Chemical defenses of the Caribbean sponges Agelas wiedenmayeri and Agelas conifera

Previous studies have determined that Caribbean reef sponges of the genus Agelas are chemically defended from fish predation by brominated pyrrole alkaloids, and that the compounds responsible for this defense have been elucidated for one species, Agelas clathrodes. In this study, we expand our understanding of chemical defense in this common sponge genus to include the characterization of defensive metabolites in the tissues of Agelas wiedenmayeri and Agelas conifera. Bioassay-directed isolation of defensive metabolites was undertaken using fish feeding assays carried out in laboratory aquaria and in the field. Agelas wiedenmayeri contained the same two major metabolites as Agelas clathrodes, 4,5-dibromopyrrole-2-carboxylic acid (1), and oroidin (2), in addition to a small amount of bromoageliferin (7). The two major metabolites were present at higher concentrations in samples of Agelas wiedenmayeri than in Agelas clathrodes, and their relative concentrations were reversed, with Agelas wiedenmayeri on average containing more 4,5-dibromopyrrole-2-carboxylic acid (1) (2.0 mg/mL) than oroidin (2) (0.8 mg/mL). Agelas conifera contained a mixture of dimeric bromopyrrole alkaloids dominated by sceptrin (3), with <10% each of dibromosceptrin (5), bromoageliferin (7), dibromoageliferin (8), ageliferin (6), and bromosceptrin (4). Mean concentration of sceptrin (3) in sponge tissue was 5.3 mg/mL; this compound deterred feeding of reef fish in aquarium assays at 1.0 mg/mL, the lowest concentration assayed. Sceptrin (3) concentrations were higher in sponges collected in the southern Bahama Islands than those collected in the middle Bahamas, but reasons for this variation remain unclear. The structure-activity relationship of the pyrrole group was investigated by assaying derivatives of the active metabolites. Feeding deterrent activity of the molecule was enhanced by the addition of bromine to the pyrrole group, but not affected by exchange of the heteroatom from N to O or S. Combining an understanding of the structure-activity relationship of Agelas metabolites with an understanding of the variation in these metabolites across the genus may provide insight into the evolution of defensive chemistry in this highly successful taxa of pan-tropical sponges

A longitudinal study on the persistence of Livestock Associated-MRSA in swine herds

In recent years, a new type of MRSA, now called livestock-associated MRSA (LA-MRSA), belonging to the clonal complex (CC) 398, has globally emerged in swine world wide. Aim of this study was to gain more insight into the persistence of LA-MRSA in different types of pig farms over a period of two years. To investigate this, 15 MRSA-positive herds from a previous study were selected; an additional pig farm was selected because this one was found to be positive with a human MRSA-strain. Starting in September 2009, five dust samples were collected every two months. Samples were analysed for MRSA and spa-typing was done to confirm that MRSA isolates belonged to CC398 and to gain insight into persistence of strains within a farm. Three herds were positive on all sampling occasions and were consistently contaminated with LA-MRSA. In the remaining herds, occasionally no positive dust samples were found at some sampling moments. The predominating spa -types were t011 and t108. A maximum of 5 different spa-types were found in two herds, with 3 different spa-types present in one sampling, indicating multiple introductions. These results show that LA-MRSA remains present on a pig farm over a long period. Most likely, transmission within the herd occurs after initial introduction, and an endemic situation seems to be the endpoint. The relatively low sensitivity of dust sampling compared to sampling of animals, the small sample size and lack of strict standardization of dust sampling might explain occasional negative samplings in overall positive herds. However, a true change of a positive MRSA-status to a negative status, followed by re-introduction cannot be ruled out in our study design

Bremsstrahlung in alpha-Decay Reexamined

A high-statistics measurement of bremsstrahlung emitted in the alpha decay of 210Po has been performed, which allows to follow the photon spectra up to energies of ~ 500 keV. The measured differential emission probability is in good agreement with our theoretical results obtained within the quasi classical approximation as well as with the exact quantum mechanical calculation. It is shown that due to the small effective electric dipole charge of the radiating system a significant interference between the electric dipole and quadrupole contributions occurs, which is altering substantially the angular correlation between the alpha particle and the emitted photon.Comment: 10 pages, 5 figures, v2: fix of small typo

Persistence of Methicillin-resistant Staphylococcus aureus (MRSA) in pig herds over a two year period

Aim of this study was to determine if a known MRSA contamination within a pig herd could persist for a period of two years. Material and Methods: 16 pig herds with a known MRSA contamination were asked to participate in this study. Per herd, five dust swabs (Sodibox®) were collected every two months for a period of two years. Samples were tested for presence of MRSA by culture and two PCR’s for confirmation of MRSA. Isolates were typed by spa- en MLVA-typing

"Safe" Coulomb Excitation of 30Mg

We report on the first radioactive beam experiment performed at the recently commissioned REX-ISOLDE facility at CERN in conjunction with the highly efficient gamma spectrometer MINIBALL. Using 30Mg ions accelerated to an energy of 2.25 MeV/u together with a thin nat-Ni target, Coulomb excitation of the first excited 2+ states of the projectile and target nuclei well below the Coulomb barrier was observed. From the measured relative de-excitation gamma ray yields the B(E2; 0+ -> 2+) value of 30Mg was determined to be 241(31) e2fm4. Our result is lower than values obtained at projectile fragmentation facilities using the intermediate-energy Coulomb excitation method, and confirms the theoretical conjecture that the neutron-rich magnesium isotope 30Mg lies still outside the ``island of inversion''