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Biomedical subjects

R H Cumming

Publications and source records attributed to R H Cumming.

17 recordsLinked to original sources
PubMed2000

Detection of protease activity in the wetted surface of gelatin-coated electrodes in air by AC impedance spectroscopy.

As a step towards developing a biosensor which can detect airborne protease droplets, a biosensor which had previously been developed to detect protease in solution is shown to be capable of detecting different concentrations of protease in liquid films on the sensor surface in air. The biosensor measured impedance change due to proteolytic digestion of its gelatin coating. In saturated air there was a rise in impedance, with a loss in weight of the gelatin, in proportion to collagenase concentration. The addition of glycerol to the gelatin caused a lower impedance response and smaller loss in weight. A critical thickness of the gelatin layer prior to a more rapid change in the rate of impedance was noted, with and without the addition of glycerol. In low air humidity (40%), with gelatin, all collagenase concentrations produced a very similar rapid increase in impedance. However, with glycerol-enhanced gelatin, there was a clear distinction between the extent of impedance change with different collagenase concentrations. The application of these findings for use in the field of bioaerosol sampling is discussed.

Aerosols↗
PubMed2000

Direct on-filter assay of subtilisin-type proteolytic enzymes for rapid analysis of analyte captured from the workplace atmosphere.

A simple assay for some proteolytic enzymes has been developed which can be performed directly on the surface of a cellulose nitrate filter used to capture the analyte during workplace monitoring for health and safety purposes. Following air sampling the analysis is performed on the filter which is retained within the air sampler. This involves two steps: first, a 15 min incubation in which the captured enzyme is dissolved and then digests an alkaline-phosphatase-labelled antibody immobilised as a small dot on the surface of the filter; and second, is a 10 min incubation with substrate solution, which follows an in situ wash under a vacuum. During the incubation colour develops on the spot at the location of the immobilised enzyme antibody conjugate. The intensity of the spot can be assessed visually within the sampler to ascertain the presence or absence of captured enzyme, or alternatively quantitative results can be obtained using an optical scanner. The limit of detection is 5 ng per filter for subtilisin (20 ng for visual discrimination between this standard and the zero). The assay is stable to the effects of ambient air sampling at 31 min(-1) for 18 h.

Air Pollution, Indoor↗
PubMed2000

Mathematical analysis for impedance change with proteolytic digestion of gelatin.

A mathematical analysis is proposed to demonstrate an inter-relationship between the proteolytic digestion of gelatin on the surface of an interdigitated gold electrode and the resulting rate of impedance change, at different collagenase concentrations, in a biosensor used to detect protease in solution. The impedance change due to digestion of the gelatin layer by collagenase for the overall digestion process was expressed in two different stages: an initial exponential period where the rate of impedance change with enzymic digestion was slow, leading to a critical thickness; after which there was a greater change in impedance associated with subsequent dissolution of the layer and partial or complete uncoating of the digits on the electrode surface. An inter-relationship between the rate of impedance change and collagenase concentration within the range 0.2-0.6 mg ml-1 was predicted for the early stages of the digestion process. A kinetic theory for the rapid rate of impedance change with collagenase concentrations could not be developed owing to the rate remaining almost constant for all concentrations of collagenase, after the critical thickness had been reached. An inter-relationship between the rate of impedance change and stirrer speed was also demonstrated.

Journal Article↗
PubMed1998

Enzyme-linked immunosorbent assay for ondansetron captured from airborne samples.

A simple and relatively rapid enzyme-linked immunosorbant assay method for the anti-emetic drug ondansetron has been developed for its quantitation in solution. This has been optimised for use with samples that have been obtained following extraction of filters after the drug's capture from air samples in the workplace. The assay has the sample throughput (40 duplicate samples in 3 h), specificity, sensitivity (LOD of 10.5 ng drug ml-1) and precision (RSD < 11%) necessary for its use in determining airborne concentrations of ondansetron in such samples as part of an occupational health and hygiene monitoring programme.

Air Pollutants, Occupational↗
PubMed1997

Direct on-filter immunoassay of some beta-lactam antibiotics for rapid analysis of drug captured from the workplace atmosphere.

A simple competitive enzyme-linked immunoassay for the antibiotic ceftazidime and structurally similar beta-lactam antibiotics has been developed which can be performed directly on the surface of a cellulose nitrate filter used to capture the airborne drug during workplace monitoring for health and safety purposes. Post sampling analysis is performed on the filter retained within the air sampler. It involves two steps; the first a 10 min incubation in which the captured drug is dissolved and competes with drug immobilised within a protein conjugate on the surface of the filter for an enzyme-labelled antibody reagent, and the second, following washing under vacuum in situ, a 5 min incubation of substrate solution when colour develops on the spot at the location of the immobilised drug-protein conjugate. The intensity of the spot can be assessed visually within the sampler to ascertain the presence or absence of captured drug, or quantitative results can be obtained using an optical scanner. The intensity of the spots in linear from 10 ng to 1 microgram (r2 = 0.9996, n = 3) and the limit of detection is 1.9 ng of captured drug (10 ng for visual discrimination between this standard and the zero). The assay is precise with between-assay RSD values of < 4% over the linear range of the assay.

