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Showing papers on "Receptor published in 1979"


Journal ArticleDOI
TL;DR: In cell cultures of glial character derived from perinatal mouse brain adenosine elicits two effects; at submicromolar concentrations it inhibits the increase in the intracellular level of cyclic AMP caused by β‐adrenoceptor agonists and at concentrations above micromolar it increases the level of CyclicAMP in the cultures.
Abstract: — In cell cultures of glial character derived from perinatal mouse brain adenosine elicits two effects. (a) At submicromolar concentrations It inhibits the increase in the intracellular level of cyclic AMP caused by β-adrenoceptor agonists. (b) At concentrations above micromolar it increases the level of cyclic AMP in the cultures. These two effects are mediated by two different adenosine receptors present on the outer surface of the cells. This is concluded from the following evidence. (a) Both effects are antagonized by methylxanthines but not by blockage of adenosine uptake or inhibition of phosphodiesterase activity. (b) In both cases activity depends on the integrity of the ribose moiety of the nucleotide. Substituents of the purine system are tolerated comparatively well. (c) The order of potency of adenosine analogues is different for the two effects. We suggest the name A1 receptors for those that mediate the inhibition and A2 for those that mediate the stimulation of cyclic AMP accumulation.

1,370 citations



Journal ArticleDOI
TL;DR: It is proposed that the number and the distribution of ACh receptors in skeletal muscle are controlled by modulation of receptor metabolism and modulation of associations between receptor molecules or between receptors and other, as yet unidentified, elements in neuromuscular junctions and at extrajunctional sites where receptors are clustered.
Abstract: An ACh receptor is the molecular entity that, in its native habitat, possesses the binding sites for ACh and all the other components required to generate the ion channels mediating the ACh response. Narrower definitions of an ACh receptor (as the binding site for ACh or the polypeptide chain that is folded to form the binding site) could lead to semantic arguments about receptor structure. Experimentally, ACh receptors are defined by their total function (when electrophysiological tests are used) or by ligand binding. There is no evidence that the ligand-binding portions of ACh receptors ever exist in vivo without the associated channel-forming mechanism and vice versa. Most data are consistent with the idea that detergent-solubilized glycoproteins retaining the ACh binding sites of the receptor also include the channel-forming components, although it appears that the mechanism is prone to denaturation or proteolytic damage. Studies of receptor-rich membranes and of solubilized receptor glycoprotein have not yet yielded a totally satisfactory image of receptor structure. Most evidence favors an ACh receptor composed of three or four different types of glycosylated polypeptide chains organized into a unit of aggregate molecular weight about 300,000--400,000 daltons. Plasma membranes are dynamic structures in two different ways. First, their constituent molecules are in rapid thermal motion and, when these molecules are not tethered to extramembranous structures or mired in large aggregates, they fairly rapidly change their position in the plane of the lipid bilayer. Second, all membrane components are continually being synthesized and degraded. Acetylcholine receptors participate in both aspects of this dynamism. In this review it is proposed that the number and the distribution of ACh receptors in skeletal muscle are controlled by modulation of receptor metabolism and modulation of associations between receptor molecules or between receptors and other, as yet unidentified, elements in neuromuscular junctions and at extrajunctional sites where receptors are clustered. The arrangements of receptors in skeletal muscle and the total number of receptors in skeletal muscle may be regulated by separate mechanisms. Clusters of ACh receptors apparently can form spontaneously in extrajunctional areas of denervated muscles and in tissue-cultured embryonic muscle. Such clusters may be positionally stable and the receptor molecules in them may be highly restricted in mobility. Nevertheless, these receptors have average lifetimes on the order of 20 h, just like the nonclustered, mobile extrajunctional receptors. Receptor clusters also form at sites of innervation. In the chick embryo the junctional receptor molecules remain short-lived. The metabolism of ACh receptors is highly regulated. The biosynthesis of receptors commences during myogenesis at about the time myogenic cells become competent to fuse. Later, biosynthesis is dramatically repressed by muscle activity and possibly by other factors...

