Foremilk, residual milk, and blood samples were studied for 10 days during acute mastitis episodes induced by endotoxin infused via the teat canal. Quarter milk and blood samples were collected frequently for 3 days after the infusion and thereafter once or twice daily. Leukocyte concentration in milk and blood was determined by flow cytometry. Within 2 hours after infusion of the endotoxin, clinical mastitis was observed. Total leukocyte concentration and proportion of neutrophils increased significantly (P < 0.05) by postinfusion hour (PIH) 2 in foremilk and by PIH 4 in residual milk. From PIH 2, serum albumin content and N-acetyl-beta-D-glucosaminidase activity were significantly increased in both fractions. Neutrophils were the predominant leukocyte population in both fractions until PIH 59. From PIH 72, lymphocytes were the predominant cell population until PIH 175 in foremilk and until PIH 223 in residual milk. Serum albumin content and N-acetyl-beta-D-glucosaminidase activity in residual milk was significantly lower than in foremilk from PIH 4 to 24 and from PIH 24 to 59, respectively. Regarding total and differential leukocyte counts, values for the 2 fractions followed the same pattern throughout the course of inflammation, probably owing to frequent sample collection. Total and differential cell counts tended to differ between the fractions during some periods, although differences were not statistically significant. When samples were taken less frequently, the total leukocyte concentration in residual milk was higher than that in foremilk. Although sample collections were frequent, clustering of immature neutrophils was not observed in the cytofluorogram of blood leukocytes in this study. Residual milk seems to be the fraction that best reflects the condition in the quarter at the particular time when the milk sample is taken. Results also indicate that residual milk reflects the condition of the secretory tissue, as well as the lower regions of the gland.

We evaluated the biochemical and hemodynamic response to hypertonic saline solution plus dextran in isoflurane-anesthetized pigs infused IV with Escherichia coli endotoxin (5 micrograms/kg of body weight for 0 to 1 hour + 2 micrograms/kg for 1 to 4 hours). After 120 minutes of endotoxemia, pigs were treated with a bolus (4 ml/kg over 3 minutes) of either normal saline solution (NSS; 0.9% NaCl), or hypertonic saline solution plus dextran (HSSD; 7.5% NaCl + 6% dextran-70). Administration of HSSD significantly (P < 0.05) increased serum osmolality and concentrations of sodium and chloride for approximately 2 hours during endotoxemia. Plasma total protein concentration decreased significantly (P < 0.05) for 2 hours after treatment with HSSD, indicating hemodilution and increased plasma volume. Although HSSD transiently increased cardiac index (CI) for approximately 15 minutes, this effect was not sustained; however, the endotoxin-induced decrease in CI was ameliorated from 120 to 180 minutes. In pigs of the endotoxin + NSS group from 180 to 240 minutes, CI decreased significantly (P < 0.05), compared with baseline and control values. The endotoxin-induced increases in mean pulmonary arterial pressure and pulmonary vascular resistance were not attenuated by HSSD. At 135 minutes, total peripheral vascular resistance was transiently lower (for approx 15 minutes) in pigs treated with HSSD, compared with control pigs. The endotoxin-induced increase in plasma lactate concentration was not attenuated by HSSD, indicating continued peripheral O2 debt. We conclude that, despite sustained increases in serum osmolality and concentrations of sodium and chloride, HSSD has only transiently beneficial cardiopulmonary effects during endotoxemia in pigs.

