Growth stimulation in inflorescences of an Arabidopsis tubulin mutant under microgravity conditions in space.

Cortical microtubules are involved in plant resistance to hypergravity, but their roles in resistance to 1 g gravity are still uncertain. To clarify this point, we cultivated an Arabidopsis α-tubulin 6 mutant (tua6) in the Cell Biology Experiment Facility on the Kibo Module of the International Space Station, and analyzed growth and cell wall mechanical properties of inflorescences. Growth of inflorescence stems was stimulated under microgravity conditions, as compared with ground and on-orbit 1 g conditions. The stems were 10-45% longer and their growth rate 15-55% higher under microgravity conditions than those under both 1 g conditions. The degree of growth stimulation tended to be higher in the tua6 mutant than the wild-type Columbia. Under microgravity conditions, the cell wall extensibility in elongating regions of inflorescences was significantly higher than the controls, suggesting that growth stimulation was caused by cell wall modifications. No clear differences were detected in any growth or cell wall property between ground and on-orbit 1 g controls. These results support the hypothesis that cortical microtubules generally play an important role in plant resistance to the gravitational force.

Modification of neodymium-doped ZnO hybrid nanoparticles under mild hydrothermal conditions.

The morphology and particle size of neodymium-doped ZnO hybrid nanoparticles were tailored through fabrication under mild hydrothermal conditions (T = 150-250 degrees C, P = autogeneous, t = 18 h) for the first time using two surface modifiers: caprylic acid and n-butylamine. Characterization of these nanoparticles was carried out using powder XRD, FTIR, SEM, zeta-potential analysis and UV-vis spectroscopy. The results revealed that modification of ZnO nanoparticles using neodymium as a dopant and caprylic acid or n-butylamine as a surfactant could change the optical and physical properties of the surface-modified neodymium-doped ZnO hybrid nanoparticles. The work proved the efficiency of caprylic acid and n-butylamine as suitable surfactants for surface modification of neodymium-doped ZnO hybrid nanoparticles.

Effect of interferon on incidence of hepatocellular carcinoma in patients with chronic hepatitis C.

BACKGROUND/AIMS: The aim of this study was to evaluate whether IFN prevents the development of HCC in patients with chronic hepatitis C. METHODOLOGY: 103 patients with chronic hepatitis C received IFN and 30 control patients were enrolled in this study. RESULTS: In 33 patients (32.0%) who received IFN, alanine aminotransferase (ALT) decreased to normal range and HCV RNA became negative (complete response: CR). In 7 patients (6.7%), ALT decreased to less than 50 IU/L or stayed within the normal range, but HCV RNA remained positive (biochemical response: BR). In 63 patients (61.1%) and 30 control patients, ALT did not change and HCV RNA remained positive (no response: NR). HCC developed in 5 (4.9%) of the 103 patients who received IFN and 7 (23.3%) of the control patients (p<0.01). In 5 patients who developed HCC, the response to IFN was NR and no HCC developed in patients with CR or BR. In addition, 5-year cumulative rate of development of HCC in 63 IFN NR patients and in control was 7.9% and 23.3% (p<0.05). CONCLUSIONS: IFN decreased the development of HCC in not only patients with CR or BR but also patients with NR.

Two-dimensional laboratory simulation of LNAPL infiltration and redistribution in the vadose zone.

A quantitative two-dimensional laboratory experiment was conducted to investigate the immiscible flow of a light non-aqueous phase liquid (LNAPL) in the vadose zone. An image analysis technique was used to determine the two-dimensional saturation distribution of LNAPL, water and air during LNAPL infiltration and redistribution. Vertical water saturation variations were also continuously monitored with miniature resistivity probes. LNAPL and water pressures were measured using hydrophobic and hydrophilic tensiometers. This study is limited to homogeneous geological conditions, but the unique experimental methods developed will be used to examine more complex systems. The pressure measurements and the quantification of the saturation distribution of all the fluids in the entire flow domain under transient conditions provide quantitative data essential for testing the predictive capability of numerical models. The data are used to examine the adequacy of the constitutive pressure-saturation relations that are used in multiphase flow models. The results indicate that refinement of these commonly used hydraulic relations is needed for accurate model prediction. It is noted in particular that, in three-fluid phase systems, models should account for the existence of a residual NAPL saturation occurring after NAPL drainage. This is of notable importance because residual NAPL can act as a non negligible persistent source of contamination.

