PubMed Health⌕ Search

Biomedical subjects

J Harb

Publications and source records attributed to J Harb.

At least 55 records · Page 3Linked to original sources
PubMed1990

Repeat hepatic resection for primary and metastatic carcinoma of the liver.

During the last 15 years, 19 patients underwent repeated hepatic resections for malignant lesions of the liver. The first hepatic resection had been performed four to 40 months earlier for treatment of hepatocellular carcinoma (nine patients) or hepatic metastases (ten patients), eight of which were of colorectal origin. Repeat resection was an extensive hepatectomy in six, a segmentectomy in six and a local excision in seven. In one patient, three wedge resections and, finally, hepatic transplantation were subsequently performed after an initial extended right lobectomy. The operative mortality rate was 5.2 per cent. The three year actuarial survival rate was 64 per cent after the second resection.

Adult↗
PubMed1989

Differences in glycosylation state of fibronectin from two rat colon carcinoma cell lines in relation to tumoral progressiveness.

We have investigated the biosynthesis and carbohydrate structure of fibronectin secreted by two rat colon carcinoma cell lines. The cell line Prob yields progressive tumors after s.c. injection in syngeneic BD IX rats while tumors developed by Regb cells disappear after 20 days. No difference was observed in the fibronectin biosynthesis from both cell lines; however, the glycosylation degree was higher in Regb than in Prob cells indicating probable differences in the posttransductional process. The analysis of the glycosylation nature shows that fibronectin doesn't bear O-linked carbohydrate chains. The fibronectin of progressive Prob cells is more sialylated than that of the regressive Regb ones. In addition, the tri- and tetraantennary glycans are more important in Prob, while the fucosylated triantennary glycans are three times higher in Regb cells. These differences in the glycosylation state of the fibronectins could explain their differential susceptibility to the proteases treatment. In fact, the low glycosylated fibronectin from the progressive Prob cells was more rapidly degraded by several proteases than that of regressive Regb cells. The identification of the specific sites of proteolytic cleavage by sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed that the cell attachment domain as well as the collagen binding domain of Regb cell fibronectin are particularly protected against proteolytic degradation.

Adenocarcinoma↗
PubMed1989

Endothelial cell growth regulation by PGE1 analog misoprostol and indomethacin.

The role of prostaglandins on growth regulation of different cell types was investigated. We studied the effect of exogenous misoprostol in the presence or absence of indomethacin on the cell growth kinetics. Our results clearly show that misoprostol strongly inhibited the growth of several cancer cells but only slightly affected that of endothelial cells. Moreover, indomethacin alone (which decreases PG synthesis) had little effect on DNA synthesis in endothelial cells or C6 cells but inhibited colonic cancer cells. Conversely, misoprostol stimulated DNA synthesis in endothelial or C6 cells preincubated with indomethacin. This phenomenon was not observed with colonic cancer cells. The role of NSAIDs in the field of cytoprotection is discussed.

Alprostadil↗
PubMed1989

Differences in the release of 5'-nucleotidase and alkaline phosphatase from plasma membrane of several cell types by PI-PLC.

1. We have compared the effect of phosphatidyl inositol specific phospholipase C (PI-PLC) on the attachment of both 5'-nucleotidase and alkaline phosphatase to the liver plasma membrane from different species. 2. Our results demonstrate differences in the susceptibilities of both enzymes to PI-PLC treatment in relation to their origin. 3. These results were confirmed by immunoblotting using polyclonal anti-5'-nucleotidase antibodies. 4. In addition, in a single animal, susceptibility of both enzymes to PI-PLC treatment is different from one tissue to another. 5. The different percentages of released enzymes could be explained either by a polymorphism in the anchoring of these proteins at the cell surface membrane, or by a different steric hindrance or environment at the cleavage site itself.

5'-Nucleotidase↗
PubMed1989

[Intraduodenal development of diverticula of the lower choledochus. Apropos of 2 cases].

Two cases of intraduodenal development of a low choledochal diverticulum were observed during the last ten years. Preoperative diagnosis of this biliary malformation is difficult. Clinical presentation consisted of chronic upper abdominal pain and high gastrointestinal obstruction, without either cholangitis or pancreatitis. In both patients, treatment consisted of resection of the diverticulum and suture of its neck via a transduodenal approach. The post-operative course was uneventful and long-term follow-up (2 and 11 years) is satisfactory, showing that cure has been achieved by means of this simple and radical procedure. This particular biliary anomaly must therefore be distinguished from other diverticula of the common bile duct, because of its clinical presentation, diagnostic approach and treatment required.

Adolescent↗
PubMed1988

Purification of bovine liver cytosolic 5'-nucleotidase. Kinetic and structural studies as compared to the membrane isoenzyme.

