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PubMed1975

The ultracytochemical demonstration of a formaldehyde-resistant dehydrogenase of leuco nitroxyl analogues.

A dehydrogenase which is relatively stable in formaldehyde fixative is demonstrated ultracytochemically by the reduction of various leuco nitroxyl analogues in rat hepatic, renal, myocardial, skeletal muscle and prostatic tubuloalveolar glandular tissues. The nonosmiophilic tetrazolium salt, t-(2'-benzothiazolyl)-5-styryl-3-(4'-phtalhydrazidyl) tetrazolium chloride, is subsequently reduced to an insoluble osmiophilic formazan by the hydrogen ions resulting from the dehydrogenase activity. Exposure of the formazan to osmium tetroxide results in electron density enabling visualization of the reaction product in the electron microscope. Known inhibitors of various dehydrogenases were utilized in an attempt to determine the existence and/or extent of any specific characteristics of the dehydrogenase(s) involved.

Animals↗
PubMed1991

Additional nucleotide derivatives of mitosenes. Synthesis and activity against parental and multidrug resistant L1210 leukemia.

Cytidine 5'-monophosphate and 5'-ara-CMP conjugates of 2,7-diaminomitosene, with the phosphate groups linked to C-1, were prepared by treating mitomycin C with the appropriate nucleotides. 5'-UMP conjugates were prepared from mitomycin A, 7 (M-83), and 8 (BMY-25282) by similar procedures. A conjugate could not be prepared from mitomycin C and 6-MPRP, but a sulfur-linked derivative was made with 6-MP ribonucleoside. The corresponding 1-hydroxy-2-aminomitosenes were prepared from the parent mitomycin analogues for structure-activity comparisons. All compounds were tested against L1210 murine leukemia in the MTT tetrazolium dye assay. In general, the conjugates were less potent than the parent mitomycins; however 5'-ara-CMP conjugate 14 derived from mitomycin C was more potent than the parent compound or any mitomycin tested except mitomycin A. It also was more potent than ara-C. This result establishes the value of this approach to prodrugs, at least in cell culture. Against a multi-drug-resistant L1210 cell line, all of the conjugates derived from mitomycin C were more potent than the parent compound. 6-Mercaptopurine ribonucleoside conjugate 15 was more active against the resistant cells than it was against the parental cell line.

Animals↗
PubMed2004

The permeability and cytotoxicity of insulin-mimetic vanadium compounds.

PURPOSE: The aim of this study was to investigate the mechanism of permeation and cytotoxicity of vanadium compounds, [VO(acac)2], [VO(ma)2], and vanadate. METHODS: Absorptive transport were carried out in Caco-2 monolayers grown on transwell inserts. Vanadium was quantified using inductively coupled plasma atomic emission spectrometry (ICP-AES). The change of Caco-2 cells in the microvilli morphology and F-actin structure was visualized by transmission electron microscopy and confocal laser scanning microscopy. RESULTS: The three vanadium compounds were taken up by Caco-2 cells via simple passive diffusion. [VO(acac)2] were mainly transcellularly transported and exhibited the highest apparent permeabilty coefficients (8.2 x 10(-6) cm(-1)). The cell accumulation of [VO(acac)2] was found to be greater than that of [VO(ma)2], and vanadate caused much less accumulation than the other two compounds. Vanadium compounds induced intracellular reactive oxygen species, reduced the transepithelial electric resistance, caused morphological change in microvilli, and led to different perturbation of F-actin structure. CONCLUSIONS: The three compounds exhibited different permeability due to different diffusion process and cellular uptake. The toxicity of vanadium complexes on Caco-2 monolayer involved F-actin-related change of tight junction and impairment of microvilli. The toxicity was also related to elevated intracellular reactive oxygen species (ROS) and their cellular accumulation.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed1990

The anti-leishmanial activity of dipeptide esters on Leishmania amazonensis amastigotes.

L-Amino acid esters, such as L-Leu-OMe, kill Leishmania amazonensis amastigotes by a mechanism which appears to involve ester hydrolysis by cysteine proteinases located in the parasite megasomes. We have examined the killing of isolated amastigotes by L-dipeptide esters and derived some structure-activity correlations. Toxicity of the compounds for the parasites was measured by a tetrazolium (MTT) reduction assay. The results show that active dipeptide esters contained at least 1 hydrophobic amino acid (Leu, Ile, Val, Phe or Trp). The activity of homodipeptide methyl esters depended on the nature of the amino acid, as indicated by the following series: Phe-Phe-OMe greater than Val-Val-OMe greater than Leu-Leu-OMe greater than Trp-Trp-OMe greater than Ile-Ile-OMe. The nature of the amino acids in Leu-X-OMe and X-Leu-OMe was relatively unimportant when X was Phe, Trp or Val. However, when X was Ala or Gly, Leu-X-OMe was several-fold more active than X-Leu-OMe. A similar preference for the more hydrophobic residue in the amino terminal position was also found in esters containing a single phenylalanine or valine. Protection of the amino group by benzyloxycarbonyl (Z) or t-butyloxycarbonyl (BOC) substituents markedly enhanced the activity of the esters. An-mPhe-Gly-OEt, a retro-inverso analogue of Bz-Phe-Gly-OEt, was several-fold more active than the parent compound. Selected esters were assayed on infected macrophages and concentrations that induced minimal toxicity to the host cells were estimated. The ED50s for intracellular parasites were 1.5 to 5-fold higher than those for isolated amastigotes.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acids↗
PubMedDate not supplied

