Biomedical subjects

G Jung

Publications and source records attributed to G Jung.

At least 19 recordsLinked to original sources

PubMed2003

Compact, low-cost Ti:Al2O3 laser for in vivo ultrahigh-resolution optical coherence tomography.

A compact, low-cost, prismless Ti:Al2O3 laser with 176-nm bandwidth (FWHM) and 20-mW output power was developed. Ultrahigh-resolution ophthalmic optical coherence tomography (OCT) ex vivo imaging in an animal model with approximately 1.2-microm axial resolution and in vivo imaging in patients with macular pathologies with approximately 3-microm axial resolution were demonstrated. Owing to the pump laser, this light source significantly reduces the cost of broadband OCT systems. Furthermore, the source has great potential for clinical application of spectroscopic and ultrahigh-resolution OCT because of its small footprint (500 mm x 180 mm including the pump laser), user friendliness, stability, and reproducibility.

Aluminum Oxide↗

PubMed2003

Fusion of small unilamellar vesicles onto laterally mixed self-assembled monolayers of thiolipopeptides.

Monolayers of the thiolipopeptide NH(2)-Cys-Ala-Ser-Ala-Ala-Ser-Ser-Ala-Pro-Ser-Ser-(Myr)Lys(Myr)-OH (III) were formed on gold surfaces by self-assembly, mixed with a lateral spacer of the same peptide composition, NH(2)-Cys-Ala-Ser-Ala-Ala-Ser-Ser-Ala-Pro-Ser-Ser-Lys-OH (I). Different mixing ratios were employed ranging from 0.1 to 1, corresponding to 10-100% thiolipopeptide. These self-assembled monolayers (SAMs) were then exposed to a suspension of liposomes with the aim of forming lipid bilayers as a function of the mixing ratio. A clear optimum with respect to homogeneity and electrical properties of the membranes was obtained in the middle region (0.5) of mixing ratio, as revealed by surface plasmon resonance spectroscopy, impedance spectroscopy, and fluorescence microscopy. The combination of these methods was shown to be a powerful tool, although a true lipid bilayer was not obtained. Instead, vesicle adsorption was shown to be the predominant process, and FRAP (fluorescence recovery after photobleaching) measurements showed that the films were not fluid on the micrometer length scale.

Lipoproteins↗

PubMed2003

CD4+ T cell-mediated immunity against prion proteins.

The prion protein (PrP(C)) is essential for susceptibility to transmissible spongiform encephalopathies. A specific conformer of this protein (PrP(Sc)) is, according to the 'protein only' hypothesis, the principal or only component of the infectious agent, designated prion. Transmission of prions between species is often inefficient, resulting in low attack rates and/or prolonged incubation times and is ascribed to a 'species barrier' caused by differences in the amino acid sequence of PrP between recipient and donor. In this report, we demonstrate that these differences in amino acid sequence result in presentation of distinct peptides on major histocompatibility complex class II molecules. These peptides result in activation of specific CD4+ T cells which leads to the induction of an effective immune response against foreign PrP as demonstrated by antibody production. Therefore, CD4+ T cells represent a crucial component of the immune system to distinguish between foreign and self PrP.

Amino Acid Sequence↗

PubMed2003

Establishment of T cell lines to bovine beta-casein and beta-casein-derived epitopes in patients with type 1 diabetes.

Enhanced cellular immune response to bovine beta-casein has been reported in patients with type 1 diabetes. In this study we aimed to establish beta-casein-specific T cell lines from newly diagnosed type 1 diabetic patients and to characterise these cell lines in terms of phenotype and epitope specificity. Furthermore, since sequence homologies exist between beta-casein and putative beta-cell autoantigens, reactivity to the latter was also investigated. T cell lines were generated from the peripheral blood of nine recent onset type 1 diabetic patients with different HLA-DQ and -DR genotypes, after stimulation with antigen pulsed autologous irradiated antigen presenting cells (APCs) and recombinant human interleukin-2 (rhIL-2). T cell line reactivity was evaluated in response to bovine beta-casein, to 18 overlapping peptides encompassing the whole sequence of beta-casein and to beta-cell antigens, including the human insulinoma cell line, CM, and a peptide from the beta-cell glucose transporter, GLUT-2. T cell lines specific to beta-casein could not be isolated from HLA-matched and -unmatched control subjects. beta-Casein T cell lines reacted to different sequences of the protein, however a higher frequency of T cell reactivity was observed towards the C-terminal portion (peptides B05-14, and B05-17 in 5/9 and 4/9 T cell lines respectively). Furthermore, we found that 1 out of 9 beta-casein-specific T cell lines reacted also to the homologous peptide from GLUT-2, and that 3 out of 4 of tested cell lines reacted also to extracts of the human insulinoma cell line, CM. We conclude that T cell lines specific to bovine beta-casein can be isolated from the peripheral blood of patients with type 1 diabetes; these cell lines react with multiple and different sequences of the protein particularly towards the C-terminal portion. In addition, reactivity of beta-casein T cell lines to human insulinoma extracts and GLUT-2 peptide was detected, suggesting that the potential cross-reactivity with beta-cell antigens deserves further investigation.

