Search PubMed⌕ Search

Biomedical subjects

R Schumann

Publications and source records attributed to R Schumann.

At least 37 records · Page 2Linked to original sources
PubMed1998

Inflammation in high-grade carotid stenosis: a possible role for macrophages and T cells in plaque destabilization.

BACKGROUND AND PURPOSE: Inflammatory mechanisms have been implicated in the pathogenesis of atherosclerosis. In this study, we investigated whether the extent of inflammatory infiltration in high-grade stenoses of the internal carotid artery (ICA) correlates to clinical features of plaque destabilization. METHODS: Endarterectomy specimens from 37 consecutive patients undergoing surgery for high-grade ICA stenosis were stained immunocytochemically for macrophages (CD68) and T cells (CD3). The staining was quantified by planimetry of immunostained areas (CD68) or counting individual cells (CD3). Clinical evidence of plaque instability was provided by the preoperative assessment of recent ischemic symptoms attributable to the stenosis and of the occurrence of cerebral microembolism in transcranial Doppler ultrasound monitoring of the ipsilateral middle cerebral artery. RESULTS: The percentage of macrophage-rich areas and number of T cells per mm2 section area were larger in recently symptomatic patients than in asymptomatic patients (macrophages: 18+/-10% versus 11+/-4%, P=0.005; T cells: 71.2+/-34.4 versus 40.5+/-31.4 mm2, P=0.005). The presence of microembolism was associated with an increase in macrophage-rich areas (P=0.011). Macrophage (19+/-10% versus 9+/-3%, P=0.0009) and T cell (71.5+/-39.0 versus 46.4+/-22 mm2, P=0.045) infiltration were more pronounced in predominantly atheromatous than in fibrous plaques, but did not correlate significantly to the presence of surface ulceration or luminal thrombosis. CONCLUSIONS: Our data suggest a role of plaque-infiltrating macrophages and T cells in the clinical destabilization of high-grade ICA stenoses. Inflammatory mechanisms may be a therapeutic target in patients with symptomatic ICA disease.

Adult↗
PubMed1996

Human monocyte CD14 is upregulated by lipopolysaccharide.

Membrane CD14 is involved in lipopolysaccharide (LPS)-induced monocyte activation; it binds LPS, and antibodies against CD14 block the effects of low-dose LPS. It is unknown how LPS regulates its own receptor CD14 in vitro. Therefore, we investigated the effects of LPS on CD14 mRNA and membrane and soluble CD14 (mCD14 and sCD14, respectively) in human monocytes and macrophages. No changes were observed during the first 3 h of LPS stimulation. After 6 to 15 h, LPS weakly reduced CD14 mRNA and mCD14 and transiently enhanced sCD14 release. A 2-day incubation with LPS caused increases in the levels of CD14 mRNA (2-fold), mCD14 (2-fold), sCD14 (1.5-fold), and LPS-fluorescein isothiocyanate binding (1.5-fold); a 5-h incubation with LPS was sufficient to induce the late effects on mCD14 and sCD14. The maximal effect on mCD14 and sCD14 was reached with > or = 1 ng of LPS per ml; the proportional distribution of the two sCD14 isoforms was not modified by LPS. Besides rough and smooth LPS, lipid A, heat-killed Escherichia coli, lipoteichoic acid, and Staphylococcus aureus cell wall extract (10 micrograms/ml) caused similar increases of mCD14. The LPS effect was blocked by polymyxin B but not by anti-tumor necrosis factor alpha, anti-interleukin-6, anti-gamma interferon, and anti-LPS-binding protein. LPS-induced tumor necrosis factor alpha production was abolished after a second 4-h challenge. In contrast, the LPS-induced increases CD14 mRNA, mCD14, and sCD14 were stronger and appeared earlier after a second LPS challenge. In conclusion, CD14 is transcriptionally upregulated by LPS and other bacterial cell wall constituents.

Adaptation, Physiological↗
PubMed1995

LPS directly induces oxygen radical production in human monocytes via LPS binding protein and CD14.

In human monocytes, superoxide (O2-) generation accompanies phagocytosis and is important for bactericidal activity. It also contributes to tissue damage in inflammation. In the present study we investigated, whether lipopolysaccharide (LPS) directly stimulates monocyte O2- production with kinetics known for other LPS effects and, if so, by which mechanism. LPS caused a time- and dose-dependent O2- release in nonadherent purified monocytes. The effect appeared after 5 min, peaked at 30 min, and disappeared after 2 h. It was maximal with 10 ng/ml lipid A (+148 +/- 22%, P < .001), 1 ng/ml LPS Escherichia coli Re (+226 +/- 68%, P < .001), and 100 ng/ml LPS Salmonella abortus equi sm (+272 +/- 52%, P < .001), respectively. The effect was not observed in buffer, even when using 10 micrograms/ml LPS. It was dependent on the presence of heat-inactivated AB serum, with a maximal effect at > or = 0.5%. Serum could be replaced by LPS-binding protein (LBP). Polymyxin B and anti-LBP antiserum, respectively, blocked the LPS effect. LPS-induced O2- generation was also completely blocked by anti-CD14 antibodies (3C10 and 63D3) and by their corresponding F(ab')2 fragments. Monocytes treated with phosphoinositol-specific phospholipase C and monocytes from patients with paroxysmal nocturnal hemoglobinuria, lacking the phosphatidylinositol-anchored CD14, did not respond to LPS stimulation with O2- production. Similarly to LPS, E. coli caused stronger O2- production with heat-inactivated serum than without, and this effect was blocked by anti-CD14 antibodies. In conclusion, these data indicate that LPS directly stimulates O2- production in human monocytes via CD14 depending on LBP.

Acute-Phase Proteins↗
PubMed1994

[Not Available].

