Effects of defoliation on sandbar willow (Salix interior) chemistry, production, and subsequent overwinter browsing by mammalian herbivores

Thesis (M.S.) University of Alaska Fairbanks, 2014.Herbivory can cause changes in plant characteristics, allowing temporally isolated herbivores to indirectly affect one another through their effects on shared host plants. The objective of this thesis was to test how defoliation of the willow Salix interior affects current annual stem production and chemistry, and how changes in these traits may indirectly affect mammalian herbivores. I studied the effect of manual defoliation on S. interior leaf and stem chemistry, and the effect of insect folivory on S. interior stem chemistry, production, and mammal herbivore offtake. Manual defoliation of S. interior affected stem chemistry by significantly increasing stem N concentration and decreasing stem C:N ratio, but did not alter leaf chemistry. Neither stem nor leaf protein precipitation capacity (PPC), a measure of tannin activity, were affected by manual defoliation. In a second field experiment I investigated the effects of natural levels of insect folivory on S. interior stem characteristics, testing the effects of insect herbivore suppression on stem production, chemical composition, protein precipitation capacity, and overwinter mammal browsing. Insect folivory did not significantly alter stem chemistry, but significantly reduced stem production by reducing mean stem diameter the following year. These findings indicate that defoliation of S. interior can improve nutritional quality and reduce availability of stems for mammal herbivores foraging over the subsequent winter.Chapter 1: Effects of defoliation on sandbar willow (Salix interior) leaf and stem chemistry -- Chapter 2: The effect of summer insect folivory on S. interior winter forage quantity, quality, and consumption by mammalian herbivores -- Conclusion

³¹P Saturation Transfer and Phosphocreatine Imaging in the Monkey Brain

³¹P magnetic resonance imaging with chemical-shift discrimination by selective excitation has been employed to determine the phosphocreatine (PCr) distribution in the brains of three juvenile macaque monkeys. PCr images were also obtained while saturating the resonance of the {gamma}-phosphate of ATP, which allowed the investigation of the chemical exchange between PCr and the {gamma}-phosphate of ATP catalyzed by creatine kinase. Superposition of the PCr images over the proton image of the same monkey brain revealed topological variations in the distribution of PCr and creatine kinase activity. PCr images were also obtained with and without visual stimulation. In two out of four experiments, an apparently localized decrease in PCr concentration was noted in visual cortex upon visual stimulation. This result is interpreted in terms of a possible role for the local ADP concentration in stimulating the accompanying metabolic response

Uncovering the neural basis of cognitive impairment following hearing loss: an all-optical electrophysiology approach

We have access to state-of-the-art equipment that will enable us to visualize specific neuron types in animal models. This is a new approach that combines several recent advances in the field of \u27optogenetics\u27, a technique that uses light to control neurons. This approach will allow us to explore how hearing loss induced by loud noise exposure leads to abnormal neural activity in areas of the brain that control learning, memory and higher cognitive function.https://ir.lib.uwo.ca/brainscanprojectsummaries/1030/thumbnail.jp

Salicylate toxicity model of tinnitus

Salicylate, the active component of the common drug aspirin, has mild analgesic, antipyretic, and anti-inflammatory effects at moderate doses. At higher doses, however, salicylate temporarily induces moderate hearing loss and the perception of a high-pitch ringing in humans and animals. This phantom perception of sound known as tinnitus is qualitatively similar to the persistent subjective tinnitus induced by high-level noise exposure, ototoxic drugs, or aging, which affects ∼14% of the general population. For over a quarter century, auditory scientists have used the salicylate toxicity model to investigate candidate biochemical and neurophysiological mechanisms underlying phantom sound perception. In this review, we summarize some of the intriguing biochemical and physiological effects associated with salicylate-induced tinnitus, some of which occur in the periphery and others in the central nervous system. The relevance and general utility of the salicylate toxicity model in understanding phantom sound perception in general are discussed

Growing new dendritic spines to correct cognitive deficits of schizophrenia

In this project, we will attempt to re-grow functional dendritic spines in an animal model of schizophrenia for the first time. By re-growing dendritic spines, we intend to restore glutamatergic neurotransmission and improve cognition.https://ir.lib.uwo.ca/brainscanprojectsummaries/1023/thumbnail.jp

Establishing a translational platform for studying sensory processing in neurodevelopmental disorders

The causes for ASD and DLD are many, complex and largely unknown. One specific cause already identified is mutation of a single gene essential for neuronal development. A useful transgenic rat model has been developed with this mutation that exhibits disabilities very reminiscient of children with ASD or DLD. We will use it to demonstrate that the same tests can show the same disruptions to the auditory system between children with ASD/DLD and this rat model. This model can then be used to undertake further exploration of the impact of ASD/DLD on the auditory system and evaluation of possible behavioural and pharmacological interventions.https://ir.lib.uwo.ca/brainscanprojectsummaries/1024/thumbnail.jp

Characterizing maternal isolation-induced ultrasonic vocalizations in a gene-environment interaction rat model for autism.

Deficits in social communication and language development belong to the earliest diagnostic criteria of autism spectrum disorders. Of the many risk factors for autism spectrum disorder, the contactin-associated protein-like 2 gene, CNTNAP2, is thought to be important for language development. The present study used a rat model to investigate the potential compounding effects of autism spectrum disorder risk gene mutation and environmental challenges, including breeding conditions or maternal immune activation during pregnancy, on early vocal communication in the offspring. Maternal isolation-induced ultrasonic vocalizations from Cntnap2 wildtype and knockout rats at selected postnatal days were analyzed for their acoustic, temporal and syntax characteristics. Cntnap2 knockout pups from heterozygous breeding showed normal numbers and largely similar temporal structures of ultrasonic vocalizations to wildtype controls, whereas both parameters were affected in homozygously bred knockouts. Homozygous breeding further exacerbated altered pitch and transitioning between call types found in Cntnap2 knockout pups from heterozygous breeding. In contrast, the effect of maternal immune activation on the offspring\u27s vocal communication was confined to call type syntax, but left ultrasonic vocalization acoustic and temporal organization intact. Our results support the double-hit hypothesis of autism spectrum disorder risk gene-environment interactions and emphasize that complex features of vocal communication are a useful tool for identifying early autistic-like features in rodent models