Genetic Contributions to Recovery following Brain Trauma: A Narrative Review.

Traumatic brain injury (TBI) is a frequently encountered form of injury that can have lifelong implications. Despite advances in prevention, diagnosis, monitoring, and treatment, the degree of recovery can vary widely between patients. Much of this is explained by differences in severity of impact and patient-specific comorbidities; however, even among nearly identical patients, stark disparities can arise. Researchers have looked to genetics in recent years as a means of explaining this phenomenon. It has been hypothesized that individual genetic factors can influence initial inflammatory responses, recovery mechanisms, and overall prognoses. In this review, we focus on cytokine polymorphisms, mitochondrial DNA (mtDNA) haplotypes, immune cells, and gene therapy given their associated influx of novel research and magnitude of potential. This discussion is prefaced by a thorough background on TBI pathophysiology to better understand where each mechanism fits within the disease process. Cytokine polymorphisms causing unfavorable regulation of genes encoding IL-1ß, IL-RA, and TNF-α have been linked to poor TBI outcomes like disability and death. mtDNA haplotype H has been correlated with deleterious effects on TBI recovery time, whereas haplotypes K, T, and J have been depicted as protective with faster recovery times. Immune cell genetics such as microglial differentially expressed genes (DEGs), monocyte receptor genes, and regulatory factors can be both detrimental and beneficial to TBI recovery. Gene therapy in the form of gene modification, inactivation, and editing show promise in improving post-TBI memory, cognition, and neuromotor function. Limitations of this study include a large proportion of cited literature being focused on pre-clinical murine models. Nevertheless, favorable evidence on the role of genetics in TBI recovery continues to grow. We aim for this work to inform interested parties on the current landscape of research, highlight promising targets for gene therapy, and galvanize translation of findings into clinical trials.

Describing Energy Expenditure in Children with a Chronic Disease: A Systematic Review.

Understanding energy expenditure in children with chronic disease is critical due to the impact on energy homeostasis and growth. This systematic review aimed to describe available literature of resting (REE) and total energy expenditure (TEE) in children with chronic disease measured by gold-standard methods of indirect calorimetry (IC) and doubly labeled water (DLW), respectively. A literature search was conducted using OVID Medline, Embase, CINAHL Plus, Cochrane, and Scopus until July 2023. Studies were included if the mean age of the participants was ≤18 y, participants had a chronic disease, and measurement of REE or TEE was conducted using IC or DLW, respectively. Studies investigating energy expenditure in premature infants, patients with acute illness, and intensive care patients were excluded. The primary outcomes were the type of data (REE, TEE) obtained and REE/TEE stratified by disease group. In total, 271 studies across 24 chronic conditions were identified. Over 60% of retrieved studies were published >10 y ago and conducted on relatively small population sizes (n range = 1-398). Most studies obtained REE samples (82%) rather than that of TEE (8%), with very few exploring both samples (10%). There was variability in the difference in energy expenditure in children with chronic disease compared with that of healthy control group across and within disease groups. Eighteen predictive energy equations were generated across the included studies. Quality assessment of the studies identified poor reporting of energy expenditure protocols, which may limit the validity of results. Current literature on energy expenditure in children with chronic disease, although extensive, reveals key future research opportunities. International collaboration and robust measurement of energy expenditure should be conducted to generate meaningful predictive energy equations to provide updated evidence that is reflective of emerging disease-modifying therapies. This study was registered in PROSPERO as CRD42020204690.

Neutrophil-to-Lymphocyte Ratio as a Predictor of Mortality for COVID-19-Related Acute Respiratory Distress Syndrome (ARDS) Patients Requiring Extracorporeal Membrane Oxygenation Therapy.

