Optimising bait size and 1080 concentration (sodium monofluoroacetate) for the control of brushtail possums Trichosurus vulpecula)

A method is presented for quantitatively assessing the likely effectiveness of specific bait size and 1080 concentration for controlling brushtail possums with a known weight distribution. Data from aerial 1080 operations for the control of brushtail possums in New Zealand show that estimates of the bait size and toxic concentration required derived from the mean parameters [pest weight, bait size, and lethal dose (LD 95)] will not be accurate. This inaccuracy is most likely to lead to an underestimate of the amount of toxin presented to each animal, so that many operations currently run the risk of sub-lethally dosing possums and thereby possibly inducing some degree of poison shyness. On the basis of more accurate quantitative assessments of bait effectiveness we recommend that the 1080 concentration be increased to 0.15% and that baits less than 5 g be excluded to ensure that when mean possum weights are less than 3 kg more than 95% of possums are lethally dosed by a single bait.

Macromolecular structure and self-assembly

The output from the molecular biology revolution has grown steadily and logarithmically from the first protein sequence, insulin (Ryle AP et al 1955 Biochem J 60:541-556), the first three-dimensional atomic structure of a macromolecule, myoglobin (Kendrew JC et al 1960 Nature 185:422-427), the first DNA gene sequence, phi X174 gene J (Sanger F et al 1977 Nature 265:687-695) and the first genome sequence for a free-living organism, Haemophilus influenzae (Fleischmann RD et al 1995 Science 269:496-512) to the current situation where the output rate is close to one new gene sequence every few minutes, several new three-dimensional structures a day and a new (bacterial) genome completed every few months. Those working in this field must readjust their horizons to this changing situation every year or two. In the area of three-dimensional structure of macromolecules and macromolecular assemblies, the methods of X-ray crystallography, nuclear magnetic resonance and electron microscopy have combined to produce powerful insights into how these molecular machines work. In this paper, I present three examples of molecular machines whose structure tells us a lot about how they work. These are the light-driven proton pump bacteriorhodopsin, the ATP synthetase molecule which contains a tiny motor and generator, and the flagellar rotary motor which provides the thrust to power physical movement of the bacterial cell. The structure itself in three-dimensional detail is thus often seen to provide the most important single insight into how things work, reducing biology to chemistry and physics. The reductionist approach in this field seems to be limited only by the accuracy by which it is possible to describe inter- and intra-molecular interactions in terms of hydrogen bonds, van der Waals interactions and electrostatic forces. At present, there is no fundamental limit in sight.

The anticarcinogenic conjugated fatty acid, 9c, 11t-18:2, in human milk: confirmation of its presence

The concentration of the anticarcinogenic fatty acid, 9c, 11t-18:2, in human milk was determined by gas-liquid chromatography (GLC). The mean concentration of 20 samples from 5 women taken at 1, 7, 14, and 21 days was: 0.18% +/- 0.02; range, 0.14-0.28%. Identity was confirmed by GLC-mass spectrometry (MS). Conjugated isomers other than 9c, 11t-18:2 were not detected. The amounts were not changed by supplementation of the maternal diet with fish oil beginning on day 1 after the milk sample was taken.

False negative factor V Leiden assay following allogeneic stem cell transplant

We report a case where a phenotypic test (an activity assay for activated protein C resistance) correctly indicated that the patient had an abnormality, whereas the initial genetic test (a PCR-based DNA assay used to detect the mutation in the FV gene) incorrectly indicated that the patient did not. The apparent false negative result of the DNA-based test was due to the use of peripheral blood leucocytes for DNA analysis. The patient had undergone a stem cell transplant several months before, and the leucocytes in her blood were derived from the stem cell donor, which lacked the FV defect.

