A MORPHOMETRIC STUDY OF SPERMATOGENESIS IN THE TESTES OF MICE OF A SENESCENCE-ACCELERATED STRAIN

The morphometric parameters of spermatogenic cells in a mouse strain p rone to accelerated senescence (SAM-P), a novel murine model of sponta neously promoted aging, were compared with those of a SAM resistant st rain (SAM-R) after birth until 40 weeks (mean life span of SAM-P). A m ixture of gonocytes and spermatogonia were present in the testis in 1- week-old mice, and no gonocytes were observed in 2-week-old mice. At 6 weeks of age, the absolute number of spermatogonia in SAM-P was 27% g reater than that in SAM-R, whereas the cell number in 40-week-old SAM- P was 17% less than in SAM-R. Primary spermatocytes were first observe d in 3-week-old animals, and the cell numbers in SAM-P at 3, 5 and 6 w eeks were 78%, 31% and 25%, respectively, greater than in SAM-R, where as the cell number in SAM-P at 40 weeks was 30% less than SAM-R. Round spermatids were first observed in all SAM-P at 4 weeks old, but 20% o f SAM-R had no spermatids and the rest had only a few. At 5 and 6 week s old, the absolute numbers of round spermatids in SAM-P were 38% and 41%, respectively, greater than in SAM-R, whereas the cell number in 4 0-week-old SAM-P was about 34% less than SAM-R. These results indicate that testicular maturation begins at an earlier age in SAM-P than SAM -R. Furthermore, at the age of 40 weeks signs of testicular deteriorat ion are evident in SAM-P mice only.