Interactions of astringent substances

Two-component mixtures of astringent materials were rated forperceived intensity of astringent and taste attributes overtime. Components included alum (a complex salt), gallic acid(the monomeric component of hydrolyzable tannins), catechin(the monomeric component of condensed tannins) and citric acid.Mixtures of alum and gallic acid showed mixture suppression,in that the 50/50 mixture was less intense than either componentin astringency, drying, roughing and puckery/drawing sensations.Suppression was seen at concentration levels producing moderateto strong astringency but was absent or less pronounced at lowerconcentration levels. A similar pattern held for citric acid,although the suppressive effects were less pronounced. Catechinand gallic acid mixtures were additive. Sensory interactionsbetween astringent materials appears to depend on the substancesinvolved and their concentrations (or intensity levels).     

Fine root production of astringent phenolics

Summary Chemical quality of fine roots (<1 mm diameter) was determined over a gradient of species composition in the Mixed Mesophytic Forest Region. Ash-free nitrogen, calcium, and phosphorus concentrations of roots declined by 49, 41, and 72%, respectively, over a gradient of increasing soil acidity (pH 5.3 to 4.7). Lignin concentration was unrelated to either the vegetation gradient or any of the soil changes it encompassed; however, astringent phenolics increased by 275% over the same gradient. Trends in the chemical constituency of fine roots suggest that the production of phenolics in below-ground plant parts is increased on nutrient-poor sites. This response is best related to changes in species composition, especially increasing importancy of Quercus spp.This investigation (No. 88-8-36) is connected with a project of the Kentucky Agricultural Experiment Station and is published with the approval of the Director     

Scatter-hoarding rodents prefer slightly astringent food

The mutualistic interaction between scatter-hoarding rodents and their seed plants is highly complex yet poorly understood. Plants may benefit from the seed dispersal behavior of rodents, as long as seed consumption is minimized. In parallel, rodents may maximize foraging efficiency and cache high-quality resources for future consumption. Defensive compounds, such as tannins, are thought to be a major mechanism for plant control over rodent behavior. However, previous studies, using naturally occurring seeds, have not provided conclusive evidence supporting this hypothesis. Here, we test the importance of tannin concentrations on the scatter-hoarding behavior of rodents by using an artificial seed system. We combined feeding trials and field observations to examine the overall impact of seed tannin concentrations on rodent behavior and health. We found that rodents favored seeds with an intermediate amount of tannin (~5%) in the field. Meanwhile, in rodents that were fed a diet with different tannin content, only diets with high tannin content (25%, 15%, and 10%) caused a significant negative influence on rodent survival and health. Significant differences were not found among treatments with tannin levels of 0-5%. In contrast to many existing studies, our results clearly demonstrate that scatter-hoarding rodents prefer slightly 'astringent' food. In the co-evolutionary arms race between plants and animals, our results suggest that while tannins may play a significant role in reducing general predation levels by the faunal community, they have no precise control over the behavior of their mutualistic partner. Instead, the two partners appear to have reached an evolutionary point where both parties receive adequate benefits, with the year-to-year outcome being dependent on a wide range of factors beyond the control of either partner.     

Systematic aspects of the astringent tannins of Acer species

Leaves of a further 25 species of Acer, mostly from Asia and N. America, show similar levels of astringency and distribution of condensed and hydrolysable tannins to those previously examined. The results are tabulated and discussed in accordance with de Jong's recent rearrangement of the genus.     

Responses of lipid membranes of taste sensor to astringent and pungent substances

Astringent substances and pungent substances were studied usinga multichannel taste sensor with lipid membranes. The electric-potentialpattern constructed of eight outputs from the membranes hasinformation of taste quality and intensity. Pungent substances,such as capsaicin, pipeline and allyl isothiocyanate, had noeffect on the membrane potentials of the lipid membranes. Onthe other hand, astringent substances such as tannic acid, catechin,gallic acid and chlorogenic acid changed the potentials remarkably.A principal component analysis of the patterns in electric potentialchanges caused by tbe taste substances revealed the astringencyis located between bitterness and sourness.     

