Nutrient dynamics of 12 Sphagnum species during establishment on a rewetted bog.

Peatland degradation through drainage and peat extraction have detrimental environmental and societal consequences. Rewetting is an option to restore lost ecosystem functions, such as carbon storage, biodiversity and nutrient sequestration. Peat mosses (Sphagnum) are the most important peat-forming species in bogs. Most Sphagnum species occur in nutrient-poor habitats; however, high growth rates have been reported in artificial nutrient-rich conditions with optimal water supply. Here, we demonstrate the differences in nutrient dynamics of 12 Sphagnum species during their establishment in a 1-year field experiment at a Sphagnum paludiculture area in Germany. The 12 species are categorized into three groups (slower-, medium- and fast-growing). Establishment of peat mosses is facilitated by constant supply of nutrient-rich, low pH, and low alkalinity surface water. Our study shows that slower-growing species (S. papillosum, S. magellancium, S. fuscum, S. rubellum, S. austinii; often forming hummocks) displayed signs of nutrient imbalance. These species accumulated higher amounts of N, P, K and Ca in their capitula, and had an elevated stem N:K quotient (>3). Additionally, this group sequestered less C and K per m2 than the fast and medium-growing species (S. denticulatum, S. fallax, S. riparium, S. fimbriatum, S. squarrosum, S. palustre, S. centrale). Lower lawn thickness may have amplified negative effects of flooding in the slower-growing species. We conclude that nutrient dynamics and carbon/nutrient sequestration rates are species-specific. For bog restoration, generating ecosystem services or choosing suitable donor material for Sphagnum paludiculture, it is crucial to consider their compatibility with prevailing environmental conditions.

Interconnected electrocatalytic Pt-metal networks by plasma treatment of nanoparticle-peptide fibril assemblies.

Noble metal catalysts possess outstanding catalytic behaviors in organic reactions, photocatalysis, electrocatalysis and many other applications. Peptide fibrils are used for the controllable nanostructuring of metal nanoparticles with specific sizes, shapes and high-surface area structures. The degradation of these fibrils with O2-plasma yields interconnected networks of nanoparticles, similar to metallic nanowires. Herein, platinum nanoparticles (Pt-NPs) were synthesized by reduction using VUV excimer radiation. The particle size was characterized by dynamic light scattering (DLS). Due to agglomeration, the metal nanoparticles were stabilized using poly(vinyl pyrrolidone) (PVP) and the same synthesis procedure. The influence of the polymer PVP molecular weight (M wt), PVP concentration (C p) and VUV irradiation time on platinum nanoparticle size was investigated. Small (2-3 nm) Pt-NPs are formed in the case of PVP with M wt = 10 000 g mol-1. With increasing PVP M wt, decreasing PVP concentration and shorter irradiation times, larger sized nanoparticles appear. The applicability of templated platinum nanoparticles, both the PVP-stabilized and non-stabilized Pt-NPs, immobilized via electrostatic interactions on the solid phase-synthesized aniline-GGAAKLVFF (AFP) peptide fibrils was investigated to serve as possible electrode material. The plasma treatment of the nanoparticle-fibril-assemblies was also studied as a novel technique. The Pt-NPs-AFP fibrils and the PVP-stabilized-Pt-NPs-AFP fibrils nanohybrids were employed to modify electrodes and then subjected to O2-plasma treatment. These O2-plasma treated/modified electrodes exhibited high electrocatalytic activities towards oxygen reduction in cyclic voltammetry measurements. Thus, the aforementioned nanocomposites hold great potential for polymer electrolyte fuel cells and other electrochemical applications in miniature devices and microfluidic chips.

Nanoscale patterning of self-assembled monolayer (SAM)-functionalised substrates with single molecule contact printing.

