Ubiquitous presence of the hammerhead ribozyme motif along the tree of life

Examples of small self-cleaving RNAs embedded in noncoding regions already have been found to be involved in the control of gene expression, although their origin remains uncertain. In this work, we show the widespread occurrence of the hammerhead ribozyme (HHR) motif among genomes from the Bacteria, Chromalveolata, Plantae, and Metazoa kingdoms. Intergenic HHRs were detected in three different bacterial genomes, whereas metagenomic data from Galapagos Islands showed the occurrence of similar ribozymes that could be regarded as direct relics from the RNA world. Among eukaryotes, HHRs were detected in the genomes of three water molds as well as 20 plant species, ranging from unicellular algae to vascular plants. These HHRs were very similar to those previously described in small RNA plant pathogens and, in some cases, appeared as close tandem repetitions. A parallel situation of tandemly repeated HHR motifs was also detected in the genomes of lower metazoans from cnidarians to invertebrates, with special emphasis among hematophagous and parasitic organisms. Altogether, these findings unveil the HHR as a widespread motif in DNA genomes, which would be involved in new forms of retrotransposable elements.     

Signaling events mediating activation of brain ethanolamine plasmalogen hydrolysis by ceramide.

Ceramide is a lipid second messenger that acts on multiple-target enzymes, some of which are involved in other signal-transduction systems. We have previously demonstrated that endogenous ceramide modifies the metabolism of brain ethanolamine plasmalogens. The mechanism involved was studied. On the basis of measurements of breakdown products, specific inhibitor effects, and previous findings, we suggest that a plasmalogen-selective phospholipase A2 is the ceramide target. Arachidonate-rich pools of the diacylphosphatidylethanolamine subclass were also affected by ceramide, but the most affected were plasmalogens. Concomitantly with production of free arachidonate, increased 1-O-arachidonoyl ceramide formation was observed. Quinacrine (phospholipase A2 inhibitor) and 1-O-octadecyl-2-O-methyl-rac-glycerol-3-phosphocholine (CoA-independent transacylase inhibitor) prevented all of these ceramide-elicited effects. Therefore, phospholipase and transacylase activities are tightly coupled. Okadaic acid (phosphatase 2A inhibitor) and PD 98059 (mitogen-activated protein kinase inhibitor) modified basal levels of ceramide and sphingomyelinase-induced accumulation of ceramide, respectively. Therefore, they provided no evidence to determine whether there is a sensitive enzyme downstream of ceramide. The evidence shows that there are serine-dependent and thiol-dependent enzymes downstream of ceramide generation. Furthermore, experiments with Ac-DEVD-CMK (caspase-3 specific inhibitor) have led us to conclude that caspase-3 is downstream of ceramide in activating the brain plasmalogen-selective phospholipase A2.     

The c-erbAα Protooncogene Induces Apoptosis in Glial Cells via a Protein Kinase C- and bcl-2-Suppressible Mechanism

Abstract: The c- erbA protooncogene encodes the thyroid hormone (3,5,3'-triiodothyronine; T₃) receptor α1 (TRα1). c- erbA /TRα1 is expressed in many cell types including glial cells, particularly in the immature state. We show here by morphological and biochemical criteria that c- erbA induces apoptosis of glial B3.1 cells in serum-deprived conditions. This effect is mostly T₃ independent. Growth factors such as platelet-derived growth factor, basic fibroblast growth factor, or transforming growth factor-α prevent B3.1 + TRα1 cell death. Protein kinase C(PKC) activators also prevent the apoptosis phenomenon, an effect that was blocked by the PKC-specific inhibitor GF109203X. Expression of an exogenous bcl-2 gene led also to B3.1 + TRα1 cell survival. Neither a series of inhibitors including GF109203X nor T₃ inhibits bcl-2 action, indicating that bcl-2 blocks a downstream step in the death-promoting process. B3.1 + TRα1 cell apoptosis is not blocked by caspase-1 or poly-ADP-ribosyltransferase inhibitors, suggesting that the activation of these classic pathways is not involved in the apoptotic mechanism. In addition, direct interaction with specific neuronal cells but not incubation with their conditioned medium inhibits also apoptosis of B3.1 + TRα1 cells. Our results show that c- erbA promotes an apoptotic process in glial B3.1 cells that is suppressible by PKC activation and bcl-2 , probably by distinct mechanisms.     

