Biomedical subjects

C Burvenich

Publications and source records attributed to C Burvenich.

At least 91 records · Page 5Linked to original sources

PubMed1993

Blood polymorphonuclear leukocyte chemotaxis during experimental Escherichia coli bovine mastitis.

The relationship between the severity of experimental Escherichia coli mastitis and the chemotactic response of blood polymorphonuclear leukocytes was investigated before and during mastitis. Experimental E. coli mastitis was induced in 10 healthy cows by inoculation of the rear right quarters with 10(3) cfu of E. coli. Cows were classified into two groups based on the severity of the mastitis. Bacterial growth in the inoculated quarter was used as parameter that indicated severity. Before and during experimental mastitis, the chemotactic response and the number of circulating polymorphonuclear leukocytes were greater for the moderately diseased cows than for the severely diseased cows. During the first 24 h of the experimental mastitis, the chemotactic response of polymorphonuclear leukocytes decreased in both groups. Recovery of the chemotactic response of white blood cells was more rapid in moderately diseased cows than in severely diseased cows. Possibly, the larger proportion of band neutrophils (the less chemotactically active band neutrophils) partially accounts for the lower chemotactic response of the circulating polymorphonuclear leukocytes during experimental mastitis in the severely diseased cows.

Animals↗

PubMed1993

Severity of experimental Escherichia coli mastitis in ketonemic and nonketonemic dairy cows.

The severity of experimental Escherichia coli mastitis in relation to in vitro chemotaxis of polymorphonuclear leukocytes was investigated in cows during negative energy balance. The negative energy balance was induced by feed restriction. Cows were classified into two groups, ketonemic and nonketonemic, based on the beta-hydroxybutyrate concentration in the peripheral blood at the moment of inoculation. Bacterial growth in the inoculated quarter was used as a parameter to indicate the severity of experimental mastitis. In the nonketonemic cows, experimental mastitis ranged from moderate to severe. Severity of experimental mastitis was negatively related to preinfection chemotactic response of polymorphonuclear leukocytes. In contrast, the course of experimental mastitis in the ketonemic group was relatively severe in all cows, regardless of preinfection chemotactic response.

3-Hydroxybutyric Acid↗

PubMed1993

Effect of somatotropin on changes in milk production and composition during coliform mastitis in periparturient cows.

The potential protective and therapeutic effects of bST during coliform mastitis in periparturient cows were evaluated. In a first study, 19 cows, classified as moderate or severe responders based on the respiratory burst activity of blood neutrophils, were treated with recombinant bST or vehicle 48 h after intramammary inoculation of Escherichia coli. Clinical status and changes in milk production and composition were compared in the four groups. In a second study, 8 cows received bST or vehicle 7 d before bacterial challenge. During mastitis, losses in milk production and compositional changes were most pronounced in infected glands and in severe responders. Milk production of bST cows recovered better than that of placebo cows. Recovery of milk components was accelerated in severe responders treated with bST, but not in moderate responders. Pretreatment of severe responders with bST enhanced milk production before infection, protected the mammary glands from excessive loss of milk during the subsequently induced coliform mastitis, and accelerated normalization of milk composition. In conclusion, the beneficial effects of bST upon normalization of milk production and composition in periparturient cows suffering from coliform mastitis seem to be restricted to the severe responders. In severe responders that had been treated with bST, changes observed during mastitis resembled those in moderate responders treated with the placebo.

Animals↗

PubMed1992

Muscarinic receptor subtypes, beta-adrenoceptors and cAMP in the tracheal smooth muscle of conventional and double-muscled calves.

The total muscarinic (M1 + M2 + M3) and beta-adrenergic receptors in the tracheal smooth muscle of conventional and double-muscled calves were identified and characterized with the non-specific antagonists [3H]quinuclidinyl benzilate ([3H]QNB) and [3H]dihydroalprenolol ([3H]DHA) respectively. Although the quantity of beta-adrenoceptors in double-muscled calves was 25% lower (p < 0.05) than in conventional calves (Bmax = 327 +/- 89 fmol/mg protein), adenylate cyclase assays indicated that the basal adenylate cyclase activity and the (-)-isopropylnoradrenaline (ISO)- and sodium fluoride (NaF)-stimulated values were not significantly different between these calves. However, the density of muscarinic receptors in double-muscled calves was 40% higher (p < 0.01) than in conventional calves (Bmax = 2955 +/- 625 fmol/mg protein). Subtypes of muscarinic receptors were studied with [3H]telenzepine (M1-receptors), [3H]AF-DX 384 (M2-receptors) and [3H]4DAMP (M1 and M3-receptors). It was found that in both double-muscled and conventional calves about 40% of the receptors were of the M3-subtype, the remaining 60% being M2-receptors. From these results, it is suggested that inflammation of the respiratory tract in double-muscled calves may be complicated by an imbalance between the cholinergic bronchoconstrictor and the beta-adrenergic bronchodilator components of the autonomic nervous system.

