Biomechanical effects of immobilization and rehabilitation on the skeletal muscle of trained and sedentary rats

Because of the scarcity of information about the comparison of training to sedentarism beforehand immobilization and rehabilitation through muscle mechanical properties, the present work investigates this theme. Seventy rats were divided into 7 groups: 1-control (C); 2-trained (T); 3-sedentary (S); 4-trained and immobilized (TI); 5-sedentary and immobilized (SI); 6-trained, immobilized and rehabilitated (TIR); 7-sedentary, immobilized and rehabilitated (SIR). Interventions: Swimming training; Sedentarism (reduced size cages); Cast immobilization (pelvic limb) and water rehabilitation. Load at the limit of proportionality (LLP), maximum limit load (MLL) and stiffness (St) were the mechanical properties determined after a mechanical test of traction of the gastrocnemius. The training improved all mechanical properties when compared to sedentarism. After immobilization, LLP and MLL were reduced in TI and SI. However, there was no difference in St between C and TI. Additionally, TI showed improved MLL when compared to SI. The comparison of TI and TIR showed significant melioration in all properties after remobilization. SIR showed an improvement only in MLL when compared to SI. Significant melioration in LLP and St was observed in TIR compared to SIR. We demonstrated that the training before immobilization and rehabilitation had a positive effect on the muscle mechanical behavior compared to sedentarism. This analysis is of fundamental importance because it helps characterize the muscle tissue under different functional demands.

Tension band wire fixation for valgus osteotomies of the proximal femur: A biomechanical study of three configurations of fixation

Background. A variety of techniques can be used to achieve stabilization of femoral valgus osteotomies in children, but what is lacking is a versatile fixation system that associates stability and versatility at different ages and for different degrees of deformity. Methods. Mechanical tests of three configurations used to fix femoral valgus osteotomies, based oil the tension band wire principle, were carried out. A 30 degrees wedge valgus osteotomy was performed at the subtrochanteric level in 60 swine femurs and fixed with three different systems. In Group 1, two Kirschner wires (K wire) were introduced from the tip of the greater trochanter to the medial cortex, crossing the osteotomy. A flexible steel wire was anchored to the K wires into holes in the lateral cortex and tightened to form a tension band. The same setup was used in Group 2, but two additional smooth K wires were inserted into the lateral surface of the greater trochanter and driven to the femoral head with the distal extremities bent and tied around tile bone shaft. In Group 3, the fixation was similar to that in Group 2, but tile ascending K wires were introduced below the osteotomy level, crossing the osteotonly. Mechanical tests in bending-compression and torsion were used to access the stability. Findings. The torsional relative stiffness was 116% greater for Group 3 (0.27 N m/degree) and no significant difference was found between Group 1 (0.10 N m/degree) and Group 2 (0.12 N m/degree). The average torque was 103% higher for Group 3 (1.86 N m). Stiffness in bending-compression was significantly higher in Group 3 (508 x 10(3) N/m) than in Group 1 (211 x 10(3) N/m) and Group 2 (219 x 10(3) N/m). Interpretation. Fixation as used in Group 3 was significantly more stable, both in torsion and bending-compression tests, than tile other two techniques. (c) 2007 Elsevier Ltd. All rights reserved.

Effect of treadmill exercise on lumbar vertebrae in ovariectomized rats: anthropometrical and mechanical analyses

The purpose of this study was to examine the preventive effect of exercise on lumbar vertebrae in ovariectomized rats. Three-month-old female Wistar rats were divided into 3 groups: control group (A, n = 10); non-exercised ovariectomized group (B, n = 7) and exercised ovariectomized group (C, n = 7). The rats from group C were subjected to treadmill exercise (15 m/minute in the initial six weeks and 19 m/minute in the next six weeks, 1 hour/day, 4 days/week) for 12 weeks. At death, the fourth lumbar vertebrae were removed and an anthropometrical analysis by a paquimeter and a mechanical compression test by a universal test machine were performed. After 12 weeks, the ovariectomy decreased the superior-inferior vertebral height and the maximal braking load in group B compared to group A, while the exercise increased the vertebral mass in group C compared to both groups A and B (p < 0.01) and the stiffness compared to group B. We concluded the physical activity has an important role to prevent the osteopenia in lumbar vertebrae.

