Comparison of accelerator mass spectrometry with gas chromatography for the determination of pesticide residues in individual items in the diets of wild birds and mammals

Methods to refine the assessment of exposure of wild birds and mammals to pesticides required measurement of pesticide residues in very small samples of their diets. Sample sizes were in the 1-100 mg range, and the target residue for measurement was 0.01 mg/kg. Gas chromatography-mass spectrometry (GC-MS) with large volume injection was compared with the use of an accelerator mass spectrometer (AMS) to measure residues of pesticide labeled at near-background levels with carbon-14. The GC-MS method was able to detect residues down to 0.1 ng per item of diet, and the AMS detected the radiolabel down to 1 mBq (0.06 disintegration per minute, 1 ng of pesticide at the specific activity used) per sample. The target residue level was achieved by the GC-MS method for samples down to 10 mg. The GC method appeared to be best suited to monitoring residues in field studies, and the AMS shows great potential for use in laboratory experiments concerning pesticide degradation.     

Expectations for population growth at new breeding locations for the vulnerable New Zealand sea lion (Phocarctos hookeri) using a simulation model

Management plans for threatened or recovering large vertebrate species that are increasing in population size and range focus on the establishment of viable populations within set temporal limits. New Zealand (Hookers) sea lions (Phocarctos hookeri) were declared a threatened species in 1997, and New Zealand legislation requires that threatened species of marine mammals must be managed to reduce human-induced mortality and achieve a non-threatened status within 20 years. The present breeding distribution of P. hookeri is highly localised, with over 95% of total annual pup production located at Auckland Islands and almost all of the remainder at Campbell Island. Breeding elsewhere has been ephemeral or restricted to <10 adult females. The only recorded sustainable breeding at a new location has been at Otago, South Island, New Zealand. This breeding population consisted of a total of four breeding females in 2002 and is derived from one immigrant female that gave birth to her first pup in the 1993/1994 breeding season. The New Zealand Department of Conservation management plan specifies that to achieve a non-threatened status P. hookeri (1) at Otago must increase in the number of breeding females to ?10, and (2) must establish ?two new breeding locations within the 20-year time frame, each with ?10 breeding females. This study 1) projects the population growth trends at a new location (Otago) to see if it will achieve ?10 breeding females within the legislated time frame, and (2) examines the likelihood that other breeding locations will establish elsewhere given the demographic information available for this species. We present 20 deterministic and three stochastic Leslie matrix model scenarios for female population growth for the initial years following the start of breeding at a new location. Our results indicate that (1) a new breeding population derived from one immigrant female is unlikely to reach 10 breeding females in 20 years; this duration is more likely to be 23-41 years (deterministic models) or 23-26 years (stochastic model), (2) the likelihood of two new sites establishing within 20 years is unquantifiable, but the probability is low, and (3) if the legislated outcome and time limit are not revised in the population management plan, the feasibility and effectiveness of re-locating young females could be investigated.     

Tylosin detection in animal feed by liquid chromatography-tandem mass spectrometry with enzymatic hydrolysis of the tylosin urea adduct

When the use of tylosin as a feed additive was forbidden by Council Regulation 2821/98, the necessity of a chemical confirmation method for the monitoring of the ban was created. Recently a method was developed for the detection of tylosin in animal feed by means of LC-MS/MS. During the validation high deviating values for the decision limit, detection capability, and repeatability for tylosin in cattle feed were observed, and the presence of urea and the formation of a tylosin urea adduct (TUA) were suggested as possible explanations. In this study two hydrolysis approaches for the TUA adduct were compared, namely, a chemical hydrolysis and an enzymatic hydrolysis with urease. The latter yielded a more complete hydrolysis of urea and was used for further validation. The recovery increased by approximately 15-25% depending on the amount of urea present in the feed (0.5-2%). The decision limit and detection capability were hardly influenced by the enzymatic hydrolysis.     

