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C Hübner

Publications and source records attributed to C Hübner.

At least 19 recordsLinked to original sources
PubMed1995

Antioxidative activity of ubiquinol-10 at physiologic concentrations in human low density lipoprotein.

Ubiquinol-10 is a powerful lipid-soluble antioxidant found in cell membranes and lipoproteins in vivo. Its mechanism of action on lipid peroxidation has been determined in model and biological systems. Data concerning antioxidative activity of ubiquinol-10 in lipoproteins, however, are still controversial. The present work examines its role in the prevention of low density lipoprotein (LDL) oxidation, specifically its influence on a copper-mediated oxidative modification of human LDL in vitro. We found that ubiquinol-10 incorporated in LDL in subnormal concentrations (0.05-0.13 mol/mol LDL incorporated in comparison with 0.10-1.20 mol/mol LDL reported as normally in human LDL) slightly but not significantly decreased production of lipid peroxidation products (lipid peroxides, conjugated dienes, thiobarbituric acid-reactive substances) during the first hours of oxidation. The extent of apolipoprotein B modification (LDL fluorescence at 360/430 nm) was also decreased. Increasing the ubiquinol-10 concentration in LDL to 0.55-1.48 mol/mol LDL made it significantly more resistant to copper-mediated oxidation than native LDL. Adding the same amounts of either ubiquinone-10 or alpha-tocopherol to the LDL suspension had almost no effect on its oxidation. Ubiquinol-10 decreased alpha-tocopherol consumption during LDL oxidation and was consumed more rapidly than the latter. These results demonstrate that LDL ubiquinol-10 content is an important factor influencing LDL susceptibility to oxidation by copper and suggest that it represents the first line of defense against oxidative modification in human LDL.

Antioxidants↗
PubMed1995

X-chromosome methylation in manifesting and healthy carriers of dystrophinopathies: concordance of activation ratios among first degree female relatives and skewed inactivation as cause of the affected phenotypes.

The X-chromosome activity states of 11 manifesting carriers of dystrophinopathies, all with normal karyotypes, were estimated by restriction fragment length polymorphism (RFLP)-methylation analysis with the probes M27 beta (DXS255), p2-19(DXS605) and pSPT/PGK (PGK1) to test the role of skewed X-inactivation ratios as the cause of their affected phenotypes. In eight cases preferential inactivation of the putative X chromosome carrying the normal dystrophin allele in > or = 90% of their peripheral lymphocytes was observed, two cases showed non-apparent deviant ratios (60:40 and 70:30) from the theoretically expected values around the mean of 50% and in one case the three markers employed yielded no information. The analysis of the X-inactivation ratio in six mother-daughter pairs, all non-manifesting Duchenne muscular dystrophy (DMD) carriers, and in the close female relatives of the patients showed: (a) neither of the two X chromosomes was preferentially inactivated with respect to their parental origin; (b) a high concordance among the activation ratios of mothers and daughters, a result difficult to explain just in terms of random X-chromosome inactivation.

Child↗
PubMed1995

In vitro effects of oxidized low density lipoprotein on CD11b/CD18 and L-selectin presentation on neutrophils and monocytes with relevance for the in vivo situation.