683 citations


Journal ArticleDOI
TL;DR: A cell line established from the pleural effusion of a patient with breast carcinoma exhibits epithelial morphology and form monolayers in culture, supported by immunohistologic detection of intracellular casein and the presence of steroid receptors characteristic of mammary tissue.

670 citations



Journal Article
TL;DR: Results indicate that a major mechanism of glucocorticoid-mediated immunosuppression may occur at the level of the TCGF-producing cell, resulting in the control of clonal expansion of activated T cells via inhibition of TCGF production.
Abstract: Although it has been clearly established that glucocorticoids inhibit mitogen- or antigen-induced lymphocyte proliferation, the mechanism underlying this effect has remained ill-defined. Recently, it has become evident that T cell proliferation is mediated by a soluble T cell growth factor (TCGF) released by mitogen/antigen stimulated T cells. Therefore it seemed probable that the inhibitory effects of glucocorticoids were manifested either at the level of TCGF production or at the level of the activated T lymphocyte. We found that differentiated cytolytic T lymphocytes harvested from TCGF-dependent long-term culture were only mildly sensitive to inhibitory effects (25 to 30% inhibition) of glucocorticoids as measured by decreased cellular proliferation and the incorporation of tritiated thymidine. The degree of inhibition observed was most probably mediated through glucocorticoid receptors in that the half maximal inhibitory glucocorticoid concentration correlated with half-maximal glucocorticoid receptor saturation. In contrast, we found that mitogen-induced TCGF production and T cell proliferation were completely inhibited by pharmacologic concentrations of dexamethasone (10 -6 M). Finally, the TCGF supplementation of mitogen-stimulated cultures treated with maximal inhibitory concentrations of dexamethasone resulted in complete amelioration of glucocorticoid suppression. These results indicate that a major mechanism of glucocorticoid-mediated immunosuppression may occur at the level of the TCGF-producing cell, resulting in the control of clonal expansion of activated T cells via inhibition of TCGF production.

581 citations



Journal ArticleDOI
12 Jul 1979-Nature
TL;DR: Receptor number is determined by hormone-induced changes in membrane conformation, irreversible ligand binding, and processing of ligand–receptor complexes during hormone action.
Abstract: Regulation of plasma membrane receptors for peptide hormones by the prevailing ligand concentration often causes altered target cell function. Receptor number is determined by hormone-induced changes in membrane conformation, irreversible ligand binding, and processing of ligand–receptor complexes during hormone action.

518 citations


Journal ArticleDOI
31 May 1979-Nature
TL;DR: TPA (12-O-tetradecanoyl-phorbol-13-acetate) reversibly inhibits the binding of 125I-labelled epidermal growth factor to treated mouse and human cells, but does not affect the bindingof various other ligands to their membrane receptors.
Abstract: TPA (12-O-tetradecanoyl-phorbol-13-acetate) reversibly inhibits the binding of 125I-labelled epidermal growth factor (EGF) to treated mouse and human cells, but does not affect the binding of various other ligands to their membrane receptors. It alters the affinity of the receptors for EGF without changing the total number of available receptors per cell. Those phorbol esters which stimulate cell growth in culture and have tumour-promoting activity in vivo alter the EGF-receptor affinity, while the biologically inactive derivatives fail to change the affinity of EGF for its receptors.

479 citations


Journal ArticleDOI
TL;DR: 3H-Prazosin binding to membranes from rat brain is saturable, Bmax, 77 fmol/mg protein, of high affinity, KD, 0.28 nM and with a drug specificity indicating that it labels alpha-adrenergic receptors, suggesting that it may be useful in identifying a subpopulation of alpha-receptors (alpha1) in the central nervous system.

