Wanyun Ma

Non-competitive immunoassay for alpha-fetoprotein using micellar electrokinetic capillary chromatography and laser-induced fluorescence detection

A non-competitive immunoassay based on micellar electrokinetic capillary chromatography (MECC) with laser-induced fluorescence (LIF) detection has been developed for the determination of alpha-fetoprotein (AFP). The anti-AFP antibody was labeled with fluorescein isothiocyanate (FITC) and the product was used as a fluorescent tracer, then AFP was mixed with the labeled antibody. After incubation, the immune AFP-antibody complex was separated from labeled free antibody by MECC. The parameters affecting separation such as the concentration of sodium dodecyl sulfate (SDS), the buffer pH and separation voltage were investigated and the following conditions were selected: 20 mM tetraborate containing 100 mM SDS at pH 9.50, and 20 kV separation voltage. The detection limit of this assay was 0.1 ng/ml with a linear range spanning two orders of magnitude. This method was applied to determine AFP in human serum.

Analysis of trace amino acid neurotransmitters in hypothalamus of rats after exhausting exercise using microdialysis.

A simple but effective coupling of microdialysis and capillary electrophoresis with laser induced fluorescence detection technique was applied to analysis of amino acid neurotransmitters in the hypothalamus of rats after acute exhausting exercise. The separation of amino acids was achieved using an uncoated fused-silica capillary (57 cm x 75 microm I.D.) with a buffer of 10 mM disodium tetraborate at pH 10 and an applied voltage of 12.5 kV. The detection limit was 10(-10) M for each amino acid. It is sufficiently sensitive and rapid for the determination of amino acids in a 5-microl Microdialysate. In comparison to pre-exercise, a significant increase in the levels of six hypothalamic amino acids (arginine, glycine, lysine, glutamic acid, alanine, gamma-amino-n-butyric acid) was found after exercise. These results demonstrate that the increase of metabolic amino acids in the hypothalamus of rats can be induced by exhausting exercise and suggests that amino acid neurotransmitters may play functional roles in the central effects of exercise.

Sensitive elemental analysis of aqueous colloids by laser-induced plasma spectroscopy

Highly sensitive elemental analysis of lead carbonate colloids was demonstrated by two-pulse laser-induced plasma spectroscopy. The first laser pulse created a vapor plume with the particulates concentrated in space because of their slower propagation. They were then ablated by an ArF laser pulse that efficiently atomized and excited the lead analyte. The lead emissions were much enhanced, while the background continuum interference was minimized. The detection limit for lead was shown to be 14.2 ppb, compared with 13 ppm achieved by conventional laser-induced breakdown spectroscopy of lead ions in water and 210 ppb for lead aerosols.

Polymerization of dental composite resins using plasma light

Five visible light-cured composite resins used as restoration or adhesive materials in dentistry, were irradiated with high energy plasma light (1300 mW/cm2), and contraction, rate of contraction, irradiation-induced temperature were analysed. A comparison was carried out with the same materials irradiated with a conventional halogen light (400 mW/cm2). The exposure to the photoactivating lights was either continuously or sequentially in three or more intervals with 10 min between intervals. Comparing the lengths of exposure of both lights, which induced the same contraction in a given material, it was found that the exposure length to the plasma light was greatly reduced, when compared with the exposure length of the halogen light (1:10). Frequently, the final contraction of plasma-irradiated materials was lower, whereas the rate of contraction, as indicated by the linear dimensional variation curves obtained by laser beam scanning method, did not show significant differences between the two lights. The temperature increase induced by plasma light on the material did not exceed the temperature induced by conventional light.

Determination of Biodegradation Products from Benzene, Toluene, Ethylbenzene and Xylenes in Seawater by Purge and Trap Gas Chromatography

Abstract Benzene, toluene, ethylbenzene and xylenes (BTEX) are commonly found in crud oil and used as the direct indicating substance in the Geochemical Investigation for Oil and Gas. BTEX are easily volatile and can be degraded by microorganism, which affects the precise measurement seriously. A method for the determination of the biodegradation process of BTEX in seawater is described. The determination is performed by dynamic headspace (purge and trap) gas chromatography with a photoionization detector (PID). The features of the described method are: detection limits of 7.3–13.2 ng l−1, no sample preparation required, and recovery rate of 92.84%–100.92%. The results of the BTEX biodegradation process are of great significance in the collection, transportation, preservation, and measurement of samples in the Geochemical Investigation for Oil and Gas.

