TIME-INTENSITY EVALUATION OF ORAL BURN1

Temporal oral burn profiles for cinnamaldehyde, piperine and capsaicin were quantified using time-intensity (TI) parameters. Despite large judge-to-judge variation, TI profiles for eaters and noneaters of chile peppers differed significantly. Eaters had lower maximum intensities, shorter total times, and slower maximum rates of onset and decay. Judges with substantial desensitization also had shorter time-to-maximum intensities. Desensitized judges not only scored the burn of capsaicin as less intense, but also the burn of cinnamaldehyde and piperine. The burn of cinnamaldehyde solutions increased and decayed quickly; whereas, burns due to piperine and capsaicin increased and decayed slowly. Capsaicin compared to cinnamaldehyde, had time-to-max, plateau time, and total time that were 1.5, 2.0 and 3.0 fold larger; whereas, the maximum rates of onset and decay were 0.7 and 0.2 fold smaller, respectively. Temporal differences are believed to reflect differences in neural pathways for the irritant species.     

Interactions between oral chemical irritation, taste and temperature

The oral chemical irritant, capsaicin, at 2, 4 and 8 p.p.m.,was combined in mixtures with sucrose (Experiment 1), sodiumchloride (Experiment 2) and soup (Experiment 3), each evaluatedat two temperatures. These mixtures were rated for their sweetnessand/or saltiness, intensity of burning sensation and total mixtureintensity. In both solution and soup, sweetness was suppressed,whereas saltiness showed only minor suppression in low NaCl,high capsaicin mixtures. The burning sensation produced by capsaicinwas uninfluenced by sucrose, while NaCl increased the burningsensation. Total mixture intensity was entirely determined bycapsaicin concentration in mixtures with sucrose, although NaClcontributed in NaCl/capsaicin mixtures. Varying temperatureinfluenced the burning sensation and total intensity of sucrose/capsaicinmixtures, but did not modulate the effects of capsaicin on taste.Explanations of taste suppression in terms of cognitive andstructural models are examined. The differential effect of capsaicinon sweetness and saltiness is also considered in terms of theirritant properties of NaCl.     

Modulation of oral heat and cold pain by irritant chemicals

Common food irritants elicit oral heat or cool sensations via actions at thermosensitive transient receptor potential (TRP) channels. We used a half-tongue, 2-alternative forced-choice procedure coupled with bilateral pain intensity ratings to investigate irritant effects on heat and cold pain. The method was validated in a bilateral thermal difference detection task. Capsaicin, mustard oil, and cinnamaldehyde enhanced lingual heat pain elicited by a 49 degrees C stimulus. Mustard oil and cinnamaldehyde weakly enhanced lingual cold pain (9.5 degrees C), whereas capsaicin had no effect. Menthol significantly enhanced cold pain and weakly reduced heat pain. To address if capsaicin's effect was due to summation of perceptually similar thermal and chemical sensations, one-half of the tongue was desensitized by application of capsaicin. Upon reapplication, capsaicin elicited little or no irritant sensation yet still significantly enhanced heat pain on the capsaicin-treated side, ruling out summation. In a third experiment, capsaicin significantly enhanced pain ratings to graded heat stimuli (47 degrees C to 50 degrees C) resulting in an upward shift of the stimulus-response function. Menthol may induce cold hyperalgesia via enhanced thermal gating of TRPM8 in peripheral fibers. Capsaicin, mustard oil, and cinnamaldehyde may induce heat hyperalgesia via enhanced thermal gating of TRPV1 that is coexpressed with TRPA1 in peripheral nociceptors.     

