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Biomedical subjects

F Gauthier

Publications and source records attributed to F Gauthier.

At least 91 records · Page 5Linked to original sources
PubMed1995

Proliferation and differentiation of a human hepatoblastoma transplanted in the Nude mouse.

A pure epithelial human hepatoblastoma was directly transplanted to athymic Nude mice to provide a model system to study proliferation and differentiation of these tumoral cells. The first transplantation selected the embryonal component of this tumor, while subsequent passages selected in addition neuroendocrine and mesenchymal cells that evolved into osteoid and bony trabeculae. The embryonal character of this hepatoblastoma was further demonstrated by the expression of glutamine synthetase mRNA and a fetal pattern of mRNAs encoding insulin-like growth factor II. However, alphafetoprotein mRNA was detectable in neither the original nor the transplanted tumors. Finally, although p53 mRNA levels were increased, no mutation was detected in the p53 gene.

Animals↗
PubMed1995

Pulmonary arteriovenous shunting in children with liver disease.

Pulmonary arteriovenous shunting (PAVS) with hypoxemia is a severe complication of cirrhosis that may regress after liver transplantation. We report PAVS in 25 children with cirrhosis and in 1 with portal vein obstruction; proof of shunting was obtained by technetium Tc 99m microaggregated albumin pulmonary scanning or a high alveoloarterial O2 gradient or both. Cyanosis or dyspnea or both occurred at ages ranging from 6 months to 14 years, earlier in children with biliary atresia and polysplenia syndrome (p < 0.01). Mean arterial oxygen tension (PaO2) was 57 mm Hg (range, 42 to 81 mm Hg) during breathing of 21% O2 and 367 mm Hg (range, 179 to 535 mm Hg) in 100% O2. Cardiac index was always raised, significantly more in children with biliary atresia and polysplenia syndrome (p < 0.01). Seven untreated children died 3 months to 8 years after the diagnosis of PAVS. Eleven underwent liver transplantation: seven are alive (follow-up, 1 to 4 years) and have no signs of PAVS. The PaO2 value during breathing of 100% O2 was > 300 mm Hg in the survivors and < 200 mm Hg in the four nonsurvivors (p < 0.01). These results indicate (1) that PAVS can occur at any age in children with portal hypertension, and that the risk is highest and earliest in children with biliary atresia and polysplenia syndrome, (2) that early liver transplantation allows regression of PAVS, and (3) that the prognosis may in part be related to the level of PaO2 while the patient is breathing 100% O2. The results indicate that systematic screening for PAVS should be part of the examination of these children.

Adolescent↗
PubMed1995

Paediatric surgical oncology. 5--Nephroblastoma. International Society of Paediatric Oncology (SIOP) Nephroblastoma Trial & Study Committee.

The favourable results from the treatment of Wilms' tumour are an example of the success of multimodal therapy in paediatric oncology. The epidemiology, methods of diagnosis, benefits of pre-operative chemotherapy, basic principles of surgery and post-operative treatment modalities are presented. The approach to the management of Wilms' tumour considered in this paper is mainly that of the International Society of Paediatric Oncology.

Chemotherapy, Adjuvant↗
PubMed1994

Outcome of ABO-incompatible liver transplantation in children with no specific alloantibodies at the time of transplantation.

The shortage of suitable liver donors for children has motivated the use of ABO-incompatible (ABO-I) grafts for transplantation in urgent situations. However, survival after ABO-I liver grafts has been reported at about 30% as compared with 80% in cases of ABO-identical or -compatible liver grafts. This difference has been attributed to antibody-mediated, hyperacute or chronic liver rejection, due to preformed ABO antibodies (alloantibodies). In this study, we report our results with ABO-I livers in children without alloantibodies at the time of transplantation. From January 1988 to June 1993, 143 OLT were performed in 122 children. Eight children received 8 ABO-I liver grafts. Of these, 7 patients were included in the study. All 7 were alloantibody free before OLT. Five children were spontaneously alloantibody free, while in 2 children, the plasma alloantibodies were eliminated before and after transplantation using intravenous infusion of specific blood group antigens of the donor blood group (soluble antigens). Immunosuppression consisted of a triple-drug treatment combining CsA, AZA, and steroids. The follow-up period was between 10 and 48 months. One child died from a surgical complication. Six children survived, but 1 died 10 months later from intestinal obstruction. There were no graft losses and no episodes of hyperacute or chronic rejection. The graft and patient survival rate was 71%. There was a 28% incidence of rejection, but all were mild (requiring steroid boluses only). Our results suggest that the absence of ABO alloantibodies at the time of and after transplantation can protect ABO-I liver grafts against antibody-mediated rejection, whether hyperacute or chronic, and that soluble antigens are effective in eliminating alloantibodies in children.

