Frog ventricle

Also, the slopes of the Hill plots in Figure 1.2B are close to unity (0.9 for the frog ventricle, 0.8... 

FIGURE 1.2 (Upper) Concentration-response relationship for the action of acetylcholine in causing contraction of the frog rectus abdominis muscle. The curve has been drawn using Eq. (1.4). (Lower) Hill plots for the action of acetylcholine on frog ventricle (curve I) and rectus abdominis (curve II). (From Clark, A. J., J. Physiol., 61, 530-547, 1926.)... 

Figure 1. Plot of exp (-E F/RT) as a function of a for frog ventricle. The line is the least squares linear regression calculated from the data points.

Ringer s Lactate. In 1883, it was discovered that the excised ventricle of the frog would beat for some hours if suppHed with an aqueous solution of sodium, potassium, and calcium salts. The concentration of potassium and calcium was found to be critical, whereas the amounts of the anions had htde effect on the frog heart. The composition of this saline, coined Ringer s solution, is given in Table 1. Many years later it was shown to be very close to that of frog plasma. 

Frog heart ventricle Cr liquid membrane micropipet (Corning exchanger 477915) Cl" 17.6 + 0.57 mM 136)... 

Ringer ST (1982/83) An investigation concerning the action of rubidium and cesium salts compared with the action of potassium salts on the ventricles of the frogs heart. J Physiolog 4 270-276. 

Figure 39. Action potential of a cell in the ventricle of the frog. (After Reference 205).

Over the past decade, we (Sagawa, 1978) have measured the ventricular pressure (P)-volume (V) relationship in an isolated and blood perfused canine heart preparation and came to consider that the ventricular end-systolic P-V relationship (ESPVR) is (a) linear as opposed to the highly nonlinear P-V relationship of the frog s ventricle reported by Otto Frank a century ago, (b) rather insensitive to the preload and afterload and (c) changes its slope (E, ) sensitively with inotropic interventions without a significant shift in the volume intercept (Vq). This is to say that our model of the ventricle merely consists of a linear volume elastance E which varies with each heart beat from a smaller end-diastolic value to a larger... 

We have been using and Cl liquid ion exchanger microelectrodes to measure intracellular activities of K+ and Cl in frog heart. In these studies we have used three kinds of heart muscle ventricle, atrium and sinus venosus. The preparations are small pieces of tissue cut from the heart and pinned down in a chamber where they are superfused with frog Ringers solution. The ventricular and atrial preparations are quiescent unless stimulated in these experiments they are driven at a frequency of 0.5 stimuli/sec. The sinus venosus preparations are spontaneously active. 

More elaborate arrangements were necessary for the study of skeletal muscle in order to measure the function (force development) of the muscle simultaneously with the NMR spectrum. Dawson et al (1977) developed a sample chamber in which four frog leg muscles could be examined simultaneously while under tension. Contacts at the ends of the chamber allowed electrical stimulation of the muscles, and a transducer measured the developed force. In the case of heart muscle, it was also desirable to measure function and P NMR spectra simultaneously and to pace the heart electrically. Figure IB shows the setup used by the Johns Hopkins group (Hollis et aU 1978a) for this purpose. A fluid-filled latex balloon is sewn into the left ventricle and is connected by a fluid column to a pressure transducer that records the pressure by the beating heart. Electrical stimulation can be... 

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