Background Aquatic species in several clades possess cement glands producing adhesive secretions of various strengths. In vertebrates, transient adhesive organs have been extensively studied in Xenopus laevis, other anurans, and in several fish species. However, the development of these structures is not fully understood. Results Here, we report on the development and functional morphology of the adhesive gland of a giant danio species, Devario malabaricus. We found that the gland is localized on the larval head, is composed of goblet‐like secretory cells framed by basal, bordering, and intercalated apical epithelial cells, and is innervated by the trigeminal ganglion. The gland allows nonswimming larvae to adhere to various substrates. Its secretory cells differentiate by 12 hours postfertilization and begin to disappear in the second week of life. Exogenous retinoic acid disrupts the gland's patterning. More importantly, the single mature gland emerges from fusion of two differentiated secretory cells fields; this fusion is dependent on nonmuscle myosin II function. Conclusions Taken together, our studies provide the first documentation of the embryonic development, structure, and function of the adhesive apparatus of a danioninae. To our knowledge, this is also the first report of a cement gland arising from convergence of two bilateral fields.

3D and 4D imaging of zebrafish heart can provide significant insights into the structural and dynamic nature of the development and growth of this important biomedical model. Transmission electron microcopy (TEM) and tomography allow high resolution ultrastructural imaging of subcellular structures, adding to our understanding of heart architecture in model organisms. Serial block face scanning electron microscopy (SBFSEM) is a novel approach to nanoscale volumetric imaging of tissues and cells. To test the usefulness of SBFSEM in investigations of structure‐function relationship in zebrafish and giant danio hearts, we acquired over 3000 serial block face scanning electron micrographs at 50 to 100 nm intervals, as well as transmission electron micrographs, of the hearts of these fish. We subsequently extracted anatomical and cellular structures of interest in larval and adult fish by semi‐automated segmentation, and generated 3D visualization of various heart regions. Our results show structural similarity in the integration of the compact and spongy hearts in these two species. Similar to the zebrafish, the adult giant danio possesses transitional cardiac myocytes and a network of cardiac fibroblasts in the junctional region. Ultrastructural analysis also reveals remodeling of the ventricular junctional space during repair and regeneration, as well as the presence of luminal lacunae and persistent intra‐myocardial space as late as 3 weeks post‐fertilization. Taken together, our studies demonstrate SBFSEM as a powerful approach to gather nanoscale volumetric structural data in developing, adult, and regenerating giant danio and zebrafish heartSupport or Funding InformationNIH R15 HD084262‐01This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Cardiovascular diseases remain that number one cause of death in the northern hemisphere and are increasing globally in developing economies. In spite of evolutionary separation between fishes and mammalian, the use of non‐mammalian model species has significantly increased our understanding of cardiac diseases. We have recently described the growth and cardiovascular development of the Devario malabaricus, a giant danio (GD) species closely related to the zebrafish. We hypothesize that the adult GD heart can serve as a robust non‐mammalian model for in vivo studies of cardiac biology. Using immunostaining, transmission electron microscopy, scanning block‐face electron microscopy, and Doppler, we have characterized the anatomical and functional characteristics of the adult GD heart. First, we found that the adult giant danio possesses a thick and highly vascularized compact heart. Second, the GD heart possesses a junctional region populated with a fibroblasts network similar to that observed in zebrafish. Third, multiple large coronary vessels investing the compact myocardium are connected to and continuous with atrioventricular (AV) canal lumen. In addition, the AV canal and bulbus are highly innervated, suggesting complex regulation in heart function. Moreover, we demonstrate that their cardiac function can be measured using Doppler flow velocity. These studies along with previous findings support the GD as a robust model for the study of cardiac biology.Support or Funding Information1R15HD084262‐01, Buehler Family FoundationThis abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

As a result of the COVID-19 pandemic, assisted living group activities and congregate dining stopped and residents were confined to their rooms. While this may have kept residents safer from contracting the virus, it also reduced their physical activity levels. The aim of this study was to investigate if rates of falls in one assisted living community varied as a result of COVID-19 restrictions. We analyzed fall incident reports from n=155 residents from October 2019 to October 2020. Results showed a total of n=802 falls in the year-long period (range of 1-30 falls per resident; mean = 5.17; SD=5.6 in the 12 month period). The majority (65%) of falls occurred in resident rooms. 55% of falls occurred between 6am and 6pm. The primary cause of these falls was loss of balance (30%). Comparing falls that occurred 5 months pre-restriction (Oct 2019-Feb 2020) with 5 months post-restriction (April 2020-August 2021) showed non-significant differences between time periods (p=.59). However, analyzing rates of falls by month showed a range of 46 - 88 falls by month with the lowest number occurring in winter months and the peak number of falls occurring in both Oct 2019 and 2020. Despite the majority of falls occurring in resident rooms, Covid restrictions of room confinement did not appear to impact the prevalence of falls in this sample. However, the seasonal variation warrants further research and those in assisted living should consider seasonal variations and proactively implement policies to prevent falls during these times.

Cement glands are transient ectodermally‐derived adhesive organs found in the larval stage of several aquatic species. We have identified a transient structure on the apical aspect of a giant danio (Devario cf. malabaricus) head, a member of the danioninae subfamily of cyprinids. We hypothesize that this structure is a cement gland (CG), the primary adhesive organ of the giant danio (GD), and that its cellular components support its function. Using a novel adhesion assay, transmission electron microscopy (TEM), scanning electron microscopy (SEM), and serial block face‐scanning electron microscopy (SBF‐SEM), we investigated the function of the CG and the structures of the cells that constitute it. Our studies have shown that the gland produces a glycoconjugates‐containing mucus that allows larvae to attach to surfaces in their environments. The larvae remain attached until day 5 when they begin swimming. Lectin staining and SEM revealed that the CG is composed primarily of goblet and epithelial cells organized in a lattice‐like pattern. These studies also show that the CG disappears by week 2. TEM confirms that the CG consists of elongated goblet cells containing granules of varying electron densities. These cells are framed apically by intercalated epithelial cells, and basally by a layer of squamous epithelium. Finally, we used SBF‐SEM and Amira 6 to reconstruct the three dimensional spatial relationship of these cells. To our knowledge, this is the first functional and ultrastructural study of a CG in a danioninae. Our results suggest that the cement gland is an important organ in GD development.Support or Funding InformationDePauw FDC, SRF, Faculty FellowshipThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.