Identification of potential HIV restriction factors by combining evolutionary genomic signatures with functional analyses

Background

Known antiretroviral restriction factors are encoded by genes that are under positive selection pressure, induced during HIV-1 infection, up-regulated by interferons, and/or interact with viral proteins. To identify potential novel restriction factors, we performed genome-wide scans for human genes sharing molecular and evolutionary signatures of known restriction factors and tested the anti-HIV-1 activity of the most promising candidates.

Results

Our analyses identified 30 human genes that share characteristics of known restriction factors. Functional analyses of 27 of these candidates showed that over-expression of a strikingly high proportion of them significantly inhibited HIV-1 without causing cytotoxic effects. Five factors (APOL1, APOL6, CD164, TNFRSF10A, TNFRSF10D) suppressed infectious HIV-1 production in transfected 293T cells by >90% and six additional candidates (FCGR3A, CD3E, OAS1, GBP5, SPN, IFI16) achieved this when the virus was lacking intact accessory vpr, vpu and nef genes. Unexpectedly, over-expression of two factors (IL1A, SP110) significantly increased infectious HIV-1 production. Mechanistic studies suggest that the newly identified potential restriction factors act at different steps of the viral replication cycle, including proviral transcription and production of viral proteins. Finally, we confirmed that mRNA expression of most of these candidate restriction factors in primary CD4+ T cells is significantly increased by type I interferons.

Conclusions

A limited number of human genes share multiple characteristics of genes encoding for known restriction factors. Most of them display anti-retroviral activity in transient transfection assays and are expressed in primary CD4+ T cells.

Electronic supplementary material

The online version of this article (doi:10.1186/s12977-015-0165-5) contains supplementary material, which is available to authorized users.

Spirostanol saponins and esculin from Rusci rhizoma reduce the thrombin-induced hyperpermeability of endothelial cells

Rusci rhizoma extracts are traditionally used against chronic venous disorders (CVD). To determine the effect of its secondary plant metabolites on the endothelium, phenolic compounds and saponins from Butcher's broom were isolated from a methanolic extract, and their activity on the thrombin-induced hyperpermeability of human microvascular endothelial cells (HMEC-1) was investigated in vitro. In addition to the six known spirostanol saponins deglucoruscin (5), 22-O-methyl-deglucoruscoside (6), deglucoruscoside (7), ruscin (8), ruscogenin-1-O-(α-l-rhamnopyranosyl-(1→2)-β-d-galactopyranoside (9) and 1-O-sulpho-ruscogenin (10), three new spirostanol derivatives were isolated and identified: 3'-O-acetyl-4'-O-sulphodeglucoruscin (1), 4'-O-(2-hydroxy-3-methylpentanoyl)-deglucoruscin (2) and 4'-O-acetyl-deglucoruscin (3). Furthermore, the coumarin esculin (4), which is also prominently present in other medicinal plants used in the treatment of CVD, was isolated for the first time from Rusci rhizoma. Five of the isolated steroid derivatives (2, 5, 8, 9 and 10) and esculin (4) were tested for their ability to reduce the thrombin-induced hyperpermeability of endothelial cells in vitro, and the results were compared to those of the aglycone neoruscogenin (11). The latter compound showed a slight but concentration-dependent reduction in hyperpermeability to 71.8% at 100μM. The highest activities were observed for the spirostanol saponins 5 and 8 and for esculin (4) at 10μM, and these compounds resulted in a reduction of the thrombin-induced hyperpermeability to 41.9%, 42.6% and 53.3%, respectively. For 2, 5 and 8, the highest concentration tested (100μM) resulted in a drastic increase of the thrombin effect. The effect of esculin observed at a concentration of 10μM was diminished at 100μM. These in vitro data provide insight into the pharmacological mechanism by which the genuine spirostanol saponins and esculin can contribute to the efficacy of Butcher's broom against chronic venous disorders.

Novel neurological and immunological targets for salicylate-based phytopharmaceuticals and for the anti-depressant imipramine

Inflammatory processes are increasingly recognised to contribute to neurological and neuropsychatric disorders such as depression. Thus we investigated whether a standardized willow bark preparation (WB) which contains among other constituents salicin, the forerunner of non-steroidal antiphlogistic drugs, would have an effect in a standard model of depression, the forced swimming test (FST), compared to the antidepressant imipramine. Studies were accompanied by gene expression analyses. In order to allocate potential effects to the different constituents of WB, fractions of the extract with different compositions of salicyl alcohol derivative and polyphenols were also investigated. Male Sprague Dawley rats (n=12/group) were treated for 14 days (p.o.) with the WB preparation STW 33-I (group A) and its fractions (FR) (groups FR-B to E) in concentrations of 30 mg/kg. The FRs were characterized by a high content of flavone and chalcone glycosides (FR-B), flavonoid glycosides and salicyl alcohol derivatives (FR-C), salicin and related salicyl alcohol derivatives (FR-D) and proanthocyanidines (FR-E). The tricyclic antidepressant imipramine (20 mg/kg) (F) was used as positive control. The FST was performed on day 15. The cumulative immobility time was significantly (p<0.05) reduced in group A (36%), group FR-D (44%) and by imipramine (16%) compared to untreated controls. RNA was isolated from peripheral blood. RNA samples (group A, group FR-D, and imipramine) were further analysed by rat whole genome microarray (Agilent) in comparison to untreated controls. Quantitative PCR for selected genes was performed. Genes (>2 fold, p<0.01), affected by WB and/or FR-D and imipramine, included both inflammatory (e.g. IL-3, IL-10) and neurologically relevant targets. Common genes regulated by WB, FR-D and imipramine were GRIA 2 ↓, SRP54 ↓, CYP26B ↓, DNM1L ↑ and KITLG ↓. In addition, the hippocampus of rats treated (27 d) with WB (15-60 mg/kg WB) or imipramine (15 mg/kg bw) showed a slower serotonin turnover (5-hydroxyindol acetic acid/serotonin (p<0.05)) depending on the dosage. Thus WB (30 mg/kg), its ethanolic fraction rich in salicyl alcohol derivatives (FR-D) (30 mg/kg) and imipramine, by being effective in the FST, modulated known and new targets relevant for neuro- and immunofunctions in rats. These findings contribute to our understanding of the link between inflammation and neurological functions and may also support the scope for the development of co-medications from salicylate-containing phytopharmaceuticals as multicomponent mixtures with single component synthetic drugs.