Animals↗

PubMed1992

Partial prostaglandin-mediated mechanism controlling the release of cortisol in plasma after intravenous administration of endotoxins.

In a first series of experiments we studied the influence of E. coli endotoxins or lipopolysaccharides (LPS) administered either intravenously (i.v.) or intramammarily (i.mam.) to lactating goats on plasma cortisol and rectal temperature (RT). Differences in the magnitude of the cortisol release and shape of the fever curve were observed. In both models maximal pyrexia and fever index (FI) were comparable. In a second series of experiments the influence of LPS on the plasma cortisol and RT was studied after i.v. injection of increasing doses of LPS:low (25 ng/kg), moderate (200 ng/kg) and relatively high (500 ng/kg). Although the cortisol response was dose dependent, the effect was not correlated with FI. The administration of flurbiprofen, a non steroidal antiinflammatory drug (NSAID), resulted in a complete inhibition of fever at all LPS doses and the cortisol release after administration of low doses LPS. This indicates a prostaglandin mediation. With moderate and high doses LPS the cortisol release was only partially inhibited and delayed suggesting a non prostaglandin mediated mechanism. In a third series of experiments the influence of flurbiprofen on fever and cortisol release was studied after i.mam. LPS administration. The observed increase of plasma cortisol and RT were completely abolished after flurbiprofen treatment. It is concluded that: 1) the increase of plasma cortisol after LPS administration in lactating goats is not related to hyperthermia per se, 2) the control of fever and cortisol release may, to some extent, differ according to the LPS dose and method of administration, 3) the cortisol release observed after moderate and high doses of LPS is probably controlled by two phenomena. The first being induced by cyclo-oxygenase metabolites, the second by intermediary mediators other than prostaglandins or by LPS itself. 4) Although an eight-fold higher dose of LPS was given i.mam., a cortisol release comparable to the lowest dose of LPS (25 ng/kg) was observed. These differences in cortisol release can be ascribed to 1) a detoxification of LPS at the level of the mammary gland or 2) a slower resorption of LPS from the mammary gland.

Animals↗

PubMed1992

Kinetics and characteristics of bovine neutrophil alkaline phosphatase during acute Escherichia coli mastitis.

Alkaline phosphatase activity of isolated bovine blood neutrophils was investigated before and during experimentally induced Escherichia coli mastitis. Activities markedly increased 1 wk after infection in neutrophils of cows suffering from moderate or from severe disease. Elevated neutrophil alkaline phosphatase activity did not correlate with a specific stage of maturating postmitotic neutrophils appearing in circulation during mastitis. Neutrophil alkaline phosphatase from healthy cows before infection and from mastitic cows was characterized by means of thermostability, specific inhibitor patterns, slab gel electrophoresis, and kinetic parameter analysis. The leukocyte enzyme from healthy and mastitic cows displayed very similar characteristics, suggesting that the increase in activity during mastitis is most probably related to the enhanced expression of the normal alkaline phosphatase enzyme.

Alkaline Phosphatase↗

PubMed1991

Quantitative buffy coat analysis related to adrenocortical function in horses during a three-day event competition.

This study was carried out to investigate stress induced in a cross-country by measuring plasma cortisol and to compare the changes in cortisol level with the leucocytic changes measured with the quantitative buffy coat (QBC) analysis, which is a new method applicable in field conditions for the evaluation of haematological parameters in horses. Seven healthy horses competing in a national three-day event were investigated. Venous blood was sampled under resting condition, 2 min and 180 min after the completion of the cross-country and analysed for haematological parameters, plasma cortisol, protein and lactate levels. Immediately after the event, there was a significant increase in all values except in the granulocytes (Gr) to lymphocytes-monocytes (LM) ratio. 180 min after the event, all the parameters returned to their resting levels while white blood cells (WBC), Gr and Gr/LM ratio were significantly higher with respect to their resting values. A high correlation (r = 0.82) was found between the relative increase in plasma cortisol levels 2 min after exercise and the relative increase in Gr/LM 180 min after exercise. Therefore it was concluded that the Gr/LM ratio measured 180 min after exercise with the QBC analysis is a reliable index to estimate the plasma cortisol levels measured 2 min after exercise. This new technique could consequently be used in order to evaluate, in field conditions, the exercise-induced stress.

