Showing papers by "University of Erlangen-Nuremberg published in 1997"

‘Sniffin’ Sticks': Olfactory Performance Assessed by the Combined Testing of Odor Identification, Odor Discrimination and Olfactory Threshold

Abstract: 'Sniffin' Sticks' is a new test of nasal chemosensory performance based on pen-like odor dispensing devices. It comprises three tests of olfactory function, namely tests for odor threshold (n-butanol, testing by means of a single staircase), odor discrimination (16 pairs of odorants, triple forced choice) and odor identification (16 common odorants, multiple forced choice from four verbal items per test odorant). After extensive preliminary investigations the tests were applied to a group of 104 healthy volunteers (52 female, 52 male, mean age 49.5 years, range 18-84 years) in order to establish test-retest reliability and to compare them with an established measure of olfactory performance (the Connecticut Chemosensory Clinical Research Center Test, CCCRC). Performance decreased with increasing age of the subjects (P < 0.001). Coefficients of correlation between sessions 1 and 2 were 0.61 for thresholds, 0.54 for discrimination and 0.73 for identification. Butanol thresholds as obtained with the CCCRC increased as a function of age; this relation to the subjects' age was not found for the CCCRC odor identification task. The test-retest reliability for CCCRC thresholds was 0.36, for odor identification it was 0.60. It is concluded that 'Sniffin' Sticks' may be suited for the routine clinical assessment of olfactory performance.

Computer graphics—principles and practice

Abstract: These are the short notes for a two hour tutorial on principles and practice of computer graphics and scientific visualization. They are intended to summarize the contents of the tutorial transparencies and slides but they cannot completely replace them since restrictions in space and print quality do not permit the inclusion of figures and example images. For further reference the following standard text should be consulted: [3, 8, 5, 1, 6, 2, 9]

Immunosuppressive effects of apoptotic cells

Abstract: Apoptotic cell death is important in the development and homeostasis of multicellular organisms1 and is a highly controlled means of eliminating dangerous, damaged or unnecessary cells without causing an inflammatory response or tissue damage1,2. We now show that the presence of apoptotic cells during monocyte activation increases their secretion of the anti-inflammatory and immunoregulatory cytokine interleukin 10 (IL-10) and decreases secretion of the proinflammatory cytokines tumour necrosis factor-α (TNF-α), IL-1 and IL-12. This may inhibit inflammation and contribute to impaired cell-mediated immunity in conditions associated with increased apoptosis, such as viral infections, pregnancy, cancer and exposure to radiation.

OFDM with reduced peak-to-average power ratio by optimum combination of partial transmit sequences

Abstract: The authors propose a very effective and flexible peak power reduction scheme for orthogonal frequency division multiplexing (OFDM) with almost vanishing redundancy. This new method works with arbitrary numbers of subcarriers and unconstrained signal sets. The core of the proposal is to combine partial transmit sequences (PTS) to minimise the peak-to-average power ratio distortion.

Viral FLICE-inhibitory proteins (FLIPs) prevent apoptosis induced by death receptors

Abstract: Viruses have evolved many distinct strategies to avoid the host's apoptotic response Here we describe a new family of viral inhibitors (v-FLIPs) which interfere with apoptosis signalled through death receptors and which are present in several gamma-herpesviruses (including Kaposi's-sarcoma-associated human herpesvirus-8), as well as in the tumorigenic human molluscipoxvirus v-FLIPs contain two death-effector domains which interact with the adaptor protein FADD, and this inhibits the recruitment and activation of the protease FLICE by the CD95 death receptor Cells expressing v-FLIPs are protected against apoptosis induced by CD95 or by the related death receptors TRAMP and TRAIL-R The herpesvirus saimiri FLIP is detected late during the lytic viral replication cycle, at a time when host cells are partially protected from CD95-ligand-mediated apoptosis Protection of virus-infected cells against death-receptor-induced apoptosis may lead to higher virus production and contribute to the persistence and oncogenicity of several FLIP-encoding viruses

Tracer particles and seeding for particle image velocimetry

Abstract: The size specifications for suitable tracer particles for particle image velocimetry (PIV), particularly with respect to their flow tracking capability, are discussed and quantified for several examples. A review of a wide variety of tracer materials used in recent PIV experiments in liquids and gases indicates that appropriately sized particles have normally been used. With emphasis on gas flows, methods of generating seeding particles and for introducing the particles into the flow are described and their advantages are discussed.

