Search PubMed⌕ Search

Biomedical subjects

O Bernard

Publications and source records attributed to O Bernard.

At least 163 records · Page 9Linked to original sources
PubMed1993

[Liver transplantation in children. Indications and results].

The results of liver transplantation in children have dramatically improved from the wide use of cyclosporine A and because of technical advances such as the use of reduced-size adult liver transplants. It is now accurate to consider that 70 to 80% of transplanted children will be alive with a normal life 5 years post-transplant. Within a few years, liver transplantation has thus become the regular treatment of many liver diseases in childhood.

Age Factors↗
PubMed1993

Characterization of translocation t(1;14)(p32;q11) in a T and in a B acute leukemia.

The TAL1 locus on chromosome band 1p32 is rearranged in 15 to 29% of human T-cell acute lymphoblastic leukemias (T-ALLs). These alterations consist of either a tald submicroscopic deletion (12-26% of T-ALL) or a t(1;14)(p32;q11) chromosomal translocation (3% of childhood T-ALL). Both types of alterations preferentially affect the 5' part of the TAL1 locus. Their main consequence appears to be transcriptional activation of the TAL1 gene. We have characterized two cases of t(1;14)(p32;q11) in ALL. Both affect the TCR delta gene segments at 14q11 and the 5' part of the TAL1 locus at 1p32. The first case represented a 'classical' t(1;14), associated with T-ALL. Its analysis indicates the use of a recombination signal-like sequence localized in the third exon of TAL1 in the translocation process. In the other case, the rearrangement to the D delta region occurred 5' to the TAL1 transcription start sites. This case exhibited a B-lymphoid immunophenotype thus suggesting that the putative oncogenicity of TAL1 activation is not restricted to T-cell malignancies.

Adult↗
PubMed1993

Molecular analysis of T-cell receptor transcripts in a human T-cell leukemia bearing a t(1;14) and an inv(7); cell surface expression of a TCR-beta chain in the absence of alpha chain.

The polymerase chain reaction (PCR) was used to amplify cDNA in order to characterize normal and hybrid T-cell receptor (TCR) gene rearrangements derived from a T-cell acute lymphoblastic leukemia (T-ALL) bearing a chromosome 7 inversion. The nucleotide sequence analysis of the amplified product showed the presence of an out-of-frame V beta/J gamma/C gamma transcript and an in-frame V gamma/J gamma/C beta transcript which result from an interlocus recombination between the TCR-beta and gamma loci and the transcription of the reciprocal hybrid TCR gene. The sequence analysis of the reciprocal DNA segment directly involved in the breakpoint of the inversion showed a recombination between a J gamma-sequence heptamer signal and a coding J beta gene segment. The exonuclease nibbling of each DNA extremity and the non-templated nucleotide insertion observed at both coding and reciprocal joints demonstrate that the inversion is mediated by the lymphocyte recombinase complex. During T-cell differentiation, TCR-beta genes are rearranged prior to TCR-alpha genes. In the present case of T-ALL, we have shown that TCR-delta genes are rearranged at both loci, excluding productive rearrangements of TCR-alpha genes. The molecular analysis of the normal TCR genes derived from the leukemic cells revealed the presence of productively rearranged TCR-beta, gamma, and delta genes. Cell surface staining of these cells showed the presence of CD3 molecules and of a TCR-beta chain corresponding to the normal beta allele expressed in a disulfide-linked complex with a protein which is not TCR-alpha, gamma, or delta. This could represent the cell surface expression of the hybrid TCR-V gamma/C beta protein or the expression of a TCR-beta homodimer.

Adult↗
PubMed1993

NYK/FLK-1: a putative receptor protein tyrosine kinase isolated from E10 embryonic neuroepithelium is expressed in endothelial cells of the developing embryo.

