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• Assembled nine Penaeid muscle transcriptomes with an average of 27,000 contigs. • Determined 1,000 orthologous genes expressed in the muscle of all nine species. • Compared sequence diversity of muscle excitation-contraction coupling proteins. • Calculated mRNA expression levels of the genes regulating muscle contraction. The natural flight response in shrimp is powered by rapid contractions of the abdominal muscle fibres to propel themselves backwards away from perceived danger. This muscle contraction is dependent on repetitive depolarization of muscle plasma membrane, triggering tightly spaced cytoplasmic [Ca2+ transients and rapidly rising tetanic force responses. To achieve such high amplitude and high frequency of Ca2+ transients requires a high abundance of sarcoplasmic/endoplasmic reticulum Ca2+ ATPase (SERCA) to rapidly clear cytoplasmic Ca2+ between each transient and an efficient Ca2+ release system consisting of the Ryanodine Receptor (RyR), and voltage gated Ca2+ channels (Ca V s). With the aim to expand our knowledge of muscle gene function and identify orthologous genes regulating muscle excitation-contraction (EC) coupling, this study assembled nine Penaeid shrimp muscle transcriptomes. On average, the nine transcriptomes contained 27,000 contigs, with an annotation rate of 36% and a BUSCO completeness of 70%. Despite maintaining their function, the crustacean RyR and Ca V proteins showed evidence of significant diversification from mammalian orthologs, while SERCA remained more conserved. Several key components of protein interaction were conserved, while others showed distinct crustacean specific evolutionary adaptations. Lastly, this study revealed approximately 1,000 orthologous genes involved in muscle specific processes present across all nine species. [ABSTRACT FROM AUTHOR]

Toll-like receptor (TLR) innate immunity signalling protects against pathogens, but excessive or prolonged signalling contributes to a range of inflammatory conditions. Structural information on the TLR cytoplasmic TIR (Toll/interleukin-1 receptor) domains and the downstream adaptor proteins can help us develop inhibitors targeting this pathway. The small molecule o-vanillin has previously been reported as an inhibitor of TLR2 signalling. To study its mechanism of action, we tested its binding to the TIR domain of the TLR adaptor MAL/TIRAP (MAL TIR ). We show that o-vanillin binds to MAL TIR and inhibits its higher-order assembly in vitro . Using NMR approaches, we show that o-vanillin forms a covalent bond with lysine 210 of MAL. We confirm in mouse and human cells that o-vanillin inhibits TLR2 but not TLR4 signalling, independently of MAL, suggesting it may covalently modify TLR2 signalling complexes directly. Reactive aldehyde-containing small molecules such as o-vanillin may target multiple proteins in the cell.

Duchenne muscular dystrophy (DMD) is characterised by respiratory muscle injury, inflammation, fibrosis and weakness, ultimately culminating in respiratory failure. The dystrophin-deficient mouse model of DMD (mdx) shows evidence of respiratory muscle remodelling and dysfunction contributing to impaired respiratory system performance. The antioxidant N-acetylcysteine (NAC) has been shown to exert anti-inflammatory and anti-fibrotic effects leading to improved respiratory muscle performance in a range of animal models of muscle dysfunction, including mdx mice, following short-term administration (2 weeks). We sought to build on previous work by exploring the effects of chronic NAC administration (3 months) on respiratory system performance in mdx mice. One-month-old male mdx mice were randomised to receive normal drinking water (n = 30) or 1% NAC in the drinking water (n = 30) for 3 months. At 4 months of age, we assessed breathing in conscious mice by plethysmography followed by ex vivo assessment of diaphragm force-generating capacity. Additionally, diaphragm histology was performed. In separate studies, in anaesthetised mice, respiratory electromyogram (EMG) activity and inspiratory pressure across a range of behaviours were determined, including assessment of peak inspiratory pressure-generating capacity. NAC treatment did not affect force-generating capacity of the mdx diaphragm. Collagen content and immune cell infiltration were unchanged in mdx + NAC compared with mdx diaphragms. Additionally, there was no significant effect of NAC on breathing, ventilatory responsiveness, inspiratory EMG activity or inspiratory pressure across the range of behaviours from basal conditions to peak system performance. We conclude that chronic NAC treatment has no apparent beneficial effects on respiratory system performance in the mdx mouse model of DMD suggesting limited potential of NAC treatment alone for human DMD., (© 2024 The Author(s). Experimental Physiology published by John Wiley & Sons Ltd on behalf of The Physiological Society.)

