Analyse quantitative des remaniements intestinaux et évolution de la synthese de l'ADN

Résumé Les remainements intestinaux affectant la paroi intestinale sont quantifiés chez les larves d'un Amphibien Anoure,Alytes obstetricans, traitées par la thyroxine. La fraction correspondant à chaque zone composant la paroi est déterminée sur coupe. La répartition et la fréquence des noyaux marqués sont recherchées chez des larves ayant reçu de la thymidine tritiée.L'indice de marquage nucléaire de l'épithélium primaire tend vers zéro durant les 3 premiers jours du traitement. Ces résultats reflètent un ralentissement de la croissance du tissue, précédant sa dégénérescence et son élimination complète au 14ème jour d'immersion dans la solution hormonale.Dès de 3ème jour de traitement, un épithélium secondaire se développe à partir de cellules-souches basales. Son indice de marquqge croît, culmine au 9ème jour avec une valeur proche de 50%, puis s'abaisse. La prolifération cellulaire est plus modérée dans la zone extra-épithéliale, qui s'épaissit toutefois au cours de cette métamorphose provoquée.

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Quantitative analysis of intestinal changes and the evolution of DNA synthesis in thyroxine-treated larvae ofAlytes obstetricans. (Amphibia, Anura)

Summary Changes in the intestinal wall ofAlytes obstetricans (Amphibia, Anura) were quantified during thyroxine treatment. The relative proportion of each intestinal wall component was determined in tissue sections. Autoradiographic studies on intestine with³H-thymidine revealed the distribution and frequency of labeled nuclei.The labeling index in the primary epithelium falls to zero by 3 days. Thyroxine treatment induces a decrease in the growth rate of this tissue, just before its degeneration and complete elimination by 14 days.Three days after T₄-treatment, a secondary epithelium develops from basal stem cells. Its labeling index rises to a maximum of about 50% by 9 days, and thereafter declines. Cell proliferation is less marked in the extraepithelial zone, which nevertheless thickens during this thyroxine-induced metamorphosis.

     

Lyme borreliosis in Lithuania: its prevalence, clinical picture and treatment efficacy

In 1988 Lyme borreliosis (LA) was diagnosed in 376 patients in Lithuania, including 101 patients who had the first stage of circular migrating erythema. Of this latter group, in 40 patients (39.6%) specific antibodies to the causative agent of LB were detected. All 101 patients were intensively treated with antibiotics for 10-14 days. The effectiveness of treatment was evaluated 4-5 months later. Information was collected only on 90 patients, including 82 patients who had undergone treatment. Complete convalescence was achieved in 52 cases (63.4%). 20 more persons considered themselves to be practically healthy. But in 10 patients (12.2%) the development of the disease continued, among them in 6 patients who stopped the prescribed course of treatment on their own accord. Out of 8 patients who had not yet even started to undergo treatment, 5 patients had signs of the manifest progress of the disease. Besides, information on the incubation period of the disease, its seasonal character, the characteristic features of erythema and concomitant symptoms in presented.     

Age- and sex-specific mortality patterns in an emerging wildlife epidemic: the phocine distemper in European harbour seals

Analyses of the dynamics of diseases in wild populations typically assume all individuals to be identical. However, profound effects on the long-term impact on the host population can be expected if the disease has age and sex dependent dynamics. The Phocine Distemper Virus (PDV) caused two mass mortalities in European harbour seals in 1988 and in 2002. We show the mortality patterns were highly age specific on both occasions, where young of the year and adult (>4 yrs) animals suffered extremely high mortality, and sub-adult seals (1-3 yrs) of both sexes experienced low mortality. Consequently, genetic differences cannot have played a main role explaining why some seals survived and some did not in the study region, since parents had higher mortality levels than their progeny. Furthermore, there was a conspicuous absence of animals older than 14 years among the victims in 2002, which strongly indicates that the survivors from the previous disease outbreak in 1988 had acquired and maintained immunity to PDV. These specific mortality patterns imply that contact rates and susceptibility to the disease are strongly age and sex dependent variables, underlining the need for structured epidemic models for wildlife diseases. Detailed data can thus provide crucial information about a number of vital parameters such as functional herd immunity. One of many future challenges in understanding the epidemiology of the PDV and other wildlife diseases is to reveal how immune system responses differ among animals in different stages during their life cycle. The influence of such underlying mechanisms may also explain the limited evidence for abrupt disease thresholds in wild populations.     

