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PubMed1984

Biotransformation of norgestimate in women.

The metabolism of norgestimate (ORF-10131; 14C-d-13-ethyl-17-acetoxy-18,19-dinor-17 alpha-pregn-4-en-20- yn -3-oxime) was studied in humans. Compound labeled with carbon-14 in the 17 alpha-ethynyl group was administered to four female subjects. An average of 46.8 percent of the administered radioactivity was excreted in the urine and 36.8 percent in the feces over a two-week collection period. About 12 percent of the urinary radioactivity represented freely extractable metabolites and another 57 percent consisted of extractable material released by enzyme hydrolysis. The ethynylated metabolites of norgestimate were separated from endogenous compounds and non- ethynylated metabolites by silver- sulfoethyl cellulose column chromatography. Metabolites were subsequently isolated by high performance liquid chromatography and thin layer chromatography. The identification of five urinary metabolites was accomplished by combined gas-liquid chromatography/mass spectrometry. These metabolites include norgestrel, 16 beta- hydroxynorgestrel , 2 alpha- hydroxynorgestrel , 3 alpha, 5 beta- tetrahydronorgestrel , and a fifth trihydroxylated metabolite of undetermined stereochemical configuration; 3,16-dihydroxy-5- tetrahydronorgestrel .

Biotransformation↗
PubMed1979

Vascular casting. A new method for the study of the arterial endothelium.

Vascular casts of the rat aorta were made using modified Batson's No. 17 anatomical corrosion compound. The outline of the silver-stained endothelial cell boundaries were clearly visible on the cast when examined using both scanning electron and light microscopy. The physical properties of the injectate were determined. The exothermic nature of the polymerization of the injectate did not grossly damage the endothelial cells. A method was developed for recovery, without damage, of the arterial tissue surrounding the cast. The technique of vascular casting appears to be a powerful tool for the study of the arterial endothelium which avoids shrinkage artifacts and maintains 3-dimensional geometry.

Animals↗
PubMed1994

Influence of colorants on crystallization and mechanical properties of lithia-based glass-ceramics.

OBJECTIVES: The objective of the present study was to test the hypothesis that colorants such as AgNO3 and FeCl3 act as conucleating agents with P2O5 in the Li2O-Al2O3-CaO-SiO2 system and that the addition of either colorant and P2O5 produces a greater effect on crystallization and selected mechanical properties than the use of P2O5 alone. METHODS: Microstructural effects were observed by SEM and optical microscopy. Mechanical properties were determined to monitor the effects of structural changes after crystallization. These include controlled-flaw flexure strength, fracture toughness (KIC), and Vickers hardness (VHN). RESULTS: Based on a glass composition of 27.84 mol% Li2O, 2.45 mol% Al2O3, 5.88 mol% CaO, and 63.84 mol% SiO2 (LACS), the mechanical properties of LACS glass-ceramics were influenced by P2O5, the colorant type, and the colorant concentration. The mean strength of the glass-ceramic disks without P2O5 increased with AgNO3 concentration to a peak value of 188 MPa at a concentration of 0.78 mmol%. The maximum value of controlled-flaw flexure strength increased from 120 MPa for one of the FeCl3 groups to 188 MPa for one of the AgNO3 groups. The maximum fracture toughness of glass-ceramic disks without P2O5 (2.45 MPa.m1/2) was associated with a AgNO3 concentration of 0.58 mmol%. This value was significantly greater (p < 0.05) than that of the corresponding group (1.90 MPa.m1/2) which also contained P2O5. There was no significant change in KIC of glass-ceramic specimens containing P2O5 as the AgNO3 concentration increased. The increase in controlled-flaw flexure strength and fracture toughness of specimen groups containing 0.58 to 0.78 mmol% AgNO3 support its use as a colorant and as a nucleating agent in LACS glass-ceramics. SIGNIFICANCE: The development of tougher, higher strength glass-ceramics can be controlled by the use of colorants that are also effective as nucleating agents. Although certain colorants are believed to act synergistically when used in combination with known nucleating agents to enhance the fracture toughness of glass-ceramics, this effect was not observed in this study for the combined use of AgNO3 and the classical nucleating agent, P2O5. In fact, the colorant used in this study (AgNO3) was more effective than P2O5 as a nucleating agent for lithia-based glass-ceramics.

