Species specific binding constants of atropine to muscarinic receptors

Toxicology ◽  
2007 ◽  
Vol 233 (1-3) ◽  
pp. 238
Author(s):  
R. Bogan ◽  
H. Thiermann ◽  
L. Szinicz
Keyword(s):  
Muscarinic Receptors ◽  
Specific Binding ◽  
Binding Constants ◽  
Species Specific

Specific binding of acrosome-reaction-inducing substance to the head of starfish spermatozoa

Zygote ◽  
1993 ◽  
Vol 1 (2) ◽  
pp. 121-127 ◽  
Author(s):  
Akira Ushiyama ◽  
Takeo Araki ◽  
Kazuyoshi Chiba ◽  
Motonori Hoshi
Keyword(s):  
Acrosome Reaction ◽  
Specific Binding ◽  
Molecular Size ◽  
Polystyrene Latex ◽  
Anterior Region ◽  
Head Region ◽  
Signal Molecule ◽  
Jelly Coat ◽  
Plot Analysis ◽  
Species Specific

In the starfish, spermatozoa undergo the acrosome reaction upon encountering the jelly coat of eggs. A highly sulphated glycoprotein in the jelly coat is called acrosome-reaction-inducing substance (ARIS) because it is the key signal molecule to trigger the acrosome reaction. The activity of ARIS is mainly attributed to its sulphate and saccharide residues. The extremely large molecular size and speciesspecific action of ARIS suggest the presence of a specific ARIS receptor on the sperm surface, but no experimental evidence for the receptor has been presented. We therefore measured specific binding of ARIS and its pronase digest (P-ARIS), which retains the full activity of ARIS, to homologous spermatozoa by using fluorescien-isothiocyanate-labelled ARIS and125 I-labelled P-ARIS, respectively. The spermatozoa had the ability to bind ARIS, as well as P-ARIS, specifically. The binding was species-specific, and mostly localised to the head region of spermatozoa. Scatchard plot analysis indicated the presence of one class of ARIS receptor on the surface of acrosome-intact speramatozoa. Furthermore, the specific binding of P-ARIS to the anterior region of sperm heads was microscopically confirmed by using P-ARIS conjugated to polystyrene latex beads with intense fluorescence. It is concluded that starfish spermatozoa have a specific receptor for ARIS on the surface of the anterior region of heads.

scholarly journals Species-specific rDNA transcription is due to promoter-specific binding factors.

1984 ◽  
Vol 4 (2) ◽  
pp. 221-227 ◽  
Author(s):  
R Miesfeld ◽  
N Arnheim
Keyword(s):  
Rna Polymerase ◽  
Transcriptional Control ◽  
Specific Binding ◽  
Rna Polymerase I ◽  
Rdna Transcription ◽  
Nucleolar Dominance ◽  
Cell Extracts ◽  
Species Specific ◽  
Polymerase I

RNA polymerase I transcription factors were purified from HeLa and mouse L cell extracts by phosphocellulose chromatography. Three fractions from each species were found to be required for transcription. One of these fractions, virtually devoid of RNA polymerase I activity, was found to form a stable preinitiation complex with small DNA fragments containing promoter sequences from the homologous but not the heterologous species. These species-specific DNA-binding factors can explain nucleolar dominance in vivo in mouse-human hybrid somatic cells and species specificity in cell-free, RNA polymerase I-dependent transcription systems. The evolution of species-specific transcriptional control signals may be the natural outcome of a special relationship that exists between the RNA polymerase I transcription machinery and the multigene family coding for rRNA.

Evidence for LH-inhibiting activity in ovine peripheral and testicular blood

1990 ◽  
Vol 123 (3) ◽  
pp. 345-352 ◽  
Author(s):  
V. Papapdopoulos ◽  
P. Kamtchouing ◽  
N. Boujrad ◽  
C. Pisselet ◽  
C. Perreau ◽  
...  
Keyword(s):  
Cyclic Amp ◽  
Breeding Season ◽  
Specific Binding ◽  
Apparent Molecular Weight ◽  
Rete Testis ◽  
Arterial Blood ◽  
Inhibiting Factor ◽  
Arterial Plasma ◽  
Species Specific ◽  
Venous Plasma

