The invasion of melanoma is complex and multi‐staged and involves changes in both cell/extracellular matrix (ECM) and cell/cell interactions. Female steroids and α‐MSH have also been reported to ...influence metastatic melanoma progression, but their mechanisms of action are unknown. Accordingly, our aim was to establish in vitro models to examine (a) the influence of sex steroids and α‐melanocyte‐stimulating hormone (α‐MSH) on tumour invasion and the influence of (b) ECM proteins and (c) adjacent cells on melanoma invasion.
In the first model, melanoma cell invasion through fibronectin over 20 hr under serum‐free conditions was used to investigate the effects of 17β‐oestradiol and oestrone on the invasion of human melanoma cell lines, A375‐SM and HBL. A375‐SM, but not HBL cells, proved very susceptible to inhibition by female steroids. However, invasion of the HBL line was inhibited by α‐MSH. Using the second model of reconstructed human skin based on de‐epidermised acellular dermis, we found that the HBL cells on their own failed to invade into the dermis (irrespective of the presence or absence of the basement membrane). However, there was a significant synergistic interaction between keratinocytes, fibroblasts and HBL cells, such that a modest invasion of HBLs into the dermis was seen within 2 weeks when other skin cells were present. In contrast, A375‐SM cells showed a significant ability to invade the dermis in the absence of other cells, with less invasion when other skin cells were present.
In summary, these models have provided new information on the extent to which melanoma cell invasion is sensitive to oestrogenic steroids and to α‐MSH and to interaction, not only with adjacent skin cells but also to the presence of basement membrane antigens.
Computer based simulation models are being used increasingly to predict the environmental fate of crop protection chemicals. Some considerations that should be given in selecting appropriate models ...for regulatory purposes include: model applicability, validation, capability, ease of use and documentation. Current applications of regulatory modeling include the rationalization of field data, evaluation of the leaching potential of pesticides and estimation of the probability of leaching. Problems commonly encountered in modeling include: limited accuracy, lack of defined objectives and standard modeling practices, and misuse of models and results. Models will continue to play an important role in the regulation of crop protection chemicals. It is important that regulators and industry agree on appropriate models and practices, and that regulatory decisions are not based solely on model results but take into account all available data.
In progressing through an engineering curriculum, students acquire familiarity with the use of modern computational tools for modeling, analyzing, and designing physical systems. Instructors put a ...lot of effort into identifying and implementing appropriate software packages for augmenting classroom material. Students undergo steep learning curves, often encountering three or more disparate packages in the course of a semester. They gain a reasonable degree of comfort with these tools, only to have new ones introduced the following semester; and the cycle repeats. To significantly reduce the burden to students of repetitively learning new software packages, a consistent computing environment can be introduced throughout the curriculum. Such an environment must be sufficiently versatile, robust, and powerful as well as extensively used by practicing engineers. While certain highly specialized functionality might be lost by eschewing specialized software, the students profit by gaining fluency and depth in using a general-purpose package. Moreover, it becomes possible to provide a vertically integrated learning experience, where experienced students can demonstrate to less-experienced students how their use of the very same package has progressively grown more sophisticated. This experiment in vertical integration is still in its early stages. However, based on student feedback, this approach is yielding the benefits of developing in senior students a confidence in their ability to communicate, work in teams, and mentor their juniors. Lower-class students are realizing the relevance of the fundamental courses to their career goals and the importance of developing their skills in computing, modeling, and analysis. Introduction As undergraduate students progress through an engineering curriculum, they are expected to acquire competence in lower-level courses in order to succeed in upper-level courses. Unfortunately, students do not always recognize the importance of retaining skills learned in one course for application in subsequent courses. Faculty members contribute to this break in continuity by collaborating in only a limited way with instructors of lower-level and higher-level courses on specific topics and tools that if emphasized would provide students with a better integrated experience. This is particularly true of computational tools. Instructors can expend considerable effort augmenting their courses with suitable computational software. Students undergo steep learning curves, often encountering three or more different software packages in a semester. They gain a degree of comfort with these tools only to have new ones introduced the following semester. It often happens that tools used in one course are not used in subsequent courses. The possibility that this expenditure of effort might be reduced raises the following question: what manner of cooperative effort can faculty implement over a sequence of courses to help students develop their cognitive and engineering skills in the most efficient manner? In response, the authors propose a form of vertical integration.
Using the hermeneutical theory of Paul Ricoeur, it is possible to discern symbolic dimensions in cultural anthropology. Symbols, here, are dominant images in anthropologists' texts, creatively ...posited by inquirers, that, most importantly, possess a surplus of meaning. A symbol's fullest surplus of meaning is a prereflexive and comprehensive "understanding" (Verstehen) that may encompass a scholar's attempts at "explanation" (Erklaren). Examples of this symbolic dimension are the "understandings" that lie implicit in two elaborate anthropological systems: Levi-Strauss's structuralism and Harris's cultural materialism. Amid their commitments to anthropological "science" and "explanation," the works of each disclose a distinctive Verstehen. For Levi-Strauss, this "understanding" is nurtured by his image "world of reciprocity." For Harris, it is carried by the image "nature." This "understanding" has two major functions. On the level of the intellectual coherence of their texts, it gives unity to their intercultural interpretations of other societies and to their intracultural interpretations of their own traditions. On a moral level, it includes modes of being-in-the-world that Levi-Strauss and Harris prefer and ocasionally press upon their readers. Discernment of symbolic dimensions of "understanding" in anthropologists' texts may be an initial step toward reflection on the matrices out of which diverse explanations are presented in anthropological literature.
