Biomedical subjects

C Burvenich

Publications and source records attributed to C Burvenich.

At least 37 records · Page 2Linked to original sources

PubMed2003

Sympathoadrenal and immune system activation during the periparturient period and their association with bovine coliform mastitis. A review.

Increased incidence of clinical mastitis in high-yielding cows during early lactation has been attributed to a depressed functional capacity of the immune system. Sympathoadrenal factors are known to play an important role in modulating the host susceptibility and resistance to infectious diseases. Of primary importance in combating acute intramammary infections are polymorphonuclear leukocytes (PMN), as they represent one of the early lines of immunological defense. The release of stress hormones at parturition and during the first weeks of lactation has been proposed to partly contribute to the impaired function of PMN. Here, we summarize the current understanding of the stress-induced peripheral effectors, i.e. the limbs of the sympathetic system and the hypothalamic-pituitary-adrenal axis, on PMN function around parturition and during coliform mastitis. The questions as to whether and how stress induced secretion of glucocorticoids and catecholamines might affect the lactating dairy cow's udder health will be addressed.

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PubMed2003

Differential leukocyte count method for bovine low somatic cell count milk.

Whereas many differential leukocyte count methods for high somatic cell count (SCC) milk from mastitic cows are available, only a few have been developed for low SCC milk. We have developed a flow cytometric differential leukocyte count method for low SCC milk. The procedure consists of 1) 1.5 ml of diluted milk sample (30%, vol/vol dilution with PBS), 2) centrifugation, 3) leukocyte labeling with SYTO 13 and 4) flow cytometric analysis. Four major leukocyte populations can be clearly identified in the green fluorescence-side scatter dot plot: lymphocytes and monocytes (LM), polymorphonuclear neutrophils (PMN), mature macrophages (Mphi), and cells with apoptotic features based on chromatin condensation and nuclear fragmentation. The optimal processing temperature was 20 degrees C. Significant differences among samples with similar differential leukocyte counts were found. Storage of milk samples during 2 d at 7 degrees C had no effect on differential leukocyte count. Using the new method, differential leukocyte count was performed in low SCC milk samples from cows in early, mid, and late lactation. In accordance with previous studies, PMN and Mphi percentages were lower and LM percentages were higher in early lactation than in the other stages of lactation. The percentage of cells with apoptotic features was higher in early lactation than in mid and late lactation. In conclusion, a rapid, simple, accurate, and reproducible standard procedure was developed to determine the differential leukocyte count (Mphi, PMN, LM, and cells with apoptotic features) of bovine low SCC milk.

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PubMed2003

L-selectin and beta2-integrin expression on circulating bovine polymorphonuclear leukocytes during endotoxin mastitis.

The aim of this in vivo study was to examine the effect of intramammarily administered endotoxin (lipopolysaccharide, LPS) on the expression of L-selectin (CD62L) and the beta2-integrin subunits CD11b and CD18 on circulating bovine PMN. Six early lactating cows were infused with Escherichia coli LPS. The adhesion molecules under study were stained at the cell surface and analyzed flow cytometrically. In addition, some of the clinical parameters associated with adhesion molecule mobilization such as fever, blood cortisol levels, somatic cell count (SCC), and total and differential blood leukocyte count were measured. In analogy with observations during clinical coliform mastitis, a progressive decrease of CD62L expression levels was observed early after LPS infusion, concomitantly with a continuous rise of CD11b and CD18 density. However, no correlation was found between the kinetics of CD11b and CD18 density. The initial changes in adhesion molecule expression paralleled the decrease in blood PMN numbers, together with the increase in rectal temperature, cortisol levels, SCC, and number of circulating immature PMN. In conclusion, intramammarily administered LPS seems to play an important role in modulating adhesion receptor expression on circulating bovine PMN. Interestingly, in contrast to coliform mastitis, the net CD18 variation is not principally influenced by CD11b upregulation during endotoxin administration. The knowledge of adhesion molecule kinetics in relation to the different parameters evaluated in the present study contributes to an improved understanding of the inflammatory reaction.

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PubMed2002

Effect of enrofloxacin treatment on plasma endotoxin during bovine Escherichia coli mastitis.