In each of 4 horses, sterile synovitis was induced by intra-articular injection of 3 micrograms of Escherichia coli endotoxin (lipopolysaccharide, LPS) into one antebrachiocarpal joint; an equal volume (2 ml) of phosphate-buffered saline solution (PBSS) was injected into the opposite, control carpus. Blood and 1.5 ml of synovial fluid were obtained at postinjection hours (PIH) 0, 2, 4, 8, 12, 18, 42, 66, and 144. Synovial fluid sample collection was accomplished by use of an indwelling, intra-articular catheter through PIH 12, and by arthrocentesis subsequently. Joint fluid samples were analyzed for cell counts, protein concentration, cytologic variables, and tumor necrosis factor (TNF), interleukin 6 (IL-6), and prostaglandin E2 (PGE2) values. Tumor necrosis factor and IL-6 activities and WBC count were also measured in blood. To monitor local inflammation, skin temperature of each carpus was imaged, using a thermographic scanner prior to each sample collection time. Horses had minimal systemic effects. Mean (SEM) rectal temperature increased significantly to 39.02 +/- 0.15 C only at PIH 18 after intra-articular injection of LPS. One horse had signs of mild depression from PIH 7 to 18, but its vital signs did not change appreciably. Each horse had mild signs of discomfort in the LPS-injected limb from PIH 1 to 3 until PIH 8 to 10. Mean peak surface temperature of the LPS-injected carpi was significantly higher than that of control carpi from PIH 8 to 144 (P < 0.05). Mean synovial fluid WBC count in the LPS-injected and control carpi increased after injection and peaked by PIH 8 (193,125 +/- 8,528 cells/microliter, LPS-treated; 16,425 +/- 8,336 cells/microliter, controls). Mean values for LPS-treated (principal) joints were significantly greater than values for control joints from PIH 2 until after PIH 66 (P < 0.05). Mean synovial fluid protein concentration increased in the principal and control joints, with values for the principal joints remaining significantly greater than values for control joints from PIH to 144 (P < 0.05). Mean TNF activity in synovial fluid was maximal at PIH 2 (10,573 +/- 5,924 U/ml). Interleukin-6 activity increased more gradually and peaked at PIH 8 (1.78 +/- 0.71 X 10(6) U/ml). Tumor necrosis factor activity did not increase above the minimal detectable value of 6 U/ml in the control joints. Mean PGE2 concentration in the principal joints peaked by PIH 2 (3.6 +/- 0.37 ng/ml) and remained significantly (P < 0.05) greater than the value for control joints from PIH 2 through 66. These results indicate that a humane model of synovitis was created by intra-articular injection of LPS and can be used to establish the basic responses of synovial TNF, IL-6, and PGE, in horses with early inflammatory joint disease.

Twenty newborn Holstein calves were allotted at random to 4 groups: group A received 0.9% sterile saline solution; group B received phenylbutazone (5 mg/kg of body weight, IV) and 0.9% sterile saline solution; group C received progressively increasing doses of endotoxin (0.1 to 15 micrograms/kg); and group D received phenylbutazone and endotoxin similarly as did calves of groups B and C, respectively. Phenylbutazone was given once daily and saline solution or endotoxin were given every 8 hours for 5 days. Clinical variables-PCV, plasma total protein and fibrinogen concentrations, platelet count, prothrombin time, activated partial thromboplastin time, and fibrin degradation products concentration were measured at 24-hour intervals. Necropsy was performed on each calf. Phenylbutazone suppressed the clinical response to endotoxin challenge until large doses (7.5 to 15 micrograms/kg) were administered. Calves of groups C and D remained stable until they abruptly developed severe dyspnea necessitating euthanasia. Thrombocytopenia and leukopenia developed after the initial endotoxin dose. Prothrombin time was prolonged and PCV suddenly decreased at 96 hours. Necropsy revealed consistent lesions in the vascular endothelium and lungs. Phenylbutazone administration did not enhance or ameliorate endotoxin-induced hemostatic alterations or pathologic lesions.

We evaluated the biochemical and hemodynamic response to hypertonic saline solution plus dextran in isoflurane-anesthetized pigs infused IV with Escherichia coli endotoxin (5 micrograms/kg of body weight for 0 to 1 hour + 2 micrograms/kg for 1 to 4 hours). After 120 minutes of endotoxemia, pigs were treated with a bolus (4 ml/kg over 3 minutes) of either normal saline solution (NSS; 0.9% NaCl), or hypertonic saline solution plus dextran (HSSD; 7.5% NaCl + 6% dextran-70). Administration of HSSD significantly (P < 0.05) increased serum osmolality and concentrations of sodium and chloride for approximately 2 hours during endotoxemia. Plasma total protein concentration decreased significantly (P < 0.05) for 2 hours after treatment with HSSD, indicating hemodilution and increased plasma volume. Although HSSD transiently increased cardiac index (CI) for approximately 15 minutes, this effect was not sustained; however, the endotoxin-induced decrease in CI was ameliorated from 120 to 180 minutes. In pigs of the endotoxin + NSS group from 180 to 240 minutes, CI decreased significantly (P < 0.05), compared with baseline and control values. The endotoxin-induced increases in mean pulmonary arterial pressure and pulmonary vascular resistance were not attenuated by HSSD. At 135 minutes, total peripheral vascular resistance was transiently lower (for approx 15 minutes) in pigs treated with HSSD, compared with control pigs. The endotoxin-induced increase in plasma lactate concentration was not attenuated by HSSD, indicating continued peripheral O2 debt. We conclude that, despite sustained increases in serum osmolality and concentrations of sodium and chloride, HSSD has only transiently beneficial cardiopulmonary effects during endotoxemia in pigs.

