Showing papers by "University of Vienna published in 1995"

The envelope glycoprotein from tick-borne encephalitis virus at 2 Å resolution

Abstract: The crystallographically determined structure of a soluble fragment from the major envelope protein of a flavivirus reveals an unusual architecture. The flat, elongated dimer extends in a direction that would be parallel to the viral membrane. Residues that influence binding of monoclonal antibodies lie on the outward-facing surface of the protein. The clustering of mutations that affect virulence in various flaviviruses indicates a possible receptor binding site and, together with other mutational and biochemical data, suggests a picture for the fusion-activating, conformational change triggered by low pH.

Evolution and extinction in a changing environment: a quantitative-genetic analysis.

Abstract: Because of the ubiquity of genetic variation for quantitative traits, virtually all populations have some capacity to respond evolutionarily to selective challenges. However, natural selection imposes demographic costs on a population, and if these costs are sufficiently large, the likelihood of extinction will be high. We consider how the mean time to extinction depends on selective pressures (rate and stochasticity of environmental change, and strength of selection), population parameters (carrying capacity, and reproductive capacity), and genetics (rate of polygenic mutation). We assume that in a randomly mating, finite population subject to density-dependent population growth, individual fitness is determined by a single quantitative-genetic character under Gaussian stabilizing selection with the optimum phenotype exhibiting directional change, 'or random fluctuations, or both. The quantitative trait is de- termined by a finite number of freely recombining, mutationally equivalent, additive loci. The dynamics of evolution and extinction are investigated, assuming that the population is initially under mutation-selection-drift balance. Under this model, in a directionally changing environment, the mean phenotype lags behind the optimum, but on the average evolves parallel to it. The magnitude of the lag determines the vulnerability to extinction. In finite populations, stochastic variation in the genetic variance can be quite pronounced, and bottlenecks in the genetic variance temporarily can impair the population's adaptive capacity enough to cause extinction when it would otherwise be unlikely in an effectively infinite population. We find that maximum sustainable rates of evolution or, equivalently, critical rates of environmental change, may be considerably less than 10% of a phenotypic standard deviation per generation.

Stress signaling in yeast

Abstract: In the yeast Saccharomyces cerevisiae three positive transcriptional control elements are activated by stress conditions: heat shock elements (HSEs), stress response elements (STREs) and AP-1 responsive elements (AREs). HSEs bind heat shock transcription factor (HSF), which is activated by stress conditions causing accumulation of abnormal proteins. STREs mediate transcriptional activation by multiple stress conditions. They are controlled by high osmolarity via the HOG signal pathway, which comprises a MAP kinase module and a two-component system homologous to prokaryotic signal transducers. AREs bind the transcription factor Yap1p. The three types of control elements seem to have overlapping, but distinct functions. Some stress proteins encoded by HSE-regulated genes are necessary for growth of yeast under moderate stress, products of STRE-activated genes appear to be important for survival under severe stress and ARE-controlled genes may mainly function during oxidative stress and in the response to toxic conditions, such as caused by heavy metal ions.

Interpolation Errors in Wind Fields as a Function of Spatial and Temporal Resolution and Their Impact on Different Types of Kinematic Trajectories

Abstract: This paper discusses some of the uncertainties that influence kinematic trajectory calculations. The interpolation errors due to different interpolation schemes are examined by degrading high-resolution wind fields from a numerical weather prediction model with respect to space and time. Under typical circumstances, the greatest errors are due to temporal interpolation, followed by horizontal and vertical interpolation. Relative errors in the vertical wind are higher than those in the horizontal wind components. These errors are quite substantial and severely affect the accuracy of trajectories. For instance, a decrease of the temporal resolution from 3 to 6 h leads to average relative interpolation errors of 16% in the horizontal wind components and 40% in the vertical wind component. These errors cause mean transport deviations of 280 km for two-dimensional model-level trajectories and 600 km for three-dimensional trajectories after 96-h travel time. The substantial deviations for three-dimensi...

