Feeding and grazing impact by small marine heterotrophic dinoflagellates on heterotrophic bacteria

ABSTRACT. We investigated the feeding of the small heterotrophic dinoflagellates (HTDs) Oxyrrhis marina , Gyrodinium cf. guttula , Gyrodinium sp., Pfiesteria piscicida , and Protoperidinium bipes on marine heterotrophic bacteria. To investigate whether they are able to feed on bacteria, we observed the protoplasm of target heterotrophic dinoflagellate cells under an epifluorescence microscope and transmission electron microscope. In addition, we measured ingestion rates of the dominant heterotrophic dinoflagellate, Gyrodinium spp., on natural populations of marine bacteria (mostly heterotrophic bacteria) in Masan Bay, Korea in 2006–2007. Furthermore, we measured the ingestion rates of O. marina , G . cf. guttula , and P. piscicida on bacteria as a function of bacterial concentration under laboratory conditions. All HTDs tested were able to feed on a single bacterium. Oxyrrhis marina and Gyrodinium spp. intercepted and then ingested a single bacterial cell in feeding currents that were generated by the flagella of the predators. During the field experiments, the ingestion rates and grazing coefficients of Gyrodinium spp. on natural populations of bacteria were 14–61 bacteria/dinoflagellate/h and 0.003–0.972 day⁻¹, respectively. With increasing prey concentration, the ingestion rates of O. marina , G . cf. guttula , and P. piscicida on bacteria increased rapidly at prey concentrations of ca 0.7–2.2 × 10⁶ cells/ml, but increased only slowly or became saturated at higher prey concentrations. The maximum ingestion rate of O. marina on bacteria was much higher than those of G . cf. guttula and P. piscicida . Bacteria alone supported the growth of O. marina . The results of the present study suggest that some HTDs may sometimes have a considerable grazing impact on populations of marine bacteria, and that bacteria may be important prey.     

TIMP-1 inhibits apoptosis in breast carcinoma cells via a pathway involving pertussis toxin-sensitive G protein and c-Src

In addition to inhibiting matrix metalloproteinases, tissue inhibitor of metalloproteinase-1 (TIMP-1) is involved in the regulation of cell growth and survival. To determine its mechanism of action, we investigated effects of TIMP-1 on cell proliferation and survival and signaling pathways induced by TIMP-1 in the human breast carcinoma T-47D cell line. Treatment of T-47D cells with TIMP-1 strongly inhibited apoptosis induced by serum deprivation, but did not affect cell proliferation. TIMP-1 induced phosphorylation of Akt and extracellular signal-regulated protein kinases (ERKs), but pertussis toxin and specific inhibitors of Src family tyrosine kinases, protein tyrosine kinases, and phosphatidylinositol-3 kinase (PI3 kinase) blocked the ability of TIMP-1 to activate Akt and ERKs as well as the anti-apoptotic effect of TIMP-1. We found that TIMP-1 enhanced the kinase activities of c-Src and PI3 kinase and that this enhancement was inhibited by pertussis toxin. Inhibition of ERK activation, however, resulted in a slight decrease of the TIMP-1-induced anti-apoptotic effect. These findings demonstrate that the ability of TIMP-1 to inhibit apoptosis in T-47D cells is mediated by the sequential activation of pertussis toxin-sensitive G protein, c-Src, PI3 kinase, and Akt.     

Co-treatment with interferon-γ and 1-methyl tryptophan ameliorates cardiac fibrosis through cardiac myofibroblasts apoptosis

Molecular and Cellular Biochemistry - Electron transfer occurs through heme-Fe across the cytochrome c protein. The current models of long range electron transfer pathways in proteins include...     

A new strategy for assessing selenoprotein function: siRNA knockdown/knock-in targeting the 3'-UTR

Selenocysteine insertion into protein in mammalian cells requires RNA elements in the 3'-untranslated regions (3'-UTRs) of selenoprotein genes. The occurrence of these conserved sequences should make selenoproteins particularly amenable for knockdown/knock-in strategies to examine selenoprotein functions. Herein, we utilized the 3'-UTR of various selenoproteins to knock down their expression using siRNAs and then knock in expression using constructs containing mutations within the target region. Thioredoxin reductase 1 (TR1) knockdown in a mouse kidney cell line resulted in the cells growing about 10% more slowly, being more sensitive to UV radiation, and having increased apoptosis in response to UV than control cells. The knockdown cells transfected with a construct encoding the wild-type TR1 gene and having mutations in the sequences targeted by siRNA restored TR1 expression and catalytic activity, rendered the knockdown cells less sensitive to UV, and protected the cells against apoptosis. We also applied this technique to other selenoproteins, selenophosphate synthetase 2 and glutathione peroxidase 1, and found that mRNA and protein levels were restored following transfection of knockdown cells with the corresponding knock-in constructs. In addition to important new insights into the functions of key mammalian selenoproteins, the data suggest that the RNAi-based knock-in technology could distinguish phenotypes due to off-targeting and provide a new method for examining many of the subtleties of selenoprotein function not available using RNAi technology alone.     

