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B Lejeune

Publications and source records attributed to B Lejeune.

At least 37 records · Page 2Linked to original sources
PubMed1998

Molecular phylogenetic approach for studying life-history evolution: the ambiguous example of the genus Medicago L.

We present a molecular phylogeny including most species of the genus Medicago L. (Fabaceae). Based on the consensus of the 48 most parsimonious trees, life-history and mating-system characters are mapped, and a putative history of the genus is suggested. The most parsimonious reconstruction suggests an ancestral annual and selfing state, and recurrent evolution towards perenniality and outcrossing. Based on theoretical predictions and classical hypotheses of the history of the genus, different assumptions about the ancestral state and different weighting schemes of evolution between the character states are made. Assuming an outcrossing, perennial ancestral state (partly supported by morphological features) does not fundamentally change the reconstruction. To meet theoretical expectations, various weighting schemes favouring evolution towards annuality and selfing are applied. Influence and validity of such weighting schemes are discussed with regard to other studies.

Base Sequence↗
PubMed1998

The Arabidopsis SHAGGY-related protein kinase (ASK) gene family: structure, organization and evolution.

Higher plants contain a multigene family encoding proteins that share a highly conserved catalytic protein kinase domain about 70% identical to SHAGGY protein kinase (SGG) and glycogen synthase kinase-3 (GSK-3), respectively, from Drosophila and mammals. In this study we have characterized the structure and evolution of the Arabidopsis SHAGGY-related protein kinase (ASK) gene family. At least ten ASK genes are present per haploid genome of Arabidopsis. The genomic sequences of five ASK genes show a strikingly high conservation of intron positions and exon lengths. Phylogenetic analyses suggested that the Arabidopsis gene family contains at least three ancient classes of genes that diverged early in land plant evolution. The different classes may reflect specificity of substrates and/or biological functions. Eight out of the ten predicted ASK genes were mapped and shown to be dispersed over the five Arabidopsis chromosomes. A tentative model for the organization and evolution of the Arabidopsis ASK genes is presented.

Arabidopsis↗
PubMed1998

Evolution of annual species of the genus Medicago: a molecular phylogenetic approach.

We performed a molecular phylogenetic study based on the nuclear ribosomal internal and external transcribed spacer (ITS and ETS). Thirty-one annual Medicago species were included in the study, representing more than half of the genus and 85% of the annuals of the genus. Major incongruences were found between phylogenetic relationships and morphological classification of the genus. Morphological and cytological traits were mapped onto the phylogeny. The most parsimonious reconstruction suggested an ancestral spiny state and a recurrent transition from spiny to spineless state. From the ancestral state of 2n=16, three loss events of chromosomes must have occurred leading to the same specific number of 14 chromosomes whereas species having 30 chromosomes form a monophyletic clade.

Chromosome Deletion↗
PubMed1998

Ribosomal External and Internal Transcribed Spacers: Combined Use in the Phylogenetic Analysis of Medicago (Leguminosae)

We have estimated the potential phylogenetic utility of the ribosomal external transcribed spacer (ETS) from the nuclear ribosomal region. The ETS was sequenced from 13 annual Medicago (Fabaceae) species upstream a highly conserved motive which was found among many different organisms. In the genus Medicago, the ETS was found to evolve 1.5 times faster than the internal transcribed spacer and to be 1.5 times more informative. Reduced ribosomal maturation process constraints on ETS are proposed to explain the different evolutionary rates between the two spacers. Maximal phylogenetic resolution and support was obtained when the two spacers were analyzed together. No incongruence between the two spacers was found and ETS appears to be a valuable source of information for solidifying ITS plant phylogeny. The phylogeny obtained in Medicago suggests that none of the three subsections included in the study is monophyletic.

Journal Article↗
PubMed1998

Perception of motion and qEEG activity in human adults.

