Mesh shrinkage and pain in laparoscopic ventral hernia repair: a randomized clinical trial comparing suture versus tack mesh fixation

Mesh fixation during laparoscopic ventral hernia repair can be performed using transfascial sutures or metal tacks. The aim of the present study is to compare mesh shrinkage and pain between two different techniques of mesh fixation in a prospective randomized trial.

Does work stress make you shorter? An ambulatory field study of daily work stressors, job control, and spinal shrinkage

Body height decreases throughout the day due to fluid loss from the intervertebral disk. This study investigated whether spinal shrinkage was greater during workdays compared with nonwork days, whether daily work stressors were positively related to spinal shrinkage, and whether job control was negatively related to spinal shrinkage. In a consecutive 2-week ambulatory field study, including 39 office employees and 512 days of observation, spinal shrinkage was measured by a stadiometer, and calculated as body height in the morning minus body height in the evening. Physical activity was monitored throughout the 14 days by accelerometry. Daily work stressors, daily job control, biomechanical workload, and recreational activities after work were measured with daily surveys. Multilevel regression analyses showed that spinal disks shrank more during workdays than during nonwork days. After adjustment for sex, age, body weight, smoking status, biomechanical work strain, and time spent on physical and low-effort activities during the day, lower levels of daily job control significantly predicted increased spinal shrinkage. Findings add to knowledge on how work redesign that increases job control may possibly contribute to preserving intervertebral disk function and preventing occupational back pain.

Hygrical shrinkage stresses in tiling systems: Numerical modeling combined with field studies

To track down potential sites of material failure in the tile–mortar–substrate systems, locations and intensities of stress concentrations owing to drying-induced shrinkage are investigated. For this purpose, mechanical properties were measured on real systems and used as input parameters for numerical modeling of the effect of shrinkage of substrate and/or mortar using the finite element code Abaqus. On the base of different geometrical set-ups we demonstrate that stress concentrations in the mortar can become critical when (i) substantial mortar shrinkage occurs, (ii) substrate shrinkage can accumulate over considerable spatial distances, particularly (iii) in situations where the mortar layer is not separated from the substrate by a flexible waterproofing membrane. Hence material failure in the system tile–mortar–substrate can be prevented (or reduced) by (i) an application of the tiles after the major stages of substrate shrinkage, (ii) the use of elasto-plastic deformable tile adhesives which can react elastically on local stress concentrations, (iii) the implementation of flexible membranes, and (iv) a reduction of the field size by the installation of flexible joints.

Rapidly excised and cryofixed rat tissue

All preparation efforts of biological samples in electron microscopy are focused to preserve structures as close as possible to the native state. To achieve this goal with tissues, it is of advantage to have a very short time between excision and fixation. The most common approach is chemical fixation: cross-linking of the tissue samples with aldehydes followed by postfixation with osmium tetroxide. Here, the fastest approach for tissue samples is perfusion. However, the diffusion of the fixation solution from blood vessels into the depth of the tissue is still slow and does not allow an overall instant fixation of a single cell. As a result, osmotic effects become evident (swelling or shrinkage of cell organelles). Another possibility is to take a tissue sample from the experimental animal. Excision of tissue can last quite some time, which results in even more pronounced autolytic induced osmotic effects. Furthermore, the animal does not survive the procedure in most cases. Alternatively, microbiopsies are an elegant technique to rapidly excise small quantities of tissue. Some tissues, such as liver and muscle, may be obtained using a non-lethal approach. To avoid the artifacts introduced by chemical fixation, high-pressure freezing of microbiopsies (brain, liver, kidney, and muscle) is a powerful alternative to chemical fixation. Here, we describe the microbiopsy method, and high-pressure freezing/freeze-substitution (HPF/FS) as a follow-up procedure. Cryosectioning of high-pressure frozen samples is optimally preserving the ultrastructure; however, it is not considered to be a routine approach yet.

