Biomedical subjects

Qingming Luo

Publications and source records attributed to Qingming Luo.

At least 19 recordsLinked to original sources

PubMed2007

Gender difference in hemodynamic responses of prefrontal area to emotional stress by near-infrared spectroscopy.

Presentation of negative pictures was used as emotional stress to assess gender differences in prefrontal area activation in a functional near-infrared spectroscopy (NIRS) study. Compared with neutral condition, the response of oxy-HB for men yielded no significant difference during stress period, but the response induced by stress pictures for women showed significant enhancement. It was indicated that it is crucial to take gender difference into account when negative stimuli are used in functional brain imaging.

Adult↗

PubMed2006

Differentiating hemodynamic responses in rat primary somatosensory cortex during non-noxious and noxious electrical stimulation by optical imaging.

Nociception in the primary somatosensory (S1) cortex remains in need of further elucidation. The spatiotemporal comparison on changes of the cerebral blood volume evoked by graded peripheral electrical stimulation was performed in rat contralateral somatosensory cortex with optical intrinsic signal imaging (OISI, optical reflectance at 550 nm). Non-noxious electrical stimulus was applied with 5 Hz pulses (0.5 ms peak duration) for 2 s at the threshold current for muscle twitch, while noxious stimulus was delivered at currents of 10x and 20x amplitude of the predetermined threshold. Although the dimensions of peak response defined in the spatial domain (cerebral blood volume increase) in the S1 cortex presented no significant difference under non-/noxious stimuli, its early response component (about 1 s after stimulation onset) revealed by OISI technique was suggested to differentiate the loci of activated cortical region due to different stimulation in this study. The magnitude and duration of the optical intrinsic signal (OIS) response was found increasing with the varying stimulus intensity. Regions activated by the delivery of a noxious stimulus were surrounded by a ring of inverted optical intrinsic signal, the amplitude of that was inversely proportional to the strength of the optical signal attributable to activation. Intense stimuli significantly augmented the inverted optical signal in magnitude and spatial extent. These results indicated that noxious stimulation evoked different response patterns in the contralateral S1 cortex. The magnitude-dependent inverted optical signal might contribute to the differentiation of nociceptive input in the S1 cortex.

Afferent Pathways↗

PubMed2006

Position of the prism in a dispersion-compensated acousto-optic deflector for multiphoton imaging.

The performance of a dispersion-compensated acousto-optic deflector (AOD) for steering femtosecond laser pulses was examined with the prism located before or after the AOD, which is regarded as prism-AOD and AOD-prism, respectively. Comparisons are made over parameters including the spot spatial pattern, output pulse width, scanning linearity, the field of view, and the transmission rate. Fluorescence images of 170 nm diameter beads and cells were measured to provide an overall evaluation for these femtosecond laser beam scanning configurations. On the basis of these experiments, the prism-AOD configuration is concluded to be more advantageous for the purpose of simultaneous compensation for the spatial and temporal dispersion.

Acoustics↗

PubMed2006

Identification and two-photon imaging of oligodendrocyte in CA1 region of hippocampal slices.

Oligodendrocyte (OL) plays a critical role in myelination and axon maintenance in central nervous system. Recent studies show that OL can also express NMDA receptors in development and pathological situations in white matter. There is still lack of studies about OL properties and function in gray matter of brain. Here we reported that some glial cells in CA1 region of rat hippocampal slices (P15-23) had distinct electrophysiological characteristics from the other glia cells in this region, while they displayed uniform properties with OL from white matter in previous report; therefore, they were considered as OL in hippocampus. By loading dye in recording pipette and imaging with two-photon laser scanning microscopy, we acquired the high spatial resolution, three-dimension images of these special cells in live slices. The OL in hippocampus shows a complex process-bearing shape and the distribution of several processes is parallel to Schaffer fiber in CA1 region. When stimulating Schaffer fiber, OL displays a long duration depolarization mediated by inward rectifier potassium channel. This suggested that the OL in CA1 region could sense the neuronal activity and contribute to potassium clearance.

Action Potentials↗

PubMed2006

Detection of MMP activity in living cells by a genetically encoded surface-displayed FRET sensor.

Matrix metalloproteinases (MMPs) are secretory endopeptidases. They have been associated with invasion by cancer-cell and metastasis. Previous studies have demonstrated that proteolytic activity could be detected using fluorescence resonance energy transfer (FRET) with mutants of GFP. To monitor MMP activity, we constructed vectors that encoded a MMP Substrate Site (MSS) between YFP and CFP. In vitro, YFP-MSS-CFP can be used to detect MMP activity and 1,10-phenathroline inhibition of MMP activity. In living cells, MMPs are secreted proteins and act outside of the cell, and therefore YFP-MSS-CFPdisplay was anchored on the cellular surface to detect extracellular MMP. A pDisplay-YC vector expressing the YFP-MSS-CFPdisplay on the cellular surface was transfected into MCF-7 cells that expressed low levels of MMP. Efficient transfer of energy from excited CFP to YFP within the YFP-MSS-CFPdisplay molecule was observed, and real-time FRET was declined when MCF-7 was incubated with MMP2. However, no such transfer of energy was detected in the YFP-MSS-CFPdisplay expressing MDA-MB 435s cells, in which high secretory MMP2 were expressed. The FRET sensor YFP-MSS-CFPdisplay can sensitively and reliably monitor MMP activation in living cells and can be used for high-throughput screening of MMP inhibitors for anti-cancer treatments.

