A FACTOR FROM GRANULOSA CELLS CAN STIMULATE OOCYTE TISSUE PLASMINOGEN ACTIVATOR ACTIVITY

Several studies indicate that substances synthesized by granulosa cells are capableof regulating oocyte activity. We have studied the effect of factors synthesized by gran-ulosa cells on tPA activity of denuded oocytes using a co- culture system. The resultsshow that an FSH- dependent factor(s) synthesized by granulosa cells (but not by theca-interstitial cells) is capable of stimulating tPA activity of denuded oocytes. This findingis important for understanding hormonal regulation of oocyte tPA activity by mediatorssynthesized in granulosa cells.     

Phase modulation in dipolar-coupled A2 spin systems: effect of maximum state mixing in H NMR in vivo

Coupling constants of nuclear spin systems can be determined from phase modulation of multiplet resonances. Strongly coupled systems such as citrate in prostatic tissue exhibit a more complex modulation than AX connectivities, because of substantial mixing of quantum states. An extreme limit is the coupling of n isochronous spins (A_n system). It is observable only for directly connected spins like the methylene protons of creatine and phosphocreatine which experience residual dipolar coupling in intact muscle tissue in vivo. We will demonstrate that phase modulation of this “pseudo-strong” system is quite simple compared to those of AB systems. Theory predicts that the spin-echo experiment yields conditions as in the case of weak interactions, in particular, the phase modulation depends linearly on the line splitting and the echo time.     

基于液氮低温冷刀系统的冻结组织温度场分布研究

设计了基于液氮的低温冷冻治疗系统,并进行动物组织实验研究,得到组织关键测温点的温度变化;并对冷冻过程进行数值模拟,将实验结果与模拟冷冻结果进行对比,根据二者的差异对数值模拟中采用的组织热物性参数进行修正,使模拟结果更接近于实际冷冻过程.     

Effect of pH on the interfacial adsorption activity of pulmonary surfactant

The effect of pH on the interfacial adsorption activity of pulmonary surfactant was examined. Measurements of the surface tension were made in a Wilhelmy-like surface microbalance specially designed to assay small volumes of hypophase in thermostatically controlled conditions. Alkaline pH caused a significant decrease of the surface activity of both pulmonary surfactant and a lipid extract from surfactant (LES) (containing all of the lipids and surfactant protein-B (SP-B) and surfactant protein-C (SP-C) hydrophobic surfactant proteins, but lacking surfactant protein-A). The pK calculated from the change of surface activity versus pH was 9.18±0.26 and 9.27±0.31 for pulmonary surfactant and LES, respectively. The results from this study support the idea that electrostatic interactions between basic residues of SP-B and SP-C and negatively charged surfactant phospholipids could be important for the interfacial adsorption activity of pulmonary surfactant.     

Quantitative images of metals in plant tissues measured by laser ablation inductively coupled plasma mass spectrometry

Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) was used for quantitative imaging of toxic and essential elements in thin sections (thickness of 30 or 40 μm) of tobacco plant tissues. Two-dimensional images of Mg, Fe, Mn, Zn, Cu, Cd, Rh, Pt and Pb in leaves, shoots and roots of tobacco were produced. Sections of the plant tissues (fixed onto glass slides) were scanned by a focused beam of a Nd:YAG laser in a laser ablation chamber. The ablated material was transported with argon as carrier gas to the ICP ion source at a quadrupole ICP-MS instrument. Ion intensities of the investigated elements were measured together with ¹³C⁺, ³³S⁺ and ³⁴S⁺ within the entire plant tissue section. Matrix matching standards (prepared using powder of dried tobacco leaves) were used to constitute calibration curves, whereas the regression coefficient of the attained calibration curves was typically 0.99. The variability of LA-ICP-MS process, sample heterogeneity and water content in the sample were corrected by using ¹³C⁺ as internal standard. Quantitative imaging of the selected elements revealed their inhomogeneous distribution in leaves, shoots and roots.     

Determination of methylmercury in organic matrices with gas chromatography/ atomic absorption spectrometry

Determinations of methylmercury in biological tissues by gas chromatography with electron-capture detection are often disturbed by electron-capturing compounds simultaneously eluting with the organo-mercury compound.Identification and quantification of methylmercury is improved by interfacing the gas chromatograph to the gas cell of a flameless atomic absorption spectrometer. The construction of the transfer line used is described.     

