scholarly journals Vitamin B12 absorption in the neonatal piglet

1985 ◽  
Vol 54 (1) ◽  
pp. 269-283 ◽  
Author(s):  
N. M. F. Trugo ◽  
J. E. Ford ◽  
D. N. Salter
Keyword(s):  
Small Intestine ◽  
Binding Sites ◽  
Protective Factor ◽  
Intrinsic Factor ◽  
Membrane Vesicles ◽  
Maximum Activity ◽  
Vitamin B ◽  
Uptake Mechanism ◽  
Ph Optimum ◽  
Lower Efficiency

1. The influence of the vitamin B12-binding protein isolated from sows' milk on the uptake of vitamin B12 was investigated using microvillus membrane vesicles prepared from the small intestine of 7- and 28-d-old piglets. Uptake of radioiodinated purified binder was also examined.2. The binder strongly promoted uptake of vitamin B12 at both ages; in the absence of the binder there was little uptake. The uptake mechanism was specific and operative in vesicles prepared from all regions of the small intestine. Uptake was a rapid process, exhibiting saturation kinetics, with a pH optimum at about 7.0, and dependent on the presence of magnesium or calcium ions for maximum activity. Atfinity constants of the binding sites for the milk binder were determined.3. Competition experiments using complexes of the binder with vitamin B12 and with non-cobalamin analogues (cobinamide and Co-α-[2-methyladenyl]cobamide) showed that the bound analogues competed with bound vitamin B12 for uptake but with lower efficiency.4. Intrinsic factor also promoted vitamin B12 uptake by the vesicles but it did not compete with the milk binder for the same binding sites. It promoted uptake only in microvilli isolated from the lower third of the small intestine, and was more effective with preparations from 28-d-old piglets, whereas the milk binder was more effective with the 7-d-old piglets. Porcine gastric cobalophilin competed with the milk cobalophilin, but with lower efficiency.5. It was concluded that a specific transport mechanism for absorption of vitamin B12, mediated by the vitamin B12-binder in milk, exists at the intestinal brush border of neonatal piglets and strongly reinforces the developing intrinsic factor-mediated mechanism during the early days or weeks of life.6. It is suggested that the binder in the milk has a wider physiological significance and acts also as a ‘host protective’ factor and as a scavenger of adventitious vitamin B12.

Some species differences in the intrinsic factor stimulation of B12 uptake by small intestine in vitro

1959 ◽  
Vol 197 (4) ◽  
pp. 926-928 ◽  
Author(s):  
T. Hastings Wilson ◽  
Elliott W. Strauss
Keyword(s):  
Small Intestine ◽  
Guinea Pig ◽  
Species Differences ◽  
Intrinsic Factor ◽  
Vitamin B ◽  
Guinea Pig Ileum ◽  
Rat Intestine ◽  
Intrinsic Factors ◽  
Stimulation Of

Sacs of everted small intestine from a variety of animals were incubated in bicarbonate-saline containing vitamin B12 with and without intrinsic factor (IF). B12 uptake by rat intestine was stimulated only by its own intrinsic factor. Guinea pig ileum responded to all intrinsic factors tested (guinea pig, rat, hog, hamster, human being and rabbit). The intestines of hamster and rabbit were intermediate in specificity, responding to some, but not all, of the IF preparations. Species differences occur in both the intestine and intrinsic factor preparations. The guinea pig ileum was suggested as a possible assay for both hog and human IF.

Intestinal distribution of intrinsic factor and vitamin B12 absorption

1965 ◽  
Vol 208 (1) ◽  
pp. 14-17 ◽  
Author(s):  
Kunio Okuda ◽  
Katsumi Sasayama
Keyword(s):  
Small Intestine ◽  
Vitamin B12 ◽  
Large Intestine ◽  
Intrinsic Factor ◽  
Vitamin B ◽  
Vitamin B12 Absorption ◽  
Small Intestine Absorption

Evidence is presented that intrinsic-factor (IF) activity is present in the small intestine as far down as the ileal end. Physiologic doses of radioactive vitamin B12 without IF were applied directly into various levels of the intestine by surgical and other means in man and rats, and significant absorption was obtained from the small intestine. Absorption inhibition by ethylenediaminetetraacetate and its counteraction by Ca ion demonstrated that such absorption was dependent on IF action. The large intestine was shown to be incapable of physiologic absorption of vitamin B12, and IF was totally ineffective. It is proposed that physiologically, gastric IF descends with some activity in the small intestine, where more of the food vitamin B12 is liberated by digestion and subjected to IF.

