Charting the progression of disability in parkinson disease: study protocol for a prospective longitudinal cohort study

Background  

People with Parkinson disease (PD), even in the presence of symptomatic relief from medical, surgical, and rehabilitative interventions, face a persistent worsening of disability. This disability is characterized by diminished quality of life, reduced functional mobility, declining performance in activities of daily living and worsening neurological impairments. While evidence has emerged supporting the clinically meaningful benefits of short-term exercise programs on these underlying factors, assertions regarding the effects of sustained programs of exercise and physical activity on the trajectory of disablement in PD are made in the absence of direct evidence. Indeed, the natural decline in quality of life and functional mobility in people diagnosed with PD is poorly understood. Moreover, outcome measures commonly used in clinical exercise trials typically do not capture the full spectrum of disability as defined by the World Health Organization (WHO).     

Cell specification in the Arabidopsis root epidermis requires the activity of ECTOPIC ROOT HAIR 3--a katanin-p60 protein.

The Arabidopsis root is composed of radial cell layers, each with distinct identities. The epidermal layer is composed of rows of hair cells flanked on either side by rows of non-hair epidermal cells. The development of hair and non-hair cells is dependent on domains of positional information with strict boundaries. The pattern of cell differentiation and the expression of molecular markers of cell fate is altered in the ectopic root hair 3 (erh3) mutant epidermis indicating that ERH3 is required for the specification of cell fates from early in development (in the meristem) through differentiation. Furthermore the expression of molecular markers indicates that the specification of cell identities is defective within other radial cell layers. ERH3 encodes a p60 katanin protein that is expressed throughout the plant. Katanin proteins are known to sever microtubules, and have a role in the organisation of the plant cell wall since mutants with decreased katanin activity have been shown to have defective walls. We suggest that microtubules are involved in the specification of cell identities in cells of the Arabidopsis root. Microtubules may be required for the localization of positional cues in the wall that have previously been shown to operate in the development of the root epidermis. Alternatively microtubules may be involved in another as yet undefined process required for the specification of cell identity in plants.