Ammonium interference reduced copper uptake by formaldehyde-crosslinked Sargassum sp. seaweed

10.7287/peerj.preprints.1228 ◽

2017 ◽

Author(s):

Wenfa Ng

Keyword(s):

Heavy Metals ◽

Metal Removal ◽

Sorption Kinetics ◽

Threshold Concentration ◽

Dependent Manner ◽

Dilute Solutions ◽

Brown Macroalgae ◽

Concentration Dependent Manner ◽

Nitrogenous Compounds ◽

Copper Sorption

Sargassum sp., a marine brown macroalgae, is an efficient sorbent for various heavy metals at high concentrations. However, the efficiency at which seaweed removes heavy metals from dilute solutions and the effect of ammonium on metal removal is not well understood; an issue of importance given the ubiquity of nitrogenous compounds in the environment arising from various surface runoffs. Herein, the effect of ammonium on copper removal (at trace to low concentration) by formaldehyde crosslinked Sargassum sp. (treated SW) was studied. Due to high copper background, equilibrium sorption experiments was inconclusive concerning treated SW’s ability in removing copper (<1000 ppb), but rapid copper sorption observed in kinetic experiments suggested potential feasibility of the process. Within initial copper concentration of 4 to 20 ppm and pH 2 to 5, experiments revealed that, above a threshold concentration of [NH4+-N] of 50 ppm, ammonium impede copper update on treated SW in a concentration dependent manner. Specifically, sorption kinetics slowed, and uptake capacity decreased with increase in [NH4+-N] from 0 to 2500 ppm. Collectively, beyond demonstrating that treated SW could remove copper from dilute solutions, revelations that ammonium reduced copper sorption highlighted the importance of accounting for the effect in data interpretation and modelling.

Download Full-text

Ammonium interference reduced copper uptake by formaldehyde-crosslinked Sargassum sp. seaweed

10.7287/peerj.preprints.1228v1 ◽

2015 ◽

Author(s):

Wenfa Ng

Keyword(s):

Heavy Metals ◽

Metal Removal ◽

Threshold Concentration ◽

Dependent Manner ◽

Copper Uptake ◽

Dilute Solutions ◽

Brown Macroalgae ◽

Concentration Dependent Manner ◽

Nitrogenous Compounds ◽

Copper Sorption

Sargassum sp., a marine brown macroalgae, is an efficient sorbent for various heavy metals at high concentrations. Nevertheless, the efficiency at which seaweed removes heavy metals from dilute solutions and the effect of ammonium on metal removal is not well understood; an issue of importance given the ubiquity of nitrogenous compounds in the environment arising from various surface run-offs. Herein, the effect of ammonium on copper removal (at trace to low concentration) by formaldehyde crosslinked Sargassum sp. (treated SW) was studied. Due to high copper background, equilibrium sorption experiments was inconclusive concerning treated SW’s ability in removing copper (<1000 ppb), but rapid copper sorption observed in kinetic experiments suggested potential feasibility of the process. Within initial copper concentration of 4 to 20 ppm and pH 2 to 5, experiments revealed that, above a threshold concentration of [NH4+-N] of 50 ppm, ammonium impeded copper uptake on treated SW in a concentration-dependent manner. Specifically, sorption kinetics slowed and uptake capacity decreased with increase in [NH4+-N] from 0 to 2500 ppm. Collectively, beyond demonstrating that treated SW could remove copper from dilute solutions, revelations that ammonium reduced copper sorption highlighted the importance of accounting for the effect in data interpretation and modelling.

