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Biomedical subjects

M Rüdiger

Publications and source records attributed to M Rüdiger.

At least 19 recordsLinked to original sources

Perinatal management of right aortic arch with aberrant left subclavian artery associated with critical stenosis of the subclavian artery in a newborn.

A right-sided aortic arch with an aberrant left subclavian artery is a congenital vascular anomaly that is easily detectable in utero at the level of the three vessels and trachea view, but which is rarely symptomatic in the neonate. We present a newborn with prenatally diagnosed right-sided aortic arch and aberrant subclavian artery who showed a clinically relevant stenosis of the subclavian artery during the first week of life. An intravascular stent was implanted into the stenosis of the aberrant left subclavian artery by catheterization. This case report demonstrates that a right-sided aortic arch with an aberrant subclavian artery can be diagnosed prenatally, that in these patients a stenosis of the subclavian artery can occur in early infancy and requires awareness of the neonatologist or pediatrician, and that stent implantation represents a minimally invasive therapeutic approach.

Adult↗

Breathing gas perfluorocarbon measurements using an absorber filled with zeolites.

BACKGROUND: Perfluorocarbon (PFC) has been widely used in the treatment of respiratory diseases; however, PFC content of the breathing gases remains unknown. Therefore, we developed an absorber using PFC selective zeolites for PFC measurement in gases and investigated its accuracy. METHODS: To generate a breathing gas with different PFC contents a heated flask was rinsed with a constant air flow of 4 litre x min(-1) and 1, 5, 10, and 20 ml of PFC were infused over 20 min using an infusor. The absorber was placed on an electronic scale and the total PFC volume was calculated from the weight gain. RESULTS: Steady-state increase in weight was achieved 3.5 min after stopping the infusion. The calculated PFC volume was slightly underestimated but the measuring error did not exceed -1% for PFC less than 1 ml. The measurement error decreased with increasing PFC volume. CONCLUSIONS: This zeolite absorber is an accurate method to quantitatively determine PFC in breathing gases and can be used as a reference method to validate other PFC sensors.

Absorption↗

Raver1, a dual compartment protein, is a ligand for PTB/hnRNPI and microfilament attachment proteins.

By screening a yeast two-hybrid library with COOH-terminal fragments of vinculin/metavinculin as the bait, we identified a new protein termed raver1. Raver1 is an 80-kD multidomain protein and widely expressed but to varying amounts in different cell lines. In situ and in vitro, raver1 forms complexes with the microfilament-associated proteins vinculin, metavinculin, and alpha-actinin and colocalizes with vinculin/metavinculin and alpha-actinin at microfilament attachment sites, such as cell-cell and cell matrix contacts of epithelial cells and fibroblasts, respectively, and in costameres of skeletal muscle. The NH2-terminal part of raver1 contains three RNA recognition motifs with homology to members of the heterogeneous nuclear RNP (hnRNP) family. Raver1 colocalizes with polypyrimidine tract binding protein (PTB)/hnRNPI, a protein involved in RNA splicing of microfilament proteins, in the perinucleolar compartment and forms complexes with PTB/hnRNPI. Hence, raver1 is a dual compartment protein, which is consistent with the presence of nuclear location signal and nuclear export sequence motifs in its sequence. During muscle differentiation, raver1 migrates from the nucleus to the costamere. We propose that raver1 may coordinate RNA processing and targeting as required for microfilament anchoring in specific adhesion sites.

Actin Cytoskeleton↗

Effects of perfluorocarbons and perfluorocarbons/surfactant emulsions on growth and viability of group B streptococci and Escherichia coli.

