Search PubMed⌕ Search

Biomedical subjects

F Gauthier

Publications and source records attributed to F Gauthier.

At least 109 records · Page 6Linked to original sources
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↗
PubMed1993

Pediatric liver transplantation for primary hepatocellular carcinoma associated with hepatitis virus infection.

We report two cases of early primary hepatocellular carcinoma (PHC) in children, after probable maternal transmission of hepatitis B, that were treated with orthotopic liver transplantation (OLT). Both children were 8.5 years old and had elevated levels of serum alpha-feto-protein. The diagnosis of PHC was made at 8 years and confirmed histologically. Serum hepatitis B surface antigen (HBs Ag) was detected in the mothers and suggested vertical transmission. An attempt at complete liver tumor resection failed, leading to OLT. In order to prevent recurrence of the hepatitis B virus (HBV) infection, hepatitis B immunoprophylaxis was used. Two years after OLT, one child presented with recurrent HBV infection. No tumor recurrence was observed at follow-up in either of the patients. From these two cases we conclude that (1) HBV infection may play an important causal role in PHC in children, with an even shorter incubation period than that in adults; (2) close follow-up is needed for children who are HBs Ag-positive carriers; and (3) liver transplantation should be proposed early after the diagnosis of PHC, when tumor resection is not feasible.

Carcinoma, Hepatocellular↗
PubMed1993

Interaction between cystatin-derived peptides and papain.

The interaction between papain and synthetic peptides which tentatively mimic cystatin surfaces was investigated both enzymatically and structurally. Measurements of dissociation equilibrium constants for the interaction of papain with these peptides modified by successive deletions or substitutions demonstrated that the QVVAG segment, which is highly conserved throughout members of the cystatin superfamily, is essential for the interaction. The glycyl-containing (N-terminal) fragments and PW-containing (C-terminal) fragments were found to be of lesser importance, since each could be deleted without significantly modifying the interaction. These fragments improved the stability of the interacting QVVAG region, which appeared to be substrate-like in all peptides tested, as it was cleaved at the A-G bond upon peptide-papain interaction. Replacement of the A residue at the scissile bond of the QVVAG by a blocked cysteinyl residue reduced the rate of cleavage of the susceptible bond and therefore shifted the resulting peptide from a substrate to an inhibitor. Derivatization of this substituted peptide at its N- and C-terminal ends by fluoresceinyl groups resulted in a dramatic decrease in the Ki to 0.5 microM. This improvement in the inhibitory properties of the substituted and derivatized peptides was correlated with structural changes as analyzed by molecular dynamic calculations. The results were compared to those proposed for the mechanisms of inhibition by natural inhibitors of the cystatin superfamily.

Amino Acid Sequence↗
PubMed1993

Cholelithiasis in infancy: a study of 40 cases.

During a 17-year period, 40 infants less than 1 year of age were investigated for cholelithiasis; 32 infants were seen within the past 10 years. Seventeen of them had no recognizable predisposing factors. In 6 infants, gallbladder lithiasis was a fortuitous finding on a plain radiograph or sonogram with no signs of common bile duct obstruction; under conservative management, no complications of lithiasis were observed on follow-up of 3 infants and spontaneous resolution occurred in 2 others. In the remaining 34 infants with lithiasis of the common duct or cystic duct or both, the initial symptoms were cholestatic jaundice in 21, acholic stools in 8, sepsis in 4, and abdominal pain in 1. Ultrasonography, performed in 33 of them, showed dilation of the biliary tract in 28, and stones in the gallbladder in 13 and in the bile ducts in 10. Percutaneous transhepatic cholangiography or operative cholangiography in 26 infants showed stones in the bile ducts in 23. In 3 infants, no lithiasis was visible, suggesting the spontaneous elimination of stones. Treatment was initially surgical in 9 infants, but starting in 1981 interventional radiologic procedures were attempted in 15 infants and were successful in 12. Spontaneous resolution of cholelithiasis occurred in 10 other infants with cholestasis. Recurrence of biliary stones was observed in 3 infants only after a follow-up of 7 months to 10 years. These results suggest that common bile duct lithiasis should be considered among the causes of cholestatic jaundice in infancy, and that some of the gallbladder calculi found in older children may have resulted from a lithogenic process that occurred during fetal life or shortly after birth. Percutaneous cholangiography with biliary drainage appears to be an effective means of treatment of infants with common bile duct obstruction; surgery can then be restricted to a limited number of cases, especially those with associated strictures of the bile ducts.

