Amiloride Effects on Taste Quality: Comparison of Single and Multiple Response Category Procedures

Although there is compelling evidence that amiloride reducesthe intensity of Na⁺ and Li⁺ salts in humans, its effects onsaltiness are conflicting. Many salts elicit not only a saltytaste but also one or more side tastes (sweetness, sournessor bitterness). Some studies have shown a suppression of saltinessby amiloride; others show no effect on saltiness but a significantreduction in sourness. In the experiments demonstrating a reductionof saltiness, subjects estimated only saltiness; in those showingan amiloride effect on sourness and not saltiness, subjectsestimated all qualities on each trial. The present study examinesthe role of the psychophysical method in these conflicting results.We have investigated the effects of amiloride on taste qualityby modifying only the instructions to the subjects, keepingall other variables constant. One group of subjects (intensity-only)gave magnitude estimates of the overall intensity of a LiCIconcentration series. A second group (salty-only) was instructedto estimate the saltiness of the stimuli, and a third group(sour-only) estimated their sourness. Finally, a fourth group(profile) rated all of the taste qualities on each stimuluspresentation, using a modified taste profile method. The ratingsof all groups were made comparable by the use of 0.1 mM quinine-HCIas a modulus. When subjects used only one response category,amiloride reduced their estimates (of intensity, saltiness orsourness), but if subjects attended to all four qualities, amiloridespecifically reduced the sourness of LJCI and had no significanteffect on its saltiness. Comparison of the saltiness estimatesof the salty-only group to the sum of the salty and sour estimatesof the profile group demonstrated that subjects combined thesesensations when presented with only one response alternative.To reveal the effect of amiloride on a specific quality of asalt, the psychophysical method must allow subjects to attendto all qualities on each trial. These data and previous resultssuggest that apical Na⁺ channels on the taste receptor cellmembrane mediate the sourness but not the saltiness of Na⁺ andLi⁺ salts. Chem. Senses 22: 267–275, 1997.     

Altered fractal dynamics of gait: reduced stride-interval correlations with aging and Huntington's disease

Hausdorff, Jeffrey M., Susan L. Mitchell, RenéeFirtion, C. K. Peng, Merit E. Cudkowicz, Jeanne Y. Wei, and Ary L. Goldberger. Altered fractal dynamics of gait: reducedstride-interval correlations with aging and Huntington's disease.J. Appl. Physiol. 82(1): 262-269, 1997.Fluctuationsin the duration of the gait cycle (the stride interval) display fractaldynamics and long-range correlations in healthy young adults. Wehypothesized that these stride-interval correlations would be alteredby changes in neurological function associated with aging and certaindisease states. To test this hypothesis, we compared thestride-interval time series of 1) healthy elderly subjects andyoung controls and of 2) subjects with Huntington's diseaseand healthy controls. Using detrended fluctuation analysis, we computed, a measure of the degree to which one stride interval is correlatedwith previous and subsequent intervals over different timescales. The scaling exponent  was significantly lower in elderlysubjects compared with young subjects (elderly: 0.68 ± 0.14; young:0.87 ± 0.15; P < 0.003). The scaling exponent  wasalso smaller in the subjects with Huntington's disease compared withdisease-free controls (Huntington's disease: 0.60 ± 0.24;controls: 0.88 ± 0.17; P < 0.005). Moreover,  was linearly related to degree of functional impairment in subjects withHuntington's disease (r = 0.78, P < 0.0005).These findings demonstrate that stride-interval fluctuations are morerandom (i.e., less correlated) in elderly subjects and in subjects with Huntington's disease. Abnormal alterations in the fractal properties of gait dynamics are apparently associated with changes in central nervous system control.

