Evidence for 'bystander effects' in vivo.

The observation of bystander effects in vitro have raised some serious questions as to the appropriate target size for calculation radiation dose. This has implications on the risk from ionizing radiation since dose is often directly related to radiation risk. This paper demonstrates that bystander effects do occur in vivo.

Changes in biomarkers from space radiation may reflect dose not risk.

This presentation evaluates differences between radiation biomarkers of dose and risk and demonstrates the consequential problems associated with using biomarkers to do risk calculations following radiation exposures to the complex radiation environment found in deep space. Dose is a physical quantity, while risk is a biological quantity. Dose does not predict risk.

Phosphorylation by cAMP-dependent protein kinase modulates the structural coupling between the transmembrane and cytosolic domains of phospholamban.

We have used frequency-domain fluorescence spectroscopy to investigate the structural linkage between the transmembrane and cytosolic domains of the regulatory protein phospholamban (PLB). Using an engineered PLB having a single cysteine (Cys(24)) derivatized with the fluorophore N-(1-pyrenyl)maleimide (PMal), we have used fluorescence resonance energy transfer (FRET) to measure the average spatial separation and conformational heterogeneity between PMal bound to Cys(24) in the transmembrane domain and Tyr(6) in the cytosolic domain near the amino terminus of PLB. In these measurements, PMal serves as a FRET donor, and Tyr(6) serves as a FRET acceptor following its nitration by tetranitromethane.

Developing a scientific basis for radiation risk estimates: goal of the DOE Low Dose Research Program.

The U.S. Department of Energy's Low Dose Radiation Research Program is a 10 y activity currently funded at $21 million per year.

8-Oxoguanine enhances bending of DNA that favors binding to glycosylases.

Molecular dynamics (MD) simulations were carried out on the DNA oligonucleotide GGGAACAACTAG:CTAGTTGTTCCC in its native form and with guanine in the central G(19):C(6) base pair replaced by 8-oxoguanine (8oxoG). A box of explicit water molecules was used for solvation, and Na(+) counterions were added to neutralize the system. The direction and magnitude of global bending were assessed by a technique used previously to analyze simulations of DNA containing a thymine dimer.

Relative effectiveness of HZE iron-56 particles for the induction of cytogenetic damage in vivo.

One of the risks of prolonged manned space flight is the exposure of astronauts to radiation from galactic cosmic rays, which contain heavy ions such as (56)Fe. To study the effects of such exposures, experiments were conducted at the Brookhaven National Laboratory by exposing Wistar rats to high-mass, high-Z, high-energy (HZE) particles using the Alternating Gradient Synchrotron (AGS). The biological effectiveness of (56)Fe ions (1000 MeV/nucleon) relative to low-LET gamma rays and high-LET alpha particles for the induction of chromosome damage and micronuclei was determined.

Microdosimetry of a 25 keV electron microbeam.

Electron microbeam experiments are planned or under way to explore in part the question regarding whether the bystander effect is a general phenomenon or is restricted to high-LET radiation. Since low-LET radiations scatter more readily compared to high-LET radiations, identifying bystander cells and assessing the potential dose that they may receive will be crucial to the interpretation of radiobiological results. This paper reports on initial calculations of the basic information needed for a stochastic model of the penetration of energetic electrons in tissue-like matter; the model will be used to predict doses delivered to adjacent regions in which bystander cells may reside.

Biomarkers of exposure, sensitivity and disease.

Purpose: This review is to evaluate the use of biomarkers as an indication of past exposure to radiation or other environmental insults, individual sensitivity and risk for the development of late occurring disease.

Overview: Biomarkers can be subdivided depending on their applications. Markers of exposure and dose can be used to reconstruct and predict past accidental or occupational exposures when limited or no physical measurements were available.

A Monte Carlo code for positive ion track simulation.

An ion interaction model has been described for simulating positive ion tracks in a variety of media with the capability of interfacing with several secondary electron transport codes. Data are presented for single-and double-differential cross-sections, binding energies, probability density distribution for delocalisation parameters for conductors and tissue, branching ratios and ionisation efficiencies for water vapour and liquid water.

Cloning, sequencing, and analysis of a gene cluster from Chelatobacter heintzii ATCC 29600 encoding nitrilotriacetate monooxygenase and NADH:flavin mononucleotide oxidoreductase.

Nitrilotriacetate (NTA) is an important chelating agent in detergents and has also been used extensively in processing radionuclides. In Chelatobacter heintzii ATCC 29600, biodegradation of NTA is initiated by NTA monooxygenase that oxidizes NTA to iminodiacetate and glyoxylate. The NTA monooxygenase activity requires two component proteins, component A and component B, but the function of each component is unclear.

Purification and characterization of chlorophenol 4-monooxygenase from Burkholderia cepacia AC1100.

Burkholderia (formerly Pseudomonas) cepacia AC1100 mineralizes the herbicide 2,4,5-trichlorophenoxyacetate (2,4,5-T), and the first intermediate of 2,4,5-T degradation is 2,4,5-trichlorophenol. Chlorophenol 4-monooxygenase activity responsible for 2,4,5-trichlorophenol degradation was detected in the cell extract. The enzyme consisted of two components separated during purification, and both were purified to more than 95% homogeneity.

Lifespan studies in rats exposed to 239PuO2 aerosol. III. Survival and lung tumours.

Female, young adult, Wistar rats were given a single inhalation exposure to a submicron sized aerosol of high-fired 239PuO2 and observed during their lifespan for primary lung tumours. Rats were distributed among sham-control (n = 1052) and exposed (n = 2105) groups. Survival was significantly reduced only in rats with lung doses > 30 Gy.