RESUMO
The Hoffmann reflex (H-wave) is produced by alpha-motoneuron activation in the spinal cord. A feature of this electromyography response is that it exhibits fluctuations in amplitude even during repetitive stimulation with the same intensity of current. We herein explore the hypothesis that physical training induces plastic changes in the motor system. Such changes are evaluated with the fractal dimension (FD) analysis of the H-wave amplitude-fluctuations (H-wave FD) and the cross-covariance (CCV) between the bilateral H-wave amplitudes. The aim of this study was to compare the H-wave FD as well as the CCV before and after track training in sedentary individuals and athletes. The training modality in all subjects consisted of running three times per week (for 13 weeks) in a concrete road of 5 km. Given the different physical condition of sedentary vs. athletes, the running time between sedentary and athletes was different. After training, the FD was significantly increased in sedentary individuals but significantly reduced in athletes, although there were no changes in spinal excitability in either group of subjects. Moreover, the CCV between bilateral H-waves exhibited a significant increase in athletes but not in sedentary individuals. These differential changes in the FD and CCV indicate that the plastic changes in the complexity of the H-wave amplitude fluctuations as well as the synaptic inputs to the Ia-motoneuron systems of both legs were correlated to the previous fitness history of the subjects. Furthermore, these findings demonstrate that the FD and CCV can be employed as indexes to study plastic changes in the human motor system.
RESUMO
BACKGROUND: Retinopathy of prematurity (ROP) is a serious complication of treatment and extension of survival in premature infants and leads to blindness unless recognized and treated early. An ROP prospective screening survey was performed, enrolling all premature newborns weighing <2000 g at delivery. METHODS: A total of 2014 infants had a retinal evaluation by indirect ophthalmoscopy at 4-6 weeks of age. If any ROP stage was detected, the patient was followed periodically to assess treatment. All premature infants with threshold retinopathy were treated by transscleral cryotherapy at the time of detection. RESULTS: We found 449 infants (22.2%) with ROP in any stage, and 230 (11.42%) with threshold retinopathy who underwent cryotherapy. In the 500-1000 g group (n = 334), 48.2% had ROP in any stage and 92 (27.5%) had threshold retinopathy. In the 1001-1500 g group (n = 1374), 257 (18.7%) had any ROP stage and 122 (8.8%) had stage 3. In the 1501-2000 g group, 306 neonates were evaluated, 31 (10%) had any ROP stage and 16 (5.2%) underwent cryotherapy. A total of 198/230 infants (86%) with threshold retinopathy who received cryotherapy had complete recovery, but 5% developed unilateral and 9% bilateral retinal detachment. There were no complications related to anesthesia. CONCLUSIONS: Overall ROP rate was 2.68/1000 deliveries and 22.2% of premature infants <2000 g had any ROP stage, 11.42% with retinal detachment risk received cryotherapy with 86% successful results.