Molecular Mechanisms Mediating the Action of Diazepam on GABA Receptors

1978 ◽  
Vol 133 (3) ◽  
pp. 239-248 ◽  
Author(s):  
E. Costa ◽  
A. Guidotti ◽  
G. Toffano
Keyword(s):  
Gaba Receptors ◽  
Molecular Mechanisms ◽  
Type A ◽  
Anxiolytic Activity ◽  
The Other ◽  
Synaptic Membranes ◽  
Kinetic Properties ◽  
Endogenous Inhibitor ◽  
High Affinity ◽  
Gaba Binding

SummaryTwo types of crude synaptic membranes have been prepared which differ in their kinetic properties to bind 3H-GABA in a Na+-free medium. One type (B) has one type of receptor (affinity or KD about 0.2 μM), the other type (A) has two populations of receptors which have a high (0.16 μM) and a low (.02 μM) KD for GABA binding. This difference is due to the presence of a selective endogenous inhibitor of the high affinity receptor for GABA, a thermostable protein of about 15,000 molecular weight. Inhibitor action is counteracted by diazepam (7 x 10-7M), competitively. Clonazepam is more active but chlordiazepoxide is less active than diazepam. Two enantiomers of a benzodiazepine were studied. One of them is endowed with anxiolytic activity and nullifies the action of the endogenous inhibitor on high affinity GABA binding, the other is devoid of anxiolytic activity and is inactive against the inhibitor. The endogenous protein inhibitor also competitively blocks the high affinity binding of 3H-diazepam to Type A membranes. It is concluded that the endogenous inhibitor and diazepam act on the same receptor; and suggested that the endogenous inhibitor may be the natural ligand for the brain receptors that bind benzodiazepines with high affinity.

scholarly journals Kinetic parameters of GABA receptor binding by rat adenohypophysis membranes under conditions of modeling various levels of corticosteroids and ACGT in the body

1993 ◽  
Vol 39 (6) ◽  
pp. 43-46
Author(s):  
T. M. Mishunina ◽  
V. Ya. Kononenko
Keyword(s):  
Kinetic Parameters ◽  
Gaba Receptors ◽  
Gaba Receptor ◽  
Plasma Membranes ◽  
Specific Binding ◽  
The Body ◽  
Noticeable Increase ◽  
High Affinity ◽  
Gaba Binding ◽  
Hormonal Levels

Kinetic parameters of l4C-GABA specific binding by rat adenohypophyseal plasma membranes were studied in experiments on modelling various corticosteroid and ACTH levels in animal body. A single hydrocortisone injection did not change Ka for high- and low-affinity GABA receptors, the number of the former (Bmax) increasing in this case. Repeated hydrocortisone injections were associated with Ko reduction for high-affinity GABA receptors and a noticeable increase of Kn for low-affinity receptors, with their number reducing. ACTH injection did not change the kinetic parameters of GABA binding with receptors. The number of high-affinity GABA receptors and their affinity reduced after removal of adrenals whereas the number of low-affinity receptors in this case was increasing. A single hydrocortisone injection to adrenalectomized rats had a normalizing effect on adenohypophyseal GABA receptors. Analysis of the results and changes in blood hormonal levels indicated that affinity changes in high-affinity receptors and changed number of low-affinity adenohypophyseal GABA receptors correlated with changes in ACTH and hydrocortisone changes.

Immunochemical Studies on Antithrombin III

1979 ◽  
Author(s):  
E.J. McKay
Keyword(s):  
Antithrombin Iii ◽  
The Other ◽  
Antigenic Determinants ◽  
Immunochemical Analysis ◽  
Paradoxical Effect ◽  
Test Protocol ◽  
Agar Gel ◽  
High Affinity ◽  
Time Required ◽  
Antigen Antibody

Depressed Antithrombin III (AT) levels Increase thrombic tendency in man, therefore value in assaying this protein has been established. Immunochemical analysis of AT in clinical disease has however proved controversial, consequently systematic studies were undertaken to rationalize the requirements necessary to optimise these methods in particular electro-Immunoassay. The known binding affinity of AT for heparin has been exploited to differentiate high affinity AT from its inhibitor - protease complexes and has resulted in reports stating that heparin added to the agar gel prior to electrophoresis significantly reduces the time required for completion of antigen/antibody complexes. Our studies however have demonstrated that the antibody required for quantitative analysis must be capable of not only reacting with “native” antigenic determinants of AT but also with “neo” antigens that are exposed when inhibitor-protease complexes are formed. Heparin should not be used in the test protocol, for it has a paradoxical effect on Immunopreclpltation in gels, masking some antigenic determinants of unbound - high affinity AT on one hand, and appear to disrupt the Immunoprecipitin “rocket” formed with the inhibitor-protease complexes during electrophoresis on the other.

scholarly journals Analysis of MCM Proteins’ Role as a Potential Target of Statins in Patients with Acute Type A Aortic Dissection through Bioinformatics

