Rabbit and human atherosclerotic lesions contain IgG that recognizes epitopes of oxidized LDL

Atherosclerotic lesions contain relatively large quantities of IgG. We have previously shown that both human and rabbit sera contain autoantibodies against epitopes of oxidized (Ox) low-density lipoprotein (LDL) and that LDL isolated from atherosclerotic lesions contains small amounts of tightly bound IgG. However, it is not known whether IgG isolated from atherosclerotic lesions recognizes epitopes present in native LDL or Ox-LDL. IgG was isolated from Watanabe heritable hyperlipidemic (WHHL) rabbit atherosclerotic lesions by sequential salt extractions, purified by fast protein liquid chromatography on protein G, and used in a solid-phase radioimmunoassay. IgG and immune complexes were also isolated from the saline extracts of human lesions by adsorption onto latex beads coated with anti-human IgG antibodies or protein A. IgG isolated from rabbit lesions showed significant titers against malondialdehyde (MDA)-modified LDL and LDL oxidized by copper ions for 4 and 18 hours but not against native LDL. On Western blots, lesion IgG stained MDA-LDL and fragments of Ox-LDL. Western blots of immune complexes isolated from human lesions revealed the presence in the isolated complexes of both apoprotein B and apoprotein B fragments, which reacted with antibodies to MDA-lysine. Furthermore, rabbit lesion IgG immunostained epitopes of Ox-LDL present in human atherosclerotic lesions. Immunostains obtained with rabbit lesion IgG were similar to those obtained with a monoclonal antibody specific for MDA-lysine. The results show that human and rabbit atherosclerotic lesions contain IgG that recognizes epitopes characteristic of Ox-LDL. These data suggest that immunologic processes may be an important component of the atherogenic process.

Correlates of suicide and violence risk 1: the suicide risk measure

A measure of suicide risk was developed using items reported to discriminate suicidal patients from controls in various studies. The new self-report scale was administered to 82 outpatients, 157 inpatients, and 83 college students. Using total scores, significant differences were found between the college sample and the two patient samples. The scale also discriminated between patients who reported one or more past suicide attempts and those who reported none. An independent cross-validation showed that half of the items continued to discriminate between patient and control groups. Sensitivity and specificity estimates were also determined. The test does not attempt to predict a specific rare event, i.e., suicide. It attempts to describe the degree to which a given individual reveals a set of characteristics that are similar to a suicide prototype.

Eosinophil-rich human polymorphonuclear leukocyte preparations characteristically release leukotriene C4 on ionophore A23187 challenge

Blood samples were obtained from a group of 20 patients with hypereosinophilia (greater than or equal to 1500 eosinophils/mm3). The polymorphonuclear leukocytes (PMNLs) were prepared from blood treated with ethylenediaminetetra-acetic acid by successive dextran sedimentation of the red blood cells, separation of mononuclear leukocytes and PMNLs on Ficoll-Paque, and ammonium chloride treatment of the PMNL fraction. The eosinophil content of the final PMNL preparations ranged from 15% to 75%, as assessed by Wright-stained smears, and the remaining leukocytes were predominantly neutrophils with only 3% to 5% mononuclear cells. The eosinophil-rich PMNL preparations as well as PMNL preparations from normal volunteers were incubated under various conditions and the arachidonic acid metabolites were analyzed by reverse-phase high-performance liquid chromatography. The synthesis of 5-lipoxygenase products was strongly stimulated by the ionophore A23187 in both normal and eosinophil-rich PMNL preparations. Whereas the normal PMNL preparations, which were eosinophil poor, produced 10 to 25 times more leukotriene B4 than leukotriene C4, the eosinophil-rich PMNL preparations characteristically released leukotriene C4 in equal or up to 20 times greater amounts than leukotriene B4.

