[1] In this study we provide a quantification of the main patterns of change of a subarctic peatland caused by permafrost decay monitored between 1957 and 2003. Up-thrusting of the peatland surface due to permafrost aggradation during the Little Ice Age resulted in the formation of an extensive peat plateau that gradually fragmented into residual palsas from the 19th century to the present. Only about 18% of the original surface occupied by permafrost was thawed in 1957, whereas only 13% was still surviving in 2003. Rapid permafrost melting over the last 50 years caused the concurrent formation of thermokarst ponds and fen-bog vegetation with rapid peat accumulation through natural successional processes of terrestrialization. The main climatic driver for accelerated permafrost thawing was snow precipitation which increased from 1957 to present while annual and seasonal temperatures remained relatively stable until about the mid-1990s when annual temperature rose well above the mean. Contrary to current expectations, the melting of permafrost caused by recent climate change does not transform the peatland to a carbon-source ecosystem as rapid terrestrialization exacerbates carbon-sink conditions and tends to balance the local carbon budget.

Knowledge of phosphorus (P) species in P-rich soils is useful for assessing P mobility and potential transfer to ground water and surface waters. Soil P was studied using synchrotron X-ray absorption near-edge structure (XANES) spectroscopy (a nondestructive chemical-speciation technique) and sequential chemical fractionation. The objective was to determine the chemical speciation of P in long-term-fertilized, P-rich soils differing in pH, clay, and organic matter contents. Samples of three slightly acidic (pH 5.5-6.2) and two slightly alkaline (pH 7.4-7.6) soils were collected from A or B horizons in two distinct agrosystems in the province of Québec, Canada. The soils contained between 800 and 2100 mg total P kg(-1). Distinct XANES features for Ca-phosphate mineral standards and for standards of adsorbed phosphate made it possible to differentiate these forms of P in the soil samples. The XANES results indicated that phosphate adsorbed on Fe- or Al-oxide minerals was present in all soils, with a higher proportion in acidic than in slightly alkaline samples. Calcium phosphate also occurred in all soils, regardless of pH. In agreement with chemical fractionation results, XANES data showed that Ca-phosphates were the dominant P forms in one acidic (pH 5.5) and in the two slightly alkaline (pH 7.4-7.6) soil samples. X-ray absorption near-edge structure spectroscopy directly identified certain forms of soil P, while chemical fractionation provided indirect supporting data and gave insights on additional forms of P such as organic pools that were not accounted for by the XANES analyses.

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Transforming growth factor ␤ (TGF-␤) signals through three high affinity cell surface receptors, TGF-␤ type I, type II, and type III receptors. The type III receptor, also known as betaglycan, binds to the type II receptor and is thought to act solely by "presenting" the TGF-␤ ligand to the type II receptor. The short cytoplasmic domain of the type III receptor is thought to have no role in TGF-␤ signaling because deletion of this domain has no effect on association with the type II receptor, or with the presentation role of the type III receptor. Here we demonstrate that the cytoplasmic domains of the type III and type II receptors interact specifically in a manner dependent on the kinase activity of the type II receptor and the ability of the type II receptor to autophosphorylate. This interaction results in the phosphorylation of the cytoplasmic domain of the type III receptor by the type II receptor. The type III receptor with the cytoplasmic domain deleted is able to bind TGF-␤, to bind the type II receptor, and to enhance TGF-␤ binding to the type II receptor but is unable to enhance TGF-␤2 signaling, determining that the cytoplasmic domain is essential for some functions of the type III receptor. The type III receptor functions by selectively binding the autophosphorylated type II receptor via its cytoplasmic domain, thus promoting the preferential formation of a complex between the autophosphorylated type II receptor and the type I receptor and then dissociating from this active signaling complex. These studies, for the first time, elucidate important functional roles of the cytoplasmic domain of the type III receptor and demonstrate that these roles are essential for regulating TGF-␤ signaling. Transforming growth factor ␤ (TGF-␤)1 is a member of a family of dimeric polypeptide growth factors which, in addition to the TGF-␤ ligands, includes the bone morphogenetic proteins (BMPs) and the activins (1). TGF-␤ regulates cellular proliferation and differentiation as well as the processes of embryonic development, wound healing, and angiogenesis in a tissue-specific manner. Mutations in TGF-␤ receptors or their intracellular signaling molecules have been described, particularly in association with the development of cancer and hereditary hemorrhagic telangiectasia. Alterations in the production of TGF-␤ ligand have also been linked to numerous disease states, including osteoporosis, hypertension, atherosclerosis, and fibrotic disease of the kidney, liver, and lung (2). TGF-␤ regulates cellular processes by binding to three high affinity cell surface receptors, the TGF-␤ type I, type II, and type III receptors. Where expressed, the type III receptor, also known as betaglycan, is the most abundant TGF-␤ receptor and is traditionally thought to function by binding TGF-␤ and then transferring it to its signaling receptor, the type II receptor. This is particularly important for the TGF-␤2 isoform, which cannot bind the type II receptor independently. The type I and II receptors contain serine/threonine protein k...