Responses to repeated oral irritation by capsaicin, cinnamaldehyde and ethanol in PROP tasters and non-tasters

Both increases (sensitization) and decreases (desensitization) in oral irritation have been reported in response to repeated short-term stimulation by compounds such as capsaicin, zingerone and menthol. It is unclear why one irritant would show sensitization and another desensitization, and this is further complicated by substantial inter-individual variation in response patterns. These variations may be the result of individual differences such as that represented by sensitivity to 6-n-propylthiouracil (PROP), which has been associated with variation in the overall intensity of irritation. In addition, comparisons between irritants have almost always involved inter-study comparisons, entailing different subject groups and frequently different methods. In the studies reported here, responses to three irritants-capsaicin, cinnamaldehyde and ethanol-were examined as a function of PROP taster status. A common core of subjects also received all three irritants, allowing an assessment of the extent to which different response patterns between irritants seen previously were the result of different properties of the irritants themselves. Over a series of ten stimuli presented at 1 min intervals, PROP taster status differentiated subject responses on the basis of overall intensity, but not the pattern of responses over repeated stimulation. The group response to ethanol and cinnamaldehyde was desensitization, a pattern also shown by most of the individual subjects. In contrast, the group response to capsaicin was neither clear sensitization nor desensitization, reflecting much greater individual variability in response patterns. It is suggested that the time course to a single irritant stimulus largely determines between irritant response variations, while the inter-stimulus interval (ISI) used for a given irritant will have critical values for showing predominantly sensitization or desensitization.     

Transition from growth to death in populations of Klebsiella terrigena and other Enterobacteriaceae in relation to temperature

Abstract Death-rate determinations indicated that a temperature a few tenths of a degree higher than T_max was more deleterious to Klebsiella terrigena (ATCC 33257) than a somewhat higher temperature. The death rate at 40°C (T_max+ 0.5°C) was approximately 0.2 log units per h but about 0.01 log units per h between 42°C and 44°C. Sequential temperature-gradient and constant temperature incubations showed the same phenomenon qualitatively among 14 Enterobacteriaceae strains representing different species.     

Calcium taste preferences: genetic analysis and genome screen of C57BL/6J x PWK/PhJ hybrid mice

To characterize the genetic basis of voluntary calcium consumption, we tested C57BL/6J mice (B6; with low avidity for calcium), PWK/PhJ mice (PWK; with high avidity for calcium) and their F₁ and F₂ hybrids. All mice received a series of 96-h two-bottle preference tests with a choice between water and the following: 50 m m CaCl₂, 50 m m calcium lactate, 50 m m MgCl₂, 100 m m KCl, 100 m m NH₄Cl, 100 m m NaCl, 5 m m citric acid, 30 μ m quinine hydrochloride and 2 m m saccharin. Most frequency distributions of the parental and F₁ but not F₂ groups were normally distributed, and there were few sex differences. Reciprocal cross analysis showed that B6 × PWK F₁ mice had a non-specific elevation of fluid intake relative to PWK × B6 F₁ mice. In the F₂ mice, trait correlations were clustered among the divalent salts and the monovalent chlorides. A genome screen involving 116 markers showed 30 quantitative trait loci (QTLs), of which six involved consumption of calcium chloride or lactate. The results show pleiotropic controls of calcium and magnesium consumption that are distinct from those controlling consumption of monovalent chlorides or exemplars of the primary taste qualities.     

TIME-INTENSITY PROPERTIES OF SWEET AND BITTER STIMULI: IMPLICATIONS FOR SWEET AND BITTER TASTE CHEMORECEPTION

Interindividual differences in sweet and bitter taste sensitivity were investigated using time-intensity (TI) measurements and multivariate statistics. TI profiles were obtained in triplicate from 25 subjects for 23 sweet and/or bitter stimuli first matched to be approximately equi-intense to 200 mM NaCl. Sweet stimuli, except for the larger sweeteners, were less persistent, and required less time to reach maximum intensity than bitter stimuli. The results of principal component (PCA) and cluster (CA) analyses of the stimuli X subjects matrices for maximum intensity (Imax), time to maximum intensity (Tmax), total duration (Tdur), and area under the curve (Area) suggest that sweet and bitter stimuli do not share common receptors; and that there are at least two receptor mechanisms each for sweet taste (one for sugars and other small compounds, and the other for large sweeteners) and bitter taste (one for PTC/PROP and one for other bitter compounds).     