Defined arrangements of individual molecules are covalenty connected ("printed") onto SAM-functionalised gold substrates with nanometer resolution. Substrates were initially pre-functionlised by coating with 3,3'-dithiodipropionic acid (DTPA) to form a self-assembled monolayer (SAM), which was characterised by atomic force microscopy (AFM), contact angle goniometry, cyclic voltammetry and surface plasmon resonance (SPR) spectroscopy. Pre-defined "ink" patterns displayed on DNA origami-based single-use carriers ("stamp") were covalently conjugated to the SAM using 1-ethyl-3-(3-dimethylamino-propyl)carbodiimide (EDC) and N-hydroxy-succinimide (NHS). These anchor points were used to create nanometer-precise single-molecule arrays, here with complementary DNA and streptavidin. Sequential steps of the printing process were evaluated by AFM and SPR spectroscopy. It was shown that 30% of the detected arrangements closely match the expected length distribution of designed patterns, whereas another 40% exhibit error within the range of only 1 streptavidin molecule. SPR results indicate that imposing a defined separation between molecular anchor points within the pattern through this printing process enhances the efficiency for association of specific binding partners for systems with high sterical hindrance. This study expands upon earlier findings where geometrical information was conserved by the application of DNA nanostructures, by establishing a generalisable strategy which is universally applicable to nearly any type of prefunctionalised substrate such as metals, plastics, silicates, ITO or 2D materials.

Diffusion and perfusion MRI to differentiate treatment-related changes including pseudoprogression from recurrent tumors in high-grade gliomas with histopathologic evidence.

BACKGROUND AND PURPOSE: Treatment-related changes and recurrent tumors often have overlapping features on conventional MR imaging. The purpose of this study was to assess the utility of DWI and DSC perfusion imaging alone and in combination to differentiate treatment-related effects and recurrent high-grade gliomas. MATERIALS AND METHODS: We retrospectively identified 68 consecutive patients with high-grade gliomas treated by surgical resection followed by radiation therapy and temozolomide, who then developed increasing enhancing mass lesions indeterminate for treatment-related changes versus recurrent tumor. All lesions were diagnosed by histopathology at repeat surgical resection. ROI analysis was performed of the enhancing lesion on the ADC and DSC maps. Measurements made by a 2D ROI of the enhancing lesion on a single slice were recorded as ADCLesion and rCBVLesion, and measurements made by the most abnormal small fixed diameter ROI as ADCROI and rCBVROI. Statistical analysis was performed with Wilcoxon rank sum tests with P = .05. RESULTS: Ten of the 68 patients (14.7%) had treatment-related changes, while 58 patients (85.3%) had recurrent tumor only (n = 19) or recurrent tumor mixed with treatment effect (n = 39). DWI analysis showed higher ADCLesion in treatment-related changes than in recurrent tumor (P = .003). DSC analysis revealed lower relative cerebral blood volume (rCBV)Lesion and rCBVROI in treatment-related changes (P = .003 and P = .011, respectively). Subanalysis of patients with suspected pseudoprogression also revealed higher ADCLesion (P = .001) and lower rCBVLesion (P = .028) and rCBVROI (P = .032) in treatment-related changes. Applying a combined ADCLesion and rCBVLesion model did not outperform either the ADC or rCBV metric alone. CONCLUSIONS: Treatment-related changes showed higher diffusion and lower perfusion than recurrent tumor. Similar correlations were found for patients with suspected pseudoprogression.

Potential role of preoperative conventional MRI including diffusion measurements in assessing epidermal growth factor receptor gene amplification status in patients with glioblastoma.

BACKGROUND AND PURPOSE: Epidermal growth factor receptor amplification is a common molecular event in glioblastomas. The purpose of this study was to examine the potential usefulness of morphologic and diffusion MR imaging signs in the prediction of epidermal growth factor receptor gene amplification status in patients with glioblastoma. MATERIALS AND METHODS: We analyzed pretreatment MR imaging scans from 147 consecutive patients with newly diagnosed glioblastoma and correlated MR imaging features with tumor epidermal growth factor receptor amplification status. The following morphologic tumor MR imaging features were qualitatively assessed: 1) border sharpness, 2) cystic/necrotic change, 3) hemorrhage, 4) T2-isointense signal, 5) restricted water diffusion, 6) nodular enhancement, 7) subependymal enhancement, and 8) multifocal discontinuous enhancement. A total of 142 patients had DWI available for quantitative analysis. ADC maps were calculated, and the ADCmean, ADCmin, ADCmax, ADCROI, and ADCratio were measured. RESULTS: Epidermal growth factor receptor amplification was present in 60 patients (40.8%) and absent in 87 patients (59.2%). Restricted water diffusion correlated with epidermal growth factor receptor amplification (P = .04), whereas the other 7 morphologic MR imaging signs did not (P > .12). Quantitative DWI analysis found that all ADC measurements correlated with epidermal growth factor receptor amplification, with the highest correlations found with ADCROI (P = .0003) and ADCmean (P = .0007). CONCLUSIONS: Our results suggest a role for diffusion MR imaging in the determination of epidermal growth factor receptor amplification status in glioblastoma. Additional work is necessary to confirm these results and isolate new imaging biomarkers capable of noninvasively characterizing the molecular status of these tumors.