Background: Particle-induced osteolysis resulting from polyethylene wear remains a source of implant failure in anatomic total shoulder designs. Modern polyethylene components are irradiated in an oxygen-free environment to induce cross-linking, but reducing the resulting free radicals with melting or heat annealing can compromise the component's mechanical properties. Vitamin E has been introduced as an adjuvant to thermal treatments. Anatomic shoulder arthroplasty models with a ceramic head component have demonstrated that vitamin E-enhanced polyethylene show improved wear compared with highly cross-linked polyethylene (HXLPE). This study aimed to assess the biomechanical wear properties and particle size characteristics of a novel vitamin E-enhanced highly cross-linked polyethylene (VEXPE) glenoid compared to a conventional ultrahigh-molecular-weight polyethylene (UHMWPE) glenoid against a cobalt chromium molybdenum (CoCrMo) head component., Methods: Biomechanical wear testing was performed to compare the VEXPE glenoid to UHMWPE glenoid with regard to pristine polyethylene wear and abrasive endurance against a polished CoCrMo alloy humeral head in an anatomic shoulder wear-simulation model. Cumulative mass loss (milligrams) was recorded, and wear rate calculated (milligrams per megacycle [Mc]). Under pristine wear conditions, particle analysis was performed, and functional biologic activity (FBA) was calculated to estimate particle debris osteolytic potential. In addition, 95% confidence intervals for all testing conditions were calculated., Results: The average pristine wear rate was statistically significantly lower for the VEXPE glenoid compared with the HXLPE glenoid (0.81 ± 0.64 mg/Mc vs. 7.00 ± 0.45 mg/Mc) (P < .05). Under abrasive wear conditions, the VEXPE glenoid had a statistically significant lower average wear rate compared with the UHMWPE glenoid comparator device (18.93 ± 5.80 mg/Mc vs. 40.47 ± 2.63 mg/Mc) (P < .05). The VEXPE glenoid demonstrated a statistically significant improvement in FBA compared with the HXLPE glenoid (0.21 ± 0.21 vs. 1.54 ± 0.49 (P < .05)., Conclusions: A new anatomic glenoid component with VEXPE demonstrated significantly improved pristine and abrasive wear properties with lower osteolytic particle debris potential compared with a conventional UHMWPE glenoid component. Vitamin E-enhanced polyethylene shows early promise in shoulder arthroplasty components. Long-term clinical and radiographic investigation needs to be performed to verify if these biomechanical wear properties translate to diminished long-term wear, osteolysis, and loosening., (Copyright © 2024 Journal of Shoulder and Elbow Surgery Board of Trustees. Published by Elsevier Inc. All rights reserved.)

DFT calculations indicate that the 19 F chemical shifts of aromatic rings containing single fluorine substituents are sensitive to the electric fields and electric field gradients at the position of the fluorine atom. The present work explores whether long-range structure restraints can be gained from changes in 19 F chemical shifts following mutations of charged to uncharged residues. 19 F chemical shifts of fluorotryptophan residues were measured in two different proteins, GB1 and the NT* domain, following mutations of single asparagine residues to aspartic acid. Four different versions of fluorotryptophan were investigated, including 4-, 5-, 6-, and 7-fluorotryptophan, which were simultaneously installed by cell-free protein synthesis using 4-, 5-, 6-, and 7-fluoroindole as precursors for the tryptophan synthase present in the S30 extract. For comparison, the 1 H chemical shifts of the corresponding nonfluorinated protein mutants produced with 13 C-labeled tryptophan were also measured. The results show that the 19 F chemical shifts respond more sensitively to the charge mutations than the 1 H chemical shifts in the nonfluorinated references, but the chemical shift changes were much smaller than predicted by DFT calculations of fluoroindoles in the electric field of a partial charge in vacuum, indicating comprehensive dielectric shielding by water and protein. No straightforward correlation with the location of the charge mutation could be established.