A protein tyrosine kinase (NYK/FLK-1), bearing all the hallmarks of a growth factor receptor, has been isolated from a cDNA library generated from enriched populations of mouse day 10 embryonic neuroepithelium and from day 18 embryonic colon. Sequence analysis of cDNAs covering the entire coding region of this 5.7 kb mRNA predicted the presence of seven immunoglobulin-like domains in the extracellular region of this molecule. This feature, coupled with the detection of an insert domain bisecting the kinase domain of the predicted protein sequence, places NYK/FLK-1 firmly in the Platelet-derived Growth Factor Receptor-related class of molecules. NYK/FLK-1 is expressed at high levels in adult heart, lung, kidney, brain and skeletal muscle, but is also expressed at lower levels in most other adult tissues. In situ hybridization of day 12.5 embryo sections demonstrated NYK/FLK-1 mRNA expression in endothelial cells lining the dorsal aorta and intervertebral veins. In addition, expression was found in cells lining the capillary plexus which surrounds the developing neuroepithelium, and in the endothelial cells which are found within the embryonic lung, spleen, liver and metanephros.

3T3 Cells↗
PubMed1992

A third tal-1 promoter is specifically used in human T cell leukemias.

A common feature of T cell acute lymphoblastic leukemias (T-ALLs) is the presence of structural alteration of the 5' part of the tal-1 locus, localized on chromosomal band 1p32. These alterations consist of either a t(1;14)(p32;q11) chromosomal translocation (3% of T-ALLs) or tald submicroscopic deletion (12-25% additional T-ALLs). We have characterized a case of T-ALL with t(1;14)(p32;q11) in which, unlike the majority of t(1;14), the recombination with the T cell receptor delta elements affected the 3' side of the tal-1 locus. In this case, tal-1 transcription is initiated from a promoter located within the fourth exon similarly to the DU 528 cell line. In a T-ALL bearing a t(1;14) affecting the 5' part of tal-1, two types of tal-1 transcripts were observed, namely those probably initiated from the D delta region juxtaposed to tal-1 by the translocation, and those from the exon 4 promoter. It is interesting that this exon 4 promotion was also found in leukemic T cell lines and T-ALL samples without apparent tal-1 genomic alteration. In contrast, no transcript initiated from the exon 4 promoter was found in T-ALL with tald1 or tald2 deletion. In these cells, tal-1 is expressed via SIL-tal-1 fused transcripts. Finally, this exon 4 initiation was detected neither in normal bone marrow, nor in malignant cells from the erythroid/megakaryocytic lineages. Taken as a whole, these data suggest that the exon 4 promoter is specifically active in T cell lineage.

Base Sequence↗
PubMed1992

FDC-P1 myeloid cells engineered to express fibroblast growth factor receptor 1 proliferate and differentiate in the presence of fibroblast growth factor and heparin.

Full-length murine fibroblast growth factor (FGF) receptor 1 (FGFR-1L) cDNA was introduced into the FDC-P1 mouse myeloid progenitor cell line, which lacks FGF receptors and depends on interleukin 3 (IL-3) or granulocyte/macrophage colony-stimulating factor (GM-CSF) for its proliferation and survival. The expression of the FGFR-1L gene in FDC-P1 cells allowed these cells to grow in the presence of FGF and heparin. The resulting cell line, designated FD FGFR-1L.A, exhibited a more mature myeloid phenotype than did the parental FD FGFR-1L cells or uninfected FDC-P1 cells. They formed mainly dispersed colonies in soft-agar cultures when grown in the presence of FGF and heparin, suggestive of myeloid differentiation. The cells can be switched between growth on FGF/heparin and IL-3. Northern blot analysis and cytochemical staining demonstrated that FD FGFR-1L.A cells expressed myeloperoxidase mRNA and protein, biochemical markers specifically expressed during differentiation from the promyelocytic to the granulocytic stages, whereas the parental FD FGFR-1L cells and FDC-P1 cells failed to express this marker. These results indicate that the expression of FGFR-1L by FDC-P1 cells transmitted signals for growth in the presence of FGF and heparin and generated an additional signal for early myeloid differentiation but failed to commit FD FGFR-1L.A cells to terminal differentiation. This in vitro culture system can be used for molecular analysis of the regulation of cellular growth and differentiation mediated by the FGFs and their receptors.

Animals↗
PubMed1992

Long-term culture of adult rat hepatocyte spheroids.