Amino Acid Sequence↗

PubMed2006

Characterization of proteinase activation dynamics by capillary electrophoresis conjugating with fluorescent protein-based probe.

In this paper, a novel strategy was reported to characterize dynamics of proteinase activation based on capillary electrophoresis (CE), using caspase-2 as the model system. A fusion protein conjugating an amino acid sequence VDVAD with two fluorescent proteins enhanced cyan fluorescence protein (ECFP) and red fluorescence protein (DsRed), ECFP-VDVAD-DsRed, was specially designed and expressed in HeLa cells as the substrate of proteinase caspase-2. In this substrate, the sequence VDVAD could be specifically recognized and cleaved by caspase-2 as soon as its activation was initiated with treatment of a certain dose of cisplatin to HeLa cells, which led to a break of the substrate into two fragments. Analyses of the cell lysates using CE in a time course of the apoptosis illustrated the dynamics of caspase-2 activation. It showed that the employment of fusion fluorescent protein greatly facilitated both CE separation and identification of the analytes. This result from cell colony by CE was compared with that from single cell achieved by optical imaging.

Electrophoresis, Capillary↗

PubMed2006

Optical molecular imaging for systems biology: from molecule to organism.

The development of highly efficient analytical methods capable of probing biological systems at system level is an important task that is required in order to meet the requirements of the emerging field of systems biology. Optical molecular imaging (OMI) is a very powerful tool for studying the temporal and spatial dynamics of specific biomolecules and their interactions in real time in vivo. In this article, recent advances in OMI are reviewed extensively, such as the development of molecular probes that make imaging brighter, more stable and more informative (e.g., FPs and semiconductor nanocrystals, also referred to as quantum dots), the development of imaging approaches that provide higher resolution and greater tissue penetration, and applications for measuring biological events from molecule to organism level, including gene expression, protein and subcellular compartment localization, protein activation and interaction, and low-mass molecule dynamics. These advances are of great significance in the field of biological science and could also be applied to disease diagnosis and pharmaceutical screening. Further developments in OMI for systems biology are also proposed.

Animals↗

PubMed2006

Long-term recording on multi-electrode array reveals degraded inhibitory connection in neuronal network development.

Spontaneous neuronal activity plays an important role in development. However, the mechanism that underlies the long-term spontaneous developmental change of cultured neuronal networks in vitro is not well understood. To investigate the contribution of inhibitory and excitatory connections to the development of neuronal networks, dissociated neurons from an embryonic rat hippocampal formation were cultured on a multi-electrode array plate and spontaneous activities were recorded by multi-channel system. These spontaneous activities were compared to bicuculline-induced firings, which were recorded by 60 electrodes simultaneously from 1 to 14 weeks in vitro (WIV). The phenomena showed that the spontaneous firing activities changed from an initial pattern of synchronized bursts to a later pattern of high frequency random spikes. The bicuculline-induced firing activities transformed from a pattern of synchronized bursts throughout all active sites in 3 WIV, to a pattern of local synchronized or random spikes appearing in the intervals of synchronized bursts after 11 WIV, while the firing rate hardly changed. Kynurenic acid, a broad-spectrum glutamate receptor antagonist, blocked all activities while CNQX inhibited only the local synchronized or random spikes. These suggest that the inhibitory connection was age-dependent degraded in vitro and the developmental spontaneous firing pattern was built by the homeostatic balance of the excitatory-inhibitory connection networks. Long-term cultures on MEA provided a useful tool to measure the relationship between spontaneous developmental change and pharmacological influence in vitro.

Animals↗

PubMed2006

Imaging cerebral blood flow through the intact rat skull with temporal laser speckle imaging.

We discovered that laser speckle temporal contrast analysis (LSTCA) is able to access the two-dimensional (2D) cerebral blood flow velocity and vessel structure through the intact rat skull. It is demonstrated that LSTCA can significantly suppress the influence of the laser speckle from the stationary structure, such as the skull, and thus reveal the blood flow and morphology of blood vessels through the laser speckle images recorded from the intact rat skull.

Algorithms↗

PubMed2006

TRAIL-induced apoptosis proceeding from caspase-3-dependent and -independent pathways in distinct HeLa cells.

