Date Palm DNA Mini-Preparation without Liquid Nitrogen

We have developed a new mini-procedure for isolation of total cellular DNA from date palm (Phoenix dactylifera L.). The procedure, which does not use liquid nitrogen, has proved useful due to temporary disruptions in supplies of liquid nitrogen that occur in countries where date palm trees are cultivated. DNA suitable for RFLP and PCR analyses is obtained.     

The HIV-1 Integrase Mutations Y143C/R Are an Alternative Pathway for Resistance to Raltegravir and Impact the Enzyme Functions

Resistance to HIV-1 integrase (IN) inhibitor raltegravir (RAL), is encoded by mutations in the IN region of the pol gene. The emergence of the N155H mutation was replaced by a pattern including the Y143R/C/H mutations in three patients with anti-HIV treatment failure. Cloning analysis of the IN gene showed an independent selection of the mutations at loci 155 and 143. Characterization of the phenotypic evolution showed that the switch from N155H to Y143C/R was linked to an increase in resistance to RAL. Wild-type (WT) IN and IN with mutations Y143C or Y143R were assayed in vitro in 3′end-processing, strand transfer and concerted integration assays. Activities of mutants were moderately impaired for 3′end-processing and severely affected for strand transfer. Concerted integration assay demonstrated a decrease in mutant activities using an uncleaved substrate. With 3′end-processing assay, IC₅₀ were 0.4 µM, 0.9 µM (FC = 2.25) and 1.2 µM (FC = 3) for WT, IN Y143C and IN Y143R, respectively. An FC of 2 was observed only for IN Y143R in the strand transfer assay. In concerted integration, integrases were less sensitive to RAL than in ST or 3′P but mutants were more resistant to RAL than WT.     

A comparative study of chromatin from lymphocyte nuclei upon activation of transcription by irradiation from an He-Ne-laser or phytohemagglutinin]

The influence of He-Ne laser radiation (632.8 nm, 56 J/m2, t = 10 s) and phytohaemagglutinin (PHA, 2 micrograms/ml) on chromatin structure in human lymphocytes was studied by electron microscopy using ultrathin cell sections. Morphometric analysis of extranuclear condensed chromatin masses was performed 1 h after the irradiation or after the beginning of PHA treatment. In the irradiated cells the following insignificant changes were revealed: decrease in the relative area of the nucleoplasmic chromatin, increase in the relative area of decondensation zones as well as increase in the number of clumps of nucleoplasmic chromatin and relative length at their boundary with nucleoplasma. The tendency of these morphological changes may be interpreted as functional activation of extranucleolar RNA synthesis in response to irradiation by red laser light. Action of PHA results in significant changes of the surfaces of chromatin clumps, namely increase in relative length of nucleoplasmic chromatin boundary and decrease in relative length of perimembranous chromatin boundary with nucleoplasma as well as some less expressed delamination of the chromatin masses from the nuclear membrane. These essential changes may reflect chromatin activation by proliferative stimulus. Peculiarities of the ultrastructural reorganisation in the condensed chromatin after irradiation and PHA-treatment probably reflect the differences in the processes of gene activation caused by the two agents.     

Dissociating Two Stages of Preparation in the Stop Signal Task Using fMRI

Often we must balance being prepared to act quickly with being prepared to suddenly stop. The stop signal task (SST) is widely used to study inhibitory control, and provides a measure of the speed of the stop process that is robust to changes in subjects’ response strategy. Previous studies have shown that preparation affects inhibition. We used fMRI to separate activity that occurs after a brief (500 ms) warning stimulus (warning-phase) from activity that occurs during responses that follow (response-phase). Both of these phases could contribute to the preparedness to stop because they both precede stop signals. Warning stimuli activated posterior networks that signal the need for top-down control, whereas response phases engaged prefrontal and subcortical networks that implement top-down control. Regression analyses revealed that both of these phases affect inhibitory control in different ways. Warning-phase activity in the cerebellum and posterior cingulate predicted stop latency and accuracy, respectively. By contrast, response-phase activity in fronto-temporal areas and left striatum predicted go speed and stop accuracy, in pre-supplementary motor area affected stop accuracy, and in right striatum predicted stop latency and accuracy. The ability to separate hidden contributions to inhibitory control during warning-phases from those during response-phases can aid in the study of models of preparation and inhibitory control, and of disorders marked by poor top-down control.     

