Quantitative Study of Distribution of Sulfhydryl Groups in the Developing Grasshopper (Melanoplus differentialis) Embryo

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Abstract
The increase of titratable -SH groups in prediapause, a leveling off during diapause, and the resumption of a rapid rise in the post-diapause period parallels the metabolic, mitotic and morpho-genetic activity of the embryo during these phases of development. The increase of embryo -SH occurs at the expense of the yolk -SH. There is no direct relationship between the sulfhydryl content and the "blocked" or diapause state in the grasshopper embryo. The excessive, abrupt rise in the titer of -SH groups during postdiapause is associated with morphogenetic growth and differentiation. The embryo is probably the site of origin of the enzyme responsible for the breakdown of protein -SH in the yolk. The non-protein -SH (probably glutathione) enters the embryonic cells, serving as a substrate for protein -SH resynthesis, as well as acting as a regulator of cell metabolism. Cytoplasmic -SH consists of protein and non-protein thiols, with all of the non-protein -SH being in the reduced state. The yolk and nuclei do not contain oxidized or reduced soluble free thiol groups. The histochemical demonstration of protein bound -SH in the embryo, qualitatively confirms the quantitative data, and indicates the localization of protein bound mercaptans in nerve and muscle tissue of postdiapause embryos.