417 citations


Journal Article
TL;DR: The nonlinear Hofstee plots are consistent with there being two types of binding sites in each of the tissues with different affinities for the drugs, and suggest that β-2-adrenergic receptors in rat brain are associated with a more homogeneously distributed cellular element than are β-1-adRenergic receptors.
Abstract: A method for determining the relative concentrations and properties of β-1 and β-2-adrenergic receptors in tissues containing both receptor subtypes has been developed. Since (125I)-iodohydroxybenzylpindolol has similar affinities for β-1 and β-2-adrenergic receptors, it is possible to determine the total concentration of β-adrenergic receptors in a tissue by Scatchard analysis of specific (125I)-iodohydroxybenzylpindolol binding. In the presence of GTP, inhibition of specific (125I)-iodohydroxybenzylpindolol binding in rat heart, lung and five regions of rat brain by agonists and antagonists that are not specific for β-1 or β-2-adrenergic receptors yields linear Hofstee plots with Hill coefficients of approximately 1.0. On the other hand, the inhibition of specific (125I)-iodohydroxybenzylpindolol binding by drugs which have been shown to have different affinities for heart (β-1) and lung (β-2) receptors in vitro results in nonlinear Hofstee plots in each of these tissues. Two of these drugs (practolol and metoprolol) are more potent on β-1 than β-2 receptors and two of these drugs (zinterol and salmefamol) are more potent on β-2 than on β-1 receptors. The nonlinear Hofstee plots are consistent with there being two types of binding sites in each of the tissues with different affinities for the drugs. The relative number of each type of binding site and the affinity of each drug for each of the two types of site has been calculated using a computer based iterative procedure. Using this method, the relative percentages of the two receptor subtypes in rat heart, lung, cerebral cortex, caudate, cerebellum, hippocampus and diencephalon were determined. In each tissue, the use of four different drugs with different in vitro selectivity (two β-1 selective and two β-2 selective) resulted in approximately the same calculated β-1/β-2 ratio. This suggests that the assumption that the nonlinear Hofstee plots are composed of only two components is correct. In addition, the calculated affinity of each drug for β-1 and β-2 receptors was quantitatively similar in each of the seven tissues examined. The calculated ratios of β-l:β-2-adrenergic receptors are: heart 83:17; lung 15:85; cortex 81:19; caudate 76:24; cerebellum 15:85; hippocampus 81:19; and diencephalon 71:29. The absolute concentrations of β-1-adrenergic receptors in the brain regions examined varied by almost 20-fold. However, the absolute concentration of β-2-adrenergic receptors varied less than 3-fold. This suggests that β-2-adrenergic receptors in rat brain are associated with a more homogeneously distributed cellular element than are β-1-adrenergic receptors.

Journal ArticleDOI
22 Jun 1979-Science
TL;DR: Ovarian steroids participate in the regulation of oxytocin receptors in a manner as yet unclarified and may regulate the response of the target organs to circulating Oxytocin and thereby control the onset of labor and lactation.
Abstract: Specific binding of tritiated oxytocin to uterine receptors of pregnant rats increases dramatically at term and is maximal during labor. In mammary glands the increase in binding is gradual, reaching a maximum during the lactation period. Concomitant changes in the sensitivity of the uterus and mammary gland to oxytocin indicate that the receptor concentration is of functional significance. Oxytocin receptors, therefore, may regulate the response of the target organs to circulating oxytocin and thereby control the onset of labor and lactation. Ovarian steroids participate in the regulation of oxytocin receptors in a manner as yet unclarified.

Journal ArticleDOI
TL;DR: Several new lines of evidence suggest the existence of two or more distinct types of benzodiazepine receptors, in contrast to earlier results suggesting the presence of only one class of receptors.
Abstract: Several new lines of evidence suggest the existence of two or more distinct types of benzodiazepine receptors, in contrast to earlier results suggesting the presence of only one class of receptors. Appropriate thermoinactivation experiments indicate two receptors with different thermostabilities. Several triazolopyridazines, with some of the pharmacological properties of anxiolytics have recently been shown to displace 3H-diazepam and 3H-flunitrazepam with Ki values in the 6 to 100 nanomolar range. These new substances are active in conflict tests in rats and monkeys and prevent metrazol induced seizures in vivo, but strikingly lack the ataxia and sedative properties of the benzodiazepines. Hill analyses of dose-response curves for some of these substances yields Hill coefficients in the range of 0.4--0.6, suggesting that these compounds may be able to discriminate between several types of benzodiazepine receptors.

