Novel ultrasound contrast agent based on microbubbles generated from surfactant mixtures of Span 60 and polyoxyethylene 40 stearate

In this study, novel perfluorocarbon-filled microbubbles as ultrasound contrast agent were fabricated using ultrasonication of a surfactant mixture of sorbitan monostearate (Span 60) and polyoxyethylene 40 stearate (PEG40S) in aqueous media. The microbubbles generated from a 1:9 mixture of PEG40S/Span 60 exhibited an average diameter of 2.08 ± 1.27 μm. More than 99% of the microbubbles had a mean particle diameter less than 8 μm, indicating that they were appropriately sized for intravenous administration as ultrasound contrast agent. The stabilization mechanism of the microbubbles was investigated by the Langmuir–Blodgett technique including the measurements of surface pressure–area (π–A) isotherms and compression–decompression cycles with a two-dimensional monolayer of Span 60 and PEG40S. The dependence on molar fraction of PEG40S in π–A isotherms of mixed monolayers provided a strong evidence of interactions between the two microbubble-forming materials. It is suggested that the monolayer shell imparts good stability to the microbubbles by three means: (1) a low surface tension monolayer hinders dissolution through the reduction of surface tension, which introduces a mechanical surface pressure that counters the Laplace pressure; (2) the presence of a monolayer shell imparts a significant barrier to gas escaping from the core into the aqueous medium; and (3) encapsulation elasticity stabilizes microbubbles against diffusion-driven dissolution and explains the long shelf-life of microbubble contrast agent. The preliminary in vivo ultrasound imaging study showed that such stabilized microbubbles demonstrated excellent enhancement under grey-scale pulse inversion harmonic imaging and power Doppler imaging.     

Microbubbles as biocompatible porogens for hydrogel scaffolds

In this study, we explored the application of lipid-shelled, gas-filled microbubbles as a method for creating on-demand microporous hydrogels for cartilage tissue engineering. The technique allowed for homogenous distribution of cells and micropores within the scaffold, increasing the absorption coefficient of large solutes (70 kDa dextran) over controls in a concentration-dependent manner. The stability of the gas phase of the microbubbles depended on several factors, including the initial size distribution of the microbubble suspension, as well as the temperature and pressure during culture. Application of pressure cycles provided controlled release of the gas phase to generate fluid-filled micropores with remnant lipid. The resulting microporous agarose scaffolds were biocompatible, leading to a twofold increase in engineered cartilage properties (E_Y = 492 ± 42 kPa for the bubble group vs. 249 ± 49 kPa for the bubble-free control group) over a 42-day culture period. Our results suggest that microbubbles offer a simple and robust method of modulating mass transfer in cell-seeded hydrogels through mild pressurization, and the methodology may be expanded in the future to include focused ultrasound for improved spatio-temporal control.     

Superparamagnetic nanoparticle-inclusion microbubbles for ultrasound contrast agents

We have developed a new type of ultrasound (US) contrast agent, consisting of a gas core, a layer of superparamagnetic iron oxide Fe(3)O(4) nanoparticles (SPIO) and an oil in water outermost layer. The newly developed US contrast agent microbubbles have a mean diameter of 760 nm with a polydisperity index (PI) of 0.699. Our in vitro and in vivo experiments have shown that they have the following advantages compared to gas-encapsulated microbbubbles without SPIO inclusion: (1) they provide better contrast for US images; (2) the SPIO-inclusion microbubbles generate a higher backscattering signal; the mean grey scale is 97.9, which is 38.6 higher than that of microbubbles without SPIO; and (3) since SPIO can also serve as a contrast agent of magnetic resonance images (MRI) in vitro, they can be potentially used as contrast agents for double-modality (MRI and US) clinical studies.     

