Données sur les transferts du 137Cs et du 60Co dans un écosystème fluvial : le Rhône

L'étude radioécologique du Rhône permet d'évaluer qualitativement et quantitativement les radionucléides présents dans le fleuve. Les études menées in situ posent des questions concernant les modalités de transfert des radionucléides. Dans ce travail des expériences sont mises au point, afin d'analyser les mécanismes de bioconcentration dans les écosystèmes aquatiques. Pour le césium-137 les échanges entre l'eau, le sédiment et divers organismes aquatiques ont permis d'élaborer un modèle mathématique que l'on peut confronter aux valeurs mesurées sur le terrain. En ce qui concerne le Cobalt-60 les auteurs décrivent des expériences permettant l'évaluation de la contribution relative de l'eau et de la nourriture dans l'accumulation du radionucléide par un poisson.The radioecology of the Rhone Basin has been studied for the last 15 years. This has been an opportunity to make a quantitative and qualitative evaluation of radionuclides as a function of their different sources. Special attention is given to 137Cs (present both in fallout and liquid wastes) and 60Co, which characterize the liquid wastes of pressurised water reactors. In order to assess the transfer and bioconcentration of these two radionuclides in freshwater ecosystems, several experimental studies were undertaken.The 137Cs transfer studies were carried out with a 5-component experimental ecosystem and the data were included in a mathematical model. For 60Co, the experimental study concerns the relative contribution of water and food in the accumulation of the radionuclide by Cyprinus carpio.Water, sediment, plants and fishes were taken from 60 sampling stations set up along the river (figure 1). Water was filtrated, then percolated on resin columns. Sediment, plants and fishes were dried and burnt to ashes in an oven at 500° C. Radioactivity was measured by gamma spectrometry and radiochemistry.137Cs experimental transfers were studied between water, sediment, midge larvae, daphnid and carp. These components were taken in pairs in order to estimate the radionuclide transfer from one to the other. Thus ten experiments were carried out (figure 2). In order to study the relative importance of food and water as 60Co sources for the carp, an experiment was carried out simultaneously on three homogeneous groups of ten juvenile fishes. The individuals of the first group were maintained in separate aquaria and offered 45 daily rations of labelled food over a 63-day period. Bach carp of the other two groups was placed in a compartment of a large tank with contaminated water. One group was fed with radioactive food, the other with non-radioactive food (table 1).Natural radioactivity remained steady all along the river. It ranged around 1 Bq.l-1 in water, 2250 Bq.kg-1 DW in sediment, 1700 Bq.kg-1 DW in aquatic plants, 110 Bq.kg-1 WW in fish. The fallout impact was characterized by 137Cs presence. PWR liquid wastes contained mainly, 58Co, 60Co, 134 Cs, 137Cs. The Chernobyl fallout gave an increase of Cs and the presence of 103Ru and 106RU+Rh specially during May and June 1986 which later decreased (tables 2, 3 and 4).137Cs transfer between water and sediment was very fast and important. Less than 2 % of the radionuclide was released from sediment into a non-radioactive water. During the transfer from water to chironomids the larvae radioactivity increased steadily (figure 3). Conversely, the transfer from the sediment to larvae did not seem to depend on the contact time. The transfer from water to carp was regular without any steady state during the 63 days of the experiment (figure 3). Then the fish concentration factor was less than 5. For 42 days, the transfer factor from sediment to carp was 3.6.10-3. The retention factor from food to carp was 0.03 when fishes were fed with daphnids and 0.13 with chironomids. An experiment showed that the various ways of 137Cs transfer could have an added impact. Thus the carp radioactivity was the sum of the separate transfers. Water was responsible for 4 % of the fish 137 Cs concentration, sediment for 45 % and chironomids for 51 %.It is possible to include the different kinetic equations in a mathematical model. If the radioactivity of one of the components is known, the nuclide concentration can be computed in others, as a relation of the contact time, the quantity and quality of ingested food, etc... This model gives a concentration factor for juvenile carp of 1000 in 180 days and 500 for 3-year old fish. Considering the field conditions (e.g. seasonal nutritive cycles) the computed concentration factor in fish was between 200 and 350. For a 1 mBq.l-1 137Cs concentration in water, the model gave a concentration of 0.2 to 0.35 Bq.kg-1 WW in carp, which was the 137Cs radioactivity level measured in the Rhone fish before the Chernobyl accident.During the 60Co accumulation phase, the mean weight of the fish in the three groups increased exponentially and the resultant relative weight gain was 52-59 % after 63 days (table 5).The 60Co accumulation kinetics showed that the steady state should be reached after 165 days for fish exposed to 60Co in food, 92 days for fish exposed to radiocobalt in water and 120 days for fish exposed to 60Co in both sources (figure 4). According to the 60Co concentration in the fish in the three treated groups, the accumulation from water accounted for 75 % of the total radioactivity and the accumulation of the radionuclide from both water and food was in addition.Depuration of 60Co from carp was a relatively intensive process reflecting a high Co turnover. Biological half-lives for loss from the long-lived compartment ranged from 35d in fish previously contaminated by food, to 87d in fish previously contaminated by food, to 87d in fish previously contaminated by water (figure 5).137Cs and 60Co are the most concentrated radionuclides in liquid wastes of the pressurised water reactors, and they are often measured in the aquatic ecosystem components. Though it accounts for the highest fraction of total radioactivity in the liquid wastes, 60Co cobalt is not the most concentrated radionuclide in fish. Experimental studies show that it is primarily transferred from the water so it is logical that its concentration in fish remains at a low level. Conversely the 137Cs has a low concentration in water but as it is transferred simultaneously from water, sediment and food, its concentration in fish is still important. Moreover its 30 years half-life means that the cesium contamination of fish is a long and important process, all the more so as the source terms can add their own effects during time and space

