Laboratory culture experiments to study the effect of lignite humic acid fractions on iron solubility and iron uptake rates in phytoplankton

The major fractions of dissolved iron in seawater exist as a complex with organic ligands. A high bioavailability of iron bound to humic acid (HA) compared to the other model ligands, such as desferrioxamine B or ferrichrome, has been reported, which implies the importance of HA to control the geochemical behavior and the transfer of Fe to marine phytoplankton, particularly in estuarine and coastal waters. In the current work, the effect of different HA fractions (>100, 100–30, 30–10, 10–5, and 5–3 kDa), which were extracted from lignite, on the comparative solubility of iron in seawater and the corresponding influence on iron uptake and growth rate of the phytoplankton Prymnesium parvum (Haptophyta) was studied using laboratory cultures. The lower-molecular-weight (MW) HA fractions, such as 30–10, 10–5, and 5–3 kDa, remained soluble in the simulated seawater medium for a longer time span compared to the higher MW fractions. The lower MW fractions facilitated higher iron solubility and assisted in achieving a better phytoplankton growth rate. However, a reciprocal impact on phytoplankton growth rates was observed when the HA concentration increased to a higher range (0.18 to 18 mg-C L−1). The highest intracellular Fe uptake in phytoplankton occurred with 30–10 kDa HA in seawater, and the extracellular dissolved Fe concentrations were higher for smaller-sized HA fractions. In summary, our study showed that the controlled addition of lower MW fractions of HA (up to 30–10 kDa) in estuarine waters could ensure the accelerated uptake of Fe in phytoplankton as well as a better growth rate. © 2016 Springer Science+Business Media DordrechtEmbargo Period 12 month

Membrane protease prostasin promotes insulin secretion by regulating the epidermal growth factor receptor pathway

Abstract Prostasin (PRSS8) is a serine protease that metabolizes and moderates the effect of specific substrates. Epidermal growth factor receptor (EGFR), which modulates insulin secretion and pancreatic β-cell proliferation, is regulated via proteolytic shedding by PRSS8. We first detected PRSS8 expression in β-cells of pancreatic islets of mice. To better understand the molecular processes involved in PRSS8-associated insulin secretion, pancreatic β-cell-specific PRSS8 knockout (βKO) and PRSS8-overexpressing (βTG) male mice were generated. We found that glucose intolerance and reduction in glucose-stimulated insulin secretion developed in βKO mice compared with the control subjects. A higher response to glucose was noted in islets retrieved from βTG mice. Erlotinib, a specific blocker of EGFR, blocks EGF- and glucose-stimulated secretion of insulin among MIN6 cells, and glucose improves EGF release from β-cells. After silencing PRSS8 in MIN6 cells, glucose-stimulated insulin secretion decreased, and EGFR signaling was impaired. Conversely, overexpression of PRSS8 in MIN6 cells induced higher concentrations of both basal and glucose-stimulated insulin secretion and increased phospho-EGFR concentrations. Furthermore, short-term exposure to glucose improved the concentration of endogenous PRSS8 in MIN6 cells through inhibition of intracellular degradation. These findings suggest that PRSS8 is involved in glucose-dependent physiological regulation of insulin secretion via the EGF–EGFR signaling pathway in pancreatic β-cells

Absorption of radionuclides from the Fukushima nuclear accident by a novel algal strain.

Large quantities of radionuclides have leaked from the Fukushima Daiichi Nuclear Power Plant into the surrounding environment. Effective prevention of health hazards resulting from radiation exposure will require the development of efficient and economical methods for decontaminating radioactive wastewater and aquatic ecosystems. Here we describe the accumulation of water-soluble radionuclides released by nuclear reactors by a novel strain of alga. The newly discovered green microalgae, Parachlorella sp. binos (Binos) has a thick alginate-containing extracellular matrix and abundant chloroplasts. When this strain was cultured with radioiodine, a light-dependent uptake of radioiodine was observed. In dark conditions, radioiodine uptake was induced by addition of hydrogen superoxide. High-resolution secondary ion mass spectrometry (SIMS) showed a localization of accumulated iodine in the cytosol. This alga also exhibited highly efficient incorporation of the radioactive isotopes strontium and cesium in a light-independent manner. SIMS analysis showed that strontium was distributed in the extracellular matrix of Binos. Finally we also showed the ability of this strain to accumulate radioactive nuclides from water and soil samples collected from a heavily contaminated area in Fukushima. Our results demonstrate that Binos could be applied to the decontamination of iodine, strontium and cesium radioisotopes, which are most commonly encountered after nuclear reactor accidents

Identification of a novel strain of green algae, <i>Parachlorella</i> sp binos (Binos). a

<p>, Microscopic image of <i>P.</i> sp <i>binos</i> (Binos) (x2000). <b>b</b>, India ink staining of <i>P.</i> sp <i>binos</i> (Binos) (x400). India ink was diluted with water to make a 10% solution. <b>c, d</b>, Phylogenetic analysis of members of the phylum Chlorophyta based on (<b>c</b>) 18S rRNA gene and (<b>d</b>) actin amino acid sequences. <b>e, f</b>, Transmission electron micrographs of (<b>e</b>) <i>P.</i> sp <i>binos</i> (Binos) and (<b>f</b>) <i>Chlorella</i> sp. <b>g</b>, Infrared spectra of the extracellular matrix of <i>P.</i> sp <i>binos</i> (red line) and purified sodium alginate (standard; black line) analyzed by Fourier transform infrared spectroscopy from 400 to 4000 cm⁻¹.</p