Abstract. Intracellular cyclic AMP and testosterone productions by purified mature rat Leydig cells were stimulated by oLH (25 μg/l) 18- and 12-fold, respectively, after a 5-h incubation period. The replacement of the incubation medium by charcoal-treated testicular venous plasma (40%, v/v) from adult rams in the breeding season induced an inhibition of cyclic AMP and testosterone productions (82 and 66%, respectively, of oLH-stimulated values). Testicular arterial plasma is less effective than testicular venous plasma, even when it originates from non-breeding season rams; in that case, testicular venous and arterial plasma strongly inhibit testosterone productions (84 and 67%, respectively of oLH-stimulated values), which probably indicates that the inhibitory activity is higher in the non-breeding season. The addition of peripheral plasma leads to a testosterone production equal to 35 and 65% of the oLH-stimulated values, respectively, for ram blood collected in non-breeding and breeding seasons. The same concentration of ovine testicular lymph or rete testis fluid is without significant effect on cyclic AMP production; however, testosterone is slightly decreased by lymph but enhanced by rete testis fluid. Increasing amounts of venous or arterial testicular blood induce a dose-related decrease of the specific binding of labelled hCG in both rat and ram testicular membranes. This inhibiting factor is present in peripheral and testicular blood of either control or hypophysectomized or castrated rams, is a protein in nature, heat-sensitive, and has an apparent molecular weight higher than 10 000 daltons. These results suggest the existence of a control of LH-specific binding to its receptors and of Leydig cell cyclic AMP and testosterone outputs; these activities are not species-specific and are more concentrated in testicular venous than in arterial blood. The origin of this inhibiting factor remains to be determined, since it is not confined to the testis and not of pituitary origin.

Characterization of muscarinic cholinergic receptors in cat tracheal gland cells

1986 ◽  
Vol 61 (4) ◽  
pp. 1375-1382 ◽  
Author(s):  
D. J. Culp ◽  
M. G. Marin
Keyword(s):  
Muscarinic Receptors ◽  
Specific Binding ◽  
Isolated Cells ◽  
High Affinity ◽  
Gland Cells ◽  
Beta Adrenergic Agonists ◽  
Muscarinic Cholinergic ◽  
Dose Dependent ◽  
Nanomolar Range

Studies of airway glands indicate a muscarinic cholinergic regulation of secretion. Because of the cellular complexity of the airways, receptor characterization in whole tissue is unfeasible. Therefore, we utilized homogenates of disaggregated gland cells isolated from cat trachea and the muscarinic antagonist [1–3H]quinuclidinyl benzilate ([3H]QNB) to characterize glandular muscarinic receptors. Receptors of isolated cells were functionally intact as assessed by carbachol (10(-4) M) stimulation of O2 consumption 86 +/- 6% (+/- SE, n = 20). Stimulation was dose dependent (mean effective concentration = 3.5 microM), inhibited by atropine [dissociation constant (KD) = 4.2 nM] but not phentolamine nor propranolol. Specific binding of [3H]QNB to cell homogenates was saturable, of high affinity (KD = 36 pM) and to a single population of receptors. Maximum binding was 58 fmol/10(6) cells or about 35,000 receptors per cell. Estimated affinities for muscarinic agents were in the micromolar range for agonists and nanomolar range for antagonists. Histamine, alpha-adrenergic, and beta-adrenergic agonists and antagonists did not inhibit specific binding. These results suggest that muscarinic receptors on tracheal gland cells are of high affinity and density.

scholarly journals Determination of the structural basis for selective binding of Epstein-Barr virus to human complement receptor type 2.

1991 ◽  
Vol 174 (6) ◽  
pp. 1299-1311 ◽  
Author(s):  
D R Martin ◽  
A Yuryev ◽  
K R Kalli ◽  
D T Fearon ◽  
J M Ahearn
Keyword(s):  
Epstein Barr Virus ◽  
Specific Binding ◽  
Glycosylation Site ◽  
Single Amino Acid ◽  
Structural Basis ◽  
Viral Receptor ◽  
Barr Virus ◽  
Preferential Binding ◽  
Epstein Barr ◽  
Species Specific

Epstein-Barr virus (EBV) is an oncogenic herpesvirus that selectively infects and immortalizes human B lymphocytes. One determinant of this narrow tropism is human CR2, the only viral receptor within the superfamily of proteins that contain short consensus repeats (SCRs). Human CR2 serves as a receptor for both C3dg and the gp350/220 glycoprotein of EBV, and binds the monoclonal antibody (mAb) OKB7, which blocks binding of both ligands to the receptor. In contrast, although murine CR2 is capable of binding human C3dg and this interaction can be blocked with the mAb 7G6, it does not bind OKB7 or EBV. We have determined the structural basis for absolute specificity of EBV for human CR2 through characterization of a panel of 24 human-murine chimeric receptors, all of which bind human C3dg. The results indicate that preferential binding of EBV to human CR2 is not due to unique amino acids that are capable of binding the virus, but reflects a distinct receptor conformation that can be achieved in murine CR2 with single amino acid substitutions in two discontinuous regions of the primary structure: replacement of proline at position 15 with the corresponding serine from human CR2, and elimination of a potential N-linked glycosylation site between SCR-1 and SCR-2. Furthermore, species-specific binding of EBV, OKB7, and 7G6 can all be manipulated through substitutions among residues 8-15, suggesting that this octapeptide is part of a structural determinant that is critical for binding of both viral and natural ligands to CR2.

