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Early ionocytes have been studied in the European sea bass (Dicentrarchus labrax) embryos. Structural and functional aspects were analyzed and compared with those observed in the same conditions (38 ppt) in post hatching stages. Immunolocalization of Na+/K+-ATPase (NKA) in embryos revealed the presence of ionocytes on the yolk sac membrane from a stage 12 pair of somites (S), and an original cluster around the first gill slits from stage 14S. Histological investigations suggested that from these cells, close to the future gill chambers, originate the ionocytes observed on gill arches and gill filaments after hatching. Triple immunocytochemical staining, including NKA, various Na+/K+/2Cl− cotransporters (NKCCs) and the chloride channel “cystic fibrosis transmembrane regulator” (CFTR), point to the occurrence of immature and mature ionocytes in early and late embryonic stages at different sites. These observations were completed with transmission electronic microscopy. The degree of functionality of ionocytes is discussed according to these results. Yolk sac membrane ionocytes and enteric ionocytes seem to have an early role in embryonic osmoregulation, whereas gill slits tegumentary ionocytes are presumed to be fully efficient after hatching.

Because of the permeability of the chorion, sea bass embryos are exposed to seawater before hatching and hence require precocious osmoregulatory processes. Several studies of other species have demonstrated the existence of ion-transporting cells located on the yolk sac membrane of embryos. In these cells, called ionocytes, ion movements are controlled by a pool of transmembrane proteins. Among them, the Na(+)/K(+)-ATPase, an abundant driving enzyme, has been used to reveal the presence or absence of ionocytes. We have immunostained the Na(+)/K(+)-ATPase in sea-bass embryos and shown the presence of the first ionocytes on the yolk sac membrane at stage 12 somites and the occurrence of ionocytes at other sites before hatching. Ionocytes located on the first gill slits have been identified at stage 14 somites. Primitive enteric ionocytes have also been detected at stage 14 somites in the mid and posterior gut. The presence of these cells might be related to the early opening of the gut to perivitelline fluids, both anteriorly by the gill slits and posteriorly by the anus. The role of embryonic ionocytes in osmoregulation before hatching is discussed.

The European sea bass Dicentrarchus labrax is a marine teleost important in Mediterranean aquaculture. The development of the entire digestive tract of D. labrax, including the pharynx, was investigated from early embryonic development to day 5 post hatching (dph), when the mouth opens. The digestive tract is initialized at stage 12 somites independently from two distinct infoldings of the endodermal sheet. In the pharyngeal region, the anterior infolding forms the pharynx and the first gill slits at stage 25 somites. The other three gill arches and slits are formed between 1 and 5 dph. Posteriorly, in the gut tube region, a posterior infolding forms the foregut, midgut and hindgut. The anus opens before hatching, at stage 28 somites. Associated organs (liver, pancreas and gall bladder) are all discernable from 3 dph. Some aspects of the development of the two independent initial infoldings seem original compared with data in the literature. These results are discussed and compared with embryonic and post-embryonic development patterns in other teleosts.

Plasma TNF-alpha levels are generally higher in heart-graft patients who experience a rejection episode than in those who do not. Because the TNF gene and its promoter are polymorphic, we studied the relationships between genetic variability at the TNF locus, the occurrence of graft rejection and TNF-alpha plasma levels in 62 heart-transplant patients in order to investigate inter-individual differences in plasma TNF-alpha levels after allogeneic stimulation. TNF-alpha was immunoenzymatically measured in blood specimens collected on the same day as endomyocardial biopsy. After PCR amplification of DNA, NcoI and AspHI polymorphisms were characterized by their restriction profiles, TNFa microsatellites by electrophoretic separation on acrylamide and the promoter region by sequencing. Plasma levels and molecular genetic results were compared to the grade of heart graft rejection established according to pathological criteria. In our study, allograft rejection was associated neither with NcoI or AspHI polymorphism nor with nucleotide changes in the TNF-A promote. We observed low TNF-alpha levels in n1/n1 homozygous patients and in subjects with G-->A at position--308 of the promoter sequence. Concerning the polymorphism of the TNFa microsatellite, our results might suggest an association with graft rejection but we have to be very careful in drawing conclusions because of the small size of the sample.

