[en] Gold nanoparticles (AuNPs) received a great deal of attention for biomedical applications, especially in diagnostic imaging and therapeutics. Even though AuNPs have potential benefits in biomedical applications, the impact of AuNPs on human and environmental health still remains unclear. The use of AuNPs which is a high-atomic-number materials, provide advantages in terms of radiation dose enhancement. However, before this can become a clinical reality, cytotoxicity of the AuNPs has to be carefully evaluated. Cytotoxicity test is a rapid, standardized test that is very sensitive to determine whether the nanoparticles produced are harmful or benign on cellular components. In this work the size and concentration dependence of AuNPs cytotoxicity in breast cancer cell lines (MCF-7) are tested by using WST-1 assay. The sizes of AuNPs tested were 13 nm, 50 nm, and 70 nm. The cells were seeded in the 96-well plate and were treated with different concentrations of AuNPs by serial dilution for each size of AuNPs. The high concentration of AuNPs exhibit lower cell viability compared to low concentration of AuNPs. We quantified the toxicity of AuNPs in MCF-7 cell lines by determining the IC₅₀ values in WST-1 assays. The IC₅₀ values (inhibitory concentrations that effected 50% growth inhibition) of 50 nm AuNPs is lower than 13 nm and 70 nm AuNPs. Mean that, 50nm AuNPs are more toxic to the MCF-7 cells compared to smaller and larger sizes AuNPs. The presented results clearly indicate that the cytotoxicity of AuNPs depend not only on the concentration, but also the size of the nanoparticles

[en] A specific and ultrasensitive, label free single-walled carbon nanotubes (SWNTs) based chemiresistive genosensor was fabricated for the early detection of Streptococcus pyogenes infection in human causing rheumatic heart disease. The mga gene of S. pyogenes specific 24 mer ssDNA probe was covalently immobilized on SWNT through a molecular bilinker, 1-pyrenemethylamine, using carbodiimide coupling reaction. The sensor was characterized by the current-voltage (I-V) characteristic curve and scanning electron microscopy. The sensing performance of the sensor was studied with respect to changes in conductance in SWNT channel based on hybridization of the target S. pyogenes single stranded genomic DNA (ssG-DNA) to its complementary 24 mer ssDNA probe. The sensor shows negligible response to non-complementary Staphylococcus aureus ssG-DNA, confirming the specificity of the sensor only with S. pyogenes. The genosensor exhibited a linear response to S. pyogenes G-DNA from 1 to1000 ng ml⁻¹ with a limit of detection of 0.16 ng ml⁻¹

[en] Withaferin A (WA), a steroidal lactone, and Plumbagin (Pi), a naphthoquinone, from the roots of Withania somnifera and Plumbage rosea, respectively, have been shows to possess growth inhibitory and radiosensitizing effects on experimental mouse tumours. An aqueous extract of the leaves of Ocimum sanctum (OE) was found to protect mice against radiation lethality. Therefore, the radiomodifying effects of the above plant products on the bone marrow of the adult Swiss mouse was studied. Single doses of WA (30 mg kg^-1) or P1 (5 mg kg^-1) were injected intraperitoneally tip) and OE (10 mg kg^-1) was injected ip once daily for five consecutive days. Administration of extracts was followed by 2 Gy whole body gamma irradiation. Bone marrow stem cell survival was studied by an exogenous spleen colony unit (CFU-S) assay. The effects of WA and P1 were compared with that of cyclophosphamide (CP) and radioprotection by OE was compared with that of WR-2721 (WR). Radiation reduced the CFU-S to less than 50% of normal. WA, CP and P1 significantly enhanced this effect and reduced the CFU-S to almost the same extent (to <20% of normal), although individually WA and P1 were less cytotoxic than CP. These results indicate that radiosensitization by WE and P1 is not tumour specific. OE significantly increased CFU-S compared with radiotherapy (RT) alone. OE + RT gave a higher stem cell survival (p < 0.05) than that produced by WR + RT. While WR alone had a toxic effect, OE treatment showed no such effect, suggesting that the latter may have an advantage over WR in clinical application. (author)