Download Full-text

Regulation of KCa-channel activity by cyclic ADP-ribose and ADP-ribose in coronary arterial smooth muscle

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.1998.275.3.h1002 ◽

1998 ◽

Vol 275 (3) ◽

pp. H1002-H1010 ◽

Cited By ~ 12

Author(s):

Pin-Lan Li ◽

Ai-Ping Zou ◽

William B. Campbell

Keyword(s):

Smooth Muscle ◽

Time Course ◽

Control Level ◽

Internal Surface ◽

Threshold Concentration ◽

Dependent Manner ◽

Channel Activity ◽

Arterial Smooth Muscle ◽

Concentration Dependent Manner ◽

Cyclic Adp Ribose

The enzymatic pathway responsible for the production and metabolism of cyclic ADP-ribose (cADP-R) in small bovine coronary arteries was characterized, and the role of cADP-R and ADP-ribose (ADP-R) in the regulation of the activity of large-conductance Ca2+-activated K+(KCa) channels was determined in vascular smooth muscle cells (SMC) prepared from these vessels. We found that cADP-R and ADP-R were produced when the coronary arterial homogenates were incubated with 1 mM β-NAD. The time course of the enzyme reactions showed that the maximal conversion rate (1.37 ± 0.03 nmol ⋅ min−1 ⋅ mg protein−1) of β-NAD to cADP-R was reached after 3 min of incubation. As incubation time was prolonged, the production of ADP-R was increased to a maximal rate of 3.66 ± 0.03 nmol ⋅ min−1 ⋅ mg protein−1, whereas cADP-R production decreased. Incubation of the homogenate with cADP-R produced a time-dependent increase in the synthesis of ADP-R. Comparison of coronary arterial microsomes with cytosols shows that the production of both cADP-R and ADP-R in microsomes was significantly greater. In excised inside-out membrane patches of single coronary SMC, the KCa channels were activated when β-NAD, the precursor for both cADP-R and ADP-R, was applied to the internal surface. This effect of β-NAD may be associated with the production of ADP-R, because the KCa-channel activity was increased by ADP-R in a concentration-dependent manner. The open-state probability of the KCa channels increased from a control level of 0.08 ± 0.03 to 0.17 ± 0.05 even at the lowest ADP-R concentration (0.1 μM) studied. However, cADP-R reduced the KCa-channel activity, and the threshold concentration of cADP-R that decreased the average channel activity of the KCa channels was 1 μM. These results provide evidence that cADP-R is produced and metabolized in the coronary arterial smooth muscle and that a cADP-R/ADP-R pathway participates in the control of the KCa-channel activity in vascular SMC.

Download Full-text

15-Hydroxyeicosatetraenoic acid-mediated potentiation of thrombin- induced platelet functions occurs via enhanced production of phosphoinositide-derived second messengers--sn-1,2-diacylglycerol and inositol-1,4,5-trisphosphate

Blood ◽

10.1182/blood.v80.11.2765.2765 ◽

1992 ◽

Vol 80 (11) ◽

pp. 2765-2773 ◽

Cited By ~ 43

Author(s):

BN Setty ◽

MH Werner ◽

YA Hannun ◽

MJ Stuart

Keyword(s):

Platelet Aggregation ◽

Intracellular Calcium ◽

Second Messengers ◽

Threshold Concentration ◽

Dependent Manner ◽

Concentration Dependent Manner ◽

Enhanced Production ◽

Inositol 1,4,5 Trisphosphate ◽

Nucleotide Release ◽

Platelet Functions

Abstract We investigated whether biologically relevant concentrations of the mono-hydroxyeicosatetraenoic acids (mono-HETEs) modulate platelet functions. We report that 15-HETE, an eicosanoid produced by endothelial cells, granulocytes, and lymphocytes, potentiated platelet aggregation, nucleotide release, and elevation in intracellular calcium levels induced by a threshold concentration of thrombin (0.025 U/mL). Significant potentiation effects on these responses were observed at concentrations between 1 and 100 nmol/L. 15-HETE at these concentrations enhanced thrombin-induced platelet aggregation by 32% to 57%, nucleotide release by 40% to 65%, and elevation of intracellular calcium by 31% to 52% (P < .05 to .01). Both 12-HETE and 5-HETE, the structural isomers of 15-HETE, also potentiated thrombin-induced platelet aggregation and nucleotide release. While 12-HETE showed a small but significant effect at 100 pmol/L, 5-HETE had effects similar to those of 15-HETE at micromolar concentrations. To understand the mechanism of the HETE modulation of platelet functions, we studied the effect of 10 and 100 nmol/L 15-HETE on the production of sn-1,2- diacylglycerol (DAG) and inositol-1,4,5-trisphosphate (1,4,5-IP3). 15- HETE enhanced thrombin-induced production of DAG and 1,4,5-IP3 in a time- and concentration-dependent manner. 15-HETE also potentiated agonist-induced phosphorylation of the 47-Kd platelet protein. These studies demonstrate an important modulatory role for 15-HETE on platelet functions. Since this eicosanoid is elevated in pathologic states associated with platelet hyperfunction, including diabetes mellitus and atherosclerosis, an elucidation of its mechanism(s) of action appears relevant to our understanding of the genesis of atherothrombotic vascular disease.