Studies on the mechanism of formation of the 5S, 12S-dihydroxy-6,8,10,14(E,Z,E,Z)-icosatetraenoic acid in leukocytes

Incubation of peripheral blood leukocytes with arachidonic acid (and ionophore A23187) led to the formation of leukotriene B4, delta 6-trans-leukotriene B4, delta 6-trans-12-epi-leukotriene B4, 5-hydroxy-icosatetraenoic acid, 12-hydroxy-icosatetraenoic acid and of 5S,12S-dihydroxy-6,8,10,14-(E,Z,E,Z)-icosatetraenoic acid (5S,12S-DiHETE). Incubation of leukocytes with leukotriene A4 resulted in the formation of leukotriene B4 and of its two delta 6-trans-isomers but not of the 5S, 12S-DiHETE. 18O2 labeling experiments have shown that the hydroxyl groups at C5 and C12 in the 5S,12S-DiHETE are derived from molecular oxygen. The tetraacetylenic analog of arachidonic acid was found to be potent inhibitor of the formation of the 5S,12S-DiHETE whereas it potentiated the synthesis of the 5-hydroxy acid and of leukotriene B4. Addition of the 12-hydroxy-icosatetraenoic acid to leukocytes, or of the 5-hydroxy-icosatetraenoic acid to a suspension of platelets caused the formation of the 5S,12S-DiHETE. It is concluded that the 5S,12S-DiHETE is not derived from leukotriene A4 but is a product of the successive reactions of arachidonic acid with two lipoxygenases of different positional specificities.

Pharmacological activity of leukotrienes A4, B4, C4 and D4 on selected guinea-pig, rat, rabbit and human smooth muscles

The myotropic activity of leukotrienes A4, B4, C4, D4 and histamine has been evaluated on selected smooth muscle preparations. LTA4, B4, C4 and D4 were several times more potent than histamine on the guinea-pig lung parenchymal strip, while on the guinea-pig trachea, LTB4 was less active. The guinea-pig ileum either in segments or in strips of longitudinal muscles responses well to LTC4, LTD4 and histamine but not to LTA4 and LTB4. Rat and rabbit lung parenchymal strip showed very little sensitivity for leukotrienes whereas human parenchymal strips and bronchi were nearly as sensitive as the guinea-pig lung.

Decreased leukotriene B4 synthesis in smokers' alveolar macrophages in vitro

Recent studies have shown that alveolar macrophages (AM) are able to release leukotrienes (LTs). Since cigarette smoking inhibits the cyclooxygenase pathway of arachidonic acid metabolism in the AM, we evaluated the LT production by AM from smokers and nonsmokers. AM were obtained from 35 volunteers, 16 nonsmokers, and 19 smokers. The cells were incubated under various conditions including stimulation with 30 microM arachidonic acid, 2 microM ionophore A23187, or both. Each experiment was performed in parallel using cells from a smoker and a nonsmoker. Lipoxygenase products were analyzed by reverse-phase high performance liquid chromatography. After stimulation, nonsmokers' AM produced LTB4 and 5-hydroxy-eicosatetraenoic acid (5-HETE). In incubations of AM with arachidonic acid and ionophore, the amounts of products formed were: LTB4, 317 +/- 56 pmol/10(6) cells and 5-HETE, 1,079 +/- 254, mean +/- SEM. No metabolites were generated under control conditions (no stimulation). In all incubations performed, the peptido-LTs (LTC4, LTD4, and LTE4) were undetectable. In comparison with AM from nonsmokers, those from smokers showed a 80-90% reduction of 5-HETE and LTB4 synthesis (P less than 0.05 to P less than 0.001 according to stimulatory conditions). This defective lipoxygenase metabolite production in AM from smokers was observed over a wide range of stimuli concentrations and incubation times; AM from smokers also had lower levels of intracellular (esterified) 5-HETE than nonsmokers' AM. We also studied blood polymorphonuclear leukocytes (PMNL) and no difference in the synthesis of 5-lipoxygenase products in these cells was noticed between smokers and nonsmokers. These data show that cigarette smoking causes a profound inhibition of the 5-lipoxygenase pathway in AM but not in blood PMNL.

