Biokinetics of iodine-131 in rat thyroid following lead and lithium supplementation

The impact of lead as an environmental pollutant on the I-131 uptake and retention in rat thyroid was assayed alone and in combination with lithium treatment. Lead treatment significantly stimulated the 2- and 24-h uptake of I-131 in the thyroid, and the 24-h uptake showed the maximum stimulation after 3 mo of lead treatment. On the contrary, lithium supplementation reduced the uptake significantly and the maximum decrease was noticed after 2 mo of lithium administration. Further, simultaneous lead and lithium treatment resulted in more pronounced increase in the uptake of I-131 by the thyroid, which was maximum after 3 mo of combined treatment. The thyroidal biological half-life of I-131 (T _biol) was found to be increased significantly following lead and lithium treatments when given separately. Interestingly, combined lead and lithium treatment given up to 2 mo further prolonged theT _biol of I-131, thus reflecting its increased retention.     

Interactive Effects of Abiotic Stress and Elevated CO2 on Physio-Chemical and Photosynthetic Responses in Suaeda Species

Suaeda fruticosa and S. monoica are important halophytes for ecological rehabilitation of saline lands. We report differential physio-chemical, photosynthetic, and chlorophyll fluorescence responses in these halophytes under 100 mM sodium chloride (NaCl), 50% strength (16.25 ppt) of seawater (SW)-imposed salinity, and 10% polyethylene glycol 6000 imposed osmotic stress at 380 (ambient) and 1200 (elevated) µmol mol^–1 CO₂ concentrations. SW salinity enhanced the growth in both species; however, compared with S. fruticosa, the S. monoica exhibited comparatively better growth and biomass accumulation under saline conditions at elevated CO₂. Results demonstrated better photosynthetic performances of S. monoica under stress conditions at both levels of CO₂, and this resulted in higher accumulation of carbon, nitrogen, sugar, and starch contents. S. monoica exhibited improved antenna size, electron transfer at PSII donor side, and efficient working of photosynthetic machinery at elevated CO₂, which might be due to efficient upstream utilization of reducing power to fix the CO₂. The δ¹³C results supported the operation of C₄ CO₂ fixation in S. monoica and C₃ or intermediate pathway of CO₂ fixation in S. fruticosa. Lower accumulation of reactive oxygen species, reduced membrane damage, lowered solute potential, and higher accumulation of proline and polyphenol contents indicated elevated CO₂-induced abiotic stress tolerance in Suaeda. Higher activity of antioxidant enzymes in both species at both levels of CO₂ help plants to combat the oxidative stress. Upregulation of NADP-dependent malic enzyme and NADP-dependent malate dehydrogenase genes indicated their role in abiotic stress tolerance as well as photosynthetic carbon (C) sequestration. Operation of C₄ type CO₂ fixation in S. monoica and an intermediate CO₂ fixation in S. fruticosa could be the possible reason for the superior photosynthetic efficiency of S. monoica under stress conditions at elevated CO₂.

     

The red seaweed Kappaphycus alvarezii antiporter gene (KaNa+/H+) confers abiotic stress tolerance in transgenic tobacco

Molecular Biology Reports - Plant establishment, growth, development and productivity are adversely affected by abiotic stresses that are dominant characteristics of environmentally...     

Synthesis of Monomethoxypolyethyleneglycol—Cholesteryl Ester and Effect of its Incorporation in Liposomes

The objective of the present study was to synthesize monomethoxypolyethyleneglycol-5000 cholesteryl ester [PEG–CH] as a cost-effective substitute for polyethyleneglycol–phosphatidylethanolamine and to evaluate the influence of its incorporation in liposomal bilayers for surface modification. PEG–CH was synthesized and characterized by infrared (IR), proton nuclear magnetic resonance spectroscopy (¹H NMR), and differential scanning calorimetry (DSC) studies. Influence of incorporation of PEG–CH in liposomes was evaluated on various parameters such as zeta potential, DSC, and encapsulation efficiency of a hydrophilic drug pentoxyfylline. Conventional and PEG–CH containing pentoxyfylline liposomes were formulated and their stability was evaluated at 4°C for 3 months. PEG–CH could be successfully synthesized with good yields and the structure was confirmed by IR, DSC, and ¹H NMR. The incorporation of PEG–CH in liposomes resulted in reduction of the zeta potential and broadening of the DSC endotherm. Furthermore, incorporation of PEG–CH in liposomes decreased the encapsulation efficiency of pentoxifylline in liposomes when compared to conventional liposomes. Conventional and PEG–CH containing pentoxyfylline liposomes did not show any signs of pentoxyfylline degradation when stored at 4°C for 3 months.     

