scholarly journals Dependence of Macrophage Phagocytic Efficacy on Antibody Concentration

2007 ◽  
Vol 75 (4) ◽  
pp. 1904-1915 ◽  
Author(s):  
Nataša Macura ◽  
Tong Zhang ◽  
Arturo Casadevall
Keyword(s):  
Dose Dependence ◽  
Critical Parameters ◽  
Phagocytic Index ◽  
Affinity Constant ◽  
Antibody Concentration ◽  
Complement Receptors ◽  
Model Calculations ◽  
Microbial Antigen ◽  
Clean System ◽  
High Concentrations

ABSTRACT Macrophages ingest the fungus Cryptococcus neoformans only in the presence of opsonins, and this provides a remarkably clean system for the detailed analysis of phagocytosis. This system is also unusual in that antibody-mediated phagocytosis involves ingestion through both Fc and complement receptors in the absence of complement. Mathematical modeling was used to analyze and explain the experimental data that the macrophage phagocytic index increased with increasing doses of antibody despite saturating concentrations and declined at high concentrations. A model was developed that explains the increase in phagocytic index with increasing antibody doses, differentiates among the contributions from Fc and complement receptors, and provides a tool for estimating antibody concentrations that optimize efficacy of phagocytosis. Experimental results and model calculations revealed that blocking of Fc receptors by excess antibody caused a reduction in phagocytic index but increased phagocytosis through complement receptors rapidly compensated for this effect. At high antibody concentrations, a further reduction in phagocytic index was caused by interference with complement receptor ingestion as a consequence of saturation of the fungal capsule. The ability of our model to predict the antibody dose dependence of the macrophage phagocytic efficacy for C. neoformans strongly suggest that the major variables that determine the efficacy of this process have been identified. The model predicts that the affinity constant of the opsonic antibody for the Fc receptor and the association-dissociation constant of antibody from the microbial antigen are critical parameters determining the efficacy of phagocytosis.

Cellular Ca2+ monitored by aequorin in adenosine-mediated smooth muscle relaxation

1985 ◽  
Vol 248 (1) ◽  
pp. H109-H117 ◽  
Author(s):  
A. B. Bradley ◽  
K. G. Morgan
Keyword(s):  
Smooth Muscle ◽  
Electrical Stimulation ◽  
Muscle Relaxation ◽  
Dose Dependence ◽  
Ionized Calcium ◽  
Smooth Muscle Relaxation ◽  
Response Curves ◽  
Light Responses ◽  
Bioluminescent Protein ◽  
High Concentrations

We studied the effect of adenosine on cytoplasmic ionized calcium-force relationships in vascular smooth muscle (VSM) and determined the dose dependence of the observed effects. The bioluminescent protein aequorin was used as an index of cytoplasmic ionized calcium and was chemically loaded into ferret portal vein strips. The VSM strips were contracted with 33 mM potassium (K+), 5 X 10(-6) M phenylephrine (PE), or electrical stimulation. Force and aequorin light, i.e., cytoplasmic ionized calcium, were simultaneously recorded. Adenosine pretreatment (3.7 X 10(-6) M) reduced both force and light responses in contractures with K+, PE, or electrical stimulation. In contrast, the addition of adenosine during PE or K+ contractions decreased force without a change in light. Dose-response curves for the effects of adenosine on K+ contractures indicated that at low doses adenosine decreases force and cytoplasmic ionized calcium but that at high concentrations (greater than 3.7 X 10(-6) M) adenosine increases light and apparently relaxes VSM by desensitizing the myofilaments to cytoplasmic ionized calcium.

