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Biomedical subjects

L M Henderson

Publications and source records attributed to L M Henderson.

At least 37 records · Page 2Linked to original sources
PubMed1996

Use of zinc tolerance test and 24-hour urinary zinc content to assess oral zinc absorption.

OBJECTIVES: The sensitivity of one plasma and two urinary methods to assess zinc absorption after oral dosing were compared over the dose range of 10 to 100 mg. METHODS: Eleven healthy subjects participated in this four-way crossover design study. After an overnight fast, the subjects received a single oral dose of zinc acetate corresponding to 10, 25, 50, or 100 mg of elemental zinc. Plasma zinc concentrations were measured at baseline (pre-zinc administration) and hourly intervals post-zinc administration for 9 hours. Urine was collected for 24 hours prior to and for 24 hours after zinc administration. During this 48-hour period, subjects consumed an isocaloric, caffeine-free diet containing 18 mg of elemental zinc per day. RESULTS: The area under the plasma zinc concentration versus time curve (PZAUC) increased linearly with doses between 10 and 50 mg, then flattened out. By contrast, urinary zinc excretion was approximately linear with doses in the 25 to 100 mg range, but no differences were observed in urinary zinc excretion after doses of 10 and 25 mg. CONCLUSIONS: Plasma zinc concentration is a useful method of evaluating oral zinc absorption from doses of 10 to 50 mg. Urinary zinc excretion is an alternative method of assessing zinc absorption, particularly when doses of 50 to 100 mg of elemental zinc are administered.

Administration, Oral↗
PubMed1995

The arachidonate-activable, NADPH oxidase-associated H+ channel. Evidence that gp91-phox functions as an essential part of the channel.

The human neutrophil NADPH oxidase-associated H+ channel acts as a charge compensator for the electrogenic generation of superoxide (O2-.). The expression of the channel activity was found to increase in parallel with that of the stimulatable generation of O2-. in differentiated HL60 cells. HL60 cells induced to differentiate in the presence of succinyl acetone (a inhibitor of heme synthesis) were unable to generate O2-., failed to express p22-phox but retained H+ channel activity. EBV transformed B lymphocyte cell lines from normal and CGD patients lacking expression of either p47-phox or p67-phox all expressed unaltered channel activity; however, the activity was completely absent in the lymphocyte cell line lacking gp91-phox. CHO cells and undifferentiated HL60 cells transfected with gp91-phox cDNA expressed H+ channel activity correlating with the expression of gp91-phox. We therefore conclude that the large subunit of the NADPH oxidase cytochrome b (gp91-phox) is the arachidonate activable H+ channel of human neutrophils.

Animals↗
PubMed1994

Assembly of contact-phase factors on the surface of the human neutrophil membrane.

H-kininogen (HK), a major factor involved in contact-phase activation, was recently immunolocalized on the external surface of human neutrophils. Experiments were, therefore, designed to consider the question of whether the complete assembly of contact factors occurs on the outer surface of the neutrophil membrane. By immunolocalization techniques, and using specific antibodies directed against the various contact factors, we now demonstrate that plasma prekallikrein (PK), factor XI (FXI), and factor XII (FXII) are present on the exterior face of the human neutrophil. Failure to localize HK, PK, or FXI by monoclonal antibodies directed to their reciprocal binding sites, and displacement of PK/FXI by peptide HK31, which mimics the relevant binding site(s) of HK, suggested that prekallikrein and FXI are anchored to the neutrophil membrane through attachment to the kininogen molecule. Probing of the kinin moiety by a specific antibody showed that kininogen molecules bound to the neutrophil cell membrane contain the kinin sequence, which can be released by plasma kallikrein or by tissue kallikrein. Our results led us to the novel conclusion that neutrophils provide a circulating platform for the components of the contact-phase system.

Cell Membrane↗
PubMed1994

Recovery of Aujeszky's disease virus recombinants from experimentally co-infected swine.