Recombinant hamster sperm receptors that exhibit species-specific binding to sperm

Zygote ◽  
1996 ◽  
Vol 4 (3) ◽  
pp. 229-236 ◽  
Author(s):  
Eveline S. Litscher ◽  
Paul M. Wassarman
Keyword(s):  
High Performance ◽  
Specific Binding ◽  
Chinese Hamster ◽  
Size Exclusion ◽  
Mouse Sperm ◽  
Mammalian Sperm ◽  
Ec Cells ◽  
Species Specific ◽  
Mouse Eggs

SummaryPrevious studies have shown that mouse sperm bind to hamster eggs and hamster sperm bind to mouse eggs in vitro. Furthermore, sperm receptor glycoprotein isolated from the zona pellucida of unfertilised hamster (hZP3) and mouse (mZP3) eggs binds to sperm from the heterologous species. Here, we expressed the hZP3 gene, under control of a constitutive promoter (pgk-1), in mouse embryonal carcinoma (EC) cells and Chinese hamster ovary (CHO) cells stably transfected with the hZP3 gene. In both cases, recombinant hZP3 (EC-hZP3 and CHO-hZP3) secreted into the culture medium was partially purified by high-performance liquid chromatography on a size-exclusion column and assayed for bioactivity using mouse and hamster gametes. Unlike hamster egg hZP3, which binds to both mouse and hamster sperm, EC-hZP3 and CHO-hZP3 exhibits species-specific binding to hamster sperm and induce hamster sperm, but not mouse sperm, to undergo the acrosome reaction in vitro. These results provide further evidence that species-specific binding of sperm to eggs in mammals is carbohydrate-mediated. Furthermore, the results suggest that recombinant forms of mammalian sperm receptors may be useful in assessing the molecular basis of species-specific fertilisation in mammals.

The character of the muscarinic receptors in different regions of the rat brain

1980 ◽  
Vol 207 (1166) ◽  
pp. 1-12 ◽  
Keyword(s):  
Rat Brain ◽  
Muscarinic Receptors ◽  
Binding Constants ◽  
Receptor Subunit ◽  
Binding Characteristics ◽  
Brain Receptors ◽  
Single Receptor ◽  
Conformational Constraints ◽  
Binding Curves

The binding characteristics of muscarinic receptors have been critically examined in six regions of the rat brain. The binding curves of antagonists are similar for all six areas but the binding curves of agonists show large differences. It is shown that in all regions there are three classes of receptors with similar binding characteristics but that these are present in different proportions. The binding constants to the three receptor types of a range of agonists were examined and evidence was produced in support of the theory that the subclasses of brain receptors are due to a single receptor subunit subject to different conformational constraints.

scholarly journals Species-specific binding of purified pili (AF/R1) from the Escherichia coli RDEC-1 to rabbit intestinal mucosa

1983 ◽  
Vol 85 (4) ◽  
pp. 837-845 ◽  
Author(s):  
Robert Berendson ◽  
Christopher P. Cheney ◽  
Peter A. Schad ◽  
Edgar C. Boedeker
Keyword(s):  
Escherichia Coli ◽  
Intestinal Mucosa ◽  
Specific Binding ◽  
Species Specific

Effects of age on muscarinic cholinergic receptors in rat myocardium

1983 ◽  
Vol 61 (8) ◽  
pp. 822-829 ◽  
Author(s):  
Njanoor Narayanan ◽  
Jo-Anne Derby
Keyword(s):  
Young Adult ◽  
Muscarinic Receptor ◽  
Muscarinic Receptors ◽  
Specific Binding ◽  
Ventricular Myocardium ◽  
Aged Rats ◽  
Adult Rats ◽  
Related Difference ◽  
Age Related ◽  
Receptor Sites

Atrial and ventricular myocardium from young (3–4 months old), young adult (7–8 months old), and aged (24–25 months old) rats were used to study the influence of age on cardiac cholinergic muscarinic receptors. The density of muscarinic receptors (expressed as fmol/mg protein or pmol/g tissue), determined by the specific binding of [3Hjquinuclidinyl benzyl ate ([3H]QNB), was significantly greater (24–29%) in atria of aged rats compared with that in atria of young or young adult rats. The muscarinic receptor density in ventricles was found to be essentially similar in all age groups studied. Antagonist as well as agonist binding characteristics of muscarinic receptor sites were examined in atria and ventricles from young and aged rats. No significant age-related difference was observed in the dissociation constant (KD) of atrial or ventricular receptors for the antagonist ligand [3H]QNB (KD apparent (nM): 1.04 ± 0.16 and 0.91 ± 0.12, respectively, for young and aged atria; 0.75 ± 0.08 and 0.76 ± 0.10, respectively, for young and aged ventricles). Similarly, the concentrations of muscarinic antagonist atropine and agonist carbachol causing 50% inhibition of [3H]QNB binding to the receptor sites (IC50) in atria and ventricles were not altered by age. Age-related difference was also not evident in the Hill coefficients for [3H]QNB, atropine, and carbachol. These results indicate that diminished responsiveness of the aged heart to vagal stimulation and exogenously administered cholinergic agents reported in the literature cannot be attributed to an age-related reduction in the number of cardiac muscarinic receptors or their affinities toward agonist or antagonist ligands.

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