Influence of light and darkness on the subcommissural organ of Rana temporaria L. A cytological and autoradiographical study.

Abstract

The influence of long daily photoperiods and of continuous darkness on the subcommissural organ (SCO) of Rana temporaria was studied. The amount of aldehyde-fuchsin (AF) positive material in the apical cell parts of the SCO proves to be less in light-adapted than in darkness-adapted animals in winter. The nuclear volume in the SCO of light- and of darkness-adapted animals, however, does not show any clear differences. Distinct differences in incorporation rate of 35S-cysteine between the SCO of light- and of darkness-adapted animals cannot be observed either in winter or in summer. The conclusion must be that light/darkness conditions hardly influence the secretory activity of the SCO cells of Rana temporaria. The results mentioned above were compared with those of experiments on pineal gland and preoptic nucleus. Incorporation of 35S-cysteine, which proceeds rather slowly, firstly takes place in the apical, i.e. supranuclear and perinuclear cell parts. Then the AF positive material located subnuclearly becomes gradually labelled. This is in support of the assumption that the apical cell parts are primarily concerned with synthesis and the basal cell parts with storage of secretory material. A marked influence of temperature on localization, appearance and amount of AF positive material in SCO cells has been observed.