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Equine Obesity-Related Hyperleptinemia, Nan Killen Huff
Equine Obesity-Related Hyperleptinemia, Nan Killen Huff
LSU Doctoral Dissertations
Plasma leptin concentrations in obese adult horses have been shown to vary widely, and horses tend to fit into two groups: low leptin (<10 ng/mL) and hyperleptinemic (10 to 50 ng/mL). Observations over time revealed that the hyperleptinemic condition was consistent, possibly indicating a relatively permanent underlying cause. Based on these observations, three experimental approaches were used to further study equine obesity-related hyperleptinemia. The first experiment determined the prevalence of hyperleptinemia among postpartum, lactating mares, evaluated its consequence on their re-breeding success, and investigated correlations between leptin levels in lactating and non-lactating mares. Postpartum mares (n = 198) and non-foaling mares (n = 31) were categorized based on their leptin status: normoleptinemic or hyperleptinemic. Leptin in the lactating mares averaged 4.8 ng/mL, and 11 of the 198 (13%) displayed hyperleptinemia. Leptin in the non-lactating mares averaged 7.5 ng/mL, with 9 mares (29%) displaying hyperleptinemia. Of the 198 lactating mares bred, 81% became pregnant; there was no effect of leptin status on re-breeding success. To study one possible cause for hyperleptinemia in well-fed horses, a second experiment explored polymorphism(s) within exon 2 of the equine leptin gene. The DNA from five hyperleptinemic and five normal mares of high body condition was used to analyze exon 2 of the leptin gene for polymorphisms. Based on the 10 mares tested, there was no polymorphism in exon 2 of the equine leptin gene; therefore, polymorphism is not a likely explanation for the high vs. low leptin difference. The third experiment explored the possible effects of hyperleptinemia on the endocrine and immune systems. Endotoxin was given to mares and geldings to investigate the role and/or regulation of leptin in the pro-inflammatory cytokine response. Of the endpoints measured, only platelet count differed between normal and hyperleptinemic horses. Endotoxin infusion caused the expected pro-inflammatory cytokine and endocrine responses, but leptin status was not a significant factor for any endpoint. It is concluded that hyperleptinemia in mares is not associated with polymorphism in exon 2 of the leptin gene, does not affect re-breeding rates of foaling mares, and does not alter the endotoxin-induced responses of the endocrine and immune systems.
Evaluation Of A Plasmid Delivery System For Production Of Gnrh And Ghrh In The Horse And Goat, William Andrew Storer
Evaluation Of A Plasmid Delivery System For Production Of Gnrh And Ghrh In The Horse And Goat, William Andrew Storer
LSU Doctoral Dissertations
The efficacy of a novel plasmid delivery system was assessed for long-term expression of gonadotropin releasing hormone (GnRH) and growth hormone releasing hormone (GHRH) in horses and goats. The efficacy of the technology was demonstrated using 3 novel plasmids: pSEAP [expressing secreted embryonic alkaline phosphatase (SEAP)], pGHRH (expressing GHRH), and pGnRH (expressing GnRH). Geldings were electroporated with a reporter plasmid expressing SEAP in 3 muscle sites. Expression of SEAP, measured from jugular plasma samples, indicated muscle specificity for uptake and expression of the plasmid. Concentrations of SEAP were greatest (P < 0.05) after pectoralis injection, which was chosen as the site for electroporation in subsequent studies. In a second experiment, stallions were electroporated with pGHRH or pSEAP to evaluate the effect of long-term GHRH treatment on the growth hormone (GH) axis and testicular function. Stallions treated with pGHRH had increased (P < 0.05) plasma concentrations of IGF-I, increased (P < 0.05) volume of accessory sex gland fluid, and increased (P < 0.05) number of normal spermatozoa in the ejaculate relative to controls. In the third experiment, stallions were electroporated with pGnRH or pSEAP to test the effects of GnRH on the reproductive axis. Treatment with pGnRH increased (P < 0.05) plasma testosterone concentrations to d 56 and increased (P < 0.01) the LH response to GnRH on d 21, but did not alter (P > 0.1) seminal characteristics evaluated after 36 d of treatment. In …
Somatic Cell Interspecies Nuclear Transfer, Marina Julia Sansinena
Somatic Cell Interspecies Nuclear Transfer, Marina Julia Sansinena
LSU Doctoral Dissertations
The low efficiency of the nuclear transfer (NT) procedure requires large number of oocytes to produce embryos and live offspring. A series of experiments were conducted to evaluate the ability of the bovine cytoplast to reprogram nuclei from horses and llamas. In a preliminary study, equine oocytes from small (<20mm diameter) follicles were either pretreated with roscovitine or placed in maturation (IVM only) prior to NT. Roscovitine pretreatment did not improve nuclear maturation rates (roscovitine pretreatment 57% vs. IVM only 66%) and no fusion was obtained from roscovitine-pretreated oocytes after NT. Another preliminary study was conducted with the objective to produce llama NT embryos and to compare their development in two in vitro culture conditions (G1.2® vs. CR1aa). No difference was found in the number of embryos cleaved after 2 d of culture. This resulted in the first scientific report of somatic cell NT, in vitro culture and transfer of NT embryos in the llama. In the next experiment, adult horse and llama fibroblasts were injected into enucleated cow oocytes. The results showed the cow cytoplasm is capable of partially reprogramming nuclei from other species and support mitotic divisions. However, this study also showed a consistent embryonic developmental arrest at the 8- to 16- cell stage when horse or llama donor cells were used as donor nuclei. When a more closely related species of donor cell (banteng) and recipient oocyte (domestic cattle) were used for NT, no embryonic developmental arrest was found. Embryos progressed to achieve high blastocyst rates (banteng male cell line 28% vs. banteng female cell line 15%). Two banteng interspecies NT pregnancies were established and subsequently lost from the banteng male cell line. In the final study, the effect of a mixed mitochondrial population (heteroplasmy) on early embryonic development was investigated. Ooplasmic transfer performed in combination with NT procedure indicated presence of foreign mitochondria clustered in a small portion of the cytoplasm in early stages of embryo development. When goat ooplasm was transferred into interspecies (cow oocyte-goat donor cell) NT embryos, fusion and cleave rates were reduced suggesting an increased level of heteroplasmy or nuclear-ooplasmic incompatibilities.
Leptin In Horses: Influences Of Body Condition, Gender, Insulin Insensitivity, Feeding, And Dexamethasone, Joshua Allen Cartmill
Leptin In Horses: Influences Of Body Condition, Gender, Insulin Insensitivity, Feeding, And Dexamethasone, Joshua Allen Cartmill
LSU Doctoral Dissertations
The experiments described herein were designed to answer questions that arose from initially attempting to determine whether treatment with dexamethasone increased concentrations of leptin in geldings. Dexamethasone treatment did in fact increase leptin concentrations in mares, geldings, and stallions. Additional experiments were designed to determine leptin's interaction, not only with the adrenal axis, but with the thyroid axis, the growth hormone/insulin-like growth factor-1 axis, as well as glucose and insulin metabolism in geldings, mares, and stallions. During the course of these experiments, differences in leptin concentrations in the horse were attributed to degree of body condition, gender, and feeding time. …