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I Köhler

Publications and source records attributed to I Köhler.

At least 19 recordsLinked to original sources
PubMed2001

In vitro antiplasmodial activity of 4-phenylcoumarins from Exostema mexicanum.

The stem bark of Exostema mexicanum (Rubiaceae) is used in Latin American folk medicine as a quinine substitute for malaria treatment. Bioassay-guided fractionation of lipophilic and hydrophilic extracts from the stem bark and branches yielded two previously undescribed 4-phenylcoumarins: 4',8-dihydroxy-5,7-dimethoxy-4-phenylcoumarin (exomexin A) and 3',4'-dihydroxy-5,7,8-trimethoxy-4-phenylcoumarin (exomexin B). Together with five known derivatives the in vitro activities against a chloroquine-sensitive strain (poW) and a chloroquine-resistant strain (Dd2) of Plasmodium falciparum have been evaluated. The most lipophilic compound, 4',5,7,8-tetramethoxy-4-phenylcoumarin (O-methylexostemin) revealed the strongest antiplasmodial activity (IC50 values: 3.6 microg/ml [poW], 1.6 microg/ml [Dd2]).

Animals↗
PubMed2000

Long-term monitoring of sister chromatid exchanges and micronucleus frequencies in pharmacy personnel occupationally exposed to cytostatic drugs.

OBJECTIVES: Many antineoplastic drugs were found to have carcinogenic, mutagenic and teratogenic potential. The aim of this study was to carry out cytogenetic and internal dose monitoring of hospital pharmacy personnel regularly involved in the preparation of cytostatic agents, in order to test possible cytostatics-induced genotoxic effects due to occupational exposure under routine working conditions, and in cases of accidental contamination. METHODS: Platinum in whole blood and anthracyclines in plasma were measured to assess internal exposure to cytostatics. The level of cytogenetic damage was determined in peripheral blood lymphocytes with the micronucleus test and the sister chromatid exchange assay. Five series of monitoring were performed over a period of 2 years. RESULTS: No significant differences in the mean frequencies of sister chromatid exchanges (SCE) and micronuclei (MN) were found between occupationally exposed probands and controls (9.9 +/- 1.4 vs 10.1 +/- 1.2 SCEs/cell and 21.2 +/- 7.2 vs 23.3 +/- 7.5 MN/2000 binucleated (BN) cells, n = 16). Significant elevations of SCE or MN were detected in seven out of 12 cases of accidental contamination at the workplace, whereas no increase in platinum in blood and anthracyclines in plasma was observed in these probands. Two cases of non-reported contamination were identified by measurement of epirubicin in plasma. Smoking was found to increase the SCE significantly. No correlation between individual SCE scores and MN scores was observed. CONCLUSIONS: Our findings support a transient increase in SCE or MN after relevant exposure to cytostatic drugs in cases of accidental contamination. The lack of significant differences in SCE and MN between hospital pharmacy personnel and unexposed controls, points to high standards of safety at the corresponding workplaces.

Adult↗
PubMed1997

Functional and phenotypic characterization of cord blood and bone marrow subsets expressing FLT3 (CD135) receptor tyrosine kinase.

