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PubMed2005

Separation and simultaneous determination of four artificial sweeteners in food and beverages by ion chromatography.

In this paper, the separation and determination of four artificial sweeteners (aspartame, sodium cyclamate, acesulfame-K and sodium saccharin) by ion chromatography coupled with suppressed conductivity detector is reported. The four artificial sweeteners were separated using KOH eluent generator. Due to the use of eluent generator, very low conductance background conductivity can be obtained and sensitivity of sweeteners has been greatly improved. Under the experimental condition, several inorganic anions, such as F-, Cl-, NO3-, NO2-, Br-, SO4(2)-, PO4(3)- and some organic acid such as formate, acetate, benzoate, and citrate did not interfere with the determination. With this method, good linear relationship, sensitivity and reproducibility were obtained. Detection limits of aspartame, sodium cyclamate, acesulfame-K, sodium saccharin were 0.87, 0.032, 0.019, 0.045 mg/L, respectively. Rate of recovery were between 98.23 and 105.42%, 99.48 and 103.57%, 97.96 and 103.23%, 98.46 and 102.40%, respectively. The method has successfully applied to the determination of the four sweeteners in drinks and preserved fruits.

Anion Exchange Resins↗
PubMed2004

In vivo evaluation of copper-64-labeled monooxo-tetraazamacrocyclic ligands.

Copper-64 (T(1/2)=12.7 h; beta(+): 0.653 MeV, 17.4%; beta(-): 0.578 MeV, 39%) has applications in positron emission tomography (PET) imaging and radiotherapy, and is conveniently produced on a biomedical cyclotron. Tetraazamacrocyclic ligands are the most widely used bifunctional chelators (BFCs) for attaching copper radionuclides to antibodies and peptides due to their relatively high kinetic stability. In this paper, we evaluated three monooxo-tetraazamacrocyclic ligands with different ring sizes and oxo group positions. H1 [1,4,7,10-tetraazacyclotridecan-11-one], H2 [1,4,8,11-tetraazacyclotetradecan-5-one] and H3 [1,4,7,10-tetraazacyclotridecan-2-one] were radiolabeled with (64)Cu in high radiochemical yields under mild conditions. The three (64)Cu-labeled complexes are all +1 charged, as determined by their electrophoretic mobility. While they demonstrated >95% stability in rat serum out to 24 h, both biodistribution and microPET imaging studies revealed high uptake and long retention of the compounds in major clearance organs (e.g., blood, liver and kidney), which suggests that (64)Cu dissociated from the complexes in vivo. Of the three complexes, (64)Cu-2(+), which has a cyclam backbone (1,4,8,11-tetraazacyclotetradecane), exhibited the lowest nontarget organ accumulation. The data from these studies may invalidate the candidacy of the monooxo-tetraazamacrocyclics as BFCs for copper radiopharmaceuticals. However, the data presented here suggest that neutral or negatively charged Cu(II) complexes of tetraazamacrocyclic ligands with a cyclam backbone (tetradecane) are optimal for copper radiopharmaceutical applications.

Animals↗
PubMed1999

Liquid chromatographic determination of aniline in table-top sweeteners based on pre-column derivatization with 1,2-naphthoquinone-4-sulfonate.

A liquid chromatographic method for the determination of aniline in cyclamate sweeteners based on a pre-column derivatization with 1,2-naphthoquinone-4-sulfonate (NQS) is proposed. Aniline traces were extracted from the cyclamate samples using dichloromethane. After solvent evaporation, the dry residue was derivatized with NQS at pH 9.5 and 85 degrees C for 1 min. The aniline derivative, which was extracted from the reacting mixture, was redissolved in the eluent solution and injected into the chromatographic system. The separation of aniline derivative from other amine impurities was carried out in a C18 column using a 2% acetic acid-methanol (40:60, v/v) mobile phase. Results from the analysis of aniline in the sweetener samples with the proposed method were compared with those from the standard method. A good concordance between the two methods was observed.

