Pinholes, Dislocations and Strain Relaxation in InGaN

We analyse by means of transmission electron microscopy (TEM) and atomic force microscopy (AFM) the strain relaxation mechanisms in InGaN layers on GaN as dependent on the In content. At the experimentally given thickness of 100 nm, the layers remain coherently strained, up to an In concentration of 14 %. We show that part of the strain is reduced elastically by formation of hexagonally facetted pinholes. First misfit dislocations are observed to form at pinholes that reach the InGaN/GaN interface. We discuss these results in the framework of the Matthews-Blakeslee model for the critical thickness considering the Peierls force for glide of threading dislocations in the different slip systems of the wurtzite lattice.

Microstructure, growth mechanisms and electro-optical properties of heteroepitaxial GaN layers on sapphire (0001) substrates

We investigate the structure, growth morphology and the related electro-optical properties of gallium nitride (GaN) films deposited on (0001) sapphire substrates by gas source molecular beam epitaxy (GSMBE) and use transmismission electron microscopy, atomic force microscopy and scanning tunneling microscopy, photoluminescence (PL) and cathodoluminescence (CL). We find two types of specimens: one type which shows a strong UV luminescence (band-to-band transition at 358nm/3.46eV) in CL and PL and only faint yellow luminescence (Gaussian shaped CL/PL peaks at around 528nm/2.35eV), specimen ‘B’, and another type, which shows a strong UV and a comparably strong yellow luminescence, specimen ‘Y’. These two types of specimens have a rough layer surface, specimen ‘Y’ even an islanded one with, facetted hexagonal islands with a width of 1-2μm at a height of 50nm. A correlation of spectrally resolved CL images to the observed defect structure shows: (i) the yellow luminescence is homogeneously distributed over the complete specimen for ‘B’ and ‘Y’ specimens. Our investigations strongly suggest the yellow luminescence to be related to screw dislocations with , which are found randomly distributed in ‘B’ and ‘Y’ specimens with a high density of 1.3·109cm−2; (ii) the strong UV luminescence in ‘Y’ specimens is located in the troughs between adjacent surface islands, where dislocations essentially in small angle grain boundaries of edge type, i.e. with or are located; (iii) in the case of the ‘B’ specimens these dislocations are randomly distributed and so is the luminescence.

Acetophenones: Highly Active Antiasthmatic Compounds of Plant Origin

In Ayurvedic medicine, Picrorrhiza kurroa Royle ex Benth. is used for the treatment of liver and lung diseases. We could identify the phenol glycoside, androsin, as an active compound preventing allergen- and PAF-induced bronchial obstruction in guinea pigs in vivo. The inhalation of androsin and its aglycon, apocynin, was more effective than the oral intake. More than 20 different acetophenones, either newly synthesized or purchased from commercial sources, have been tested in several pharmacological systems. 3,5-Dimethoxy-4-hydroxyacetophenone (Acetosyringenin) is by far the most active compound preventing allergen- and PAF-induced bronchial obstruction by more than 80% after one single dose of 0.5 mg (aerosol).

Noninvasive Analysis of Lung Function in Small Animals: Compressed Air, Thoracic Gas Volume, Airway Resistance, Maximal Flow Rates, Tidal Volume, Breathing Frequency, l/E Ratio

We present a noninvasive and highly sensitive system for measuring lung function in small animals. It is based on a two-chambered body plethysmography. Head and body chambers are separated by a cuff around the head of the animal. Aerosols for pharmacologic investigations are generated. Breathing-dependent changes in pressure and/or volume are registered, the signals are digitized. All data are processed in an IBM compatible PC/AT. A multitasking real time operation system shows the signals on line. A special software offers seven different lung function parameters (compressed air, airway resistance, thoracic gas volume, maximal flow rates, tidal volume, breathing frequency, I/E ratio). The results are presented as graph and text documents. Result files are submitted to calculation by standard soft ware. The computer-aided handling allows the simultaneous performance of up to nine pharmacological tests.

A genome-wide search for linkage to asthma. German Asthma Genetics Group

Asthma is among the most frequent chronic diseases in childhood. Although numerous environmental risk factors have already been identified, the basis for familial occurrence of asthma remains unclear. Previous genome screens for atopy in British/Australian families and for asthma in different American populations showed inconsistent results. We report a sib pair study of a sample of 97 families, including 415 persons and 156 sib pairs. Following an extensive clinical evaluation, all participants were genotyped for 351 polymorphic dinucleotide markers. Linkage analysis for asthma identified four chromosomal regions that could to be linked to asthma: chromosome 2 (at marker D2S2298, P = 0.007), chromosome 6 (around D6S291, lowest P = 0.008), chromosome 9 (proximal to D9S1784, P = 0.007), and chromosome 12 (D12S351, P = 0.010). These linkage regions could be reproduced for all loci by analysis of total or specific immunoglobulin E (minimum P values at these regions were 0. 003, 0.001, 0.010, and 0.015, respectively).

