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At least 127 records · Page 7Linked to original sources
PubMed1985

Evaluation of a new assay kit for intrinsic factor blocking antibody (type I) as an aid in the diagnosis of pernicious anemia.

Sera from 39 patients with pernicious anemia and 251 patients with various other diseases and 42 healthy normal subjects were tested for intrinsic factor blocking antibody by a Corning commercial kit. Twenty-five (64%) out of 39 pernicious anemia patients showed a positive reaction to the intrinsic factor blocking antibody. The positive incidence of intrinsic factor blocking antibody by this method agreed well with the results obtained in this laboratory over the past 10 years using the charcoal method. No sera from normal subjects tested were positive for the intrinsic factor blocking antibody. All 226 sera with vitamin B12 levels less than 3,500 pg/ml which came from patients without pernicious anemia, were negative for the intrinsic factor blocking antibody. In 15 sera with B12 levels greater than 3,500 pg/ml from patients who received recent B12 medications, 11 sera showed false positive results. On the other hand, no false positive results were obtained by this method in 10 sera with endogenous serum B12 levels greater than 3,500 pg/ml collected from patients with chronic myelogenous leukemia. It is reasonable to presume that this assay is clinically useful for detection of intrinsic factor blocking antibody in the diagnosis of pernicious anemia, if false positive results due to B12 medication are excluded.

Adolescent↗
PubMed1991

Effect of the cobalt-N coordination on the cobamide recognition by the human vitamin B12 binding proteins intrinsic factor, transcobalamin and haptocorrin.

The binding of several corrinoids to the binding site of human intrinsic factor, transcobalamin or haptocorrin was investigated, p-Cresolyl cobamide and 2-amino-vitamin B12 are complete corrinoids, whose nucleotide at the lower face of the corrin ring is not coordinated to the cobalt. These corrinoids were greater than or equal to 10(3) times less efficiently recognized by intrinsic factor or transcobalamin than vitamin B12, which contains a Co-coordinated nucleotide. Pseudovitamin B12, with a weak Co-N coordination bond, revealed only moderate affinity to intrinsic factor. From these findings it is concluded that the cobamide binding to intrinsic factor and transcobalamin is strongly affected by the Co-N coordination bonds of their lower cobalt nucleotide ligands. We suggest that the Co-N coordination bond positions the nucleotide at a critical distance to the corrin ring, which is recognized by the binding proteins. Human haptocorrin, however, disclosed to distinctive selectivity regarding the different corrinoid structures. The protein bound all corrinoids with similar efficiency, independent of the strength of their Co-N coordinations, or the structures of their lower Co alpha ligands. Hence, the corrin ring, rather than a structural feature induced by the Co-N coordination, has to be considered responsible for the corrinoid binding to haptocorrin.

Binding Sites↗
PubMed1989

Repeated high oral doses of omeprazole do not affect intrinsic factor secretion: proof of a selective mode of action.

The effect of 60 mg oral omeprazole daily for 9 days on intrinsic factor and gastric acid secretion was studied in eight healthy volunteers. Gastric secretion studies were performed during saline and 0.1 M HCl perfusion before and after omeprazole administration. During dosing with omeprazole, basal gastric acid output diminished by 94%, and pentagastrin-stimulated acid output by 97%. Basal, peak and steady-state stimulated intrinsic factor output were unaffected by omeprazole. It is concluded that high oral doses of omeprazole suppress gastric acid secretion to very low levels but they do not affect intrinsic factor secretion. Intrinsic factor secretion was also unaffected by profound hypochlorhydria.

Achlorhydria↗
PubMed1975

Spurious Schilling test results obtained with intrinsic factor enclosed in capsules.

