Seasonal Ammonia Emissions from a Free-Stall Dairy in Central Texas

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Single-cell gene expression analysis: implications for neurodegenerative and neuropsychiatric disorders

Technical and experimental advances in microaspiration techniques, RNA amplification, quantitative real-time polymerase chain reaction (qPCR), and cDNA microarray analysis have led to an increase in the number of studies of single-cell gene expression. In particular, the central nervous system (CNS) is an ideal structure to apply single-cell gene expression paradigms. Unlike an organ that is composed of one principal cell type, the brain contains a constellation of neuronal and noneuronal populations of cells. A goal is to sample gene expression from similar cell types within a defined region without potential contamination by expression profiles of adjacent neuronal subpopulations and noneuronal cells. The unprecedented resolution afforded by singlecell RNA analysis in combination with cDNA microarrays and qPCR-based analyses allows for relative gene expression level comparisons across cell types under different experimental conditions and disease states. The ability to analyze single cells is an important distinction from global and regional assessments of mRNA expression and can be applied to optimally prepared tissues from animal models as well as postmortem human brain tissues. This focused review illustrates the potential power of single-cell gene expression studies within the CNS in relation to neurodegenerative and neuropsychiatric disorders such as Alzheimer’s disease (AD) and schizophrenia

Asymmetric Generalization and Interaction Profiles in Rhesus Monkeys Discriminating Intravenous Cocaine or Intravenous Heroin from Vehicle

Many polydrug abusers combine cocaine with heroin in the form of a “speedball.” This study investigated the discriminative stimulus (DS) effects of speedballs in rhesus monkeys trained to discriminate either intravenous cocaine or intravenous heroin from vehicle. Initial substitution tests revealed an asymmetry in the generalization profile of dopamine and opioid agonists such that μ agonists partially substituted for cocaine, but direct and indirect dopamine agonists did not substitute for heroin. Subsequent speedball tests in which drug mixtures were administered by coinjecting the component drugs while keeping the dose-ratio constant revealed an additional asymmetry. In cocaine-trained monkeys, coadministration of cocaine and heroin produced leftward shifts in the cocaine dose-response function. Heroin's cocaine-enhancing effects were mimicked by the μ agonists fentanyl and methadone and less consistently by the δ agonist (+)-4-[(αR)-α-((2S,5R)-4-allyl-2,5-dimethyl-1-piperazinyl)-3-methoxybenzyl]-N,N-diethylbenzamide (SNC 80) and reversed by the μ antagonist naltrexone and the δ antagonist naltrindole. In heroin-trained monkeys, coadministration of cocaine and heroin attenuated the DS effects of heroin. Cocaine's heroin-attenuating effects were mimicked by the D1-like agonist 6-chloro-7,8-dihydroxy-1-phenyl-2,3,4,5-tetrahydro-(1H)-3-benzazepine (SKF 81297) and the D2-like agonist R-(−)-propylnorapomorphine and reversed by the D1-like antagonist (6aS-trans)-11-chloro-6,6a,7,8,9,13b-hexahydro-7-methyl-5H- benzo[d] aphtha[2,1-b]azepin-12-ol hydrobromide (SCH 39166) and the D2-like antagonist raclopride. Attenuation of the effects of heroin was accompanied by decreases in response rate. These results suggest that heroin enhances the DS effects of cocaine via μ, and to a lesser extent δ, receptor mechanisms; whereas cocaine-induced inhibition of the DS effects of heroin probably was due at least in part to masking of the heroin DS presumably via stimulation of both D1- and D2-like receptors

Glutamatergic Gene Expression Is Specifically Reduced in Thalamocortical Projecting Relay Neurons in Schizophrenia

BACKGROUND: Impairment of glutamate neurons which relay sensory and cognitive information from the medial dorsal thalamus to the dorsolateral prefrontal cortex and other cortical regions may contribute to the pathophysiology of schizophrenia. In this study we have assessed the cell-specific expression of glutamatergic transcripts in the medial dorsal thalamus. METHODS AND MATERIALS: We used laser-capture microdissection to harvest two populations of medial dorsal thalamic cells, one enriched with glutamatergic relay neurons, and the other with GABAergic neurons and astroglia, from postmortem brains of subjects with schizophrenia (n=14) and a comparison group (n=20). Quantitative polymerase chain reaction (QPCR) of extracted RNA was used to assay gene expression in different cell populations. RESULTS: The transcripts encoding the ionotropic glutamate receptor subunits NR2D, GluR3, GluR6, GluR7, and the intracellular proteins GRIP1 and SynGAP1 were significantly decreased in relay neurons but not in the mixed glial and interneuron population in schizophrenia. DISCUSSION: Our data suggest that reduced ionotropic glutamatergic expression occurs selectively in neurons giving rise to the cortical projections of the medial dorsal thalamus in schizophrenia, rather than in thalamic cells which function locally. Our findings indicate that glutamatergic innervation is dysfunctional in the circuitry between the medial dorsal thalamus and cortex