ABO Blood-Group System↗
PubMed1994

Identification of the U-937 membrane-associated proteinase interacting with the V3 loop of HIV-1 gp120 as cathepsin G.

We have purified a serine proteinase from the membrane of U-937 cells that was inhibited in a tight-binding manner by recombinant gp120 and by peptides mimicking the V3 loop of gp120 [(1993) FEBS Lett. 317, 167-172]. This proteinase has now been characterized, both structurally and functionally. It has a dual trypsin- and chymotrypsin-like specificity, and N-terminal sequence analysis of the first 32 residues indicates complete identity with leukocyte cathepsin G. Cathepsin G-like material was located at the surface of U-937 cells using a monoclonal antibody directed against leukocyte cathepsin G, and polyclonal anti-cathepsin G antibodies precipitated the purified proteinase. However, the U-937 enzyme differs slightly from commercial leukocyte cathepsin G in its apparent M(r) because of different glycosylation. No other protein structurally related to cathepsin G was found upon screening a U-937 cDNA library using several oligonucleotide probes constructed from the membrane proteinase N-terminal amino acid sequence. The possible interaction of a cathepsin G-like proteinase at the surface of U-937 cells with the V3 loop of HIV-1 gp120 is discussed.

Amino Acid Sequence↗
PubMed1994

Lessons from the first 100 liver transplantations in children at Bicêtre Hospital.

The authors report their experience with 100 liver transplantations at Bicêtre Hospital. From 1988 to 1991, 85 children received a total of 100 liver grafts (mean age, 44.4 months; two thirds were under 3 years of age). Fifty-four percent of the grafts were reduced-size. Cyclosporine, steroids, and azathioprine were used for immunosuppression. The actuarial survival rate at 4 years is 86%. Retransplantation was performed in 14 children (16%). Forty-four patients (49%) had another operation. Biliary complications (17%), hepatic artery thrombosis (HAT) (14%), and hemoperitoneum (14%) were the most frequent surgical complications. Retransplantation was avoided in 50% of the patients who underwent urgent artery revision for thrombotic complications. It appeared that ABO-incompatible were better tolerated in children without ABO alloantibodies at the time of transplantation. The survival rates of ABO-identical, -compatible, and -incompatible liver grafts did not differ (61%, 50%, and 57% respectively). The results suggest that an aggressive policy of reintervention, including retransplantation, is necessary to achieve a satisfactory survival rate and quality of life. Children lacking ABO alloantibodies at the time of transplantation might tolerate ABO-incompatible liver grafts better.

ABO Blood-Group System↗
PubMed1994

Application of spheroid culture to human hepatocytes and maintenance of their differentiation.

Human hepatocytes cultured with a hormonally defined medium on non-adherent poly-(2-hydroxyethyl methacrylate)-coated surface were able to form spheroids. The maintenance of liver-specific functions was assessed by following secretion of albumin, transferrin and alpha 1-antitrypsin that were still detectable after 4 months of spheroidal culture. Moreover, cytochrome P-450 IA was induced by methylcholanthrene for up to 2 weeks. This cell system is very promising for long-term in vitro studies of human hepatocyte functions.

Albumins↗
PubMed1994

New substrates of papain, based on the conserved sequence of natural inhibitors of the cystatin family.