Bile↗
PubMed1993

A simple method for calibrating collagenase/pronase E ratio to optimize heart cell isolation.

A mixture of crude collagenase and non-specific proteases has been used to isolate guinea pig ventricular heart cells. Measurements of collagenase activity with Wünsch's substrate and protein content with sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) suggest that collagenase enzymes do not play a major role in heart cell isolation. On the other hand, an important factor in heart digestion seems to consist of some fractions of the proteases present in crude collagenase. It is also noted that crude collagenases do not present any sensitivity to added calcium but because this ion is important to obtain isolated cells its role is discussed. According to our results, the SDS-PAGE method can be used to determine the appropriate enzyme concentrations to obtain calcium-tolerant myocytes. These myocytes have electrophysiological properties as reported in the literature.

Amino Acid Sequence↗
PubMed1993

[Surgery of liver transplantation in children].

From 1988 until 1992, 94 children with end-stage liver disease were put forward for orthotopic liver transplantation (OLT) by the surgical and anesthesic teams of the Bicetre Hospital. Due to a majority of adult donors, and to the young age of the recipients (mean = 3 years 3 months), a reduced-size graft was prepared in 64 out of the 111 transplants performed (58%). A number of children (42) had to be reoperated on due to complications: hepatic artery thrombosis, one of the most severe complications following pediatric OLT, occurred in 14 cases, and was an indication for seven out of the 17 retransplantations in this series. The eight deaths which occurred in the early postoperative period were the toll of this particularly challenging surgery.

Adolescent↗
PubMed1992

Inhibition of rat tissue kallikrein gene family members by rat kallikrein-binding protein and alpha 1-proteinase inhibitor.

The regulation of tissue kallikrein activity by plasma serine proteinase inhibitors (serpins) was investigated by measuring the association rate constants of six tissue-kallikrein family members isolated from the rat submandibular gland, with rat kallikrein-binding protein (rKBP) and alpha 1-proteinase inhibitor (alpha 1-PI). Both these serpins inhibited kallikreins rK2, rK7, rK8, rK9 and rK10 with association rate constants in the 10(3)-10(4) M-1.s-1 range, whereas only 'true' tissue kallikrein rK1 was not susceptible to alpha 1-PI. This results in slow inhibition of rK1 by plasma serpins, which could explain why this kallikrein is the only member of the gene family identified so far that induces a transient decrease in blood pressure when injected in minute amounts into the circulation.

Animals↗
PubMed1992

An immunochemical approach to investigating the mechanism of inhibition of cysteine proteinases by members of the cystatin superfamily.

Antibodies were raised against a synthetic dodecameric peptide KGAGQVVAGPWK (K12K), encompassing sequences thought to be important for the function of the cysteine proteinase inhibitors of the cystatin superfamily. These antibodies specifically recognized molecules of family 3, i.e., kininogens, in the serum of seven mammalian species tested in this study. The only notable exception was that of rat thiostatin (T kininogen) which is structurally related to the kininogen family. The antibodies also discriminated between family 2 (cystatins) and family 3 (kininogens) of the cystatin superfamily, since neither chicken cystatin nor human and rat cystatins C and S, which all belong to family 2 were recognized. The cystatin-like inhibitory domains resulting from fragmentation of human low molecular weight kininogen by bovine trypsin, were still recognized by antibodies, indicating that discrimination does not require two neighbouring inhibitory sites on the kininogen heavy chain. The antibodies blocked the capacity of kininogens to inhibit papain, suggesting that they recognize a conformational epitope at or near the kininogen inhibitory sites. The inhibitory properties of family 2 cystatins remained unchanged, confirming that members of this family do not interact with anti K12K antibodies. These antibodies are thus a new tool able to discriminate functionally and structurally between the members of the cystatin superfamily.

