Molecular dynamics simulation of nanocolloidal amorphous silica particles: part III

Explicit-solvent molecular dynamics simulations were applied to four pairs of amorphous silica nanoparticles, two pairs having a diameter of 2.0 nm and two pairs with diameter 3.2 nm. The silica nanoparticles were immersed in a background electrolyte consisting of Ca(2+) and Cl(-) ions and water and mean forces acting between the pair of silica nanoparticles were extracted at four different background electrolyte concentrations. The pH was indirectly accounted for via the ratio of silicon to sodium used in the simulations. Dependence of the interparticle potential of mean force on the center-of-mass separation and the silicon to sodium ratio (5:1 and 20:1) is demonstrated. A Si:Na(+) ratio of 5:1 gave more repulsive interparticle potentials and lower numbers of internanoparticle or "bridging" hydrogen bonds. Conversely a Si:Na(+) ratio of 20:1 yielded more attractive potentials and higher numbers of bridging hydrogen bonds. The nature of the interaction of the counterions with charged silica surface sites (deprotonated silanols) was also investigated. The effect of the sodium double layer on water ordering was observed. The number of water molecules trapped inside the nanoparticles was investigated, and at the highest background ionic concentrations were found to consistently behave in accordance with there being an osmotic pressure. This study highlights the effect of divalent (Ca(2+)) background ions on the interparticle potentials compared with previous work using monovalent (Na(+)) background ions. Mechanisms of coagulation and the stability of silica nanocolloids found from this work appear to be in agreement with findings from experiments described in the literature.

The prognostic impact of NF-kappaB p105, vimentin, E-cadherin and Par6 expression in epithelial and stromal compartment in non-small-cell lung cancer

Vimentin, nuclear factor-κB (NF-κB) p105, fascin, E-cadherin, TGF-β, Par6 and atypical PKC are molecular markers that play an important role in cell differentiation. Herein, we investigate their prognostic impact in primary non-small-cell carcinoma (NSCLC). Tumour tissue samples from 335 resected patients with stage I–IIIA were used. Tissue microarrays were constructed from duplicate cores of both neoplastic cells and stromal cells and were immunohistochemically evaluated. In univariate analyses, high tumour epithelial cell expressions of NF-κB p105 (P=0.02) and E-cadherin (P=0.03) were positive prognostic indicators for disease-specific survival (DSS), whereas high tumour epithelial cell expression of vimentin (P=0.001) was a negative prognostic indicator. High expression of NF-κB p105 (P=0.001) and Par6 (P=0.0001) in the stromal compartment correlated with a good prognosis. In multivariate analyses, the tumour epithelial cell expression of NF-κB p105 (P=0.0001) and vimentin (P=0.005) and the stromal cell expression of NF-κB p105 (P=0.007) and Par6 (P=0.0001) were independent prognostic factors for DSS. High expression of NF-κB p105 and low expression of vimentin in tumour epithelial cells are independent predictors of better survival in primary NSCLC. In stromal cells, high expressions of NF-κB p105 and Par6 are both favourable independent prognostic indicators.

Polymorphisms in cytokine genes influence long-term survival differently in elderly male and female patients

OBJECTIVES

We asked if single nucleotide polymorphisms (SNP) in inflammatory cytokine genes related to 3-year survival in ill elderly subjects and if genotypes differed between the elderly and a younger control population.

DESIGN

Prospective observational study.

SETTING

Two geriatric departments at a university hospital.

SUBJECTS

Eighty three acutely admitted geriatric patients (83 +/- 7 year, 70% women) and 207 young healthy subjects (40 +/- 1 year, 37% women) were included.

OUTCOME MEASURES

Single nucleotide polymorphisms in the genes of tumour necrosis factor (TNF)-alpha-308 G/A, interleukin (IL)-1beta-511 C/T, IL-6-174 G/C and IL-10-1082 A/G were analysed. In the geriatric patients SNP in lymphotoxin (LT)-alpha +252 G/A and serum levels of TNF-alpha, IL-6, IL-10, soluble IL-I receptor(R)II were also determined, as well as the 3-year mortality.

