Letters to the Editor

The following is the abstract of the article discussed inthe subsequent letter:

Yuan, Huichin, Edward P. Ingenito, and BélaSuki. Dynamic properties of lung parenchyma: mechanicalcontributions of fiber network and interstitial cells. J. Appl.Physiol. 83(5): 1420-1431, 1997.We investigated thecontributions of the connective tissue fiber network and interstitialcells to parenchymal mechanics in a surfactant-free system. In eightstrips of uniform dimension from guinea pig lung, we assessed thestorage (G') and loss (G") moduli by using pseudo-random lengthoscillations containing a specially designed set of seven frequenciesfrom 0.07 to 2.4 Hz at baseline, during methacholine (MCh) challenge,and after death of the interstitial cells. Measurements were made atmean forces of 0.5 and 1 g and strain amplitudes of 5, 10, and 15% andwere repeated 12 h later in the same, but nonviable samples. Theresults were interpreted using a linear viscoelastic modelincorporating both tissue damping (G) and stiffness (H). The G' and G"increased linearly with the logarithm of frequency, and both G and Hshowed negative strain amplitude and positive mean force dependence. After MCh challenge, the G' and G" spectra were elevated uniformly, andG and H increased by <15%. Tissue stiffness, strain amplitude, andmean force dependence were virtually identical in the viable andnonviable samples. The G and hence energy dissipation were ~10%smaller in the nonviable samples due to absence of actin-myosin cross-bridge cycling. We conclude that the connective tissue network may also dominate parenchymal mechanics in the intact lung, which canbe influenced by the tone or contraction of interstitial cells.

     

Letters to the Editor

Abstract

Hot commercial dishwashing detergent has been used to deparaffinize and hydrate formalin fixed, paraffin embedded sections for immunohistochemistry. Fifty-five antibodies, used routinely for diagnosis, were used to compare hot detergent dewaxing with the proprietary hydrocarbon-based dewaxing reagent supplied with the Bond Max immunohistochemistry system^®. A 2% concentration of commercial dishwashing detergent in distilled water was heated to 90° C and paraffin sections were treated twice for 1 min each. Nearly all antibodies gave equivalent results except CD10 and CD57 (hydrocarbon-based dewaxing better) and CD45 and alpha fetoprotein (detergent dewaxing better); the differences, however, were minimal. There also was a significant cost saving using detergent dewaxing.