Epiluminescence Microscopy: A Useful Tool for the Diagnosis of Pigmented Skin Lesions for Formally Trained Dermatologists

Abstract: Background and Design: Epiluminescence microscopy (ELM) is a noninvasive technique that, by employing the optical phenomenon of oil immersion, makes subsurface structures of the skin accessible for in vivo examination and thus provides additional criteria for the clinical diagnosis of pigmented skin lesions. At present, almost all studies about the value and clinical importance of ELM are based on data derived from ELM experts (ie, dermatologists specifically trained in this technique). In the present study, we attempt to determine whether the clinical diagnosis of pigmented skin lesions is significantly improved using ELM and whether ELM-trained individuals and dermatologists not trained in this technique profit equally from this technique. Randomly selected histologically proven pigmented skin lesion specimens, photographed with (ELM) and without oil immersion (surface microscopy) were presented by slide projection to six ELM experts and 13 ELM nonexperts (ie, dermatologists not formally trained in ELM) for diagnosis. To evaluate the diagnostic performance of ELM experts and nonexperts with and without the oil immersion technique (ie, ELM vs surface microscopy), the following parameters were obtained: intraobserver and interobserver agreement by κ statistics and sensitivity and specificity of diagnostic performance. Results: Our results show that by usinbetter-ELM technique the ELM experts reach a substantially hetter intraobserver agreement than nonexperts (median κ, 0.56 vs 0.36). The interobserver agreement was markedly increased in the ELM experts group (average gain, 7%) but decreased in the ELM nonexperts group (average loss, 6%). The sensitivity of diagnosis was significantly increased in the ELM experts group (average gain, 10%), but decreased in the nonexperts group (average loss, 10%). Finally, the specificity of diagnosis was excellent in the ELM experts group, both with and without oil immersion (0.91) and was somewhat improved by ELM in the nonexperts group (0.77 vs 0.85). Conclusions: We conclude that the ELM technique increases sensitivity in formally trained dermatologists, but may decrease the diagnostic ability in dermatologists not formally trained in the ELM technique. Consequently, formal broad-based training in ELM should be offered to the dermatologic community. (Arch Dermatol. 1995;131:286-291)

Neuropathological Diagnostic-criteria for Creutzfeldt-jakob-disease (cjd) and Other Human Spongiform Encephalopathies (prion Diseases)

Abstract: Neuropathological diagnostic criteria for Creutzfeldt-Jakob disease (CJD) and other human transmissible spongiform encephalopathies (prion diseases) are proposed for the following disease entities: CJD - sporadic, iatrogenic (recognised risk) or familial (same disease in 1st degree relative): spongiform encephalopathy in cerebral and/or cerebellar cortex and/or subcortical grey matter; or encephalopathy with prion protein (PrP) immunoreactivity (plaque and/or diffuse synaptic and/or patchy/perivacuolar types). Gerstmann-Straussler-Scheinker disease (GSS) (in family with dominantly inherited progressive ataxia and/or dementia): encephalo(myelo)pathy with multicentric PrP plaques. Familial fatal insomnia (FFI) (in member of a family with PRNP178 mutation): thalamic degeneration, variable spongiform change in cerebrum. Kuru (in the Fore population). Without PrP data, the crucial feature is the spongiform change accompanied by neuronal loss and gliosis. This spongiform change is characterised by diffuse or focally clustered small round or oval vacuoles in the neuropil of the deep cortical layers, cerebellar cortex or subcortical grey matter, which might become confluent. Spongiform change should not be confused with non-specific spongiosis. This includes status spongiosus (''spongiform state''), comprising irregular cavities in gliotic neuropil following extensive neuronal (including also lesions of ''burnt-out'' ''spongy'' changes in brain oedema and metabolic encephalopathies, and artefacts such as superficial cortical, perineuronal, or perivascular vacuolation; focal changes indistinguishable from spongiform change may occur in some cases of Alzheimer's and diffuse Lewy body diseases. Very rare cases might not be diagnosed by these criteria. Then confirmation must be sought by additional techniques such as PrP immunoblotting, preparations for electron microscopic examination of scrapie associated fibrils (SAF), molecular biologic studies, or experimental transmission.

