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Biomedical subjects

D Rickwood

Publications and source records attributed to D Rickwood.

At least 19 recordsLinked to original sources
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↗
PubMed1978

Isolation and partial characterization of a mitochondrial deoxyribonucleic acid-protein complex from sea urchin embryos.

Lysis of mitochondria from sea urchin embryos with Triton X-100 led to a complete conversion of DNA-containing mitochondrial residues into protein-DNA complex with a density higher than 1.22 g/cm3 in sucrose solutions. This complex banded isopycnically in metrizamide gradients at a density of 1.26 g/cm3. Exposure to mixtures of Triton X-100 with Tween 80 resulted in progressively less delipitated and disorganized mitochondria over Tween/Triton weight ratios from 1 to 2, with the retention of the starting buoyant density in sucrose of approximately 1.16 g/cm3 at Tween/Triton ratios above 2.5. The DNA-internal protein complex sedimented with the bulk of the surviving mitochondrial structure under all conditions studied. No free DNA could be detected under any conditions of membrane removal.

Animals↗
PubMed1978

The isolation and partial characterization of low-molecular-weight phosphorylated component of the non-histone proteins of mouse nuclei.

After labelling of mouse liver nuclei with [gamma-32P]ATP in vitro, 10-20% of the radioactivity incorporated into the saline-soluble nuclear and HAP2 chromatin fractions was located in a low-molecular-weight component (component 10) with pI near 4.5 in urea. By using combinations of ion-exchange chromatography, preparative thin-layer isoelectric focusing and gel filtration, this component was isolated from both nuclear fractions. Recovery from the saline-soluble fraction was poor under conditions that allow endogenous phosphatases to be active. Component 10 was shown to be a phosphoprotein on the basis of enzyme-digestion experiments and the detection of phosphoserine and phosphothreonine. The 32P radioactivity did not appear to be associated with phosphorylated basic amino acids. Its molecular weight was determined by gel chromatography and electrophoresis in sodium dodecyl sulphate/polyacrylamide gels as approx. 10000, and tryptic digestion of the reduced carboxymethylated protein in urea yielded two 32P-labelled peptides. It has not been possible as yet to assign a function to component 10, though its similarity to other low-molecular-weight acidic proteins is discussed.

Amino Acids↗
PubMed1978

Studies of Epstein-Barr virus (EBV)-associated nuclear antigen: solubilization from Raji cell chromatin with 5 M-urea-2 M-nacl and fractionation on hydroxyapatite.

EBNA-containing chromatin from Raji cells was solubilized by treatment with high concentrations of urea and salt and fractionated by hydroxyapatite chromatography. Fractions eluting at different phosphate concentrations were analysed for the presence of EBNA by means of an anti-EBNA-specific 125I-labelled IgG absorption assay. The antigen was found in fractions containing non-histone chromatin proteins.

Antigens, Viral↗
PubMed1977

The modification of nuclear proteins by ADP-ribosylation.

When incubated in vitro purified mouse nuclei incorporate NAD into poly(ADP-Rib). Analysis of the product on CsDl/urea gradients showed that a large proportion of the poly(ADP-Rib) was not attached to protein. The free poly(ADP-Rib) did not appear to arise through degradation and its chain length was significantly longer than the poly(ADP-Rib) attached to proteins. Fractionation of the proteins on hydroxyapatite revealed that tissue-specific modification of both the histones and non-histone proteins, had occurred. In the case of one protein species there was evidence for the existence of several forms with different numbers of ADP-Rib residues.

Animals↗
PubMed1977

Solubilisation of Epstein-Barr virus (EBV)-associated nuclear antigen from Raji cells and chromatin by treatment with various molarities of NaCl.

The solubilisation of Epstein-Barr virus (EBV)-associated nuclear antigen (EBNA) by treatment with various molarities of NaCl was investigated using the 125I--IgG absorption assay. Ninety percent of the antigenic activity detected using the 125I--IgG absorption assay was insoluble at 0.15 M NaCl. It could be rendered soluble by treatment with 2.0 M NaCl, but reprecipitated upon return to 0.15 M NaCl. EBNA was partially extracted from Raji chromatin by treatment with 0.35 M NaCl. The efficiency of extraction was increased by homogenisation in 2.0 M NaCl followed by dialysis to 0.35 M NaCl. The data demonstrate the close association of EBNA with Raji chromatin and suggest that it may be a chromatin-associated non-histone protein.

Antigens, Viral↗
PubMed1975

Improved techniques for the fractionation of non-histone proteins of chromatin on hydroxyapatite.

The effect of the dissociation medium on the fractionation of chromatin on hydroxyapatite has been studied. Optimal separations of the histones and non-histone protein are only achieved when columns are run in buffers containing high concentrations of sodium ions. We have modified our previously published method such that the chromosomal proteins can be recovered in virtually quantitative yields. Each of the hydroxyapatite fractions has been analysed with respect to nucleic acid content and the proteins have been analysed by two-dimensional gel electrophoresis.

Animals↗