Densitometric measurement of two cellular parameters related to the secretory activity of the subcommissural organ.

The subcommissural organ (SCO) of vertebrates is located in the roof of the third brain ventricle, and secretes into this ventricle a glycoproteinaceous, fibre-like structure, the liquor fibre or Reissner's fibre. A method is described for the densitometric measurement by means of computer-controlled scanning cytophotometry of two cellular parameters directly related to the secretory activity of the subcommissural organ in European green frogs. These parameters are: i) the amount of stained secretory material in the SCO, and ii) the amount of secretory material in the SCO labelled by a radioactive precursor. It appears that scanning cytophotometry offers a fairly rapid, accurate, objective and reproducible method to measure these parameters in stained sections and in autoradiographs of the SCO if this histological material fulfils certain conditions.