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Background: Arteriovenous malformations (AVMs) are vascular anomalies characterized by abnormal shunting between arteries and veins. The progression of the AVMs and their hemodynamic and rheological relations are poorly studied, and there is a lack of a feasible experimental model., Objective: To establish a model that cause only minimal micro-rheological alterations, compared to other AV models., Methods: Sixteen female Sprague Dawley rats were randomly divided into control and AVM groups. End-to-end anastomoses were created between the saphenous veins and arteries to mimic AVM nidus. Hematological and hemorheological parameters were analyzed before surgery and on the 1st, 3rd, 5th, 7th, 9th, and 12th postoperative weeks., Results: Compared to sham-operated Control group the AVM group did not show important alterations in hematological parameters nor in erythrocyte aggregation and deformability. However, slightly increased aggregation and moderately decreased deformability values were found, without significant differences. The changes normalized by the 12th postoperative week., Conclusions: The presented rat model of a small-caliber AVM created on saphenous vessels does not cause significant micro-rheological changes. The alterations found were most likely related to the acute phase reactions and not to the presence of a small-caliber shunt. The model seems to be suitable for further studies of AVM progression.

Background: Rheopheresis is a selective extracorporal double cascade filtration treatment, which can extract high molecular weight proteins being responsible for hyperviscosity. As the whole blood and plasma viscosity decrease microcirculation improves., Objective: In this preliminary study we aimed to analyze additional beneficial effects of rheopheresis treatment with changes of pro-inflammantory cytokine levels in diabetic foot syndrome patients., Methods: Two rheopheresis treatments were performed for 6 patients with diabetic foot ulcer and/or neuropathy on consecutive days. Before and after the treatments whole blood and plasma viscosity, as well as IL-6, IL-8, and TNF-alpha serum levels were determined, and complex angiological and ENG examinations were performed., Results: Rheopheresis decreased the whole blood and plasma viscosity, and the serum levels of IL-6, IL-8, and TNF-alpha were markedly reduced. The life quality of the patients improved, the ulcers healed, the pain decreased. Daily dose of analgesics decreased in the follow-up period (6 months). The ENG showed improving amplitude and/or normalizing conduction speed., Conclusion: Application of rheopheresis in patients with diabetic foot syndrome has a beneficial effect, providing favorable rheological condition, normalizing cytokine profile and reducing the sensorineural symptoms.

Background: Red blood cell (RBC) aggregation plays an important role in the physiological processes of the microcirculation. The complete mechanism of aggregation is still unclear, and it is influenced by several cellular and plasmatic factors. One of these factors is the hematocrit (Hct)., Objective: We hypothesized that the relation of RBC aggregation and Hct differs between species., Methods: From anticoagulated blood samples of healthy volunteers, rats, dogs, and pigs, 20, 40, and 60 %Hct RBC, autologous plasma suspensions were prepared. Hematological parameters and RBC aggregation was determined by light-transmission and light-reflection method., Results: Suspensions at 20%and 60%Hct expressed lower RBC aggregation than of 40%Hct suspensions, showing inter-species differences. By curve fitting the Hct at the highest aggregation value differed in species (human: 45.25%- M 5 s, 40.86%- amp; rat: 44.44 %- M1 10 s, 39.37%- amp; dog: 42.48%- M 5 s, 44.29%- amp; pig: 47.63%- M 5 s, 52.8%- amp)., Conclusion: RBC aggregation - hematocrit relation shows inter-species differences. Human blood was found to be the most sensitive for hematocrit changes. The more obvious differences could be detected by M 5 s by light-transmission method and amplitude parameter using light-reflection method.

Background: The effects of temperature on micro-rheological variables have not been completely revealed yet., Objective: To investigate micro-rheological effects of heat treatment in human, rat, dog, and porcine blood samples., Methods: Red blood cell (RBC) - buffer suspensions were prepared and immersed in a 37, 40, and 43°C heat-controlled water bath for 10 minutes. Deformability, as well as mechanical stability of RBCs were measured in ektacytometer. These tests were also examined in whole blood samples at various temperatures, gradually between 37 and 45°C in the ektacytometer., Results: RBC deformability significantly worsened in the samples treated at 40 and 43°C, more expressed in human, porcine, rat, and in smaller degree in canine samples. The way of heating (incubation vs. ektacytometer temperation) and the composition of the sample (RBC-PBS suspension or whole blood) resulted in the different magnitude of RBC deformability deterioration. Heating affected RBC membrane (mechanical) stability, showing controversial alterations., Conclusion: Significant changes occur in RBC deformability by increasing temperature, showing inter-species differences. The magnitude of alterations is depending on the way of heating and the composition of the sample. The results may contribute to better understanding the micro-rheological deterioration in hyperthermia or fever.