Etiopathogenesis of Hepatic Osteodystrophy in Wistar Rats with Cholestatic Liver Disease

The pathophysiology of hepatic osteodystrophy (HO) remains poorly understood. Our aim was to evaluate bone histomorphometry, biomechanical properties, and the role of the growth hormone (GH)/insulin-like growth factor-I (IGF-I) system in the onset of this disorder. Forty-six male Wistar rats were divided into two groups: sham-operated (SO, n = 23) and bile duct-ligated (BDL, n = 23). Rats were killed on day 30 postoperatively. Immunohistochemical expression of IGF-I and GH receptor was determined in liver tissue and in the proximal growth plate cartilage of the left tibia. Histomorphometric analysis was performed in the right tibia, and the right femur was used for biomechanical analysis. The maximal force at fracture and the stiffness of the mid-shaft femur were, respectively, 53% and 24% lower in BDL compared to SO. Histomorphometric measurements showed low cancellous bone volume and decreased cancellous bone connectivity in BDL, compatible with osteoporosis. This group also showed increased mineralization lag time, indicating disturbance in bone mineralization. Serum levels of IGF-I were lower in BDL (basal 1,816 +/- A 336 vs. 30 days 1,062 +/- A 191 ng/ml, P < 0.0001). BDL also showed higher IGF-I expression in the liver tissue but lower IGF-I and GH receptor expression in growth plate cartilage than SO. Osteoporosis is the most important feature of HO; BDL rats show striking signs of reduced bone volume and decreased bone strength, as early as after 1 month of cholestasis. The endocrine and autocrine-paracrine IGF-I systems are deeply affected by cholestasis. Further studies will be necessary to establish their role in the pathogenesis of HO.

T allele of-344C/T polymorphism in aldosterone synthase gene is not associated with resistant hypertension

Resistant hypertension (RH) is the maintenance of elevated blood pressure concurrent with the use of three different antihypertensive drugs, one of which is a diuretic. The Renin-Angiotensin-Aldosterone System plays a major role in volume-dependent hypertension. Therefore, its components are interesting targets for genetic association studies. This work focused on the -344 C/T polymorphism in the CYP11b2 gene, which encodes aldosterone synthase. This work evaluates the association between T allele and resistance to anti-hypertensive treatment. Genotyping analysis included 88 subjects with RH, 142 who were responsive to anti-hypertensive treatment and 110 subjects as a control group. Plasmatic concentrations of aldosterone, renin and cortisol, carotid intima-media thickness and carotid-femoral pulse wave velocity were assessed in a smaller subset of hypertensive patients. An association was found between T allele and hypertension (P < 0.005), but there was no difference in allele frequencies between both hypertensive groups. There was no difference in plasmatic parameters either, in remodeling indicators between the genotypic groups.

Covariance functions for body weight from birth to maturity in Nellore cows

The objective of this study was to estimate (co)variance functions using random regression models on Legendre polynomials for the analysis of repeated measures of BW from birth to adult age. A total of 82,064 records from 8,145 females were analyzed. Different models were compared. The models included additive direct and maternal effects, and animal and maternal permanent environmental effects as random terms. Contemporary group and dam age at calving (linear and quadratic effect) were included as fixed effects, and orthogonal Legendre polynomials of animal age (cubic regression) were considered as random co-variables. Eight models with polynomials of third to sixth order were used to describe additive direct and maternal effects, and animal and maternal permanent environmental effects. Residual effects were modeled using 1 (i.e., assuming homogeneity of variances across all ages) or 5 age classes. The model with 5 classes was the best to describe the trajectory of residuals along the growth curve. The model including fourth- and sixth-order polynomials for additive direct and animal permanent environmental effects, respectively, and third-order polynomials for maternal genetic and maternal permanent environmental effects were the best. Estimates of (co) variance obtained with the multi-trait and random regression models were similar. Direct heritability estimates obtained with the random regression models followed a trend similar to that obtained with the multi-trait model. The largest estimates of maternal heritability were those of BW taken close to 240 d of age. In general, estimates of correlation between BW from birth to 8 yr of age decreased with increasing distance between ages.

