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Density arrested AKR-2B cells die rapidly in response to serum starvation or treatment by Anisomycin. Cell death is associated with typical hallmarks of apoptosis including membrane blebbing and chromatin condensation but lacks energy dissipation in mitochondria and intranucleosomal fragmentation. During apoptosis a considerable DEVDase activity has been detected which seemed to be represented by a single enzyme. This enzyme had typical effector caspase characteristics, like caspase-3, but exhibited an unusual high KM values of ~100 µM and its large subunit exhibited a molecular weight of 19 kDa, instead of expected 17 kDa. In the present study, this enzyme was identified to be caspase-3 with the help of the generation of recombinant mcaspase-3 protein. N-terminal sequencing of the recombinant mcaspase-3 protein revealed that its prodomain cleavage site differs from that in the human homologue (Asp-9 instead of Asp-28). Thus the large subunit of active caspase-3 was found to be 19 kDa. Furthermore the KM value of recombinant mcaspase-3 was ~100 µM in perfect agreement with that found in cell extracts. Affinity labeling in combination with 2D-GE confirmed that indeed caspase-3 is activated as the main executioner in AKR-2B cells during apoptosis. Since the receptor mediated pathway has already been excluded previously [129], a possible involvement of mitochondria mediated pathway in the activation of caspase-3 was examined. Gel filtration experiments revealed that caspase-3 is mainly eluted as free enzyme and in lower levels within the differently sized high molecular weight complexes of ~600 kDa and 250 kDa in response to serum starvation or Anisomycin treatment. Though the apparent molecular weight of the complexes containing caspase-3 are in accordance with recently published data, they were devoid of Apaf-1 and caspase-9. Apparently, mitochondria mediated pathway is also not involved since neither formation of high molecular weight complexes of Apaf-1 nor cleavage of caspase-9 was observed. Thus, the activation of caspase-3 is caused by a noncanonical pathway during apoptosis. In addition a new 450 kDa complex containing activated caspase-6 was found in response to serum starvation which is clearly separated from caspase-3 containing complexes. Generally caspase-3 has been found to be responsible for most of the morphological changes during apoptosis. One of those is intranucleosomal fragmentation. Although caspase-3 was found to be the main executioner caspase in AKR-2B cells the lack of the intranucleosomal fragmentation led to examine its localization. As detected by overexpression of the Caspase-3-GFP fusion construct in AKR-2B, procaspase-3 was localized in the cytoplasm, wheras the active caspase-3 was mainly found in the membrane blebs and partially in the cytoplasm. Clearly no nuclear localization of active caspase-3 was detected. These data gave first hints on the mechanism of degradation of AKR-2B cells demonstrating that cytoplasmic membrane is the primary site of activation of caspase-3. The possible role of caspase-12 and ER stress mediated pathway of apoptosis was also examined in AKR-2B cells. Kinetic studies showed that caspase-12 is activated at the same time together with caspase-3 in response to serum starvation or Anisomycin treatment resulting in two cleavage products of 47 kDa and 35 kDa, respectively. It was therefore examined whether these two caspases were eluted in the same complexes. Gel filtration experiments revealed that caspase-12 is released as free enzyme during apoptosis. To date all the studies have identified that caspase-12 is specifically activated in response to ER stress. After serum starvation or Anisomycin addition there was no increase of the protein expression level of the chaperone protein Grp 78 which is known to be higly elevated in response to ER stress indicating that both treatments did not lead to ER stress. In contrast treatment with ER stressor substances i.e. Thapsigargin, A23187 (ionophore) induced an ER stress in AKR-2B which lead to unspecifically degradation of caspase-12. Thus it is unlikely that caspase-12 is activated in response to ER stress in AKR-2B cells. However, after the in vitro addition of recombinant caspase-3 to cytosolic extracts caspase-12 is cleaved into 47 kDa and 35 kDa fragments similiar to those observed in vivo. In conclusion the present data demostrated that caspase-12 is activated in AKR-2B cells during apoptosis triggered through pathways that do not involve (the) ER stress and provided evidence that caspase-3 might be involved in activation of caspase-12. Thus the present study in AKR-2B cells gives hints for the existence of additional pathways for apoptosis other than the classical ones.
