Use of Erythropoietin as adjuvant therapy in nerve reconstruction.

BACKGROUND AND AIMS: Adjuvant therapies may improve the outcome after nerve reconstruction. We analyzed the influence of recombinant human Erythropoietin (rHuEpo), which has proven angiogenic and neuroprotective effects, on the quality of peripheral nerve regeneration. METHODS: Thirty two female Lewis rats underwent nerve reconstruction by means of tubulization (groups I and II) or autologous sciatic nerve grafting (groups III and IV). Groups I and III received daily subcutaneous rHuEpo injections over 2 weeks (1,000 U/kg bw) with normal saline injections as controls (groups II and IV). Data on histology and muscle weight were collected after 7 weeks. Axon count and diameter were assessed by a new method based on digital segmentation. RESULTS: Atrophy of the tibial muscle was less severe in the rHuEpo-treated group compared to controls resulting in significant higher muscle weight quotients (p = 0.006). The same trend was found in the gastrocnemius muscle, but without being statistically significant. No significant differences in axon count or axon diameter were detected in the presence of rHuEpo treatments. CONCLUSION: Our findings give evidence for a positive effect of Erythropoietin on functional recovery after nerve grafting. Muscle recovery benefited from rHuEpo administration despite absence of improved neural morphology. Semi-automated axon detection facilitated accurate morphometrical assessment.

Factors affecting reaction times to short anterior postural disturbances.

One source of falls in the elderly may be an inability to sufficiently adjust to transient postural perturbations or slips. Identifying useful predictors of fall potential, as well as factors that affect the ability of an individual to detect a movement of the standing support surface may provide insight into postural stability and methods to increase stability in elders. The effects of acceleration, displacement, neurological status, and age on movement detection reaction times were studied in 25 individuals--1 young adults, seven neurologically intact elderly adults, and six elders with (diabetic) peripheral neuropathy. Acceleration detection thresholds for anterior perturbations of 1, 4, and 16 mm of the support surface was previously determined for each subject via a two-alternative forced choice (2AFC) protocol, with longer (16 mm) moves yielding lower 2AFC thresholds (12-39 mm/s(2)) that varied by group. Using the acceleration threshold value determined, and 125% of that threshold (suprathreshold), reaction times to the start of the platform movement were determined for all three displacements. Reaction times to an additional superthreshold movement (4 mm at 100 mm/s(2)) were also measured. Lower acceleration values over longer moves required longer reaction times for motion detection. Reaction times were also influenced by peak energy imparted to the subject through the move. The higher prevalence of falls in the elderly and elderly diabetic may be due to slowing reaction times compounded by larger amounts of imparted energy needed for detection of a slipping event.

Acceleration threshold detection during short anterior and posterior perturbations on a translating platform.

Balance control systems have usually been studied under two conditions, during quiet standing or under large postural perturbations of a magnitude that requires a postural adjustment to prevent falling. Between these two extremes lie perturbations that can be repeated and measured while not forcing adaptive strategies from the postural control system. Unlike other studies of postural control, we employed very short translations with varying accelerations at the edge of psychophysical detectability. These perturbations were vibration-free anterior or posterior translations of the platform on which a subject stood. Using a full Latin-square design set of perturbations in the forward or backward direction, with a smooth or jerk acceleration profile, and of length 4 or 20 mm, were presented to five subjects. Perceptual peak acceleration thresholds were determined by an iterative psychophysical method that forced the subjects to choose in which of two sequential intervals that they perceived a stimulus to have been presented. The only factor found that significantly correlated with detection was perturbation length. The 4 mm peak thresholds averaged 14.51 mm/s2 while 20 mm thresholds averaged 8.55 mm/s2. For the short perturbations employed in this study, detection of motion thus was dependent upon the magnitude of the acceleration, but it was independent of the acceleration profile (jerk versus smooth) or movement direction. By understanding the influences on the ability to perceptually detect motion underfoot, we can begin to understand what elements of the postural control system might be involved in the second-to-second control of balance.