When offered a choice between brown seaweeds (Phaeophyta) from shallow inshore populations versus deeper offshore populations along the mid-Atlantic coast of the United States of America, the ...herbivorous amphipod Ampithoe longimana consistently preferred plants from the inshore populations. This was the case for three species (Dictyota menstrualis, Spatoglossum schroederi, and Sargassum filipendula) collected from each of a single inshore and offshore site, and for one species (D. menstrualis) collected from each of three inshore and three offshore sites. Bioassay-guided fractionation of chemical crude extracts from D. menstrualis suggested that the relative unpalatability of the offshore plants was due to the lipid-soluble secondary metabolites 4β-hydroxydictyodial A and 18,O-dihydro-4β-hydroxy-dictyodial A 18-acetate, along with minor compounds that were not fully identified. The inshore-offshore pattern did not appear to result from induction of defenses due to herbivory by mesograzers, as mesograzer densities were higher on the more palatable inshore plants. Herbivore feeding preferences for inshore versus offshore seaweeds matched the effects of those seaweeds on their fitness. When juvenile amphipods were raised on inshore versus offshore tissues of D. menstrualis, amphipod survivorship, growth, and ovulation were significantly suppressed on the offshore compared to the inshore tissues. Few previous investigations have studied intraspecific variance in seaweed palatability. We extend these by showing that between-population differences in palatability can persist for several years and by demonstrating that this variance is chemically based and has dramatic effects on herbivore fitness.
We tested whether interactions among phytoplankton competitors affect toxin dynamics involving the red tide dinoflagellate
Karenia brevis, whose brevetoxins incapacitate and kill coastal wildlife. ...The addition of a live diatom,
Skeletonema costatum, led to decreased concentrations of brevetoxin B (PbTx-2) associated with
K. brevis cells in co-culturing experiments and with two of three natural bloom samples containing
K. brevis. Similar decreases in PbTx-2 concentration, but not PbTx-3 concentration, occurred when a mixture of brevetoxins (without live
K. brevis cells) was exposed to
S. costatum, indicating that
S. costatum metabolizes waterborne PbTx-2. Liquid chromatography–mass spectrometry (LC–MS) and ELISA analyses indicated that PbTx-2 is probably not transformed into other brevetoxins or into known brevetoxin metabolites, and instead is biotransformed by a previously unrecognized mechanism. Four different
S. costatum strains from around the world caused similar loss of PbTx-2, suggesting that evolutionary experience with
K. brevis is not a pre-requisite for the ability to metabolize PbTx-2. Additionally, phytoplankton-associated bacteria were found to play no role in the loss of PbTx-2, as bacteria-free
S. costatum strains metabolized PbTx-2. Finally, loss of waterborne PbTx-2 caused by exposure to a dinoflagellate, a cryptophyte, and two additional diatom species indicates that this phenomenon is widespread among phytoplankton. Our results unexpectedly suggest that competing phytoplankton species present during
K. brevis blooms, and possibly other red tides, could mediate bloom toxicity and therefore ecosystem-level consequences of red tides.
This work aims at constraining the size, shape, and geometric albedo of the dwarf planet candidate 2002 MS4 through the analysis of nine stellar occultation events. Using multichord detection, we ...also studied the object's topography by analyzing the obtained limb and the residuals between observed chords and the best-fitted ellipse. We predicted and organized the observational campaigns of nine stellar occultations by 2002 MS4 between 2019 and 2022, resulting in two single-chord events, four double-chord detections, and three events with three to up to sixty-one positive chords. Using 13 selected chords from the 8 August 2020 event, we determined the global elliptical limb of 2002 MS4. The best-fitted ellipse, combined with the object's rotational information from the literature, constrains the object's size, shape, and albedo. Additionally, we developed a new method to characterize topography features on the object's limb. The global limb has a semi-major axis of 412 \(\pm\) 10 km, a semi-minor axis of 385 \(\pm\) 17 km, and the position angle of the minor axis is 121 \(^\circ\) \(\pm\) 16\(^\circ\). From this instantaneous limb, we obtained 2002 MS4's geometric albedo and the projected area-equivalent diameter. Significant deviations from the fitted ellipse in the northernmost limb are detected from multiple sites highlighting three distinct topographic features: one 11 km depth depression followed by a 25\(^{+4}_{-5}\) km height elevation next to a crater-like depression with an extension of 322 \(\pm\) 39 km and 45.1 \(\pm\) 1.5 km deep. Our results present an object that is \(\approx\)138 km smaller in diameter than derived from thermal data, possibly indicating the presence of a so-far unknown satellite. However, within the error bars, the geometric albedo in the V-band agrees with the results published in the literature, even with the radiometric-derived albedo.