Growth, diet and metabolism of common wolf–fish in the North Sea, a fast–growing population

The von Bertalanffy growth parameters for common wolf–fish Anarhichas lupus in the North Sea were: male: L ∞=111·2 cm, t ₀=–0·43 and K =0·12; and female: L ∞=115·1 cm, t ₀=–0·39 and K =0·11, making this the fastest growing stock reported. Resting metabolic rates (RMR±S.E.) and maximum metabolic rates (MMR±S.E.) for six adult common wolf–fish (mean weight, 1·39 kg) at 5° C were 12·18±1·6 mg O₂ kg^–1 h^–1 and 70·65±7·63 mg O₂ kg^–1 h^–1 respectively, and at 10° C were 25·43±1·31 mg O₂ kg^–1 h^–1 and 113·84±16·26 mg O₂ kg^–1 h^–1. Absolute metabolic scope was 53% greater at 10° C than at 5° C. The diet was dominated by Decapoda (39% overall by relative occurrence), Bivalvia (20%) and Gastropoda (12%). Sea urchins, typically of low energy value, occupied only 7% of the diet. The fast growth probably resulted from summer temperatures approximating to the optimum for food processing and growth, but may have been influenced by diet, and reduced competition following high fishing intensity.     

What physiological acclimation supports increased growth at high CO2 conditions?

Chlamydomonas acidophila Negoro is a green algal species abundant in acidic waters (pH 2–3.5), in which inorganic carbon is present only as CO₂. Previous studies have shown that aeration with CO₂ increased its maximum growth rate, suggesting CO₂ limitation under natural conditions. To unravel the underlying physiological mechanisms at high CO₂ conditions that enables increased growth, several physiological characteristics from high- and low-CO₂-acclimated cells were studied: maximum quantum yield, photosynthetic O₂ evolution (P_max), affinity constant for CO₂ by photosynthesis (K_0.5,p), a CO₂-concentrating mechanism (CCM), cellular Rubisco content and the affinity constant of Rubisco for CO₂ (K_0.5,r). The results show that at high CO₂ concentrations, C. acidophila had a higher K_0.5,p, P_max, maximum quantum yield, switched off its CCM and had a lower Rubisco content than at low CO₂ conditions. In contrast, the K_0.5,r was comparable under high and low CO₂ conditions. It is calculated that the higher P_max can already explain the increased growth rate in a high CO₂ environment. From an ecophysiological point of view, the increased maximum growth rate at high CO₂ will likely not be realised in the field because of other population regulating factors and should be seen as an acclimation to CO₂ and not as proof for a CO₂ limitation.     

High- and Low-Affinity Transport of D-Glucose from Blood to Brain

Abstract: Measurements of the unidirectional blood-brain glucose flux in rat were incompatible with a single set of kinetic constants for transendothelial transport. At least two transfer mechanisms were present: a high-affinity, low-capacity system, and a low-affinity, high-capacity system. The low-affinity system did not represent passive diffusion because it distinguished between D-and L-glucose. The T_max and K _m, for the high-affinity system were 0.16 mmol 100 g⁻¹ min⁻¹ and 1 mM; for the low-affinity system, ∼ 5 mmol 100 g⁻¹ min⁻¹ and ∼ 1 M. With these values, physiological glucose concentrations were not sufficient to saturate the low-affinity system. In normoglycemia, therefore, three independent pathways of glucose transport from blood to brain appear to exist: a high-affinity facilitated diffusion pathway of apparent permeability 235·10⁻⁷ cm s⁻¹, a specific but nonsaturable diffusion pathway of permeability 85·10⁻⁷ cm s^−l, and a nonspecifc passive diffusion pathway of permeability 2·10⁻⁷ cm s⁻¹.     