Aminoguanidine inhibits oxidative modification of low density lipoprotein protein and the subsequent increase in uptake by macrophage scavenger receptors

Aminoguanidine decreases the formation of advanced glycosylation end products that occurs during chronic hyperglycemia. Presumably this occurs because early glycosylation products preferentially bind to aminoguanidine rather than to lysine groups of adjacent proteins. Because oxidative modification of low density lipoprotein (LDL) also involves derivatization of lysine residues of apolipoprotein (apo) B by reactive aldehydes formed during the decomposition of oxidized fatty acids, we postulated that aminoguanidine might also inhibit the oxidatively induced modification of LDL protein. To test this hypothesis we oxidized LDL by incubation with Cu2+ or with endothelial cells in the absence or presence of aminoguanidine. Aminoguanidine prevented apo B lysine modification, as measured by fluorescence spectroscopy, and inhibited in a dose-dependent manner the oxidatively induced increase in subsequent macrophage uptake. At concentrations that inhibited apo B modification (5-10 mM), aminoguanidine increased the lag time in diene conjugation but did not affect the plateau value reached. These data indicate that aminoguanidine inhibits oxidative modification of LDL protein in large part by binding reactive aldehydes formed during lipid peroxidation and preventing their subsequent conjugation to apo B. Thus, aminoguanidine (and related compounds) may be of dual benefit in inhibiting atherosclerosis, both by inhibiting formation of advanced glycosylation end products and by inhibiting the modification of LDL apo B that makes it a ligand for scavenger receptors.

Is there a relation between the seriousness of suicidal intent and the lethality of the suicide attempt?

The relation between the strength of an individual's intent to commit suicide and the nature and seriousness (lethality) of any suicide attempt has been a controversial one. Some studies suggest a positive correlation, while others report no connection. The present investigation included 60 patients, who were studied shortly after they had been admitted to a medical service after a suicide attempt. Measures of depression, impulsivity, suicidal intent, seriousness of the attempt, and efforts to prevent intervention were obtained. Results reveal that both depression and impulsivity correlate positively with the strength of the intent to commit suicide, but there appears to be almost no correlation in this population between measures of intent and seriousness of the attempt.

Psychological mindedness as a predictor of psychotherapy outcome: a preliminary report

This study investigated the properties of a new measure of psychological mindness (PM). A 45-item self-report questionnaire was administered to consecutive admissions to a large outpatient clinic that provides primarily psychodynamically oriented individual psychotherapy. The PM scores of a sample of 44 of these patients who attended a median of 15 sessions were correlated with several outcome measures obtained from retrospective chart reviews. These measures consisted of the number of sessions attended, discharge ratings, and change scores on a Global Assessment Scale (GAS) and on a symptom checklist. Coefficient alpha for the Psychological Mindedness (PM) Scale indicated high reliability. Total PM score correlated significantly with three of the outcome measures. Twenty of the 45-items were good predictors of one or more outcome measures.

Activation of leukotriene synthesis in human neutrophils by exogenous arachidonic acid: inhibition by adenosine A(2a) receptor agonists and crucial role of autocrine activation by leukotriene B(4)

We report here that the apparent inability of isolated human polymorphonuclear leukocytes (PMNs) to efficiently transform arachidonic acid (AA) is the consequence of A(2a) receptor engagement by endogenous adenosine accumulating in incubation media. Indeed, when adenosine is eliminated from PMN suspensions by the addition of adenosine deaminase, or when cells are incubated with adenosine A(2a) receptor antagonists, important quantities (40-80 pmol/10(6) cells) of 5-lipoxygenase products are synthesized by PMN incubated with 1 to 5 microM exogenous AA. The selective A(2a) receptor agonist CGS21680 was a very potent inhibitor of the AA-induced leukotriene (LT) synthesis, showing an IC(50) of approximately 1 nM. The mechanism of AA-induced stimulation of LT synthesis observed in the absence of extracellular adenosine was investigated. In adenosine deaminase-treated PMN, exogenous AA induced Ca(2+) mobilization and the translocation of 5-lipoxygenase to nuclear structures. A time lag of 20 to 60 s (variable between PMN preparations) was observed consistently between the addition of AA and the elevation of intracellular Ca(2+) concentration (and LT synthesis), indicating that AA itself did not trigger the Ca(2+) mobilization in PMN. This AA-induced Ca(2+) mobilization, as well as the corresponding 5-lipoxygenase translocation and stimulation of LT synthesis, was blocked efficiently by the LT synthesis inhibitor MK0591, the LTB(4) receptor antagonists CP105696 and LY223982, and the LTA(4) hydrolase inhibitor SC57461A. These data demonstrate that AA is a highly potent and effective activator of LT synthesis and acts through a mechanism that requires an autocrine stimulatory loop by LTB(4).

