First Observation of P-odd γ Asymmetry in Polarized Neutron Capture on Hydrogen.

We report the first observation of the parity-violating gamma-ray asymmetry A_{γ}^{np} in neutron-proton capture using polarized cold neutrons incident on a liquid parahydrogen target at the Spallation Neutron Source at Oak Ridge National Laboratory. A_{γ}^{np} isolates the ΔI=1, ^{3}S_{1}→^{3}P_{1} component of the weak nucleon-nucleon interaction, which is dominated by pion exchange and can be directly related to a single coupling constant in either the DDH meson exchange model or pionless effective field theory. We measured A_{γ}^{np}=[-3.0±1.4(stat)±0.2(syst)]×10^{-8}, which implies a DDH weak πNN coupling of h_{π}^{1}=[2.6±1.2(stat)±0.2(syst)]×10^{-7} and a pionless EFT constant of C^{^{3}S_{1}→^{3}P_{1}}/C_{0}=[-7.4±3.5(stat)±0.5(syst)]×10^{-11} MeV^{-1}. We describe the experiment, data analysis, systematic uncertainties, and implications of the result.

Observation of Gravitationally Induced Vertical Striation of Polarized Ultracold Neutrons by Spin-Echo Spectroscopy.

We describe a spin-echo method for ultracold neutrons (UCNs) confined in a precession chamber and exposed to a |B0|=1 µT magnetic field. We have demonstrated that the analysis of UCN spin-echo resonance signals in combination with knowledge of the ambient magnetic field provides an excellent method by which to reconstruct the energy spectrum of a confined ensemble of neutrons. The method takes advantage of the relative dephasing of spins arising from a gravitationally induced striation of stored UCNs of different energies, and also permits an improved determination of the vertical magnetic-field gradient with an exceptional accuracy of 1.1 pT/cm. This novel combination of a well-known nuclear resonance method and gravitationally induced vertical striation is unique in the realm of nuclear and particle physics and should prove to be invaluable for the assessment of systematic effects in precision experiments such as searches for an electric dipole moment of the neutron or the measurement of the neutron lifetime.

[Development of Brassica rapa L. embryos under conditions of microgravity].

Results of comparative studies of the embryos of identical age formed under microgravity and ground laboratory control are presented. Significant similarity of a rate of embryo development and degree of their differentiation in both variants has been shown. The single cases of the disturbances in embryo formation, and also a certain acceleration of endosperm development at the early stages of seed formation in microgravity are revealed.

L-AP3 does not antagonize hippocampal synaptic depression induced by 1S,3R-ACPD.

1-Aminocyclopentane-trans-1S,3R-dicarboxylic acid (1S,3R-ACPD), a compound which selectively activates a metabotropic glutamate receptor (mGluR), suppresses hippocampal excitatory synaptic transmission. This depression is not antagonizable by L-2-amino-3-phosphonoproprionic acid (L-AP3), an agent which counteracts mGluR-induced phosphoinositide (PI) metabolism in several neuronal systems. Therefore, we believe that 1S,3R-ACPD activates a novel hippocampal mGluR subtype that is either insensitive to L-AP3 blockade and/or linked to an effector system that does not involve PI turnover.

Coactivation of metabotropic and NMDA receptors is required for LTP induction.

Induction of long-term potentiation (LTP) of synaptic transmission in the CA1 region of the hippocampus is dependent on N-methyl-D-aspartate (NMDA) receptor activation. However, NMDA receptor stimulation alone is not adequate to trigger LTP. Results from the present study indicate that, in addition to NMDA receptors, there is a requirement for co-stimulation of a postsynaptic metabotropic glutamate receptor (mGluR). The mGluR involved in eliciting LTP is not antagonized by L-2-amino-3-phosphonopropionic acid (L-AP3, 500 microM), nor is it coupled to phosphoinositide metabolism. We demonstrate that a novel mGluR, which is stimulated by trans-ACPD and is linked to increase in adenosine 3',5'-monophosphate (cAMP), is physiologically relevant to the induction of LTP.

Breast cancer and organochlorines: a marker for susceptibility?

