Phytographische Beiträge

Ohne Zusammenfassung     

Stereochemistry and enantiomeric purity of a novel anxiolytic agent, deramciclane fumarate.

The synthesis, stereostructure, and enantiomeric separation by chromatography of a new, chiral anxiolytic agent, deramciclane fumarate (2, (-)-[1R,2S,4R]-2-(2-dimethylaminoethoxy)-2-phenyl-1,7, 7-trimethylbicyclo[2.2.1]heptane fumarate, EGIS-3886), is described. The optical antipode and the racemate of compound 2 were also prepared. The structure was determined by single crystal X-ray diffraction analysis. The enantiomeric separation was accomplished by HPLC on Chiralcel OD (250 x 4.6 mm; 10 microm) and hexane-ethanol (99.5:0.5) as mobile phase at room temperature. The enantiomeric purity of the synthesized drug substance proved to be very high (>99. 9%). Some statements published earlier on the stereostructure of deramciclane fumarate are critically discussed.     

Prognostic impact of B-cell density in cutaneous melanoma

Studies on the prognostic importance of tumor-infiltrating lymphocytes have mainly focused on T cells, while little is known about the role of tumor-infiltrating B lymphocytes. We investigated the prevalence of CD20⁺ B cells by immunohistochemistry in primary melanoma samples of 106 patients and analyzed in relation to clinicopathological parameters and patients’ survival. The majority of samples contained a significant amount of B lymphocytes, predominantly dispersed in the stroma surrounding tumor deposits (mean peritumoral and intratumoral densities: 178.7 ± 156.1 vs. 4.9 ± 6.9 cells/mm², respectively). B cells organized in follicle-like aggregates were also observed in 26% of the samples. B-cell density correlated with that of activated (CD25⁺ or OX40⁺) T lymphocytes. Infiltration by CD20⁺ lymphocytes did not correlate with tumor thickness, while the presence of B-cell aggregates was observed more frequently in thick melanomas. On the other hand, B-cell infiltration was more pronounced in nonmetastatic or lymph node metastatic tumors, compared to visceral metastatic ones. Accordingly, high number of these cells provided significant survival advantage (P = 0.0391 and P = 0.0136 for intra- and peritumoral infiltration, respectively). Furthermore, combination of peritumoral B-cell density with the number of activated T lymphocytes identified patient subgroups with different disease outcome, which was most favorable in the case of high density, while very poor in the case of low density of both cell types. Multivariate survival analysis identified tumor thickness and CD20⁺/OX40⁺ cell density combination as significant independent prognostic factors. Taken together, our results show correlation between low number of CD20⁺ B lymphocytes and melanoma progression, indicating a possible role of tumor-infiltrating B cells in antitumoral immune response. It was also reflected in better outcome of the disease since the density of B lymphocytes alone as well as in combination with that of activated T cells proved of prognostic importance in patients with malignant melanoma.     

Quantitative Genome-Wide Genetic Interaction Screens Reveal Global Epistatic Relationships of Protein Complexes in Escherichia coli

Large-scale proteomic analyses in Escherichia coli have documented the composition and physical relationships of multiprotein complexes, but not their functional organization into biological pathways and processes. Conversely, genetic interaction (GI) screens can provide insights into the biological role(s) of individual gene and higher order associations. Combining the information from both approaches should elucidate how complexes and pathways intersect functionally at a systems level. However, such integrative analysis has been hindered due to the lack of relevant GI data. Here we present a systematic, unbiased, and quantitative synthetic genetic array screen in E. coli describing the genetic dependencies and functional cross-talk among over 600,000 digenic mutant combinations. Combining this epistasis information with putative functional modules derived from previous proteomic data and genomic context-based methods revealed unexpected associations, including new components required for the biogenesis of iron-sulphur and ribosome integrity, and the interplay between molecular chaperones and proteases. We find that functionally-linked genes co-conserved among γ-proteobacteria are far more likely to have correlated GI profiles than genes with divergent patterns of evolution. Overall, examining bacterial GIs in the context of protein complexes provides avenues for a deeper mechanistic understanding of core microbial systems.     

Platelet-activating factor mediated effects on human neutrophil function are inhibited by pertussis toxin

Pretreatment of human neutrophils with pertussis toxin inhibits platelet-activating factor-mediated chemotaxis, superoxide generation, aggregation, and release of lysozyme. By contrast, superoxide generation observed in the presence of phorbol-12-myristate-13 acetate is unaffected. Our results suggest that a target protein for pertussis toxin, probably a GTP binding protein termed "Ni", is involved in the actions of platelet-activating factor on human neutrophils.     

Human platelet adenylate cyclase: persistent binding of guanine nucleotide is central to the regulation of both hormone-stimulated and basal activities

Prostaglandin E1 stimulation of human platelet adenylate cyclase, in purified plasma membranes, occurs without the addition of exogenous GTP. Possible contamination of the adenylate cyclase assay mixture by GTP either from nonspecifically bound nucleotide in the plasma membrane or from the substrate ATP was ruled out as follows: (a) variation of the membrane concentration, repeated washing, inclusion of EDTA, GDP beta S, or GMP in the wash step, or UDP in the assay, are all without effect, and (b) analysis of the substrate by high-performance liquid chromatography revealed no contaminating GTP. Other prostaglandins (I2, E2, D2) also activate cyclase without the addition of GTP. In sharp contrast, stimulation of adenylate cyclase in the human neutrophil plasma membrane by prostaglandin E1 shows an obligatory requirement for GTP, under identical assay conditions. GDP beta S pretreatment amplifies the fold cyclase stimulation by GTP in the presence and absence of prostaglandin E1, by lowering the basal activity. This alteration occurs without lowering the GTP-independent prostaglandin E1 activation, and is specific for inhibitory guanine nucleotides (GDP beta S, GMP, GDP) in the pretreatment. Extensive washing with buffer or incubation with other nucleotides, epinephrine, or prostaglandin E1 prior to the assay, is without effect. GTP gamma S treatment of the membrane induces a high-activity state and abolishes the GDP beta S effect on basal activity as well as prostaglandin E1 activation of cyclase. The results suggest distinct patterns of prostaglandin stimulation in platelet and neutrophil cyclase systems, and further imply that guanine nucleotide, prebound to specific sites within the GTP-regulatory proteins, may modify the kinetic characteristics of platelet adenylate cyclase.     

