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H Lucas

Publications and source records attributed to H Lucas.

At least 37 records · Page 2Linked to original sources
PubMed1995

Composition of human zona pellucida as revealed by SDS-PAGE after silver staining.

The macromolecular composition of zona pellucida (ZP) isolated from human oocytes and embryos was characterized by one- and two-dimensional sodium dodecyl sulfate polyacrylamide gel electrophoresis (1-D- and 2-D-SDS-PAGE) under reducing conditions after silver staining. ZP specimens obtained after in vitro fertilization were removed from pools of heavily fragmented embryos and inseminated oocytes that failed to fertilize. For unfertilized oocytes, two major bands with an apparent molecular weight of, respectively, 96 and 76-54 kDa were observed after 1-D-SDS-PAGE and silver staining. When ZP were isolated from fragmented embryos, the electrophoretic pattern showed a marked attenuation of the 96-kDa band. Silver-stained 2-D-SDS-PAGE analysis of ZP components from unfertilized oocytes revealed the presence of four protein trains: ZP1 (Mr = 92-80 kDa, pl = 4.9-5.9), ZP2 (Mr = 66-58 kDa, pl = 5.0-6.0), ZP3H (high) (Mr = 72-58 kDa, pl = 3.5-5.1), and ZP3L (low) (Mr = 62-54 kDa, pl = 3.5-5.1). The human ZP3 family (ZP3H and ZP3L) showed marked heterogeneity. Fertilization-associated changes were apparent in the electrophoretic pattern. ZP1 (Mr = 92-86 kDa, pl = 5.0-5.8) displayed a dramatic decrease in intensity, and a new component had migrated to a position similar to that of ZP2. This modification may have been responsible for one aspect of the zona reaction, and could have contributed to a zona block to polysperma.

Electrophoresis, Gel, Two-Dimensional↗
PubMed1995

[Identification of spermatozoa L-selectin and two potential pellucida ligands].

At the molecular level, gamete interactions partly depend on zona pellucida-glycoproteins fucosylation. We show, by immunocytochemistry, the sialyl-lewisx and sialyl-lewisa oligosaccharides on human zonae pellucidae. These epitopes are potential ligands of cell adhesion molecules named selectins which are known to play a role in endothelium-leukocyte interactions. By immunofluorescence, we find the leukocyte selectin (L-selectin) on the spermatozoa head. Preincubation of spermatozoa with an anti-L-selectin monoclonal antibody produces a significant inhibition of zona pellucida tight binding, under hemizona assay conditions. In contrast, preincubation of the zonae pellucidae with anti-sialyl-lewisx or anti-sialyl-lewisa antibodies does not produce a significant inhibition of spermatozoa binding. Western blot analysis of spermatozoa-detergent extracts revealed a band at approximatively 90 kDa with the anti-L-selectin monoclonal antibody. This spermatozoa selectin could play a role in human spermatozoa-zona pellucida binding. Zona-ligands have yet to be precisely defined.

Blotting, Western↗
PubMed1994

Functional analysis of the tobacco Tnt1 retrotransposon.

Retroelements represent by far the largest and most widespread class of mobile genetic elements. Representative of several classes of retrotransposons have been characterized in a broad range of plant species, but only a few of them have been shown to be active. Among these, the tobacco Tnt1 retrotransposon has been isolated after insertion mutagenesis and is one of the very few to be transcriptionally active. Tnt1 expression is strongly regulated in a tissue-specific and developmental manner. Moreover, Tnt1 expression is induced by a range of biotic or abiotic elicitors, which all have in common the ability to induce the plant defense response. Regulatory sequences involved in this elicitor-mediated induction have been located in the LTR U3 region. The link between Tnt1 activation and the plant defense response might represent an example of the involvement of transposable elements in genome restructurations needed in response to environmental fluctuations such as pathogen attacks.

Base Sequence↗
PubMed1994

Feasible synthesis and biological properties of six 'non-glycosamino' glycan analogues of the antithrombin III binding heparin pentasaccharide.

In this paper, we report the synthesis of 'non-glycosamino' glycan analogues 5-10 of the antithrombin III binding pentasaccharide 1. Pentasaccharides 5-10 feature a pseudo-alternating EFGH tetrasaccharide sequence, that is, the disaccharide fragments EF and GH have the same substitution pattern. In the synthetic strategy applied for the synthesis of pentasaccharides 5-10, the properly protected EF disaccharide fragments 19 and 20 are obtained from their GH counterparts 17 and 18 by base-catalyzed epimerization. Series I, comprising pentasaccharides 5-7, has an invariable EFGH tetrasaccharide containing 2-O-sulfate 3-O-methyl uronic acid moieties. Series II, on the other hand, contains pentasaccharides 8-10 and has an invariable EFGH tetrasaccharide containing 2,3-di-O-methyl uronic acid moieties. Coupling disaccharides 17 with 25 and 18 with 26 exclusively afforded the alpha-coupled tetrasaccharides 27 and 28, respectively. Glycosylation of acceptor tetrasaccharides 29 and 30 with glucosyl donors 35, 36 and 39 provided, after deprotection and sulfation, the title-compounds 5-10. Biological data obtained with series I and II indicate that the in vivo half-life but not the intrinsic anti-Xa activity depends on the substitution pattern of the D-unit. In addition, the applicability of reversed UV capillary electrophoresis as an analytical tool to determine the purity of these 'non-glycosamino' glycans is demonstrated.

