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21.
Scavenger receptor class B type I (SR-BI) has an established role in mediating the selective uptake of cholesterol from HDL in hepatocytes, steroidogenic cells, and other tissues. SR-BI is present on the plasma membrane but also localizes to stable intracellular compartments of unknown function. Using indirect immunofluorescence and subcellular fractionation, we have investigated the subcellular distribution of SR-BI. We report that red fluorescent protein-tagged mouse SR-BI (RFP-mSR-BI) colocalizes with the late endosomal and lysosomal markers, Rab7, LBPA, and Rab9. In addition, endogenous SR-BI is also found on lysosomes and colocalizes with LAMP-2 in primary hepatocytes. Furthermore, we demonstrate that the trafficking of SR-BI through these compartments is Rab7 dependent. Interestingly, filipin staining indicates accumulation of lysosomal cholesterol in SR-BI-deficient ((-/-)) as compared with wild-type hepatocytes. In addition to its role as a plasma membrane receptor, SR-BI may function in cholesterol trafficking from late endosomes/lysosomes. 相似文献
22.
Hepatitis C virus (HCV) often causes a persistent infection associated with hypergammaglobulinemia, high levels of antiviral antibody and circulating immune complexes, and immune complex disease. We previously reported that only a limited neutralizing activity to vesicular stomatitis virus or HCV pseudotype is generated in animals immunized with recombinant HCV envelope proteins and chronically infected HCV patient sera. Interestingly, when some of these neutralizing sera were diluted into a range of concentrations below those that reduced virus plaque number, an increase in pseudotype plaque formation was observed. Purified HCV E2-specific human monoclonal antibodies were used to further verify the specificity of this enhancement, and one- to twofold increases were apparent on permissive Huh-7 cells. The enhancement of HCV pseudotype titer could be inhibited by the addition of a Fc-specific anti-human immunoglobulin G Fab fragment to the virus-antibody mixture prior to infection. Treatment of cells with antibody to Fc receptor I (FcRI) or FcRII, but not FcRIII, also led to an inhibition of pseudotype titer enhancement in an additive manner. Human lymphoblastoid cell line (Raji), a poor host for HCV pseudotype infection, exhibited a four- to sixfold enhancement of pseudotype-mediated cell death upon incubation with antibody at nonneutralizing concentrations. A similar enhancement of cell culture-grown HCV infectivity by a human monoclonal antibody was also observed. Taken together, antibodies to viral epitopes enhancing HCV infection need to be taken into consideration for pathogenesis and in the development of an effective vaccine. 相似文献
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24.
Homozygous Defects in LMNA, Encoding Lamin A/C Nuclear-Envelope Proteins, Cause Autosomal Recessive Axonal Neuropathy in Human (Charcot-Marie-Tooth Disorder Type 2) and Mouse 总被引:13,自引:0,他引:13 下载免费PDF全文
Annachiara De?Sandre-Giovannoli Malika Chaouch Serguei Kozlov Jean-Michel Vallat Meriem Tazir Nadia Kassouri Pierre Szepetowski Tarik Hammadouche Antoon Vandenberghe Colin L. Stewart Djamel Grid Nicolas Lévy 《American journal of human genetics》2002,70(3):726-736
The Charcot-Marie-Tooth (CMT) disorders comprise a group of clinically and genetically heterogeneous hereditary motor and sensory neuropathies, which are mainly characterized by muscle weakness and wasting, foot deformities, and electrophysiological, as well as histological, changes. A subtype, CMT2, is defined by a slight or absent reduction of nerve-conduction velocities together with the loss of large myelinated fibers and axonal degeneration. CMT2 phenotypes are also characterized by a large genetic heterogeneity, although only two genes---NF-L and KIF1Bbeta---have been identified to date. Homozygosity mapping in inbred Algerian families with autosomal recessive CMT2 (AR-CMT2) provided evidence of linkage to chromosome 1q21.2-q21.3 in two families (Zmax=4.14). All patients shared a common homozygous ancestral haplotype that was suggestive of a founder mutation as the cause of the phenotype. A unique homozygous mutation in LMNA (which encodes lamin A/C, a component of the nuclear envelope) was identified in all affected members and in additional patients with CMT2 from a third, unrelated family. Ultrastructural exploration of sciatic nerves of LMNA null (i.e., -/-) mice was performed and revealed a strong reduction of axon density, axonal enlargement, and the presence of nonmyelinated axons, all of which were highly similar to the phenotypes of human peripheral axonopathies. The finding of site-specific amino acid substitutions in limb-girdle muscular dystrophy type 1B, autosomal dominant Emery-Dreifuss muscular dystrophy, dilated cardiomyopathy type 1A, autosomal dominant partial lipodystrophy, and, now, AR-CMT2 suggests the existence of distinct functional domains in lamin A/C that are essential for the maintenance and integrity of different cell lineages. To our knowledge, this report constitutes the first evidence of the recessive inheritance of a mutation that causes CMT2; additionally, we suggest that mutations in LMNA may also be the cause of the genetically overlapping disorder CMT2B1. 相似文献
25.
