Tendon and ligament injuries are common causes of impaired performance in equine athletes. Gray-scale ultrasonography is the current standard method for diagnosing and monitoring these injuries, however this modality only provides morphologic information. Elastography is an ultrasound technique that allows detection and measurement of tissue strain, and may provide valuable mechanical information about equine tendon and ligament injuries. The purpose of this study was to determine the feasibility, reproducibility, and repeatability of elastography; and to describe elastographic characteristics of metacarpal tendons in sound horses. Nineteen legs for 17 clinically sound horses without evidence of musculoskeletal pathology were included. Elastographic images of the superficial and deep digital flexor tendons and the branches of the suspensory ligament (tendon of the interosseous muscle) were described quantitatively and qualitatively. There was no statistically significant difference between operators (P = 0.86) nor within operators (P = 0.93). For qualitative assessments, reproducibility (0.46) was moderate and repeatability (0.78) was good. Similar to human Achilles tendons, equine tendons were classified as predominantly hard using elastography. There was no statistically significant difference in stiffness of the flexor tendons (P = 0.96). No significant difference in stiffness was found with altered leg position during standing (P = 0.84) and while nonweight bearing (P = 0.61). The flexor tendons were softer when imaged in longitudinal versus transverse planes (P < 0.01) however, the suspensory branches were not (P = 0.67). Findings supported future clinical application of elastography as a noninvasive "stall-side" imaging modality for evaluation of the tendons and ligaments of the distal forelimb in horses.

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Experiments with intact plants of Lolium perenne previously grown with "NO3-revealed significant efflux of this isotopic species when the plants were transferred to solutions of highly enriched "NO3-. The exuded "NO3-was subsequently reabsorbed when the ambient solutions were not replaced. When they were frequently replaced, continual efflux of the '4NO3-was observed. Influx of "NOs-was significantly greater than influx of "NO3-from solutions of identical NO3-concentration. (2, 4-6, 8, 13, 14, 21, 25), but evidence for NO3-efflux is quite limited. When wheat seedlings were exposed sequentially to "5NO3-and "NO3-, Ashley (1) failed to recover in the tissue all of the "NO3-previously removed from the solution. His data indicate that about one-fourth of the absorbed 15NO3-may have been lost from the roots during exposure to "NO3-. Net loss of NO3-to ambient solution has been observed when plants previously cultured on NO3-were placed in NO03-free solutions (15,16). These results suggest that continuous NO3-efflux may be a common feature of net NO3-uptake by roots of higher plants.In general, ion efflux studies have focused on the process itself rather than on the possible relationship between concurrent efflux and ion accumulation by plants. The Ca(NO3), was doubled. On the 21st day, the nutrient solutions were removed, the roots were rinsed with a strong jet of distilled water, and then in 10 changes of distilled water. After draining thoroughly, the plants were exposed to solutions containing 0.75 mM CaCNO3). or MgC'NO3). with a "N enrichment of 97.5 atom %. Duplicate containers were harvested after 3, 6, 12, and 18 hr of continuous illumination (238 hlx) at 24 + 1 C. The solutions were analyzed for total NO3-by ultraviolet absorption at 207 nm (3). The quantities of NO,-in the solutions were not sufficiently high to contribute significantly to absorbance, and absence of other ultraviolet-absorbing components was confirmed by spectral scanning. The atom per cent "N of all solutions was determined mass spectrometrically (23) following reduction of NO3-to NH3 using Devarda's alloy. Solution NO2-was measured using equal volumes of 1% sulfanilamide in 3 N HCl and 0.01% N-(1-naphthyl)-ethylenediamine dihydrochloride. Ninhydrin-reactive amino nitrogen (before and after refluxing in 6 N HCl for 16 hr) was determined by the method of Yemm and Cocking (26). Experiment 2. Perennial ryegrass plants were grown essentially as in experiment 1. On the day of the experiment, each culture was mounted in an opaque, 60-ml leaching funnel. A stopcock permitted rapid removal of the continuously aerated solutions (55 ml) as desired. Each of the four treatments consisted of six replications of these single culture assemblies. The experiment was conducted at 70.2 hlx and 23 + 1 C. Prior to imposition of the treatments, all cultures received a pretreatment (initiated 1 hr after onset of the dark period) of 0.75 mm Ca('NO3),, pH 5.0, for 3 hr. These solutions were then replaced with the appropriate treatment solutions after 267...