Predicting the impact of long-term temperature changes on the epidemiology and control of schistosomiasis: a mechanistic model

Background

Many parasites of medical and veterinary importance are transmitted by cold-blooded intermediate hosts or vectors, the abundance of which will vary with ambient temperatures, potentially altering disease prevalence. In particular, if global climate change will increase mean ambient temperature in a region endemic with a human pathogen then it is possible that the incidence of disease will similarly increase. Here we examine this possibility by using a mathematical model to explore the effects of increasing long-term mean ambient temperature on the prevalence and abundance of the parasite Schistosoma mansoni, the causative agent of schistosomiasis in humans.

Principal Findings

The model showed that the impact of temperature on disease prevalence and abundance is not straightforward; the mean infection burden in humans increases up to 30°C, but then crashes at 35°C, primarily due to increased mortalities of the snail intermediate host. In addition, increased temperatures changed the dynamics of disease from stable, endemic infection to unstable, epidemic cycles at 35°C. However, the prevalence of infection was largely unchanged by increasing temperatures. Temperature increases also affected the response of the model to changes in each parameter, indicating certain control strategies may become less effective with local temperature changes. At lower temperatures, the most effective single control strategy is to target the adult parasites through chemotherapy. However, as temperatures increase, targeting the snail intermediate hosts, for example through molluscicide use, becomes more effective.

Conclusions

These results show that S. mansoni will not respond to increased temperatures in a linear fashion, and the optimal control strategy is likely to change as temperatures change. It is only through a mechanistic approach, incorporating the combined effects of temperature on all stages of the life-cycle, that we can begin to predict the consequences of climate change on the incidence and severity of such diseases.     

Formulation and Evaluation of Fast Dissolving Films for Delivery of Triclosan to the Oral Cavity

The present investigation was undertaken with the objective of formulating TC containing fast dissolving films for local delivery to oral cavity. Various film forming agents, film modifiers and polyhydric alcohols were evaluated for optimizing the composition of fast dissolving films. The potential of poloxamer 407 and hydroxypropyl-β- cyclodextrin (HPBCD) to improve solubility of TC was investigated. Fast dissolving films containing hydroxypropyl methylcellulose (HPMC), xanthan gum, and xylitol were formulated. Use of poloxamer 407 and HPBCD resulted in significant improvement in the solubility of TC. Fast dissolving films containing TC-HPBCD complex and TC-Poloxamer 407 were formulated and were evaluated for the in vitro dissolution profile and in vitro microbiological assay. Films containing TC-Poloxamer 407 exhibited better in vitro dissolution profile and in vitro antimicrobial activity as compared to the films containing TC-HPBCD complex. Effect of incorporation of eugenol on the in vivo performance of TC-Poloxamer 407 containing films was evaluated in human volunteers. Eugenol containing films improved the acceptability of TC-Poloxamer 407 films with respect to taste masking and mouth freshening without compromising the in vivo dissolution time.     

Aryl Hydrocarbon Receptor Facilitates DNA Strand Breaks and 8-Oxo-2��-deoxyguanosine Formation by the Aldo-Keto Reductase Product Benzo[a]pyrene-7,8-dione