Journal ArticleDOI
07 Sep 1979-Science
TL;DR: Iodinated beta H-[2-D-alanine]endorphin exhibits specific binding to cultured human lymphocytes, which suggests the existence of a specific, non-opiate binding site (receptor) for beta- endorphin.
Abstract: Iodinated beta H-[2-D-alanine]endorphin exhibits specific binding to cultured human lymphocytes The binding is inhibited by low concentrations of beta-endorphin and its D-alanine derivative, but is not affected by opiate agonists and antagonists, or by enkephalin analogs, beta-lipotropin, adrenocorticotrophic hormone, or alpha-melanocyte-stimulating hormone; this suggests the existence of a specific, non-opiate binding site (receptor) for beta-endorphin The carboxy-terminal region of beta-endorphin is essential for this binding activity, since alpha-endorphin is not active beta-Endorphin may be a circulating hormone with peripheral physiological effects that are not primarily mediated through interactions with opiate or enkephalin receptors

Journal ArticleDOI
TL;DR: Investigations of plasma membrane transferring receptors on a variety of lymphoid cell lines and normal peripheral blood lymphocytes during activation and cell growth cycles anticipate nuclear changes during cell activation and subsequent mitosis of normal cells.
Abstract: This report describes investigations of plasma membrane transferring receptors on a variety of lymphoid cell lines and normal peripheral blood lymphocytes during activation and cell growth cycles. Transformed lymphoid cell lines have as many as 1,000 times the number of receptors found on normal resting lymphocytes. The number of iron transferrin receptors on continuous cell lines as well as normal human fibroblasts is down-regulated during the transition from log-phase growth to stationary plateau growth. When normal lymphocytes are transformed by mixed lymphocyte culture or mitogens, they rapidly express a 50-fold increase in the number of transferrin binding sites. This appearance of iron transferrin receptors anticipates nuclear changes during cell activation and subsequent mitosis of normal cells.

Journal ArticleDOI
TL;DR: Brain insulin and brain receptor content, which is equivalent to receptor content on peripheral tissues, appears to be regulated entirely independently of hormone and receptor in the periphery, consistent with the hypothesis that insulin in the central nervous system is synthesized by the neural elements, and plays a role in thecentral nervous system which is unrelated to peripheral glucose metabolism.
Abstract: In view of the potent influences of the central nervous system on glucose metabolism and on its hormonal regulators, and our recent finding of insulin and insulin receptors throughout the central nervous systsem, we have examined extreme conditions of hyperinsulinemia (obese mice) and hypoinsulinemia (streptozotocin-treated rats) with respect to changes in brain insulin and receptor content. Sprague-Dawley rats given streptozotocin (100 mg/kg body wt) developed severe diabetes and by 48 h showed no change in brain insulin. Rats given 65 mg/kg streptozotocin also had severe diabetes, but survived longer. Both at 7 d and at 30 d after streptozotocin treatment there was no significant change in brain insulin or in brain content of insulin receptors, despite the fact that peripheral hepatic receptors were elevated and pancreatic insulin was markedly depleted. The obese mice were studied at 8-10 wk when peripheral plasma insulin concentrations were 50-fold elevated and receptors on peripheral target cells were reduced to congruent with40-50% of normal; brain insulin concentrations and receptor content were indistinguishable from those of thin littermates. Thus, brain insulin, which is typically 10 times higher than plasma insulin concentrations, and brain receptor content, which is equivalent to receptor content on peripheral tissues, appears to be regulated entirely independently of hormone and receptor in the periphery. These findings are consistent with the hypothesis that insulin in the central nervous system is synthesized by the neural elements, and plays a role in the central nervous system which is unrelated to peripheral glucose metabolism.

Journal ArticleDOI
25 May 1979-Science
TL;DR: The results suggest that the beta-adrenergic receptors in rat cortex involved in neuronal function are primarily of the beta1 subtype.
Abstract: Repeated administration of the tricyclic antidepressant desmethylimipramine to adult rats for 10 days caused a 40% decrease in the density of beta1-adrenergic receptors in the cerebral cortex but had no effect on the density of beta2-adrenergic receptors. Conversely, destruction of noradrenergic neurons by administration of 6-hydroxydopamine to neonatal rats caused a 64% increase in the density of beta1-adrenergic receptors in adult cerebral cortex with no change in the density of beta2-adrenergic receptors. These results suggest that the beta-adrenergic receptors in rat cortex involved in neuronal function are primarily of the beta1 subtype.