Amino Acid Sequence↗
PubMed1994

A fucose-containing epitope potentially involved in gamete interaction on the human zona pellucida.

The oligosaccharide moiety of human, porcine and bovine zonae pellucidae was studied with lectins and monoclonal antibodies specific for tri- or tetra-saccharidic epitopes containing at least one terminal alpha-L-fucose. Animal eggs were collected from follicular aspirates, human eggs were collected from in-vitro fertilization and embryo transfer programmes and pooled into six groups. By direct immunofluorescence, the lectins reactivity was detected for the animal or the human zonae pools in the same way. Reactivity of Aleuria aurantia lectin demonstrated the presence of alpha-L-fucose terminal residues in the zonae from the three species studied. By indirect immunofluorescence, the 2-25 antibody reactivity was detected in every pool of human zonae whereas there was no evidence of any antibody reactivity on animal zonae. Using an anti-Lewis-b blood group antibody (2-25), we observed expression of this antigen as an intrinsic component of the human zona pellucida, independently of patients' Lewis red blood cell phenotypes. Antibody 2-25 inhibited the spermatozoa-zona binding in a hemizona assay, suggesting that this fucose-containing antigen could be part of a sperm-zona receptor.

Animals↗
PubMed1992

Sequence analysis of WIS-2-1A, a retrotransposon-like element from wheat.

WIS-2-1A, a 8624 bp insertion in the Glu-1A-2 locus of chromosome 1A of wheat, consists of two 1755 bp long terminal repeats enclosing a 5114 bp internal region. No long open reading frames could be found, but inspection of the predicted amino acid sequence showed regions with homology to retrotransposon structures, including a methionine tRNA initiator binding site, a nucleotide binding domain, a protease, an integrase and a polymerase. DNA replication errors have resulted in frame-shifts in the protein coding region, suggesting that retrotransposition of WIS-2-1A, if it occurs, must be mediated by trans-acting factors.

Amino Acid Sequence↗
PubMed1992

Inverted repeats in the long-terminal repeats of the wheat retrotransposon Wis 2-1A.

The wheat insertion sequence Wis 2-1A possesses all the structural features characteristic of retrotransposons. Its long-terminal repeats (LTRs) are unusually long (1,755 bp) compared with those of other retrotransposons. Sequence analysis revealed that they differ from each other by only six point mutations. They contain a few tandem direct repeats, which could be explained by slippage mechanisms during replication. Almost half (44%) of the length of the LTRs is occupied by hairpin structures, which may relate to their large size. Possible origins of these inverted repeats are proposed, including the insertion and imprecise excision of transposable elements and errors when the DNA replication intermediate switches RNA template during retrotransposon replication.

Base Sequence↗
PubMed1991

A family of retrotransposons and associated genomic variation in wheat.

A family of related retroelements was characterized in the genomes of some Graminease species. The structure of these retroelements indicates that they are retrotransposons containing reading frames with sequence similarity to the polyproteins of copia and Ty. This family of retroelements (termed WIS-2) occurs in the genomes of barley, wheat, rye, oats, and Aegilops species. Ongoing genomic variation both within individual plants of a wheat variety and within and between varieties of wheat is associated with some members of the WIS-2 family.

Amino Acid Sequence↗
PubMed1990

An internal part of the chloroplast atpA gene sequence is present in the mitochondrial genome of Triticum aestivum: molecular organisation and evolutionary aspects.

An internal part of the chloroplast atpA gene has been identified in the mitochondrial DNA of Triticum aestivum. It is located near the 18S-5S ribosomal genes and partially contained within a repeated sequence. Comparison of the transferred sequence with the original ct sequence reveals several nucleotide changes and shows that neither 5' nor 3' ends are present in the mt genome. No transcript of this region could be detected by Northern analysis. This sequence is present in mitochondrial genomes of other tetraploid and diploid species of Triticum, also in the vicinity of the 18S-5S ribosomal genes, suggesting a unique transfer event. The date of this event is discussed.

Adenosine Triphosphatases↗
PubMed1990

[Antigenicity and allergenicity of acarians. Study of 7 varieties in a population of 33 allergic patients].

A population of 33 patients who were known to be sensitive to mites were studied by the authors to establish whether 7 types of mites were responsible. A complementary and comparative study by the same Immunology laboratory compared the RAST and TDBH values as an addition to the skin test responses. The role of storage mites seemed to be sufficiently clear to advise increase in systematic research. The discovery of possibly frequent presence of Pyroglyphus africanus was a discovery that justifies other epidemiological and ethnic investigations.

Adult↗
PubMed1981

'Preparedness' and the development of aversive associations.

The paper presents two studies investigating the role of the preparedness value of stimulus content in an aversive compound signal conditioning procedure. It was predicted that greater compound to component transfer would occur to 'potentially phobic' compared to 'neutral' stimulus components, and that responses to potentially phobic components would show a relatively greater resistance to extinction. Results from both studies failed to support these hypotheses thus questioning the generality of the previously demonstrated role of 'preparedness' in average associative processes.

Adult↗