Cycles Of Preconditioning Research Articles

In vitro skin puncture methodology for material characterization

Quantifying the mechanical behavior of skin has been foundational in applications of cosmetics, surgical techniques, forensic science, and protective clothing development. However, previous puncture studies have lacked consistent and physiological boundary conditions of skin. To determine natural skin tension, excision of in situ porcine skin resulted in significantly different diameter reduction (shrinkage) in leg (19.5 %) and abdominal skin (38.4 %) compared to flank skin (28.5 %) (p = 0.047). To examine effects of initial tension and pre-conditioning, five conditions of initial tension (as percentage of diameter increase) and pre-conditioning were tested in quasistatic puncture with a 5 mm spherical impactor using an electrohydraulic load frame and custom clamping apparatus. Samples with less than 5 % initial tension resulted in significantly greater (p = 0.011) force at failure (279.2 N) compared to samples with greater than 25 % initial tension (195.1 N). Eight pre-conditioning cycles of 15 mm displacement reduced hysteresis by 45 %. The coefficient of variance was substantially reduced for force, force normalized by cutis thickness, displacement, stiffness, and strain energy up to 46 %. Pre-conditioned samples at physiological initial tension (14–25 %) resulted in significantly greater (p = 0.03) normalized forces at failure (278.3 N/mm) compared to non-conditioned samples of the same initial tension (234.4 N/mm). Pre-conditioned samples with 14–25 % initial tension, representing physiological boundary conditions, resulted in the most appropriate failure thresholds with the least variation. For in vitro puncture studies, the magnitude of applied initial tension should be defined based on anatomical location, through a shrinkage experimentation, to match natural tension of skin. Characterizing the biological behavior and tolerances of skin may be utilized in finite element models to aid in protective clothing development and forensic science analyses.

Biomechanical Properties of Knee Medial Collateral Ligament Compared to Palmaris Longus for Ulnar Collateral Ligament Reconstruction

Ulnar collateral ligament reconstruction (UCLR) is frequently performed among injured overhead-throwing athletes. One of the most common graft choices when performing a UCLR is the ipsilateral palmaris longus tendon (PL). The purpose of this study was to investigate the material properties of aseptically processed cadaveric knee collateral ligaments (kMCL) as a potential graft source for UCLR and compare them to the gold standard PL autograft. Each PL and kMCL cadaveric sample was subjected to cyclic preconditioning, stress relaxation, and load-to-failure testing, and the mechanical properties were recorded. PL samples exhibited a greater average decrease in stress compared to the kMCL samples during the stress-relaxation test (p < 0.0001). PL samples also demonstrated a greater average Young’s modulus in the linear region of the stress–strain curve compared to the kMCL samples (p < 0.01). The average yield strain and maximum strain of kMCL samples were significantly greater than the PL, p = 0.03 and 0.02, respectively. Both graft materials had comparable maximum toughness and demonstrated a similar ability to deform plastically without rupture. The clinical significance of our result is that prepared knee medial collateral ligament allografts may provide a viable graft material for use in the reconstruction of elbow ligaments.

Traction mechanical characterization of porcine mitral valve annulus

The Mitral Annulus (MA) is an anisotropic, fibrous, flexible and dynamical structure. While MA dynamics are well documented, its passive mechanical properties remain poorly investigated to complete the design of adequate prostheses.Mechanical properties in traction on four sections of the MA (aortic, left, posterior and right segments) were assessed using a traction test system with a 30 N load cell and pulling jaws for sample fixation. Samples were submitted to a 1.5 N pre-load, 10 pre-conditioning cycles. Three strain rates were tested (5 %/min, 7 %/min and 13 %/min), the first two up to 10 % strain and the last until rupture. High-resolution diffusion-MRI provided microstructural mapping of fractional anisotropy and mean diffusion within muscle and collagen fibres.Ten MA from porcine hearts were excised resulting in 40 tested samples, out of which 28 were frozen prior to testing. Freezing samples significantly increased Young Moduli for all strain rates. No significant differences were found between Young Moduli at different strain rates (fresh samples 2.4 ± 1.1 MPa, 3.8 ± 2.2 MPa and 3.1 ± 1.8 MPa for increasing strain rates in fresh samples), while significant differences were found when comparing aortic with posterior and posterior with lateral (p < 0.012). Aortic segments deformed the most (24.1 ± 9.4 %) while lateral segments endured the highest stress (>0.3 MPa), corresponding to higher collagen fraction (0.46) and fractional anisotropy.Passive machinal properties differed between aortic and lateral segments of the MA. The process of freezing samples altered their mechanical properties. Underlying microstructural differences could be linked to changes in strain response.

