Sialic acid, glutathione metabolism, and electrical conductivity in bovine mastitic udder tissue

Cyanidin-3-O-β-glucopyranoside, a natural free-radical scavenger against aflatoxin B1- and ochratoxin A-induced cell damage in a human hepatoma cell line (Hep G2) and a human colonic adenocarcinoma cell line (CaCo-2)

Recent findings have suggested that oxidative damage might contribute to the cytotoxicity and carcinogenicity of aflatoxin B1 (AFB1). Induction of oxidative stress also plays an important role in the toxicity of another mycotoxin, ochratoxin A (OTA). In the present study, the protective effect of cyanidin-3-O-β-glucopyranoside (C-3-G; an anthocyanin contained in oranges, blackberries, strawberries and cranberries) against AFB1- and OTA-induced cytotoxicity was investigated in a human hepatoma-derived cell line (Hep G2) and a human colonic adenocarcinoma cell line (CaCo-2). The ability of C-3-G to reduce the production of reactive oxygen species (ROS), the inhibition of protein and DNA synthesis and the apoptosis caused by the two mycotoxins was also investigated in both cell lines. Our experiments proved the significant cytoprotective effect of C-3-Gin vitroagainst OTA- and AFB1-induced cell damage. In particular, 24 h of pretreatment with 50 μm-C-3-G inhibited the cytotoxicity of 10 μm-AFB1 (by 35 %) and of 10 μm-OTA (by 25 %) in Hep G2 cells (P<0·001) and of 10 μm-AFB1 (by 10 %,P<0·01) and of 10 μm-OTA (by 14 %,P<0·05) in CaCo-2 cells. Moreover, 50 μm-C-3-G attenuated ROS production induced by the two toxins in both cell lines (P<0·05). Inhibition of DNA and protein synthesis induced by the mycotoxins was counteracted by pretreatment with the antioxidant at 50 μm. Similarly, apoptotic cell death was prevented as demonstrated by a reduction of DNA fragmentation and inhibition of caspase-3 activation. Thein vitrofree-radical scavenging capacity of the anthocyanin was tested with the Briggs–Rauscher oscillating reaction. This system works at pH approximately 2. The results showed good scavenging power, in accordance with the observed inhibition of ROS production.

Possible involvement of selenium in Staphylococcus aureus inhibition in cow's whey

Previous investigations have shown that selenium supplementation inhibits growth of mastitis pathogens in cow's milk. The present study was performed to clarify the role of selenium in defence mechanisms of mammary gland. We have examined the effects of selenium supplementation on Staphylococcus aureus growth inhibiting activity in whey. Six selenium-supplemented and six non-supplemented Estonian dairy cows were used for this study. Selenium-supplemented cows received 4 mg organic selenium in the form of selenium yeast in their daily diet for 8-week period. Cows from non-supplemented group received the same amount of yeast free of selenium in their diet. All cows had initially low blood glutathione peroxidase (GPx) activity (<or=1.02 microkat/g Hb). During the 8-week experiment these cows had low somatic cell count (<300,000 cells/ml) and negative bacteriological findings in their quarter milk samples. Bacterial growth inhibitory activity in specific whey fractions was clearly evident in 3 out of 6 cows supplemented with selenium. The inhibitory effect was more profound if the cow's blood GPx activity exceeded 4 microkat/g Hb, whereas in non-supplemented cows the inhibition of S. aureus growth was not observed. This study confirms the presence of selenium-dependent antibacterial activity in cow's milk.

Role of plasma fatty acids, prostaglandins and antioxidant balance in bovine mastitis

Plasma levels of free fatty acids (FFA) were measured in cows with mastitis. FFA levels are known to be elevated in milk of affected cows, and similar increases were now observed in blood plasma. Of the long-chain polyunsaturated fatty acids which serve as precursors for prostaglandins (PGs), leukotrienes (LT) and related eicosanoids, arachidonic acid (C20: 4 omega-6) was elevated by 156 per cent and C20: 3 (consisting of both omega-3 and omega-6) 153 per cent; eicosapentaenoic acid (20: 5 omega-3), not present in the plasma of healthy animals, was detected in blood of mastitic animals. Arachidonic acid correlated positively with the plasma levels of PGs. Total plasma phospholipids were increased as well, and they were positively correlated with the levels of linoleic and arachidonic acids. Changes in FFA levels correlated positively with parameters of inflammation, like bovine serum albumin and serum N-acetyl-beta-D-glucosaminidase, but negatively with the antioxidant status of the animals (vitamin E, glutathione peroxidase). As PGs and LTs are mediators of inflammation, and products of lipid peroxidation, the increase of plasma FFA could be related to tissue damage caused by oxygen free radicals. Similar processes are, however, involved also in host defence, e.g. in oxidative killing of pathogens.

Free fatty acids and lipid peroxidation in normal and mastitic bovine milk

Milk levels of free fatty acids (FFA) and prostaglandins (PGs) were determined in healthy cows and in those with mastitis and compared with some parameters commonly used for diagnosing mastitis. A modified gas chromatography-mass spectrometry method was used. In mastitis there was a substantial overall increase in FFA levels in milk. Specific attention was paid to the fate of the long-chain polyunsaturated fatty acids, known as precursors for the production of PGs, leukotrienes and other eicosanoids. Both the omega-6 and omega-3 lines of these lipids were increased in mastitis, but only in proportion to other FFA. The milk levels of PGs (PGF2, PGF2 alpha, thromboxane B2) were elevated in the same proportion. The possible importance of lipid peroxidation, inflammatory reaction and host defence are evaluated in relation to tissue destruction and oxidative killing of pathogens. It may be possible to manipulate the intake and fate of FFA in the organism by dietary intake, antioxidants and proper storing of feed. It is concluded that in studies concerning FFA special attention should be given to those long-chain fatty acids that are precursors for the formation of eicosanoids.