Evolution of the Sweetness Receptor in Primates. I. Why Does Alitame Taste Sweet in all Prosimians and Simians, and Aspartame only in Old World Simians?

In the order Primates the responses to sucrose, alitame and aspartame were ascertained. All primates tested to date like sucrose and prefer this sweet substance to tap water. The artificial dipeptide aspartame was found to be not sweet in Prosimii and Platyrrhini (New World monkeys). Only the Cercopithecoidea (Old World monkeys) and Hominoidea (apes and humans) show the same response to aspartame and to sucrose. In contrast, all primates tested so far prefer alitame, another artificial dipeptide sweetener, which is structurally closely related to aspartame. This phylogenetic difference is consistent with the existence in catarrhine primates of a sweetness receptor containing two differently located hydrophobic recognition sites, one for the hydrophobic binding site of alitame, the other for the hydrophobic binding site of aspartame. On the basis of these results, it is suggested that the alitame-related hydrophobic recognition site, which is found in the sweetness receptor of all primates, could be a requisite for the interaction of the receptor with sucrose, while the aspartame-related hydrophobic recognition site, which is found exclusively in the sweetness receptor of Old World simians, could have been a crucial factor in the improvement in detection or selection of sucrose in foods, so favouring the mental development of these simians and maybe the emergence of humans. Chem. Senses 20: 573-584, 199

Data-Driven Disturbance Estimation and Control with Application to Blood Glucose Regulation

A data-driven control approach for nonlinear systems is proposed, called data-driven estimation and control (D2EC), which combines a disturbance estimator and a nonlinear control algorithm. The estimator provides a signal representing the unknown disturbances affecting the plant to control. This signal is used by the control algorithm to improve its performance. A real-data study is presented, concerned with the regulation of blood glucose concentration in type 1 diabetic patients. Preliminary tests of the D2EC approach are also carried out using a diabetic patient simulator, obtained from a revised version of the well-known University of Virginia/Padova model. Both the real-data and the simulator-based studies indicate that the proposed approach has the potential to become an effective tool in the context of diabetes treatment and, more in general, in the biomedical field, where accurate first-principle models can seldom be found and relevant disturbances are present

Evolution of the Sweetness Receptor in Primates. II. Gustatory Responses of Non-human Primates to Nine Compounds Known to be Sweet in Man

The gustatory responses of nine compounds, namely glycine, D-phenylalanine, D-tryptophan, cyanosuosan, magapame, sucrononate, campame, cyclamate and superaspartame, all known as sweet in man, were studied in 41 species or subspecies of non-human primates, selected among Prosimii (Lemuridae and Lorisidae), Platyrrhini (Callitrichidae and Cebidae) and Catarrhini (Cercopithecidae, Hylobatidae and Pongidae). The first six compounds are generally sweet to all primates, which implies that they interact with the primate sweetness receptors essentially through constant recognition sites. Campame is sweet only to Cebidae and Catarrhini, cyclamate only to Catarrhini, superaspartame principally to Callitrichidae and Catarrhini, which implies that all these compounds interact with the receptors partly through variable recognition sites. From the present work, from other previous results (where notably it was observed that alitame is sweet to all primates, ampame only to Prosimii and Catarrhini, and aspartame only to Catarrhini), and from the multipoint attachment (MPA) theory of sweetness reception (as elaborated by Nofre and Tinti from a detailed study of structure-activity relationships of various sweeteners in man), it is inferred that the primate sweetness receptors are very likely made up of eight recognition sites, of which the first, second, third, fourth, seventh and eighth are constant, and the fifth and sixth variable. From these results and from the MPA theory, it is also inferred that the recognition sites of the primate sweetness receptors could be: Asp-1 or Glu-1, Lys-2, Asp-3 or Glu-3, Thr-4, X-5, X-6, Thr-7, Ser-8, where the variable recognition sites X-5 and X-6 would be: Ala-5 and Ala-6 for Callitrichidae, Ser-5 and Ala-6 for Cebidae, Ala-5 and Thr-6 for Prosimii, and Thr-5 and Thr-6 for Catarrhini. By using Tupaiidae (tree shrews) as a reference outgroup and by means of other structural and functional molecular considerations, it appears that Callitrichidae have retained the most primitive receptor among the four types of primate receptors. The possible taxonomic and phylogenetic implications of these findings are discussed. Chem. Senses 21: 747-762, 199

Visual experience is not necessary for efficient survey spatial cognition: Evidence from blindness

This study investigated whether the lack of visual experience affects the ability to create spatial infer-ential representations of the survey type. We compared the performance of persons with congenital blindness and that of blindfolded sighted persons on four survey representation-based tasks (Experiment 1). Results showed that persons with blindness performed better than blindfolded sighted controls. We repeated the same tests introducing a third group of persons with late blindness (Experiment 2). This last group performed better than blindfolded sighted participants, whereas differences between participants with late and congenital blindness were nonsignificant. The present findings are compatible with results of other studies, which found that when visual perception is lacking, skill in gathering environmental spatial information provided by nonvisual modalities may contribute to a proper spatial encoding. It is concluded that, although it cannot be asserted that total lack of visual experience incurs no cost, our findings are further evidence that visual experience is not a necessary condition for the development of spatial inferential complex representations. There is a general consensus on the crucial role of visual perception in guiding many of our daily movements in large- and small-scale environ

The role of shear fabric in controlling breakdown processes during laboratory slow-slip events

Understanding the physical mechanisms at the origin of slow-slip events has been proven a very challenging task. In particular, little is known on the role of fault heterogeneity during slow slip. In this study, we provide evidences that fault fabric controls slip velocity time histories during slow-slip events generated in the laboratory. We performed experiments using a double-direct biaxial shear apparatus and two different fault gouges, homogeneous quartz powder, and heterogeneous anhydrite/dolomite mixture. We measure details of fault slip to resolve the slip velocity function and volumetric deformation that, coupled with an analysis of the resulting microstructure, allow us to infer the mechanical processes at play. Our results show that slow-slip events can be generated for both fault gouges when k ~ kc with similar values of breakdown work. The shear fabric exerts a strong influence during the coseismic breakdown stage. In quartz, where most of the slip occurs on a very localized slipping surface, the peak slip velocity is attained near the final stage of friction breakdown and therefore a relevant amount of the mechanical work is absorbed during slip acceleration. In anhydrite/dolomite mixture, the peak slip velocity is suddenly reached after a relatively small drop in friction, accompanied by fault dilation, implying that most of the mechanical work is absorbed during slip deceleration. For anhydrite/dolomite mixture these results are likely related to heterogeneous slip distribution along the observed foliation. Taken together, these observations suggest that the mechanics of slow-slip events depends on shear zone fabric