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Skeletal Muscle Aug 2023The occurrence of hyperplasia, through myofibre splitting, remains a widely debated phenomenon. Structural alterations and fibre typing of skeletal muscle fibres, as...
BACKGROUND
The occurrence of hyperplasia, through myofibre splitting, remains a widely debated phenomenon. Structural alterations and fibre typing of skeletal muscle fibres, as seen during regeneration and in certain muscle diseases, can be challenging to interpret. Neuromuscular electrical stimulation can induce myofibre necrosis followed by changes in spatial and temporal cellular processes. Thirty days following electrical stimulation, remnants of regeneration can be seen in the myofibre and its basement membrane as the presence of small myofibres and encroachment of sarcolemma and basement membrane (suggestive of myofibre branching/splitting). The purpose of this study was to investigate myofibre branching and fibre type in a systematic manner in human skeletal muscle undergoing adult regenerative myogenesis.
METHODS
Electrical stimulation was used to induce myofibre necrosis to the vastus lateralis muscle of one leg in 5 young healthy males. Muscle tissue samples were collected from the stimulated leg 30 days later and from the control leg for comparison. Biopsies were sectioned and stained for dystrophin and laminin to label the sarcolemma and basement membrane, respectively, as well as ATPase, and antibodies against types I and II myosin, and embryonic and neonatal myosin. Myofibre branches were followed through 22 serial Sects. (264 μm). Single fibres and tissue blocks were examined by confocal and electron microscopy, respectively.
RESULTS
Regular branching of small myofibre segments was observed (median length 144 μm), most of which were observed to fuse further along the parent fibre. Central nuclei were frequently observed at the point of branching/fusion. The branch commonly presented with a more immature profile (nestin + , neonatal myosin + , disorganised myofilaments) than the parent myofibre, together suggesting fusion of the branch, rather than splitting. Of the 210 regenerating muscle fibres evaluated, 99.5% were type II fibres, indicating preferential damage to type II fibres with our protocol. Furthermore, these fibres demonstrated 7 different stages of "fibre-type" profiles.
CONCLUSIONS
By studying the regenerating tissue 30 days later with a range of microscopy techniques, we find that so-called myofibre branching or splitting is more likely to be fusion of myotubes and is therefore explained by incomplete regeneration after a necrosis-inducing event.
Topics: Male; Adult; Infant, Newborn; Humans; Muscle Fibers, Skeletal; Muscle, Skeletal; Regeneration; Myosins; Necrosis
PubMed: 37573332
DOI: 10.1186/s13395-023-00322-2 -
ELife May 2019To understand how chromosomes are segregated, it is necessary to explain the precise spatiotemporal organization of microtubules (MTs) in the mitotic spindle. We use...
To understand how chromosomes are segregated, it is necessary to explain the precise spatiotemporal organization of microtubules (MTs) in the mitotic spindle. We use egg extracts to study the nucleation and dynamics of MTs in branched networks, a process that is critical for spindle assembly. Surprisingly, new branched MTs preferentially originate near the minus-ends of pre-existing MTs. A sequential reaction model, consisting of deposition of nucleation sites on an existing MT, followed by rate-limiting nucleation of branches, reproduces the measured spatial profile of nucleation, the distribution of MT plus-ends and tubulin intensity. By regulating the availability of the branching effectors TPX2, augmin and γ-TuRC, combined with single-molecule observations, we show that first TPX2 is deposited on pre-existing MTs, followed by binding of augmin/γ-TuRC to result in the nucleation of branched MTs. In sum, regulating the localization and kinetics of nucleation effectors governs the architecture of branched MT networks.