Detecting interaction(s) and assessing the impact of component subsets in a chemical mixture using fixed-ratio mixture ray designs

An important environmental and regulatory issue is the protection of human health from potential adverse effects of cumulative exposure to multiple chemicals. Earlier literature suggested restricting inference to specific fixed-ratio rays of interest. Based on appropriate definitions of additivity, single chemical data are used to predict the relationship among the chemicals under the zero-interaction case. Parametric comparisons between the additivity model and the model fit along the fixed-ratio ray(s) are used to detect departure from additivity. Collection of data along reduced fixed-ratio rays, where subsets of chemicals of interest are removed from the mixture and the remaining compounds are at the same relative ratios as considered in the full ray, allow researchers to make inference about the effect of the removed chemicals. Methods for fitting simultaneous confidence bands about the difference between the best fitting model and the model predicted under additivity are developed to identify regions along the rays where significant interactions occur. This general approach is termed the “single chemicals required” (SCR) method of analysis. A second approach, termed “single chemicals not required” (SCNR) method of analysis, is based on underlying assumptions about the parameterization of the response surface. Under general assumptions, polynomial terms for models fit along fixed-ratio rays are associated with interaction terms. Consideration is given to the case where only data along the mixture rays are available. Tests of hypotheses, which consider interactions due to subsets of chemicals, are also developed.     

Statistical analysis of interactive cytotoxicity in human epidermal keratinocytes following exposure to a mixture of four metals

Exposure to mixtures of chemicals is an important and relevant environmental issue. Of particular interest is the detection and characterization of departure of biological effects from additivity. Methodology based on the assumption of additivity is used in fitting single-chemicaldata. Interactionsare determined and characterized by making comparisons between the observed and predicted responses at mixtures along a fixed ratio ray of the component substances. Two simultaneous tests are developed for testing for any departure from additivity. Multiple comparisons procedures are used to compare observed responses to that predicted under additivity. A simultaneous confidence band on the predicted responses along the mixture ray is also developed. The methods are illustrated with cytotoxicity data that arise when human epidermal keratinocytes are exposed to a mixture of arsenic, chromium, cadmium, and lead. Synergistic, antagonistic, and additive cytotoxicities were observed at different dose levels of the four-metal mixture.     

Subtotal pericardectomy and epicardial excision for treatment of coccidioidomycosis-induced effusive-constrictive pericarditis in dogs: 17 cases (1999-2003)

OBJECTIVE: To determine the history, clinicopathologic findings, and results of surgery for effusive-constrictive pericarditis associated with Coccidioides immitis infection in dogs. DESIGN: Retrospective study. ANIMALS: 17 client-owned dogs that underwent a subtotal pericardectomy and epicardial excision. PROCEDURE: Hospital records from May 1999 to June 2003 were reviewed. Data collected included history, clinicopathologic findings, treatments, and outcome. Follow-up information was obtained via recheck examination and by use of standardized telephone interviews with referring veterinarians and owners. RESULTS: All dogs were of large breeds, and most were male (mean age, 4.66 years). Ten dogs had no prior history of C. immitis infection, and 7 dogs had chronic infection with C. immitis. Having a chronic C. immitis infection reduced the odds of survival, compared with no previous infection. All dogs had clinical signs of right-sided heart failure. All dogs had serum titers (range, 1:8 to 1:256) for antibodies against C. immitis prior to surgery, and titers were not significantly associated with outcome. Predominant echocardiographic findings were thickened pericardium, reduced right ventricular filling, and pleural or pericardial effusion. All dogs underwent a subtotal pericardectomy and epicardial excision and had fibrosing pyogranulomatous pericarditis in biopsy specimens obtained during surgery. The perioperative mortality rate was 23.5%, and the 2-year postdischarge survival rate was 82%. CONCLUSIONS AND CLINICAL RELEVANCE: Surgical treatment via subtotal pericardectomy and epicardial excision is successful at relieving right-sided heart failure in dogs with effusive-constrictive pericarditis secondary to C. immitis infection, but long-term treatment with antifungal agents may still be required.     

Biochemical analysis of the articular cartilage and subchondral and trabecular bone of the metacarpophalangeal joint of horses with early osteoarthritis

OBJECTIVE: To assess whether site-related changes in biochemical composition are present in the cartilage and subchondral and trabecular bone of the metacarpophalangeal joint of horses with early osteoarthritis. SAMPLE POPULATION: Right metacarpophalangeal joints from 59 mature warmblood horses. PROCEDURE: Biochemical data (cross-link, amino acid, DNA, and ash contents; denatured collagen and glycosaminoglycan [GAG] concentrations; bone mineral density; and mineral composition) were obtained from 2 differently loaded sites of phalanx I cartilage and subchondral and trabecular bone samples; data were compared with previously published values from nonosteoarthritic equine joints. RESULTS: Compared with findings in nonosteoarthritic joints, GAG concentration was lower in cartilage from osteoarthritic joints and there was a loss of site differences in cellularity and lysylpyridinoline (LP) cross-link content. In subchondral bone, LP cross-link content was decreased overall and there was a loss of site differences in osteoarthritic joints; ash content was higher in the osteoarthritic joints. Hydroxyproline content in trabecular bone from osteoarthritic joints was greater than that in nonosteoarthritic trabecular bone. In all 3 layers and at both sites, the linear increase of the pentosidine cross-link content with age had diminished or was not apparent in the horses with osteoarthritic joints. CONCLUSIONS AND CLINICAL RELEVANCE: In equine metacarpophalangeal joints with early osteoarthritis, distinct biochemical changes were detected in the cartilage and subchondral and trabecular bone. The dissimilarity in response of the different tissues and differences between the sites that are affected may be related to differences in biomechanical loading and transmission and dissipation of force.     

