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G Sosnovsky

Publications and source records attributed to G Sosnovsky.

At least 19 recordsLinked to original sources
PubMed1992

Simultaneous measurements of the intra- and extra-cellular oxygen concentration in viable cells.

An EPR method that can measure the intra- and extra-cellular oxygen concentration [O2] simultaneously in vitro has been developed using specially designed nitroxides. In the presence of Fe(CN)6(3-) in the medium, intracellular [O2] is measured by a neutral 15N-nitroxide and extracellular [O2] is measured by a negatively charged 14N-nitroxide, since charged species do not enter cells and the EPR spectrum of a 15N-nitroxide does not overlap with that of a 14N-nitroxide. The method is based in part on the minimal broadening of negatively charged nitroxides by Fe(CN)6(3-) and the very effective broadening of neutral nitroxides by the same paramagnetic ions. Results with this method confirm the existence of gradients in [O2] between the extracellular and intracellular compartments in CHO cells and M5076 tumor cells, even without stimulation of cellular respiration by CCCP. The nature of the barrier that needs to be involved to account for the experimental results raises some significant questions.

Animals↗
PubMed1992

A critical evaluation of the present status of toxicity of aminoxyl radicals.

The literature on the toxicity of aminoxyl radicals was critically reviewed. It was concluded that, in general, the aminoxyl radicals possess a very low toxicity and are not mutagenic. In support of this contention, several aminoxyl radicals were evaluated in vitro. Thus, aminoxyl radicals 3-carboxy-2,2,5,5-tetramethylpyrroline-1-oxyl (1), 3-carboxy-2,2,5,5-tetramethylpyrrolidine-1-oxyl (PCA; 2), 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl (Tempol;3), and N-(1-hydroxymethyl-2,3-dihydroxypropyl)-3-carboxyamino-2,2,5,5- tetramethylpyrrolidine-1-oxyl (NAT; 4) were evaluated using Salmonella typhimurium tester strains TA 102 and TA 104, with a supplement of xanthine oxidase enzyme. 1, 2, and 4 were found to be nonmutagenic, while 3 elicited in TA 104 only about a twofold increase in the number of revertants above the control. This response is considered to be, at best, marginal in view of wide fluctuations of experimental scores. The results of the present study are in agreement with those of other studies confirming the nonmutagenicity of aminoxyl radicals investigated to date. However, these conclusions are different from those of a study where 3 was tested in the presence of a generated toxic oxygen species that can cause mutagenic changes of the environment.

Animals↗
PubMed1991

Chemical and electrochemical reduction rates of cyclic nitroxides (nitroxyls).

The reduction rates of five-membered pyrrolidine and pyrroline, and six-membered piperidine nitroxides (alternatively termed nitroxyls) containing various substituents were determined under homogeneous conditions using ascorbate, and electrochemically under heterogeneous conditions. The results were compared with data from the literature. It was shown that the increased rates of reduction of six-membered nitroxides, compared with those of the five-membered nitroxides, cannot be explained on the basis of differences in electrochemical potentials but, rather, can be ascribed to differences in the accessibility of the nitroxide group. A double bond in the five-membered nitroxyls increases the reduction rate. Within any ring system, the reduction rates of nitroxides using ascorbate can be correlated with the inductive substituent constants. The half-way potentials for electrochemical reduction within a series of nitroxides based on the same ring correlate with logarithms of the rates using ascorbate and with the inductive constants. The potentials for one-electron oxidation of the nitroxides were related to the inductive constants.

Ascorbic Acid↗
PubMed1991

In the search for new anticancer drugs. XXIII: Exploration of a predictive design for anticancer drugs of carbohydrates containing N-nitrosochloroethylamino, N-nitrosomethyl, and N-nitrosoaminoxyl components.

