[Truncated abstract] The activity of the reproductive endocrine axis is the result of interactions among many organs and tissues, particularly the hypothalamus, pituitary gland and gonad. However, it depends on more than the communication between anatomical structures because it is also affected by genotype, internal factors (e.g., metabolic inputs) and external factors (e.g., photoperiod, socio-sexual cues, stress, nutrition). This multifactorial complexity makes it difficult to use animal experimentation to investigate the pathways and mechanisms involved. Therefore, in this study, I have turned to mathematical modelling. The general hypothesis was that, by modelling the hormonal feedback loop that links the hypothalamus, pituitary gland and gonad, I would be able to discover the critical control points in this homeostatic system. This would allow me to inform and direct research into the processes that control reproduction, including inputs from environmental factors. My studies began with the development of a model of the negative feedback loop through which testosterone controls the secretion of pulses of gonadotrophin-releasing hormone (GnRH) by the hypothalamus. The model incorporated two critical factors: testosterone concentration and a time delay in the inhibition of the activity of the GnRH 'pulse generator' by testosterone. The general assumptions were: i) there are two positive feedforward processes (GnRH pulses stimulate LH pulses, and, in turn, LH pulses stimulate testosterone secretion); ii) testosterone exerts negative feedback that reduces the frequency of GnRH pulses. The model incorporated a group of equations that represent the GnRH pulse generator, through which the inhibitory effect of testosterone acted to reduce GnRH pulse frequency. Simulations were run with various values for the time delay in feedback and, as model development progressed, the simulations were extended to include combinations of time delays and levels of sensitivity of the GnRH pulse generator to inhibition by testosterone. The output of the simulations showed clearly that a time delay in negative feedback, as well as the concentration of testosterone, can greatly affect the frequency of GnRH pulses and the shape of the GnRH secretory profile. Importantly, the effect of the time delay depends on the sensitivity of the pulse generator to testosterone. In addition, the simulations suggested two additional components that might be involved in the control of the GnRH pulse generator: i) a delay in the rate of adaptation to a change in steroid feedback; and ii) a minimum pulse interval (maximum frequency). These studies iii therefore suggest that the regulation of the activity of the GnRH pulse generator, and thus the frequency and profile of GnRH and LH pulses, requires interactions among these four components. These interactions should be tested in animal experimentation. In the next stage, I extended the model so I could test whether the feedback delay might involve the process of aromatization in which testosterone is converted to oestradiol at brain level. ... This information can be used to direct future experimental studies that will help us to understand the factors that underlie the dynamic behaviour of the hypothalamic and pituitary systems that control reproduction.

Submitted by Renata Lopes (renatasil82@gmail.com) on 2017-03-10T11:22:40Z No. of bitstreams: 1 cintiadeoliveirarezende.pdf: 819221 bytes, checksum: 339dce17ba20eb705cadcbe3177dd19d (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2017-03-10T14:33:29Z (GMT) No. of bitstreams: 1 cintiadeoliveirarezende.pdf: 819221 bytes, checksum: 339dce17ba20eb705cadcbe3177dd19d (MD5) / Made available in DSpace on 2017-03-10T14:33:29Z (GMT). No. of bitstreams: 1 cintiadeoliveirarezende.pdf: 819221 bytes, checksum: 339dce17ba20eb705cadcbe3177dd19d (MD5) Previous issue date: 2016-12-19 / O uso de telefones móveis tem aumentado e junto a isso a preocupação dos seus possíveis efeitos à saúde tem aumentado também. Nosso laboratório tem desenvolvido estudos mostrando que a radiação emitida por aparelhos celulares pode afetar parâmetros reprodutivos e apresenta efeito programador na prole alterando o conteúdo de catecolaminas adrenal e glicose sérica, o que poderia influenciar no metabolismo energético desses animais. Pouco se sabe ainda sobre o efeito programador desse tipo de radiação no metabolismo energético. Mas tem sido mostrado que a radiação é capaz de afetar as células da tireoide aumentado a apoptose e levando ao hipotiroidismo, o que de certa forma também poderia influenciar no metabolismo. Sendo assim, este estudo teve como objetivo avaliar o efeito de ondas eletromagnéticas