Use of Compton suppression gamma ray spectrometry to determine 239Pu.

239Pu has been characterized by gamma-ray spectroscopy for a level higher than the usual environmental ones typically needing alpha spectrometry, ICP-MS or TIMS. The higher activities typically have applications in reprocessing, safeguards verification, and nuclear forensics. For activities of hundreds of Bq/g, it is possible to use gamma ray spectrometry for 239Pu characterization. A soil reference standard of 185 Bq/g (75 ng/g) was measured on a 79% efficient HPGe with a digital Compton suppression system. The ratios of the counting statistics for suppressed and unsuppressed uncertainties for various 239Pu photopeaks were determined. The effects of self-attenuation on the low energy gamma rays were evaluated, and it was determined that Compton suppression was an effective characterization method of 239Pu after accounting for self-attenuation.

SOURCES: a code for calculating (alpha,n), spontaneous fission, and delayed neutron sources and spectra.

SOURCES is a computer code that determines neutron production rates and spectra from (alpha,n) reactions, spontaneous fission and delayed neutron emission owing to the decay of radionuclides in homogeneous media, interface problems and three-region interface problems. The code is also capable of calculating the neutron production rates due to (alpha,n) reactions induced by a monoenergetic beam of alpha particles incident on a slab of target material. The (alpha,n) spectra are calculated using an assumed isotropic angular distribution in the centre-of-mass system with a library of 107 nuclide decay alpha-particle spectra, 24 sets of measured and/or evaluated (alpha,n) cross sections and product nuclide level branching fractions, and functional alpha particle stopping cross sections for Z < 106. Spontaneous fission sources and spectra are calculated with evaluated half-life, spontaneous fission branching and Watt spectrum parameters for 44 actinides. The delayed neutron spectra are taken from an evaluated library of 105 precursors. The code outputs the magnitude and spectra of the resultant neutron sources. It also provides an analysis of the contributions to that source by each nuclide in the problem.

Recent developments and applications for the University of Texas Thermal Neutron Imaging Facility.

The Thermal Neutron Imaging Facility (UT-TNIF) at the University of Texas at Austin is being modified to begin work with the non-destructive evaluation of carbon fiber composite materials intended for use in space. The use of high-resolution borated micro channel plate (MCP) detectors has been investigated. MCNP calculations to redesign the external radiation shielding to allow UT-TNIF operation at higher reactor powers and to minimize internal neutron scattering have been performed.

Identification and characterisation of PEX6 orthologues from plants.

The sunflower (Helianthus annuus) orthologue of PEX6, an AAA ATPase essential for the biogenesis of peroxisomes in yeasts and mammals, was isolated. HaPex6p is immunologically related to Pichia pastoris Pex6p. Like other genes involved in peroxisome biogenesis and function HaPEX6 mRNA and protein levels peak in early post-germinative growth and mRNA levels also increase in senescent tissue. HaPEX6 identifies probable orthologues in Arabidopsis and rice.

Correlation of estradiol in pregnancy and anterior cruciate ligament laxity.

The purpose of this study was to determine whether a correlation existed between estradiol in pregnancy and laxity of the anterior cruciate ligament by measuring anterior tibial translation. All patients underwent measurement of anterior tibial translation using KT-1000 knee arthrometer testing and serum estradiol determination during the third trimester of pregnancy and postpartum. Forty knees were studied. The average serum estradiol levels decreased from 10,755.0 ng/L to 50.3 ng/L. There was an average decrease anterior tibial translation with a manual maximum displacement of 3.0 mm (range, 1 mm-5 mm) from the first to second examinations. Average measurement of anterior tibial translation in pregnant women showed a statistically significant increase in laxity in the third trimester of pregnancy compared with the postpartum laxity. The results of this study show that high serum estradiol levels during the third trimester of pregnancy correlate with increased anterior tibial translation and that this anterior tibial translation decreases with the return of serum estradiol to nonpregnant levels.

Epicondylitis in the athlete.

Epicondylitis plagues a significant proportion of athletes and can result in prolonged symptoms and suboptimal athletic performance. The diagnosis can be confused with many other pathologic entities affecting the elbow, some of which can occur concurrently. Most patients will respond favorably to a well-guided nonsurgical treatment protocol. A minority of patients will have persistent problems and will require surgical intervention that can relieve pain effectively and return patients to their preinjury level of activity.

Stress induces peroxisome biogenesis genes.

Peroxisomes are the cellular location of many antioxidants and are themselves significant producers of reactive oxygen species. In this report we demonstrate the induction of peroxisome biogenesis genes in both plant and animal cells by the universal stress signal molecule hydrogen peroxide. Using PEX1-LUC transgenic plants, rapid local and systemic induction of PEX1-luciferase could be demonstrated in vivo in response to physiological levels of hydrogen peroxide. PEX1-luciferase was also induced in response to wounding and to infection with an avirulent pathogen. We propose a model in which various stress situations that lead to the production of hydrogen peroxide can be ameliorated by elaboration of the peroxisome compartment to assist in restoration of the cellular redox balance.

Biochemical and molecular approaches to understanding protein import into peroxisomes.

Peroxisomes are eukaryotic organelles that perform diverse and variable functions. Although genetic studies in yeasts and mammals have identified approximately 20 genes (PEX genes) required for the biogenesis of this important organelle, biochemical studies of protein targeting and import have lagged behind and in many cases we have no idea of the function of the PEX gene products (peroxins). Using an import assay in vitro derived from sunflower cotyledon cells and recombinant proteins, we have obtained translocation intermediates on the peroxisome import pathway and are using cross-linking to identify interacting partners. We have also used antibodies raised against human PEX14 to inhibit the import of matrix proteins in this system. To obtain homologous antibodies for inhibition experiments, to immunoprecipitate cross-linked products and to enable us to study the import pathways of peroxins we have cloned and characterized plant orthologues of three PEX genes, PEX6, PEX10 and PEX14.