In the current work, several well-known pharmaceuticals (1,4-dihydrazinophthalazine sulfate, caffeine, and papaverine hydrochloride) and new organometallic compounds (nickel(II) cupferronato complexes NiL2An, L = PhN2O2-, n = 1, A = o-phenanthroline (1), o,o’-bipyridine (2) and n = 2, A = H2O (3), o-NH2Py (4), o-C6H4(NH2)2 (5); silylene-bridged dinuclear iron complexes [Cp(OC)2Fe]2SiX2 (X = H (6), F (7), Cl (8), Br (9), I (10)); 3-silaoxetane 3,3-dimethyl-2,2,4,4-tetraphenyl-1-oxa-3-silacyclobutane (11) and 3-silathietane 3,3-dimethyl-2,2,4,4-tetraphenyl-1-sila-3-thiacyclobutane (12) compounds), which have successfully been characterized by using vibrational spectroscopy in conjunction with accurate density functional theory (DFT) calculations, are presented. The DFT computed molecular geometries of the species of interest reproduced the crystal structure data very well and in conjunction with IR and Raman measurements helped us to clarify the structures of the compounds, for which no experimental data were available; and this, especially for the new organometallic compounds, where the X-Ray analysis was limited by the non-availability of single crystals (3, 5, 10). Furthermore, a natural population analysis (NPA) and natural bond orbital (NBO) calculations together with a detailed analysis of the IR and Raman experimental as well as calculated spectra of the new organometallic compounds, allowed us to study some special bonding situations (1-12) or to monitor the structural changes observed with the change in temperature during the Raman experiments (11, 12). By combining these two methods (DFT and vibrational spectroscopy), the auspicious results obtained on the organometallic compounds 6-12 and overall in literature, made us confident of the power of theoretical calculations in aiding the interpretation of rich SERS spectra by solving some interesting issues. Consequently, the Raman and SERS spectra of well-known pharmaceuticals (1,4-dihydrazinophthalazine sulfate, caffeine, and papaverine hydrochloride) or new potentially biological active organometallic complexes (1-5), that were synthetized by our coworkers, were discussed with the assistance of the accurate results obtained from DFT calculations (structural parameters, harmonic vibrational wavenumbers, Raman scattering activities), and many previous incomplete assignments have been analyzed and improved. This allowed us to establish the vibrational behavior of these biological compounds near a biological artificial model at different pH values or concentrations (Ag substrate), taking into account that information about the species present under particular conditions could be of great importance for the interpretation of biochemical processes. The total electron density of molecules and the partial charges situated on selected atoms, which were determined theoretically by NPA, allowed us to establish the probability of different atoms acting as an adsorptive site for the metal surface. Moreover, a closer examination of the calculated orbitals of molecules brought further arguments on the presence or absence of the photoproducts at the Ag surface during the irradiation (1,4-dihydrazinophthalazine sulfate). Overall, the results provide a benchmark illustration of the virtues of DFT in aiding the interpretation of rich vibrational spectra attainable for larger polyatomic adsorbates by using SERS, as well as in furnishing detailed insight into the relation between the vibrational properties and the nature of the Ag substrate-adsorbate bonding. Therefore, we strongly believe that theoretical calculations will become a matter of rapidly growing scientific and practical interest in SERS.
During the Mesoproterozoic large volumes of magma were repeatedly emplaced within the basement of NW Namibia. Magmatic activity started with the intrusion of the anorthositic rocks of the Kunene Intrusive Complex (KIC) at 1,385-1,347 Ma. At its south-eastern margin the KIC was invaded by syenite dykes (1,380-1,340 Ma) and younger carbonatites (1,140-1,120 Ma) along ENE and SE trending faults. Older ferrocarbonatite intrusions, the ‘carbonatitic breccia’, frequently contain wallrock fragments, whereas subordinate ferrocarbonatite veins are almost xenolith-free. Metasomatic interaction between carbonatite-derived fluids and the neighbouring and incorporated anorthosites led to the formation of economically important sodalite deposits. Investigated anorthosite samples display the magmatic mineral assemblage of Pl (An37-75) ± Ol ± Opx ± Cpx + Ilm + Mag + Ap ± Zrn. Ilmenite and pyroxene are surrounded by narrow reaction rims of biotite and pargasite. During the subsolidus stage sporadic coronitic garnet-orthopyroxene-quartz assemblages were produced. Thermobarometry studies on amphiboles yield temperatures of 985-950°C whereas the chemical composition of coronitic garnet and orthopyroxene indicate a subsolidus re-equilibration of the KIC at conditions of 760 ± 100°C and 7.3 ± 1 kbar. In the syenites Kfs, Pl, Hbl and/or Cpx crystallized first, followed by a second generation of Kfs, Hbl, Fe-Ti oxides and Ttn. Crystallization of potassium feldspar occurred under temperatures of 890-790°C. For the crystallization of hastingsite pressures of 6.5 ± 0.6 kbar are obtained. In order to constrain the source rocks of the two suites, oxygen isotope analyses of feldspar as well as geochemical bulk rock analyses were carried out. In case of the anorthosites, the general geochemical characteristics are in excellent agreement with their derivation from fractionated basaltic liquids, with the d18O values (5.88 ± 0.19 ‰) proving their derivation from mantle-derived magmas. The results obtained for the felsic suite, provide evidence against consanguinity of the anorthosites and the syenites, i.e. (1) compositional