The previous fossil record of limbed vertebrates of the Iberian peninsula started in the Triassic (245 Ma). The discovery of a new temnospondyl from the Late Carboniferous (Stephanian C, 290 Ma) extends the fossil record of stegocephalians in this region by at least 45 Ma. Early stegocephalians are usually thought to have been unable to live in salt water, but the new temnospondyl described below appears to have lived in a coastal region, presumably in salt water.
It is generally difficult to find any relationship between the morphogenesis of an organ and its final function. A priori, such a relationship has no reason to exist, since organs do not actually function during their formation. I will show in this article that, for a very large class of organs – the branched organs – there exists a hidden relationship between their morphogenesis and their function. This class of organs comprises : the lungs, the salivary mammary and lacrymal glands, the kidneys, the pancreas, and possibly other organs, such as testes. For all these organs, a fundamental fact that comes from recent developments in physics explains at the same time how they form, and why they work. This suggests, first, that complex organs are not the result of gradual and long selection processes, and, second, that this specific structure for the organs is imposed by the laws of physics. The growth process, as described here, is possibly the only one that allows both to build a fluid-secreting organ, and make it work.
An ultrastructural study of Weddellomyces epicallopisma (ascomata wall, asci, ascospores and vegetative hyphae), the first done on the family Dacampiaceae, confirms most of the observations made in light microscopy. Moreover it shows that ascospores are provided with an endospore (not visible in light microscope) and that the structure of the ascospore septum is more complex. The similarity of the wall structure between the ascospore and the hyphoid appendages, developed on the upper part of the ascoma, is emphasized.
Fourteen types of physical structures produced by ecosystem engineers were sampled at the surface of a savanna soil of Colombia. Invertebrates implicated in the creation of these structures were identified. Some physical (aggregate size and stability, bulk density) and chemical (C, N, P contents, pH, etc) properties of structures were assessed. Three large groups of structures were identified: (i) earthworm casts characterised by a high bulk density (1.3–1.4 g·cm–3), constituted of aggregates (7–10 mm), high in organic C (3–4 %) and assimilable nutrients; (ii) termite mounds with low bulk density (0.6–0.9 g·cm–3), constituted of aggregates (8–9 mm), high in organic C (3.5–10 %) and assimilable nutrients; and (iii) slightly compact (0.4–0.7 g·cm–3) and granular (aggregate size < 1.5 mm) termite superficial channels and ant mounds low in organic C (less than 1.5 %) and assimilable nutrients. These results underline the large diversity of the biogenic structures produced at the surface of the studied soil. They suggest the feasibility of a functional classification of engineer organisms that would take into account simultaneously the different functional attributes reflected by these structures.
The distribution of the 36 palm species of New Caledonia is studied in relation to several parameters: elevation, rainfall, geological substrate, phytogeographical sectors and vegetation types. The climate (thermal gradient and rainfall) appears to be the principal factor influencing the distribution of palms, the substrate effect being subordinate to the climatic pattern. Nearly all palm populations are included within the 1 500 mm isoline. Maximum levels of species richness and endemism are located in four areas receiving more than 3 000 mm of annual rainfall. We interpret these areas as former Pleistocene refugia of lowland rain forest based on three lines of evidence: 1) all locally endemic lowland palm species and genera are restricted to these areas; 2) local endemics occur on east-facing slopes receiving the highest rainfall and most likely to have sustained rain forests during the driest periods; and 3) several pairs of sister species are disjunct between the southeastern and northeastern high rainfall areas.
Isotopic analysis of 13C and 15N of 47 bones from Saint-Laurent de Grenoble cemetery (Grenoble, Isère), from the end of medieval period (XIIIth–XVth centuries AD) allowed to define the food status of animals with regard to the humans and to discuss the variability amongst adults. Adults who died young and those with small stature may have had diets poor in animal protein. The consumption of animal proteins was more important in the XVth than in the XIVth century and could illustrate a typical urban food economy providing its population with a more diversified diet than in rural areas.