[Clinical application of extracts of Echinacea purpurea or Echinacea pallida. Critical evaluation of controlled clinical studies]

The phytotherapy should be understood as being integrated into the rational pharmacotherapy. The modern phytotherapy tries hard to proof effects with pharmacological and clinical studies. The task force E of the federal bureau of health of Germany has made a statement regarding this problem. This article reviews only controlled clinical trials about the application of extracts of echinacea purpura or echinacea pallida.

Determinants of cord-blood IgE concentrations in 6401 German neonates

For screening atopy risk in 6401 (84%) of all infants born during the year 1990 in six obstetric departments of five German cities, cord-blood IgE values were determined with CAP-RAST-FEIA. After cases with elevated IgA values had been excluded, 25% of the values were above the detection limit of 0.35 kU/l, and 8.5% were above 0.9 kU/l. Boys had significantly higher values than girls (P < 0.001). The distribution of values was significantly different for different nationalities of mothers (P < 0.001). The percentage of elevated values (> 0.9 kU/l) increased significantly with the number of close family members with atopic history (P < 0.001). Regarding the atopic history of the father, siblings, and mother separately, only the mother's history had a significant association with the cord-blood IgE class (P < 0.001). The IgE values of 81 twin pairs correlated significantly with a coefficient of r = 0.4909 (P < 0.001). The smoking history of the parents during pregnancy showed an association with cord-blood IgE values (P < 0.02). No significant association could be shown between cord-blood IgE distribution and other variables, i.e., gestational age, birth size, birth modus, Apgar score, cord-blood pH value, neonatal problems, parity, age of the mother, medication during pregnancy, educational level of mother or father, time of year, or obstetric department. It is hypothesized that, in addition to some postpartum contamination or placental transfer of maternal IgE, cord-blood IgE values are also determined by the fetal immunologic reaction to intrauterine exposure to allergens and trigger factors, and by genetic influences.

Tetragalloylquinic acid, the major antiasthmatic principle of Galphimia glauca

In the search for antiasthmatic principles in plant drugs, a bioguided fractionation of an alcoholic extract of Galphimia glauca was performed using a plethysmographic in vivo model. Tetragalloylquinic acid (G1), which was found together with other compounds (gallic acid, methyl gallate, ellagic acid, and flavonoid acylglycosides), showed the highest activity against bronchial hyperreactivity and allergic reactions. Using mass and NMR spectroscopy in combination with energy calculations, the structure G1 was elucidated as tetra-O-galloylquinic acid. Depending on the solvent used, the quinic acid skeleton can occupy a fixed conformation or several interconverting ones on the NMR time scale.

Antiasthmatic effects of Galphimia glauca, gallic acid, and related compounds prevent allergen- and platelet-activating factor-induced bronchial obstruction as well as bronchial hyperreactivity in guinea pigs

A methanolic extract from Galphimia glauca (320 mg/kg, orally) inhibited acute bronchial reactions to allergen (ovalbumin, 10 mg/ml) and platelet-activating factor (PAF, 1 microgram/ml) inhalation challenges, but not to histamine or acetylcholine in spontaneously breathing guinea pigs. Furthermore, the PAF-induced bronchial hyperreactivity was markedly reduced. Gallic acid and related compounds as well as the flavonoid, quercetin, were identified as active compounds. Gallic acid, methyl gallate and quercetin showed significant effects after a single oral dose of 45 mg/kg, tetragalloyl quinic acid after 5 mg/kg. Continuous treatment of the animals with one certain fraction (GG II, 3 days, 3 x 2 mg/kg) containing all active compounds reduced allergen- and PAF-induced bronchial reactions by more than 70%.

In vitro IgE eluation and histamine releasability from peripheral leukocytes of atopics and normals

The relation between the amount of cell-bound IgE and the histamine 'releasability' of peripheral leukocytes was studied in 28 patients with atopic diseases and 26 non-atopic controls after in vitro stimulation with anti-IgE. Cell-bound IgE was eluted in acid buffer (pH 3.7) and the amount of histamine released (HR) into supernatant at this pH was measured. Incubation with acetate buffer (pH 3.7) induced significantly higher spontaneous HR (32 net percent) in atopics compared to 18% in controls. The amount of IgE eluted was significantly higher in atopics: The calculated number of IgE molecules/basophil was 332,000 in atopics compared to 177,000 in controls. There was a significant positive correlation between plasma IgE and in vitro elutable IgE in atopics (r = 0.73) compared to controls (r = 0.24). After a careful washing procedure attempts were made to 'resensitize' the basophils through incubation with autologous plasma or standard IgE solutions. When resensitization was possible, there was no correlation between histamine releasability after resensitization and original IgE content of basophils. It is concluded that the increased histamine releasability from leukocytes of atopic individuals after stimulation with anti-IgE is only in part due to an increased number of IgE molecules per basophil surface. A non-specific increased releasability was demonstrated by increased spontaneous HR rates in acid buffer (pH 3.7). A resensitization with autologous plasma-IgE was possible only in half of the subjects investigated, most of them being atopic. The data support the concept of an altered releasability both towards IgE-dependent and independent stimuli being one possible factor in the pathogenesis of atopic eczema.

