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MIKKO NIEMI and MARTTI KORMANO

Summary.

The non-specific esterase in the seminiferous tubules of the adult rat testis was shown to be water-soluble and its activity resistant to an organophosphorus (E-600) inhibitor and to p-chloromercuric benzoate. The enzyme exhibited substrate preference for substituted naphthol-AS-type acetates and indoxyl acetates rather than simple naphthol acetate. Histochemically, it behaved as an esterase of the C-type.

The localization of the C-esterase activity in the seminiferous epithelium strongly suggests that the Sertoli cells are the site of enzymatic activity. Cyclical changes have been described in the activity of the Sertoli cells during the spermatogenic cycle. Enzymatic activity was highest during the acrosome stages 3 to 5 when the maturing spermatids had their heads deep in the epithelium. Weakest enzymatic activity was recorded at the time of the sperm release.

During the pubertal development of the testis a weak C-type esterase activity was seen in the supporting cells of the immature seminiferous tubules. This activity increased as these cells differentiated to mature Sertoli cells. In 20-day rats the adult level of enzyme activity was reached in those tubules where germ cell maturation was most advanced.

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J. SUOMINEN, S. MULTAMÄKI and MIKKO NIEMI

Summary.

High dipeptidase and aminopeptidase activity is present in human seminal plasma. The two activities can be easily and clearly separated from each other by chromatographic procedures. Each of the three dipeptidase fractions has characteristic substrate specificity but is not affected by divalent metals. The seminal aminopeptidase activity is inhibited by EDTA and activated by cobalt.