BACKGROUND: The neutrophil-to-lymphocyte ratio (NLR) has been studied as an indicator of systemic inflammation and as a prognostic tool in multiple areas of medicine. Previous research has suggested that higher NLR and rapid increase to peak NLR are associated with poorer outcomes in patients with coronavirus disease 2019 (COVID-19), particularly in those experiencing acute respiratory distress syndrome (ARDS). Within vascular surgery, there is data to suggest a positive correlation between elevated pre-extracorporeal membrane oxygenation (ECMO) NLR and higher rates of mortality following major procedures. This study explores the prognostic value of peri-ECMO NLR in patients requiring veno-venous ECMO (VV-ECMO) therapy for COVID-19-related ARDS. The objective of this study was to explore the utility of pre-ECMO NLR as an easily accessible prognostic factor for patients suffering from COVID-19-associated ARDS that require VV-ECMO. METHODS: This was a retrospective cohort study within a tertiary care hospital conducted between April 2020 and January 2021. Patients requiring VV-ECMO therapy for COVID-19-associated ARDS were included. Peri-ECMO NLR values, length of stay (LOS), duration on VV-ECMO, and discharge status were recorded. Receiver operating characteristic (ROC) curve analysis and Youden's J statistics were performed to calculate a cut-off value of 11.005 for pre-ECMO NLR and 17.616 for on-ECMO NLR. Pre-ECMO and on-ECMO Kaplan-Meyer curves were generated for two groups of patients, those above and below NLR cutoff thresholds. Two-sample T-test was performed to test for significant differences in LOS and duration on VV-ECMO. RESULTS: Twenty-six patients were included in the study for final analyses. There was an overall mortality of 39% (n = 10). ROC curve analysis and Youden's J statistic revealed an optimal cut-off value of pre-ECMO NLR = 11.005 and on-ECMO NLR = 17.616. Results showed that the patient group placed on VV-ECMO with a pre-ECMO NLR less than 11.005 experienced no mortality (n = 7) and a median LOS of 28 days (IQR = 14.5-64.5 days). The patient group on VV-ECMO with a pre-ECMO NLR greater than 11.005 (n = 19) included all mortality (n = 10) and had a median LOS of 49 days (IQR = 25.5-63.5 days). The patient group with on-ECMO NLR less than 17.616 also conferred a survival advantage. There was no significant difference in LOS or duration on VV-ECMO between the two groups, pre-ECMO or on-ECMO. CONCLUSIONS:  A pre-ECMO NLR cutoff was identified and offered statistically significant prognostic value in predicting mortality. A lower on-ECMO NLR value also indicated a survival advantage. Future studies should include NLR within multivariate models to better discern the effect of NLR and elucidate how it can be factored into clinical decision-making. Importantly, this data can be expanded to assess the predictive value of NLR pertaining to the COVID-19-induced ARDS population and matched cohorts.

Direct aortic access for endovascular thoracoabdominal aneurysm repair using a bifurcated endograft as a branched device.

Aortic aneurysms (AA) are a common complication in patients with large-vessel vasculitis, such as chronic phase Takayasu arteritis, that often require surgical management to prevent a lethal rupture. Historically, mainstay of treatment for AA in the setting of arteritis was traditional open repair. However, in this case study an alternative surgical approach was devised to successfully treat an extent III thoracoabdominal AA in a patient with a diagnosis of Takayasu arteritis and a complex surgical history that made her high risk for an open surgical intervention. This case study summarizes a hybrid surgical approach that successfully excluded a thoracoabdominal AA and revascularized the superior mesenteric artery and left renal artery, by directly accessing the infrarenal aorta and using a bifurcated abdominal aortic endograft as a two-vessel branched device.

The dual distinct role of telomerase in repression of senescence and myofibroblast differentiation.

Many aging related diseases such as cancer implicate the myofibroblast in disease progression. Furthermore genesis of the myofibroblast is associated with manifestation of cellular senescence of unclear significance. In this study we investigated the role of a common regulator, namely telomerase reverse transcriptase (TERT), in order to evaluate the potential significance of this association between both processes. We analyzed the effects of TERT overexpression or deficiency on expression of CDKN2A and ACTA2 as indicators of senescence and differentiation, respectively. We assess binding of TERT or YB-1, a repressor of both genes, to their promoters. TERT repressed both CDKN2A and ACTA2 expression, and abolished stress-induced expression of both genes. Conversely, TERT deficiency enhanced their expression. Altering CDKN2A expression had no effect on ACTA2 expression. Both TERT and YB-1 were shown to bind the CDKN2A promoter but only YB-1 was shown to bind the ACTA2 promoter. TERT overexpression inhibited CDKN2A promoter activity while stimulating YB-1 expression and activation to repress ACTA2 gene. TERT repressed myofibroblast differentiation and senescence via distinct mechanisms. The latter was associated with TERT binding to the CDKN2A promoter, but not to the ACTA2 promoter, which may require interaction with co-factors such as YB-1.

Healing and Functional Results of Dermal Allograft Augmentation of Complex and Revision Rotator Cuff Repairs.

