Dynamic Light Scattering from Semidilute Actin Solutions: A Study of Hydrodynamic Screening, Filament Bending Stiffness and the Effect of Tropomyosin/Troponin-Binding

Quasi-elastic light scattering (QELS) is applied to investigate the effect of the tropomyosin/troponin complex (Tm/Tn) on the stiffness of actin filaments. The importance of hydrodynamic screening in semidilute solutions is demonstrated. A new concentration dependent expression for the dynamic structure factor $g(\bm k,t)$ of semiflexible polymers in semidilute solutions is used to analyze the experimental QELS data. A concentration independent value for the bending modulus $\kappa$ is thus obtained. It increases by 50\% as a consequence of Tm/Tn binding in a 7:1:1 molar ratio of actin/Tm/Tn. In addition a new expression for the initial slope of the dynamic structure factor of a semiflexible polymer is used to determine the effective hydrodynamic diameter of the actin filament. Our results confirm the general relevance of the concept of (intrinsic) semiflexibility to polymer dynamics.Comment: 9 pages, RevTeX, 9 figures, all uuencoded gzipe

Combat‐Related Posttraumatic Stress Disorder and Comorbid Major Depression in U.S. Veterans: The Role of Deployment Cycle Adversity and Social Support

Posttraumatic stress disorder (PTSD) and major depressive disorder (MDD) commonly co‐occur in combat veterans, and this comorbidity has been associated with higher levels of distress and more social and economic costs compared to one disorder alone. In a secondary analysis of a multisite randomized controlled trial of a sample of veterans with combat‐related PTSD, we examined the associations among pre‐, peri‐, and postdeployment adversity, social support, and clinician‐diagnosed comorbid MDD. Participants completed the Deployment Risk and Resilience Inventory and the Beck Depression Inventory–II as well as structured clinical interviews for diagnostic status. Among 223 U.S. veterans of the military operations in Iraq and Afghanistan (86.9% male) with primary combat‐related PTSD, 69.5% had current comorbid MDD. After adjustment for sex, a linear regression model indicated that more concerns about family disruptions during deployment, f2 = 0.065; more harassment during deployment, f2 = 0.020; and lower ratings of postdeployment social support, f2 = 0.154, were associated with more severe self‐reported depression symptoms. Interventions that enhance social support as well as societal efforts to foster successful postdeployment reintegration are critical for reducing the mental health burden associated with this highly prevalent comorbidity in veterans with combat‐related PTSD.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/155948/1/jts22496_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/155948/2/jts22496.pd

The loss of a fellow service member: Complicated grief in postâ 9/11 service members and veterans with combatâ related posttraumatic stress disorder

Bereavement is a potent and highly prevalent stressor among service members and veterans. However, the psychological consequences of bereavement, including complicated grief (CG), have been minimally examined. Loss was assessed in 204 postâ 9/11, when service members and veterans with combatâ related posttraumatic stress disorder (PTSD) took part in a multicenter treatment study. Those who reported the loss of an important person completed the inventory of complicated grief (ICG; nâ =â 160). Over three quarters (79.41%) of the sample reported an important lifetime loss, with close to half (47.06%) reporting the loss of a fellow service member (FSM). The prevalence of CG was 24.75% overall, and nearly one third (31.25%) among the bereaved. CG was more prevalent among veterans who lost a fellow service member (FSM) (41.05%, nâ =â 39) compared to those bereaved who did not (16.92%, nâ =â 11; ORâ =â 3.41, 95% CI: 1.59, 7.36). CG was associated with significantly greater PTSD severity, functional impairment, traumaâ related guilt, and lifetime suicide attempts. Complicated grief was prevalent and associated with adverse psychosocial outcomes in veterans and service members with combatâ related PTSD. Clinicians working with this population should inquire about bereavement, including loss of a FSM, and screen for CG. Additional research examining CG in this population is needed.The loss of a fellow service member occurs commonly and is associated with complicated grief (CG) amongst service members and veterans with combatâ related posttraumatic stress disorder (PTSD). The presence of CG in this study was associated with more severe PTSD, guilt, and lifetime suicide attempts, as well as poorer functioning.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/139942/1/jnr24094_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/139942/2/jnr24094.pd