OBJECTIVE: Partial liquid ventilation with perfluorocarbons (PFC) might be used as a new ventilatory strategy to treat respiratory insufficiency in congenital pneumonia. The present study investigates for the first time effects of PFC on growth and viability of group B streptococci (GBS) and Escherichia coli, bacteria frequently causing congenital pneumonia. DESIGN: Prospective, in vitro study. SETTING: Research laboratory in a university. MATERIAL: Group B streptococci 090 Ia HD Colindale and E. coli K12, JM 101. INTERVENTIONS: E. coli (10(7)/mL) were grown in the absence or presence of different PFC (RM 101, PF 5080, FO 6167) for up to 6 hrs. To study bacterial viability, GBS (5 x 10(7)/mL) were incubated in saline with or without different PFC, PFC/surfactant emulsions, or surfactant (Curosurf) for up to 5 hrs. Every 2 hrs, the colony forming units were determined by plating different dilutions of bacteria on agar. MEASUREMENTS AND MAIN RESULTS: RM 101 or PF 5080 alone and in emulsions with surfactant had no effect on viability of GBS or growth of E. coli. For FO 6167, a previously described toxicity was found, even if 1 mL of GBS suspension was incubated with only 100 microL of FO 6167, verifying the experimental design that guarantees a PFC bacteria contact. The toxic effects were almost prevented by forming a PFC-in-surfactant emulsion but not by preincubation of GBS with surfactant and subsequent FO 6167 exposure. CONCLUSION: RM 101 and PF 5080 did not influence bacterial growth in vitro; direct effects on bacterial proliferation during partial liquid ventilation in congenital pneumonia seem, therefore, unlikely. Interestingly, we found that the known toxic effects of FO 6167 can be prevented by covering PFC with a surfactant film. Surfactant reduced the cytotoxic effects of FO 6167, probably by preventing a direct contact between FO 6167 and the bacterial cell wall.

Biological Products↗

Disturbed surface properties in preterm infants with pneumonia.

Congenital pneumonia in preterm infants is often associated with respiratory insufficiency requiring mechanical ventilation. This study was performed to show whether pneumonia in these infants is associated with an inhibition or deficiency of surfactant. The ratio of lecithin and sphingomyelin (L/S ratio) and minimal surface tension were determined in pharyngeal aspirates from 90 term born infants (healthy) and in tracheal aspirates from preterm infants with wet lung (n = 13), congenital pneumonia (n = 21) and respiratory distress syndrome (RDS) (n = 90). The L/S ratio was lower (p < 0.0001) in the RDS group (8.6) when compared with healthy (48.6), wet lung (42.9) and pneumonia (28.9). Surface tension was higher (p < 0.001) in RDS (37 mN/m) and pneumonia (33.7) when compared with healthy (22.9) or wet lung (21.2). For infants with RDS, L/S ratio <16.5 detects surfactant deficiency with 96% specificity and 70% sensitivity, surface tension >29 mN/m represents surfactant inhibition (specificity 97%, sensitivity 92%). Using these cut-off values in infants with pneumonia, 81% had a sufficient amount of surfactant but only 21% of infants with pneumonia had appropriate surface tension. Our study shows that lung effluent of respiratory insufficient infants with pneumonia, who need mechanical ventilation, has disturbed surface properties despite a sufficient amount of surfactant. In these infants, surfactant substitution could be beneficial.

Case-Control Studies↗

Single-molecule detection technologies in miniaturized high throughput screening: binding assays for g protein-coupled receptors using fluorescence intensity distribution analysis and fluorescence anisotropy.

G Protein-coupled receptors (GPCRs) represent one of the most important target classes for drug discovery. Various assay formats are currently applied to screen large compound libraries for agonists or antagonists. However, the development of nonradioactive, miniaturizable assays that are compatible with the requirements of ultra-high throughput screening (uHTS) has so far been slow. In this report we describe homogeneous fluorescence-based binding assays that are highly amenable to miniaturization. Fluorescence intensity distribution analysis (FIDA) is a single-molecule detection method that is sensitive to brightness changes of individual particles, such as those induced by binding of fluorescent ligands to membrane particles with multiple receptor sites. As a confocal detection technology, FIDA inherently allows reduction of the assay volume to the microliter range and below without any loss of signal. Binding and displacement experiments are demonstrated for various types of GPCRs, such as chemokine, peptide hormone, or small-molecule ligand receptors, demonstrating the broad applicability of this method. The results correlate quantitatively with radioligand binding data. We compare FIDA with fluorescence anisotropy (FA), which is based on changes of molecular rotation rates upon binding of fluorescent ligands to membranes. While FA requires a higher degree of binding, FIDA is sensitive down to lower levels of receptor expression. Both methods are, within these boundary conditions, applicable to uHTS.

Drug Evaluation, Preclinical↗

Preterm infants with high polyunsaturated fatty acid and plasmalogen content in tracheal aspirates develop bronchopulmonary dysplasia less often.

