Search Results

You are looking at 1 - 10 of 24 items for

  • Author or Editor: Jeffrey Lakritz x
  • Refine by Access: All Content x
Clear All Modify Search

Abstract

Objective—To characterize gelatinases in bronchoalveolar lavage fluid (BALF) and gelatinases produced by alveolar macrophages of healthy calves.

Sample Population—Samples of BALF and alveolar macrophages obtained from 20 healthy 2-month-old calves.

Procedure—BALF was examined by use of gelatin zymography and immunoblotting to detect gelatinases and tissue inhibitor of metalloproteinase (TIMP)-1 and -2. Cultured alveolar macrophages were stimulated with lipopolysaccharide (LPS), and conditioned medium was subjected to zymography. Alveolar macrophage RNA was used for reverse transcriptasepolymerase chain reaction assay of matrix metalloproteinases (MMPs), cyclooxygenase-2, and inducible nitric oxide synthase.

Results—Gelatinolytic activity in BALF was evident at 92 kd (14/20 calves; latent MMP-9) and 72 kd (18/20; latent MMP-2). Gelatinolytic activity was evident at 82 kd (10/20 calves; active MMP-9) and 62 kd (17/20; active MMP-2). Gelatinases were inhibited by metal chelators but not serine protease inhibitors. Immunoblotting of BALF protein and conditioned medium confirmed the MMP-2 and -9 proteins. Endogenous inhibitors (ie, TIMPs) were detected in BALF from all calves (TIMP-1) or BALF from only 4 calves (TIMP-2). Cultured alveolar macrophages expressed detectable amounts of MMP-9 mRNA but not MMP-2 mRNA.

Conclusions and Clinical Relevance—Healthy calves have detectable amounts of the gelatinases MMP-2 and -9 in BALF. Endogenous inhibitors of MMPs were detected in BALF (ie, TIMP-1, all calves; TIMP-2, 4 calves). Lipopolysaccharide-stimulated alveolar macrophages express MMP-9 but not MMP-2 mRNA. The role of proteases in the pathogenesis of lung injury associated with pneumonia has yet to be determined. (Am J Vet Res 2004;65:163–172)

Restricted access
in American Journal of Veterinary Research

Abstract

Objective—To determine effects of prior feeding on pharmacokinetics and estimated bioavailability of orally administered microencapsulated erythromycin base (MEB) in healthy foals.

Animals—6 healthy foals, 3 to 5 months old.

Procedure—Foals were given 2 doses of MEB (25 mg/kg of body weight, PO). One dose was administered after food was withheld overnight, and the other was administered after foals had consumed hay. The study used a crossover design with a 2-week period between doses. Blood was collected via a jugular vein prior to and at specific times after drug administration. Concentrations of erythromycin A and anhydroerythromycin A in plasma were determined, using highperformance liquid chromatography. Results pharmacokinetic analysis of plasma concentration-time data for food-withheld and fed conditions were compared.

Results—Plasma concentrations of erythromycin A for foals were lower after feeding than concentrations when food was withheld. Area under the plasma concentration- time curve, maximum plasma concentration, and estimated bioavailability were greater in foals when food was withheld than when foals were fed. Anhydroerythromycin A was detected in plasma after administration of MEB in all foals.

Conclusions and Clinical Relevance—Foals should be given MEB before they are fed hay. Administration of MEB to foals from which food was withheld overnight apparently provides plasma concentrations of erythromycin A that exceed the minimum inhibitory concentration of Rhodococcus equi for approximately 5 hours. The dosage of 25 mg/kg every 8 hours, PO, appears appropriate. (Am J Vet Res 2000;61:1011–1015)

Restricted access
in American Journal of Veterinary Research

Abstract

Objective—To determine pharmacokinetics and plasma concentrations of erythromycin and related compounds after intragastric administration of erythromycin phosphate and erythromycin estolate to healthy foals.

Animals—11 healthy 2- to 6-month-old foals.

Procedure—Food was withheld from foals overnight before intragastric administration of erythromycin estolate (25 mg/kg of body weight; n = 8) and erythromycin phosphate (25 mg/kg; 7). Four foals received both drugs with 2 weeks between treatments. Plasma erythromycin concentrations were determined at various times after drug administration by use of high-performance liquid chromatography. Maximum plasma peak concentrations, time to maximum concentrations, area under plasma concentration versus time curves, half-life of elimination, and mean residence times were determined from concentration versus time curves.

