Is Tree Species Diversity or Species Identity the More Important Driver of Soil Carbon Stocks,C/N Ratio,and pH?

We explored tree species diversity effects on soil C stock, C/N ratio, and pH as compared with effects of tree species identity. We sampled forest floors and mineral soil (0–40 cm) in a diversity gradient of 1–5 tree species composed of conifers and broadleaves in Bia?owie?a Forest, Poland. Diversity was a weaker driver than identity of soil C stocks, C/N ratio, and pH in the soil profile. However, there were significant non-additive effects of diversity and significant effects of identity on C stock and C/N ratio within different parts of the soil profile. More diverse forests had higher C stocks and C/N ratios in the 20–40 cm layer, whereas identity in terms of conifer proportion increased C stocks and C/N ratios only in forest floors. A positive relationship between C stocks and root biomass in the 30–40 cm layer suggested that belowground niche complementarity could be a driving mechanism for higher root carbon input and in turn a deeper distribution of C in diverse forests. Diversity and identity affected soil pH in topsoil with positive and negative impacts, respectively. More diverse forests would lead to higher soil nutrient status as reflected by higher topsoil pH, but there was a slight negative effect on N status as indicated by higher C/N ratios in the deeper layers. We conclude that tree species diversity increases soil C stocks and nutrient status to some extent, but tree species identity is a stronger driver of the studied soil properties, particularly in the topsoil.     

Comparative assay of Vipera ammodytes antivenom potency

The finding of the most appropriate way to assess precisely the antivenom efficacy represents one of the major issues for antivenom standardization and success increasing of antivenom therapy. The efficacy of experimental Vipera ammodytes antivenom raised in sheep was determined using in vivo mouse lethality test, respectively, L-aminoacid oxidase, total proteinase and phospholipase A₂ antienzymatic effectiveness. The values gained for the antivenom potency depend on the method of measure. So, some of the most toxic venom proteins own phospholipase A₂ activity and provide the highest antivenom potency (lowest effective dose) values by antienzymatic assay method. This value is similar with total antiproteolytic antivenom potency value, but almost three times higher than value obtained by L-aminoacid oxidase (low toxic viper venom protein) antienzymatic assay method.     

COMT Val158Met genotype is associated with reward learning: a replication study and meta‐analysis

Identifying mechanisms through which individual differences in reward learning emerge offers an opportunity to understand both a fundamental form of adaptive responding as well as etiological pathways through which aberrant reward learning may contribute to maladaptive behaviors and psychopathology. One candidate mechanism through which individual differences in reward learning may emerge is variability in dopaminergic reinforcement signaling. A common functional polymorphism within the catechol‐O‐methyl transferase gene (COMT; rs4680, Val¹⁵⁸Met) has been linked to reward learning, where homozygosity for the Met allele (linked to heightened prefrontal dopamine function and decreased dopamine synthesis in the midbrain) has been associated with relatively increased reward learning. Here, we used a probabilistic reward learning task to asses response bias, a behavioral form of reward learning, across three separate samples that were combined for analyses (age: 21.80 ± 3.95; n = 392; 268 female; European‐American: n = 208). We replicate prior reports that COMT rs4680 Met allele homozygosity is associated with increased reward learning in European‐American participants (β = 0.20, t = 2.75, P < 0.01; ΔR² = 0.04). Moreover, a meta‐analysis of 4 studies, including the current one, confirmed the association between COMT rs4680 genotype and reward learning (95% CI ?0.11 to ?0.03; z = 3.2; P < 0.01). These results suggest that variability in dopamine signaling associated with COMT rs4680 influences individual differences in reward which may potentially contribute to psychopathology characterized by reward dysfunction.     

Leptin reverses long-term potentiation at hippocampal CA1 synapses

The hormone leptin crosses the blood brain barrier and regulates numerous neuronal functions, including hippocampal synaptic plasticity. Here we show that application of leptin resulted in the reversal of long-term potentiation (LTP) at hippocampal CA1 synapses. The ability of leptin to depotentiate CA1 synapses was concentration-dependent and it displayed a distinct temporal profile. Leptin-induced depotentiation was not associated with any change in the paired pulse facilitation ratio or the coefficient of variance, indicating a post-synaptic locus of expression. Moreover, the synaptic activation of NMDA receptors was required for leptin-induced depotentiation as the effects of leptin were blocked by the competitive NMDA receptor antagonist, D-aminophosphovaleric acid (D-AP5). The signaling mechanisms underlying leptin-induced depotentiation involved activation of the calcium/calmodulin-dependent protein phosphatase, calcineurin, but were independent of c- jun NH₂ terminal kinase. Furthermore, leptin-induced depotentiation was accompanied by a reduction in α-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA) receptor rectification indicating that loss of glutamate receptor 2 (GluR2)-lacking AMPA receptors underlies this process. These data indicate that leptin reverses hippocampal LTP via a process involving calcineurin-dependent internalization of GluR2-lacking AMPA receptors which further highlights the key role for this hormone in regulating hippocampal synaptic plasticity and neuronal development.     

