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D Bray

Publications and source records attributed to D Bray.

At least 37 records · Page 2Linked to original sources
PubMed1985

Effects of the uncoupling agents FCCP and CCCP on the saltatory movements of cytoplasmic organelles.

Two potent uncoupling agents, carbonylcyanide-4-trifluoromethoxyphenylhydrazone (FCCP) and carbonylcyanide-3-chlorophenylhydrazone (CCCP) inhibit the movement of organelles in neurites of chick sensory neurones in culture. FCCP applied for 30 minutes at 10 microM reduces the number of moving organelles by 78% and a similar treatment with CCCP causes a reduction of 47%. At 100 microM either compound abolishes all directed movements both in neurites and in cultured 3T3 cells. These effects are probably not due to the discharge of proton gradients since 2,4-dinitrophenol (DNP), at concentrations shown to uncouple mitochondria by the discharge of the permeant cationic fluorescent probe rhodamine 123, fails to inhibit cytoplasmic movements. The inhibition of cytoplasmic movements by FCCP and CCCP is likely to be a consequence of their inhibitory action on a variety of enzymes, including dynein and myosin ATPases, through a reaction with sulfhydryl groups.

Adenosine Triphosphatases↗
PubMed1985

Analysis of microspike movements on the neuronal growth cone.

Growth cones of chick sensory ganglion neurons in tissue culture were photographed at 60-sec intervals as they advanced over the substratum. Numbers of microspikes (or "filopodia") were recorded together with the time and position of their appearance, their rate of elongation, their lateral movements, their lifespan, and the position and manner of their disappearance. All microspikes go through cycles of extension, lateral movement, and shortening. These are irregular and unpredictable but show systematic differences depending on where on the growth cone they occur. At the leading edge of the growth cone microspike extension occurs at highest frequency and microspike shortening occurs at the lowest frequency; when the latter occurs in this region it often involves the advance of the margin of the cell in the form of a lamellipodium. Microspike loss occurs most often at the base of the growth cone, usually by the retraction of the microspike into the cell. Calculations of the gain and loss of microspikes at different regions of the growth cone show that they undergo a net retrograde flow, the rate of which is correlated with the forward advance of the growth cone. Individual microspikes can also move backward from the growth cone onto the axon (or "neurite"), an event that occurs most often on adhesive substrata. Our observations support a direct role of microspike movement in the advance of the growth cone. The primary force for axonal elongation appears to be the contraction of microspikes pulling the leading margin of the growth cone forward. At more proximal and peripheral regions of the growth cone, microspikes undergo a retrograde sweeping motion, followed by retraction into the cell, which may also contribute to the forward movement of the growth cone. We interpret these movements as arising from a flow of actin filaments and associated proteins which are incorporated into microspikes and lamellipodia at the leading edge of the growth cone, passing backward, and being deposited into the actin-rich membrane-associated cortex of the axonal cylinder.

Actins↗
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↗