Development and testing of a model for predicting tillage effects on nitrate leaching from cracked clay soils

Both water movement and nitrate leaching in structured soils are strongly influenced by the nature of the macro-porosity. That macro-porosity can however also be manipulated by choice of tillage operations. In order to investigate the potential impacts of tillage on rates of nitrate leaching from structured soils, a model specific to these soils, CRACK-NP was developed. The model, its application and validation for an experimental site on a heavy clay soil (Verti-Eutric Gleysoil) at Brimstone Farm, Oxfordshire, UK, is described. The model considers the soil as a series of aggregates whose size is also the spacing of the macro-porosity. Water and solutes move in the macro-pores, but within the peds they move only by diffusion, internal infiltration and root uptake (evaporation). The model reflects the influence of diffusion limitation in the release of solutes to by-passing water. The model was then used to investigate the influence of variable ped spacings which were created by variations in tillage practices. The results both from the model and from the field data demonstrated that finer soil structures, which have larger surface contact areas and shorter diffusion path lengths, present greater opportunities for interaction between peds and the water moving around them, and so release more nitrates through the drainage waters.     

Phosphorylation by p38 MAPK as an alternative pathway for GSK3beta inactivation

Glycogen synthase kinase 3beta (GSK3beta) is involved in metabolism, neurodegeneration, and cancer. Inhibition of GSK3beta activity is the primary mechanism that regulates this widely expressed active kinase. Although the protein kinase Akt inhibits GSK3beta by phosphorylation at the N terminus, preventing Akt-mediated phosphorylation does not affect the cell-survival pathway activated through the GSK3beta substrate beta-catenin. Here, we show that p38 mitogen-activated protein kinase (MAPK) also inactivates GSK3beta by direct phosphorylation at its C terminus, and this inactivation can lead to an accumulation of beta-catenin. p38 MAPK-mediated phosphorylation of GSK3beta occurs primarily in the brain and thymocytes. Activation of beta-catenin-mediated signaling through GSK3beta inhibition provides a potential mechanism for p38 MAPK-mediated survival in specific tissues.     

A REVIEW OF EQUINE RENAL IMAGING TECHNIQUES

Radiography has a limited role in the evaluation of the kidneys in foals and adult horses. Ultrasonography is the current method of choice for structural evaluation of the kidneys in horses as it provides additional information to standard serum chemistry and urinalysis evaluation. A variety of structural abnormalities have been identified in diseased equine kidneys with the use of ultrasound. Ultrasound guided renal biopsy is the preferred method for performing renal biopsy in the horse. The use of Duplex Doppler ultrasound may allow for the characterization of regional hemodynamics of the equine kidneys, but is currently an untapped method for evaluation of equine renal hemodynamics.
Radionuclide methods including scintigraphy and quantitative renal function measurement can be used to provide further information about equine renal function. Scintigraphy can provide structural and possibly functional information. Quantitative methods using radiopharmaceuticals can provide precise measurement of glomerular filtration rate and effective renal blood flow. This method is especially helpful in identifying acute renal failure and in guiding response to treatment.
All equine renal imaging techniques should be a supplement to the physical examination and standard laboratory tests. Additional diagnostic aids such as urinary tract endoscopy should also be considered in horses with hematuria, hydroureter, and suspected calculi. Taken together, all these modalities provide a through evaluation of the equine renal system and provide a basis for the clinician to select treatment options and provide prognostic information to the owner.     

Effects of microbial and host variables on the interaction of rotavirus and Escherichia coli infections in gnotobiotic calves

