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Biomedical subjects

D Bray

Publications and source records attributed to D Bray.

At least 19 recordsLinked to original sources
PubMed1992

Low response of BALB/c macrophages to priming and activating signals.

Trehalose dimycolate (TDM), a mycobacterial glycolipid, is a powerful macrophage-priming agent. However, its efficiency seems limited in the case of BALB/c mice. Peritoneal macrophages harvested from TDM-treated BALB/c mice did not control BCG growth in vitro as efficiently as similar macrophages from two other mouse strains, (B6 x D2)F1 and C57BL/6, which are respectively Bcgr and Bcgs. BALB/c macrophages elicited by TDM also exhibited a low capacity to produce hydrogen peroxide and, after activation by lipopolysaccharide (LPS), weak cytostatic activity against P815 mastocytoma cells. Finally, alkaline phosphodiesterase, a marker of resident and inflammatory macrophages, was still expressed at a high level in macrophages of BALB/c mice treated with TDM. Low responsiveness of BALB/c macrophages to stimuli was not observed with TDM only; activation for tumor cytotoxicity of thioglycolate-elicited macrophages from BALB/c mice required also higher doses of interferon-gamma, and LPS. L-Arginine-dependent production of nitric oxide was inducible in macrophages from BALB/c mice, but the conditions required for its induction were more stringent. Thus, the reduced antiproliferative effects of BALB/c macrophages may be due to uncomplete induction of NO synthase after suboptimal stimulation.

Amino Acid Oxidoreductases↗
PubMed1992

Actin depolymerizing factor is a component of slow axonal transport.

We examined the low molecular weight proteins transported with actin in the chicken sciatic nerve after injection of [35S]methionine into the lumbar spinal cord. A prominent component of slow axonal transport with apparent molecular mass 19 kDa comigrated on two-dimensional gels with chicken actin depolymerizing factor (ADF), previously shown to be a major actin-binding protein in brain. There was comparatively little radioactivity associated with the actin monomer sequestering proteins, profilin or cofilin, and examination of the rapid component of axonal transport failed to reveal appreciable quantities of actin, ADF, profilin, or cofilin. These results show that both actin and ADF are carried by slow axonal transport and raise the possibility that actin travels within the axon in an unpolymerized form in a complex with ADF.

Actin Depolymerizing Factors↗
PubMed1992

Collagen fibril diameters in the healing adult rabbit medial collateral ligament.

This study was carried out to test the hypothesis that improvements in ligament scar mechanical behavior during healing may be related, in part, to increases in collagen fibril diameters. Forty-eight adult female New Zealand White rabbits had standardized midsubstance gap injuries created in their right medial collateral ligaments (MCLs) and were allowed normal cage activity until sacrifice in groups of 12 at 3, 6, 14 or 40 weeks post-injury. Eight animals in each group had both MCLs tested biomechanically while 4 animals had transmission EM investigation of midsubstance collagen fibril diameters by a standardized protocol. Results of mechanical tests showed a three- to fourfold increase in scar strength and stiffness over the intervals of healing studied while there was no change in collagen mean fibril minimum diameters. These results demonstrate no correlation between material or structural properties of scar and collagen fibril diameters in this model of healing and suggest that other mechanisms for scar mechanical improvement under these conditions must be investigated.

Animals↗
PubMed1991

A new phloroglucinol derivative from Hypericum calycinum with antifungal and in vitro antimalarial activity.

The new phloroglucinol derivative 1 has been isolated from the light petroleum ether extract of the aerial parts of Hypericum calycinum. Its structure has been established by means of 1H- and 13C-NMR spectroscopy and by nOe, MHQC, and HMBC experiments on its monomethyl ether derivative 3. Compound 1 was fungicidal against Cladosporium cucumerinum in a TLC bioassay. In addition, this new phloroglucinol derivative was also found to exert an interesting antimalarial activity in an in vitro test system.

Animals↗
PubMed1991

Responses of growth cones to changes in osmolality of the surrounding medium.

