We describe the development of a cell system for in vivo screening of inhibitors of the mevalonate pathway. To this aim, we have constructed a bicistronic mRNA, transcribed from a constitutive ...cytomegalovirus promoter, containing the Renilla reniformis luciferase RNA open reading frame sequence as first cistron and the Firefly luciferase RNA sequence as a second cistron. The intercistronic space is made of the R17 binding sequence of the bacteriophage R17 protein. A chimeric protein able to bind to a specific sequence in the hairpin and to induce internal ribosome entry in the RNA switches on translation of the second cistron. This chimeric protein is made up of the bacteriophage RNA binding domain (R17) fused to the ribosome recruitment core of the eIF-4G1 eukaryotic translation initiation factor and to the CAAX box of H-Ras addressing the protein to the plasma membrane where it is not efficient. Internal ribosome entry upstream of the Firefly cistron is therefore under the dependence of the mevalonate pathway inhibitors. Indeed, products that are able to inhibit protein farnesylation rescue the cytoplasmic location of the R17-eIF-4G-CAAX protein, which once more becomes a translation factor for the expression of the second cistron. To exemplify the system, the present work checks the ability of various antiestrogens to interfere with the mevalonate pathway. It seems that pure antiestrogen, able to selectively bind the estrogen receptor, is unable to switch on the second Firefly cistron although selective antiestrogen-binding-site ligands are able to do so.
Toxicity of trifluoroacetate to aquatic organisms Berends, Albert G.; Boutonnet, Jean Charles; Rooij, Christ G. De ...
Environmental toxicology and chemistry,
19/May , Letnik:
18, Številka:
5
Journal Article
Recenzirano
As a result of the atmospheric degradation of several hydrofluorocarbons and hydrochlorofluorocarbons, trifluoroacetate (TFA) will be formed. Through precipitation, TFA will enter aquatic ecosystems. ...To evaluate the impact on the aquatic environment, an aquatic toxicity testing program was carried out with sodium trifluoroacetate (NaTFA). During acute toxicity tests, no effects of NaTFA on water fleas (Daphnia magna) and zebra fish (Danio rerio) were found at a concentration of 1,200 mg/L. A 7‐d study with duckweed (Lemna gibba G3) revealed a NOEC of 300 mg/L. On the basis of the results of five toxicity tests with Selenastrum capricornutum, we determined a NOEC of 0.12 mg/L. However, algal toxicity tests with NaTFA and Chlorella vulgaris, Scenedesmus subspicatus, Chlamydomonas reinhardtii, Dunaliella tertiolecta, Euglena gracilis, Phaeodactylum tricornutum, Navicula pelliculosa, Skeletonema costatum, Anabaena flos‐aquae, and Microcystis aeruginosa resulted in EC50 values that were all higher than 100 mg/L. The toxicity of TFA to S. capricornutum could be due to metabolic defluorination to monofluoroacetate (MFA), which is known to inhibit the citric acid cycle. A toxicity test with MFA and S. capricornutum revealed it to be about three orders of magnitude more toxic than TFA. However, a bioactivation study revealed that defluorination of TFA was less than 4%. On the other hand, S. capricornutum exposed to a toxic concentration of NaTFA showed a recovery of growth when citric acid was added, suggesting that TFA (or a metabolite of TFA) interferes with the citric acid cycle. A recovery of the growth of S. capricornutum was also found when TFA was removed from the test solutions. Therefore, TFA should be considered algistatic and not algicidic for S. capricornutum. On the basis of the combined results of the laboratory tests and a previously reported semi‐field study, we can consider a TFA concentration of 0.10 mg/L as safe for the aquatic ecosystem.
Internal Ribosome Entry Sites (IRES) are cis-acting RNA sequences able to mediate internal entry of the 40S ribosomal subunit on some eukaryotic and viral messenger RNAs upstream of a translation ...initiation codon. These sequences are very diverse and are present in a growing list of mRNAs. Novel IRES sequences continue to be added to public databases every year and the list of unknown IRESes is certainly still very large. The IRES database is a comprehensive WWW resource for internal ribosome entry sites and presents currently available general information as well as detailed data for each IRES. It is a searchable, periodically updated collection of IRES RNA sequences. Sequences are presented in FASTA form and hotlinked to NCBI GenBank files. Several subsets of data are classified according to the viral taxon (for viral IRESes), to the gene product function (for cellular IRESes), to the possible cellular regulation or to the trans-acting factor that mediates IRES function. This database is accessible at http://ifr31w3.toulouse.inserm.fr/IRESdatabase/.
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Alkali metal trimethylsilanolates, TMSO
−, M
+, has been used for efficient conversion of methyl esters into their corresponding anhydrous acid salts under mild non-aqueous ...conditions. This strategy has been applied to SPPS for the preparation of neurotoxin cyclic analogues and in (
S)-5-hydroxynorvaline synthesis.
An asynchronous version of a binary pixel readout circuit has been implemented in an array with 16 columns at 500 mu m pitch and 63 rows at 75 mu m pitch. This readout chip has been bonded with ...solder bumps to a silicon detector with matching pixel elements. Event information in a pixel can be strobed into a local memory by a trigger signal and subsequently read out. Without a strobe the information in this memory is continuously cleared. The complete hybrid detector has been successfully tested with ionizing particles from a radioactive source. Three such devices have been used in the CERN heavy ion experiment WA94 in the Omega spectrometer where they recorded particle tracks from high multiplicity /sup 32/S interactions.< >
This paper describes a mixed analog and digital full-custom circuit designed to read the coordinates of silicon pixels used as particle detectors for high-energy physics. This high-speed readout ...includes zero suppression (Sparse Data Scan), and is ambiguity free. The design methodology is also discussed.< >
The DELPHI very forward tracker for LEP200 Andreazza, A; Aubret, C; Baubillier, M ...
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment,
12/1995, Letnik:
367, Številka:
1
Journal Article, Conference Proceeding
Recenzirano
The design of a new silicon tracker detector for the forward region in the DELPHI experiment is presented. It consists of two layers of macropixel and two layers of ministrip detectors in both the ...forward directions. The motivations and the requirements for this detector will be shown together with test beam results.