Effectiveness of the Copenhagen adduction modified position stage 1: EMG measurements and hand-held dynamometer analysis in young and healthy men.

OBJECTIVES: To verify the effectiveness of the use of a modified position of the Copenhagen Adduction (CA) stage 1 compared to the original position. DESIGN: Cross-sectional study. SETTING: Laboratory. PARTICIPANTS: 31 healthy men aged 23.7 ± 1.9 years with no recent or chronic general pathology. MAIN OUTCOME MEASURES: Differences between EMG amplitudes for the adductor longus (AL), rectus femoris (RF) and semi tendinous (ST) during dynamic contractions and adductor maximal isometric voluntary contraction (MIVC) force values between CA stage 1 standard and modified positions were assessed with either Wilcoxon or paired t-test. RESULTS: No significant differences were observed for EMG amplitudes of the AL (p-value = 0.724) and for the RF muscle (p-value = 0.337) and for the adductor force (p-value = 0.361) between the two positions. A significant difference was obtained for the ST (p-value<0.001) mainly explained by the adapted position of the non-dominant leg which unlocked the hip joint and generated less muscle activity in the hamstrings. CONCLUSIONS: Muscle activity of the AL muscle and adductor force being similar in both positions, the CA stage 1 modified position could be of interest for rehabilitation after adductor injury or strengthening of the adductors in elite athletes.

Does muscle-type myosin have ADPase activity?

Adenosine diphosphate (ADP) is a nucleotide that is structurally very similar to ATP but lacks one of the two high-energy bonds due to hydrolysis. In muscle studies, ADP is usually considered exclusively as a product formed during myosin cross-bridge cycling and is not otherwise involved in this process. In our study, we question the widely held view of ADP as a final product formed during muscle contraction. Using biophysical and biochemical methods, we managed to show that ADP can act as a substrate for myosins in at least three types of muscles: smooth and striated adductor muscles of bivalves (Mytilidae and Pectinidae), and also vertebrate skeletal muscles. According to our data, the differences in the effect of ATP and ADP on the optical, biochemical, and structural properties of actomyosins are exclusively quantitative. We explain the previous ideas about ADP as a compound capable of inhibiting the ATPase activity of actomyosin by the ability of ATP and ADP to depolymerize the polymeric myosin when the concentration in the medium reaches more than 0.3 mM.

Transcriptome analysis reveals tissue-specific responses of Mytilus unguiculatus to Vibrio alginolyticus infection.

Mytilus unguiculatus is an important economic bivalve species with wide consumption and aquaculture value. Disease is one of the primary limiting factors in mussel aquaculture, thus understanding the response of different tissues of M. unguiculatus to pathogens is crucial for disease prevention and control. In this study, we investigated the physiological and transcriptomic responses of the gills, adductor muscle, and mantle of M. unguiculatus infected with Vibrio alginolyticus. The results showed that V. alginolyticus infection caused inflammation and tissue structure changes in the gill, adductor muscle and mantle of M. unguiculatus. Meanwhile, the activities of superoxide dismutase and catalase in the three tissues increased, while the total antioxidant capacity decreased, suggesting that M. unguiculatus have an activated defense mechanism against infection-induced oxidative stress, despite a compromised total antioxidant capacity. Transcriptomic studies reveal that infected M. unguiculatus exhibits upregulation of endocytosis, lysosome activity, cellular apoptosis, and immune-related signaling pathways, indicating that M. unguiculatus responds to pathogen invasion by upregulating efferocytosis. Compared with the gill and adductor muscle, the mantle had a higher level of mytimycin, mytilin and myticin, and the three tissues also increased the expression of mytimycin to cope with the invasion of pathogens. In addition, the analysis of genes related to taste transduction pathways and muscle contraction and relaxation found that after infection with V. alginolyticus, M. unguiculatus may reduce appetite by inhibiting taste transduction in the gill, while improving muscle contraction of the adductor muscle and keeping the shell closed, to resist further invasion of pathogens and reduce the risk of pathogen transmission in the population.

Isolated adductor longus avulsion in a young semi-professional football player: Imaging contribution and therapeutic considerations.