Identification of allergens in fruits and vegetables: IgE cross-reactivities with the important birch pollen allergens Bet v 1 and Bet v 2 (birch profilin)

Abstract: Background: In this study serum samples collected from 20 patients with birch pollen allergy were investigated. All patients had experienced allergic symptoms after contact with or ingestion of particular fresh fruits and vegetables known as birch pollen-related foods. Methods: Serum samples were tested by means of immunoblotting for IgE reactivities with proteins in extracts of birch pollen, apple, pear, celery, carrot, and potato. Anti-Bet v 1 and anti-Bet v 2 antibodies were used to investigate cross-reactivity. Inhibition studies were performed by preincubation of sera with recombinant Bet v 1 and Bet v 2. Results: IgE binding to proteins, corresponding to the major birch pollen allergen Bet v 1 and to Bet v 2 (birch pollen profilin) could be observed. An allergen homologous to Bet v 1 could be detected in apple, pear, and celery when a Bet v 1-specific monoclonal antibody was used. Testing a polyclonal rabbit anti-Bet v 2 antibody with extracts of the respective plants revealed the presence of profilins in every source tested. Inhibition with recombinant Bet v 1 and Bet v 2 led to complete blocking or marked reduction of IgE binding to proteins of comparable molecular weights in the respective food extracts, indicating IgE cross-reactivity. Conclusion: Our results indicate that many plant-derived food agents contain proteins with high homology to the birch pollen allergens Bet v 1 and Bet v 2 and must therefore be considered as potentially threatening for patients with tree pollen allergy. (J ALLERGY CLIN IMMUNOL 1995;95:962-9.)

Mutational meltdowns in sexual populations

Abstract: Although it is widely acknowledged that the gradual accumulation of mildly deleterious mutations is an important source of extinction for asexual populations, it is generally assumed that this process is of little relevance to sexual species. Here we present results, based on computer simulations and supported by analytical approximations, that indicate that mutation accumulation in small, random-mating monoecious populations can lead to mean extinction times less than a few hundred to a few thousand generations. Unlike the situation in obligate asexuals in which the mean time to extinction (te ) increases more slowly than linearly with the population carrying capacity (K), te increases approximately exponentially with K in outcrossing sexual populations. The mean time to extinction for obligately selfing populations is shown to be equivalent to that for asexual populations of the same size, but with half the mutation rate and twice the mutational effect; this suggests that obligate selfing, like obligate asexuality, is inviable as a long-term reproductive strategy. Under all mating systems, the mean time to extinction increases relatively slowly with the logarithm of fecundity, and mutations with intermediate effects (similar to those observed empirically) cause the greatest risk of extinction. Because our analyses ignore sources of demographic and environmental stochasticity, which have synergistic effects that exacerbate the accumulation of deleterious mutations, our results should yield liberal upper bounds to the mean time to extinction caused by mutational degradation. Thus, deleterious mutation accumulation cannot be ruled out generally as a significant source of extinction vulnerability in small sexual populations or as a selective force influencing mating-system evolution.

Effect of high-intensity focused ultrasound on human prostate cancer in vivo.

