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PubMed2006

A study of the role of apoptotic cell death and cell cycle events mediating the mechanism of action of 6-hydroxycoumarin-3-carboxylatosilver in human malignant hepatic cells.

Previously our research group has studied the anti-proliferative effects of a series of hydroxylated derivatives and silver (I) complexes of coumarin-3-carboxylic acid (C-3-COOH) using two human-derived carcinoma cell lines (A-498 and Hep-G2). Results obtained suggested that both hydroxylation and complexation with silver served to significantly augment the cytotoxic properties of C-3-COOH, to yield a compound, namely 6-hydroxycoumarin-3-carboxylatosilver (6-OH-C-COO-Ag) which could act as a potent and cyto-selective agent, capable of killing cancer cells, and with limited toxicity to cells derived from normal tissue. Here we seek to expand on these findings by probing the molecular mechanism underlying this effect. Results from cytological staining clearly illustrated cellular changes consistent with the induction of apoptotic cell death and which occurred 24 h post-drug-treatment. Additionally, electrophoretic analysis of genomic DNA showed the presence of a ladder pattern, characteristic of apoptotic cell death. This result was subsequently confirmed using a selection of biochemical assays, where increased activity of pro-apoptotic caspases 3 and 9, and increased cleavage of poly(ADP-ribose)-polymerase protein (PARP) were observed. This result was further underpinned by the appearance of a sub-G(1) peak, representing hypo-diploid cells, using flow cytometric analysis. Furthermore, 6-OH-C-COO-Ag was seen to function through an alteration in the percentage of cells entering the G(0)/G(1) phase of cell cycle. Consequently, 6-OH-C-COO-Ag has been shown to a more potent and selective anti-cancer agent than cisplatin, capable of altering key biochemical events leading to the execution of apoptotic cell death as early as 24 h post-treatment, suggesting that it may represent a novel therapeutic agent for the safe and effective treatment of cancer in man.

Antineoplastic Agents↗
PubMedDate not supplied

Evidence of DNA repair in organ cultures of hamster tracheal epithelium following exposure to gas phase singlet oxygen.

Autoradiographic identification of unscheduled DNA synthesis (UDS) in short-term organ culture of hamster tracheal epithelium has been used as a predictive test for mutagenic and/or carcinogenic compounds. Tracheal explants were treated for 2 h with singlet delta oxygen plus [3H]thymidine. Silver grains over the nuclei of epithelial cells from the superficial layer of the mucosa were observed, indicating UDS. Control cultures, exposed to the gas phase without singlet oxygen, failed to elicit UDS.

Animals↗
PubMed1997

Ultrasound in natural products synthesis: applications to the synthesis of histrionicotoxin via nitroalkanal acetals.

Ultrasound promoted the Kornblum reaction of silver nitrite or sodium nitrite with haloalkyl acetals to afford the corresponding C-nitro compounds. The acetalprotected nitro compounds were used as reactants in a 'double Henry' reaction to produce the key intermediate nitrocyclohexane diol with a masked aldehyde side chain. The nitrodiol was then subjected to an ultrasound-promoted one-pot/single operation sequence involving a reduction deprotection followed by a cyclization-reduction. The entire sequence provided the core spiropiperidine substructure of the histrionicotoxins.

Acetals↗
PubMed2005

Solid state density functional calculations for the group 11 monohalides.

The group 11 monohalides are characterized by a variety of different solid-state structures and modifications. The copper halides crystallize mainly in a cubic zinc blende structure, while silver halides are mostly found in a rock salt modification. Completely different are the gold compounds where relativistic effects change the symmetry from a cubic to a chainlike AuX arrangement (X = F, Cl, Br, I) with short Au-Au internuclear distances. Here we present a systematic study of all solid state group 11 halides by scalar relativistic density functional theory for the experimentally known and observed structures, as well as for other unknown modifications and compare their relative stability.

Journal Article↗
PubMed2006

Concise assembly of the polycyclic frameworks associated with the hapalindole and fischerindole alkaloids.

[reaction: see text] Reaction of N-methylindole (4) with 6,6-dibromobicyclo[3.1.0]hexane (5) in the presence of silver tetrafluoroborate affords conjugate 7 in 67% yield. This product can be readily elaborated to compounds 12b and 13b which embody the polycyclic frameworks associated with members of the hapalindole and fischerindole classes of alkaloids. The chiral-auxiliary-substituted 6,6-dibromobicyclo[3.1.0]hexanes 21 and 22 react with indole to give adducts likely to be useful in the enantioselective total synthesis of the title alkaloids.