BACKGROUND: Primary rotator cuff repairs in complex cases (older patient age, larger tear sizes, chronic tears) and revision repairs are at high risk for failure of healing. PURPOSE: To examine clinical outcomes and healing rates in complex and revision rotator cuff repairs with dermal allograft augmentation. STUDY DESIGN: Case series; Level of evidence, 4. METHODS: A retrospective study was made of cases performed by 3 fellowship-trained surgeons via a uniform technique involving rotator cuff repairs with allograft augmentation. In all cases, a 1.5-mm, human, decellularized dermal graft was tied on top of the tendon at the medial row and compressed to the rotator cuff footprint using a double-row technique. Postoperative magnetic resonance imaging (MRI) was performed at a minimum of 6 months and American Shoulder and Elbow Surgeons (ASES), Single Assessment Numeric Evaluation (SANE), and 12-Item Short Form Health Survey scores were collected at a minimum of 2 years postoperatively. RESULTS: A total of 35 patients (23 revision repairs, 12 primary complex repairs) were included. The mean patient age was 57.9 years (range, 41.0-70.5 years). All shoulders had 2-tendon tears (supraspinatus and infraspinatus), and 8 included the upper 50% of the subscapularis. At a minimum of 2 years after surgery (mean, 3.2 years), mean ASES and SANE scores improved from 42.4 and 35.3 to 77.6 and 73.5, respectively (P < .001). In the 23 patients (66%) with postoperative MRI evaluation, 11 (48%) had images showing the tendons were retorn. ASES (89.7 vs 66.4; P = .04) and SANE (84.1 vs 50.5; P = .02) scores were higher in healed patients than those with retears. The retear group had a higher degree of preoperative fatty atrophy of the infraspinatus (P = .024). CONCLUSION: Double-row arthroscopic repair with dermal allograft augmentation of complex and revision rotator cuff tears led to improved functional outcomes. Approximately half of patients experienced a failure of healing, which was associated with poorer functional results.

The effect of critical shoulder angle on functional compensation in the setting of cuff tear arthropathy.

INTRODUCTION: Critical shoulder angle (CSA) has been shown to influence rates of rotator cuff tears and glenohumeral arthritis with a larger CSA associated with rotator cuff tears and a smaller CSA associated with glenohumeral arthritis. There has been no study to determine whether such radiographic measurement influences the function of patients with demonstrated cuff tear arthropathy (CTA). The purpose of this study was to examine whether smaller CSAs were associated with greater range of motion (ROM) in patients diagnosed with CTA. MATERIALS AND METHODS: Ninety-three patients with a diagnosis of CTA with adequate anteroposterior shoulder radiographs were included in the study. Patient demographics were recorded. The presence of a rotator cuff tear was confirmed via advanced imaging or when applicable via the operative report. Patients' ROM was evaluated through the physician's office note. Shoulder radiographs were used to measure CSA, glenoid inclination, acromial index (AI), and acromiohumeral interval. Patient ROM was measured and grouped into 2 different tiered cohorts: cohort 1 had 4 subgroups of forward elevation (FE) (ie, ≤45°, 45°-90°, 91°-135°, and 136°-180°) and cohort 2 had 2 subgroups of FE (ie, ≤90° and >90°). We then analyzed FE between these groups in the context of their radiographic measurements. RESULTS: The average patient age was 73.8 ± 8.0 years. There was no significant difference in acromiohumeral interval. AI was found to be significantly different between patients presenting with ≤90° in FE compared with those >90° (P = .02). Average CSA was significantly lower in patients with FE greater than 90° at 33.7° ± 3.9° compared with patients with FE less than 90° at 37.1° ± 6.3° (P = .002). There was also a significant difference with regard to CSAs, with those patients with FE ≤ 45° having a mean CSA of 38.2° ± 8.3° compared with those patients with FE ≥ 135° having a mean CSA of 33.3° ± 4.3° (P = .02). CONCLUSION: Patients diagnosed with CTA can significantly vary in their shoulder function and ability to forward elevate. Lower CSA was found to be associated with higher FE in patients with CTA preoperatively. In addition, patients with a smaller AI were also found to have better overhead function. Analyzing CSA on plain radiographs may help manage functional expectations in patients with CTA.

Selective Intraoperative Vasopressor Use Is Not Associated with Increased Risk of DIEP Flap Complications.