Magnetic field conditioned taste aversion in rats

Conditioned taste aversion is a common classic conditioning procedure used to identify noxious stimuli. When a rat is given a taste solution, the conditioned stimulus (CS), followed by an unpleasant experience, the unconditioned stimulus (US), the rat will avoid consumption of the CS in future presentations. These experiments use the taste aversion procedure to examine the effect of exposure to a high magnetic field. A solution consisting of 3.0 g glucose and 1.25 g saccharin per 1 L of solution (G+S) was used as the CS and a 9.4-T magnet served as the US. In Experiment 1, all rats received a 10 min presentation of the G+S solution followed by either a 30 min exposure to the magnetic field (Magnet, n = 8), a 30-min exposure in a container with similar conditions but lacking the magnetic field (Sham, n = 8), or no exposure (Control, n = 8). The Magnet Group showed a taste aversion on the first day of preference testing (p < 0.05). Experiment 2 employed the same US-CS protocol for 3 consecutive days of conditioning. The Magnet Group demonstrated a taste aversion for the postexposure Days 1-8 (p < 0.01). There was no difference between the Sham and Control Groups in either experiment. The results of this study clearly demonstrate that the rats associated the G+S solution with the experience of being exposed to the high magnetic field and avoided the solution in subsequent presentations.

Efficacy of strength training in prepubescent to early postpubescent males and females: effects of gender and maturity

There has been considerable debate concerning the benefits of children participating in weight training programs. With the potential benefits of such training in specific rehabilitation regimens, the safety/efficacy of weight training is a topic in need of scientific study. Fifty-two experimental and 39 control subjects participated in this study. A 2 x 2 x 2 (gender by treatment by Tanner stage) ANOVA was used to examine pre- to post-test differences in six strength measures, eight anthropometric measures, five motor performance measures, and one flexibility measure associated with participation in a 12-week progressive resistance programme. In addition, safety of the weight training programme was examined. For strength differences, there were two significant main effects favouring strength gains in males and four favouring the experimental group. For anthropometric changes, 3-way interactions occurred that were not easily explained. However, the predominant main effect was treatment; the experimental group generally experienced gains in body segment girths with decreases in skinfold thickness. For motor performance, the experimental group had greater improvements in three of five parameters. The experimental group also had significantly greater gains in flexibility. The weight training programme was associated with only one injury. These findings support the general observation that physical benefits can be gained safely by children who participate in a weight training programme.

A controlled trial of fluoxetine in nondepressed patients with Huntington's disease

To examine the antidepressant specificity of fluoxetine in Huntington's disease (HD), we carried out a randomized, double-blind, placebo-controlled trial of this medication in nondepressed HD patients. Thirty patients with early HD who were depressed (Hamilton Depression Inventory < 16) were randomized to placebo (N = 13) or fluoxetine 20 mg/day (N = 17) and were followed up for 4 months. Outcome measures included changes in total functional capacity (TFC) and in standardized neurological, cognitive, and behavioral ratings. After adjustment for the higher education level found in the placebo group at baseline, no differences between the treatment groups were found in TFC, neurological, or cognitive ratings. Fluoxetine-treated patients did show a slight reduction in agitation and in the need for routine. Although fluoxetine may be a useful antidepressant in depressed HD patients, it failed to exert substantial clinical benefits in nondepressed HD patients.

Electron diffraction studies of light-induced conformational changes in the Leu-93 --> Ala bacteriorhodopsin mutant

We previously have presented evidence for prominent structural changes in helices F and G of bacteriorhodopsin during the photocycle. These changes were determined by carrying out electron diffraction analysis of illuminated two-dimensional crystals of wild-type bacteriorhodopsin or the Asp-96 --> Gly mutant that were trapped at a stage in the photocycle after light-driven proton release, but preceding proton uptake from the aqueous medium. Here, we report structural analysis of the long-lived O intermediate observed in the photocycle of the Leu-93 --> Ala mutant, which accumulates after the release and uptake of protons, but before the reisomerization of retinal to its initial all-trans state. Projection Fourier difference maps show that upon illumination of the Leu-93 --> Ala mutant, significant structural changes occur in the vicinity of helices C, B, and G, and to a lesser extent near helix F. Our results suggest that (i) all four helices that line the proton channel (B, C, F, and G) participate in structural changes during the late stages of the photocycle, and (ii) completion of the photocycle involves significant conformational changes in addition to those that are associated with steps in proton transport.

Maternal vitamin A deficiency and child growth failure during human immunodeficiency virus infection

Although vitamin A is thought to influence growth, the relationship between maternal vitamin A deficiency during pregnancy and child growth is unknown. A longitudinal cohort study of 467 HIV-infected women and their children was conducted in Blantyre, Malawi. The children's weight and height were measured every 3 months until they were 24 months old. Maternal vitamin A deficiency was independently related to both linear and ponderal growth after adjustment for effects of body mass index, child gender, and child HIV status. By 12 months of age, infants born to mothers who were vitamin A-deficient during pregnancy weighed approximately 8% less (p < 0.001) and were approximately 2% shorter (p < 0.001) than infants born to mothers who were not deficient. This study suggests children born to HIV-infected women who are vitamin A-deficient during pregnancy are more likely to have growth failure.