Catalysis↗
PubMed1998

Structure and strength of low-mercury dental amalgams prepared with liquid Hg-47.4% In alloy.

Two low-mercury amalgams: (1) low-copper lathe-cut and (2) high-copper (Tytin) were prepared by amalgamation with liquid Hg-47.4% In alloy. The strength-structure relationship of these amalgams was investigated and compared with standard amalgams (i.e. amalgams prepared with the same powders and pure mercury). The matrix phase of the low-mercury amalgam was found to be depleted of mercury and may be thought of as In4Ag9 compound with some mercury dissolved, indicating that less mercury (compared with standard amalgam) combines with silver, thus producing a strong amalgam matrix. On the other hand, an increase was observed in the consumption of the initial gamma (Ag3Sn)-phase, leading to an increase of the tin released. As a result, the potential of [HgSn]-phase formation in low-mercury amalgams increases. The observed increase in the quantity of gamma2(Sn7-8Hg)-phase in low-copper amalgam, or its appearance in high-copper amalgam (where it is normally absent), contributes to a deterioration in the strength of the investigated amalgam. The conclusion drawn was that low-mercury amalgam may be prepared with liquid Hg-47.4%In alloy but, in order to eliminate gamma2-phase formation, novel and possibly tin-free amalgamable alloys should be developed.

Journal Article↗
PubMed2003

[Qualitative and quantitative analysis of ammonium salts of hexamethylenetetramine and 1,10-phenanthroline].

By use of chemical and physicochemical methods the qualitative and quantitative analysis of bacteriostatic agents N-carbamoylmethylhexamethylenetetraamonium chloride (U-77) and 1-propyl-1,10-phenanthrolinium iodide (X-50) was carried out. The color reactions of these salts with various agents, e. g., concentrated acids, precipitants, oxidizers, indicators, ninhydrin, salts of heavy metals were assesssed. Some characteristic color reactions were found for analysis of quaternary ammonium salts. Experimental results indicate that interaction of N-carbamoylmethyhexamethylenetetraammonium chloride with silver nitrate leads to precipitate of the free silver in the form of a mirror under the proper conditions. It is a result of degradation of hexamethylenetetramine to formaldehyde and its oxidation, which is accompanied by reduction of silver ion to free silver. By use of thin-layer chromatography and ultraviolet spectrophotometry the physicochemical properties of compounds were tested. The suitability of qualitative methods, such as argentometry, mercurimetry, iodometry, extraction photometric analysis was detected. The results suggest, that the most suitable and precise method is argentometry.

Anti-Infective Agents↗
PubMed1986

Pharmacological modulation of cardiac and vascular contractile protein function.

The Ca2+-dependent regulation of contractile protein interactions in cardiac and vascular smooth muscle involves structurally related but distinct Ca2+ binding proteins. In vascular smooth muscle, Ca2+ binds to calmodulin, and Ca2+-calmodulin activates myosin light chain (MLC) kinase with ultimate stimulation of MLC phosphorylation and actin-myosin interactions. The largest class of inhibitors of vascular contractile protein interactions are the calmodulin antagonists which include certain Ca2+ entry blockers. Pharmacologically, some of these agents can be distinguished from pure Ca2+ entry blockers by being more effective vs. vasoconstrictor agents in vitro, less cardiac depressant, and more effective as platelet aggregation inhibitors. An even greater distinction from Ca2+ entry blockers is evident with another series of agents, isoquinolinesulfonamides, which directly inhibit protein kinase activity. Cardiac muscle myofibrillar regulation involves Ca2+ binding to troponin C (TnC). Some cardiotonics, such as Vardax and APP 201-533, increase the Ca2+ sensitivity of cardiac myofibrillar ATPase activity with a concomitant increase in Ca2+ binding to TnC. Several calmodulin antagonists, Ca2+ blockers, and structurally related agents differentially affect cardiac myofibrillar ATPase activity. Potency and efficacy of some of these stimulating agents is markedly greater than Vardax or APP 201-533. Mechanistically, all agents do not affect cardiac MLC phosphorylation, but directly enhance the Ca2+ sensitivity of ATPase activity. However, differential effects on basal and maximum ATPase activity by some agents suggest more complex or additional effects which are related to the type of agent as well as the species (dog vs. hamster). A major subcellular defect in congestive heart failure in various small animal models is a depressed maximum ATPase activity. Thus, a desired goal would be a pharmacological modulator which increases maximum ATPase activity, not necessarily Ca2+ sensitivity. In sum, it is possible to identify agents, Ca2+ binding protein modulators, which directly inhibit vascular smooth muscle and stimulate cardiac muscle contractile protein interactions. The potential advantages/disadvantages of this approach for vasodilator/cardiotonic drug development will have to await future development of novel compounds targeted specifically for these cellular regulatory processes.

