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Biomedical subjects

R A Thompson

Publications and source records attributed to R A Thompson.

At least 19 recordsLinked to original sources
PubMed1992

Direct liquid chromatographic separation of enantiomers on immobilized protein stationary phases. IX. Influence of the cross-linking reagent on the retentive and enantioselective properties of chiral sorbents based on bovine serum albumin.

Three modifications of silica-bound, cross-linked bovine serum albumin (BSA) were evaluated as chiral sorbents for use in the liquid chromatographic separation of enantiomers. Glutaraldehyde, formaldehyde and di-(N-succinimidyl) carbonate were used as bifunctional reagents for the immobilization of BSA. The sorbents all contain the same loading of BSA (14.4 +/- 0.1%, w/w) and differ only with respect to the cross-linker used for immobilization. Despite their apparent similarity, the sorbents show very different chromatographic properties, not only with respect to retention of analyte enantiomers (k' and alpha), but also with respect to column efficiency (affecting Rs values). The data obtained indicate that the chemical structure of the cross-linking reagent affects to a large extent the accessibility of important chiral binding sites. Although the data obtained are difficult to interpret in any detail, certain generalizations concerning the different behaviour of the sorbents can be made.

Albendazole↗
PubMed1992

Endothelium myeloperoxidase-antimyeloperoxidase interaction in vasculitis.

Antibodies to myeloperoxidase (MPO) are found in the sera of patients with microscopic polyarteritis and idiopathic crescentic glomerulonephritis. Their pathogenicity is unknown. Studies were carried out on the binding of MPO to cultured human umbilical vein endothelial cells and the recognition of endothelium-bound MPO by antibody to MPO. Endothelial cells were cultured from human umbilical veins. The binding of MPO to endothelial cells and its inhibition by poly-D-lysine was detected using a monoclonal antibody to MPO and direct staining with APAAP and also by an enzyme-linked immunoassay (ELISA). The binding of anti-MPO antibody in the sera of patients with microscopic polyarteritis to endothelium-coated MPO was detected by ELISA. MPO bound to endothelial cells both on direct staining and ELISA and this binding was inhibited by the polycation poly-D-lysine, suggesting that it was charge mediated. Binding of anti-MPO antibody in the sera of patients with microscopic polyarteritis to endothelium-coated MPO was significantly higher than the binding of sera from normal subjects (P = 0.04), patients with idiopathic glomerulonephritis (P = 0.0005), and patients with lupus nephritis (P = 0.009). MPO binds to cultured human umbilical vein endothelium probably by a charge mechanism, and can react with anti-MPO antibodies in the sera of patients with microscopic polyarteritis as well as with a mouse monoclonal anti-MPO antibody. This binding of anti-MPO antibody to MPO fixed to the endothelial cell surface provides a mechanism by which endothelial injury and inflammation might occur in microscopic polyarteritis.

Endothelium, Vascular↗
PubMed1990

Lymphokine-activated killer (LAK) cells. V. 8-Mercaptoguanosine as an IL-2-sparing agent in LAK generation.

Guanine ribonucleosides, substituted at the C8 position with either a bromine or a thiol group, have recently been shown to regulate several immunologic responses. We have previously shown that 8-mercaptoguanosine (8MG) can replace the requirement for cytokines in the generation of MHC-restricted CTL. In this paper, we examined the ability of 8MG to induce MHC-nonrestricted killer cells. We found that 8MG did not induce significant lytic activity from normal resting lymphocytes. However, 8MG was able to synergize with minimal amounts of IL-2 in inducing lytic activity similar to lymphokine-activated killers (LAK) in that both NK-sensitive and NK-resistant tumor cells were killed. Both the precursors and effectors of 8MG-LAK activity were similar to NK cells and were CD4- CD8- asialo-GM1+ NK1.1+. Similar to IL-2-induced LAK, 8MG-LAK were B220+. 8MG appeared to "stage" these precursor lymphocytes to become more responsive to IL-2 because optimal induction of 8MG-LAK required preincubation with 8MG before the addition of IL-2. This "staging" appeared to be due to the release of a "second signal" since it was readily inhibited by cyclosporine A. Anti-IFN-alpha beta was as efficient as cyclosporine A in inhibiting 8MG-LAK generation, whereas anti-IFN-gamma and anti-IL-1 did not exhibit significant inhibition. These findings suggest that 8MG can be of possible utility as an IL-2-sparing agent in LAK generation from NK cells.

