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Biomedical subjects

M Müller

Publications and source records attributed to M Müller.

At least 865 records · Page 48Linked to original sources
PubMed1995

Transcranial Doppler ultrasound in the evaluation of collateral blood flow in patients with internal carotid artery occlusion: correlation with cerebral angiography.

PURPOSE: To determine the accuracy of transcranial Doppler (TCD) ultrasound for evaluation of collateral supply through the circle of Willis in patients with internal carotid artery (ICA) occlusion. METHODS: The evaluation of the collateral pathways through the circle of Willis with TCD ultrasound and with cerebral angiography was compared in 40 patients (30 men, 10 women; mean age, 55 +/- 9 years) in a total of 44 ICA occlusions of which 43 had a suitable ipsilateral temporal bone window for TCD examination. RESULTS: By TCD, a patent anterior communicating artery is indicated by a reversal blood flow in the A1-segment of the anterior cerebral artery or by a prompt fall of blood velocity in the middle cerebral artery after compression of the nonoccluded contralateral carotid artery. In 42 of 43 instances of ICA occlusion, TCD and angiography agreed in the evaluation of a present or absent anterior communicating artery collateral supply. TCD's sensitivity was 95%, its specificity 100%. A collateral supply through the basilar artery was assumed with TCD when there was: (a) a basilar artery blood velocity of more than 70 cm/s; (b) a marked increase of basilar artery blood velocity after compression of the nonoccluded carotid artery; (c) an evident side-to-side asymmetry of the blood velocity of the posterior cerebral arteries with high blood velocity ipsilateral to the ICA occlusion. For evaluating the collateralization via the basilar artery, TCD and angiography agreed in 37 of 40 ICA occlusions. TCD's sensitivity was 87%, its specificity 95%. CONCLUSIONS: TCD is a reliable tool for the evaluation of the collateral supply in patients with ICA occlusions.

Adult↗
PubMed1995

4,5-bis(4-fluoroanilino)phthalimide: A selective inhibitor of the epidermal growth factor receptor signal transduction pathway with potent in vivo antitumor activity.

Deregulated signal transduction via the epidermal growth factor (EGF) receptor family of tyrosine protein kinase growth factor receptors is associated with proliferative diseases such as cancer and psoriasis. In an attempt to selectively block signal transduction from the EGF receptor, we have synthesized a new class of dianilino-phthalimide tyrosine protein kinase inhibitors with selectivity for the EGF receptor tyrosine protein kinase. 4, 5-Dianilino-phthalimide (DAPH 1) was metabolized in vitro by mouse liver fractions and in vivo. The major metabolite has been identified as 4-(4-hydroxyanilino)-5-anilino-phthalimide. To specifically block this biotransformation (hydroxylation), we have synthesized 4,5-bis(4-fluoroanilino)phthalimide (DAPH 2), a potent and selective EGF receptor tyrosine protein kinase inhibitor. DAPH 2 inhibits the EGF receptor and protein kinase C beta2 enzymes with equal potency. In cells, DAPH 2 inhibits signal output from the EGF receptor, but not from other classes of receptor protein tyrosine kinases, such as the platelet-derived growth factor receptor, fibroblast growth factor receptor, insulin-like growth factor I receptor, and insulin receptor. Selective antitumor activity was demonstrated in vivo at well-tolerated doses in mice. This publication describes the biological profile of DAPH 2 and investigates its cellular and in vivo mechanism of action.

3T3 Cells↗
PubMed1994

Overexpression of the gene encoding the multidrug resistance-associated protein results in increased ATP-dependent glutathione S-conjugate transport.

