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At least 181 records · Page 10Linked to original sources
PubMed2006

Is the effect of silicon on rice uptake of arsenate (AsV) related to internal silicon concentrations, iron plaque and phosphate nutrition?

Solution culture experiments were conducted to investigate the effects of silicon (Si) on arsenate (As(V)) uptake by rice. The addition of Si to the pretreatment or uptake solution significantly decreased shoot and root As concentrations (P<0.001 and P<0.05). The presence of Si in the pretreatment or uptake solution also significantly decreased shoot P concentrations (P<0.001). The data demonstrated that both internal and external Si inhibited the uptake of As and P. Results of As uptake kinetics showed that the mechanism of the effect of Si on arsenate uptake is not caused by direct competition for active sites of transporters with As. The effect of Si on As uptake was not entirely mediated through the effect of Si on P uptake. Although the addition of Si to pretreatment solutions still significantly decreased shoot and root As concentrations, the extent of reduction became smaller when rice roots were coated with iron plaque.

Arsenates↗
PubMed1993

Vitrectomy with silicone oil or perfluoropropane gas in eyes with severe proliferative vitreoretinopathy. Silicone Study Report 3.

Between 1985 and 1990, 340 eyes with rhegmatogenous retinal detachment (RRD) and severe (stage C3 or worse) proliferative vitreoretinopathy (PVR) were treated with vitrectomy and randomly selected to receive perfluoropropane gas or silicone oil; 183 eyes had undergone no prior vitrectomy (group 1), and 157 eyes had undergone prior vitrectomy with intraocular gas tamponade (group 2). No differences were found between eyes in the two groups in achieving visual acuity of 5/200 or better (44% vs. 39%), macular reattachment (78% vs. 77%), or complete retinal reattachment (67% for both groups). In group 1, 74 eyes achieved complete retinal reattachment after only one operation; 41 additional eyes achieved reattachment after a second surgical procedure. In group 2, these numbers were 74 and 26, respectively. Eyes treated successfully after more than one operation were less likely to regain a visual acuity of 5/200 or better than those successfully treated with one operation (P < 0.01). There was no difference in hypotony between groups, but keratopathy was more frequent in eyes in group 2 (P < 0.05). The results suggest that differences in outcomes between group 1 and group 2 eyes are not as great as previously believed.

Adult↗
PubMed2006

Germanium-68 as an adequate tracer for silicon transport in plants. Characterization of silicon uptake in different crop species.

A basic problem in silicon (Si) uptake studies in biology is the lack of an appropriate radioactive isotope. Radioactive germanium-68 ((68)Ge) has been used previously as a Si tracer in biological materials, but its suitability for the study of Si transport in higher plants is still untested. In this study, we investigated (68)Ge-traced Si uptake by four crop species differing widely in uptake capacity for Si, including rice (Oryza sativa), barley (Hordeum vulgare), cucumber (Cucumis sativus), and tomato (Lycopersicon esculentum). Maintenance of a (68)Ge:Si molar ratio that was similar in the plant tissues of all four plant species to that supplied in the nutrient solution over a wide range of Si concentrations demonstrated the absence of discrimination between (68)Ge and Si. Further, using the (68)Ge tracer, a typical Michaelis-Menten uptake kinetics for Si was found in rice, barley, and cucumber. Compared to rice, the relative proportion of root-to-shoot translocated Si was lower in barley and cucumber and especially in tomato (only 30%). Uptake and translocation of Si in rice, barley, and cucumber (Si accumulators) were strongly inhibited by 2,4-dinitrophenol and HgCl(2), but in tomato, as a Si-excluding species, both inhibitors produced the opposite effect. In conclusion, our results suggest the use of the (68)Ge tracer method as an appropriate choice for future studies of Si transport in plants. Our findings also indicate that the restriction of Si from symplast to apoplast in the cortex of Si excluders is a metabolically active process.

Biological Transport↗
PubMed2006

Importance of plant species and external silicon concentration to active silicon uptake and transport.

