CHANGES OF THE PENETRATION STRENGTH OF THE LUMBAR VERTEBRAE TRABECULAR BONE OF ATHLETES DURING TRAINING

INTRODUCTION: Great static and dynamic load during athletic trainings with weightlifting exercises influence the skeleton, especially spine, of athletes. Some athletes feel pain in lumbar region during such athletic training. Changes in vertebrae bone tissue are mentioned as one of the reasons for pain (1). The osteopenetromethry method has been used for the evaluation of vertebra trabecular bone during the previous years (2,3). The purpose of this study was to examine the changes of vertebra penetration strength (PS) in lumbar region of athletes during the athletic training with weight-lifting exercises using this method. METHODS:120 athletes (aged 18 to 26) from different sports (Tab.1) were examined. We examined PS of 3 to 5 lumbar vertebrae on the 1st, 7th, 14th, 21st and 28th day of athletic training, according to the method described by Logins (3). RESULTS:The PS of lumbar vertebrae of the athlets on the 1st training day was from 4.2 MPa up to 5.1 MPa. On the 7th day of training the decrease from 17% to 35% of the initial value of PS was denoted. According to the level of PS decrease, we conditionally divided the athlets into two groups. The PS of the first group athlets was decreased for 20% of the initial value. The PS decrease of the second group of athlets exceeded 20% of the initial value (Tab.2) [Tab.2.] On the 14th day of athletic training’s the rehabilitation of the initial level of PS of lumbar vertebrae was denoted for the first group athletes and stayed the same during all the time of intensive load (28 days). For the second group of athletes during the time of intensive load the decrease of PS of lumbar vertebrae was denoted up to 2.7±0.38 MPa on the 28th day of athletic training. CONCLUSIONS: The results of our investigation prove that intensive physical load during athletic training’s with weight-lifting exercise of athletes causes changes to the structural organization of vertebral trabecular bone and bone mineral content. If the load exceeds the functional possibilities of spine, the remarkable changes of the vertebral trabecular bone strength take place in 7th day of training. REFERENCE: 1. Silva MJ.Gibson JA.(1997) Bone 21(2):191-199. 2. Hvid I. (1988) Clin Orthop.227: 210-221. 3. Logins V (1996) Mechanics of Composit.Materials 4:564-573

Biomechanical properties of human dilated ascending aorta

Publisher Copyright: © 2019 Ivars Brečs et al., published by Sciendo 2019. Copyright: Copyright 2019 Elsevier B.V., All rights reserved.Aneurysms of ascending aorta are dilatation of the first part of the human aorta. They commonly show no clinical symptoms. This condition increases the risk of aorta dissection, which is a life-threatening condition. In this study we attempted to elucidate the changes in the biomechanical properties that occur in the dilated human ascending aorta. Fourteen specimens of ascending aorta wall were mechanically tested under a uniaxial tensile test. Two specimens from each ascending aorta anterior region were cut in longitudinal and circumferential directions. The samples were stretched until rupture of the sample occurred. The obtained experimental data were processed to determine maximal stress, maximal strain and the tangential modulus of elasticity in the linear part of the stress-strain curve. The obtained results showed a remarkable anisotropy of the ascending aorta tissue. We found higher strength of the tissue in the circumferential direction than in the longitudinal direction. There were no statistically significant differences between the strains of the samples. Tangential modulus of elasticity of the aortic samples in the longitudinal direction was significantly lower than the elastic modulus of the samples in the circumferential direction. The tissue in the circumferential direction is stronger and stiffer than in the longitudinal direction.Peer reviewe

Comparison of biomechanical and structural properties between human aortic and pulmonary valve

Funding Information: This study was supported by a grant from the Latvian Council of Science.Objective: Pulmonary valve autografts have been reported as clinically effective for replacement of diseased aortic valve (Ross procedure). Published data about pulmonary valve mechanical and structural suitability as a long-term substitute for aortic valve are limited. The aim of this study was to compare aortic and pulmonary valve properties. Methods: Experimental studies of biomechanical properties and structure of aortic and pulmonary valves were carried out on pathologically unchanged human heart valves, collected from 11 cadaveric hearts. Biomechanical properties of 84 specimens (all valve elements: cusps, fibrous ring, commissures, sinotubular junction, sinuses) were investigated using uniaxial tensile tests. Ultrastructure was studied using transmission and scanning electron microscopy. Results: Ultimate stress in circumferential direction for pulmonary valve cusps is higher than for aortic valve (2.78±1.05 and 1.74±0.29 MPa, respectively). Ultimate stress in radial direction for pulmonary and aortic cusps is practically the same (0.29±0.06 and 0.32±0.04 MPa, respectively). In ultrastructural study, different layout and density in each construction element are determined. The aortic and pulmonary valves have common ultrastructural properties. Conclusions: Mechanical differences between aortic and pulmonary valve are minimal. Ultrastructural studies show that the aortic and pulmonary valves have similar structural elements and architecture. This investigation suggests that the pulmonary valve can be considered mechanically and structurally suitable for use as an aortic valve replacement.Peer reviewe

