What is the function of the claustrum?

The claustrum is a thin, irregular, sheet-like neuronal structure hidden beneath the inner surface of the neocortex in the general region of the insula. Its function is enigmatic. Its anatomy is quite remarkable in that it receives input from almost all regions of cortex and projects back to almost all regions of cortex. We here briefly summarize what is known about the claustrum, speculate on its possible relationship to the processes that give rise to integrated conscious percepts, propose mechanisms that enable information to travel widely within the claustrum and discuss experiments to address these questions.     

What Capabilities for the Animal?

In this essay, I defend a bi-constructivist approach to ethology—a constructivist ethology assuming that each animal adopts constructivist strategies. I put it in opposition to what I call a realist-Cartesian approach, which is currently the dominant approach to ethology and comparative psychology. The starting point of the bi-constructivist approach can be formulated as a shift from the classical Aristotelian question “What is an animal?” to the Spinozean question, which is much less classical but which seems to me to be much stronger: “What are the capacities of the animal?”. Is it possible to conceptualize an ethology which insists on interpretation and therefore on invention, innovation and creativity, rather than on causality, the monotony of behavioural routines, and/or genetic or environmental determination? Such an ethology would be based not on the fiction of an absent observer but on fully recognizing the necessity of an observer, who is effectively present in order to get an observation. A pluralistic ethology does not dissociate itself from the marginal epistemologies of practitioners like animal trainers, hunters, stockbreeders etc., or, moreover, non-western experts. An ethology of this kind is not clamped within the boundaries of purely academic epistemology, obsessed by demarcation lines between the human and the animal. My work on the bi-constructivist approach represents a contribution towards the elaboration of an authentically biosemiotic ethology, one which is significantly different from the mechanical ethology of today.     

What makes the cell differentiate?

In the present paper, I propose a hypothesis whereby the necessity to maintain the permanent energy-dissipating metabolic flux represents the primary force that determines the eukaryotic cell's choice to grow, divide and/or differentiate. This view is based on the universal structure and the strict redox neutrality of the core metabolic network. I propose that the direct substrate level coupling between metabolism and gene expression through epigenetic mechanisms provides a mechanistic explanation of how this control is implemented.     

What was the evolutionary synthesis?

There has not been another scientific revolution that caused as much turmoil and dissension as the darwinian one. For almost 80 years it was again and again pronounced to be a failure and to be totally refuted, and at least three major alternatives were proposed to replace it. Yet, in the 1930s-1940s the opposing views were quickly and decisively refuted and a largely unified evolutionary theory emerged. Why and how this happened, however, is still rather controversial.     

What determines the substrate specificity of the multi-drug-resistance pump?

Multi-drug-resistance protein (P-glycoprotein) turns out to be an ATP-hydrolysing transmembrane pump that increases the resistance of cells in which it is expressed by actively extruding toxic chemicals. The baffling question is how does the pump know which chemicals to extrude? Common features among its substrates are still elusive. The question raised here concerns the relationship between this pump and that known for many years as capable of extruding glutathionyl and cysteinyl S-conjugates of xenobiotics. Are excreted drugs conjugated before excretion? Does the multi-drug-resistance pump recognize a simple chemical tag put on xenobiotics by a family of transferase enzymes?     

What is the function of centrioles?

The function of centrioles has been controversial and remains incompletely resolved. This is because centrioles, in and of themselves, do not directly perform any physiological activity. Instead, their role is only to act as a jig or breadboard onto which other functional structures can be built. Centrioles are primarily involved in forming two structures-centrosomes and cilia. Centrioles bias the position of spindle pole formation, but because spindle poles can self-organize, the function of the centriole in mitosis is not obligatory. Consequently, lack of centrioles does not generally prevent mitosis, although recent experiments suggest acentriolar spindles have reduced fidelity of chromosome segregation. In contrast, centrioles are absolutely required for the assembly of cilia, including primary cilia that act as cellular antennae. Consistent with this requirement, it is now becoming clear that many ciliary diseases, including nephronophthisis, Bardet-Biedl syndrome, Meckel Syndrome, and Oral-Facial-Digital syndrome, are caused by defects in centriole-associated proteins.