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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
3.
Cu50?xCox Zr50 (x = 0, 0.5, 1, 2, 3, 4 and 5 at.%) alloys were cast in a cylindrical copper mold by a suction casting device. In order to investigate the thermal behavior of the as-cast rods, the samples were heated from 313 to 573 K and then cooled down to about 253 K. The structure of the samples was studied by X-ray diffraction and optical microscopy. Thermal cycling measurements were also done for alloys with 2, 3, 4 and 5 at.% cobalt. It was found that increasing the cobalt content decreases martensite (Ms) and austenite (As) start temperatures, while it increases the temperature region in which austenite is stable. Thermal cycling measurements revealed that by increasing the number of cycles, the austenite start temperature increases while martensite start temperature shifts to lower temperatures. 相似文献
4.
A 7.5-250-hp range of variable-frequency ac motor drives has been under development at the Westinghouse R & D Center since early in 1981. Design and performance details for prototype equipment rated for 10, 20, and 50 hp will be discussed. The drive system comprises a three-phase thyristor controlled ac/dc converter in conjunction with a dc/ac adjustable-frequency inverter using gate turn-off thyristors (GTO's). The output of the inverter is a six-step voltage wave in the range of 6-120 Hz, suitable for driving three-phase ac induction or synchronous motors. Details of the inverter design, including means to protect the gate turn-off thyristors from output line-to-line or line-to-ground short circuits, will be given special attention. 相似文献
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6.
Friedemann Mattern 《Algorithmica》1990,5(1):325-340
The principle of message counting is used to detect termination of distributed computations which consist of processes asynchronously communicating over non-FIFO channels. The solution is symmetric and not based on a predefined communication structure. An efficient variant of the echo algorithm, which dynamically builds a spanning tree, allows a parallel and distributed evaluation of the termination predicate in time proportional to the diameter of the communication graph. Concurrent and repeated initiation of the detection algorithm by different processes is possible at any time without prior synchronization due to a subtle method of collision detection and wave extinction, which can be regarded as a distributed election scheme where the average message complexity increases only logarithmically with the number of concurrent initiators. Control messages have a small length and additional communication links are not required. Only a fixed number of simple variables is needed in every process, global knowledge such as the total number of processes or the structure of the network is not used, making the scheme useful for dynamic systems. Several variations of the basic principle are presented, important issues such as message complexity and fault-tolerance are discussed.This work was supported by the German National Science Foundation (Deutsche Forschungsgemeinschaft) as part of research project SFB124. 相似文献
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Stamford P. Bickford T. Hsiao H. Mattern W. 《IEEE engineering in medicine and biology magazine》1999,18(4):45-52
Telemedicine is evolving into an important tool in delivering services to emergency departments (EDs) in rural areas. However, we do not yet know what kinds of services can be effectively delivered or the degree to which these services might be useful. In this pilot study, a high-speed, high-quality video, 24-hour ATM (asynchronous transfer mode) network linked a rural ED to an ED of a major medical center. The objective was to measure the utilization of telemedical consulting services. Specifically, this one-year study examined the significance of telemedicine in changing diagnosis and treatment and the influence on patient transfers 相似文献
9.
Shannon Mattern 《Nexus Network Journal》2010,12(3):389-420
In Louis I. Kahn’s library at Phillips Exeter Academy geometries of architecture and media function as parallel rhetorical
systems, sometimes complementing, sometimes contradicting one another. This present paper examines how the geometric forms
of the library shape patrons’ relationships to media in the collection, and how Kahn’s elementary geometries have accommodated
new media characterized by non-geometric, non-linear forms. 相似文献
10.