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1.
Genetic Sensitivity to 6-n-Propylthiouracil (PROP) and Hedonic Responses to Bitter and Sweet Tastes 总被引:1,自引:1,他引:0
Genetically mediated sensitivity to the bitter taste of 6-n-propylthiouracil(PROP) has been associated with greater acuity for bitter andfor some sweet tastes. Thus far, few studies have explored therelationship between PROP taste sensitivity and hedonic responsesto bitter and sweet. In this study, 87 normal-weight young womenwere divided into PROP non-tasters (n = 18), regular tasters(n = 49), and supertasters (n = 20), based on their PROP detectionthresholds and the scaling of five suprathreshold solutionsof PROP and NaCl. Non-tasters had thresholds >1.8 x 104mol/l PROP. Supertasters had thresholds <3.2 x 105mol/l PROP and PROP/NaCl ratios >1.70. As expected, dislikeof the bitter taste of PROP was determined by its perceivedintensity, which was greater among supertasters than among regulartasters or non-tasters. Significant correlations were observedbetween PROP taste thresholds and the sum of intensity ratings(r = 0.61) and between summed intensity and summed hedonicratings (r = 0.80). PROP taste sensitivity was weaklylinked to enhanced perception of sweet taste, but did not predicthedonic responses to sucrose or to saccharin solutions. Giventhat the dislike of PROP solutions is determined by their perceivedintensity, hedonic responses to PROP solutions may provide arapid way of screening for PROP taster status. Chem. Senses22: 2737, 1997. 相似文献
2.
The percentage of non-tasters for phenylthiocarbamide in 915Japanese students was 9.4%. The thresholds of the edge and backof the tongue to quinine hydrochloride were significantly smallerin the non-tasters than in the tasters. The thresholds of anytongue portions to NaCl, acetic acid or sucrose did not differbetween the tasters and the non-tasters. Chem. Senses 22: 547551,1997. 相似文献
3.
The NADP$-specific isocitrate dehydrogenase was partially purifiedfrom photosynthetically-grown Rhodospirillum rubrum. The pHoptimum is between 7.5 and 9.0 in phosphate buffer. The apparentKm is 3.1x105 M for isocitrate, 5.1x105 M forNADP$, 1.7x105 M for manganese, 1.5x104 M formagnesium, and 3.5x103 M for inorganic orthophosphate.Arsenate exerts a slight inhibition. The Q10 between 17.5°Cand 40°C is 1.62, and the energy of activation at 25°Cis 9.74 Kcal/mole. Glyoxylate and oxalacetate cause concertedinhibition of the enzyme activity. Various nucleotides inhibitthe activity. The kinetics of inhibition by ATP was found tobe mixed type with respect to NADP$ and isocitrate, the Ki valuesbeing 1.17x103 M and 1.10x103 M respectively.The inhibition between ATP and orthophosphate is competitivewith a Ki of 104M. Thiol binding reagents are inhibitory;this inhibition is reversed by cysteine or reduced glutathione. (Received October 1, 1971; ) 相似文献
4.
Five inbred strains (129/J, BALB/cByJ, C3HeB/FeJ, C57BI/6J andDBA/2J) were examined with two-bottle (48 h) preference ratiotesting across concentrations of sodium saccharin (3 x 104M, 103 M, 3 x 103 M and 102 M), d-phenylalanine(103 M, 102 M and 101 M), and l-glutamine(102 M, 3 x 102 M, 101 M and 3 x 101M). Three consistent groupings of strains were observed acrosssubstances and concentrations:
- C57BI/6J (preference at low andhigh concentrations);
- BALB/cByJ and C3HeB/FeJ (preferenceat high concentrations);
- 129/J and DBA/2J (preference at highconcentration for sodiumsaccharin and indifference to d-phenylalanineand l-glutamine).
5.
The olfactory discrimination process of male cabbage loopermoths, Trichoplusa ni (Hübner), was assessed by measuringtheir response to one of two emission sources within a windtunnel. The males discriminated between (1) Z712:Ac concentrations;(2) Z712:Ac alone and the volatile emission from excisedfemale sex pheromone glands; and (3) Z712:Ac and theemission from a mixture of six synthetic pheromone componentsthat mimics the volatile emissions of a female gland. Althoughmales could discriminate between a freshly excised female sexpheromone gland and 7.4x 1011 M Z712:Ac, theycould not discriminate between a gland and 78.5x1011M Z712:Ac. Males also could not discriminate betweenthe mixture of six volatile compounds and 28.7x1011 Mof Z712:Ac. The data show that male cabbage looper mothshave difficulty discriminating between Z712:Ac aloneand in mixtures with other female-emitted volatile compounds. 相似文献
6.
