Matching Items (54)

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Role of S6K1 on structural and molecular changes in the brain of a mouse model of AD

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The aims of this project are: (i) to identify structural and molecular changes in the brains of 3xTg-AD mice and (ii) to determine whether decreasing S6K1 protects the brain from

The aims of this project are: (i) to identify structural and molecular changes in the brains of 3xTg-AD mice and (ii) to determine whether decreasing S6K1 protects the brain from these changes. To achieve our goals, we decided to remove one copy of the S6K1 gene in 3xTg-AD mice by breeding them with S6K1 knockout mice (S6K1+/-). In previous studies, we have seen that reducing S6K1 levels in 3xTg-AD mice improved spatial memory and synaptic plasticity which was associated with reduced A and tau pathology. Here, we used a multiparametric MRI to assess volumetric and blood flow changes in the brain of 20-month-old 3xTg-AD mice. We found that 3xTg-AD/S6K1+/- mice had higher blood flow and cortical volume compared to 3xTg-AD mice. However, we saw no significant differences between 3xTg-AD mice and NonTg mice. We further found A levels and plaque numbers were significantly lower in 3xTg-AD/S6K1+/- mice compared to 3xTg-AD mice. This reduction in plaques could account for the improvement in blood flow in 3xTg-AD/S6K1+/- mice. To try to understand the reason behind the increase in cortical volume in the 3xTg-AD/S6K1+/- when compared to the 3xTg-AD, we measured markers of synaptic density, PSD95, and synaptophysin. We found that PSD95 levels were not different between the four groups. However, synaptophysin levels were significantly lower in 3xTg-AD mice compared to NonTg levels and returned to baseline levels in 3xTg-AD mice lacking one copy of the S6K1 gene. This difference in synaptophysin could explain, at least in part, the difference in volume between the four groups analyzed. Overall, this represents the first evidence showing that reducing mTOR signaling improves blood flow and cortical volume in a mouse model of AD.

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  • 2018-05

Acute tau knockdown in the hippocampus of adult mice causes learning and memory deficits

Description

To date, it has been difficult to elucidate the role of tau in learning and memory during adulthood due to developmental compensation of other microtubule associated proteins in Tau knockout

To date, it has been difficult to elucidate the role of tau in learning and memory during adulthood due to developmental compensation of other microtubule associated proteins in Tau knockout (KO) mice. Here, we generated an adeno-associated virus (AAV) expressing a doxycycline (doxy)-inducible short-hairpin (sh) RNA targeted to tau, and stereotaxically and bilaterally injected 7-month-old C57BL/6 mice with either the AAV-shRNAtau or an AAV expressing a scramble shRNA sequence. Seven days after the injections, all animals were administered doxy for thirty-five days to induce expression of shRNAs, after which they were tested in the open field, rotarod and Morris water maze (MWM) to assess anxiety like behavior, motor coordination and spatial reference memory, respectively. Our results show that reducing tau in the adult hippocampus produces significant impairments in motor coordination, endurance and spatial memory. Tissue analyses shows that tau knockdown reduces hippocampal dendritic spine density and the levels of BDNF and synaptophysin, two proteins involved in memory formation and plasticity. Our approach circumvents the developmental compensation issues observed in Tau KO models and shows that reducing tau levels during adulthood impairs cognition.

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  • 2018-05

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Characterization of 18kDa Mitochondrial Translocator Protein in Relation to Neuropathological Elements of Neurodegenerative Diseases

Description

Neuroinflammation is mediated by activated microglia, the chief immune response of the central nervous system. Mitochondrial 18kDa translocator protein (TSPO) is upregulated in activated microglia and has been used in

Neuroinflammation is mediated by activated microglia, the chief immune response of the central nervous system. Mitochondrial 18kDa translocator protein (TSPO) is upregulated in activated microglia and has been used in PET scans to analyze peripheral and central inflammation with TSPO radioligand [18F]DPA-714. To test the hypothesis that TSPO is involved in microglial mediation of inflammatory responses to Aβ and other Alzheimer’s pathological elements, TSPO expression was evaluated in relation to microglia specific markers (IBA1 and LN3 antibodies) and markers for AD pathology, Aβ (6E10 antibody) and hyperphosphorylated tau (AT8 antibody). To test that TSPO is involved in inflammatory pathways, HEK cells transfected with TSPO plasmids were assessed for oxidative stress in response to Alzheimer’s disease pathogenic agents, β Amyloid (Aβ), and Parkinson’s disease α-synuclein (α-syn).

