There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

Probability Distributions.- Linear Models for Regression.- Linear Models for Classification.- Neural Networks.- Kernel Methods.- Sparse Kernel Machines.- Graphical Models.- Mixture Models and EM.- Approximate Inference.- Sampling Methods.- Continuous Latent Variables.- Sequential Data.- Combining Models.

Pattern Recognition and Machine Learning

Two types of cannabinoid receptor have been discovered so far, CB(1) (2.1: CBD:1:CB1:), cloned in 1990, and CB(2) (2.1:CBD:2:CB2:), cloned in 1993. Distinction between these receptors is based on differences in their predicted amino acid sequence, signaling mechanisms, tissue distribution, and sensitivity to certain potent agonists and antagonists that show marked selectivity for one or the other receptor type. Cannabinoid receptors CB(1) and CB(2) exhibit 48% amino acid sequence identity. Both receptor types are coupled through G proteins to adenylyl cyclase and mitogen-activated protein kinase. CB(1) receptors are also coupled through G proteins to several types of calcium and potassium channels. These receptors exist primarily on central and peripheral neurons, one of their functions being to inhibit neurotransmitter release. Indeed, endogenous CB(1) agonists probably serve as retrograde synaptic messengers. CB(2) receptors are present mainly on immune cells. Such cells also express CB(1) receptors, albeit to a lesser extent, with both receptor types exerting a broad spectrum of immune effects that includes modulation of cytokine release. Of several endogenous agonists for cannabinoid receptors identified thus far, the most notable are arachidonoylethanolamide, 2-arachidonoylglycerol, and 2-arachidonylglyceryl ether. It is unclear whether these eicosanoid molecules are the only, or primary, endogenous agonists. Hence, we consider it premature to rename cannabinoid receptors after an endogenous agonist as is recommended by the International Union of Pharmacology Committee on Receptor Nomenclature and Drug Classification. Although pharmacological evidence for the existence of additional types of cannabinoid receptor is emerging, other kinds of supporting evidence are still lacking.

https://pharmrev.aspetjournals.org/content/pharmrev/54/2/161.full.pdf

International Union of Pharmacology. XXVII. Classification of Cannabinoid Receptors

http://www.back-in-business-physiotherapy.com/images/files/DescendingControl.pdf

Descending control of pain.

The endogenous cannabinoid receptor agonist anandamide is a powerful vasodilator of isolated vascular preparations, but its mechanism of action is unclear. Here we show that the vasodilator response to anandamide in isolated arteries is capsaicin-sensitive and accompanied by release of calcitonin-gene-related peptide (CGRP). The selective CGRP-receptor antagonist 8-37 CGRP, but not the cannabinoid CB1 receptor blocker SR141716A, inhibited the vasodilator effect of anandamide. Other endogenous (2-arachidonylglycerol, palmitylethanolamide) and synthetic (HU 210, WIN 55,212-2, CP 55,940) CB1 and CB2 receptor agonists could not mimic the action of anandamide. The selective 'vanilloid receptor' antagonist capsazepine inhibited anandamide-induced vasodilation and release of CGRP. In patch-clamp experiments on cells expressing the cloned vanilloid receptor (VR1), anandamide induced a capsazepine-sensitive current in whole cells and isolated membrane patches. Our results indicate that anandamide induces vasodilation by activating vanilloid receptors on perivascular sensory nerves and causing release of CGRP. The vanilloid receptor may thus be another molecular target for endogenous anandamide, besides cannabinoid receptors, in the nervous and cardiovascular systems.

Vanilloid receptors on sensory nerves mediate the vasodilator action of anandamide

In mouse neuroblastoma N18TG2 cells prelabeled with [3H]arachidonic acid ([3H]AA) the biosynthesis of 2-arachidonoylglycerol (2-AG) is induced by ionomycin in a fashion sensitive to an inhibitor of diacylglycerol (DAG) lipase, RHC 80267, but not to four different phospholipase C (PLC) blockers. Pulse experiments with [3H]AA showed that ionomycin stimulation leads to the sequential formation of [3H]phosphatidic acid ([3H]PA), [3H]DAG, and [3H]2-AG. [3H]2-AG biosynthesis in N18TG2 cells prelabeled with [3H]AA was counteracted by propranolol and N-ethylmaleimide, two inhibitors of the Mg2+/Ca2+-dependent brain PA phosphohydrolase. Pretreatment of cells with exogenous phospholipase D (PLD) led to a strong potentiation of ionomycin-induced [3H]2-AG formation. These data indicate that DAG precursors for 2-AG in intact N18TG2 cells are obtained from the hydrolysis of PA and not through the activation of PLC. The presence of 2% ethanol during ionomycin stimulation failed to elicit the synthesis of [3H]phosphatidylethanol and did not counteract the formation of [3H]PA, thus arguing against the activation of PLD by the Ca2+ ionophore. Selective inhibitors of secretory phospholipase A2 and the acyl-CoA acylase inhibitor thimerosal significantly reduced [3H]2-AG biosynthesis. The implications of these latter findings, and of the PA-dependent pathways of 2-AG formation described here, are discussed.

https://onlinelibrary.wiley.com/doi/pdf/10.1046/j.1471-4159.1999.0722113.x

Phosphatidic acid as the biosynthetic precursor of the endocannabinoid 2-arachidonoylglycerol in intact mouse neuroblastoma cells stimulated with ionomycin.