Background: Shoulder arthroplasty procedures are widely indicated, and the number of shoulder arthroplasty procedures has drastically increased over the years. Rapid expansion of the utilization of reverse total shoulder arthroplasty has outpaced the more modest growth of anatomic total shoulder arthroplasty (aTSA) while shoulder hemiarthroplasty (HA) has trended down. Recently, shoulder prostheses have transitioned to increasingly modular systems offering more individualized options with the potential for decreased pain and increased range of motion. However, increased primary procedures has resulted in increased revision surgeries, with one potential cause being fretting and corrosion damage within these modular systems., Methods: Following institutional review board approval, 130 retrieved aTSA and 135 HA explants were identified through database query. Humeral stem and head components were included in all 265 explants, whereas 108 included polyethylene glenoid liner components. All explanted components were macroscopically evaluated for standard damage modes, and taper junctions were microscopically examined for fretting/corrosion using a modified Goldberg-Cusick classification system that was 4-quadrant graded for both the male and female component. Medical records were reviewed for patient demographics and surgical information., Results: In this series, 158 of explants were from female patients (male = 107), and 162 explants were from the right shoulder. Average age at implantation was 61 years (range: 24-83), average age at explanation was 66 years (range, 32-90), and average duration of implantation was 61.4 months (range, 0.5-240). Scratching, edge deformation, and burnishing were the most commonly observed standard damage modes. Of the 265 explants, 146 had a male stem component vs. 118 with a female stem component. Average summed fretting grades on male and female stem components were 8.3 and 5.9, respectively (P < .001). Average summed corrosion grades for male and female stem components were 8.2 and 6.2, respectively (P < .001). Wider male tapers (>11 mm) showed significantly less fretting and corrosion (P < .001). Lastly, mismatched metal compositions between the head and stem components showed greater fretting and corrosion damage (P = .002)., Conclusion: In this series of 265 aTSA and HA explants, there was substantial damage present on the explanted components. All components demonstrated macroscopic damage. In this retrieval study, small-tapered male stems with small, thin female heads and mismatched metal composition between components were risk factors for increased implant wear. As shoulder arthroplasty volume increases, optimizing design is paramount for long-term success. Additional work could determine the clinical significance of these findings., (Copyright © 2023 The Author(s). Published by Elsevier Inc. All rights reserved.)

Despite profound diaphragm weakness, peak inspiratory pressure-generating capacity is preserved in young mdx mice revealing adequate compensation by extra-diaphragmatic muscles of breathing in early dystrophic disease. We hypothesised that loss of compensation gives rise to respiratory system compromise in advanced dystrophic disease. Studies were performed in male wild-type (n = 196) and dystrophin-deficient mdx mice (n = 188) at 1, 4, 8, 12 and 16 months of age. In anaesthetised mice, inspiratory pressure and obligatory and accessory respiratory EMG activities were recorded during baseline and sustained tracheal occlusion for up to 30-40 s to evoke peak system activation to task failure. Obligatory inspiratory EMG activities were lower in mdx mice across the ventilatory range to peak activity, emerging in early dystrophic disease. Early compensation protecting peak inspiratory pressure-generating capacity in mdx mice, which appears to relate to transforming growth factor-β1-dependent fibrotic remodelling of the diaphragm and preserved accessory muscle function, was lost at 12 and 16 months of age. Denervation and surgical lesion of muscles of breathing in 4-month-old mice revealed a greater dependency on diaphragm for peak inspiratory performance in wild-type mice, whereas mdx mice were heavily dependent upon accessory muscles (including abdominal muscles) for peak performance. Accessory EMG activities were generally preserved or enhanced in young mdx mice, but peak EMG activities were lower than wild-type by 12 months of age. In general, ventilation was reasonably well protected in mdx mice until 16 months of age. Despite the early emergence of impairments in the principal obligatory muscles of breathing, peak inspiratory performance is compensated in early dystrophic disease due to diaphragm remodelling and facilitated contribution by accessory muscles of breathing. Loss of compensation afforded by accessory muscles underpins the emergence of respiratory system morbidity in advanced dystrophic disease. KEY POINTS: Despite diaphragm weakness, peak inspiratory performance is preserved in young dystrophin-deficient mdx mice revealing adequate compensation by extra-diaphragmatic muscles. Peak obligatory muscle (diaphragm, external intercostal, and parasternal intercostal) EMG activities are lower in mdx mice, emerging early in dystrophic disease, before the temporal decline in peak performance. Peak EMG activities of some accessory muscles are lower, whereas others are preserved. There is greater recruitment of the trapezius muscle in mdx mice during peak system activation. In phrenicotomised mice with confirmed diaphragm paralysis, there is a greater contribution made by extra-diaphragmatic muscles to peak inspiratory pressure in mdx compared with wild-type mice. Surgical lesion of accessory (including abdominal) muscles adversely affects peak pressure generation in mdx mice. Diaphragm remodelling leading to stiffening provides a mechanical advantage to peak pressure generation via the facilitated action of extra-diaphragmatic muscles in early dystrophic disease. Peak accessory EMG activities are lower in 12-month-old mdx compared to wild-type mice. Peak inspiratory pressure declines in mdx mice with advanced disease. We conclude that compensation afforded by accessory muscles of breathing declines in advanced dystrophic disease precipitating the emergence of respiratory system dysfunction., (© 2023 The Authors. The Journal of Physiology published by John Wiley & Sons Ltd on behalf of The Physiological Society.)