This study was designed to relate visual perception of motion to cortical activity, by evaluation of the association of quantified electroencephalogram (qEEG) parameters with a video film projection. The EEG was recorded from 14 sites according to the International 10-20 system and a common average reference was used. Forty right-handed volunteers (mean age = 24 years) were examined. The video film consisted of 20 s sequences showing still shots and moving shots with human movements or object movements. The EEG was then subjected to spectral analysis; the spectral powers for the theta, alpha and beta bands were calculated for 14 s epochs and compared with sequences of the video film. All analyses were based on logarithmically transformed absolute spectral power values. The power values of each frequency band were analysed in a 3-way repeated measure ANOVA (Hemisphere x Electrode x Sequence). The results were represented by EEG cartography. Significant decreases in the alpha 1, beta 1 and beta 2 power values of EEG in centro-parietal regions of both hemispheres were shown during perception of human motion sequences. This suggests participation of the sensorimotor cortex during visual observation of human motion.

Adolescent↗
PubMed1998

Is there a future for spermatid injections?

Microinjection of spermatids into oocytes has proven to be a successful assisted reproduction procedure in the animal model. In the human, low fertilization and cleavage to the 4-cell stage were reported after intracytoplasmic sperm injection (ICSI) with round spermatids. In comparison with a conventional ICSI-testicular sperm extraction (TESE) programme, the implantation rate after round spermatid injection is dramatically low. Different problems have been encountered during the development of the spermatid injection technique and they could be partially responsible for the lower outcome when using round spermatids. Compared with the round spermatid cells, spermatids in the elongation phase are easy to isolate and identify from other round cells present in a wet preparation. The morphological identification does not reveal anything about the viability or the genetic normality of the round spermatids. Severe testicular dysfunction may have consequences on the quality of the few spermatogenic cells present. Others factors, such as the pathology of the patient, play an important role in the successful treatment. Even if the results are extremely low, spermatid injection seems more favourable for men who have already proven their capacity to produce some spermatozoa. A spermatogenic block at the round spermatid level has led to early abortions, increasing the suspicion of the role of a genetic factor. In order for this technique to be safe for use in clinics, more intensive work is needed to improve the selection and handling of cells and to ascertain the genomic imprinting and gene expression necessary for embryonic development. Hence, when using immature cells for conception, the screening of the patient and the follow-up of the pregnancies and babies should be mandatory.

Animals↗
PubMed1998

Molecular phylogeny of the genus Hypochaeris using internal transcribed spacers of nuclear rDNA: inference for chromosomal evolution.

Sequences of the internal transcribed spacers (ITSs) of 18S-26S nuclear ribosomal DNA were used to resolve phylogenetic relationships and chromosomal evolution among 14 species of the genus Hypochaeris (Asteraceae). Parsimony analysis was performed for phylogenetic reconstruction, and sequence divergence between species was estimated. Pairwise sequence divergence within Hypochaeris genus ranged from 0% to 25.68% in ITS1 and from 0% to 17.08% in ITS2. A highly resolved strict-consensus tree was obtained that showed the phylogenetically useful information of ITS sequences within the genus Hypochaeris. Four clades could be well distinguished, one of them formed by the single species H. robertia, which appeared to be the most related to the ancestral species of the genus. The results agree with taxonomic classification based on morphological data, and the tree obtained, when indels are coded as missing data, aggregates the species having the same chromosome number, except in one clade. According to the ITS phylogenetic tree, the chromosomal evolution within the genus Hypochaeris conflicts with the previous hypothesis and suggests that karyotype evolution in Hypochaeris was accompanied with both decreasing and increasing dysploidy, probably with several chromosomal rearrangements, and from an ancestral basic chromosome number of 4 or 5.

Asteraceae↗
PubMed1998

Extent of antigenic diversity in the V3 region of the surface glycoprotein, gp120, of human immunodeficiency virus type 1 group M and consequences for serotyping.