BACKGROUND: During deep inferior epigastric perforator (DIEP) flap cases, anesthesiologists commonly avoid intravenous vasopressor administration because of the theoretical concern of inducing vasospasm, thrombosis, or congestion in the vessels of the anastomosis, potentially resulting in poor flap perfusion and ischemia and necessitating revision. In the setting of hypotension, however, vasopressor administration may actually improve outcomes by augmenting flap perfusion by means of increased mean arterial pressure. METHODS: The authors reviewed 475 consecutive DIEP flap cases in 333 patients at a single large academic medical center over a 3-year period, addressing potential confounders using univariate analyses. RESULTS: Ephedrine administration was significantly associated with decreased risk of intraoperative flap complications (OR, 0.88), including vasospasm, thrombosis, and congestion requiring revision, compared with controls, after controlling for the severity and duration of hypotension. Phenylephrine had no significant association with complication rates. Vasopressor administration was not associated with an increased risk of reoperation in the setting of necrosis within 60 days. CONCLUSIONS: Ephedrine treatment for hypotension during DIEP flap cases is associated with decreased intraoperative flap complication rates compared with controls who did not receive vasopressors, whereas phenylephrine has no significant association. The common clinical practice of complete abstinence from vasopressors out of concern for worsening DIEP flap outcomes is not supported by this study. CLINICAL QUESTION/LEVEL OF EVIDENCE: Therapeutic, III.

Advances in Guanidine Ligand Design: Synthesis of a Strongly Electron-Donating, Imidazolin-2-iminato Functionalized Guanidinate and its Properties on Iron.

Imidazolin-2-imines (ImRN-), derived from N-heterocylic carbenes, have been shown to be strong electron donors when directly coordinated to metals or when used as a substituent in larger ligand frameworks. In an attempt to enhance the electron-donating properties of the popular guanidine ligand class, the effect of appending an ImRN- backbone onto a guanidinate scaffold was investigated. Addition of 1 equiv of [Li(Et2O)][Im tBuN] to the aryl carbodiimide (dippN)2C (dipp = 2,6-diisopropylphenyl) cleanly affords the lithium Im tBuN-functionalized guanidinate [Li(THF)2][(Im tBuN)C(Ndipp)2] (1). Subsequent metalation of the ligand with FeBr2 gives the yellow Fe(II) complex {[(Im tBuN)C(Ndipp)2]FeBr}2 (4) in good yield. Solid-state structural analyses of both 1 and 4 shows the Im tBuN- group acts as a non-coordinating backbone substituent. Direct structural comparison of 4 to the closely related guanidinate and ketimine-guanidinate complexes {[(X)C(Ndipp)2]FeBr}2 (X = t Bu2C=N (5); N( i Pr)2 (6)), differing only in their backbone, reveals a detectable resonance contribution of the Im tBuN- group to the guanidinate ligand electronic structure. Moreover, the Fe(II)/Fe(III) redox couple of 4 (E1/2 = -0.67 V) is cathodically shifted by greater than 200 mV from the oxidation potentials of 5 (E1/2 = -0.42 V) and 6 (E1/2 = -0.45 V), demonstrating the [(Im tBuN)C(Ndipp)2]- system to be a quantifiably superior electron donor.

Neuraxial Anesthesia in Parturients with Thrombocytopenia: A Multisite Retrospective Cohort Study.

BACKGROUND: The primary aim of this study was to estimate the risk of neuraxial hematoma associated with neuraxial anesthetic procedures in thrombocytopenic parturients. METHODS: A multicenter retrospective cohort study design was used to estimate the risk for spinal-epidural hematoma in parturients with a platelet count of <100,000/mm receiving neuraxial anesthesia and the risk of complications in thrombocytopenic parturients who receive general anesthesia. RESULTS: No cases of spinal hematoma were observed in 102 thrombocytopenic parturients receiving epidural analgesia or 71 receiving spinal anesthesia. Including data from the previous published series (total n = 499), the exact binomial 95% confidence interval for the risk of spinal-epidural hematoma was 0% to 0.6%. Given the small number of patients at each specific platelet count, the theoretical risks at individual platelet count strata are presented. Overall aggregate serious morbidity rate in women who received general anesthesia secondary to thrombocytopenia was 6.5% (95% confidence interval, 2.1%-14.5%). CONCLUSIONS: Our work supports the relative maternal safety of neuraxial anesthesia in parturients with mild thrombocytopenia and estimates the maternal complication rate associated with the avoidance of neuraxial anesthesia. Remaining uncertainties at lower platelet counts make a national "low platelet" registry critical to a more accurate assessment of the risk of epidural hematoma and would aid in standardization of anesthesia practice.

Minimally invasive aortic valve replacement with orthotopic liver transplantation: report of a case.

