Osmotic gradient ektacytometry (measuring elongation index in the function of osmolality at a constant shear stress) is a sensitive method to analyze red blood cell (RBC) deformability and investigating the optimal osmolality range for the cells in normal or pathophysiological cellular and micro-environmental conditions. However, the methodological conditions are different, since the results are infl uenced by the applied shear stress (SS). In this study we investigated rat, dog, pig and human blood samples at SS of 1, 2, 3, 5, 10, 20 and 30 Pa. To describe the range being related to the cell deformability, we introduced new calculated parameters obtained from the raw data of the elongation index (EI)-osmolality (O) curves. Our results showed that: (1) Osmoscan data tested at 20 or 30 Pa do not differ signifi cantly from each other; (2) Under SS of 20 Pa the EImax, the O (EImax), the EI min and the area under curve nearly linearly decrease in the function of SS with different slope in rat, dog, pig and human blood; (3) Measurements under 3 Pa SS become unstable; (4) The differences between minimal and maximal EI and the belonging osmolality values, and their ratios, as new calculated parameters ( Δ EI, Δ O, Δ EI/ Δ O, EImax/EImin and O (EImax)/Omin) can be suitable for further analysis of the osmoscan curves together with other hemorheological parameters describing RBC deformability; and (5) Decreased erythrocyte deformability (by rigidifying with glutaraldehyde) can be refl ected well with the following, calculated osmoscan parameters: Δ O, rO, rEI/rO and Δ EI/ Δ O.

Although growing number of evidences supports the gender differences of hemorheological variables in human, little is known about this question in experimental animals. Investigating this question and giving laboratory-specific reference values, blood samples from healthy male and female CD rats and beagle dogs were tested for hematological parameters (microcell counter), blood and plasma viscosity (capillary viscometer), erythrocyte deformability (bulk filtrometry and ektacytometry), erythrocyte aggregation (light transmission aggregometer) and fibrinogen concentration (coagulometer).Besides the inter-species alterations we found hematological gender differences too regarding the red blood cell count and hematocrit. In rats the erythrocyte aggregation index was higher in females, while in beagle dogs the males showed significantly higher aggregation index values. In rats the red blood cell deformability showed better values in females. In beagle dogs this was the opposite, the males had better elongation index (EI) values in the function of shear stress (SS). Besides this it was also experienced that the shape of the canine EI -SS curves differed from the rats' values.Gender differences with inter-species alterations can be observed in laboratory animals (rats and dogs) that have to be taken under consideration during planning experiments and evaluating results.

The hemorheological parameters, such as whole blood viscosity, plasma viscosity, hematocrit, fibrinogen concentration as well as the micro-rheological properties of red blood cells (red blood cell deformability and aggregation) play an important role in tissue perfusion. The alternating hemorheological parameters, which are also inter-related, have important effects in determining hemodynamical properties, as well. The altered hemorheological status has a direct effect on endothelial function by changing shear force profile on the endothelial wall, and impairment of red blood cell deformability and aggregation (presence of rigid red blood cell, and enhanced red blood cell aggregation) slows down microcirculation with disturbing capillary perfusion. In experimental surgery vascular clamping and release cause ischemia-reperfusion, which affect red blood cells in many ways: changes pH level, leads to free-radical release, changes osmolarity and lactate and NO concentrations as well as it causes mechanical trauma. Understanding of these pathophysiological processes and determining the extent of reversible-irreversible changes may help to delineate underlying causes in tissue perfusion and microcirculation better, and develop prophylactic and therapeutic possibilities. The challenges of experimental surgery also include the questions of comparability in different measurement methods, and understanding of interspecies-differences of experimental/laboratory animal models in order to increase the relevance of results in terms of applicability for the original, clinical question.

The aim of this study was to investigate intestinal ischemia-reperfusion and its local and systemic hemorheological relations in the rat. Ten anaesthetized female CD outbred rats were equally divided into 2 experimental groups. (1) Ischemia-reperfusion (I/R): the superior mesenterial artery was clipped for 30 minutes. After removing the clip, 60 minutes of the reperfusion was observed before extermination. Blood samples were taken from the caudal caval vein and from the portal vein before ischemia, 1 minute before and after clip removal, and at the 15th, 30th, and 60th minutes of the reperfusion. (2) Sham operation: median laparotomy and blood sampling were done according to the timing as in I/R group. Hematological parameters, red blood cell aggregation, and deformability were determined. Leukocyte count and mean volume of erythrocytes increased slightly but continuously in portal venous samples during the reperfusion period. Red blood cell aggregation values were higher in portal blood by the end of ischemia, and then became elevated further comparing to the caval venous blood. Both in caval and portal venous samples of I/R group red blood cell deformability significantly worsened during the experimental period compared to its base and Sham group. In portal blood red blood cell deformability was impaired more than in caval vein samples. Histology showed denuded villi, dilated capillaries, and the inflammatory cells were increased after a 30 minutes ischemia. In conclusion, intestinal ischemia-reperfusion causes changes in erythrocyte deformability and aggregation, showing local versus systemic differences in venous blood during the first hour of reperfusion.

Abstract. Laboratory investigations often require centrifugation of blood samples for various erythrocyte tests. Although there 8 is a lack of data about the effect of centrifugation at various g force levels on erythrocyte rheological properties. We aimed 9 to investigate the effect of a 10-minute centrifugation at 500, 1000 or 1500 g at 15• C of rat, dog, pig and human venous 10 (K3-EDTA, 1.5 mg/ml) blood samples. Hematological parameters, erythrocyte deformability, cell membrane stability, osmotic 11 gradient ektacytometry (osmoscan) and erythrocyte aggregation were determined. Hematological and erythrocyte deformability 12 parameters showed interspecies differences, centrifugation caused no significant alterations. Cell membrane stability for human other hand, erythrocyte deformability parameters were stable, cell membrane stability and osmoscan data show minor shifts.

PURPOSE:The failure of small-caliber vascular grafts still means a serious problem. Concerning the early postoperative complications we aimed to investigate the hemostaseological and hemorheological aspects of this issue in a canine model. METHODS:In the Control group only anesthesia was induced. In the Grafted group under general anesthesia a 3.5-cm segment was resected unilaterally from the femoral artery and replaced with a PTFE graft (diameter: 3 mm). On the 1 st -3 rd -5 th -7 th and 14 th postoperative days the skin temperature of both hind limbs was measured, and blood sampling occurred for hematological, hemostaseological and hemorheological tests. RESULTS:The skin temperature of the operated versus intact limbs did not differ. In the Grafted group leukocyte count was elevated by the 1 st postoperative day, while platelet count increased over the entire follow-up period. Fibrinogen concentration rose on the 1 st -5 th days, activated partial thromboplastin time increased on the 3 rd -7 th days. Erythrocyte aggregation was enhanced significantly on the 1 st -5 th days. In specimens taken on the 14 th day, histologically we found matured thrombus narrowing the graft lumen. CONCLUSIONS:Small-caliber PTFE graft implantation into the femoral artery caused significant changes in several hemostaseological and hemorheological parameters. However, better clarifying the factors leading to early thrombosis of these grafts needs further studies.Key words: Vascular Grafting. Graft Occlusion, Vascular. Erythrocyte Aggregation. Blood Coagulation. Models, Animal. Dogs. Early postoperative changes in hematological, erythrocyte aggregation and blood coagulation parameters after unilateral implantation of polytetrafluoroethylene vascular graft in the femoral artery of beagle dogs

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