Specific C-Receptors for Itch in Human Skin

Abstract: In microneurography experiments 56 unmyelinated nerve fibers were studied in the cutaneous branch of the peroneal nerve of healthy volunteers. Units were identified with the “marking” technique as mechanically and heat-responsive (CMH; n = 30), heat-responsive (CH; n = 13), or unresponsive to mechanical and heat stimulation (CM i H i ; n = 13). None of the units showed spontaneous activity. These units were tested for responsiveness to iontophoresis of histamine (1 mA, 20 sec) from a small probe (diameter, 6 mm), which induced itch sensations lasting several minutes. Twenty-three units were unresponsive to histamine, and 25 units responded weakly with a few spike discharges after iontophoresis. Eight units, however, responded with sustained discharges to histamine, and their discharge patterns were matching the time course of the itch sensations. All C-units in this group were mechanically insensitive, and five of them were heat-responsive. They had very low conduction velocities of only 0.5 m/sec, on average, which is significantly lower than conduction velocities of the “polymodal” CMH units. This slow conduction velocities attributable to small axon diameters may be one reason why these units have not been encountered in previous studies. Histamine-sensitive C-units had very large innervation territories extending up to a diameter of 85 mm on the lower leg. We conclude that these C-fibers represent a new class of afferent nerve fibers with particularly thin axons but excessive terminal branching. This type of C-fiber probably represents the afferent units long searched for mediating itch sensations.

Range of antinuclear antibodies in "healthy" individuals

Abstract: Objective. To determine the range of antinuclear antibodies (ANA) in “healthy” individuals compared with that in patients with systemic lupus erythematosus (SLE), systemic sclerosis (SSc; scleroderma), Sjogren's syndrome (SS), rheumatoid arthritis (RA), or soft tissue rheumatism (STR). Methods. Fifteen international laboratories experienced in performing tests for ANA by indirect immunofluorescence participated in analyzing coded sera from healthy individuals and from patients in the 5 different disease groups described above. Except for the stipulation that HEp-2 cells should be used as substrate, each laboratory used its own in-house methodology so that the data might be expected to reflect the output of a cross-section of worldwide ANA reference laboratories. The sera were analyzed at 4 dilutions: 1:40, 1:80, 1:160, and 1:320. Results. In healthy individuals, the frequency of ANA did not differ significantly across the 4 age subgroups spanning 20–60 years of age. This putatively normal population was ANA positive in 31.7% of individuals at 1:40 serum dilution, 13.3% at 1:80, 5.0% at 1:160, and 3.3% at 1:320. In comparison with the findings among the disease groups, a low cutoff point at 1:40 serum dilution (high sensitivity, low specificity) could have diagnostic value, since it would classify virtually all patients with SLE, SSc, or SS as ANA positive. Conversely, a high positive cutoff at 1:160 serum dilution (high specificity, low sensitivity) would be useful to confirm the presence of disease in only a portion of cases, but would be likely to exclude 95% of normal individuals. Conclusion. It is recommended that laboratories performing immunofluorescent ANA tests should report results at both the 1:40 and 1:160 dilutions, and should supply information on the percentage of normal individuals who are positive at these dilutions. A low-titer ANA is not necessarily insignificant and might depend on at least 4 specific factors. ANA assays can be a useful discriminant in recognizing certain disease conditions, but can create misunderstanding when the limitations are not fully appreciated.

Generation of Mature Dendritic Cells from Human Blood

Abstract: Efficient methods to generate large numbers of dendritic cells have been developed in the past five years. Caux et al.1 have introduced the approach to grow dendritic cells from rare CD34+ progenitor cells in (cord) blood using GM-CSF and TNF-α as the critical cytokines. On the other hand, Sallusto et al.2 and Romani et al.3 have established procedures that make use of the more abundant monocytic CD34-negative and CD14+precursors in peripheral blood. GM-CSF and IL-4 were the necessary cytokines. Both approaches have since been widely used, even up to the stage of clinical trials.

