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PubMed1975

Experiences with the dominant lethal test in female mice: effects of alkylating agents and artificial sweeteners on pre-ovulatory oocyte stages.

Pre-ovulatory oocytes are especially sensitive to mutagenic influences. Since post-dictyotene oocytes are not subject to selection and elimination before fertilization, they may reveal mutagenic effects directly and unrestrictedly. Presuming that a chemical is administered at pro-estrus to female mice one can conclude that the substance or its active metabolite has the chance to reach the gamete during the sensitive pre-fertilization stages. We proved the usefulness of the test system by investigating the effects of alkylating agents. A second step was to investigate other substances. The following treatments induced dominant lethal effects: methyl methanesulfonate 100 mg/kg i.m., cyclophosphamide 200 mg/kg per os, triaziquone 0.25 mg/kg i.p. In contrast, the following agents were ineffective and can be classified as not mutagenic in this method: sodium cyclamate 10 000 mg/kg per os, saccharine sodium, 10 000 mg/kg per os, cyclohexamine sulfate 150 mg/kg per os, ethanol 5 ml/kg per os.

Animals↗
PubMed1990

Aspartame: effects on learning, behavior, and mood.

The effect of aspartame on the learning, behavior, and mood of children was evaluated in two experiments. After an overnight fast and a standard breakfast, 20 healthy 9- to 10-year-old children were given the treatments in a double-blind crossover design at 10:30 AM. Lunch was served at 12:00 noon. In experiment 1, the treatment consisted of an ice slurry of strawberry Kool-Aid containing 1.75 g/kg of carbohydrate (polycose) plus either aspartame (34 mg/kg) or the equivalent sweetness as sodium cyclamate and amino acids as alanine. In experiment 2, the treatment consisted of a drink of cold unsweetened strawberry Kool-Aid, containing either 1.75 g/kg of sucrose or 9.7 mg/kg of aspartame. Measures of associative learning, arithmetic calculation, activity level, social interaction, and mood were unaffected by treatment in experiment 1. In experiment 2, the only significant treatment effect was that on the frequency of minor and gross motor behaviors, which were less frequent after the consumption of sucrose than after aspartame. Thus, the effect of aspartame on the short-term behavior of healthy 9- to 10-year-old children appears to be related to its absence of metabolic consequences rather than to its amino acid composition and putative neurochemical impact.

Affect↗
PubMed1990

The effects of energy content and sweet taste on food consumption in restrained and non-restrained eaters.

To characterize restrained eating behavior, we fed pudding mixtures (preloads) varying in energy content and sweet taste to subjects before measuring their intake of a variety of appetizing foods in a laboratory setting. Twenty-four female subjects were divided into three groups: normal-weight restrained eaters (no. = 8), normal-weight non-restrained eaters (no. = 7), and over-weight restrained eaters (no. = 9). Classification of subjects was based on body mass and restrained eating score. Five preloads varying in energy content (393 or 67 kcal) and type of sweeteners (sucrose or cyclamate) were served 1/2 hour before test meals of assorted hors d'oeuvres. Subjects were not informed of the specific aim of the study, and were instructed to eat until full. Multivariate analysis of variance of repeated measures showed that food intake of all subjects was higher after eating low-energy preloads than after eating high-energy preloads, although subjects did not recognize the effect in self-reports (p less than .01). The energy intake of restrained normal-weight eaters was significantly (p less than .05) lower after eating sweet preloads than after eating non-sweet preloads. Findings suggest that a food-intake control mechanism responds to short-term energy deficits among subjects of varied body mass and restrained eating indexes. J Am Diet Assoc 90:1223-1228, 1990.

Adult↗
PubMed1989

Electrical membrane properties of a cell clone derived from human nonpigmented ciliary epithelium.

