PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Transcobalamins”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 901 records · Page 50Linked to original sources
PubMed1989

Why vitamin B12 deficiency should be managed aggressively.

Recent evidence suggests that vitamin B12 deficiency in the elderly is more than classic pernicious anemia. Instead, it is a continuum from negative B12 balance to frank deficiency, which can be detected by low serum B12 levels long before changes occur in hemoglobin levels. Current findings in the literature suggest that subtle B12 deficiency is indeed clinically significant. Treatment may prevent significant neurologic and/or hematologic disease.

Aged↗
PubMed1989

Immunological characterization and clinical implication of cobalamin binding protein in human gastric cancer.

Cobalamin (vitamin B12) binding protein was purified from gastric cancer extracts and from serum-free culture medium of cancer cell line KATOH-III. The molecular weight, determined by immunoprecipitation and sodium dodecyl sulfate-polyacrylamide gel electrophoresis, was 70,000 and the pI was 2.8 to 3.2. From biochemical and immunological properties, this cobalamin binding protein was considered to be an isoprotein of cobalamin R binder. Monoclonal antibodies were produced against saliva R and cobalamin binding protein in culture medium to study their antigenic determinants. Monoclonal antibody 55-D reacted to an epitope of peptide in both binders, whereas WK-1 and H-12 reacted to determinants of a carbohydrate moiety, including sialic acid, in cancer cell-derived binder. In addition, we carried out an enzyme-linked immunoassay and examined plasma levels of immunoreactive R binder in patients with gastric cancer (n = 72), benign gastrointestinal disease (n = 30), and healthy individuals (n = 40). Even in patients without liver metastasis, the level of immunoreactive R binder detected by monoclonal antibody H-12 was elevated in some patients and decreased after excision of the tumor. R binder was also elevated in cancer tissue extract. Immunoreactive binder was histochemically detected in the cytosol of cancer cells and metaplastic cells of the gastric mucosa. The present findings suggest that cobalamin R binder is de novo synthesized in gastric cancer cells and that its plasma level increases in some patients. This binding protein may be a useful diagnostic and therapeutic parameter.

Adult↗
PubMed1989

[Evaluation of exocrine pancreatic function by the haptocorrin degradation test of the duodenal fluid collected by endoscopy].

Two groups of biological methods are commonly used to evaluate the exocrine pancreatic function: tests which require tubes for the collection of duodenal juice and the tubeless tests which are indirect tests of pancreatic function. In this study we have attempted to improve a new test: the test of haptocorrin degradation (THD). This test measures the transfer of labelled cobalamin from haptocorrin to the intrinsic factor which is provoked by the degradation of the haptocorrin by proteases in the duodenal juice. We present the results of this test in 90 patients with chronic pancreatitis. THD was first assayed with basal duodenal juice collected by naso duodenal tubing during secretin cerulein stimulation. In this study the sensitivity and specificity of THD was 0.86 and 0.93, respectively. In the second part of this study we demonstrated that the means of collecting duodenal juice had no effect on the results of THD. Duodenal juice was collected during a secretin cerulein test or during a routine upper gastrointestinal endoscopy after pancreatic stimulation with secretin. The sensitivity and specificity of THD was 0.90 and 0.94, respectively, when duodenal juice was collected during endoscopy. THD was significantly correlated with the NBT-PABA test, steatorrhea, and with the activity of trypsin and chymotrypsin in the duodenal juice. In this study, NBT-PABA was less sensitive than THD for the diagnosis of chronic pancreatitis (sensitivity was 0.70 and 0.89, respectively). The specificity of THD was estimated at 0.94. THD seemed to be a valuable adjunct to test pancreatic function. As upper gastrointestinal endoscopy is usually performed in patients with proved or suspected chronic pancreatitis, THD seems to have a place of choice among the other tests of pancreatic exocrine function. Further evaluation of this test by a multicentric prospective trial is now needed.

Adult↗
PubMed1989

Construction and use of a RIA-gram.

All equilibrium protein binding assays, as exemplified by radioimmunoassays (RIA) are governed by the law of mass action. If the reactants are homogenous, then the reaction is characterized by a simple apparent dissociation constant (Kd). We have calculated a set of binding curves, a RIA-gram, in which all concentrations are expressed with Kd as unit. This RIA-gram can be generally employed to optimise equilibrium protein binding assays. Using the RIA-gram we illustrate three points. First, the sensitivity of a given assay is related to either the Kd or the concentration of the labeled ligand, whichever is the larger. Second, if Kd determines the sensitivity of the assay, one can not improve the sensitivity by decreasing the concentration of the labeled ligand below 0.1Kd. Finally, in order to obtain an optimal assay the fraction of ligand bound when only labeled ligand is present depends on the concentration of labeled ligand and on the concentration for which one wants the highest sensitivity of the assay.

