Biomedical subjects

V Stephan

Publications and source records attributed to V Stephan.

At least 37 records · Page 2Linked to original sources

PubMed1992

High-affinity IgE receptor-mediated stimulation of rat basophilic leukemia (RBL-2H3) cells induces early and late protein-tyrosine phosphorylations.

We reported previously that stimulation of RBL-2H3 cells through the high-affinity IgE receptor resulted in tyrosine phosphorylation of a 72-kDa protein (pp72) that was coupled to signal transduction. In the present study, although pp72 tyrosine phosphorylation was induced only by antigen triggering, stimulation of RBL-2H3 cells by either antigen or the calcium-ionophore A23187 led to increased tyrosine phosphorylation of a 110-kDa protein (pp110). This tyrosine phosphorylated protein was also observed when RBL-2H3 cells were transfected with the G protein-coupled m3 muscarinic receptor and then stimulated to secrete with carbachol. In contrast to tyrosine phosphorylation of pp72, antigen-induced pp110 tyrosine phosphorylation required extracellular calcium, was absent in cells depleted of protein kinase C, and was detected between 1 and 5 min after stimulation. The protein-tyrosine kinase inhibitor genistein blocked both histamine release and tyrosine phosphorylation induced by A23187. Altogether, the data suggest a role for pp110 in secretion. However, protein kinase C activation induced pp110 tyrosine phosphorylation but not histamine release demonstrating that pp110 tyrosine phosphorylation alone is not sufficient for degranulation. We conclude that tyrosine phosphorylation of pp72 is associated with the early steps of IgE receptor-generated signaling, whereas pp110 tyrosine phosphorylation occurs secondary to calcium influx and protein kinase C activation.

Animals↗

PubMed1992

Fc epsilon RI-induced protein tyrosine phosphorylation of pp72 in rat basophilic leukemia cells (RBL-2H3). Evidence for a novel signal transduction pathway unrelated to G protein activation and phosphatidylinositol hydrolysis.

Recently, we demonstrated that aggregation of the high affinity IgE receptor in rat basophilic leukemia (RBL-2H3) cells results in rapid tyrosine phosphorylation of a 72-kDa protein (pp72). Here we investigated the relationship of pp72 phosphorylation to guanine nucleotide-binding protein (G protein) activation and phosphatidylinositol hydrolysis. The activation of G proteins by NaF in intact cells or by guanosine 5'-O-(3-thiotriphosphate) in streptolysin O-permeabilized cells induced both phosphatidylinositol hydrolysis and histamine release without tyrosine phosphorylation of pp72. Similarly, in RBL-2H3 cells expressing the G protein-coupled muscarinic acetylcholine receptor, carbachol activated phospholipase C and induced secretion without concomitant pp72 phosphorylation. Therefore, pp72 phosphorylation was not induced by G protein activation or as a consequence of phosphatidylinositol hydrolysis. To investigate whether pp72 tyrosine phosphorylation precedes the activation of phospholipase C, we studied the effect of the tyrosine kinase inhibitor genistein. Preincubation of cells with genistein decreased, in parallel, antigen-induced tyrosine phosphorylation of pp72 (IC50 = 34 micrograms/ml) and histamine release (IC50 = 31 micrograms/ml). However, genistein at concentrations of up to 60 micrograms/ml did not inhibit phosphatidylinositol hydrolysis nor did it change the amount of the secondary messenger inositol (1,4,5)-triphosphate. Previous observations showed that there was no pp72 tyrosine phosphorylation after activation of protein kinase C or after an increase in intracellular calcium. Taken together, these results suggest that pp72 tyrosine phosphorylation represents a distinct, independent signaling pathway induced specifically by aggregation of the Fc epsilon RI.

3T3 Cells↗

PubMed1992

Longitudinal variability of skin prick test results.

