The resistance of goose (Anser anser f. domestica) eggs to damage was determined by measuring the average rupture force, specific deformation and rupture energy during their compression at different compression speeds (0.0167, 0.167, 0.334, 1.67, 6.68 and 13.36 mm/s). Eggs have been loaded between their poles (along X axis) and in the equator plane (Z axis). The greatest amount of force required to break the eggs was required when eggs were loaded along the X axis and the least compression force was required along the Z axis. This effect of the loading orientation can be described in terms of the eggshell contour curvature. The rate sensitivity of the eggshell rupture force is higher than that observed for the Japanese quail's eggs.
- MeSH
- Biomechanical Phenomena MeSH
- Geese * MeSH
- Compressive Strength * MeSH
- Surface Properties MeSH
- Materials Testing * MeSH
- Egg Shell MeSH
- Eggs * MeSH
- Animals MeSH
- Check Tag
- Animals MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
Cílem práce je upozornit na to, že postižení horních končetin z přetížení vede v posledních letech k nárůstu nemocnosti a žádosti o odškodnění pro nemoc z povolání. Tento nárůst nesouvisí pravděpodobně s vzestupem incidence této poruchy, ale se změnou povědomí pracovníků i lékařů o možnosti nepříznivého vlivu silových a často se opakujících pohybů horních končetin na jejich funkci, rozšířením diagnostiky a jejich hlášení. Je nutno zvládnout diagnostiku těchto nemocí a interpretaci nálezů pomocných vyšetření, aby nedocházelo k nedostatečnému odškod- nění postižených jedinců a na druhé straně ke zhroucení či nefunkčnosti finančního zabezpečení v této oblasti. Řada syndromů uvedeného okruhu má velmi málo objektivních příznaků a abnormních nálezů pomocných vyšetření. Diagnostika úžinových syndromů má oproti jiným poruchám velkou oporu v elektrofyziologických technikách, jejich vysoké senzitivitě i specificitě (1, 15). Je proto pojednáno o jejich problematice a navržena elektrofyziologická kritéria středního stupně postižení u syndromu karpálního tunelu, který je podmínkou odškodnění nemoci z povolání, a která byla u nás dosud stanovena zatím jen rámcově.
The objective of the presented study was to motile that cumulative trauma disorders of the upper extremities in recent years leads to a rising morbidity and applications for compensation for occupational diseases. This rise is probably not associated with an increase of this disorder but a different awareness of workers and doctors as regards the possible adverse effect of forceful and frequently repeated movements of the upper extremities on their function, extended diagnostics and notification. It is important to master the diagnosis of these diseases and interpretation of auxiliary examinations to prevent inadequate payment of damages to the affected subjects and on the other hand to prevent breakdown or in adequate function of the financial provisions in this area. A number of syndromes of the mentioned conditions has very few objective symptoms and abnormal results of auxiliary examinations. The diagnosis of stenotic syndromes has as compared with other disorders great support in electrophysiological techniques, their high sensitivity and specificity (1, 15). The authors discuss therefore their problems and suggest electrophysiological criteria of medium grade affections in the carpal tunnel syndrome which is the condition for compensation for occupational disease and which so far was defined only roughly in this country.
INTRODUCTION: The aim of this study was to find out the impact of degradation and regeneration of force over time at NiTi springs on the value and course of the final acting force and to verify the possibility of using these phenomena for a directed transition to the reverse plateau and its maintaining. METHODS: Static and cyclic mechanical loadings were performed. At first unused springs were tested. Afterwards the springs were mechanically stabilized by stress cycling and finally tested again. The difference in shape of the working curves was assessed. For simulation and description of the force degradation the modified Voight model was used. RESULTS: New springs, mainly those with large hysteresis, showed a significant stress-strain curve movement and shape changes during the cycling. The effect of the stress-strain curve course change disappeared fully in the stabilized springs. Multiple loading led to an overall decrease of force value during the measurement. The effect of force degradation and regeneration over time by simple static loading varies in the range of percentage of the nominal force in the plateau area. The transition between stress-strain curve phases caused by the degradation or regeneration of the force wasn't observed in case of mechanically stabilized springs. CONCLUSIONS: Springs should be mechanically stabilized before their application. The degree of force degradation over time is insignificant for mechanically stabilized springs. Degradation or regeneration of force over time, mechanical stabilization or micromovements in the mouth don't cause any transition between individual stress-strain curve phases.