gaps between the geochemical data of the two suites, (2) trace element data of the felsic suite points to a mixed crustal-mantle source, (3) syenites do not exhibit ubiquitous negative Eu-anomalies in their REE patterns, which would be expected from fractionation products of melts that previously formed plagioclase cumulates and (4) feldspar d18O values from the syenites fall in a range of 7.20-7.92 ‰, which, however, is about 1.6 ‰ higher than the average d18O of the anorthosites. Conformably, the crustal-derived felsic and the mantle-derived anorthositic suite are suggested to be coeval but not consanguineous. Their spatial and temporal association can be accounted for, if the heat necessary for crustal melting is provided by the upwelling and emplacement of mantle-derived melts, parental to the anorthosites. In order to constrain the source of the 1,140-1,120 Ma carbonatites and to elucidate the fenitizing processes, which led to the formation of the sodalite, detailed mineralogical and geochemical investigations, stable isotope (C,O,S) analyses and fluid inclusion measurements (microthermometrical studies and synchrotron-micro-XRF analyses) have been combined. There is striking evidence that carbonatites of both generations are magmatic in origin. They occur as dykes with cross-cutting relationships and margins disturbed by fenitic aureoles, and contain abundant flow-oriented xenoliths. The mineral assemblage of both carbonatite generations of Ank + Cal + Ilm + Mag + Bt ± Ap ± pyrochlore ± sulphides in the main carbonatite body and Ank + Cal + Mag ± pyrochlore ± rutile in the ferrocarbonatite veins, their geochemical characteristics and the O and C isotope values of ankerite (8.91 to 9.73 and –6.73 to –6.98, respectively) again indicate igneous derivation, with the 18O values suggesting minor subsolidus alteration. NaCl-rich fluids, released from the carbonatite melt mainly caused the fenitization of both, the incorporated and the bordering anorthosite. This process is characterized by the progressive transformation of Ca-rich plagioclase into albite and sodalite. Applying conventional geothermobarometry combined with fluid-inclusion isochore data, it was possible to reconstruct the P-T conditions for the carbonatite emplacement and crystallization (1200-630°C, 4-5 kbar) and for several mineral-forming processes during metasomatism (e.g. formation of sodalite: 800-530°C). The composition and evolutionary trends of the fenitizing solution were estimated from both the sequence of metasomatic reactions within wallrock xenoliths in the carbonatitic breccia and fluid inclusion data. The fenitizing solutions responsible for the transformation of albite into sodalite can be characterised as of NaCl-rich aqueous brines (19-30 wt.% NaCl eq.), that contained only minor amounts of Sr, Ba, Fe, Nb, and LREE.
Age related macular degeneration (AMD) is the leading cause of visual impairment in the elderly and the major cause of blindness in the developed world. To date, the molecular mechanisms underlying the disease are not well understood although in recent years a primary involvement of the retinal pigment epithelium (RPE) has become evident. The aim of the present study is to systematically analyse genes which are differentially expressed in the RPE, and to assess their possible association with mechanisms and pathways likely to be related to retinal disease, in particular AMD. Towards this goal, 2379 expressed sequence tags (ESTs) were established from an inhouse generated RPE cDNA library. This library was constructed by using the suppression subtraction hybridization (SSH) technique which normalises redundant sequences and ensures enrichment of rare transcripts. In a first phase, 1002 ESTs were sequenced and subjected to comprehensive alignment with public nucleotide and protein databases. A search of the 1002 ESTs against the human genome draft sequence yielded 168 known genes, 51 predicted genes, 15 unknown transcripts and 41 clones with no significant similarity. Reverse Northern blot hybridization was performed for 318 EST clusters to identify abundantly expressed genes in the RPE and to prioritize subsequent analyses. Representative clones were spotted onto a nylon membrane and hybridized with cDNA probes of driver (heart and liver) and tester (RPE) used in the cDNA library construction. Subsequently, 107 EST clusters were subjected to Northern blot hybridizations. These analyses identified 7 RPE-specific, 3 retina-specific, 7 RPE/retina-specific, and 7 tissue restricted transcripts, while 29 EST clusters were ubiquitously expressed, and evaluation was not possible for another 54 EST clusters. Of the 24 transcripts with specific or restricted expression, 16 clones were selected for further characterization. The predicted gene MGC2477 and 2 novel isoforms of the human transient receptor potential cation channel, subfamily M, member 3 (TRPM3) were cloned and further described in detail. In addition, polymorphic variations for these 2 genes as well as for the human MT-Protocadherin gene were determined. For MGC2477, 15 single nucleotide polymorphisms (SNPs) were identified, with 13 having a frequency of the minor allele greater than 20%. 10 of the 15 SNPs have not been reported in so far in public SNP repertoires. Partial assessment of the TRPM3 gene yielded 35 SNPs. Of these, 30 (85.7%) were highly frequent (0.17-0.5%), and 14 (40%) were novel. The MT-Protocadherin gene revealed 35 SNPs, including 28 (80%) with high frequency of the minor allele. 23 (65.7%) were novel SNPs. These SNPs will be used to construct the most common haplotypes. These will be used in case/control association studies in 400 AMD patients and 200 ethnically and aged matched controls to assess a possible contribution of these genes in the etiology of AMD.
