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21.
PURPOSE: The purpose was to determine tumor neovascularisation via colour-coded Doppler (duplex) sonography and the "power mode", both visually and quantitatively, by means of videodensitometry. MATERIAL AND METHODS: 6 VX2 tumours of 4 to 11 mm size were implanted in 4 rabbits at various sites. The colour-coded duplex sonography and the new sonographic power technique were tested before and after having injected a new contrast medium (SH U 616A). RESULTS: If no contrast medium was injected, tumour neovascularisation was identified in only 50% of the cases. Injection of contrast medium increased signal intensity three to fourfold with all examined tumors. Combined use of the sonographic method by the power technique with injection of contrast medium is outstandingly suitable for tumor vessel imaging even of small tumors, as these initial results seem to show. CONCLUSION: If these results are corroborated by further studies, contrast-medium supported sonographic technique may possibly become established as an alternative method to other imaging procedures.  相似文献   
22.
The influence of the choleretic drug methylumbilliferone on bile formation in the isolated perfused rat liver is characterized. The compound induces rapidly an elevation of bile flow, bile acid secretion and soium excretion. The increased production of bile is of canalicular origin. The choleretic effect was defined as "bile acid like" choleresis due to excretion of the drug into the bile. It is discussed that the excretion of methylumbilliferone can influence the transport of bile in form of a positive cooperation on transport mechanism.  相似文献   
23.
We present a cryogenic source of periodic streams of micrometer-sized hydrogen and argon droplets as ideal mass-limited target systems for fundamental intense laser-driven plasma applications. The highly compact design combined with a high temporal and spatial droplet stability makes our injector ideally suited for experiments using state-of-the-art high-power lasers in which a precise synchronization between the laser pulses and the droplets is mandatory. We show this by irradiating argon droplets with multi-terawatt pulses.  相似文献   
24.
Two hundred open-heart cases were anaesthetized with a diazepam-ketamine combination. The results were excellent. A "Micro-Mini" drip technique insured low, even, but adequate dose levels of ketamine and less drug was used. Induction and maintenance are simple and smooth. Effects on the cardiovascular system and respiratory system are minimal. The margin of safety is wide and 100% oxygen can be used whenever needed.  相似文献   
25.
A system made of an atmosphere, a liquid metal and an oxide phase at a given temperature and total pressure is zero-variant and allows only a particular set of partial pressures, compatible with thermodynamic equilibrium. For any different gas composition the system will show a tendency to evolution. Therefore, classical thermodynamics cannot give the answers to a number of problems of major interest, such as those concerning the conditions for interface saturation and oxide formation. Strictly speaking these are kinetic problems, but they can still be treated as pseudo-thermodynamic questions. The key to the problem is in considering the characteristic times of evolution, which suggest stationary state approximation for the condensed phases. In many instances, the evaluation of gas-atmosphere mass exchanges under stationary conditions makes it possible to determine the effective oxygen pressure at which the oxidation of the metal becomes evident. Surface tension measurements allow this condition to be detected with a good accuracy. According to experimental evidence, the effective oxygen pressure can be many orders of magnitude greater than the equilibrium value. The problem needs different theoretical approaches according to the molecular mechanisms involved. Moreover, from the experimental point of view, there are particularly delicate questions regarding the accuracy and the significance of the oxygen control and measurement.  相似文献   
26.
The aim of this study was to analyze the influence of nanoporous structure of polymeric biomaterials on the in vitro osteogenic induction of human stem cells. An electronic search in three databases (MEDLINE, SCOPUS, and Web of Science) was performed for articles that were published before May 2018. In vitro studies were included if they met the following criteria: (1) the use of polymeric scaffolds (natural or synthetic); (2) the co-culture of human stem cells with the scaffold; and (3) cell viability, proliferation, and osteogenic differentiation assays. The main characteristics of the published studies were summarized, and a quality assessment tool was used to analyze methodological features. Eighty-eight potential articles were firstly retrieved. Thirteen were eligible for qualitative analysis. Only three studies characterized cell stemness. Nanostructure of the scaffolds showed a significant influence on viability, proliferation, and osteogenic differentiation of human stem cells. Combination of porosity between 72 and 93% and a large range diameter between 50 and 224 μm resulted in more remarkable cellular proliferation and differentiation. Porous polymeric scaffolds can be functionalized by stem cells leading to osteogenic induction. High standards of laboratory practice and accurate methodological reporting are essential for the credibility of the results.  相似文献   
27.