The multidrug resistance-associated protein (MRP) is a 180- to 195-kDa glycoprotein associated with multidrug resistance of human tumor cells. MRP is mainly located in the plasma membrane and it confers resistance by exporting natural product drugs out of the cell. Here we demonstrate that overexpression of the MRP gene in human cancer cells increases the ATP-dependent glutathione S-conjugate carrier activity in plasma membrane vesicles isolated from these cells. The glutathione S-conjugate export carrier is known to mediate excretion of bivalent anionic conjugates from mammalian cells and is thought to play a role in the elimination of conjugated xenobiotics. Our results suggest that MRP can cause multidrug resistance by promoting the export of drug modification products from cells and they shed light on the reported link between drug resistance and cellular glutathione and glutathione S-transferase levels.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1994

Two novel mutations in the vasopressin V2 receptor gene in patients with congenital nephrogenic diabetes insipidus.

Families with congenital nephrogenic diabetes insipidus were analyzed with regard to mutations in the vasopressin V2 receptor gene. Family 1 shows an X-chromosomal recessive inheritance of the disease over 4 generations. A patient from this family was found to have a T-->A transversion at nucleotide 1095, predictive for a substitution of serine 167 (which is highly conserved among G-protein-coupled receptors), by threonine. Both the mutant and the normal allele were detected in the maternal genome. The patient's healthy brother was homozygous for the normal allele. The patient from family 2 showed a T-->C transition at nucleotide 727, predictive for a substitution of leucine 44 by proline. Analysis of the maternal genome revealed homozygosity for the normal allele. Thus a de novo mutation seems to have occurred. The nature and site of the mutation in family 2 suggest that it is responsible for the patient's disease.

Amino Acid Sequence↗
PubMed1994

Distribution of cadmium in the food chain (soil-plant-human) of a cadmium exposed area and the health risks of the general population.

Since 1960, extensive cadmium emissions from a factory producing fluorescent substances and cadmium pigments resulted in cadmium accumulation in the urban area of Bad Liebenstein. We show cadmium exposure of soils and plants in Bad Liebenstein and the meadows near the Grumbach brook. Lettuce and parsley from Bad Liebenstein contained 6- and 9-fold levels of cadmium (2140 and 1194 micrograms/kg dry matter) when compared with control plants. Vegetables from gardens in the immediate vicinity of the Grumbach brook contained cadmium levels which partly exceeded the limit values of the Federal Office of Health. The cadmium status of the inhabitants of Bad Liebenstein was tested by means of hair, whole blood and urine samples. The values were within the normal range (389 micrograms/kg dry matter hair; 1.06 micrograms/l whole blood; 0.24 microgram/l urine). In a duplicate study, the cadmium intake amounted to 10 micrograms/day in men and to 9 micrograms/day in women, which is only 12 or 15% of the WHO limit value. Hence, it follows that the cadmium exposure of soils and flora is not reflected in the food chain of the inhabitants of Bad Liebenstein and health risks caused from cadmium can be excluded.

Cadmium↗
PubMed1994

Signal transduction. Just another signalling pathway.

The recently identified JAK-STAT signal transduction pathway plays a major role in signalling the arrival of cytokines at the cell surface and can, in part, account for the pleiotropic and redundant effects of cytokines.

Animals↗
PubMed1994

Prognostic significance of serum antibodies to human papillomavirus-16 E4 and E7 peptides in cervical cancer.

