Phytotoxicity, not nitrogen immobilization, explains plant litter inhibitory effects: evidence from solid-state 13C NMR spectroscopy

Litter decomposition provides nutrients that sustain ecosystem productivity, but litter may also hamper root proliferation. The objectives of this work were to assess the inhibitory effect of litter decomposition on seedling growth and root proliferation; to study the role of nutrient immobilization and phytotoxicity; and to characterize decomposing litter by (13)C NMR spectroscopy. A litter-bag experiment was carried out for 180 d with 16 litter types. Litter inhibitory effects were assessed by two bioassays: seed germination and root proliferation bioassays. Activated carbon (C) and nutrient solutions were used to evaluate the effects of phytotoxic factors and nutrient immobilization. An inhibitory effect was found for all species in the early phase of decomposition, followed by a decrease over time. The addition of activated C to litter removed this inhibition. No evidence of nutrient immobilization was found in the analysis of nitrogen dynamics. NMR revealed consistent chemical changes during decomposition, with a decrease in O-alkyl and an increase in alkyl and methoxyl C. Significant correlations were found among inhibitory effects, the litter decay rate and indices derived from NMR. The results show that it is possible to predict litter inhibitory effects across a range of litter types on the basis of their chemical composition.     

Expression and Developmental Regulation of the Cystine/Glutamate Exchanger (x<Stack><Subscript>c</Subscript><Superscript>−</Superscript></Stack>) in the Rat

The cystine/glutamate exchanger (antiporter x_c⁻) is a membrane transporter involved in the uptake of cystine, the rate-limiting amino acid in the synthesis of glutathione. Recent studies suggest that the antiporter plays a role in the slow oxidative excitotoxity and in the pathological effects of β-N-oxalylamino-l-alanine, the molecule responsible for neurolathyrism, a neurotoxic upper motor neuron disease. The mouse cystine/glutamate exchanger has been cloned and showed to be composed of two distinct proteins, one of which being a novel protein, named xCT, of 502 amino acids and 12 putative trans-membrane domains. We have generated and purified a polyclonal antibody to mouse xCT and studied its expression in rat brain and in different cultured cells (astrocytes, fibroblasts and neurons) using Western blot and immunocytochemical techniques. Expression of xCT was also studied in rat brain and muscle at different developmental stages. Parallel experiments were carried out with antibodies to the heavy chain of 4F2 surface antigen, the non-specific subunit of the antiporter x_c⁻. xCT antibody detected in all cell and tissue extracts a specific band of about 40 kDa. Subcellular fractionation demonstrated that xCT is concentrated mainly in the microsomal-mitochondrial fraction, in accord with its structure as transmembrane protein. Immunocytochemical analysis showed a strong staining in all cells examined, included neurons. Furthermore, both xCT and the heavy chain of 4F2 surface antigen increased in the brain during development, reaching the highest expression in adulthood. The study of the expression and developmental profile of xCT represents a first step towards a better characterization of its biochemical properties and function, which in turn may help to understand the relative contribution of the x_c⁻ antiporter in the pathogenesis of certain neurodegenerative diseases.     

New SNP of the porcine Perilipin 2 (<Emphasis Type="Italic">PLIN2</Emphasis>) gene,association with carcass traits and expression analysis in skeletal muscle

PLIN2 (perilipin 2) is a cytosolic protein that promotes the formation and stabilization of the intracellular lipid droplets, organelles involved in the storage of lipid depots. Porcine PLIN2 gene represents a biological and positional candidate for fat deposition, a polygenic trait that affects carcass and meat quality. The aim of the present study was to screen PLIN2 gene for polymorphisms, to evaluate the association with carcass quality traits, and to investigate the gene expression in skeletal muscle. Six new single nucleotide polymorphisms (SNP) were detected by sequencing 32 samples from five pig breeds (Italian Large White, Italian Duroc, Italian Landrace, Belgian Landrace, Pietrain). Two SNP localized in introns, two in the 3′-untranslated region (UTR), and two missense SNP were found in exons. A 3′-UTR mutation (GU461317:g.98G>A), genotyped in 290 Italian Duroc pigs by High Resolution Melting, resulted significantly associated (P < 0.01) with average daily gain, feed conversion ratio, lean cuts and hams weight estimated breeding values. PLIN2 gene expression analysis in skeletal muscle of Italian Large White and Italian Duroc pigs divergent for backfat thickness and visible intermuscular fat showed a trend of higher expression level in pigs with higher intermuscular fat. These results suggest that PLIN2 can be a marker for carcass quality in pigs. Further investigation at both gene and protein level could elucidate its role on fat deposition.     

Copepods in spring annual sea ice at Terra Nova Bay (Ross Sea,Antarctica)

The aim of this study was to investigate patterns of abundance, distribution, temporal changes and species composition of the dominant ice-associated copepods in the spring annual pack ice, platelet ice and water column at Terra Nova Bay, Ross Sea, during late spring 1997. Ice cores were drilled for temporal and spatial scales. Stephos longipes and Harpacticus furcifer dominated the sea ice meiofauna in terms of numbers in the lower few centimeters of the bottom ice associated with high chlorophyll a and phaeopigment levels. Nauplii dominated the S. longipes population (91.6%) and occurred in extremely high concentrations. In contrast, copepodids were the dominant stages in H. furcifer. How H. furcifer carries out its entire life cycle and how it differs from ecologically similar species such as Drescheriella glacialis should be examined in more detail.     