Three urinary excretion tests of vitamin B12 absorption were done in 12 patients with classic pernicious anemia. The 24-hour urinary excretion of radioactivity was 2.1% +/- 0.7% (mean +/- SEM) of the ingested dose of cyanocobalamin-57 Co. When cyanocobalamin-57 Co was mixed with hog intrinsic factor in water, excretion increased to 15.6% +/- 1.6%. When cyanocobalamin-57 Co and intrinsic factor were given in two separate capsules, which is now a frequent practice, excretion was 9.5% +/- 2.2%. In 6 patients, use of the results obtained with capsules could have led to an incorrect diagnosis. When cyanocobalamin-57 Co and intrinsic factor are given in separate capsules, binding of radioactive vitamin to intrinsic factor may be incomplete due to inadequate mixing in the stomach or to binding of intrinsic factor to blocking antibody in the gastric juice. The classic technique in which intrinsic factor and cyanocobalamin-57 Co are mixed in water before administration should be used.

Capsules↗
PubMed1981

The effect of cyanide on serum cobalamin and on cobalamin analogues when measured by radioassay using R-protein and intrinsic factor.

Concentrations of cobalamin measured in human serum by radioassay differ when R-protein or intrinsic factor is used as the binding determinant. Experiments were carried out to determine whether the concentration of cyanide used to extract the serum cobalamin could account for this difference. When either R-protein or intrinsic factor was used, the cobalamin measured in serum extracted in the absence of cyanide was low. As the concentration of cyanide was raised in the extraction mixture, the cobalamin concentration that was measured increased when either protein binder was used, but the absolute increase was greater with R-protein. R-protein or intrinsic-factor-reactive cobalamin could be recovered from serum proteins precipitated in the absence of cyanide and reextracted in the presence of cyanide. There was low recovery of hydroxo, methyl, or adenosyl cobalamins added to serum when the serum was extracted in the absence of cyanide, but recovery was quantitative when using either protein binder with cyanide in the extraction step. With 0.25 microgram of potassium cyanide/ml of extraction mixture and R-protein as the binding determinant in the radioassay, sera with normal, moderately low, and very low cobalamin concentrations could by separated. These experiments indicate that the concentration of cyanide used to extract cobalamin from the serum may account for some but not all of the differences observed when R-protein and intrinsic factor are used in the radioassay. The range of normal and low serum cobalamin are method-dependent and must be established by each laboratory for the radioassay procedure used.

Binding Sites↗
PubMed1981

Bile acid inhibition of vitamin B12 binding by intrinsic factor in vitro.

The effect of conjugated and unconjugated bile acids on the binding of vitamin B12 to intrinsic factor was investigated. The dihydroxy bile acids (deoxycholic, glycodeoxycholic, taurodeoxycholic, glycochenodeoxycholic, and taurochenodeoxycholic) inhibit the binding of intrinsic factor to vitamin B12 at physiological concentrations. On the other hand, the trihydroxy bile acids (cholic, glycocholic, and taurocholic) are not effective in this respect. The inhibition is dependent both on concentration and time, and its pattern is similar to that previously reported for duodenal juice. On column chromatography, there is a close correlation between the degree in intrinsic factor inhibition and the total acid concentration in the duodenal juice. The binding of vitamin B12 by R protein in saliva is not affected by bile acids. The results show that bile acids at concentrations found in duodenal juice inhibit intrinsic factor vitamin B12 binding. It is suggested that this observation may have physiological significance for vitamin B12 absorption.

Bile Acids and Salts↗
PubMed1978

Formation of transcobalamin II--vitamin B12 complex by guinea-pig ileal mucosa in organ culture after in vivo incubation with intrinsic factor--vitamin B12.

