S. The non-stimulated and phorbol 12-myristate 13-acetate (PMA)-stimulated luminol-augmented cellular chemiluminescence (CL) response and viability of milk and blood polymorphonuclear leukocytes (PMN) were determined in lactating dairy cows during different stages of lactation. In the first study, ten healthy cows each in early, mid and late lactation were compared. In a second study, the same measurements as in the first study were evaluated longitudinally in 12 cows during 1 month following parturition. The CL activity and myeloperoxidase (MPO) content of milk PMN and macrophages (M) were also compared. Milk M did not possess MPO activity and were devoid of any luminol-enhanced CL. The CL activity of milk and blood PMN was significantly lower in early lactation than in mid and late lactation (P 0n001). Whereas little changes were observed in viability of blood PMN, the viability of milk PMN was lower in early lactation than in mid and late lactation (P 0n001). The percentage of PMN in isolated milk cells was also lower during early lactation than during mid and late lactation (P 0n001). The CL activity in response to PMA during early, mid and late lactation increased 13, 59 and 42-fold in blood PMN and 1n7, 2n6 and 2n4-fold in milk PMN, respectively, in comparison with non-stimulated PMN. The CL activity, both in milk and blood PMN, the milk PMN viability and the percentage of milk PMN were lowest between 3 d and 11 d post partum. These observed changes immediately after calving could contribute to a higher susceptibility to mastitis in that period.

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 speciesgenerating 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.

No abstract

No abstract

A postnuclear cell fraction from resting horse polymorphonuclear (PMN) leukocytes incubated with fatty acid-salt ions such as oleate or linoleate generated a NADPH-dependent oxygen consumption and superoxide production. Oxidative activity was negligible or absent in the postnuclear fraction from mononuclear leukocytes, p-chloromercuribenzene sulfonic acid-treated granulocytes, and granulocytes from a patient with chronic granulomatous disease. Although consistently associated with the membrane fraction from resting PMN leukocytes, the superoxide-generating activity was shown to be dependent on a thus far unknown cytosolic constituent. The apparent Km's for NADPH and NADH (66 and 1,600 microM, respectively), the pH optimum for the reaction (7.0), the cyanide insensitivity, and transient nature of the reaction together with the stoichiometric relationship between oxygen uptake and NADPH oxidation led to the conclusion that in the presence of cytosol a cell-free latent respiratory burst oxidase can be converted into an active enzyme by interaction with oleate micelles.