Malika Faouzi Valérie Chopin Ahmed Ahidouch Halima Ouadid-Ahidouch 《The Journal of membrane biology》2010,234(1):47-56
Prolactin (PRL) is a polypeptidic hormone which acts both systemically and locally to cause lactation by interacting with
the PRL receptor, a Janus kinase (JAK2)-coupled cytokine receptor family member. Several studies have reported that serum
PRL level elevation is associated with an increased risk for breast cancer, and evidence has suggested that PRL is one actor
in the pathogenesis and progression of this cancer. We previously reported the involvement of hIKCa1 in breast cell cycle
progression and cell proliferation. However, mechanisms by which PRL cooperates with these channels to modulate breast epithelial
cell proliferation remain unknown. Our results showed that, in the MCF-7 breast cancer cell line, PRL increased hIKCa1 current
density. These channels were functional and regulated the resting membrane potential. The PRL effects were inhibited by TRAM-34
and clotrimazole, the most used hIKCa1 blockers. Moreover, PRL increased proliferation in a dose-dependent manner without
overexpressing hIKCa1. To determine whether PRL-induced proliferation and hIKCa1 activity involved the JAK2 pathway, we used
pharmacological JAK2 inhibitors (AG490 and JAK inhibitor I). Indeed, PRL-induced JAK2 phosphorylation was required for both
cell proliferation and hIKCa1 activity. In the presence of either hIKCa1 blockers or siRNA-hIKCa1, PRL failed to increase
cell proliferation and hIKCa1 activity. Taken together, our results demonstrate that PRL plays a role in breast cancer cell
proliferation by increasing hIKCa1 activity through the JAK2 signaling pathway. 相似文献
26.
Malika Ibrahim-Ouali 《Steroids》2009,74(2):133-64
The Diels-Alder reaction continues to dominate the developments in steroid synthesis. A review of literature on the Diels-Alder route to steroids is presented. 相似文献
27.
Malika Virah-Sawmy Katherine J. Willis Lindsey Gillson 《Global Ecology and Biogeography》2009,18(1):98-110
Aim Coastal biodiversity hotspots are globally threatened by sea‐level rise. As such it is important to understand how ecosystems resist, respond and adapt to sea‐level rise. Using pollen, geochemistry, charcoal and diatom records in conjunction with previously published palaeoclimatic records, we investigated the mechanism, interactions and ecosystem response and resilience of Madagascar's littoral forest to late Holocene sea‐level rise. Location Sediment sequences were collected along the south‐east coast of Madagascar in two adjacent habitats in Mandena; the highly diverse littoral forest fragment and species‐poor Erica‐matrix. Methods We used a multi‐proxy approach to investigate the relative influence of environmental changes on the littoral ecosystem. We reconstructed past vegetation and fire dynamics over the past 6500 years at two sites in the littoral forest using fossil pollen and macrofossil charcoal contained in sedimentary sequences. Alongside these records we reconstructed past marine transgressions from the same sedimentary sequences using geochemical analyses, and a salinity and drought index through the analysis of fossil diatoms. Results Our findings indicated that it was the synergistic effect of sea‐level rise coupled with rainfall deficits that triggered a threshold event with a switch from two types of littoral forest (an open Uapaca forest and a closed littoral forest fragment) to an Erica–Myrica heath/grassland occurring in approximately less than 100 years. Resilience to sea‐level rise differed in the two adjacent habitats, suggesting that the littoral forest fragment was more resilient to the impacts of sea‐level change and aridity than the open Uapaca woodland. Conclusions We demonstrated that the littoral ecosystem was influenced by late Holocene sea‐level rise and climatic desiccation. While climate change‐integrated conservation strategies address the effects of climate change on species distribution and dispersal, our work suggests that more attention should be paid to the impacts of interactive climatic variables that affect ecosystem thresholds. 相似文献
28.
