Tissue Strain Research Articles

Design and performance analysis of 3D-printed stiffness gradient femoral scaffold

Studies on 3D-printed porous bone scaffolds mostly focus on materials or structural parameters, while the repair of large femoral defects needs to select appropriate structural parameters according to the needs of different parts. In this paper, a kind of stiffness gradient scaffold design idea is proposed. Different structures are selected according to the different functions of different parts of the scaffold. At the same time, an integrated fixation device is designed to fix the scaffold. Finite element method was used to analyze the stress and strain of homogeneous scaffolds and the stiffness gradient scaffolds, and the relative displacement and stress between stiffness gradient scaffolds and bone in the case of integrated fixation and steel plate fixation. The results showed that the stress distribution of the stiffness gradient scaffolds was more uniform, and the strain of host bone tissue was changed greatly, which was beneficial to the growth of bone tissue. The integrated fixation method is more stable, less stress and evenly distributed. Therefore, the integrated fixation device combined with the design of stiffness gradient can repair the large femoral bone defect well.

Light-driven biological actuators to probe the rheology of 3D microtissues

The mechanical properties of biological tissues are key to their physical integrity and function. Although external loading or biochemical treatments allow the estimation of these properties globally, it remains difficult to assess how such external stimuli compare with cell-generated contractions. Here we engineer microtissues composed of optogenetically-modified fibroblasts encapsulated within collagen. Using light to control the activity of RhoA, a major regulator of cellular contractility, we induce local contractions within microtissues, while monitoring microtissue stress and strain. We investigate the regulation of these local contractions and their spatio-temporal distribution. We demonstrate the potential of our technique for quantifying tissue elasticity and strain propagation, before examining the possibility of using light to create and map local anisotropies in mechanically heterogeneous microtissues. Altogether, our results open an avenue to guide the formation of tissues while non-destructively charting their rheology in real time, using their own constituting cells as internal actuators.

Relative motion between the flexor digitorum superficialis tendon and subsynovial connective tissue is time dependent.

The subsynovial connective tissue is an integral component of flexor tendon gliding in the carpal tunnel, which is strained during longitudinal tendon displacement. We tested the effects of repetition frequency and finger load on flexor tendon function throughout active finger movement. Eleven participants performed metacarpophalangeal joint flexion/extension of the long finger cyclically at three repetition frequencies (0.75, 1.00, 1.25 Hz) and two finger loads (3.5, 7 N). Relative displacement between the flexor digitorum superficialis tendon and subsynovial connective tissue was assessed as the shear-strain index with color ultrasound throughout the entire time history of finger flexion and extension. In addition, long finger joint angles were measured with electrogoniometry while flexor digitorum superficialis and extensor digitorum muscle activities were measured with fine-wire electromyography to characterize the finger movements. The shear-strain index increased with greater finger flexion (p = 0.001), representing higher relative displacement between tendon and subsynovial connective tissue; however, no changes were observed throughout finger extension. The shear-strain index also increased with higher repetition frequencies (p = 0.013) and finger loads (p = 0.029), further modulating time-dependent effects during finger flexion versus extension. Using ultrasound, we characterized the time-dependent response of the shear-strain index, in vivo, providing valuable data on flexor tendon function during active finger movement. Our results infer greater subsynovial connective tissue strain and shear during repetitive and forceful finger movements. Future research characterizing time-dependent effects in carpal tunnel syndrome patients may further elucidate the relations between subsynovial connective tissue function, damage, and carpal tunnel syndrome.

Tension-suppressed degradation of collagen controls tissue stiffness scaling with fibrillar collagen.