The class III receptor tyrosine kinase FLT3/FLK2 (FLT3; CD135) represents an important molecule involved in early steps of hematopoiesis. Here we compare cell-surface expression of FLT3 on bone marrow (BM) and cord blood (CB) cells using monoclonal antibodies (MoAbs) specific for the extracellular domain of human FLT3. Flow cytometric analysis of MACS-purified BM and CB cells showed that 63% to 82% of BM CD34+ and 88% to 95% of the CB CD34+ cells coexpress FLT3. Clonogenic assays and morphological characterization of FACS-sorted BM CD34+ cells demonstrate that colony-forming unit-granulocyte-macrophage (CFU-GM) and immature myelo-monocytic precursor cells are enriched in the subpopulation staining most brightly with the FLT3 MoAb whereas the majority of the burst-forming units-erythroid (BTU-E) and small cells with lymphoid morphology are found in the FLT3- population. In contrast, statistically indistinguishable proportions of CFU-granulocyte-erythrocyte-megakaryocyte-macrophage (CFU-GEMM) and more primitive cobblestone area forming cells (CAFC) were detected in both fractions, albeit the FLT3+ fraction consistently showed more CAFC activity than the FLT3- fraction. Although in both, BM and CB the majority of CD34+CD117+ (KIT+), CD34+CD90+ (Thy-1+), and CD34+CD109+ cells coexpress FLT3, three-color phenotypic analyses are consistent with the functional findings and suggest that the most primitive cells defined as CD34+CD38-, CD34+CD71low, CD34+HLA-DR-, CD34+CD117low, CD34+CD90+, and CD34+CD109+ express low levels of cell-surface FLT3 and were therefore not enriched to a statistically significant extent with the bright versus negative sorting scheme. Thus, clear segregation of the most primitive progenitors from BM CD34+ cells was confounded by low apparent levels of FLT3 cell-surface expression on these cells, whereas myeloid progenitors unambiguously segregated with the FLT3 brightest cells and erythroid progenitors with the FLT3 dimmest. Additional phenotypic analyses using MoAbs against progenitor/stem cell markers including the mucinlike molecule MGC-24v (CD164), the receptor tyrosine kinases TIE, FMS (CD115), and KIT (CD117) further illustrate the differences in surface antigen expression profiles of BM and CB CD34+ cells. Notably, CD115 is rarely detected on CB CD34+ cells, whereas 20% to 25% of the BM CD34+FLT3+ cells are CD115+. Furthermore, 80% to 95% of the CB CD34+CD117+ but only 60% to 75% of the BM CD34+CD117+ cells coexpress FLT3. Only a negligible amount of CD34+CD19+ are detected in CB, while in BM 20% to 30% of CD34+CD19+ presumed pro/pre-B cells coexpress FLT3. In contrast, the majority of the CD34+CD164+ and CD34+TIE+ subsets in both CB and BM coexpress FLT3. Analysis of unseparated cells showed that FLT3 expression is not restricted to CD34+ subsets. About 65% to 70% of lymphocyte-gated BM CD34-FLT3+ cells are positive for the monocytic marker CD115 whereas 25% to 30% of these cells consist of CD10 expressing B-cell precursors. Finally, CD34- monocytes in BM, CB, and PB express FLT3 whereas granulocytes are FLT3-. Our data show that detectable FLT3 appears first at low levels on the surface of primitive multilineage progenitor cells and disappears during defined stages of B-cell development, but is upregulated and maintained during monocytic maturation.

Bone Marrow↗
PubMed1996

Preferential expression of T-cell receptor V beta-chains in atopic eczema.

Chronic skin colonization with Staphylococcus aureus is a characteristic feature of atopic eczema, and about 60% of S. aureus strains isolated from the skin of patients with atopic eczema secrete enterotoxins. T-cell stimulation by staphylococcal enterotoxins is restricted to the V beta-chain of the T-cell receptor. Therefore, the expression of different V beta-chains (V beta 3, 5 a,b,c, 6, 8, 12) on peripheral blood T-cells (CD4+) from patients with atopic eczema was measured by flowcytometry before and after stimulation with staphylococcal enterotoxin B. Lymphocytes from healthy donors served as controls. Additionally, the expression of V beta-chains in normal skin and in lesional skin of patients with atopic eczema was determined by immunofluorescence histology. In atopic eczema, higher numbers of CD4+ T-cells expressed V beta 3, V beta 8 and V beta 12 compared to the control group. No correlation between S. aureus enterotoxin B-stimulated V beta-expression and HLA-haplotypes was found. In lesional skin of patients with atopic eczema most of the infiltrating T-cells were V beta 3+, whereas in normal skin only very few T-cell receptor-expressing cells were detected. To evaluate the significance of these T-cell clones for allergic inflammation, T-cells from patients with atopic eczema and normal donors were stimulated with monoclonal antibodies against V beta 3, 5(c) and 8. Afterwards, the proliferative response of lymphocytes as well as IL-5 and IFN gamma synthesis were measured. T-cells from patients with atopic eczema showed a significantly higher proliferation and IL-5 secretion than normal donors after stimulation with monoclonal antibodies against V beta 3 and V beta 8. In contrast, the monoclonal antibodies directed to V beta 5(c) induced a markedly elevated proliferation and IFN gamma production of normal lymphocytes compared to patients with atopic eczema. Our results suggest a preferential expression of certain V beta-subgroups during inflammation in atopic eczema; this may be explained by a selective stimulation of TH2-cells via S. aureus-derived enterotoxins.

Cells, Cultured↗
PubMed1995

Cytokine-mediated effects of peripheral blood mononuclear cells from patients with atopic eczema on keratinocytes (HaCaT) in a new coculture system.

