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Klaus Arnold

Publications and source records attributed to Klaus Arnold.

32 records · Page 2Linked to original sources
PubMed2003

Influence of tidal volume on pulmonary NO release, tissue lipid peroxidation and surfactant phospholipids.

Mechanical stress during ventilation may cause or aggravate acute lung injury. This study investigates the influence of low vs. high tidal volume (V(t)) on factors known to play key roles in acute lung injury: nitric oxide release, eNOS and iNOS gene expression, lipid peroxidation (LPO), and surfactant phospholipids (PL). Isolated rabbit lungs were subjected to one of three ventilation patterns for 135 min (V(t)-PEEP): 6 ml/kg-0 cm H(2)O. 12 ml/kg-0 cm H(2)O 6 ml/kg-5 cm H(2)O, 12 ml/kg-0 cm H(2)O, and 6 ml/kg-5 cm H(2)O resulted in comparable peak inspiratory pressure (PIP). This allowed comparing low and high V(t) without dependence on PIP. Ventilatory patterns did not induce changes in pulmonary artery pressure, vascular permeability (K(f,c)), PIP or pulmonary compliance. High V(t) in comparison with both of the low V(t) groups caused an increase in BALF-nitrite (30.6+/-3.0* vs. 21.4+/-2.2 and 16.2+/-3.3 microM), BALF-PL (1110+/-19* vs. 750+/-68 and 634+/-82 microg/ml), and tissue LPO product accumulation (0.62+/-0.051* vs. 0.48+/-0.052 and 0.43+/-0.031 nmol/mg), *P<0.05 each. Perfusate nitrite and BALF-PL composition (assessed by use of 31P-NMR spectroscopy and MALDI-TOF mass spectrometry) did not differ among the groups. High V(t) ventilation reduced eNOS gene expression but did not affect iNOS expression. The increased release of NO and the accumulation of LPO products may represent early lung injury while elevated BALF-PL may reflect distension-induced surfactant secretion.

Animals↗
PubMed2003

Structural and dynamical changes of the bindin B18 peptide upon binding to lipid membranes. A solid-state NMR study.

Structural and dynamical features of the B18 peptide from the sea urchin sperm binding protein were determined in the crystalline state and in zwitterionic lipid bilayers at a peptide:lipid molar ratio of 1:12 using solid-state NMR spectroscopy. The study was focused on three (13)C and (15)N uniformly labeled leucine residues, which were introduced into three different B18 peptides at positions evenly distributed along the B18 primary structure. Isotropic (13)C and (15)N chemical shift measurements showed that while B18 possesses a nonhelical and non-sheet-like structure in the crystalline state, the peptide adopts an oligomeric beta-sheet structure in the membrane in the presence of Zn(2+) ions at high peptide:lipid ratio. Torsion angle measurements for the three leucine sites supported these results, with phi torsion angles between -80 degrees and -90 degrees in the crystalline state and between -110 degrees and -120 degrees in the membrane-bound form. These phi torsion angles determined for membrane-bound B18 are consistent with a parallel beta-sheet secondary structure. Analysis of motionally averaged dipolar coupling measurements established an increase of the mobility in the leucine side chains upon binding to the membrane, whereas the backbone mobility remained essentially unchanged, except in the binding site of Zn(2+) ions. This difference in mobility was related to the H-bond network in the parallel beta-sheet structure, which involves the backbone and excludes the side chains of leucine residues. The parallel beta-sheet structure of B18 in the membrane in the presence of Zn(2+) appears to be an active state for the fusion of zwitterionic membranes in the presence of Zn(2+). A fluorescence fusion assay indicated that high B18 concentrations are required to induce fusion in these systems. Therefore, it was hypothesized that the oligomeric beta-sheet secondary structure revealed in the study represents an active state of the peptide in a membrane environment during fusion.