Reduction Kinetics of Iron Ore Materials by Gases

2009 ◽  
Vol 283-286 ◽  
pp. 45-52 ◽  
Author(s):  
A.N. Dmitriev ◽  
Yu.A. Chesnokov
Keyword(s):  
Blast Furnace ◽  
Mass Exchange ◽  
Iron Ore ◽  
Graphical Representation ◽  
Furnace Operation ◽  
Critical Parameters ◽  
Blast Furnace Process ◽  
Heat And Mass Exchange ◽  
Model Calculations ◽  
Furnace Process

The proposed balance logic-statistical model of the blast furnace process is based on the use of material and thermal balances along with calculations of heat- and mass exchange taking into account the non-uniformity of gas and burden distribution on the radius of the furnace and influence of the basic metallurgical characteristics of iron ore raw materials and coke on the indices of blast furnace operation. As a check of the applicability of the model, calculations on the most critical parameters of the blast furnace process – the smelting of ferromanganese and iron nickel with a graphical representation of heat- and mass exchange processes, dynamics of oxides reduction on the height and radius of the blast furnace have been carried out.

scholarly journals Characterization of the Binding of Adenosine Diphosphate to Human Platelet Membranes

1977 ◽  
Author(s):  
C. Legrand ◽  
B. Bauvois ◽  
J. P. Caen
Keyword(s):  
Binding Sites ◽  
Plasma Membranes ◽  
Specific Binding ◽  
Adenosine Diphosphate ◽  
Affinity Constant ◽  
Membrane Bound ◽  
High Concentrations ◽  
Kinetics Of

ADP-mediated platelet aggregation is a routinely employed test but its mechanism is poorly understood. The aim of this study was to compare the binding of ADP to plasma membranes isolated from normal platelets and thrombasthenic platelets (which do not aggregate with ADP). Binding of ADP to isolated membranes was assayed by incubation with 14C-ADP followed by Mill i pore filtration. In standard conditions, 14C-ADP was not transformed and non specific binding represented lessthan 3 % of the total binding. Using 1 μM 14C-ADP, the binding has been shown to be a rapid (t 1/2 = 2 mn 30 sec), saturable and reversible phenomenon at 37° C. The existence of a major population of binding sites, with an affinity constant Ka = 0.43 (+ 0.1) χ 106M-1, has been demonstrated. The kinetics of the binding was normal with membranes Tsolated from the platelets of 4 thrombasthenic patients and the affinity constant, when determined, was in the normal range. Dissociation of the membrane-bound 14C-ADP occurred rapidly at 37° C (t l/2c≃3mn) when samples were diluted enough (dilution 1 : 100 was currently employed) to avoid rebinding of the radioligand. Accelerated dissociation (t 1/2 ≃ 1 mn) was observed when the dilution was performed in the presence of an excess of unlabeled ADP, suggesting the existence of negatively cooperative site-site interactions among the ADP binding sites. This effect was only observed at high concentrations of ADP (> 10–5M) and its eventual role in vivo remains to be established. Two thrombasthenic membrane preparations studied in the same way dissociated as did the control membranes.

The binding of insulin-like growth factor II to the erythroleukemia cell line K562

1984 ◽  
Vol 4 (12) ◽  
pp. 1071-1077 ◽  
Author(s):  
Michael Tally ◽  
Tang Xin-Zhi ◽  
Gösta Enberg ◽  
Kerstin Hall
Keyword(s):  
Growth Factor ◽  
Cell Line ◽  
Specific Binding ◽  
Affinity Constant ◽  
Scatchard Analysis ◽  
Insulin Like Growth Factor ◽  
Factor Ii ◽  
Igf I ◽  
Erythroleukemia Cell ◽  
High Concentrations

The erythroleukemia cell line K562 was previously shown to have specific binding sites for insulin but not for insulin-like growth factor I (IGF-I). In this study the presence of specific receptors for insulin-like growth factor II (IGFqI) is established. Scatchard analysis of the competition curve for IGF-II disclosed a non-cooperative binding kinetic with a calculated affinity constant of 2.4 × 108 M−1 and a receptor number of 4.8 × 104 sites/cell. IGF-I displayed 10% crossreactivity over the IGF-II receptor but insulin did not crossreact at all. Instead insulin, present in high concentrations, enhanced the binding of IGF-II. The presence of IGF II but not IGF-I receptors makes the K562 cell line suitable for studying properties of the type-2 receptor.

