Haemoglobin oxygen affinity and regulating factors of the blood oxygen transport in canine and feline blood

Complete dynamic oxygen equilibrium curves (OEC) on dogs and cats whole blood were measured at 33, 37 and 41 degrees C. OEC were also run at three partial carbon dioxide pressures (20, 40 and 80 mmHg) as well as at five pH levels (7.2, 7.3, 7.4, 7.5 and 7.6). 2,3- diphosphoglycerate (DPG) concentrations were determined. Results were compared to those previously published in humans, using the same experimental method [Comp. Biochem. Physiol. 106 (1993) 687]. In standard conditions (pH 7.4, pCO2 40 mmHg and temperature 37 degrees C), the partial oxygen pressure at half-saturation of haemoglobin (p50) was 30.0+/-1.3 mmHg for dogs and 34.1+/-1.8 mmHg for cats. Cat's OEC was thus rightshifted compared to dog's OEC, itself rightshifted compared to human OEC. 2,3-DPG concentrations were higher in dogs than in men until they were very low in cats. Contrary to that observed in human medicine, no significant correlation was identified between standard p50 and canine 2,3-DPG values. Influence of pH, pCO2 and temperature on the OEC was saturation dependent. In dogs, Delta log p50/Delta pH was equal to -0.370, Delta log p50/Delta log pCO2 was 0.093 and Delta log p50/Delta T was 0.020. In cats, Delta log p50/Delta pH was equal to -0.405, Delta log p50/Delta log pCO2 was 0.080 and Delta log p50/Delta T was 0.016. Practically, temperature and pH variations exert a lesser influence in domestic carnivores than in humans, effect of pCO2 being similar in both.     

Efficacy of ceftiofur and flunixin in the early treatment of bronchopneumonia in weaners

Three groups of five pigs were inoculated intratracheally with Escherichia coli lipopolysaccharides, and 24 hours later with 10 x 10(9) colony-forming units of a non-toxigenic strain of Pasteurella multocida type A; a fourth group was left uninoculated as controls. The three inoculated groups received either no treatment (positive controls), or were treated with 3 mg/kg ceftiofur intramuscularly once a day for five consecutive days, either alone or combined with 2 mg/kg flunixin intramuscularly once a day for three consecutive days. The sustained coughing and hyperthermia recorded in the positive controls disappeared after two days and three days of treatments, respectively, in the treated animals, and the reductions in daily weight gain and changes in breathing pattern observed in the controls were not observed in the treated animals. There were no significant differences between the pigs treated with ceftiofur alone or ceftiofur combined with flunixin. In the positive controls, the number of inflammatory cells in samples of bronchoalveolar lavage fluid continued to increase up to 15 days after inoculation, whereas in the treated animals there were similar increases at six days but the numbers had decreased to baseline levels after 15 days. Similarly, in the treated animals the volume of the lung lesions was significantly less than in the control animals, but the inclusion of flunixin in the treatment regimen had no significant additional effect.     

The effect of colic on oxygen extraction in horses

Blood oxygen transport and oxygen extraction were assessed in horses with colic. A gravity score (GS) ranging from 1 to 3 was attributed to each colic case with healthy horses used as controls. Jugular venous and carotid arterial blood samples were collected and concentrations of 2,3-diphosphoglycerate, adenosine triphosphate, inorganic phosphate and chloride were determined. pH and partial pressures of carbon dioxide (PCO(2)), and oxygen (PO(2)) were also measured. Oxygen equilibrium curves (OEC) were constructed under standard conditions and oxygen extraction ratios calculated. Haemoglobin oxygen affinity measured under standard conditions (P50(std)) was unchanged in colic horses compared with healthy controls. Horses with the highest GS, i.e. 3 had lower blood pH values than healthy animals. Arterial and venous partial pressures of oxygen at 50% haemoglobin saturation (P50(a) and P50(v)) were significantly higher in horses suffering from colic (GS=3) than in healthy horses. The oxygen extraction ratio was also significantly increased in colic horses with a GS of 3. A rise in the oxygen extraction ratio detected in the most severely affected animals seemed to reflect the compensatory properties of the oxygen transport system where extraction of oxygen from the blood increases when systemic oxygen delivery decreases, as might be anticipated in horses with colic.     

Influence of Reducing Conditions on Solubility of Trace Metals in Contaminated Soils

Dissolved trace metals Cd, Pb, Zn, andother solutes were determined after reducingconditions have been imposed to samples of anagricultural polluted soil. The ploughed layer wassampled as undisturbed blocks for floodingexperiments, and sieved samples were incubated inaqueous suspensions at controlled pH (pH 6.2) underdifferent redox conditions. Redox potential and pH,concentrations of major and trace elements, andorganic and inorganic ligands, were measured in thesolutions. Their chemical speciation was calculated byusing the programme Soilchem.These experiments and calculations have shown that pHvariations definitively influence trace metalsolubility, whatever they are induced by reductivedissolution, organic acid formation, or otherprocesses, and that strong acidification can beobtained with well buffered soil when about 1%available carbon is anaerobically transformed intoorganic acids. The organic acids also intervene bycomplexation, particularly for Pb. On another hand,denitrification can limit these effects by consumingprotons and organic substances. Given a steady pH,reducing conditions enhance the mobility of tracemetals, at first by dissolution of manganic and ferricoxides; Pb appeared more sensitive to these processesthan Zn, and finally Cd. As a general rule,hydromorphy in a well-buffered contaminated soil at afirst step should increase the mobility of divalenttrace metals, by decreasing pH and reducing Mn and Feoxides, but prolonged flooding can lead to fix tracemetals again, rather by re-adsorption or precipitationphenomena than by formation of insoluble sulphides.     