Journal ArticleDOI
TL;DR: Findings indicate that enhancement of phospholipid methylation by L-isoproterenol decreases membrane microviscosity and thus increases lateral movement of the beta-adrenergic receptors and coupling with adenylate cyclase.
Abstract: The beta-adrenergic agonist L-isoproterenol stimulated the enzymic synthesis of phosphatidyl-N-monomethylethanolamine and phosphatidylcholine in rat reticulocyte ghosts containing the methyl donor S-adenosyl-L-methionine. The stimulation was stereospecific, dose-dependent, and inhibited by the beta-adrenergic agonist propranolol. The addition of GTP inside the resealed ghosts shifted the dose-response of phospholipid methylation by L-isoproterenol to the left by 2 orders of magnitude. Direct stimulation of adenylate cyclase [ATP pyrophosphate-lyase (cyclizing), EC 4.6.1.1] with sodium fluoride or cholera toxin did not increase the methylation of phospholipids. At a concentration of S-adenosyl-L-methionine that stimulates synthesis of phosphatidyl-N-monomethylethanolamine, the activity of isoproterenol-sensitive adenylate cyclase was increased 2-fold without changes in the basal activity of adenylate cyclase and the number of beta-adrenergic receptors. The increase of phospholipid methylation by L-isoproterenol decreased membrane viscosity and increased translocation of methylated lipids. These findings indicate that enhancement of phospholipid methylation by L-isoproterenol decreases membrane microviscosity and thus increases lateral movement of the beta-adrenergic receptors and coupling with adenylate cyclase.

Journal ArticleDOI
TL;DR: It was established that the binding activity could be restored to the canine or human E apoproteins following apo-E l DMPC complex formation and phospholipids appear to function not only to bind the apoprotein but also to confer to the E apobrotein the requisite physical state or conformation required for its binding to the cell surface receptor.

Journal ArticleDOI
24 May 1979-Nature
TL;DR: It is demonstrated that specific, high-affinity LH/hCG receptors can be induced by FSH in isolated granulosa cells cultured in a chemically defined medium, but not in isolatedgranulosa Cells cultured with serum.
Abstract: THE rat ovarian granulosa cell is an excellent model for studying the mechanisms and control of hormone-dependent cell differentiation. During graafian follicle development, the granulosa cells sequentially develop specific membrane receptor sites for follicle-stimulating hormone (FSH)1,2 and luteinising hormone (LH)3. In vivo studies on the mechanism of granulosa cell differentiation have established that FSH induces the appearance of the LH receptor sites in the granulosa cell4,5. The FSH-induced increase in LH receptors is essential for preparing the graafian follicle for the pre-ovulatory surge of LH which initiates ovulation and subsequent luteinisation of the granulosa cells. Studies of cultured granulosa cells have led to the suggestion that the FSH induction of LH receptors is not a direct process but requires an interaction between the granulosa cell and other ovarian cell types, a concept consistent with the known importance of cell–cell interaction in cell differentiation6. This hypothesis stemmed from the observation that LH receptors can be induced by FSH in granulosa cells in vivo and in organ cultures of intact ovarian follicles, but not in isolated granulosa cells cultured as monolayers in medium containing serum7,8. We show here that the inability of previous workers7,8 to induce LH receptors in isolated granulosa cells may have been due to the use of serum in their tissue culture medium. We demonstrate that specific, high-affinity LH/hCG receptors can be induced by FSH in isolated granulosa cells cultured in a chemically defined medium, but not in isolated granulosa cells cultured with serum. In addition, we show that these receptors are capable of mediating important steroidogenic responses.