Collagen V insufficiency in a mouse model for Ehlers Danlos-syndrome affects viscoelastic biomechanical properties explaining thin and brittle corneas

Ehlers–Danlos syndrome (EDS) is a genetic disease leading to abnormalities in mechanical properties of different tissues. Here we quantify corneal biomechanical properties in an adult classic EDS mouse model using two different measurement approaches suited for murine corneal mechanical characterization and relate differences to stromal structure using Second Harmonic Generation (SHG) microscopy. Quasi-static Optical Coherence Elastography (OCE) was conducted non-invasively during ambient pressure modulation by − 3 mmHg. 2D-extensometry measurements was conducted invasively consisting of a pre-conditioning cycle, a stress-relaxation test and a rupture test. In a total of 28 eyes from a Col5a1+/− mouse model and wild-type C57BL/6 littermates (wt), Col5a1+/− corneas were thinner when compared to wt, (125 ± 11 vs 148 ± 10 μm, respectively, p < 0.001). Short-term elastic modulus was significantly increased in OCE (506 ± 88 vs 430 ± 103 kPa, p = 0.023), and the same trend was observed in 2D-extensometry (30.7 ± 12.1 kPa vs 21.5 ± 5.7, p = 0.057). In contrast, in stress relaxation tests, Col5a1+/− corneas experienced a stronger relaxation (55% vs 50%, p = 0.01). SHG microscopy showed differences in forward and backward scattered signal indicating abnormal collagen fibrils in Col5a1+/− corneas. We propose that disturbed collagen fibril structure in Col5a1+/− corneas affects the viscoelastic properties. Results presented here support clinical findings, in which thin corneas with global ultrastructural alterations maintain a normal corneal shape.

Skin under Strain: From Epithelial Model Tissues to Adult Epithelia.

Formation of a barrier capable of protecting tissue from external damage, chemical factors, and pathogens is one of the main functions of the epidermis. Furthermore, upon development and during aging, mechanoprotective epidermal functions change dramatically. However, comparative studies between embryonic and adult skin in comparison to skin equivalents are still scarce which is especially due to the lack of appropriate measurement systems with sufficient accuracy and long-term tissue compatibility. Our studies fill this gap by developing a combined bioreactor and tensile testing machine for biomechanical analysis of living epithelia. Based on this tissue stretcher, our data clearly show that viscoelastic and plastic deformation behavior of embryonic and adult skin differ significantly. Tissue responses to static strain compared to cyclic strain also show a clear dependence on differentiation stage. Multilayered unkeratinized epidermis equivalents, on the other hand, respond very similar to mechanical stretch as adult tissue. This mechanical similarity is even more evident after a single cycle of mechanical preconditioning. Our studies therefore suggest that skin equivalents are well suited model systems to analyze cellular interactions of epidermal cells in natural tissues.

Biomechanical testing of fixed and adjustable femoral cortical suspension devices for ACL reconstruction under high loads and extended cyclic loading