scholarly journals Tigecycline attenuates polymorphonuclear leukocyte (PMN) receptors but not functions

2011 ◽  
Vol 61 (3) ◽  
pp. 297-302 ◽  
Author(s):  
Are Naess ◽  
Hristina Andreeva ◽  
Steinar Sørnes
Keyword(s):  
Staphylococcus Aureus ◽  
Flow Cytometry ◽  
Oxidative Burst ◽  
Polymorphonuclear Leukocyte ◽  
Polymorphonuclear Leukocytes ◽  
Complement Receptors ◽  
Fcγ Receptors ◽  
Human Pmns ◽  
Intracellular Concentrations ◽  
High Concentrations

Tigecycline attenuates polymorphonuclear leukocyte (PMN) receptors but not functionsTigecycline achieves high intracellular concentrations in polymorphonuclear leukocytes (PMNs). To evaluate the effects of tigecycline on human PMNs, PMNs were incubated with tigecycline dilutions (0.1 to 100 mg L-1). Phagocytosis-associated PMN Fcγ- and complement receptors as well as phagocytosis and oxidative burst induced byStaphylococcus aureuswere measured by flow cytometry. Incubation with tigecycline caused small but significant decreases in the density of complement receptors CD11b and CD35 (all concentrations) and Fcγ receptors CD16 and CD32 (high concentrations), but not in the percentages of receptor-bearing cells, except for small reductions in the proportions of CD16 positive cells at high concentrations. Tigecycline had no effect on phagocytosis or oxidative burst induced byS. aureus. Tigecycline was thus associated with decreased density of PMN complement and (at high concentrations) Fcγ receptors. Although statistically significant, the differences were small and did not influence the PMN function as measured by phagocytosis and oxidative burst.

scholarly journals Steady-state kinetics of catecholamine transport by chromaffin-granule ‘ghosts’

1974 ◽  
Vol 144 (2) ◽  
pp. 319-325 ◽  
Author(s):  
J H Phillips
Keyword(s):  
Steady State ◽  
Competitive Inhibitor ◽  
Affinity Constant ◽  
Chromaffin Granule ◽  
Affinity Constants ◽  
Steady State Kinetics ◽  
Low Concentrations ◽  
High Concentrations ◽  
Chromaffin Granule Ghosts ◽  
Kinetics Of

Resealed chromaffin-granule ‘ghosts’ were used to study the steady-state kinetics of catecholamine transport. The pump has a high affinity for (-)-noradrenaline, (-)-adrenaline, tyramine and 5-hydroxytryptamine (serotonin), but a lower affinity for (+)-noradrenaline. The measured rates of incorporation do not conform to Michaelis–Menten kinetics, but affinity constants for the former substrates are in the range 8–18μm. Reserpine is a potent inhibitor. Incorporation as a function of ATP concentration also fails to show simple kinetics; the affinity constant for ATP is deduced to be about 3mm at 1mm-MgCl2. Adenylyl (βγ-methylene)diphosphonate is a competitive inhibitor at low concentrations, but inhibits more strongly at high concentrations. The pump has a transition temperature at 29°C and does not seem to be identical with the Mg2+-stimulated adenosine triphosphatase of chromaffin granules.