Numerous studies have investigated chemical defenses among sessile species growing on hard substrates, but few have addressed this for mobile species in soft-sediment communities. We investigated the ...palatability and potential chemical defenses of 11 worm species from soft-sediment systems in southern Florida, USA. Three species were unpalatable to the bluehead wrasseThalassoma bifasciatum. The polychaeteCirriformia tentaculataand the hemichordatePtychodera bahamensiswere uniformly unpalatable. For the polychaeteEupolymnia crassicornis, the exposed tentacles were unpalatable, but the body, which remains protected in a deeply buried tube, was palatable. These unpalatable worms were chemically defended; extracts ofC. tentaculata,P. bahamensis, and the tentacles ofE. crassicornisdeterred fish feeding. ForC. tentaculata, bioassay-guided fractionation demonstrated that a mixture of 3 closely related alkylpyrrole sulfamates deterred fish at naturally occurring concentrations (2-n-hexylpyrrole sulfamate 1.6% of worm dry mass, 2-n-heptylpyrrole sulfamate 3.1% dry mass, and 2-n-octylpyrrole sulfamate 0.8% dry mass). This appears to be the first documentation of characterized natural products defending a marine worm from consumers. ForP. bahamensisand the tentacles ofE. crassicornis, deterrent effects of crude extracts decomposed before specific compounds could be identified.
This paper reports on the European Space Agency (ESA) SARSimHT-NG experiment conducted in 2022 over a well-researched location in southern Italy. The experiment involved extensive ground data ...gathering coordinated with the German Aerospace Center's (DLR) F-SAR airborne acquisitions in C- and L-bands. The campaign aimed to simulate and analyse geostationary Synthetic Aperture Radar (GeoSAR) measurements over an agricultural area. Besides, it explored the synergy between GeoSAR systems and other Low Earth Orbit (LEO) satellite missions, namely Sentinel-1 Next Generation (NG) and the Radar Observation System for Europe in L-band (ROSE-L). The hyper-temporal repeat cycle of GEoSAR systems is instrumental in investigating the rapid processes of the water cycle. The concept was developed for the Hydroterra mission proposal submitted to the ESA Earth Explorer 10 call and studied in phase 0. The paper illustrates the soil and vegetation in situ data collected together with the L- and C-band fully polarimetric SAR time series acquired at a very high revisit. Moreover, insights into the retrieval of the surface dynamics of the water cycle are also provided.
Rye germ lectin was isolated by extraction of defatted rye germ, fractionation of the extract by ammonium sulfate precipitation, affinity chromatography of the active substances on chitin-beta-glucan ...and gel filtration on Sephadex G-50. The lectin shows erythroagglutinating activity at a minimum concentration of 2.5 micrograms/ml. The erythroagglutinating activity is the same against human red blood cells of all types of the ABO system and is inhibited by N-acetyl-D-glucosamine. The lectin has no mitogenic activity against mouse splenic lymphocytes. According to the results of polyacrylamide gel electrophoresis the lectin obtained is a mixture of three very similar isolectins of equal erythroagglutinating activity. Sedimentation analysis indicates homogeneity of the lectin preparation; the molecular weight was 56000 as estimated by sedimentation equilibrium. In the presence of urea and sodium dodecyl sulfate the lectin dissociates into 2 types of subunits with molecular weights of 35000 and 19000. The rye germ lectin contains about 2% of neutral sugar and 1% of D-glucosamine. The amino acid composition of the lectin is characterized by a very high content of glycine and half cystine and a low content of apolar amino acids. N-terminal amino acids of the lectin are apparently blocked.