Electron beam-based functionalization of polymer membranes.

A new electron beam-based approach for the direct functionalization of polyethersulfone, polyvinylidene fluoride, polysulfone as well as polyacrylonitrile membranes in a one-step procedure is presented. Aqueous solutions of functional molecules were immobilized on the membrane surface by electron beam treatment. The resulting membranes show significantly increased flux and water wettability accompanied by decreased protein adsorption. Stability tests demonstrated the permanence of the modification. This new method neither requires any preceding surface functionalization nor the use of catalysts/photoinitiators or other toxic reagents. In addition, it avoids the synthesis of hydrophilic monomers/polymers, thus avoiding additional synthetic and purification steps as well as the use of organic solvents.

Reduction of human visual cortex excitability using 1-Hz transcranial magnetic stimulation.

The effects of low-frequency (1-Hz) repetitive transcranial magnetic stimulation on visual cortex excitability were investigated by measuring phosphene thresholds (PTs) and stimulus-response curves. Stimulation over the visual cortex led to significantly decreased visual cortex excitability, expressed as an increase in PT. The motor threshold of the hand muscles did not change, indicating the topographic specificity of this effect. This intervention may be useful in situations associated with a hyperexcitable visual cortex.

Relationships between DNA damage and the survival of murine bone marrow cells irradiated in situ.

The relationships between DNA damage and the survival of murine bone marrow cells irradiated in situ were examined. Cell survival was assayed by the ability of bone marrow cells from irradiated mice to form colonies in vitro (CFU-C). DNA double-strand breaks (DSBs) were measured by neutral (nondenaturing) filter elution and pulsed-field gel electrophoresis (PFGE). Double-strand breaks were measured in the proliferating bone marrow cells, identified by injecting the mice with [3H]dThd at various times before gamma irradiation, as a model of the behavior of the radiosensitive target cells. To assess how the DNA lesions measured using these techniques correlated with cell killing, the effect of the radioprotective agent WR-2721 on the induction of DSBs in proliferating bone marrow cells was compared with its effect on CFU-C survival. WR-2721 protected against the killing of both granulocyte-macrophage and erythroid burst-forming CFU-C by a factor of about 2. In contrast, little (1.2-fold) protection was observed in the PFGE assay at radiation doses between 5 and 20 Gy. Similarly, at the lowest dose studied (5 Gy) there was little protection against DSBs as measured by neutral elution; only after doses of between 10 and 30 Gy was significant protection observed. Thus the previously reported predictive relationship between DSBs and cell survival in vitro does not appear to extend directly to murine bone marrow cells irradiated in vivo.

Influence of intracellular thiol and polyamine levels on radioprotection by aminothiols.

We examined the effect of manipulating the levels of two endogenous radioprotectors, glutathione (GSH) and polyamines, on the ability of exogenous aminothiols to protect Chinese hamster ovary cells from the lethal effects of gamma-radiation. Treatment with 0.5 mmol dm-3 buthionine sulfoximine (BSO) for 24 h depleted GSH levels to < 1% of control and significantly sensitized the cells to irradiation in air. Undepleted control cells were protected by WR-1065 (4 mmol dm-3; 30-min preirradiation treatment at 37 degrees C) by 2.09-fold (range 1.98-2.21) at the 10% survival level, whereas BSO-treated cells were protected by a factor of 1.98 (range 1.95-2.14) at this survival level. Thus, GSH depletion had no significant effect on the radioprotective capacity of WR-1065. Treating cells with 1 mmol dm-3 alpha-difluoromethyl ornithine (DFMO) for 48 h depleted the polyamines putrescine and spermidine to very low levels, while spermine was not significantly depleted. DFMO also sensitized cells to aerobic irradiation. WR-1065 protected DFMO-treated cells by 2.29-fold (range 2.08-2.53), whereas undepleted control cells were protected by 2.09-fold (range 1.98-2.21) at the 10% survival level. Thus, WR-1065 appeared to offset the radiosensitizing effect of the DFMO treatment. Cysteamine, on the other hand, protected control and DFMO-treated cells to the same extent. We also examined the effect of combinations of exogenous thiols on radiosensitivity. Cells were treated with WR-1065 (4 mmol dm-3) for 30 min and then with increasing concentrations of dithiothreitol for 5 min prior to irradiation. The protective effects of these two thiols were simply additive.

