Epicuticle Research Articles

Root Penetration Is Associated with Root Diameter and Root Growth Rate in Tropical Forage Grasses

Soil compaction impedes root exploration by plants, which limits access to nutrients and water, ultimately compromising survival. The capability of roots to penetrate hard soils is therefore advantageous. While root penetration has been studied in various annual crops, the relationships between root growth and root penetration are poorly understood in tropical perennial grasses. This study aimed to compare root penetration capability in 10 tropical perennial forage grasses and identify relationships between root penetration, root diameter and vertical root growth. Root penetration of each species, namely Urochloa (syn. Brachiaria) brizantha cv. Mekong Briz, U. decumbens cv. Basilisk, U. humidicola cv. Tully, U. hybrid cv. Mulato II, U. mosambicensis cv. Nixon, U. ruziziensis cv Kennedy, Panicum coloratum cv. Makarikariense, Megathyrsus maximus (syn. Panicum maximum) cv. Tanzânia, Paspalum scrobiculatum (syn. Paspalum coloratum) cv. BA96 10 and Setaria sphacelata cv Solendar, was evaluated using wax layers of varying resistances, created from a mixture of 40% (1.39 MPa) and 60% (2.12 MPa) paraffin wax, combined with petroleum jelly. Reference root sizes were determined for the grass species by measuring root diameter and root lengths of seedlings grown in growth pouches. Vertical root growth rate for each species was measured in grasses grown in 120 cm deep rhizotrons. Species with greater root penetration at both resistances had significantly higher shoot growth rates (r = 0.65 at 40% wax and 0.66 at 60% wax) and greater root diameters (r = 0.67 at 40% wax and 0.68 at 60% wax). Root penetration was significantly higher in species with greater vertical root growth rate only in the 60% wax treatment (r = 0.82). Root penetration at higher resistance was correlated with the root diameter and rapid vertical root growth of the species. This may indicate a contribution of these traits to root penetration ability. The combination of greater root diameter and root vertical growth rate, as observed in M. maximus, may assist in the identification of perennial forage grasses suitable for agroecosystems challenged by soil compaction and rapidly drying soil surface.

The Aedes aegypti mosquito evolves two types of prophenoloxidases with diversified functions

Insect phenoloxidase, presented as an inactive precursor prophenoloxidase (PPO) in hemolymph, catalyzes melanin formation, which is involved in wound healing, pathogen killing, reversible oxygen collection during insect respiration, and cuticle and eggshell formation. Mosquitoes possess 9 to 16 PPO members across different genera, a number that is more than that found in other dipteran insects. However, the reasons for the redundancy of these PPOs and whether they have distinct biochemical properties and physiological functions remain unclear. Phylogenetic analysis confirmed that Aedes aegypti PPO6 (Aea-PPO6) is an ortholog to PPOs in other insect species, classified as the classical insect type, while other Aea-PPOs are unique to Diptera, herein referred to as the dipteran type here. We characterized two Aea-PPO members, Aea-PPO6, the classical insect type, and Aea-PPO10, a dipteran type, which exhibit distinct substrate specificities. By resolving Aea-PPO6's crystal structure and creating a chimera protein (Aea-PPO6-cm) with Motif 1 (217GDGPDSVVR225) from Aea-PPO10, we identified the motif that determines PPO substrate specificity. In vivo, loss of Aea-PPO6 led to larval lethality, while Aea-PPO10 was involved in development, pigmentation, and immunity. Our results enhance the understanding of the functional diversification of mosquito PPOs.

Terrestrial insect defences in the face of metal toxicity.

Recently, there has been growing concern about the impacts of metal pollutants on insect populations, particularly as human societies increasingly rely on metal-based technologies. Unlike organic pollutants, metals - both essential and non-essential - are non-degradable and readily accumulate in insect tissues, sometimes reaching hazardous levels. While numerous studies address how insects cope with pesticide pollution, there is a notable scarcity of knowledge regarding their abilities to confront metal pollution. This paper reviews the routes of entry for metals into insect cells and the molecular damages they trigger. Additionally, it examines the defence mechanisms insects may employ to counteract metal pollution. Firstly, insects may detect and avoid metals in their environment, thereby escaping contaminated food, substrates, and oviposition sites. Secondly, the insect cuticle and gut lining, including the gut microbiota, may serve as physical barriers preventing metal entry into the hemolymph, thereby protecting other organs. Thirdly, insect cells may detoxify metals by sequestering them in metal-scavenging proteins (e.g., metallothioneins) and excreting them via faeces or the cuticle. Fourthly, when metal-related damage occurs, including oxidative stress, protein unfolding, and DNA deformation, insect cells may respond by upregulating antioxidant molecules, chaperone proteins, and DNA repair mechanisms. Enhancing our knowledge of insect-metal interactions sounds crucial for the conservation of insect populations in an increasingly metal-dependent world.