Genes ◽  
2021 ◽  
Vol 12 (3) ◽  
pp. 387
Author(s):  
Zheyong Liang ◽  
Yongjian Zhang ◽  
Qiang Chen ◽  
Junjun Hao ◽  
Haichen Wang ◽  
...  
Keyword(s):  
Aortic Dissection ◽  
Molecular Mechanisms ◽  
Vascular Diseases ◽  
Enrichment Analysis ◽  
Type A ◽  
Protective Role ◽  
Gene Expression Omnibus ◽  
Pathway Enrichment Analysis ◽  
Acute Type ◽  
Type A Aortic Dissection

Acute aortic dissection is one of the most severe vascular diseases. The molecular mechanisms of aortic expansion and dissection are unclear. Clinical studies have found that statins play a protective role in aortic dissection development and therapy; however, the mechanism of statins’ effects on the aorta is unknown. The Gene Expression Omnibus (GEO) dataset GSE52093, GSE2450and GSE8686 were analyzed, and genes expressed differentially between aortic dissection samples and normal samples were determined using the Networkanalyst and iDEP tools. Weight gene correlation network analysis (WGCNA), functional annotation, pathway enrichment analysis, and the analysis of the regional variations of genomic features were then performed. We found that the minichromosome maintenance proteins (MCMs), a family of proteins targeted by statins, were upregulated in dissected aortic wall tissues and play a central role in cell-cycle and mitosis regulation in aortic dissection patients. Our results indicate a potential molecular target and mechanism for statins’ effects in patients with acute type A aortic dissection.

NaCl-dependent expression of amiloride-blockable Na+ channel in Xenopus oocytes

1992 ◽  
Vol 262 (2) ◽  
pp. G244-G248 ◽  
Author(s):  
C. Asher ◽  
D. Singer ◽  
R. Eren ◽  
O. Yeger ◽  
N. Dascal ◽  
...  
Keyword(s):  
Xenopus Oocytes ◽  
The Other ◽  
Na Channel ◽  
Channel Activity ◽  
High Affinity ◽  
Other Hand ◽  
Exogenous Rna ◽  
Lower Intestine ◽  
Regulation Of Transport

RNA was isolated from chicken lower intestine (both colon and coprodeum) and injected into Xenopus oocytes. 22Na+ fluxes measured after 1-4 days demonstrated the induction of an amiloride-blockable pathway. The Na+ transporter expressed by the exogenous RNA had a high affinity to amiloride (inhibitory constant less than 0.1 microM), but was insensitive to ethylisopropyl amiloride, i.e., it is likely to be the apical Na+ channel. Functional channels were readily expressed in oocytes injected with RNA derived from chickens fed a low-NaCl diet. On the other hand, no channel activity was detected in oocytes injected with RNA isolated from chickens fed a high-NaCl diet. Thus the previously reported regulation of transport by the dietary NaCl intake involves modulations in the level of mRNA that codes either for the Na+ channel or a posttranscriptional regulator of the channel.

scholarly journals Gating Competence of Constitutively Open CLC-0 Mutants Revealed by the Interaction with a Small Organic Inhibitor

2003 ◽  
Vol 122 (3) ◽  
pp. 295-306 ◽  
Author(s):  
Sonia Traverso ◽  
Laura Elia ◽  
Michael Pusch
Keyword(s):  
Chloride Channels ◽  
Bound State ◽  
Side Chain ◽  
Pore Channel ◽  
Kinetic Properties ◽  
Wild Type ◽  
High Affinity ◽  
Critical Residue ◽  
Fast Gating

Opening of CLC chloride channels is coupled to the translocation of the permeant anion. From the recent structure determination of bacterial CLC proteins in the closed and open configuration, a glutamate residue was hypothesized to form part of the Cl−-sensitive gate. The negatively charged side-chain of the glutamate was suggested to occlude the permeation pathway in the closed state, while opening of a single protopore of the double-pore channel would reflect mainly a movement of this side-chain toward the extracellular pore vestibule, with little rearrangement of the rest of the channel. Here we show that mutating this critical residue (Glu166) in the prototype Torpedo CLC-0 to alanine, serine, or lysine leads to constitutively open channels, whereas a mutation to aspartate strongly slowed down opening. Furthermore, we investigated the interaction of the small organic channel blocker p-chlorophenoxy-acetic acid (CPA) with the mutants E166A and E166S. Both mutants were strongly inhibited by CPA at negative voltages with a >200-fold larger affinity than for wild-type CLC-0 (apparent KD at −140 mV ∼4 μM). A three-state linear model with an open state, a low-affinity and a high-affinity CPA-bound state can quantitatively describe steady-state and kinetic properties of the CPA block. The parameters of the model and additional mutagenesis suggest that the high-affinity CPA-bound state is similar to the closed configuration of the protopore gate of wild-type CLC-0. In the E166A mutant the glutamate side chain that occludes the permeation pathway is absent. Thus, if gating consists only in movement of this side-chain the mutant E166A should not be able to assume a closed conformation. It may thus be that fast gating in CLC-0 is more complex than anticipated from the bacterial structures.

