| Sources of individual differences in sweet preferences and habits areone of the most fundamental mysteries of human behavior and a basicquestion of food science. Up to date, we don't know about the detailcytological and physiological mechanism except for some behaviorobservations about it. We hypothesized that the plasticity of taste systemis the basis of sweet preference formation, and that there are sensitiveperiods during which the animal pup is particularly likely to form sweetpreference. So, we set up a particularly apt model system with ICR mouseand carried out serial experiments to explore potential variationscharacteristic during the early sensitive periods. In the present studies,Immunofluorescence for confocal micrography, liquidchromatography-mass spectrometry, reversed phase high performanceliquid chromatography and behavior methods have been used to explorethe relationship among the changes of distribution pattern,α-gustducinexpression pattern of fungiform (FF) taste buds and preferencepercentage to sweet solution of the mouse, which exposed toacesulfame-K (AK) solution during the early days of development. 1. Effects to sweet preference of adult mice after orochemicalexposure to AK solution during postnatal early development.In order to observe the sweet preference pattern and percentagechanges of adult mice after exposing to AK solution from postnatal day 4to day 21 compared the control group (intraoral infusion of distilledwater), two-bottle tests were carried out. The preference pattern and themost preferred concentration were not be changed, the preference patternto AK solution and sucrose solution were"indifference-preference-avoidance" and "indifference-preference", andthe most preferred concentration were 13.28 mmol/L and 125.00 mmol/L,respectively. However, the preference threshold to AK solution andsucrose solution was degraded, also, the preference percentage to abovesolutions was increased significantly in the exposed group compared withthe control group, the average percentage of increase was 25.12% and30.10%, respectively. That is to say, the sweet preference percentage wasincreased significantly after orochemical exposure to AK solution duringpostnatal early development, behavior basis for the study of sweetpreference mechanism was provided.2. Effects to distribution pattern of FF taste buds in mice afterorochemical exposure to AK solution during postnatal earlydevelopment.In order to observe the distribution pattern and regional differences of FF taste buds in the control mice and the effects after intraoral infusionsof AK solution during postnatal early development, histological andcytological tests were carried out. At birth, about fifty taste buds (with orwithout pores) were observed on the FF (47.00±2.24). The number ofFF taste buds increased and reached a steady level (117.80±2.85) at 2week of age. The number of pored taste buds was 10.20±0.58 at birthday, and increased rapidly before the weanling day, the numbercontinuously increased until 9 weeks of age, reaching 117.60±2.52,accounted for 92% pf the total taste buds. In controls, there was apronounced anterior to posterior gradient in taste bud densities. The veryanterior tongue (1 mm) had a much greater density of taste buds; the firstmillimeter of tongue had mean (±SEM) of 72.00±0.84 taste buds, whilethe posterior tongue (last 4 mm) only had mean (±SEM) of 55.80±0.86taste buds.The mean height and width of the FF taste buds at birth only were12.52±0.33μm and 18.69±0.42μm, respectively, then the height andwidth increased until 3 and 1 weeks of age, respectively, and both typesreached a steady level at 5 week of age, reaching 45.40±1.39μm and36.88±1.38μm at 9 weeks of age, respectively. The ratio of height/widthincreased significantly before the age of 3 weeks, and then reached asteady level, the ratio ranged between 0.69 to 1.26 from birth to adult,indicating that the shape of FF taste buds was nearly spherical (onion-like appearance). The overall size of FF taste buds increased significantlybefore the age of 5 weeks, reaching 1310.34±38.34μm~2 at 9 weeks ofage.Comparing with the control group, the number of total taste budsincreased significantly from 3 to 9 weeks of age in the P4 exposure group,reaching 128.00±1.87 and 122.20±1.32 (P=0.035＜0.05) at 3 weeksof age, and 133.60±1.47 and 127.80±1.07 (P=0.013＜0.05) at 9 weeksof age, respectively, the average increase was 4.97%. There was a moresignificant effect on the number of pored taste buds than that of total tastebuds in the P4 exposure group, the percentage of pored taste budsincreased significantly at 2 weeks of age compared with the control group,reaching 53.92±0.50% and 46.84±0.99% (P=0.00023＜0.001),respectively.The height, width and size of taste buds in the P4 exposure group weresignificantly larger than those of the control group in adult (height: P=0.0093＜0.01; width: P=0.0144＜0.05; size: P=0.0019＜0.01,respectively). However, there was no significant difference between theexposure and control group. So, the FF taste buds remained onion-likeappearance, though the overall size increased in the P4 exposure group.There were regional differences in taste bud volume along theanterior-posterior axis in adult mice. The first millimeter of tongue, whichwill be referred to as the anterior tongue, contained significantly smaller taste buds(24635.68±1049.88μm~3, P=0.00234＜0.01) than in the moreposterior region, which will be referred to as the posterior tongue(32197.92±1123.18μm~3), the volume of taste bud in the posteriortongue was bigger about 