Download Full-text

Polyethylene glycol exerted toxicity to growth of Bacillus subtilis NRS-762

10.7287/peerj.preprints.26817 ◽

2018 ◽

Author(s):

Wenfa Ng

Keyword(s):

Bacillus Subtilis ◽

Polyethylene Glycol ◽

Optical Density ◽

Culture Broth ◽

Threshold Concentration ◽

Dependent Manner ◽

Concentration Dependent Manner ◽

Ph Variation ◽

The One ◽

The Impact

Polyethylene glycol is commonly used in fermentations as an anti-foam for preventing the rise of foam to the top plate of the bioreactor, which increases contamination risk. However, its potential toxicity to growth of various microorganisms is not well understood at the strain and species level. Hence, the objective of this study was to understand the impact of different concentrations of polyethylene glycol (0, 1, 5 and 10 g/L) on the aerobic growth of Bacillus subtilis NRS-762 (ATCC 8473) in LB Lennox medium in shake flasks at 30 oC and 230 rpm rotational shaking. Experiment results indicated that polyethylene glycol (PEG) (molecular weight ~8000 Da), at all concentrations tested, exerted some toxicity towards the growth of B. subtilis NRS-762 in LB Lennox medium. Specifically, maximal optical density obtained declined with greater exposure to PEG in a concentration-dependent manner, up to a threshold concentration of 5 g/L PEG. For example, maximal optical density obtained in B. subtilis NRS-762 without addition of PEG was 4.4, but the value obtained on exposure to 1 g/L of the anti-foam decreased to 4.1 and a further 3.8 on exposure of cells to 5 g/L and 10 g/L PEG. Similarly, growth rates of B. subtilis NRS-762 also decreased in a concentration-dependent manner with PEG concentration up to a threshold concentration of 5 g/L PEG. pH variation in culture broth, however, revealed that the pH profiles for exposure to PEG at all concentrations overlapped each other and was similar to the one of cells without exposure to the anti-foam; thereby, highlighting that metabolic processes in B. subtilis NRS-762 were not significantly affected by exposure to PEG. Collectively, polyethylene glycol anti-foam exerted toxicity effect on B. subtilis NRS-762 biomass formation, and possibly metabolism. The latter may not be sufficiently significant to affect the types of metabolites secreted by the bacterium, and thus, could not be detected by measurement of culture broth pH. Overall, the results should inform the choice and concentration of PEG for culturing B. subtilis in biotechnological applications.

Download Full-text

15-Hydroxyeicosatetraenoic acid-mediated potentiation of thrombin- induced platelet functions occurs via enhanced production of phosphoinositide-derived second messengers--sn-1,2-diacylglycerol and inositol-1,4,5-trisphosphate

Blood ◽

10.1182/blood.v80.11.2765.bloodjournal80112765 ◽

1992 ◽

Vol 80 (11) ◽

pp. 2765-2773 ◽

Cited By ~ 1

Author(s):

BN Setty ◽

MH Werner ◽

YA Hannun ◽

MJ Stuart

Keyword(s):

