scholarly journals Recovery of surface membrane in anterior pituitary cells. Variations in traffic detected with anionic and cationic ferritin

1978 ◽  
Vol 77 (3) ◽  
pp. R35 ◽  
Author(s):  
MG Farquhar
Keyword(s):  
Anterior Pituitary ◽  
Secretory Pathway ◽  
Negative Charge ◽  
Positive Charge ◽  
Surface Membrane ◽  
Pituitary Cells ◽  
Net Charge ◽  
Secretion Granules ◽  
Lysosomal System ◽  
Net Positive Charge

Cells dissociated from rat anterior pituitaries were incubated with native or cationized ferritin (CF) to trace the fate of surface membrane. Native ferritin, which did not bind to the cell surface, was taken up in small amounts by bulk-phase endocytosis and was found increasingly (over 1-2 h) concentrated in lysosomes. CF at 100-fold less concentrations bound rapidly to the cell membrane, was taken up by endocytosis in far greater amounts, and within 15-60 min was found increasingly within multiple stacked Golgi cisternae, around forming secretion granules, and within elements of GERL, as well as within lysosomes. The findings demonstrate that the fate of the tracer--and presumably also that of the surface membrane--varies with the same molecule differing only in net charge: vesicles carrying anionic ferritin (net negative charge) fuse only with elements of the lysosomal system whereas those carrying CF (net positive charge) can fuse not only with elements of the lysosomal system, but also with elements along the secretory pathway (Golgi cisternae and condensing granules) as well.

scholarly journals The mechanism of spray electrification: the waterfall effect

2016 ◽  
Author(s):  
James K. Beattie
Keyword(s):  
Negative Charge ◽  
Positive Charge ◽  
Hydrophobic Hydration ◽  
General Phenomenon ◽  
Aqueous Interfaces ◽  
Preferential Adsorption ◽  
Negative Surface ◽  
Negative Surface Charge ◽  
Low Permittivity ◽  
Net Positive Charge

Abstract. The waterfall effect describes the separation of charge by splashing at the base of a waterfall. Smaller drops that have a net negative charge are created, while larger drops and/or the bulk maintain overall charge neutrality with a net positive charge. Since it was first described by Lenard (1892) the effect has been confirmed many times, but a molecular explanation has not been available. Application of our fluctuation-correlation model of hydrophobic hydration accounts for the negative charge observed at aqueous interfaces with low permittivity materials. The negative surface charge observed in the waterfall effect is created by the preferential adsorption of hydroxide ions generated from the autolysis of water. On splashing, shear forces generate small negative drops from the surface, leaving a positive charge on the remaining large fragment. The waterfall effect is a manifestation of the general phenomenon of the negative charge at the interface between water and hydrophobic surfaces that is created by the preferential adsorption of hydroxide ions.

THE EFFECT OF PROCOAGULANT PHOSPHOLIPID VESICLES WITH NET POSITIVE CHARGE ON THE ACTIVITY OF PROTHROMBINASE

1987 ◽  
Author(s):  
J Rosing ◽  
H Speijer ◽  
J W P Govers-Riemslag ◽  
R F A Zwaal
Keyword(s):  
Vitamin K ◽  
Negative Charge ◽  
Positive Charge ◽  
Coagulation Factor ◽  
Phospholipid Vesicles ◽  
Electrostatic Model ◽  
Acidic Phospholipid ◽  
Positively Charged ◽  
Net Positive Charge ◽  
Prothrombin Activation