Background Metabolomics could provide new insights into the pathophysiology of cystic fibrosis (CF) by identifying profiles of endogenous metabolites. Objectives To investigate whether metabolomics of exhaled breath condensate could discriminate between patients with unstable CF, stable CF and healthy subjects, and whether selected metabolites were responsible for between-group differences. Methods Twenty-nine patients with stable CF, 24 with unstable CF and 31 healthy subjects (age 9–24 years) participated in a cross-sectional study. Metabolomics was performed with high-resolution nuclear magnetic resonance spectroscopy. Partial least squares-discriminant analysis was used as classifier. The results were validated in a second independent study. Results Intraclass correlation coefficients for between-day and technical repeatability were 0.93 and 0.96, respectively. Bland–Altman analysis showed good within-day repeatability. Correct classification rate of CF (n=53) vs healthy subjects (n=31) was 96% (R 2 =0.84; Q 2 =0.79). Model validation with a testing sample set obtained from subjects not included in the primary analysis (23 CF and 25 healthy subjects) showed a sensitivity of 91% and a specificity of 96%. The classification rate of stable CF (n=29) vs unstable CF patients (n=24) was 95% (R 2 =0.82; Q 2 =0.78). Model external validation in 14 patients with stable CF and 16 with unstable CF showed a sensitivity of 86% and a specificity of 94%. Ethanol, acetate, 2-propanol and acetone were most discriminant between patients with CF and healthy subjects, whereas acetate, ethanol, 2-propanol and methanol were the most important metabolites for discriminating between patients with stable and unstable CF. Conclusions Nuclear magnetic resonance spectroscopy of exhaled breath condensate is reproducible, discriminates patients with CF from healthy subjects and patients with unstable CF from those with stable CF, and identifies the metabolites responsible for between-group differences.

https://thorax.bmj.com/content/thoraxjnl/67/3/222.full.pdf

NMR spectroscopy metabolomic profiling of exhaled breath condensate in patients with stable and unstable cystic fibrosis

Cannabimimetic Fatty Acid Derivatives: The Anandamide Family and Other “Endocannabinoids”

Exhaled breath condensate (EBC) is a noninvasive method for the study of airway lining fluid. Nuclear magnetic resonance (NMR) spectroscopy can provide biochemical profiles of metabolites in biological samples. The aim of the present study was to validate the NMR metabonomic analysis of EBC in adults, assessing the role of pre-analytical variables (saliva and disinfectant contamination) and the potential clinical feasibility. In total, 36 paired EBC and saliva samples, obtained from healthy subjects, laryngectomised patients and chronic obstructive pulmonary disease patients, were analysed by means of (1)H-NMR spectroscopy followed by principal component analysis. The effect on EBC of disinfectant, used for reusable parts of the condenser, was assessed after different washing procedures. To evaluate intra-day repeatability, eight subjects were asked to collect EBC and saliva twice within the same day. All NMR saliva spectra were significantly different from corresponding EBC samples. EBC taken from condensers washed with recommended procedures invariably showed spectra perturbed by disinfectant. Each EBC sample clustered with corresponding samples of the same group, while presenting intergroup qualitative and quantitative signal differences (94% of the total variance within the data). In conclusion, the nuclear magnetic resonance metabonomic approach could identify the metabolic fingerprint of exhaled breath condensate in different clinical sets of data. Moreover, metabonomics of exhaled breath condensate in adults can discriminate potential perturbations induced by pre-analytical variables.

https://erj.ersjournals.com/content/erj/32/5/1175.full.pdf

Dominique Melck

Papers

Phosphatidic acid as the biosynthetic precursor of the endocannabinoid 2-arachidonoylglycerol in intact mouse neuroblastoma cells stimulated with ionomycin.

NMR spectroscopy metabolomic profiling of exhaled breath condensate in patients with stable and unstable cystic fibrosis

Cannabimimetic Fatty Acid Derivatives: The Anandamide Family and Other “Endocannabinoids”

Metabonomic analysis of exhaled breath condensate in adults by nuclear magnetic resonance spectroscopy

Novel inhibitors of brain, neuronal, and basophilic anandamide amidohydrolase.