1: Biochim Biophys Acta  1987 Apr 29;908(3):263-7 

Changes of the DNA packaging mode during boar sperm maturation.

Ashikawa I, Kinosita K Jr, Ikegami A, Tobita T.

Changes in the mode of DNA packaging in nuclei during spermatogenesis were
studied by measuring of the fluorescence anisotropy decay of an ethidium dye
intercalated in the DNA in whole nuclei. The nuclei were isolated from boar
spermatid or sperm cells at three distinct stages of spermatogenesis: just
before the completion of a maturation process in the testis (late spermatid),
immediately after a subsequent transformation into spermatozoa (caput
spermatozoon), and after full maturation (cauda spermatozoon). Although these
three kinds of nucleus were morphologically indistinguishable from each other,
the anisotropy decay detected a clear difference. In the late spermatid nuclei,
in which the replacement of histones by protamine was still in progress, the
anisotropy decayed extensively. The decay suggested that the DNA in the
spermatid nuclei contained very flexible regions, in which the interaction of
the DNA and proteins may be weak. The rapid and extensive anisotropy decay was
absent in the caput and cauda nuclei. The flexible portions must have turned
into very rigid structure during transformation from the late spermatid into the
caput spermatozoon.

PMID: 3567199 [PubMed - indexed for MEDLINE]