irradiadas por aparelhos celulares sobre o metabolismo da prole adulta submetida durante o período intra-uterino. Para isso ratas prenhes foram expostas à radiofrequência emitida por telefones celulares (1,8 GHz) durante o período gestacional. Ao atingir a idade adulta a prole foi analisada para os possíveis efeitos programadores no metabolismo energético desses animais através da dosagem de hormônios tireoidianos: Hormônio Estimulante da Tireóide (TSH), Triiodotironina (T3) e Tetraiodotironina (T4) e hormônios relacionados ao metabolismo como: insulina, adiponectina e leptina. Não foram encontradas diferenças significativas nos hormônios analisados nem na prole adulta de fêmeas e nem de machos. Sugerindo assim que no modelo estudado a radiação não altera os hormônios analisados relacionados ao metabolismo energético. / The use of mobile phones has increased and along with it the concern of the possible health effects has increased as well. Our laboratory has developed studies showing that radiation from mobile phones can affect reproductive parameters and features programmer effect on offspring by changing the adrenal catecholamine content and serum glucose, which could influence the energy metabolism of these animals. Little is yet known about the programmer effect of this radiation in energy metabolism. But it has been shown that radiation can affect the thyroid cells increased apoptosis and leading to hypothyroidism, which in a way could also influence the metabolism. Thus, this study aimed to evaluate the effect of electromagnetic waves radiated by cell phones on the metabolism of the adult offspring submitted during the intrauterine period. For that pregnant rats were exposed to radio frequency emitted by mobile phones (1.8 GHz) during pregnancy. Upon reaching adulthood offspring was analyzed for potential programmers effects on energy metabolism of these animals by the dosage of thyroid hormones: Hormone Stimulant Thyroid (TSH), triiodothyronine (T3) and Tetraiodothyronine (T4) and hormones related to metabolism as: insulin, adiponectin and leptin. No significatives differences were observed on hormones evaluated either on male and female offspring. Suggesting that the model studied the radiation does not alter the hormones analyzed related to energy metabolism.

Up to 60% of individuals with type 2 diabetes (T2DM) do not participate in regular physical activity (PA) despite the known benefits. To encourage these individuals to increase PA behavior, this study tested the feasibility and implementation of a nurse-directed counseling intervention using continuous glucose monitoring system (CGMS). The study used a framework derived from self-efficacy theory to 1) compare changes in self-efficacy, BP and activity counts between participants receiving CGMS counseling and standard T2DM counseling, 2) examine relationships between PA self-efficacy and BP and activity counts, 3) evaluate recruitment, retention, and screening strategies, and 4) assess instrument reliability and utility. Adults (N=52) with T2DM (non-insulin requiring, inactive) were randomized to intervention (n=27) or control groups (n=25). Both groups received 90 minutes of diabetes education with a follow-up phone call at 4 weeks. The intervention group also received feedback on their own CGMS graphs and a role model's graph depicting PA related reductions in glucose levels. PA benefits/barriers were discussed and goals were set. Outcomes were recorded at 1 and 8 weeks. Participants were older (57±14 years), predominantly (90%) white, about half (52%) female, and had diabetes for 8±7 years. Relative to the control group, participants receiving the intervention had higher self-efficacy scores at 8 weeks, indicating more confidence in sticking to a PA program. Their light/sedentary activity minutes decreased significantly and moderate activity minutes increased significantly; systolic BP, A1c and BMI decreased significantly. Only self-efficacy for "Sticking to it" was positively associated with moderate activity. The most successful recruitment media was multiple newspaper press releases. Most referrals came from endocrinology physicians. Of 231 study volunteers, 106 did not meet the criterion of A1c≥7.5%. These data suggest that CGMS feedback is feasible for counseling individuals with T2DM to improve PA and may improve risk factors for diabetes-related complications. Newspaper press releases are effective for recruiting participants with T2DM. Less restrictive inclusion criteria in a larger study may allow more participation by sedentary individuals with T2DM but may reduce effect size. CGMS was well tolerated and its data aided diabetes-related teaching.

