A Method for Evaluation the Fatigue Microcrack Propagation in Human Cortical Bone Using Differential X-ray Computed Tomography

Fatigue initiation and the propagation of microcracks in a cortical bone is an initial phase of damage development that may ultimately lead to the formation of macroscopic fractures and failure of the bone. In this work, a time-resolved high-resolution X-ray micro-computed tomography (CT) was performed to investigate the system of microcracks in a bone sample loaded by a simulated gait cycle. A low-cycle (1000 cycles) fatigue loading in compression with a 900 N peak amplitude and a 0.4 Hz frequency simulating the slow walk for the initialization of the internal damage of the bone was used. An in-house developed laboratory X-ray micro-CT imaging system coupled with a compact loading device were employed for the in situ uni-axial fatigue experiments reaching a 2μm effective voxel size. To reach a comparable quality of the reconstructed 3D images with the SEM microscopy, projection-level corrections and focal spot drift correction were performed prior to the digital volume correlation and evaluation using differential tomography for the identification of the individual microcracks in the microstructure. The microcracks in the intact bone, the crack formation after loading, and the changes in the topology of the microcracks were identified on a volumetric basis in the microstructure of the bone.     

C-reactive protein,renal function,and cardiovascular outcome in patients with symptomatic peripheral artery disease and preserved left ventricular systolic function

AimTo investigate the prognostic role of C-reactive protein (CRP) and renal function for the occurrence of major adverse cardiovascular events (MACE) in patients with symptomatic peripheral artery disease (PAD) and preserved left ventricular ejection fraction (LVEF).MethodsThe occurrence of MACE, defined as composite endpoint of acute myocardial infarction, urgent coronary revascularization, stroke, and death was assessed in 319 consecutive PAD patients admitted to the University Hospital between January 2010 and January 2014 (66.5% men, mean [±standard deviation] age 70 ± 10 years, mean ankle brachial index 0.58 ± 0.14) with normal LVEF (>50%). Multivariate Cox regression analysis adjusted for age, sex, traditional cardiovascular risk factors, anemia, polyvascular disease, critical limb ischemia (CLI), statin treatment, CRP (>5 mg/L), and impaired renal function (estimated glomerular filtration rate <60 mL/min) was applied to assess the independent predictors of MACE.ResultsDuring median follow-up period of 24 months (interquartile range, 16-34 months), 77 patients (24%) experienced MACE. Compared to patients without MACE, these patients were older, more likely to have CLI, polyvascular disease, anemia, elevated CRP, and impaired renal function. In multivariate regression analysis, age (HR 1.04, 95% CI 1.01-1.07), polyvascular disease (HR 1.95, 95% CI 1.23-3.09), elevated CRP (HR 1.89, 95% CI 1.18-3.02), and impaired renal function (HR 1.68, 95% C 1.01-2.78) remained independent predictors of MACE. Patients with both impaired renal function and high CRP values on admission were 3.59 times more likely to experience MACE than patients with normal CRP and preserved renal function.ConclusionElevated admission CRP and renal impairment are independent predictors of MACE in symptomatic PAD patients with preserved LVEF.C-reactive protein (CRP) is a simple marker, widely commercially available and regularly used in daily clinical practice. While CRP is well studied in acute coronary syndromes, its predictive role in symptomatic peripheral artery disease (PAD) is less clear (1). Conflicting data were published regarding the prognostic significance of admission CRP in patients with PAD (2-5). Its prognostic relevance may be affected by disease severity, duration of follow-up period, and inclusion of traditional risk factors.Patients with chronic kidney disease have an increased risk of developing PAD (6,7). Data regarding the prognostic implication of impaired renal function in PAD patients are scarce. Despite interrelated pathophysiology of inflammation and renal function, their prognostic role has not been clarified in the clinical setting of symptomatic PAD. Left ventricular systolic dysfunction is associated with worse outcome and its prevalence is significantly higher in patients with peripheral vascular disease than in general population (8,9). However, this parameter was not included in prior outcome studies. Therefore, the aim of our research was to investigate the prognostic impact of CRP and impaired renal function for MACE in a cohort of consecutive patients with symptomatic PAD and preserved left ventricular systolic function.     