PurposeTo compare loop elongation after 5000 cycles, loop-elongation at failure, and load at failure of the fixed-loop G-Lok device and three adjustable-loop devices (UltraButton, RigidLoop Adjustable and ProCinch RT), during testing over extended cycles under high loading.MethodsFive devices of each type were tested on a custom-built rig fixed to an Instron machine. The testing protocol had four stages: preloading, cyclic preconditioning, incremental cyclic loading and pull-to-failure. Outcome measures were loop elongation after 5000 cycles, loop-elongation at failure, and load at failure.ResultsThe loop elongation after 5000 cycles for G-Lok was 1.46 ± 0.25 mm, which was comparable to that of RigidLoop (1.51 ± 0.16 mm, p = 1.000) and ProCinch (1.60 ± 0.09 mm, p = 1.000). In comparison, the loop elongation for UltraButton was 2.66 ± 0.28 mm, which was significantly larger than all other devices (p = 0.048). The failure load for all devices ranged between 1455 and 2178 N. G-Lok was significantly stronger than all adjustable-loop devices (p = 0.048). The elongation at failure was largest for UltraButton (4.20 ± 0.33 mm), which was significantly greater than G-Lok (3.17 ± 0.33 mm, p = 0.048), RigidLoop (2.88 ± 0.20 mm, p = 0.048) and ProCinch (2.78 ± 0.08 mm, p = 0.048). There was no significant difference in elongation at failure for the rest of the devices.ConclusionsOur study has shown that the G-Lok fixed-loop device and the three adjustable-loop devices (UltraButton, RigidLoop Adjustable and ProCinch RT) all elongated less than 3 mm during testing over an extended number of cycles at high loads, nonetheless, the fixed loop device performed best in terms of least elongation and highest load at failure.

Mechanical Properties and Microstructural Collagen Alignment of the Ulnar Collateral Ligament During Dynamic Loading

Background: The ulnar collateral ligament (UCL) microstructural organization and collagen fiber realignment in response to load are unknown. Purpose/Hypothesis: The purpose was to describe the real-time microstructural collagen changes in the anterior bundle (AB) and posterior bundle (PB) of the UCL with tensile load. It was hypothesized that the UCL AB is stronger and stiffer with more highly aligned collagen during loading when compared with the UCL PB. Study Design: Descriptive laboratory study. Methods: The AB and PB from 34 fresh cadaveric specimens were longitudinally sectioned to allow uniform light passage for quantitative polarized light imaging. Specimens were secured to a tensile test machine and underwent cyclic preconditioning, a ramp-and-hold stress-relaxation test, and a quasi-static ramp to failure. A division-of-focal-plane polarization camera captured real-time pixelwise microstructural data of each sample during stress-relaxation and at the zero, transition, and linear points of the stress-strain curve. The SD of the angle of polarization determined the deviation of the average direction of collagen fibers in the tissue, while the average degree of linear polarization evaluated the strength of collagen alignment in those directions. Since the data were nonnormally distributed, the median ± interquartile range are presented. Results: The AB has larger elastic moduli than the PB (P < .0001) in the toe region (median, 2.73 MPa [interquartile range, 1.1-5.6 MPa] vs 0.65 MPa [0.44-1.5 MPa]) and the linear region (13.77 MPa [4.8-40.7 MPa] vs 1.96 MPa [0.58-9.3 MPa]). The AB demonstrated larger stress values, stronger collagen alignment, and more uniform collagen organization during stress-relaxation. PB collagen fibers were more disorganized than the AB during the zero (P = .046), transitional (P = .011), and linear (P = .007) regions of the stress-strain curve. Both UCL bundles exhibited very small changes in collagen alignment (SD of the angle of polarization) with load. Conclusion: The AB of the UCL is stiffer and stronger, with more strongly aligned and more uniformly oriented collagen fibers, than the PB. The small changes in collagen alignment indicate that the UCL response to load is due more to its static collagen organization than to dynamic changes in collagen alignment. Clinical Relevance: The UCL collagen organization may explain its susceptibility to injury with repetitive valgus loads.

Twist–coil coupling fibres for high stroke tensile artificial muscles

A new concept for tensile artificial muscles is introduced in which the torsional actuation of a twisted polymer fibre drives a twist to writhe conversion in a serially attached elastomeric fibre. Thermally induced torsional rotation of the twisted fibre caused formation of coils in the elastomeric fibre which resulted in overall muscle length contraction. Theoretical predictions of the muscle strain were developed by means of a modified single-helix theory. Experimental tests were conducted to measure the isotonic contraction strains for elastomeric fibres of different diameters and lengths. A good agreement between the measured and calculated results was found. Practical applicability of this muscle is evaluated by using different mechanical loading conditions. Actuation contraction strains as high as 10% were observed with excellent reversibility. Unlike original coiled fibre tensile actuators, these twist-coil artificial muscles did not require any pre-conditioning cycles.