Adolescent↗

PubMed2002

[Modern diagnostic imaging: MR urography].

MR-urography presents a new diagnostic approach to the urinary system, resulting in images comparable to those known from i.v.-urography. T2-weighted MR-urograms demonstrate static fluid without ionizing radiation or nephrotoxic contrast media. The excretory renal function can be examined by the use of gadolinium-enhanced T1-urography. The degree and cause of ureteric obstruction can be diagnosed with high sensitivity and specificity. On the other hand, urolithiasis is frequently misdiagnosed by MR-urography and, in this case, spiral CT should be used. Pediatric or pregnant patients can be examined as well as donors before and patients after renal transplantation. Furthermore, in case of a tumor MR-imaging, including MR-angiography, is a potential diagnostic "all-in-one" approach.

Adult↗

PubMed2002

Epitope-mapping of transglutaminase with parallel label-free optical detection.

The gastrointestinal disorder coeliac disease (CD) is induced by the ingestion of wheat gluten and is characterized by damage of the typical structure of the intestinal mucosa. The enzyme tissue transglutaminase (tTGase) was identified as the major target of disease-specific antibodies in-patients. We performed an epitope fine-mapping with a series of pentadecapeptides synthesized using parallel multiple peptide synthesis. For the detection of biomolecular interactions a label-free parallel method, reflectometric interference spectroscopy (RIfS), was used. This is the first optical label-free method adapted to a high throughput screening (HTS) format and the experimental results demonstrate its applicability as a biological screening device. A high titer of anti-tTGase antibodies is found in the serum of coeliac patients. We have taken the first step towards a fast non-surgical test for the detection of these antibodies. In order to identify and characterize a continuous epitope with high affinity against the anti-tTGase antibody a screening of 21 pentadecapeptides has been accomplished with the parallel RIfS system. A single channel RIfS-system with high resolution was used to determine binding constants of identified peptides with high affinity.

Animals↗

PubMed2002

Lipopeptide adjuvants: monitoring and comparison of P3CSK4- and LPS-induced gene transcription.

Bacteria-derived synthetic lipoproteins constitute potent macrophage activators in vivo and are effective stimuli, enhancing the immune response especially with respect to low or non-immunogenic compounds. N-palmitoyl-S-[2,3-bis(palmitoyloxy)-(2R,S)-propyl]-(R)-cysteinyl-seryl-(lysyl)3-lysine (P3CSK4), exhibiting one of the most effective lipopeptide derivatives, represents a highly efficient immunoadjuvant in parenteral, oral, nasal and genetic immunization either in combination with or after covalent linkage to antigen. In order to further elucidate its molecular mode of action with respect to the transcriptional level, we focused our investigations on the P3CSK4-induced modulation of gene transcription. We could show that P3CSK4 activates/represses an array of at least 140 genes partly involved in signal transduction and regulation of the immune response. P3CSK4 activates the expression of tumor suppressor protein p53 (p53), c-rel, inhibitor of nuclear factor kappa B (NFkappaB) alpha (IkappaB alpha), type 2 (inducible) nitric oxide (NO) synthase (iNOS), CD40-LR, intercellular adhesion molecule-1 (ICAM-1) and interleukin 1/6/15 (IL-1/6/15). We detected no activation of heat shock protein (HSP) 27, 60, 84 and 86, osmotic stress protein 94 (Osp 94), IL-12, extracellular signal-regulated protein kinase 1 (ERK1), p38 mitogen activated protein (MAP)-kinase (p38), c-Jun NH2-terminal kinase (JNK), signal transducer and activator of transcription 1 (STAT1), CD14 and caspase genes. Furthermore, we monitored inhibition of STAT6, Janus kinase 3 (Jak3) and cyclin D1/D3 gene transcription after stimulating bone marrow-derived macrophages (BMDM) with lipopeptide. In addition, we monitored significant differences after lipopeptide and lipopolysaccharide (LPS) stimulation of bone marrow-derived murine macrophages. Our findings are of importance for further optimizing both conventional and genetic immunization, and for the development of novel synthetic vaccines.

