Modification of hydrophilic and hydrophobic surfaces using an ionic-complementary peptide

Ionic-complementary peptides are novel nano-biomaterials with a variety of biomedical applications including potential biosurface engineering. This study presents evidence that a model ionic-complementary peptide EAK16-II is capable of assembling/coating on hydrophilic mica as well as hydrophobic highly ordered pyrolytic graphite (HOPG) surfaces with different nano-patterns. EAK16-II forms randomly oriented nanofibers or nanofiber networks on mica, while ordered nanofibers parallel or oriented 60° or 120° to each other on HOPG, reflecting the crystallographic symmetry of graphite (0001). The density of coated nanofibers on both surfaces can be controlled by adjusting the peptide concentration and the contact time of the peptide solution with the surface. The coated EAK16-II nanofibers alter the wettability of the two surfaces differently: the water contact angle of bare mica surface is measured to be <10°, while it increases to 20.3±2.9° upon 2 h modification of the surface using a 29 µM EAK16-II solution. In contrast, the water contact angle decreases significantly from 71.2±11.1° to 39.4±4.3° after the HOPG surface is coated with a 29 µM peptide solution for 2 h. The stability of the EAK16-II nanofibers on both surfaces is further evaluated by immersing the surface into acidic and basic solutions and analyzing the changes in the nanofiber surface coverage. The EAK16-II nanofibers on mica remain stable in acidic solution but not in alkaline solution, while they are stable on the HOPG surface regardless of the solution pH. This work demonstrates the possibility of using self-assembling peptides for surface modification applications.

Protection of oligodeoxynucleotides against nuclease degradation through association with self-assembling peptides

Aggregates of the self-assembling peptide EAK16II or EAK16IV and oligodeoxynucleotides (ODNs) were prepared, and their stability upon diluting the solution was investigated by UV-vis spectroscopy. The aggregates prepared at pH 4 and pH 7 did not dissociate after the solution was diluted 5- and 10-fold. The resistance against Escherichia coli exonuclease I of the ODN located in the EAK-ODN aggregates was studied by fluorescence resonance energy transfer (FRET) after the ODN had aggregated with EAK16II or EAK16IV at pH 4 or pH 7. The effect that the peptide sequence, peptide concentration, pH, and centrifugation had on protecting the aggregated ODN against nuclease degradation was investigated. Significant nuclease resistance was obtained after the EAK-ODN aggregates had been prepared at pH 4, with an EAK16IV concentration greater than a threshold value, and ensuring that the solution was not centrifuged immediately after sample preparation. Centrifuging the EAK16IV-ODN solution immediately after sample preparation resulted in the loss of this nuclease protection. However, if the solution of EAK-ODN aggregates was centrifuged 24 h after sample preparation, the nuclease protection afforded by the EAK16IV-ODN aggregates to the ODN was maintained even after being subject to a 10-fold dilution and up to 4 rounds of centrifugation over 4 days.

Carbon sinks and sources in China's forests during 1901-2001

This paper reports the annual carbon (C) balance of China's forests during 1901-2001 estimated using the Integrated Terrestrial Ecosystem C-budget model (InTEC). Annual carbon source and sink distributions are simulated for the same period using various spatial datasets including land cover and leaf area index (LAI) obtained from remote sensing, soil texture, climate, forest age, and nitrogen deposition. During 1901-1949, China's forests were a source of 21.0+/-7.8 Tg C yr(-1) due to disturbances (human activities). Its size increased to 122.3+/-25.3 Tg C yr(-1) during 1950-1987 due to intensified human activities in the late 1950s, early 1960s, 1970s and early 1980s. The forests became large sinks of 176.7+/-44.8 Tg C yr(-1) during 1988-2001, owing to large-scale plantation and forest regrowth in previously disturbed areas as well as growth stimulation by nondisturbance factors such as climatic warming, atmospheric CO(2) fertilization, and N deposition. From 1901 to 2001, China's forests were a small carbon source of 3.32 Pg C, about 32.9+/-22.3 Tg C yr(-1). The overall C balance in biomass from InTEC generally agrees with previous results derived from forest inventories of China's forests. InTEC results also include C stock variation in soils and are therefore more comprehensive than previous results. The uncertainty in InTEC results is still large, but it can be reduced if a detailed forest age map becomes available.