Multivalent ligands of ion channels have proven to be both very rare and highly valuable in yielding unique insights into channel structure and pharmacology. Here, we describe a bivalent peptide from the venom of Xibalbanus tulumensis, a troglobitic arthropod from the enigmatic class Remipedia, that causes persistent calcium release by activation of ion channels involved in muscle contraction. The high-resolution solution structure of φ-Xibalbin3-Xt3a reveals a tandem repeat arrangement of inhibitor-cysteine knot (ICK) domains previously only found in spider venoms. The individual repeats of Xt3a share sequence similarity with a family of scorpion toxins that target ryanodine receptors (RyR). Single-channel electrophysiology and quantification of released Ca 2+ stores within skinned muscle fibers confirm Xt3a as a bivalent RyR modulator. Our results reveal convergent evolution of RyR targeting toxins in remipede and scorpion venoms, while the tandem-ICK repeat architecture is an evolutionary innovation that is convergent with toxins from spider venoms., (© 2023. The Author(s).)

Receptor avidity through multivalency is a highly sought-after property of ligands. While readily available in nature in the form of bivalent antibodies, this property remains challenging to engineer in synthetic molecules. The discovery of several bivalent venom peptides containing two homologous and independently folded domains (in a tandem repeat arrangement) has provided a unique opportunity to better understand the underpinning design of multivalency in multimeric biomolecules, as well as how naturally occurring multivalent ligands can be identified. In previous work, we classified these molecules as a larger class termed secreted cysteine-rich repeat-proteins (SCREPs). Here, we present an online resource; ScrepYard, designed to assist researchers in identification of SCREP sequences of interest and to aid in characterizing this emerging class of biomolecules. Analysis of sequences within the ScrepYard reveals that two-domain tandem repeats constitute the most abundant SCREP domain architecture, while the interdomain "linker" regions connecting the functional domains are found to be abundant in amino acids with short or polar sidechains and contain an unusually high abundance of proline residues. Finally, we demonstrate the utility of ScrepYard as a virtual screening tool for discovery of putatively multivalent peptides, by using it as a resource to identify a previously uncharacterized serine protease inhibitor and confirm its predicted activity using an enzyme assay., (© 2023 The Authors. Protein Science published by Wiley Periodicals LLC on behalf of The Protein Society.)

Exposure to acute intermittent hypoxia (AIH) elicits a form of respiratory plasticity known as long-term facilitation (LTF). Interest has grown in developing AIH interventions to treat ventilatory insufficiency, with promising results in spinal cord injury and amyotrophic lateral sclerosis. Therapeutic AIH may have application in neuromuscular disorders including muscular dystrophies. We sought to establish hypoxic ventilatory responsiveness and the expression of ventilatory LTF in X-linked muscular dystrophy (mdx) mice.Experiments were performed in 15 male wild-type (BL10) and 15 male mdx mice at 4 months of age. Ventilation was assessed using whole-body plethysmography. Baseline measures of ventilation and metabolism were established. Mice were exposed to 10 successive bouts of hypoxia, each lasting 5 min, interspersed with 5-min bouts of normoxia. Measurements were taken for 60 min following termination of AIH.In mdx mice, ventilation was significantly increased 60 min post-AIH compared to baseline. However, metabolic CO 2 production was also increased. Therefore, ventilatory equivalent was unaffected by AIH exposure, i.e., no ventilatory LTF manifestation. In wild-type mice, ventilation and metabolism were not affected by AIH.Eliciting ventilatory LTF is dependent on many factors and may require concomitant isocapnia or hypercapnia during AIH exposures and/or repeated daily AIH exposures, which is worthy of further pursuit., (© 2023. The Author(s), under exclusive license to Springer Nature Switzerland AG.)

