Reduction and Block Staining of Human Hair Shafts and Insect Cuticles by Ammonium Thioglycolate to Enhance Transmission Electron Microscopic Observations

Shigeru Sato,Tokuya Omi,Akiko Adachi,Yoshihiro Sasaki

doi:10.4236/jcdsa.2013.32025

Abstract

We have developed a method where, after glutaraldehyde fixation, human hair shafts and insect cuticles are treated with ammonium thioglycolate (ATG) to improve ultrastructural staining. Conventional transmission electron microscopic (TEM) preparations do not distinguish the A-layer and the exocuticles of hair shafts. However, after ATG treatment, the A-layer appears in higher contrast. ATG treatment has also been used to observe the fibrillar structure in the cortex. In the cuticle of beetles, the epicuticle is stained by ATG. Although the human hair shaft (keratin) and insect cuticle (chitin) are composed of different materials, both can be reduced by the ATG solution. The ammonium in the ATG solution reacts with hair shafts and insect cuticles, causing a reduction of swelled cuticles. Therefore, ATG not only stains, but also reduces human hair shafts and the cuticles of beetles.

Highlights

2-mercaptoethanol in phosphate buffer is used for electron microscopic observations, called the reduction-osmication method
We have developed a method where, after glutaraldehyde fixation, human hair shafts and insect cuticles are treated with ammonium thioglycolate (ATG) to improve ultrastructural staining
The cell membrane complex (Figures 1 and 2 arrows) consists of two electron-lucent layers and a central electron-dense layer, which are clearly seen after ATG staining more than by conventional transmission electron microscopic (TEM) between each cuticle cell (Figure 2 arrows)

Summary

Introduction

2-mercaptoethanol ( known as thioglycol) in phosphate buffer is used for electron microscopic observations, called the reduction-osmication method. This method has proven to be the most successful for visualizing the fibrillar structures in the cortex [1,2,3]. When ammonium thioglycolate (ATG) solution is used for permanent waving of human hair shafts, changes in the physical and mechanical properties of human hair shafts occur, including a reduction in tensile strength the same as occurs with 2-mercaptoethanol [4,5]. Treatment with ATG or 2-mercaptoethanol in phosphate buffer has been used to observe the fibrillar structure in the cortex. The A-layer in hair cuticle cells is stained [6,7]

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