Suppression of leukotriene B4 biosynthesis by endogenous adenosine in ligand-activated human neutrophils

Adenosine (Ado) has been shown to suppress several functional responses of human polymorphonuclear leukocytes (PMNs). The current study investigated whether endogenous Ado regulates the biosynthesis of leukotriene (LT)B4 in ligand-stimulated PMNs. Measurements of Ado in PMN resuspended in Hanks' buffered salt solution (HBSS) or plasma showed a cell concentration- and time-dependent accumulation of the nucleoside. The removal of endogenous Ado with either Ado deaminase or the blockade of its action by the Ado A2a receptor antagonist, 8-(3-chlorostyryl) caffeine, markedly increased LTB4 biosynthesis upon ligand stimulation in HBSS. Similarly, LTB4 synthesis by ligand-stimulated PMNs in plasma (containing recombinant LTA4 hydrolase to allow the conversion of protein-bound LTA4) was strongly enhanced by addition of Ado deaminase. Addition of red blood cells to suspensions of PMNs in plasma mimicked the effect of adding Ado deaminase and LTA4 hydrolase in enhancing LTB4 biosynthesis upon ligand stimulation. This effect of red blood cells on LTB4 biosynthesis was blocked by dipyridamole, an inhibitor of Ado transport, or captopril, an inhibitor of LTA4 hydrolase. These results demonstrate that endogenous Ado efficiently downregulates ligand-stimulated LTB4 biosynthesis in PMN suspensions, pointing out a potentially important regulatory function of Ado in inflammatory exudates. These results also unveil a dual role for red blood cells in upregulating LTB4 biosynthesis, namely, the removal of endogenous Ado and the conversion of LTA4 released by activated PMNs.

Tomato exo-(1-->4)-beta-D-galactanase. Isolation, changes during ripening in normal and mutant tomato fruit, and characterization of a related cDNA clone

An exo-(1-->4)-beta-D-galactanase was isolated from ripe tomato fruit (Lycopersicon esculentum Mill. cv Ailsa Craig and cv Better Boy) using anion-exchange, gel filtration, and cation-exchange chromatography. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the most active fraction revealed a predominant protein band at 75 kD and several minor bands. A 30-amino acid N-terminal sequence from this 75-kD protein showed a high degree of homology with other recently identified beta-galactosidase/ galactanase proteins from persimmon and apple fruits (I.-K. Kang, S.-G. Suh, K.C. Gross, J.-K. Byun [1994] Plant Physiol 105: 975-979; G.S. Ross, T. Wegrzyn, E.A. MacRae, R.J. Redgwell [1994] Plant Physiol 106: 521-528) and with the predicted polypeptide sequence encoded by the ethylene-regulated SR12 gene in carnation (K.G. Raghothama, K.A. Lawton, P.B. Goldsbrough, W.R. Woodson [1991] Plant Mol Biol 17: 61-71). The enzyme focused to a single band of beta-galactosidase activity on an isoelectrofocusing gel at pH 9.8. The enzyme was specific for (1-->4)-beta-D-galactan substrates with a pH optimum of 4.5. The only reaction product detected was monomeric galactose, indicating that the enzyme was an exo (1-->4)-beta-D-galactanase. beta-Galactanase activity increased at the onset of ripening in normal fruit, but no similar increase was detected in the nonripening mutants nor and rin. A tomato homolog (pTombetagal1) was isolated using the SR12 cDNA clone from carnation as a probe. This clone showed 73% identify at the amino acid level with beta-galactosidase-related sequences from apple and asparagus and 66% identity with SR12. pTombetagal1 is a member of a gene family. Northern analysis demonstrated that pTombetagal1 expression was ripening related in normal fruits, with lower levels apparent in the nonsoftening mutants.