Involvement of Sonic hedgehog (Shh) in mouse embryonic lung growth and morphogenesis

Branching morphogenesis of the embryonic lung requires interactions between the epithelium and the mesenchyme. Previously, we reported that Sonic hedgehog (Shh) transcripts are present in the epithelium of the developing mouse lung, with highest levels in the terminal buds. Here, we report that transcripts of mouse patched (Ptc), the homologue of a Drosophila gene encoding a putative transmembrane protein required for hedgehog signaling, are expressed at high levels in the mesenchyme adjacent to the end buds. To investigate the function of SHH in lung development, Shh was overexpressed throughout the distal epithelium, using the surfactant protein-C (SP-C)-enhancer/promoter. Beginning around 16.5 dpc, when Shh and Ptc RNA levels are normally both declining, this treatment caused an increase in the ratio of interstitial mesenchyme to epithelial tubules in transgenic compared to normal lungs. Transgenic newborn mice die soon after birth. Histological analysis of the lungs at the light and electron microscope level shows an abundance of mesenchyme and the absence of typical alveoli. In vivo BrdU labeling indicates that Shh overexpression results in increased mesenchymal and epithelial cell proliferation at 16.5 and 17.5 dpc. However, analysis of CC-10 and SP-C expression reveals no significant inhibition in the differentiation of proximal and distal epithelial cells. The expression of genes potentially regulated by SHH was also examined. No difference could be observed between transgenic and control lungs in either the level or distribution of Bmp4, Wnt2 and Fgf7 RNA. By contrast, Ptc is clearly upregulated in the transgenic lung. These results thus establish a role for SHH in lung morphogenesis, and suggest that SHH normally regulates lung mesenchymal cell proliferation in vivo.

The need for policy and risk analysis--the Department of Energy experience

Reduction of major risks to the public and workers is a top priority of all federal agencies. Given current and future budget realities, agencies cannot attempt to address all risks simultaneously nor to address certain relatively lower risk activities as rapidly as some would like. The assumptions and judgments inherent in using risk analysis in the absence of data, however, have to be clearly stated. What is needed is an integrated risk assessment and management process that meets the current and future needs of the government, as well as of stakeholders. Yet there have been many questions raised regarding risk assessment: our ability to define the risks on a specific substance or site basis and in a systematic way; methodology questions about identifying and assessing diverse hazards and risks as well as uncertainties in the estimates, data gaps, and concern over the quality of information; and the fact that "who" performs the risk assessment matters. Knowing these controversies surrounding risk and the use of risk-based approach, the Department of Energy (DOE) requested the National Academy of Sciences-National Research Council to determine whether and how risk and risk-based decisions could be incorporated into a major federal program, the DOE's Office of Environmental Management. The report identified the major obstacles, issues, and barriers to implementing a risk-based management approach. The report concluded that the use of risk-based approach could help compare outcomes, build consensus, and gain early public involvement to include cultural, socioeconomic, historical, and religious values, if its purposes and limitations are well defined. A status of the DOE's ability to implement the recommendations presented in the report on the use of risk assessment in a major federal program and the adoption of principles for using risk analysis will be given.

Reduced incidence of rectal cancer, compared to gastric and colonic cancer, in a population of 73,076 men and women chronically immunosuppressed

The incidence of gastric, colonic, and rectal cancers was determined in a cohort of 73,076 men and women chronically immunosuppressed after heart or renal transplantation, to test the hypothesis that there would be a reduced incidence of gastric cancer by dampening chronic gastritis secondary to infection caused by Helicobacter pylori. Follow-up was from 1-13 years. No change in the incidence of gastric cancer was found (32 cases observed, 32.86 expected). An increase in colon cancer was found (75 cases observed, 62.27 expected). A significant reduction in the incidence of rectal cancer was found (15 cases observed, 41.5 expected). This led to a chi2 of 16.92 with 1 degree of freedom, significant at the 0.1% level. The effect was greater in men than women and more marked in heart recipients than in those receiving renal transplants. This unexpected finding led to a review of experiments in mice and rats that present evidence for immune promotion of large-bowel cancers induced by carcinogens by gut-associated lymphoid tissue. We conclude that an analysis of immune function in gut-associated lymphoid tissue in the stomach, colon, and rectum in healthy and immunosuppressed patients may lead to a better understanding of immunosurveillance in the colon and immune promotion of rectal cancers.

