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Introduction: Persistent bacterial infection prolongs hospitalizations, leading to increased healthcare costs. Treatment of these infections costs several billion dollars annually. Biofilm production is one mechanism by which bacteria become resistant. With the help of biofilms, bacteria withstand the host immune response and are much less susceptible to antibiotics. Currently, there is interest in the use of laser-generated shockwaves (LGS) to delaminate biofilm from infected wound surfaces; however, the safety of such an approach has not yet been established. Of particular concern are the thermal and mechanical effects of the shockwave treatment on the epidermis and the underlying collagen structure of the dermis. The present study is a preliminary investigation of the effect of LGS on freshly harvested ex vivo porcine skin tissue samples.

Objective: In vivo visualization and quantification of edema, or 'tissue swelling' following injury, remains a clinical challenge. Herein, we investigate the ability of reflective terahertz (THz) imaging to track changes in tissue water content (TWC)-the direct indicator of edema-by comparison to depth-resolved magnetic resonance imaging (MRI) in a burn-induced model of edema., Methods: A partial thickness and full thickness burns were induced in an in vivo rat model to elicit unique TWC perturbations corresponding to burn severity. Concomitant THz surface maps and MRI images of both burn models were acquired with a previously reported THz imaging system and T 2 -weighted MRI, respectively, over 270 min. Reflectivity was analyzed for the burn contact area in THz images, while proton density (i.e., mobile TWC) was analyzed for the same region at incrementally increasing tissue depths in companion, transverse MRI images. A normalized cross correlation of THz and depth-dependent MRI measurements was performed as a function of time in histologically verified burn wounds., Results: For both burn types, strong positive correlations were evident between THz reflectivity and MRI data analyzed at greater tissue depths (>258 μm). MRI and THz results also revealed biphasic trends consistent with burn edema pathogenesis., Conclusion: This paper offers the first in vivo correlative assessment of mobile TWC-based contrast and the sensing depth of THz imaging., Significance: The ability to implement THz imaging immediately following injury, combined with TWC sensing capabilities that compare to MRI, further support THz sensing as an emerging tool to track fluid in tissue.

Introduction: The aims of this study were to evaluate (1) grasping forces with the application of a tactile feedback system in vivo and (2) the incidence of tissue damage incurred during robotic tissue manipulation. Robotic-assisted minimally invasive surgery has been shown to be beneficial in a variety of surgical specialties, particularly radical prostatectomy. This innovative surgical tool offers advantages over traditional laparoscopic techniques, such as improved wrist-like maneuverability, stereoscopic video displays, and scaling of surgical gestures to increase precision. A widely cited disadvantage associated with robotic systems is the absence of tactile feedback., Methods and Procedure: Nineteen subjects were categorized into two groups: 5 experts (six or more robotic cases) and 14 novices (five cases or less). The subjects used the da Vinci with integrated tactile feedback to run porcine bowel in the following conditions: (T1: deactivated tactile feedback; T2: activated tactile feedback; and T3: deactivated tactile feedback). The grasping force, incidence of tissue damage, and the correlation of grasping force and tissue damage were analyzed. Tissue damage was evaluated both grossly and histologically by a pathologist blinded to the sample., Results: Tactile feedback resulted in significantly decreased grasping forces for both experts and novices (P < 0.001 in both conditions). The overall incidence of tissue damage was significantly decreased in all subjects (P < 0.001). A statistically significant correlation was found between grasping forces and incidence of tissue damage (P = 0.008). The decreased forces and tissue damage were retained through the third trial when the system was deactivated (P > 0.05 in all subjects)., Conclusion: The in vivo application of integrated tactile feedback in the robotic system demonstrates significantly reduced grasping forces, resulting in significantly less tissue damage. This tactile feedback system may improve surgical outcomes and broaden the use of robotic-assisted minimally invasive surgery.

Whole-body stiffness in fishes has important consequences for swimming mode, speed and efficiency, but the contribution of vertebral column stiffness to whole-body stiffness is unclear. In our opinion, this lack of clarity is due in part to the lack of studies that have measured both in vitro mechanical properties of the vertebral column as well as in vivo vertebral kinematics in the same species. Some lack of clarity may also come from real variation in the mechanical role of the vertebral column across species. Previous studies, based on either mechanics or kinematics alone, suggest species-specific variation in vertebral column locomotor function that ranges from highly stiff regimes that contribute greatly to whole-body stiffness, and potentially act as a spring, to highly compliant regimes that only prohibit excessive flexion of the intervertebral joints. We review data collected in combined investigations of both mechanics and kinematics of three species, Myxine glutinosa, Acipenser transmontanus, and Morone saxatilis, to illustrate how mechanical testing within the context of the in vivo kinematics more clearly distinguishes the role of the vertebral column in each species. In addition, we identify species for which kinematic data are available, but mechanical data are lacking. We encourage further investigation of these species to fill these mechanical data gaps. Finally, we hope these future combined analyses will identify certain morphological, mechanical, or kinematic parameters that might be associated with certain vertebral column functional regimes with respect to body stiffness., (Copyright © 2013 Elsevier GmbH. All rights reserved.)