It is generally thought that procoagulant phospholipid surfaces that promote the activation of vitamin K-dependent coagulation factors should have a net negative charge in order to promote calcium-dependent binding of the enzymes (FVIIa, FIXa and FXa) and substrates (prothrombin and FX) of the coagulation factor-activating complexes. Two models have been proposed to explain calcium-mediated association of vitamin K-dependent proteins with phospholipid: a) an electrostatic model, in which a positively-charged protein-calcium complex is attracted by a negatively-charged phospholipid surface and b) a chelation model in which a coordination complex is formed between calcium ions, γ-carboxyglutamic acids of the proteins and negatively-charged membrane phospholipids. To study the effect of the electrostatic potential of phospholipid vesicles on their activity in the pro-thrombinase complex the net charge of vesicles was varied by introduction of varying amounts of positively-charged stearylamine in the membrane surface. Introduction of 0-15 mole% stearylamine in phospholipid vesicles that contained 5 mole% phosphatidylseri-ne (PS) hardly affected their activity in prothrombin activation. Electrophoretic analysis showed that vesicles with > 5 mole% stearylamine had a net positive charge. The procoagulant activity of vesicles that contained phosphatidic acid, phosphatidylglyce-rol, phosphatidylinositol or phosphatidyl-glactate (PLac) as acidic phospholipid was much more effected by incorporation of stearylamine. Amounts of stearylamine that compensated the negative charge of acidic phospholipid caused considerable inhibition of the activity of the latter vesicles in prothrombin activation. The comparison of vesicles containing PS and PLac as acidic phospholipid is of special interest. PS and PLac only differ by the presence of NH+ 3-group in the serine moiety of PS. Thus, in spite of the fact that vesicles with PLac are more negatively charged than vesicles with PS, they are less procoagulant. Our results show that a) although procoagulant membranes have to contain acidic phospholipids there is no requirement for a net negative charge, b) the amino group of phosphatidylserine has an important function in the interaction of procoagulant membranes with vitamin K-dependent proteins and c) the chelation model can satisfactorily explain calcium-mediated lipid-protein association.

scholarly journals Pathways followed by membrane recovered from the surface of plasma cells and myeloma cells

1980 ◽  
Vol 152 (1) ◽  
pp. 1-19 ◽  
Author(s):  
PD Ottosen ◽  
PJ Courtoy ◽  
MG Farquhar
Keyword(s):  
Secretory Pathway ◽  
Plasma Cells ◽  
Surface Membrane ◽  
Secretory Cells ◽  
Secretory Product ◽  
Vesicle Membrane ◽  
Myeloma Cells ◽  
Glandular Cells ◽  
Lysosomal System ◽  
Endocytic Vesicles

Evidence for recovery of surface membrane and its fusion with Golgi cisternae has been obtained previously in several glandular cells. This study was conducted to determine whether or not membrane is similarly retrieved from the surfaces of plasma cells from lymph nodes (of rats immunized with horseradish peroxidase [HRP]) and mouse myeloma cells (RPC 5.4 and X63 Ag 8 cell lines). Electron-dense tracers (cationic and anionic ferritin, HRP) were used to trace the pathways followed by surface membrane recovered by endocytosis, and immunocytochemistry was used to identify the secretory compartments. When plasma cells or myeloma cells were incubated with cationized ferritin (CF), it bound to the cell surfaces and was taken up in endocytic vesicles, for the most part bound to the vesicle membrane. After 30-60 min, it was found increasingly within lysosomes and in several secretory compartments- notably in multiple stacked Golgi cisternae and secretory vacuoles. By immunocytochemistry the secretory product (immunoglobulins) and CF could be demonstrated in the same Golgi components. When myeloma cells were incubated with native (anionic) ferritin or in HRP, these tracers were taken up in much smaller amounts, primarily within the contents of endocytic vesicles. With continued incubation, they appeared only in lysosomes. When cells were doubly incubated, first in CF and then in HRP, both tracers were taken up (often within the same endocytic vesicle), but they maintained their same destinations as when incubated in a single tracer alone: the content marker, HRP, was localized exclusively within the lysosomal system, whereas the membrane marker, CF, was found within elements along the secretory pathway as well as within lysosomes. The findings demonstrate the existence of considerable membrane traffic between the cell membrane and the Golgi cisternae and lysosomes in both normal plasma cells and myeloma cells. Because myeloma cells behave like the glandular cells studied previously with regard to pathways of retrieved surface membrane, they represent a suitable and promising system for further studies of mechanisms and pathways of membrane retrieval and recycling in secretory cells.

scholarly journals Human salivary MUC7 mucin peptides: effect of size, charge and cysteine residues on antifungal activity

2003 ◽  
Vol 375 (1) ◽  
pp. 175-182 ◽  
Author(s):  
Hongsa SITU ◽  
Guoxian WEI ◽  
Christina J. SMITH ◽  
Shirin MASHHOON ◽  
Libuse A. BOBEK
Keyword(s):  
Antifungal Activity ◽  
Fungicidal Activity ◽  
Positive Charge ◽  
Critical Role ◽  
Helical Conformation ◽  
Cysteine Residues ◽  
Clear Correlation ◽  
Potential Candidate ◽  
Net Charge ◽  
Net Positive Charge

