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At least 487 records · Page 27Linked to original sources
PubMed1987

Absorption and metabolism of vitamin K in Swiss 3T3 mouse fibroblasts--a model system for study of vitamin K absorption and metabolism.

The vitamin K cycle previously described in liver has been demonstrated in Swiss 3T3 mouse fibroblasts. Vitamin K epoxide and gamma-carboxyglutamic acid were isolated from the cells and chemically characterized. Menaquinone (MK4) is also metabolized to its epoxide and vitamin K epoxide is reduced to vitamin K in these cells. Thus Swiss 3T3 mouse fibroblasts provide a useful model system for the study of vitamin K metabolism. Possible functions of the vitamin K-dependent protein(s) in fibroblasts are discussed.

1-Carboxyglutamic Acid↗
PubMed2006

Nanoscale analysis of protein and peptide absorption: insulin absorption using complexation and pH-sensitive hydrogels as delivery vehicles.

Recent advances in the discovery and delivery of drugs to cure chronic diseases are achieved by combination of intelligent material design with advances in nanotechnology. Since many drugs act as protagonists or antagonists to different chemicals in the body, a delivery system that can respond to the concentrations of certain molecules in the body is invaluable. For this purpose, intelligent therapeutics or "smart drug delivery" calls for the design of the newest generation of sensitive materials based on molecular recognition. Biomimetic polymeric networks can be prepared by designing interactions between the building blocks of biocompatible networks and the desired specific ligands and by stabilizing these interactions by a three-dimensional structure. These structures are at the same time flexible enough to allow for diffusion of solvent and ligand into and out of the networks. Synthetic networks that can be designed to recognize and bind biologically significant molecules are of great importance and influence a number of emerging technologies. These synthetic materials can be used as unique systems or incorporated into existing drug delivery technologies that can aid in the removal or delivery of biomolecules and restore the natural profiles of compounds in the body.

Absorption↗
PubMed1999

Evaluation of cytotoxicity and absorption enhancing effects of melittin - a novel absorption enhancer.

Melittin is the major active ingredient in bee venom and has been widely studied for its membrane-fusion property. We have explored the possibility of determining a concentration range of melittin where it is relatively safe to be used as an adsorption enhancer. Melittin's potential use as an adsorption enhancer for mannitol was determined using Caco-2 cells as the model epithelial membrane. The results indicated that at concentrations below 2.4 (M melittin is safe. Using a melittin concentration of 1.5 (M there was 3.5 times increased transepithelial transport of mannitol across Caco-2 cell monolayers.

Caco-2 Cells↗
PubMed1999

Use of truncated areas to measure extent of drug absorption in bioequivalence studies: effects of drug absorption rate and elimination rate variability on this metric.

PURPOSE: To compare the applicability and accuracy of truncated area (AUCt; where t represents truncated time) versus area to the last quantifiable time point [AUC(O-T)] for assessing bioequivalence. Drugs with either very low or very high intra-subject variability in clearance (CL) were selected for study. Clearance variability was defined by the number of subjects with a quantifiable plasma value (Cp) at each collection time from 24 hrs to last collection time (T). METHODS: Data for amiodarone and danazol, drugs with different distributions of subject CL were examined. For amiodarone, the number of subject samples observed (test + reference) at the time of the last quantifiable concentrations was 60 at 240 hrs(T), 16 at 144 hrs and 4 at 96 hrs: while danazol had 4 at 96 hr(T), 3 at 72 hrs, 16 at 60 hrs, 7 at 48 hrs, 14 at 36 hrs, 11 at 24 hrs, 13 and 2 at 16 and 12 hrs, respectively. Simulations (Scenarios A and B) were performed to obtain populations (N = 24) with CL patterns similar to those of amiodarone and danazol. For scenario A (CL pattern similar to amiodarone), log-normally distributed CL values (28.8 L/HR) with intra-subject coefficient of variation (CV) of 25%, 40% and 60% gave the desired CL pattern. Scenario B (CL pattern similar to danazol) required that a subpopulation with an increase in CL of 40% from baseline (i.e., 40.32 L/HR) in 5%, 10% and 20% of the population represent the desired distribution. Power was evaluated by the percentage of times the simulated trials were declared bioequivalent (i.e., the number of times the test vs. reference 90% CI was within 80-125%), while accuracy was determined when the true difference in fraction absorbed (i.e., 1.25) was within the CI. Each simulation was repeated 300 times. RESULTS: The simulation results for Scenario A indicated that the statistical results using truncated area (AUCt) had power and accuracy equivalent to that obtained using the AUC(O-T) metric. However, results for Scenario B indicated that AUCt had less power and accuracy than that obtained using AUC(0-T). The confidence interval (CI) for amiodarone was the same whether AUC (0-T) or AUCt was used as the metric for extent, while for danazol, the AUC(0-T) and AUCt differed in the lower limit by 7%. CONCLUSIONS: The truncated area, AUCt, has the greatest power and accuracy when the population clearance is such that most subjects have measurable plasma concentrations at last collection time(T), resulting in a proportional loss of data from each subject.

Adult↗
PubMed1981

The role of glutathione in amino-acid absorption. Lack of correlation between glutathione turnover and amino-acid absorption by the yeast Candida utilis.

The rate of degradation of glutathione has been determined in the yeast Candida utilis by using a method that minimizes the effect of amino-acid recycling. When yeast are grown in amino-acid-free medium, the half-life of glutathione was found to be 230 min. C. utilis was also found to absorb various L-amino acids rapidly without producing any significant decrease in the half-life of glutathione. While the gamma-glutamyl cycle is thus operating in C. utilis, the rate of degradation of glutathione is found to be 100 times too slow for the cycle to be mediating the transport of these amino acids.

Absorption↗