P- and E-selectin mediate recruitment of T-helper-1 but not T-helper-2 cells into inflamed tissues

Abstract: When activated, T helper cells differentiate into one of two subsets, Th1 and Th2, characterized by distinct profiles of cytokine production. Th1 cells activate pro-inflammatory effector mechanisms involved in protection and autoimmunity, whereas Th2 cells induce humoral and allergic responses and downregulate local inflammation. Apart from differences in the repertoire of cytokines, no phenotypic attributes are established that distinguish the two subsets. Here we show that Th1 cells, but not Th2 cells, are able to bind to P-selectin and E-selectin. Moreover, only Th1 cells can efficiently enter inflamed sites in Th1-dominated models, such as sensitized skin or arthritic joints, but not in a Th2-dominated allergic response. Immigration of Th1 cells into inflamed skin can be blocked by antibodies against P- and E-selectin. These results provide evidence for adhesion mechanisms to distinguish between the two T helper subsets and mediate their differential trafficking. They indicate that selective recruitment is an additional level of regulation for both effector function profile and character of a local immune response.

Intrinsic SiC/SiO2 Interface States

Abstract: The energy distribution of electron states at SiC/SiO 2 interfaces produced by oxidation of various (3C, 4H, 6H) SiC polytypes is studied by electrical analysis techniques and internal photoemission spectroscopy. A similar distribution of interface traps over the SiC bandgap is observed for different polytypes indicating a common nature of interfacial defects. Carbon clusters at the SiC/SiO 2 interface and near-interfacial defects in the SiO 2 are proposed to be responsible for the dominant portion of interface traps, while contributions caused by dopant-related defects and dangling bonds at the SiC surface are not observed.

Dendritic Cells as Adjuvants for Immune-mediated Resistance to Tumors

Abstract: T he Problem: Tumor Immunity Is Not Effectively Induced in Tumor-bearing Hosts. Animal experiments as well as clinical experience, notably in melanoma, indicate that the immune system can recognize and kill tumor cells. In particular , CTLs recognize MHC class I–peptide complexes on the tumor cell surface, and the peptides are derived from nonmutated or mutated genes that can be primarily expressed in the tumors (1–3). Why then does the immune system fail to eradicate most antigenic cancers? One clue is the observation that CTLs for melanoma and other human tumors are not known to be expanded. For example, CTL precursors are not increased in melanoma patients, whereas humans who are infected with a virus like influenza frequently show expansions in virus-specific CTLp. Therefore tumors have antigens for T cells, but these do not appear to be immunogenic in vivo. The Hypothesis: Lack of Tumor Antigen Presentation by Den-dritic Cells In Vivo Is a Major Problem that Can Be Bypassed by Delivery of Tumor Antigens on Autologous Dendritic Cells. One possible reason for a lack of tumor immunity is that the an-tigens are not being presented by dendritic cells (DCs). DCs are antigen-presenting cells that are specialized to prime helper and killer T cells in vivo (recently reviewed in references 4 and 5). To do so, DCs perform a series of coordinated tasks. Immature DCs develop from hematopoi-etic progenitors and are strategically located at body surfaces and in interstitial spaces of most tissues. There, DCs are equipped to capture antigens and to produce large numbers of immunogenic MHC–peptide complexes. In the presence of maturation-inducing stimuli such as inflammatory cytokines or stimulation via CD40 (6), DCs upregulate adhesion and costimulatory molecules to become more potent , terminally differentiated, stimulators of T cell immunity. At the same time, numerous intracellular MHC II compartments seem to discharge MHC II–peptide complexes to the cell surface where they can be unusually long lived (7, 8). DCs also migrate to secondary lymphoid organs to select and stimulate rare antigen-specific T cells (9, 10). Nonetheless, there is no evidence that DCs capture and process antigens from malignant cells in vivo. Tumors, for example, can make products like IL-10 (11, 12) and vascu-lar endothelial growth factor (13) that could decrease DCs development and function. Is a lack of tumor antigen presentation by DCs a major problem in generating T cell– mediated resistance to tumors in vivo? If so, …

Absence of integrin alpha 7 causes a novel form of muscular dystrophy.