Heightened immune response to autocitrullinated porphyromonas gingivalis peptidylarginine deiminase: a potential mechanism for breaching immunologic tolerance in rheumatoid arthritis

Background: Rheumatoid arthritis (RA) is characterised by autoimmunity to citrullinated proteins, and there is increasing epidemiologic evidence linking Porphyromonas gingivalis to RA. P gingivalis is apparently unique among periodontal pathogens in possessing a citrullinating enzyme, peptidylarginine deiminase (PPAD) with the potential to generate antigens driving the autoimmune response. Objectives: To examine the immune response to PPAD in patients with RA, individuals with periodontitis (PD) and controls (without arthritis), confirm PPAD autocitrullination and identify the modified arginine residues. Methods: PPAD and an inactivated mutant (C351A) were cloned and expressed and autocitrullination of both examined by immunoblotting and mass spectrometry. ELISAs using PPAD, C351A and another P gingivalis protein arginine gingipain (RgpB) were developed and antibody reactivities examined in patients with RA (n=80), individuals with PD (n=44) and controls (n=82). Results: Recombinant PPAD was a potent citrullinating enzyme. Antibodies to PPAD, but not to Rgp, were elevated in the RA sera (median 122 U/ml) compared with controls (median 70 U/ml; p<0.05) and PD (median 60 U/ml; p<0.01). Specificity of the anti-peptidyl citrullinated PPAD response was confirmed by the reaction of RA sera with multiple epitopes tested with synthetic citrullinated peptides spanning the PPAD molecule. The elevated antibody response to PPAD was abolished in RA sera if the C351A mutant was used on ELISA. Conclusions: The peptidyl citrulline-specific immune response to PPAD supports the hypothesis that, as a bacterial protein, it might break tolerance in RA, and could be a target for therapy

Novel Role for the Golgi Membrane Protein TMEM165 in Control of Migration and Invasion for Breast Carcinoma