Abstract: Transrectal high-intensity focused ultrasound (HIFU) was recently established as a highly effective means of inducing contact and irradiation-free intraprostatic coagulative necrosis. This technique, therefore, appears potentially useful for treating localized prostate cancer (PC). To evaluate this issue, a total of 29 human prostates with localized cancer was subjected to HIFU treatment in vivo before radical retropubic prostatectomy. HIFU therapy was performed with the use of HIFU transducers with focal lengths of 3.0 cm (n = 3), 3.5 cm (n = 19), and 4.0 cm (n = 7), and the site intensity was varied from 1260 to 2000 W/cm2. The extent of intraprostatic necrosis was determined by planimetrical analysis of whole mount prostatic sections. Transrectal HIFU consistently induced sharply delineated intraprostatic coagulative necrosis within the target area, whereas alterations of perioprostatic structures were never observed. The cross-sectional area of necrosis increased from 1.1 +/- 0.7 cm2 (SD; n = 3; 3.0-cm focal length; 1428 W/cm2) to 1.2 +/- 0.7 cm2 (n = 2; 3.5-cm focal length; 1428 W/cm2), 1.8 +/- 0.17 cm2 (n = 8; 3.5-cm focal length; 1680 W/cm2), 2.8 +/- 0.32 cm2 (n = 9; 3.5-cm focal length; 2000 W/cm2) and 3.8 +/- 0.4 cm2 (n = 7; 4.0 cm focal length; 1260 W/cm2). HIFU beam transmission and the therapeutic effect were comparable in benign and malignant prostatic tissue. Interstitial thermometry (n = 6) revealed maximum intraprostatic temperatures in the focal zone up to 98.6 degrees C. Outside the focal zone and on the rectal wall, no significant temperature rises were noted. Subsequently, HIFU was applied to unilateral histologically proven T2a/T2b PC (n = 10) in an attempt to destroy all cancer before radical retropubic prostatectomy. PC was always correctly targeted. In 7 individuals, PC was partially (mean, 53%; range, 38-77%) destroyed; in the remaining 3 cases the entire tumor was ablated. Although these histological data permit no definitive conclusion on the clinical efficacy of this approach, transrectal HIFU seems to be an attractive novel minimally invasive treatment option for localized PC.

An international two-stage genome-wide search for schizophrenia susceptibility genes.

Abstract: Schizophrenia is thought to be a multifactorial disease with complex mode of inheritance. Using a two-stage strategy for another complex disorder, a number of putative IDDM-susceptibility genes have recently been mapped. We now report the results of a two-stage genome-wide search for genes conferring susceptibility to schizophrenia. In stage I, model-free linkage analyses of large pedigrees from Iceland, a geographical isolate, revealed 26 loci suggestive of linkage. In stage II, ten of these were followed-up in a second international collaborative study comprising families from Austria, Canada, Germany, Italy, Scotland, Sweden, Taiwan and the United States. Potential linkage findings of stage I on chromosomes 6p, 9 and 20 were observed again in the second sample. Furthermore, in a third sample from China, fine mapping of the 6p region by association studies also showed evidence for linkage or linkage disequilibrium. Combining our results with other recent findings revealed significant evidence for linkage to an area distal of the HLA region on chromosome 6p. However, in a fourth sample from Europe, the 6p fine mapping finding observed in the Chinese sample could not be replicated. Finally, evidence suggestive of locus heterogeneity and oligogenic transmission in schizophrenia was obtained.

Identification of "premyelination" by diffusion-weighted MRI.

Abstract: Objective The purpose of this study was to compare white matter maturation as demonstrated with diffusion-weighted MRI and with myelin-sensitive histological staining. Materials and methods The diffusion-, T1-, and T2-weighted SE MRI at 4.7 T was performed weekly in a total of 16 rat pups, aged from 5 days to 8 weeks, 2 animals evaluated per week. Heavily diffusion-weighted sequences were obtained with the diffusion-sensitizing gradient switched alternately in two orthogonal directions. To enhance signal intensity of anisotropic structures, a synthesized image (referred to as the "anisotropy index map") was constructed from the ratio of pairs of images acquired with diffusion sensitization of identical magnitude but orthogonal direction sensitivity. The anisotropy index maps were used for comparison with T1-weighted and heavily T2-weighted SE sequences and histological sections, respectively. Results The first evidence of diffusion anisotropy on anisotropy index maps preceded initial myelin as well as neurofibril staining by 5-12 days and T2 shortening by 2 weeks. The T1-weighted sequences did not yield visible changes and were not helpful for the assessment of ongoing white matter maturation in this model. Conclusion Magnetic resonance imaging signal intensity changes based on anisotropic water diffusion were demonstrated in regions of unmyelinated cerebral white matter tracts of albino rat pups before the onset of histologically detectable myelin. The ability of in vivo mapping of premyelinating white matter maturation indicates a new diagnostic use of MRI in evaluating cerebral white matter maturation.

