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Biomedical subjects

G K Wolfer

Publications and source records attributed to G K Wolfer.

5 recordsLinked to original sources
PubMed1989

Influence of ligand valency on ligand-influenced monomer-dimer equilibrium systems and biological control mechanisms.

Two specific ligand-influenced monomer-dimer equilibrium systems are discussed. Each has a ligand-to-dimer subunit ratio of 0.5. Equilibrium characteristics of the system are described in terms of the effect of a bivalent ligand on both experimental and theoretical analysis. It is shown that Hill expressions need to be modified for multivalent ligand systems, and care is needed in equilibrium parameter determination. Some unique properties of these systems are retained, yet others are altered in the presence of a multivalent ligand. A suggestion as to the minimum amount of information needed to describe completely a ligand-influenced monomer-dimer system is given. The estrogen-receptor system is presented as an attractive biological model for both theoretical and experimental study of ligand-influenced polymerizing systems and their role in cellular control requirements.

Kinetics↗
PubMed1987

Protocols for use of ultrafiltration in determination of free ligand concentration and of complexity of ligand/protein interactions.

Analysis of a simple ligand/binding-protein association model predicts a decrease in the percentage of free hormone during ultrafiltration. Re-analysis of the original data validating ultrafiltration in free-ligand determinations (Sophianopoulos et al., Arch Biochem Biophys 1978;187:132-7) confirms this prediction. Binding data indicating a constant percentage of free hormone (Hammond et al., J Biol Chem 1980;255;5023-6) require a more complex ligand-protein interaction model. Application of these procedures to any new ligand system requires measurement of the percentage free, or of free-ligand concentration, as a function of filtration time or volume. The protocol becomes important if values for percentage free are to be accurate.

Chemistry, Clinical↗
PubMedDate not supplied

Quantification of the effects of respiration and parallax on inferior vena caval filter position.

PURPOSE: The change in inferior vena caval (IVC) filter position at follow-up relative to the filter position at implantation has been used as a criterion for evaluation and comparison of these devices. Perceived changes in filter position may be due to respiratory movement and/or changes in parallax between the initial and follow-up imaging studies. In this study the authors evaluated and attempted to quantify the effects of respiratory movement and parallax. PATIENTS AND METHODS: After placement of an IVC filter, radiographs of the abdomen were taken at maximum inspiration and maximum expiration in 30 patients. The effect of parallax on apparent filter movement was studied by using a phantom. RESULTS: The average filter movement on inspiration/expiration radiographs (corrected for magnification) was 3.6 mm +/- 2.2. An 8.5-mm maximal change secondary to parallax was seen in the phantom study. CONCLUSION: When follow-up images are obtained, efforts should be made to closely reproduce patient positioning and patient respiration to reduce errors in the interpretation of filter migration.

Follow-Up Studies↗