The stability of L-ATC hydrolase participating in L-cysteine production

Summary In the production of L-cysteine from D,L-ATC stability of the relevant enzymes produced byPseudomonas sp. was tested, and strategies to improve the stability of L-ATC hydrolase were investigated in view of water activity and ionic strength. Among the three enzymes which participate in L-cysteine production, i.e., ATC racemase, L-ATC hydrolase, and S-carbamyl-L-cysteine hydrolase, L-ATC hydrolase is the least stable. Various mixtures of salts and sorbitol were added to adjust the water activities of the tested solutions. As water activity decreased from 0.93 to 0.80, the stability of L-ATC hydrolase was sharply enhanced. In the absence of sorbitol the stability of L-ATC hydrolase increased in proportion to ionic strength. Even though enzyme stability was not good at a low ionic strength, it was enhanced by lowering water activity with addition of sorbitol. The half life of L-ATC hydrolase in sorbitol-salt mixtures increased by tenfold to twentyfold compared to that of a control.     

The Effects of Dietary Selenium and Vitamin E and their Combination on the Fatty Acids of Erythrocytes,Bone Marrow and Spleen Tissue Lipids of Lambs

The object was to determine the influence of dietary vitamin E, selenium and their combination on the fatty acid con-tent of erythrocytes, bone marrow and spleen lipids of Akkaraman lambs. After supplementation for 15 days, the amount of all fatty acids was slightly higher (p < 0·05) in the vitamin E as compared to the control group, whereas the amount of longer fatty acids was significantly higher (p < 0·01, p < 0·001) in the selenium and combination groups. On the thirtieth day, the amount of all fatty acids was slightly high (p < 0·5) in all the supplemented groups in comparison with the control group. In the bone marrow lipids, the amount of longer fatty acids was decreased (p < 0·05, p < 0·01, p < 0·001) in the vitamin E and combination groups as compared to the control. Although the amount of some fatty acids was high (p < 0·05, p < 0·01) in the selenium group compared to the control, linoleic (18:2), linolenic (18:3) and the polyunsaturated fatty acids (PUFA) were lower (p < 0·05, p < 0·001). In the spleen lipids, the amount of longer fatty acids was slightly decreased (p < 0·05) in the vitamin E group as compared with the control; however the amount of longer fatty acids was significantly higher (p < 0·05, p < 0·01) in the selenium and combination groups in comparison to the control group. Thus dietary supplementation with selenium was more effective than dietary vitamin E supplementation in altering the fatty acid content of the erythrocyte, bone marrow and spleen lipids. © 1997 John Wiley & Sons, Ltd.     

Hyponatremia Predicts New-Onset Cardiovascular Events in Peritoneal Dialysis Patients

Background and Aim

Cardiovascular (CV) disease is the leading cause of morbidity and mortality in patients on peritoneal dialysis (PD). Hyponatremia was recently shown to be a modifiable factor that is strongly associated with increased mortality in PD patients. However, the clinical impact of hyponatremia on CV outcomes in these patients is unclear.

Methods

To determine whether a low serum sodium level predicts the development of CV disease, we carried out a prospective observational study of 441 incident patients who started PD between January 2000 and December 2005. Time-averaged serum sodium (TA-Na) levels were determined to investigate the ability of hyponatremia to predict newly developed CV events in these patients.

Results

During a mean follow-up of 43.2 months, 106 (24.0%) patients developed new CV events. The cumulative incidence of new-onset CV events after the initiation of PD was significantly higher in patients with TA-Na levels ≤ 138 mEq/L than in those with a TA-Na > 138 mEq/L. After adjustment for multiple potentially confounding covariates, an increase in TA-Na level was found to be associated with a significantly lower risk of CV events (subdistribution hazard ratio per 1 mEq/L increase, 0.90; 95% confidence interval, 0.83–0.96; p = 0.003). Patients with a TA-Na ≤ 138 mEq/L had a 2.31-fold higher risk of suffering a CV event.

Conclusions

These results provide evidence of a clear association between low serum sodium and new-onset CV events after dialysis initiation in PD patients. Whether the correction of hyponatremia for this indication provides additional protection for the development of CV disease in these patients remains to be addressed in interventional studies.     

FE65 as a link between VLDLR and APP to regulate their trafficking and processing

Background

Loss-of-function mutations in PTEN-induced kinase 1 (PINK1) have been linked to familial Parkinson??s disease, but the underlying pathogenic mechanism remains unclear. We previously reported that loss of PINK1 impairs mitochondrial respiratory activity in mouse brains.

Results

In this study, we investigate how loss of PINK1 impairs mitochondrial respiration using cultured primary fibroblasts and neurons. We found that intact mitochondria in PINK1?/? cells recapitulate the respiratory defect in isolated mitochondria from PINK1?/? mouse brains, suggesting that these PINK1?/? cells are a valid experimental system to study the underlying mechanisms. Enzymatic activities of the electron transport system complexes are normal in PINK1?/? cells, but mitochondrial transmembrane potential is reduced. Interestingly, the opening of the mitochondrial permeability transition pore (mPTP) is increased in PINK1?/? cells, and this genotypic difference between PINK1?/? and control cells is eliminated by agonists or inhibitors of the mPTP. Furthermore, inhibition of mPTP opening rescues the defects in transmembrane potential and respiration in PINK1?/? cells. Consistent with our earlier findings in mouse brains, mitochondrial morphology is similar between PINK1?/? and wild-type cells, indicating that the observed mitochondrial functional defects are not due to morphological changes. Following FCCP treatment, calcium increases in the cytosol are higher in PINK1?/? compared to wild-type cells, suggesting that intra-mitochondrial calcium concentration is higher in the absence of PINK1.

Conclusions

Our findings show that loss of PINK1 causes selective increases in mPTP opening and mitochondrial calcium, and that the excessive mPTP opening may underlie the mitochondrial functional defects observed in PINK1?/? cells.