Acid potentiation of the capsaicin receptor determined by a key extracellular site

The endocannabinoid anandamide (AEA) and some of its oxidative metabolites are putative ligands for the vanilloid receptor (VR₁). AEA affords protection against excitotoxicity induced in vivo by ouabain, a Na⁺/K⁺-ATPase inhibitor. This effect is only partly dependent of the cannabinoid CB₁ receptor. Here, we assessed whether VR₁ is involved in neuroprotection by AEA and arvanil, which is a hydrolysis-stable ligand for both VR₁ and CB₁. Using magnetic resonance imaging we show that: (i) modulation of VR₁, by the agonists arvanil and capsaicin and the antagonist capsazepine, leads to neuroprotective effects in the late but not acute phase after i.c. ouabain-injection; (ii) arvanil is a potent neuroprotectant, acting at both CB₁ and VR₁; and (iii) the neuroprotective effects of AEA are mediated by CB₁ but not by lipoxygenase metabolites or VR₁.     

31P NMR Relaxation Does Not Affect the Quantitation of Changes in Phosphocreatine, Inorganic Phosphate, and ATP Measured In Vivo During Complete Ischemia in Swine Brain

Abstract: Ischemia-induced changes in ³¹P NMR relaxation were examined in 16 piglets. NMR spectra were acquired under control conditions and during complete cerebral ischemia induced via cardiac arrest. Changes in T ₁ were assessed directly in six animals during control conditions and after 30–45 min of complete ischemia when changes in brain P₁ levels had reached a plateau. The T ₁ for P₁ did not change, i.e., 2.3 ± 0.5 s during control conditions versus 2.4 ± 1.0 s during ischemia. To evaluate phosphocreatine and ATP, two types of spectra, with a long (25-s) or short (1-s) interpulse delay time, were collected during the first 10 min of ischemia (n = 10). Both types of spectra showed the same time course of changes in phosphocreatine and ATP levels, implying that the T ₁ relaxation times do not change during ischemia. There were no changes in the linewidths of phosphocreatine, ATP, or P₁ during ischemia, implying that the T *₂ values remain constant. Our results suggest that the ³¹P T ₁ and T *₂ for phosphocreatine, P_i, and ATP do not change during ischemia, and therefore changes in ³¹P NMR peak intensity accurately reflect changes in metabolite concentrations.     

Physiology of a sucrose-sensitive cell on the galea of the eastern spruce budworm larva, Choristoneura fumiferana

ABSTRACT The lateral styloconic sensillum on the galea of the eastern spruce budworm larva Choristoneura fumiferana Clem. (Lepidoptera: Tortricidae) contains a cell which responds to sucrose. The electro-physiologial threshold for response is below 0.5 mM sucrose. The K_b for the response is 1.5 mM, and the V_max is 200 impulses/s. The physiological data are interpreted with respect to the sucrose-stimulated feeding behaviour of the larva.     

Sweet taste receptor interacting protein CIB1 is a general inhibitor of InsP3-dependent Ca2+ release in vivo

In a search for sweet taste receptor interacting proteins, we have identified the calcium- and integrin-binding protein 1 (CIB1) as specific binding partner of the intracellular carboxyterminal domain of the rat sweet taste receptor subunit Tas1r2. In heterologous human embryonic kidney 293 (HEK293) cells, the G protein chimeras Gα_16gust44 and Gα_15i3 link the sweet taste receptor dimer TAS1R2/TAS1R3 to an inositol 1,4,5-trisphosphate (InsP₃)-dependent Ca²⁺ release pathway. To demonstrate the influence of CIB1 on the cytosolic Ca²⁺ concentration, we used sweet and umami compounds as well as other InsP₃-generating ligands in FURA-2-based Ca²⁺ assays in wild-type HEK293 cells and HEK293 cells expressing functional human sweet and umami taste receptor dimers. Stable and transient depletion of CIB1 by short-hairpin RNA increased the Ca²⁺ response of HEK293 cells to the InsP₃-generating ligands ATP, UTP and carbachol. Over-expression of CIB1 had the opposite effect as shown for the sweet ligand saccharin, the umami receptor ligand monosodium glutamate and UTP. The CIB1 effect was dependent on the thapsigargin-sensitive Ca²⁺ store of the endoplasmic reticulum (ER) and independent of extracellular Ca²⁺. The function of CIB1 on InsP₃-evoked Ca²⁺ release from the ER is most likely mediated by its interaction with the InsP₃ receptor. Thus, CIB1 seems to be an inhibitor of InsP₃-dependent Ca²⁺ release in vivo .     

