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Biomedical subjects

D Bray

Publications and source records attributed to D Bray.

At least 73 records · Page 4Linked to original sources
PubMed1978

Growth cone formation in cultures of sensory neurons.

Three experimental situations have been found in which cultured sensory neurons from embryonic chicken will form growth cones from positions along the length of the neurite. If the neurons are dissected with a remaining short axonal stump and plated into serum-free medium, they can form a morphologically normal growth cone from the stump within 15 min, even in the presence of cycloheximide or puromycin. When neurites growing in culture media with low levels of serum are cut at any point with microneedles, growth cones are produced quickly from the amputated stump, usually within 20 min. Treatment of growing neurons with low concentrations of colchicine, Colcemid, or podophyllotoxin results in the progressive appearance of lateral filopodia and regions of flattened cytoplasm that closely resemble growth cones except for their preterminal positions. These observations show that the potential to form growth cones is distributed throughout the neuron and suggest that this normally repressed in some way by the neuronal microtubules.

Axons↗
PubMed1975

The actin content of fibroblasts.

Cultures of chick skin fibroblasts were dissolved in solutions of sodium dodecyl sulphate, and their entire protein content was examined by gel electrophoresis. The most abundant species migrated in the same position as muscle actin. It gave a similar pattern of iodinated peptides after reaction with radioactive sodium iodide and digestion with proteinases, and contained comparable amounts of Nt-methylhistidine. Its amount was estimated by quantitative densitometry of stained gels with bovine serum albumin as an internal standard, and by radioactive assay of cultures that had been grown in the presence of [35S]methionine. The values obtained ranged from 7 to 14% of the total cellular protein, with an average of 8.5%. A protein band in the position of muscle myosin was also present and accounted for about 2.5% of the total protein. Both this and the actin band increased in relative amount with the age of the cultures.

Actins↗
PubMed1973

Branching patterns of individual sympathetic neurons in culture.

The growth of single sympathetic neurons in tissue culture was examined with particular regard to the way in which the patterns of axonal or dendritic processes (here called nerve fibers), were formed. The tips of the fibers were seen to advance in straight lines and to grow at rates that did not vary appreciably with time, with their position in the cell outgrowth, or with the fiber diameter. Most of the branch points were formed by the bifurcation of a fiber tip (growth cone), apparently at random, and thereafter remained at about the same distance from the cell body. It seemed that the final shape of a neuron was the result of the reiterated and largely autonomous activities of the growth cones. The other parts of the cell played a supportive role but, apart from this, had no obvious influence on the final pattern of branches formed.

Animals↗
PubMed1970

Surface movements during the growth of single explanted neurons.

The processes of isolated rat sympathetic neurons growing in culture were marked with glass or carmine particles and observed with timelapse microphotography. Particles on the processes moved with the cell in relation to the dish and underwent continual small jerky movements. They did not, however, show any over-all distal motion and for long periods, during which the growth cone progressed more than 100 mu, the particles remained at about the same distance from the cell body. The most obvious explanation for this result is that new fiber surface, and perhaps the plasma membrane, is deposited in the region of the growing tip.

Animals↗