Polycyclic aromatic hydrocarbon (PAH) o-quinones produced by aldo-keto reductases are ligands for the aryl hydrocarbon receptor (AhR) (Burczynski, M. E., and Penning, T. M. (2000) Cancer Res. 60, 908–915). They induce oxidative DNA lesions (reactive oxygen species-mediated DNA strand breaks and 8-oxo-7,8-dihydro-2′-deoxyguanosine (8-oxo-dGuo) formation) in human lung cells. We tested whether the AhR enhances PAH o-quinone-mediated oxidative DNA damage by translocating these ligands to the nucleus. Using the single cell gel electrophoresis (comet) assay to detect DNA strand breaks in murine hepatoma Hepa1c1c7 cells and its AhR- and aryl hydrocarbon receptor nuclear translocator-deficient variants, benzo[a]pyrene-7,8-dione (B[a]P-7,8-dione) produced fewer DNA strand breaks in AhR-deficient cells compared with aryl hydrocarbon receptor nuclear translocator-deficient and wild type Hepa1c1c7 cells. Decreased DNA strand breaks were also observed in human bronchoalveolar H358 cells in which the AhR was silenced by siRNA. The antioxidant α-tocopherol and the iron chelator/antioxidant desferal decreased the formation of B[a]P-7,8-dione-mediated DNA strand breaks indicating that they were reactive oxygen species-dependent. By coupling the comet assay to 8-oxoguanine glycosylase (hOGG1), which excises 8-oxo-Gua, strand breaks dependent upon this lesion were measured. hOGG1 treatment produced more DNA single strand breaks in B[a]P-7,8-dione-treated Hepa cells and H358 cells than in its absence. The levels of hOGG1-dependent DNA strand breaks mediated by B[a]P-7,8-dione were lower in AhR-deficient Hepa and AhR knockdown H358 cells. The AhR antagonist α-naphthoflavone also attenuated B[a]P-7,8-dione-mediated DNA strand breaks. The decrease in 8-oxo-dGuo levels in AhR-deficient Hepa cells and AhR knockdown H358 cells was validated by immunoaffinity capture stable isotope dilution ([¹⁵N₅]8-oxo-dGuo) liquid chromatography-electrospray ionization/multiple reaction monitoring/mass spectrometry. We conclude that the AhR shuttles PAH o-quinone genotoxins to the nucleus and enhances oxidative DNA damage.Polycyclic aromatic hydrocarbons (PAHs)² are ubiquitous environmental pollutants that include over 200 compounds with two or more fused benzene rings. PAHs are formed as a result of incomplete combustion of fossil fuels (e.g. coal and oil) and are present in car and diesel exhaust and smoked or charbroiled food (1–3). They are also found in cigarette smoke condensate and tobacco products and are suspect agents in the causation of human lung cancer (4, 5). PAHs must be metabolically activated to reactive genotoxins to cause their mutagenic and carcinogenic effects.Two major metabolic activation pathways are possible starting from the proximate PAH carcinogen (−)B[a]P-7,8-trans-dihydrodiol (Fig. 1). The P4501A1/1B1 pathway converts (−)B[a]P-7,8-trans-dihydrodiol to yield (+)-anti-7,8-dihydroxy-9α,10β-epoxy-7,8,9,10-tetrahydroB[a]P (6–8). This diol epoxide forms stable N²-2′-deoxyguanosine (dGuo) adducts in vitro and in vivo (9, 10) and leads to mutation in H-ras (11) and may account for mutations in “hot spots” in p53 observed in lung cancer (12). The G to T transversions most often observed in these genes might arise because of the action of one or more trans-lesional by-pass DNA polymerases that read through stable diol-epoxide DNA adducts with low processivity and fidelity (13, 14).Open in a separate windowFIGURE 1.PAH activation by AKRs to cause oxidative DNA damage.As an alternative, human aldo-keto reductases (AKR1A1 and AKR1C1-AKR1C4) catalyze the NADP⁺-dependent oxidation of (±)B[a]P-7,8-trans-dihydrodiol to produce the electrophilic and redox-active B[a]P-7,8-dione (15, 16). In this pathway, AKRs convert B[a]P-7,8-trans-dihydrodiol to form a ketol that rearranges to a catechol. The catechol then undergoes two subsequent one-electron oxidations to yield the fully oxidized o-quinone. Once formed, B[a]P-7,8-dione amplifies reactive oxygen species (ROS) by entering futile redox cycles that deplete cellular reducing equivalents (e.g. NADPH) (17). PAH o-quinones can undergo 1,4- or 1,6-Michael addition with guanine and adenine bases to form stable N²-dGuo and N⁶-dAdo adducts in vitro (18–20). They can also react with the N7 position of guanine to yield depurinating adducts (21). It is possible that these covalent PAH o-quinone adducts could give to G to T transversion mutations.PAH o-quinones also cause oxidative DNA damage in vitro and in vivo (22–25). Nanomolar concentrations of PAH o-quinones under redox cycling conditions (NADPH and Cu(II)) lead to significant 8-oxo-dGuo formation in bulk DNA, and the responsible oxidant was found to be singlet oxygen (¹O₂) (24, 26). Under these conditions, PAH o-quinones produced 8-oxo-dGuo as the most dominant lesion among the three types of oxidative lesions measured (abasic sites, 8-oxo-dGuo, and oxidized pyrimidines) (26). In a yeast reporter gene assay, which scored loss-of-function mutations in p53, PAH o-quinones were found to be highly mutagenic but only under redox cycling conditions. The dominant mutation observed was a G to T transversion that was suppressed by ROS scavengers (27). Subsequent HPLC analysis coupled with electrochemical detection showed that there was a linear correlation between 8-oxo-dGuo formation in p53 and mutation frequency, indicating that 8-oxo-dGuo was the likely adduct responsible for the G to T transversions observed (28). These data suggest that oxidative DNA lesions caused by PAH o-quinones are more relevant in causing mutation than covalent PAH o-quinone-DNA adducts. In the latter case even if these adducts form, they do not appear to be mutagenic on p53.Recently, using either a hOGG1-coupled comet assay or an immunoaffinity capture-stable isotope dilution liquid chromatography/electrospray ionization/multiple reaction monitoring/mass spectrometry (LC/ESI/MRM/MS) assay, it was shown that both the AKR substrate (B[a]P-7,8-trans-dihydrodiol) and the AKR product (B[a]P-7,8-dione) caused significant DNA strand breaks and 8-oxo-dGuo formation in human lung adenocarcinoma A549 cells (25). Similar results were not observed with (+)-anti-7,8-dihydroxy-9α,10β-epoxy-7,8,9,10-tetrahydroB[a]P or the regioisomer B[a]P-4,5-trans- dihydrodiol in these AKR-expressing cells. Subsequent use of the fluorescent dye dichlorofluorescein diacetate revealed that B[a]P-7,8-dione generated ROS in the nuclear compartment of the cells, suggesting that the PAH o-quinone was transported into the nucleus to increase the ROS-mediated DNA strand breaks and 8-oxo-dGuo (25). In addition, earlier disposition studies detected significant amounts of [³H]B[a]P-7,8-dione in the cell pellets of primary rat hepatocytes within 0.5 h, which caused extensive strand scission of the genomic DNA (29), suggesting that B[a]P-7,8-dione reached the nucleus. However, how PAH o-quinones gain entry into the nucleus and induce oxidative DNA damage is currently unknown.PAH o-quinones are ligands for the aryl hydrocarbon receptor (AhR) (30). These quinones can promote translocation of AhR to nucleus to induce P4501A1 expression. Upon binding with PAH o-quinones, the AhR dissociates from heat shock protein 90 and is rapidly translocated into nucleus where it dimerizes with the aryl hydrocarbon receptor nuclear translocator (ARNT) (31, 32). The quinone-bound AhR·ARNT complex then binds to the xenobiotic response element (XRE) and robustly activates the expression of AhR-regulated genes (30). These data raise the possibility that oxidative DNA damage caused by PAH o-quinones occurs because of their transportation and concentration in the nucleus mediated by the AhR. However, this hypothesis has not been formally tested.We now show that B[a]P-7,8-dione produces AhR-dependent DNA strand breaks and 8-oxo-dGuo formation using murine Hepa1c1c7 cells but not in its AhR-deficient variant. Similar results were obtained in human bronchoalveolar carcinoma H358 cells, but these effects were attenuated when the AhR was knocked down with siRNA. DNA lesions were measured by using the comet assay, which was coupled with hOGG1. These results were also confirmed by LC-ESI/MRM/MS assay for 8-oxo-dGuo. Our finding shows that PAH o-quinones produced by AKRs can cause ROS-mediated genotoxicity via an AhR-dependent mechanism, and this might contribute to PAH-mediated carcinogenesis.     

