Myosin light chain-actin interaction regulates cardiac contractility

The amino-terminal domain of the essential myosin light chain (MLC-1) binds to the carboxy terminus of the actin molecule. We studied the functional role of this interaction by two approaches: first, incubation of intact and chemically skinned human heart fibers with synthetic peptide corresponding to the sequences 5 through 14 (P5-14), 5 through 8 (P5-8), and 5 through 10 (P5-10) of the human ventricular MLC-1 (VLC-1) to saturate actin-binding sites, and second, incubation of skinned human heart fibers with a monoclonal antibody (MabVLC-1) raised against the actin-interacting N-terminal domain of human VLC-1 using P5-14 as antigen to deteriorate VLC-1 binding to actin. P5-14 increased isometric tension generation of skinned human heart fibers at both submaximal and maximal Ca2+ activation, the maximal effective peptide dosage being in the nanomolar range. A scrambled peptide of P5-14 with random sequence had no effects up to 10(-8) mol/L, ie, where P5-14 was maximally effective. P5-8 and P5-10 increased isometric force to the same extent as P5-14, but micromolar concentrations were required. Amplitude of isometric twitch contraction, rate of tension development, rate of relaxation, and shortening velocity at near-zero load of electrically driven intact human atrial fibers increased significantly on incubation with P5-14. These alterations were not associated with modulation of intracellular Ca2+ transients as monitored by fura 2 fluorescence measurements. Incubation of skinned human heart fibers with MabVLC-1 increased isometric tension at both submaximal and maximal Ca2+ activation levels, having a maximal effective concentration in the femtomolar range

Covalent RGD modification of the inner pore surface of polycaprolactone scaffolds

Scaffold production for tissue engineering was demonstrated by means of a hot compression molding technique and subsequent particulate leaching. The utilization of spherical salt particles as the pore-forming agent ensured complete interconnectivity of the porous structure. This method obviated the use of potentially toxic organic solvents. To overcome the inherent non-cell-adhesive properties of the hydrophobic polymer polycaprolactone (PCL) surface activation with a diamine was performed, followed by the covalent immobilization of the adhesion-promoting RGD-peptide. The wet-chemical approach was performed to guarantee modification throughout the entire scaffold structure. The treatment was characterized by means of chemical and physical methods with respect to an exclusive surface modification without altering the bulk properties of the polymer. RGD-modified scaffolds were tested in cell-culture experiments to investigate the initial attachment and the proliferation of three different cell types

A novel in vitro model for the study of plaque development in atherosclerosis.

For the study of atherogenesis in vitro, coculture systems have been devised, in which two or more cell types can be cultured in close contact to each other. Herein, we describe a novel in vitro model that aims at the simulation of the morphology of a normal muscular artery allowing for the study of the initial events in atherosclerosis. Using a modified fibrin gel as a scaffold for the coculture of endothelial cells (ECs) and smooth muscle cells (SMCs), we generated an autologous in vitro model with a multilayer growth of SMCs (intima-like structure) covered by an endothelium. The production of extracellular matrix (ECM) could be visualized histologically and verified by (i) ascorbic-acid dependent secretion of procollagen I into the supernatant and (ii) deposition of collagens I and III as well as laminin in the gel as assessed by immunohistochemistry. By BrdU-incorporation and Ki67 expression, the SMCs exhibited minimal proliferative activity, even when the culture period was extended to 6 weeks. Lipoprotein insudation was investigated under simulated hypo-, normo- and hypercholesterolemic conditions through addition of 0.5, 1 or 2 mg/mL LDL to the medium with subsequent time and dose dependent insudation of LDL. When human monocytes were added to the culture medium, infiltration and foam cell formation of macrophages and SMCs as well as expression of interleukin-8 (IL-8) was demonstrated. The in vitro model of the human vascular wall described herein appears to be suitable for the study of pivotal events in atherosclerotic plaque development. The applicability for long-term culture, the ability to study cell-matrix interactions and the opportunities for histomorphological and immunohistochemical examinations represent additional advantages of this model

A Multicenter Experience With a New Fenestrated-Branched Device for Endovascular Repair of Thoracoabdominal Aortic Aneurysms.