The role of interleukin-1 (IL-1), interleukin-6 (IL-6), and tumor necrosis factor a during endotoxin-induced mastitis in cows was characterized. Six cows had 10 microgram of Escherichia coli lipopolysaccharide infused into 1 mammary gland. Three other cows served as nontreated controls. Within 1.5 to 2.5 hours after infusion, endotoxin caused obvious edema of the mammary gland and increased serum albumin concentration in milk of infused glands 6 times. Milk somatic cell count began to increase 3 to 5 hours after infusion in all treated glands. At 7 hours after infusion, somatic cell counts were increased > 10 times, compared with counts in milk from control cows. Pyrexia of > 1 C developed in only 1 cow, but all treated cows had serum cortisol concentrations > 50 ng/ml in response to endotoxin treatment. High concentrations of IL-1 (10 to 600 U/ml) and IL-6 (2 to 22 U/ml) were detected in milk of infused glands beginning 2.5 to 4 hours after infusion. Endotoxin did not induce detectable amounts of tumor necrosis factor activity in milk or serum. Swelling and mammary gland permeability changes preceded any detectable increase in IL-1 and IL-6 activity, indicating that these clinical signs of inflammation were not mediated by these cytokines. Systemic responses and the leukocytic influx into endotoxin-infused glands developed after or concurrently with initial increases in IL-1 and IL-6 activities in milk. These results suggested that IL-1 and IL-6 may have a role in mammary gland defenses and in the pathophysiologic changes during endotoxin-induced mastitis.

Age, species, and disease state may substantially alter the disposition and clearance of pharmacologic agents. This is particularly important when drugs with low therapeutic index are used in ill neonates. Pharmacokinetic variables for phenylbutazone were determined in 24- to 32-hour-old healthy and endotoxemic calves after IV administration of a single dose (5 mg/kg of body weight, IV). Elimination halflife was 207 and 168 hours, and clearance was 0.708 and 0.828 ml/kg/h in healthy and endotoxemic calves, respectively. Intravenous infusion of endotoxin at the dose (2 micrograms/kg over 4 hours) given did not significantly alter any of the calculated pharmacokinetic variables. Serum thromboxane B2 concentration was significantly (P = 0.05) suppressed for 3 hours after phenylbutazone administration in healthy calves and for 4 hours in endotoxin-challenged calves. Daily administration of phenylbutazone (10 mg/kg loading, then 5 mg/kg for 9 days) to healthy and endotoxemic calves failed to induce any lesions consistent with nonsteroidal anti-inflammatory drug toxicosis.

We examined the effect of infusion of lipopolysaccharide (LPS) on serum tumor necrosis factor alpha (TNF alpha) concentration and clinical attitude in 2- to 3-day-old colostrum-fed (CF) and colostrum-deprived (CD) foals. Eleven CF and 8 CD neonatal foals were given a bolus IV infusion of Escherichia coli 055:B5 lipopolysaccharide (0.5 microgram/kg of body weight) in sterile saline (0.9% NaCl) solution. Four CF and 2 CD foals were given saline solution alone. Serum IgG concentration and serum anti-LPS IGG(T) antibody titer were determined for each foal prior to infusion. A depression index was used to score clinical abnormalities. Serum TNF alpha concentration was estimated by use of an in vitro cytotoxicity bioassay that used WEHI 164 clone 13 cells as targets. The cytotoxic serum factor was identified as TNF alpha by immunoprecipitation with caprine antisera raised against the 15 NH2-terminal amino acids of human TNF alpha. Tumor necrosis factor alpha was not detected in any preinfusion serum samples nor in any samples from foals given saline solution alone. Serum TNF alpha concentration increased in all LPS-infused foals and peaked between 60 and 90 minutes after infusion. Serum TNF alpha concentrations, expressed as mean percentage of peak serum TNF alpha concentration, persisted longer in CD foals given LPS than in CF foals given LPS. All LPS-infused foals displayed clinical signs of endotoxemia, but mean depression index scores of the CF and CD foals given LPS were not significantly different at any time. Serum TNF alpha concentrations were correlated with depression index scores in both LPS-infused groups. Mean rectal temperature increased by 1 hour and remained high for 4 hours after infusion in CF foals given LPS. Mean rectal temperature in CD foals given LPS was significantly less than that for CF foals given LPS 1 and 2 hours after infusion and was higher than mean rectal temperature prior to infusion 3 and 4 hours after infusion. Neither preinfusion total serum IgG concentration nor serum anti-LPS IgG(T) antibody titer correlated with peak serum TNF alpha concentration in the 19 LPS-infused foals.