Here, we characterized silicon (Si) uptake and xylem loading in Oryza sativa, Zea mays, Helianthus annuus and Benincase hispida in a series of hydroponic experiments. Both active and passive Si-uptake components co-exist in all the plants tested. The active component is the major mechanism responsible for Si uptake in O. sativa and Z. mays. By contrast, passive uptake prevails in H. annuus and B. hispida at a higher external Si concentration (0.85 mM), while the active component constantly exists and contributes to the total Si uptake, especially at a lower external Si concentration (0.085 mM). Short experiments showed that Si uptake was significantly suppressed in O. sativa and Z. mays by metabolic inhibitors or low temperature, regardless of external Si concentrations. By contrast, Si uptake in H. annuus and B. hispida was inhibited more significantly by metabolic inhibitors or low temperature at lower (for example, 0.085 mM) than at higher (for example, 1.70 mM) external Si concentrations. It can be concluded that both active and passive Si-uptake components co-exist in O. sativa, Z. mays, H. annuus and B. hispida, with their relative contribution being dependent much upon both plant species and external Si concentrations.

Biological Transport, Active↗
PubMed2005

Influence of polarized bias and porous silicon morphology on the electrical behavior of Au-porous silicon contacts.

This paper reports the surface morphology and I-V curves of porous silicon (PS) samples and related devices. The observed fabrics on the PS surface were found to affect the electrical property of PS devices. When the devices were operated under different external bias (10 V or 3 V) for 10 min, their observed obvious differences in electrical properties may be due to the different control mechanisms in the Al/PS interface and PS matrix morphology.

Electrochemistry↗
PubMed2001

Supplemental silicon increases plasma and milk silicon concentrations in horses.

The primary objective of this research was to determine the effect of supplemental dietary silicon (Si) on plasma and milk Si concentrations of lactating mares and the subsequent effect on plasma Si concentrations in nursing foals. Additionally, the role of Si on altering biochemical markers of bone turnover was investigated, because supplemental Si may be advantageous in enhancing bone health. Twelve Arabian mare/foal units were pair-matched by foaling date and randomly assigned to two groups, Si-supplemented (Supplemented) or control (Control). Blood and milk samples were taken on d 0, 15, 30, and 45, d 0 being the 1st d after parturition. Plasma and milk (or colostrum) Si concentrations were determined and serum was analyzed for osteocalcin, carboxy-terminal pyridinoline cross-linked telopeptide region of type I collagen, and pyridinoline and deoxypyridinoline crosslinks. All Supplemented mares had higher (P < 0.01) plasma Si concentrations than Control by d 30, and Supplemented mares' milk had higher (P < 0.01) Si concentrations on d 45 than Control mares' milk. By d 45, foals of Supplemented mares had higher (P < 0.01) plasma Si concentrations than foals of Control mares. Supplemental Si did not influence (P > 0.36) bone metabolism in foals; however, trends (P < 0.10) for altered bone metabolism were observed in postpartum mares. Results indicate that supplemental Si increases plasma and milk Si concentrations. Further research is required to determine whether Si has a role in altering serum biochemical markers of bone and collagen activity.

Amino Acids↗
PubMed2007

Optical characterization of porous silicon and crystalline silicon by the Kramers-Kronig method.

The electronic structure of porous silicon (PS) has been characterized by optical reflectance spectra analyses. Using a Cary-500 spectrometer, the reflectance spectra of PS are measured in the photon energy range of 0.4-6 eV. The spectral responses of optical constants are calculated for PS and Si by Kramers-Kronig analysis. The analysis clarified strong evidence for widening and direct bandgaps for PS samples. Also, the optical constants of PS layers as a function of porosity have been studied. Our results indicate that PS retains some of the characteristic optical features of crystalline Si. However, in the visible region, PS shows that the imaginary part of the complex refractive index increases, and the real part decreases as porosity increases. This feature could be related to the surface roughness of PS and its role in surface absorption and scattering.

Journal Article↗