Unexpected spatial stability of water chemistry in headwater stream networks

Understanding how water and solutes enter and propagate through freshwater landscapes in the Anthropocene is critical to protecting and restoring aquatic ecosystems and ensuring human water security. However, high hydrochemical variability in headwater streams, where most carbon and nutrients enter river networks, has hindered effective modelling and management. We developed an analytical framework informed by landscape ecology and catchment hydrology to quantify spatiotemporal variability across scales, which we tested in 56 headwater catchments, sampled periodically over 12 years in western France. Unexpectedly, temporal variability in dissolved carbon, nutrients and major ions was preserved moving downstream and spatial patterns of water chemistry were stable on annual to decadal timescales, partly because of synchronous variation in solute concentrations. These findings suggest that while concentration and flux cannot be extrapolated among subcatchments, periodic sampling of headwaters provides valuable information about solute sources and subcatchment resilience to disturbance.     

Macroalgal mass development in the Wadden Sea: First experiences with a monitoring system

The distribution and cover density of macroalgae (Chlorophyta, Ulvaceae) were estimated by means of aerial surveys in 1990–1992 in the Wadden Sea of Niedersachsen, an intertidal area of some 1200 km² situated at the German North Sea coast. Each year, up to a maximum of 15% of the total area was covered by algae. The spatial distribution was heterogeneous. In some subregions the macroalgal carpets covered from 30% up to 60% of the tidal flats. The cover density was at its peak in 1990. Additionally, tentative ground truth investigations were carried out on species composition. Reviewing other reports of macroalgal mass development at various sites in Europe, it is assumed that in the German Wadden Sea the recent macroalgal blooms have to be regarded as a response to eutrophication, and will presumably remain a chronic problem for many years to come.     

Isolation and characterization of the circulating form of human endostatin

Recently, fragments of extracellular proteins, including endostatin, were defined as a novel group of angiogenesis inhibitors. In this study, human plasma equivalent hemofiltrate was used as a source for the purification of high molecular weight peptides (10–20 kDa), and the isolation and identification of circulating human endostatin are described. The purification of this C-terminal fragment of collagen α1(XVIII) was guided by MALDI-MS and the exact molecular mass determined by ESI-MS was found to be 18 494 Da. N-terminal sequencing revealed the identity of this putative angiogenesis inhibitor and its close relation to mouse endostatin. The cysteine residues 1–3 and 2–4 in the molecule are linked by disulfide bridges. In vitro biological characterization of the native protein demonstrated no anti-proliferative activity on different endothelial cell types. These data indicate that human endostatin, which is a putative angiogenesis inhibitor, is present in the circulation.     

Regioselective oxidative phenol couplings of 2,3′,4,6-tetrahydroxybenzophenone in cell cultures of Centaurium erythraea RAFN and Hypericum androsaemum L.

A crucial step in plant xanthone biosynthesis is the cyclization of an intermediate benzophenone to a xanthone. In cultured cells of Centaurium erythraea RAFN, 2,3′,4,6-tetrahydroxybenzophenone (THBP) was shown to be intramolecularly coupled to 1,3,5-trihydroxyxanthone, whereas in cell cultures of Hypericum androsaemum L. it was coupled to form the isomeric 1,3,7-trihydroxyxanthone. These regioselective cyclizations that occur ortho and para, respectively, to the 3′-hydroxy group of the benzophenone depend on cytochrome P ₄₅₀, as shown by the effectiveness of established P ₄₅₀ inhibitors and blue-light-reversible carbon monoxide inhibition. Furthermore, the reactions absolutely require NADPH and O₂. The underlying reaction mechanism is probably an oxidative phenol coupling that is catalyzed regioselectively by xanthone synthases. These enzymes are proposed to be cytochrome P ₄₅₀ oxidases. The intramolecular cyclizations of THBP to 1,3,5- and 1,3,7-trihydroxyxanthones catalyzed by the two xanthone synthases represent an important branch point in the plant xanthone biosynthetic pathway. Received: 24 March 1997 / Accepted: 28 May 1997     

