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The condition of gastrointestinal tract determines in many respects the regenerative capacity and the risk of complications in patients with extensive skin burns. However, the mechanism of developing vascular dysfunction in the colon in the burned individuals has so far been poorly studied. The aim of the investigation is to study intramural circulatory disorders of the colon using optical coherence tomography angiography (OCTA) and laser Doppler flowmetry (LDF) in different time periods after modeling a thermal burn., Materials and Methods: A deep thermal skin burn was induced on the area covering 10% of the body surface of Wistar rats (n=15). The blood flow of the colon wall was continuously monitored for 15 min before and 45 min after the burn using OCTA and LDF. The colon wall was again studied on days 7 and 14 using the same OCTA and LDF techniques. At each time point (45 min, day 7 and 14), 5 animals were withdrawn from the experiment, the colon wall was taken for histological study. The colon wall samples from three control rats without thermal skin burns were also histologically investigated., Results: During 45 min after the induction of the thermal burn, the in vivo OCTA and LDF techniques registered changes in intramural blood flow in the form of dropping of some arterioles and capillaries out of the general blood flow with concurrent activation of vascular shunts as a compensatory mechanism. Histologically, a marked edema of the submucosa, erythrocyte aggregation, and stasis in the capillary network were observed in this period. According to the OCTA and LDF data, the microcirculatory disorders in the colon were partially resolved by day 7, and by day 14 the analyzed indicators returned to the initial level. The data of the histological evaluation have shown that on day 7 after the burn induction, submucosal edema was absent, however, the signs of microcirculatory disorder and inflammatory changes remained. On day 14, the pathological changes in the tissues were not observed., Conclusion: The OCTA and LDF methods allowed us to establish experimentally that during the first 45 min thermal burn causes considerable disturbances of the blood flow in the colon wall, which normalizes only by day 14 if no therapy is administered. The obtained data on the mechanism of circulatory disorder development in the colon may become a basis for choosing therapy directed to prevention of intestine dysfunction in people with burns., Competing Interests: Conflicts of interest. The authors have no conflicts of interest to declare.

The aim of the study was to use multimodal optical coherence tomography (MM OCT) to evaluate microstructure and microcirculation in the proximal and distal sections of the intestine relative to the resected area in acute mesenteric ischemia., Materials and Methods: The study was carried out using three groups of male Wistar rats weighing 270-435 g (n=18). Acute occlusive arterial ischemia of the small intestine was initiated in all animals. After 80-90 min, the ischemic non-viable part of the intestine was resected, and the operation was completed by stoma exteriorization (group 1, n=6), by applying purse-string sutures (group 2, obstructive resection, n=6), or by internal drainage of the proximal and distal ends of the small intestine (group 3, bypass, n=6). Relaparotomy and anastomosis formation were performed 2 days later.With the help of MM OCT at each stage of the surgical intervention, images were obtained from the serous membrane side: the intestinal wall microstructure (layers) was viewed using cross-polarization OCT (CP OCT) and the intramural circulation - using optical coherent angiography (OCA). The MM OCT images obtained from the terminal intestine sections immediately after resection and 2 days later (before the anastomosis formation) were compared between the experimental groups, as well as with the pre-ischemic data (norm). All resected sections of the intestine were then histologically examined. The MM OCT data were compared with the histological and intravital macroscopy data., Results: As a result of studying the intestinal wall microstructure by in vivo CP OCT, it was found that during ostomy (group 1) and obstructive resection (group 2), the images showed signs of tissue edema and destructive changes in the mucous membrane that were confirmed histologically, while with bypass surgery (group 3), there were minimal changes as compared with the norm.According to the OCA data, on day 2 of ostomy in the proximal and distal segments of the intestine, there was a noticeable disappearance of small and medium blood vessels; mainly large arteries and veins could be visualized. Following obstructive resection (purse-string suturing) or bypass surgery, the most noticeable changes (a decrease in the number of visualized blood vessels) were observed in the distal part of the intestine. The L index calculated from OCA images and characterizing the total length of the intramural perfused vasculature, showed a statistically significant decrease during ostomy: 12.18 [10.40; 14.20] μm - in the proximal and 10.67 [7.98; 13.05] μm - in the distal section; for comparison, the L index before ischemia was 18.90 [17.98; 19.73] μm and 18.74 [17.46; 19.90] μm, respectively (p=0.0001). In obstructive resection (group 2), statistically significant differences in the L parameter were found only for the distal bowel section: 16.39 [12.37; 18.10] μm compared with 18.74 [17.46; 19.90] μm before ischemia (p=0.041). After bypass surgery (group 3), there were no significant deviations in the L index., Conclusion: By using MM OCT, we found that in treating the remaining sections of the intestine after its emergency resection for acute mesenteric ischemia, the type of surgical technique determines the tissue structure in the period before the delayed anastomosis is applied.The least pronounced and most balanced changes occur in the proximal and distal segments of the intestine when operated using the bypass technique. However, to recommend this type of surgery, the development of reliable, safe, and effective bypass instruments is needed., Competing Interests: Conflicts of interest. The authors have no conflicts of interest.