Hydrogen-induced structural changes at the nickel site of the regulatory [NiFe] hydrogenase from Ralstonia eutropha detected by X-ray absorption spectroscopy

For the first time, the nickel site of the hydrogen sensor of Ralstonia eutropha, the regulatory [NiFe] hydrogenase (RH), was investigated by X-ray absorption spectroscopy (XAS) at the nickel K-edge. The oxidation state and the atomic structure of the Ni site were investigated in the RH in the absence (air-oxidized, RH(ox)) and presence of hydrogen (RH(+H2)). Incubation with hydrogen is found to cause remarkable changes in the spectroscopic properties. The Ni-C EPR signal, indicative of Ni(III), is detectable only in the RH(+H2) state. XANES and EXAFS spectra indicate a coordination of the Ni in the RH(ox) and RH(+H2) that pronouncedly differs from the one in standard [NiFe] hydrogenases. Also, the changes induced by exposure to H(2) are unique. A drastic modification in the XANES spectra and an upshift of the K-edge energy from 8339.8 (RH(ox)) to 8341.1 eV (RH(+H2)) is observed. The EXAFS spectra indicate a change in the Ni coordination in the RH upon exposure to H(2). One likely interpretation of the data is the detachment of one sulfur ligand in RH(+H2) and the binding of additional (O,N) or H ligands. The following Ni oxidation states and coordinations are proposed: five-coordinated Ni(II)(O,N)(2)S(3) for RH(ox) and six-coordinated Ni((III))(O,N)(3)X(1)S(2) [X being either an (O,N) or H ligand] for RH(+H2). Implications of the structural features of the Ni site of the RH in relation to its function, hydrogen sensing, are discussed.     

Expression of peroxisome proliferator-activated receptors alpha and gamma in differentiating human colon carcinoma Caco-2 cells

The expression of peroxisome proliferator-activated receptors alpha (PPARalpha) and gamma (PPARgamma) was studied in the human adenocarcinoma Caco-2 cells induced to differentiate by long term culture (15 days). The differentiation of Caco-2 cells was attested by increases in the activities of sucrase-isomaltase and alkaline phosphatase (two brush border enzymes), fatty acyl-CoA oxidase (AOX) and catalase (two peroxisomal enzymes), by an elevation in the protein levels of villin (a brush border molecular marker), AOX, peroxisomal bifunctional enzyme (PBE), catalase and peroxisomal membrane protein of 70 kDa (PMP70). and by the appearance of peroxisomes. The expression of PPARalpha and PPARgamma was investigated by Western blotting, immunocytochemistry, Northern blotting and S1 nuclease protection assay during the differentiation of Caco-2 cells. The protein levels of PPARalpha, PPARgamma, and PPARgamma2 increased gradually during the time-course of Caco-2 cell differentiation. Immunocytochemistry revealed that PPARalpha and gamma were localized in cell nuclei. The PPARgamma1 protein was encoded by PPARgamma3 mRNA because no signal was obtained for PPARgamma1 mRNA using a specific probe in S1 nuclease protection assay. The amount of PPARgamma3 mRNA increased concomitantly to the resulting PPARgamma1 protein. On the other hand, the mRNA of PPARalpha and PPARgamma2 were not significantly changed, suggesting that the increase in their respective protein was due to an elevation of the translational rate. The role played by the PPAR subtypes in Caco-2 cell differentiation is discussed.     

Water and bromide in the active center of vanadate-dependent haloperoxidases

Two aqua-oxovanadium complexes, viz. [A-VO(H2O)(sal-L-Leu)] (1) and [VO(H2O)2(5-Br-sal-Gly)] x H2O(2 x H2O), containing the water ligands in cis- and trans-positions to the oxo group at V-OH2 distances ranging from 2.008 to 2.228 A, have been structurally characterized in order to model the apical electron density feature found in the structures of fungal and algal vanadate-dependent peroxidases. Br K-edge XAS of bromide-treated bromoperoxidase from Ascophyllum nodosum and model compounds (including 2 x H2O) has been used to show that the substrate bromide does not bind to active site vanadium but to a light atom, possibly carbon, in its vicinity.     

Impacts on biodiversity at Baltic Sea beaches

Sandy and shingle beaches were investigated in 2009 and 2010 along the coast of the Baltic Sea in northern Germany with the purpose of assessing biodiversity gradients from shingle to sandy beaches, from beach to primary dunes, and the impacts of tourism on biodiversity. On nine beach sites, ranging between 100% shingle and 99% sand without shingle, Carabidae, Staphylinidae, and Araneae were studied. Two of the six sandy beaches were open and four were closed to tourists. Additionally, trampling effects from tourists, species richness of plants, and plant cover were investigated on sixteen beaches. According to results, primary dunes showed higher species richness in carabids and spiders, but not in staphylinds. Shingle beaches exhibited lower species richness in Staphylinidae and Araneae, but not in Carabidae. As estimated by the Jackknife II method, shingle beaches were the lowest in total species richness. Trampling intensity ranged from 0 footprints m⁻² day⁻¹ on closed beaches, up to a maximum of 30 footprints m⁻² day⁻¹. On “intensively” used beaches (12 footprints m⁻² day⁻¹, on average), reduction of plant cover was more pronounced than on “extensively” used beaches (7 footprints m⁻² day⁻¹, on average). Both plant cover and plant species richness were lower on intensively and extensively used beaches than on closed beaches. In arthropods, only staphylind and spider species richness was significantly lower on open beaches than on closed beaches, but no differences were found in carabids. Referring to our results, trampling effects from tourists have high impact on species richness of sandy beaches, on both intensively and extensively used sites.