PubMed Health⌕ Search

Biomedical subjects

G Lefranc

Publications and source records attributed to G Lefranc.

At least 19 recordsLinked to original sources
PubMed1992

Ultrastructural and cytochemical analysis of Na+, K+, ATPase and H+, K+, ATPase in parietal cells of gastric mucosa in the rabbit.

Rabbit gastric secretion has the physiological peculiarity of being continuous and uninfluenced by food intake. In this respect, ultrastructural analysis of rabbit parietal cells has revealed morphofunctional features situated between states of rest and very active acid secretion. Our cytochemical study shows that Mg2+ ATPase and ADPase activities vary from cell to cell and can even be totally absent. These activities concern either microcanaliculi or laterobasal folds or both, but never tubulovesicles. Application of the technique of Mayahara to K+ pNPP, associated or not with inhibitors (ouabain, vanadate, N-ethyl-maleimide, sodium fluoride), enabled us to confirm the coexistence of H+, K+, ATPase and Na+, K+, ATPase activities in the rabbit and to determine that these activities concern basolateral folds, microcanaliculi, hyaloplasm and tubulovesicles. The global activity of K+, pNPPase varied considerably in intensity. The results of using inhibitors suggest that proton transport ceases completely in certain cells. The signs of functional alternation found in this study are in agreement with physiological data relative to this animal.

Animals↗
PubMed1991

Biological half-life of normal and truncated human IgG3 in scid mice.

The fractional catabolic rate of IgG in the body is regulated with precision in order to maintain appropriate serum concentrations. We have investigated the turnover rate of normal human IgG3, a newly identified, naturally occurring, truncated form of IgG3 and a human-mouse chimeric IgG3 antibody in an immunodeficient mouse strain, C.B-17 (SCID), lacking endogenous Ig. The half-life of non-truncated, normal serum IgG3 as well as the chimeric antibody was about 7 days, whereas truncated IgG3 had a shorter half-life of about 5 days. Due to the inherent immune defect, the SCID mouse could represent a versatile animal model for the determination of turnover rates, inasmuch as an immune response will not be mounted against foreign antigens.

Animals↗
PubMed1991

Polymorphism of the T-cell receptor gamma variable and constant region genes in a Chinese population.

The human T-cell receptor gamma gene region spans 160 kb genomic DNA. Restriction fragment length polymorphisms (RFLPs) have been previously documented for the constant region (TRGC) genes, the joining (TRGJ) segments and the variable (TRGV) genes. We have recently defined the alleles of the T-cell receptor gamma V, J and C genes and we have described seven haplotypes of the V gamma subgroup I genes characterized either by RFLPs or by deletion or insertion of V gamma genes. The number of V gamma I genes may vary from 7 to 10 per haploid genome, the 9-gene haplotype being the most frequent. Allelic fragments can unambiguously characterize the TRGC2 gene with duplication or triplication of the exon 2. These alleles and haplotypes have been analyzed in four different populations (French, Lebanese, Tunisian and Black African). In this paper, we compare these allele and haplotype frequencies with those found in a Chinese population and we describe new TRGV allelic restriction fragments found only in the Chinese samples. These results and the previous data demonstrate the flexibility of the human T cell receptor gamma locus and the importance of unequal crossing-overs in the evolution of that locus. Moreover, they underline the importance of studying these polymorphisms in population genetics.

Alleles↗
PubMed1991

Process for analysis of an area delimited by a nonparametric curve and divided into microdomains, and for localization of possible constituents: exploitation by "digisector" software.

The process presented here was designed and developed for study of various cell parameters in electron microscopy photographs and analysis of the location of certain differentiated cell-constituents relative to plasma membrane. It can also be used for many other applications, for example, in metallurgy, petrography and geostrategy. A photograph is analyzed using a plotting table interfaced with a microcomputer.

Image Processing, Computer-Assisted↗
PubMed1991

Three-dimensional analysis demonstrates the presence of exocrine cytoplasmic vela between endocrine cells and basal lamina in the stomach of mammals.