Results—Maximum peak concentration of erythromycin A after administration of erythromycin phosphate was significantly greater than after administration of erythromycin estolate (2.9 ± 1.1 µg/ml vs 1.0 ± 0.82 µg/ml). Time to maximum concentration was shorter after administration of erythromycin phosphate than after erythromycin estolate (0.71 ± 0.29 hours vs 1.7 ± 1.2 hours). Concentrations of anhydroerythromycin A were significantly less 1 and 3 hours after administration of erythromycin estolate than after administration of erythromycin phosphate.

Conclusions and Clinical Relevance—Plasma concentrations of erythromycin A remained > 0.25 µg/ml (reported minimum inhibitory concentration for Rhodococcus equi) for at least 4 hours after intragastric administration of erythromycin phosphate or erythromycin estolate, suggesting that the recommended dosage for either formulation (25 mg/kg, q 6 h) should be adequate for treatment of R equi infections in foals. (Am J Vet Res 2000;61:914–919)

Restricted access
in American Journal of Veterinary Research

Abstract

Objective—To measure the effects of lowmolecular-weight inhibitors on the activity of bovine neutrophil matrix metalloproteinase 9 (MMP-9).

Sample Population—Bovine MMP-9 purified from bovine neutrophilconditioned medium.

Procedures—Neutrophils were degranulated by stimulation with phorbol ester. Enzyme purification was performed by use of gelatin affinity and gel-filtration chromatography. Activated enzyme was incubated with inhibitors prior to addition of substrate (gelatin fluorescein conjugate or fluorogenic peptide). Rates of enzymatic cleavage were determined by monitoring fluorescence as the reactions progressed. Values of IC50 (molar concentration of compound that inhibits specific activity by 50%) and KI (in vitro inhibition constant) were determined.

Results—Rates of enzymatic activity of monomeric and dimeric bovine MMP-9 measured by use of gelatin and peptide substrates were linear with respect to time and concentrations of enzyme and substrate. The MMP-9 was potently inhibited by hydroxamic acids (IC50 for gelatin, 29.2 to 55.7nM; IC50 for peptide, 4.8 to 24.6nM; KI, 0.2 to 0.5nM), whereas tetracyclines (IC50 for gelatin, 30.1 to 112.7MM; IC50 for peptide, 48.0 to 123.8MM; KI, 25.2 to 61.4µM) and chlorhexidine (IC50 for gelatin, 139.1MM; IC50 for peptide, 672.5MM to 1.7mM; KI, 495.0 to 663.0MM) had limited inhibition. Gelatinase-specific inhibitor SB-3CT had intermediate potency (IC50 for peptide, 185.0 to 290.0nM; KI, 66.5 to 86.0nM).

Conclusions and Clinical Relevance—Bovine MMP-9 was potently inhibited by hydroxamic acids and gelatinase inhibitor. These compounds may be useful as modulators of neutrophil-mediated protease activity in cattle.

Restricted access
in American Journal of Veterinary Research

Abstract

Objective—To determine whether cattle exposed to heat stress alone or heat stress while consuming endophyte-infected fescue (EIF) have lower wholeblood (WB) concentrations of glutathione (GSH).

Animals—10 Simmental cows.

Procedure—Cows were sequentially exposed to thermoneutral (TN; 2 weeks; 18 C, 50% relative humidity [RH]), heat stress (HS; 2 weeks; alternating 4-hour intervals at 26 and 33 C; 50% RH), and heat stress while consuming EIF (10 µg of ergovaline/kg/d; 2 weeks; HS + EIF). Blood samples were collected after each period and tested for GSH and oxidized glutathione (GSSG) concentrations.

Results—Feed consumption was similar when data were analyzed for time points at which WB concentrations of GSH or GSSG were determined. However, significant effects of treatment, cow, days exposed to heat, cow-by-treatment interaction, and treatment-bydays exposed to heat interaction were detected when data were considered simultaneously. Mean ± SD hematocrit for TN, HS, and HS + EIF were 35.3 ± 3, 33.3 ± 2, and 37.1 ± 3%, respectively. Mean WBGSH concentrations for TN, HS, and HS + EIF were 3.2 ± 0.65, 2.7 ± 0.62, and 2.4 ± 0.56 mmol/L of RBC, respectively. Reduced WBGSH concentrations were associated with reduced feed intake during the later part of each heat period.