Soluble guanylyl cyclase (sGC) is the best established receptor for nitric oxide (NO) and regulates a great number of important physiological functions. Surprisingly, despite the wellappreciated roles of this enzyme in regulation of vascular tone, smooth muscle cell proliferation, platelet aggregation, renal sodium secretion, synaptic plasticity, and other functions, extremely little is known about the regulation of sGC activity and protein levels. To date, the only well-proven physiologically relevant sGC regulator is NO. In the present study, some additional possibilities for sGC regulation were shown. Firstly, we evaluated the ability of different NO donors to stimulate sGC. Significant differences in the sGC stimulation by SNP and DEA/NO were found. DEA/NO stimulated sGC much stronger than did SNP. Interestingly, no correlation between the sGC protein and maximal activity distribution was found in rat brain regions tested, suggesting the existence of some additional regulatory mechanisms for sGC. The failure of SNP to stimulate sGC maximally might be one of the reasons why the lack of correlation between the distribution of sGC activity and proteins in brain was not detected earlier. Prolonged exposure of endothelial cells to NO donors produced desensitization of the cGMP response. This desensitization cannot be explained by increased PDE activity, since PDE inhibitors were not able to prevent the NO donor-induced decrease of the maximal cGMP response in endothelial cells. The failure of SH-reducing agents to improve the cGMP response after its desensitization by NO suggests that a SH-independent mechanism mediates NO effects. Demonstration that the potency of the recently described activator of oxidized (heme-free) sGC, BAY58-2667, to stimulate sGC increases after prolonged exposure of the cells to an NO donor, DETA/NO, suggests that oxidation of heme may be a reason for NOinduced desensitization of sGC and decrease in sGC protein level. Indeed, the well-known heme-oxidizing agent ODQ produces a dramatic decrease in sGC protein levels in endothelial cells and BAY58-2667 prevents this effect. Although the mechanism of sGC activation and stabilization by BAY58-2667 is unknown, this substance is an interesting candidate to modulate sGC under conditions where sGC heme iron is oxidized. Very little is known about regulation of sGC by intracellular localization or translocation between different intracellular compartments. In the present study, an increase in sGC sensitivity to NO under membrane association was demonstrated. Treatment of isolated lung with VEGF markedly increased sGC in membrane fractions of endothelial cells. Failure of VEGF to stimulate sGC membrane association in cultured endothelial cells allows us to propose a complex mechanism of regulation of sGC membrane association and/or a transient character of sGC membrane attachment. A very likely mechanism for the attachment of sGC to membranes is via sGCinteracting proteins. These proteins may participate also in other aspects of sGC regulation. The role of the recently described sGC interaction partner, Hsp90, was investigated. Shortterm treatment of endothelial cells with an Hsp90 inhibitor does not affect NO donor or calcium ionophore-stimulated cGMP accumulation in the cells. However, inhibition of Hsp90 results in a rapid and dramatic decrease in sGC protein levels in endothelial cells. These effects were unrelated to changes in sGC transcription, since inhibition of transcription had much slower effect on sGC protein levels. In contrast, inhibitors of proteasomes abolished the reduction in sGC protein levels produced by an Hsp90 inhibitor, suggesting involvement of proteolytic degradation of sGC proteins during inhibition of Hsp90. All these data together suggest that Hsp90 is required to maintain mature sGC proteins. In conclusion, in the present study it was demonstrated that multiple mechanisms are involved in the regulation of sGC activity and its sensitivity to NO. Oxidation of sGC heme by NO seems to be one of the mechanisms for negative regulation of sGC in the presence of high or prolonged stimulation with NO. Another possible means of regulating sGC sensitivity to NO is via the intracellular translocation of the enzyme. It has been also demonstrated here that attachment of sGC to the membrane fraction results in an apparent increase in the enzyme sensitivity to NO. Additionally, Hsp90 was required to maintain sGC protein in endothelial and other cell types. However, we could not find any acute affect of Hsp90 on sGC activity, as reported recently. All these findings demonstrate that the regulation of sGC activity and protein level is a much more complex process than had been assumed earlier.
