Hamster intrinsic factor (IF) preparations markedly enhanced the uptake of 57cobalt-labeled cyanocobalamin (B12-57Co) by brush borders and microvillous membranes isolated from villous absorptive cells obtained from the distal but not the proximal half of hamster intestine. A similar effect was observed with rat and rabbit IF preparations, but IF preparations obtained from man, dog, and hog were ineffective. After fractionation of hamster IF preparations by gel filtration or ion exchange chromatography, the extent to which each fraction enhanced B12-57Co uptake by brush borders correlated closely with the vitamin B12 binding capacity of the fraction. IF-mediated attachment of B12-57Co to brush borders occurred rapidly, was not diminished by removal of glucose or oxygen from the incubation medium, and was not significantly altered when incubation temperatures were reduced from 37° C to 7° C. Marked reduction in uptake occurred, however, in the absence of divalent cations.
Robert M. Donaldson Jr., Iain L. Mackenzie, Jerry S. Trier
Usage data is cumulative from September 2023 through September 2024.
Usage | JCI | PMC |
---|---|---|
Text version | 133 | 0 |
81 | 22 | |
Scanned page | 506 | 1 |
Citation downloads | 38 | 0 |
Totals | 758 | 23 |
Total Views | 781 |
Usage information is collected from two different sources: this site (JCI) and Pubmed Central (PMC). JCI information (compiled daily) shows human readership based on methods we employ to screen out robotic usage. PMC information (aggregated monthly) is also similarly screened of robotic usage.
Various methods are used to distinguish robotic usage. For example, Google automatically scans articles to add to its search index and identifies itself as robotic; other services might not clearly identify themselves as robotic, or they are new or unknown as robotic. Because this activity can be misinterpreted as human readership, data may be re-processed periodically to reflect an improved understanding of robotic activity. Because of these factors, readers should consider usage information illustrative but subject to change.