Adjuvants, Immunologic↗

PubMed2001

Broadband detection electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry to reveal enzymatically and chemically induced deamidation reactions within peptides.

Among the numerous forms of chemical degradation of peptides or proteins, deamidation is one of the alterations observed most frequently. In this irreversible reaction, a glutamine or an asparagine side chain is hydrolyzed to glutamic acid or aspartic acid, respectively (conversion of NH2 to OH). Besides its influence in the deterioration of biotechnological and food products, deamidation represents a defined posttranslational modification reaction with respect to proteomics. Here mass spectrometric techniques play a leading role in determining posttranslational modifications. However, not all mass spectrometers are able to resolve signal differences of 0.0193 Da (mass difference of 12CO vs 13CNH) for singly charged molecules, the mass difference between the first isotopic signal of an asparagine/glutamine-containing peptide and the monoisotopic signal of the corresponding partially deamidated aspartate/glutamate derivative. To detect partial deamidation within peptides, advantage has been taken of the ability of Fourier transform ion cyclotron resonance mass spectrometry to perform very high mass resolution. In this work, we investigated up to triply charged ions produced by electrospray ionization using direct infusion. Although the special heterodyne detection mode enables higher mass resolution than the routinely used broadband detection, often only a small mass window can be investigated. Using broadband detection, we were able to resolve ions with a difference of m/z 0.0064 to detect partially deamidated peptides formed either enzymatically or under acidic and basic conditions.

Amides↗

PubMed2001

AMP deaminase in rat brain: localization in neurons and ependymal cells.

The purine nucleotide cycle enzyme AMP deaminase (AMPD) catalyzes the irreversible hydrolytic deamination of AMP. The physiological function of the purine nucleotide cycle in the brain is unknown. In situ hybridization and immunocytochemical studies were performed to identify the regional and cellular expression of AMPD in rat brain with the goal of elucidating the neural function of the purine nucleotide cycle. AMPD messenger RNA was detected in ventricular ependymal cells and cells of the choroid plexus and in neurons of distinct brain areas. Although only low antibody titers were obtained by immunization with the purified sheep brain AMPD, immunization of mice with synthetic lipopeptide vaccines containing oligopeptides derived from a known partial complementary DNA sequence of the enzyme yielded an antiserum suitable for immunocytochemistry. Immunostaining of cells in culture showed that neurons but not astroglial cells express appreciable amounts of the enzyme. Results of immunocytochemical staining performed on rat brain slices were in accord with the localization of AMPD messenger RNA, thus confirming the expression of AMPD in neurons of the brain stem, hippocampus, cerebellar nuclei and mesencephalic nuclei, as well as in ventricular ependymal cells and their cilia.

AMP Deaminase↗

PubMed2001

Promotion of neural cell adhesion by electrochemically generated and functionalized polymer films.

New strategies for spatially controllable cell adhesion have been developed for brain cells from embryonic chicken. They are based on electrochemically active phenol and pyrrole derivatives, and can be used for the selective coverage of electroconductive substrates. Besides mimicking standard laminin-related adhesion promoting mechanisms by means of an electroactive monomer-linked 18-peptide segment from laminin (SRARKQAASIKVAVSADR), electrochemically generated thin (6-30 nm) polymer films of 3-hydroxybenzyl-hydrazine (3HBH) and 2-(3-hydroxyphenyl)-ethanol (2(3HP)E) with and without mechanically entrapped or covalently linked D-lysine have proved to promote cell adhesion in serum-free medium on indium-doped tin oxide (ITO) substrates during the first 6 culturing days in vitro. The effectiveness of the peptide was strongly density-dependent. Unexpectedly, laminin itself or a combination of laminin and poly-D-lysine (PDL) did not promote cell adhesion and neuron differentiation in serum-free cultures on ITO. However, they worked perfectly well on regular polystyrene substrates in serum-free medium or on ITO when medium with serum was used. This finding might suggest that the adhesion efficiency of laminin does not depend only on the kind of medium supplement but also on the type of substrate. In contrast, the adhesion-promoting properties of "artificial" polymeric films seemed to be based on a more direct cell-film interaction, with the film masking the substrate properties.

Animals↗

PubMed2001

Analysis of the proliferative responses to peptides in individuals with vigorous Gag protein-specific proliferation.