OBJECTIVE AND DESIGN: To investigate the effect of enrofloxacin on endotoxin resorption during bovine Escherichia coli mastitis. ANIMALS: 12 healthy early post partum Holstein cows. TREATMENT: Mastitis was induced by intramammary infusion of 10(4) cfu E. coli P4:032. Six cows were treated twice according to the usual enrofloxacin therapy: 5 mg/kg enrofloxacin 1) intravenously at 10 h and 2) subcutaneously at 30 h after challenge. The other 6 cows served as non-treated controls. METHODS: Blood and milk samples were collected at several time points after challenge. LPS in plasma was quantified using the limulus amoebocyte lysate (LAL) assay. The somatic cell count (SCC) and cfu of milk samples were also analysed. RESULTS: Occasional LPS peaks were detected in the plasma of 2 control cows at 6 h post-challenge and of 1 enrofloxacin-treated cow at 10 h post-challenge (P < 0.01 and P < 0.05, respectively, in comparison with time 0), just before enrofloxacin treatment. After enrofloxacin treatment, no significant LPS amounts were detected in the plasma of treated cows, but neither in the control cows. CONCLUSION: During induced coliform mastitis, LPS resorption in plasma occured only sporadically and within 10 h post-challenge. Whereas enrofloxacin treatment clearly limited bacterial growth in milk, significant effects on LPS resorption could not be detected. This suggests that enrofloxacin treatment of E. coli mastitis is predominantly beneficial by its bactericidal activity and is not associated with enhanced resorption of endotoxins.

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PubMed2002

Effect of apoptosis on phagocytosis, respiratory burst and CD18 adhesion receptor expression of bovine neutrophils.

Polymorphonuclear neutrophil leukocytes (PMN) play an important role in intramammary defense against infections by Escherichia coli. During mastitis, PMN are confronted with various inflammatory mediators that can modulate their function. In severely diseased cows, increased concentrations of lipopolysaccharide (LPS) and tumor necrosis factor (TNF)-alpha (TNF-alpha) are detected in plasma. Binding of LPS to membrane bound CD14 molecules on monocytes cause release of inflammatory mediators such as TNF-alpha. Because apoptosis of PMN promotes resolution of inflammation and because the LPS and TNF-alpha response in milk and blood is related to the severity of E. coli mastitis, the effect on apoptosis of bovine PMN of increased concentrations LPS and TNF-alpha was studied together with the functionality of apoptotic PMN. Bovine PMN apoptosis, as determined with annexin-V, was induced with high concentrations of either LPS (1000 and 10,000ng/mL) or TNF-alpha (10,000ng/mL) in whole blood following a 6h incubation at 37 degrees C. The apoptosis inducing effect of LPS on PMN was not inhibited following coculture with either anti-bovine TNF-alpha or anti-ovine CD14 monoclonal antibodies. When compared to controls, apoptotic PMN had a similar level of CD18 expression but lacked phagocytic and respiratory burst activity. This is the first study reporting the effects of apoptosis on bovine PMN function. These functional impairments in apoptotic PMN could be important in contributing to the establishment of intramammary infection. Well functioning PMN could finally determine the severity of mastitis following an invasion of bacteria in the mammary gland.

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PubMed2002

Composition and milk cell characteristics in quarter milk fractions of dairy cows with low cell count.

Variation in milk composition and milk polymorphonuclear neutrophil leukocyte (PMN) characteristics and functions among quarter milk fractions were investigated in order to evaluate the optimal fraction for the determination of local immune response. Five fractions were classified during milking: foremilk (I), cisternal milk (II), main milk (III), strippings (IV) and residual milk (V). Somatic cell count (SCC), fat, protein, lactose, sodium, potassium, chloride, polymorphonuclear leukocyte necrosis, apoptosis and oxidative burst were analysed in each fraction. The logSCC and fat concentration were highest in residual milk (P < 0.05), whereas protein and lactose concentration were highest in the earliest fractions (I, II, III) (P < 0.05). Polymorphonuclear neutrophil leukocyte necrosis was lowest in strippings and residual milk (P < 0.05), and PMN apoptosis was lowest in residual milk (P < 0.001). The highest percentage of PMN with oxidative burst was found in residual milk (P < 0.05), and was associated with the highest mean fluorescence intensity (MFI) (P < 0.05). In conclusion, late fractions have more PMN and more active PMN. Nevertheless, it is suggested that each fraction is appropriate in the study of local immune response of the mammary gland, however the fraction used in the study has to be specified.

