扬子鳄眼球的胚胎发生

在２４例扬子鳄胚胎中，观察了眼球的发生及其组织分化过程。孵化后第２ｄ，视泡已从前脑突出形成，第６ｄ形成双层视杯和晶状体泡。晶状体纤维先由晶状体泡后壁上皮生成，然后由赤道部的泡壁上皮生成。虹膜、角膜内皮和基质均由视杯周围的间充质迁入形成。视网膜的色素上皮层最先分化。神经上皮在第１６ｄ出现节细胞的内迁。第１８ｄ可辨认节细胞层和神经纤维层。第２４ｄ可辨认内网层。第３０ｄ开始出现外核层与内核层的分化。第３     

扬子鳄胚胎气管,支气管的发生

通过对２８例扬子鳄胚胎气管、支气管的发生过程的观察，发现孵化第６ｄ出现喉气管沟，第８ｄ形成气管芽和支气管芽。第１４－４０ｄ中，气管与支气管上皮周围的间充质细胞逐渐聚集，并分化形成粘膜下层、软骨片及外膜的纤维膜。第２０－４６ｄ中，气管及支气管的上皮由复层柱状上皮逐步演弯为单层或假复层柱状上皮。本文还对扬子鳄气管、支气管组织发生的部分特点作了讨论。     

扬子鳄胚胎中肾发生及退化

目的：在11个不同发育时期扬子鳄胚胎中观察中肾的发生及退化过程。方法：采用电镜、细胞化学及免疫组织化学方法。结果：孵育第6期在中肾管前端附近出现一些中肾小泡。第8期形成“S”形中肾小管。第13—17期鳄胚体前部部分中肾小管盲端内陷，形成原始的肾小囊和肾血管球，中肾小管显著伸长并迂回曲折。第20一22期，体前后部中肾组织均已形成完整的肾单位。中肾小管颈段由纤毛柱状上皮细胞组成，近球小管上皮细胞含丰富的PAS阳性物质并呈表皮生长因子(EGF)、转化生长因子(TGFβ1)和生长抑素(SS)免疫阳性反应。第24—28期，体前部至后部的中肾组织依次退化。结论：(1)扬子鳄中肾除重吸收作用外还具有内分泌功能；(2)中肾退化时，细胞凋亡依次表现为核固缩，出现大量凋亡小体，线粒体数目剧增并膨胀，线粒体等细胞器自溶及核消失；(3)中肾退化可能与小管细胞中TGFβ1及SS大量表达有关。     

扬子鳄胚胎后肾发生的组织学及细胞化学观察

目的：通过对扬子鳄胚胎后肾组织发生过程的观察,探讨其后肾发生及分化的规律和特点。材料与方法：用组织学及细胞化学染色法,在光镜下对９个不同发育时期的胚胎进行了观察。结果：孵育第１８天,从泄殖腔附近发出的输尿管芽向生后肾组织侵入生长,生后肾组织产生许多生后肾小泡。第２４天出现集合管及肾小管、肾小囊的雏形。第３０天肾小管显著伸长并发生折叠,出现近曲小管、远曲小管和肾小管中间段的形态分化。第４０￣６２天,肾小体逐渐发育成熟,肾小管各段逐步出现机能分化。在后肾发育过程中,ＰＡＳ阳笥物质首先出现于集合管上皮细胞,其次是远曲小管,最后是肾小管中间段和近曲小管。第２４￣３０天中,集合管、肾小管及肾小囊上皮细胞中ＲＮＡ含量均丰富,呈弥散型分布,第４０天以后肾组织中ＲＮＡ含量迅速减少。结论：扬子鳄后肾不同区域肾单位的发生与分化存在     

扬子鳄胚胎舌表面的扫描电镜观察

在扫描电镜下观察了孵化第３６ｄ至第６２ｄ孵出的扬子鳄（Ａｌｌｉｇａｔｏｒｓｉｎｅｎｓｉｓ）胚胎舌表面的形态变化过程。舌表面于孵化第３８ｄ形成少数大的隆起与凹陷，第４刚开始出现舌乳头。舌上皮细胞的表面在第３６～４２ｄ为圆形，表面光滑，中央凹陷，以后逐渐变成扁平细胞，第５２ｄ细胞呈规则的多边形，表面微绒毛清晰，细胞中央有一向外隆起的圆形或卵圆形核区，第５６ｄ后老化的舌上皮出现脱落现象。孵化第４２ｄ舌后部及中部的上皮内陷形成较大的舌腺腺孔。第４８～５６ｄ中，较小的舌腺孔显著增多，而大舌腺孔数目无明显增加。第６２ｄ多数大舌腺孔内可见有粘液样分泌物。舌表面味蕾的形成很迟，第５６ｄ才出现Ⅰ、Ⅱ、Ⅲ型发育中的味蕾，第６２ｄ形成部分成熟的味蕾。本文对扬子鳄舌腺及味蕾的形态发生特点作了讨论。     

