Biomedical subjects

S Betz

Publications and source records attributed to S Betz.

10 recordsLinked to original sources

PubMed2001

Selection and orientation of adjacent genes influences DAM-mediated male sterility in transformed maize.

Anther-targeted expression of E. coli DNA (Adenosine-N6-)-Methyltransferase (DAM) in maize was tested as a means to produce male-sterile plants. A high frequency of male-sterile plants with reduced anther size was observed when DAM was regulated by the maize anther-specific promoter 5126 (5126:DAM) and placed upstream of the herbicide resistance gene, pat, regulated by the cauliflower mosaic virus (CaMV) 35S promoter (35S:PAT). In contrast, placement of 5126:DAM upstream of a pat gene regulated by either the maize ubiquitin (UBI:PAT) or rice actin (rACTIN:PAT) promoters resulted in male-fertile plants. Based on these observed differences, DAM-mediated sterility was used as a phenotypic marker to assess the contribution of factors affecting gene expression such as orientation of the transcription units, choice of regulatory sequences mediating expression of adjacent genes, and effects of varying the anther-specific promoter regulating DAM. Constructs that place a portion of the CaMV 35S promoter, including the native AS-1 sequences, between 5126:DAM and UBI:PAT yielded a high frequency of male-sterile plants with reduced anther size. Significant differences in the frequency of male-sterile events and the associated anther size were also observed when the position of 35S:PAT was changed relative to 5126:DAM. These data provide evidence that gene expression in transformed maize plants can be impacted by simply altering the order, orientation or regulatory sequences of adjacent genes.

Acetyltransferases↗

PubMed1999

Differences in the DNA-stainability of spermatozoa from fertile and suspected infertile men.

The aim of this work was to determine whether it is possible to distinguish between fertile (control group, already fathers) and infertile men (suspected infertility), by comparing the fluorescence intensity of the sperm-DNA after incubation with appropriate dyes. First we examined two different DNA-specific dyes (DAPI and YOYO-1) using bull spermatozoa. Based on good results in immunohistochemical applications, YOYO-1 was chosen for further work. The fluorescence-intensity of 200 single, morphologically normal spermatozoa in each semen sample were measured in a cytophotometer, means + SD determined and histograms delineated. Of 20 samples from the control group, 17 had markedly higher fluorescence-intensity than did 7/15 of the suspected infertile men. It is concluded that the DNA of the latter seven samples was less accessible to the dye than was the DNA of the control group. There are cases of infertility known in which there is loss of one or more of the DNA-binding proteins, which in spermatozoa are mainly (85%) protamines. The relationship between the stainability of the sperm-DNA and the packaging with DNA-binding proteins is discussed. Two of the histograms showed abnormalities in the distribution of the fluorescence-intensities, one sample was extremely fragile and most of the sperm lysed during the staining-procedure. Five samples showed normal histograms in comparison with the control group.

Animals↗

PubMed1995

Design of two-stranded and three-stranded coiled-coil peptides.

The structural features required for the formation of two- versus three-stranded coiled coils have been explored using de novo protein design. Peptides with leucine at the 'a' and 'd' positions of a coiled-coil (general sequence: Leua Xaab Xaac Leud Glue Xaaf Lysg) exist in a non-cooperative equilibrium between unstructured monomers and helical dimers and helical trimers. Substituting valine into each 'a' position produces peptides which still form trimers at high concentrations, whereas substitution of a single asparagine at the 'a' position of the third heptad yields a dimer. During the course of this work, we also re-investigated a helical propensity scale derived using a series of coiled-coil peptides previously believed to exist in a monomer-dimer equilibrium (O'Neil & DeGrado 1990). Detailed analysis of the concentration dependence of ellipticity at 222 nm reveals that they exist in a non-cooperative monomer-dimer-trimer equilibrium. However, the concentration of trimer near the midpoint of the concentration-dependent transition is small, so the previously determined values of delta delta G alpha using the approximate monomer-dimer scheme are indistinguishable from the values obtained employing the complete monomer-dimer-trimer equilibrium.

Amino Acid Sequence↗

PubMed1995

Gunshot injuries.

If current trends for this nation continue, by the year 2003 the number of people killed by firearms will exceed the number of people killed in motor vehicle accidents. Critical care practitioners must understand the mechanism of injury associated with firearm injuries to provide optimal care. This article reviews internal, exterior, and terminal ballistics, bullet design, wound classification, and initial assessment and treatment of firearm injuries.

Critical Care↗

PubMed1994

Different growth factor requirements for human Th2 cells may reflect in vivo induced anergy.