Antiasthmatic effects of Picrorhiza kurroa: androsin prevents allergen- and PAF-induced bronchial obstruction in guinea pigs

In the Ayurvedic medicine, Picrorhiza kurroa Royle ex Benth. is used for the treatment of liver and lung diseases. Using different chemical and pharmacological methods, we could identify the phenol glycoside androsin as active compound preventing allergen and platelet-activating factor induced bronchial obstruction in guinea pigs in vivo (10 mg/kg p.o.; 1 h prior to the inhalation challenge). Histamine release from human polymorphonuclear leukocytes in vitro was inhibited by other compounds yet to be identified.

New antiasthmatic drugs from traditional medicine?

Several plants are used in traditional medicine for the treatment of bronchial asthma. We are trying to identify the active compound(s) and their mode of action. For the isolation and identification of the active principles, different chromatographic methods, HPLC, MPLC, elementary analysis, UV, mass, 1H- and 13C-NMR spectroscopy are used. Whole plant extracts, fractionated extracts and pure compounds are tested in the following pharmacological systems: cyclooxygenase and lipoxygenase pathway of arachidonic acid metabolism, bronchial obstruction of guinea pigs after inhalation of allergens, platelet-activating factor (PAF), histamine or acetylcholine, PAF-induced bronchial hyperreactivity of guinea pigs, histamine release, chemoluminescence and chemotaxis of human polymorphonuclear leukocytes as well as thromboxane biosynthesis of human platelets. As active compounds in onion extracts, thiosulfinates and cepaenes could be identified. They exert a wide spectrum of pharmacologic activities, both in vitro and in vivo. Tetragalloyl quinic acid from Galphimia glauca, suppressed allergen- and PAF-induced bronchial obstruction, PAF-induced bronchial hyperreactivity (5 mg/kg orally) in vivo and thromboxane biosynthesis in vitro. Hitherto unknown alkaloids from Adhatoda vasica showed pronounced protection against allergen-induced bronchial obstruction in guinea pigs (10 mg/ml aerosol). Androsin from Picrorhiza kurroa prevented allergen- and PAF-induced bronchial obstruction (10 mg/kg orally; 0.5 mg inhalative). Histamine release in vitro was inhibited by other compounds of the plant extract yet to be identified. Pharmacological effects of plant extracts and pure compounds in man are under investigation.

[Bronchial asthma: allergy and inflammation. Principles of rational asthma therapy]

Improved concepts concerning the pathogenesis of chronic bronchial asthma, the role of air pollutants, infections, and allergic reactions are the basis of established therapeutic principles and the development of new drugs: Allergens initiate long lasting inflammatory processes ("late phase reactions") in the bronchial system. This inflammation causes bronchial hyperreactivity and altered lung function. A large number of inflammatory cells and mediators are involved. Air pollutants and infections can act in the same way. Asthma treatment should focus in the inflammatory process, start early and prevent and treat both chronic inflammation and acute bronchospasm.

Antiasthmatic effects of onions: inhibition of 5-lipoxygenase and cyclooxygenase in vitro by thiosulfinates and "Cepaenes"

Nine thiosulfinates (TS) and four "Cepaenes" (CS) isolated from onions and/or synthetized by us showed dose dependent (0.25 to 100 microM) marked inhibitory effects on both cyclooxygenase (CA, tested on sheep seminal vesicle microsomes) and 5-lipoxygenase activity (LO, tested on porcine leukocytes). The following rank order of activity was observed: saturated aliphatic TS less than aromatic TS approximately alpha, beta-unsaturated TS less than CS. CS inhibited both CA and LO by more than 75% at 10 and 1 microM concentrations respectively. Most likely, these in vitro effects are responsible for antiinflammatory and antiasthmatic properties of onion extracts observed in vivo, at least in part.