Primary radiotherapy with or without chemotherapy in non-metastatic esophageal squamous cell carcinoma: a retrospective study

The purpose of this study was to report the outcome of radio(chemo)therapy in the curative management of esophageal squamous cell carcinoma (ESCC). We retrospectively analyzed 163 patients with T1-T4, N0-1, M0 ESCC who were treated between January 1988 and December 2006 at the Technische Universität München. One hundred sixty patients were inoperable due to a poor performance status, comorbidities or locally advanced unresectable disease. External beam radiation therapy (EBRT) was performed with (n= 146) or without (n= 17) systemic chemotherapy. Fifty-four patients received an additional boost with intraluminal brachytherapy (IBT). Surviving patients were followed for a median of 72 months (range 10-173 months). The estimated overall survival (OS) at 2 and 5 years was 27 ± 4% and 11 ± 3%, respectively. Loco-regional recurrence at the primary site was observed in 29% of patients (n= 47). The recurrence-free survival (RFS) at 2 and 5 years was 24 ± 3% and 9 ± 2%, respectively. In multivariate analyses, the ECOG performance status (P= 0.004), 3D conformal (vs conventional) radiotherapy (P= 0.031) and continuous standard fractionation (vs split-course radiotherapy, P= 0.048) were associated with a better OS. Simultaneous chemotherapy (P= 0.49) or IBT (P= 0.31) had no significant impact on survival. Outcome for patients with ESCC is poor. Despite the very unfavorable patient selection (poor performance status, high rate of comorbidities, and advanced disease), long-term survival with radio(chemo)therapy was achieved in about 10% of patients. The introduction of modern treatment techniques/modalities (3D conformal planning/ continuous standard fractionation) might be associated with better outcomes.

Contribution of flavonoids and catechol to the reduction of ICAM-1 expression in endothelial cells by a standardised Willow bark extract

INTRODUCTION

A quantified aqueous Willow bark extract (STW 33-I) was tested concerning its inhibitory activity on TNF-α induced ICAM-1 expression in human microvascular endothelial cells (HMEC-1) and further fractionated to isolate the active compounds.

RESULTS

At 50 μg/ml the extract, which had been prepared from Salix purpurea L., decreased ICAM-1 expression to 40% compared to control cells without showing cytotoxic effects. Further liquid-liquid partition revealed an ethyl acetate phase with potent reduction of ICAM-1 expression to 40% at 8 μg/ml. This fraction was comprehensively characterised by the isolation of flavanone aglyca and their corresponding glycosides, chalcone glycosides, salicin derivatives, cyclohexane-1,2-diol glycosides, catechol and trans-p-coumaric acid. All compounds were investigated for their activity on TNF-α induced ICAM-1 expression. The flavonoid and chalcone glycosides were not active up to 50 μM, whereas catechol and eriodictyol at the same concentration showed a significant reduction of ICAM-1 expression to 50% of control. Interestingly, other isolated flavanone aglyca like taxifolin, dihydrokaempferol and naringenin showed only weak or moderate inhibitory activity. Eriodictyol was a minor compound in the extract, whereas the catechol content in the extract (without excipients) reached 2.3%, determined by HPLC. One of the isolated cyclohexan-1,2-diol glucosides, 6'-O-4-hydroxybenzoyl-grandidentin, is a new natural compound.

CONCLUSION

As catechol is quantitatively important in Willow bark extracts it can be concluded from the in vitro data that not only flavonoids and salicin derivatives, but also catechol can probably contribute to the anti-inflammatory activity of Willow bark extracts.

Prediction of adverse events by in vivo gene expression profiling exemplified for phytopharmaceuticals containing salicylates and the antidepressant imipramine

BACKGROUND AND OBJECTIVE

Gene expression profiles of Sprague-Dawley (SD) rats treated with a standardized willow bark extract (WB), its salicin rich ethanol fraction (EtOH-FR) or the tricyclic antidepressant imipramine were evaluated for their potential to induce adverse events. Treatments had shown antidepressant-like effects.

METHODS

Gene expression profiles (Agilent Whole Genome Array, n=4/group) obtained from the peripheral blood of male SD rats treated with WB (STW 33-I), EtOH-FR (30 mg/kg bw) or imipramine (20 mg/kg bw) were analysed comparatively by the Ingenuity Systems Programme, which allows to conduct model calculations of thresholds for theoretical potential adverse events (AE).

RESULTS

The number of genes regulated by the three treatments were 1673 (WB), 117 (EtOH-FR) and 1733 (imipramine). The three treatments related to 47 disease clusters. The WB extract reached the threshold for a potential AE in one disease cluster (cardiac hypertrophy), whereas the EtOH-FR exceeded the threshold in 5 disease clusters (cardiac arteriopathy and stenosis, glomerular injury, pulmonary hypertension, alkaline phosphatase levels ⇑). Imipramine treatment hit 13 disease clusters: tachycardia, palpitation, myocardial infarction, arrhythmias, heart block, precipitation of congestive heart failure; urinary retention, altered liver functions. Those correspond to known potential adverse events. Glomerular injury and altered liver functions are part of the side effect profile of salicylic acid derivatives in agreement with the findings for the salicin rich EtOH-FR.

CONCLUSION

There is no linear relationship between the number of constituents of a drug (preparation) and the number of different targets hit in a biological system on the gene expression level. Therefore, the number of genetic targets in a biological system does not necessarily increase with the complexity of the treatment corresponding to the non-linear behaviour of biological systems. Regarding gene expression levels AE of single treatments are not necessarily additive in combination treatments. The applied method appears to be an interesting screening tool for the prediction of potential AE. The phenomena that imipramine crossed the potential threshold for AEs several times whereas the WB extract did reach the threshold level only once, however not backed by clinical data for this AE, deserves to be further investigated. It questions the commonly assumed principle that substances with low number or without AE will have a poor efficacy.

Pitfalls in cell culture work with xanthohumol

Xanthohumol, the most abundant prenylated chalcone in hop (Humulus lupulus L.) cones, is well known to exert several promising pharmacological activities in vitro and in vivo. Among these, the chemopreventive, anti-inflammatory and anti-cancer effects are probably the most interesting. As xanthohumol is hardly soluble in water and able to undergo conversion to isoxanthohumol we determined several handling characteristics for cell culture work with this compound. Recovery experiments revealed that working with xanthohumol under cell culture conditions requires a minimal amount of 10% FCS to increase its solubility to reasonable concentrations (-50-75 micromol/l) for pharmacological in vitro tests. Additionally, more than 50% of xanthohumol can be absorbed to various plastic materials routinely used in the cell culture using FCS concentrations below 10%. In contrast, experiments using fluorescence microscopy in living cells revealed that detection of cellular intake of xanthohumol is hampered by concentrations above 1% FCS.