Air Pollutants, Occupational↗
PubMed1996

Effects of heat shock on gram negative bacteria: use of lysis by sodium dodecyl sulphate as a probe for the integrity of DNA.

Rheograms of Alcaligenes eutrophus (NCIMB 40529) and Escherichia coli (C90 NCIMB 10616) cells lysed by sodium dodecyl sulphate were compared before and after a variety of heat shock regimes. It was found that unheated cells produced a very characteristic shear thickening rheogram which could be destroyed by DNase treatment. Cells which had been subjected to heat shock produced rheograms very similar to DNase digested material. We thus suggest that the rheogram is largely due to the presence of intact DNA molecules. The extent and nature of the heat shock affected the shape of the rheogram of the SDS lysed material. Heat shock of cells after SDS lysis did not appear to significantly damage the DNA. Storage of the cells at 10 degrees C before heat shock considerably reduced the shear thinning effect of subsequent heat shock at 90 degrees C. We attribute the shear thinning effect of the heat shock to the action of nucleases which are activated and then depolymerise the DNA molecules.

Alcaligenes↗
PubMed1996

Flocculation of Esch. coli with cationic polymers: a model for the dose curve based on charge.

Continuously grown cells from a glucose limited chemostat were flocculated with four different cationic polymers. The polymer was added to the cells either dropwise or as a slug at the start of the flocculation period. Dose curves for each polymer type and using each method of polymer addition were constructed. It was evident that classical overdose was possible with all four polymers if slug addition was used. Continuous addition produced dose curves overdose was possible with all four polymers if slug addition was used. Continuous addition produced dose curves with no overdosing except when low molecular weight, low charge density polymer was used. The dose curves could be combined if they were based on amount of charge added. The dose curve was not linear, but fitted a logarithmic model well. Charge density was much more important than MW of the polymer.

Biotechnology↗
PubMed1994

Enzyme linked immunosorbent assay for ceftazidime in airborne samples.

A simple and rapid enzyme linked immunosorbent assay (ELISA) method for the cephalosporin, ceftazidime, has been developed for the quantification of this antibiotic in solutions that have been eluted from filters following the capture of air samples in the workplace. The assay has the specificity, sensitivity and precision necessary for its use in determining airborne concentrations of ceftazidime in the workplace as part of an occupational health and hygiene programme.

Air Pollutants, Occupational↗
PubMed1979

Evidence for a therapeutic effect of plasmapheresis in patients with systemic lupus erythematosus.

Fourteen patients with active systemic lupus erythematosus (SLE) have been treated with plasmapheresis at a rate of two litres daily on three to four days per week, over a period of two to three weeks. Plasma was replaced isovolemically with either fresh frozen plasma or with human plasma protein fractions. Ten patients were receiving treatment with prednisone at the time of plasmapheresis, and four had received no prior treatment. Eight patients showed evidence of either clinical improvement or clinical and immunochemical improvement, at the time of plasmapheresis. In the three patients who showed high levels of circulating complexes before treatment, there was a sudden fall in the level of circulating immune complexes, which was quantitatively greater than could be explained by the amount removed. This suggests that in some patients with SLE, clearance of complexes by the mononuclear phagocytic system is initially blocked by high levels of circulating complexes and that one effect of plasmapheresis may be to relieve this blockade. Five patients showed a clinical response to plasmapheresis despite the fact that tests for immune complexes were negative. Three patients showed no response to plasmapheresis, and three were regarded as unevaluable. In a limited number of patients, who show a high level of circulating immune complexes, and whose condition is deteriorating despite treatment with corticosteroids, there may be an important therapeutic role for plasmapheresis.

Adolescent↗
PubMed1977

Relationship between anti-DNA antibodies complement consumption and circulating immune complexes in systemic lupus erythematosus.

Eighty-nine sera from nineteen patients with systemic lupus erythematosus (SLE) have been studied to determine the relationship between levels of DNA-binding activity, complement consumption and evidence of circulating immune complexes. There was a good correlation between the height of DNA binding, a rising C3i and a reciprocal fall in C3, C4 and CH50 levels. These latter measurements provided useful supplemental information when studied serially. There was a good correlation between the results of the various methods used for the detection of circulating immune complexes, and these were found in almost half the sera with DNA binding over 70%. It is concluded that serial studied of DNA binding, complement levels, and direct tests for immune complexes, may provide valuable information in the management of patients with SLE.

