Nexus of frog ventricle.

Nexus of frog ventricle

Here were demonstrate in Rana pipiens ventricle a nexus with very unusual morphology. This tissue has been reported previously to lack nexuses. The nexus appears in thin sections of ventricle, fixed in aldehyde and OsO4 or permanganate as a series of punctate membrane appositions regularly alternating with regions of membrane separation. The junctional width at membrane appositions, as determin...

Effects of epinephrine on frog ventricle.

Spontaneous mechanical activity in depolarized frog ventricle

Spontaneous mechanical activity can be produced in depolarized frog ventricle by bathing the tissue in a solution with low Na, Iow Ca, and high K+. The contractions can be inhibited by depleting the tissue of Ca first, but they are relatively insensitive to changes in either extracellular [Ca++] or [Ca++]/[Na+]2. They are terminated very rapidly by raising [Na+] to 40 mM. Local anesthetics enha...

Spontaneous Mechanical Activity in Depolarized Frog Ventricle

I N T R O D U C T I O N Although it is generally believed that depolar izat ion o f the surface m em b ran e o f an amphibian hear t initiates the process o f contract ion and that direct activation o f the contractile proteins is p roduced by saturat ion o f Ca binding sites on t roponin , the source o f this calcium and the relat ionship o f its release to depolar izat ion are not known. In v...

The plateau of the action potential of the frog ventricle.

A study was made of the change's produced in action potentials of frog ventricular cells by variation in ion concentrations, by administration of NaN3, 2: 4 DNP, NaCN, NalA and N2 which shortened the potentials. The exposure of the perfused tissue to ionized acridines, barbiturates and desoxyglucose caused a prolongation of the action potentials. These actions as obtained were reversible. The e...