Tea catechins' affinity for human cannabinoid receptors

Among the many known health benefits of tea catechins count anti-inflammatory and neuroprotective activities, as well as effects on the regulation of food intake. Here we address cannabimimetic bioactivity of catechin derivatives occurring in tea leaves as a possible cellular effector of these functionalities. Competitive radioligand binding assays using recombinant human cannabinoid receptors expressed in Chem-1 and CHO cells identified (-)-epigallocatechin-3-O-gallate, EGCG (K(i)=33.6 microM), (-)-epigallocatechin, EGC (K(i)=35.7 microM), and (-)-epicatechin-3-O-gallate, ECG (K(i)=47.3 microM) as ligands with moderate affinity for type 1 cannabinoid receptors, CB1. Binding to CB2 was weaker with inhibition constants exceeding 50 microM for EGC and ECG. The epimers (+)-catechin and (-)-epicatechin exhibited negligible affinities for both CB1 and CB2. It can be concluded that central nervous cannabinoid receptors may be targeted by selected tea catechins but signaling via peripheral type receptors is less likely to play a major role in vivo.

Determining the cytotoxicity of catanionic surfactant mixtures on HeLa cells

The cytotoxicity of commonly used synthetic surfactants and catanionic mixtures of those was evaluated using MTT on HeLa cells. The 50% inhibition concentration (IC(50)) for MTT reduction was calculated. The effect on chain length increase and inclusion of polyoxyethylene groups on the toxicity was tested on single surfactant systems. A general trend of increasing toxicity with increasing chain length and the presence of polyoxyethylene groups was observed. The measured IC(50) values of catanionic systems lie between those of participating surfactants. The increase in toxicity as the cationic surfactant is added to the anionic one is however not linear. A steep decrease of the IC(50) values (and therefore increase in the toxic properties) is observed immediately already at low concentrations of the cationic surfactants. This behavior is analogous to the enzyme activity in catanionic microemulsions.

Spontaneous formation of bilayers and vesicles in mixtures of single-chain alkyl carboxylates: effect of pH and aging and cytotoxicity studies

We report the observation of bilayer fragments, some of which close to form vesicles, over a large range of pH at room temperature from mixtures of single-chain biocompatible commercially available nontoxic alkyl carboxylic surfactants after neutralization with HCl. The pH at which the morphological transitions occur is varied only by changing the ratio between two surfactants: the alkyloligoethyleneoxide carboxylate and sodium laurate. The effect of aging of the mixed surfactant systems in the pH region desired for dermatologic application (4.5 < pH < 7) is also studied. Finally, we show results of cytotoxicity studies on the surfactant mixtures.

Ex vivo/in vitro absorption of STW 5 (Iberogast) and its extract components

To correlate the pharmacological effects of the fixed herbal combination STW 5 (Iberogast) containing nine extract components with its confirmed clinical efficacy, ex vivo/in vitro absorption tests were performed. For the investigation, the everted gut sac technique and, in a pilot study, the Caco-2-cell model were used. The absorption rate of the extracts was determined by measuring characteristic marker substances of each of the individual extracts using HPLC or GC techniques. The results allow us to conclude that the investigated substances from STW 5 possess a good bioavailability, which is in accordance with the rapid onset of the therapeutic efficacy and explains its known pharmacological effects and clinical efficacy in terms of multiple drug action and multi-target therapy, respectively.

The anthelmintic efficacy of five plant products against gastrointestinal trichostrongylids in artificially infected lambs

Forty-eight helminth-free lambs were divided into eight groups (A-H) of six animals. Groups A-G were infected artificially with 10,000 third stage larvae of Haemonchus contortus and 20,000 third stage larvae of Trichostrongylus colubriformis, whereas group H remained uninfected. Thirty days post-infection the lambs were treated orally with a single dosage of one of the following products: group A with 3 mg/kg body weight (BW) of an aqueous ethanol extract (70%, v/v) of the seeds of Azadirachta indica A. Juss syn. Melia azedarach L. (Meliaceae); group B with 1 g/kg BW of a raw powder of the leaves of Ananas comosus (L.) Merr. (Bromeliaceae); group C with 0.3 mg/kg BW of an aqueous ethanol extract of a 1:1 mixture (g/g) of Vernonia anthelmintica (L.) Willd. (Asteraceae) seeds and Embelia ribes Burm (Myrsinaceae) fruits; group D with 183 mg/kg BW of an aqueous ethanol extract of the whole plants of Fumaria parviflora Lam. (Fumariaceae); group E with 28 mg/kg BW of an aqueous ethanol extract of the seeds of Caesalpinia crista L. (Caesalpiniaceae); group F with 25 mg/kg BW of pyrantel tartrate and group G with 50% ethanol. Group H remained untreated. Only the ethanol extract of F. parviflora caused a strong reduction of the faecal egg counts (100%) and a 78.2 and 88.8% reduction of adult H. contortus and T. colubriformis on day 13 post-treatment. The extract was as effective as the reference compound pyrantel tartrate. Therefore, the ethanol extract itself or single constituents of F. parviflora could be a promising alternative source of anthelmintic for the treatment of gastrointestinal trichostrongylids in small ruminants.

Studies on the antioxidative activity of phloroglucinol derivatives isolated from hypericum species

Twenty-one phloroglucinol derivatives, belonging to 8 different carbon skeletons, were tested for their ability to influence the oxidative burst of polymorphonuclear cells (PMNs) after stimulation with N-formyl-methionyl-leucyl-phenylalanine (FMLP) or opsonized zymosan (OZ). Results revealed a strong reduction of oxygen production by PMNs after stimulation with FMLP for the compounds ialibinone E ( 5), hyperguinone B ( 15) and hyperforin ( 21). The IC 50 values obtained were 2.5 microM ( 5), 3.3 microM ( 15) and 1.8 microM ( 21), respectively. Slight modifications of the substituents or variation of the stereochemistry resulted in a significant loss of activity. None of the active compounds showed antioxidative activity after stimulation with OZ. The influence of compounds 5, 15 and 21 on the production of oxygen radicals in an H 2 O 2 /horseradish peroxidase system was investigated and revealed potent activity only for compound 5 (IC 50 1 microM). The superoxide-scavenging properties of ialibinone E ( 5) and hyperguinone B ( 15) were additionally tested in a cytochrome c assay and only ialibinone E ( 5) was found to be significantly active at lower micromolar concentrations. Ialibinone E ( 5) was not active in a xanthine oxidase assay (urate formation) in concentrations up to 100 microM and its activity is therefore not attributable to the inhibition of this enzyme. It can be assumed that the activity of compounds 5 and 15 in the different cellular and enzymatic assays, is most likely caused by different and maybe specific mechanisms and cannot be explained by a radical scavenger activity alone. None of the active phloroglucinols showed cytotoxic effects against the PMNs.

