Transcript levels of phytoene desaturase gene in Dunaliella salina Teod. as affected by PbS nanoparticles and light intensity.

Phytoene synthase (Psy) and Phytoene desaturase (Pds) are the first two regulatory enzymes in the carotenoids biosynthetic pathway. The genes Psy and Pds are under transcriptional control in many photosynthetic organisms. In the present study, using quantitative real time- PCR (qRT-PCR), the effects of uncoated and gum-Arabic coated PbS nanoparticles (GA-coated PbS NPs) and light intensity on the mRNA levels of Pds were investigated. Relative to mRNA level of Pds at 100 µmol photon m-2 s-1 light intensity (control culture), 2.2-fold increase in transcript levels occurred after 12 h of exposure to higher light intensity, which is significantly (P<0.05) different compared to control. After 48 h of exposure, the mRNA level of Pds was reduced to that in control. This indicates that light intensity regulates Pds at the mRNA level. In the presence of uncoated and GA-coated PbS NPs, the transcript levels of Pds were decreased over time, with uncoated PbS NPs having more inhibitory effects on mRNA levels compared to GA- coated PbS NPs. This shows that PbS NPs have adverse effects on transcription or post transcriptional processing and coating nanoparticles with biopolymers reduces their toxicity to organisms. Being under control, it seems that genetic manipulation of Pds may result in increased biotechnological production of carotenoids by D. salina.

Effects of Sodium Nitrate and Mixotrophic Culture on Biomass and Lipid Production in Hypersaline Microalgae Dunaliella Viridis Teod

To access the potential application of Dunaliella viridis Teod. for biofuel production, the effects of culture media composition on biomass and lipid content of this microalgae were investigated. Measured at the 20 th day, sodium nitrate at 5.0 mM augmented biomass production by 26.5 percent compared to control (1 mM sodium nitrate). Total lipids expressed as µg mL-1 of culture also increased with increase in nitrate concentration up to 5.0 mM sodium nitrate, whereas when expressed on the per cell basis, total lipids stayed relatively constant at most of the tested nitrate concentrations except at 0.5 mM which was 31.4 percent higher compared to 1.0 mM nitrate. At 5.0 mM sodium nitrate, by using 20 g L-1 of glucose in mixotrophic culture of D. viridis, cell number augmented by 36.4 percent compared to the cultures with no added glucose. Llipid content per cell and per mL of culture was increased by 71.4 and 135.1 percent, respectively. Among plant hormones, 10-9 M indole-3- acetic acid (IAA) plus 10 -8 M trans-zeatin riboside led to 22.8 percent higher biomass relative to control (without hormone and at 1.0 mM sodium nitrate). It is concluded that altering the growth conditions of D. viridis can lead to higher cell densities and higher lipids content which can be exploited for biofuel production.

Influence of PbS nanoparticle polymer coating on their aggregation behavior and toxicity to the green algae Dunaliella salina.

The potential hazards of nanoparticles (NPs) to the environment and to living organisms need to be considered for a safe development of nanotechnology. In the present study, the potential toxic effects of uncoated and gum Arabic-coated lead sulfide nanoparticles (GA-coated PbS NPs) on the growth, lipid peroxidation, reducing capacity and total carotenoid content of the hypersaline unicellular green algae Dunaliella salina were investigated. Coatings of PbS NPs with GA, as confirmed by Fourier transform infrared spectroscopy, reduced the toxicity of PbS NPs. Uncoated PbS NP toxicity to D. salina was attributed to higher algal cell-NP agglomerate formation, higher lipid peroxidation, lower content of total reducing substances and lower total carotenoid content. Low levels of Pb(2+) in the growth culture media indicate that PbS NP dissolution does not occur in the culture. Also, the addition of 100 µM Pb(2+) to the culture media had no significant (P>0.05) effect on algal growth. The shading of light (shading effect) by PbS NPs, when simulated using activated charcoal, did not contribute to the overall toxic effect of PbS NPs which was evident by insignificant (P>0.05) reduction in the growth and antioxidant capacity of the algae. When PbS NP aggregation in culture media (without algal cells) was followed for 60 min, uncoated form aggregated rapidly reaching aggregate sizes with hydrodynamic diameter of over 2500 nm within 60 min. Effective particle-particle interaction was reduced in the GA-coated NPs. Aggregates of about 440 nm hydrodynamic diameter were formed within 35 min. Afterwards the aggregate size remained constant. It is concluded that PbS NPs have a negative effect on aquatic algae and their transformation by GA capping affects NPs aggregation properties and toxicity.

Evaluation of antioxidant potential and reduction capacity of some plant extracts in silver nanoparticles' synthesis.

The green synthesis of metallic nanoparticles is an active research area in nanotechnology. In the present study, antioxidant potential, total reducing capacity and silver nanoparticles' (Ag NPs) synthetic potential of methanolic leaf extracts of seven plant species were evaluated and compared. Antioxidant capacity, expressed as µmol Trolox equivalents g-1 DW (µmol TE g-1 DW), ranged from 116.0 to 1.80. The plants Rosmarinus sp. and Zataria Multiflora showed highest antioxidant capacities with IC50 of 1.07 and 1.22 mg ml-1, respectively. Total reducing capacity ranged from 7.6 to 0.17 mg gallic acid equivalent to g-1 DW (mg GAE g-1 DW). Plants with high antioxidant potentials also showed higher total reducing capacity. In fact, the order of the plants' reducing capacity was similar to that of their antioxidant potential. The same two plant species, i.e., Zataria Multiflora and Rosmarinus sp, with high reducing capacities, showed higher potentials for Ag NPs synthesis. It is concluded that reducing substances in the extracts contribute significantly to the antioxidant potential of the tested plant species, and plants with a high reducing capacity are excellent sources for the green synthesis of metallic nanoparticles. In addition, synthetic antioxidants have adverse effects on human health; therefore, to benefit more from the health promoting properties of plant species, evaluating their novel natural antioxidants is recommended.

Cadmium-induced infertility in male mice.

The effects of cadmium in a concentration similar to that found in Maharloo Lake (Shiraz, Iran) on male reproductive system was studied in adult Balb/c male mice that received 0, 23, and 50 mg/kg of cadmium chloride in 0.5 mL distilled water for 45 days. Sperm count and motility, sperm nuclear maturity and chromatin structure tests were carried out. Testis of each mouse was examined histologically. The treated male mice were mated with females. Prostatic and nonprostatic acid phosphatase activity in blood serum, testis, and prostate, lipid peroxidation and cadmium accumulation in testis, seminal vesicle, and middle 1/3 of the quadericeps femoris muscle were measured. The sperm count, sperm motility, sperm maturity, and the level of testosterone decreased significantly in the high dose adminstered group. Histological studies showed a severe necrosis and atrophy in the testis of high dose group, consequently, there was no successful mating in some groups. The number of newborns and their weights and crown rump lengths reduced. Cadmium accumulation in testis and middle of the quadriceps femoris muscle was significantly higher in animals receiving 50 mg/kg cadmium chloride. Nonprostatic acid phosphatase activity decreased, whereas prostatic acid phosphatase activity increased significantly in serum of animals receiving 50 mg/kg cadmium chloride. Also prostatic acid phosphatase activity decreased significantly in prostate of animals receiving 50 mg/kg cadmium chloride. Lipid peroxidation was significantly higher in testis of animals treated with 50 mg/kg cadmium chloride compared with control group. Cadmium affects male reproductive system activity and can cause infertility in mice as an animal model.