Simple method for sub-diffraction resolution imaging of cellular structures on standard confocal microscopes by three-photon absorption of quantum dots

This study describes a simple technique that improves a recently developed 3D sub-diffraction imaging method based on three-photon absorption of commercially available quantum dots. The method combines imaging of biological samples via tri-exciton generation in quantum dots with deconvolution and spectral multiplexing, resulting in a novel approach for multi-color imaging of even thick biological samples at a 1.4 to 1.9-fold better spatial resolution. This approach is realized on a conventional confocal microscope equipped with standard continuous-wave lasers. We demonstrate the potential of multi-color tri-exciton imaging of quantum dots combined with deconvolution on viral vesicles in lentivirally transduced cells as well as intermediate filaments in three-dimensional clusters of mouse-derived neural stem cells (neurospheres) and dense microtubuli arrays in myotubes formed by stacks of differentiated C2C12 myoblasts

High-performance liquid chromatography/tandem mass spectrometric assay for the simultaneous measurement of dopamine, norepinephrine, 5-hydroxytryptamine and cocaine in biological samples

A rapid liquid chromatography/tandem mass spectrometry (LC-MS/MS) method has been developed for the measurement of dopamine (DA), 5-hydroxytryptamine (5HT) and norepinephrine (NE) in brain microdialysates. The assay has also been utilised for the simultaneous measurement of these neurotransmitters and cocaine in brain dialysates. The neurotransmitters and cocaine were resolved in a single 4-min run using a binary gradient elution profile. The analytes were detected using tandem mass spectrometry in the positive ion electrospray mode. The limits of detection for DA, NE, 5HT and cocaine were 200, 1000, 900 pM and 1 pg ml(-1), respectively

Correlation between serum ghrelin levels and cocaine-seeking behaviour triggered by cocaine-associated conditioned stimuli in rats

Ghrelin is a brain\u2013gut peptide with growth hormone-releasing and appetite-inducing activities. A growing body of evidence suggests that ghrelin may affect the central reward system and modulate the activity of the mesolimbic system. Recent clinical studies also showed a significant positive correlation between plasma ghrelin levels and craving in alcoholics. Accordingly, the present study investigated the potential role of serum ghrelin levels in the reinstatement of cocaine-seeking behaviour triggered by cocaine-associated cues. In addition, serum corticosterone levels were determined in the light of evidence suggesting that corticosterone plays a modulatory role in cocaine-seeking behaviour. Male Lister Hooded rats under a restricted diet regime were first trained to intravenously self-administer cocaine under a fixed ratio-1 schedule of reinforcement. Conditioned stimuli (CS: tone and cue-light on for 5 seconds) were presented contingently with cocaine delivery. Once a stable baseline of cocaine self-administration was observed, lever presses were extinguished to less than 30% of baseline rates by removing both cocaine and CS. Reinstatement of responding was then induced by re-exposure to cocaine-associated CS. Blood samples for the enzyme immunoassay determination of serum ghrelin and the radioimmunoassay determination of serum corticosterone levels were collected 30 minutes before the beginning of reinstatement sessions. Rats significantly reinstated their responding when exposed to CS. A positive and significant correlation was observed between ghrelin levels (r = 0.64; P < 0.05), but not corticosterone (r = 0.37; NS), and the increased active lever presses only in animals exposed to CS. These findings suggest a potential role of ghrelin in the modulation of cue-triggered reinstatement of cocaine-seeking behaviour

High-performance liquid chromatography/tandem mass spectrometry assay for the rapid high sensitivity measurement of basal acetylcholine from microdialysates

A high-throughput liquid chromatography tandem mass spectrometry (LC/MS/MS) method has been developed for the analysis of acetylcholine (ACh) in brain dialysates. This separation of ACh is based on cation exchange chromatography with elution buffer consisting of a mixture of ammonium acetate, ammonium formate and acetonitrile. Using isocratic separation conditions, ACh was resolved within a minute and detected using tandem mass spectrometry in the positive ion electrospray mode. The limit of detection for ACh was found to be 1 fmol on column with a S/N ratio of 3:1. The assay has been used routinely for the measurement of ACh in brain dialysates from awake freely moving rats. Furthermore, separation conditions were modified to allow simultaneous measurement of ACh and the acetylcholine esterase inhibitor, neostigmine