Mesozooplankton of the Kosi Bay lakes,South Africa

The Kosi coastal lake system, a chain of four interconnected basins, is located in the subtropical north-eastern corner of South Africa. Little information is available on zooplankton of the system and the main aim of this study is to report on zooplankton samples collected during 2002 and 2003. The set of samples consists of seasonal, subsurface mesozooplankton samples that were collected during nighttime in each of the lakes. A well-developed salinity gradient was evident along the interconnected lakes in the subsurface water during all seasons, ranging from freshwater in the upper lake Amanzamnyama to a maximum of 22 recorded in Lake Makhawulani. The zooplankton community structures of the lakes reflected the salinity gradient of the system, with some coastal marine taxa recorded in the lakes closer to the mouth and only freshwater taxa recorded in Lake Amanzamnyama. Mesozooplankton diversity and abundance were relatively low compared to other estuarine systems along the eastern coast of South Africa. The dominant taxa were calanoid copepods Acartiella natalensis and Pseudodiaptomus stuhlmanni and the mysid Mesopodopsis africana in the lower lakes, whereas cyclopoids Mesocyclops sp. and Thermocyclops sp. dominated the freshwater lake Amanzamnyama.     

Role of a pertussis toxin substrate in the control of lectin-induced cap formation in human neutrophils.

We have examined the role of GTP-binding proteins and the associated cyclic AMP- and calcium-related transduction mechanisms in the regulation of capping in human neutrophils. Pertussis toxin (PT), a probe for the GTP-binding protein Ni, abolished capping induced by fluorescein isothiocyanate-conjugated concanavalin A (Con-A), whereas cholera toxin, a probe for the GTP-binding protein Ns, was without effect. Consistent with the latter finding, ligands acting at receptors associated with the Ns protein, namely the prostaglandin E1 and beta-adrenergic agonists, were without effect on the capping reaction. The possible role of mobilization of internal calcium was evaluated by using Quin2-loaded cells. Calcium mobilization was observed at concentrations of Con-A which yielded optimal capping (10 micrograms/ml). Treatment with PT, phorbol myristrate acetate or 8-(NN-diethylamino)octyl-3,4,5-trimethoxybenzoate (TMB-8) abolished both calcium mobilization and capping. Colchicine, which substantially enhanced capping, had no effect on calcium mobilization. At concentrations of the lectin above those required for capping, superoxide generation and enzyme release were noted. These reactions were less susceptible to inhibition by PT, effects being observed only on the Kact. for Con-A-mediated superoxide generation with little effect on the Vmax. The degree of PT-mediated inhibition for enzyme release with Con-A was much lower than that observed with fMet-Leu-Phe. Our results imply that a step involving Ni-mediated calcium mobilization, sensitive to phorbol myristate acetate, is essential to the regulation of capping; a distinct mechanism may be involved in colchicine-mediated enhancement of capping; and Ni may play a relative minor role in the regulation of lectin-mediated exocytosis.     

A step sensitive to pertussis toxin and phorbol ester in human neutrophils regulates chemotaxis and capping but not phagocytosis

Treatment of human neutrophils with pertussis toxin (PT) abolishes chemotaxis in response to either platelet-activating factor (PAF) or f-Met-Leu-Phe (FMLP), and capping induced via the concanavalin A (Con A) receptor. These functional effects are accompanied by the inhibition of calcium mobilization by PAF, FMLP and Con A. The agent phorbol 12-myristate-13-acetate (PMA) also inhibits chemotaxis and capping as well as calcium mobilization by these receptors. In sharp contrast, neither PT, cholera toxin (CT), nor PMA, inhibits the phagocytosis of non-opsonized and opsonized Candida albicans, sheep erythrocytes or fluorescent latex beads. Our results suggest that receptor-initiated chemotaxis and capping involve a step that is sensitive to PT and PMA, and that phagocytosis is not regulated in a similar fashion.     

Effect of melittin-induced membrane alterations on rat heart adenylate cyclase activity

Melittin, a surface-active, 26-amino acid polypeptide from bee venom, has been reported to alter a variety of membrane properties including stability, permeability, and fluidity, the latter having been shown to be altered in a biphasic manner. Melittin induced a biphasic alteration of rat heart microsomal adenylate cyclase activity, stimulating it at low concentration (<30 μg/ml) and inhibiting it at higher concentrations (100 μg/ml or higher). Melittin potentiated sodium fluoride and 5′-guanylylimidodiphosphate activation of adenylate cyclase below 40 μg/ml but it inhibited at high concentrations, except in the presence of high concentrations of 5′-guanylylimidodiphosphate (10^?4m). Basal and fluoride-activated adenylate cyclase exhibited no significant change in the K_m for ATP in the presence of melittin at <40 μg/ml, but the V was elevated. Potentiation by melittin of adenylate cyclase was observed at all fluoride, 5′-guanylylimidodiphosphate, and magnesium concentrations tested. The observed effects of melittin on rat heart adenylate cyclase are consistent with it acting by altering the properties of membrane lipids with which the enzyme is associated.