Urokinase plasminogen activator receptor, beta 2-integrins, and Src-kinases within a single receptor complex of human monocytes.

Abstract: The glycosylphosphatidylinositol (GPI)-anchored membrane protein urokinase plasminogen activator-receptor (uPA-R; CD87) is one of the key molecules involved in migration of leukocytes and tumor cells. uPA bound to uPA-R provides the cell proteolytic potential used for degradation of extracellular matrix. uPA-R is also involved in induction of cell adhesion and chemotaxis. Here, we provide a molecular explanation for these uPA-R-related cellular events. By size fractionation of monocyte lysate and affinity isolation on its natural ligand uPA, we demonstrate uPA-R as a component of a receptor complex of relatively large size. Reprecipitation and immunoblotting techniques allowed us to detect the protein tyrosine kinases (PTKs) p60fyn, p53/56lyn, p58/64hck, and p59fgr as components of this "uPA-R complex". Activation of monocytes even with enzymatically inactivated uPA resulted in induction of tyrosine phosphorylation, suggesting modulation of uPA-R-associated PTKs upon ligand binding. In spite of their presence in large complexes, we did not find the GPI-linked proteins CD14, CD58, and CD59 in the uPA-R complex, which indicates the presence of different receptor domains containing GPI-linked proteins in monocytes. However, we identified the leukocyte integrins LFA-1 and CR3 as components of the uPA-R complex as indicated by coisolation of these molecules, as well as by cocapping and comodulation of uPA-R and leukocyte integrins on the monocyte surface. The assemblage of uPA-R, PTKs and membrane spanning beta 2-integrins in one receptor complex indicates functional cooperation. In regard to the involvement of these molecules in pericellular proteolysis, signal transduction, as well as adhesion and chemotactic movement, we suggest uPA-R complex as a potential cellular device for cell migration.

High-Glucose–Triggered Apoptosis in Cultured Endothelial Cells

Abstract: High ambient glucose concentration, linked to vascular complications in diabetes in vivo, modulates mRNA expression of fibronectin, collagen, tissue-type plasminogen activator, and plasminogen activator inhibitor and induces delayed replication and excess cell death in cultured vascular endothelial cells. To determine the role of high ambient glucose (30 mmol/l) in apoptosis, paired cultures of individual isolates of human umbilical vein endothelial cells (HUVECs) were exposed to both high (30 mmol/l) and low (5 mmol/l) concentrations of glucose for short-term (24, 48, and 72 h) and long-term (13 +/- 1 days) experiments. Incubation of HUVECs with high glucose for > 48 h increased DNA fragmentation (13.7 +/- 6.5% of total DNA, mean +/- SD) versus cultures kept in 5 mmol/l glucose (10.9 +/- 5.6%, P < 0.005), as measured by [3H]thymidine assays. Data were confirmed by apoptosis-specific fluorescence-activated cell sorter analysis of confluent HUVEC cultures, which displayed after long-term exposure to 30 mmol/l glucose a 1.5-fold higher prevalence of apoptosis than control cultures exposed to 5 mmol/l glucose (P < 0.005). In contrast, no increase in DNA fragmentation in response to 30 mmol/l glucose was seen for standardized cell lines (K 562, P 815, YT) and fibroblasts. Expression of clusterin mRNA, originally reported to be a molecular marker of apoptosis, was only slightly affected by short-term (24-h) high-glucose exposure but was significantly reduced after long-term incubation in 30 mmol/l glucose (82.2 +/- 13.8% of control) versus 5 mmol/l glucose, which questions the role of clusterin gene expression as a marker of apoptosis.(ABSTRACT TRUNCATED AT 250 WORDS)

The high affinity IgE receptor (Fc epsilon RI) mediates IgE-dependent allergen presentation.