The in vivo incubation of intrinsic factor--[57Co]vitamin B12 in an ileal loop of a guinea-pig followed by in vitro culturing of segments of the ileum for 180 min has been used to study the transepithelial transport of vitamin B12. Analysis of the solubilized supernate of mucosa following the in vivo phase demonstrated that 44% of the [57Co]vitamin B12 was bound to intrinsic factor (IF), 26% was free, and 16% was bound to transcobalamin II (TCII). Following culture, similar analysis demonstrated that 18% of the vitamin was now bound to IF, 49% was free, and 35% ws bound to TCII. In the culture medium, 54% of the [57Co]vitamin B12 was free and 37% was bound to TCII. The formation of TCII-[57Co]vitamin B12 did not occur if homogenized mucosa was incubated with free[57Co]vitamin B12, but it did form in cultures of ileal segments from animals given an excess of unlabelled vitamin to saturate all circulating TCH, and in the medium containing puromycin. Indirect immunofluorescence using chicken anti-TCII demonstrated that TCII was associated with the mucosal cells of both the ileum and jejunum. These studies demonstrate that following transepithelial flux of vitamin B12 through the ileal mucosa, the vitamin becomes coupled to TCII. This coupling requires a structurally intact mucosa and the source of the TCII appears to be the ileal mucosal cell rather than unsaturated TCII circulating in the blood.

Animals↗
PubMed1969

Dissociation of intrinsic factor from its antibody: application to study of pernicious anaemia gastric juice specimens.

Intrinsic factor antibody may sometimes be concealed in the gastric secretions of pernicious anaemia subjects, being complexed with residual amounts of intrinsic factor.A method is described for dissociating intrinsic factor from its antibody. Antibody to the vitamin-B(12)-binding site of intrinsic factor was identified in 16 (57%) out of 28 samples of pernicious anaemia gastric juice after dissociation but in only 10 before dissociation. There was no clear relationship between the incidence of antibody in the serum and in the gastric juice of these patients.

Anemia, Pernicious↗
PubMed1980

Solubilization of the pig ileal intrinsic factor receptor with papain treatment and studies on the solubilized receptor.

The intrinsic factor receptor, known to consist of two subunits alpha and beta, has been solubilized by papain digestion from porcine small intestine. Papain liberates a part of the outermost subunit (alpha) of the receptor. The solubilized part was called papain-alpha. It was purified by affinity chromatography on Sepharose-vitamin B-12-intrinsic factor gel and its molecular dimensions were measured. Its molecular weight measured with SDS-polyacrylamide gel electrophoresis is 45000, its isoelectric point is 4.2 and it binds the cobalamin-intrinsic factor complex in the same way as the whole receptor.

Animals↗
PubMed1988

[Congenital intrinsic factor deficiency. Apropos of 3 cases in a sibship].

Three familial cases of congenital intrinsic factor deficiency are reported: the stress is put on the interest of gastric investigations and especially of the quantity of intrinsic factor in the gastric juice when investigating megaloblastic anemia due to vitamin B12 deficiency. The study of the level of intrinsic factor in the gastric juice is proposed as a test for identifying carriers.

Anemia, Macrocytic↗
PubMed1975

Pernicious anaemia: its pathogenesis in the light of the beneficial effect of duodenal intrinsic factor.

Oral ingestion of powdered duodenal mucosa with small doses of vitamin B12 proved efficient in four cases of untreated pernicious anaemia. The erythropoietic as well as the other responses were similar as those elicited by any reliable anti-pernicious drug. It has thus been confirmed that the growth factor demonstrated earlier in human duodenal juice by means of E. coli mutant corresponds in fact to the intrinsic factor. It is suggested that besides the deficiency of gastric intrinsic factor the duodenal intrinsic factor and the immune mechanisms neutralizing it are also involved in the pathogenesis. It has been shown that the aqueous extracts of hog stomach and duodenum differ in addition to their growth factor and nitrogen contents, also in aminoacid composition.

Anemia, Pernicious↗
PubMedDate not supplied

[Disability in schizophrenia. Intrinsic factors and prediction of psychosocial outcome. An analysis of literature].