Study results of the stress-strain states of the crown parts of molars restored with composite, ceramic and zirconium onlays

The relevance of the research is determined by the significant need for effective restorative treatment of caries decayed teeth. The purpose of the study is comparison of the stress-strain states in simulated models of non-homogeneous composite structural elements for typical geometric characteristics of onlays made of composite, ceramic, and zirconium dioxide in the restoration of the decayed mandibular molar. Computer simulation models of biomechanical systems were obtained by digital scanning of the mandibular molar in STEP format. Control was carried out in the form of numerical characteristics and graphical visualization in the EXOCAD program. The numerical method of finite elements, information technologies and program codes of the ANSYS Workbench 12.1 system were used to solve applied problems of biomechanics. After testing the developed discrete models, they were checked for adequacy and coincidence of numerical results in areas of high voltage gradients using the tools and methods of the ANSYS 12.1 code system. The maximum displacements, gradients, and amplitudes of the Mises-equivalent stress in the structural elements of each biomechanical system were evaluated. The stress values were calculated using the method of linear scaling of the results of the numerical solution of the boundary value problems of the theory of elasticity for small deformations to correspond to the functional force load of the mandibular molar of 100 N. The estimated values of the coefficients of the strength reserve of the structural elements were calculated as the ratio of the strength limit values to the maximum calculated values of the Mises-equivalent stress, scaled by a coefficient of 10 for a force load of 100 N. It was established that the largest voltage gradients are registered at the border of the cement layer. However, the nature of force transmission, as well as stress distribution, was different for different structural materials. The maximum stress was observed in the model with a composite onlay in the local area of the surface of the force load in the cement layer. For the ceramic onlay, the maximum stress was found on the lower support surface of contact with the onlay, where its values were 1.4 times higher than on other surfaces. The analysis of the zones of maximum stress for the zirconium onlay revealed their predominant localization in the center of its occlusal surface and in the zone of change in its spatial configuration at the border with cement. The highest stress values, along with the lowest coefficients of safety margin, were found for the molar model restored with a composite onlay, which indicated the lowest endurance of this material to functional load. While the zirconium onlay provided optimal stress distribution and it was characterized by the largest safety factor, which makes this method the most acceptable for molar restoration. The obtained results should be taken into account when choosing a material for the prosthetics of lateral teeth with onlays.

Impact of saline irrigation on the early mechanical characteristics and microstructure of bone cement

Very high heat is generated during the polymerization of poly (methyl methacrylate) (PMMA) bone cement, which is used for implant fixation in orthopedic surgery. As such, it has been suggested that irrigating the bone cement layer in the surgical site with a saline solution is a way of cooling the layer. In this study, we aimed to determine the influence of irrigation with a saline solution on the flexural strength and the microstructure of the test specimens of two PMMA bone cement brands: Simplex P and FIX 1. Specimens were assigned to three groups: (1) irrigation with normal saline solution at 25 °C (RS group), (2) irrigation with cold saline at 4 °C (CS group), and (3) no irrigation (control group). For each of the groups, the specimens were tested after various times of aging in phosphate-buffered saline solution (PBS) at 37 °C for 1 h, 24 h, and 7 days. Flexural strength was measured following ISO 5833 protocol, and the surface microstructure was determined using scanning electron microscopy (SEM). The flexural strength results showed that for each of the cement brands, the difference between the groups was not significant, except for Simplex P specimens aged for 24 h, for which flexural strength of the RS and CS group specimens was lower than in the control group. The microstructural features of the surface of the specimens were similar across groups. These findings suggest that in a cemented arthroplasty, irrigation of the bone cement for the purpose of cooling it must only be used after very careful consideration.

Esterified Lignin Nanoparticles for Targeted Chemical Delivery in Plant Protection.

