Invivo effect of adenosine on adenine nucleotides and inorganic phosphate in rat blood

The effect of adenosine and the time response on adenine nucleotide and Pi levels in rat blood was investigated. an increase in adenine nucleotide with a concommitant decrease in Pi concentration 30, 60, and 90 minutes after the nucleoside administration were observed. Though the 100 mg/Kg dose showed the highest effect on nucleotide concentration, the maximal response on Pi content was achieved with the 50 mg/Kg dose. The results are discussed at the light of previous data obtained in hepatocytes, and using as indicators the energy charge and the phosphorylation potential.     

The influence of wind-induced mixing on the vertical distribution of buoyant and sinking phytoplankton species

In this study we exploit recent advances in high-resolution autonomous monitoring to investigate the impact of short-term variations in wind-induced mixing on the surface biomass and vertical distribution of buoyant and sinking phytoplankton species. An autonomous platform (the Automatic Water Quality Monitoring Station) moored in a Mediterranean reservoir provided minute-by-minute records of wind speed and the phytoplankton fluorescence during winter and summer. This information was then used here to quantify the impact of short-term changes in the weather on the vertical distribution of diatoms and cyanobacteria. Additionally, we apply an empirical model to determine the extent of entrainment of diatoms and cyanobacteria within the turbulent upper layers of the water column. During winter, the surface time series of fluorescence was positively correlated with the short-term variations in wind speed. In contrast, during the summer, fluorescence was negatively correlated with wind speed. In the latter case, turbulence overcame the flotation velocity of buoyant cyanobacteria, thus homogenizing their vertical distribution and decreasing surface biomass. In both cases, the dynamic response of surface phytoplankton biomass to short-term changes in wind stress was rapid, within the minute scale. As far as we know from the literature, this is the first study in which the interaction between wind stress and surface phytoplankton fluorescence has been quantified on such a fine temporal scale. Finally, relevance for forecasting and reservoir management is pointed out.     

Cytogenetic damage of bone marrow cells produced by chronic alcohol consumption

Pair-feeding of rats with nutritionally adequate liquid diets containing 36% of total energy either as ethanol or as additional carbohydrate (in the controls) resulted in blood ethanol concentrations similar to those observed in alcoholics. Alcohol feeding for six weeks increased the frequency of micronuclei in bone marrow erythrocytes, an index of chromosomal damage in precursor cells. This was associated with bone marrow hypoplasia and erythrocyte macrocytosis, alterations commonly found in alcoholics. By contrast, acute ethanol administration produced no changes in the bone marrow. Cytogenetic damage of stem cells could lead to alterations persisting after alcohol withdrawal beyond the life span of effector cells.     

Biological properties of the phage-tail-like particles from Myxococcus coralloides D

Abstract Electron microscopy of preparations of the Myxocococcus coralloides D autolytic supernatants revealed the presence of phage-tail-like particles. The particles consisted of a core, a contractile sheath and a baseplate with fibers. The induction of the defective prophage occurred when the cultures reached the stationary phase, but the events occurring during induction did not lead to cell lysis. Particles nerver appeared during exponential growth. They were not observed when M. coralloides D grew on solid media, either. Purified samples of phage tails were able to inhibit most of the myxobacterial strains which were tested when the particles were in the extended state, but they were unable to multiply on the sensitive strains.     

Structure of the Saccharomyces cerevisiae cell wall: Mannoproteins released by zymolyase and their contribution to wall architecture

Purified zymolyase containing β-glucanase activity preferentially released a 29 kDa mannoprotein from isolated yeast cell walls and a high-molecular-mass (greater than 120 kDa) material. Endo-β-N-acetylglucosaminidase H digestion indicated that the 29 kDa mannoprotein contains a unique core coligosaccharide N-glycosidically linked to a 26 kDa peptide moiety. Cells grown in the presence of tunicamycin incorporated the nonglycosylated 26 kDa peptide into the wall, but not the large mannoprotein molecules. Treatment of isolated walls with SDS solubilized more than 30 different mannoproteins, one of tehm being the 29 kDa species, but the large-size molecules were not affected. Regenerating protoplasts incorporated into the forming walls most of the SDS-solubilizable species seen in mature cell walls, but the zymolyase-solubilizable mannoproteins were absent. Wall mannoproteins have also been compared with those of the periplasmic space, most of the species being commonly present at both compartments. Turnover of individual species has been studied by pulse and chase experiments. While mannoproteins from the walls remain stable for long periods, periplasmic molecules exhibit a rapid turnover rate.     

Ligand binding and self‐association cooperativity of β‐lactoglobulin

Unlike most small globular proteins, lipocalins lack a compact hydrophobic core. Instead, they present a large central cavity that functions as the primary binding site for hydrophobic molecules. Not surprisingly, these proteins typically exhibit complex structural dynamics in solution, which is intricately modified by intermolecular recognition events. Although many lipocalins are monomeric, an increasing number of them have been proven to form oligomers. The coupling effects between self‐association and ligand binding in these proteins are largely unknown. To address this issue, we have calorimetrically characterized the recognition of dodecyl sulfate by bovine β‐lactoglobulin, which forms weak homodimers at neutral pH. A thermodynamic analysis based on coupled‐equilibria revealed that dimerization exerts disparate effects on the ligand‐binding capacity of β‐lactoglobulin. Protein dimerization decreases ligand affinity (or, reciprocally, ligand binding promotes dimer dissociation). The two subunits in the dimer exhibit a positive, entropically driven cooperativity. To investigate the structural determinants of the interaction, the crystal structure of β‐lactoglobulin bound to dodecyl sulfate was solved at 1.64 Å resolution. Copyright © 2013 John Wiley & Sons, Ltd.     

Deciphering the Acylation Pattern of Yersinia enterocolitica Lipid A

Pathogenic bacteria may modify their surface to evade the host innate immune response. Yersinia enterocolitica modulates its lipopolysaccharide (LPS) lipid A structure, and the key regulatory signal is temperature. At 21°C, lipid A is hexa-acylated and may be modified with aminoarabinose or palmitate. At 37°C, Y. enterocolitica expresses a tetra-acylated lipid A consistent with the 3′-O-deacylation of the molecule. In this work, by combining genetic and mass spectrometric analysis, we establish that Y. enterocolitica encodes a lipid A deacylase, LpxR, responsible for the lipid A structure observed at 37°C. Western blot analyses indicate that LpxR exhibits latency at 21°C, deacylation of lipid A is not observed despite the expression of LpxR in the membrane. Aminoarabinose-modified lipid A is involved in the latency. 3-D modelling, docking and site-directed mutagenesis experiments showed that LpxR D31 reduces the active site cavity volume so that aminoarabinose containing Kdo₂-lipid A cannot be accommodated and, therefore, not deacylated. Our data revealed that the expression of lpxR is negatively controlled by RovA and PhoPQ which are necessary for the lipid A modification with aminoarabinose. Next, we investigated the role of lipid A structural plasticity conferred by LpxR on the expression/function of Y. enterocolitica virulence factors. We present evidence that motility and invasion of eukaryotic cells were reduced in the lpxR mutant grown at 21°C. Mechanistically, our data revealed that the expressions of flhDC and rovA, regulators controlling the flagellar regulon and invasin respectively, were down-regulated in the mutant. In contrast, the levels of the virulence plasmid (pYV)-encoded virulence factors Yops and YadA were not affected in the lpxR mutant. Finally, we establish that the low inflammatory response associated to Y. enterocolitica infections is the sum of the anti-inflammatory action exerted by pYV-encoded YopP and the reduced activation of the LPS receptor by a LpxR-dependent deacylated LPS.