Aggravation of left ventricular dysfunction in patients with biopsy-proven cardiac human herpesvirus A and B infection

BackgroundHuman herpesvirus 6 (HHV-6) A and B are lymphotropic viruses with life-long persistence, primarily associated with non-cardiac diseases, and discussed as a possible etiologic factor of myocarditis and cardiomyopathy.ObjectiveTo analyze the long-term spontaneous course of cardiac patients suffering from suspected inflammatory cardiomyopathy (CMi) with persisting HHV-6 A and B infections by follow-up biopsies.Study designWe prospectively evaluated patients (n = 73) with biopsy-proven viral HHV-6 A and B infection in endomyocardial biopsies (EMBs), followed up by reanalysis of EMBs and left ventricular ejection fraction (LV-EF) measurements after a median period of 8.8 months (range 4–73 months). Beyond, we studied HHV-6 prevalence in isolated peripheral blood cells (PBCs) and HHV-6 species in EMBs. HHV-6 species-specific cellular infection sites within the myocardium were identified by immunohistochemistry (IHC).ResultsWe identified 73 patients with cardiac HHV-6 A and B persistence or newly detected in follow-up EMB (95.0% B). Proof of HHV-6 in PBCs was primarily associated with A. Persistence of cardiac HHV-6 B genome was significantly associated with cardiac dysfunction at follow-up (LV-EF deteriorated from 58.2 ± 16.0 to 51.8 ± 17.2%, p < 0.001), and LV improvement was observed when HHV-6 B persistence resolved (LV-EF increased from 54.9 ± 15.4 to 60.7 ± 13.1%, p < 0.001).ConclusionsPersistence of cardiac HHV-6 B genomes was significantly associated with cardiac dysfunction, and hemodynamic parameters improved in association with HHV-6 B clearance.     

Shape memory polymer foams for cerebral aneurysm reparation: Effects of plasma sterilization on physical properties and cytocompatibility

Shape memory polyurethanes (SMPUs) represent promising candidate materials for aneurysm embolization, since they could enable clinical problems still associated with these clinical procedures to be overcome. In this work, we report on the characterization of physicochemical, thermomechanical and in vitro interface properties of two SMPU foams (Cold Hibernated Elastic Memory, CHEM), proposed as a material for embolization devices in minimally invasive procedures. Moreover, because device sterilization is mandatory for in vivo applications, effects on the properties of the foams after plasma sterilization were also evaluated. Both foams (CHEM 3520 and CHEM 5520) showed excellent shape recovery ability (recovery rate, R_r, up to 99%) in conventional shape recovery tests, performed at constant heating rate. Transition temperatures (T_trans), determined by tan δ peaks in dynamic mechanical analysis (DMA), were 32.2 and 45.1 °C, for CHEM 3520 and 5520, respectively. The value of T_trans affects shape memory ability in the recovery test at 37 °C, which simulates the behavior after implantation of the device: in fact, R_r was significantly higher for lower T_trans foam (R_r ≈ 82% and R_r ≈ 46%, respectively, for CHEM 3520 and CHEM 5520). After plasma sterilization performed by a Sterrad^® sterilization system, an increase in open porosity was observed: this is probably due to the sterilization cycle; however, no effects on shape recovery behavior were observed. Furthermore, plasma treatment had no significant effect on L929 cells in in vitro cytotoxicity tests, performed on cell culture medium extracts in contact with foams for up to 7 days. Moreover, direct cytocompatibility tests showed a good colonization and growth from L929 cells on CHEM foams, suggesting the effectiveness of an in vivo healing process. All these results seem to suggest that CHEM foams could be advantageously used for manufacturing devices for mini-invasive embolization procedures of aneurysms.     

Role of Left Atrial Reservoir Strain Rate in Left Atrial Remodeling in Severe Mitral Regurgitation

Background

Impaired left atrial (LA) reservoir deformation has been found to be associated with poor functional capacity and outcomes in severe chronic mitral regurgitation (MR). Among patients with primary MR (valve incompetence due to mitral valve pathology), we focus on Carpentier II classification (prolapse or flail mitral valve) and aim to investigate determinants for decreased LA reservoir deformation and its impact on LA remodeling in severe MR.

