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ABSTRACT: Human embryonic germ (hEG) cells, which have been advanced as one of the most important sources of pluripotent stem cells [the other one being human embryonic stem cells], can be propagated in vitro indefinitely in the primitive undifferentiated state while being capable of developing into all three germ layer derivatives, hence have become anticipated developing novel strategies of tissue regeneration and transplantation in the treatment of degenerative diseases. In the experiments here, we derived hEG cells from cultured human primordial germ cells (PGCs) of 6- to 9-week-post-fertilization embryos. They satisfied the criteria previously used to define hEG cells, including the expression of markers characteristic of pluripotent cells-abundant alkaline phosphatase (AP) activity, stage specific embryonic antigen (SSEA)-1(+), SSEA-3(-), SSEA-4(+), TRA-1-60(+), TRA-1-81(+), Oct-4(+), and hTERT(+), the retention of normal karyotypes, and possessing pluripotency by forming embryoid bodies (EBs) in vitro. Furthermore, these derived cells tended to neurally differentiate in vitro, especially under high-density culture conditions. We successfully isolated neural progenitor cells from differentiating hEG cultures and about 10% cells induced by 2microM all-trans-retinoic acid (RA) or 0.1mM dibutyryl cyclic AMP (dbcAMP)/1mM forskolin to mature neurons expressing microtubule-associated protein 2ab (MAP2ab), synaptophysin, beta-tubulin III, neuron-specific enolase (NSE), tyrosine hydroxylase (TH), but no glial fibrillary acid protein (GFAP) and choline acetyl transferase (ChAT). The data suggested that hEG cells may provide a potential source of cells for use in transplantation therapy for neurological degenerative diseases.
Biochemical and Biophysical Research Communications 03/2005; 327(2):548-56. · 2.48 Impact Factor
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ABSTRACT: Cognitive deficits could be alleviated by transplantation of neural stem cells in animals. Grafted cells may differentiate into neurons, thereby improving animal cognition. Alternatively, grafted cells may provide neurotrophic factors to modify neuronal functions and to alleviate cognitive deficits. To test which mechanism is underlying this recovery process, senescence-accelerated mice were transplanted with human neural stem cells into the hippocampus. The effect of cell transplantation was assessed in the Morris water maze. The survival and differentiation of grafted cells and the expression of NMDA receptors were examined. The data suggested that in addition to the neural differentiation of grafted neural stem cells, up-regulation of NMDA receptors after transplantation also contributed to the alleviation of cognitive deficits in this animal model.
Neuroreport 09/2004; 15(11):1739-43. · 1.66 Impact Factor
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ABSTRACT: In order to obtain better mechanical properties, fine particles in several micron or submicron diameter are used as reinforcement to reduce stress concentration which are usually induced by larger particles. Zn–22% Al matrix composites with fine alumina particulate reinforcement are fabricated by high intensity ultrasonic treatment. The particulate sizes are chosen with the minimum 0.5 μm. Comparing the height change of composite samples before and after remelted, which have been degassed with semisolid compression, the relation between apparent viscosity and reinforcement diameter is obtained. Experimental results show that there is no interface reactive product involved in the apparent viscosity change. With smaller particulate size, the viscous force is enhanced. That is the dominating reason for the composite melt apparent viscosity increment. An additional reason is the gas introduced with the particulates.
Journal of Materials Processing Technology.
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ABSTRACT: Experiments to continuously separate inclusions from aluminum melt were conducted on a laboratory-scale apparatus by using high-frequency alternating magnetic field. It was found that the separating efficiency of 6-μm alumina inclusions can exceed 95%. The separating efficiency for the square separator channels is significantly higher than that for the circular separator channels under the close processing conditions, which supports that the separating efficiency can be improved by disturbance in the melt.
Materials Letters. 55(5):322-326.
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ABSTRACT: A new refining method—melt thermal treatment without additive to melt is studied in this paper. Microstructure analysis and property evaluation of hypoeutectic Al–Si alloys treated with this method show that the solidification microstructure can be refined significantly with a considerable increase in elongation ratio and strength. Effects such as cooling rate, holding time and alloy composition on the solidification microstructure and mechanical properties have been evaluated. It is shown that the strengthening and toughening effects on the treated samples vary with alloy composition. The property increment of the alloy rich of iron is relatively more remarkable than those rich of Cu or Mg element. Specifically, the structure of the low temperature melt is identified as a primary factor, on which the solidification structure of the treated melt is dependent.
Materials Science and Engineering: A. 338:101-107.
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ABSTRACT: Trajectories of inclusion particles in aluminium melt flowing in a square channel were calculated numerically. It is found that secondary flow of the melt accelerates the transportation of the particles from the inner region to the vicinity of the wall and greatly shortens the separation time of those particles.
Scripta Materialia. 48(9):1385-1390.
