Pietro U. Angeletti

Nerve growth factor.

Nerve growth factor (NGF) is a signaling protein [4] and growth factor implicated in a wide range of development and maintenance functions. NGF was discovered through a series of experiments in the 1950s on the development of the chick [5] nervous system. Since its discovery, NGF has been found to act in a variety of tissues throughout development and adulthood. It has been implicated in immune function, stress response, nerve maintenance, and in neurodegenerative diseases. It is named for its effect on the critical role it plays in the growth and organization [6] of the nervous system during embryonic development.

Essential role of the nerve growth factor in the survival and maintenance of dissociated sensory and sympathetic embryonic nerve cells in vitro

Abstract Sensory and sympathetic nerve cells were dissociated by trypsinization and cultured in CO 2 -conditioned liquid media. Eagles medium alone and Eagles medium supplemented with 10% horse serum proved to be inadequate for the survival and maintenance of these cells. Addition of a specific protein factor (nerve growth factor) at a concentration of 0.05 μg per milliliter of the culture medium, resulted in the survival and maintenance of the sensory and sympathetic nerve cells. These results add new evidence in support of the concept that the NGF plays an essential role in the life of the above cells.

Analysis of the effects of the antiserum to the nerve growth factor in adult mice.

Abstract The effect of the nerve growth factor antiserum (NGF-AS) on adult mice has been studied at morphological and biochemical levels. A 5-day treatment of 3-month-old mice results in a marked volume reduction of sympathetic chain ganglia. This decrease in volume appears to be due in part to cell death, but to a major extent to atrophy of residual neurons. A severe impairment of the sympathetic function also obtains, as indicated by a marked decrease of catecholamine uptake and content in peripheral organs. A few weeks after the end of treatment, a gradual and progressive recovery of the sympathetic function ensues, and the nerve cells regain their normal appearance. These results are described in connection with the problem of the site of action of NGF antibodies in immature and in fully differentiated sympathetic neurons.

Growth control of the sympathetic system by a specific protein factor.

The growth, differentiation, and maintenance of the sympathetic nerve cells were found to depend upon a specific protein factor.-The chemical, biological, and immunological properties of this factor are discussed in connection with the recent findings of the presence of the growth factor in the sympathetic nerve cells of a variety of mammals, including man.

In vitro effects of the nerve growth factor on the fine structure of the sensory nerve cells

Summary Dorsal root ganglia from 8-day chick embryos were explanted in semisolid media with or without a specific nerve growth factor (NGF). The ganglia were incubated for a period of 4 and 12 h and examined with the electron microscope. The presence of the NGF in the culture medium calls forth striking and rapid changes in the fine structure of the neurons. The nuclei develop an irregular contour and denser clumped chromatin in comparison with the controls. In the cytoplasm the Golgi apparatus is dilated; in some cells there is a massive increase in ribosomes associated with increased number of membranous elements of endoplasmic reticulum. Neurofilaments and neurotubules, sparse in control cultures, are already prominent after 4 h of incubation in the presence of the NGF. After 12 h, the cytoplasm of most ganglionic cells is packed with large masses of neurofilaments.

METABOLIC ASPECTS OF THE EFFECT OF NERVE GROWTH FACTOR ON SYMPATHETIC AND SENSORY GANGLIA: PROTEIN AND RIBONUCLEIC ACID SYNTHESIS.

Evidence is presented that the nerve growth factor markedly stimulates the rate of amino acid incorporation and turnover in sensory and sympathetic ganglia in vitro. Under these conditions the nerve growth factor calls forth an even higher increase in RNA synthesis as proved by labeled uridine experiments. Inhibitor experiments with puromycin and actinomycin D suggest that the nerve growth factor stimulation of protein synthesis is dependent on a primary effect on nuclear RNA synthesis.

Testosterone induction of estero-proteolytic activity in the mouse submaxillary gland.

Abstract Testosterone injections sharply increase the estero-proteolytic activity in submaxillary gland extracts of female and of adolescent mice. A major form of hormone-dependent enzyme has been isolated and purified from male gland extracts. The enzyme has a molecular weight of about 32000 and appears to be a peptide hydrolase with strong esterolytic activity. A specific antiserum to the purified enzyme was prepared and used for immunochemical titrations. The results indicate that the increased enzyme activity in the gland following testosterone treatment is due to an increased concentration of enzyme molecules. Incorporation studies gave additional evidence that the hormone stimulates the rate of the enzyme synthesis in the gland.

Alterations in the fine structure of nucleoli in sympathetic neurons following NGF-antiserum treatment.

Summary Antiserum to the nerve growth factor (NGF) produces a severe cytotoxic effect on sympathetic nerve cells when injected into newborn mice. The early cytological lesions were studied by electron microscopy in superior cervical ganglia of 1-day-old mice 12 and 24 h after antiserum treatment. In line with previous observations, early and marked ultrastructural changes were observed in the nuclear compartment. Alterations in the fine structure of nucleoli of the nerve cells are very prominent by 12 h after the As injection. The early alterations consist of condensation and disarrangement of the nucleolar components, which become progressively more severe in the following hours. Distinct dense bodies form from the separation and condensation of the nucleolar material and eventually the nuclear envelope breaks down and cytoplasmic and nuclear material mix. In later stages, marked disorganization of ribosomes and mitochondria is apparent in the cell cytoplasm. Incorporation experiments show that RNA synthesis is markedly reduced in the experimental ganglia already 12 h after the As injection.

Ultrastructural changes in sympathetic neurons of newborn and adult mice treated with nerve growth factor

Purified nerve growth factor (NGF) induces a marked hypertrophy of the sympathetic chain ganglia when injected into newborn and adult mice. A 5-day treatment of newborn or adult mice with daily injections of NGF (20 μ g/g body weight) results in both instances in a striking increase in wet weight of sympathetic ganglia. When examined at the electron microscope, the NGF—treated neurons appear very enlarged: the endoplasmic reticulum and free ribosomes are very abundant. The cytoplasmic area is filled with the interlacing bundles and threads of neurofilaments. This extraordinary production of neurofilaments and neurotubuli appears to be the most striking feature of the NGF—treated neurons.

Structural and ultrastructural changes in developing sympathetic ganglia induced by guanethidine

Abstract Injections of guanethidine into newborn mice and rats result in progressive and irreversible lesion of sympathetic ganglia and in a complete sympathectomy similar to that obtained with a specific antiserum to the nerve growth factor (NGF) (immunosympathectomy) and with 6-hydroxydopamine (chemical sympathectomy). Studies at the optical microscope performed in the first days after administration of guanethidine show the progressive disappearance of immature neurons and a marked increase of glial and satellite cells. Two months after discontinuation of the treatment the sympathetic ganglia are reduced to sclerotic nodules barely detectable at the dissection microscope. The nerve cell population of para- and prevertebral chain ganglia is reduced to 3–5% of that of controls. Studies at the electron microscope performed toward the end of the first week of treatment on the superior cervical ganglion show, in some neurons, mitochondrial lesions and in others dilation and disruption of the endoplasmic reticulum. The destructive effects caused by guanethidine are discussed and compared with those caused by 6-hydroxydopamine and bretylium tosylate.