The possible involvement of osmotically generated hydrostatic pressure in driving actin-rich extensions of the cell surface was examined using cultures of chick neurons. Estimation of the excess internal osmotic pressure of chick neural tissue by vapor pressure deficit osmometry, and of the excess internal hydrostatic pressure in cultured chick neurons using a calibrated pressure pipette, gave upper limits of 10 mosM and 0.1 atmosphere (1 atmosphere = 101325 Pa), respectively. Increases in the osmolality of the medium surrounding cultured neurons by addition of sucrose, mannitol or polyethylene glycol by amounts that should eliminate any internal pressure not only failed to arrest the growth of filopodia but caused them to increase in length up to twofold in 3-5 min. Lamellipodia remained unchanged following hyperosmotic shifts of 20 mosM, but higher levels caused a small decrease in area. Reduction of osmolality by the addition of water to the culture fluid down to 50% of its normal value failed to show any detectable change in either filopodial length or lamellipodia area. These observations argue against an osmotic mechanism for growth cone extension and show that the growth of filopodia, in particular, is unlikely to be driven by osmotically generated hydrostatic pressure. In contrast to the short-term effects on growth cone morphology, the slower elongation of the neuritic cylinder showed a consistent osmotic response. Growth rates were reduced following addition of osmolytes and increased in rate (as much as sixfold) following addition of water to the culture medium.(ABSTRACT TRUNCATED AT 250 WORDS)

Actins↗
PubMed1991

Radiation dose rates from paediatric patients undergoing 99Tcm investigations.

Infants or children undergoing nuclear medicine investigations may subsequently come into close contact with nurses or parents responsible for their care. In order to estimate the radiation dose to these individuals, and to formulate appropriate recommendations, dose rates were measured at distances of 0.1, 0.5 and 1.0 m from 148 paediatric patients who had undergone one of 12 99Tcm studies. The maximum dose rates of 70, 14 and 5 microSv h-1 at these distances were not greater than the corresponding maximum values found in an earlier study of adult patients. However, the maximum dose rates per unit activity of 0.5, 0.2 and 0.1 microSv h-1 MBq-1 were greater than the corresponding maximum 99Tcm adult values, consistent with a general increase of dose rate per unit activity with decrease of body weight observed in the paediatric measurements. A parent caring for and feeding a young infant is most unlikely to receive a dose equivalent of 1 mSv, and a nurse attending to one young radioactive patient is most unlikely to receive a dose equivalent in a working day of 60 microSv. The data obtained should allow radiation doses to be estimated and appropriate recommendations to be formulated for other circumstances, including any future legislative changes in dose limits or derived levels.

Adolescent↗
PubMed1990

Intracellular signalling as a parallel distributed process.

Living cells respond to their environment by means of an interconnected network of receptors, second messengers, protein kinases and other signalling molecules. This article suggests that the performance of cell signalling pathways taken as a whole has similarities to that of the parallel distributed process networks (PDP networks) used in computer-based pattern recognition. Using the response of hepatocytes to glucagon as an example, a procedure is described by which a PDP network could simulate a cell signalling pathway. This procedure involves the following steps: (a) a bounded set of molecules is defined that carry the signals of interest; (b) each of these molecules is represented by a PDP-type of unit, with input and output functions and connection weights corresponding to specific biochemical parameters; (c) a "learning algorithm" is applied in which small random changes are made in the parameters of the cell signalling units and the new network is then tested by a selection procedure in favour of a specific input-output relationship. The analogy with PDP networks shows how living cells can recognize combinations of environmental influences, how cell responses can be stabilized and made resistant to damage, and how novel cell signalling pathways might appear during evolution.

Animals↗
PubMed1990

Chicken growth-associated protein GAP-43 is tightly bound to the actin-rich neuronal membrane skeleton.

We have identified the chicken equivalent of growth-associated protein GAP-43 in a detergent-resistant membrane skeleton from cultures of chick neurones and embryonic chick brain. Antisera to the membrane skeleton protein, the 3D5 antigen, precipitate the translation product of chick GAP-43 cDNA, and the 3D5 antigen is also detected by antisera against synthetic peptides from the known amino acid sequence of rat GAP-43. The chick protein and the rat GAP-43 are biochemically similar proteins that both serve as major targets of phosphorylation by endogenous protein kinase C. The detergent-resistant complex in which GAP-43 is found also contains actin (approximately 5% of the total protein) and a neurone-specific cell surface glycoprotein. We suggest that the membrane skeleton of neurones may be a primary site of action of GAP-43.