Aniline Compounds↗
PubMed1998

Effects of artificial sweeteners on insulin release and cationic fluxes in rat pancreatic islets.

Beta-L-glucose pentaacetate, but not alpha-D-galactose pentaacetate, was recently reported to taste bitter and to stimulate insulin release. This finding led, in the present study, to the investigation of the effects of both bitter and non-bitter artificial sweeteners on insulin release and cationic fluxes in isolated rat pancreatic islets. Sodium saccharin (1.0-10.0 mM), sodium cyclamate (5.0-10.0 mM), stevioside (1.0 mM) and acesulfame-K (1.0-15.0 mM), all of which display a bitter taste, augmented insulin release from islets incubated in the presence of 7.0 mM D-glucose. In contrast, aspartame (1.0-10.0 mM), which is devoid of bitter taste, failed to affect insulin secretion. A positive secretory response to acesulfame-K was still observed when the extracellular K+ concentration was adjusted to the same value as that in control media. No major changes in 86Rb and 45Ca outflow from pre-labelled perifused islets could be attributed to the saccharin, cyclamic or acesulfame anions. It is proposed that the insulinotropic action of some artificial sweeteners and, possibly, that of selected hexose pentaacetate esters may require G-protein-coupled receptors similar to those operative in the recognition of bitter compounds by taste buds.

Animals↗
PubMed2001

Improved water solubility of neohesperidin dihydrochalcone in sweetener blends.

Significant technological advantages in terms of sweetness synergy and hence cost-saving can be obtained if neohesperidin dihydrochalcone (NHDC) is used in sweetener blends with other intense or bulk sweeteners. The combination of NHDC with sodium saccharin or sodium cyclamate is an excellent method to improve the water solubility at room temperature of NHDC. In the case of NHDC-sodium saccharin, two different methods for blend preparation, a simple mixture and a cosolubilized mixture, can be used, with similar results obtained for solubility and solution stability properties. To improve temporally the water solubility of NHDC in combination with sodium cyclamate, it is absolutely necessary to prepare cosolubilized blends.

Chalcone↗
PubMed2003

Molecular mechanism of AMD3100 antagonism in the CXCR4 receptor: transfer of binding site to the CXCR3 receptor.

AMD3100 is a symmetric bicyclam, prototype non-peptide antagonist of the CXCR4 chemokine receptor. Mutational substitutions at 16 positions located in TM-III, -IV, -V, -VI, and -VII lining the main ligand-binding pocket of the CXCR4 receptor identified three acid residues: Asp(171) (AspIV:20), Asp(262) (AspVI:23), and Glu(288) (GluVII:06) as the main interaction points for AMD3100. Molecular modeling suggests that one cyclam ring of AMD3100 interacts with Asp(171) in TM-IV, whereas the other ring is sandwiched between the carboxylic acid groups of Asp(262) and Glu(288) from TM-VI and -VII, respectively. Metal ion binding in the cyclam rings of AMD3100 increased its dependence on Asp(262) and provided a tighter molecular map of the binding site, where borderline mutational hits became clear hits for the Zn(II)-loaded analog. The proposed binding site for AMD3100 was confirmed by a gradual build-up in the rather distinct CXCR3 receptor, for which the compound normally had no effect. Introduction of only a Glu at position VII:06 and the removal of a neutralizing Lys residue at position VII:02 resulted in a 1000-fold increase in affinity of AMD3100 to within 10-fold of its affinity in CXCR4. We conclude that AMD3100 binds through interactions with essentially only three acidic anchor-point residues, two of which are located at one end and the third at the opposite end of the main ligand-binding pocket of the CXCR4 receptor. We suggest that non-peptide antagonists with, for example, improved oral bioavailability can be designed to mimic this interaction and thereby efficiently and selectively block the CXCR4 receptor.

