Interaction of nucleotides with Asp(351) and the conserved phosphorylation loop of sarcoplasmic reticulum Ca(2+)-ATPase

The nucleotide binding properties of mutants with alterations to Asp(351) and four of the other residues in the conserved phosphorylation loop, (351)DKTGTLT(357), of sarcoplasmic reticulum Ca(2+)-ATPase were investigated using an assay based on the 2', 3'-O-(2,4,6-trinitrophenyl)-8-azidoadenosine triphosphate (TNP-8N(3)-ATP) photolabeling of Lys(492) and competition with ATP. In selected cases where the competition assay showed extremely high affinity, ATP binding was also measured by a direct filtration assay. At pH 8.5 in the absence of Ca(2+), mutations removing the negative charge of Asp(351) (D351N, D351A, and D351T) produced pumps that bound MgTNP-8N(3)-ATP and MgATP with affinities 20-156-fold higher than wild type (K(D) as low as 0.006 microM), whereas the affinity of mutant D351E was comparable with wild type. Mutations K352R, K352Q, T355A, and T357A lowered the affinity for MgATP and MgTNP-8N(3)-ATP 2-1000- and 1-6-fold, respectively, and mutation L356T completely prevented photolabeling of Lys(492). In the absence of Ca(2+), mutants D351N and D351A exhibited the highest nucleotide affinities in the presence of Mg(2+) and at alkaline pH (E1 state). The affinity of mutant D351A for MgATP was extraordinarily high in the presence of Ca(2+) (K(D) = 0.001 microM), suggesting a transition state like configuration at the active site under these conditions. The mutants with reduced ATP affinity, as well as mutants D351N and D351A, exhibited reduced or zero CrATP-induced Ca(2+) occlusion due to defective CrATP binding.

Measurement of the relative sweetness of stevia extract, aspartame and cyclamate/saccharin blend as compared to sucrose at different concentrations

Special diets are used to mitigate many human diseases. When these diets require changes in carbohydrate content, then sweetness becomes an important characteristic. The range of low-calorie sweeteners available to the food industry is expanding. It is essential to have an exact knowledge of the relative sweetness of various sweeteners in relation to different sucrose concentrations. The objective of this study was to determine the variation on the relative sweetness of aspartame (APM), stevia [Stevia rebaudiana (Bert.) Bertoni] leaf extract (SrB) and the mixture cyclamate/saccharin--two parts of cyclamate and one part of saccharin--(C/S) with the increase in their concentrations, and in neutral and acid pH in equisweet concentration to 10% sucrose, using magnitude estimation. Sweetness equivalence of SrB in relation to sucrose concentrations of 20% or higher and of APM and C/S to sucrose concentrations of 40% or higher could not be determined, because a bitter taste predominated. The potency of all sweeteners decreased as the level of sweetner increased. In equi-sweet concentration of sucrose at 10%, with pH 7.0 and pH 3.0, the potency was practically the same for all sweeteners evaluated.

Genetics of alcoholism: rapid development of a new high-ethanol-preferring (HEP) strain of female and male rats

A genetically based animal model of alcoholism has been developed in a relatively short period of 3 years. The new strain is characterized by an intense preference for ethanol over water as well as unique behavioral, neurochemical and other attributes. This new strain, termed high-ethanol-preferring (HEP) rats, was derived initially from selective cross-breeding of a variant strain of female Harlan Sprague-Dawley (SD) rats with the outbred Wistar line of male ethanol-preferring (P) rats. In this study, drinking patterns of both genders were obtained over 10 days by presenting water and ethanol in concentrations ranging from 3% to 30%. To expedite the development of the new strain, only three to five female and male rats served as breeders, which were chosen from all litters on the basis of their maximum g/kg intake integrated with proportion of ethanol to total fluid values. Profiles of intake of preferred concentrations of ethanol were obtained over 24 h of unlimited access as well as during 2-h intervals of limited access to ethanol. Levels of blood ethanol were measured in both female and male HEP animals during bouts of ethanol drinking in the limited access paradigm. By the sixth generation of HEP rats, ethanol consumption of the females often exceeded that of any other rat genetically bred to drink ethanol (e.g., at a concentration of 15.7%, 10.3 g/kg per day). Seven additional characteristics are notable: 1) the HEP rats prefer ethanol in the presence of a nutritious chocolate drink or nonnutrient sweetened solution (aspartame); 2) high levels of blood ethanol are associated with their drinking; 3) females drink significantly greater g/kg amounts of ethanol than HEP males and prefer a higher percent concentration of ethanol; 4) the drinking of ethanol by the female HEP animals does not fluctuate during the estrous cycle; 5) neurochemical assays show differential profiles of 5-HT, dopamine, and their metabolites in different regions of the brain; 6) measures of activity using the elevated plus maze, open field, and cork gnawing reveal differences between genders of HEP rats and SD rats; and 7) the HEP animals are without phenotypically expressed abnormalities. Finally, one cardinal principle derived from this study revealed that the breeding strategy to develop high-ethanol-drinking rats centers on the use of multiple solutions of ethanol whereby the intakes of ethanol in concentration of 9% through 20% dictate the ultimate selection of breeding pairs over successive F generations. Further, it is concluded that because of an intense rise in ethanol drinking of the F1 generation of female HEP rats well above that of the parental SD female breeders, the complex genotypic characteristic of the male P rat is predominantly responsible for evoking ethanol drinking in female offspring.

