In vitro prediction of canine urolith mineral composition using computed tomographic mean beam attenuation measurements

Determination of urolith mineral composition is critical for management of urolithiasis in dogs and cats. Using computed tomography, urolith physical density, and hence chemical composition, can be quantified using mean beam attenuation measurements (Hounsfield units; HU). This study was designed to establish in vitro reference ranges for three types of compositionally pure uroliths retrieved from dogs. Sixty-six canine uroliths (22 uric acid, 21 calcium oxalate, 14 struvite, nine mixed or compound) were placed in a phantom array. Uroliths were scanned at 120 kVp, 200 mA, and 80 kVp, 200 mA. The region of interest (ROI) for mean HU calculation was determined using two techniques, and reference ranges were calculated for each kVp using either ROI technique. HU for urolith types of pure composition were statistically different (Wilcoxon's two-sample test, P < 0.0083 [Bonferonni correction with six comparisons for total P < 0.05]) using both ROI techniques at either kVp. Struvite uroliths were not statistically different from mixed or compound uroliths. The accuracy for determination of composition of pure uroliths ranged from 86% to 93%; the prediction accuracy for each urolith mineral type and for all uroliths in general was highest when the ROI was hand-drawn just within the visible urolith border at 80 kVp. Technique of ROI determination and kVp that yielded the highest sensitivity, specificity, and positive and negative predictive values varied for each urolith type. Therefore, in this study, HU could be used to differentiate three types of uroliths of pure mineral composition in vitro. Further studies are needed to determine the predictive value of HU in vivo.     

ECHOCARDIOGRAPHIC PARAMETERS IN TRAINING COMPARED WITH NON-TRAINING GREYHOUNDS

Echocardiographic parameters were compared between training and non-training greyhound dogs. When indexed to body weight there was a statistically significant increase (p<0.05) in the interventricular septal thickness (systole) and when indexed to body surface area there were increased interventricular septal (systole) and left ventricular free wall measurements (systole) in training compared with non-training greyhounds. When each gender was analyzed separately and echocardiographic parameters were indexed to body size, both genders had an increase in the interventricular septal thickness (diastolic in the female, systolic in the male) in the training compared with non-training greyhounds. In male training greyhounds there was additionally an increase in the left ventricular internal dimension (systole) and free wall thickness (systole) when echocardiographic parameters were indexed to body surface area compared with non-training greyhounds (p<0.05). The results indicate that certain training greyhound echocardiographic parameters are larger than non-training greyhound echocardiographic parameters. The potential effects of training, body size and gender should be considered when interpreting echocardiographic parameters in populations of greyhounds.     

Abnormalities of the Thoracic Bellows: Stress Fractures of the Ribs and Hiatal Hernia

The thoracic bellows mechanism consists of the rib cage and the diaphragm. The purpose of this study was to determine if nontraumatically acquired lesions of the bellows were secondary to underlying disease. Abnormalities of the bellows, specifically stress fractures of the ribs and hiatal hernia, were found in 21 dogs and cats with underlying cardiopulmonary disease, neuromuscular disease, or metabolic disease. A case-control study of Bulldogs demonstrated that hiatal hernia was associated with the more severe manifestations of brachycephalic syndrome. Stress fractures occurred mostly in females and in cats, and involved multiple ribs. Fractures were usually related to severe respiratory effort, but also occurred in association with metabolic disease. Hiatal hernia was also associated with severe respiratory effort, but may be exacerbated if a neuromuscular disorder affecting the diaphragm is present. Abnormalities of the thoracic bellows, such as rib stress fractures and hiatal hernia, may be signs of underlying disease, rather than being primary causes of disease.     

Evaluation of a technique to occlude the internal carotid artery of horses

OBJECTIVE: To evaluate an occlusion technique for the internal carotid artery of horses using an intravascular, detachable, self-sealing, latex balloon distally and ligatures proximally. STUDY DESIGN: Experimental study. ANIMALS: Six healthy adult horses. METHODS: In each horse, the left internal carotid artery was occluded by placement of an intravascular, detachable, self-sealing, latex balloon distally and two ligatures proximally. Radiographs were taken on days 2, 5, 10, and 30 after surgery to evaluate balloon inflation and position. Endoscopic examination of the left guttural pouch was performed 10 days after surgery to evaluate the integrity of the internal carotid artery and surrounding tissues. At 30 days, the left and right, common, internal, and external carotid arteries were examined grossly and then processed for histologic evaluation. RESULTS: Immediate and long-term occlusion of the left internal carotid artery was achieved in all horses. The surgical procedure was technically straightforward and no intraoperative or postoperative complications were encountered. The balloons remained inflated and in their original position throughout the study. Maturing to mature, organized thrombi were present in the left internal carotid artery in all horses at 30 days. The cerebral arterial circle and common carotid artery were patent at their junctions with the internal carotid artery in all horses. CONCLUSIONS: Use of an intravascular, detachable, self-sealing, latex balloon distally and ligatures proximally is an effective technique for occluding the internal carotid artery of horses. CLINICAL RELEVANCE: This technique may be useful for prevention of fatal hemorrhage in horses with lesions of the internal carotid artery.     

