Top-site adsorption for potassium on Ni(111).
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Journal Article↗
Biomedical subjects
D Fisher
Publications and source records attributed to D Fisher.
Heterogeneity in the circulating neutrophil pool: studies on subpopulations separated by continuous flow electrophoresis.
Isolated blood neutrophils from healthy individuals have been separated by continuous flow electrophoresis (CFE) as a Gaussian-shaped profile extending over 12-15 fractions, on the basis of differences in cell surface electrical charge. The fractions were pooled into three or four subpopulations; the mean electrophoretic mobilities of the least and most electronegative cells were 0.96 and 1.22 microns/sec/V/cm, respectively. Each pool of neutrophils was analyzed for functional and biochemical differences. Expression of respiratory burst in terms of the rate of superoxide production by the least and most electronegative cells to fixed concentrations of N-formyl-methionyl-leucyl-phenylalanine (fMLP, 10(-7) M) or phorbol myristate acetate (PMA, 1 microgram/ml) revealed that the least electronegative cells generated superoxide anion (O2-) at approximately twice the rate of the most electronegative cells. However, when lower concentrations of fMLP were used (1-5 x 10(-9) M), the most electronegative cells were most active. The least electronegative cells were also the most active in terms of phagocytosis and chemotaxis. In accordance with these differences in motile function, the basal F-actin content of the least electronegative cell pool was greater than the F-actin levels found in the most electronegative cells and remained so upon stimulation with fMLP. Such neutrophil heterogeneity as detected by CFE may be important in selective margination and recruitment of cells to inflammatory foci and sites of infection and may in part represent subsets of cells within the circulation that are primed in vivo to respond to inflammatory stimuli.
Actins↗
Effect of intravenous and oral omeprazole on 24-hour intragastric acidity in duodenal ulcer patients.
Nine patients with duodenal ulcer were on separate occasions given omeprazole, 20 mg orally, 10 mg intravenously (IV), and 40 mg IV once daily for 5 days. On day 1, the median reduction of 24-hour intragastric acidity was 42.2% for the 20-mg oral dose and 54.8% and 88.4% for the two IV doses, respectively, but the between-patient variability was considerable for all three doses. On day 5, the degree of reduction had increased for all three doses to a median value of 99.9% for the 20-mg oral dose and 95.7% and 99.9% for the two IV doses, respectively. Plasma omeprazole concentrations increased significantly from day 1 to day 5 only for the 20-mg oral and 40-mg IV doses. Thus, the increased pharmacological effect of omeprazole during repeated once daily administration can only partly be explained by increased plasma concentrations, suggesting that some additional factor(s) must influence the degree of reduction of 24-hour intragastric acidity. Thus, when determining the optimal dose of omeprazole for acid inhibition, the route and duration of administration must be taken into consideration; after 5 days of once-daily administration of doses as low as 10 mg IV and 20 mg orally are effective and dependable in reducing 24-hour intragastric acidity in patients with duodenal ulcer. However, a daily dose of 40 mg IV omeprazole is not sufficient to keep intragastric pH above 4 in all patients during the first day of treatment.
Administration, Oral↗
Successful resuscitation of a cold water submersion victim with the use of cardiopulmonary bypass.
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Cardiopulmonary Bypass↗
Early state organization and follow-up over one year.
Evaluations of state organization at 36 weeks postconceptional age (PCA) were conducted in the special care nursery on 24 low birth weight preterm neonates who were subsequently assessed on three dimensions of outcome at 1 year postterm. Half the subjects (N = 12) had been cared for in an alternative supportive nursery from 32 to 36 weeks PCA; the other half had remained in the regular intermediate care nursery. Although subjects from the alternative nursery demonstrated superior state organization before nursery discharge at 36 weeks PCA (p less than .05), they were not superior on any outcome measures at 1 year postterm. Subjects demonstrating superior state organization within their nursery group were compared with subjects demonstrating inferior state organization within their nursery group. Significant differences in 1-year outcome were found between these two groups of good and poor neonatal state organizers on gross morbidity, on the Bayley motor scale, and on a measure of recovery of state organization observed in the Strange Situation (p less than .05).
