Highlights • Descending pathways play a critical role in the central modulation of pain. • A particular descending PAG–RVM pathway mediates the phenomenon of stress-induced analgesia. • Opioids and ...cannabinoids are proposed to activate this system via a process of GABA disinhibition. • Recent evidence has emerged which conflicts with the GABA disinhibition hypothesis. • Alternative models have been proposed to account for descending analgesia.
•We describe mass analyzers for liquid chromatography-mass spectrometry (LC-MS).•We review LC-MS technology used for the determination of contaminants in food.•We discuss advantages/disadvantages of ...LC-MS for targeted vs. non-targeted analyses.•We discuss advantages/disadvantages of LC-MS for quantification and identification.
As a result of the range and the variety of toxic and undesirable substances in food, which pose a potential hazard to human health, there is an ever-increasing demand for analytical methods that can reliably detect and quantify contaminants and residues in foods. This review presents the state-of-the-art technology used in the determination of trace residues and contaminants in food by liquid chromatography-mass spectrometry (LC-MS). LC-MS instruments utilize many different types of mass analyzer to improve selectivity and also confidence in assigning the identity of the contaminants detected and to offer different approaches to analysis. We discuss current analytical approaches together with the major benefits and the limitations of these technologies with respect to screening, quantification and identification of contaminants and residues in food.
Protein solubility is a critical prerequisite to any proteomics analysis. Combination of urea/thiourea and 3-(3-cholamidopropyl)dimethylammonio-1-propanesulfonate (CHAPS) have been routinely used to ...enhance protein solubilization for oil palm proteomics studies in recent years. The goals of these proteomics analysis are essentially to complement the knowledge regarding the regulation networks and mechanisms of the oil palm fatty acid biosynthesis. Through omics integration, the information is able to build a regulatory model to support efforts in improving the economic value and sustainability of palm oil in the global oil and vegetable market. Our study evaluated the utilization of sodium deoxycholate as an alternative solubilization buffer/additive to urea/thiourea and CHAPS. Efficiency of urea/thiourea/CHAPS, urea/CHAPS, urea/sodium deoxycholate and sodium deoxycholate buffers in solubilizing the oil palm (Elaeis guineensis var. Tenera) mesocarp proteins were compared. Based on the protein yields and electrophoretic profile, combination of urea/thiourea/CHAPS were shown to remain a better solubilization buffer and additive, but the differences with sodium deoxycholate buffer was insignificant. A deeper mass spectrometric and statistical analyses on the identified proteins and peptides from all the evaluated solubilization buffers revealed that sodium deoxycholate had increased the number of identified proteins from oil palm mesocarps, enriched their gene ontologies and reduced the number of carbamylated lysine residues by more than 67.0%, compared to urea/thiourea/CHAPS buffer. Although only 62.0% of the total identified proteins were shared between the urea/thiourea/CHAPS and sodium deoxycholate buffers, the importance of the remaining 38.0% proteins depends on the applications. The only observed limitations to the application of sodium deoxycholate in protein solubilization were the interference with protein quantitation and but it could be easily rectified through a 4-fold dilution. All the proteomics data are available via ProteomeXchange with identifier PXD013255. In conclusion, sodium deoxycholate is applicable in the solubilization of proteins extracted from oil palm mesocarps with higher efficiency compared to urea/thiourea/CHAPS buffer. The sodium deoxycholate buffer is more favorable for proteomics analysis due to its proven advantages over urea/thiourea/CHAPS buffer.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The endocannabinoid system has emerged as a key player in the control of eating. Endocannabinoids, including 2-arachidonoylglycerol (2-AG) and anandamide (AEA), modulate neuronal activity via ...cannabinoid 1 receptors (CB1Rs) in multiple nuclei of the hypothalamus to induce or inhibit food intake depending on nutritional and hormonal status, suggesting that endocannabinoids may act in the hypothalamus to integrate different types of signals informing about the animal's energy needs. In the mesocorticolimbic system, (endo)cannabinoids modulate synaptic transmission to promote dopamine release in response to palatable food. In addition, (endo)cannabinoids act within the nucleus accumbens to increase food's hedonic impact; although this effect depends on activation of CB1Rs at excitatory, but not inhibitory inputs in the nucleus accumbens. While hyperactivation of the endocannabinoid system is typically associated with overeating and obesity, much evidence has emerged in recent years suggesting a more complicated system than first thought – endocannabinoids promote or suppress feeding depending on cell and input type, or modulation by various neuronal or hormonal signals. This review presents our latest knowledge of the endocannabinoid system in non-homeostatic and homeostatic feeding circuits. In particular, we discuss the functional role and cellular mechanism of action by endocannabinoids within the hypothalamus and mesocorticolimbic system, and how these are modulated by neuropeptide signals related to feeding. In light of recent advances and complexity in the field, we review cannabinoid-based therapeutic strategies for the treatment of obesity and how peripheral restriction of CB1R antagonists may provide a different mechanism of weight loss without the central adverse effects.