Anti-HIV Agents↗
PubMed1992

Pseudo-streaming potentials in Necturus gallbladder epithelium. I. Paracellular origin of the transepithelial voltage changes.

Apparent streaming potentials were elicited across Necturus gallbladder epithelium by addition or removal of sucrose from the apical bathing solution. In NaCl Ringer's solution, the transepithelial voltage (Vms) change (reference, basolateral solution) was positive with sucrose addition and negative with sucrose removal. Bilateral Cl- removal (cyclamate replacement) had no effect on the polarity or magnitude of the Vms change elicited by addition of 100 mM sucrose. In contrast, bilateral Na+ removal (tetramethylammonium [TMA+] replacement) inverted the Vms change (from 2.7 +/- 0.3 to -3.2 +/- 0.2 mV). Replacement of Na+ and Cl- with TMA+ and cyclamate, respectively, abolished the change in Vms. Measurements of cell membrane voltages and relative resistances during osmotic challenges indicate that changes in cell membrane parameters do not explain the transepithelial voltage changes. The initial changes in Vms were slower than expected from concomitant estimates of the time course of sucrose concentration (and hence osmolality) at the membrane surface. Paired recordings of the time courses of paracellular bi-ionic potentials (partial substitution of apical Na+ with tetrabutylammonium [TBA+]) revealed much faster time courses than those produced by sucrose addition, although the diffusion coefficients of sucrose and TBACl are similar. Hyperosmotic and hypoosmotic challenges yielded initial Vms changes at the same rate; thereafter, the voltage increased with hypoosmotic solution and decreased with hyperosmotic solution. These late voltage changes appear to result from changes in width of the lateral intercellular spaces. The early time courses of the Vms changes produced by osmotic challenge are inconsistent with the expectations for water-ion flux coupling in the junctions. We propose that they are pseudo-streaming potentials, i.e., junctional diffusion potentials caused by salt concentration changes in the lateral intercellular spaces secondary to osmotic water flow.

Action Potentials↗
PubMed2004

Artificial sweeteners--do they bear a carcinogenic risk?

Artificial sweeteners are added to a wide variety of food, drinks, drugs and hygiene products. Since their introduction, the mass media have reported about potential cancer risks, which has contributed to undermine the public's sense of security. It can be assumed that every citizen of Western countries uses artificial sweeteners, knowingly or not. A cancer-inducing activity of one of these substances would mean a health risk to an entire population. We performed several PubMed searches of the National Library of Medicine for articles in English about artificial sweeteners. These articles included 'first generation' sweeteners such as saccharin, cyclamate and aspartame, as well as 'new generation' sweeteners such as acesulfame-K, sucralose, alitame and neotame. Epidemiological studies in humans did not find the bladder cancer-inducing effects of saccharin and cyclamate that had been reported from animal studies in rats. Despite some rather unscientific assumptions, there is no evidence that aspartame is carcinogenic. Case-control studies showed an elevated relative risk of 1.3 for heavy artificial sweetener use (no specific substances specified) of >1.7 g/day. For new generation sweeteners, it is too early to establish any epidemiological evidence about possible carcinogenic risks. As many artificial sweeteners are combined in today's products, the carcinogenic risk of a single substance is difficult to assess. However, according to the current literature, the possible risk of artificial sweeteners to induce cancer seems to be negligible.

Aspartame↗
PubMed1996

Alteration of intercellular communication in a human urothelial carcinoma cell-line by tumor-promoting agents.