The spin-labeled glucose nitrosoureas 13-16, streptozotocin (18), chlorozotocin (31), streptozotocin analogues of galactosyl 24 and mannosyl 28, and their tetra-O-acetyl derivatives 25 and 29, MCNU (Cymerin, 34), and glucamine (21) were synthesized and evaluated in vivo for their anticancer activities against the murine lymphocytic leukemia P388. Compounds 13-16, 18, 24, 28, 31, and 34 possessed activities ranging from 33 to 603% increase in life span (%ILS), whereas 21, 25, and 29 were inactive (%ILS = 9 to 10). All CD2F1 male mice treated with the most active compounds (13, 14, and 34) at 20 mg/kg were alive after 30 days, whereas all mice treated with the clinical drug streptozotocin (18) and clinically tested chlorozotocin (31) succumbed. Compounds 13-16, 18, 31, and 34 were further evaluated for their antineoplastic activity against lymphoid leukemia L1210. Compounds 13 and 34 on day 60 exhibited %ILS values of 557 and 713, respectively, as compared with %ILS values of 646 and 713 for CCNU (1) and the spin-labeled SLCNU (3), respectively. The lipophilicities of 13-16, 18, 21, 24, 25, 28, 29, 31, and 34 were determined using EPR and/or UV methods. A predictive design pattern was observed, with the most active drug (34) possessing some hydrophobic property (log P = 1.24), followed by 13 (log P = 1.87) and 14 (log P = 1.81) as the more active drugs with higher hydrophobicity than 34. The clinical drugs streptozotocin (18) and chlorozotocin (31) were distinctly hydrophilic and less active. Finally, it was concluded that various scattered results of anticancer activity in the literature can be explained by a linear correlation of activities with lipophilicities.

Animals↗
PubMed1989

Development of nitroxides for selective localization inside cells.

The use of nitroxides to measure intracellular phenomena, especially oxygen concentrations, is a new and potentially important approach to a number of physiological and pathophysiological studies. This study provides data indicating the feasibility of developing nitroxides that localize selectively in the intracellular compartment; it is based on the use of readily hydrolysed ester linkages, such that the nitroxides become converted intracellularly to ionic derivatives that do not cross cell membranes readily. Up to 120-fold increased concentrations of intracellular nitroxides (and their one electron reduction product, the hydroxylamines) were obtained. The ESR spectra of the intracellular nitroxides were consistent with their conversion to the ionic species. Preliminary studies indicate that these nitroxides have the properties needed for their use as probes of intracellular concentrations of oxygen and that it should be feasible to synthesize nitroxides that will be even more effective for this purpose.

Animals↗
PubMed1989

Evaluation of spin labeled TEPA and CCNU analogs against osteosarcoma and MNU-induced mammary carcinoma of the SD-rat.

The effectiveness to reduce tumor growth by 1-(2-chloroethyl)-3-(1-oxyl-2,2,6,6-tetramethylpiperidinyl)- 1-nitrosourea (SLCNU) and N,N,N,'N'- bis(1,2-ethanediyl)-N"-(1-oxyl-2,2,6,6-tetramethyl- 2-piperidinylaminocarbonyl)-phosphoric triamide (SLDU) was studied in osteosarcoma and MNU-induced mammary carcinoma in the SD-rat. Both compounds elicited neither an inhibitory effect on these tumors nor an increase in the mean/median life span as compared to the control group.

Animals↗
PubMed1988

Cellular pharmacology of N,N',N''-triethylene thiophosphoramide.

N,N',N''-triethylene thiophosphoramide (Thio-TEPA) is an alkylating agent whose antineoplastic activity has been known for nearly 30 years. Human plasma pharmacokinetic studies revealed the presence of TEPA, a Thio-TEPA metabolite which after 4 h achieved plasma concentrations equal to those of the parent compound. We studied the activity of both Thio-TEPA and TEPA against murine leukemia P388 cells in culture. We found that Thio-TEPA is approximately two-fold more active than TEPA in arresting cell growth (IC50 = 2.8 microM for TEPA and 1.5 microM for Thio-TEPA). In inhibiting [3H]thymidine incorporation, Thio-TEPA and TEPA have the same activity (IC50 = 2 microM for both compounds). Experiments in which drug was removed from cell cultures which were further incubated in drug-free media, revealed that the bulk of the cell damage occurs during the first 4 h of incubation. Cell cultures exposed to 0.5 microM Thio-TEPA for 22 h fully recovered their [3H]thymidine incorporation ability after 24 h of drug-free incubation. Cells exposed to 2.5 microM Thio-TEPA for 22 h partially recovered their ability to incorporate [3H]thymidine. Cells exposed to 10 microM Thio-TEPA for 22 h did not recover their ability to incorporate [3H]thymidine. Gas liquid chromatographic analysis of the media from incubated cells showed that the concentration of Thio-TEPA remained unchanged during the incubations and that TEPA was not present. In Thio-TEPA doses ranging from 0.1 microM to 100 microM, [3H]uridine and [3H]-leucine incorporation were less affected than [3H]thymidine incorporation. This may indicate that a longer observation time may be needed to allow the DNA damage to be expressed in terms of protein or RNA synthesis.