This article is part of the Special Issue entitled “A New Dawn in Cannabinoid Neurobiology”.
Endocannabinoid modulation of the mesocorticolimbic and hypothalamic circuits: a highly interconnected circuit of excitatory (glutamatergic) and inhibitory (GABAergic) pathways exist between the ventral tegmental area (VTA), nucleus accumbens (NAc), medial prefrontal cortex (mPFC) and hypothalamus (Hyp). Furthermore, the VTA sends prominent dopamine projections to the NAc and mPFC. A number of synaptic inputs onto principal neurons within the VTA (dopamine neurons), NAc (medium spiny neurons), mPFC (pyramidal neurons) and hypothalamus express CB1 receptors, and are sensitive to endocannabinoid-mediated, short-term plasticity (DSI/DSE) and/or long-term plasticity (LTD/iLTD) in naive animals. Exposure to a palatable/high-fat diet (or omega-3 deficient diet) or the development of diet-induced obesity can alter these forms of synaptic plasticity Insets: +/− indicates present/absent, while ↑/↓/ = /? indicate increase/decrease/no change/unknown, respectively. Display omitted
•Endocannabinoids act in multiple hypothalamic nuclei to integrate signals informing about the animal’s energy needs.•Endocannabinoids modulate synaptic transmission in the VTA and NAc to promote dopamine release in response to palatable food.•Peripherally restricted cannabinoid receptor antagonists may be therapeutic in the treatment of obesity.
Circuit-specific signaling of ventral tegmental area (VTA) dopamine neurons drives different aspects of motivated behavior, but the neuromodulatory control of these circuits is unclear. We tested the ...actions of co-expressed lateral hypothalamic peptides, orexin A (oxA) and dynorphin (dyn), on projection-target-defined dopamine neurons in mice. We determined that VTA dopamine neurons that project to the nucleus accumbens lateral shell (lAcbSh), medial shell (mAcbSh), and basolateral amygdala (BLA) are largely non-overlapping cell populations with different electrophysiological properties. Moreover, the neuromodulatory effects of oxA and dyn on these three projections differed. OxA selectively increased firing in lAcbSh- and mAcbSh-projecting dopamine neurons. Dyn decreased firing in the majority of mAcbSh- and BLA-projecting dopamine neurons but reduced firing only in a small fraction of those that project to the lAcbSh. In conclusion, the oxA-dyn input to the VTA may drive reward-seeking behavior by tuning dopaminergic output in a projection-target-dependent manner.
Display omitted
•The distribution and properties of VTA dopamine neurons differ with projection target•Orexin increases firing of NAc-projecting, but not BLA-projecting, dopamine neurons•Both nucleus accumbens and BLA-projecting dopamine neurons were inhibited by dynorphin
Baimel et al. find that the projection target is an important determinant of neuromodulation by the lateral hypothalamic orexin and dynorphin input. Moreover, both the anatomical distribution and the intrinsic properties of VTA dopamine neurons are also defined by projection target.
There has been increasing concern over the contamination of drinking water and food with perchlorate. Studies have reported perchlorate in a variety of foods, including lettuce, milk, fruits, and ...juices. In this study, 150 food samples were analyzed by ion chromatography tandem mass spectrometry (IC-MS/MS) to determine the concentrations of perchlorate in imported and domestic fruits and vegetables available from retail outlets in Ottawa, Canada. Perchlorate was found in most of the tested food types with concentrations appearing to vary by commodity and country of origin. Levels ranged from nondetectable to 536 μg/kg, with Guatemalan cantaloupes (156 ± 232 μg/kg), United States spinach (133 ± 24.9 μg/kg), Chilean green grapes (45.5 ± 13.3 μg/kg), and United States Romaine lettuce (29.1 ± 10.5 μg/kg) having the highest concentrations. Dietary exposure to perchlorate from analyzed fruits and vegetables was estimated to be approximately 36.6 and 41.1 ng/kg bw/day for toddlers (1−4 yrs) and children (5−11yrs), respectively.
