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D Blache

Publications and source records attributed to D Blache.

At least 73 records · Page 4Linked to original sources
PubMed1995

Enhanced susceptibility of cholesteryl sulfate-enriched low density lipoproteins to copper-mediated oxidation.

Cholesteryl sulfate (CS) is a minor component of cell membranes, also present in lipoproteins, and its exact function is unknown. Since oxidation of low density lipoproteins (LDL) is thought to be an important determinant of atherogenesis, we investigated the influence of CS enrichment on copper-mediated oxidation of LDL. CS was found to act as a pro-oxidant, as measured by lipid oxidation parameters. The results also suggest that these effects were dependent on the sulfate group since pure cholesterol or cholesteryl acetate did not promote Cu(2+)-mediated oxidation. Our findings imply that CS may affect the oxidizability and hence the potential atherogenicity of LDL.

Arteriosclerosis↗
PubMed1995

Pro-oxidant effects of 7-hydroperoxycholest-5-en-3 beta-ol on the copper-initiated oxidation of low density lipoprotein.

In low density lipoproteins (LDL) supplemented with aged cholesterol and oxidized in the presence of Cu2+, an increase of the lipid oxidation parameters was observed compared with pure cholesterol-enriched LDL. A compound, identified as 7-hydroperoxycholesterol (7HPC), isolated from aged cholesterol and added to LDL, reproduced the above effects. The results indicate that the pro-oxidant effect of 7HPC is dependent on the hydroperoxy group since the corresponding alcohol derivative, 7 alpha-hydroxycholesterol, had no such effect. These data suggest that among the LDL-associated lipid peroxides, cholesterol peroxides may have important implications in the susceptibility of this lipoprotein to oxidation.

Cholesterol↗
PubMed1995

Influence of a long-term zinc-deficient diet on rat platelet function and fatty acid composition.

A reduced zinc intake is associated with numerous abnormalities and, in particular, with hemostasis dysfunction. In this report, we studied the effects of a long-term dietary zinc restriction on platelet function. Three groups of rats were analyzed: a zinc-deficient group (ZD) and two zinc-adequate fed groups, one pair-fed (PF) and one ad libitum fed (AL). We found that ZD diet (0.2 p.p.m.) impaired ADP-induced aggregation of washed platelet after 4 and 8 weeks of diet. Thrombin-induced aggregation was impaired in ZD rats and PF rats after 8 weeks. The thrombin-induced mobilization of radiolabeled arachidonate preincorporated into platelet phospholipids was followed as well as the subsequent formation of labeled cyclooxygenase and lipoxygenase products. Stimulated platelets of ZD rats exhibited a decreased production of cyclooxygenase and lipoxygenase products, particularly after 8 weeks of diet. Moreover, platelet thromboxane generation was decreased in the ZD group as studied using a radioimmunoassay after thrombin stimulation. In addition, we measured the total fatty acid compositions of platelet and plasma. As a whole, 20:5 (n - 3) and 22:5 (n - 3) fatty acids content were significantly increased in platelet lipids after 8 weeks. On the other hand, it is known that enrichment of these fatty acids through dietary studies, both in animal and human as well as in vitro incorporation in platelets, resulted in an inhibition of platelet function. Consequently, these changes in platelet membrane fatty acid composition may contribute to the impaired platelet aggregation observed in ZD rats.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
PubMed1995

Involvement of hydrogen and lipid peroxides in acute tobacco smoking-induced platelet hyperactivity.