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PubMed2002

Apoptosis of bovine neutrophils following diapedesis through a monolayer of endothelial and mammary epithelial cells.

In a two-chamber system, isolated blood polymorphonuclear neutrophil leukocytes (PMN) were allowed to migrate (5 h, 37degrees C) in response to bovine complement component C5a across calfskin and rat-tail type I collagen-coated micropore membranes, arterial endothelial, or mammary epithelial cell monolayer on calfskin and rat-tail collagen-coated membranes, respectively. Migration through calfskin collagen-coated membranes resulted in 14.5% +/- 3.4% apoptotic PMN, which was significantly higher than 6.6% +/- 1.2% apoptotic nonmigrated C5a-treated PMN. The addition of an endothelial or epithelial cell monolayer to collagen-coated membranes prevented apoptosis of migrated PMN. After removing the membranes, nonmigrated (untreated and C5a treated) and migrated PMN were incubated for an additional 20 h. At this time point, 69.1% +/- 4.5% and 47% +/- 4.5% of PMN that have migrated through a calfskin-coated membrane and an endothelial monolayer, respectively, were apoptotic, compared with 28.2% +/- 3.0% and 21.1% +/- 4.5% apoptotic untreated and C5a-treated PMN, respectively; 46.9% +/- 4.8% of PMN that have migrated through rat-tail-coated membranes were apoptotic compared with 14.7% +/- 2.3% and 9.3% +/- 1.2% apoptotic untreated and C5a-treated PMN, respectively. Migration across rat-tail collagen-coated membranes with a monolayer of epithelial cells did not affect apoptosis of migrated PMN, even after 20 h of incubation. In conclusion, migration of PMN across collagen-coated membranes (either calfskin or rat-tail collagen) induced an apoptotic response, which was downregulated by a monolayer of endothelial cells and was negated by an epithelial cell monolayer.

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PubMed2002

Functional maturation during bovine granulopoiesis.

Granulocytic precursor cells undergo morphologic changes in the nucleus and the cytoplasm during the process of granulopoiesis, which takes place in the bone marrow. These changes are associated with the development of stage-specific proteins necessary for the highly specialized roles of polymorphonuclear leukocytes in phagocytosis, bacterial killing, and in mediating the inflammatory process. The objective of the current study was to sequence the various events that occur upon functional development of granulocytic bone marrow cells in the bovine species. Cells were obtained from the bone marrow of clinically healthy cows and separated into different stages of maturation using density gradient centrifugation. Three cellular fractions were obtained that were enriched for either early immature, late immature or mature granulocytic cells. Functions and receptor expressions assessed in the three maturation stages were:Fc-IgG2 receptor and CD11b expression, phagocytosis of Escherichia coli, respiratory burst activity, and cellular myeloperoxidase activity. Immature cells expressed already Fc-IgG2 receptor and CD11b on their cytoplasma membrane. Phagocytic ability was acquired in the myelocytic stage, but only the more mature forms were readily capable of phagocytosis. Promyelocytes, myelocytes and metamyelocytes showed no respiratory burst activity. Only band and segmented cells produced reactive oxygen species. Myeloperoxidase was present at all stages of maturity. Thus, each of the maturation stages was characterized by a selective expression of one or more functions and receptors. Therefore, sequential biochemical maturation is postulated during bovine granulopoiesis.

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PubMed2001

Separation of bovine bone marrow into maturation-related myeloid cell fractions.

A prerequisite for studies on bovine myeloid cells in relation to maturity is a reliable separation method, in order to obtain enriched and partially purified cell fractions of different maturation stages. Since current techniques for bovine bone marrow cell isolation fall short of this requirement, a technique for fractionating bovine bone marrow using a three-layer discontinuous Percoll gradient was developed. Three maturation-dependent myeloid cell fractions were obtained at specific densities, as maturation of cells is accompanied with a progressive density increase. Early immature myeloid cells, i.e. myeloblasts and promyelocytes, were found at a density of 1.060g/ml. Late immature myeloid cells, i.e. myelocytes and metamyelocytes, were retrieved at 1.080g/ml. Bands and segmented cells, representing the mature fraction, accumulated in the high-density pellet (>1.080g/ml). Myeloid cell populations were identified in each fraction by flow cytometry based on their forward and side scatter pattern. Confirmation was provided by light microscopy of flow cytometrically sorted myeloid populations, using morphological characteristics. The developed method provides a unique tool for studying maturation-dependent functions in bovine bone marrow.

