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L J Roberts

Publications and source records attributed to L J Roberts.

At least 73 records · Page 4Linked to original sources
PubMed1999

Increased cerebral cortical lipid peroxidation and abnormal phospholipids in aged homozygous apoE-deficient C57BL/6J mice.

Aged homozygous apolipoprotein E gene-deficient (apoE -/-) mice have been proposed as an experimental model for the role of human apoE isoforms in Alzheimer's disease (AD). However, results from different laboratories have been in conflict regarding the presence or absence of neurodegeneration in these mice. Moreover, despite apoE being the major lipid trafficking molecule in the central nervous system, there has been no investigation of brain lipid levels in apoE -/- mice. Here we have examined male and female apoE -/- and control mice aged 10 to 12 months, testing the hypothesis that lack of apoE leads to some of the neuropathological changes seen in AD. Our results failed to demonstrate significant neurodegeneration, histopathological changes, or reduction in cerebral cortical synaptophysin in apoE -/- mice. However, we did observe a significant reduction in cerebral cortical phospholipids and their constituent fatty acids, as well as elevated lipid peroxidation products, in apoE -/- mice compared to apoE +/+ mice with the same genetic background. Our results suggest that the brains of aged apoE -/- mice display some of the lipid abnormalities associated with AD; however, these changes alone, at the magnitudes achieved in the apoE -/- mice, do not directly lead to the major neurodegenerative changes of AD.

Aging↗
PubMed1999

The magnitude of brain lipid peroxidation correlates with the extent of degeneration but not with density of neuritic plaques or neurofibrillary tangles or with APOE genotype in Alzheimer's disease patients.

Numerous post mortem studies have demonstrated increased accumulation of lipid peroxidation products in diseased regions of Alzheimer's disease (AD) brain; however, few have used techniques that quantify the magnitude of lipid peroxidation in vivo. F(2)-isoprostanes (F(2)-IsoP's) are exclusive products of free radical-mediated peroxidation of arachidonic acid, and their quantification has been widely used as an in vivo biomarker of the magnitude of lipid peroxidation. We have determined F(2)-IsoP concentrations in lateral ventricular fluid (VF) from 23 AD and 12 age-matched controls and correlated these with neuropathological and genetic markers of AD. VF F(2)-IsoP levels were significantly elevated in AD patients compared with controls (p < 0.01) and were significantly correlated with three different measures of brain degeneration: reduction in brain weight (p < 0.01), degree of cortical atrophy (p < 0.01), and Braak stage (p = 0.02). When analysis was restricted to AD patients only, VF F(2)-IsoP levels still were significantly correlated to reduction in brain weight and degree of cortical atrophy (p < 0.05). VF F(2)-IsoP concentrations were not related to density of neuritic plaques or neurofibrillary tangles in seven brain regions, or to the number of epsilon4 alleles of the apolipoprotein E gene (APOE). These data suggest that the magnitude of brain lipid peroxidation is closely related to the extent of brain degeneration in AD but is not significantly influenced by the density of neuritic plaques or neurofibrillary tangles, or the number of epsilon4 alleles of APOE.

Aged↗
PubMed1999

Mass spectrometric quantification of F2-isoprostanes in biological fluids and tissues as measure of oxidant stress.

This chapter has outlined methods to assess lipid peroxidation associated with oxidant injury in vivo by quantifying concentrations of free F2-IsoPs in biological fluids and levels of F2-IsoPs esterified in tissue lipids. The mass spectrometric assay described herein is highly precise and accurate. A potential shortcoming with this approach is that it requires expensive instrumentation, i.e., a mass spectrometer. However, several immunoassays for an F2-IsoP, 8-iso-PGF2 alpha, have become available from commercial sources. At this time, the accuracy and reliability of these assay for quantifying F2-IsoPs in biological fluids has not been fully validated by mass spectrometry. If these immunoassays prove to be a reliable measure of F2-IsoPs, however, this should greatly expand the use of F2-IsoPs to assess oxidant stress. In conclusion, studies carried out over the past several years have shown that measurement of F2-IsoPs has overcome many of the limitations associated with other methods to assess oxidant status, especially when applied to the measurement of oxidant stress in vivo in humans. Therefore, the quantification of F2-IsoPs represents an important advance in our ability to assess the role of oxidant stress and lipid peroxidation in human disease.