Meniscus is a semilunar fibrocartilaginous tissue, serving important roles in load buffering, stability, lubrication, proprioception, and nutrition of the knee joint. The degeneration and damage of meniscus has been proved to be a risk factor of knee osteoarthritis. Mechanical stimulus is a critical factor of the development, maintenance and repair of the meniscus fibrochondrocytes. However, the mechanism of the mechano-transduction process remains elusive. Here we reported that cyclic hydrostatic compress force (CHCF) treatment promotes proliferation and inhibits apoptosis of the isolated primary meniscus fibrochondrocytes (PMFs), via upregulating the expression level of integrin ?5ß1. Consequently, increased phosphorylated-ERK1/2 and phosphorylated-PI3K, and decreased caspase-3 were detected. These effects of CHCF treatment can be abolished by integrin ?5ß1 inhibitor or specific siRNA transfection. These data indicate that CHCF regulates apoptosis of PMFs via integrin ?5ß1-FAK-PI3K/ERK pathway, which may be an important candidate approach during meniscus degeneration.
- MeSH
- Apoptosis physiology drug effects MeSH
- Mechanotransduction, Cellular physiology MeSH
- Chondrocytes metabolism drug effects MeSH
- Fibroblasts metabolism drug effects MeSH
- Hydrostatic Pressure MeSH
- Integrin alpha5beta1 antagonists & inhibitors metabolism MeSH
- Rats MeSH
- Cells, Cultured MeSH
- RNA, Small Interfering administration & dosage MeSH
- Meniscus cytology metabolism MeSH
- Compressive Strength physiology MeSH
- Rats, Sprague-Dawley MeSH
- Cell Proliferation physiology MeSH
- Animals MeSH
- Check Tag
- Rats MeSH
- Animals MeSH
- Publication type
- Journal Article MeSH
Patients suffering form epilepsy have an increased risk for fractures. Beside fractures caused by fall or accident muscles forces alone generated during tonic-clonic seizure can result in severe musculoskeletal injury. Contractions of strong paraspinal muscles can lead to compression fracture of the mid-thoracic spine. We report a patient who had suffered from a tonic-clonic seizure during early morning hours. After a cracking sound the patient woke up in a state of post-ictal disorientation, loss of urine and tongue bite. He was admitted to our facilities with the suspected vertebral fracture albeit he just reported of mild lower back pain. Native X-rays and computer-tomography scans showed instable burst fractures of L2 and L4. The fractures were stabilised with a dorsally instrumented internal fixator from L1 to L5 followed by hemi-laminectomy and ventral spondylodesis. Muscle force alone can result in severe skeletal trauma including vertebral fractures.This example emphasizes the importance of critical examination of patients after grand mal seizures. Seizures-induced injuries can appear clinically asymptomatic and can easily be overseen due to absence of trauma and post-ictal impairment of consciousness.
- MeSH
- Epilepsy, Tonic-Clonic complications MeSH
- Spinal Fractures etiology surgery therapy MeSH
- Humans MeSH
- Orthopedic Procedures MeSH
- Muscle Contraction MeSH
- Check Tag
- Humans MeSH
- Publication type
- Case Reports MeSH
Komprese nervus suprascapularis v incisura scapulae superior nebo ve spinoglenoidním zářezu je vzácnou mononeuropatií. Pacienti si stěžují na bolesti v oblasti lopatky a ramenního kloubu, objevuje se selektivní oslabení m. supra- a infraspinatus s oslabením abdukce a zevní rotace paže. Typickým příznakem jsou bolesti v rameni při pokusu o abdukci horní končetiny. Při EMG vyšetření se zpravidla nacházejí projevy denervace v obou svalech. Rozvoj kompresivního syndromu nervu bývá spojován s chronickým přetěžováním, úrazy ramenního kloubu, s chirurgickými zákroky, po fixaci ramene. Autoři prezentují vlastní soubor 10 pacientů operovaných pro lézi n. suprascapularis v průběhu sedmiletého období (2002–2008). U většiny pacientů bylo možno odhalit mechanismus rozvoje komprese nervu. V pooperačním období pravidelně docházelo k různě výraznému zmírnění bolesti a ke zlepšení motoriky. V diskusi autoři rozebírají diferenciální diagnostiku, možnosti zobrazovacích metod, zdůrazňují význam EMG vyšetření.