Topics: Animals; Cell Cycle Proteins; Chromosome Segregation; Microtubule-Associated Proteins; Microtubule-Organizing Center; Microtubules; Protein Binding; Spindle Apparatus; Tubulin; Xenopus Proteins; Xenopus laevis
PubMed: 31066674
DOI: 10.7554/eLife.43890 -
Neural Regeneration Research Dec 2023The peripheral nervous system has an extensive branching organization, and peripheral nerve injuries that ablate branch points present a complex challenge for clinical... (Review)
Review
The peripheral nervous system has an extensive branching organization, and peripheral nerve injuries that ablate branch points present a complex challenge for clinical repair. Ablations of linear segments of the PNS have been extensively studied and routinely treated with autografts, acellular nerve allografts, conduits, wraps, and nerve transfers. In contrast, segmental-loss peripheral nerve injuries, in which one or more branch points are ablated so that there are three or more nerve endings, present additional complications that have not been rigorously studied or documented. This review discusses: (1) the branched anatomy of the peripheral nervous system, (2) case reports describing how peripheral nerve injuries with branched ablations have been surgically managed, (3) factors known to influence regeneration through branched nerve structures, (4) techniques and models of branched peripheral nerve injuries in animal models, and (5) conclusions regarding outcome measures and studies needed to improve understanding of regeneration through ablated branched structures of the peripheral nervous system.
PubMed: 37449590
DOI: 10.4103/1673-5374.373679 -
The Journal of Veterinary Medical... Mar 2023In this study, we investigated the aortic arch (AA) branching pattern in the Eurasian otter (Lutra lutra). We performed arterial silicone casting of the AA of 18...
In this study, we investigated the aortic arch (AA) branching pattern in the Eurasian otter (Lutra lutra). We performed arterial silicone casting of the AA of 18 Eurasian otters (8 males and 10 females). We analyzed the AA branching pattern at three levels: the AA, brachiocephalic trunk (BCT), and subclavian artery (SB), using different classification methods at each level. We introduced new criteria for classifying the SB branching pattern applicable for Eurasian otter and other carnivores based on the sequence of the four main branches: vertebral artery (VT), internal thoracic artery (IT), costocervical artery (CCT), and superficial cervical artery (SC). In all Eurasian otters, two major branches emerged directly from the AA, i.e., the BCT and left SB. The BCT branched off the left common carotid artery and terminated in the right common carotid artery and right SB in 17 of 18 Eurasian otters; the BCT formed a bicarotid artery in the remaining case. The SBs showed various branching patterns, with the main branching pattern involving branching to the VT and IT at the same position, followed by the CCT and SC. The SB branching pattern in the Eurasian otter differed from that in dogs in that the two first branching arteries were VT and IT, rather than VT and CCT. Here, we present the anatomical characteristics of the AA branching patterns in the Eurasian otter and new analysis methods applicable for comparative studies of other carnivores.
Topics: Male; Female; Animals; Dogs; Otters; Aorta, Thoracic; Subclavian Artery; Mammary Arteries; Carotid Artery, Common
PubMed: 36792211
DOI: 10.1292/jvms.22-0517 -
Journal of Vascular Surgery Jan 2022Despite a shared degenerative vascular phenotype, Marfan syndrome (MFS), Loeys-Dietz syndrome (LDS), and other genetically distinct connective tissue diseases (CTDs)...
OBJECTIVE
Despite a shared degenerative vascular phenotype, Marfan syndrome (MFS), Loeys-Dietz syndrome (LDS), and other genetically distinct connective tissue diseases (CTDs) have unique extravascular pathologies that impact the outcomes of aortic replacement. The aim of our study was to investigate the association of CTD genotype with postoperative outcomes and branch patency following open thoracoabdominal aortic replacement in a large institutional cohort.
METHODS
All patients undergoing open branched thoracoabdominal aortic replacement at a single academic center from 2006 to 2020 were included and classified as CTD or non-CTD based on the presence of genotypic documentation. Outcomes were compared using analysis of variance and χ testing for continuous and discrete variables, respectively. Kaplan-Meier curves were utilized to examine patency of graft branches over time.