人胚胎视网膜发育过程中突触囊泡蛋白的表达

用光、电镜免疫组织化学方法研究了６～３８周人胚胎视网膜突触囊泡蛋白的表达及超微定位。结果显示：１．人胎１４周突触囊泡蛋白才出现在早期视细胞的胞质中，随后，内网层及节细胞的胞体也相继出现，且由视网膜的中央区向周边区发展；２．随着胎龄增长，神经细胞发育长大，突触囊泡蛋白的含量也逐渐增加，并从核周质中转移至突触前末梢，３２周时基本与成人相似；３．突触囊泡蛋白主要定位于突触前终末的突触小泡，核周质及轴突中     

扬子鳄牙齿的发生和替换

目的：探讨扬子鳄牙齿发生与替换的特点。方法：用石蜡切片观察扬子鳄牙齿的发生和替换过程，用扫描电镜观察牙齿的结构。结果：孵化第20d外胚层开始内陷形成牙褶；孵化第56d，牙胚已形成；幼鳄孵出后第16d，牙冠已形成，同时牙胚已转移至牙槽底部。1-5龄鳄中已牙齿的牙槽底部均保留1个牙胚，该牙胚可发育成为新生牙来替换已脱落的旧牙。结论：扬子鳄口腔边缘粘膜中的外胚层向固有层内陷形成的牙褶在牙齿的胚胎发生中可能起诱导作用；而在新生牙替换旧牙的过程中，由牙槽底部保留的牙胚直接形成新生牙。     

扬子鳄大脑皮层后期胚胎发育的超微结构

目的：研究扬子鳄大脑皮层的后期胚胎发育,为比较胚胎学提供资料。方法：电镜观察。结果：大脑皮层可分为梨状皮质、新皮质、海马皮质3部分。孵化40d,梨状皮质和新皮质均处于较幼稚状态,海马皮质发育稍好。孵化50d,梨状皮质变化小大;新皮质中幼稚神经细胞数量明显减少;海马皮质得到进一步发育。孵出期,梨状皮质中仍见小到较成熟的神经细胞,新皮质和海马已基本成熟,但新皮质中仍有不少不成熟的神经细胞。结论：扬子鳄大脑皮层各部分的胚胎发育具不同步性。验证了爬行类动物的起源是多样化的。     

Fine structure of the developing epidermis in the embryo of the American alligator (Alligator mississippiensis,Crocodilia, Reptilia)

The morphological transition from the simple epidermis that contacts the amniotic fluid of embryonic crocodilians to the adult epidermis required in a terrestrial environment has never been described. We used light and electron microscopy to study the development, differentiation and keratinisation of the epidermis of the American alligator, Alligator mississippiensis, between early and late stages of embryonic skin formation. In early embryonic development, the epidermis consists of a flat bilayer. As it develops, the bilayered epidermis comes to lie beneath the peridermis. Glycogen is almost absent from the bilayered epidermis but increases in basal and suprabasal cells when scales form. Glycogen disappears from suprabasal cells that accumulate keratin. The peridermis and 1 or 2 subperidermal layers form an embryonic epidermis that is partially or totally lost before hatching. These cells accumulate coarse filaments and form reticulate bodies. Mucous and lamellate granules are produced in the Golgi apparatus and are partly secreted extracellularly. The embryonic cells darken with the formation of larger reticulate bodies that aggregate with intermediate filaments and other cell organelles, as their nuclear chromatin condenses. Thin β‐cells resembling those of scutate scales of birds develop beneath the embryonic epidermis and form a stratified β‐layer that varies in thickness in different body regions. The epidermis differentiates first in the back, tail and belly. At the beginning of β‐cell differentiation, the cytoplasm contains sparse bundles of α‐keratin filaments, glycogen and lipid droplets or vacuoles apparently derived from the endoplasmic reticulum and Golgi apparatus. These organelles disappear rapidly as irregular bundles of electron‐dense β‐keratin filaments accumulate and form larger bundles. The larger bundles consist of 3 nm thick electron‐pale keratin microfibrils and are derived from the assemblage of β‐keratin molecules produced by ribosomes. While in mammals the epidermal barrier is formed by α‐keratinocytes, in the alligator the barrier is formed by β‐keratin cells. The β‐layer is reduced or absent from the small hinge region between scales. In the latter areas the barrier is made of a or a mixture of α/β keratinocytes. Thus alligators resemble birds where the β‐keratin molecules are deposited directly over an α‐keratin scaffold, rather than an initial production of β‐keratin packets which then merge with α‐keratin, as occurs in the Chelonia and Lepidosauria. The pigmentation of the epidermis of embryos is mostly derived from epidermal melanocytes.     