The rise in human papillomavirus (HPV)-associated oropharyngeal squamous cell carcinoma (OPSCC) has prompted a quest for further understanding of the role of high-risk HPV in tumor initiation and progression. Patients with HPV-positive OPSCC (HPV+ OPSCC) have better prognoses than their HPV-negative counterparts; however, current therapeutic strategies for HPV+ OPSCC are overly aggressive and leave patients with life-long sequalae and poor quality of life. This highlights a need for customized treatment. Several clinical trials of treatment de-intensification to reduce acute and late toxicity without compromising efficacy have been conducted. This article reviews the differences and similarities in the pathogenesis and progression of HPV-related OPSCC compared to cervical cancer, with emphasis on the role of prophylactic and therapeutic vaccines as a potential de-intensification treatment strategy. Overall, the future development of novel and effective therapeutic agents for HPV-associated head and neck tumors promises to meet the challenges posed by this growing epidemic.  相似文献   
28.
mitochondrial neuro-gastrointestinal encephalomyopathy (MNGIE) is a rare genetic disorder characterized by thymidine phosphorylase (TP) enzyme defect. The absence of TP activity induces the imbalance of mitochondrial nucleotide pool, leading to impaired mitochondrial DNA (mtDNA) replication and depletion. Since mtDNA is required to ensure oxidative phosphorylation, metabolically active tissues may not achieve sufficient energy production. The only effective life-saving approach in MNGIE has been the permanent replacement of TP via allogeneic hematopoietic stem cell or liver transplantation. However, the follow-up of transplanted patients showed that gut tissue changes do not revert and fatal complications, such as massive gastrointestinal bleeding, can occur. The purpose of this study was to clarify whether the reintroduction of TP after transplant can recover mtDNA copy number in a normal range. Using laser capture microdissection and droplet-digital-PCR, we assessed the mtDNA copy number in each layer of full-thickness ileal samples of a naive MNGIE cohort vs. controls and in a patient pre- and post-TP replacement. The treatment led to a significant recovery of gut tissue mtDNA amount, thus showing its efficacy. Our results indicate that a timely TP replacement is needed to maximize therapeutic success before irreversible degenerative tissue changes occur in MNGIE.  相似文献   
29.
In this work we investigate a generalized interpolation approach using radial basis functions to reconstruct implicit surfaces from polygonal meshes. With this method, the user can define with great flexibility three sets of constraint interpolants: points, normals, and tangents; allowing to balance computational complexity, precision, and feature modeling. Furthermore, this flexibility makes possible to avoid untrustworthy information, such as normals estimated on triangles with bad aspect ratio. We present results of the method for applications related to the problem of modeling 2D curves from polygons and 3D surfaces from polygonal meshes. We also apply the method to problems involving subdivision surfaces and front-tracking of moving boundaries. Finally, as our technique generalizes the recently proposed HRBF Implicits technique, comparisons with this approach are also conducted.  相似文献   
30.
Variable-order fractional derivatives and their numerical approximations   总被引:1,自引:0,他引:1  
This paper addresses the different possible definitions of variable-order derivatives and their numerical approximations; both approximations based upon the definitions and approximations consisting of non-linear transfer functions (in particular combining existing approximations of constant-order fractional derivatives, such as the Crone approximation, with fuzzy logic) are considered. There are different possible configurations, implementing variable-order fractional derivatives both with and without memory of past values of the time-dependent differentiation order.  相似文献   
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