Oxidized LDL (oxLDL) has been identified as a potent stimulus of leukocyte adhesion to endothelium, a hallmark of early atherogenesis. A cytofluorometric study was performed to further characterize the mechanisms by which oxLDL stimulates the rapid adhesion of leukocytes to endothelium in vitro and in vivo. Incubation (30 minutes at 37 C) of whole blood (diluted with buffered saline to 1 x 10(6) leukocytes/ml) with oxLDL (0.85 mg LDL cholesterol/ml; oxidized by 7.5 mumol/L Cu2+ for 18 hours) but not native LDL stimulated the upregulation of CD11b/CD18 adhesion receptors on neutrophils (anti-leu-15 binding: 178 +/- 16% of baseline, P < 0.01, means +/- SD of n = 10 experiments) and on monocytes (169 +/- 34% of baseline, P < 0.01). This phenomenon was almost entirely inhibited by n-butanol or the vasoactive drug pentoxifylline (PTX), which also significantly reduced oxLDL-induced leukocyte adhesion to venular and arteriolar endothelium, as assessed by intravital microscopy on the dorsal skinfold chamber in hamsters (venules: 49 +/- 19 versus 120 +/- 34 cells/mm2, P < 0.05; arterioles: 9 +/- 4 versus 52 +/- 7 cells/mm2, P < 0.01) 30 minutes after intravenous injection of oxLDL (4 mg/kg body weight; means +/- SD of n = 7 hamsters per group). Butanol and PTX also significantly reduced the upregulation of CD11b/CD18 by f-methionyl-leucyl-phenylalanine (fMLP) and platelet-activating factor (PAF) but not by phorbol myristate acetate (PMA). Whereas fMLP and PAF stimulate leukocytes via binding to specific cell surface receptors and triggering complex signal transduction pathways, PMA bypasses these pathways and directly activates intracellular protein kinase C. By analogy, we propose that oxLDL upregulates CD11b/CD18 through its previously documented ability to stimulate the generation of second messengers. The effect of n-butanol and PTX on receptor presentation cannot be explained by changes in plasma membrane fluidity, as both agents failed to reverse the decrease in plasma membrane fluidity of neutrophils after stimulation with oxLDL, as assessed by fluorescence anisotropy measurement of the membrane marker diphenylhexatriene. Incubation of isolated neutrophils but not of whole blood with oxLDL resulted in a significant loss of L-selectin from the neutrophil surface (anti-TQ-1 binding: 40 +/- 13% of baseline, P < 0.01). A significant loss of this adhesion receptor on neutrophils and monocytes was also observed after stimulation of isolated neutrophils and whole blood with fMLP, PAF, and PMA.(ABSTRACT TRUNCATED AT 400 WORDS)

1-Butanol↗
PubMed1995

Deteriorating free radical-trapping capacity and antioxidant status in plasma during bone marrow transplantation.

Organ toxicity in BMT may in part be due to free radical damage. Therefore the 'Total Radical-trapping Antioxidant Parameter of plasma' (TRAP), individual plasma antioxidants, serum iron and linoleic acid, a main substrate of lipid peroxidation, were monitored before and after BMT, and they were compared with values obtained from healthy controls. Seven patients (3 AML, 3 CML, 1 multiple myeloma) receiving 16 mg/kg busulfan, 30-45 mg VP-16 and 120 mg/kg cyclophosphamide were investigated. TRAP values declined during chemotherapy by about 40% (day -9: 1019 +/- 245 mumol/l, mean +/- s.d.; day 0: 660 +/- 164 mumol/l; P < 0.05). The concentration of uric acid, one of the main antioxidants in plasma, decreased markedly (day -9: 339 +/- 108 mumol/l, day 0: 148 +/- 61 mumol/l; P < 0.05) and paralleled TRAP values. Vitamin E and bilirubin did not change from day -9 to 0 whereas vitamin C increased (day -9: 46 +/- 16 mumol/l, day 0: 89 +/- 44 mumol/l; P < 0.05). Serum iron rapidly increased within the pre-transplantation period, reaching values normally seen only in iron overload (day -9: 11.8 +/- 5.2 mumol/l, day 0: 40.6 +/- 6.5 mumol/l; P < 0.05). Linoleic acid levels were normal at the start and decreased substantially (27.0 +/- 1.6 wt% at day -9; 15.7 +/- 4.9 wt% at day 0; P < 0.05), indicating possible lipid peroxidation during high-dose chemotherapy. In conclusion, complex monitoring of the antioxidant status before and after BMT revealed a breakdown of plasma antioxidant defence and of radical-vulnerable lipids, which was associated with high circulating levels of iron.

Adult↗
PubMed1994

P-selectin mediates the interaction of circulating leukocytes with platelets and microvascular endothelium in response to oxidized lipoprotein in vivo.

