The Functional Anatomy of the Cornea and Anterior Chamber in Lampreys: Insights From the Pouched Lamprey, Geotria australis (Geotriidae, Agnatha)

Extant lampreys (Petromyzontiformes) are one of two lineages of surviving jawless fishes or agnathans, and are therefore of critical importance to our understanding of vertebrate evolution. Anadromous lampreys undergo a protracted lifecycle, which includes metamorphosis from a larval ammocoete stage to an adult that moves between freshwater and saltwater with exposure to a range of lighting conditions. Previous studies have revealed that photoreception differs radically across the three extant families with the Pouched lamprey Geotria australis possessing a complex retina with the potential for pentachromacy. This study investigates the functional morphology of the cornea and anterior chamber of G. australis, which is specialised compared to its northern hemisphere counterparts. Using light microscopy, scanning and transmission electron microscopy and microcomputed tomography, the cornea is found to be split into a primary spectacle (dermal cornea) and a scleral cornea (continuous with the scleral eyecup), separated by a mucoid layer bounded on each side by a basement membrane. A number of other specialisations are described including mucin-secreting epithelial cells and microholes, four types of stromal sutures for the inhibition of stromal swelling, abundant anastomosing and branching of collagen lamellae, and a scleral endothelium bounded by basement membranes. The structure and function of the cornea including an annular and possibly a pectinate ligament and iris are discussed in the context of the evolution of the eye in vertebrates.

Functional Anatomy of the TDP-43 Redox Sensor

TAR binding protein 43 (TDP-43) is an RNA binding protein that assists in the maturation, export and sub-cellular localization of mRNA. The carboxyl terminal 153 residues of TDP-43 are of low sequence complexity and allow for self-association of the protein in a manner leading to its phase separation from an aqueous environment. These interactions assist TDP-43 in forming cytoplasmic RNA granules involved in the transport of mRNA for localized translation. Self-association of the TDP-43 low complexity (LC) domain is facilitated by a region of twenty five residues that are of extreme evolutionary conservation. The molecular basis for self-adherence of the protein through this region has been illuminated by a combination of structural and biochemical studies, allowing definition of a morphologically specific cross-β structure predicted to be weakly assembled by main chain hydrogen bonds. In this study we have investigated the importance of individual, Pauling hydrogen bonds hypothesized to facilitate self-adherence of the TDP-43 LC domain.

External or subcomissural annuloplasty in bicuspid aortic valve repair: which is better?

Patients with a bicuspid aortic valve (BAV) are at increased risk of valvular regurgitation compared to their counterparts with a tri-leaflet aortic valve. There is now increasing emphasis to offer BAV repair to mitigate the risks of prosthesis-related complications, including thromboembolism, haemorrhage and endocarditis, as well as structural valve deterioration and future re-operation with conventional valve replacement, particularly in younger populations. Furthermore, over the preceding two decades, our greater understanding of the functional anatomy of the BAV, pathophysiological mechanisms of BAV insufficiency and the development of a functional classification of aortic regurgitation have significantly contributed to the evolution of aortic valve reconstructive surgery. In this commentary, we discuss a recent article from the Journal of Cardiac Surgery comparing external annuloplasty and subcommissural annuloplasty as techniques for BAV repair.

Fascicles split or merge every ~560 microns within the human cervical vagus nerve

Vagus nerve stimulation (VNS) is FDA approved for stroke rehabilitation, epilepsy and depression; however, the underlying vagus functional anatomy underlying the implant is poorly understood. We used microCT to quantify fascicular structure and neuroanatomy within human cervical vagus nerves. Fascicles split or merged every ~560 μm (17.8 ± 6.1 events/cm). The high degree of splitting and merging of fascicles in humans may explain the clinical heterogeneity in patient responses.

Biochemical propensity mapping for structural and functional anatomy of importin α IBB domain

Importin α has been described as a nuclear protein transport receptor that enables proteins synthesized in the cytoplasm to translocate into the nucleus. Besides its function in nuclear transport, an increasing number of studies have examined its non-nuclear transport functions. In both nuclear transport and non-nuclear transport, a functional domain called the IBB domain (importin b binding domain) plays a key role in regulating importin α behavior, and is a common interacting domain for multiple binding partners. However, it is not yet fully understood how the IBB domain interacts with multiple binding partners, which leads to the switching of importin α function that determines cell fate. In this study, we have distinguished the location and properties of amino acids important for each function of the importin α IBB domain by mapping the biochemical/physicochemical propensities of evolutionarily conserved amino acids of the IBB domain onto the structure associated with each function. We found important residues that are universally conserved for IBB functions across species and families, in addition to those previously known, as well as residues that are presumed to be responsible for the differences in complex-forming ability between families and for functional switching to control cell fate.

Outsourced hearing in spiders by using their webs as auditory sensors

Hearing is a fundamental sense of many animals, including all mammals, birds, some reptiles, amphibians, fish and arthropods1,2. The auditory organs of these animals are extremely diverse in anatomy after hundreds of millions of years of evolution3-5, yet all are made up of cellular tissue and are embodied meaning that its functional anatomy is constrained by developmental morphogenesis. Here we show hearing in the orb-weaving spider, Larinioides sclopetarius is not constrained by embodiment but is extended through outsourcing hearing to its proteinaceous, self-manufactured orb-web, and hence under behavioral control, not developmental biology. We find the wispy, wheel-shaped orb-web acts as a hyperacute acoustic array to capture the sound-induced air particle movements that approach the maximum physical efficiency, better than the acoustic responsivity of all previously known ears6,7. By manipulating the web threads with its eight vibration-sensitive legs8-10, the spider remotely detects and localizes the source of an incoming airborne acoustic wave emitted by approaching prey or predators. By outsourcing its acoustic sensors to its web, the spider is released from embodied morphogenetic constraints and permits the araneid spider to increase its sound-sensitive surface area enormously, up to 10,000 times greater than the spider itself11. The use of the web also enables a spider the flexibility to functionally adjust and regularly regenerate its 'external ear' according to its needs. This finding opens a new perspective on animal hearing - the 'outsourcing' and 'supersizing' of auditory function in a spider, one of the earliest animals to live on land12. The novel hearing mechanism provides unique features for studying extended and regenerative sensing13-15, and designing novel acoustic flow detectors for precise fluid dynamic measurement and manipulation16-18.