The Placopsis trachyderma – Raoulia – community, a special type of biological soil crusts in the braided rivers of southern New Zealand

The braided rivers with their ever-changing water channels are recognized as one of New Zealand's most distinctive and important ecosystem. We made a survey of the vegetation on the shingle plains in the upper reaches of the braided rivers of South Island. A well-defined colonizing vegetation type was recognized. It consists of lichens, mosses, low herbs, low cushion plants and tufted grasses, and mat-forming plants. Because of the close mechanical connection between the thalli of the lichens of the genus Placopsis (Agyraceae: Ascomycota) with moss cushions and spreading mats of vascular plants, we see this Placopsis trachyderma – Raoulia – community as a special type of biological soil crusts.     

Apoptotic DNA fragmentation is not related to the phosphorylation state of histone H1

Changes in chromatin structure, histone phosphorylation and cleavage of DNA into nucleosome-size fragments are characteristic features of apoptosis. Since H1 histones bind to the site of DNA cleavage between nucleosomal cores, the question arises as to whether the state of H1 phosphorylation influences the rate of internucleosomal cleavage. Here, we tested the relation between DNA fragmentation and H1 phosphorylation both in cultured cells and in vitro. In Jurkat cells, hyperosmotic mannitol concentration resulted in apoptosis, including nucleosomal fragmentation, whereas apoptosis induction by increased NaCl concentration was not accompanied by DNA fragmentation. However, both treatments induced dephosphorylation of H1 histones. In contrast, treatment of Raji cells with alkylphosphocholine led to induction of apoptosis with internucleosomal fragmentation, albeit without notable histone H1 dephosphorylation. These results demonstrate that dephosphorylation of H1 histones is neither a prerequisite for nor a consequence of internucleosomal cleavage. Moreover, we observed with an in vitro assay that the known enhancing effect of H1 histones on the activity of the apoptosis-induced endonuclease DFF40 is independent of the subtype or the phosphorylation state of the linker histone.     

Human Risk Assessment for Nonylphenol

This article presents a risk assessment for human exposure to nonylphenol (NP). We critically reviewed and assessed all relevant full-text publications based on a variety of data quality attributes. Two categories of data, environmental monitoring and biomonitoring from exposed individuals, were used to estimate human exposure to NP. Environmental monitoring data included the measurement of NP in food, water, air, and dust. From these data and estimates of human intake rates for the sources, exposures were estimated from each source and source-specific Margins of Exposure (MOEs) calculated. However, the nature of the populations studied prevented the calculation of aggregate exposure calculations from these data. Rather, the most reliable estimates of aggregate exposure to NP were those derived from biomonitoring studies in exposed individuals. Using the daily absorbed dose estimates for NP, MOEs were calculated for these populations. The MOEs were based on the use of a No-Observed-Adverse-Effect-Level (NOAEL) for sensitive toxicological endpoints of interest, that is, systemic and reproductive toxicity from continuous-feeding more than 3.5 generations (13 mg/kg/day). The MOEs were all greater than 1000 (ranging from 2863 to 8.4 × 10⁷), clearly indicating reasonable certainty of no harm for source-specific and aggregate (based on biomonitoring) exposures to NP.     

Colloidal structure and stability of DNA/polycations polyplexes investigated by small angle scattering

Polyplexes of short DNA-fragments (300 b.p., 100 nm) with tailor-made amine-based polycations of different architectures (linear and hyperbranched) were investigated in buffer solution as a function of the mixing ratio with DNA. The resulting dispersed polyplexes were characterized using small-angle neutron and X-ray scattering (SANS, SAXS) as well as cryo-TEM with respect to their mesoscopic structure and their colloidal stability. The linear polyimines form rather compact structures that have a high tendency for precipitation. In contrast, the hyperbranched polycation with enzymatic-labile pentaethylenehexamine arms (PEHA) yields polyplexes colloidally stable for months. Here the polycation coating of DNA results in a homogeneous dispersion based on a fractal network with low structural organization at low polycation amount. With increasing polycation, bundles of tens of aligned DNA rods appear that are interconnected in a fractal network with a typical correlation distance on the order of 100 nm, the average length of the DNA used. With higher organization comes a decrease in stability. The 3D network built by these beams can still exhibit some stability as long as the material concentration is large enough, but the structure collapses upon dilution. SAXS shows that the complexation does not affect the local DNA structure. Interestingly, the structural findings on the DNA polyplexes apparently correlate with the transfection efficiency of corresponding siRNA complexes. In general, these finding not only show systematic trends for the colloid stability, but may allow for rational approaches to design effective transfection carriers.     