A series of peptide substrates with different fluorogenic leaving groups has been synthesized. The peptide moiety in these substrates mimics a highly conserved sequence (QVVAG) in the natural reversible inhibitors of cysteine proteinases, the cystatins, that participates to the tight binding of target proteinases. This sequence is invariably cleaved at the A-G bond when synthetic peptides containing it were incubated with papain. AEC and AMC fluorophores were therefore attached to the Ala residue to construct new substrates for cysteine proteinases. The solubility of the resulting substrates was improved by attaching a N-terminal gluconoyl group, or by introducing an arginyl residue at P5 (nomenclature of Schechter I, Berger A (1967) Biochem Biophys Res Commun 27, 157-162). Neither induced significant changes in the kcat/Km values with papain. Those values were all in the 10(5) M-1 s-1 range. The kcat/Km was increased 10-50-fold by using substrates with intramolecularly quenched fluorescence. With these, the enzyme specificity on both sides of the scissile bond can be investigated. The substrate Abz-QVVAGA-EDDnp is among the most sensitive papain substrates ever reported, with a kcat/Km value of 29 10(6) M-1 s-1. The positioning and conformation of the bound QVVA moiety within the active site of papain were predicted by molecular modelling using the X-ray coordinates of a peptide inhibitor-papain complex.

Amino Acid Sequence↗
PubMed1994

Synthesis and biodistribution of [5-131I]iodotropapride: a potential D2 dopamine receptor imaging agent.

[5-131I]Iodotropapride is a benzamidic compound which displays high affinity and selectivity for dopaminergic receptors. It was prepared from the corresponding brominated compound by a nucleophilic substitution with [131I]iodine (t1/2 = 8.02 days, E gamma = 364 keV) based on the use of Cu(I) as catalyst and high specific activity of [131I]NaI. After i.v. injection in rats the tracer crosses the blood-brain barrier (0.42 +/- 0.06% of injected dose in the total brain) and demonstrates a high affinity binding to the striatum. The striatum-to-cerebellum ratio increases with time and reaches values of 9 and 22 at 30 and 120 min after injection, respectively. This specific uptake in the striatum is saturable and can be blocked by pretreatment with different D2 antagonists. When labeled with 123I (t1/2 = 13 h, E1 = 159 keV), the corresponding [123I]iodotropapride may be useful for the investigation of the D2 dopamine receptors in humans with single photon emission computer tomography (SPECT).

Animals↗
PubMed1994

[Small intestine ulcers 12 years after ileosigmoid anastomosis for neonatal necrotizing enterocolitis].

BACKGROUND: Ileal ulcers can be seen several years after surgery for neonatal necrotizing enterocolitis. They may be due to chronic bacterial colonisation of the intestine. CASE REPORT: A 12 year-old boy admitted suffering from chronic severe anemia (hemoglobin 6.5 g/dl), hypochromic and microcytic. Digestive bleeding was negative and the patient was successfully given iron for 6 months. Anemia was found again several months after cessation of treatment. Rectosigmoidoscopy showed several ulcers with inflammatory mucosa, near anastomosis secondary to an extensive bowel resection due to necrotizing enterocolitis. Ulcers of the distal small bowel persisted despite mesalazine and iron therapy and required resection of the intestine on both sides of the anastomosis. A few months later, recurrence of both ulcers and anemia led to the search for bacterial overgrowth which was confirmed by breath hydrogen testing. The patient was then given metronidazole plus amoxicillin by alternate courses and is well one year later. CONCLUSIONS: Chronic bacterial colonization can be responsible for ileal ulcers several years after intestinal resection, requiring a prolonged controlled follow-up.

Anastomosis, Surgical↗
PubMed1994

[Vascular complications of liver transplantation: surgical treatment].

Vascular complications constitute a major cause of morbidity and mortality after liver transplantation. They are dominated by arterial complications, the most frequent being hepatic artery thrombosis. Venous complications essentially consist of portal vein thrombosis. The preventive treatment of vascular complications is based on a better understanding of the risk factors. Close cooperation between surgeon, and radiologist is essential for effective surgical correction, which requires a rapid diagnosis and is designed to save not only the patient's life, but also, whenever possible, the liver transplant.

Aneurysm, False↗
PubMed1993

A new, sensitive fluorogenic substrate for papain based on the sequence of the cystatin inhibitory site.