The pitcher of the carnivorous plant Sarracenia purpurea L.contains an entrapped body of liquid within which its prey isdigested. Free calcium in the pitcher is derived from eitherthe pitcher walls or from prey falling into the pitcher; inthe absence of exogenous (prey-derived) calcium it will dependon the active and passive calcium regulatory properties of thepitcher walls and may to some extent therefore mimic calciumin the apoplast of plant cells. Using a calcium-specific electrode,the free calcium concentration of the pitchers of Sarraceniaplants was investigated and the effect of adding a variety ofconcentrations of calcium in water determined. The mean pitcherfree calcium concentration in vivo was 2.3 x 105 M±2.5x 105 M; when pitchers were washed and filled with watercontaining lower calcium concentrations, the concentration inthe pitcher water rose to 15 x 105 M. When highercalcium concentrations (up to 1 x 104 M) were added,the pitcher calcium concentration declined to 17 x 105M. Concentrations of calcium above 1 x 104 M were alsoreduced, but to a lesser extent. Metabolic inhibition of activeion transport, while inhibiting pitcher acidification, did notinhibit regulation of pitcher free calcium, suggested that itoccurs as a result of calcium exchange sites in the pitcherwalls. The data are discussed in relation to the physiologyof Sarracenia pitchers and to the usefulness of the pitcheras a model for free calcium in the higher plant apoplast. Sarracenia purpurea L., carnivorous plant, pitcher, free calcium, plant apoplast 相似文献
7.
Incorporation of polyamine-spermidine into the nutrient mediumat 106 and 105 M concentrations stimulates pollen-tubegrowth in vitro in Catharanthus roseus L. G. Don. MGBG, an inhibitorof spermidine biosynthesis, at 0.5 x 103 and 1 x 103M concentrations reduced the percentage of germination as wellas tube growth and at a concentration of 1.5 x 103 Mgermination was totally inhibited. Pollen grains incubated inthe medium containing 1.5 x 103 M MGBG, when transferredto a fresh medium with 105 M spermidine, resulted in80% germination recovery, along with considerable tube growth.Experiments with actinomycin-D indicate that stimulation ofpollen-tube growth by spermidine may involve de novo synthesisof protein. Catharanthus roseus, pollen germination, tube growth, spermidine, MGBG, inhibition, actinomycin-D 相似文献
8.
Effects of indoleacetic, p-chlorophenoxyisobutyric and 2,4,6-trichlorophenoxyacetic acids on three phases of rooting in Azukia cuttings 总被引:1,自引:0,他引:1
In adventitious root formation of disbudded epicotyl cuttingstaken from light-grown, 5-day-old Azukia angularis seedlings,indoleacetic acid (IAA), 1 x 104 M, applied during thefirst day showed no effect, but enhanced the effect of IAA,1 x 104 M, applied during the second day. Treatment duringthe second day promoted rooting by about 70%, and a combinationof treatments for the first and second days promoted rootingsome 200%. p-Chlorophenoxyisobutyric acid (PCIB), 3 x 104M, and2,4,6-trichlorophenoxyacetic acid (2,4,6-T), 2 x 1044M, applied the first day also enhanced the effect of IAA, 2x 104 M, applied the second day. When applied the second day, PCIB, 2 x 104M, increasedthe number of root primordia or clusters of small cells, butnot die number of protruded roots. Formation of the cell clusterwas inhibited by 2,4,6-T, 3 x 104M, applied the secondday. Rooting processes in Azukia cuttings seem to include at leastthree phases: the first phase is induced not only by IAA butalso by PCIB or 2,4,6-T, the second phase is induced by IAAor PCIB and the diird phase depends specifically on IAA. (Received October 28, 1970; ) 相似文献
9.