Humans↗
PubMed1988

Kinetics and activation parameters of the reaction of cyanide with free aquocobalamin and aquocobalamin bound to a haptocorrin from chicken serum.

The kinetics of the reaction of cyanide with free aquocobalamin (H2OCbl) and with aquocobalamin bound to a vitamin B12-binding protein (haptocorrin) from chicken serum (HC-H2OCbl) have been investigated as a function of temperature and pH. The mechanism of replacement of H2O from protein-bound and free H2OCbl is apparently the same and involves attack of both CN- (k1) and HCN (k2). The reactions with HC-H2OCbl are somewhat slower than those with free H2OCbl, k1 being 22-fold smaller and k2 7-fold smaller at 25 degrees C. The relatively small effect of the protein on the rate constants supports the view that the metal in HC-H2OCbl is readily accessible to solvent. Activation parameters suggest that the transition states for ligand substitution are stabilized by nucleophilic participation (at least by CN-) and that ligand substitution on the protein-bound cobalamin proceeds through more ordered, concerted transition states. The latter effect suggests that the Co-O bond of H2OCbl is strengthened upon binding to the haptocorrin.

Animals↗
PubMed1988

Expression of vitamin B12 R-binder in breast tumors. An immunohistochemical study.

Vitamin B12 R-binder, a vitamin B12-specific binding protein, was demonstrated by immunohistochemistry in 103 cases of breast tumors of various types and grades. In normal breast tissues, R-binder was found on the luminal surface of interlobular, intralobular, and small terminal ducts. R-binder localization was observed in all fibroadenomas and phyllode tumors, in 90% of the benign epithelial tumors, and in 33% of the carcinomas. Among malignant tumors, 43% of the ductal carcinomas expressed the R-binder, whereas none of the lobular or mucinous carcinomas were positive. In invasive ductal carcinomas, R-binder expression was demonstrated more often in well-differentiated lesions.

Breast Neoplasms↗
PubMed1988

The diagnosis of sarcoidosis.

The diagnosis of sarcoidosis depends on the clinical and radiologic features along with histologic evidence of epithelioid-cell granulomas on biopsy. The amount of histologic support required varies inversely with the certainty with which the pattern of clinical features is recognized. It is essential to exclude other recognized causes of granulomatous disease. On the basis of our experience and that of other workers, we believe that sarcoidosis must be considered in the differential diagnosis when optic nerve thickening is encountered on CT, MRI or echography. Chest roentgenography is the easiest way to confirm the diagnosis. However, as many as 15% of patients will have a normal x-ray film, and other tests may be needed to help confirm the diagnosis. Biopsy of the involved tissues may be the only way to make the diagnosis. Once a provisional diagnosis is made, investigation for systemic sarcoidosis should include chest roentgenography, determination of the serum ACE level, 67Ga scanning, pulmonary function studies, testing for delayed skin reactions (with tuberculin, C. albicans, Trichophyton and mumps virus) and blood studies (determination of the erythrocyte sedimentation rate and levels of immunoglobulins, albumin, calcium and alkaline phosphatase). Finally, conjunctival biopsy is simple to do and is quite useful in supporting the diagnosis if no other tissue is readily available.

Biopsy↗
PubMed1985

Volume-dependent human blood polymorphonuclear leukocyte heterogeneity demonstrated with counterflow centrifugal elutriation.

Human peripheral blood polymorphonuclear leukocytes (PMNs) have recently been recognized as a heterogeneous population of cells. Consideration has not been given to the possibility that size may be an additional physical characteristic demonstrating heterogeneity. Using counterflow centrifugal elutriation, we have demonstrated that PMNs can be isolated into at least six volume-dependent fractions. A positive correlation exists for PMN size and superoxide anion release upon stimulation with f-Met-Leu-Phe or phorbol myristate acetate. Total granule contents were also noted to be greater in larger PMN fractions, with a constant percent of release upon stimulation. The implications of these findings are discussed.

Cell Separation↗
PubMed1985

Neutrophils autoinactivate secretory products by myeloperoxidase-catalyzed oxidation.

