Peter W . Baas

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We have analyzed the polarity orientation of microtubules in the axons and dendrites of cultured rat hippocampal neurons. As previously reported of axons from other neurons, microtubules in these axons are uniform with respect to polarity; (+)-ends are directed away from the cell body toward the growth cone. In sharp contrast, microtubules in the mid-region(More)
Local changes in microtubule organization and distribution are required for the axon to grow and navigate appropriately; however, little is known about how microtubules (MTs) reorganize during directed axon outgrowth. We have used time-lapse digital imaging of developing cortical neurons microinjected with fluorescently labeled tubulin to follow the(More)
Previous work from our laboratory suggested that microtubules are released from the neuronal centrosome and then transported into the axon (Ahmad, F.J., and P.W. Baas. 1995. J. Cell Sci. 108: 2761-2769). In these studies, cultured sympathetic neurons were treated with nocodazole to depolymerize most of their microtubule polymer, rinsed free of the drug for(More)
We have explored the composition and stability properties of individual microtubules (MTs) in the axons of cultured sympathetic neurons. Using morphometric means to quantify the MT mass remaining in axons after various times in 2 micrograms/ml nocodazole, we observed that approximately 48% of the MT mass in the axon is labile, depolymerizing with a t1/2 of(More)
Recent studies have shown that the transport of microtubules (MTs) and neurofilaments (NFs) within the axon is rapid, infrequent, asynchronous, and bidirectional. Here, we used RNA interference to investigate the role of cytoplasmic dynein in powering these transport events. To reveal transport of MTs and NFs, we expressed EGFP-tagged tubulin or NF proteins(More)
It has long been known that microtubule depletion causes axons to retract in a microfilament-dependent manner, although it was not known whether these effects are the result of motor-generated forces on these cytoskeletal elements. Here we show that inhibition of the motor activity of cytoplasmic dynein causes the axon to retract in the presence of(More)
Microtubules in the dendrites of cultured hippocampal neurons are of nonuniform polarity orientation. About half of the microtubules have their plus ends oriented distal to the cell body, and the other half have their minus ends distal; in contrast, microtubules in the axon are of uniform polarity orientation, all having their plus ends distal (Baas, P.W.,(More)
tween a radial array of microtubules during interphase Introduction and a bipolar spindle of microtubules during mitosis. Neurons are the principle signaling cells of the nervous The microtubules are associated with their sites of nusystem. In order to transmit signals, neurons stop dividcleation within the single interphase centrosome or ing early in(More)
Hippocampal neurons in culture initially extend several minor processes that are approximately 20 microns in length. The first minor process to grow approximately 10 microns longer than the others will continue to grow rapidly and become the axon (Goslin and Banker, 1989). We sought to define changes in the microtubule (MT) array that occur during axon(More)
Axons within the brain branch principally by the formation of collaterals rather than by bifurcation of the terminal growth cone (O'Leary and Terashima, 1988). This same behavior is recapitulated in cultures of embryonic hippocampal neurons (Dotti et al., 1988), rendering them ideal for studies on the cell biological mechanisms underlying collateral branch(More)