ABSTRACT
The acini of the cockroach salivary apparatus consists of two morphologically distinct types of cell. These have been described by Bland & House (1971) and have been called peripheral and central cells. Ducts which convey the saliva to the hypopharynx are also associated with the acini. Electrophysiological experiments (Ginsborg, House & Silinsky, 1974) have demonstrated the presence of low-resistance junctions between the cells of the acini (coupling resistance of less than 0·2 MΩ). Septate desmosomes are a common feature of the acini and ducts and have been observed to link all of the cell types (Bland & House, 1971). Although in the past several authors suggested that septate desmosomes could act as low-resistance couplings between cells (e.g. Loewenstein, 1966; Gilula, Branton & Satir, 1970), it now seems probable that gap junctions are the sites of low-resistance pathways between cells (for reviews see : Sotelo & Korn, 1978; Peracchia, 1980). Gap junctions are often incorporated in septate desmosomes (Berridge & Oschmann, 1972; Satir & Gilula, 1973; Noirot-Timothée et al. 1978).