Observations of the Askaryan effect in ice

We report on observations of coherent, impulsive radio Cherenkov radiation from electromagnetic showers in solid ice. This is the first observation of the Askaryan effect in ice. As part of the complete validation process for the ANITA experiment, we performed an experiment at the Stanford Linear Accelerator Center in June 2006 using a 7.5 metric ton ice target. We measure for the first time the large-scale angular dependence of the radiation pattern, a major factor in determining the solid-angle acceptance of ultrahigh-energy neutrino detectors.

Measures needed to strengthen strategic HIV/AIDS prevention programmes in China

This paper traces the commonly believed three phases of the HIV/AIDs epidemic in China from the early 1980s to the present time and reviews how the Chinese Government and NGOs are dealing with the crisis. Transmission routes for HIV infection in China are thought to be via IDUs, blood plasma donors, sexual contacts and from mother-to-child transmissions. The author examined interventions for HIV/ AIDS prevention tried in other countries that could provide useful lessons learned and discussed how they could be adapted or replicated in China. While recognising the need for the treatment of HIV positive persons and AIDS patients, this paper is limited to suggesting a number of proven strategic interventions to prevent new HIV infections in China among the "general population", adolescents in schools, sex workers and their clients, injecting drug users, and, prevention of mother to child transmission of HIV/AIDS to stem the epidemic. An extensive literature search of articles in published academic journals, published and unpublished documents of international agencies and development NGOs and media reports was conducted for data source to this paper. Internet search engines such as ProQuest, PubMed, Google and Yahoo search engines were used as well as hard copies of reports and internal documents available at the UNFPA Country Technical Services Team's Office in Bangkok tapped for information.

Interaction of a self-assembling peptide with oligonucleotides: complexation and aggregation

Molecular interaction of a self-assembling peptide, EAK16-II, to single- and double-stranded oligodeoxynucleotides (ODNs) was investigated under various solution conditions. The molecular events leading to EAK-ODN complexation and further aggregation were elucidated using a series of spectroscopic and microscopic methods. Despite the ability to self-assemble, EAK molecules bind to ODN molecules first upon mixing, resulting in EAK-ODN complexes. The complexes further associate to form EAK-ODN aggregates. A method based on UV-Vis absorption and centrifugation was developed to quantify the fraction of ODNs in the aggregates. The results were used to construct binding isotherms via a binding density function analysis. To compare the effects of different pH values and nucleotide types, the modified noncooperative McGhee and von Hippel model was used to extract binding parameters from the binding isotherms. The binding constant of EAK to ODNs was higher at pH 4 than at pH 7, and no binding was observed at pH 11, indicating that the interaction involved is primarily electrostatic in nature. EAK bound more strongly to single-stranded ODNs. The EAK-ODN aggregates were further visualized using atomic force microscopy; their size distribution as a function of EAK concentration was monitored by dynamic light scattering. The timescale for the EAK-ODN aggregation was on the order of minutes by fluorescence anisotropy and steady-state light scattering experiments. Fluorescence quenching experiments demonstrated that the ODNs in the aggregates were less accessible to the solvent, demonstrating a potential of oligonucleotide encapsulation by the self-assembling peptide.

Surface-assisted assembly of an ionic-complementary peptide: controllable growth of nanofibers

Numerous studies have shown that a surface can direct and regulate molecular assembly. In this study, the nanofiber growth of an ionic-complementary peptide, EAK16-II, on a mica surface was investigated under various solution conditions via in situ atomic force microscopy. In comparison to the assembly in bulk solution, nanofiber growth of EAK16-II on mica is surface-assisted and involves two steps: (1) adsorption of nanofibers and fiber clusters (from the bulk solution) on the surface, serving as the "seeds"; (2) fiber elongation of the "seeds" from their active ends. The nanofiber growth can be controlled by adjusting the solution pH since it modulates the adsorption of the "seeds" on mica and their growth rates. The amount of the adsorbed "seeds" decreases with increasing solution pH, while the growth rate under different solution conditions is found to follow the order pure water > 1 mM HCl > 1 mM NaOH > 10 mM HCl approximately 10 mM NaOH approximately 0. The pH-dependent nanofiber growth is due to the surface charge of the peptides and peptide assemblies in various solutions as indicated by zeta-potential measurements. A simple model was proposed to describe surface-assisted nanofiber growth. This study provides insights into the assembly of peptide/protein on a surface, which is essential to understand such physiological protein aggregation systems as amyloid fibrillogenesis. In addition, the potential of this finding to construct biocompatible electrodes for biomolecular sensing is also discussed.