Efficacy and specificity of monoclonal antibodies to progesterone in preventing the establishment of pregnancy in the mouse

1988 ◽  
Vol 118 (1) ◽  
pp. 69-80 ◽  
Author(s):  
S. T. Ellis ◽  
R. B. Heap ◽  
A. R. Butchart ◽  
V. Rider ◽  
N. E. Richardson ◽  
...  
Keyword(s):  
Monoclonal Antibody ◽  
Monoclonal Antibodies ◽  
Effective Dose ◽  
Half Life ◽  
Slow Rate ◽  
Affinity Constant ◽  
High Affinity ◽  
Mouse Immunoglobulin ◽  
High Concentrations ◽  
Ig G

ABSTRACT Anti-progesterone monoclonal antibody prevents the establishment of pregnancy in BALB/c mice by the prevention of implantation when injected i.p. 32 h after mating. To determine the specificity of this effect, mice were injected with immune and non-immune purified mouse immunoglobulins. The results show that anti-implantation efficacy was due to high-affinity antibody which bound progesterone since two further mouse immunoglobulin (Ig) G1 preparations, mouse IgA and mouse IgM which failed to bind the steroid, had no effect on pregnancy rates. From a panel of anti-progesterone monoclonal antibodies, six with a high affinity (affinity constant, 0·24–0·80 litres/nmol) and specificity for progesterone were selected for additional studies. Anti-implantation efficacy for five antibodies was similar, with a 50% effective dose within the range of 0·8–2·0 nmol. Antibody reached high concentrations in plasma within 12 h after i.p. injection, and declined with a half-life of about 80 h. Purified F(ab′)2 fragments of antibody also bound progesterone, but were less effective than the native molecule in blocking pregnancy. The results show that implantation in the mouse can be blocked by a high-affinity antibody that binds progesterone and which is removed from the blood at a slow rate. J. Endocr. (1988) 118, 69–80

scholarly journals Monovalent fragments (Fab) of monoclonal antibodies to a sporozoite surface antigen (Pb44) protect mice against malarial infection.

1980 ◽  
Vol 151 (6) ◽  
pp. 1504-1513 ◽  
Author(s):  
P Potocnjak ◽  
N Yoshida ◽  
R S Nussenzweig ◽  
V Nussenzweig
Keyword(s):  
Monoclonal Antibodies ◽  
Plasmodium Berghei ◽  
Passive Transfer ◽  
Cross Linking ◽  
Antibody Concentration ◽  
Complete Protection ◽  
Degree Of Protection ◽  
Malarial Infection ◽  
Fab Fragments ◽  
High Concentrations

Monoclonal antibodies (IG1, k) directed against a surface component of Plasmodium berghei sporozoites (Pb-44) confer complete protection to mice against a lethal inoculum of parasites. The degree of protection is a function of the number of parasites used in the challenge and of the antibody concentration in serum. Passive transfer of 10 micrograms of antibody per mouse abolished or profoundly diminished the infectivity of 10(3) sporozoites, but much higher amounts of antibody were required for complete protection against challenge with 10(4) parasites. Fab fragments of the monoclonal antibodies were as effective as the intact antibodies in mediating protection as determined by the neutralizing assay. This observation suggests that the antibodies interfere with a parasite function necessary for its infectivity, such as, for example, the ability to penetrate into the target cell or to multiply in the hepatocytes. When sporozoites are incubated with the intact monoclonal antibodies at 37 degrees C, a long filament appears at its posterior end (circumsporzoite precipitation [CSP] reaction). Fab fragments are ineffective at high concentrations. However, if after treatment with Fab, the sporozoites are incubated with rabbit antibodies to mouse k-chains, a strong CSP reaction is observed. We conclude that the CSP reaction can result from the cross-linking of Pb44 and that it has the characteristics of a capping reaction followed by the shedding of the immune complexes.

scholarly journals Inhibition of hormonal induction of tyrosine aminotransferase by polyamines in freshly isolated rat hepatocytes

1983 ◽  
Vol 214 (3) ◽  
pp. 679-685 ◽  
Author(s):  
P Auberger ◽  
M Samson ◽  
A Le Cam
Keyword(s):  
Enzyme Activity ◽  
Rat Hepatocytes ◽  
Fold Increase ◽  
Dose Dependence ◽  
Tyrosine Aminotransferase ◽  
Enzyme Inactivation ◽  
Post Translational Modification ◽  
Isolated Rat Hepatocytes ◽  
Hormonal Induction ◽  
High Concentrations