NO displays both pro- and anti-apoptotic properties. The parameters governing these effects begin to be elucidated. Among these figure the nature of the cells, their redox state, the flow and concentration of NO, its possibility to react with superoxide generated at the level of mitochondria. The targets of NO include molecules involved in DNA repair, such as PARP, the DNA-dependent protein kinase (DNA-PK) and p53 which control the transcription of various genes involved in the apoptotic process (bax, cdk inhibitors), and the proteasome which control the degradation of several apoptotic proteins. The inhibition by NO of caspases through S-nitrosylation of their active sites provides a rationale for our understanding of the anti-apoptotic effect of NO, but other mechanisms are involved, such as a regulation of the mitochondrial permeability. A better knowledge of the various steps of the apoptotic process that are affected by NO would allow the design of new pharmacological tools.
Serotonin (5-hydroxytryptamine, 5-HT) is a well-known neurotransmitter and immunomodulator, which has been reported to affect the function of cells in the immune system. The purpose of the herein reported experiments was to investigate whether serotonin could regulate the proliferation of a human T lymphoblastic leukemia cell line (CCRF-CEM cells) and to characterize the 5-HT receptor(s) involved in this phenomenon using a pharmacological approach. The herein presented results show that serotonin alone stimulated the proliferation of CCRF-CEM cells and that this effect could be mimicked by two 5-HT1B/1D receptor agonists (L-694,247 and GR 46611). Serotonin- or L-694,247-induced increase in cell proliferation was inhibited by a selective 5-HT1B receptor antagonist, SB-224289. A recently identified endogenous tetrapeptide, 5-HT-moduline (Leu–Ser–Ala–Leu, LSAL), which specifically antagonizes 5-HT1B/1D receptor activity, was also shown to reverse the stimulating action of L-694,247 on T cell proliferation. Taken together, these results establish the existence of a direct serotonergic control of the T cell proliferation mediated through h5-HT1B receptors. In addition, these results are in favour of an immunomodulatory role of 5-HT-moduline.
The early knowledge of the sex may be crucial for the understanding of many features of ecological and evolutive biology, including offspring sex-ratio adjustment and evolution of breeding systems. In coypu (Myocastor coypus), significant variation in birth sex-ratios can be observed and selective abortion of entire litters is one of the cited mechanisms. In order to determine the sex of coypu embryos in the earlier stages of gestation (second week), we developed a molecular technique based on PCR amplification of a region of the Sry gene. These method used the combination of two sets of primers: one specific of the Y-chromosome; the other one, autosomal, is a positive control for amplification. Because of the direct amplification of embryo lysate without DNA extraction, the present sexing technique is rapid, relatively simple and inexpensive, and presents numerous advantages for the study at population scale.
Based on inversion of gap fraction data (Poisson model of foliage distribution), three optical methods using the Demon, the Plant Canopy Analyzer LAI-2000 (PCA) and hemispherical photographs, have been compared to estimate canopy openness (CO) and leaf area index (LAI) in a mature, neutrophil, oak-beech-hornbeam forest on mull in eastern France. Mean CO over the whole hemisphere was similar for PCA (7.9 %) and hemispherical photographs (8.0 %). The needle method, a vertical point quadrat method, applied to the litter after leaf fall has served as a reference to LAI (4.7). The Demon provided the estimate (4.9) closest to the reference value. The PCA and hemispherical photographs underestimate mean LAI by 30 % (3.3) and 19 % (3.8), respectively, if used without correction. Based on fish-eye sensors, LAI estimates can be improved if 3 annuli (4.2) or 2 annuli (4.5) are used in place of 5 with the PCA, or by means of logarithmic averaging of gap fractions over azimuth at an appropriate angular resolution (180°: 4.6, or 120°: 5.2) with hemispherical photographs. Not taking into account azimuthal variation in gap fraction distribution generates a more important error than the error induced by light scattering near horizon. In order to improve LAI estimates, an original iterative procedure is presented, which allows the simultaneous calculation of LAI over a broad range of angular azimuthal resolutions.
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