Theses and Dissertations

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Open Access
Cloning and expression of a porcine zona pellucida gene: an approach to immunocontraception
(Colorado State University. Libraries, 1991) Fontenot, Gregory Kenneth, author; Bowen, R. A., advisor; Jonathan Carlson, committee member; Niswender, Gordon, committee member
Immunization with native porcine zona pellucida (ZP) proteins has been shown to induce infertility in females of several species and is thus a potentially valuable method of contraception. However, more extensive testing and commercialization of such a vaccine has been hampered by the limited availability of ZP proteins from natural sources. Availability of recombinant ZP proteins should simplify production of a practical ZP vaccine. The objective of this research was to clone a porcine ZP gene and use it to develop a recombinant ZP vaccine for use in pet animals. Polyadenylated RNA isolated from swine ovary was used to generate a cDNA library in the bacteriophage lambda gt11. This library was screened immunologically for ZP sequences using a polyclonal antiserum raised against solubilized porcine ZP. One immunoreactive clone, PZP, contained an insert of approximately 2.6 kb and was characterized further. The three Eco RI fragments constituting PZP were isolated and subcloned into a plasmid vector. The amino acid sequence deduced from the nucleotide sequence of PZP is considered to represent 305 residues from the carboxyterminal end of the ZP protein. A putative N-glycosylation site is present at residue 288 of this polypeptide. Comparison of the deduced amino acid sequence of PZP with deduced protein sequences from all of the other ZP proteins published to date failed to reveal significant homology. To confirm that PZP represented a ZP mRNA, a 418 bp fragment of the cDNA was expressed as a fusion protein in E. coli and used to hyperimmunize a rabbit. Antibodies to the PZP fusion protein bound to ZP surrounding porcine oocytes, stained ZP in sections of porcine ovary and immunoprecipitated a porcine ZP protein that was tentatively identified as ZP2. The PZP fusion protein was preliminarily evaluated as a vaccine in rabbits. Two groups of four adult rabbits were immunized three or four times with PZP2 fusion protein emulsified in either one of two adjuvants. Reproductive function was evaluated eight and sixteen weeks after initial immunization. In comparison to control rabbits, no effect of vaccination on reproductive function was observed.
Open Access
Identification and characterization of two ovine membrane receptors for progesterone
(Colorado State University. Libraries, 2007) Ashley, Ryan L., author; Nett, Terry M., advisor
Classically, progesterone (P4) has been thought to act only through the well-known genomic pathway involving hormone binding to nuclear receptors (PR) and subsequent modulation of gene expression. Alternatively, there is increasing evidence for rapid, nongenomic effects of P4 in a variety of mammalian tissues; however the receptor responsible for these actions is yet to be characterized. The likelihood of a membrane P4 receptor (mPR) causing these events is quite plausible. Sheep are the experimental model often used in our laboratory, because regulation of reproductive function is very similar in ewes and women. Nongenomic actions of P4 have been described in sheep, but the receptor(s) responsible has not been identified. The objective of this dissertation was to isolate and characterize an ovine mPR distinct from the nuclear PR. A membrane protein found to bind P4 was first isolated from porcine liver and is now known as P4 receptor membrane component 1 (PGRMC1). Since PGRMC1 is expressed in a variety of species and tissues, I hypothesized that PGRMC1 was the protein responsible for the nongenomic effects of P4 in sheep. As such, the purpose of my initial studies was to determine if PGRMC1 was expressed in the sheep and further verify if PGRMC1 was present in the plasma membrane of the ovine corpus luteum (CL). A protein lacking homology to the nPRs but homologous to other reported PGRMC1 proteins was isolated from the sheep and contains a single transmembrane domain at the N-terminus. Despite the transmembrane domain, the ovine PGRMC1 displays predominant localization in the endoplasmic reticulum. During my initial studies, another putative mPR was cloned from the seatrout that displayed seven transmembrane domains, indicative of a G-protein-coupled receptor (GPCR) and upon ligand activation, also caused rapid induction of second messenger pathways. As such, I wanted to determine if this mPR was also present in the sheep. An ovine mPR distinct from the nuclear PR was isolated and characterized. The ovine mPR is a 350 amino acid protein that, based on predicted structural analysis, possesses seven transmembrane domains and is expressed in the hypothalamus, pituitary, uterus, ovary and CL. The first characterization of mPR expression throughout the ovine estrous cycle in the hypothalamus, pituitary, uterus, ovary, and CL is also reported. In CHO cells that overexpress a mPR-GFP fusion protein the ovine mPR was uniquely localized to the endoplasmic reticulum and not the plasma membrane. The ovine mPR specifically binds only progestins. Progesterone, 20α-hydroxyprogesterone and 17α-hydroxyprogesterone significantly (P < 0.001) displaced binding of 3H-P4 to membrane fractions from CHO cells expressing ovine mPR. Additionally, the ovine mPR directly induces Ca2+ release from the endoplasmic reticulum upon ligand activation. Further, the ovine mPR appears to activate the MAPK pathway, specifically by phosphorylation of JNK1/2 upon ligand activation. This novel method of signaling at the endoplasmic reticulum adds to the intricacy of signaling in cells and provides a mechanistically unique method for initiating actions of P4 that may alter classical dogma regarding the mechanisms by which steroid hormones act.
Open Access
Energy substrates, metabolic regulators, and lipid accumulation during culture of in vitro-produced bovine embryos
(Colorado State University. Libraries, 2007) Barceló-Fimbres, Moisés, author; Seidel, George E., Jr., advisor
The main objective of this experiment was to optimize in vitro culture conditions for bovine embryonic development, using alternative energy sources and metabolic regulators. Replacing glucose with fructose in culture medium consistently increased blastocyst production per oocyte and decreased lipid content in bovine embryos. The use of phenazine ethosulphate (PES) or fetal calf serum (FCS) supplementation did not affect embryonic development; however, PES consistently decreased, and FCS increased lipid content of embryos compared to the control. There was no effect of glucose or fructose on survival of embryos after cryopreservation by slow freezing or vitrification; however, embryos-treated with PES to reduce lipid content resulted in improved cryotolerance, and FCS decreased cryotolerance compared to the control. Transfer of embryos treated with PES during in vitro culture did not affect pregnancy rates, conceptus losses, or fetal or post-natal development in calves born normally. The sex ratio of calves born was skewed toward males. This effect likely was due to a toxic effect of glucose to female embryos cultured in vitro. Therefore, the more expanded day 7 blastocysts were mostly male embryos.