Intracellular potentials were measured in a SV-40 virus-transformed cell clone derived from human nonpigmented ciliary epithelium using the microelectrode technique. (1) Membrane potential averaged -50.2 mV (+/- 0.6, n = 207). (2) Increasing the extracellular K+ concentration depolarized the membrane voltage. The amplitude of this potential response was reduced in the presence of 1 mM Ba2+. (3) Superfusing the cells with a Ca2+-free solution containing 1 mM EGTA depolarized the intracellular potential and diminished the voltage response upon increasing extracellular K+. (4) Extracellular alkalinization hyperpolarized the membrane potential and increased the voltage amplitude on increasing extracellular K+. (5) Addition of ouabain immediately reduced the intracellular potential. Removing extracellular K+ depolarized membrane voltage, readdition of K+ after K+ depletion transiently hyperpolarized intracellular voltage. Both potential responses were inhibited in the presence of ouabain. (6) Replacing extracellular Cl- by cyclamate resulted in a transient depolarization followed by a hyperpolarization. In the presence of SITS or DIDS (greater than or equal to 0.1 mM) the electrical responses of the cell membrane to Cl- replacement were blocked. We conclude that cultured human nonpigmented ciliary epithelial cells possess an electrogenic Na+/K+-ATPase, a K+ conductance modulated by Ca2+ and pH, and a Cl- conductance sensitive to stilbene derivatives.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed1979

Regulation of carcinogenic food additives and drugs in the US.

The four components of the process by which a decision is made about the acceptability of human exposure to a chemical are outlined. The quantity and quality of the data that are required have increased considerably in recent years, and the standards governing the conduct of the studies done to obtain them have become more stringent. Thus, many chemicals now in widespread use were admitted on the basis of evidence that is now considered woefully inadequate; the steps being taken in the US to remedy this situation are described. Since such testing is long and expensive, four regulatory agencies have joined together to develop guidelines that can be used by each. The interpretation of data presents yet another problem. Further, what constitutes adequate evidence for safety is a matter subject to wide ranges of opinion: this is illustrated by the example of cyclamate. The difficulties of extrapolating results to actual situations are outlined; and the limitations of the usefulness of experimental testing are pointed out. Determination of an acceptable ratio between benefits and risks depends on a wide variety of factors, and regulatory decisions in this regard thus depend on several kinds of scientific judgements and on policy decisions based on cultural aspects.

Animals↗
PubMed1984

[Prophylaxis of dental caries using sugar substitutes].

Among the three measures, which are capable of producing a preventive effect against caries only when applied combined, i.e. adequate fluoride supply, proper mouth hygiene and healthy nutrition, the latter is dealt with in greater detail. The use of sugar substitutes is discussed under the aspects of caries prevention, substitute composition and production technology as well as from a medical point of view. Among the presently available sugar substitutes with nutritive value are mentioned Xylite, Lycasine, Mannite, Sorbite, Palatinite, the non-calorific substitutes such as the natural Aspartame as well as the synthetic sweetening agents Saccharine and Cyclamate. The possibilities and limitations of using these sugar substitutes in the prevention of caries in adults and children are presented.

Adult↗
PubMed1977

Modification by fiber of toxic dietary effects.

There is evidence that type of diet may affect the course of chemical carcinogenesis. In experiments with acetylaminofluorene, rats maintained on stock diet exhibit fewer tumors than do rats fed semi-purified diets. Rats fed stock diet augmented with high levels of sodium cyclamate (2.5-10%), amaranth (5%) or Tween (15%) showed normal weight gain, whereas addition of these toxicants to a fiber-free basal diet caused severely restricted weight gain and decreased survival. The latter effect can be overcome by addition of 10% pectin, alfalfa or cellulose to the basal diet. On the other hand, mice fed a fiber-free diet survived pneumococcal infection better than did mice fed modified stock diets. The mechanism(s) by which fiber affects carcinogenicity or toxicity are unelucidated. The effect of fiber and other aspects of diet on drug action is an area of research that should be developed.

2-Acetylaminofluorene↗
PubMed1997

Characterization of an inwardly rectifying chloride conductance expressed by cultured rat cortical astrocytes.

