Assembly of the cardiac I-band region of titin/connectin: expression of the cardiac-specific regions and their structural relation to the elastic segments.

The giant molecule titin (also called connectin) provides an elastic connection in the I-band between the Z-disk and A-band of striated muscle. This region is assembled in a tissue-specific way by extensive differential splicing events. We have raised monoclonal antibodies against the two N2-line isoforms of titin and demonstrate that both forms of cardiac I-band titin are constitutively co-expressed in atrial and ventricular muscle.

Ionic currents on type-I cells of the rabbit carotid body measured by voltage-clamp experiments and the effect of hypoxia.

Type-I cells (from rabbit embryos) in primary culture were studied in voltage-clamp experiments using the whole cell arrangement of the patch-clamp technique. With a pipette solution containing 130 mM K+ and 3 mM Mg-ATP, large outward currents were obtained positive to a threshold of about -30 mV by clamping cells from -50 mV to different test pulses (-80 to 50 mV). Negative to -30 mV, the slope conductance was low (outward rectification).

Calcium influx in cultured carotid body cells is stimulated by acetylcholine and hypoxia.

Calcium influx was measured in cultured carotid body and glioma cells. In carotid body cells stimulation with acetylcholine (ACh, 10(-5) mol/l) increased the calcium influx to 135% of control values after 1 min and to 163% after 30 min. With a reduction of the pO2 to nearly zero calcium influx increased to 170% of control values.