Comparison of three methods for arthrodesis of the distal intertarsal and tarsometatarsal joints in horses

OBJECTIVE: To evaluate the effects of diode laser surgery (LS), surgical drilling (SD), and intraarticular sodium monoiodoacetate (MIA) as methods for fusing the distal intertarsal (DIT) and tarsometatarsal (TMT) joints in horses. STUDY DESIGN: Experimental study. ANIMALS: Adult horses (15) without radiographic signs of osteoarthritis (OA) of the DIT and TMT joints. METHODS: Group 1 (n=3) had LS performed bilaterally on DIT and TMT joints; 1 horse was evaluated for 1 week and 2 horses were evaluated for 2 weeks. Group 2 (n=6) had LS on DIT and TMT joints of 1 tarsus and MIA administration into the contralateral DIT and TMT joints and were evaluated for 6 months. Group 3 (n=6) had LS performed on DIT and TMT joints of 1 tarsus and SD of the contralateral DIT and TMT joints and were evaluated for 12 months. Postoperative comfort, lameness, radiography, microradiography, and histology scores were compared using repeated measures ANOVA, and paired or 2 sample t-tests; significance was set at P<.05. RESULTS: LS caused the least postoperative morbidity. In group 2, horses were less lame in 4 LS-treated limbs and 2 MIA-treated limbs at 6 months when compared with the contralateral limb. In group 3, horses were less lame in 5 LS-treated limbs and 1 SD-treated limb at 6 and 12 months compared with the contralateral limb. On microradiography, 11 MIA joints and 2 LS joints had bone bridging the joint at 6 months whereas 8 SD joints and 5 LS joints had bone bridging at 12 months. Significantly more joint space was bridged by bone in MIA- (51.4%) and SD (46.2%)-treated joints compared with LS joints at 6 (30.6%) and 12 (28.5%) months, respectively (P<.05). CLINICAL RELEVANCE: SD and MIA resulted in more bone bridging of the distal 2 tarsal joints, than LS. However, LS seemingly caused less pain and discomfort to horses in the immediate postoperative period; horses were generally less lame in the LS limb. More laser energy may need to be applied to these joints to promote fusion; however, it may also have beneficial effects beyond fusion. Further research on horses with OA of the distal 2 tarsal joints is needed to determine whether LS can cause soundness without facilitating bony fusion.     

Accuracy and optimization of force platform gait analysis in Labradors with cranial cruciate disease evaluated at a walking gait

OBJECTIVE: To determine the combination of ground reaction forces (GRFs) that best discriminates between lame and non-lame dogs. To compare the sensitivity of force platform gait analysis and visual observation at detecting gait abnormalities in Labradors after surgery for rupture of the cranial cruciate ligament (CCL). ANIMALS: All dogs were adult Labrador Retrievers: 17 free of orthopedic and neurologic abnormalities, 100 with unilateral CCL rupture, and 131 studied 6 months after surgery for unilateral CCL injury, 15 with observable lameness. PROCEDURE: Dogs were walked over a force platform with GRF recorded during the stance phase. Analytic properties of force platform gait analysis were calculated for several combinations of forces. The probability of visual observation detecting a gait abnormality was compared with that of force platform gait analysis. RESULTS: We determined that a combination of peak vertical force (PVF) and falling slope were optimal for discriminating sound and lame Labradors. After surgery, many dogs (75%) with no observable lameness failed to achieve GRFs consistent with sound Labradors. CONCLUSION: A force platform is an accurate method of assessing lameness in Labradors with CCL rupture and is more sensitive than visual observation. Assessing lameness with a combination of GRFs is better than using univariate GRFs. CLINICAL RELEVANCE: Therapies for stifle lameness can be accurately and objectively evaluated using 2 vertical ground reaction forces obtained from a force platform.