Matching Items (6)

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Peg Forest Rehabilitation Mitigates the Onset of Injury-Induced Cognitive Disability in Juvenile Rats

Description

Traumatic brain injury (TBI)—sudden impact or acceleration trauma to the head—is a major cause of death and disability worldwide and is particularly amplified in pediatric cases. TBI is the leading

Traumatic brain injury (TBI)—sudden impact or acceleration trauma to the head—is a major cause of death and disability worldwide and is particularly amplified in pediatric cases. TBI is the leading cause of mortality and morbidity in children and adolescents. Adolescence is a critical time where the brain undergoes cognitive development and brain injury-induced disruptions to these processes can lead to life-long debilitating morbidities. The aim of this study was to determine if exercising spatial and contextual memory circuits using a novel rehabilitation strategy called Peg Forest Rehabilitation (PFR) could mitigate the onset of injury-induced cognitive deficits in juvenile rats subjected to diffuse TBI. The PFR aims to synthesize neuroplasticity-based enrichment to improve cognitive outcomes after TBI. We hypothesized that PFR treatment would mitigate the onset of brain injury-induced cognitive deficits and reduce neuroinflammation. Juvenile male Sprague-Dawley rats (post-natal day 35) were subjected to diffuse traumatic brain injury via midline fluid percussion injury or a control surgery. One-week post-injury, rats were exposed to PFR or cage control exploration (15 min/day). PFR allowed free navigation through random configuration of the peg-filled arena for 10 days over 2 weeks. Control rats remained in home cages in the center of the arena with the peg-board removed for 15 min/day/10 days. One-week post-rehabilitation (one-month post-injury), cognitive performance was assessed for short-term (novel object recognition; NOR), long-term (novel location recognition; NLR), and working (temporal order recognition; TOR) memory performance, calculated as a discrimination index between novel and familiar objects. Tissue was collected for immunohistochemistry and stained for ionized calcium binding proteins (Iba-1) to visualize microglia morphology, and somatostatin. PFR attenuated TBI-induced deficits on the NOR task, where the TBI-PFR treatment group spent significantly more time with the novel object compared with the familiar (*p=0.0046). Regardless of rehabilitation, brain-injured rats had hyper-ramified microglia in the hypothalamus indicated by longer branch lengths and more endpoints per cell compared with uninjured shams. Analysis of somatostatin data is ongoing. In this study, passive, intermittent PFR that involved dynamic, novel spatial navigation, prevented TBI-induced cognitive impairment in adolescent rats. Spatial navigation training may have clinical efficacy and should be further investigated.

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Date Created
  • 2020-05

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Neuroinflammation Following Experimental Diffuse Brain Injury in Pre-pubertal and Peri-pubertal Rats

Description

Traumatic brain injury is the leading cause of mortality and morbidity in children and adolescents. Adolescence is a critical time in development where the body and brain undergoes puberty, which

Traumatic brain injury is the leading cause of mortality and morbidity in children and adolescents. Adolescence is a critical time in development where the body and brain undergoes puberty, which not only includes reproductive maturation, but also adult social and cognitive development. Brain-injury-induced disruptions can cause secondary inflammation processes and as a result, pediatric TBI can lead to significant life-long and debilitating morbidities that continue long after initial injury. In this study, neuroinflammation following diffuse brain injury was explored in prepubertal and peripubertal rats using an adapted method of midline fluid percussion injury (mFPI) for juvenile rats to further understand the relationship between pediatric TBI and puberty disruption due to endocrine dysfunction. We expect the adapted mFPI model to be effective in producing diffuse, moderate brain injury in juvenile rats and hypothesize that pre-pubertal rats (PND35) will have increased neuroinflammation compared to peri-pubertal rats (PND17) and shams because of the potential neuroprotective nature of sex steroids. Male Sprague-Dawley rats (n=90) were subjected to either a diffuse midline fluid percussion injury (mFPI) or sham injury at post-natal day (PND) 17 (pre-puberty) or PND35 (peri-puberty). Animals were sacrificed at different time points defined as days post injury (DPI) including 1DPI, 7DPI and 25DPI to represent both acute and chronic time points, allowing for comparisons within groups (injury vs. sham) and across groups (PND17 vs PND35). Body weight of the rats was measured postoperatively at various time points throughout the study to follow recovery. Tissue was collected and subjected to Heamatoxylin and Eosin (H&E) stain to visualize histology and evaluate the application of diffuse mFPI to juvenile rats. In addition, tissue underwent immunohistochemical analysis using 3,3'-diaminobenzidine (DAB) to stain for ionized calcium binding proteins (Iba1) in order to assess injury-related neuroinflammation in the form of microglia activation. Diffuse brain injury using the mFPI model did not affect rat body weight or cause overt cell death, suggesting adaption of the adult mFPI model for juvenile rats is representative of moderate diffuse brain injury. In addition, diffuse TBI lead to morphological changes in microglia suggesting there is an increased inflammatory response following initial insult, which may directly contribute to improper activation of pubertal timing and progression in adolescent children affected. Since there is little literature on the full effects of puberty dysfunction following TBI in the pediatric population, there is a significant need to further assess this area in order to develop improved interventions and potential therapies for this affected population.

