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Biomedical subjects

A Bergner

Publications and source records attributed to A Bergner.

At least 19 recordsLinked to original sources
PubMed2006

How many types of cholinergic sympathetic neuron are there in the rat stellate ganglion?

Sympathetic cholinergic postganglionic neurons are present in many sympathetic ganglia. Three classes of sympathetic cholinergic neuron have been reported in mammals; sudomotor neurons, vasodilator neurons and neurons innervating the periosteum. We have examined thoracic sympathetic ganglia in rats to determine if any other classes of cholinergic neurons exist. We could identify cholinergic sudomotor neurons and neurons innervating the rib periosteum, but confirmed that cholinergic sympathetic vasodilator neurons are absent in this species. Sudomotor neurons contained vasoactive intestinal peptide (VIP) and calcitonin gene-related peptide (CGRP) and always lacked calbindin. Cholinergic neurons innervating the periosteum contained VIP and sometimes calbindin, but always lacked CGRP. Cholinergic neurons innervating the periosteum were usually surrounded by terminals immunoreactive for CGRP. We conclude that if any undiscovered populations of cholinergic neurons exist in the rat thoracic sympathetic chain, then they are indistinguishable in size, neurochemistry and inputs from sudomotor or cholinergic neurons innervating the periosteum. It may be that the latter two populations account for all cholinergic neurons in the rat thoracic sympathetic chain ganglia.

Acetylcholine↗
PubMed2006

Bronchial hyperreactivity is correlated with increased baseline airway tone.

Physiologically, airways are not completely relaxed but maintain a baseline airway tone (BAT). Although not fulfilling the criteria for obstructive airway disease, increased BAT may nevertheless be important because the same amount of airway narrowing can be well tolerated or can cause severe airway obstruction depending on the starting point of the narrowing. In this study, we aimed at studying if BAT is correlated with bronchial hyperreactivity (BHR). For in vitro studies, airways in murine lung slices were digitally recorded and the change in cross-sectional area with time was quantified. BAT was measured by the amount of relaxation induced by permeabilization of the cell membrane with beta-escin in zero external calcium. BHR was induced by incubation of lung slices with interleukin-13 (IL-13). T-bet knock-out mice served as an additional model for BHR. T-bet knock-out mice show a shift towards TH2-lymphocytes and display histological as well as functional characteristics of asthma. In vivo, the specific airway resistance of healthy non-smoking volunteers was assessed before and after inhalation of formoterol and bronchial challenge was performed using methacholin. In murine lung slices that had been cultivated without serum, only a minimal BAT could be observed. But, after cultivation with 10 % new born calve serum, airways showed a BAT of approximately 13 % that could be reduced by incubation with an IL-13 receptor antagonist. Atropine, isoproterenol and indomethacin failed to relax airways regardless of cultivation with serum. Incubation of lung slices without serum but with IL-13 increased BAT as well as airway responsiveness to acetylcholine and both effects were more pronounced in small compared to large airways. In lung slices from T-bet knock-out mice, airways were hyperreactive compared to airways in slices from wild type mice and BAT was found to be increased. Again, both effects were more pronounced in small compared to large airways. In human non-smokers without airway obstruction, increased BAT was correlated with bronchial hyperreactivity. We therefore conclude that although not fulfilling the criteria for obstructive airway disease, increased airway tone may yet be relevant in asthma.

Acetylcholine↗
PubMed2006

[Ca2+-signaling in smooth muscles cells of the airways in T-bet knock-out mice].

BACKGROUND: Airway smooth muscle cells (ASMC) play a key role in bronchial hyperresponsiveness (BHR). A major component of the signalling cascade leading to ASMC contraction is calcium. T-bet knock-out (KO) mice show the key features of allergic asthma such as a shift towards T (H2)-lymphocytes and display a broad spectrum of asthma-like histological and functional characteristics. In this study, we aimed at investigating whether Ca (2+)-homeostasis of ASMC is altered in T-bet KO-mice as an experimental model of asthma. METHODS: Lung slices of 100 to 200 microm thickness were obtained from T-bet KO- and wild-type mice. Airway contractions in response to acetylcholine (ACH) were measured by video-microscopy and Ca (2+)-signaling in single ASMC of lung slices was assessed using two-photon microscopy. RESULTS: Airways from T-bet KO-mice showed increased baseline airway tone (BAT) and BHR compared to those of wild-type mice. The increased BAT was correlated with an increased incidence of spontaneous changes in intracellular Ca (2+)-concentrations, whereas BHR correlated with higher ACH-induced Ca (2+)-transients and an increased proportion of ASMC showing Ca (2+)-oscillations. Emptying intracellular Ca (2+)-stores using caffeine or cyclopiazonic acid induced higher Ca (2+)-elevations in ASMC from T-bet KO compared to wild-type mice. CONCLUSIONS: Altered Ca (2+)-homeostasis of ASMC contributes to increased BAT and BHR in lung slices from T-bet KO mice as a murine asthma model. We propose that a higher Ca (2+)-content of the intracellular Ca (2+)-stores is involved in the pathophysiology of these changes.