Binding of radionuclides in contaminated water and soil samples from Fukushima. a

<p>, Soil and water soil samples were collected from Namie-machi, approximately 20 km from the Fukushima Daiichi Nuclear Plant. The upper photograph shows a signboard prohibiting entry to the 20 km exclusion zone. Gross radioactivity of ground samples measured using a Geiger-Müller counter was approximately 60 kcpm (lower photograph). Water samples (<b>b</b>) and soil-water extracts (<b>c</b>) contaminated by radioactive fallout were incubated with algal cells under illumination at 2000 lux for 8 h. Gross β radioactivity (closed bars) and γ radioactivity (open bars) from ¹³⁷Cs were measured by liquid scintillation and γ counters, respectively.</p

Binding of radioisotopes of cesium with <i>P.</i> sp <i>binos.</i> a

<p>, 10, 30, and 100 mg/ml of wet algal cells were incubated with 1.92 kBq of ¹³⁷CsCl at room temperature for 10 min. Radioactivity accumulated in algal cells were measured, and data are shown as % of total radioactivity (mean ± SD). *, <i>P</i><0.05, **, <i>P</i><0.01 (n = 4). <b>b</b>, After 10 min incubation, the radioactivities of pellets and supernatant were measured and the bound/free ratios were calculated (n = 4). <b>c</b>, Ten mg/ml of wet algal cells were incubated with nonradioactive CsCl (solid circles) or NaCl (open circles) and 1.92 kBq of ¹³⁷CsCl at room temperature for 10 min. Radioactivity accumulated in algal cells were measured, and data are shown as % of control uptake without nonradioactive CsCl. Non-linear curve fitting to the model of two binding sites with high and low affinities was performed using the CsCl and NaCl competition data (n = 4).</p

Radioiodine uptake by <i>P.</i> sp <i>binos</i> (Binos). a

<p>, Ten mg/ml of <i>P.</i> sp <i>binos</i> was incubated with 1.48 kBq of Na¹²⁵I at room temperature under illumination at 2000 lux (open circles) or in the dark (solid circles) (n = 4). Radioactivity accumulated in algal cells were measured, and data are shown as maximal uptake. <b>b</b>, Algal cells incubated with Na¹²⁵I at room temperature under illumination for 24 h. Radioactivity accumulated in algal cells were measured, and data are shown as % of total radioactivity. *, <i>P</i><0.05, **, <i>P</i><0.01 (n = 4). <b>c</b>, After 24 h incubation, pellet and supernatant radioactivities were measured and the bound/free ratios of ¹²⁵I were calculated (n = 4). <b>d</b>, Ten mg/ml of wet algal cells were incubated with nonradioactive NaI and 1.48 kBq of Na¹²⁵I (n = 4). Radioactivity accumulated in algal cells were measured, and data are shown as % of control uptake without nonradioactive NaI <b>e</b>, Algal cells were incubated with or without 10 µM of hydrogen peroxide (H₂O₂) for 24 h (n = 3). <b>f, g</b>, After incubation of algal cells with 1 µM of sodium iodide for 24 h, elemental distribution of ¹²C¹⁴N (f) and ¹²⁷I (g) on the section of algal cells were visualized by NanoSIMS. <b>h</b>, Marged image of <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0044200#pone-0044200-g002" target="_blank">Figure 2f and 2g</a>.</p

Distinct cell clusters touching islet cells induce islet cell replication in association with over-expression of Regenerating Gene (REG) protein in fulminant type 1 diabetes.

BACKGROUND: Pancreatic islet endocrine cell-supporting architectures, including islet encapsulating basement membranes (BMs), extracellular matrix (ECM), and possible cell clusters, are unclear. PROCEDURES: The architectures around islet cell clusters, including BMs, ECM, and pancreatic acinar-like cell clusters, were studied in the non-diabetic state and in the inflamed milieu of fulminant type 1 diabetes in humans. RESULT: Immunohistochemical and electron microscopy analyses demonstrated that human islet cell clusters and acinar-like cell clusters adhere directly to each other with desmosomal structures and coated-pit-like structures between the two cell clusters. The two cell-clusters are encapsulated by a continuous capsule composed of common BMs/ECM. The acinar-like cell clusters have vesicles containing regenerating (REG) Iα protein. The vesicles containing REG Iα protein are directly secreted to islet cells. In the inflamed milieu of fulminant type 1 diabetes, the acinar-like cell clusters over-expressed REG Iα protein. Islet endocrine cells, including beta-cells and non-beta cells, which were packed with the acinar-like cell clusters, show self-replication with a markedly increased number of Ki67-positive cells. CONCLUSION: The acinar-like cell clusters touching islet endocrine cells are distinct, because the cell clusters are packed with pancreatic islet clusters and surrounded by common BMs/ECM. Furthermore, the acinar-like cell clusters express REG Iα protein and secrete directly to neighboring islet endocrine cells in the non-diabetic state, and the cell clusters over-express REG Iα in the inflamed milieu of fulminant type 1 diabetes with marked self-replication of islet cells