One of the main components underlying drug addiction is the emergence of tolerance. Although its development is a complex issue, and is believed to have both psychological and physiological connotations, it is clear that some physiological change must occur that would enable an organism to withstand drug concentrations lethal to a naïve system. The purpose of this thesis was to identify and study a physiological mechanism, whose characteristics were altered due to chronic exposure to ethanol. Vasopressin (AVP), whose primary function is to control water balance, release from the neurohypophysis is suppressed by an acute ethanol challenge. Therefore, I hypothesized; 1) that chronic ethanol exposure would reduce the normal suppression of AVP release during an acute ethanol challenge and 2) that the ion channels that are acutely sensitive to ethanol, involved in the control of AVP release, would exhibit a change in their ethanol sensitivity and characteristics. To study the hypothesis, I utilized the neurohypophysis from rats chronically exposed to ethanol and yoked controls to determine whether chronic exposure would modify the acute ethanol sensitivity of the neurohypophysial vasopressin release mechanism. I examined whether the long-term ethanol exposure affected the suppression of vasopressin release from either or both the intact neurohypophysis and the isolated neurohypophysial terminals. In addition, I investigated how chronic exposure affected two types of potassium channels, the ethanol sensitive large conductance Ca+2-activated (BK) channel and the fast inactivating (IA) channel known to be insensitive to physiologically relevant concentrations of ethanol. I was able to establish that chronic ethanol exposure reduced the suppression of vasopressin release by an acute ethanol challenge from both the intact neurohypophysis and the isolated neurohypophysial terminals. In addition, I discovered that oxytocin release was affected similarly. I concluded from this data that chronic exposure to ethanol affected a general mechanism, which controlled hormone release from the neurohypophysis, and that this mechanism could be isolated to the neurohypophysial terminals. I also used electrophysiological techniques to study ion channel characteristics of both the BK and IA potassium channels. I found that in naïve rats, BK channels were potentiated and IA channels insensitive to physiological relevant concentrations of ethanol. But in chronic ethanol-exposed rats the BK channels exhibited a reduced sensitivity to ethanol while IA channels were inhibited. In addition, the current density of the BK channel was significantly reduced. These results show that at least one characteristic of each potassium channel has been modified. This suggests that chronic exposure can not only modify the ethanol sensitivity of ion channels known to be ethanol-sensitive, but also those believed to be relatively insensitive. Therefore, since modifications in these channels have previously been shown to alter the duration and frequency of action potentials, I conclude that these ethanol-induced modifications play a role in the modified hormone release patterns observed in the chronically exposed rats.

Strategies aimed at expanding functional beta cell mass remain a prime goal of diabetes research. Both the insulin signaling pathway, as well as the G1/S transition of the cell cycle are critically important for the maintenance of beta cell mass. We previously demonstrated in a mouse model of diabetes, insulin receptor substrate 2 (Irs2) deficient mice, that beta cell failure was attributed to reduced islet expression of Cyclin D2, and that overexpressing Cyclin D2 rescued proliferation in Irs2 deficient beta cells in vitro. Since Cyclin D2 partners with CDK4 to drive cell cycle progression, we hypothesized that an activated form of CDK4, Cdk4-R24C (resistant to inhibition by the INK4A cell cycle inhibitor p16), would rescue the in vivo proliferation defect in Irs2 deficient mice. Interestingly, Irs2 knockout mice with the active Cdk4 R24C allele, displayed rescued blood glucose, and normalized glucose tolerance, without affecting peripheral insulin resistance. I found that both and beta cell mass and proliferation were rescued in vivo, contributing to the rescue of glucose tolerance. Interestingly, the dedifferentiated phenotype of Irs2 knockout islets (ALDH1A3+ cells, nuclear FOXO1 and suppressed PDX1) was completely restored with the active Cdk4 allele, suggesting that CDK4 may play a role in promoting beta cell differentiation. Utilizing various in vitro models where FOXO1 represses Pdx1, overexpression of CDK4/CyclinD2 was consistently able to rescue the FOXO1-mediated repression of Pdx1, without significant impacts on FOXO1 subcellular localization. These results suggested that FOXO1 regulation in the beta cell is more complex than previously described, and also suggested that CDK4/Cyclin D2 may be instead modulating the acetylation status of FOXO1, impacting its transcriptional activity. To this end, inhibiting histone acetylate transferases (HATs) partially rescued FOXO1-mediated Pdx1 suppression, while inhibiting histone deacetylase enzymes (HDACs) showed the reverse effect of trending towards blocking the Cyclin D2/CDK4-mediated rescue of Pdx1. Finally, I found that CDK4/Cyclin D2 increases phosphorylation of sirtuin 1 (SIRT1), an HDAC that modulates the acetylation status, and transcriptional activity of FOXO1, and that CDK4/Cyclin D2 promotes FOXO1 degradation. In sum, we conclude that activated CDK4 rescues beta cell failure due to IRS2 deficiency through multiple mechanisms related to not only cell cycle regulation but also to beta cell differentiation status, primarily through modulation of FOXO1 transcriptional activity.