Conclusion and Clinical Relevance—Decreased GSH and increased GSSG concentrations were evident during heat stress, especially when cattle consumed EIF. These were associated with reduced feed intake during heat stress. Heat stress, reductions in feed intake, and thermoregulatory effects of EIF may induce oxidative stress in cattle. (Am J Vet Res 2002;63:799–803)

Restricted access
in American Journal of Veterinary Research

Abstract

Objective—To develop protocols for helical computed tomography (CT) and axial high-resolution CT (HRCT) of lungs and correlate densitometric CT values with morphometric and histologic data for normal pulmonary tissue in dogs.

Animals—8 healthy adult dogs.

Procedure—2 dogs were used to establish a protocol for helical CT and HRCT of lungs. Six dogs were used to acquire densitometric CT data regarding normal lungs. After the dogs were euthanatized, their lungs were fixed and sampled for morphometric and histologic evaluation. Four CT acquisitions were compared by means of paired t tests.

Results—For normal lung tissue of dogs, mean densitometric CT value obtained during helical CT scans reconstructed in a sharp algorithm was -846 Hounsfield units. Values obtained via helical CT or HRCT acquisitions and reconstructed with sharp or standard algorithms did not differ significantly. Morphometric analysis was used to determine the proportion of lung parenchymal (82%) and nonparenchymal tissue (18%). Alveolar size, estimated by mean linear intercept, was approximately 172 µm, and alveolar surface area-to-volume ratio was 0.024 to 0.026 µm–1. Histologic evaluation confirmed the presence of normal lung tissue.

Conclusions and Clinical Relevance—Correlation of densitometric CT data with morphometric and histologic findings and the establishment of helical CT and HRCT protocols were attained; clinical use of this information may facilitate investigation of pulmonary disease in dogs. Sharp helical CT acquisitions were preferred because of better lung parenchyma detail and rapid image acquisitions, compared with HRCT. (Am J Vet Res 2003;64:935–944)

Restricted access
in American Journal of Veterinary Research

Abstract

OBJECTIVE To describe concentration-over-time data for ampicillin and sulbactam in the digital and systemic circulations and synovial fluid (SYN) of cattle following a single injection of ampicillin-sulbactam as a regional IV perfusion (RIVP).

ANIMALS 6 healthy adult nonlactating Jersey-crossbred cows.

PROCEDURES The right hind limb of each cow was aseptically prepared. A tourniquet was applied around the midmetatarsal region, and 1.0 g of ampicillin with 0.5 g of sulbactam in a combined formulation was administered as an RIVP into the dorsal common digital vein (DCDV). Blood samples from the DCDV and jugular vein and SYN samples from the metatarsophalangeal joint of the prepared limb were collected immediately before and at predetermined times for 24 hours after RIVP. One blood sample was obtained from the abaxial proper plantar vein of the lateral digit of the prepared limb 0.25 hours after RIVP. Serum and SYN ampicillin and sulbactam concentrations were determined by high-performance liquid chromatography.

RESULTS Mean ± SD maximum concentration of ampicillin in SYN and serum obtained from the abaxial proper plantar and jugular veins was 1,995 ± 1,011 μg/mL, 5,422 ± 1,953 μg/mL, and 2.5 ± 1.6 μg/mL, respectively. Corresponding serum and SYN concentrations of sulbactam were lower but followed the same pattern over time as those for ampicillin. Synovial fluid ampicillin concentration remained above 8 μg/mL for a mean time of 18.9 hours.

CONCLUSIONS AND CLINICAL RELEVANCE Potentially therapeutic concentrations of ampicillin were achieved in regional serum and SYN samples; SYN concentrations remained at potentially therapeutic values for > 12 hours following RIVP of 1.5 g of ampicillin-sulbactam in the hind limb of healthy cows.

Restricted access
in American Journal of Veterinary Research

Abstract

OBJECTIVE

To assess the analgesic efficacy of an IV constant rate infusion (CRI) of a morphine-lidocaine-ketamine (MLK) combination in calves undergoing umbilical herniorrhaphy.

ANIMALS

20 weaned Holstein calves with umbilical hernias.

PROCEDURES

Calves were randomly assigned to receive a CRI of an MLK solution (0.11 mL/kg/h; morphine, 4.8 μg/kg/h; lidocaine, 2.1 mg/kg/h; and ketamine, 0.42 mg/kg/h) for 24 hours (MLK group) or 2 doses of flunixin meglumine (1.1 mg/kg, IV, q 24 h) and a CRI of saline (0.9% NaCl) solution (0.11 mL/kg/h) for 24 hours (control group). The assigned CRI was begun after anesthesia induction. A pain-scoring system and incisional algometry were used to assess pain, and blood samples were obtained to measure serum cortisol concentration at predetermined times for 120 hours after CRI initiation.