Extremely soft tissues such as developing hearts or adult brain contain far less collagen than highly stiff adult tissues such as tendons, but cell and molecular mechanisms for such homeostatic differences remain unclear. We hypothesized that cell-generated or exogenous forces combine with tension-suppressed collagen degradation in order to sculpt extracellular matrix (ECM) collagen levels in tissues. For various mature mice tissues and beating embryonic chick hearts, we find collagen-sensitive second harmonic generation (SHG) image intensity scales non-linearly versus tissue stiffness, aligning well with the results from cellularized gels of collagen. Chick hearts beating at ∼5% strain maintain collagen levels until their contractile strain is suppressed by myosin-II inhibition and endogenous matrix metalloproteinases (MMPs) then degrade collagens within ∼30-60 minutes - based on SHG and mass spectrometry proteomics. Although tendons composed of oriented collagen fibrils exhibit heterogeneous strain distributions upon deformation, the addition of exogenous MMP or bacterial collagenase suppresses collagen degradation for strains within physiological limits (i.e., up to ∼5-8%). Sequestration of collagen cleavage sites by tissue strain is a likely mechanism because molecular permeation and mobility prove strain-independent whereas artificial collagen cross-links accelerate strain-dependent collagen degradation via collagen molecular unfolding. Tension-suppressed degradation of collagen thus underlies tissue stiffness scaling.

Measuring Local Tissue Strains in Tendons via Open-Source Digital Image Correlation.

There is considerable scientific interest in understanding the strains that tendon cells experience in situ and how these strains influence tissue remodeling. Based on this interest, several analytical techniques have been developed to measure local tissue strains within tendon explants during loading. However, in several cases, the accuracy and sensitivity of these techniques have not been reported, and none of the algorithms are publicly available. This has made it difficult for the more widespread measurement of local tissue strains in tendon explants. Therefore, the objective of this paper was to create a validated analysis tool for measuring local tissue strains in tendon explants that is readily available and easy to use. Specifically, a publicly available augmented-Lagrangian digital image correlation (ALDIC) algorithm was adapted for measuring 2D strains by tracking the displacements of cell nuclei within mouse Achilles tendons under uniaxial tension. Additionally, the accuracy of the calculated strains was validated by analyzing digitally transformed images, as well as by comparing the strains with values determined from an independent technique (i.e., photobleached lines). Finally, a technique was incorporated into the algorithm to reconstruct the reference image using the calculated displacement field, which can be used to assess the accuracy of the algorithm in the absence of known strain values or a secondary measurement technique. The algorithm is capable of measuring strains up to 0.1 with an accuracy of 0.00015. The technique for comparing a reconstructed reference image with the actual reference image successfully identified samples that had erroneous data and indicated that, in samples with good data, approximately 85% of the displacement field was accurate. Finally, the strains measured in mouse Achilles tendons were consistent with the prior literature. Therefore, this algorithm is a highly useful and adaptable tool for accurately measuring local tissue strains in tendons.

Strain and Depot-specific Differences in Adipose Tissues of Obese BFMI Mice.

Obesity is associated with the structural and functional disorders related to the molecules of the tissues, cells, and membranes. This study aimed to examine the alterations in the secretion of inflammatory cytokines and metabolic factors and structural changes in inguinal (IF) and gonadal (GF) adipose tissues at the molecular level. The IF and GF tissues of Berlin Fat Mouse Inbred (BFMI) lines namely BFMI852, BFMI856, BFMI860, BFMI861 obese and DBAJ control mouse lines were used for mRNA expression and Attenuated Total Reflection - Fourier Transform Infrared Spectroscopy (ATR-FTIR) studies. The mRNA levels of inflammatory cytokines including leptin, interleukin 6 (IL-6), tumor necrosis factor-alpha (Tnf-α), and insulin-like growth factor-1 (Igf-1), and peroxisome proliferator-activated receptor gamma 2 (Pparγ-2), were investigated using quantitative reverse transcriptase real-time PCR (qRT-PCR). Infrared spectroscopy does not provide information about specific proteins, instead, it gives information about overall (total) proteins, which is called global information. Therefore, in the current study, adequate information about secondary structures of adipose tissues proteins was obtained using artificial neural network (ANN) and secondary derivative-vector normalization methods based on the spectral profiles. According to the mRNA expression studies, high leptin resistance was found in all BFMI lines. Differences were observed in the levels of measured factors except for Igf-1 among BFMI lines. Protein secondary structure studies showed an increase in random coil contents, especially for BFMI860, which indicates denaturation of the proteins. Among the spontaneous obese BFMI mouse lines, the BFMI860 line is the most suitable for obesity studies. Obesity-induced effect on the adipose tissues varies considerably with location, type of adipose tissue, and animal line.