Theranostic Gd(III)-lipid microbubbles for MRI-guided focused ultrasound surgery

We have synthesized a biomaterial consisting of Gd(III) ions chelated to lipid-coated, size-selected microbubbles for utility in both magnetic resonance and ultrasound imaging. The macrocyclic ligand DOTA-NHS was bound to PE headgroups on the lipid shell of pre-synthesized microbubbles. Gd(III) was then chelated to DOTA on the microbubble shell. The reaction temperature was optimized to increase the rate of Gd(III) chelation while maintaining microbubble stability. ICP-OES analysis of the microbubbles determined a surface density of 7.5 × 10⁵ ± 3.0 × 10⁵ Gd(III)/μm² after chelation at 50 °C. The Gd(III)-bound microbubbles were found to be echogenic in vivo during high-frequency ultrasound imaging of the mouse kidney. The Gd(III)-bound microbubbles also were characterized by magnetic resonance imaging (MRI) at 9.4 T by a spin-echo technique and, surprisingly, both the longitudinal and transverse proton relaxation rates were found to be roughly equal to that of no-Gd(III) control microbubbles and saline. However, the relaxation rates increased significantly, and in a dose-dependent manner, after sonication was used to fragment the Gd(III)-bound microbubbles into non-gas-containing lipid bilayer remnants. The longitudinal (r₁) and transverse (r₂) molar relaxivities were 4.0 ± 0.4 and 120 ± 18 mM⁻¹s⁻¹, respectively, based on Gd(III) content. The Gd(III)-bound microbubbles may find application in the measurement of cavitation events during MRI-guided focused ultrasound therapy and to track the biodistribution of shell remnants.     

Predicting bulk mechanical properties of cellularized collagen gels using multiphoton microscopy

Cellularized collagen gels are a common model in tissue engineering, but the relationship between the microstructure and bulk mechanical properties is only partially understood. Multiphoton microscopy (MPM) is an ideal non-invasive tool for examining collagen microstructure, cellularity and crosslink content in these gels. In order to identify robust image parameters that characterize microstructural determinants of the bulk elastic modulus, we performed serial MPM and mechanical tests on acellular and cellularized (normal human lung fibroblasts) collagen hydrogels, before and after glutaraldehyde crosslinking. Following gel contraction over 16 days, cellularized collagen gel content approached that of native connective tissues (～200 mg ml^–1). Young’s modulus (E) measurements from acellular collagen gels (range 0.5–12 kPa) exhibited a power-law concentration dependence (range 3–9 mg ml^–1) with exponents from 2.1 to 2.2, similar to other semiflexible biopolymer networks such as fibrin and actin. In contrast, cellularized collagen gel stiffness (range 0.5–27 kPa) produced concentration-dependent exponents of 0.7 uncrosslinked and 1.1 crosslinked (range ～5–200 mg ml^–1). The variation in E of cellularized collagen hydrogels can be explained by a power-law dependence on robust image parameters: either the second harmonic generation (SHG) and two-photon fluorescence (TPF) (matrix component) skewness (R² = 0.75, exponents of -1.0 and -0.6, respectively); or alternatively the SHG and TPF (matrix component) speckle contrast (R² = 0.83, exponents of ?0.7 and ?1.8, respectively). Image parameters based on the cellular component of TPF signal did not improve the fits. The concentration dependence of E suggests enhanced stress relaxation in cellularized vs. acellular gels. SHG and TPF image skewness and speckle contrast from cellularized collagen gels can predict E by capturing mechanically relevant information on collagen fiber, cell and crosslink density.     

Assessment of cortical bone elasticity and strength: Mechanical testing and ultrasound provide complementary data

Cortical bone is a compact tissue with anisotropic macroscopic mechanical properties determined by a microstructure and the quality of a mineralised collagen matrix. Anisotropic elastic properties and strength are usually measured on different groups of sample which can hardly be pooled; as a consequence little is known on the relationships between strength and elasticity in the different anatomical directions. A method is presented to measure on a same cortical bone sample: (1) Young's modulus and strength (σ_max) in the longitudinal direction; (2) stiffness (C₁₁) in the transverse direction. Longitudinal and transverse direction are taken along and perpendicular to the diaphysis axis, respectively. Ultrasonic techniques yield Young's modulus (E_a) and C₁₁; three-point bending tests yield Young's modulus (E) and σ_max. The relationships between strength, elasticity and density and their anatomical distributions were investigated for 36 human femur samples. (i) A marginal negative correlation was obtained for E_a and C₁₁ (R = ?0.21; p = 0.08); (ii) σ_max was significantly correlated to E and E_a (R ～ 0.5; p < 0.005) but not to C₁₁ (p > 0.2); (iii) density was not correlated with E and moderately with strength (R = 0.38; p < 0.3). Small density variability (±30 kg m^?3) may partly explain the results. The techniques presented are suited to a systematic characterization of bone samples.     

