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Biomedical subjects

R Luxton

Publications and source records attributed to R Luxton.

14 recordsLinked to original sources
PubMed2001

The use of coated paramagnetic particles as a physical label in a magneto-immunoassay.

An ideal label for use in an immunoassay would require no further chemical or electromagnetic stimulation prior to its detection and would be free from interference from the sample matrix. Micron sized paramagnetic particles are able to perturb magnetic fields. This perturbation can be directly detected using a suitable electronic device and is independent of the sample matrix. In this study coated paramagnetic particles were used as a physical label in a non-competitive solid phase "sandwich" assay for the detection of human transferrin. The transferrin acted as a "biological bridge" allowing a dose dependant immobilization of the paramagnetic particles to a polyethylene terephthalate solid phase. Quantitation of the paramagnetic label was achieved using an electronic detection system allowing a linear dose response with a femtomolar detection limit (260 fmol).

Animals↗
PubMed2001

A novel measuring system for the determination of paramagnetic particle labels for use in magneto-immunoassays.

Coated micrometer-sized paramagnetic particles (PMPs) are readily available and widely used in immunoassays, mainly for separation and as a solid phase. We have described in a separate paper a model sandwich assay in which approximately 1 x 10(5) to 1 x 10(6) PMPs (2.8 microm diameter) are immobilised on a plastic strip at the end of the assay. In this paper, we describe the design of an instrument that is capable of determining the number of PMPs on the plastic strip. The paper also describes a method of making standard plastic strips with known numbers of PMPs on them. A strip, when placed in a coil of wire in parallel with a capacitor, causes the resonant frequency of the coil to decrease because of the presence of the PMPs. The decrease in frequency relates directly to the number of PMPs on the strip. A circuit based on a voltage-controlled oscillator and a phase-locked loop is used to accurately measure the resonant frequency of the coil. The instrument is capable of detecting at least 1 x 10(5) PMPs immobilised on a plastic strip and has a linear response (r=0.99) for up to at least 3.33 x 10(6) PMPs. In terms of the iron content of the PMPs, the detection limit is approximately equal to 1.2 microg Fe in the paramagnetic particles and the sensitivity is approximately equal to 3 Hz per microg of Fe. The instrument is small and compact and together with a suitable magneto-immunoassay will have many applications, including near-patient monitoring.

Biosensing Techniques↗
PubMed1997

Studies towards a disposable screen-printed amperometric biosensor for progesterone.

A screen-printed carbon electrode (SPCE) has been investigated as the base transducer for a disposable amperometric progesterone biosensor. The biorecognition element was a monoclonal sheep anti-progesterone antibody (mAb). This was immobilized onto the transducer by interaction with a layer of rabbit IgG which had been previously coated onto the SPCE; optimum conditions for these loadings were deduced experimentally. The device was employed in a competitive assay using alkaline phosphatase-labelled progester-one. Three possible substrates for the enzyme were considered, namely, phenyl phosphate, phenolphthalein phosphate and 4-aminophenol phosphate. Cyclic voltammetry and amperometry were carried out on the corresponding aromatic phenols and phenol itself was found to give the best electrochemical characteristics; consequently, phenyl phosphate was employed as the substrate. Chronoamperometry was used to measure the phenol produced by the reaction of bound enzyme-labelled progesterone and substrate. The chronoamperometric response was dependent on unlabelled progesterone over at least three orders of magnitude with a detection limit of about 1 x 10(-9) mol/dm3. This suggests that the device may have applications for the analysis of biological fluids.

Aminophenols↗
PubMed1996

Serum oligoclonal IgG is a common and persistent finding in multiple sclerosis, and has a systemic source.

Synthesis of oligoclonal IgG within the central nervous system is a well established feature of multiple sclerosis. The occurrence of oligoclonal IgG in the serum of patients with multiple sclerosis has received little attention. We detected such a serum response in 20/45 consecutive patients (44%, 95% CI 30-59%) but in only 3/41 age- and sex-matched healthy controls (p < 0.01). We present qualitative and quantitative evidence that this oligoclonal IgG has a systemic origin. The plasma cell clones responsible for the serum response are often also represented in the intrathecal compartment. In a further study of the clinical significance of serum oligoclonal bands, in 80 patients, their presence was associated with elevated levels of intrathecal synthesis, increasing age, later disease onset and the presence of serum autoantibodies. These findings add to the evidence that there is a systemic immune disturbance in multiple sclerosis.

Adult↗
PubMed1993

Lymphocytic meningitis following insertion of a porcine dermis dural graft.

We describe a case of lymphocytic meningitis following insertion of a porcine dermis implant to repair an operative dural defect. Histology of the excised implant revealed local abscess formation with a granulomatous reaction. Oligoclonal Immunoglobulin G, part of which could be removed by absorbtion with the porcine dermis, was present in the patient's cerebrospinal fluid, and, to a less marked degree, in his serum. The cerebrospinal fluid glucose was markedly depressed. An unusual hypersensitivity reaction to the porcine implant was considered the most likely explanation for this meningitic illness. The patient went on to make a full recovery following excision of the implant.

Adult↗
PubMed1993

The significance of serum oligoclonal bands in neurological diseases.