Previous studies have established that cigarette smoking results in acute platelet hyperaggregability. We investigated whether changes in plasma oxidative properties could occur after smoking and whether such changes could be responsible for this enhanced platelet activity. In the present work, we report that platelets from nonsmokers become hyperactive after incubation with plasma prepared from blood of smokers obtained 10 min after smoking. This effect was not observed with presmoking plasma and could be inhibited in vitro by adding either catalase or reduced glutathione plus peroxidase to plasma or 2,6-di-tert-butyl-p-cresol (BHT) to platelets before incubation. Comparison of pre- and postsmoking plasma showed that smoking resulted in a decrease in vitamin E (18%, P < 0.01) and increases in conjugated diene (35%, P < 0.001), thiobarbituric acid-reactive substance (23%, P < 0.02), and free fatty acid (FFA, 40%, P < 0.005) plasma concentrations. The FFA fraction was peroxidized to a higher extent when extracted from postsmoking than from presmoking plasma. This peroxidized FFA fraction enhanced the thrombin-induced aggregation of platelets from nonsmokers. This increased response was inhibited either when the peroxidized FFA fractions were isolated from plasma treated with reduced glutathione and peroxidase or by pretreatment of the platelets with BHT. We conclude that the enhanced formation of lipid hydroperoxides found in postsmoking plasma seems to be responsible for the acute and marked platelet hyperactivity observed after smoking.

Adenosine Diphosphate↗
PubMed1995

The role of intracerebral insulin in the effect of nutrition on gonadotrophin secretion in mature male sheep.

The effect of nutrition on gonadotrophin secretion may be exerted through a central metabolic signal that reflects nutritional status. We have previously found that glucose and insulin concentrations are elevated in the cerebrospinal fluid (CSF) of rams in which the secretion of gonadotrophins has been stimulated by a nutritional supplement of lupin grain (Lupinus angustifolius). In the present study, we tested the hypothesis that insulin and/or glucose is a metabolic modulator of GnRH secretion and mediates the effects of nutrition on gonadotrophin secretion. Six mature rams were fed a diet that maintained live weight and then given a series of infusions, each for 12 h/day for 4 days, in a cross-over design. The treatments were: artificial CSF (aCSF), glucose (50 mumol/h) in aCSF, insulin (0.6 ng/h) in aCSF, and glucose (50 mumol/h) plus insulin (0.6 ng/h) in aCSF; all infused at a rate of 5 microliters/min. At the same time as the infusion treatments, two other groups of four rams without cerebral cannulae were fed either the maintenance diet or the same diet supplemented with 750 g lupin grain per head per day for 4 days, again in a cross-over design. Rams fed the lupin supplement showed an increase in both LH pulse frequency and mean FSH on day 4 (P < 0.05). Infusion of aCSF or glucose did not affect gonadotrophin secretion. Rams infused with insulin or insulin plus glucose showed an increase (P < 0.05) in LH pulse frequency but no increase in FSH concentrations on day 4 of infusion.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗
PubMed1994

Zinc prevents the structural and functional properties of free radical treated-insulin.

We have previously reported that zinc deficiency could increase in vivo lipid peroxidation and decrease rat insulin sensitivity. In the present paper, we address the hypothesis of the role of zinc on insulin molecule in relation to free radical damage. From native recombinant human insulin, we prepared a zinc-depleted insulin. Both preparations were subjected to controlled free radical attack by incubation in the presence of 2,2'-azobis(2-amidinopropane) hydrochloride (AAPH). To obtain minimally oxidized insulin, the oxidation process was monitored by measuring the intrinsic fluorescence of the insulin preparations. For 2.5 mM of AAPH, the autofluorescence of zinc-depleted insulin markedly decreased as compared to that of native insulin. These data are in favor of conformational changes of the insulin molecule which were further studied by quenching of fluorescence by means of potassium iodide. Using the euglycaemic hyperinsulinic glucose clamp technique in rats, the in vivo activities of the different insulin preparations, showed that oxidized zinc-depleted insulin had a marked reduced activity as compared to oxidized native insulin. From our results, we suggest that structural modification of the insulin molecule took place after zinc depletion and free radical treatment. Moreover, zinc depletion appeared to increase the susceptibility of insulin to free radicals.

Animals↗
PubMed1994

Microdialysis measurement of neurochemical changes in the mediobasal hypothalamus of ovariectomized ewes during oestrus.

