... CHAPTER 6 Embryo Slices Kevin B. Hotary, Lynn T. Landmesser,* and Kathryn W. Tosneyt Departme... more ... CHAPTER 6 Embryo Slices Kevin B. Hotary, Lynn T. Landmesser,* and Kathryn W. Tosneyt Department of Internal Medicine and ... the interactions, molecules, and intracellular mechanisms behind directed cell movements in a greatly simplified environment (reviewed by Levi et al ...
... "Somites in Developing Embryos." Plenum, New York. Kathryn W. Tosney et al.... more ... "Somites in Developing Embryos." Plenum, New York. Kathryn W. Tosney et al. Bronner-Fraser, M., and Stern, C. (1991). Effects of mesodermal tissues on avian neural crest cell migration. Dev. Biol. 143, 213-217. French, V., Ingham, P., Cooke, J., and Smith, J., eds. (1988). ...
The Journal of neuroscience : the official journal of the Society for Neuroscience, 1985
We quantitatively analyzed several features of orthogradely labeled peripheral growth cones in th... more We quantitatively analyzed several features of orthogradely labeled peripheral growth cones in the lumbosacral region of the chick embryo. We compared motoneuron growth cones in regions where they appear to express specific directional preferences (the plexus region and regions where muscle nerves diverge from main nerve trunks), which we operationally defined as "decision regions," to motoneuron growth cones in other pathway regions (the spinal nerve, nerve trunk, and muscle nerve pathways) which we termed, for contrast, "non-decision region." We found that motoneuron growth cones are larger, more lamellepodial, and have more complex trajectories in decision regions. Sensory growth cone populations, which are thought to be dependent upon motoneurons for outgrowth (Landmesser, L., and M. Honig (1982) Soc. Neurosci. Abstr. 8: 929), do not enlarge or become more lamellepodial in motoneuron decision regions, suggesting that this local environment does not affect all...
The Journal of neuroscience : the official journal of the Society for Neuroscience, Jan 15, 2002
In this study, adhesions on individual filopodial shafts were shown to control veil (lamellar) ad... more In this study, adhesions on individual filopodial shafts were shown to control veil (lamellar) advance and to be modulated by guidance cues. Adhesions were detected in individual filopodia of sensory growth cones using optical recordings, adhesion markers, and electron microscopy. Veils readily advanced along filopodia lacking shaft adhesions but rarely advanced along filopodia displaying shaft adhesions. Experiments altering adhesion showed that this relationship is not caused by veils removing adhesions as they advanced. Reducing adhesion with antibodies decreased the proportion of filopodia with shaft adhesions and coordinately increased veil advance. Moreover, the inhibitory relationship was maintained: veils still failed to advance on individual filopodia that retained shaft adhesions. These results support the idea that shaft adhesions inhibit veil advance. Of particular interest, guidance cues can act by altering shaft adhesions. When a cellular cue was contacted by a filopod...
The somites are arrayed in a repeating pattern along the longitudinal axis of the embryo, as are ... more The somites are arrayed in a repeating pattern along the longitudinal axis of the embryo, as are the developing sensory and sympathetic ganglia and the spinal nerves. This pattern is not a coincidence: the somite imposes a segmental pattern on the cells and axons that invade it. Both neural crest cells and axons prefer the anterior portion of the sclerotome (the ventral part of the somite) for outgrowth. What differences in anterior and posterior sclerotome are responsible? I used scanning electron microscopy to ask whether these populations differed on the tissue level in chick embryos. This study shows that differences in tissue organization are of insufficient magnitude or develop too late to explain the preference of neural crest cells and axons for the anterior half of each sclerotome. For instance, the extracellular matrix does not differ dramatically in density at the dorsal sclerotome boundary and yet neural crest cells promptly enter the anterior sclerotome when they reach this boundary. These cells have access to the cell processes of somitic cells that extend through the matrix. This suggests that neural crest cells could detect important differences in anterior and posterior populations by direct cell contact. Likewise, barriers and consistent differences in cell density, shape or orientation were not obvious before or during initial axon outgrowth. The absence of significant differences in tissue organization suggests that axons and neural crest cells become segmented by responding to diffusible cues, to differences in extracellular material or to the cell surfaces of individual anterior and posterior sclerotome cells.