Anterior cruciate ligament fixation: Is radial force a predictor of the pullout strength of soft-tissue interference devices?

BackgroundIn anterior cruciate ligament (ACL) reconstruction, an interference device achieves soft-tissue graft fixation by radially compressing the graft against the bone.PurposeThe objective of this study was to measure the radial force generated by different interference devices and evaluate the effect of this radial force on the pullout strength of graft-device constructs.Study DesignControlled laboratory study.MethodsA resultant force (F_R) was used as a representative measure of the total radial force generated. Bovine tendons were fixated in either synthetic bone or porcine tibia using one of following devices: (1) RCI titanium screw, (2) PEEK screw, (3) IntraFix sheath-and-screw device, and (4) ExoShape sheath-and-insert device. F_R was measured while each device was inserted into synthetic bone mounted on a test machine (n = 5 for each device). In a subsequent test series, graft-device constructs were loaded to failure at 50 mm/min. The pullout strength was measured as the ultimate load before failure (n = 10 for each device).ResultsThe F_R values generated during insertion into synthetic bone were 777 ± 86 N, 865 ± 140 N, 1313 ±198 N, and 1780 ± 255 N for the RCI screw, PEEK screw, IntraFix, and ExoShape, respectively. The pullout strengths in synthetic bone for the RCI screw, PEEK screw, IntraFix and ExoShape were 883 ± 125 N, 716 ± 249 N, 1147 ± 142 N, and 1233 ± 190 N, respectively.ConclusionsThese results suggest that the F_R generated during interference fixation affects the pullout strength with sheath-based devices providing superior F_R compared with interference screws. The use of synthetic bone was validated by comparing the pullout strengths to those when tested in porcine tibia.Clinical relevanceThese results could be valuable to a surgeon when determining the best fixation device to use in the clinical setting.     

A novel microbubble construct for intracardiac or intravascular MR manometry: a theoretical study

It has been demonstrated that gas-filled microbubble contrast agents, based on their volume changes, can serve as pressure probes in an MR field. It was recently reported that such an MR-based pressure measurement with microbubbles at 1.5 T must make use of microbubbles that have a volumetric magnetic susceptibility difference with the blood of at least 34 ppm in SI units. In this work, we show through analytical approximations and numerical simulations that such a microbubble formulation can be achieved by coating typical lipid-shelled microbubbles with particles of high dipole moment. Through finite-element simulations we demonstrate that the effective volumetric magnetic susceptibility of a coated microbubble is dependent on the radius, the shell volume fraction and the magnetic susceptibility of the particulates on the shell. Our calculations suggest that a suitable microbubble formulation which will be MR-sensitive to small pressure changes at 1.5 T must be 2-3 microm in radius and be uniformly coated with single-domain magnetic nanoparticles, such as magnetite, at shell volume fractions below 5%.     

Arsenic trioxide is an immune adjuvant in liver cancer treatment

Tumor cells are inhibited effectively by As₂O₃ in vitro and in vivo, although the underlying immune regulatory mechanisms remain unknown. Regulatory T cells play a key role in tumor immune escape. In the present study, we aimed to assess the in vivo effects of As₂O₃ on the immune status in hepatic cancer and its in vitro regulatory role in cytokine-induced killers(CIKs)cytotoxicity. In a tumor H22 xenograft model of hepatic cancer, we demonstrated that As₂O₃ treatment decreased tumor volumes and weights, and improved survival by reducing Tregs infiltration into the tumor. Moreover, our data indicated that the exact immune regulatory mechanism of As₂O₃ might involve elevated CD3 + T lymphocyte amounts more than reduced Tregs levels. Furthermore, As₂O₃ significantly improved CIKs cytotoxicity in vitro by decreasing CD4 + T lymphocytes and Tregs, and increasing CD8 + T lymphocytes. Our results suggested that As₂O₃ might act as an immune adjuvant in liver carcinoma treatment by increasing T lymphocytes and decreasing Treg infiltrated into the tumor.     