BACKGROUND: Oxidized low density lipoprotein (oxLDL) has been demonstrated to stimulate leukocyte/endothelium interaction, an early feature of atherogenesis. Using the skinfold chamber model for intravital microscopy in hamsters and mice, we have shown that oxLDL-induced leukocyte adhesion to microvascular endothelium shares many characteristics with leukocyte adhesion during inflammation and ischemia/reperfusion, including the involvement of beta 2 integrin adhesion molecules. In light of the two-step model of leukocyte adhesion, we have examined the contribution of P-selectin to oxLDL-induced leukocyte/endothelium interaction. P-selectin is an inducible adhesion molecule on platelets and endothelium, mediating the initial steps of leukocyte margination and rolling along the endothelial lining, as well as of aggregate formation between platelets and leukocytes. EXPERIMENTAL DESIGN: For our studies, we used the dorsal skinfold chamber model for intravital fluorescence microscopy on awake Syrian golden hamsters. Hamsters were treated 10 minutes before oxLDL-injection (oxidized by Cu2+, 4 mg/kg body weight, intravenously) with blocking antibodies to P-selectin (2 mg/kg body weight intravenously, N = 7). RESULTS: In seven control animals (pretreated with an irrelevant IgG antibody), oxLDL injection elicited leukocyte rolling and adhesion on both venular and arteriolar endothelium, and also the formation of aggregates tumbling down the microvessels and firmly adhering to the microvascular endothelium. The aggregates consisted of leukocytes and activated, dendritic platelets, as assessed by scanning electron microscopy of the buffy coat isolated by density gradient centrifugation of whole blood taken from hamsters 15 minutes after injection of oxLDL. Leukocyte adhesion to venular and arteriolar endothelium, as well as the formation of leukocyte/platelet aggregates were significantly reduced by pretreatment of the animals with anti-P-selectin antibodies. CONCLUSIONS: These data emphasize the similarities between leukocyte adhesion in response to oxLDL and in other pathophysiologic conditions, identifying P-selectin as a crucial player in the interaction between leukocytes and microvascular endothelium as well as in the formation of circulating leukocyte/platelet aggregates.

Animals↗
PubMed1992

Exposure of HIV-infected cells to phospholipid leads to membrane alterations and selective growth retardation.

The effect of exogenous phosphatidylcholine on structure and function of plasma membranes from HIV-1-producing cells and from their non-infected counterparts was determined. The membrane protein composition was not affected by phospholipid treatment. Membrane fluidity and Ca(2+)-permeability were increased in virus-producing cells and in control cells after lipid treatment. The triacylglycerol content of the plasma membranes was increased in virus-producing cells after lipid treatment, whereas the content of phospholipid and cholesterol was not changed. The increased triacylglycerol content was in accordance with a relatively higher rate of [14C]oleic acid incorporation into triacylglycerols of the virus-producing cells after lipid treatment as shown by metabolic labeling. The results suggest that a latent cytopathic effect of HIV-infection becomes manifest if the cells are exposed to exogenous phospholipid and this may open a way to preferentially eliminate HIV-producing cells.

Calcium↗
PubMed1992

Experimental and first clinical experiences with implantable ultrasonic Doppler probes for postoperative bypass control after coronary surgery.

Concerning postoperative bypass hemodynamics after open heart surgery only few data are known. With this new implantable doppler probe we developed an easy-to-use bedside method for monitoring postoperative bypass function after coronary artery bypass grafting. The accuracy of our method is shown by using a circulation model and by animal studies. Furthermore first clinical data are shown which support our conclusion of having found a sensitive method for monitoring small vessels' hemodynamics.

Aged↗
PubMed1992

Superoxide-dependent stimulation of leukocyte adhesion by oxidatively modified LDL in vivo.