The presence of oligoclonal bands (OCBs) of immunoglobulin G (IgG) in CSF provides evidence for the occurrence of a humoral immune response, but it is not always appreciated that the oligoclonal IgG may have originated in the serum. To determine the diagnostic significance of serum OCBs 146 patients with serum OCBs were identified among 1874 patients with suspected neurological disorders (7.6%). Clear diagnoses had been made in 112 of these patients: in 56 identical CSF and serum bands were present, revealing a systemic immune response, while in 46 additional unique CSF bands indicated that intrathecal IgG synthesis was also occurring. In the first group neoplasia and peripheral neuropathies accounted for over 50% of the diagnoses, infections and systemic inflammatory disorders for 32%, and multiple sclerosis was diagnosed in only one case. These figures contrast considerably with those reported for patients with CSF OCBs alone. Diagnoses in the second group of patients, with unique CSF OCBs in addition to serum OCBs, resembled those among patients with CSF OCBs alone. Examining CSF and serum in parallel for OCBs of IgG provides more diagnostic information than examining CSF alone, and the latter is potentially misleading.

Antibody Formation↗
PubMed1993

Hairy leukaemic cell influx into the cerebrospinal fluid secondary to encephalomyelitis.

A case report of a 53 year old male with hairy cell leukaemia is presented in whom encephalomyelitis caused by toxoplasmosis resulted in an influx of hairy cells into the cerebrospinal fluid following disruption of the blood-brain barrier. These cells subsequently disappeared as the barrier reformed. It is suggested that the presence of hairy cells in the cerebrospinal fluid is a secondary self-limiting phenomenon.

Central Nervous System↗
PubMed1992

IgG paraproteins in neurological diseases: lack of association with neurotropic viral/bacterial antigens.

In this study we tested the hypothesis that IgG paraproteins in neurological diseases might be regarded as an anti-idiotypic response raised by a nervous system antigen associated with certain neurotropic agents. After initial ELISA screen, positive samples from 34 neurological patients who had paraproteins in their CSF and serum on routine IEF investigation, were tested by immunoblot technique for the presence of specific monoclonal immunoglobulin G (IgG) against eight different neurotropic antigens. Only one patient had specific monoclonal IgG against herpes simplex virus. The results of this study did not confirm our hypothesis. Further study of IgM/IgA paraproteins is indicated.

Adolescent↗
PubMed1992

Oligoclonal immunoglobulin D in the cerebrospinal fluid of neurologic patients.

Oligoclonal immunoglobulin D (IgD) bands were observed in 20 of 110 CSF samples investigated by our method for isoelectric focusing (IEF) of IgD in unconcentrated CSF. These were mostly from demyelinating disorders, viral CNS infections, and CNS tumors. The patterns of expression of IgD were similar to that of IgG, except in cases with tumors where oligoclonal IgD may occur independently of IgG. The study shows for the first time the presence of oligoclonal IgD in CSF from neurologic patients.

Humans↗
PubMed1991

A new qualitative method for detecting IgD in unconcentrated cerebrospinal fluid.

We report a method which is capable of demonstrating the isoelectric focusing (IEF) pattern of immunoglobulin D in unconcentrated cerebrospinal fluid (CSF) samples containing as little as 0.1-0.5 ng of total IgD. The method used was an immuno-sandwich technique, with alkaline phosphatase enzyme amplification. Oligoclonal and polyclonal IgD patterns were seen in CSF samples. No cross-reactivity with other immunoglobulins (IgG, IgA and IgM) was detected.

Humans↗
PubMed1990

The occurrence of oligoclonal IgG in tears from patients with MS and systemic immune disorders.

Using isoelectric focusing (IEF) and immunoperoxidase staining of proteins transferred to nitrocellulose membranes, we have examined the IgG band pattern in tears and matched serum and CSF specimens of 28 patients with MS, 4 patients with optic neuritis (ON), 30 individuals with systemic, inflammatory, or other neurologic diseases, and 5 patients with tension headache. We found no evidence of positive oligoclonal IgG in tears in any MS or ON patients, while 10 out of 16 cases with systemic immune disorders or infections of the CNS had positive tear oligoclonal bands. We are thus not able to support the hypothesis that tears from MS patients reveal abnormalities in their humoral immune response.

Adult↗
PubMed1987

Maternal leucocyte zinc deficiency at start of third trimester as a predictor of fetal growth retardation.

Leucocyte zinc concentrations were measured in 70 mothers at the beginning of the third trimester of pregnancy and compared with the weight centiles of their subsequently delivered babies. The median maternal leucocyte zinc concentrations rose progressively with weight centile. Thus the median leucocyte zinc concentration of the mothers delivering babies weighing below the 10th centile was 112 nmol/10(9) leucocytes and that of the mothers with babies weighing above the 90th centile was 229.5 nmol/10(9) leucocytes. A maternal leucocyte zinc concentration less than 120 nmol/10(9) leucocytes strongly predicted a baby weighing below the 10th centile (positive predictive value = 71.9%, negative predictive value = 91.5%, sensitivity = 64.3%, specificity = 81.8%). These findings suggest that maternal zinc concentration might have a role in antenatal screening, but larger studies are required.

Birth Weight↗