Caveolin-1 recruitment to the trailing edge of motile cells results in focal adhesion disassembly and nascent interaction with actin stress fibers

The protein caveolin-1 has been shown to positively affect angiogenesis and vascular remodeling in vivo via studies using knockout mice. In fact, defects in these two processes are among the major hallmarks of an otherwise benign caveolin-null phenotype. Current dogma on the function of caveolin-1 does not predict or account for these deficits. The overall objective of the following studies was to uncover the role of caveolin-1 in angiogenesis and vascular remodeling through study of the protein in cell-substratum remodeling during cell motility in vitro.;In the first study, caveolin-1 and its parent organelle, caveolae, conspicuously polarize to the rear of migrating human umbilical vein endothelial cells. Moreover, caveolin-1 localizated at the cell rear is mutually exclusive with focal adhesion staining and lamellipodial protrusion. Acute caveolin-1 knockdown by small, interfering RNA diminished the ability of endothelial cells to polarize and migrate toward a chemotactic stimulus.;In the second study, live cell imaging was used to study the dynamics between caveolin-1, focal adhesions, and the actin cytoskeleton. Caveolin-1 recruitment and transient association with focal adhesions at the trailing edge resulted in adhesion sliding and disassembly, concomitant with recoil of the trailing edge into the cell body proper. Moreover, association of caveolin-1 with actin stress fibers previously associated with adhesions in the collapsing trailing edge was observed. Mouse embryonic fibroblasts from caveolin-1 null mice demonstrated defects in trailing edge recoil compared to control cells with no decrease in cell contractility, suggesting a specific deficit in adhesion disassembly. Furthermore, caveolin-null cells displayed a decrease in overall chemokinetic motility and an increase in directional persistence, an indication that caveolin-1 contributes to movement plasticity via trailing edge focal adhesion disassembly.;In the final study, the interaction of polarized caveolin-1 with actin stress fibers at the cell rear was characterized. Caveolin-1 predictably associated with the cell perimeter depending on the direction of cell migration. Importantly, inhibition on non-muscle myosin by blebbistatin treatment abrogated initial polarization of caveolin-1, but did not affect caveolin-1 that had already polarized. Using live cell imaging in conjunction with photobleaching, actin-associated caveolin-1 was found to be extremely static upon polarization to the cell rear. In contrast, the initial polarization of caveolin-1 to retracting areas was highly dynamic. Furthermore, GM1 internalization at the cell rear was negligible, confirming that polarized caveolae are highly static. Forced disruption of the actin cytoskeleton by cytochalasin D treatment resulted in caveolin-1 depolarization and disaggregation into small puncta displaying frenetic, kiss-and-run movement. Furthermore, cytoskeletal remodeling in response to change in direction of a cell resulted in similar caveolin depolarization.;In summary, stress fibers associate with and exert traction on trailing edge focal adhesions during cell motility. This traction force is prerequisite for caveolin-1 recruitment. Arrival and transient association of caveolin-1 with focal adhesions results in adhesion disassembly and stable interaction of caveolin with actin stress fibers. Thus, a novel mechanism in cellular mechanotransduction can be described, whereby cells utilize caveolin-1 recruitment to relieve strain generated at the cell perimeter by the actin cytoskeleton during movement. This novel function of caveolin-1 may analogously occur in vivo, beyond the context of endothelial cell migration. The deficits in angiogenesis and vascular remodeling seen in caveolin-1 null mice might thus be explained by the role of caveolin-1 in cell-substratum remodeling in response to strain

A comparison of two gluteus maximus EMG maximum voluntary isometric contraction positions

Background. The purpose of this study was to compare the peak electromyography (EMG) of the most commonly-used position in the literature, the prone bent-leg (90°) hip extension against manual resistance applied to the distal thigh (PRONE), to a novel position, the standing glute squeeze (SQUEEZE). Methods. Surface EMG electrodes were placed on the upper and lower gluteus maximus of thirteen recreationally active females (age = 28.9 years; height = 164 cm; body mass = 58.2 kg), before three maximum voluntary isometric contraction (MVIC) trials for each position were obtained in a randomized, counterbalanced fashion. Results. No statistically significant (p \u3c 0.05) differences were observed between PRONE (upper: 91.94%; lower: 94.52%) and SQUEEZE (upper: 92.04%; lower: 85.12%) for both the upper and lower gluteus maximus. Neither the PRONE nor SQUEEZE was more effective between all subjects. Conclusions. In agreement with other studies, no single testing position is ideal for every participant. Therefore, it is recommended that investigators employ multiple MVIC positions, when possible, to ensure accuracy. Future research should investigate a variety of gluteus maximus MVIC positions in heterogeneous samples

Health Care Resource Utilization for Children Requiring Prolonged Mechanical Ventilation via Tracheostomy

