Tosiro Tiba

Regularities and Irregularities in the Structure of the Seminiferous Epithelium in the Domestic Fowl (Gallus domesticus)

A cellular association demarcated by two perpendiculars which were drawn between adjacent bundles of elongate spermatids from the tubular lumen to the basement membrane, was made the unit of histometrical observation in this study (provisionally called a “column”). Cell counting revealed that the average numbers per column of various types of germ cells do not show any significant differences among 5 fowls and between paired testes. The frequency of spermiogenic steps (numbered 1–8) was investigated in each column. A definite and common pattern was found in the frequency distribution in the 5 fowls observed. A relationship between spermiation and younger spermatid steps was also investigated in each column. The spermiation was found at different steps, but most frequently at step 2 (30.6 %). Based on these observations and referring to other authors information, an average time interval between two successive spermiations was calculated roughly at 3.3 ± 1.2 days. Theoretically, this value is equal to an average length of one epithelial cycle. Such a variable cycle may have caused irregular cellular associations in this species.

Undifferentiated Spermatogonia and their Role in the Seasonally Fluctuating Spermatogenesis in the Mink, Mustela vison

Three classes of spermatogonia were discerned: undifferentiated A spermatogonia (Ais, Apr, Aal), differentiated A spermatogonia (A1, A2) and differentiated B spermatogonia (B1, B2). Cell counts performed throughout the seminiferous epithelial cycle in the breeding season revealed that the number of undifferentiated A spermatogonia was lowest in the presence of differentiated A1 and A2 spermatogonia during stages I–II to III–IV. In the non‐breeding season a highly significant increase in the number of undifferentiated spermatogonia occurred in an animal with moderate germ cell loss exclusively at stages I–II to III–IV, when the Ai and A2 spermatogonia degenerated. In three other animals involved in severe cell loss, enhanced proliferation of undifferentiated spermatogonia was much greater than in the animal mentioned above. These results suggest the presence of a feedback mechanism between undifferentiated and differentiated spermatogonia, which may be considered to play an important role in regulating seasonal changes in spermatogonial proliferation.

Enhanced proliferation of undifferentiated spermatogonia after treatment of short photoperiod exposure in the Syrian hamster, Mesocricetus auratus.

Five Syrian hamsters were exposed to a short photoperiod (8L:16D) during 159 days. Atrophied testes were removed, fixed in Allens solution; paraffin sections of the testicular tissues and whole‐mounted seminiferous tubules were prepared. The numbers of various types of spermatogonia were investigated and compared with those in animals maintained in natural photoperiod (12L: 12D). All the types of differentiated spermatogonia (A1, A2, In, B1, B2) were significantly decreased in number after the treatment of short photoperiod exposure, while undifferentiated spermatogonia (isolated, paired and aligned type) were significantly increased at stages V–VI and VII–VIII of the seminiferous epithelial cycle. This strictly local reaction of the undifferentiated spermatogonia to the loss of the differentiated spermatogonia suggests the presence of a feedback effect of a certain type(s) of differentiated cells to the undifferentiated spermatogonia! proliferation. This feedback mechanism may also play an important role for regulating annual changes in spermatogenesis of seasonal breeders, not only in laboratory but also in natural habitat.

Postpartum Recovery of the Genital Organs and Fertility as Obserued by Diagnostic Ultrasonography and Determination of Skim Milk Progesterone in Dairy Cows

Postpartum Recovery of the Genital Organs and Fertility as Obserued by Diagnostic Ultrasonography and Determination of Skim Milk Progesterone in Dairy Cows Hirofumi MIYAKE1), Yumi OHSHIMA1), Toshio TSUBOTA1), Isao KITA1), Tosiro TIBA1) and Eiji MORIMOTO2) 1) Faculty of Agriculture, Gifu University, Gifu-shi, Gifu-ken 501-11 2) Experimental Farm of Faculty of Agriculture, Gifu University, Gifu-shi, Gifu-ken 501-11, Japan