Fluorescence↗
PubMed2003

Membrane insertion of a lipidated ras peptide studied by FTIR, solid-state NMR, and neutron diffraction spectroscopy.

Membrane binding of a doubly lipid modified heptapeptide from the C-terminus of the human N-ras protein was studied by Fourier transform infrared, solid-state NMR, and neutron diffraction spectroscopy. The 16:0 peptide chains insert well into the 1,2-dimyristoyl-sn-glycero-3-phosphocholine phospholipid matrix. This is indicated by a common main phase transition temperature of 21.5 degrees C for both the lipid and peptide chains as revealed by FTIR measurements. Further, (2)H NMR reveals that peptide and lipid chains have approximately the same chain length in the liquid crystalline state. This is achieved by a much lower order parameter of the 16:0 peptide chains compared to the 14:0 phospholipid chains. Finally, proton/deuterium contrast variation of neutron diffraction experiments indicates that peptide chains are localized in the membrane interior analogous to the phospholipid chains. In agreement with this model of peptide chain insertion, the peptide part is localized at the lipid-water interface of the membrane. This is revealed by (1)H nuclear Overhauser enhancement spectra recorded under magic angle spinning conditions. Quantitative cross-peak analysis allows the examination of the average location of the peptide backbone and side chains with respect to the membrane. While the backbone shows the strongest cross-relaxation rates with the phospholipid glycerol, the hydrophobic side chains of the peptide insert deeper into the membrane interior. This is supported by neutron diffraction experiments that reveal a peptide distribution in the lipid-water interface of the membrane. Concurring with these experimental findings, the amide protons of the peptide show strong water exchange as seen in NMR and FTIR measurements. No indications for a hydrogen-bonded secondary structure of the peptide backbone are found. Therefore, membrane binding of the C-terminus of the N-ras protein is mainly due to lipid chain insertion but also supported by interactions between hydrophobic side chains and the lipid membrane. The peptide assumes a mobile and disordered conformation in the membrane. Since the C-terminus of the soluble part of the ras protein is also disordered, we hypothesize that our model for membrane binding of the ras peptide realistically describes the membrane binding of the lipidated C-terminus of the active ras protein.

Dimyristoylphosphatidylcholine↗
PubMed2003

Analysis of the lipid composition of bull spermatozoa by MALDI-TOF mass spectrometry--a cautionary note.

In this study we demonstrated the combination of MALDI-TOF MS and TLC as a fast and powerful tool to investigate the phospholipid (PL) composition of organic extracts of bull spermatozoa. Since phosphatidylcholine (PC) is the dominant PL species, an adequate resolution of MALDI-TOF spectra for sphingomyelin (SM) or phosphatidylethanolamine (PE) was achieved only after previous PL separation by TLC. We found a poor diversity especially for PE and PC, mainly containing ether-linked fatty acids which were 1-palmityl-2-docosahexaenoyl-PL and the corresponding alkenyl-acyl compound (plasmalogen) 1-palmitenyl-2-docosahexaenoyl-PL. For PC, both lipids were quantified after phospholipase A2 digestion to represent 44.2 and 37.2%, respectively, of the total PC. In contrast, the diacyl-PC content of bull spermatozoa was comparatively low (18.6% of total PC). In the presence of trifluoroacetic acid (TFA), which is routinely added to the MALDI-TOF matrix to improve the signal to noise ratio, a high lysophospholipid (LPL) content was detected in the PL extracts of bull spermatozoa, whereas TLC did not reveal significant amounts of LPL. The TFA mediated hydrolysis of the acid-labile alkenyl-acyl PL to the corresponding LPL was shown to cause this discrepancy. This assumption was verified by analysing the PL composition by MALDI-TOF MS before and after (i) digestion of sperm cell lipids with phospholipase A2 and (ii) exposition of spermatozoa to HCl fumes. We conclude that the analysis of samples containing alkenyl-acyl-PL by MALDI-TOF has to be performed with great caution.