Proliferative responses to recombinant HIV proteins in infected individuals may represent a correlate of protection from disease progression. In this study, the proliferative responses to HIV p24, p55 and gp120 were evaluated in infected subjects. Whereas, vigorous proliferative responses directed at the Gag proteins were detected in several individuals, Env-specific proliferation was observed in only one subject. Epitope mapping using overlapping peptides demonstrated proliferative responses of PBMC to Gag peptides. Responses were broadly directed at multiple peptides in some subjects. Although several of the peptides that induced proliferative responses also contain CTL epitopes potentially relevant in the particular individuals, many additional Gag T cell epitopes were present in each subject. This finding may be relevant for the design and testing of HIV candidate vaccines.

AIDS Vaccines↗

PubMed2001

Mimetics of a T cell epitope based on poly-N-acylated amine backbone structures induce T cells in vitro and in vivo.

Peptidomimetics of the major histocompatibility complex (MHC) class I-restricted ovalbumin-derived T cell epitope SIINFEKL were generated by replacing parts of the peptide backbone by a poly-N-acylated amine (PAA) backbone with aromatic, heteroaromatic, and pseudoaromatic side chains that branch off of the main chain at the amine nitrogen. The structure of the PAAs was designed to position this side chain in the central epitope anchor pocket of the MHC molecule. A number of biologically active PAAs were found that induced cytolysis by the mouse cytotoxic T cell clone 4G3. Competition experiments with independent peptides that are known to bind to the restricting MHC molecule H-2K(b) suggest that the PAAs are bound by the MHC molecules at the same site as conventional peptide epitopes. The PAAs were active also in vivo and induced primary cytotoxic T cell responses in mice.

Acylation↗

PubMed2001

Spatially resolved single bead analysis: homogeneity, diffusion, and adsorption in cross-linked polystyrene.

Spatially resolved single bead analysis in the micrometer range was employed as a tool for evaluating homogeneity, diffusion, and adsorption in solid-phase supported reactions. Fluorescence microscopy (confocal and non-confocal) as well as IR microscopy were used to detect both the distribution of products and the formation of product gradients in representative reactions. For the first time, the optical slices of whole beads obtained by confocal fluorescence microscopy were compared with the fluorescence images of microtome-sliced beads. The experiments revealed that only physical slices of polystyrene beads deliver realistic representations of the distribution of fluorophores, and confirmed-in contrast to a recent report-the homogeneity of functional site distribution in polystyrene beads. Moreover, the pattern of product formation obtained from an acylation reaction as well as from an alkylation reaction were employed as probes to study the impact of bead size, diffusion, and adsorption on the reaction progress. A simulation of the diffusion process was conducted and compared with the experimental results. Diffusional control was found neither in the case of the alkylation nor in the case of the acylation reaction under investigation. As a consequence, the reaction progress was not a function of the bead sizes as proposed in the literature. Interestingly, in the case of rhodamine acylation with substoichiometric amounts an adsorption-controlled reaction was found. This result highlights the significance of adsorptive effects in solid-phase supported chemistry.

Adsorption↗

PubMed2001

Optical biosensors. Monitoring studies of glycopeptide antibiotic fermentation using white light interference.

This paper describes the design, characterization, and use of an optical biosensor suited for the process control of biotechnological processes. The detector principle is based on reflectometric interference spectroscopy (RIfS). RIfS enables a label-free, product-specific monitoring, with a future outline for on-line process control. The potential of the RIfS biosensor is exemplified by the qualitative and quantitative monitoring of the microbial production of vancomycin-type glycopeptide antibiotics.

Actinomycetales↗

PubMed2001

Superoxide dismutase mutations of familial amyotrophic lateral sclerosis and the oxidative inactivation of calcineurin.

Approximately 10% of all familial cases of amyotrophic lateral sclerosis (fALS) are linked to mutations in the SOD1 gene, which encodes the copper/zinc superoxide dismutase (CuZnSOD). Recently, wild-type CuZnSOD was shown to protect calcineurin, a calcium/calmodulin-regulated phosphoprotein phosphatase, from inactivation by reactive oxygen species. We asked whether the protective effect of CuZnSOD on calcineurin is affected by mutations associated with fALS. For this, we monitored calcineurin activity in the presence of mutant and wild-type SOD. We found that the degree of protection against inactivation of calcineurin by different SOD mutants correlates with the severity of the phenotype associated with the different mutations, suggesting a potential role for calcineurin-SOD1 interaction in the etiology of fALS.

