The Mechanical Consequences of the Interplay of Mineral Distribution and Organic Matrix Orientation in the Claws of the Sea Slater Ligia pallasii

Exposed regions of the arthropod exoskeleton have specialized structure and mineral composition. Their study can provide insights into the evolutionary optimization of the cuticle as a material. We determined the structural and compositional features of claws in the crustacean Ligia pallasii using X-ray micro-computed tomography, scanning electron microscopy (SEM), and analytical scanning transmission electron microscopy (STEM). In addition, we used nanoindentation to determine how these features fine-tune the mechanical properties of the claw cuticle. We found that the inner layer of the claw cuticle—the endocuticle—contains amorphous calcium phosphate, while the outer layer—the exocuticle—is not mineralized and contains elevated amounts of bromine. While the chitin–protein fibers in crustacean exoskeletons generally shift their orientation, they are aligned axially in the claws of L. pallasii. As a consequence, the claw cuticle has larger elastic modulus and hardness in the axial direction. We show that amorphous calcium phosphate mineralization and the brominated cuticle are widespread in isopod crustaceans inhabiting terrestrial habitats. We discuss how the features of the claw cuticle may aid in minimizing the likelihood of fracture. Ultimately, our study points out the features that increase the durability of thin skeletal elements.

Forensic Engineering Analysis of a Commercial Dry Storage Marina Reinforced Concrete Runway Slab

An important element of a commercial marina is the landside site work behind the bulkhead. At many dry storage marinas, boats are launched, retrieved, and handled by large forklifts with axle loads up to 100 tons. In this case, the owner of a commercial marina sued the general contractor, alleging numerous design and construction defects in the reinforced concrete “runway” between the dry storage buildings and the bulkhead. This auger cast pile supported structure served as a relieving platform carrying vertical loads below the depth of the adjacent bulkhead. Some of the observed deficiencies were random cracking, joint damage, excessive edge settlement, and readily visible live load deflections. This paper presents the methods used to investigate the design and construction of this specialized structure. A finite element model (FEM) was used to review the original design intent and help establish the cost to cure. The original design of the runway and pile foundations was found to be inadequate.

Diagnostic imaging of the ciliary body: Technologies, outcomes, and future perspectives

The ciliary body (CB) is part of the uvea and is a complex, highly specialized structure with multiple functions and significant relationships with nearby structures. Its functions include the aqueous humor (AH) production in the ciliary processes, the regulation of the AH output through the uveoscleral pathway, and accommodation, which depends on the ciliary muscle. Also, the CB is an important determinant of angle width as it forms part of the ciliary sulcus. Until recently, knowledge of the CB was based on histological studies. However, this structure can currently be assessed in vivo using imaging techniques such as ultrasound biomicroscopy (UBM) and optical coherence tomography (OCT). Both techniques have shown good reproducibility of their measurements allowing for quantification of CB dimensions and their localization. In effect, studies have shown a larger CB in myopia and its diminishing size with age. Swept-source OCT devices offer fast, non-invasive high-resolution imaging allowing the identification of multiple structures. UBM requires contact and is uncomfortable for the patient. However, this technique offers deeper imaging and therefore remains the gold standard for assessing the posterior chamber, ciliary processes, or zonula. The clinical utility of CB imaging includes its assessment in different types of glaucoma such as angle-closure, malignant or plateau iris. Diagnostic CB imaging is also invaluable for the assessment of ciliochoroidal detachment when suspected, the position after the implantation of a pre-crystalline or sulcus-sutured lenses, diagnosis or monitoring of cysts or tumors, sclerotomies after retinal surgery, intermediate uveitis, or accommodation.

The flying insect thoracic cuticle is heterogenous in structure and in thickness-dependent modulus gradation

The thorax is a specialized structure central to insect flight. In the thorax, flight muscles are surrounded by a thin layer of cuticle. The structure, composition, and material properties of this chitinous structure may influence the efficiency of the thorax in flight. However, these properties, as well as their variation throughout anatomical regions of the thorax or between insect taxa, are not known. In this work, we provide a multi-faceted assessment of thorax cuticle for fliers with asynchronous (honey bee; Apis mellifera) and synchronous (hawkmoth; Manduca sexta) muscles. We investigated cuticle structure using histology, material composition through confocal laser scanning microscopy, and modulus gradation with nanoindentation. Our results suggest that cuticle properties of the thorax are highly dependent on anatomical region and species. Modulus gradation, but not mean modulus, differed between the two types of fliers. In some regions, A. mellifera had a positive linear modulus gradient from cuticle interior to exterior of about 2 GPa. In M. sexta, the modulus gradients were variable and were not well represented by linear fits with respect to cuticle thickness. We utilized finite element modeling to assess how measured modulus gradients influenced maximum stress in cuticle. Stress was reduced when cuticle with a linear gradient was compressed from the high modulus side. These results support the protective role of the A. mellifera thorax cuticle. Our multi-faceted assessment advances our understanding of thorax cuticle structural and material heterogeneity and the potential benefit of material gradation to flying insects.