The incidence of breast cancer is increasing and despite extensive research efforts, the etiology of this disease is largely unknown. Most women exhibit no known risk factors except for their age and sex. It has recently been postulated that the increased breast cancer incidence might be attributed to exposure to environmental carcinogens such as the organochlorine compounds. In this article, the scientific literature with respect to this possibility is reviewed and alternative hypotheses, which may in part explain the possible role of organochlorine compounds in the etiology of breast cancer, are presented.

Unilateral injections of a D2 but not D1 agonist into the frontal cortex of rats produce a contralateral directional bias.

Unilateral manipulations of frontocortical dopamine have been found in previous studies to produce a directional bias in the circling behaviour of rats. Agonists produced contralateral circling and antagonists produced ipsilateral turning. To examine the role of dopamine receptor subtypes, the present studies investigated the ability of unilateral intrafrontal cortical microinjections of the D1 agonist, SKF 38393 or the D2 agonist, quinpirole to produce contralateral circling in rats. The antagonist, cis-flupenthixol was also tested and was expected to produce ipsilateral circling. In 3 separate experiments, rats received 7 50-min sessions in a circular arena separated by at least 48 hr. The first and final sessions were preceded by no injection, the second and sixth by saline [or the inactive trans isomer (2.5 micrograms) in the flupenthixol experiment] and the middle 3 sessions by doses of cis-flupenthixol (1, 10, 25 micrograms in 0.5 microliter), quinpirole (3, 6, 12 micrograms) or SKF 38393 (2, 4, 8 micrograms), the order being counterbalanced across rats. cis-Flupenthixol and quinpirole produced dose-dependent ipsi- and contralateral circling, respectively, whereas SKF 38393 was without significant effect. No reliable directional bias was seen in any no-injection, saline or trans-flupenthixol sessions. Results suggested that the D2 receptor may mediate the motor effects of frontal cortical dopamine.

Antagonism of selected ethanol-enhanced brain stimulation properties by Ro 15-4513.

Low doses of ethanol increase responding for brain stimulation. Recently, other intoxicating effects of ethanol have been reversed by the imidazobenzodiazepine, Ro 15-4513. Possibly, Ro 15-4513 blockade also acts on reward-enhancing properties of ethanol. Rats trained to alternately shuttle between nose poke and lever operanda for rewarding stimulation to the medial forebrain bundle, were tested following intragastric intubations of ethanol (18%, 1.35 g/kg), Ro 15-4513 (3 mg/kg in 18% ethanol), or vehicle. Ro 15-4513 reversed ethanol-enhanced effects on reinforced responses. Because Ro 15-4513 did not completely block instrumental responding for brain stimulation, we conclude its effects on ethanol were not acting on the same reward substrate as the current and consummatory response.

The use of inhaled nitric oxide as adjuvant therapy in patients with burn injuries and respiratory failure.

Inhaled nitric oxide (NO) is a relatively new modality in the management of acute respiratory distress syndrome. The purpose of this study was to examine our experience with inhaled NO in 10 adult patients with burn injuries and acute respiratory distress syndrome-related oxygenation failure. The patients had a mean age of 50 +/- 19 years and a mean burn size of 41% +/- 20% of the total body surface area. Seven patients died and 3 survived. The survivors and nonsurvivors did not differ with respect to age, burn size, pre-NO ventilator settings, or indices of oxygenation including PaO2, oxygen saturation in arterial blood, PaO2/fraction of inspired oxygen (FIO2) ratio, and alveolar-arterial oxygen tension difference. The concentration of NO administered ranged between 5 ppm and 30 ppm. PaO2, oxygen saturation in arterial blood, and the PaO2/FIO2 ratio increased in all patients. Although it was not statistically significant, survivors tended to have a more vigorous and sustained response than non-survivors; this was best exemplified by the change in PFR. During the first hour of therapy, the PaO2/FIO2 ratio increased from 64.3 +/- 12.7 to 231.8 +/- 154.5 in survivors and from 93.9 +/- 44.0 to 161.5 +/- 81.8 in the nonsurvivors. After 12 hours of therapy, the PaO2/FIO2 ratio was 306.2 +/- 333.7 in the survivors and 178.9 +/- 69.9 in the nonsurvivors. There were no complications associated with the use of inhaled NO. Although a stronger early response to NO seems to occur in survivors, we cannot definitely conclude that the early response pattern is predictive of recovery. Nonetheless, we believe that inhaled NO has a useful role in the treatment of patients with burn injuries and severe acute respiratory distress syndrome-related oxygenation failure.