Myocardial strain assessment by 2D Speckle Tracking to evaluate the effect of cardiac rehabilitation in patients with or without heart failure

Cardiac rehabilitation improves the subjective condition of the patient, but little is known about associated structural and functional cardiac adaptations specifically the myocardial strain. To evaluate the impact of rehabilitation on structural and functional cardiac parameters using myocardial strain assessment by 2D Speckle Tracking. The study group consisted of 86 patients: 46 with heart failure with optimal medical treatment and 40 patients after acute myocardial infarction. A monocentric cohort study has included all patients who performed a 2-months cardiac rehabilitation program during one year. Clinical characteristics, a resting electrocardiogram, 2-dimensional Doppler echocardiography with tissue Doppler and strain imaging, and an incremental maximal exercise test on a bicycle ergometer were collected before and after the rehabilitation program. Paired Student t-test for comparison and Pearson's correlation coefficient were used for the statistical analysis. Eighty-six patients (46 with heart failure with optimal medical treatment and 40 patients after acute myocardial infarction) were included. Performance capacity was significantly improved after cardiac rehabilitation (Table 1): performance in watts 112 watts (±50) vs. 69.8 watts (±34.5); effort test duration 10.7 min (±4.4) vs. 6.9 min (±3.1) and 6 min walking time 565 m (±127) vs. 496 m (±113). Echographic parameters were also significantly improved: LVFE 52.9% (±13) vs. 46.9% (±12.7), E/E′ 6.7 (±1.54) vs. 7.38 (±2.9). Significant difference of strain before and after cardiac rehabilitation 15.38% (±4.72) vs. 14.12 (±4.79) has been also recorded. BNP level decreased by 29 ng/dL but not statistically significant from baseline. Nonetheless, no significant correlation was found between biological, functional and echocardiographic parameters. Both the performance capacity and left ventricular function on Doppler imaging were significantly improved in the 2 groups after the rehabilitation program in contrast to the BNP level. Strain imaging could be an interesting additional parameter to evaluate the positive response and structural improvement in patients with or without chronic heart failure who are undergoing cardiac rehabilitation.

A polymer network architecture provides superior cushioning and lubrication of soft tissue compared to a linear architecture.

We report the relationships between linear vs. network polymer architecture and biomechanical outcomes including lubrication and cushioning when the polymers are applied to the surface of articulating knee cartilage. Aqueous formulations of the bioinspired polymer poly(2-methacryloyloxylethyl phosphorylcholine) (pMPC) exhibit tuneable rheological properties, with network pMPC exhibiting increased elasticity and viscosity compared to linear pMPC. Application of a polymer network, compared to a linear one, to articulating tissue surfaces reduces friction, lessens tissue strain, minimizes wear, and protects tissue - thereby improving overall tissue performance. Administration of the network pMPC to the middle carpal joint of skeletally mature horses elicits a safe response similar to saline as monitored over a 70 day period.

Особенности профиля экспрессии генов 3D-сфероидов в сравнении с 2D-культурами клеток и тканевыми штаммами высокозлокачественных диффузных глиом

Особенности профиля экспрессии генов 3D-сфероидов в сравнении с 2D-культурами клеток и тканевыми штаммами высокозлокачественных диффузных глиом

The Correlation between Mechanobiology and Fracture Healing; Osteosynthesis, Biomaterial Optimization and TRIZ Design Principles to Develop Ameliorative Implants for Reconstruction of Median Osteochondrotomy of the Sternum.

