Histochemical and immunocytochemical study of the migration of neurons from the rat olfactory placode

Immunocytochemical and histochemical methods have been used to describe the neuronal population migrating from the rat olfactory placode and to analyze the spatio-temporal evolution of this neuronal migration during development. Several neuronal markers, such as binding to the lectin Ulex europaeus (UEA I) and the presence of neuron-specific enolase (NSE), olfactory marker protein (OMP), and luteinizing hormone-releasing hormone (LHRH), have been tested in order to determine whether migrating neurons originate from both the medial and the lateral parts of the placode and whether they all express LHRH. Our data show that a large population of differentiated migrating neurons can be identified with an antibody against NSE from the 14th day of gestation and with UEA I one day later. Migrating neurons are closely associated with both the vomeronasal axon fascicles emerging from the medial pit and the olfactory axons originating from the lateral pit. However, the neuron migration from the lateral pit appears to be more discrete than that from the medial pit. No LHRH immunoreactivity has been detected among neurons migrating from the lateral pit. Some neurons accompanying the olfactory axon fascicles exhibit a high level of maturation as shown by their OMP-positivity. Numerous neurons positive for both NSE and UEA I have also been observed within the presumptive olfactory nerve layer in early embryonic stages.     

Interactions of HIV-1 and HIV-2 envelope glycoproteins with sulphated polysaccharides and mannose-6-phosphate

Envelope glycoproteins of human immunodeficiency viruses (HIV-1and HIV-2) can interact with high-mannose glycans and with themannosyl or N-acetylglucosaminyl core of complex-type oligosaccharidicstructures. HIV-1 glycoproteins also specifically bind sulphatedpolysaccharides such as dextran sulphate (DS) and heparin. Here,we show that the latter property is shared by HIV-2 recombinantgp140 (rgpl40) precursor glycoprotein. Binding of rgpl40 andof corresponding rgp160 of HIV-1 to heparin- and DS-substituted(sulphated dextran beads; SDB) affinity matrices was inhibitedby the soluble specific ligand and also by fetuin, asialofetuinor the anionic simple carbohydrate derivative manncsse-6-phosphate(M6P). Interaction of HIV-1 rgpl20 subunit with the two affinitymatrices was also inhibited by M6P, but only rgpl20 bindingto heparin-agarose, and not that to SDB, was affected by fetuinand asialofetuin. These results suggest that HIV-1 and HIV-2envelope glycoproteins presumably display different sulphatedpolysaccharide and carbohydrate recognition sites. Some of thesemay be common or in close proximity: with respect to rgpl60,for example, the sites may be common on the gp41 moiety and/orin a region of gp120 which would be more accessible when expressedon rgpl60 than on processed gpl20, while they may be distincton the cleaved gpl20 subunit. Finally, because M6P is a markerof lysosomal enzymes, we verified that HIV-1 and HIV-2 envelopeglycoproteins could specifically bind in a M6P-inhibitable mannerto a representative lysosomal enzyme, bovine liver ß-glucuronidasecoupled to agarose, suggesting that they may possibly interferewith lysosomal enzyme sorting in HIV-infected cells. env glycoproteins HIV lectin mannose-6-phosphate sulphated polysaccharides     

Some biochemical properties of an acyclic oligonucleotide analogue. A plausible ancestor of the DNA?

As acyclic oligonucleotides have been suggested as a primitive model of DNA or RNA in prebiotic times, we compared some biochemical properties of these analogues to that of natural ones. Firstly, an acyclic analogue of deoxyribonucleoside triphosphates was tested as a potential substrate of enzymes intervening in nucleic acids synthesis. GlyTTP, a dTTP analogue with a missing 2-methylene group is notaccepted as a substrate by either DNA polymerase or deoxynucleotidyl terminal transferase (TdT). Secondly, themodified dodecathymidylate (GlyT)₁₂, the racemic acyclic sugar analogue of (dT)₁₂, proved to be anefficient primer for DNA polymerase and TdT, though the associative properties of (GlyT)₁₂ are very weak as shown by UV spectroscopy in phosphate buffer without magnesium chloride. But (GlyT)₁₂ has the advantage to be 500-times more stable against hydrolysis by snake venom phosphodiesterase than the corresponding oligothymidylate.     

