College of Agriculture & Natural Resources
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The collections in this community comprise faculty research works, as well as graduate theses and dissertations.
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Item INVESTIGATING SPERM MATURATION DURING EPIDIDYMAL TRANSIT IN THE DOMESTIC CAT FOR THE DEVELOPMENT OF ASSISTED REPRODUCTIVE TECHNIQUES(2017) Rowlison, Tricia Marie; Ottinger, Mary Ann; Comizzoli, Pierre; Animal Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Understanding the physiological processes involved in the sperm maturation process is critical to elucidating mechanisms underlying male infertility. Maturation of the spermatozoa during epididymal transit is associated with the integration of specific proteins and acquisition of functionality. Many underlying processes are unclear thereby making it challenging to develop applications for assisted reproductive technologies. The goal of this research was to understand key phases in the sperm maturation process associated with functional effects of protein incorporation via epididymosome secretion on sperm cell motility and fertilization. Specific objectives were to (1) identify essential proteins that contribute to sperm centrosome maturation throughout epididymal transit, (2) characterize the transfer of key factors via epididymosomes between the epididymis and maturing sperm cells and (3) demonstrate the impact of such mechanisms on the acquisition of motility and fertilizing ability by the spermatozoa. Using the domestic cat model (Felis catus), we demonstrated that the secreted epididymal vesicles termed epididymosomes supply critical proteins to the developing spermatozoa and examined the effects of exposure of these vesicles on motility and ability to successfully fertilize an oocyte. Exposure of immature sperm cells to epididymosomes in vitro resulted in the significant incorporation of cenexin, critical for the maturation of the sperm centrosome, which then enables proper pronuclear syngamy and formation of the first mitotic spindle following oocyte penetration. Furthermore, this research focused on assessing the impact of malformed spermatozoa at the centrosome on fertilization success in the domestic cat. Findings revealed that improper maturation of the centrosome may be a source of infertility in this species as well as in wild felids. In summary, this research has provided insights into the sperm cell maturation process which will enhance the use of assisted reproductive techniques and reproductive success of many species including the human and wild felids.Item Investigation of spermatozoal metabolism and substrate utilization in domestic and non-domestic felids(2015) Weiner, Halli Sigal; Keefer, Carol L; Animal Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Cryopreservation of spermatozoa is a critical aspect of assisted reproduction. However in most cases, this process causes diminished spermatozoal function and low cellular survival. The effects of cryopreservation are further compounded in spermatozoa from individuals with disorders known to affect fertility. Teratospermia, characterized by the ejaculation of >60% morphologically abnormal spermatozoa, is one such disorder. Sperm from individuals with this condition exhibit reduced motility, impaired mitochondrial function, and a reduced ability to bind, penetrate, and fertilize an oocyte compared to sperm from normospermic males. Interestingly, even spermatozoa from teratospermic males that appear normal exhibit reduced functional capacity and following cryopreservation all cells are further impaired. More than 90% of felid species are affected by this condition, and it is prevalent among humans. Previous research suggested that impaired sperm metabolism in cheetahs – a ubiquitously teratospermic species – contributes to their poor cryosurvival and function, but the specific mechanisms are unknown. In this research, we hypothesized that inherent differences exist between the substrates and metabolic pathways utilized by sperm from normospermic and teratospermic individuals and on a species-specific basis. Gas chromatography - mass spectrometry (GC-MS) was used to investigate felid sperm metabolism using semen collected from domestic cats (Felis catus), cheetahs (Acinonyx jubatus), and clouded leopards (Neofelis nebulosa). The main objectives of this research were to: 1) characterize the metabolome of spermatozoa and seminal fluid; 2) investigate the role of β-oxidation in sperm motility and metabolism; and 3) interrogate the significance of specific metabolic pathways using metabolic activity profiling and heavy isotope tracers. Using GC-MS enabled the identification of metabolites which were unique to each species and sperm status (normospermic vs. teratospermic). Additionally, treatment of sperm with a β-oxidation inhibitor caused impaired motility in cheetah - but not domestic cat or clouded leopard - spermatozoa. Finally, fluxomic analysis demonstrated that glucose, fructose, and pyruvate are metabolized by felid sperm, but pathway utilization is species-specific. This is the first study to utilize a metabolomic and fluxomic approach to studying felid sperm, and the results of these studies illustrate the complexity of sperm metabolism on a species-specific basis. Understanding metabolic pathway activity in these cells will aid in the development of improved assisted reproduction techniques that may better facilitate sperm function and survival.