漫谈味觉

漫谈味觉陈英水（福建省松溪县第一中学３５３５００）味蕾是味觉感受器,分布在舌乳头、舌穴等处．舌乳头是舌面上许多粘膜小突起。它有４种类型,丝状、菌状、叶状和轮廓乳头。舌穴是舌乳头旁边的细管。味蕾的分布有年龄差异。成人味蕾主要分布于舌面（特别是舌尖和舌侧...     

双峰驼舌的大体解剖和舌粘膜的组织学结构

目的 研究双峰驼舌的形态结构和舌粘膜的组织学结构.方法 肉眼观察舌的形态结构,用直尺和游标卡尺测量各个参数;光镜下,观察舌粘膜的组织学结构.结果 双峰驼的舌由舌尖、舌体和舌根3部分组成;舌背粘膜厚而粗糙,舌腹粘膜薄而光滑;舌乳头包括丝状乳头、菌状乳头、轮廓乳头、锥状乳头和豆状乳头.舌表面角质化程度高,舌尖有明显的正中沟和横向的皱褶.菌状乳头味蕾不很发达,丝状乳头粗而长;舌根宽而厚,锥状和豆状等机械乳头相当发达,轮廓乳头较大;舌肌的横纹肌发达,味腺只见于舌根部.结论 双峰驼舌的形态学特点和组织学结构与其生长的荒漠、半荒漠环境及摄食多刺而粗糙植物的习性相适应.     

哺乳动物舌面味蕾的发育

根据近年来有关大鼠、小鼠味觉发育方面的大量研究,对哺乳动物味蕾(taste buds)发育的情况进行了综述和讨论.哺乳动物舌面上的味蕾分布在菌状乳头(fungiform papillae,FF)、叶状乳头(foliate papillae,FL)、轮廓状乳头(circumvallate papillae,CV)之中,味蕾细胞(taste bud cells)不断地进行着周期性的更新,味蕾的形态、数量和功能随动物随年龄而变化.有关味孔头的研究表明,味乳头(gustatory papillae)在味蕾形成和维持味蕾存在及正常发育方面有着独特的功能.味乳头和味蕾的发育过程与细胞信号分子(signaling molecules)、味觉神经(gustatory nerve fibers)等许多因素有着密切的关系,其中有些作用机理至今尚无定论.     

Sonic Hedgehog在味乳头发育过程中的作用

Shh是一种作用于脊椎动物细胞分化和组织诱导的信号分子,它通过跨膜蛋白Ptc受体和信号转录因子Glil参与信号转导机制。从胚胎期（E12）到成年,Shh信号在鼠舌味乳头中的表达都非常广泛。在味乳头最初发育阶段,Shh信号的作用包括调节上皮和间质细胞的交互作用、控制乳头形成和成型、限定乳头的分布模式、决定细胞分化的命运等,破坏Shh信号会导致菌状数量增多、面积增大以及乳头分布区域更广。     

鳜早期味蕾发育的组织学特征

采用石蜡切片、H.E染色研究了3 ~ 28日龄鳜（Siniperca chuatsi）味蕾发育的组织学特征,并通过扫描电镜观察28日龄鳜口咽腔组织味蕾类型与数目。结果表明,未开口期（3日龄）,鳜口裂未张开,味蕾尚未分化;开口期（7日龄）,鳜口裂张开明显,味蕾呈椭圆形,突起高度平缓,主要分布在上下颌上皮上,舌、咽、鳃弓上皮上有少量分布;稚鱼期（14日龄）,味蕾呈圆锥形,突起高度上升,舌和咽上味蕾数目增加;21日龄,味蕾呈近梯形,突起高度不变,下颌、舌、咽上味蕾数增加,鳃弓上味蕾数目显著增加;28日龄,味蕾发育完全,口咽腔味蕾数继续增加。扫描电镜观察表明,鳜味蕾主要有3种类型：Ⅰ型味蕾近球形,含有大量微绒毛,突起高于上皮,味孔向外突起;Ⅱ型味蕾含有少量微绒毛,突起略高于黏膜上皮,味孔向内凹陷;Ⅲ型味蕾微绒毛含量最少,突起几乎与黏膜上皮共面,味孔平坦或凹陷。上下颌、咽、鳃中以Ⅰ型味蕾数量最多,Ⅱ型味蕾最少,舌上主要分布Ⅰ型味蕾,无Ⅲ型味蕾。结果表明,鳜早期味蕾结构发育与其摄食关联,推测其主要通过Ⅰ型味蕾和Ⅱ型味蕾对食物的机械性和化学成分进行识别。     

