Histochemical picture in the skin of rats 1, 3, 7, 14, 21 and 30 days after burning of ІІ-ІІІ degrees on the background of injection during first 7 days of 0.9% NaCl solution

For pathogenetically grounded therapy of burn disease, aimed at reducing the severity of the pathological process, the rapid recovery of microcirculation and stimulation of reparative processes, it is necessary to study the fine mechanisms of reparative regeneration in the skin on the microscopic and biochemical levels. The purpose of the study is to investigate the state of elastic and collagen fibers, as well as glycoproteins and glycosaminoglycans in the intercellular substance of the dermis of rats 1, 3, 7, 14, 21 and 30 days after the burning of the II-III degree, with the background of the injection during first 7 days of 0.9% NaCl solution. An experimental study of structural changes in the skin after burn injury was performed on laboratory white rats, males weighing 150-160 g. Rats were divided into 2 groups, which previously, under the conditions of propofol anesthesia 60 mg/kg internally, catheterization of the femoral vein and depilation lateral surfaces of the trunk of rats. Group 1 - animals without thermal trauma of the skin, which once a day for the first 7 days were injected intravenous infusion of 0.9% NaCl solution in a dose of 10 ml per kg. Group 2 - animals who were also injected once a day with the first 7 days of infusion of 0.9% NaCl solution in a dose of 10 ml per kg after 2-3 degree skin burns, with a total area of 21-23% of the body surface of the rat. Euthanasia of rats was performed after propofol anesthesia (60 mg/kg i/v) by decapitation. Changes in the histochemical structure of bits of skin from the edge of the wound were studied after 1, 3, 7, 14, 21, and 30 days from the beginning of the experiment. Histological sections 5-6 microns thick were stained with Weigert’s elastic stain and dyed with picric acid by Van Gieson’s method (for the detection of elastic and collagen fibers); the PAS + Hale reaction was performed by the Moury method (detection of glycoproteins and glycosaminoglycans in the intercellular substance of the dermis). The histochemical investigations of the area of the II-III degree of skin damaged by burns on the background of the injection of 0.9% NaCl solution found that the degree of change depends on the duration of the experiment. In the early stages of the experiment, the reorganization of the intercellular substance of the dermis manifests itself as damage to the fibrous structures of its papillary and reticular layers. Histochemically, the components of amorphous connective tissue substance are dominated by glycoproteins, the content of acidic glycosaminoglycans is small. In the late stages of the experiment (after 14, 21 and 30 days) in the connective tissue of the affected skin in the central and marginal regions poorly structured collagen and elastic fibers are observed. The pronounced “Hale”-positive coloration reflects an increase in the content of sulfated glycosaminoglycans in the amorphous substance of the connective tissue. Thus, the experimental thermal trauma of skin II-III degree on the background of the introduction during the first 7 days, 0.9% of the NaCl solution is histochemically characterized by reorganization of the intercellular substance of the connective tissue of the dermis. In the early stages of the experiment there is damage to the fibrous structures of the papillary and reticular layers, the prevalence of glycoproteins and the insignificant content of acidic glycosaminoglycans in the amorphous substance, indicating a significant inhibition of adaptive-compensatory processes. In the long term, after the thermal defeat in the dermis, histochemically, an increase in the amount of acid glycosaminoglycans is detected and the PAS positivity of the collagen fibers of the intercellular substance is well expressed. This indicates a slow updating of the amorphous substance and fibrous structures of the connective tissue of the dermis, a violation of regenerative processes.

Crystal Structure of Neurotropism-Associated Variable Surface Protein 1 (Vsp1) of Borrelia turicatae

ABSTRACT Vsp surface lipoproteins are serotype-defining antigens of relapsing fever spirochetes that undergo multiphasic antigenic variation to allow bacterial persistence in spite of an immune response. Two isogenic serotypes of Borrelia turicatae strain Oz1 differ in their Vsp sequences and in disease manifestations in infected mice: Vsp1 is associated with the selection of a neurological niche, while Vsp2 is associated with blood and skin infection. We report here crystal structures of the Vsp1 dimer at 2.7 and 2.2 Å. The structures confirm that relapsing fever Vsp proteins share a common helical fold with OspCs of Lyme disease-causing Borrelia. The fold features an inner stem formed by highly conserved N and C termini and an outer “dome” formed by the variable central residues. Both Vsp1 and OspC structures possess small water-filled cavities, or pockets, that are lined largely by variable residues and are thus highly variable in shape. These features appear to signify tolerance of the Vsp-OspC fold for imperfect packing of residues at its antigenic surface. Structural comparison of Vsp1 with a homology model for Vsp2 suggests that observed differences in disease manifestation may arise in part from distinct differences in electrostatic surface properties; additional predicted positively charged surface patches on Vsp2 compared to Vsp1 may be sufficient to explain the relative propensity of Vsp2 to bind to acidic glycosaminoglycans.