Calibration and validation of TRUST MRI for the estimation of cerebral blood oxygenation

Recently, a T₂‐Relaxation‐Under‐Spin‐Tagging (TRUST) MRI technique was developed to quantitatively estimate blood oxygen saturation fraction (Y) via the measurement of pure blood T₂. This technique has shown promise for normalization of fMRI signals, for the assessment of oxygen metabolism, and in studies of cognitive aging and multiple sclerosis. However, a human validation study has not been conducted. In addition, the calibration curve used to convert blood T₂ to Y has not accounted for the effects of hematocrit (Hct). In this study, we first conducted experiments on blood samples under physiologic conditions, and the Carr‐Purcell‐Meiboom‐Gill T₂ was determined for a range of Y and Hct values. The data were fitted to a two‐compartment exchange model to allow the characterization of a three‐dimensional plot that can serve to calibrate the in vivo data. Next, in a validation study in humans, we showed that arterial Y estimated using TRUST MRI was 0.837 ± 0.036 (N=7) during the inhalation of 14% O2, which was in excellent agreement with the gold‐standard Y values of 0.840 ± 0.036 based on Pulse‐Oximetry. These data suggest that the availability of this calibration plot should enhance the applicability of T₂‐Relaxation‐Under‐Spin‐Tagging MRI for noninvasive assessment of cerebral blood oxygenation. Magn Reson Med, 2011. © 2011 Wiley‐Liss, Inc.     

Stimulatory effect of ghrelin on isolated porcine somatotropes

Research on the mechanism for growth hormone secretagogue (GHS) induction of growth hormone secretion led to the discovery of the GHS receptor (GHS-R) and later to ghrelin, an endogenous ligand for GHS-R. The ability of ghrelin to induce an increase in the intracellular Ca(2+) concentration - [Ca(2+)](i) - in somatotropes was examined in dispersed porcine pituitary cells using a calcium imaging system. Somatotropes were functionally identified by application of human growth hormone releasing hormone. Ghrelin increased the [Ca(2+)](i) in a dose-dependent manner in 98% of the cells that responded to human growth hormone releasing hormone. In the presence of (D-Lys(3))-GHRP-6, a specific receptor antagonist of GHS-R, the increase in [Ca(2+)](i) evoked by ghrelin was decreased. Pretreatment of cultures with somatostatin or neuropeptide Y reduced the ghrelin-induced increase of [Ca(2+)](i). The stimulatory effect of ghrelin on somatotropes was greatly attenuated in low-calcium saline and blocked by nifedipine, an L-type calcium channel blocker, suggesting involvement of calcium channels. In a zero Na(+) solution, the stimulatory effect of ghrelin on somatotropes was decreased, suggesting that besides calcium channels, sodium channels are also involved in ghrelin-induced calcium transients. Either SQ-22536, an adenylyl cyclase inhibitor, or U73122, a phospholipase C inhibitor, decreased the stimulatory effects of ghrelin on [Ca(2+)](i) transiently, indicating the involvement of adenylyl cyclase-cyclic adenosine monophosphate and phospholipase C inositol 1,4,5-trisphosphate pathways. The nonpeptidyl GHS, L-692,585 (L-585), induced changes in [Ca(2+)](i) similar to those observed with ghrelin. Application of L-585 after ghrelin did not have additive effects on [Ca(2+)](i). Preapplication of L-585 blocked the stimulatory effect of ghrelin on somatotropes. Simultaneous application of ghrelin and L-585 did not cause an additive increase in [Ca(2+)](i). Our results suggest that the actions of ghrelin and synthetic GHS closely parallel each other, in a manner that is consistent with an increase of hormone secretion.     

Comparison of 3 Fusion Techniques in the Treatment of the Degenerative Cervical Spine Disease. Is Stand-Alone Autograft Really the "Gold Standard?": Prospective Study With 2-Year Follow-up