Rational Design and Development of Anisotropic and Mechanically Strong Gelatin‐Based Stress Relaxing Hydrogels for Osteogenic/Chondrogenic Differentiation

Rational design and development of tailorable simple synthesis process remains a centerpiece of investigational efforts toward engineering advanced hydrogels. In this study, a green and scalable synthesis approach is developed to formulate a set of gelatin‐based macroporous hybrid hydrogels. This approach consists of four sequential steps starting from liquid‐phase pre‐crosslinking/grafting, unidirectional freezing, freeze‐drying, and finally post‐curing process. The chemical crosslinking mainly involves between epoxy groups of functionalized polyethylene glycol and functional groups of gelatin both in liquid and solid state. Importantly, this approach allows to accommodate different polymers, chitosan or hydroxyethyl cellulose, under identical benign condition. Structural and mechanical anisotropy can be tuned by the selection of polymer constituents. Overall, all hydrogels show suitable structural stability, good swellability, high porosity and pore interconnectivity, and maintenance of mechanical integrity during 3‐week‐long hydrolytic degradation. Under compression, hydrogels exhibit robust mechanical properties with nonlinear elasticity and stress‐relaxation behavior and show no sign of mechanical failure under repeated compression at 50% deformation. Biological experiment with human bone marrow mesenchymal stromal cells (hMSCs) reveals that hydrogels are biocompatible, and their physicomechanical properties are suitable to support cells growth, and osteogenic/chondrogenic differentiation, demonstrating their potential application for bone and cartilage regenerative medicine toward clinically relevant endpoints.     

Instrument design and characterization for high resolution MALDI-MS imaging of tissue sections

In previous work, we have reported using a MALDI imaging time-of-flight mass spectrometer for the detection of protein ions from tissue sections with spatial resolution of 25 microm. We present here imaging mass spectrometry results obtained with a high-resolution scanning MALDI time-of-flight mass spectrometer, equipped with a coaxial laser illumination ion source, capable of achieving irradiation areas as small as 40 microm(2) (ca 7 microm diameter). MALDI-generated analyte ion signals from these very small irradiation volumes can be observed in a molecular weight range up to 27,000. High-resolution imaging mass spectrometry images were successfully generated from matrix thin film samples and tissue sections with scanning resolutions at and below 10 microm. This work also provides fundamental characterization of the ion signal dependence as a function of various focus and fluence parameters that will be required for extension to tissue imaging at the subcellular level.     

Patterned co-culture of primary hepatocytes and fibroblasts using polyelectrolyte multilayer templates

This paper describes the formation of patterned cell co-cultures using the layer-by-layer deposition of synthetic ionic polymers and without the aid of adhesive proteins/ligands such as collagen or fibronectin. In this study, we used synthetic polymers, namely poly(diallyldimethylammonium chloride) (PDAC) and sulfonated polystyrene (SPS) as the polycation and polyanion, respectively, to build the multilayer films. We formed SPS patterns on polyelectrolyte multilayer (PEM) surfaces either by microcontact printing PDAC onto SPS surfaces or vice-versa. To create patterned co-cultures on PEMs, we capitalize on the preferential attachment and spreading of primary hepatocytes on SPS as opposed to PDAC surfaces. In contrast, fibroblasts readily attached to both PDAC and SPS surfaces, and as a result, we were able to obtain patterned co-cultures of fibroblast and primary hepatocytes on synthetic PEM surfaces. We characterized the morphology and hepatic-specific functions of the patterned cell co-cultures with microscopy and biochemical assays. Our results suggest an alternative approach to fabricating controlled co-cultures with specified cell-cell and cell-surface interactions; this approach provides flexibility in designing cell-specific surfaces for tissue engineering applications.     

Orthogonal organic and aqueous‐based washes of tissue sections to enhance protein sensitivity by MALDI imaging mass spectrometry

Imaging mass spectrometry (IMS) is an emergent and innovative approach for measuring the composition, abundance and regioselectivity of molecules within an investigated area of fixed dimension. Although providing unprecedented molecular information compared with conventional MS techniques, enhancement of protein signature by IMS is still necessary and challenging. This paper demonstrates the combination of conventional organic washes with an optimized aqueous‐based buffer for tissue section preparation before matrix‐assisted laser desorption/ionization (MALDI) IMS of proteins. Based on a 500 mM ammonium formate in water–acetonitrile (9:1; v/v, 0.1% trifluororacetic acid, 0.1% Triton) solution, this buffer wash has shown to significantly enhance protein signature by profiling and IMS (~fourfold) when used after organic washes (70% EtOH followed by 90% EtOH), improving the quality and number of ion images obtained from mouse kidney and a 14‐day mouse fetus whole‐body tissue sections, while maintaining a similar reproducibility with conventional tissue rinsing. Even if some protein losses were observed, the data mining has demonstrated that it was primarily low abundant signals and that the number of new peaks found is greater with the described procedure. The proposed buffer has thus demonstrated to be of high efficiency for tissue section preparation providing novel and complementary information for direct on‐tissue MALDI analysis compared with solely conventional organic rinsing. Copyright © 2013 John Wiley & Sons, Ltd.