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21.
We investigated individual and combined effects of salinity, soil boron (B), silicon (Si) and salicylic acid (SA) on the activities
of major antioxidant enzymes (superoxide dismutase, SOD; catalase, CAT and ascorbate peroxidase, APX) and non-enzymatic antioxidants
(AA), proline, chlorophyll, anthocyanin, H2O2 concentration, stomatal resistance (SR), lipid peroxidation (MDA), membrane permeability (MP), and the uptake of sodium (Na),
chloride (Cl), boron and Si of spinach plants. In general, salinity significantly increased H2O2 and proline concentrations, antioxidant activity, membrane permeability, lipid peroxidation and SR of the spinach plants,
indicating that they were stressed, whereas application of B only increased proline concentration. However, plant fresh weights
did not decline with either treatment. The application of Si decreased H2O2 and increased the activity of SOD and CAT. The application of SA increased SOD activity. Neither SA nor Si had any effect
on the proline concentration, or MP. However, application of Si increased chlorophyll concentration and decreased lipid peroxidation
(MDA concentration). Si treatment had no effect on SR. The concentration of B in the tissues, which was strongly increased
by B treatment, was decreased by NaCl. As a result of salinity, concentrations of Na+ and Cl− ions were increased in the plant tissues, and application of Si slightly increased these concentrations. These results indicate
that exogenous Si application increases stress tolerance of spinach, a plant that is naturally reasonably resistant to combined
salinity and B toxicity, by the enhancement of antioxidant mechanisms that reduce membrane damage. Exogenous SA has a less
obvious effect, although the levels of salinity and boron stress applied were not sufficient in this experiment to reduce
plant fresh weight. 相似文献
22.
Whisker-mediated transformation of embryogenic callus of maize 总被引:4,自引:0,他引:4
The present study was designed to establish embryogenic callus as a target tissue for whisker-mediated transformation of
maize (Zea mays L.). Silicon carbide whiskers were used to deliver the bar and uidA (GUS) genes into embryogenic maize callus. Samples of osmotically-treated Type II callus were vigorously agitated in the
presence of whiskers and plasmid DNA using a standard laboratory vortex or a modified dental amalgamator. On average, three
transgenic callus lines were obtained per 100 samples treated. Plants were regenerated from several GUS-expressing callus
lines and DNA analyses confirmed stable integration and inheritance. As with other direct DNA delivery methods involving embryogenic
maize callus, integration patterns of the inserted DNA appeared to be complex. Although currently less efficient than microparticle
bombardment on a per target basis, whisker-mediated transformation of embryogenic callus represents a viable method for transgenic
maize production.
Received: 14 May 1999 / Revision received: 11 October 1999 / Accepted: 11 October 1999 相似文献
23.
Izu A Kumai T Tohno Y Tohno S Minami T Yamada G Yamada MO 《Biological trace element research》2006,113(3):297-316
Vertebral columns were dissected and analyzed after birth with oral administration of silicon for 4 wk and for 8 wk. The silicon
level was lower (20 μg/g) at the beginning. It remains unchanged after 4 wk and then increases twice as much as that for those
mice bred for 8 wk than those bred for 4 wk. This increase depends remarkably on the mass ratio of Si/Ca (M/M). The ratio increases to three times higher than that of the control at the beginning of the experiments (5 wk after birth).
Although the S and P contents appeared to be lower, these increased when Si was administered in combination with phosphopeptide.
Other elements, such as Ca, Mg, Fe, and Zn, appeared to be unchanged as the weeks proceeded. These findings seem to support
a proposal that silicon is necessary for the growth of backbones in mice. 相似文献
24.
