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Characterization of normal adipose tissue and pansteatitic tissue in the nile crocodile (crocodylus niloticus) : possible mechanism(s) of pathogenesis and pathophysiology
Thesis (PhD (Veterinary Anatomy and Physiology))--University of Pretoria, 2017.
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2026
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| _version_ | 1867613641109405696 |
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| access_status_str | Open Access |
| author2 | Chamunrowa, Joseph Panashe |
| author_browse | Chamunrowa, Joseph Panashe |
| author_facet | Chamunrowa, Joseph Panashe |
| collection | Thesis |
| description | Thesis (PhD (Veterinary Anatomy and Physiology))--University of Pretoria, 2017. |
| format | Thesis |
| id | oai:repository.up.ac.za:2263/110110 |
| institution | University of Pretoria (South Africa) |
| language | English |
| last_indexed | 2026-06-10T12:39:22.254Z |
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| provenance_str_mv | Harvested via OAI-PMH from UPSpace — University of Pretoria Institutional Repository |
| publishDate | 2026 |
| publishDateRange | 2026 |
| publishDateSort | 2026 |
| record_format | dspace |
| source_str | UPSpace — University of Pretoria Institutional Repository |
| spelling | oai:repository.up.ac.za:2263/110110 Characterization of normal adipose tissue and pansteatitic tissue in the nile crocodile (crocodylus niloticus) : possible mechanism(s) of pathogenesis and pathophysiology Chamunrowa, Joseph Panashe Oosthuizen, Marinda C. Meintjes, Roy Azeez, Odunayo Ibraheem Characterization Adipose tissues Pansteatitis Transcriptome Nile Thesis (PhD (Veterinary Anatomy and Physiology))--University of Pretoria, 2017. Concerted efforts to identify the pathogenesis and mechanism(s) involved in pansteatitis, (a generalized inflammation of the adipose tissue), that was attributed to the recent crocodile die off in the Olifants River and Loskop Dam in Kruger National Park, Mpumalanga, South Africa have been in the forefront of research in recent time. As part of the efforts, molecular and structural characterization, and determination of long chain fatty acid (LCFA) composition was carried out in healthy and pansteatitis adipose tissues of the Nile crocodile (Crocodylus niloticus). Molecular characterization was carried out by RNA sequencing (RNA-Seq) through Next Generation Sequencing (NGS) and de novo assembly of the entire transcriptome and differential gene expression analysis. Standard methods were used to prepare samples for structural characterization – histomorphological and ultrastructural studies: while LCFA composition was determined through fatty acid methyl-ester (FAME) analysis. Healthy adipose tissue consisting of fifty samples were collected from the subcutaneous, visceral, intermuscular adipose tissues and the abdominal fat body of ten 4 years old juvenile crocodiles from Izintaba Crocodile Farm (Pty) Ltd, Farm 59 (435JQ) Vissershoek, De Wildt Area, Pretoria, South Africa. Ten pansteatitis samples consisting five each were collected from visceral and intermuscular adipose tissues of five crocodiles that were dying of pansteatitis. Histomorphology revealed regional variations in adipocyte shapes, collagen content of the extracellular matrix (ECM), adipose tissue perfusion as well as division into lobes and lobules in healthy samples while pansteatitis showed fibrosis, mononuclear cell infiltration and toxic changes in the nucleus. No structural variation was observed in the transmission electron micrograph (TEM) of the adipose tissue. FAME analysis also showed regional variation in lipid composition especially in Myristoleic (C14:1), Erucic acid (C22:1n9), and Docosadienoic acid (C22:2n6). Saturated fatty acids such as Palmitic (C16:0) Stearic (C18:0) acids and monounsaturated Oleic (C18:1n9) acid were found to be considerably higher in healthy adipose tissue, when compared to liver samples. Most of the saturated and trans fatty acids were also found in significant (P<0.001) quantities in the pansteatitis samples, but had very low levels of the cis fatty acid and the essential fatty acids with C18 backbone. Forty-two thousand, two hundred and one (42,201) transcripts were assembled from the Next Generation Sequencing using RNA-Seq, out of which 37, 835 had previously been characterized. The de novo assembled transcriptome had an N50 (average sequence) of 436bp, percentage GC content of 43.92 which compared well with previously assembled transcripts in the salt water crocodile. Seventy genes were differentially expressed and upregulated genes in pansteatitis included genes for ECM signalling ligands, inflammatory cytokines and tumour necrosis factor alpha (TNF_) receptors, fatty acid synthase and fatty acid binding proteins, peroxisome proliferatoractivated receptor gamma (PPARG), nuclear factor and apoptosis signalling ligands, and mitogen activated protein kinase enzymes among others. Majority of the upregulated genes were found to be involved in hypoxia inducible pathways for activation of NFkB and inflammation, apoptosis, Toll-like receptor pathway and PPARG. Bicaudal homologous 2 Drosophila gene (BICD2) associated with spinal and lower extremity muscle atrophy was also upregulated in pansteatitis while Sphingosine -1-phosphate phosphatase 2 (SGPP2) involved in Sphingosine -1- phosphate metabolism and Doublesex –mab-related transcription factor 1 (DMRT1) responsible for sex gonad development and germ cell differentiation was downregulated. Thus, from the present study, the presence of saturated fatty acids especially palmitic acid (a marker of adipocyte hypertrophy, which stimulates Toll-like receptors (TLRs)), hypoxia inducible factors, PPARG, IL1 and IL6 receptors, which are all involved in inflammation and NF_B activation were identified. NF_B when activated, results in desensitization of insulin receptor substrates (IRS) leading to insulin resistance. It also leads to production of more inflammatory cytokines by the adipose tissue in a feed forward manner, which would exacerbate the condition. It can therefore be inferred, based on the upregulated genes in pansteatitis that affected Nile crocodiles might have died partly due to their inability to utilize stored triglycerides due to insulin resistance leading to starvation in the midst of plenty. Anatomy and Physiology PhD (Veterinary Anatomy and Physiology) 2026-05-15T17:26:19Z 2026-05-15T17:26:19Z 17/04/28 2017 Thesis http://hdl.handle.net/2263/110110 en application/pdf |
| spellingShingle | Characterization Adipose tissues Pansteatitis Transcriptome Nile Characterization of normal adipose tissue and pansteatitic tissue in the nile crocodile (crocodylus niloticus) : possible mechanism(s) of pathogenesis and pathophysiology |
| title | Characterization of normal adipose tissue and pansteatitic tissue in the nile crocodile (crocodylus niloticus) : possible mechanism(s) of pathogenesis and pathophysiology |
| title_full | Characterization of normal adipose tissue and pansteatitic tissue in the nile crocodile (crocodylus niloticus) : possible mechanism(s) of pathogenesis and pathophysiology |
| title_fullStr | Characterization of normal adipose tissue and pansteatitic tissue in the nile crocodile (crocodylus niloticus) : possible mechanism(s) of pathogenesis and pathophysiology |
| title_full_unstemmed | Characterization of normal adipose tissue and pansteatitic tissue in the nile crocodile (crocodylus niloticus) : possible mechanism(s) of pathogenesis and pathophysiology |
| title_short | Characterization of normal adipose tissue and pansteatitic tissue in the nile crocodile (crocodylus niloticus) : possible mechanism(s) of pathogenesis and pathophysiology |
| title_sort | characterization of normal adipose tissue and pansteatitic tissue in the nile crocodile crocodylus niloticus possible mechanism s of pathogenesis and pathophysiology |
| topic | Characterization Adipose tissues Pansteatitis Transcriptome Nile |
| url | http://hdl.handle.net/2263/110110 |