Moral credentials and the expression of prejudice.

Three experiments supported the hypothesis that people are more willing to express attitudes that could be viewed as prejudiced when their past behavior has established their credentials as nonprejudiced persons. In Study 1, participants given the opportunity to disagree with blatantly sexist statements were later more willing to favor a man for a stereotypically male job. In Study 2, participants who first had the opportunity to select a member of a stereotyped group (a woman or an African American) for a category-neutral job were more likely to reject a member of that group for a job stereotypically suited for majority members. In Study 3, participants who had established credentials as nonprejudiced persons revealed a greater willingness to express a politically incorrect opinion even when the audience was unaware of their credentials. The general conditions under which people feel licensed to act on illicit motives are discussed.

Evaluation of a new reactive solid phase for radioimmunoassay of serum specific IgE against muscle relaxant drugs.

Until now, immunoassays for detection of anti-muscle relaxant IgE in serum have been performed with the drug coupled to epoxy-activated Sepharose or to RAST papers dics. In the present work we have used a quaternary ammonium-Sepharose in which the quaternary ammonium reactive group (choline chloride) was directly coupled to Sepharose via an ether linkage. 50 microliters of the quaternary ammonium solid phase (QAS) was incubated with 50 microliters of serum for 3 h, washed, incubated 18 h with 125I-anti-IgE and washed again. The results were expressed as the percentage of 125I-anti-IgE absorbed onto the solid phase. The results were at 1.3 +/- 0.5% for 20 control sera, with an upper normal limit estimated to 2.3%. The within-run reproducibility ranged from 3.2% to 10.0%. The results were significantly correlated with those obtained with either alcuronium-epoxy-Sepharose, choline-epoxy-Sepharose, the RAST-alcuronium or with the RAST-succinyl choline (respectively, r = 0.66, r = 0.80, r = 0.81, r = 0.40 and r = 0.85). The values obtained with the sera of 83 patients ranged from 0.3 to 38.5%. The sensitivity was estimated at 87.9%, 66.7% and 40.7% with the QAS-RIA, the RAST-succinyl choline and the RAST-alcuronium, respectively. The inhibition of adsorption of specific IgE onto the gel ranged from 13.0 to 90.6% in presence of 130 nmol of soluble muscle relaxants. In 83.3% of 30 cases, the highest inhibition was obtained with the muscle relaxant which was clinically incriminated.(ABSTRACT TRUNCATED AT 250 WORDS)

Physicochemical characterization and biological activity of intrinsic factor in cystic fibrosis.

Absorption of crystalline labeled cobalamin is strongly decreased in cases of cystic fibrosis. In order to determine if this is due to an alteration or a lack of activation of intrinsic factor by proteases, the physicochemical properties and biological activity of intrinsic factor have been studied. Intrinsic factor was purified 800-fold from stimulated gastric juice of cystic fibrosis patients with a yield of 64.2%. Cystic fibrosis intrinsic factor had an estimated Mr of 57,000 in SDS-polyacrylamide gel electrophoresis. Its carbohydrate content resembled that of normal human intrinsic factor, except that the ratio fucose/sialic acid was higher (6.1 and 1.6, respectively) and that the content in N-acetylgalactosamine was decreased. The same alterations in carbohydrate composition were observed for Hc purified from cystic fibrosis saliva. Purified intrinsic factor from cystic fibrosis gastric juice was biologically active in vitro in the presence of ileal solubilized receptor as well as in vivo (Schilling test). The fate of iodinated cystic fibrosis intrinsic factor in guinea pig ileum studied by high-resolution radioautography was similar to that of normal intrinsic factor. In conclusion, despite modifications of the carbohydrate content of the molecule, the biological activity of intrinsic factor is not altered in cases of cystic fibrosis. The malassimilation of crystalline cobalamin observed in cystic fibrosis is due to a mechanism independent from intrinsic factor secretion.

Purification of intrinsic factor receptor from pig ileum using as affinity medium human intrinsic factor covalently bound to Sepharose.

