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Biomedical subjects

J Hoffmeyer

Publications and source records attributed to J Hoffmeyer.

8 recordsLinked to original sources
PubMed2000

Code-duality and the epistemic cut.

Howard Pattee has claimed that an epistemic cut separates the world from observers and therefore from organisms. The epistemic cut imputes a linguistic mode of operation to living systems. Among evolutionary systems-theorists on the other hand there seems to be a tendency to consider living systems as just one among many other kinds of evolutionary systems that, in principle, can all be described on the basis of thermodynamics or infodynamics. This paper searches a third position, in which the epistemic cut position is defended without adopting Pattee's distinction between a dynamic and a linguistic mode. It is observed that even the dynamic mode in living systems is always a semiotic mode although index- and analog-coded rather than symbolic and digitally coded. The analog-coded messages corresponds to a kind of tacit knowledge hidden in macromolecular structure and shape (e.g., molecular complementarity), and in organismic architecture and communication, that is, in the semiotic interactions of the body.

Biological Evolution↗
PubMed1971

Metabolism of exogenous purine bases and nucleosides by Salmonella typhimurium.

Purine-requiring mutants of Salmonella typhimurium LT2 containing additional mutations in either adenosine deaminase or purine nucleoside phosphorylase have been constructed. From studies of the ability of these mutants to utilize different purine compounds as the sole source of purines, the following conclusions may be drawn. (i) S. typhimurium does not contain physiologically significant amounts of adenine deaminase and adenosine kinase activities. (ii) The presence of inosine and guanosine kinase activities in vivo was established, although the former activity appears to be of minor significance for inosine metabolism. (iii) The utilization of exogenous purine deoxyribonucleosides is entirely dependent on a functional purine nucleoside phosphorylase. (iv) The pathway by which exogenous adenine is converted to guanine nucleotides in the presence of histidine requires a functional purine nucleoside phosphorylase. Evidence is presented that this pathway involves the conversion of adenine to adenosine, followed by deamination to inosine and subsequent phosphorolysis to hypoxanthine. Hypoxanthine is then converted to inosine monophosphate by inosine monophosphate pyrophosphorylase. The rate-limiting step in this pathway is the synthesis of adenosine from adenine due to lack of endogenous ribose-l-phosphate.

Adenine↗
PubMedDate not supplied

Life and reference.

The paper recommends a broadening of Howard Pattee's seminal distinction between a dynamic and a linguistic mode of living systems. It is observed that even the dynamic mode is always a semiotic mode although indexical and analogically coded rather than symbolic and digitally coded. The analogically coded messages corresponds to a kind of tacit knowledge hidden in macromolecular structure and shape (e.g. molecular complementarity) and in organismic architecture and communication, i.e. in the semiotic interactions of the body. It is claimed that the origin of referential processes is tied to the flow of historical singularities. The function of analog and digital codes in evolutionary systems is discussed.

Biological Evolution↗