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41.
†Daniel Guillaume Philippe Bertrand Doris Dea ‡Jean Davignon †§ Judes Poirier 《Journal of neurochemistry》1996,66(6):2410-2418
Abstract: Apolipoprotein (apo) E is likely involved in redistributing cholesterol and phospholipids during compensatory synaptogenesis in the injured CNS. Three common isoforms of apoE exist in human (E2, E3, and E4). The apoE4 allele frequency is markedly increased in both late-onset sporadic and familial Alzheimer's disease (AD). ApoE concentration in the brain of AD subjects follows a gradient: ApoE levels decrease as a function of E2 > E3 ? E4. It has been proposed that the poor reinnervation capacity reported in AD may be caused by impairment of the apoE/low-density lipoprotein (LDL) receptor activity. To understand further the role of this particular axis in lipid homeostasis in the CNS, we have characterized binding, internalization, and degradation of human 125I-LDL to primary cultures of rat astrocytes. Specific binding was saturable, with a KD of 1.8 nM and a Bmax of 0.14 pmol/mg of proteins. Excess unlabeled human LDL or very LDL (VLDL) displaced 70% of total binding. Studies at 37°C confirmed that astrocytes bind, internalize, and degrade 125I-LDL by a specific, saturable mechanism. Reconstituted apoE (E2, E3, and E4)-liposomes were labeled with 125I and incubated with primary cultures of rat astrocytes and hippocampal neurons to examine specific binding. Human LDL and VLDL displaced binding and internalization of all apoE isoforms similarly in both astrocytes and neurons. 125I-ApoE2 binding was significantly lower than that of the other 125I-apoE isoforms in both cell types. 125I-ApoE4 binding was similar to that of 125I-apoE3 in both astrocytes and neurons. On the other hand, 125I-apoE3 binding was significantly higher in neurons than in astrocytes. These isoform-specific alterations in apoE-lipoprotein pathway could explain some of the differences reported in the pathophysiology of AD subjects carrying different apoE alleles. 相似文献
42.
Harry Adams Neil A. Bailey Philippe Bertrand Simon R. Collinson David E. Fenton Simon J. Kitchen 《Inorganica chimica acta》1996,250(1-2):139-148
The cyclocondensation of 2,5-diformylthiophene and the amines N,N-bis-(2-aminoethyl)-2-phenylethylamine, N,N-bis-(2aminoethyl)-t-butyl-amine and N,N-bis-(2-aminoethyl)-t-butyl-amine in the presence of silver(I) salts yields homodinuclear bibracchial tetraimine Schiff base macrocyclic complexes. The structures of two such complexes are also reported. The complex Ag2L4(NO3)(PF6) (2) crystallises in the triclinic space group
, No. 2) and has unit-cell dimensions a = 12.834(6), B = 13.183(6), C = 14.588(7) Å, = 64.86(4), β = 79.77(4), γ = 69.44(3)° with Z = 2; there is a monodentate and singly bridging nitrate anion present and the Ag---Ag separation is 4.161 Å. The complex Ag2L4(CH3CN)2(BF4)2·CH3CN (9) crystallises in the triclinic space group
, No. 2) and has unit-cell dimensions a = 9.297(4), B = 12.985(3), C = 21.770(5) Å, = 91.570(10), β = 92.33(3), γ = 97.92(3) ° with Z = 2; there is a strongly bonded acetonitrile molecule coordinated to each silver atom and the Ag---Ag separation is 4.920 Å. 相似文献
43.
Hexadecane mineralization by a bacterial consortium isolated from a non heavily contaminated coastal seawater was largely increased by an enrichment with Inipol EAP 22 (10% w/w). In the conditions of the experiment, the efficiency of this oleophilic nutrient is linked to the organic N and P sources (urea and lauryl-phosphate) and, to a lesser extent, to the presence of a readily available carbon source (oleic acid). Otherwise, the micro emulsion nature of the formulation and its physical properties seem to play a major role in accelerating hexadecane mineralization. 相似文献
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46.
Eric Dufour Paul Robert Dominique Bertrand Tomasz Haertlé 《Journal of Protein Chemistry》1994,13(2):143-149
Fourier transform infrared spectroscopy has been applied to investigate the secondary structural changes of-lactoglobulin in water/ethanol mixtures. The studies were carried out at two differentpHs and at high protein concentrations. The spectra were recorded using an attenuated total reflection cell. The amide I band of-lactoglobulin in water reveals large amounts of intra extended-sheet structure. About 20% ethanol,-lactoglobulin unfolds and-strand formation is observed.-Helices are built up by increasing the ethanol concentration up to 30%. In 50% ethanol,-lactoglobulin gels providing the apparent pH are neutral. The secondary structural changes of-lactoglobulin were observed on the similarity maps obtained by Principal Component Analysis. 相似文献
47.
A 2-year study of three natural populations of the distylousJasminum fruticans showed that mean fruit and seed production were significantly greater in shortstyled plants (thrums) than in long-styled
plants (pins). In this study, we investigated the role of four sequential factors which may differentially influence fruit
and seed set in the two floral morphs: (1) differences in flowering phenology, (2) a limitation of pollen transfer towards
pins, (3) a differential capacity of the two morphs to act through famale and male function and (4) differential fruit abortion
in the two morphs. Fruit set was significantly influenced by differences in flowering phenology although there were no differences
in flowering time between the two morphs. supplementary pollinations in a natural population significantly increased fruit
set and reduced the difference in fruit set between the two morphs in relation to controls, indicating a limitation on pollen
transfer which was most severe towards pin stigmas. In reciprocal crosses, seed set was significantly dependent on the paternal
and maternal identity of the pin parent. There was no significant variation among thrums for their performance as male or
female parent. Furthermore, individual pin plants with relatively high percentage seed set as female parents gave poor seed
set as male parents and vice-versa. Whereas fruit removal had no effect on seed number in thrum plants, a greater proportion
of viable seeds were produced on pin plants which were left to naturally mature their fruits than on pins which had fruits
artificially removed, suggesting the occurrence of selective fruit abortion in pins but not in thrums. The initially greater
maternal fitness of thrums due to their greater success as pollen recipients may thus be opposed by increased viable seed
set in the pins due to factors acting after the pollination stage. The relative reproductive success of floral morphs in the
distylousJ. fruticans is thus differentially influenced by ecological factors occurring at different stages of the reproductive process. 相似文献
48.