We have analysed the effects of natural aliphatic polyamines on hormonal induction of tyrosine aminotransferase (TAT) in suspensions of hepatocytes isolated from adult fed rats. Glucagon or cyclic AMP derivatives (dibutyryl and 8-bromo) used alone caused a 4-5 fold increase in enzyme activity within 4h. This effect was independent of glucocorticoids, which also increased TAT activity (2.5-fold); when combined, the effects of the two inducers were additive. Spermine and putrescine totally inhibited the hormonally-mediated increase in enzyme activity when added at the onset of incubation with the inducers. Furthermore, polyamines could block the hormonal effect at any time during the course of TAT induction, with, however, a 30 min lag period, suggesting that they must enter the cells. Hepatocytes were indeed shown to take up spermine. At low external concentrations (less than 50 microM), an Na+-dependent, saturable and concentrative mechanism was predominant; at high concentrations (greater than 0.5 mM) transport occurred mainly through a non-saturable, Na+-independent mechanism, building up intracellular concentrations slightly lower than those in the medium. Dose-dependence analysis of the polyamine effect on enzyme induction indicated that half-maximal and maximal inhibition occurred with 0.75 mM- and 2.5 mM-spermine respectively, whereas 2.5mM- and 7.5 mM-putrescine were required respectively to obtain similar effects. Spermidine was much less effective and cadaverine had virtually no effect. None of the polyamines affected the rate of decay of TAT, nor did they directly or indirectly cause enzyme inactivation, indicating that a post-translational modification was unlikely to account for the polyamine effects. Similarly, these effects could not be ascribed to a non-specific inhibition of overall protein synthesis. We conclude that, in hepatocytes, polyamines (or their metabolites) directly interfere with one or several steps controlled by hormones in the synthesis of tyrosine aminotransferase.

Postprandial free fatty acids stimulate activity of human corticosteroid binding globulin

1995 ◽  
Vol 269 (6) ◽  
pp. E1067-E1075 ◽  
Author(s):  
M. Haourigui ◽  
S. Sakr ◽  
M. E. Martin ◽  
N. Thobie ◽  
A. Girard-Globa ◽  
...  
Keyword(s):  
Fatty Acids ◽  
Free Fatty Acids ◽  
Binding Activity ◽  
Affinity Constant ◽  
Binding Studies ◽  
Vitro Binding ◽  
Corticosteroid Binding Globulin ◽  
High Concentrations ◽  
Mixed Oil

The effect of postprandial variation of free fatty acids (FFA) on serum corticosteroid binding globulin (CBG) properties and cortisol (hydrocortisone) concentrations were explored in 11 women (20-30 yr) during 8 h after an oral load of tallow (26% C16:0, 18% C18:0, and 43% C18:1), oleic-sunflower (oleic-SF; 73% C18:1), sunflower (SF; 67% C18:2), and mixed oil (MO; 39% C18:1 and 48% C18:2). Serum FFA increased little after SF and MO but more than doubled in the late postprandial period (6 and 8 h) after oleic-SF (due to monounsaturated FFA) or tallow (due to saturated and monounsaturated FFA). CBG concentrations remained unchanged, but in relation with the postprandial elevation of serum FFA, CBG binding activity was increased after tallow or oleic-SF as a result of a combined two- to threefold increase in affinity constant and a 50% reduction in binding sites. Immunological and in vitro binding studies showed the changes in CBG behavior to be conformational and to be mediated mainly by monounsaturated FFA, especially C18:1. The modifications of CBG properties were associated with sustained high concentrations of cortisol (suppression of midday decrease) 6 and 8 h after tallow or oleic-SF. Thus dietary FFA may have an impact on bioavailability of glucocorticoids.

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