Comparison of Direct and Remote Ischaemic Preconditioning of Renal Ischaemia Reperfusion Injury in Rats

One of the methods that can be used to prevent ischaemia reperfusion (IR) injury is ischaemic preconditioning. The aim of this study was to evaluate and compare the effects of remote and direct ischaemic preconditioning (RIPC and DIPC) histopathologically in the rat renal IR injury model. After obtaining an approval from the Dokuz Eylül University School of Medicine Ethics Committee, 28 Wistar Albino male rats were divided into four groups. In Group I (Sham, n=7), laparotomy and left renal pedicle dissection were performed, but nothing else was done. In Group II (IR, n=7), after 45 minutes of left renal pedicle occlusion, reperfusion lasting 4 hours was performed. In Group III (DIPC+IR, n=7), after four cycles of ischaemic preconditioning applied to the left kidney, renal IR was performed. In Group IV (RIPC+IR, n=7), after three cycles of ischaemic preconditioning applied to the left hind leg, renal IR was performed. All rats were sacrificed, and the left kidney was processed for conventional histopathology. The histopathological injury score of the kidney was significantly lower in the sham group compared with the other groups (p<0.01). The injury scores of the DIPC+IR and RIPC+IR groups were significantly lower than in the IR group (p<0.05). In the RIPC+IR group, the injury score for erythrocyte extravasation was found to be significantly lower than in the DIPC+IR group (p<0.05). In the present study, it was demonstrated that both DIPC and RIPC decreased renal IR injury, but RIPC was found to be more effective than DIPC. This protective effect requiresfurther detailed experimental and clinical studies.

Acute Hemodynamic Effects of Remote Ischemic Preconditioning on Coronary Perfusion Pressure and Coronary Collateral Blood Flow in Coronary Heart Disease.

The aim of this study was to assess the acute hemodynamic effects of remote ischemic preconditioning (RIPC) on coronary perfusion pressure and coronary collateral blood flow. A total of 17 patients with coronary heart disease with severe (70%-85%) stenosis in one or two vessels confirmed by angiography were enrolled into this study. They were randomly divided into the RIPC group (9 patients) and the control group (8 patients). Distal pressure of coronary artery stenosis before balloon dilation (non-occlusive pressure, Pn-occl) and distal coronary artery occlusive pressure (Poccl) during balloon dilation occlusion were measured in all patients. The patients in the RIPC group received three cycles of lower limb ischemia-reperfusion preconditioning (5 minutes inflation of a blood pressure cuff, followed by 5 minutes reperfusion). For controls, the cuff was not inflated. After this process, Pn-occl and Poccl were measured again in each patient. There were no significant differences in angiographic characteristics between the two groups (all p > 0.05). Troponin I (TNI) levels after percutaneous coronary intervention (PCI) were lower in the RIPC group than in the control group (p = 0.004). In the RIPC group, mean Pn-occl and Poccl were significantly increased after RIPC compared to before RIPC [(72.78 ± 10.10) mmHg vs. (79.67 ± 9.79) mmHg, p = 0.002, (20.89 ± 8.61) mmHg vs. (26.78 ± 10.73) mmHg, p = 0.001, respectively]. RIPC can improve distal coronary perfusion pressure and rapidly increase distal coronary occlusive pressure thereby improving coronary collateral blood flow.