The apoptotic pathway in higher eukaryotes remains controversial with respect to the necessity of activation of caspase-3 in TRAIL (tumor necrosis factor-related apoptosis-inducing ligand)-treated cells. In this study, a fluorescence resonance energy transfer (FRET) probe was developed to image the activation of caspase-3 and the related apoptotic pathway in TRAIL-treated cells in real time. Both kinds of apoptotic pathways were observed simultaneously in the same experiment proceeding from activation and non-activation of caspase-3. The total apoptotic rate was 56.08%, the apoptotic rates for activation and non-activation of caspase-3 pathways were 21.5% and 34.58%, respectively, which were examined later for Hoechst 33258 staining and morphological characteristics. The apoptotic rate due to the activation of caspase-3 pathways in TRAIL-treated cells has been independently measured to be around 25.11% by capillary electrophoresis (CE) analysis, which confirmed the apoptotic rate due to activation of caspase-3 pathways as found by FRET analysis. This result also suggests that rest apoptosis is preceded by caspase-3-independent pathways, as CE has the ability to quantitatively detect caspase-dependent apoptosis. The observation of the coexistence of caspase-3-dependent and caspase-3-independent apoptotic pathways in the TRAIL-treated cells was unusual in comparison with the previous reports.

Apoptosis↗

PubMed2006

Dynamic analysis of optimality in myocardial energy metabolism under normal and ischemic conditions.

To better understand the dynamic regulation of optimality in metabolic networks under perturbed conditions, we reconstruct the energetic-metabolic network in mammalian myocardia using dynamic flux balance analysis (DFBA). Additionally, we modified the optimal objective from the maximization of ATP production to the minimal fluctuation of the profile of metabolite concentration under ischemic conditions, extending the hypothesis of original minimization of metabolic adjustment to create a composite modeling approach called M-DFBA. The simulation results are more consistent with experimental data than are those of the DFBA model, particularly the retentive predominant contribution of fatty acid to oxidative ATP synthesis, the exact mechanism of which has not been elucidated and seems to be unpredictable by the DFBA model. These results suggest that the systemic states of metabolic networks do not always remain optimal, but may become suboptimal when a transient perturbation occurs. This finding supports the relevance of our hypothesis and could contribute to the further exploration of the underlying mechanism of dynamic regulation in metabolic networks.

Computer Simulation↗

PubMed2006

Origin sites of spontaneous cortical spreading depression migrated during focal cerebral ischemia in rats.

Spontaneous cortical spreading depression (CSD) has been found to occur in the penumbral zone of the brain in rats with focal cerebral ischemia, and has been shown to promote expansion of infarction. Electrophysiological recording of CSD has been used for monitoring the penumbral zone, but with an inherently low spatial resolution; consequently, optical intrinsic signal imaging (OISI) was applied to characterize the spontaneous CSD waves following permanent left middle cerebral artery occlusion (MCAO) in rats under alpha-chloralose/urethane anesthesia. Besides the previous report about the regional variation of optical reflectance during spontaneous CSD following MCAO, the origin site of CSD was easily determined using OISI with the benefit of high resolution in the present study. Those origin points (n = 82) were dynamically located in the ipsilateral hemisphere cortex: sometimes outside of the 6 mm x 8 mm observation area in the parietal cortex (n = 19, 23%), and sometimes inside (n = 63, 77%). The data showed a general trend towards the medial cortex (0.40 +/- 0.15 mm per CSD). Because the lateral cortex of the rat brain proved to be infarcted with 2% 2,3,5-triphenyltetrazolium chloride (TTC) staining after 4 h occlusion, the migration of the origin sites implied a growth of the infarcted area. Hence, the determination of origins of spontaneous CSD using OISI would contribute to the continued study of stroke.

Animals↗

PubMed2006

Simultaneous compensation for spatial and temporal dispersion of acousto-optical deflectors for two-dimensional scanning with a single prism.

The dispersive nature of the acousto-optical deflector (AOD) presents a challenge to applications of two sequential orthogonal AODs (a two-dimensional AOD) as XY scanners in multiphoton microscopy. Introducing a prism before the two-dimensional (2D) AOD allows both temporal and spatial dispersion to be compensated for simultaneously. A 90 fs laser pulse was broadened to 572 fs without compensation, and 143 fs with compensation. The ratio of long axis to short axis of the exiting laser beam spot was 3.50 without compensation and 1.14 with compensation. The insertion loss was 37%. Two-photon fluorescence microscopy used the compensated 2D AOD scanner to image a fluorescent microsphere, which improves signal intensity -15-fold compared with the uncompensated scanner.

Artifacts↗

PubMed2006

The origin of spontaneous synchronized burst in cultured neuronal networks based on multi-electrode arrays.

