{'fraction_non_alphanumeric': 0.029013539651837523, 'fraction_numerical': 0.0029013539651837525, 'mean_word_length': 5.2727272727272725, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Insulin‐like growth factor I: A mitogen for rat schwann cells in the presence of elevated levels of cyclic AMP

To develop effective procedures for improving the regeneration of peripheral nerves and for preventing the formation of neurofibromas, it is necessary to identify the different mitogens that stimulate the proliferation of Schwann cells. Insulinlike growth factor I (IGF‐I), which is a potent autocrine growth factor in many tissues, is synthesized by proliferating Schwann cells. However, the role of IGF‐I in stimulating their division is still uncertain. Here we show that nanomolar concentrations of IGF‐I stimulate the growth of Schwann cells in primary culture. IGF‐I alone was uneffective but in the presence of forskolin (5 μM) or dibutyryl cyclic AMP (dbcAMP, 10 μM), it became a potent mitogen. Neither IGF‐II nor epidermal growth factor (EGF) were effective, even in the presence of forskolin. Insulin also stimulated Schwann cell proliferation in the presence of forskolin, but only at micromolar concentration.