The HLA-DM molecule catalyses the CLIP/antigen peptide exchange in the classical class II peptide-binding groove. As such, DM is an antigen presentation regulator and may be linked to autoimmune diseases. Using PCR derived methods, a relationship was revealed between DM gene polymorphism and IDDM, in a Corsican population. The DMA*0101 allele was observed to confer a significant predisposition to this autoimmune disease while the DMA*0102 allele protected significantly. Experiments examining polymorphism of the HLA-DRB1 gene established that these relationships are not a consequence of linkage disequilibrium with HLA-DRB1 alleles implicated in this pathology. The study of the DMA gene could therefore be an additional tool for early IDDM diagnosis in the Corsican population.

Plasma TNF-alpha levels are generally higher in heart-graft patients who experience a rejection episode than in those who do not. Because the TNF gene and its promoter are polymorphic, we studied the relationships between genetic variability at the TNF locus, the occurrence of graft rejection and TNF-alpha plasma levels in 62 heart-transplant patients in order to investigate inter-individual differences in plasma TNF-alpha levels after allogeneic stimulation. TNF-alpha was immunoenzymatically measured in blood specimens collected on the same day as endomyocardial biopsy. After PCR amplification of DNA, NcoI and AspHI polymorphisms were characterized by their restriction profiles, TNFa microsatellites by electrophoretic separation on acrylamide and the promoter region by sequencing. Plasma levels and molecular genetic results were compared to the grade of heart graft rejection established according to pathological criteria. In our study, allograft rejection was associated neither with NcoI or AspHI polymorphism nor with nucleotide changes in the TNF-A promote. We observed low TNF-alpha levels in n1/n1 homozygous patients and in subjects with G--A at position--308 of the promoter sequence. Concerning the polymorphism of the TNFa microsatellite, our results might suggest an association with graft rejection but we have to be very careful in drawing conclusions because of the small size of the sample.

Since 1989, several HLA-DQA1 PCR-RFLP genotyping protocols have been published. These methods require complete digestion of the PCR products and determination of the restriction fragments length. The HLA-DQA1 PCR-RFLP genotyping protocol describe here uses one amplification step through PCR, digestion of the PCR-products with 8 restriction endonucleases, and determination of the fragments size after polyacrylamide gel electrophoresis. Five of the enzymes, having no more than one restriction site in each allele (ApaLI, HphI, BsaJI, FokI and MboII), allow distribution of all the genotypes in 19 allelic-combination groups on the base of the digestion pattern: cut/not cut. Three additional enzymes (MnlI, DdeI and RsaI), having at least 2 restriction sites in each allele, are used to assign the genotype in each allelic-combination group on the base of the restriction fragments length observed. Eight of the 13 alleles, 36 of the 91 HLA-DQA1 genotypes could be characterized. Four to 8 samples could be characterized each day, including DNA extraction. The number of endonucleases used could act as internal control of enzymatic activities and the genotyping protocol can include new HLA-DQA1 alleles without modification of the experimental steps. This protocol can be applied easily in a laboratory without specific technical training or specific equipment.

The HLA-DMA gene, along with the HLA-DMB gene, encodes the not classical class II molecule. This molecule catalyzes the class-II-associated invariant-chain peptide (CLIP)-antigen peptide exchange in classical class II molecule peptide-binding groove. As such, the DM heterodimer is an antigen presentation regulator and may be linked to immune system deficiencies such as those observed in autoimmune diseases. The study of DMA gene polymorphism seems be a reasonable approach to provide an answer to this question. Thanks to PCR-derived methods, the relationship between DMA gene polymorphism and rheumatoid arthritis (RA) was demonstrated in the present study. The DMA*0101 allele was observed to confer a significant predisposition to RA while the DMA*0102 allele significantly protected from this disease. Polymorphism experiments with the HLA-DRB1 gene revealed that this relationship between DMA polymorphism and RA is not a consequence of a linkage disequilibrium with the HLA-DRB1 alleles implicated in this pathology. The study of the DMA gene could therefore prove to be very useful in the early diagnosis of RA.