Open Access
The use of chronic models of temporal lobe epilepsy in antiepileptic drug development
(Colorado State University. Libraries, 2007) Grabenstatter, Heidi, author; Dudek, F. Edward, advisor
A chronic animal model with altered ion channels, transmitter receptors and/or neural circuitry similar to temporal lobe epilepsy (TLE) may be useful in the discovery of new antiepileptic drugs (AEDs). The hypothesis was that rats with kainate-induced epilepsy are pharmacosensitive to AEDs, but high doses do not block all spontaneous seizures (i.e., these rats are "pharmacoresistant"). A repeated-measures cross-over protocol was used to show single intraperitoneal injections of topiramate, RWJ-333369, and carbamazepine reduced the frequency of spontaneous motor seizures. The same protocol with administration of 30 mg/kg and 100 mg/kg carbamazepine in specially-formulated food pellets was as effective as intraperitoneal injections, and 100 mg/kg carbamazepine administered in food three times per day completely suppressed motor seizures in 50% of the animals for a prolonged time period (i.e., 24 h) while reducing any stress to the animals. Video-EEG showed carbamazepine preferentially reduced spontaneous convulsive seizures compared to nonconvulsive seizures at 100 mg/kg, reduced seizure duration in some animals at 100 mg/kg, and caused a subtle decrease in the maximum frequency of population spikes during seizures at 30 mg/kg. These data suggest that animal models of TLE with spontaneous seizures can be used efficiently to test AEDs, and that this repeated-measures cross-over protocol is amenable to both dose-effect and time-course-of-recovery studies for the direct comparison of AEDs. This approach can provide statistical power to compensate for seizure clusters and variability across animals. These experiments also show that rats with kainate-induced epilepsy are pharmacosensitive to standard and experimental AEDs; additional studies are required to determine if this model is also pharmacoresistant.
Open Access
Characterization of periattachment factor
(Colorado State University. Libraries, 2008) Purcell, Scott H., author; Anthony, Russell V., advisor; Seidel, George E., advisor
The purpose of these studies was to characterize expression of periattachment factor (PF) mRNA in the developing sheep conceptus, localize PF in the sheep conceptus, determine if degrading PF mRNA in the sheep conceptus was detrimental to development, and characterize PF in human tissues and cells. Sheep conceptuses were collected on d 11, 13, 15, 16, 17, 21, and 30 post-mating. oPF mRNA exhibited a quadratic expression pattern (P<0.05). No oPF mRNA was detected in d 11 conceptuses. From d 13, oPF mRNA increased to a peak at d 16 before declining. Peak expression of oPF mRNA in the conceptus occurs during rapid elongation and initial attachment of the conceptus to the endometrium. Immunolocalization of PF in a d 15 conceptus showed predominantly nuclear staining in trophectoderm and trophendoderm. Next, embryos collected from superovulated ewes on d 8 post-mating were infected with either a lentivirus expressing a short-hairpin (sh) RNA designed to target PF mRNA for degradation, a lentivirus expressing a shRNA containing 3 mismatched nucleotides, or a control lentivirus expressing no shRNA. Following infection, blastocysts were transferred into recipient ewes and collected back on d 15 of gestation. While 94 and 88% of the control and mismatched shRNA-treated conceptuses elongated by d 15, none of the embryos treated with the lentivirus expressing shRNA against PF mRNA elongated, and most died. This indicates that oPF is required for conceptus elongation and survival. Human PF mRNA was detected in human carcinomas and in the first trimester cytotrophoblast cell line, hTR8. Immunohistochemistry showed PF in the nuclei of carcinomas and in first and second trimester cytotrophoblasts. PF was also present in the invading cytotrophoblast columns. In an in vitro invasion assay of first trimester cytotrophoblasts, hPF mRNA increased from 0, 3, to 12 h as invasion occurred. To further characterize PF in human cells, a lentiviral construct expressing an shRNA targeting the hPF mRNA sequence was developed that resulted in 63% mRNA reduction in BeWo cells.
Open Access
Behavioral effects of estrogen receptor beta acting locally to regulate the expression of tryptophan hydroxylase 2 (THP2) in serotonergic neurons of the dorsal raphe nuclei
(Colorado State University. Libraries, 2008) Donner, Nina Caroline, author; Handa, Robert J., advisor; Tjalkens, Ronald, committee member; Clay, Colin McKeown, committee member; Tobet, Stuart, committee member
Affective disorders often involve serotonin (5-HT)-related dysfunctions and are twice as common in women than men. Interactions between estrogen and the brain 5-HT system have long been proposed to contribute to sex differences in mood and anxiety disorders, but the mechanisms underlying this phenomenon have yet to be revealed. Estrogen signaling is mediated by two different receptors termed estrogen receptor alpha and estrogen receptor beta. While estrogen receptor alpha (ERalpha) has mainly reproductive responsibilities, in brain, estrogen receptor beta (ERbeta) has been shown to attenuate anxiety- and despair-like behaviors in rodent models. However, little is known about ERbeta regulation of function in the brainstem raphe nuclei. The raphe nuclei are the main 5-HT system of the brain, and projections from the dorsal raphe nuclei (DRN) innervate many important forebrain and limbic areas. The work presented in this thesis addressed the possibility that ERbeta may be involved in the regulation of 5-HT gene expression specifically in DRN neurons. My studies examined the effects of systemic versus local, intracerebral application of the selective ERbeta agonist diarylpropionitrile (DPN) and the nonselective ERligandestradiol (E) on tryptophan hydroxylase 2 (TPH2) mRNA expression within the DRN of female rats. TPH2 is the brain-specific, rate-limiting enzyme catalyzing 5-HT synthesis, and is expressed in every 5-HT neuron. Thus, it provides an excellent tool to assess the capacity for 5-HT production with the DRN. In these studies, TPH2 mRNA expression was assessed via in situ hybridization. In addition, relevant behavioral parameters were tested in all animals to evaluate each compound’s effect on two closely related, but yet different mental states, anxiety-like and despair-like behavior. Both, chronic systemic and chronic local DPN administration to ovariectomized (OVX) female rats significantly enhanced TPH2 mRNA expression in mid- and caudal subregions of the DRN after 8 days of treatment. Respective controls received systemic vehicle (27% hydroxypropyl-beta-cyclodextrin) or blank control pellets. Local application of DPN caused a stronger effect than systemic drug delivery. Chronic local delivery of E (0.5 μM) increased TPH2 mRNA expression in the same subregions of the DRN as did DPN, but its overall effect was weaker compared to the selective ERbeta agonist. Interestingly, while systemic DPN-administration confirmed the anxiolytic nature of ERbeta in two separate anxiety tests (elevated plus maze and open field test), the effect was lost when DPN was delivered locally. However, local DPN- as well as E-treatment both resulted in attenuated despair-like behavior, as measured in the forced-swim test. Chapter 3 describes the experimental design, results and interpretation of these studies in depth. Taken together, my data indicate that local actions of ERbeta agonist onto DRN neurons are sufficient to decrease despair-like behavior, whereas ERbeta stimulation of other brain regions is necessary to alter anxiety-like behaviors. Correspondingly, ERbeta acts locally to control TPH2 mRNA expression and presumably 5-HT synthesis in the certain subregions of the rat DRN. These results suggest an important role of ERbeta for regulating cellular events in the female DRN, and offer new opportunities for therapeutic treatments of depressive disorders.