Abstract: Integrin alpha 7 beta 1 is a specific cellular receptor for the basement membrane protein laminin-1 (refs 1,2), as well as for the laminin isoforms -2 and -4 (ref. 3). The alpha 7 subunit is expressed mainly in skeletal and cardiac muscle and has been suggested to be involved in differentiation and migration processes during myogenesis. Three cytoplasmic and two extracellular splice variants that have been described are developmentally regulated and expressed in different sites in the muscle. In adult muscle, the alpha 7A and alpha 7B subunits are concentrated in myotendinous junctions but can also be detected in neuromuscular junctions and along the sarcolemmal membrane. To study the potential involvement of alpha 7 integrin, during myogenesis and its role in muscle integrity and function, we generated a null allele of the alpha 7 gene (Itga7) in the germline of mice by homologous recombination in embryonic stem (ES) cells. Surprisingly, mice homozygous for the mutation are viable and fertile, indicating that the alpha 7 beta 1 integrin is not essential for myogenesis. However, histological analysis of skeletal muscle revealed typical symptoms of a progressive muscular dystrophy starting soon after birth, but with a distinct variability in different muscle types. The observed histopathological changes strongly indicate an impairment of function of the myotendinous junctions. These findings demonstrate that alpha 7 beta 1 integrin represents an indispensable linkage between the muscle fibre and the extracellular matrix that is independent of the dystrophin-dystroglycan complex-mediated interaction of the cytoskeleton with the muscle basement membrane.

Design, fabrication and testing of microlens arrays for sensors and microsystems

Abstract: We report on our activities in design, fabrication, characterization and system integration of refractive microlens arrays for sensors and microsystems. Examples for chemical analysis systems (, blood gas sensor), neural networks and multiple pupil imaging systems for photolithography (microlens and smart mask lithography) are presented.

Cell-homologous genes in the Kaposi's sarcoma-associated rhadinovirus human herpesvirus 8: determinants of its pathogenicity?

Abstract: The epidemiology of Kaposi’s sarcoma (KS) among patients with AIDS has suggested that a sexually transmitted infectious agent other than human immunodeficiency virus (HIV) must be involved in its pathogenesis. KS is about 20,000 times more common in patients with AIDS than in the general population of the United States, and other immunosuppressed groups develop KS approximately 600 times more frequently than the healthy population. During the first decade of the AIDS epidemic, about 20% of homosexual and bisexual patients developed KS, in contrast to about 1% of men with hemophilia. Women were more likely to have KS if their partners were bisexual rather than parenterally infected men (4). This led to a broad search by PCR in patients with KS for the presence of viruses known to affect humans, such as cytomegalovirus (53, 57), human herpesvirus 6 (HHV-6) (29), and BK virus (43). Some of these viruses were found frequently in KS biopsy specimens, but none of them was consistently present (25, 30). A new era of KS research began when Y. Chang, P. S. Moore, and their colleagues (14) detected by representational difference analysis (35) two short DNA fragments from a herpesvirus that was distinct from all previously known herpesviruses. Remarkably, more than 90% of KS tissues obtained from patients with AIDS contained the virus. The viral sequences were not present in biopsy specimens from patients without AIDS but were found in 15% of non-KS tissue DNA from patients with AIDS. The new virus, tentatively termed KS-associated herpesvirus or HHV-8, was soon found to be common in all epidemiological forms of KS (24). Viral DNA is consistently present in AIDS-associated KS lesions (1, 36) and in the vast majority of classical European-Mediterranean KS lesions (1, 18), while it is far less frequent in uninvolved skin of patients with KS and in the various biopsy specimens from Caucasian patients without KS and HIV. AIDS-associated African KS specimens (92%) and non-AIDS-associated KS lesions in Uganda (85%) had the virus (16). Based on PCR, the prevalence of HHV-8 appeared to be high in the general population in Uganda, while searches in non-KS tumors and in normal tissues showed that the virus is rarely detectable in Caucasians. While some lymphomas carry other herpesviruses, such as Epstein-Barr virus (EBV) and HHV-6 (22), those specimens did not contain HHV-8 DNA. However, one type of lymphoid tumor, the AIDS-associated body cavity-based lymphoma (BCBL), was positive for HHV-8 DNA by PCR and Southern

Aerobic glycolysis by proliferating cells: a protective strategy against reactive oxygen species.