Adrenal Cortex↗

PubMed1990

Preinfection functions of blood polymorphonuclear leukocytes and the outcome of experimental Escherichia coli mastitis in the cow.

The relationship between preinfection functions of blood neutrophils and outcome of experimental Escherichia coli mastitis was studied in 11 cows. Random migration, chemotaxis, phagocytosis, and chemiluminescence by neutrophils were determined in white blood cell suspensions, and in purified neutrophil suspensions. The course of E. coli mastitis (10(4) E. coli 0:157 in rear quarters) was monitored using clinical parameters, counts of E. coli in mastitic secretion, and milk production. Regressions were calculated for areas under curves of these parameters and preinfection activities of neutrophils. Chemiluminescence by nonstimulated neutrophils in white blood cell suspensions was negatively correlated with counts of E. coli in secretion and with losses in milk production. The chemotactic differential in white blood cell suspensions minus the chemotactic differential in purified suspensions of neutrophils referred to as delta varied from -.66 to +.50, indicating, respectively, inhibition and stimulation of chemotactic activity of neutrophils in white blood cell suspensions. Delta correlated negatively with counts of E. coli in mastitis secretion, inhibition of the amplitude of rumen contractions, and losses in milk production. We hypothesize that a factor in white blood cell suspensions may be involved in the down-regulation of the migratory response of neutrophils during E. coli mastitis.

Animals↗

PubMed1990

Interaction between the respiratory burst activity of neutrophil leukocytes and experimentally induced Escherichia coli mastitis in cows.

The respiratory burst activity of neutrophil leukocytes from bovine peripheral blood was studied before and during an experimentally induced Escherichia coli mastitis. The competence of neutrophils to generate reactive oxygen species following stimulation with opsonized particles prior to infection was negatively correlated with severity of subsequently induced E. coli mastitis. In the presence of the soluble activator, phorbol myristate acetate, no such correlation was obtained. However, combination of blood neutrophil numbers with phorbol myristate acetate induced respiratory burst competence, called reactive oxygen species-generating capacity, displayed a negative correlation with the intensity of a subsequent inflammation of the bovine mammary gland. At the onset of mastitis, a concomitant reduction in blood neutrophil numbers, a strong shift in cell types, and a substantial decrease in production of reactive oxygen species occurred. Reestablishment and even enhancement of the respiratory burst activity coincided with the reappearance of mature neutrophils. Possible stimulatory effects on neutrophil superoxide generation are discussed. Data suggest that generation of reactive oxygen species by mature neutrophils may be of primary importance for microbial killing during the onset and recovery from mastitis.

Animals↗

PubMed1989

Determination of beta-adrenoceptors and cAMP in muscle from normal and splayleg Belgian Landrace pigs.

beta-Adrenoceptors were identified and characterized by [3H]dihydroalprenolol ([ 3H]DHA) binding experiments in muscle membrane preparations from piglets. The [3H]DHA binding was rapid, reversible and stereoselective. Catecholamines competed for specific binding with a rank order of potency (-)-isopropylnoradrenaline greater than (-)-epinephrine much greater than (-)-norepinephrine, indicating a beta 2-subtype of adrenoceptor. Saturation binding experiments with [3H]DHA showed no significant difference for either the number of binding sites or the equilibrium dissociation constants in normal and splayleg pigs. Adenylate cyclase assays indicated that the basal adenylate cyclase activity and the prostaglandin E1 (PGE1)-, (-)-isopropylnoradrenaline (ISO)-, 5'-guanylyl-imidodiphosphate (GppNHp)- and sodium fluoride (NaF)-stimulated values were not significantly different in normal and splayleg pigs. In both groups, PGE1 did not affect basal activity, whereas ISO and GppNHp stimulated adenylate cyclase activity significantly (p less than 0.001) to about 40% above basal level. NaF induced a significant (p less than 0.001) increase of cAMP in normal and splayleg pigs amounting to 48% and 61% respectively. Significant correlations between absolute adenylate cyclase responses to ISO (r = 0.83***), NaF (r = 0.72**) and GppNHp (r = 0.61*) and basal activity in the splayleg pigs were the most striking findings. In contrast, these correlations could not be detected in the normal pigs. Whether or not this observation reflects an alteration in the signal transduction system needs to be further investigated. To the best of our knowledge this is the first biochemical study which relates an altered beta-adrenoceptor function and porcine splayleg.

Adenylyl Cyclases↗

PubMed1989

Comparison of fat and cream content in normal and mastitic milk of cows.