We previously reported the isolation of allergen-specific Th2 lines and clones from atopy patch test (APT) sites of atopic dermatitis (AD) patients. Upon stimulation with allergen or anti-CD3+ phorbol myristate acetate (PMA) IL-4 was released with or without IL-5, while no (or extremely low concentrations of) IL-2 and interferon-gamma (IFN-gamma) were detectable. A high IL-4/IFN-gamma ratio facilitates production of allergen-specific IgE, of which high levels are observed in AD patients. Here we show that the above mentioned Th2 cells are notably different from murine Th2 cells. Not IL-4, which is the autocrine acting growth factor for murine Th2 cells, but IL-2 was needed for proliferation of these human APT-derived Th2 lines and clones. Of significance, unless exogenous IL-2 was added, no proliferative response to allergen, presented by Epstein-Barr virus-transformed B (EBV-B) cells, non-T cells or IgE-bearing Langerhans cells (LC), occurred. Lack of proliferation and IL-2 production after full T cell receptor (TCR) triggering is a characteristic first described for in vitro anergized T cells. However, like the clones we describe in this study, anergic T cells may retain production of cytokines other than IL-2. A further resemblance between anergic T cells and the human Th2 clones reported here is that IL-4 can enhance IL-2-driven proliferation, but is not capable of inducing T cell growth by itself. The absence of IL-4-driven proliferation differentiates human Th2 cells from murine Th2 cells. Both produce IL-4 when stimulated in a cognate fashion, but only murine Th2 cells will proliferate. We conclude that the presently reported human Th2 cells are different from murine Th2 cells, in that they need other T cells to produce IL-2 required for their expansion. Moreover, the Th2 cells phenotypically resemble anergic T cells. As yet, however, we have no clue as to whether these features account for the current Th2 cells only or for human Th2 cells in general. We hypothesize that the Th2 phenotype of AD skin-derived, allergen-specific T cells may be induced in vivo by LC, which lack CD80, and therefore do not provide secondary signals through CD28-CD80 interaction.

Adult↗

PubMed1993

Increased expression of CD11b and functional changes in eosinophils after migration across endothelial cell monolayers.

Eosinophils from sputum, nasal polyps, and bronchoalveolar lavages of asthmatics demonstrated a considerably increased CD11b expression, compared with blood eosinophils. Furthermore, the tissue eosinophils expressed ICAM-1 (CD54) and HLA-DR, whereas peripheral blood eosinophils did not. In vitro migration of peripheral blood eosinophils across IL-1-activated human umbilical vein endothelial cell monolayers caused a considerable up-regulation of CD11b and CD35 expression, no induction of ICAM-1 or HLA-DR, and a small but significant decrease in CD11a, CD29, and CD32 expression. These changes were only partially inducible with supernatants from nonactivated or IL-1-activated endothelial cells, platelet-activating factor, or a variety of recombinant cytokines. Thus, cell-cell interactions mediated by receptor-ligand binding or endothelial cell membrane-bound mediators, rather than soluble factors, are responsible for the altered eosinophil surface marker expression. Indeed, preparations of membrane fragments from IL-1-stimulated endothelial cells were able to induce up-regulation of CD11b, which was not inhibitable with the platelet-activating factor antagonist WEB 2086 or antibodies against ELAM-1, VCAM-1, or ICAM-1. Investigation of the functional significance of the increased CD11b expression on eosinophils revealed only minimal changes in the adherence or transmigration capacity. Nevertheless, increased CD11b expression was related to an increased capacity to generate superoxide after stimulation with opsonized zymosan. Thus, cell-cell interactions between eosinophils and endothelial cells induce a considerable up-regulation of CD11b and CD35 on eosinophils and an increased capacity to generate an oxidative burst.

Antigens, CD↗

PubMed1993

Eosinophil migration in atopic dermatitis. I: Increased migratory responses to N-formyl-methionyl-leucyl-phenylalanine, neutrophil-activating factor, platelet-activating factor, and platelet factor 4.

Eosinophil granular protein deposits have been demonstrated in lesional atopic dermatitis skin. This suggests active tissue infiltration of eosinophils. To find an explanation for the tissue influx of eosinophils, eosinophil migration was studied in vitro by means of a microchemotaxis assay. Eosinophils from the circulation of patients with atopic dermatitis showed an altered capacity to respond to chemotactic stimuli in vitro compared with eosinophils from healthy donors. Eosinophils from patients with atopic dermatitis had significantly increased migratory responses toward dose ranges of N-formyl-methionyl-leucyl-phenylalanine, neutrophil-activating factor, platelet-activating factor, and platelet factor 4. Eosinophils from normal individuals did not respond to N-formyl-methionyl-leucyl-phenylalanine and neutrophil-activating factor and responded only slightly to platelet factor 4. The migratory responses toward tumor necrosis factor-alpha and complement factor C5a were identical in both groups. Interleukin-5, an eosinophil-selective cytokine, is a strong modulator of the migratory responses to these chemotaxins in eosinophils from normal donors. A migratory response toward N-formyl-methionyl-leucyl-phenylalanine and neutrophil-activating factor was induced by interleukin-5, whereas the migratory response toward platelet-activating factor and platelet factor 4 was markedly potentiated. In contrast, the response to complement fragment C5a was only slightly influenced. Our findings indicate that the increased migratory responsiveness of eosinophils from patients with atopic dermatitis to various chemotaxins reflects in vivo "priming" of eosinophils, presumably by circulating cytokines such as interleukin-5. This in vivo "priming" is not optimal because it can be further potentiated by renewed contact with interleukin-5.