Animals↗
PubMed2005

Monitoring of expiratory flow rates and lung volumes during a high altitude expedition.

BACKGROUND: Data on lung volumes and changes in flow-volume spirometry at high altitude are few and do not provide comprehensive assessment of the occurring changes. This study characterizes alterations of the forced expiratory flow-volume curve (FEFV-curve) and lung volumes at increasing altitude. METHODS: FEFV-curve and lung volumes at increasing altitude were characterized by daily assessment of peak expiratory flow (PEF), forced expiratory volume in one second (FEV1), forced vital capacity (FVC) and maximal expiratory flow rates (MEF 25, 50, 75) at 25%, 50% and 75% of the FEFV-curve with a portable spirometer (turbinometric method) three times a day during an expedition to Mustagh Ata (7545m) in 15 healthy mountaineers. RESULTS: With increasing altitude FVC and FEV1 were reduced by up to 25% (74.8% / 74.6% of baseline) and MEF25 was reduced to 81.5% of baseline values. PEF initially increased up to 4451m and returned to baseline values above 5000m. After descent below 2000m, all values normalized within one day. There were weak negative correlations between AMSS and FEV1, FVC and PEF (r = -0.23, p<0.001). CONCLUSIONS: We found increasing pulmonary restriction at high altitude without a marked reduction of PEF. Assessment of the FEFV-curve at high altitudes with a portable spirometer is a practical method reflecting the true field situation and may provide clinically relevant information (impending pulmonary edema).

Adult↗
PubMed2005

Cell cycle effects of radiation on human bronchial epithelium and lung carcinoma cells in monolayer cultures and a three-dimensional co-culture system.

The aim of this study was to investigate whether the three-dimensional structure of the bronchial tissue and the contact of non-malignant with malignant cells influence the effectiveness of radiotherapy. Monolayer cultures of cells of the human bronchial epithelial cell line BEAS 2B, monolayer co-cultures of BEAS 2B cells and cells of the GFP-transfected lung carcinoma cell line EPLC 32M1, organ cultures of human bronchial epithelium, and organ co-cultures with EPLC 32M1 cells were irradiated with 10 Gy, and the DNA content was analyzed using flow cytometry. In non-malignant epithelial cells, BEAS 2B monolayer cultures without tumor cells were highly radiosensitive. However, contact with tumor cells in monolayer co-cultures markedly reduced radiosensitivity. Non-malignant cells in three-dimensional organ cultures and organ co-cultures with tumor cells showed moderate radiosensitivity. In EPLC 32M1 tumor cells, proliferation was increased without irradiation when the cells were in contact with epithelial cells in both organ and monolayer co-cultures. Radiosensitivity was higher in organ co-cultures than in monolayer cultures and monolayer co-cultures. These data indicate that organ co-cultures in combination with flow cytometry allow investigation of the effects of radiation in an in vivo-like environment and that both the spatial organization and the interaction of non-malignant and tumor cells are crucial for the effectiveness of radiotherapy.

Bronchi↗
PubMed2003

Effects of single-dose irradiation on bronchial epithelium: a comparison of BEAS 2B cell monolayers, human organ cultures, and Goettinger minipigs.