Bertrand D. Eardly Mara Cloutier Taejung Chung Sofia Roitman Fabricio R. Vieira Mary Ann V. Bruns 《Restoration Ecology》2023,31(1):e13695
From 1913 to 1980, two zinc smelters in Palmerton, Pennsylvania, emitted large quantities of atmospheric pollutants nearly eliminating forests along a ridge above the town. In 2008, a remediation treatment was applied to the land above one of the smelters that included the planting of several locally adapted plant species. It also included mineral fertilization and mycorrhizal inoculation. One of the species, the Pitch pine (Pinus rigida, Mill.), is a native tree that is both tolerant of metalliferous soils and obligatorily ectomycorrhizal. This report summarizes the results of two observational studies conducted 5 years after the remediation treatment. The first study's objective was to compare ectomycorrhizal communities on treated Pitch pine saplings, with communities on naturally regenerating saplings in an adjacent non-remediated area. The second study's objective was to determine if the composition of the fungal communities on root tips of naturally regenerating Pitch pine saplings differed with distance from the smelters. Fungal community compositions were determined using internal transcribed spacer rRNA sequences. Comparisons of sequences from the remediated and non-remediated sites revealed that communities at the remediated sites had lower taxonomic diversity and were dominated by members of a genus in the remediation inoculant. The results of the smelter-proximity study indicated that although fungal diversity did not differ markedly with distance from the smelters, the relative abundances of some taxa were greater on saplings growing directly above the smelters, where the soils contained highest concentrations of zinc and cadmium. 相似文献
49.
Sylvie Nadeau Martin Bilodeau Alain Delisle Witold Chmielewski A.Bertrand Arsenault Denis Gravel 《Journal of electromyography and kinesiology》1993,3(4):205-213
Different behaviours of the EMG power spectrum across increasing force levels have been reported for the masseter muscle. A factor that could explain these different behaviours may be the type of contraction used, as was recently shown for certain upper limb muscles5. The purpose of this study was to compare, between two types of isometric contractions, the behaviour of EMG power spectrum statistics (median frequency (MF) and mean power frequency (MPF)) obtained across increasing force levels. Ten women exerted, while biting in the intercuspal position, three 5 s ramp contractions that increased linearly from 0 to 100% of the maximal voluntary contraction (MVC). They also completed three step contractions (constant EMG amplitude) at each of the following levels: 20, 40, 60 and 80% MVC. EMG signals from the masseter muscle were recorded with miniature surface electrodes. The RMS, as well as the MPF and MF of the power spectrum were calculated at 20, 40, 60 and 80% MVC for each type of contraction. As expected, the RMS values showed similar increases with increasing levels of effort for both types of contractions. Different behaviours for both MPF (contraction*force interaction, ANOVA, P<0.05) and MF (contraction*force interaction, ANOVA, P>0.05) across increasing levels of effort were found between the two types of contraction. The use of step contractions gave rise to a decrease of both MPF and MF with increasing force, while the use of ramp contractions gave rise to an increase in both statistics up to at least 40% MVC followed by a decrease at higher force levels. These findings suggest that the type of contraction used does influence the behaviour of the spectral statistics across increasing force levels and that this could explain the differences obtained in previous studies for the masseter muscle. 相似文献
50.
Maria A. Soto Dhwani Desai Catherine Bannon Julie LaRoche Erin M. Bertrand 《Environmental microbiology》2023,25(7):1300-1313
Cobalamin availability can influence primary productivity and ecological interactions in marine microbial communities. The characterization of cobalamin sources and sinks is a first step in investigating cobalamin dynamics and its impact on productivity. Here, we identify potential cobalamin sources and sinks on the Scotian Shelf and Slope in the Northwest Atlantic Ocean. Functional and taxonomic annotation of bulk metagenomic reads, combined with analysis of genome bins, were used to identify potential cobalamin sources and sinks. Cobalamin synthesis potential was mainly attributed to Rhodobacteraceae, Thaumarchaeota, and cyanobacteria (Synechococcus and Prochlorococcus). Cobalamin remodelling potential was mainly attributed to Alteromonadales, Pseudomonadales, Rhizobiales, Oceanospirilalles, Rhodobacteraceae, and Verrucomicrobia, while potential cobalamin consumers include Flavobacteriaceae, Actinobacteria, Porticoccaceae, Methylophiliaceae, and Thermoplasmatota. These complementary approaches identified taxa with the potential to be involved in cobalamin cycling on the Scotian Shelf and revealed genomic information required for further characterization. The Cob operon of Rhodobacterales bacterium HTCC2255, a strain with known importance in cobalamin cycling, was similar to a major cobalamin producer bin, suggesting that a related strain may represent a critical cobalamin source in this region. These results enable future inquiries that will enhance our understanding of how cobalamin shapes microbial interdependencies and productivity in this region. 相似文献