scholarly journals Low Temperature Dynamic Chromatography for the Separation of the Interconverting Conformational Enantiomers of the Benzodiazepines Clonazolam, Flubromazolam, Diclazepam and Flurazepam

Symmetry ◽  
2021 ◽  
Vol 13 (6) ◽  
pp. 1012
Author(s):  
Roberta Franzini ◽  
Alessia Rosetti ◽  
Claudio Villani
Keyword(s):  
Low Temperature ◽  
Binding Sites ◽  
Chiral Stationary Phase ◽  
Forensic Toxicology ◽  
High Rate ◽  
Wide Range ◽  
Stereogenic Centers ◽  
The Central Nervous System ◽  
Clinical And Forensic Toxicology ◽  
Temperature Dynamic

Benzodiazepines (BZDs) are an important class of psychoactive drugs with hypnotic-sedative, myorelaxant, anxiolytic and anticonvulsant properties due to interaction with the GABAa receptor in the central nervous system of mammals. BZDs are interesting both in clinical and forensic toxicology for their pharmacological characteristics and potential of abuse. The presence of a non-planar diazepine ring generates chiral conformational stereoisomers, even in the absence of stereogenic centers. A conformational enrichment of BZD at the binding sites has been reported in the literature, thus making interesting a stereodynamic screening of a wide range of BZDs. Herein, we report the investigation of three stereolabile 1,4-benzodiazepine included in the class of “designer benzodiazepines” (e.g., diclazepam, a chloro-derivative of diazepam, and two triazolo-benzodiazepines, flubromazolam and clonazolam) and a commercially available BZD known as flurazepam, in order to study the kinetic of the “ring-flip” process that allows two conformational enantiomers to interconvert at high rate at room temperature. A combination of low temperature enantioselective dynamic chromatography on chiral stationary phase and computer simulations of the experimental chromatograms allowed us to measure activation energies of enantiomerization (ΔG‡) lower than 18.5 kcal/mol. The differences between compounds have been correlated to the pattern of substitutions on the 1,4-benzodiazepinic core.

Is the hypotensive effect of clonidine and related drugs due to imidazoline binding sites?

1997 ◽  
Vol 273 (5) ◽  
pp. R1580-R1584 ◽  
Author(s):  
Patrice G. Guyenet
Keyword(s):  
Binding Sites ◽  
Hypotensive Effect ◽  
Genetically Engineered ◽  
Therapeutic Effects ◽  
Genetically Engineered Mice ◽  
Wide Range ◽  
The Central Nervous System ◽  
Imidazoline Binding Sites ◽  
Cellular Components

Clonidine and related α2-adrenergic receptor (α2AR) agonists lower arterial pressure primarily by an action within the central nervous system. These drugs also have varying degrees of affinity for other cellular components called nonadrenergic imidazoline binding sites (NAIBS). For over 20 years, the α2AR agonist activity of clonidine-like drugs was thought to account for their therapeutic effects (α2 theory). However, several groups have recently proposed a competing “imidazoline theory” according to which the hypotensive effect of clonidine-like drugs would in fact owe more to their affinity for one type of NAIBS, called I1receptors. The α2-theory is strongly supported by four main types of congruent data. First, the hypotensive effect of systemically administered clonidine is blocked by α2AR antagonists that are without affinity for I1 NAIBs. Second, the hypotensive effect of intravenous clonidine is absent in genetically engineered mice in which a defective α2AAR has been substituted for the normal one. Third, the sympatholytic effect of clonidine is consistent with the presence of conventional inhibitory α2ARs on sympathetic preganglionic neurons and on their main excitatory inputs in the medulla oblongata. Fourth, the first I1 ligand without affinity for α2ARs was found to be biologically inactive. The imidazoline theory is supported by a limited repertoire of whole animal “in vivo” pharmacological experiments that remain open to a wide range of interpretations. In conclusion, the bulk of the evidence strongly supports a largely predominant role of α2AR mechanisms in the action of most clonidine-like agents at therapeutically relevant doses or concentrations. Even the small pharmacological differences between these agents cannot yet be linked with certainty to their relative affinity for I1 NAIBS.

scholarly journals Experimental central composite design-based dispersive liquid-liquid microextraction for HPLC-DAD determination of diazinon in human urine samples: method development and validation