Amino Acid Sequence↗
PubMed1992

Protein products of the rat kallikrein gene family. Substrate specificities of kallikrein rK2 (tonin) and kallikrein rK9.

Two closely related kallikrein-like proteinases having little activity toward the standard synthetic amide substrates of tissue kallikreins were isolated from the rat submandibular gland. They were found to be the protein products of the rKlk2 (tonin) and the rKlk9 genes by amino acid sequence analysis (nomenclature of the genes and proteins of the kallikrein family is according to the proposal of the discussion panel from the participants of the KININ '91 meeting held Sept. 8-14, 1991, in Munich, Germany). These two proteinases of similar structure also had very similar physicochemical properties. They differed from other kallikrein-related proteinases in having high pHi values of 6.20 (rK2) and 6.85 (rK9). Kallikrein rK2 was purified as a single peptide chain, whereas rK9 appeared as a two-chain protein after reduction. Their enzymatic properties were also very similar and differed significantly from those of other rat kallikrein-related proteinases. Unlike the five other kallikrein-related proteinases we have purified so far, kallikrein rK9 was not inhibited by aprotinin. rK9 also differed from rK2 by its tissue localization. The prostate gland contained only rK9 where it was the major kallikrein-like component. The amino acids preferentially accommodated by the proteinase S3 to S2' subsites were identified using synthetic amide and protein substrates. Unlike other kallikrein-related proteinases, rK2 had a prevalent chymotrypsin-like specificity, whereas rK9 had both chymotrypsin-like and trypsin-like properties. Both rK2 and rK9 preferred a prolyl residue in position P2 of the substrate and did not accommodate bulky and hydrophobic residues at that position, as did most of the other kallikrein-related proteinases. This P2-proline-directed specificity is necessary for processing the precursors of several biologically active peptides. Subsites accommodating residues COOH-terminal to the scissile bond were also important in determining the overall substrate specificity of these proteinases. rK2 and rK9 both showed a preference for hydrophobic residues in P2'. Other subsites upstream of the S3 subsite were found to intervene in substrate binding and hydrolysis. The restricted specificity of rK2 and rK9 is consistent with the presence of an extended substrate binding site, and hence with a processing enzyme function. Their P1 specificities enabled both proteinases to release angiotensin II from angiotensinogen and from angiotensinogen I, but rK9 was at least 100 times less active than rK2 on both substrates. The substrate specificities of rK2 and rK9 were correlated with key amino acids defining their substrate binding site.(ABSTRACT TRUNCATED AT 400 WORDS)

Amino Acid Sequence↗
PubMed1992

Production of the cysteine proteinase inhibitor cystatin C by rat Sertoli cells.

The Sertoli cells of the rat testis produce cystatin C, a cysteine proteinase inhibitor. Primary culture of Sertoli cells secreted both unglycosylated and glycosylated forms of rat cystatin C. Despite the low concentration of cystatin C in rete testis fluid, equilibrium dissociation constants (Ki) for the interaction between cystatin C and lysosomal cathepsins indicate that this molecule could be involved in the local regulation of testicular cysteine proteinase activity which may be necessary for spermatogenesis and spermiogenesis.

Amino Acid Sequence↗
PubMed1992

Immunological characterization of rat kininogens with monoclonal antibodies to T-kininogen. Distinction between the different domains of T-kininogen and the multiple rat kininogens.