There is substantial interest in the identification of genes underlying susceptibility to complex human diseases because of the potential utility of such genes in disease prediction and therapy. The complex age-related macular degeneration (AMD) is a prevalent cause of legal blindness in industrialized countries and predominantly affects the elderly population over 75 years of age. Although vision loss in AMD results from photoreceptor cell death in the central retina, the initial pathogenesis likely involves processes in the retinal pigment epithelium (RPE) (Liang and Godley, 2003). The goal of the current study was to identify and characterize genes specifically or abundantly expressed in the RPE in order to determine more comprehensively the transcriptome of the RPE. In addition, our aim was to assess the role of these genes in AMD pathogenesis. Towards this end, a bovine cDNA library enriched for RPE transcripts was constructed in-house using a PCR-based suppression subtractive hybridization (SSH) technique (Diatchenko et al., 1996, 1999), which normalizes for sequence abundance and achieves high enrichment for differentially expressed genes. CAP3 (Huang and Madan, 1999) was used to assemble the high quality sequences of all the 2379 ESTs into clusters or singletons. 1.2% of the 2379 RPE-ESTs contains vector sequences and was excluded from further analysis. 5% of the RPE-ESTs showed homology to multipe chromosomes and were not included in further assembly process. The rest of the ESTs (2245) were assembled into 175 contigs and 509 singletons, which revealed approximately 684 unique genes in the dataset. Out of the 684, 343 bovine RPE transcripts did not align to their human orthologues. A large fraction of clones were shown to include a considerable 3´untranslated regions of the gene that are not conserved between bovine and human. It is the coding regions that can be conserved between bovine and human and not the 3’ UTR (Sharma et al., 2002). Therefore, more sequencing from the cDNA library with reclustering of those 343 ESTs together with continuous blasting might reveal their human orthologoues. To handle the large volume of data that the RPE cDNA library project has generated a highly efficient and user-friendly RDBMS was designed. Using RDBMS data storage can be managed efficiently and flexibly. The RDBMS allows displaying the results in query-based form and report format with additional annotations, links and search functions. Out of the 341 known and predicted genes identified in this study, 2 were further analyzed. The RPE or/and retina specificity of these two clones were further confirmed by RT-PCR analysis in adult human tissues. Construction of a single nucleotide polymphism (SNP) map was initiated as a first step in future case/control association studies. SNP genotyping was carried out for one of these two clones (RPE01-D2, now known as RDH12). 12 SNPs were identified from direct sequencing of the 23.4-kb region, of which 5 are of high frequency. In a next step, comparison of allele frequencies between AMD patients and healthy controls is required. Completion of the expression analysis for other predicted genes identified during this study is in progress using real time RT-PCR and will provide additional candidate genes for further analyses. This study is expected to contribute to our understanding of the genetic basis of RPE function and to clarify the role of the RPE-expressed genes in the predisposition to AMD. It may also help reveal the mechanisms and pathways that are involved in the development of AMD or other retinal dystrophies.
The study deals with the area of the allosteric modulation of the muscarinic M2 receptors. The allosteric modulators have an influence on binding of orthosteric ligands (agonists and antagonists) to the classical orthosteric binding site of the muscarinic M2-receptors. The modulators are able to enhance (positive cooperativity) or decrease (negative cooperativity)the affinity of ligands to the orthosteric binding site. The allosteric binding site is located at the entrance of the receptor binding pocket. It is less conserved than the orthosteric binding site which is located in a narrow cavity created by the seven transmembrane domains. Consequently, development of subtype selective allosteric ligands is easier than subtypeselective muscarinic agonists or antagonists. Furthermore, subtype selectivity can be achieved by differently cooperative interactions between the allosteric and orthosteric ligand at different receptor subtypes. For example, the allosteric modulators that are positively cooperative with ACh at M1 receptors and neutrally cooperative at the other receptor subtypes could be beneficial for treatment of the Alzheimer’s disease. Bisquaternary analogues of the Strychnos alkaloid caracurine V are among the most potent allosteric modulators of muscarinic M2-receptors. The very rigid ring skeleton comprises the pharmacophoric elements of two positively charged nitrogens at an approximate distance of 10 surrounded by two aromatic ring systems in a distinct spatial arrangement. Owing to the close structural relationship of caracurine V salts to the strong muscle relaxants toxiferine and alcuronium, they are likely to exhibit neuromuscular blocking activity, which would limit their usefulness as research tools and make the therapeutical use impossible. Reduction of the caracurine V ring skeletons to structural features responsible for good allosteric potency could possibly lead to compounds with negligible neuromuscular blocking activity and very high affinity to the allosteric binding site at M2 receptor. Thus, the aim of this study was to synthesize and pharmacologically evaluate analogues of a novel heterocyclic ring system, which comprises the pharmacophoric elements mentioned previously. The key step of the synthesis of the desired 6,7,14,15-tetrahydro[1,5]diazocino[1,2-a:6,5-a]-diindole ring system (6) involved the intermolecular double N-alkylation of the bromoethylindole (5), which was prepared from the known indolyl methylacetate (3) by reduction of the ester group to alcohol and subsequent substitution by bromine. 3 could be prepared in three steps involving N,N-dibenzylation of tryptamine followed by introduction of the dimethyl malonate moiety at C-2 of indole ring and a subsequent demethoxycarbonylation. The total synthesis of 6,7,14,15-tetrahydro[1,5]diazocino[1,2-a:6,5-a]diindole ring system (6) is shown in Scheme 24. In order to examine the influence of the length of the side-chain on muscarinic activity,exchange of the ethylamine moieties of 14 by the methylamino groups was planned. This should be accomplished by dimerization of the unsubstituted 2-bromoethylindole (32), and subsequent Mannich aminomethylation of the resulting unsubstituted pentacyclic ring. The total synthesis of the 6,7,14,15-tetrahydro-15aH-azocino[1,2-a:6,5-b]diindole ring system(35) is shown in Scheme 25. 