Biomedical subjects

L X Tang

Publications and source records attributed to L X Tang.

9 recordsLinked to original sources

PubMed2001

Lipid peroxidation and platelet activation in murine atherosclerosis.

BACKGROUND: Lipid peroxidation and platelet activation are thought to be important contributors to the pathogenesis of atherosclerosis. The relevance of their interaction in vivo, however, is unknown. METHODS AND RESULTS: LDL receptor-deficient (LDLR(-/-)) mice on a high-fat diet developed extensive atherosclerosis and had increased urinary levels of 8,12-iso-isoprostane (iP) F(2alpha)-VI and 2,3-dinor-thromboxane (Tx) B(2), markers of in vivo lipid peroxidation and platelet activation, respectively. Vitamin E supplementation suppressed 8,12-iso-iPF(2alpha)-VI biosynthesis and reduced atherosclerosis (65%) without having a significant effect on lipid levels or TxB(2) biosynthesis. Addition of the platelet inhibitor indomethacin to vitamin E simultaneously suppressed 8,12-iso-iPF(2alpha)-VI and TxB(2), significantly reduced soluble intercellular adhesion molecule-1 and monocyte chemoattractant protein-1, and remarkably, further reduced atherosclerosis (80%). CONCLUSIONS: These results indicate that in vivo lipid peroxidation and platelet activation coexist in murine atherosclerosis and that lipid peroxidation does not contribute to platelet activation and reflects the oxidant component of the inflammatory response. Our findings suggest that oxidant stress and platelet activation represent 2 distinct therapeutic targets in atherogenesis. We propose that a combination of antioxidants and platelet inhibitors might be rationally evaluated in the prevention of progression of human atherosclerosis.

Animals↗

PubMed2001

Serum free light-chain measurements for identifying and monitoring patients with nonsecretory multiple myeloma.

Using sensitive, automated immunoassays, increased concentrations of either kappa or lambda free light chains (and abnormal kappa/lambda ratios) were detected in the sera of 19 of 28 patients with nonsecretory multiple myeloma. Four other patients had suppression of one or both light chains, and the remaining 5 sera had normal or raised free light-chain concentrations with substantially normal kappa/lambda ratios. Six of the patients with an elevated single free light chain, who were studied during follow-up, had changes in disease activity that were reflected by the changes in free light-chain concentrations. It is concluded that quantification of free light chains in serum should prove useful for the diagnosis and monitoring of many patients with nonsecretory myeloma.

Culture Media, Serum-Free↗

PubMed2001

Highly sensitive, automated immunoassay for immunoglobulin free light chains in serum and urine.

BACKGROUND: Bence Jones proteins or monoclonal immunoglobulin kappa and lambda free light chains (FLCs) are important markers for identifying and monitoring many patients with B-cell tumors. Automated immunoassays that measure FLCs in urine and serum have considerable clinical potential. METHODS: Sheep antibodies, specific for FLCs, were prepared by immunization with pure kappa and lambda molecules and then adsorbed extensively against whole immunoglobulins. The antibodies were conjugated onto latex particles and used to assay kappa and lambda FLCs on the Beckman IMMAGE protein analyzer. RESULTS: The unconjugated antibodies showed minimal cross-reactivity with intact immunoglobulins or other proteins. With latex-conjugated antibodies, kappa and lambda FLCs could be measured in normal sera and most normal urine samples. Patients with multiple myeloma had increased concentrations of the relevant serum FLC, whereas both FLCs were increased in the sera of patients with systemic lupus erythematosus. CONCLUSIONS: We developed sensitive, automated immunoassays for kappa and lambda FLC measurements in serum and urine that should facilitate the assessment of patients with light chain abnormalities.

Animals↗

PubMed2000

Down's syndrome is associated with increased 8,12-iso-iPF2alpha-VI levels: evidence for enhanced lipid peroxidation in vivo.

Postmortem and in vitro studies have shown that oxidative stress plays a role in the pathogenesis of many of the clinical features of Down's syndrome. The isoprostane 8,12-iso-iPF2alpha-VI is a specific marker of lipid peroxidation. We found elevated levels of this isoprostane in urine samples of subjects with Down's syndrome compared with those of matched controls, which correlated with the duration of the disease. These results suggest that increased in vivo lipid peroxidation is a prominent component early in the course of Down's syndrome.