Oestrus behaviour and the luteinizing hormone (LH) surge are induced in ovariectomized ewes by oestradiol (E2) after a period of progesterone priming with a low level of E2 (Pge2) and we have previously shown that these effects are primarily mediated through their action on the mediobasal hypothalamus (MBH). The aim of the present study was to assess what neurochemical changes in the MBH are induced by these steroids that might mediate their action on oestrus behaviour and LH release. Eight ovariectomized ewes were implanted with microdialysis probes in the MBH and submitted to three artificial cycles, so that they exhibited either both oestrus behaviour and an LH surge (Pge2 + E2), an LH surge alone (E2 alone) or neither oestrus behaviour nor an LH surge (Pge2 alone). Microdialysis and blood samples were collected every 30 min from 4 h before the end of Pge2 treatment until the end of oestrus. Behavioural tests with a ram were made to assess receptivity. Dopamine (DA) levels were found to increase significantly at the termination of Pge2 treatment after both Pge2 + E2 and Pge2 treatments. When the ewes received E2 after a Pge2 + low estradiol priming (Pge2 + E2), DA levels decreased 16 h later (4 h after E2) whereas they did not change after E2 or Pge2 alone. By contrast, serotonin (5HT) levels did not change significantly during the first 24 h but then increased when ewes received E2 alone and decreased when they were treated with Pge2 + E2. gamma-Aminobutyric acid (GABA) concentrations decreased significantly at the beginning of the sampling period after all treatments but this decrease lasted longer after Pge2 + E2 and was most pronounced at the beginning of receptivity. No significant long term effects of these steroid treatments were found on noradrenaline (NA), aspartate, glutamate, glycine and taurine levels. However, E2 administration was followed during the next few hours by a significant increase in glycine and to a smaller extent in glutamate and GABA. More importantly, when ewes were treated with Pge2 + E2, NA levels increased significantly following the behavioural interactions with a ram when the ewes were sexually receptive. In contrast to this, DA levels only increased during interactions with the ram when the ewes were not receptive. 5HT levels increased after tests where the ewe was either receptive or unreceptive to the male. GABA, aspartate and glycine levels increased in the sample just preceding the test and then decreased during it.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1994

Oestrogen receptors in the preoptico-hypothalamic continuum: immunohistochemical study of the distribution and cell density during induced oestrous cycle in ovariectomized ewe.

Oestrogen plays a key role in the regulation of the endocrine and behavioural events associated with the oestrous cycle. It is important, therefore, to know the location of neurones receptive to this steroid and to know whether their distribution varies with the oestrous cycle. We have undertaken experiments to identify the location of oestrogen receptors (ER) within the preoptico-hypothalamic continuum of ovariectomized ewes submitted to a variety of different hormone replacement regimes which mimic the different stages of the oestrous cycle. We used a monoclonal antibody to ER and detected receptors with immunohistological methods in the non-vascular part of the organum vasculosum of the lamina terminalis, the lateral septum, the medial preoptic area, the supraoptic, suprachiasmatic and arcuate (ARC) nuclei, the ventromedial hypothalamus (HVM) and in the region close to the mamillari recess. ER neurones were scarce or absent from the anterior hypothalamus and the paraventricular nucleus. The density of ER staining in the HVM, but in no other localization, was found to be higher, and in a more lateral position, during the induced luteal phase (progesterone treatment) than during the follicular phase (7 days of progesterone treatment followed by oestradiol) or in the ovariectomized female. In all areas studied, except for the ARC, the apparent surface area of the nucleus in ER immunoreactive cells varied with hormonal treatment. These data, and especially those in the HVM, contribute towards our understanding of how steroids may act in the ovine to control sexual behaviour.

Animals↗
PubMed1993

The role of oxytocin release in the mediobasal hypothalamus of the sheep in relation to female sexual receptivity.

