Responses of photosynthetic properties and chloroplast ultrastructure of Bryum argenteum from a desert biological soil crust to elevated ultraviolet‐B radiation

Our understanding of plant responses to enhanced ultraviolet‐B (UV‐B) radiation has improved over recent decades. However, research on cryptogams is scarce and it remains controversial whether UV‐B radiation causes changes in physiology related to photosynthesis. To investigate the effects of supplementary UV‐B radiation on photosynthesis and chloroplast ultrastructure in Bryum argenteum Hedw., specimens were cultured for 10 days under four UV‐B treatments (2.75, 3.08, 3.25 and 3.41 W m^–2), simulating depletion of 0% (control), 6%, 9% and 12% of stratospheric ozone at the latitude of Shapotou, a temperate desert area of northwest China. Analyses showed malondialdehyde content significantly increased, whereas chlorophyll (Chl) fluorescence parameters and Chl contents decreased with increased UV‐B intensity. These results corresponded with changes in thylakoid protein complexes and chloroplast ultrastructure. Overall, enhanced UV‐B radiation leads to significant decreases in photosynthetic function and serious destruction of the chloroplast ultrastructure of B. argenteum. The degree of negative influences increased with the intensity of UV‐B radiation. These results may not only provide a potential mechanism for supplemental UV‐B effects on photosynthesis of moss crust, but also establish a theoretical basis for further studies of adaptation and response mechanisms of desert ecosystems under future ozone depletion.     

Biocontrol of Postharvest Rhizopus Decay of Peaches with Pichia caribbica

A new yeast antagonist, Pichia caribbica, isolated in our laboratory from the soil collected from unsprayed orchards, was evaluated for its biocontrol capability against Rhizopus stolonifer on peaches and the possible mechanisms involved. The decay incidence and lesion diameter of Rhizopus decay of peaches treated by P. caribbica were significantly reduced compared with the control fruits, and the higher the concentration of P. caribbica, the better the efficacy of the biocontrol. Rapid colonization of the yeast in peach wounds stored at 25 °C was observed. In peaches, the activities of peroxidase (POD), catalase (CAT), and phenylalanine ammonia-lyase (PAL) were significantly induced by P. caribbica treatment compared to those of the control fruits. All these results indicated that P. caribbica has a great potential for the development of commercial formulations to control postharvest Rhizopus decay of peaches. Its modes of action were based on competition for space and nutrients with pathogens, inducement of activities of defense-related enzymes such as POD, CAT, and PAL of peaches.     

Effects of ROS and caspase-3-like protein on the growth and aerenchyma formation of Potamogeton perfoliatus stem

Protoplasma - Aerenchyma formation plays an important role in the survival of Potamogeton perfoliatus in submerged environment. To understand the regulatory role of reactive oxygen species (ROS)...     

Development of a refined ex vivo model of peritoneal adhesion formation,and a role for connexin 43 in their development

Molecular and Cellular Biochemistry - Despite many advances across the surgical sciences, post-surgical peritoneal adhesions still pose a considerable risk in modern-day procedures and are highly...     

Mechanical Signaling on the Single Protein Level Studied Using Steered Molecular Dynamics

Efficient communication between the cell and its external environment is of the utmost importance to the function of multicellular organisms. While signaling events can be generally characterized as information exchange by means of controlled energy conversion, research efforts have hitherto mainly been concerned with mechanisms involving chemical and electrical energy transfer. Here, we review recent computational efforts addressing the function of mechanical force in signal transduction. Specifically, we focus on the role of steered molecular dynamics (SMD) simulations in providing details at the atomic level on a group of protein domains, which play a fundamental role in signal exchange by responding properly to mechanical strain. We start by giving a brief introduction to the SMD technique and general properties of mechanically stable protein folds, followed by specific examples illustrating three general regimes of signal transfer utilizing mechanical energy: purely mechanical, mechanical to chemical, and chemical to mechanical. Whenever possible the physiological importance of the example at hand is stressed to highlight the diversity of the processes in which mechanical signaling plays a key role. We also provide an overview of future challenges and perspectives for this rapidly developing field.     

Effects of tensile stress on the α1 nicotinic acetylcholine receptor expression in maxillofacial skeletal myocytes

The present study was to test the hypothesis that 11,12-epoxyeicosatrienoic acid (11,12-EET), a metabolic product of arachidonic acid by cytochrome P450 epoxygenase, regulates nitric oxide (NO) generation of the l-arginine/NO synthase (NOS) pathway in human platelets. Human platelets were incubated in the presence or absence of different concentrations of 11,12-EET for 2 h at 37°C, followed by measurements of activities of the l-arginine/NOS pathway. Incubation with 11,12-EET increased the platelet NOS activity, nitrite production, cGMP content, and the platelet uptake of l-[³H]arginine in a concentration-dependent manner. In addition, 11,12-EET attenuated intracellular free Ca²⁺ accumulation stimulated by collagen, which was at least partly mediated by EET-activated l-arginine/NOS pathway. It is suggested that 11,12-EET regulates platelet function through up-regulating the activity of the l-arginine/NOS/NO pathway.     

Changes in proteomics profile during maturation of marrow-derived dendritic cells treated with oxidized low-density lipoprotein

Increasing evidence suggests that dendritic cells (DCs) and oxidized low-density lipoprotein (ox-LDL) participate in atherosclerosis. However, few data on the molecular mechanisms of this process are available. To address this question, we used iTRAQ labeling followed by LC-MS/MS analysis to identify many proteins that changed markedly during the maturation of dendritic cells stimulated with ox-LDL. Among a total of 781 identified proteins, 93 were upregulated and 100 were downregulated. The major and significant changes in upregulated proteins were that ox-LDL not only affected the levels of intracellular cathepsins G, Z, D and S, but also significantly enhanced cathepsin S secretion by the treated cells. Our results may provide clues for a more comprehensive understanding the pathogenesis of atherosclerosis.     

Synchronous and early activation of planarian Hox genes and the re-specification of body axes during regeneration in Dugesia (G.) tigrina (Turbellaria; Tricladida)

Seven Hox cluster-related genes (Dthox-A to -G) have been isolated from the freshwater triclad Dugesia (G.) tigrina, their sequence compared to other Hox genes and their expression in intact and regenerating organisms analyzed by whole mount in situ hybridization. Sequence comparison analyses show high similarities of D. tigrina Hox genes to anterior and medial groups of coelomate Hox genes. Expression analyses show very early, synchronous, and overlapping expression of Dthox -A, -E, -G and -F in anterior, posterior and lateral regenerative tissues. At one hour of regeneration all Dthox genes studied showed a neat, clear expression at the wound boundary. Later, as the blastema grows, the expression area expands to more proximal regions covering the blastema and the distal postblastema regions. Blastemas formed by intercalary regeneration also show a synchronous expression of the same Hox genes though the onset of activation is much delayed. The finding that the same set of Hox genes is synchronously activated in anterior, posterior, intercalary and lateral regeneration is in sharp contrast to its well established role in specifying antero-posterior pattern during embryonic development. The implications of these results as regards ancestral versus co-opted roles of Hox genes in development and regeneration are discussed. This revised version was published online in July 2006 with corrections to the Cover Date.