Relationships between DNA damage and the survival of radiosensitive mutant Chinese hamster cell lines exposed to gamma-radiation: Part 2. Effect of cellular redox status.

To characterize further the nature of the defects underlying the differential radiosensitivities of the Chinese hamster ovary cell lines NM2, EM9, and UV41, we compared the abilities of anoxia and of the thiol WR-1065 to protect these mutants and their parent cell line, AA8, from the lethal effects of gamma-radiation. Wide differences in oxygen enhancement ratios (OERs) for cell killing were observed in the different cell lines, those for UV41 and NM2 cells (1.8 and 2.1, respectively) being reduced and that for EM9 cells (3.3) being slightly (although significantly) increased compared with wild-type AA8 cells (2.9). These OER data support the hypothesis that repair-deficient mutants are hypersensitive to radiation under redox conditions that favour the formation of the particular lesions that correspond to their repair defect, and also support the earlier suggestion that the underlying molecular bases of the radiosensitivity of EM9 and NM2 cells are very different. In contrast to protection by anoxia, a 30-min preirradiation treatment with WR-1065 (4 mmol dm-3) protected aerated AA8, EM9, NM2, and UV41 cells to a similar extent with respect to both cell killing and the efficiency of DNA double-strand break (dsb) induction as measured by neutral elution. This observation is in marked contrast with reports of a greatly reduced protection by thiols for some repair-deficient cell lines and with the above-mentioned anoxia data. Thus, the particular types of mutations characteristic of NM2, EM9, and UV41 cells that give rise to their unusual OERs have little impact on the ability of WR-1065 to modify either cell killing or dsb induction, supporting radiochemical evidence that the types of deoxyribose radicals modifiable by oxygen and thiols are qualitatively different. Furthermore, because the extent of protection of these CHO mutants by thiols and anoxia show no correlation, oxygen depletion cannot be a major component of protection of aerated cells by thiols under these conditions.

Relationships between DNA damage and the survival of radiosensitive mutant Chinese hamster cell lines exposed to gamma-radiation. Part 1: Intrinsic radiosensitivity.

In this study we used the neutral elution technique (at pH 9.6) to compare the efficiency of DNA double-strand break (dsb) induction and cell killing in two radiosensitive Chinese hamster ovary cell lines, EM9 and NM2, and their parent cell line, AA8, after exposure to low doses (2.5-12 Gy) of 137Cs gamma-radiation. The survival curves indicated that at all radiation doses examined EM9 cells were the most radiosensitive and AA8 cells were the least radiosensitive. We found significant differences among the three cell lines in the neutral elution assay. While NM2 cells showed the same immediate postirradiation dose response for DNA damage as the parent cell line, EM9 cells showed a two-fold greater elution rate than AA8 cells per unit dose. Either the dsb induction efficiency was greater in EM9 than in AA8 cells, or the same frequency of dsb in EM9 and AA8 cells gave rise to a different DNA elution rate, perhaps because of differences in their chromatin structure. We also used a mitotic selection technique to examine the duration of the gamma-ray-induced mitotic delay in the three cell lines. Mitotic delay was less severe in NM2 cells than in AA8 cells, but was significantly longer in EM9 cells than in AA8 cells. Thus the measurements obtained using both neutral elution and mitotic selection suggest that the underlying molecular bases of the radiosensitivity of EM9 and NM2 cells are very different.

Effect of thiols on micronucleus frequency in gamma-irradiated mammalian cells.