BACKGROUND: Most of the findings that support a good association between inhibition of intercellular communication and tumor promotion have been demonstrated by studies of animal cells, while it has been accepted that most tumor-promoting agents are specific to species and organs. Therefore, the influence of tumor-promoting agents on intercellular communication was investigated using a human urothelial cell-line. METHODS: The effects of six tumor-promoting agents, including dichlorodiphenyltrichloroethane (DDT), butylated hydroxyanisole (BHA), saccharin, cyclamic acid, phenobarbital, and DL-tryptophan, on intercellular communication in a human urothelial cell-line (JTC-30) were investigated by using a dye-transfer assay after 48- and 96-hour exposure to each agent. Cytotoxicity was determined using the colony-forming method after 48-hour and 7-day exposure to each agent. RESULTS: DDT, BHA, saccharin, and cyclamic acid inhibited intercellular communication after either 48- or 96-hour exposure at concentrations that were nontoxic to the cells after 7-day exposure. Phenobarbital and DL-tryptophan inhibited intercellular communication only at toxic concentrations. CONCLUSIONS: Since the former four agents are known to be direct tumor promoters, and the metabolites of the later two agents have been regarded as tumor promoters, the results suggest that current methodology using the JTC-30 cell-line may be applicable to the screening to detect direct tumor promoters of human urothelium.

Adult↗
PubMed1973

Relationship between tubular net sodium reabsorption and peritubular potassium uptake in the perfused Necturus kidney.

1. K influx from peritubular space into renal tubular cells, varphi(i) (K), was measured in doubly perfused Necturus kidneys by studying tissue uptake of (42)K added exclusively to the portal circulation. Concomitantly, net tubular Na reabsorption, varphi(n) (Na), was measured by clearance techniques. varphi(n) (Na) and varphi(i) (K) were varied widely by replacing solutions of physiological composition (controls) with solutions containing high K, low K, low Na, cyclamate instead of Cl, ouabain (10(-7)-10(-4)M) or ethacrynic acid (10(-5)-10(-4)M).2. The ratio of varphi(n) (Na) to varphi(i) (K) was found to vary with the experimental conditions, the control value of about 2 was maintained over a threefold variation in absolute Na reabsorption. This ratio increased with low K or ouabain to values near 4. With high K, ethacrynic acid, low Na or cyclamate the relationship was one or lower. Thus, net Na reabsorption can be uncoupled from peritubular K influx.3. These results can be best explained if there are two Na pumps working in parallel: pump A transporting Na (with Cl) and pump B, a Na-for-K-exchange pump. The ratio of Na efflux to K influx could approach infinity if only pump A works (if B is inhibited) and could approach one if only B works. It should vary between these limits in controls when both pumps are active, or when neither of the two pumps is completely inhibited.4. Alternatively, the experimental findings could be explained by a Na pump with a coupling ratio that varies within two extreme values, from high Na-K ratios (with Na reabsorption at, or near, control values but with very low K influx values) to low ratios (with normal K influx values but with low Na reabsorption values).

Absorption↗
PubMed1994

Highly potent and selective inhibition of human immunodeficiency virus by the bicyclam derivative JM3100.

Bicyclams, in which the cyclam (1,4,8,11-tetraazacyclotetradecane) moieties are tethered via an aliphatic bridge (i.e., propylene, as in JM2763) are potent and selective inhibitors of human immunodeficiency virus type 1 (HIV-1) and type 2 (HIV-2) (E. De Clercq, N. Yamamoto, R. Pauwels, M. Baba, D. Schols, H. Nakashima, J. Balzarini, Z. Debyser, B. A. Murrer, D. Schwartz, D. Thornton, G. Bridger, S. Fricker, G. Henson, M. Abrams, and D. Picker, Proc. Natl. Acad. Sci. USA 89:5286-5290, 1992). We have now found that the bicyclam JM3100, in which the cyclam moieties are tethered by an aromatic bridge [i.e., phenylenebis(methylene)], inhibits the replication of various HIV-1 and HIV-2 strains in various cell lines at a 50% effective concentration (EC50) of 1 to 10 ng/ml, which is about 100-fold lower than the concentration required for JM2763 to inhibit HIV replication and at least 100,000-fold lower than the cytotoxic concentration (> 500 micrograms/ml). In primary T4 lymphocytes or primary monocytes, JM3100 proved inhibitory to HIV-1(IIIB) and several clinical HIV-1 isolates at an EC50 of less than 1 ng/ml. On the basis of time-of-addition experiments, JM3100 appeared to interact with a viral uncoating event, and this was further corroborated by an uncoating assay in which RNase sensitivity of [5-3H]uridine-labeled virions was monitored. In addition, but possibly mechanistically related, JM3100 blocks formation of infectious particles. JM3100 was also found to interfere directly with virus-induced syncytium formation, albeit at a higher concentration (1 to 2 microgram/ml) than that required for inhibition of viral replication. Following subcutaneous injection of 10 mg of JM3100 per kg of body weight to rabbits, anti-HIV activity was detected in serum corresponding to serum drug levels exceeding for at least 6 h by >100-fold the EC(50) required to inhibit HIV replication in vitro. When combined with either 3'-azido-2',3' -dideoxythymidine or 2',3' -dideoxyinosine, JM3100 achieved a additive inhibition of HIV replication, and when repeatedly subcultivated in the presence of JM3100, the virus remained sensitive to the compound for at least 30 passages (120 days) in cell culture.