Actins↗
PubMed1989

Electron microscopic quantification of collagen fibril diameters in the rabbit medial collateral ligament: a baseline for comparison.

To establish a normal baseline for comparison, thirty-one thousand collagen fibril diameters were measured in calibrated transmission electron (TEM) photomicrographs of normal rabbit medial collateral ligaments (MCL's). A new automated method of quantitation was used to compare statistically fibril minimum diameter distributions in one midsubstance location in both MCL's from six animals at 3 months of age (immature) and three animals at 10 months of age (mature). Pooled results demonstrate that rabbit MCL's have statistically different (p less than 0.001) mean minimum diameters at these two ages. Interanimal differences in mean fibril minimum diameters were also significant (p less than 0.001) and varied by 20% to 25% in both mature and immature animals. Finally, there were significant differences (p less than 0.001) in mean diameters and distributions from side-to-side in all animals. These mean left-to-right differences were less than 10% in all mature animals but as much as 62% in some immature animals. Statistical analysis of these data demonstrate that animal-to-animal comparisons using these protocols require a large number of animals with appropriate numbers of fibrils being measured to detect small intergroup differences. With experiments which compare left to right ligaments, far fewer animals are required to detect similarly small differences. These results demonstrate the necessity for rigorous control of sampling, an extensive normal baseline and statistically confirmed experimental designs in any TEM comparisons of collagen fibril diameters.

Animals↗
PubMed1988

Cortical flow in animal cells.

A concerted flow of actin filaments associated with the inner face of the plasma membrane may provide the basis for many animal cell movements. The flow is driven by gradients of tension in the cell cortex, which pull cortical components from regions of relaxation to regions of contraction. In some cases cortical components return through the cytoplasm to establish a continuous cycle. This cortically located motor may drive cell locomotion, growth cone migration, the capping of antigens on a lymphocyte surface, and cytokinesis.

Actins↗
PubMed1988

Surface movements during the spreading of blood platelets.

When human blood platelets spread on a substratum they increase their surface area as much as 4-fold. We investigated the mechanism of spreading by light microscopy and by scanning and transmission electron microscopy. Contact of a platelet with a glass surface induces formation of thin extensions which spread out over the substratum. These extensions resemble the actin-containing microspikes and lammelipodia of tissue cells in culture and appear to be drawn from the peripheral cortical layer associated with the plasma membrane. If platelets are initially labeled on their external surface with cationic ferritin or lentil-conjugated gold particles and then allowed to spread, the labels are retained in the central region, or granulomere. Proteins released by the spreading platelet--fibronectin and fibrinogen--also remain in this central unspread region. Peripheral regions of spread platelet surface (hyalomere) were unlabeled following the above procedures but could be labeled with cationic ferritin or lentil-conjugated gold provided these were applied after spreading was completed. These markers are cleared with time from the periphery, moving centripetally to accumulate at the granulomere. We suggest, on the basis of these observations, that platelets spread onto a substratum by a closely similar mechanism to that used by cells such as fibroblasts. In both cases the spreading involves the peripheral actin cortex and is accompanied by a continual centripetal movement of surface components--a "membrane flow"--which continues even after spreading is completed.

Actins↗
PubMed1987

Geometry of isolated sensory neurons in culture. Effects of embryonic age and culture substratum.