B cell receptor signal transduction in the GC is short-circuited by high phosphatase activity

Germinal centers (GCs) generate memory B and plasma cells, which are essential for long-lived humoral immunity. GC B cells with high-affinity B cell receptors (BCRs) are selectively expanded. To enable this selection, BCRs of such cells are thought to signal differently from those with lower affinity. We show that, surprisingly, most proliferating GC B cells did not demonstrate active BCR signaling. Rather, spontaneous and induced signaling was limited by increased phosphatase activity. Accordingly, both SH2 domain-containing phosphatase-1 (SHP-1) and SH2 domain-containing inositol 5 phosphatase were hyperphosphorylated in GC cells and remained colocalized with BCRs after ligation. Furthermore, SHP-1 was required for GC maintenance. Intriguingly, GC B cells in the cell-cycle G(2) period regained responsiveness to BCR stimulation. These data have implications for how higher-affinity B cells are selected in the GC.     

Calculation of bovine haemoglobin oxygen saturation by algorithms integrating age,haemoglobin content,blood pH,partial pressures of oxygen and carbon dioxide in the blood,and temperature

In human and veterinary medicine, arterial and venous haemoglobin oxygen saturations are often used to estimate the severity of a disease and to guide therapeutic decisions. In veterinary medicine, haemoglobin oxygen saturation (SO(2)) is usually calculated using a blood gas analyser and algorithms developed for humans. It is possible, therefore, that the values obtained in animals may be distorted, particularly in animals with a high haemoglobin oxygen affinity, like young calves. In order to verify this hypothesis, we compared the arterial (SaO(2)) and venous (SvO(2)) haemoglobin oxygen saturations calculated using three different algorithms, and the oxygen exchange fraction (OEF) at the tissue level, which is the degree of haemoglobin desaturation between arterial and venous blood (SaO(2)-SvO(2)), with the values obtained from the whole bovine oxygen equilibrium curve (OEC) determined by a reference method. The blood gas analysers underestimated SvO(2) values; consequently, the OEF was overestimated (by about 10%). Two methods of reducing these errors were assessed. As the haemoglobin oxygen affinity decreases during the first month of life in calves a relationship between PO(2) at 50% haemoglobin saturation (P50) and age was established in order to correct the calculated values of venous and arterial SO(2), taking into account the estimated position of the OEC. This method markedly reduced the error for SvO(2) and OEF. Secondly, the SO(2) was calculated using a mathematical model taking into account the age of the animal and the specific effects of pH, PCO(2), and temperature on the bovine OEC. Using this method, the mean difference between the OEF values calculated using the mathematical model and those calculated by the reference method was close to zero. The errors produced by blood gas analysers can thus be minimised in two ways: firstly, by simply introducing a P50 estimated from the age of the calf into the analyser before the measurement; and secondly, by calculating the SO(2) using a mathematical model applied to the bovine OEC.     

Heavy Metal Determination in Atmospheric Deposition and Other Fluxes in Northern France Agrosystems

Water, Air, &; Soil Pollution - The aim of this study is to assess the annual balance of the fluxes of Cd, Cu, Ni, Pb and Zn within different cropping systems, in an experimental site located...     

Fate of airborne metal pollution in soils as related to agricultural management. 1. Zn and Pb distributions in soil profiles

The fate of airborne metal pollutants in soils is still relatively unknown. We studied the incorporation of such airborne metal pollution in two soils under long-term permanent pasture (PP) and conventional arable land (CA). Both soils were located at an almost equal distance from a former zinc smelter complex and developed under comparable pedogenetic conditions. Profiles of total concentrations of Zn, chosen as a mobile, and Pb as a little- or non-mobile element, were examined and compared with macro- and micromorphological soil characteristics (soil colour, biological activity). The two soils showed different profiles of total Zn and Pb concentrations, with a marked decrease of concentrations of both elements under the plough layer in CA, whereas the decrease was more progressive in PP. However, the stocks of Zn and Pb for the 1-m soil profiles of CA and PP were comparable. Correlation of Zn and Pb concentration at different depths with total Fe contents and comparison with estimated data for the local geochemical background (LGCB), suggests transport of Zn from the surface to depth in CA and PP, and Pb movement in PP. In CA, 53% of Zn and 92.5% of Pb stocks derived from airborne metal pollution were located at depths < 26 cm. In PP, only 40% of Zn and 82% of Pb, derived from airborne pollution, were found in the A11 and A12 horizons (< 26 cm), the remaining 18% of the Pb stock being incorporated until 50 cm depth; one-third of total Zn stock ascribed to airborne pollution was found at depths > 50 cm. Studies of the composition of gravitational water collected in soils from the same study area suggest two mechanisms for metal movement. First, mobile metal ions (Zn²⁺) move in the soil solution and are intercepted by iron-clay complexes in deeper soil horizons. Second, observed only in PP, simultaneous movement of Zn and Pb is ascribed to bioturbation by earthworms.