CD36与脂类味觉感受

CD36是一种脂类结合蛋白,在大鼠和小鼠的舌上皮细胞中均被发现,与长链脂肪酸（LCFA）具有高度亲和力,是啮齿类动物感受脂类的重要因子之一。研究表明这种蛋白质受体在口腔的脂类感受中起着至关重要的作用。CD36位于啮齿类口腔味蕾部分神经感受细胞的顶端部分,任轮廓状乳头中有特别高的表达,在叶状乳头中有少量表达,而在菌状乳头中几乎没有表达。     

扬子鳄味蕾及口腔上皮形态学初步观察

本文用光镜对扬子鳄味蕾的分布及口腔上皮的形态进行了观察。结果表明,味蕾主要集中在舌中间和腭帆的上皮中,舌腺分布于舌中部固有层内。本文还对扬子鳄味蕾分布的特点进行了讨论。     

运动性疲劳对大鼠乳头体nNOS表达的影响

目的：探讨乳头体中神经元型一氧化氮合酶（nNOS）与运动性疲劳的关系。方法：建立运动性疲劳动物模型,用免疫组织化学方法检测乳头体内侧核内侧部（mmm）、乳头体内侧核外侧部（mml）、乳头体内侧核后部（mmp）和乳头体外侧核（1m）等部位nNOS的表达。结果：疲劳组大鼠mm／n处nNOS阳性神经元数量为（4．504±2．84）cells／U,面积为（179．81±130．15）μm^2,均大于对照组（P〈0．05,P（0．01）;疲劳组大鼠mml处nNOS阳性神经元数量为（43．7±6．93）cells／U,面积为（5208．63±1253．20）μm^2,均大于对照组（P〈0．01）;疲劳组大鼠mmp处nNOS阳性神经元数量为（8．88±4．26）cells／U,面积为（202．75±109．67）μm^2,均大于对照组（P〈0．05）;疲劳组大鼠lm处nNOS阳性神经元数量为（27．2±6．94）cells／U,面积为（2763．23±1107．35）μm^2,均大于对照组（P〈0．01）;疲劳组大鼠mmp处和lm处nNOS阳性神经元灰度值分别为54．274±14．86和72．454±28．07,均大于对照组（P〈0．01,P〈0．05）。结论：乳头体nNOS神经元与运动性疲劳密切相关,NO可能在乳头体对疲劳应激反应的调节中发挥重要作用。     

味觉的生理学研究进展

味觉的生理学研究进展陈建国（江苏省启东肝癌研究所,启东２２６２００）沈福民（上海医科大学遗传医学研究中心,上海２０００３２）目录一、味觉的生理学基础（一）味蕾的刺激活动（二）味觉阈值分类二、尝味及味感觉机理（一）尝味试验的味扰作用（二）味感觉及舌图三...     

人乳头瘤病毒芯片寡核苷酸探针的研究

高危型人乳头瘤病毒（Human papillomavims,HPV）是宫颈癌的主要致病因子。利用Arraydesigner2．0和BLAST等生物学软件对10种型别的人乳头瘤病毒全基因组序列进行分析,设计高特异性、熔解温度（Tm）和GC含量相近的60mer HPV型特异性寡核苷酸探针,用于HPV检测芯片的制备,并对其中四型最常见HPV病毒（HPV6,11,16,18）探针的有效性进行初步验证,结果表明设计所得的探针型特异性好,可以应用于HPV的检测与分型。     

Induction of apoptosis by colchicine in taste bud and epithelial cells of the mouse circumvallate papillae

Apoptotic cells in the taste buds and epithelia of mouse circumvallate papillae after colchicine treatment were examined by the methods of in situ DNA nick-end labeling, immunocytochemistry, and electron microscopy. After colchicine treatment, numerous positive cells appeared in the taste buds by DNA nick-end labeling, and some epithelial cells in the basal and suprabasal layers in and around the circumvallate papillae also revealed positive staining. Condensed and fragmented nuclei with a high density were occasionally found in the taste bud cells and in the basal and suprabasal layer epithelial cells by electron-microscopic observation. An immunocytochemical reaction for tubulin revealed weak staining in taste bud cells, because of the depolymerization of microtubules, and a decrease of the microtubules in the taste bud cells was observed by electron microscopy. These results indicate that colchicine treatment of mice induces the apoptosis of taste bud and epithelial cells in the circumvallate papillae and dorsal epithelial cells around the circumvallate papillae.     