STUDY DESIGN.: A prospective study. OBJECTIVE.: The aim of this study was to compare the 3 different methods of interbody fusion of the cervical spine-autograft in stand-alone technique, autograft with anterior plate, and polyetheretherketone cage supported by anterior plate. The clinical and radiological data obtained were analyzed and discussed. SUMMARY OF BACKGROUND DATA.: Although degenerative cervical spine disease has been treated by an anterior approach for more than 50 years, there is not one generally accepted operative approach. There is a very low-quality evidence of little or no difference in pain relief between each of the techniques. Iliac crest autograft still seems to be the "gold standard" for interbody fusion. METHODS.: Prospective study collecting clinical and radiological data of 81 patients undergoing anterior cervical interbody fusion, in which the interbody fusion of 1 or 2 motion segments from C3 to C7 was done by any of the 3 techniques--stand-alone insertion of autograft (group 1: 28 patients), autograft and anterior plate (group 2: 18 patients), and polyetheretherketone cage filled with beta-tricalcium phosphate and plate (group 3: 29 patients). Patients were followed for 2 years after surgery. RESULTS.: Significant interaction of relative height in the segment and time was found (P < 0.001). The values of the relative height of stand-alone autograft dropped below 95% of initial height and the values of the other 2 groups remained above 105%. Significant interaction of time and group was found for Cobb S angles (P < 0.001). Values of group 1 decreased substantially and remained significantly lower than values of other 2 groups. Fusion rate was 100% in all groups. Neck Disability Index group and time interaction was found (P = 0.023). During postoperative follow-up, group 1 scored in all controls higher than the other 2 groups, but differences were not significant. Visual analogue scale showed effect of time (P < 0.001). This was due to a smaller improvement of patients in group 1 during the whole follow-up in comparison with the other 2 groups. Highest proportion of unsatisfied patients was in group 1 compared with the other 2 groups after 2 years (P = 0.034). CONCLUSION.: Significantly worse radiological and clinical results after 2 years of follow-up were achieved using stand-alone autograft technique in comparison with autograft supported by anterior plating similarly as in comparison with cage implant and anterior plating. Using artificial fusion substrate together with plate and cage can offer the same clinical and radiological results such as iliac autograft and plating. Anterior plating seems to be an important factor influencing the postoperative cervical spine alignment and also the clinical outcome.     

Are two‐stage hepatectomies associated with more complications than one‐stage procedures?

BackgroundTwo-stage liver resections with portal vein occlusion have become standard in patients with low volume future liver remnants. Whether they are associated with more complications is unclear. The aim of this study was to compare complications of one- and two-stage resections in a retrospective study.MethodsPatients with two-stage right liver resections with a previous portal vein occlusion were compared with patients with one-stage right liver resections between 2002 and 2010. Primary endpoints were the incidence of complications by severity. Secondary endpoints were mortality, post-operative liver- and kidney function tests, length of hospitalization and transfusion events. Logistic and linear regression analyses were performed to adjust for confounders.ResultsThe groups were comparable except for right trisectionectomies, pre-operative chemotherapy and underlying liver disease. Overall complications occurred in 25 out of 35 patients with two-stage and 106 out of 163 in one-stage procedures. Severe complications were observed in 47 out of 163 patients versus 9 out of 35 patients, respectively. Two-stage procedures had no increased adjusted risk for complications [relative risk (RR) 0.9, P = 0.79]. Mortality (5.7% versus 3.7%) and post-operative liver failure rates (2.9% versus 3.1%) were low. Secondary endpoints showed no adjusted differences in risk.ConclusionThis study suggests that liver resections in two stages are not associated with more post-operative complications than one-stage resections. These results should support the adoption of two-stage liver resections in selected patients.     

Synergistic Effects of GDNF and VEGF on Lifespan and Disease Progression in a Familial ALS Rat Model

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by the progressive loss of motor neurons in the brain and spinal cord. We have recently shown that human mesenchymal stem cells (hMSCs) modified to release glial cell line-derived neurotrophic factor (GDNF) decrease disease progression in a rat model of ALS when delivered to skeletal muscle. In the current study, we determined whether or not this effect could be enhanced by delivering GDNF in concert with other trophic factors. hMSC engineered to secrete GDNF (hMSC-GDNF), vascular endothelial growth factor (hMSC-VEGF), insulin-like growth factor-I (hMSC-IGF-I), or brain-derived neurotrophic factor (hMSC-BDNF), were prepared and transplanted bilaterally into three muscle groups. hMSC-GDNF and hMSC-VEGF prolonged survival and slowed the loss of motor function, but hMSC-IGF-I and hMSC-BDNF did not have any effect. We then tested the efficacy of a combined ex vivo delivery of GDNF and VEGF in extending survival and protecting neuromuscular junctions (NMJs) and motor neurons. Interestingly, the combined delivery of these neurotrophic factors showed a strong synergistic effect. These studies further support ex vivo gene therapy approaches for ALS that target skeletal muscle.