Induction and repair of DNA strand breaks in bovine lens epithelial cells after high LET irradiation

The lens epithelium is the initiation site for the development of radiation induced cataracts. Radiation in the cortex and nucleus interacts with proteins, while in the epithelium, experimental results reveal mutagenic and cytotoxic effects. It is suggested that incorrectly repaired DNA damage may be lethal in terms of cellular reproduction and also may initiate the development of mutations or transformations in surviving cells. The occurrence of such genetically modified cells may lead to lens opacification. For a quantitative risk estimation for astronauts and space travelers it is necessary to know the relative biological effectiveness (RBE), because the spacial and temporal distribution of initial physical damage induced by cosmic radiation differ significantly from that of X-rays. RBEs for the induction of DNA strand breaks and the efficiency of repair of these breaks were measured in cultured diploid bovine lens epithelial cells exposed to different LET irradiation to either 300 kV X-rays or to heavy ions at the UNILAC accelerator at GSI. Accelerated ions from Z=8 (O) to Z=92 (U) were used. Strand breaks were measured by hydroxyapatite chromatography of alkaline unwound DNA (overall strand breaks). Results showed that DNA damage occurs as a function of dose, of kinetic energy and of LET. For particles having the same LET the severity of the DNA damage increases with dose. For a given particle dose, as the LET rises, the numbers of DNA strand breaks increase to a maximum and then reach a plateau or decrease. Repair kinetics depend on the fluence (irradiation dose). At any LET value, repair is much slower after heavy ion exposure than after X-irradiation. For ions with an LET of less than 10,000 keV micrometers-1 more than 90 percent of the strand breaks induced are repaired within 24 hours. At higher particle fluences, especially for low energetic particles with a very high local density of energy deposition within the particle track, a higher proportion of non-rejoined breaks is found, even after prolonged periods of incubation. At the highest LET value (16,300 keV micrometers-1) no significant repair is observed. These LET-dependencies are consistent with the current mechanistic model for radiation induced cataractogenesis which postulates that genomic damage to the surviving fraction of epithelial cells is responsible for lens opacification.

Transport of alkamides from Echinacea species through Caco-2 monolayers

To gain more insights into the human intestinal absorption of alkamides from Echinacea species, transport studies were performed with the human adenocarcinoma colonic cell line Caco-2 (ATCC) as a model to assess the epithelial transport of dodeca-2 E,4 E,8 Z,10 E/ Z-tetraenoic acid isobutylamides (1/ 2). 30 minutes after apical loading of 25 microg/ml 1/ 2, about 15 % of these alkamides were detectable on the basolateral side. Close monitoring of the transport during 6 hours revealed a nearly complete transport to the basolateral side after 4 hours and no significant metabolism was observable. Transport experiments performed at 4 degrees C showed only a slight decrease in transport, which is a strong hint that dodeca-2 E,4 E,8 Z,10 E/ Z-tetraenoic acid isobutylamides (1/ 2) cross biological membranes by passive diffusion. Nearly the same results were obtained after preincubation of the Caco-2 cells with lipopolysaccharides (LPS) or phorbol 12-myristate-13-acetate (PMA) to mimic an inflammatory status. These results support the assumption that the alkamides can be easily transported from the intestinum and hence may contribute to the in vivo effects of Echinacea preparations.

Absorption of dodeca-2E,4E,8Z,10E/Z-tetraenoic acid isobutylamides after oral application of Echinacea purpurea tincture

Alkamides are suspected to contribute to the activity of Echinacea preparations. In preliminary experiments a quantification method for dodeca-2E,4E,8Z,10E/Z-tetraenoic acid isobutylamides in human blood has been developed by which it was possible to detect dodeca-2E,4E,8Z,10E/Z-tetraenoic acid isobutylamides in human blood after oral application of Echinacea purpurea mother tincture.

Minor cytotoxic and antibacterial compounds from the rhizomes of Amomum aculeatum

A new cytotoxic 1,7-dioxa-dispiro[5.1.5.2]pentadeca-9,12-dien-11-one derivative, aculeatin D, and a new alkenone, 5-hydroxy-hexacos-1-en-3-one, have been isolated as minor compounds from the rhizomes of Amomum aculeatum. Their structures have been determined mainly by NMR spectroscopy and mass spectrometry. Aculeatin D showed high cytotoxicity against the KB and the L-6 cell line with IC(50) of 0.38 microg/ml and 1 microg/ml, respectively. Additionally, it revealed remarkable activity against two Plasmodium falciparum strains, as well as against Trypanosoma brucei rhodesiense and Trypanosoma cruzi. 5-Hydroxy-hexacos-1-en-3-one exhibited neither cytotoxic nor antiprotozoal activity, whereas antibacterial testing against Bacillus cereus, Escherichia coli and Staphylococcus epidermidis showed moderate to strong activity for both compounds.

The influence of glutathione and cysteine levels on the cytotoxicity of helenanolide type sesquiterpene lactones against KB cells

The biological activities of sesquiterpene lactones have been attributed to their reactivity with the cysteine residues of functional proteins forming covalent bonds via Michael type addition. In the present study we investigated the influence of different L-cysteine (cys) and glutathione (GSH) concentrations on the cytotoxicity of the sesquiterpene lactones (STLs) helenalin, 11alpha,13-dihydrohelenalin acetate and chamissonolide against KB cells. Due to the significantly higher reactivity of the alpha-methylene-gamma-lactone (ML) towards cys as compared with the cyclopentenone (CP) site at physiological pH, addition of 20, 50 and 100 molar equivalents of cys decreased the cytotoxicity of helenalin and chamissonolide, whereas the cytotoxicity of 11alpha,13-dihydrohelenalin acetate remained unaffected. In contrast, the influence of GSH addition on the cytotoxicity of 11alpha,13-dihydrohelenalin acetate depends on the concentration of GSH added. Concentration-effect curves obtained for chamissonolide and GSH resembled the decline in cytotoxicity after cys addition. Helenalin showed a biphasic shape of the concentration-effect curve for the 100:1 GSH/helenalin ratio resembling at higher doses the chamissonolide and in lower doses the 11alpha,13-dihydrohelenalin acetate curve at 50-fold excess. These results can be explained by the different reactivity and equilibrium conditions for thiol addition of the two reactive centers of bifunctional STLs in cellular test systems and verified a clear correlation between the different reactivity of their electrophilic centers and the observed biological effects in in-vitro cell systems.