Factors controlling B12 uptake by intestinal sacs in vitro

1960 ◽  
Vol 198 (1) ◽  
pp. 103-107 ◽  
Author(s):  
Elliott W. Strauss ◽  
T. Hastings Wilson
Keyword(s):  
Small Intestine ◽  
Low Temperature ◽  
Guinea Pig ◽  
Calcium Ion ◽  
Intrinsic Factor ◽  
Intestinal Wall ◽  
Vitamin B ◽  
Anaerobic Conditions ◽  
Intestinal Uptake

Sacs of everted small intestine were incubated in bicarbonate-saline containing radioactive vitamin B12 with or without a source of gastric intrinsic factor (IF). In both the hamster and guinea pig the lowest ileum was most active in B12 uptake in the presence of intrinsic factor, the upper jejunum showing little or no uptake. Low temperature and anaerobic conditions completely abolished the stimulatory effect of IF on B12 uptake. Intrinsic factor did not bind to the intestinal wall in the absence of B12 (even in the presence of calcium ion) as the IF activity could be completely removed by gentle washing of the tissue. The vitamin and intrinsic factor must be present together to cause intestinal uptake of B12.

scholarly journals Binding of Adenosine Diphosphate (ADP) to Isolated Human Platelet Membranes

1977 ◽  
Author(s):  
J. Lips ◽  
J. J. Sixma
Keyword(s):  
Binding Sites ◽  
Association Constant ◽  
Plasma Membranes ◽  
Human Platelet ◽  
Membrane Vesicles ◽  
Adenosine Diphosphate ◽  
Ph Optimum ◽  
High Affinity ◽  
Absolute Requirement ◽  
Millipore Filtration

Human platelet plasma membranes were isolated according to the glycerol loading technique of Barber and Jamieson. The binding of 14C ADP was studied with Millipore filtration in a Ca2+ and Mg2+ containing buffer at pH 7,4. At least two types of binding sites were found: A high affinity system with a maximum binding of 160 pMoles/mg protein and an association constant of 1,1 χ 106 M-1; and alow affinity system with a maximum binding of about 4500 pMoles/mg protein and an association constant of 0,6 χ 1θ4 M-1. The binding according to the high affinity system showed little temperature dependency (Q10 = 1,10). The pH optimum was at 7,3. Ca2+ ions were an absolute requirement for binding.Nucleoside diphosphokinase (NDPK) was found in the membrane vesicles. Evidence that this enzyme was not responsible for ADP binding was obtained. The enzyme is Mg2+ dependent and is inhibited by AMP, in contrast to ADP binding. The Q10 was 1,44.ADP binding was inhibited by ATP, IDP and β/γ-imidoadenosine triphosphate.

Vitamin B12 absorption in dogs with chronic isolated intestinal loops

1969 ◽  
Vol 47 (6) ◽  
pp. 497-504
Author(s):  
R. M. Taylor ◽  
J. A. Hildes ◽  
J. F. Lind
Keyword(s):  
Small Intestine ◽  
Vitamin B12 ◽  
Intrinsic Factor ◽  
Cellular Mechanism ◽  
Vitamin B ◽  
Absorption Factor ◽  
Ileal Mucosa ◽  
Ileal Loop ◽  
Simultaneous Absorption ◽  
Vitamin B12 Absorption

The absorption of physiological amounts of vitamin B12 is thought to occur only from the ileum, but the nature of the mechanism involved has not been established. A method utilizing the detection of radioactive vitamin B12 in plasma was used to investigate the mechanism of vitamin B12 absorption in dogs with isolated Thiry–Vella loops of small intestine, either ileum or jejunum. An animal with a Thiry–Vella loop of the entire ileum failed to absorb orally administered vitamin B12, but did absorb the vitamin from the isolated ileal loop when it was given with intrinsic factor, but not when given without. Attempts to restore absorption of orally administered vitamin B12 by the administration of ileal juice (either resting or stimulated), by the administration of an extract of ileal mucosa, or by the simultaneous absorption of non-radioactive vitamin B12 from the ioslated loop, all failed. In contrast, the animal with a jejunal Thiry–Vella loop absorbed vitamin B12 given orally but not when administered into the isolated jejunum alone, in combination with intrinsic factor, or with intrinsic factor and ileal juice. Under the conditions of these experiments the results confirm that vitamin B12 absorption is limited to the ileum, but fail to provide support for the hypothesis that the ileum liberates, either locally or systemically, a vitamin B12 absorption factor. Thus the hypothesis that ileal mucosa contains a special cellular mechanism for vitamin B12 absorption gains indirect support from these results.

scholarly journals Solubilization of the ileal receptor for intrinsic factor–vitamin B-12 complex by digestion with papain

1981 ◽  
Vol 200 (2) ◽  
pp. 225-229
Author(s):  
R C Beesley
Keyword(s):  
Alkaline Phosphatase ◽  
Brush Border Membrane ◽  
Intrinsic Factor ◽  
Membrane Vesicles ◽  
Receptor Activity ◽  
Vitamin B ◽  
Isolation And Purification ◽  
Vitamin B 12 ◽  
Soluble Supernatant ◽  
Insoluble Pellet