OBJECTIVE: Many different factors, both related to the individual and illness ("intrinsic" factors) and to the environment ("extrinsic" factors), contribute in different ways to the development of disability. Basing on data of literature, this review focuses the main "intrinsic" factors predicting disability in schizophrenia. METHOD: A systematic search on Mediline of all papers published during the period 1965-2001 was performed, using "schizophrenia", "outcome", "psychosocial outcome", "social disability" and "social adjustment" as key words. Only papers reporting specifically data about predictive factors and psychosocial outcome variables were considered; prospective follow-up studies were considered, but retrospective and cross-sectional studies were also taken into account when data deriving from prospective studies were inconsistent. RESULTS: Male sex predicts a higher disability among demographic factors; lower social and occupational adjustment are premorbid personality factors associated with higher disability; among factors related to illness, younger age at onset of illness, "nuclear", "non paranoid" and in particular "deficit" forms of schizophrenia seem to predict more disability. The latter seems to be predicted also by higher levels of negative symptoms and neuropsychological deficits; the role of depressive symptoms seems to be less supported by follow-up data; a continuous course of the illness predicts more disability, although some evidences show a progressive reduction of disability, at least in the long term. CONCLUSIONS: Disability shows a largely autonomous course respect to symptoms and has to be considered an independent parameter of outcome. Few intrinsic factors show a predictive role also in the long term.

Adaptation, Psychological↗
PubMed1983

Malabsorption of vitamin B12 and intrinsic factor secretion during biguanide therapy.

In a survey of 46 randomly selected diabetic patients on biguanide therapy, 30% had malabsorption of vitamin B12. Withdrawal of the drug resulted in normal absorption in only half of those with malabsorption. In most patients with persistent malabsorption, the results of absorption tests with exogenous intrinsic factor suggested the diagnosis of coincidental intrinsic factor deficiency. Further considerations, however, led to the concept that biguanides can induce malabsorption by two different mechanisms. One of these is temporary and unrelated to intrinsic factor secretion and the other is permanent and mediated by depression of intrinsic factor secretion.

Adult↗
PubMed1979

Dissociation of the intrinsic factor--vitamin B12 complex by bile: contributing factor to B12 malabsorption in pancreatic insufficiency.

Human bile incubated with vitamin B12 bound to intrinsic factor in human gastric juice will effectively dissociate this complex, and the vitamin will transfer to non-intrinsic factor unsaturated binding protein(s) contained in bile. Preincubation of the bile with pancreatic enzymes, particularly trypsin, and pepsin, decreases this effect of bile on the intrinsic factor--vitamin B12 complex by digesting the unsaturated binder(s) in the bile. These studies help explain why there is malabsorption of tracer amounts of vitamin B12 in some patients with pancreatic insufficiency, and why this abnormality is correctable by the administration of pancreatic extract.

Bile↗
PubMed1985

Purification of human intrinsic factor using high-performance ion-exchange chromatography as the final step.

Human intrinsic factor was purified 1430-fold from gastric juice with a yield of 75% using two steps: labile ligand affinity chromatography and high-performance ion-exchange chromatography. Intrinsic factor precipitated in the presence of specific autoantibodies and 15% sodium sulfate, had an estimated Mr of 59 000 in 5% SDS electrophoresis and could bind to the specific ileal receptor in vitro. Its carbohydrate composition could be related to N-lactosaminic and O-glycosidic chains. High-performance ion-exchange chromatography was a mild, rapid and efficient procedure to separate completely intrinsic factor from haptocorrin (another glycoprotein of gastric juice which binds cobalamin) and from other contaminating proteins.

Chromatography, Gel↗
PubMed1977

Binding proteins from fish sera and intrinsic factor compared in vitamin B12 radioassay.