Flavonoid, iridoid, and lignan glycosides from Putoria calabrica

From the aerial parts of Putoria calabrica, two new flavonol triglycosides were isolated and their structures were elucidated as quercetin-3-O-[alpha-L-rhamnopyranosyl-(1-->2)-alpha-L-arabinopyranoside]-7-O-beta-D-glucopyranoside (1, calabricoside A) and quercetin-3-O-[4' "-O-caffeoyl-alpha-L-rhamnopyranosyl-(1-->2)-alpha-L-arabinopyranoside]-7-O-beta-D-glucopyranoside (2, calabricoside B). Additionally, seven iridoid and three lignan glycosides were isolated and characterized. Radical scavenging activities of all compounds were determined by quantifying their effects on luminol-enhanced chemiluminescence in formyl-methionyl-leucyl-phenylalanine (FMLP) stimulated human polymorphonuclear neutrophils (PMNs). Calabricoside A and B showed strong radical scavenging activity with IC(50) values of 0.25 and 0.3 microM, respectively.

Further phenols and polyacetylenes from the rhizomes of Atractylodes lancea and their anti-inflammatory activity

From the rhizomes of Atractylodes lancea, 2-[(2'E)-3',7'-dimethyl-2',6'-octadienyl]-4-methoxy-6-methylphenol (1) was isolated as a new natural product. The compound showed strong inhibitory effects on 5-lipoxygenase (5-LOX) and cyclooxygenase-1 (COX-1), but exhibited only weak antioxidative activities [IC50 = 0.1 microM (5-LOX), 2 microM (COX-1), 9 microM (PMN/FMLP), 28 microM (PMNIOZ)]. Moreover, five new acetylenes were isolated and elucidated as (3Z,5E,11E)-tridecatriene-7,9-diynyl-1-O-(E)-ferulate (2), erythro-(1,3Z,11E)-tridecatriene-7,9-diyne-5,6-diyl diacetate (3), (1Z)-atractylodin (4), (1Z)-atractylodinol (5), (1Z)-acetylatractylodinol (6) plus the known (4E,6E,12E)-tetradecatriene-8,10-diyne-1,3-diyl diacetate (7). Among the acetylenes, only 2 showed strong inhibition of 5-LOX and COX-1 activity (IC50 (5-LOX) = 3 microM, IC50 (COX-1) = 1 microM). In addition, the fatty acids linoleic acid, oleic acid and palmitic acid with previously established 5-LOX-/COX-1 inhibitory actions were identified as major constituents of the n-hexane extract and thus seem to contribute to the plant's in vitro activity.

New prenylated bi- and tricyclic phloroglucinol derivatives from Hypericum papuanum

Five new prenylated tricyclic and three new bicyclic acylphloroglucinol derivatives have been isolated by bioactivity-guided fractionation of the petroleum ether extract of the dried aerial parts of Hypericum papuanum. The tricyclic compounds (1--5) were named papuaforins A--E. The bicyclic compounds were isolated together with their corresponding tautomers and were named hyperguinones A and B (6/6a,7/7a) and hyperpapuanone (8/8a), respectively. Their structures were elucidated on the basis of extensive 1D and 2D NMR experiments, as well as mass spectrometry. Furthermore, the cytotoxicity toward KB nasopharyngeal carcinoma cells and the antibacterial activity of the isolated compounds were determined.

Two novel cyclic peptides with antifungal activity from the cyanobacterium Tolypothrix byssoidea (EAWAG 195)

Two novel cyclic tridecapeptides, tolybyssidins A (1) and B (2), were isolated from the culture medium of mass cultured cyanobacterium Tolypothrix byssoidea (EAWAG 195) by means of bioguided isolation. The gross structures of these peptides were determined by 1D and 2D NMR experiments and tandem mass spectrometry. Both peptides contain the nonnatural amino acid dehydrohomoalanine (Dhha) as well as proteinogenic amino acids albeit with D- or L-configuration. The compounds exhibit moderate antifungal activity against the yeast Candida albicans.

New tirucallane-type triterpenes from Dysoxylum variabile

Eight new tirucallane-type triterpenes, dyvariabilins A-H (1-8), three known tirucallanes, niloticin (9), dihydroniloticin (10), and tirucalla-7,24-diene-3 beta,23-diol (11), and two known sesquiterpenes, 1-(1-hydroxy-2-methylpropyl)-3a-methyl-7-methyleneoctahydroinden-4-ol and (+)-aphanamol I, were isolated from the stem bark of Dysoxylum variabile. Tirucallanes 1 and 11 with an allylic hydroxy group in the side chain and dyvariabilin C (3) with an alpha-epoxy group at positions 7 and 8 showed high instability in acidic medium and formed five hitherto unknown semisynthetic tirucallanes. Dyvariabilins B (2) and C (3) as well as the mixtures of dyvariabilins E and F (5 and 6) and dyvariabilins G and H (7 and 8) showed weak cytotoxicity against KB cells.

Bisanthraquinone glycosides of Hypericum perforatum with binding inhibition to CRH-1 receptors

Four new bisanthraquinone glycosides, S-(+)-skyrin-6-O-beta-glucopyranoside (1), R-(-)-skyrin-6-O-beta-glucopyranoside (2), S-(+)-skyrin-6-O-beta-xylopyranoside (3) and S-(+)-skyrin-6-O-beta-alpha-arabinofuranoside (4), have been isolated from an ethanol-water (1:1, v/v) dry extract of the aerial parts of Hypericum perforatum L. The structures were elucidated by spectroscopic methods, mainly NMR and mass spectrometry. Circular dichroism was used to determine their axial stereochemistry revealing 1 and 2 to be atropisomers. 1 and 2 inhibited [125I]sauvagine binding to corticotropin releasing hormone (CRH-1) receptors.