Ceramics↗
PubMed1994

Influence of P205, AgNO3, and FeCl3 on color and translucency of lithia-based glass-ceramics.

OBJECTIVES: The objective of this study was to characterize the influence of various metals, metal compounds, and P2O5 as a nucleating agent on the color and translucency of a Li2O-Al2O3-CaO-SiO2 glass-ceramic. METHODS: Glass frits of Li2O-Al2O3-CaO-SiO2 (LACS), LACS with 1 mol% P2O5 (LACSP), and/or LACS with one of 16 colorants were melted, poured into a cylindrical graphite mold, cut into disks, annealed, nucleated, crystallized, and annealed again. Ten translucency measurements of each of five disks were made using a tristimulus colorimeter and a D65 standard CIE illuminant. The color of each disk was analyzed using the CIE L*a*b* color space system (1976) as a function of colorant, colorant concentration, and P2O5. RESULTS: Mean L* values of glass-ceramic disks ranged from 63.5 for LACS containing 6.2 mmol% FeCl3 (LACSP-6.2Fe) to 84.1 for LACS. No significant difference (p > 0.05) was found between the mean L* values for LACS, LACSP, and LACS with 0.19 mmol% AgNO3 (LACS-0.19Ag). The mean contrast ratio of glass-ceramic specimens ranged from 0.42 (LACS and LACS-1.0Fe) to 0.98 (LACS-0.78Ag). Mean color difference values varied from 5.8 (LACSP-1.0Fe vs. LACS) to 36.3 (LACSP-0.78Ag vs. LACSP). SIGNIFICANCE: The results of this study indicate that, because certain colorants in glass-ceramics affect opacity as well as hue and chroma, the development of glass-ceramics should be simplified by: 1) employing a nucleating agent that does not affect hue or chroma significantly, 2) controlling fixed levels of translucency consistent with mechanical and physical property requirements, and 3) varying the hue and chroma by means of colorants that do not affect the crystallization process. This implies that the volume fraction and mean size of crystals must be controlled, since the translucency or opacity of glass-ceramics is associated with scattering of light at the interfaces between adjacent crystals, and between crystals and the glass phase because of differences in refractive indices (McMillan, 1979a).

Analysis of Variance↗
PubMed2005

Fundamental considerations on the mechanisms of silver cementation onto zinc particles in the Merril-Crowe process.

Studies on the Merrill-Crowe process as applied to silver recovery have shown that one half of the used zinc powder is wasted in water reduction at high cyanide concentrations, while the other half reduces silver ions from the cyanide solution. However, the cementation mechanisms as an electrochemical process taking place on the zinc surface do not explain the split of the electric current resulting from the anodic dissolution of zinc into two equal values. This study demonstrates that the mechanism for silver precipitation at high and low cyanide concentrations differs considerably. At low cyanide concentrations cementation is essentially an electrochemically-controlled process following a shrinking-core behavior. At high cyanide concentrations, the process seems not to be electrochemically controlled. The areas for zinc dissolution and silver deposition are not connected by an electrical-conducting medium and reduction of silver-cyano complex ions takes place by hydrogen adsorbed onto silver growing outward from the cementing zinc particles. The results are based on scanning electron microscopy of solids recovered from cementations in stirred reactors and in situ observations by optical microscopy of the cementation process on the edge of thin zinc disks in cyanide solutions.

Adsorption↗
PubMed2003

Antibacterial properties of resin composites and dentin bonding systems.

This paper reviews the research conducted on the evaluation of antibacterial properties of commercial composites and adhesive systems, in addition to the discussion on many attempts to achieve antibacterial composites or adhesives. With regard to composites, commercially available products including fluoride-releasing materials have no antibacterial effect after being cured, which may explain why composites accumulate more plaque than other filling materials. The attempts to provide composites with antibacterial properties involve alterations to the resin components and filler components, and the trials can be subsequently classified into two groups based on the release profile of antibacterial components; agent-releasing or non-agent-releasing materials. Each type of antibacterial composite has advantages and disadvantages, and further modifications are needed to achieve clinically useful materials. Among proprietary dentin bonding systems (DBS), the products which contain glutaraldehyde or have an acidic property exhibit some antibacterial effects. However, the antibacterial properties shown by these products are only side-effects which are derived from the constituents included to produce superior bonding characteristics, and appear to be unreliable. Inclusion of antibacterial components into DBS has also been attempted using several methods, and the results of in vitro tests indicate that some of the trials seem promising. It is worthy of continuing the attempts to develop DBS which can inhibit invading bacteria after the placement of restoration as well as residual bacteria in the cavity. Achievement of bio-functional composites or DBS with therapeutic effects would contribute to prevent secondary caries.