Animals↗
PubMed1989

Membrane effects of chloride substitutes in guinea pig gallbladder epithelial cells.

Differences in the responses of guinea pig gallbladder epithelial cells to replacement of luminal Cl- with either isethionate (I), gluconate (G), sulfate (S), or cyclamate (C) were investigated in vitro using intracellular microelectrode techniques. In prostaglandin E1 (PGE1)-treated tissues (10(-6) M, serosal side), where electrodiffusive apical membrane Cl- permeability (PCla) is high, replacement of luminal Cl- caused transient membrane depolarizations of similar magnitudes but different times to peak (C greater than G = S greater than I). The subsequent shifts in membrane voltages were, at steady state, straight correlated with the concomitant increases in apparent ratio of apical to basolateral membrane resistances (Ra/Rb). Increases followed the rank order I greater than G = S greater than C, which was also found to be the case in the peak membrane hyperpolarizations on restoring luminal Cl-. Under control conditions (no PGE1, low PCla), three of the substitutes caused a slow hyperpolarization, C greater than G = S, whereas an I-for-Cl- substitution evoked a transient depolarization and a drop in Ra/Rb. Under both control and PGE1 conditions, a transient depolarization followed luminal I-for-C substitution. Our results are best explained by a stimulatory effect of I (and, less marked, G and S) on PCla. Intrinsic effects of cyclamate are not ruled out; however, among the substitutes examined, it is the most inert.

Animals↗
PubMed1994

Inhibition of human immunodeficiency virus proliferation by macrocyclic polyamines and their metal complexes.

The macrocyclic polyamines, cyclen and cyclam, and their derivatives have been tested for inhibitory activity against the cytopathogenic effect (CPE) of human immunodeficiency virus type 1 strain HTLV-IIIB (HIV-1IIIB) on CD4+ human lymphoblastoma MT-4 cells. Cyclam and its derivatives were complexed with a variety of transition metal ions NiII, ZnII, CuII, FeIII and CoIII. The divalent metal complexes effected lower toxicity and greater anti-HIV-1 activity, while the trivalent metal complexes had no effect on HIV-1-dependent CPE. When dimerized, the anti-HIV activity of monomers was significantly enhanced. A potent inhibition of CPE by biscyclam was transiently observed 4 d after the virus infection, but was not seen at 6 d due to severe toxicity. The toxicity of biscyclam, referred to as delayed toxicity, could be overcome by a metal complexation. The strain specificities of biscyclams were further studied by testing their effects on syncytium formation between HIV-infected and uninfected human acute lymphoblastic leukemia MOLT-4 cells. The 50% inhibitory concentrations of biscyclams against HIV-2GH-1-dependent syncytium formation were less than one hundredth those for the other HIV strains (HIV-1IIIB, HIV-1RF and HIV-1SF-2).

Cations, Divalent↗
PubMed1978

The determination of mixtures of some artificial sweeteners.

