Biomedical subjects

C Dolman

Publications and source records attributed to C Dolman.

8 recordsLinked to original sources

PubMed2005

International collaborative study to evaluate a candidate reference preparation to define an appropriate specified limit of anti-D in intravenous immunoglobulin products.

BACKGROUND AND OBJECTIVES: The aim of the study was to evaluate a lyophilized intravenous immunoglobulin (IVIG) preparation containing anti-D (02/228; nominal reciprocal titre of 8) for its suitability to define the maximum limit of anti-D in IVIG products when used in a proposed reference method of direct haemagglutination of papain-treated erythrocytes, in an international collaborative study. MATERIALS AND METHODS: Twenty laboratories tested 02/228 along with a negative control IVIG preparation and four IVIG samples containing different levels of anti-D. Nineteen laboratories performed direct haemagglutination methodology using papain-treated erythrocytes; five of these laboratories and one additional laboratory performed their in-house haemagglutination methodology (all indirect antiglobulin tests). RESULTS: The mode titre of 02/228, obtained by using the proposed reference method, was 8 (62.5% of tests). However, there was wide variation in haemagglutination titres between laboratories for three of the four samples. Correcting the titres of the samples relative to those of the proposed reference preparation reduced the interlaboratory variability and increased the frequency of the mode titres in three out of four samples. The indirect antiglobulin tests also showed wide interlaboratory variability and were less sensitive than the direct method in four laboratories. Eleven of the 14 laboratories that expressed an opinion considered that the level of anti-D in 02/228 was appropriate to define a specified limit. CONCLUSIONS: Our results demonstrate the necessity of using a reference preparation to define the maximum level of anti-D in IVIG products and ensure sufficient sensitivity in haemagglutination testing methodology. On the basis of these results, members of the European Pharmacopoeia Expert Group 6B recommended revision of the appropriate monograph to include this new specification and test. The Food and Drug Administration in the USA intends to adopt the same maximal specification defined by the reference preparation and to recommend the same test for the safety of IVIG products. Preparations 02/228 and 02/226 were also established by the World Health Organization as International Reference Reagents to standardize haemagglutination testing for anti-D in normal IVIG products.

Cooperative Behavior↗

PubMed2001

Enhanced efficacy of anti-D immunoglobulin for treating ITP is not explained by higher immunoglobulin polymer content.

Several reports have suggested that low dose anti-D immunoglobulin is superior to high dose immunoglobulin for treatment of idiopathic thrombocytopenia purpura (ITP). However, some findings suggest that it is not the anti-D activity per se that is responsible for efficacy for treatment of ITP with anti-D immunoglobulin. Amongst alternative explanations for the mechanism of action is a relatively higher immunoglobulin polymer content of anti-D compared to other immunoglobulin products, which is more efficient in causing reticuloendothelial Fc receptor blockade. In order to investigate this we have evaluated the polymeric IgG content of anti-D and other immunoglobulin products. Different products showed considerable variation in immunoglobulin polymer content. There was no clear correlation between aggregate or dimer content and product type and anti-D as a class of product did not contain higher amounts of either dimer or aggregate compared to other products. Some manufacturers' products increased in polymer content on storage, but others did not show this effect. Therefore, higher immunoglobulin dimer and/or aggregate content cannot explain the increased efficacy of anti-D immunoglobulin for treatment of ITP. The role of polymeric Ig in efficacy for treatment of ITP is unclear.

Biopolymers↗

PubMed2000

Neutralizing antibodies to granulocyte-macrophage colony-stimulating factor, interleukin-1alpha and interferon-alpha but not other cytokines in human immunoglobulin preparations.

