EQUINE PITUITARY PARS INTERMEDIA DYSFUNCTION (PPID): PATHOPHYSIOLOGY AND A SURGICAL APPROACH TO TREATMENT

Equine pituitary pars intermedia dysfunction (PPID) is a common endocrine disease of the older horse. First described in 1932, and likened to human Cushing’s disease, it is associated with an enlargement of the pituitary gland that was classically termed an adenoma. The underlying mechanism is attributable to a lack of dopaminergic inhibition of the pars intermedia. Treatment methods have remained essentially unchanged for 30 years and the prevalence data have mainly stemmed from Eastern Australia and the USA. The general objective of this thesis was to explore the feasibility of developing a targeted cell-specific approach for the treatment of equine PPID. The specific aims were to confirm the need for this advanced therapy by determining the prevalence of PPID in horses globally; to continue the investigation of the underlying cellular mechanism of PPID by confirming the role of pro-hormone convertases, and sequence the equine pro-opiomelanocortin, prohormone convertase 1 and 2 genes; and to investigate the methodology for site-specific applications of future therapy for equine PPID. These aims were met by reporting the prevalence data from a worldwide audience of veterinarians using an internet-based survey tool; by describing partial gene sequences of the equine proopiomelanocortin and prohormone convertase enzymes and their expression in normal and PPID horses; and by showing how low-volume contrast enhancement of the brain using computed tomography can delineate the margins of the pituitary gland, showing how general anesthesia effects the pulsitility and concentration of adrenocorticotrophic hormone, and finally, modifying a previously reported technique, by developing a novel surgical approach to the treatment of this classical condition

The effect of acute equine temporomandibular joint inflammation on response to rein-tension and kinematics

BackgroundAlthough the temporomandibular joint (TMJ) is the major contact point between the reins in the riders’ hand, the bit in the mouth, and the rest of the horse under saddle, the role of inflammation of this joint on equine locomotion and rein tension is unknown.ObjectiveTo determine the effect of acute TMJ inflammation on rein-tension and horse movement when horses were long-reined on a treadmill.Study designA randomized, controlled, cross-over design.MethodsFive horses were trained by one clinician to walk and trot on a treadmill wearing long-reining equipment instrumented with a rein-tension device and reflective optical tracking markers. Subjective assessment of horse’s dominant side, and movement, were determined without rein-tension (free walk and trot); and with rein-tension (long-reined walk and trot). Continuous rein-force data from both sides were collected over ~60s from each trial. Movement was recorded using a 12-camera optical motion capture system. One randomly assigned TMJ was subsequently injected with lipopolysaccharide and the treadmill tests repeated by investigators blinded to treatment side. A second, identical assessment was performed 10 days later with the opposite TMJ being the target of intervention.ResultsAll horses showed reduced rein-tension on the injected (inflamed) side. Increased rein-tension was required on the non-injected side at trot, to maintain them in the correct position on the treadmill post-injection. The only kinematic variable to show any significant change due to rein tension or TMJ inflammation during the walk or trot was an increase in forward head tilt in the presence of rein tension in the trot after injection.Main limitationsLow number of horses and investigation of response to acute inflammation only.ConclusionTMJ inflammation changed, subjectively and objectively, the response to rein-input, but the horses did not become lame

Contrast arthrography of the equine temporomandibular joint

BackgroundDisorders of the equine temporomandibular joint (TMJ) cause clinical problems and detailed investigations of this joint are becoming more common. Specialist radiographic projections have the potential to highlight osseous abnormalities; however, the ability to assess the intra-articular soft tissue structures is currently limited to computed tomography (with, or without contrast enhancement) or magnetic resonance imaging. Both modalities are expensive and not readily accessible.ObjectiveTo develop a technique of contrast arthrography of both compartments of the equine TMJ in cadavers and then perform the refined technique in three living horses as a proof-of-principle.Study designA descriptive, experimental, study.MethodsContrast arthrography of the discomandibular and discotemporal joint compartments of both TMJs was performed in 12 cadaveric equine heads using needles placed in the caudal pouches of the respective joint compartments. Radiographs were taken using previously published techniques, repeated with the mouth open and after air had been injected into the joints, to perform a double-contrast study. The TMJs of three healthy horses were subsequently examined to determine the validity of the procedure in live animals.ResultsSingle and double-contrast arthrography allowed delineation of the dorsal and ventral surfaces of the intra-articular disc in addition to filling the rostral and caudal joint pouches of the independent joint compartments. Contrast extravasation was common, and in two instances iatrogenic disc penetration resulted in the false diagnosis of pathologic disc perforation. The techniques were well tolerated in all three live horses.Main limitationsLow number of horses.ConclusionContrast arthrography allows interpretation of intra-articular soft tissue structures, but caution is advised in diagnosing intra-articular disc perforation. Even with experience, accessing the discomandibular joint can be challenging

Chloridobis(1,10-phenanthroline)zinc(II) tetra­chlorido(1,10-phenan­throline)bis­muthate(III) monohydrate