2020 ◽  
Vol 71 (1) ◽  
pp. 48-55 ◽  
Author(s):  
Reza Mohammadzaheri ◽  
Mehdi Ansari Dogaheh ◽  
Maryam Kazemipour ◽  
Kambiz Soltaninejad
Keyword(s):  
Central Composite Design ◽  
Forensic Toxicology ◽  
Urine Samples ◽  
Critical Parameters ◽  
Array Detector ◽  
Wide Range ◽  
Dispersive Liquid Liquid Microextraction ◽  
Clinical And Forensic Toxicology ◽  
Central Composite ◽  
Liquid Microextraction

AbstractDiazinon poisoning is an important issue in occupational, clinical, and forensic toxicology. While sensitive and specific enough to analyse diazinon in biological samples, current methods are time-consuming and too expensive for routine analysis. The aim of this study was therefore to design and validate a simple dispersive liquid-liquid microextraction (DLLME) for the preparation of urine samples to be analysed for diazinon with high performance liquid chromatography with diode-array detector (HPLC-DAD) to establish diazinon exposure and poisoning. To do that, we first identified critical parameters (type and volume of extraction and disperser solvents, pH, surfactant, and salt concentrations) in preliminary experiments and then used central composite design to determine the best experimental conditions for DLLME-HPLC-DAD. For DLLME they were 800 µL of methanol (disperser solvent) and 310 µL of toluene (extraction solvent) injected to the urine sample rapidly via a syringe. The sample was injected into a HPLC-DAD (C18 column, 250×4.6 mm, 5 μm), and the mobile phase was a mixture of acetonitrile and buffer (63:37 v/v, pH 3.2; flow rate: 1 mL/ min). Standard calibration curves for diazinon were linear with the concentration range of 0.5–4 µg/mL, yielding a regression equation Y=0.254X+0.006 with a correlation coefficient of 0.993. The limit of detection and limit of quantification for diazinon were 0.15 µg/mL and 0.45 µg/mL, respectively. The proposed method was accurate, precise, sensitive, and linear over a wide range of diazinon concentrations in urine samples. This method can be employed for diazinon analysis in routine clinical and forensic toxicology settings.

Rapid Freezing of Freeze-Etch Specimens

1980 ◽  
Vol 38 ◽  
pp. 752-755
Author(s):  
A. Elgsaeter ◽  
T. Espevik ◽  
G. Kopstad
Keyword(s):  
Low Temperature ◽  
Metal Surface ◽  
Relative Velocity ◽  
Thermal Contact ◽  
High Rate ◽  
Rapid Freezing ◽  
Temperature Decrease ◽  
Freeze Etching

The importance of a high rate of temperature decrease (“rapid freezing”) when freezing specimens for freeze-etching has long been recognized1. The two basic methods for achieving rapid freezing are: 1) dropping the specimen onto a metal surface at low temperature, 2) bringing the specimen instantaneously into thermal contact with a liquid at low temperature and subsequently maintaining a high relative velocity between the liquid and the specimen. Over the last couple of years the first method has received strong renewed interest, particularily as the result of a series of important studies by Heuser and coworkers 2,3. In this paper we will compare these two freezing methods theoretically and experimentally.

GABAA receptors: Various stoichiometrics of subunit arrangement in α1β3 and α1β3ε receptors

2018 ◽  
Vol 24 (17) ◽  
pp. 1839-1844 ◽  
Author(s):  
Ahmad Tarmizi Che Has ◽  
Mary Chebib
Keyword(s):  
Central Nervous System ◽  
Gabaa Receptors ◽  
Binding Sites ◽  
New Drugs ◽  
Pharmacological Properties ◽  
Receptor Complex ◽  
The Third ◽  
Γ Subunit ◽  
Subunit Stoichiometry ◽  
The Central Nervous System