Fluorescence microscopy of TSPO transfected HEK cell cultures labeled with Carboxy-H2DCFDA and treated with Beta Amyloid (Aβ) and α-synuclein (α-syn) resulted in DAPI fluorescing Human Embryonic Kidney (HEK) nuclei in blue and Green Fluorescent Protein (GFP) fluorescing reactive oxygen species (ROS) or oxidative stress in cell cytoplasm in green. Preliminary study suggests TSPO transfected cells may be used to test oxidative stress with disease pathological elements (Aβ and α-synuclein). In IHC, TSPO immunoreactivity was observed in IBA1 and LN3 marked microglia with varying degrees of expression. Beaded structures were also observed with TSPO immunoreactivities, possibly representing microglia processes. TSPO immunoreactivity was observed in and surrounding amyloid plaques and p-tau immunoreactive neurites. This demonstrates that TSPO is predominantly expressed in microglia and are closely associated with Alzheimer’s disease pathological elements, suggesting involvement of TSPO-expressing microglia in neurodegenerative processes.

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  • 2018-05

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An Evaluation of the Cognitive Effects of a Short-Term and a Long-Term Ovarian Hormone Deprivation in a Transgenic Mouse Model of Alzheimer's Disease: Addressing the Critical Window

Description

With no known cure, Alzheimer's disease (AD) is the most common dementia, affecting more than 5.5 million Americans. Research has shown that women who undergo surgical menopause (i.e. removal of

With no known cure, Alzheimer's disease (AD) is the most common dementia, affecting more than 5.5 million Americans. Research has shown that women who undergo surgical menopause (i.e. removal of the ovaries) before the onset of natural menopause are at a greater risk for AD. It is hypothesized that this greater relative risk of developing AD is linked to ovarian hormone deprivation associated with surgical menopause. The purpose of these studies was to evaluate the behavioral changes that occur after a short-term (ST) and a long-term (LT) ovarian hormone deprivation in a mouse model of AD. Wildtype (Wt) or APP/PS1 (Tg) mutation mice underwent either a sham surgery or an ovariectomy (Ovx) surgery at three months of age. Study 1 consisted of a short-term cohort that was behaviorally tested one month following surgery on a battery of spatial memory tasks including, the Morris water maze, delayed matched-to-sample water maze, and visible platform task. Study 2 consisted of a long-term cohort that was behaviorally tested on the same cognitive battery three months following surgery. Results of Study 1 revealed that genotype interacted with surgical menopause status, such that after a short-term ovarian hormone deprivation, Ovx induced a genotype effect while Sham surgery did not. Results of Study 2 showed a similar pattern of effects, with a comparable interaction between genotypes and surgical menopause status. These findings indicate that the cognitive impact of ovarian hormone deprivation depends on AD-related genotype. Neuropathology evaluations in these mice will be done in the near future and will allow us to test relations between surgical menopause status, cognition, and AD-like neuropathology.

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Date Created
  • 2017-12

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Food Based Strategies Against Alzheimer's Disease

Description

The purpose of this project is to present and consolidate current research on various nutrients and diet patterns and assess their role on the development of Alzheimer's Disease. I will

The purpose of this project is to present and consolidate current research on various nutrients and diet patterns and assess their role on the development of Alzheimer's Disease. I will begin with an explanation of Alzheimer's Disease that includes general health related information and the statistical prevalence of the disease. Following the informational overview, I will be presenting the most current research and summarizing the findings for seven single nutrients and five dietary patterns. Following the assessment will be an expository segment discussing epigenetics nutrigenomics and how this process works with different nutrients and diet patterns to impact the likelihood of developing Alzheimer's Disease from a genetic perspective. Based on the research found in the single nutrients segment, the dietary pattern segment, and the epigenetics nutrigenomics segment, I will conclude with a holistic diet plan that is the most preventative against Alzheimer's Disease.

