Apparent Permeability
Apparent Permeability - Related Videos
01:09
Apparent Weight
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2023
True weight is the measure of the gravitational force acting on an object. However, if the object accelerates, its measured weight is different from its true weight. Similar observations can be made when the object is submerged in water. An object's weight in water is its apparent weight, which is equal to the difference between its true weight and the buoyant forces. Consider a person standing on a bathroom scale inside an elevator. If the scale is accurate at rest, its reading equals the...
01:28
Apparent Weight and the Earth's Rotation
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2023
Since all objects on the Earth's surface move through a circle every 24 hours, there must be a net centripetal force on each object, directed towards the center of that circle. The points of the north and south poles are the only exception to this rule. For an object on the Earth's equator, the net centripetal force that accounts for its rotation is the Earth's pull towards its center, or the weight minus the normal force that prevents it from piercing into the Earth's surface. This force,...
06:37
An Assay for Permeability of the Zebrafish Embryonic Neuroepithelium
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Cited by 11 •
2012
We describe a live whole animal quantitative measurement for permeability of the embryonic zebrafish brain. The technique analyzes the ability to retain cerebrospinal fluid and molecules of different molecular weights within the neural tube lumen and quantifies their movement out of the ventricles. This method is useful for determining differences in epithelial permeability and maturation during development and disease.
07:03
An in vivo Assay to Test Blood Vessel Permeability
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Cited by 335 •
2013
We are presenting an in vivo assay to test blood vessel permeability. This assay is based on intravenous injection of a dye and subsequent visualization of its diffusion into interstitial spaces.
01:25
Permeability of Concrete
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2024
Permeability in the context of concrete refers to how easily liquids or gases can pass through the material. This quality is crucial for assessing the water-tightness and durability of concrete structures and their resistance to chemical attacks. Concrete permeability can be determined through comparative laboratory tests. These tests typically involve sealing a concrete specimen from the sides, applying water pressure to the top surface with pressure, and measuring the amount of water passing...
FAQs
Passive diffusion moves a compound across the barrier without a transport process, whereas active transport can enhance or restrict its movement. Because both contributions may occur during an assay, the measured value represents the combined behavior of the compound and the cellular barrier. This distinction helps researchers investigate why compounds with similar structures may show different transport profiles.
An intact cell monolayer provides the barrier properties needed for meaningful transport comparisons. If barrier integrity changes, the measured compound flux may reflect altered cell-layer resistance rather than the compound’s inherent transport behavior. Assessing integrity therefore supports more reliable comparisons among drug candidates and helps researchers interpret whether differences arise from the compound or the biological model.
The assay outcome depends on more than a compound’s ability to diffuse through cell membranes. Active transport processes can increase or decrease movement, while the condition of the cultured barrier can also affect flux. Consequently, apparent permeability is most useful as an integrated indicator of barrier crossing and transport behavior, rather than as an isolated measurement of passive diffusion.
Intestinal epithelial models support comparisons related to movement across barriers involved in oral drug absorption. Blood-brain barrier models address transport relevant to central nervous system exposure. Using these distinct cultured cell systems allows researchers to examine whether a candidate’s behavior is broadly favorable or particularly limited at a barrier associated with a specific therapeutic objective.
Researchers first use a cultured cell monolayer to represent the biological barrier, then expose one side of the system to the compound while monitoring its appearance in the receiver compartment. They determine the rate of compound flux and normalize it to membrane area and the concentration difference between compartments. This produces a value suitable for comparing candidates or conditions.
Results allow researchers to compare how readily different compounds cross a selected biological barrier and to identify transport patterns that may influence pharmacokinetics. In medicine, intestinal measurements can inform expectations about oral absorption, while blood-brain barrier measurements can support evaluation of central nervous system exposure. These comparisons help prioritize candidates for further investigation.