Pharmacokinetic-pharmacodynamic relationships and dose response to meloxicam in horses with induced arthritis in the right carpal joint

OBJECTIVE: To determine pharmacokinetic-pharmacodynamic (PK-PD) relationships and dose effects for meloxicam in horses and to propose a suitable dosage for use in clinical studies. ANIMALS: 6 adult horses. PROCEDURE: The study was conducted by use of a randomized, Latin-square design. Arthritis was induced in the right carpal joint of each horse by administration of Freund's complete adjuvant. Various dosages of meloxicam (0, 0.25, 0.5, 1.0, and 2.0 mg/kg, IV) were then administered. Validated endpoints including stride length and overall clinical lameness score (scale of 0 to 20) were used to assess the effect of meloxicam. The dose-effect relationship was quantified by use of a maximum possible effect (Emax) model. RESULTS: For stride length (expressed as a relative percentage increase from control values), the median effective dose (ED50) was 0.120 mg/kg for an Emax of 11.15%. For clinical lameness score (expressed as an absolute increase from the control value), the ED50 was 0.265 mg/kg for an Emax of 9.16 units. The PK-PD analysis allowed calculation of a median effective concentration of 130 ng/mL for stride length and 195 ng/mL for lameness score. Use of the Emax model predicted a maximal possible increase in effect of 19.5% for stride length and 13.91 units for lameness score. For stride length and lameness score, the Hill coefficient (slope) was extremely high, which suggested a steep dose-effect relationship. CONCLUSIONS AND CLINICAL RELEVANCE: Results of this study suggest that meloxicam is a potent anti-inflammatory drug in horses. A dosage of 0.6 mg/kg/d would be appropriate for use in a clinical study.     

Wheat Leaf Rust Uredospore Production on Adult Plants: Influence of Leaf Nitrogen Content and Septoria tritici Blotch

ABSTRACT Leaf rust uredospore production and lesion size were measured on flag leaves of adult wheat plants in a glasshouse for different lesion densities. We estimated the spore weight produced per square centimeter of infected leaf, per lesion, and per unit of sporulating area. Three levels of fertilization were applied to the plants to obtain different nitrogen content for the inoculated leaves. In a fourth treatment, we evaluated the effect of Septoria tritici blotch on leaf rust uredospore production. The nitrogen and carbon content of the spores was unaffected or marginally affected by lesion density, host leaf nitrogen content, or the presence of Mycosphaerella graminicola on the same leaf. In leaves with a low-nitrogen content, spore production per lesion was reduced, but lesion size was unaffected. A threshold effect of leaf nitrogen content in spore production was however, evident, since production was similar in the medium- and high-fertilizer treatments. In leaves inoculated with M. graminicola and Puccinia triticina, the rust lesions were smaller and produced fewer spores. The relationships among rust lesion density, lesion size, and uredospore production were fitted to a model. We determined that the density effect on spore production resulted mainly from a reduction in lesion size, the spore production per unit of sporulating surface being largely independent of lesion density. These results are consistent with those obtained previously on wheat seedlings. The main difference was that the sporulation period lasted longer in adult leaves.     

Genetic diversity of Mycoplasma hyopneumoniae isolates of abattoir pigs

Mycoplasma hyopneumoniae, the causative agent of porcine enzootic pneumonia, is present in swine herds worldwide. However, there is little information on strains infecting herds in Canada. A total of 160 swine lungs with lesions suggestive of enzootic pneumonia originating from 48 different farms were recovered from two slaughterhouses and submitted for gross pathology. The pneumonic lesion scores ranged from 2% to 84%.Eighty nine percent of the lungs (143/160) were positive for M. hyopneumoniae by real-time PCR whereas 10% (16/160) and 8.8% (14/160) were positive by PCR for M. hyorhinis and M. flocculare, respectively. By culture, only 6% of the samples were positive for M. hyopneumoniae (10/160). Among the selected M. hyopneumoniae-positive lungs (n = 25), 9 lungs were co-infected with M. hyorhinis, 9 lungs with PCV2, 2 lungs with PRRSV, 12 lungs with S. suis and 10 lungs with P. multocida. MLVA and PCR-RFLP clustering of M. hyopneumoniae revealed that analyzed strains were distributed among three and five clusters respectively, regardless of severity of lesions, indicating that no cluster is associated with virulence. However, strains missing a specific MLVA locus showed significantly less severe lesions and lower numbers of bacteria. MLVA and PCR-RFLP analyses also showed a high diversity among field isolates of M. hyopneumoniae with a greater homogeneity within the same herd. Almost half of the field isolates presented less than 55% homology with selected vaccine and reference strains.     

Gender and resource management: Households and groups, strategies and transitions

Rural families must constantly negotiate their livelihoods by obtaining access to natural resources, labor, capital, knowledge, and markets. Successful negotiation leads to enhanced family well-being and sustainable use of natural resources. Unsuccessful negotiation threatens family survival, threatens sustainable use of natural resources, and reduces bio-diversity. These negotiation processes are mediated by gender relations. The ideas of negotiation and of survival strategies outlined here provide a framework within which the articles of this issue can be situated. The articles are the result of research on gender and natural resource management conducted in Latin America, Asia, Africa, and North America. Each experience illustrates the consequences for natural resources and family well being when they have voice and when they do not have voice in household decisions. This revised version was published online in June 2006 with corrections to the Cover Date.     

Long-term effects of metal-containing farmyard manure and sewage sludge on soil organic matter in a fluvisol

Our aim was to establish the long-term effects of repeated applications after 20 y of organic amendments (farmyard manure at 10 t ha⁻¹ y⁻¹, and urban sewage sludge at two different rates, 10 t ha⁻¹ y⁻¹ and 100 t ha⁻¹ every 2 y) on the quality of a sandy and poorly buffered soil (Fluvisol, pH 6). Chemical characteristics and biodegradability of the labile organic matter, which is mainly derived from microbial biomass and biodegradation products of organic residues, were chosen as indicators for soil quality. The organic C content had reached a maximal value (30.6 g C kg⁻¹ in the 100 t sludge-treated soil), i.e. about 2.5 times that in the control. Six years after the last application, the organic C content and the microbial biomass content remained higher in sludge-treated soils than in the control. In contrast, the proportion of labile organic matter was significantly lower in sludge-treated soils than in manure-treated and control soils. The labile organic matter of sludge extracts appeared less humified than that of manure-treated and control soils.     

From the editor

Editorial Board

From the editor     

Influence of gravity waves on the internal rotation and Li abundance of solar-type stars

The Sun's rotation profile and lithium content have been difficult to understand in the context of conventional models of stellar evolution. Classical hydrodynamic models predict that the solar interior must rotate highly differentially, in disagreement with observations. It has recently been shown that internal waves produced by convection in solar-type stars produce an asymmetric, shear layer oscillation, similar to Earth's quasi-biennial oscillation, that leads to efficient angular momentum redistribution from the core to the envelope. We present results of a model that successfully reproduces both the rotation profile and the surface abundance of lithium in solar-type stars of various ages.