Open Access
Status epilepticus, recurrent seizures, hippocampal damage and the estrous cycle in a model of temporal lobe epilepsy
(Colorado State University. Libraries, 2008) Fawley, Jessica, author; Dudek, F. Edward, advisor
Temporal lobe epilepsy is the most common form of epilepsy and is associated with hippocampal sclerosis and spontaneous recurrent seizures. These pathologies generally develop after a latent period from a precipitating brain injury, which often results in status epilepticus (SE). Sex and hormones have been reported to influence SE and mortality in both clinical and experimental settings. Temporal lobe epilepsy is also associated with an increase in reproductive disorders, which are often the result of altered pulsatile release of luteinizing hormone (LH). Gonadotropin-releasing hormone (GnRH) controls LH release; therefore, reproductive abnormalities associated with epilepsy could hypothetically involve hypothalamic disturbances, particularly to the GnRH network, resulting in altered secretion of GnRH. The aim of this dissertation was to (1) to examine the effects of SE and/or temporal lobe epilepsy on the GnRH neuronal network and (2) utilize recordings of electroencephalogram (EEG) activity to systematically quantify sex and hormone influences on SE and the subsequent recurrent seizures. I report that pilocarpine-induced SE resulted in reproductive alterations in two rodent models of temporal lobe epilepsy, which were not due to a detectable reduction in GnRH-positive neurons. There were no significant differences between the EEG parameters of SE or recurrent seizures between groups. Sex and the stage of the estrous cycle may influence pyramidal cell loss in the hippocampus at 24 h but the stage of the estrous cycle and/or sex do not seem to be predictors of long-term hippocampal damage. In summary, these data do not support the hypothesis that SE and/or temporal lobe epilepsy results in a reduction in the number of GnRH neurons or the hypothesis that sex/cycle stage influences SE, or the progression to temporal lobe epilepsy. However, these models of SE/temporal lobe epilepsy will be useful to further study temporal lobe epilepsy-associated reproductive alterations.
Open Access
Characterization of mediators of cardiac and renal development in response to increased prenatal testosterone
(Colorado State University. Libraries, 2008) Maresh, Ryan W., author; Anthony, Russell, advisor
Previously reported differences in cardiac and kidney weights of offspring from ewes prenatally treated with testosterone suggested the development of systemic hypertension. To determine if prenatal androgen excess influences the expression of key mediators, angiopoietin 1 (Ang1), angiopoietin 2 (Ang2), tunica interna endothelial cell kinase-2 (Tie2), angiotensin II receptor subtypes 1 and 2 (AT1 and AT2), endothelial nitric oxide synthase (eNOS), vascular endothelial growth factor (VEGF), VEGF receptor 1 (VEGF R1), VEGF receptor 2 (VEGF R2), insulin receptor β (IRβ), glucose transporter 1 (GLUT1), and glucose transporter 4 (GLUT4) were evaluated from fetal hearts, fetal kidney, left ventricle (LV), right ventricle (RV), and kidney. We hypothesized that mRNA and protein concentrations were altered and that the changes persist into adulthood. At fetal Day 90 a significant increase (p = 0.021) in IRβ mRNA concentration of was seen in the heart, whereas VEGF mRNA concentration was significantly reduced (p = 0.044) in the kidney. In 9 month RV, eNOS mRNA concentration was significantly reduced in the treatment group (p = 0.019). In the 9 month kidney, significant increases in GLUT4 mRNA concentration (p = 0.047) and eNOS protein concentration (p = 0.027) were seen in the treatment group. At 21 months of age, Ang1 mRNA concentration in the treatment group was significantly reduced (p = 0.025) in the LV. AT1 mRNA concentration was significantly decreased (p = 0.004) in the RV of the treatment group. LV eNOS concentration was significantly reduced (p = 0.032), while RV eNOS mRNA concentration was significantly decreased (p < 0.001) in the treatment group. Significant decreases in GLUT1 mRNA concentration were detected in the LV (p = 0.013) and RV (p = 0.006), and RV GLUT4 mRNA concentration was significantly decreased (p = 0.003) in the treatment group. LV IRβ concentration was significantly reduced (p = 0.036) in the treatment group. In the kidney, VEGF R2 mRNA concentration was significantly reduced (p = 0.024) in the treatment group. Taken together, the data supports the development of systemic hypertension and insulin resistance with age following prenatal androgen exposure.