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Date Created
  • 2018-05

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Microglial activation in the amygdala following traumatic brain injury

Description

Neuroinflammation is an important secondary injury response occurring after traumatic brain injury (TBI). Anxiety-like disorders are commonly exacerbated after TBI and are mediated through the amygdala; however, the amygdala remains

Neuroinflammation is an important secondary injury response occurring after traumatic brain injury (TBI). Anxiety-like disorders are commonly exacerbated after TBI and are mediated through the amygdala; however, the amygdala remains understudied despite its important contribution in processing emotional and stressful stimuli. Therefore, we wanted to study neuroinflammation after experimental TBI using midline fluid percussion in rodent models. We assessed microglia morphology over time post-injury in two circuit related nuclei of the amygdala, the basolateral amygdala (BLA) and central amygdala of the nucleus (CeA), using skeletal analysis. We also looked at silver staining and glial fibrillary acidic protein (GFAP) to evaluate the role of neuropathology and astrocytosis to evaluate for neuroinflammation in the amygdala. We hypothesized that experimental diffuse TBI leads to microglial activation in the BLA-CeA circuitry over time post-injury due to changes in microglial morphology and increased astrocytosis in the absence of neuropathology. Microglial cell count was found to decrease in the BLA at 1 DPI before returning to sham levels by 28 DPI. No change was found in the CeA. Microglial ramification (process length/cell and endpoints/cell) was found to decrease at 1DPI compared to sham in the CeA, but not in the BLA. Silver staining and GFAP immunoreactivity did not find any evidence of neurodegeneration or activated astrocytes in the respectively. Together, these data indicate that diffuse TBI does not necessarily lead to the same microglial response in the amygdala nuclei, although an alternative mechanism for a neuroinflammatory response in the CeA likely contributes to the widespread neuronal and circuit dysfunction that occurs after TBI.

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Date Created
  • 2018-05

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Microglia Motility in the Context of a PDGF Induced Glioblastoma

Description

Tumor associated microglia-and-macrophages (TAMS) may constitute up to 30% of the composition of glioblastoma. Through mechanisms not well understood, TAMS are thought to aid the progression and invasiveness of glioblastoma.

Tumor associated microglia-and-macrophages (TAMS) may constitute up to 30% of the composition of glioblastoma. Through mechanisms not well understood, TAMS are thought to aid the progression and invasiveness of glioblastoma. In an effort to investigate properties of TAMS in the context of glioblastoma, I utilized data from a PDGF-driven rat model of glioma that highly resembles human glioblastoma. Data was collected from time-lapse microscopy of slice cultures that differentially labels glioma cells and also microglia cells within and outside the tumor microenvironment. Here I show that microglia localize in the tumor and move with greater speed and migration than microglia outside the tumor environment. Following previous studies that show microglia can be characterized by certain movement distributions based on environmental influences, in this study, the majority of microglia movement was characterized by a power law distribution with a characteristic power law exponent lower than outside the tumor region. This indicates that microglia travel at greater distances within the tumor region than outside of it.

