Frog sartorius muscle

Sea urchin toxins extracted from spines or pedicellariae have a variety of pharmacological actions, including electrophysiological ones (75). Dialyzable toxins from Diadema caused a dose-dependent increase in the miniature end-plate potential frequency of frog sartorius muscle without influencing membrane potential (76). A toxin from the sea urchin Toxopneustes pUeolus causes a dose-dependent release of histamine (67). Toxic proteins from the same species also cause smooth muscle contracture in guinea pig ileum and uterus, and are cardiotoxic (77). 

The neurotoxins isolated from Aph. flos-aquae were shown to have similar chemical and biological properties to paralytic shellfish poisons (PSP) (25,29,38) Sawyer et al. in 1968 (25) were the first to demonstrate that the crude preparation of aphantoxins behave like saxitoxin, the major paralytic shellfish poison. They showed that the toxins had no effect on the resting membrane potential of frog sartorius muscle blocked action potential on de-sheathed frog sciatic nerve and also abolished spontaneous contractions in frog heart. Sasner et al. (1981) (29) using the lab cultured strain reported similar results. 

Fig. 20. Meridional intensity profile from frog sartorius muscle recorded on a long laboratory-based X-ray camera by Haselgrove (1975). This shows the effects of interference on peaks arising from C-protein, troponin, and myosin. For details, see text.

Bordas, J., Diakun, G. P., Diaz, F. G., Harries, J. E., Lewis, R. A., Lowy, J., Mant, G. R., Martin- Fernandez, M. L., and Towns-Andrews, E. (1993). Two-dimensional time-resolved X-ray diffraction studies of live isometrically contracting frog sartorius muscle./. Muscle Res. Cell Motil. 14, 311-324. 

Huxley, H. E., Brown, W., and Holmes, K. C. (1965). Constancy of spacings in frog sartorius muscle during contraction. Nature 206, 1358. 

A study of the irreversible cholinesterase Inhibitor, dllsopropyl-fluorophosphate, on time course of endplate currents In frog sartorius muscle. J. Pharmacol. Exp. Ther. 189 499-512. 

Patlak JB, Ortiz M 1986 Two modes of gating during late Na channel currents in frog sartorius muscle. J Gen Physiol 87 305-326... 

Agin, Hersh and Holtzman have shown that eq 3 gives an excellent correlation for the relation between minimum blocking concentration (MBC) of 39 local anesthetics in frog sartorius muscle with polarizability (a) and the ionization potential (I) of the drugs. 

GIO. Gilbert, D. L., and Lowenberg, W, E., Influence of high oxygen pressure on the resting membrane potential of frog sartorius muscle. J. Cellular Comp. Physiol. 64, 271-278 (1964). 

Studies on skeletal muscle also support an intracellular site of action of the MDIs. Thus, pr-MDI (10 4m) significantly blocked caffeine-induced contractures of the rat diaphragm both in presence and in absence of extracellular calcium (33). Such caffeine-induced contractures are believed to be mediated by intracellular calcium mobilized from the sarcoplasmic reticulum or other intracellular calcium pool (34). Furthermore, bu-MDI (10 M) depresses activation heat in the frog sartorius muscle upon stimulation (35), indicating a reduction in the quantity of calcium released from the sarcoplasmic reticulum, since activation heat represents the energy liberated in association with calcium mobilization and sequestration in contracting muscle (36,... 

In molecular biology, certain structural features may not show up in electron microscopy. This is, for example, the case for the cycloskeletal lattice of frog sartorius muscle [29]. 

Adrian, R.H. and L.D. Peachey (1973). Reconstruction of the action potential of frog sartorius muscle. /. Physiol. (Lond.) 235,103-131. 

FIGURE 25.3 Simulated sarcolemmal and tubular action potentials of frog sartorius muscle fiber, (a) Temporal membrane action potentials calculated in a transverse plane 5 mm from the end-plate zone of a fiber with radius a = 50 /xm. Curve 1 Sarcolemmal action potential curves 2 to 4 action potentials in tubular membrane patches at r = a (2), r = a/2 (3), and r = a/20 (4). (b) Sarcolemmal action potentials for fibers with radius 70 (1), 50 (2), and 30 (3) /xm. The time axes have been expanded and truncated. 

FIGURE 25.4 Simulated currents and extracellular potentials of frog sartorius muscle fiber (radius a = 50 /xm). (a) The net fiber current density is the summation of the current density through the sarcolemma and that passing the tubular mouth, (b) Extracellular action potentials calculated at increasing radial distances (in units of fiber radius) using a bidomain volume conductor model and the net current source in panel (a). The time axes have been expanded and truncated. 

In 1970, Hill described the same properties for intact frog sartorius muscle." Hill reported a linear increase in isometric tension on raising the temperature from 0° to 23° C, but on raising the temperature higher there occurred a more... 

Bozler and Cole (1935) measured the electrical impedance of frog sartorius muscle from 1.1 kHz to 1.1 MHz. Measurements were first done approximately 2 h after dissection. The tissue was then stimulated to induce contraction, and the tissue was measured again, approximately 3 h after dissection. They found a minor arc of a circle when the data were plotted in the complex impedance plane. Between the relaxed and contracted state, Rq was found to increase by 75% whereas Roo increased only 2%. As usual, Rq and Ra> denote the resistances measured at very low and very high frequency, respectively. The significant increase in Rq was interpreted as a reduced ionic conduction through the cell membranes. 

The experiments were carried out on the frog sartorius muscle, perfused with Ringer solution. The end-plate region was conventionally voltage clamped with two intracellular microelectrodes (3M KCl, resistance 8-15 MQ). Acetylcholine (ACh) was applied by a third microelectrode (2M acetylcholine chloride, resistance 15-20 M ) to the chemosensitive area of the muscle fibre. The iontophoretic micropipette tip was moved towards the point of maximum response as to achieve the maximum receptor density in the epicenter of the micropipette. 

When the analysis, using a microelectrode to pass the current, was extended to striated muscle by Katz (1948), it became clear that muscle was anomalous in that the membrane capacity was substantially larger than in nerve fibres. In frog sartorius muscle fibres appeared to be about 5 yF/cm of fibre surface. In time it became clear that this was due to the extensive membranes of the transverse tubular system in muscle fibres. Several studies using A.C. impedance methods were undertaken to define the equivalent circuit of the morphologically complex membranes in a muscle fibre (Falk Fatt, 1964 Schneider, 1970 Valdiosera, Clausen Eisenberg, 1974). 

Conway et at. (1946) concluded that the cells of the frog proximal tubule, like frog sartorius muscle, are freely permeable to K and Cl and that these two ions are distributed in accordance with the Donnan relationship of electrochemical equilibrium. This means that the intracellular and extracellular products of K and Cl concentrations are equal. 

Cerium nitrate has a curariform action on frog striated muscle and the decreased muscle contractility depends on the particular rare earth being investigated (Haley, 1965). La has been shown to influence both the pre- and postjunctional membrane receptor processes of the frog sartorius muscle and... 

Table 3. Changes in Glycogen, Hexose-6-phosphate and Lactate in Isolated Frog Sartorius Muscle 2 Hours after Recovery from Stimulation...

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