Ante Svetina

Lipid status, paraoxonase-1 activity and metabolic parameters in serum of heifers and lactating cows related to oxidative stress

The objective of this study was to investigate serum lipids, metabolic parameters and activity of the anti-oxidative enzyme paraoxonase-1 (PON1). The study was conducted on non-pregnant heifers with optimal health status and on healthy dairy cows in the period of intensive lactation, assuming that the energy and metabolic demands during lactation reduce anti-oxidative protection. Total cholesterol and HDL-cholesterol concentrations were significantly higher (P<0.05) in lactating cows than in heifers. Bilirubin concentration and γ-glutamyltransferase (GGT) activity were also significantly higher in lactating cows (P<0.05), indicating increased hepatic efforts of cows to meet energy requirements for lactation. Significantly lower PON1 activity and PON1/HDL ratio in lactating cows compared to heifers (P<0.05) showed that metabolic efforts during pregnancy, parturition and lactation influence PON1 activity due to oxidative stress. Concurrent increase in total and HDL-cholesterol during lactation indicated that the HDL particle is a major carrier of cholesterol in cows.

The influence of sex on biochemical markers of bone turnover in dogs

Biochemical markers of bone turnover have been shown to be useful as inexpensive and noninvasive tools for monitoring skeletal health. The reference range for bone markers in dogs has been set by different age groups. However, other sources of biological variations were not fully investigated in dogs. To explore whether sex influences the interpretation of bone marker data we examined serum bone markers in 33 male and 25 female dogs. The bone markers selected for this study were: bone alkaline phosphatase (BALP) and osteocalcin (OC) as indicators of bone formation, and C-terminal telopeptide (CTx) of type I collagen as marker of bone resorption. All concentrations of bone markers were lower, but still within the reference range reported for dogs. We found statistically significant differences of the median OC and CTx serum concentrations between males and females. The results of this study suggest that there are sex differences in biochemical markers of bone turnover in dogs which should be considered in interpretation of bone marker data.

Effect of Splenectomy and Autologous Spleen Transplantation on the Serum Platelet-Activating Factor Acetylhydrolase (PAF-AH) Activity and Acute Phase Response (APR) in a Porcine Model

The aim of this study was to evaluate the inflammatory response after total splenectomy and spleen autotransplantation in a porcine model by measuring serum platelet-activating factor acetylhydrolase activity, C-reactive protein and albumin concentrations. Nineteen piglets were used in the experiment. After induction of anesthesia, animals were randomly divided into three groups: sham-operation with spleens intact (n = 6), total splenectomy (n = 6), and splenic autotransplantation (n = 7) with small fragments of the spleen autotransplanted into the greater omentum. The blood samples were taken just before surgery and on day 1st, 5th, 12th, 26th and 40th postoperatively. PAF-AH activity, CRP and albumin concentrations were assayed in the sera. After total splenectomy, PAF-AH activity was significantly increased on day 5th, while there was no significant increase after spleen autotransplantation or the sham-operation. CRP was significantly increased after surgery in all experimental groups. Albumin was significantly decreased after surgery from day 5th until day 40th in splenectomized and autotransplanted pigs. Increased PAF-AH activity after splenectomy and spleen autotransplantation might be attributed to inflammatory conditions due to the loss of splenic tissue and trauma. Time-course increase of CRP, in all groups after surgery suggests post-injury inflammatory response due to tissue lesion during operation.

Relevance of paraoxonase-1, platelet- activating factor acetylhydrolase and serum amyloid A in bovine mastitis

Bovine mastitis is the most economically important production disease in dairy cows. The pathogenesis of mastitis involves an inflammatory reaction resulting from production of cytokines at the site of infection. Proinflammatory cytokines stimulate the synthesis of acute phase proteins (APPs) predominantly in liver but also in other tissues including mammary gland (Eckersall et al., 2006). Serum amyloid A (SAA) is one of the major APP in ruminants whose concentration rises dramatically during acute phase response (APR). During APR, SAA associates rapidly with high density lipoproteins (HDL), displacing apo A-1 (the major apolipoprotein of native HDL) and becoming the predominant apolipoprotein (apo SAA) in HDL. Native HDL contains paraoxonase-1 (PON1) and platelet-activating factor acetylhydrolase (PAF-AH), both antioxidative/anti-inflammatory enzymes being responsible for anti-inflammatory/anti-oxidative properties of HDL. Concomitantly with SAA enrichment of HDL during APR, PON1 and PAF-AH levels decrease within HDL, what impairs anti-oxidative properties of HDL which from an anti-inflammatory particle becomes a proinflammatory particle, i.e. acute phase HDL (AP-HDL) (Van Lenten at al., 1995).