Mechanisms of the priming effect of lipopolysaccharides on the biosynthesis of leukotriene B4 in chemotactic peptide-stimulated human neutrophils

The goal of this study was to explain the priming effect of lipopolysaccharides (LPS) in human polymorphonuclear leukocytes on leukotriene B4 (LTB4) biosynthesis after stimulation with the receptor-mediated agonist formyl-methionyl-leucyl-phenylalanine (fMLP). This priming effect for LTB4 biosynthesis was maximal after a 30 min preincubation with LPS but was lost when incubations were extended to 90 min or longer. Priming with LPS resulted in an enhanced maximal activation of 5-lipoxygenase (5- to15-fold above unprimed cells) as well as a prolonged activation of the enzyme after stimulation with fMLP compared to that measured in unprimed cells. The activation of 5-lipoxygenase was associated with its translocation to the nuclear fraction of the cell after stimulation of LPS-primed cells but not of unprimed cells. Priming of cells with LPS also resulted in an enhanced capacity (fivefold increase) for arachidonic acid (AA) release after stimulation with fMLP compared to unprimed cells as measured by mass spectrometry. This release of AA was very efficiently blocked in a dose-dependent manner by the 85 kDa cytosolic phospholipase A2 (PLA2) inhibitor MAFP (IC50=10nM) but not by the 14 kDa secretory PLA2 inhibitor SB 203347 (up to 5 microM), indicating that the 85 kDa cPLA2 is the PLA2 responsible for AA release in response to receptor-mediated agonists. In accord with inhibitor studies, the LPS-mediated phosphorylation of cPLA2 followed the same kinetics as the priming for AA release, and a measurable fMLP-induced translocation of cPLA2 was observed only in primed cells. As with AA release and LTB4 biosynthesis, both the phosphorylation and capacity to translocate cPLA2 were reversed when the preincubation period with LPS was extended to 120 min. These results explain some of the cellular events responsible for the potentiation and subsequent decline of functional responses of human polymorphonuclear leukocytes recruited to inflammatory foci.

Evidence for a mediator role of thromboxane A2 in the myotropic action of leukotriene B4 (LTB4) on the guinea-pig lung

The mechanism of action of LTB4 has been investigated on the guinea-pig lung parenchymal strip. Mepacrine (20 microgram/ml), an inhibitor of phospholipase A2, abolished the action of LTB4 on parenchymal strips. Eicosatetraynoic acid (10 microgram/ml) and BW755C (40 microgram/ml) which are inhibitors of cyclooxygenase and lipoxygenase pathways, produced a marked inhibition of the lung strip contraction to LTB4. Similarly, aspirin (30 micrograms/ml) and flufenamate (1 microgram/ml) showed a strong inhibition of the contraction of parenchymal strips to LTB4; these results suggested that cyclooxygenase products mediate the action of LTB4. The response to LTB4 was unaffected by 15-hydroperoxyeicosatatraenoic acid (15-HPETE; 1 microgram/ml) while L8027 (25 ng/ml) reduced the contraction by 50%, suggesting that thromboxane A2 rather than prostacyclin was involved. Since parenchymal strips do not appear to be very sensitive to PGF2 alpha, PGE2 and the endoperoxides, and since effluents from LTB4-treated lungs produced contractions of lung strip and rabbit aorta which were reduced after 5 min. at 25 degrees, thromboxane A2 was postulated to mediate the lung effect of LTB4. The release of thromboxane B2 (TxB2) from lungs stimulated with LTB4 was confirmed by gas-chromatography-mass spectrometric (GC-MS) analyses.

Altered expression of inhibitory guanine nucleotide regulatory proteins (Gi alpha) in spontaneously hypertensive rats

We have recently shown that the stimulatory effects of guanine nucleotides and some agonists on adenylate cyclase activity were diminished in aorta and heart sarcolemma (SL) of spontaneously hypertensive rats (SHR). In the present studies we have examined the activity of GTP-binding proteins (G-proteins) at ADP-ribosylation level, by using pertussis toxin (PT) and cholera toxin (CT) at protein level, by using specific antibodies against Gi (inhibitory) and at mRNA level, by using cDNA probes encoding G-proteins. The labeling of Gi by PT was significantly increased in the aorta and heart SL from SHR as compared to their Wistar-Kyoto control rats (WKY). However, no change in the labeling of Gs (stimulatory) by CT was observed in SHR. Furthermore, immunoblotting experiments using AS/7 antibody which reacts with both Gi alpha-1 and showed an increased immunoprecipitation of Gi alpha-2 in heart SL from SHR. In addition, when the expression of G-proteins was probed at the mRNA levels by Northern blot analysis using cDNA probes, the mRNA levels of Gi2 alpha and Gi3 alpha were significantly enhanced in aorta and heart from SHR. However, the mRNA levels of Gs alpha were not altered in SHR. These results indicate that the gene of Gi and not of Gs is overexpressed in heart and aorta from SHR.