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PubMed2001

Respiratory burst activity of blood and milk neutrophils in dairy cows during different stages of lactation.

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 < 0.001). 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 < 0.001). The percentage of PMN in isolated milk cells was also lower during early lactation than during mid and late lactation (P < 0.001). The CL activity in response to PMA during early, mid and late lactation increased 13, 59 and 42-fold in blood PMN and 1.7, 2.6 and 2.4-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.

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PubMed2001

Decreased number and bactericidal activity against Staphylococcus aureus of the resident cells in milk of dairy cows during early lactation.

Phagocytic and bactericidal activity of polymorphonuclear neutrophil leukocytes (PMN) isolated from blood and milk, against Staphylococcus aureus, was compared between groups of six healthy dairy cows in early, mid- and late lactation using a bacteriological assay. PMN were isolated from blood with a high degree of purity, but the cells isolated from milk contained variable amounts of macrophages (Mphi) and lymphocytes (L). The results were therefore calculated using the percentage PMN in order to evaluate phagocytosis and killing by PMN only. Blood PMN phagocytosed 82% Staph. aureus and milk PMN 43% on average and there was no significant difference between the different stages of lactation. The bactericidal activity of blood PMN against Staph. aureus was 36+/-8% in early lactation (significantly different from mid lactation, P < 0.05), 64+/-10% in mid lactation and 53+/-6% in late lactation. Milk PMN killed only 6+/-3% Staph. aureus in early lactation (significantly different from mid lactation, P < 0.01), 27+/-3% in mid lactation and 20+/-9% Staph. aureus in late lactation. The ratio of the bactericidal activity of milk to blood PMN was 0.08, 0.43 and 0.22 in early, mid- and late lactation, respectively. In addition to the decreased function. the number of cells in milk (somatic cell count, SCC) was also 60% lower in early lactation than in mid lactation cows (P < 0.01). Our results suggest an impairment of blood and milk-resident PMN bactericidal activity against Staph. aureus and a decreased number of milk-resident PMN in dairy cows at the onset of lactation.

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PubMed2001

Culture of bovine bone marrow progenitor cells in vitro.

In vitro methylcellulose cultures of bovine bone marrow progenitor cells were developed. An existing technique described for bovine species was compared to a method for human tissue and further adapted during subsequent experiments. Bovine bone marrow samples were collected at the slaughterhouse, and mononuclear cells were separated by gradient centrifugation (1.077 g/ml specific density and 400 g). The use of 3% bovine leucocyte-conditioned medium, produced by stimulation of blood lymphocytes with 4 microg/ml concanavalin A and harvested on day 4 of culture, gave better results than the use of supernatant of the human bladder carcinoma 5637, which is widely used in human bone marrow cultures. However, bovine leucocyte-conditioned medium was not added to erythroid cultures because inhibitory effects were observed. Erythroid colonies were stimulated with erythropoietin, and hemin was added to enable microscopic identification. Reduced oxygen tension was necessary to induce growth of erythroid colonies. This was not necessary for myeloid cultures. In conclusion, the results of this study show that the growth of myeloid and erythroid colonies in methylcellulose-based medium requires different culture conditions, which are different from the culture conditions for human cells.

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PubMed2000

Effect of isoproterenol and dexamethasone on the lipopolysaccharide induced expression of CD11b on bovine neutrophils.

The present experiments investigate the changes in expression of CD11b on bovine neutrophils and its modulation by isopropylnoradrenaline (IPN, isoproterenol), dexamethasone (DX), phenylephrine (alpha-agonist) and clenbuterol (beta-agonist). Both IPN and DX caused a dose-dependent inhibition of LPS-induced CD11b expression. A combination of IPN and DX elicited a synergistical decrease of the CD11b expression. Clenbuterol mimicked the effect of IPN, whereas phenylephrine did not. The effect of IPN and DX could at least partly be mediated through a decreased TNF-alpha production by monocytes since tumor necrosis factor-alpha (TNF-alpha) is shown to mediate a dose-dependent CD11b up-regulation. Stimulation of stress hormone receptors partly immuno-suppresses neutrophil functions by inhibition of CD11b expression on the neutrophil surface upon LPS stimulation. This inhibition is probably related to a decrease in TNF-alpha production. A similar mechanism of immuno-suppression could contribute to the higher susceptibility of cattle to Gram-negative bacterial infections of the udder and lung during periods of stress.