The effect of interleukin-8 on the viability of injected adipose tissue in nude mice

Adipose tissue injection as a free graft for the correction of soft-tissue defects is a widespread procedure in plastic surgery. The main problem in achieving long-term soft-tissue augmentation is partial absorption of the injected fat and hence the need for overcorrection and re-injection. The purpose of this study was to improve the viability of the injected fat by the use of interleukin-8. The rationale for the use of interleukin-8 was its abilities to accelerate angiogenesis and attract inflammatory cells and fibroblasts, providing the injected adipocytes more feeding vessels and a well-established graft bed to enhance their viability. Human adipose tissue, obtained by suction-assisted lipectomy, was re-injected into the subcutis in the scalp of nude mice. Interleukin-8 (0.25 ng) was injected subcutaneously to the scalp as a preparation of the recipient site 24 hours before the fat injection and was added to the fat graft itself (25 ng per 1 cc of injected fat). In the control group, pure fat without interleukin-8 was injected and no interleukin-8 was added for the preparation of the recipient site. One cubic centimeter of fat was injected in each animal in both the study and control groups. There were 10 animals in each group. The animals were euthanized 15 weeks after the procedure. Graft weight and volume were measured and histologic evaluation was performed. In addition, triglyceride content and adipose cell sizes were measured as parameters for fat cells viability. Histologic analysis demonstrated significantly less cyst formation in the group treated with interleukin-8. No significant differences were found between the groups with regard to graft weight and volume or the other histologic parameters investigated. No significant differences were demonstrated in adipose cell sizes and their triglyceride content. In conclusion, less cyst formation, indicating improved quality of the injected fat, can be obtained by the addition of interleukin-8. Further studies of various dosages of interleukin-8 and their long-term effect are required before these encouraging results could be applied clinically.     

Characterization of nonstructural protein membrane anchor deletion mutants expressed in the context of the hepatitis C virus polyprotein

Protein-protein interactions involved in formation of the membrane-associated hepatitis C virus (HCV) replication complex are poorly understood. Here, we investigated nonstructural proteins with deletions in their membrane anchor domains when expressed in the context of the entire HCV polyprotein. Interactions among cytosolic domains of HCV nonstructural proteins were found not to be sufficiently strong to rescue such mutants to the membrane. Thus, the membrane anchor domains of nonstructural proteins are essential for incorporation of these proteins into the HCV replication complex while interactions among the cytosolic domains appear to be relatively weak. This feature may provide the nonstructural proteins with a certain flexibility to perform their multiple functions during HCV replication.     

The alpha helix dipole: screened out?

Aligned alpha helix peptide dipoles sum to a "macroscopic" dipole parallel to the helix axis that has been implicated in protein folding and function. However, in aqueous solution the dipole is counteracted by an electrostatic reaction field generated by the solvent, and the strength of the helix dipole may reduce drastically from its value in vacuum. Here, using atomic-detail helix models and Poisson-Boltzmann continuum electrostatics calculations, the net effective dipole moment, mu(eff), is calculated. Some initially surprising results are found. Whereas in vacuum mu(eff) increases with helix length, the opposite is found to be the case for transmembrane helices. In soluble proteins, mu(eff) is found to vary strongly with the orientation and position of the helix relative to the aqueous medium. A set of rules is established to estimate of the strength of mu(eff) from graphical inspection of protein structures.     

Experimental Helicobacter pylori infection induces antral-predominant, chronic active gastritis in hispid cotton rats (Sigmodon hispidus)

BACKGROUND: The hispid cotton rat has proven to be an excellent animal model for a variety of human infectious disease agents. This study was performed to evaluate the use of the cotton rat as a model of Helicobacter pylori infection. MATERIALS AND METHODS: Thirty-eight inbred cotton rats were orogastrically inoculated with a human strain of H. pylori. Twenty-eight control cotton rats were dosed with vehicle only. Animals were sacrificed at 2, 4, 12, 26, or 38 weeks after inoculation for bacterial and histologic and immunologic examinations. RESULTS: Helicobacter pylori was cultured from the glandular stomach of 89% of the infected cotton rats. The level of colonization was consistently high (approximately 10(4-6) colony-forming units/g tissue). Histologically, the spiral bacteria were demonstrated on the epithelial surface and in the foveolae of the gastric mucosa with highest numbers in the antrum. H. pylori infection was associated with antral-predominant, chronic active gastritis which progressively increased in severity over time. By week 26 of infection, moderate antral gastritis had developed with frequent involvement of the submucosa and formation of lymphocytic aggregates. Splenic T cells from infected cotton rats expressed mRNAs for interferon-gamma, interleukin-4, interleukin-6, and interleukin-10 following in vitro stimulation with H. pylori. Serum levels of H. pylori-specific immunoglobulin G were significantly elevated after 12 weeks of infection. CONCLUSIONS: The H. pylori-infected cotton rat represents a novel animal model that should prove useful for studies of H. pylori-induced chronic active gastritis and factors affecting gastric colonization by this pathogen.