Open Access
Estrogen receptors alpha and beta: Opposing roles in hypothalamic-pituitary-adrenal axis function and stress-related behaviors
(Colorado State University. Libraries, 2008) Weiser, Michael James, author; Handa, Robert, advisor
Estradiol has reported effects on mood ranging from anxiogenic to anxiolytic and depressant to anti-depressant. These opposing actions of estradiol may be explained by the existence of two distinct estrogen receptor (ER) systems, ER alpha (ERα) and ER beta (ERβ). Furthermore, there exists a sex difference in stress-related psychiatric disorders such as anxiety and depression, for which women are more susceptible than men. Common to the pathology of these disorders is a dysfunctional hypothalamic-pituitary-adrenal (HPA) axis where glucocorticoid negative feedback is impaired leading to chronically high levels of circulating glucocorticoids. The HPA axis is the main neuroendocrine axis that governs physiological responses to stressors. In rodents, basal and stress-induced activity of the HPA axis is higher in females than in males. This suggests that, if transferable to humans, the sex difference observed in HPA axis function in animal models may help explain the female predisposition for certain psychiatric disorders. The studies described in this dissertation were aimed at characterizing the distinct roles for ERα and ERβ in HPA axis activity and stress-related behaviors. The studies in Chapter 3 examine the effect of estradiol signaling through ERα or ERβ on glucocorticoid negative feedback of the HPA axis. Results indicate that estradiol impairs glucocorticoid-dependent negative feedback by activating ERÎ± specifically at the level of the paraventricular nucleus (PVN). The studies in Chapter 4 examine the effect of estradiol signaling through ERα or ERβ on anxiety-like and depressive-like behaviors. Results indicate that selective activation of ERα is anxiogenic and depressant, whereas selective activation of ERβ is anxiolytic and antidepressant. Finally, the studies in Chapter 5 examine the effect of estradiol signaling through ERβ on behavior and HPA axis activity induced by glucocorticoid receptor (GR) activation in the central nucleus of the amygdala (CeA). Results indicate that delivery of a GR agonist to the CeA is anxiogenic and augments the HPA axis response to a stressor, and peripheral administration of an ERβ agonist blocks this effect. Collectively, these studies point to an antagonistic relationship between estradiol signaling through ERα and ERβ with respect to HPA axis activity and stress-related behaviors.
Open Access
Mechanism of neuronal cell death in canine glaucoma
(Colorado State University. Libraries, 2009) Alyahya, Khaleel I., author; Madl, James E., advisor
Glaucoma is one of the most important causes of blindness in human and dogs. Glaucoma is characterized by a progressive loss of retinal ganglion cells that is often associated with increased intraocular pressure and decreased retinal blood flow. In previous investigations, we found that changes in glutamate distribution occur selectively in damaged areas of retinas of dogs with primary glaucoma. This glutamate redistribution is consistent with high levels of extracellular glutamate (â†‘GluE) contributing to excitotoxic damage to neurons. In this dissertation, we used immunohistochemical methods to test three mechanisms by which this glutamate redistribution may occur in retinas from clinical cases of canine glaucoma. First, we tested if ischemia due to microvessel loss causes the changes in glutamate distribution. We found significantly lower microvessel density in damaged regions, consistent with ischemia occurring in canine glaucoma. Second, we tested if loss of glutamine synthetase induces the glutamate redistribution. We have found significantly decreased amounts of glutamine synthetase in areas with neuronal damage and glutamate redistribution, consistence with decreased glutamate synthetase contributing to glutamate redistribution. Third, leakage of glutamate from blood vessels from inflamed areas may lead to glutamate redistribution. We found that there is albumin leakage from blood vessels in damaged regions with other inflammatory indicators in those areas. The smaller size of glutamate suggests that it should also diffuse out of blood into the extracellular fluid of the retina even more readily than albumin. Increase leakiness of blood vessels in canine glaucoma is consistent with glutamate leakage contributing to glutamate redistribution. In conclusion, our results are consistent with all three mechanisms contributing to glutamate redistribution in canine glaucoma. The dissertation includes further discussion of more refined hypotheses of the mechanisms by which glutamate redistribution and neuronal damage may occur.
Open Access
The effect of aging on gene expression and mitochondrial DNA in the equine oocyte and follicle
(Colorado State University. Libraries, 2009) Campos-Chillon, Lino Fernando, author; Carnevale, Elaine, advisor
The decline in fertility of aged mares is linked to declining oocyte quality. Oocyte viability is dependant on the ability of oocytes to remain in meiotic arrest until the initiation of maturation and adequate cumulus communication. We hypothesize that aging is associated with quantitative and temporal differences in meiotic arrest and resumption in oocytes, decreased oocyte secretion of paracrine factors and lower mitochondrial numbers, ultimately resulting in a dissociation of oocyte and follicular maturation. The objectives of this study were to clone and determine quantitative and temporal differences in mRNA content of the LH receptor (LHR), amphiregulin (AREG) and epiregulin (EREG) in granulosa cells; PDE4 in cumulus cells; and PDE3A, GPR3, GDF9, BMP15, and mitochondrial DNA (mtDNA) in oocytes during in vivo maturation in young (3-12 yr) and old (>20 yr) mares. Oocytes and follicular cells were collected by transvaginal follicular aspiration. Follicle maturation was induced in estrous mares with a follicle >30 mm by injection of 750 µg of recombinant equine LH. Aspirations were conducted at 0, 6, 9, and 12 h after LH administration. Total RNA was isolated from single denuded oocytes and associated lysed cumulus and granulosa cells. For each gene, mean mRNA copy number for each time point and age group were compared by ANOVA and Fisher's LSD. Regression coefficients were generated to compare oocyte mitochondrial numbers and correlations between gene expression within age groups. Expression of LHR mRNA in granulosa cells was different (p<0.05) between age groups. Young mares displayed a significant drop in LHR mRNA between 0 h and 6, 9, and 12 h; while the pattern of expression in old mares was similar (p>0.05) among times and higher (p<0.05) at 6 h than in young mares. Expression of AREG mRNA in granulosa cells peaked (p<0.05) at 9 h; however, the magnitude of expression at 6 and 9 h was higher (p<0.05) in old than young mares. Similarly, EREG expression peaked (p<0.05) at 9 h in young and old mares but was higher (p<0.05) for old mares. Expression of PDE4D peaked (p<0.05) at 6 and 12 h in old and young mares, respectively. The patterns of expression of GPR3 for oocytes of young and old mares were different and peaked (p<0.05) at 9 and 12 h, respectively. Magnitude of expression of PDE3A for oocytes of old mares at 6 and 9 h was higher (p<0.05) than in young mares. Expression of GDF9 and BMP15 was different (p<0.05) between ages. Mean expression of both genes in the old group was similar over time; however, in young mare oocytes maximum expression was at 6 h (p<0.05). Correlation coefficients between GDF9 and BMP15 for old and young mares were 0.94 and 0.99, respectively. Numbers of copies of oocyte mtDNA did not vary in young mares; however, there was a temporal decrease (p<0.05) of oocyte mitochondrial copy numbers in old mares. The main effect for age for mtDNA was similar for old and young mares.
