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2012 Research Showcase
Neurobiology Abstracts
Abstract Title : Looking at Histone Deacetylase Inhibitors in Mouse Models as Potential Treatment in Human Huntington?s Disease
Abstract : Prior research has already demonstrated that histone deacetylase (HDAC) inhibitors show a promising future towards treatment of neurological disorders by targeting certain HDAC enzymes that alter gene expression. These alterations in gene expression are associated with specific pathologies of the brain, such as those characteristic of Huntington?s disease. Huntington?s disease (HD) is a neurodegenerative and progressive disorder caused by a CAG repeat expansion within the coding region of the Huntingtin (HTT) gene. This expansion has been associated with a toxic gain of function of the HTT gene, which leads to dysregulated gene expression in the brain. The disease also presents itself as progressive loss of cognitive and motor function in humans, symptoms that are also present in mouse models of the disease, such as HD-transgenic mice. In this study, we tested a panel of novel HDAC inhibitors for their ability to improve motor behavior and to provide neuroprotective effects in two different transgenic mouse models of HD, R6/2 and N171-82Q transgenic mice. To study these effects, we measured the volume of the striatum in post-mortem brain tissue of vehicle- and drug-treated mice to assess atrophy of the striatum. Behavioral tests involved the open-field apparatus to measure distance traveled, ambulatory time, and various other measurements over the course of ten minutes. Our results demonstrate that treatment with novel HDAC inhibitors can improve HD phenotypes in mouse models and suggest that inhibition of certain HDACs may show potential therapeutic benefits for human HD.
Advisor : JING WANG PHD.
Abstract Title : Olfactory imprinting in Drosophila
Abstract : Title: Olfactory imprinting in Drosophila Abstract During a sensitive period, usually early in the life of many animal species, sensory experiences play an important role in shaping foraging patterns and habitat selection. Sensory cues signaling for safety and for food are quickly learned by young animals and encoded in their memories through modification of neurons in the sensory neural circuit. Imprinting of sensory cues is an important survival mechanism and a rudimentary form of learning. The imprinting of sensory cues can guide and shape an animal?s preferences and behavior. However, it is not well understood how early sensory experiences can contribute to the neural plasticity that influences behavior and thus has been the focus of the present study. Our results demonstrate that olfactory preference in adult Drosophila is markedly influenced by odor experiences during critical period?the first two days following eclosion. Exposure to apple cider vinegar during the critical period dramatically increases the flies? preference for that odor in the later stages of the animal?s life. We found that conditioned responses are abolished in Or83 mutant flies, suggesting that olfactory receptor neurons (ORNs) function is required for olfactory conditioning. We aim to isolate the neural substrate that mediates the acquisition and retrieval phase of conditioned response. We found that blocking Or42b ORN output during acquisition abolishes olfactory conditioning suggesting that Or42b ORN output is required in the acquisition phase. In addition, flies do not exhibit increased behavioral response towards apple cider vinegar in the absence of Or42b ORN output during testing. This indicates that Or42b ORN output is required for retrieval. In conclusion my work provides a causal link between sensory neural plasticity and behavioral modification.
Abstract Title : Synthesis of Molecular Rotors to Visualize Alzheimer?s Disease Amyloid Deposit
Abstract : Molecular rotors is a class of organic probes that fluoresce in an environment-dependent manner. In this study, we present two innovative uses of these probes. First, modifications to the molecular rotors motif were introduced to explore their capability to fluorescently label aggregated amyloid-Beta (Aβ) plaques in Alzheimer?s Disease. In ex vivo experimentation with human brain tissues from Alzheimer?s patient, these probes fluorescently labeled Aβ peptide in low micromolar concentration. Second, we present the synthesis and spectroscopic characterization of a ratiometric, self-calibrating hydrophobic dye, as non-mechanical viscosity sensor. Cell localization experiments of this dye suggest that it cross the cell membrane and potentially can be used for viscosity measurements in the cell. With this study, we envision the development of these probes as low cytotoxic and highly fluorescent probes to study biological and physiological environment common in human diseases.