Interactions between keratinocytes and mononuclear cells via cytokines and adhesion molecules are thought to play a crucial part in inflammatory skin diseases. The cytokine-mediated effects of peripheral blood mononuclear cells (PBMC) from patients with atopic eczema (AE) and healthy individuals on keratinocytes (HaCaT) were investigated in vitro. A new coculture model (Transwell system) which consists of a lower and an upper compartment, which are separated by a polycarbonate-treated membrane, was established. 3[H]thymidine incorporation of keratinocytes and lymphocytes, as well as IL-6, IL-8 and IFN-gamma synthesis, were measured. Keratinocyte proliferation was significantly enhanced in the presence of PBMC from patients with AE. In contrast, PBMC from normal donors did not enhance HaCaT cell proliferation when they were cocultured. Lymphocytes from patients with AE showed a significantly enhanced proliferation after coculture with keratinocytes. However, PBMC from normal donors did not proliferate in the presence of HaCaT cells. Keratinocyte supernatants incubated with PBMC from either atopic or normal volunteers induced a suppression of lymphocyte 3[H]thymidine incorporation. In supernatants from cocultures of PBMC from patients with AE and keratinocytes, significantly enhanced amounts of IL-6 and IL-8, compared with normal donor's lymphocytes and HaCaT cells, were measured. No differences in IFN gamma production were observed. When PBMC were cultured without HaCaT cells, supernatants contained equal levels of IL-6, IL-8 and IFN-gamma in normal donors and in patients with AE. Interestingly, HaCaT cells spontaneously secrete measurable amounts of IL-6, IL-8 and IFN-gamma. Blocking experiments with neutralizing antibodies against these interleukins showed a complete inhibition of keratinocyte proliferation when PBMC from normal donors were used whereas the proliferative potency of PBMC supernatants from patients with AE on keratinocytes remained. Our data indicate that (i) PBMC from patients with AE stimulate keratinocyte proliferation via soluble factor(s) that are different from IL-6, IL-8 and IFN-gamma; (ii) probably, HaCaT cells spontaneously produce lymphocyte/monocyte inhibitory soluble factors and IL-6, IL-8 as well as IFN-gamma; and (iii) secretion and/or activity of keratinocyte-derived inhibitory mediators is regulated via cytokines of PBMC infiltrating inflammatory skin.

Antibodies, Monoclonal↗
PubMed1995

Elevated serum levels of soluble adhesion molecules ICAM-1 and ELAM-1 in patients with severe atopic eczema and influence of UVA1 treatment.

BACKGROUND: ICAM-1 is known to be strongly expressed on keratinocytes in lesional atopic eczema correlating with the degree of inflammation. ELAM-1 was found to be expressed on dermal vascular endothelium in lesional atopic eczematous skin. OBJECTIVE: The present study was performed to investigate whether elevated serum levels of soluble forms of these molecules are detectable in patients with severe atopic eczema and whether these parameters could be useful markers for disease activity. METHODS: Serum levels of soluble ICAM-1 (sICAM-1) and ELAM-1 (sELAM-1) were measured by ELISA in 18 patients with severe atopic eczema before and after UVA1 therapy. RESULTS: Before onset of treatment, serum sICAM-1 (565 +/- 99 ng/ml) and sELAM-1 (89.7 +/- 29.9 ng/ml) levels were significantly (p < 0.001) elevated compared to 22 healthy control persons (296 +/- 46 and 48.8 +/- 22.7 ng/ml). After achievement of significant clinical improvement after 3 weeks of UVA1 therapy, there was neither a decrease in serum sICAM-1 nor in sELAM-1 levels. The posttherapeutic serum sICAM-1 and sELAM-1 values remained elevated (p < 0.001) above the normal range. CONCLUSION: Based on these data we suggest that (1) serum sICAM-1 and sELAM-1 are elevated in patients with severe atopic eczema, (2) sICAM-1 does not decrease together with reduction of ICAM-1-positive keratinocytes in atopic eczema following clinical improvement and might therefore be mainly of a different origin, i.e. leukocytes/endothelial cells, and that (3) sICAM-1 and sELAM-1 seem not to be suitable markers of actual disease activity in severe atopic eczema.

Adult↗
PubMed1995

Low dose versus medium dose UV-A1 treatment in severe atopic eczema.

Twenty-two patients with severe atopic eczema were included in a therapy study with UV-A1 (wavelengths > 340 nm) treatment. The patients were divided into two dose groups, each consisting of 11 patients. One group received 10 J/cm2 and the other 50 J/cm2 five times a week for 3 consecutive weeks. No topical or systemical steroids or antihistamines were allowed. Using the SCORAD index as a measure of disease activity before onset of therapy and after 10 and 15 treatments, we observed a significant improvement in both dose groups after 15 treatments (10 J/cm2: p < 0.05, 50 J/cm2: p < 0.005). After 10 treatments only the improvement in the 50 J/cm2 group was significant (p < 0.005); the difference between the two dose groups was significant (p < 0.05). The clinical efficacy of treatment was reflected neither by a decrease of serum IgE nor by a decrease of elevated serum levels of soluble adhesion molecules sICAM-1 and sELAM-1 in the two dose groups. In contrast, a marked but not significant decrease of serum ECP could be observed in the 50 J/cm2 group only. We conclude from these and other published data that although 10 J/cm2 UV-A1 has a limited effect on patients with severe atopic eczema, higher doses are of higher efficiency in the treatment of this condition.

