Morphological features of the simulated gunshot wounds of rabbits’ soft tissues at different temperatures of injuring object

The article presents the results of experimental modeling of super­ficial fragment gunshot wounds of soft tissues, obtained in low-energy gunshot wounds. The pathomorphosis of gunshot wounds was studied, and the features and timing of their healing were compared depending on the temperature of the damaging fragments. The aim of the work was to study the effect of the temperature of the injuring shrapnel on the healing processes of the soft tissues of experimental animals with superficial low-energy fragment gunshot wounds. Using the random number method, laboratory animals (rabbits) were divided into 3 experimental groups (15 animals each). In each group, wounding was with fragments with different temperatures − 18°С, 50°С and 100°С. The control group consisted of 10 intact animals. On day 14th, 30th and 60th, 5 animals from each group were withdrawn from the experiment. Microscopic examination of soft tissues was performed using a PRIMO STAR light microscope (Carl Zeiss, Germany) at magnification by 56 and 400 times. When assessing the state of tissues in the area of wound damage, it was established that as the temperature of the injuring fragment increases, a slower filling of the defect formed by the necrotic detritus in the process of utilization of necrotic detritus is observed. The high temperature of the injuring fragment along with the mechanical rupture of tissues causes thermal coagulation necrosis. Dense coagulated necrotic masses covering the wound canal from the inside, not only increase the volume of necrotic masses, but also complicate the process of wound healing. At a temperature of wounding fragments 100°C, the formation of a necrotic crust on the surface of the wound occurred on average 3±1.2 days later than at temperatures of 18°C and 50°C, the least pronounced healing took place at the bottom of the wound and in the muscle tissue. Microscopically necrotic, not dystrophic changes were observed in myocytes. Thus, a comparative analysis of the pathomorphosis of soft tissues in a wound when injured from an air rifle MP-532 with different temperature of the fragments showed differences from both the alteration of the tissues and the regenerative potential.

Mechanical Rupture-Based Antibacterial and Cell-Compatible ZnO/SiO2 Nanowire Structures Formed by Bottom-Up Approaches

There are growing interests in mechanical rupture-based antibacterial surfaces with nanostructures that have little toxicity to cells around the surfaces; however, current surfaces are fabricated via top-down nanotechnologies, which presents difficulties to apply for bio-surfaces with hierarchal three-dimensional structures. Herein, we developed ZnO/SiO2 nanowire structures by using bottom-up approaches and demonstrated to show mechanical rupture-based antibacterial activity and compatibility with human cells. When Escherichia coli were cultured on the surface for 24 h, over 99% of the bacteria were inactivated, while more than 80% of HeLa cells that were cultured on the surface for 24 h were still alive. This is the first demonstration of mechanical rupture-based bacterial rupture via the hydrothermally synthesized nanowire structures with antibacterial activity and cell compatibility.

Scar-Like Self-Reinforced and Failure-Tolerant Dielectric Elastomer Actuator With AgNWs Electrode

Scar structures of natural animals can reinforce the wounds both mechanically and biologically to maintain the functions of the injured muscle and skin. Inspired by the scar structure, we present a dielectric elastomer (DE) with silver nanowire electrodes possessing the scar-like ability. This DE membrane can tolerate the failures by both electric breakdown and mechanical rupture. The DE actuator (DEA) can maintain their performances of force and displacement output after multiple failures. Scanning electronic microscope (SEM) images show that the scar-like structures accumulate around the electromechanical failure locations on the DE membrane as the stiffened and insulated regions, which prevent further short current and membrane rupture. J-integrals and stress distribution around the failure location have been calculated by finite element analysis to verify the mechanical reinforcements of the scar-like structures over crack propagation.

Tension-activated channels in the mechanism of osmotic fitness in Pseudomonas aeruginosa

Pseudomonas aeruginosa (PA) is an opportunistic pathogen with an exceptional ability to adapt to a range of environments. Part of its adaptive potential is the ability to survive drastic osmolarity changes. Upon a sudden dilution of external medium, such as during exposure to rain, bacteria evade mechanical rupture by engaging tension-activated channels that act as osmolyte release valves. In this study, we compare fast osmotic permeability responses in suspensions of wild-type PA and Escherichia coli (EC) strains in stopped-flow experiments and provide electrophysiological descriptions of osmotic-release channels in PA. Using osmotic dilution experiments, we first show that PA tolerates a broader range of shocks than EC. We record the kinetics of cell equilibration reported by light scattering responses to osmotic up- and down-shocks. PA exhibits a lower water permeability and faster osmolyte release rates during large osmotic dilutions than EC, which correlates with better survival. To directly characterize the PA tension-activated channels, we generate giant spheroplasts from this microorganism and record current responses in excised patches. Unlike EC, which relies primarily on two types of channels, EcMscS and EcMscL, to generate a distinctive two-wave pressure ramp response, PA exhibits a more gradual response that is dominated by MscL-type channels. Genome analysis, cloning, and expression reveal that PA possesses one MscL-type (PaMscL) and two MscS-type (PaMscS-1 and 2) proteins. In EC spheroplasts, both PaMscS channels exhibit a slightly earlier activation by pressure compared with EcMscS. Unitary currents reveal that PaMscS-2 has a smaller conductance, higher anionic preference, stronger inactivation, and slower recovery compared with PaMscS-1. We conclude that PA relies on MscL as the major valve defining a high rate of osmolyte release sufficient to curb osmotic swelling under extreme shocks, but it still requires MscS-type channels with a strong propensity to inactivation to properly terminate massive permeability response.