We have previously shown that MUC7 (human salivary low-molecular-mass mucin) 20-mer: LAHQKPFIRKSYKCLHKRCR (residues 32–51 of the parent MUC7, with a net positive charge of 7) possesses a broad-spectrum antimicrobial activity [Bobek and Situ (2003) Antimicrob. Agents Chemother. 47, 645–652]. The aims of the present study were to determine the minimum peptide chain length and its location within the 20-mer region that retains potent antifungal activity against Candida albicans and Cryptococcus neoformans and to examine the effect of net charge of the peptide as well as the role of cysteine residues on the fungicidal activity. First, several C-terminal truncated MUC7 20-mer fragments (16-mer, 12-mer, 11-mer, 10-mer and 8-mer) and one N-terminal fragment (8-mer-N) were synthesized and tested. The results showed that MUC7 12-mer, located at the C-terminal region of MUC7 20-mer, having a net charge of +6 and exhibiting an amphipathic helical conformation, not only retained but exceeded the antifungal activity of that of 20-mer. Secondly, several variants of the 12-mer peptide containing a lower or no net positive charge, or no cysteine residues were synthesized and tested. A clear correlation between the net positive charge of the 12-mer, its potency and initial interaction of peptide with fungal cells was found by killing assays, fluorescence microscopy and fungal cell-membrane potential measurements. Furthermore, cysteine residues, which play a critical role in bacterial binding, were found to be not important for the fungicidal activity of these peptides. These results identified MUC7 12-mer as a potential candidate for development into a novel antifungal therapeutic agent.

Evidence that alteration of charge modifies proximal tubular shunt pathway permselectivity

1989 ◽  
Vol 257 (6) ◽  
pp. F1079-F1086
Author(s):  
S. W. Weinstein ◽  
S. M. Jones ◽  
R. J. Weinstein
Keyword(s):  
Negative Charge ◽  
Positive Charge ◽  
Paracellular Pathway ◽  
Disulfonic Acid ◽  
Physiological Control ◽  
Membrane Charge ◽  
Cation Permeability ◽  
Diffusive Permeability ◽  
Proximal Tubular ◽  
Net Positive Charge

Experiments were performed to test the hypothesis that membrane charge is an important determinant of paracellular pathway ion permselectivity in the proximal tubule. Net negative charge in or around the paracellular pathway should favor cation permeability; net positive charge should favor anion permeability. Therefore compounds such as amiloride and 4-acetamido-4'-isothiocyanostilbene-2,2'-disulfonic acid (SITS), capable of changing net membrane charge, should predictably change the diffusive permselectivity of the paracellular pathway to anions and cations. In the first group of experiments amiloride, a compound capable of increasing net positive membrane charge, inhibited cation and enhanced anion diffusive permeability. In a second group of experiments, SITS, a compound capable of increasing net negative membrane charge, inhibited anion and enhanced cation diffusive permeability. The effects of amiloride and SITS were symmetrical; the lumen-to-bath and the bath-to-lumen diffusion potentials were not significantly different in magnitude. In addition these effects were completely and rapidly reversible. Our results suggest that amiloride increases net positive charge, and SITS increases net negative charge within the paracellular pathway. The most likely site for the actions of SITS and amiloride is the tight junction because the effects of the inhibitors were symmetrical. Both compounds act at low concentrations and reversibly such that removal of the inhibitor rapidly reverses its effects. We propose, on the basis of the ease with which these alterations in charge and thus paracellular pathway permselectivity occurred, that the permselectivity of this pathway may not be fixed and constant for any given proximal tubular segment. In fact, permselectivity may vary and thus serve as an important physiological control mechanism for proximal tubular solute and water reabsorption.

scholarly journals The Analyses of High Infectivity Mechanism of SARS-CoV-2 and Its Variants

COVID ◽  
2021 ◽  
Vol 1 (4) ◽  
pp. 666-673
Author(s):  
Yonghua Lu ◽  
Tianfu Zhao ◽  
Ming Lu ◽  
Yaopeng Zhang ◽  
Xiang Yao ◽  
...  
Keyword(s):  
Angiotensin Converting Enzyme ◽  
Charge Distribution ◽  
Negative Charge ◽  
Positive Charge ◽  
Spike Protein ◽  
Converting Enzyme ◽  
Net Charge ◽  
Angiotensin Converting Enzyme 2 ◽  
Charge Distributions ◽  
High Infectivity