Anterolateral ligament reconstruction with autologous grafting: A biomechanical study

BackgroundTo evaluate the reliability of the Iliotibial band compared to gracilis tendon as a graft to be used in anterolateral ligament reconstruction. MethodsGracilis tendon and a strip of Iliotibial band compared were harvested from 8 fresh human cadaveric knees. The gracilis tendon was prepared to obtain a graft of 10cm in length (Group 1). Iliotibial band compared was prepared to obtain a graft of 10cm in length and 0.5cm in width from the middle portion (Group 2). All the specimens were fixed on a servo hydraulic tensile machine with dedicated cryo-clamp. The loading protocol, used to compare the previously published results of ultimate failure load and Stiffness of the anterolateral ligament (Group 3), included a cyclic preconditioning between 10 and 25N at 0.1Hz for 10cycles and then a load to failure test at 20mm/min. FindingsGracilis tendon showed higher Ultimante Failure Load and stiffness when compared to a strip of Iliotibial band.Gracilis tendon and a strip of Iliotibial band compared showed higher Ultimante Failure Load and stiffness when compared with native anterolateral ligament as reported by Kennedy. InterpretationBoth grafts tested in the present studies are suitable for an anatomical anterolateral ligament reconstruction.

Protective effects of dexmedetomidine and remote ischemic preconditioning on renal ischemia reperfusion injury in rats.

The aim of this study was to evaluate the effects of remote ischemic preconditioning (RIPC) and dexmedetomidine as pharmacological conditioning in a rat renal ischemia/reperfusion (IR) injury model. Total of 28 male Wistar Albino rats weighing 250 to 300 g were divided into 4 equal groups. Group I (Sham; n=7): Laparotomy and renal pedicle dissection were performed, and the rats were observed under anesthesia without any intervention. Group II (IR; n=7): Following laparotomy and 45 minutes of left renal pedicle occlusion, 4 hours of reperfusion was performed. Group III (IR+D; n=7): Following laparotomy and ischemia, dexmedetomidine was administrated intraperitoneally (100 µg/kg) at fifth minute of reperfusion. Group IV (RIPC+IR; n=7): Under anesthesia, 3 cycles of ischemic preconditioning were applied to the left hind leg, and after 5 minutes, renal IR was performed. All rats were sacrificed after the left kidney was processed for conventional histomorphology. Total histomorphological renal injury score was significantly lower in the Sham group compared with the other groups (p<0.01). Total renal injury score of IR group was significantly higher than IR+D and RIPC+IR groups (p<0.01). There was no significant difference in the total renal injury score between the dexmedetomidine and RIPC groups (p=0.89). In the present study, it was demonstrated histomorphologically that both dexmedetomidine and RIPC decreased renal IR injury significantly. In addition, no significant difference was found between dexmedetomidine and RIPC groups.

Efectos de la dexmedetomidina en conjunto con el precondicionamiento isquémico remoto en la lesión de isquemia-reperfusión renal en ratones

Background and objectivesThe aim of this study was to evaluate the effects of remote ischemic preconditioning by brief ischemia of unilateral hind limb when combined with dexmedetomidine on renal ischemia-reperfusion injury by histopathology and active caspase-3 immunoreactivity in rats. Methods28 Wistar albino male rats were divided into 4 groups. Group I (Sham, n=7): laparotomy and renal pedicle dissection were performed at 65th minute of anesthesia and the rats were observed under anesthesia for 130min. Group II (ischemia-reperfusion, n=7): at 65th minute of anesthesia bilateral renal pedicles were clamped. After 60min ischemia 24h of reperfusion was performed. Group III (ischemia-reperfusion+dexmedetomidine, n=7): at the fifth minute of reperfusion (100μg/kg intra-peritoneal) dexmedetomidine was administered with ischemia-reperfusion group; reperfusion lasted 24h. Group IV (ischemia-reperfusion+remote ischemic preconditioning+dexmedetomidine, n=7): after laparotomy, three cycles of ischemic preconditioning (10min ischemia and 10min reperfusion) were applied to the left hind limb and after 5min with group iii. ResultsHistopathological injury scores and active caspase-3 immunoreactivity were significantly lower in the Sham group compared to the other groups. Histopathological injury scores in groups iii and iv were significantly lower than group ii (P=.03 and P=.05). Active caspase-3 immunoreactivity was significantly lower in the group iv than group ii (P=.01) and there was no significant difference between group ii and group iii (P=.06). ConclusionsPharmacologic conditioning with dexmedetomidine and remote ischemic preconditioning when combined with dexmedetomidine significantly decreases renal ischemia-reperfusion injury histomorphologically. Combined use of two methods prevents apoptosis via active caspase-3.