Adductor longus injuries are usually observed at the proximal musculo-tendinous junction, but isolated tendinous ruptures (i.e., avulsion) at the origin on the pubic bone are uncommon. In this article, we report a new case of isolated adductor longus avulsion that occurred in a young athlete and was treated with conservative therapy. An 18 years old semi-professional football player, in the attempt to reach the ball with his right leg, reported acute pain and functional limitation in his left adductor area. Clinical examination showed tenderness on palpation associated with mild swelling. Manual strength testing of adductor muscles showed weakness and elicited moderate pain in the proximal groin region near the pubic bone. The diagnostic evaluations (ultrasound [3-14 MHz linear probe] and magnetic resonance imaging [1.5 Tesla magnetic field]), performed a few days after the event, showed a complete isolated avulsion of the proximal adductor longus tendon associated with a fluid collection, with a gap of about 9.5 mm from its insertion on the pubic bone. Degenerative alterations (sub-chondral sclerosis, bone edema, erosions, cortical irregularities, calcifications) were found. These findings were crucial in the treatment choice because conservative management is suggested when the gap is below 1 cm and when no important displacement of proximal torn tendon's end at dynamic ultrasound is appreciated. A structured rehabilitation protocol was implemented, allowing the player to come back to his full athletic activity after 146 days. Return to play was allowed when several subjective and objective parameters were fully satisfied (full hip range of motion, pain-free football-specific activities, less than a 5%-10% difference in hip adduction strength between the injured and uninjured legs, advanced anatomical healing of the adductor longus tendon seen on diagnostic exams, and Hip And Groin Outcome Score [HAGOS] scores similar to baseline data). This case report emphasizes the importance of diagnostic imaging and clinical assessments in the management of an adductor longus avulsion with short retraction (about 1 cm). Both imaging techniques are non-invasive and without risks, allow contra-lateral examination and may guide in the treatment choice; moreover, they significantly influence the post-care approach by enabling to fine-tune a safe return to full athletic activity with minor re-injury rate. While US can be used as primary imaging modality, MRI offers a higher level of accuracy.

Microanatomy and behaviour of the date mussel's adductor and foot muscles after chronic exposure to bisphenol A, with inhibition of ATPase enzyme activities and DNA damage.

Environmental contaminants with estrogenic activity have recently received attention due to the potential harm they could cause to humans and wildlife. To assess the toxic effects of bisphenol A (BPA) on marine mussels, Lithophaga lithophaga were exposed for 4 weeks to 0, 0.25, 1, 2, and 5 µg/L BPA. Aside from DNA damage, a behavioural study including valve closure duration (VCD), valve opening duration (VOD), levels of malondialdehyde (MDA), and total glutathione, as well as superoxide dismutase (SOD) and ATPase activities in adductor muscle extracts, and histopathological examination of the adductor muscle and foot were performed. The behavioural response was marked by an increase in the percentage of VCD and a decrease in the percentage of VOD during 8 h. Furthermore, BPA treatments resulted in a significant concentration-dependent increase in muscle MDA and total glutathione levels. However, when compared to controls, SOD and ATPase activity was significantly reduced in the adductor muscles of BPA treatments. Histological examination of the adductor and foot muscles revealed qualitatively distinct abnormalities. DNA damage was strongly induced in a concentration-dependent manner. Our findings suggested that BPA exposure altered detoxification, antioxidation, ATPase activity, histopathological characteristics, and DNA damage, which resulted in behavioural changes. The multi-biomarker approach used suggests that clear relationships exist between genotoxic and higher-level effects in some cases, which could be used as an integrated tool to evaluate various long-term toxic effects of BPA.

Recovery of two elite footballers from adductor strain with dry needling and eccentric strengthening: Two case studies.