The Journal of neuroscience : the official journal of the Society for Neuroscience, 2000
Growth cones sense cues by filopodial contact, but how their motility is altered by contact remai... more Growth cones sense cues by filopodial contact, but how their motility is altered by contact remains unclear. Although contact could alter motile dynamics in complex ways, our analysis shows that stable contact with Schwann cells induces motility changes that are remarkably discrete and invariant. Filopodial contact invariably induces local veil extension. Even when contacts are brief, veils always extend before the filopodia retract. Contact at filopodial tips suffices for induction. Moreover, veils extend significantly sooner than on filopodia contacting laminin, which often detach without extending veils. The overall behavioral responses of the growth cone, such as increased area and turning, result from integrating multiple discrete responses. Cycles of veil induction enlarge the growth cone and often lead it onto the cell. Invariant veil induction is abolished by blocking N-cadherin signaling. We propose an axonal guidance model in which different guidance cues act by inducing d...
The Journal of neuroscience : the official journal of the Society for Neuroscience, 1999
During pathfinding, growth cones respond to guidance cues by altering their motility. This study ... more During pathfinding, growth cones respond to guidance cues by altering their motility. This study shows that motile responses can be highly specific: filopodial contact with two different, physiologically relevant cells differentially alters discrete elements of motility. With each cell type, the responses to contact are invariant. Each cell induces a distinct response in sensory growth cones with every filopodial contact. Contact with an inhibitory cell, posterior sclerotome, alters a discrete motile characteristic; contact locally inhibits the ability of veils to extend down contacting filopodia. The inhibition is precise. Contact fails to alter other individual veil characteristics such as initiation frequency or extension rate. Moreover, despite local veil inhibition, the general level of extension across the growth cone is retained, as though protrusive activity is regulated to some set point. Contact with a stimulatory cell, anterior sclerotome, elicits a biphasic response. Fir...
... CHAPTER 6 Embryo Slices Kevin B. Hotary, Lynn T. Landmesser,* and Kathryn W. Tosneyt Departme... more ... CHAPTER 6 Embryo Slices Kevin B. Hotary, Lynn T. Landmesser,* and Kathryn W. Tosneyt Department of Internal Medicine and ... the interactions, molecules, and intracellular mechanisms behind directed cell movements in a greatly simplified environment (reviewed by Levi et al ...
... "Somites in Developing Embryos." Plenum, New York. Kathryn W. Tosney et al.... more ... "Somites in Developing Embryos." Plenum, New York. Kathryn W. Tosney et al. Bronner-Fraser, M., and Stern, C. (1991). Effects of mesodermal tissues on avian neural crest cell migration. Dev. Biol. 143, 213-217. French, V., Ingham, P., Cooke, J., and Smith, J., eds. (1988). ...
The Journal of neuroscience : the official journal of the Society for Neuroscience, 1985
We quantitatively analyzed several features of orthogradely labeled peripheral growth cones in th... more We quantitatively analyzed several features of orthogradely labeled peripheral growth cones in the lumbosacral region of the chick embryo. We compared motoneuron growth cones in regions where they appear to express specific directional preferences (the plexus region and regions where muscle nerves diverge from main nerve trunks), which we operationally defined as "decision regions," to motoneuron growth cones in other pathway regions (the spinal nerve, nerve trunk, and muscle nerve pathways) which we termed, for contrast, "non-decision region." We found that motoneuron growth cones are larger, more lamellepodial, and have more complex trajectories in decision regions. Sensory growth cone populations, which are thought to be dependent upon motoneurons for outgrowth (Landmesser, L., and M. Honig (1982) Soc. Neurosci. Abstr. 8: 929), do not enlarge or become more lamellepodial in motoneuron decision regions, suggesting that this local environment does not affect all...