Adaptation, Psychological↗
Polyethylene glycol (PEG) modification of granulocyte-macrophage colony stimulating factor (GM-CSF) enhances neutrophil priming activity but not colony stimulating activity.
PEG-modified proteins have numerous advantages over their unmodified counterparts (increased half life, reduced antigenicity, improved solubility), but almost without exception, they show a modest to marked reduction in biological or enzymatic activity. However, while investigating a new protocol for the preparation of PEG-proteins, we compared PEG-modified and unmodified GM-CSF with respect to their polymorphonuclear neutrophil granulocyte (PMN) priming activities. PEG-GM-CSF was unexpectedly more active than GM-CSF in its ability to prime neutrophils to respond to the synthetic peptide n-formyl-methionyl-leucyl-phenylalanine (FMLP) with an oxidative burst (assessed both by nitroblue tetrazolium reduction and ferricytochrome c reduction). These results were in contrast to the findings for colony stimulating activity and with GM-CSF induced thymidine uptake, where the biological activity was unchanged or reduced. The enhanced neutrophil priming activity of PEG-GM-CSF was confirmed using FPLC fractionated PEG-modified GM-CSF. This showed changes in the bioactivity profile consistent with both the shift in protein elution profile and enhanced activity of the PEG-modified material (reflected in the increased area under the bioactivity curve). We also excluded a neutrophil priming action for PEG-modified fetal calf serum proteins, carrier proteins and 'irrelevant' cytokine, erythropoietin. The dissociation of the two bioactivities was confirmed using individual FPLC fractions. These results suggest the presence of differences in either binding, receptor/ligand processing or signal transduction for neutrophils versus progenitors, that are differentially affected by PEG-modification of GM-CSF. The demonstration that PEG-modification can partially dissociate two biological activities suggests the feasibility of using PEG-modification to produce proteins with subtly altered spectra of biological activity and hence new ranges of clinical applications.
Cells, Cultured↗
Red cell aplasia caused by human parvovirus B19 in acute leukaemia.
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Adolescent↗
The uses and properties of PEG-linked proteins.
Poly(ethylene glycol) (PEG) is a water soluble polymer that when covalently linked to proteins, alters their properties in ways that extend their potential uses. PEG-modified conjugates are being exploited in many different fields. The improved pharmacological performance of PEG-proteins when compared with their unmodified counterparts prompted the development of this type of conjugate as a therapeutic agent. Enzyme deficiencies for which therapy with the native enzyme was inefficient (due to rapid clearance and/or immunological reactions) can now be treated with equivalent PEG-enzymes. PEG-adenosine deaminase has already obtained FDA approval. PEG-modified cytokines have been constructed and, interestingly, one of the conjugates, PEG-modified granulocyte-macrophage colony-stimulating factor, showed dissociation of two biological properties. This novel observation may open new horizons to the application of PEGylation technology. The biotechnology industry has also found PEG-proteins very useful because PEG-enzymes can act as catalysts in organic solvents, thereby opening the possibility of producing desired stereoisomers, as opposed to the racemic mixture usually obtained in classical organic synthesis. Covalent attachment of PEG to proteins requires activation of the hydroxyl terminal group of the polymer with a suitable leaving group that can be displaced by nucleophilic attack of the epsilon-amino terminal of lysine residues (other nucleophilic groups can also interact). Several chemical groups have been exploited to activate PEG, thereby giving rise to a variety of PEG-proteins. Some of these varieties retain part of the activating group as a coupling moiety between PEG and protein and others provide a direct linkage. For each particular application, different coupling methods provide distinct advantages.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
Polyethylene glycol (PEG)-modified granulocyte-macrophage colony-stimulating factor (GM-CSF) with conserved biological activity.