32 was prepared from indole-2-carboxylic acid in six steps involving reduction of the acid to the corresponding alcohol 26, benzoylation of 26 followed by nucleophilic substitution with KCN, hydrolysis of the cyanide 28 to indolyl acetic acid 29,reduction of 29 to the corresponding alcohol 30, and finally bromination of 30 to give the bromide 32. Since dimerization attempts of 32 provided only 2-vinylindole (33), the tosylate 34 was used as starting material for the intermolecular alkylation to give exclusively an isomeric pentacyclic ring system, 7,14,15-tetrahydro-15aH-azocino[1,2-a:6,5-b]diindole (35). The formation of the novel, asymmetric ring skeleton can be explained by the ambident nucleophilic character of the indolyl anion that can be alkylated either at nitrogen or at C-3 of indole ring. 35 was subjected to a Mannich reaction to give 2,13-dimethylaminoalkylated product 37 as well as small amounts of the 13-monosubstituted compound (36). The geometry of novel ring systems 6 was elucidated by means of NMR spectroscopy and semiempirical calculations. The diazocinodiindole ring skeleton of 6 exists in chloroform solution at room temperature in a twisted-boat conformation, as indicated by 600 MHz ROESY experiment, vicinal coupling constants within the eight-membered ring, and AM1 calculations. In order to obtain potent allosteric ligands, the new heterocycles 6 and 37 were quarternized with methyliodide to the corresponding ammonium salts 14 and 38, respectively. Additionally, the N,N -diallylsalts of 37 (compound 39) was prepared. The allosteric effect of 14, 38, and 39 on the dissociation of the orthosteric radioligand [3H]Nmethylscopolamine([3H]NMS) and their effects on [3H]NMS equilibrium binding were studied in homogenates of porcine heart ventricles. The concentration of an allosteric agent for a half-maximum effect on orthosteric ligand dissociation (EC50,diss) corresponds to a 50 % occupancy of the liganded receptors by the respective allosteric test compounds. Due to the presence of two benzyl groups on each nitrogen in the side chains of 14, its binding affinity can be best compared with that of N,N -dibenzylcaracurinium V dibromide (EC50,diss = 69 nM). Compound 14 exhibited the comparable affinity to N,N -dibenzylcaracurinium V dibromide with EC50,diss = 54 nM. This result suggested that replacement of the bulky benzyl groups of 14 by smaller substitutents will probably increase the allosteric potency, since dimethyl- and diallylcaracurinium salts showed a 5-fold increase of binding affinity relative to the dibenzyl analogue. Even though the new azocinodiindole ring system of 38 and 39, is not included in the caracurine V ring skeleton, it comprises the essentially pharmacophoric elements of allosteric potency. Due to the different spatial arrangements of the aromatic rings, as well as to different internitrogen distances in both ring systems, compound 38 and 39 exhibited 4-fold lower M2 binding affinity (EC50,diss = 35 and 48 nM, respectively) than the corresponding caracurine V analogues. This study deals with the synthesis of the first representative (Compound 6) of a novel pentacyclic ring system derived from caracurine V. The high allosteric potency of its dimethyl analogue reveals the [1,5]diazocino[1,2-a:6,5-a]-diindole ring system as a new promising lead structure for allosteric modulators of muscarinic M2 receptors. Future research will be focused on structural modifications of the new ring system in order to increase the affinity to the muscarinic receptors. Furthermore, the binding affinities of the new synthesized compounds to the muscle type of nicotinic ACh-receptor should reveal structural features responsible for the muscarinic/nicotinic selectivity.
The mammalian Vasodilator Stimulated Phosphoprotein (VASP) is a founding member of the Ena/VASP family of proteins that includes Drosophila Enabled (ena), the mammalian Ena homologue (Mena) and the Ena-VASP-like protein (Evl). VASP was initially discovered and characterized as a substrate for cGMP- and cAMP-dependent protein kinases (cGKs and cAKs). Ena/VASP proteins are involved in Actin-filament formation, plasma membrane protrusion, acceleration of Actin-based motility of Listeria and the establishment of cell-cell adhesion. Moreover, Ena/VASP proteins have been implicated as inhibitory factors in repulsive axon guidance and inhibition of plasma membrane activity and random motility in fibroblast. In order to study the physiological function of VASP, VASP-deficient mice had been generated in the laboratory by homologous recombination. VASP-/- mice showed hyperplasia of megakaryocytes in the bone marrow and spleen and a two-fold increase in thrombin- and collagen-induced platelet activation. To further investigate the cellular function of VASP, I established cardiac fibroblast cell lines derived from both wild type and VASP-/- mice. Both cell lines presented similar growth rates and normal contact dependent-growth inhibition but showed differences in morphology, migration and adhesion. Adherent VASP-/- cells, despite normal Mena and Evl expression levels, were highly spread. VASP-/- cells covered about twice the substrate surface area as wild type cells, while the cell volumes were unchanged. This shape difference suggests that VASP is involved in the regulation of spreading. Since the small GTPases Rac and Cdc 42 and their effector p21-activated kinase (Pak) are key regulators of lamellipodia formation and cell spreading, I analyzed this signalling pathway in VASP-/- cells stimulated with Platelet Derived Growth Factor-BB (PDGF-BB) or fetal calf serum. In wild type cells Rac and Pak were rapidly and transiently activated by PDGF or serum; however, in the absence of VASP both Rac and Pak activation was dramatically prolonged. The Rac/Pak pathway is known to play an essential role in cell motility. VASP deficient cells showed compromised migration and reorientation in a wound healing assay, probably due to enhanced Rac activity. The spreading phenotype, compromised migration and the effect observed on the Rac and Pak activities were reverted in VASP-/- cells stably transfected with full lenght human VASP, indicating a VASP dependent modulation of the Rac/Pak pathway and Rac/Pak regulated processes. Moreover, adhesion and detachment of VASP-deficient cells were significantly slower when compared to wild type cells. Preincubation of VASP+/+ cells with a cGMP analog accelerated adhesion. This acceleration did not take place in the VASP-/- cells, suggesting a VASP dependent effect. The second part of this work focused on VASP function in platelets. On the one hand I investigated the possibility of VASP-dependent Rac regulation in mouse platelets. Murine platelets are a good model for studying Rac regulation since they express high levels of VASP but not Mena/Evl and since VASP-deficient platelets show an increased platelet activation. Rac was activated by platelet agonists which was inhibited by preincubation with cGMP and cAMP analogs. Initial results which need to be extended showed that the cGMPcaused inhibition of Rac activation was VASP-dependent. Finally, in vivo platelet adhesion (platelet-vessel wall interactions) was studied using VASP-deficient mice. These studies demonstrated in-vivo that VASP down regulates platelet adhesion to the vascular wall under both physiological and pathophysiological conditions.