Platelet Aggregation ◽

Intracellular Calcium ◽

Second Messengers ◽

Threshold Concentration ◽

Dependent Manner ◽

Concentration Dependent Manner ◽

Enhanced Production ◽

Inositol 1,4,5 Trisphosphate ◽

Nucleotide Release ◽

Platelet Functions

We investigated whether biologically relevant concentrations of the mono-hydroxyeicosatetraenoic acids (mono-HETEs) modulate platelet functions. We report that 15-HETE, an eicosanoid produced by endothelial cells, granulocytes, and lymphocytes, potentiated platelet aggregation, nucleotide release, and elevation in intracellular calcium levels induced by a threshold concentration of thrombin (0.025 U/mL). Significant potentiation effects on these responses were observed at concentrations between 1 and 100 nmol/L. 15-HETE at these concentrations enhanced thrombin-induced platelet aggregation by 32% to 57%, nucleotide release by 40% to 65%, and elevation of intracellular calcium by 31% to 52% (P < .05 to .01). Both 12-HETE and 5-HETE, the structural isomers of 15-HETE, also potentiated thrombin-induced platelet aggregation and nucleotide release. While 12-HETE showed a small but significant effect at 100 pmol/L, 5-HETE had effects similar to those of 15-HETE at micromolar concentrations. To understand the mechanism of the HETE modulation of platelet functions, we studied the effect of 10 and 100 nmol/L 15-HETE on the production of sn-1,2- diacylglycerol (DAG) and inositol-1,4,5-trisphosphate (1,4,5-IP3). 15- HETE enhanced thrombin-induced production of DAG and 1,4,5-IP3 in a time- and concentration-dependent manner. 15-HETE also potentiated agonist-induced phosphorylation of the 47-Kd platelet protein. These studies demonstrate an important modulatory role for 15-HETE on platelet functions. Since this eicosanoid is elevated in pathologic states associated with platelet hyperfunction, including diabetes mellitus and atherosclerosis, an elucidation of its mechanism(s) of action appears relevant to our understanding of the genesis of atherothrombotic vascular disease.

Download Full-text

HBV Core Protein Is in Flux between Cytoplasmic, Nuclear, and Nucleolar Compartments

mBio ◽

10.1128/mbio.03514-20 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Smita Nair ◽

Adam Zlotnick

Keyword(s):

Core Protein ◽

Large Fraction ◽

Disease Status ◽

Wide Distribution ◽

Threshold Concentration ◽

Viral Rna ◽

Dependent Manner ◽

Concentration Dependent Manner ◽

Viral Capsids ◽

Cellular Compartments

ABSTRACT Hepatitis B virus (HBV) core protein (Cp) can be found in the nucleus and cytoplasm of infected hepatocytes; however, it preferentially segregates to a specific compartment correlating with disease status. Regulation of this intracellular partitioning of Cp remains obscure. In this paper, we report that cellular compartments are filled and vacated by Cp in a time- and concentration-dependent manner in both transfections and infections. At early times after transfection, Cp, in a dimeric state, preferentially localizes to the nucleolus. Later, the nucleolar compartment is emptied and Cp progresses to being predominantly nuclear, with a large fraction of the protein in an assembled state. Nuclear localization is followed by cell-wide distribution, and then Cp becomes exclusively cytoplasmic. The same trend in Cp movement is seen during an infection. Putative nucleolar retention signals have been identified and appear to be structure dependent. Export of Cp from the nucleus involves the CRM1 exportin. Time-dependent flux can be recapitulated by modifying Cp concentration, suggesting transitions are regulated by reaching a threshold concentration. IMPORTANCE HBV is an endemic virus. More than 250 million people suffer from chronic HBV infection and about 800,000 die from HBV-associated disease each year. HBV is a pararetrovirus; in an infected cell, viral DNA in the nucleus is the template for viral RNA that is packaged in nascent viral capsids in the cytoplasm. Inside those capsids, while resident in cytoplasm, the linear viral RNA is reverse transcribed to form the circular double-stranded DNA (dsDNA) of the mature virus. The HBV core (or capsid) protein plays a role in almost every step of the viral life cycle. Here, we show the core protein appears to follow a programmed, sequential localization from cytoplasmic translation then into the nucleolus, to the nucleus, and back to the cytoplasm. Localization is primarily a function of time, core protein concentration, and assembly. This has important implications for our understanding of the mechanisms of antivirals that target HBV capsid assembly.