Polyethylene glycol (PEG) modification improves the pharmacological properties of proteins, usually extending plasma half-life and concomitantly increasing in vivo bioactivity, reducing both antigenicity and immunogenicity, and increasing solubility and resistance to proteolysis. Despite these established benefits, few PEG proteins are in use. Current coupling methods are either traumatic for the protein or involve lengthy and difficult procedures to activate monomethoxyPEG (MPEG). We have applied a new coupling method that allows coupling of MPEG directly to proteins under physiological conditions. Using this method with recombinant human (rh)granulocyte-macrophage colony-stimulating factor (GM-CSF) we were able to construct biologically active PEG-GM-CSF. Fast protein liquid chromatography (FPLC) and phase-partitioning confirmed the presence of PEG modification, and the former was used to fractionate modified and unmodified material. Bioactivity was measured in colony assays of normal human bone marrow cells and by tritiated thymidine uptake (of chronic myeloid leukemia cells and TF-1 cells). With both uptake and colony assays, using unfractionated material, we observed only a modest reduction in biological activity. Assays of FPLC-fractionated material confirmed that much of the bioactivity of the PEG-GM-CSF preparations was due to the modified species and any residual unmodified GM-CSF. Species uncontaminated by tresylmonomethoxyPEG (TMPEG; which was somewhat inhibitory in the thymidine uptake assay and eluted over a broad region of the FPLC profile) had no significant reduction in activity, but we cannot rule out the possibility that PEG-GM-CSF species eluting elsewhere in the profile had modest reduction of activity. Subcutaneous injection into mice confirmed the anticipated improved half-life in vivo and demonstrated a longer uptake from the injection site. This is, as far as we are aware, the first successful construction of PEG-GM-CSF with conserved biological activity.
Animals↗
Fractionation of human neutrophils into subpopulations by countercurrent distribution: surface charge and functional heterogeneity.
Isolated blood neutrophils from normal healthy subjects were separated into fractions by sequential countercurrent distribution (CCD) in a charge-sensitive dextran/polyethylene glycol aqueous phase system. The neutrophils separated as a broad profile, and in a charged phase procedure the separation was based upon differences in cell surface electrokinetic properties, as confirmed by electrophoretic mobility measurements of fractions across the profile using analytical cytopherometry. The CCD cell fractions were generally pooled as three or four major subfractions for analysis of functional and metabolic differences. These included measurements of chemotaxis, phagocytosis, and respiratory burst. An inverse relationship was found between the electrophoretic mobility (EPM) of the subfraction pools and their functional competence, with the less electronegative cell fraction pools often as much as 2 to 3-fold more active than the more electronegative pools. This demonstration of electrokinetic and functional heterogeneity in 'resting' neutrophil subpopulations separated by CCD may reflect changes during their sojourn in the circulation that determine selective margination and recruitment of cells to inflammatory foci and sites of infection.
Cell Separation↗
A method for the purification of DNA/protein complexes applied to DNA topoisomerase II cleavage sites.
The object of this study was to devise a purification method for DNA/topoisomerase II complexes, with which to examine the enzyme's cleavage site specificity in cellular differentiation. Retinoic acid-induced differentiation involves topoisomerase II-mediated transient changes in DNA supercoiling, but it is not known whether this occurs at specific sites in the genome. Topoisomerase II forms a covalent DNA enzyme complex as it acts, which can be recovered by the sodium dodecyl sulfate (SDS)/KCl precipitation method, but this method fails to recover significantly more DNA from cells induced to differentiate. This may in part reflect the low numbers of retinoic acid-induced protein-linked breaks in DNA and also the method's relative inefficiency for DNA with few attached topoisomerase molecules. This suggested that an additional purification method would be required to enrich sufficiently for cleavage site DNA to address the issue of site specificity. The principle of our method is to couple poly(ethylene glycol) (PEG) to topoisomerase while it is covalently attached to DNA and then to use phase partitioning in an aqueous two-phase system of PEG and phosphate to separate free DNA from DNA bound to PEG-modified topoisomerases (which have high affinities for the phosphate-rich and PEG-rich phases, respectively). The method can be used in conjunction with DNase protection and, unlike the SDS/KCl method, can fractionate short fragments of DNA to which single protein molecules are attached. Using the SDS/KCl precipitation and new method in series, we have recovered protein-linked DNA from HL60 cells induced to differentiate to the granulocyte lineage (by retinoic acid) or to the monocyte/macrophage lineage (by phorbol myristate acetate) and have demonstrated that specific sequences become protein linked, probably to topoisomerase II, during induced differentiation.