Hepatocytes from adult rats were cultured on poly-HEMA-coated surface to form spheroids in hormonally defined media as previously shown with newborn rat hepatocytes. Spheroidal aggregates of adult rat hepatocytes were morphologically similar to those of newborn rat hepatocytes and could also form a monolayer of uniform liver parenchyma-like cells when transferred on collagen-coated surfaces even after 2 months of culture. Under these culture conditions, albumin and transferrin secreted in vitro by adult rat hepatocyte spheroids were detectable by immunoprecipitation method at least until 2 months of culture. The production of proteins by hepatocyte spheroids could be regulated in vitro by IL-6: the secretion of alpha 2-macroglobulin was increased and the secretion of albumin was decreased in the presence of this cytokine. In addition, cytochrome P450 IA1 was strongly induced by methylcholanthrene in adult rat hepatocyte spheroids, and the induction remained relatively constant up to 22 days of culture. These cells were also able to metabolize lidocaine to monoethylglycinexylidine when measured up to 14 days of culture, showing the presence of a relatively high level of P450 IIIA2. The UDP-glucuronyltransferase activity, specific for bilirubin conjugation, decreased to 18% of the initial value after 2 weeks of culture. This work showed that adult rat hepatocytes in long-term spheroid culture kept differentiated functions, providing a new model for the in vitro study of hepatocyte functions and complementing that of newborn rat hepatocytes using the same system.

Albumins↗
PubMed1992

L-myc and N-myc influence lineage determination in the central nervous system.

The N-myc and the L-myc proto-oncogenes are expressed during embryonal development mainly in the developing brain. Studies of their expression in single neuroepithelial cells revealed that neural precursors not yet committed to the glial or the neuronal lineage expressed both genes, but after lineage commitment they expressed either N-myc or L-myc. Moreover, enforced expression of L-myc in the neural precursor cell line 2.3D caused neuronal differentiation, while the expression of N-myc promoted glial differentiation. These results indicate that L-myc and N-myc play critical roles in lineage determination for the central nervous system.

Animals↗
PubMed1992

Study of CYP2D6 gene in children with autoimmune hepatitis and P450 IID6 autoantibodies.

Cytochrome P450 IID6 is an autoantigen recognized by the sera of children affected with a subtype of autoimmune hepatitis. It was hypothesized that a mutation in the CYP2D6 gene could explain the autoimmune response in these patients. To examine this question, genomic DNA from peripheral lymphocytes (n = 9) and liver (n = 1) of 10 patients with anti-LKM-1 antibody was analysed by Southern blot for genetic association studies between a particular CYP2D6 haplotype and autoimmune hepatitis. In addition, a region of CYP2D6, from the same genomic DNA, was amplified by polymerase chain reaction (PCR) and digested by BstNI, in a search for the most prevalent 29B mutation, described in subjects who do not express the P450 IID6. Total RNA and proteins, prepared from the liver of an anti-LKM-1+ patient, were analysed by Northern and Western (immunoblot) blots respectively. Our results do not reveal any major structural change in the DNA of this patient at the CYP2D6 locus that could explain their autoimmune response. Corroborating this observation, no changes were noted either in P450 IID6 mRNA size or in the corresponding protein. However, these data do not exclude the possibility of subtle changes in the protein due to point mutations in critical regions that might trigger an autoimmune response.

Autoantibodies↗
PubMed1992

Emergency liver transplantation for fulminant liver failure in infants and children.

We report our results with orthotopic liver transplantation in children with fulminant liver failure. Thirty-five children with fulminant liver failure were evaluated for liver transplantation. The main causes of liver failure were viral hepatitis (54.2%), drug-induced liver injury (14.2%) and Wilson's disease (11.4%). Children were considered as candidates for liver transplantation only if hepatic encephalopathy was associated with a decrease in the level of factor V to below 25%. Seven children (20%) did not meet this criterion and recovered spontaneously. Six children (17.1%) had contraindications for liver transplantation and died. In three of these six children, contraindications included irreversible brain damage at the time of admission. Twenty-two children (62.8%) met the criteria for liver transplantation and were placed on the emergency transplant list. Three of them died awaiting grafts. Nineteen children underwent liver transplantation; 13 of them (68.4%) are alive without sequelae, after 6 mo to 4 yr of follow-up, at this writing. Four of the children who died after surgery had severe encephalopathy on admission that did not improve after liver transplantation. In conclusion, emergency liver transplantation appears to be an effective treatment for children with fulminant liver failure. Nevertheless, irreversible brain damage developed in 10 patients, and they died before or after surgery. We postulate that many of these deaths could have been avoided if children had been transferred to a liver transplantation facility and had undergone transplantation earlier. We emphasize that children with acute liver failure should be transferred to a center that performs liver transplantation before the development of hepatic encephalopathy.