SARS-CoV-2 has high infectivity and some of its variants have higher transmissibility. To explore the high infectivity mechanism, the charge distributions of SARS-CoV, SARS-CoV-2, and variants of concern were calculated through a series of net charge calculation formulas. The results showed that the SARS-CoV-2 spike protein had more positive charges than that of SARS-CoV. Further results showed that the variants had similar but higher positive charges than preexisting SARS-CoV-2. In particular, the Delta variant had the greatest increase in positive charges in S1 resulting in the highest infectivity. In particular, the S1 positive charge increased greatly in the Delta variant. The S1 positive charge increased, and due to the large negative charge of angiotensin-converting enzyme-2 (ACE2), this resulted in a large increase in Coulomb’s force between S1 and ACE2. This finding agrees with the expectation that the positive charges in the spike protein result in more negative charges on SARS-CoV-2 antibodies than that of SARS-CoV. Thus, the infectivity of a novel SARS-CoV-2 variant may be evaluated preliminarily by calculating the charge distribution.

Reduction of Fe(III) in griffithite

Clay Minerals ◽  
2000 ◽  
Vol 35 (4) ◽  
pp. 625-634 ◽  
Author(s):  
P. Komadel ◽  
J. Madejová ◽  
D. A. Laird ◽  
Y. Xia ◽  
J. W. Stucki
Keyword(s):  
Negative Charge ◽  
Positive Charge ◽  
Sodium Dithionite ◽  
Basic Rock ◽  
Octahedral Sheet ◽  
Bicarbonate Buffer ◽  
Structural Differences ◽  
Trioctahedral Smectite ◽  
Net Positive Charge

AbstractGriffithite is a trioctahedral smectite with dioctahedral domains, found in the <2 μm fraction of weathered basic rock from Griffith Park, California, USA. Crystalline admixtures (albite, calcite, quartz and maghemite) are concentrated in the 0.2 – 2 μm fraction, while the <0.06 μm fraction contains only trace amounts of other minerals. Griffithite is primarily an Fe–rich saponite with negative charge located in the tetrahedral sheets. The octahedral occupancy is ∼91%, and ∼26% of the octahedra contain trivalent atoms imparting a net positive charge to the octahedral sheet. Medium levels of Fe(III) reduction in griffithite, up to 60% of total Fe, can be achieved by adding solid sodium dithionite to clay dispersions in a citrate–bicarbonate buffer. By contrast >90% reduction of Fe(III) to Fe(II) is achieved in nontronites using the same method. The lower reducibility of Fe(III) in griffithite relative to nontronites may be due to structural differences between griffithite and nontronites, such as a more negative tetrahedral charge and a positive octahedral charge.

Changes in the surface charge of bacteria caused by heavy metals do not affect survival

1996 ◽  
Vol 42 (7) ◽  
pp. 621-627 ◽  
Author(s):  
Y. E. Collins ◽  
G. Stotzky
Keyword(s):  
Heavy Metals ◽  
Surface Charge ◽  
Negative Charge ◽  
Positive Charge ◽  
Agrobacterium Radiobacter ◽  
Charge Reversal ◽  
Ph Values ◽  
A Charge ◽  
Net Positive Charge ◽  
Cu And Zn

Bacillus subtilis and Agrobacterium radiobacter remained viable when exposed to Ni (1 × 10−4 M; ionic strength (μ) = 3 × 10−4) at pH values known to cause a change of the net negative charge of the cells to a net positive charge (charge reversal). The gross morphology, as determined by scanning electron microscopy, of these and other bacteria and of Saccharomyces cerevisiae was not altered in the presence of Ni, Cu, and Zn (1 × 10−4 M; μ = 3 × 10−4), which caused a charge reversal at pH values between 6.0 and 9.0. Similar results were obtained in the presence of Na and Mg, which did not cause charge reversal at the same μ and pH values. These results confirmed that cells remain viable when their surface charge is changed in the presence of some heavy metals at high pH values.Key words: heavy metals, electrokinetic properties, survival of bacteria.