Inter- and intra-species intercropping of barley cultivars and legume species,as affected by soil phosphorus availability 总被引:1,自引:0,他引:1
Tegan Darch Courtney D. Giles Martin S. A. Blackwell Timothy S. George Lawrie K. Brown Daniel Menezes-Blackburn Charles A. Shand Marc I. Stutter David G. Lumsdon Malika M. Mezeli Renate Wendler Hao Zhang Catherine Wearing Patricia Cooper Philip M. Haygarth 《Plant and Soil》2018,427(1-2):125-138
Aims
Intercropping can improve plant yields and soil phosphorus (P) use efficiency. This study compares inter- and intra-species intercropping, and determines whether P uptake and shoot biomass accumulation in intercrops are affected by soil P availability.Methods
Four barley cultivars (Hordeum vulgare L.) and three legume species (Trifolium subterreneum, Ornithopus sativus and Medicago truncatula) were selected on the basis of their contrasting root exudation and morphological responses to P deficiency. Monocultures and barley-barley and barley-legume intercrops were grown for 6 weeks in a pot trial at very limiting, slightly limiting and excess available soil P. Above-ground biomass and shoot P were measured.Results
Barley-legume intercrops had 10–70% greater P accumulation and 0–40% greater biomass than monocultures, with the greatest gains occurring at or below the sub-critical P requirement for barley. No benefit of barley-barley intercropping was observed. The plant combination had no significant effect on biomass and P uptake observed in intercropped treatments.Conclusions
Barley-legume intercropping shows promise for sustainable production systems, especially at low soil P. Gains in biomass and P uptake come from inter- rather than intra-species intercropping, indicating that plant diversity resulted in decreased competition between plants for P.29.
Yassine Djelaila Christiane Denys Emmanuelle Stoetzel Raphaël Cornette Aude Lalis Malika Adamou-Djerbaoui Mohamed Boukhemza 《Comptes rendus biologies》2018,341(1):28-42
In North Africa, the rodents of the species complex Meriones shawii–grandis have a considerable ecological, economic and epidemiological importance. Until now, the systematics of these species was subject to discussion due to the presence of populations displaying high morphological variability. By means of an approach of traditional morphometrics based on cranial distances and by using the method of the log shape-ratio, we attempt to characterize morphologically these two taxa. The results show significant differences in size and shape between the specimens of Morocco, on the one hand, and those of Algeria and Tunisia, on the other hand. The samples of Morocco that have been molecularly typed and attributed to M. grandis have larger tooth rows and narrower skulls, as well as relatively small tympanic bullae. On the other hand, those of Algeria and Tunisia assigned to M. shawii are characterized by small tooth rows and wide skulls with well-developed tympanic bullae. The morphological distance is relatively strong between both clades (79.5%), which corresponds to the molecular distance. However, the discriminant analysis performed after molecularly-typed specimens allows the correct classification of only 91.8% of the individuals. 相似文献
30.
Low genetic diversity contrasts with high phenotypic variability in heptaploid Spartina densiflora populations invading the Pacific coast of North America 下载免费PDF全文
Jesús M. Castillo Blanca Gallego‐Tévar Enrique Figueroa Brenda J. Grewell Dominique Vallet Hélène Rousseau Jean Keller Oscar Lima Stéphane Dréano Armel Salmon Malika Aïnouche 《Ecology and evolution》2018,8(10):4992-5007
Species can respond to environmental pressures through genetic and epigenetic changes and through phenotypic plasticity, but few studies have evaluated the relationships between genetic differentiation and phenotypic plasticity of plant species along changing environmental conditions throughout wide latitudinal ranges. We studied inter‐ and intrapopulation genetic diversity (using simple sequence repeats and chloroplast DNA sequencing) and inter‐ and intrapopulation phenotypic variability of 33 plant traits (using field and common‐garden measurements) for five populations of the invasive cordgrass Spartina densiflora Brongn. along the Pacific coast of North America from San Francisco Bay to Vancouver Island. Studied populations showed very low genetic diversity, high levels of phenotypic variability when growing in contrasted environments and high intrapopulation phenotypic variability for many plant traits. This intrapopulation phenotypic variability was especially high, irrespective of environmental conditions, for those traits showing also high phenotypic plasticity. Within‐population variation represented 84% of the total genetic variation coinciding with certain individual plants keeping consistent responses for three plant traits (chlorophyll b and carotenoid contents, and dead shoot biomass) in the field and in common‐garden conditions. These populations have most likely undergone genetic bottleneck since their introduction from South America; multiple introductions are unknown but possible as the population from Vancouver Island was the most recent and one of the most genetically diverse. S. densiflora appears as a species that would not be very affected itself by climate change and sea‐level rise as it can disperse, establish, and acclimate to contrasted environments along wide latitudinal ranges. 相似文献