Young adult born neurons enhance hippocampal dependent performance via influences on bilateral networks

Adult neurogenesis supports performance in many hippocampal dependent tasks. Considering the small number of adult-born neurons generated at any given time, it is surprising that this sparse population of cells can substantially influence behavior. Recent studies have demonstrated that heightened excitability and plasticity may be critical for the contribution of young adult-born cells for certain tasks. What is not well understood is how these unique biophysical and synaptic properties may translate to networks that support behavioral function. Here we employed a location discrimination task in mice while using optogenetics to transiently silence adult-born neurons at different ages. We discovered that adult-born neurons promote location discrimination during early stages of development but only if they undergo maturation during task acquisition. Silencing of young adult-born neurons also produced changes extending to the contralateral hippocampus, detectable by both electrophysiology and fMRI measurements, suggesting young neurons may modulate location discrimination through influences on bilateral hippocampal networks.United States. National Institutes of Health (1DP2NS082126)National Institute of Mental Health (U.S.) (5R00MH085944)United States. National Institutes of Health (R01-DA028299)United States. Defense Advanced Research Projects Agency (W911NF-10-0059)Pew Charitable TrustsAmerican Federation for Aging ResearchAlfred P. Sloan FoundationNational Institute of Mental Health (U.S.) (1R21MH109941

The impact of digitalisation on tax transparency

No abstractMini Dissertation (MCom)--University of Pretoria, 2019.TaxationMCom (Taxation)Unrestricte

Applying remote sensing for large‐landscape problems: Inventorying and tracking habitat recovery for a broadly distributed Species At Risk

Abstract Anthropogenic habitat alteration is leading to the reduction of global biodiversity. Consequently, there is an imminent need to understand the state and trend of habitat alteration across broad areas. In North America, habitat alteration has been linked to the decline of threatened woodland caribou. As such, habitat protection and restoration are critical measures to support recovery of self‐sustaining caribou populations. Broad estimates of habitat change through time have set the stage for understanding the status of caribou habitat. However, the lack of updated and detailed data on post‐disturbance vegetation recovery is an impediment to recovery planning and monitoring restoration effectiveness. Advances in remote sensing tools to collect high‐resolution data at large spatial scales are beginning to enable ecological studies in new ways to support ecosystem‐based and species‐based management. We used semi‐automated and manual methodologies to fuse photogrammetry point clouds (PPC) from high‐resolution aerial imagery with wide‐area light detection and ranging (LiDAR) data to quantify vegetation structure (height, density, class) on disturbances associated with caribou declines. We also compared vegetation heights estimated from the semi‐automated PPC‐LiDAR fusion to heights estimated in the field, using stereoscopic interpretation, and using multi‐channel TiTAN LiDAR. Vegetation regrowth was occurring on many of the disturbance types, though there was local variability in the type, height and density of vegetation. Heights estimated using PPC‐LiDAR fusion were highly correlated (r ≥ 0.87 in all cases) with heights estimated using stereomodels, TiTAN multi‐channel LiDAR and field measurements. We demonstrated that PPC‐LiDAR fusion can be operationalized over large areas to collect comprehensive and consistent vegetation data across landscape levels, providing opportunities to link fine‐resolution remote sensing to landscape‐scale ecological studies. Crucially, these data can be used to estimate rates of habitat recovery at resolutions that are not feasible using more commonly used satellite‐based sensors, bridging the gap between resolution and extent. Such data are needed to achieve effective and efficient habitat monitoring to support caribou recovery efforts, as well as a myriad of additional forest management needs

White spotting variant mouse as an experimental model for ovarian aging and menopausal biology

OBJECTIVE: Menopause is a unique phenomenon in modern women, as most mammalian species possess a reproductive period comparable to their lifespan. Menopause is caused by the depletion of germ cell-containing ovarian follicles, and in laboratory studies is usually modeled in animals in which the ovarian function is removed by ovariectomy or chemical poisoning of the germ cells. Our objective was to explore and characterize the white spotting variant (Wv) mice that have reduced ovarian germ cell abundance, a result of a point mutation in the c-kit gene that decreases the kinase activity, as a genetic model for use in menopausal studies. METHODS: Physiological and morphological features associated with menopause were determined in female Wv/Wv mice compared to age-matched wildtype controls. Immunohistochemistry was used to evaluate the presence and number of follicles in paraffin-embedded ovaries. Bone density and body composition were evaluated using the PIXImus X-ray densitometer, and lipids, calcium, and hormone levels were determined in serum using antigen-specific EIAs. Heart and body weight were measured, and cardiac function was evaluated by transthoracic echocardiography. RESULTS: The ovaries of the Wv/Wv females have a greatly reduced number of normal germ cells at birth compared to wildtype mice. The remaining follicles are depleted by around 2 months, and the ovaries develop benign epithelial lesions that resemble morphological changes that occur during ovarian aging, whereas a normal mouse ovary has numerous follicles at all stages of development and retains some follicles even in advanced age. Wv mice have elevated plasma gonadotrophins and reduced estrogen and progesterone levels, a significant reduction in bone mass density, and elevated serum cholesterol and lipoprotein levels. Moreover, the Wv female mice have enlarged hearts and reduced cardiac function. CONCLUSIONS: The reduction of c-kit activity in Wv mice leads to a substantially diminished follicular endowment in newborn mice and premature depletion of follicles in young mice, though the mutant females have a normal lifespan after cessation of ovarian function. The Wv female mice exhibit consistent physiological changes that resemble common features of postmenopausal women. These alterations include follicle depletion, morphological aging of the ovary, altered serum levels of cholesterol, gonadotropins, and steroid hormones, decreased bone density, and reduced cardiac function. These changes were not observed in male mice, either age-matched male Wv/Wv or WT mice, and are unlikely caused by global loss of c-kit function. The Wv mouse may be a genetic, intact-ovary model that mimics closely the phenotypes of human menopause to be used for further studies to understand mechanisms of menopausal biology