A comparative assessment by optical coherence tomography of the performance of the first and second generation of the everolimus-eluting bioresorbable vascular scaffolds

The first generation of the everolimus-eluting bioresorbable vascular scaffold (BVS 1.0) showed an angiographic late loss higher than the metallic everolimus-eluting stent Xience V due to scaffold shrinkage. The new generation (BVS 1.1) presents a different design and manufacturing process than the BVS 1.0. This study sought to evaluate the differences in late shrinkage, neointimal response, and bioresorption process between these two scaffold generations using optical coherence tomography (OCT).

Evaluation of the second generation of a bioresorbable everolimus drug-eluting vascular scaffold for treatment of de novo coronary artery stenosis: six-month clinical and imaging outcomes

The first generation of the bioresorbable everolimus drug-eluting vascular scaffold showed signs of shrinkage at 6 months, which largely contributed to late luminal loss. Nevertheless, late luminal loss was less than that observed with bare metal stents. To maintain the mechanical integrity of the device up to 6 months, the scaffold design and manufacturing process of its polymer were modified.

Evaluation of the second generation of a bioresorbable everolimus-eluting vascular scaffold for the treatment of de novo coronary artery stenosis: 12-month clinical and imaging outcomes

The aim of this study was to demonstrate that the prevention of early scaffold area shrinkage of the ABSORB BVS (Rev.1.1, Abbott Vascular, Santa Clara, California) was sustained and not simply delayed by a few months.

Rapid cytopathic effects of Clostridium perfringens beta-toxin on porcine endothelial cells

Clostridium perfringens type C isolates cause fatal, segmental necro-hemorrhagic enteritis in animals and humans. Typically, acute intestinal lesions result from extensive mucosal necrosis and hemorrhage in the proximal jejunum. These lesions are frequently accompanied by microvascular thrombosis in affected intestinal segments. In previous studies we demonstrated that there is endothelial localization of C. perfringens type C beta-toxin (CPB) in acute lesions of necrotizing enteritis. This led us to hypothesize that CPB contributes to vascular necrosis by directly damaging endothelial cells. By performing additional immunohistochemical studies using spontaneously diseased piglets, we confirmed that CPB binds to the endothelial lining of vessels showing early signs of thrombosis. To investigate whether CPB can disrupt the endothelium, we exposed primary porcine aortic endothelial cells to C. perfringens type C culture supernatants and recombinant CPB. Both treatments rapidly induced disruption of the actin cytoskeleton, cell border retraction, and cell shrinkage, leading to destruction of the endothelial monolayer in vitro. These effects were followed by cell death. Cytopathic and cytotoxic effects were inhibited by neutralization of CPB. Taken together, our results suggest that CPB-induced disruption of endothelial cells may contribute to the pathogenesis of C. perfringens type C enteritis.

Fine structure of hippocampal mossy fiber synapses following rapid high-pressure freezing

Synapses of hippocampal neurons play important roles in learning and memory processes and are involved in aberrant hippocampal function in temporal lobe epilepsy. Major neuronal types in the hippocampus as well as their input and output synapses are well known, but it has remained an open question to what extent conventional electron microscopy (EM) has provided us with the real appearance of synaptic fine structure under in vivo conditions. There is reason to assume that conventional aldehyde fixation and dehydration lead to protein denaturation and tissue shrinkage, likely associated with the occurrence of artifacts. However, realistic fine-structural data of synapses are required for our understanding of the transmission process and for its simulation. Here, we used high-pressure freezing and cryosubstitution of hippocampal tissue that was not subjected to aldehyde fixation and dehydration in ethanol to monitor the fine structure of an identified synapse in the hippocampal CA3 region, that is, the synapse between granule cell axons, the mossy fibers, and the proximal dendrites of CA3 pyramidal neurons. Our results showed that high-pressure freezing nicely preserved ultrastructural detail of this particular synapse and allowed us to study rapid structural changes associated with synaptic plasticity.