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Date Created
  • 2013-12

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Time-Lapse Visualization of Microglia Cell Processes using Fluorescent Miniature (Miniscope) Imaging

Description

In the United States, an estimated 2 million cases of traumatic brain injury (TBI) resulting in more than 50,000 deaths occur every year. TBI induces an immediate primary injury resulting

In the United States, an estimated 2 million cases of traumatic brain injury (TBI) resulting in more than 50,000 deaths occur every year. TBI induces an immediate primary injury resulting in local or diffuse cell death in the brain. Then a secondary injury occurs through neuroinflammation from immune cells in response to primary injury. Microglia, the resident immune cell of the central nervous system, play a critical role in neuroinflammation following TBI. Microglia make up 10% of all cells in the nervous system and are the fastest moving cells in the brain, scanning the entire parenchyma every several hours. Microglia have roles in both the healthy and injured brain. In the healthy brain, microglia can produce neuroprotective factors, clear cellular debris, and organize neurorestorative processes to recover from TBI. However, microglia mediated neuroinflammation during secondary injury produces pro-inflammatory and cytotoxic mediators contributing to neuronal dysfunction, inhibition of CNS repair, and cell death. Furthermore, neuroinflammation is a prominent feature in many neurodegenerative diseases such as Alzheimer’s, and Parkinson’s disease, of which include overactive microglia function. Microglia cell morphology, activation, and response to TBI is poorly understood. Currently, imaging microglia can only be performed while the animal is stationary and under anesthesia. The Miniscope technology allows for real-time visualization of microglia in awake behaving animals. The Miniscope is a miniature fluorescent microscope that can be implanted over a craniectomy to image microglia. Currently, the goals of Miniscope imaging are to improve image quality and develop time-lapse imaging capabilities. There were five main sub-projects that focused on these goals including surgical nose cone design, surgical holder design, improved GRIN lens setup, improved magnification through achromatic lenses, and time-lapse imaging hardware development. Completing these goals would allow for the visualization of microglia function in the healthy and injured brain, elucidating important immune functions that could provide new strategies for treating brain diseases.

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Date Created
  • 2019-05

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Diffuse Brain Injury Incites Sexual Differences and Hypothalamic-Pituitary-Adrenal Axis Disruptions

Description

Of the 2.87 million traumatic brain injuries (TBI) sustained yearly in the United States, 75% are diffuse injuries. A single TBI can have acute and chronic influences on the neuroendocrine

Of the 2.87 million traumatic brain injuries (TBI) sustained yearly in the United States, 75% are diffuse injuries. A single TBI can have acute and chronic influences on the neuroendocrine system leading to hypothalamic-pituitary-adrenal axis (HPA) dysregulation and increased affective disorders. Preliminary data indicate TBI causes neuroinflammation in the hippocampus, likely due to axonal damage, and in the paraventricular nucleus of the hypothalamus (PVN), where no axonal damage is apparent. Mechanisms regulating neuroinflammation in the PVN are unknown. Furthermore, chronic stress causes HPA dysregulation and glucocorticoid receptor (GR)-mediated neuroinflammation in the PVN. The goal of this project was to evaluate neuroinflammation in the HPA axis and determine if GR levels change at 7 days post-injury (DPI).

Adult male and female Sprague Dawley rats were subjected to midline fluid percussion injury. At 7 DPI, half of each brain was post-fixed for immunohistochemistry (IBA-1) and half biopsied for gene/protein analysis. IBA-1 staining was analyzed for microglia activation via skeleton analysis in the hypothalamus and hippocampus. Extracted RNA and protein were used to quantify mRNA expression and protein levels for GRs. Data indicate increased microglia cell number and decreased endpoints/cell and process length in the PVN of males, but not females. In the dentate gyrus, both males and females have an increased microglia cell number after TBI, but there is also an interaction between sex and injury in microglia presentation, where males exhibit a more robust effect than females. Both sexes have significant decreases of endpoints/cell and process length. In both regions, GR protein levels decreased for injured males, but in the hippocampus, GR levels increased for injured females. Data indicate that diffuse TBI causes alterations in microglia morphology and GR levels in the hypothalamus and hippocampus at 7 DPI, providing a potential mechanism for HPA axis dysregulation at a sub-acute time point.

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Date Created
  • 2019