The TMEM165 gene encodes for a multiple pass membrane protein localized in the Golgi that has been linked to congenital disorders of glycosylation. The TMEM165 protein is a putative ion transporter that regulates H+/Ca++/Mn++ homeostasis and pH in the Golgi. Previously, we identified TMEM165 as a potential biomarker for breast carcinoma in a glycoproteomic study using late stage invasive ductal carcinoma tissues with patient-matched adjacent normal tissues. The TMEM165 protein was not detected in non-malignant matched breast tissues and was detected in invasive ductal breast carcinoma tissues by mass spectrometry. Our hypothesis is that the TMEM165 protein confers a growth advantage to breast cancer. In this preliminary study we have investigated the expression of TMEM165 in earlier stage invasive ductal carcinoma and ductal carcinoma in situ cases. We created a CRISPR/Cas9 knockout of TMEM165 in the human invasive breast cancer cell line MDAMB231. Our results indicate that removal of TMEM165 in these cells results in a significant reduction of cell migration, tumor growth, and tumor vascularization in vivo. Furthermore, we find that TMEM165 expression alters the glycosylation of breast cancer cells and these changes promote the invasion and growth of breast cancer by altering the expression levels of key glycoproteins involved in regulation of the epithelial to mesenchymal transition such as E-cadherin. These studies illustrate new potential functions for this Golgi membrane protein in the control of breast cancer growth and invasion

A human embryonic kidney 293T cell line mutated at the Golgi -mannosidase II locus

Disruption of Golgi -mannosidase II activity can result in type II congenital dyserythropoietic anemia and can induce lupus-like autoimmunity in mice. Here, we isolate a mutant human embryonic kidney (HEK) 293T cell line, called Lec36, that displays sensitivity to ricin that lies between the parental HEK 293T cells, whose secreted and membrane-expressed proteins are dominated by complex-type glycosylation, and 293S Lec1 cells, which only produce oligomannose-type N-linked glycans. The stem cell marker, 19A, was transiently expressed in the HEK 293T Lec36 cells, and in parental HEK 293T cells with and without the potent Golgi -mannosidase II inhibitor, swainsonine. Negative-ion nano-electrospray ionization mass spectra of the 19A N-linked glycans from HEK 293T Lec36 and swainsonine-treated HEK 293T cells were qualitatively indistinguishable and, as shown by collision-induced dissociation spectra, dominated by hybrid-type glycosylation. Nucleotide sequencing revealed mutations in each allele of MAN2A1, the gene encoding Golgi -mannosidase II: a point mutation in one allele mapping to the active site and an in-frame deletion of twelve-nucleotides in the other. Expression of wild-type but not the mutant MAN2A1 alleles in Lec36 cells restored processing of the 19A reporter glycoprotein to complex-type glycosylation. The Lec36 cell line will be useful for expressing therapeutic glycoproteins with hybrid-type glycans and provides a sensitive host for detecting mutations in human MAN2A1 causing type II congenital dyserythropoietic anemia

Unlocking our understanding of intermittent rivers and ephemeral streams with genomic tools

Intermittent rivers and ephemeral streams (IRES) – waterways in which flow ceases periodically or that dry completely – are found worldwide, and their frequency and extent are expected to increase in the future in response to global climate change and growing anthropogenic demand for fresh water. Repeated wet–dry cycles generate highly dynamic settings within river networks composed of aquatic and terrestrial habitats, which act as evolutionary triggers for aquatic and terrestrial biota. Drying also alters functions and processes within river networks, with consequences for ecosystem services. Despite the emergence of promising conceptual and methodological developments, our understanding of the occurrence and diversity of organisms in these ecosystems is limited primarily due to their coupled aquatic–terrestrial characteristics. Novel genomic tools based on high-throughput sequencing have the potential to tackle unanswered questions of pivotal importance to predict future change in IRES. Here, we outline why genomic tools are needed to assess these dynamic ecosystems from the population to the metacommunity scale, and their potential role in bridging ecological–evolutionary dynamics

Mutations in TRAPPC11 are associated with a congenital disorder of glycosylation.