Both a combined oral contraceptive and depot medroxyprogesterone acetate impair endothelial function in young women

Background: The study was conducted to determine whether the use of a combined oral contraceptive (COC) or depot medroxyprogesterone acetate (DMPA) interferes with endothelial function. Study Design: The study was conducted on 100 women between the ages of 18 and 30 years. Fifty women had not used hormonal contraception (control group) for at least 12 months, 25 were current users of a COC (ethinylestradiol 30 mcg+levonorgestrel 150 mcg) and 25 were current users of DMPA (150 mg) for at least a 6-month period. All women were evaluated for brachial flow-mediated dilation (FMD), intima-media thickness, carotid distensibility and stiffness index, arterial pressure, body mass index, waist circumference, heart rate and lipid profile. Results: A significant difference in FMD was observed between the COC and control groups (6.4 +/- 2.2% vs. 8,7 +/- 3.4%, p<.01) and between the DMPA and control groups (6.2 +/- 2.1% vs. 8.7 +/- 3.4%, p<.01). The DMPA group had lower values of total cholesterol (TC) and low-density lipoprotein (LDL-C) than COC users and the control group (TC: DMPA=139.9 +/- 21.5 mg/dL vs. controls=167.1 +/- 29.2 mg/dL vs. COC=168.2 +/- 37.5. p=.001; LDL-C: DMPA-85.3 +/- 20.1 mg/dL vs. controls=102 +/- 24.5 mg/dL vs. COC=106.7 +/- 33.3 mg/dL, p=.01). The control group had higher levels of high-density lipoprotein (HDL-C) than the DMPA and COC groups (controls=52.4 +/- 14.1 mg/dL vs. DMPA=42.2 +/- 7.2 mg/dL vs. COC=45.4 +/- 9.1 mg/dL, p=.001). No significant differences were observed regarding the other variables. Conclusions: FMD was lower among COC and DMPA users, Suggesting that these hormonal contraceptives may promote endothelial dysfunction. (C) 2009 Elsevier Inc. All rights reserved.

Sonographic evaluation of endothelial function in letrozole and tamoxifen users

Objectives: Studies have shown that women previously treated for breast cancer present fewer cardiovascular events, indicating a possible protective effect of tamoxifen treatment. The effects of these aromatase inhibitors on cardiovascular protection remain controversial. The aim of this study was to compare some cardiovascular risk markers among breast cancer survivors following treatment with tamoxifen group (TMXg), letrozole group (LTZg) or no endocrine treatment group (NETg). Methods: A total of 103 breast cancer survivors: 35 using TMXg, 34 using letrozole group (LTZg) and 34 using no endocrine treatment group (NETg) were evaluated. Ultrasonographic evaluation of brachial artery flow-mediated dilation (FMD), carotid intima-media thickness (IMT) and stiffness index (beta); blood total cholesterol, HDL and triglycerides were assessed. Results: All three groups presented similar values of HDL and IMT. TMXg showed the lowest total cholesterol (219.29 +/- 36.31 mg/dL vs. 250.59 +/- 38.37 mg/dL vs. 245.09 +/- 35.35 mg/dL; TMXg vs. LTZg vs. NETg, respectively; p < 0.01-ANOVA), the highest triglycerides (139.34 +/- 41.82 mg/dL vs. 111.35 +/- 28.22 mg/dL vs.122.09 +/- 33.42 mg/dL; p < 0.01), the highest FMD (6.32 +/- 2.33% vs. 4.10 +/- 2.06% vs. 4.66 +/- 2.52%; p < 0.01) and the lowest stiffness index (beta) (5.08 +/- 1.68 vs. 6.28 +/- 1.75 vs. 5.99 +/- 1.86; p=0.01). LTZg did not differ significantly from NETg on any evaluated parameter. Conclusions: We did not observe any effect of LTZg on the evaluated cardiovascular risk parameters compared to NETg. As such, the observed difference on lipid values, stiffness index (beta) and FMD between women receiving tamoxifen anti letrozole might be best attributed to the beneficial effect of tamoxifen than to a detrimental effect of letrozole. (C) 2008 Elsevier Ireland Ltd. All rights reserved.

Brachial artery pulsatility index change 1 minute after 5-minute forearm compression - Comparison with flow-mediated dilatation