Influence of pinealectomy and long-term melatonin administration on bone metabolism in orchidectomized rats

INTRODUCTION: The aim of the study was to demonstrate whether pinealectomy and long-term MEL administration can affect bone metabolism (as evaluated on the basis of serum concentrations of PICP and ICTP) in orchidectomized rats. MATERIAL AND METHODS: The study included 248 adult male Wistar rats; 6 remained intact, 120 were orchidectomized (Orch), and the remaining ones underwent a sham operation (SOrch). Two weeks after surgery, the rats were divided into 8 groups: 1) SOrch + SPx; 2) SOrch + SPx + MEL; 3) Orch + SPx; 4) Orch + SPx + MEL; 5) SOrch + Px; 6) SOrch + Px + MEL; 7) Orch + Px; 8) Orch + Px + MEL. Animals from 5(th), 6(th), 7(th) and 8(th) groups were pinealectomized (Px) while the remaining ones underwent a sham operation (SPx). Two weeks after surgery rats in the 2(nd), 4(th), 6(th) and 8(th) groups were administered MEL (50 microg/100 g of bm) intraperitoneally while the remaining animals were administered solvent only (daily between 5 and 6 pm during a month). The animals were decapitated before the experiment (intact rats), after 2 weeks from Orch and SOrch, Px and SPx, after 4 weeks from MEL or solvent administration and after 4 and 8 weeks from discontinuing administration of MEL, and blood was collected for PICP and ICTP concentrations assays with the use of RIA method. DISCUSSION: In Orch rats, a distinct tendency to increase the studied bone markers, especially ICTP was shown. Pinealectomy had inducing, while MEL suppressing effect upon the level of PICP and ICTP; these changes were more pronounced in Orch + Px and SOrch + Px + MEL groups, respectively. After discontinuing administration of MEL distinct tendency to increase of PICP and ICTP level was shown. CONCLUSIONS: Our findings indicate that MEL is an important modulator of bone tissue metabolism in male rats and that deficiency of MEL concentration may be a co-factor in osteoporosis development.     

Acetylcholine nicotinic receptors: finding the putative binding site of allosteric modulators using the “blind docking” approach

Allosteric potentiation of acetylcholine nicotinic receptors is considered to be one of the most promising approaches for the treatment of Alzheimer’s disease. However, the exact localization of the allosteric binding site and the potentiation mechanism at the molecular level are presently unknown. We have performed the “blind docking” of three known allosteric modulators (galanthamine, codeine and eserine) with the Acetylcholine Binding Protein and models of human α7, α3β4 and α4β2 nicotinic receptors, created by homology modeling. Three putative binding sites were identified in the channel pore, each one showing different affinities for the ligands. One of these sites is localized opposite to the agonist binding site and is probably implicated in the potentiation process. On the basis of these results, a possible mechanism for nicotinic acetylcholine receptor (nAChRs) activation is proposed. The present findings may represent an important advance for understanding the allosteric modulation mechanism of nAChRs. Electronic supplementary material Supplementary material is available for this article at     

New near-infrared optical probes of cardiac electrical activity

Styryl voltage-sensitive dyes (e.g., di-4-ANEPPS) have been widely and successfully used as probes for mapping membrane potential changes in cardiac cells and tissues. However, their utility has been somewhat limited because their excitation wavelengths have been restricted to the 450- to 550-nm range. Longer excitation/emission wavelength probes can minimize interference from endogenous chromophores and, because of decreased light scattering and lower absorption by endogenous chromophores, improve recording from deeper tissue layers. In this article, we report efforts to develop new potentiometric styryl dyes that have excitation wavelengths ranging above 700 nm and emission spectra extending to 900 nm. Three dyes for cardiac optical mapping were investigated in depth from several hundred dyes containing 47 variants of the styryl chromophores. Absorbance and emission spectra in ethanol and multilamellar vesicles, as well as voltage-dependent spectral changes in a model lipid bilayer, have been recorded for these dyes. Optical action potentials were recorded in typical cardiac tissues (rat, guinea pig, pig) and compared with those of di-4-ANEPPS. The voltage sensitivities of the fluorescence of these new potentiometric indicators are as good as those of the widely used ANEP series of probes. In addition, because of molecular engineering of the chromophore, the new dyes provide a wide range of dye loading and washout time constants. These dyes will enable a series of new experiments requiring the optical probing of thick and/or blood-perfused cardiac tissues.     