Sensory evaluation of mixtures of maltitol or aspartame, sucrose and an orange aroma

The suitability of Beidler's mixture equation for mixtures of sucrose and maltitol as well as for mixtures of sucrose and aspartame was examined in the presence of an orange aroma. The mean scores for the attribute sweet remained constant for each combination of sucrose and maltitol and for each combination of sucrose and aspartame. Therefore, Beidler's mixture equation can be used to choose combinations of sucrose and maltitol and of sucrose and aspartame giving the same sweetness. Quantitative descriptive analysis of different solutions indicated that the flavour profiles of sucrose and maltitol did not differ significantly at a constant concentration of orange aroma. However, flavour profiles of solutions with increasing aspartame concentrations (but constant aroma levels) showed significantly higher scores for the attributes sour, chemical and aftertaste. Addition of orange aroma provided the different solutions with a more distinct flavour. The mean scores for the attributes orange, sour, fruity and aftertaste increased significantly for most of the sucrose-maltitol mixtures. This effect of orange aroma was even more pronounced in solutions containing combinations of sucrose and aspartame. Further comments on the attribute aftertaste showed similar terms for the different solutions, the most often mentioned being orange, sour, fruity and chemical for solutions containing the orange aroma. The aftertaste of solutions containing relatively more aspartame was mainly described as sweet and chemical.

Volitional consumption of ethanol by fawn-hooded rats: effects of alternative solutions and drug treatments

Behavioral and neurochemical measures of brain 5-hydroxytryptamine (5-HT) function in the Fawn-Hooded rat are abnormal relative to outbred strains of rats. Fawn-Hooded rats freely drink large amounts of 10% ethanol in the presence of water and have been proposed to be an animal model for studies related to alcoholism. In this study, Fawn-Hooded rats were given solutions of ethanol increasing in concentration from 3% to 30% (w/v in tap water) over 10 days with tap water in a second drinking tube and a third tube left empty. The solutions of ethanol that produced maximal drinking with a preference (ml ethanol/ml total fluid) near 50% ranged from 5% to 13%, which became the fixed individual concentrations for each rat. After a 5-day baseline period the rats were offered a solution in the third drinking tube of either 0.5% aspartame or chocolate Ultra SlimFast (diluted with water 2:1). The chocolate drink, but not aspartame, significantly reduced the consumption of alcohol by 73%. For the drug experiments, the rats were given successive 4-day periods of: baseline drinking; drug or saline injections b.i.d.; and a posttreatment period. Neither ipsapirone, a 5-HT1a partial agonist, nor naltrexone injected inhibited the intakes of ethanol solutions. Treatment with 2.5 mg/kg of amperozide, a 5-HT2 antagonist, decreased the consumption of ethanol by 38%, but also caused a decrease in consumption of food. These results show a pattern of drinking of increasing concentrations of ethanol different than other strains of rats.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of age on the recognition thresholds of three sweeteners: sucrose, saccharin and aspartame

It is believed that people's sensitivity to taste declines with age but the evidence is inconclusive. This study was designed to test the hypothesis that taste recognition thresholds (TRTs) for sweetness are higher in older than in younger individuals, using groups of 16 younger subjects (18-30) and 16 older subjects (60-85). Three test substances were used: sucrose, aspartame and saccharin. A questionnaire recorded variables which might have affected TRTs, but data failed to show any trend that might have biased the principle variate-age. There was a significant alteration with age of recognition thresholds, at least for sucrose and saccharin. The differences between the groups for the three sweeteners were due to the fact that all the very sensitive subjects were young. None of the older subjects had particularly poor discrimination: all but one had TRTs within the range of younger subjects. Although there are age-related taste changes, they are much less dramatic than commonly occurs with other senses, such as sight and hearing. The findings of this study have implications for institutional catering and the dietary management of older people using non-sugar sweeteners.