Abstract: The discovery that the high affinity IgE receptor (Fc epsilon RI) is expressed on APCs of patients with atopic diseases raised the possibility that the functional importance of Fc epsilon RI in the pathogenesis of atopy may extend beyond its role in type I allergic reactions. Here we show that, following removal of in vivo-bound IgE by lactic acid treatment, targeting of allergens to monocytes by Ag-specific IgE critically depends on Fc epsilon RI expression. Even more importantly, lactic acid-treated, monocyte-enriched PBMCs present allergen to T cells 100- to 1000-fold more effectively if the allergen has been targeted to Fc epsilon RI on these cells via allergen-specific IgE. This mechanism may critically lower the atopic individual's threshold to mount allergen-specific T cell responses capable of promoting IgE production and delayed-type hypersensitivity reactions.

Antigenic oscillations and shifting immunodominance in HIV-1 infections

Abstract: A typical protein antigen contains several epitopes that can be recognized by cytotoxic T lymphocytes (CTL), but in a characteristic antiviral immune response in vivo, CTL recognize only a small number of these potential epitopes, sometimes only one, this phenomenon is known as immunodominance. Antigenic variation within CTL epitopes has been demonstrated for the human immunodeficiency virus HIV-1 (ref. 11) and other viruses and such 'antigenic escape' may be responsible for viral persistence. Here we develop a new mathematical model that deals with the interaction between CTL and multiple epitopes of a genetically variable pathogen, and show that the nonlinear competition among CTL responses against different epitopes can explain immunodominance. This model suggests that an antigenically homogeneous pathogen population tends to induce a dominant response against a single epitope, whereas a heterogeneous pathogen population can stimulate complicated fluctuating responses against multiple epitopes. Antigenic variation in the immunodominant epitope can shift responses to weaker epitopes and thereby reduce immunological control of the pathogen population. These ideas are consistent with detailed longitudinal studies of CTL responses in HIV-1 infected patients. For vaccine design, the model suggests that the major response should be directed against conserved epitopes even if they are subdominant.

Oligomeric rearrangement of tick-borne encephalitis virus envelope proteins induced by an acidic pH.

Abstract: The flavivirus envelope protein E undergoes irreversible conformational changes at a mildly acidic pH which are believed to be necessary for membrane fusion in endosomes. In this study we used a combination of chemical cross-linking and sedimentation analysis to show that the envelope proteins of the flavivirus tick-borne encephalitis virus also change their oligomeric structure when exposed to a mildly acidic environment. Under neutral or slightly alkaline conditions, protein E on the surface of native virions exists as a homodimer which can be isolated by solubilization with the nonionic detergent Triton X-100. Solubilization with the same detergent after pretreatment at an acidic pH, however, yielded homotrimers rather than homodimers, suggesting that exposure to an acidic pH had induced a simultaneous weakening of dimeric contacts and a strengthening of trimeric ones. The pH threshold for the dimer-to-trimer transition was found to be 6.5. Because the pH dependence of this transition parallels that of previously observed changes in the conformation and hydrophobicity of protein E and that of virus-induced membrane fusion, it appears likely that the mechanism of fusion with endosomal membranes involves a specific rearrangement of the proteins in the viral envelope. Immature virions in which protein E is associated with the uncleaved precursor (prM) of the membrane protein M did not undergo a low-pH-induced rearrangement. This is consistent with a protective role of protein prM for protein E during intracellular transport of immature virions through acidic compartments of the trans-Golgi network.

