Decrease in the Number of Human Ap and Ad Spermatogonia and in the Ap/Ad Ratio with Advancing Age New Data on the Spermatogonial Stem Cell

Abstract

The numbers of Ap and Ad spermatogonia per unit section of the testis were calculated in autopsy specimens from young adults and elderly men without testicular pathology. The number of Ap spermatogonia decreased from the 6th decade of life, whereas that of Ad spermatogonia began to decrease in the 8th decade. Although it has been reported that Ad spermatogonia are more sensitive to noxious agents than Ap spermatogonia, the involution of Ap spermatogonia precedes that of Ad spermatogonia. These findings provide new information on concepts relating to the spermatogonia precedes that of Ad spermatogonia. These findings provide new information on concepts relating to the spermatogonial stem cell in man.

Immunohistochemical study of nuclear changes associated with male germ cell death and spermiogenesis

“…For example, differences exist in the morphological routes taken between cells with a high versus low ratio of cytoplasmic volume:nuclear volume (Suciu 1983). It is worth noting that immature rat spermatogonia, with their oblong nuclei, have a low ratio of cytoplasmic volume:nuclear volume (Russell et al 1990;De Rooij and Russell 2000) compared to human and primate germ cells with their round nuclei (Nistal et al 1987;Johnson et al 2001;Marshall et al 2005). Lastly, size differences between early-stage and late-stage spermatogonia in the shark testis are also reflected in the way they die, which is via pyknosis of the entire nucleus in apoptotic immature spermatogonia and multinucleate cell formation among apoptotic mature spermatogonia (McClusky 2005(McClusky , 2006.…”

A germ-line-selective advantage rather than an increased mutation rate can explain some unexpectedly common human disease mutations

“…A new variant, which in principle could match the data and for which the effect of the disease mutations is perhaps less extreme, is to allow all adult SrAp to alternate between symmetric divisions, asymmetric divisions, and sometimes not dividing at all; in this model, the mutant SrAp would divide symmetrically more often than the nonmutants. We have also considered cell death; if all cells are equally likely to die, this affects the parameter values of the models but not the conclusions; if the mutant SrAp are less likely to die, this process would be another form of selection, but because the total number of SrAp are estimated to decrease by only 25% from age 35 to 65 (33), this reduction is not great enough to produce the observed mutation clusters. Likewise, if the mutant SrAp cells were to have a higher asymmetric division rate than the nonmutant cells, this would be yet another form of selection, but the change in division rate necessary to produce the intensity of the observed mutation clusters is unrealistically high.…”

Analyse morphométrique semi quantitative de l’histologie testiculaire au cours du vieillissement

“…Les cellules de la lign6e [2,12] sont elles aussi tr~s sensibles aux alt6rations testiculaires de l'homme ag6. Si pour certains la perte des cellules germinales d6termine probablement les alt6rations des cellules de Sertoli [15], les perturbations observ6es sur les cellules de Sertoli peuvent directement retentir sur la production des spermatozoides [22].…”

“…La disparition progressive des spermatogonies contribue la disparition des spermatozo'fdes [12]. L'arr~t de la spermatogenbse est cependant tr~s fr6quent au stade pachyt~ne [4], qui est un stade de blocage fr6quent de la spermatogen~se dans diff6rentes situations d'alt6ration du tissu testiculaire.…”

“…Des signes de d6g6n6rescence des cellules de Leydig ont 6t6 observ6s parallblement 5 une baisse de testost6rone plasmatique [10,14,16,21]. Au niveau des tubes s6minif~res plusieurs signes ont 6t6 d6crits : un 6paississement de la membrane propre [15], des anomalies des cellules de Sertoli qui paraissent ~tre les dernibres disparaitre [13,15], et enfin, en ce qui concerne la lign6e germinale, une perte progressive des cellules commen,ant par les spermatozo~des et les spermatides avec un arrSt fr6quent au stade pachytbne [2,4,12].…”