There is a growing demand for biobased functional materials that can ensure targeted pesticide delivery and minimize active ingredient loss in the agricultural sector. In this work, we demonstrated the use of esterified lignin nanoparticles (ELNPs) as carriers and controlled-release agents of hydrophobic compounds. Curcumin was selected as a hydrophobic model compound and was incorporated during ELNP fabrication with entrapment efficiencies exceeding 95%. ELNPs presented a sustained release of curcumin over 60 days in an oil medium, with a tunable release rate dependent on the lignin-to-curcumin mass ratio. The ELNPs showed a strong adhesion interaction with the hydrophobic wax surface. Quartz crystal microbalance with dissipation monitoring (QCM-D) and atomic force microscopy (AFM) analysis suggested that the ELNPs permeated into the wax layer, potentially preventing pesticide loss due to runoff or rainwater leaching. Rapidly decreasing contact angles between a droplet containing an aqueous dispersion of the ELNPs and a fresh leaf surface provided further evidence of a favorable interaction between the two. Overall, our results portray ELNPs as promising biobased nanoparticulate systems for pesticide delivery to hydrophobic plant surfaces.

New Composite Packaging Material from Edible Oil By-Product Coated with Paraffin Wax for Dry Apricot Slice Packing Under a Modified Atmosphere.

Composite biopolymer hydrogel as food packaging material, apart from being environmentally favorable, faces high standards set upon food packaging materials. The feature that favors biopolymer film application is their low gas permeability under room conditions and lower relative humidity conditions. However, most biopolymer-based materials show high moisture sensitiveness and limited water vapor permeability, which limits their application for food packaging. In this paper, a new packaging material derived from an edible oil industry byproduct (pumpkin oil cake) coated with a thin layer of paraffin wax was obtained. Compared to the film without wax coating, the new material showed reduced water sensitivity and significantly reduced water vapor transmission rate (56.98 ± 7.42 g/m2 24 h). The new material was tested for packing dry apricot slices under a modified atmosphere (100% N2). Gas composition in PuOC/wax pouches' headspace was minimally changed during 105 days of storage. The low moisture content (6.76-10.60%) of dried apricot slices was preserved throughout the storage period (p > 0.05), as well as high rehydration power (65-75%). Changes in sensorial properties during storage were minimal. Total phenol content was minimally reduced during storage, followed by antioxidant activity (FRAP and ABTS trial). The microbial profile of dried apricot slices showed that a safe product was obtained throughout the storage. Considering the results, the functionality of new material for packing dry apricots under a modified atmosphere was proven.

Metarhizium acridum transcription factor MaFTF1 negatively regulates virulence of the entomopathogenic fungus by controlling cuticle penetration of locusts.

The entomopathogenic fungus (EPF) Metarhizium acridum, a typical filamentous fungus, has been utilized for the biological control of migratory locusts (Locusta migratoria manilensis). Fungal-specific transcription factors (TFs) play a crucial role in governing various cellular processes in fungi, although TFs with only the Fungal_trans domain remain poorly understood. In this study, we identified a unique fungal-specific TF in M. acridum, named MaFTF1, which contains only a Fungal_trans domain and functions as a negative regulator of M. acridum virulence by influencing cuticle penetration. The virulence of the MaFTF1 knockout strain (ΔMaFTF1) against L. migratoria was increased, with a median lethal time (LT50) ~0.91 days shorter than that of the wild-type (WT) strain when inoculated topically, mimicking natural infection conditions. Correspondingly, ΔMaFTF1 penetrated the cuticle earlier than did the WT strain. Our investigation revealed that the development of appressoria was accelerated in ΔMaFTF1 compared with the WT strain. Furthermore, the appressoria of the ΔMaFTF1 displayed higher turgor pressure and an upregulated expression of fungal hydrolases active toward the insect cuticle. RNA sequencing analysis indicated that the differences in appressorium behavior between the strains were due to MaFTF1 regulating a complex metabolism pathway. This study revealed that MaFTF1 acts as a negative regulator of virulence, impacting the process of cuticle penetration by slowing the formation of appressoria, decreasing their turgor pressure, and reducing the expression of hydrolases in appressoria, revealing an unexpected strategy in the EPFs. © 2024 Society of Chemical Industry.

