Search PubMed⌕ Search

Biomedical subjects

D Rickwood

Publications and source records attributed to D Rickwood.

At least 37 records · Page 2Linked to original sources
PubMed1993

Evidence of surface antigen detachment during incubation of cells with immunomagnetic beads.

We have studied the attachment of immunomagnetic beads to different cells, with particular interest in cells that did not, as expected, appear to bind antibody-coated beads. Through the use of immunofluorescence and laser scanning confocal microscopy it was possible to demonstrate that beads can detach significant amounts of antigen from the surface of cells. This results in the appearance of antigen-depleted yet viable cells. Moreover, the detached antigen is found to be bound to beads and is associated with fragments of cell membrane which can also carry other (non-bead binding) cell surface proteins. After reculturing, antigen-depleted cells can recover their normal levels of surface antigen. Our results demonstrate the existence of an immunobead-induced cell membrane detachment phenomenon that can lead to the removal of all of a specific surface antigen without killing the cells, as judged by both vital staining and reculturing. An important aspect of this phenomenon is that immunoidentification of immunobead-selected populations of cells will give erroneous results. This may thus be of significance for the immunobead-based cell depletion methods that are used in medicine.

Antigens, CD↗
PubMed1993

Use of density perturbation to isolate immunologically distinct populations of cells.

Experiments have been carried out to demonstrate that, using antibody coated-Dynabeads as a model system for density labelling MOLT-4 T cells, the overall density of cells can be increased such that the cells that bind particles can be separated on isopycnic isotonic density gradients from cells that bind fewer particles. The increase in density is dependent on the cell volume and the number of particles bound. After centrifugation, cells with bound particles were found at positions in the gradient that reflected their increased density. Observed density ranges for cells with particular numbers of particles bound coincided closely with calculated expected density ranges. These results indicate the potential for separation of different subpopulations of cells on the basis of the immunological identity of the surface of cells using density perturbation methods involving antibody coated-density particles.

Cell Separation↗
PubMed1993

Ketorolac and diclofenac for postoperative pain relief following oral surgery.

A double-blind clinical study was designed to compare the efficacy and safety of intramuscular and oral ketorolac, a new non-steroidal anti-inflammatory analgesic with that of diclofenac and placebo for patients undergoing removal of impacted mandibular third molar teeth. Results showed that both analgesic preparations were more effective than placebo (p = 0.0029) and that ketorolac provided a similar degree of pain relief to that of diclofenac. It is concluded that ketorolac is important new addition to the available intra-muscular NSAID preparations.

Acetaminophen↗
PubMed1992

Differentiation-related changes in quantitative binding of immunomagnetic beads.

Experiments have been carried out to demonstrate that cell viability and phenotypic characteristics are not affected by exposure to constant magnetic fields or growth in the presence of Dynabeads. This paper also demonstrates that the changes in the surface concentration of the antigens, SSEA-1 (stage-specific embryonic antigen-1) and histocompatibility antigen (MHC H2-Db) during differentiation as determined by flow cytometric analysis, are mirrored by changes in the numbers of bound immunomagnetic particles (Dynabeads) targeted with monoclonal antibodies to these cell surface antigens. These results clearly indicate that the numbers of beads bound to cells reflect the numbers of specific surface antigens present on the cells.

Animals↗
PubMed1991

A centrifugation method for the isolation of plasmid DNA without the use of an ultracentrifuge.

This paper describes the use of a high-performance high-speed centrifuge, a Sorvall RC-28S, for the preparation of plasmid DNA using standard CsCl-ethidium bromide gradients. If the sample is layered into the bottom of the gradient, the plasmid DNA can be banded in 24 hours; this is comparable with the time required for ultracentrifuge separations. Alternatively, plasmids can be banded in a fixed-angle rotor in 36 hours when the sample is mixed throughout the gradient solution.

Centrifugation↗
PubMed1990

A new one-step method for the isolation of human mononuclear cells.

This paper describes a radical new, one-step method for the routine isolation of the mononuclear cells from human blood in high yield and purity. In this procedure the blood sample is mixed with a Nycodenz separation medium prior to centrifugation. Erythrocytes and polymorphogranulocytes are pelleted during centrifugation leaving the mononuclear cells in the supernatant. The method can be used for a wide range of blood sample volumes and can be carried out with greater ease than the currently accepted methods.

Cell Separation↗
PubMed1990

A new, rapid, one-step method for the isolation of platelets from human blood.

We describe a new, rapid method for the isolation of platelets from human blood using a single centrifugation step through Nycodenz, an inert, nontoxic, nonionic medium. As judged by aggregation and nucleotide release studies, the platelets are recovered in high yield and in excellent functional condition.

Adenosine Diphosphate↗
PubMed1990

Isolation of the major subcellular organelles from mouse liver using Nycodenz gradients without the use of an ultracentrifuge.

Commonly, subcellular organelles such as nuclei, mitochondria, lysosomes, and Golgi membranes are isolated first by differential centrifugation in low-speed or high-speed centrifuges and then purified by gradient centrifugation in ultracentrifuges. We have prepared these organelles using a new high-speed centrifuge (28,000 rpm max) which allows the generation of higher radial centrifugal forces (rcfs) than are available in standard machines. We have shown that most subcellular organelles can be purified by using low-viscosity Nycodenz gradients at rcfs lower than those normally used in ultracentrifuges, without increasing the time of centrifugation. Use of Nycodenz also allows rapid harvesting of material from gradients and we have adapted a number of enzyme assays to facilitate gradient analysis.

Animals↗
PubMed1989

Effect of DNA conformation on the transcription of mitochondrial DNA.