Genetic control of susceptibility to Candida albicans in susceptible A/J and resistant C57BL/6J mice

The importance of host factors in determining susceptibility to systemic Candida albicans infections is evident in both humans and mice. We have used a mouse model to study the genetic basis of susceptibility, using the inbred strains A/J and C57BL/6J, which are susceptible and resistant, respectively, based on different parameters of the response to infection. To identify genes responsible for this differential host response, brain and kidney fungal load were measured in 128 [A/J x C57BL/6J] F(2) mice 48 h after infection with 5 x 10(4) C. albicans blastospores. Segregation analysis in this informative population identified complement component 5 (C5/Hc) as the major gene responsible for this differential susceptibility (LOD of 22.7 for kidney, 19.0 for brain), with a naturally occurring mutation that causes C5 deficiency leading to enhanced susceptibility. C5 was also found to control heart fungal load, survival time, and serum TNF-alpha levels during infection. Investigation of the response to C. albicans challenge in a series of AcB/BcA recombinant congenic strains validated the importance of C5 in determining the host response. However, the strains BcA67 and BcA72 showed discordant phenotypes with respect to their C5 status, suggesting additional complexity in the genetic control of the inter-strain difference in susceptibility observed in A/J and C57BL/6J following systemic infection with C. albicans.

Prevention of bone loss by EM-800 and raloxifene in the ovariectomized rat

Some undesirable effects are associated with chronic estrogen and progestin administration used to prevent bone loss in postmenopausal women, thus leading to poor compliance and the need for improved therapeutic and preventive agents. We have thus studied the ability of the new antiestrogen EM-800 (SCH 57050) to prevent bone loss and lower serum cholesterol levels and compared its effects with those of raloxifene. Ovariectomized (OVX) female rats were treated by oral gavage for 37 weeks with increasing daily doses (0.01, 0.03, 0.1, 0. 3 or 1 mg/kg) of EM-800 or raloxifene. At 35 weeks after OVX, lumbar spine bone mineral density (BMD) was 19% lower than in intact animals (P<0.01), while the OVX animals given EM-800 or raloxifene had 90-93 and 85-90%, respectively, of the BMD values observed in intact rats. Similar effects were observed on femoral BMD. Bone histomorphometry measurements were performed on proximal tibia. At the 0.01 mg/kg dose, EM-800 prevented the effect of OVX on TBV by 34% (P<0.01), while raloxifene had no detectable effect. Treatment with 1 mg/kg EM-800 and raloxifene resulted in, respectively, 68% (P<0.01) and 64% (P<0.01) prevention of the OVX-induced decrease in TBV. In addition, the administration of 0.01 and 0.03 mg/kg EM-800 caused, respectively, 54% (P<0.01) and 56% (P<0.01) inhibitions of serum cholesterol levels, while raloxifene administered at the same doses caused, respectively, 24% (P<0.01) and 41% (P<0.01) decreases of the value of the same parameter. At the highest doses used (0.1-1 mg/kg), both compounds lowered serum cholesterol levels by approximately 65% (P<0.01). No stimulatory effect of EM-800 was observed on the endometrial epithelial cells at doses up to 1 mg/kg, while hypertrophy of uterine epithelium was observed with raloxifene. EM-800 and raloxifene achieve the same degree of effectiveness on bone and serum cholesterol at higher doses, but EM-800 is at least three to ten times more potent than raloxifene at lower concentrations and has no stimulatory effect on uterine epithelium. The present data show the potent effect of EM-800 preventing bone loss and lower serum cholesterol levels without the negative effect on the endometrium, thus suggesting the particular interest of this new fully tissue-specific selective estrogen receptor modulator.