The Journal of neuroscience : the official journal of the Society for Neuroscience, Jan 15, 2002
In this study, adhesions on individual filopodial shafts were shown to control veil (lamellar) ad... more In this study, adhesions on individual filopodial shafts were shown to control veil (lamellar) advance and to be modulated by guidance cues. Adhesions were detected in individual filopodia of sensory growth cones using optical recordings, adhesion markers, and electron microscopy. Veils readily advanced along filopodia lacking shaft adhesions but rarely advanced along filopodia displaying shaft adhesions. Experiments altering adhesion showed that this relationship is not caused by veils removing adhesions as they advanced. Reducing adhesion with antibodies decreased the proportion of filopodia with shaft adhesions and coordinately increased veil advance. Moreover, the inhibitory relationship was maintained: veils still failed to advance on individual filopodia that retained shaft adhesions. These results support the idea that shaft adhesions inhibit veil advance. Of particular interest, guidance cues can act by altering shaft adhesions. When a cellular cue was contacted by a filopod...
The somites are arrayed in a repeating pattern along the longitudinal axis of the embryo, as are ... more The somites are arrayed in a repeating pattern along the longitudinal axis of the embryo, as are the developing sensory and sympathetic ganglia and the spinal nerves. This pattern is not a coincidence: the somite imposes a segmental pattern on the cells and axons that invade it. Both neural crest cells and axons prefer the anterior portion of the sclerotome (the ventral part of the somite) for outgrowth. What differences in anterior and posterior sclerotome are responsible? I used scanning electron microscopy to ask whether these populations differed on the tissue level in chick embryos. This study shows that differences in tissue organization are of insufficient magnitude or develop too late to explain the preference of neural crest cells and axons for the anterior half of each sclerotome. For instance, the extracellular matrix does not differ dramatically in density at the dorsal sclerotome boundary and yet neural crest cells promptly enter the anterior sclerotome when they reach this boundary. These cells have access to the cell processes of somitic cells that extend through the matrix. This suggests that neural crest cells could detect important differences in anterior and posterior populations by direct cell contact. Likewise, barriers and consistent differences in cell density, shape or orientation were not obvious before or during initial axon outgrowth. The absence of significant differences in tissue organization suggests that axons and neural crest cells become segmented by responding to diffusible cues, to differences in extracellular material or to the cell surfaces of individual anterior and posterior sclerotome cells.
The Journal of neuroscience : the official journal of the Society for Neuroscience, 2000
Growth cones sense cues by filopodial contact, but how their motility is altered by contact remai... more Growth cones sense cues by filopodial contact, but how their motility is altered by contact remains unclear. Although contact could alter motile dynamics in complex ways, our analysis shows that stable contact with Schwann cells induces motility changes that are remarkably discrete and invariant. Filopodial contact invariably induces local veil extension. Even when contacts are brief, veils always extend before the filopodia retract. Contact at filopodial tips suffices for induction. Moreover, veils extend significantly sooner than on filopodia contacting laminin, which often detach without extending veils. The overall behavioral responses of the growth cone, such as increased area and turning, result from integrating multiple discrete responses. Cycles of veil induction enlarge the growth cone and often lead it onto the cell. Invariant veil induction is abolished by blocking N-cadherin signaling. We propose an axonal guidance model in which different guidance cues act by inducing d...
The Journal of neuroscience : the official journal of the Society for Neuroscience, 1999
During pathfinding, growth cones respond to guidance cues by altering their motility. This study ... more During pathfinding, growth cones respond to guidance cues by altering their motility. This study shows that motile responses can be highly specific: filopodial contact with two different, physiologically relevant cells differentially alters discrete elements of motility. With each cell type, the responses to contact are invariant. Each cell induces a distinct response in sensory growth cones with every filopodial contact. Contact with an inhibitory cell, posterior sclerotome, alters a discrete motile characteristic; contact locally inhibits the ability of veils to extend down contacting filopodia. The inhibition is precise. Contact fails to alter other individual veil characteristics such as initiation frequency or extension rate. Moreover, despite local veil inhibition, the general level of extension across the growth cone is retained, as though protrusive activity is regulated to some set point. Contact with a stimulatory cell, anterior sclerotome, elicits a biphasic response. Fir...
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