The role of the intestinal spiral valve on whole-body nitrogen homeostasis in marine elasmobranchs
| dc.contributor.author | Hoogenboom, Janine Lisa | |
| dc.contributor.examiningcommittee | Weihrauch, Dirk (Biological Sciences) | en_US |
| dc.contributor.examiningcommittee | Eck, Peter (Food and Human Nutritional Sciences) | en_US |
| dc.contributor.examiningcommittee | Wright, Patricia A. (Integrative Biology, University of Guelph) | en_US |
| dc.contributor.supervisor | Anderson, W. Gary | |
| dc.date.accessioned | 2023-01-15T20:28:00Z | |
| dc.date.available | 2023-01-15T20:28:00Z | |
| dc.date.copyright | 2023-01-15 | |
| dc.date.issued | 2022-12-30 | |
| dc.date.submitted | 2022-12-30T22:41:33Z | en_US |
| dc.date.submitted | 2023-01-15T18:37:32Z | en_US |
| dc.degree.discipline | Biological Sciences | en_US |
| dc.degree.level | Doctor of Philosophy (Ph.D.) | en_US |
| dc.description.abstract | Marine elasmobranchs are ureosmotic, retaining large concentrations of urea (>300 mM) to counterbalance the osmotic pressure of the external environment. The retention of urea requires physiological mechanisms to acquire, retain, and transport the nitrogen necessary to synthesize urea. To understand this unique urea-centric osmoregulatory strategy, previous studies have focused on the elasmobranch gills and kidney as the primary sites of nitrogen loss and retention, and the liver as the primary site of urea synthesis. More recently, research has turned to the spiral valve in an effort to understand how the acquisition of exogenous nitrogen contributes to the synthesis of urea, and how it affects the nitrogen balance of these animals. To elucidate how nitrogen is acquired and transported across the intestinal tissues, I utilized various methods, including: manipulated feeding studies, in vitro gut sac and Ussing chamber flux studies, determination of mRNA abundance of transport proteins, and immunohistochemical staining to identify transport protein localization. The ingestion of excess urea (700 mM) showed no significant effects on urea flux across in vitro gut sacs, nor on whole-body nitrogen balance, as evidenced by no detectable rise in plasma urea. The ingestion of 15N highlighted the ability of these animals to acquire, circulate, and incorporate prandial nitrogen throughout various tissues within 20 h post-feeding, and retain that nitrogen for at least 7 days, with the acquisition of the 15N shown to occur primarily across the anterior spiral valve. Additionally, glutamine synthetase (GS) and arginase (ARG) activity, as well as the mRNA abundance of GS, ARG, and two other ornithine urea cycle enzymes (carbamoyl phosphate synthetase III, CPS III, and ornithine transcarbamylase, OTC), as well as the presence of 15N-glutamine and 15N-urea within the intestinal tissues, are all evidence that urea synthesis occurs within the spiral valve epithelium. Histochemical staining identified Rhp2 along the apical brush-border membrane of the spiral valve epithelium, and UT along the basolateral membrane and blood vessels. The data presented here aids in our understanding of how marine elasmobranchs acquire prandial nitrogen, transport it across the intestinal tissues, incorporate it into various tissues, and use it to synthesize nitrogenous compounds. | en_US |
| dc.description.note | February 2023 | en_US |
| dc.description.sponsorship | Research Manitoba Graduate Scholarship, Manitoba Graduate Fellowship, University of Manitoba Graduate Fellowship, University of Manitoba Faculty of Science Fieldwork Support Program, NSERC Canada Graduate Scholarships – Michael Smith Foreign Study Supplements Program (11020182019Q41742) | en_US |
| dc.identifier.uri | http://hdl.handle.net/1993/37113 | |
| dc.language.iso | eng | en_US |
| dc.rights | open access | en_US |
| dc.subject | Elasmobranch | en_US |
| dc.subject | Spiral valve | en_US |
| dc.subject | Transport protein | en_US |
| dc.subject | Nitrogen | en_US |
| dc.subject | Urea | en_US |
| dc.subject | Ammonia | en_US |
| dc.title | The role of the intestinal spiral valve on whole-body nitrogen homeostasis in marine elasmobranchs | en_US |
| dc.type | doctoral thesis | en_US |
| local.subject.manitoba | no | en_US |
| oaire.awardNumber | 11020182019Q11736 | en_US |
| oaire.awardTitle | NSERC Alexander Graham Bell Canada Graduate Scholarship - Doctoral (CGS D) | en_US |
| oaire.awardURI | https://search.open.canada.ca/grants/?keyword=&page=1&search_api_fulltext=&sort_by=date_clean&sort_order=DESC&sort=agreement_start_date+desc&search_text=hoogenboom | en_US |
| project.funder.identifier | https://doi.org/10.13039/501100000038 | en_US |
| project.funder.name | Natural Sciences and Engineering Research Council of Canada | en_US |