To assess the effects of radiation on bronchial epithelium, BEAS 2B cells cultured as monolayers and human bronchial epithelium cultured as organ cultures were exposed to single doses of 0, 10 and 30 Gy. The lactate dehydrogenase in the supernatant of the BEAS 2B cells increased markedly 24 h after irradiation, whereas in the organ cultures only a minor increase was found after 48 h. The nucleosomes in the supernatant of the BEAS 2B cells showed a massive increase in response to irradiation, whereas in the organ cultures no change could be seen. The number of BEAS 2B cells was dramatically diminished after 96 h, whereas in the organ cultures a smaller decrease was observed no earlier than 21 days after irradiation. To assess the effects of brachytherapy in bronchial epithelium in vivo, brachytherapy with 30 Gy was performed in Goettinger minipigs, and histological sections of the bronchi were analyzed for morphological alterations and cell numbers. After 2 weeks, only slight cell damage was observable, and after 3 weeks, moderate morphological changes and decreased cell numbers were found. However, after 8 weeks, the epithelium had nearly regained its normal structure. We conclude that the bronchial epithelium has a remarkably high radioresistance and that organ cultures, but not monolayers of BEAS 2B cells, reflect the effects of radiation in vivo.

Animals↗
PubMed2001

Bivalent inhibition of human beta-tryptase.

BACKGROUND: Human beta-tryptase is a mast cell specific trypsin-like serine protease that is thought to play a key role in the pathogenesis of diverse allergic and inflammatory disorders like asthma and psoriasis. The recently resolved crystal structure revealed that the enzymatically active tetramer consists of four quasi-identical monomers. The spatial display of the four identical active sites represents an ideal basis for the rational design of bivalent inhibitors. RESULTS: Based on modeling experiments homobivalent inhibitors were constructed using (i) 6A,6D-dideoxy-6A,6D-diamino-beta-cyclodextrin as a rigid template to bridge the space between the two pairs of identical active sites and (ii) 3-(aminomethyl)benzene as a headgroup to occupy the arginine/lysine specific S1 subsites. A comparative analysis of the inhibitory potencies of synthetic constructs that differ in size and type of the spacer between headgroup and template revealed that the construct contained two 3-(aminomethyl)benzenesulfonyl-glycine groups linked to the 6A,6D-diamino groups of beta-cyclodextrin as an almost ideal bivalent inhibitor with a cooperativity factor of 1.9 vs. the ideal value of 2. The bivalent binding mode is supported by the inhibitor/tetramer ratio of 2:1 required for inactivation of tryptase and by X-ray analysis of the inhibitor/tryptase complex. CONCLUSION: The results obtained with the rigid cyclodextrin template underlined the importance of a minimal loss of conformational entropy in bivalent binding, but also showed the limitations imposed by such rigid core molecules in terms of optimal occupancy of binding sites and thus of enthalpic strains in bidentate binding modes. The main advantage of bivalent inhibitors is their high selectivity for the target enzyme that can be achieved utilizing the principle of multivalency.

Binding Sites↗
PubMed2000

The human mast cell tryptase tetramer: a fascinating riddle solved by structure.

Tryptases, the predominant proteins of human mast cells, have been implicated as pathogenetic mediators of allergic and inflammatory conditions, most notably asthma. Until recently, the fascinating properties that distinguish tryptases among the serine proteinases, particularly their activity as a heparin-stabilized tetramer, resistance to most proteinaceous inhibitors, and preference for peptidergic over macromolecular substrates presented a riddle. This review solves this riddle with the help of the crystal structure of the human beta(2)-tryptase tetramer, but also indicates controversies between the unique quaternary architecture and some experimental data.

Amino Acid Sequence↗
PubMed2000

Dialysate related cytokine induction and response to recombinant human erythropoietin in haemodialysis patients.