Open Access
Two types of melanopsin retinal ganglion cell in the mouse retina: the regulation of melanopsin expression
(Colorado State University. Libraries, 2009) Baver, Scott Benjamin, author; Tobet, Stuart, advisor
Rods, cones and a subset of retinal ganglion cells (RGCs) that express the photopigment melanopsin are the sensory photoreceptors of the mammalian retina. The light-driven signals that are initiated by the photoreceptors are relayed from the retina to the brain. In addition to the role of light information in regulating the perception of colors, objects and movement, it also controls pupil size and the synchronization of daily physiological rhythms to the day/night cycle. The melanopsin-expressing RGCs, which are intrinsically photosensitive (ipRGCs), contribute especially to these two latter processes. The focus of this dissertation is the ipRGCs of the mouse retina.
Open Access
The role of interferon-tau (IFNT) in luteal gene expression, steroidogenesis, and luteal lifespan in the ewe
(Colorado State University. Libraries, 2009) Bott, Rebecca Clark, author; Bruemmer, Jason, advisor; Niswender, Gordon, advisor
Interferon-tau (IFNT) was evaluated for endocrine actions on the corpus luteum (CL). The hypothesis was that infusion of IFNT would increase luteal expression of interferon-stimulated gene (ISG)-15, and the length of time for ewes to return to estrus. Osmotic pumps containing 200 μg IFNT or BSA (n=12 each) were connected to the uterine vein of non-pregnant ewes 10 days post-estrus. Messenger RNA encoding ISG15 was elevated in CL from pregnant and IFNT-infused ewes (P<0.05) compared to nonpregnant and BSA-treated ewes, respectively. Luteal mRNA encoding ISG15 from ewes treated with IFNT was greater than in ewes treated with BSA (P<0.05). Serum concentrations of progesterone were not different in ewes that received infusions of BSA or IFNT. Progesterone decreased by six hours (P<0.05) in ewes that received BSA+PGF or IFNT+PGF, but did not differ in ewes that received infusions of IFNT +/- PGF at 8, 10, or 12 hours after PGF. There were no differences in prostaglandin E synthase (PGES) or prostaglandin F synthase (PGFS), or in prostaglandin dehydrogenase (PGDH), steroidogenic acute regulatory protein (StAR), peripheral type benzodiazepine receptor (PBR), cytochrome P450 side chain cleavage enzyme (CYP-11A), or 3μ-hydroxysteroid dehydrogenase (3μ-HSD). Seven day infusion of IFNT during the time frame of maternal recognition of pregnancy resulted in 20% of IFNT-treated ewes returning to estrus by d19 compared to 100% of BSA-treated ewes (P<0.01). In conclusion IFNT acts systemically, alters gene expression in the corpus luteum, and decreases the number of ewes returning to estrus by d19.
Open Access
Evaluation of kisspeptin in the mare
(Colorado State University. Libraries, 2010) Magee, Christianne, author; Clay, Colin M., advisor; Tobet, Stuart A., committee member; Nett, Torrance M., committee member; Goodrich, Laurie R., committee member; Duval, Dawn L., committee member
Identified in 2003 for their role in reproductive physiology, kisspeptins have become major players in the field of reproductive neuroendocrinology. With the ability to act as a central regulator for the onset of reproductive function in prepubertal and seasonal animals, the possibility that kisspeptin signaling could be used to modify seasonal reproductive function in the horse held great promise. My hypothesis was that kisspeptin, acting via a hypothalamic signaling mechanism to stimulate the GnRH neuron, could initiate reproductive function in the horse. The initial objectives of these studies were to (1) establish biological and physiological evidence for kisspeptin signaling in the hypothalamus of the mare, (2) demonstrate peripheral administration of kisspeptin could elicit a rise in serum luteinizing hormone (LH) concentrations in the diestrous mare, and (3) demonstrate that kisspeptin, acting via LH, could induce ovulation in the estrous mare. The diestrous mare has kisspeptin immunoreactive neurons in the hypothalamus that are in close proximity to Gonadotropin Releasing Hormone (GnRH) neurons. At the time of these initial studies, the equine sequence for the kisspeptin decapeptide (Kp-10) was not yet available; therefore, I utilized the rodent Kp-10 (rKp-10, YNWNSFGLRY-NH2). Even though I was using a heterologous ligand, the diestrous mare was responsive to administration of rKp-10 (0.5 and 1.0 mg) such that there was a short (< 1 hour), but significant (2-fold) rise in circulating levels of LH and follicle stimulating hormone (FSH) after kisspeptin administration. I was also able to establish a threshold dose for kisspeptin responsiveness in the diestrous mare as there was no change in serum gonadotropin levels following a 1.0 μg dose of rKp-10. In the estrous mare, a single injection of 1.0 mg rKp-10 IV was unable to induce ovulation (173), presumably due to the short duration of the kisspeptin induced LH surge as compared to the 3-5 day endogenous peri-ovulatory LH surge (306). To understand the dynamic of kisspeptin signaling to the hypothalamus and the anterior pituitary gland, I sought to determine the effect of treating mares with repeated injection of kisspeptide in diestrus and estrus. If the future of kisspeptin in the horse involves the use of modified agonists or antagonists, it will be necessary to understand how the mare responds to repeated stimulation with kisspeptin. Before beginning these studies, the equine sequence for Kp-I0 (eKp-10, YRWNSFGLRY-NH2) had become available. Therefore, I used the homologous peptide for these studies. By treating mares with eKp-10 (0.5 mg IV every 4 hours), the hypothalamus and pituitary gland were repeatedly stimulated to elicit a GnRH and gonadotropin response. Repeated administration of kisspeptin in the diestrous mare is not able to sustain a 2-fold increase in LH concentration for 48 hours following the initial injection. Interestingly, kisspeptin caused a decrease in basal LH, but not FSH levels, indicating a decrease in LH synthesis or secretion via a pituitary effect. Although the mare does not exhibit a change in peripheral LH levels following eKp-10 if a GnRH antagonist (e.g. Antide) has been administered, I sought some evidence for kisspeptin signaling directly to the anterior pituitary. To support the idea of a direct pituitary effect of kisspeptin, I challenged primary pituitary cells in culture with 100 nM GnRH and 100 nM of eKp-10. Surprisingly, I identified three populations of cells that respond with a change in intracellular calcium concentration and grouped them as follows: cells that responded to (1) both GnRH and eKp-l0, (2) only GnRH, or (3) only eKp-10. The identification of gonadotrope and non-gonadotrope kisspeptin responsive pituitary cells is the first evidence for a direct mechanism for kisspeptin signaling at the level of the equine pituitary gland. In the estrous mare, repeated administration of eKp-10 is not able to shorten the interval to ovulation whether it is administered before or after the development of a dominant follicle. Another surprising finding was a significant decrease in sexual receptivity in mares within 48 hours of beginning treatment with kisspeptin, which is likely due to a decrease in estradiol synthesis by the maturing follicle. Given the lack of ovulation induction in the estrous mare and the changes in behavioral receptivity, I do not recommend the use of kisspeptin as an ovulation inducing agent at this time. However, there was no decrease in basal LH levels in the estrous mares. Thus, kisspeptin may be signaling via different mechanisms in the estrous vs. diestrous mare. In summary, these studies do provide evidence for kisspeptin signaling in the mare, but they reveal that the signaling mechanism in the horse may be more complex than my original hypothesis of a simple, linear process that is working only through the GnRH neuron.