Amyotrophic Lateral Sclerosis↗

PubMed2001

Cyclofunctionalization and free-radical-based hydrogen-transfer reactions. An iterative reaction sequence applied to the synthesis of the C(7)-C(16) subunit of zincophorin.

The strategy considered herein features an iodocyclofunctionalization/hydrogen-transfer reaction sequence for the elaboration of propionate motifs. Proceeding with excellent yield and diastereoselectivity, the synthetic sequence proposed gives access to the anti-anti dipropionate motif when the reduction step is performed under the control of the exocyclic effect. The tandem sequence is applied successfully to the synthesis of the C(7)-C(16) subunit of zincophorin, and iteration of the process gives the desired anti-anti-anti-anti polypropionate stereopentad. Modifications of the reaction sequence--including phenylselenocyclofunctionalization, carbonate hydrolysis, and chelation-controlled radical reduction reactions--lead to the formation of the anti-syn dipropionate motif with remarkable diastereocontrol.

Journal Article↗

PubMed2001

The Dictyostelium CARMIL protein links capping protein and the Arp2/3 complex to type I myosins through their SH3 domains.

Fusion proteins containing the Src homology (SH)3 domains of Dictyostelium myosin IB (myoB) and IC (myoC) bind a 116-kD protein (p116), plus nine other proteins identified as the seven member Arp2/3 complex, and the alpha and beta subunits of capping protein. Immunoprecipitation reactions indicate that myoB and myoC form a complex with p116, Arp2/3, and capping protein in vivo, that the myosins bind to p116 through their SH3 domains, and that capping protein and the Arp2/3 complex in turn bind to p116. Cloning of p116 reveals a protein dominated by leucine-rich repeats and proline-rich sequences, and indicates that it is a homologue of Acan 125. Studies using p116 fusion proteins confirm the location of the myosin I SH3 domain binding site, implicate NH(2)-terminal sequences in binding capping protein, and show that a region containing a short sequence found in several G-actin binding proteins, as well as an acidic stretch, can activate Arp2/3-dependent actin nucleation. p116 localizes along with the Arp2/3 complex, myoB, and myoC in dynamic actin-rich cellular extensions, including the leading edge of cells undergoing chemotactic migration, and dorsal, cup-like, macropinocytic extensions. Cells lacking p116 exhibit a striking defect in the formation of these macropinocytic structures, a concomitant reduction in the rate of fluid phase pinocytosis, a significant decrease in the efficiency of chemotactic aggregation, and a decrease in cellular F-actin content. These results identify a complex that links key players in the nucleation and termination of actin filament assembly with a ubiquitous barbed end-directed motor, indicate that the protein responsible for the formation of this complex is physiologically important, and suggest that previously reported myosin I mutant phenotypes in Dictyostelium may be due, at least in part, to defects in the assembly state of actin. We propose that p116 and Acan 125, along with homologues identified in Caenorhabditis elegans, Drosophila, mouse, and man, be named CARMIL proteins, for capping protein, Arp2/3, and myosin I linker.

Actin Depolymerizing Factors↗

PubMed2001

A triangle-square equilibrium of metallosupramolecular assemblies based on pd(II) and pt(II) corners and diazadibenzoperylene bridging ligands.

Tetraaryloxy-substituted diazadibenzoperylene bridging ligands 1a,b were employed in transition metal-directed self-assembly with Pd(II) and Pt(II) phosphane triflates 2a,b which resulted in complex dynamic equilibria between molecular triangles 3a-d and molecular squares 4a-d in solution. Characterization of the equilibria and assignment of the metallacycles was accomplished by (1)H and (31)P[(1)H] NMR spectroscopy in combination with electrospray ionization Fourier transform ion cyclotron mass spectrometry (ESI-FTICR-MS). It was found that the equilibria depend on several factors, such as the metal ion (Pd(2+) or Pt(2+)), the solvent, and the steric demand of the phenoxy substituents of the diazadibenzoperylene ligands 1a,b. Introduction of bulky tert-butyl groups in 1b shifts the equilibrium significantly in the direction of the molecular squares. Molecular dynamics simulations of the triangle and square structures revealed critical steric effects and restricted conformational flexibilities of the phosphane and diazadibenzoperylene ligands that help explain the distinct dynamic behavior observed in variable-temperature NMR studies. Concentration-dependent UV/vis and fluorescence spectroscopy revealed the limited stability of the assemblies and confirmed the reversible nature of the dynamic equilibria.

Journal Article↗