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Date Created
  • 2018-05

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NupL2 Protein and mRNA Expression is Downregulated in Alzheimer's Disease

Description

The nuclear pore complex is a structure that is found in the nuclear envelope. The nuclear pore complex is made of proteins known as nucleoporins, or Nups. There are many

The nuclear pore complex is a structure that is found in the nuclear envelope. The nuclear pore complex is made of proteins known as nucleoporins, or Nups. There are many classes of Nups, one of which is Nups with phenylalanine-guanine repeats (FG-Nups). The FG-Nups help control the transport of material through the nuclear pore complex. One type of FG-Nup is NupL2. Previous mRNA data have shown that there is lower expression of NupL2 in Alzheimer's Disease brains than there is in control brains. However, these data are specific to mRNA expression, and do not necessarily extend to NupL2 protein levels. This study focuses on NupL2 levels in non-diseased samples and Alzheimer's Disease samples. Immunohistochemistry (IHC) with 3,3'-diaminobenzidine was performed on temporal neo-cortical brain tissue. Western blots were also performed to quantify the protein levels in non-diseased samples and Alzheimer's Disease samples, and were completed using middle temporal gyrus lysates. The IHC results show that there is more NupL2 protein expression in non-diseased samples than there is in Alzheimer's Disease samples. Likewise, the western blot data show higher NupL2 protein levels in non-diseased samples than in Alzheimer's Disease samples. Both the IHC data and the western blot data indicate that there are higher NupL2 expression levels in non-diseased samples than in Alzheimer's Disease samples. Decreased NupL2 expression in Alzheimer's Disease may indicate that it is not functioning properly. This could lead to the leaking of material between the nucleoplasm and the cytoplasm, which may in turn contribute to Alzheimer's Disease pathogenesis.

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  • 2018-05

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Discrepancies in the Morris water maze versus the IntelliCage in the APP/PS1 mouse model of Alzheimer’s disease; a sex-based examination

Description

Dementia is a collective term used to describe symptoms of cognitive impairment in learning and memory. The most prevalent form of dementia is Alzheimer’s disease (AD). In order to understand

Dementia is a collective term used to describe symptoms of cognitive impairment in learning and memory. The most prevalent form of dementia is Alzheimer’s disease (AD). In order to understand the pathological mechanisms associated with AD, animal models have been created. These various mouse models replicate the pathology found in humans with AD. As a consequence of the fact that this disease impairs cognitive abilities in humans, testing apparatuses have been developed to measure impaired cognition in animal models. One of the most common behavioral apparatuses that has been in use for nearly 40 years is the Morris water maze (MWM). In the MWM, animals are tasked to find a hidden platform in a pool of water and thereby are subjected to stress that can unpredictably influence cognitive performance. In an attempt to circumvent such issues, the IntelliCage was designed to remove the external stress of the human experimenter and provide a social environment during task assessment which is fully automated and programable. Additionally, the motivation is water consumption, which is less stressful than escaping a pool. This study examined the difference in performance of male and female cohorts of APP/PS1 and non-transgenic (NonTg) mice in both the MWM and the IntelliCage. Initially, 12-month-old male and female APP/PS1 and NonTg mice were tested in the hippocampal-dependent MWM maze for five days. Next, animals were moved to the IntelliCage and underwent 39 days of testing to assess prefrontal cortical and hippocampal function. The results of this experiment showed significant sex differences in task performance, but inconsistency between the two testing paradigms. Notably, males performed significantly better in the MWM, which is consistent with prior research. Interestingly however, APP/PS1 females showed higher Amyloid-β plaque load and performed significantly better in the more complex tasks of the IntelliCage. This suggests that Aβ plaque load may not directly contribute to cognitive deficits, which is consistent with recent reports in humans with AD. Collectively, these results should inform scientists about the caveats of behavioral paradigms and will aid in determining translation to the human condition.