A review of NAPL source zone remediation efficiency and the mass flux approach.

A number of previous studies are reviewed to examine the actual reduction of NAPL from source zones and the effectiveness of the specific technique of remediation used at sites under study. It has been shown that complete removal of the NAPL in free phase or residual is not possible due to the complex entrapment architecture of NAPLs at field sites. Consequently, the assessment of remediation efficiency should not be solely based on the reduction of entrapped NAPL mass from source zone. Instead, it should be based on the reduction of risk achieved through the lowering of the concentration of the dissolved constituents emanating from the entrapped NAPL during source zone clean-up. The prediction of the concentration in the plume requires a knowledge of the dissolution of NAPLs in the source zone. Attention is directed to the need for the understanding the mass transfer from entrapped NAPLs in the source zone before and after remediation. In this paper, the current knowledge of mass transfer processes from the non-aqueous phase to the aqueous phase is summarised and the use of mass flux measurements (monitoring the concentration of contaminants in aqueous phase due to source zone NAPL-groundwater mass transfer) is introduced as a potential tool to assess the efficiency of technologies used in source zone remediation. Preliminary results of numerical simulations reveal that factors such as source zone morphology as determined by the heterogeneity of the formation control the post-remediation dissolution behaviour, than the local mass transfer. Thus, accurate site characterization is essential for predicting NAPL dissolution and mass flux relationships as well as for assigning site-specific remediation target values.

Effect of NAPL entrapment conditions on air sparging remediation efficiency.

The effect of soil heterogeneity and the entrapment condition of NAPL source on the mass removal efficiency of air sparging coupled with soil vapour extraction (AS/SVE) was investigated using an intermediate scale two-dimensional laboratory soil tank. Four different NAPL entrapments were created by varying the height of the water table in heterogeneous soil models. Different mass removal efficiencies were achieved for different NAPL entrapment conditions, which were governed by soil heterogeneity and water table height before and during AS/SVE operation. Remobilization and redistribution of toluene and water improved the mass removal. Overall results suggested that it was difficult to achieve the complete remediation of NAPL source due to complex entrapment in heterogeneous soil system. In order to assess the potential contamination in the post-remediation stage, gas and dissolved concentrations of toluene were measured after the AS/SVE operation. The results showed that gas concentration close to remaining NAPL source zone increased rapidly and reached to steady state values, which were much smaller than the vapour pressure, whereas the aqueous phase concentrations increased continuously toward the solubility limit.

Hypergravity-induced changes in gene expression in Arabidopsis hypocotyls.

Under hypergravity conditions, the cell wall of stem organs becomes mechanically rigid and elongation growth is suppressed, which can be recognized as the mechanism for plants to resist gravitational force. The changes in gene expression by hypergravity treatment were analyzed in Arabidopsis hypocotyls by the differential display method, for identifying genes involved in hypergravity-induced growth suppression. Sixty-two cDNA clones were expressed differentially between the control and 300 g conditions: the expression levels of 39 clones increased, whereas those of 23 clones decreased under hypergravity conditions. Sequence analysis and database searching revealed that 12 clones, 9 up-regulated and 3 down-regulated, have homology to known proteins. The expression of these genes was further analyzed using RT-PCR. Finally, six genes were confirmed to be up-regulated by hypergravity. One of such genes encoded 3-hydroxy-3-methylglutaryl-Coenzyme A reductase (HMGR), which catalyzes a reaction producing mevalonic acid, a key precursor of terpenoids such as membrane sterols and several types of hormones. The expression of HMGR gene increased within several hours after hypergravity treatment. Also, compactin, an inhibitor of HMGR, prevented hypergravity-induced growth suppression, suggesting that HMGR is involved in suppression of Arabidopsis hypocotyl growth by hypergravity. In addition, hypergravity increased the expression levels of genes encoding CCR1 and ERD15, which were shown to take part in the signaling pathway of environmental stimuli such as temperature and water, and those of the alpha-tubulin gene. These genes may be involved in a series of cellular events leading to growth suppression of stem organs under hypergravity conditions.