OBJECTIVE: Oxygen toxicity causes chronic bronchopulmonary dysplasia (BPD) in extremely preterm infants. Polyunsaturated fatty acids (PUFA) and plasmalogens are the two main substrates for lipid peroxidation in the pulmonary surfactant. In the present study, we tested whether low concentrations of both were associated with development of BPD and whether both were further reduced during mechanical ventilation with oxygen. DESIGN: Prospective, noninterventional, descriptive study. SETTING: Level III neonatal intensive care unit in a university hospital. PATIENTS: In 25 extremely low birth weight infants with respiratory distress syndrome, tracheal aspirates were collected immediately after birth and in the following 4 days. As control, tracheal and pharyngeal aspirates were collected from healthy infants immediately after birth. The amount of PUFA and dimethylacetals (DMA, representing plasmalogens) was determined gas-chromatographically. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: The relative percentages of PUFA and DMA on all fatty acids in non-BPD infants (PUFA% 26+/-8.9, DMA% 3.5+/-1.2) were higher compared with infants who developed BPD (PUFA% 14.5+/-3.8, DMA% 1.8+/-0.9). In term healthy infants, DMA% and PUFA% were in the same range as in the BPD group. The higher levels found for non-BPD infants decreased after day 1 to values equal to the BPD group and remained low. CONCLUSIONS: The results suggest that initially higher levels of PUFA and plasmalogens in the tracheal effluent are associated with a reduced risk of developing BPD and are reduced during the first day of ventilation.

Bronchopulmonary Dysplasia↗

Affinity mass spectrometry-based approaches for the analysis of protein-protein interaction and complex mixtures of peptide-ligands.

Combined applications of affinity purification procedures and mass-spectrometric analyses (affinity mass spectrometry or affinity-directed mass spectrometry) have gained broad interest in various fields of biological sciences. We have extended these techniques to the purification and analysis of closely related peptides from complex mixtures and to the characterization of binding motifs and relative affinities in protein-protein interactions. The posttranslational modifications in the carboxy-terminal region of porcine brain tubulin are used as an example for the applicability of affinity mass spectrometry in the characterization of complex patterns of related peptides. We also show that affinity mass spectrometry allows the mapping of sequential binding motifs of two interacting proteins. Using the ActA/Mena protein-protein complex as a model system, we show that we can selectively purify Mena-binding peptides from a tryptic digest of ActA. The results from this assay are compared to data sets obtained earlier by classical methods using synthetic peptides and molecular genetic experiments. As a further expansion of affinity mass spectrometry, we have established an internally standardized system that allows comparison of the affinities of related ligands for a given protein. Here the affinities of two peptide ligands for the monoclonal tubulin-specific antibody YL1/2 are determined in terms of half-maximal competition.

Amino Acid Sequence↗

Binding of the Shigella protein IpaA to vinculin induces F-actin depolymerization.

Shigella flexneri, the causative agent of bacillary dysentery, enters into epithelial cells by a macropinocytic process. IpaA, a Shigella protein secreted upon cell contact, binds to the focal adhesion protein vinculin and is required for efficient bacterial uptake. IpaA was shown here to bind with high affinity to the N-terminal residues 1-265 of vinculin. Using co-sedimentation and solid-phase assays, we demonstrated that binding of IpaA to vinculin strongly increases the association of vinculin with F-actin. We also characterized a depolymerizing activity on actin filaments associated with the vinculin-IpaA complex both in vitro and in microinjected cells. We propose that the conformational change of vinculin induced by IpaA binding allows interaction of the vinculin-IpaA complex with F-actin and subsequent depolymerization of actin filaments.

Actin Cytoskeleton↗

Monoclonal antibody ID5: epitope characterization and minimal requirements for the recognition of polyglutamylated alpha- and beta-tubulin.