Download Full-text

Polyethylene glycol exerted toxicity to growth of Bacillus subtilis NRS-762

10.7287/peerj.preprints.26817v1 ◽

2018 ◽

Author(s):

Wenfa Ng

Keyword(s):

Bacillus Subtilis ◽

Polyethylene Glycol ◽

Optical Density ◽

Culture Broth ◽

Threshold Concentration ◽

Dependent Manner ◽

Concentration Dependent Manner ◽

Ph Variation ◽

The One ◽

The Impact

Polyethylene glycol is commonly used in fermentations as an anti-foam for preventing the rise of foam to the top plate of the bioreactor, which increases contamination risk. However, its potential toxicity to growth of various microorganisms is not well understood at the strain and species level. Hence, the objective of this study was to understand the impact of different concentrations of polyethylene glycol (0, 1, 5 and 10 g/L) on the aerobic growth of Bacillus subtilis NRS-762 (ATCC 8473) in LB Lennox medium in shake flasks at 30 oC and 230 rpm rotational shaking. Experiment results indicated that polyethylene glycol (PEG) (molecular weight ~8000 Da), at all concentrations tested, exerted some toxicity towards the growth of B. subtilis NRS-762 in LB Lennox medium. Specifically, maximal optical density obtained declined with greater exposure to PEG in a concentration-dependent manner, up to a threshold concentration of 5 g/L PEG. For example, maximal optical density obtained in B. subtilis NRS-762 without addition of PEG was 4.4, but the value obtained on exposure to 1 g/L of the anti-foam decreased to 4.1 and a further 3.8 on exposure of cells to 5 g/L and 10 g/L PEG. Similarly, growth rates of B. subtilis NRS-762 also decreased in a concentration-dependent manner with PEG concentration up to a threshold concentration of 5 g/L PEG. pH variation in culture broth, however, revealed that the pH profiles for exposure to PEG at all concentrations overlapped each other and was similar to the one of cells without exposure to the anti-foam; thereby, highlighting that metabolic processes in B. subtilis NRS-762 were not significantly affected by exposure to PEG. Collectively, polyethylene glycol anti-foam exerted toxicity effect on B. subtilis NRS-762 biomass formation, and possibly metabolism. The latter may not be sufficiently significant to affect the types of metabolites secreted by the bacterium, and thus, could not be detected by measurement of culture broth pH. Overall, the results should inform the choice and concentration of PEG for culturing B. subtilis in biotechnological applications.

Download Full-text

The Anti-Atherogenic Properties of Sesamin are Mediated via Improved Macrophage Cholesterol Efflux Through PPARγ1-LXRα and MAPK Signaling

International Journal for Vitamin and Nutrition Research ◽

10.1024/0300-9831/a000195 ◽

2014 ◽

Vol 84 (1-2) ◽

pp. 79-91 ◽

Cited By ~ 7

Author(s):

Amin F. Majdalawieh ◽

Hyo-Sung Ro

Keyword(s):