BACKGROUND: The objective of this study was to investigate the prognostic significance of serum antibodies to human papillomavirus (HPV)-16 peptides in patients with squamous cell cervical cancer. METHODS: Pretreatment sera from 78 patients and 198 control women were tested by an enzyme-linked immunosorbent assay technique for reactivity with HPV-16 E4 (E401p) and E7 (E701p) synthetic peptides. The presence and serum level of these antibodies were correlated with tumor stage, histologic features, and prognostic parameters. RESULTS: The median follow-up was 65 months (range, 6-97 months). Antibodies to E401p peptide were found in 5 of the 198 (3%) control subjects, 4 of the 43 (9%) patients with low tumor stage (International Federation of Gynecology and Obstetrics [FIGO] Ia, Ib, IIa), and 7 of the 35 (20%) patients with advanced tumor stage (FIGO IIb, III, IVa). Antibodies to E701p were found in 25 (13%), 11 (26%), and 11 (31%) women, respectively. The differences between patients and control subjects were significant (P < 0.002). Seropositivity against these peptides showed no correlation with tumor stage. Antibody levels to both peptides were significantly higher in patients compared with control subjects (P < 0.05). Furthermore, antibody levels to E401p were higher in patients with advanced tumor stage versus patients with low tumor stage (P = 0.0097). Such a relation was not found for anti-E701p antibodies. In the univariate analysis, a high level of anti-E701p antibodies was associated with a shorter disease free interval (P = 0.012) and poor survival (P = 0.049). However, this variable possessed no prognostic value after adjusting for FIGO stage and tumor size. CONCLUSIONS: The authors' findings indicate that the prognostic significance of serum antibodies to the HPV-16 E4 and E7 peptides used in this study of patients with cervical cancer is limited.

Adult↗
PubMed1994

Interfacial adsorption and aggregation associated changes in secondary structure of human calcitonin monitored by ATR-FTIR spectroscopy.

The peptide hormone human calcitonin (hCT) has a marked tendency to aggregate in aqueous solutions, resulting in viscous and turbid dispersions consisting of long fibrils approximately 80 A in diameter. Both transmission (T-FTIR) and attenuated total reflection Fourier transform infrared (ATR-FTIR) experiments were applied on hCT adsorption and aggregation kinetics. By means of the surface sensitive ATR-FTIR spectroscopy at a hydrophobic/hydrophilic interface, early adsorption and aggregation steps of hCT could be followed in situ under real time conditions. Since the aggregation of hCT is associated with conformational changes, the secondary structure sensitive amide I'-band (D2O) could be used as a diagnostic marker. ATR-FTIR spectra recorded during the aggregation kinetics of hCT showed an increase of the amide I'-band intensity by a factor of 3.4, interpreted as pronounced adsorption of hCT molecules from bulk solution to the germanium plate. Furthermore, variations in the line shape of the amide I'-band were interpreted. At the beginning, hCT adopted a random coil conformation followed by distinct formations of alpha-helical and intermolecular parallel beta-sheet structures. Finally, the random coil content declined to 63%, whereas alpha and beta contents rose to 8% and 29%, respectively. From our kinetics results the alpha-structures were formed faster than the beta-structures. This was interpreted as an initial induction of amphiphilic helices during the adsorption process of hCT monomers. ATR-FTIR spectroscopy provides a sensitive analytical tool suggested to monitor interfacial adsorption and aggregation phenomena also of other peptides and proteins.

Adsorption↗
PubMed1994

Photodynamic antitumor agents: beta-methoxyethyl groups give access to functionalized porphycenes and enhance cellular uptake and activity.

Porphycene photosensitizers bearing two or four methoxyethyl side chains were synthesized in nine steps from commercially available starting materials. Ether cleavage led to (hydroxyethyl)- and (bromoethyl)porphycenes that were converted to vinyl and benzo derivatives. Five of the side chain-functionalized porphycenes were biologically studied in comparison with two tetra-n-propylporphycenes. Porphycenes were incorporated in small unilamellar liposomes and incubated with cultivated SSK2 murine fibrosarcoma cells. Cellular uptake and phototoxicity 24 h after 5 J/cm2 laser light treatment were determined. The porphycenes tested were between 17 and 220 times more photodynamically active than the currently clinically used sensitizer Photofrin, although extinction coefficients of the porphycenes' irradiated bands are only approximately 10-fold higher. The LD50 concentration for SSK2 cells in the incubation medium was as low as (8.5 +/- 2.8) x 10(-9) M for tetrakis(methoxyethyl)porphycene. Two methoxy or hydroxy groups enhanced cellular uptake, three or four methoxy groups both enhanced and accelerated cellular uptake of tetraalkylporphycenes. Half-life times of the uptake processes varied between (0.14 +/- 0.04) and (14 +/- 4) h and cellular saturation levels between (1.2 +/- 0.2) and (26 +/- 3) pmol/10(5) cells. When individual uptake rates were accounted for, all porphycenes had a similar "cellular" phototoxicity, pointing toward a common mechanism of action. Evidence is presented for the assumption that cell membranes are the primary targets of the tested porphycenes and that membrane solubility may play a critical role in their photodynamic efficiency. The results show that nonionic polar side chain functionalities can strongly enhance cellular uptake and antitumor activity of lipophilic porphyrinoids and thus that the known lipophilicity/activity relationship can be reversed for very hydrophobic sensitizers.