In vitro study of the proteolytic activity of rumen anaerobic fungi

Abstract To better define the antigenic structure of the outer cell membranes of Legionellae, a panel of 6 monoclonal antibodies was raised against partially purified outer membranes of Legionella pneumophila serogroup 1, Corby strain. This study describes the purification and characterization of one of these monoclonal antibodies reacting with a 135-kDa protein, which was shown to be common to all 14 serogroups of Legionella pneumophila . It shows no cross-reactivity with 20 other Legionella species, or 9 other Gram-negative species tested by SDS-PAGE and Western blotting procedures. The epitope would appear to be predominantly surface exposed and, from preliminary detergent extraction studies, not peptidoglycan-associated.     

Widespread formation of intracellular calcium carbonates by the bloom-forming cyanobacterium Microcystis

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.     

Interactions between the toxicity of the heavy metals cadmium,copper, zinc in combinations and the detoxifying role of calcium in the brown algaCystoseira barbata

The toxicity of three heavy metals, Cd, Cu and Zn, and the detoxifying role of Ca have been studied for the brown algaCystoseira barbata formaaurentia after a 4-week laboratory culture. The experimental design was based upon a complete factorial design 2^k, which seems to be the first time it has been used in algal physiology. It was demonstrated that these three elements, applied jointly, act on weight-growth, chlorophyll a, c and carotenoid synthesis and Cd, Cu and Zn uptake. Cd and Zn act in synergy or in antagony, depending on their exogenous concentrations, on chlorophyll a and on carotenoid synthesis. Zn is antagonistic towards Cd and Cu on weight-growth in the combination Cd-Cu-Zn. From different element combinations, the protective role of Ca appears evident on weight-growth (Cd-Zn-Ca and Cu-Ca), chlorophyll a (Cd-Cu-Ca and Cu-Zn-Ca), chlorophyll c (Cd-Ca), carotenoid synthesis (Cd-Cu-Ca and Cu-Zn-Ca), Cd and Cu uptake (Cd-Cu-Ca) and Zn uptake (Cu-Zn-Ca). This role is confirmed by cytological investigations. This is apparently the first report concerning a Ca interaction with toxicity of heavy metals applied in combinations. However, the mechanisms of tolerance remain unknown.     

Design of new inhibitors specific to the adenosine triphosphate binding site of DNA topoisomerases II

Summary DNA topoisomerases II are involved in the segregation of chromosomes which occurs after DNA replication. These enzymes proceed by nicking and resealing of a phosphodiester bond of the DNA double helix and require the hydrolysis of ATP into ADP and inorganic phosphate. Studies of ATP hydrolysis showed specific properties according to the source of isolation of the enzymes, suggesting the existence of an evolution of the ATP binding site of DNA topoisomerases II. In order to study this evolution, two experimental strategies were followed, first of all an analysis of the topography of the ATP binding site by forming UV crosslinks between ATP and the enzymes, and second the effects of new inhibitors.     

Plasmodium cynomolgi: immunization of a rhesus monkey with exoerythrocytic stages cultured in autologous hepatocytes

To investigate the immune response to exoerythrocytic stages of malaria parasites, a rhesus monkey was immunized with autologous primary hepatocyte cultures infected with 7-day-old liver stage parasites of Plasmodium cynomolgi. A primary antibody response against EE stage antigens was obtained, and boosted after injection of homologous viable sporozoites. Antibodies directed against sporozoites and blood stages were also detected. The polyvalent immune response observed demonstrates the antigenicity of the liver stages and suggests their involvement in the general immune response against malaria.     

High activity of inclusion bodies formed in Escherichia coli overproducing Clostridium thermocellum endoglucanase D

The formation of cytoplasmic inclusion bodies by Escherichia coli overproducing Clostridium thermocellum endoglucanase D (EGD) was investigated. EGD was found in inclusion bodies as a 68 kDa form, whereas the size of the cytoplasmic form was 65 kDa. Upon solubilization with urea followed by dialysis, the 68 kDa form was converted to the 65 kDa species. Proteolysis occurred within the COOH-terminal, reiterated region of the 68 kDa form, which is conserved among most C. thermocellum endoglucanases, but is not required for catalytic activity. The specific activity of the enzyme embedded in inclusion bodies was close to that of the purified protein. Thus, inclusion body formation does not involve denaturation of the catalytic domain of EGD, but, more likely, the participation of the reiterated, conserved region in intermolecular interactions.