Adult↗
PubMed1995

Activation of gene transcription by IL-4, IL-13 and IFN-gamma through a shared DNA binding motif.

Both interleukin-4 (IL-4) and interleukin-13 (IL-13) induce the transcription factor NF-IL4 (nuclear factor IL-4) which preexists in an inactive form and binds to an IL-4 responsive element (IL-4RE) in the promoter regions of IL-4/IL-13-dependent genes. UV-crosslinking and SDS gel electrophoresis indicate that NF-IL4 consists of at least two DNA-binding components of 50 kDa and 100-130 kDa. The IL-4 responsive element is also recognized by an interferon-gamma (IFN-gamma)-induced DNA binding protein for which a Mr of 50 kDa has been determined. A common DNA binding motif for different transcription factors might provide the basis for the frequently observed functional antagonism between IL-4/IL-13 and IFN-gamma. The activation of transcription factors by IL-4/IL-13 and IFN-gamma could be blocked by inhibitors of tyrosine kinases and ser/thr phosphatases but not by a PKC inhibitor, suggesting related signal transduction pathways for these cytokines.

Animals↗
PubMed1994

Human interleukin-13 activates the interleukin-4-dependent transcription factor NF-IL4 sharing a DNA binding motif with an interferon-gamma-induced nuclear binding factor.

The effects of interleukin-13 (IL-13) and interleukin-4 (IL-4) on cellular functions were shown to be quite similar. We provide evidence that in monocytes as well as in T lymphocytes both IL-4 and IL-13 activate the same recently identified transcription factor NF-IL4 which binds to the specific responsive element IL-4RE. In addition, we show that a nuclear factor activated by interferon-gamma also interacts with the IL-4RE. It differs from NF-IL4 in the electrophoretic mobility of the complex with DNA, in its DNA-binding specificity and in the proteins interacting with the DNA sequence. Sensitivity against various enzyme inhibitors suggests that components of the signal transduction pathway are shared by all three cytokines.

Animals↗
PubMed1993

Allergy-associated I epsilon and Ec epsilon receptor II (CD23b) genes activated via binding of an interleukin-4-induced transcription factor to a novel responsive element.

Interleukin-4 (IL-4) has important regulatory functions in the immune system, particularly in the generation of immunoglobulin E, the principal mediator of allergic responses. The molecular basis of IL-4 action has remained elusive so far. Here we report on a novel human transcription factor, termed nuclear factor IL-4 (NF-IL4), which is posttranslationally activated by IL-4 in lymphoid and monocytic cells. Homologous binding sequences for NF-IL4 were identified in the promoter regions of the IL-4 controlled CD23b and I epsilon genes. We defined a palindromic 9-bp consensus sequence (5'-TYCYRRGAA-3') as IL-4-responsive element (IL-4RE). Point mutation analysis of the CD23b promoter showed that binding of NF-IL4 to the IL-4RE is essential for the initiation of gene transcription in response to IL-4. NF-IL4 was not activated by Ca2+ ionophore, phorbol ester and cAMP either alone or in combination suggesting a non classical pathway for IL-4 signal transduction.

Base Sequence↗
PubMed1983

Synthesis of biotin-labelled dexamethasone derivatives. Novel hormone-affinity probes.

A new, general methodology for 'sandwich' affinity chromatography of steroid hormone receptors is proposed, the part purification of the human spleen tumor glucocorticoid receptor is quoted as an illustration. 9-Fluoro-16 alpha-methyl-11 beta, 17-dihydroxy-1,4-androstadiene-3-one-17 beta-carboxylic acid was coupled to biotin using pentamethylenediamine (BioDex 1) as a spacer. The bifunctional derivative binds to glucocorticoid receptors and avidin-Sepharose and efficiently protects the glucocorticoid receptor against inactivation when previously added during homogenisation. We have standardized the capacity and optimum conditions for elution of receptor-BioDex-1 complexes which are bound to avidin-Sepharose. Receptor purification of several thousand fold can be obtained with good yield.

Affinity Labels↗