Growth restoration in azuki bean and maize seedlings by removal of hypergravity stimuli.

Hypergravity stimuli, gravitational acceleration of more than 1 x g, decrease the growth rate of azuki bean epicotyls and maize coleoptiles and mesocotyls by decreasing the cell wall extensibility via an increase in the molecular mass of matrix polysaccharides. An increase in the pH in the apoplastic fluid is hypothesized to be involved in the processes of the increase in the molecular mass of matrix polysaccharides due to hypergravity. However, whether such physiological changes by hypergravity are induced by normal physiological responses or caused by physiological damages have not been elucidated. In the present study, we examined the effects of the removal of hypergravity stimuli on growth and the cell wall properties of azuki bean and maize seedlings to clarify whether the effects of hypergravity stimuli on growth and the cell wall properties are reversible or irreversible. When the seedlings grown under hypergravity conditions at 300 x g for several hours were transferred to 1 x g conditions, the growth rate of azuki bean epicotyls and maize coleoptiles and mesocotyls greatly increased within a few hours. The recovery of growth rate of these organs was accompanied by an immediate increase in the cell wall extensibility, a decrease in the molecular mass of matrix polysaccharides, and an increase in matrix polysaccharide-degrading activities. The apoplastic pH also decreased promptly upon the removal of hypergravity stimuli. These results suggest that plants regulate the growth rate of shoots reversibly in response to hypergravity stimuli by changing the cell wall properties, by which they adapt themselves to different gravity conditions. This study also revealed that changes in growth and the cell wall properties under hypergravity conditions could be recognized as normal physiological responses of plants. In addition, the results suggest that the effects of microgravity on plant growth and cell wall properties should be reversible and could disappear promptly when plants are transferred from microgravity to 1 x g. Therefore, plant materials should be fixed or frozen on orbit for detecting microgravity-induced changes in physiological parameters after recovering the materials to earth in space experiments.

Effects of source zone heterogeneity on surfactant-enhanced NAPL dissolution and resulting remediation end-points.

The effectiveness of removal of nonaqueous phase liquids (NAPLs) from the entrapment source zone of the subsurface has been limited by soil heterogeneity and the inability to locate all entrapped sources. The goal of this study was to demonstrate the uncertainty of degree of source removal associated with aquifer heterogeneity. In this demonstration, source zone NAPL removal using surfactant-enhanced dissolution was considered. Model components that simulate the processes of natural dissolution in aqueous phase and surfactant-enhanced dissolution were incorporated into an existing code of contaminant transport. The dissolution modules of the simulator used previously developed Gilland-Sherwood type phenomenological models of NAPL dissolution to estimate mass transfer coefficients that are upscaleable to multidimensional flow conditions found at field sites. The model was used to simulate the mass removal from 10 NAPL entrapment zone configurations based on previously conducted two-dimensional tank experiments. These entrapment zones represent the NAPL distribution in spatially correlated random fields of aquifer hydraulic conductivity. The numerical simulations representing two-dimensional conditions show that effectiveness of mass removal depends on the aquifer heterogeneity that controls the NAPL entrapment and delivery of the surfactant to the locations of entrapped NAPLs. Flow bypassing resulting from heterogeneity and the reduction of relative permeability due to NAPL entrapment reduces the delivery efficiency of the surfactant, thus prolonging the remediation time to achieve desired end-point NAPL saturations and downstream dissolved concentrations. In some extreme cases, the injected surfactant completely bypassed the NAPL source zones. It was also found that mass depletion rates for different NAPL source configurations vary significantly. The study shows that heterogeneity result in uncertainties in the mass removal and achievable end-points that are directly related to dissolved contaminant plume development downstream of the NAPL entrapment zone.

Gravitational force regulates elongation growth of Arabidopsis hypocotyls by modifying xyloglucan metabolism.