Two experiments were conducted using completely randomized designs to study the bioavailability of Si from three sources to
growing rats and turkeys fed semipurified diets. The basal diets were dextrose-egg albumin for rats and dextrose-casein for
turkeys. The Si sources were tetraethylorthosilicate (TES), sodium silicate (NaSil), and sodium zeolite A (NaZA). Rats and
turkeys were supplemented at 500 and 270 ppm Si, respectively, from each source. A control group of unsupplemented rats and
turkeys was included in each experiment. In general, irrespective of Si source, Si supplementation slowed (p < 0.05 orp < 0.01) growth rates in both rats and turkeys. Although dietary Si supplementation reduced (p < 0.05) plasma Mg levels and liver Zn concentrations in rats, it increased (p < 0.05) plasma P and reduced (p < 0.05) plasma Cu levels in turkeys. Rats on TES had significantly slower (p < 0.05 orp < 0.01) growth rates (5–10%) than those on NaSil or NaZA. In rats, NaZA and TES reduced (p < 0.05) hemoglobin concentrations and plasma Zn, respectively. However, plasma Mg levels were higher (p < 0.05) in TES than
NaSil-or NaZA-fed rats. The source of the dietary Si did not affect (p < 0.05) the organ weights of rats and their mineral concentrations. Turkeys on TES diets grew at a significantly faster (p < 0.05) rate (15%) than those on NaSil or NaZA diets during the first 2 wk of experimentation. However, after 4 wk, there were
no significant (p > 0.05) differences in growth between the Si sources. In turkeys, NaZA increased (p < 0.05) hematocrit levels and plasma Mg levels. Turkeys on NaZA diets had larger (p < 0.05) hearts and livers than those on
NaSil but not TES. Liver Mn content was higher (p < 0.05) in turkeys on NaSil than TES or NaZA. Heart Zn was lower (p < 0.05) in turkeys on NaSil than TES, but not NaZA. 相似文献
25.
Jacek Najda Jan Gmiński Marian Dróżdż Franciszek Zych 《Biological trace element research》1993,37(2-3):101-106
The influence of silicon-treatment on the levels of TSH and thyroid hormones was studied in rats. Concentrations of thyrotropin
(TSH), triiodothyronine (T3), and thyroxine (T4) were estimated in sera of rats receiving per os a soluble silicon compound—sodium metasilicate nonahydrate (Na2SiO3·9H2O), dissolved in the animals' drinking water. An increase in the TSH level in the tested group was observed, without statistically
significant differences in T3 and T4 concentrations between the two groups of animals. The results provide evidence for the influence of silicon on the endocrine
balance. They could also prove that this chemical element is capable of modifying the rate of some hormones' synthesis. 相似文献
26.
An epi-illuminated microscope configuration for use in fluorescence correlation spectroscopy in bulk solutions has been analyzed. For determining the effective sample dimensions the spatial distribution of the molecule detection efficiency has been computed and conditions for achieving quasi-cylindrical sample shape have been derived. Model experiments on translational diffusion of rhodamine 6G have been carried out using strong focusing of the laser beam, small pinhole size and an avalanche photodiode in single photon counting mode as the detector. A considerable decrease in background light intensity and measurement time has been observed. The background light is 40 times weaker than the fluorescence signal from one molecule of Rh6G, and the correlation function with signal-to-noise ratio of 150 can be collected in 1 second. The effect of the shape of the sample volume on the autocorrelation function has been discussed.
Correspondence to: R. Rigler 相似文献
27.
Summary Electron probe microanalysis of unfixed freeze-substituted rat liver tissue embedded in Spurr's low viscosity epoxy resin demonstrated the occurrence of Si as well as P, S, and Cl in the nucleus, nucleolus, mitochondria, and rough endoplasmic reticulum. Chemical analysis confirmed that the Si in the organelles did not originate from instrumental contaminants. This suggests that Si may be involved in the biochemistry of these subcellular organelles.Supported by Grant GM-08229-12-13 from the National Institutes of Health, USPHS.We are grateful to the Kevex Corporation and Mr. Glenn W. Meyer, Sales Engineer, for the use of the Kevex X-ray spectrometer; we wish to thank as well the Perkin-Elmer Corporation and their Western Branch Manager, Mr. Michael E. Mullen and Senior Microscopist, Mr. Minoru Shinorhara, for use of and assistance with the Hitachi HU 12 A transmission electron microscope. We also wish to acknowledge Mary Louise Chiappino for her technical assistance in preparing the thin sections, the final micrographs and the X-ray photographs, and Darlene Lum for technical assistance in the laboratory. 相似文献
28.
Steve W. Blecker Stagg L. King Louis A. Derry Oliver A. Chadwick James A. Ippolito Eugene F. Kelly 《Biogeochemistry》2007,86(2):189-199
Slight differences in the chemical behavior of germanium (Ge) and silicon (Si) during soil weathering enable Ge/Si ratios
to be used as a tracer of Si pathways. Mineral weathering and biogenic silicon cycling are the primary modifiers of Ge/Si
ratios, but knowledge of the biogenic cycling component is based on relatively few studies. We conducted two sets of greenhouse
experiments in order to better quantify the range and variability in Ge discrimination by plants. Graminoid species commonly
found in North American grassland systems, Agropyron smithii, Schizachyrium scoparium, and Andropogon gerardii were grown under controlled hydroponic environmental conditions. Silicon leaf contents were positively correlated with solution
Si and ambient temperature but not with nutrient solution pH, electrical conductivity, or species. The Ge/Si ratio incorporated
into phytoliths shows a distribution coefficient [(Ge/Si)phytolith/(Ge/Si)solution] of about 0.2 and is remarkably invariant between species, photosynthetic pathway, and solution temperature. Ge seems to
be discriminated against during the uptake and translocation of Si to the opal deposition sites by about a factor of five.