Efficient numerical methods in non-uniform sampling theory

Abstract: Summary. We present a new “second generation” reconstruction algorithm for irregular sampling, i.e. for the problem of recovering a band-limited function from its non-uniformly sampled values. The efficient new method is a combination of the adaptive weights method which was developed by the two first named authors and the method of conjugate gradients for the solution of positive definite linear systems. The choice of ”adaptive weights” can be seen as a simple but very efficient method of preconditioning. Further substantial acceleration is achieved by utilizing the Toeplitztype structure of the system matrix. This new algorithm can handle problems of much larger dimension and condition number than have been accessible so far. Furthermore, if some gaps between samples are large, then the algorithm can still be used as a very efficient extrapolation method across the gaps.

Serum IgG autoantibodies directed against the alpha chain of Fc epsilon RI: a selective marker and pathogenetic factor for a distinct subset of chronic urticaria patients?

Abstract: While it is well established that acute allergic urticaria is caused by degranulation of skin mast cells occurring after allergen/IgE-dependent cross-linking of high affinity IgE receptors (FcepsilonRI), the pathophysiologic mechanisms operative in chronic urticaria (CU) are less well understood. Some evidence points to the existence of histamine-releasing activity in the serum of CU patients which possibly acts via triggering of FcepsilonRI. In this study, we aimed to better characterize this anti-FcepsilonRIalpha reactivity of CU patients using affinity-purified, IgE-depleted IgG fractions of such individuals (CU-IgG). Using immobilized, recombinant soluble FcepsilonRIalpha as a a reaction target for Western blot studies, we found that 12/32 (37%) CU-IgG serum samples exhibited IgG autoreactivity against FcepsilonRI- alpha. These findings were confirmed by experiments demonstrating that immunoblot-reactive, but not immunoblot-nonreactive, CU-IgG preparations precipitated the FcepsilonRIalpha from FcepsilonRI- alphagamma-transfected cells. No anti-FcepsilonRIalpha reactivity was observed in IgG fractions from atopic dermatitis (AD) patients (0/15) or healthy control individuals (CO:0/15). As opposed to the selective occurrence of IgG anti-Fc epsilon RI alpha autoantibodies in CU patients, IgG anti-IgE antibodies were detected in all groups investigated (CU: 69%; AD: 73%; CO: 26%). While both types of autoantibodies can exhibit histamine-releasing properties, not all of the autoantibodies proved to be functional in vitro. Our results indicate that the occurrence of IgG anti-FcepsilonRIalpha reactivity defines an autoimmune-mediated subentity of CU and provide a basis for the development of new diagnostic procedures and, perhaps, therapeutic strategies for this disease.

Holins: form and function in bacteriophage lysis

Abstract: During the lytic cycle of most bacteriophages, a phage-encoded peptidoglycan-degrading activity is elaborated. At least four entirely distinct types of enzymes fulfill this role and are given the generic name ‘endolysin’. Endolysins characterized to date are synthesized without a signal sequence and thus accumulate fully folded and active in the cytosol during the vegetative phase. Small membrane proteins are required in order for endolysins to gain access to the peptidoglycan. Because the available data suggest that the membrane lesion formed by these proteins is stable and non-specific, these proteins have been given the designation ‘holins’ (‘hole’-formers). Analysis of the primary sequence suggests a simple membrane topology with two or more membrane-spanning helical domains and a highly charged, hydrophilic C-terminus. Comparison of the sequences of holins from phages of Gram-negative hosts suggests there are at least two major holin groups. Putative holin genes have also been found in bacteriophages of Gram-positive bacteria. Altogether, in phages of Eubacteria, 11 or more unrelated gene families which share the functional and structural characteristics of holins have been identified. Genetic and physiological analysis suggest that holins are primarily regulated at the level of function. Holin function is modulated in some cases by a second protein encoded by the holin gene. The primary regulation of holin function, however, appears to be intrinsic to the holin structure itself, since a missense allele of the S holin gene of phage λ has been found which abolishes the normal delay that allows the vegetative phase to generate a useful number of progeny.