Animals↗
PubMed1999

Chronic aminoguanidine attenuates renal dysfunction and injury in aging rats.

We have previously shown that aging is associated with increased lipid peroxidation, reductions in renal function, and increased glomerular sclerosis. The mechanism(s) responsible for these age-related changes are not clear. The purpose of the present studies was to determine if there was an increase in inducible nitric oxide synthase (iNOS) with aging, and if so, whether inhibition of iNOS would prevent aging injury by preventing free radical-mediated lipid peroxidation. iNOS protein expression in the kidney increased by approximately 90% by 24 months. Inhibition of iNOS by aminoguanidine (0.1% in drinking water) for 9 months, beginning at 13 months of age, reduced blood pressure, improved glomerular filtration rate by 70%, and renal plasma flow by 40%, whereas glomerular sclerosis was considerably reduced. Renal F2-isoprostanes and malondialdehyde levels, markers of oxidative stress and lipid peroxidation, were not reduced by aminoguanidine. Aminoguanidine also did not attenuate immunostaining for advanced glycosylation end products (AGE) in the kidneys. These findings suggest that aminoguanidine attenuates aging renal dysfunction by inhibiting a pathophysiologic function of iNOS that is independent of free radical-mediated lipid peroxidation or significant effects on AGE deposition.

Aging↗
PubMed1999

Giving and receiving help: interpersonal transactions in mutual-help meetings and psychosocial adjustment of members.

The helping transactions that occur in group meetings have been theorized to be important therapeutic mechanisms within mutual-help (or self-help) groups. Hypothesized links between giving and receiving help and psychosocial adjustment were examined in a mutual-help group for individuals with serious mental illness (GROW). Participants' adjustment was assessed at two time points and helping behaviors were measured with observational coding of weekly group interactions during the period between assessments. Frequencies of helping behaviors were used to predict Time 2 adjustment after controlling for initial adjustment. Consistent with the helper therapy principle, giving help to others predicted improvements in psychosocial adjustment; giving advice was a unique predictor. Total amount of help received was not associated with adjustment, but receiving help that provided cognitive reframing was associated with better social adjustment. A predicted interaction suggested that receiving help was related to better functioning when members experienced high levels of group integration.

Adaptation, Psychological↗
PubMed1999

Methods for defining and determining the clinical significance of treatment effects: description, application, and alternatives.

This article summarizes and scrutinizes the growth of the development of clinically relevant and psychometrically sound approaches for determining the clinical significance of treatment effects in mental health research by tracing its evolution, by examining modifications in the method, and by discussing representative applications. Future directions for this methodology are proposed.

Clinical Trials as Topic↗
PubMed1999

Molluscum contagiosum, swimming and bathing: a clinical analysis.

The link between swimming and bathing behaviour, and molluscum contagiosum (MC), in a sample of 198 patients with clinically confirmed MC was investigated. Results show that of all the swimming behaviour variables tested, only one (swimming in a school swimming pool) was significant. In relation to the bathing variables tested, only two (sharing a bath sponge with a MC-infected person, and sharing a bath towel with a MC-infected person), were significant. No relationship was found between MC and swimming in a private (home) pool, swimming in a public pool, swimming at the beach, sharing a bath tub with a MC-infected person, and using a private (home) spa. The Relative Risk (RR) ratio of a person sharing a bath sponge with an infected person is three times more at risk of procuring a severe case of MC infection (i.e. > 26 lesions) than a person who does not share a bath sponge with an infected person (r = 0.5; P < 0.01). There was a correlation found between the mode of MC acquisition by site location (r = 0.63; P < 0.05). The anatomical position of MC lesions was shown to be highly dependent on the way the patient was primarily infected. There was also an additive effect with the mode of transmission in that patients who were in the upper extremes in terms of the total number of lesions (average, 124 lesions; mean diameter size, 4.2 mm; n = 42), were those patients who shared a number of fomites (bath sponge, bath towel) with a known MC-infected person, and also swam at the school swimming pool.

Adolescent↗
PubMed1999

Increased formation of thromboxane in vivo in humans with mastocytosis.