Impact of immediate and delayed light activation on self-polymerization of dual-cured dental resin luting agents

This study investigated the impact of immediate and delayed light activation on self-polymerization of a model dual-cured luting agent. The material presented the following components: base paste – 2,2-bis[4-(2-hydroxy-3-methacryloxyprop-1-oxy)phenyl]propane/triethylene glycol dimethacrylate (TEGDMA), camphorquinone, dimethyl-p-toluidine, butylated hydroxytoluene (BHT), glass fillers; catalyst paste – bisphenol-A ethoxylated dimethacrylate/TEGDMA, benzoyl peroxide, BHT, fillers. The pastes were mixed and seven polymerization scenarios tested: immediate light activation using low (5 J cm^?2) or high (20 J cm^?2) energy dose; delayed light activation (after 2 min – short delay) using low or high dose; delayed light activation (after 10 min – long delay) using low or high dose; and self-polymerization only. The degree of conversion (DC) and rate of polymerization (R_p) were evaluated for 30 min by real-time infrared spectroscopy. The lowest DC was detected for the self-polymerized and immediate–low dose groups, whereas the immediate–high dose and short delay–high dose groups showed the highest values. For the self-polymerized and immediate–high dose samples, R_p^max was detected after approximately 7 s, whereas this took approximately 14 s for the immediate–low dose group. R_p^max for the immediate–high dose group was higher than for the self-polymerized sample, which in turn was higher than for the immediate–low dose group. R_p^max for the short delay groups was higher than for the long delay groups. In conclusion, the extent of self-polymerization was influenced by the light dose reaching the material, which was dependent on high radiant exposure for optimal polymerization and the moment at which the light was applied; the short delay increased the DC for lower doses, while also generally decreasing the R_p for all scenarios.     

Association between KIR gene polymorphisms and rheumatoid arthritis susceptibility: A meta-analysis

ObjectivesThe results of studies on association between KIR (killer cell immunoglobulin-like receptors) polymorphisms and susceptibility to RA (rheumatoid arthritis) are inconsistent. To comprehensively evaluate the effect of KIR polymorphisms on the risk of RA, a meta-analysis was carried out.MethodsThe Web of Science, PubMed, the Chinese Biomedical Database (CBM) and Chinese National Knowledge Infrastructure (CNKI) databases were systematically searched to select studies on the association between KIR polymorphisms and RA. The odds ratio (OR) with 95% confidence interval (95%CI) was obtained.ResultsNine qualified case–control studies were included in this meta-analysis. The results showed there were two positive associations of 2DL1, 2DS1 (OR_2DL1 = 2.20, 95%CI = 1.20–4.01, P_raw = 0.01, P_FDR = 0.03; OR_2DS1 = 1.84, 95%CI = 1.19–2.85, P_raw = 0.006, P_FDR = 0.018) and one negative association of 2DL3 (OR_2DL3 = 0.42, 95%CI = 0.22–0.79, P_raw = 0.006, P_FDR = 0.018) with susceptibility to RA in East Asians, but not in Caucasians.ConclusionThe current meta-analysis provides evidence that 2DL3 might be a potential protective factor and 2DL1, 2DS1 might be risk factors for RA in East Asians but not in Caucasians.     

Association study of rs924080 and rs11209032 polymorphisms of IL23R-IL12RB2 in a Northern Chinese Han population with Behcet’s disease