Intrinsic factor receptor was purified from hog ileum using human intrinsic factor covalently bound to Sepharose. A yield of 49.6% and a specific activity of about 2500 pmol/mg protein were achieved. The purified receptor was very unstable: 24 h of storage or addition of sodium phosphate precipitated it. The association constant of the receptor for the cyano[57Co]cobalamin-intrinsic factor complex was estimated to be 2.1 nM-1. In native polyacrylamide gel electrophoresis it resolved in two 256 and 320 kDa bands; beta-mercaptoethanol treatment cleared it into four bands corresponding to molecular masses of 107, 81.8, 63.5 and 53.2 kDa. An additional 39.3 kDa band was considered to be an artefact due to the presence of Triton X-114. Isoelectric focusing polyacrylamide gel electrophoresis resolved the receptor into two isoproteins isoelectric at pH 4.7 and 5.1. A similar result was obtained in column electrofocusing with the 125I-iodinated receptor. The 125I-labelled receptor did not crossreact with rabbit anti-human intrinsic factor antiserum. The electrophoretic properties of the receptor purified with intrinsic factor covalently bound to Sepharose were compared to those of the receptor purified by the use of the classical cobalamin-affinity medium. It was concluded that a disassembled receptor was produced using the classical method.

Effect of glycosidases and proteinases on cobalamin binding and physicochemical properties of purified saturated haptocorrin and intrinsic factor.

The effect of exoglycosidase, N-glycanase, trypsin and chymotrypsin was studied on the binding capacity and physicochemical properties of intrinsic factor and of haptocorrin using Superose 6 gel filtration. Intrinsic factor was purified as recently described by us. Haptocorrin was purified 6000-fold from human saliva using thermolabile affinity chromatography and high-performance cationic exchange chromatography with a specific activity of 20.6 nmol of cobalamin (Cbl) per mg protein and a yield of 44.7%. Exoglycosidases provoked a decrease of 54.3 and 78.2% of the Cbl binding capacity of haptocorrin and intrinsic factor, respectively. The sequential incubation of haptocorrin and intrinsic factor wit exoglycosidases and proteinases provoked a decrease of, respectively, 100 and 92.7% of their Cbl binding capacity, whereas the incubation with proteinase decreased the Cbl binding capacity of, respectively, 67.9 and 7.9%. The result of the incubation of [3H]intrinsic factor or [3H]haptocorrin with chymotrypsin and trypsin gave, respectively, no change in the elution position and a shift corresponding to a decrease of 50% of the estimated molecular mass. The estimated molecular mass of Cbl-intrinsic factor and of Cbl-haptocorrin decreased, respectively, to 57.1 kDa and to 88.1 kDa after incubation with exoglycosidases. It was concluded that (1) the carbohydrate core of intrinsic factor protects the whole protein whereas the carbohydrate core of haptocorrin protects only half part of the protein and (2) the carbohydrates are implicated in the formation of the cobalamin binding site of haptocorrin and intrinsic factor.

Radioautographic localisation of iodinated human intrinsic factor in the guinea pig ileum using electron microscopy.

The uptake of iodinated human intrinsic factor by guinea pig ileum was studied in vivo using electron microscopy radioautography. Iodination of intrinsic factor cobalamin complex with N-chlorobenzene-sulphonamide beads did not modify its physicochemical properties in gel filtration, nor in iso-electrofocusing. It didn't affect its biological activity either in vitro in presence of solubilised receptor, or in vivo in the Schilling test. The 125I-intrinsic factor cobalamin complex was instilled in vivo in ileal blind loops in presence of either CaCl2, EDTA, bile or intestinal juice. The labelled complex was predominantly located in the intermicrovillous pits of the apical membrane and in the apical cytoplasm. The uptake was about five-fold lower in presence of EDTA. On the apical membrane, the number of grains (per 80 micron length of epithelium) increased from 2.7 (0.2) up to 9.4 (1.7) respectively for 15 minutes and two hours of delay. This suggests a recycling of the intrinsic factor receptor complex. In the apical compartment, the silver grains were often detected over non-coated vesicles and over the infoldings of the lateral membrane. These results show that intrinsic factor is internalised into enterocytes during cobalamin absorption, and that a part of intrinsic factor enters the blood circulation through transcytosis.

Gastric intrinsic factor hypersecretion stimulated by pentagastrin in cystic fibrosis.