Cholesterol Efflux ◽

Transcriptional Activity ◽

Molecular Mechanisms ◽

Foam Cell ◽

Mapk Signaling ◽

Luciferase Reporter ◽

Foam Cell Formation ◽

Dependent Manner ◽

Concentration Dependent Manner ◽

Macrophage Cholesterol Efflux

Background: Foam cell formation resulting from disrupted macrophage cholesterol efflux, which is triggered by PPARγ1 and LXRα, is a hallmark of atherosclerosis. Sesamin and sesame oil exert anti-atherogenic effects in vivo. However, the exact molecular mechanisms underlying such effects are not fully understood. Aim: This study examines the potential effects of sesamin (0, 25, 50, 75, 100 μM) on PPARγ1 and LXRα expression and transcriptional activity as well as macrophage cholesterol efflux. Methods: PPARγ1 and LXRα expression and transcriptional activity are assessed by luciferase reporter assays. Macrophage cholesterol efflux is evaluated by ApoAI-specific cholesterol efflux assays. Results: The 50 μM, 75 μM, and 100 μM concentrations of sesamin up-regulated the expression of PPARγ1 (p< 0.001, p < 0.001, p < 0.001, respectively) and LXRα (p = 0.002, p < 0.001, p < 0.001, respectively) in a concentration-dependent manner. Moreover, 75 μM and 100 μM concentrations of sesamin led to 5.2-fold (p < 0.001) and 6.0-fold (p<0.001) increases in PPAR transcriptional activity and 3.9-fold (p< 0.001) and 4.2-fold (p < 0.001) increases in LXR transcriptional activity, respectively, in a concentration- and time-dependent manner via MAPK signaling. Consistently, 50 μM, 75 μM, and 100 μM concentrations of sesamin improved macrophage cholesterol efflux by 2.7-fold (p < 0.001), 4.2-fold (p < 0.001), and 4.2-fold (p < 0.001), respectively, via MAPK signaling. Conclusion: Our findings shed light on the molecular mechanism(s) underlying sesamins anti-atherogenic effects, which seem to be due, at least in part, to its ability to up-regulate PPARγ1 and LXRα expression and transcriptional activity, improving macrophage cholesterol efflux. We anticipate that sesamin may be used as a therapeutic agent for treating atherosclerosis.

Download Full-text

Neutrophil Elastase Potentiates Cathepsin G-lnduced Platelet Activation

Thrombosis and Haemostasis ◽

10.1055/s-0038-1646319 ◽

1992 ◽

Vol 68 (05) ◽

pp. 570-576 ◽

Cited By ~ 20

Author(s):

Mary A Selak

Keyword(s):

Neutrophil Elastase ◽

Cell Activation ◽

Thromboxane A2 ◽

Creatine Phosphate ◽

Dense Granule ◽

Cathepsin G ◽

Dependent Manner ◽

Concentration Dependent Manner ◽

Low Concentrations ◽

High Concentrations

SummaryWe have previously demonstrated that human neutrophil cathepsin G is a strong platelet agonist that binds to a specific receptor. This work describes the effect of neutrophil elastase on cathepsin G-induced platelet responses. While platelets were not activated by high concentrations of neutrophil elastase by itself, elastase enhanced aggregation, secretion and calcium mobilization induced by low concentrations of cathepsin G. Platelet aggregation and secretion were potentiated in a concentration-dependent manner by neutrophil elastase with maximal responses observable at 200 nM. Enhancement was observed when elastase was preincubated with platelets for time intervals of 10–60 s prior to addition of a low concentration of cathepsin G and required catalytically-active elastase since phenylmethanesulphonyl fluoride-inhibited enzyme failed to potentiate cell activation. Neutrophil elastase potentiation of platelet responses induced by low concentrations of cathepsin G was markedly inhibited by creatine phosphate/creatine phosphokinase and/or indomethacin, indicating that the synergism between elastase and cathepsin G required the participation of ADP and thromboxane A2. On the other hand, platelet responses were not attenuated by the PAF antagonist BN 52021, signifying that PAF-acether did not play a role in elastase potentiation. At higher concentrations porcine pancreatic elastase exhibits similar effects to neutrophil elastase, demonstrating that the effect of elastase was not unique to the neutrophil protease. While neutrophil elastase failed to alter the ability of cathepsin G to hydrolyze a synthetic chromogenic substrate, preincubation of platelets with elastase increased the apparent affinity of cathepsin G binding to platelets. In contrast to their effect on cathepsin G-induced platelet responses, neither neutrophil nor pancreatic elasatse potentiated aggregation or dense granule release initiated by ADP, PAF-acether, arachidonic acid or U46619, a thromboxane A2 mimetic. Moreover, unlike its effect on cathepsin G, neutrophil elastase inhibited thrombin-induced responses. The current observations demonstrate that elastase can potentiate platelet responses mediated by low concentrations of cathepsin G, suggesting that both enzymes may function synergistically to activate platelets under conditions where neutrophil degranulation occurs.

Download Full-text