How genes find their way inside the cell nucleus

Recent progress in live cell imaging suggests a role for nuclear actin in chromatin movement. In this issue, for the first time, a gene locus moving toward a subnuclear compartment was tracked. Motion of the locus is actin dependent, raising the question of whether chromatin movements are random or directed.     

Polarization vision: how insects find their way by watching the sky

Scientists have long studied how some animals exploit celestial cues to solve navigational tasks. Recent discoveries show how locusts obtain unambiguous information from time-dependent patterns of polarized and unpolarized light in the sky.     

Protein Traffic in Gram-negative bacteria - how exported and secreted proteins find their way

Gram-negative bacteria assemble many proteins into the inner and outer membranes and export a large number of proteins to the periplasm or to the extracellular medium. During the billions of years bacteria have been around, they have evolved a number of different pathways with sophisticated machines to accurately and efficiently move proteins from one location to another. In this review, we first introduce specific proteins that are representative substrates of the protein transport pathways and describe their function. Then, their specific routes from synthesis to their destinations are described mentioning the signal peptide that may initiate their export and discuss what is known about the folding state of the substrates during transport. The membrane translocation device involved, the energy source required for transport, and whether a chaperone is needed will be discussed.     

Exotoxin secretion: getting out to find the way in

During infection, most pathogenic bacteria deliver proteins to the host cell cytoplasm to manipulate host behavior. In this issue of Cell Host & Microbe, Spanò and colleagues describe a system where a bacterium produces an exotoxin while inside the host cell. Only after this exotoxin is transported to the mammalian cell surface and secreted into the extracellular milieu can it intoxicate the infected cell or noninfected distant cells.     

By way of introduction: modelling living systems, their diversity and their complexity: some methodological and theoretical problems

Some principles for a current methodology for biological systems' modelling are presented. It seems possible to promote a model-centred approach of these complex systems. Among present questions, the role of mechanisms producing random or quasi-random issues is underlined, because they are implied in biological diversification and in resulting complexity of living systems. Now, biodiversity is one of our societies' and scientific research's main concerns. Basically, it can be interpreted as a manner, for Life, to resist environmental hazards. Thus, one may assume that biodiversity producing mechanisms could be selected during evolution to face to corresponding risks of disappearance: necessity of chance? Therefore, analysing and modelling these ‘biological and ecological roulettes’ would be important, and not only their outputs like nowadays by using the theory of probabilities. It is then suggested that chaotic behaviours generated by deterministic dynamical systems could mimic random processes, and that ‘biological and ecological roulettes’ would be represented by such models. Practical consequences can be envisaged in terms of biodiversity management, and more generally in terms of these ‘roulettes’ control to generate selected biological and ecological events' distribution. To cite this article: A. Pavé, C. R. Biologies 329 (2006).     

Sometimes sperm whales (Physeter macrocephalus) cannot find their way back to the high seas: a multidisciplinary study on a mass stranding

Background

Mass strandings of sperm whales (Physeter macrocephalus) remain peculiar and rather unexplained events, which rarely occur in the Mediterranean Sea. Solar cycles and related changes in the geomagnetic field, variations in water temperature and weather conditions, coast geographical features and human activities have been proposed as possible causes. In December 2009, a pod of seven male sperm whales stranded along the Adriatic coast of Southern Italy. This is the sixth instance from 1555 in this basin.

Methodology/Principal Findings

Complete necropsies were performed on three whales whose bodies were in good condition, carrying out on sampled tissues histopathology, virology, bacteriology, parasitology, and screening of veins looking for gas emboli. Furthermore, samples for age determination, genetic studies, gastric content evaluation, stable isotopes and toxicology were taken from all the seven specimens.The animals were part of the same group and determined by genetic and photo-identification to be part of the Mediterranean population. Causes of death did not include biological agents, or the “gas and fat embolic syndrome”, associated with direct sonar exposure. Environmental pollutant tissue concentrations were relatively high, in particular organochlorinated xenobiotics. Gastric content and morphologic tissue examinations showed a prolonged starvation, which likely caused, at its turn, the mobilization of lipophilic contaminants from the adipose tissue. Chemical compounds subsequently entered the blood circulation and may have impaired immune and nervous functions.

Conclusions/Significance

A multi-factorial cause underlying this sperm whales'' mass stranding is proposed herein based upon the results of postmortem investigations as well as of the detailed analyses of the geographical and historical background. The seven sperm whales took the same “wrong way” into the Adriatic Sea, a potentially dangerous trap for Mediterranean sperm whales. Seismic surveys should be also regarded as potential co-factors, even if no evidence of direct impact has been detected.     

Adaptive evolution of eye degeneration in the Mexican blind cavefish

The evolutionary mechanisms responsible for eye degeneration in cave-adapted animals have not been resolved. Opposing hypotheses invoking neural mutation or natural selection, each with certain genetic and developmental expectations, have been advanced to explain eye regression, although little or no experimental evidence has been presented to support or reject either theory. Here we review recent developmental and molecular studies in the teleost Astyanax mexicanus, a single species consisting of a sighted surface-dwelling form (surface fish) and many blind cave-dwelling forms (cavefish), which shed new light on this problem. The manner of eye development and degeneration, the ability to experimentally restore eyes, gene expression patterns, and comparisons between different cavefish populations all provide important clues for understanding the evolutionary forces responsible for eye degeneration. A key discovery is that Hedgehog midline signaling is expanded and inhibits eye formation by inducing lens apoptosis in cavefish embryos. Accordingly, eyes could have been lost by default as a consequence of natural selection for constructive traits, such as feeding structures, which are positively regulated by Hh signaling. We conclude from these studies that eye degeneration in cavefish may be caused by adaptive evolution and pleiotropy.     

Natural history and trophic ecology of three populations of the Mexican cavefish,Astyanax mexicanus

Environmental Biology of Fishes - The Mexican cavefish, Astyanax mexicanus (Characidae), has become an important model in evolutionary physiology and developmental biology, providing insights into...     

Supernumerary teeth in the European lynx, Lynx lynx lynx, and their evolutionary significance

Supernumerary upper second deciduous premolars and lower second molars are reported in lynx, Lynx lynx lynx (L.), from Norway at frequencies comparable with the situation reported from lynx populations in other countries. Other authors have interpreted these anomalies as true atavisms in response to altered environmental conditions, and consequently as being contradictory with Dollo's law. The author suggests an alternative interpretation of the appearance of supernumerary teeth, which brings such phenomena in line with Dollo's law and the recent modern synthesis of evolution.     

The Hoosier cavefish,a new and endangered species (Amblyopsidae,Amblyopsis) from the caves of southern Indiana

We describe a new species of amblyopsid cavefish (Percopsiformes: Amblyopsidae) in the genus Amblyopsis from subterranean habitats of southern Indiana, USA. The Hoosier Cavefish, Amblyopsis hoosieri sp. n., is distinguished from A. spelaea, its only congener, based on genetic, geographic, and morphological evidence. Several morphological features distinguish the new species, including a much plumper, Bibendum-like wrinkled body with rounded fins, and the absence of a premature stop codon in the gene rhodopsin. This is the first new cavefish species described from the United States in 40 years and exemplifies how molecular data can alert us to the presence of otherwise cryptic biodiversity.