Adjuvants, Immunologic↗
PubMed1990

N-(9-acridinyl)-bromoacetamide--a powerful reagent for phase-transfer-catalyzed fluorescence labeling of carboxylic acids for liquid chromatography.

Phase-transfer-catalyzed esterification of various carboxylic acids has been carried out on a microanalytical scale with a new reagent, N-(9-acridinyl)-bromoacetamide, in aqueous/organic two-phase systems. The procedure gives esters showing very high fluorescence intensity in acid solution. The large Stokes' shift (greater than 120 nm) means that a low background can be achieved even when using a large emission bandwidth. These derivatives show very good chromatographic behavior on reversed-phase liquid chromatographic columns with the use of aqueous acetonitrile, containing 0.2% of phosphoric acid, as the mobile phase. Detection limits (S/N = 2) as low as 10 fmol can be obtained under optimal conditions.

Aminoacridines↗
PubMed1990

Anti-myeloperoxidase antibodies in systemic vasculitis.

Anti-neutrophil cytoplasmic antibodies (ANCA) are important diagnostic markers in vasculitic disorders. In a study of 164 patients with various clinical syndromes associated with vasculitis, 60 were found to have the antibody, as detected by indirect immunofluorescence; 23 had the so-called perinuclear antibody pattern, and of these, 15 had antibodies to neutrophil myeloperoxidase in an ELISA. These patients had multi-system involvement, and 14 of the 15 had histological evidence of small-vessel arteritis in the kidneys. In preliminary experiments, the isolated IgG from one patient was shown to inhibit luminol-dependent chemiluminescence of fluid phase myeloperoxidase.

Autoantibodies↗
PubMed1990

Antimicrobial activity of betaine esters, quaternary ammonium amphiphiles which spontaneously hydrolyze into nontoxic components.

A series of quaternary ammonium compounds that are esters of betaine and fatty alcohols with hydrocarbon chain lengths of 10 to 18 carbon atoms were tested with respect to antimicrobial activities and rates of hydrolysis. When the tetradecyl derivative was tested against some selected microorganisms, the killing effect was comparable to that of the stable quaternary ammonium compound cetyltrimethylammonium bromide. At higher pH values, both the antimicrobial effect and the rate of hydrolysis of the esters increased. However, whereas at pH 6 greater than 99.99% killing of Salmonella typhimurium was achieved with 5 micrograms/ml in 3 min, the rate of hydrolysis was less than 20% in 18 h. At pH 7, a similar killing effect was achieved in 2 min and 50% hydrolysis occurred in ca. 5 h. Thus, it is possible to exploit the rapid microbicidal effect of the compounds before they hydrolyze. The rate of hydrolysis was reduced by the presence of salt. The bactericidal effect of the betaine esters increased with the length of the hydrocarbon chain of the fatty alcohol moiety up to 18 carbon atoms. Since the hydrolysis products are normal human metabolites, the hydrolysis property may extend the use of these quaternary ammonium compounds as disinfectants and antiseptics for food and body surfaces.

Bacteria↗
PubMed1990

Infective conjunctivitis and corneal scarring in three brothers with sex linked hypogammaglobulinaemia (Bruton's disease).

The ocular findings in three brothers with Bruton's disease are reported. All three boys had purulent conjunctivitis, but the two older brothers also developed marked corneal scarring with visual impairment. Haemophilus influenzae was cultured from conjunctival swabs; it was resistant to neomycin but sensitive to chloramphenicol. Tear analysis showed that the three subjects had normal levels of lysozyme but no detectable IgA.

Agammaglobulinemia↗
PubMed1990

Technical improvements in the immunoperoxidase study of renal biopsy specimens.