INTRODUCTION: Groin injuries are common in sports, almost 68% adductor strain among them, which generally more prone in football, soccer, hockey, and other games. The available literature well describes the rehabilitation phase of adductor strain but an application of dry needling on adductor injuries are not yet established. CASE DESCRIPTION: Two national-level younger football players were clinically diagnosed with the adductor strain. They had severe pain on medial aspect of the thigh, aggravated with kicking and functional activity (VAS- 8/10, LEFS 58/80, 69/80). The therapist assessed the patients and designed their rehabilitation protocol as per their findings of the examination. OUTCOME: The lower extremity functional scale (LEFS), global rating scale, and VAS were used as outcome variables. The total intervention was given for 10-12 weeks, follow up had been taken for 4 months. DISCUSSION: The application of dry needling reduced the pain, improved and relieved the symptoms. The eccentric strengthening of the adductors and core stability improved the strength as well as functional activity of the lower limb. The case study is not generalized the effect of treatment. Thus, a randomized control trial is suggested for further study.

MicroRNA expression signature in the striated and smooth adductor muscles of Yesso scallop Patinopecten yessoensis.

Increasing evidences point to the potential role of microRNAs (miRNAs) in muscle growth and development in animals. However, knowledge on the identity of miRNAs and their targets in molluscs remains largely unknown. Scallops have one large adductor muscle, composed of fast (striated) and slow (smooth) muscle types, which display great differences in muscle fibers, meat quality, cell types and molecular components. In the present study, we performed a comprehensive investigation of miRNA transcriptomes in fast and slow adductor muscles of Yesso scallop Patinopecten yessoensis. As a result, 47 differentially expressed miRNAs representing ten miRNA families were identified between the striated and smooth adductor muscles. The KEGG enrichment analysis of their target genes were mainly associated with amino acid metabolism, energy metabolism and glycan biosynthesis. The target genes of miR-133 and miR-71 were validated by the dual-luciferase reporter assays and miRNA antagomir treatment in vivo. The identification and functional validation of these different miRNAs in scallops will greatly help our understanding of miRNA regulatory mechanism that achieves the unique muscle phenotypes in scallops. The present findings provide the direct evidences for muscle-specific miRNAs involved in muscle growth and differentiation in molluscs.

First Immunodetection of Sensory and Nervous Systems of Parasitic Larvae (Glochidia) of Freshwater Bivalve Nodularia douglasiae.

Most freshwater mussels have an unusual life cycle that requires host fish species for larval (glochidia) development and dispersal. Glochidia have a unique morphological structure that adapts to parasitic lifestyles and survival. The morphology of the glochidial shells of most Unionoidea, a group of freshwater bivalve mollusks, has been studied in detail using light and scanning electron microscopy. This study summarizes our data on the glochidia shell morphology of the Asian mussel Nodularia douglasiae from two localities in the Primorsky Territory, the Russian Far East. In contrast to the shell morphology of glochidia, little is known about the neurodevelopment of the Unionoidea. Herein, we first demonstrate that the structures of the sensory, muscle, and nervous systems of the glochidia larvae of N. douglasiae differ dramatically from those of the comparable larval systems of marine bivalve species, as revealed through alpha-acetylated tubulin, serotonin (5-HT), and FMRFamide antibodies as well as phalloidin for detection of F-actin and whole-mount confocal microscopy. We found that the glochidia sensory system included four pairs of tubulin-lir multicilia hair cells. Non-ciliar tubulin-lir cells synthesize the neuropeptide FMRFamide and are identified as afferent neurons collecting information from peripheral tubulin-lir hair sensory cells to nervous regulators. The glochidia's muscular system was represented by a smooth adductor, retractors, and minor muscle bundles associated with the shell and visceral organs. The 5-HT-lir larval system is arranged most simply and consists of two immunopositive neurons innervating the adductor. The FMRFamide-lir system is more complicated and consists of several neuronal centers comprising neuronal bodies and their neurites in different areas of the larva. The FMRFamide-lir neurons are closely associated with sensory hair cells, and others, together with 5-HT-lir neurons, may be involved in the anlagen of adult ganglia. Thus, the nervous system of N. douglasiae glochidia is drastically different from other mollusks and lophotrochozoans because of the absence of an apical organ and the location and composition of FMRFamide and 5-HT cells. Morphological, molecular, and behavioral investigations of Unionoidea taxa need to be further conducted to investigate the parasite-host relationship, nerve-dependent regulation of parasite behavior, and evolution of mollusks.

Molecular Characterization and Expression Pattern of Paramyosin in Larvae and Adults of Yesso Scallop.