Human immunoglobulin preparations are used therapeutically for various disorders. Such therapy is generally safe but adverse effects occasionally occur in recipients. It has been suggested that antibodies to cytokines present in clinical immunoglobulin products may contribute to undesirable effects in recipients. Therefore, we investigated intravenous and intramuscular immunoglobulin products for the presence of cytokine-specific neutralizing antibodies. Using validated bioassays, we detected neutralizing activity against human granulocyte-macrophage colony-stimulating factor (GM-CSF), interferon-alpha2a (IFN-alpha2a) and interleukin-1alpha (IL-1alpha) in immunoglobulin products. We found no neutralization of granulocyte colony-stimulating factor, macrophage colony-stimulating factor, stem cell factor, IL-1beta, IL-2, IL-3, IL-4, IL-6, IL-9, IL-10, IL-12, tumour necrosis factor-alpha, oncostatin M (OSM) and IFN-gamma. Most batches which neutralized IFN-alpha2a activity also neutralized other IFN-alpha subtypes, IFN-omega and IFN-beta. Most products (94%) neutralized the biological activity of GM-CSF. No correlation between batches and their ability to neutralize bioactivities of GM-CSF, IFN-alpha2a and IL-1alpha was found. This neutralizing activity could be traced to plasma pools used for manufacture of immunoglobulins. The neutralization was mediated by specific cytokine antibodies contained within immunoglobulin products as it was present in specific immunoglobulin G (IgG) fractions eluted from cytokine affinity chromatography columns. Specific binding of such IgG fractions to cytokines in immunoblots and in enzyme-linked immunosorbent assays (ELISAs) was observed. This contrasts with the broad non-specific recognition of cytokine proteins observed using unfractionated immunoglobulins in ELISAs. This is the first comprehensive study showing the presence of neutralizing antibodies against GM-CSF, IL-1alpha, or IFN-alpha2a in immunoglobulin products.

Antibodies, Monoclonal↗

PubMed1997

Temporal dynamics of acute isovolume bronchoconstriction in the rat.

The time course of lung impedance changes after intravenous injection of bronchial agonist have produced significant insights into the mechanisms of bronchoconstriction in the dog (J. H. T. Bates, A.-M. Lauzon, G. S. Dechman, G. N. Maksym, and T. F. Shuessler. J. Appl. Physiol. 76: 616-626, 1994). We studied the time course of acute induced bronchoconstriction in five anesthetized paralyzed open-chest rats injected intravenously with a bolus of methacholine. For the 16 s immediately after injection, we held the lung volume constant while applying small-amplitude flow oscillations at 1.48, 5.45, and 19.69 Hz simultaneously, which provided us with continuous estimates of lung resistance (RL) and elastance (EL) at each frequency. This procedure was repeated at initial lung inflation pressures of 0.2, 0.4, and 0.6 kPa. Both RL and EL increased progressively after methacholine administration; however, the rate of change of EL increased dramatically as frequency was increased, whereas RL remained relatively independent of frequency. We interpret these findings in terms of a three-compartment model of the rat lung, featuring two parallel alveolar compartments feeding into a central airway compartment. Model simulations support the notions that both central airway shunting and regional ventilation inhomogeneity developed to a significant degree in our constricted rats. We also found that the rates of increase in both RL and EL were greatly enhanced as the initial lung inflation pressure was reduced, in accord with the notion that parenchymal tethering is an important mechanism limiting the extent to which airways can narrow when their smooth muscle is stimulated to contract.

Airway Resistance↗

PubMed1996

Subpopulations of fetal-like gingival fibroblasts: characterisation and potential significance for wound healing and the progression of periodontal disease.

Wound healing in the adult is commonly compromised by excessive scar formation. In contrast, fetal wound healing is a regenerative process characterised by the conspicuous absence of scarring. Available evidence suggests that phenotypic differences between fetal and adult fibroblasts are important determinants of these distinct modes of tissue repair. In this context, a number of groups (including our own) have documented differences between fetal and adult fibroblasts with respect to such potentially relevant characteristics as migratory activity, motogenic response to cytokines and the synthesis of motility factors, cytokines and matrix macromolecules. The oral mucosa appears to be a privileged site in the adult in that it continues to display a fetal-like mode of wound healing. Data are presented in this review indicating that a subpopulation of gingival fibroblasts expresses several 'fetal-like' phenotypic characteristics. These observations are discussed in terms of both the continued expression of a fetal-like mode of wound healing in the oral mucosa and the possible differential involvement of distinct fibroblast subpopulations in the progression of periodontal disease.

Adult↗

PubMed1996

Substratum-dependent stimulation of fibroblast migration by the gelatin-binding domain of fibronectin.