Assessment of Stress Distribution Around Traditional and Sleeve Fixed Partial Denture Designs: Finite Element Analysis.

The aim of this research is to evaluate/compare the use of traditional versus sleeve fixed partial denture (PD) designs made from different materials on supporting structures. The comparison included three- and four-unit PD cases. Four finite element models are used in the research. The three-unit PD consists of the mandibular second premolar, first molar (as a pontic), and second molar. The four-unit PD includes the first premolar. The PD materials assessed were zirconia, E-max, and Celtra Duo. Bone has been simplified representing it as two cuboids. Each PD has been loaded to two cases over the pontic's central fossa: 300 N compressive, 150 N obliquely applied with 45 degrees forming 24 cases. The three-unit traditional and sleeve PDs material change showed a slight change in cortical bone stress under vertical loading. Under oblique loading, cortical bone Von Mises stresses were higher by about 12 to 15% more than vertical loading. On the other hand, the four-unit PDs showed minor effect by changing PD material, while using sleeve design PD can reduce the cortical bone stresses up to 20% in comparison to traditional PD design. The mucosa and spongy bone were negligibly affected by changing PD material, and the traditional and sleeve designs showed close values to each other. Superiority of sleeve design appeared by reducing cement layer stresses dramatically, while PD body material rigidity affects its response. Within the limitations of this study, the higher rigid PD material can dissipate loadings over it more preferably regarding its effect on the underlying structures. Sleeve PD design is equivalent to the traditional one for three-unit PDs, while it showed better performance with four-unit PDs. Zirconia three-unit PDs' bodies received the lowest stresses and redistributed and transferred the applied load to the underneath structures better than the other two tested materials. This finding was reversed with four-unit PDs.

Grain and Domain Microstructure in Long Chain N-Alkane and N-Alkanol Wax Crystals.

Waxes comprise a diverse set of materials from lubricants and coatings to biological materials such as the intracuticular wax layers on plant leaves that restrict water loss to inhibit dehydration. Despite the often mixed hydrocarbon chain lengths and functional groups within waxes, they show a propensity for ordering into crystalline phases, albeit with a wealth of solid solution behavior and disorder modes that determine chemical transport and mechanical properties. Here, we reveal the microscopic structure and heterogeneity of replica leaf wax models based on the dominant wax types in the Schefflera elegantissima plant, namely C31H64 and C30H61OH and their binary mixtures. We observe defined grain microstructure in C31H64 crystals and nanoscale domains of chain-ordered lamellae within these grains. Moreover, nematic phases and dynamical disorder coexist with the domains of ordered lamellae. C30H61OH exhibits more disordered chain packing with no grain structure or lamellar domains. Binary mixtures from 0-50% C30H61OH exhibit a loss of grain structure with increasing alcohol content accompanied by increasingly nematic rather than lamellar chain packing, suggesting a partial but limited solid solution behavior. Together, these results unveil the previously unseen microstructural features governing flexibility and permeability in leaf waxes and outline an approach to microstructure analysis across agrochemicals, pharmaceuticals, and food.

Chlorbenzuron downregulated HcLCP-17 expression by depressing two 20E-responsive transcription factors Br-C and βFTZ-F1 in Hyphantria cunea (Lepidoptera: Erebidae) larvae.

Cuticular proteins (CPs) play essential roles in forming cuticular structures in insects. However, the specific functions and regulatory mechanisms of CPs remain largely unexplored. In this study, the Larval cuticular protein 17 (HcLCP-17) gene was identified from Hyphantria cunea, a highly destructive and polyphagous forest pest. To investigate the role of HcLCP-17 in cuticular function and transcriptional regulation mediated by 20E-responsive transcription factors (ERTFs), we employed RNA interference (RNAi) and yeast one-hybrid assay techniques. Additionally, we examined the molecular mechanism by which chlorbenzuron, a type of benzoylphenylurea (BPU) that functions as a chitin synthesis inhibitor (CSI), affects the 20E signaling pathway and ultimately regulates HcLCP-17 expression. HcLCP-17 encodes a polypeptide consisting of 393 amino acids, which includes a chitin-binding domain. Silencing HcLCP-17 resulted in a disturbance in the structural organization of the larval cuticle and a notable reduction in chitin levels. HcLCP-17 expression was controlled by the interaction between Broad-Complex (Br-C)and beta Fushi Tarazu Factor-1 (βFTZ-F1) with its promoter fragment. Furthermore, the inhibitory effect of chlorbenzuron on HcLCP-17 expression was found to be potentially mediated by Br-C and βFTZ-F1. The study presents a novel mode of action for the 20E signaling pathway in regulating the expression of CPs and reveals the potential mode-of-action of BPUs in insect cuticles. These findings provide a theoretical basis for future utilization of LCP-17 as a pesticide target making a significant contribution to the development of effective pest management strategies. © 2024 Society of Chemical Industry.

