Two types of dwarf mutants of the mouse were used: dwarf (dw), and Ames dwarf (df). Dwarf mice are sterile but males produce living spermatozoa and females undergo oestrous cycles. Failure to become pregnant or pseudopregnant after mating and lack of acidophilic cells in the hypophysis suggest lack of luteotrophin (LtH).
A constant supply of LtH was provided by grafting the hypophyses from normal mice into the renal capsules of dwarfs. Of thirty-eight female recipients of grafts, eighteen produced living young. All except three lactated and raised their litters to weaning. Most remained fertile for several months and produced two to seven litters. It is concluded that lack of LtH may be the sole cause for sterility of female dwarf mice. Of seven male dwarf mice that received hypophysial grafts six became fertile. The role of LtH in promoting male fertility is not clear as dwarf males become fertile after receiving growth hormone or thyroxine and, occasionally, without any treatment.
To determine if spermatozoa from untreated dwarf males are able to fertilize ova, artificial inseminations were performed. From forty-four normal females inseminated with spermatozoa of dwarfs, six became pregnant.
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