Adolescent↗
PubMed1992

Orthotopic liver transplantation with a reduced-size graft: an ideal compromise in pediatrics?

This study retrospectively reviewed the results of 81 orthotopic liver transplantations in 72 pediatric patients with either a full-size graft (n = 41) or a reduced-size graft (n = 40) during a 4-year period. Two types of liver reduction were used to obtain a left lobe graft (n = 30) or a left lateral segment graft (n = 10). The choice of the reduction technique was based on two criteria: the donor/recipient body weight ratio and the transverse size of the recipient's abdomen. The patients who underwent transplantation with a reduced-size graft were younger and smaller than those who received a full-size graft. The mortality rate of the candidates on the pediatric transplantation waiting list was 2.7% during the same period. The 3-year survival rate after elective transplantation was 85% and 75% in the full-size graft group and the reduced-size graft group, respectively (difference not significant). The use of reduced-size grafts was associated with higher amounts of red cell and fresh-frozen plasma transfusions after graft revascularization. The incidence of postoperative bleeding and bile leakage from the transected surface was low, whereas hepatic artery and biliary complications were less frequent in the reduced-size graft group than in the full-size graft group. At the time of follow-up, liver biochemical test results and quality of life were not different between the two groups. Despite the constraining technique and the increase in intraoperative blood loss, orthotopic liver transplantation with a reduced-size graft allows us to overcome the shortage of pediatric donors and improve the overall survival rate of children with end-stage liver disease.

Activities of Daily Living↗
PubMed1991

Dysmyelination in transgenic mice resulting from expression of class I histocompatibility molecules in oligodendrocytes.

Major histocompatibility complex (MHC) molecules are not normally expressed in the central nervous system (CNS). However, aberrant expression has been observed in multiple sclerosis lesions and could contribute to the destruction of myelin or the myelinating cells known as oligodendrocytes. The mechanism of cell damage associated with aberrant MHC molecule expression is unclear: for example, overexpression of class I and class II MHC molecules in pancreatic beta cells in transgenic mice leads to nonimmune destruction of the cells and insulin-dependent diabetes mellitus. We have generated transgenic mice that express class I H-2Kb MHC molecules, under the control of the myelin basic protein promoter, specifically in oligodendrocytes. Homozygous transgenic mice have a shivering phenotype, develop tonic seizures and die at 15-22 days. This phenotype, which we term 'wonky', is due to hypomyelination in the CNS, and not to involvement of the immune system. The primary defect appears to be a shortage of myelinating oligodendrocytes resulting from overexpression of the class I MHC molecules.

Animals↗
PubMed1991

Expression of two different forms of fibroblast growth factor receptor 1 in different mouse tissues and cell lines.

The fibroblast growth factor receptors (FGFRs) form a multigene family of at least four members, all having extracellular regions consisting of either two or three immunoglobin-like (Ig-like) domains. By RNase protection analysis we have analyzed the expression of FGFR-1 mRNA in various tissues and cell lines and demonstrated that all of the cell lines studied expressed at least two different forms of the FGFR-1 at similar levels. Although muscle and heart express forms having either two [FGFR-1 short (FGFR-1S)] or three [FGFR-1 long (FGFR-1L)] Ig-like domains, the developing brain and adult brain express only mRNA encoding the longer form. The two forms of the receptor were characterized further by stably introducing expression vectors expressing them into Rat-2 fibroblasts and FDC-P1 myeloid cells. Treatment of the transfected Rat-2 cells with acidic FGF (aFGF) or basic FGF (bFGF) resulted in focus formation. The transformed phenotype was observed even without addition of ligand after growth in culture for greater than 2 months. Cross-linking of 125I-labeled bFGF (125I-bFGF) to Rat-2 cells expressing either FGFR-1L or FGFR-1S yielded two similar complexes of 150 and 110 kDa. Although Rat-2 cells expressing FGFR-1L yielded similar complexes with 125I-labeled aFGF (125I-aFGF), only the 150-kDa complex was formed with cells expressing FGFR-1S. The 150-kDa complex was also observed when 125I-aFGF or 125I-bFGF was cross-linked to FDC-P1 cells expressing FGFR-1L. Significantly, these complexes were only observed when heparin was present in the cross-linking reaction. FDC-P1 cells expressing FGFR-1 bound aFGF and bFGF with high affinity but only in the presence of heparin. The factor dependence of these cells could be switched from interleukin 3 to FGF in the presence of heparin.