Biological activity of endomorphin and [Dmt1]endomorphin analogs with six-membered proline surrogates in position 2

Endogenous μ-opioid receptor (MOR) selective peptides, endomorphin-1 (EM-1) and endomorphin-2 (EM-2), unlike so called ‘typical opioids’, are characterized by the presence of Pro² residue, which is a spacer connecting aromatic pharmacophoric residues. In order to investigate structural requirements for position 2, we synthesized endomorphin analogs incorporating, instead of Pro, unnatural amino acids with six-membered heterocyclic rings, such as piperidine 2-, 3- or 4-carboxylic acids (Pip, Nip and Inp, respectively). (R)-Nip residue turned out to be favourable for improving MOR affinity. Introduction of 2′,6′-dimethyltyrosine (Dmt) instead of Tyr¹ led to obtaining [Dmt¹, (R)-Nip²]EM-2 which showed exceptional MOR affinity and high stability against enzymatic degradation in rat brain homogenate. In in vivo hot-plate test in mice, this analog given intracerebroventicularly (i.c.v.), produced profound supraspinal analgesia, being much more potent than EM-2. The antinociceptive effect of this analog lasted about 170 min and was almost completely reversed by β-funaltrexamine (β-FNA), a selective MOR antagonist.     

The Ku80 Carboxy Terminus Stimulates Joining and Artemis-Mediated Processing of DNA Ends