ASTROCULTURE (TM) root metabolism and cytochemical analysis.

Physiology of the root system is dependent upon oxygen availability and tissue respiration. During hypoxia nutrient and water acquisition may be inhibited, thus affecting the overall biochemical and physiological status of the plant. For the Astroculture (TM) plant growth hardware, the availability of oxygen in the root zone was measured by examining the changes in alcohol dehydrogenase (ADH) activity within the root tissue. ADH activity is a sensitive biochemical indicator of hypoxic conditions in plants and was measured in both spaceflight and control roots. In addition to the biochemical enzyme assays, localization of ADH in the root tissue was examined cytochemically. The results of these analyses showed that ADH activity increased significantly as a result of spaceflight exposure. Enzyme activity increased 248% to 304% in dwarf wheat when compared with the ground controls and Brassica showed increases between 334% and 579% when compared with day zero controls. Cytochemical staining revealed no differences in ADH tissue localization in any of the dwarf wheat treatments. These results show the importance of considering root system oxygenation in designing and building nutrient delivery hardware for spaceflight plant cultivation and confirm previous reports of an ADH response associated with spaceflight exposure.

Spaceflight hardware for conducting plant growth experiments in space: the early years 1960-2000.

The best strategy for supporting long-duration space missions is believed to be bioregenerative life support systems (BLSS). An integral part of a BLSS is a chamber supporting the growth of higher plants that would provide food, water, and atmosphere regeneration for the human crew. Such a chamber will have to be a complete plant growth system, capable of providing lighting, water, and nutrients to plants in microgravity. Other capabilities include temperature, humidity, and atmospheric gas composition controls. Many spaceflight experiments to date have utilized incomplete growth systems (typically having a hydration system but lacking lighting) to study tropic and metabolic changes in germinating seedlings and young plants. American, European, and Russian scientists have also developed a number of small complete plant growth systems for use in spaceflight research. Currently we are entering a new era of experimentation and hardware development as a result of long-term spaceflight opportunities available on the International Space Station. This is already impacting development of plant growth hardware. To take full advantage of these new opportunities and construct innovative systems, we must understand the results of past spaceflight experiments and the basic capabilities of the diverse plant growth systems that were used to conduct these experiments. The objective of this paper is to describe the most influential pieces of plant growth hardware that have been used for the purpose of conducting scientific experiments during the first 40 years of research.

Plant reproduction in spaceflight environments.

Because plant reproduction is a complex developmental process there are many possible sites of perturbation by the unusual environments of orbital spacecraft. Previous long-duration experiments on Soviet platforms shared features of slowed development through the vegetative stage of plant growth and aborted reproductive function. Our goal has been to understand how special features of the spaceflight environment impact physiological function and reproductive development. In a series of short-duration experiments in the Shuttle mid-deck we studied early reproductive development in Arabidopsis thaliana. Pollen and ovule development aborted at an early stage in the first experiment on STS-54 which utilized closed plant growth chambers. Post-flight analysis suggested that the plants may have been carbon dioxide limited. Subsequent experiments utilized carbon dioxide enrichment (on STS-51) and cabin air flow-through with an air exchange system (on STS-68). Both modifications allowed pollen and ovule development to occur normally on orbit, and full reproductive development up to the stage of an immature seed occurred on STS-68. However, analysis of plant roots from these experiments demonstrated a limitation in rootzone aeration in the spaceflight material that was not mitigated by these procedures. In the future, additional resources (crew time, upgraded flight hardware, and special platforms) will invite more elaborate, long-duration experimentation. On the ISS, a variable speed centrifuge and upgraded plant habitats will permit detailed experiments on the role of gravity in shaping the plant micro-environment, and what influence this plays during reproduction.

A ground-based comparison of nutrient delivery technologies originally developed for growing plants in the spaceflight environment.