Animals↗
PubMed1980

Quantification by gas chromatography of N,N'-di-(2-chloroethyl)-phosphorodiamidic acid in the plasma of patients receiving isophosphamide.

A sensitive method, based on gas chromatography using a phosphorus-specific flame photometric detector, has been developed for quantifying N,N'-di-(2-chloroethyl)phosphorodiamidic acid (isophosphoramide mustard), the putative active metabolite of isophosphamide, in human plasma. Phosphoramide mustard was used as internal standard, and the two compounds were converted into separable trimethyl derivatives by reaction with methyliodide in the presence of silver oxide. The chemistry of the derivatization process has been elucidated using gas chromatography-electron impact mass spectrometry and selected ion monitoring. Levels of isophosphamide and of isophosphoramide mustard were measured in the plasma of patients receiving isophosphamide (2 g/sq m). Peak plasma levels of isophosphoramide mustard of 18.6 to 30.3 nmol/ml occurred at 2 to 4 hr, and levels were still appreciable (6.3 to 11.3 nmol/ml) at 24 hr.

Chromatography, Gas↗
PubMedDate not supplied

Methods for analysis of conjugated linoleic acids and trans-18:1 isomers in dairy fats by using a combination of gas chromatography, silver-ion thin-layer chromatography/gas chromatography, and silver-ion liquid chromatography.

Conjugated linoleic acids (CLA) are octadecadienoic acids (18:2) that have a conjugated double-bond system. Interest in these compounds has expanded since CLA were found to be associated with a number of physiological and pathological responses such as cancer, metastases, atherosclerosis, diabetes, immunity, and body fat/protein composition. The main sources of these conjugated fatty acids are dairy fats. Rumen bacteria convert polyunsaturated fatty acids, especially linoleic and linolenic acids, to CLA and numerous trans- containing mono- and diunsaturated fatty acids. It has been established that an additional route of CLA synthesis in ruminants and monogastric animals, including humans, occurs via delta9 desaturation of the trans-18:1 isomers. To date, a total of 6 positional CLA isomers have been found in dairy fats, each occurring in 4 geometric forms (cis,trans; trans,cis; cis,cis; and trans,trans) for a total of 24. All of these CLA isomers can be resolved only by a combination of gas chromatography (GC), using 100 m highly polar capillary columns, and silver-ion liquid chromatography, using 3 of these 25 cm columns in series. Complete analysis of all the trans-18:1 isomers requires prior isolation of trans monoenes by silver-ion thin-layer chromatography (TLC), followed by GC analysis using the same 100 m capillary columns operated at low temperatures starting from 120 degrees C. These analytical techniques are required to assess the purity of commercial CLA preparations, because their purity will affect the interpretation of any physiological and/or biochemical response obtained. Prior assessment of CLA preparations by TLC is also recommended to determine the presence of any other impurities. The availability of pure CLA isomers will permit the evaluation and analysis of individual CLA isomers for their nutritional and biological activity in model systems, animals, and humans. These techniques are also essential to evaluate dairy fats for their content of specific CLA isomers and to help design experimental diets to increase the level of the desired CLA isomers in dairy fats. These improved techniques are further required to evaluate the CLA profile in monogastric animals fed commercial CLA preparations for CLA enrichment of animal products. This is particularly important because absorption and metabolism will alter the ingested-CLA profile in the animal fed.

Animals↗
PubMed1994

Heterogeneity of sulfated microdomains within basement membranes of pulmonary airway epithelium.