The biophysical and pharmacological properties of the inwardly rectifying Cl- conductance (IClh), expressed in rat type-1 neocortical cultured astrocytes upon a long-term treatment (1-3 weeks) with dibutyryl-cyclic-AMP (dBcAMP), were investigated with the whole-cell patch-clamp technique. Using intra- and extra-cellular solutions with symmetrical high Cl- content and with the monovalent cations replaced with N-methyl-D-glucamine, time- and voltage-dependent Cl- currents were elicited in response to hyperpolarizing voltage steps from a holding potential of 0 mV. The inward currents activated slowly and did not display any time-dependent inactivation. The rising phase of the current traces was best fitted with two exponential components whose time constants decreased with larger hyperpolarization. The steady-state activation of IClh was well described by a single Boltzmann function with a half-maximal activation potential at - 62 mV and a slope of 19 mV that yields to an apparent gating charge of 1.3. The anion selectivity sequence was Cl- = Br- = I- > F- > cyclamate > or = gluconate. External application of the putative Cl- channel blockers 4,4 diisothiocyanatostilbene-2,2 disulphonic acid or 4-acetamido-4-isothiocyanatostilbene-2,2-disulphonic acid did not affect IClh. By contrast, anthracene-9-carboxylic acid, as well as Cd2+ and Zn2+, inhibited, albeit with different potencies, the Cl- current. Taken together, these results indicate that dBcAMP-treated cultured rat cortical astrocytes express a Cl- inward rectifier, which exhibits similar but not identical features compared with those of the cloned and heterologously expressed hyperpolarization-activated Cl- channel ClC-2.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed1986

Food additives and contaminants. An update.

Food additives continue to be a source of benefits to the consuming public but there are also perceived risks. Concern for the latter in the last decade has produced a society afflicted with cancer phobia. The intentional additives including sugars, salt, corn syrup, and dextrose make up 90% of the direct additives. These, along with a limited number of familiar items make up a large proportion of the remainder of the additives. Such common ingredients as nitrates and nitrites, solanine, cyanogenetic compounds, arsenic, etc., are unavoidably consumed in the diet and with little if any evidence for public health consequences. Major concern on the part of the public in recent years has been focused on man-made chemicals which are intentionally added to foods to enhance flavors and acceptability, nutrient value, shelf life and increased availability. These include food colors, nonnutritive and low-nutrient sweeteners, (saccharin, cyclamate, aspartame); antioxidants; and nitrites. Contaminants, sometimes incorrectly included in lists of food additives, present the greatest potential threat to public health. Such contaminants as mycotoxins, nitrosamines, polychlorinated biphenyls (PCBs), pesticides, among others, provide a continuing challenge to our regulatory agencies and to public health authorities. Evidence to date indicate that these responsible for food safety are doing an admirable job, and as a society, our food supply has never been better, or safer, and, as a population, we have never been healthier. Aside from contaminants, major concerns relate to an excess of good food and to obesity. These comments should not be taken to infer that we should relax our concern and surveillance; instead more concern and surveillance should be exerted toward those uncontrolled substances such as natural plant products and alleged natural nutrients, roots, herbs, etc., which are given much credit for positive health effects, without meeting the high standards of our legitimate food industry.

Animals↗
PubMed2001

Coupled molecular switches: a redox-responsive ligand and the redox-switched complexation of metal ions.