A monoclonal antibody (ID5) raised against the synthetic tetradecapeptide corresponding to the C-terminal region of detyrosinated alpha-tubulin showed an unexpected cross-reactivity with beta-tubulin from pig brain tissue. The specificity and the minimal epitope requirements of ID5 were characterized by competitive enzyme-linked immunosorbent assay (ELISA) and spot blots using a series of synthetic peptides and the natural peptides of beta-tubulin and detyrosinated alpha-tubulin from brain. The epitope of ID5 is comprised of the carboxyterminal sequence -XEE carrying the terminal alpha-carboxylate group with X being a variable residue. All linkages in the epitope involve alpha-peptide bonds. This epitope is provided by the detyrosinated alpha-tubulin main chain and the polyglutamyl side chains of both brain alpha- and beta-tubulins. Affinity purification of beta-tubulin peptides and mass spectrometric characterization reveal that peptides carrying three to nine glutamyl residues in the side chain are recognized by ID5. These results show that except for the first gamma-peptide linkage the alpha-peptide bond is the preferred linkage type in the tubulin polyglutamyl side chains.

Amino Acids↗

Utility of deadspace and capnometry measurements in determination of surfactant efficacy in surfactant-depleted lungs.

OBJECTIVE: To investigate if bronchoalveolar lavage leads to increased alveolar and physiologic deadspace or a deadspace/ tidal volume ratio and if surfactant replacement restores the lung to its prelavage condition. DESIGN: Prospective, animal cohort study. SETTING: An animal laboratory in a university medical center. SUBJECTS: Seven adult rabbits receiving artificial ventilation. METHODS: Our single-breath CO2 analysis station contained the following equipment: pneumotachometer Ventrak 1550, a mainstream capnometer Capnogard 1265, a signal processor, and computer software. Repeated bronchoalveolar lavage was performed in seven adult rabbits to simulate acute respiratory distress syndrome. Surfactant therapy was administered after bronchoalveolar lavage induced a 20% reduction in baseline arterial PO2. The calculated parameters of alveolar and physiologic deadspace and the deadspace/tidal volume ratio were derived from the single-breath CO2 plot by Ventrak 1550 in combination with the Capnogard 1265. The arterial end-tidal Pco2 difference, the alveolar-arterial PO2 difference, and the arterial/alveolar PO2 ratio were obtained by capnography and arterial blood gas analysis. Measurements of these parameters were performed before bronchoalveolar lavage, during bronchoalveolar lavage, and after surfactant application. MEASUREMENTS AND MAIN RESULTS: The alveolar and physiologic deadspace and the deadspace/tidal volume ratio were significantly higher in lavaged animals. After application of natural surfactant, these parameters were significantly reduced but the baseline values could not be reached. Bronchoalveolar lavage led to a significant fall in the arterial/alveolar PO2 ratio, which increased after surfactant therapy. There was a negative correlation between the arterial/alveolar PO2 ratio and the deadspace/tidal volume ratio. The alveolar and physiologic deadspace and the deadspace/tidal volume ratio correlated with the arterial end-tidal Pco2 difference. The best correlation was obtained between the arterial end-tidal Pco2 difference and the alveolar deadspace/tidal volume ratio (r = 0.98). CONCLUSIONS: Bronchoalveolar lavage elevates the alveolar and physiologic deadspace and the deadspace/tidal volume ratios and is combined with a fall in the arterial/alveolar PO2 ratio. Surfactant treatment improves the gas exchange but does not restore the lung to its prebronchoalveolar lavage condition, which indicates that the exogenous surfactant affects only partly the recruitment of the atelectatic areas.

Animals↗

Differential actin organization by vinculin isoforms: implications for cell type-specific microfilament anchorage.

Vinculin is found in all adherens junctions, while metavinculin, a larger splice variant, is coexpressed with vinculin only in smooth and cardiac muscle. To understand the significance of metavinculin expression, we compared ligand binding between turkey vinculin and metavinculin. Residues 1-258 were found essential for head-tail interactions in both proteins. The tail domains (VT and MVT, respectively) both bind to F-actin. However, while VT bundles F-actin, MVT generates highly viscous F-actin webs. In transfected PtK2 cells, VT causes F-actin needles or coils, while MVT-expressing cells display a diffuse F-actin distribution. Thus, the MVT-specific insert induces an F-actin supraorganization different from the VT-based form, suggesting that metavinculin has a specific role in muscle.

Actin Cytoskeleton↗

Vinculin is part of the cadherin-catenin junctional complex: complex formation between alpha-catenin and vinculin.

