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B Buchner

Publications and source records attributed to B Buchner.

11 recordsLinked to original sources
PubMed2000

From antiferromagnetic order to static magnetic stripes: the phase diagram of (La,Eu)2-xSrxCuO4

The magnetic order of (La,Eu)2-xSrxCuO4 ( x</=0.2) has been investigated with &mgr;SR techniques. In this system a low temperature tetragonal (LTT) structure is present in the entire range of doping and it is possible to follow the evolution from the long range antiferromagnetic state at x = 0 to the static magnetic stripes. We find a nonmonotonic change of the Neel temperature with increasing x and the obtained magnetic phase diagram of the LTT phase resembles the generic phase diagram of the cuprates where the superconductivity is replaced by a second antiferromagnetic phase.

Journal Article↗
PubMed2000

Cu NQR study of the stripe phase local structure in the lanthanum cuprates

Using Cu nuclear quadrupole resonance (NQR) in Eu-doped La2-xSrxCuO4 we find the evidence of the pinned stripe phase at 1.3 K for 0. 08</=x</=0.18. The pinned fraction increases by 1 order of magnitude near hole doping x = 1/8. The NQR line shape reveals three inequivalent Cu positions: (i) sites in the charged stripe, (ii) nonmagnetic sites outside the stripes, and (iii) sites with a magnetic moment of 0.29&mgr;(B) in the antiferromagnetically correlated regions. A dramatic change of the NQR signal for x>0.18 correlating with the onset of bulk superconductivity corresponds to the depinning of the stripe phase.

Journal Article↗
PubMed1999

Specific interaction of oxidized low-density lipoprotein with macrophage-derived foam cells isolated from rabbit atherosclerotic lesions.

Interaction of oxidized LDL (OxLDL) with macrophage-derived foam cells is one of the key events in the development and progression of atherosclerosis. To study this interaction, macrophage-derived foam cells were isolated from rabbit atherosclerotic lesions and the expression of scavenger receptors for OxLDL was examined. Atherosclerosis was induced in rabbits by denudation of the large arteries, followed by a hypercholesteremic diet. Macrophage-derived foam cells, characterized by immunostaining with an RAM-11 antibody (a macrophage marker), contained a high content of intracellular lipid. Maximal binding of radiolabeled OxLDL to isolated macrophage-derived foam cells (1652+/-235 ng 125I-OxLDL/mg of cell protein) was 20-fold higher compared with Bmax values of monocytes. Levels of association of OxLDL to macrophage-derived foam cells isolated from atherosclerotic lesions 12 weeks after denudation were >3-fold higher compared with the levels expressed by macrophage-derived foam cells isolated after 6 weeks. Association of 125I-OxLDL could be completely blocked by OxLDL, and partially by acetylated LDL and polyinosinic acid, indicating the presence of a specific binding site for OxLDL on macrophage-derived foam cells. The induction of scavenger receptors for OxLDL on macrophage-derived foam cells during the development of atherosclerosis, as described in this study, may facilitate the lipid accumulation in macrophage-derived foam cells, as observed in advanced atherosclerotic lesions.

Animals↗
PubMed1998

Acute effects of oxidized low density lipoprotein on metabolic responses in macrophages.

The immediate effects of oxidized low density lipoprotein (OxLDL) on the metabolic activity of cultured macrophages (RAW 264.7) were studied using a microphysiometer. Administration of OxLDL acutely induced a concentration-dependent increase in metabolic activity, with an EC50 of 16 +/- 3 microg/ml OxLDL and a maximal effect of 35% +/- 4% (mean +/- SEM; n=5). A biphasic response was measured after administration of 75 or 100 microg/ml OxLDL consisting of an initial sharp increase, followed by the induction of a long-lasting hypoactivity of 80% of the control value. Incubation of cells with polyinosinic acid (polyI; 100 microg/ml) for 30 min prior to OxLDL administration could completely block the effect of 25 microg/ml OxLDL. In addition, polyI acted as a full antagonist on the decrease of the biphasic response of cells generated by 75 and 100 microg/ml OxLDL. Macrophages used in this study possessed a specific binding site for OxLDL, with a dissociation constant (KD) of 9 +/- 2 microg/ml and a maximal binding of 610 +/- 32 ng 125I-OxLDL/mg cell protein. Binding of 125I-OxLDL to macrophages could be completely competed for by unlabeled OxLDL, by polyI for 58%, and by AcLDL for 46%. In conclusion, OxLDL can acutely activate the metabolic state of macrophages by a receptor-mediated process in a concentration-dependent fashion, which could be antagonized by polyI. Metabolic responses to OxLDL may underlie the changes observed in macrophages in the early atherosclerotic plaque.