Anti-Infective Agents, Local↗
PubMed2000

Quantitating silver-stained neurodegeneration: the neurotoxicity of trimethlytin (TMT) in aged rats.

This report describes the development of a histoanalytical procedure to measure the degree of neurodegeneration produced by the organometal toxicant trimethyltin (TMT). Based on a previous, non-quantitated experiment we hypothesized that the same dose of TMT would produce greater damage in animals of increasing age. Male rats aged 6, 12, 18, or 24 months at the time of dosing were given either 4.5 mg/kg TMT or saline (i.p.). One month after dosing, rats were perfused and their brains removed and processed to selectively silver-impregnate degenerating cell bodies as well as axon terminals and dendrites. Neurodegeneration was most prominent in the hippocampi (especially CA1 stratum radiatum) of TMT-treated rats, but not in the controls. Computer-assisted counting of the silver grains marking damage indicated greater neurotoxicity from the same dose of TMT when given to the older animals. Thus the grain density in the 6-month-old TMT-treated rats was not significantly elevated from the 6-month-old controls (P>0.10). The 12-month-old TMT-treated rats had significantly increased grain densities compared to their controls (P<0.05), but still larger increases of grain counts were observed in the 18- and 24-month-old rats (both P-values<0.01). Our findings with TMT are similar to previous, but nonquantitative, reports that the neurotoxic effects of kainic acid and methionine sulfoximine were also greater in older rats. An increased sensitivity to neurotoxicants might help explain the apparently spontaneous degeneration of cortical neurons in aging and in the neurological diseases of old age. The method we report here for quantitation of silver grains marking neurodegeneration should be adaptable to a wide range of histologically-based neurotoxicology investigations.

Aging↗
PubMed2000

The use of a sodium tungstate developer markedly improves the electron microscopic localization of zinc by the Timm method.

The Timm's sulfide-silver method is frequently used for the demonstration of the mossy fiber bundle or sprouted mossy fibers in the normal or epileptic hippocampal dentate gyrus. Under the light microscope the results are excellent, but the ultrastructure is considerably impaired and the silver grains produced are too large as compared to the sizes of intra-synaptic structures. The present study was meant to test a series of physical developers containing, instead of gum arabic, sodium tungstate as protective colloid. One of them left the ultrastructure fairly intact and produced small, round silver grains, making it possible to precisely locate zinc in mossy terminals. With this method, it could be demonstrated that zinc is contained inside synaptic vesicles in the resting axon terminals of granule cells. As a consequence of prolonged sodium sulfide perfusion, zinc is released from synaptic vesicles and enters the synaptic cleft.

Animals↗
PubMed1986

Calcium efflux from sarcoplasmic reticulum microsomes due to oxidation and sulfhydryl-binding agents.

Calcium permeability of sarcoplasmic reticulum (SR) microsomes was measured after aging or after exposure to peroxydisulfate or to sulfhydryl-binding agents. Under conditions where the Ca2+-ATPase was active, the maximum net release of Ca2+ was not significantly different between control and oxidized SR. However, when calcium uptake was prevented by EGTA or apyrase, the Ca2+ permeability of oxidized microsomes was 2 to 3 times greater than control of low (10(-9), 10(-7) M) but not high (10(-6) M) levels of external calcium. The observation that vesicles preincubated with 5 mM dithiothreitol loaded up to 3 times as much calcium and had a slightly lower calcium permeability coefficient than control vesicles suggested that sulfhydryl oxidation might modulate calcium flux. This hypothesis was tested by exposing to sulfhydryl-binding agents: silver, arsenite, and p-chloromercuriphenylsulfonic acid. Sulfhydryl-binding agents initiated a rapid release of calcium from microsomes, and release was halted by dithiothreitol. Inhibition of calcium transport could not entirely account for the apparent increase in permeability because the calcium permeability of SR treated with sulfhydryl-binding agents was 5 times greater than that of SR exposed to Ca2+-ATPase inhibitors. These results suggest that oxidation may increase the calcium permeability of SR by allowing calcium loss through a channel that can be gated by sulfhydryl oxidation.