Personality profiles and state aggressiveness in Finnish alcoholic, violent offenders, fire setters, and healthy volunteers

BACKGROUND

Based on clinical observations in a series of studies on Finnish alcoholic, violent offenders, we asserted that the impulsive offenders represented an extreme group of type 2 alcoholics. We also observed that these subjects were vulnerable to hypoglycemia after the administration of oral glucose load. Furthermore, we believe that while being hypoglycemic, the impulsive offenders are particularly irritable and aggressive. In the present study, we addressed these issues by studying psychological trait and state variables in a new group of violent offenders and fire setters, and age- and sex-matched healthy volunteers.

METHODS

Fifty-eight alcoholic, violent offenders and impulsive fire setters and 21 healthy volunteers were administered the Karolinska scales of personality and the Rosenzweig picture frustration test after an oral aspartame and glucose challenge.

RESULTS

The psychological test results and the criminal histories of the offenders, together with biochemical measurements, suggest that a low 5-hydroxyindoleacetic acid concentration in cerebrospinal fluid in the alcoholic offenders is associated with irritability and impaired impulse control, and a high free testosterone concentration in cerebrospinal fluid is associated with increased aggressiveness, monotony avoidance, sensation seeking, suspiciousness, and reduced socialization.

CONCLUSION

Finnish alcoholic, impulsive offenders have personality profiles characteristic of Scandinavian early-onset male alcoholics with antisocial traits, who have been also referred to as type 2 alcoholics.

Nonhuman primate model of alcohol abuse: effects of early experience, personality, and stress on alcohol consumption

Twenty-two 50-month-old rhesus monkeys were provided concurrent free access to an aspartame-sweetened 7% ethanol solution and an aspartame-sweetened vehicle before, during, and after social separation. Subjects had been reared for their first 6 months of life either without access to adults but with constant access to age mates (peer reared), a condition producing reduced exploration and increased fear-related behaviors, or as controls with their mothers; thereafter, all subjects received identical treatment. During home-cage periods, for 1 hr each day, 4 days a week, when the ethanol solution and vehicle were freely available, peer-reared subjects consumed significantly more alcohol than mother-reared subjects. When stress was increased via social separation, mother-reared animals increased their alcohol consumption to a level nearly as high as that of peer-reared monkeys. Average individual differences in alcohol consumption were markedly stable over time. In addition, there were strong positive correlations between alcohol consumption and distress behaviors. Biological indices of increased stress, such as plasma cortisol and corticotropin, were higher in peer-reared subjects. Within the peer- and mother-reared groups, these indices were positively correlated with alcohol consumption. The results suggest that early rearing experiences that predispose monkeys to increased fear-related behaviors produce excessive alcohol consumption under normal living conditions. Furthermore, a major challenge such as social separation increases alcohol consumption to levels producing intoxication even in monkeys not particularly vulnerable to stress.

[Sugar substitutes in the prevention of dental caries: review of the literature]

The prevention of dental caries is not only limited to the use of fluorides or sealants which, in combination with health education programmes and an appropriate oral hygiene, decrease the prevalence of the disease. The partial substitution of sucrose with nonfermentable sweeteners in the diet have shown to have a caries-inhibitory effect. A literature review regarding sugar substitutes is presented. The objective is to identify and describe the different kinds of sweeteners, with special emphasis in sugar alcohols like xylitol and sorbitol, which have shown to have such caries inhibitory-effect.

[Nutrition recommendations (1990)]

As of last year, new Canadian dietary recommendations and nutritional requirements have been established. The combination of these two documents evolved as a result of a better understanding of nutrition, as well as, an awareness that the problems related to nutritional deficiencies have resulted in numerous chronic diseases. This article, after an initial review of the origin of these documents, highlights the main changes that have occurred and reviews how this information is used and interpreted by various health care professionals.

Long-term continuous synthesis of aspartame precursor in a column reactor with an immobilized thermolysin

N-(Benzyloxycarbonyl)-L-asparty-L-phenylalanine methyl ester, the precursor of the synthetic sweetener aspartame, was continuously synthesized in an immobilized thermolysin plug-flow type reactor at 25 degrees C with the substrates (N-benzyloxycarbonyl-L-aspartic acid and L-phenylalanine methyl ester) dissolved in ethyl acetate. The immobilized enzyme was quite stable in ethyl acetate containing 2.5% 0.01 M 2-(N-morpholino)ethanesulphonic acid-NaOH buffer, pH 6.0, and 20 mM CaCl2 with or without the substrate at 25 degrees C. By periodically washing the column, we could conduct a continuous reaction for over 500 h with an average yield of 95% and a space velocity of 1.85 h-1.