Animals↗
PubMed2002

Dynamics of lipid chain attached fluorophore 7-nitrobenz-2-oxa-1,3-diazol-4-yl (NBD) in negatively charged membranes determined by NMR spectroscopy.

We have determined the average location and dynamic reorientation of the fluorophore 7-nitrobenz-2-oxa-1,3-diazol-4-yl (NBD) attached to a C12 sn-2 chain of a phosphatidylserine (PS) analogue (C12-NBD-PS) in zwitterionic phosphatidylcholine (PC) and negatively charged phosphatidylserine (PS) host membranes. (1)H magic angle spinning nuclear Overhauser enhancement spectroscopy indicates a highly dynamic reorientation of the aromatic molecule in the membrane. The average location of NBD is characterized by a broad distribution function along the membrane director with a maximum indicating the location of the probe in the lipid/water interface of the lipid membrane. This behavior can be explained by a backfolding of the sn-2 chain towards the aqueous phase. Small differences in the distribution profiles of the NBD group along the membrane normal between PC and PS host membranes were found: in a PC host membrane, the NBD distribution has its maximum in the glycerol region; in a PS host membrane, NBD resides mostly in the upper chain region. These differences may be accounted for by packing differences in the PC versus PS host membranes. As seen by (2)H NMR order parameters, PS bilayers show a much higher packing density compared to PC membranes. Consequently, backfolding of the sn-2 chain with the NBD group attached causes a larger decrease of molecular order of the sn-1 chain in PS than in PC membranes. The broad distributions obtained for lipid chain attached NBD molecules reflect the motional freedom and molecular disorder in the liquid-crystalline lipid membrane.

4-Chloro-7-nitrobenzofurazan↗
PubMed2002

Application of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry for monitoring the digestion of phosphatidylcholine by pancreatic phospholipase A(2).

Different methods were established for monitoring the phospholipase A(2)(PLA(2)) activity but all of them are rather cumbersome and time consuming. In this paper we have investigated the suitability of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) for the determination of the PLA(2) activity. Phosphatidylcholine (PC) was digested with pancreatic PLA(2) under different conditions, i.e., various Ca(2+), PC, and PLA(2) concentrations. The digestion products were analyzed by MALDI-TOF MS and the concentration of lysophosphatidylcholine (LPC)-generated upon PLA(2) digestion-was determined by the application of an internal standard (known concentration) and by a comparison of their signal-to-noise ratios. The results clearly demonstrate that the LPC concentration determined from the MALDI-TOF mass spectra correlates directly with the activity of the applied enzyme. Additionally, LPC concentration increased with an increase in Ca(2+), as well as in the PC concentration. A single MALDI-TOF mass spectrum provides immediate information on the digestion products as well as on the residual substrate without requirements for any previous derivatization. MALDI-TOF MS can be easily and simply applied for monitoring the PLA(2) activity and we assume that this method might also be useful for other types of phospholipases.

Animals↗
PubMed2002

Self-diffusion of polymers in cartilage as studied by pulsed field gradient NMR.

Pulsed field gradient (PFG) nuclear magnetic resonance (NMR) was used to investigate the self-diffusion behaviour of polymers in cartilage. Polyethylene glycol and dextran with different molecular weights and in different concentrations were used as model compounds to mimic the diffusion behaviour of metabolites of cartilage. The polymer self-diffusion depends extremely on the observation time: The short-time self-diffusion coefficients (diffusion time Delta approximately 15 ms) are subjected to a rather non-specific obstruction effect that depends mainly on the molecular weights of the applied polymers as well as on the water content of the cartilage. The observed self-diffusion coefficients decrease with increasing molecular weights of the polymers and with a decreasing water content of the cartilage. In contrast, the long-time self-diffusion coefficients of the polymers in cartilage (diffusion time Delta approximately 600 ms) reflect the structural properties of the tissue. Measurements at different water contents, different molecular weights of the polymers and varying observation times suggest that primarily the collagenous network of cartilage but also the entanglements of the polymer chains themselves are responsible for the observed restricted diffusion. Additionally, anomalous restricted diffusion was shown to occur already in concentrated polymer solutions.

