Étude analytique d’une clavicule complète de subadulte d’Homo antecessor (site de Gran Dolina, Sierra d’Atapuerca, Burgos, Espagne)

This study reports on the skeletal remains of an infant clavicle - specimen ATD6-37 - belonging to the Homo antecessor species, unearthed at Lower Pleistocene level TD6 of the Gran Dolina site (Sierra de Atapuerca). Studied alongside a further adult specimen - ATD6-50 -, they provide us with significant information on two key paleobiological aspects of these early humans: body shape and development. Based on the analytical results, the paper proposes a more accurate proportional method for determining age at death is applied to the fossilized infant clavicle under study. It goes on to hypothesize on postcranial growth and body shape and discusses morphological patterns and age at death of these early humans through comparisons with a wide range of infant dental samples and clavicular specimens in early and modern humans.     

Les récentes découvertes à Baerya dans le district de Bijie, au nord de la province de Guizhou (Chine)

Fauna associated with stone artifacts have recently been uncovered, in the course of a survey from a cave site named Baerya, town land of Bijie, Guizhou province. The first observations suggest a human occupation. In the absence of chrono-stratigraphic data, it is not possible to assess the age of the site. Nevertheless the presence of lower Pleistocene fauna suggests a very ancient age for this human occupation. Further field research will be necessary to determinate the age and nature of the site.     

Le bassin de l’homme du Pléistocène supérieur de Liujiang, Sud de la Chine : taille du corps, forme du corps et encéphalisation

The Late Pleistocene hominin fossil assemblage from Liujiang, South China include a fairly well-preserved cranium, a right os coxa, a complete sacrum, and other postcranial elements all belonging to a single individual. This rare discovery offers us a unique and singular opportunity in understanding this Late Pleistocene hominin's body proportion and relative cranial capacity (encephalization quotient [EQ]), and also pelvic morphology. Using the available right innominate and its mirror-imaged left side, we reconstruct Liujiang hominin's pelvis. Our analysis of the pelvis indicates that the Liujiang hominin has a very gracile and modern-like pelvic morphology. Indeed, all of the pelvic dimensions are smaller than those of other Pleistocene hominins. Moreover, the pelvic characteristics typical of Middle and Late Pleistocene hominins including Neanderthals cannot be identified in the Liujiang pelvis. In contrast, both Liujiang's metric and non-metric features indicate affinities to more recent human populations including our modern Chinese collections from Guangxi of south China. Further support of this assessment comes from the EQ value of 5.754 for Liujiang which is closer to Minatogawa 2 and modern Chinese populations than to Middle and Late Pleistocene fossil hominins. Our analysis of body shape shows that Liujiang has body proportion (i.e. body height relative to body breadth) typical of warm-adapted populations. Based on these findings, we reason that the modern physical characteristics of Liujiang may allude to a more recent geological age. Alternatively, its morphological “modernity” could also point to a much higher degree of skeletal variation within Late Pleistocene hominins in East Asia.     

Cooperation strategies, signals and symbiosis

The authors of models concerning cooperation found an interesting application point in mutualism and symbiosis. Phenomena which are to be found in symbiosis are integrated by the various models in relation to the 'Prisoner's Dilemma': 'cost-benefit' ratio components, signals, neighbourhood interaction or reciprocity. Reciprocal altruism is found in symbiosis, but others strategies seem more to reflect human societies, where choice is unrestricted. It is very difficult to give a value to cost and benefit equilibriums. The biological environment interferes and a model based on a dominant strategy is often limited or insufficient to report on the living system's evolution.     

Recognition of messenger RNA during translational initiation in Escherichia coli

The structural aspects of recognition by E. coli ribosomes of translational initiation regions on homologous messenger RNAs have been reviewed. Also discussed is the location of initiation region on mRNA, its confines, typical nucleotide sequences responsible for initiation signal, and the influence of RNA macrostructure on protein synthesis initiation. Most of the published DNA nucleotide sequences surrounding the start of various E. coli genes and those of its phages have been collected.     

On the mechanism of reductive activation in the mode of action of some anticancer drugs

Bioactivation of a number of DNA-specific antitumor drugs depends on oxidoreduction. Bleomycin, neocarzinostatin and anthracycline glycosides are the best known among such drugs in terms of reductive activation processes. Their reduction results in short-lived radical or electrophilic intermediates attacking DNA stereospecifically. The physico-chemical properties of these drugs and the nature of DNA damage are reviewed. Models for DNA-intercalation, electron-donor systems involved in drug metabolisation, and the role of oxygen in radical reactions, are discussed in the light of recent reports.     

Ecological time-series analysis through structural modelling with latent constructs: concepts, methods and applications

Time-series analyses in ecology usually involve the use of autoregressive modelling through direct and/or delayed difference equations, which severely restricts the ability of the modeler to structure complex causal relationships within a multivariate frame. This is especially problematic in the field of population regulation, where the proximate and ultimate causes of fluctuations in population size have been hotly debated for decades. Here it is shown that this debate can benefit from the implementation of structural modelling with latent constructs (SEM) to time-series analysis in ecology. A nonparametric bootstrap scheme illustrates how this modelling approach can circumvent some problems posed by the climate-ecology interface. Stochastic Monte Carlo simulation is further used to assess the effects of increasing time-series length and different parameter estimation methods on the performance of several model fit indexes. Throughout, the advantages and limitations of the SEM method are highlighted.     

Molecular biology and genetics of Alzheimer's disease

Like several other adult onset neurodegenerative diseases, Alzheimer's disease is a multifactorial illness with both genetic and non-genetic causes. Recent genetic studies have identified four genes associated with inherited risk for AD (presenilin 1, presenilin 2, amyloid precursor protein, and apolipoprotein E). These genes account for about half of the total genetic risk for Alzheimer's disease. It is suspected that several other Alzheimer's disease-susceptibility genes exist, and their identification is the subject of ongoing research. Nevertheless, biological studies on the effects of mutations in the four known genes has led to the conclusion that all of these genes cause dysregulation of amyloid precursor protein processing and in particular dysregulation of the handling of a proteolytic derivative termed Abeta. The accumulation of Abeta appears to be an early and initiating event that triggers a series of downstream processes including misprocessing of the tau protein. This cascade ultimately causes neuronal dysfunction and death, and leads to the clinical and pathological features of Alzheimer's disease. Knowledge of this biochemical cascade now provides several potential targets for the development of diagnostics and therapeutics.