Decreased Resting Functional Connectivity after Traumatic Brain Injury in the Rat

Traumatic brain injury (TBI) contributes to about 10% of acquired epilepsy. Even though the mechanisms of post-traumatic epileptogenesis are poorly known, a disruption of neuronal networks predisposing to altered neuronal synchrony remains a viable candidate mechanism. We tested a hypothesis that resting state BOLD-fMRI functional connectivity can reveal network abnormalities in brain regions that are connected to the lesioned cortex, and that these changes associate with functional impairment, particularly epileptogenesis. TBI was induced using lateral fluid-percussion injury in seven adult male Sprague-Dawley rats followed by functional imaging at 9.4T 4 months later. As controls we used six sham-operated animals that underwent all surgical operations but were not injured. Electroencephalogram (EEG)-functional magnetic resonance imaging (fMRI) was performed to measure resting functional connectivity. A week after functional imaging, rats were implanted with bipolar skull electrodes. After recovery, rats underwent pentyleneterazol (PTZ) seizure-susceptibility test under EEG. For image analysis, four pairs of regions of interests were analyzed in each hemisphere: ipsilateral and contralateral frontal and parietal cortex, hippocampus, and thalamus. High-pass and low-pass filters were applied to functional imaging data. Group statistics comparing injured and sham-operated rats and correlations over time between each region were calculated. In the end, rats were perfused for histology. None of the rats had epileptiform discharges during functional imaging. PTZ-test, however revealed increased seizure susceptibility in injured rats as compared to controls. Group statistics revealed decreased connectivity between the ipsilateral and contralateral parietal cortex and between the parietal cortex and hippocampus on the side of injury as compared to sham-operated animals. Injured animals also had abnormal negative connectivity between the ipsilateral and contralateral parietal cortex and other regions. Our data provide the first evidence on abnormal functional connectivity after experimental TBI assessed with resting state BOLD-fMRI.