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1.
Cancer invasion and metastasis are associated with matrix degradation. We describe a novel in vivo model of invasion by squamous epithelial neoplastic cells derived from transgenic mice grown on acellular human dermis. Human dermis was subjected to multiple freeze-thaw cycles to render it acellular, maintaining the basement membrane of the former dermal-epidermal junction. Cells representing discrete stages of a multistep transgenic mouse model of epidermal carcinogenesis (neonatal transgenic keratinocytes, moderately/poorly differentiated squamous cell carcinoma, and lymph node metastasis) were seeded onto the basement membrane surface, grown in culture for 4 days, grafted in a subpannicular pocket of athymic mice, and harvested after 3 weeks. Histological analysis demonstrated that neonatal transgenic keratinocytes did not degrade the basement membrane or invade the underlying dermis. In contrast, malignant cells derived from both a moderately differentiated squamous carcinoma and a lymph node metastasis were highly invasive. Immunohistochemical analysis revealed collagenase only in nests of invading malignant cells in contact with the dermal matrix, but not in the tumor mass remaining above the basement membrane, suggesting that this proteinase may be required for stromal invasion. This novel model recapitulates the events seen in malignant invasion: transgenic keratinocytes are unable to penetrate the dermis while cells from a moderately differentiated carcinoma and from lymph node metastasis consistently invade. 相似文献
2.
In this report the effects of single doses of ionizing radiation on the mRNA expression of several proteins involved in multiple drug resistance were analyzed. Murine NIH 3T3 cells treated with single doses of 5, 10 and 20 Gy during the time interval from 1.5 to 72 h after irradiation were compared with their corresponding controls at the same points of time. The glutathione S-transferase-pi (GST pi) level was elevated in cells treated with 10 or 20 Gy from 24 to 72 h after irradiation compared with the control. Topoisomerase II alpha and thymidylate synthase were decreased in irradiated cells 24-72 h after exposure. These down-regulations were associated with cellular proliferation, determined by mRNA expression of the proliferation marker histone 3. Irradiated cells exhibited no alteration in the P-glycoprotein or glutathione peroxidase mRNA content. The finding that GST pi mRNA was overexpressed after irradiation was validated by investigations on a human lung carcinoma cell line (LXF 289) on the mRNA and protein level. Thus, our results indicate that irradiation alters the expression of proteins involved in multidrug resistance and may, therefore, play a role in clinical drug response. 相似文献
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4.
Dynamics of a single fluxon in an annular Josephson junction is studied in the presence of an externally applied magnetic
field H. Due to the interaction of the fluxon with the radial field component, the fluxon moves in a potential well which
height is proportional to H. Several spectacular features of fluxon dynamics analogous to the motion of a particle in a washboard
potential are clearly observed experimentally. Periodic revolutions of the fluxon in the junction lead to a potential induced
emission of plasma waves. These waves are indicated by a resonance at a certain fluxon velocity which depends on the junction
length. Good agreement between experiment, theoretical model and numerical simulations is found. 相似文献
5.
Norbert Delatte 《Canadian Metallurgical Quarterly》2004,130(1):37-43
For the last seven years, a summer Research Experiences for Undergraduates site in structural engineering, funded by the National Science Foundation, has operated at the University of Alabama at Birmingham. During this time, 33 students from 22 colleges and universities have participated in the site. Participants are recruited nationally and have come from as far away as California and Puerto Rico. The program is intended to provide students interested in graduate studies with an introduction to research methods, and to provide students who will not continue their studies past a bachelor of science in civil engineering with a better understanding of how research provides the theoretical foundation of engineering practice. Students work individually with faculty on literature reviews, computer modeling, laboratory testing, and field research. Three students have researched structural failure case studies and the technical and ethical lessons to be learned from them. Participants also have the opportunity to tour construction sites and construction material manufacturers’ and fabricators’ facilities. During the past three years, an ethics seminar series has been added. At the end of the program, students prepare research papers and Web pages documenting their work and present their results to faculty, students, and other participants. 相似文献
6.
The variation in the behaviour of bulk solids as a result of sudden pressure changes in the surrounding gas phase is of interest in the application of lock hoppers for transfer of bulk solids into pressure vessels. By using such sluice systems, problems occur due to consolidation of the pressurized bulk solids. This paper presents the results of experimental and theoretical research, which allow to describe the influence of several parameters on pressure compensation and the degree of consolidation. With reference to the forces and mechanisms responsible for consolidation, it is possible to describe the different consolidation behaviour of incompressible (limestone) and compressible (hard coal) bulk solids. 相似文献
7.
Norbert J. Kubilus 《Information Systems Management》1991,8(2):54-61
For many companies, involvement in mergers or acquisitions is quite common, Unfortunately, what is not so common is the IS department's role in preparing for the organizational changes that occur after a merger or acquisition has taken place. This article identifies some of the corporate issues and problems the IS department faces following a merger or acquisition and discusses how IS managers can best prepare for and manage the impact of such transactions on their IS departments. 相似文献
8.
We present dynamic studies of surface reactions using video-Field Ion Microscopy (FIM) along with Pulsed Field Desorption
Mass Spectrometry (PFDMS). Catalytic water formation is followed using rhodium and platinum 3D field emitter crystals for
the oxidation of hydrogen with either oxygen (Rh) or NO (Pt). Strongly non-linear dynamics are observed with nanoscale spacial
resolution. For both reactions quasi-oscillatory behaviour exists under certain conditions of temperatures and partial pressures.
An influence of the probing electric field is observed and possibly essential in establishing oscillatory behaviour. Local
chemical probing of selected surface areas with up to 400 atomic surface sites proves catalytic water formation to take place.
Since water ions (H2O+/H3O+) cause image formation of the O2–H2 reaction on Rh, respective videos provide space-time resolved information on the catalytically active sites. Atom-probe data
also reveal that the surface of the Rh sample reversibly switches from a metallic to an oxidized state during oscillations.
As to the NO–H2 reaction on Pt, fast ignition phenomena are observed to precede wave fronts. After catalytic water formation, NO molecules
diffuse into emptied areas and cause high image brightness. Depending on the size of the Pt crystal, the reaction may ignite
in planes or kinked ledges along the <100> zone lines. Thus FIM provides clear experimental evidence that kinks are more reactive
than steps in the catalytic NO + H2 reaction. Pt surface oxidation occurs and has probably been underestimated in previous FIM studies. 相似文献
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10.
Significant progress has been made in recent years regarding the photooxidation of olefin copolymers, but questions still remain. This paper reviews the progress and probes the photooxidative chemistry of ethylene–propylene (EP) and ethylene/propylene/diene monomer (EPDM) copolymers. Both stabilized and unstabilized polymer plaques were irradiated in a xenon are and the surface chemistry followed using infra-red spectroscopy. Model compounds were used to help elucidate the chemistry caused by unique structural features present in the copolymers. Volatile products evolved during photooxidation were determined giving valuable insight into the degradation chemistry. 相似文献