Low density lipoprotein modified by oxidation (Ox-LDL) causes adhesion of leukocytes to the endothelium, a feature common in early atherogenesis. Because leukocyte adhesion under various pathophysiological conditions involves superoxide generation, we explored the possibility that superoxide is likewise involved in leukocyte adhesion in response to Ox-LDL. For our studies, we used the dorsal skin fold chamber model for intravital microscopic observation of leukocyte-endothelium interactions in hamsters. We show here that injection of human LDL (4 mg/kg LDL cholesterol oxidatively modified by incubation in 7.5 microM Cu2+ for 18 hours at 37 degrees C) elicited in control hamsters (n = 7) the rolling and adhesion of circulating leukocytes along the endothelium of arterioles and postcapillary venules. This adhesion was significantly attenuated when hamsters were pretreated with bovine copper-zinc-superoxide dismutase (CuZn-SOD, 0.25 mg/kg, n = 7) or heparin (2,000 IU/kg, n = 7). The CuZn-SOD infusion and the heparin-induced release of extracellular SOD from endothelial cell surfaces to plasma resulted in nearly equal plasma SOD activities. Further inhibition of Ox-LDL-induced leukocyte adhesion could not be achieved by increasing the dose of CuZn-SOD to 5 mg/kg (n = 6). Pretreatment of the hamsters with inactivated CuZn-SOD showed no effect. These results indicate that Ox-LDL stimulates leukocyte adhesion through a superoxide-dependent step, and they indicate a possible mechanism by which antioxidants might inhibit the onset of experimental and clinical atherosclerosis.

Animals↗
PubMed1992

[Muscular strength: an indicator of nutritional status].

A hand dynamometer was used to measure muscle strength in 207 patients admitted to the Gastroenterology service of a general hospital. Validation of international standards in a normal population of both sexes and different ages revealed that our normals perform at the 25% percentile of international values. Results were correlated with other measurements of nutritional status, namely anthropometric measurements, serum albumin level and tuberculin test. Compared to normals, muscle strength was significantly (p < 0.01) lower in patients with body mass index under 19, cutaneous tricipital folding < 85%, brachial circumference < 85%, and serum albumin < 3.5 g/dl. No difference in muscle strength between tuberculin positive or negative subjects was observed. None of the nutritional parameter was helpful to predict complications in patients submitted to surgery. Thus, muscle strength is a useful parameter to evaluate nutritional status but, similar to other measurements, is not predictive of surgical complications.

Adolescent↗
PubMed1991

Dietary fish oil blocks the microcirculatory manifestations of ischemia-reperfusion injury in striated muscle in hamsters.

Epidemiologic observations and experimental studies have demonstrated a protective effect of dietary fish oil on the clinical manifestations of ischemia-reperfusion injury. To investigate the underlying mechanisms, we used the dorsal skinfold chamber model for intravital fluorescence microscopy of the microcirculation in striated muscle of awake hamsters. In control hamsters (n = 7), reperfusion after a 4-hr pressure-induced ischemia to the muscle tissue elicited the adhesion of fluorescently stained leukocytes to the endothelium of postcapillary venules, capillary obstruction, and the break-down of endothelial integrity. These microvascular manifestations of ischemia-reperfusion injury were significantly attenuated in animals (n = 7) when fed with a fish oil-enriched diet for 4 weeks prior to the experiments. In leukocyte total lipids, the fish oil diet resulted in a substantial displacement of arachidonic acid, the precursor of the potent adhesion-promoting leukotriene (LT) B4, by fish oil-derived eicosapentaenoic acid, the precursor of biologically less potent LTB5, emphasizing the mediator role of LTB4 in ischemia-reperfusion injury. These results suggest that the preservation of microvascular perfusion by dietary fish oil contributes to its protective effects on the clinical manifestations of ischemia-reperfusion injury.

Animals↗
PubMed1991

Oxidatively modified human low-density lipoprotein stimulates leukocyte adherence to the microvascular endothelium in vivo.

In vitro studies indicate that oxidatively modified low-density lipoprotein (oxLDL) promotes leukocyte sticking to the vascular endothelium, a constant feature of early atherogenesis. Using intravital fluorescence microscopy in the dorsal skinfold chamber model in hamsters, we investigated whether systemic administration of human LDL, oxidized by Cu2+, elicited leukocyte/endothelium interaction in vivo. While no effect was seen after injection of native LDL, oxLDL administration resulted in an immediate induction of leukocyte rolling along the microvascular endothelium and subsequent firm sticking to the wall of postcapillary venules as well as arterioles. The presented model may provide an alternative experimental approach to long-term feeding studies with atherogenic diets for the in vivo investigation of leukocyte/endothelium interaction in early atherogenesis.