Reticulocalbin 3 is involved in postnatal tendon development by regulating collagen fibrillogenesis and cellular maturation

Tendon plays a critical role in the joint movement by transmitting force from muscle to bone. This transmission of force is facilitated by its specialized structure, which consists of highly aligned extracellular matrix consisting predominantly of type I collagen. Tenocytes, fibroblast-like tendon cells residing between the parallel collagen fibers, regulate this specialized tendon matrix. Despite the importance of collagen structure and tenocyte function, the biological mechanisms regulating fibrillogenesis and tenocyte maturation are not well understood. Here we examine the function of Reticulocalbin 3 (Rcn3) in collagen fibrillogenesis and tenocyte maturation during postnatal tendon development using a genetic mouse model. Loss of Rcn3 in tendon caused decreased tendon thickness, abnormal tendon cell maturation, and decreased mechanical properties. Interestingly, Rcn3 deficient mice exhibited a smaller collagen fibril distribution and over-hydroxylation in C-telopeptide cross-linking lysine from α1(1) chain. Additionally, the proline 3-hydroxylation sites in type I collagen were also over-hydroxylated in Rcn3 deficient mice. Our data collectively suggest that Rcn3 is a pivotal regulator of collagen fibrillogenesis and tenocyte maturation during postnatal tendon development.

Transcriptome Profiling Reveals Key Genes In Regulation Of The Tepal Trichome Development In Lilium Pumilum D.C.

Trichome is a specialized structure found on the surface of the plant with important function in survival against abiotic and biotic stress. It is also an important economic trait in crop breeding. Extensive research has investigated the foliar trichome in model plants (Arabidopsis and tomato). However, the developmental mechanism of tepal trichome remains elusive. Lilium pumilum is an edible ornamental bulb and a good breeding parent possessing cold and salt-alkali resistance. Here, we found a natural mutant of Lilium pumilum grown on a highland whose tepals are covered by trichomes. Our data indicate that trichomes of this mutant are multicellular and branchless. Notably, stomata are also developed on the tepal of the mutant as well, suggesting there may be a correlated between trichome and stomata regulation. Furthermore, we isolated 27 differentially expressed genes (DEGs) by comparing the transcriptome profiling between the natural mutant and the wild type. These twenty-seven genes belong to four groups: epidermal cell cycle and division, trichome morphogenesis, stress response, and transcription factors. Quantitative real-time PCR in Lilium pumilum (natural mutant and the wild type) and other lily species (Lilium leichtlinii var. maximowiczii/ trichome; Lilium davidii var. willmottiael, trichomeless) confirmed the validation of RNA-seq data and identified several trichome-related genes.

Electron microscopy reveals novel external specialized organs housing bacteria in eagle ray tapeworms

Nutritionally-based mutualisms with bacteria are known to occur in a wide array of invertebrate phyla, although less commonly in the Platyhelminthes. Here we report what appears to be a novel example of this type of association in two geographically disparate and phylogenetically distant species of tapeworms of eagle rays—the lecanicephalidean Elicilacunosus dharmadii off the island of Borneo and the tetraphyllidean Caulobothrium multispelaeum off Senegal. Scanning and transmission electron microscopy revealed that the grooves and apertures on the outer surfaces of both tapeworms open into expansive cavities housing concentrations of bacteria. This led us to reject the original hypothesis that these structures, and their associated mucopolysaccharides, aid in attachment to the host mucosa. The cavities were found to be specialized in-foldings of the tapeworm body that were lined with particularly elongate filitriches. Given tapeworms lack a gut and employ filitriches to assist in nutrient absorption, enhanced nutrient uptake likely occurs in the cavities. Each tapeworm species appeared to host different bacterial monocultures; those in E. dharmadii were coccoid-like in form, while those in C. multispelaeum were bacillus-like. The presence of bacteria in a specialized structure of this nature suggests the structure is a symbiotic organ. Tapeworms are fully capable of obtaining their own nutrients, and thus the bacteria likely serve merely to supplement their diet. Given the bacteria were also extracellular, this structure is more consistent with a mycetome than a trophosome. To our knowledge, this is not only the first evidence of an external symbiotic organ of any type in a nutritionally-based mutualism, but also the first description of a mycetome in a group of invertebrates that lacks a digestive system. The factors that might account for the independent evolution of this unique association in these unrelated tapeworms are unclear—especially given that none of their closest relatives exhibit any evidence of the phenomenon.