RESULTS

The allele distribution did not differ significantly between the elderly and the young. In the female elderly, 3-year survival was doubled (P < 0.05) in those with the high-producing genotypes of IL-6 -174 GG and TNF-alpha -308 GA compared with those with low-producing alleles. In contrast, men with high-producing LT-alpha +252 AA and IL-1beta-511 CT&TT genotypes displayed halved 3-year survival (P < 0.05) compared with those with low-producing genotypes, whereas possession of the high-producing IL-10 -1082 GG genotype favoured survival. Serum IL-10 was higher in the high-producing IL-10 genotype in females.

CONCLUSION

As high-producing IL-6 -174 genotype favoured 3-year survival in women, whereas the likewise high-producing LT-alpha +252 and IL-1beta -511 genotypes were associated with poor survival in men, we conclude that the specific genotypes, in association with gender, may act as determinants for survival in elderly patients.

Maternally determined adaptation to acidity in Rana arvalis: Are laboratory and field estimates of embryonic stress tolerance congruent?

Geographic variation indicating local adaptation, as well as its quantitative genetic basis, is commonly investigated in common garden experiments in the laboratory. However, the applicability of laboratory results to the complex conditions experienced by populations in the wild may be limited. Our previous laboratory experiments showed maternally determined local adaptation in embryonic acid-stress tolerance (viz. survival) of the moor frog, Rana arvalis Nilsson, 1842. Here we tested whether this laboratory finding holds even when embryos are exposed to acid stress in the wild. We conducted reciprocal crosses between an acid-origin population and a neutral-origin population of R. arvalis and transplanted the embryos to an acid site (pH ~4) in the field. Embryonic survival was much lower in the field experiment than in previous laboratory experiments, but, consistent with laboratory work, embryos from acid-origin females had threefold higher survival than embryos from neutral-origin females. These results suggest that laboratory tests can provide appropriate estimates of among population variation, as well as the quantitative genetic basis of acid-stress tolerance in amphibians.

Prognostic impact of angiogenic markers in tumor and stromal cells in non-small cell lung cancer (NSCLC)

10596

Background: The vascular endothelial growth factors (VEGFs) -A, -C, -D and the vascular endothelial growth factor Receptors (VEGFRs) -1, -2 and -3 are important molecular markers in angiogenesis and lymphangiogenesis. This study elucidates the prognostic significance of these molecular markers in tumor cells as well as in the tumor stroma of resected NSCLC tumors. Methods: Tumor tissue samples from 335 resected patients with stage I to IIIA were obtained and tissue microarrays were constructed from duplicate cores of tumor cells and surrounding stromal tissue from each resected specimen. Immunohistochemistry was used to evaluate the expression of each molecular marker. Results: In univariate analyses, high tumor cell expression of VEGF-A (P = .0005), VEGFR-1 (P = .013), VEGFR-2 (P = .006) and VEGFR-3 (P = .0003), were negative prognostic indicators for disease-specific survival (DSS). The most significant correlations between angiogenic marker expression and DSS were observed in patients with T2 stage and/or with sqamous cell carcinomas. In tumor stroma, however, high expression of VEGF-A (P = .017), VEGF-C (P = .003), VEGF-D (P = .009), VEGFR-1 (P = .01) and VEGFR-2 (P = .019), correlated with good prognosis. In multivariate analyses, high expression in tumor cells of VEGFR-3 (P = .007) was an independent negative prognostic factor for DSS, whereas high VEGF-C (P = .004) expression in stromal cells had an independent positive impact on survival. Conclusions: While high tumor cell expression of VEGFR-3 is an independent predictor of reduced survival in primary NSCLC, high VEGF-C expression in stromal cells is, in contrast, a favorable independent prognostic indicator.

No significant financial relationships to disclose.

Spectrum of electronic excitations due to the adsorption of atoms on metal surfaces

The time-dependent, mean-field Newns-Anderson model for a spin-polarized adsorbate approaching a metallic surface is solved in the wide-band limit. Equations for the time evolution of the electronic structure of the adsorbate-metal system are derived and the spectrum of electronic excitations is found. The behavior of the model is demonstrated for a set of physically reasonable parameters.