Using bacteriophages to overcome the increasing resistance of microorganisms to antibiotics is a novel research venue of clinical importance. Among other challenges, this technique is expected to create and maintain an adequate local concentration of bacteriophages at the site of application. In addition, the possibility of combining the phage preparation with antioxidants and anesthetics may provide new options for stimulating the reparative process. The aim of the study was to assess the viability and lytic activity of bacteriophages incorporated into a hydrogel-based wound dressing that contains polyvinyl alcohol, phosphate buffer, with optional additions of succinic acid and lidocaine., Materials and Methods: A technique for incorporating bacteriophages into the complex hydrogel wound dressing ex tempore has been proposed. The bacteriolytic activity of phages inside the hydrogel was determined using standard microbiological techniques. Specifically, we used nutrient media with lawn cultures of Staphylococcus aureus added with the following antibacterial combinations: bacteriophages + succinic acid, bacteriophages + lidocaine, and bacteriophages + succinic acid + lidocaine. The lytic activity of bacteriophages was assessed within 1 to 7 days after the formation of the hydrogel., Results: In all samples containing bacteriophages, the presence of viable and lytically active phages was noted within 1 to 7 days, as evidenced by the "negative colonies" on the culture lawns. On days 1 to 3, no secondary growth was recorded in the phage-containing samples. In hydrogel samples containing phages, succinic acid, and lidocaine, secondary bacterial colonies were detected starting from day 4 indicating some reduction in the lytic activity., Conclusion: The results suggest that bacteriophages immobilized in the hydrogel maintain their viability and lytic activity, and this activity persists when the phages are combined with succinic acid and lidocaine., Competing Interests: Conflict of interest. There is no conflict of interest among the authors and other interested parties.

The aim of the study was to evaluate the performance of trans-serosal multimodal OCT (MM OCT) in in vivo detecting of changes in microstructure and blood circulation of the small intestine wall caused by arteriovenous ischemia resulted from intestine strangulation., Materials and Methods: In experiments on Wistar rats (n=22), we examined the small intestine wall in vivo using MM OCT; the access to the intestine was reached through laparotomy. The microvasculature and microstructure of the wall were studied before and after acute arteriovenous ischemia created by ligation of a small bowel segment. The results were then added with data obtained from histological and intravital microscopic examination., Results: Trans-serous MM OCT allowed us to visualize the bowel wall to its entire thickness, distinguish between the serous-muscular and mucous-submucosal layers, and detect the villi and functioning blood vessels. The structures were best seen after a fat emulsion had been administered into the bowel lumen. In OCT images made in the optical coherent angiography (OCA) mode, large paired vessels (arteries and veins) and micro-vessels with a diameter of >15 μm could be seen. Most of the blood vessels were imaged in the depth range of 80-300 μm from the surface. Capillaries with a diameter of 7-10 μm were not seen, but they produced an overall bright background. In the OCA images reconstructed from a volume of 2.4×2.4×1.8 mm, the total length of the vascular bed before ischemia was 18.3 [16.6; 19.8] mm.Strangulation of the intestinal loop was associated with changes in the CP OCT picture: the villi-associated vertical pattern and shadows of blood vessels disappeared and the depth of tissue visualization in the cross-channel decreased. The optical equivalents of the serous-muscular layer were preserved; after 180±12 min of ischemia, their proportion in the intestinal wall thickness increased from 25 [18; 32] to 42 [31; 55]% (p=0.031). At that time-point, OCA images of the strangulated bowel loop looked all similar: a uniform dark background with isolated fragmentary large vessels and no signs of blood flow in the microvascular network., Conclusion: Trans-serous MM OCT provides for in vivo visualization of microstructures critical for surgical gastroenterology: the intestinal wall layers including villi and blood vessels of each layer, as confirmed by histological analysis. Destructive processes in the intestinal wall resulting from bowel ligation bring about optical changes, which can be detected using real-time MM OCT., Competing Interests: Conflict of interests. The authors have no conflict of interest.