Anti-inflammatory effects of onions: inhibition of chemotaxis of human polymorphonuclear leukocytes by thiosulfinates and cepaenes

Seven different synthetic thiosulfinates, and cepaene- and/or thiosulfinate-rich onion extracts were found to inhibit in vitro the chemotaxis of human granulocytes induced by formyl-methionine-leucine-phenylalanine in a dose-dependent manner and at a concentration range of 0.1-100 microM. Diphenylthiosulfinate showed the highest activity and was found to be more active than prednisolone. The anti-inflammatory properties of onion extracts are related, at least in part, to the inhibition of inflammatory cell influx by thiosulfinates and cepaenes.

Anti-asthmatic effects of onions. Alk(en)ylsulfinothioic acid alk(en)yl-esters inhibit histamine release, leukotriene and thromboxane biosynthesis in vitro and counteract PAF and allergen-induced bronchial obstruction in vivo

Five alk(en)ylsulfinothioic acid alk(en)yl-esters isolated from onions and four synthetic thiosulfinates inhibited 5-lipoxygenase of porcine leucocytes, histamine release and leukotriene B4 and C4 biosynthesis of human polymorphonuclear leucocytes, thromboxane B2 biosynthesis by human platelets and allergen- and PAF-induced bronchial obstruction of guinea-pigs. The anti-asthmatic and anti-inflammatory effects of onions depend in part on the thiosulfinate moiety: (Formula: see text).

Pancreatic and gastric responses to gastric versus jejunal beer in humans

To investigate the influence of beer on gastric and pancreatic secretion, 14 fasted volunteers were studied on two different days. A multilumen intestinal tube allowed measurement of intraluminal pressures and collection of gastric and duodenal juices. Seven subjects received in random order 250 ml of either beer or glucose (5.6%, w/v) intragastrically; seven other subjects received these intrajejunally. After 15 min, 48 +/- 8% of beer and 47 +/- 6% of glucose were emptied into the duodenum. Intragastric beer induced a nearly sevenfold increase in gastric acid output as compared with glucose (16.3 +/- 2.9 mmol/h versus 2.5 +/- 0.6 mmol/h; p less than 0.05), intrajejunal beer induced a nearly threefold increase (5.1 +/- 0.8 mmol/h versus 1.7 +/- 0.3 mmol/h). The stimulated gastric acid output was threefold higher after intragastric than after intrajejunal beer. Trypsin output was slightly but significantly (p less than 0.05) stimulated by intragastric beer as compared with glucose (4,639 +/- 460 U/h versus 3,628 +/- 399 U/h) and nearly threefold by intrajejunal beer (2,579 +/- 455 U/h versus 849 +/- 181 U/h) (p less than 0.05). Trypsin response to intragastric beer was 1.8 times higher than after intrajejunal beer (p less than 0.05). Intragastric beer induced a nearly ninefold increase of the 1 h integrated plasma gastrin response as compared with glucose (998 +/- 347 pM min vs 115 +/- 70 pM min) (p less than 0.05). Intrajejunal beer and glucose did not release gastrin. We conclude that both intragastric and intrajejunal beer stimulate gastric acid and pancreatic enzyme secretion; intragastric beer being a more potent stimulant. Gastrin might partially mediate the responses to intragastric but not to intrajejunal beer.

Comparison of histamine release and prostaglandin E2 production of human basophils in atopic and normal individuals

The influence of arachidonic acid (AA) metabolism upon histamine release (HR) from human basophils after stimulation with anti-IgE was studied in 23 atopic and 11 normal individuals. HR occurred significantly faster in atopics than in normals; the total amount of HR after a 40 min incubation period was not significantly different between the two groups. Indomethacin and acetylsalicylic acid (ASA) increased the quantity of HR significantly both in atopics and normals without influencing the time course. Addition of exogenous PGE2 decreased HR; here atopics were more affected than normals 5 and 10 min after challenge with anti-IgE. Production of PGE2 after stimulation with anti-IgE was very low in both groups (in the range of 30-50 pg/10(6) cells) and often below detection limit (10-20 pg/ml). Addition of glutathione (GSH), a coenzyme of PGE2-isomerase, increased PGE2 production 2 to 5-fold during stimulation with anti-IgE. These data support the idea that arachidonic acid metabolites play an important role in modulating the "releasability" of human basophils. It is suggested that the basophils of atopic individuals may release their histamine faster than normals - perhaps on the basis of a more slowly acting endogenous feedback mechanism by PGE2. Both phenomena support the idea of an altered "releasability" of basophils from atopics compared to normals.