Changes in number and morphology of fungiform taste buds in rat after transection of the chorda tympani or chordalingual nerve

In normal rats there is one taste bud on the apical surfaceof each fungiform papilla. These taste buds are innervated bythe chorda tympani proper nerve (CT). According to general consensus,after cutting the nerve the taste buds should disappear. Inthis study, performed on 24 rats divided in six groups, theCT nerve on the left side (singly denervated) and the combinedchorda-lingual (CT-L) nerve on the other side (doubly denervatedwere permanently interrupted. The animals were sacrificed after5, 10, 20, 35,60 and 100 days and their tongues serially sectionedfor light microscope examiation. Some papillae were examinedunder an electron microscope. The papillae were categorizedinto three groups: papillae with a normal looking taste bud,with an abnormal looking taste bud and without a taste bud.The results showed a substantial number of papillae with a normallooking taste bud present at all time intervals in all animals.More specifically, on the singly denervated side the proportionof normal looking taste buds stayed below 10% until day 60,when it increased to 15% and to 23% on day 100. The proportionof abnormal looking taste buds decreased from above 92% by day5 to 49% on day 100. The percentage of fungiform papillae withoutsigns of a taste bud was relatively low on the singly denervatedside at times (1, 5, 16, 29, 34 and 28%). On the doubly denervatedside fewer than than 4% normal looking taste buds were foundthroughout the time period. The proportion of abnormal lookingtaste buds decreased from {small tilde} 96% by day 5 to 35%on day 100. A significantly higher proportion of papillae withno taste bud was observed on this side from day 10 onwards.(1, 29, 32, 52, 60 and 63%). The reasons for the differencein tast bud number between the doubly and singly denervatedsides are unknown, but it is possible that collaterals fromother (non-gustatory) nerves have an ability, although limited,to induce and maintain fungiform taste buds. In other words,the capacity to induce taste bud formation is not limited exclusivelyto gustatory nerves.     

Distribution and characterization of functional amiloride-sensitive sodium channels in rat tongue

The role of amiloride-sensitive Na+ channels (ASSCs) in the transduction of salty taste stimuli in rat fungiform taste buds has been well established. Evidence for the involvement of ASSCs in salt transduction in circumvallate and foliate taste buds is, at best, contradictory. In an attempt to resolve this apparent controversy, we have begun to look for functional ASSCs in taste buds isolated from fungiform, foliate, and circumvallate papillae of male Sprague-Dawley rats. By use of a combination of whole-cell and nystatin-perforated patch-clamp recording, cells within the taste bud that exhibited voltage-dependent currents, reflective of taste receptor cells (TRCs), were subsequently tested for amiloride sensitivity. TRCs were held at - 70 mV, and steady-state current and input resistance were monitored during superfusion of Na(+)-free saline and salines containing amiloride (0.1 microM to 1 mM). Greater than 90% of all TRCs from each of the papillae responded to Na+ replacement with a decrease in current and an increase in input resistance, reflective of a reduction in electrogenic Na+ movement into the cell. ASSCs were found in two thirds of fungiform and in one third of foliate TRCs, whereas none of the circumvallate TRCs was amiloride sensitive. These findings indicate that the mechanism for Na+ influx differs among taste bud types. All amiloride-sensitive currents had apparent inhibition constants in the submicromolar range. These results agree with afferent nerve recordings and raise the possibility that the extensive labeling of the ASSC protein and mRNA in the circumvallate papillae may reflect a pool of nonfunctional channels or a pool of channels that lacks sensitivity to amiloride.     

Immunohistochemical localization of carbonic anhydrase isozyme II in the gustatory epithelium of the adult rat.

The distribution of carbonic anhydrase isozyme II (CA II)-like immunoreactivity (-LI) in the gustatory epithelium was examined in the adult rat. In the circumvallate and foliate papillae, CA II-LI was observed in the cytoplasm of the spindle-shaped taste bud cells, with weak immunoreaction in the surface of the gustatory epithelium. No neuronal elements displayed CA II-LI in these papillae. There was no apparent difference in the distribution pattern between the anterior and posterior portions of the foliate papillae. In immunoelectron microscopy, immunoreaction products for CA II were diffusely distributed in the entire cytoplasm of the taste bud cells having dense round granules at the periphery of the cells. No taste bud cells displaying CA II-LI were detected in the fungiform papillae, but a few thick nerve fibers displayed CA II-LI. In the taste buds of the palatal epithelium, neither taste bud cells nor neuronal elements exhibited CA II-LI. The present results indicate that CA II was localized in the type I cells designated as supporting cells in the taste buds located in the posterior lingual papillae of the adult animal.     

Time course of morphological alterations of fungiform papillae and taste buds following chorda tympani transection in neonatal rats

The time course of structural changes in fungiform papillae was analyzed in rats that received unilateral chorda tympani nerve transection at 10 days of age. Morphological differences between intact and denervated sides of the tongue were first observed at 8 days postsection, with an increase in the number of fungiform papillae that did not have a pore. In addition, the first papilla with a filiform-like appearance was noted on the denervated side at 8 days postsectioning. By 11 days after surgery, the total number of papillae and the number of papillae with a pore were significantly lower on the transected side of the tongue as compared to the intact side. At 50 days postsection, there was an average of 70.5 fungiform papillae on the intact side and a mean of only 20.8 fungiform papillae the denervated side. Of those few remaining papillae on the cut side, an average of 13.5 papillae were categorized as filiform-like, while no filiform-like papillae occurred on the intact side. Significant reduction in taste bud volume was noted at 4 days posttransection and further decrements in taste bud volume were noted at 8 and 30 days postsection. Electron microscopy of the lingual branch of the trigeminal nerve from adult rats that received neonatal chorda tympani transection showed normal numbers of both myelinated and unmyelinated fibers. Thus, in addition to the well-characterized dependence of taste bud maintenance on the chorda tympani nerve, the present study shows an additional role of the chorda tympani nerve in papilla maintenance during early postnatal development.     