We have designed and tested a new papain substrate with intramolecularly quenched fluorescence. It is based on a highly conserved sequence in all members of the cystatin superfamily that participates in the inhibition of cysteine proteinases. This substrate, O-aminobenzoyl (Abz)-QVVAGA-ethylenediamine-2-4-dinitrophenyl (EDDnp) is very sensitive to papain with a second-order rate constant kcat/Km of 3.1 10(7) M-1S-1. It is also efficiently hydrolyzed by cathepsin L, although the kcat/Km for this proteinase is about 60-fold lower than that for papain. This change is due to a decrease in kcat, the Km's are almost identical. This allows clear functional discrimination between these two proteinases, and may lead to the development of selective inhibitors for individual cysteine proteinases. Unlike most commonly used papain substrates, Abz-QVVAGA-EDDnp is not hydrolyzed by trypsin. The papain cleavage site was identified as the A-G bond by N-terminal amino acid sequencing. The use of sensitive and specific substrates such as the one described here will prove invaluable for investigating cysteine proteinase activities in parasite infections. The close interaction between papain or cathepsin L with Abz-QVVAGA-EDDnp is compared to that with cystatin inhibitors, which all include a QxVxG consensus segment in their structure.

Amino Acid Sequence↗
PubMed1993

[Transplantation of reduced-size livers in children].

Nowadays, liver reduction techniques make it possible to use livers obtained from adults or adolescents for implantation in children. These techniques have been evaluated by analysis of 100 liver transplantations performed between January 1988 and October 1991 in 85 children. Forty-six full-size grafts implanted in 38 children (group 1) were compared with 54 reduced-size grafts implanted in 47 children (group 2). The overall actuarial survival at 4 years was 86 percent. There was no statistical significant difference between the two groups as regards the rates of death (8 versus 19 percent), reoperation (54 versus 64 percent), retransplantation (15 versus 16 percent), hepatic artery thrombosis (13 versus 15 percent) and graft survival (82 versus 70 percent) respectively. Haemorrhage was significantly more frequent in group 1 than in group 2 (P = 0.04), irrespective of whether transplantation was performed urgently or electively. Using reduced-size livers considerably increases the number of liver grafts available to children. Apart from a greater risk of haemorrhage, the results obtained with reduced-size livers were identical with those obtained with full-size livers.

Adolescent↗
PubMed1993

Initial assessment of the beneficial effect of partial splenectomy in hereditary spherocytosis.

Clinical manifestations of hereditary spherocytosis (HS), the most common red blood cell (RBC) membrane disorder, can be abrogated or markedly reduced by splenectomy. However, concerns regarding risks from overwhelming infections after splenectomy have restricted its use, especially in children. This study was designed to determine if partial splenectomy can decrease the hemolytic rate while maintaining phagocytic function of the spleen. Partial splenectomy was performed in 11 children (age 2 to 13) with HS. The effect on hemolytic rate was assessed by comparing the presurgical and postsurgical values for hemoglobin, reticulocyte number, and RBC life span. The residual splenic phagocytic function was assessed using technetium 99m scans and by enumerating the percentage of pitted RBCs in circulation. There were no complications from the surgical procedure in any of the 11 individuals. Following partial splenectomy, hemoglobin increased on the average by 3 g/dL, reticulocyte count decreased by 300 x 10(6)/L, and RBC life span was substantially prolonged. Normal technetium uptake was noted in the splenic remnant and the percentage of pitted RBCs was in the normal range. Partial splenectomy is effective in decreasing the hemolytic rate while maintaining residual splenic phagocytic function of the spleen in HS. We conclude that the use of this procedure as treatment for RBC membrane disorders warrants consideration, especially in infants under 5 years of age who need frequent transfusions.

Adolescent↗
PubMed1993

Interaction between a membrane-associated serine proteinase of U-937 monocytes and peptides from the V3 loop of the human immunodeficiency virus type 1 (HIV-1) gp120 envelope glycoprotein.

A trypsin-like proteinase which is inhibited by recombinant gp120 and by synthetic peptides of various lengths spanning the conserved sequence of the V3 loop has been purified and partially characterized from a U-937 cell membrane extract. V3 loop peptides behave as competitive inhibitors of the enzyme, while gp120 exerts a tight-binding inhibition, reacting in stoichiometric amounts with the proteinase to provide significant inhibition. Though the properties of the U-937 membrane proteinase towards gp120 and synthetic peptides of the V3 loop resemble those of the Molt-4 T-cell tryptase TL2, these two proteinases differ by their physicochemical properties and their susceptibility to other inhibitors of serine proteinases. These results give support to the concept of a membrane-associated proteinase as a complementary or alternative receptor to the CD4, for allowing virus to enter host cells and thus spreading HIV infection.

Amino Acid Sequence↗