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1.
PrPC is associated with a variety of functions, and its ability to interact with a multitude of partners, including itself, may largely explain PrP multifunctionality and the lack of consensus on the genuine physiological function of the protein in vivo. In contrast, there is a consensus in the literature that alterations in PrPC trafficking and intracellular retention result in neuronal degeneration. In addition, a proteolytic modification in the late secretory pathway termed the α-cleavage induces the secretion of PrPN1, a PrPC-derived metabolite with fascinating neuroprotective activity against toxic oligomeric Aβ molecules implicated in Alzheimer disease. Thus, studies focusing on understanding the regulation of PrPC trafficking to the cell surface and the modulation of α-cleavage are essential. The objective of this commentary is to highlight recent evidences that PrPC homodimerization stimulates trafficking of the protein to the cell surface and results in high levels of PrPN1 secretion. We also discuss a hypothetical model for these results and comment on future challenges and opportunities. 相似文献
2.
Valérie Maxime Jean-Pierre Pennec Claude Peyraud 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1991,161(6):557-568
Summary The effects of increased ambient salinity (35 mg · ml-1) were studied at 1, 6, and 24 h after direct transfer of rainbow trout from freshwater to seawater. Two series of experiments were carried out successively. The first series was designed to simultaneously study all the respiratory (except Hb affinity for O2), circulatory, and acid-base variables in each fish. In this series, fish were fitted with catheters chronically inserted into the cardiac bulbus, the dorsal aorta, and the opercular and buccal cavities. In the second series, designed to study haemoglobin O2 affinity, fish were fitted with only a dorsal aorta catheter. The ventilatory flow (
) was markedly increased just after transfer (by 55% at 1 h), then more moderately (by 20% at 6 h and 32% at 24 h). The initial hyperventilation peak was associated with frequent couphing motions. These ventilatory changes resulted essentially from increase in ventilatory amplitude. Initially, standard oxygen consumption (MM}O2) decreased slightly, the moderately increased (by 12% at 24 h), so that the oxygen convection requirement (
) increased substantially. In spite of an increased ventilation, the partial pressure of oxygen in arterial blood (P
aO2) decreased slightly at 1 h, prior to returning to control levels, while partial pressure of carbon dioxide in arterial blood (P
aCO2) was not significantly decreased. Gill oxygen transfer factor decreased substantially at 1 h (by 35%) then more moderately (by 7% at 1 h and 12% at 24 h). These results suggest a decrease in gas diffusing capacity of the gills. As P
aCO2 remained approximatively unchanged, the gradual decrease in arterial pH (pHa) from 7.94 to 7.67 at 24 h must therefore be regarded as a metabolic acidosis. The strong ion difference decreased markedly because the concentration of plasma chloride increased more than that of sodium. Arterial O2 content (C
aO2) gradually decreased (by 38% at 24 h) simultaneously with the decrease in pHa, while the ratio P
aO2/C
aO2 increased. In parallel, seawater exposure induced a marked decrease in affinity of haemoglobin for O2, so that at 24 h, P50 was increased by 26% above the value obtained in freshwater-adapted trout. The increase in
could be ascribed initially (at 1 h) to the decrease of P
aO2 and later to a stimulation of respiratory neurons resulting from the lowered medullary interstitial pH. The decrease in C
aO2 could be interpreted mainly as a consequence of a decreased affinity of haemoglobin for O2, likely to be due to the blood acidosis and a predictable increase in chloride concentration within erythrocytes. Cardiac output (
) slightly decreased at 1 h, then progressively increased by 30% at 24 h. Branchial vascular resistance increased at 1 h by 28%, then decreased by 18% of the control value at 24 h. Systemic vascular resistance decreased markedly by 40% at 24 h. As heart rate (HR) remained significantly unchanged, the cardiac stroke volume initially decreased then increased in relation to the changes in
. The increase of
, allowing compensation for the effect of decreased C
aO2 in tissue O2 supply, was interpreted as a passive consequence of the decrease in total vascular resistance occurring during seawater exposure.Abbreviations a.u.
arbitrary units
-
C
aO2
arterial oxygen content
- pH50
arterial pH at P50
-
C
vO2
venous oxygen content
- Hb
haemoglobin
- HR
heart rate
- Hct
hematocrit
- nHill
Hill coefficient
- O2
standard oxygen consumption
-
P
aCO2
arterial partial pressure of carbon dioxide
-
P
aO2
arterial partial pressure of oxygen
-
P
vO2
oxygen partial pressure in mixed venous blood
- P50
oxygen tension at half saturation of haemoglobin
-
P
VA, P
DA
blood pressure in ventral and dorsal aorta
- pHa
arterial pH
-
PIO2, PEO2
oxygen partial pressure of inspired and expired water
-
PO2
oxygen partial pressure
-
cardiac output
- SEM
standard error of mean
- S.I.D.
strong ion difference
- SV
cardiac stroke volume
- TO2
gill oxygen transfer factor
- U
oxygen extraction coefficient
- VA
ventilatory amplitude
- VF
ventilatory frequency
- VRG, VRS
branchial and systemic vascular resistances
-
ventilatory flow
-
ventilatory oxygen convection requirement 相似文献
3.