Effect of topical rh-TGF-beta 1 on second intention wound healing in horses

OBJECTIVE: To investigate the effects on wound healing of transforming growth factor-beta 1 as a topical treatment to full-thickness, excisional wounds of the distal limb of horses. DESIGN: A randomised block study using four horses, each with wounds assigned to four treatment groups. ANIMALS: Four adult Standardbred geldings. PROCEDURE: Four, 4 cm2, full-thickness wounds were created on the dorsomedial and dorsolateral aspect of the metacarpus or metatarsus of each limb of four horses, giving a total of 64 wounds. For each limb, wounds were randomly assigned to four treatment groups: no treatment (control), carrier (Methyl Cellulose gel), 50 ng/wound rhTGF-beta 1 in carrier, and 500 ng/wound rhTGF-beta 1 in carrier. Wounds were treated on day 0 and day 8. Effects of treatment were evaluated on the basis of the presence of exuberant granulation tissue requiring excision, number of times excision was required, total wound area, area of epithelialisation, area of granulation, and histological evaluation of biopsy samples of wounds on day 8 and excised wounds on day 21. RESULTS: Topical application of TGF-beta 1 at the two concentrations studied had no significant effect on the total area of wounds (P = 0.7), the area of granulation tissue (P = 0.78), the area of epithelialisation (P = 0.92), histological assessment or subjective clinical assessment of wounds. CONCLUSION: TGF-beta 1 had no beneficial effects on wound healing. Additional trials are needed to test if it has value for wound treatment in horses.     

The activation of nicotinic acetylcholine receptors in the nematode parasite Ascaris suum by the application of levamisole to the cytoplasmic surface of muscle membrane

The patch-clamp technique was used to examine activation by levamisole of nicotinic acetylcholine receptors in muscle vesicle preparations from Ascaris suum. Previous experiments have shown that levamisole, when applied at concentrations greater than 30 μM to the extracellular surface of the membrane, activated channels which showed characteristics of a voltage-sensitive open channel-block and desensitisation. In this study initial experiments were performed where channels were activated with levamisole (2 μM ) applied in the patch-pipette. Isolated inside-out patches were used. In addition, levamisole (30-926 μM ) was added to the cytoplasmic membrane surface via the bath solution. In eight out of nine experiments, addition of levamisole to the bath solution resulted in an increase in channel activity, a voltage-sensitive open channel-block and desensitisation. The open channel-block occurred at hyperpolarised potentials, an observation consistent with levamisole (a cationic substance) blocking the channel from the extracellular surface. Thus it was concluded that levamisole crossed from the cytoplasmic side of the membrane, via the lipid phase, to the extracellular surface of the patch. In the presence of high cytoplasmic concentrations of levamisole, open channel-block was not observed at depolarised potentials, suggesting channel asymmetry.     

Constraints to farmers managing dryland salinity in the central wheatbelt of Western Australia

There is an increasingly well‐founded understanding of the chief drivers and constraints to widespread adoption by Australian landholders to practices to manage dryland salinity. However, each specific situation depends on a range of biophysical, social and economic factors. Such is the case in this study that examines farmers' salinity management in the Wallatin‐O'Brien catchments in the low‐medium rainfall zone of the Western Australian wheatbelt. The study involved interviews with landholders and economic modelling of representative farms and salinity management options to gain an understanding of the farmers' adoption behaviour regarding salinity management. Most landholders interviewed saw dryland salinity as a second order farm management issue, due first to the relatively slow rate of expansion of saline land within the catchments and second, because the changes in land use required to prevent further loss of land to salinity were viewed as being uneconomic. The exception to this was the minority (<15 per cent) of farmers in the catchment that have most of the saline land and have experienced most of the recent increase, and for these farmers (primarily located in the valley floor) salinity is a pressing issue. The scale and pattern of isolated outbreaks on adjacent slopes means that salinity is merely a nuisance problem for farmers who only have this type of salinity. For all farmers, a disincentive to invest in salinity management was the landholders' lack of knowledge about the proper placement, needed scale of adoption and economic viability of salinity management options. Saltland pastures, surface water management and lucerne were viewed positively, with several desirable characteristics such as ease of trialling and complementarity to existing farm practices. By contrast, engineering options such as deep drainage, where considerable investment is involved and disposal of groundwater is problematic, were rated less favourably. Bioeconomic modelling of these salinity management options generated results that largely confirmed the merits of what landholders in the catchments currently do. The findings showed that there was little economic merit in wide‐scale adoption of these salinity management options in these catchments. However, the findings did highlight the need to match salinity management options to a farm's particular circumstance, if best use of the options is to be made by the different farms in the catchments. Copyright © 2009 John Wiley & Sons, Ltd.     

Within-field variability of wheat yield and economic implications for spatially variable nutrient management

Economic justification for varying fertiliser inputs to match crop yield potential of different areas or zones in fields is limited by lack of understanding of the relationship between the extent of within-field yield variation and economic gains from zone versus uniform management. We conducted a survey of yield monitor data from 199 fields on the northern sandplain of the wheatbelt in Western Australia in order to document the extent of sub-field yield variation and test if variation is related to attributes such as yield and field area. The economic significance to zone management of the yield variation found in the survey along with variation in size of management zones, costs and prices, and soil fertility status was then assessed using a simple nutrient response model.