Congenital disorders of glycosylation (CDG) are a heterogeneous and rapidly growing group of diseases caused by abnormal glycosylation of proteins and/or lipids. Mutations in genes involved in the homeostasis of the endoplasmic reticulum (ER), the Golgi apparatus (GA), and the vesicular trafficking from the ER to the ER-Golgi intermediate compartment (ERGIC) have been found to be associated with CDG. Here, we report a patient with defects in both N- and O-glycosylation combined with a delayed vesicular transport in the GA due to mutations in TRAPPC11, a subunit of the TRAPPIII complex. TRAPPIII is implicated in the anterograde transport from the ER to the ERGIC as well as in the vesicle export from the GA. This report expands the spectrum of genetic alterations associated with CDG, providing new insights for the diagnosis and the understanding of the physiopathological mechanisms underlying glycosylation disorders

Hypoxic oligodendrocyte precursor cell-derived VEGFA is associated with blood–brain barrier impairment

Abstract Cerebral small vessel disease is characterised by decreased cerebral blood flow and blood–brain barrier impairments which play a key role in the development of white matter lesions. We hypothesised that cerebral hypoperfusion causes local hypoxia, affecting oligodendrocyte precursor cell—endothelial cell signalling leading to blood–brain barrier dysfunction as an early mechanism for the development of white matter lesions. Bilateral carotid artery stenosis was used as a mouse model for cerebral hypoperfusion. Pimonidazole, a hypoxic cell marker, was injected prior to humane sacrifice at day 7. Myelin content, vascular density, blood–brain barrier leakages, and hypoxic cell density were quantified. Primary mouse oligodendrocyte precursor cells were exposed to hypoxia and RNA sequencing was performed. Vegfa gene expression and protein secretion was examined in an oligodendrocyte precursor cell line exposed to hypoxia. Additionally, human blood plasma VEGFA levels were measured and correlated to blood–brain barrier permeability in normal-appearing white matter and white matter lesions of cerebral small vessel disease patients and controls. Cerebral blood flow was reduced in the stenosis mice, with an increase in hypoxic cell number and blood–brain barrier leakages in the cortical areas but no changes in myelin content or vascular density. Vegfa upregulation was identified in hypoxic oligodendrocyte precursor cells, which was mediated via Hif1α and Epas1. In humans, VEGFA plasma levels were increased in patients versus controls. VEGFA plasma levels were associated with increased blood–brain barrier permeability in normal appearing white matter of patients. Cerebral hypoperfusion mediates hypoxia induced VEGFA expression in oligodendrocyte precursor cells through Hif1α/Epas1 signalling. VEGFA could in turn increase BBB permeability. In humans, increased VEGFA plasma levels in cerebral small vessel disease patients were associated with increased blood–brain barrier permeability in the normal appearing white matter. Our results support a role of VEGFA expression in cerebral hypoperfusion as seen in cerebral small vessel disease

Domain Organization of Long Signal Peptides of Single-Pass Integral Membrane Proteins Reveals Multiple Functional Capacity

Targeting signals direct proteins to their extra - or intracellular destination such as the plasma membrane or cellular organelles. Here we investigated the structure and function of exceptionally long signal peptides encompassing at least 40 amino acid residues. We discovered a two-domain organization (“NtraC model”) in many long signals from vertebrate precursor proteins. Accordingly, long signal peptides may contain an N-terminal domain (N-domain) and a C-terminal domain (C-domain) with different signal or targeting capabilities, separable by a presumably turn-rich transition area (tra). Individual domain functions were probed by cellular targeting experiments with fusion proteins containing parts of the long signal peptide of human membrane protein shrew-1 and secreted alkaline phosphatase as a reporter protein. As predicted, the N-domain of the fusion protein alone was shown to act as a mitochondrial targeting signal, whereas the C-domain alone functions as an export signal. Selective disruption of the transition area in the signal peptide impairs the export efficiency of the reporter protein. Altogether, the results of cellular targeting studies provide a proof-of-principle for our NtraC model and highlight the particular functional importance of the predicted transition area, which critically affects the rate of protein export. In conclusion, the NtraC approach enables the systematic detection and prediction of cryptic targeting signals present in one coherent sequence, and provides a structurally motivated basis for decoding the functional complexity of long protein targeting signals