Tissue homogenates were obtained from swine experimentally co-infected with two vaccine strains of Aujeszky's disease virus (ADV). Viral isolates were derived by serial plaque purification directly from tissue homogenates, without an intervening step of isolation and amplification on cell cultures. Use of limiting dilutions and recovery of virus isolates as individual plaques minimized the likelihood of in vitro recombination serving as a confounding source of recombinant ADV. The tyhmidine kinase and glycoprotein X gene sequences were classified as wildtype or deleted, using a battery of polymerase chain reaction assays. On the basis of pairwise combinations of the allelic forms of the thymidine kinase and glycoprotein X genes, the isolates were characterized as recombinant and parental genotypes. The results substantiate the observation that ADV vaccine strains can form genetic recombinants in vivo after experimentally induced co-infection. A full description of this study is available (Am. J. Vet. Res. 54 (4) 540-545, 1993).

Animals↗
PubMed1993

Dihydrorhodamine 123: a fluorescent probe for superoxide generation?

Imaging techniques, such as confocal microscopy and fluorescent activated cells scan are facilitating the study of responses at the single-cell level. Superoxide is reported to oxidise the non-fluorescent dihydrorhodamine 123 (DHR) to rhodamine 123. The generation of rhodamine 123 by human neutrophils, stimulated by the phorbol ester phorbol 12-myristate 13-acetate was inhibited slowly by diphenylene iodonium and rapidly by azide, but not by superoxide dismutase. In the absence of enzymes H2O2 (but not O2-.) oxidised DHR slowly but the rate was greatly enhanced by peroxidases. The rhodamine 123 generated by phorbol-ester-stimulated neutrophils was observed to be located within the cell despite the fact that neutrophils failed to accumulate external rhodamine 123. This stimulated rise in cellular fluorescence was eliminated by excess extracellular catalase. It appears that H2O2, released on the outside, crosses the plasma membrane where oxidation of DHR is catalysed by cellular peroxidases. Since in a mixed population DHR failed to distinguish between O2-.-producing and non-producing HL60 cells it is not a suitable probe for single-cell observations. We conclude that DHR oxidation reports only the presence of H2O2 and intracellular peroxidases, and not the generation of O2-. by any one cell. Only peroxidase-containing cells fluoresce.

Cell Separation↗
PubMed1993

The immediate activator of the NADPH oxidase is arachidonate not phosphorylation.

Superoxide generation is rapidly triggered following the addition of a stimulus to neutrophils. The signal-transduction pathway culminates in the activation of protein kinase C, whose phosphorylation of a protein component is considered to activate the oxidase. Arachidonate stimulated the oxidase in a concentration-dependent manner but, unlike phorbol-12-myristate-13-acetate (PMA), was not inhibited by staurosporine, a protein kinase inhibitor. Increase protein phosphorylation, apparent with PMA, was not observed when superoxide generation was triggered by arachidonate. Inhibitors of phospholipase A2 inhibit the PMA activation of the oxidase. Therefore, we propose that arachidonate and not phosphorylation is the immediate stimulus for superoxide generation.

Alkaloids↗
PubMed1993

In vitro potency assays for nonreplicating veterinary vaccines: comparison to in vivo assays and considerations in assay development.

Each finished batch or serial of veterinary vaccine must be potency tested to assure the quality of marketed product. The potency assay must be correlated to efficacy in the target species. Potency assays of nonreplicating vaccines have traditionally measured the immune response to the vaccine in host or laboratory animals by serology or protection from challenge. Such tests are expensive, time-consuming, and raise animal welfare concerns. As disease agent protective antigens are described, in vitro techniques for quantitating them can be applied to vaccine potency measurement. However, in many cases the immunological adjuvants critical to the efficacy of the biological interfere with in vitro antigen quantitation techniques. The development of techniques that remove or compensate for the effect of adjuvants on the assays, sham vaccines containing no antigen, reference preparations containing a proven protective immunogen dose, characterization of the immunological reactants, and appropriate design and data analysis have contributed to the development of rapid, reproducible, humane, and relatively inexpensive in vitro potency assays to be used in the evaluation of veterinary biologicals.

Animal Testing Alternatives↗
PubMed1993

Treatment of diabetic neuropathy with gamma-linolenic acid. The gamma-Linolenic Acid Multicenter Trial Group.

