SENSORY DIFFERENCE TESTS: THURSTONIAN AND SSA PREDICTIONS FOR VANILLA FLAVORED YOGURTS

The Thurstonian prediction that judges will get a higher proportion of correct 3-AFC tests than triangle tests was confirmed using a yogurt system. As predicted, d' values for the triangle and 3-AFC tests corresponded. Sequential Sensitivity Analysis predictions for the sensitivity of various tasting sequences were confirmed for the 3-AFC test but not the triangle test. Further predictions that the 2-AFC is more sensitive than the 3-AFC were confirmed. This increase in sensitivity more than offset the greater statistical power of the 3-AFC. Difficulties of specifying the nature of the difference for the 2-AFC and 3-AFC tests were overcome using a warm-up procedure.     

THURSTONIAN MODELS AND VARIANCE I: EXPERIMENTAL CONFIRMATION OF COGNITIVE STRATEGIES FOR DIFFERENCE TESTS AND EFFECTS OF PERCEPTUAL VARIANCE

For the triangle, duo‐trio, same‐different and 2‐AFC methods, using a model system, mean d′ values for the same subjects, discriminating between the same taste stimuli, were not significantly different. This confirmed the postulated cognitive strategies used for these methods in their respective Thurstonian/signal detection models. Introduction of perceptual variance as a result of the effects of sequences of tasting within a test, forgetting stimulus perceptions and τ‐criterion variation resulted in the 2‐AFC eliciting a significantly higher d′ than the other three methods. Yet, after a warm‐up procedure, which not only significantly increased values of d′ for all methods but also aligned subjects' τ‐criteria, the same‐different test had a d′ comparable to that of the 2‐AFC, while both d′ values were significantly higher than those of the triangle and duo‐trio. This suggested that effects of memory were more important those of sequence of tasting.     

Taste perception and diet in individuals with Chinese and European ethnic backgrounds

Relationships between taste perception and diet were investigatedin two ethnic groups. The Chinese subjects (n = 30) were bornin the People's Republic of China and were currently livingin the United States. The U.S. subjects (n = 30) were of Europeanancestry. Psychophysical taste intensity functions for sucrosesolutions, NaCl solutions and NaCl in soup were obtained usingmagnitude matching. Pleasantness ratings for the above stimuli,plus sucrose in cookies and NaCl in crackers were obtained usingcategory rating scales. Three-day dietary records and the frequencyof sweet food consumption were also collected. Chinese subjectsassigned higher pleasantness ratings to the higher concentrationsof sucrose in water and showed a tendency to rate sucrose incookies as tasting more pleasant. These higher pleasantnessratings of sucrose were not reflected in increased sugar intake.The Chinese subjects also assigned higher pleasantness ratingsto and preferred higher concentrations of salt in crackers andthis was reflected in the data from the dietary records. TheChinese Na/Kcal and Na/K ratios were greater than those of theU.S. group.     

Rated taste perception in two cultural groups

Intensity and pleasantness ratings of various concentrationsof sucrose, caffeine and NaCl were examined in two culturallydifferent groups of subjects. One group was made up of studentsof European descent born in the United States while the othergroup was made up of students of Chinese descent born in Taiwan.A subsample of subjects from each group was retested similarlywith cookies containing varying levels of sucrose. The Taiwanesesubjects rated sucrose as tasting sweeter regardless of whetherit was in solution or cookies. Group differences in pleasantnessratings depended upon whether the sucrose was presented in acookie or a solution. The Taiwanese students assigned highersweetness ratings to sucrose in solution when compared to USstudents. When the sucrose was in cookies, the Taiwanese groupassigned higher pleasantness ratings at the lower sucrose concentrations.At the higher sucrose concentrations, the US group assignedhigher pleasantness ratings. There was no significant ethniceffect upon rated bitterness or pleasantness of caffeine. Taiwaneserated low concentrations of salt as tasting saltier and highconcentrations of salt as tasting less salty when compared toUS students. The Taiwanese generally rated the sodium chloridesolutions as tasting more pleasant. These group differencesmay be related to the way sucrose and salt are used in the twocultures.     