Cardiac surgery and liver transplantation (LT) are rarely performed at the same time, because of the potential risks of coupling two such complex surgical procedures [1-3]. This combined surgery is typically reserved for patients with structural heart disease, including multivessel obstructive coronary artery disease and severe valvular disease with heart failure and end-stage liver disease, in whom the untreated organ may decompensate if only one organ is addressed [4]. Combined aortic valve replacement (AVR) and LT is the rarest of such combined surgery, with only ten cases published previously. We present the first reported case of combined minimally invasive AVR and LT and review the literature on similar combined surgery.

Effect of age and cytoskeletal elements on the indentation-dependent mechanical properties of chondrocytes.

Articular cartilage chondrocytes are responsible for the synthesis, maintenance, and turnover of the extracellular matrix, metabolic processes that contribute to the mechanical properties of these cells. Here, we systematically evaluated the effect of age and cytoskeletal disruptors on the mechanical properties of chondrocytes as a function of deformation. We quantified the indentation-dependent mechanical properties of chondrocytes isolated from neonatal (1-day), adult (5-year) and geriatric (12-year) bovine knees using atomic force microscopy (AFM). We also measured the contribution of the actin and intermediate filaments to the indentation-dependent mechanical properties of chondrocytes. By integrating AFM with confocal fluorescent microscopy, we monitored cytoskeletal and biomechanical deformation in transgenic cells (GFP-vimentin and mCherry-actin) under compression. We found that the elastic modulus of chondrocytes in all age groups decreased with increased indentation (15-2000 nm). The elastic modulus of adult chondrocytes was significantly greater than neonatal cells at indentations greater than 500 nm. Viscoelastic moduli (instantaneous and equilibrium) were comparable in all age groups examined; however, the intrinsic viscosity was lower in geriatric chondrocytes than neonatal. Disrupting the actin or the intermediate filament structures altered the mechanical properties of chondrocytes by decreasing the elastic modulus and viscoelastic properties, resulting in a dramatic loss of indentation-dependent response with treatment. Actin and vimentin cytoskeletal structures were monitored using confocal fluorescent microscopy in transgenic cells treated with disruptors, and both treatments had a profound disruptive effect on the actin filaments. Here we show that disrupting the structure of intermediate filaments indirectly altered the configuration of the actin cytoskeleton. These findings underscore the importance of the cytoskeletal elements in the overall mechanical response of chondrocytes, indicating that intermediate filament integrity is key to the non-linear elastic properties of chondrocytes. This study improves our understanding of the mechanical properties of articular cartilage at the single cell level.

Identification of a 3Kbp mechanoresponsive promoter region in the human cartilage oligomeric matrix protein gene.

Expression of chondrocyte-specific genes is regulated by mechanical force. However, despite the progress in identifying the signal transduction cascades that activate expression of mechanoresponsive genes, little is known about the transcription factors that activate transcription of mechanoresponsive genes. The DNA elements that confer mechanoresponsiveness within a cartilage gene promoter have yet to be identified. We have established an experimental system to identify the DNA elements and transcription factors that mediate the mechanoresponse of a promoter to nominal compressive stress in primary human chondrocytes and stem cells in a three-dimensional culture system. Our results demonstrate that the proximal 3 Kb of the human cartilage oligomeric matrix protein promoter is sufficient to mediate a mechanoresponse in human articular chondrocytes and stem cells, and that the magnitude of mechanoresponse correlates to the regulation of the endogenous gene at the RNA and protein level. This information is critical to understanding how mechanical force regulates the transcriptional activation of cartilage genes in three-dimensional culture.

Perioperative management of partial face transplantation involving a heparin antibody-positive donor.

Heparin-induced thrombocytopenia (HIT) is an immunologic condition that may lead to thrombosis. We present a case of face transplantation from a donor who had suffered a severe stroke, possibly from HIT, during cardiac surgery. The procedure was planned to include full heparinization. The anesthesia team was involved in the early planning phase and had detailed access to the donor's medical history; alternative anticoagulation for the donor and recipient was suggested so as to avoid a possible complication.

Identification and development of novel inhibitors of Toxoplasma gondii enoyl reductase.