Evaluation of polyaryletherketone materials as post-core abutments for removable partial dentures: A finite element analysis

ObjectiveThe purpose was to compare the biomechanical behavior of single-piece post-core restorations made from polyaryletherketone materials with fiber post-core restorations when serving as abutments for RPD using finite element analysis (FEA). MethodsPhantom maxillary central incisor and mandibular second premolar were trimmed 1-mm coronally to cemento-enamel junction; root canals were enlarged and the teeth were scanned. Data was transferred to a solid modeling software.Twenty four models, including six post-core restorations:glass-fiber post/composite core (GFH/GFL) and single-piece post-core groups as, PEKK(PKH/PKL);Ti02-reinforced PEEK(TH/TL);ceramic reinforced PEEK(CeH/CeL);carbon fiber reinforced PEEK(CaH/CaL);glass fiber reinforced PEEK(GFPH/GFPL) with hybrid ceramic/lithium disilicate crowns on each tooth were constructed.Loads of 100 N for central incisor, and 300 N for premolar in a 45°oblique direction were applied to simulate masticatory forces. Clasp removal force of a RPD was simulated as 5 N vertically.FEA was employed to evaluate the von Mises stresses.Strain at cement layer was also investigated. ResultsCaH/CaL groups revealed the lowest stress for both teeth at root while TH/TL groups revealed the highest stress. The lowest stress values in the post-core were in GFH/GFL groups while the highest stress occurred in the CaH/CaL groups for both teeth. SignificanceGlass-fiber post-cores exhibited the lowest stresses in the post under masticatory and clasp removal forces. It may suggest a potentially lower risk of post fracture compared to polyaryletherketone group materials. TiO2-reinforced PEEK post-cores exhibited the lowest stresses among PAEK materials, indicating a potentially high fracture resistance.

On the hygrothermal environment of spaces with exposed walls – thermal bridging effect of mortar layers of cement and lime

On the hygrothermal environment of spaces with exposed walls – thermal bridging effect of mortar layers of cement and lime

Characterization of an RR-2 cuticle protein DcCP8 and its potential application based on SPc nanoparticle-wrapped dsRNA in Diaphorina citri.

The insect cuticle consists of chitin fibers and a protein matrix, which plays an important role in protecting the body from invasion of various pathogens and prevents water loss. Periodic synthesis and degradation of the cuticle is required for the growth and development of insects. Key genes involved in cuticle formation have long been considered a potential target for pest control. In this study, a member of the RR-2 subfamily of cuticular protein 8 (DcCP8) was identified from the Diaphorina citri genome database. Immunofluorescence analysis suggested that DcCP8 was mainly located in the Diaphorina citri exocuticle and can be induced to up-regulate 12 h following 20-hydroxyecdysone (20E) treatment. Silencing of DcCP8 by RNA interference (RNAi) significantly disrupted the metamorphosis to the adult stage, and improved the permeability of the cuticle. Transmission electron microscopy (TEM) analysis revealed that the synthesis of the exocuticle was impressed after silencing of DcCP8. Furthermore, the recombinant DcCP8 protein exhibited chitin-binding properties in vitro, down-regulation of DcCP8 significantly inhibited expression levels of chitin metabolism-related genes. Additionally, a sprayable RNAi method targeting DcCP8 based on star polycation (SPc) nanoparticles-wrapped double-stranded RNA (dsRNA) significantly increased Diaphorina citri mortality. Transcriptome sequencing further confirmed that genes associated with the endocytic pathway and immune response were up-regulated in Diaphorina citri after SPc treatment. The current study indicated that DcCP8 is critical for the formation of Diaphorina citri exocuticles, and lays a foundation for Diaphorina citri control based on large-scale dsRNA nanoparticles. © 2024 Society of Chemical Industry.