Two methods for estimating fat and cream content in cow's milk were compared in normal and mastitic milk. Fat content in milk from periparturient cows was estimated simultaneously by the method of Gerber and by simply spinning small samples of untreated milk in a haematocrit centrifuge. Mastitis was experimentally induced by inoculating mammary glands with Escherichia coli. On the average, cream content in milk from normal, and uninfected mammary glands measured by the haematocrit method was 20 to 23% higher than milk fat measured by the method of Gerber. In mastitic milk from infected mammary glands haematocrit readings were 40% higher than those of Gerber. Milk fat values as measured by both methods were highly correlated. It is concluded that the haematocrit method can be used for rapid estimation of milk fat content in normal milk of cows. The greater difference between cream and fat content in mastitic milk compared to normal milk can probably, at least partly, be ascribed to the presence of large clots of cells and fat in the milk during mastitis. During centrifugation of the viscous mastitic milk samples, milk cells and fat probably are not completely separated. This results in overestimated readings of milk cream content with the haematocrit method. It therefore seems advisable to use the Gerber method for accurate measurements of milk fat in mastitic milk.

Animals↗

PubMed1989

Changes in N-acetyl-beta-D-glucosaminidase activities in relation to other milk components throughout normal lactation in the guinea pig.

Changes in milk production, NAGase activities, Na, Cl, K, lactose, total N, and fat were followed throughout normal lactation in 26 healthy guinea pigs. Appropriate microassays were used and all determinations were performed on the same small skim milk sample (microhematocrit tube). A very sensitive and rapid spectrofluorimetric determination of NAGase in 10-microliters skim milk samples was evaluated. Four days after parturition, daily milk production reached a maximum of about 20 ml. Thereafter milk yield decreased progressively to about 7 ml on d 15. During the entire course of lactation, a progressive increase in NAGase, total N, fat, Na, and Cl was observed. However, K and lactose decreased. Highly significant positive correlations between NAGase and Na, Cl, fat, and total N were evident, whereas correlations were negative between NAGase and K, lactose, and milk production. These changes can be explained on basis of alterations that occur at the level of the blood-milk barrier. The short lactation period of the guinea pig, the easy handling and milking practices, together with the available sensitive micromethods can lead to the establishment of a convenient guinea pig mastitis model.

Acetylglucosaminidase↗

PubMed1989

Relationship between numbers of alpha 2- and beta 2-adrenoceptors in teat tissue and blood cells and milkability of primiparous cows.

Milking characteristics were measured on 14 cows at morning milkings. After collection of blood, cows were slaughtered and teats were removed. beta 2-Adrenoceptors on teat tissue and lymphocyte membranes were identified by binding of [3H]dihydroalprenolol. For the determination of alpha 2-adrenoceptors on teat tissue and blood platelet membranes, [3H]rauwolscine was used. In teat tissue and blood cells, except for the amount of milk collected during the 3rd min, all other milking parameters were highly correlated with the ratio of beta 2-adrenoceptors to alpha 2-adrenoceptors. Good milkability appears to be associated with low ratio of beta 2-adrenoceptors to alpha 2-adrenoceptors densities in teat tissue, and a high ratio of beta 2- to alpha 2-adrenoceptors densities in blood cells. We postulated earlier that a low ratio of beta 2- to alpha 2-adrenoceptors in teat tissue of fast milking cows probably reflects changes of mainly prejunctional adrenoceptors. From our results on blood cells, we are now hypothesizing that in teat tissue prejunctional and extra junctional alpha 2- and beta 2-adrenoceptors might have been identified together, whereas alpha 2- and beta 2-adrenoceptors identified on blood platelets and lymphocytes, respectively, are reflecting by preference extra junctional adrenoceptors are activated primarily by circulating epinephrine. The high ratio of beta 2- to alpha 2-adrenoceptors observed in blood cells of fast milking cows might indicate a decreased vasomotor tone in the teat and an increased dilatation of the teat sphincter in these animals.

Animals↗

PubMed1988

Pathophysiological effects of endotoxins in ruminants. 1. Changes in body temperature and reticulo-rumen motility, and the effect of repeated administration.

Data from the literature on the clinical effects of bacterial endotoxins in ruminants are reviewed. Special attention is paid to the effects on body temperature and reticulo-rumen motility. Furthermore, the effects of repeated intravenous injection of endotoxin are summarised. Pathophysiological disturbances after intramammary infusion of endotoxins proved to be identical to those found after intravenous injection of non-lethal doses. Strikingly, however, no marked inhibitory effect on rumen motility nor abortion was observed after intramammary infusion of endotoxins. Moreover, in cows that were made tolerant to endotoxin by daily intravenous injections, intramammary infusion of one-fifth of this daily dose produced a maximum effect on body temperature and plasma Zn concentrations. This suggests that inflammatory endogenous mediators were released in the udder and then absorbed into the blood circulation, rather than the absorption of endotoxin.

