What did SR Cajal described as the interstitial cells? The structure of the nerve plexuses in the guinea-pig small intestine stained by the Champy-Maillet (ZIO) method was investigated by light microscopy and transmission electron microscopy. Scanning electron microscopic examination of the nerve elements in various layers of the intestinal wall was also performed. Results indicated that the peripheral innervation consisted of autonomic groundplexus in which neuronal processes ran along a glial-cell framework. Projections of all the neurons formed a network of bundles, while being separated from each other and not making any interconnection. The glial cells enclosed and supported these bundles of neuronal projections. In the light microscopy of the ZIO stained specimen, amalgamation of glial cells and neuronal projections frequently occurred. They represented the structure described by Cajal as interstitial cells. The so-called interstitial cells of Cajal which many histologists looked for in the earlier half of the 20th century were not true cells but these stained structural artefacts of the autonomic groundplexus and/or nearby cellular elements. The interstitial cells defined by later authors including many electron microscopists from 1960s to 1980s were another type of cells such as fibroblast-like cells. For references, see Kobayashi et al.: Arch. Histol. Cytol. 52: 267-286, 1989.

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Yoshida, M. and Koeda, T. Studies on the intramural nerves of the hamster and mouse gallbladders. J. Smooth Muscle Res., 27 (1), 23-34, 1991-We first carried out microscopic observation of the intramural nerves of hamster and mouse gallbladders which were fixed and stained with a solution of OsO₄ and ZnI₂. For this microscopic observation, the guinea-pig gallbladder was used as a control. We then investigated the relationship between the motility and intramural nerves of the isolated gallbladder in both the hamster and mouse. The following results were obtained: 1. The ganglionated plexus and the perivascular nerves as the intramural nerves of the guinea-pig gallbladder were observed in the subserosal layer. These perivascular nerves were not possessed of ganglia. On the other hand, the nerve plexus and the perivascural nerves as the intramural nerves of the gallbladders of hamster and mouse were observed in the subserosal layer. These nerves, that is, the nerve plexus and the perivascural nerves, were not possessed of ganglia. That is to say, no ganglionated plexus or ganglia were observed in the subserosal layer of the walls of hamster and mouse gallbladders. 2. The isolated hamster and mouse gallbladders evoked spontaneous motility. This spontaneous motility was little affected by either atropine (1 × 10^-6 M) or tetrodotoxin (1 × 10^-7 M). 3. The hamster and mouse gallbladders showed a contractile response to electrical stimulation with rectangular pulses (50 volt, 40 Hz) of durations of 0. 5, 1, 2, 3, 4, 5 or 6 msec for a period of 10 sec. Thesecontractile responses were little affected by either atropine (1 × 10^-6 M) ortetrodotoxin (1 × 10^-7 M). 4. The long duration of the contractile response was mediated by electrical stimulation with rectangular pulses (50 volt, 40 Hz) of durations of 4, 5 or 6 msec for a period of 10 sec. That is to say, its duration time was approximately from 8 to 15 minutes for both hamster and mouse. These results suggest that the hamster and mouse gallbladders may not contain the nervesthat take part in the movement of the gallbladder. That is to say, the contractile response of the hamster and mouse gallbladders seems to be myogenic rather than neurogenic in its control. It is, however, possible that some substance other than the neurotransmitter in the walls of these gallbladders may also play a part in the control of the contractile response, although further study will be necessary to verify this suggestion.

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In order to investigate the pathological condition of the intestinal tract after irradiation, experimental radiated intestinal tracts were prepared in adult rabbits, and motile functions of the terminal ileum of these rabbits were observed under electromyography. The results were also examined in relation to histological changes in corresponding region. The following results were obtained:
1. In the irradiation groups, findings different from the non-irradiation group were observed corresponding to the irradiation dose and time after the irradiation.
2. No correlation was observed between basic electric rhythm (BER) and irradiation dose. However, BER showed a slight decreasing tendency over time.
3. The active phase duration times in the irradiation groups were prolonged up to an irradiation dose of 80 Gy, then shortened in groups radiated with 120 Gy or more, as compared with the non-irradiation group.
4. The frequency of antiperistaltic propagation of electric stimuli showed an increas-ing tendency as the irradiation dose increased.
5. Dysrhythmia of electric discharge observed in the irradiation groups was enhanced by increase in irradiation doses and over time.
6. Motile function of the intestinal tract was enhanced in groups radiated up to 80 Gy and inhibited in groups radiated with 120 Gy or more.
7. In the 80 Gy irradiation group, motile function of the intestinal tract was enhanced at early phases after irradiation and inhibited at later phases.
8. Radiated intestinal tracts showed increasing tendencies in stimulation thresholds against agents such as Neostigmine and PGF2α.
9. Histological changes in the intestinal wall were more marked in the mucous side. As the irradiation dose increased, the degrees of disorders were enhanced. At the early phases in the irradiation groups, inflammatory changes were the major histological changes seen. At later phases, chronic organic changes in the muscular layers, especially consisting of destruction of intermuscular plexus and degeneration decrease in ganglion cells, were marked. These irreversible changes were suggested to influence abnormalities in the motile function of the intestinal tract.

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The present investigation was performed in order to clarify whether the motion of the intramural portion of the ureter is passive or active.
In Experiment I, electromyograms of the extravesical and intramural portions of the ureter were recorded using bipolar suspended electrodes and bipolar needle electrodes for 52 ureters in 26 adult mongrel dogs to study the relationship between both portions of the ureters in the nondiuretic and diuretic state.
In Experiment II, using 14 ureters in 10 adult mongrel dogs, electromyograms were recorded and the local forces of the ureteral walls of the extravesical and intramural portions were measured with a special needle electrode concurrently. Results:
(1) Experiment I demonstrated in the nondiuretic and diuretic state, (1) no significant differences in the ureteral discharge frequency between the extravesical and intramural portion of the ureters, and (2) a 1: 1 correspondence in the extravesical and intramural action potentials.
(2) Increases were observed in the local forces of the ureteral walls of the intramural portion of the ureters following action potentials.
From these experimental results, it was suggested that the intramural portion of the ureter actively moves due to muscular excitation from the upper ureter and participates in urine transport.

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he research on intracellular signal transduction and the smooth muscle contraction have made much progress since 1970. Effects of relaxin, a peptide hormone mainly produced and released from ovary, are reviewed in the above point of view. Cyclic AMP content in myometrial cells is increased by relaxin. One site of relaxin action can be the suppression of myosin light chain kinase activity. Another effect of relaxin is the suppression of action potential, whereby the Ca-influx is reduced. However, relaxin up to 300 mU does not hyperpolarize the myometrial membrane of estrogen-primed rat, which differs from the adrenergic β-action. Unrealed signal transduction seems involved in the relaxin action.

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