The effects of the thiols cysteamine, WR-1065, and WR-255591 on radiation-induced micronucleus (MN) frequency and cell killing were compared in cultured Chinese hamster ovary cells. MN were measured using the cytochalasin B assay of Fenech and Morley (1985), which minimizes the effect of cytokinetic perturbations on MN expression. The dose-response curves for MN induction were curvilinear both for control cells at doses between 1.5 and 4.5 Gy and for thiol-treated cells at doses between 3 and 9 Gy. Protection against MN induction by each thiol was independent of radiation dose. Furthermore, there was a close correlation between the degree of modification of MN induction and cell survival by each thiol, i.e., the MN frequency closely predicted the survival level regardless of the presence of absence of the thiols. A similar predictive relationship has also been reported by us for cell survival and DNA double-strand break (DSB) induction in this cell line following treatment with these same thiols. Collectively, these data support the hypothesis that, for DNA-repair-proficient mammalian cells treated with radiomodifying agents that do not alter DNA-repair processes, MN and DSB induction are predictive of the level of radiation lethality and of each other.

Comparative effect of the thiols dithiothreitol, cysteamine and WR-151326 on survival and on the induction of DNA damage in cultured Chinese hamster ovary cells exposed to gamma-radiation.

We compared the ability of three thiols--dithiothreitol (DTT), cysteamine and WR-151326--to protect aerated Chinese hamster ovary cells from the lethal and DNA-damaging effects of gamma-radiation. These results were compared with earlier measurements for WR-1065 and WR-255591. The time-course and the concentration dependence of protection against cell killing was determined after 10 Gy of gamma-rays. The aminothiols cysteamine and WR-151326 protected at much lower extracellular concentrations than the simple thiol DTT; however, there was no clear difference between the behaviour of cysteamine, WR-151326, WR-1065 and WR-255591 in this respect. Protection by DTT and cysteamine was complete within 1 min, whereas for WR-151326, WR-1065 and WR-255591 about 30 min was required before protection began to reach a plateau. Based on these data, complete radiation survival curves were generated for each thiol and protection factors calculated. Effects on the induction of DNA single-strand breaks (ssb) and double-strand breaks (dsb) by gamma-rays were measured using alkaline (pH 12.1) and neutral (pH 7.0 and 9.6) elution, respectively. All three thiols protected against ssb induction, although to a significantly lower extent than against cell killing measured under identical conditions. Each thiol also protected against dsb induction. After high radiation doses the protection factors for dsb induction were also less than the protection factors for cell survival; however, when dsb were assayed using the low-dose replicate plating neutral elution method, the relative effect of each thiol on cell survival and on dsb induction appeared to be equivalent. The hierarchy of protection against both ssb and dsb induction (based on the extracellular thiol concentration required to produce a given degree of protection) was similar to that for cell survival, i.e., WR-151326 congruent to cysteamine less than DTT.

Radioprotection of cultured mammalian cells by the aminothiols WR-1065 and WR-255591: correlation between protection against DNA double-strand breaks and cell killing after gamma radiation.

We compared the effects of the radioprotective aminothiols WR-1065 and WR-255591 on the induction of DNA double-strand breaks (DSBs) and on the survival of aerated Chinese hamster ovary cells exposed to 60Co gamma radiation. DSBs were measured using the pH 9.6 neutral elution method. In agreement with earlier studies, protection factors for both drugs measured using the end point of clonogenic cell survival were significantly greater than the protection factors for DSB induction when DSBs were measured after gamma-ray doses ranging from 20 to 90 Gy. However, when DSBs and cell survival measurements were made on the same cell populations after low radiation doses (between 3 and 30 Gy) using the replicate plating method, there appeared to be a close correlation between the modification of DSB induction and the modification of cell survival produced by both drugs. The major influence accounting for the differences between these and previously obtained results appears to be the range of radiation doses used, suggesting that protection against DSB induction is radiation-dose dependent.

[Macrodacryocystography--a review of 232 cases]. / Die Makrodakryozystographie. Ubersicht über 232 Fälle.

During the last four years 232 macrodacryocystographies have been performed. The results are compared with the clinical evaluation of these patients. There are two groups of findings, simple stenosis on one side and anatomical abnormalities on the other side. The stenosis is mostly located before the lacrimal sac and most often involves the common canaliculus.--In the second part of the paper examples of alterations of the lacrimal apparatus show the value of the method in evaluating pathological anatomy.