Effects of amiloride on salt taste in humans

Amiloride reduces several responses of the taste system to NaCl.These effects are crucial support for the ion transport theoryof salt taste. Here, three experiments tested for the inhibitoryeffect of amiloride on salt taste in normal, whole-mouth tastingin humans. There was no evidence that amiloride reduces thesaltiness of NaCl when used as a pretreatment, mixed into solutionwith NaCl, or both. In a fourth experiment, pretreating thetongue with amiloride-soaked filter paper and presenting NaClon filter paper within the treated area also had no effect onsaltiness. In addition, amiloride, a bitter compound, did notsuppress the taste of sucrose, and caffeine did not enhancethe taste of NaCl. These results suggest the ion transport theoryof NaCl taste needs to be modified or extended to account fornormal whole-mouth tasting of NaCl in humans. ¹ Present address: 1605 Harbor Court Tower, 10 East Lee St.,Baltimore, MD 21202, USA     

Suppression of Bitterness by Sodium: Variation Among Bitter Taste Stimuli

Taste interactions between salts (NaCl, LiCl, KCl, L-arginine:L-asparticacid, Na-acetate and Na-gluconate) and bittertasting compounds(urea, quinine HCI, magnesium sulphate, KCI, amiloride HCI andcaffeine) were investigated. In each study binary combinationsof three or four concentrations of one bitter compound withfour concentrations (0, 0.1, 0.3 and 0.5 M) of one salt wererated for bitterness and saltiness using the method of magnitudeestimation. In most cases, perceived bitterness was suppressedby salts, although the degree of suppression varied. In general,bitterness suppression was not accompanied by an equivalentreciprocal suppression of saltiness. Only MgSO₄ and amiloridehad suppressing effects on the saltiness of NaCl at the intermediateconcentrations and no bitter compound affected the saltinessat the high concentrations of NaCl. Since salt suppressed thebitterness of urea effectively, a detailed analysis of suppressionof the bitterness of urea by different salts was conducted.Those studies indicated that the key component in this effectwas the sodium or lithium ion for two reasons: first, all threesodium salts and the lithium salt had a suppressive effect onbitterness, whereas KCl did not; secondly, the effect of a salton suppression of the bitterness of urea was independent ofits perceived saltiness; that is, NaCl, Na-acetate (which isperceived as less salty than NaCl), and Na-gluconate (whichis perceived as less salty than Na-acetate) reduced bitternesscomparably. These results suggest that there is a major peripheralcomponent to the suppression of the bitterness of urea, andperhaps other bitter tasting compounds, by sodium. Chem. Senses20: 609–623, 1995.     

Running to the taste of salt in mineralocorticoid-treated rats

In the present series of studies, the running speed of rats in a runway was used to measure appetitive motivation for different concentrations of salt solutions. We found that when rats were thirsty, they were not interested in running for concentrated salt solutions; when they were rendered salt hungry by mineralocorticoid treatment in addition to the thirst, or even without thirst, they ran vigorously for salty tasting solutions, as high as 24% NaCl. The running speed is correlated with the degree of the mineralocorticoid treatment and the salt concentration. Moreover, drinking 5 cc of a 3% NaCl solution before the runway test decreases the running speed of the mineralocorticoid-treated rat. The experiments are discussed in the context of the effects of hormonal events on the movitation to ingest salt solutions.     

SEED GERMINATION RESPONSE AND EVIDENCE FOR HEIGHT ECOPHENES IN SPARTINA ALTERNIFLORA FROM NORTH CAROLINA

A study was conducted to determine germination response to temperature and salinity and seedling response to salinity by three height forms of the salt marsh grass Spartina alterniflora Loisel. Germination tests showed that seeds cannot withstand drying at moderate temperature, as viability was lost within 40 days in seeds stored dry at 72 F. Cold storage at 43 F is adequate to prevent desiccation up to 40 days, but after 8 months viability is lost. Viability is retained at least 8 months when seeds are stored in sea water at 43 F. Germination response was good in a 65–95 F alternating diurnal thermoperiod but was poor in a 72 F constant thermoperiod. Germination response to salinity was an inverse curvilinear relationship with germination inhibition at high salinities apparently due to osmotic effects. The maximum tolerance limit for germination lies between 6 and 8 % NaCl. Seeds from short, medium, and tall plants responded similarly in storage and temperature studies. However, in salinity studies, seeds of the Ocracoke Island short form and the Oak Island tall form performed best. A logarithmic curve best described seedling growth response to various NaCl levels. Growth response as measured by seedling dry weight was best in 0.5 % NaCl solution. Seedlings grew taller in both 0.5 and 1.0 % NaCl than in 0 % NaCl. No significant difference in seedling growth response due to height form of the parent plant was detected. Thus, on the basis of germination and seedling responses, the height forms of S. alterniflora in North Carolina salt marshes are best described as ecophenes.     