Inter-rater agreement for a retrospective exposure assessment of asbestos, chromium, nickel and welding fumes in a study of lung cancer and ionizing radiation

A retrospective exposure assessment of asbestos, welding fumes, chromium and nickel (in welding fumes) was conducted at the Portsmouth Naval Shipyard for a nested case-control study of lung cancer risk from external ionizing radiation. These four contaminants were included because of their potential to confound or modify the effect of a lung cancer-radiation relationship. The exposure assessment included three experienced industrial hygienists from the shipyard who independently assessed exposures for 3519 shop/job/time period combinations. A consensus process was used to resolve estimates with large differences. Final exposure estimates were linked to employment histories of the 4388 study subjects to calculate their cumulative exposures. Inter-rater agreement analyses were performed on the original estimates to better understand the estimation process. Although concordance was good to excellent (78-99%) for intensity estimates and excellent (96-99%) for frequency estimates, overall simple kappa statistics indicated only slight agreement beyond chance (kappa < 0.2). Unbalanced distributions of exposure estimates partly contributed to the weak observed overall inter-rater agreement. Pairwise weighted kappa statistics revealed better agreement between two of the three panelists (kappa = 0.19-0.65). The final consensus estimates were similar to the estimates made by these same two panelists. Overall welding fume exposures were fairly stable across time at the shipyard while asbestos exposures were higher in the early years and fell in the mid-1970s. Mean cumulative exposure for all study subjects was 520 fiber-days cc(-1) for asbestos and 1000 mg-days m(-3) for welding fumes. Mean exposure was much lower for nickel (140 microg-days m(-3)) and chromium (45 microg-days m(-3)). Asbestos and welding fume exposure estimates were positively associated with lung cancer in the nested case-control study. The radiation-lung cancer relationship was attenuated by the inclusion of these two confounders. This exposure assessment provided exposure estimates that aided in understanding of the lung cancer-radiation relationship at the shipyard.

Targeted deletion of HIF-1alpha gene in T cells prevents their inhibition in hypoxic inflamed tissues and improves septic mice survival

Background

Sepsis patients may die either from an overwhelming systemic immune response and/or from an immunoparalysis-associated lack of anti-bacterial immune defence. We hypothesized that bacterial superantigen-activated T cells may be prevented from contribution into anti-bacterial response due to the inhibition of their effector functions by the hypoxia inducible transcription factor (HIF-1α) in inflamed and hypoxic areas.

Methodology/Principal Findings

Using the Cre-lox-P-system we generated mice with a T–cell targeted deletion of the HIF-1α gene and analysed them in an in vivo model of bacterial sepsis. We show that deletion of the HIF-1α gene leads to higher levels of pro-inflammatory cytokines, stronger anti-bacterial effects and much better survival of mice. These effects can be at least partially explained by significantly increased NF-κB activation in TCR activated HIF-1 α deficient T cells.

Conclusions/Significance

T cells can be recruited to powerfully contribute to anti-bacterial response if they are relieved from inhibition by HIF-1α in inflamed and hypoxic areas. Our experiments uncovered the before unappreciated reserve of anti-bacterial capacity of T cells and suggest novel therapeutic anti-pathogen strategies based on targeted deletion or inhibition of HIF-1 α in T cells.

Immunization of mice with plasmids coexpressing HPV16 E5 and the novel oncogene hWAPL

The novel human oncogene hWAPL is associated with uterine cervical cancer. The HPV16 E5 oncoprotein could induce genomic instability in normal human cells. However, the mechanism of E5 interaction with hWAPL still awaits definition. In our present studies, the eukaryotic expression plasmids, pcDNA3-hWAPL and pcDNA3-hWAPL-E5 were constructed and carried out to vaccinate mice directly. The result that indicated the polyclonal antibody titer in immunized mice sera was increased by enzyme-linked immunosorbent assay. In addition, the proliferative responses of immunized mice spleen cells showed the optical densities values in vaccinated group remarkably higher than that in the control group. In conclusion, the recombinant plasmids could induce strong humoral and cellular immune response and exhibited great potential as therapeutic targets in the treatment of cervical cancer. However, the result didn't show significant difference in group with coexpression of HPV16 E5-hWAPL and group with only hWAPL expression. Consistent with these observations, we demonstrated that HPV16 E5 was not the optimal factor to cooperate with hWAPL in gene therapy.

