Tension wood is an important anatomical structure for its participation in the orientation of the trunk and the architecture of the branches as a function of structural reinforcement. However, its presence in large amounts significantly affects the technological properties of wood, just as in the rubber tree. Nevertheless, there is still demand for information about the origin, distribution and structural features in this species. Thus, this study aims to characterize the cellular structures in tension and opposite wood in Hevea brasiliensis (rubber tree), as well as its radial and longitudinal distribution. Discs at the base and the middle of the commercial logs were collected from three trees in a commercial plantation located in Tabapoã - SP. Tangential diameter of vessels, fiber length (gelatinous and non-gelatinous fibers), microfibril angle and proportionality of cellular elements (vessels, axial parenchyma, ray, gelatinous fibers and non-gelatinous fibers) were measured, and influence of gelatinous fiber presence in vessel diameter was observed. Gelatinous fibers were observed in the two types of wood and in the two trunk heights. Both types of wood were distinguished by gelatinous fiber length and the proportion of axial parenchyma. The tension wood in mid-trunk was the most different, with long gelatinous fibers and less abundant, larger vessel diameter and vessel proportion. Moreover, smaller vessel diameter was observed in the regions with a high proportion of gelatinous fibers, suggesting that the plant invests more support than in liquid transport.

Backgroud: Low back pain (LBP) has been associated with severe impairments, primarily related to activities of daily living, functional ability and quality of life. A multimodal approach to pain management, such as transcranial direct current stimulation (tDCS) and peripheral electrical stimulation (PES), may improve outcomes in chronic LBP. However, the optimal cerebral target for stimulation still remains controversial. This pilot trial aims to investigate whether active stimulation could promote additional gains to the PES results in LBP patients. Our secondary objective is to investigate whether the stimulation of primary motor cortex and dorsolateral prefrontal cortex results in distinct clinical effects for the patients involved. Methods: Sixty patients with chronic low back pain will be randomized into one of three tDCS groups associated with PES: motor primary cortex, dorsolateral prefrontal cortex and sham stimulation. Each group will receive transcranial direct current stimulation at an intensity of 2 mA for 30 minutes daily for 10 consecutive days. Patients will be assessed with a Brief Pain Inventory (BPI), Roland Morris Disability Questionnaire (RMDQ), Medical Outcomes Study 36-item Short - Form Health Survey (SF-36) and electromyography at baseline, endpoint (after 10 sessions) and 1-month follow up. Discussion: This study will help to clarify the additive effects of tDCS combined with peripheral electrical stimulation on pain relief, muscle function and improvement in quality of life. Additionally, we will provide data to identify optimal targets for management of chronic low back pain.