Whole-body stiffness has a substantial impact on propulsive wave speed during axial undulatory locomotion in fishes. The connective tissues of the vertebral column may contribute to body stiffness, but without mechanical and kinematic analysis it is unclear whether the in vivo range of motion of intervertebral joints (IVJs) is great enough to stress IVJ tissues, thus generating stiffness. The present study used 2D videoradiography and 3D X-ray reconstruction of moving morphology (XROMM) to quantify vertebral kinematics during the startle response in striped bass (Morone saxatilis). X-ray video revealed two distinct patterns of bending: pattern I begins in the abdominal region and then proceeds to maximum IVJ angles in the caudal region, whereas pattern II begins in the cervical region and proceeds to maximum IVJ angles in the abdominal and then the caudal joints. In pattern II bends, the cervical joints exhibit a greater in vivo range of motion than previously reported in other species. XROMM analysis of caudal IVJs suggests primarily lateral bending: mean axial and dorsoventral rotations were less than 2 deg and inconsistent across 51 sequences analyzed from five individuals, whereas mean maximum lateral bending angles were 10.4±3.57 deg. These angles, combined with previous investigations of mechanical properties, reveal that the maximum angles all occur within the neutral zone of bending, indicating that little stress is experienced about the joint. This suggests that the IVJs of striped bass are quite compliant and likely do not contribute significantly to whole-body stiffness or elastic recoil during swimming in vivo.

Unlike mammalian, disc-shaped intervertebral joints (IVJs), the IVJs in fishes are biconid structures, filled with fluid and thought to act as hydrostatic hinge joints during swimming. However, it remains unclear which IVJ structures are dominant in mechanical resistance to forces in fishes, and whether variation in these tissues might impact the function of the vertebral column along its length. Here, we measured the dynamic mechanical behaviour of IVJs from striped bass, Morone saxatilis. During lateral bending, angular stiffness was significantly lower in the caudal and cervical regions, relative to the abdominal region. The neutral zone, defined as the range of motion (ROM) at bending moments less than 0.001 Nm, was longer in the caudal relative to the abdominal IVJs. Hysteresis was 30-40% in all regions, suggesting that IVJs may play a role in energy dissipation during swimming. Cutting the vertical septum had no statistically significant effect, but cutting the encapsulating tissues caused a sharp decline in angular stiffness and a substantial increase in ROM and hysteresis. We conclude that stiffness decreases and ROM increases from cranial to caudal in striped bass, and that the encapsulating tissues play a prominent role in mechanical variation along the length of the vertebral column.

The vertebral column of fishes has traditionally been divided into just two distinct regions, abdominal and caudal. Recently, however, developmental, morphological, and mechanical investigations have brought this traditional regionalization scheme into question. Alternative regionalization schema advocate the division of the abdominal vertebrae into cervical, abdominal, and in some cases, transitional regions. Here, we investigate regional variation at the level of the vertebrae and intervertebral joint (IVJ) tissues in the striped bass, Morone saxatilis. We use gross dissection, histology, and polarized light imaging to quantify vertebral height, width, length, IVJ length, IVJ tissue volume and cross-sectional area, and vertical septum fiber populations, and angles of insertion. Our results reveal regional differences between the first four (most rostral) abdominal vertebrae and IVJs and the next six abdominal vertebrae and IVJs, supporting the recognition of a distinct cervical region. We found significant variation in vertebral length, width, and height from cranial to caudal. In addition, we see a significant decline in the volume of notochordal cells and the cross-sectional area of the fibrous sheath from cranial to caudal. Further, polarized light imaging revealed four distinct fiber populations within the vertical septum in the cervical and abdominal regions in contrast with just one fiber population found in the caudal region. Measurement of the insertion angles of these fiber populations revealed significant differences between the cervical and abdominal regions. Differences in vertebral, IVJ, and vertical septum morphology all predict greater range of motion and decreased stiffness in the caudal region of the fish compared with the cervical and abdominal regions., (Copyright © 2011 Wiley Periodicals, Inc.)

The northern spearnose poacher, Agonopsis vulsa, is a benthic, heavily armored fish that swims primarily using pectoral fins. High-speed kinematics, whole-body lift measurements, and flow visualization were used to study how A. vulsa overcomes substantial negative buoyancy while generating forward thrust. Kinematics for five freely swimming poachers indicate that individuals tend to swim near the bottom (within 1cm) with a consistently small (less than 1 degrees ) pitch angle of the body. When the poachers swam more than 1cm above the bottom, however, body pitch angles were higher and varied inversely with speed, suggesting that lift may help overcome negative buoyancy. To determine the contribution of the body to total lift, fins were removed from euthanized fish (n=3) and the lift and drag from the body were measured in a flume. Lift and drag were found to increase with increasing flow velocity and angle of attack (ANCOVA, p<0.0001 for both effects). Lift force from the body was found to supply approximately half of the force necessary to overcome negative buoyancy when the fish were swimming more than 1cm above the bottom. Lastly, flow visualization experiments were performed to examine the mechanism of lift generation for near-bottom swimming. A vortex in the wake of the pectoral fins was observed to interact strongly with the substratum when the animals approached the bottom. These flow patterns suggest that, when swimming within 1cm of the bottom, poachers may use hydrodynamic ground effect to augment lift, thereby counteracting negative buoyancy.

Mantis shrimp (Stomatopoda) generate extremely rapid and forceful predatory strikes through a suite of structural modifications of their raptorial appendages. Here we examine the key morphological and kinematic components of the raptorial strike that amplify the power output of the underlying muscle contractions. Morphological analyses of joint mechanics are integrated with CT scans of mineralization patterns and kinematic analyses toward the goal of understanding the mechanical basis of linkage dynamics and strike performance. We test whether a four-bar linkage mechanism amplifies rotation in this system and find that the rotational amplification is approximately two times the input rotation, thereby amplifying the velocity and acceleration of the strike. The four-bar model is generally supported, although the observed kinematic transmission is lower than predicted by the four-bar model. The results of the morphological, kinematic and mechanical analyses suggest a multi-faceted mechanical system that integrates latches, linkages and lever arms and is powered by multiple sites of cuticular energy storage. Through reorganization of joint architecture and asymmetric distribution of mineralized cuticle, the mantis shrimp's raptorial appendage offers a remarkable example of how structural and mechanical modifications can yield power amplification sufficient to produce speeds and forces at the outer known limits of biological systems.