Cytosolic 5'-nucleotidase from bovine liver has been purified to homogeneity. Two affinity chromatographies on concanavalin A and 5'AMP-Sepharose columns result in a 12,000-fold purification. The sequential elution of glycoproteins from the concanavalin-A-Sepharose column with methyl alpha-D-glucoside and methyl alpha-D-mannoside greatly increases the degree of purification of the enzyme. Polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate shows two subunits having apparent molecular masses of 65 kDa and 57 kDa respectively, while only one band at 70 kDa is observed in the case of the membrane-bound 5'-nucleotidase. Both the Stokes radii, measured by gel exclusion HPLC, and the sedimentation coefficient, determined by density gradient ultracentrifugation, indicate that the cytosolic enzyme is a heterodimer of about 130 kDa. This contrasts with the membrane-bound 5'-nucleotidase which is a homodimer of 140 kDa. Moreover, the antibodies raised against the membrane 5'-nucleotidase inhibited the cytosolic form indicating that a common antigenic determinant(s) exists between the two isoenzymes. However, structural differences are revealed by immunoblotting. In the same way, the effect of lectins suggests that differences in the structure of the carbohydrate chains exist between the two isoenzymes. The purified cytosolic enzyme has lower affinity for the nucleotides than does the membrane enzyme. In addition, while ADP, [alpha,beta-CH2]ADP and ATP were strong competitive inhibitors of the membrane enzyme, ADP and ATP activate the cytosolic form and [alpha,beta-CH2]ADP has no effect. Moreover, two pH optima at 7.5 and 9.5 are observed in the cytosolic enzyme while only one at 7.5 occurred in the membrane form. Finally the exogenous cations, MgCl2 and MnCl2, are necessary for the maximal activity of the cytosolic but not of the membrane 5'-nucleotidase. All these observations indicate that the two isoenzymes are different.

5'-Nucleotidase↗
PubMed1987

Ontogeny of secretory function and cholecystokinin binding capacity in immature rat pancreas.

Isolated acini were prepared from the pancreas of immature rats (age less than 1 hr. - 48 hrs) in order to study the development of the secretory process. The ultrastructural integrity of the acinar cells was maintained after digestion and stimulation with secretagogues. Acini prepared from rats aged 24 - 48 hours responded to both CCK-8 and carbachol with significant increases in amylase release. Although typical biphasic dose response curves were obtained, the curves were shifted to the right by 1 - 2 log units, compared to the responses of adult acini. At ages younger than 24 hours, acini were insensitive to secretagogues but were sensitive to the calcium ionophore A23187. CCK receptors were virtually absent from membranes prepared from newborn pancreases, but binding of CCK, although small, was measurable at 12 hours and slowly increased up to 48 hours. A greater amount of binding was seen at 72 hours, which appeared constant up to 14 days. At 21 days, adult levels of binding were found. These results confirm previous studies that the rat pancreas is insensitive to secretagogues in the first 24 hours of life. After age 24 hours the secretory process is intact but less sensitive to secretory agents than the more mature pancreas. In the case of CCK, this may be due to lesser numbers of CCK receptors and/or affinity of CCK for its receptor.

Age Factors↗
PubMed1986

Chemical modification of essential carboxyl group and histidine residue in the plasma-membrane 5'-nucleotidase.

An investigation, using specific chemical reagents, of the amino acids involved in the catalytic activity of the purified 5'-nucleotidase (5'-ribonucleotide phosphohydrolase, EC 3.1.3.5) from bovine liver plasma membranes, was carried out. The enzyme was irreversibly inactivated by N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline (EEDQ). The inhibition kinetics were of the first-order type and decreased partially in the presence of nucleotides and divalent cations. These results indicate for the first time that a carboxyl group is essential for the catalytic process of 5'-nucleotidase. Moreover, chemical modification by diethylpyrocarbonate also produced inactivation of the enzyme and showed a differential spectrum with a peak at 240 nm characteristic of N-carbethoxyhistidine residues. This inactivation was efficiently released upon decarbethoxylation by hydroxylamine only when the extent of inactivation, due to low concentration of diethylpyrocarbonate, was limited. The time-dependent inactivation followed first-order kinetics and nucleotides afforded significant protection against diethylpyrocarbonate modification. The results indicate the involvement of the histidine residue in catalysis.

5'-Nucleotidase↗
PubMed1985

Structural differences between plasma-membrane 5'-nucleotidase in different cell types as evidenced by antibodies.

Antibodies raised against bovine 5'-nucleotidase inhibit this enzyme as well as 5'-nucleotidase from other bovine tissues, showing common structure(s) between these proteins. However, an IgG fraction directed against the glucidic moiety of the liver enzyme did not cross-react with the enzyme from lymphocyte or caudate nuclei, a clear indication that within the same species the 5'-nucleotidase differs from one cell type to another. In addition, immunoblots after electrophoresis show that the previous antibodies recognize 5'-nucleotidase from human, mouse or chicken origin. However, only human 5'-nucleotidase activity can be inhibited by the antibodies. Thus at least three groups of antigenic determinants must exist on the 5'-nucleotidase: one related to the glucidic moiety of the glycoprotein whose binding inhibits the enzyme activity, another related to the catalytic site, as its binding also led to enzyme inhibition, and a last one of structural nature. It seems that the third group of determinant is common to many species, whereas the second one is more restricted.