Landscapes and Their Correlation Functions

Abstract: Fitness landscapes are an important concept in molecular evolution. Many important examples of landscapes in physics and combinatorial optimization, which are widely used as model landscapes in simulations of molecular evolution and adaptation, are "elementary," i.e., they are (up to an additive constant) eigenfunctions of a graph Laplacian. It is shown that elementary landscapes are characterized by their correlation functions. The correlation functions are in turn uniquely determined by the geometry of the underlying configuration space and the nearest neighbor correlation of the elementary landscape. Two types of correlation functions are investigated here: the correlation of a time series sampled along a random walk on the landscape and the correlation function with respect to a partition of the set of all vertex pairs.

The adaptive advantage of phenotypic memory in changing environments.

Abstract: The adaptive value of carry-over effects, the persistence of induced phenotypes for several generations despite the change in the conditions that first induced these phenotypes, is studied in the framework of a simple model. Three different organismal strategies-non-inducible (genetic), completely inducible (plastic), and intermediate (carry-over)-are compared in fitness terms within three different environments. Analytical results and numerical simulations show that carry-over effects can have an advantage in stochastic environments even over organisms with high adaptive plasticity. We argue that carry-over effects represent an adaptive mechanism on the ecological timescale that fills the gap between short-term individual adaptations and long-term evolutionary adaptations. An extension of the concept of plasticity to incorporate the time dimension and include the stability of induced phenotypes through both clonal and sexual generations, is suggested.

Clinical importance of hepatic cytochrome P450 in drug metabolism

Abstract: (1995). Clinical Importance of Hepatic Cytochrome P450 in Drug Metabolism. Drug Metabolism Reviews: Vol. 27, No. 3, pp. 397-417.

Quantitative detection of reverse transcriptase-PCR products by means of a novel and sensitive DNA stain.

Abstract: We constructed a plasmid for the in vitro synthesis of a competitor RNA for use as an internal exogenous control during reverse transcriptase--PCR (RT-PCR) detection of epidermal growth factor receptor (EGFR) expression. The competitor RNA harbors a 32-base deletion compared with wild-type EGFR mRNA and generates a PCR product that is easily distinguished from the wild-type PCR product by agarose gel electrophoresis. We encountered the problem of heteroduplex formation during later stages of PCR, which could be solved by decreasing the PCR cycle number. This was accompanied by a significant loss of sensitivity. Sensitivity could be restored by using a novel and extremely sensitive DNA stain (SYBR Green I) instead of ethidium bromide.

Molecular Characterization of Api g 1, the Major Allergen of Celery (Apium graveolens), and Its Immumological and Structural Relationships to a Group of 17-kDa Tree Pollen Allergens

Abstract: Individuals suffering from immediate hypersensitivity (type-I allergy) to a particular pollen frequently display intolerance to several foods of plant origin. In this respect, individuals sensitized to birch pollen and/or mugwort pollen frequently display type-I allergic symptoms after ingestion of celery. In this study, we expressed the major allergenic protein of celery, Api g 1, which is responsible for the birch-celery syndrome, in the form of a non-fusion protein. The open reading frame of the cDNA of Api g 1 codes for a protein of 153 amino acids with a molecular mass of 16.2 kDa and 40% identity (60% similarity) to the major allergen of birch pollen, Bet v 1. Furthermore, Api g 1 exhibited similar characteristics to (a) two proteins in parsley induced by fungal infection, (b) the major tree pollen allergens and (c) pathogenesis-related and stress-induced proteins in other plant species. The reactivity of recombinant Api g 1 with IgE antibodies present in sera from celery intolerant patients was comparable to that of the natural celery allergen. Cross-reactivity with Bet v 1 was proven by cross-inhibition experiments, which provides further support for the existence of the birch-celery syndrome and for the suggestion that allergies to some vegetable foods are epiphenomena to allergies caused by inhalation of tree pollen.