Background: The optimal timing of remote ischemic preconditioning (RIPC) in renal ischemia-reperfusion (I/R) injury is still unclear. We aimed to compare early- and delayed-effect RIPC with hematological, microcirculatory and histomorphological parameters., Methods: In anesthetized male CrI:WI Control rats (n = 7) laparotomy and femoral artery cannulation were performed. In I/R group (n = 7) additionally a 45-minute unilateral renal ischemia with 120-minute reperfusion was induced. The right hind-limb was strangulated for 3×10 minutes (10-minute intermittent reperfusion) 1 hour (RIPC-1 group, n = 7) or 24 hour (RIPC-24 group, n = 6) prior to the I/R. Hemodynamic, hematological parameters and organs' surface microcirculation were measured., Results: Control and I/R group had the highest heart rate (p < 0.05 vs base), while the lowest mean arterial pressure (p < 0.05 vs RIPC-1) were found in the RIPC-24 group. The highest microcirculation values were measured in the I/R group (liver: p < 0.05 vs Control). The leukocyte count increased in I/R group (base: p < 0.05 vs Control), also this group's histological score was the highest (p < 0.05 vs Control). The RIPC-24 group had a significantly lower score than the RIPC-1 (p = 0.0025 vs RIPC-1)., Conclusion: Renal I/R caused significant functional and morphological, also in the RIPC groups. According to the histological examination the delayed-effect RIPC method was more effective.

Background: Chronic kidney disease (CKD) models are known to study pathophysiology and various treatment methods. Renal dysfunction could influence erythrocytes through several pathways. However, hemorheological and microcirculatory relation of CKD models are not completely studied yet., Objective: To evaluate erythrocyte micro-rheology, microcirculatory and structural compensatory mechanisms in a rat model of CKD., Methods: Female Sprague-Dawley rats were subjected to nephrectomy group (NG, n = 6) or sham-operated group (SG, n = 6). NG rats were subjected to 5/6 nephrectomy in two stages. In SG no intervention was made on kidneys. Hemorheological and hematological measurements were carried out after each stage, and 5 weeks after the last operation. Histological and microcirculatory studies were done on the remaining kidney and compared with sham rats., Results: Serum creatinine increased in NG (p = 0.008), accompanied with decrease of red blood cell count (p = 0.028) and hemoglobin (p = 0.015). Erythrocyte aggregation parameters slightly increased in NG, while the elongation index didn't show significant changes. Microcirculation was intact in the remnant kidney of NG. However, in comparison with SG, the diameter of glomeruli increased significantly (p < 0.01)., Conclusions: Erythrocyte mass was influenced more than micro-rheological properties in this model. The main compensation mechanism was rather structural than at microcirculatory level.

Background: Pathomechanism and optimal renoprotective protocol for remote ischemic preconditioning (RIPC) have not been completely revealed yet., Objective: To investigate micro-rheological effects of early and delayed RIPC in renal ischemia-reperfusion (I/R) in the rat., Methods: In Control group the left femoral artery was cannulated and the left kidney was gently exposed. In the I/R group 45-minute renal ischemia with 120-minute reperfusion period was monitored. In the RIPC groups a 3×10-minute protocol was applied using tourniquet around the right hind-limb 1 hour (RIPC-1) or 24 hours (RIPC-24) prior to the I/R. Blood samples were taken for testing blood gas, acid-base, metabolic and hemorheological parameters., Results: Lactate and potassium concentration significantly increased in I/R that could be reduced by RIPC, especially in RIPC-24. Creatinine concentration increased further in RIPC groups. I/R and RIPC-1 decreased the pH, RIPC-24 increased. RIPC-24 reduced the drop in base excess. Erythrocyte deformability worsened by renal I/R. In RIPC groups deformability decreased additively. However, RIPC-1 could improve the condition. RIPC-24 showed the highest erythrocyte aggregation values during reperfusion., Conclusions: Renal I/R worsened metabolic and micro-rheological parameters that could be modulated by RIPC protocols. However, it could not be decided whether the early or the delayed protocol is better.