Open Access
Optimizing storage of bovine sperm between semen collection and sexing
(Colorado State University. Libraries, 2010) Anema, Jennifer Lea, author; Seidel, George, Jr., advisor; Graham, James, committee member; Peel, Richard Kraig, committee member
To view the abstract, please see the full text of the document.
Open Access
Regulation of trophoblast stem cell maintenance and differentiation by LIN28 and AP-2γ
(Colorado State University. Libraries, 2010) Fromme, Brittany A., author; Winger, Quinton A., advisor; Bouma, Gerrit J., advisor; Bailey, Susan M., committee member; Anthony, Russell V., committee member
The placenta is a unique organ essential for survival of the fetus in all eutherian mammals. Failure to develop a normal placenta in humans can lead to diseases, such as pre-eclampsia, with high morbidity and mortality for both the mother and the fetus. These diseases are thought to be caused by abnormal proliferation and differentiation of cells in the placenta. A mouse trophoblast stem (TS) cell culture system is a useful tool in studying TS cell proliferation and differentiation into trophoblast giant cells (TGCs). TS cells cultured in proliferative media (70% conditioned media, 30% TS media, FGF4, and heparin sulfate) will remain proliferative, and TS cells cultured under differentiation media (100% TS media) will differentiate into TGCs. LIN28 is a protein that regulates mRNAs and miRNAs, and is abundantly expressed in many undifferentiated tissues. AP- 2y has been shown to be essential for TS cell maintenance and TGC formation. AP-2y null mutants display embryonic lethality at E7.5 due to a severely disrupted extraembryonic portion of the embryo. In TS cells, AP-2y has been shown to bind to the promoter region of Lin28. This study investigates the hypothesis that Liti28 and Ap-2y are necessary regulators of trophoblast stem cell maintenance and differentiation into TGCs. This study shows the pluripotency genes, Lin28, Sox2, and NrObl, to be differentially expressed in proliferating TS cells and differentiated TGCs. MiRNAs can be used as markers for proliferation or differentiation. 28 significantly different miRNAs were detected between TS cells and TGCs, 18 up-regulated in TGCs and 9 downregulated in TGCs. Expression of the miR-290 family, initially thought to be ES cell specific, was detected in proliferating TS cells suggesting TS cells have similar miRNA mediated regulation of proliferation compared to ES cells. The Let-7 family of miRNAs was found to be up-regulated in differentiated TGCs. The Let-7 family has been shown to be regulated by LIN28, where LIN28 prevents accumulation of mature Let-7 miRNAs. In this study Lin28 was highly expressed in proliferating cells and the Let-7’s are upregulated in differentiated TGCs. Lin28 function in TS cells was assessed by knocking down Lin28 using shRNA lentiviral technology. Lin28 knockdown TS cells were used to observe results of knockdown. We obtained a 78% reduction of Lin28 mRNA, but found that loss of Lin28 in TS cells did not affect morphology, proliferation or differentiation. AP-2y null TS cells grown in culture fail to differentiate morphologically into TGCs. Lin28, Sox2, and NrObl show no difference in expression when grown in conditions to differentiate the cells, indicating a failure of AP-2y null TS cells to differentiate into TGCs. RO3306 is a compound used to block Cyclin-dependent Protein Kinase 1 and force endoreduplication, causing TS cells to differentiate into TGCs. AP-2y null TS cells cannot be forced to differentiate into TGCs, and instead undergo cell death, when cultured with RO3306. Additionally, AP-2y null TS cells express the pluripotency markers Oct4, Stella, and Nanog which only are expressed in ES cells and germ cells. MiRNA profiling of AP-2y null TS cells indicates that cells in proliferative conditions resemble wild type counterparts, but when proliferative conditions are removed we observe an increase in expression of the ES cell specific miR-302 cluster. While there was no effect of proliferation in wild type cells, loss of Lin28 in AP-2y null TS cells via lentiviral knockdown leads to a partial rescue of TGC formation. This suggests that Liii28 must be down-regulated in order for TGC formation, and that AP-2y regulates Lin28 in TS cells. Taken together these data suggest a role for Lin28 in mouse TS cell proliferation and differentiation, where Lin28 must become down regulated in order for differentiation into TGCs. AP-2y has been shown to bind to the Lin28 promoter in TS cells; this regulation enables TS cell differentiation into TGCs. This study also shows the necessity of AP-2y for TS cell differentiation into TGCs; loss of AP-2y leads to a more pluripotent state rather than allowing for differentiation. Loss of AP-2y leads to expression of pluripotency markers Oct4, Nanog, and Stella, and the ES cell specific miR-302 cluster, indicating an increase in pluripotency. We conclude that AP-2y and LIN28 are essential molecular regulators of TS cell proliferation and differentiation.
