Disassembly and reconstitution of the Ca2+-sensitive thin filaments of vascular smooth muscle

AbstractThe Ca2+-sensitive thin filaments of aorta smooth muscle have been, disassembled into their constituent proteins, actin, tropomyosin and a 120-kDa protein. The 120-kDa protein bound to aorta actin-tropomyosin and inhibited its ability to activate myosin MgATPase. This inhibition correlated with the binding of one 120-kDa protein molecule per 29 actin monomers. Upon the addition of calmodulin to the actintropomyosin-120-kDa protein complex, the inhibition was relieved in 10−4 M Ca2+ but not 10−9 M Ca2+. The full release of inhibition was not accompanied by a full release of 120-kDa protein binding to actintropomyosin. A fully active, Ca2+-sensitive aorta thin filament has thus been reconstituted from just four components: actin, tropomyosin, 120-kDa protein and calmodulin

Bundling of actin filaments by aorta caldesmon is not related to its regulatory function

AbstractCa2+-sensitive thin filaments from vascular smooth muscle were disassembled into their constituent proteins, actin, tropomyosin and caldesmon. Caldesmon bound to both actin and to actin-tropomyosin and inhibited actin-tropomyosin activation of skeletal muscle myosin MgATPase. It also promoted the aggregation of actin or actin-tropomyosin into parallel aligned bundles. Quantitative electron microscopy measurements showed that with 1.1 μM actin-tropomyosin, 1.6 ± 0.5% (n = 3) of the filaments were in bundles. At 0.073 μM, caldesmon inhibited MgATPase activity by 50%, whereas bundling was 3.0 ± 1.3% (n = 4). At 0.37 μM caldesmon, MgATPase inhibition was 83% while 28.1 ± 6.9% (n = 4) of filaments were in bundles. Experiments at 4.4 μM in which MgATPase and bundling were measured in the same samples gave similar results. Small bundles of 2–3 filaments showed the most frequent occurrence at 1.1 μM actin. At 4.4 μM actin the most common bundle size was 3-5 filaments, with the occasional occurrence of large bundles consisting of up to 120 filaments. The incidence of bundling was the same in the presence and absence of tropomyosin. Thus caldesmon can induce the formation of actin bundles but this property bears no relationship to its inhibition of MgATPase activity

Ordering of timescales predicts applicability of quasi-linear theory in unstable flows

We discuss the applicability of quasilinear-type approximations for a turbulent system with a large range of spatial and temporal scales. We consider a paradigm fluid system of rotating convection with a vertical and horizontal temperature gradients. In particular, the interaction of rotating with the horizontal temperature gradient drives a ``thermal wind'' shear flow whose strength is controlled by a horizontal temperature gradient. Varying the parameters systematically alters the ordering of the shearing timescale, the convective timescale, and the correlation timescale. We demonstrate that quasilinear-type approximations work well when the shearing timescale or the correlation timescale is sufficiently short. In all cases, the Generalised Quasilinear approximation (GQL) systematically outperforms the Quasilinear approximation (QL). We discuss the consequences for statistical theories of turbulence interacting with mean gradients. We conclude with comments about the general applicability of these ideas across a wide variety of non-linear physical systems.Comment: 5 pages, 3 figure

Using Trends in Biometric Data to Predict Interest in Enrolling in an Employer-Sponsored National Diabetes Prevention Program Focusing on Diet and Exercise: A Retrospective Cohort Study

Background: Evidence-based lifestyle programs including the Diabetes Prevention Program can delay an individual’s risk of developing type 2 diabetes. Identifying which individuals are less likely to enroll in these programs and tailoring recruitment approaches to encourage participation among those with perceived barriers is an effective strategy to increase engagement in health promotion. This study aimed to identify the pre-enrollment differences in biometric trends between individuals with prediabetes who did and did not express interest in free worksite diabetes prevention programs.Subjects and Method: This retrospective cohort study was conducted among individuals in the Midwest enrolled in a private insurance plan from 2011 to 2014. Data was combined from annual biometric screenings and a health survey. Demographic characteristics were summarized for the study population (n=2,066). The dependent variable for this study was interest in the DPP, while the independent variables included body mass index, waist circumference, body weight, lipid measurements, and blood pressure. Linear mixed models with random intercepts were used to compare bio-metric trajectories for body mass index, waist circumference, body weight, lipid measurements (triglycerides and cholesterol), and blood pressure for the two groups.Results: No differences were observed in biometric trends for those who did and did not choose to enroll in the free worksite program.Conclusion: Examining pre-enrollment biometric trend data is a relatively novel approach to evaluating engagement in health programs. More research is needed to understand how this information can be used to identify an individual’s interest in enrolling in health programming

Characterisation of the effects of mutation of the caldesmon sequence 691glu-trp-leu-thr-lys-thr696 to pro-gly-his-tyr-asn-asn on caldesmon-calmodulin interaction

AbstractWe have investigated the functional properties of a mutant (Cg1) derived from the C-terminal 99 amino acids of chicken caldesmon, 658–756 (658C) where the sequence 691glu-trp-leu-thr-lys-thr696 is changed to pro-gly-his-tyr-asn-asn. Cg1 bound Ca2+-calmodulin with (1/7)th of the affinity as compared to 658C or whole caldesmon. NMR titrations indicate that the contacts of Ca2+-calmodulin with the Trp-722 region of the peptide are retained but that those at the mutated site are lost. Most importantly Ca2+-calmodulin is not able to reverse the Cg1-induced inhibition. We conclude that the interaction of calmodulin with this caldesmon sequence is crucial for the reversal of caldesmon inhibition of actin-tropomyosin activation of myosin ATPase. The results are interpreted in terms of multi-site attachment of actin and Ca2+-calmodulin to overlapping sequences in caldesmon domain 4b

Sertraline Treatment of Elderly Patients with Depression and Cognitive Impairment

Background There is little information on the efficacy and side effects of antidepressant treatment in elderly patients with combined depression and cognitive impairment without dementia (DEP-MCI), and it is unclear if cognitive performance improves with antidepressant response in these patients. Methods In 39 elderly DEP-MCI patients, changes in depression and cognitive impairment were evaluated with open sertraline treatment up to 200 mg/day for 12 weeks. Results Of the 26 completers, 17 were responders and nine were non-responders. Diagnostic subtype of depression was unrelated to response. ANCOVA on WAIS-R digit symbol percent change scores revealed a significant effect for responder status (F = 5.59, p < 0.03), and age (F = 0.24, p < 0.64) and education (F = 1.64, p < 0.22) were not significant covariates. From pre-trial to post-trial, responders improved in WAIS-R digit symbol percent change scores (Mean −10% SD 24) while non-responders declined (Mean 14% SD 18; t = 2.60, p < 0.02). Other neuropsychological measures were unrelated to response. Percent change in HRSD scores showed significant inverse correlations with percent change in several cognitive measures. Conclusions DEP-MCI patients showed moderate clinical response to sertraline treatment. When responders were compared to non-responders, cognitive improvement was limited to one measure of attention and executive function. Overall, there was little cognitive improvement with antidepressant treatment. The findings indirectly suggest that lack of improvement in cognition following treatment of depression in DEP-MCI patients may be associated with increased risk of meeting diagnostic criteria for dementia during follow-up