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PubMed2000

Adhesion receptor CD11b/CD18 contributes to neutrophil diapedesis across the bovine blood-milk barrier.

epithelium. Neutrophil migration across mammary arterial endothelial cells was almost completely dependent on CD18, the beta-chain of the beta(2) integrins, and to a lesser extent on CD11b, one of the alpha-chains of the beta(2) integrins. Neutrophil migration across collagen was partially blocked by monoclonal antibodies to CD18. No inhibition was observed by monoclonal antibodies to CD11b. Conversely, neutrophil diapedesis across mammary epithelial cells was dependent to a greater extent on CD11b. These results provide evidence for different CD11b/CD18-dependent mechanisms for neutrophil diapedesis across the various cell layers of the blood-milk barrier.

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PubMed2000

Immune surveillance of mammary tissue by phagocytic cells.

The leukocytes in milk consist of lymphocytes, neutrophil polymorphonuclear leukocytes (PMN) and macrophages. Lymphocytes together with antigen-presenting cells function in the generation of an effective immune response. Lymphocytes can be divided into two distinct subsets, T- and B-lymphocytes, that differ in function and protein products. The professional phagocytic cells of the bovine mammary gland are PMN and macrophages. In the normal mammary gland macrophages are the predominate cells which act as sentinels to invading mastitis causing pathogens. Once the invaders are detected, macrophages release chemical messengers called chemoattractants that cause the directed migration of PMN into the infection. Migration of neutrophils into mammary tissue provides the first immunological line of defense against bacteria that penetrate the physical barrier of the teat canal. However, their presence is like a double-edged sword. While the PMN are phagocytosing and destroying the invading pathogens, they inadvertently release chemicals which induces swelling of secretory epithelium cytoplasm, sloughing of secretory cells, and decreased secretory activity. Permanent scarring will result in a loss of milk production. Resident and newly migrated macrophages help reduce the damage to the epithelium by phagocytosing PMN that undergo programmed cell death through a process called apoptosis. Specific ligands on the neutrophil surface are required for directed migration and phagocytosis. In response to infection, freshly migrated leukocytes express greater numbers of cell surface receptors for immunoglobulins and complement and are more phagocytic than their counterparts in blood. However, phagocytic activity rapidly decreases with continued exposure to inhibitory factors such as milk fat globules and casein in mammary secretions. Compensatory hypertrophy in non-mastitic quarters partially compensates for lost milk production in diseased quarters. Advances in molecular biology are making available the tools, techniques, and products to study and modulate host-parasite interactions. For example the cloning and expression of proteins that bind endotoxin may provide ways of reducing damaging effects of endotoxin during acute coliform mastitis. The successful formation of bifunctional monoclonal antibodies for the targeted lysis of mastitis causing bacteria represents a new line of therapeutics for the control of mastitis in dairy cows.

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PubMed2000

Immunological aspects of pregnancy-associated glycoproteins.

The incidence of severe cases of acute E. coli mastitis in dairy cows is highest during early lactation. This phenomenon has been associated with a decreased function and decreased numbers of circulating polymorphonuclear neutrophil leukocytes (PMN). The cause of this impaired function and decreased number is poorly understood. Stress, hormonal and metabolic alterations around parturition and the onset of lactation may play a role in this phenomenon. Several molecules, such as cortisol and beta-hydroxybutyrate have been found to alter the oxidative burst activity of circulating PMN around parturition. Pregnancy-Associated Glycoprotein (bPAG) could also be involved. The theory of immunosuppression by bPAG was investigated because analogous glycoproteins produced by the placenta of other species exert local immunosuppression in order to maintain the histoincompatible feto-maternal unit. The production and subsequent release into the maternal circulation of bPAG is ensured by the binucleate cells from the trophoblast and starts already at implantation. However, peak levels are only reached 1 week before parturition. Due to the long half-life time of this molecule, high levels are found in plasma until 2 weeks after calving. The co-occurrence of the impairment of PMN oxidative burst activity in the early postpartum period and a peak in plasma bPAG concentrations might support the hypothesis of an immunosuppressive effect of PAG. Moreover, an inhibitory effect of bPAG on the proliferation of bovine bone marrow progenitor cells has been found recently in our laboratory. bPAG occurs in colostrum, but its effect on milk cells has not been clarified. It is concluded that interaction between the physiology of reproduction and lactation on the one side and immune function on the other side in dairy cattle requires further research.