Effects of Larch Woolly Adelgid Infestation on Morphological, Histological and Allelochemical Traits of European Larch Needles.

The study was carried out to assess the effect of the larch wooly adelgid Adelges laricis Vallot (Hemiptera: Adelgidae) infestation on its secondary host, the European larch Larix decidua Mill. Morphology and anatomy of adelgid-infested needles, and content of defense phenolic compounds including individual flavonoids isorhamnetin, kaempferol, quercetin, rutin, catechin, epicatechin, apigenin, ampelopsin and taxifolin, were analyzed. The amount of total phenols in needles from adelgid-infested twigs of L. decidua increased following the development of the A. laricis population, from the end of April until the end of June. The most abundant among flavonoids were the flavanols, mainly catechin and epicatechin, which predominated in the larch needles during the whole period of adelgid infestation. The content of catechin and epicatechin increased following the increase in the adelgid population number. An increase in content occurred also in flavanonols ampelopsin and taxifolin, while the content of the flavonol kaempferol decreased as the population number of A. laricis increased. The analysis of the anatomical structure of needles showed changes in the shape of the needles, the presence of a thicker layer of epicuticular waxes, and a higher number of mesophyll layers as a result of adelgid feeding.

CRISPR-Cas9-mediated enhancement of Beauveria bassiana virulence with overproduction of oosporein

Biocontrol agents play a pivotal role in managing pests and contribute to sustainable agriculture. Recent advancements in genetic engineering can facilitate the development of entomopathogenic fungi with desired traits to enhance biocontrol efficacy. In this study, a CRISPR-Cas9 ribonucleoprotein system was utilized to genetically improve the virulence of Beauveria bassiana, a broad-spectrum insect pathogen used in biocontrol of arthropod pests worldwide. CRISPR-Cas9-based disruption of the transcription factor-encoding gene Bbsmr1 led to derepression of the oosporein biosynthetic gene cluster resulting in overproduction of the red-pigmented dibenzoquinone oosporein involved in host immune evasion, thus increasing fungal virulence. Mutants defective for Bbsmr1 displayed a remarkable enhanced insecticidal activity by reducing lethal times and concentrations, while concomitantly presenting negligible or minor pleiotropic effects. In addition, these mutants displayed faster germination on the insect cuticle which correlated with higher density of free-floating blastospores in the hemolymph and accelerated mortality of the host. These findings emphasize the utility of genetic engineering in developing enhanced fungal biocontrol agents with customized phenotypic traits, and provide an efficient and versatile genetic transformation tool for application in other beneficial entomopathogenic fungi.

Efficient Homogenization of Multicomponent Metamaterials: Chiral Effects

Herein, an efficient homogenization procedure is extended based on a Haydock representation of the microscopic wave operator for the calculation of the retarded macroscopic dielectric response of a binary periodic composite to the case of an arbitrary number of components of arbitrary composition. As a test, this numerical procedure is applied to the calculation of the optical properties of a Bouligand structure, made up of a large number of anisotropic layers stacked on top of each other and progressively rotated. This system constitutes a photonic crystal with circularly polarized electromagnetic normal modes, naturally occurring in the cuticle of several arthropods. It presents a gap for one helicity, which corresponds to the observation of circularly polarized strong metallic like reflections. This numerical procedure is validated through its good agreement with the results of alternative formulations, including an analytical solution for this simple chiral system.

A histological procedure for the study of insect chitinized tissues in light microscopy

We present a procedure to obtain histological preparations of insect cuticles for their observation in ligth microscopy. The use of EDTA (ethylendiaminetetraacetic acid), as a chelator of certain metals present in chitin, soften the tissues and allows us to cut them. The tissues were embbeding in plastic resines in two different protocols and cutted by cryostat (20–30 μm) and ultramicrotome (4 μm) respectively. This procedure, based on traditional histology products, allows us to obtain preparations observable under an optical microscope, facilitating the study of the internal structure of the cuticule, e.g. visualizing the different layers or structures such as glands or setae.