     

Correlation between ventilation and EEG-defined arousal during sleep onset in young subjects

Trinder, John, John A. Van Beveren, Philip Smith, JanKleiman, and Amanda Kay. Correlation between ventilation and EEG-defined arousal during sleep onset in young subjects.J. Appl. Physiol. 83(6):2005-2011, 1997.In studies of elderly individuals, ventilationand EEG-defined arousal have been shown to vary periodically andsynchronously. Such results have been interpreted as indicating theprimacy of sleep/wake state in causing ventilatory instability duringsleep onset. However, because the elderly individuals studied wereperiodic breathers, the results do not unequivocally support thisconclusion. In this study the relationship between ventilation andEEG-defined arousal was assessed in a group of 21 young, healthy men inwhom ventilatory instability during sleep onset was not periodic.Ventilation and EEG(O₁-A₂)recordings were collected, and the longest uncontaminated periods fromearly and late in sleep onset were selected for subsequent analysis.The 84 time series (21 subjects, 2 variables, and 2 occasions in sleeponset) were subjected to spectral analysis to identify periodicity, and the relationship between the two variables was determined bycross-correlational methods. The results indicated that the time serieswere nonperiodic, yet significant correlations were observed betweenthe two variables. The data support the view that during sleep onsetventilatory instability is driven primarily by variations in sleep/wakearousal level.

     

Exposures to conditioned flavours with different hedonic values induce contrasted behavioural and brain responses in pigs

This study investigated the behavioural and brain responses towards conditioned flavours with different hedonic values in juvenile pigs. Twelve 30-kg pigs were given four three-day conditioning sessions: they received three different flavoured meals paired with intraduodenal (i.d.) infusions of 15% glucose (F(Glu)), lithium chloride (F(LiCl)), or saline (control treatment, F(NaCl)). One and five weeks later, the animals were subjected to three two-choice feeding tests without reinforcement to check the acquisition of a conditioned flavour preference or aversion. In between, the anaesthetised pigs were subjected to three (18)FDG PET brain imaging coupled with an olfactogustatory stimulation with the conditioned flavours. During conditioning, the pigs spent more time lying inactive, and investigated their environment less after the F(LiCl) than the F(NaCl) or F(Glu) meals. During the two-choice tests performed one and five weeks later, the F(NaCl) and F(Glu) foods were significantly preferred over the F(LICl) food even in the absence of i.d. infusions. Surprisingly, the F(NaCl) food was also preferred over the F(Glu) food during the first test only, suggesting that, while LiCl i.d. infusions led to a strong flavour aversion, glucose infusions failed to induce flavour preference. As for brain imaging results, exposure to aversive or less preferred flavours triggered global deactivation of the prefrontal cortex, specific activation of the posterior cingulate cortex, as well as asymmetric brain responses in the basal nuclei and the temporal gyrus. In conclusion, postingestive visceral stimuli can modulate the flavour/food hedonism and further feeding choices. Exposure to flavours with different hedonic values induced metabolism differences in neural circuits known to be involved in humans in the characterization of food palatability, feeding motivation, reward expectation, and more generally in the regulation of food intake.     

A parametric study of flavoured food avoidance in chicks

It has previously been shown that the ability of the chick toassociate the consumption of novel flavoured substances withsubsequent malaise is specific to the mode of ingestion (Gilletteet al., 1980), i.e., chicks will readily form conditioned aversionsto weakly flavoured solutions but not to relatively stronglyflavoured foods. The present series of four experiments indicatedthat the failure of chicks to develop conditioned aversionsto flavoured food is not due to the parameters of flavour intensity (salience), conditioned stimulus duration, or tastequality. Altering the validity of visual cues did not facilitateflavour avoidance nor did compounding the flavour cue with avisual cue. Although chicks showed increasing neophobia forincreasing concentrations of NaCl flavoured food, they did notlearn to avoid the food relative to controls (Experiment 1).Similarly, varying the amount of time allowed for ingestingthe NaCl flavoured food produced no differences between groups(Experiment 2). Since it was possible that NaCl might produceconsiderable malaise in its own right, the third experimentwas a partial replication of Experiment 2 using sucrose flavouredfood. Again, there was no effect due to conditioned stimulusduration. The final experiment showed, firstly, that the failureto develop flavour aversions cannot be attributed to overshadowingby familiar visual cues and, secondly, that aversions for NaClflavoured food cannot be potentiated by the presence of a noveland highly salient visual cue. These results suggest that previousfailures to demonstrate flavoured food aversions in chicks arenot due to procedural inadequacies but, rather, due to an organismicconstraint. Whether this constraint is associative, physiologicalor attentional remains to be determined. The authors express appreciation to Marion Connors, Paula Halland Graeme Negri for technical assistance.     

