The avian lung is highly specialized and is both functionally and morphologically distinct from that of their closest extant relatives, the crocodilians. It is highly partitioned, with a unidirectionally ventilated and immobilized gas‐exchanging lung, and functionally decoupled, compliant, poorly vascularized ventilatory air‐sacs. To understand the evolutionary history of the archosaurian respiratory system, it is essential to determine which anatomical characteristics are shared between birds and crocodilians and the role these shared traits play in their respective respiratory biology. To begin to address this larger question, we examined the anatomy of the lung and bronchial tree of 10 American alligators (Alligator mississippiensis) and 11 ostriches (Struthio camelus) across an ontogenetic series using traditional and micro‐computed tomography (µCT), three‐dimensional (3D) digital models, and morphometry. Intraspecific variation and left to right asymmetry were present in certain aspects of the bronchial tree of both taxa but was particularly evident in the cardiac (medial) region of the lungs of alligators and the caudal aspect of the bronchial tree in both species. The cross‐sectional area of the primary bronchus at the level of the major secondary airways and cross‐sectional area of ostia scaled either isometrically or negatively allometrically in alligators and isometrically or positively allometrically in ostriches with respect to body mass. Of 15 lung metrics, five were significantly different between the alligator and ostrich, suggesting that these aspects of the lung are more interspecifically plastic in archosaurs. One metric, the distances between the carina and each of the major secondary airways, had minimal intraspecific or ontogenetic variation in both alligators and ostriches, and thus may be a conserved trait in both taxa. In contrast to previous descriptions, the 3D digital models and CT scan data demonstrate that the pulmonary diverticula pneumatize the axial skeleton of the ostrich directly from the gas‐exchanging pulmonary tissues instead of the air sacs. Global and specific comparisons between the bronchial topography of the alligator and ostrich reveal multiple possible homologies, suggesting that certain structural aspects of the bronchial tree are likely conserved across Archosauria, and may have been present in the ancestral archosaurian lung.

Mechanisms to reduce lameness associated with osteoarthritis (OA) are vital to equine health and performance. This study was designed to quantify response to autologous, intra-articular platelet-rich plasma (PRP) in horses with OA. Kinetic gait analysis was performed on 12 horses with unilateral forelimb lameness and OA in the same limb before and after intra-articular anesthesia (IAA). Radiographs and kinetic data were obtained before and 6 and 16 weeks after PRP administration to same joint, 4 weeks after IAA. Statistical evaluations included filtration effect on platelet concentration, relationship between kinetic variable changes after IAA versus PRP in the affected limb, and associations between response to PRP and response to IAA, platelet concentration, and radiographic OA. A positive response to IAA or PRP was defined as ≥5% improvement in peak vertical force, vertical impulse, or breaking impulse of the affected limb. Out of 10 horses that responded to IAA, 3 responded to PRP at both time points and 4 responded at one. Of the two horses that did not respond to IAA, one responded to PRP at both time points. Filtration increased platelet concentration significantly. The relationship between kinetic variable alterations of the affected limb after IAA and PRP was not significant, and response to PRP was not associated with response to IAA, platelet concentration, or radiographic OA. Changes in kinetic variables following IAA in joints with naturally occurring OA provide a custom standard to assess intra-articular therapy. Kinetic gait changes after intra-articular PRP are variable in horses with moderate to severe forelimb OA.

Background The frontonasal ectodermal zone (FEZ) is a signaling center that regulates patterned development of the upper jaw, and Sonic hedgehog (SHH) mediates FEZ activity. Induction of SHH expression in the FEZ results from SHH‐dependent signals from the brain and neural crest cells. Given the role of miRNAs in modulating gene expression, we investigated the extent to which miRNAs regulate SHH expression and FEZ signaling. Results In the FEZ, the miR‐199 family appears to be regulated by SHH‐dependent signals from the brain; expression of this family increased from HH18 to HH22, and upon activation of SHH signaling in the brain. However, the miR‐199 family is more broadly expressed in the mesenchyme of the frontonasal process and adjacent neuroepithelium. Downregulating the miR‐199 genes expanded SHH expression in the FEZ, resulting in wider faces, while upregulating miR‐199 genes resulted in decreased SHH expression and narrow faces. Hypoxia inducible factor 1 alpha (HIF1A) and mitogen‐activated protein kinase kinase kinase 4 (MAP3K4) appear to be potential targets of miR‐199b. Reduction of MAP3K4 altered beak development but increased apoptosis, while reducing HIF1A reduced expression of SHH in the FEZ and produced malformations independent of apoptosis. Conclusions Our results demonstrate that this miRNA family appears to participate in regulating SHH expression in the FEZ; however, specific molecular mechanisms remain unknown.

Cortical and trabecular bone biopsies can be successfully collected from the tuber coxa using a simple technique that creates minimal morbidity and allows sequential samples to be collected. The biopsies were larger than those described previously, provided adequate bone for multiple histologic sections, and had intact, undamaged architecture on examination with microCT and light microscopy.