NT4/5 mutant mice have deficiency in gustatory papillae and taste bud formation.

Neurotrophins are key determinants for controlling the survival of peripheral neurons during development. Brain-derived neurotrophic factor (BDNF) and neurotrophin-4/5 (NT4/5) exert their action through a common trkB receptor but independently support gustatory sensory neurons. To assess the role of NT4/5 during development, we examined the postnatal development and maintenance of fungiform taste buds in mice carrying a deletion of NT4/5. The absence of NT4/5 results in embryonic deficits in gustatory innervation and a reduced number of fungiform papillae at birth. No degenerative deficits of fungiform papillae were observed for the first 3 weeks of postnatal development. However, these remaining fungiform papillae were smaller in appearance and many did not contain taste pores. By postnatal day 60, there was 63% decrease in the number of fungiform papillae, and remaining papillae were smaller in size or modified into filiform-like spines. These papillae had either no taste bud or a taste bud with a reduced number of taste cells compared to controls. These findings demonstrate that the NT4/5 gene functions in the maintenance of fungiform gustatory papillae and raises the possibility for an earlier role in development.     

Pharmaco-histochemical studies on a specific monoamine in the gustatory epithelia of the rabbit.

The foliate, vallate and fungiform papillae of the rabbit's tongue were studied fluorescence-histochemically under normal and experimental conditions. In normal animals a yellow fluorescence suggesting the presence of a serotonin-like monoamine was demonstrated only in taste bud cells of the foliate papilla, though its intensity was very weak. The fluorescence disappeared completely following reserpine treatment, while it was significantly enhanced by the treatment with nialamide. The fluorescence of taste bud cells could be clearly distinguished from that of catecholamines by the treatment with alpha-MMT followed by nialamide. When 5-HTP, 5-HT and 5,6-DHT were administered separately, each of these drugs was selectively taken up in taste bud cells of the foliate and vallate papillae, but no fluorescent cells were observed in the fungiform papilla. From the present results, it seems reasonable to conclude that the fluorigenic amine of taste bud cells may be 5-HT (serotonin), or at least an indoleamine derivative. Also, it is suggested that the taste bud of the vallate papilla contains a cell type which can potentially synthesize a biogenic amine in situ, or is actually synthesizing it in a very small amount just like in the case of the taste bud of the foliate one.     

Neural crest contribution to lingual mesenchyme, epithelium and developing taste papillae and taste buds

The epithelium of mammalian tongue hosts most of the taste buds that transduce gustatory stimuli into neural signals. In the field of taste biology, taste bud cells have been described as arising from "local epithelium", in distinction from many other receptor organs that are derived from neurogenic ectoderm including neural crest (NC). In fact, contribution of NC to both epithelium and mesenchyme in the developing tongue is not fully understood. In the present study we used two independent, well-characterized mouse lines, Wnt1-Cre and P0-Cre that express Cre recombinase in a NC-specific manner, in combination with two Cre reporter mouse lines, R26R and ZEG, and demonstrate a contribution of NC-derived cells to both tongue mesenchyme and epithelium including taste papillae and taste buds. In tongue mesenchyme, distribution of NC-derived cells is in close association with taste papillae. In tongue epithelium, labeled cells are observed in an initial scattered distribution and progress to a clustered pattern between papillae, and within papillae and early taste buds. This provides evidence for a contribution of NC to lingual epithelium. Together with previous reports for the origin of taste bud cells from local epithelium in postnatal mouse, we propose that NC cells migrate into and reside in the epithelium of the tongue primordium at an early embryonic stage, acquire epithelial cell phenotypes, and undergo cell proliferation and differentiation that is involved in the development of taste papillae and taste buds. Our findings lead to a new concept about derivation of taste bud cells that include a NC origin.     

Immunocytochemistry of keratins in the mucous membrane of the rat tongue]

C12 and E2 monoclonal antibodies to keratins stained taste bud cells of foliate papillae as well as the cells of the associated glands. H4 monoclonal antibody to keratin reacted with the surrounding epithelial cells and did not react with the taste bud cells. The results show that the keratin subtype differs between taste bud and surrounding epithelial cells. The similar keratin composition of taste bud and associated gland cells confirms the view about existence of the same type cells in these two structures.