Chemical Fractionation↗
Influence of surface hydrophilicity of liposomes on their interaction with plasma protein and clearance from the circulation: studies with poly(ethylene glycol)-coated vesicles.
Well-defined liposome systems have previously established the influence of size, surface charge lipid composition and surface ligands, on in vivo fate and behaviour of model compounds entrapped in liposomes. In the present study, preformed liposomes which quantitatively retain aqueous markers were covalenty coupled via dipalmitoylphosphatidyl-ethanolamine, to the hydrophilic polymer, monomethoxypoly(ethylene glycol) (MPEG 5000). Such liposomes retain the coating in the presence of plasma, and appear to adsorb plasma components more slowly than liposomes without the polymer, shown using an aqueous two-phase partitioning technique. MPEG-coupled liposomes were cleared from the blood circulation up to 30% more slowly than liposomes without MPEG after intravenous administration to mice, despite the unmodified liposomes being of a composition and size shown previously to favour achievement of maximum half-life. It is suggested that the polymer acts as a surface barrier to plasma factors which otherwise bind to liposomes in the blood and accelerate vesicle removal.
1,2-Dipalmitoylphosphatidylcholine↗
Separation of cell mixtures by immunoaffinity cell partitioning: strategies for low abundance cells.
The partitioning of cells in aqueous two-phase systems formed by poly(ethylene glycol) (PEG) and dextran can be changed by incubating the cells with a PEG-modified antibody directed specifically against its surface. We have developed a new approach for immunoaffinity cell partitioning (IACP) in which the antibodies are first reacted with tresylated monomethoxy PEG (TMPEG) in sodium phosphate buffer, pH 7.5, the excess TMPEG is quenched by reaction with bovine serum albumin, and the resulting preparation is used directly for incubation with the cells without any isolation of the monomethoxyPEG (MPEG)-antibody conjugates. We have demonstrated the specificity of this IACP method by showing that MPEG-modified anti-human red blood cell antibody increases the partition of human erythrocytes from the interface to the PEG-rich top phase (up to 100%) but not the partitioning of either neutrophils or HL60 cells. Irrelevant antibodies do not affect the partitioning of red blood cells. The partitioning behaviors of erythrocytes and HL60 cells in mixtures varying from 75 to 10% red blood cells subjected to IACP are similar to those of the pure cell population, i.e., erythrocytes ca. 100% and HL60 cells 3% in top phase. Thus, the population of erythrocytes can be almost completely extracted into the top phase in a single step. The contaminant cells represent only a small percentage (less than 5% in most of the cases) of the cell mixture recovered in top phase. Both cell populations can be completely separated by countercurrent distribution (CCD).(ABSTRACT TRUNCATED AT 250 WORDS)
Antibody Affinity↗
Radiolabeled antibody therapy of human B cell lymphomas.
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Antibodies, Monoclonal↗
Closed-wound drainage systems. The Solcotrans Plus versus the Stryker-CBC ConstaVAC.
Ninety-six patients (63 females and 33 males) who underwent total joint arthroplasty or spinal reconstructive surgery were randomized to receive either a Solcotrans Plus or a Stryker-CBC ConstaVAC closed-wound drainage system. A binomial test showed that the Stryker-CBC ConstaVAC system was significantly preferred over the Solcotrans Plus system for ease of use, as reported by nurses. However, Solcotrans Plus was more cost-effective because a larger volume of blood shed by a patient could be reinfused while maintaining the standards of the American Association of Blood Banks. The difference in the occurrence of side effects between the two systems was not statistically significant.