Adverse effects of acetylcysteine on human and guinea pig bronchial asthma in vivo and on human fibroblasts and leukocytes in vitro

The term 'allergen tachyphylaxis' denotes decreasing bronchial reactivity to allergen after repeated allergen inhalation challenges. In guinea pig bronchial asthma this self-protecting mechanism depends on endogenous prostaglandin E biosynthesis and can be inhibited by certain thiols. Therefore, we tested the effect of acetylcysteine (AC), a secretolytic thiol, on allergen tachyphylaxis in 25 guinea pigs. We observed inhibition of allergen tachyphylaxis and prolongation of each single asthmatic reaction. A possible clinical relevance of this observation was tested by the following experiments: Human lung fibroblasts (Wi-38) were stimulated with arachidonic acid and calcium ionophore and exposed to increasing amounts of AC. PgE biosynthesis was reduced from 2,408 pg/ml (control) to 84.2 pg/ml (0.6% AC) and 18.6 pg/ml (6% AC). Histamine release (HR) from human peripheral leukocytes was induced by anti-IgE. AC (0.016, 0.16, 1.6%) augmented both spontaneous HR (0-51.8%) and anti IgE induced HR (23.5-57.9%, p less than 0.001). Patients with isolated immediate bronchial reactions after allergen challenge inhaled 3 times a constant allergen dose. In few cases the reaction decreased from one test to another. This 'allergen tachyphylaxis' was inhibited by AC. We conclude that AC should be used with caution in patients suffering from bronchial asthma.

Antiasthmatic effects of onion extracts--detection of benzyl- and other isothiocyanates (mustard oils) as antiasthmatic compounds of plant origin

Previous studies showed the inhibitory effects of crude ethanolic onion extracts (COE) on allergic skin reactions in man as well as on allergen-induced bronchial asthma in man and guinea-pigs. Work is in progress in order to identify both the mode of action of COE and the active substance(s). The present study describes asthma-protective effects of isothiocyanates. Groups of at least 5 guinea-pigs sensitized to ovalbumin were challenged twice (time 0 and 10 min) by the inhalation of ovalbumin 30 min after oral treatment with increasing doses of the agent tested or control solutions. Bronchial obstruction (BO) was measured by whole body plethysmography. Chloroform extracts of onions showed similar protective effects on BO as COE. The water-soluble fraction of COE was inactive. Benzyl-isothiocyanate (BITC) was identified as one component of onion lipids by combined gas chromatography/mass spectrometry. BITC inhibited BO in a dose-dependent fashion: 150 mg/kg: 89%; 75 mg/kg: 76%; 30 mg/kg: 66%; 15 mg/kg: 49%. Ethyl-isothiocyanate and allyl-isothiocyanate showed similar effects; p-hydroxy-benzyl-isothiocyanate, a very unstable mustard oil, was ineffective. Additional experiments showed no antagonistic effects of COE on histamine- or acetylcholine-induced BO. The antiasthmatic effects of onions and - perhaps - other plants may be mediated at least in part by isothiocyanates.

Sequential histamine inhalations cause increased bronchial histamine reactivity in guinea pigs: role of platelets, thromboxanes and prostacyclin

Groups of 6-15 guinea pigs sensitized to ovalbumin were challenged by repeated inhalations of a constant histamine dose at time 0, 10, 20, 60 and 70 min. Bronchial obstruction was measured by whole body plethysmography. The degree of bronchial obstruction increased from one challenge to the other reaching maximal values after 70 min. This increase of bronchial responsiveness to histamine after repeated histamine challenges was reduced by pretreatment with clemastine (histamine H1-receptor antagonist, 0.12 mg/kg i.p., n = 7, P less than 0.05) and more effectively by combined clemastine/cimetidine pretreatment (combined H1-H2-receptor antagonists, 0.12 resp. 10 mg/kg, n = 7, P less than 0.001); pretreatment with acetylsalicylic acid (10 mg/kg orally) accelerated the increase of bronchial responsiveness to histamine (n = 9, P less than 0.01 at the second challenge), inhalation of prostacyclin (1 microgram) prior to each histamine inhalation prevented the increase of bronchial histamine sensitivity totally (n = 10, P less than 0.001), whereas inhibition of thromboxane biosynthesis (imidazol, 10 mg/kg i.p., n = 6; 4-[2-(1H-imidazol-1-yl)ethoxy]benzoic acid, 10 mg/kg i.p., n = 9; imidazo(1,5-a)pyridine-5-hexanoic acid, 1 mg/kg i.p., n = 8) as well as immunologic platelet depletion were ineffective in our test system. We conclude that prostacyclin inhibits the increase of bronchial responsiveness to histamine after sequential histamine inhalation challenges by a platelet independent mechanism. 1-(3-phenyl-2-propenyl)-1H-imidazol, the fourth type of thromboxane synthetase inhibitor tested (10 mg/kg i.p., n = 15) showed specific effects which may be attributed to antihistamine functions.