Abstract Title : Characterization of Optimal Developmental Stage of Spinal Cord Neural Precursors for Formation of Functional Relays After Spinal Cord Injury
Abstract : To ultimately regain function after adult spinal cord injury, neural circuitry has to be re-established to allow signal propagation from the brain, across the injury site, and to appropriate neuronal targets beyond the lesion. Anatomical mechanisms through which neural circuitry might be re-established include regeneration of lesioned adult host axons over long distances beyond the lesion, or establishment of novel, functional relays across the lesion. Functional relays provide certain advantages: (1) injured adult host axons only have to regenerate short distances to reach relay-neurons grafted into the lesion site, (2) inhibitory molecules around and within the injury site are not an obstacle to extension of axons from grafted relay-neurons due to their enhanced intrinsic growth capacity, (3) grafted relay-neurons extend axons rapidly over long distances, and form synapses on host neuronal cell bodies caudal to the lesion. In this study we investigated the developmental differences in spinal relays emerging from transplanted dissociated embryonic spinal cord cells within a mouse C4 dorsal column wire-knife lesion. Spinal cord derived neural precursor cells from developmental stages E10 to E15 were grafted into the adult lesioned spinal cord. We find that: (1) the differentiation of grafted cells, (2) the production of mature neurons within the graft, and (3) axonal elongation from the graft into the host is influenced by the developmental stage of the grafted cells. Further investigation of the necessity of each cellular component for the creation of functional relays will be conducted to translate this model of embryonic spinal cord graft towards an ES cell or IPSC derived graft functional relay model.
Abstract Title : Immunohistochemical assessment of brain pathology in an experimental model of HIV infection and METH exposure
Abstract : Background Glucocorticoids, particularly cortisol in humans, are secreted by the adrenal glands in response to signals from the hypothalamus/pituitary. While the hypothalamus and pituitary are largely involved in regulating autonomic functions, and cortisol secretion is part of circadian rhythm (i.e. elevated after awakening and decreasing throughout the day), the HPA axis is also involved in the stress response and is integrated into other ?higher? functional areas of the brain as well. There is abundant literature on the effects of glucocorticoid excess and brain function. The widely accepted model is that chronic glucocorticoid signaling in neurons renders them vulnerable to degeneration leading to decreased volume of brain structures such as the hippocampus. Although some neural populations are identified as particularly susceptible to cortisol-induced vulnerability (for example the CA1 and CA3 fields of the hippocampus), no molecular mechanism explains how this occurs. Dysregulation of intracellular calcium homeostasis may contribute to cognitive decline with age and METH use. Neuronal expression of calbindin 1 (Calb1, a calcium binding protein) in the rodent hippocampus is regulated by glucocorticoid signaling via the mineralocorticoid receptor (MR). To determine whether the hippocampal expression of Calb1 protein was associated with aging-related memory impairment, we used a set of 22 young and 18 aged mice, in which the aged group performed poorer than the young in the novel object recognition test (determined by the discrimination ratio [DR], a measure of memory performance). The immunohistochemical reactivity normalized to the anatomic area measured (IRn) for Calb1 both in the hippocampal CA1 and dentate gyrus correlated directly with DR in aged mice. These findings suggest that the hippocampal expression of Calb1 protein in aged mice, regulated by MR signaling, affects the memory performance by maintaining the neuronal calcium homeostasis. Results Neuropathologic assessment of gp120 TG animals treated with METH The preliminary immunohistochemical studies of necropsy brain tissues from gp120 TG animals and controls revealed the following: 1) Decreased synaptic complexity in the hippocampus of gp120TG/METH mice and reduced number of interneurons in the cortex 2) HIV and METH impact GR signaling in the brain - Increased FKBP 51 in the soma of cortical neurons of HAND human subjects; but not specific to METH - Increased FKBP52 and GR in the hippocampus of gp120 mice treated with METH, mostly in females We are now validating and expanding the preliminary results using brain necropsy specimens from another cohort of METH-treated HIV gp102 transgenic animals and controls, using quantitative immunohistochemistry for markers of gliosis (GFAP, IbA1), neuronal homeostasis (calbindin and DAT), stress (GR) and immunophilin response (FKBP51 and 52). Future plans By using the Aperio slide scanner available through the HNRP we are currently assembling a repository of digital files of standardized immunohistologic assessment on entire tissue sections from key brain regions both in brain necropsy materials from transgenic animals and human brain autopsy archived materials; this will allow future neuropathologic measurements using novel algorithms and data mining by investigators seeking correlational analyses with various biomarkers and clinical data.
