Cytochemical and autoradiographic studies of the localization and turnover of chromatin and nucleolar associated phospholipids in plant and animal tissues.

The localization of chromatin-associated phospholipids has been demonstrated on chromosomes and on chromatin of interphase nuclei by cytochemical methods either in plant and in animal tissues. Three methods of fixation are suggested which can be combined which two cytochemical methods for phospholipids detection. An additional method is represented by autoradiographic technique after incorporation of a radioactive precursor such as [3H] ethanolamine. This method has been used with good results in nuclei of lateral root apices of Vicia faba on 1 micron thick section, thus avoiding any possible contamination by nuclear membrane. In these nuclei the phospholipids appear associated with the chromatin and more intensely with the nucleolar regions. The positivity of the cytochemical reaction disappears after extraction of fixed tissue with acidified methanol chloroform and after treatment of unfixed sections with phospholipase D. The use of phospholipid precursor has allowed the study of chromatin-phospholipids synthesis in root apices of Vicia faba with respect to timings of the cell cycle. The results show that there is a strong case for a pattern of chromatin phospholipid synthesis which operates during S phase. Concerning the role of phospholipids it is suggested that they may be linked to acidic protein and may have a structural function, particularly on the nucleoli.

Evidence for the association of acyl transferases with the production of nuclear evaginations in maturing eggs of the fern Dryopteris filix-mas.

Utilizing the ability of free CoA to reduce ferricyanide, evidence is presented that acyl transferase activity is associated with the nuclear envelope in the maturing egg of the fern Dryopteris filix-mas. This activity is particularly marked in the nuclear evaginations. This strengthens the view that the evaginations are distinct structures formed by localized growth of the envelope, and not transient extensions of the nucleus.

The cytochemistry of the walls of the spermatocytes of Ceratopteris thalictroides.

By means of staining and fluorescence microscopy the walls of the spermatocytes of Ceratpteris thalictroides have been shown to contain callose and lipid. It is suggested that these substances form a barrier to the ingress of metabolites, and are responsible for the failure of differentiating spermatocytes to incorporate C(14)-cysteine.