In this study we report on the establishment of novel conditions which permit efficient retrovirus-mediated gene transfer of human adenosine deaminase (ADA) into murine hematopoietic progenitors. Using Southern blot analysis and an ADA probe, we demonstrated that prestimulation of bone marrow cells over an in vitro culture of adherent stromal cell layers (ACLs) for two days provides favorable conditions for gene transfer in the absence of exogenous growth factors. In bone marrow transplant recipients reconstituted with retrovirally-marked cells, ADA was detected in spleen, thymus and bone marrow cells of the recipients eight months after transplantation. These observations were also seen in transplants of embryonal hematopoietic stem cells. By using different incubation protocols, it was found that the developmental fate of hematopoietic stem cells varied with the presence of exogenous growth factors or an ACL in the prestimulation phase. Polyclonal hematopoiesis with multiple clones appearing simultaneously was revealed in mice reconstituted with growth factor-stimulated cells four months after transplantation. This was detected by multiple integration patterns of ADA integration into the genomes of individual colony forming units-spleen (CFU-S) in transplantation recipient mice. In contrast, two to five months after transplantation, polyclonal hematopoiesis was not observed in mice reconstituted with cells infected in the absence of growth factors. It appears that utilization of the bone marrow microenvironment through the use of an ACL results in a narrower spectrum of integration patterns, suggesting that a type of oligoclonal or monoclonal hematopoiesis is occurring. These studies demonstrate that an ACL provides novel conditions for successful gene transfer and stable integration of the vector into the genome. Use of an ACL may be advantageous for successful hematopoietic stem cell gene therapy. 相似文献
A cyclopropanation reaction of allylmethacrylate (1) with ethyldiazoacetate (2) lead to the formation of 2-(2-methyl-acryloyloxymethyl)-cyclopropanecarboxylic acid ethyl ester (3) as a mixture of cis/trans isomers in molar ratio 2:1. The cis isomer could be selectively hydrolyzed by use of Pig liver esterase (PLE). An isolated cis-2-(2-methyl-acryloyloxymethyl)-cyclopropanecarboxylic acid (4) exhibited optical activity. The monomer 3 was easily polymerized using AIBN and benzopinacol as free radical initiators at 65 and 130 °C, respectively. 1H NMR and FT-IR analyses confirmed the presence of the chemically stable cyclopropane ring in both monomer and polymers. The obtained polymers were also characterized by GPC and DSC measurements. A depolymerization behaviour was observed heating the polymers at 200-250 °C. The regeneration of starting cis/trans isomers of 3 can be taken as a proof of the high thermal stability of the cyclopropane ring. 相似文献
We present experimental and computational results that explain some aspects of measured energy release in explosions of unconfined trinitrotoluene [TNT, C6H2(NO2)3CH3], and an aluminum‐containing explosive formulation, and show how this energy release can influence shock wave velocities in air. In our interpretation, energy release is divided into early, middle, and late time regimes. An explanation is provided for the interdependence of the time regimes and their influence on the rate at which energy (detonation/explosion and afterburn) is released. We use a merging of the thermodynamic and chemical kinetic processes that predicts how chemical kinetics may determine the time delay of the afterburn of combustible gases produced by the initial detonation/explosion/fast reaction. The thermodynamic computer code CHEETAH is used to predict gaseous and solid products of early time energy release, and a chemical kinetic reaction mechanism (CHEMKIN format) is used to describe the subsequent afterburn of the gas phase products in air. Results of these calculations are compared with field measurements of unconfined explosions of 2 kg charge weights of TNT and an aluminum‐containing explosive formulation. 相似文献
Based on the crystal structures of human α‐GalCer–CD1d and iNKT–α‐GalCer–CD1d complexes, nonglycosidic analogues of α‐GalCer were synthesized. They activate iNKT cells resulting in dendritic cell maturation and the priming of antigen‐specific T and B cells. Therefore, they are attractive adjuvants in vaccination strategies for cancer and infectious diseases.
Sarcomatoid carcinomas (SC) of the lung are the most common pulmonary neoplasms that exhibit a composition by spindled or pleomorphic tumor cells. As such, many of them may be confused easily with true sarcomas diagnostically unless special immunohistological or ultrastructural analyses are performed. Reactivity is expected for keratin, epithelial membrane antigen, or collagen type IV in the sarcomalike elements in SC, although it may be focal. Electron microscopy often shows the presence of junctional complexes between tumor cells, with or without pericellular basal lamina and cytoplasmic skeins of intermediate filaments. Current terminological preferences are such that several formerly used terms--including "spindle-cell carcinoma," "pulmonary blastoma," "squamous cell carcinoma with pseudosarcomatous stroma," "pseudosarcoma," and "carcinosarcoma"--are now encompassed by the more generic designation of "sarcomatoid carcinoma." The clinical course of patients with this neoplasm is aggressive, with an overall 5-year survival rate approximating 20%. 相似文献
The strength and fatigue resistance of silicon nitride was determined from specimens machined from two hot–pressed billets. The results indicate that although fatigue resistance is not affected up to 1100°C, differences in chemical composition between the two billets result in different high–temperature strengths. Billet acceptance criteria include both high–temperature strength and oxidation resistance specifications. 相似文献