The skin prick test (SPT) is a commonly used procedure for assessing a specific sensitization. The longitudinal variability of test results is of interest for clinical as well as epidemiological investigations. The sensitization to four common aeroallergens (grass pollen, birch pollen, Dermatophagoides pteronyssinus, cat dander) is investigated within the framework of three consecutive SPTs at 11-month intervals for a population of 587 schoolchildren. The prevalence of sensitization based on a weal diameter of at least 2 mm was between 12.9% (cat dander) and 23.9% (grass pollen) in the initial testing. The positive predictive values of the initial SPT were between 75.3% (birch pollen) and 88.2% (cat dander) for the two subsequent SPTs. In the case of initially negative tests with positive second and third SPTs the incidence ranged between 3.2% (cat dander) and 4.3% (birch pollen) per year. A clear increase in the intensity of reaction in subsequent tests was observed in a number of probands testing positively in the initial SPT. In conclusion, our data indicate a high long-term stability of a specific sensitization to aeroallergens in SPT.

Adolescent↗

PubMed1992

[Urinary N-methylhistamine excretion. Following exogenous histamine administration and allergy/exercise-induced bronchoconstriction].

Histamine is partly metabolized to a stabile metabolite N-methyl-histamine and excreted in the urine. We analysed the degradation of infused histamine and the N-methyl-histamine-excretion in atopic and normal individuals as in patients with a bronchoconstriction due to allergen/exercise challenge. N-methyl-histamine was determined by a newly developed radioimmunoassay. 60 controls and 38 atopic individuals were investigated. There is a proportional increase of N-methyl-histamine in the urine in young children. However, no significant difference between allergic and non-allergic individuals was found. After parenteral administration of a standardized amount of histamine 12% of the applied amount was secreted in the urine as N-methylhistamine. The most significant increase of N-methylhistamine-excretion was observed in the first hour after application. Only an 0.1% rise of N-methyl-histamine was observed following an oral administration of histamine. Neither bronchial challenge with specific allergen nor physical exercise elicited significant changes of N-methylhistamine excretion. The secretion of N-methyl-histamine demonstrates the degradation of histamine in the circulation, the measurement oft this metabolite in the urine should be considered when analysing the cause of severe systemic allergic reaction as anaphylaxis but not asthma or atopic disposition.

Adolescent↗

PubMed1991

Immunoprecipitation of membrane proteins from rat basophilic leukemia cells by the antiganglioside monoclonal antibody AA4.

In previous studies, mAb AA4 inhibited IgE binding, induced rapid morphologic changes, and blocked histamine release in rat basophilic leukemia (RBL-2H3) cells. It bound to two novel derivatives of ganglioside GD1b (Ag I and Ag II) that appear to be present only in rat mast cells. The present study demonstrates the importance of gangliosides Ag I and Ag II for binding of mAb AA4 to intact cells. We also investigated the presence of gangliosides Ag I and Ag II and proteins immunoprecipitated with mAb AA4 in the parental and four variant cell lines. In comparison with the parental RBL-2H3, two variant cell lines had very low (0.5% and 2.0%) and two others had intermediate levels (9% and 18%) of 125I-AA4 binding. mAb AA4 inhibited 125I-IgE binding to the parental RBL-2H3 cells and to only one variant with intermediate amounts of gangliosides Ag I and Ag II. Therefore, there are variations in the proximity of these gangliosides to the high affinity IgE receptor (Fc epsilon RI) among different cell lines. mAb AA4 immunoprecipitated proteins of 50 to 60, 120, and 135 kDa from 125I-surface labeled cells. These were different from the subunits of Fc epsilon RI. The amount of gangliosides Ag I and Ag II in cell extracts correlated with the number of mAb AA4 binding sites on the cell surface and with the quantity of proteins precipitated from the different cell lines. Thus, these membrane proteins appear to be associated with gangliosides Ag I and Ag II. The binding of mAb AA4 to the surface gangliosides could induce intracellular changes through transmembrane signaling by these proteins.

Animals↗

PubMed1991

[Air pollutant burden and bronchial asthma in school children].