Paramyosin is an important myofibrillar protein in molluscan smooth muscle. The full-length cDNA encoding paramyosin has been identified from Yesso scallop Patinopecten yessoensis. The length of paramyosin molecule has been found to be 3715 bp, which contains an open reading frame (ORF) of 2805 bp for 934 amino acid residues. Characterization of P. yessoensis paramyosin reveals the typical structural feature of coiled-coil protein, including six α-helix (α1-α6) and one coil (η) structures. Multiple phosphorylation sites have been predicted at the N-terminus of paramyosin, representing the unique phosphorylation sites in scallops. The highest levels of mRNA and protein expression of paramyosin have been found in foot and the smooth adductor muscle. According to whole-mount in situ hybridization (WISH), strong paramyosin mRNA signals were detected in the symmetric positions of anterior and posterior adductor muscles at late larval stages. These findings support that paramyosin may serve as the most important components for myogenesis and catch regulation in scallops. The present findings will not only help uncover the potential function of myofibrillar proteins in molluscs but also provide molecular evidence to infer evolutionary relationships among invertebrates.

Thigh Muscularity and Sprinting Performance of National-Level Long-Distance Runners.

Long-distance runners require aerobic capacity as well as sprinting ability for superior performance; however, the factors which determine the sprinting ability of long-distance runners remain undetermined. Therefore, the purpose of our study was to examine the association between thigh muscle size and sprinting ability in national-level male long-distance runners. Nineteen male long-distance runners with 5000 m personal-best times of 13:12.63-14:14.87 participated in this study, and transaxial images of their right thighs were collected using magnetic resonance imaging. The cross-sectional areas of the quadriceps femoris, hamstrings, and adductor muscles were calculated from the transaxial images at 30%, 50%, and 70% of the distance from the greater trochanter to the lower edge of the femur; these areas were normalized by body mass. Sprint times for 100 m and 400 m were recorded on an all-weather track. The results revealed positive correlations between the normalized cross-sectional areas of the quadriceps femoris at 50% and 70% of the thigh length and the 100 m (r = 0.666, p = 0.002 and r = 0.531, p = 0.019, respectively) and 400 m sprint times (r = 0.769, p < 0.001 and r = 0.580, p = 0.009, respectively); hence, the larger the quadriceps, the slower the sprint speed. However, no association was found between the normalized cross-sectional areas of the hamstrings or adductor muscles and sprinting performance. Therefore, running motions which activate the quadriceps femoris much more than the hamstrings and adductor muscles should be avoided by national-level long-distance runners.

Effects of Ultrasound-Assisted Vacuum Impregnation Antifreeze Protein on the Water-Holding Capacity and Texture Properties of the Yesso Scallop Adductor Muscle during Freeze-Thaw Cycles.

The effect of antifreeze protein (AFP) on the water-holding capacity (WHC) and texture properties of the Patinopecten yessoensis adductor muscles during freeze-thaw cycles (FTCs) were evaluated based on three impregnation methods: general impregnation (GI), vacuum impregnation (VI), and ultrasound-assisted VI (US-VI). The WHC, texture properties, and tissue microstructure were all evaluated. Results showed that the WHC and texture properties of adductor muscle were significantly improved in the VI and US-VI groups during FTCs (p < 0.05). The WHC of the adductor muscle in the US-VI group was maximally enhanced in terms of yield (6.63%), centrifugal loss, cooking loss, and T22. The US-VI group of the adductor muscle had the optimal chewiness and springiness compared to others, and the shear force and hardness were most effectively enhanced by VI. The growth and recrystallization of ice crystals in the frozen adductor muscle were significantly inhibited by VI and US-VI. The average cross-sectional area and roundness of ice crystals in the US-VI group were decreased by 61.89% and increased by 22.22% compared with those of the control, respectively. The partial least squares regression (PLSR) model further confirmed that the WHC and texture properties of the adductor muscle were correlated appreciably with the degree of modification of ice crystal morphology through the AFP.

Hip Adductor Muscle Abscess Descending From Septic Symphysitis.

