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Biomedical subjects

A Paraf

Publications and source records attributed to A Paraf.

At least 55 records · Page 3Linked to original sources
PubMed1981

Immunological evidence that plasma-membrane 5'-nucleotidase is a transmembrane protein.

Antibodies inhibiting specifically plasma membrane-bound 5'nucleotidase were used to determine the disposition of the enzyme in various lymphoma cell lines. Fluorescent Fab fragments of the inhibiting antibodies bound to MF2s and MOPC 173 plasmacytoma cells, whereas no fluorescence was observed with P 1798 thymoma cells in which the enzyme was absent. The relative potency of the antiserum in inhibiting the enzyme in right-side-out and inside-out plasma membrane vesicles prepared from the above cell lines indicated that various group of antigenic determinants were present. One group of antigenic determinants was present at the external face of the cell, and a second was associated with the inner surface of the membrane. A third group of antigenic determinants was located in the vicinity of the active site of the enzyme and it is the group that varied in the various plasmacytoma cells studied. The results are interpreted as immunological evidence that 5'nucleotidase is a transmembrane glycoprotein.

5'-Nucleotidase↗
PubMed1981

Significance of intra- and extrahepatic portasystemic shunting in survival of cirrhotic patients.

Survival and incidence of hemorrhage and encephalopathy were studied in 121 medically managed cirrhotic patients according to the type of naturally occurring portasystemic shunting. Three types of shunting were distinguishable using scintillation splenoportography, a method whereby morphological and hemodynamic data on portal and hepatic circulation were obtained by external detection. The three patterns were: (1) extrahepatic shunting with partial splenic blood flow diversion, (2) spontaneous total splenic blood flow diversion, and (3) intrahepatic shunting corresponding to portohepatic communications with a diameter larger than 10 mum. The probability of 4-year survival was much lower in case of portasystemic shunting (18%) than in its absence (73%, P less than 0.01). Patients with intrahepatic shunting had a survival rate not significantly different from that of patients with extrahepatic shunting. However, they had the highest incidence of hemorrhage (71%), and hemorrhage was not due to rupture of esophageal varices. The highest incidence of encephalopathy was seen in patients with total splenic blood diversion (40%), but it was not significantly different from that of other cirrhotic patients. No group of patients can be significantly identified as a high-risk group.

Humans↗
PubMed1981

11C-L-methionine for evaluation of pancreatic exocrine function.

Pancreatic uptake of a natural amino acid, L-methionine, was measured in 58 patients using a scintillation camera. This was possible by labelling L-methionine with 11C, a short-lived isotope produced in a cyclotron. Time-activity-curves obtained in areas of interest selected over the pancreas in 25 normal subjects and in 14 alcoholic patients showed a plateau or a slight increase of activity with time. In contrast, in 19 patients with chronic pancreatitis an initial increase in radioactivity was followed by a decrease for 10 to 20 minutes and then by a plateau. The ratio of the height of the plateau at the 50th minute to the height of the peak was 0.74 +/- 0.21 in these patients, whereas it was 0.96 +/- 0.09 in the other subjects (P less than 0.001). This result was compared with direct measurements of 11C radioactivity and of amylase and bicarbonate in duodenal aspirate. The median amount of 11C incorporated into protein at the 70th minute was 53% of total activity in the control group, 28% in alcoholic patients, and only 3% in chronic pancreatitis, the differences between these values were highly significant. The absence of a peak of radioactivity in the duodenal juice, and the existence of a correlation between total 11C output and amylase output suggested that there was no release of protein in the duodenum in chronic pancreatitis. These results also suggested that the peak observed by external detection could be due to amino acid back-diffusion from the pancreas into the blood. External detection with 11C-L-methionine could be used for the assessment of pancreatic dysfunction in man.

Adult↗
PubMed1981

Plasma membrane enzymes in BALB/c lymphomas with either T or B cell properties, I. 5'-Nucleotidase.

Comparison of membrane bound 5'-nucleotidase activity has been made in crude extracts and plasma membrane fractions from Abelson virus transformed lymphomas, IgM, IgG and IgA producing plasmacytomas and from thymomas with different surface antigen markers. 5'Nucleotidase activity was characterised by the following criteria : 1) optimal pH for enzyme activity, 2) specificity of 5'AMP as a substrate at the optimal pH, 3) specific inhibition of the enzyme by alpha beta methylene ADP, 4) inhibition by EDTA. 5'-Nucleotidase was found to be present on the following B cells : Abelson virus transformed lymphomas, plasmacytomas and LPS-stimulated blasts from nu/nu spleens. The enzyme was also found in one thymoma Lut 13, but it was absent from all the other thymomas studied. A possible relationship between 5'-Nucleotidase and purine metabolism in lymphocyte subpopulations is suggested by the results.

5'-Nucleotidase↗
PubMed1980

[Cirrhosis of the liver and "lymphomas": five new cases (author's transl)].

Five patients who manifested an association between chronic liver disease and lymphoma are reported by the authors. Lymphoma developed long after the presence of liver disease or was discovered simultaneously in the five cases. A review of the available literature yielded a total of thirteen similar cases. Several mechanisms may be operative in the pathogenesis of this association: presence of HBs Ag, chronic antigenic stimulation, decrease in cellular immunity, and immunosuppressive therapy.

Adult↗
PubMed1979

[Purification of a membrane protein modifying the sensitivity of Na+/K+ ATPase to ouabain from a supernatant of plasma membrane treated with EDTA].

A membrane protein of M. W. 32,000 D and pI 5 has been purified from EDTA-treated plasma membrane supernatants by Page without detergents. These membranes are purified from the MF2S cell line issued from the murine plasmacytoma MOPC 173. The purified protein was able to induce a 300 fold increase in the Na+/K+ ATPase resistance to ouabaïn thus mimicking the original resistance of the enzyme to the drug.

Animals↗
PubMed1979

Inhibition of (Na+ + K+)-ATPase by ouabain: involvement of calcium and membrane proteins.

Treatment of plasma membrane isolated from murine plasmocytoma MOPC 173 with an EDTA-containing buffer resulted in a 300-fold increase in sensitivity of (Na+ + K+)-stimulated Mg2+-ATPase to ouabain. This phenomenon was associated with the solubilization by EDTA of phospholipid free proteins (approx. 30 000-34 000 daltons) from the cytoplasmic face of the plasma membrane and with removal of about 90% of the membrane bound Ca2+. The recovery of the original resistance to ouabain required specifically Ca2+ and was associated with a binding of the solubilized proteins to the membrane.

Animals↗
PubMed1979

Induction of specific anti-actin antibodies and their measurement by ELISA technique.

Using the ELISA technique we have been able to quantify antibodies directed against actin and to follow the kinetics of antibody production. Specific anti-actin antisera have been raised in rabbits by immunization with chemically modified white muscle rabbit actin. Two or three dinitrophenyl groups linked per actin molecule were sufficient to break natural tolerance, while linkage of three phosphorylcholine groups to actin was not.

Actins↗