[en] Analysis of biological activity in intact cells or tissues is essential to understand many life processes. Techniques for these in vivo measurements have not been well developed. We present here a nondestructive method to image water in living plants using a neutron beam. This technique provides the highest resolution for water in tissue yet obtainable. With high specificity to water, this neutron beam technique images water movement in seeds or in roots imbedded in soil, as well as in wood and meristems during development. The resolution of the image attainable now is about 15 μm. We also describe how this new technique will allow new investigations in the field of plant research. (author)

[en] Dry matter production of lettuce plant in different seasons was studied quantitatively based on the amount of intercepted solar radiation by plant. (1) Top dry weight was a linear function of the total amount of intercepted solar radiation by plant and the relationship between the two parameters did not differ between seasons. Daily dry matter increase (delta-DW) mainly depended on the daily amount of intercepted solar radiation by plant (DIR) and radiation-sue efficiency (RUE; the ratio of the amount of dry matter production to the amount of intercepted solar radiation) was considered to be almost constant throughout the growth period in every experiment. (2) DIR could be resolved into daily amount of solar radiation and effective area (A), modified vertically projected area of plant (VPA) with planting density and light absorptivity of plant. A simple model which calculated A with VPA was developed. This model indicated that delta-DW is influenced proportional by VPA until VPA reaches the area given as the product of row interval and plant interval and there after the VPA increase does not exert any additional effect on the productivity. (3) a simple model for calculating A with top dry weight was also developed. This model used different parameters between seasons because of the difference in the relationship of VPA and top dry weight between seasons. This model indicated that at the early growth stage, A value per top dry weight in winter was lower than that in autumn but that A reached almost the same level in both seasons. (4) Differences in delta-DW due to season could be attributed to the difference in solar radiation and VPA. Negligible difference in VPA per top fresh weight between seasons and low water content of top in winter suggested that suppressed water uptake due to low temperature may result in low VPA in winter

[en] Potential yield in several crop species is affected by radiation and temperature when they are grown under unstressed conditions. This issue has been not explored for sunflower (Helianthus annuus L), and the objectives of our experiments were (i) to analyze the dependence of seed number (SN, seeds m⁻²) on the thermal and light conditions during the period from floret initiation to the end of seed-setting and (ii) to determine whether sensitivity of SN to radiation differs between pre- and post-anthesis. Inter and intra-annual variations in sowing dates and artificial shading were used to expose irrigated crops to different conditions of radiation (range 14-24 MJ m⁻² d⁻¹) and temperature (20–24°C) (temperature/radiation combinations = 18). Significant positive (P < 0.00001) relationships between SN (range 3499-11547 seeds -s) and intercepted (r² = 0.65) an incident (r² = 0.56) short-wave radiation during the floret initiation to seed-setting period were found. A weaker negative association with temperature (r² = 0.29; P < 0.05) was also found. The relationship between SN and a photothermal quotient [PQ = mean radiation/ (mean temperature-base temperature), MJ m⁻² d⁻¹ °C⁻¹], calculated with intercepted radiation was better than that achieved by either variable alone (SN = −436 + 9214 PQ; r² = 0.74; P < 0.000001). We conclude that PQ would be a better tool to predict SN in sunflower than the use of radiation or temperature alone. Crops subjected to shading after anthesis suffered significantly greater (P < 0.05) reductions in SN, at equivalent PQ, than those exposed to shading before anthesis. (author)

[en] A new stable mutant of Arabidopsis thaliana with a spotted pigment in the seed coat, named anthocyanin spotted testa (ast), was induced by carbon ion irradiation. The spotted pigmentation of ast mutant was observed in immature seeds from 1-2 days after flowering (DAF), at the integument of the ovule, and spread as the seed coat formed. Anthocyanin accumulation was about 6 times higher in ast mutant than in the wild-type at 6 DAF of the immature seeds, but was almost the same in mature dry seeds. A higher anthocyanin accumulation was not observed in the seedlings, leaves or floral buds of ast mutant compared with the wild-type, which suggests that a high accumulation of anthocyanins is specific to the seed coat of the immature ast seeds. Reciprocal crosses between ast mutant and the wild-type indicated that ast is a single recessive gene mutation and segregates as a delayed inheritance. The results of crossing with tt7 and ttg mutants also confirmed that the AST gene is probably a regulatory locus that controls flavonoid biosynthesis. A mapping analysis revealed that the gene is located on chromosome I and is closely linked to the SSLP DNA marker nga280 with a distance of 3.2 cM. AST has been registered as a new mutant of Arabidopsis

