Faculty Bibliography

Dopamine-beta-hydroxylase activity is present in mouse neuroblastoma C-1300 tumors. The activity is proportional to the weight of the tumor. Serum activity is markedly increased in mice that bear the tumors. Treatment of mice with 5-bromodeoxyuridine causes marked inhibition of tumor growth and decrease of dopamine-beta-hydroxylase activity in the serum. The histochemical studies reveal that 1-5% of the cells in mouse C-1300 neuroblastoma tumors contain catecholamines and that catecholamine-containing processes terminate mainly around blood vessels of the tumor. Dopamine-beta-hydroxylase is present in clonal neuroblastoma cell lines. The cell line with the greater tendency to form axon-like processes has a higher activity of this enzyme

1. Ganglion cell discharges were evoked by extrinsic polarization of the horizontal cells in the retina of the smooth dogfish (Mustelus canis). Depolarization of the horizontal cell gave rise to a discharge similar to that evoked by a spot of light (centre type response) and hyperpolarization of the horizontal cell, a discharge similar to that by an annulus (surround type response).2. Procion dye injection established that the current-passing electrode was sometimes located in the external horizontal cell. Other possibilities, such as middle and internal horizontal cells, were neither confirmed nor excluded.3. Activation of ganglion cells by current was possible under completely dark-adapted conditions and for several log units above this level.4. Depolarizing current enhanced the ganglion cell response evoked by a light spot in the centre of its receptive field; hyperpolarizing current antagonized the response to the same flash.5. The results are consistent with the supposition that a potential change in the horizontal cell, irrespective of its polarity, or whether produced by light or current, spreads within a laminar layer (the S-space). The effect of the potential change is to modulate the response of bipolar cells and their input into the ganglion cell.