|
| ||
|
|
||
Biochemical Signals (biochemical + signal)
Selected AbstractsHierarchical Mechanochemical Switches in AngiostatinCHEMBIOCHEM, Issue 11 2006Fabio Grandi Abstract We wish to propose a novel mechanism by which the triggering of a biochemical signal can be controlled by the hierarchical coupling between a protein redox equilibrium and an external mechanical force. We have characterized this mechanochemical mechanism in angiostatin, and we have evidence that it can switch the access to partially unfolded structures of this protein. We have identified a metastable intermediate that is specifically accessible under thioredoxin-rich reducing conditions, like those met by angiostatin on the surface of a tumor cell. The structure of the same intermediate accounts for the unexplained antiangiogenic activity of angiostatin. These findings demonstrate a new link between redox biology and mechanically regulated processes. [source] Resting spore formation of aphid-pathogenic fungus Pandora nouryi depends on the concentration of infective inoculumENVIRONMENTAL MICROBIOLOGY, Issue 7 2008Zhi-Hong Huang Summary Resting spore formation of some aphid-pathogenic Entomophthorales is important for the seasonal pattern of their prevalence and survival but this process is poorly understood. To explore the possible mechanism involved in the process, Pandora nouryi (obligate aphid pathogen) interacted with green peach aphid Myzus persicae on cabbage leaves under favourable conditions. Host nymphs showered with primary conidia of an isolate (LC50: 0.9,6.7 conidia mm,2 4,7 days post shower) from air captures in the low-latitude plateau of China produced resting spores (azygospores), primary conidia or both spore types. Surprisingly, the proportion of mycosed cadavers forming resting spores (Pcfrs) increased sharply within the concentrations (C) of 28,240 conidia mm,2, retained high levels at 240,1760, but was zero or extremely low at 0.3,16. The Pcfrs,C relationship fit well the logistic equation Pcfrs = 0.6774/[1 + exp(3.1229,0.0270C)] (r2 = 0.975). This clarified for the first time the dependence of in vivo resting spore formation of P. nouryi upon the concentration of infective inoculum. A hypothesis is thus proposed that some sort of biochemical signals may exist in the host,pathogen interaction so that the fungal pathogen perceives the signals for prompt response to forthcoming host-density changes by either producing conidia for infecting available hosts or forming resting spores for surviving host absence in situ. [source] Targeted mechanical properties for optimal fluid motion inside artificial bone substitutesJOURNAL OF ORTHOPAEDIC RESEARCH, Issue 8 2009L.D. Blecha Abstract Our goal was to develop a method to identify the optimal elastic modulus, Poisson's ratio, porosity, and permeability values for a mechanically stressed bone substitute. We hypothesized that a porous bone substitute that favors the transport of nutriments, wastes, biochemical signals, and cells, while keeping the fluid-induced shear stress within a range that stimulates osteoblasts, would likely promote osteointegration. Two optimization criteria were used: (i) the fluid volume exchange between the artificial bone substitute and its environment must be maximal and (ii) the fluid-induced shear stress must be between 0.03 and 3 Pa. Biot's poroelastic theory was used to compute the fluid motion due to mechanical stresses. The impact of the elastic modulus, Poisson's ratio, porosity, and permeability on the fluid motion were determined in general and for three different bone substitute sizes used in high tibial osteotomy. We found that fluid motion was optimized in two independent steps. First, fluid transport was maximized by minimizing the elastic modulus, Poisson's ratio, and porosity. Second, the fluid-induced shear stress could be adjusted by tuning the bone substitute permeability so that it stayed within the favorable range of 0.03 to 3 Pa. Such method provides clear guidelines to bone substitute developers and to orthopedic surgeons for using bone substitute materials according to their mechanical environment. © 2009 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 27: 1082,1087, 2009 [source] Low-level mechanical strain induces extracellular signal-regulated kinase 1/2 activation in alveolar epithelial cellsRESPIROLOGY, Issue 6 2008Xiaobo HU Background and objective: The pattern and the degree of mechanical stimuli may determine cellular responses, but little is known about how low magnitude stimuli are converted into biochemical signals in alveolar epithelial cells (AEC). The aim of this study was to explore whether extracellular signal-regulated kinases 1/2 (ERK1/2) are activated by low-level strain in A549 cells and how mechanical factors affect ERK1/2 phosphorylation. Methods: A549 cells (an AEC line) were exposed to cyclic tensile strain via a four-point bending system, with strains of different magnitude (437, 874, 1748, 3496 µstrain), duration (5, 15, 30, 60, 120 min) and frequency (0.5, 1 Hz). Phosphorylation of ERK1/2 proteins was assessed by western blot. Results: Maximal ERK1/2 phosphorylation occurred in the 874 µstrain group (a 2.25-fold increase, P < 0.01). In this group, the peak response occurred after 30 min of exposure and slowly decreased to baseline after 90 min. Static strain did not produce a statistically significant increase in ERK1/2 phosphorylation, whereas a frequency of 0.5 Hz produced a 4.56-fold increase compared with the control (P < 0.05). A 10.87-fold increase in response with frequency of 1 Hz was found. Conclusion: Low-level strain activates ERK1/2 in A549 cells. ERK1/2 may be the key signalling molecules mediating strain-induced cellular responses. [source] | ||||||||||