Toxoplasmosis causes significant morbidity and mortality, and yet available medicines are limited by toxicities and hypersensitivity. Because improved medicines are needed urgently, rational approaches were used to identify novel lead compounds effective against Toxoplasma gondii enoyl reductase (TgENR), a type II fatty acid synthase enzyme essential in parasites but not present in animals. Fifty-three compounds, including three classes that inhibit ENRs, were tested. Six compounds have antiparasite MIC(90)s < or = 6 microM without toxicity to host cells, three compounds have IC(90)s < 45 nM against recombinant TgENR, and two protect mice. To further understand the mode of inhibition, the cocrystal structure of one of the most promising candidate compounds in complex with TgENR has been determined to 2.7 A. The crystal structure reveals that the aliphatic side chain of compound 19 occupies, as predicted, space made available by replacement of a bulky hydrophobic residue in homologous bacterial ENRs by Ala in TgENR. This provides a paradigm, conceptual foundation, reagents, and lead compounds for future rational development and discovery of improved inhibitors of T. gondii.

Volumetric and voxel-based morphometry findings in autism subjects with and without macrocephaly.

This study sought to replicate Herbert et al. (2003a), which found increased overall white matter (WM) volume in subjects with autism, even after controlling for head size differences. To avoid the possibility that greater WM volume in autism is merely an epiphenomena of macrocephaly overrepresentation associated with the disorder, the current study included control subjects with benign macrocephaly. The control group also included subjects with a reading disability to insure cognitive heterogeneity. WM volume in autism was significantly larger, even when controlling for brain volume, rate of macrocephaly, and other demographic variables. Autism and controls differed little on whole-brain WM voxel-based morphometry (VBM) analyses suggesting that the overall increase in WM volume was non-localized. Autism subjects exhibited a differential pattern of IQ relationships with brain volumetry findings from controls. Current theories of brain overgrowth and their importance in the development of autism are discussed in the context of these findings.

Large-scale functional annotation and expanded implementations of the P{wHy} hybrid transposon in the Drosophila melanogaster genome.

Whole genome sequencing of the model organisms has created increased demand for efficient tools to facilitate the genome annotation efforts. Accordingly, we report the further implementations and analyses stemming from our publicly available P{wHy} library for Drosophila melanogaster. A two-step regime-large scale transposon mutagenesis followed by hobo-induced nested deletions-allows mutation saturation and provides significant enhancements to existing genomic coverage. We previously showed that, for a given starting insert, deletion saturation is readily obtained over a 60-kb interval; here, we perform a breakdown analysis of efficiency to identify rate-limiting steps in the process. Transrecombination, the hobo-induced recombination between two P{wHy} half molecules, was shown to further expand the P{wHy} mutational range, pointing to a potent, iterative process of transrecombination-reconstitution-transrecombination for alternating between very large and very fine-grained deletions in a self-contained manner. A number of strains also showed partial or complete repression of P{wHy} markers, depending on chromosome location, whereby asymmetric marker silencing allowed continuous phenotypic detection, indicating that P{wHy}-based saturational mutagenesis should be useful for the study of heterochromatin/positional effects.

Distribution of basal membrane complex components in elongating lens fibers.

PURPOSE: To localize specific components of the Basal Membrane Complex (BMC) of elongating lens fibers at defined points in their migration to the posterior sutures. METHODS: Normal, juvenile (4-6 week old) Sprague-Dawley rat lenses (n=46) were utilized. Lenses were either decapsulated to obtain whole mounts of lens capsules or sectioned with a vibrating knife microtome. Sections (100 microm thick) were cut parallel to the equatorial plane, beginning at the posterior pole. On both sections and whole mounts, F-actin was localized using phalloidin-FITC while myosin, cadherins, and beta1 integrin were localized using immunofluorescent labeling. Specimens were visualized on a laser scanning confocal microscope. RESULTS: F-actin labeling in the equatorial and peri-sutural regions was predominately localized to the periphery of basal fiber ends (consistent with our prior results). At sutures, labeling for F-actin in the BMC was rearranged into numerous small profiles. Furthermore, labeling intensity for F-actin was increased at sutures. Myosin was present in the BMC in all locations examined as a diffuse plaque at fiber ends. Similarly, beta1 integrin was also distributed throughout the BMC within the actin-rich borders in all regions except adjacent to and at the suture branches. In that location immunofluorescence for beta1 integrin appeared to be reduced. In the equatorial, lateral-posterior, and peri-sutural regions, cadherin showed strong localization around the periphery of basal fiber ends. However, cadherin labeling was markedly reduced in the BMC as fibers detached from the capsule and abutted to form sutures (i.e. in the sutural region). Cadherin was concentrated along the short faces of elongating fiber mid-segments. CONCLUSIONS: It appears that F-actin, cadherin and beta1 integrin components of the BMC undergo controlled rearrangements in the final stages of migration and detachment from the capsule.