The ever-increasing prevalence of diabetes mellitus and its associated healthcare costs in the United States has led to our healthcare system's need for cost-effective health resources and chronic disease management. The interventions of Community Health Workers (CHWs) can cost-effectively improve population health and prevent the unnecessary utilization of some medical services especially in rural, low-income, minority populations, where there is often limited access to healthcare. The purpose of this study is to investigate the relationship between the number of total CHWs in rural counties and the mean diabetes-related preventable hospitalization rates in Latino patients diagnosed with diabetes in those rural counties. The main goal of this research study is to contribute to the existing literature about the importance of CHWs especially in rural counties and the effect their presence has on diabetes-related preventable hospitalizations. Quantitative rural county data sets were analyzed to determine the correlation between the number of CHWs per rural county and the rate of diabetes-related preventable hospitalizations per rural county. Due to the COVID-19 pandemic outbreak, this research project was modified to be completed in a timely manner. A statistically insignificant moderately negative linear relationship was found between the two variables. Therefore, there was not enough statistical evidence in the sample to say that this correlation exists in the rural America population. Future research is needed to investigate this relationship more thoroughly.

Noninvasive assessment of diabetic cardiovascular autonomic neuropathy (AN): Cardiac and vascular dysfunctions resulting from AN are complications of diabetes, often undiagnosed. Our objectives were to: 1) determine sympathetic and parasympathetic components of compromised blood pressure regulation in patients with polyneuropathy, and 2) rank noninvasive indexes for their sensitivity in diagnosing AN. Continuous 12-lead electrocardiography (ECG), blood pressure (BP), respiration, regional blood flow and bio-impedance were recorded from 12 able-bodied subjects (AB), 7 diabetics without (D0), 7 with possible (D1) and 8 with definite polyneuropathy (D2), during 10 minutes supine control, 30 minutes 70-degree head-up tilt and 5 minutes supine recovery. During the first 3 minutes of tilt, systolic BP decreased in D2 while increased in AB. Parasympathetic control of heart rate, baroreflex sensitivity, and baroreflex effectiveness and sympathetic control of heart rate and vasomotion were reduced in D2, compared with AB. Baroreflex effectiveness index was identified as the most sensitive index to discriminate diabetic AN. Four-dimensional multiscale modeling of ECG indexes of diabetic autonomic neuropathy: QT interval prolongation which predicts long-term mortality in diabetics with AN, is well known. The mechanism of QT interval prolongation is still unknown, but correlation of regional sympathetic denervation of the heart (revealed by cardiac imaging) with QT interval in 12-lead ECG has been proposed. The goal of this study is to 1) reproduce QT interval prolongation seen in diabetics, and 2) develop a computer model to link QT interval prolongation to regional cardiac sympathetic denervation at the cellular level. From the 12-lead ECG acquired in the study above, heart rate-corrected QT interval (QTc) was computed and a reduced ionic whole heart mathematical model was constructed. Twelve-lead ECG was produced as a forward solution from an equivalent cardiac source. Different patterns of regional denervation in cardiac images of diabetic patients guided the simulation of pathological changes. Minimum QTc interval of lateral leads tended to be longer in D2 than in AB. Prolonging action potential duration in the basal septal region in the model produced ECG and QT interval similar to that of D2 subjects, suggesting sympathetic denervation in this region in patients with definite neuropathy.