Abstract Title : Interaction of Multiple Contexts in Modulating Behavioral Choice of the Medicinal Leech
Abstract : In any given moment, animals are faced with multiple types of stimuli that can influence their decisions about what behaviors to engage in. Due in part to their relatively small repertoire of stereotyped behaviors, the medicinal leech (Hirudo verbana) is an excellent model organism for studying the complex mechanisms of behavioral choice. The purpose of the current experiment was to study the interaction between two stimulus contexts (stimulus location and surrounding water depth) on the behavioral choice of the leech. Seven leeches were electrically stimulated on the dorsal surface of 10 segments ranging from the middle to the posterior of the leech, and behavioral responses were tested at each of four water depths relative to the leech?s diameter: 0.5x, 1x, 2x, and 4x. Leeches displayed one of four behaviors in response to the initial stimulation: crawling, swimming, a hybrid of crawling and swimming, and local bending (longitudinal shortening at the site of the stimulus and a relaxation at the side of the body opposing the stimulus). The hybrid swim/crawl behavior occurred in shallow water depths (0.5x and 1x), but not in deeper water depths (2x and 4x). The occurrence of local bending was dependent on stimulus location (it occurred more following stimulation to the mid body than stimulation to the posterior), but was independent of water depth. In contrast, the effect of water depth and stimulus location on swimming and crawling was multiplexed. In shallow water, leeches crawled more than they swam, however, in deeper water they swam and crawled with roughly equal frequency. This effect of water depth on behavioral choice was dependent on the site of stimulation: when the mid body of the leech was stimulated, equal occurrence of both behaviors was first observed at a water depth of 1x, whereas when the posterior region was stimulated, equal occurrence of both behaviors did not occur until a water depth of 4x. In leech locomotive behaviors (crawling and swimming), there is a significant interaction of the effects of different stimulus contexts on behavioral choice. These results are an important part of a larger behavioral project examining the multiplexed effects of stimulus location, water depth and time since last feeding on the behavioral choice of the leech.
Abstract Title : Effects of Immunosuppressants Cyclosporin A and FK506 on Central Axon Outgrowth in vitro
Abstract : Spinal cord injuries and disorders disrupt movement, sensation and function of the central nervous system leading to lifelong debilitations, and often paralysis. Unlike axons in the peripheral nervous system (PNS), injured axons in the adult mammalian central nervous system (CNS) do not regenerate after injury. Novel research in our lab has shown that grafts of embryonic nervous tissue can induce functional recovery of severed axons in the CNS. However, grafts of embryonic tissue require immunosuppression, and clinical applications of embryonic nervous tissue grafts in the future will require immunosuppression. Conventional immunosuppressants such as cyclosporin (CsA), and tacrolimus (FK506) have been shown to inhibit axonal regeneration in the PNS (Tessier-Lavigne et al, 2003). The current research investigates the effects of CsA and FK506 on CNS axons. Time course information and concentration dependence data are investigated in an isolated setting in vitro, in order to elucidate the molecular and cellular effects of common immunosuppressants, CsA and FK506, on CNS axons.
Abstract Title : In Vivo Evaluation of the Signaling Mechanisms of Melanopsin
Abstract : Melanopsin is a newly described photopigment expressed only in a small number of retinal ganglion cells (RGCs), most of which project to the non-image forming brain centers. Ectopic expression of melanopsin in many cell types renders them photosensitive. However, the mechanisms of melanopsin function, including those determining its response kinetics are currently unknown. This has limited its development as an optogenetic tool for research and therapy, including its use to restore vision in blind individuals. Viral-mediated expression of melanopsin in the surviving neurons of retina-degenerated mice restores some visual responses; however, the light response kinetics of the transduced retina is still far from ideal. Melanopsin C-terminus cytoplasmic region is suspected to be critical for its interaction with downstream signaling components. We generated more than 100 different truncation and point mutants of mouse melanopsin to test the role of the long C-terminus region in functional melanopsin. Expressing mutant melanopsin in the mouse RGCs allowed us to measure photoresponses in vitro with MEA recordings, and then in vivo through conditional expression of some melanopsin mutants in mRGCs and assay of the pupillary reflexes to light. Comparison of the light responses of the mutants defined a region that plays an important role in interaction with beta arrestins, potential activity-dependent phosphorylation, and photo bleaching, all of which are important processes related to photosensitivity. Thus, expression of wild type or mutant melanopsin in vivo in the mouse RGCs was shown to impart photosensitivity, affecting response amplitude, kinetics and adaptation. This study intends to comprehensively evaluate the signaling properties of engineered melanopsin in the mouse retina. Results from these experiments will significantly advance our understanding of the melanopsin signaling mechanism and generate optogenic tools for vision rescue in blind individuals.
