Biomedical subjects

C Burvenich

Publications and source records attributed to C Burvenich.

116 records · Page 7Linked to original sources

PubMed1977

Mammary blood flow during experimental Escherichia coli endotoxin induced mastitis in goats and cows.

The effect of intramammary infusion of Escherichia coli endotoxin upon mammary blood flow was studied in lactating goats and cows. Blood flow was recorded by means of an electromagnetic flow probe chronically implanted around one mammary artery. Endotoxin mastatis was always accompanied by a significant increase in mammary blood flow, characterized by 2 conspicuous peaks. The flow returned to control values by the thirteenth hour after infusion. Other symptoms of acute mastitis were: fever, increased heart rate, swelling, heat and pain of the gland, increased chloride and total cell count in milk.

Animals↗

PubMedDate not supplied

A comparative study of bovine blood and milk neutrophil functions with luminol-dependent chemiluminescence.

In this study, a technique was developed for the chemiluminescence (CL) measurement of bovine milk polymorphonuclear leukocytes (PMN). In the first study, the effects of cell number and the concentration of phorbol-12-myristate-13-acetate (PMA), luminol, latex bead particles, dimethyl sulphoxide (DMSO) and gelatin on the luminol-dependent cellular CL (LDCL) response were assessed with healthy cows in different stages of lactation. In the second study, the LDCL and in vitro bactericidal activity of blood and milk PMN towards Staphylococcus aureus was investigated. In general, the CL activity of blood PMN was consistently higher than that of milk PMN. We found that (a) the optimal cell density in blood and milk cells for maximal LDCL response ranged from 1.5 x 10(6) to 5 x 10(6) cells/mL; (b) the optimal concentrations of PMA, latex beads and luminol for maximal LDCL response were 100-200 ng/ml, 500 particles/PMN and 0.1 mmol/L, respectively. Concentrations of DMSO of 0.5-1% (v/v) did not significantly affect the maximal CL response of PMN. Gelatin concentrations of 0.1 -0.5 mg/ml had no effect on the LDCL of PMN. In addition, the LDCL of PMN was significantly correlated with bactericidal activity towards S. aureus (r = 0.78, p < 0.001 for blood PMN and r = 0.66, p < 0.01 for milk PMN). Under the optimal experimental conditions for measurement of CL produced by bovine blood and milk PMN defined in this study, LDCL assay is an accurate and reproducible technique for the rapid quantification of PMN bactericidal activity in physiological and pathological conditions of high-yielding dairy cows.

Algorithms↗

PubMedDate not supplied

Decreased neutrophil bactericidal activity during phagocytosis of a slime-producing Staphylococcus aureus strain.

Phagocytosis and intracellular killing by bovine polymorphonuclear leukocytes (PMN) are important host defence mechanisms against mastitis caused by Staphlylococcus aureus. We compared the phagocytosis and overall killing of a non slime-producing (NSP) S. aureus and its slime-producing (SP) variant by blood PMN, using an in vitro bacteriological assay. Seven clinically healthy Holstein-Friesian dairy cows in mid-lactation stage were used for this purpose. The percentages of overall killing for the NSP and SP variant were 34+/-3% and 21+/-4% (P < 0.05) and the corresponding percentages of phagocytosis were 40+/-4% and 31+/-4%, respectively. A significant positive correlation (r = 0.79; P < 0.001) was found between phagocytosis and overall killing. These results suggest that the presence of slime was responsible for a decreased phagocytic ingestion and overall killing.

Animals↗

PubMedDate not supplied

Local and systemic effects of endotoxin mastitis on the chemiluminescence of milk and blood neutrophils in dairy cows.

The local and systemic effects of intramammary lipopolysaccharide (LPS) injection on the chemiluminescence (CL) of milk and blood polymorphonuclear leukocytes (PMN) were investigated in six healthy early lactation cows. Clinical signs of acute mastitis such as fever, increased heart rate and a decreased milk production were observed in all cows. Before LPS challenge, the CL activity of milk PMN was significantly lower than that of blood PMN (P < 0.01). A significant negative correlation was found between pre-challenge milk and blood PMN CL and, the decreased milk production in unchallenged quarters. The CL activity of milk PMN from LPS-injected quarters increased following LPS challenge, whereas it remained unchanged in control quarters. The CL activity of blood PMN showed a biphasic increase, with two peaks and a valley below pre-challenge CL activity (P < 0.01). At post-challenge hours (PCH) 6 and 12, the CL activity of milk PMN from LPS-injected quarters exceeded that of blood PMN (P < 0.05 and P < 0.001, respectively). The decreased CL activity of blood PMN and the enhanced CL activity of milk PMN during endotoxin-induced mastitis was reflected by changes in the shape of the CL curve. In blood PMN, a decrease of the second peak of the CL curve suggests that the myeloperoxidase (MPO)-H2O2 system is impaired during endotoxin-induced mastitis. In contrast, the MPO-H2O2 system was enhanced in milk PMN from challenged quarters. The highest duration and intensity of reactive oxygen intermediate (ROI) production was observed in milk PMN from LPS-injected quarters at PCH 12. The increased viability of PMN in LPS-injected quarters and to a lesser extent in control quarters suggests possible effects of both facilitated diapedesis and inflammatory mediators on milk PMN survival. In conclusion, our results suggest that a combination of local and systemic action of E. coli endotoxin is involved in the priming of milk PMN during mastitis.

Animals↗

PubMedDate not supplied

Apoptosis and necrosis of blood and milk polymorphonuclear leukocytes in early and midlactating healthy cows.