The importance of the conformation of the DNA template for in vitro transcription experiments was investigated using a mitochondrial RNA polymerase preparation from Xenopus laevis oocyte mitochondria. A premature termination transcription assay has been devised and the levels of the formation of transcriptional complexes have been identified using agarose gel electrophoresis. It was found that accurate initiation of transcription from in vivo promoter sequences was enhanced by supercoiling and that the two mitochondrial DNA-binding proteins, previously characterized by us, inhibited the transcription of DNA as gauged by these assays.

Animals↗
PubMed1988

The Xenopus laevis mitochondrial protein mtDBP-C cooperatively folds the DNA in vitro.

The binding of the Xenopus laevis mitochondrial protein mtDBP-C to DNA was studied by equilibrium density banding, agarose gel electrophoresis and electron microscopy. The results obtained show that the mtDBP-C binds cooperatively to DNA irrespective of whether the DNA is supercoiled, relaxed or linear and it induces the formation of superhelical turns locally leading to the formation of a highly folded structure. It appears that this protein could be involved in the compaction of DNA in the mitochondrial nucleoid.

Animals↗
PubMed1988

Assessment of methods for covalent binding of nucleic acids to magnetic beads, Dynabeads, and the characteristics of the bound nucleic acids in hybridization reactions.

Dynabeads are magnetic monosized beads with high stability, high uniformity, unique paramagnetic properties, low particle-particle interaction, and high dispersibility. Different reactive groups; hydroxyl, carboxyl and amino groups can be attached to the surface. Several methods for covalent attachment of DNA or oligonucleotides to the beads were investigated. Best coupling yields were obtained by carbodiimide-mediated end-attachment of 5'-phosphate and 5'-NH2 modified nucleic acids to respectively amino and carboxyl beads. The carboxyl beads showed a low degree of non-specific binding, while a better yield of end-attached nucleic acids was obtained using the amino beads. The DNA-beads worked efficiently in hybridization experiments, and the kinetics of hybridization approach those of solution hybridization.

Chemical Phenomena↗
PubMed1987

A rapid method for the preparation of the neutrophil fraction of granulocytes from human blood by centrifugation on isotonic Nycodenz gradients.

A rapid method for the preparation of neutrophils of the granulocyte fraction of human blood is described. A leucocyte-rich fraction is loaded onto preformed isotonic Nycodenz gradients, formed by mixing a stock isotonic Nycodenz solution with a NaCl diluent solution. After low speed centrifugation a neutrophil fraction of high viability, yield and purity can be isolated from the gradients.

Cell Separation↗
PubMed1986

Characterisation of RNA polymerase activity in yeast mitochondria.

This paper reports on the optimal incubation conditions for in vitro transcription in isolated yeast mitochondria. The mitochondrial RNA polymerase has an absolute requirement for all four nucleoside triphosphates and Mg2+. The enzyme is inhibited by Mn2+, Ca2+, Cd2+ and KCl while low concentrations of NaCl stimulate activity. Transcription is maximal in Tris/HCl buffer at pH 7.9 and the optimum incubation temperature is 28 degrees C.

Cations, Divalent↗
PubMed1986

A new method of representing DNA sequences which combines ease of visual analysis with machine readability.

A new method of representing DNA sequences has been devised which is termed stave projection. Compared with other formats for showing the base sequences of DNA, this method greatly enhances the ease of visual analysis of the sequences of bases and it is also in a machine readable form. Using this method it is possible to identify and annotate all of the functional features found in DNA sequences.

Base Sequence↗
PubMed1986

Social support, dementia and depression among the elderly living in the Hobart community.

In a community sample of the elderly (N = 274) in Hobart, Tasmania, cases of dementia and depression were ascertained by the Canberra Geriatric Mental State and the Mini Mental State Examination. Social relationships and support were examined by means of the Interview Schedule for Social Interaction. The elderly had fewer social relationships than younger adults, but were more content with what they did have. Elderly women had more affectional ties than elderly men. The presence of offspring in the same town increased the number of close ties and of social relationships, but was more important for men than for women. Persons with cognitive impairment or an established dementia reported that they had less social interaction than they would like. Depressed subjects reported having markedly less social interaction than the mentally healthy elderly, but did not complain that it was too little. This study provides a systematic description of the social environment of the elderly, both in mental health and in states of depression or impaired cognition.

Aged↗
PubMed1985

Major changes in phosphorylation of chromatin-associated non-histone proteins accompany development in the slime mould Dictyostelium discoideum.

Striking changes in protein and RNA synthesis were shown to accompany development in the slime mould Dictyostelium discoideum. These changes are, at least in part, directly attributable to control at the level of transcription. Analysis of nuclear proteins and their states of phosphorylation by two-dimensional gel electrophoresis and autoradiography showed only minor changes in the species of proteins detectable by Coomassie Blue staining during the vegetative growth and development phases. Major changes, however, were detected in their patterns of phosphorylation, with major differences from the vegetative pattern occurring during both early development (0-2h) and late development (8-12h). These changes coincide with major changes in polypeptide synthesis and in nuclear and cytoplasmic RNA complexity.

Cell Differentiation↗
PubMed1985

Characterization of DNA-protein complexes from the mitochondria of Xenopus laevis oocytes.

Mitochondrial DNA (mtDNA)-protein complexes (nucleoids) from Xenopus laevis oocytes were purified either on rate-zonal sucrose or isopyknic metrizamide gradients. From electron microscopic studies and staphylococcal nuclease digestion experiments mtDNA appears to be packaged into regular beaded structures. Protein electrophoretic analysis and M banding results show that mtDNA is associated with the membrane structures and also with few specific proteins including one acid-soluble polypeptide of 28 kD.

Animals↗