NaCl reflection coefficients in proximal tubule apical and basolateral membrane vesicles. Measurement by induced osmosis and solvent drag.

Two independent methods, induced osmosis and solvent drag, were used to determine the reflection coefficients for NaCl (sigma NaCl) in brush border and basolateral membrane vesicles isolated from rabbit proximal tubule. In the induced osmosis method, vesicles loaded with sucrose were subjected to varying inward NaCl gradients in a stopped-flow apparatus. sigma NaCl was determined from the osmolality of the NaCl solution required to cause no initial osmotic water flux as measured by light scattering (null point). By this method sigma NaCl was greater than 0.92 for both apical and basolateral membranes with best estimates of 1.0. sigma NaCl was determined by the solvent drag method using the Cl-sensitive fluorescent indicator, 6-methoxy-N-[3-sulfopropyl]quinolinium (SPQ), to detect the drag of Cl into vesicles by inward osmotic water movement caused by an outward osmotic gradient. sigma NaCl was determined by comparing experimental data with theoretical curves generated using the coupled flux equations of Kedem and Katchalsky. By this method we found that sigma NaCl was greater than 0.96 for apical and greater than 0.98 for basolateral membrane vesicles, with best estimates of 1.0 for both membranes. These results demonstrate that sigma NaCl for proximal tubule apical and basolateral membranes are near unity. Taken together with previous results, these data suggest that proximal tubule water channels are long narrow pores that exclude NaCl.     

Revisiting sugar-fat mixtures: sweetness and creaminess vary with phenotypic markers of oral sensation

Genetic variation in oral sensation presumably influences ingestive behaviors through sensations arising from foods and beverages. Here, we investigated the influence of taste phenotype [6-n-propylthiouracil (PROP) bitterness, fungiform papillae (FP) density] on sweet and creamy sensations from sugar/fat mixtures. Seventy-nine subjects (43 males) reported the sweetness and creaminess of water or milk (skim, whole, heavy cream) varying in sucrose (0-20% w/v) on the general Labeled Magnitude Scale. Sweetness grew with sucrose concentration and when shifting from water to milk mixtures--the growth was greatest for those tasting PROP as most bitter. At higher sucrose levels, increasing fat blunted the PROP-sweet relationship, whereas at lower levels, the relationship was effectively eliminated. Perceived sweetness of the mixture exceeded that predicted from the sum of components at low sucrose concentrations (especially for those tasting PROP most bitter) but fell below predicted at high concentrations, irrespective of fat level. Creaminess increased greatly with fat level and somewhat with sucrose. Those tasting PROP most bitter perceived greater creaminess in the heavy cream across all sucrose levels. Perceived creaminess was somewhat lower than predicted, irrespective of PROP bitterness. The FP density generally showed similar effects as PROP on sweetness and creaminess, (but to a lesser degree) and revealed potential taste-somatosensory interactions in weakly sweet stimuli. These data support that taste phenotype affects the nature of enhancement or suppression of sweetness and creaminess in liquid fat/sugar mixtures. Taste phenotype effects on sweetness and creaminess likely involve differential taste, retronasal olfactory, and somatosensory contributions to these perceptual experiences.     

NaCl intake and preference threshold of spontaneously hypertensive rats.

Both male and female spontaneously hypertensive (SH) rats have an appetite for NaCl solution. The appetite is present when a choice is offered between distilled water and either isotonic or hypertonic (0.25 M) NaCl solution to drink. Total fluid intake (water plus NaCl solution) was greater for SH rats than for controls while food intakes (g/100 g body wt/day) of SH rats were not different from controls. Mean body weight of SH rats was always less than that of controls. The appetite for NaCl solution was accompanied by a significant reduction in preference (detection) threshold. SH rats could detect the difference between distilled water and NaCl solution when the concentration of the latter was 12 mEq/liter compared to a control threshold of 30 mEq/liter. The NaCl appetite and reduced NaCl preference threshold induced by spontaneous hypertension is in marked contrast to the NaCl aversion induced by other types of experimentally induced hypertension in rats. The mechanism or mechanisms responsible for these differences remain for further study.     

