Biomedical subjects

B McMullin

Publications and source records attributed to B McMullin.

4 recordsLinked to original sources

PubMed2000

Remarks on autocatalysis and autopoiesis.

The notions of collective autocatalysis and of autopoiesis are clearly related; equally clearly, they are not quite the same. The purpose of this paper is to try to clarify the relationship. Specifically I suggest that autopoiesis can be at least roughly characterized as collective autocatalysis plus spatial individuation. Although some mechanism of spatial confinement or concentration is probably necessary to the effective operation of any collectively autocatalytic reaction network, autopoiesis requires, in addition, that the mechanism for maintaining this confinement should itself be a product of the reaction network--and should thus (?) be capable of separating or individuating otherwise identically organized networks. I suggest an informal heuristic test to discriminate the (merely) collectively autocatalytic from the (properly) autopoietic. Finally, in the light of this, I review a variety of published abstract or model systems, Alchemy, alpha-universes, Tierra, and SCL.

Catalysis↗

PubMed2000

John von Neumann and the evolutionary growth of complexity: looking backward, looking forward...

In the late 1940s John von Neumann began to work on what he intended as a comprehensive "theory of [complex] automata." He started to develop a book length manuscript on the subject in 1952. However, he put it aside in 1953, apparently due to pressure of other work. Due to his tragically early death in 1957, he was never to return to it. The draft manuscript was eventually edited, and combined for publication with some related lecture transcripts, by Burks in 1966. It is clear from the time and effort that von Neumann invested in it that he considered this to be a very significant and substantial piece of work. However, subsequent commentators (beginning even with Burks) have found it surprisingly difficult to articulate this substance. Indeed, it has since been suggested that von Neumann's results in this area either are trivial, or, at the very least, could have been achieved by much simpler means. It is an enigma. In this paper I review the history of this debate (briefly) and then present my own attempt at resolving the issue by focusing on an analysis of von Neumann's problem situation. I claim that this reveals the true depth of von Neumann's achievement and influence on the subsequent development of this field, and further that it generates a whole family of new consequent problems, which can still serve to inform - if not actually define - the field of artificial life for many years to come.

Artificial Intelligence↗

PubMed1997

Computing machinery and mentality.

I reconsider the status of computationalism (or, in a weak sense, functionalism): the claim that being a realization of some (as yet unspecified) class of abstract machine is both necessary and sufficient for having genuine, full-blooded, mentality. This doctrine is now quite widely (though by no means universally) seen as discredited. My position is that, though it is undoubtedly an unsatisfactory (perhaps even repugnant) thesis, the arguments against it are still rather weak. In particular, I critically reassess John Searle's infamous Chinese Room Argument and also some relevant aspects of Karl Popper's theory of the Open Universe. I conclude that the status of computationalism must still be regarded as undecided, and that it may still provide a satisfactory framework for research.

Animals↗

PubMed1993

Phase I trial of a 90-minute infusion of the fusion toxin DAB486IL-2 in hematological cancers.

DAB486IL-2, a recombinant fusion toxin in which the native receptor binding domain of diphtheria toxin has been replaced with interleukin-2 (IL-2), has displayed significant activity in patients with chemotherapy refractory hematological cancers. To further investigate the safety and antitumor effect of this agent, we conducted a single arm, dose escalation study of a 90-min infusion of DAB486IL-2 daily for 5 days. Patients with cancers of a histology previously reported to express the p55 component of the IL-2 receptor and who could not receive potentially more effective therapy were eligible for enrollment. Fifteen men and 8 women with a median age of 49 years were given a total of 51 courses of DAB486IL-2. The maximum tolerated dose was 0.3 mg/kg/day defined by renal insufficiency associated with hemolysis and thrombocytopenia. The clearance of DAB486IL-2 from serum fit a one-compartment model with a half-life of 11.5 +/- 4.3 (SD) min at the 0.2-mg/kg dose. Two patients sustained a partial response and 4 patients had tumor reduction not qualifying for an objective response. No tumors that were negative for expression of the p55 subunit of the receptor responded to DAB486IL-2 treatment. Reduction in size occurred in 2 tumors in which p55 expression was unknown and 4 patients with tumors that were known to be p55 positive. Dosing determined by specific activity rather than mass also appeared to be an important determinant of response. This study suggests that the presence of p55 expression on tumor cells is necessary, but alone may not be sufficient to achieve a tumor response. The correlation of additional variables such as specific activity of DAB486IL-2 and tumor expression of the p75 subunit of the IL-2 receptor and receptor function will also require further study.

Adult↗