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  • 2020-05

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Assisted Cycle Therapy (ACT) Did Not Improve Depression in Older Adults with Down Syndrome

Description

The purpose of this study was to examine the influence of Assisted Cycling Therapy (ACT) on depression in older adults with Down Syndrome (DS). We predicted that older adults with

The purpose of this study was to examine the influence of Assisted Cycling Therapy (ACT) on depression in older adults with Down Syndrome (DS). We predicted that older adults with Down Syndrome would see an improvement in their depressive symptoms after ACT and Voluntary Cycling (VC). However, we predicted there would be a greater improvement in depressive symptoms after ACT in comparison to VC. Depression was measured using a modified version of the Children's Depression Inventory 2 (CDI 2) due to the low mental age of our participant population. Twenty-one older adults with DS were randomly assigned to one of three interventions, which took place over an eight-week period of time. Eleven older adults with DS completed the ACT intervention, which is stationary cycling on a recumbent bicycle with the assistance of a motor to maintain a cadence at least 35% greater than the rate of voluntary cycling. Nine participants completed the voluntary cycling intervention, where they cycled at a cadence of their choosing. One participant composed our no cycling control group. No intervention group reached results that achieved a conventional level of significance. However, there was a trend for depression to increase after 8 weeks throughout all three intervention groups. We did see a slightly slower regression of depression in the ACT group than the VC and control. Our results were discussed with respect to social and cognitive factors relevant to older adults with DS and the subjective nature of the CDI2. This study brings attention to the lack of accurate measures and standardized research methods created for populations with intellectual disabilities in regards to research.

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  • 2018-05

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Utilizing MRI Texture Analysis and APOE Genotype to Predict the Aging Brain as a Potential Method for Early Assessment of Alzheimer's Disease

Description

Background: Noninvasive MRI methods that can accurately detect subtle brain changes are highly desirable when studying disease-modifying interventions. Texture analysis is a novel imaging technique which utilizes the extraction of