Direct magnitude estimation of salt taste intensity with continuous correction for salivary adaptation

Subjects sipped and expectorated NaCl solutions, estimatingintensities by direct magnitude estimation, with and withoutinterstimulus rinsing, while saliva samples were taken priorto each tasting and analysed for sodium. Interstimulus rinsingwas seen to reduce salivary sodium concentrations and elicithigher intensity estimates. Exponents for simple psychophysicalpower functions were seen to be higher in the no-rinsing condition,confirming earlier studies. When the functions were correctedfor adaptation level and chemical activity, the trend in exponentswas reversed; this can be interpreted in terms of context effects.It was also found that power functions only produced the bestfit for approximately half the functions; parabolic functionsproduced approximately half, while a few were best fitted byexponential, linear and logarithmic functions.     

SENSORY SPECIFIC SATIETY IN LEMONADE USING A JUST RIGHT SCALE FOR SWEETNESS1

Lemonade samples varying in sucrose concentration (4-15%) were evaluated by either a sip procedure (subjects tasted 10 mL samples) or a drink procedure (subjects consumed 60 mL samples) using a “just right” scale. The order of tasting the four lemonade samples was also balanced among subjects. Neither the amount of lemonade consumed during the test nor the sex of the subjects had an effect on the scores assigned to the samples or the just right sucrose concentration determined by linear regressions. The less pleasant samples (those scored farther from the just right point) showed sensory specific satiety evidenced by a shift away from the just right point on repeated tasting. Samples rated more pleasant or closer to the just right point did not show evidence of sensory specific satiety.     

Gestational and early postnatal dietary NaCl levels affect NaCl intake, but not stimulated water intake, by adult rats

We examined body fluid regulation by weanling (21-25 days) and adult (>60 days) male rats that were offspring of dams fed chow containing either 0.1, 1, or 3% NaCl throughout gestation and lactation. Weanling rats were maintained on the test diets until postnatal day 30 and on standard 1% NaCl chow thereafter. Ad libitum water intake by weanlings was highest in those fed 3% NaCl and lowest in those fed 0.1% NaCl. Adult rats maintained on standard NaCl chow consumed similar amounts of water after overnight water deprivation or intravenous hypertonic NaCl (HS) infusion regardless of early NaCl condition. Moreover, baseline and HS-stimulated plasma Na(+) concentrations also were similar for the three groups. Nonetheless, adult rats in the early 3% NaCl group consumed more of 0.5 M NaCl after 10 days of dietary Na(+) deprivation than did rats in either the 1% or 0.1% NaCl group. Interestingly, whether NaCl was consumed in a concentrated solution in short-term, two-bottle tests after dietary Na(+) deprivation or in chow during ad libitum feeding, adult rats in the 3% NaCl group drank less water for each unit of NaCl consumed, whereas rats in the 0.1% NaCl group drank more water for each unit of NaCl consumed. Thus gestational and early postnatal dietary NaCl levels do not affect stimulated water intake or long-term body fluid regulation. Together with our previous studies, these results suggest that persistent changes in NaCl intake and in water intake associated with NaCl ingestion reflect short-term behavioral effects that may be attributable to differences in NaCl taste processing.     

Behavioral and neural responses of toads to salt solutions correlate with basolateral membrane potential of epidermal cells of the skin

Dehydrated toads initiated water absorption response (WR) behavior and absorbed water from dilute NaCl solutions. With 200-250 mM NaCl, WR behavior and water absorption were both suppressed. With 200-250 mM Na-gluconate, WR initiation was significantly greater than with NaCl but water loss was greater. Neural recordings from spinal nerve #6 showed a greater integrated response to 250 mM NaCl than to 250 mM Na-gluconate, whereas a larger rinse response was seen with Na-gluconate. Studies with isolated epithelium showed a large increase in conductance (G(t)) when 250 mM NaCl replaced NaCl Ringer's as the apical bathing solution that was accompanied by depolarization of the transepithelial potential (V(t)) and basolateral membrane potential (V(b)). Depolarization of V(b) corresponded with the neural response to 250 mM NaCl. When 250 mM Na-gluconate replaced Ringer's as the apical solution G(t) remained low, V(b) transiently hyperpolarized to values near the equilibrium potential for K(+) and corresponded with the reduced neural response. These results support the hypothesis that chemosensory function of the skin is analogous to that of mammalian taste cells but utilizes paracellular ion transport to a greater degree.     