The application of stainless-steel wire is still the "standard of care" and is believed to be the "gold standard" after trans-sternal thoracotomy. To overcome postoperative instability and surgical wound infection there had been the development of a variety of circumferential, Hemi-circular, and surface on-lay implant designs to enhance bone healing of the sternum particularly in compromised patients. This fundamental descriptive theoretical research study probes into biology and effects of mechanical environment on fracture healing in general and various types of ossifications that may occur during healing of the sternum. Following surgical anatomy of the sternum, the biology of fracture (osteotomy) healing, an update on the conventional and newer biomaterials, and role of 3D printing in custom additive manufacturing of the surgical implants have been discussed in detail. There is discussion on design principles and structural optimization in-line with patient-specific and patient-appropriate osteosynthesis. In support, the Teorija Rezhenija Izobretatelskikh Zadatch engineering principles have been applied to improve implant design in the face of the current strategies to relieve some of the recalcitrant deficiencies underlying the mechanics of the most favored implant for the reconstruction of the sternum. Several scientific domains of the engineering design principles and fracture healing processes have been connected leading to four newly conceptualized prototype designs for the reconstruction of the sternum. In conclusion, despite increased knowledge of the fracture healing process there are limited means to mitigate the adverse mechanical environment experienced by the healing sternum. There are uncertainties how to transfer the well-known facts of tissue strain during healing from the experimental platform to the operating table at the time of fracture fixation and reconstruction of the sternum for its optimal healing.

The Politics of Banana Planting in Waingmaw Township

Abstract: Since 2018, a steady stream of media reports has described the rapid expansion of tissue banana plantations in the Waingmaw area of Kachin State in Northeast Myanmar, noting the widespread environmental degradation and disenfranchisement of local residents. We conducted field research in two villages connected to banana plantations, interviewing residents, plantation workers, government officials, and health workers. Using assemblage theory, we analyze the local political ecology of food production, and how the particularities of local geography, especially in peripheral regions, result in different practical political settlements. These settlements involve a range of different actors including ethnic armed organizations, foreign merchants, government officials, and local brokers. Arrangements of power in border areas are implicit and negotiated, rather than explicit and formalized. These are appropriated through new spatial arrangements (e.g., banana plantations) and spatial relationships (e.g., migrant workers from Rakhine State) in which older identities and modes of living are redefined. A key component of this frontier assemblage is the banana itself, in particular, the practice of cultivating imported tissue strains which are reliant on imported technology and fertilizers. This, in turn, influences the form of the assemblage and power relations within it, illustrating the critical role of material and technological elements within assemblages.

A novel tissue mechanics-based method for improved motion tracking in quasi-static ultrasound elastography.

Most cancers are associated with biological and structural changes that lead to tissue stiffening. Therefore, imaging tissue stiffness using quasi-static ultrasound elastography (USE) can potentially be effective in cancer diagnosis. USE techniques developed for stiffness image reconstruction use noisy displacement data to obtain the stiffness images. In this study, we propose a technique to substantially improve the accuracy of the displacement data computed through ultrasound tissue motion tracking techniques, especially in the lateral direction. The proposed technique uses mathematical constraints derived from fundamental tissue mechanics principles to regularize displacement and strain fields obtained using Global Ultrasound Elastography (GLUE) and Second-Order Ultrasound Elastography (SOUL) methods. The principles include a novel technique to enforce (1) tissue incompressibility using 3D Boussinesq model and (2) deformation compatibility using the compatibility differential equation. The technique was validated thoroughly using metrics pertaining to Signal-to-Noise-Ratio (SNR), Contrast-to-Noise-Ratio (CNR) and Normalized Cross Correlation (NCC) for four tissue-mimicking phantom models and two clinical breast ultrasound elastography cases. The results show substantial improvement in the displacement and strain images generated using the proposed technique. The tissue-mimicking phantom study results indicate that the proposed method is superior in improving image quality compared to the GLUE and SOUL techniques as it shows an average axial strain SNR and CNR improvement of 44% and 63%, and lateral strain SNR and CNR improvement of 130% and 435%, respectively. The results of the phantom study also indicate higher accuracy of displacement images obtained using the proposed technique, including improvement ranges of 7-84% and 26-140% for axial and lateral displacement images, respectively. For the clinical cases, the results indicate average improvement of 48% and 64% in SNR and CNR, respectively, in the axial strain images, and average improvement of 40% and 41% in SNR and CNR, respectively, in the lateral strain images. The proposed method is very effective in producing improved estimate of tissue displacement and strain images, especially with the lateral displacement and strain where the improvement is highly remarkable. While the method shows promise for clinical applications, further investigation is necessary for rigorous assessment of the method's performance in the clinic.