GABAA receptors are members of the Cys-loop family of ligand-gated ion channels which mediate most inhibitory neurotransmission in the central nervous system. These receptors are pentameric assemblies of individual subunits, including α1-6, β1-3, γ1-3, δ, ε, π, θ and ρ1-3. The majority of receptors are comprised of α, β and γ or δ subunits. Depending on the subunit composition, the receptors are located in either the synapses or extrasynaptic regions. The most abundant receptors are α1βγ2 receptors, which are activated and modulated by a variety of pharmacologically and clinically unrelated agents such as benzodiazepines, barbiturates, anaesthetics and neurosteroids, all of which bind at distinct binding sites located within the receptor complex. However, compared to αβγ, the binary αβ receptors lack a benzodiazepine α-γ2 interface. In pentameric αβ receptors, the third subunit is replaced with either an α1 or a β3 subunit leading to two distinct receptors that differ in subunit stoichiometry, 2α:3β or 3α:2β. The consequence of this is that 3α:2β receptors contain an α-α interface whereas 2α:3β receptors contain a β-β interface. Apart from the replacement of γ by α1 or β3 in binary receptors, the incorporation of ε subunit into GABAA receptors might be more complicated. As the ε subunit is not only capable of substituting the γ subunit, but also replacing the α/β subunits, receptors with altered stoichiometry and different pharmacological properties are produced. The different subunit arrangement of the receptors potentially constructs novel binding sites which may become new targets of the current or new drugs.

scholarly journals SARS-CoV-2 and the Nervous System: From Clinical Features to Molecular Mechanisms

2020 ◽  
Vol 21 (15) ◽  
pp. 5475 ◽  
Author(s):  
Manuela Pennisi ◽  
Giuseppe Lanza ◽  
Luca Falzone ◽  
Francesco Fisicaro ◽  
Raffaele Ferri ◽  
...  
Keyword(s):  
Nervous System ◽  
Molecular Mechanisms ◽  
Neuronal Damage ◽  
Neurological Complications ◽  
Neurological Manifestations ◽  
Wide Range ◽  
Inflammatory State ◽  
Acute Polyneuropathy ◽  
The Central Nervous System ◽  
The Impact

Increasing evidence suggests that Severe Acute Respiratory Syndrome-coronavirus-2 (SARS-CoV-2) can also invade the central nervous system (CNS). However, findings available on its neurological manifestations and their pathogenic mechanisms have not yet been systematically addressed. A literature search on neurological complications reported in patients with COVID-19 until June 2020 produced a total of 23 studies. Overall, these papers report that patients may exhibit a wide range of neurological manifestations, including encephalopathy, encephalitis, seizures, cerebrovascular events, acute polyneuropathy, headache, hypogeusia, and hyposmia, as well as some non-specific symptoms. Whether these features can be an indirect and unspecific consequence of the pulmonary disease or a generalized inflammatory state on the CNS remains to be determined; also, they may rather reflect direct SARS-CoV-2-related neuronal damage. Hematogenous versus transsynaptic propagation, the role of the angiotensin II converting enzyme receptor-2, the spread across the blood-brain barrier, the impact of the hyperimmune response (the so-called “cytokine storm”), and the possibility of virus persistence within some CNS resident cells are still debated. The different levels and severity of neurotropism and neurovirulence in patients with COVID-19 might be explained by a combination of viral and host factors and by their interaction.

scholarly journals RELaTED Project: New Developments on Ultra-Low Temperature District Heating Networks

Proceedings ◽  
2020 ◽  
Vol 65 (1) ◽  
pp. 25
Author(s):  
Antonio Garrido Marijuan ◽  
Roberto Garay ◽  
Mikel Lumbreras ◽  
Víctor Sánchez ◽  
Olga Macias ◽  
...  
Keyword(s):  
Low Temperature ◽  
High Performance ◽  
Waste Heat ◽  
District Heating ◽  
Hot Water ◽  
Thermal Systems ◽  
Heating Source ◽  
Wide Range ◽  
Thermal Sources ◽  
Heating Networks

District heating networks deliver around 13% of the heating energy in the EU, being considered as a key element of the progressive decarbonization of Europe. The H2020 REnewable Low TEmperature District project (RELaTED) seeks to contribute to the energy decarbonization of these infrastructures through the development and demonstration of the following concepts: reduction in network temperature down to 50 °C, integration of renewable energies and waste heat sources with a novel substation concept, and improvement on building-integrated solar thermal systems. The coupling of renewable thermal sources with ultra-low temperature district heating (DH) allows for a bidirectional energy flow, using the DH as both thermal storage in periods of production surplus and a back-up heating source during consumption peaks. The ultra-low temperature enables the integration of a wide range of energy sources such as waste heat from industry. Furthermore, RELaTED also develops concepts concerning district heating-connected reversible heat pump systems that allow to reach adequate thermal levels for domestic hot water as well as the use of the network for district cooling with high performance. These developments will be demonstrated in four locations: Estonia, Serbia, Denmark, and Spain.