[The effect pf antacids on the tissue histamine and prostaglandin (PGE2) content of the gastric mucosa]

Stimulation tests (pentagastrin) induced significant changes in tissue histamine levels in the gastric mucosa within 30 minutes. Acid secretion and a decrease of histamine after application of antacids containing calcium could not be observed in our study; neither was application of antacids over a period of eight days followed by a change in gastric mucosal tissue histamine concentrations. Patients under non-steroidal antiphlogistic medication showed diminished histamine levels. Administration of antacids did not produce changes in histamine levels, but induced a rise of PGE2 levels in the fundal and corpus area of the stomach. This may be due to a cytoprotective effect of antacids containing calcium on the gastric mucosa.

Prevention of allergen-induced bronchial obstruction in sensitized guinea pigs by crude alcoholic onion extract

Thirteen guinea pigs, sensitized to ovalbumin, were pretreated with either 1 ml alcoholic onion extract (= 12% v/v ethanol) or 1 ml 12% ethanol solution (control) according to a randomized crossover protocol. Thirty minutes later the animals were challenged twice for 30 sec (n = 5), respectively 60 sec (n = 8), by the inhalation of ovalbumin (1 ml 1% ovalbumin solution nebulized in 10 l air). The intensity of bronchial obstruction was measured by whole body plethysmography using as parameter the amount of 'compressed air'. Oral pretreatment of guinea pigs with onion extract markedly reduced the asthmatic response (p less than 0.02). After onion pretreatment near normal values were obtained after 30 sec challenge (0.04 +/- 0.06 ml compared to 0.24 +/- 0.15 ml in the control) and only slightly increased values after 60 sec challenge (0.16 +/- 0.07 ml compared to 0.33 +/- 0.25 ml in the control).

In vivo allergen tachyphylaxis in guinea pig lung is mediated by endogenous prostaglandin E biosynthesis

The term "allergen tachyphylaxis" (AT) describes a progressively decreased bronchial reactivity to allergen exposition after repeated allergen challenge [in our test system measured by sequential inhalative antigen challenge of sensitized guinea pigs (GP)]. The hypothesis that AT is mediated by endogenous prostaglandin E (PGE) biosynthesis was tested in vivo on GP sensitized to ovalbumin (OA). Different groups of animals were challenged with simultaneous inhalation of OA (repeatedly at time 0, 10, 20, 60 and 70 min) together with inhibitors of PGE-biosynthesis ( parachloromercurobenzoic acid = PCMB, copper sulfate = Cu, copper dithiotreitol complex = CuDTT , dithiotreitol = DTT and dimercaptopropanol = DMP) or agents increasing PGE production (aurothioglucose = Au, zinc dithiotreitol complex = ZnDTT and reduced glutathion = GSH). Bronchial obstruction was measured by whole body plethysmography . PCMB, Cu, CuDTT , DTT and DMP inhibited AT, whereas Au and ZnDTT enhanced AT. Acetylsalicylic acid (ASA) treatment prevented AT. Aerosols of PGE2, but not of prostacyclin or prostaglandin D2 restored AT in ASA treated animals. In addition to these in vivo experiments in vitro investigations showed that PCMB, Cu and DTT decreased while ZnDTT increased PGE biosynthesis of allergen challenged GP lungs. It is concluded that AT, an important self-protecting mechanism of GP bronchial asthma, is mediated at least in part via endogenous PGE.

Suppression of immediate and late anti-IgE-induced skin reactions by topically applied alcohol/onion extract

In a double blind study, alcohol/onion extract (5% ethanol) was injected simultaneously with 20 IU and 200 IU rabbit anti-human-IgE intradermally in 12 adult volunteers (6 atopics, 6 non-atopics). Diameters of wheals and flares were measured 10 min after and compared with control sites challenged with 20 IU and 200 IU anti-IgE in a 5% ethanol solution. The skin sites were then treated epidermally with 45% alcohol/onion extract and 45% ethanol under occlusion. Diameters of late cutaneous reactions were measured hourly. Oedema formation was clinically estimated according to an arbitrary scale and skin thickness measured with a calliper. In the onion-treated skin sites the wheal areas were significantly reduced (20 IU: control: 108 +/- 53 mm2; onion 69 +/- 42 mm2, P less than 0.05; 200 IU anti-IgE: control: 152 +/- 25 mm2, onion: 138 +/- 26 mm2, P less than 0.02). The oedema formation during the late phase skin reaction was markedly depressed (P less than 0.005 at 2 h, P less than 0.01 at 4 and 6 h, P less than 0.02 at 8 h). The extent of late skin reactions was slightly, but not significantly reduced. Obviously, onions contain pharmacologically active substances with anti-inflammatory and/or allergic properties.