Repair of DNA double-strand breaks (DSBs) is predominantly mediated by nonhomologous end joining (NHEJ) in mammalian cells. NHEJ requires binding of the Ku70-Ku80 heterodimer (Ku70/80) to the DNA ends and subsequent recruitment of the DNA-dependent protein kinase catalytic subunit (DNA-PK_CS) and the XRCC4/ligase IV complex. Activation of the DNA-PK_CS serine/threonine kinase requires an interaction with Ku70/80 and is essential for NHEJ-mediated DSB repair. In contrast to previous models, we found that the carboxy terminus of Ku80 is not absolutely required for the recruitment and activation of DNA-PK_CS at DSBs, although cells that harbored a carboxy-terminal deletion in the Ku80 gene were sensitive to ionizing radiation and showed reduced end-joining capacity. More detailed analysis of this repair defect showed that DNA-PK_CS autophosphorylation at Thr2647 was diminished, while Ser2056 was phosphorylated to normal levels. This resulted in severely reduced levels of Artemis nuclease activity in vivo and in vitro. We therefore conclude that the Ku80 carboxy terminus is important to support DNA-PK_CS autophosphorylation at specific sites, which facilitates DNA end processing by the Artemis endonuclease and the subsequent joining reaction.DNA double-strand breaks (DSBs) classify among the most detrimental DNA damages, because they have the ability to cause chromosome breakage and translocations. DSBs are readily caused by common exogenous and endogenous agents, including certain oxygen radicals, products of normal metabolism, and ionizing radiation. Effective genomic maintenance therefore requires the presence of a mechanism to repair DSBs. DSB repair in eukaryotic cells is executed by either homologous recombination or by nonhomologous end joining (NHEJ) (15, 30).In vertebrates, DSB repair is not only essential for genomic maintenance, but also for the development of a working immune system. The assembly of immunoglobulin or T-cell receptor genes via V(D)J recombination routinely necessitates the introduction and subsequent NHEJ-mediated repair of DSBs (13).The NHEJ pathway facilitates DSB repair by direct ligation of the two ends of a broken DNA molecule (31, 36). This requires the sequential loading of several enzymes on both DNA ends. The first event in NHEJ-mediated repair is the association of a Ku70-Ku80 heterodimer (Ku70/80) with each DNA terminus. The Ku70/80 molecule has a ring-shaped structure, made up by the amino-terminal and central domains of both the Ku70 and the Ku80 polypeptides, which exactly fits a DNA helix in its center (33).The DNA-Ku complex functions as a scaffold to attract the other known NHEJ factors to the DSB. One of the enzymes that are recruited to the DNA-Ku scaffold is the DNA-dependent protein kinase catalytic subunit (DNA-PK_CS), a 469-kDa serine/threonine kinase. The Ku-DNA-PK_CS complex is commonly referred to as DNA-PK. It has been well established that the DNA-PK_CS kinase activity is essential for efficient DSB repair, although the mechanism via which DNA-PK_CS exerts its function is a matter of current debate (19, 35, 36). Several autophosphorylation sites have been mapped in the DNA-PK_CS protein. The most important clusters are found between residues 2609 and 2647 (ABCDE cluster) and between residues 2023 and 2056 (PQR cluster). Phosphorylation of the ABCDE cluster was found to specifically stimulate processing and joining of DNA ends, while PQR phosphorylation reduced the level of DNA end processing (35). These findings prompted a model in which DNA-PK_CS functions as a gatekeeper molecule that regulates access to the DNA termini by changing its phosphorylation status (35). Therefore, DNA-PK_CS autophosphorylation may regulate the next steps in the NHEJ process.These next steps include the processing and joining of DNA ends. Processing enzymes prepare nonligatable DNA termini, primarily blocked ends and incompatible single-strand overhangs, for subsequent ligation by the XRCC4/ligase IV complex. The chemistry of the ligation reaction necessitates the addition of 5′ phosphate groups or the removal of 3′ phosphate groups by polynucleotide kinase (3). Processing of single-strand overhangs is performed by either filling or resection and therefore requires a polymerase or a nuclease, respectively (16, 36). Several enzymes with single-strand filling capability, including polymerase λ, polymerase μ, and terminal deoxynucleotidyltransferase, have been suggested to function as processing enzymes during NHEJ (16). In contrast, only one nuclease has been conclusively shown to play a role in NHEJ: the endonuclease Artemis.Artemis was first described as an essential contributor to V(D)J recombination, catalyzing the opening of hairpin structures at coding ends (17, 21, 24). However, because Artemis deficiency not only causes impairment of V(D)J recombination but also increased sensitivity to DSB-inducing ionizing radiation, it was soon recognized that Artemis may act as a processing enzyme for other types of DNA ends during NHEJ as well. The Artemis protein forms a complex with DNA-PK and carries the endonuclease activity that is necessary for the hairpin opening or overhang processing (14, 17). It is likely that the Artemis protein is recruited to the repair complex by interaction with the DNA-Ku-DNA-PK_CS complex.Because the NHEJ core factors DNA-PK_CS, XRCC4/ligase IV, and Artemis are attracted to a DSB by the DNA-Ku scaffold, we set out to examine the influence of specific deletions of the Ku80 protein on the recruitment and activation of these core factors. It has been previously reported that the Ku80 carboxy terminus is important for effective NHEJ, evidenced by the fact that deletion of the Ku80 carboxy terminus results in markedly increased sensitivity to ionizing radiation and decreased retention of DNA-PK_CS at DNA ends (11). Several authors have suggested that the Ku80 carboxy terminus mediates activation of the DNA-PK_CS kinase and may therefore be directly responsible for regulation of the NHEJ process (11, 12, 25).In contrast to that hypothesis, we here show that the Ku80 carboxy terminus is not an essential prerequisite for recruitment or activation of the DNA-PK_CS kinase in vivo. Surprisingly, however, deletion of the Ku80 carboxy terminus resulted in less efficient phosphorylation of specific DNA-PK_CS autophosphorylation sites and diminished Artemis endonuclease activity. These findings provide a comprehensive explanation for the increased radiation sensitivity that is associated with deletion of the Ku80 carboxy terminus.     

Synthesis of 5‐(4′‐carboxyphenyl)‐10,15,20‐tris‐(4 pyridyl)‐porphyrin and its peptidyl phosphonate derivatives

The synthesis and characterization of three new 4‐pyridyl porphyrin‐peptidyl‐phosphonate compounds, containing a diphenyl 3‐pyridylmethyl‐phosphonate moiety, is described in this article. Nitrogen atoms in the pyridine rings of the obtained compounds were alkylated using methyl iodide, to give additional three, water soluble derivatives of these peptidyl‐porphyrin conjugates. All the synthesized compounds could serve as potential photosensitizers for the photodynamic therapy (PDT) method of tumor therapy and displayed activity as inhibitors of aminopeptidase N. Copyright © 2009 European Peptide Society and John Wiley & Sons, Ltd.