Réflexions critiques sur l'écologieet la systématique des Lingules actuelles et fossiles

New topics on ecology and systematics of recent and fossil Lingulids lead to an obvious revision of our knowledges on this zoological group. At first, the recent species need systematics and taxonomy on the bases of new described specific criteria (as, morphology of deltidial areas, muscle disposition); the results are briefly indicated. But, in fossil species, disorder and disparity of used characteristics are emphasized.The general conceiving on ecology of Lingulids are reviewed and discussed, especially on bathymetry and salinity; sediment and oxygenation conditions; taphocoenosis and lingulid «communities. On recent species, all these points are also studied, especially some ecological requirements (salinity, bathymetry, grain size), and mechanism of burrowing ability, burrow living positions in the sediments, as shell preservations after death and fossilization, to facilitate the paleobiotope interpretations. Recent animals are euryhalin, surviving at salinities from about 13 to 42‰; they could be considered as well adapted to waters with strong salinity fluctuations. They show preference to fine sand bottoms (lowest particle size about 40–60 μm). Their bathymetric distribution occurs between 0 and about 500 m (Lingula especially between 5–50 m; Glottidia 15–70 m). The isotherms 8–10°C seem to restrict their geographical and bathymetric distribution.Therefore, some post-palaeozoic lingulid bedsare studied or redescribed on the bases of the above discussed characteristics, and new interpretations on the environmental situation are given (Trias of Vosges Mountains; Oligocene from Japan; Eocene of London Basin). More caution must be used in study of fossil Lingulids that are not especially animals living in infralittoral bottoms with low salinity and deficient oxygenation, as generally accepted.     

Nuclear magnetic resonance study of hydrogen-bonded ring protons in oligonucleotide helices involving classical and nonclassical base pairs.

A study of the exchangeable ring nitrogen protons in aqueous solutions of oligonucleotide complexes involving Watson-Crick base pairs as well as Hoogsteen pairs and other nonclassical hydrogen bonding schemes shows that resolvable resonances in the low-field (-10 to -16 ppm from sodium 4,4-dimethyl-4-silapentanesulfonate) region can be detected in a variety of structures other than double stranded helices. Ring nitrogen proton resonances arising from the following hydrogen-bonding situations are reported: (1) AT and GC Watson-Crick base pairs in a self-complementary octanucleotide, dApApApGpCpTpTpT; (2) U-A-U base triples in complexes between oligo-U15 and AMP; (3) C-G-C+ base triples in complexes between oligo-C17 and GMP at acid pH; (4) s4U-A-s4U base triples in complexes between oligo-s4U15 and AMP, all of which involve both Watson-Crick and Hoogsteen base pairing to form triplexes; (5) C-C+ base pairing between protonated and unprotonated C residues in oligo-C17 at acid pH; and (6) I4 base quadruples in the four strand association among oligo-I at high salt. The behavior of the dA3G-CT3 helix is consistent with both fraying of the terminal base pairs and presence of intermediate states as the helix opens. In the monomer-oligomer complexes, under the conditions used here, the exchange appears to be governed by the dissociation rate of monomer from the complex. These findings suggest that those tertiary structure hydrogen bonds in tRNA involving ring nitrogen protons should have representative resonances in the low-field (11-16 ppm) proton NMR region in H2O.     

Systematic relationships in the narrow-leaved species of chenopodium of the Western United States

Brittonia - In a study of ten taxa ofChenopodium occurring primarily in the western United States and designated as the narrow-leaved complex, data from morphology, flavonoid chemistry, and somatic...     

Interactions of lectins with (Na+ + K+)-ATPase of eel electric organ.

Interaction of lectins with a detergent-solubilized ATPase from eel electric organ was studied. Concanavalin A, which binds to alpha-mannosides, altered the rate of enzyme migration in agar and inhibited the formation of an antigen-antibody precipitate: other lectins had no such effects. Concanavalin A similar amounts partially inhibited (Na+ + K+)-ATPase; this inhibition was reversible by alpha-methylglucoside. There was no corresponding effect of concanavalin A on the potassium p-nitrophenylphosphatase. Concanavalin A also did not interfere with ouabain binding. Thus, concanavalin A binds to an antigenic region also involved in Na+ and/or ATP binding, but does not interact with a K+ site.     

VAMP2 and synaptotagmin mobility in chromaffin granule membranes: implications for regulated exocytosis

Granule-plasma membrane docking and fusion can only occur when proteins that enable these reactions are present at the granule-plasma membrane contact. Thus, the mobility of granule membrane proteins may influence docking and membrane fusion. We measured the mobility of vesicle associated membrane protein 2 (VAMP2), synaptotagmin 1 (Syt1), and synaptotagmin 7 (Syt7) in chromaffin granule membranes in living chromaffin cells. We used a method that is not limited by standard optical resolution. A bright flash of strongly decaying evanescent field produced by total internal reflection was used to photobleach GFP-labeled proteins in the granule membrane. Fluorescence recovery occurs as unbleached protein in the granule membrane distal from the glass interface diffuses into the more bleached proximal regions, enabling the measurement of diffusion coefficients. We found that VAMP2-EGFP and Syt7-EGFP are mobile with a diffusion coefficient of ∼3 × 10⁻¹⁰ cm²/s. Syt1-EGFP mobility was below the detection limit. Utilizing these diffusion parameters, we estimated the time required for these proteins to arrive at docking and nascent fusion sites to be many tens of milliseconds. Our analyses raise the possibility that the diffusion characteristics of VAMP2 and Syt proteins could be a factor that influences the rate of exocytosis.     

Effect of High-Intensity Interval Training on Cardiac Apoptosis Markers in Methamphetamine-Dependent Rats

Chronic methamphetamine use increases apoptosis, leading to heart failure and sudden cardiac death. Previous studies have shown the importance of high-intensity interval training (HIIT) in reducing indices of cardiac tissue apoptosis in different patients, but in the field of sports science, the molecular mechanisms of apoptosis in methamphetamine-dependent rats are still unclear. The present article aimed to investigate the changes in cardiac apoptosis markers in methamphetamine-dependent rats in response to HIIT. Left ventricular tissue was used to evaluate caspase-3, melusin, FAK, and IQGAP1 gene expression. Rats were divided into four groups: sham, methamphetamine (METH), METH-control, and METH-HIIT. METH was injected for 21 days and then the METH-HIIT group performed HIIT for 8 weeks at 5 sessions per week. The METH groups showed increased caspase-3 gene expression and decreased melusin, FAK, and IQGAP1 when compared to the sham group. METH-HIIT showed decreased caspase-3 and increased melusin and FAK gene expression compared with the METH and METH-control groups. The IQGAP1 gene was higher in METH-HIIT when compared with METH, while no difference was observed between METH-HIIT and METH-control. Twenty-one days of METH exposure increased apoptosis markers in rat cardiac tissue; however, HIIT might have a protective effect, as shown by the apoptosis markers.