The cellular response induced in the host animal by endotoxin contributes greatly to the morbidity and mortality of gram-negative infections in bovine neonates. We characterized the temporal sequence, magnitude, and duration of mediator release during endotoxemia and evaluated the effect of endotoxin dose and method of administration. Thromboxane B2 (TxB2), and 6-keto prostaglandin F(1 alpha) (PGF 1 alpha) concentrations and tumor necrosis factor (TNF), and interleukin-1 beta (IL-1 beta) activities were measured in 34 newborn calves given Escherichia coli endotoxin at dosage of 0 (saline solution), 0.2, 2.0, or 20 micrograms/kg of body weight, either by IV administered bolus or infusion over 50 minutes. In all groups and at each lipopolysaccharide dosage, mediators peaked in this sequence; TxB2 and TNF, followed by PGF 1 alpha, then IL-1 beta. Neither dose nor method of administration affected the sequence of mediator release. The magnitude of eicosanoid response to endotoxin was dose-dependent. During induced endotoxemia, duration and/or magnitude of mediator response reflected the dose of endotoxin administered, indicating that the outcome of endotoxemia, in neonatal calves, may be related to the amount of circulating endotoxin.

To investigate the feasibility of using changes in body or mammary temperature to detect mastitis, radiotransmitters were implanted midway between rear udder quarters and in the peritoneal cavity of 5 Holstein cows (1 to 3 months in lactation) housed in an environmental chamber (16 +/- 2 C; lights on 7:00 AM to 11:00 PM). After a 6-week control period, Escherichia coli endotoxin (0.5 mg) was injected after the morning milking into left rear teat cisterns via the teat canal. Wisconsin mastitis test score and somatic cell count in all quarters increased significantly (P < 0.01) by the next milking. Effects were greatest in the endotoxin-exposed quarters. Milk yields for all quarters decreased significantly (P < 0.01) by the first milking after endotoxin injection. Udder and body temperatures at milkings were similar and were not affected by treatment. When temperatures were averaged for the 5 cows for each of 120 time points/d, average temperatures, relative to time of injection of endotoxin, were increased by 0.5 C above baseline at 2.75 hours, peaked at + 2.9 C at 6.50 hours, and remained high through 9.25 hours after injection. Power spectra calculated for individual cows on a daily basis universally indicated an increase in power at low frequencies on the day of injection. Subsequently, Streptococcus agalactiae (200 colony-forming units) was injected into right rear teat cisterns. Wisconsin mastitis test score increased at the second milking after injection. Cell count and quarter milk yield decreased by the third milking. As with endotoxin, injection of S agalactiae could not be detected via a change in temperature at milkings. Of the 5 cows, 3 had a peak in temperature after injection of S agalactiae. Average temperatures for these 3 cows relative to time of injection, were increased by 0.5 C above baseline at 24.25 hours, peaked at + 1.4 C at 26.25 hours, and remained high through 28.75 hours after injection. Power spectra calculated for the day in which a temperature peak was detected for these 3 cows indicated an increase in power at low frequencies, compared with spectra for all other days. Similar increases in power were also detected for the 2 cows that did not have temperature peaks. When clinical signs of mastitis are obvious at milking, there is little advantage of using body temperature for detection of infection. When clinical signs are not obvious, body temperature is often only minimally increased. Thus, monitoring body temperature at milkings adds little to the ability to detect mastitis. Of more interest is the ability to detect transient temperature increases that often develop in association with less-severe infections. Also, as early treatment increases the likelihood of successful treatment, detection of the onset of temperature increases would be advantageous for treatment of severe infections. Detection of a transient temperature peak requires taking temperature readings every 2 hours. To detect mastitis when a temperature peak does not occur requires measurement every 15 minutes to calculate power spectra. The ability to detect the onset of acute clinical infections and subclinical infections, using frequent temperature readings, indicates that development of a practical radiotelemetry system for use on farms may be warranted, depending on cost. The added potential of using body temperature to monitor general health and to detect estrus enhances the economic feasibility of developing such a system.