Heart Rate and Systolic Blood Pressure Variability in the Time Domain in Patients with Recent and Long-Standing Diabetes Mellitus

Diabetes Mellitus (DM) affects the cardiovascular response of patients. To study this effect, interbeat intervals (IBI) and beat-to-beat systolic blood pressure (SBP) variability of patients during supine, standing and controlled breathing tests were analyzed in the time domain. Simultaneous noninvasive measurements of IBI and SBP for 30 recently diagnosed and 15 long-standing DM patients were compared with the results for 30 rigorously screened healthy subjects (control). A statistically significant distinction between control and diabetic subjects was provided by the standard deviation and the higher moments of the distributions (skewness, and kurtosis) with respect to the median. To compare IBI and SBP for different populations, we define a parameter, α, that combines the variability of the heart rate and the blood pressure, as the ratio of the radius of the moments for IBI and the same radius for SBP. As diabetes evolves, α decreases, standard deviation of the IBI detrended signal diminishes (heart rate signal becomes more “rigid”), skewness with respect to the median approaches zero (signal fluctuations gain symmetry), and kurtosis increases (fluctuations concentrate around the median). Diabetes produces not only a rigid heart rate, but also increases symmetry and has leptokurtic distributions. SBP time series exhibit the most variable behavior for recently diagnosed DM with platykurtic distributions. Under controlled breathing, SBP has symmetric distributions for DM patients, while control subjects have non-zero skewness. This may be due to a progressive decrease of parasympathetic and sympathetic activity to the heart and blood vessels as diabetes evolves.     

Preliminary studies on the production ani composition of the extracellular polysaccharide synthesized byPseudomonas sp. EPS-5028

Summary Exopolysaccharide production byPseudomonas sp. strain EPS-5028 increased under conditions of high C/N ratios at the pH range 6.7–8 and 25°C. The polymer was formed from a variety of carbon substrates and contains D-glucose, D-galactose and uronic acid in the approximate molar ratio of 325. The polysaccharide produced is of high viscosity (1,600 cP; 1% polymer in D. I. water).     

Production of an Extracellular Polysaccharide by Haloferax mediterranei

The extremely halophilic archaebacterium Haloferax mediterranei produces an exocellular polymeric substance that gives the colonies a typical mucous character and is responsible for the appearance of a superficial layer in unshaken liquid medium. This exocellular polymeric substance can be obtained from the supernatant of shaken liquid cultures by cold ethanol precipitation, and yields as high as 3 mg/ml have been detected. The substance was produced under all the conditions tested and with all substrates assayed, although higher yields were obtained with sugars, particularly glucose, as carbon and energy source. The total exocellular polymeric substance produced was proportional to the total biomass. The polymer is a heteropolysaccharide containing mannose as the major component. Glucose, galactose, and another unidentified sugar were also present, as well as amino sugars, uronic acids, and a considerable amount of sulfate, which accounts for the acidic nature of the polymer. The infrared spectrum and specific assays showed the absence of acyl groups. The rheological properties of polymer solutions were studied, showing a pseudoplastic behavior and a high apparent viscosity at relatively low concentrations. Viscosity was remarkably resistant to extremes of pH, temperature, or salinity. These characteristics make this polymer interesting for enhanced oil recovery and other applications for which a very resistant thickening agent is required.     

Induction of Rat Brain Tubulin Following Ammonium Ingestion

The effect of oral administration of ammonium acetate for 2, 15, 30, and 100 days on protein synthesis in rat brain was investigated. Although protein synthesis changes were modest, i.e., maximal increase of 24%, there was induction of synthesis and accumulation of a protein with an Mr of 55,000. We show, on the basis of its position on two-dimensional electrophoresis and its immunological reactivity, that this protein is tubulin. Its content increased by 33% as determined by isolation of tubulin after 15 days of oral administration of ammonium and to 49% after 100 days as determined by quantitative immunoblotting.     

Development of a PCR assay combined with a short enrichment culture for detection of Campylobacter jejuni in estuarine surface waters

Abstract Two extraction procedures were examined, and it was found that DNA recovered from Campylobacter jejuni lysed by the cetyltrimethylammonium bromide (CTAB) method was more suitable for use as a PCR template than DNA released by the boiling method. The region targeted for PCR amplification was a 1.73-kb portion of the flagellin A gene of C. jejuni . The detection limit was lower than 30 cells per 100 ml in artificially contaminated waters. PCR assay and conventional culturing method had the same sensitivity, but results of the PCR technique were available within 48 h and so shortened the time necessary for detection by 48 h.