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21.
This paper reveals the formation of annular lamellar body (ALB) in the ganglion of leech by means of in situ fixation and the lanthanum nitrate tracer technique. This formation involves both wrapping and internalization of the gap junctions between glial processes themselves, as well as between neuron and glial process. The results indicate that there is probably an active process of internalization of membrane structures involving gap junctions between neuron and glial cell in the central nervous system in leech. The functions of ALB are discussed. 相似文献
22.
Lijun Kong 《European Polymer Journal》2006,42(12):3171-3179
In order to increase the biocompatibility and bioactivity of chitosan, hydroxyapatite had been in situ combined into chitosan scaffolds. The bioactivity of the composite scaffolds was studied by examining the apatite formed on the scaffolds by incubating in simulated body fluid and the activity of preosteoblasts cultured on them. The apatite layer was assessed using scanning electronic microscope (SEM), X-ray diffraction (XRD), Fourier-Transformed Infrared spectroscopy (FTIR) and weight measurement. Composite analysis showed that after incubation in simulated body fluid on both of the scaffolds carbonate hydroxyapatite was formed. With increasing nano-hydroxyapatite content in the composite, the quantity of the apatite formed on the scaffolds increased. Compared with pure chitosan, the composite with nano-hydroxyapatite could form apatite more readily during the biomimetic process, which suggests that the composite possessed better mineralization activity. Furthermore, preosteoblast cells cultured on the apatite-coated scaffolds showed different behavior. On the apatite-coated composite scaffolds cells presented better proliferation than on apatite-coated chitosan scaffolds. In addition, alkaline phosphatase activities of cells cultured on the scaffolds in conditioned medium were assessed. The cells on composite scaffolds showed a higher alkaline phosphatase activity which suggested a higher differentiation level. The results indicated that the addition of nano-hydroxyapatite improved the bioactivity of chitosan/nano-hydroxyapatite composite scaffolds. On the other hand, that is to say composition of substrates could affect the apatite formation on them, and pre-loaded hydroxyapatite can enhance the apatite-coating. It will also be significant in preparation of apatite-coating polymer scaffolds for bone tissue engineering. 相似文献
23.
Hejun WANG 《数学年刊B辑(英文版)》2024,45(2):179-192
This paper concerns the even Lp Gaussian Minkowski problem in n-dimensional
Euclidean space R
n
. The existence of the solution to the even Lp Guassian Minkowski
problem for p > n is obtained. 相似文献
24.
John Kalliongis Darryl McCullough 《Transactions of the American Mathematical Society》1996,348(5):1739-1755
The observation that the quotient orbifold of an orientation- reversing involution on a 3-dimensional handlebody has the structure of a compression body leads to a strong classification theorem, and general structure theorems. The structure theorems decompose the action along invariant discs into actions on handlebodies which preserve the -fibers of some -bundle structure. As applications, various results of R. Nelson are proved without restrictive hypotheses.
25.
以含铈铝锂合金为研究对象,研究了磁场对含稀土铝锂合金时效过程的影响,从断裂特征及微观组织两方面分析了磁场作用规律。实验结果表明:未加磁场时,合金的断裂特征以理断裂为主;扁平晶粒厚度不匀,在磁场作用下,此合金的断裂特征与微观组织发生明显改观,随磁感应强度增强,合金主断裂面上准解理断裂特征减弱,同时二次裂纹增多,分层比较升高;扁平晶粒厚度变薄,尺寸趋于均匀。用少体物理理论,探讨了磁场对含稀土合金原子扩散过程的影响,为进一步研究稀土元素在磁场中的行为及其局域效应提供了一定的实验依据。 相似文献
26.
S. Bhattacharyya A. N. Sil T. K. Mukherjee P. K. Mukherjee P. Vasu 《International journal of quantum chemistry》2007,107(4):946-951
Electron affinity of plasma embedded muonium (μ+e?) and pionium (π+e?) has been estimated using a general three‐body formalism within variational framework. Electron correlation is taken care of using extended Hylleraas basis sets. The stability of the three‐body systems have been studied under the Debye screening model of the plasma, which changes the Coulombic potential to the screened Coulomb one. The electron affinity of the muonium and pionium is maximum for free systems, and it decreases gradually toward zero with increase of the plasma strength, which tends to push the three‐body system toward gradual instability. The electron correlation contribution to the affinity has been analyzed. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007 相似文献
27.
Molecular chaperones, folding catalysts, and the recovery of active recombinant proteins fromE. coli
Jeffrey G. Thomas Amanda Ayling François Baneyx 《Applied biochemistry and biotechnology》1997,66(3):197-238
The high-level expression of recombinant gene products in the gramnegative bacteriumEscherichia coli often results in the misfolding of the protein of interest and its subsequent degradation by cellular proteases or its deposition
into biologically inactive aggregates known as inclusion bodies. It has recently become clear that in vivo protein folding
is an energy-dependent process mediated by two classes of folding modulators. Molecular chaperones, such as the DnaK-DnaJ-GrpE
and GroEL-GroES systems, suppress off-pathway aggregation reactions and facilitate proper folding through ATP-coordinated
cycles of binding and release of folding intermediates. On the other hand, folding catalysts (foldases) accelerate rate-limiting
steps along the protein folding pathway such as thecis/trans isomerization of peptidyl-prolyl bonds and the formation and reshuffling of disulfide bridges. Manipulating the cytoplasmic
folding environment by increasing the intracellular concentration of all or specific folding modulators, or by inactivating
genes encoding these proteins, holds great promise in facilitating the production and purification of heterologous proteins.
Purified folding modulators and artificial systems that mimic their mode of action have also proven useful in improving the
in vitro refolding yields of chemically denatured polypeptides. This review examines the usefulness and limitations of molecular
chaperones and folding catalysts in both in vivo and in vitro folding processes. 相似文献
28.
We have developed a time-reversible rigid-body (rRB) molecular dynamics algorithm in the isothermal-isobaric (NPT) ensemble. The algorithm is an extension of rigid-body dynamics [Matubayasi and Nakahara, J Chem Phys 1999, 110, 3291] to the NPT ensemble on the basis of non-Hamiltonian statistical mechanics [Martyna, G. J. et al., J Chem Phys 1994, 101, 4177]. A series of MD simulations of water as well as fully hydrated lipid bilayer systems have been undertaken to investigate the accuracy and efficiency of the algorithm. The rRB algorithm was shown to be superior to the state-of-the-art constraint-dynamics algorithm SHAKE/RATTLE/ROLL, with respect to computational efficiency. However, it was revealed that both algorithms produced accurate trajectories of molecules in the NPT as well as NVT ensembles, as long as a reasonably short time step was used. A couple of multiple time-step (MTS) integration schemes were also examined. The advantage of the rRB algorithm for computational efficiency increased when the MD simulation was carried out using MTS on parallel processing computer systems; total computer time for MTS-MD of a lipid bilayer using 64 processors was reduced by about 40% using rRB instead of SHAKE/RATTLE/ROLL. 相似文献
29.
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