Oxygen Metabolic Responses of Three Species of Large Benthic Foraminifers with Algal Symbionts to Temperature Stress

<div><p>Water temperature affects the physiology of large benthic foraminifers (LBFs) with algal symbionts dwelling in coral reef environments. However, the detailed physiological responses of LBF holobionts to temperature ranges occurring in their habitats are not known. We report net oxygen (O₂) production and respiration rates of three LBF holobionts (<i>Baculogypsina sphaerulata</i> and <i>Calcarina gaudichaudii</i> hosting diatom symbionts, and <i>Amphisorus kudakajimensis</i> hosting dinoflagellate symbionts) measured in the laboratory at water temperatures ranging from 5°C to 45°C in 2.5°C or 5°C intervals and with light saturation levels of ∼500 µmol m⁻² s⁻¹. In addition, the recovery of net O₂ production and respiration rates after exposure to temperature stress was assessed. The net O₂ production and respiration rates of the three LBF holobionts peaked at ∼30°C, indicating their optimal temperature for a short exposure period. At extreme high temperatures (≥40°C), the net O₂ production rates of all three LBF holobionts declined to less than zero and the respiration rates slightly decreased, indicating that photosynthesis of algal symbionts was inactivated. At extreme low temperatures (≤10°C for two calcarinid species and ≤5°C for <i>A. kudakajimensis</i>), the net O₂ production and respiration rates were near zero, indicating a weakening of holobiont activity. After exposure to extreme high or low temperature, the net O₂ production rates did not recover until the following day, whereas the respiration rates recovered rapidly, suggesting that a longer time (days) is required for recovery from damage to the photosystem by temperature stress compared to the respiration system. These results indicate that the oxygen metabolism of LBF holobionts can generally cope well with conditions that fluctuate diurnally and seasonally in their habitats. However, temporal heat and cold stresses with high light levels may induce severe damage to algal symbionts and also damage to host foraminifers.</p></div

Summary of linear models of the metabolic recovery of large benthic foraminifers with algal symbionts at different temperatures (<i>T</i>).

<p>SS: sum of square, df: degree of freedom, <i>F</i>: F value, <i>p</i>: p value.</p><p>Significant p values are indicated in bold.</p

Summary of the analysis of temperature effects on net photosynthesis and respiration for each of three species of large benthic foraminifers with algal symbionts using a linear model (LM) and a generalized additive model (GAM) with only temperature as an explanatory variable, and the results of a likelihood ratio test (LRT) for the two models.

<p>Resid df: residual degree of freedom, Resid dev: residual deviance, edf: estimated degree of freedom, Ref. df: reference degree of freedom, <i>F</i>: F value, <i>p</i>: p value.</p><p>Significant p values are indicated in bold.</p

Metabolic recovery of large benthic foraminifers with algal symbionts after exposure to temperature stress.

<p>Net O₂ production and respiration rates at 25°C on the day following exposure to temperatures stress (≤15°C or ≥35°C) (<i>P</i>_25:after, <i>R</i>_25:after) were compared with those initially measured at 25°C at the start of each trial (<i>P</i>_25:initial, <i>R</i>_25:initial). Filled circles indicate observed data. The solid line is the significant regression curve estimated by the linear model with temperature as an explanatory variable. Dashed lines are the 95% confidence intervals of the curve.</p

Net photosynthesis and respiration rates of large benthic foraminifers with algal symbionts at different water temperatures.

<p>Filled circles indicate observed data. The solid line is the curve fitted by a generalized additive model (GAM) with temperature as an explanatory variable. Dashed lines are 95% confidence intervals.</p

Summary of the peak point of net O₂ production and respiration rates with 95% confidence interval (CI) and their temperatures inferred from the generalized additive model.