In the crystal structure of the title monohydrate salt, [ZnCl(C12H8N2)2][BiCl4(C12H8N2)]·H2O, the ionic components are linked into three-dimensional supra­molecular channels by five pairs of C—H⋯Cl hydrogen bonds and π–π stacking inter­actions with an inter­planar distance of 3.643 (2) Å. The solvent water mol­ecules are lodged in the channels

The effect of acute equine temporomandibular joint inflammation on response to rein-tension and kinematics

BackgroundAlthough the temporomandibular joint (TMJ) is the major contact point between the reins in the riders’ hand, the bit in the mouth, and the rest of the horse under saddle, the role of inflammation of this joint on equine locomotion and rein tension is unknown.ObjectiveTo determine the effect of acute TMJ inflammation on rein-tension and horse movement when horses were long-reined on a treadmill.Study designA randomized, controlled, cross-over design.MethodsFive horses were trained by one clinician to walk and trot on a treadmill wearing long-reining equipment instrumented with a rein-tension device and reflective optical tracking markers. Subjective assessment of horse’s dominant side, and movement, were determined without rein-tension (free walk and trot); and with rein-tension (long-reined walk and trot). Continuous rein-force data from both sides were collected over ~60s from each trial. Movement was recorded using a 12-camera optical motion capture system. One randomly assigned TMJ was subsequently injected with lipopolysaccharide and the treadmill tests repeated by investigators blinded to treatment side. A second, identical assessment was performed 10 days later with the opposite TMJ being the target of intervention.ResultsAll horses showed reduced rein-tension on the injected (inflamed) side. Increased rein-tension was required on the non-injected side at trot, to maintain them in the correct position on the treadmill post-injection. The only kinematic variable to show any significant change due to rein tension or TMJ inflammation during the walk or trot was an increase in forward head tilt in the presence of rein tension in the trot after injection.Main limitationsLow number of horses and investigation of response to acute inflammation only.ConclusionTMJ inflammation changed, subjectively and objectively, the response to rein-input, but the horses did not become lame

Computational fluid dynamic analysis of upper airway procedures in equine larynges

IntroductionComputational fluid dynamics (CFD) has proven useful in the planning of upper airway surgery in humans, where it is used to anticipate the influence of the surgical procedures on post-operative airflow. This technology has only been reported twice in an equine model, with a limited scope of airflow mechanics situations examined. The reported study sought to widen this application to the variety of procedures used to treat equine recurrent laryngeal neuropathy (RLN). The first objective of this study was to generate a CFD model of an ex-vivo box model of ten different equine larynges replicating RLN and four therapeutic surgeries to compare the calculated impedance between these procedures for each larynx. The second objective was to determine the accuracy between a CFD model and measured airflow characteristics in equine larynges. The last objective was to explore the anatomic distribution of changes in pressure, velocity, and turbulent kinetic energy associated with the disease (RLN) and each surgical procedure performed.MethodsTen equine cadaveric larynges underwent inhalation airflow testing in an instrumented box while undergoing a concurrent computed tomographic (CT) exam. The pressure upstream and downstream (outlet) were measured simultaneously. CT image segmentation was performed to generate stereolithography files, which underwent CFD analysis using the experimentally measured outlet pressure. The ranked procedural order and calculated laryngeal impedance were compared to the experimentally obtained values.Results and discussionThe CFD model agreed with the measured results in predicting the procedure resulting in the lowest post-operative impedance in 9/10 larynges. Numerically, the CFD calculated laryngeal impedance was approximately 0.7 times that of the measured calculation. Low pressure and high velocity were observed around regions of tissue protrusion within the lumen of the larynx. RLN, the corniculectomy and partial arytenoidectomy surgical procedures exhibited low pressure troughs and high velocity peaks compared to the laryngoplasty and combined laryngoplasty/corniculectomy procedures. CFD modeling of the equine larynx reliably calculated the lowest impedance of the different surgical procedures. Future development of the CFD technique to this application may improve numerical accuracy and is recommended prior to consideration for use in patients

Humidity-tolerant ultrathin NiO gas-sensing films

When the gas sensor active layer film thickness is decreased, increased sensitivity to changes in the adsorbate concentration is expected when measuring the resistance of the layer, in particular when this thickness is on the order of the Debye length of the material (one–tens of nanometers); however, this is demonstrated only for a limited number of materials. Herein, ultrathin NiO films of different thicknesses (8–21 nm) have been deposited via chemical vapor deposition to fabricate gas sensor devices. Sensor performance for a range of NO2 concentrations (800 part-per-billion to 7 part-per-million) was evaluated and an optimum operating temperature of 125 °C determined. The dependence of the potential relative changes with respect to the NO2 concentration and of the sensor signal with respect to the geometrical parameters was qualitatively evaluated to derive a transduction model capable of fitting the experimental results. The selective sensitivity toward NO2 was confirmed by the limited response for different reducing gases, CO, CH4, NH3, and SO2, under optimum operating conditions, and the sensor signal toward NO2 increased with decreasing thickness, demonstrating that the concept of a Debye length dependence of sensitivity is applicable for the p-type semiconductor NiO. In addition, these NiO sensors were exposed to different relative levels of humidity over a wide range of operating temperatures and were found to display humidity tolerance far superior to those in previous reports on SnO2 materials