Do Children with Autism have Expectancies about the Social Behaviour of Unfamiliar People?

Eight low-functioning and non-verbal children with autism were presented with a modified version of the ‘still face’ paradigm (still face/imitative interaction/still face) performed by a stranger. The children’s reactions illustrate the development of expectancies concerning human social behaviour. While they ignored the stranger and did not show any concern about her odd behaviour during the first still episode, they all focused on the adult during the second still episode. In this episode, they exhibited a mixed social pattern of positive overtures and negative emotional expressions which resembles the still face effect found in normally developing infants. These findings suggest that low-functioning children with autism are able to integrate their previous experience with a partner and detect social contingency, but that they are not able to form a generalized expectancy for social contingency in human beings with whom they have not yet had contact. This may explain why they generally ignore strangers.

Late Cretaceous Antarctic fish diversity

New material from the Santa Marta Formation (late Coniacian-?early Maastrichtian) of James Ross Island contributes significantly to the current knowledge of Late Cretaceous Antarctic fish diversity. The taxon list for the Santa Marta Formation is extended, and new records of neoselachians and teleosts are reported. The stratigraphic ranges of some previously known taxa are enlarged, and the palaeobiogeography and palaeoecology of Late Cretaceous Antarctic fishes are discussed. Top predators that occupied the higher levels in the food chain along with marine tetrapods dominate the marine faunas from the Santa Marta and López de Bertodano formations. The only fish adapted to crushing hard-shelled invertebrates were the chimeroids. Rays, an important component of marine fish associations, as well as fish from lower trophic levels, remain unknown from the Late Cretaceous of Antarctica.

Box-modeling of bone and tooth phosphate oxygen isotope compositions as a function of environmental and physiological parameters

A time-dependent box model is developed to calculate oxygen isotope compositions of bone phosphate as a function of environmental and physiological parameters. Input and output oxygen fluxes related to body water and bone reservoirs are scaled to the body mass. The oxygen fluxes are evaluated by stoichiometric scaling to the calcium accretion and resorption rates, assuming a pure hydroxylapatite composition for the bone and tooth mineral. The model shows how the diet composition, body mass, ambient relative humidity and temperature may control the oxygen isotope composition of bone phosphate. The model also computes how bones and teeth record short-term variations in relative humidity, air temperature and delta18O of drinking water, depending on body mass. The documented diversity of oxygen isotope fractionation equations for vertebrates is accounted for by our model when for each specimen the physiological and diet parameters are adjusted in the living range of environmental conditions.

Actin-binding properties and colocalization with actin during spermiogenesis of mammalian sperm calicin

The nucleus of mammalian spermatozoa is surrounded by a rigid layer, the perinuclear theca, which is divided into a subacrosomal layer and a postacrosomal calyx. Among the proteins characterized in the perinuclear theca, calicin is one of the main components of the calyx. Its sequence contains three kelch repeats and a BTB/POZ domain. We have studied the association of boar calicin with F-actin and the distribution of boar and human calicin during spermiogenesis compared with the distribution of actin. Calicin was purified from boar sperm heads under nondenaturating conditions. The molecule bound actin with high affinity (K(d) = approximately 5 nM), and a stoichiometry of approximately one calicin per 12 actin monomers was observed. Gel filtration studies showed that calicin forms homomultimers (tetramers and higher polymers). According to immunocytochemical results, calicin is present (together with actin) in the acrosomal region of round spermatids and is mainly localized in the postacrosomal region of late spermatids and spermatozoa. Taken together, the results suggest that the affinity of calicin to F-actin allows targeting of calicin at the subacrosomal space of round spermatids, and that its ability to form homomultimers contributes to the formation of a rigid calyx.

Formation of carbonates in the Tatahouine meteorite

The Tatahouine meteorite, in southern Tunisia, shows terrestrial contamination that developed during 63 years of exposure on Earth's surface. Samples collected on the day of the fall in 1931 contained fractures, with no secondary minerals, whereas samples collected in 1994 contain calcite aggregates (70 to 150 micrometers) and rod-shaped forms (100 to 600 nanometers in length and 70 to 80 nanometers in diameter) on the fractures. Carbon isotope analysis of the carbonates within the Tatahouine meteorite [delta13C = -2.0 per mil Pee Dee belemnite standard (PDB)] and the underlying ground (delta13C = -3.2 per mil PDB) confirm their terrestrial origin.