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PubMedDate not supplied

[The interaction of organosilicon bisammonium compounds with the cholinesterases of Far-Eastern squids and vertebrates. The comparative enzymological, kinetic and conformational aspects].

The research of interaction of cholinesterases from human erythrocytes, horse blood serum, brain of the frog Rana temporaria, optical ganglia of the Pacific squid Todarodes pacificus, as well as optical ganglia of specimens of the Comandor squid Berryteuthis magister from different areas in the Bering sea with 13 organosilicon bis (trimethylammonium) compounds (silane and siloxane rows) as reversible cholinesterase inhibitors have been first studied and generalized. Calculations of the effector structure using the method of theoretical conformational analysis showed higher rigidity of interonium chain of siloxane derivatives and gave grounds to accept the asymmetry of hydrate envelope for these compounds. The data of conformational and kinetic analysis allowed to propose that specificity of antienzymic effect of organosilicon compounds was mainly due to conformational flexibility of interonium chain and the nature of hydration of effector molecule. The new information on the mechanism of catalytic reactions effected by cholinesterases from animals at different evolutionary stages was obtained.

Animals↗
PubMedDate not supplied

Development of rational in vitro models for drug resistance in breast cancer and modulation of MDR by selected compounds.

BACKGROUND: [corrected] The effectiveness of chemotherapy is limited by the emergence of multidrug resistance (MDR). MDR is caused by the activity of various ATP binding cassette (ABC) transporters that pump anticancer drugs out of the cells in an ATP-dependent manner. Additionally some other cellular mechanisms of MDR have been reported. The purpose of this study was to investigate mechanisms of MDR in drug resistant MCF-7 cell lines and to modulate P-glycoprotein (P-gp) and MRP1-based MDR. MATERIALS AND METHODS: Paclitaxel (MCF-7/Pac), docetaxel (MCF-7/Doc), doxorubicin (MCF-7/Dox) and vincristine (MCF-7/Vinc) resistant sublines were developed from the parent MCF-7 cell line (MCF-7/S) by stepwise selection in dose increments over two years. Flow cytometry, MTT cytotoxicity assay, RT-PCR, caspase-3 activity assay and checkerboard combination assay were performed to investigate the degree of resistance developed in sublines and to reverse drug resistance phenotype. RESULTS: The flow cytometry histograms of drug accumulation assays demonstrated that the drug-resistant cell lines are P-gp and MRPI positive. RT-PCR results showed that the resistant sublines express both MDR1 and MRP1 genes. Resistance indices of each subline to each anticancer drug were determined using the MTT cytotoxicity assay and it was found that all the sublines were resistant to their respective agents. Caspase-3 activities of the cell lines were also determined. Caspase-3 activity is an important indicator of apoptosis in the cell. The reversal of MDR was attempted by two cinnamylidene ketone and two organosilicon compounds. The results indicated that these compounds modulated P-gp effectively, but they were not very effective at reversing MRP1 activity in the MCF-7 sublines. Four selective anticancer drugs (paclitaxel, docetaxel, doxorubicin and vincristine) and four synthetic MDR modulators [2-(2-methoxycinnamylidene) indan-1-one (cinnamylidene-1), 2-(2- methoxycinnamylidene)-3, 4-dihydro-2H-naphthelen-1-one) (cinnamylidene-2), ALIS 409 and ALIS 421] were applied to the sublines in combination. The fractional inhibitory indices illustrated that combined applications of cinnamylidene ketones and organosilicon compounds with paclitaxel, docetaxel or vincristine exerted significant antiproliferative effects on the resistant sublines. CONCLUSION: This report demonstrates the development of rational models for drug resistance MCF-7 cell lines and reversal of acquired drug resistance.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1999

Gas chromatographic determination of some alkoxysilanes for use in occupational exposure assessment.

