The relationships between microbiological attributes and soil and litter quality in pure and mixed stands of native tree species in southeastern Bahia, Brazil

This study was conducted to link soil and litter microbial biomass and activity with soil and litter quality in the surface layer for different pure and mixed stands of native tree species in southeastern Bahia, Brazil. The purpose of the study was to see how strongly the differences among species and stands affect the microbiological attributes of the soil and to identify how microbial processes can be influenced by soil and litter quality. Soil and litter samples were collected from six pure and mixed stands of six hardwood species (Peltogyne angustifolia, Centrolobium robustum, Arapatiella psilophylla, Sclerolobium chrysophyllum, Cordia trichotoma, Macrolobium latifolium) native to the southeastern region of Bahia, Brazil. In plantations of native tree species in humid tropical regions, the immobilization efficiency of C and N by soil microbial biomass was strongly related to the chemical quality of the litter and to the organic matter quality of the soil. According to the variables analyzed, the mixed stand was similar to the natural forest and dissimilar to the pure stands. Litter microbial biomass represented a greater sink of C and N than soil microbial biomass and is an important contributor of resources to tropical soils having low C and N availability.     

Phytochelatins govern zinc/copper homeostasis and cadmium detoxification in Cuscuta campestris parasitizing Daucus carota

Cuscuta sp., known with the common name of “dodder”, is an obligate parasite capable of invading stems and leaves of a wide range of host plants. Dodder stem usually coils counterclockwise around the host and, within a few days, develops haustorial structures at each point of contact. As soon as dodder haustoria reach host vascular bundles, they start tapping water, photosynthates and minerals. Metal ions such as zinc (Zn) and copper (Cu) are essential for dodder growth and metabolism, although an exceedingly high (over-homeostatic) supply of these micronutrients can result in growth inhibition and cellular toxicity. Even more so, non-essential metals such as cadmium (Cd), if transferred from the host to the parasite, need to be neutralized by timely detoxification mechanisms. In this work, we showed that Cuscuta campestris Yuncker establishes effective haustorial connections with leaf petioles and blades of Daucus carota L. (carrot), with the consequent transfer of Cd and essential metals (such as Zn and Cu) from the host vascular bundles to the parasite. Following up to this point, we detected the presence in the parasite of significant amounts of glutathione and phytochelatins, even in the absence of Cd exposure. This suggests that thiol peptides in dodder might be particularly important for Zn and Cu homeostasis as well as for Cd detoxification. Finally, we demonstrated that dodder is capable of synthesizing phytochelatins on its own, rather than massively importing them from the host, and also provided evidence for the existence of an endogenous, constitutively expressed, dodder's phytochelatin synthase.     

Present status and new perspectives in laser welding of vascular tissues

The laser welding of biological tissues is a particular use of lasers in surgery. The technique has been proposed since the 1970s for surgical applications, such as repairing blood vessels, nerves, tendons, bronchial fistulae, skin and ocular tissues. In vascular surgery, two procedures have been tested and optimized in animal models, both ex vivo and in vivo, in order to design different approaches for blood vessels anastomoses and for the repair of vascular lesions: the laser-assisted vascular anastomosis (LAVA) and the laser-assisted vessel repair (LAVR). Sealing tissues by laser may overcome the problems related to the use of conventional closuring methods that are generally associated with various degrees of vascular wall damage that can ultimately predispose to vessel thrombosis and occlusion. In fact, the use of a laser welding technique provides several advantages such as simplification of the surgical procedure, reduction of the operative time, suppression of bleeding, and may guarantee an optimal healing process of vascular structures, very similar to restitutio ad integrum. Despite the numerous preclinical studies performed by several research groups, the clinical applications of laser-assisted anastomosis or vessel repair are still far off. Substantial breakthrough in the laser welding of biological tissues may come from the advent of nanotechnologies. Herein we describe the present status and the future perspectives in laser welding of vascular structures.     

Interaction with damaged vessel wall in vivo in humans induces platelets to express CD40L resulting in endothelial activation with no effect of aspirin intake