31% than that of the anterior tongue. Theaverage cell number in single taste bud of the posterior tongue was biggerabout 18% than that of the anterior tongue, reaching 36.95±0.92 and31.37±1.62 (P=0.00892＜0.01), respectively.Comparing with the control group, the taste bud volume of anteriortongue increased significantly in the P4 exposure group (P=0.00625＜0.01), reaching 31852.42±1658.28μm~3 and 24635.68±1049.88μm~3,respectively, and increasing about 30%. So did the taste bud volume ofposterior tongue (P=0.01815＜0.05), reaching 34827.78±1062.09μm~3and 32197.92±1148.40μm~3, respectively, and increasing about 15%.The cell number of single taste bud in the anterior tongue increasedsignificantly in the P4 exposure group compared with the control group(P=0.00195＜0.01), reaching 39.90±0.96 and 31.37±1.62 respectively,and increasing about 27%. So did the taste bud cell number in theposterior tongue (P=0.03983＜0.05), reaching 45.38±2.06 and 36.95±0.92, respectively, and increasing about 23%. The increase percentages oftaste bud volume and cell number in the anterior tongue were bigger thanthose of the posterior tongue, so, the regional differences both volumeand cell number vanished in the P4 exposure group. Present experiment demonstrated that orochemical exposure to AKsolution to pups of mice from postnatal day 4 to 21 promoted thedevelopment and maturation and increased the volume through increasingthe cell number of taste bud in adult.3. Effects to expression pattern ofα-gustducin of FF taste buds inmice after orochemical exposure to AK solution during postnatalearly development.In order to detect the expression pattern and regional differences ofα-gustducin of FF taste buds in the control mice and the effects afterintraoral infusions of AK solution during postnatal early development,histological and Immunofluorescence for confocal tests were carried out.The immumoreactivity forα-gustducin could not be identified at birth,and a few positive taste buds were traced at 1 day of age (12.00±1.16),then the number of positive taste buds increased rapidly and reached asteady level at 2 weeks of age, and reaching 105.67±2.91 at 9 weeks ofage; The immunoreactivity cell number increased quickly beforeweanling and continuously increased until 9 weeks of age, reaching 9.43±0.23 positive cells in single taste bud of FF.The positive taste buds and positive cell numbers in single taste bud inthe P4 exposure group had significant increase compared with the controlgroup. The positive taste buds had an increase about 12%, reaching118.00±1.53 and 105.67±2.91 (P=0.01983＜0.05) at 9 weeks of age, respectively. The positive cells in single taste bud also had an increasearound 34%, reaching 12.60±0.27 and 9.43±0.23 (P=0.00085＜0.001),respectively.There were significant effects on the distribution pattern (the numberof taste buds, pored taste buds and the ratio of them) of taste buds andexpression pattern (the number of positive taste buds and positive cell ofsingle taste bud) ofα-gustducin after exposing to AK solution frompostnatal day 4 to day 21.4. Effects to sweet preference pattern of adult mice after dietaryexposure to AK during pregnancy and lactation.No significant differences in preference pattern and the most preferredconcentration to sweet solution were detected after dietary exposure toAK during pregnancy and lactation. The preference pattern to AKsolution and sucrose solution were "indifference-preference-avoidance"and "indifference-preference", and the most preferred concentration were13.28 mmol/L and 125.00 mmol/L, respectively. However, early exposuredegraded the preference threshold, those to AK solution of the control,the pregnancy and the lactation groups were 1.33 mmol/L, 0.42 mmol/Land 0.13 mmol/L, and those to sucrose solution of them were 12.00mmol/L, 3.80 mmol/L and 3.80 mmol/L, respectively. Comparing withthe control group, the preference percentages increased significantly inthe exposure group, the extent of AK solution concentration in the pregnancy and lactation group were 0.42-13.28 mmol/L and 0.13-13.28mmol/L, the average increase percentages were 18.47% and 16.83%,respectively, and that of sucrose solution concentration in above groupswere 3.80 mmol/L, the average increase percentages were 48.13% and49.79%.AK contents and its' dynamic change within twenty-four hours weredetected in the amniotic fluid and milk sample after oral infusion of AKsolution during pregnancy and lactation, with the methods of liquidchromatography-mass spectrometry (LC-MS) and reserved phase highperformance liquid chromatography (RP-HPLC). The results indicatedthat the AK existed in the amniotic fluid and milk sample after oralinfusion.Above results indicated that early exposure to AK at different periodscan promote the development and mature of taste buds andα-gustducinexpression in the mice, and those significant changes provide structureand function basis for the plasticity of sweet preference.5. Relationship between fungiform papillae density and perceptionthreshold in human.High pixel digital camera was used to detect the density of humanfungiform papillae, and sensory evaluation methods were used to evaluatethe relationship between the density of fungiform papillae and theperception threshold and preferred concentration of sucrose solution. The results indicated that the average density of fungiform papillae was 96.87±43.53/cm~2, and a negative correlation between the density offungiform papillae and the perception threshold and the preferredconcentration of sucrose solution.
|
PDF Full Text Request