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D. A. JAMES and S. M. YOSHIDA

Summary.

Blastocyst-elicited immunity in mice was tested by adoptive transfer, cytotoxic assay and incubation of blastocysts in vitro with serum and lymphocytes from primary blastocyst recipients. These tests suggest that blastocyst-elicited immunity may not be an immunological phenomenon.

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M. Fujisawa, O. Matsumoto, S. Kamidono, F. Hirose, K. Kojima and S. Yoshida

Summary. The activities of DNA polymerase α (EC 2.7.7.7) and topoisomerase I did not fluctuate up to 7 days after surgery to induce cryptorchidism and showed no significant difference from those in control testes (sham-operated). In contrast, the activity of DNA polymerase β decreased by 43% at 5 days (P < 0·01) and by 47% at 7 days (P < 0·001). The activity of DNA polymerase γ also decreased by 46% at 3 days (P < 0·02) and by 78% at 7 days (P < 0·01) after surgery. The amount of mRNA for DNA polymerase β decreased in parallel with enzyme activity. Since the sensitivity to heat inactivation of testicular DNA polymerase β was exactly the same as that from liver, the decrease in DNA polymerase β activity may be, at least in part, due to reduced biosynthesis of enzyme protein. The morphological changes in cryptorchid testes suggested that the decrease in DNA polymerase β and γ activities might be related to the deleterious effects of elevated temperature on spermatogenesis.

Keywords: DNA polymerase α, β, γ; topoisomerase I; rat; cryptorchid testes

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C A Rezende-Melo, A L Caldeira-Brant, A L Drumond-Bock, G M Buchold, G Shetty, F R C L Almeida, M M Matzuk, K Hara, S Yoshida, M L Meistrich and H Chiarini-Garcia

The existence of cytoplasmic passages between germ cells and their potential function in the control of the spermatogenic process has long been an intriguing question. Evidence of the important role of such structures, known as intercellular bridges (ICB), in spermatogenesis has been implicated by the failure of spermatogenesis in testis-expressed gene 14 (Tex14) mutant mice, which lack the ICBs, to progress past the pachytene spermatocyte stage. Using these Tex14 mutants, the present study evaluated, for the first time, the behavior and synchrony of the spermatogonial lineage in the absence of ICBs. Our data suggest that the absence of these cytoplasmic connections between cells affects the expansion of the undifferentiated type A (Aundiff) spermatogonia compartment and their transition to A1, resulting in a significant numerical reduction of differentiating A1 spermatogonia, but did not interfere with cell amplification during subsequent mitotic steps of differentiating spermatogonia from A1 through intermediate (In). However, beginning at the type B spermatogonia, the synchrony of differentiation was impaired as some cells showed delayed differentiation compared to their behavior in a normal seminiferous epithelium cycle. Thus although spermatogonial development is able to proceed, in the absence of ICBs in Tex14−/ mutants, the yield of cells, specific steps of differentiation, the synchrony of the cell kinetics, and the subsequent progression in meiosis are quantitatively lower than normal.