Mucopolysaccharide osmotic pressure in the measurement of interstitial pressure

Our plain-English summary of Mucopolysaccharide osmotic pressure in the measurement of interstitial pressure, by P.D. Snashall (The American Journal of Physiology, 1977).

The study

• Author: P.D. Snashall
• Journal: The American Journal of Physiology
• Published: 1977;232(6):H608-16
• Cited by: 19 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Subatmospheric pressures were recorded from cotton wicks inserted into Wharton's jelly of human umbilical cords (mean=-7.6+/-5.0 (SD) cmH2O; n=10). Hyaluronate concentrations (mean=0.69+/-0.30 g/100 g) and wick pressures correlated negatively (r=-0.825; P less than 0.01) but calculated hyaluronate osmotic pressures (mean=4.0+/-2.7 cmH2O) were insufficient to explain the full wick pressure. In model systems composed of asbestos fibers (mean radius=0.5 micron) and 0.9% saline, subatmospheric pressures were recorded which varied with the volume of saline added. When hyaluronate (1 g/100 g) was substituted for saline, lower wick pressures were recorded at each volume. The pressure lowering effect of hyaluronate was not seen in a matrix of glass fibers (mean radius=1.0 micron). It is suggested that the effect of hyaluronate in asbestos fibers is due to its immobilization by the matrix and the consequent development of osmotic pressure recorded via the wick. In the coarser glass-fiber matrix, hyaluronate was not immobilized and therefore had no osmotic effect. These experiments support the hypothesis that subatmospheric interstitial pressures result from osmotic pressure of immobilized mucopolysaccharide macromolecules.

In plain English

This laboratory physiology study did not examine asbestos as a health hazard. It used asbestos fibers only as an artificial material in model experiments. The author studied why cotton wicks placed in tissue record pressures below atmospheric pressure, testing whether this comes from the osmotic pressure of hyaluronate, a large molecule found in connective tissue. In 10 term human umbilical cords, every wick reading was below atmospheric pressure (mean -7.6 cmH2O). Lower wick pressure went with higher hyaluronate concentration (r = -0.825; P less than 0.01). However, the calculated hyaluronate osmotic pressure (mean 4.0 cmH2O) was too small to account for the full size of the negative wick pressures. In model systems, putting hyaluronate instead of saline into a matrix of amphibole asbestos fibers (mean radius 0.5 micrometers) lowered wick pressure by 6 to 4 cmH2O. Hyaluronate had no detectable effect in coarser glass fibers, and albumin had no significant effect in asbestos. The author concluded that wick pressure can be influenced by osmotic forces. The author noted that the cords were not randomly selected.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Laboratory study: measurements on human umbilical cord tissue plus in vitro model experiments using asbestos and glass-fiber matrices
• Who was studied: 10 term human umbilical cords, frozen after delivery and chosen for widely differing thickness and amount of Wharton's jelly. The article does not state where or when the cords were collected.
• Exposure: No human or animal asbestos exposure was studied. Amphibole asbestos (Fisher Scientific, prepared for Gooch crucibles; fiber radius 0.25 to 0.5 micrometers, mean 0.5 micrometers) and glass-fiber wool (radius 1.0 micrometers) were used as artificial fibrous matrices. These were mixed with saline, hyaluronate (1 g/100 ml) or albumin (5 g/100 ml).
• Main results:
  • In the 10 umbilical cords, wick pressure was significantly related to hyaluronate concentration (r = -0.825; P less than 0.01). Every wick measurement was below atmospheric pressure.
  • In the cords, mean wick pressure (-7.6 cmH2O) was lower than expected from the calculated hyaluronate osmotic pressure. The mean hyaluronate concentration of 0.69 g/100 ml Wharton's jelly water gave a calculated osmotic pressure of 4.0 cmH2O.
  • After adjusting hyaluronate data for exclusion by the fibrous matrix and proteins, the cord data showed less scatter (r = -0.93) than the raw data (r = -0.83).
  • In asbestos matrices, hyaluronate solutions gave lower wick pressures than saline at each volume. The decrease ranged from 6 cmH2O at the lowest volume to 4 cmH2O at the highest.
  • When the wick was also soaked in hyaluronate, wick pressure in the asbestos matrix with hyaluronate was 1.5-2.5 cmH2O lower than with saline. The author interpreted this as a partial reversal of the effect.
  • In glass-fiber matrices, wick pressures with hyaluronate were not detectably different from those with saline.
  • Albumin in the asbestos matrix did not significantly change wick pressure compared with saline.
  • Umbilical cord slices swelled in saline by an average of 84.7% of starting weight.
• The authors' conclusion: The author concluded that wick pressure can be influenced by osmotic forces in a simple model system. The author also concluded that, in one tissue (umbilical cord), mucopolysaccharide concentrations are compatible with causing the observed subatmospheric pressure by osmosis.
• Limitations the authors state:
  • Cords were not selected at random, so their values may not be typical of umbilical cords in general.
  • Chondroitin sulfate was ignored, and all uronic acid was assumed to come from hyaluronate.
  • The molecular and fiber dimensions used in the volume-exclusion calculation were arbitrarily chosen from within possible ranges.

Topics

Medical terms in this study, explained in our Lexicon: Interstitial.

Related studies

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• Exercise alveolar-arterial oxygen pressure difference in interstitial lung disease — C. Risk, G.R. Epler, et al. (1984)
• Mesothelioma of spermatic cord: electron microscopic and histochemical characteristics of its mucopolysaccharides — P. Pizzolato, J. Lamberty (1976)
• The relation between connective tissue cells and intercellular substances, including basement membranes — P. Davies, A.C. Allison, et al. (1975)
• Allele-specific effects of ecSOD on asbestos-induced fibroproliferative lung disease in mice — S. Jun, C.L. Fattman, et al. (2011)

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