Guided-Motion Bicruciate-Stabilized Total Knee Arthroplasty Reproduces Native Medial Collateral Ligament Strain.

Background and Objectives: Guided-motion bicruciate-stabilized (BCS) total knee arthroplasty (TKA) includes a dual cam-post mechanism with an asymmetric bearing geometry that promotes normal knee kinematics and enhances anterior-posterior stability. However, it is unclear whether the improved biomechanics after guided-motion BCS TKA reproduce soft tissue strain similar to the strain generated by native knees. The purpose of this cadaveric study was to compare medial collateral ligament (MCL) strain between native and guided-motion BCS TKA knees using a video extensometer. Materials and Methods: Eight cadaver knees were mounted onto a customized knee squatting simulator to measure MCL strain during flexion in both native and guided-motion BCS TKA knees (Journey II-BCS; Smith & Nephew, Memphis, TN, USA). MCL strain was measured using a video extensometer (Mercury® RT RealTime tracking system, Sobriety s.r.o, Kuřim, Czech Republic). MCL strain level and strain distribution during knee flexion were compared between the native and guided-motion BCS TKA conditions. Results: The mean and peak MCL strain were similar between native and guided-motion BCS TKA knees at all flexion angles (p > 0.1). MCL strain distribution was similar between native and BCS TKA knees at 8 of 9 regions of interest (ROIs), while higher MCL strain was observed after BCS TKA than in the native knee at 1 ROI in the mid portion of the MCL at early flexion angles (p < 0.05 at ≤30° of flexion). Conclusions: Guided-motion BCS TKA restored the amount and distribution of MCL strain to the values observed on native knees.

Association between nanoscale strains and tissue level nanoindentation properties in age-related hip-fractures

Measurement of the properties of bone as a material can happen in various length scales in its hierarchical and composite structure. The aim of this study was to test the tissue level properties of clinically-relevant human bone samples which were collected from donors belonging to three groups: ageing donors who suffered no fractures (Control); untreated fracture patients (Fx-Untreated) and patient who experienced hip fracture despite being treated with bisphosphonates (Fx-BisTreated). Tissue level properties were assessed by (a) nanoindentation and (b) synchrotron tensile tests (STT) where strains were measured at the ‘tissue’, ‘fibril’ and ‘mineral’ levels by using simultaneous Wide-angle - (WAXD) and Small angle- X-ray diffraction (SAXD). The composition was analysed by thermogravimetric analysis and material level endo- and exo-thermic reactions by differential scanning calorimetry (TGA/DSC3+). Irrespective of treatment fracture donors exhibited significantly lower tissue, fibril and mineral strain at the micro and nanoscale respectively and had a higher mineral content than controls. In nanoindentation only nanohardness was significantly greater for Controls and Fx-BisTreated versus Fx-Untreated. The other nanoindentation parameters did not vary significantly across the three groups. There was a highly significant positive correlation (p < 0.001) between organic content and tissue level strain behaviour. Overall hip-fractures were associated with lower STT nanostrains and it was behaviour measured by STT which proved to be a more effective approach for predicting fracture risk because evidently it was able to demonstrate the mechanical deficit for the bone tissue of the donors who had experienced fractures.