In vivo microdialysis and retrodialysis were used to investigate the role of oxytocin (OXY) release in the mediobasal hypothalamus (MBH) of the ewe in the control of sexual receptivity. Initial experiments showed that OXY release was significantly increased in ovariectomized animals treated with progesterone and oestradiol when they were sexually receptive towards males and received intromissions. No such increases were seen during tests where the ewes were receptive but the males were prevented from achieving intromission. By contrast, OXY release was significantly reduced in tests where the ewes were not receptive to the male. In a second experiment artificial vaginocervical stimulation (VCS) was found to significantly increase OXY release when the animals were treated with oestradiol and this effect was potentiated by progesterone priming. OXY release in the MBH was not significantly altered by VCS in the presence of progesterone priming alone. Plasma OXY concentrations were significantly increased by VCS following all three hormone treatments but no one treatment was significantly more effective than another. Noradrenaline release in the MBH was only significantly increased following VCS when progesterone priming was given before oestradiol treatment. No effects of VCS on release of GABA, glutamate or dopamine were seen but their basal concentrations were significantly increased by the combined steroid treatment compared to oestradiol alone. In a third experiment it was found that OXY (10 microM) infused bilaterally into the MBH of receptive ewes, by retrodialysis, significantly decreased sexual receptivity and increased the release of noradrenaline and GABA.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acids↗
PubMed1993

Zinc deficiency and dietary folate metabolism in pregnant rats.

Five groups of pregnant Wistar rats (zinc-deficient diet without folate supplementation; folinic acid, folate monoglutamate, folate polyglutamate-supplemented groups receiving zinc-deficient diet; pair-fed groups as controls) were fed from day one of fertilization with a semisynthetic zinc-deficient diet containing 0.2 mg/kg of Zn in the diet for the 4 deficient groups and 100 mg/kg for the pair-fed group. After 20 days, the zinc status (plasma, liver, femoral bone) was significantly decreased in the zinc-deficient groups. The liver and plasma folate levels were lower in the zinc-deficient groups compared to the pair-fed group. Moreover, the folinic acid and the polyglutamate folate supplementations (100 mg/kg diet) did not normalize the folate status of the animals. Only the supplementation with folate monoglutamate led to correct folate levels in the pregnant rats. Nevertheless, no form of folate supplementation prevented fetal growth retardation in any of the zinc-deficient groups. These results indicate that zinc deficiency in pregnant rats decreases folate bioavailability of folinic acid, folate polyglutamates and, to a lesser extent, that of folate monoglutamate. However, no form of folate supplementation (i.e., folate monoglutamate) prevents fetal growth defect and the incidence of malformation in zinc-deficient rats.

Animals↗
PubMed1992

Immunohistochemical colocalization of tyrosine hydroxylase and estradiol receptors in the sheep arcuate nucleus.

In sheep, the arcuate nucleus contains numerous tyrosine hydroxylase (TH) and estradiol receptor (rE2) immunoreactive (IR) perikarya and it has been shown previously in this species that catecholaminergic neurons can mediate the gonadal steroid action on the reproductive function. In the present study, double immunohistochemical labelling with antibodies against TH and rE2 have been used to demonstrate the presence of rE2 in TH-IR neurons in the arcuate nucleus where the distribution of TH-IR and rE2-IR neurons overlap each other. Only less than 10% of all the rE2-IR perikarya presented TH immunoreactivity. It was therefore hypothesized that either such a low number of double labelled neurons can support the effects of estradiol in this area or that the effect of this steroid was indirect. In the latter case it might be first mediated by beta-endorphin neurons which have been previously described in this nucleus.

Animals↗
PubMed1992

A method for specific analysis of free fatty acids in biological samples by capillary gas chromatography.

The present report describes a simple method to selectively extract free fatty acids and analyze them by capillary gas-liquid chromatography. The procedure is based on the use of fumed silicon dioxide. In the presence of plasma, this material induces a rapid rise in the viscosity of the mixture and presents the ability to trap large particles such as emulsified lipids and lipoproteins. Albumin-bound fatty acids are thus left in the aqueous media. We present applications of our procedure for the analysis of free fatty acids in 0.2 ml of plasma from rat or human. By comparison with the method utilizing thin-layer chromatography for the separation of fatty acids and gas chromatography analysis, the present method has been found to be reliable and simple. The recovery of linoleic acid was 92.1 +/- 8.2%, a value which is about twice better than that obtained with the procedure using thin-layer chromatography. In particular, long-chain polyunsaturated fatty acids were better preserved. Our procedure does not require the use of organic solvents and its simplicity and reproducibility make it suitable for routine specific determination of the composition of free fatty acids in biological samples.

