Not Nerve Growth Factor Research Articles

Expression of trkC in a Mouse Osteoblastic Cell Line and Its Response to Neurotrophin-3

In a cultured osteoblastic cell line, MC3T3-E1 derived from newborn mouse calvaria, the mRNA encoding TRKC, which is the receptor molecule of neurotrophin-3 (NT-3), was detected by the polymerase chain reaction (PCR) method. The mRNAs of the normal type and one alternative form (C14) were highly expressed in the exponential growth phase of MC3T3-E1 cells and decreased as the cells reached the differentiation stage. NT-3, but not nerve growth factor (NGF), stimulated the poliferation of MC3T3-E1 cells in a dose-dependent manner. NT-3 also stimulated calcium incorporation through the surface of MC3T3-E1 cells, indicating the association of NT-3 and its receptor on the cell surface.

Calcium-destabilizing and neurodegenerative effects of aggregated β-amyloid peptide are attenuated by basic FGF

The mechanisms that contribute to neuronal degeneration in Alzheimer's disease (AD) are not understood. Abnormal accumulations of β-amyloid peptide (βAP) are thought to be involved in the neurodegenerative process, and recent studies have demonstrated neurotoxic actions of βAPs. We now report that the mechanism of βAP-mediated neurotoxicity in hippocampal cell culture involves a destabilization of neuronal calcium homeostasis resulting in elevations in intracellular calcium levels ([Ca 2+] i) that occur during exposure periods of 6 hr to several days. Both the elevations of [Ca 2+] i and neurotoxicity were directly correlated with aggregation of the peptide as assessed by βAP immunoreactivity and confocal laser scanning microscopy. Exposure of neurons to βAP resulted in increased sensitivity to the [Ca 2+] i-elevating and neurodegenerative effects of excitatory amino acids. Moreover, [Ca 2+] i responses to membrane depolarization and calcium ionophore were greatly enhanced in βAP-treated neurons. Neurons in low cell density cultures were more vulnerable to βAP toxicity than were neurons in high cell density cultures. Basic fibroblast growth factor (bFGF), but not nerve growth factor (NGF), significantly reduced both the loss of calcium homeostasis and the neuronal damage otherwise caused by βAP. In AD, βAP may endanger neurons by destabilizing calcium homeostasis and bFGF may protect neurons by stabilizing intracellular calcium levels. Aggregation of βAP seems to be a major determinant of its [Ca 2+] i-destabilizing and neurotoxic potency.

Potentiation of developing neuromuscular synapses by the neurotrophins NT-3 and BDNF.

The neurotrophins are a family of neurotrophic factors that promote survival and differentiation of various neuronal populations. Although the long-term effects of neurotrophins on neuronal survival and differentiation have been intensively studied, nothing is known about their effects on synaptic function. Here we report that acute exposure to neurotrophin-3 (NT-3) or brain-derived neurotrophic factor (BDNF), but not nerve growth factor (NGF), rapidly potentiates the spontaneous and impulse-evoked synaptic activity of developing neuromuscular synapses in culture. The effect appears to be presynaptic in origin and to be mediated by the Trk family of receptor tyrosine kinases. These results provide evidence for the regulation of the function of developing synapses by neurotrophins.

Distribution of pluripotent neural crest cells in the embryo and the role of brain‐derived neurotrophic factor in the commitment to the primary sensory neuron lineage

Many early migratory neural crest cells are pluripotent in the sense that their progeny are able to generate more than one differentiated phenotype (Sieber-Blum and Cohen, 1980, Dev. Biol. 80:95-106; Baroffio, Dupin, and Le Douarin, 1988, Proc. Natl. Acad. Sci. USA 85:5325-5329; Bronner-Fraser and Fraser, 1988, Nature 335:161-164; Sieber-Blum, 1989a, Science 243:1608-1611; Ito and Sieber-Blum, 1991, Dev. Biol. 148:95-106). At trunk levels, the neural crest contains two classes (Sieber-Blum and Cohen, 1980) and at posterior rhombencephalic levels, three different classes of pluripotent cells (Ito and Sieber-Blum, 1991). We investigated cell differentiation by in vitro clonal analysis to determine when in development the pool of pluripotent neural crest cells becomes exhausted. The data suggest that different classes of pluripotent cells, precursor cells with more restricted developmental potentials, and apparently committed cells, exist at sites of advanced migration (posterior branchial arches) and even at target sites of neural crest cell differentiation [posterior branchial arches, dorsal root ganglia (DRG), sympathetic ganglia (SG), and epidermal ectoderm]. Some putative classes of pluripotent cells persist well into the second half of embryonic development. These observations have implications for our understanding of the mechanisms that control neural crest cell migration and differentiation. They support the idea that cues originating from the microenvironment affect differentiation of pluripotent neural crest cells. One such signal appears to be brain-derived neurotrophic factor (BDNF). In the presence of BDNF, but not nerve growth factor (NGF), there is a significant increase in the number of neural crest cells per colony that express a sensory neuron-specific marker. Because this increase is not accompanied by a corresponding increase in the total number of cells per colony, this suggests that BDNF plays a role in cell type specification.

Cell culture of cryopreserved human fetal cerebral cortical and hippocampal neurons: neuronal development and responses to trophic factors

Past knowledge of the human brain at the cellular and molecular levels has come largely from studies of postmortem fixed tissue or by way of extrapolation from studies of lower mammalian species. The ability to study living human brain neurons would provide a new avenue for further insight into mechanisms operative in human brain development, function, and disease. The present study established procedures for the cryopreservation and culture of human fetal cerebral cortical and hippocampal neurons, and characterized the development of the cells in culture. The predominant cell type in both cortical and hippocampal cultures was pyramidal-like neurons that extended one long axon-like process and a few minor dendrite-like processes. Bipolar and stellate-like glia were also present in cultures from both brain regions. Fibroblast growth factor (FGF), but not nerve growth factor (NGF), enhanced long-term neuronal survival in both cerebral cortical and hippocampal cultures. Immunocytochemistry demonstrated the presence of both FGF- and NGF-like immunoreactivities in neurons and glia, from both cerebral cortex and hippocampus, suggesting that these endogenous growth factors may play roles in human fetal brain development. The ability to cryopreserve large numbers of viable dissociated human fetal brain neurons, and subsequently study them in cell cultures, provides new opportunities to understand dynamic aspects of the human brain at the cellular and molecular levels.