PAGE KENNETH R.; KELDAY LEWIS S.; BOWLING DUDLEY J. F. 《Journal of experimental botany》1981,32(1):55-58
The diffusion of salt from the tips of 3 M KCI filled micro-electrodesis measured. The leakage of KCI in 3 min is found to be 5.70x 10121.08 x 1011 mol for tips of 0.20.6µm diameter, and 2.70 x 1011 mol for tips of 0.61.0µm diameter. The observed leakages compare with estimatesbased on the diffusion coefficient of KCI and micro-electrodegeometry. The results confirm that the use of 3 M KCI in micro-electrodesmay lead to serious contamination of impaled cells providedthe electrode tips remain unoccluded. 相似文献
10.
Fluid consumption and preference behavior were evaluated asa function of dietary zinc content during adulthood. Dietarytreatment of sixteen adult male rats was initiated 30 days priorto preference testing: eight rats were fed ad libitum a zinc-deficientdiet and eight rats were match-fed a zincreplete diet. Preferencetesting was performed using a 96-hour, two bottle free-choicetechnique. Rats were exposed to each of the following tastant-containingsolutions for successive 4-day periods: 1.5, 3.0, and 4.5x101M sodium chloride; 1.0x102 M sucrose; 2.5x103M hydrochloric acid, and 1.28x106 M quinine sulfate. The two groups had essentially equivalent weights prior to thedietary manipulation. The zinc-deficient rats weighed significantlyless than replete rats throughout preference testing, but didnot appear as physically debilitated as do weanling rats feda zinc-deficient diet for equivalent durations. The deficientrats demonstrated increased preferences for most of the tastantsolutions, accompanied by increased total volume intakes. Thesealterations were attributable to increases in tastant volumeintake by the deficient rats while water intake remained normal.Results were interpreted as supporting the hypothesis that zincdeficiency decreases gustatory sensitivity; however, the etiologyof this effect remains unclear. 相似文献
11.
The effects of cytochalasin B, N-ethylmaleimide (NEM), colchicine,vinblastine and cycloheximide on the formation of birefringentcell wall layers were studied. Birefringent layers accumulatedoutside the plasma membrane of daughter semicells when cellswere cultured in a 0.16 M mannitol solution without any inhibitors.In cells treated with 2 x 105 M cytochalasin B, 3 x 105M NEM, 104 M vinblastine or 105 M cycloheximidefor 24 hr, birefringent layers were not observed outside theplasma membrane, but were present in cells treated with 102M colchicine. The possibility is discussed that substances necessaryfor wall synthesis could be transported from the cytoplasm tothe outside of the plasma membrane by a system associated withmicrofilaments, microtubules and myosin-like structures. (Received June 26, 1981; Accepted September 24, 1981) 相似文献
12.
L-Leucine Transport in Isolated Protoplasts of Vinca Suspension Culture: Characterization of Uptake 总被引:1,自引:0,他引:1
The uptake of L-leucine into Vinca protoplasts was studied undervarious conditions. The uptake was highly pH-dependent, withthe optimal pH between 3.0 and 4.0. The uptake was also energydependent, since azide, 2,4-dinitrophenol (DNP), carbonyl cyanidem-chlorophenyl hydrazone (CCCP), and iodoacetate inhibited theuptake. Oligomycin, N,N'-dicycIohexyI carbodiimide (DCCD) andvanadate, but not ouabain, inhibited the uptake, suggestingthat ATPase for H+ electrogenic extrusion was necessary to theuptake of L-leucine. The uptake showed stereospecificity, butwas partially inhibited by other L-amino acids. A kinetic studyof the uptake showed that the uptake was multiphasic with threesaturable phases and one unsaturable phase which occurred atconcentrations of L-leucine over 1 mM. The Km values of thethree affinity sites were 1.4 x 103 M, 1.3 x 104M, 4.3 x 105 M; the maximum velocity values were 3.3x 108, 4.5 x 109, 1.8 x 109 mol/10 min/4x 106 cells. (Received April 18, 1981; Accepted August 25, 1981) 相似文献
13.
Two groups of tiger salamanders (Ambystoma tigrinum) were conditionedto respond to odorant-air mixtures of n-butyl acetate (8.9 x105M) or n-butyl alcohol (6.7 x l05M). They werethen given tests with various concentrations of the trainingodorants presented using a temporal forced-choice method ofascending limits. Results showed that reliable responses toodorant-air presentations were obtained with concentrationsof n-butyl acetate above 2.4 x l07M and with concentrationsof n-butyl alcohol above 8.5 x 108M. These results arein substantial agreement with previous dectrophysiological findings. 相似文献
14.