Animals↗
PubMed1994

In vivo footprinting of the IRF-1 promoter: inducible occupation of a GAS element next to a persistent structural alteration of the DNA.

GAS (gamma activated sequence) and GAS-like elements are found in a rapidly growing number of genes. Data from EMSA (electromobility shift assay) and transient transfection assays using heterologous promoter systems do not necessarily reflect transcriptional involvement and protein occupation of a binding site in vivo. This has been shown recently by in vivo footprinting of the NF-kappa B site at -40 in the interferon regulatory factor-1 (IRF-1) promoter. Here we show by in vivo footprinting using dimethylsulfate (DMS) that the GAS of the IRF-1 promoter, which also contains an overlapping putative NF-kappa B site, is occupied upon treatment with gamma-interferon (IFN gamma) but not with phorbol 12-myristate 13-acetate (PMA). Irrespective of induction, we detect a very strong DMS hypersensitivity at a guanosine just adjacent to GAS and a less persistent minor DMS hypersensitivity at a central cytosine. Our data confirm the crucial role of GAS in transcriptional activation by IFN gamma and are consistent with induced binding of p91 to GAS. In addition, our data suggest a major conformational distortion of the DNA at the GAS element of the IRF-1 promoter and that this GAS element is not involved in transcriptional activation by PMA.

Base Sequence↗
PubMed1994

The effects of methylprednisolone on oxidative phosphorylation in Concanavalin-A-stimulated thymocytes. Top-down elasticity analysis and control analysis.

The glucocorticoid methylprednisolone has clinically important anti-inflammatory effects at high concentrations through unknown mechanisms. Methylprednisolone at 0.2 mg/10(7) cells inhibits respiration in Concanavalin-A(ConA)-stimulated thymocytes from rats by about 20%. We have used top-down elasticity analysis to identify the blocks of reactions within oxidative phosphorylation in thymocytes whose kinetics are significantly affected by treatment with methylprednisolone. At this concentration methylprednisolone greatly inhibited the reactions of substrate oxidation and increased mitochondrial proton leak but did not significantly affect the synthesis and and turnover of ATP by the phosphorylating system. Metabolic control analysis showed that oxygen consumption by ConA-treated thymocytes was controlled largely (0.51) by the phosphorylating system but also by proton leak (0.32) and substrate oxidation (0.17); this is similar to the distribution of control in hepatocytes, suggesting that this pattern may be general in cells. Methylprednisolone lowered control by the phosphorylating system to 0.26 and raised control by substrate oxidation to 0.37. From these results we conclude that the inhibition of respiration in ConA-stimulated thymocytes by methylprednisolone at this concentration results from an inhibition of substrate oxidation and a smaller stimulation of mitochondrial proton leak, with only a minor contribution of any effects within the phosphorylating system.

Adenosine Triphosphate↗
PubMed1994

[Pulmonary aspergillosis in an immunocompetent female patient].