Bioactive coumarin derivatives from the fern Cyclosorus interruptus

Three new coumarin derivatives, compounds 1-3, three new furanocoumarins, compounds 4-6, and a novel dioxocane derivative, compound 7, were isolated from the fern Cyclosorus interruptus (Willd.) H. Itô. Based on spectrometric and spectroscopic analysis (FAB or El mass spectrometry as well as 1D and 2D NMR experiments) their structures were characterised as 5,7-dihydroxy-6-methyl-4-phenyl-8-(3-phenylpropionyl)-1-benzopyran-2-one (1), 5,7-dihydroxy-6-methyl-4-phenyl-8-(3-phenyl-trans-acryloyl)-1- benzopyran-2-one (2), 5,7-dihydroxy-8-(2-hydroxy-3-phenylpropionyl)-6-methyl-4-phenyl-1- benzopyran-2-one (3), 8-benzyl-5,8-dihydroxy-6-methyl-4-phenylfuro[2,3-h]-1-benzopyran-2,9- dione (4), 8-benzyl-5,8 beta,9 beta-trihydroxy-6-methyl-4-phenyl-8,9-dihydro- furo[2,3-h]-1-benzopyran-2-one (5), 8-benzyl-5,8 beta,9 alpha-trihydroxy-6-methyl-4-phenyl-8,9-dihydro- furo[2,3-h]-1-benzopyran-2-one (6) and 5,11-dihydroxy-6-methyl-4-phenyl-11-(1-phenylmethyl)-7,10-dioxocane [5,6-h]-1-benzopyran-2,12-dione (7). For these compounds we propose the trivial names interruptins A-F. Compounds 1, 5/6 and 7 showed antibacterial activity while compounds 1 and 2 were cytotoxic to a KB cell line.

Tetrahydrofuran lignans from Illicium floridanum and their activity in a luminol enhanced chemiluminescence assay

Two lignans of the tetrahydrofuran type, di-O-methyltetrahydrofuroguaiacin B (1) and (+)-veraguensin (2) were isolated from fruits and leaves of Illicium floridanum Ellis (Illiciaceae). These compounds are the first genuine lignans isolated from the genus Illicium. We investigated their radical scavenging potency towards 1,1-diphenyl-2-picrylhydrazyl radical reagent and their influence on luminol enhanced chemiluminescence (CHL) induced by different stimuli in human polymorphonuclear neutrophils (PMN). Both compounds were inactive in the TLC assay for chemical radical scavenge. In the PMN assay, the symmetric lignan 1 at concentrations below 1.0 microM displayed a strong inhibition of CHL induced by N-formyl-methionyl-leucyl-phenylalanine (fMLP). At concentrations above 5 microM, 1 led to a pronounced increase of fMLP induced CHL. When CHL was stimulated with opsonized zymosan, both compounds were completely inactive. Thus, 1 must interfere selectively with a step in the signal cascade evoked by fMLP. In addition to their known PAF-receptor antagonism tetrahydrofuran lignans may thus also interfere with inflammatory responses by inhibition of free radical formation.

Radical scavenger activity of phenylethanoid glycosides in FMLP stimulated human polymorphonuclear leukocytes: structure-activity relationships

Radical scavenger activities of 21 phenylethanoid glycosides, including 15 ester derivatives of caffeic, ferulic, vanillic and syringic acid as well as 6 deacyl derivatives were determined by quantifying their effects on the production of reactive oxygen species (ROS) in a luminol-enhanced chemiluminescence assay with formyl-methionyl-leucyl-phenylalanine (FMLP) stimulated human polymorphonuclear neutrophils (PMNs). All phenylethanoids acylated with phenolic acids showed strong antioxidant activity whereas the deacyl derivatives were more than 30-fold less active. Therefore, the antioxidant activity is mainly related to the number of aromatic methoxy and hydroxy groups and the structure of the acyl moiety (C6-C1 or C6-C3). In contrast, modification of the sugar chain or replacement of hydroxy groups by methoxy groups in the acyl or the phenylethanoid moiety is of minor importance. The position of the acyl moiety is without significance. Free caffeic, ferulic, vanillic and syringic acid are less active compared to the phenylethanoid derivatives. This points to the importance of dissociation and lipophilicity of these acids in a cellular test system.

New antibacterial metabolites from the cyanobacterium Nostoc commune(EAWAG 122b)

Two new compounds, a diterpenoid and an anthraquinone, as well as an indane derivative, which is reported as a natural product for the first time, have been isolated from the cells of the cultured cyanobacterium Nostoc commune (EAWAG 122b) by means of bioguided isolation. The structures were determined by spectroscopic methods, mainly NMR, infrared spectroscopy, and mass spectrometry. All isolates exhibit antibacterial activity.

Cytotoxic cardenolides and antibacterial terpenoids from Crossopetalum gaumeri

From the methanol extract of the roots of (Crossopetalum gaumeri, four new highly cytotoxic cardenolides, securigenin-3beta-O-beta-6-deoxyguloside (2), 19-hydroxy-sarmentogenin-3beta-O-beta-6-deoxyguloside (4), sarmentogenin-3beta-O-[alpha-allosyl-(1-->4)-beta-6-deoxy alloside] (5), and securigenin-3beta-O-[alpha-allosyl-(1-->4)-beta-6-deoxyal loside] (6) were isolated. The dichloromethane extract afforded the new diterpene 3,15-dihydroxy-18-norabieta-3,8,11,13-tetraene (7) as well as the new triterpene 2,3,7-trihydroxy-6-oxo-1,3,5(10),7-tetraene-24-nor-friedelane-29-o ic acid methylester (11). The new terpenoids lack cytotoxicity and the antibacterial activity is moderate to low.

Novel extracellular diterpenoids with biological activity from the cyanobacterium Nostoc commune

Five novel extracellular metabolites with an unprecedented diterpenoid skeleton, 5-[(5-carboxy-2-hydroxy)benzyl]-11-hydroxymethyl-2,5,6,8a, 11-pentamethyldodecahydrocyclopenta<a>naphthalene (1), 5-[(5-carboxy-2-hydroxy)benzyl]-11-formyl-2,5,6,8a, 11-pentamethyl-dodecahydrocyclopenta<a>naphthalene (2), 5-[(5-carboxy-2-hydroxy)benzyl]-11-carboxy-2,5,6,8a, 11-pentamethyl-dodecahydrocyclopenta<a>naphthalene (3), 5-[(5-carboxy-2-hydroxy)benzyl]-11-dihydroxymethyl-2,5,6,8a, 11-pentamethyldodecahydrocyclopenta<a>naphthalene (4), and 5-[(5-carboxy-2-hydroxy)benzyl]-11-acetyl-2,5,6, 8a-tetramethyldodecahydrocyclopenta<a>naphthalene (5), have been isolated from the culture medium of the terrestrial cyanobacterium Nostoc commune by means of bioguided isolation. The molecules were designated as comnostins A-E. The structures were determined by spectroscopic methods, mainly NMR and mass spectrometry. The relative stereochemistry of comnostin A was confirmed by single-crystal X-ray structure analysis. All comnostins showed antibacterial activities. Additionally, cytotoxic and molluscicidal activities were found for comnostin B.