scholarly journals Dissecting the Molecular Determinants of GABAA Receptors Current Rundown, a Hallmark of Refractory Human Epilepsy

2021 ◽  
Vol 11 (4) ◽  
pp. 441
Author(s):  
Pierangelo Cifelli ◽  
Silvia Di Angelantonio ◽  
Veronica Alfano ◽  
Alessandra Morano ◽  
Eleonora De Felice ◽  
...  
Keyword(s):  
Gabaa Receptors ◽  
Drug Resistant ◽  
Human Embryonic Kidney Cells ◽  
Inhibitory Function ◽  
Human Epilepsy ◽  
Wide Range ◽  
Molecular Determinants ◽  
The Central Nervous System ◽  
Heterologous Expression Systems ◽  
Important Therapeutic Target

GABAA receptors-(Rs) are fundamental for the maintenance of an efficient inhibitory function in the central nervous system (CNS). Their dysfunction is associated with a wide range of CNS disorders, many of which characterized by seizures and epilepsy. Recently, an increased use-dependent desensitization due to a repetitive GABA stimulation (GABAA current rundown) of GABAARs has been associated with drug-resistant temporal lobe epilepsy (TLE). Here, we aimed to investigate the molecular determinants of GABAA current rundown with two different heterologous expression systems (Xenopus oocytes and human embryonic kidney cells; HEK) which allowed us to manipulate receptor stoichiometry and to study the GABAA current rundown on different GABAAR configurations. To this purpose, we performed electrophysiology experiments using two-electrode voltage clamp in oocytes and confirming part of our results in HEK. We found that different degrees of GABAA current rundown can be associated with the expression of different GABAAR β-subunits reaching the maximum current decrease when functional α1β2 receptors are expressed. Furthermore, the blockade of phosphatases can prevent the current rundown observed in α1β2 GABAARs. Since GABAAR represents one important therapeutic target in the treatment of human epilepsy, our results could open new perspectives on the therapeutic management of drug-resistant patients showing a GABAergic impairment.

scholarly journals Caprine Arthritis Encephalitis Virus Is Associated with Renal Lesions

Viruses ◽  
2021 ◽  
Vol 13 (6) ◽  
pp. 1051
Author(s):  
Brian G. Murphy ◽  
Diego Castillo ◽  
Asli Mete ◽  
Helena Vogel ◽  
Dayna Goldsmith ◽  
...  
Keyword(s):  
Renal Injury ◽  
Binding Sites ◽  
Encephalitis Virus ◽  
Clinical Consequence ◽  
Viral Isolate ◽  
Viral Promoter ◽  
Caprine Arthritis Encephalitis Virus ◽  
Renal Lesions ◽  
Cardiac Lesions ◽  
The Central Nervous System

Caprine arthritis encephalitis virus (CAEV) is a monocyte/macrophage-tropic lentivirus that primarily infects goats resulting in a well-recognized set of chronic inflammatory syndromes focused on the joint synovium, tissues of the central nervous system, pulmonary interstitium and mammary gland. Clinically affected animals generally manifest with one or more of these classic CAEV-associated tissue lesions; however, CAEV-associated renal inflammation in goats has not been reported in the peer-reviewed literature. Here we describe six goats with chronic, multisystemic CAEV infections in conjunction with CAEV-associated renal lesions. One of the animals had CAEV antigen-associated thrombotic arteritis resulting in infarction of both the kidney and heart. These goats had microscopic evidence of inflammatory renal injury (interstitial nephritis) with detectable renal immunolabeling for CAEV antigen in three of six animals and amplifiable proviral sequences consistent with CAEV in all six animals. Cardiac lesions (vascular, myocardial or endocardial) were also identified in four of six animals. Within the viral promoter (U3) region, known transcription factor binding sites (TFBSs) were generally conserved, although one viral isolate had a duplication of the U3 A region encoding a second gamma-activated site (GAS). Despite the TFBS conservation, the isolates demonstrated a degree of phylogenetic diversity. At present, the clinical consequence of CAEV-associated renal injury is not clear.

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