Symptoms of bronchopneumonia developed over 4 months in a 63-year-old woman in previously good health. The symptoms worsened despite treatment with tetracycline (500 mg twice daily for 10 days). Middle-lobe pneumonia was diagnosed both clinically and radiologically, but monotherapy with ofloxacin (200 mg twice daily) was ineffective, as well as combined treatment with gentamycin (80 mg), oxacillin (1 g) and azlocillin (5 g), each three times daily intravenously. Bronchoscopy revealed obstruction of the lumen of the right middle lobe bronchus by viscous purulent secretion which contained a high count of Aspergillus fumigatus, previously found in several sputum samples. The inflammatory process regressed completely within 12 days on itraconazole (200 mg twice daily), combined with nystatin inhalation (100,000 IU five times daily). The only possible aetiologically significant risk factor in this immunocompetent woman could have been her frequent use of a bio-waste container.

Administration, Inhalation↗
PubMed1994

Nuclear magnetic resonance solution structure of the fushi tarazu homeodomain from Drosophila and comparison with the Antennapedia homeodomain.

The three-dimensional structure of a recombinant 70-residue polypeptide containing the complete fushi tarazu (ftz) homeodomain from Drosophila melanogaster has been determined by nuclear magnetic resonance (NMR) spectroscopy in solution. On the basis of 915 upper distance constraints derived from nuclear Overhauser effects and 178 dihedral angle constraints, a group of 20 conformers representing the solution structure of the ftz homeodomain was computed with the program DIANA and energy-minimized with the program OPAL. The average of the pairwise root-mean-square deviations of the individual NMR conformers relative to the mean coordinates is 0.50 A for the backbone atoms N, C alpha and C' of residues 8 to 53. The molecular architecture includes three helices comprising the residues 10 to 21, 28 to 38, and 42 to 52, a loop of residues 22 to 27 between the helices I and II, and a turn of residues 39 to 41 linking the helices II and III. Comparisons with the structure of the mutant Antennapedia homeodomain with Cys39 replaced by Ser, Antp (C39S), shows that the two proteins contain the same molecular fold for residues 8 to 53, whereas the more flexible fourth helix comprising residues 53 to 59 in the Antp (C39S) homeodomain has no counterpart in the ftz homeodomain. Considering that important intermolecular interactions in the DNA complexes with the Antp, engrailed and Mat alpha 2 homeodomains involve the fourth helix, it was rather unexpected that the stability of the complex of ftz with the BS2 operator site was found to be comparable to or even somewhat higher than that of the Antp complex with BS2. Another difference is that the Antp homeodomain is more stable with respect to thermal denaturation, with denaturation temperatures at pH 4.8 of 27 degrees C and 48 degrees C, respectively, for ftz and Antp.

Amino Acid Sequence↗
PubMed1994

Identification of a soluble SecA/SecB complex by means of a subfractionated cell-free export system.

We have reconstituted the cell-free synthesis of the Escherichia coli precursor protein LamB from partially purified subfractions of an E. coli cell extract. PreLamB synthesized in this manner is translocated into salt-extracted plasma membrane vesicles only in the presence of SecA/SecB- or SecB-containing preparations of the E. coli cytosol. The most active preparations obtained upon purification were those containing a soluble SecA/SecB complex. Complex formation between SecA and SecB was verified by co-sedimentation and co-immunoprecipitation. When preLamB was synthesized in the presence of this material, a considerable amount of precursor was recovered from a soluble ternary complex consisting of preLamB, SecA, and SecB. Our results suggest that a soluble SecA/SecB complex participates in the export of preLamB and that this complex is functionally equivalent to a previously described 12 S (7 S) export factor (Müller, M., and Blobel, G. (1984) Proc. Natl. Acad. Sci. U.S.A. 81, 7737-7741; Watanabe, M., and Blobel, G. (1989) Proc. Natl. Acad. Sci. U.S.A. 86, 2728-2732).

Adenosine Triphosphatases↗
PubMed1994

Precursor-specific requirements for SecA, SecB, and delta muH+ during protein export of Escherichia coli.