5'-Nucleotidase↗
PubMed1984

Evidence for a metalloprotein structure of plasma membrane 5'-nucleotidase.

To point out the metalloprotein structure of bovine liver plasma membrane 5'-nucleotidase, we studied the inhibition mechanism of the purified enzyme by EDTA: this apparently non-competitive inhibition seems to be dependent on EDTA concentration, pH, temperature and incubation time. When the restoration of activity was assayed by addition of divalent cations or by gel filtration, the inhibition became progressively irreversible with time. Incubation of the enzyme with [14C]EDTA allowed us to observe, after gel filtration as well as after sucrose gradient ultracentrifugation, that the chelating agent is bound to 5'-nucleotidase.

5'-Nucleotidase↗
PubMed1984

5'-Nucleotidase from bovine caudate nucleus synaptic plasma membranes: specificity for substrates and cations; study of the carbohydrate moiety by glycosidases.

We studied 5'-nucleotidase in preparations of synaptic plasma membranes from bovine caudate nucleus. The best substrates for this membrane-bound enzyme were purine nucleotides, particularly 5'AMP. Effects of metal cations and chelating agents suggest that 5'-nucleotidase is a metalloprotein. Optimal conditions for solubilization of the 5'-nucleotidase were found by using a low concentration of the zwitterionic detergent sulfobetaine 14. In contrast, another membrane-bound enzyme, acetylcholinesterase, was not solubilized under these conditions, but only in the presence of Triton X-100. The effects of lectins (concanavalin A, Lens culinaris agglutinin, wheat germ agglutinin, and Limulus polyphemus agglutinin) showed that both enzymes are glycoproteins. Sequential hydrolysis with specific glycosidases produced modifications of the effect of lectins on these enzymes. The results suggest the presence of a complex-type glycosylation, with a fucose residue on the internal N-acetyl-D-glucosamine of the pentasaccharide core.

5'-Nucleotidase↗
PubMed1983

Purification and properties of bovine liver plasma membrane 5' nucleotidase.

5'-Nucleotidase from bovine liver plasma membranes has been extracted by the zwitterionic detergent sulfobetaine 14, and purified to apparent homogeneity. Two affinity chromatographies on concanavalin-A-Ultrogel and 5' AMP-Sepharose 4B followed by AcA-54-Ultrogel filtration resulted in a purification of 16000 times relative to the homogenate. Sodium dodecyl sulphate gel electrophoresis indicates that the apparent molecular weight of the subunit is 70000. Cross-linking of the native enzyme with dimethylpimelimidate followed by gel electrophoresis shows a band with an apparent molecular weight of 140000 indicating that the enzyme is a dimer. 5'-Nucleotidase is a glycoprotein and its activity is inhibited to different degrees by various lectins, indicating a direct interaction with the enzyme. The purified enzyme shows a sevenfold greater affinity for AMP than the membrane-bound enzyme. The optimum activity of the purified enzyme occurs at pH 7.5 while the membrane-bound enzyme showed a wide range of pH optimum (7.5-8.3). An Arrhenius plot of the membrane-bound enzyme shows a break at 28 degrees C, which disappears in the purified enzyme. The enzyme was inhibited by EDTA, and this inhibition was reversed by divalent cations. This, as well as other evidence, indicates that the enzyme contains a highly bound metal cation, perhaps Mn2+ or Mg2+.

5'-Nucleotidase↗
PubMed1983

Distinguishing characteristics of a new neuroblastoma cell line.

The characteristics of a new neuroblastoma cell line (MC-NB-1) established from the bone marrow of a 2-year-old male are described. Morphologically, the cells appear as flattened and epithelial-like or as small and spherical. Electron microscopy demonstrated microtubules and dense core secretory granules. The doubling time was approximately 35 hr. Isoenzyme patterns and catecholamine secretion indicated a human line of neuronal origin. The soft agar tumor colony forming system demonstrated drug resistance in vitro comparable to in vivo nonresponsiveness. The stemline karyotype of MC-NB-1 is 44,Y,del(1) (p22:), -4, -7, +del(7)(q22:), -16, +t(7;16)(16pter leads to 16q24::7q22 leads to 7q32), -17. Additionally, double-minute bodies were observed. However, no evidence of homogeneous staining regions (HSRs) were detected.

Carboxylesterase↗
PubMed1982

[Assay of acetylcholine receptor antibodies in myasthenia gravis. A study of 329 sera (author's transl)].

Antibodies directed against acetylcholine receptors were investigated in 329 sera by a radioimmunological technique using human muscle. Eighty-six per cent of patients with generalized myasthenia gave positive results. The percentage of positivity reached 90% when a receptor lipid extract was used. Fifty-six per cent of 25 sera from patients with ocular myasthenia were positive. Conversely, no antibody was detected in controls (other neurological diseases, normal subjects), except for two lupus patients. In addition to its diagnostic value, the assay of antibodies to acetylcholine receptors proved useful in the follow-up of myasthenic patients (notably neonates) treated by thymectomy, immunodepressants and plasmapheresis.

Adolescent↗