4-Chloromercuribenzenesulfonate↗
PubMed2000

Triazene drug metabolites. Part 17: Synthesis and plasma hydrolysis of acyloxymethyl carbamate derivatives of antitumour triazenes.

A series of 3-acyloxymethyloxycarbonyl-1-aryl-3-methyltriazenes 5 was synthesised by the sequential reaction of 1-aryl-3-methyltriazenes with (i) chloromethyl chloroformate, (ii) NaI in dry acetone, and (iii) either the silver carboxylate or the carboxylic acids in the presence of silver carbonate. The hydrolysis of these compounds was studied in pH 7.7 isotonic phosphate buffer and in human plasma. Triazene acyloxycarbamates demonstrated their ability to act as substrates for plasma enzymes. For compound 5f, a pH-rate profile was obtained which showed the hydrolysis to involve acid-base catalysis. The reaction is also buffer catalysed. Thus, at pH 7.7, pH-independent, base-catalysed and buffer-catalysed processes all contribute to the hydrolysis reaction. The sensitivity of the hydrolysis reaction to various structural parameters in the substrates indicates that hydrolysis occurs at the ester rather than the carbamate functionality. In plasma, the rates of hydrolysis correlate with partition coefficients, the most lipophilic compounds being the most stable. An aspirin derivative suffers two consecutive enzymatic reactions, the scission of the aspirin acetyl group being followed by the scission of the acyloxy ester group. These results indicate that triazene acyloxymethyl carbamates are prodrugs of the antitumour monomethyltriazenes. They combine chemical stability with a rapid enzymatic hydrolysis, and are consequently good candidates for further prodrug development. Moreover, this type of derivative allowed the synthesis of mutual prodrugs, associating the antitumour monomethyltriazenes with anti-inflammatory NSAIDs as well as with the anticancer agent butyric acid.

Antineoplastic Agents↗
PubMed2005

Metal-metal interactions in platinum(II)/gold(I) or platinum(II)/silver(I) salts containing planar cations and linear anions.

The salts [Pt{C(NHMe)(2)}(4)][Au(CN)(2)](2), [Pt{C(NHMe)(2)}(4)][Ag(2)(CN)(3)][Ag(CN)(2)], [Pt(en)(2)][Au(CN)(2)](2), [Pt(en)(2)][Ag(CN)(2)](2), and [Pt(bipy)(2)][Au(CN)(2)](2) have been prepared by mixing solutions of salts containing the appropriate cation with solutions of K[Au(CN)(2)] or K[Ag(CN)(2)]. Because the platinum atom in the cation is sterically protected, the structures of [Pt{C(NHMe)(2)}(4)][Au(CN)(2)](2) and [Pt{C(NHMe)(2)}(4)][Ag(2)(CN)(3)][Ag(CN)(2)] reveal no close metal-metal interactions. Colorless crystals of [Pt(en)(2)][Au(CN)(2)](2) and [Pt(en)(2)][Ag(CN)(2)](2) are isostructural and involve extended chains of alternating cations and anions that run parallel to the crystallographic a axis, along with isolated anions. In the chains, the metal-metal separations are relatively short: Pt...Au, 3.1799(3) Angstroms; Pt...Ag, 3.1949(2) Angstroms. In [Pt(bipy)(2)][Au(CN)(2)](2), each cation has axial interactions with the anions through close Pt...Au contacts [3.1735(6) Angstroms]. In addition, the anions are weakly linked through Au...Au contacts of 3.5978(9) Angstroms. Unlike the previously reported Pt/Au complex [Pt(NH(3))(4)][Au(CN)(2)](2).1.5H(2)O, which is luminescent, none of the salts reported here luminesce.

Anions↗
PubMed2004

Chiral induction in self-assembled helicates: CHIRAGEN type ligands with ferrocene bridging units.

The aim of this work was the preparation of enantiomerically pure bis(pinene-bipyridine) ligands containing the ferrocenyl moiety. Several such ligands (1-3) were synthesized and completely characterized. These molecules can be diastereoselectively deprotonated at the acidic methylene group of the pinene moiety using a strong and sterically hindered base such as LDA. Subsequent reaction of the formed anion with alkyl halides yield the family of C(2)-symmetric enantiopure compounds (1a-c). Copper(I), silver(I), or zinc(II) complexes with several ligands (C1-C8) were prepared and structurally characterized in the solid state and in solution. Self-assembled helical species are formed in several cases. It became evident that the chiral groups present in the ligand do not completely determined the helical configuration of the assemblages. Diastereoselectivity is thus not complete with this type of ligands, contrary to other, similar ligands studied before.

