Enhancing prosthesis stability at the cricoid cartilage in equine laryngoplasty using 3-D-printed laryngeal clamps: An ex vivo model study.

OBJECTIVE: To assess a three-dimensional (3-D)-printed laryngeal clamp (LC) designed to enhance the anchoring of laryngeal prostheses at the cricoid cartilage. STUDY DESIGN: Ex vivo biomechanical study. SAMPLE POPULATION: A total of 22 equine larynges. METHODS: Two experimental groups included larynges with standard prosthetic laryngoplasty (PL; n = 10) and larynges with prosthetic laryngoplasty modified with laryngeal clamps (PLLC; n = 10). All constructs underwent 3000 cycles of tension loading and a single tension to failure. Recorded biomechanical parameters included maximum load, actuator displacement, and construct failure. Finite element analysis (FEA) was performed on one PL and one PLLC construct. RESULTS: The maximum load at single tension to failure was 183.7 ± 46.8 N for the PL construct and 292.7 ± 82.3 N for the PLLC construct (p = .003). Actuator displacement at 30 N was 1.7 ± 0.5 mm and 2.7 ± 0.7 mm for the PL and PLLC constructs, respectively (p = .011). The cause of PL constructs failure was mostly tearing through the cartilage whereas the PLLC constructs failed through fracture of the cricoid cartilage (p = .000). FEA revealed an 11-fold reduction in the maximum equivalent plastic strain, a four-fold reduction in maximum compressive stress, and a two-fold increase in the volume of engaged cartilage in PLLC constructs. CONCLUSION: The PLLC constructs demonstrated superior performance in biomechanical testing and FEA compared to standard PL constructs. CLINICAL SIGNIFICANCE: The use of 3-D-printed laryngeal clamps may enhance the outcomes of laryngoplasty in horses. In vivo studies are necessary to determine the feasibility of performing laryngoplasty using the laryngeal clamp in horses.

Diagnostic Pathology of Equine Toxicoses.

This article is intended to highlight toxicosis-associated pathology in horses that might be observed by a clinician in the living animal and at gross necropsy. When the clinician is aware of these pathologic changes (particularly when coupled with a suggestive environmental or herd history), then collaboration with a diagnostic laboratory can begin to help identify specific toxicants. Proper sampling and communication with the diagnostic laboratory will vastly improve the likelihood of a specific diagnosis; postmortem sampling and specimen submission are reviewed in the last section of this article.

Ex-vivo Mechanical Testing of Novel Laryngeal Clamps Used for Laryngeal Advancement Constructs.

Rostral laryngeal advancement, also known as laryngeal tie-forward, is used to treat horses for intermittent dorsal displacement of the soft palate and has a morbidity rate of about 6%. We hypothesized that a novel laryngeal clamp would prevent morbidity associated with the sutures tearing through the thyroid cartilage. Larynges (n = 35 horses) were used for ex vivo testing. For uniaxial testing, 15 equine larynges were tested in one of three laryngeal tie-forward constructs [standard laryngeal tie-forward; modified laryngeal tie-forward using a suture-button; and modified laryngeal tie-forward using a laryngeal clamp]. For biaxial testing, 20 larynges were tested in one of two treatment groups: laryngeal tie-forward and laryngeal tie-forward using a laryngeal clamp. Constructs were tested in single cycle-to-failure. Statistical analyses were performed using ANOVA for uniaxial testing and t-tests for biaxial testing. The laryngeal tie-forward using a laryngeal clamp construct was superior to laryngeal tie-forward and laryngeal tie-forward using a suture-button constructs in resistance to pullout in uniaxial testing. The laryngeal tie-forward using a laryngeal clamp presented a significantly different method of failure than the standard laryngeal tie-forward in the biaxial testing. Failure modes for each construct were primarily by suture failure at the clamp (laryngeal tie-forward using a laryngeal clamp), suture pullout through the thyroid cartilage, or, less commonly, tearing of the cricothyroid ligament (laryngeal tie-forward). In uniaxial testing, the laryngeal tie-forward using a laryngeal clamp failed most commonly due to tearing of the cricothyroid ligament, whereas the standard laryngeal tie-forward and the laryngeal tie-forward using a suture-button failed due to the tearing of the cartilage. The laryngeal clamps provided greater stiffness, load at yield, and tensile stress at yield than did the standard construct. Laryngeal clamps may offer an alternative to standard methods of anchoring the thyroid cartilage when performing the laryngeal tie-forward procedure. Further testing and clinical trials are needed to elucidate the utility of the laryngeal tie-forward using a laryngeal clamp.

Changes in Detected Anticoagulant Rodenticide Exposure in Barn Owls ( Tyto alba) in Kentucky, USA, in 2012-16.

Anticoagulant rodenticides (ARs) are widely used across North America to control rodent infestations but may cause direct mortality or nonlethal effects when secondarily consumed by raptors. Barn Owls ( Tyto alba) are at high risk for secondary consumption because they specialize in rodent prey and often live in human-made structures. We investigated the exposure of Barn Owls in Kentucky, US, to ARs and to dicoumarol, an anticoagulant compound naturally found in certain moldy forages. We tested the liver tissue of 48 Barn Owl carcasses collected during 2012-16. We confirmed exposure to one or more ARs in 33% of the birds examined and detected dicoumarol in 13% of the samples. Rodenticides detected included brodifacoum, coumachlor, and bromadiolone. The prevalence of detected exposure to brodifacoum for after-hatch-year birds (65%) was significantly ( P=0.012) higher than hatch-year birds (22%). Brodifacoum was the most commonly detected AR, found in 88% of AR-positive birds. The pesticide registration for this chemical in the US was canceled in 2015 for general consumer products, which likely resulted in a decreasing rate of detected exposure to brodifacoum during our study. We present these results as an example of secondary exposure rates during a period when a pesticide has been restricted and then removed from the consumer market.