Compression of suprascapular nerve at the suprascapular notch or spinoglenoid notch can be a cause of a rare mononeuropathy. Patients complain of pain in scapula and shoulder, and selective wasting and weakness of the supraspinatus and infraspinatus muscles. Tenderness at the suprascapular notch and pain by forced abduction of arm are typical and useful signs. Electromyographic signs of various grade denervation are regularly found in both muscles. Development of entrapment syndromes is associated with chronic overload, shoulder injuries, with surgical procedures, or with shoulder-arm fixation. The authors present their own group of 10 patients, who were operated on for entrapment syndrome of suprascapular nerve during 7 year period. Direct or indirect traumatic mechanisms of development of nerve compression were disclosed in most patients. During postoperative period there was not only substantial decrease of pain, but also regression of weakness and wasting of both muscles. In discussion, necessity of differential diagnostic procedures in case of pain and muscle wasting, use of appropriate imaging techniques, demand of purposeful EMG examination, and postoperative follow-ups are emphasized.
- MeSH
- Shoulder Pain etiology MeSH
- Adult MeSH
- Muscle, Skeletal innervation MeSH
- Middle Aged MeSH
- Humans MeSH
- Young Adult MeSH
- Shoulder innervation MeSH
- Aged MeSH
- Nerve Compression Syndromes diagnosis etiology surgery MeSH
- Check Tag
- Adult MeSH
- Middle Aged MeSH
- Humans MeSH
- Young Adult MeSH
- Male MeSH
- Aged MeSH
- Female MeSH
The strike force in combat sports strongly depends on the protective material's mechanical properties and energy absorption capacity. Therefore, this study aimed to estimate the effect of the protective layer thickness and repeated loading on the net force in a falling weight impact test. A falling 8-kg weight dropped from 15 cm, 25 cm, and 50 cm was used to simulate impact peak forces in an upper limb strike. Transfer linear regression functions were identified for three layers of different thickness (1.8 cm, 3.6 cm, and 5.4 cm) between the measured force and undamped force that would be measured if no protective layer was used. A decrease in damping performance under repetitive loading was assessed for the same amount of energy (30 J) absorbed by the specimens. There were 36 specimens examined in 126 tests. When the measuring apparatus was covered with one, two or three layers of Trocellen foam, the undamped force was approximately 2.8, 6.1, and 11.1 times higher, respectively (p < 0.05, R2 ≥ 0.95), than the force measured in the kinetic design. This allows researchers to select the number of layers according to the individual needs in terms of safety and injury prevention. A single layer of Trocellen foam used in this study may be insufficient to ensure the safety of athletes in upper limb strike experiments due to possible compaction of the foam structure for deformations exceeding 80% compression and forces exceeding 5 kN, although no injury was previously observed.
- Publication type
- Journal Article MeSH
Mechanobiology-on-a-chip is a growing field focusing on how mechanical inputs modulate physico-chemical output in microphysiological systems. It is well known that biomechanical cues trigger a variety of molecular events and adjustment of mechanical forces is therefore essential for mimicking in vivo physiologies in organ-on-a-chip technology. Biomechanical inputs in organ-on-a-chip systems can range from variations in extracellular matrix type and stiffness and applied shear stresses to active stretch/strain or compression forces using integrated flexible membranes. The main advantages of these organ-on-a-chip systems are therefore (a) the control over spatiotemporal organization of in vivo-like tissue architectures, (b) the ability to precisely control the amount, duration and intensity of the biomechanical stimuli, and (c) the capability of monitoring in real time the effects of applied mechanical forces on cell, tissue and organ functions. Consequently, over the last decade a variety of microfluidic devices have been introduced to recreate physiological microenvironments that also account for the influence of physical forces on biological functions. In this review we present recent advances in mechanobiological lab-on-a-chip systems and report on lessons learned from these current mechanobiological models. Additionally, future developments needed to engineer next-generation physiological and pathological organ-on-a-chip models are discussed.
- Publication type
- Journal Article MeSH
- Review MeSH
