Comparitive study of the milk fat globule membrane and the mouse mammary tumour virus prepared from the milk of an infected strain of Swiss albino mice

Milk fat globule membranes and mammary tumour virus particles (d = 1.17 g/cm³) have been obtained from the milk of a Swiss albino mice strain. Comparitive biochemistry shows that these two structures differ significantly in the phospholipid, polypeptide and glycopolypeptide patterns and enzymatic activities. However, the lipid profile and the morphology of both structures suggest a filiation with the plasma membrane. Density fractions obtained from the crude virus preparation have been thoroughly investigated. The results suggest that most of these fractions represent degraded virus and/or atypical virus assembly.     

Broadly Neutralizing Antibody VRC01 Prevents HIV-1 Transmission from Plasmacytoid Dendritic Cells to CD4 T Lymphocytes

Plasmacytoid dendritic cells (pDC) poorly replicate human immunodeficiency virus type 1 (HIV-1) but efficiently transfer HIV-1 to adjacent CD4 T lymphocytes. We found that coculture with T lymphocytes downregulates SAMHD1 expression, enhances HIV-1 replication, and increases pDC maturation and alpha interferon (IFN-α) secretion. HIV-1 transfer to T lymphocytes is inhibited by broadly neutralizing antibody VRC01 with efficiency similar to that of cell-free infection of T lymphocytes. Interestingly, prevention of HIV-1 transmission by VRC01 retains IFN-α secretion. These results emphasize the multiple functions of VRC01 in protection against HIV-1 acquisition.     

Enhanced bacterial virulence through exploitation of host glycosaminoglycans

Present in the extracellular matrix and membranes of virtually all animal cells, proteoglycans (PGs) are among the first host macromolecules encountered by infectious agents. Because of their wide distribution and direct accessibility, it is not surprising that pathogenic bacteria have evolved mechanisms to exploit PGs for their own purposes, including mediating attachment to target cells. This is achieved through the expression of adhesins that recognize glycosaminoglycans (GAGs) linked to the core protein of PGs. Some pathogens, such as Bordetella pertussis and Chlamydia trachomatis, may express more than one GAG-binding adhesin. Bacterial interactions with PGs may also facilitate cell invasion or systemic dissemination, as observed for Neisseria gonorrhoeae and Mycobacterium tuberculosis respectively. More-over, pathogenic bacteria can use PGs to enhance their virulence via a shedding of PGs that leads to there lease of effectors that weaken the host defences.The exploitation of PGs by pathogenic bacteria is thus a multifaceted mechanistic process directly related to the potential virulence of a number of microorganisms.     

Molecular level probing of preferential hydration and its modulation by osmolytes through the use of pyranine complexed to hemoglobin

Two spectroscopic probes are used to expose molecular level changes in hydration shell water interactions that directly relate to such issues as preferential hydration and protein stability. The major focus of the present study is on the use of pyranine (HPT) fluorescence to probe as a function of added osmolytes (PEG, urea, trehalose, and magnesium), the extent to which glycerol is preferentially excluded from the hydration shell of free HPT and HPT localized in the diphosphoglycerate (DPG) binding site of hemoglobin in both solution and in Sol-Gel matrices. The pyranine study is complemented by the use of vibronic side band luminescence from the gadolinium cation that directly exposes the changes in hydrogen bonding between first and second shell waters as a function of added osmolytes. Together the results form the basis for a water partitioning model that can account for both preferential hydration and water/osmolyte-mediated conformational changes in protein structure.     

New mutations of CIAS1 that are responsible for Muckle-Wells syndrome and familial cold urticaria: a novel mutation underlies both syndromes