[Quantitative method of determining the activity of zinc- and copper-dependent superoxide dismutase in biological material].

The activity of superhydroxide dismutase was estimated by following rate of inhibition of non-enzymatic reduction of tetrazolium salt in reaction with superhydroxide ions, which were continuously generated in a photochemical system. The quantitative estimations were achieved by using para-nitrotetrazolium chloride, which was reduced to formazanes soluble in acetone. Formation of formazanes by the photochemical system (riboflavin + tetramethylethylene diamine + O2 + para-nitrotetrazolium chloride + light) in presence of biological material and cyanide was compared with formation of formazanes in absence of cyanide for specific estimation of Zn, Cu-dependent forms of superhydroxide dismutase. The rate of enzymatic cyanide sensitive inhibition of the photochemical formation of formazanes from paranitrotetrazolium chloride was determined by the activity of Zn, Cu-dependent superhydroxide dismutase in biological material and might be expressed in units of the activity -- un. ac. = 10/(0,026.% inhibition--1,3).

Animals↗
PubMed2004

Bioguided isolation and identification of the nonvolatile antioxidant compounds from fennel (Foeniculum vulgare Mill.) waste.

A bioguided isolation of an aqueous extract of fennel waste led to the isolation of 12 major phenolic compounds. Liquid chromatography coupled to atmospheric pressure chemical ionization mass spectrometry (LC/UV/APCI-MS) combined with spectroscopic methods (NMR) was used for compound identification. Radical scavenging activity was tested using three methods: DPPH*, superoxide nitro-blue tetrazolium hypoxanthine/xanthine oxidase, and *OH/luminol chemiluminescence. In addition to products described in the literature, eight antioxidant compounds were isolated and identified for the first time in fennel: 3-caffeoylquinic acid, 4-caffeoylquinic acid, 1,5-O-dicaffeoylquinic acid, rosmarinic acid, eriodictyol-7-O-rutinoside, quercetin-3-O-galactoside, kaempferol-3-O-rutinoside, and kaempferol-3-O-glucoside. The structures of eriodictyol-7-O-rutinoside and quercetin-3-O-glucuronide were completely elucidated by two-dimensional NMR experiments. The isolated compounds exhibited a strong antiradical scavenging activity, which may contribute to the interpretation of the pharmacological effects of fennel.

Antioxidants↗
PubMed1999

Influence of uranium(VI) speciation for the evaluation of in vitro uranium cytotoxicity on LLC-PK1 cells.

Very few data are available concerning the in vitro toxicity of uranium. In this work, we have determined the experimental chemical conditions permitting the observation of uranium(VI) cytotoxicity on LLC-PK1 cells. Uranium solutions made either by dissolving uranyl acetate or nitrate crystals, or by complexing uranium with bicarbonate, phosphate or citrate ligands, were prepared and tested. Experiments demonstrated that only uranium solutions containing citrate and bicarbonate ligands concentrations tenfold higher than the metal, were soluble in the cell culture medium. Cytotoxicity studies of all these uranium compounds were performed on LLC-PK1 cells and compared using LDH release, neutral red uptake and MTT assays. Dose dependent cytotoxicity curves were only obtained with uranium-bicarbonate medium. This study has revealed a toxicity of uranium-bicarbonate complexes for 24 h expositions and for concentrations ranging from 7 x 10(-4)-10(-3) M, under these conditions, the CI50 (cytotoxicity index) was evaluated between 8.5 and 9 x 10(-4) M. In contrast, we noticed a lack of cytotoxicity response for uranium(VI)-citrate complexes. Electron transmission microscopy studies revealed, when LLC-PK1 cells were exposed to the uranium-bicarbonate system, that uranium penetrated and precipitated within the cytoplasmic compartment. Morphological studies conducted with citrate complexes did not show any cellular intake of uranium.

Animals↗
PubMed1995

Poly(vinyl chloride) formulations: acute toxicity to cultured human cell lines.