Sixty five renal biopsy specimens were used to compare a direct immunofluorescence technique on frozen sections with immunoperoxidase techniques on paraffin wax sections. For the immunoperoxidase techniques, dewaxed sections were treated with protease at 37 degrees C. Sections were examined at intervals on a microscope and digestion was stopped when plasma was removed from glomerular capillary loops. This permitted intense staining of immunoproteins on immunoperoxidase. There was agreement between immunoperoxidase and immunofluorescence in the staining for IgG, IgA, and IgM in 50 biopsy specimens and discordant findings did not affect the diagnosis. Immunoperoxidase did not detect C3 in 16 biopsy specimens. Findings with antiserum to another complement component, C9, detected by immunoperoxidase correlated with C3 findings detected by immunofluorescence in 17 biopsy specimens. It is concluded that microscopical observation of the progress of digestion permits optimal staining by immunoperoxidase methods, thus overcoming the problem of variability in proteolytic digestion of sections. Inconsistency in the demonstration of complement deposition can be avoided by staining for C9 rather than C3.

Complement C3↗
PubMed1990

Vulnerability in research: a developmental perspective on research risk.

Assessing potential risks to children who participate in developmental research is a challenging task because children are a heterogeneous population, varying in developmental competencies and in background characteristics. This essay offers a developmental perspective on research risk, emphasizing that children's vulnerability to research risk changes in complex ways: some risks decrease with increasing age, some increase as the child matures, others change in a curvilinear fashion, while some remain essentially stable with development. Because vulnerability in research does not simply decline linearly with age, assessments of research risk must entail multidimensional considerations that vary over developmental time. In a similar manner, individual characteristics of children at any age (e.g., maltreatment, at-risk status, etc.) may also heighten their vulnerability to certain risks which require special consideration by researchers. Finally, this discussion of developmental vulnerability and the principles underlying research ethics suggests that in addition to the conventional risk/benefit analysis, researchers are in an optimal position to establish and maintain standards of decent treatment of children in research that safeguard their rights as research participants. Suggestions for fostering this process in the research community are outlined.

Adolescent↗
PubMed1989

Purification of human blood eosinophils by negative selection using immunomagnetic beads.

A simple method for isolating highly purified eosinophils from human blood is described. Buffy coats from normal individuals (eosinophil counts less than 0.4 x 10(9)/litre) were centrifuged through a two layer Percoll density gradient, to produce a granulocyte fraction containing neutrophils and eosinophils. Neutrophils were extracted from this fraction using a monoclonal antibody (CLB FcR gran 1) against CD 16 (Fc gamma R III) in a direct or indirect selection procedure using immunomagnetic beads (Dynabeads). This negative immunoselection produced eosinophils of greater purity and with a superior capacity to mount a respiratory burst than eosinophils isolated by a method employing metrizamide.

Antigens, Differentiation↗
PubMed1989

Microbial growth and accumulation in industrial metal-working fluids.

The dynamics of microbial growth in metal-working fluids (MWF) and the effect of the addition of biocides were studied in large fluid systems, in this case, one central tank which holds 150 m3. In this system, populations of Pseudomonas pseudoalcaligenes (greater than 10(8) CFU/ml) were sustained for a year, although large quantities of biocides were added. Quantitation of 3-OH lauric acid, a marker for many Pseudomonas spp., by gas chromatography indicated that the bacterial biomass exceeded the viable counts by approximately 15 times. Fungi were grown on several occasions, the dominating genera being Fusarium and Candida. Soon after the old MWF was removed and the tank was provided with fresh MWF, which consisted of an emulsion of mineral oil in water, there was a massive growth of P. pseudoalcaligenes that reached levels of greater than 10(8) bacteria per ml. Initially, only low concentrations of other species were found for some weeks. After this period, different enterobacteria and other gram-negative rods often appeared at high concentrations (10(7) and 10(8) bacteria per ml, respectively). Bacteria identified as P. pseudoalcaligenes showed great variation with respect to colony morphology and a certain heterogeneity with respect to biochemical characteristics. Certain bacterial species grew as microcolonies on metal strips immersed in the circulating MWF, but P. pseudoalcaligenes was not recovered from this habitat. The total bacterial count in the air surrounding the machines in the metal-working shop showed an inverse relation to increasing distance from the machine. The concentration of bacteria in the air varied because of the number of machines in use, temperature, and humidity.(ABSTRACT TRUNCATED AT 250 WORDS)

Air Microbiology↗