Aminoguanidine has both pro-oxidant and antioxidant activity toward LDL

We previously demonstrated that aminoguanidine (AMGN) was able to prevent oxidative modification of LDL. Initially, we thought that this occurred solely because AMGN trapped reactive breakdown products of lipid peroxidation and prevented apoB modification, similar to AMGN's proposed ability to trap reactive glucose intermediates and prevent advanced glycosylation end-product formation. We now demonstrate that AMGN also displays dose-dependent pro-oxidant and antioxidant activity toward LDL. Moderate doses of AMGN (0.05 to 1.0 mmol/L) prevented lipid peroxidation in LDL exposed to copper. AMGN prevented the loss of polyunsaturated fatty acids and delayed or prevented conjugated-diene formation, both of which are sensitive indicators of lipid peroxidation. The same doses of AMGN also prevented apoB modification, a step distal to lipid peroxidation, as evidenced by the ability to (1) prevent fluorescence at 420 nm, (2) block enhanced electrophoretic mobility, and (3) prevent changes leading to enhanced macrophage uptake. Thus, AMGN inhibits LDL modification both by inhibiting lipid peroxidation as well as by trapping reactive breakdown products of lipid peroxidation. It was also demonstrated that for every LDL, there was also a very low dose of AMGN (about 0.01 mmol/L) that actually promoted lipid oxidation and subsequent protein modification. This activity of AMGN could be enhanced by increasing the content of lipid hydroperoxide in the LDL, eg, by aging or radioiodinating the LDL. Conversely, the pro-oxidant activity could be reduced by pretreatment of LDL with ebselen or vitamin E. We propose a mechanism by which AMGN effects pro-oxidant activity toward LDL at very low concentrations and antioxidant activity at higher concentrations and discuss the practical implications of these observations.

Predominant androgenic component in the stimulatory effect of dehydroepiandrosterone on bone mineral density in the rat

In order to assess the relative roles of the androgenic and/or estrogenic components in the stimulatory effect of dehydroepiandrosterone (DHEA) on bone mineral content (BMC) and density (BMD), ovariectomized (OVX) female rats received DHEA administered alone or in combination with the antiandrogen flutamide (FLU) or the antiestrogen EM-800 for 12 months. We also evaluated, for comparison, the effect of estradiol (E2) and dihydrotestosterone (DHT) constantly released by Silastic implants as well as medroxyprogesterone acetate (MPA) released from poly(lactide-co-glycolide) microspheres. Femoral BMD was decreased by 11% 1 year after OVX, but treatment of OVX animals with DHEA increased BMD to a value 8% above that of intact animals. The administration of FLU reversed by 76% the stimulatory effect of DHEA on femoral BMD and completely prevented the stimulatory effect of DHEA on total body and lumbar spine BMD. Similar results were obtained for BMC. On the other hand, treatment with the antiestrogen EM-800 did not reduce the action of DHEA on BMD or BMC. At the doses used, MPA, E2 and DHT increased femoral BMD, but to a lesser degree than observed with DHEA. Bone histomorphometry measurements were also performed. While DHEA treatment partially reversed the marked inhibitory effect of OVX on the tibial trabecular bone volume, the administration of FLU inhibited by 51% (P < 0.01) the stimulatory effect of DHEA on this parameter. The addition of EM-800 to DHEA, on the other hand, increased trabecular bone volume to a value similar to that of intact controls. DHEA administration markedly increased trabecular number while causing a marked decrease in the intertrabecular area. The above stimulatory effect of DHEA on trabecular number was reversed by 54% (P < 0.01) by the administration of FLU, which also reversed by 29% the decrease in intertrabecular area caused by DHEA administration. On the other hand, the addition of EM-800, while further decreasing the intertrabecular space achieved by DHEA treatment, also led to a further increase in trabecular number to a value not significantly different from that of intact control animals, suggesting an additional effect of EM-800 over that achieved by DHEA. Treatment with DHEA caused a 4-fold stimulation of serum alkaline phosphatase, a marker of bone formation, while the urinary excretion of hydroxyproline, a marker of bone resorption, was decreased by DHEA treatment. Treatment with DHEA and DHEA + EM-800 decreased serum cholesterol levels by 22 and 65% respectively, while the other treatments had no significant effect on this parameter. The present data indicate that the potent stimulatory effect of DHEA on bone in the rat is mainly due to the local formation of androgens in bone cells and their intracrine action in osteoblasts.