Acrylamide in food productschiefly in commercially available potato chips, potato fries, cereals, and breadwas determined by liquid chromatography−tandem mass spectrometry (LC-MS/MS). Samples were ...homogenized with water/dichloromethane, centrifuged, and filtered through a 5 kDa filter. The filtrate was cleaned up on mixed mode, anion and cation exchange (Oasis MAX and MCX) and carbon (Envirocarb) cartridges. Analysis was done by isotope dilution (D3- or 13C3acrylamide) electrospray LC-MS/MS using a 2 × 150 mm (or 2 × 100 mm) Thermo HyperCarb column eluted with 1 mM ammonium formate in 15% (or 10% for the 2 × 100 mm column) methanol. Thirty samples of foods were analyzed. Concentrations of acrylamide varied from 14 ng/g (bread) to 3700 ng/g (potato chips). Acrylamide was formed during model reactions involving heating of mixtures of amino acids and glucose in ratios similar to those found in potatoes. In model reactions between amino acids and glucose, asparagine was found to be the main precursor of acrylamide. Thus, in the reaction between nitrogen-15 (amido)-labeled asparagine and glucose, corresponding 15N-labeled acrylamide was formed. The yield of the model reaction is ∼0.1%. Keywords: Acrylamide; model; glucose; asparagine; Maillard reaction; LC-MS/MS
The midbrain periaqueductal gray (PAG) plays a central role in pain modulation via descending pathways. Opioids and cannabinoids are thought to activate these descending pathways by relieving ...intrinsic GABAergic inhibition of PAG neurons which project to the rostroventromedial medulla (RVM), a process known as disinhibition. However, the PAG also receives descending extrinsic GABAergic inputs from the central nucleus of the amygdala (CeA) which are thought to inhibit PAG GABAergic interneurons. It remains unclear how opioids and cannabinoids act at these different synapses to control descending analgesic pathways. We used optogenetics, tract tracing and electrophysiology to identify the circuitry underlying opioid and cannabinoid actions within the PAG of male and female rats. It was observed that both RVM-projection and nonprojection PAG neurons received intrinsic-PAG and extrinsic-CeA synaptic inputs, which were predominantly GABAergic. Opioids acted via presynaptic µ-receptors to suppress both intrinsic and extrinsic GABAergic inputs onto all PAG neurons, although this inhibition was greater in RVM-projection neurons. By contrast, cannabinoids acted via presynaptic CB1 receptors to exclusively suppress the direct descending GABAergic input from the CeA onto RVM-projection PAG neurons. These findings indicate the CeA controls PAG output neurons which project to the RVM via parallel direct and indirect GABAergic pathways. While µ-opioids indiscriminately inhibit GABAergic inputs onto all PAG neurons, cannabinoids selectively inhibit a direct extrinsic GABAergic input from the amygdala onto PAG projection neurons. These differential actions of opioids and cannabinoids provide a flexible system to gate the descending control of analgesia from the PAG.
The disinhibition hypothesis of analgesia states that opioids activate the midbrain periaqueductal gray (PAG) descending pathway by relieving the tonic inhibition of projection neurons from GABAergic interneurons. However, the PAG also receives extrinsic GABAergic inputs and is the locus of action of cannabinoid analgesics. Here, we show the relative sensitivity of GABAergic synapses to opioids and cannabinoids within the PAG depends on both the origin of presynaptic inputs and their postsynaptic targets. While opioids indiscriminately inhibit all GABAergic inputs onto all PAG neurons, cannabinoids selectively inhibit a direct extrinsic GABAergic input from the amygdala onto PAG descending projection neurons. These differential actions of opioids and cannabinoids provide a flexible system to gate PAG descending outputs.
Background
The adoption of four‐dimensional cone beam computed tomography (4DCBCT) for image‐guided lung cancer radiotherapy is increasing, especially for hypofractionated treatments. However, the ...drawbacks of 4DCBCT include long scan times (∼240 s), inconsistent image quality, higher imaging dose than necessary, and streaking artifacts. With the emergence of linear accelerators that can acquire 4DCBCT scans in a short period of time (9.2 s) there is a need to examine the impact that these very fast gantry rotations have on 4DCBCT image quality.
Purpose
This study investigates the impact of gantry velocity and angular separation between x‐ray projections on image quality and its implication for fast low‐dose 4DCBCT with emerging systems, such as the Varian Halcyon that provide fast gantry rotation and imaging. Large and uneven angular separation between x‐ray projections is known to reduce 4DCBCT image quality through increased streaking artifacts. However, it is not known when angular separation starts degrading image quality. The study assesses the impact of constant and adaptive gantry velocity and determines the level when angular gaps impair image quality using state‐of‐the‐art reconstruction methods.