The gastric pentagastrin-stimulated secretions of acid (peak acid output) and of unsaturated intrinsic factor in eight cystic fibrosis patients (1.4 +/- 0.5 mEq/kg/h and 0.27 +/- 0.12 nmol/kg/h, respectively) were significantly enhanced (p less than 0.05) when compared with six normal controls (0.27 +/- 0.16 mEq/kg/h and 0.10 +/- 0.02 nmol/kg/h, respectively). Despite the gastric hypersecretion of intrinsic factor, no significant physicochemical modification of this glycoprotein was observed in cystic fibrosis when using gel filtration and isoelectrofocusing. Haptocorrin (a cobalamin glycoproteic binder that does not promote the assimilation of cobalamin) also increased in gastric juice after stimulation. Since the sequestration of cobalamin to haptocorrin is pH dependent, the gastric acid hypersecretion observed in cystic fibrosis may explain that the malabsorption of crystalline cobalamin is much more frequent in cystic fibrosis than in chronic pancreatitis.

Excretion of cobalamin and haptocorrin in the meconium of cystic fibrosis, premature, and control neonates.

Excretion of haptocorrin (R binder), cobalamin, and other corrinoids was studied in meconium from cystic fibrosis (n = 4), premature (n = 3), and control neonates (n = 13). Corrinoids content was 1.67 +/- 0.92 pmol/mg protein in meconium of cystic fibrosis (CF) neonates but only 0.33 +/- 0.37 and 0.48 +/- 0.47 pmol/mg protein, respectively, in that of prematures and controls. Considering its molecular mass (110,100 +/- 10,100) and its mean isoelectric point (3.67 +/- 0.20), haptocorrin remained undergraded in the meconium of CF neonates whereas it was partially degraded in the meconium of prematures and in most of the meconium from controls. Sequestration of cobalamin by undergraded haptocorrin can explain its increased excretion in CF meconium. Cobalamin-binding capacity of haptocorrin was 22.13 +/- 15.50 pmol/mg protein in CF meconium and about 400-fold lower in meconium of prematures and controls. This may correspond to a fetal intestinal hypersecretion in cases of CF.

In vitro and in vivo evidences that the malabsorption of cobalamin is related to its binding on haptocorrin (R binder) in chronic pancreatitis.

The intraluminal transport of cobalamin (Cbl) remains controversial in chronic pancreatitis. We have determined the ability of intestinal juice to degrade the digestive holohaptocorrin (R binder) and the binding of endogenous Cbl in basal intestinal juice from 22 chronic pancreatitis patients and 22 controls. The intestinal juice from patients and controls degraded 34.7 +/- 32.3% and 95.2 +/- 7.2% of holohaptocorrin, respectively. This percentage was correlated with the trypsin output but not with the Schilling test. The unsaturated Cbl-binding capacity was similar in both groups. Respectively, 62.5 +/- 26.6% and 19.6 +/- 11.7% of endogenous Cbl was bound to haptocorrin in intestinal juice from patients and controls. These percentages were correlated with the Schilling test and with the ability of intestinal juice to degrade haptocorrin. We concluded that 1) the sequestration of Cbl to haptocorrin is one of the factors responsible for the malabsorption of crystalline Cbl in patients with chronic pancreatitis and 2) enterohepatic circulation of Cbl can be interrupted in some cases of chronic pancreatitis.

Biliary excretion of cobalamin and cobalamin analogues in man.

Using dialysis, gel filtration, isoelectrofocusing and radioaffinity assay, we studied the unsaturated and saturated binders of bile and the biliary concentration of cobalamin (Cbl) and Cbl analogues compared to the corresponding serum concentrations in 7 choledochodomized patients. Bile contained a single saturated or unsaturated R binder with a molecular mass of about 120,000. Differences in the isoelectrofocusing pattern were observed between unsaturated and saturated R binders and could correspond to two secretion origins, mucosal secretion and hepatocyte clearance, respectively. The concentration of total corrinoids is about 4 times higher in bile than in serum, and this could be explained by a hepatic clearance of serum Cbl analogue-R binder complexes, as previously described in the rabbit. Moreover, the enterohepatic circulation of Cbl seems likely in healthy individuals since the saturated biliary R binder is degraded by pancreatic juice.