Nélida Nora Polini

Comparative study of some haematological parameters of two wildChaetophractus villosus (mammalia, dasypodidae) populations

The study of haematological parameters of a species is of great interest both for the comprehension of its biological characteristics in general and its physiological adaptations in particular. In this work, we studied haematological parameters of two wild populations of armadilloChaetophractus villosus (population I,n=25 and population II,n=30). The animals came from a range of 150 km to the north west of Bahía Blanca, Argentina. Blood samples were obtained from anaesthetised animals by cardiac puncture, between 8:00 a.m. and 10:00 a.m. Blood was collected in EDTA and processed for haematological screen by routine techniques. Erythrocyte parameters (total erythrocytes, haematocrit, haemoglobin, erythrocyte indices and erythrocyte sedimentation rate) and leucocyte parameters (total leucocytes and percentage composition) were studied. Population I had higher values for erythrocytes, haematocrit and haemoglobin than population II. With the exception of eosinophils (p>0.05), no differences were found between populations of erythrocyte indices, erythrocyte sedimentation rate, total leucocytes and leucocyte percentage composition. The sample of population II featured a greater number of young animals than population I, age may therefore partially account for the differences. These results may also be influenced by a higher loading of parasites observed in population II.

Comparative vertebrate fibrinolysis

Fibrinolysis is a feature in the phylogeny of vertebrates. This review analyzes the fibrinolytic mechanism in different species compared to healthy adult humans. Additionally, it introduces the armadillo Chaetophractus villosus (Mammalia, Xenarthra, Dasypodidae) whose lytic process remains quite unknown until now. The analysis was conducted in a phylogenetic order: fish, amphibians, reptiles, birds, and mammals. It was designed to assess the fibrinolytic system in its various stages: global, specific, and degradation. The results are represented in tables grouped by test: fibrinogen, whole blood lysis time, whole blood diluted lysis time, euglobulin lysis time, plasminogen, fibrin/fibrinogen degradation products, D dimer, plasminogen activator inhibitor type 1, and alpha 2 antiplasmin activity. Global knowledge of the mechanism of fibrinolysis in vertebrates is a contribution of scientific interest not only in biology, but also for the development of experimental models applicable to the study of thrombotic and thrombolytic agents.

Haemostatic mechanisms of the armadillo Chaetophractus villosus (Xenarthra, Dasypodidae)

Haemostatic mechanisms in humans are formed by two activation pathways, named tissular factor pathway and contact system pathway, and a common pathway, that promotes the formation of the fibrin clot. These mechanisms have also been identified in other mammals. In this work we evaluate their presence in the armadillo Chaetophractus villosus, a mammal of the neotropical Xenarthra Order. Twenty animals (ten males and ten females), previously adapted to captivity, were used. Fibrinogen (Fbg) was measured at the beginning and at the end of the experimental period; prothrombin time (PT), activated partial thromboplastin time (APTT) and thrombin time (TT) were measured at the same time during the experience. Neither Fbg nor the other parameters evaluated showed sex-related differences, but Fbg diminished during the experimental period. TT related to PT and APTT showed longer times and larger dispersion of the individual values. Compared to the human beings, PT and TT were longer and APTT was shorter. Considering those results, we conclude that C. villosus has the same basic coagulation system as human beings. However, in this species the contact system pathway seems to play a greater role in the activation of the coagulation system than it does in man, and the common pathway appears to limit the velocity of the system.