1,1'-(OC2H4OTos)2-ferrocene was treated with various diaza-[n]-crown-m (n/m = 12/4, 15/5, 18/6) to give three ferrocene cryptands (n/m = 12/4 (FcCrypt), 15/5, 18/6). The complexation of Group 1 and 2 metal ions by FcCrypt leads to large shifts in the redox potentials (up to +500 mV relative to FcCrypt) and consequently to a drastic decrease in the binding strength (up to 10(8)) in the ferrocene cryptands. The redox potential of Fcpda (1,1'-N,N'-bis-(dipicol-2-ylamino)-3.3',4,4'-tetraphenylferrocene) can be modified reversibly by complexation of Zn2 (E(Fcdpa) = -0.13 V, E(Fcdpa-2Zn+) = +0.66 V and E(Fcdpa-Zn2+) = +0.72 V). The X-ray crystal structure of FcCrypt-Ca-(ClO4)2 . H2O was determined; Ca2+ is coordinated by six oxygen (Ca2+-O 238.7, 239.1, 239.5, 242.6, 243.6, 247.7 pm) and two nitrogen donors (Ca2+-N 256.1, 259.2 pm) and displays a short Fe-Ca2+ contact (402.7 pm). The stability constants of FcCrypt-Na+ (IgK=8.32 in CH3CN) and FcCrypt-K+ (IgK = 4.54 in CH3CN) were determined. The precise adjustment of complex stability and redox potentials of Fcdpa, Fcdpa-Zn2+, FcCrypt (+0.12 V), and FcCrypt-Na+ (+0.395 V) allows coupling of the redox-switchable ferrocene cryptand and the redox-responsive aminoferrocene. In a cyclic process starting from a mixture of Fcdpa+PF6- and FcCrypt-Na+ the addition of Zn(CF3SO3)2 raises the redox potential of Fcdpa+ to that of Fcdpa+-Zn2+. This complex oxidizes FcCrypt-Na+, while the oxidized crypt- and displays a drastically reduced affinity towards Na+, so that a mixture containing FcCrypt+, Fcdpa-Zn2+, and uncoordinated Na+ results. The alkali metal ion is recomplexed after cyclam-assisted removal of Zn2+ from the Fcdpa-Zn2+ complex, since Fcdpa is oxidized by FcCrypt+ with reformation of FcCrypt-Na+. Thus two independent chemical processes--the complexation/ decomplexation of Zn2+ and of Na+--are linked indirectly with mediation by electron-transfer reactions.

Journal Article↗
PubMed2002

Light-emitting molecular machines: pH-induced intramolecular motions in a fluorescent nickel(II) scorpionate complex.

A cyclam-like macrocycle has been synthesized with a pendant arm containing a dansylamide group. In the corresponding nickel(II) complex, binding of the pendant arm to the metal is pH controlled. In particular, at pH 4.3, the sulfonamide group deprotonates and coordinates the NiII center, giving rise to a complex of trigonal bipyramidal stereochemistry, as shown by X-ray diffraction studies performed on the crystalline complex salt. At pH 7.5, an OH- ion binds the metal and a six-coordinate species forms. The binding-detachment of the pendant arm to/from the NiII center is signaled by changes in the emission properties of the dansyl subunit in the side chain; the fluorescence of this side chain is high when the pendant arm is not coordinated and low when the sulfonamide group is bound to the metal. The system investigated represents the prototype of a light-emitting molecular machine, driven by a pH change.

Crystallography, X-Ray↗
PubMed2004

Does a reinforced kinetic macrocyclic effect exist? the demetallation in strong acid of copper(II) Complexes with open and cyclic tetramines containing a piperazine fragment.

The demetallation in acidic solution of the Cu(II) complexes with open-chain and cyclic tetramines containing a piperazine unit (2 and 3) has been investigated in terms of its kinetic aspects and compared with the behaviour of unsubstituted counterparts (tetramines 1 and 4). The presence of the piperazine fragment slows demetallation of the open-chain-ligand complex owing to the activation barrier associated with the conformational change from boat-to-half-boat; however, it does not affect the demetallation of the macrocyclic complex, which involves the spontaneous boat-to-twist conformational change. Thus, lateral reinforcement of a cyclam-like ligand does not add any further contribution to the typical inertness in demetallation of macrocyclic complexes.

Journal Article↗
PubMed1983

Artificial sweeteners and absence of bladder cancer risk in Copenhagen.

During the years 1979 to 1981 a population-based case-control study of bladder cancer including papillomas was performed in Greater Copenhagen. After exclusions some 388 patients (290 males; 98 females) and an age- and sex-matched group of 787 controls (592 males; 195 females) remained for analysis. Controls were selected at random from the general population of the study area. All persons were interviewed concerning use of artificial sweeteners in addition to their exposure to a number of other known or suspected risk factors for bladder cancer. Fifty-five male bladder cancer patients (19.4%) and 150 controls (25.7%) had at some time used artificial sweeteners regularly. Among females 27.1% of cases and 25.9% of controls regularly used sweeteners. In neither sex was the relative risk significantly increased in users compared with non-users of artificial sweeteners. The relative risk of 0.78 in the two sexes combined was not significantly different from 1.0 (95% C.I.: 0.58-1.05). There was no indication of a regular increase in risk with increasing daily consumption of table-top sweeteners nor was there any indication of an increase in risk with a duration of regular use of artificial sweeteners. Taking into account a possible latency period between first regular use and bladder cancer development did not change the finding of an absence of association between use of artificial sweeteners and the risk of bladder cancer. Neither saccharine nor cyclamate users had an increased risk of bladder cancer. This population-based case-control investigation provides further evidence that it is highly unlikely that the consumption of artificial sweeteners has contributed to current bladder cancer rates in man.

