Ethan Clarke
The Plastic Occlusion Stress Test (POST) is a procedure used to study the effects of lipid removal on the stratum corneum water-holding capacity of the skin barrier. The test involves delipidizing the volar forearm of subjects using ether/acetone (EA; 1:1) and chloroform/methanol (CM; 2:1). A third site is used as a control. The water desorption curve after the removal of the occlusion is then recorded in terms of skin surface water loss (SSWL) using an evaporimeter for 30 minutes. This test is particularly useful for monitoring the water-holding capacity of visually non-irritated skin.
| Characteristics | Values |
|---|---|
| Purpose | To develop an in vivo model to study the effects of lipid removal on the skin barrier |
| Subjects | 16 (age 41 +/- 8) |
| Procedure | Subjects were delipidized in vivo on the volar forearm using ether/acetone (EA; 1:1) and chloroform/methanol (CM; 2:1). A third site served as a control. Water holding capacity (WHC) was measured using an evaporimeter for 30 minutes. |
| Results | The CM-treated site showed significantly higher water loss compared to the control and EA-treated sites. |
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What You'll Learn
- The plastic occlusion stress test (POST) is used to study the effects of lipid removal on skin barrier
- Water holding capacity (WHC) is measured using an evaporimeter for 30 minutes
- The water desorption curve is recorded in terms of skin surface water loss (SSWL)
- The POST procedure is performed on the volar forearm
- Ether/acetone (EA) and chloroform/methanol (CM) are used for delipidization
The plastic occlusion stress test (POST) is used to study the effects of lipid removal on skin barrier
The plastic occlusion stress test (POST) is a procedure used to study the effects of lipid removal on the skin barrier. The test is performed in vivo, on the volar forearm of subjects. The skin is delipidized using ether/acetone (EA; 1:1) and chloroform/methanol (CM; 2:1), with a third site serving as a control.
The test specifically measures the water-holding capacity (WHC) of the skin, which is an important indicator of the skin's barrier function. The water desorption curve after the removal of the occlusion is recorded in terms of skin surface water loss (SSWL) using an evaporimeter for 30 minutes. The SSWL decay constants reflect the desorption rate of water from the skin and provide insights into the skin's ability to retain water.
The results of the POST show significant differences between the control and treated sites. The CM-treated site, for example, exhibits higher SSWL decay constants, indicating an increased desorption rate of water and suggesting that CM delipidization impacts the skin's ability to retain water.
The POST is a valuable tool for understanding how lipid removal affects the skin barrier and can provide insights into the development of skin care products and treatments that enhance the skin's water-holding capacity and overall barrier function.
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Water holding capacity (WHC) is measured using an evaporimeter for 30 minutes
To measure WHC, the water desorption curve after the removal of occlusion is recorded in terms of skin surface water loss (SSWL) using an evaporimeter for 30 minutes. This method is known as the plastic occlusion stress test (POST) procedure, and it is used to study the effects of lipid removal on the skin barrier. The POST procedure is performed in vivo on the volar forearm of subjects, and the SSWL decay constants reflecting the desorption rate of water are calculated.
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The water desorption curve is recorded in terms of skin surface water loss (SSWL)
The POST-induced variation of SSWL can be evaluated using the two-parameter Fujita fitting model, which is based on Fick's laws and Fujita's concentration-dependent approximation for SC diffusivity. The model pays particular attention to the transepidermal water loss (TEWL), water concentration profile, water content, wet thickness of SC, and the time lag associated with desorption after the application of occlusion.
The water desorption curve is a representation of the temporary variation of SSWL, which gradually decreases towards the baseline value of TEWL, measured at the same level of ambient humidity. The SSWL decay constants reflect the desorption rate of water from the skin surface.
The SSWL decay curve can also be influenced by factors such as occlusion and sweating, as seen in studies where both forearm and vulvar SSWL were measured simultaneously in healthy women. Irregular SSWL increases, or 'bursts', were observed in vulvar skin and attributed to sweating.
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The POST procedure is performed on the volar forearm
During the procedure, the volar forearm is delipidized in vivo using two different solutions: ether/acetone (EA; 1:1) and chloroform/methanol (CM; 2:1). A third site is left untreated to serve as a control. After delipidization, the water desorption curve is recorded to measure the skin's water-holding capacity. This is done by measuring skin surface water loss (SSWL) using an evaporimeter for 30 minutes.
The results of the study showed that the CM-treated site had a significantly higher rate of water loss compared to the control and EA-treated sites. This indicates that the CM solution was more effective at removing lipids and impacting the skin's water-holding capacity.
By performing the POST procedure on the volar forearm, researchers can gain valuable insights into the skin's barrier function and how it is affected by lipid removal. This knowledge can then be applied to the development of skin care products and treatments that effectively protect and enhance the skin's natural barrier.
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Ether/acetone (EA) and chloroform/methanol (CM) are used for delipidization
The Plastic Occlusion Stress Test (POST) is a model used to investigate the effects of skin delipidization on the stratum corneum water holding capacity in vivo. The test aims to study the effects of lipid removal on the skin barrier.
In one such study, 16 subjects (age 41 +/- 8) underwent delipidization in vivo on the volar forearm. The delipidization process involved the use of ether/acetone (EA; 1:1) and chloroform/methanol (CM; 2:1). These solvents are known for their ability to efficiently extract lipids from biological tissues. A third site served as a control.
Ether and acetone are non-polar solvents that can effectively dissolve neutral lipids. Acetone, in particular, is a versatile solvent that can be used in both hot and cold conditions. It is often used in combination with other solvents, such as methanol, to enhance its lipid extraction capabilities.
Chloroform and methanol are commonly used together in a classical lipid extraction method known as the Folch method or Bligh and Dyer method. This combination of solvents has been shown to yield a higher amount of total lipids compared to other methods. The chloroform/methanol mixture is effective due to its ability to disrupt the protein-lipid complexes and dissolve lipids efficiently.
After the delipidization process, the water holding capacity (WHC) was measured using the POST procedure. The water desorption curve was recorded by measuring skin surface water loss (SSWL) using an evaporimeter for 30 minutes. The results showed that the CM-treated site had a significantly different water desorption curve compared to the control and EA-treated sites. This indicated that the CM delipidization process had a notable effect on the bound water in the skin.
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