BACKGROUND: More children are discharged from ICUs on prolonged mechanical ventilation (PMV) via tracheostomy than ever before. These patients have long hospitalizations with high resource expenditure. Our objective was to describe the characteristics of these resource-intensive patients and to evaluate their costs of care. We hypothesized that subjects requiring PMV for neurologic diagnoses would have higher costs, longer hospital length of stay (LOS), and worse outcomes than those with primarily respiratory diagnoses. METHODS: We identified 50 pediatric subjects between January 2015 and December 2017 at our institution who had a new tracheostomy placement and were enrolled in a home mechanical ventilation program. Collected data included demographics, indication for tracheostomy, LOS, hospital costs, readmissions, and outcomes. We also compared subjects who required PMV for respiratory diagnoses versus neurologic diagnoses. RESULTS: Of 50 subjects, 41 were < 12 months old at the time of tracheostomy. Thirty-four subjects had a respiratory diagnosis requiring PMV, 14 had a neurologic diagnosis, and 2 had a cardiac diagnosis. The total initial hospitalization cost was $31,133,582, which averages to$622,671 per subject. The average initial hospitalization LOS was 155 d. Respiratory subjects had longer LOS and higher average costs than neurologic subjects. The average readmission rate was 2.16 per subject in the first year after discharge, and the average readmission cost per subject was $73,144. Eight subjects died in the first year after discharge, and 4 suffered a serious morbidity. CONCLUSIONS: This descriptive study evaluated the social and medical characteristics of subjects being discharged from the pediatric ICU with PMV via tracheostomy, as well as quantified the financial impact of their care. Those requiring PMV for neurologic diagnoses had shorter hospital LOS and lower hospital costs than those with respiratory diagnoses. No definitive differences in outcomes were found

Low serum albumin levels prior to pediatric allogeneic HCT are associated with increased need for critical care interventions and increased 6-month mortality

Poor nutritional status in HCT patients is a negative prognostic factor. There are no pediatric studies evaluating albumin levels prior to HCT and need for critical care interventions. We hypothesized that pediatric patients with low albumin levels, routinely measured 30 days (±10 days) prior to allogeneic HCT, have a higher risk of critical care interventions in the post-transplant period. We performed a 5-year retrospective study of pediatric patients who underwent allogeneic HCT for any indication. Patients were categorized based on albumin level. Hypoalbuminemia was defined as <3.1 g/dL. A total of 73 patients were included, with a median age of 7.4 years (IQR 3.3, 13.2). Patients with hypoalbuminemia had higher needs for critical care interventions including non-invasive ventilation (44% vs 8%, P=.01), mechanical ventilation (67% vs 17%, P<.01), and vasoactive therapy (56% vs 16%, P=.01). Patients with hypoalbuminemia also had a higher 6-month mortality (56% vs 17%, P=.02). Our data demonstrate that children undergoing allogeneic HCT with hypoalbuminemia in the pretransplant period are more likely to require critical care interventions and have higher 6-month mortality. These findings identify an at-risk population in which nutritional improvements may be instituted prior to HCT in hopes of improving outcomes

Availability of substance abuse treatment services in Spanish: A GIS analysis of Latino communities in Los Angeles County, California

<p>Abstract</p> <p>Background</p> <p>The percentage of Latino clients entering outpatient substance abuse treatment (OSAT) in the United States has increased significantly in the past 10 years. Evidence suggests that a lack of services in Spanish is a significant barrier to treatment access among Latinos.</p> <p>Methods</p> <p>Using a geographic information system (GIS) approach, data from the U.S. Census Bureau and the National Survey of Substance Abuse Treatment Services (N-SSATS) were analyzed to determine the geographic distance between OSAT facilities with services in Spanish and Latino communities throughout Los Angeles County, CA. Data from N-SSATS were also analyzed using logistic regression models to examine organizational characteristics and their association with offering services in Spanish. Our GIS methods are tested in their ability to provide baseline measures to inform future analysis comparing changes in demography and service infrastructure.</p> <p>Results</p> <p>GIS analysis revealed cold spots representing high-density Latino communities with extensive travel distance to facilities offering services in Spanish. The average linear distance between Latino communities and facilities offering Spanish-language services ranged from 2 to 6 miles, while the location of the cold spots pointed to a need for services in Spanish in a particular subregion of the county. Further, secondary data analysis revealed that, on average, being privately owned (<it>OR </it>= .23, 95% CI = 0.06-0.90) was associated with a lower likelihood of providing services in Spanish compared to public facilities. Additionally, a facility with a state license (<it>OR </it>= 2.08, 95% CI = 1.12-3.88) or a higher number of Medicaid recipients (<it>OR </it>= 2.98, 95% CI = 1.76-5.05) was twice as likely to offer services in Spanish.</p> <p>Conclusion</p> <p>Despite the significant presence of Latinos in L.A. County in 2000, low capacity was found in discrete Latino communities in terms of offering OSAT services in Spanish. Funding and regulation play a significant role in facilities' capacity to offer these services. Future studies should build from our multi-method approach to compare changes in population demography and system infrastructure and inform health care policy that seeks to improve providers' capacity to provide linguistically competent care.</p