ObjectivesTwo genome-wide association studies (GWAS) have identified the IL-23 receptor- IL-12 receptor β2 (IL23R-IL12RB2) as the susceptibility genetic region in Turkish and Japanese population with Behçet’s disease (BD). We investigated the association of this region with BD in a Northern Chinese Han population.MethodsA total of 407 patients with BD and 421 healthy controls were genotyped for single nucleotide polymorphisms (SNPs) rs924080 and rs11209032 using the Sequenom MassArray system.ResultsStatistically significant associations with BD were detected at two SNPs namely, rs924080 and rs11209032, both, by allele analysis (OR = 1.58, 95% CI = 1.25–2.00, P_c = 2.52 × 10⁻⁴, and OR = 1.45, 95% CI = 1.19–1.76, P_c = 3.46 × 10⁻⁴, respectively), and genotype analysis (P_c = 1.22 × 10⁻³ and P_c = 1.77 × 10⁻³, respectively). Significant differences were observed in the genotype frequency distribution for these SNPs under the additive, dominant and recessive models (all P_c < 0.05). The haplotypes (AT and GC) formed by the two SNPs were associated with BD (all permutation P < 0.05). A meta-analysis also appeared to support the association of the two SNPs with BD.ConclusionSNPs (rs924080 and rs11209032) of the IL23R-IL12RB2 region were found to be associated with BD in a Northern Chinese Han population.     

Definition of a simple statistical parameter for the quantification of orientation in two dimensions: Application to cells on grooves of nanometric depths

Contact guidance is generally evaluated by measuring the orientation angle of cells. However, statistical analyses are rarely performed on these parameters. Here we propose a statistical analysis based on a new parameter σ, the orientation parameter, defined as the dispersion of the distribution of orientation angles. This parameter can be used to obtain a truncated Gaussian distribution that models the distribution of the data between ?90° and +90°. We established a threshold value of the orientation parameter below which the data can be considered to be aligned within a 95% confidence interval. Applying our orientation parameter to cells on grooves and using a modelling approach, we established the relationship σ = α_meas + (52° ? α_meas)/(1 + C_GDER) where the parameter C_GDE represents the sensitivity of cells to groove depth, and R the groove depth. The values of C_GDE obtained allowed us to compare the contact guidance of human osteoprogenitor (HOP) cells across experiments involving different groove depths, times in culture and inoculation densities. We demonstrate that HOP cells are able to identify and respond to the presence of grooves 30, 100, 200 and 500 nm deep and that the deeper the grooves, the higher the cell orientation. The evolution of the sensitivity (C_GDE) with culture time is roughly sigmoidal with an asymptote, which is a function of inoculation density. The σ parameter defined here is a universal parameter that can be applied to all orientation measurements and does not require a mathematical background or knowledge of directional statistics.     

A critical analysis of whole body bioimpedance spectroscopy (BIS) for the estimation of body compartments in health and disease

Aim of the study was to assess the accuracy and precision of a BIS device and the relative contribution of BIS beyond the anthropometric parameters. The output of the Impedimed device (SFB7) and the relative contribution of height, weight, age, sex and resistance values at zero and infinite frequency (R_zero and R_inf respectively) to the prediction of total body water (TBW_d, deuterium space), of extracellular fluid (ECF_br, sodium bromide space) and of fat mass (FM_DXA) were assessed in 116 subjects (32 healthy subjects and 84 patients with disorders of body composition). Using a repeated randomization procedure, new equations for TBW, ECF and FM were derived.The SFB7 gave measures of determination similar to those obtained with equations that included only anthropometric data. The SFB7, but not the newly derived regression equations, underestimated TBW and ECF by 3.82 ± 3.37 (mean ± SD) and by 0.93 ± 2.62 l and overestimated FM by 6.55 ± 3.86 kg. Nine of 16 patients with ECF overload as detected by ECF_br were also detected by BIS. BIS measurements contribute marginally but not significantly beyond anthropometric data to the prediction of TBW, ECF and FM, either in healthy subjects or in patients with disturbed body composition.     

Micro-CT evaluation of bone defects: Applications to osteolytic bone metastases,bone cysts,and fracture