Objective. Endothelial impairment evaluation by sonographic measurement of flow-mediated dilatation (FMD) has become broadly used. However, this method has 2 main caveats: the dilatation depends on the baseline arterial diameter, and a high precision level is required. Vasodilatation leads to an amplified fall in impedance. We hypothesized that assessment of the pulsatility index change (PI-C) 1 minute after 5-minute forearm compression might evaluate that fall in impedance. The aim of this study was to compare the PI-C with FMD. Methods. Flow-mediated dilatation and the PI-C were assessed in 51 healthy women aged between 35.1 and 67.1 years. We correlated both FMD and the PI-C with age, body mass index, waist circumference, cholesterol level, high-density lipoprotein level, glucose level, systolic and diastolic blood pressure, pulse pressure, brachial artery diameter, simplified Framingham score, intima-media thickness, and carotid stiffness index. Intraclass correlation coefficients between 2 FMD and PI-C measurements were also examined. Results. Only FMD correlated with baseline brachial diameter (r=-0.53). The PI-C had a high correlation with age, body mass index, waist circumference, cholesterol level, systolic blood pressure, pulse pressure, simplified Framingham score, and intima-media thickness. The correlation between FMD and the PI-C was high (r=-0.66). The PI-C had a higher intraclass correlation coefficient (0.991) than FMD (0.836) but not brachial artery diameter (0.989). Conclusions. The PI-C had a large correlation with various markers of cardiovascular risk. Additionally, PI-C measurement does not require offline analysis, extra software, or electrocardiography We think that the PI-C could be considered a marker of endothelial function. However, more studies are required before further conclusions.

Lower Extremities Magnetic Resonance Angiography With Blood Pressure Cuff Compression: Quantitative Dynamic Analysis

Purpose: To quantitatively evaluate changes induced by the application of a femoral blood-pressure cuff (BPC) on run-off magnetic resonance angiography (MRA). which is a method generally previously proposed to reduce venous contamination in the leg. Materials and Methods: This study was Health Insurance Portability and Accountability Act (HIPAA)- and Institutional Review Board (IRB)-compliant, We used time-resolved gradient-echo gadolinium (Gd)-enhanced MRA to measure BPC effects on arterial, venous, and soft-tissue enhancement. Seven healthy volunteers (six men) were studied with the BPC applied at the mid-femoral level unilaterally using a 1.5T MR system after intravenous injection of Gd-BOPTA. Different statistical tools were used such as the Wilcoxon signed rank test and a cubic smoothing spline fit. Results: We found that BPC application induces delayed venous filling (as previously described), but also induces significant decreases in arterial inflow, arterial enhancement, vascular-soft tissue contrast, and delayed peak enhancement (which have not been previously measured). Conclusion: The potential benefits from using a BPC for run-off MRA must be balanced against the potential pitfalls, elucidated by our findings.

Arthrodesis of the equine proximal interphalangeal joint: a biomechanical comparison of 3-Hole 4.5 mm locking compression plate and 3-hole 4.5 mm narrow dynamic compression plate, with two transarticular 5.5 mm cortex screws

Objectives To compare the biomechanical characteristics of 2 arthrodesis techniques for the equine proximal interphalangeal joint (PIP) using either a 3-hole 4.5 mm locking compression plate (LCP) or 3-hole 4.5 mm narrow dynamic compression plate (DCP), both with 2 transarticular 5.5 mm cortex screws. Study Design Experimental. Sample Population Cadaveric adult equine forelimbs (*n=6 pairs). Methods For each forelimb pair, 1 limb was randomly assigned to 1 of 2 treatment groups and the contralateral limb by default to the other treatment group. Construct stiffness, gap formation across the PIP joint, and rotation about the PIP joint were determined for each construct before cyclic axial loading and after each of four, 5000 cycle loading regimens. After the 20,000 cycle axial loading regimen, each construct was loaded to failure. Results There were no significant differences in construct stiffness, gap formation, or sagittal plane rotation between the LCP and DCP treatment groups at any of the measured time points. Conclusion Biomechanically, fixation of the equine PIP joint with a 3-hole 4.5 mm LCP is equivalent to fixation with a 3-hole 4.5 mm narrow DCP under the test conditions used.

Finite Element Modeling for Development and Optimization of a Bone Plate for Mandibular Fracture in Dogs

This study aimed to develop a plate to treat fractures of the mandibular body in dogs and to validate the project using finite elements and biomechanical essays. Mandible prototypes were produced with 10 oblique ventrorostral fractures (favorable) and 10 oblique ventrocaudal fractures (unfavorable). Three groups were established for each fracture type. Osteosynthesis with a pure titanium plate of double-arch geometry and blocked monocortical screws offree angulanon were used. The mechanical resistance of the prototype with unfavorable fracture was lower than that of the fcworable fracture. In both fractures, the deflection increased and the relative stiffness decreased proportionally to the diminishing screw number The finite element analysis validated this plate study, since the maximum tension concentration observed on the plate was lower than the resistance limit tension admitted by the titanium. In conclusion, the double-arch geometry plate fixed with blocked monocortical screws has sufficient resistance to stabilize oblique,fractures, without compromising mandibular dental or neurovascular structures. J Vet Dent 24 (7); 212 - 221, 2010