To investigate the outcomes of patients who were treated for thoracoabdominal aortic aneurysms (TAAAs) using custom-made fenestrated-branched stent-grafts. A consecutive series of 108 patients (mean age 73.5 years; 73 men) with TAAA were treated with E-xtra Design Engineering customized fenestrated-branched stent-grafts between November 2011 and January 2017. Data on baseline characteristics, procedures, and clinical follow-up were collected from 6 regional European surgical centers for retrospective analysis of endoleaks, reinterventions, and target vessel patency. The median aneurysm diameter was 6.75 cm (range 5.5-13). The distribution of the TAAA according to the modified Crawford classification of extent was 25 (24%) type I, 19 (17%) type II, 20 (18%) type III, 29 (27%) type IV, and 15 (14%) type V. Technical success was achieved in 95% (103/108) of cases. Major early perioperative complications occurred in 40 (37%) patients. The 30-day mortality was 9.2% (10/108), and perioperative spinal cord ischemia was observed in 6 (5.5%) patients [2 (1.8%) permanent]. During the mean follow-up of 17.6 months (range 3-52), 28 (26%) patients required late reintervention. Two patients died due to aneurysm- or procedure-related causes. The estimated survival rates at 1, 2, and 4 years were 87%, 84%, and 51%, respectively. The estimated target vessel patency rates at the same time points were 95%, 91%, and 90%, respectively. The freedom from reintervention estimates were 84% and 73% at 1 and 4 years, respectively. Endovascular repair of TAAA using Jotec customized fenestrated-branched stent-grafts appears to be safe and effective in the early to midterm. The considerable rate of secondary interventions indicates that further improvements, graft surveillance, and follow-up are required

In-vitro examination of the positive inotropic effect of caffeine and taurine, the two most frequent active ingredients of energy drinks

Abstract Background Our study aimed to evaluate changes in the contractile behavior of human myocardium after exposure to caffeine and taurine, the main active ingredients of energy drinks (EDs), and to evaluate whether taurine exhibits any inotropic effect at all in the dosages commonly used in EDs. Methods Myocardial tissue was removed from the right atrial appendages of patients undergoing cardiac surgery and prepared to obtain specimens measuring 4 mm in length. A total of 92 specimens were exposed to electrical impulses at a frequency of 75 bpm for at least 40 min to elicit their maximum contractile force before measuring the isometric contractile force (ICF) and duration of contraction (CD). Following this, each specimen was treated with either taurine (group 1, n = 29), or caffeine (group 2, n = 31) or both (group 3, n = 32). After exposure, ICF and CD measuring were repeated. Post-treatment values were compared with pre-treatments values and indicated as percentages. Results Exposure to taurine did not alter the contraction behavior of the specimens. Exposure to caffeine, in contrast, led to a significant increase in ICF (118 ± 03%, p < 0.01) und a marginal decrease in CD (95 ± 1.6%, p < 0.01). Exposure to a combination of caffeine and taurine also induced a statistically significant increase in ICF (124 ± 4%, p < 0.01) and a subtle reduction in CD (92 ± 1.4%, p < 0.01). The increase in ICF achieved by administration of caffeine was similar to that achieved by a combination of both caffeine and taurine (p = 0.2). The relative ICF levels achieved by administration of caffeine and a combination of taurine and caffeine, respectively, were both significantly higher (p < 0.01) than the ICF resulting from exposure to taurine only. Conclusion While caffeine altered the contraction behavior of the specimen significantly in our in-vitro model, taurine did not exhibit a significant effect. Adding taurine to caffeine did not significantly enhance or reduce the effect of caffeine