Adolescent↗
On the relation between surface area and partitioning of particulates in two-polymer aqueous phase systems.
Partitioning in dextran-poly(ethylene glycol) aqueous two-phase systems is an established method for the separation of biomaterials. Size and surface properties are generally regarded as parameters which contribute to the determination of the materials' partition coefficients, K. While molecular weight or surface area can be one of the determinants of the K value of biomaterials in the size range of macromolecules to very small particulates (e.g. some viruses), partitioning liposomes of identical surface properties and different but distinct sizes indicate that surface areas greater than about 0.2 microns 2 do not affect the K value obtained. Analysis of available partitioning data of much larger particulates (i.e. cells) reveals that surface properties per unit area outweight surface area per se in determining the K value in non-charge-sensitive, charge-sensitive and biospecific affinity phase systems.
Animals↗
High dose radiolabeled antibody therapy of lymphoma.
A trial has been initiated testing the effects of high dose radiolabeled monoclonal antibody administered in conjunction with marrow transplantation for treatment of lymphoma. This study is based on observations in mice demonstrating that radiolabeled antibody against a normal lymphocyte-associate antigen can induce regression of lymphoma masses. These preclinical studies also showed that large amounts of antibody are needed to achieve adequate biodistribution in vivo and that potentially curative doses of radionuclide induce substantial hematopoietic toxicity. Consequently, in patients with recurrent lymphoma, we are first evaluating the influence of dose on the biodistribution of a pan B-cell antibody, MB-1 (anti-CD37). In four patients, the biodistribution studies indicated that at the highest amount of antibody tested 131I-labeled antibody MB-1 (10 mg/kg) could deliver more radiation to tumor than to normal organs. These patients were treated with antibody MB-1 labeled with 250 to 482 mCi 131I estimated to deliver 380 to 1570 cGy to normal organs and 850 to 4260 cGy to tumor. Myelosuppression occurred in all patients and required infusion of cryopreserved marrow in one patient. Complete tumor regressions were observed in each patient. In three other patients with splenomegaly and/or large tumor burden, biodistribution studies indicated that 131I-labeled antibody could not deliver more radiation to tumor than to normal organs and these patients were not treated. Thus, tumor burden and spleen size may determine the feasibility of treatment with radiolabeled antibody. Treatment with this antibody labeled with high doses of 131I was well tolerated and may prove therapeutically useful. These studies are being continued to determine the maximal doses of radiation that can be tolerated by nonhematopoietic tissues after infusion of 131I-labeled antibody.
Animals↗
Measuring blood pressure in the elderly: does atrial fibrillation increase observer variability?
OBJECTIVE: To compare the interobserver and intraobserver variability of blood pressure measurements in geriatric patients in atrial fibrillation and in sinus rhythm. DESIGN: Prospective assessment of blood pressure measurements carried out in random order in two groups of elderly patients by five doctors unaware of the aims of the study. SETTING: Acute assessment wards for geriatric medicine, Cardiff Royal Infirmary. PATIENTS: 50 Elderly patients in sinus rhythm and 50 in atrial fibrillation. MAIN OUTCOME MEASURES: Interobserver and intraobserver variability of blood pressure measurements in the two groups expressed as the coefficient of variability and compared by the Mann-Whitney U test. RESULTS: Interobserver variability was significantly greater in the patients with atrial fibrillation for both systolic and diastolic pressures. Intraobserver variability was significantly greater in the atrial fibrillation group for diastolic pressures but the difference was not significant for systolic pressures. These differences were not related to pulse rate, age, or level of blood pressure. CONCLUSIONS: The findings suggest that in the presence of atrial fibrillation physicians' interpretations of Korotkoff sounds are less uniform, which may have important clinical implications. Possibly a standardised methodology may overcome this problem.
Aged↗