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  • 1
    Electronic Resource
    Electronic Resource
    Transient growth in circular pipe flow. I. Linear disturbances (1994)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 6 (1994), S. 3643-3651 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The behavior of very low-amplitude disturbances in a circular pipe is considered. Direct simulation of the Navier–Stokes equations is used to compute the evolution of two- and three-dimensional waves and the results are found to be in good agreement with solutions to the Orr–Sommerfeld equation for Hagen–Poiseuille flow. Transient growth mechanisms are also investigated computationally, in which case it is found that the growth of disturbances with large but finite streamwise wavelength exhibits a very rich structure of temporal evolution depending on the particular initial condition chosen. Comparison with recent results reported by Bergström on optimal disturbances is also given. In Part II of this study these findings will be extended to the nonlinear development of like disturbances.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.868421
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  • 2
    Electronic Resource
    Electronic Resource
    Transient growth in circular pipe flow. II. Nonlinear development (1994)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 6 (1994), S. 3652-3664 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The Navier–Stokes equations for circular pipe flow are integrated using direct numerical simulation for the case of transitional Reynolds number. Previous work on linear disturbances (reported in Part I) is exploited for the simulation of low to moderate amplitude disturbances where it is found that the transient growth mechanism persists in the nonlinear development with the evolution attributable to the linear mechanism remaining of considerable significance. A hypothesis of Trefethen et al. [Science 261, 578 (1993)] concerning the role of nonlinearity in the transition process and ultimately in turbulence is elucidated and given support. It is suggested that nonlinearity is essential in continually perturbing the eigenmodes of the flow in such a way that each mode is never permitted to relax to its least stable eigenstate (damped in the subcritical case). In this way, the linear growth mechanism can be regarded as an underpinning component of the general nonlinear feedback insofar as it is the only part which can extract energy from the mean flow and thus yield a net increase in disturbance energy. The physical aspects of the flow simulations are consistent with puff formation where, using a pair of helical waves as initial data, a sharp trailing front is formed naturally; axisymmetric ring vortices are generated and the general flow characteristics are in broad agreement with experiment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.868422
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  • 3
    Electronic Resource
    Electronic Resource
    Deficiency in immunoglobulin G2 antibodies against staphylococcal enterotoxin C1 defines a subgroup of patients with atopic dermatitis (2005)
    Oxford, UK : Blackwell Science Ltd
    Clinical & experimental allergy 35 (2005), S. 0 
    Details
    ISSN: 1365-2222
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Background and aim Atopic dermatitis (AD) is a common chronic inflammatory skin disease often accompanied by cutaneous Staphylococcus aureus colonization and, in this regard, especially complicated by the presence of superantigen-producing strains. Because IgG antibodies comprise an important defence mechanism of the adaptive immune system against bacteria, it was investigated whether AD patients have an abnormal pattern or distribution of superantigen-specific IgG subclass antibodies in association with disease severity and activity.Methods Staphylococcal enterotoxin B (SEB) and staphylococcal enterotoxin C1 (SEC1) specific IgG antibody subclasses were assessed in n=89 adult AD patients with mild to severe disease activity as determined by the SCORAD score and in n=28 healthy age-matched controls. Results were correlated with the current status of bacterial skin colonization and severity score.Results Thirty-eight per cent of the AD patients showed a selective deficiency in IgG2 antibodies against SEC1 compared with only 14% in the control group. The absence of these antibodies was found in both currently colonized and non-colonized AD patients and was associated with a severe phenotype (SCORAD more than 40 points in two-thirds of the deficient patients). However, these patients had normal production levels of IgG2 antibodies against pneumococcal capsular polysaccharide (PCP) and SEB, but higher IgG1 and IgG4 titres against SEC1. Except for elevated total IgG1, total IgG subclass levels were normal in this AD subgroup. Yet, peripheral blood mononuclear cells (PBMCs) derived from these patients clearly produced IL-4 and IL-5 upon SEC1 re-stimulation whereas PBMCs from those providing SEC1-specific IgG2 antibodies failed in the production of these cytokines.Conclusion A subgroup of AD patients suffers from a selective deficiency to produce anti-SEC1 IgG2 antibodies. This patient group is characterized by a severe AD phenotype.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2222.2005.02192.x
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  • 4
    Electronic Resource
    Electronic Resource
    Alpha-toxin is produced by skin colonizing Staphylococcus aureus and induces a T helper type 1 response in atopic dermatitis (2005)
    Oxford, UK : Blackwell Science Ltd
    Clinical & experimental allergy 35 (2005), S. 0 
    Details
    ISSN: 1365-2222
