Effects of malathion on survival, growth, development, and equilibrium posture of bullfrog tadpoles (Rana catesbeiana).

Bullfrog (Rana catesbeiana) tadpoles were exposed to malathion in water in a 28-d static renewal test. The effects of malathion on survival, growth, development, and loss of equilibrium posture were determined. Survival was significantly decreased at malathion concentrations of 2,500 micrograms/L and higher. Development of tadpoles was delayed significantly by malathion exposure as indicated by a dose-related decrease in developmental stage over time. Development of tadpoles in the 1,000-microgram/L and higher treatment groups was significantly delayed from that observed in the control. The effects of malathion on developmental stage suggest that malathion may decrease thyroid function in tadpoles, as it does in other species. Maintenance of equilibrium posture following agitation of the test containers was significantly impaired in tadpoles in all the malathion treatment groups (500 to 3,000 micrograms/L) relative to the control. Maintenance of equilibrium posture was thus the most sensitive end point measured in this study. Loss of equilibrium posture could increase predation losses and decrease feeding in populations of bullfrog tadpoles in the field. However, concentrations of malathion that produced adverse effects in our study are higher than published, measured concentrations found in wetlands or streams.

Proenzyme to urokinase-type plasminogen activator in human colon cancer: in vitro inhibition by monocyte minactivin after proteolytic activation.

Marked increases of plasminogen activator activity were observed in human colon cancer tissue, compared to corresponding normal tissues. This increase was attributable to urokinase-type activator (HPA52), with no increase evident in the level of the tissue-type plasminogen activator (HPA66). Human monocyte minactivin specifically inhibited HPA52 activity in cancer tissue homogenates and in colon cancer cell supernatants, an effect that was greatly enhanced by preincubation with plasminogen, indicating that the predominant form of HPA52 in tissue and the form that is secreted in vitro is the proenzyme. Inactivation of HPA52 by minactivin was shown to be dependent on proteolytic activation of HPA52 proenzyme. Utilization of HPA52 activity by tumors in vivo could therefore be dependent upon a protease, such as plasmin, to generate the extracellular proteolytic activity necessary to digest the intercellular matrix and permit invasion of normal tissue structures by colon cancer cells.

Interference between gait and cognitive tasks in a rehabilitating neurological population.

OBJECTIVES: To quantify the extent of interference between gait and cognitive tasks after brain injury; to investigate whether such interference is common to various cognitive tasks, or confined to specific cognitive modules; to investigate whether such interference declines during recovery from brain injury. METHOD: Fifty participants were recruited from a neurological rehabilitation unit (33 people, 75% of sample); the stroke rehabilitation ward of an acute hospital (11 people, 20%); and a young disabled unit (six people, 5%). Measures of stride duration were taken in single task conditions, and in conjunction with each of four cognitive tasks. Outcome measures were dual task decrements in gait and in cognitive task performance. RESULTS: Overall, a 7% decrement in stride duration was recorded under dual task conditions compared with single task, with stride duration being significantly longer during simultaneous performance of each cognitive task. There was a 4% decrement on average in cognitive task performance under dual task conditions, with significant decrements being recorded for word generation while walking and paired associate monitoring while walking. A significant correlation (r=0.45) was found between dual task decrements and scores on a standard measure of disability-the Barthel activities of daily living scale-but the correlation with 10 m walking time was not significant (r=0.18). CONCLUSION: Interference between cognitive tasks and motor control activities such as gait is a problem in neurological rehabilitation settings. Interference between cognition and locomotor tasks may be important in assessing neurological patients' ability to function independently, and in designing therapies for both cognitive and motor rehabilitation.