Hip adductor muscle abscesses that descend from an infected symphysis pubis are rare but cause serious morbidity. We present a case of a 73-year-old male patient with unilateral hip adductor muscle abscess that descended from septic symphysitis caused by Staphylococcus aureus. Surgical debridement of the adductor compartment could not clear the infection and secondary debridement of the symphysis was necessary to eradicate S. aureus. Additionally, we review another four cases with similarities to our case comparing their investigation, treatment, and outcome.

Mitochondrial activity as an indicator of scallop (Mizuhopecten yessoensis) adductor muscle in early cold storage.

The purpose of this study was to reveal the role of mitochondria in indicating a change in the freshness of the adductor muscle of Mizuhopecten yessoensis during cold storage and hardening. The adductor muscle hardens after 96 h of cold storage and reaches the maximum degree of hardening in 6 h. In this study, after hardening (102 h), the muscle fiber structure obviously broke and curled, and the sarcomere structure disappeared at 150 h. After hardening (102 h), the morphology of the mitochondria changed, including swelling, cristea breaking and membrane structure disappearance. The arginine phosphate content decreased gradually from the initial 4.618 to 1.306 µmol/g at 48 h, and there was no further obvious change. The ATP content decreased from 6.02 to 1.07 µmol/g in 120 h. The mitochondrial membrane potential (Δφ) was measured by a fluorescence method (JC-1). The changes in freshness could be divided into three classes according to the Δφ difference between the mitochondria in the adductor muscle after adding ADP and CCCP. Mitochondrial function was complete from 0 to 6 h; mitochondrial function began to decline at 6 to 48 h; and mitochondrial function completely disappeared after 48 h. The results showed that the mitochondrial membrane potential compared with other indicators could more sensitively reflect the changes in freshness during the cold storage hardening process of the adductor muscle. PRACTICAL APPLICATION: It is very important to interprete the post-mortem energy metabolism for controlling the muscle quality of Yesso scallop. The K value which was developed based on ATP-related compounds is widely used in evaluating the freshness of seafood. Mitochondria is the main sites of cellular energy metabolism and the changes of its structure and activity can sensitively reflect the quality changes in muscle cell. It is expected to develop a more sensitive freshness evaluation index.

Relationship between Condition Index Values and Expression Levels of Gene and Protein in the Adductor Muscle of Diploid and Triploid Oysters Crassostrea gigas.

Three proteins [myosin heavy chain (MHC), filamin-C fragment (FIL-C), and actin 2 (ACT2)] were identified in adductor muscle from diploid and triploid Pacific oysters (Crassostrea gigas) and the relationship between the condition index (CI) and mRNA expression of these genes was investigated, together with the mRNA expression of molluscan insulin-related peptide (MIP), C. gigas insulin receptor-related receptor (CIR), and insulin-like growth factor binding protein complex acid labile subunit (IGFBP-ALS). Monthly changes in the CI were similar to the changes in the tissue weight rate in both groups. ACT2 and MHC mRNA expression was statistically higher in the triploid than the diploid, while FIL-C mRNA expression was significantly higher in the diploid (p<0.05). The MIP, CIR, and IGFBP-ALS mRNA expression of the diploid oysters were all significantly higher in July than in other months (p<0.05). The MIP, CIR, and IGFBP-ALS mRNA expression in the triploid oysters was high in July, but there were no significant differences (p>0.05). Changes in the expression levels of the genes investigated in this study could be used as intrinsic indicators of the annual growth, maturity, and spawning period of cultured diploid and triploid C. gigas in Tongyeong, Korea.

Ambient ultraviolet B radiation induced valve behavioral acclimation of Pacific oyster which resulted from the different response strategies of smooth and striated adductor muscles.

Light not only conveys image-forming vision but also has an impact on various physiological functions. In particular, ultraviolet B (UVB) radiation has the closest relationship with living organisms. For Pacific oysters (Crassostrea gigas), alteration of valve behavior is one of the most important ways responding to ambient UVB. In the present study, the response of adult C. gigas to sunlight (especially UVB) was evaluated by monitoring valve activity and further elucidated at the physiological and metabolomic levels. After exposure, the valve activity of C. gigas demonstrated flexible acclimation to the ambient conditions. The potential adjustment of osmoregulation and oxidative stress might be related to ambient UVB radiation. Mycosporine-like amino acids might contribute to the protection of C. gigas against UVB, while precursors of ß-alanine and degradation products of 5-hydroxytryptamine might adjust the contraction of the adductor muscles. The different responses of the adductor muscles (smooth and striated) were manifested in signal transduction and metabolisms of energy and nucleotide. This study not only indicated the correlation between the valve behavioral changes in oysters and light radiation, especially UVB, but illustrated the acclimation strategies of oysters to ambient light (UVB) environment.