We compare translocation into inside-out plasma membrane vesicles (INV) of the in vitro synthesized outer membrane proteins LamB and OmpA and the periplasmic protein Skp of Escherichia coli and demonstrate a precursor-specific dependence on the export factors SecA, SecB, and the proton-motive force (delta mu H+). A partial reduction in soluble SecA caused a 50% decrease in translocation of preLamB. In contrast, removal of INV-bound SecA by urea extraction was required to see a decrease in translocation of preOmpA and preSkp, with 8% of preSkp still being translocated into urea-treated INV. Translocation of the three precursors into INV showed a corresponding differential sensitivity toward dissipation of delta mu H+ following removal of the F1-ATPase from the INV. While depletion of both F1 and SecA or simply lowering of the reaction temperature resulted in an inhibition of complete transmembrane translocation, it interfered less severely with signal sequence cleavage, indicating the formation of translocation intermediates under these conditions. The relative amounts of intermediate obtained were also different for the three preproteins correlating a low requirement for SecA and delta mu H+ with a facilitated initiation of translocation. Whereas preSkp was translocated independently of SecB, preLamB was not even targeted to the INV in its absence. Functional targeting of preOmpA required the presence of SecB during incubation of the precursor with INV and not during its synthesis. SecB, exogenously added during the period of synthesis, did not prevent the formation of translocation-incompetent preLamB. The latter results are consistent with an important targeting function of SecB, which so far has mostly been described as a molecular chaperone. The findings are discussed with respect to current models of bacterial protein export usually derived from the analysis of a single precursor.

Adenosine Triphosphatases↗
PubMed1994

ATP-dependent transport of amphiphilic cations across the hepatocyte canalicular membrane mediated by mdr1 P-glycoprotein.

The ATP-dependent transport of the three 3H-labeled, amphiphilic cations quinidine, N-(n-pentyl)-quinidinium, and N-(4',4'-azo-n-pentyl)-21-deoxyajmalinium was studied in rat canalicular plasma membrane vesicles. N-Alkylation of quinidine with an n-pentyl residue resulted in a permanently charged cationic substrate for ATP-dependent transport which exhibited a 10-fold higher transport rate relative to quinidine. The Km value was 0.4 microM for N-(n-pentyl)-quinidinium and 5 microM for quinidine. The permanently cationic and photolabile derivative of ajmaline, N-(4',4'-azo-n-pentyl)-21-deoxyajmalinium, was also an efficient substrate and served to label canalicular membrane proteins with molecular masses of 143 kDa and 108 kDa. ATP-dependent transport of the permanently charged amphiphilic cations was inhibited by the P-glycoprotein inhibitors and substrates quinidine, verapamil, and daunorubicin. The data demonstrate that N-alkylation of quinidine and ajmaline results in most efficient substrates for mdr1 P-glycoprotein-mediated ATP-dependent transport.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1994

Dianilinophthalimides: potent and selective, ATP-competitive inhibitors of the EGF-receptor protein tyrosine kinase.

Dianilinophthalimides represent a novel class of inhibitors of the EGF-receptor protein tyrosine kinase with a high degree of selectivity versus other tyrosine and serine/threonine kinases. Steady-state kinetic analysis of compound 3, which showed potent inhibitory activity, revealed competitive type kinetics relative to ATP. Despite a highly symmetrical structure of compound 3, X-ray studies revealed an unsymmetrical propeller-shaped conformation of the molecule which differs clearly from that of the constitutionally related staurosporine aglycons. These conformational differences may explain the reversal of the selectivity profile of compound 3 relative to the staurosporine aglycons. In cellular assays compounds 3 and 4 have been shown to inhibit EGF-induced receptor autophosphorylation, c-fos induction and EGF-dependent proliferation of Balb/c MK cells. This inhibition was selective as compounds had no effect on PDGF-induced receptor autophosphorylation and c-fos induction. Furthermore, compound 3 showed potent antitumor activity in vivo at well-tolerated doses.

3T3 Cells↗