Nanoscale characterization of collagen structural responses to in situ loading in rat Achilles tendons

The specific viscoelastic mechanical properties of Achilles tendons are highly dependent on the structural characteristics of collagen at and between all hierarchical levels. Research has been conducted on the deformation mechanisms of positional tendons and single fibrils, but knowledge about the coupling between the whole tendon and nanoscale deformation mechanisms of more commonly injured energy-storing tendons, such as Achilles tendons, remains sparse. By exploiting the highly periodic arrangement of tendons at the nanoscale, in situ loading of rat Achilles tendons during small-angle X-ray scattering acquisition was used to investigate the collagen structural response during load to rupture, cyclic loading and stress relaxation. The fibril strain was substantially lower than the applied tissue strain. The fibrils strained linearly in the elastic region of the tissue, but also exhibited viscoelastic properties, such as an increased stretchability and recovery during cyclic loading and fibril strain relaxation during tissue stress relaxation. We demonstrate that the changes in the width of the collagen reflections could be attributed to strain heterogeneity and not changes in size of the coherently diffracting domains. Fibril strain heterogeneity increased with applied loads and after the toe region, fibrils also became increasingly disordered. Additionally, a thorough evaluation of radiation damage was performed. In conclusion, this study clearly displays the simultaneous structural response and adaption of the collagen fibrils to the applied tissue loads and provide novel information about the transition of loads between length scales in the Achilles tendon.

The Effect of Intraocular Pressure Load Boundary on the Biomechanics of the Human Conventional Aqueous Outflow Pathway.

Aqueous humor outflow resistance in the trabecular meshwork (TM), juxtacanalicular connective tissue (JCT), and Schlemm's canal (SC) endothelium of the conventional outflow pathway actively contribute to intraocular pressure (IOP) regulation. Outflow resistance is actively affected by the dynamic outflow pressure gradient across the TM, JCT, and SC inner wall tissues. The resistance effect implies the presence of a fluid-structure interaction (FSI) coupling between the outflow tissues and the aqueous humor. However, the biomechanical interactions between viscoelastic outflow tissues and aqueous humor dynamics are largely unknown. A 3D microstructural finite element (FE) model of a healthy human eye TM/JCT/SC complex was constructed with elastic and viscoelastic material properties for the bulk extracellular matrix and embedded elastic cable elements. The FE models were subjected to both idealized and a physiologic IOP load boundary using the FSI method. The elastic material model for both the idealized and physiologic IOP load boundary at equal IOPs showed similar stresses and strains in the outflow tissues as well as pressure in the aqueous humor. However, outflow tissues with viscoelastic material properties were sensitive to the IOP load rate, resulting in different mechanical and hydrodynamic responses in the tissues and aqueous humor. Transient IOP fluctuations may cause a relatively large IOP difference of ~20 mmHg in a very short time frame of ~0.1 s, resulting in a rate stiffening in the outflow tissues. Rate stiffening reduces strains and causes a rate-dependent pressure gradient across the outflow tissues. Thus, the results suggest it is necessary to use a viscoelastic material model in outflow tissues that includes the important role of IOP load rate.

Abstract 14076: Myocardial Tissue Characterization and Strain by Cardiac Magnetic Resonance and Their Relationship in Pediatric Patients With Acute Myocarditis Within 2 Weeks of Presentation

Introduction: Cardiac magnetic resonance (CMR) provides rich data on myocardial function, including indices such as strain, as well as tissue characterization. There is no published data on these values within 2 weeks of the diagnosis of myocarditis. We sought to describe these findings in children with acute myocarditis who underwent CMR early after presentation and determine relationships between these values. Methods: We retrospectively reviewed the clinical and imaging data of patients &lt;21 years clinically diagnosed with acute myocarditis and underwent CMR within 14 days of presentation. Those who suffered cardiac arrest or with autoimmune disease, known cardiomyopathy or congenital heart disease were excluded. Strain was measured using CMR feature tracking. Spearman’s correlation was utilized. Significance was P &lt;0.05. Results: 85 patients underwent CMR at a median of 2 days following presentation (IQR 2 - 4) with median age 16.3 years (IQR 14.3, 17.5). Tissue characteristics, ventricular function and strain are listed in Table 1. 77 studies (90.6%) met Lake Louise criteria for myocarditis and 66 (77.7%) showed late gadolinium enhancement. Global circumferential (GCS) and longitudinal strain correlated with T2 values, biventricular ejection fractions, and peak brain natriuretic peptide (BNP); GCS also correlated with T1 values (Table 1, Figure 1). Conclusions: We present the first data on early strain and tissue characterization for myocarditis. Both global longitudinal and circumferential strain correlated with tissue characteristics and serum measures of acute injury. Strain imaging may be a sensitive marker of myocardial injury in patients with myocarditis.