Many neural networks in mammalian central nervous system (CNS) fire single spike and complex spike burst. In fact, the conditions for triggering burst are not well understood. In the paper multi-electrode arrays (MEA) are used to record the spontaneous electrophysiological activities of cultured rat hippocampal neuronal network for a long time. After about 3 weeks culture, a transition from single spike to burst is observed in several networks. All of these spikes fire quickly before burst begins. The firing rate during the burst is lower than that just before the burst, but differences of inter-spike intervals (ISIs) between two firing patterns are not clear. Moreover, the electrical activities on neighboring electrodes show strong synchrony during the burst activities. In a word, the generation of the burst requires that network should have a sufficient level of excitation as well as a balance of synaptic inhibition.

Animals↗

PubMed2006

A high-resolution anatomical rat atlas.

This paper reports the availability of a high-resolution atlas of the adult rat. The atlas is composed of 9475 cryosectional images captured in 4600 x 2580 x 24-bit TIFF format, constructed using serial cryosection-milling techniques. Cryosection images were segmented, labelled and reconstructed into three-dimensional (3D) computerized models. These images, 3D models, technical details, relevant software and further information are available at our website, http://vchibp.vicp.net/vch/mice/.

Animals↗

PubMed2005

Time-varying spreading depression waves in rat cortex revealed by optical intrinsic signal imaging.

This study aimed to investigate the variation of propagation patterns of successive spreading depression (SD) waves induced by K+ in rat cortex. SD was elicited by 1 M KCl solution in the frontal cortex of 18 Sprague-Dawley rats under alpha-chloralose/urethane anesthesia. We applied optical intrinsic signal imaging (OISI) at an isosbestic point of hemoglobin (550 nm) to examine regional cerebral blood volume (CBV) changes in the parieto-occipital cortex. In 6 of the 18 rats, OISI was performed in conjunction with DC potential recording of the cortex. CBV changes appeared as repetitive propagation of wave-like hyperemia at a speed of 3.7+/-0.4 mm/min, which was characterized by a significant negative peak (-14.3+/-3.2%) in the reflectance signal. Among the observed 186 SDs, the first wave always propagated through the entire imaged cortex in every rat, whereas following waves were likely to bypass the medial area of the imaged cortex (partially propagated waves, n=65, 35%). Correspondingly, DC potential shifts showed non-uniform in the medial area, and they seemed closely related to the changes in reflectance. For partially propagated SD waves, the mean time interval to the previous SD wave (217.0+/-24.3 s) was significantly shorter than for fully propagated SD waves (251.2+/-29.0 s). The results suggest that the propagation patterns of a series of SD waves are time-varying in different regions of rat cortex, and the variation is related to the interval between SD waves.

Action Potentials↗

PubMed2005

Continuous wave-based multiphoton excitation fluorescence for capillary electrophoresis.

It was reported that a novel detection method, continuous wave (CW)-based multiphoton excitation (MPE) fluorescence detection with diode laser (DL), has been firstly proposed for capillary electrophoresis (CE). Special design of end-column detection configuration proved to be superior to on-column type, considering the detection sensitivity. Three different kinds of fluorescent tags that were widely used as molecular label in bio-analysis, such as small-molecule dye, fluorescent protein and nano particle or also referred to as quantum dot (QD), have been evaluated as samples for the constructed detection scheme. Quantitative analyses were also performed using rhodamine species as tests, which revealed dynamic linear range over two orders of magnitude, with detection limit down to zeptomole-level. Simultaneous detection of fluorescent dyestuffs with divergent excitation and emission wavelengths in a broad range showed advantage of this scheme over conventional laser-induced fluorescence (LIF) detection. Further investigations on CW-MPE fluorescence detection with diode laser for capillary zone electrophoresis (CZE) and micellar electrokinetic chromatography (MEKC) separations of fluorescein isothiocyanate (FITC) labeled amino acids indicated good prospect of this detection approach in various micro or nano-column liquid phase separation technologies.

Electrophoresis, Capillary↗

PubMed2005

Micro-separation toward systems biology.

Current biology is experiencing transformation in logic or philosophy that forces us to reevaluate the concept of cell, tissue or entire organism as a collection of individual components. Systems biology that aims at understanding biological system at the systems level is an emerging research area, which involves interdisciplinary collaborations of life sciences, computational and mathematical sciences, systems engineering, and analytical technology, etc. For analytical chemistry, developing innovative methods to meet the requirement of systems biology represents new challenges as also opportunities and responsibility. In this review, systems biology-oriented micro-separation technologies are introduced for comprehensive profiling of genome, proteome and metabolome, characterization of biomolecules interaction and single cell analysis such as capillary electrophoresis, ultra-thin layer gel electrophoresis, micro-column liquid chromatography, and their multidimensional combinations, parallel integrations, microfabricated formats, and nano technology involvement. Future challenges and directions are also suggested.

Chromatography, Liquid↗