Planning for intracavitary anti-EGFR radionuclide therapy of gliomas. Literature review and data on EGFR expression

Targeting with radionuclide labelled substances that bind specifically to the epidermal growth factor receptor, EGFR, is considered for intracavitary therapy of EGFR-positive glioblastoma multiforme, GBM. Relevant literature is reviewed and examples of EGFR expression in GBM are given. The therapeutical efforts made so far using intracavitary anti-tenascin radionuclide therapy of GBM have given limited effects, probably due to low radiation doses to the migrating glioma cells in the brain. Low radiation doses might be due to limited penetration of the targeting agents or heterogeneity in the expression of the target structure. In this article we focus on the possibilities to target EGFR on the tumour cells instead of an extracellular matrix component. There seems to be a lack of knowledge on the degree of intratumoral variation of EGFR expression in GBM, although the expression seemed rather homogeneous over large areas in most of the examples (n=16) presented from our laboratory. The observed homogeneity was surprising considering the genomic instability and heterogeneity that generally characterises highly malignant tumours. However, overexpression of EGFR is, at least in primary GBMs, one of the steps in the development of malignancy, and tumour cells that lose or downregulate EGFR will probably be outgrown in an expanding tumour cell population. Thus, loss of EGFR expression might not be the critical factor for successful intracavitary radionuclide therapy. Instead, it is likely that the penetration properties of the targeting agents are critical, and detailed studies on this are urgent.

Situations influencing habits in diet and exercise among nurses working night shift

OBJECTIVES

The aim of the investigation was to describe situations with a significant influence on healthy diet and exercise habits among nurses working night shift.

METHODS

A qualitative descriptive design with a Critical Incident Technique approach was used. Situations were collected by means of interviews with 27 registered/enrolled community nurses.

RESULTS

A total of 143 situations were identified comprising two main areas: coping ability at work and coping ability during leisure hours. Coping ability at work included 81 critical incidents grouped into two categories: the nurses' diet and exercise habits were influenced by social interaction with colleagues at work and by the disruption to their circadian rhythm. Coping ability during leisure hours included 62 critical incidents grouped into two categories: the diet and exercise habits were influenced when the nurses recovered from the disruption to their circadian rhythm and when they took advantage of the freedom of action offered by night work.

CONCLUSIONS

By identifying the factors that influence diet and exercise habits among nurses working night shift, strategies can be developed in order to strengthen the factors with a positive influence.

Femtosecond laser induced associative desorption of H2 from Ru(0001): Comparison of “first principles” theory with experiment

A three dimensional model based on molecular dynamics with electronic frictions is developed to describe the femtosecond laser induced associative desorption of H2 from Ru(0001)(1 x 1)H. Two molecular coordinates (internuclear separation d and center of mass distance to surface z) and a single phonon coordinate are included in the dynamics. Both the potential energy surface and the electronic friction tensor are calculated by density functional theory so that there are no adjustable parameters in the comparison of this model with the wide range of experiments available for this system. This "first principles" dynamic model gives results in semiquantitative agreement with all experimental results; nonlinear fluence dependence of the yield, isotope effect, two pulse correlation, and energy partitioning. The good agreement of theory with experiment supports a description of this surface femtochemistry in terms of thermalized hot electron induced chemistry with coupling to nuclear coordinates through electronic frictions. By comparing the dynamics with the analytical one dimensional frictional model used previously to fit the experiments for this system, we show that the success of the one dimensional model is based on the rapid intermixing of the z and d coordinates as the H-H climbs out of the adsorption well. However, projecting the three dimensional dynamics onto one dimension introduces a fluence (adsorbate temperature) dependent "entropic" barrier in addition to the potential barrier for the chemistry. This implies that some caution must be used in interpreting activation energies obtained in fitting experiments to the one dimensional model.

Theoretical evidence for nonadiabatic vibrational deexcitation in H2(D2) state-to-state scattering from Cu(100)

Dynamical calculations are presented for electronically nonadiabatic vibrational deexcitation of H2 and D2 in scattering from Cu(111). Both the potential energy surface and the nonadiabatic coupling strength were obtained from density functional calculations. The theoretically predicted magnitude of the deexcitation and its dependence on incident energy and isotope are all in agreement with state-to-state scattering experiments [on Cu(100)], and this gives indirect evidence for a nonadiabatic mechanism of the observed deexcitation. Direct evidence could be obtained by measuring the chemicurrent associated with the deexcitation, and its properties have been predicted.