Label-free subcellular 3D live imaging of preimplantation mouse embryos with full-field optical coherence tomography

Early patterning and polarity is of fundamental interest in preimplantation embryonic development. Label-free subcellular 3D live imaging is very helpful to its related studies. We have developed a novel system of full-field optical coherence tomography (FF-OCT) for noninvasive 3D subcellular live imaging of preimplantation mouse embryos with no need of dye labeling. 3D digitized embryos can be obtained by image processing. Label-free 3D live imaging is demonstrated for the mouse embryos at various typical preimplantation stages with a spatial resolution of 0.7 [micro sign]m and imaging rate of 24 fps. Factors that relate to early patterning and polarity, such as pronuclei in zygote, shapes of zona pellucida, location of second polar body, cleavage planes, and the blastocyst axis, can be quantitatively measured. The angle between the two second cleavage planes is accurately measured to be 87 deg. It is shown that FF-OCT provides a potential breakthrough for early patterning, polarity formation, and many other preimplantation-related studies in mammalian developmental biology.

Age-related changes in the localization of DNA methyltransferases during meiotic maturation in mouse oocytes

The effects of maternal aging on the localization of DNA methyltransferases were evaluated during mouse oocyte maturation using fluorescence staining. And we conclude that maternal aging affects the cytoplasmic-to-nuclear trafficking of DNA methyltransferases in mouse oocytes during the time from germinal vesicle breakdown to metaphase I.

Study of dental materials by laser beam scanning

Several properties of dental materials are characterized by dimensional variation induced by different parameters. In this work a non-contact method used for measurement of linear dimensional variation is shown. The accuracy is +/- 1 micron for sample length ranging from 1 to 70 mm.

Understanding three-dimensional spatial relationship between the mouse second polar body and first cleavage plane with full-field optical coherence tomography

Abstract. The morphogenetic relationship between early patterning and polarity formation is of fundamental interest and remains a controversial issue in preimplantation embryonic development. We use a label-free three-dimensional (3-D) imaging technique of full-field optical coherence tomography (FF-OCT) successfully for the first time to study the dynamics of developmental processes in mouse preimplantation lives. Label-free 3-D subcellular time-lapse images are demonstrated to investigate 3-D spatial relationship between the second polar body (2PB) and the first cleavage plane. By using FF-OCT together with quantitative study, we show that only 25% of the predicted first cleavage planes, defined by the apposing plane of two pronuclei, pass through the 2PB. Also only 27% of the real cleavage planes pass through the 2PB. These results suggest that the 2PB is not a convincing spatial cue for the event of the first cleavage. Our studies demonstrate the feasibility of FF-OCT in providing new insights and potential breakthroughs to the controversial issues of early patterning and polarity in mammalian developmental biology.

Intracellular structural changes under the stress of applied force at a nanometre range investigated by atomic force microscopy

The cytoskeleton is a dynamic structural framework fundamental to cell shape and to intracellular structural elements within each cell and their functioning. Using techniques and concepts from the fields of physics and cell biology, our study attempted to find out whether and how the intracellular structures change under applied stress acting on the cytoskeletal fibres within living cells. Here we report that in vitro atomic force microscopy, using the force curve technique during the tapping mode, was used as a tool to apply a nanonewton force. This was achieved by tapping a cytoskeletal fibre bundle within living rat cerebral microvessel endothelial cells on a nanometre scale. The results show that tapping a single point on a certain cytoskeletal fibre bundle artificially removes certain structural elements and to a certain degree results in the rebuilding of the cytoskeletal networks. This suggests that certain stress-sensitivity points exist on the cytoskeletal fibre network and elaborate change in cell structure and shape could be achieved through the application of stress from outside cells.