Neuroprotective effects of ginsenoside Rb1 on transient cerebral ischemia in rats

Previous experiments showed that ginsenoside Rb1 (GRb1) reduced infarct and neuronal deficit in rats followed by transient cerebral ischemia. The mechanism of this neuroprotective function is unclear. Here, we tested whether the effect of GRb1 can be achieved through preventing ischemic neuronal death, modulating apoptotic-related genes and affecting glial-derived neurotrophic factor (GDNF) expression in rats subjected to occlusion of the middle cerebral artery. When GRb1(40 mg/kg, i.p.) was administered immediately after reperfusion, the apoptotic cells in the GRb1 group were decreased significantly from 12 to 72 h of reperfusion compared to the ischemia group by TdT-mediated dUTP-biotin nick-end labeling. Immunostaining and Western blotting analysis showed that the expression of GDNF from 3 to 120 h of the GRb1 group was significantly increased compared to the ischemia group, and GDNF expression peaked at 48 h after reperfusion. The enhanced GDNF mRNA in the GRb1 group was not detected by RT-PCR and in situ hybridization compared to the ischemia group, but GDNF mRNA at 48 h after reperfusion was strongly increased in both the ischemia and GRb1 group when compared to other time points. The number of bcl-2-positive cells was significantly increased from 12 to 120 h of reperfusion compared to the ischemia group. However, the number of bax-positive cells in the GRb1 group was significantly declined compared to the ischemia group. In the GRb1 group, the number of neuronal apoptosis inhibitory protein-positive cells from 12 to 120 h after reperfusion was evidently higher than that in the ischemia group. Therefore, ginsenoside Rb1 prevents ischemic neuronal death induced by transient cerebral ischemia, and this mechanism of which is related to increase the expression of the antiapoptotic genes and modulate the expression of GDNF.

Enhanced prediction of fracture risk combining vertebral fracture status and BMD

Prevalent vertebral fractures are associated with increased fracture risk, but the magnitude of this effect across a range of BMD T-scores has not been quantified. In this analysis, for any given BMD T-score, incident fracture risk varied up to twelve fold when information regarding prevalent radiographic vertebral fracture status was considered.

BACKGROUND

Clinical fracture risk evaluation of older women usually includes assessment of bone mineral density (BMD) but often not vertebral fracture status. In this analysis, we quantified the impact of vertebral fracture burden on two year fracture risk across a range of BMD T-scores.

METHODS

Data were from 2,651 postmenopausal women who were assigned to the placebo groups of the Fracture Prevention Trial (median observation 21 months) and the Multiple Outcomes of Raloxifene Evaluation Trial (MORE; observation 2 years). Using the Genant visual semiquantitative criteria, we defined prevalent vertebral fracture status as: a) presence or absence of fracture; b) fracture number; c) maximum semi-quantitative (SQ) score (normal=0, mild fracture=1, moderate fracture=2, severe fracture=3); and d) spinal deformity index (SDI) score (sum of SQ scores of T4 to L4 vertebrae). Incident fractures over two years were identified via lateral spine radiographs and outside the spine by questioning of patients and review of radiographs or radiographic reports.

RESULTS

Femoral neck BMD T-score provided significant information regarding fracture risk. Across the range of T-scores, vertebral fracture status provided additional prognostic information. The risk increased with increasing number and severity of prevalent vertebral fractures and SDI, a summary measure of spine fracture burden. Across a range of BMD values, prevalent spine fracture burden as assessed by SDI increased the risk of incident vertebral fractures by up to 12-fold, nonvertebral fractures by about twofold, and any fractures by up to sevenfold.

CONCLUSIONS

These findings indicate that at any given BMD T-score, the risk of incident vertebral, non-vertebral, and any fracture depended heavily on prevalent radiographic vertebral fracture status. Assessment of vertebral fracture status, in addition to BMD, provides practical and relevant clinical information to aid in predicting fracture risk in postmenopausal women.