Mastl is required for timely activation of APC/C in meiosis I and Cdk1 reactivation in meiosis II

In mitosis, the Greatwall kinase (called microtubule-associated serine/threonine kinase like [Mastl] in mammals) is essential for prometaphase entry or progression by suppressing protein phosphatase 2A (PP2A) activity. PP2A suppression in turn leads to high levels of Cdk1 substrate phosphorylation. We have used a mouse model with an oocyte-specific deletion of Mastl to show that Mastl-null oocytes resume meiosis I and reach metaphase I normally but that the onset and completion of anaphase I are delayed. Moreover, after the completion of meiosis I, Mastl-null oocytes failed to enter meiosis II (MII) because they reassembled a nuclear structure containing decondensed chromatin. Our results show that Mastl is required for the timely activation of anaphase-promoting complex/cyclosome to allow meiosis I exit and for the rapid rise of Cdk1 activity that is needed for the entry into MII in mouse oocytes.     

Role of anti-cyclic citrullinated peptide antibodies in discriminating patients with rheumatoid arthritis from patients with chronic hepatitis C infection-associated polyarticular involvement

This study was performed to assess the utility of anti-cyclic citrullinated peptide (anti-CCP) antibodies in distinguishing between patients with rheumatoid arthritis (RA) and patients with polyarticular involvement associated with chronic hepatitis C virus (HCV) infection. Serum anti-CCP antibodies and rheumatoid factor (RF) were evaluated in 30 patients with RA, 8 patients with chronic HCV infection and associated articular involvement and 31 patients with chronic HCV infection without any joint involvement. In addition, we retrospectively analysed sera collected at the time of first visit in 10 patients originally presenting with symmetric polyarthritis and HCV and subsequently developing well-established RA. Anti-CCP antibodies and RF were detected by commercial second-generation anti-CCP2 enzyme-linked immunosorbent assay and immunonephelometry respectively. Anti-CCP antibodies were detected in 23 of 30 (76.6%) patients with RA but not in patients with chronic HCV infection irrespective of the presence of articular involvement. Conversely, RF was detected in 27 of 30 (90%) patients with RA, 3 of 8 (37.5%) patients with HCV-related arthropathy and 3 of 31 (9.7%) patients with HCV infection without joint involvement. Finally, anti-CCP antibodies were retrospectively detected in 6 of 10 (60%) patients with RA and HCV. This indicates that anti-CCP antibodies can be useful in discriminating patients with RA from patients with HCV-associated arthropathy.     

Implication of tissue transglutaminase and desmoplakin in cell adhesion mechanism in human epidermis

The distribution patterns of both tissue and keratinocyte transglutaminases (TGase), as well as that of desmoplakin (DP), have been immunohistochemically investigated in human skin cultured in the absence or presence of cystamine and enalapril, two acantholytic agents. In the control samples, tissue TGase is predominantly expressed in lower layers of the epidermis and is located intercellularly. Conversely, in tissues cultured with cystamine or enalapril, a diffuse cytoplasmatic staining was observed. Similarly, DP, detected on the cell membrane in the control, shifts into the cytosol of the keratinocytes following treatment. The distribution pattern of the keratinocyte enzyme in the acantholytic epidermis was identical to that observed in the normal one. Since cystamine and enalapril are TGase inhibitors and DP was shown to act as a TGase substrate in vitro, we suggest that DP and tissue enzyme may participate in cell adhesion at the intraepidermal level.     

Glyoxalase 1 sustains the metastatic phenotype of prostate cancer cells via EMT control

Metastasis is the primary cause of death in prostate cancer (PCa) patients. Effective therapeutic intervention in metastatic PCa is undermined by our poor understanding of its molecular aetiology. Defining the mechanisms underlying PCa metastasis may lead to insights into how to decrease morbidity and mortality in this disease. Glyoxalase 1 (Glo1) is the detoxification enzyme of methylglyoxal (MG), a potent precursor of advanced glycation end products (AGEs). Hydroimidazolone (MG‐H1) and argpyrimidine (AP) are AGEs originating from MG‐mediated post‐translational modification of proteins at arginine residues. AP is involved in the control of epithelial to mesenchymal transition (EMT), a crucial determinant of cancer metastasis and invasion, whose regulation mechanisms in malignant cells are still emerging. Here, we uncover a novel mechanism linking Glo1 to the maintenance of the metastatic phenotype of PCa cells by controlling EMT by engaging the tumour suppressor miR‐101, MG‐H1‐AP and TGF‐β1/Smad signalling. Moreover, circulating levels of Glo1, miR‐101, MG‐H1‐AP and TGF‐β1 in patients with metastatic compared with non‐metastatic PCa support our in vitro results, demonstrating their clinical relevance. We suggest that Glo1, together with miR‐101, might be potential therapeutic targets for metastatic PCa, possibly by metformin administration.