Publications by authors named "Ken K C Yeung"

Background: Exposure to Δ-tetrahydrocannabinol (THC) is an established risk factor for later-life neuropsychiatric vulnerability, including mood- and anxiety-related symptoms. The psychotropic effects of THC on affect and anxiogenic behavioral phenomena are known to target the striatal network, particularly the nucleus accumbens, a neural region linked to mood and anxiety disorder pathophysiology. THC may increase neuroinflammatory responses via the redox system and dysregulate inhibitory and excitatory neural balance in various brain circuits, including the striatum.

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The majority of lifetime smokers begin using nicotine during adolescence, a critical period of brain development wherein neural circuits critical for mood, affect and cognition are vulnerable to drug-related insults. Specifically, brain regions such as the medial prefrontal cortex (mPFC), the ventral tegmental area (VTA), nucleus accumbens (NAc) and hippocampus, are implicated in both nicotine dependence and pathological phenotypes linked to mood and anxiety disorders. Clinical studies report that females experience higher rates of mood/anxiety disorders and are more resistant to smoking cessation therapies, suggesting potential sex-specific responses to nicotine exposure and later-life neuropsychiatric risk.

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With increasing maternal cannabis use, there is a need to investigate the lasting impact of prenatal exposure to Δ9-tetrahydrocannabinol (THC), the main psychotropic compound in cannabis, on cognitive/memory function. The endocannabinoid system (ECS), which relies on polyunsaturated fatty acids (PUFAs) to function, plays a crucial role in regulating prefrontal cortical (PFC) and hippocampal network-dependent behaviors essential for cognition and memory. Using a rodent model of prenatal cannabis exposure (PCE), we report that male and female offspring display long-term deficits in various cognitive domains.

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Many diverse species of fungi naturally occur as endophytes in plants. The majority of these fungi produce secondary metabolites of diverse structures and biological activities. Culture extracts from 288 fungi isolated from surface-sterilized blueberries, cranberries, raspberries, and grapes were analyzed by LC-HRMS/MS.

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Metformin, used to treat Type 2 diabetes, is the active ingredient of one of the most prescribed drugs in the world, with over 120 million yearly prescriptions globally. In wastewater-treatment plants (WWTPs), metformin can undergo microbial transformation to form the product guanylurea, which could have toxicological relevance in the environment. Surface water samples from 2018 to 2020 and sediment samples from 2020 were collected from six mixed-use watersheds in Quebec and Ontario, Canada, and analyzed to determine the metformin and guanylurea concentrations at each site.

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Chronic exposure to Δ-9-tetrahydrocannabinol (THC) during adolescence is associated with long-lasting cognitive impairments and enhanced susceptibility to anxiety and mood disorders. Previous evidence has revealed functional and anatomical dissociations between the posterior vs. anterior portions of the hippocampal formation, which are classified as the dorsal and ventral regions in rodents, respectively.

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Despite increased prevalence of maternal cannabis use, little is understood regarding potential long-term effects of prenatal cannabis exposure (PCE) on neurodevelopmental outcomes. While neurodevelopmental cannabis exposure increases the risk of developing affective/mood disorders in adulthood, the precise neuropathophysiological mechanisms in male and female offspring are largely unknown. Given the interconnectivity of the endocannabinoid (ECb) system and the brain's fatty acid pathways, we hypothesized that prenatal exposure to Δ-tetrahydrocannabinol (THC) may dysregulate fetal neurodevelopment through alterations of fatty-acid dependent synaptic and neuronal function in the mesolimbic system.

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The efficient reduction of accumulated waste biomass and red mud by converting them into a value-added magnetic adsorbent is both difficult and tempting in terms of sustainability. This study focused on investigating the reaction mechanism of co-pyrolysis of different biomasses, including pine wood, cellulose, and lignin, with red mud at 500, 650, and 800 °C, and the comprehensive characterizations of the produced bio-magnetic particles. The performance of biomass and red mud based magnetic adsorbents is also evaluated, and their primary adsorption mechanisms for organic pollutants are revealed by using different organic model compounds.

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Inorganic nanostructured materials such as silicon, carbon, metals, and metal oxides have been explored as matrices of low-background signals to assist the laser desorption/ionization (LDI) mass spectrometric (MS) analysis of small molecules, but their applications for imaging of small molecules in biological tissues remain limited in the literature. Titanium dioxide is one of the known nanoparticles (NP) that can effectively assist LDI MS imaging of low molecular weight molecules (LMWM). TiO NP is commercially available as dispersions, which can be applied using a chemical solution sprayer.

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Periventricular white matter hyperintensities (pvWMHs) are a neurological feature detected with magnetic resonance imaging that are clinically associated with an increased risk of stroke and dementia. pvWMHs represent white matter lesions characterized by regions of myelin and axon rarefaction and as such likely involve changes in lipid composition; however, these alterations remain unknown. Lipids are critical in determining cell function and survival.

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Background: It is estimated that 20-30% of ginseng crops in Canada are lost to root rot each harvest. This disease is commonly caused by fungal infection with , previously known as Previous reports have linked the virulence of fungal disease to the production of siderophores, a class of small-molecule iron chelators. However, these siderophores have not been identified in .

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The Colorado potato beetle (CPB) is one of the most adaptable insect pests to both plant toxins and synthetic insecticides. Resistance in CPB is reported for over 50 classes of insecticides, and mechanisms of insecticide-resistance include enhanced detoxification enzymes, ABC transporters and target site mutations. Adaptation to insecticides is also associated with changes in behaviour, energy metabolism and other physiological processes seemingly unrelated to resistance but partially explained through genomic analyses.

