Does Endurance Training Compensate for Neurotrophin Deficiency Following Diabetic Neuropathy?

Background: A lack of neurotrophic support is believed to contribute to the development of diabetic neuropathy. On the other hand, neurotrophins have consistently been shown to increase in the central and peripheral nervous system following exercise, but the effects of exercise intervention on brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF) in diabetic neuropathy are not understood. Objectives: This experimental studywas designed and carried out at the Tarbiat Modares university(TMU) in Tehran, Iran, to investigate the hypothesis that increased activity as endurance training can help to increase the endogenous expression of neurotrophins in diabetic rats. Methods: This was an experimental study with 2× 2 factorial plans performed at TMU in Iran. Sampling was accidental and 28 adult male Wistar rats in the body mass range of 326.3 ± 8.4 g comprised the sample, with each rat randomly assigned to four groups: diabetic control (DC), diabetic training (DT), healthy control (HC), and healthy training (HT). To induce diabetic neuropathy, after 12 hours of food deprivation, an intraperitoneal injection of streptozotocin (STZ) solution (45 mg/Kg) method was used. Two weeks after STZ injection, the endurance training protocol was performed for 6 weeks; 24 hours after the last training session, the rats were sacrificed. Real-time PCR was used for BDNF and NGF expression. Results: The data indicate that diabetes decreasesBDNF andNGF expression in sensory(92%, P=0.01; 90%, P=0.038, respectively) and motor (93%, P = 0.05; 60%, P = 0.029, respectively) roots. However, NGF mRNA levels in the DT group were significantly higher than in the HC group ((7.1-fold), P = 0.01; (2.2-fold), P = 0.001, respectively, for sensory and motor roots), but this was not shown for BDNF. In addition, endurance training can increase NGF expression in healthy rats ((7.4-fold), P = 0.01; (3.8-fold), P = 0.001, respectively, for sensory and motor roots). Conclusions: This study shows that BDNF and NGF expression decreases in diabetic neuropathy. However, this decrease can be reversed through endurance training. These results alsoindicate that endurance trainingmayhave apotential rolein compensating for neurotrophin deficiency following diabetic neuropath

Energy dissipation in adhesive and bolted pultruded GFRP double-lap joints under cyclic loading

Fiber-reinforced polymer (FRP) structures, due to their low mass, are valuable alternatives to traditional steel or concrete structures in seismic areas. However, to resist seismic actions, FRP structures must be able to dissipate a significant amount of inelastic energy. Since FRP materials are brittle, this dissipation must occur in the joints. Monotonic tension and cyclic tension-compression experiments were thus performed on adhesive and bolted double-lap joints composed of pultruded glass fiber-reinforced polymer (GFRP) profiles; a flexible adhesive was used in the adhesive joints. A significant amount of energy was dissipated in the adhesive joints at lower and medium displacement rates through viscoelastic friction and damage in the adhesive, while almost no energy dissipation occurred at the highest rate. The energy in the bolted joints was dissipated by progressive crushing and shear-out failures in the inner laminates. Although the dimensions and monotonic strength of the adhesive and the bolted joints were similar, the former dissipated significantly more energy at the two lower applied displacement rates. The obtained results can contribute to the seismic design of inelastic joints in FRP structures. (c) 2020 The Authors. Published by Elsevier Ltd

A novel fatigue life prediction methodology based on energy dissipation in viscoelastic materials

This paper introduces a new fatigue life prediction methodology for viscoelastic materials in the tension-tension fatigue loading region. The model was established based on the total amount of energy dissipated during fatigue loading, and offers two main advantages with respect to existing models in the literature, i.e. it considers the creep effect on fatigue behavior and requires less input data. The model was applied to three different materials an angle-ply glass/epoxy fiber-reinforced polymer composite, a cross-ply glass/epoxy fiber-reinforced polymer composite, and an epoxy adhesive - to cover a wide range of structural viscoelastic materials used in the industry. It was observed that the model predicted the fatigue life of the studied materials well at different stress ratios including those close to 1.0 where the creep effect was considerable. The model was used to plot constant life diagrams (CLDs) by considering the cyclic-creep interaction to counter the lack of accuracy of existing models at high stress ratios. A new definition for the cyclic-creep interaction was also proposed, which suggests that the participation of the creep and cyclic parts in the cyclic-creep interaction is equal to the total amount of energy dissipated by each. Accordingly, the proposed model was employed to simulate cyclic-creep interaction and determine the cyclic- and creep-dominated regions in CLDs