Two diarylbutane derivatives of dihydroguaiaretic acid have been isolated from emergent portions of the southeastern United States freshwater angiosperm
Saururus cernuus L. (Saururaceae). ...Bioassay-guided fractionation of organic extracts of
S. cernuus led to the compounds, sauriols A and B, in addition to five previously known lignoids. These metabolites deter feeding by the omnivorous crayfish
Procambarus clarkii. The two lignans were identified by analysis of nuclear magnetic resonance and mass spectral data, and by comparison with spectral data of dihydroguaiaretic acid.
2,3,4-Tribromopyrrole (1) and 2,3,5-tribromopyrrole (2) were each synthesized from pyrrole. Spectral data and antifeedant effects for synthetic 1 and the antipredatory chemical defense compound of ...the marine hemichordate Saccoglossus kowalevskii were in agreement, confirming the structure of the deterrent natural product as 1. Spectral data for 2 differed from synthetic and natural 1.
Peptide toxins have been valuable probes in efforts to identify amino acid residues that line the permeation pathway of cation-selective channels. However, no peptide toxins have been identified that ...interact with known anion-selective channels such as the cystic fibrosis transmembrane conductance regulator (CFTR). CFTR channels are expressed in epithelial cells and are associated with several genetic disorders, including cystic fibrosis and polycystic kidney disease. Several organic inhibitors have been used to investigate the structure of the Cl- permeation pathway in CFTR. However, investigations of the wider cytoplasmic vestibule have been hindered by the lack of a high-affinity blocker that interacts with residues in this area. In this study we show that venom of the scorpion Leiurus quinquestriatus hebraeus reversibly inhibits CFTR, in a voltage-independent manner, by decreasing single-channel mean burst duration and open probability only when applied to the cytoplasmic surface of phosphorylated channels. Venom was able to decrease burst duration and open probability even when CFTR channels were locked open by treatment with either vanadate or adenosine 5'-(beta,gamma-imido)triphosphate, and block was strengthened on reduction of extracellular Cl- concentration, suggesting inhibition by a pore-block mechanism. Venom had no effect on ATP-dependent macroscopic opening rate in channels studied by inside-out macropatches. Interestingly, the inhibitory activity was abolished by proteinase treatment. We conclude that a peptide toxin contained in the scorpion venom inhibits CFTR channels by a pore-block mechanism; these experiments provide the first step toward isolation of the active component, which would be highly valuable as a probe for CFTR structure and function.
The authors analyzed an epidemic of viral hepatitis B during which 43% patients of the hemodialyzation centre in K were infected. Using the method of sequence analysis of the DNA of hepatitis B virus ...they identified the source of infection. They monitored serologically the course of infection in all infected subjects and the state of specific antibody immunity in patients and staff. 22% infections were manifested clinically and 75% infected HBsAg positive patients developed chronic hepatitis. Although 38 of 42 hemodialyzed patients were vaccinated against hepatitis B, 20 patients lacked anti-HBs antibodies before the epidemic. Only one of the patients without anti-HBs was not infected. In 10 immune patients the rise of antibody levels confirmed that they were also exposed to HBV. The effectiveness of vaccination against VHB in hemodialyzed patients is markedly lower. Vaccination of these patients is an important but only supplementary provision in VHB prevention. Sequence analysis of HBV DNA may be a useful tool of epidemiological analysis.
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