Journal ArticleDOI
15 Mar 1979-Nature
TL;DR: It is reported here that in homogenates of human PRL adenomas, in which dopaminergic agonists act as inhibitors of PRL secretion, basal adenylate cyclase is inhibited by DA and the DA receptors mediating this inhibition have the same pharmacological properties as those regulatingPRL secretion.
Abstract: THERE is evidence for the existence of multiple forms of dopamine (DA) receptors1–3. In particular, some of these receptors are coupled to adenylate cyclase (DA-stimulating enzyme activity), whereas others seem to be independent3–5. These two classes of receptors, which have been designated D-1 and D-2, respectively, would also have different pharmacological properties3. Pituitary mammotroph DA receptors regulating prolactin (PRL) secretion are considered to be typical D-2 receptors. A DA-stimulated adenylate cyclase has not been detected in normal anterior pituitaries3,5,6; furthermore, several studies indicate that cyclic AMP is stimulatory and not inhibitory to PRL secretion7,8. We report here that in homogenates of human PRL adenomas, in which dopaminergic agonists act as inhibitors of PRL secretion, basal adenylate cyclase is inhibited by DA. The DA receptors mediating this inhibition have the same pharmacological properties as those regulating PRL secretion.

Journal ArticleDOI
29 Mar 1979-Nature
TL;DR: The effects of a single and of multiple electroconvulsive shocks (ECS) on rat brain monoaminergic receptor binding sites are investigated and it is reported that the density of β-adrenergic receptors is decreased.
Abstract: CHRONIC administration of either tricyclic antidepressant drugs or monoamine oxidase inhibitors, which are effective in the treatment of endogenous depression, has been shown to decrease the sensitivity of nor adrenaline (NA)-stimulated adenylate cyclase1–5 and to decrease the apparent density of β-adrenergic receptor binding sites in rat brain6–10. This alteration in receptor mechanisms by antidepressant drugs seems to be selective, as neither α-adrenergic nor serotonergic receptor binding in rat cortex is altered by the tricyclic drug desipramine7. It is therefore of interest to know whether other forms of antidepressant intervention alter receptor mechanisms in the brain and if so, whether they display a time course and selectivity similar to that of antidepressant drugs. Here, we have investigated the effects of a single and of multiple electroconvulsive shocks (ECS) on rat brain monoaminergic receptor binding sites and report that the density of β-adrenergic receptors is decreased.

Journal ArticleDOI
TL;DR: Evidence from fetal fibroblast adsorption-elution and aggregated IgG blocking experiments suggested that the LGL with strong expression of Fc receptors were initially cytotoxic “mature” NK-cells, but contact with K-562 “augmented” or “recruited” them to nonselective cytotoxicity.

Journal ArticleDOI
TL;DR: The results suggest that insulin enhances LDL receptor activity by increasing the number of LDL receptors rather than by influencing binding affinity, and provides a mechanism whereby the cell could theoretically increase its supply of cholesterol during times of additional need.
Abstract: Low-density lipoproteins (LDL) receptor activity, as reflected by LDL degradation, was stimulated by the addition of insulin to cultures of human skin fibroblasts. These changes occurred independently of the glucose concentration of the incubation medium and occurred whether or not LDL receptor activity was suppressed. A comparison of the saturation kinetics of LDL receptor activity in the presence and absence of insulin indicated that insulin produced a 35% increase in Vmax with no difference in "apparent Km". These results suggest that insulin enhances LDL receptor activity by increasing the number of LDL receptors rather than by influencing binding affinity. In confirmation, LDL degradation by receptor negative cells was not enhanced by insulin. Sterol synthesis from [14C]acetate was also stimulated by insulin, but egress of cholesterol and cellular cholesterol content were unaffected by the hormone. The effect of insulin on LDL receptors was not dependent on its known ability to enhance cellular DNA synthesis and proliferation, because insulin stimulated LDL receptor activity in cells kept quiescent by maintenance in plasma-derived serum that was devoid of platelet derived growth factor. Nevertheless, the effect of insulin in enhancing LDL receptor number, coupled with stimulation of endogenous cholesterol synthesis, provides a mechanism whereby the cell could theoretically increase its supply of cholesterol during times of additional need.