Evaluating the role of tumor necrosis factor-alpha in experimental pulmonary tuberculosis in the guinea pig.

Tumor necrosis factor-alpha (TNF-alpha) is suggested to play multiple roles in immune and pathologic responses in tuberculosis. In this study, we have developed a system for the expression of recombinant guinea pig TNF-alpha (rgpTNF-alpha). Using rgpTNF-alpha along with neutralizing anti-rgpTNF-alpha antiserum, we tested the effect of modulating the levels of TNF-alpha on antigen-specific T cell proliferation in splenocytes. By neutralizing TNF-alpha in the supernatant of PPD-pulsed splenocytes with anti-rgpTNF-alpha, we observed hyperproliferation. Conversely, the addition of rgpTNF-alpha resulted in a significant suppression of PPD-induced lymphoproliferation. In addition, when unvaccinated and BCG-vaccinated guinea pigs were treated with polyclonal rgpTNF-alpha antiserum throughout the first 3 weeks following low-dose, pulmonary infection with Mycobacterium tuberculosis H37Rv, we observed splenomegaly in BCG-vaccinated guinea pigs. We also detected higher levels of splenic granuloma organization in the non-vaccinated group as well as a significant number of plasma cells associated with granulomata from the BCG-vaccinated group. These results suggest that modulating the availability of TNF-alpha in BCG-vaccinated guinea pigs can lead to immuno-dysregulation and, perhaps, the inappropriate enhancement of humoral immunity. Conversely, abrogating TNF-alpha activity in the context of a hyperinflammatory response in non-vaccinated guinea pigs may, in fact, rescue them from immunopathological consequences of overproducing TNF-alpha.

Effect of neutralizing transforming growth factor beta1 on the immune response against Mycobacterium tuberculosis in guinea pigs.

Transforming growth factor beta (TGF-beta) is a cytokine which has been shown to suppress the antimycobacterial immune responses of humans and experimental animals. In this study, the contributions of TGF-beta to cytokine production in vivo were investigated by using the established guinea pig model of tuberculous pleurisy. Mycobacterium bovis BCG-vaccinated guinea pigs were injected intrapleurally with heat-killed virulent Mycobacterium tuberculosis. Eight days following induction of an antigen-specific pleural effusion, guinea pigs were injected intrapleurally with anti-TGF-beta1 or isotype control antibody. The following day, pleural exudates were removed, and the fluid volume and characteristics of the infiltrating cells were determined. Pleural fluid was analyzed for total interferon (IFN) and tumor necrosis factor (TNF) protein levels by using appropriate bioassays. RNA from pleural effusion cells was examined to determine TGF-beta1, TNF-alpha, IFN-gamma, and interleukin-8 mRNA levels by using real-time PCR. Proliferative responses of pleural effusion lymphocytes were examined in response to concanavalin A and purified protein derivative (PPD) in vitro. Treatment with anti-TGF-beta1 resulted in decreased pleural fluid volume and decreased cell numbers in the pleural space along with an increased percentage of lymphocytes and a decreased percentage of neutrophils. The bioactive TNF protein levels in pleural fluid were increased in guinea pigs treated with anti-TGF-beta1, while the bioactive IFN protein concentrations were not altered. Expression of TGF-beta1 and TNF-alpha mRNA was significantly increased following TGF-beta1 neutralization. Finally, PPD-induced proliferative responses of pleural cells from anti-TGF-beta1-treated animals were significantly enhanced. Thus, TGF-beta1 may be involved in the resolution of this local, mycobacterial antigen-specific inflammatory response.

Effect of Mycobacterium bovis BCG vaccination on Mycobacterium-specific cellular proliferation and tumor necrosis factor alpha production from distinct guinea pig leukocyte populations.

In this study, we focused on three leukocyte-rich guinea pig cell populations, bronchoalveolar lavage (BAL) cells, resident peritoneal cells (PC), and splenocytes (SPC). BAL cells, SPC, and PC were stimulated either with live attenuated Mycobacterium tuberculosis H37Ra or with live or heat-killed virulent M. tuberculosis H37Rv (multiplicity of infection of 1:100). Each cell population was determined to proliferate in response to heat-killed virulent H37Rv, whereas no measurable proliferative response could be detected upon stimulation with live mycobacteria. Additionally, this proliferative capacity (in SPC and PC populations) was significantly enhanced upon prior vaccination with Mycobacterium bovis BCG. Accordingly, in a parallel set of experiments we found a strong positive correlation between production of antigen-specific bioactive tumor necrosis factor alpha (TNF-alpha) and prior vaccination with BCG. A nonspecific stimulus, lipopolysaccharide, failed to induce this effect on BAL cells, SPC, and PC. These results showed that production of bioactive TNF-alpha from mycobacterium-stimulated guinea pig cell cultures positively correlates with the vaccination status of the host and with the virulence of the mycobacterial strain.

Rapid accumulation of eosinophils in lung lesions in guinea pigs infected with Mycobacterium tuberculosis.

Guinea pig eosinophils were positively identified in bronchoalveolar lavage populations and in the lung granulomas of Mycobacterium tuberculosis-infected guinea pigs. It is possible that the rapid influx of these cells, and their subsequent degranulation during acute pulmonary tuberculosis, may play a key role in the susceptibility of this animal model.