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Background Staphylococcus aureus is a well known trigger factor of atopic dermatitis (AD). Besides the superantigens, further exotoxins are produced by S. aureus and may have an influence on the eczema.Objective To explore the impact of staphylococcal α-toxin on human T cells, as those represent the majority of skin infiltrating cells in AD.Methods Adult patients with AD were screened for cutaneous colonization with α-toxin producing S. aureus. As α-toxin may induce necrosis, CD4+ T cells were incubated with sublytic α-toxin concentrations. Proliferation and up-regulation of IFN-γ on the mRNA and the protein level were assessed. The induction of t-bet translocation in CD4+ T cells was detected with the Electrophoretic Mobility Shift Assay.Results Thirty-four percent of the patients were colonized with α-toxin producing S. aureus and α-toxin was detected in lesional skin of these patients by immunohistochemistry. Sublytic α-toxin concentrations induced a marked proliferation of isolated CD4+ T cells. Microarray analysis indicated that α-toxin induced particularly high amounts of IFN-γ transcripts. Up-regulation of IFN-γ was confirmed both on the mRNA and the protein level. Stimulation of CD4+ T cells with α-toxin resulted in DNA binding of t-bet, known as a key transcription factor involved into primary T helper type 1 (Th1) commitment.Conclusion α-toxin is produced by S. aureus isolated from patients with AD. We show here for the first time that sublytic α-toxin concentrations activate T cells in the absence of antigen-presenting cells. Our results indicate that α-toxin is relevant for the induction of a Th1 like cytokine response. In AD, this facilitates the development of Th1 cell dominated chronic eczema.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2222.2005.02295.x
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  • 5
    Electronic Resource
    Electronic Resource
    Late eczematous reactions to food in children with atopic dermatitis (2004)
    Oxford, UK : Blackwell Science Ltd
    Clinical & experimental allergy 34 (2004), S. 0 
    Details
    ISSN: 1365-2222
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Background Food allergy is a common problem in patients with atopic dermatitis (AD), particularly in children. While immediate reactions to food are well characterized, the importance of food as a provocation factor for late eczematous reactions has been a subject of debate for several decades.Objective To investigate the importance of food for the induction of late eczematous reactions in children with AD and to correlate the clinical outcome to the results of specific IgE determinations and atopy patch tests (APTs).Methods One hundred and six double-blind placebo-controlled food challenges (DBPCFCs) to cow's milk, hen's egg, wheat and soy in 64 children with AD (median age 2 years) were analysed retrospectively. Total and food-specific IgE were determined by CAP RAST FEIA and APTs with native foodstuff were performed. The diagnostic values of specific IgE and APT results were calculated.Results Forty-nine (46%) of the challenges were related to a clinical reaction. An exacerbation of AD (late eczematous reaction) commonly occurred 24 h after the ingestion of food. Isolated late eczematous reactions were seen in 12% of all positive challenges. Forty-five percent of the positive challenges were associated with late eczematous responses, which followed immediate-type reactions. The sensitivity of food-specific IgE and the APT was 76% and 70%, respectively. Specific IgE and APT were often false positive, which resulted in low positive predictive values (64% and 45%, respectively).Conclusions Late eczematous reactions may often be observed upon food challenge in children with AD. Due to the poor reliability of food-specific IgE and APT results DBPCFCs have still to be regarded as the gold standard for the appropriate diagnosis of food responsive eczema in children with AD.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2222.2004.1953.x
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  • 6
    Electronic Resource
    Electronic Resource
    Birch pollen-related food as a provocation factor of allergic symptoms in children with atopic eczema/dermatitis syndrome (2004)
    Oxford, UK : Munksgaard International Publishers
    Allergy 59 (2004), S. 0 
    Details
    ISSN: 1398-9995
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Background:  Food allergy to cow's milk or hen's egg is a common problem in children with atopic eczema/dermatitis syndrome (AEDS) but the role of birch pollen-related food for the induction of allergic symptoms is still not clear.Patients/methods:  Twelve children (median age 5 years) with AEDS underwent an oral challenge with those birch pollen-related foods which were reported to induce no immediate symptoms, but were consumed on a regular basis. Total IgE and specific IgE to birch pollen, Bet v 1/2 and various birch pollen-related foods were determined.Results:  Seven of 12 children showed immediate and/or late eczematous reactions upon ingestion of birch pollen-related foodstuff. Four children showed a worsening of eczema 24 h upon oral challenge with a significant difference in SCORAD before and after challenge. There were no differences in terms of total IgE or birch pollen-specific IgE between children with a late eczematous response and non-reacting children.Conclusions:  Birch pollen-related food may induce allergic symptoms in children with AEDS who exhibit a sensitization to birch pollen. Oral challenge tests should be performed in those children who suffer from severe AEDS and who are highly sensitized to birch pollen allergens even in the absence of a history suggestive of food allergy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1398-9995.2004.00493.x
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  • 7
    Electronic Resource
    Electronic Resource
    Urine eosinophil protein X (EPX) is an in vitro parameter of inflammation in atopic dermatitis of the adult age (2001)
    Copenhagen : Munksgaard International Publishers
    Allergy 56 (2001), S. 0 
    Details