[en] The identification of chemical substances which increase the efficiency of radiation is important to make easier the obtention of plants with structural chromosome aberrations which may be used in an alternative program for hybrid maize production. The present work was carried out to investigate the effect of the chemical substance metronidazole in maize seedlings submitted to gamma radiation. Several treatments were done, soaking the seeds in solutions with varied concentrations of the active substance combined with solution filtration and gamma radiation. On the third day of the experiment, germination percentage, root and stem lengths were evaluated. At a high concentration (1,250 mg/50 mL) metronidazole behaved as a radiosensibilizer in the presence of radiation. Even at a low concentration (250 mg/50 mL; 750 mg/50 mL) and in the absence of radiation, metronidazole behaved as toxic substance. (author)

[en] Isolated cell walls from maize coleoptiles prepared under conditions that preserve the ability for enzymatic hemicellulose autolysis release UV-absorbing substances into the incubation medium in a time-dependent reaction with an optimal rate at pH 6–7. The reaction can be inhibited by low temperature and protein-denaturing treatments, indicating an enzymatic process. Spectroscopic and chromatographic analyses showed that the liberated substances represent a complex mixture of free and bound (alkali-hydrolyzable) phenolic compounds with similar absorption spectra restricted to the range below 300 nm and thus excluding hydroxycinnamic acids from cell-wall esters. A spectroscopically and chromatographically similar mixture of soluble UV-absorbing substances is released if living (abraded) maize coleoptiles or coleoptile segments are incubated in water or buffer, suggesting that insoluble phenolic materials in the cell wall are metabolized also in vivo. This reaction can be promoted by anaerobic conditions and application of fusicoccin whereas auxin had a slightly inhibitory effect. No clear relationship to elongation growth could be demonstrated. We conclude from these results that polymeric phenolic constituents of the cell wall are subject to enzymatic degradation in muro similar to polysaccharide autolysis and that this process is under metabolic control

[en] Parental cultivars (Oryza sativa L. Japanese lowland cultivars Sasanishiki and Norin 1), F₂ plants, and F₃ Iines were grown under visible light with or without supplemental UV-B radiation in a phytotron, to determine whether the accumulation of UV-absorbing compounds plays a role in the difference in UV-B resistance between these rice cultivars. The level of UV-absorbance per unit leaf area increased with the UV-B treatuent in all the leaves of these two rice cultivars, but was higher in Sasanishiki than in Norin 1 irrespective of UV-B treatment. An analysis by thin-layer chromatography and the UV-absorption spectra of the extracts did not show any qualitative difference in UV-absorbing compounds in leaf tissues between these two cultivars. There was a significant positive correlation between the level of UV-absorbance per unit leaf area and the fresh weight of aerial parts in the F₂ plants exposed to UV-B radiation. Furthermore, the level of UV-absorbance per unit leaf area tended to be higher in the F₃ Iines resistant to UV-B radiation than in those sensitive to such radiation regardless of whether these F₃ lines were exposed to supplemental UV-B radiation. These results suggest that the differences in UV-B resistance between Sasanishiki and Norin 1 are associated with genetic differences in the level of accumulation of UV-B absorbing compounds in leaf tissues. Based on these results we suggest that the accumulation of UV-B absorbing compounds is an important factor contributing to UV-B resistance in rice cultivars. Since the accumulation of UV-absorbing compounds in leaves appears to minimize the latent negative impact of UV-B radiation on rice production, it may be a useful character to select in ordinary breeding. (author)