Two quantitative cytotoxicity assay methods (cytoplasmic retention of carboxyfluorescein and mitochondrial cleavage of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT)) have been used to evaluate the response of two cultured human cell lines; HepG2 (hepatoma) and W138va13 (transformed lung fibroblasts) to extracts of a range of poly(vinyl chloride) (PVC) formulations. Two plasticizers; di(2-ethylhexyl)phthalate (DEHP) and di-isooctyl phthalate and a range of tin and non-tin stabilizers were incorporated in the study. Only those formulations containing both a plasticizer and a tin-based stabilizer produced extracts which were toxic. Extracts of those formulations which contained both plasticizer and dibutyl tin dimaleate stabilizer were toxic to both cell lines in both assay methods. Extracts of a formulation containing plasticizer and a dioctyl tin mercaptide were toxic to both cell lines in the carboxyfluorescein assay but were only toxic to the WI38va13 cells in the MTT assay. The WI38va13 cells were generally more sensitive to the extracts than the HepG2 cells. When serial dilutions of the extracts were evaluated, the carboxyfluorescein assay proved to be the more sensitive of the two. The acute toxicity of extracts of these PVC formulations cannot be directly attributed to the plasticizers or to the tin stabilizers. It is likely that a synergistic mechanism, such as plasticizer facilitated extraction of the tin stabilizer, exists.

Carcinoma, Hepatocellular↗
PubMed1988

A critical reevaluation of some assay methods for superoxide dismutase activity.

We have compared the direct method of pulse radiolysis to the indirect methods of cytochrome c and nitroblue tetrazolium for assaying the superoxide dismutase activity of a compound. We have shown that with pulse radiolysis, where high concentrations of O2- are generated, the "turnover" rate constant, kcat, can be determined directly, while with the indirect methods, where relatively low steady state concentrations of O2- are formed, the value of kcat determined by these methods, can be orders of magnitude lower than that determined directly. The main reason for the lower values obtained with the indirect methods is due to the fast reoxidation of the reduced compound by molecular oxygen. Additional problems which arise with the use of indirect methods for determining superoxide dismutase catalytic activity are discussed.

Copper↗
PubMed2000

The role of perisynaptic Schwann cells in development of neuromuscular junctions in the frog (Xenopus laevis).

Fluorescence microscopy was used to study the behavior of perisynaptic Schwann cells (PSCs) in relation to motor nerve terminals and postsynaptic clusters of acetylcholine receptors, during the development of the neuromuscular junction (NMJ) in the frog Xenopus laevis. Pectoral (supracoracoideus) muscles were labeled with monoclonal antibody 2A12 for Schwann cells, the dye FM4-64 for nerve terminals (NTs), alpha-bungarotoxin for acetylcholine receptors (AChRs), and Hoechst 33258 for cellular nuclei, in animals from tadpole stage 57 to fully grown adults. When muscle fibers first appeared in stage 57, NMJs consisted of tightly apposed NTs and AChRs and were only partially covered with PSCs or their processes. Within a few stages, PSCs fully occupied and overgrew the NMJs, extending fine sprouts between a few micrometers and hundreds of micrometers beyond the borders of the junction. Sprouts of PSCs were most abundant during the time when secondary myogenesis, synaptogenesis, and synaptic growth occurred at their highest rates. PSCs were recruited to NMJs during synaptic growth, at rates between 1.3 PSCs/100 microm junctional length early on and 0.4 PSCs/100 microm later. Shortly after metamorphosis, PSC sprouts disappeared and NMJs acquired the adult appearance, in which PSCs, NTs, and AChRs were mostly congruent. The results suggest that, although PSCs may not be required for initial nerve-muscle contacts, PSCs sprouts lead synaptic growth and play a role in the extension and maturation of developing NMJs.

Age Factors↗
PubMed1994

Copper(II)[2,3-butanedionebis(N4-methylthiosemicarbazone)], a stable superoxide dismutase-like copper complex with high membrane penetrability.

To obtain a superoxide dismutase (SOD)-like drug that could readily cross the cell membrane, we investigated the SOD-like activity, intracellular uptake, and stability of several Cu(II)Bisthiosemicarbazones (Cu(II)BTS). Among these Cu(II)BTS chelates, Cu(II)[2,3-Butanedionebis(N4-methylthiosemicarbazone)] (Cu(II)BMTS) was the most effective SOD-like compound with activity similar to activity reported for various previously reported SOD-like Cu complexes. Biodistribution studies in mice indicated that Cu(II)BMTS rapidly distributed to all tissues and readily crossed cell membranes as well as the blood-brain barrier with high distributions to the brain and the heart. Moreover, Cu(II)BMTS was stable in mouse brain homogenate and mouse blood. These results suggest that Cu(II)BMTS has the potential to be used as a SOD-like drug capable of reaching intracellular superoxide generating sites.

Animals↗