Evidence for Symplasmic Ion Transport in Maize Roots 总被引:1,自引:0,他引:1
Excised maize roots, placed in saturated water vapour to limitthe external ionic supply, continued to produce exudates attheir basal ends for at least 24 h. The mean rate of fluid exudationfrom roots in water vapour was about 28 per cent of the correspondingrate in control roote placed in a solution containing0.1 mil CaCl2 and 1 mM KC1. Moreover, the net fluxes (mean ±S.E.)of potassium and calcium ions into the exudate were reducedfrom (35.8±3.2) x 10 and (4.37±0.39) xlO9 mole cm2 h for roots in solution to(10.9±0.6) x 109 and (l.00±0.06)x 109molecm2 h1 respectively for roots in vapour. It isconsidered that the observation of a prolonged exudation ofwater and ions from the roots placed in water vapour demonstratesthe existence of an alternative ionic supply within the roottissue itself and that this parallel route of ion transportto the exudate constitutes the cortical symplasmic pathway. Pre-treatment of the excised roots with 0.8 M mannitol beforeexudation studies in water vapour and solution led to a significantreduction in the rates of fluid and ion exudation which hadbeen observed in untreated roots under similar conditions. Itis concluded that the plas-molysis, induced by mannitol, disruptedthe symplasmic connections between root cells and that thisperturbation significantly reduced the operation of the symplasmicmode of ion transport into the exudate. 相似文献
15.
Carrias Jean-Francois; Amblard Christian; Bourdier Gilles 《Journal of plankton research》1994,16(5):471-485
Seasonal population dynamics and the vertical distribution ofciliates were studied in relation to the particular food resourcesoccurring in a humic and moderately acidic lake (Lake Vassivière).The abundance (1.4 x 10320.4 x 103 cells l1 mean= 4.8 x 103 cells l1) and biomass (0.534.6 µgC l1, mean = 6.0 µg C l1) of ciliated protozoawere low and close to values reported for oligotrophic environments.The species composition of the population varied greatly withdepth. Whereas large-sized species of oligotrichs, some of whichwere mixotrophic, dominated at the surface, haptorids were bestrepresented in deep waters. The spatial distribution of thevarious groups of ciliates was largely determined by light andthe vertical distribution of microbial food resources (detritus,bacteria, algae) within the water column of this brown-coloredlake. 相似文献
16.
Why are there about 5000 species of phytoplankton in the sea? 总被引:1,自引:0,他引:1
The relative abundances of phytoplankton taxa conform approximatelyto a finite geometric series in which there are 2025species per decade of ranked abundance. Such series can contain160400 species between the commonest (10221026cells) and the rarest (10101014 cells). Thus, between12 and 31 such series are needed to explain the observed diversity,5x103 species, of marine phytoplankton. The number of seriesis similar to the number (2025) of upper-ocean watermasses defined by dilution time scale of order 101102years. Interpretations of this coincidence are discussed. 相似文献
17.
Guttation was used as a non-destructive way to study the flowof water and mineral ions from the roots and compared with parallelmeasurements of root exudation. Guttation of the leaves of barley seedlings depends on age andon the culture solution. Best rates of guttation were obtainedwith the primary leaves of 6- to 7-day-old seedlings grown onfull mineral nutrient solution. The growing leaf tissue becomessaturated with K+ below 1.5 mM K+ in the medium, whereas K+concentration in the guttated fluid still increases furtheras K+ concentration in the medium is raised. At 3 mM K+ averagevalues of guttation were 1.42.4 mm3 h1 per plantwith a K+ concentration of 1020 mM; for exuding plantsthe flow was 4.27.6 mm3 h1 per plant and K+ concentration3555 mM. Abscisic acid (ABA) at 106 to 104 M 02h after addition to the root medium increased volume flow ofguttation and exudation and the amount of K+ exported. Threeh after addition of ABA both volume and amount of K+ were reduced.There was an ABA-dependent increase in water permeability (Lp)of exuding roots shortly after ABA addition. Later Lp was decreasedby 35 per cent and salt export by 60 per cent suggesting aneffect of ABA on salt transport to the xylem apart from itseffect on Lp. Benzyladenine (5 x 108 to 105 M)and kinetin (5 x 106 M) progressively reduced volumeflow and K+ export in guttation and exudation and reduced Lp. Guttation showed a qualitatively similar response to phytohormonesas found here and elsewhere using exuding roots. Hordeum vulgare L., barley, guttation, abscisic acid, cytokinins, benzyl adenine, kinetin 相似文献
18.
