Actinide and metal toxicity to prospective bioremediation bacteria

Bacteria may be beneficial for alleviating actinide contaminant migration through processes such as bioaccumulation or metal reduction. However, sites with radioactive contamination often contain multiple additional contaminants, including metals and organic chelators. Bacteria-based bioremediation requires that the microorganism functions in the presence of the target contaminant, as well as other contaminants. Here, we evaluate the toxicity of actinides, metals and chelators to two different bacteria proposed for use in radionuclide bioremediation, Deinococcus radiodurans and Pseudomonas putida, and the toxicity of Pu(VI) to Shewanella putrefaciens. Growth of D. radiodurans was inhibited at metal concentrations ranging from 1.8 microM Cd(II) to 32 mM Fe(III). Growth of P. putida was inhibited at metal concentrations ranging from 50 microM Ni(II) to 240 mM Fe(III). Actinides inhibited growth at mM concentrations: chelated Pu(IV), U(VI) and Np(V) inhibit D. radiodurans growth at 5.2, 2.5 and 2.1 mM respectively. Chelated U(VI) inhibits P. putida growth at 1.7 mM, while 3.6 mM chelated Pu(IV) inhibits growth only slightly. Pu(VI) inhibits S. putrefaciens growth at 6 mM. These results indicate that actinide toxicity is primarily chemical (not radiological), and that radiation resistance does not ensure radionuclide tolerance. This study also shows that Pu is less toxic than U and that actinides are less toxic than other types of metals, which suggests that actinide toxicity will not impede bioremediation using naturally occurring bacteria.     

Evaluation of a portable light device for phase advancing the circadian rhythm in the home environment

This study evaluated the effectiveness of a head-mounted portable light device, Re-Timer, for phase advancing the circadian rhythm of healthy sleepers in the home environment. The Re-Timer was designed to address the limitations of traditional bright light boxes, making it more practical and efficient for administering light therapy. Eighteen healthy participants underwent a crossover design treatment protocol, consisting of seven consecutive mornings of using Re-Timer compared with the same procedure but not using Re-Timer. Circadian phase was measured using salivary dim light melatonin onset (DLMO) and subjective sleepiness was also assessed for other phase-change effects. After using the Re-Timer for seven mornings, a significant phase advance in DLMO of 41 min compared to a 10-min delay in the no-light control condition was observed. However, subjective sleepiness did not differ significantly between the two conditions. A few minor and transient side effects were experienced by participants, but no treatment was required. The Re-Timer is an effective and safe device for advancing the circadian rhythm of healthy sleepers at home. Future research on its clinical utility could make Re-Timer a practical and affordable way to self-administer bright light therapy for sleep disorders.

     

Characterization of cathepsins in cartilage

The presence of a cathepsin B-like enzyme in rabbit ear cartilage was established by the use of the synthetic substrates benzoyl-l-arginine amide and benzoyl-dl-arginine 2-naphthylamide. This was facilitated by using a technique that permits the incubation of a fixed weight of thin (18mu) cartilage sections with an appropriate exogenous substrate. The enzymic properties of cathepsin B in cartilage have been compared with an endogenous enzyme that liberates chondromucopeptide by degrading the cartilage matrix autocatalytically at pH5. Besides being maximally active at pH4.7, these cartilage enzymes are enhanced in activity by cysteine and inhibited by arginine analogues, iodoacetamide, chloroquine and mercuric chloride. They are not inhibited by EDTA, di-isopropyl phosphorofluoridate and diethyl p-nitrophenyl phosphate. When inhibiting the release of chondromucopeptide from cartilage at pH5, the arginine-containing synthetic substrates are hydrolysed simultaneously. These enzymes also share the same heat-inactivation characteristics at various pH values, being stable at acid pH and unstable at neutral and alkaline pH. The experimental evidence indicates that a cathepsin B-like enzyme may be partly responsible for the autolytic degradation of cartilage matrix at pH5.     

Distribution and conservation of mobile elements in the genus Drosophila

Essentially nothing is known of the origin, mode of transmission, and evolution of mobile elements within the genus Drosophila. To better understand the evolutionary history of these mobile elements, we examined the distribution and conservation of homologues to the P, I, gypsy, copia, and F elements in 34 Drosophila species from three subgenera. Probes specific for each element were prepared from D. melanogaster and hybridized to genomic DNA. Filters were washed under conditions of increasing stringency to estimate the similarity between D. melanogaster sequences and their homologues in other species. The I element homologues show the most limited distribution of all elements tested, being restricted to the melanogaster species group. The P elements are found in many members of the subgenus Sophophora but, with the notable exception of D. nasuta, are not found in the other two subgenera. Copia-, gypsy-, and F-element homologues are widespread in the genus, but their similarity to the D. melanogaster probe differs markedly between species. The distribution of copia and P elements and the conservation of the gypsy and P elements is inconsistent with a model that postulates a single ancient origin for each type of element followed by mating-dependent transmission. The data can be explained by horizontal transmission of mobile elements between reproductively isolated species.      

Phagnalon rechingeri (Inuleae,Asteraceae), a new species from Iran

Phagnalon rechingeri spec. nova from S Baluchestan (Iran) is described as a species new to science and illustrated; its relationships to other species of the genus, in particular to thePh. woodii group from S Arabia, are discussed.Dedicated to Hofrat Univ.-Prof. DrK. H. Rechinger on the occasion of his 80th birthday.