Nanomolar concentrations of native fibronectin and its RGDS-containing cell-binding domain have previously been reported to stimulate fibroblast migration in the transmembrane (or 'Boyden chamber') assay; in contrast, the gelatin-binding domain (GBD) of fibronectin has consistently been reported to be devoid of migration-stimulating activity in this assay. We have examined the effects of fibronectin and several of its purified functional domains on the migration of human skin fibroblasts in what is presumably a more physiologically relevant assay involving the movement of cells into a 3-D matrix of native type I collagen fibrils. We report that: (a) femtomolar concentrations of GBD stimulate fibroblast migration into such collagen matrices; and (b) fibronectin, as well as peptides containing all other of its functional domains, do not exhibit migration-stimulating activity when tested in the femtomolar to nanomolar concentration range (i.e. 0.1 pg/ml to 1 microgram/ml). The correct assignment of migration-stimulating activity to GBD, rather than to a contaminant, was confirmed by: (a) the use of several fibronectin and GBD purification protocols; (b) the neutralization of GBD migration-stimulating activity by monoclonal antibodies directed against epitopes present in this domain; (c) the time-dependent generation of migration-stimulating activity by the proteolytic degradation of native fibronectin; and (d) obtaining an identical dose-response curve with a genetically engineered GBD peptide. The cryptic migration-stimulating activity of GBD was not affected by the presence of serum or native fibronectin, but was inhibited by TGF-beta 1. Parallel experiments using the transmembrane assay confirmed that GBD was devoid of migration-stimulating activity in this assay when membranes coated with gelatin were used, but revealed that significant stimulation of migration was achieved with membranes coated with native type I collagen. Cells preincubated with GBD for 24 hours whilst growing on plastic tissue culture dishes and then plated onto native collagen matrices in the absence of further GBD also displayed an elevated migration compared to controls. Taken together, these observations suggest that: (a) the interaction of GBD with a putative cell surface receptor (and not the collagen substratum) initiates a persistent alteration in cell phenotype which is manifest by an increase in migratory activity when these cells are cultured on a native collagen substratum; and (b) GBD may play a hitherto unrecognised role in the control of cell migration in response to the local release of proteases during pathological processes, such as tumour invasion and wound repair.

Cell Movement↗

PubMed1995

Determination of the inorganic ion composition of rat airway surface fluid by capillary electrophoresis: direct sample injection to allow multiple analyses from nanoliter volumes.

The pulmonary airways are covered by a layer of airway surface fluid (ASF) which is typically < 30 microm in thickness. ASF composition is an important factor in the pathogenesis of several lung diseases including cystic fibrosis. Because of the very small volume of ASF, it is difficult to determine ASF composition, Particularly for inorganic ions, since sampling by lavage is not suitable. With nanoliter injected volumes, capillary electrophoresis (CE) is ideally suited to ASF analysis. We have developed a novel technique using separate sampling and injection capillaries whereby submicroliter volumes of ASF (typically approximately 100 nL) can be collected from airways and then analyzed by CE. Cations (Na+, K+, Ca2+, Mg2+) and anions (including Cl-) are quantitated (RSD < 10%) using indirect UV detection. In healthy rat lungs, ASF was found to be hypotonic, consistent with observations made in human airways. This technique has been developed using rats, which have not previously been studied because their small size prohibits the use of other sampling techniques.

Animals↗

PubMed1986

Measurement of urinary retinol-binding protein by enzyme-linked immunosorbent assay, and its application to detection of tubular proteinuria.

An enzyme-linked immunosorbent assay (ELISA) for urinary retinol-binding protein (RBP) has been developed and compared with urinary beta 2-microglobulin for the detection of tubular proteinuria. The assay has a working range of 10 to 250 micrograms of RBP per liter of urine. The within-assay CV was 3.2-7.1%, the between-assay CV 12.5%. A control population of 118 male subjects gave a geometric mean urinary RBP concentration of 7.7 micrograms per millimole of creatinine and a 95th centile of 22 micrograms per millimole of creatinine. Comparison of urinary RBP and beta 2-microglobulin concentrations in 80 control subjects and 117 subjects exposed to cadmium fumes gave correlations of r = 0.59 and 0.91, respectively. Of the 117 subjects exposed to cadmium fumes, 103 gave both RBP and beta 2-microglobulin concentrations on the same side of the upper 95th centile values of 22 and 38 micrograms per millimole of creatinine for RBP and beta 2-microglobulin respectively (Chi-square analysis p less than 0.001), demonstrating that RBP and beta 2-microglobulin detect tubular proteinuria with equal sensitivity and specificity. ELISA and an established latex immunoassay gave well-correlated results.

Adult↗