Transgressive gene expression and expression plasticity under thermal stress in a stable hybrid zone.

Interspecific hybridization can lead to myriad outcomes, including transgressive phenotypes in which the hybrids are more fit than either parent species. Such hybrids may display important traits in the context of climate change, able to respond to novel environmental conditions not previously experienced by the parent populations. While this has been evaluated in an agricultural context, the role of transgressive hybrids under changing conditions in the wild remains largely unexplored; this is especially true regarding transgressive gene expression. Using the blue mussel species complex (genus Mytilus) as a model system, we investigated the effects of hybridization on temperature induced gene expression plasticity by comparing expression profiles in parental species and their hybrids following a 2-week thermal challenge. Hybrid expression plasticity was most often like one parent or the other (50%). However, a large fraction of genes (26%) showed transgressive expression plasticity (i.e. the change in gene expression was either greater or lesser than that of both parent species), while only 2% were intermediately plastic in hybrids. Despite their close phylogenetic relationship, there was limited overlap in the differentially expressed genes responding to temperature, indicating interspecific differences in the responses to high temperature in which responses from hybrids are distinct from both parent species. We also identified differentially expressed long non-coding RNAs (lncRNAs), which we suggest may contribute to species-specific differences in thermal tolerance. Our findings provide important insight into the impact of hybridization on gene expression under warming. We propose transgressive hybrids may play an important role in population persistence under future warming conditions.

Surgical resection of a large posttraumatic middle meningeal artery pseudoaneurysm with associated epidural hematoma.

BACKGROUND: Middle meningeal artery (MMA) pseudoaneurysms are rare but can occur secondary to trauma with an associated skull fracture and can present with a variety of hemorrhage patterns. Epidural, subdural, subarachnoid, and intraparenchymal hematomas have all been reported. Given the wide range of clinical presentations and radiographic findings, multiple treatment strategies have been employed, including surgical removal, endovascular intervention, and conservative treatment. MMA pseudoaneurysms typically range from 2 to 5 mm in size and have been shown to have unpredictable growth patterns. CASE DESCRIPTION: A 54-year-old male identifying as a Jehovah's Witness presented after a fall and was found to have an epidural hematoma with an accompanying temporal bone fracture. Imaging demonstrated a traumatic pseudoaneurysm of the MMA. Given the patient's religious preferences, the emphasis was made during surgical planning for the minimization of blood loss. The epidural hematoma was evacuated, and the MMA pseudoaneurysm was directly visualized and surgically excised after ligation of its tributaries. The patient tolerated the procedure well without significant blood loss and made a complete neurological recovery. CONCLUSION: A well-circumscribed hypodensity on CT within a surrounding hyperintense collection should raise suspicion of MMA pseudoaneurysm in the setting of overlying temporal bone fracture as supported by previous imaging findings of large MMA pseudoaneurysms. The early detection of MMA pseudoaneurysm is imperative, as the presence may dictate more urgent intervention and changes in operative technique. Although not much is known about the nature and progression of these lesions, surgical excision has remained a safe, reliable method of treatment.

Mechanical properties of infant bone.

Although an understanding of bone material properties is crucial for interpreting and predicting fracture patterns due to injury or defining the effects of disease on bone strength, information about infant bone properties is scant in the literature. In this study we present the mechanical testing results from 47 tibia and 52 rib specimens taken from 53 infant decedents in order to further our understanding of infant bone strength. Bone specimens were imaged using microCT and tested in three-point bending until failure. Extrinsic and intrinsic properties demonstrated an increase in strength and stiffness over the first year of life, while ductility measures remained largely unchanged. Donor race had no effect on the material properties, but tibia bone specimens showed significant sex differences, with the elastic modulus from females being larger than males. When compared to properties from adolescent and adult donors, infant bone is less strong, less stiff, and more ductile.

WGA-Alexa Conjugates for Axonal Tracing.

Anatomical labeling approaches are essential for understanding brain organization. Among these approaches are various methods of performing tract tracing. However, a major hurdle to overcome when marking neurons in vivo is visibility. Poor visibility makes it challenging to image a desired neuronal pathway so that it can be easily differentiated from a closely neighboring pathway. As a result, it becomes impossible to analyze individual projections or their connections. The tracer that is chosen for a given purpose has a major influence on the quality of the tracing. Here, we describe the wheat germ agglutinin (WGA) tracer conjugated to Alexa fluorophores for reliable high-resolution tracing of central nervous system projections. Using the mouse cerebellum as a model system, we implement WGA-Alexa tracing for marking and mapping neural circuits that control motor function. We also show its utility for marking localized regions of the cerebellum after performing single-unit extracellular recordings in vivo. © 2017 by John Wiley & Sons, Inc.