The manufacture and application of organosilicon compounds, especially silanes, have increased dramatically during recent decades. This has led to an increase in the number of exposed workers in different areas of industry. Therefore, there is an urgent need for an analytical method which can assess exposure to these compounds. A capillary column gas chromatographic (GC) method was developed for detecting 3-methacryloxypropyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane and 3-aminopropyltriethoxysilane. The silanes diluted in heptane were analysed by GC using flame ionisation detection. Gas chromatography-mass spectrometry was used to confirm the identity of the GC peaks. The analytical range of the method varied from 1 or 5 micrograms ml-1 to 500 micrograms ml-1 depending on the silane being studied. The detection limits were 1 microgram ml-1 for 3-methacryloxypropyltrimethoxysilane and 3-glycidoxypropyltrimethoxysilane and 5 micrograms ml-1 for 3-aminopropyltriethoxysilane. The mean recovery of silanes tested with patch samples was > 95% for all of the silanes. The repeatability of the patch sample method for silanes varied from 6.5 to 10.1%. This new GC method allows the simultaneous determination of three organosilicon compounds for occupational exposure assessment.

Chromatography, Gas↗
PubMed1987

Hypocholesterolemic action of 1-ethoxysilatrane.

Intraperitoneal administration of the organosilicon compound 1-ethoxysilatrane to the rat caused a 25% decrease in the concentration of cholesterol in serum without affecting that of triacylglycerols. The specific activity of 3-hydroxy-3-methylglutaryl CoA reductase, the rate-limiting enzyme in cholesterol biosynthesis, was depressed in hepatic microsomes of silatrane-treated animals.

Animals↗
PubMedDate not supplied

[The effect of new biologically active substances on effector T-lymphocytes in vitro].

Levamisole has been demonstrated to stimulate the activity of T effectors in patients with rheumatic arthritis directly and indirectly via production of the factors influencing effector functions. The organosilicon compound minval was beneficial both in patients and donors. Its activity was mediated by the production of factors in donors, whereas in patients it showed direct and indirect actions, being higher than that of levamisole. The bioflavonoid derived from the Rosa L. root was shown to exert no action on T-effector function.

Adjuvants, Immunologic↗
PubMed1984

Organosilicone induced malformation of rat sperms, a histochemical study.

The effects of an organosilicon compound SOC, a derivative of 1,3-dioxa-2-sila-cyclopentane, on rat spermiogenesis were studied with the help of histochemical and enzyme histochemical methods. The rats were injected with SOC i.p. daily for 3 weeks (dosage: 25 mg SOC/kg body weight). Two changes were observed: a) formation of a distinct vacuole within the acrosomal cap of spermatids b) the splitting of the tails of mature sperms.

Acrosome↗
PubMedDate not supplied

New silicon compounds as resistance modifiers against multidrug-resistant cancer cells.

The efficiency of chemotherapy is often decreased by the development of resistance of cancer cells to cytostatic drugs. This phenomenon is in most cases caused by the activity of the various ABC transporters, multidrug-resistance (MDR) gene-encoded p-glycoproteins, that pump anticancer drugs out of the cells. The inhibition of the activities of the MDR proteins MDR1 and MRP was investigated via the administration of two new organosilicon compounds, alis-409 and alis-421. The study was focused on the inhibition of MDR by blocking the ADR1 gene expression and through the inhibition of the pump-function of mdr-p-glycoprotein, in human breast cancer cell lines expressing mrp and prostate cancer cell line (PC-3). Apoptosis induction and the interaction between epirubicin and the silicon-substituted compounds were studied in human MDR-1 gene-transfected mouse lymphoma and its parent cell line, Colo320/MDR-LRP and sensitive subline Colo205, by means of rhodamine 123 accumulation. The activity of MRP1 p-glycoprotein was studied in human breast cancer cell lines such as HTB-26/MRP1 and two MRP-negative breast cancer cell lines, T47D and MCF7, by carboxyfluorescein accumulation, and on a stomach cancer cell line. The activity of MRP in 257P/MDR and its drug-sensitive derivative were studied in human stomach cancer cells by daunorubicin accumulation in a flow cytometer. The two representative organosilicon derivatives, alis-409 and alis-421, showed antiproliferative effects without apoptosis induction. The drug accumulation in the human MDR1 gene-transfected mouse lymphoma cells was increased without down-regulation of the MDR1 gene expression tested by RT-PCR assay. The rhodamine uptake was increased in L5178/MDR1 and Colo320/MDR1-LRP, but not drug-sensitive human breast cancer MCF-7 and T47D, and L5178 mouse lymphoma parent cells in the presence of alis-409 and alis-421. The MRP-mediated carboxyfluorescein accumulation in HTB-26/MRP human breast cancer cells and daunorubicin accumulation in human stomach cancer cells 257P/MDR were not modified by these alis compounds. A synergistic interaction between epirubicin and the silicon-substituted resistance modifiers was found only in MDR1-mediated MDR in the case of colo-320/MDR1-LRP cells and mouse lymphoma cells transfected with the human MDR1 gene. The results indicate that the organosilyl derivatives specifically act on MDR1 p-glycoprotein 170. The alis compounds act on pgp170 in a way which is similar to verapamil isomers.

