Existing data suggest the extracellular matrix (ECM) of vertebrate skeletal muscle consists of several morphologically distinct layers: an endomysium, perimysium, and epimysium surrounding muscle fibers, fascicles, and whole muscles, respectively. These ECM layers are hypothesized to serve important functional roles within muscle, influencing passive mechanics, providing avenues for force transmission, and influencing dynamic shape changes during contraction. The morphology of the skeletal muscle ECM is well described in mammals and birds; however, ECM morphology in other vertebrate groups including amphibians, fish, and reptiles remains largely unexamined. It remains unclear whether a multilayered ECM is a common feature of vertebrate skeletal muscle, and whether functional roles attributed to the ECM should be considered in mechanical analyses of non‐mammalian and non‐avian muscle. To explore the prevalence of a multilayered ECM, we used a cell maceration and scanning electron microscopy technique to visualize the organization of ECM collagen in muscle from six vertebrates: bullfrogs (
To investigate the ploughing mechanism associated with tractional force formation on the temporomandibular joint (
Ten left
Confined compression tests characterized mechanical
Biphasic mechanical properties were determined in five
Sustained mechanical loading may play a role in load carriage within the
- NSF-PAR ID:
- 10246953
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- Orthodontics & Craniofacial Research
- Volume:
- 20
- Issue:
- S1
- ISSN:
- 1601-6335
- Page Range / eLocation ID:
- p. 151-156
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract ), turkeys (Lithobates catesbeianus ), alligators (Meleagris gallopavo ), cane toads (Alligator mississippiensis ), laboratory mice (Rhinella marina ), and carp (Mus musculus ). All muscles studied contained a collagen‐reinforced ECM with multiple morphologically distinct layers. An endomysium surrounding muscle fibers was apparent in all samples. A perimysium surrounding groups of muscle fibers was apparent in all but carp epaxial muscle; a muscle anatomically, functionally, and phylogenetically distinct from the others studied. An epimysium was apparent in all samples taken at the muscle periphery. These findings show that a multilayered ECM is a common feature of vertebrate muscle and suggest that a functionally relevant ECM should be considered in mechanical models of vertebrate muscle generally. It remains unclear whether cross‐species variations in ECM architecture are the result of phylogenetic, anatomical, or functional differences, but understanding the influence of such variation on muscle mechanics may prove a fruitful area for future research.Cyprinus carpio -
Abstract While it is well known that mechanical signals can either promote or disrupt intervertebral disc (IVD) homeostasis, the molecular mechanisms for transducing mechanical stimuli are not fully understood. The transient receptor potential vanilloid 4 (TRPV4) ion channel activated in isolated IVD cells initiates extracellular matrix (ECM) gene expression, while TRPV4 ablation reduces cytokine production in response to circumferential stretching. However, the role of TRPV4 on ECM maintenance during tissue‐level mechanical loading remains unknown. Using an organ culture model, we modulated TRPV4 function over both short‐ (hours) and long‐term (days) and evaluated the IVDs' response. Activating TRPV4 with the agonist GSK101 resulted in a Ca2+flux propagating across the cells within the IVD. Nuclear factor (NF)‐κB signaling in the IVD peaked at 6 h following TRPV4 activation that subsequently resulted in higher interleukin (IL)‐6 production at 7 days. These cellular responses were concomitant with the accumulation of glycosaminoglycans and increased hydration in the nucleus pulposus that culminated in higher stiffness of the IVD. Sustained compressive loading of the IVD resulted in elevated NF‐κB activity, IL‐6 and vascular endothelial growth factor A (VEGFA) production, and degenerative changes to the ECM. TRPV4 inhibition using GSK205 during loading mitigated the changes in inflammatory cytokines, protected against IVD degeneration, but could not prevent ECM disorganization due to mechanical damage in the annulus fibrosus. These results indicate TRPV4 plays an important role in both short‐ and long‐term adaptations of the IVD to mechanical loading. The modulation of TRPV4 may be a possible therapeutic for preventing load‐induced IVD degeneration.