Localization of p24 putative cargo receptors in the early secretory pathway depends on the biosynthetic activity of the cell

2001 ◽  
Vol 360 (2) ◽  
pp. 421-429 ◽  
Author(s):  
Roland P. KUIPER ◽  
Gerrit BOUW ◽  
Karel P. C. JANSSEN ◽  
Jutta RÖTTER ◽  
François van HERP ◽  
...  
Keyword(s):  
Subcellular Localization ◽  
Anterior Pituitary ◽  
Secretory Pathway ◽  
Protein Transport ◽  
Pituitary Cells ◽  
Biosynthetic Activity ◽  
Early Secretory Pathway ◽  
Highly Active ◽  
Anterior Pituitary Cells ◽  
P24 Proteins

Members of the p24 family of putative cargo receptors (subdivided into p24-α, −β, −γ and −δ) are localized in the intermediate-and cis-Golgi compartments of the early secretory pathway, and are thought to play an important role in protein transport. In the present study, we wondered what effect increased biosynthetic cell activity with resulting high levels of protein transport would have on the subcellular localization of p24. We examined p24 localization in Xenopus intermediate pituitary melanotrope cells, which in black- and white-adapted animals are biosynthetically highly active and virtually inactive respectively. In addition, p24 localization was studied in Xenopus anterior pituitary cells whose activity is not changed during background adaptation. Using organelle fractionation, we found that in the inactive melanotropes and moderately active anterior pituitary cells of white-adapted animals, the p24-α, −β, −γ and −δ proteins are all located in the Golgi compartment. In the highly active melanotropes, but not in the anterior cells of black-adapted animals, the steady-state distribution of all four p24 members changed towards the intermediate compartment and subdomains of the endoplasmic reticulum (ER), most probably the ER exit sites. In the active melanotropes, the major cargo protein pro-opiomelanocortin was mostly localized to ER subdomains and partially co-localized with the p24 proteins. Furthermore, in the active cells, in vitro blocking of protein biosynthesis by cycloheximide or dispersion of the Golgi complex by brefeldin A led to a redistribution of the p24 proteins, indicating their involvement in ER-to-Golgi protein transport and extensive cycling in the early secretory pathway. We conclude that the subcellular localization of p24 proteins is dynamic and depends on the biosynthetic activity of the cell.

scholarly journals Zerumbone Inhibits Helicobacter pylori Urease Activity

Molecules ◽  
2021 ◽  
Vol 26 (9) ◽  
pp. 2663
Author(s):  
Hyun Jun Woo ◽  
Ji Yeong Yang ◽  
Pyeongjae Lee ◽  
Jong-Bae Kim ◽  
Sa-Hyun Kim
Keyword(s):  
Helicobacter Pylori ◽  
Carbon Atom ◽  
Natural Compound ◽  
Urease Activity ◽  
Negative Charge ◽  
Positive Charge ◽  
Gastric Epithelium ◽  
Functional Inhibition ◽  
Electrical Gradient ◽  
H Pylori

Helicobacter pylori (H. pylori) produces urease in order to improve its settlement and growth in the human gastric epithelium. Urease inhibitors likely represent potentially powerful therapeutics for treating H. pylori; however, their instability and toxicity have proven problematic in human clinical trials. In this study, we investigate the ability of a natural compound extracted from Zingiber zerumbet Smith, zerumbone, to inhibit the urease activity of H. pylori by formation of urease dimers, trimers, or tetramers. As an oxygen atom possesses stronger electronegativity than the first carbon atom bonded to it, in the zerumbone structure, the neighboring second carbon atom shows a relatively negative charge (δ−) and the next carbon atom shows a positive charge (δ+), sequentially. Due to this electrical gradient, it is possible that H. pylori urease with its negative charges (such as thiol radicals) might bind to the β-position carbon of zerumbone. Our results show that zerumbone dimerized, trimerized, or tetramerized with both H. pylori urease A and urease B molecules, and that this formation of complex inhibited H. pylori urease activity. Although zerumbone did not affect either gene transcription or the protein expression of urease A and urease B, our study demonstrated that zerumbone could effectively dimerize with both urease molecules and caused significant functional inhibition of urease activity. In short, our findings suggest that zerumbone may be an effective H. pylori urease inhibitor that may be suitable for therapeutic use in humans.

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