To examine the possibility of an effect of indoor and outdoor exposures on the prevalence of asthma in childhood we conducted a cross-sectional study in the area of Freiburg city and two communities in the Black Forest. The study group consists of 704 children aged 7 to 16 years. The children and their mothers took part in a standardized interview and a medical examination. Indoor exposures were assessed from information gathered in the interview by two different indices: (a) heating system and single room heating, and (b) the amount of indoor ventilation. The measurement of outdoor pollutants took into account weekly estimations of NO2 and combustion particles. The presence of asthma was recorded according to a previous medical diagnosis. Confounders were assessed during the interview (passive smoking, genetic predisposition to asthma etc.) or during the medical examination (cutaneous sensitization with a skin prick test). For the analysis of the data we applied logistic regression models and estimated odds-ratios. Only one of the four hypothesis variables displays a significant effect on the prevalence of asthma: Stoves as heating device carry a 4.8-fold relative risk for asthma compared to other types of heating. Among the confounding variables controlled for in the explanatory model, cutaneous reactions showed a relative risk of eight.

Adolescent↗

PubMed1990

[The immunogenicity and allergenicity of an experimental cow's milk protein hydrolysate].

Recently hydrolyzed cow milk proteins have been introduced for the production of infant formulas and are available as hypoallergenic infant formulas. To achieve a decrease in antigenicity and allergenicity a protein hydrolysis (mostly enzymatic) is performed. Sera of different groups were tested for IgG and IgE antibody-binding: 31 controls, 36 atopic children, and 20 children with cow milk protein allergy. Histamine release from basophil leucocytes after incubation with the cow milk proteins beta-lactoglobuline and casein, as with the cow milk protein hydrolysate, was determined additionally for five control, 10 atopic, and five cow milk allergic children. IgG binding to cow milk protein and to the hydrolysate was found in the majority of the sera tested. IgE binding was detectable in sera of only five of the 10 cow milk allergic children, despite detection of specific IgE-antibodies against cow milk proteins in all sera. Histamine release by the cow milk hydrolysate was observed for five atopic and two cow milk allergic children. The cow milk hydrolysate demonstrated a decreased but partially conserved antigenic/allergenic potency compared with cow milk proteins.

Adolescent↗

PubMed1990

Determination of N-methylhistamine in urine as an indicator of histamine release in immediate allergic reactions.

The use of the urine histamine metabolite, N-methylhistamine (N-MH), as a parameter of histamine release in immediate allergic reactions was investigated. Baseline levels were determined in 34 normal control subjects and 29 atopic patients. Increases of urine N-MH values were measured during histamine infusions and in venom-allergic patients receiving bee-sting challenges. N-MH was determined by a newly developed radioimmunoassay. Baseline levels in control subjects and atopic patients demonstrated no significant differences. With regard to challenge tests, fluctuation of N-MH levels during a 6-hour period was measured. Random 6-hour increases in healthy and atopic subjects ranged from 5% to 41%. Before infusion of histamine (0.25 micrograms/kg/min for 30 minutes), baseline values were 137 +/- 11.4 micrograms N-MH per gram of creatinine and 9 +/- 1.1 micrograms N-MH per hour (n = 9). Levels peaked 1 hour after infusion at 275 +/- 45 micrograms/gm of creatinine and 44 +/- 5.6 micrograms/hr and decreased to resting levels after 2 hours. Metabolization by N-MH accounted for 9.5% +/- 4.9% (range, 2.4% to 18.4%) of infused histamine in the urine of the nine subjects. Bee-sting challenges were performed in 12 patients and three control subjects. Only in three patients experiencing generalized urticaria, nausea, dyspnea, and hypotension were significant increases of urine N-MH levels (138%, 144%, and 238%) observed. All other patients and three normal control subjects demonstrated normal local reactions without increase of N-MH values.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1989

Relevance of basophil histamine release changes during venom immunotherapy.