In the work here presented four distinctly different problems were investigated. The first problem was an investigation into the degradation of Dichloroethylene (DCE) and 1,1-bis (p-Chlorophenyl)-2-dichloroethylene (DDE) utilising pure bacterial cultures. The second investigation dealt with the degradation of DDE and polychlorinated Biphenyl’s (PCB’s) utilising anaerobic sediments and soils from New Zealand. The third investigation worked on the Granulation of anaerobic River-sediments in Upflow Anaerobic Sludge Blanket (UASB) Reactors. The last investigation describes the commissioning of an industrial aerobic Wastewater Treatment Plant and the Implementation of biological Nitrogen- and Phosphate removal in this Wastewater Treatment Plant. Since the chemical Structure of DCE and DDE have certain similarities, Bacteria that were capable of degrading DCE, were tested here, whether they would also be able to degrade DDE utilising a co-metabolic pathway. In the experiments the aerobic bacteria Methylosinus trichosporium and Mycobacterium vaccae and the anaerobic bacteria Acetobacterium woodii and Clostridium butyricum were used. Approximately 60% of the added DCE was degraded by M. vaccae, while M. trichosporium degraded approximately 50%. A. woodii and C. butyricum degraded 40% and 30% respectively of the added DCE. Further experiments with these cultures and DDE lead to a microbial degradation of DDE to an extent of 34.6% for M. vaccae, 14.1% for C. butyricum, 2.2% for A. woodii and 10.5% for M. trichosporium. Additional experiments, utilising [14C]-DDE, showed that the DDE had not been degraded but were attached to the bacterial cells. The second investigation utilised anaerobic soils and sediments from New Zealand to study the anaerobic co-metabolic degradation of DDE and PCB’s. The soils and sediments originated from the River Waikato, from Wastewater Ponds in Kinleith, Marine-Sediments from Mapua, and a variety of soils comtaminated with Pentachlorophenyl (PCP). The cultures from these soils and sediments were raised on a variety of Carbon- and Energy-sources. Beside DDE, Aroclor 1260, and a mix of four pure PCB-Congeneres (one Tetra-, one Hexa, one Hepta- and one Deca-Chlorobiphenyl) were used to test for the reductive dechlorination. The cultivation process of the baceria lasted six months. Samples of the cultures were taken after zero, three and six months. These samples were tested for the increase of cell-protein, the degradation of carbon- and energy-sources, and the removal of the added polychlorinated chemicals. The organochlorines were analysed using reversed phase HPLC and FID-GC. When a change in the Chromatogram was detected the respective cultures were further analysed using ECD-GC and GC-MS. The results showed that the culutres grew under these conditions, but no degradation of DDE and the PCB-Mix could be detected, and only small changes in the composition/chromatograms of Aroclor 1260 were found. The third investigation worked on the Granulation of River-Sediments in UASB-Reactors. Sediments from the River Waikato in New Zealand and the River Saale in Germany were used. In both cases the Granulation process was successful, which was demonstrated by microscopic comparisons of the Sediments and the resulting Granules. The two main bacterial cultures detected were Methanosarcina- and Methanothrix-like cultures. The main carbon- and energy-source was Lactic Acid, which was used at a concentration of 21,8 g COD/L. The Granulation-Process was a combination of using high a COD-Concentration combined with a low Volumetric Loading-Rate. Comparisons of the specific degradation-rates of a variety of carbon- and energy-sources between the Sediments and the Granules, showed no increased degradation rates in regard to the same cell-mass, but the increased bio-mass in the Granules allowed for higher degradation-rates within the UASB-reactors. The fourth investigation describes the commissioning of an industrial Wastewater Treatment Plant for a Dairy-Site in Edendale, Southland, New Zealand. This Plant consists of a DAF-Unit (Dissolved Air Flotation), two Extended Aeration Lagoons with Activated Sludge and two Clarifiers, one for the Activated Sludge and the second for the dosing of Aluminium-Sulphate and the removal of Phosphat-Sulphate. Biological processes for the removal of carbon- and energy-sources were optimised and biological processes for the reduction of Nitrogen- and Phosphate-Concentrations within the wastewater were implemented and optimised. Bilogical removal rates for COD of 95% and above, for Nitrogen of 85-92% and Phosphate of 64-83% were achieved.
