Validation of the Auditory Stroop Task to increase cognitive load in walking tasks in healthy elderly and persons with Parkinson's disease.

BACKGROUND: The development of treatments for freezing of gait (FOG) in Parkinson's disease (PD) requires experimental study set-ups in which FOG is likely to occur, and is amenable to therapeutic interventions. We explore whether the 'Auditory Stroop Task' (AST) can be used to increase cognitive load (and thereby elicit FOG), simultaneously with visual cues (as a therapeutic intervention for FOG). We additionally examined how these two contrasting effects might interact in affecting gait and FOG parameters. OBJECTIVES: We investigated whether: (1) the 'Auditory Stroop Task' (AST) influences gait in healthy elderly and persons with PD who experience FOG, and increases the frequency of FOG events among PD patients; (2) the AST and visual cues interact; and (3) different versions of the AST exert different cognitive loads. METHODS: In 'Experiment 1', 19 healthy elderly subjects performed a walking task while performing a high and low load version of the AST. Walking with a random numbers task, and walking without cognitive load served as control conditions. In 'Experiment 2', 20 PD patients with FOG and 18 healthy controls performed a walking task with the AST, and no additional cognitive load as control condition. Both experiments were performed with and without visual cues. Velocity, cadence, stride length, and stride time were measured in all subjects. FOG severity was measured in patients. RESULTS: Compared to the control conditions, the AST negatively affected all gait parameters in both patients and controls. The AST did not increase the occurrence of FOG in patients. Visual cues reduced the decline in stride length induced by cognitive load in both groups. Both versions of the AST exerted similar effects on gait parameters in controls. CONCLUSIONS: The AST is well-suited to simulate the effects of cognitive load on gait parameters, but not FOG severity, in gait experiments in persons with PD and FOG.

Continuous beta-galactosidase production with a recombinant baculovirus insect-cell system in bioreactors.

Insect cells were exploited to produce bacterial beta-galactosidase by infecting them with a recombinant nuclear polyhedrosis virus (baculovirus) of Autographa californica. The insect cells were cultured in a continuous stirred tank reactor (CSTR) and led to a second CSTR where they were infected with a recombinant virus in which the lacZ gene from Escherichia coli was inserted. In the effluent of the production reactor, maximum activities of 15 units beta-galactosidase per 10(6) cells were measured. For about 25 d beta-galactosidase production remained constant, but then rapidly declined. This drop was due to a decrease in production of active beta-galactosidase rather than to inactivation of this enzyme. It was concluded that the reduced production was due to reduced polyhedrin promoter-driven synthesis.