Adolescent↗

PubMed1993

The involvement of eosinophils in the patch test reaction to aeroallergens in atopic dermatitis: its relevance for the pathogenesis of atopic dermatitis.

Atopic dermatitis (AD) is considered a T-cell mediated disease. Activated T-cells, mainly of the CD4-subtype, are abundantly present in lesional AD skin. Although not many intact eosinophils are present, deposits of eosinophil derived major-basic-protein (MBP) and eosinophil-cationic-protein (ECP) suggest eosinophil involvement. After patch testing AD patients with aeroallergens, an eczematous reaction develops after 24-48 hr at the site of application. This patch test reaction shows macroscopic resemblance to lesional AD skin and does not take place in normal individuals, asthma and allergic rhinitis patients. Lymphocytes together with eosinophils infiltrate into the dermis 2-6 hr after allergen application. Twenty-four to forty-eight hours after patch testing, eosinophils are in an activated state since they release ECP (being EG2-positive). At this point in time eosinophils have also infiltrated the epidermis. Here they are EG2-negative. Forty-eight to seventy-two hours after patch testing the eczematous reaction decreases. This coincides with disappearance of eosinophils from both the dermis and the epidermis; then, a dendritic staining pattern can be observed in the epidermis with anti-eosinophil peroxidase. Thus, eosinophils infiltrate the dermis and epidermis after patch testing AD patients with aeroallergens and release part of their granular constituents. Recent in vitro investigations revealed that eosinophils from the circulation of AD patients react more powerfully in in vitro test systems such as chemiluminescence, chemotaxis and endothelial adherence and transmigration. It is very likely that this activated (= primed) state is caused by the influence of lymphocyte-derived cytokines like IL-3, IL-5 and GM-CSF, since activated lymphocytes in the circulation (and tissue) may release these cytokines. The primed state of the eosinophils may facilitate tissue infiltration. The subsequent activation of eosinophils within the tissue leading to mediator release and the function of these mediators need to be further elucidated. The close similarity between the cellular events after a patch test reaction to aeroallergens in AD patients and those present in lesional AD skin suggests that the patch test reaction may be a helpful in vivo model to study the pathogenesis of AD. The prominent involvement of lymphocytes and eosinophils in this reaction also suggests some similarity with late phase reactions (LPR) observed in the skin after intracutaneous allergen challenge.

Allergens↗

PubMed1992

[Eosinophilic granulocytes and their significance in allergic diseases].

Eosinophils are found in the blood and tissues of patients with allergic diseases such as asthma, allergic rhinitis and also atopic dermatitis. The number of eosinophils in the diseased tissue generally correlates with the expression of clinical symptoms. Originally, the eosinophil was regarded as having an exclusively protective role, for example in host defense against parasites. More recently, the eosinophil is recognized as being a pro-inflammatory cell that can mediate allergic disease. The eosinophil is active in inflammation through the release of granule proteins and the synthesis and release of inflammatory mediators. The important eosinophil granule proteins are major basic protein (MBP), eosinophil cationic protein (ECP), eosinophil derived neurotoxin (EDN) and eosinophil peroxidase (EPO). These proteins have toxic effects on the surrounding tissue. Of additional importance for the allergic inflammatory reactions are membrane-derived mediators such as leukotriene C4 (LTC4), platelet activating factor (PAF) and Charcot-Leyden crystals. These mediators are synthesized and released after eosinophil activation, and act toxic on surrounding cells. Eosinophils are active in asthma, and increased numbers and eosinophil-derived mediator concentrations have been documented in bronchial biopsies, BAL and sputum. In addition, eosinophil granule proteins and inflammatory mediators are found in nasal secretions in allergic rhinitis. In atopic dermatitis one finds activated eosinophils and depositions of eosinophil granule proteins in skin biopsies. Eosinophils are not only active in mediating allergic inflammation, but interact in cellular networks with antigen presenting cells (APC), mast cells, and T lymphocytes. These other cells influence eosinophil maturation, mobilization, tissue localization and activation.

Asthma↗

PubMed1991

An improved immunomagnetic procedure for the isolation of highly purified human blood eosinophils.

A simple method is described for the isolation of human peripheral blood eosinophils by an immunomagnetic procedure. Superparamagnetic particles were coupled to a monoclonal antibody against CD16, a molecule present on neutrophils but not on eosinophils. A peripheral blood granulocyte preparation, containing neutrophils and eosinophils, was incubated with these anti-CD16 particles. In the magnetic field of a permanent magnet, magnetically labelled neutrophils were then retained on columns with a ferromagnetic matrix. By this negative selection procedure, eosinophils of 99.5% purity were obtained from normal individuals and 99.6% purity from patients with eczema. A comparison was made between the immunomagnetic method and eosinophil isolation after N-formyl-methionyl-leucyl-phenyl-alanine treatment. Even in the case of individuals with very low eosinophil counts, the immunomagnetic method permits the efficient isolation of highly purified and functionally active eosinophils.

Antigens, CD↗