Journal Article↗
PubMed2006

Coordination chemistry of tetradentate N-donor ligands containing two pyrazolyl-pyridine units separated by a 1,8-naphthyl spacer: dodecanuclear and tetranuclear coordination cages and cyclic helicates.

The tetradentate ligand L(naph) contains two N-donor bidentate pyrazolyl-pyridine units connected to a 1,8-naphthyl core via methylene spacers; L45 and L56 are chiral ligands with a structure similar to that of L(naph) but bearing pinene groups fused to either C4 and C5 or C5 and C6 of the terminal pyridyl rings. The complexes [Cu(L(naph))](OTf) and [Ag(L(naph))](BF4) have unremarkable mononuclear structures, with Cu(I) being four-coordinate and Ag(I) being two-coordinate with two additional weak interactions (i.e., "2 + 2" coordinate). In contrast, [Cu4(L(naph))4][BF4]4 is a cyclic tetranuclear helicate with a tetrafluoroborate anion in the central cavity, formed by an anion-templating effect; electrospray mass spectrometry (ESMS) spectra show the presence of other cyclic oligomers in solution. The chiral ligands show comparable behavior, with [Cu(L45)](BF4) and [Ag(L45)](ClO4) having similar mononuclear crystal structures and with the ligands being tetradentate chelates. In contrast, [Ag4(L56)4](BF4)4 is a cyclic tetranuclear helicate in which both diastereomers of the complex are present in the crystal; the two diastereomers have similar gross geometries but are significantly different in detail. Despite their different crystal structures, [Ag(L45)](ClO4) and [Ag4(L56)4](BF4)4 behave similarly in solution according to ESMS studies, with a range of cyclic oligomers (up to Ag9L9) forming. With transition-metal dications Co(II), Cu(II), and Cd(II), L(naph) generates a series of unusual dodecanuclear coordination cages [M12(L(naph))18]X24 (X- = ClO4- or BF4-) in which the 12 metal ions occupy the vertices of a truncated tetrahedron and a bridging ligand spans each of the 18 edges. The central cavity of each cage can accommodate four counterions, and each cage molecule is chiral, with all 12 metal trischelates being homochiral; the crystals are racemic. Extensive aromatic stacking between ligands around the periphery of the cages appears to be a significant factor in their assembly. The chiral analogue L45 forms the simpler tetranuclear, tetrahedral coordination cage [Zn4(L45)6](ClO4)(8), with one anion in the central cavity; the steric bulk of the pinene chiral auxiliaries prevents the formation of a dodecanuclear cage, although trace amounts of [Zn12(L45)18](ClO4)24 can be detected in solution by ESMS. Formation of [Zn4(L45)6](ClO4)8 is diastereoselective, with the chirality of the pinene groups controlling the chirality of the tetranuclear cage.

Borates↗
PubMed2005

Temperature- or guest-induced drastic single-crystal-to-single-crystal transformations of a nanoporous coordination polymer.

Aside from a temperature-induced structural transformation, a new nanoporous coordination polymer [Ag6Cl(atz)4].OH.6H2O (Hatz = 3-amino-1,2,4,-triazole) comprised of interpenetrated Ag3(atz)2 coordination nets exhibits a single-crystal-to-single-crystal transformation of a 5-fold to 6-fold net interpenetration change triggered by guest desorption/absorption.

Crystallization↗
PubMed1975

Preparation and antitumor activity of a rearranged ester of cephalotaxine.

For further evaluation of structure-activity relationships among the Cephalotaxus alkaloids, a "rearranged" ester (2b) of cephalotaxine was prepared, one which is an isomer of deoxyharringtonine (5a). The parent alkaloid, cephalotaxine (1a), was allowed to react with thionyl chloride to replace its hydroxyl group with chlorine. The resulting chloro compound 1b, on treatment with the silver salt of half ester 6, yielded 2b via an allylic rearrangement followed by further double bond migration. The new "rearranged" deoxyharringtonine isomer 2b proved to be inactive in the P-388 lymphocytic leukemia system and thus further delineated the structural requirements for antitumor activity in this series of alkaloids.

Alkaloids↗