Electrotonic spread of applied potentials was observed between longitudinal and circular muscle layers of the small intestine with no rectification. Nexal junctions were demonstrated between muscle fibers of each layer. Connective tissue cells bridged between the two muscle layers. These showed structural characteristics of fibrocytes and of interstitial cells. Some nexuses were seen between connective tissue cells and between these cells and muscle fibers of each layer but in most junctions the membranes were 10-18 nm apart. Since connective tissue can serve for electrical conduction between cultured heart cells and since electrical properties of intestinal muscle permit transmission with low degrees of coupling, it is suggested that interstitial cells and fibrocytes may electrically couple longitudinal and circular muscle layers of cat intestine.

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ExtractThe retrograde perfusion assay of Mangos for the sodium reabsorption inhibitory effect in sweat and mixed saliva from patients with cystic fibrosis (CF) was modified by (I) using the second parotid gland of the rat as a control, (2) carefully controlling the quantity of saliva perfused into the rat parotid gland so that the ratio of milliliters perfused to gram dry gland weight fell between 1.8 and 2.8, and (3) reporting the inhibitory effect as percentage of inhibition of the rate of sodium reabsorption (RNa) in the perfused gland calculated from the difference between the RNals in the two glands. Using this modified assay we were able to confirm that significant differences exist in the percentage of inhibition of RNa caused by CF and normal mixed saliva (47.0 f 24.8 and 18.0 -1. 8.3, mean f SD). In addition, similar significant differences in the percentage ' of inhibition of R~~ by submandibular gland secretions (39.7 f 13.5 and 16.0 f 11.8). sublinrrual dand secretions (39.5 f 6.0 and 19.7 + 14.3), and'submu~osal gland secretions (34.0 f 11.7 and 21.7 f 12.7) between CF and normal subjects were observed. However, parotid gland secretions from CF subiects showed no increased inhibitory effect (12.5 + 7.9 and" 12.5 f 6.6). These findings demonstrate, that the sodium reabsorption inhibitory effect is produced by the secretions from some but not all salivary glands of patients with CF. SpeculationThese results indicate that the substance or substances responsible for the sodium reabsorption inhibitory effect of CF secretions is produced by cells present in submandibular, sublingual, and submucosal glands of patients with CF. Because mucus-producing cells are abundant in submandibular, sublingual, and submucosal glands, but are sparse in parotid glands (1) we suggest, as have Johansen e t al. (4), that the inhibitory effect is in some way related to the mucous secretory product of the cystic fibrosis glands.Cystic fibrosis is an inherited disease involving the exocrine glands. The most consistent finding in this disease is that of elevated concentrations of chloride and sodium in sweat (2) and secretions of the minor salivary glands (14). The pathophysiology of this alteration has not been clearly defined. Mangos e t al. (12) and Mangos and McSherry (10) have shown that retrograde perfused CF sweat and saliva inhibit sodium reabsorption in the ducts of the rat parotid glands. Studies by Kaiser e t al. (5) also show that sweat from CF patients causes inhibition of sodium reabsorption when it is perfused into normal human sweat gland ducts. A specific sodium reabsorption inhibitory factor (5, 10-12) may be the cause of the elevated sodium concentrations found in these secretions; however, such a factor has not been identified.The sodium reabsorption inhibitory effect in rat parotid gland ducts has not been reproduced by other laboratories. Using a modification of the Mangos technique we now have been able to demonstrate a sodium reabsorption inhibitory effect in mixed saliva of patients with CF. Further wor...

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A process of nucleolar reorganization apparently identical to that encountered in intestinal epithelial cells (Adamstone and Taylor, '72) develops in kidney cells of aging rats. The polymorphic nucleoli of young tubule cells soon change to amphinucloeli and, while terminal nucleolar reorganization is delayed in cells of collecting tubules, in the nephrons nucleoli soon begin to undergo terminal reorganization becoming bipartite structures with separate plasmosomes and karyosomes. This suggests disruption of the DNA-dependent RNA protein transcription system and failure to maintain the flow of messenger RNA into the cytoplasm. Old cells are not discarded immediately from the kidney tubules and they retain much rough endoplasmic reticulum, numerous ribosomes and polysomes and large plasmosomes. Thus a high RNA concentration is known to develop in old kidney tissue while protein synthesis is also known to be low (Kanungo et al., '70; Buetow and Ghandi, '73). Nucleolar counts show gradual increase in bipartite nucleoli at the expense of amphinucleoli and in the senescent kidney bipartite nucleoli predominate. It is suggested that nucleolar reorganization, with final separation of plasmosomes and karyosomes, includes the process of nucleolar segregation and is triggered by some innate nucleolar mechanism in response to encoded genetic information stored in the nucleolus during nucleogenesis. At this time both DNA and RNA are incorporated into the developing nucleolus. It is also to be noted that two shifts in nucleolar dominance occur with advancing age. These may be fundamental to the process of aging and to the onset of senescence. Furthermore, the changes in dominant nucleolar types are the direct result of the process of nucleolar reorganization.