In epithelial cells, alpha-, beta-, and gamma-catenin are involved in linking the peripheral microfilament belt to the transmembrane protein E-cadherin. alpha-Catenin exhibits sequence homologies over three regions to vinculin, another adherens junction protein. While vinculin is found in cell-matrix and cell-cell contacts, alpha-catenin is restricted to the latter. To elucidate, whether vinculin is part of the cell-cell junctional complex, we investigated complex formation and intracellular targeting of vinculin and alpha-catenin. We show that alpha-catenin colocalizes at cell-cell contacts with endogenous vinculin and also with the transfected vinculin head domain forming immunoprecipitable complexes. In vitro, the vinculin NH2-terminal head binds to alpha-catenin, as seen by immunoprecipitation, dot overlay, cosedimentation, and surface plasmon resonance measurements. The Kd of the complex was determined to 2-4 x 10(-7) M. As seen by overlays and affinity mass spectrometry, the COOH-terminal region of alpha-catenin is involved in this interaction. Complex formation of vinculin and alpha-catenin was challenged in transfected cells. In PtK2 cells, intact alpha-catenin and alpha-catenin1-670, harboring the beta-catenin- binding site, were directed to cell-cell contacts. In contrast, alpha-catenin697-906 fragments were recruited to cell-cell contacts, focal adhesions, and stress fibers. Our results imply that in vivo alpha-catenin, like vinculin, is tightly regulated in its ligand binding activity.

Animals↗

The interaction of the cell-contact proteins VASP and vinculin is regulated by phosphatidylinositol-4,5-bisphosphate.

BACKGROUND: Focal adhesion sites are cell-matrix contacts that are regulated by phosphatidylinositol-4,5-bisphosphate (PIP2)-dependent pathways. Vinculin is a major structural component of these sites and is thought to be engaged in multiple ligand interactions at the cytoplasmic face of these contacts. Cytoplasmic vinculin is considered to be inactive due to its closed conformation involving intramolecular head-tail interactions. Recently, the vasodilator-stimulated phosphoprotein (VASP), a substrate of cyclic AMP-dependent or cyclic GMP-dependent kinases and a component of focal adhesion sites, was shown to bind to vinculin. RESULTS: VASP-vinculin complexes could be immunoprecipitated from cell lysates and, using immunofluorescence, both proteins were found to colocalize in nascent focal adhesions. Consistent with the view that vinculin must be activated at these sites, we found that PIP2, levels of which are elevated during the early stages of adhesion, bound to two discrete regions in the vinculin tail, disrupting the intramolecular head-tail interaction and inducing vinculin oligomerization. Vinculin-VASP complex formation was greatly enhanced by PIP2 and both the EVH1 and EVH2 domains of VASP participated in vinculin binding. CONCLUSIONS: Focal contact assembly involves interaction between VASP and vinculin, which is enhanced by PIP2-induced vinculin activation and oligomerization. Given that vinculin and VASP both bind to F-actin, vinculin-VASP complexes might bundle the distal ends of actin filaments in focal contacts. We propose that PIP2-dependent signalling modulates microfilament organization at cellular adhesion sites by regulating vinculin-VASP complexes.

Actins↗

Vinculin and alpha-catenin: shared and unique functions in adherens junctions.

Vinculin and alpha-catenin are two functionally related proteins of adherens junctions, structures in which cells make contacts to neighboring cells or to the extracellular matrix. At these sites, the actin cytoskeleton of animal cells is anchored to the plasma membrane. Junction assembly and disassembly are coordinated in processes as different as mitosis, cell movement and tissue formation. Since adherens junctions are assembled from a large number of proteins, these molecules have to be coordinately activated and spatially regulated. Vinculin and alpha-catenin have been characterized as tumor suppressors, suggesting that they have a regulatory function in addition to their structural role. Several possible modes of vinculin and alpha-catenin regulation are discussed here, as the published data favor the concept that no single model fully explains the complexity of adherens junctions. Most probably, cells select from a variety of possibilities to solve the problem of making specific contacts.

Actins↗

Development of pulmonary lipophilic antioxidants and peroxidizable lipids during lung maturation.