Presence and Analysis of Plasmids in Human and Animal Associated Arcobacter Species

In this study, we report the screening of four Arcobacter species for the presence of small and large plasmids. Plasmids were present in 9.9% of the 273 examined strains. One Arcobacter cryaerophilus and four Arcobacter butzleri plasmids were selected for further sequencing. The size of three small plasmids isolated from A. butzleri and the one from A. cryaerophilus strains ranged between 4.8 and 5.1 kb, and the size of the large plasmid, isolated from A. butzleri, was 27.4 kbp. The G+C content of all plasmids ranged between 25.4% and 26.2%. A total of 95% of the large plasmid sequence represents coding information, which contrasts to the 20 to 30% for the small plasmids. Some of the open reading frames showed a high homology to putative conserved domains found in other related organisms, such as replication, mobilization and genes involved in type IV secretion system. The large plasmid carried 35 coding sequences, including seven genes in a contiguous region of 11.6 kbp that encodes an orthologous type IV secretion system found in the Wolinella succinogenes genome, Helicobacter pylori and Campylobacter jejuni plasmids, which makes this plasmid interesting for further exploration.     

Chrysonila sitophila (TFB-27441): A hyperlignolytic strain

Summary C. sitophila strain TFB-27441 showed 2–3 times higher lignolytic activity thanPhanerochaete chrysosporium (BKM-F-1767 strain). Lignin had a marked effect on the ligninase activity indicating that some induction or activation mechanism is involved in lignin degradation byC. sitophila.     

An evaluation of the recycling in measurements of photorespiration

All measurements of photorespiration and gross photosynthesis in leaves, whether using isotopes or not, are underestimated because of the recycling of O₂ or CO₂. On the basis of a simple diffusion model, we propose a method for the calculation of the recycling and the corresponding underestimation of the measurements. This procedure can be applied when the stomatal resistance is known, and allows for a correction of certain results in the literature. It is found that measurements of the photorespiratory CO₂ release are usually underestimated by 20 to 100%, which sets the estimated rate of CO₂ photorespired at 30 to 50% of the net photosynthesis in C3 plants under normal conditions. In water stress studies, the correction of the photorespiration is still more important (1.5-3.3) because the stomata are closed more. Analysis of the diffusion of O₂ shows that its recycling is low and that the underestimation of photorespiration with ¹⁸O₂ is negligible.     

Properties of the estrogen receptors contained in the MtTF4 tumor whose growth is inhibited by estradiol: 17 beta-estradiol, 17 alpha-estradiol and DNA bindings

The steroid and the DNA bindings of the estrogen receptor of the MtTF4 tumor whose growth is inhibited by estradiol where characterized and compared to those of uterine estrogen receptors. In the tumor cytosol: E protects its binding sites against thermal denaturation, depending on the effects of sodium molybdate upon the dissociation rate of [3H]E at 20 degrees C and the ability of receptor to bind to DNA, the activation (or transformation) process, supposed to be necessary for the full action of estrogen ligand, occurs on estrogen receptor complexes and the calf thymus DNA interacts with estrogen receptor with an affinity similar to that of uterine estrogen receptor. Kinetic and equilibrium studies with 17 alpha-[3H]E both in uterus and tumor indicate that this ligand is fast-associating, fast-dissociating and that its affinity for ER is 2- to 4-fold lower than that of 17 beta-[3H]estradiol one. Competition experiments between 17 beta-[3H]estradiol and the unlabelled 17 alpha epimer reveal, in both uterus and tumor, a time-dependent decrease of the apparent potency of 17 alpha-E to inhibit the binding of [3H]E. It is concluded that the estrogen receptors are very similar in MtTF4 tumor and uterus and the diversity of the response of cell growth to E is due rather to differences at the post-receptor level.     

Preferential Photosynthetic Uptake of Exogenous HCO(3) in the Marine Macroalga Chondrus crispus

The rate of HCO₃⁻ uptake by the red macroalga Chondrus crispus has been investigated. Unbalanced concentrations of free CO₂ and HCO₃⁻, generated by the photosynthetic activity, were detected in steady state conditions by using an exchange column apparatus linked to an assimilation chamber. Observing the variations of this gradient as influenced by the time of seawater transit from the assimilation chamber towards the column allowed an experimental determination of: (a) the actual gradient created by the photosynthetic activity, (b) the rate constant of the chemical conversion of free CO₂ to HCO₃⁻. With a value of 0.115 per second at pH 8.92, this rate constant was in good agreement with a previous estimation. By using a simple model, we show that the photosynthetic rate of HCO₃⁻ consumption can be estimated by the product of the actual gradient and the rate constant. In the conditions of the experiments reported here, this rate represented more than 90% of the whole photosynthetic flux.