Animals↗
PubMed2002

Comparison of collagen dynamics in articular cartilage and isolated fibrils by solid-state NMR spectroscopy.

Native pig articular cartilage was investigated by (13)C cross polarization (CP) magic angle spinning (MAS) NMR at a magnetic field strength of 17.6 T. CP MAS spectra of cartilage are dominated by resonances from rigid collagen, while only low-intensity signals from the glycosaminoglycans are observed. The spectral resolution of collagen fibrils in native cartilage is somewhat higher than for isolated collagen fibrils from bovine achilles tendon investigated for comparison. This is confirmed qualitatively by (1)H-(1)H wideline separation spectra that show much lower line widths for cartilage collagen compared to isolated collagen. The strength of (1)H-(13)C dipolar couplings was measured in a 2D LG CP experiment providing a motionally averaged dipolar coupling value for each resolved signal. These scaled couplings were converted to molecular order parameters for the CH bond vector. Typical order parameters for isolated collagen were 0.91-0.96 for sidechains and 0.98-1.00 for the backbone. Somewhat lower order parameters were determined for cartilage collagen; 0.79-0.90 for the sidechain and 0.92-0.97 for the backbone. The only glycosaminoglycan signals that could be detected by CP MAS show order parameters of 0.48-0.92 and are assigned to relatively rigid hyaluronan and keratan sulfate. The higher mobility of collagen in cartilage is due to the high water content and collisions with the isotropically mobile glycosaminoglycans, such as chondroitin sulfate. Therefore, the mobility of cartilage macromolecules is broadly distributed from almost completely rigid to highly mobile, which lends cartilage its mechanical strength and shock-absorbing properties.

Achilles Tendon↗
PubMed2002

Cartilage degradation by stimulated human neutrophils: elastase is mainly responsible for cartilage damage.

Although neutrophilic granulocytes are assumed to contribute to cartilage degradation during rheumatic diseases, there is still a discussion whether reactive oxygen species (ROS) or proteolytic enzymes that are both released by the neutrophils are most relevant to cartilage degradation. To gain further insight into these processes, an in vitro approach to study the interaction between the products of stimulated neutrophilic granulocytes and cartilage was used: Neutrophils from the blood of healthy volunteers were treated with different stimulators (e.g., Ca(2+) ionophores) in order to induce degranulation. Supernatants of neutrophils were afterward incubated with thin slices of pig articular cartilage. Some experiments were also performed in the presence of selected enzyme inhibitors. Supernatants of cartilage were subsequently assayed by one- and two-dimensional high-resolution proton NMR spectroscopy, and the content of soluble carbohydrates in the supernatant was additionally determined by biochemical methods. The selective inhibition of elastase decreased most significantly the extent of cartilage degradation, whereas all other inhibitors had much smaller effects. These results were additionally confirmed by measuring the effect of isolated elastase on articular cartilage in the absence and presence of different inhibitors. It is concluded that elastase released [EC 3.4.21.37] by neutrophils is the most relevant enzyme for cartilage degradation.

Animals↗
PubMed2002

Are obese adolescents and young adults at higher risk for mental disorders? A community survey.

