiR), were selected to be tested in vivo. Day 9 blastocysts were harvested from naturally mated donor ewes, infected with one of the lentiviral constructs, and 2 to 3 blastocysts were surgically transferred to recipient ewes. At 55 dGA, uterine vein (UtV) blood and placental tissues were collected for analysis of oPL expression, and compared to naturally mated controls (NMC). Based on a 95% confidence interval created from UtV oPL concentrations in NMC pregnancies (n=4), 3 out of 4 hLL3.7 tg6 pregnancies, 3 out of 4 hEF tg2 pregnancies and 4 out of 4 oPGK tg6 pregnancies were classified as responder pregnancies. Compared to NMC pregnancies, UtV oPL concentrations were significantly reduced (P≤0.05) in responder pregnancies. While we hypothesized that oPL deficiency will result in IUGR near-term, at 55 dGA there were no differences in fetal weights. To test our overall hypothesis, we generated 8 hEF-1-SC (human elongation factor-1α promoter expressing scrambled control shRNAmiR), 9 hEF-1 tg2, 7 hEF-1 tg6 (human elongation factor-1α promoter expressing oPL tg6 shRNAmiR) and 9 hLL3.7 tg6 singleton pregnancies that were harvested at 135 dGA. Based on two standard deviations below the mean placental weight of the hEF-1 SC pregnancies, 2 out of 7 hEF-1 tg6 pregnancies and 6 out of 9 hLL3.7 tg6 pregnancies were classified as tg6 responder pregnancies (tg6). Tg6 pregnancies resulted in significantly decreased (P≤0.05) oPL mRNA concentrations, placental weight and fetal body weight compared to the controls at 135 days of gestation. These data confirm the effect of lentiviral-oPL targeting vectors and suggest that oPL plays a significant role in early placental development. Interestingly, we also observed that tg6 pregnancies had significantly increased (P≤0.05) placental efficiency relative to controls, which may function as a coping mechanism to maintain pregnancy in the face of oPL deficiency. Uterine artery to uterine vein glucose gradients were also increased (P≤0.05) in tg6 pregnancies compared to controls, which may be indicative of increased glucose uptake by the placenta in order to maintain function. Further analysis revealed that circulating fetal insulin tended to be decreased in the umbilical artery (P≤0.10) of tg6 fetuses relative to control fetuses, thus supporting a role for oPL in altering fetal insulin production. Finally, mRNA concentrations of insulin-like growth factors (IGF) -I and -II, and insulin-like growth factor binding proteins (IGFBP) -2 and -3 were significantly reduced (P≤0.05) in fetal liver tissue of tg6 fetuses compared to the controls. While this could be an indirect result of IUGR, oPL may well induce the expression of fetal insulin-like growth factors during in utero development. Based on these results, our hypothesis that oPL deficiency during gestation would result in intrauterine growth restriction appears correct. Surprisingly, it appears that oPL may have its greatest impact during early pregnancy when the placenta is developing, however the presence of adequate oPL is likely to be important throughout gestation for healthy fetal growth.
Open Access
The physiological ramifications of chorionic somatomammotropin RNA interference
(Colorado State University. Libraries, 2021) Tanner, Amelia R., author; Anthony, Russell V., advisor; Rozance, Paul J., advisor; Engle, Terry E., committee member; Thomas, Milton G., committee member; Winger, Quinton A., committee member
To view the abstract, please see the full text of the document.