Methods
This study considers fast low‐dose 4DCBCT acquisitions (60–80 s, 200‐projection scans). To assess the impact of adaptive gantry rotations, the angular position of x‐ray projections from adaptive 4DCBCT acquisitions from a 30‐patient clinical trial were analyzed (referred to as patient angular gaps). To assess the impact of angular gaps, variable and static angular gaps (20°, 30°, 40°) were introduced into evenly separated 200 projections (ideal angular separation). To simulate fast gantry rotations, which are on emerging linacs, constant gantry velocity acquisitions (9.2 s, 60 s, 120 s, 240 s) were simulated by sampling x‐ray projections at constant intervals using the patient breathing traces from the ADAPT clinical trial (ACTRN12618001440213). The 4D Extended Cardiac‐Torso (XCAT) digital phantom was used to simulate projections to remove patient‐specific image quality variables.
Image reconstruction was performed using Feldkamp‐Davis‐Kress (FDK), McKinnon‐Bates (MKB), and Motion‐Compensated‐MKB (MCMKB) algorithms. Image quality was assessed using Structural Similarity‐Index‐Measure (SSIM), Contrast‐to‐Noise‐Ratio (CNR), Signal‐to‐Noise‐Ratio (SNR), Tissue‐Interface‐Width‐Diaphragm (TIW‐D), and Tissue‐Interface‐Width‐Tumor (TIW‐T).
Results
Patient angular gaps and variable angular gap reconstructions produced similar results to ideal angular separation reconstructions, while static angular gap reconstructions produced lower image quality metrics. For MCMKB‐reconstructions, average patient angular gaps produced SSIM‐0.98, CNR‐13.6, SNR‐34.8, TIW‐D‐1.5 mm, and TIW‐T‐2.0 mm, static angular gap 40° produced SSIM‐0.92, CNR‐6.8, SNR‐6.7, TIW‐D‐5.7 mm, and TIW‐T‐5.9 mm and ideal produced SSIM‐1.00, CNR‐13.6, SNR‐34.8, TIW‐D‐1.5 mm, and TIW‐T‐2.0 mm. All constant gantry velocity reconstructions produced lower image quality metrics than ideal angular separation reconstructions regardless of the acquisition time. Motion compensated reconstruction (MCMKB) produced the highest contrast images with low streaking artifacts.
Conclusion
Very fast 4DCBCT scans can be acquired provided that the entire scan range is adaptively sampled, and motion‐compensated reconstruction is performed. Importantly, the angular separation between x‐ray projections within each individual respiratory bin had minimal effect on the image quality of fast low‐dose 4DCBCT imaging. The results will assist the development of future 4DCBCT acquisition protocols that can now be achieved in very short time frames with emerging linear accelerators.
Background and Purpose
The midbrain periaqueductal grey (PAG) plays a central role in modulating pain through a descending pathway that projects indirectly to the spinal cord via the rostroventral ...medial medulla (RVM). While opioids are potent analgesics that target the PAG, their cellular actions on descending projection neurons are unclear.
Experimental Approach
Patch clamp recordings in voltage‐ and current‐clamp mode were made from acutely prepared PAG slices from animals that received retrograde tracer injections into the RVM.
Key Results
The μ‐agonist DAMGO reduced GABAergic evoked inhibitory postsynaptic currents (IPSCs) in retro‐labelled, RVM‐projecting neurons to a greater extent than in unlabelled neurons. The κ‐opioid agonist U69593 reduced evoked IPSCs to a similar extent in both neuronal groups, while the δ‐opioid agonist deltorphin‐II was without effect. DAMGO and U69593 both produced a reduction in the rate, but not amplitude of spontaneous miniature IPSCs and asynchronous evoked IPSCs in retro‐labelled neurons. DAMGO and U69593 also suppressed glutamatergic EPSCs in retro‐labelled and unlabelled neurons. The DAMGO inhibition of evoked EPSCs, however, was less than that for evoked IPSCs in retro‐labelled, but not unlabelled neurons. In current clamp, DAMGO produced a depolarizing increase in evoked postsynaptic potentials in retro‐labelled neurons, but directly inhibited unlabelled neurons.
Conclusion and Implications
These findings suggest that μ‐opioids activate the descending analgesic pathway from the midbrain PAG by a combination of presynaptic disinhibition of RVM‐projecting neurons and postsynaptic inhibition of presumptive interneurons.
PDF