Mutations of CIAS1 have recently been shown to underlie familial cold urticaria (FCU) and Muckle-Wells syndrome (MWS), in three families and one family, respectively. These rare autosomal dominant diseases are both characterized by recurrent inflammatory crises that start in childhood and that are generally associated with fever, arthralgia, and urticaria. The presence of sensorineural deafness that occurs later in life is characteristic of MWS. Amyloidosis of the amyloidosis-associated type is the main complication of MWS and is sometimes associated with FCU. In FCU, cold exposure is the triggering factor of the inflammatory crisis. We identified CIAS1 mutations, all located in exon 3, in nine unrelated families with MWS and in three unrelated families with FCU, originating from France, England, and Algeria. Five mutations--namely, R260W, D303N, T348M, A439T, and G569R--were novel. The R260W mutation was identified in two families with MWS and in two families with FCU, of different ethnic origins, thereby demonstrating that a single CIAS1 mutation may cause both syndromes. This result indicates that modifier genes are involved in determining either a MWS or a FCU phenotype. The finding of the G569R mutation in an asymptomatic individual further emphasizes the importance of such modifier a gene (or genes) in determining the disease phenotype. Identification of this gene (or these genes) is likely to have significant therapeutic implications for these severe diseases.     

Key Features of Intertidal Food Webs That Support Migratory Shorebirds

The migratory shorebirds of the East Atlantic flyway land in huge numbers during a migratory stopover or wintering on the French Atlantic coast. The Brouage bare mudflat (Marennes-Oléron Bay, NE Atlantic) is one of the major stopover sites in France. The particular structure and function of a food web affects the efficiency of carbon transfer. The structure and functioning of the Brouage food web is crucial for the conservation of species landing within this area because it provides sufficient food, which allows shorebirds to reach the north of Europe where they nest. The aim of this study was to describe and understand which food web characteristics support nutritional needs of birds. Two food-web models were constructed, based on in situ measurements that were made in February 2008 (the presence of birds) and July 2008 (absence of birds). To complete the models, allometric relationships and additional data from the literature were used. The missing flow values of the food web models were estimated by Monte Carlo Markov Chain – Linear Inverse Modelling. The flow solutions obtained were used to calculate the ecological network analysis indices, which estimate the emergent properties of the functioning of a food-web.The total activities of the Brouage ecosystem in February and July are significantly different. The specialisation of the trophic links within the ecosystem does not appear to differ between the two models. In spite of a large export of carbon from the primary producer and detritus in winter, the higher recycling leads to a similar retention of carbon for the two seasons. It can be concluded that in February, the higher activity of the ecosystem coupled with a higher cycling and a mean internal organization, ensure the sufficient feeding of the migratory shorebirds.     

Simulated herbivory effects on rhizosphere organisms in pea (Pisum sativum) depended on phosphate

The effects of simulated aboveground herbivory and phosphate addition to soil on rhizosphere organisms (arbuscular mychorrhiza (AM), Rhizobium spp., bacteria, protozoa and nematodes) were studied in a 2 by 2 factorial designed pot experiment with Pea plants (Pisum sativum). Measurements were performed on 24 day old plants that were still in the nutrient acquisition phase before flowering. AM colonization and bacterial feeding nematodes were stimulated by high simulated her- bivory especially when plants were phosphate deficient. Total number of nematodes was higher with phosphate deficiency. Furthermore, non-significant peak values in soil respiration, total number of nematodes, and bacterial number were observed in phosphate deficient plants with high simulated herbivory. In phosphate amended plants, fast-growing protozoa and bacterial feeding nematodes decreased at high simulated herbivory. These results support the hypothesis that the plant regulates abundances of both AM and free-living rhizosphere organisms and thereby the amount of plant-available nutrients, according to demand via root exudation. Rhizobium spp. was significantly stimulated by phosphate addition but not affected by simulated herbivory. Metabolites produced by rhizosphere bacteria from plants exposed to high simulated herbivory in phosphate amended soil stimulated seed performance. Possible interactions between protozoa and nematodes in relation to production and composition of bacteria in the rhizosphere are discussed.     

Assessing the diversity and abundances of larvae and juveniles of coral reef fish: a synthesis of six sampling techniques

