Is Vitamin B12 in Bound or Free form in the Tapeworm Diphyllobothrium Latum?

1957 ◽  
Vol 9 (4) ◽  
pp. 383-387 ◽  
Author(s):  
W. Nyberg ◽  
R. Gräsbeck
Keyword(s):  
Vitamin B12 ◽  
Free Form ◽  
Diphyllobothrium Latum

scholarly journals An Isotopic Method for the Determination of Vitamin B12 Levels in Blood

Blood ◽  
1963 ◽  
Vol 21 (1) ◽  
pp. 70-79 ◽  
Author(s):  
RUSSEL M. BARAKAT ◽  
ROGER P. EKINS
Keyword(s):  
Vitamin B12 ◽  
Binding Sites ◽  
Specific Activity ◽  
Specific Binding ◽  
Normal Subjects ◽  
Free Form ◽  
Protein Binding Sites ◽  
Isotopic Method ◽  
Specific Binding Protein

Abstract Vitamin B12 is normally present in plasma mainly bound to a specific binding protein. Addition of exogenous vitamin ultimately results in saturation of protein binding sites and excess vitamin remains in free form. The ratio of free to bound fractions thus quantitatively depends upon the concentration of exogenous compound. This observation has been utilized to determine amounts of vitamin B12 extracted from the blood of normal subjects and of patients with certain pathologic conditions. The method is simple and reproducible. The sensitivity of the method is such that vitamin levels down to roughly 20 µµg./ml. may be evaluated using labeled vitamin B12 of a specific activity of about 1 µc./µg. Repeated assays on identical specimens of normal plasma have shown a reproducibility of about 5-6 per cent. Results on 39 normal subjects gave a range of 330-1070 µµg./ml. with an average of 611 ± 167. Values observed in plasma taken from patients suffering from pernicious anemia were around 100 µµg./ml. or less. Results on subjects with other pathologic conditions are also presented and the limitations of the method are discussed.

Hepatic Vitamin B12 Release and Transcobalamin II Synthesis in the Rat

1974 ◽  
Vol 47 (6) ◽  
pp. 531-545 ◽  
Author(s):  
W. G. E. Cooksley ◽  
J. M. England ◽  
L. Louis ◽  
M. C. Down ◽  
A. S. Tavill
Keyword(s):  
Vitamin B12 ◽  
Rat Liver ◽  
Plasma Concentrations ◽  
High Plasma ◽  
Free Form ◽  
Isolated Perfused Rat Liver ◽  
Low Concentrations ◽  
High Concentrations ◽  
Transcobalamin Ii

1. The release of 57Co-labelled vitamin B12 ([57Co]B12) and synthesis of transcobalamin II (TCII) by the isolated perfused rat liver were studied 10–42 days after the parenteral administration of a trace dose of 15 pmol (approximately 20 ng) of radioactive cyanocobalamin. 2. The rate of release of [57Co]B12 into plasma and bile was linear and constituted approximately 0.9% and 0.3% respectively of the initial hepatic radioactivity per hour of perfusion. 3. [57Co]B12 released into plasma was bound to TCII. Saturation of the total TCII by the addition of cyanocobalamin before perfusion resulted in the appearance of the hepatic [57Co]B12 in the free form. 4. These data were found to be compatible with the following observations in vivo: (i) rates of [57Co]B12 release as measured by urinary [57Co]B12 excretion after saturation of plasma binders with non-labelled cyanocobalamin; (ii) rates of biliary excretion of [57Co]B12. 5. Liver damage produced by hypoxaemia was associated with a fall in the rate of release of [57Co]B12. 6. TCII release occurred at a linear rate of almost twenty times that required for the binding of newly released hepatic vitamin B12. 7. Cycloheximide at a dose sufficient to inhibit release of TCII did not prevent the release of [57Co]B12 from the liver into plasma or bile. 8. Alteration of perfusate composition to contain either high plasma concentrations of vitamin B12 and low concentrations of unsaturated TCII or high plasma concentrations of vitamin B12 and high concentrations of unsaturated TCII had no effect on the rate of [57Co]B12 release into plasma or bile. 9. It is concluded that the fluxes of hepatic vitamin B12 and TCII are very rapid and that the release of vitamin B12 by the rat liver is controlled in the short term by factors other than the synthesis of TCII and the concentration of vitamin B12 or unsaturated transcobalamin in the plasma.

Serum Vitamin B12 Levels and Incidence of Tapeworm Anemia in a Population Heavily Infected with Diphyllobothrium Latum

1961 ◽  
Vol 9 (5) ◽  
pp. 606-612 ◽  
Author(s):  
WOLMAR NYBERG ◽  
RALPH GRÄSBECK ◽  
MATTI SAARNI ◽  
BERTEL VON BONSDORFF
Keyword(s):  
Vitamin B12 ◽  
Serum Vitamin ◽  
Diphyllobothrium Latum
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