Cell type diversity in scallop adductor muscles revealed by single-cell RNA-Seq.

Studies on cell atlas in marine invertebrates provide a better understanding of cell types, stem cell maintenance, and lineages of cell differentiation. To investigate the molecular features of various cell types in molluscan muscles, we performed single-cell RNA sequencing (scRNA-seq) to map cell types in scallop adductor muscles. We uncovered the cell type-specific features of 20 cell clusters defined by the expression of multiple specific molecular markers. These cell clusters are mainly classified into four broad classes, including mesenchymal stem cells, muscle cells, neurons, and haemolymph cells. In particular, we identified a diverse repertoire of neurons in the striated adductor muscle, but not in the smooth muscle. We further reconstructed the cell differentiation events using all the cell clusters by single-cell pseudotemporal trajectories. By integrating dual BrdU-PCNA immunodetection, neuron-specific staining and electron microscopy observation, we showed the spatial distribution of mesenchymal stem cells and neurons in striated adductor muscle of scallops. The present findings will not only be useful to address the cell type-specific gene expression profiles in scallop muscles, but also provide valuable resources for cross-species comparison of marine organisms.

Adductor Muscle Injuries in UEFA Soccer Athletes: A Matched-Cohort Analysis of Injury Rate, Return to Play, and Player Performance From 2000 to 2015.

BACKGROUND: The effects of adductor muscle injury on performance in soccer athletes are unknown. PURPOSE: To (1) determine the rate and time to return to play (RTP) after adductor muscle injury, (2) investigate the rate of reinjury after RTP, and (3) investigate any long-term effects of injury on elite soccer player performance. STUDY DESIGN: Cohort study; Level of evidence, 3. METHODS: Using publicly available records, athletes sustaining adductor muscle injury were identified across the 5 major European soccer leagues (English Premier League, Bundesliga, La Liga, Ligue 1, and Serie A) between 2000 and 2015. Injured athletes were matched to controls by demographic characteristics and performance metrics from 1 season before the index timepoint. Investigations included the rate of RTP, reinjuries, player characteristics associated with RTP within 2 seasons, player availability, field time, and performance metrics during the 4 seasons after injury. RESULTS: A total of 671 players with adductor muscle injury were included. Based on time to RTP, 86% of injuries were mild to moderate (4-28 days missed), and 4% required surgical intervention. Players with adductor muscle injury were absent for a median of 22 days (range, 1-700 days) and 4 games (range, 1-76 games). A total of 521 (78%) players returned at the same level, with no demographic or clinical characteristics associated with RTP on the multivariable regression. Of those returning to play, 143 (21%) experienced adductor reinjury. After RTP, defenders demonstrated decreased field time compared with controls (P < .05). As compared with controls, defenders and midfielders scored more points and goals per game during the season of the injury (P < .01), while attackers recorded more goals and assists per game the season after injury (P < .05). CONCLUSION: Only 3 in 4 players (78%) returned to participate in an official match, and the reinjury rate was high (21%). After RTP, defenders demonstrated decreased field time versus controls. On the other hand, defenders and midfielders recorded more points and goals per game, while attackers recorded more goals and assists per game versus controls. Although the multivariable analysis results did not identify player characteristics associated with RTP, there was a position-dependent association on player performance after RTP.

Effect of hip flexion angle on stiffness of the adductor longus muscle during isometric hip flexion.