Anatomie, histologie et affinités de l'appareil séricigène des Hersilia Sav. et Aud. (Araneae: Hersiliidae)

1984 ◽  
Vol 62 (1) ◽  
pp. 97-106 ◽  
Author(s):  
Jacqueline Kovoor
Keyword(s):  
Type A ◽  
The Other ◽  
Secretory Cells ◽  
Evolutionary Stage ◽  
Type B ◽  
Outer Coat ◽  
Silk Glands ◽  
Single Protein

Although hersiliid spiders do not spin any webs, their silk glands, which belong to six types, are large and complex. Two groups of ampullate glands, one opening on the anterior spinnerets and the other on the median spinnerets, secrete two proteins each. About 180 pyriform glands are clearly bipartite. Over 200 type A aciniform glands opening on the median and posterior spinnerets are made up of three categories of secretory cells. Silk from these glands consists of two proteins (core and outer coat) joined together by an intermediary layer of acidic glycoprotein. All the 160 type B aciniform glands opening on the posterior spinnerets secrete a single protein. Fifty tubuliform glands opening on the median and posterior spinnerets produce two proteins, one of which is coloured. As in Urocteinae, long posterior spinnerets and large, numerous aciniform and tubuliform glands are correlated with swathing of prey and egg-cocoon construction. In Lycosidae and Agelenidae, the ampullate glands show the same number and distribution according to the spinnerets. However, anatomical and histochemical features of hersiliid aciniform and ampullate glands are close to those of some Araneoidea. Apart from peculiar characteristics, silk glands of Hersilia might represent an intermediate evolutionary stage towards Araneoidea.

scholarly journals Transmembrane-truncated αvβ3 integrin retains high affinity for ligand binding: evidence for an ‘inside-out’ suppressor?

1998 ◽  
Vol 330 (2) ◽  
pp. 861-869 ◽  
Author(s):  
J. Raj MEHTA ◽  
Beate DIEFENBACH ◽  
Alex BROWN ◽  
Eilish CULLEN ◽  
Alfred JONCZYK ◽  
...  
Keyword(s):  
Ligand Binding ◽  
Wound Repair ◽  
Molecular Mechanisms ◽  
Full Length ◽  
Αvβ3 Integrin ◽  
Cytoplasmic Domains ◽  
Bivalent Cation ◽  
High Affinity ◽  
Cellular Environment

The molecular mechanisms of αvβ3 integrin affinity regulation have important biological implications in tumour development, wound repair and angiogenesis. We expressed, purified and characterized recombinant forms of human αvβ3 (r-αvβ3) and compared the activation state of these with αvβ3 in its cellular environment. The ligand specificity and selectivity of recombinant full-length and double transmembrane truncations of r-αvβ3 cloned in BacPAK6 vectors and expressed in Sf9 and High Five insect cells were compared with those of native placental αvβ3 and the receptor in situ on the cell surface. r-αvβ3 integrins were purified by affinity chromatography from detergent extracts of cells (full-length), and from the culture medium of cells expressing double-truncated r-αvβ3. r-αvβ3 had the same epitopes, ligand-binding specificities, bivalent cation requirements and susceptibility to RGD-containing peptides as native αvβ3. On M21-L4 melanoma cells, αvβ3 mediated binding to vitronectin, but not to fibrinogen unless activated with Mn2+. Non-activated αIIbβ3 integrin as control in M21-L-IIb cells had the opposite profile, mediating binding to fibrinogen, but not to vitronectin unless activated with Mn2+. Thus these receptors had moderate to low ligand affinity. In marked contrast, purified αvβ3 receptors, with or without transmembrane and cytoplasmic domains, were constitutively of high affinity and able to bind strongly to vitronectin, fibronectin and fibrinogen under physiological conditions. Our data suggest that, in contrast with the positive regulation of αIIbβ3 in situ, intracellular controls lower the affinity of αvβ3, and the cytoplasmic domains may act as a target for negative regulators of αvβ3 activity.

The infrared spectrum of di-imide near 7.6 μm

1981 ◽  
Vol 59 (5) ◽  
pp. 663-672 ◽  
Author(s):  
K-E. J. Hallin ◽  
J. W. C. Johns ◽  
A. Trombetti
Keyword(s):  
Infrared Spectrum ◽  
Gas Phase ◽  
Type A ◽  
Phase Spectrum ◽  
The Other ◽  
Mode Analysis ◽  
Simultaneous Presence ◽  
Torsional Mode ◽  
Bending Mode ◽  
Type C

The gas phase spectrum of N2H2 has been investigated in the region of 7.6 μm at a resolution of about 0.06cm−1. Two bands have been identified; one, near 1288 cm−1, is a type C band and must correspond to ν4 (the hitherto unidentified Au torsional mode), and the other, near 1317 cm−1, is a type A–B hybrid and corresponds to ν6 (the Bu bending mode). Analysis of the spectrum is complicated by the simultaneous presence of strong A-type and B-type Coriolis interactions which couple the observed levels.

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