Effects of invasive Green Iguanas (<Emphasis Type="Italic">Iguana iguana</Emphasis>) on seed germination and seed dispersal potential in southeastern Puerto Rico

Green Iguanas (Iguana iguana) are invasive in Puerto Rico due to a variety of negative economic effects, yet we know very little about their ecological impacts. Because they are herbivorous, defecate intact seeds, move through the forest, and have long gut-passage times, Green Iguanas may affect seed germination and seed dispersal. In summer 2013, a total of 258 Green Iguana scat samples were collected at the Humacao Natural Reserve in southeastern Puerto Rico. Seeds extracted from scat and collected from fruit were planted under common garden conditions using experimental treatments designed to tease apart the effects of feces, fruit, and ingestion on seed germination. Green Iguanas decreased the time for seeds to germinate in Ficus spp. by removing fruit pulp, but had no effect on germination of native Annona glabra seeds. For non-native P. pterocarpus and Pterocarpus spp., Green Iguanas produced conflicting results, decreasing the percentage of seeds germinating, but at the same time, reducing the time for seeds to germinate. Green Iguanas likely disperse most seeds beyond the canopies of parental tree at our site. Government and economic resources are being used to eradicate Green Iguana populations in Puerto Rico, but the lack of consistent effects of Green Iguanas on seed germination for the plant species consumed at our site complicates generalizing about their ecological effects and developing management plans that minimize negative effects for native plant communities. We recommend additional studies that target both species of particular concern, such as threatened native or invasive species, as well as studies of sensitive habitats in Puerto Rico.     

Science ohne Fiction

Science without fiction Almost every newspaper and magazine, many TV stations and internet sites report on scientific topics. But what of it is trustworthy – and what is just sensationalism (a sensation message to create) to increase circulation? This article identifies criteria for good science journalism and shows why so many reports do not contribute to a good public information even in so‐called quality media.     

Pilot Preclinical and Clinical Evaluation of (4S)-4-(3-[18F]Fluoropropyl)-L-Glutamate (18F-FSPG) for PET/CT Imaging of Intracranial Malignancies

Purpose

(S)-4-(3-[¹⁸F]Fluoropropyl)-L-glutamic acid (18F-FSPG) is a novel radiopharmaceutical for Positron Emission Tomography (PET) imaging. It is a glutamate analogue that can be used to measure x_C^- transporter activity. This study was performed to assess the feasibility of 18F-FSPG for imaging orthotopic brain tumors in small animals and the translation of this approach in human subjects with intracranial malignancies.

Experimental Design

For the small animal study, GS9L glioblastoma cells were implanted into brains of Fischer rats and studied with 18F-FSPG, the 18F-labeled glucose derivative 18F-FDG and with the 18F-labeled amino acid derivative 18F-FET. For the human study, five subjects with either primary or metastatic brain cancer were recruited (mean age 50.4 years). After injection of 300 MBq of 18F-FSPG, 3 whole-body PET/Computed Tomography (CT) scans were obtained and safety parameters were measured. The three subjects with brain metastases also had an 18F-FDG PET/CT scan. Quantitative and qualitative comparison of the scans was performed to assess kinetics, biodistribution, and relative efficacy of the tracers.

Results

In the small animals, the orthotopic brain tumors were visualized well with 18F-FSPG. The high tumor uptake of 18F-FSPG in the GS9L model and the absence of background signal led to good tumor visualization with high contrast (tumor/brain ratio: 32.7). 18F-FDG and 18F-FET showed T/B ratios of 1.7 and 2.8, respectively. In the human pilot study, 18F-FSPG was well tolerated and there was similar distribution in all patients. All malignant lesions were positive with 18F-FSPG except for one low-grade primary brain tumor. In the 18F-FSPG-PET-positive tumors a similar T/B ratio was observed as in the animal model.

Conclusions

18F-FSPG is a novel PET radiopharmaceutical that demonstrates good uptake in both small animal and human studies of intracranial malignancies. Future studies on larger numbers of subjects and a wider array of brain tumors are planned.

Trial Registration

ClinicalTrials.gov {"type":"clinical-trial","attrs":{"text":"NCT01186601","term_id":"NCT01186601"}}NCT01186601