The Klebsiella pneumoniae nifJ promoter: analysis of promoter elements regulating activation by the NifA promoter.

The nifJ and nifH promoters of Klebsiella pneumoniae are divergently transcribed sigma 54-dependent promoters that are positively activated by the NifA protein. NifA binds to upstream activator sequences (UASs), usually located 60-200 bp upstream of the start of transcription. Bound NifA is presented to the RNA polymerase-sigma 54 complex (E sigma 54) via DNA loop formation, mediated by the binding of integration host factor protein (IHF) between E sigma 54 and NifA. The nifJ promoter sequence contains three potential NifA binding sites (UAS1, 2 and 3) and two potential RNA polymerase-sigma 54-binding sites (downstream promoter elements, DPEs 1 and 2). DPE2 is located 420 bp into the coding region and DPE1 overlaps UAS1 by 5 bp. Mutational and footprinting analyses have shown efficient activation of the nifJ promoter requires that NifA is bound at UAS 2 and 3. Transcription is initiated at DPE1. Only a weak interaction of NifA with the UAS overlapping DPE1 was detected. Footprints demonstrated that E sigma 54 forms a closed complex at DPE1 but not DPE2 and that bound E sigma 54 closely approaches the -15 region of DPE1. Stimulation of nifJ promoter activity by IHF was not as great as that observed for other nif promoters. In the absence of IHF nifH promoter sequences stimulated activation of the nifJ promoter. This appeared to require NifA bound at the nifH UAS. Thus, one additional role of IHF may be to partition NifA between the two promoters by constraining the topology of the DNA.

Organization and function of binding sites for the transcriptional activator NifA in the Klebsiella pneumoniae nifE and nifU promoters.

The interaction of the Klebsiella pneumoniae NifA protein, a sigma 54-dependent activator, with the nifE and nifU promoters was analysed. At these promoters NifA established contacts in addition to those predicted by the minimal formulation NifA binding site (5'-TGT-N10-ACA). The positions of the contacts indicate that bound NifA molecules could assemble to form an oligomer. At both promoters contacts with NifA are made predominantly on one face of the DNA helix, and all contacts appear necessary for full activation by NifA. The close contacts made by NifA appear to be made by the DNA-binding domain of NifA. This domain shows specific DNA-binding activity in vitro. The binding of NifA to one site in the nifU promoter depends upon occupancy of additional upstream sequences by NifA. At the nifE promoter NifA binds adjacent to an integration host factor (IHF) binding site, but in contrast to results obtained with the nifU promoter IHF does not diminish nifE promoter occupancy by NifA. The IHF requirement for efficient in vivo activation of the nifU promoter by NifA was greater than that of the nifE promoter. Accordingly, the affinity of IHF for the nifU promoter is higher than for the nifE promoter. Amongst promoters utilizing the sigma 54 holoenzyme, the nifE promoter appears somewhat atypical in having the activator bound at around position -74 rather than the usual 100 base-pairs or more upstream from the transcription start site.

Primary angle-closure glaucoma among Alaskan Eskimos.

An epidemiological study of the occurrence of angle-closure glaucoma was made under the Eskimos population of the Norton Sound and Bering Straits region of Alaska. Among 1673 Alaskan Natives examined 14 cases (0.8%) of angle-closure glaucoma were found, in 0.5% of the men and 1.2% of the women; for persons above the age of 40 years these figures were 2.1% and 5.5% respectively. Angle-closure glaucoma was found in 11.8% of women above the age of 60 years. A shallow anterior chamber was seen twice as frequently in women as in men. Above the age of 30 years the chamber angle was considered to be occludable in 2% of men and 7.5% of women on gonioscopic examination. The average intra-ocular pressure of the right eyes of men was 11.7 mm Hg (s.d. 3.3) and of women 12.0 mm Hg (s.d. 3.4). Primary open-angle glaucoma was not seen in the population being studied.

Leaf anatomy, water relations and crassulacean acid metabolism in the chlorenchyma and colourless internal water-storage tissue of Carpobrotus edulis and Senecio ?mandraliscae.

Both Carpobrotus edulis and Senecio ?mandraliscae possess leaves with a peripheral chlorenchyma and colourless internal water-storage tissue. Water stress in C. edulis growing under semi-natural conditions resulted in the induction of weak Crassulacean acid metabolism (CAM) whereas well-watered plants of S. ?mandraliscae exhibited a similar degree of CAM. Titratable acidity in the separated water-storage tissue was substantially lower than in the chlorenchyma in both species but, nevertheless, increased during the night and decreased during the day either when sampled from the intact plant or from incubated tissue slices. Indeed, the increase in nocturnal titratable acidity produced by the water-storage tissue in situ accounted for approx. 30% of total acidification on a per-leaf basis. It appears that during the night the water-storage tissue in these species is able to fix CO2 which is subsequently released during the day to enter the photosynthetic carbon-reduction cycle of the chlorenchyma. Diurnal rhythms of water potential (Ψ) and osmotic potential (Ψs) were measured in separated chlorenchyma and water-storage tissue by thermocouple psychrometry. Both parameters increased during the latter part of the daytime and initial nocturnal period and decreased during the rest of the night and into the post-dawn period. The chlorenchyma of water-stressed plants of C. edulis appeared to possess a marked negative turgor pressure (as determined from Ψ-Ψs) but this was caused by a severe underestimation in the measurement of the chlorenchyma Ψ. It is suggested that this artefact arose from release of colloidal polysaccharide mucilage, or possibly tannins, from broken tannin cells producing a lowering of water activity when measured using thermocouple psychrometry.