Open Access
Association of oocyte and early embryo morphology with age and the establishment and maintenance of pregnancy after ICSI in mares
(Colorado State University. Libraries, 2010) Frank-Guest, Bethany Linda, author; Carnevale, Elaine, advisor; Seidel, George, Jr., committee member; Hendrickson, Dean, committee member
Increasing maternal age in humans, horses and lab animals has been associated with a decrease in fertility. Oocyte quality and morphology have been implicated as primary causes of reduced fertility in older mares. Selected oocyte morphological parameters have been correlated with pregnancy development in humans and horses. Objective measurements of morphology to assess oocyte quality would provide a critical evaluation and help identify zygotes with the highest developmental potential for transfer, to optimize recipient utilization and pregnancy rates. The hypotheses of the research were that oocyte and early embryo morphology differ with donor mare age and correspond with developmental potential. Objectives for the first study were to compare: 1) oocyte donor age with oocyte morphology and developmental competency after ICSI, and 2) oocyte morphology with developmental competency (cleavage, early pregnancy, late pregnancy and pregnancy loss) after ICSI. Objectives for the second study were to compare developmental potential of ICSI produced embryos with: 1) oocyte donor age, and 2) cleavage characteristics, and 3) rate of embryonic development. Oocytes were collected from donor mares in a clinical ICSI programs. The mares were divided into the following age groups and fertility categories: 1) 3-13 yr with Known fertility, 2) 2-13 yr with Unknown fertility, 14-19 yr, 20-23 yr and 24-27 yr. Approximately 24 h after induction of follicle maturation, and oocytes were collected and cultured approximately 18 h before being stripped of cumulus cells. Photographic images (200x) were captured before oocytes were injected with sperm. Images of oocytes were measured using digital calipers within a computer software program. Ooplasm volume was larger (p<0.05) for oocytes from mares 14-19 yr and 20-23 yr than mares 3-13 yr Known than for mares 24-27 yr. Perivitelline space volume was similar between mares 3-13 yr Unknown and mares 20-23 yr, but was smaller (p<0.05) between mares 3-13 Unknown and the other age groups. Oocyte diameter (OD) was smaller (p=0.05) between oocytes from donors 3-13 yr Known and donors 14 -19 yr, but similar among all other groups. Inner zona pellucida diameter (IZPD) differed (p=0.03) only between mares 14-19 yr and mares 3-13 yr Unknown, with oocytes from mares 14- 19 yr having the largest numerical IZPD and mares 3-13 yr Unknown having the smallest IZPD. Ooplasm diameter (OpD) was smaller (p≤0.02) for oocytes from mares 3-13 yr Known than from mares 14-19 or 20-23 yr. The diameter of the zona pellucida with the surrounding matrix (ZPTM) was greater (p<0.05) for mares 3-13 yr Unknown than for all other groups. The rate of embryo development (hours per cell) prior to oviductal embryo transfers was faster (P<0.05) for embryos that did versus did not produce an early pregnancy and tended (P≤0. l) to be faster for embryos that did versus did not produce a late pregnancy. Embryonic vesicles that had a more rapid increase in diameter were more often (p<0.05) maintained to the late pregnancy stage. Donor mare age exerted a large effect on the development and outcome of pregnancies. Oocyte morphology was not a reliable indicator of oocyte developmental potential, although speed of early embryonic development was associated with embryonic competency.
Open Access
Membrane organization of luteinizing hormone receptors during signal transduction
(Colorado State University. Libraries, 2010) Wolf-Ringwall, Amber L., author; Roess, Deborah, advisor; Miller, Charles, committee member; Graham, James, committee member; Barisas, B. George, committee member
Mechanisms involved in signal transduction by luteinizing hormone (LH) receptors are important for regulating key events in mammalian reproduction, such as ovulation, sex hormone production and maintenance of pregnancy. Studying the organization of LH receptors in the plasma membrane during hormone-mediated signaling provides insights into the protein interactions needed for important physiological responses. We used biochemical and biophysical methods to examine the role of the plasma membrane in contributing to LH receptor desensitization. Using single particle tracking and sucrose gradient ultracentrifugation, we determined that individual human LH receptors are confined in small membrane compartments and localize in membrane rafts for several hours following desensitization. These receptors do not demonstrate signaling via cyclic adenosine monophosphate (cAMP) while they are confined, suggesting that the microenvironment within these compartments may be different for desensitized versus actively signaling receptors. We also investigated self-association of human LH receptors using homotransfer fluorescence resonance energy transfer (homo-FRET) and fluorescence correlation spectroscopy. We determined that human LH receptors self-associate following desensitization and in response to increasing concentrations of human chorionic gonadotropin (hCG). LH receptors demonstrated the highest degree of aggregation in response to saturating concentrations of 100 nM hCG. Using single particle tracking, we examined whether native LH receptors expressed on KGN human granulosa-like tumor cells, or M l7 human neuroblastoma cells, become confined in small membrane compartments in response to hormone binding. We found that confinement of native LH receptors in small plasma membrane compartments depended on hCG concentration. With increasing concentrations of hCG, more LH receptors became confined in small membrane compartments with an average diameter of less than 100 nm. These receptors also exhibited slower rates of lateral diffusion. We reported the movement of non-functional hormone-receptors, labeled with deglycosylated hCG, into small membrane compartments in response to hCG treatment that saturated other available LH receptors on the membrane. This finding suggests that interactions between functional and non-functional LH receptors may occur in membrane microdomains during signal transduction.
