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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
PubMed1981

Serial analysis of microtubules in cultured rat sensory axons.

A fascicle of axons in an organotypic culture of rat dorsal root ganglion was analysed in 190 serial transverse sections, a total fascicle length calculated to be 12.8 micrometer. The number, position and continuity of microtubules and components of smooth endoplasmic reticulum (SER) were examined. The 187 microtubules traced in 27 axons showed a total of 32 terminations in the series; 14 of these were 'starts' and 18 were 'stops' in relation to progression away from the neuronal soma; three tubules began and ended in the series. Microtubules overall were long, their lengths calculated to average 108 micrometer. Terminations usually occurred close to the plasma membrane but otherwise exhibited no obvious morphological specialization. Microtubules in some axons were concentrated in the periphery of the axon, a region from which neurofilaments were excluded. The relative position of tubules in the axon did not change in any systematic way (for example, by rotation) throughout the series. The SER showed marked variation in form, from the expected membrane-bounded vesicle to profiles that resembled a microtubule or a thinner densely stained filament.

Animals↗
PubMed1981

Cytoskeletal elements in neurons.

Neurotubules and neurofilaments are homologous with cytoplasmic microtubules and microfilaments which are seen with the electron microscope in most plant and animal cells. Their subunits are transported to the growth cone of the outgrowing axon, where the subunits are added to the distal ends of the neurotubules.

Animals↗
PubMed1979

Mechanical tension produced by nerve cells in tissue culture.

Evidence is presented that (a) the growth cone of cultured neurons can exert mechanical tension, and (b) that the direction of advance of the growth cone is determined by the tension existing between it and the rest of the cell. (a) The evidence that growth cones can pull comes from a vectorial analysis of the outlines of individually isolated sensory neurons. The angles formed in these outgrowths are very close to those of tension-generated networks anchored at their free ends and these values are restored shortly after an experimental displacement. The relative mechanical tension on each segment of an outgrowth can be calculated by standard methods and is found to decrease at each branch point. It appears to be correlated with the diameter of the fibre so that thicker fibres maintain more tension than thinner ones. (b) The influence of tension on the direction of advance of the growth cone is shown by 2 kinds of experient. If a growing neurite is pulled to one side with a microelectrode then the direction of its advance is changed immediately according to the new stress. If the mechanical tension on the growth cone of a neurite is released by amputation or displacement the growth cone is found to have a high probability of branching shortly afterwards. The ability of the growth cone to exert tension is discussed in relation to evidence that microspikes have contractile properties and in terms of the distribution of microfilaments within the neurite. It is suggested that the exertion of tension by a growth cone could serve to guide the neurite along paths of high adhesivity both in vitro and in vivo.

Animals↗
PubMed1978

Risks of facial plastic surgery in an otolaryngology program.

By reviewing 680 rhinoplasty, facelift, blepharoplasty, otoplasty, and chin implant procedures that were performed during a two-year period by UCLA Head and Neck Surgery (Otolaryngology) residents, we have found that the rate of major and minor complications compares favorably with that rate achieved by physicians in practice who have reported their results in the literature. Three hundred and sixty-eight rhinoplasties resulted in 1.6% major complications, 14.4% in minor complications, and 5.2% in revision surgeries. One hundred fourteen facelifts had 5.3% major complications, and 24.5% had minor complications. One hundred fifty-six blepharoplasties had no major complications, and 7.7% had minor complications; 21 chin implants resulted in no major complications, and 9.5% resulted in minor complications; and 21 bilateral otoplasties had no major complications, and 14.3% had minor complications, with 4.8% revisions.

Chin↗
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↗