Beverages↗
PubMed2006

Direct simultaneous determination of eight sweeteners in foods by capillary isotachophoresis.

A method for isotachophoretic determination of sweeteners of different character in candies and chewing gums was developed. A capillary of 0.8 mm ID and 90 mm effective length made of fluorinated ethylene-propylene copolymer is filled with an electrolyte system consisting of 10 mM HCl + 14 mM Tris, pH 7.7 (leading electrolyte) and 5 mM L-histidine + 5 mM Tris, pH 8.3 (terminating electrolyte). The analysis is performed at a driving current of 200 microA and for detection current is decreased to 100 microA. Boric acid is added to the aqueous sample solution to form borate complexes with substances of polyhydroxyl nature and make them migrate isotachophoretically. Using conductivity detection, the calibration curves in the tested concentration range up to 2.5 mM were linear for all components of interest: acesulfame K, saccharine, aspartame, cyclamate, sorbitol, mannitol, lactitol, and xylitol. The concentration detection limits ranged between 0.024 and 0.081 mM. Good precision of the ITP method is evidenced by favorable RSD values ranging from 0.8 to 2.8% obtained at the analyte concentration of 1.0 mM (n = 6). The analysis time was about 20 min. Simplicity, accuracy, and low cost of analyses make ITP an alternative procedure to methods used so far for the determination of ionizable sweeteners.

Calibration↗
PubMed1994

Effects of liquid preloads with different fructose/fibre concentrations on subsequent food intake and ratings of hunger in women.

Preloads (250 ml) of 2% or 10% fructose containing 1% soluble fibre and 1% insoluble fibre or 10% fructose with 3% soluble fibre and 1% insoluble were administered 60 min before lunch to 24 healthy women, who were slightly overweight and considerably weight concerned. The fibre consisted of guar gum, partly hydrolysed for the soluble form. The placebo consisted of a solution of sweeteners (cyclamate and saccharin). After the experiment with three preload-types and a placebo, a random subset of 15 subjects returned for an experiment with one preload-type and a placebo, given 30 or 60 min before lunch. Food intake during the subsequent lunch was only significantly different from after the placebo in this subset of 15 subjects after the 10% fructose/3% soluble and 1% insoluble fibre preload after intervals of 30 or 60 min. However, energy intake of preload and meal was significantly higher than energy intake of placebo and meal. At the 30-min delay, eating rate was significantly lower after the preload than after the placebo; also, hunger ratings were lower after intake of a preload and meal than after intake of the placebo+meal, from immediately after lunch until 5 hours later. Energy intake over 24 h was not affected by administration of fructose/fibre or placebo 30 or 60 minutes before lunch in the 24 women.

Adult↗
PubMed2001

Interactions of selected gold(III) complexes with calf thymus DNA.

DNA represents the primary target for platinum antitumor metal complexes and is the probable target for newly developed cytotoxic gold(III) complexes. To test this hypothesis the reactions with calf thymus DNA of five representative gold(III) complexes--namely [Au(en)(2)]Cl(3), [Au(dien)Cl]Cl(2), [Au(cyclam)](ClO(4))(2)Cl, [Au(terpy)Cl]Cl(2) and [Au(phen)Cl(2)]Cl--were analyzed in vitro through various physicochemical techniques including circular dichroism, absorption spectroscopy, DNA melting, and ultradialysis. It is shown that all tested complexes interact with DNA and modify significantly its solution behavior. The solution conformation of DNA is affected to variable extents by the individual complexes as shown by CD titration experiments. Notably, in all cases, the gold(III) chromophore is not largely perturbed by addition of calf thymus DNA ruling out occurrence of gold(III) reduction. Ultradialysis experiments point out that the binding affinity of the various complexes for the DNA double helix is relatively low; in most cases the gold(III)/DNA interaction is electrostatic in nature and reversible. The implications of these findings for the mechanism of action of antitumor gold(III) complexes are discussed.