Grazing and ingestion rates of laboratory-born Thalia democraticaaggregates and Dolioletta gegenbauri gonozooids, phorozooidsand oozooids were determined while fed Isochrysis galbana (45µm diameter) alone or in combination with Peridinium trochoideum(1618 µm diameter) at concentrations of 0.150.70mm3 x 11. Grazing rates (ml x zooid1 x 24 h 1)ranged from 10 to 355, and at zooid weights greater than 5 µgcarbon were in order oozooid > gonozooid > aggregate.Grazing rates increased exponentially with increasing zooidweight. Weight-specific grazing rates (ml x µgC1x 24 h1) were independent of the four-fold initial foodconcentration. Mean weight-specific grazing rates increasedlinearly with increasing zooid weight for the aggregates andoozooids, but gonozooid mean rates were independent of zooidweight. Aggregate and gonozooid ingestion rates (106 µm3x zooid1 x 24 h1) ranged from 4 to 134 while oozooidrates ranged from 3 to 67. All ingestion rates were independentof the initial food concentration but increased linearly withincreasing zooid weight at similar rates. All mean weight-specificingestion rates (ml x µgC1 x 24 h1) wereindependent of zooid weight. The mean aggregate daily ration(µgC ingested x µg body C1) was 59% and themean doliolid ration was 132%. Field studies indicate that normalconcentrations of D. gegenbauri in the Georgia Bight clear theirresident water volume (1 m3) in about 4 months, but that highlyconcentrated, swarm populations which occur along thermohalinefronts clear their resident water volume in less than 1 day.
1Current address: MacLaren Plansearch Ltd., P.O.Box 13250, sta.A.,St.John's, Nfld. A1B 4A5 相似文献
19.
The purpose of the investigation is the determination of thevolumes and numbers of cells of the meristematic dome and ofeach of the first 7 primordia and internodes at the apex ofthe shoot of Lupinui albus. This system occupies a zone whichis about 0·4 mm. in length. Techniques are describedfor dissecting the region in which the observations are made,for determining the numbers of cells and the volumes of theseveral fragments. From the number of cells and the volume ofeach fragment an average cell volume it calculated. It is shown that in the midphase of the plastochron the domecontains 3,500 cells and has a volume of 1·6 x103mm.3,the first primordium contains 1,630 cells and has a volume of0·38 x103 mm.3, and the first intemode containsabout 700 cells and has a volume of about 1·4 x103mm3The number of cells and the volume of the primordium increaseexponentially with increasing plastochron age, and the seventhprimordium contains 26,000 cells and has a volume of 20·9x 103mm3 The seventh intemode contains about 5,000 cellsand has a volume of 8·6x103mm3 The average cell volume in the dome is 4·7 x 107mm.3in the first primorndium it is 2·3 x 107mm.3 andin the first internode it is 20·9x 107mm.3 Inthe seventh primordium the average cell volume increases to7·9 x 107mm.3 In the internodes there is little,if. any, change in cell volume from the first to the seventhof the series. The significance of these changes is discussed. 相似文献
20.
Kinetin (4.7 x 105 M) and 6-benzyladenine (2.22 x 105M) were found to increase ca. 2-fold the putrescine contentin cotyledons of lettuce (Lactuca sativa L.) seedlings grownfor 3 days under fluorescent light. On the other hand, severalinorganic ions (K+, Na+, Ga++, Mg++) at a concentration of 3x 102 M reduced the putrescine content. The combinationof kinetin with one of several inorganic ions at the same levelmarkedly increased the spermine content, but the putrescinecontent decreased; calcium and magnesium ions were less effective.The physiological significance of these findings is discussed. (Received July 4, 1982; Accepted November 6, 1982) 相似文献