Clinical manifestations of mastocytosis are mediated, at least in part, by release of the mast cell mediators histamine and prostaglandin D2. It has been previously reported that in addition to prostaglandin D2, mast cells produce other eicosanoids, including thromboxane. Nonetheless, little information exists regarding the formation of other prostanoids in vivo. The most accurate method to examine the systemic production of eicosanoids in vivo is the quantitation of urinary metabolites. We previously developed a highly accurate assay employing mass spectrometry to measure a major urinary metabolite of thromboxane, 11-dehydro-thromboxane B2, in humans. We utilized this assay to quantitate thromboxane production in 17 patients with histologically proven mastocytosis. We report that thromboxane formation was significantly increased (>2 SD above the mean) in at least one urine sample from 65% of patients studied. Of these, 91% of patients with documented systemic involvement had elevated thromboxane generation. In addition, endogenous formation of thromboxane was highly correlated with the urinary excretion of the major urinary metabolite of prostaglandin D2 (r = 0.98) and Ntau-methylhistamine (r = 0.91), suggesting that the cellular source of increased thromboxane in vivo could be the mastocyte. Enhanced thromboxane formation in patients with this disorder is unlikely to be of platelet origin as other markers of platelet activation, platelet factor 4 and beta-thromboglobulin, were not increased in three patients with marked overproduction of thromboxane. Furthermore, the recovery of 11-dehydro-thromboxane B2 excretion in two patients after the administration of aspirin occurred significantly more rapidly than the recovery of platelet thromboxane generation. These studies, therefore, report that thromboxane production is significantly increased in the majority of patients with mastocytosis that we examined and provide the basis to elucidate the role of this eicosanoid in disorders of mast cell activation.

6-Ketoprostaglandin F1 alpha↗
PubMed1999

The isoprostanes: unique prostaglandin-like products of free-radical-initiated lipid peroxidation.

The discovery of IsoPs as products of nonenzymatic lipid peroxidation has opened up new areas of investigation regarding the role of free radicals in human physiology and pathophysiology. The quantification of IsoPs as markers of oxidative stress status appears to be an important advance in our ability to explore the role of free radicals in the pathogenesis of human disease. An important need in the field of free-radical medicine is information regarding the clinical pharmacology of antioxidant agents. Because of the evidence implicating free radicals in the pathogenesis of a number of human diseases, large clinical trials are planned or underway to assess whether antioxidants can either prevent the development or ameliorate the pathology of certain human disorders. However, data regarding the most effective doses and combination of antioxidant agents to use in these clinical trials is lacking. As mentioned previously, administration of antioxidants suppresses the formation of IsoPs, even in normal individuals. Thus, measurement of IsoPs may provide a valuable approach to define the clinical pharmacology of antioxidants. In addition to being markers of oxidative stress, several IsoPs possess potent biological activity. The availability of additional IsoPs in synthetic form should broaden our knowledge concerning the role of these molecules as mediators of oxidant stress. Despite the fact that considerable information has been obtained since the initial report of the discovery of IsoPs [6], much remains to be understood about these molecules. With continued research in this area, we believe that much new information will emerge that will open up additional important new areas for future investigation.

Dinoprost↗
PubMed1999

New developments in the isoprostane pathway: identification of novel highly reactive gamma-ketoaldehydes (isolevuglandins) and characterization of their protein adducts.

The bicyclic endoperoxide prostaglandin (PG) H2 undergoes nonenzymatic rearrangement not only to PGE2 and PGD2, but also to levuglandins (LG) E2 and D2, which are highly reactive gamma-ketoaldehydes. Isoprostanes (IsoPs) are PG-like compounds that are produced by nonenzymatic peroxidation of arachidonic acid. PGH2-like endoperoxides are intermediates in this pathway. Therefore, we explored whether the IsoP endoperoxides also undergo rearrangement to form IsoLGs. Oxidation of arachidonic acid in vitro resulted in the formation of abundant quantities of compounds that were established to be IsoLGs by using mass spectrometric analyses. However, the formation of IsoLGs could not be detected in biological systems subjected to an oxidant stress. We hypothesized that this was due to extremely rapid adduction of IsoLGs to proteins. This notion was supported by the finding that LGE2 adducted to albumin at a rate that exceeded that of 4-hydroxynonenal by several orders of magnitude: >50% of LGE2 had adducted within 20 s. We therefore undertook to characterize the nature of LG adducts. Using liquid chromatography electrospray tandem mass spectrometry, we established that LGs form oxidized pyrrole adducts (lactams and hydroxylactams) with the epsilon-amino group of lysine. Oxidation of low density lipoprotein resulted in readily detectable IsoLG adducts on apolipoprotein B after enzymatic digestion of the protein to individual amino acids. These studies identify a novel class of ketoaldehydes produced by the IsoP pathway that form covalent protein adducts at a rate that greatly exceeds that of other known aldehyde products of lipid peroxidation. Elucidation of the nature of the adducts formed by IsoLGs provides the basis to explore the formation of IsoLGs in vivo and investigate the potential biological ramifications of their formation in settings of oxidant injury.