BACKGROUND: Chronic inflammatory disorders or infections represent a major cause of hyporesponsiveness to recombinant human erythropoietin (rHuEpo). To test the hypothesis that dialysate-related cytokine induction alters the response to rHuEpo, we conducted a prospective study with matched pairs of chronic haemodialysis patients. We compared the effect of two dialysis fluids, differing in their microbiological quality, on the rHuEpo therapy. METHODS: Thirty male patients with end-stage renal disease maintained on regular haemodialysis were assigned either to a group treated with conventional (potentially microbiologically contaminated) dialysate (group I) or to a group treated with online-produced ultrapure dialysate (group II). Randomization was stratified according to the maintenance dose of rHuEpo necessary to maintain a target haemoglobin level of 10-10.5 g/dl. Patients were followed for 12 months. Kt/V was calculated by the formula of Daugirdas. Haemoglobin levels were measured weekly and serum ferritin concentrations were determined at 6-week intervals. C-reactive protein (CRP) and interleukin-6 (IL-6) was measured by an ELISA at the start of the study and after 3, 6 and 12 months. RESULTS: In group I, continuous use of bicarbonate dialysate did not change the rHuEpo dosage given to achieve the target haemoglobin level and was associated with elevated surrogate markers (CRP, IL-6) of cytokine-induced inflammation. The switch from conventional to online-produced ultrapure dialysate in group II resulted in a lower bacterial contamination with a significant decrease of CRP and IL-6 blood levels. It was accompanied by a significant and sustained reduction of the rHuEpo dosage, which was required to correct the anaemia. Using multiple regression analysis, IL-6 levels are shown to have a strong predictive value for rHuEpo dosage in both groups. CONCLUSIONS: Our data demonstrate that dialysate-related factors such as low bacterial contamination can induce the activation of monocytes, resulting in elevated serum levels of IL-6. Dialysate-related cytokine induction might diminish erythropoiesis. The use of pyrogen free ultrapure dialysate resulted in a better response to rHuEpo. Not only would it save money, but it would also help to maintain an optimal haemoglobin level without further increase in rHuEpo dosage.

Bacteria↗
PubMed2000

Urethanyl-3-amidinophenylalanine derivatives as inhibitors of factor Xa. X-ray crystal structure of a trypsin/inhibitor complex and modeling studies.

Hydrophobic urethanyl derivatives of 3-amidinophenylalanine methyl ester were found to be relatively potent and selective factor Xa inhibitors. These compounds consist of the arginine-mimetic 3-benzamidino group as P1 residue and of hydrophobic residues as potential interaction partners for the S3/S4 aryl binding site of the enzyme. Attempts to possibly identify their binding mode to factor Xa via the X-ray crystal structure of a trypsin/inhibitor complex and analogy modeling on the crystal structure of factor Xa failed. However, synthesis of enantiomerically pure (R)- and (S)-derivatives, combined with modeling experiments, led to an hypothetical non-substrate like binding mode, which was fully confirmed by the remarkably enhanced inhibitory potency of derivatives in which the methyl ester was replaced by arylamides for interactions with the S3/S4 enzyme binding subsites. With adamantyloxycarbonyl-(R)-3-amidinophenylalanine-phenethylamide+ ++ a nanomolar inhibiton was obtained, thus indicating this new class of factor Xa inhibitors as a highly promising lead structure.

Animals↗
PubMed1999

The structure of the human betaII-tryptase tetramer: fo(u)r better or worse.

Tryptases, the predominant serine proteinases of human mast cells, have recently been implicated as mediators in the pathogenesis of allergic and inflammatory conditions, most notably asthma. Their distinguishing features, their activity as a heparin-stabilized tetramer and resistance to most proteinaceous inhibitors, are perfectly explained by the 3-A crystal structure of human betaII-tryptase in complex with 4-amidinophenylpyruvic acid. The tetramer consists of four quasiequivalent monomers arranged in a flat frame-like structure. The active centers are directed toward a central pore whose narrow openings of approximately 40 A x 15 A govern the interaction with macromolecular substrates and inhibitors. The tryptase monomer exhibits the overall fold of trypsin-like serine proteinases but differs considerably in the conformation of six surface loops arranged around the active site. These loops border and shape the active site cleft to a large extent and form all contacts with neighboring monomers via two distinct interfaces. The smaller of these interfaces, which is exclusively hydrophobic, can be stabilized by the binding of heparin chains to elongated patches of positively charged residues on adjacent monomers or, alternatively, by high salt concentrations in vitro. On tetramer dissociation, the monomers are likely to undergo transformation into a zymogen-like conformation that is favored and stabilized by intramonomer interactions. The structure thus provides an improved understanding of the unique properties of the biologically active tryptase tetramer in solution and will be an incentive for the rational design of mono- and multifunctional tryptase inhibitors.

Amino Acid Sequence↗
PubMed1998

Crystal structure of L-arginine:inosamine-phosphate amidinotransferase StrB1 from Streptomyces griseus: an enzyme involved in streptomycin biosynthesis.