Animals↗
PubMed2004

Effect of conformational changes on a one-electron reduction process: evidence of a one-electron P-P bond formation in a bis(phosphinine).

EPR spectra show that one-electron reduction of bis(3-phenyl-6,6-(trimethylsilyl)phosphinine-2-yl)dimethylsilane (1) on an alkali mirror leads to a radical anion that is localized on a single phosphinine ring, whereas the radical anion formed from the same reaction in the presence of cryptand or from an electron transfer with sodium naphthalenide is delocalized on the two phosphinine rings. Density functional theory (DFT) calculations show that in the last species the unpaired electron is mainly confined in a loose P-P bond (3.479 A), which results from the overlap of two phosphorus p orbitals. In contrast, as attested by X-ray spectroscopy, the P-P distance in neutral 1 is large (5.8 A). As shown by crystal structure analysis, addition of a second electron leads to the formation of a classical P-P single bond (P-P 2.389 A). Spectral modifications induced by the presence of cryptand or by a change in the reaction temperature are consistent with the formation of a tight ion pair that stabilizes the radical structure localized on a single phosphinine ring. It is suggested that the structure of this pair hinders internal rotation around the C-Si bonds and prevents 1 from adopting a conformation that shortens the intramolecular P-P distance. The ability of the phosphinine radical anion to reversibly form weak P-P bonds with neutral phosphinines in the absence of steric hindrance is confirmed by EPR spectra obtained for 2,6-bis(trimethylsilyl)-3-phenylphosphinine (2). Moreover, as shown by NMR spectroscopy, in this system, which contains only one phosphinine ring, further reduction leads to an intermolecular reaction with the formation of a classical P-P bond.

Crystallization↗
PubMed2005

Ring-opening protonolysis of sila[1]ferrocenophanes as a route to stabilized silylium ions.

The ring-opening reactions of a series of sila[1]ferrocenophanes with protic acids of anions with various degrees of noncoordinating character have been explored. Ferrocenyl-substituted silyl triflates FcSiMe2OTf (5 a) and Fc(3)SiOTf (5 b) (Fc=(eta5-C5H4)Fe(eta5-C5H5)) were synthesized by means of HOTf-induced ring-opening protonolysis of strained sila[1]ferrocenophanes fcSiMe2 (3 a) and fcSiFc2 (3 b) (fc=(eta5-C5H4)2Fe). Reaction of 3 a and 3 b with HBF4 yielded fluorosubstituted ferrocenylsilanes FcSiMe2F (6 a) and Fc3SiF (6 b) and suggested the intermediacy of a highly reactive silylium ion capable of abstracting F- from the [BF4]- ion. Generation of the solvated silylium ions [FcSiMe2THF]+ (7a+), [Fc3SiTHF]+ (7b+) and [FcSiiPr2OEt2]+ (7c+) at low temperatures, by reaction of the corresponding sila[1]ferrocenophanes (3 a, 3 b, and fcSiiPr2 (3 c), respectively) with H(OEt2)(S)TFPB (S=Et2O or THF; TFPB=tetrakis[3,5-bis(trifluoromethyl)phenyl]borate) was monitored by using low-temperature 1H, 13C, and 29Si NMR spectroscopy. In situ reaction of 7a+, 7b+, and 7c+ with excess pyridine generated [FcSiMe2py]+ (8a+), [Fc3Sipy]+ (8b+), and [FcSiiPr2py]+ (8c+), respectively, as observed by 1H, 13C, and 29Si NMR spectroscopy. A preparative-scale reaction of 3 b with H(OEt2)(THF)TFPB at -60 degrees C and subsequent addition of excess pyridine gave isolable red crystals of 8b-[TFPB]CHCl3, which were characterized by 1H and 29Si NMR spectroscopy as well as by single-crystal X-ray diffraction.

Crystallography, X-Ray↗