Older adults can maximally activate the biceps brachii muscle by voluntary command

De Serres, Sophie J., and Roger M. Enoka. Older adultscan maximally activate the biceps brachii muscle by voluntary command.J. Appl. Physiol. 84(1): 284-291, 1998.Because some of the decline in strength with age may beexplained by an impairment of muscle activation, the purpose of thisstudy was to determine the activation level achieved in biceps brachiiby older adults during a maximum voluntary contraction (MVC). Thiscapability was assessed with two superimposition techniques: onecalculated the activation level that was achieved during an MVC, andthe other provided an estimate of the expected MVC force based on extrapolation with submaximal forces. The activation level in bicepsbrachii was incomplete (<100%) for the young(n = 16) and elderly(n = 16) subjects, with the elderlysubjects exhibiting the greater deficit. In contrast, there was nodifference between the measured and expected MVC forces for eithergroup of subjects, whether the extrapolation involved a third-orderpolynomial or linearization of the data. Because of the lowersignal-to-noise ratio associated with the measurement of activationlevel and the greater number of measurements that contributed to theestimate of the expected MVC force, we conclude that the older adultswere able to achieve complete activation of the biceps brachii muscle during an MVC.

     

Odor Perception Phenotypes: Multiple, Specific Hyperosmias to Musks

Olfactory detection thresholds for 11 structurally diverse muskodorants and one non-musk odorant were obtained from 32 subjects.Hierarchical cluster analysis produced four groups of subjects.One group (n = 12) was uniformly sensitive to all musks; another(n = 16) was uniformly insensitive. Two groups of subjects containedotherwise insensitive individuals who were exceptionally sensitiveto cyclopentadecanone and musk xylol (n = 2) and to delta9-hexadecenolactoneand tonalid (n = 2) respectively. We propose that the lattertwo groups are odor perception phenotypes (MSHM1 and MSHM2)that consist of multiple, specific hyperosmias to musk odorants.Chem. Senses 21: 411– 416, 1996. ¹Present address: Synesthetics, Inc., Montclair, NJ 07043, USA     

An improved statistical methodology to estimate and analyze impedances and transfer functions

Curran-Everett, Douglas, Yiming Zhang, M. Douglas Jones,Jr., and Richard H. Jones. An improved statistical methodology toestimate and analyze impedances and transfer functions. J. Appl.Physiol. 83: 2146-2157, 1997.Estimating the mathematical relationship between pulsatile time series (e.g., pressure and flow) isan effective technique for studying dynamic systems. Thefrequency-domain relationship between time series, often calculated asan impedance (pressure/flow), is known more generally as a frequency-response or transfer function (output/input). Current statistical methods for transfer function analysis 1) assumeerroneously that repeated observations on a subject are independent,2) have limited statistical value and power, or 3) arerestricted to use in single subjects rather than in an entire sample.This paper develops a regression model for transfer function analysisthat corrects each of these deficiencies. Spectral densities of the input and output time series and the cross-spectral density between them are first estimated from discrete Fourier transforms and then usedto obtain regression estimates of the transfer function. Statisticalcomparisons of the transfer function estimates use a test statisticthat is distributed as ². Confidence intervals foramplitude and phase can also be calculated. By correctly modelingrepeated observations on each subject, this improved statisticalapproach to transfer function estimation and analysis permits thesimultaneous analysis of data from all subjects in a sample, improvesthe power of the transfer function model, and has broad relevance tothe study of dynamic physiological systems.