Antibodies, Antinuclear↗
PubMed1976

Plasmapheresis in the management of acute systemic lupus erythematosus?

Eight patients with systemic lupus erythematosus (S.L.E.) have been treated with plasmapheresis. In four patients in whom immunochemical studies indicated high levels of circulating immune complexes, the removal of 5-8 litres of plasma weekly produced a striking clinical and immunochemical improvement. The four other patients, with only minor complement disturbances and no direct evidence of circulating immune complexes, could not be shown to benefit from plasmapheresis and one patient in this group died of cerebral lupus despite intensive treatment with cytotoxic drugs. It is concluded that plasmapheresis may be of value as an adjuvant to the treatment of acute S.L.E.

Acute Disease↗
PubMed1976

Necrotizing vasculitis: a circulating immune complex producing inflammatory skin lesions.

A patient with acute necrotizing vasculitis is described in whom tests for circulating immune complexes were negative. The patient's serum injected intradermally produced lesions which closely resembled those occurring spontaneously. When the serum was fractionated, the skin-reactive fraction was found to be associated with IgG, but was of a higher molecular weight than normal IgG. Immunofluorescent studies showed that lesions induced by this active fraction contained IgG and complement in the epidermal basement membrane zone and within the small dermal vessels. We conclude that an immune complex of relatively low molecular weight is present in the active fractions, and capable of initiating the lesions of acute necrotizing vasculitis.

Antigen-Antibody Complex↗
PubMed1976

Evidence for circulating immune complexes in erythema nodosum and early sarcoidosis.

Twenty-two patients were investigated during acute attacks of erythema nodosum with a series of tests for circulating immune complexes. Nineteen had bilateral hilar lymphadenopathy and were considered to have sarcoidosis. Evidence of circulating immune complexes was found in 18, out of 22 patients (including 15 out of the 19 cases of sarcoidosis). The most frequent abnormality was the detection of elevated levels of C3 breakdown products (C3i), which were found in 14 out of 18 tests. The test results returned gradually to normal as symptoms subsided in 20-40 days, but 2 patients still showed abnormalities at 40 days despite the disappearance of symptoms. It is concluded that free immune complexes appear in the circulation during the early stages of acute sarcoidosis and gradually disappear as symptoms subside.

Antigen-Antibody Complex↗
PubMed1976

Penicillamine nephropathy in rheumatoid arthritis. A clinical, pathological and immunological study.

Fourteen patients who developed persistent proteinuria while on penicillamine for rheumatoid arthritis, were collected over a period of one year. Eleven patients had a frank nephrotic syndrome and three had a lesser degree of proteinuria but no oedema. The patients had received penicillamine (mean daily dose 1015 mg) for less than one year (mean 7-5 months) when the nephropathy was detected. Clinical investigations have been correlated with renal biopsy material. Light microscopy detected no abnormalities except for minimal hypercellularity in a few patients. In markde contrast, the electron-microscope revealed numerous electron-dense deposits (EED's) in the outer layer of the basement membrane. Immunofluorescence showed the presence of IgG and complement in the basement membrane, the intensity of which correlated with the number of EED's. The pathological picture was essentially the same in those patients with the nephrotic syndrome and those with proteinuria. In this series, we found no evidence that penicillamine induced renal damage by any other mechanism except immune complex deposition. Serological tests revealed little evidence for complement activation or consumption and platelet aggregation was the only positive direct test for circulating immune complexes. Renal biopsies were performed at differing intervals after the cessation of penicillamine therapy, which allowed assessment of the natural history of the pathological lesion and revealed a striking persistence of EDD's in some patients. Two patients showed an almost identical picture initially and at re-biopsy one year later. Persistent proteinuria was also a feature of the group as a whole. The pathological picture has similarities with that of idiopathic membranous glomerulopathy. This study suggests that the use of penicillamine in rheumatoid arthritis may induce persistent renal damage.

Adult↗
PubMedDate not supplied

Shear thickening of DNA in SDS lysates.

Cells of Escherichia coli were subjected to lysis by an alkali detergent treatment (sodium dodecyl sulphate). The rate of detergent lysis was not first order. The rheological properties of the lysate were measured using a controlled stress rheometer. Detergent-lysed cells produced a lysate which showed marked non-Newtonian properties. The material showed a shear thickening at specific low shear stress conditions. The acceleration of the cone during the ascent stage of a flow curve, influenced the shape of the flow curves. These findings are discussed in relation to the form of bacterial DNA in solution.

DNA, Bacterial↗