Human immunodeficiency virus type 1 (HIV-1) may be studied by molecular or immunological approaches. Most analyses have been performed by genetic comparison of isolates and have led to the definition of clades or subtypes within the major (M) group of HIV-1. Five subtypes (A to E) were initially identified by comparison of genomic sequences. Four new subtypes (F to I) were identified more recently. Amino acid differences in the immunogenic V3 loop between isolates have also been studied, leading to a phenetic classification of at least 14 clusters (1 to 14) of sequences (B. T. M. Korber, K. McInnes, R. F. Smith, and G. Myers, J. Virol. 68:6730-6744, 1994). In this study, we compared the antigenicity of the V3 consensus sequences defined by phylogenetic analysis to the antigenicity of those defined by phenetic analysis. We used a recently developed subtype-specific enzyme immunoassay (SSEIA) that uses the principle of blocking with an excess of peptide in the liquid phase. Two SSEIAs were performed, the first with five V3 sequences defined by phylogenetic analysis and the second with 14 V3 sequences defined by phenetic analysis. A total of 168 HIV-1 sera taken from seropositive individuals from seven different countries or regions were studied. Experimental and statistical data, including correlation matrix and cluster analyses, demonstrated associations between the genetic subtypes and phenetically associated groups. Most of these were predicted by Korber et al. (J. Virol. 68:6730-6744, 1994) by theoretical analysis. We also found that V3 sequences can be grouped into between three and five antigenically unrelated categories. Residues that may be responsible for major antigenic differences were identified at the apex of the V3 loop, within the octapeptide xIGPGxxx, where x represents the critical positions. Our study provides evidence that there is a limited number of V3 serotypes which could be easily monitored by serological assays to study the diversity and dynamics of HIV-1 strains.

Amino Acid Sequence↗
PubMed1998

Genetic analysis of Aspergillus nidulans unstable transformants obtained by the biolistic process.

Mitotically unstable Aspergillus nidulans argB+ transformants obtained by the biolistic process were studied in the present work. Hybridization signals from undigested DNA and pulsed-field chromosomal bands of the transformants suggested the introduced plasmid occurred as free concatenated molecules. Fifteen vigorous growth sectors released from the transformants were analysed in order to understand the mechanisms involved in their formation. All sectors showed the integration of exogenous genes into the fungal genome by homologous or heterologous recombinant events.

Arginine↗
PubMed1997

Characterization of two members of the Arabidopsis thaliana gene family, At beta fruct3 and At beta fruct4, coding for vacuolar invertases.

We have isolated and characterized two Arabidopsis thaliana cDNAs and their cognate genes, At beta fruct3 and At beta fruct4, encoding vacuolar forms of invertase. Our sequencing results showed that the gene At beta fruct3 is located downstream of the 3-ketoacyl-acyl carrier protein synthase III gene (AtKasIII). At beta fruct3 and 4 are functional and organized into seven exons and six introns with an identical organization. The At beta fruct3 and At beta fruct4 genes encode, respectively, polypeptides of 648 and 664 residues that contain all the characteristic hallmarks of vacuolar invertases. A. thaliana is the first plant of which both cell-wall (At beta fruct1 and At beta fruct2) and vacuolar (At beta fruct3 and At beta fruct4) genes are characterized. The same number of exons and introns is seen in the genes At beta fruct1, At beta fruct3 and At beta fruct4 as well as in all other invertase genes described to date. However, the position of the third intron is different in At beta fruct3 and At beta fruct4. At beta fruct2 shows a different organization. A neighbour-joining distance tree shows that the A. thaliana vacuolar invertases described here are, as expected, more closely related to vacuolar invertases from other plant species (e.g., carrot) than to the A. thaliana cell-wall invertases. The evolution of plant invertase genes from a common ancestral gene is discussed. Our results demonstrate that in A. thaliana, at least two genes encoding vacuolar invertases are expressed during the development of the plant. Southern blot hybridization experiments suggest the presence of one copy of, respectively, At beta fruct3 and At beta fruct4 per haploid genome, and Northern blot analysis demonstrates that vacuolar invertase genes are highly expressed in stems, roots, flowers and at very low levels in mature leaves.