Animals↗
PubMed1978

Food additives.

The use of additives to food fulfils many purposes, as shown by the index issued by the Codex Committee on Food Additives: Acids, bases and salts; Preservatives, Antioxidants and antioxidant synergists; Anticaking agents; Colours; Emulfifiers; Thickening agents; Flour-treatment agents; Extraction solvents; Carrier solvents; Flavours (synthetic); Flavour enhancers; Non-nutritive sweeteners; Processing aids; Enzyme preparations. Many additives occur naturally in foods, but this does not exclude toxicity at higher levels. Some food additives are nutrients, or even essential nutritents, e.g. NaCl. Examples are known of food additives causing toxicity in man even when used according to regulations, e.g. cobalt in beer. In other instances, poisoning has been due to carry-over, e.g. by nitrate in cheese whey - when used for artificial feed for infants. Poisonings also occur as the result of the permitted substance being added at too high levels, by accident or carelessness, e.g. nitrite in fish. Finally, there are examples of hypersensitivity to food additives, e.g. to tartrazine and other food colours. The toxicological evaluation, based on animal feeding studies, may be complicated by impurities, e.g. orthotoluene-sulfonamide in saccharin; by transformation or disappearance of the additive in food processing in storage, e.g. bisulfite in raisins; by reaction products with food constituents, e.g. formation of ethylurethane from diethyl pyrocarbonate; by metabolic transformation products, e.g. formation in the gut of cyclohexylamine from cyclamate. Metabolic end products may differ in experimental animals and in man: guanylic acid and inosinic acid are metabolized to allantoin in the rat but to uric acid in man. The magnitude of the safety margin in man of the Acceptable Daily Intake (ADI) is not identical to the "safety factor" used when calculating the ADI. The symptoms of Chinese Restaurant Syndrome, although not hazardous, furthermore illustrate that the whole ADI cannot always be ingested as a single dose on an empty stomach with impunity.

Animals↗
PubMed1985

Anion dependence of electrical effects of bicarbonate and sodium on cultured bovine corneal endothelial cells.

Using intracellular microelectrode technique, the effect of anion substitution on the voltage responses to extracellular bicarbonate and sodium was explored in cultured bovine corneal endothelial cells. The overall amplitude of voltage changes induced by periodic changes of [HCO-3]o (depolarization upon removal of HCO-3 and hyperpolarization upon readdition) was reduced when Cl- was replaced by organic anions (cyclamate, methylsulfate, benzenesulfonate) or by SO4(2-), and to a lesser extent by substitution with Br-. There was a similar effect of anion substitution on the response to changes of [Na+]o. In both cases, in the absence of Cl, the voltage V returned at a slower rate to baseline levels after it had been transiently changed by either an imposed Na- or HCO3- gradient, indicating a slower dissipation of these gradients. The direct response of V to these imposed gradients was affected only to a minor degree. Replacement of Cl- by SO4(2-) or organic anions led to a slow, reversible depolarization of the cell, while substitution with Br- had only a slight effect. The effect of anion substitution on the voltage responses to HCO-3 or Na+ could not be mimicked by a depolarization induced by Ba2+ (1 mM). Furosemide (10(-3) M) led to a slight reduction of the voltage responses to HCO-3, but could not suppress the effect of anion substitution on these reactions. It could neither suppress the depolarization induced by anion substitution and had no effect on steady-state PD. It is suggested, that cultured bovine corneal endothelial cells, in addition to a previously demonstrated electrogenic HCO-3-Na+-cotransport, which is probably not dependent on Cl, possess an electroneutral mechanism for HCO-3 and/or Na+-movement, which depends on Cl. No evidence for a Cl-conductance could be obtained.

Animals↗