Effect of 15-hydroxyeicosatetraenoic acid (15-HETE) on anti-immunoglobulin E- and calcium ionophore-induced histamine release from human leukocytes. Comparison with the effects of eicosatetraynoic acid and nordihydroguaiaretic acid

15-Hydroxyeicosatetraenoic acid (15-HETE) was prepared by soybean lipoxygenase-mediated oxygenation of arachidonic acid to 15-hydroperoxyeicosatetraenoic acid (15-HETE) and subsequent reduction by NaBH4. 15-HETE was identified, purified and proved as biologically active by thin layer chromatography, high pressure liquid chromatography, gas chromatography/mass spectrometry and biological experiments on horse thrombocytes and rabbit peritoneal leukocytes. 15-HETE (0.1-40 microM) was added to peripheral leukocytes of 48 human donors (33 atopics, 15 nonatopics) which were challenged with rabbit anti-human-IgE or calcium ionophore A 23187. Its effect was compared with the effects of nordihydroguaiaretic acid (NDGA) and eicosatetraynoic acid (ETYA). NDGA and ETYA markedly inhibited histamine release (17 microM: 74 +/- 11 and 39 +/- 14,3%, respectively), whereas 15-HETE neither stimulated nor inhibited spontaneous anti-IgE- or calcium ionophore A 23187-induced histamine release.

A selective inhibitor of thromboxane biosynthesis enhances immediate and inhibits late cutaneous allergic reactions in man

Thromboxanes may be involved in late cutaneous reactions (LCRs). A new selective inhibitor of thromboxane biosynthesis was studied for its effect on immediate skin test reactions (WFRs) and LCRs in nine adult nonatopic volunteers (open study) and eight adult atopic patients (double-blind study vs. placebo). WFRs and LCRs were elicited by intradermal injections of 25 micrograms of compound 48/80 and 200 IU of rabbit anti-human IgE antibodies, and the patients' receiving injections of 0.32, 1.6, 8, 40, and 200 IU of anti-IgE antibodies. Dazoxiben (100 mg orally three times once every 4 hr) increased the diameter of wheals (p less than 0.005 in volunteers; p less than 0.05 in six patients receiving no additional drug treatment), favored their dispersion (lymphangitis/pseudopodia), and caused systemic reactions (headache, chills) in at least two out of eight patients. Edema formation during LCRs was markedly depressed in 13 out of 16 persons. Flare diameter and erythemata during LCRs were not altered. These data suggest a role of thromboxanes and their natural antagonists (e.g., prostacyclin) in the regulation of allergic inflammatory processes.

Mediator studies in skin blister fluid from patients with dual skin reactions after intradermal allergen injection

Skin blister fluid (SBF) samples obtained after allergen skin testing in a total of 26 patients with late cutaneous reactions (LCRs) were examined for the presence of various vasoactive mediators. Histamine was predominant during the early phase of the wheal and flare reaction(206 +/- 40 ng/ml) and decreased with the development of the LCR toward normal SBF levels (around 20 ng/ml). Kallikrein activity was measurable in low amounts (around 5 ng/ml) in three out of 13 SBF samples taken 30 min after skin testing and in five of 13 SBF samples taken 6 hr after allergen testing. The thromboxane B2 content of SBF showed an increase with the development of LCR (control skin 976 +/- 483 ng/ml; allergen-tested skin 30 min after allergen injection, 1465 +/- 1566 ng/ml; allergen-tested skin 6 hr after antigen injection, 1775 +/- 731 ng/ml). SBF obtained from normal skin as well as from allergen-tested skin showed significant platelet-activating property as measured in an in vitro serotonin-release assay from washed human platelets. It is concluded that during the development of late-phase reactions a complex interaction of various mediator systems takes place.

Histamine1--histamine2 antagonism: effect of combined clemastine and cimetidine pretreatment on allergen and histamine-induced reactions of the guinea pig lung in vivo and in vitro

In a preliminary study high doses of the H1-antagonist clemastine (clem) and the H2-antagonist cimetidine (cim) were used in order to detect the side effects of both drugs on allergic reactions. After pretreatment with clem or clem/cim different guinea pigs were challenged with either OA or histamine. Bronchial obstruction was measured by body plethysmography using a new parameter ('compressed air'). Pretreatment with clem/cim in high doses protected guinea pigs against OA-induced bronchial obstruction much more effectively than H1-receptor antagonism alone; lower cim doses produced insignificant effects. In histamine-challenged animals cim showed no protective effects. In vitro clem/cim caused a marked reduction of histamine release measured in perfused lungs from 16.9 +/- 4.2 ng/ml (eight control cases) to 2.8 +/- 1.7 ng/ml (n = 8). Our preliminary data suggest that high doses of clem/cim can protect sensitized guinea pigs against allergen-induced bronchial obstruction by inhibiting histamine release.

Allergen tachyphylaxis of guinea pigs in vivo; a prostaglandin E mediated phenomenon?

