[Effect of salicylic acid on the growth and physiological performance of Ulva prolifera]. / æ°´æ¨é ¸å¯¹æµ’è‹”ç”Ÿé•¿å’Œç”Ÿç†ç‰¹æ€§çš„å½±å“.

In order to study the effects of salicylic acid on the growth and physiological performance of Ulva prolifera with different proliferative styles, we took U. prolifera from vegetative (VU) and spore proliferative cells (SU) as materials, and cultured them under different salicylic acid concentrations to investigate their growth rate, chlorophyll fluorescence, SOD and soluble protein content. The results showed that the growth of both VU and SU was promoted by low concentration of salicy-lic acid, especially for VU. Under 0.2 Μg·mL-1 salicylic acid treatment, VU showed the highest relative growth rate of 21.0%, and the maximum photochemical efficiency (Fv/Fm) increased by 9.8% compared with SU. Additionally, salicylic acid affected the SOD activity significantly, and the enzyme activity of VU increased by 52.0% and 198.6% under 0.2 and 0.5 Μg·mL- 1 salicylic acid treatment, and that of SU increased by 54.1% and 38.0%, respectively. Salicylic acid also promoted the relative electron transfer rate (rETR), photosynthesis and protein content of both VU and SU. In conclusion, salicylic acid benefited the growth of two kinds of U. prolifera, especially for VU.

[Effect of exogenous salicylic acid and ultraviolet radiation on Ulva prolifera under different light conditions]. / ä¸åŒå ‰ç §æ¡ä»¶ä¸‹å¤–æºæ°´æ¨é ¸å¯¹æµ’è‹”å“åº”ç´«å¤–è¾å°„èƒè¿«çš„å½±å“.

To study the combined effects of exogenous salicylic acid (SA) and ultraviolet radiation (UV) on marine green algae Ulva prolifera under high (160 Μmol·m-2·s-1) and low (70 Μmol·m-2·s-1) light intensities, the growth, chlorophyll fluorescence parameters, photosynthetic rate of oxygen, superoxide dismutase (SOD) activity, soluble polysaccharide and soluble protein contents were investigated after they grew with or without ultraviolet (UV, 3.2 W·m-2) radiation in the presence or absence of SA (10 Μg·mL-1) for three days. The treatments included control group (CK), SA, UV and UV+SA treatments. Results showed that under the low light intensity without UV condition, the relative growth rate was enhanced, Chl a and soluble protein contents were decreased by SA. Under the high light intensity without UV condition, the relative growth rate was decreased, Chl a content, respiratory rate, photosynthetic rate of oxygen, soluble polysaccharide and soluble protein contents were enhanced by SA. Under the high light intensity with UV condition, the relative growth rate, Chl a and soluble polysaccharide contents were enhanced by UV+SA. Additionally, under the low light intensity with UV condition, compared to UV treatment, the maximum photochemical efficiency (Fv/Fm) and soluble protein contents were respectively increased by 139.8% and 32.2% under the UV+SA treatment. In conclusion, SA reduced the inhibitory effects of U. prolifera induced by UV, and the effects were more significant under the high light intensity.

Molecular consequences of genetic variations in the glutathione peroxidase 1 selenoenzyme.

Accumulating data have implicated the selenium-containing cytosolic glutathione peroxidase, GPx-1, as a determinant of cancer risk and a mediator of the chemopreventive properties of selenium. Genetic variants of GPx-1 have been shown to be associated with cancer risk for several types of malignancies. To investigate the relationship between GPx-1 enzyme activity and genotype, we measured GPx-1 enzyme activity and protein levels in human lymphocytes as a function of the presence of two common variations: a leucine/proline polymorphism at codon 198 and a variable number of alanine-repeat codons. Differences in GPx activity among these cell lines, as well as in the response to the low-level supplementation of the media with selenium, indicated that factors other than just genotype are significant in determining activity. To restrict the study to genotypic effects, human MCF-7 cells were engineered to exclusively express allelic variants representing a combination of either a codon 198 leucine or proline and either 5 or 7 alanine-repeat codons following transfection of GPx-1 expression constructs. Transfectants were selected and analyzed for GPx-1 enzyme activity and protein levels. GPx-1 with 5 alanines and a leucine at codon 198 showed a significantly higher induction when cells were incubated with selenium and showed a distinct pattern of thermal denaturation as compared with GPx-1 encoded by the other examined alleles. The collective data obtained using both lymphocytes and MCF-7 indicate that both intrinsic and extrinsic factors cooperate to ultimately determine the levels of this enzyme available to protect cells against DNA damage and mutagenesis.

Molecular mechanisms by which selenoproteins affect cancer risk and progression.

Selenoproteins comprise a unique class of proteins that contain selenium in the form of selenocysteine. Several selenoproteins have been implicated in the risk or development of cancers in humans by genetic data. These include Selenoprotein P, 3 members of the glutathione peroxidase family of anti-oxidant enzymes and Sep15. At-risk alleles in the germline indicate a likely role in determining susceptibility to cancer, while loss of heterozygosity or chromosomal epigenetic silencing indicate that the reduction in the levels of the corresponding proteins contribute to malignant progression. Lower levels of these proteins are likely to be detrimental due to the resulting cellular stress and perturbations in important regulatory signaling pathways. The genetic data indicating the involvement of these selenoproteins in cancer etiology are discussed, as are the possible mechanisms by which these genes might promote carcinogenesis.

Selenium and GPx-1 overexpression protect mammalian cells against UV-induced DNA damage.

Supplementation of the culture media of human MCF-7 breast carcinoma cells or mouse fibroblasts with low levels of selenium (30 nM) provided as sodium selenite was shown to protect these cells from ultraviolet (UV)-induced chromosome damage, as quantified by micronucleus assay. Selenium supplementation was also effective in reducing UV-induced gene mutations as measured in the lacI shuttle vector model. Protection was dependent on functional BRCA1 activity, a protein implicated in breast cancer risk and DNA damage repair. In addition, overexpression of GPx-1, a selenoprotein with antioxidant activity, also attenuated UV induced micronuclei formation in the absence of selenium supplementation. Combining selenium supplementation with GPx-1 overexpression further reduced UV-induced micronucleus frequency. These data provide evidence that the benefits of selenium supplementation might be either through the prevention or repair of DNA damage, and they implicate at least one selenoprotein (GPx-1) in the process.