    ISSN: 1398-9995
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Background: Eosinophils are important effector cells in several atopic diseases. The levels of eosinophil granule-derived mediators (ECP, EPX) in serum and body fluids have been proven to be correlated with disease activity in atopic respiratory diseases and atopic dermatitis. The study aimed to demonstrate an interrelationship between urine EPX and disease activity in adult patients with atopic dermatitis. Methods: We determined urine EPX concentration, serum ECP concentration, and peripheral blood eosinophil count in 40 adult patients with mild to severe atopic dermatitis and compared it with the disease activity as assessed with the SCORAD index. Results: Urine EPX and serum ECP concentrations were significantly higher in patients with severe atopic dermatitis than in patients with mild or moderate disease (median values 123.5 vs 78.3 µg/mmol creatinine, P〈0.0001; 25.4 vs 14.9 µg/l, P〈0.0001, respectively). We found a significant correlation between urine EPX levels, serum ECP levels, and the SCORAD (r=0.36, P〈0.0001 and 0.34, P〈0.0001, respectively). Conclusions: Urine EPX is a useful in vitro parameter of inflammation in atopic dermatitis of the adult age.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1034/j.1398-9995.2001.056008780.x
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  • 8
    Electronic Resource
    Electronic Resource
    Bacterial infections and atopic dermatitis (2001)
    Copenhagen : Munksgaard International Publishers
    Allergy 56 (2001), S. 0 
    Details
    ISSN: 1398-9995
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1034/j.1398-9995.2001.00146.x
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  • 9
    Electronic Resource
    Electronic Resource
    Severe atopic dermatitis is associated with sensitization to staphylococcal enterotoxin B (SEB) (2000)
    Copenhagen : Munksgaard International Publishers
    Allergy 55 (2000), S. 0 
    Details
    ISSN: 1398-9995
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Background: Staphylococcus aureus has been identified as a possible trigger factor in atopic dermatitis (AD). Some 30–60% of S. aureus strains isolated from patients with AD are able to produce exotoxins with superantigenic properties, mostly staphylococcal enterotoxins A, B, C, and D (SEA–D) and toxic shock syndrome toxin-1 (TSST-1). Recently, it was demonstrated that the presence of IgE antibodies to SEA and SEB is correlated with the severity of skin lesions in children with AD. To determine the relevance of staphylococcal enterotoxins in adult patients with AD, we investigated the relationship between the severity of skin lesions and sensitization to SEA and SEB. Methods: Clinical severity was determined by the SCORAD index. Circulating IgE antibodies to SEA and SEB, serum eosinophil cationic protein (ECP) levels, and urine eosinophil protein X (EPX) levels were measured. Results: The skin condition was significantly worse in patients sensitized to SEB than in unsensitized patients. Serum ECP and urine EPX levels were found to be significantly higher in SEB-sensitized patients, confirming the higher degree of cutaneous inflammation. Conclusions: Our results demonstrate a relationship between severity of skin lesions and sensitization to SEB in adult patients with AD, but a relationship between disease activity and sensitization to SEA could not be shown.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1034/j.1398-9995.2000.00432.x
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  • 10
    Electronic Resource
    Electronic Resource
    Staphylococcus aureus: colonizing features and influence of an antibacterial treatment in adults with atopic dermatitis (2002)
    Oxford, UK : Blackwell Science Ltd
    British journal of dermatology 147 (2002), S. 0 
    Details
    ISSN: 1365-2133
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Summary Background  The skin of up to 100% of patients with atopic dermatitis (AD) is colonized with Staphylococcus aureus. Of all S. aureus strains isolated from lesional skin, up to 65% have been shown to produce exotoxins with superantigenic properties. Patients colonized with S. aureus have been treated with antibiotics in several open and double-blind placebo-controlled studies, with conflicting results. These studies did not consider the anterior nares as a reservoir of S. aureus, or the possibility of transmission between patients and their contacts. Moreover, adult patients have not so far been investigated. Objectives  To investigate the colonizing features of S. aureus in adults with AD and in their contacts, and the effect of an antimicrobial treatment of the patients and their partners. Methods Swabs were taken from the skin and anterior nares of 66 adults with AD. S. aureus strains were screened for the production of exotoxins in 32 patients. Ten patients (two with toxigenic strains, eight with non-toxigenic strains) were treated orally with cefalexin, chlorhexidine ointment was applied to the skin, and the anterior nares were treated with mupirocin ointment. A bath containing potassium permanganate was taken daily. In addition, their partners were treated topically. Results  Sixty-two of 66 patients (94%) were carriers of S. aureus, and mostly harboured the bacteria on both skin and anterior nares. Ten of 32 (31%) patients were colonized with toxigenic strains. The Severity Scoring in AD (SCORAD) score decreased in nine of 10 patients who received antimicrobial treatment (P 〈 0·001), and this effect was more pronounced in patients with a baseline SCORAD 〉 50. Conclusions  S. aureus may play an important role as an aggravating factor in adults with AD, as antimicrobial treatment leads to a significant improvement of AD in patients who are colonized with the bacterium.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2133.2002.04872.x
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