     

Ontogeny of Song Recognition in Birds

SYNOPSIS. This paper reviews song recognition in two congenericspecies of sparrow the swamp sparrow (Melospiza georgiana) andsong sparrow (Melospiza melodia). Data from psychophysical studiesof hearing, tutoring experiments with young birds, and fieldplayback studies with adult birds are considered together inorder to gain insight into the mechanisms of species recognitionthrough song development. In aggregate, the evidence suggestsa multi-stage process of song development consisting of an earlyperceptual preference for learning conspecific song, a sensorimotorphase of song development during which vocal output matchesan auditory memory as if through trial and error, and a finalphase of full song which functions in territorial defense andmate attraction.     

Maternal Effects on Offspring Quality in Poeciliid Fishes

SYNOPSIS. We evaluated the effects of maternal environment onoffspring size and composition in three species of poeciliidfishes. We chose food availability as the environmental factorfor study. Mature females were assigned to either high or lowfood for an interval of time, then randomly reassigned to highor low food, with the restriction that there be equal numbersin each of four treatments: high-high, high-low, lowhigh, andlow-low food availability. The three species chosen for studydiffer in the pattern of maternal provisioning. Poecilia reticulataand Priapichthys festae mothers provide all resources necessaryfor development as yolk, prior to fertilization. In contrast,Heterandria formosa mothers continue to provision the youngthroughout development. These species also differ in whetheror not they have superfetation, or the ability to carry multiplebroods of young in different stages of development. P. reticulatadoes not have superfetation while the other two species do.We were interested in whether the pattern of maternal provisioningor superfetation influenced the maternal effect. The two lecithotrophicspecies responded to low food by producing larger young withgreater fat reserves. H. formosa, the matrotrophic species,responded to low food by producing smaller young. We proposethat the production of large young in the face of low food availabilitymight represent adaptive plasticity; matrotrophy might representa constraint that prevents such an adaptive response. Superfetationhad no impact on this maternal effect.     

高黎贡山赧亢白眉长臂猿食性及日取食量

通过确定白眉长臂猿的取食特征及日取食量,探讨不同个体间和春、秋季间日取食量是否存在差异,分析影响日取食量和取食特征的因素,为白眉长臂猿日能量需求及其营养容纳量研究奠定基础。2007—2008年春、秋季,在高黎贡山赧亢采用焦点动物取样法观察和记录数据。结果发现,白眉长臂猿取食36种食物的40个部位,其果实的食物单元、取食速度、单个鲜重值等取食特征不同于嫩叶。春、秋季白眉长臂猿每日取食果实量所占百分比最高、嫩叶所占百分比次之、茎和花所占百分比最低。春、秋季家群中雌猿的日取食量均高于雄猿。与家群的雌猿相比,独猿(♀)春季的日取食量稍高。在春季,独猿取食果实持续时间约为家群的2倍,而取食嫩叶的则与家群几乎相等。相同个体秋季的日取食量高于春季的,且春、秋季日取食各部位的量所占百分比也不同。分析结果表明,食性及日取食部位的量反映了白眉长臂猿选择食物的最基本策略。雌雄个体大小差异、能量消耗、食物特征、动物生理需求等因素影响白眉长臂猿的日取食量。白眉长臂猿取食持续时间与觅食树的食物资源量相关。     

Recalling Taste Intensities in Sweetened and Salted Liquids

The effect of training on recalling taste intensities over 6weeks was studied using an ad libitum mixing procedure. Subjectstasted sweet and salty standards labeled as ‘weak’and ‘strong’ (3 and 8% sucrose in redcurrant juice;0.4 and 1.2% NaCl in beef broth). They subsequently mixed unsweetenedand sweetened juice, and unsalted and salted broth, to producetaste intensities that corresponded to the standards. A minimumtraining (MT) group (n = 13) produced comparison stimuli bytasting and directly comparing with standards in one sessiononly; an extensive training (ET) group (n = 13) did this insix sessions before producing comparison stimuli based on memoryonly at 1 h, 1 day, 1 week and 6 weeks. An upward bias (chemicallydetermined concentrations of comparison stimuli exceeding thoseof standards) occurred at 1 day or 1 week in MT subjects for‘weak’ and ‘strong’ sweetness, and for‘strong’ saltiness, and sustained thereafter. Theupward tendency was also observed in ET subjects but was significantonly for ‘strong’ sweetness. It is important torecognize memory effects such as the one described, as theyaffect food perceptions and can be a major source of bias insensory food research. Chem. Senses 21: 29–34, 1996. ³Current address: Psychonomics Department, Utrecht University,Heidelberglaan 2, 3584 CS Utrecht, The Netherlands     

