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Biomedical subjects

D Bray

Publications and source records attributed to D Bray.

At least 37 records · Page 2Linked to original sources
PubMed1987

Water distribution in creams prepared using cetostearyl alcohol and cetrimide.

The water distribution in an antiseptic cream formulation prepared using cetostearyl alcohol and cetrimide has been studied using thermogravimetric analysis, differential scanning calorimetry, ultracentrifugation and scanning electron microscopy. In addition to a free water phase two types of interlamellarly fixed water were found, one associated with the liquid crystalline network around the oil droplets and one associated with the liquid crystalline network of the bulk. The latter was in equilibrium with the free water and can be classed as freely drainable.

Cetrimonium↗
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↗
PubMed1984

Axonal growth in response to experimentally applied mechanical tension.

A machine was constructed, called a Cell Puller, that allows the steady advance or withdrawal of a microelectrode at very slow speeds-up to 170 microns/hr. Specially prepared microelectrodes held in the Cell Puller were placed in cultures of dissociated chick sensory ganglion neurons in such a way that growth cones attached to their tips. Movements of the microelectrodes, at speeds up to about 100 microns/hr, then resulted in the elongation of the neurites for up to 24 hr and for increases in length up to 960 microns; more rapid towing failed to cause extensive neurite elongation. Estimates of neurite diameter before and after "towing" indicated that a net increase in neurite volume had occurred. Furthermore, long neurites could be produced by towing from previously rounded neuronal cell bodies confined to small adhesive "islands" on a nonadhesive substratum. Neurites produced by microelectrode towing had a normal appearance, showed rapid saltatory movements of internal organelles and were capable of resuming growth on the substratum. Electron microscopy of bundles of neurites produced in this way from explanted dorsal root ganglia showed an ultrastructure typical of cultured neurites, with abundant longitudinally aligned microtubules and neurofilaments. These experiments demonstrate that neurites can grow in response to mechanical tension under tissue culture conditions. It is proposed that they do so also in normal development, the tension in this case being supplied initially by the locomotory activity of the growth cones and subsequently by the morphogenetic movements of the surrounding tissues.

Animals↗
PubMed1984

Disseminating the principles of a community support program.

Oregon's Living in the Community (LINC) program for chronic patients succeeds because of effective collaboration between a state hospital and a community treatment and rehabilitation program. The authors trace the development of the LINC program from its beginning in the early 1970s as a progressive retraining project for Eastern Oregon State Hospital's "back ward" patients. They describe principles derived from the original project, such as the provision of training in the patient's natural environment, adoption of these principles into the Oregon community support program, and dissemination of LINC projects to other parts of the state. The authors conclude that such model programs can be transferred to urban and rural settings when supported by a statewide planning effort.

Chronic Disease↗
PubMed1983

Actin polymerization and synthesis in cultured neurones.

The protein content of sympathetic neurones explanted from 10-11-day old chick embryos into culture medium containing nerve growth factor (NGF) increases steadily from about 100 to about 400 pg/cell in 7 days. Actin remains at close to 5% of the total protein during this period, but the proportion of unpolymerized actin falls. As measured by the inhibition of DNase I activity, rounded neurones without neurites contain 70 +/- 7% of their total actin in monomeric form, whereas cells in mature, neurite-bearing cultures contain 39 +/- 7%. When allowance is made for the increase in size of the neuronal cell bodies, the actin present in the neurites ('axons') alone is found to be almost entirely in filamentous form. Cultures exposed to radioactive leucine rapidly incorporate radioactivity into both sedimentable and non-sedimentable forms of actin. Actin-specific activities in the two fractions--estimated after isolation of the actin on small DNase I--Sepharose affinity columns--are similar after labelling for less than 1 h. Direct incorporation of newly-synthesized actin into filaments is suggested from these results. Pulse-chase experiments show that non-sedimentable protein in cultured sympathetic neurones turns over more rapidly than sedimentable protein. However, this is not true for actin, which shows a similar specific activity in sedimentable and non-sedimentable forms--even after 6 days of cold chase. This anomalous behaviour is simply explained by an exchange of actin molecules between filamentous and non-filamentous forms. Control experiments indicate that exchange does not occur to this degree during preparation of subcellular fractions. It is consequently attributed to exchange processes in the living cell.

Actins↗
PubMed1983

Isolation of a Ca2+-dependent actin-fragmenting protein from brain, spinal cord, and cultured neurones.

Extracts of ox spinal cord and chicken brain were fractionated by ion-exchange chromatography and assayed for their ability to reduce the viscosity of muscle F-actin solutions. Two distinct peaks of activity were obtained, one of which was further purified by affinity chromatography on a DNAase-actin Sepharose column. Following molecular exclusion chromatography, the actin component appeared as a complex of 1 molecule of a protein with molecular weight 90,000 and 2 molecules of actin (42,000). This tightly bound complex was resistant to most methods of protein separation, but was resolvable into its component proteins by sodium dodecyl sulphate acrylamide gel electrophoresis. The protein of molecular weight 90,000 could be eluted from such a gel in a fully active form. The activity of the protein from ox spinal cord was closely similar to that of gelsolin, an actin-fragmenting protein originally isolated from rabbit lung macrophages. Like gelsolin, the protein from ox spinal cord produced fragmentation of muscle F-actin filaments at Ca2+ concentrations greater than 10(-7) M, and had a nucleating effect on the polymerisation of muscle actin; the latter was measured most easily by the enhancement of fluorescence of muscle actin conjugated to N-(1-pyrenyl)iodoacetamide. Nucleation was more effective in the presence of Ca2+, but also occurred in its absence, and the same was true of complex formation between the 90,000 protein and muscle G-actin. On the basis of its actin-fragmenting activity, we estimate that the 90,000 molecular weight protein constitutes 0.2% of the protein initially extracted from ox spinal cord. A very similar protein, indistinguishable in its action on actin but containing variable amounts of a protein of molecular weight 85,000 as well as 90,000, was isolated from chicken brain. A similar protein was also detected in pure cultures of sympathetic neurones by enrichment on a DNAase-actin affinity column and by immune blotting and by immunofluorescence. We conclude that a protein similar, if not identical to macrophage gelsolin is present in neurones and that it probably plays a part in the actin-based movements of these cells.

Actins↗
PubMed1983

Cost benefit analysis of lactation therapy with somatic cell counts as indications for treatment.

Lactating dairy cows (487) from five commercial herds were in a study of benefits from lactation therapy of sub-clinical mastitis. Bacterial isolations and composite milk samples for somatic cell counts were taken from each cow each month for 15 mo. Cows (254) in the experimental group were infused with cephapirin in all quarters for two consecutive milkings if somatic cell counts rose above 400,000 cells/ml; 103 cows were so treated. Stepwise regression showed that lactation number, somatic cell counts, days in milk, and percent quarters infected explained variation in milk production, but treatment group, herd, and season did not. Also, there were no significant differences between production of infected experimental and control cows with high somatic cell counts on test dates after treatment. With the experimental program, there was a net loss of +19.65/cow. Intramammary lactation therapy based on somatic cell counts less than 400,000 cells/ml is not recommended.

Animals↗
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↗