Activated platelets express CD40L on their plasma membrane and release the soluble fragment sCD40L. The interaction between platelet surface CD40L and endothelial cell CD40 leads to the activation of endothelium contributing to atherothrombosis. Few studies have directly demonstrated an increased expression of platelet CD40L in conditions of in vivo platelet activation in humans, and no data are available on its relevance for endothelial activation. We aimed to assess whether platelets activated in vivo at a localized site of vascular injury in humans express CD40L and release sCD40L, whether the level of platelet CD40L expression attained in vivo is sufficient to induce endothelial activation, and whether platelet CD40L expression is inhibited by aspirin intake. We used the skin-bleeding-time test as a model to study the interaction between platelets and a damaged vessel wall by measuring CD40L in the blood emerging from a skin wound in vivo in healthy volunteers. In some experiments, shed blood was analyzed before and 1 h after the intake of 500 mg of aspirin. Platelets from the bleeding-time blood express CD40L and release soluble sCD40L, in a time-dependent way. In vivo platelet CD40L expression was mild but sufficient to induce VCAM-1 expression and IL-8 secretion in coincubation experiments with cultured human endothelial cells. Moreover, platelets recovered from the bleeding-time blood activated endothelial cells; an anti-CD40L antibody blocked this effect. On the contrary, the amount of sCD40L released by activated platelets at a localized site of vascular injury did not reach the concentrations required to induce endothelial cell activation. Soluble monocyte chemoattractant protein-1, a marker of endothelium activation, was increased in shed blood and correlated with platelet CD40L expression. Aspirin intake did not inhibit CD40L expression by platelets in vivo. We concluded that CD40L expressed by platelets in vivo in humans upon contact with a damaged vessel wall activates endothelium; aspirin treatment does not inhibit this mechanism.     

Molecular dynamics simulation of β₂-microglobulin in denaturing and stabilizing conditions

β₂‐Microglobulin has been a model system for the study of fibril formation for 20 years. The experimental study of β₂‐microglobulin structure, dynamics, and thermodynamics in solution, at atomic detail, along the pathway leading to fibril formation is difficult because the onset of disorder and aggregation prevents signal resolution in Nuclear Magnetic Resonance experiments. Moreover, it is difficult to characterize conformers in exchange equilibrium. To gain insight (at atomic level) on processes for which experimental information is available at molecular or supramolecular level, molecular dynamics simulations have been widely used in the last decade. Here, we use molecular dynamics to address three key aspects of β₂‐microglobulin, which are known to be relevant to amyloid formation: (1) 60 ns molecular dynamics simulations of β₂‐microglobulin in trifluoroethanol and in conditions mimicking low pH are used to study the behavior of the protein in environmental conditions that are able to trigger amyloid formation; (2) adaptive biasing force molecular dynamics simulation is used to force cis‐trans isomerization at Proline 32 and to calculate the relative free energy in the folded and unfolded state. The native‐like trans‐conformer (known as intermediate 2 and determining the slow phase of refolding), is simulated for 10 ns, detailing the possible link between cis‐trans isomerization and conformational disorder; (3) molecular dynamics simulation of highly concentrated doxycycline (a molecule able to suppress fibril formation) in the presence of β₂‐microglobulin provides details of the binding modes of the drug and a rationale for its effect. Proteins 2011. © 2010 Wiley‐Liss, Inc.     

Two-phase olive mill waste composting: community dynamics and functional role of the resident microbiota

In this study, physico-chemical modifications and community dynamics and functional role of the resident microbiota during composting of humid husk from a two-phase extraction system (TPOMW) were investigated. High mineralization and humification of carbon, low loss of nitrogen and complete degradation of polyphenols led to the waste biotransformation into a high-quality compost. Viable cell counts and denaturing gradient gel electrophoresis (DGGE) profiling of the 16S rRNA genes showed that the thermophilic phase was characterized by the strongest variations of cell number, the highest biodiversity and the most variable community profiles. The isolation of tannin-degrading bacteria (e.g. Lysinibacillus fusiformis, Kocuria palustris, Tetrathiobacter kashmirensis and Rhodococcus rhodochrous) suggested a role of this enzymatic activity during the process. Taken together, the results indicated that the composting process, particularly the thermophilic phase, was characterized by a rapid succession of specialized bacterial populations with key roles in the organic matter biotransformation.     

Effect of surgical stress on nuclear and mitochondrial DNA from healthy sections of colon and rectum of patients with colorectal cancer

Surgical resection at any location in the body leads to stress response with cellular and subcellular change, leading to tissue damage. The intestine is extremely sensitive to surgical stress with consequent postoperative complications. It has been suggested that the increase of reactive oxygen species as subcellular changes plays an important role in this process. This article focuses on the effect of surgical stress on nuclear and mitochondrial DNA from healthy sections of colon and rectum of patients with colorectal cancer. Mitochondrial DNA copy number, mitochondrial common deletion and nuclear and mitochondrial 8-oxo-2′-deoxyguanosine content were measured. Both the colon and rectal tissue were significantly damaged either at the nuclear or mitochondrial level. In particular, mitochondrial DNA was more damaged in rectum than in colon. The present investigation found an association between surgical stress and nuclear and mitochondrial DNA damage, suggesting that surgery may generate an increase in free radicals, which trigger a cascade of molecular changes, including alterations in DNA.