Journal ArticleDOI
TL;DR: Binding levels of tritium-LSD, presumably associated with postsynaptic 5HT receptors, were reduced 40% to 50% in samples from schizophrenics in three independent studies, whereas no other consistent alteration was observed in levels of binding associated with other receptors or in the activity of GAD.
Abstract: • Frontal cerebral cortex brain samples from schizophrenics and controls have been assayed for binding associated with muscarinic cholinergic, serotonin (5HT), γ-aminobutyric acid (GABA), and β-adrenergic receptors as well as for the activity of the GABA-synthesizing enzyme glutamic acid decarboxylase (GAD). Binding levels of tritium-LSD, presumably associated with postsynaptic 5HT receptors, were reduced 40% to 50% in samples from schizophrenics in three independent studies, whereas no other consistent alteration was observed in levels of binding associated with other receptors or in the activity of GAD. This change in receptor binding levels does not seem to be attributable to postmortem changes, to influences of drugs received by the patients, or to demographic features of the patient populations.

Journal ArticleDOI
TL;DR: The use of [ 3 H] dihydroergocryptine displacement curves generated with selective alpha receptor antagonists coupled with subsequent computer modeling provides a precise and powerful method for quantifying the alpha receptor population of a tissue.

Journal ArticleDOI
02 Aug 1979-Nature
TL;DR: The light microscopic autoradiographic localisation of BZ receptors in mammalian central nervous system (CNS) and, to the authors' knowledge, the first receptor autorardiography in human brain tissue are reported for the first time.
Abstract: THE benzodiazepine (BZ) drugs are used as anxiolytics, hypnotics, anticonvulsants and muscle relaxants. They are the most widely prescribed of all psychotropic drugs and seem to exert their action by binding to a specific receptor site on brain membranes1–2. This receptor appears to interact with neurotransmission mediated by γ-aminobutyric acid (GABA)3–8. Biochemical studies of BZ receptor distributions in brain reveal large regional variations9,10. An increase in resolution of localisation of BZ receptors would provide greater insight into mechanisms of actions of BZs. In this study, we report for the first time the light microscopic autoradiographic localisation of BZ receptors in mammalian central nervous system (CNS) and, to our knowledge, the first receptor autoradiography in human brain tissue. We observed striking variations in receptor densities in different areas which, in some cases, were species dependent.

Journal Article
TL;DR: Several compounds previously reported to be either β-1 (dobutamine) or β-2 (terbutaline and metaproterenol) selective agonists had similar potencies for stimulation of adenylate cyclase from both tissues, but the apparent discrepancy appears to be due to the fact that these drugs which are partial agonists in the lung are competitive antagonists in the heart.
Abstract: The potency and selectivity of a variety of agonists and antagonists were determined for β-1 and β-2 adrenergic receptors on membranes prepared from rat ventricular muscle and lung. Activation or inhibition of β-adrenergic receptor stimulated adenylate cyclase activity and inhibition of specific (125I)-iodohydroxybenzylpindolol binding were used as in vitro measurements of receptor occupancy. With both assays the relative potencies of isoproterenol, epinephrine and norepinephrine with cardiac membranes was approximately 1:10:10, indicating a population of mainly β-1 adrenergic receptors. With membranes from lung the order of potency of these compounds was approximately 1:10:100, indicating a population mainly of β-2 adrenergic receptors. Several drugs previously reported to be β-2 selective agonists (salbutamol, soterenol, salmefamol, zinterol and fenoterol) activated adenylate cyclase in the lung but not in the heart. These compounds turned out to be partial agonists and isoproterenol-stimulated adenylate cyclase activity was inhibited by them in both tissues. Several compounds previously reported to be either β-1 (dobutamine) or β-2 (terbutaline and metaproterenol) selective agonists had similar potencies for stimulation of adenylate cyclase from both tissues. A series of compounds reported to be β-1 selective antagonists were also investigated. Metoprolol and practolol were 10-fold, and atenolol was 3-fold more potent in the heart than the lung. Butoxamhe, a β-2 antagonist, was 2-4 fold more potent in the lung than the heart, while H35/25 showed no specificity. The ability of antagonists to inhibit [125I]-iodohydroxybenzylpindolol binding to membranes prepared from the heart and lung agreed well with their effects on adenylate cyclase. The β-2 selective agonists zinterol and salmefamol also showed a 10-50 fold greater potency in inhibiting [125I]-iodohydroxybenzylpindolol binding in the lung than the heart. However salbutamol, soterenol and fenoterol, which selectively activated adenylate cyclase in the lung, inhibited [125I]-iodohydroxybenzylpindolol binding in the two tissues with equal potency. This apparent discrepancy appears to be due to the fact that these drugs which are partial agonists in the lung are competitive antagonists in the heart, and that the Ki values in the heart are very similar to the K act values in the lung.

