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Publications and source records attributed to E Page.

At least 109 records · Page 6Linked to original sources
PubMed1977

Ultrastructural changes in the ischemic zone bordering experimental infarcts in rat left ventricles.

Ultrastructural changes in myocardial cells from the ischemic border of infarcts (produced in rat left ventricles by ligating the anterior coronary artery in vivo) were examined 1 to 24 hours after ligation. Twenty-four hours after ligation, irreversibly injured cells showed a selective spreading of Z-band material over the I band; disappearance of M bands, prominent N bands, and disassembly of A bands were also noteworthy. Sixty minutes after ligation the cells of the ischemic border were ultrastructurally normal except for paradoxically relaxed sarcomeres, indicative of an inability to contract in response to the calcium influx produced by osmium tetroxide; progressive vacuolization of this zone was evident after 4 to 12 hours. Paradoxical relaxation may be an ultrastructural correlate of acute ischemic "pump failure".

Animals↗
PubMed1972

The surface area of sheep cardiac Purkinje fibres.

1. Measurements combining the techniques of point counting and line integration were performed on light and electron micrographs of Purkinje fibres from the sheep's heart. The measurements were aimed at determining membrane areas of importance for the cellular electrophysiology of this tissue.2. The mean volume fractions of the cells occupied by various constituents were: myofibrils, 0.234; mitochondria, 0.103; and nuclei, 0.009. The mean volume fraction of the fibres occupied by the interspaces between the tightly packed cells was 0.0023.3. The mean fractions of intercellular surface area occupied by junctional specializations were: nexus, 0.17; desmosome, 0.023; and fascia adherens, 0.014.4. The mean surface to volume ratio of the Purkinje cells and fibres was 0.46 mu(-1) which is 11.5 times the value of the surface to volume ratio of a long right circular cylinder 100 mu in diameter.5. There are two reasons for the increment in the surface to volume ratio of the fibre (when compared to that of a long right circular cylinder 100 mu in diameter): the multicellular composition of the fibres and the extensive folding of the surface of the cells.6. After correction for the intercellular nexal area the surface to volume ratio of a long cylindrical fibre 100 mu in diameter was 0.39 mu(-1), or about 10 times the value for a long right circular cylinder 100 mu in diameter. The surface to volume ratio of the tissue interspaces in the same fibre was 170 mu(-1).7. It was concluded that the total sarcolemmal area in this tissue is great enough so that the specific membrane capacitance could be about 1 muF/cm(2) and the specific membrane resistance 20,000 Omega cm(2).

Animals↗
PubMed1972

Magnesium exchange in rat ventricle.

1. The exchange of cellular Mg with external (28)Mg in the rat left ventricle was measured in vivo and, under conditions approximating a steady state, in an isolated, working rat heart perfused and contracting at 36-38 degrees C.2. About 98% of cellular Mg exchanged at a single rate.3. The rate of exchange in vivo was the same as that observed in independent in vitro measurements of the influx and efflux at the physiological external Mg(2+) concentration of 0.56 mM. The rate was 0.15 +/- 0.02 m-mole/(kg dry ventricle.min) or 0.21 +/- 0.02 p-mole/(cm(2).sec).4. In the perfused heart the dependence of the influx on the external Mg concentration was hyperbolic with an apparent V(max) of 0.31 +/- 0.04 m-moles/(kg dry weight.min) and an apparent K(m) of 0.57 +/- 0.08 mM.5. The Mg efflux into a solution containing 2.8 mM-Mg was markedly faster than that into a Mg-free solution.6. These results are interpreted as consistent with a carrier-mediated transport of Mg across the plasma membrane.

Animals↗
PubMed1971

Sterological measurements of cardiac ultrastructures implicated in excitation-contraction coupling.

Electron micrographs of osmium-fixed left ventricles from 200-g female rats were analyzed by stereological techniques. By the use of equations developed by H. Sitte it was possible to determine volume fractions of organelles and absolute membrane areas per unit cell volume for cellular membrane systems implicated in excitation-contraction coupling. The fractions of cell volume were: mitochondria 0.34, myofibrils 0.481, T-system 0.012, total sarcotubules 0.035, other 0.13. The membrane areas per unit cell volume (mum(2)/mum(3)) were: external sarcolemma 0.27, external sarcolemma + T-system 0.34, total sarcotubules 1.3. Diads made up 0.08 of sarcotubular volume and 0.12 of sarcotubular membrane area. 0.14 of the external sarcolemmal membrane area was involved in diadic complexes with underlying subsarcolemmal cisterns.

Animals↗
PubMed1971

Magnesium in single skeletal muscle cells of Balanus.

Single skeletal muscle cells of Balanus contain 48 +/- 1 mmoles magnesium/kg dry weight. Although (28)Mg can be shown either to enter the cells or to be bound to the cell surface within less than 10 min, only 2.1 +/- 0.3% of cellular or cell surface Mg exchanges with this isotope even after several hours. Glycerinated cells washed out in Tris buffer at low ionic strength retain approximately 70% of the Mg present in intact cells. About 85% of this Mg is removed by extraction with KCl or NaCl at concentrations of K and Na which prevail in intact cells, as well as by pyrophosphate, Tris-ATP, or reduction of the ionized Mg concentration to 1 microM. Lowering the ionized Mg concentration to 0.1 microM does not further reduce the Mg content of glycerinated cells. The pH dependence of KCl-inextractable Mg suggests that more than one class of binding sites is involved. A significant fraction of the KCl-inextractable Mg bound to glycerinated cells fails to exchange with (28)Mg even after long equilibration. It is suggested that this fraction may be actin-bound Mg incorporated into the thin filaments during the polymerization of actin.

Adenosine Triphosphate↗
PubMed1971

The effect of potassium and chloride ions on the volume and membrane potential of single barnacle muscle cells.

1. In single barnacle skeletal muscle cells cell diameter has been measured as a function of external osmolality, and cell diameter and membrane potential have been measured during changes of external K and Cl concentrations ([K](o) and [Cl](o)) like those described in frog muscle by Hodgkin & Horowicz (1959). The diameter was monitored microscopically with a precision of 0.2-0.4% (S.D.). [K](o) was varied from 1 to 18 mM, a range of concentrations which does not cause contracture.2. At pH 8.0 the Cl permeability was so low that net KCl and water movements were absent. Such net movements were present at pH 4.5, corresponding to a change in the ratio (Cl conductance/K conductance) from approximately 1/12 at pH 8.0 to 1/2 at pH 4.5.3. Characteristically long time constants were observed for membrane potential responses to a change in [K](o) and/or [Cl](o), even at constant [K](o).[Cl](o). This phenomenon is attributed to a delayed equilibration by diffusion within the system of sarcolemmal invaginations and T-tubules. The delay in the response was increased by introducing polyvinylpyrrolidone (PVP) into this system, presumably because PVP raises intratubular viscosity.4. At pH 4.5 anomalous rectification for net movements of K was demonstrated by measurements of cell diameter and of membrane potential.

Animals↗