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In the mature adult brain, there are voice selective regions that are especially tuned to familiar voices. Yet, little is known about how the infant's brain treats such information. Here, we investigated, using electrophysiology and source analyses, how newborns process their mother's voice compared with that of a stranger. Results suggest that, shortly after birth, newborns distinctly process their mother's voice at an early preattentional level and at a later presumably cognitive level. Activation sources revealed that exposure to the maternal voice elicited early language-relevant processing, whereas the stranger's voice elicited more voice-specific responses. A central probably motor response was also observed at a later time, which may reflect an innate auditory-articulatory loop. The singularity of left-dominant brain activation pattern together with its ensuing sustained greater central activation in response to the mother's voice may provide the first neurophysiologic index of the preferential mother's role in language acquisition.

Our ability to discriminate and recognize human voices is amongst the most important functions of the human auditory system. The current study sought to determine whether electrophysiological markers could be used as objective measures of voice familiarity, by looking at the electrophysiological responses [mismatch negativity (MMN) and P3a] when the infrequent stimulus presented is a familiar voice as opposed to an unfamiliar voice. Results indicate that the MMN elicited by a familiar voice is greater than that elicited by an unfamiliar voice at FCz. The familiar voice also produced a greater P3a wave than that triggered by the unfamiliar voice at Fz. As both the MMN and the P3a were elicited as participants were instructed not to pay attention to incoming stimulation, these findings suggest that voice recognition is a particularly potent preattentive process whose neural representations can be objectively described through electrophysiological assessments.

In response to cancer chemotherapeutic drugs, cells rapidly trigger the apoptotic program or undergo growth arrest and senescence at specific phases of the cell cycle. Mitochondrial bcl-xL plays a central role in preventing alteration of mitochondrial dysfunction, cytochrome c release, caspase activation, DNA fragmentation and apoptosis. However, its pleitropic function depends on its subcellular localization. Here, we show that in addition to its mitochondrial effect that delays apoptosis, bcl-xL colocalizes and binds to cdk1(cdc2) during G 2 /M cellcycle checkpoint and its overexpression stabilizes a G 2 /Marrest senescence program in surviving cells after DNA damage. Bcl-xL potently inhibits cdk1(cdc2) kinase activity, which is reversible by a synthetic peptide between the 41st amino acid and 60th amino acid surrounding of the Thr47 and Ser62 phosphorylation sites, and Asn52 deamidation site, within the flexible loop domain of bclxL. A mutant deleted of this region does not alter the antiapoptotic function of bcl-xL, but impedes its effect on cdk1(cdc2) activity and on the G 2 /M-arrest senescence program after DNA damage. The nuclear interaction of bcl-xL and cdk1(cdc2) suggests that bcl-xL is coupled to the stabilization of a cell-cycle checkpoint induced by DNA damage, and this effect is genetically distinct from its function on apoptosis.