Brush-border-membrane vesicles isolated from hamster ileum were incubated with either papain or Pronase P and subsequently centrifuged to obtain soluble (supernatant) and insoluble (pellet) fractions. Papain (4 units/ml) solubilized 95--100% of the sucrase and leucine naphthylamide-hydrolysing activities but only 30% of the alkaline phosphatase. Digestion with papain also resulted in the solubilization of more than 75% of the ileal receptor for intrinsic factor-vitamin B-12 complex with a corresponding decrease in receptor activity in the pellet. Essentially 100% of the receptor activity was recovered. In contrast, digestion with Pronase P resulted in a decrease in total receptor activity. Papain-solubilized receptor was not sedimented by centrifugation at 105 000 g for 90 min and was eluted in the included volume of Sepharose 6B. Like the binding to more intact preparations, binding of intrinsic factor-vitamin B-12 complex to papain-solubilized receptor was rapid, reaching 50% of maximum in 8 min, and required Ca2+. Although Mg2+ could not completely substitute for Ca2+, Mg2+ did stimulate Ca2+-dependent binding at low Ca2+ concentrations. These results demonstrate that the ileal receptor for intrinsic factor-vitamin B-12 complex can be solubilized with papain, and suggest that papain solubilization may be a useful first step in the isolation and purification of this receptor.

scholarly journals Assessment of vitamin B12 deficiency and B12 screening trends for patients on metformin: a retrospective cohort case review

2021 ◽  
pp. bmjnph-2020-000193
Author(s):  
Darby Martin ◽  
Jeet Thaker ◽  
Maria Shreve ◽  
Lois Lamerato ◽  
Kartazyna Budzynska
Keyword(s):  
Retrospective Cohort ◽  
Protective Factor ◽  
Vitamin B12 Deficiency ◽  
Older Age ◽  
Secondary Outcome ◽  
Vitamin B ◽  
Case Review ◽  
Large Hospital ◽  
Hospital System ◽  
B12 Deficiency

ObjectivesOur study investigated the use of vitamin B12 testing in a large cohort of patients on metformin and assesses appropriateness and benefits of screening recommendations for vitamin B12 deficiency.DesignThis retrospective cohort study included insured adult patients who had more than 1 year of metformin use between 1 January 2010 and 1 October 2016 and who filled at least two consecutive prescriptions of metformin to establish compliance. The comparison group was not exposed to metformin. Primary outcome was incidence of B12 deficiency diagnosed in patients on metformin. Secondary outcome was occurrence of B12 testing in the patient population on metformin. Records dated through 31 December 2018 were analysed.SettingLarge hospital system consisting of inpatient and outpatient data base.ParticipantsA diverse, adult, insured population of patients who had more than 1 year of metformin use between 1 January 2010 and 1 October 2016 and who filled at least two consecutive prescriptions of metformin.ResultsOf 13 489 patients on metformin, 6051 (44.9%) were tested for vitamin B12 deficiency, of which 202 (3.3%) tested positive (vs 2.2% of comparisons). Average time to test was 990 days. Average time to test positive for deficiency was 1926 days. Factors associated with testing were linked to sex (female, 47.8%), older age (62.79% in patients over 80 years old), race (48.98% white) and causes of malabsorption (7.11%). Multivariable logistic regression showed older age as the only factor associated with vitamin B12 deficiency, whereas African-American ethnicity approached significance as a protective factor.ConclusionsBased on our study’s findings of vitamin B12 deficiency in patients on metformin who are greater than 65 years old and have been using it for over 5 years, we recommend that physicians consider screening in these populations.

Hydrolysis and transglycosylation activities of glycosidases from small intestine brush-border membrane vesicles

2021 ◽  
Vol 139 ◽  
pp. 109940
Author(s):  
Lesbia Cristina Julio-Gonzalez ◽  
F. Javier Moreno ◽  
María Luisa Jimeno ◽  
Elisa G. Doyagüez ◽  
Agustín Olano ◽  
...  
Keyword(s):  
Small Intestine ◽  
Brush Border ◽  
Brush Border Membrane ◽  
Membrane Vesicles ◽  
Brush Border Membrane Vesicles

scholarly journals Characterization of verapamil binding sites in cardiac membrane vesicles.

1984 ◽  
Vol 259 (24) ◽  
pp. 15013-15016 ◽  
Author(s):  
M L Garcia ◽  
M J Trumble ◽  
J P Reuben ◽  
G J Kaczorowski
Keyword(s):  
Binding Sites ◽  
Membrane Vesicles ◽  
Cardiac Membrane
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