poly ( adp-ribosylation ) of all the aforementioned proteins is very low in isolated intact nuclei of testis from 8-day-old animals ( only spermatogonia present in seminiferous tubules ) , increases significantly by 16-day ( pachytene spermatocytes appear ) and reaches adult proportions by 32 days ( condensing spermatids present ) .
C0037866
spermatogonia
C0036630
seminiferous tubules