The effect of tesofensine on appetite sensations

Tesofensine (TE), an inhibitor of monoamine presynaptic reuptake, has produced twice the weight loss seen with currently marketed drugs. However, its long term effect on appetite in humans has not been studied. A multicentre phase II trial was divided into two parts (24 weeks each). Part 1 had a randomized, double‐blind, placebo‐controlled design and Part 2, an open‐labeled, single‐group, uncontrolled design. A drug‐free period (12 ± 3 weeks) separated them. In Part 1, participants (n = 158) were assigned to 0.25, 0.5 or 1.0 mg TE, or placebo. Completers of Part 1 were invited to participate in Part 2 (n = 113), during which they all received 0.5 or 1.0 mg TE. Appetite sensations and a composite satiety score (CSS = satiety + fullness + (100 − hunger) + (100 − prospective food consumption) were assessed. In Part 1 TE induced a dose‐dependent increase in CSS at week 12 that correlated with weight loss during the 24 weeks (r = 0.36, P < 0.0001). However, CSS diminished over time as weight loss progressed (e.g., for 1.0 mg; 52 ± 17 mm; 64 ± 13 mm; 55 ± 13 mm at baseline, week 12 and week 24, respectively). After drug withdrawal CSS returned to baseline values (50 ± 17 mm, in the whole sample.), despite the participants' reduced‐weight state (−7.2 ± 6.7 kg, P < 0.0001). The reintroduction of TE in Part 2 increased CSS again (56 ± 17 mm at week 60), regardless of initial treatment/weight loss. We postulate that enhanced satiety is involved in early weight loss. Whether the attenuated effect on appetite seen after 24 weeks is due to a counteracting effect in the weight reduced state or whether the appetite suppressing effect of TE per se diminishes over time is, however, still unclear.     

Gating of spontaneous somatic sensations by movement

Movement is known to attenuate the perception of tactile stimuli delivered on the moving part of the body, and this gating diminishes the greater the distance from the moving part. However, does it influence the perception of sensations occurring spontaneously without external triggers? In Experiment 1, participants were asked to focus on one hand while moving or not moving their thumb, and thereafter to map and describe the spatial and qualitative attributes of sensations perceived over the remaining, motionless part of the hand. The results show that movement reduces the frequency, spatial extent, and intensity of sensations, but also participants’ confidence about their spatial characteristics. As expected, gating decreased the greater the distance from the moving thumb. Furthermore, gating was greater for distal than proximal segments of the hand, suggesting a hierarchical proximo-distal suppression. Experiment 2 ruled out the possibility that these effects were due to tactile sensations elicited by movement. Possible mechanisms of gating in the case of spontaneous sensations are discussed.     

Intraspecific variation in production of astringent phenolics over a vegetation-resource availability gradient

Summary The chemical constituency of flowering dogwood (Cornus florida L.) and red maple (Acer rubrum L.) foliage was analyzed over a species compositional gradient to test the hypothesis that over subtle gradients of moisture and nutrient availability production of phenolic compounds will be increased on sites of greatest stress. Calcium and nitrogen concentrations declined along the gradient in both species, while phosphorus showed a significant decline only in red maple. Lignin concentrations in both species were unrelated to the vegetation gradient, but astringent phenolics increased by 156% and 159% in dogwood and red maple, respectively. The correlation between production of polyphenolds and site quality supports previous observations that under conditions of environmental stress production of many secondary compounds is increased, and suggests that this relationship is significant over subtle environmental gradients.This investigation (No. 86-8-104) is connected with a project of the Kentucky Agricultural Experiment Station and is published with the approval of the director. This is publication no. 10 of Lilley Cornett Woods: Appalachian Research Station of Eastern Kentucky University, Richmond, Kentucky     

Turbidity as a measure of salivary protein reactions with astringent substances

Binding of tannins to proline-rich proteins has been proposed as an initial step in the development of astringent sensations. In beer and fruit juices, formation of tannin-protein complexes leads to the well-known effect of haze development or turbidity. Two experiments examined the development of turbidity in human saliva when mixed with tannins as a potential in vitro correlate of astringent sensations. In the first study, haze was measured in filtered human saliva mixed with a range of tannic acid concentrations known to produce supra-threshold psychophysical responses. The second study examined relationships among individual differences in haze development and the magnitude of astringency ratings. Mostly negative correlations were found, consistent with the notion that high levels of salivary proteins protect oral tissues from the drying effects of tannic acid.     

Thresholds of microwave-evoked warmth sensations in human skin

We measured thresholds for microwave-evoked skin sensations of warmth at frequencies of 2.45, 7.5, 10, 35, and 94 GHz. In the same subjects, thresholds of warmth evoked by infrared radiation (IR) were also measured for comparison. Detection thresholds were measured on the skin in the middle of the back in 15 adult male human subjects at all microwave (MW) frequencies and with IR. Long duration (10-s), large area (327-cm²) stimuli were used to minimize any differential effects of temporal or spatial summation. Sensitivity increased monotonically with frequency throughout the range of microwave frequencies tested. The threshold at 94 GHz (4.5 ± 0.6 mW/cm²) was more than an order of magnitude less than at 2.45 GHz (63.1 ± 6.7 mW/cm²), and it was comparable to the threshold for IR (5.34 ± 1.07 mW/cm²). Bioelectromagnetics 18:403–409, 1997. © 1997 Wiley-Liss, Inc.     