Effect of loading angle and fabrication materials on stress distribution with periodontal splint in compromised periodontal tissues: a finite element study

Objective: To evaluate the effect of polyetheretherketone (PEEK) periodontal splints and splints made from other materials under static loading on stress distributions in periodontal tissues, cement layer, and splints themselves. Methods: A finite element model based on cone-beam CT imaging data of a 25-year-old male patient (treated at the Department of Prosthodontics, School of Stomatology, The Fourth Military Medical University in October 2021 for a cracked maxillary molar) with a healthy and intact mandibular dentition and periodontal health was constructed. The finite element model included anterior mandible dentition, mandibular bone model without bone resorption (WBR group), a periodontally compromised mandible model (control group), and three types of periodontal splints: a PEEK periodontal splint (0.7 mm thick, Young's modulus: 4.1 MPa), a fiber-reinforced resin (FRC) splint (1.0 mm thick, Young's modulus: 37.0 MPa), and a titanium splint (1.2 mm thick, Young's modulus: 110.0 MPa). The bone resorption models fixed with different periodontal splints constituted the experimental groups (PEEK group, FRC group and titanium group). Loading of 100 N was applied on the midpoint of the incisal edge of tooth 41. The direction was set at 0°, which was parallel to the long axis of the tooth and downward. The buccal to lingual and downward angles were 30°and 60°, respectively, perpendicular to the long axis of the tooth and 90° to the lingual side. The finite element analysis software was utilized to analyze the stress distribution characteristics of the periodontal tissues, adhesive layer, and the splint itself in the anterior mandibular teeth among the different group. Results: Under the different loading simulation, in the control group, the maximal von Mises stresses of periodontal ligament and bone were 15.7-50.2 MPa and 38.8-130.3 MPa, respectively, and in the WBR group, the maximal von Mises stresses of periodontal ligament and bone were 3.6-6.4 MPa and 16.5-42.7 MPa, respectively. Under the same loading conditions, the magnitude of maximal von Mises stresses in periodontal tissues in the PEEK group was 4.6-6.2 MPa, and the magnitude of stresses in the periodontal ligament of 41 teeth in the WBR group was similar to that in the PEEK group, but higher than that in the FRC and titanium groups. The maximal von Mises stresses of each group is primarily distributed in the periodontal ligament and alveolar bone at the cervical area of the tooth. The higher the elastic modulus of the splint, the higher its own maximal von Mises stresses, and the smaller the maximal principal stresses transmitted to the adhesive layer. In the PEEK group and titanium group, the stress distribution area in the adhesive layer and the splint was near the splint connection adjacent to tooth 41. Conclusions: Periodontal splints fabricated from three types of materials, are effective in distributing stress within the periodontal tissues of the abutment teeth. Compared to FRC and titanium group, the higher PEEK splint stress value was obtained, and the smaller the stress value was transmitted to its adhesive layer.

Neuropeptide Bursicon and its receptor-mediated the transition from summer-form to winter-form of Cacopsylla chinensis.

Seasonal polyphenism enables organisms to adapt to environmental challenges by increasing phenotypic diversity. Cacopsylla chinensis exhibits remarkable seasonal polyphenism, specifically in the form of summer-form and winter-form, which have distinct morphological phenotypes. Previous research has shown that low temperature and the temperature receptor CcTRPM regulate the transition from summer-form to winter-form in C. chinensis by impacting cuticle content and thickness. However, the underling neuroendocrine regulatory mechanism remains largely unknown. Bursicon, also known as the tanning hormone, is responsible for the hardening and darkening of the insect cuticle. In this study, we report for the first time on the novel function of Bursicon and its receptor in the transition from summer-form to winter-form in C. chinensis. Firstly, we identified CcBurs-α and CcBurs-β as two typical subunits of Bursicon in C. chinensis, which were regulated by low temperature (10 °C) and CcTRPM. Subsequently, CcBurs-α and CcBurs-β formed a heterodimer that mediated the transition from summer-form to winter-form by influencing the cuticle chitin contents and cuticle thickness. Furthermore, we demonstrated that CcBurs-R acts as the Bursicon receptor and plays a critical role in the up-stream signaling of the chitin biosynthesis pathway, regulating the transition from summer-form to winter-form. Finally, we discovered that miR-6012 directly targets CcBurs-R, contributing to the regulation of Bursicon signaling in the seasonal polyphenism of C. chinensis. In summary, these findings reveal the novel function of the neuroendocrine regulatory mechanism underlying seasonal polyphenism and provide critical insights into the insect Bursicon and its receptor.