The objective of this article is to test whether the concentration of potentially oxidizable lipids (polyunsaturated fatty acids [PUFA], total and free cholesterol) and lipophilic antioxidants (plasmalogens, vitamin E) in the fetal lung correlate with lung maturation (P/S ratio). In amniotic fluid palmitic/stearic acid (P/S) ratio, concentrations of PUFA, total and free cholesterol, vitamin E, and plasmalogens were measured. Ratio of PUFA to stearic acid (PUFA/S ratio) was determined in lung effluent of 15 preterm infants with IRDS and compared with values from 15 term healthy infants. Concentrations of plasmalogens, PUFA, total and free cholesterol increase significantly with increasing P/S ratio. No correlation of vitamin E with lung maturation has been found. The PUFA/S ratio is significantly lower in lung effluent of preterm (0.79 +/- 0.27) when compared with term infants (2.02 +/- 0.38). Our results suggest that the higher susceptibility of preterm infants for oxidative lung injury is not caused by an unfavorable ratio of oxidizable lipids to lipophilic antioxidants in surfactant, but rather by a lower amount of PUFA containing surfactant lipids. Our results are in accordance with data from Sosenko et al. who have shown that high levels of PUFA in the rat lung have a protective effect against oxygen-induced lung damage.

Amniotic Fluid↗

Plasmalogens effectively reduce the surface tension of surfactant-like phospholipid mixtures.

The alkenyl-acyl subclass of phosphatidylethanolamine (PtdEtn) and phosphatidylcholine (plasmalogens) are minor components of alveolar surfactant. Plasmalogens promote and stabilize hexagonal structures of phospholipids. In another study (W.R. Perkins, R.B. Dause, R.A. Parente, S.R. Michey, K.C. Neuman, S.M. Gruner, T.F. Taraschi, and A.S. Janoff. Science 273: 330-332, 1996), it was shown that polymorphic phase behavior may have an important role in the effective functioning of pulmonary surfactant. Therefore, we hypothesized that surface properties of phospholipid mixtures that contain plasmalogens are superior to plasmalogen-free mixtures. The effect of plasmalogens on surface tension of surfactant-like phospholipid mixtures (70 mol% dipalmitoyl phosphatidylcholine, 10 mol% phosphatidylglycerol, and 20 mol% PtdEtn) was measured. Using the pulsating bubble surfactometer, we show that an increasing amount of ethanolamine plasmalogens [plasmenylethanolamine (PlsEtn) results in reduction of surface tension (0 mol% PlsEtn 44.7 +/- 1.7, 2 mol% 33.5 +/- 1.7, 4 mol% 36 +/- 3.1, 6 mol% 26.2 +/- 2.9, and 8 mol% 22.2 +/- 0.3 mN/m). By means of the captive bubble surfactometer, minimal surface tension reached with 8 mol% PlsEtn was even lower (3.8 +/- 0.7 mN/m). With regard to morphological studies (B. Fringes, K. Gorgas, and A. Reith. Eur. J. Cell Biol. 46: 136-143, 1988), clofibrate treatment of rats might increase the plasmalogen content of alveolar surfactant. However, in the present study, we could not show that synthesis and secretion of plasmalogens are affected by clofibrate treatment.

1,2-Dipalmitoylphosphatidylcholine↗

Are biochemical parameters of lung maturation from gastric, tracheal, and pharyngeal aspirates comparable?

Phospholipid parameters -- lecithin/sphingomyelin (L/S) ratio and palmitic acid/stearic acid (P/S) ratio -- of gastric (GA), pharyngeal (PA), and tracheal aspirates (TA) have often been used for estimation of lung maturation. However, it was not known whether values from different sources can be alternatively used. The study was performed to test whether P/S and L/S ratios in GA, PA, and TA are comparable. 11 GA, 30 PA, and 10 TA were obtained from infants within 10 min after birth. All infants were healthy, vaginally delivered with no respiratory distress, and had a gestational age > or = 34 weeks. Patterns of fatty acids were determined by gas chromatography and the L/S ratio by high-performance liquid chromatography. We found lower L/S ratios in GA (16.5 +/- 5.2) when compared with PA(39 +/- 16) or TA (41 +/- 15; p < 0.01); there were no differences between PA and TA. The P/S ratio was in the same range in PA and TA, but lower in GA. As compared with TA and PA, in GA the relative percentage of palmitic acid of all fatty acids was lower, the percentage of monounsaturated fatty acids, however, higher. We conclude that phospholipid parameters of lung maturation in PA and TA, but not in GA, can be alternatively used.

Gastric Juice↗