Relationship between opercular girth, maximum girth and total length of fishes caught in gillnets in the estuarine and lower river sections of Shatt al-Arab River (Basrah Province, Iraq)

In fisheries, the two morphological parameters of opercular and maximum girth are related to the effectivity of capture methods in gilled and wedged fish, respectively. The present work investigates the relationship between opercular ( G _ope) and maximum girths ( G _max) to total length ( L _t) for 10 fish species captured from Shatt al-Arab River, Basrah, Iraq. Data were collected October 2005 to December 2006. Cyprinids were the best represented family with six species; engraulids, silurids, heteropneustids and mugilids were each represented by one species. G _ope and G _max were found to increase linearly with total length of all species, all r ² values being greater than 0.73 and statistically significant (P < 0.01). When G _ope and G _max for all species were plotted against total length, two groups were identified ( G 1, G 2), corresponding to general girth-length relationships: (a) G 1 = −0.252 + 0.424 L _t and G 2 = −0.262  +  0.600 L _t for opercular girth and, (b) G 1 = 1.538 + 0.419 L _t and G 2  =  1.538  +  0.696 L _t for maximum girth. These groups correspond to different body shapes of fishes: G 1-round and G 2-compressed. These relationships have implications when using length data and mesh size to determine size selectivity of gill nets.     

Capsaicin inhibits calmodulin-mediated oxidative burst in rat macrophages

In this study we seek to elucidate the interaction of capsaicin with the calmodulin mediated signal pathways in macrophages, by comparing its action on macrophage functions with a known calmodulin antagonist, fluphenazine. Kinetics of capsaicin uptake by macrophages (10³ cells) revealed that a maximum of 200 μM capsaicin was taken up within 10 min. Ca²⁺ ionophore triggered generation of superoxide anion and hydrogen peroxide by macrophages was inhibited in a dose-dependent manner by fluphenazine (IC₅₀, 20 μM and 12 μM, respectively) and also by capsaicin (IC₅₀, 30 μM and 9 μM, respectively), suggesting an involvement of calmodulin in the regulation of NADPH oxidase. In vitro both fluphenazine and capsaicin inhibited Ca²⁺-Mg²⁺ ATPase and cAMP-phosphodiesterase from macrophages and this inhibition was reversed by exogenous addition of calmodulin. Fluorescence studies revealed a direct Ca²⁺ dependent interaction of capsaicin with calmodulin. From these results we suggest that capsaicin acts via calmodulin to inhibit stimulus-induced macrophage oxidative burst and also that calmodulin regulates the oxidative burst in macrophages.     

Activation of Protein Kinase C by the Capsaicin Analogue Resiniferatoxin in Sensory Neurones