Corticosterone inhibits expression of the microglial glutamate transporter GLT-1 in vitro

The present study investigates the effect of the glucocorticoid corticosterone on microglial glutamate transporters in vitro. Microglial cultures obtained from rat cerebral cortex were found to express the excitatory amino acid transporter GLT-1, but not GLAST, and this expression was increased by 1 ng/ml lipopolysaccharide after 12 h of stimulation. This increase has previously been shown to be mediated by tumor necrosis factor-alpha, a cytokine released by microglia during pathological conditions. Furthermore, lipopolysaccharide increased the microglial release of tumor necrosis factor-alpha and 1 microM corticosterone inhibited this effect. Corticosterone also inhibited the lipopolysaccharide-induced increase of the GLT-1 expression as well as the expression in non-activated cells. The effect of corticosterone on the GLT-1 expression was dose dependent and accompanied by similar effects on the microglial glutamate uptake capacity. Additionally, exogenous tumor necrosis factor-alpha was found to counteract the effect of corticosterone on microglial GLT-1 expression. The effect of corticosterone appeared to be glucocorticoid receptor specific since 10 microM of the glucocorticoid receptor antagonist mifepristone inhibited the effect. Thus, corticosterone decreased the microglial uptake of glutamate by decreasing the expression of glutamate transporters, probably due to the inhibited microglial tumor necrosis factor-alpha release. These results provide insights into the mechanisms behind microglial glutamate transporter expression during pathological conditions, and contribute to the debate about the beneficial or harmful effects of glucocorticoids.

Cell-type-specific expression of p53 and p21 in giant cell arteritis

The aim of the present study was to investigate the expression of TP53 (p53) and CDKN1A (CIP1; p21) in the arterial wall in giant cell arteritis (GCA). Cross-sections from 18 temporal artery biopsies displaying GCA and 8 control arteries were double-stained with monoclonal antibody directed at p53 or p21 on the one hand and alpha-smooth muscle actin, CD68 (macrophage) or CD3 (T-cell) on the other. Nuclear p53 was expressed in CD68-positive cells and smooth muscle cells in 16 of the 18 inflamed arteries. P21-positive nuclei were found in CD68-positive cells in 14 biopsies and in smooth muscle cells in all the specimens. All p53-positive giant cells also contained p21-positive nuclei. In the giant cells, immunopositive nuclei were mixed with negative ones. CD3-positive T-cells did not express p53 or p21. Only one p53-positive smooth muscle cell nucleus was found in the non-GCA controls and, compared with GCA, p21 expression was noted in few smooth muscle nuclei. The presence of p53 and p21 in the same types of cell in GCA indicates that the former protein is functional; p21 expression is induced by wild-type, functional p53 but not by its mutant form. The current observations suggest cellular stress in GCA, the nature of which requires further investigation.

How adiabatic is activated adsorption/associative desorption?

Using density-functional theory we calculate friction coefficients describing the damping of nuclear motion into electron-hole pair excitation for the two best-known examples of activated adsorption: H2 dissociation on a Cu(111) surface and N2 dissociation on a Ru(0001) surface. In both cases, the frictions increase dramatically along the reaction path towards the transition state and can be an order of magnitude larger there than typical in the molecularly adsorbed state. In addition, the frictions for N2/Ru(0001) are typically an order of magnitude larger than for H2/Cu(111). We rationalize these trends in terms of the electron structure as the systems proceed to dissociation along the reaction paths. Combining these friction coefficients with the potential-energy surface in quasiclassical dynamics allows first-principles studies of the importance of the breakdown in the Born-Oppenheimer approximation in describing the chemistry. We find that nonadiabatic effects are minimal for the H2/Cu(111) system, but are quite important for N2/Ru(0001).

In vitro evaluation of the astatinated chimeric monoclonal antibody U36, a potential candidate for treatment of head and neck squamous cell carcinoma

PURPOSE

The purpose of this study was to analyse the properties of the astatinated chimeric MAb (cMAb) U36 as a conjugate to selectively target and eradicate head and neck squamous cell carcinoma (HNSCC).

METHODS

cMAb U36 was labelled with 211At via the linker N-succinimidyl 4-(trimethylstannyl)benzoate (SPMB). The quality of the conjugate was extensively evaluated for binding and internalisation capacity, and compared with 125I-SPMB-cMAb U36. The cellular toxicity of the astatinated conjugate was assessed in two types of in vitro growth assay and compared with 131I-labelled cMAb U36 (directly labelled).