AIMIE: a web-based environment for detection and interpretation of significant sequence motifs in prokaryotic genomes

Motivation: Genomes contain biologically significant informationthat extends beyond that encoded in genes. Some of this informationrelates to various short dispersed repeats distributed throughoutthe genome. The goal of this work was to combine tools for detectionof statistically significant dispersed repeats in DNA sequenceswith tools to aid development of hypotheses regarding theirpossible physiological functions in an easy-to-use web-basedenvironment. Results: Ab Initio Motif Identification Environment (AIMIE)was designed to facilitate investigations of dispersed sequencemotifs in prokaryotic genomes. We used AIMIE to analyze theEscherichia coli and Haemophilus influenzae genomes in orderto demonstrate the utility of the new environment. AIMIE detectedrepeated extragenic palindrome (REP) elements, CRISPR repeats,uptake signal sequences, intergenic dyad sequences and severalother over-represented sequence motifs. Distributional patternsof these motifs were analyzed using the tools included in AIMIE. Availability: AIMIE and the related software can be accessedat our web site http://www.cmbl.uga.edu/software.html. Contact: mrazek{at}uga.edu Associate Editor: Alex Bateman     

SW.B6-Soab Nontaster Congenic Strains Completed and a Sucrose Octaacetate Congenic Quartet Tested with other Bitters

Ten SW.B6 SOA nontaster strains congenic with the SWR/J SOAtaster inbred strain were bred via repeated backcross-intercrosscycles, with selection for nontasting in each cycle. Preferenceratio distributions and phenotypic proportions across cyclesat 0.1 mM SOA were consistent with monogenic predictions. TheSW.B6 mice completed a congenic quartet with the SWR/J, B6.SWSOA taster and C57BL/6J SOA nontaster strains. The Soa locuscontrolled avoidance differences within the quartet for SOA,raffinose undecaacetate, glucose pentaacetate and brucine. Backgroundgenes not linked to Soa controlled avoidance differences forL-phenylalanine and ethanol. Avoidance of bitter picric acidwas influenced by the Soa locus, but avoidance of acetic acidwas not. The quartet pattern for quinine HCl was unclear, withindications of both Soa and background effects. Two forms ofribose tetraacetate yielded different patterns. Avoidance differencescontrolled by the Soa locus were found for the pyranose form;however, all four strains avoided the furanose form. The pleiotropiceffects of Soa allele substitution within the quartet were limitedto a subset of bitter compounds. Chem. Senses 21: 507–517,1996.     

FOOD SELECTION IN THE LAND SNAIL LIMICOLARIA FLAMMEA MULLER (PULMONATA: ACHATINIDAE)

Food consumption by juvenile and adult specimens Limicolariaflammea was measured as dry weight of food eaten. The snailwas fed weekly for 15 months on four types of food (lettuce,potato, apple and carrot) and chalk provided, hence an opportunityto select for food. Juvenile snails showed greater selectivitydepending on whether the food was needed for somatic growthor reproduction. On the other hand, when fed exclusively onone each of the same food items and given no opportunity tochoose, the snails grew better on the same food items they selectedin the choice experiment. The absorption efficiencies (AD) werehigh, the utilisation efficiency (ECI) was 1–13% and showeddistinct peaks corresponding to egg production. Values for ECDwere 1.25–15.5%. Variation in growth rates was due mainlyto utilisation efficiencies of the four foods tested. Largeamounts of chalk were eaten during the period of somatic growthand greatly reduced during the reproductive phase of L. flammea.The significance of these findings to the snails ecology isdiscussed. (Received 9 April 1991; accepted 11 June 1991)     