Abstract: Resiniferatoxin and capsaicin are sensory neurone-specific excitotoxins that operate a common cation channel in nociceptors. Resiniferatoxin is structurally similar to capsaicin and to phorbol esters. Specific [³H]-resiniferatoxin binding, which was detected in the membrane ( K _D value 1.8 ± 0.2 n M ) but not cytosolic fraction of rat dorsal root ganglia, could not be displaced by phorbol 12,13-dibutyrate. Conversely, resiniferatoxin did not displace [³H]phorbol 12,13-dibutyrate binding in either the cytosolic or membrane fraction. Resiniferatoxin and capsaicin both caused translocation of protein kinase C in dorsal root ganglion neurones (EC₅₀ value 18 ± 3 n M ). This translocation was greatly reduced but not abolished, in the absence of external Ca²⁺, suggesting that it was secondary to Ca²⁺ entry. Resiniferatoxin also caused direct activation of a Ca²⁺- and lipid-dependent kinase (or kinases) in the cytosolic fraction of dorsal root ganglia, at concentrations (100 n M to 10 µ M ) higher than required for displacement of [³H]resiniferatoxin binding or translocation of protein kinase C. Capsaicin (up to 10 µ M ) was unable to mimic this effect. These data imply that although resiniferatoxin-induced translocation of protein kinase C in dorsal root ganglion neurones was mainly indirect, it also caused direct activation of a protein kinase C-like kinase in these cells.     

Glycolate metabolism in cyanobacteria

A comparative analysis of glycolate excretion in 11 cyanobacteria showed that 8 strains, although grown and assayed in air, excreted glycolate. The largest quantities were excreted by the filamentous strains Plectonema boryanum 73110 and Anabaena cylindrica (Lemm). The carbon lost by excretion was at most 9% of the net fixed carbon in air for heterocystous cyanobacteria but increased (up to 60%) in some strains under a high pO₂ (0.03 kPa CO₂ in pure O₂). A. cylindrica excreted glycolate at a maximum level of 2 and 10 μmol (mg chl a )⁻¹ h⁻¹ in air and at high pO₂, respectively. The excretion continued for several hours. Increases in light intensity and pO₂ and a shift in pH from 7 to 9 increased the amount of glycolate excreted. A. cylindrica also showed the most O₂-sensitive fixation of CO₂. In vitro activity of phosphoglycolate phosphatase (EC 3.1.3.18) was found in all strains tested, with the highest activities noted for Gloeobacter violaceus 7.82 and Gloeothece 6909 and for young cultures of A. cylindrica . The lowest activities were found in Anabaena 7120 and Anacystis nidulans 625, strains excreting no or only minor quantities of glycolate.     

Empirical relationships to estimate asymptotic length, length at first maturity and length at maximum yield per recruit in fishes, with a simple method to evaluate length frequency data

Empirical relationships are presented to estimate in fishes, asymptotic length (L∞) from maximum observed length (L_max), length at first maturity (L_m) from L_∞, life span (t_max) from age at first maturity (t_m), and length at maximum possible yield per recruit (L_opt) from L_∞ and from L_m, respectively. The age at L_opt is found to be a good indicator of generation time in fishes. A spreadsheet containing the various equations can be downloaded from the Internet at http://www.fishbase.org/download as popdynJFB.zip. A simple method is presented for evaluation of length–frequency data in their relationship to L_∞, L_m and L_opt. This can be used to evaluate the quality of the length–frequency sample and the status of the population. Three examples demonstrate the usefulness of this method. 2000 The Fisheries Society of the British Isles     

The link between respiratory capacity and changing metabolic demands during growth of northern pike, Esox lucius L.

The relationship between metabolic rate of pike (Y, mgO2) and body weight (X, g) over the range 40–1291 gat 15° C is of the form: Y=aX^b. For resting metabolic rate (V_o2, rest), the scaling coefficient, b , is 0.80 and for maximum metabolic rate measured after exhaustive swimming (V₀₂, max), b is 0.99. Factorial metabolic scope (V₀₂, max/ V₀₂, rest) increases with body weight. Peak postprandial oxygen consumption (V₀₂, ASDA) is a constant multiple of V₀₂ rest for any discrete meal (expressed as % of body weight) up to 10% body weight. V₀₂ASDA after a single meal can utilize the entire metabolic scope (V₀₂, max—V₀₂, rest) of juvenile but not adult pike.