Pituitary pars intermedia dysfunction (PPID) is one of the most common endocrine diseases affecting senior horses. PPID causes abnormally high concentrations of adrenocorticotropic hormone (ACTH) in the plasma and a very distinct, long, shaggy haircoat (hypertrichosis). At present, the recommended treatment for PPID is daily oral administration of pergolide mesylate. Due to the increased ACTH levels associated with PPID, it is commonly thought that these horses are immunosuppressed and at increased risk of opportunistic infections, although current research in this area is sparse. Additionally, it is not well-understood how treatment with Prascend® (pergolide tablets) affects endocrine measures other than ACTH and if it also impacts the immune response. To better understand how PPID influences endocrine and immune function in the horse, Non-PPID horses (n=10), untreated PPID horses (n=9), and PRASCEND-treated PPID horses (n=9) were followed over 15 months. Endocrine measures assessed included basal ACTH, ACTH responses to thyrotropin-releasing hormone (TRH) stimulation tests, basal insulin, insulin responses to oral sugar tests (OST), total cortisol, and free cortisol. Systemic immune function measures included basal and stimulated whole blood and peripheral blood mononuclear cell (PBMCs) cytokine and receptor expression, plasma myeloperoxidase levels, and complete blood counts. Localized immune function measures within the lung included cytokine and receptor expression after stimulation of cells obtained via bronchoalveolar lavage (BAL), myeloperoxidase levels in BAL fluid, and BAL fluid cytology. We hypothesized that PPID would affect immune function, but that any alterations would be corrected by treatment with PRASCEND. Results for the endocrine analyses showed that basal ACTH was reduced in the PRASCEND-treated horses to the levels of the Non-PPID horses, but ACTH in response to TRH stimulation was only reduced in the PRASCEND-treated horses at non-fall timepoints. PPID did not affect basal insulin, insulin responses to OSTs, total cortisol, or free cortisol, and PRASCEND treatment did not appear to have an impact on these measures either. These results suggest that PPID and hyperinsulinemia/insulin dysregulation are distinct endocrine conditions, and that the excess ACTH in horses with PPID is inactive, as it is unable to stimulate a normal cortisol response. In the immune function analyses, PPID horses had decreased expression of interferon gamma (IFNγ) from PBMCs stimulated with Rhodococcus equi and Escherichia coli and increased transforming growth factor beta (TGFβ) expression from the E. coli-stimulated PBMCs. TGFβ was also increased in PPID horses in the unstimulated whole blood samples. These results suggest that PPID horses are unable to mount an appropriate Th1 response, and that the regulatory subset of T-lymphocytes may be contributing to this decreased Th1 response. Results for the localized immune function analyses may indicate altered Th2 responses within the lung of PPID horses, although these results were severely limited by the sample size available for analyses. PRASCEND did not appear to affect immune function as measured in this study. In summary, PRASCEND successfully reduces basal ACTH in PPID horses and remains the best choice for veterinarians in monitoring dosage and response to PRASCEND treatment. Insulin, total cortisol, and free cortisol were not affected by PPID status or PRASCEND treatment in this study. Immune function was altered in horses with PPID, and it is likely that these horses are indeed at increased risk of opportunistic infection. PRASCEND treatment did not correct the differences in immune function in this study. Additional research is needed to further understand which mechanisms are driving the alterations in immune function for horses with PPID.

Due to the current rise of exposure to natural and synthetic compounds in our daily life, the debate concerning the safety of many substances is becoming increasingly relevant. The estrogenic activity of various compounds, described as xenoestrogens, is the major part of this debate. Humans beings are exposed to these substances from different environmental contaminations ranging from conscious intake of estrogenic substances, as in contraception or in hormone replace therapy (HRT), to unconscious exposure, from food, the use of synthetic material in daily life and air and water pollution. At this point the need for methods to investigate the activity and the safety of these substances is becoming increasingly important. Classical methods for the analysis of the estrogenic activity of substances, like batteries of in vivo test systems on the rat uterotrophic assay are not able to describe the different pathways of action of recently discovered estrogenic substances. This evidence was already shown by the Organization for Economic Cooperation and Development (OECD), introducing new test guidelines for the investigation of effects of endocrine disruptors (according to enhanced Test Guideline 407). As reviewed by Nilsson (Nilsson et al., 2001), after the interaction of the estrogens with the Estrogen Receptor (ER) in the cells, the mechanism of activation possible is not only via direct binding of the ER to the Estrogen Responsive Elements (EREs) present in the promoter region of the target gene, very well described for many target genes, but that also other mechanisms are used: the interaction of the ER with the AP 1, Sp 1 and NFkB modes, that are discovered but not yet comprehensively described. The aim of my work is to produce a microarray DNA chip for the investigation of the estrogenic activity of