Efeitos de dexmedetomidina em conjunto com o pré‐condicionamento isquêmico remoto em lesão de isquemia‐reperfusão renal em ratos

Background and objectivesThe aim of this study was to evaluate the effects of remote ischemic preconditioning by brief ischemia of unilateral hind limb when combined with dexmedetomidine on renal ischemia–reperfusion injury by histopathology and active caspase‐3 immunoreactivity in rats. Methods28 Wistar albino male rats were divided into 4 groups. Group I (Sham, n=7): Laparotomy and renal pedicle dissection were performed at 65th minute of anesthesia and the rats were observed under anesthesia for 130min. Group II (ischemia–reperfusion, n=7): At 65th minute of anesthesia bilateral renal pedicles were clamped. After 60min ischemia 24h of reperfusion was performed. Group III (ischemia–reperfusion+dexmedetomidine, n=7): At the fifth minute of reperfusion (100μg/kg intra‐peritoneal) dexmedetomidine was administered with ischemia–reperfusion group. Reperfusion lasted 24h. Group IV (ischemia–reperfusion+remote ischemic preconditioning+dexmedetomidine, n=7): After laparotomy, three cycles of ischemic preconditioning (10min ischemia and 10min reperfusion) were applied to the left hind limb and after 5min with group III. ResultsHistopathological injury scores and active caspase‐3 immunoreactivity were significantly lower in the Sham group compared to the other groups. Histopathological injury scores in groups III and IV were significantly lower than group II (p=0.03 and p=0.05). Active caspase‐3 immunoreactivity was significantly lower in the group IV than group II (p=0.01) and there was no significant difference between group II and group III (p=0.06). ConclusionsPharmacologic conditioning with dexmedetomidine and remote ischemic preconditioning when combined with dexmedetomidine significantly decreases renal ischemia–reperfusion injury histomorphologically. Combined use of two methods prevents apoptosis via active caspase‐3.

ACL double bundle linked cortical-aperture tibial fixation: a technical note.

The purpose of this technical note is to describe the tibial fixation characteristics for an all-inside anatomic anterior cruciate ligament (ACL) reconstruction method that links extra-cortical button suspensory and aperture fixation replicating double bundle soft tissue graft function in single femoral and tibial sockets. A 55° drill guide aligned guidewires in the ACL footprint center of 8 porcine tibiae (mean apparent bone mineral density = 1.15 g/cm(2)). A Flipcutter created 27 mm sockets and 15 mm guidewire channels. Advancement sutures seated porcine soft tissue graft-PEEK implants to achieve both socket aperture and extra-cortical button suspensory fixation. Potted specimens were loaded into a 6º of freedom clamp with the servohydraulic loading vector in direct socket alignment. Constructs were pre-loaded to 25 N, underwent 10 pre-conditioning cycles (0-50 N, 0.5 Hz), and 500 submaximal loading cycles (50-250 N, 1 Hz) prior to load to failure testing (20 mm/min). Mode of failure was recorded. Descriptive statistical analysis was performed. All specimens survived the biomechanical test protocol. Displacement during cyclic loading was 2.8 ± 0.9 mm, yield load was 475.2 ± 36 N, ultimate load at failure was 671.4 ± 98 N, stiffness was 127.5 ± 15 N/mm. The most common failure mode was suture pulling through the soft tissue graft. This ACL reconstruction method combines the high ultimate load to failure and low graft slippage of extra-cortical button suspensory fixation with the high stiffness of aperture fixation. Biomechanical test findings were comparable or better to previous reports for displacement during submaximal loading, ultimate failure load, and construct stiffness. Based on current understanding of soft tissue graft ACL reconstruction biomechanics, this fixation method should enhance graft-bone socket integration during healing, facilitate long-term graft survival, and improve patient outcomes. Clinical studies are needed to confirm in vivo efficacy.