Ovalbumin (OA) sensitized guinea pigs were repeatedly challenged with 1% OA in saline nebulized ultrasonically at the 0, 10, 20, 60 and 70th min. The intensity of bronchial obstruction was measured by body plethysmography. The first three challenges (0. 10, 20 min) caused strong asthmatic reactions in all animals, the last two (60, 70 min) only mild one in 10 out of 15 animals. The development of this "tachyphylaxis" was markedly reduced by pretreatment of the animals with cyclooxygenase inhibitors (indomethacin 10 mg/kg intraperitoneally resp, acetylsalicylic acid 10 mg/kg orally 2 h before tests). The effect of both inhibitors (i.e. inhibition of tachyphylaxis) was abolished by supplementing prostaglandin E2 as aerosol simultaneously to the allergen (100-200 ng per inhalation). The results suggest that allergen tachyphylaxis we have observed in vivo might be due to synthesis of cyclooxygenase products, e.g. prostaglandin E.

Continuous recording of intrapulmonary "compressed air" as a sensitive noninvasive method of measuring bronchial obstruction in guinea pigs

The method presented is based on whole-body plethysmography. The apparatus consisted of two chambers (a = respiratory, b = body chamber) separated by a tight water-filled rubber cuff which was fixed around the head of the animal. Experiments were performed under constant gas conditions: temperature 30 degrees C, 100% relative humidity, the volumes of the two chamber being identical. Volume changes in the chamber (delta Va, delta Vb) were recorded continuously by means of pressure transducers. Respiratory flow was calculated by differentiation of delta Va with respect to time. The three parameters delta Va, delta Vb and respiratory flow allowed the calculation of breathing frequency, inspiration/expiration ratio, (peak) expiratory flow and specific airway conductance. In addition we describe a new parameter indicating bronchial obstruction: a graphical plot of delta Vb against delta Va produces a closed loop, the area of which reflects the degree of airway obstruction, and we read off the parameter we term "compressed air" from this graph. In our hands this parameter was more than ten times as sensitive as other measures of bronchial obstruction. Using this new technique we have carried out pharmacological studies with eicosatetraynoic acid (ETYA), 2-aminomethyl 4-t-butyl-6-iodophenol (MK 447 = radical scavenger), the histamine antagonist clemastine and the histamine antagonist cimetidine. In allergen-tested animals we observed mild protective effects of ETYA when given as an aerosol (3 mg) and pronounced effects of MK 447 (4 mg i.p.). Combined H1 H2-antagonism was much more effective in preventing allergen-induced bronchial obstruction than H1-antagonism alone.

Induction of late cutaneous reactions by skin-blister fluid from allergen-tested and normal skin

Ten healthy volunteers (five atopic, five nonatopic) and seven patients suffering from allergic bronchial asthma and rhinitis/conjunctivitis as well as showing dual reactions after intradermal or bronchial allergen challenge were investigated. Using the suction blister technique, we obtained skin-blister fluid (SBF) from dual skin reactions 30, 60, 180, and 300 min after allergen injection and from normal untested skin. The biologic activity of SBF was tested by intradermal reinjection of the fluid into the donor. SBF taken from dual skin reactions 30 or 60 min after allergen injection produced late cutaneous reactions (LCRs) quite similar to those induced by the allergen. SBF taken from LCR areas 180 or 300 min after antigen testing had much weaker effects, similar to SBF from untested skin. A possible content of allergen extract in SBF from allergen-tested skin areas was not responsible for the observed effects as demonstrated in passive cutaneous anaphylaxis experiments in monkeys. High doses of SBF from untested skin were able to induce LCRs similar to but weaker than LCRs produced by SBF taken at early phases from dual skin reactions. Similar volumes of autologous heparin-plasma or serum did not induce LCRs. It is concluded that during the initial phase of dual skin reactions, factors are formed that are able to induce LCRs. The generation of these mediators seems to be caused at least in part by the extravasation of plasma.

Effect of topical indomethacin on allergen-induced dual skin reactions

Twelve asthmatics with dual bronchial and skin reactions after allergen challenge received topical treatment with a 5%-indomethacin cream half an hour before and up to 7 h after intradermal allergen and histamine injections. The erythema during the first 20 min of the wheal and flare reaction (WFR) was not affected, neither were the diameters of wheals and flares. 40 to 60 min after injection we observed a marked reduction of the erythema in histamine- and allergen-tested skin areas of 10 patients. This effect lasted up to the 5th h after injection of high allergen doses. During the fully developed late cutaneous reactions (LCR) no effect of indomethacin on the erythema was observed, the edema of LCR was only insignificantly reduced. These results suggest that the erythema in LCR between the 1st and 4th h is caused, at least in part, by local formation of prostaglandins.