Functional analysis of the immunosenescence of the human B cell system: dissociation of normal activation and proliferation from impaired terminal differentiation into IgM immunoglobulin-secreting cells

The abilities of B cells from 24 young (mean 26 yr) and 24 elderly (mean 86 yr) humans to proliferate and differentiate into immunoglobulin-secreting cells (ISC) were investigated. Initial studies in young subjects demonstrated that a Staph protein A (SpA)-driven system could simultaneously assess the proliferative and differentiative capabilities of B cells resulting in IgM production. B cell proliferative responses were found to be partially T cell-dependent, whereas differentiation was absolutely T cell-dependent. Also, no significant differences could be detected in the abilities of nonproliferating allogeneic and autologous T cells to support B cell responsiveness. Although B cells from elderly subjects continuously exposed to SpA displayed proliferative responses equal to young subjects, the differentiation of B cells from elderly subjects into IgM ISC was markedly reduced as compared to young subjects. Analyses of results from co-culture experiments showed that the differentiation impairments of B cells from some elderly subjects could be partially corrected by allogeneic T cells from young subjects, whereas the impairments of others were more refractory. Moreover, T cells from elderly subjects were able to promote the differentiation of B cells from young subjects. Other experiments in elderly subjects showed that significant impairments of B and T cell functions rarely coexisted and that compensatory increases in B or T cell function were not evident. Thus, B cells from certain elderly humans have intrinsic impairments of differentiation required for optimal IgM production even though activation and proliferation remain normal in the presence of SpA. These impairments in differentiation are sometimes improved by T cells from young subjects, although in some elderly individuals, the differentiative impairments fail to be reversed.     

A fuzzy guided genetic algorithm for operon prediction

Motivation: The operon structure of the prokaryotic genome isa critical input for the reconstruction of regulatory networksat the whole genome level. As experimental methods for the detectionof operons are difficult and time-consuming, efforts are beingput into developing computational methods that can use availablebiological information to predict operons. Method: A genetic algorithm is developed to evolve a startingpopulation of putative operon maps of the genome into progressivelybetter predictions. Fuzzy scoring functions based on multiplecriteria are used for assessing the ‘fitness’ ofthe newly evolved operon maps and guiding their evolution. Results: The algorithm organizes the whole genome into operons.The fuzzy guided genetic algorithm-based approach makes it possibleto use diverse biological information like genome sequence data,functional annotations and conservation across multiple genomes,to guide the organization process. This approach does not requireany prior training with experimental operons. The predictionsfrom this algorithm for Escherchia coli K12 and Bacillus subtilisare evaluated against experimentally discovered operons forthese organisms. The accuracy of the method is evaluated usingan ROC (receiver operating characteristic) analysis. The areaunder the ROC curve is around 0.9, which indicates excellentaccuracy. Contact: roschen_csir{at}rediffmail.com     

Food perception with age and its relationship to pleasantness

Differences between elderly subjects (n = 46, 61-86 years) and young subjects (n = 36, 18-25 years) in food perception and food liking were investigated. Intensity and liking ratings were assessed for custard dessert, in which flavor enrichment, textural change, and irritant addition were incorporated as strategies to compensate for sensory losses with increasing age. The sensory acuity (taste, olfaction, irritation, chewing efficiency) of both young and elderly subjects was measured with the help of different sensitivity tests. The elderly perceived the custards differently from the young, mainly as less intense in flavor (cherry/vanilla) and less intense in creaminess/swallowing effort. Several of the observed interaction effects were different for the elderly and the young. The majority of these differences manifested as lower intensity slopes for the elderly. Losses in sensitivity to taste and to olfactory and trigeminal stimuli as well as a reduced chewing efficiency were observed on average for the elderly compared with the young. Furthermore, subgroups of the elderly were observed in which the compensatory strategies flavor enrichment, textural change, and irritant addition led to an increase in food liking. However, these subgroups did not differ in their sensory acuity. The present study does not support the assumption that age-associated changes in food perception-caused by losses in sensory acuity-inevitably reduce the food liking of the elderly.