Effects of dexmedetomidine in conjunction with remote ischemic preconditioning on renal ischemia–reperfusion injury in rats

Background and objectivesThe aim of this study was to evaluate the effects of remote ischemic preconditioning by brief ischemia of unilateral hind limb when combined with dexmedetomidine on renal ischemia–reperfusion injury by histopathology and active caspase-3 immunoreactivity in rats. Methods28 Wistar albino male rats were divided into 4 groups. Group I (Sham, n=7): Laparotomy and renal pedicle dissection were performed at 65th minute of anesthesia and the rats were observed under anesthesia for 130min. Group II (ischemia–reperfusion, n=7): At 65th minute of anesthesia bilateral renal pedicles were clamped. After 60min ischemia 24h of reperfusion was performed. Group III (ischemia–reperfusion+dexmedetomidine, n=7): At the fifth minute of reperfusion (100μg/kg intra-peritoneal) dexmedetomidine was administered with ischemia–reperfusion group. Reperfusion lasted 24h. Group IV (ischemia–reperfusion+remote ischemic preconditioning+dexmedetomidine, n=7): After laparotomy, three cycles of ischemic preconditioning (10min ischemia and 10min reperfusion) were applied to the left hind limb and after 5min with group III. ResultsHistopathological injury scores and active caspase-3 immunoreactivity were significantly lower in the Sham group compared to the other groups. Histopathological injury scores in groups III and IV were significantly lower than group II (p=0.03 and p=0.05). Active caspase-3 immunoreactivity was significantly lower in the group IV than group II (p=0.01) and there was no significant difference between group II and group III (p=0.06). ConclusionsPharmacologic conditioning with dexmedetomidine and remote ischemic preconditioning when combined with dexmedetomidine significantly decreases renal ischemia–reperfusion injury histomorphologically. Combined use of two methods prevents apoptosis via active caspase-3.

Trimethylaluminum-based Atomic Layer Deposition of MO2 (M=Zr, Hf): Gate Dielectrics on In0.53Ga0.47As(001) Substrates

As post-Si era for digital device is incipient, In0.53Ga0.47As is good candidate among n-type active channels with high electron mobility but - unlike Si - it lacks a well-established technology for dielectric gating which may bear aggressive device scaling. Here we propose a viable route for the atomic layer deposition (ALD) of high-κ dielectrics taking advantage from the well-known self-cleaning effect of the trimethylaluminum (TMA) precursor on the III-V compound surfaces. In this respect, the incorporation of Al2O3 cycles both as pre-conditioning surface treatment and inside the ALD growth of a MO2 host matrix (M=Zr, Hf) is here investigated. Al:MO2/In0.53Ga0.47As heterojunctions have been scrutinized by in situ spectroscopic ellipsometry and ex situ chemical depth-profiling analysis which validate a good physical quality of the oxide and elucidate the effect of the pre-conditioning cycles at the interface level. The resulting MOS capacitors have been characterized by means of multifrequency capacitance-voltage measurements and conductance analysis therein yielding a permittivity of 19{plus minus}1 both for Al:HfO2 and Al:ZrO2 and similar electrical quality of the interfaces. On the other hand, Al:HfO2 appears to be electrically more robust against leakage and endowed with a lower frequency dispersion in accumulation.

A Viable Route to Enhance Permittivity of Gate Dielectrics on In0.53Ga0.47As(001): Trimethylaluminum-Based Atomic Layer Deposition of MeO2 (Me = Zr, Hf)