Juliette Gaëtan Sébastien Halary Maxime Millet Cécile Bernard Charlotte Duval Sahima Hamlaoui Amandine Hecquet Muriel Gugger Benjamin Marie Neha Mehta David Moreira Fériel Skouri-Panet Cynthia Travert Elodie Duprat Julie Leloup Karim Benzerara 《Environmental microbiology》2023,25(3):751-765
The formation of intracellular amorphous calcium carbonates (iACC) has been recently observed in a few cultured strains of Microcystis, a potentially toxic bloom-forming cyanobacterium found worldwide in freshwater ecosystems. If iACC-forming Microcystis are abundant within blooms, they may represent a significant amount of particulate Ca. Here, we investigate the significance of iACC biomineralization by Microcystis. First, the presence of iACC-forming Microcystis cells has been detected in several eutrophic lakes, indicating that this phenomenon occurs under environmental conditions. Second, some genotypic (presence/absence of ccyA, a marker gene of iACC biomineralization) and phenotypic (presence/absence of iACC) diversity have been detected within a collection of strains isolated from one single lake. This illustrates that this trait is frequent but also variable within Microcystis even at a single locality. Finally, one-third of publicly available genomes of Microcystis were shown to contain the ccyA gene, revealing a wide geographic and phylogenetic distribution within the genus. Overall, the present work shows that the formation of iACC by Microcystis is common under environmental conditions. While its biological function remains undetermined, this process should be further considered regarding the biology of Microcystis and implications on the Ca geochemical cycle in freshwater environments. 相似文献
4.
Brice Maxime Nkouayeb Nangmou Hermine Laure Maza Djomkam Georges Bellier Tabekoueng Willifred Dongmo Tékapi Tsopgni Gabin Thierry Mbahbou Bitchagno Michel Arnaud Mbock Raceline Gounoue Kamkumo Marcel Frese Bruno Ndjakou Lenta Silvère Augustin Ngouela Nobert Sewald Anatole Guy Blaise Azebaze 《化学与生物多样性》2023,20(4):e202200271
The root extract of Nauclea xanthoxylon (A.Chev.) Aubrév. displayed significant 50 % inhibition concentration (IC50s) of 0.57 and 1.26 μg/mL against chloroquine resistant and sensitive Plasmodium falciparum (Pf) Dd2 and 3D7 strains, respectively. Bio-guided fractionation led to an ethyl acetate fraction with IC50s of 2.68 and 1.85 μg/mL and subsequently, to the new quinovic acid saponin named xanthoxyloside ( 1 ) with IC50s of 0.33 and 1.30 μM, respectively against the tested strains. Further compounds obtained from ethyl acetate and hexane fractions were the known clethric acid ( 2 ), ursolic acid ( 3 ), quafrinoic acid ( 4 ), quinovic acid ( 5 ), quinovic acid 3-O-β-D-fucopyranoside ( 6 ), oleanolic acid ( 7 ), oleanolic acid 3-acetate ( 8 ), friedelin ( 9 ), β-sitosterol ( 10a ), stigmasterol ( 10b ) and stigmasterol 3-O-β-D-glucopyranoside ( 11 ). Their structures were characterised with the aid of comprehensive spectroscopic methods (1 and 2D NMR, Mass). Bio-assays were performed using nucleic acid gel stain (SYBR green I)-based fluorescence assay with chloroquine as reference. Extracts and compounds exhibited good selectivity indices (SIs) of >10. Significant antiplasmodial activities measured for the crude extract, the ethyl acetate fraction and xanthoxyloside ( 1 ) from that fraction can justify the use of the root of N. xanthoxylon in ethnomedicine to treat malaria. 相似文献
5.
6.
Sophie-Marie Aicher Felix Streicher Maxime Chazal Delphine Planas Dongsheng Luo Julian Buchrieser Monika Nemcova Veronika Seidlova Jan Zukal Jordi Serra-Cobo Dominique Pontier Bertrand Pain Gert Zimmer Olivier Schwartz Philippe Roingeard Jiri Pikula Laurent Dacheux Nolwenn Jouvenet 《Journal of virology》2022,96(14)
7.