Amino Acid Sequence↗
PubMed1997

Genes encoding subunit 6 of NADH dehydrogenase and subunit 6 of ATP synthase are co-transcribed in maize mitochondria.

The mitochondrial nad6 gene of maize was identified and mapped 1 kb downstream from the atp6 gene. It encodes a 220 amino-acid polypeptide. Using Northern hybridization experiments and RT-PCR analysis, we showed that both nad6 and atp6 are co-transcribed in maize mitochondria. RNA editing of the mitochondrial nad6 transcript was studied by cDNA sequencing. Twelve edited sites were identified at the same positions as those already identified in the wheat mitochondria nad6 transcript. Alignments of nucleotide and amino-acid sequences of the mitochondrial nad6 genes of maize, wheat, and Brassica campestris, show that the wheat gene encodes a shorter polypeptide (229 amino acids) than was previously thought.

Amino Acid Sequence↗
PubMed1997

Intracytoplasmic injection of spermatids retrieved from testicular tissue: influence of testicular pathology, type of selected spermatids and oocyte activation.

Spermatid microinjection into oocytes has proven to be a successful assisted reproduction procedure in the animal model and in the human species, since in the latter a few full-term pregnancies were actually obtained. Patients entering our spermatid injection study included those with a total absence of spermatozoa in the testicular tissue notwithstanding previous positive biopsies (n = 29): an obstructive problem (n = 3), secretory azoospermia (n = 26), and those with total arrest at the spermatogenesis level in previous explorative biopsies (n = 15). In the latter group, absence of spermatids was recorded in four cases. Mature, elongated, elongating and round spermatids (ROS) were injected in respectively 3, 2, 3, and 32 attempts. A total of 260 metaphase II oocytes were injected with ROS, 36 oocytes with spermatids at other stages of maturity. The rates of oocytes showing two pronuclei (2PN) and two polar bodies reached 22% and 64% respectively after injection of round or elongated-mature spermatids. The fertilization rate after ROS injection was influenced by the percentage of spermatozoa observed in a previous biopsy. Patients with a positive preliminary biopsy had significantly more 2PN (33%) when compared to those with a severe spermatogenic dysfunction and in whom no spermatozoa were found (only 11%) (P < 0.05). Incubation of oocytes in calcium ionophore after ROS injection had a positive effect on the rate of 2PN formation (36 versus 16%). Ninety per cent of all the normally fertilized oocytes cleaved. The percentage of grade A and B embryos depended on the type of injected cells: 12% after ROS and 30% with the other types of haploid cells. A total of 39 transfers resulted in five pregnancies: three full term with healthy babies delivered (one after ROS injection, and two after injection of an elongating and a mature spermatid), one 4 months ongoing (after elongating spermatid injection) and one miscarriage at 4 weeks (after elongated cell injection). Compared to our conventional intracytoplasmic sperm injection-testicular sperm extraction (ICSI-TESE) programme, the implantation rate after ROS injection was very low (5.5 versus 10.5%).

Animals↗
PubMed1997

Age-related changes in phospholipid fatty acid composition and monoaminergic neurotransmission in the hippocampus of rats fed a balanced or an n-3 polyunsaturated fatty acid-deficient diet.