Bone defects can occur in various forms and present challenges to performing a standard micro-CT evaluation of bone quality because most measures are suited to homogeneous structures rather than ones with spatially focal abnormalities. Such defects are commonly associated with pain and fragility. Research involving bone defects requires quantitative approaches to be developed if micro-CT is to be employed. In this study, we demonstrate that measures of inter-microarchitectural bone spacing are sensitive to the presence of focal defects in the proximal tibia of two distinctly different mouse models: a burr-hole model for fracture healing research, and a model of osteolytic bone metastases. In these models, the cortical and trabecular bone compartments were both affected by the defect and were, therefore, evaluated as a single unit to avoid splitting the defects into multiple analysis regions. The burr-hole defect increased mean spacing (Sp) by 27.6%, spacing standard deviation (SpSD) by 113%, and maximum spacing (Sp_max) by 72.8%. Regression modeling revealed SpSD (β = 0.974, p < 0.0001) to be a significant predictor of the defect volume (R² = 0.949) and Sp_max (β = 0.712, p < 0.0001) and SpSD (β = 0.271, p = 0.022) to be significant predictors of the defect diameter (R² = 0.954). In the mice with osteolytic bone metastases, spacing parameters followed similar patterns of change as reflected by other imaging technologies, specifically bioluminescence data which is indicative of tumor burden. These data highlight the sensitivity of spacing measurements to bone architectural abnormalities from 3D micro-CT data and provide a tool for quantitative evaluation of defects within a bone.     

Continuous monitoring of electromyography (EMG), mechanomyography (MMG), sonomyography (SMG) and torque output during ramp and step isometric contractions

In this study we simultaneously collected ultrasound images, EMG, MMG from the rectus femoris (RF) muscle and torque signal from the leg extensor muscle group of nine male subjects (mean ± SD, age = 30.7 ± .4.9 years; body weight = 67.0 ± 8.4 kg; height = 170.4 ± 6.9 cm) during step, ramp increasing, and decreasing at three different rates (50%, 25% and 17% MVC/s). The muscle architectural parameters extracted from ultrasound imaging, which reflect muscle contractions, were defined as sonomyography (SMG) in this study. The cross-sectional area (CSA) and aspect ratio between muscle width and thickness (width/thickness) were extracted from ultrasound images. The results showed that the CSA of RF muscles decreased by 7.25 ± 4.07% when muscle torque output changed from 0% to 90% MVC, and the aspect ratio decreased by 41.66 ± 7.96%. The muscle contraction level and SMG data were strongly correlated (R² = 0.961, P = 0.003, for CSA and R² = 0.999, P < 0.001, for width/thickness ratio). The data indicated a significant difference (P < 0.05) in percentage changes for CSA and aspect ratio among step, ramp increasing, and decreasing contractions. The normalized EMG RMS in ramp increasing was 8.25 ± 4.00% higher than step (P = 0.002). The normalized MMG RMS of step contraction was significantly lower than ramp increasing and decreasing, with averaged differences of 12.22 ± 3.37% (P = 0.001) and 12.06 ± 3.37% (P = 0.001), respectively. The results of this study demonstrated that the CSA and aspect ratio, i.e., SMG signals, can provide useful information about muscle contractions. They may therefore complement EMG and MMG for studying muscle activation strategies under different conditions.     

Construction of nanoscale protein particle using temperature-sensitive elastin-like peptide and polyaspartic acid chain

Temperature-responsive monodisperse spheres are useful for various in vivo and in vitro applications. Size, response temperature and biocompatibility are particularly important consideration with in vivo applications. In this work, we constructed fusion proteins of low antigenic elastin-like peptide (ELP) and a polyaspartic acid chain, and studied the particles that had a favorable size and temperature of formation of particle. From DLS analysis, we confirmed that some of them formed particles with less than 100 nm in diameter around 37 °C, while the diameter of ELPs alone is larger than 1 μm in diameter. The (PGVGV)₁₆₀D₂₂, which is composed of a short aspartic acid chain and a long ELP region, had a tendency to form large particles. The temperature of formation and collapse of the protein particle were dependent on the length of the ELP and the polyaspartic acid chain, and the concentration of proteins. The direct observation with TEM indicated that the morphologies of the particles were spherical except when (PGVGV)₁₆₀D₂₂ was used. The intensities of the environment-sensitive hydrophobic fluorescence increased at 37 °C more than 1.5 times as much as at 25 °C both in free form and modified at the ELP region. These results indicated that the polarity of the environment surround the fluorescence decreased or the movement of fluorescence was limited, and thus, implied that the ELP formed a more hydrophobic or rigid region and could hold hydrophobic drugs. These results suggest that a temperature-responsive protein particle with favorable size and temperature of formation can be constructed that is suitable for any in vitro or in vivo application.