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spp. occur as plant pathogens worldwide under field and storage conditions. They lead to food spoilage and also produce several classes of secondary metabolites that contaminate the food production chain.

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Ischemic stroke is a complex and devastating event characterized by cell death resulting from a transient or permanent arterial occlusion. Astrocytic connexin43 (Cx43) gap junction (GJ) proteins have been reported to impact neuronal survival in ischemic conditions. Consequently, Cx43 could be a potential target for therapeutic approaches to stroke.

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Matrix assisted laser desorption ionization (MALDI) imaging mass spectrometry (IMS) is used to perform mass spectrometric analysis directly on biological samples providing visual and anatomical spatial information on molecules within tissues. A current obscuration of MALDI-IMS is that it is largely performed on fresh frozen tissue, whereas clinical tissue samples stored long-term are fixed in formalin, and the fixation process is thought to cause signal suppression for lipid molecules. Studies have shown that fresh frozen tissue sections applied with an ammonium formate (AF) wash prior to matrix application in the MALDI-IMS procedure display an increase in observed signal intensity and sensitivity for lipid molecules detected within the brain while maintaining the spatial distribution of molecules throughout the tissue.

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Ginseng root is an economically valuable crop in Canada at high risk of yield loss caused by the pathogenic fungus formerly known as . While this pathogen has been well-characterized from morphological and genetic perspectives, little is known about the secondary metabolites it produces and their role in pathogenicity. We used an untargeted tandem liquid chromatography-mass spectrometry (LC-MS)-based approach paired with global natural products social molecular networking (GNPS) to compare the metabolite profiles of virulent and avirulent strains.

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Rationale: Microbial natural products are often biosynthesized as classes of structurally related compounds that have similar tandem mass spectrometry (MS/MS) fragmentation patterns. Mining MS/MS datasets for precursor ions that share diagnostic or common features enables entire chemical classes to be identified, including novel derivatives that have previously been unreported. Analytical data analysis tools that can facilitate a class-targeted approach to rapidly dereplicate known compounds and identify structural variants within complex matrices would be useful for the discovery of new natural products.

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Perturbations of ganglioside homeostasis have been observed following stroke whereby toxic simple gangliosides GM2 and GM3 accumulate, while protective complex species GM1 and GD1 are reduced. Thus, there is a need for therapeutic interventions which can prevent ganglioside dysregulation after stroke. A pharmacological intervention using chloroquine was selected for its transient lysosomotropic properties which disrupt the activity of catabolic ganglioside enzymes.

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: Neonicotinoids are among the most widely used insecticides. Recently, there has been concern associated with unintended adverse effects on honeybees and aquatic invertebrates at low parts-per-trillion levels. : There is a need for LC-MS/MS methods that are capable of high-throughput measurements of the most widely used neonicotinoids at environmentally relevant concentrations in surface water.

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Rationale: This work focuses on direct matrix-assisted laser desorption/ionization imaging mass spectrometry (MALDI-IMS) detection of intraperitoneally (IP)-injected dipeptide ZP1609 in mouse brain tissue. Direct analysis of drug detection in intact tissue sections provides distribution information that can impact drug development. MALDI-IMS capabilities of uncovering drug transport across the blood-brain barrier are demonstrated.

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Background: Accumulation of simple gangliosides GM2 and GM3, and gangliosides with longer long-chain bases (d20:1) have been linked to toxicity and the pathogenesis of Alzheimer's disease (AD). Conversely, complex gangliosides, such as GM1, have been shown to be neuroprotective. Recent evidence using matrix-assisted laser desorption ionization imaging mass spectrometry (MALDI-IMS) has demonstrated that a-series gangliosides are differentially altered during normal aging, yet it remains unclear how simple species are shifting relative to complex gangliosides in the prodromal stages of AD.

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The use of MALDI MS as a fast and direct method to detect the Aβ oligomers of different masses is examined in this paper. Experimental results suggest that Aβ oligomers are ionized and detected as singly charged ions, and thus, the resulting mass spectrum directly reports the oligomer size distribution. Validation experiments were performed to verify the MS data against artifacts.

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Alterations in the long chain base of the sphingosine moiety of gangliosides have been shown to play a role in neurodevelopment and neurodegeneration. Indeed, the accumulation of d20:1 sphingosine has been referred to as a metabolic marker of aging in the brain, however, this remains to be shown in simple gangliosides GM2 and GM3. In this study, Matrix-assisted laser desorption/ionization Imaging Mass Spectrometry (MALDI IMS) was used to examine the neuroanatomical distribution of A-series gangliosides with either 18 or 20 carbon sphingosine chains (d18:1 or d20:1) in Fisher 344 rats across the lifespan.

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1,6-Diphenyl-1,3,5-hexatriene (DPH) is a commonly used fluorescence probe for studying cell membrane-lipids due to its affinity toward the acyl chains in the phospholipid bilayers. In this work, we investigated its use in matrix-assisted laser desorption/ionization (MALDI) as a new matrix for mass spectrometry imaging (MSI) of mouse and rat brain tissue. DPH exhibits very minimal matrix-induced background signals for the analysis of small molecules (below m/z of 1000).

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Several moderately pathogenic Fusarium species produce enniatins, a family of cyclohexadepsipeptides with insecticidal and phytotoxic activities. A semi-targeted LC-MS/MS approach utilizing reversed-phase C8 UHPLC column chromatography that combines both product ion and neutral loss filtering was developed to detect enniatins and structurally-related compounds in a sample. Using this methodology, resolution of all major enniatins was achieved with a 6-min LC run.

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