Abstract: The structure, thermodynamics, and kinetics of heat-induced unfolding of sperm whale apomyoglobin core formation have been studied. The most rudimentary core is formed at pH(*) 3.0 and up to 60 mM NaCl. Steady state for ultraviolet circular dichroism and fluorescence melting studies indicate that the core in this acid-destabilized state consists of a heterogeneous composition of structures of approximately 26 residues, two-thirds of the number involved for horse heart apomyoglobin under these conditions. Fluorescence temperature-jump relaxation studies show that there is only one process involved in Trp burial. This occurs in 20 micro s for a 7 degrees jump to 52 degrees C, which is close to the limits placed by diffusion on folding reactions. However, infrared temperature jump studies monitoring native helix burial are biexponential with times of 5 micro s and 56 micro s for a similar temperature jump. Both fluorescence and infrared fast phases are energetically favorable but the slow infrared absorbance phase is highly temperature-dependent, indicating a substantial enthalpic barrier for this process. The kinetics are best understood by a multiple-pathway kinetics model. The rapid phases likely represent direct burial of one or both of the Trp residues and parts of the G- and H-helices. We attribute the slow phase to burial and subsequent rearrangement of a misformed core or to a collapse having a high energy barrier wherein both Trps are solvent-exposed.

Abstract: Besides focusing on the adaptive significance of collective movements, it is crucial to study the mechanisms and dynamics of decision-making processes at the individual level underlying the higher-scale collective movements. It is now commonly admitted that collective decisions emerge from interactions between individuals, but how individual decisions are taken, i.e. how far they are modulated by the behaviour of other group members, is an under-investigated question. Classically, collective movements are viewed as the outcome of one individual's initiation (the leader) for departure, by which all or some of the other group members abide. Individuals assuming leadership have often been considered to hold a specific social status. This hierarchical or centralized control model has been challenged by recent theoretical and experimental findings, suggesting that leadership can be more distributed. Moreover, self-organized processes can account for collective movements in many different species, even in those that are characterized by high cognitive complexity. In this review, we point out that decision-making for moving collectively can be reached by a combination of different rules, i.e. individualized (based on inter-individual differences in physiology, energetic state, social status, etc.) and self-organized (based on simple response) ones for any species, context and group size.

Abstract: We examined whether very young dairy calves are able to discriminate between two people, and whether they use the colour of clothing or other indices to do so. During the familiarisation phase, one person (the familiar rewarder), who always wore the same colour clothes, gave milk, spoke gently and patted the calves in their individual pen for 6 days each week. During the test phase, the calf had to make a choice in an Y-maze placed in front of the gate of its stall. When the calves chose the familiar rewarder, they received 200 ml of milk as reinforcement. When they made the incorrect choice, they received nothing and were returned to their stall. On each test day, the calves made eight choices. The criterion of success was that the calf made at least six correct choices in eight trials on each of two consecutive test days (P<0.021 by the binomial law). The first experiment was carried out with fourteen 1-week-old male and female Holstein calves to see if calves could approach a person, who changed position in the maze, in order to obtain a feed reward. The familiar rewarder wore the same clothes as during the period of familiarisation and was in one arm of the Y-maze. The other arm was empty and the position of the familiar rewarder in the maze was randomised. Eleven of the 14 calves reached the criterion for success, after only three tests. The second experiment, carried out with five 2-week-old calves, examined whether the calves can differentiate the familiar rewarder (wearing the same clothing as during the period of familiarisation) from another person (the non-rewarder) wearing clothes of a different colour. The criterion of success was reached by all five calves. The third experiment was carried out with seven 2-week-old calves. It examined whether the calves can differentiate the familiar rewarder and the non-rewarder, when the two people are wearing clothes of the same colour (i.e. the same colour worn by the familiar rewarder during the phase of familiarisation). None of the calves were able to reach the criterion of success within a limited number of four test days. Often, calves would always choose the same arm of the maze. The fourth experiment was carried out on six 1-month-old calves. It was similar to experiment 3 with the difference that the familiar rewarder and the non-rewarder both wore the same colour clothes, but which were not the same colour as worn during the phase of familiarisation. Only one calf achieved the criterion of success within two test days. Results demonstrated that colour cues help very young calves to discriminate between two people, when these people wear different colour clothing. Some calves may be able to use other indicators than the colour of clothing. The Y-maze method is an promising way of examining calves' abilities to recognise people.

Abstract: Social relationships are important in social species. These relationships, based on repeated interactions, define each partner's expectations during the following encounters. The creation of a relationship implies high social cognitive abilities which require that each partner is able to associate the positive or negative content of an interaction with a specific partner and to recall this association. In this study, we tested the effects of repeated interactions on the memory kept by 23 young horses about humans, after 6 and 8 months of separation. The association of a reward with a learning task in an interactional context induced positive reactions towards humans during training. It also increased contact and interest, not only just after training, but also several months later, despite no further interaction with humans. In addition, this ‘positive memory’ of humans extended to novel persons. Overall, positive reinforcement enhanced learning and memorization of the task itself. These findings suggest remarkable social cognitive abilities that can be transposed from intraspecific to interspecific social contexts.