Effects of surfactant on the in vivo alveolar surface-to-volume ratio

Abstract

To investigate how pulmonary surfactant influences alveolar structure in vivo, we examined the alveolar surface area-to-lung volume (S/V) ratio of the lung parenchyma of a live dog by light-scattering stereology before and after saline lavage. We measured the backscattered light pattern produced by applying a laser beam to the pleural surface of a ventilated animal and obtained the S/V [equivalent to the inverse of the optical mean free path (lambda)]. After saline lavage, V at transpulmonary pressure (P) of 30 cmH2O (defined as total lung capacity) decreased by 11.1 +/- 3.1% (SD) and the P-V curve shifted to a lower V. The lambda-V curve was shifted to a higher lambda and to a lower V after saline lavage. S/V decreased after saline lavage (lambda increased by 38 +/- 27% on the deflation limb at a V of 80% of control total lung capacity). The alveolar surface tension increased after saline lavage, and the increase in surface tension was greater on inflation than on deflation. We conclude that depletion of pulmonary surfactant increases the alveolar surface tension in vivo, resulting in a decrease in S/V.

The fates of different types of adipose tissue after transplantation in mice

“…The higher surface area-to-volume ratio of the smaller beige adipocytes and the superior vascularization of the donor adipose tissue are believed to facilitate the exchange nutrients and metabolites especially in early stage of engraftment, and to further enhance the vascularization of transplanted fat, which promotes its survival. [27][28][29] However, despite the fact that BAT contains the smallest adipocytes, BAT grafts had the worst survival rates. Therefore, there must be as yet unidentified factors that differentially affect the survival of beige AT and BAT grafts.…”

Induced Beige Adipocytes Improved Fat Graft Retention by Promoting Adipogenesis and Angiogenesis

“…Beige adipocytes have a smaller cell size, with a higher surface-to-volume ratio than white adipocytes, which facilitates the exchange of nutrients and wastes. 22 Thus, smaller adipocytes may better tolerate avascular environments and have a better survival rate. The level of VEGF expression was significantly higher in the induced beige adipocyte and adipose-derived stem cell groups than in the phosphate-buffered saline group (*p < 0.05).…”

“…Beige adipocytes have a smaller cell size, with a higher surface-to-volume ratio than white adipocytes, which facilitates the exchange of nutrients and wastes. 22 Thus, smaller adipocytes may better tolerate avascular environments and have a better survival rate.…”