Animals↗
PubMed1992

Effect of vitamin E on acute iron load-potentiated aggregation, secretion, calcium uptake and thromboxane biosynthesis in rat platelets.

In the present study performed on rats, we investigated the influence of an in vivo acute iron load on several platelet parameters and their modification after vitamin E supplementation. Iron load was achieved by injecting iron dextran corresponding to 0.1 mg Fe3+ per kg in the gluteus muscles. Control rats were injected with an equal amount of a dextran solution. Analyses were performed 18 h after injection. By comparison with controls, in iron-injected animals, we found significant increases of: (1) serum total iron (by 110%); (2) aggregation of isolated platelets induced by low concentration of thrombin and ADP (by 350% and 120%, respectively); (3) thrombin-induced endogenous serotonin secretion (by 94%). We also studied the mobilization of radiolabeled arachidonate preincorporated into platelet phospholipids. The results indicated that the thrombin-stimulated release of arachidonate and formation of cyclooxygenase and lipoxygenase products (particularly thromboxane B2), were significantly increased. We also found in plasma an increase (by 67%) of malondialdehyde (MDA) as well as a decrease of vitamin E (by 60%). When vitamin E was injected the day before iron injection, platelet hyperactivity and thromboxane biosynthesis were reduced as well as the plasma MDA concentration. Consequently, given the key role of calcium flux in the activation processes in platelets, we also investigated the thrombin-induced Ca2+ uptake by means of radiocalcium. We found that in platelets from iron-treated rats the Ca2+ uptake amounted to 3670 +/- 201 pmol/10(9) platelets (plt) and was significantly different from controls (1680 +/- 192 pmol/10(9) plt, P < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Acute influence of smoking on platelet behaviour, endothelium and plasma lipids and normalization by aspirin.

This study was conducted to investigate acute effects of smoking on platelet function, endothelial cells and plasma lipids and to follow these parameters after Aspirin ingestion. Twelve fasting smokers each inhaled the smoke of one cigarette. Blood was drawn before and 10 min after smoking. Plasma nicotine, measured by gas chromatography, increased from 13.48 before smoking to 78.41 nM after smoking. Platelet aggregation to thrombin and ADP increased significantly (P less than 0.001). The platelet aggregate ratio decreased from 0.95 to 0.75 (P less than 0.005). Plasma beta-thromboglobulin also increased in post-smoking samples as measured using radioimmunoassay. 'Circulating endothelial cells' increased significantly after smoking (P less than 0.005). Triglycerides decreased (P less than 0.005) in plasma and in the VLDL fraction (P less than 0.05). Both post-smoking plasma free fatty acids and free glycerol increased, respectively, as compared with respective values. Lipase activity ascribable to lipoprotein lipase and hepatic lipase, absent in pre-smoking plasma samples, could be detected in post-smoking plasma without heparin injection. At least 1 week later, the subjects returned to follow an identical protocol except that they had ingested Aspirin (650 mg) 10-14 h before blood sampling. The same parameters were measured before and after smoking the same cigarette. Except for plasma nicotine, all the smoking-induced changes were abolished by ingestion of Aspirin. The results of this study indicate an interrelationship between platelet hyperactivity, endothelial injury and plasma lipids. They also demonstrate an inhibition of the major smoking-induced changes by Aspirin in the presence of high plasma nicotine levels. It is concluded that Aspirin may offset several of the deleterious acute effects of smoking. However, our conclusions cannot be, in any way, extended for long-term effects of both smoking and Aspirin treatment. Based on these data, it is suggested that there may be some links between platelet hyperactivity, endothelium injury and plasma lipids.

Adult↗
PubMed1992

Liver fibrosis in a patient with familial homozygous hypobetalipoproteinaemia: possible role of vitamin supplementation.