Zinc Finger Protein 1 (ZFP1) Is Involved in Trichome Initiation in Arabidopsis thaliana

Arabidopsis trichome is specialized structure that develops from epidermal cells, and is an excellent model system for studying various aspects of plant cell development and cell differentiation. Our previous studies have shown that C2H2 zinc finger protein family genes, including GIS, GIS2, GIS3, ZFP5, ZFP6 and ZFP8, play an important role in controlling trichome initiation in Arabidopsis. Here, our novel results showed a C2H2 zinc finger protein, ZFP1, which also plays an important role in trichome initiation in Arabidopsis. ZFP1 over-expression lines display significantly increased trichome number on cauline leaves, lateral branches and main stems in comparison with wild type plants. ZFP1 RNAi lines and loss-of-function mutants showed the opposite phenotype. Furthermore, our study also found that ZFP1 mediates the regulation of trichome initiation by cytokinin signaling. The molecular and genetic analyses reveal that ZFP1 acts upstream of key trichome initiation factors, GL3 and TRY.

Dynamics of Pollen Activation and the Role of H+-ATPase in Pollen Germination in Blue Spruce (Picea pungens)

Pollen is a highly specialized structure for sexual plant reproduction. Early stages of pollen germination require the transition from dormant state to active metabolism. In particular, an important role during this early phase of angiosperm pollen germination is played by H+-ATPase. Very little is known about pollen activation in gymnosperm species, and information on the involvement of H+-ATPase is lacking. We tracked four indicators characterizing the physiological state of pollen: membrane potential, intracellular pH, anion efflux and oxygen uptake, in order to monitor the dynamics of activation in Picea pungens. Based on pH dynamics during activation, we assumed the important role of H+-ATPase in spruce pollen germination. Indeed, germination was severely suppressed by P-type ATPase inhibitor orthovanadate. In spruce pollen tubes, a pronounced pH gradient with a maximum in the apical zone was found, which was different from the pollen tubes of flowering plants. Using orthovanadate and fusicoccin, we found that the proton pump is largely responsible for maintaining the gradient. Immunolocalization of the enzyme in pollen tubes showed that the distribution of H+-ATPase generally coincides with the shape of the pH gradient: its maximum accumulation is observed in the apical zone.

Identifying ligand-binding specificity of the oligopeptide receptor OppA from Bifidobacterium longum KACC91563 by Structure-based molecular modeling

Background: The OppA receptor as a ATP-binding cassette (ABC) transporter plays key roles in protecting host organism and transport nutrients across the intestine by the oligopeptide transporter from symbiotic bacteria directs maturation of the host immune system. Among lactic acid bacteria, Bifidobacterium longum KACC91563, isolated from fecal samples of healthy Korean neonates, has the capability to alleviate food allergy effects. The extracellular OppA receptor from gram-positive Bifidobacterium longum KACC91563 translocate nutrients-peptides from the outside environment of intestinal tract to the inside of the symbiotic cell, as a peptide importer. Hence, it was attempting to explicate the relationship between the substrate’s specificity from the OppA importer and the probiotic effects of B. logum KACC91563 in the host intestine. The probiotic effects of B. logum KACC91563 were attributed to the enhancement of the epithelial barrier by several different strain sepcific ways to prevent the strong adhesion of pathogens. The specialized structure-function relationship from the OppA importer could provide the abstract of substrate specificity into unique immunological properties of that the host organism.Results: In the study, we characterized the extracellular OppA importer from B. longum KACC91563 of intestinal microbiome by various protein structure-based modelings in silico. Structural characterization by conserved 5 patches and 4 functional motifs from specific trace residues of the OppA importer. The hydrate surface of the binding site had been decipted by specific trace residues of the OppA that trace residues of Thr58, Lys185, Trp443, and Tyr447, which were characterized in highly exposed hydrophobic binding pocket by its aggregation prones. Therefore, the spatial aggregation propensity in the binding site of the extracellular OppA importer plays a vital role in the specific interaction determinant for peptide binding. In addition, alanine mutation energy values allowed for the virtual determination of the relationships between the energy effects of the peptide binding site mutation on the transporter structural stability, the peptide binding affinity, and the transporter-related peptide substrate selectivity from OppA importer. In particular, distinctive seven pharmacophoric features comprised of two H-bonding donor(P1), three H-bonding acceptor(P8), and two hydrophobic points (P5 and P8) matched the the OppA receptor-peptide ligand interactions within their binding pocket structure. There are distinct interactions to fix the positions of the N(P1) and C(P8) termini of the complex of OppA-peptide from B. longum KACC91563 such as side chain-specific interactions with the OppA, compared to that of the Lactococcus latis (L. lactics) OppA.Conclusions: The specialized structure-function relationship from the OppA import could provide the abstract of substrate specificity into unique immunological properties of the host organism by stucutre-based molecular modeling. In the current study, we attempted explication of the relationship between the substrate’s specificity from the OppA importer and the probiotic effects of B. longum KACC91563 in the host intestine based on the structure-function perspectives of the OppA importer. Moreover, functional characterization of solute-binding proteins (such as 15 cell wall proteins and 20 extracellular proteins) on the B. longum KACC91563 genome will lead to insight of key switch for substate’s metabolism into reprogramming immune responses in the host intestine.