Association of the APOE epsilon 4 allele with clinical subtypes of late life depression

The APOE genotypes of 45 elderly inpatients with major depression were determined to investigate the relationship of this disorder to irreversible dementia in late life. We specifically tested the hypothesis that the frequency of the APOE epsilon 4 allele is elevated in depressed elders with cognitive impairment or psychotic features, subtypes that have been reported to be at increased risk of developing Alzheimer's disease (AD). The frequency of epsilon 4 allele was not elevated in the overall group of 45 inpatients and, contrary to our expectation, was not associated with cognitive impairment in this group. In contrast, the epsilon 4 allele frequency for the patients with psychotic features was nearly four times that for the patients without psychotic features and nearly double that of elderly controls. These data suggest that elderly depressed inpatients with cognitive impairment are at risk for developing AD by an epsilon 4-independent pathway, while those with psychotic features are at risk for developing AD by an epsilon 4-dependent pathway. These findings suggest that subtypes of idiopathic major depression in late life may serve as landmarks that distinguish separable pathogenetic pathways to AD.

Public-private interaction in pharmaceutical research

We empirically examine interaction between the public and private sectors in pharmaceutical research using qualitative data on the drug discovery process and quantitative data on the incidence of coauthorship between public and private institutions. We find evidence of significant reciprocal interaction, and reject a simple "linear" dichotomous model in which the public sector performs basic research and the private sector exploits it. Linkages to the public sector differ across firms, reflecting variation in internal incentives and policy choices, and the nature of these linkages correlates with their research performance.

hprt mutation frequency among workers exposed to 1,3-butadiene in China

Hypoxanthine-guanine phosphoribosyl transferase (hprt) mutation frequency (M(f)) was studied in workers at a polybutadiene rubber production facility in Yanshan, China. Exposed workers included for study were active either as process analysts, who sampled butadiene production process lines and analyzed product by gas chromatography, or as process operators, who did routine process control, minor maintenance and, as needed, major repair operations. For process analysts at the polymer and dimethyl formamide (DMF) facilities, the median air levels of BD were 1.0 and 3.5 ppm, respectively. Among process operators, air levels of 1.1 ppm were found during routine activities, while the median air level during pump repair and related operations was 45 ppm (6-h time-weighted average). Overall, M(f) was similar in unexposed (mean M(f) = 20.2 x 10(-6)) and butadiene-exposed (mean M(f) = 21.6 x 10(-6)) workers (P = 0.68). M(f) decreased with cloning efficiency, increased with age, and was moderately greater in women than in men. After adjustment by multiple regression analysis for mean age, sex, and cloning efficiency, the adjusted mean M(f)(Xadj) was 13.6 x 10(-6) in unexposed and 18.0 x 10(-6) in butadiene-exposed. This 32% difference was, however, not statistically significant (P = 0.13). Butadiene exposure was associated with a modest, if any, increase in hprt M(f) in this population of Chinese workers.

Electron-crystallographic refinement of the structure of bacteriorhodopsin

Using electron diffraction data corrected for diffuse scattering together with additional phase information from 30 new images of tilted specimens, an improved experimental density map has been calculated for bacteriorhodopsin. The atomic model has then been rebuilt into this new map with particular attention to the surface loops. All the residues from 7 to 227 as well as ten lipid molecules are now included, although a few amino acid residues in three of the six surface loops, about half of the lipid hydrophobic chains and all of the lipid head groups are disordered. The model has then been refined against the experimental diffraction amplitudes to an R-factor of 28% at 3.5 angstrom resolution with strict geometry (0.005 angstrom) bond length deviation) using the improvement of the "free" phase residual between calculated and experimental phases from images as an objective criterion of accuracy. For the refinement some new programs were developed to restrain the number of parameters, to be compatible with the limited resolution of our data. In the final refined model of the protein (2BRD), compared with earlier co-ordinates (1BRD), helix D has been moved towards the cytoplasm by almost 4 angstrom, and the overall accuracy of the co-ordinates of residues in the other six helices has been improved. As a result the positions of nearly all the important residues in bacteriorhodopsin are now well determined. In particular, the buried, protonated Asp115 is 7 angstrom from, and so not in contact with, the retinal and Met118 forms a cap on the pocket occupied by the beta-ionone ring. No clear density exists for the side-chain of Arg82, which forms a central part of the extracellular half-channel. The only arginine side-chain built into good density is that of Arg134 at the extracellular end of helix E, the others being disordered near one of the two surfaces. The interpretation of the end of helix F on the extracellular surface is now clearer; an extra loose helical turn has been built bringing the side-chain of Glu194 close to Arg134 to form a probable salt bridge. The model provides an improved framework for understanding the mechanism of the light-driven proton pumping. A number of cavities that could contain water molecules were found by searching the refined model, most of them above or below the Schiff base in the half-channels leading to the two surfaces. The ordered and disordered regions of the structure are described by the temperature factor distribution.