A case of apolipoprotein B-related disorder is reported in which liver fibrosis developed without long term administration of medium chain triglycerides, previously incriminated in the pathogenesis of this lesion. The patient was a young woman in whom the diagnosis of familial homozygous hypobetalipoproteinaemia was made at the age of 21. A first liver specimen taken at diagnosis revealed steatosis, hypertrophic Golgi apparatus and proliferating smooth endoplasmic reticulum. The patient was treated with vitamin A and E supplementation only. Two years later, a second liver biopsy, carried out because of increased serum alanine aminotransferase concentrations, showed fibrosis, mild cytolysis and marked mitochondrial alterations. Hepatic level of vitamin A was increased. This finding supports the hypothesis that liver disease observed in our patient might be an adverse effect of vitamin supplementation. Our observation underlines the importance of including liver function tests in the follow up of patients with apolipoprotein B-related disorders.

Adult↗
PubMed1992

Comparative inhibitory effects of dihydropyridines on platelet aggregation, calcium uptake and cyclic AMP concentration.

We studied the in vitro effects of several calcium channel blockers from the dihydropyridine (DHP) family on platelet aggregation and endogenous serotonin secretion, calcium uptake and cyclic AMP (cAMP) concentration using washed rat platelets. We found that, after 1 min incubation, nifedipine (Nif), nitrendipine (Nit) and nisoldipine (Nis) inhibited the thrombin-induced platelet aggregation and serotonin secretion with IC50 of about 140, 5 and 2 mumol/l, respectively. Nis and Nit are thus much more active than Nif. We also found that the thrombin-induced Ca2+ uptake amounted to 2,600 +/- 326 pmol Ca2+/10(9) platelets in control conditions. In the presence of 10 mumol/l of the DHP, this uptake was decreased by 19, 49 or 77%, with Nif, Nit or Nis, respectively. Compound BAY K 8644 (BK) with known agonistic properties on the calcium channel had inhibitory effects on the studied parameters. These compounds were in the order of Nif < BK < Nit < Nis. When added to previously aggregated platelets, Nit caused them to deaggregate. These results seem to be similar to those obtained with cAMP analogues or adenylate cyclase activators. The platelet resting cAMP concentration was therefore measured in the presence of the DHP. A nonsignificant increase was found with 20 mumol/l Nif whereas significant increases of 20 and 68% as compared with controls were obtained with 20 mumol/l Nit and Nis, respectively. Partition studies between platelets and plasma lipoproteins indicated that the effects might be related to the lipophilicity of the compounds. These data suggest that these agents work on platelet activity by multiple effects located intracellularly or at the membrane level.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Ventromedial hypothalamus as a target for oestradiol action on proceptivity, receptivity and luteinizing hormone surge of the ewe.

Most of the literature suggests that in sheep as in rodents nervous structures involved in female sexual behaviour are not necessarily identical to those involved in the LH surge. In rodents, oestradiol triggers female sexual behaviour by acting on a restricted area of the mediobasal hypothalamus whereas the concomitant induction of the preovulatory LH surge is at least partially under the control of more anterior structures. The central sites of oestradiol action, however, remained poorly defined in sheep. To provide this definition, 37 ovariectomized ewes were stereotaxically implanted unilaterally or bilaterally with a guide cannula in preoptic area (POA), anterior, mediobasal, lateral, or posterior hypothalamus (AH, MBH, LHT, PH). Experiments were made during the breeding season (Br) and the anoestrous period (An: unilat only) and females were primed with a peripheral treatment of progesterone and a dose of 17 beta-oestradiol subthreshold for both the LH surge and sexual behaviour. Intracranial implants (i.d. = 0.45 mm) of crystalline E2 were lowered 16 h after progesterone removal and left in the brain for 48 h. Whereas POA implants never had any significant effects on either the behaviour or the LH surge, all MBH implants caused receptivity (11 bilat, 5 unilat Br and 5 unilat An). Bilateral MBH implants also induced proceptivity in 9 of 11 ewes and increased the LH levels in 7 of them. These proportions do not differ significantly from those observed after a 25 microgram peripheral injection of E2. Unilateral MBH implants had no significant effect on proceptivity and LH increase but oestrous behaviour was induced by some implants placed laterally to the MBH (25 recept and 3/5 procept).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