The first appearance of spermatogenic cell types related to the age of the animal was studied in sections and tubular whole mounts of testes of normal mice (Cpb-N strain) up to 34 days pp. The first intermediate spermatogonia and leptotene spermatocytes were seen at days 4 and 7 p.p., respectively. It was found that the subsequent types of spermatogenic cells appear earlier than could be expected if spermatogenesis was to proceed at adult speed. [3H]thymidine labelling studies revealed that within a given interval of time, spermatocytes and spermatids in immature mice develop into more advanced cell types than in adults. The labelling studies and the observation that the cellular associations are always identical to those in the adult, indicate that the rate of acceleration in young mice is the same for spermatogonia, spermatocytes and spermatids. The mean duration of the cycle of the seminiferous epithelium during the age interval of 10 to 30 days p.p. is 7.51 +/- 0.10 days, compared to 8.61 +/- 0.08 in the adult. It increases gradually towards the adult level, reaching the value of 8.45 +/- 0.17 days between days 33 and 56 p.p.

Spermatogonial proliferation was studied in mice from day 13 p.p. when the seminiferous epithelium is incomplete, until week 12 p.p. when a steady state at adult levels has been attained. Counts of undifferentiated, A1 and intermediate spermatogonia and primary spermatocytes in stages IV and IX of the cycle of the seminiferous epithelium were made in whole mounted seminiferous tubules. Sertoli cell proliferation was studied in a separate series from 6 to 14 days p.p. employing the 3H-thymidine labeling index. It appeared that 1. Sertoli cell proliferation stops at day 12 whereafter the cells obtain their adult appearance; 2. The numbers of stem cell spermatogonia and the production of differentiating A1 spermatogonia increase almost twofold between day 13 and week 12; 3. The efficiency of the divisions of the differentiating A1-B spermatogonia is similar to that in the adult throughout this period; 4. At all ages studied, the cell counts revealed an almost constant numerical relationship between Sertoli cells and germ cells, which suggests a function of Sertoli cells in the regulation of spermatogonial proliferation.

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SummaryMucus glycoproteins from the rat stomach were characterized after their isolation from homogenates of the superficial gastric mucosa by equilibrium centrifugation in CsC1 density gradients. Water-soluble as well as water-insoluble glycoproteins were studied. The latter were solubilized by 2-mercaptoethanol reduction of the homogenate. From both homogenate fractions the same two glycoproteins 1 and 2 were purified, glycoprotein 1 being present in considerably higher amount than glycoprotein 2. Their respective buoyant densities in a CsC1 gradient were 1.47--1.50 g/ml and 1.56--1.58 g/ml. The two glycoproteins expressed slight differences in gel electrophoresis and gel filtration. The results from column chromatographic comparisons between reduced and unreduced glycoproteins indicated strongly that both glycoproteins 1 and 2 were built from subunits kept together by S-S bonds. The s20,w values of the reduced glycoproteins 1 and 2 were 15.7 S and 11.6 S. Glycoprotein 1 contained 5% protein, 70% carbohydrate and 1--2% sulphate, whereas these percentages for glycoprotein 2 were 10% protein, 65% carbohydrate and 10% sulphate. The molar proportions of the main sugar components galactose, fucose, glucosamine and galactosamine were 4 : 2 : 4 : 1 (glycoprotein 1) and 3 : 2 : 3 : 1 (glycoprotein 2). Blood-group activity A was expressed by glycoprotein 1, whereas glycoprotein 2 showed mainly blood-group activity Le b, some B activity and also some A activity, but to a lesser extent than glycoprotein 1.