Evidence from normal expression and targeted misexpression that bone morphogenetic protein (Bmp-4) plays a role in mouse embryonic lung morphogenesis

Epithelial-mesenchymal interactions are critical for the branching and differentiation of the lung, but the mechanisms involved are still unclear. To investigate this problem in mouse embryonic lung, we have studied the temporal and spatial expression of genes implicated in the morphogenesis of other organs. At 11.5 days p.c., hepatocyte nuclear factor-3beta (Hnf-3beta) is expressed uniformly throughout the epithelium, while Wnt-2 expression is confined to the distal mesenchyme. Sonic hedgehog (Shh) transcripts are found throughout the epithelium, with high levels in the distal tips of the terminal buds, while bone morphogenetic protein-4 (Bmp-4) transcripts are localized at high levels in the distal tips of the epithelium, with lower levels in the adjacent mesenchyme. Epithelial expression is also seen for Bmp-7, but transcripts are less dramatically upregulated at the distal tips. The Type I Bone morphogenetic protein receptor gene (Bmpr/Tfr-11/Brk-1) is expressed at low levels in the epithelium and in the distal mesenchyme. To investigate the role of Bmp-4 in lung development, we have misexpressed the gene throughout the distal epithelium of transgenic lungs using a surfactant protein C enhancer/promoter. From 15.5 days p.c., transgenic lungs are smaller than normal, with grossly distended terminal buds and, at birth, contain large air-filled sacs which do not support normal lung function. Labeling with BrdU reveals an inhibition of epithelia] proliferation in 15.5 days p.c. transgenic lungs. A small but significant stimulation of proliferation of mesenchymal cells is also observed, but this is accompanied by an increase in cell death. In situ hybridization with riboprobes for the proximal airway marker, CC10, and the distal airway marker, SP-C, shows normal differentiation of bronchiolar Clara cells but a reduction in the number of differentiated Type II cells in transgenic lungs. A model is proposed for the role of BMP4 and other signalling molecules in embryonic lung morphogenesis.

Hemodynamic correlates of spontaneous echo contrast in the descending aorta

To identify the hemodynamic association of spontaneous echo contrast (SEC) in the descending aorta (DA), we measured aortic flow parameters in 102 consecutive patients studied with transesophageal echocardiography. SEC in the DA was identified in 19 of 102 patients (19%). Patients with SEC in the DA were older (67 +/- 9 vs 57 +/- 17 years; p = 0.001), had a higher proportion of chronic atrial arrhythmia (13 of 19 vs 11 of 83; p = 0.000001), and had a higher frequency of decreased left ventricular performance (10 of 19 vs 19 of 83; p = 0.01). Patients with SEC in the DA had larger aortic diameters (2.9 +/- 0.5 vs 2.3 +/- 0.4 cm; p = 0.0001), lower maximal velocity in the DA (42.6 +/- 12.8 vs 75.6 +/- 34.4 cm/s; p = 0.0001), and lower maximal shear rate (61.6 +/- 20.3 vs 139.9 +/- 78.8 s-1; p = 0.0001). There was no difference in volumetric flow in the DA between groups. In multivariate analysis, only arrhythmia (p = 0.008) and maximal shear rate (p = 0.002) were identified as significant independent predictors of SEC in the DA. We conclude that SEC in the DA is related to chronic atrial arrhythmia and shear rate but not to volumetric flow.