For the incipient post-Si era of digital devices, III-V compounds are mature candidates among n-type active channels as technology booster to increase electron mobility, but – unlike Si – they lack a well-established technology for dielectric gating which may bear aggressive device scaling. Here we propose a viable route to grow gate dielectrics with high permittivity (high-κ) on In0.53Ga0.47As(001) substrates by means of atomic layer deposition (ALD) by taking advantage from the well-known clean-up effect of the trimethylaluminum (TMA) precursor on the III-V compound surfaces and from a permittivity enhancement due to transition metal doping. To this purpose, Al2O3 pre-conditioning cycles are performed to passivate the surface and Al2O3 cycles are intercalated during the ALD growth of MeO2 films (Me = Zr, Hf). The resulting Al:MeO2/In0.53Ga0.47As heterojunctions are investigated in their structural and compositional details by means of ex situ X-ray reflectivity and compositional depth profiling analysis. Metal-oxide-semiconductor capacitors incorporating the Al:MeO2/In0.53Ga0.47As heterojunctions result in a permittivity of 19 ± 1 and relatively satisfactory electrical quality of the interfaces compared to the Al2O3/InGaAs interface. Al:HfO2 appears to be electrically more robust against leakage and endowed with a lower density of traps causing frequency dispersion of the capacitance-voltage curves in accumulation.

Single-row Versus Double-row Repair of the Distal Achilles Tendon: A Biomechanical Comparison

Surgery for recalcitrant insertional Achilles tendinopathy often consists of partial or total release of the insertion site, debridement of the diseased portion of the tendon, calcaneal ostectomy, and reattachment of the Achilles to the calcaneus. Although single-row and double-row techniques exist for repair of the detached Achilles tendon, biomechanical data are lacking to support one technique over the other. Based on data extrapolated from the study of rotator cuff repairs, we hypothesized that a double-row construct would provide superior fixation strength over a single-row repair. Eighteen human cadaveric Achilles tendons (9 matched pairs) with attached calcanei were repaired with single-row or double-row techniques. Specimens were mounted in a servohydraulic materials testing machine, subjected to a preconditioning cycle, and loaded to failure. Failure was defined as suture breakage or pullout, midsubstance tendon rupture, or anchor pullout. Among the failures were 12 suture failures, 5 proximal-row anchor failures, and 1 distal-row anchor failure. No midsubstance tendon ruptures or testing apparatus failures were observed. There were no statistically significant differences in the peak load to failure between the single-row and double-row repairs (p = .46). Similarly, no significant differences were observed with regards to mean energy expenditure to failure (p = .069). The present study demonstrated no biomechanical advantages of the double-row repair over a single-row repair. Despite the lack of a clear biomechanical advantage, there may exist clinical advantages of a double-row repair, such as reduction in knot prominence and restoration of the Achilles footprint.

Comparative study of the cardioprotective effects of local and remote preconditioning in ischemia/reperfusion injury

AimsThough the cardioprotective effects of local or remote preconditioning have been estimated, it is still unclear which of them is more reliable and provides more cardioprotection. The present investigation was directed to compare, in one study, the cardioprotective effects of different cycles of local or remote preconditioning in ischemia/reperfusion (I/R)-induced electrophysiological, biochemical and histological changes in rats. Main methodsRats were randomly assigned into 10 groups. Groups 1 and 2 were normal and I/R groups, respectively. Other groups were subjected to 1, 2, 3, 4 cycles of local or remote preconditioning before myocardial I/R (40min/10min). Heart rate and ventricular arrhythmias were recorded during I/R progress. At the end of reperfusion, plasma creatine kinase-MB (CK-MB) activity and total nitrate/nitrite (NOx) were determined. In addition, lactate, adenine nucleotides, thiobarbituric acid reactive substances (TBARS), reduced glutathione (GSH) and myeloperoxidase (MPO) activity were estimated in the heart left ventricle. Histological examination was also performed to visualize the protective cellular effects of the effective cycle of local or remote preconditioning. Key findingsIn general, local preconditioning was more effective than remote preconditioning in reducing ventricular arrhythmias, CK-MB release, lactate accumulation and elevated MPO activity as well as preserving adenine nucleotides. Concerning the most effective group in each therapy, 3 cycles of local preconditioning provided more cardioprotection than that of remote preconditioning in the histological examination. SignificanceDespite being invasive, local preconditioning provided more effective cardioprotection than remote preconditioning in ameliorating the overall electrophysiological, biochemical and histological changes.