Dynamic ventrorostral displacement of the dorsal laryngeal mucosa in horses.

The objectives of this report were to describe the occurrence and features of dynamic ventrorostral displacement of the dorsal laryngeal mucosa (VRDDLM) in a group of Thoroughbred horses presented for investigation of poor performance and/or abnormal respiratory noise. Records from 600, dynamic, endoscopic examinations of the upper respiratory tract of horses were reviewed. Horses with VRDDLM were identified as those in which the dorsal laryngeal mucosa progressively obscured the interarytenoid notch and dorsoaxial portion of the corniculate processes of the arytenoid cartilages during high-speed exercise. The condition was recognised in 12 horses. Concurrent abnormalities of the respiratory tract of eight horses were also identified and included, axial deviation of the aryepiglottic folds, vocal cord prolapse, unilateral and bilateral ventromedial luxation of the apex of the corniculate process of the arytenoid cartilage, and intermittent dorsal displacement of the soft palate. VRDDLM is a rare abnormality of the upper portion of the respiratory tract of horses that may be associated with abnormal respiratory noise and potentially poor performance. The significance of the condition is not known, but the presence of this condition in combination with other, obstructive diseases of the equine airway warrants further investigation.

Comparison of dynamic and resting endoscopy of the upper portion of the respiratory tract in 57 Thoroughbred yearlings.

REASONS FOR PERFORMING THE STUDY: Endoscopic examination of Thoroughbred (TB) yearlings is performed routinely to determine the suitability of horses for racing and to ensure that the conditions of sale are satisfied. However, previous research has demonstrated that resting endoscopic examination can be inaccurate in the diagnosis of functional pathology of the upper portion of the respiratory tract (URT). OBJECTIVES: To investigate the feasibility of performing dynamic overground endoscopy in a group of TB yearlings and to compare the results of resting and dynamic endoscopic examination of the URT. STUDY DESIGN: Prospective cohort study. METHODS: Resting (pre- and post exercise) and exercising endoscopy was performed on 57 TB yearlings at a single training yard. Observed abnormalities were recorded and graded. The results of resting and dynamic examination were compared. RESULTS: Dynamic overground endoscopy was well tolerated and was performed with few complications. Laryngeal asymmetry (29 cases) was the most common abnormality identified at rest, while intermittent dorsal displacement of the soft palate (IDDSP; 19 cases) was the most common at exercise. Significant variation in laryngeal function and variation in the occurrence of IDDSP was noted between examinations. Other potentially significant pathology that was not noted at rest but was present during exercise included collapse of the apex of the corniculate process, pharyngeal collapse and cricotracheal ligament collapse. The occurrence of IDDSP at exercise was significantly associated with epiglottic structure grade>2 and a recent history of respiratory tract infection. CONCLUSIONS: Dynamic overground endoscopy is safe and potentially useful when assessing URT function in TB yearlings. Significant variations in the results of endoscopy at rest and during exercise were identified, which indicate that resting endoscopy may not be sufficient to predict the occurrence of pathology during exercise. POTENTIAL RELEVANCE: Dynamic overground endoscopic examination could be considered a suitable means of assessing URT function in TB yearlings and may provide additional pertinent information to that obtained during standard resting examination.

Long-term cost-effectiveness of single indirect restorations in selected dental practices.

OBJECTIVE: To determine the relative cost-effectiveness of alternative methods for restoring large tooth substance loss in adults. METHODS: Long-term survival estimates and discounted costs for 245 large indirect restorations were used to calculate their incremental cost-effectiveness over 15 years when compared with direct placement Class II cusp-overlay amalgams and Class IV multisurface resin composites, placed in 100 patients from three private dental practices. RESULTS: The direct placement restorations were more cost-effective than the indirect restorations at all time intervals over the 15-year study period. The full gold crown and the ceramometal crown were the most cost-effective indirect posterior and anterior restorations respectively. The cast gold onlay and the porcelain jacket crown were the least cost-effective indirect posterior and anterior restorations respectively. CONCLUSIONS: When clinically practicable, large direct placement restorations should be placed initially in preference to indirect restorations.

Studies on valproate-induced perturbations of neurulation in the explanted chick embryo.

The effect of the anticonvulsant sodium valproate on in vitro neurulation of the chick embryo, explanted after a 25-h in ovo incubation period, is described. Sodium valproate, at concentrations of 0.5-1.5 mM did not appear to have any profound effect on embryo growth when assessed by light microscopy. However scanning electron microscopy revealed a dose-dependent increase in the incidence of open anterior and posterior neuropores after 20 h of in vitro development (Stage 11). Concentrations of sodium valproate which were greater than 1.5 mM markedly increased the number of gross malformations, which were manifested as a complete disruption of the neural tube along its entire length. Failure of neuropore closure could not be attributed to a drug-induced neurodevelopmental delay as these defects were still apparent following 27 h of in vitro culture, a time coincident with the onset of embryo torsion.

Postnatal D2-CAM/N-CAM sialylation state is controlled by a developmentally regulated Golgi sialyltransferase.

Golgi-enriched fractions have been isolated from rat brain of increasing postnatal age and defined by electron microscopy and distribution of marker enzymes. The expression of sialyltransferase activity associated with these fractions has been demonstrated to developmentally decrease and this appeared to be, in part, dependent on endogenous competitive inhibition. The developmental regulation of this activity paralleled the sialylation state of the neural cell adhesion molecule (D2-CAM/N-CAM) and could be demonstrated to be capable of endogenously sialylating this protein in the isolated Golgi fractions. In 12-day-old animals the majority of the transferred [14C]sialic acid was found to be associated with the high-molecular-weight [greater than 200 kilodaltons (kd)] form of D2-CAM/N-CAM, indicative of the protein having been heavily sialylated. Sialylation of the individual D2-CAM/N-CAM polypeptides was also demonstrated in both 12-day and adult animals and transfer was evident only in the 180-kd and 115-kd components and not in the 140-kd component. In contrast, Golgi-enriched fractions prepared from adult animals showed little capability of heavily sialylating D2-CAM/N-CAM to any significant extent.