Animals↗
PubMed1999

Divergence of brain prostaglandin H synthase activity and oxidative damage in mice with encephalitis.

Several lines of evidence point to inflammation and increased oxidant injury in brain regions of patients with Alzheimer disease (AD). Prostaglandin H synthase (PGHS) catalyzes the limiting step in prostaglandin synthesis and generates a potent oxidizing agent as by-product. One form of PGHS, PGHS-2, is induced by pro-inflammatory signals; thus leading to the 2-step hypothesis that pro-inflammatory signals in AD brain induce PGHS-2 that in turn contributes to brain oxidant injury. Here we have tested directly this 2-step hypothesis in a murine reovirus type 3 encephalitis model by measuring cerebral PGHS activity and quantifying oxidant injury. Our results showed a robust chronic inflammatory infiltrate and a 2-fold increase in PGHS activity in encephalitic mice compared with controls. Despite these changes, there was no significant increase in F2-isoprostanes or F4-neuroprostanes, accurate in vivo biomarkers of oxidant injury, and only minimal accumulation of protein adducts from the lipid peroxidation product 4-hydroxy-2-nonenal in the most intensely inflamed brain regions. These results challenge the proposal of others that pro-inflammatory induction of PGHS activity significantly contributes to oxidant injury in brain.

Aldehydes↗
PubMed1999

Enhanced in vivo lipid peroxidation at elevated plasma total homocysteine levels.

An elevated plasma total homocysteine level (tHcy) is considered an independent risk factor for atherosclerosis. The mechanisms by which hyperhomocysteinemia induces atherosclerosis are only partially understood, but promotion of LDL oxidation and endothelial injury have been suggested. The purpose of this study was to test the hypothesis that a high plasma tHcy is associated in men with increased in vivo lipid peroxidation, as measured by plasma F2-isoprostane concentrations. We investigated this association in a subset of the participants in the Antioxidant Supplementation in Atherosclerosis Prevention (ASAP) study. Of 256 male participants, a subsample of 100 consecutive men was selected for F2-isoprostane assays. The mean tHcy was 11.0 micromol/L, and the mean F2-isoprostanes was 29.6 ng/L. The simple correlation coefficient for association between tHcy and F2-isoprostane was 0.40 (P<0.001). In a linear regression model, the variables with the strongest associations with F2-isoprostane were tHcy (standardized coefficient 0.33, P<0.001), serum triglycerides (0.21, P=0.042), carbohydrate-deficient transferrin (0.15, P=0.132), and plasma lipid-standardized alpha-tocopherol (-0.11, P=0.252) (R2=0.24, P<0. 001 for model). Plasma F2-isoprostane levels increased linearly across quintiles of tHcy (P<0.001). The unadjusted mean (95% confidence interval) F2-isoprostanes was 47.5% greater in the highest tHcy quintile (37.4, 31.1 to 43.6 ng/L) than in the lowest quintile (25.3, 21.3 to 29.3 ng/L). Adjustment for the strongest other determinants of F2-isoprostane reduced this difference to 28. 2% (P=0.010). Our present data suggest that elevated fasting plasma tHcy is associated with enhanced in vivo lipid peroxidation in men.

Arteriosclerosis↗
PubMed1999

Allergen-induced synthesis of F(2)-isoprostanes in atopic asthmatics. Evidence for oxidant stress.