How haptic size sensations improve distance perception

Determining distances to objects is one of the most ubiquitous perceptual tasks in everyday life. Nevertheless, it is challenging because the information from a single image confounds object size and distance. Though our brains frequently judge distances accurately, the underlying computations employed by the brain are not well understood. Our work illuminates these computions by formulating a family of probabilistic models that encompass a variety of distinct hypotheses about distance and size perception. We compare these models' predictions to a set of human distance judgments in an interception experiment and use Bayesian analysis tools to quantitatively select the best hypothesis on the basis of its explanatory power and robustness over experimental data. The central question is: whether, and how, human distance perception incorporates size cues to improve accuracy. Our conclusions are: 1) humans incorporate haptic object size sensations for distance perception, 2) the incorporation of haptic sensations is suboptimal given their reliability, 3) humans use environmentally accurate size and distance priors, 4) distance judgments are produced by perceptual "posterior sampling". In addition, we compared our model's estimated sensory and motor noise parameters with previously reported measurements in the perceptual literature and found good correspondence between them. Taken together, these results represent a major step forward in establishing the computational underpinnings of human distance perception and the role of size information.     

Improving recognition of respiratory sensations in healthy adults

In two discrimination training studies, we noted improvements in the ability of healthy individuals to discriminate between respiratory sensations. We trained individuals to discriminate between respiratory sensations elicited during inspiration in Experiment 1 and during expiration in Experiment 2. We elicited respiratory sensations by having participants breathe through circuits that differed in their resistance to air flow. Training, in both experiments, was conducted within the context of a task in which individuals judged which member of a series of respiratory circuit pairs was easier to breathe through. To improve the accuracy of judgments, we gave participants feedback of their performance, and we faded air flow resistance. The latter procedure consisted of presenting circuit pairs in order of increasing similarity. Individuals who received performance feedback with fading of air flow resistance demonstrated reliable improvements in discrimination from pre- to posttraining in both experiments, but controls, who received either performance feedback or practice in discrimination did not. These findings may contribute to improving awareness of respiratory sensations in asthma patients, and thereby bolster efforts to manage asthma.This research was supported by a Biomedical Research Support Grant from the National Institute of Health to Ohio University and by an Academic Challenge Grant from the State of Ohio to the Ohio University Psychology Department.     

Time-course data prediction for repeatedly measured gene expression

Variability in time course gene expression data is a natural phenomenon. The intention of this work is to predict the future time point data through observed sample data point. The Bayesian inference is carried to serve the objective. A total of 6 replicates 3 time point's data of 218 genes expression is adopted to illustrate the method. The estimates are found consistent with HPD interval to predict the future time point gene expression value. This proposed method can be adopted in other gene expression data setup to predict the future time course data.     

Time-course of cardiac myocyte injury due to oxidative stress

Time course of changes in cell morphology, cation content, lipid peroxidation and high energy phosphates was examined in isolated rat cardiac myocytes exposed to oxygen radicals for 0 to 20 min. Xanthine (2 mM) and xanthine oxidase (10 U/L) mixture was used as a source of oxygen radicals. A significant decrease in the number of rod-shape cells with a concomitant increase in the number of hypercontracted cells was observed within 5 min of exposure to xanthine-xanthine oxidase (x-xo). At 10,15 and 20 min of exposure to x-xo, there was a time-dependant increase in the number of round cells. Lipid peroxide content, as indicated by the thiobarbituric acid reactive material, was significantly and progressively increased between 10 to 20 min of perfusion with x-xo. In myocytes exposed to x-xo, Ca²⁺ and Na⁺ were increased by 15% and 45% at 15 min and by 55% and 100% at 20 min respectively. Levels of adenosine tri- and di- phosphates were significantly depressed and that of adenosine mono- phosphate were higher at 20 min. These data support the hypothesis that reactive oxygen intermediates can directly influence myocyte structure and function, but these changes seem to occur more slowly in isolated myocytes than in whole hearts.     

Time-course analysis of cyanobacterium transcriptome: detecting oscillatory genes

The microarray technique allows the simultaneous measurements of the expression levels of thousands of mRNAs. By mining these data one can identify the dynamics of the gene expression time series. The detection of genes that are periodically expressed is an important step that allows us to study the regulatory mechanisms associated with the circadian cycle. The problem of finding periodicity in biological time series poses many challenges. Such challenge occurs due to the fact that the observed time series usually exhibit non-idealities, such as noise, short length, outliers and unevenly sampled time points. Consequently, the method for finding periodicity should preferably be robust against such anomalies in the data. In this paper, we propose a general and robust procedure for identifying genes with a periodic signature at a given significance level. This identification method is based on autoregressive models and the information theory. By using simulated data we show that the suggested method is capable of identifying rhythmic profiles even in the presence of noise and when the number of data points is small. By recourse of our analysis, we uncover the circadian rhythmic patterns underlying the gene expression profiles from Cyanobacterium Synechocystis.