A new rhynchocephalian from the late jurassic of Germany with a dentition that is unique amongst tetrapods.

Rhynchocephalians, the sister group of squamates (lizards and snakes), are only represented by the single genus Sphenodon today. This taxon is often considered to represent a very conservative lineage. However, rhynchocephalians were common during the late Triassic to latest Jurassic periods, but rapidly declined afterwards, which is generally attributed to their supposedly adaptive inferiority to squamates and/or Mesozoic mammals, which radiated at that time. New finds of Mesozoic rhynchocephalians can thus provide important new information on the evolutionary history of the group. A new fossil relative of Sphenodon from the latest Jurassic of southern Germany, Oenosaurus muehlheimensis gen. et sp. nov., presents a dentition that is unique amongst tetrapods. The dentition of this taxon consists of massive, continuously growing tooth plates, probably indicating a crushing dentition, thus representing a previously unknown trophic adaptation in rhynchocephalians. The evolution of the extraordinary dentition of Oenosaurus from the already highly specialized Zahnanlage generally present in derived rhynchocephalians demonstrates an unexpected evolutionary plasticity of these animals. Together with other lines of evidence, this seriously casts doubts on the assumption that rhynchocephalians are a conservative and adaptively inferior lineage. Furthermore, the new taxon underlines the high morphological and ecological diversity of rhynchocephalians in the latest Jurassic of Europe, just before the decline of this lineage on this continent. Thus, selection pressure by radiating squamates or Mesozoic mammals alone might not be sufficient to explain the demise of the clade in the Late Mesozoic, and climate change in the course of the fragmentation of the supercontinent of Pangaea might have played a major role

Akt1 in Osteoblasts and Osteoclasts Controls Bone Remodeling

Bone mass and turnover are maintained by the coordinated balance between bone formation by osteoblasts and bone resorption by osteoclasts, under regulation of many systemic and local factors. Phosphoinositide-dependent serine-threonine protein kinase Akt is one of the key players in the signaling of potent bone anabolic factors. This study initially showed that the disruption of Akt1, a major Akt in osteoblasts and osteoclasts, in mice led to low-turnover osteopenia through dysfunctions of both cells. Ex vivo cell culture analyses revealed that the osteoblast dysfunction was traced to the increased susceptibility to the mitochondria-dependent apoptosis and the decreased transcriptional activity of runt-related transcription factor 2 (Runx2), a master regulator of osteoblast differentiation. Notably, our findings revealed a novel role of Akt1/forkhead box class O (FoxO) 3a/Bim axis in the apoptosis of osteoblasts: Akt1 phosphorylates the transcription factor FoxO3a to prevent its nuclear localization, leading to impaired transactivation of its target gene Bim which was also shown to be a potent proapoptotic molecule in osteoblasts. The osteoclast dysfunction was attributed to the cell autonomous defects of differentiation and survival in osteoclasts and the decreased expression of receptor activator of nuclear factor-κB ligand (RANKL), a major determinant of osteoclastogenesis, in osteoblasts. Akt1 was established as a crucial regulator of osteoblasts and osteoclasts by promoting their differentiation and survival to maintain bone mass and turnover. The molecular network found in this study will provide a basis for rational therapeutic targets for bone disorders

Interpenetrating inclusion lattices: Comparison of the β-hydroquinone and ellipsoidal clathrate structures

Crystallization of 2,7-dimethyltricyclo[4.3.1.13,8]undecane-syn-2,syn-7-diol 2 from acetonitrile or dichloromethane yields the compounds (2)4· (guest) in space group I41/acd which are further examples of the ellipsoidal clathrate structure. Both enantiomers of 2 are linked through (O-H)4 cycles of hydrogen bonds to form a three-dimensional sublattice. Two inversion related sublattices interpenetrate thereby generating a superlattice with guest-occupied voids situated between the two individual sublattices. The two X-ray structures are compared and contrasted with that of Powell's (hydroquinone)3· (SO2) clathrate compound

Prediction and structure of polymorphic lattice inclusion compounds of 2,7-dimethyltricyclo[4.3.1.0^3,8]undecane-syn-2,syn-7-diol

The host molecule 2,7-dimethyltricyclo[4.3.1.03,8]undecane-syn-2,syn-7-diol 1 is known to form two different structural types of lattice inclusion compound dependent on the guest molecule chosen. Guests, including 1,2-dichlorobenzene 2, have now been predicted which result in the formation of both lattice types according to the crystallisation conditions employed. Crystal structures of the ellipsoidal clathrate type: (Racemic-1)4.(1,2-Dichlorobenzene), space group I41/acd; and the helical tubulate type: (Resolved-1)3.(1,2-Dichlorobenzene), space group P3121 are presented. The latter polymorph is transformed into the former on heating in a sealed system. © 1993