A comparison of the strength of biodiversity effects across multiple functions

In order to predict which ecosystem functions are most at risk from biodiversity loss, meta-analyses have generalised results from biodiversity experiments over different sites and ecosystem types. In contrast, comparing the strength of biodiversity effects across a large number of ecosystem processes measured in a single experiment permits more direct comparisons. Here, we present an analysis of 418 separate measures of 38 ecosystem processes. Overall, 45 % of processes were significantly affected by plant species richness, suggesting that, while diversity affects a large number of processes not all respond to biodiversity. We therefore compared the strength of plant diversity effects between different categories of ecosystem processes, grouping processes according to the year of measurement, their biogeochemical cycle, trophic level and compartment (above- or belowground) and according to whether they were measures of biodiversity or other ecosystem processes, biotic or abiotic and static or dynamic. Overall, and for several individual processes, we found that biodiversity effects became stronger over time. Measures of the carbon cycle were also affected more strongly by plant species richness than were the measures associated with the nitrogen cycle. Further, we found greater plant species richness effects on measures of biodiversity than on other processes. The differential effects of plant diversity on the various types of ecosystem processes indicate that future research and political effort should shift from a general debate about whether biodiversity loss impairs ecosystem functions to focussing on the specific functions of interest and ways to preserve them individually or in combination.     

Dibenzocyclooctadiene-type lignans from Magnolia pyramidata

Eight dibenzocyclooctadiene-type lignans, pyramidatin A-H, were isolated from the leaves of Magnolia pyramidata. Their structures were established by spectral methods, mainly 2D NMR spectroscopic techniques, which involved combined applications of COSY, DEPT. 1H, 13C correlations, COLOC, INAPT and long-range inverse 1H, 13C NMR correlations. The molecular structures of pyramidatin A and B were determined by single crystal X-ray diffraction. The absolute configurations of all eight lignans were derived from CD spectral correlations with structurally related dibenzocyclooctadienes of known absolute configuration.     

Reconstitution of types I and II adenosine cyclic 3',5'-phosphate dependent protein kinase

Fluorescence intensity and anisotropy measurements using the fluorescent adenosine cyclic 3',5'-phosphate (cAMP) analogue 1,N6-ethenoadenosine cyclic 3',5'-phosphate (epsilon-cAMP) are sensitive to the dissociation of epsilon-cAMP which occurs when either the type I or the type II regulatory subunit (RI or RII) of cAMP-dependent protein kinase associates with the catalytic subunit. Studies using epsilon-cAMP show that MgATP has opposite effects on the reconstitution of both types of protein kinase: MgATP strongly stabilizes the type I holoenzyme while it slightly destabilizes the type II holoenzyme. The synthetic substrate Kemptide has a small inhibitory effect on the reconstitution of both holoenzymes when tested at 10 microM concentration. The protein kinase inhibitor has a larger effect which is especially pronounced in the reassociation of the type I enzyme. The diminished relative ability of the type I regulatory subunit to compete with the protein kinase inhibitor suggests that the combined effects of the two opposing equilibria (epsilon-cAMP and catalytic subunit binding) are different for the two types of regulatory subunits. Displacement experiments show that cAMP and epsilon-cAMP bind about equally well to the type I subunit. Slow conformational changes accompanying the binding of epsilon-cAMP by both regulatory subunits are greatly accelerated with the holoenzymes, suggesting that dissociation of the holoenzymes occurs via ternary complexes. The time courses of epsilon-cAMP binding also show the heterogeneity of binding characteristics of RII. The 37 000-dalton fragment of type II subunit retains the epsilon-cAMP binding properties of the native subunit. However, only a fraction of the fragment preparation (approximately 32% estimated from sedimentation measurements) binds the catalytic subunit well, suggesting heterogeneity of cleavage.     

SIRT1 deacetylase protects against neurodegeneration in models for Alzheimer's disease and amyotrophic lateral sclerosis

A progressive loss of neurons with age underlies a variety of debilitating neurological disorders, including Alzheimer's disease (AD) and amyotrophic lateral sclerosis (ALS), yet few effective treatments are currently available. The SIR2 gene promotes longevity in a variety of organisms and may underlie the health benefits of caloric restriction, a diet that delays aging and neurodegeneration in mammals. Here, we report that a human homologue of SIR2, SIRT1, is upregulated in mouse models for AD, ALS and in primary neurons challenged with neurotoxic insults. In cell-based models for AD/tauopathies and ALS, SIRT1 and resveratrol, a SIRT1-activating molecule, both promote neuronal survival. In the inducible p25 transgenic mouse, a model of AD and tauopathies, resveratrol reduced neurodegeneration in the hippocampus, prevented learning impairment, and decreased the acetylation of the known SIRT1 substrates PGC-1alpha and p53. Furthermore, injection of SIRT1 lentivirus in the hippocampus of p25 transgenic mice conferred significant protection against neurodegeneration. Thus, SIRT1 constitutes a unique molecular link between aging and human neurodegenerative disorders and provides a promising avenue for therapeutic intervention.     

Cernunnos interacts with the XRCC4 x DNA-ligase IV complex and is homologous to the yeast nonhomologous end-joining factor Nej1

DNA double strand breaks are considered as the most harmful DNA lesions and are repaired by either homologous recombination or nonhomologous end joining (NHEJ). A new NHEJ factor, Cernunnos, has been identified, the defect of which leads to a severe immunodeficiency condition associated with microcephaly and other developmental defects in humans. This presentation is reminiscent to that of DNA-ligase IV deficiency and suggests a possible interplay between Cernunnos and the XRCC4 x DNA-ligase IV complex. We show here that Cernunnos physically interacts with the XRCC4 x DNA-ligase IV complex. Moreover, a combination of sensitive methods of sequence analysis revealed that Cernunnos can be associated with the XRCC4 family of proteins and that it corresponds to the genuine homolog of the yeast Nej1 protein. Altogether these results shed new lights on the last step, the DNA religation, of the NHEJ pathway.     

SMN-mediated assembly of RNPs: a complex story

Although many RNA-protein complexes or ribonucleoproteins (RNPs) assemble spontaneously in vitro, little is known about how they form in the environment of a living cell. Insight into RNP assembly has come unexpectedly from functional analyses of the survival motor neuron (SMN) protein, a gene product that is affected in the neuromuscular disease spinal muscular atrophy. These studies show that the assembly of spliceosomal U-rich small nuclear RNPs in vivo depends on the activity of two large protein complexes, one of which contains the SMN protein. These complexes might also facilitate the assembly of other cellular RNPs.     

A technique for joint center analysis using a stored program calculator

For a long time in the study of joint kinematics, the instant center of rotation in plane motion was obtained through graphic drawings. Since then the study of joint kinematics has become three-dimensional involving the use of computers. For this paper a stored-program calculator has been used as it is a precise instrument and several films can be used even if their positions are very close to one another.

A movement is never perfectly plane, it was important to define a coefficient (in percentage) to qualify the more or less plane character of a movement.

We believe that an analytical location is a better way than using graphic drawings of I.C.R.:

1. (1) to smooth the raw coordinates;

2. (2) to calculate the plane motion coefficient in order to eliminate an X-Ray picture of a whole series of pictures for lack of plane character;

3. (3) to define in the results an error rectangle whose dimensions are linked to errors in the observation and then to pick out among the points of a body those with the smallest risk for error.

To probe this method the two radio-ulnaris joints have been studied. At present studies are being carried on to compare the I.C.R.'s behaviour of the lumbar spine during a motion of lateral inflexion both in the case of normal people and people with scoliosis.