Adolescent↗

PubMed1997

Effects of additional iron-chelators on Fe(2+)-initiated lipid peroxidation: evidence to support the Fe2+ ... Fe3+ complex as the initiator.

The addition of chelated Fe2+ ions in a liposomal system often results in a short lag period before peroxidation starts. The addition of a second chelator at the end of the lag period results in an inhibition of the lipid peroxidation. The degree of inhibition depends on the stability constants of the chelator in ligating Fe2+ and/or Fe3+. A more striking inhibitory effect was observed for the chelators with higher stability constant for either or both Fe(2+)- and Fe(3+)-complex, but much less inhibition was found for those with lower stability constants for both complexes. Assuming that the "initiator" for iron-dependent lipid peroxidation is formed through the redox process of iron ion and finally emerged at the end of the latent period, the inhibitory effect of the second chelator may be explained as the abstraction of either Fe2+ or Fe3+ from the initiator by an additional free chelator, which results in the decomposition of the initiator. This study supports the hypothesis that a Fe2+ ... Fe3+ complex is responsible for iron-initiated lipid peroxidation.

Adenosine Diphosphate↗

PubMed1994

Effects of lead on temporal response properties of retinal ganglion cells in developing rats.

Neonatal rats have taken in lead, during the period from their parturition to their weaning, from the milk of dams fed with water containing 0.2% lead acetate solutions. The alterations in the temporal response properties of retinal ganglion cells in adult rats (90 days) following the lead exposure at their developing stage have been studied. The results of this investigation demonstrate that the lead exposure in neonatal rats causes decreases in the optimal temporal frequency, bandwidth at half amplitude, temporal resolution and response phase of the retinal ganglion cells in adult rats. Compared with the sustained cells, the transient cells have a much greater alteration in temporal response properties.

Action Potentials↗

PubMed1990

Optimisation of enzyme electrodes.

Enzyme electrodes have been fabricated in a variety of ways and used successfully for aqueous solution measurement. Knowledge about the fundamental basis of their operation has increased substantially in recent years, but the final, partly technological, hurdle of adaptation for practical use remains to be fully surmounted. Key aspects requiring attention are dependence on solution parameters capable of changing the kinetics of the immobilised enzyme reaction, direct fouling at the enzyme electrode, and the distorting effect of the biological matrix, notably blood and tissue, on the electrode environment due to the deposition of surface-active macromolecules and cellular elements. This review of enzyme electrode optimisation deals primarily with the various membranes which have been used to try to overcome such highly practical limitations to the biomedical use of enzyme electrodes. The classical amperometric glucose electrode based on detection of H2O2/O2 by the underlying sensor will be emphasised, but pH-based sensors for pyruvate and urea will also be discussed. The amperometric systems described indicate that with appropriate covering membranes, many, though by no means all, interfacing problems can be overcome, and also that the type of optimisation engineered is dictated by the specific application envisaged.

Biocompatible Materials↗

PubMed1989

The needle glucose electrode: in vitro performance and optimisation for implantation.

The classical glucose needle electrode based on detection of H2O2 from glucose oxidase has been studied. Dip-coating of a series of outer polyurethane layers of increasing concentration (10-50% W/V) achieved devices with extended linearity (greater than or equal to 30 mM glucose) with greater reliability than a single dip-coat. In vitro performance in unstirred whole blood was acceptable, and all devices were stir-independent. Nevertheless, signal size was affected by a high solution viscosity, and this may have implications for the use of enzyme electrodes in subcutaneous tissue.

Biosensing Techniques↗

PubMedDate not supplied

Effects of low-level lead on retinal ganglion sustained and transient cells in developing rats.

Neonatal rats were exposed to lead from parturition to weaning via the milk of dams drinking 0.2% lead acetate solutions. The alterations in the excitability and temporal response properties of retinal ganglion cells in adult rats (90 days) following developmental lead exposure were studied. The results of this investigation demonstrated that the lead exposure in neonatal rats caused an increase in excitability, and a decrease in optimal temporal frequency, bandwidth at half amplitude, temporal resolution, and response phase of the retinal ganglion cells in adult rats. Compared with the sustained cells, the transient cells had a much greater alteration in excitability and temporal response properties.

Action Potentials↗