Influence of Different Arsenic Species on the Bioavailability and Bioaccumulation of Arsenic by Sargassum horneri C. Agardh: Effects under Different Phosphate Conditions.

The growth response and incorporation of As into the Sargassum horneri was evaluated for up to 7 days using either arsenate (As(V)), arsenite (As(III)) or methylarsonate (MMAA(V) and DMAA(V)) at 0, 0.25, 0.5, 1, 2, and 4 µM with various phosphate (P) levels (0, 2.5, 5 and 10 µM). Except As(III), algal chlorophyll fluorescence was almost similar and insignificant, regardless of whether different concentrations of P or As(V) or MMAA(V) or DMAA(V) were provided (p > 0.05). As(III) at higher concentrations negatively affected algal growth rate, though concentrations of all As species had significant effects on growth rate (p < 0.01). Growth studies indicated that toxicity and sensitivity of As species to the algae followed the trend: As(III) > As(V) > MMAA(V) ~ DMAA(V). As bioaccumulation was varied significantly depending on the increasing concentrations of all As species and increasing P levels considerably affected As(V) uptake but no other As species uptake (p < 0.01). The algae accumulated As(V) and As(III) more efficiently than MMAA(V) and DMAA(V). At equal concentrations of As (4 µM) and P (0 µM), the alga was able to accumulate 638.2 ± 71.3, 404.1 ± 70.6, 176.7 ± 19.6, and 205.6 ± 33.2 nM g-1 dry weight of As from As(V), As(III), MMAA(V), and DMAA(V), respectively. The influence of low P levels with increased As(V) concentrations more steeply increased As uptake, but P on other As species did not display similar trends. The algae also showed passive modes for As adsorption of all As species. The maximum adsorption of As (63.7 ± 6.1 nM g-1 dry weight) was found due to 4 µM As(V) exposure, which was 2.5, 7.3, and 6.9 times higher than the adsorption amounts for the same concentration of As(III), MMAA(V), and DMAA(V) exposure, respectively. The bioavailability and accumulation behaviors of As were significantly influenced by P and As species, and this information is essential for As research on marine ecosystems.

Role of Fe plaque on arsenic biotransformation by marine macroalgae.

Macroalgae can cycle arsenic (As) in the environment. In this study, the role of iron (Fe) plaque manipulation at active sites in the As biotransformation mechanism was investigated. The strain of marine macroalgal species, Pyrophia yezoensis, was inoculated in association with arsenate (As(V)) (1.0 µmol L-1) and phosphate (10 µmol L-1) in the medium for 7 days under laboratory-controlled conditions. The Fe plaque was removed by washing the Ti(III)-citrate-EDTA solution before inoculation. The limitation of Fe plaque did not significantly (p > 0.05) affect the chlorophyll fluorescence due to cellular regeneration, which was initiated immediately after washing. However, the speciation and uptake rate of As(V) increased significantly and reduced the inhibitory effect of P on the intracellular uptake of As(V) by P. yezoensis. In the culture medium without Fe plaque, approximately 66% of As(V) was removed with Vmax = 0.32 and Km = 1.92. In the absence of Fe plaque, methylated As species, such as dimethylarsinate (DMAA(V)), was recorded 0.28 µmol L-1, while in the presence of Fe plaque, the value was 0.16 µmol L-1. Inorganic trivalent As (As(III)) was absent in the washed samples; however, 0.53 µmol L-1 concentration of As(III) was still found in the presence of Fe plaque on day 7 of incubation. The results indicated that the absence of Fe plaque promoted higher intracellular uptake of As species, reduced the inhibitory effect of P, mitigated the co-precipitation bond between AsFe plaque and enhanced the detoxification process by DMAA excretion from the cell.

Comparative biotransformation and detoxification potential of arsenic by three macroalgae species in seawater: Evidence from laboratory culture studies.

Algae accumulate and metabolize arsenic (As) and facilitate cycling and speciation of As in seawater. The laboratory-controlled macroalgal cultures were exposed to different molar ratios of As(V) and phosphate (P) in seawater for evaluating the uptake and metabolism of As, as a function of As(V) detoxification through biotransformation. Chlorophyll fluorescence of algal species was not significantly affected by the culture conditions (p > 0.05). Addition of 10 µM P positively reduce As stress, but different As(V)/P ratios significantly affect the growth rate (p < 0.05). Algae readily accumulated As(V) after the inoculation, transformed intracellularly, and released gradually into the medium along the incubation period, depending on As(V)/P molar ratios. Reduction and methylation were the leading processes of As(V) metabolism by Pyropia yezoensis, whereas Sargassum patens showed only the reduction. Sargassum horneri reduced As(V) under low level (0.1 µM), but both reduction and methylation were observed under a high level (1 µM). At the end of incubation, 0.17, 0.15, 0.1 µM of reduced metabolite (As[III]) were recorded from 1 µM of As(V)/P containing cultures of Sargassum horneri, Sargassum patens, and Pyropia yezoensis, respectively. On the other hand, 0.024 and 0.28 µM of methylated metabolite (DMAA[V]) were detected under the same culture conditions from Sargassum horneri and Pyropia yezoensis, respectively. The results also indicated that P in medium inhibits the intracellular uptake of As(V) and subsequent extrusion of biotransformed metabolites into the medium. These findings can help to understand the metabolic diversity of macroalgae species on As biogeochemistry in the marine environment.