New phloroglucinol derivatives from Hypericum papuanum

Bioactivity-guided fractionation of the petroleum ether extract of the aerial parts of Hypericum papuanum led to the isolation of five new tricyclic phloroglucinol derivatives. On the basis of extensive 1D and 2D NMR experiments as well as MS studies, their structures were elucidated as the C-3 epimers of 8-hydroxy-4,4, 7-trimethyl-9-(2-methylpropionyl)-3-(1-methylvinyl)-5beta -H-tricyclo[ 5.3.1.0(1,5)]undec-8-ene-10,11-dione (1,2); the C-3 epimers of 8-hydroxy-4,4, 7-trimethyl-9-(2-methylbutyryl)-3-(1-methylvinyl)-5beta-H-++ +tricyclo[5. 3.1.0(1,5)]undec-8-ene-10,11-dione (3, 4), and 8-hydroxy-4,4, 7-trimethyl-9-(2-methylpropionyl)-5beta-H-tricyclo[5.3 .1.0(1, 5)]undec-8-ene-10,11-dione (5), and their corresponding tautomers (1a, 2a, 3a, 4a, 5a). Compounds 1/1a-5/5a were named ialibinones A-E, respectively. Compounds 1/1a-4/4a showed antibacterial activity against Bacillus cereus, Staphylococcus epidermidis, and Micrococcus luteus.

New triterpenoids with antibacterial activity from Zizyphus joazeiro

The stem bark of the Brazilian medicinal plant Zizyphus joazeiro C. Mart. was phytochemically investigated. Three known compounds (betulinic, ursolic and alphitolic acid) and three new derivatives of betulinic acid, 7 beta-(4-hydroxybenzoyloxy)-betulinic acid, 7 beta-(4-hydroxy-3'-methoxybenzoyloxy)-betulinic acid and 27-(4-hydroxy-3'-methoxybenzoyloxy)-betulinic acid which showed a considerable activity against Gram-positive bacteria were isolated from the dichloromethane extract. The structures were established on the basis of NMR spectroscopy and mass spectrometry.

Subcellular localization of chromogranins, calcium channels, amine carriers, and proteins of the exocytotic machinery in bovine splenic nerve

Subcellular fractionation of bovine splenic nerves, which consist mainly of sympathetic nerve fibers, has been useful for characterizing cellular organelles en route to the terminal. In the present study we have characterized the subcellular distribution of both secretory and membrane proteins. A newly discovered chromogranin-like protein, NESP55, was found in large dense-core vesicles. The endogenous processing of NESP55 was comparable to that of chromogranins but more limited than that of secretogranin II and chromogranin B. For membrane proteins three major types of distribution were found. The amine carrier VMAT2 was confined to large dense-core vesicles. VAMP or synaptobrevin was present both in large dense-core vesicles and in lighter vesicles, whereas SNAP-25, syntaxin, and two types (N and L) of Ca2+ channels were found in a special population of lighter vesicles but were not present in large dense-core vesicles or at the most in very low concentrations. The plasma membrane norepinephrine transporter was apparently present in a separate type of vesicle, but this requires further study. These results further characterize vesicles en route to the terminal and establish for the first time that peptides involved in exocytosis (syntaxin, SNAP-25, and N- and L-type Ca2+ channels) are apparently transported to the terminal in a special type of vesicle. The exclusive presence of the amine carrier in large dense-core vesicles indicates that the formation of small dense-core vesicles in the terminals requires a reuse of membrane components of large dense-core vesicles.

Brain perfusion scintigraphy with 99mTc-HMPAO or 99mTc-ECD and 123I-beta-CIT single-photon emission tomography in dementia of the Alzheimer-type and diffuse Lewy body disease

Dementia of the Alzheimer-type (DAT) is characterized by progressive cognitive decline, variably combined with frontal lobe release signs, parkinsonian symptoms and myoclonus. The features of diffuse Lewy body disease (DLBD), the second most common cause of degenerative dementia, include progressive cognitive deterioration, often associated with levodopa-responsive parkinsonism, fluctuations of cognitive and motor functions, psychotic symptoms (visual and auditory hallucinations, depression), hypersensitivity to neuroleptics and orthostatic hypotension. A recent report suggests that positron emission tomography studies in patients with degenerative dementia may be useful in the differential diagnosis of DAT and DLBD. However, the diagnostic role of single-photon emission tomography (SPET) studies remains to be established. The aim of this study was therefore to evaluate regional cerebral perfusion [with either technetium-99m hexamethylpropylene amine oxime (99mTc-HMPAO) or 99mTc-ethyl cysteinate dimer (99mTc-ECD) SPET] and striatal dopamine transporter density [using iodine-123 2 beta-carboxymethoxy-3 beta-[4-iodophenyl]tropane (123I-beta-CIT) SPET] in patients with DAT and DLBD. Six patients with probable DAT and seven patients with probable DLBD were studied. Blinded qualitative assessment by four independent raters of 99mTc-HMPAO or 99mTc-ECD SPET studies revealed bilateral temporal and/or parietal hypoperfusion in all DAT patients. There was additional frontal hypoperfusion in two patients and occipital hypoperfusion in one patient. In the DLBD group, regional cerebral perfusion had a different pattern. In addition to temporoparietal hypoperfusion there was occipital hypoperfusion resembling a horseshoe defect in six of seven patients. In the DAT group, the mean 3-h striatal/cerebellar ratio of 123I-beta-CIT binding was 2.5 +/- 0.4, with an increase to 5.5 +/- 1.1 18 h after tracer injection. In comparison, in the DLBD patients the mean 3-h striatal/cerebellar ratio of 123I-beta-CIT binding was significantly reduced to 1.7 +/- 0.3, with a modest increase to 2.1 +/- 0.4 18 h after tracer injection (P < 0.05, Scheffe test, ANOVA). These results suggest that 99mTc-HMPAO or 99mTc-ECD and 123I-beta-CIT SPET may contribute to the differential diagnosis between DAT and DLBD, showing different perfusion patterns and more severe impairment of dopamine transporter function in DLBD than in DAT.