different compounds present in the environment. The chip will consist of a selection of 100 genes that are estrogen responsive and it will cover the spectrum of activities of estrogenic compounds in various organs of the body. In the gene selection, genes were chosen that are estrogen responsive in the classical target tissues of estrogens, linked to reproduction, like uterus and mammary gland, and also in tissues not related to reproduction like liver, bones and capillars. In addition, other genes are included to monitor different pathways that are related to disease states; control of cell proliferation, apoptosis or cancer related genes. Currently these kinds of investigations are already in process, but by other methods which are more time consuming and with a lower throughput e.g. the gene expression profiling using the real time RT-PCR. The use of microarray’s satisfies the need for a less time consuming, high throughput method, to obtain a fast characterization of the gene expression finger print of the candidate substances and their mechanism of action in the organism. In my work I investigated the estrogenic potency of different Xenoestrogens that commonly occur in our daily life, in rat cells and tissue using well known estrogen sensitive genes like C3, Clu, IGFBP1 and CaBP9k. I focused on their effect on cell proliferation, studying PCNA expression. For the first time sensitivity of the gene CA2 was proofed in liver and uterus. A new identified mRNA sequence, r52, was characterized for its sensitivity to estrogenic exposure. This sequence was investigated at the molecular level expanding the known nucleic sequence. I produce a microarray chip with 16 genes to investigate the estrogenic potency of different compounds. As proof of principle of the microarray method completely produced in house I compared the result of gene expression obtained by the chip to that obtained by real time RT PCR finding a similarity of results. This new established method is less sensitive than the real-time RT PCR but allows a high throughput of gene expression analysis producing at the end a more complete picture of the expression signature of a compound.

The retina is a thin layer of tissue lining the back of the eye and is primarily responsible for sight in vertebrates. The neural retina has a distinct layered structure with three dense nuclear layers, separated by plexiform layers comprising of axons and dendrites, and a layer of photoreceptor segments. The retinal and choroidal vasculatures nourish the retina from either side, with an avascular layer comprised largely of photoreceptor cells. Diseases that directly affect the neural retina like retinal degeneration as well as those of vascular origin like diabetic retinopathy can lead to partial or total blindness. Early detection of these diseases can potentially pave the way for a timely intervention and improve patient prognosis. Current techniques of retinal imaging rely mainly on optical techniques, which have limited depth resolution and depend mainly on the clarity of visual pathway. Magnetic resonance imaging is a versatile tool that has long been used for anatomical and functional imaging in humans and animals, and can potentially be used for retinal imaging without the limitations of optical methods. The work reported in this thesis involves the development of high resolution magnetic resonance imaging techniques for anatomical and functional imaging of the retina in rats. The rats were anesthetized using isoflurane, mechanically ventilated and paralyzed using pancuronium bromide to reduce eye motion during retinal MRI. The retina was imaged using a small, single-turn surface coil placed directly over the eye. The several physiological parameters, like rectal temperature, fraction of inspired oxygen, end-tidal CO2, were continuously monitored in all rats. MRI parameters like T1, T2, and the apparent diffusion coefficient of water molecules were determined from the rat retina at high spatial resolution and found to be similar to those obtained from the brain at the same field strength. High-resolution MRI of the retina detected the three layers in wild-type rats, which were identified as the retinal vasculature, the avascular layer and the choroidal vasculature. Anatomical MRI performed 24 hours post intravitreal injection of MnCl2, an MRI contrast agent, revealed seven distinct layers within the retina. These layers were identified as the various nuclear and plexiform layers, the photoreceptor segment layer and the choroidal vasculature using Mn54Cl2emulsion autoradiography. Blood-oxygenlevel dependent (BOLD) functional MRI (fMRI) revealed layer-specific vascular responses to hyperoxic and hypercapnic challenges. Relative blood volume of the retina calculated by using microcrystalline iron oxide nano-colloid, an intravascular contrast agent, revealed a superfluous choroidal vasculature. Fractional changes to blood volume during systemic challenges revealed a higher degree of autoregulation in the retinal vasculature compared to the choroidal vasculature, corroborating the BOLD fMRI data. Finally, the retinal MRI techniques developed were applied to detect structural and vascular changes in a rat model of retinal dystrophy. We conclude that retinal MRI is a powerful investigative tool to resolve layerspecific structure and function in the retina and to probe for changes in retinal diseases. We expect the anatomical and functional retinal MRI techniques developed herein to contribute towards the early detection of diseases and longitudinal evaluation of treatment options without interference from overlying tissue or opacity of the visual pathway.