Animals↗
PubMed1987

In the search for new anticancer drugs. XX: A comparison of the in vitro growth inhibition of P388 cells by TEPA and N,N;N',N'-bis (1,2-ethanediyl)-N''-(1-oxyl-2,2,6,6-tetramethyl-4- piperidinylaminocarbonyl) phosphoric triamide and congeners.

We tested the in vitro growth inhibitory activity of TEPA, and three analogs against P388 murine lymphocytic leukemia cells in culture. The analogs consist of spin-labeled TEPA and two reduced forms containing the NH and NOH groups instead of the nitroxyl function. Spin label TEPA was obtained by replacing one of the aziridine groups in TEPA with spin-labeled urea. In a concentration range of 10(-6)-10(-5) M, only the reduced analog containing the NH group was active. That is, to achieve a 50% inhibition of cell growth, a five-fold excess in concentration of this analog (IC50 = 10 X 10(-6) M) was needed as compared to the parent compound TEPA (IC50 = 2 X 10(-6) M). These results are in contrast with those obtained in vivo against the same leukemia cell line, indicating inherent discrepancies between in vivo and in vitro evaluation of antitumor agents.

Animals↗
PubMed1986

Human erythrocyte membrane permeability and nitroxyl spin-label reduction.

Nitroxyl spin labels are paramagnetic compounds that have demonstrated utility as contrast enhancing agents in proton magnetic resonance imaging. The time-course of contrast enhancement depends on distribution and elimination of these agents. Reduction, resulting in formation of the diamagnetic hydroxylamine, is the major metabolic pathway observed in vivo. This bioreduction has implications for the design of contrast agents and for understanding their imaging behavior. Bioreduction has been shown to occur, at least in part, intracellularly. As such, cell membrane permeability to nitroxyl spin labels may influence their bioreduction. In this study, this influence was examined using eight nitroxyl derivatives and the human erythrocyte suspension as a model biomembrane system. Ionizable weak acids and bases were found to equilibrate rapidly across the erythrocyte membrane with half-times of equilibration ranging from less than 10 s to 1.6 min. These derivatives had low octanol:buffer distribution coefficients and were extensively ionized at the pH of the system (7.0). A strong acid, a phosphate ester, and a quaternary amine derivative were excluded by the cell membrane. Reduction of nitroxyl spin labels by the erythrocyte was shown to occur intracellularly. Except for the impermeable probes, the reduction rate was slow in comparison with the membrane penetration rate. The structural dependence of reduction rate was unrelated to penetration rate but correlated well with that observed in other reducing systems, namely, ascorbic acid solution and rat tissue homogenates.

Buffers↗
PubMed1986

In the search for new anticancer drugs. XVIII. Various mono- and bis-anthraquinone hydrazones containing the N,N;N',N'-bis(1,2-ethanediyl)phosphoric diamide moiety.

The structure-anticancer activity and the activity-lipophilicity relationship of 8 mono- and bis-anthraquinone hydrazones containing the N,N;N',N'-bis(1,2-ethanediyl) phosphoric diamide moiety were evaluated. These compounds were tested in vivo, using murine lymphocytic leukemia P388. Seven of these compounds were active and one was marginal at optimum doses. The highest activity was exhibited by the bis[N,N;N',N'-bis(1,2-ethanediyl)-[N2-(1',4',5',8'-tetrahydroxy anthracenylidene)-N1-methyl hydrazin-1-yl]]-phosphoric triamide, bis[N,N;N',N'-bis(1,2-ethanediyl)-[N2-(1',4'-dihydroxy anthracenylidene)-N1-methylhydrazin-1-yl]]phosphoric triamide and bis-[N,N;N',N'-bis(1,2-ethanediyl)-[N2-(1',4',5',8'-tetrahydroxy anthracenylidene)-N1-phenylhydrazin-1-yl]]phosphoric triamide as is evidenced by their percent T/C of 183, 175 and 172, respectively. The correlation of the anticancer activities of these compounds with their lipophilicities leads to the general hypothesis that the intercalating and alkylating capabilities of a potential drug may play only a secondary role as compared to the selective permeability of the drug through normal and cancerous membranes.