Radical scavenger activity of three flavonoid metabolites studied by inhibition of chemiluminescence in human PMNs

3,4-Dihydroxyphenylacetic acid, 3-hydroxyphenylacetic acid, and 3-(4-hydroxyphenyl)-propionic acid, metabolites which arise from quercetin glycosides, respectively, from flavones and probably from procyanidins by the human intestinal microflora, have been tested for their effects on oxygen radical production by human PMNs stimulated with FMLP or opsonized zymosan. Oxygen radicals were detected by luminol-augmented chemiluminescence measurements. Furthermore free radical scavenging activity of these metabolites was investigated in a cell-free system in which oxygen radicals were generated by horseradish peroxidase with H2O2 as substrate. 3,4-Dihydroxyphenylacetic acid reduced considerably chemiluminescence in PMNs in an amount which was much more pronounced than those of the other two metabolites. Concentrations of 1 mumol/l showed an inhibition by 84% with FMLP as stimulant and by 15% with opsonized zymosan, indicating that different signal transduction pathways are influenced in PMNs. Using the same conditions the unmetabolized quercetin showed an inhibition of chemiluminescence by 74% (FMLP), resp. 20% (opsonized zymosan). In the cell free system 3,4-dihydroxyphenylacetic acid suppressed much more effectively chemiluminescence than 3-hydroxyphenylacetic acid. In contrast, 3-(4-hydroxyphenyl)-propionic acid led to an increase of chemiluminescence generated in the cell-free system (FMLP and zymosan), i.e. by 30% by 25%, at the highest concentration of 4 mumol/l. In conclusion, flavonoid metabolites differ in their effects on free radical production of PMNs and their radical scavenging potencies.

Measurement of intracellular dna double-strand break induction and rejoining along the track of carbon and neon particle beams in water

PURPOSE

The study was aimed at the measurement of effect-depth distributions of intracellularly induced DNA damage in water as tissue equivalent after heavy ion irradiation with therapy particle beams.

METHODS AND MATERIALS

An assay involving embedding of Chinese hamster ovary (CHO-K1) cells in large agarose plugs and electrophoretic elution of radiation induced DNA fragments by constant field gel electrophoresis was developed. Double-strand break production was quantified by densitometric analysis of DNA-fluorescence after staining with ethidium-bromide and determination of the fraction of DNA eluted out of the agarose plugs. Intracellular double-strand break induction and the effect of a 3 h rejoining incubation were investigated following irradiation with 250 kV x-rays and 109 MeV/u carbon- and 295 MeV/u neon-ions.

RESULTS AND CONCLUSION

While the DNA damage induced by x-irradiation decreased continuously with penetration depth, a steady increase in the yield of double-strand breaks was observed for particle radiation, reaching distinct maxima at the position of the physical Bragg peaks. Beyond this, the extent of radiation damage dropped drastically. From comparison of DNA damage and calculated dose profiles, relative biological efficiencies (RBEs) for both double-strand break induction and unrejoined strand breaks after 3 h were determined. While RBE for the induction of DNA double-strand breaks decreased continuously with penetration depth, RBE maxima greater than unity were found with carbon- and neon-ions for double-strand break rejoining near the maximum range of the particles. The method presented here allows for a fast and accurate determination of depth profiles of relevant radiobiological effects for mixed particle fields in tissue equivalent.

Induction and rejoining of DNA double-strand breaks in CHO cells after heavy ion irradiation

DNA double-strand breaks (DSBs) are the crucial events ultimately leading to cell inactivation. Aimed at understanding the biological action of the charged particle component of cosmic radiation, the induction of DSBs and their repairability was evaluated in Chinese hamster ovary (CHO-K1) cells after exposure to accelerated particles. Irradiations were performed with various ion species including O, Ni and Ca, covering a LET range from 20 to 2000 keV/micrometer. DSBs were determined for plateau-phase cells using the electrophoretic elution of radiation-induced DNA fragments in a static electric field combined with fluorescence scanning of ethidium bromide stained gels. Assuming a DSB yield of 22 DSB per Gy per cell, as derived from X-irradiation, cross-sections for DSB production were calculated from the corresponding fluence-effect curves at a fraction of 0.7 of DNA retained. The same ordinate was used as a reference for the calculation of relative biological efficiency (RBE) for DSB induction. At low LETs (< or = 20 keV/micrometer) RBE values slightly above unity were obtained, but a decrease of RBE was observed with increasing LET. In the region of 100-200 keV/micrometer the RBE for initial DSB induction was clearly below unity. Rejoining of DSBs was assessed by measuring the fraction of DNA retained following post-irradiation incubation of cells under culture conditions. After exposure to Ca ions, DSB rejoining was considerably impaired compared to X-rays.

Radical scavenger activity of different 3',4'-dihydroxyflavonols and 1,5-dicaffeoylquinic acid studied by inhibition of chemiluminescence

To gain more insights into structure-activity relationships, four 3',4'-dihydroxyflavonols differing in the substitution of the A and C rings and 1,5-dicaffeolyquinic acid were evaluated for their ability to inhibit chemiluminescence of human neutrophils stimulated with opsonized zymosan or FMLP as well as in an enzymatic system with H2O2 and horseradish peroxidase. It could be shown that an additional o-dihydroxy structure in the A-ring, or a 6-methoxy group, respectively, has no significant influence, thus confirming the o-dihydroxy group of the B-ring as the most important structural feature for the radical scavenger activity. It can be supposed that the main effect of the tested flavonols is based on their inhibition of myeloperoxidase, besides inhibition of enzymes involved in activating the NADPH-oxidase, and a direct reaction with oxygen radicals. Inhibition of chemiluminescence by 1,5-dicaffeoylquinic acid was in the same order as those observed with the flavonols.

Induction of DNA double-strand breaks in CHO-K1 cells by carbon ions

Radiation-induced DNA double-strand breaks (dsbs) were measured in CHO-K1 cells by means of an experimental approach involving constant-field gel electrophoresis and densitometric scanning of ethidium bromide stained gels. For X-irradiation, an induction efficiency of 36 +/- 5 dsbs (Gy x cell)-1 was determined. With this set-up, the induction of dsbs was investigated in CHO-K1 cells after irradiation with accelerated carbon ions with specific energies ranging from 2.7 to 261 MeV/u. This set of particle beams covers the important linear energy transfer (LET) range between 17 and 400 keV/microns, where maximum efficiencies have been reported for other cellular endpoints like inactivation or mutation induction. For LETs up to 100 keV/microns, RBEs of approximately 1 have been determined, while efficiencies per unit dose decline for higher LETs. No RBE maximum > 1 was found. Data are compared with published results on dsb induction in mammalian cells by radiations of comparable LET.