Reactogenicity of Biomaterials as Studied by Biochemical, Morphological and Ultrastructural Techniques

Reactogenicity is a characteristic of biocompatible materials that provokes the reparative and proliferative reaction of connective tissues, a compulsory stage of which is inflammation. Thus, reactogenicity studies should include experiments in vivo. A quantitative assessment of reactogenicity can be obtained by subcutaneous implantation of standard olive-shaped specimens covered by the biomaterial under study followed by biochemical, histological and scanning electron microscopical studies of the capsule developing around the implant. Reactogenicity of surgical threads is evaluated by semiquantitative histological analysis of the wound healing process after suture application. Biomaterial reactogenicity can be modified by changing the structure of the surface and its chemical characteristics, and in particular, by applying different biologically active substances including atrane-containing compounds. The reactogenicity indices suggested present the results of the interaction between the biomaterials and the cells

The fusion of tissue spheroids attached to pre-stretched electrospun polyurethane scaffolds

Publisher Copyright: © 2014, © The Author(s) 2014. Copyright: Copyright 2019 Elsevier B.V., All rights reserved.Effective cell invasion into thick electrospun biomimetic scaffolds is an unsolved problem. One possible strategy to biofabricate tissue constructs of desirable thickness and material properties without the need for cell invasion is to use thin (<2 µm) porous electrospun meshes and self-assembling (capable of tissue fusion) tissue spheroids as building blocks. Pre-stretched electrospun meshes remained taut in cell culture and were able to support tissue spheroids with minimal deformation. We hypothesize that elastic electrospun scaffolds could be used as temporal support templates for rapid self-assembly of cell spheroids into higher order tissue structures, such as engineered vascular tissue. The aim of this study was to investigate how the attachment of tissue spheroids to pre-stretched polyurethane scaffolds may interfere with the tissue fusion process. Tissue spheroids attached, spread, and fused after being placed on pre-stretched polyurethane electrospun matrices and formed tissue constructs. Efforts to eliminate hole defects with fibrogenic tissue growth factor-β resulted in the increased synthesis of collagen and periostin and a dramatic reduction in hole size and number. In control experiments, tissue spheroids fuse on a non-adhesive hydrogel and form continuous tissue constructs without holes. Our data demonstrate that tissue spheroids attached to thin stretched elastic electrospun scaffolds have an interrupted tissue fusion process. The resulting tissue-engineered construct phenotype is a direct outcome of the delicate balance of the competing physical forces operating during the tissue fusion process at the interface of the pre-stretched elastic scaffold and the attached tissue spheroids. We have shown that with appropriate treatments, this process can be modulated, and thus, a thin pre-stretched elastic polyurethane electrospun scaffold could serve as a supporting template for rapid biofabrication of thick tissue-engineered constructs without the need for cell invasion.publishersversionPeer reviewe

Social innovation between necessity and opportunity

The contribution of social innovation to the institutional change has been studied in the case of promoting healthy ageing. While major institutional change is well memorized by the present generation, the iterative approach to social innovation build up, and reaching the critical mass for a leap is viewed in the context of a specific region and social group. Selected types of social innovations are projected in their impact on societal challenges and institutional transformation potential

Effects of Optical Radiation on the Healing of Bone Defect in Rabbits

Hypothesis, that optical radiation is able to alter surface electrochemical potential and due to this affect bone remodeling processes have been proposed. Besides, researches, being done beforehand, in majority used laser radiation of single wavelength; the latter usually does not match well with optical absorption bands of the bone, obtained in a series of in-vitro experiments. The goal of the present work was to evaluate in-vivo influence of the optical light of different wavelength on the bone remodeling / reconstruction process. For this, artificial defect have been made at the mandible bone of female rabbits. During operation and 10 days after surgery operation site was irradiated with optical radiation with either long (550 – 5000 nm) or short (350 – 550) wavelength. Results demonstrated that light treatment suppresses rate of healing of the bone defect for both experimental groups comparing with the control. The suppression effect is more expressed for short-wavelength irradiation