Streptobactin, a tricatechol-type siderophore from marine-derived Streptomyces sp. YM5-799.

A new catechol-type siderophore, streptobactin (1), was isolated from a culture broth of the marine-derived actinomycete Streptomyces sp. YM5-799. The structure of streptobactin was determined by NMR and MS analyses and ESIMS/MS experiments to be a cyclic trimer of benarthin. A dibenarthin (2), a tribenarthin (3), and benarthin (4) were also obtained. The production of 1 was regulated by an iron concentration in the culture. The iron-chelating activity of the compounds was evaluated by the chrome azurol sulfonate assay.

Expression and localization of aquaporins, members of the water channel family, during development of the rat submandibular gland.

The expression and localization of aquaporins (AQP1-AQP5), members of the water channel family, in the developing rat submandibular gland were analysed using RT-PCR, Northern blotting and immunohistochemistry to explore their relation to the development of this salivary gland. RT-PCR analysis revealed unique expression patterns of each AQP. AQP1 was expressed constitutively during prenatal development, whereas the expression of AQP5 became more intense in the course of development from embryonic day 16.5 (E16) to E20. These expression patterns concurred with the results of Northern blot analysis. AQP3 and AQP4 mRNAs in the prenatal development were not detected in Northern blots, although they were detected by RT-PCR. During postnatal development, AQP5 and AQP1 mRNAs were expressed continuously, but no message for AQP3 or AQP4 was detected. AQP2 mRNA was not detected during either prenatal or postnatal development in this tissue. Immunohistochemical studies revealed that AQP5 was first localized at the apical membrane of proacinar cells at E18, and then became clearly distributed at the apical membrane of acinar cells in accordance with the differentiation and establishment of the mature acini. In addition, some vasculature also showed immunoreactivity for AQP5. AQP1 was immunolocalized in the blood vessels, including capillaries, of the gland throughout development. These observations suggest the existence of transcriptional regulation of rat AQP5, which is one of the most probable regulators of saliva production and secretion, during the establishment of the functional submandibular salivary gland.

Sarpogrelate treatment reduces restenosis after coronary stenting.

BACKGROUND: Sarpogrelate, a serotonin blocker, has been reported to inhibit the serotonin-induced proliferation of rat aortic smooth muscle cells. The aim of this study was to investigate whether sarpogrelate reduces restenosis after coronary stenting as a result of prevention of intimal hyperplasia. METHODS: We examined 79 patients with stable angina undergoing elective coronary stenting on de novo lesions of native coronary arteries in a prospective, randomized trial. All enrolled patients received aspirin and ticlopidine, and one third of the patients were assigned to receive oral sarpogrelate. RESULTS: Treatment with sarpogrelate in addition to aspirin and ticlopidine caused no major adverse cardiovascular events or hemorrhagic adverse effects during the 6-month follow-up period. The restenosis rate in the group of patients receiving sarpogrelate was 4.3%, which was significantly lower than the 28.6% rate found in the group of patients not receiving sarpogrelate. CONCLUSIONS: Sarpogrelate treatment reduces restenosis after coronary stenting, which suggests that serotonin released from activated platelets may play an important role in stent restenosis.

Divergent expression and localization of aquaporin 5, an exocrine-type water channel, in the submandibular gland of Sprague-Dawley rats.

By Western blot analysis, the expression level of aquaporin (AQP) 5 in the submandibular gland (SMG) was found to be different among individual rats of the Sprague-Dawley (SD) strain. Such differences were observed for AQP5 but not for AQP1 and consequently the SD strain was divided into two groups, one expressing a high level of AQP5 and the other a low one. The difference in average intensity of expression between the two groups was more than twofold. Immunohistochemical analysis of the SMG demonstrated that the AQP5 protein was localized in the basal and apical/lateral plasma membrane of acinar cells in rats expressing the high level of AQP5. In the rat expressing the low level, however, this channel protein was localized strongly in the apical/lateral plasma membrane, but only very weakly in the basal membrane of the acinar cells. Such a diverse localization of AQP5 was confirmed by Western blotting as well. Breeding between brother and sister was repeated for two times within high expressers and low expressers to obtain the third generation progenies (F2); the AQP5 level of the SMG in the third generation (F2 rats) from high expressers was significantly higher than the F2 from low expressers. Our present study suggests the existence of genetic variation in the expression of a water channel protein, AQP5, in rats.