Explore the source record for details and available documents.

Books↗
PubMed1993

[The endotoxin receptor CD14].

The knowledge about molecular mechanisms of endotoxin (LPS) recognition by cellular receptor CD14 and its consequences as well as the relationship between soluble and membrane-bound receptor is reviewed. The binding of endotoxins to membrane-bound CD14 is mediated by special so-called LPS-binding serum proteins. The mechanism of signal transduction is not yet known. After activation by LPS, monocytes produce free oxygen radicals, IL-1, IL-6, TNF alpha and other mediators. CD14 is present in normal serum as soluble receptor which can neutralize endotoxins in respect to their monocyte activating capacity.

Antigens, CD↗
PubMed1992

A universal expression-purification system based on the coiled-coil interaction of myosin heavy chain.

We have constructed a series of Escherichia coli expression vectors that produce high yields of fusion proteins containing the C-terminal fragment of light meromyosin (LMM) from rabbit fast skeletal muscle. The fusion proteins retain the ability of LMM to form polymers in low salt and to be soluble in high salt. Thus they can be easily purified from bacterial extracts with a high salt-low salt extraction procedure and still retain their biochemical properties. We demonstrate the utility of this system for the heterologous production and simple purification of LMM fusions of p21H-ras, the neurofibromatosis type I protein and the Tat and protease proteins of HIV-1.

Amino Acid Sequence↗
PubMed1990

Three-dimensional structures of H-ras p21 mutants: molecular basis for their inability to function as signal switch molecules.

The X-ray structures of the guanine nucleotide binding domains (amino acids 1-166) of five mutants of the H-ras oncogene product p21 were determined. The mutations described are Gly-12----Arg, Gly-12----Val, Gln-61----His, Gln-61----Leu, which are all oncogenic, and the effector region mutant Asp-38----Glu. The resolutions of the crystal structures range from 2.0 to 2.6 A. Cellular and mutant p21 proteins are almost identical, and the only significant differences are seen in loop L4 and in the vicinity of the gamma-phosphate. For the Gly-12 mutants the larger side chains interfere with GTP binding and/or hydrolysis. Gln-61 in cellular p21 adopts a conformation where it is able to catalyze GTP hydrolysis. This conformation has not been found for the mutants of Gln-61. Furthermore, Leu-61 cannot activate the nucleophilic water because of the chemical nature of its side chain. The D38E mutation preserves its ability to bind GAP.

Adenosine Triphosphate↗
PubMed1990

Density-dependent tumor cell death and reversible cell cycle arrest: mutually exclusive modes of monocyte-mediated growth control.

The population development of five human tumor cell lines is examined under the influence of elutriator-prepared human monocytes in a serum-free hormone- and growth factor-supplemented medium. Analysis was performed by electronic counting and sizing of tumor cell nuclei and flow cytometric detection of cell cycle phases. Tumor cell death is triggered at rather low monocyte:tumor cell ratios (1:2 to 1:4) whereas it is strongly reduced at high monocyte densities. Furthermore, it is shown that confluence of the target cell population is a necessary prerequisite for lysis. The data suggest that in monocyte/tumor cell cocultures the decision on target cell lysis is not made by the effector cell, but rather by the target cell and that the criterion for this decision is the target cell's ability or inability to respond to a monocyte challenge by arresting the cell cycle in G1. Interactions between target cells play an important role in determining the result of this decision process. A common basis is suggested for this kind of density-dependent monocyte-triggered lysis and density-dependent cell death in 3T3 cell cultures as described previously.

Cell Cycle↗
PubMed1989

[Prosthetic management following submucous vestibuloplasty].

20 patients who had been treated with a submucous maxillary vestibuloplasty were examined 1 to 3 years postoperatively. The postoperative result of surgery and the prosthetic conditions were evaluated according to fixed criteria by a maxillofacial surgeon and a prosthodontist. From the prosthetic point of view, the postoperative result was good in 15 cases, sufficient in 2 cases and, due to false diagnoses, unacceptable in 3 cases. 13 patients were completely satisfied by the postoperatively inserted dentures, 6 were only partially satisfied and 1 person was dissatisfied. Although 13 patients were satisfied, only 10 dentures were without significant defects.

Consumer Behavior↗
PubMed1988

[CT morphology of malignant schwannoma].

Thirty patients with histologically confirmed malignant schwannomas were examined. In five patients the lesions were malignant neurofibromas, as part of von Recklinghausen's disease, the others were solitary malignant schwannomas. CT appearances of malignant schwannomas are variable. Shape, structure and attenuation vary considerably. Most malignant schwannomas present with the CT criteria of benign tumours. Altogether neither the solitary schwannomas, nor those associated with von Recklinghausen's disease show specific diagnostic features, whether for the primary tumour or for recurrences. Reliable information on the nature of these lesions is possible in a few cases only.

Adult↗
PubMed1985

Cloning and sequencing of the adenylate kinase gene (adk) of Escherichia coli.

Adenylate kinase, the product of the adk locus in Escherichia coli K12, catalyzes the conversion of AMP and ATP to two molecules of ADP. The gene has been cloned by complementation of an adk temperature sensitive mutation. The DNA sequence of the complete coding region and of 5'- and 3'-untranslated regions were determined. The resulting protein sequence was found to contain several regions of high homology with cytosolic adenylate kinase of pig muscle (AK1), whose three-dimensional structure has been determined. The most significant of the amino acid exchanges is the replacement of histidine 36 with glutamine. This residue is believed to play a role in catalysis through metal ion binding. The codon usage pattern and the determination of adenylate kinase molecules per cell shows that the enzyme is one of the more abundant soluble proteins of the bacterial cells.

Adenylate Kinase↗