Isolation of haloarchaea that grow at low salinities

Summary Archaea, the third domain of life, were long thought to be limited to environmental extremes. However, the discovery of archaeal 16S rRNA gene sequences in water, sediment and soil samples has called into question the notion of Archaea as obligate extremophiles. Until now, none of these novel Archaea has been brought into culture, a critical step for discovering their ecological roles. We have cultivated three novel halophilic Archaea (haloarchaea) genotypes from sediments in which the pore-water salinity was close to that of sea water. All previously reported haloarchaeal isolates are obligate extreme halophiles requiring at least 9% (w/v) NaCl for growth and are typically the dominant heterotrophic organisms in salt and soda lakes, salt deposits and salterns. Two of these three newly isolated genotypes have lower requirements for salt than previously cultured haloarchaea and are capable of slow growth at sea-water salinity (2.5% w/v NaCl). Our data reveal the existence of Archaea that can grow in non-extreme conditions and of a diverse community of haloarchaea existing in coastal salt marsh sediments. Our findings suggest that the ecological range of these physiologically versatile prokaryotes is much wider than previously supposed.     

Thirst and salt appetite responses in young and old Brown Norway rats

Male Brown Norway rats aged 4 mo (young) and 20 mo (old) received a series of experimental challenges to body fluid homeostasis over approximately 3 mo. Water was available for drinking in some tests, and both water and 0.3 M NaCl were available in others. The series included three episodes of extracellular fluid depletion (i.e., furosemide + 20 h of sodium restriction), two tests involving intracellular fluid depletion (i.e., hypertonic saline: 1 or 2 M NaCl at 2 ml/kg body wt sc), one test involving overnight food and fluid restriction, and testing with captopril adulteration of the drinking water (0.1 mg/ml) for several days. Old rats were significantly heavier than young rats throughout testing. Old rats drank less water and 0.3 M NaCl after sodium deprivation than young rats, in terms of absolute and body weight-adjusted intakes. Old rats drank only half as much water as young rats in response to subcutaneous hypertonic NaCl when intakes were adjusted for body weight. Old rats drank less 0.3 M NaCl than young rats after overnight food and fluid restriction when intakes were adjusted for body weight. In response to captopril adulteration of the drinking water, young rats significantly increased daily ingestion of 0.3 M NaCl when it was available as an alternative to water and significantly increased daily water intakes when only water was available, in terms of absolute and body weight-adjusted intakes. Old rats had no response to captopril treatment. These results add important new information to previous reports that aging rats have diminished thirst and near-absent salt appetite responses to regulatory challenges.     

影响干红葡萄酒感官质量的因素分析

以116个干红葡萄酒酒样为样本,通过多项式回归构建出反映陈酿时间、酒精含量、残糖量以及是否在橡木桶中陈酿与感官质量之间关系的方程．并且通过回归方程的预测,确定出感官分析结果与各影响因素之间的数量关系。     

SELEX selection of high-affinity oligonucleotides for bacteriophage Ff gene 5 protein

The Ff gene 5 protein (g5p) is a cooperative ssDNA-binding protein. SELEX was used to identify DNA sequences favorable for g5p binding at physiological ionic strength (200 mM NaCl) and 37 degrees C. Sequences were selected from a library of 58-mers that contained a central variable segment of 26 nucleotides. DNA sequences selected after eight rounds of SELEX were mostly G-rich, with multiple copies of CPuGGPy, TPuGGGPy, and/or PyPuPuGGGPy motifs. This was unexpected, since g5p has higher binding affinities for polypyrimidine than for polypurine sequences. The most recurrent G-rich sequence, named I-3, was found to have g5p-binding properties that were correlated with a structural transition. At 10 mM NaCl, I-3 existed in a single-stranded form that was saturated by g5p in an all-or-none fashion. At 200 mM NaCl, I-3 existed in a structured form that showed CD spectral features of G-quadruplexes. The g5p binding affinity for this structured form of I-3 was >100-fold higher than for the single-stranded form. Moreover, the structured I-3 was saturated by g5p in two steps, the first of which was the formation of an apparent initiation complex consisting of one I-3 strand and about three g5p dimers. Nuclease S1 footprinting and other experiments showed that g5p molecules in the initiation complex at 200 mM NaCl were bound directly to the G-rich variable segment and that the structure of I-3 was retained after saturation by g5p. Thus, G-rich motifs may form structures favorable for initiation of g5p binding and also provide the actual g5p-binding sites.