Characterization of intra-tissue strain fields in articular cartilage explants during post-loading recovery using high frequency ultrasound

This study aims to demonstrate the potential of ultrasound elastography as a research tool for non-destructive imaging of intra-tissue strain fields and tissue quality assessment in cartilage explants. Osteochondral plugs from bovine patellae were loaded up to 10, 40, or 70 N using a hemi-spherical indenter. The load was kept constant for 15 min, after which samples were unloaded and ultrasound imaging of strain recovery over time was performed in the indented area for 1 h. Tissue strains were determined using speckle tracking and accumulated to LaGrangian strains in the indentation direction. For all samples, strain maps showed a heterogeneous strain field, with the highest values in the superficial cartilage under the indenter tip at the bottom of the indent and decreasing values in the deeper cartilage. Strains were higher at higher load levels and tissue recovery over time was faster after indentation at 10 N than at 40 N and 70 N. At lower compression levels most displacement occurred near the surface with little deformation in the deep layers, while at higher levels strains increased more evenly in all cartilage zones. Ultrasound elastography is a promising method for high resolution imaging of intra-tissue strain fields and evaluation of cartilage quality in tissue explants in a laboratory setting. In the future, it may become a clinical diagnostic tool used to identify the extent of cartilage damage around visible defects.

Persistence of DNA from canine parvovirus modified-live virus in canine tissues.

Canine parvovirus (CPV-2) modified-live virus vaccine strain can replicate in lymphoid tissues and intestinal mucosa after administration, being shed through canine faeces. Detection of vaccine strains has been reported in the bloodstream and faeces, potentially interfering with molecular diagnostic tests. The persistence of these strains in canine tissues has not yet been described. With this aim, canine tissues were tested during a molecular survey to screen for the presence of canine enteric viruses. Tissue samples from 165 dead dogs were tested by a conventional PCR assay. Positive samples and five commercial vaccines were subjected to sequence analysis. Vaccinal strains were detected and virus load was measured by using a set of real-time PCR assays using minor-groove binder (MGB) probes. Seventy-five dogs (45.4%) tested positive for CPV-2. Strains from 70 dogs were characterised as field variants. The presence of CPV sequences of vaccine origin was observed in the spleen, intestine, and mesenteric lymph nodes of five young dogs. Vaccinal strains were detected from 12 to 24 days after the last vaccine administration. Viral loads comprised between 6.3 × 102 and 9.95 × 104 DNA copies/10 µl of template. This study confirms that CPV vaccinal strains can be detected in canine tissues after vaccination, so post-mortem diagnosis of CPV infection needs further molecular analyses to assess the viral type (vaccine or field strains). The present study updates the current information on the persistence of CPV vaccine strains in canine tissues and their possible interference with molecular assays.

Assessment of left atrial and left ventricular functions in hypertensive patients with sinus rhythm and atrial fibrillation using tissue Doppler imaging

If treated, hypertension (HTN) may reduce the risk of cardiovascular disease (CVD) and overall mortality (1). Life expectancy in adults is reduced by five years due to HTN, which is commonly misdiagnosed or improperly treated despite the widespread availability of effective pharmacological medicines and updated clinical recommendations (2). Hypertensive heart disease is a cardiovascular sequela of hypertension and is characterised by left ventricular hypertrophy (LVH), left atrial enlargement, left ventricular diastolic dysfunction, functional mitral regurgitation, and neuro-hormonal alterations (3). Doppler tissue imaging has paved the way for novel echocardiography modalities like as tissue tracking and strain rate imaging, which may be utilized to evaluate regional LV systolic shortening. Myocardial stretching or shortening may be determined using strain rate analysis (4).