Abstract Title : Loss of SNX27 from Dopamine Neurons is Independent of Survival Rate in Mice and Displays Wild-type Cocaine Sensitization Response
Abstract : SNX27 is a gene shown to be regulated following repeated methamphetamine and cocaine intake. SNX27 is also known to regulate currents in the neurons of the brain by increasing the activity of GIRK channels, which are known to hyperpolarize and contribute to inhibitory responses. Knocking out SNX27 from the entire mouse is lethal early in life of mice. Therefore, preconditional 'floxed' mice were crossed to Dat-cre to knockout SNX27 only in Dopamine(DA) neurons, and mice were found to be able to survive. Sensitization to cocaine were observed utilizing locomotor activity recordings. Locomotor activity measured mice activity by distance it travels before and after injection of cocaine for a period of 6 days. Mice were found to display normal cocaine response and show no particular deviation from response of cocaine treatment of wild-type mice.
Advisor : JING WANG
Abstract Title : Neural Mechanisms underlying the Regulation of Food Search Behavior by Social Cues Tricia Ngo, Susy Kim, Orel Zaninovich, Kang Ko, Jing Wang UCSD
Abstract : The male Drosphila pheromone, cis-vaccenyl acetate (cVA) is an odor cue that modifies several innate behaviors (i.e. food search, aggression, courtship) in fruit flies in a context dependent manner. In food search behaviors, the presence of cVA enhances the attractive properties of food odors such as vinegar. To investigate the neural mechanisms underlying this property of cVA, we used a food search paradigm to measure the amount of time it takes for individual flies to find a food source. In the presence of a mixture of cva and vinegar, a higher percentage of flies successfully found a food target within 10 minutes. Cva is detected by Or67d ORNs and DA1 projection neurons which project to the mushroom bodies and the lateral horn. At the level of the antennal lobe, we found that the Or67d ORNs, were required for this behavior. In addition, silencing the ventral, but not the lateral DA1 projection neurons blocked this behavior. At the level of the mushroom body, silencing the α, β but not the γ lobes of the mushroom bodies, also blocked the enhanced attraction to the mixture of cVA and vinegar. From our experiments, we have determined that the mushroom bodies are crucial for the enhanced attraction to the mixture of cVA and Vinegar possibly because they serve as a convergence point for the relay of information.
Abstract Title : Synesthetic blindsight in a projector synesthete: Lower-level processing of colors allows for faster recognition of graphemes. Ramachandran, V.S., Seckel, E., Patel, P., Samermit, P.
Abstract : Blindsight is when a person has no conscious perception of an object but is still able to recognize it on a subconscious level. Our subject AB is a ?projector? synesthete: when she perceives a feature in one modality, she also experiences it in another. When she sees graphemes ? printed letters and numbers ? she sees colors that are superimposed on them. We wanted to see whether the colors were elicited in early sensory processing, prior to conscious recognition of the graphemes themselves. We presented her with three different puzzle pictures with hidden letters or mirror-reversed words in order to test her reaction time. In comparison with the normals, AB?s reaction time was three times faster. She identified the letters and mirror-reversed words by recognizing their colors first rather than consciously being able to read the words. From this, we suggest that synesthetes process graphemes unconsciously in a form of synesthetic blindsight by activating lower-level processes in V4 prior to information processing in higher levels that enable grapheme recognition.
Abstract Title : Through The Looking Glass: Using Mirror Box Therapy to Treat Phantom Limb Pain in Port-au-Prince, Haiti
Abstract : The day following the devastating 2010 earthquake in Haiti, the queue for amputations was more than 1,000 patients long. Surgeons therefore had to resort to guillotine-style amputations, which may increase the prevalence of phantom limb pain ? the vivid impression that the limb is not only still present but extremely painful. We have previously shown (Ramachandran and Rogers-Ramachandran, 1996; Altschuler and Scott, 2011) that mirror box therapy using visual feedback may relieve pain present in a phantom limb.  We explored the effectiveness in treating phantom limb pain with mirror box therapy in a disaster stricken area, specifically Port-au-Prince, Haiti. Patients were recruited from the Hanger Clinic, a prosthetics clinic on the campus of the Albert Schweitzer Hospital.  Seventeen out of eighteen lower limb amputees reported a significant reduction in phantom pain while using mirror box therapy. The foundation was laid for the on-going practical implementation of this inexpensive and non-intrusive therapy.  Further studies might explore how this therapy could best be integrated into the challenging medical environment of the region.