Animals↗
PubMed1991

Late cholangitis after successful surgical repair of biliary atresia.

Bacterial cholangitis is a frequent complication of successful surgical repair of biliary atresia, occurring in 93% of patients before the age of 1 year, but thought to be rare after 2 years of age. Among 76 children free of jaundice more than 5 years after operation, four presented with late cholangitis (7 to 13.5 years old), consisting of fever, jaundice, and abdominal pain with biochemical features of an inflammatory process and cholestasis. Liver biopsy specimens consistently demonstrated histological features of cholangitis, growth of microorganism, or both. Cholangitis subsided spontaneously in one patient or in response to intravenous administration of antibiotics. Cholangiography consistently demonstrated biliary abnormalities but no definite obstruction to the bilioenteric anastomosis. All the children had good hepatic function 3 weeks to 4 years after the episode of cholangitis. These results suggest that cholangitis may occur several years after surgery but does not seem to alter prognosis.

Acute Disease↗
PubMed1991

Cell lines derived from mouse neural crest are representative of cells at various stages of differentiation.

In order to study mammalian neural crest differentiation in vitro, a series of clonal neural crest (NC) cell lines have been generated by infection of migrating mouse neural crest cells with two recombinant retroviruses containing either the c-myc or N-myc proto-oncogenes. Many cell lines were generated which could be subdivided into three groups based on their appearance in culture. Eleven of these cell lines representative of each of the morphological groups were characterized for the expression of six antigenic markers expressed by neural cells. In addition, mRNA was prepared from these cell lines and analyzed for the expression of a number of neural specific genes. These analyses show that the cell lines are representative of the following cell types: (1) neural crest-like cell lines that do not differentiate in 10% serum; (2) progenitor cell lines, some of which can partially differentiate in culture; and (3) mature neuronal cell lines or bipotential cell lines. Southern blot analysis of DNA from these lines indicated that they have multiple integration sites for the provirus and suggest that phenotypically different cell types have arisen from a single cell. None of the cell lines showed any proliferative or morphological response to nerve growth factor (NGF), whereas over two-thirds of the lines showed both marked proliferative and morphological responses to fibroblast growth factor (FGF). These data indicate that we have generated a range of cell lines representative of a spectrum of mouse neural crest derivatives.

Animals↗
PubMed1991

Biliary complications after transplantation in children: role of imaging modalities.

Among a series of 140 liver transplantations in children, 21 biliary complications (BC) (15%) are reported. BC were identified from 2 days to 3 months after LT. Positive US findings were present in 20 cases. Cholangiography was obtained by opacification of a surgical drain in 3 cases, per-operatively in 3 and by PTC in 15. Drainage was placed in 9 and balloon dilatation performed in 2. Causes of BC include hepatic artery (HA) thrombosis in 7, HA stenosis in 1, anastomosis stricture in 7, anastomosis kink in 3, mucocele of cystic duct remnant in 2 and sludge in 1. Treatment was surgical in all, but 2 cases were treated percutaneously. There is a great difference in severity of prognosis between complications secondary to HA thrombosis and isolated BC. Role of US in diagnosis and of PTC and interventional radiology in treatment are emphasized.

Adolescent↗
PubMed1991

Identification of the main epitope on human cytochrome P450 IID6 recognized by anti-liver kidney microsome antibody.

Antibodies present in the sera of a group of children with autoimmune hepatitis react with human cytochrome P450 IID6. cDNA constructions of various fragments of human P450 IID6 were made and expressed and the resulting peptides were tested in immunoblot with patients' sera. These allowed identification of at least two antigenic sites on the P450 molecule. The main one, recognized by all sera tested, is located between amino acids 239 and 271. Synthesis of three peptides covering this area of the molecule allowed identification of a sequence of three amino acids (tyrosine-tryptophane-asparagine) located at position 261-263 that constitutes the essential part of the epitope. A protein sequence data-base search revealed homologies between this region of human P450 and proteins from Salmonella typhimurium, from human T lymphotropic virus types 1 and 2 and Herpes simplex virus type 1.

Amino Acid Sequence↗