Fanconi anemia (FA) is a genetically and phenotypically heterogenous autoso- mal recessive disease associated with chromosomal instability, progressive bone marrow failure, typical birth defects and predisposition to neoplasia. The clinical phenotype is similar in all known complementation groups (FA-A, FA-B, FA-C,FA-D1, FA-D2, FA-E, FA-F and FA-G). The cellular phenotype is characterized by hypersensitivity to DNA crosslinking agents (MMC,DEB), which is exploited as a diagnostic tool. Alltogether, the FA proteins constitute a multiprotein pathway whose precise biochemical function(s) remain unknown. FANCA, FANCC, FANCE, FANCF and FANCG interact in a nuclear complex upstream of FANCD2. Complementation group FA-D1 was recently shown to be due to biallelic mutations in the human breast cancer gene 2 (BRCA2). After DNA damage, the nuclear complex regulates monoubiquitylation of FANCD2, result- ing in targeting of this protein into nuclear foci together with BRCA1 and other DNA damage response proteins. The close connection resp. identity of the FA genes and known players of the DSB repair pathways (BRCA1, BRCA2, Rad51) firmly establishs an important role of the FA gene family in the maintenance of genome integrity. The chapter 1 provides a general introduction to the thesis describing the current knowledge and unsolved problems of Fanconi anemia. The following chapters represent papers submitted or published in scientific literature. They are succeeded by a short general discussion (chapter 7). Mutation analysis in the Fanconi anemia genes revealed gene specific mutation spectra as well as different distributions throughout the genes. These results are described in chapter 1 and chapter 2 with main attention to the first genes identified, namely FANCC, FANCA and FANCG. In chapter 2 we provide general background on mutation analysis and we report all mutations published for FANCA, FANCC and FANCG as well as our own unpublished mutations until the year 2000. In chapter 3 we report a shift of the mutation spectrum previously reported for FANCC after examining ten FA-patients belonging to complementation group C. Seven of those patients carried at least one previously unknown mutation, whereas the other three patients carried five alleles with the Dutch founder mu- tation 65delG and one allele with the Ashkenazi founder mutation IVS4+4A>T, albeit without any known Ashkenazi ancestry. We also describe the first large deletion in FANCC. The newly detected alterations include two missense mu- tations (L423P and T529P) in the 3´-area of the FANCC gene. Since the only previously described missense mutation L554P is also located in this area, a case can be made for the existence of functional domain(s) in that region of the gene. In chapter 4 we report the spectrum of mutations found in the FANCG gene com- piled by several laboratories working on FA. As with other FA genes, most muta- tions have been found only once, however, the truncating mutation, E105X, was identified as a German founder mutation after haplotype analysis. Direct compar- ison of the murine and the human protein sequences revealed two leucine zipper motifs. In one of these the only identified missense mutation was located at a conserved residue, suggesting the leucine zipper providing an essential protein-protein interaction required for FANCG function. With regard to genotype-phenotype correlations, two patients carrying a homozygous E105X mutation were seen to have an early onset of the hematological disorder, whereas the missense mutation seems to lead to a disease with later onset and milder clinical course. In chapter 5 we explore the phenomenon of revertant mosaicism which emerges quite frequently in peripheral blood cells of patients suffering from FA. We de- scribe the types of reversion found in five mosaic FA-patients belonging to com- plementation groups FA-A and FA-C. For our single FA-C-patient intragenic crossover could be proven as the mechanism of self-correction. In the remaining four patients (all of them being compound heterozygous in FANCA), either the paternal or maternal allele has reverted back to WT sequence. We also describe a first example of in vitro phenotypic reversion via the emergence of a compensat- ing missense mutation 15 amino acids downstream of the constitutional mutation explaining the MMC-resistance of the lymphoblastoid cell line of this patient. In chapter 6 we report two FA-A mosaic patients where it could be shown that the spontaneous reversion had taken place in a single hematopoietic stem cell. This has been done by separating blood cells from both patients and searching for the reverted mutation in their granulocytes, monocytes, T- and B-lymphocytes as well as in skin fibroblasts. In both patients, all hematopoietic lineages, but not the fibroblasts, carried the reversion, and comparison to their increase in erythrocyte and platelet counts over time demonstrated that reversion must have taken place in a single hematopoietic stem cell. This corrected stem cell then has been able to undergo self-renewal and also to create a corrected progeny, which over time repopulated all hematopoietic lineages. The pancytopenia of these patients has been cured due to the strong selective growth advantage of the corrected cells in vivo and the increased apoptosis of the mutant hematopoietic cells.