Three-dimensional reconstruction of the hexagonal bilayer hemoglobin of the hydrothermal vent tube worm Riftia pachyptila by cryoelectron microscopy

A frozen-hydrated specimen of the V1 hemoglobin of the hydrothermal vent tube worm Riftia pachyptila was observed in the electron microscope and subjected to three-dimensional reconstruction by the method of random conical tilt series. The 3D volume possesses a D₆ point-group symmetry. When viewed along its 6-fold axis the vertices of its upper hexagonal layer are 16° clockwise rotated compared to those of the lower layer. A central linker complex is decorated by 12 hollow globular substructures. The linker complex comprises (i) a central hexagonal toroid, (ii) two internal bracelets onto which the hollow globular substructures are built, and (iii) six structures connecting the two hexagonal layers. The hollow globular substructures, related to the dodecamers of globin chains resulting from the dissociation of the hexagonal bilayer hemoglobin, have a local pseudo 3-fold symmetry and are composed each of three elongated structures visible when the volume is displayed at high threshold. At a resolution of 36 Å, the 3D volumes of the hexagonal bilayer hemoglobins of Riftia pachyptyla and of the leech Macrobdella decora look almost perfectly identical. © 1996 Wiley-Liss, Inc.     

Ascidian embryos: from the birth of experimental embryology to the analysis of gene regulatory networks

Ascidian embryos were the first animal embryos to be experimentally manipulated by Man at the end of the 19th century. The mosaic theory of development was born from these experiments and those carried out by Conklin 20 years later. These astonishing animals, some of which are eaten as delicacies in France and other countries, belong to the tunicates, which are the only animals to produce cellulose. They are, however, the closest living relatives to the vertebrates. Neglected throughout most of the 20th century, ascidians have recently come back in the limelight in the wake of the sequencing of the genomes of Ciona intestinalis and Ciona savignyi. These small, unduplicated genomes harbour 16,000 to 20,000 genes and are 20 times smaller than the human genome. Ciona eggs can be microinjected and easily electroporated, which make this system suitable for the study of developmental gene regulatory networks.     

Hormone-regulated expression and distribution of versican in mouse uterine tissues

Background  

Remodeling of the extracellular matrix is one of the most striking features observed in the uterus during the estrous cycle and after hormone replacement. Versican (VER) is a hyaluronan-binding proteoglycan that undergoes RNA alternative splicing, generating four distinct isoforms. This study analyzed the synthesis and distribution of VER in mouse uterine tissues during the estrous cycle, in ovariectomized (OVX) animals and after 17beta-estradiol (E2) and medroxyprogesterone (MPA) treatments, either alone or in combination.     

Interaction of cationic bilayer fragments with a model oligonucleotide

The interaction between cationic bilayer fragments and a model oligonucleotide was investigated by differential scanning calorimetry, turbidimetry, determination of excimer to monomer ratio of 2-(10-(1-pyrene)-decanoyl)-phosphatidyl-choline in bilayer fragment dispersions and dynamic light scattering for sizing and zeta-potential analysis. Salt (Na?HPO?), mononucleotide (2'-deoxyadenosine-5'-monophosphate) or poly (dA) oligonucleotide (3'-AAA AAA AAA A-5') affected structure and stability of dioctadecyldimethylammonium bromide bilayer fragments. Oligonucleotide and salt increased bilayer packing due to bilayer fragment fusion. Mononucleotide did not reduce colloid stability or did not cause bilayer fragment fusion. Charge neutralization of bilayer fragments by poly (dA) at 1:10 poly (dA):dioctadecyldimethylammonium bromide molar ratio caused extensive aggregation, maximal size and zero of zeta-potential for the assemblies. Above charge neutralization, assemblies recovered colloid stability due to charge overcompensation. For bilayer fragments/poly (dA), the nonmonotonic behavior of colloid stability as a function of poly (dA) concentration was unique for the oligonucleotide and was not observed for Na?HPO? or 2'-deoxyadenosine-5'-monophosphate. For the first time, such interactions between cationic bilayer fragments and mono- or oligonucleotide were described in the literature. Bilayer fragments/oligonucleotide assemblies may find interesting applications in drug delivery.     

Peroxynitrite reacts with biological nitrogen-containing cyclic molecules by a radical pathway, as demonstrated by ultraweak luminescence coupled with ESR technique.

Ultraweak luminescence (uwCL) was coupled with electron spin resonance to study the reactions of 3 heterocyclic compounds (tryptophan, serotonin and imidazole) with peroxynitrite at pH 8.7. Tryptophan and serotonin reacted with emission of a flash peak of light (5 s) followed by a long-living light emission of +/- 80 s. Addition of the spin trap 4-POBN at different intervals, after the beginning of reaction revealed that a short-living free radical was produced in the case of serotonin and imidazole, but that with tryptophan, the initial radical rearranged into a relatively long-living radical, which was still formed when 4-POBN was added after 55 s (decreasing phase of uwCL).