Inosamine-phosphate amidinotransferases catalyze two nonconsecutive transamidination reactions in the biosynthesis of the streptomycin family of antibiotics. L-Arginine:inosamine-phosphate amidinotransferase StrB1 from Streptomyces griseus (StrB1) was cloned as an N-terminal hexa-histidine fusion protein, purified by affinity chromatography, and crystallized, and its crystal structure was solved by Patterson search methods at 3.1 A resolution. The structure is composed of five betabeta alphabeta-modules which are arranged circularly into a pseudo-5-fold symmetric particle. The three-dimensional structure is closely related to the structure of human L-arginine:glycine amidinotransferase (AT), but five loops (the 40-, 170-, 220-, 250-, and 270-loop) are organized very differently. The major changes are found in loops around the active site which open the narrow active site channel of AT to form an open and solvent-exposed cavity. In particular, module II of StrB1 is AT-like but lacks a 10-residue alpha-helix in the 170-loop. The concomitant reorganization of neighboring surface loops that surround the active site, i.e., the 40-loop and the 270-loop, results in an arrangement of loops which allows an unrestricted access of substrates to the cavity. However, the residues which are involved in substrate binding and catalysis are conserved in AT and StrB1 and are at equivalent topological positions, suggesting a similar reaction mechanism among amidinotransferases. The binding site for L-arginine had been deduced from its complex with AT. Molecular modeling revealed a possible binding mode for the second substrate scyllo-inosamine 4-phosphate.

Amidinotransferases↗
PubMed1998

Design of benzamidine-type inhibitors of factor Xa.

A series of derivatives of rac-benzenesulfonyl-glycyl-phenylalanine or its ethyl ester with a combination of thioamido/amidino or amidino/amidino substituents in the benzene rings was synthesized as potential inhibitors of factor Xa (fXa). Among these, the racemic 4'-amidinobenzenesulfonyl-glycyl-4-amidinophenylalanine ethyl ester was found to exhibit the highest affinity for fXa despite the unfavored location of the amidino substituent in the para position. X-ray structural analysis of the trypsin complex with this bis-benzamidine compound revealed a retro-binding mode if compared to those of similar compounds, so far analyzed in complexes with trypsin or fXa. This noncanonical binding mode as well as its slow plasma clearance rates in rats, if compared to those of other benzamidine derivatives, suggests this compound as an interesting new lead structure for the design of fXa inhibitors.

Animals↗
PubMed1998

Human beta-tryptase is a ring-like tetramer with active sites facing a central pore.

Human tryptase, a mast-cell-specific serine proteinase that may be involved in causing asthma and other allergic and inflammatory disorders, is unique in two respects: it is enzymatically active only as a heparin-stabilized tetramer, and it is resistant to all known endogenous proteinase inhibitors. The 3-A crystal structure of human beta-tryptase in a complex with 4-amidinophenyl pyruvic acid shows four quasi-equivalent monomers arranged in a square flat ring of pseudo 222 symmetry. Each monomer contacts its neighbours at two different interfaces through six loop segments. These loops are located around the active site of beta-tryptase and differ considerably in length and conformation from loops of other trypsin-like proteinases. The four active centres of the tetramer are directed towards an oval central pore, restricting access for macromolecular substrates and enzyme inhibitors. Heparin chains might stabilize the complex by binding to an elongated patch of positively charged residues spanning two adjacent monomers. The nature of this unique tetrameric architecture explains many of tryptase's biochemical properties and provides a basis for the rational design of monofunctional and bifunctional tryptase inhibitors.

Amino Acid Sequence↗
PubMed1998

The ternary microplasmin-staphylokinase-microplasmin complex is a proteinase-cofactor-substrate complex in action.

The serine proteinase plasmin is the key fibrinolytic enzyme that dissolves blood clots and also promotes cell migration and tissue remodeling. Here, we report the 2.65 A crystal structure of a ternary complex of microplasmin-staphylokinase bound to a second microplasmin. The staphylokinase 'cofactor' does not affect the active-site geometry of the plasmin 'enzyme', but instead modifies its subsite specificity by providing additional docking sites for enhanced presentation of the plasminogen 'substrate' to the 'enzymes's' active site. The activation loop of the plasmin 'substrate', cleaved in these crystals, can be reconstructed to show how it runs across the active site of the plasmin 'enzyme' prior to activation cleavage. This is the first experimental structure of a productive proteinase-cofactor-macromolecular substrate complex. Furthermore, it provides a template for the design of improved plasminogen activators and plasmin inhibitors with considerable therapeutical potential.

Amino Acid Sequence↗