Background: Noninvasive MRI methods that can accurately detect subtle brain changes are highly desirable when studying disease-modifying interventions. Texture analysis is a novel imaging technique which utilizes the extraction of a large number of image features with high specificity and predictive power. In this investigation, we use texture analysis to assess and classify age-related changes in the right and left hippocampal regions, the areas known to show some of the earliest change in Alzheimer's disease (AD). Apolipoprotein E (APOE)'s e4 allele confers an increased risk for AD, so studying differences in APOE e4 carriers may help to ascertain subtle brain changes before there has been an obvious change in behavior. We examined texture analysis measures that predict age-related changes, which reflect atrophy in a group of cognitively normal individuals. We hypothesized that the APOE e4 carriers would exhibit significant age-related differences in texture features compared to non-carriers, so that the predictive texture features hold promise for early assessment of AD. Methods: 120 normal adults between the ages of 32 and 90 were recruited for this neuroimaging study from a larger parent study at Mayo Clinic Arizona studying longitudinal cognitive functioning (Caselli et al., 2009). As part of the parent study, the participants were genotyped for APOE genetic polymorphisms and received comprehensive cognitive testing every two years, on average. Neuroimaging was done at Barrow Neurological Institute and a 3D T1-weighted magnetic resonance image was obtained during scanning that allowed for subsequent texture analysis processing. Voxel-based features of the appearance, structure, and arrangement of these regions of interest were extracted utilizing the Mayo Clinic Python Texture Analysis Pipeline (pyTAP). Algorithms applied in feature extraction included Grey-Level Co-Occurrence Matrix (GLCM), Gabor Filter Banks (GFB), Local Binary Patterns (LBP), Discrete Orthogonal Stockwell Transform (DOST), and Laplacian-of-Gaussian Histograms (LoGH). Principal component (PC) analysis was used to reduce the dimensionality of the algorithmically selected features to 13 PCs. A stepwise forward regression model was used to determine the effect of APOE status (APOE e4 carriers vs. noncarriers), and the texture feature principal components on age (as a continuous variable). After identification of 5 significant predictors of age in the model, the individual feature coefficients of those principal components were examined to determine which features contributed most significantly to the prediction of an aging brain. Results: 70 texture features were extracted for the two regions of interest in each participant's scan. The texture features were coded as 70 initial components andwere rotated to generate 13 principal components (PC) that contributed 75% of the variance in the dataset by scree plot analysis. The forward stepwise regression model used in this exploratory study significantly predicted age, accounting for approximately 40% of the variance in the data. The regression model revealed 5 significant regressors (2 right PC's, APOE status, and 2 left PC by APOE interactions). Finally, the specific texture features that contributed to each significant PCs were identified. Conclusion: Analysis of image texture features resulted in a statistical model that was able to detect subtle changes in brain integrity associated with age in a group of participants who are cognitively normal, but have an increased risk of developing AD based on the presence of the APOE e4 phenotype. This is an important finding, given that detecting subtle changes in regions vulnerable to the effects of AD in patients could allow certain texture features to serve as noninvasive, sensitive biomarkers predictive of AD. Even with only a small number of patients, the ability for us to determine sensitive imaging biomarkers could facilitate great improvement in speed of detection and effectiveness of AD interventions..

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Date Created
  • 2016-05

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Engineering a Human Induced Pluripotent Stem Cell (hiPSC)-Based Model of Alzheimer's Disease

Description

Alzheimer’s Disease (AD) affects over 5 million individuals in the U.S. and has a direct cost estimated in excess of $200 billion per year. Broadly speaking, there are two forms

Alzheimer’s Disease (AD) affects over 5 million individuals in the U.S. and has a direct cost estimated in excess of $200 billion per year. Broadly speaking, there are two forms of AD—early-onset, familial AD (FAD) and late-onset-sporadic AD (SAD). Animal models of AD, which rely on the overexpression of FAD-related mutations, have provided important insights into the disease. However, these models do not display important disease-related pathologies and have been limited in their ability to model the complex genetics associated with SAD.

Advances in cellular reprogramming, have enabled the generation of in vitro disease models that can be used to dissect disease mechanisms and evaluate potential therapeutics. To that end, efforts by many groups, including the Brafman laboratory, to generated patient-specific hiPSCs have demonstrated the promise of studying AD in a simplified and accessible system. However, neurons generated from these hiPSCs have shown some, but not all, of the early molecular and cellular hallmarks associated with the disease. Additionally, phenotypes and pathological hallmarks associated with later stages of the human disease have not been observed with current hiPSC-based systems. Further, disease relevant phenotypes in neurons generated from SAD hiPSCs have been highly variable or largely absent. Finally, the reprogramming process erases phenotypes associated with cellular aging and, as a result, iPSC-derived neurons more closely resemble fetal brain rather than adult brain.

It is well-established that in vivo cells reside within a complex 3-D microenvironment that plays a significant role in regulating cell behavior. Signaling and other cellular functions, such as gene expression and differentiation potential, differ in 3-D cultures compared with 2-D substrates. Nonetheless, previous studies using AD hiPSCs have relied on 2-D neuronal culture models that do not reflect the 3-D complexity of native brain tissue, and therefore, are unable to replicate all aspects of AD pathogenesis. Further, the reprogramming process erases cellular aging phenotypes. To address these limitations, this project aimed to develop bioengineering methods for the generation of 3-D organoid-based cultures that mimic in vivo cortical tissue, and to generate an inducible gene repression system to recapitulate cellular aging hallmarks.

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Date Created
  • 2018-05