This study examined the effect of hip flexion angle on the stiffness of the adductor longus (AL) muscle during isometric hip flexion. Seventeen men were recruited. Ten participants performed submaximal voluntary contraction at 0%, 25%, 50%, and 75% of maximal voluntary contraction (MVC) during isometric hip flexion after performing MVC at 0°, 40°, and 80° of hip flexion. Seven participants performed submaximal voluntary tasks during isometric hip extension in addition to hip flexion task. The shear modulus of the AL muscle was used as the index of muscle stiffness, and was measured using ultrasound shear-wave elastography during the tasks at each contraction intensity for each hip flexion angle. During hip flexion, the shear modulus of the AL muscle was higher at 0° than at 40° and 80° of hip flexion at each contraction intensity (p < 0.016). Conversely, a significant effect was not found among hip flexion angle during hip extension at 75% of MVC (p = 0.867). These results suggest that mechanical stress of the AL muscle may be higher at 0° of hip flexion during isometric hip flexion.

Shell-adductor muscle attachment and Ca2+ transport in the bivalves Ostrea stentina and Anomia ephippium.

Among bivalve muscles, the adductors are particularly important for animal survival because they control valve closure. Most studies have addressed the type and morphology of this muscle in bivalves but few have focused on the mechanism that anchors it to the shell myostracum layer. Moreover, the possible calcium transport mechanism through the adductor muscle cells to the myostracum shell layer, which is necessary for bivalve biomineralisation, has never been addressed. Our results indicate that the muscle cell-shell attachment is mediated by the outer mantle epithelial cell layer, here termed tendon cells. These cells are modified at the muscle scar zone by the presence of actin cytoskeletal bundles, which anchor cells to the extracellular matrix via focal adhesion (or focal contact) junctions at the basal side and to extrapallial matrix at the apical side, both rich in collagen. From apical focal adhesions, bundles of collagen-rich fibres cross the extrapallial space and penetrate the myostracum shell layer. The latter constitutes one of the strongest anchoring structures among invertebrates. Numerous vesicles protrude from the tendon cells into the extrapallial space. TEM-EDX analysis reveals the presence of Ca2+ inside some of these vesicles both in tendon cells and in the extrapallial space. This suggests a potential mechanism for calcium transport from cells to the myostracum. STATEMENT OF SIGNIFICANCE: The interfaces between bivalve shells and muscular attachments are unique and of special interest as adhesive functional biomaterials, being one of the strongest invertebrate anchoring structures. We present an updated ultrastructural model of the adductor muscle-shell attachment. Muscle cells connect with the shell through epithelial `tendon cells`, which have a cytoskeleton of actin microfilaments that connect to the extracellular matrix via focal adhesions. Collagen-rich fibres arise from apical focal adhesions, cross the nanometric extrapallial space and penetrate the myostracum where they form an organic network. Calcium is present inside vesicles that are released into the extrapallial space. The lack of direct cellular control on secretion restricts the myostracal microstructure to prismatic aragonitic similar to its inorganic counterpart.

Adverse effects of total hip arthroplasty on the hip abductor and adductor muscle lengths and moment arms during gait.

BACKGROUND: Precise evaluation of the hip abductor and adductor muscles function in total hip arthroplasty (THA) patients during gait could help prevent postoperative complications and optimize the rehabilitation training program. The purpose of this study was to elucidate the effects of THA on the hip abductor and adductor muscle lengths and moment arms of in vivo patients during gait. METHODS: Ten unilateral THA patients received CT scans and dual fluoroscopic imaging for the hip kinematics during gait. The hip abductor and adductor muscle insertions were digitized on the 3D hip model for the determination of their dynamic lines of action and moment arms. Changes in the hip abductor and adductor muscle lengths and moment arms of THA patients between the implanted and non-implanted sides were quantified during gait. RESULTS: The adductor longus, adductor brevis, and pectineus of the implanted hips had significantly (P < 0.05) less elongation than that of the non-implanted side during the stance phase. The gluteus medius, gluteus minimus, and piriformis moment arms of the implanted side were significantly shorter. The piriformis muscle moment arm was significantly larger. In the double support phase, the adductor magnus and adductor longus moment arms of the implanted sides were significantly decreased. CONCLUSIONS: Results suggested that the adverse effects of THA on hip stability. Development of a rehabilitation program considering the effects of THA is essential. Accurate surgical techniques may reduce the impact of THA on the peripheral muscles.