RESULTS

Mean pain scores did not differ significantly between the MLK and control groups at any time. Mean algometry score for the MLK group was significantly greater (calves were less responsive to pressure) than that for the control group at 4 hours after CRI initiation. Mean cortisol concentration decreased over time for both groups and was significantly greater for the MLK group than the control group at 1, 4, and 18 hours after CRI initiation.

CONCLUSIONS AND CLINICAL RELEVANCE

A CRI of MLK provided adequate postoperative analgesia to calves that underwent umbilical herniorrhaphy. However, the technical support required for CRI administration limits its use to hospital settings. Kinetic analyses of MLK infusions in cattle are necessary to establish optimal dosing protocols and withdrawal intervals.

Restricted access
in American Journal of Veterinary Research

Abstract

Objective—To determine hepatic and pulmonary phase-I and phase-II enzyme activities in horses.

Sample population—Pulmonary and hepatic tissues from 22 horses that were 4 months to 32 years old.

Procedure—Pulmonary and hepatic tissues from horses were used to prepare cytosolic (glutathione S-transferase and soluble epoxide hydrolase) and microsomal (cytochrome P450 monooxygenases) enzymes. Rates of microsomal metabolism of ethoxyresorufin, pentoxyresorufin, and naphthalene were determined by high-performance liquid chromatography. Activities of glutathione S-transferase and soluble epoxide hydrolase were determined spectrophotometrically. Cytochrome P450 content was determined by carbon monoxide bound-difference spectrum of dithionite-reduced microsomes. Activity was expressed relative to total protein concentration.

Results—Microsomal protein and cytochromeP450 contents were detectable in all horses and did not vary with age. Hepatic ethoxyresorufin metabolism was detected in all horses; by comparison, pulmonary metabolism of ethoxyresorufin and hepatic and pulmonary metabolism of pentoxyresorufin were detected at lower rates. Rate of hepatic naphthalene metabolism remained constant with increasing age, whereas rate of pulmonary naphthalene metabolism was significantly lower in weanlings (ie, horses 4 to 6 months old), compared with adult horses. Hepatic glutathione S-transferase activity (cytosol) increased with age; however, these changes were not significant. Pulmonary glutathione S-transferase activity (cytosol) was significantly lower in weanlings than adult horses. Hepatic and pulmonary soluble epoxide hydrolase did not vary with age of horses.

Conclusions and Clinical Relevance—Activity of cytochrome P450 isoforms that metabolize naphthalene and glutathione S-transferases in lungs are significantly lower in weanlings than adult horses, which suggests reduced ability of young horses to metabolize xenobiotics by this organ. (Am J Vet Res 2000;61:152–157)

Restricted access
in American Journal of Veterinary Research

Abstract

Objective—To determine whether prepartum intramammary treatment of dairy heifers with pirlimycin hydrochloride would reduce the prevalence of intramammary infection (IMI) and lower the somatic cell count (SCC) during early lactation or improve 305-day mature equivalent milk production.

Design—Prospective clinical trial.

Animals—183 Holstein-Friesian heifers (663 quarters) from 2 dairy farms.

Procedure—Heifers were assigned to treatment and control groups. Treated heifers received a single 50-mg dose of pirlimycin in each mammary quarter approximately 10 to 14 days prior to parturition. Prepartum mammary gland secretions and postpartum milk samples were collected for bacterial culture. Postpartum milk samples were also collected for determination of SCC or California mastitis testing and were tested for pirlimycin residues. Mature equivalent 305-day milk production data were recorded.

Results—Treated heifers in herd A had a higher overall cure rate, higher cure rates for IMI caused by coagulase-negative staphylococci (CNS) and Staphylococcus aureus, lower SCC, and lower prevalence of chronic IMI, compared with control heifers. Treated heifers in herd B had a higher overall cure rate and cure rate for IMI caused by CNS, compared with control heifers, but postpartum California mastitis test scores and prevalence of chronic IMI did not differ between groups. Mature equivalent 305-day milk production did not differ between herds or treatment groups. No pirlimycin residues were detected in postpartum milk samples.

Conclusions and Clinical Relevance—Results suggest that prepartum treatment of dairy heifers with pirlimycin may reduce the prevalence of early lactation IMI, particularly IMI caused by CNS, without causing pirlimycin residues in milk. (J Am Vet Med Assoc 2005;227:1969–1974)

Restricted access
in Journal of the American Veterinary Medical Association