The pronase resistance of cholesterol-nucleating glycoproteins in human bile

BACKGROUND & AIMS: Many putative pronucleating proteins have been isolated from the biliary concanavalin A (con A)-binding fraction. The pronase resistance of the overall nucleating-promoting activity was almost never taken into consideration. The aim of this study was to identify the major pronase-resistant con A-binding glycoproteins. METHODS: Pronase-treated and -untreated con A-binding glycoproteins were separated on a Superose 12 gel permeation column (Pharmacia, Uppsala, Sweden) and tested in a crystal growth assay. Proteins were identified by amino-terminal sequencing. RESULTS: Con A-binding pronucleating activity eluted in two peaks on the Superose column. This activity was unaltered after pronase treatment. Activity peak I contained too little protein to allow amino-terminal sequencing. In activity peak II, the major pronase-resistant con A-binding glycoproteins were identified as alpha 1-antitrypsin and alpha 1- antichymotrypsin. The 130-kilodalton nucleation promoter was identified as aminopeptidase N, but the full pronase resistance of this protein, reported earlier, was not confirmed. Immunoabsorptive removal of alpha 1-antitrypsin and alpha 1-antichymotrypsin and immunopurification showed that only alpha 1-antichymotrypsin had pronucleating activity. CONCLUSIONS: The pronase resistance of the nucleating-promoting activity of the con A-binding glycoprotein fraction was confirmed. An important part of this activity could be attributed to alpha 1- antichymotrypsin. It is an acute-phase protein, as are many other pronucleating proteins, which might indicate a general mechanism of action in gallstone formation. (Gastroenterology 1996 Jun;110(6):1926-35)     

ACUTE LYMPHOBLASTIC LEUKÆMIA IN CHILDREN: CLASSIFICATION AND PROGNOSIS

Immunological (surface-marker) tests have been used to define four subgroups of acute lymphoblastic leukæmia (A.L.L.) in childhood: T-A.L.L., B-A.L.L., common-A.L.L., and null-A.L.L. A study of 94 children shows that the common-A.L.L. subgroup achieves a much longer duration of remission than T-A.L.L.; our findings also confirm the association of some clinical features with T-cell A.L.L. Within the common-A.L.L. subgroup, initial white-cell count correlates with prognosis.     

Bencyclane as an anti-sickling agent

A vasodilating Ca²⁺ channel blocker, bencyclane, was used in 18 patients with homozygous sickle cell anaemia (SCD) to test the possible anti-sickling effect. With bencylane intervention the Na⁺-K⁺ ATPase activity increased from 256±29 to 331±37 nmol Pi/mg protein/h ( P <0.0001) and the Ca²⁺-Mg²⁺ ATPase level increased from 172±12 to 222±44 nmol Pi/mg protein/h ( P <0.0001). The intracytoplasmic Ca²⁺ concentration reduced from 3.5±0.6 to 2.7±0.25 μmol/l ( P <0.0001). The patient's blood contained fewer irreversibly sickled cells (ISCs) (a reduction from 21.4% to 14.4%) ( P <0.05). At the same time MCHC of the erythrocytes decreased from 34.5 to 33.0 g/dl ( P <0.05). Bencyclane appears to be a promising anti-sickling agent that can be used orally in SCD.     

Emergence of CD52 , glycosyiphosphatidylinositol-anchor deficient lymphocytes in rheumatoid arthritis patients following Campath-1H treatment

CD52 is a glycosylphosphatidyl-inositol (GPI)-llnked glycoproteinexpressed at high levels on normal T and B lymphocytes and atlower levels on monocytes, while being absent on granulocytesand bone marrow stem cell precursors. The emergence of CD52^– lymphocytes of both T and B cell lineages was observedIn three out of 25 rheumatoid arthritis patients treated withthe humanized antibody Campath-1H in phase II clinical trial.Whereas the majority of CD52^– B cells had disappearedfrom the peripheral blood by 3 months post-treatment, both CD52^–CD4⁺ and CD8⁺ T cells persisted in the circulation for at least20 months. In the two patients that were tested, the GPI-anchoredsurface molecules CD55 and CD59 were also absent on the CD52^–cells, although expression of other cell surface transmembraneproteins (CD3, CD4 and CD2) was unaffected. The CD52^–cells maintained a stable phenotype in vitro despite repeatedre-stimulation in culture. Both CD52^– and CD52⁺ clones,established from one of the patients, responded to a similarextent to several T cell mitogens, as assessed by proliferation,suggesting that a general defect in expression of GPI-llnkedmolecules does not impair T cell activation. These data showthat an immune attack against a GPI-anchored surface moleculecan result in the selection of a GPI-anchor-deficient cell population.Despite the persistence of CD52^– T cells in the peripheralblood, no adverse reactions associated with the presence ofthese cells were noted in any of the patients; in fact theyresponded with longer remission times after Campath-1H treatmentthan the other patients in the trial. Received 16 May 1995, accepted 27 November 1995.     

Synergistic inhibition of platelet activation by plasmin and prostaglandin I2

Endothelial cell prostacyclin (PGI2) inhibits platelet activation by raising platelet cyclic AMP. Previously, platelet activation was also shown to be blocked by plasmin formed by endothelium-derived tissue plasminogen activator (TPA). We have now studied interactions between PGI2 and plasmin in the control of platelet function. PGI2 and plasmin cause synergistic inhibition of thrombin- and ADP-induced aggregation of washed platelets. Inhibition by PGI2 is similarly potentiated by TPA added to platelet-rich plasma to generate plasmin. Thrombin-stimulated rise in platelet cytosolic Ca2+, measured by fura2 fluorescence, and thromboxane A2 formation, measured by radioimmunoassay (RIA), are likewise synergistically inhibited by PGI2 and plasmin. Plasmin neither increases nor potentiates PGI2-stimulated increases in platelet cyclic AMP. Thus, PGI2 and plasmin cause synergistic inhibition of platelet activation by both cyclic AMP-dependent and independent mechanisms. This interaction between two different endothelium-derived products may play an important role in localizing the hemostatic plug to a site of vascular injury by preventing further thrombin-mediated accrual of platelets.