De filosofie naast en tegenover de natuurwetenschap. Ontwikkelingen sedert 1800

Wantin

AgNOR staining may reflect the growth potential of pilocytic astrocytomas

The value of AgNOR staining as a tumor biological marker was tested in 26 children with pilocytic astrocytomas (20) and fibrillary astrocytomas (6). All patients were surgically treated and then followed up by periodic MRI or CT scans. Follow-up ranged from 8 to 84 months, with a mean of 44 months. AgNOR expression was determined by using semi-automated computer-assisted surface area measurements. AgNOR values ranged from 1.4 to 81.4 mu m(2) per cell, with a mean of 26.6 and a median of 15.2. The median value was taken as a "cut-off" score separating two groups of patients with low and high AgNOR scores. Of the 13 patients in the low scoring group, 8 had total resections without recurrence, 3 had stable residual tumors, I had regressing residual tumor after irradiation and 1 had a recurrence 5 years after neuroradiologically complete resection of a fibrillary astrocytoma. In the group with high AgNOR scores only 2 patients had total resections without recurrence; 5 had stable residual tumors and 6 had residual tumors that showed progression, all within 1 year after surgery. Among the patients with classic juvenile pilocytic astrocytomas of the cerebellum 7 had residual tumor, which progressed in 2 patients, both of whom had high AgNOR scores. Among 7 patients with optic/hypothalamic tumors the 3 with rapidly progressing tumors all had very high AgNOR scores. The determination of AgNOR expression might be helpful in selection of patients with residual tumor after surgery, who may benefit from additional chemotherapy or (stereotactic) radiation therapy

The efficacy of alginate encapsulated CHO-K1 single chain-TRAIL producer cells in the treatment of brain tumors

Objective: Patients with astrocytic tumors in the central nervous system (CNS) have low survival rates despite surgery and radiotherapy. Innovative therapies and strategies must be developed to prolong survival of these patients. The alginate microencapsulation method, used to continuously release a certain cytotoxic agent in the vicinity of the tumor, is such a novel therapeutic strategy. The biological functionality of the apoptosis inducing scFv425:sTRAIL protein, which was released through the microencapsulation method, was studied in vitro. Analysis of the intracerebral biocompatibility of alginate capsules was performed by implantation of empty alginate capsules in the brain of mice. Method: Chinese Hamster Ovary cells (CHO-K1) were recombinantly engineered to produce the single chain anti-EGFR-sTRAIL protein (scFv425:sTRAIL). The CHO-K1 producer cells were encapsulated in an alginate capsule with a semi-permeable membrane through which the scFv425:sTRAIL protein could be released. Results: In vitro studies show maintained biological functionality of the released scFv425:sTRAIL protein. There was no immunological tissue response detectable after intracerebral implantation of the alginate capsules in mice brains. Conclusion: Biological functionality of the produced scFv425:sTRAIL protein is maintained and intracerebral biocompatibility of the capsules is warranted. Alginate encapsulation of CHO-K1 - scFv425:sTRAIL - producer cells and subsequently their intracerebral implantation is technically feasible. This study justifies further in vivo experiments

Mathematics, metaphor and economic visualisability

The mathematisation of economic theory is an issue that has been discussed many times. These discussions have been dominated by debate about the appropriateness of the deductive method for economics. This rather narrow focus has pushed a number of important methodological issues regarding the nature of mathematical economics aside. In this paper, it is argued that mathematical economics involves the construction of metaphor and is therefore metaphorical in nature. Whilst mathematical economics has been responsible for what are generally regarded to be notable theoretical achievements and retains a place in economics as an apparatus for the development of economic science, the meaning of mathematical economics is restricted to those elements of economic reality that may be talked about in terms of mathematical objects and there is a danger of declining economic visualisability as the metaphors of mathematical economics become less vivid