Morphological and morphometric study of blood leucocytes fromChaetophractus villosus (Mammalia Dasypodidae)

The aim of this work was to study some morphological and morphometric parameters of leucocytes from blood smears of adult armadillosChaetophractus villosus (Mammalia, Dasypodidae). We also analysed the significance of the different sources of variation in these measurements. Blood samples were obtained through heart puncture, using plastic syringes without anticoagulant, in anaesthetised, wild, healthy animals (n=25). Two blood smears of each animal were stained with May Grünwald-Giemsa. Maximum and minimum diameters were measured for each type of leucocyte (n=10 for the most abundant ones: neutrophils and lymphocytes, andn=5 for others: eosinophils, basophils and monocytes). A hierarchical decomposition of the different sources of variation (animals, samples and cells) was carried out using pure model II nest ANOVA. This analysis was applied to both measured parameters. The variation components related to cells were always higher than those related to animals. Estimation of the selected parameters was only marginally changed between samples of the animal. The nuclei of both neutrophils and eosinophils were morphologically similar, generally with four or more lobes. The cytoplasm and neutrophils was only lightly stained. Lymphocytes are the smallest cell type, whereas basophils and lymphocytes are the roundest ones. Eosinophils and basophils are the cell types most variable in size. We suggest that for further studies the effort of sampling be aimed at measuring a larger number of cells from a moderate number of animals. Our results should represent the normal morphological and morphometrical characteristics of leucocytes of wild, healthy animals of this species.

Principal coagulation factors and natural anticoagulants in the armadillo Chaetophractus villosus (Mammalia, Xenarthra, Dasypodidae)

Blood coagulation is an important process regulated by a large number of proteins, which transform fibrinogen into fibrin. This mechanism was identified in several species other than humans. In this work we study the coagulation factors and principal natural anticoagulants in armadillos (Chaetophractus villosus). Coagulation factors FVII, FXII, FIX, FXI, FX, FVIII, FV, antithrombin (AT), protein C (PC), and protein S (PS) were identified. The activities of all factors were homogeneous for both sexes. Correlation studies showed associations between FVII and FX, FVII and FIX, FVII and FXI, FIX and FXI, and FIX and FX. Sex-related differences were observed for PS but not for AT or PC. There was positive correlation between PS and FV in females. These data constitute the first contribution to the knowledge of the proteins participating in the coagulation in this species and they demonstrate that the hemostatic process is similar in the armadillos and man.

A study of platelets in the armadillo chaetophractus villosus (xenarthra, dasypodidae).

Nothing is known about haemostasis in Xenarthra, a widely distributed Order of American mammalians. Chaetophractus villosus, a member of the Dasypodidae family of this group, which is easily adapted to captivity, is of growing interest for biomedical research. In this work, we studied platelet number, MPV, ultrastructure of the platelets by SEM and TEM, and aggregation responses to ADP and ristocetin in this species. Blood samples were obtained by cardiac puncture in 20 anaesthetised animals. Platelet count and MPV were evaluated at the beginning and at the end of a 3-year experimental period, to detect possible variations related to time of captivity. SEM and TEM were done by routine methods adapted to the material, and aggregation response to ADP and ristocetin were evaluated by the Born method. The parameters studied did not show any sex-related differences, nor did the platelet count change during captivity. Nevertheless, MPV decreased during this period. Platelets were ultrastructurally similar to those of other mammals and human beings and responded to proven agonists. Data provided in this study will contribute to the understanding of the haemostatic process in this species.

Fibrinolytic system of the armadillo Chaetophractus villosus (Xenarthra, Dasypodidae)

The fibrinolytic mechanism in the armadillo Chaetophractus villosus (Mammalia, Xenarthra, Dasypodidae) quite unknown until now was studied. Results were compared with those corresponding to healthy adult human beings. Whole blood lysis time and diluted blood lysis time were not detectable in armadillos. Euglobulin clot lysis time and plasminogen activity (Plg) were lower than in healthy humans. We established the presence of the fibrinolytic system in Ch. villosus through the measurement of fibrin fibrinogen degradation products. The activity of the plasminogen activator inhibitor was two to four times greater than in healthy humans. The activity of the alpha 2 anti-plasmin (α2AP) was similar and displaced toward lower values. The Plg/α2AP relation was lower. The results obtained suggest that Ch. villosus has a hypercoagulable and hypofibrinolytic profile. Our findings are not only the first contribution to elucidate the physiology of the fibrinolytic system in Xenarthra but also contribute to develop an animal model for studies in haemostasis and thrombosis.