Mechanisms of equine recurrent airway obstruction: changes in understanding and management

Recurrent airway obstruction (RAO) is an inflammatory and obstructive disease that is more prevalent in horses stabled for long periods. The most common clinical signs include cough, exercise intolerance, dyspnea, nasal secretion and absence of fever. The pathophysiological effects of RAO in the lungs include goblet cell metaplasia, alveolar fibrosis, neovascularization, airway wall thickening affecting all tissue layers, and bronchial smooth muscle hypertrophy. The alveolar macrophage is the main effector of particle elimination in the inflammatory process of RAO, with the ability to increase or suppress inflammatory responses. Activation of macrophages increases the release of cytokines that enhance the inflammatory reaction, such as interleukin-1, tumor necrosis factor alpha, and interleukin-8, resulting in the attraction of neutrophils to the alveolar environment, which becomes the predominant cell type during periods of crisis. Although the clinical signs of RAO are well-defined, the underlying immunologic mechanisms are still being investigated. This review provides information about this disease, the understanding of which has changedover time.

Structural analysis of biological macromolecular assemblies by scanning transmission electron microscopy

Separation of the resolution and contrast affecting components and the optimized placement of detectors for the collection of elastic (contrast-forming) electrons on Brookhaven dedicated STEM make it possible to quantitatively detect greater than 90% of the available elastically scattered electrons. The high contrast and superior signal-to-noise ratio associated with the STEM annular detector allow for the imaging of unstained freeze-dried biological macromolecular complexes (chromatin, viruses, nucleic acids) at radiation doses as low as 1 e/Å. Specimens prepared in this way are free of the main resolution-limiting conditions of conventional TEM i.e. staining , air drying and radiation damage. The image intensity of unstained specimens can be related to their local projected mass and used for calculation of the total mass and mass distribution within any selected particle. Elimination of staining makes it possible to use heavy metals as high-resolution markers for topographical mapping of components and/or functional sites on a particular macromolecular complex.