RESULTS

Comparisons between 211At-cMAb U36 and 125I-cMAb U36 demonstrated an optimal functional capacity of the labelled products. Immunoreactivity and affinity assays showed high immunoreactive fractions (>93%), and an affinity in good agreement between the astatinated and iodinated antibodies. For both conjugates, specific binding to HNSCC cells could be demonstrated, as well as some internalisation. Retention of the astatinated conjugate was just slightly lower than for the iodinated conjugate and still reasonable for therapeutic use (31+/-2% vs 42.6+/-1.0% at 22 h), demonstrating no adverse effects from astatination of the antibody. Studies on cellular toxicity demonstrated a dose-dependent and antigen-specific cellular toxicity for 211At-cMAb U36, with about 10% cell survival at 50 decays per cell. The 131I-labelled conjugate was not as efficient, with a surviving cell fraction of about 50% at 55 decays per cell.

CONCLUSION

These results indicate that 211At-cMAb U36 might be a promising future candidate for eradicating HNSCC micrometastases in vivo.

Electronic nonadiabatic effects in the adsorption of hydrogen atoms on metals

The time-dependent, mean-field Newns-Anderson model for a spin-polarized adsorbate approaching a metallic surface is solved in the wide-band limit. Equations for the time evolution of the occupation of the spin dependent adsorbate states and for the nonadiabatic and nearly adiabatic adsorbate-surface energy transfer rates are derived. Numerical solutions are obtained using characteristic parameters derived from density functional theory calculations for the H/Cu(111) system. The time evolution of the model system is shown to be strongly nonadiabatic in the vicinity of the transition point between spin-polarized and nonpolarized ground states. Away from the spin transition the nonadiabatic energy transfer is in close agreement with the nearly adiabatic limit. Near the transition, nonadiabatic effects are large and the nearly adiabatic approximation fails.

Localization of the Cu111 surface state by single Cu adatoms

The Cu adatom-induced localization of the two-dimensional Shockley surface state at the Cu(111) surface was identified from experimental and simulated scanning tunneling microscopy spectra. The localization gives rise to a resonance located just below the surface state band edge. The adatom-induced surface state localization is discussed in terms of the existence theorem for bound states in any attractive two-dimensional potential. We also identify adatom-induced resonance states deriving from atomic orbitals in both experimental and simulated spectra.

Carbon dioxide inhibits the growth rate of Staphylococcus aureus at body temperature

BACKGROUND

Since the 1930s, carbon dioxide (CO(2)) has been combined with cold storage for the preservation of food. However, its use for the prevention of surgical wound infection was long considered to be impractical. Now CO(2) is widely used during laparoscopic procedures, and a method has been developed to create a CO(2) atmosphere in an open wound. The aim of this study was to investigate the effect of CO(2) on the growth of Staphylococcus aureus at body temperature.

METHODS

First, S. aureus inoculated on blood agar were exposed to pure CO(2) (100%), standard anaerobic gas (5% CO(2), 10% hydrogen, 85% nitrogen), or air at 37 degrees C for a period of 24 h; then a viable count of the bacteria was made. Second, S. aureus inoculated in brain-heart infusion broth and kept at 37 degrees C were exposed to CO(2) or air for 0, 2, 4, 6, and 8 h; then the optical density of the bacteria was measured.

RESULTS

After 24 h, the number of S. aureus on blood agar was about 100 times lower in CO(2) than in anaerobic gas (p = 0.001) and about 1,000 times lower than in air (p = 0.001). Also, in broth, there were fewer bacteria with CO(2) than with air (p < 0.01). After 2 h, the number of bacteria was increased with air (p < 0.001) but not with CO(2) (p = 0.13). After 8 h, the optical density had increased from zero to 1.2 with air but it had increased only to 0.01 with CO(2) (p = 0.001).

CONCLUSION

Pure CO(2) significantly decreased the growth rate of S. aureus at body temperature. The inhibitory effect of CO(2) increased exponentially with time. Its bacteriostatic effect may help to explain the low infection rates in patients who undergo laparoscopic procedures.