The purpose of this study was to determine whether the cytochemically defined distribution of sulfated macromolecules is significantly different in microdomains of basement membranes (BMs) associated with different levels of pulmonary airways. The high iron diamine-thiocarbohydrazide-silver proteinate (HID-TCH-SP) technique, which is highly specific for sulfate esters of glycosaminoglycans and some glycoproteins, was used as a probe to compare the BM of trachea, bronchi, and three different sizes of bronchioles. When HID-reactive sites were counted and statistically compared, significant differences were found between the three known anatomically distinct layers of the BM--lamina lucida (LL), lamina densa (LD), and lamina reticularis (LR)--relative to the airway level. The highest concentration of HID reactivity in trachea, bronchi, and large bronchiole was found in LR and the lowest in LD. By comparison, HID-reactive sites were found to be more concentrated in the LL in medium and small bronchioles. HID reactivity was consistently low in LD as compared with LL and LR in all five locations. The overall degree of HID reactivity in BMs was clearly highest in large bronchioles and lowest in medium and small bronchioles. This cytochemically detectable heterogeneity in the distribution of HID reactivity in BM microdomains may represent specific compositional differences in pulmonary BMs which are important determinants of epithelial cell function and might be expected to impact key biologic processes in normal and pathologic states.

Animals↗
PubMed2004

Sensitive silver staining of protein in sodium dodecyl sulfate-polyacrylamide gels using an azo dye, calconcarboxylic acid, as a silver-ion sensitizer.

A highly sensitive silver staining method for detecting proteins in sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) was developed. It is based on the silver nitrate staining method but also employs an azo dye, calconcarboxylic acid (NN), as a silver-ion sensitizer. It increases silver binding on protein bands or spots by the formation of a silver-dye complex and also increases the reducing power of silver ions to metallic silver by NN itself with formaldehyde. After a 2 h gel fixing step, the protocol including sensitization, silver-ion impregnation, and reduction steps can be completed in 1 h. The sensitivity is superior to that of silver stain with glutardialdehyde as a silver-ion sensitizer. The detection limit of NN-silver stain is 0.05-0.2 ng protein. Considering the high sensitivity without using glutardialdehyde, the NN-silver stain would be useful for routine silver staining of proteins.

Azo Compounds↗
PubMed2004

Metabolism of cyanide by Chinese vegetation.

Cyanide is a high-volume production chemical and the most commonly used leaching reagent for gold and silver extraction. Its environmental behavior and fate is of significant concern because it is a highly toxic compound. Vascular plants possess an enzyme system that detoxifies cyanide by converting it to the amino acid asparagine. This paper presents an investigation of the potential of Chinese vegetation to degrade cyanide. Detached leaves (1.5 g fresh weight) from 28 species of 23 families were kept in glass vessel with 100 ml of aqueous solution spiked with potassium cyanide at 23.5 degrees C for 28 h. Cyanide concentrations ranged from 0.83 to 1.0 CN mg l(-1). The disappearance of cyanide from the aqueous solution was analyzed spectrophotometrically. The fastest cyanide removal was by Chinese elder, Sambucus chinensis, with a removal capacity of 8.8 mg CN kg(-1) h(-1), followed by upright hedge-parsley (Torilis japonica) with a value of 7.5 mg CN kg(-1) h(-1). The lowest removal capacity had the snow-pine tree (Credrus deodara (Roxb.) Loud). Results from this investigation indicated that a wide range of plant species is able to efficiently metabolize cyanide. Therefore, cyanide elimination with plants seems to be a feasible option for cleaning soils and water contaminated by cyanide from gold and silver mines or from other sources.

Biodegradation, Environmental↗
PubMed2005

Study on the photocatalysis performance and degradation kinetics of X-3B over modified titanium dioxide.

In this paper, reactive brilliant X-3B was used as a model compound to study the photocatalytic activity of TiO2. Experimental results showed that the adulteration of iron and silver on TiO2 could greatly improve the activity of TiO2, and the optimum adulteration amount of iron and silver was 0.1 wt.% (Fe/TiO2) and 0.05 wt.% (Ag/TiO2), respectively, at the adulteration range of experiments. The photocatalytic degradation kinetics of X-3B on TiO2, Fe/TiO2 and Ag/TiO2 were also studied. The results showed that the degradation of X-3B on all of them were in accordance with the Langmiur-Hinshelwood kinetics model well, and the sequence of apparent reaction rate constants k of X-3B degradation catalyzed by TiO2, Fe/TiO2 and Ag/TiO2 was Ag/TiO2>Fe/TiO2>TiO2, while adsorption equilibrium constants KA of X-3B on Fe/TiO2 and Ag/TiO2 were approximately the same, and both were greater than that of TiO2.