Abstract Title : Glaucoma - are certain subtypes of Retinal Ganglion Cells more susceptible to the disease?
Abstract : Glaucoma is defined as vision loss due to the death of retinal ganglion cells (RGCs), which are the only neurons that connect the eyes to the brain. In the mammalian visual system there are ~ 20 subtypes of retinal ganglion cells. Each subtype is believed to be distinct. But a fundamental unresolved issue is whether certain subtypes of RGCs die from glaucoma while other subtypes are resistant to the disease. It is also unknown whether certain RGC subtypes die at a faster rate than other subtypes. I addressed these questions using mouse lines that selectively express green fluorescent protein (GFP) in different subtypes of RGCs, and with other subtype specific markers. I also successfully implemented a surgical glaucoma model in mice that demonstratively increased interocular pressure. The data is still forthcoming, but no matter what the result of this project, the answer will be interesting because it is currently unknown and there will be an underlying molecular explanation for the outcome. This leaves the potential for interesting work to follow-up this project and guide the development of treatments for this and other neurodegenerative diseases.
Abstract Title : Conditioned place preference to assess anti-hyperalgesic effect of gabapentin on cisplatin?induced painful neuropathy in mice
Abstract : The cancer chemotherapeutic cisplatin evokes a potent sensitization to light touch (allodynia) in humans and rodents which is believed to reflect a painful neuropathy. It is hypothesized in rodent models that the allodynia is accompanied by a state of negative affect (discomfort). The allodynia in rodent models and in humans after chemotherapeutics is diminished by agents such as gabapentin. To examine the effects of the gabapentin on the affective dimension of this neuropathy in the mouse model, we examined the effects of gabapentin in mice treated with cisplatin and showing a robust allodynia. To address possible effects on the affective component of the neuropathic state the Conditioned Place Preference Paradigm (CPP) was employed to determine concomitantly whether subjects are in fact in a state of distress, and if the anti-neuropathic agent gabapentin is an effective anti-hyperalgesic as evidenced by the animal developing a preference for the location where gabapentin versus vehicle was injected. We also hypothesized that gabapentin will not elicit a CPP for mice that are not in pain, thus characterizing gabapentin as lacking any positive re-inforcing effects in the absence of pain. We found there to be a significant preference for the location that mice in a persistent pain state received Gabapentin, and also that non allodynic mice did not develop a preference for gabapentin. This work supported the use of this CPP as a tool in developing analgesic drugs for chronic pain states.
Abstract Title : Novel Role of Mannose Binding Lectin in Age Related Neuroinflammation and Neurocognitive Consequences in HIV Infected Brain
Abstract : The advent of HAART has led to a larger number of individuals with HIV surviving into old age. While aging alone leads to a weakened immune system, immune complex deposition, and neuroinflammation in the brain, previous studies have found that HIV infection worsens these effects. Among the synergistic effects is an increased deposition of beta amyloid (BA), a protein associated with Alzheimer?s disease. Complement activation is a crucial part of innate immunity that recognizes and initiates an immune response to pathogens via three different pathways. The lectin pathway, mediated by mannose binding lectin (MBL), is one such pathway. MBL can bind to mannose residues on HIV-1 GP120 envelope protein, leading to complement activation. Previous work has shown that there is an increased MBL expression in individuals with HIV encephalitis vs. non-HIVE and that there is an overall activation of lectin complement pathway in HIVE. An age-dependent association of neuroinflammation and neurocognitive consequences with MBL mediated complement activation has not been shown. Here, we examined the expression and colocalization, via Immunofluorescence, of MBL, GP120, BA, and MBL associated serine protease-2 (MASP-2), an enzyme that is a marker of lectin pathway mediated complement activation, in post-mortem brain tissue derived from HIV+ individuals with/without HIVE and HIV- individuals. Our preliminary results show that there was an increase in MBL, BA, and MASP-2 expression and colocalization with increasing age in HIVE vs. non-HIVE/HIV+ and in non-HIVE/HIV+ vs. HIV- cases. In summary, an age dependent increase in colocalized MBL, BA and GP120 in HIVE as compared to non-HIVE/HIV+ was observed. Thus, there is evidence that MBL and MBL mediated complement activation plays a part in HIV disease progression, with implications that MBL functions in immune complex deposition with BA and HIV viral protein. Future work will focus on further investigation of MBL pathway and related immune response in age dependent neuroinflammation and neurodegeneration in HIV-1 infected individuals.