Naturally occurring mixed infections with Escherichia coli and rotavirus have been associated with fatal diarrhea of calves about 1 week old. Experiments were designed to reproduce this syndrome in gnotobiotic calves. Clinical, microbiological, and pathologic data were used to assess severity of disease and mechanisms of the interaction between the 2 infections. An initial study involved 5- to 8-day-old gnotobiotic calves inoculated with a strain of enterotoxigenic E coli (ETEC) and a strain of rotavirus. Calves were observed for 2 days after they were inoculated; fatal diarrhea was not produced. In later studies, variables were tested to identify those that might contribute to fatal diarrhea. Variables which did not result in fatal or severe diarrhea or which did not cause disease that was more severe in dually inoculated calves than that in monoinoculated calves were increasing feed to 2 times base line, increasing dose of ETEC to 10 times base line, inoculating calves when they were 2 days old, using a strain of E coli that causes colisepticemia, and using a different strain of rotavirus. When the observation period was extended from 2 days to 6 days after calves were inoculated, severe, watery, fatal diarrhea occurred in 6 of 12 calves by 32 to 72 hours after dual inoculation was given. Fatal diarrhea was associated with intensive colonization by the ETEC in the caudal half of the small intestine. Microscopic lesions were similar between dually inoculated and rotavirus-monoinoculated calves, except there was more severe atrophy of ileal villi of dually inoculated calves.(ABSTRACT TRUNCATED AT 250 WORDS)     

A comparison of end-tidal halothane concentrations measured at proximal and distal ends of the endotracheal tube in the horse.

Measurements (n = 126) of end-tidal halothane concentrations were taken from 21 horses anesthetized for routine and emergency surgery. One hundred five paired values allowed comparison of gas samples taken near the oral end of the endotracheal tube (Y1) to samples obtained at the cuffed end of the endotracheal tube (Y2). Twenty-one paired readings were assessed to compare samples taken 25 cm beyond the cuffed end of the tube (Y3) to samples from Y1. Measurements were made at all locations at 15-minute intervals starting 30 minutes after beginning halothane. All measurements were made in triplicate at end-expiration, and both sites were sampled within 1 minute of each other. Halothane concentration was measured by rapid infrared analysis with a gas sampling rate of 150 ml/min and displayed as a digital reading. Calibration of the machine was checked regularly. The difference between readings (Y1-Y2 or Y1-Y3 = Sdif) was tested using general linear models and a significance level of p less than 0.05 was used. The variable Sdif was analyzed with respect to time, mode of ventilation, and type of recumbency; no effects of these variables were detected. The mean values (+/- SD) of 105 readings for Y1 and Y2 were 2.41 vol% (+/- 0.49) and 2.39 vol% (+/- 0.49) respectively, and the Pearson's correlation coefficient (Y1 vs Y2) was 0.96. The mean values (+/- SD) of 21 measurements for Y1 and Y3 were 2.31 vol% (+/- 0.27) and 2.32 vol% (+/- 0.28) respectively and the Pearson's correlation coefficient (Y1 vs Y3) was 0.98.     

THE EFFECT OF DEXMEDETOMIDINE ON RADIOGRAPHIC CARDIAC SILHOUETTE SIZE IN HEALTHY CATS

Dexmedetomidine, an alpha₂‐adrenergic agonist, may be used in companion animals for chemical restraint, including cardiac evaluation. Echocardiographic changes associated with alpha₂‐adrenergic agonists have been described; however reports of radiographic changes in cats were not found at the time of this study. Aims of this observational, prospective, experimental study were to describe the effects of dexmedetomidine on the radiographic appearance of the cardiac silhouette in healthy, adult cats. Fourteen healthy adult cats received dexmedetomidine 40 mcg/kg IM. Right lateral, left lateral, ventrodorsal, and dorsoventral thoracic radiographs were obtained for each cat at three time points: presedation, intrasedation, and postsedation (≥ two hours after reversal with atipamezole). Radiographs were evaluated in a blinded, randomized fashion by two independent observers using the vertebral heart score on all four views, the number of intercostal spaces on lateral projections, and the percent width of thorax on ventrodorsal and dorsoventral projections. Median vertebral heart score on right lateral view was significantly increased intrasedation (median = 7.8; range = 7.25–8.25) compared to presedation (median = 7.5; range = 7–8 [P = 0.001]). Median percentage width was significantly higher intrasedation (70% on VD; range 65–80 [P = 0.001], and 75% on DV; range 65–80 [P = 0.006]) compared to presedation (65%; range 65–75 on both projections). Dexmedetomidine was associated with a small but significant increase in cardiac silhouette size on right lateral (vertebral heart score), ventrodorsal (percentage width), and dorsoventral (percentage width) radiographs in healthy adult cats. This effect should be taken into consideration for future interpretation of thoracic radiographs in dexmedetomidine‐sedated cats.