Demonstration of electron-dense material in clear synaptic vesicles using cationic ferrocenyl compounds

Visualization of anionic sites using polyethyleneimine-metal complexes

17 Polyethyleneimine-metal complexes were synthesized and 3 of them were tested cytochemically for visualization of negative tissue charges. The demonstration of the anionic sites was carried out on rat cerebral cortex and on frog cutaneous pectoral muscle. As controls, neuraminidase digestion, methylation, and omission of osmium-postfixation were used. The osmiophilic properties of polyethyleneimine, polyethyleneimine salts, and polyethyleneimine-metal complexes were discussed.

Demonstration of negative tissue charges by means of polyethyleneimine-metal complexes

Three polyethyleneimine-metal complexes were synthesized and cytochemically tested for demonstration of negatively charged sites. For this purpose rat cerebral cortex synaptosomes were used. It was established that both types of polyethyleneimine-copper complexes labeled the synaptosomal membrane and synaptic vesicles with electron-dense granules, whereas the polyethyleneimine-lead complex marked the anionic sites with amorphous electron-dense material.

Lead-dependent deposits in diverse synaptic vesicles: suggestive evidence for the presence of anionic binding sites

We have observed electron dense deposits dependent on incubation of aldehyde-fixed tissues with lead ions within synaptic vesicles of several types of neurons that differ in the neurotransmitters utilized and in the secretory granules of the adrenal medulla. Evidently, vesicle components that can interact with lead ions are widespread. A plausible explanation for the occurrence of the deposits is the presence of anionic binding sites within the vesicles. This would agree well with other biochemical, cytochemical, and immunocytochemical evidence, such as that indicating the presence of sulfated macromolecules in certain synaptic vesicles. Anionic binding sites could play significant roles by participating in processes such as Ca2+ storage, stabilization of pH gradients, or the control of osmotic phenomena.

Distribution of negative charges of rat brain synaptosomes established by means of protamine-ferritin conjugate

The negative electric charges on the synaptosomes from rat cerebral cortex were studied by means of protamine-ferritin conjugate. The synaptic vesicles in some synaptosomes were heavily labelled with the positively charged conjugate. The synaptosomal membranes including presynaptic and postsynaptic membranes were also stained but in a lesser degree. It was established that the major dense line and the intraperiod line of myelin contaminants were labelled, too.