<p>Summary of the peak point of net O₂ production and respiration rates with 95% confidence interval (CI) and their temperatures inferred from the generalized additive model.</p

Cell cycle progression of HT-29 cells cultured in the presence of alk(en)yl trisulfides having various structures

HT-29 cells were cultured in the presence or absence of alkyl trisulfides (dimethyl trisulfide, diethyl trisulfide, DPTS, dibutyl trisulfide and dipentyl trisulfide), alkenyl trisulfides (DATS, dibutenyl trisulfide and dipentenyl trisulfide) or mixed ank(en)yl trisulfide (allyl methyl trisulfide) at a concentration of 10 μM for 12 h. Then, the cell cycle distribution in G/M phase was analyzed by using a flow cytometer, as described in Materials and Methods (panel ). Values are the mean ± SE of three independent experiments. ** ( <p><b>Copyright information:</b></p><p>Taken from "Alkenyl group is responsible for the disruption of microtubule network formation in human colon cancer cell line HT-29 cells"</p><p></p><p>Carcinogenesis 2008;29(7):1400-1406.</p><p>Published online 29 May 2008</p><p>PMCID:PMC2500214.</p><p></p

Induction of mitotic arrest by DATS through the inhibition of mitotic spindle formation

Detection of Ser10-phosphorylated histone H3, a sensitive marker for cells at the M phase, was detected in HT-29 cells cultured with DATS (10 μM) for 12 h by using a flow cytometer (panel ). Spindle formation of HT-29 cells cultured with vehicle or DATS (10 μM) was assessed by the immunofluorescence method using anti-β-tubulin antibody, as described in Materials and Methods (green; panel ). The nucleus was counterstained with propidium iodide (magenta). Scale bar 20 μm.<p><b>Copyright information:</b></p><p>Taken from "Alkenyl group is responsible for the disruption of microtubule network formation in human colon cancer cell line HT-29 cells"</p><p></p><p>Carcinogenesis 2008;29(7):1400-1406.</p><p>Published online 29 May 2008</p><p>PMCID:PMC2500214.</p><p></p

BSO enhanced and sustained the DATS-induced cell cycle arrest but had little influence on DPTS-treated cells

HT-29 cells were pretreated with 500 μM BSO for 24 h and then the cells were treated with 10 μM DATS ( and ) or DPTS ( and ) for the times as indicated. The cell cycle distribution of the cells was analyzed by using a flow cytometer.<p><b>Copyright information:</b></p><p>Taken from "Alkenyl group is responsible for the disruption of microtubule network formation in human colon cancer cell line HT-29 cells"</p><p></p><p>Carcinogenesis 2008;29(7):1400-1406.</p><p>Published online 29 May 2008</p><p>PMCID:PMC2500214.</p><p></p

Effect of LKB1 knockdown on AMPK phosphorylation and CE-stimulated glucose uptake.

<p>Differentiated C2C12 cells (A) were transfected with LKB1 siRNA for 24 h. Two different fields of observation are shown. B: Quantitative real-time PCR was used to determine the mRNA expression levels of LKB1 by the C2C12 cells that had been treated with LKB1 siRNA. The data represent the mean ± S.E. of 3 different experiments. **: <i>p</i><0.01 (Student’s t test). C: Effect of siRNA duplexes designed to reduce LKB1 expression on the LKB1 protein levels and on the phosphorylation of LKB1 in C2C12 myotube cells examined by Western blotting. These silencing effects were observed even in the culture at 24 h after the transfection. The data represent the mean ± S.E. of 4 different experiments. *: <i>p</i><0.05 <i>vs</i> control; †: <i>p</i><0.05 <i>vs</i> CE; ns: indicates no significant difference (Bonferroni test). D: CE (30 µg/ml) was added or not to LKB1 siRNA-transfected cells or negative control siRNA-transfected cells, which were then incubated for 30 min and thereafter harvested and analyzed by Western blotting using anti-phospho-AMPK, and anti-AMPK antibodies. The data represent the mean ± S.E. of 3 different experiments. *: <i>p</i><0.05 <i>vs</i> control; †: <i>p</i><0.05 <i>vs</i> CE; ns: indicates no significant difference (Bonferroni test). E: Differentiated C2C12 cells were transfected or not with LKB1 siRNA or negative control siRNA for 24 h and then treated or not with CE (30 µg/ml) for 30 min. The glucose uptake was measured by the method as described in the Materials and Methods section. The data represent the mean ± S.E. of 3 different experiments. *: <i>p</i><0.05 <i>vs</i> control; †: <i>p</i><0.05 <i>vs</i> CE; ns: indicates no significant difference (Bonferroni test).</p