Conformation-activity relationship of sweet molecules. Comparison of aspartame and naphthimidazolesulfonic acids

The shape of the active site of the receptor for sweet molecules was previously defined on the basis of a combination of both rigid (saccharins) and flexible (aspartame) molds. In this paper, the sweetness receptor is refined with use of the shapes of 3-anilino-2-styryl-3H-naphtho[1,2-d]imidazolesulfonate (sweet) and of 3-anilino-2-phenyl-3H-naphtho[1,2-d]imidazolesulfonate (tasteless), two large and almost completely rigid tastants. The minimum-energy conformations of the flexible portions of these tastants have been determined by using a detailed conformational analysis based on ab initio calculations. The refined receptor site is still consistent with all previously examined sweet molecules. In order to unequivocally assign the prochiral beta-CH2 protons of the Phe moiety of aspartame, (2S,3S)-[2H]-alpha-L-Asp-L-PheOMe was synthesized and examined by 500-MHz 1H NMR spectroscopy. The results indicate that the minimum-energy conformation for aspartame in water, DMSO-d6, and CDCl3 (as a crown ether complex) is different from that originally proposed (FIIDII instead of FIDII, according to a notation referred to the side chains). Although this conformation is not directly consistent with the shape of the sweet receptor, the interconversion of FIIDII to FIDII was found to require only 1 kcal/mol. Furthermore, a 120-ps molecular dynamics simulation in vacuo confirms the high flexibility of aspartame and the accessibility of the FIDII conformer whose topology is fully consistent with our model.

Similarity assessment and attribute scaling of sucrose and aspartame in grape drink

The present study investigated the perception of sweetness of aspartame in comparison to various concentrations of sucrose. Twenty-seven subjects were randomly assigned to taste a chilled or room temperature Kool-Aid beverage sweetened with either aspartame or five different concentrations of sucrose. Subjects assessed the perceived similarity in sweetness of an aspartame-aspartame pair and five different aspartame-sucrose pairings and rated each beverage on five bipolar adjectives. Analysis of the similarity ratings revealed that subjects did not perceive the pairs of beverages to differ in perceived sweetness. Analysis of the adjective ratings revealed that aspartame and the lower sucrose concentrations were perceived as being less sweet and more sour than the higher sucrose concentrations.

Influence of the sense of taste on broiler chick feed consumption

This study was performed to determine the effects of five flavored diets on feed consumption, weight gain, and feed efficiency of broiler cockerels. Isocaloric diets were flavored with .06% saccharin, 6% citric acid, 5% salt, .10% quinine, or .13% aspartame. In Experiment 1, 1-wk-old broiler cockerels were fed an unflavored control diet ad libitum from a divided feed tray for 3 wk. Sides of the feed tray were rotated daily, every other day, or not at all, to determine the effect of position on preference. In Experiment 2, 1-day-old broiler cockerels were offered a choice between an unflavored control diet and a flavored diet, in an ad libitum feeding arrangement, for 3 wk. In Experiment 3, 1-day-old broiler cockerels were offered a choice between two flavored diets fed ad libitum for 3 wk. Daily rotation of the feed tray eliminated preferences due to position. When each side of the feed tray contained the same unflavored diet and was rotated daily, there were no significant differences in feed consumption, weight gain, or feed efficiency. In Experiment 2, there were significant differences in feed consumption between the control diet and all flavored diets except aspartame. The birds offered saccharin, citric acid, salt, and quinine ate significantly less of these diets than of the unflavored control diet. In Experiment 3, the birds detected the differences in flavor and consumed the feed in a specific order of preference: aspartame, saccharin, citric acid, salt, quinine.

Effect of sucrose-containing snacks on blood glucose control

To determine whether ingestion of sucrose-containing snacks would affect blood glucose (BG) control, 16 subjects with insulin-dependent diabetes mellitus participated in a 5-day double-blind study at a diabetes camp. Eight subjects in the sucrose group ate sucrose-sweetened snacks twice a day, and 8 subjects in the control group ingested snacks that were sweetened with aspartame. The percentage of total daily calories derived from added sucrose was 7% for the sucrose group and 1% for the control group. Metabolic control was assessed by daily capillary BG measurements obtained before meals and the bedtime snack and by determination of serum fructosamine (F) concentrations on arrival at camp (day 0) and after 5 days on the study protocol (day 5). No significant difference was seen between the groups on day 0 (sucrose group [mean +/- SD]: BG 9.9 +/- 3.6 mM, F 3.54 +/- 0.38 mM; control group: BG 9.1 +/- 2.8 mM, F 3.74 +/- 0.71 mM) or day 5 (sucrose group: BG 8.8 +/- 2.6 mM, F 2.94 +/- 0.32 mM; control group: BG 7.4 +/- 2.8 mM, F 2.92 +/- 0.59 mM). We conclude that ingestion of sucrose, added to snacks in an amount up to 7% of total energy intake, does not adversely affect short-term BG control.