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Premise of the Study Polyploidy has been long recognized as an important force in plant evolution. Previous studies had suggested widespread occurrence of polyploidy and the allopolyploid origin of several species in the diverse neotropical genus
Lachemilla (Rosaceae). Nonetheless, this evidence has relied mostly on patterns of cytonuclear discordance, and direct evidence from nuclear allelic markers is still needed.Methods Here we used
PCR target enrichment in combination with high throughput sequencing to obtain multiple copies of the nuclear ribosomal (nr)DNA cistron and 45 regions of the plastid genome (cpDNA ) from 219 accessions representing 48 species ofLachemilla and to explore the allopolyploid origin of species in this group.Key Results We were able to identify multiple nr
DNA ribotypes and establish clear evidence of allopolyploidy in 33 species ofLachemilla , showing that this condition is common and widespread in the genus. Additionally, we found evidence for three autopolyploid species. We also established multiple, independent origins of several allopolyploid species. Finally, based solely on the cpDNA phylogeny, we identified that the monotypic genusFarinopsis is the sister group ofLachemilla and allied genera within subtribe Fragariinae.Conclusions Our study demonstrates the utility of the nuclear ribosomal
DNA cistron to detect allopolyploidy when concerted evolution of this region is not complete. Additionally, with a robust chloroplast phylogeny in place, the direction of hybridization events can be established, and multiple, independent origins of allopolyploid species can be identified. -
Objective To elucidate the role of decorin, a small leucine‐rich proteoglycan, in the degradation of cartilage matrix during the progression of post‐traumatic osteoarthritis (
OA ).Methods Three‐month–old decorin‐null (Dcn−/−) and inducible decorin‐knockout (Dcni
KO ) mice were subjected to surgical destabilization of the medial meniscus (DMM ) to induce post‐traumaticOA . TheOA phenotype that resulted was evaluated by assessing joint morphology and sulfated glycosaminoglycan (sGAG ) staining via histological analysis (n = 6 mice per group), surface collagen fibril nanostructure via scanning electron microscopy (n = 4 mice per group), tissue modulus via atomic force microscopy–nanoindentation (n = 5 or more mice per group) and subchondral bone structure via micro–computed tomography (n = 5 mice per group). Femoral head cartilage explants from wild‐type and Dcn−/−mice were stimulated with the inflammatory cytokine interleukin‐1β (IL ‐1β) in vitro (n = 6 mice per group). The resulting chondrocyte response toIL ‐1β and release ofsGAG s were quantified.Results In both Dcn−/−and Dcni
KO mice, the absence of decorin resulted in acceleratedsGAG loss and formation of highly aligned collagen fibrils on the cartilage surface relative to the control (P < 0.05). Also, Dcn−/−mice developed more salient osteophytes, illustrating more severeOA . In cartilage explants treated withIL ‐1β, loss of decorin did not alter the expression of either anabolic or catabolic genes. However, a greater proportion ofsGAG s was released to the media from Dcn−/−mouse explants, in both live and devitalized conditions (P < 0.05).Conclusion In post‐traumatic
OA , decorin delays the loss of fragmented aggrecan and fibrillation of cartilage surface, and thus, plays a protective role in ameliorating cartilage degeneration. -
Summary Boron is a micronutrient that is required for the normal growth and development of vascular plants, but its precise functions remain a subject of debate. One established role for boron is in the cell wall where it forms a diester cross‐link between two monomers of the low‐abundance pectic polysaccharide rhamnogalacturonan‐
II (RG ‐II ). The inability ofRG ‐II to properly assemble into a dimer results in the formation of cell walls with abnormal biochemical and biomechanical properties and has a severe impact on plant productivity. Here we describe the effects onRG ‐II structure and cross‐linking and on the growth of plants in which the expression of aGDP ‐sugar transporter (GONST 3/GGLT 1) has been reduced. In the ‐silenced plants the amount of L‐galactose in side‐chain A ofGGLT 1RG ‐II is reduced by up to 50%. This leads to a reduction in the extent ofRG ‐II cross‐linking in the cell walls as well as a reduction in the stability of the dimer in the presence of calcium chelators. The silenced plants have a dwarf phenotype, which is rescued by growth in the presence of increased amounts of boric acid. Similar to themur1 mutant, which also disruptsRG ‐II cross‐linking, ‐silenced plants display a loss of cell wall integrity under salt stress. We conclude thatGGLT 1GGLT 1 is probably the primary GolgiGDP ‐L‐galactose transporter, and providesGDP ‐L‐galactose forRG ‐II biosynthesis. We propose that the L‐galactose residue is critical forRG ‐II dimerization and for the stability of the borate cross‐link.