OBJECTIVE: Associations between body mass index (BMI) and mental disorders meeting Axis-I diagnoses according to the Diagnostic and Statistical Manual for Mental Disorders IV (DSM-IV) were investigated in The Early Developmental Stages of Psychopathology Study in a large population-based sample, which included adolescents and young adults of both genders for the first time. RESEARCH METHODS AND PROCEDURES: A total of 3021 German subjects ranging from 14 to 24 years of age were assessed for specific DSM-IV diagnoses derived from a modified version of the standardized Composite International Diagnostic Interview, and general psychological disturbances, using the Symptom Checklist-90-Revised. BMI percentiles for age and gender were calculated to avoid systematic bias in the BMI distribution resulting from the young age range represented in the sample. Additionally, subjects with a lifetime diagnosis of any eating disorder were excluded from statistical analysis to control the confounding effect of body weight-related eating disorders on associations between BMI and psychopathology. RESULTS: The results based on logistic regression analyses and MANOVAs demonstrate that the BMI is not associated with mental disorders or general psychopathologies. There were no significant associations between BMI and mood, anxiety, substance, and somatoform disorders, a result that contrasts with almost all previous clinical studies. Additionally, in contrast to clinical investigations and most epidemiological studies, neither obesity nor underweight was significantly associated with any kind of general psychopathology. DISCUSSION: The overall finding that obesity is not significantly related to marked psychopathology in the general German population of adolescents and young adults has important clinical implications.

Adolescent↗
PubMed2002

Application of high resolution 31P NMR spectroscopy to the characterization of the phospholipid composition of tissues and body fluids - a methodological review.

The detailed analysis of lipids, especially phospholipids, has become progressively important, since these molecules represent intercellular messenger molecules and are involved in a number of diseases. Therefore, the analysis of the lipid pattern of blood, for example, may also be useful as a diagnostic tool. Unfortunately, suitable methods of phospholipid analysis are often time-consuming and tedious, since most of them include a variety of separation and derivatization steps. Methods allowing lipid analysis in a single step would be highly useful. The aim of this review is to show that high resolution 31P NMR spectroscopy is a convenient and precise analytical tool for the phospholipid analysis of extracts from biological samples (tissues and body fluids). The first part of this review discusses the physiological relevance of individual kinds of phospholipids and related, established analytical techniques for their investigation. The second part contains an overview on the requirements for 31P NMR to improve spectral resolution and sensitivity, its capabilities and its limitations. In the third part, we discuss the application of 31P NMR to the most important phospholipid classes, as well as different tissue and body fluid extracts. The article concludes with a brief look at future developments and potential applications of this technique.

Animals↗
PubMed2001

1H High-Resolution Magic Angle Spinning NMR Spectroscopy for the Investigation of a Ras Lipopeptide in a Lipid Membrane This work was supported by the Deutsche Forschungsgemeinschaft (SFB 197 and Innovationskolleg "Chemisches Signal und biologische Antwort"). D.H. is grateful for a BASF fellowship through the Studienstiftung des Deutschen Volkes. The authors thank Dr. A. Pampel for technical support with the DRX600.

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Journal Article↗
PubMedDate not supplied

Effects of lysophospholipids on the generation of reactive oxygen species by fMLP- and PMA-stimulated human neutrophils.

In this study, the effects of exogenous lysophospholipids--lysophosphatidic acid, lysophosphatidylcholine, lysophosphatidylethanolamine and lysophosphatidylserine--on the kinetics of reactive oxygen species (ROS) production by human neutrophils are described. The ROS production by human neutrophils was monitored by luminol-amplified chemiluminescence after cell stimulation with the chemotactic tripeptide, fMLP, or with the phorbol ester, PMA. The interaction of lysophospholipids with the membrane of human neutrophils was additionally tested by mass spectrometry. Lysophosphatidylcholine showed the most pronounced effect on the chemiluminescence pattern, as well as the intensity of the fMLP and PMA-stimulated cells, whereas lysophosphatidic acid showed a slight priming effect when fMLP was used for stimulation. In the case of fMLP-stimulated cells, lysophosphatidylcholine inhibited the first phase and enhanced the second phase of chemiluminescence, whereas the chemiluminescence of PMA-stimulated neutrophils was inhibited in a concentration-dependent manner. We conclude that lysophosphatidylcholine is able to interact with protein kinase C-dependent signalling pathways leading to NADPH oxidase activation.

Cell Membrane↗