A scheme is suggested for the analysis of mixtures of saccharin sodium, sodium cyclamate and sorbitol. It depends upon: --Determination of saccharin sodium by precipitation of silver saccharinate. --Determination of sodium cyclamate by spectrophotometric titration with sodium nitrite. --Complexometric determination of sorbitol via its copper complex.

Chemical Phenomena↗
PubMed1995

[Changes in cytomembrane and surface cells of the large intestine resulting from the action of sweetening agents].

Saccharin and cyclamates have been proved to cause organic damage. This work attempt to describe drug-induced changes brought about by drugs in 1/1000 saccharin and cyclamate-fed rats for 90 days. The ultrastructural findings show: microvilli hypertrophy; membranous mitochondrial increase in absorptive cells; and secretion changes in calciform cells. Such changes are cell-response phenomena to interference or mutagenic action on nuclear DNA or on cytoplasmatic metabolism.

Animals↗
PubMed1977

The importance of synergy between weak carcinogens in the induction of bladder cancer in experimental animals and humans.

It is now well established that the interaction of multiple environmental factors may increase the incidence of some human cancers more than exposure to a single carcinogen. With an in vivo experimental rat model, we have demonstrated a synergistic effect in bladder carcinogenesis between a subcarcinogenic dose of the strong bladder carcinogen, N-methyl-N-nitrosourea, and saccharin- or cyclamate-containing diets. If these artificial sweeteners are capable of interacting with other environmental bladder carcinogens, their potential for increasing the incidence of human bladder cancer is greater than many more potent chemical carcinogens, because of their wide distribution as food additives to all sections of the population. Retrospective epidemiology shows no evidence of such risk from saccharin at current levels of consumption. No comparable studies are available for cyclamate, which was consumed in greater quantities but for relatively few years. It is emphasized that it is possible for interaction between multiple factors to contribute to the incidence of human bladder cancer as it does in other human organs and in other animal species.

2-Naphthylamine↗
PubMed1991

Approaches to the design of semisynthetic metal-dependent catalytic antibodies.

The binding site of the Fab fragment of antibody MOPC315 was chemically modified with cyclam (1,4,8,11-tetraazacyclotetradecane) and 1,10-phenanthroline. In the presence of the metal ions cobalt(II), copper(II), gallium(III), iron(II), nickel(II), zinc(II), these semisynthetic antibodies did not catalyse the hydrolysis of amides or phosphate ester substrates, or the oxidation of a 1-hydroxy-2-alkene or of 3,4-dihydrobenzamide substrates. Hydrolysis of a coumarin ester substrate was catalysed by the Fab derivatized with a cyclam moiety with a kcat of 0.063 min-1 and Km of 11.7 microM; the presence of metal ions was not required for catalysis.

Antibodies↗
PubMed2004

Behavioral study in the gray mouse lemur (Microcebus murinus) using compounds considered sweet by humans.

This study presents the results from two-bottle preference (TBP) tests performed on the gray mouse lemur (Microcebus murinus), a small Malagasy primate. We found that of 18 compounds considered sweet by humans, M. murinus preferred only six: D-tryptophan, dulcin, fructose, sucrose, SC45647, and xylitol. The animals neither preferred nor rejected acesulfame-K, alitame, aspartame, N-4-cyanophenyl-N'-cyanoguanidineacetate (CCGA), cyanosuosan, cyclamate, monellin, saccharin, suosan, super-aspartame, N-trifluoroacetyl-L-glutamyl-4-aminophenylcarbonitrile (TGC), and thaumatin. Together with previously recorded taste-nerve responses in M. murinus to acesulfame-K, alitame, aspartame, cyclamate, monellin, saccharin, and suosan [Hellekant et al., Chem Senses 18:307-320, 1993b], the current results suggest that these compounds either do not taste sweet to M. murinus or they have an aversive taste component. In this work we also relate these findings to phylogeny.

Animals↗