Due to an increasing emphasis for fish population survey and regulation, efficient tools for evaluating the abundance and diversity of fish from various life stages are needed, especially for coral reef species that present a high taxonomic diversity. The characteristics of six different techniques used for sampling pelagic larvae (a plankton-net and two light-traps), newly settled juveniles (one type of artificial reef), and older juveniles (an underwater seine net in seagrass and macroalgal beds, and rotenone poisoning in coral patches) are described in this study. Larvae belonging to 70 families and juveniles belonging to 34 families were collected. An analysis of similarity (ANOSIM) showed that the taxonomic composition of assemblages collected with the plankton-net and the two light-traps were overlapping but clearly different, due to the higher occurrence of Gobiidae in the plankton-net and of Pomacentridae in both light-traps. Larvae being 2–4 mm standard length (SL) dominated in the plankton-net, whereas larvae being 9–11 mm SL dominated in both light-traps. Pomacentridae juveniles were more abundant in rotenone samples, whereas Labridae dominated in the underwater seine. Juvenile fish collected with the artificial reefs, the underwater seine, and rotenone poisoning largely overlapped in size, with mean sizes of 22, 38, and 33 mm SL, respectively. Seven families were caught by the six sampling techniques, but with unequal success. This study provides ecologists and managers with a unique review of six techniques for sampling a wide range of developmental stages of young fish in different habitats of a coral reef lagoon.

The kinesin of the flagellum attachment zone in Leishmania is required for cell morphogenesis,cell division and virulence in the mammalian host

Leishmania parasites possess a unique and complex cytoskeletal structure termed flagellum attachment zone (FAZ) connecting the base of the flagellum to one side of the flagellar pocket (FP), an invagination of the cell body membrane and the sole site for endocytosis and exocytosis. This structure is involved in FP architecture and cell morphogenesis, but its precise role and molecular composition remain enigmatic. Here, we characterized Leishmania FAZ7, the only known FAZ protein containing a kinesin motor domain, and part of a clade of trypanosomatid-specific kinesins with unknown functions. The two paralogs of FAZ7, FAZ7A and FAZ7B, display different localizations and functions. FAZ7A localizes at the basal body, while FAZ7B localizes at the distal part of the FP, where the FAZ structure is present in Leishmania. While null mutants of FAZ7A displayed normal growth rates, the deletion of FAZ7B impaired cell growth in both promastigotes and amastigotes of Leishmania. The kinesin activity is crucial for its function. Deletion of FAZ7B resulted in altered cell division, cell morphogenesis (including flagellum length), and FP structure and function. Furthermore, knocking out FAZ7B induced a mis-localization of two of the FAZ proteins, and disrupted the molecular organization of the FP collar, affecting the localization of its components. Loss of the kinesin FAZ7B has important consequences in the insect vector and mammalian host by reducing proliferation in the sand fly and pathogenicity in mice. Our findings reveal the pivotal role of the only FAZ kinesin as part of the factors important for a successful life cycle of Leishmania.     

In Situ Fe and S isotope analyses in pyrite from the 3.2 Ga Mendon Formation (Barberton Greenstone Belt,South Africa): Evidence for early microbial iron reduction

On the basis of phylogenetic studies and laboratory cultures, it has been proposed that the ability of microbes to metabolize iron has emerged prior to the Archaea/Bacteria split. However, no unambiguous geochemical data supporting this claim have been put forward in rocks older than 2.7–2.5 giga years (Gyr). In the present work, we report in situ Fe and S isotope composition of pyrite from 3.28‐ to 3.26‐Gyr‐old cherts from the upper Mendon Formation, South Africa. We identified three populations of microscopic pyrites showing a wide range of Fe isotope compositions, which cluster around two δ⁵⁶Fe values of ?1.8‰ and +1‰. These three pyrite groups can also be distinguished based on the pyrite crystallinity and the S isotope mass‐independent signatures. One pyrite group displays poorly crystallized pyrite minerals with positive Δ³³S values > +3‰, while the other groups display more variable and closer to 0‰ Δ³³S values with recrystallized pyrite rims. It is worth to note that all the pyrite groups display positive Δ³³S values in the pyrite core and similar trace element compositions. We therefore suggest that two of the pyrite groups have experienced late fluid circulations that have led to partial recrystallization and dilution of S isotope mass‐independent signature but not modification of the Fe isotope record. Considering the mineralogy and geochemistry of the pyrites and associated organic material, we conclude that this iron isotope systematic derives from microbial respiration of iron oxides during early diagenesis. Our data extend the geological record of dissimilatory iron reduction (DIR) back more than 560 million years (Myr) and confirm that micro‐organisms closely related to the last common ancestor had the ability to reduce Fe(III).