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PubMed2000

Tumor necrosis factor-alpha and nitrite/nitrate responses during acute mastitis induced by Escherichia coli infection and endotoxin in dairy cows.

Concentrations of tumor necrosis factor-alpha (TNF-alpha) and of NO(x) (sum of nitrite and nitrate as indicators of endogenous nitric oxide production) in milk and blood plasma were measured in three mastitis models in dairy cows in early lactation. Escherichia coli P4:O37 bacteria or endotoxin O111:B4 were administered into both left quarters of 12 and 6 cows, respectively. Six of the E. coli-infected cows were treated with a bactericidal antibiotic (Enrofloxacin; Bayer AG, Leverkusen, Germany) i.v. at 10 hr and subcutaneously (sc) at 30 hr after infection. NO(x) concentrations transiently increased maximally 10- to 11-fold in milk of E. coli-infected quarters with or without antibiotic treatment at 24 hr and after endotoxin administration. NO(x) concentrations did not change in milk of unchallenged quarters and in blood plasma. Increases of NO(x) were proceeded by a transient (96- to 149-fold) rise of milk TNF-alpha concentrations, which in endotoxin-administered quarters was maximal at 6 hr and in infected quarters without or with Enrofloxacin treatment at 10 and 14 hr. In blood plasma TNF-alpha concentrations only moderately increased to peaks in endotoxin-administered cows at 6 hr and in E. coli-infected cows at 14 hr postchallenge. In one severely sick, nontreated E. coli-infected cow milk, TNF-alpha response at 14 hr was excessive and followed by a spectacular rise of NO(x) concentration in milk between 48 and 72 hr. In conclusion, a possible clinical relevance of nitric oxide production associated with a rise of intramammary and systemic TNF-alpha during acute mastitis by E. coli infection and endotoxin in lactating dairy cows is indicated, but could not be inhibited by antibiotic treatment.

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PubMed2000

Chemiluminescence of bovine polymorphonuclear leucocytes during the periparturient period and relation with metabolic markers and bovine pregnancy-associated glycoprotein.

The respiratory burst activity of polymorphonuclear leucocytes (PMN) was evaluated in eight Holstein cows from 8 weeks before until 6 weeks after calving by chemiluminescence (CL). The CL response started to decrease 1 week before parturition, reaching a minimum during the first 2 weeks after calving. From week 3 of lactation, CL increased again and returned to original levels by week 6 of lactation. Plasma concentrations of 3-hydroxybutyric acid, total bilirubin and bovine pregnancy-associated glycoprotein started to increase before parturition to reach a maximum during the first or second week of lactation. The concentrations of glutamic-oxaloacetic transaminase, lactate dehydrogenase, non-esterified fatty acids and bilirubin increased after calving, reaching a maximum during the second week. A small decrease in plasma cholesterol during the week before and after calving was followed by an increase. The CL response of the PMN showed significant temporal relationships with the plasma concentrations of 3-hydroxybutyric acid, bovine pregnancy-associated glycoprotein, bilirubin, glutamic-oxaloacetic transaminase, non-esterified fatty acids; that with cholesterol was nearly significant. This means that the change in the CL response with time coincided with the changes in plasma concentrations of these substances with time and that these changes were significantly related with each other. The results of this study show that the decreased respiratory burst activity of bovine PMN around parturition may be related to the extent of the metabolic and hormonal changes. Although the causative relationships are not proven, these results support earlier results suggesting that 3-hydroxybutyric acid and bovine pregnancy-associated glycoprotein may directly affect neutrophil function, whereas non-esterified fatty acids, cholesterol, bilirubin, and liver enzymes may have potential as diagnostic markers of impaired neutrophil function and consequently increased disease risk around parturition.

3-Hydroxybutyric Acid↗