Maxime Willems Mieke Boone Marjolein Couvreur Katrien De Mulder Jelka Van Ranst Tom Artois Gaëtan Borgonie 《Development genes and evolution》2009,219(5):273-279
A method for studying whole mount flatworm embryos based on freeze-cracking of the eggs is described. This method allows successful
immunohistological and immunocytological studies of whole mount embryos. It does not require the use of sharpened needles
or a microinjection system to puncture the eggshell. Moreover, this method is more practical and less time-consuming than
classical puncturing and much cheaper than the use of a microinjection system. The advantages of this method are illustrated
by results of several immunolocalisation experiments in the macrostomid flatworm Macrostomum lignano. The optimal procedure and crucial steps for this method are discussed.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
8.
Sandrine Faure Maxime Georges Jennifer McKey Sébastien Sagnol Pascal de Santa Barbara 《Gene expression patterns : GEP》2013,13(8):287-292
Regulation of the Bone Morphogenetic Protein (BMP) signaling pathway is essential for the normal development of vertebrate gastrointestinal (GI) tract, but also for the differentiation of the digestive mesenchymal layer into smooth muscles and submucosal layer. Different studies demonstrated that Bapx1 (for bagpipe homeobox homolog 1) negatively regulates the BMP pathway, but its precise expression pattern during the development and the differentiation of the GI tract mesenchyme actually remains to be examined. Here, we present the spatio-temporal expression profile of Bapx1 in the chick GI tract. We show that Bapx1 is first expressed in the undifferentiated mesenchyme of the gizzard and the colon. After the differentiation of the digestive mesenchyme, we found Bapx1 strongly expressed in the gizzard smooth muscle and in the submucosa layer of the colon. This expression pattern provides new insights into the roles of Bapx1 during the regionalization of the GI tract and the differentiation of the digestive mesenchyme of the colon and the stomach. 相似文献
9.
Volodymyr Trotsiuk Florian Hartig Maxime Cailleret Flurin Babst David I. Forrester Andri Baltensweiler Nina Buchmann Harald Bugmann Arthur Gessler Mana Gharun Francesco Minunno Andreas Rigling Brigitte Rohner Jonas Stillhard Esther Thürig Peter Waldner Marco Ferretti Werner Eugster Marcus Schaub 《Global Change Biology》2020,26(4):2463-2476
The response of forest productivity to climate extremes strongly depends on ambient environmental and site conditions. To better understand these relationships at a regional scale, we used nearly 800 observation years from 271 permanent long‐term forest monitoring plots across Switzerland, obtained between 1980 and 2017. We assimilated these data into the 3‐PG forest ecosystem model using Bayesian inference, reducing the bias of model predictions from 14% to 5% for forest stem carbon stocks and from 45% to 9% for stem carbon stock changes. We then estimated the productivity of forests dominated by Picea abies and Fagus sylvatica for the period of 1960–2018, and tested for productivity shifts in response to climate along elevational gradient and in extreme years. Simulated net primary productivity (NPP) decreased with elevation (2.86 ± 0.006 Mg C ha?1 year?1 km?1 for P. abies and 0.93 ± 0.010 Mg C ha?1 year?1 km?1 for F. sylvatica). During warm–dry extremes, simulated NPP for both species increased at higher and decreased at lower elevations, with reductions in NPP of more than 25% for up to 21% of the potential species distribution range in Switzerland. Reduced plant water availability had a stronger effect on NPP than temperature during warm‐dry extremes. Importantly, cold–dry extremes had negative impacts on regional forest NPP comparable to warm–dry extremes. Overall, our calibrated model suggests that the response of forest productivity to climate extremes is more complex than simple shift toward higher elevation. Such robust estimates of NPP are key for increasing our understanding of forests ecosystems carbon dynamics under climate extremes. 相似文献
10.
How populations of growing cells achieve cell-size homeostasis remains a major question in cell biology. Recent studies in rod-shaped bacteria support the “incremental rule” where each cell adds a constant length before dividing. Although this rule explains narrow cell-size distributions, its mechanism is still unknown. We show that the opportunistic pathogen Pseudomonas aeruginosa obeys the incremental rule to achieve cell-length homeostasis during exponential growth but shortens its cells when entering the stationary phase. We identify a mutant, called frik, which has increased antibiotic sensitivity, cells that are on average longer, and a fraction of filamentous cells longer than 10 μm. When growth slows due to entry in stationary phase, the distribution of frik cell sizes decreases and approaches wild-type length distribution. The rare filamentous cells have abnormally large nucleoids, suggesting that a deficiency in DNA segregation prevents cell division without slowing the exponential elongation rate. 相似文献