It is thought that reactive oxygen species (ROS) participate in the inflammation which characterizes asthma, but the evidence supporting this contention is incomplete. F(2)-isoprostanes (F(2)-IsoPs) are arachidonate products formed on membrane phospholipids by the action of ROS and thereby represent a quantitative measure of oxidant stress in vivo. Using a mass spectrometric assay we measured urinary release of F(2)-IsoPs in 11 patients with mild atopic asthma after inhaled allergen challenge. The excretion of F(2)-IsoPs increased at 2 h after allergen (1.5 +/- 0.2 versus 2.6 +/- 0.3 ng/mg creatinine) and remained significantly elevated in all urine collections for the 8-h period of the study (analysis of variance [ANOVA]). The measured compounds were of noncyclooxygenase origin because neither aspirin nor indomethacin given before challenge suppressed them. Urinary F(2)-IsoPs remained unchanged after inhaled methacholine challenge. In nine atopic asthmatics, F(2)-IsoPs were quantified in bronchoalveolar lavage fluid (BALF) at baseline values and in a separate segment 24 h after allergen instillation. F(2)-IsoPs were elevated late in the BALF (0.9 +/- 0.2 versus 11.4 +/- 3.0 pg /ml, baseline versus allergen, respectively, p = 0.007). The increase was inhibited by pretreatment of the subjects with inhaled corticosteroids. These findings provide a new evidence for a role for ROS and lipid peroxidation in allergen-induced airway inflammation.

Administration, Inhalation↗
PubMed1999

Increased CSF F2-isoprostane concentration in probable AD.

OBJECTIVE: To quantify F2-isoprostane levels in CSF obtained from the lumbar cistern of patients with AD, ALS, and controls. BACKGROUND: Studies of human postmortem tissue and experimental models have suggested a role for oxidative damage in the pathogenesis of several neurodegenerative diseases, especially AD and ALS. F2-isoprostanes are exclusive products of free-radical-mediated peroxidation of arachidonic acid that have been widely used as quantitative biomarkers of lipid peroxidation in vivo in humans. Recently, we showed that F2-isoprostane concentrations are significantly elevated in CSF obtained postmortem from the lateral ventricles of patients with definite AD compared with controls. METHODS: F2-isoprostanes were quantified by gas chromatography/negative ion chemical ionization mass spectrometry. RESULTS: CSF F2-isoprostanes were increased significantly in patients with probable AD, but not in ALS patients, compared with controls. CONCLUSIONS: Increased CSF F2-isoprostanes are not an inevitable consequence of neurodegeneration and suggest that increased brain oxidative damage may occur early in the course of AD.

Aged↗
PubMed1999

Novel eicosanoids. Isoprostanes and related compounds.

The discovery of IsoPs has been an interesting development for a number of reasons, apart from the fact that it involves novel biochemistry. The simple fact that prostanoids are produced nonenzymatically in prodigous quantities in vivo and in much greater quantities than prostaglandins generated by the cyclooxygenase enzyme was a remarkable finding. The observation that detectable quantities of F2-IsoPs are present in all tissues and human biological fluids carries interesting implications. Previously, there had been little convincing evidence for the occurrence of lipid peroxidation in vivo except under unusual conditions of severe oxidative stress. However, the finding that F2-IsoPs can be easily detected in normal humans suggests a continuous level of ongoing oxidative injury that is not completely suppressed by the elaborate system of antioxidant defenses that have evolved. Another very important aspect of the discovery of IsoPs is that it has brought to the field a long sought after reliable approach to assess oxidative stress status in vivo. The continuing and expanded use of measurements of IsoPs for this purpose will contribute in a very valuable way to advancing our understanding of the role of free radicals in human disease processes. Further, the finding that these compounds are not simply markers of oxidant injury but can also exert potent biological actions both by interaction with specific receptors and, in the case of IsoLGs and cyclopentenenone IsoPs, by virtue of their chemical reactivity, has identified several new classes of molecules that are produced by free radical-induced lipid peroxidation that may mediate some of the adverse sequela of oxidant injury. The elucidation of the variety of compounds that are produced as products of the IsoP pathway and more recently the NP pathway provides vast new areas for scientific inquiry that should yield new and interesting information as this area continues to advance.

Antioxidants↗