Increased milk somatic cell counts (SCC) are used as an indicator for bovine mastitis. During mastitis, polymorphonuclear leukocytes (PMN) become the predominant cell type. Shortly after parturition, the severity of mastitis is increased and several PMN functions are downregulated. Apoptotic and necrotic processes of PMN could influence SCC and PMN functions. In this study, the percentages of apoptotic and necrotic PMN in blood and milk from early and midlactating healthy cows were compared. Apoptosis and necrosis of PMN were quantified using a dual-color flow cytometric procedure with fluorescein labeled annexin-V (green) and propidium iodide (red). Using this technique three different subpopulations of bovine PMN could be detected: apoptotic cells (high intensive green fluorescence), necrotic cells (high intensive green and high intensive red fluorescence) and viable cells (low intensive green and low intensive red fluorescence). Following a 4 h incubation of blood from both groups of cows at 37 degrees C to induce apoptosis, the mean percentage of apoptotic blood PMN was significantly higher (P < 0.01) in early lactating cows (15.1%, n = 9) compared with midlactating cows (5.3%, n = 10). The mean percentage of necrotic PMN remained lower than 5% in all cows. In contrast to blood, no significant difference was found between the percentage of apoptotic PMN in milk from early (41.2%, n = 7) and midlactating cows (34.0%, n = 8). The percentage of necrotic PMN in milk from early lactating cows (25.9%, n = 7) was significantly higher than that in midlactating cows (14.2%, n = 8) (P < 0.05). Higher percentages of apoptotic as well as necrotic PMN were consistently found in milk compared to blood in all cows. From these results, it can be concluded that spontaneously induced apoptosis was higher in blood PMN from early lactating cows than in blood PMN from midlactating cows. The higher percentage of necrotic milk PMN in early lactating cows than in midlactating cows could be explained by the induction of secondary necrosis.

Animals↗

PubMedDate not supplied

Effect of milk sampling techniques on milk composition, bacterial contamination, viability and functions of resident cells in milk.

Three different milk sampling techniques were evaluated during milk sampling: a direct aseptic collection from the udder through a sterile cannula was used as the reference technique, compared with either a manual or a mechanical sampling method. In this study 30 high-yielding Holstein-Friesian dairy cows at different stages of lactation and free of udder infection were used. For each milk sample, the influence of milk sampling techniques was determined for the following parameters: somatic cell count, milk composition, bacterial contamination, viability, in vitro phagocytosis and overall killing of Staphylococcus aureus Newbould 305, and cellular chemiluminescence. Because milk sampling occurred throughout lactation, the differences between early, mid- and late lactation were estimated. It was concluded that bacterial contamination was not significantly different in manual milking samples and the reference technique; bacterial contamination was, however, significantly (P < 0.001) higher in machine milking samples than in the reference technique. Among the different sampling techniques, no significant effects on SCC, milk composition, viability and functions of the cells isolated from milk were observed. It was found that viability, intracellular killing and cellular chemiluminescence of milk PMN were significantly lower (P < 0.05) in early lactation compared to mid-lactation. Phagocytosis was significantly (P < 0.05) higher in early lactation compared to mid- and late lactation, and no significant differences were observed between mid- and late lactation. From this study, it can be concluded that despite a higher bacterial contamination obtained with the mechanical sampling method, the 3 milk sampling techniques described in this study can be used for the evaluation of milk cell functions.

Animals↗

PubMedDate not supplied

Comparison of bovine platelet and teat alpha 2-adrenoceptor characteristics by [3H]rauwolscine binding.

Alpha 2-adrenoceptors on platelet membranes, isolated from "slaughterhouse cows," were characterized by [3H]-rauwolscine binding. There were 30 +/- 3 [3H]rauwolscine sites per platelet, corresponding to 194 +/- 18 fmol/mg protein. These had an equilibrium dissociation constant (KD) of 5.25 +/- 0.56 nM, a Hill coefficient of 1.00 +/- 0.01 (n = 9), and were competed for by adrenergic compounds stereoselectively. The rank order of catecholamines coincided with that expected for alpha 2-adrenoceptors. Ki-values for inhibition of specific [3H]rauwolscine binding by 7 agonists and 6 antagonists were in the same range as previously observed in teat tissue. It is therefore concluded that quite similar [3H]rauwolscine binding sites were identified and characterized in both bovine teats and platelets. Direct comparison of binding characteristics between alpha 2-adrenoceptors from teat tissue and platelets of the same "primiparous cows," revealed no difference in binding affinity, although a significant higher platelet receptor number was noted in the platelets (platelets: 353 fmol/mg protein; teat tissue: 91 fmol/mg protein; n = 10).

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PubMedDate not supplied

[3H]CGP-12177 binding to beta-adrenoceptors of intact bovine mononuclear leukocytes.

Saturation and inhibition binding studies, using [3H]CGP-12177 as radioligand, reveal the presence of a single class of beta-adrenoceptors on intact bovine mononuclear leukocytes. Receptor binding is inhibited by beta-adrenergic agonists with a rank order of potency (-)-isoproterenol > (-)-epinephrine > (-)-norepinephrine, indicating that the receptors are of the beta 2-subtype. By Scatchard analysis, the mean receptor density was 707 +/- 168 receptors/cell and the dissociation constant was 0.89 +/- 0.47 nM. Specific binding was very high and amounted to 80-90%. It is concluded that [3H]CGP-12177 is a promising compound for the reliable determination of the binding characteristics of bovine mononuclear leukocytes.

Adenylyl Cyclases↗