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1.
Hardies SC; Martin SL; Voliva CF; Hutchison CA d; Edgell MH 《Molecular biology and evolution》1986,3(2):109-125
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The feasibility of radioisotope-fueled circulatory support systems depends on the ability of the body to dissipate the reject heat from the power source driving the blood pump as well as to tolerate chronic intracorporeal radiation. Our studies have focused on the use of the circulating blood as a heat sink. Initial in vivo heat transfer studies utilized straight tube heat exchangers (electrically and radioisotope energized) to replace a segment of the descending aorta. More recent studies have used a left ventricular assist pump as a blood-cooled heat exchanger. This approach minimizes trauma, does not increase the area of prosthetic interface with the blood, and minimizes system volume. Heat rejected from the thermal engine (vapor or gas cycle) is transported from the nuclear power source in the abdomen to the pump in the thoracic cavity via hydraulic lines. Adjacent tissue is protected from the fuel capsule temperature (900 to 1200 degrees F) by vacuum foil insulation and polyurethane foam. The in vivo thermal management problems have been studied using a simulated thermal system (STS) which approximates the heat rejection and thermal transport mechanisms of the nuclear circulatory support systems under development by NHLI. Electric heaters simulate the reject heat from the thermal engines. These studies have been essential in establishing the location, suspension, surgical procedures, and postoperative care for implanting prototype nuclear heart assist systems in calves. The pump has a thermal impedance of 0.12 degrees C/watt. Analysis of the STS data in terms of an electrical analog model implies a heat transfer coefficient of 4.7 x 10(-3) watt/cm(2) degrees C in the abdomen compared to a value of 14.9 x 10(-3) watt/cm(2) degrees C from the heat exchanger plenum into the diaphragm. 相似文献
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The malignant potential of solid tumors is related to the ability to invade adjacent tissue and to metastasize. These properties of cancer cells depend on the synthesis of proteolytic enzymes which are able to digest adjacent connective tissue and basement membranes. We hypothesized that all elements of the plasminogen activation system might be overexpressed in malignant human breast tumors, functioning as an essential element in tumor invasion and metastasis. As determined by histopathological methods, the malignant tumors showed statistically significantly higher expression of urokinase plasminogen activator (uPA), type-1 plasminogen activator inhibitor (PAI-1), and especially urokinase plasminogen activator receptor (uPAR) than benign tissues. All those elements were present in higher amounts in the cancer cells than in the cells of benign or normal breast tissues. High exhibition of tissue plasminogen activator (tPA) found in cancer seems to be random and not related to the malignant or benign state, since benign and malignant tumors show overexpression of tissue plasminogen activator with similar frequency. When the tumors express high amounts of uPA, they express a high amount of uPAR in 50% of cases and PAI-1 in 57.3% of cases. When urokinase is expressed in low amount, the receptor is low in 28.6% and inhibitor in 21.4% of malignant breast tumors. This statistically significant consensus, 78.6% in the case of urokinase and its receptor and 78.6% in case of urokinase and its inhibitor, suggests that these activities may be the result of a unique mechanism of control, activated in the last steps of malignant transformation. 相似文献
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Jing Xu Jinwoo Kim Benjamin J. Koestler Jeong‐Hyeon Choi Christopher M. Waters Clay Fuqua 《Molecular microbiology》2013,89(5):929-948
Many bacteria colonize surfaces and transition to a sessile mode of growth. The plant pathogen Agrobacterium tumefaciens produces a u nip olar p olysaccharide (UPP) adhesin at single cell poles that contact surfaces. Here we report that elevated levels of the intracellular signal cyclic diguanosine monophosphate (c‐di‐GMP) lead to surface‐contact‐independent UPP production and a red colony phenotype due to production of UPP and the exopolysaccharide cellulose, when A. tumefaciens is incubated with the polysaccharide stain Congo Red. Transposon mutations with elevated Congo Red staining identified presumptive UPP‐negative regulators, mutants for which were hyperadherent, producing UPP irrespective of surface contact. Multiple independent mutations were obtained in visN and visR, activators of flagellar motility in A. tumefaciens, now found to inhibit UPP and cellulose production. Expression analysis in a visR mutant and isolation of suppressor mutations, identified three diguanylate cyclases inhibited by VisR. Null mutations for two of these genes decrease attachment and UPP production, but do not alter cellular c‐di‐GMP levels. However, analysis of catalytic site mutants revealed their GGDEF motifs are required to increase UPP production and surface attachment. Mutations in a specific presumptive c‐di‐GMP phosphodiesterase also elevate UPP production and attachment, consistent with c‐di‐GMP activation of surface‐dependent adhesin deployment. 相似文献
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Hansen RK Parra I Hilsenbeck SG Himelstein B Fuqua SA 《Biochemical and biophysical research communications》2001,282(1):186-193
The small heat shock protein hsp27 is associated with aggressive tumor behavior in certain subsets of breast cancer patients. Previously we demonstrated that hsp27 overexpression in breast cancer cells increased in vitro and in vivo invasiveness, suggesting that hsp27 influences the metastatic process. To investigate this role for hsp27, we have utilized MDA-MB-231 breast cancer cells that overexpress hsp27 and cDNA expression array technology. We demonstrate that hsp27 overexpression up-regulates MMP-9 expression and activity and down-regulates Yes expression. Furthermore, our results suggest that Yes may be involved in regulating MMP-9 expression, as well as in vitro invasion. Reconstitution of Yes expression by transfection into hsp27-overexpressing cells decreased MMP-9 expression, and increased in vitro invasiveness, abrogating the phenotype conferred by hsp27 overexpression. Therefore, our results provide a new potential mechanism by which hsp27 affects the metastatic cascade-through regulation of MMP-9 and Yes expression. 相似文献
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Bacteria communicate at high cell density through quorum sensing, however, there are no reports about this mechanism in archaea. The archaeon Natronococcus occultus produces an extracellular protease at the end of growth. Early production of protease activity was observed when a low density culture was incubated with late exponential conditioned medium suggesting the presence of factor(s) inducing this activity. Conditioned medium and ethyl acetate extracts corresponding to the transition from exponential to stationary phase showed a positive signal in Agrobacterium biosensor. We report the detection of potential autoinducer molecules of the acylated homoserine lactone type in the archaeon N. occultus. These molecules may be responsible for the production/activation of extracellular protease. 相似文献