Open Access
Characterization of selected gene expression patterns as potential markers for oocyte quality in young versus old mares
(Colorado State University. Libraries, 2010) Rodrigues, Bernardo de Lima, author; Clay, Colin M., advisor; Carnevale, Elaine M., advisor; Tjalkens, Ronald B., committee member; Bouma, Gerrit J., committee member; Bruemmer, Jason E., committee member
As a female ages a series of alterations in normal physiology take place, during this process fecundity decreases. The reproductive system starts to shut down as a consequence of hormonal, histological and anatomical changes, and in the middle of this process, playing a critical role, is the oocyte. As in women, fertility decreases with aging in mares. Recently the mare has been suggested as a promising model to study age-related infertility in women due to similarities in the reproductive cycle and similar age-associated reproductive changes. During the last decades the use of assisted reproductive techniques (ART) in human and veterinary medicine to treat infertility has increased. Unfortunately, ART can only partially compensate for declining fertility- particularly the age related decline in fertility. Therefore, we need to understand the mechanisms involved in age-associated infertility and improve both the diagnostic tools and the techniques currently used in ART. In that regard the identification of reliable oocyte quality markers is of great interest, specifically of extrinsic markers in follicular cells and follicular fluid (FF). Follistatin (FS1) and anti-müllerian hormone (AMH) have been suggested as potential oocyte quality markers. In addition, the rate of apoptosis in follicular cells has also been suggested to be a good indicator of oocyte quality In this study, our goal was to use the young and old mare model to obtain competent and incompetent oocytes, respectively, to try and elucidate the involvement of apoptosis of follicular cells and/or of the oocyte in the determination of oocyte quality. Oocytes, follicular fluid, granulosa and cumulus cells were collected through transvaginal follicular aspirations from young ( 4-10 years) and old (>20 years) mares. Preovulatory follicles were aspirated 30-36 h post induction of follicular maturation, which was performed by administration (i.v) of a combination of deslorelin and hCG when the biggest follicle reached 35 mm. We used real time PCR to examine expression of pro-apoptotic ( CASP2, CASP 3) and pro-survival (XIAP) genes, as well as of FST and AMH expression in these cell types. In addition we measured androgens and estrogens in FF and calculated the androgens to estrogens ratio to assess follicular atresia. We also sought to determine FF concentrations of FST and AMH, and relate it to oocyte quality. There was no difference in CASP3 expression levels in granulosa and cumulus cells between the two age groups. In addition, there was no difference in CASP2 and CASP3 mRNA expression in oocytes from young and old mares. XIAP mRNA levels were expressed 3.3 fold higher in oocytes from young when compared to old mares, and there was a tendency for XIAP to be more highly expressed in granulosa cells of young mares. In contrast, the levels of XIAP mRNA in cumulus cells were 1.46 fold higher in old when compared to young mares. There was no difference in the expression levels of AMH in granulosa cells between young and old mares, but in cumulus cells there was a tendency for AMH to be higher expressed in cells from old vs. young mares. Unfortunately we were not able to analyze AMH FF concentrations. FST mRNA levels in oocytes were similar between the age groups, but FST concentrations in FF of preovulatory follicles from young mares (197 ± 16.7 ng/mL) were higher (p=0.02) than in FF from old (153.3 ± 22.7 ng/mL) mares. In both age groups FST FF concentrations in preovulatory follicles significantly decreased when compared to mid-estrus and post-deviation follicles. In conclusion, we believe that our data suggest that FST follicular fluid levels can be a non-invasive marker to assess oocyte quality in the horse, and that FST levels decrease in preovulatory follicles of the horse. In addition, expression levels of caspase-3 in follicular cells, and caspases 3 and 2 in the oocyte, does not seem to be involved in the mechanism of fertility loss in the old mare. Finally, XIAP mRNA levels may be important for oocyte quality in the horse.
Open Access
Preimplantation genetic diagnosis of equine embryos
(Colorado State University. Libraries, 2010) Cullingford, Erika L., author; Seidel, George Jr., advisor; McCue, Patrick, advisor; Ahola, Jason K., committee member; Bouma, Gerrit, committee member
In horses, determination of certain genetic traits/alleles in embryos before embryo transfer would be advantageous due to the costs of resulting pregnancies. An attractive option is preimplantation genetic diagnosis (PGD), but to date few biopsied equine embryos have resulted in pregnancies. In the current experiment, 37 embryos ranging from 160 - 575 μm in diameter were biopsied. To obtain embryos, donor mares were monitored using transrectal ultrasonography. When a follicle > 35 mm in diameter was observed, 2,500 IU hCG or 1.5 mg deslorelin acetate was administered, and mares were inseminated daily until ovulation was detected. Embryos were recovered nonsurgically on days 6.5 – 7 (day 0 = ovulation). Trophoblast biopsies were collected in a 30 μl droplet of Syngro Holding Medium (Bioniche, Belleville, ON) using a piezo drill and beveled injection pipette. After removal of the embryo, the droplet containing the biopsied cells was moved into an Eppendorf tube and centrifuged. Supernatant was removed leaving ~5 μl sample, which was snap frozen for later genetic testing. Fifteen biopsied embryos were immediately transferred nonsurgically into uteri of synchronized recipients. Day 16 pregnancy rate for embryos ≤ 300 μm was 75.0% (6 of 8; 175 – 240 μm), which was not significantly different from control embryos of the same size (77.3%; 17 of 22). For embryos > 300 μm, day 16 pregnancy rate was 28.6% (2 of 7; 320 and 400 μm), which was not significantly different from control embryos of the same size (62.5%; 10 of 16). Additionally, 22 embryos (150 - 440 μm) were vitrified by standard procedures after biopsying and later warmed and transferred directly. No embryos > 300 μm (n = 3) became pregnancies after vitrification. Day 16 pregnancy rate for ≤ 300 μm was 47.4% (9 of 19; 150 – 225 μm), which was significantly different (p < 0.05) from direct transfer and control embryos of the same size (75.0% and 77.3%, respectively). Three of these pregnancies (150 - 200 μm) resulted in the formation of empty trophoblastic vesicles by 25 d. All pregnancies were terminated on or after 25 d to collect embryos for further genetic testing. For preimplantation genetic testing, a duplex nested polymerase chain reaction (PCR) was developed for amplification of the DNA from the biopsied cells using primers for sex chromosome-linked zinc finger protein genes (ZFx/ZFy; 445 bp), and 2 pairs of primers for equine-specific sex-determining region on the Y-chromosome (SRY; 217 bp, 121 bp). Experiments on XX and XY genomic DNA from white blood cells revealed accurate genetic testing on as little as ~9 pg DNA, which equals ~1 cell. Sex determination on biopsied material occurred for 30% of samples, one of which was confirmed from a placental sample. Low PGD results indicate either lack of sensitivity of the test, or more likely the loss of cells during the steps of transfering the biopsied cells to Eppendorf tubes. We concluded that biopsy collection, preimplantation genetic diagnosis, and direct transfer can be performed on equine embryos without compromising pregnancy rates when performed on embryos ≤ 300 μm. Vitrification lowered pregnancy rates of biopsied embryos (p < 0.05). Continued effort in improving genetic tests and in vitrifying equine embryos, especially those > 300 μm, is warranted.