Lack of association between carotid intima-media thickness and paraoxonase gene polymorphism in non-insulin dependent diabetes mellitus

Paraoxonase (PON) is an HDL-bound enzyme capable of hydrolyzing lipid peroxides and believed to be in part responsible for the protective effect of HDL against LDL oxidation. Its activity is mainly determined by a gene polymorphism of the PON 1 gene (Glu-Arg 192). Low activity has been related to an elevated incidence of myocardial infarction. In several case-control studies, however, the high activity B allele is paradoxically more prevalent in patients. We have re-investigated this relationship, using carotid intima-media thickness (IMT) as a surrogate continuous variable for macroangiopathy. Genotypes were determined in 197 non insulin-dependent diabetic patients (HbAlc 8.8+/-0.15%, BMI 28.3+/-0.36). IMT, measured by high resolution mode B ultrasound, was the same for all genotypes (AA: 0.83+/-.013, AB 0.82+/-.017 and BB: 0.81+/-.034 mm). Bearers of the B allele displayed higher Lp(a) concentration (AA: 197+/-28, AB: 221+/-26, BB: 225+/-45 mg/l, P=0.024) with a significant linear trend (P < 0.005). Multiple regression showed age and systolic blood pressure, but not Lp(a), to be the main determinants of IMT variability without the contribution of the PON genotype. No consistent differences could be found between genotypes in the peroxidizability of LDL (lag-time, rate of diene production and maximal concentration). Our data support the view that there is no association between the early changes of atherosclerosis as defined by carotid IMT and variation in codon 192 of PON 1.

Induction of intrauterine growth restriction with a low-sodium diet fed to pregnant rats

OBJECTIVE

A low-sodium diet fed to female rats before mating through parturition leads to pups of lower weight. We characterized the effect of low dietary sodium during the last week of gestation (after fetal organogenesis) on fetal and maternal homeostasis.

STUDY DESIGN

Pregnant Sprague-Dawley rats were randomly assigned to a control group or to a group fed a low-sodium diet from gestational days 15 through 22. Systolic blood pressures were measured throughout pregnancy. On day 22 plasma volume was measured and blood samples were taken for electrolyte and hormonal measurements. Fetal and placental weights were also determined.

RESULTS

Plasma renin activity and aldosterone level were significantly higher in the experimental group than in the control group. Plasma volume was significantly lower in pregnant rats receiving a low-sodium than in those receiving a control diet. Rats receiving a low-sodium diet had pups of lower weight and length (4.45 +/- 0.22 g, 3.90 +/- 0.06 cm) than pups of the control group (5.21 +/- 0.12 g, 4.10 +/- 0.02 cm). Pups born to mothers with low-sodium diets recuperated from intrauterine growth restriction by 14 days after birth.

CONCLUSION

These data indicate that a low-sodium diet given to pregnant rats for the last 7 days of gestation leads to reduced plasma volume expansion and fetal growth restriction. This could prove to be a simple animal model for studying the relationship between maternal plasma volume and fetal growth.

Sulphur fate and anaerobic biodegradation potential during co-digestion of seaweed biomass (Ulva sp.) with pig slurry

Seaweed (Ulva sp.) stranded on beaches were utilized as co-substrate for anaerobic digestion of pig slurry in three-month co-digestion tests in pilot scale anaerobic digesters in the laboratory. The methanogenic potential of Ulva sp. was low compared to that of other potential co-substrates available for use by farmers: 148 N m3CH4/t of volatile solids or 19 N m3CH4/t of crude product. When used as a co-substrate with pig manure (48%/52% w/w), Ulva sp. seaweed did not notably disrupt the process of digestion; however, after pilot stabilisation, biogas produced contained 3.5% H2S, making it unsuitable for energy recovery without treatment. Sequentially addition of the sulphate reduction inhibitor, potassium molybdate, to a final concentration of 3mM, temporarily reduced H2S emissions, but was unable to sustain this reduction over the three-month period. According to these pilot tests, the use of seaweed stranded on beaches as co-substrate in farm-based biogas plants shows some limitations.