Adult↗
PubMed1991

Dextran sulphate reduces diphenylhexatriene anisotropy in human peripheral blood lymphocytes: impact on plasma membrane fluidity and HIV-cytopathogenicity.

Cytopathogenicity of HIV and other enveloped viruses is reduced by membrane fluidizing agents and by dextran sulphate (DS). To investigate whether DS exerts its antiviral action via plasma membrane fluidization of host cells, we performed anisotropy measurements on human peripheral blood lymphocytes (PBL) using the fluorescent marker diphenylhexatriene. Anisotropy was decreased in DS-exposed PBL indicating increased fluidity in the hydrophobic membrane interior.

Adult↗
PubMed1991

Dietary fish oil reduces leukocyte/endothelium interaction following systemic administration of oxidatively modified low density lipoprotein.

BACKGROUND: In vitro and in vivo experiments have demonstrated the role of oxidatively modified low density lipoprotein (oxLDL) in eliciting leukocyte/endothelium interaction during early atherogenesis. METHODS AND RESULTS: In the present study we investigated the effect of dietary fish oil on oxLDL-induced leukocyte/endothelium interaction using intravital fluorescence microscopy in the dorsal skinfold chamber model in awake Syrian golden hamsters. Hamsters were fed for 4 weeks prior to the experiments with either standard laboratory chow or a diet supplemented with 5% of a fish oil concentrate (18% eicosapentaenoate, 12% docosahexaenoate). The efficacy of the fish oil diet was demonstrated by the incorporation of fish oil-derived omega-3 fatty acids into plasma, leukocyte, and erythrocyte lipids. In control hamsters (n = 7) and fish oil-fed hamsters (n = 7), leukocyte/endothelium interaction was assessed in the time course after intravenous injection of human LDL (4 mg/kg), oxidized by 7.5 microM Cu2+ (6 hours, 37 degrees C). In control hamsters, injection of oxLDL elicited the rolling and sticking of leukocytes to the endothelium of arterioles and postcapillary venules with a maximum 15 minutes after injection (arterioles: from 3 +/- 1 to 91 +/- 25 cells/mm2 at 15 minutes; venules: from 13 +/- 6 to 150 +/- 46 cells/mm2 at 15 minutes; mean +/- SD). This phenomenon was significantly reduced in fish oil-fed hamsters, where 15 minutes after injection of oxLDL leukocyte sticking reached a maximum of only 15 +/- 7 and 20 +/- 5 cells/mm2 in arterioles and postcapillary venules, respectively (p less than 0.01 versus control animals). CONCLUSIONS: The results of the present study suggest that inhibition of leukocyte/endothelium interaction may be one of the mechanisms by which dietary fish oil exerts its protective effects on experimental and clinical atherogenesis.

Animals↗
PubMed1991

Role of leukotrienes in leukocyte adhesion following systemic administration of oxidatively modified human low density lipoprotein in hamsters.

In vitro studies indicate that oxidatively modified low density lipoprotein (oxLDL) promotes leukocyte adhesion to the vascular endothelium, a constant feature of early atherogenesis. Using intravital fluorescence microscopy in the dorsal skinfold chamber model in awake Syrian golden hamsters, we studied whether (a) oxLDL elicits leukocyte/endothelium interaction in vivo, and whether (b) leukotrienes play a mediator role in this event. Leukocyte/endothelium interaction was assessed in the time course after intravenous injection of native human LDL (4 mg/kg body wt) and of oxLDL (7.5 microM Cu++, 6 h, 37 degrees C) into control hamsters and into hamsters, pretreated with the selective leukotriene biosynthesis inhibitor MK-886 (20 mumol/kg, i.v.). While no effect was seen after injection of native LDL, oxLDL elicited an immediate induction of leukocyte adhesion to the endothelium of arterioles and postcapillary venules. Total and differential leukocyte counts suggest that all leukocyte subsets were likewise affected by oxLDL with no specific preference for monocytes. Stimulation of leukocyte adhesion was entirely prevented in inhibitor-treated animals, suggesting the important mediator role of leukotrienes in oxLDL-induced leukocyte/endothelium interaction.