A panel of 16 monoclonal antibodies (mAb) were produced against rat T-kininogen to characterize this family of proteins. These mAbs bound 125I-T-kininogen by radioimmunoassay as well as reacting strongly with immobilized T-kininogen in an enzyme-linked immunosorbent assay (ELISA). The reactivity of these antibodies with proteolytic fragments of T-kininogen demonstrated the recognition of several different epitopes. One antibody was specific for the domain 1 of the heavy chain and/or the light chain, twelve antibodies were specific for domain 2 and three antibodies were specific for domain 3. All monoclonal antibodies recognized the two forms of T-kininogen encoded by the two different T-kininogen genes, TI and TII kininogen, except antibody TK 16-3.1 which uniquely reacted with TII kininogen. Two antibodies recognizing domain 2 cross-reacted with the high-molecular-mass kininogen (H-kininogen), whereas all the other monoclonal antibodies were specific to T-kininogen and did not recognize the heavy chain of H-kininogen. None of the antibodies tested altered the thiol protease inhibitory activity of T-kininogen, its partial proteolysis by rat mast cell chymase or the hydrolysis of H-kininogen by rat urinary kallikrein. The use of these antibodies in the development of sensitive ELISA to measure T-kininogen levels in plasma, urine, liver microsomes and hepatocytes is described. Two different forms of T-kininogen were distinguished by these monoclonal antibodies in Western blotting using rat plasma. The localization of T-kininogen was defined using these monoclonal antibodies by immunohistochemistry in rat liver hepatocytes and rat kidney.

Animals↗
PubMed1992

Functional diversity of proteinases encoded by genes of the rat tissue kallikrein family.

A group of proteinases closely related to tissue kallikrein was purified from the rat submandibular gland. Physicochemical characterization of these proteinases, including amino terminal sequencing, allowed correlation with the genes of the rat kallikrein family. In spite of their similar structure, these proteinases have different substrate specificities and different susceptibilities to inhibitors which suggest that they do not share the same biological function. Kallikrein-like proteinases also have restricted specificities that are probably related to their extended substrate binding site. This makes them good candidates for processing inactive protein or peptide precursors into biologically active peptides. A general approach to identifying the putative biological substrates of individual proteinases based on analysis of the specific cleavage of synthetic and natural peptide substrates by kallikrein-related proteinases is described.

Amino Acid Sequence↗
PubMed1992

Is there a place for radiation therapy in the management of hepatoblastomas and hepatocellular carcinomas in children?

From May 1978 to August 1988, 15 children with a primary malignant liver tumor received radiation therapy as part of their management at the Institut Gustave-Roussy. Age ranged from 4 months to 13 years. The male to female ratio was 1.5. Eleven patients had a histologically proven hepatoblastoma, two a hepatocellular carcinoma, and histology was not documented in two. Resection of the primary liver tumor was performed in nine cases, and all patients also received sequential chemotherapy, generally preoperative and alternating vincristine, doxorubicin, cyclophosphamide with vincristine, cyclophosphamide, and cis-platinum. Radiotherapy was performed postoperatively in eight incompletely resected patients. Six of eight are alive and free of disease 4-83 months following treatment (median 39 months) and 11-98 months since diagnosis (median 45 months). All but one were treated to limited fields to a total dose of 25-45 Gy (median 40 Gy). One patient became resectable by a combination of 24 Gy to the whole liver and concomitant 5FU and Cis-Platinum and remains with no evidence of disease 68 months following radiation therapy. Of four unresectable primaries, only one was controlled by radiotherapy. Neither of two children with pulmonary metastases were controlled by whole lung irradiation to a dose of 18 and 20 Gy, respectively, and one still remains stable 41 months after resection of a residual metastatic nodule. Neither of two hepatocellular carcinomas were controlled by doses up to 40 Gy. This small series suggests that in hepatoblastoma, radiotherapy to a total of 25-45 Gy fractionated doses, combined with chemotherapy, can play a role in selected inoperable children and also in those with minimal postoperative residues below 2 cm. It also indicates that in hepatocellular carcinoma, radiotherapy is ineffective in this dose-range.

Adolescent↗
PubMed1992

Cystatin mimicry by synthetic peptides.

Synthetic peptides which tentatively mimic the cystatin inhibitory surface were used to study the mechanism of inhibition of cysteine proteinases by their natural inhibitors. The inhibitory properties of these peptides depend mainly on the presence of the QxVxG consensus sequence. N and C-terminal peptide derivatives bearing large hydrophobic groups showed dramatically improved inhibition. Molecular dynamic studies after energy minimization showed that the non covalent interaction between these hydrophobic groups induced the formation of a loop structure which probably favours inhibition. Antibodies were raised against one of these peptides, which recognized kininogens in the serum of all mammal species tested, but not cystatins from family two.

Animals↗