Sensory neurons were dissociated from lumbar dorsal root ganglia of embryonic chick and put into culture, either directly or after removing non-neuronal cells by density gradient centrifugation. The cells were grown on culture substrata of various kinds in medium containing nerve growth factor (NGF). After 24 h the cultures were fixed, mounted and analysed. Lengths of neurites were measured, and the numbers of primary processes formed at the cell body and of growth cones were counted. From these values, the rates of growth cone advance and frequency of growth cone branching were calculated. Neuronal outgrowths increased strikingly in length and complexity with embryonic age; there was a 3.5-fold increase in total neurite length and a 3-fold increase in the number of growth cones when neurons from 15-day embryos (E15) were compared with those from 8-day embryos (E8) grown on the same substratum (glass). Growth was markedly greater on surfaces prepared with laminin or conditioned medium compared with plain glass or air-dried collagen. When E15 neurons grown on glass were compared with those grown on laminin, for example, a 2.5-fold increase in total neurite length and a 3-fold increase in the number of growth cones was observed. Calculations showed that a major factor in these changes was an increase in the frequency of growth cone branching. The number of initial processes emanating from the cell body changed with age, but not with the different substrata tested. Non-neuronal cells when present in low numbers and in contact with neurons did not appear to influence neuronal geometry in a systematic way. Our results document the fact that both external factors (in this case, the nature of the culture substratum) and intrinsic factors (stage of development of the neuron) can influence the geometry of neurite outgrowth.

Animals↗
PubMed1987

Distribution and cellular localization of actin depolymerizing factor.

Actin depolymerizing factor (ADF) is a low molecular mass (19 kD) protein that forms a tightly bound dimeric complex with actin. We have raised a rabbit antiserum to chick brain ADF and used it to analyze the distribution and cellular localization of ADF. We find that ADF is a major constituent of all chick embryonic and most adult tissues examined, accounting for 0.1-0.4% of the total protein. Some tissues have as much as 0.6 mol ADF per mole actin. Adult heart and skeletal muscle are unusual in having very low levels of ADF: less than 0.02% of the soluble protein. During the development of skeletal muscle, ADF levels are maximal up to approximately 11 d in ovo and then decline to reach their adult levels by 14 d posthatching. Brain tissue and cultured cell lines from several other vertebrates, including mammals, all possess proteins of identical size to ADF that are recognized by the ADF antiserum. No proteins are specifically recognized by the ADF antiserum in extracts from Acanthamoeba castellanii or from nerve tissue of several invertebrates. Indirect immunofluorescence shows that ADF is present throughout the cytosol of most cells and at the leading edge of ruffled membranes and in the neuronal growth cone. Its abundance and widespread distribution together with its ability to sequester actin molecules, even those in an already polymerized state, suggest that ADF is a major factor in the regulation of actin filaments in many vertebrate cells.

Actin Depolymerizing Factors↗
PubMed1987

Rapidly transported organelles containing membrane and cytoskeletal components: their relation to axonal growth.

We have examined the movements, composition, and cellular origin of phase-dense varicosities in cultures of chick sympathetic and sensory neurons. These organelles are variable in diameter (typically between 0.2 and 2 microns) and undergo saltatory movements both towards and away from the neuronal cell body. Their mean velocities vary inversely with the size of the organelle and are greater in the retrograde than the anterograde direction. Organelles stain with the lipophilic dye 1, 1'-dioctadecyl-3,3,3',3'-tetramethyl-indocarbocyanine and with antibodies to cytoskeletal components. In cultures double-stained with antibodies to alpha-tubulin and 70-kD neurofilament protein (NF-L), approximately 40% of the organelles stain for tubulin, 30% stain for NF-L, 10% stain for both tubulin and NF-L, and 40% show no staining with either antibody. The association of cytoskeletal proteins with the organelles shows that these proteins are able to move by a form of rapid axonal transport. Under most culture conditions the predominant direction of movement is towards the cell body, suggesting that the organelles are produced at or near the growth cone. Retrograde movements continue in culture medium lacking protein or high molecular mass components and increase under conditions in which the advance of the growth cone is arrested. There is a fourfold increase in the number of organelles moving retrogradely in neurites that encounter a substratum-associated barrier to elongation; retrograde movements increase similarly in cultures exposed to cytochalasin at levels known to block growth cone advance. No previously described organelle shows behavior coordinated with axonal growth in this way. We propose that the organelles contain membrane and cytoskeletal components that have been delivered to the growth cone, by slow or fast anterograde transport, in excess of the amounts required to synthesize more axon. In view of their rapid mobility and variable contents, we suggest that they be called "neuronal parcels."

Animals↗
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↗