Journal ArticleDOI
TL;DR: On the basis of the clgM staining, NALM‐6‐M1 seems to be arrested at an early stage in B‐cell development and is considered to be of the pre‐B cell phenotype possessing a chromosomal abnormality.
Abstract: NALM-6-M1, one of eight leukemia cell lines cultured from the blood of a 19-year-old boy with non-T, non-B acute lymphoblastic leukemia (ALL) in relapse, was characterized. This cell line was found to be more than 90% cytoplasmic Immuno-globulin positive (clg+) for both mu heavy and lambda light chains, but surface immunoglobulln (slg) and complement receptor (CR) negative. NALM-6-M1 was clg∼ for alpha, delta, and gamma heavy chains and kappa light chain. About 45% of the cells exhibited sheep erythrocyte receptors. Approximately 12% of cells were positive for Fc receptors. Approximately 90% of the cultured cells had a deleted long arm of chromosome 5 (5q−) and a marker Y chromosome. The remaining 10% of cells were found to have some additional chromosomal material on the long arm of chromosome 12, suggesting a partial translocation. No other karyotypic abnormalities were found. The cell line was found to react strongly with anti-p23, 30, suggesting la-like activity, but it only weakly stimulated normal lymphocytes in mixed leukocyte culture (MLC). The cells expressed HLA antigens. NALM-6-M1 failed to react with anti-thymocyte serum (ATS), did not possess Epstein-Barr membrane or nuclear antigens, nor did it exhibit phagocytosis for zymosan. NALM-6-M1 reacted positively with oil red O and Sudan black stains. On the basis of the clgM staining, NALM-6-M1 seems to be arrested at an early stage in B-cell development and is considered to be of the pre-B cell phenotype possessing a chromosomal abnormality.

Journal ArticleDOI
TL;DR: In this paper, a biologically active 1:1 conjugate of EGF and ferritin (F-EGF) was used as an indirect marker to localize the receptor for peptide hormone.
Abstract: Previous studies using a biologically active 1:1 conjugate of EGF and ferritin (F-EGF) have traced the binding and internalization of the hormone molecules. In the present report, we develop ultrastructural criteria for identification of the F-EGF·receptor complex, and, thereby, enable utilization of the F-EGF as an indirect marker to localize the receptor for this peptide hormone. The ferritin cores of bound F-EGF are situated 4-6 nm from the extracellular surface of the membrane. When cells were incubated for up to 30 min at 37°C, this characteristic spatial relationship was observed in all uptake stages (surface clustering, endocytosis, and incorporation into multivesicular bodies), indicating that the hormone·receptor complex remains intact through these steps. However, when incubation was continued for periods sufficient to allow hormone degradation (30-60 min), pools of free ferritin were observed in lysosomes. In the presence of various amine inhibitors of hormone degradation, internalization and multivesicular body incorporation proceeded, but hormone·receptor degradation was blocked as evidenced by preservation of the ferritin—membrane relationship; i.e., no pools of free ferritin were seen after 60 min. These data provide morphological support for the hypothesis that down-regulation of surface receptors involves internalization of intact hormone·receptor complexes. In addition, we have developed a method for viewing the surface of intact cells en face, allowing closer scrutiny of the clustering of F-EGF·receptor complexes in the plane of the membrane prior to internalization. The particles in the F-EGF clusters observed by this method are spaced at 12 nm center-to-center, serving to set upper limits on the packing dimensions of the EGF·receptor complex.