OBJECTIVE: To compare the effects of placebo and GLA on the course of mild diabetic neuropathy over 1 yr. RESEARCH DESIGN AND METHODS: We entered 111 patients with mild diabetic neuropathy from seven centers into a randomized, double-blind, placebo-controlled parallel study of GLA at a dose of 480 mg/day. MNCV, SNAP, CMAP, hot and cold thresholds, sensation, tendon reflexes, and muscle strength were assessed by standard tests in upper and lower limbs. RESULTS: For all 16 parameters, the change over 1 yr in response to GLA was more favorable than the change with placebo, and for 13 parameters, the difference was statistically significant. Sex, age, and type of diabetes did not influence the result, but treatment was more effective in relatively well-controlled than in poorly-controlled diabetic patients. CONCLUSIONS: GLA had a beneficial effect on the course of diabetic neuropathy.

Analysis of Variance↗
PubMed1993

Direct isolation and identification of recombinant pseudorabies virus strains from tissues of experimentally co-infected swine.

Tissue homogenates were obtained from swine co-infected with 2 vaccine strains of pseudorabies virus (PRV). Viral isolates derived by serial plaque purification directly from tissue homogenates, without an intervening step of isolation and amplification on cell cultures, were characterized as recombinant and parental PRV genotypes on the basis of thymidine kinase and glycoprotein X gene combinations. Use of limiting dilutions and recovery of virus isolates as individual plaques minimized the likelihood of in vitro recombination serving as a confounding source of recombinant PRV. The thymidine kinase and glycoprotein X gene sequences were classified as wild-type or deleted, using a battery of polymerase chain reaction assays. Results substantiate the observation that PRV vaccine strains can form genetic recombinants in vivo after experimentally induced co-infection.

Animals↗
PubMed1992

The NADPH-oxidase-associated H+ channel is opened by arachidonate.

The H+ channel associated with the generation of O2.- by NADPH oxidase and the oxidase itself must both be activated in response to stimuli (e.g. phorbol esters, chemotactic peptides, certain fatty acids). We have investigated the effects of membrane potential, an imposed pH gradient and a combination of the two (the protonmotive force) on the H+ conductivity of the cytoplast membrane. H+ conductivity was observed only in the presence of arachidonate and not in its absence. In the presence of arachidonate, H+ movement was determined by the protonmotive force. The effect of arachidonate was probably on a channel, since this fatty acid did not significantly increase the H+ permeability of artificial phospholipid membranes. It appears, therefore, that arachidonate is required both for the activation of O2.- production and the associated H(+)-channel-mediated efflux.

Arachidonic Acid↗
PubMed1992

Immunovisualization of high (HK) and low (LK) molecular weight kininogens on isolated human neutrophils.

An immunocytochemical study was performed to examine the cellular localization and the subcellular distribution of kininogens in human blood cells. Kininogens were visualised using the immunogold-silver staining method and confocal scanning laser microscopy. We confirmed the existence of high molecular weight kininogen in human neutrophils and describe for the first time the presence of low molecular weight kininogen on these cells. Both high and low molecular weight kininogens were restricted to the neutrophils where they localized as clusters of immunogold particles on the cell membrane. No labeling was observed intracellularly in organelles such as mitochondria, endoplasmic reticulum, and azurophilic or specific granules after permeabilization of the neutrophils with Triton X-100, a procedure that permitted the visualization of elastase in the azurophilic granules. Clusters of high molecular weight kininogen molecules attached to the neutrophil surface could serve as receptors for plasma kallikrein and/or be the source of substrate for a discrete and circumscribed formation of kinins that may in turn facilitate the local diapedesis of neutrophils and the transudation of plasma constituents during acute inflammation.

Antibodies, Monoclonal↗
PubMed1992

Immunovisualisation of plasma prekallikrein and H-kininogen on human neutrophils and in human hepatocytes.

Both plasma prekallikrein and H-kininogen were immunolocalised in human hepatocytes by the use of immunocytochemical techniques in conjunction with the confocal optical scanning microscopy. In contrast, both proteins were demonstrated on the external surface of human blood neutrophils. However, detection of H-kininogen on non-fixed but not on fixed neutrophils with the anti-domain 6 antibody (directed at the prekallikrein binding site on H-kininogen), suggested that access to the epitope was blocked by the presence of the bound plasma prekallikrein. Therefore, we prepose that H-kininogen provides the binding site for plasma prekallikrein on circulating neutrophils.

Adult↗