In the second experiment, a wider range of graminoid species (Agropyron smithii, Bouteloua gracilis, Buchloe dactyloides, Oryzopsis hymenoides, Schizachyrium scoparium and Andropogon gerardii) were grown in two different soil mediums. Plant phytoliths showed a distribution factor of about 0.4 for field grown grasses,
and 0.6 for potting soil grown grasses with no clear trends among the species. Evidence of the direction and degree of biological
Ge discrimination during plant uptake provides a geochemical finger print for plants and improves the utility of Ge/Si ratios
in studies of terrestrial weathering and links between Si cycles in terrestrial and marine systems. 相似文献
29.
E.L. Kostoryz Q. Zhu Hong Zhao A.G. Glaros J.D. Eick 《Mutation Research - Genetic Toxicology and Environmental Mutagenesis》2007,634(1-2):156-162
The potential reactivity and structural properties of oxiranes (epoxides) are advantageous when considering polymers for medical devices. However, epoxy compounds are widely known to have genotoxic properties. The objective of the study was to evaluate the cytotoxicity and primary DNA damage effects induced by oxiranes and siloranes, silicon containing oxiranes. The siloranes, Ph-Sil, Tet-Sil, and Sil-Mix and the oxiranes Cyracure™ UVR-6105 and 1,3-bis[2-(2-oxiranylmethyl) phenoxy]pentane (OMP-5) were dissolved in organic solvents and dilutions containing less than 0.5% solvent were used in biological assays. The concentration that reduced the viability of 50% (TC50) of L929 cells was measured using the MTT assay and guided the selection of subtoxic doses for evaluation of DNA damage. Ph-Sil was more cytotoxic than OMP-5, Cyracure™ UVR-6105 and Sil-Mix. However, the TC50 value of Tet-Sil could not be determined due to its poor solubility. DNA damage was evaluated in the sister chromatid exchange (SCE) assay with CHO cells, and the alkaline comet assay with L929 cells. In contrast to the siloranes, the oxiranes exhibited significant increases (p > 0.05) in SCE frequencies and DNA migration relative to their solvent controls. Our findings support previous reports that siloranes have low genotoxic potential and can be suitable components for development of biomaterials. 相似文献
30.
S.J. Lugowski D.C. Smith H. Bonek J. Lugowski W. Peters J. Semple 《Journal of trace elements in medicine and biology》2000,14(1):31-42
The increase, in the last two decades, in the application of silicones (polysiloxanes) and inorganic silicon compounds in medicine and the food industry, has exposed the human body to extensive contacts with these substances. Most silicone breast implants contain a gel consisting of a crosslinked silicone elastomer swollen by silicone oil (PDMS). Diffusion of PDMS through the silicone elastomer envelope and rupture of the envelope with release of the gel contents both occur clinically. The amount and distribution of silicone compounds in various tissues are key issues in the assessment of health problems connected with silicone implants. We have measured by GFAAS the Si content of tissues from normal and implant patients and the organic solvent extractable Si levels (assumed to be silicone), using careful control of sample collection and preparation. Whole blood levels were: implant patients mean 38.8 (SD 25.6) (microg/kg), controls mean 24.2 (SD 26.7) (microg/kg) in one study and subsequently 103.8 (SD 112.1) and 74.3 (SD 86.5) (microg/kg) in another study. Capsular tissue levels were: gel implants 25047 (SD 39313) (mg/kg of dry tissue), saline implants 20.0 (SD 27.3) (mg/kg of dry tissue) and controls 0.24 (SD 0.39) (mg/kg of dry tissue). Breast milk levels were: implant patients mean 58.7 (SD 33.8) (microg/kg), controls mean 51.1 (SD 31.0) (microg/kg); infant formula mean was 4.40 (mg/kg). Various precautions were undertaken to avoid Si contamination in this work, the most important being a) the use of a Class 100 laboratory for sample preparation and b) application of strict and elaborate washing procedure for specimen collection tools and laboratory plasticware. This data demonstrated that to properly interpret the importance of these numbers for human health, a larger study of "normal" levels of Si in human tissues should be undertaken and factors such as diet, water, race and geographical location should be considered. 相似文献