The thyroid stimulating hormone (TSH)-immunoreactive cells (TSH cells) in the pars tuberalis (PT-TSH cell) of the male rat pituitary gland show an intense spot-like TSH immunoreaction in the paranuclear cytoplasm. However, the ontogenic origin and characteristics of these spot-like stained PT-TSH cells remain to be elucidated. The present study was designed to investigate the distribution and characteristics of PT-TSH cells in the foetal and adult rat pituitary by immunostaining for Pit-1 factor and thyroid hormone receptors (TRs) and reverse transcriptase-polymerase chain reaction (RT-PCR). TSH cells first appeared in the PT at 15.5 days of gestation and were either stained diffusely throughout the cytoplasm or displayed a strongly stained, spotty appearance in the paranuclear region. By 15.5 days of gestation, the rostral part of the PT consisted of columnar epithelium, in which TSH immunoreactivity was spot-like in the apical region of cytoplasm corresponding to the Golgi apparatus. At the 16.5 days of gestation, TSH cells were present in the pars distalis (PD); however, the cells were mostly larger and polygonal with strong staining throughout the cytoplasm. These differences between the PT and PD were retained throughout foetal and neonatal rat development. The TSH cells in the PD of the adult or gestational rat were observed to contain Pit-1 factor by double immunostaining. However, TSH cells in the PT lacked Pit-1 factor. RT-PCR confirmed the absence of Pit-1 and TRbeta2 mRNA in the PT of the adult and late gestation rat pituitary gland. These results suggest that apparently distinct types of TSH cells in the PT develop independently from TSH cells in the PD.

Im Vergleich mit den von Sempee. ('70) und Wiegmann ('93) untersuchten Arten hat H. septentrionalis mit 105 die geringste Anzahl von Gliedern in der Querreihe, während jener JAPANISCHE BESCHALTE PULMONATEN. 9 Bezahnnng zwischen 120 [H. bisligensis, Freycineti) und 620 (politissimtis) schwankt. Masse der einzelnen Gruppen von Zahnplatten sind (7=0,0456 mm. i=0,0550 mm. üf=0,0513 mm. Wir kommen zu den Genitalorganen. Ursprungstätte der GeschlechtsstofFe ist eine aus mehreren gesonderten Kugeln bestehenden Zwitterdrüse (Fig. 7, zd), von der ein nur wenig geschlängelter Gang zu der Ehceissdrüse (ed) führt, einem massigen Organe von Dreiecksform, Ueber das "Divertikel" des Zwitterganges werden unten bei Ganesella japonica einige Worte folgen. Hier ist es durch eine einfache Knickung nur eben angedeutet. Der anschliessende Ovispermatodukt (osd) ist vielfach krausenartig gefältelt und vom breiten sich deutlich abhebenden Prostatabande begleitet. Er wird nach Abzweigung des Samenleiters