Alkylating Agents↗
PubMed1986

In the search for new anticancer drugs. 17. Linear and cyclic polyether analogues of N,N:N',N':N'',N''-tri-1,2-ethanediylphosphoric triamide and N,N:N',N':N'',N''-tri-1,2-ethanediylphosphorothioic triamide.

Linear and cyclic polyether derivatives of N,N:N',N':N'',N''-tri-1, 2-ethanediylphosphoric triamide (TEPA) and N,N:N',N':N'',N''-tri-1,2-ethanediylphosphorothioic triamide (thio-TEPA) are synthesized and evaluated for their antineoplastic activity against the murine lymphocytic leukemia P388. All compounds, except for 7d, were active ranging from 42% to 287% increase in life span (% ILS). All CD2F1 male mice treated with the most active compound (7a) at 90 mg/kg per day for 9 days were alive after 30 days, whereas all mice treated with the clinical drug thio-TEPA were dead. The % ILS for compound 7a on day 60 was 525. A correlation is presented between the structural features of compounds and their lipophilicities and antineoplastic activities.

Animals↗
PubMed1986

In the search for new anticancer drugs. 19. A predictive design of N,N:N',N':N'',N''-tri-1,2-ethanediylphosphorothioic triamide (TEPA) analogues.

The nitroxyl-labeled analogues of N,N:N',N':N",N"-tri-1,2-ethanediylphosphoric triamide (TEPA), N,N:N',N'-bis(1,2-ethanediyl)-N"-[[(2,2,6,6-tetramethyl-1-oxypiperidi n-4- yl)amino]carbonyl]phosphoric triamide (5a) and N,N:N',N'-bis(1,2-ethanediyl)-N"-[[(2,2,5,5-tetramethyl-1-oxypyrrolid in-3- yl)amino]carbonyl]phosphoric triamide (11a), possess therapeutic indexes that are 8-12 times higher than those of thio-TEPA (1) and TEPA (2). The introduction of methyl groups into the aziridine ring, or the replacement of the nitroxyl moiety with hydroxylamine or amine derivatives, or with an adamantane moiety, results in compounds of lesser activity. An attempt is made to rationalize these results using a lipophilicity scale. A predictive design pattern is established.

Animals↗
PubMed1986

Diradical nitroxyl spin label contrast agents for magnetic resonance imaging. A comparison of relaxation effectiveness.

The proton relaxation enhancement characteristics of seven potential MRI contrast agents containing two nitroxyl spin labels per molecule (diradicals) were compared with eight similar agents with only one spin label per molecule (monoradicals). Diradical nitroxyls were evaluated to test the hypothesis that multiple paramagnetic centers in one molecule will result in stronger proton relaxation enhancement characteristics, allowing effective contrast enhancement at lower molar concentrations and thus a reduced osmotic load and greater safety. The acute toxicity of these agents is believed to be largely related to osmotic load. Five of seven diradical nitroxyls tested had spin-lattice relaxivities that were substantially greater than all eight of the monoradicals tested. The spin-spin relaxation properties of these agents and other pertinent characteristics are favorable for contrast enhancement. The results indicate that diradical nitroxyl spin labels may be used advantageously for the design of safer, more effective MRI contrast agents.

Chemical Phenomena↗
PubMed1985

In the search for new anticancer drugs. X. N,N; N',N'-bis(1,2-ethanediyl)-N''-(1-oxyl-2,2,6,6-tetramethyl- 4-piperidinylaminocarbonyl) phosphoric triamide--a new potential anticancer drug of high activity and low toxicity.