The influence of aging (2, 6, 12, and 24 months) on hippocampal lipid composition and neurochemical markers (endogenous noradrenaline, serotonin levels, monoamine oxidase (MOA) activities) was studied in rats fed a control or an n-3 polyunsaturated fatty acid (PUFA)-deficient diet. The n-3 PUFA deficiency reduced the 22:6 (n-3) level, compensated by the increase in 22:5 (n-6). However, the difference in 22:6 (n-3) content between control and deficient rats was less between 2 and 12 months and then became stable. There was an overall age-induced decrease in the major phospholipid classes phosphatidylethanolamine (PE), and phosphatidylcholine (PC) whereas the minor classes, phosphatidylinositol (PI), phosphatidylserine (PS), and sphingomyelin (SM), were greatly increased, regardless of diet. The n-3 PUFA deficiency induced a reduction in the PS level, concomitant with a higher level in MAO-B activity as compared to control rats at the age of 24 months. The age-related evolution of the MAO-B activity was parallel with that of noradrenaline levels in both dietary groups. The noradrenaline and serotonin levels were modified according to age but without effect of the n-3 PUFA deficiency. Results showed that the hippocampus sustained specific age-induced modifications in lipid composition and neurotransmission factors, often with a transition period between 6 and 12 months.

Aging↗
PubMed1997

[Andrologic/gynecologic microsurgery and fertilization in vitro: complementary approaches?].

The authors give their detailed results of andrological and gynecological microsurgical procedures and compare these to the cumulative results of their IVF work. They do defend the idea that to abandon microsurgery in favour of IVF and its last developments such as MESA & TESE is unreasonable and believe that every case demands a precise evaluation in which the gynecological situation and the age of the partner is mandatory.

Age Factors↗
PubMed1997

[Knowledge and beliefs of 4th-year medical students concerning professional practices in general medicine. Results of a survey conducted at the School of Medicine of Brest].

As part of preparations for the first seminar in general practice, organized for medical students in their forth year at the Brest faculty of medicine, students were asked to fill in a questionnaire concerning their beliefs and knowledge concerning general-practice medicine. Fifty-two students, or 89.6% of the class, completed the questionnaires. The results showed that despite the lack of formal contacts with this type of practice during their studies, the students had a good idea of what general-practice medicine is and of the role of the general practitioner in our health-care system. However, this study has illustrated the difficulties students experience in defining their future professional direction, since they receive no information during their training on the different options in medical practice.

Adult↗
PubMed1996

Diversity of antibody binding to V3 peptides representing consensus sequences of HIV type 1 genotypes A to E: an approach for HIV type 1 serological subtyping.

We investigated whether V3-binding assays might be useful to analyze human immunodeficiency virus type 1 (HIV-1) variants in different geographic regions. We showed that strong cross-reactivity between subtype-specific V3 peptides is almost inevitable in standard indirect enzyme-linked immunosorbent assays (EIA), impairing precise serological subtyping. We therefore developed a subtype-specific EIA (HIV-1 SSEIA) that uses the principle of blocking by an excess of peptide in the liquid phase. Using 231 serum samples collected from HIV-1-infected individuals in 10 different geographical areas from 4 continents, we showed that this approach detected the dominant subtype reactivity in more than 97% of the cases. Internal controls (0 and 100% blocking) were used for every sample such that comparative analysis was possible, independent of both the individual humoral response and the time of collection during the course of infection. This was validated by the excellent concordance of the serological profiles of couples and the temporal stability of the serological profile in individuals. The geographical distribution of the various subtypes in the SSEIA was in agreement with the present knowledge of the distribution of the various genotypes. Although the goal of this study was not an extensive seroepidemiological survey, our results showed that the various profiles in most of the regions were relatively homogeneous, but in central Africa there was a large diversity of serological profiles. Cluster analysis identified a limited number of V3 serogroups of serotypes within the HIV-1 group M. Five serogroups, some of them divided into subgroups, were identified and characterized by a mean serological profile. Our data confirmed that subtypes A and C, although being dissimilar genetic subtypes, present conserved antigenic properties in the V3 region, and that the D subtype is probably the most divergent within the group M (B Korber et al., J Virol 1994;68:6730). Cluster analysis showed a clear correlation between position within the dendrogram and geographical origin of the samples. This is further support for the reliability and thereof the usefulness of the SSEIA. This simple methodology may help facilitate the analysis of the distribution of various HIV-1 subtypes circulating in different populations and regions.

Amino Acid Sequence↗