The effects of several
dehydration treatments on the synaptonemal complex (SC),
histone solubility in 2.0 M NaCl, and
histone-
DNA interaction in unfixed rat spermatocytes were evaluated. Freeze substitution with
ethanol or
dehydration with
polyethylene glygol resulted in loss of the SC, preservation of
histone solubility and
DNA-
histone salt linkages.
Dehydration with
ethylene gylcol or
hexylene glycol resulted in preservation of SC with a clear delineation of attachment of the
chromatin fibrils to the lateral elements, but a loss of
histone solubility and
histone-
DNA linkages.
Dehydration to a fifty percent concentration with
glycerol with completion of
dehydration with
ethylene glycol had the same effect but also resulted in an even distribution of
chromatin fibrils.
Dehydration with
glycerol alone resulted in clumping of
chromatin and loss of SC structure,
histone solubility and
histone-
DNA linkages. Partial
dehydration to a fifty percent concentration with these three
solvents followed by freeze substitution with
ethanol resulted in the loss of SC structure and
histone solubility but the preservation of
histone-
DNA linkages. It is likely that these nonaqueous
solvents affected the
histone hydrophobic groups and thereby altered
histone conformation and interactions. These alterations, depending on the treatment used, resulted in the loss or preservation of SC,
histone solubility and
histone-
DNA interactions thereby indicating that the hydrophobic interactions of the
histones are crucial for the preservation of these feature of meiotic chromosomes. These results also demonstrate that neither does the preservation of the
histone-
DNA salt linkages suffice for the preservation of the SC nor does their disruption necessarily result in its loss. The
lysine-rich
histones, particularly that one unique to meiotic cells, may through their interactions play a crucial role in SC structure.