A new nitroxyl labeled TEPA derivative 5 containing the urea bridge between the phosphorus and the nitroxyl moiety, and the congeners containing the NOH and NH groups instead of the nitroxyl function were synthesized, and tested in vivo on CD2F1 mice for anticancer activity against P388 and L1210. The nitroxyl compound is more active than the reduced forms. The nitroxyl compound 5 elicits 170% ILS at 90 mg/kg after 30 days and 439% ILSmax after 60 days against P388, and has a higher therapeutic ratio (26.4) than the clinically used Thio-TEPA (2.75). The LD50 of 5 is 270 mg/kg, while that of Thio-TEPA is 18 mg/kg. Consequently, the nitroxyl compound 5 is a promising new anticancer drug.

Animals↗
PubMed1985

In the search for new anticancer drugs XII. Synthesis and biological evaluation of spin labeled nitrosoureas.

The spin labeled nitrosourea 1-(2-chloroethyl)-3-(1-oxyl-2,2,6,6- tetramethyl-piperidinyl)-1-nitrosourea (SLCNU, 4) and its analogues 5-7 were synthesized either by a regio-selective method or by a conventional route via the nitrosation of the spin labeled intermediates (11a-e). Nitrosation of the ureas 11a-e with dinitrogen tetraoxide resulted in better yields than those obtained with sodium nitrite. The nitrosoureas 4-8 were tested for their anticancer activity against the lymphocytic leukemia P388 in mice. Thus, either at the equal molar dose or at the dose of equal toxicity level, the SLCNU (4) was found to be more active than the clinically used CCNU (1). Unlike CCNU (1) whose LD50 is 56 mg/kg, the SLCNU (4) possesses a low toxicity (LD50 123 mg/kg). Therefore, SLCNU (4) is a promising new entry into the nitrosourea class of anticancer drugs.

Animals↗
PubMed1985

On the search for new anticancer drugs 14: the plasma pharmacokinetics and tissue distribution of spin-labeled thio-TEPA (SL-O-TT).

We defined the plasma and tissue concentrations and pharmacokinetics of SL-O-TT, a spin-labeled analog of thio-TEPA, in 35-44-g male Swiss Webster mice that had received spin-labeled thio-TEPA at a dosage of 10 mg/kg. Concentrations of spin-labeled thio-TEPA in ethyl acetate extracts of tissue and plasma were determined by gas-liquid chromatography and electron spin resonance spectroscopy. Plasma concentrations of spin-labeled thio-TEPA declined in a biexponential fashion that was well described by the equation: Ct = 21.5e-0.276t + 2.30e-0.026t indicating a half-life alpha of 2.5 min and a half-life beta of 26.6 min. After 2 h there was still spin-labeled thio-TE-PA in plasma, but not in tissues. In tissues, no spin-labeled thio-TEPA was detected with gas-liquid chromatography 15 min after injection, but with electron-spin resonance label was found in lung and skeletal muscle. The main metabolite of spin-labeled thio-TEPA is spin-labeled TEPA, where oxidative desulfurization is invoked as the main metabolic mechanism. Reduction of the spin label to the hydroxylamine was also observed with time.

Animals↗
PubMed1985

In the search for new anticancer drugs. XV. Various aliphatic and aromatic hydrazones containing the N,N;N',N'-bis(1,2-ethanediyl)phosphoric diamide moiety.

The scope of the structure-anticancer activity relationship among various aliphatic and aromatic hydrazones containing the N,N,N',N'-bis(1,2-ethanediyl)-phosphoric diamide moiety was studied. A total of 19 compounds were tested in vivo, using murine lymphocytic leukemia P388. At optimum dose all these compounds were active. The highest activity was exhibited by the N,N;N',N'-bis(1,2-ethanediyl)-[N2-(p-chlorobenzylidene)-N1- hydrazin-1-yl]phosphoric triamide, N,N;N',N'-bis(1,2-ethanediyl)-N2-(p-chlorobenzylidene)-N1- methylhydrazin-1-yl]phosphoric triamide and N,N;N',N'-bis(1,2-ethanediyl)-[N2-(p-chlorobenzylidene)-N1- phenylhydrazin-1-yl]phosphoric triamide as is evidenced by the percent T/C of 212, 194 and 192, respectively. An attempt was made to correlate the anticancer activities with the corresponding lipophilicities. On the basis of the activity-lipophilicity results, it is concluded that, in general, the activity scale follows the lipophilicity scale in the reverse order, i.e. the more active compounds possess lower lipophilicity than the less active compounds.

Animals↗