High-pressure phase diagram of the drug mitotane in compressed and/or supercritical CO(2)

This work provides experimental phase diagram of mitotane, a drug used in the chemotherapy treatment of adrenocortical carcinoma, in compressed and/or supercritical CO(2). The synthetic-static method in a high-pressure variable-volume view cell coupled with a transmitted-light intensity probe was used to measure the solid-fluid (SF) equilibrium data. The phase equilibrium experiments were determined in temperature ranging from (298.2 to 333.1) K and pressure up to 22 MPa. Peng-Robinson equation of state (PR-EoS) with classical mixing rule was used to correlate the experimental data. Excellent agreement was found between experimental and calculated values. (C) 2009 Elsevier Ltd. All rights reserved.

Long-term stability of dentin matrix following treatment with various natural collagen cross-linkers

Objectives: Collagen disorganization is one of the main degradation patterns found in unsuccessful adhesive restorations. The hypothesis of this study was that pretreatment using natural collagen cross-linking agents rich in proanthocyanidin (PA) would improve mechanical properties and stability over time of the dentin collagen and, thus, confer a more resistant and lasting substrate for adhesive restorations. Methods: PA-based extracts, from grape seed (GSE), cocoa seed (CSE), cranberry (CRE), cinnamon (CNE) and acai berry (ACE) were applied over the demineralized dentin. The apparent elastic modulus (E) of the treated dentin collagen was analyzed over a 12 month period. Specimens were immersed in the respective solution and E values were obtained by a micro-flexural test at baseline, 10, 30, 60, 120 and 240 min. Samples were stored in artificial saliva and re-tested after 3, 6 and 12 months. Data was analyzed using ANOVA and Tukey test. Results: GSE and CSE extracts showed a time-dependent effect and were able to improve [240 min (MPa): GSE = 108.96 +/- 56.08: CSE = 59.21 +/- 24.87] and stabilize the E of the organic matrix [12 months (MPa): GSE = 40.91 +/- 19.69; CSE = 42.11 +/- 13.46]. CRE and CNE extracts were able to maintain the E of collagen matrices constant over 12 months [CRE = 11.17 +/- 7.22; CNE = 9.96 +/- 6.11; MPa]. ACE (2.64 +/- 1.22 MPa) and control groups immersed in neat distilled water (1.37 +/- 0.69 MPa) and ethanol-water (0.95 +/- 0.33 MPa) showed no effect over dentin organic matrix and enable their degradation and reduction of mechanical properties. Significance: Some PA-based extracts were capable of improving and stabilizing collagen matrices through exogenous cross-links induction. (C) 2011 Elsevier Ltd. All rights reserved.

Mechanical characterization of proanthocyanidindentin matrix interaction

Objectives To characterize the properties of dentin matrix treated with two proanthocyanidin rich cross-linking agents and their effect on dentin bonded interfaces. Methods Sound human molars were cut into 0.5mm thick dentin slabs, demineralized and either treated with one of two cross-linking agents (grape seedGSE and cocoa seedCOE extracts) or left untreated. The modulus of elasticity of demineralized dentin was assessed after 10 or 60min and the swelling ratio after 60min treatment. Bacterial collagenase was also used to assess resistance to enzymatic degradation of samples subjected to ultimate tensile strength. The effect of GSE or COE on the resindentin bond strength was evaluated after 10 or 60min of exposure time. Data were statistically analyzed at a 95% confidence interval. Results Both cross-linkers increased the elastic modulus of demineralized dentin as exposure time increased. Swelling ratio was lower for treated samples when compared to control groups. No statistically significant changes to the UTS indicate that collagenase had no effect on dentin matrix treated with either GSE or COE. Resindentin bonds significantly increased following treatment with GSE regardless of the application time or adhesive system used. Significance Increased mechanical properties and stability of dentin matrix can be achieved by the use of PA-rich collagen cross-linkers most likely due to the formation of a PAcollagen complex. The short term resindentin bonds can be improved after 10min dentin treatment.(C) 2010 Academy of Denta lMaterials. Published by Elsevier Ltd. All rights reserved.