A ground-based comparison of plant nutrient delivery systems that have been developed for microgravity application was conducted for dwarf wheat (Triticum aestivum L. 'Yecora Rojo') and rapid-cycling brassica (Brassica rapa L. CrGC#1-33) plants. These experiments offer insight into nutrient and oxygen delivery concerns for greenhouse crop production systems. The experiments were completed over a 12-day period to simulate a typical space shuttle-based spaceflight experiment. The plant materials, grown either using the porous-tube nutrient delivery system, the phenolic foam support system, or a solidified agar nutrient medium, were compared by plant-growth analysis, root zone morphological measurements, elemental composition analysis, and alcohol dehydrogenase enzyme activity assay. The results of these analyses indicate that the porous tube plant nutrient delivery and the phenolic foam systems maintain plant growth at a higher level than the solidified agar gel medium system. Root zone oxygenation problems associated with the agar system were manifested through biochemical and morphological responses. The porous tube nutrient delivery system outperformed the other two systems on the basis of plant growth analysis parameters and physiological indicators of root zone aeration. This information is applicable to the current crop production techniques used in greenhouse-controlled environments.

Dynamics of storage reserve deposition during Brassica rapa L. pollen and seed development in microgravity.

Pollen and seeds share a developmental sequence characterized by intense metabolic activity during reserve deposition before drying to a cryptobiotic form. Neither pollen nor seed development has been well studied in the absence of gravity, despite the importance of these structures in supporting future long-duration manned habitation away from Earth. Using immature seeds (3-15 d postpollination) of Brassica rapa L. cv. Astroplants produced on the STS-87 flight of the space shuttle Columbia, we compared the progress of storage reserve deposition in cotyledon cells during early stages of seed development. Brassica pollen development was studied in flowers produced on plants grown entirely in microgravity on the Mir space station and fixed while on orbit. Cytochemical localization of storage reserves showed differences in starch accumulation between spaceflight and ground control plants in interior layers of the developing seed coat as early as 9 d after pollination. At this age, the embryo is in the cotyledon elongation stage, and there are numerous starch grains in the cotyledon cells in both flight and ground control seeds. In the spaceflight seeds, starch was retained after this stage, while starch grains decreased in size in the ground control seeds. Large and well-developed protein bodies were observed in cotyledon cells of ground control seeds at 15 d postpollination, but their development was delayed in the seeds produced during spaceflight. Like the developing cotyledonary tissues, cells of the anther wall and filaments from the spaceflight plants contained numerous large starch grains, while these were rarely seen in the ground controls. The tapetum remained swollen and persisted to a later developmental stage in the spaceflight plants than in the ground controls, even though most pollen grains appeared normal. These developmental markers indicate that Brassica seeds and pollen produced in microgravity were physiologically younger than those produced in 1 g. We hypothesize that microgravity limits mixing of the gaseous microenvironments inside the closed tissues and that the resulting gas composition surrounding the seeds and pollen retards their development.

Realizing the potential of rapid-cycling Brassica as a model system for use in plant biology research.

Rapid-cycling Brassica populations were initially developed as a model for probing the genetic basis of plant disease. Paul Williams and co-workers selected accessions of the six main species for short time to flower and rapid seed maturation. Over multiple generations of breeding and selection, rapid-cycling populations of each of the six species were developed. Because of their close relationship with economically important Brassica species, rapid-cycling Brassica populations, especially those of B. rapa (RCBr) and B. oleracea, have seen wide application in plant and crop physiology investigations. Adding to the popularity of these small, short-lived plants for research applications is their extensive use in K-12 education and outreach.

Respiratory changes with chilling injury of soybeans.

The leakage of solutes from cotyledons of soybeans (cv. Chippewa 64) was markedly stimulated by a chilling treatment (1 to 4 C) during the 1st minute of imbibition, but chilling after even 1 minute of water uptake resulted in little or no leakage increase. The respiratory rate of soybean particles was reduced more than 60% if a chilling treatment (15 minutes at 1 to 4 C) was given during the first minutes of imbibition, and little or no reduction was obtained if the chilling treatment was begun at 5 to 15 minutes after the start of imbibition. Using KCN as an inhibitor of cytochrome oxidase pathway of respiration and salicylhydroxamic acid as an inhibitor of the alternative pathway, it was found that the chilling injury involved a major reduction in the cytochrome pathway in whole axes and cotyledons and an engagement of the alternative pathway of respiration in cotyledon tissue. The suggestion is made that the chilling injury involves lesions resulting from temperature stress during the reorganization of membranes with water entry, and that both the leakage and the respiratory effects are consequences of these membrane lesions.