Animals↗

PubMed1988

Pathophysiological effects of endotoxins in ruminants. 2. Metabolic aspects.

Metabolic disturbances following intravenous and intramammary administration of endotoxins in ruminants are described. In contrast to the similarity in response of blood biochemical parameters after intravenous and intramammary administrations of endotoxins, responses in plasma concentrations of enzyme activities, the thyroid hormones, cortisol, and somatotropin differ markedly. Biochemical changes in blood after endotoxin administration are predominantly dose-dependent; thus some of the biochemical parameters - especially plasma concentrations of Fe and Zn - serve also to evaluate the effects of certain drugs in endotoxin models. Changes in milk composition have been documented only after intramammary infusion of endotoxins and can partly be explained by the increased permeability of the blood/milk barrier. Appearance and production of milk returns to normal within a week after intramammary endotoxin treatment, indicating that the mammary gland is only temporarily damaged by endotoxin-induced mastitis.

Animals↗

PubMed1987

Isolation of bovine lymphocytes for beta 2-adrenoceptor determination by means of the radioligand technique: some practical implications.

The present investigation was undertaken to demonstrate saturable beta 2-adrenoceptor binding sites on cell membranes of bovine lymphocytes by means of the non-selective antagonist (3H)dihydroalprenolol. Although the classical density gradient centrifugation technique was used as described for the isolation of these cells from human blood, striking differences in binding characteristics were observed. It is suggested that differences in physical properties of blood might be responsible for these phenomena. Since receptor density and affinity of beta 2-adrenoceptors in lymphocytes are used in human medicine (and will be in the future in veterinary medicine) for correlation with several physiological and pathophysiological conditions, attention is drawn to the effect of dilution of blood during the preparation of these cells; in lactating cows, the best results were obtained with the dilution 1:0.5.

Adult↗

PubMed1987

Comparison of the milk leakage potencies of adrenergic agonists in lactating cows.

The activities of epinephrine (2-6 micrograms) and of norepinephrine (20-60 micrograms) on the relaxation of teat sphincter muscles were compared by measuring milk leakage from the full udder of 5 lactating cows. Substances were injected into the external pudic artery after pretreatment with an alpha-adrenoceptor blocking agent (prazosin or phentolamine). Milk leakage was induced by creating a vacuum (-30 cm of water) in a plethysmographic chamber enclosing one teat and volumes of milk loss were measured every min. In a second series of experiments the activities of the beta 2-adrenoceptor selective agonist zinterol (0.5-2.5 micrograms) and of the nonselective beta-agonist isoproterenol (3-22.5 micrograms) on sphincter muscle relaxation were compared. Epinephrine was found to be more potent than norepinephrine in inducing relaxation of sphincter muscles. Zinterol was more active than isoproterenol. It is concluded that there is a predominance of beta 2-adrenoceptors in the teat sphincters.

Adrenergic alpha-Agonists↗

PubMed1986

Effects of valerate and isobutyrate on fatty acid secretion by the isolated perfused mammary gland of the lactating goat.

The isolated mammary glands of six lactating goats were perfused with heparinized and oxygenated blood for 8 to 11 h. Adequate quantities of glucose, acetate and amino acids (including valine) were added to the perfusate. Either unlabelled valerate or unlabelled isobutyrate was added in excess to the perfusate of one gland, while the respective symmetrical gland was used as a control. After the administration of valerate, the proportions of the odd-numbered fatty acids (C11:0, C13:0, C15:0) in the milk fat, collected every hour during perfusion, rose progressively after 5 h until the end. The synthesis of milk fatty acids from valerate is discussed. After isobutyrate was added to the perfusate, isoC12:O, isoC14:0 and isoC16:0 in the milk fat increased as compared to the control. The effect of isobutyrate indicated that valine acted as a precursor of milk iso-branched fatty acids after its metabolisation to isobutyryl-CoA. During perfusion in the presence of the complete substrate mixture, the proportion of certain major milk fatty acids (C10:0, C12:0, C14:0 and C16:0) increased, whereas the proportion of C18:0 and C18:1 decreased. These effects have been ascribed to the presence of acetate and beta-hydroxybutyrate in the substrate mixture.

Animals↗