This paper presents a set of eleven functional Dynamic Neuromuscular Stabilization (DNS) tests corresponding with specific infantile developmental stages, clarifying desired postural-locomotion patterns from a developmental perspective, while also describing frequently-observed disturbances of these patterns., (Copyright © 2020 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Peptide toxins isolated from animal venom secretions have proven to be useful pharmacological tools for probing the structure and function of a number of molecular receptors. Their molecular structures are stabilized by posttranslational formation of multiple disulfide bonds formed between sidechain thiols of cysteine residues, resulting in high thermal and chemical stability. Many of these peptides have been found to be potent modulators of ion channels, making them particularly influential in this field. Recently, several peptide toxins have been described that have an unusual tandem repeat organization, while also eliciting a unique pharmacological response toward ion channels. Most of these are two-domain peptide toxins from spider venoms, such as the double-knot toxin (DkTx), isolated from the Earth Tiger tarantula ( Haplopelma schmidti ). The unusual pharmacology of DkTx is its high avidity for its receptor (TRPV1), a property that has been attributed to a bivalent mode-of-action. DkTx has subsequently proven a powerful tool for elucidating the structural basis for the function of the TRPV1 channel. Interestingly, all tandem repeat peptides functionally characterized to date share this high avidity to their respective binding targets, suggesting they comprise an unrecognized structural class of peptides with unique structural features that result in a characteristic set of pharmacological properties. In this article, we explore the prevalence of this emerging class of peptides, which we have named Secreted, Cysteine-rich REpeat Peptides, or "SCREPs." To achieve this, we have employed data mining techniques to extract SCREP-like sequences from the UniProtKB database, yielding approximately sixty thousand candidates. These results indicate that SCREPs exist within a diverse range of species with greatly varying sizes and predicted fold types, and likely include peptides with novel structures and unique modes of action. We present our approach to mining this database for discovery of novel ion-channel modulators and discuss a number of "hits" as promising leads for further investigation. Our database of SCREPs thus constitutes a novel resource for biodiscovery and highlights the value of a data-driven approach to the identification of new bioactive pharmacological tools and therapeutic lead molecules.

Although subjects with recurrent low back pain (LBP) demonstrate altered trunk control, the kinematic and kinetic responses of the trunk have not been carefully investigated. This study was conducted to compare the standing time, spine range of motion (ROM), and dynamic postural steadiness index (DPSI) based on visual condition between subjects with and without recurrent LBP during upright one leg standing. Sixty-three individuals participated in the study, including 34 control subjects and 29 subjects with recurrent LBP. The DPSI was a composite of the medio-lateral (MLSI), anterior-posterior (APSI), and vertical steadiness indices (VSI) on a force platform. The control group demonstrated longer standing time (s) during the eyes-open condition than the LBP group (26.82±6.03 vs. 19.87±9.36; t=2.96, p=0.01). Regarding spine ROM, visual condition was significantly different between groups (F=7.09, p=0.01) and demonstrated interactions with spine region and group (F=5.53, p=0.02). For the kinetic measures, there was a significant interaction between visual conditions and indices (F=25.30, p=0.001). In the LBP group, the DPSI was significantly correlated with the MLSI (r=0.59, p=0.002), APSI (r=0.44, p=0.03), and VSI (r=0.98, p=0.01) in the eyes-closed condition. Overall, the results of this study indicated that the LBP group decreased thorax and lumbar spine rotations during the eyes-closed condition. The LBP group also demonstrated positive correlations with the kinetic indices, enhancing dynamic postural steadiness in the eyes-closed condition in order to possibly avoid pain or further injury. This dynamic postural steadiness strategy is necessary to improve kinetic and kinematic chain reactions in the LBP group. This compensatory pattern supports the development of optimal postural correction strategies to prevent LBP recurrence and might represent a chain reaction to protect trunk control without visual input., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

We examined the influence of female feeding regime on polyandry in the nuptially feeding nursery web spider (Pisaura mirabilis). In this species, the nuptial gift, a dead prey item wrapped in the male's silk, is physically separate from the ejaculate. We manipulated female feeding regime (starved or fed) and the presence or absence of a gift with three successive males to test direct-benefits hypotheses (nuptial gift or sperm supply) for the expression of polyandry. The presence of a gift was necessary for copulation, as no male without a gift successfully copulated. Female mating behavior most strongly supports polyandry due to the accumulation of gifted food items ("nuptial gift" direct-benefits hypothesis). Starved females that were presented with a gift accepted significantly more gifts and inseminations than fed females. Most starved females (74%) copulated two or more times, as opposed to only 3% of the fed females. Nearly all of the females that accepted a gift subsequently copulated. The nuptial gift item seems to function as male mating effort and females appear to receive multiple matings as part of a feeding strategy.