Three-dimensional analysis demonstrated the presence of cytoplasmic vela extending from exocrine cells into the space between endocrine cells and basal lamina in the gastrointestinal epithelium of the rabbit; these structures were also observed in various other mammals. The following techniques were used to determine the morphologic characteristics of these vela and to study their significance: preparation of semiserial thin sections, three-dimensional reconstruction in plexiglass and lanthanum staining of pericellular spaces. It was found that these fine vela, devoid of major differentiated cell-constituents, sometimes form a pseudocircular crown at the base of endocrine cells. If the zone of basal apposition of the plasma membrane is referred to as ZBA and the zones of lateral apposition as ZLA, the presence of this velum makes it possible to distinguish a zone of immediate apposition without interposition (ZIA) and a mediate zone of apposition with interposition (ZMA) within the ZBA. Exocrine cell processes can also penetrate within endocrine cells in invaginations, and the depth of these invaginations can be demonstrated by lanthanum staining. Adjacent to the membrane zones defined above, other cytoplasmic microdomains-M(ZLA) and M(ZBA), as well as M(ZIA) and M(ZMA) of different morphofunctional significance may also be envisaged.

Animals↗
PubMed1991

Reciprocal hybrid joints demonstrate successive V-J rearrangements on the same chromosome in the human TCR gamma locus.

Novel variable (V)--joining (J) gene rearrangements are described in the human T cell receptor gamma locus, in which, on the one hand, the V3 variable gene is joined to the heptamer--nonamer recombination signals of the J1 segment and, on the other hand, the J1 segment is joined to the V3 recombination signals through head-to-head fusion. These recombination products, or hybrid joints, have been originated through an inversion of 47 kb DNA. Interestingly the inverted DNA stretch contains a normal V9-J9 rearrangement. These findings are the first direct demonstration that successive rearrangements occur, on the same chromosome, in the human T cell receptor gamma locus, and suggest that the chronology of the joining events plays a role in the ontogeny of T cells and their differentiation in gamma/delta + and alpha/beta + lineages.

Amino Acid Sequence↗
PubMed1991

[Immunogenetic markers (BF, C2, C4, 21-OH, TNF alpha, TCR beta, Ig) and insulin-dependent diabetes in the Tunisian population: serological and molecular study].

48 Tunisian people suffering from the IDDM auto-immune disease were compared to 35 control healthy persons for the polymorphisms of the complement BF, C2 and C4 proteins and genes, of the IgG (Gm allotypes) as well as of the TNF alpha and TCR C beta genes. Our study shows that the BFF1-C4A3-C4BQO and BFS-C4AQ0-C4B1 complotypes are associated to IDDM (RR of 2.97 and 3.07 respectively), as previously reported for other circummediterranean populations. The frequency of the Gm 21.28; 1.17; .. haplotype is increased, but not significantly, among the patients. The RFLP analysis reveals that the 2.65 kb SacI allelic restriction fragment of the C2 gene may be considered as a genetic marker of susceptibility to IDDM because its frequency raises to 0.206 among the patients vs 0.021 in the healthy individuals (p less than 0.001). The frequencies of the C4AQ0 and C4BQ0 alleles are more important among the IDDM patients than within the control sample, but the only C4BQ0 allele frequency is significantly increased. Both C4AQ0 and C4BQO result mainly from deletions. The frequencies of the allelic restriction fragments of the TNF alpha and TCRC beta genes are not significantly different among the patients and the controls. But the small sample size don't allow us to conclude definitively. It would be very interesting to extend the RFLP analysis to the TCR V beta and V alpha gene regions on more numerous samples.

Adolescent↗
PubMed1991

Gene deletions in the human immunoglobulin heavy chain constant region locus: molecular and immunological analysis.

Single and extensive multigene deletions have been described in the Ig CH immunoglobulin heavy-chain constant region genes, some of these encompassing up to 160 kilobases. To date six different multigene deletion haplotypes have been identified, designated I to VI according to the chronological order of their findings; deletion I (del G1-EP1-A1-GP-G2-G4), II (del EP1-A1-GP), III (del A1-GP-G2-G4-E), IV (del EP1-A1-GP-G2-G4), V (del GP-G2-G4-E-A2), VI (del G1-EP1-A1-GP-G2). Individuals were found either homozygous for one type of deletion or heterozygous for two different deletions, mainly in the Mediterranean area. The high level of consanguinity in the Tunisian population accounts for the high frequency of individuals homozygous for one or the other of these multigene deletions which involve highly homologous regions as hot spots of recombinations, outside of the switch sequences, in the Ig CH locus. In 15 cases out of 16, these multigene deletions have been observed in healthy people, although these individuals lacked several immunoglobulin subclasses and, even, one class. Such an immunological situation makes it possible to study the importance of these subclasses for the overall immunity, and to analyse the specific immune responses by the retained IgG and IgA subclasses.

Chromosome Deletion↗