Differential Survival in Isolated Strips of Frog Intestine

As part of the problem of survival of isolated tissue it became desirable to determine what elements within the tissue itself are responsible for the failure of spontaneous activity. Data are presented here correlating the physiological activity as measured by spontaneous movements with the histological picture in surviving strips of small intestine taken from the common leopard frog, Rana pipiens Shreber. In all, 50 frogs were used and over 250 series of activity records taken.

Segments one to 2 cm. in length, either intact or split lengthwise along the greatest curvature, were cut from the upper portion of the small intestine and transferred to shallow glass dishes containing 5 cc. of Ringer's fluid, buffered to pH 7.4-7.5 with carbonates and phosphates. No bacteriostatic substance was used, but the Ringer's fluid was changed twice daily. The strips were held at 5°C. except for an 80-minute period each day when each strip was mounted, by means of threads attached at the time of its removal from the frog, in a warm chamber filled with Ringer's fluid at 37.5°C. During this 80-minute period a continuous record of all spontaneous movements of the longitudinal muscle fibers was taken on an electric kymograph.

Frog intestine under such conditions survived for long periods as compared with the reported survivals of other smooth muscle preparations. One group of 16 frogs strictly comparable in all details shows the range of survival found in these tests, the minimal survival being 143 hours, the average 180 hours, the maximal 239 hours. Thirty-one percent of the survivals exceeded 200 hours. The maximal survival as indicated by the spontaneous activity of these frog intestine strips, 239 hours, was twice the survival time for activity of isolated rabbit intestine reported by Gunn and Underbill, 1 and equalled the maximal survival of irritability in the retractor penis of the horse, as demonstrated by Sertoli.