Abstract: Our laboratory has reported that glucose is essential for glycolytic enzyme induction and proliferation of mitogen-activated rat thymocytes (41). Here we show that: 1) Resting thymocytes meet their ATP demand mainly by oxidative glucose breakdown (88%), whereas proliferating thymocytes produce 86% by glycolytic degradation of glucose to lactate and only 14% by oxidation to CO2 and water. 2) In contrast to nonstimulated resting thymocytes, production of PMA primed reactive oxygen species (ROS) in the proliferating cells is nearly abolished. 3) Consistent with this finding, no ROS formation is observed in proliferating human promyelocytic HL-60 cells, whereas differentiated, nonproliferating HL-60 cells exert a marked response upon priming with PMA. 4) The observed reduction of ROS formation by resting thymocytes incubated with pyruvate suggests a function of pyruvate as an H(2)O(2) scavenger. 5) The respiratory chain is a potential origin for ROS because inhibitors of the mitochondrial electron transport s...

Deep Defect Centers in Silicon Carbide Monitored with Deep Level Transient Spectroscopy

Abstract: Electrical data obtained from deep level transient spectroscopy investigations on deep defect centers in the 3C, 4H, and 6H SiC polytypes are reviewed Emphasis is put on intrinsic defect centers observed in as-grown material and subsequent to ion implantation or electron irradiation as well as on defect centers caused by doping with or implantation of transition metals (vanadium, titanium, chromium, and scandium)

Time-resolved coherent photoelectron spectroscopy of quantized electronic states on metal surfaces

Abstract: Time-resolved two-photon photoemission in combination with the coherent excitation of several quantum states was used to study the ultrafast electron dynamics of image-potential states on metal surfaces. For a (100) surface of copper, the spectroscopy of quantum beats made previously unresolved high-order states (quantum numbern ≥ 4) experimentally accessible. By exciting electrons close to the vacuum level, electron wave packets could be created and detected that described the quasi-classical periodic motion of weakly bound electrons. They traveled more than 200 A away from the surface and oscillated back and forth with a period of 800 femtoseconds.

Herpes viral cyclin/Cdk6 complexes evade inhibition by CDK inhibitor proteins.

Abstract: The passage of mammalian cells through the restriction point into the S phase of the cell cycle is regulated by the activities of Cdk4 and Cdk6 complexed with the D-type cyclins and by cyclin E/Cdk2 (refs 1,2,3). The activities of these holoenzymes are constrained by CDK inhibitory proteins4,5. The importance of the restriction point is illustrated by its deregulation in many tumour cells6,7 and upon infection with DNA tumour viruses8. Here we describe the properties of cyclins encoded by two herpesviruses, herpesvirus saimiri (HVS) which can transform blood lymphocytes9 and induce malignancies of lymphoid origin in New World primates9,10, and human herpesvirus 8 (HHV8) implicated as a causative agent of Kaposi's sarcoma and body cavity lymphomas11,12. Both viral cyclins form active kinase complexes with Cdk6 that are resistant to inhibition by the CDK inhibitors p16Ink4a, p21Cip1and p27Kip1. Furthermore, ectopic expression of a viral cyclin prevents G1 arrest imposed by each inhibitor and stimulates cell-cycle progression in quiescent fibroblasts. These results suggest a new mechanism for deregulation of the cell cycle and indicate that the viral cyclins may contribute to the oncogenic nature of these viruses.

Pyoderma gangrenosum: a report of 44 cases with follow-up.

Abstract: Results of a study of 44 patients with pyoderma gangrenosum (PG) are presented. Each patient was diagnosed using standardized diagnostic criteria and followed up systematically. Thirty patients were women and 14 men. Their mean age was 50 years (range 11-80). Twenty patients had idiopathic and 14 parainflammatory occurrences (e.g. ulcerative colitis, Crohn's disease), whereas in 10 patients an associated haemoproliferative disease or neoplasia was noted. Whereas idiopathic and parainflammatory PG was found predominantly in women, the association with haemoproliferative diseases occurred more often in men. The lower legs and feet represented the typical predilection sites. Fifty-two per cent of patients had one lesion, 37% had up to five, and 11% had more than five lesions. Histologically, lymphocytic and/or leucocytoclastic vasculitis was present in 73% of the biopsy specimens obtained from the borders of the lesions. Long-term follow-up (n = 42, median follow-up 26.5 months) revealed that eight patients had died, in six cases due to the PG and/or the underlying diseases. Of the remaining 34 patients, 44% are in complete remission without further treatment, whereas continuing therapy is needed in 56%. No difference between idiopathic and parainflammatory PG was demonstrable in the follow-up and in no patient with idiopathic PG was a possibly related disease diagnosed in the follow-up. These data suggest that PG should be considered to be an independent disease and not a purely cutaneous complication in most patients.