Animals↗
PubMed1996

Chronic rejection of concordant aortic xenografts in the hamster-to-rat model.

Several groups have demonstrated that it is possible to obtain long-term graft survival of concordant xenografts. One of the important questions that remains is whether xenografts are susceptible to chronic rejection. To answer this question we used the aorta transplantation model. One centimetre of hamster aorta was interposed in the abdominal aorta of Lewis rat recipients. The recipients were either untreated (group 1), or treated with 10 mg/kg cyclosporine (CsA), given intramuscularly three times a week (group 2). Rats were sacrificed at day 7, 14, 21, 28, 56 and 84 and the thickness of the intima, the media and the adventitia was measured. Furthermore, the cellularity of the media and the adventitia was assessed by counting the number of nuclei per 0.05 mm2 and immunohistochemistry of the aortic grafts was performed. Graft arteriosclerosis developed in aortic xenografts of both group 1 and group 2. In group 1, intimal lesions were already present from day 21 onwards in all rats, whereas in group 2 they were present only in 33% (2/6) of the rats. At day 84 all the grafts in group 1 were totally occluded, while those in group 2 were still open. The thickness of the media was slightly increased in both groups during the whole observation period, mainly due to edema. Although a few infiltrating macrophages could be seen, the number of nuclei per 0.05 mm2 of the media remained constant during the first 21 days, but declined sharply from day 21 onwards, as a consequence of disappearing myocytes. Thickness of the adventitia in both groups increased after transplantation due to infiltrating macrophages and T cells, reaching a peak at day 14. After day 14 the adventitial thickness in group 1 decreased rapidly to reach values comparable to group 2 from day 28 onwards. In conclusion, graft arteriosclerosis, as a sign of chronic rejection, occurs in concordant aortic xenografts. The lesions in the xenografts develop extremely rapidly, and compared to data from the literature, faster than in aortic allografts. The process of chronic rejection in aortic xenografts can be reduced by CsA.

Animals↗
PubMedDate not supplied

Evaluation of a confidential method of excluding blood donors exposed to human immunodeficiency virus.

A confidential self-administered questionnaire was given to all donors prior to blood donation (n = 95,917). The questionnaire describes acquired immunodeficiency syndrome (AIDS) high-risk groups and requires the donor to designate his blood for either laboratory purposes or for transfusion. Six-hundred and twenty-seven people (0.65%; 78% men) designated their blood for laboratory purposes. In addition to routine enzyme-linked immunoassay (EIA) screening for human immunodeficiency virus (HIV) antibody, all units from the latter group of donors were tested by Western blot (WB) irrespective of the EIA result. An equal number of donor units was selected from those designating their blood for transfusion (age, sex and clinic matched) and these too were tested by WB irrespective of the EIA result. We found that donors designating their blood for laboratory purposes had a 10 times (vs transfusion-designated controls) to 100 times (vs general donor population) greater exposure to HIV. In the laboratory-designated group, an EIA negative donor was WB positive, yielding an estimated EIA false-negative rate of 16 per million. A confidential questionnaire, as described, is a valuable adjunct in ascertaining high-risk blood donors.

Acquired Immunodeficiency Syndrome↗
PubMedDate not supplied

Evaluation of a confidential method of excluding blood donors exposed to human immunodeficiency virus: studies on hepatitis and cytomegalovirus markers.

A confidential self-administered questionnaire was given to all blood donors prior to donation (n = 95,917). The questionnaire describes groups at increased risk of acquired immunodeficiency syndrome (AIDS) and requires the donor to designate his blood either for laboratory purposes or for transfusion. In a previous communication, we reported that donors in the former group had a much higher prevalence of antibody to human immunodeficiency virus (HIV) than age, sex and clinic matched controls or a group of "miscellaneous" donors who did not fill out the form properly. In this communication, we report results of tests for other viral markers performed on the three designation groups, namely laboratory-designated, miscellaneous and controls. We found that the former two groups had a higher prevalence of antibody to hepatitis B surface antigen (anti-HBs), hepatitis B core antigen (anti-HBc) and cytomegalovirus (anti-CMV) than controls, but there were no differences in alanine aminotransferase (ALT) levels among the groups. In addition, the laboratory-designated group had a higher prevalence of hepatitis B surface antigen (HBsAg) than the general donor population. These data indicate that a questionnaire designed to ascertain AIDS high-risk donors is valuable in excluding donors who may be carriers of other viruses as well.

Acquired Immunodeficiency Syndrome↗