RESULTS
Overall, 172 patients were included, with a mean follow-up of 30.5 ± 34.9 months. CTD was present in 45 patients (26%); specifically, 32 had MFS, five had LDS, and eight had another CTD. Patients with CTDs had more extent II thoracoabdominal aneurysms (40% vs 15%), more reconstructed branches (3.5 vs 1.8), more frequently reconstructed visceral branches (86.7% vs 22.7%), and higher intraoperative blood loss (13.3 vs 6.8 L; all P < .05) compared with non-CTD patients. Patients with MFS were more frequently systemically anticoagulated preoperatively (50% vs 5%) and demonstrated higher rates of postoperative deep vein thrombosis/pulmonary embolism compared with non-CTD patients (9% vs 2%; both P < .05). Five-year renal branch patency was decreased among all patients compared with visceral branches (87.3% vs 95.6%; P = .05), but there were no individual branch patency differences between patients with and without CTDs (P = .086). Overall branch patency at 1 and 5 years was significantly higher in patients with MFS than in non-CTD patients (98.9% vs 89.1% at 5 years); there were no significant patency differences between non-CTD patients and any other CTD subgroup, mostly due to early patency loss.
CONCLUSIONS
Open thoracoabdominal reconstruction in patients with CTD is technically challenging and associated with increased transfusion and postoperative thromboembolic events when compared with non-CTD patients. Technical outcomes of the procedure are excellent and are differentially associated with genotype, with patients with MFS experiencing significantly improved branch patency over both non-CTD patients and patients with other CTDs, a finding which has multifactorial drivers.
Topics: Adolescent; Adult; Aged; Aortic Aneurysm, Thoracic; Blood Vessel Prosthesis Implantation; Case-Control Studies; Child; Female; Graft Occlusion, Vascular; Humans; Loeys-Dietz Syndrome; Male; Marfan Syndrome; Middle Aged; Retrospective Studies; Stents; Vascular Patency; Young Adult
PubMed: 34186165
DOI: 10.1016/j.jvs.2021.05.062 -
Lumbrical Muscles Neural Branching Patterns: A Cadaveric Study With Potential Clinical Implications.Hand (New York, N.Y.) Sep 2022Lumbrical muscles originate in the palm from the 4 tendons of the flexor digitorum profundus and course distally along the radial side of the corresponding...
BACKGROUND
Lumbrical muscles originate in the palm from the 4 tendons of the flexor digitorum profundus and course distally along the radial side of the corresponding metacarpophalangeal joints, in front of the deep transverse metacarpal ligament. The first and second lumbrical muscles are typically innervated by the median nerve, and third and fourth by the ulnar nerve. A plethora of lumbrical muscle variants has been described, ranging from muscles' absence to reduction in their number or presence of accessory slips. The current cadaveric study highlights typical and variable neural supply of lumbrical muscles.
MATERIALS
Eight (3 right and 5 left) fresh frozen cadaveric hands of 3 males and 5 females of unknown age were dissected. From the palmar wrist crease, the median and ulnar nerve followed distally to their terminal branches. The ulnar nerve deep branch was dissected and lumbrical muscle innervation patterns were noted.
RESULTS
The frequency of typical innervations of lumbrical muscles is confirmed. The second lumbrical nerve had a double composition from both the median and ulnar nerves, in 12.5% of the hands. The thickest branch (1.38 mm) originated from the ulnar nerve and supplied the third lumbrical muscle, and the thinnest one (0.67 mm) from the ulnar nerve and supplied the fourth lumbrical muscle. In 54.5%, lumbrical nerve bifurcation was identified.
CONCLUSION
The complex innervation pattern and the peculiar anatomy of branching to different thirds of the muscle bellies are pointed out. These findings are important in dealing with complex and deep injuries in the palmar region, including transmetacarpal amputations.
Topics: Cadaver; Female; Hand; Humans; Male; Median Nerve; Muscle, Skeletal; Ulnar Nerve
PubMed: 33349041
DOI: 10.1177/1558944720963881