Adsorption↗
PubMed2002

Spectrophotometric determination of biologically active thiols with eosin, silver(I) and adenine.

A simple and highly sensitive spectrophotometric method for the determination of biologically active thiols based on the fading of eosin-silver(I)-adenine ternary complex was established. In the determination of 6-mercaptopurine (MP), Beer's law was obeyed in the range 0.02-0.30 microg ml(-1), with an effective molar absorptivity at 562 nm and the relative standard deviation being 3.5 x 10(5) dm3 mol(-1) cm(-1) and 0.72% (n = 5). Analytical data for various biologically active thiols were determined with the proposed method. This method is about 5-10 times more sensitive than the conventional spectrophotometric methods. A compound having a disulfide bond (-S-S-), such as cystine, could also be determined by the conversion of disulfides to free thiols with the sulfite ion. The procedure was successfully applied to assays of various biologically active thiols in actual medicines.

Adenine↗
PubMed2004

Multi-component adsorption of Ag(I), Cd(II) and Cu(II) by natural carbonaceous materials.

Adsorption of silver, cadmium and copper from aqueous solutions by natural carbonaceous materials was investigated. The studied series of natural materials (spruce wood, pine bark, cork, peat, fusinite, lignite, oxidised lignite, bituminous coal and anthracite) was extended to include industrial carbon-rich materials: coke, activated carbon F-400 and Multisorb 100. Adsorption was tested on a single-component system and on the binary and ternary mixtures. All the materials used differ in their ability to adsorb selected metals. The adsorption of metals is significantly affected by the presence of other ions in solution. Total metal uptake was considerably higher in a mixture than single-ion adsorption. Chemical reactions, such as precipitation and reduction of metallic silver, play a role in metal uptake by bituminous coal, coke and activated carbon.

Adsorption↗
PubMed1952

The role of sulfhydryl groups in the bleaching and synthesis of rhodopsin.

The condensation of retinene(1) with opsin to form rhodopsin is optimal at pH about 6, a pH which favors the condensation of retinene(1) with sulfhydryl rather than with amino groups. The synthesis of rhodopsin, though unaffected by the less powerful sulfhydryl reagents, monoiodoacetic acid and its amide, is inhibited completely by p-chloromercuribenzoate (PCMB). This inhibition is reversed in part by the addition of glutathione. PCMB does not attack rhodopsin itself, nor does it react with retinene(1). Its action in this system is confined to the -SH groups of opsin. Under some conditions the synthesis of rhodopsin is aided by the presence of such a sulfhydryl compound as glutathione, which helps to keep the -SH groups of opsin free and reduced. By means of the amperometric silver titration of Kolthoff and Harris, it is shown that sulfhydryl groups are liberated in the bleaching of rhodopsin, two such groups for each retinene(1) molecule that appears. This is true equally of rhodopsin from the retinas of cattle, frogs) and squid. The exposure of new sulfhydryl groups adds an important element to the growing evidence that relates the bleaching of rhodopsin to protein denaturation. The place of sulfhydryl groups in the structure of rhodopsin is still uncertain. They may be concerned directly in binding the chromophore to opsin; or alternatively they may furnish hydrogen atoms for some reductive change by which the chromophore is formed from retinene(1). In the amperometric silver titration, the bleaching of rhodopsin yields directly an electrical variation. This phenomenon may have some fundamental connection with the role of rhodopsin in visual excitation, and may provide a model of the excitation process in general.

Animals↗
PubMed2003

The influence of silver additives on titania photoactivity in the photooxidation of phenol.

Photodeposition of small amounts of metal silver on the surface of titanium(IV) oxide enhances its photoactivity in phenol decomposition. The applied method of in situ metal photoreduction resulted in preparing better Ag/TiO(2) systems than those already described in literature. Optimum silver loading on titania amounts to 0.5 wt%. The photoreaction, which finally leads to total phenol mineralization, proceeds via intermediate compounds. Hydroquinone, benzoquinone and catechol are the main intermediates determined quantitatively. Photooxidation of the compounds competes with the photooxidation of phenol. At higher phenol concentration, >6 x 10(-4)mol dm(-3), the rate of the photocatalytic reaction is strongly retarded. The photoreaction was conducted in a specially designed, three-phase fluidal photoreactor.

Coloring Agents↗