Adult↗
PubMed1990

Effects of membrane lipid and fluidity modifications on HIV-1 infectibility of primate lymphocytes in vitro.

Although most non-human primates, except the chimpanzee and the gibbon in vivo are not infectible by HIV-1, lymphocytes of several of these species can be infected by HIV-1 in vitro. In order to investigate whether the in vitro infectibility of primate lymphocytes might be attributed to plasma membrane adaptation processes or to serum factors, we compared HIV-1 infectibility of cultivated peripheral blood lymphocytes of macaques and of baboons on day one and on day ten of cultivation. These data were correlated to plasma membrane lipid composition and membrane fluidity. We found a correlation between increased HIV-1 in vitro infectibility and changes in plasma membrane lipid composition resulting in decreased membrane fluidity of cultured primate lymphocytes.

Animals↗
PubMed1990

Decreased binding of HIV-1 and vasoactive intestinal peptide following plasma membrane fluidization of CD4+ cells by phenytoin.

Plasma membrane fluidity of intact peripheral blood lymphocytes (PBL) of phenytoin-treated nonepileptic patients and phenytoin-treated CD4+ lymphoid cells H9 and K37 was determined by fluorescence anisotropy measurements. Anisotropy values of the membrane probe 6-(9-anthroyloxy) stearic acid were decreased in all cell types as compared with controls, indicating increased plasma membrane fluidity of phenytoin-treated cells. Specific binding of 125I-labeled vasoactive intestinal peptide (VIP) to its cellular receptor CD4 on PBL was decreased in PBL of phenytoin-treated patients as compared with untreated, healthy subjects. Adsorption of a different ligand to the CD4 receptor on PBL, the human immunodeficiency virus type 1 (HIV-1), was likewise abolished to PBL of phenytoin-treated patients and phenytoin-treated CD4+ H9 and K37 cells, as assessed by indirect immunofluorescence. Subsequent HIV-1 infection of phenytoin-treated H9 and K37 cells was reduced as measured by indirect immunofluorescence and p24 antigen production. These data indicate that CD4 receptor availability for VIP and HIV-1 was reduced in phenytoin-treated cells. Using the DNA-specific dye Hoechst 33258, we examined cell cycle phase distributions of HIV-1 adsorbing and nonadsorbing H9 cells, as separated by flow cytometry. The majority of HIV-1 adsorbing cells were found to be in the G2/M phase, while nonadsorbing cells were mainly in the G0/G1 phase, during which plasma membrane fluidity is supposed to be increased. This study indicates that plasma membrane fluidization by phenytoin may serve to disrupt CD4 receptor function and emphasizes the impact of plasma membrane properties on HIV-1 adsorption and infection.

Adsorption↗
PubMed1989

Decreased plasma membrane fluidity of peripheral blood lymphocytes after diethyldithiocarbamate (DTC) therapy in HIV-infected patients.

In seeking the putative mechanism of action of diethyldithiocarbamate (DTC) on the immune status of HIV infected patients, the plasma membrane fluidity of peripheral blood lymphocytes (PBL) from DTC-treated and untreated patients (CDC III-IVc1) was determined. Anisotropy values of the fluorescent probe 6-(9-anthroyloxy) stearic acid were increased in DTC-treated patients (0.175 vs 0.161), indicating decreased PBL plasma membrane fluidity. The membrane rigidifying effect was significantly greater 4 h after i.v. drug administration (0.185 in treated patients). As the membrane fluidity and the function of membrane embedded antigen are interdependent, it is possible that alterations in biophysical and/or biochemical properties of membranes may account for the beneficial effect of DTC on the immune function and clinical status of HIV infected patients.

Acquired Immunodeficiency Syndrome↗