Response of Two Wheat Cultivars to CO(2) Enrichment under Subambient Oxygen Conditions.

Two cultivars of wheat (Triticum aestivum L. cvs Sonoita and Yecora Rojo) were grown to maturity in a growth chamber within four sub-chambers under two CO(2) levels (350 or 1000 microliters per liter) at either ambient (21%) or low O(2) (5%). Growth analysis was used to characterize changes in plant carbon budgets imposed by the gas regimes. Large increases in leaf areas were seen in the low O(2) treatments, due primarily to a stimulation of tillering. Roots developed normally at 5% O(2). Seed development was inhibited by the subambient O(2) treatment, but this effect was overcome by CO(2) enrichment at 1000 microliters per liter. Dry matter accumulation and seed number responded differently to the gas treatments. The greatest dry matter production occurred in the low O(2), high CO(2) treatment, while the greatest seed production occurred in the ambient O(2), high CO(2) treatment. Growth and assimilation were stimulated more by either CO(2) enrichment or low O(2) in cv Yecora Rojo than in Sonoita. These experiments are the first to explore the effect of whole plant low O(2) treatments on growth and reproduction. The finding that CO(2) enrichment overcomes low O(2)-induced sterility may help elucidate the nature of this effect.

A growth analysis of waterlogging damage in mung bean (Phaseolus aureus).

Mung beans (Phaseolus aureus Roxb.) were grown for 2 weeks in gravel-vermiculite soilless mix in a growth chamber and subjected to a 1-week waterlogging period followed by a 1-week recovery period. Sequential harvests were made to determine the time course of effects of waterlogging and subsequent recovery on growth parameters by techniques of growth analysis. Root dry matter was the first to be affected, along with an increase in leaf dry matter and specific leaf weight. After a 1-week waterlogging period, specific leaf weight had more than doubled in the stressed plants. Leaf area declined in relation to the control plants as did the ratio of root dry matter to shoot dry matter. During the recovery period there was an increase in the dry matter allocation to the roots relative to the shoot. Specific leaf weight fell to control levels although the rate of leaf area elaboration did not increase during this time, suggesting a redistribution of stored assimilates from the leaves. Net assimilation rate increased during the waterlogging period, probably due to a restriction in root metabolism and reduced translocation out of the leaf rather than to an increase in photosynthesis. Net assimilation rate of waterlogged plants was severely reduced compared with control plants during the recovery period. Both relative growth rate and leaf area duration declined during the waterlogging period and declined further subsequent to the waterlogging treatment. The results illustrate the interrelationships between root and shoot carbon budgets in mung bean during response to the stress of waterlogging.

Dynamics of vegetative cytoplasm during generative cell formation and pollen maturation in Arabidopsis thaliana.

Ultrastructural changes of pollen cytoplasm during generative cell formation and pollen maturation in Arabidopsis thaliana were studied. The pollen cytoplasm develops a complicated ultrastructure and changes dramatically during these stages. Lipid droplets increase after generative cell formation and their organization and distribution change with the developmental stage. Starch grains in amyloplasts increase in number and size during generative and sperm cell formation and decrease at pollen maturity. The shape and membrane system of mitochondria change only slightly. Dictyosomes become very prominent, and numerous associated vesicles are observed during and after sperm cell formation. Endoplasmic reticulum appears extensively as stacks during sperm cell formation. Free and polyribosomes are abundant in the cytoplasm at all developmental stages although they appear denser at certain stages and in some areas. In mature pollen, all organelles are randomly distributed throughout the vegetative cytoplasm and numerous small particles appear. Organization and distribution of storage substances and appearance of these small particles during generative and sperm cell formation and pollen maturation are discussed.

Reproduction during spaceflight by plants in the family Brassicaceae.

NASA: Researchers report on studies of reproduction in Arabidopsis thaliana in space during during the Chromex-03 on STS-54, Chromex-04 on STS-51, and Chromex-05 on STS-68 missions. The obstacles to seed formation were related to carbon dioxide levels. Other experiments examined in flight pollination and seed production in Brassica rapa during parabolic flight, a 4-1/2 month stay on Mir, and on STS-87. During the Mir experiment, Brassica seeds were harvested from seeds sown in flight. The second generation seeds grew to produce new seeds that contained more starch and less protein and lipid when compared to ground control seeds.^ieng