Hindlimb unloading producing effects on bone biomechanical properties in mature male rats

Aging is associated with decline in muscle mass and strength and reduced bone density. Age-related bone loss is a primary factor in osteoporosis and all individuals are potential candidates for osteoporosis because bone loss with aging occurs in men and women, but less studied in men. To examine the appropriateness of hindlimb elevation, by tail suspension as a model for diminished mechanical loading, and to determine the influence of age on bone responsiveness to skeletal unloading, we use dual X ray absorptiometry (DXA) and digital radiographic images to analyze the response of the femur from mature rats to biomechanical loads. Femurs from male Wistar rats (9-mo-old) were scanned using DXA and DIGORA and measures obtained in ephipyseal and diaphyseal regions of interest. The mechanical testing was divided into compression load to fracture the head and a three-point bending load to fracture the femur middiaphysis. In femoral epiphysis from hindlimb unload (HU), animals presented significant differences between mineral bone content and density assessed by DXA. Detailed regions of femoral epiphysis (head, throcanteric fossa, throcanter and metaphysis) presented significant lower values from radiographic density. Only compressive load necessary to fracture the femoral head neck was also significantly diminished in HU animals. Disuse induced, as in elderly patients, deterioration of the trabecular bone architecture with critical effect on bone fragility. Rats with 21 days of hindlimb unloading can simulate disuse, suggesting that certain sub-regions of their aging bones are more susceptible to fracture, while other, i.e. diaphyses, are not.

The effect of locked screw angulation on the biomechanical properties of the S.P.S. Free-Block plate

Objectives: Among the locked internal fixators is one denominated S.P.S. (Synthesis Pengo System) Free-Block, which was designed with a locking ring that allows the screw to be locked and positioned obliquely. Due to the paucity of biomechanical studies on this system, the present work aimed to evaluate the influence of locked screw angulation on the resistance of the S.P.S. Free--Block plate. Methods: Forty synthetic bone cylinders with 10 mm fracture gap were used. Forty seven-hole 3.5 mm stainless steel plates (two AO-like dynamic compression holes and five locked holes) were assembled according to the orientation of the locked screws: mono cortical screws were positioned at 90° to the long axis of the cylinder (Group 1), and monocortical screws were positioned at 70° to its cylinder long axis (Group 2). In both groups, AO-like dynamic compression hole screws were positioned bicortically and neutrally. For each group, six specimens were tested until failure, three in bending and three in compression, to determine the loads for fatigue testing. Subsequently, for each group, 14 specimens were tested for failure --seven by bending and seven in compression. Results: No significant failure differences were observed between Groups 1 and 2 under static-loading or fatigue test. Clinical significance: In a fracture gap model the orientation of the locked monocortical screws did not show any influence on the mechanical performance of the S.P.S. Free-Block to tests of axial compression and four-point bending. © Schattauer 2013.

Effects of ionizing radiation and preservation on biomechanical properties of human costal cartilage

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Effect of diclofenac sodium on the healing process of end-to-end anastomosis in carotid arteries of rabbits. Histopathological and biomechanical studies

Aim. Diclofenac sodium is a non-steroidal anti-inflammatory drug commonly used to attenuate painful inflammatory reactions in surgery. However, it may delay healing in the skin and gastrointestinal tract. The aim of this study was to evaluate the influence of Diclofenac in vascular healing. Methods. Ninety rabbits had their carotid arteries sectioned and reconstructed by end-to-end anastomosis with interrupted sutures. The animals were randomly allocated into 3 groups of 30 each and treated by intramuscular route with saline (control), 5 mg/kg/day of diclofenac sodium (DS-5), and 10 mg/kg/day of diclofenac sodium (DS-10). Treatment began on the day of surgery and lasted 4 days. Angiography, biomechanical properties (failure load, failure elongation, yield point, yield point elongation, and stiffness were obtained from the load/elongation curve), macroscopic and histological examinations (hematoxylin-eosin, Masson, Calleja, Picrossirius-red), and scanning electron microscopy were studied in both arteries on the 3rd and 15th postoperative days. Results. No significant differences in biomechanical properties were observed either in the 3 groups or the experimental times. The carotid artery healing process was similar in the 3 groups. Conclusion. Diclofenac sodium did not cause alterations nor delayed carotid artery healing.

Effects of neonatal castration and androgenization on sexual dimorphism in bone, leptin and corticosterone secretion

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Analysis of the effects of irradiation in osseointegrated dental implants

Objective: The purpose of the present study was to evaluate the influence of radiation in osseointegrated dental implants installed in tibiae of rats.Material and methods: Screw-shaped implants (2.5 mm diameter by 3.5 mm length) were custom made from commercially pure titanium bars. Titanium implants were blasted and sterilized before implantation. Animals were divided into two groups of 12 animals each and the rats were not paired after the groups' formation. The experimental group (group 1) received external irradiation 4 weeks after surgery while in the control group (group 2) animals were kept free of radiation. The shear strength required to detach the implant from bone was measured by push-out testing and osseointegration was histologically evaluated.Results: Results showed that the compressive strength of irradiated implants (33.49 MPa) was significantly lower than the compressive strength of non-irradiated implants (48.05 MPa).Conclusions: We concluded that the mechanical strength bonding between implants and host tissues decreased after irradiation.

Propriedades mecânicas de três fios de sutura no reparo do tendão do músculo flexor profundo do dedo de cães

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Efeito da corrente elétrica contínua isolada e da iontoforese transdermal, associada ao zinco, sobre a resistência mecânica e o conteúdo de hidroxiprolina de cicatrizes realizadas na pele de ratos diabéticos aloxânicos

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Efeitos da castração e androgenização neonatal sobre o dimorfismo sexual esquelético e secreção de leptina e corticosterona em ratos

Pós-graduação em Ciências Fisiológicas - FOA

Efeitos a longo-prazo do tratamento neonatal com glutamato-monossódico no dimorfismo sexual esquelético e secreção de leptina e corticosterona

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Repercussões minerais ósseas no alcoolismo crônico associado à deficiência hormonal em ratos

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Avaliação da qualidade óssea no reparo de defeitos ósseos sob a ação do risedronato e da deficiência estrogênica

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Efeito do treinamento resistido na densidade mineral óssea e no conteúdo de GLUT4 em ratos diabéticos (tipo 2) osteopênicos

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Morphofunctional characterization of decellularized vena cava as tissue engineering scaffolds

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Avaliação da sensibilidade insulínica, transdução do sinal insulínico e da densidade mineral óssea em ratas tratadas com fluoreto de sódio

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)