SignalTransduction by Nerve Growth Factorand FibroblastGrowth FactorinPC12 CellsRequiresa Sequence ofSrcand Ras Actions

A method and apparatus for producing (e.g. heavy oil) through a wellbore which passes through a permafrost layer. To maintain an acceptable flow temperature inside the production tubing, a heating element (e.g. electrical power cable having its leads short-circuited) is lowered down the production tubing to generate heat inside the tubing when electricity is supplied thereto. A sensor is provided to sense the temperature inside the tubing and activate a source to supply electricity to the cable whenever the temperature inside the production tubing drops below the desired temperature.