507 research outputs found

    Path Analysis

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    Unusual Aphasias - Slowly Progressive Aphasia

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    The Limb Apraxia Test: Development of a Short Form

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    Daphnia predation on the amphibian chytrid fungus and its impacts on disease risk in tadpoles

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    Direct predation upon parasites has the potential to reduce infection in host populations. For example, the fungal parasite of amphibians, B atrachochytrium dendrobatidis ( B d), is commonly transmitted through a free‐swimming zoospore stage that may be vulnerable to predation. Potential predators of B d include freshwater zooplankton that graze on organisms in the water column. We tested the ability of two species of freshwater crustacean ( D aphnia magna and D . dentifera ) to consume B d and to reduce B d density in water and infection in tadpoles. In a series of laboratory experiments, we allowed D aphnia to graze in water containing B d while manipulating D aphnia densities, D aphnia species identity, grazing periods and concentrations of suspended algae ( A nkistrodesmus falcatus ). We then exposed tadpoles to the grazed water. We found that high densities of D . magna reduced the amount of Bd detected in water, leading to a reduction in the proportion of tadpoles that became infected. Daphnia dentifera , a smaller species of D aphnia , also reduced B d in water samples, but did not have an effect on tadpole infection. We also found that algae affected B d in complex ways. When D aphnia were absent, less B d was detected in water and tadpole samples when concentrations of algae were higher, indicating a direct negative effect of algae on B d. When D aphnia were present, however, the amount of B d detected in water samples showed the opposite trend, with less B d when densities of algae were lower. Our results indicate that D aphnia can reduce B d levels in water and infection in tadpoles, but these effects vary with species, algal concentration, and D aphnia density. Therefore, the ability of predators to consume parasites and reduce infection is likely to vary depending on ecological context. We tested the ability of two species of freshwater crustacean ( Daphnia magna and D. dentifera ) to consume zoospores of the amphibian parasite, Batrachochytrium dendrobatidis (Bd), and to reduce parasite density in water and infection in tadpoles. In a series of laboratory experiments, we allowed Daphnia to graze in water containing Bd, then exposed tadpoles to the grazed water. Our results show that Daphnia can reduce Bd levels in water and infection in tadpoles, but these effects vary with species, algal concentration and Daphnia density.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/100311/1/ece3777.pd

    Progressive Apraxia of Speech: Might There Be Subtypes?

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    This study examined speech and language characteristics of three groups of individuals with neurodegenerative disease: (1) primary progressive apraxia of speech (AOS) without aphasia (N=18), (2) agrammatic primary progressive aphasia (agPPA) less severe than AOS (N=10), and (3) agPPA more severe than AOS (N=9). Findings indicate that differences in the predominant characteristics of AOS (predominance of articulatory versus prosodic abnormalities) distributed differently among the three groups, independent of AOS severity. Neuroimaging findings also differed among the groups. Results suggest that neurodegenerative AOS may include perceptually distinguishable subtypes that are related to the presence or absence of aphasia and neuroimaging findings
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