Lighting and perceptual cues: effects on gait measures of older adults at high and low risk for falls.

BACKGROUND: The visual system plays an important role in maintaining balance. As a person ages, gait becomes slower and stride becomes shorter, especially in dimly lighted environments. Falls risk has been associated with reduced speed and increased gait variability. METHODS: Twenty-four older adults (half identified at risk for falls) experienced three lighting conditions: pathway illuminated by 1) general ceiling-mounted fixtures, 2) conventional plug-in night lights and 3) plug-in night lights supplemented by laser lines outlining the pathway. Gait measures were collected using the GAITRite© walkway system. RESULTS: Participants performed best under the general ceiling-mounted light system and worst under the night light alone. The pathway plus night lights increased gait velocity and reduced step length variability compared to the night lights alone in those at greater risk of falling. CONCLUSIONS: Practically, when navigating in more challenging environments, such as in low-level ambient illumination, the addition of perceptual cues that define the horizontal walking plane can potentially reduce falls risks in older adults.

Effects of nitric oxide and angiotensin II and their interaction on water uptake in Rana catesbeiana.

Nitric oxide and angiotensin II are involved in regulation of water uptake at the pelvic patch of empty-bladder Rana catesbeiana. In whole animal studies, inhibition of nitric oxide synthase decreased water uptake by 25% and decreased the sodium content of skin from the pelvic patch region by 30%. The inhibitor of nitric oxide synthase also had no effects on permeability of isolated, unperfused skin from the pelvic patch region. These studies indicate that nitric oxide is regulating tissue salt concentration. Injection of angiotensin II stimulated water uptake at the pelvic patch by 23%, which was correlated with an increase in both the vascular resistance and the mean arterial pressure in the sciatic artery. Inhibition of nitric oxide synthase enhanced angiotensin II constriction of aortic rings from frogs. However, in the whole animal studies, inhibition of nitric oxide synthase before angiotensin II injection did not enhance water uptake as predicted. It is hypothesized that the pre-capillary bed of the pelvic patch in Rana catesbeiana lacks angiotensin II receptors.