Terence F. McDonald

Development of Sensitivity to Tetrodotoxin in Beating Chick Embryo Hearts, Single Cells, and Aggregates

The spontaneous activity of intact embryonic heart becomes progressively more sensitive to tetrodotoxin block with increasing age of the embryo. The activity of isolated single heart cells in culture was relatively insensitive, independent of embryo age. Aggregates formed from single cells responded to tetrodotoxin in the same manner as intact hearts; aggregated cells from older hearts were sensitive.

External potassium and baby hamster kidney cells: intracellular ions, ATP, growth, DNA synthesis and membrane potential.

Abstract The relationship between cell multiplication, DNA synthesis and external potassium concentration has been investigated in baby hamster kidney (BHK) cells. Alterations in the rate of 3 H-thymidine incorporation were paralleled by changes in the rate of growth. The optimal external potassium concentration was 64 m M and either an increase or decrease from this level was inhibitory. Changes in 3 H-thymidine incorporation with the various potassium media appeared to be immediate (5 min pulse). Intracellular sodium and potassium concentrations measured at 5 min, 2 hr, and 24 hr at various external potassium concentrations indicated that the changes in 3 H-thymidine incorporation were not related to changing intracellular ion levels. The ATP content of potassium-inhibited cells was not significantly different than control cells. The membrane potential was primarily dependent on the potassium distribution and could be manipulated by changing the ratio of external to internal potassium. The relationship between membrane potential and 3 H-thymidine was explored by varying the external potassium concentration from 1.75 to 121 m M . To distinguish between the effects of external potassium per se and the membrane potential, 3 H-thymidine incorporation was measured at 5 or 93 m M external potassium in normal and potassium-depleted cells. The results raise the possibility that the cell membrane potential may influence DNA synthesis.

Multiple effects of ouabain on BHK cells.

Abstract The effects of ouabain on BHK cells have been investigated. Ouabain (4 × 10 −4 M) inhibited growth, reduced the incorporation of 3 H-thymidine and 14 C-amino acids, promoted a loss of cell potassium and gain of sodium, and reduced the membrane potential. Ouabain (1 × 10 −4 M) had very little effect while 2 × 10 −4 M ouabain had an intermediate effect. ATP content was not reduced after 24 h ouabain treatment except at a dose of 10 −3 M. The recovery from ouabain treatment was dependent on the concentration of ouabain and the period of exposure.

Electrical activity in embryonic heart cell aggregates developmental aspects

SummaryAction potential parameters were measured in beating heart cell aggregates which were formed from trypsin-dissociated cells of embryonic chick hearts aged

Ion Levels and Membrane Potential in Chick Heart Tissue and Cultured Cells

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TETRODOTOXIN SENSITIVITY OF CULTURED EMBRYONIC HEART CELLS DEPENDS ON CELL INTERACTIONS

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Tetrodotoxin Desensitization in Aggregates of Embryonic Chick Heart Cells

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Muscle-like Arrays in a Fibroblast Line

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Membrane potentials of BHK (baby hamster kidney) cell line: Ionic and metabolic determinants

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