The neutrophil response to inflammatory stimuli involves the formation of reactive oxygen species and secretion of granule enzymes. In studying secretion of vitamin B12 binding protein by human neutrophils, we noted a major decrease in total recoverable activity from the extracellular fluid plus the stimulated cells (54% of resting cells). Recovery of B12 binding protein from neutrophils exposed to phorbol myristate acetate or opsonized zymosan was significantly enhanced on addition of heme enzyme inhibitors (azide, cyanide) or catalase or when halide-free medium was used. The changes in B12 binding protein recovery were attributable entirely to increases in extracellular fluid levels, and cell pellet content was unaffected. These data indicate extracellular destruction of functional B12 binding protein by the halide-dependent heme enzyme myeloperoxidase and H2O2. Kinetic studies demonstrated rapid secretion of B12 binding protein in the first two to five minutes, followed by its inactivation over the next 20 to 30 minutes. A cell-free extract of vitamin B12 binding protein was readily inactivated on exposure to purified myeloperoxidase, H2O2, and a halide. These findings document a functional interaction among products of the neutrophil specific granules (B12 binding protein), azurophil granules (myeloperoxidase), and metabolic burst (H2O2). They provide an interesting model for the modulation of the inflammatory response by oxidation of secretory products of neutrophils.

Catalysis↗
PubMed1988

Combined congenital deficiencies of intrinsic factor and R binder.

Coexisting deficiencies of both intrinsic factor (IF) and R binder were identified in an Algerian boy who presented with severe megaloblastic anemia, growth retardation, and neurologic dysfunction with typical features of subacute combined degeneration of the spinal cord. The anemia responded completely to cyanocobalamin and folic acid. IF was absent from gastric juice, but acid secretion and gastric mucosa were normal. R binders were absent from gastric juices as well as from serum, saliva, and polymorphonuclear leukocytes. The patient's father exhibited absence of R binder in his serum with a low serum vitamin B12 level and was asymptomatic. This unique case of simultaneous IF and R binder deficiencies suggests a genetic association between these two functionally and immunologically dissimilar, but structurally close vitamin B12-binding proteins.

Adolescent↗
PubMed1988

B12 deficiency in AIDS.

Explore the source record for details and available documents.

Acquired Immunodeficiency Syndrome↗
PubMed1988

Characterization of the vitamin B12-binding protein isolated from sow's milk and its affinity for cyanocobalamin and other corrinoids.

1. Unsaturated vitamin B12-binding protein was isolated from sow's milk whey by affinity chromatography on a vitamin B12-Sepharose column with a yield of 54% (3920-fold purification). The purified binding protein was homogeneous by the criteria of polyacrylamide gel electrophoresis and high speed sedimentation equilibrium. 2. The isolated vitamin B12-binding protein was a glycoprotein with 24% carbohydrates (fucose, galactose, mannose, galactosamine, glucosamine and sialic acid) and high levels of aspartic and glutamic acids. The protein which has a molecular weight of 61,800 determined by ultracentrifugation, consisted of a single polypeptide chain, bound vitamin B12 on an equimolar basis and had a partial specific volume of 0.697 ml/g (mechanical oscillator technique). 3. Its dissociation constant, Kd, for cyanocobalamin was 8.8 x 10(-10)M. The binding protein showed similar affinities for hydroxo-, methyl-, and adenosylcobalamin when compared to cyanocobalamin relative affinity ratios, but lower affinities (31-49%) for cobinamide, Co-alpha-[adenyl] cobamide and Co-alpha-[2-methyl-adenyl] cobamide. Therefore, the substitution of the axial ligand to the cobalt atom in the corrin ring of vitamin B12 had no effect on affinity, whereas the differences in the nucleotide part of the molecule caused a small decrease in energy of the interaction. 4. The present results indicate close similarity of the vitamin B12-binding protein from sow's milk to vitamin B12-binding proteins from other sources, especially those from human milk and from porcine gastric mucosa (nonintrinsic factor). Whether this similarity extends to antigenic and physiological properties remains to be investigated.

Animals↗
PubMed1987

Beta 2-microglobulin in neutrophils: an intragranular protein.

The subcellular localization of beta2-microglobulin (beta 2m) in human neutrophils was determined by an enzyme-linked immunosorbent assay on subcellular fractions obtained by Percoll density gradient centrifugation of neutrophils disrupted by nitrogen cavitation. The neutrophils were found to contain 160 ng beta 2m/mg protein. Approximately two-thirds co-located with the markers for specific granules and was released from intact cells during degranulation, whereas one-third of the beta 2m was located together with markers of the plasma membrane. This fraction was not further enriched during degranulation. These results indicate that beta 2m cannot be universally used as a plasma membrane marker as hitherto assumed, but beta 2m may serve as an indicator of neutrophil degranulation.

Cell Compartmentation↗