OFDM with reduced peak-to-average power ratio by multiple signal representation

Abstract: Deux methodes sont proposees pour reduire la puissance de crete ďun signal ofdm. Elles sont efficaces, souples et sans distorsion et elles apportent un accroissement faible de la complexite des calculs. De plus elles fonctionnent avec des nombres quelconques. La premiere methode produit plusieurs signaux multiporteurs et choisit celui qui a la plus faible puissance de crete pour la transmission. La seconde combine des sequences transmises partielles pour minimiser le facteur de crete. Apres ľanalyse theorique, les performances sont evaluees par simulation.

Human herpesvirus 8 encodes a homolog of interleukin-6.

Abstract: Kaposi's sarcoma is a multifocal lesion that is reported to be greatly influenced by cytokines such as interleukin-6 (IL-6) and oncostatin M. DNA sequences of a novel human gammaherpesvirus, termed human herpesvirus 8 (HHV-8) or Kaposi sarcoma-associated herpesvirus, have been identified in all epidemiological forms of Kaposi's sarcoma with high frequency. The presence of HHV-8 DNA is also clearly associated with certain B-cell lymphomas (body cavity-based lymphomas) and multicentric Castleman's disease. Sequence analysis of a 17-kb fragment revealed that adjacent to a block of conserved herpesvirus genes (major DNA-binding protein, glycoprotein B, and DNA polymerase), the genome of HHV-8 encodes structural homolog of IL-6. This cytokine is involved not only in the pathogenesis of Kaposi's sarcoma but also in certain B-cell lymphomas and multicentric Castleman's disease. The viral counterpart of IL-6 (vIL-6) has conserved important features such as cysteine residues involved in disulfide bridging or an amino-terminal signal peptide. Most notably, the region known to be involved in receptor binding is highly conserved in vIL-6. This conservation of essential features and the remarkable overlap between diseases associated with HHV-8 and diseases associated with IL-6 disregulation clearly suggest that vIL-6 is involved in HHV-8 pathogenesis.

Doping of SiC by Implantation of Boron and Aluminum

Abstract: Experimental studies on aluminum (Al) and boron (B) implantation in 4H/6H SiC are reported; the implantation is conducted at room temperature or elevated temperatures (500 to 700 C). Both Al and B act as ``shallow`` acceptors in SiC. The ionization energy of these acceptors, the hole mobility and the compensation in the implanted layers are obtained from Hall effect investigations. The degree of electrical activity of implanted Al/B atoms is determined as a function of the annealing temperature. Energetically deep centers introduced by the Al{sup +}/B{sup +} implantation are investigated. The redistribution of implanted Al/B atoms subsequent to anneals and extended lattice defects are monitored. The generation of the B-related D-center is studied by coimplantation of Si/B and C/B, respectively. (orig.) 60 refs.

Polymer Bulk Erosion

Abstract: A theoretical model was developed that explains why the erosion of biodegradable bulk-eroding polymers follows the same kinetics on different time scales. poly(d,l-lactic acid-co-glycolic acid) 1:1 of various molecular weight served as a model compound. After a period of no mass loss, these polymers erode by spontaneously losing more than half of their mass, which is typical for bulk-eroding polymers in general. Until now this was explained with degradation accelerated by auto catalysis inside the bulk compared to the surface of polymer matrices. To investigate if other mechanisms might be involved as well, an erosion model was developed. It assumes that erosion can start only after the polymers are degraded to water-soluble products and after these degraded polymer areas have contact to the erosion medium. Simulations revealed that percolation phenomena may be responsible for the spontaneous mass loss and that the time of onset is a function of the degradation velocity. Degradation rate constants determi...

Glycoconjugated aroma compounds: occurrence, role and biotechnological transformation.

Abstract: The present paper reviews the occurrence of glycosidically bound aroma compounds in the plant kingdom and discusses different hypotheses concerning their role in plants. Emphasis is on biotechnological methods for flavor release and flavor enhancement through enzymatic hydrolysis of glycoconjugated aroma substances.