Growth of dark-grown Arabidopsis hypocotyls was suppressed under hypergravity conditions (300 g), or was stimulated under microgravity conditions in space (Space Shuttle STS-95). The mechanical extensibility of cell walls decreased and increased under hypergravity and microgravity conditions, respectively. The amounts of cell wall polysaccharides (pectin, hemicellulose-I, hemicellulose-II and cellulose) per unit length of hypocotyls increased under hypergravity conditions, and decreased under microgravity conditions. The amount and the molecular mass of xyloglucans also increased under the hypergravity conditions, while those decreased under microgravity conditions. The activity of xyloglucan-degrading enzymes extracted from hypocotyl cell walls decreased and increased under hypergravity and microgravity conditions, respectively. These results indicate that the amount and the molecular mass of xyloglucans are affected by the magnitude of gravity and that such changes are caused by changes in xyloglucan-degrading activity. Modifications of xyloglucan metabolism as well as the thickness of cell walls by gravity stimulus may be the primary event determining the cell wall extensibility, thereby regulating the growth rate of Arabidopsis hypocotyls.

Changes in the apoplastic pH are involved in regulation of xyloglucan breakdown of azuki bean epicotyls under hypergravity conditions.

Hypergravity inhibited elongation growth of azuki bean (Vigna angularis Ohwi et Ohashi) epicotyls by decreasing the mechanical extensibility of cell walls via the increase in the molecular mass of xyloglucans [Soga et al. (1999) Plant Cell Physiol. 40: 581]. Here, we report that the pH value of the apoplastic fluid in epicotyls increased from 5.8 to 6.6 by hypergravity (300 x g) treatment. When the xyloglucan-degrading enzymes extracted from cell walls of the 1 x g control epicotyls were assayed in buffer at pH 6.6 and 5.8, the activity at pH 6.6 was almost half of that at pH 5.8. In addition, when enzymically active cell wall preparations obtained from 1 x g control epicotyls were autolyzed in buffer at pH 5.8 and 6.6 and then xyloglucans were extracted from the autolyzed cell walls, the molecular mass of xyloglucans incubated at pH 5.8 decreased during the autolysis, while that at pH 6.6 did not change. Thus, the xyloglucans were not depolymerized by autolysis at the pH value (6.6) observed in the hypergravity-treated epicotyls. These findings suggest that in azuki bean epicotyls, hypergravity decreases the activities of xyloglucan-degrading enzymes by increasing the pH in the apoplastic fluid, which may be involved in the processes of the increase in the molecular mass of xyloglucans, leading to the decrease in the cell wall extensibility.

Involvement of ethylene and gibberellin signalings in chromosaponin I-induced cell division and cell elongation in the roots of Arabidopsis seedlings.

Chromosaponin I (CSI), a triterpenoid saponin isolated from pea, stimulates the growth of roots in Arabidopsis thaliana seedlings on wetted filter paper in the light for 14 d. The growth rates of roots in Columbia (Col) and Landsberg erecta (Ler) wild-types were 0.92 and 0.26 mm d(-1), respectively, and they were accelerated to 3.46 (Col) and 2.20 (Ler) mm d(-1) by treating with 300 microM CSI. The length of mature epidermal cells was increased by 1.8-fold (Col) and 2.81-fold (Ler) compared with control and the number of epidermal cells was increased by a factor of 1.65 (Col) and 2.12 (Ler). Treatment with 2-aminoethoxyvinylglycine (AVG), an inhibitor of ethylene biosynthesis, also increased cell length but not cell number. The effects of CSI on root growth were not detected in the ethylene-insensitive mutant ein2-1. CSI did not inhibit ethylene production but stimulated the growth of roots in ctr1-1, the constitutive triple response mutant for ethylene, indicating that CSI inhibits ethylene signaling, especially downstream of CTR1. In the GA-insensitive mutant gai and the mutant spy-3, in which the basal level of GA signaling is activated, CSI did not increase cell number, although both CSI and AVG stimulated cell elongation in these mutants. These results suggest that the inhibition of ethylene signaling is the cause of CSI-induced cell elongation. A possible involvement of both GA and ethylene signalings is discussed for the CSI-induced cell division.