We compare serum proteins from rainbow trout, chinook salmon, coho salmon, and oyster toadfish with intrinsic factor as binding proteins in a simplified radioassay for B12. Regression analysis of B12 values, determined in 21 serum samples, shows good correlation (r greater than .975) between results for the fish sera and intrinsic factor. The accuracy of the five assays, as evaluated by analytical recovery of B12 added to pooled human serum, ranges from 90 to 110%. Intra-assay precision ranges from 2.6% for coho salmon serum to 5.5% for intrinsic factor, Ionic strength and variations in pH influence binding of [57Co]vit B12 to the fish sera. Maximum binding occurs from pH 6 to 10 at an ionic strength of 0.1 for all sera. The sera are stable for longer than two years when stored at -20 degrees C. Important advantages of fish sera are their high binding capacity (typical assay dilutions range from 1500-fold for trout serum to more than 50 000-fold for chinook salmon); high affinity for B12 (K greater than 10(12) liter/mol); their relative constant binding characteristics as compared to commercial intrinsic factor preparations; and the finding that the accuracy of radioassays with use of fish sera is not significantly affected by the amount of B12 or human serum proteins present.

Animals↗
PubMed1982

Secretion of intrinsic factor from dispersed mucosal cells isolated from guinea pig and rabbit stomach.

In dispersed mucosal cells prepared from rabbit and guinea pig stomach, the secretion of intrinsic factor was constant (0.3-0.4%/min) for at least 30 min incubation at 37 degrees C. Histamine or isobutyl methylxanthine increased cyclic AMP and intrinsic factor secretion in both cells preparations. Isobutyl methylxanthine potentiated and cimetidine competitively inhibited (ki = 5.10-7 M) both effects of histamine. Dibutyryl cyclic AMP (1.0 mM), also caused a 3-fold increase in intrinsic factor secretion. These results suggest that in rabbit and guinea pig histamine interacts with H2-receptors to increase cyclic AMP which mediates the rise in the rate of intrinsic factor secretion.

1-Methyl-3-isobutylxanthine↗
PubMed1973

Characterization of ileal vitamin B12 Binding using homogeneous human and hog intrinsic factors.

Elucidation of the mechanism of intrinsic factor (IF)-mediated vitamin B(12) (B(12)) binding to ileal binding sites has been hampered by the use of crude or only partially purified preparations of IF in previous studies. We have used homogeneous human IF and hog IF isolated by affinity chromatography to study [(57)Co]B(12) binding to ileal mucosal homogenates. The following observations were made: (a) Human IF-B(12) and hog IF-B(12) were bound to human, monkey, hog, dog, rabbit, mouse, hamster, and guinea pig ileal, but not jejunal, homogenates in amounts significantly greater than free B(12) or B(12) bound to five other homogeneous B(12)-binding proteins; (b) only IF-mediated B(12) binding was localized to ileal homogenates and was inhibited by EDTA; (c) values for the association constant (K(a)) for the various ileal homogenates mentioned above and human IF-B(12) and hog IF-B(12) ranged from 0.3 x 10(9) M(-1) to 13.0 x 10(9) M(-1). Apparent differences in the K(a) for human IF-B(12) and hog IF-B(12) existed in most species; (d) the number of ileal IF-B(12) binding sites per gram (wet weight) of ileal mucosa ranged from 0.3 x 10(12) to 4.9 x 10(12). The same value was always obtained with human IF-B(12) and hog IF-B(12) for any given homogenate preparation; (c) 100-fold excesses of free B(12) or human IF and hog IF devoid of B(12) did not significantly inhibit human IF-B(12) and hog IF-B(12) binding to human and hog ileal homogenates. THESE EXPERIMENTS PERFORMED WITH HOMOGENEOUS IF INDICATE THAT: (a) gastric factors other than IF are not required for B(12) binding to ileal IF-B(12)-binding sites: (b) the mechanism of ileal IF-B(12) binding is different from that of free B(12) or of B(12) bound to non-IF-B(12)-binding proteins; (c) human IF and hog IF have different structures; (d) human IF-B(12) and hog IF-B(12) bind to the same ileal binding sites; and (c) human and hog ileal IF-B(12) binding sites bind free B(12) and human and hog IF devoid of B(12) poorly, if at all.

Animals↗