We investigated the effect of rush and long-term venom immunotherapy on histamine release parameters in bee venom allergic patients. Ten patients received rush venom immunotherapy, and histamine release data were obtained immediately before and after treatment. 17 patients were assessed by histamine release 24 to 63 months after termination of long-term venom immunotherapy. A control group of 10 non-allergic subjects was included in this study. Histamine released from whole blood was determined in a sensitive radio-enzymatic assay using a single isotope technique. Bee venom phospholipase A-induced histamine release from whole blood proved to be a test procedure of high specificity and sensitivity. Eight of 10 untreated patients and no control subject showed significant antigen-induced histamine release. Results obtained from patients immediately after successful rush venom immunotherapy showed an important decrease (mean 45.9%) of total histamine content of basophil leukocytes in all patients. Antigen-induced maximum histamine release was found to be increased in one, decreased in two and unchanged in seven patients. In patients who received long-term immunotherapy cell sensitivity to phospholipase A was significantly lower than in a group of untreated patients (P less than or equal to 0.002). These results suggest that even years after discontinuation of immunotherapy, histamine release parameters reflect patients' protection from systemic sting reactions as assessed by sting challenges. Histamine depletion of basophils induced by rush immunotherapy may play an important role in patients' protection immediately after termination of the rush regimen.

Adolescent↗

PubMed1989

Anti-IgE- and complement-induced histamine release from peripheral leukocytes in normals and atopics.

Anti-IgE- and complement-induced histamine release from isolated basophils was compared in normal and atopic subjects. Activated complement was generated by incubation of a serum pool from normal donors with zymosan. Histamine was measured by a single-isotope radioenzymatic assay. In atopics, the mean histamine release induced by heterologous complement was significantly higher than in normals (p less than or equal to 0.01). Anti-IgE-mediated histamine release showed no differences between atopics and normals. Regarding the histamine release as a function of the age of the donor, we observed significantly higher complement-induced release values in normal children aged 1-10 years compared to those aged 10-20 and greater than 20 years (p less than or equal to 0.05). Anti-IgE-induced histamine release showed no age-related differences in normals or atopic patients. As a high complement-mediated leukocytic histamine release was more commonly found in atopics with heterologous complement, this phenomenon appears not to be due to a higher rate of complement activation in the serum of atopics, but rather to an intrinsic cell abnormality. Moreover, these results suggest that age-related releasability patterns might be considered when studying complement-induced histamine release. Differences between IgE- and complement-mediated histamine release indicated that parameters of releasability must be defined with respect to each stimulus.

Age Factors↗

PubMed1989

[Epidemiologic recording of bronchial asthma in the school child].

Bronchial asthma is the most frequent chronic disease in childhood. Nevertheless, no definition of the disease is known that would enable a satisfactory epidemiological recording of asthma. In 704 schoolchildren, typical signs and symptoms of asthma were recorded within the framework of a standardized interview. The occurrence of asthmatic symptoms was quantified by means of a symptom score. In 555 of the probands, bronchial reactivity was tested by means of an inhalative challenge with carbachol. The information gathered from the interview and the carbachol challenge test was placed in relationship to the family doctor's diagnosis of "bronchial asthma". Lifetime prevalence of asthma diagnosed by the family doctors is 4.97% with a clear male predominance. The asthmatic symptoms showed varying frequencies and validity compared with the family doctor's diagnosis. The occurrence of dyspnoea appears to be particularly sensitive (77%). Dyspnoea coincident with exercise is highly specific (99%). The sensitivity of the combination of carbachol test and symptom score is 92% and the specificity is 75%. The instruments described above offer a reliable possibility for epidemiological field research to record the prevalence of bronchial asthma in schoolchildren.

Adolescent↗

PubMed1989

[Bronchial asthma and bronchial hyperreactivity].

Bronchial hyperreactivity to allergens and non-allergic stimuli is a feature of most patients with asthma as measured by the response to inhalants as pharmacological agents and physical stimuli. In contrast to adults there is an obvious relation of asthmatic episodes to allergen exposure in childhood. However, the development and persistence of bronchial hyperreactivity is well described by interaction of inflammation cells and their mediators. Not only the severity of asthma is related to the severity of bronchial hyperresponsiveness but also the therapeutic strategies.

Asthma↗

PubMed1972