扬子鳄大肠和输尿管的神经肽分布

目的:观察扬子鳄大肠的神经肽Y（neuropeptide Y,NPY）、血管活性肠肽（vasoactive intestinal peptide,VIP）和输尿管的P物质（substance P,SP）、血管活性肠肽分布。方法:免疫荧光方法。结果:扬子鳄大肠的NPY和VIP免疫反应（NPY-and VIP-immunoreactive,NPY和VIP-IR）阳性神经纤维皆呈弯曲的细线状,主要位于粘膜下层,其次为浅部肌层,且在粘膜下层NPY-IR神经纤维交织成密集的神经丛;VIP-IR神经纡维在粘膜下层构成稀疏的网络状。输尿管的SP免疫反应（SP-immunoreactive,SP-IR）和VIP-IR神经纤维均呈点线状;其中,SP-IR神经纤维位于外膜层,较稀疏,VIP-IR神经纤维位于肌层,较密集,纤维间可见两个近似圆形的VIP-IR阳性神经细胞体。结论:扬子鳄大肠和输尿管分别存在有NPY、VIP和SP、VIP神经分布。     

扬子鳄食管颈段一氧化氮合酶(NOS)阳性神经元及神经纤维的分布

本实验采用还原型尼克酰胺腺嘌呤二核苷酸脱氢酶(NADPH-d)方法,观察扬子鳄食管颈段NOS阳性神经元和神经纤维的分布.结果食管颈段的粘膜下层和肌层分布着较丰富的NOS阳性神经纤维,一些神经纤维交织成丛状,其间散在分布着NOS阳性神经元胞体.粘膜下一些NO S阳性神经丛环绕血管壁走行.     

扬子鳄胸髓一氧化氮合酶和乙酰胆碱酯酶阳性神经元的分布

目的观察一氧化氮合酶(NOS)和乙酰胆碱酯酶(AChE)阳性神经元在扬子鳄胸髓的分布。方法采用还原型尼克酰胺腺嘌呤二核苷酸脱氢酶(NADPH-d)法和亚铁氰化铜法观察扬子鳄胸髓NOS和AChE阳性神经元的分布。结果扬子鳄胸髓前角、后角和中央灰质内可见NOS和AChE阳性神经元,白质内含有丰富的NOS和AChE阳性神经纤维。结论扬子鳄胸髓有NOS和AChE阳性神经元分布。     

扬子鳄卵巢内血管活性肠肽、神经肽Y和P物质的分布

目的:观察扬子鳄卵巢内血管活性肠肽（vasoactive　intestinal　peptide,VIP）、神经肽Y（neuropeptide Y,NPY）和P物质（substance P,SP）的分布情况。方法:免疫荧光法。结果:扬子鳄卵巢内的VIP免疫反应（VIP-immunoreac-tive,VIP-IR）阳性神经纤维呈波浪状,部分包绕卵泡,大部分交织在卵泡间血管周围,并构成较密集的网络;SP和NPY免疫反应（SP-and NPY-immunoreactive,SP-和NPY-IR）阳性神经纤维均为点线状,主要沿卵泡间血管周围分布,其中,部分NPY-IR纤维也构成较密集的网络。切片中均未见到三种肽能神经元的细胞体。结论:扬子鳄卵巢内存在有VIP、NPY和SP阳性神经纤维分布,主要位于卵泡间血管周围。     

5-Hydroxytryptamine and Dopamine Neurons in the Cerebellum of the New-Hatching Yangtze Alligator Alligator sinensis

Nissl and immunohistochemical staining methods were used to morphologically characterize the cerebellum of the new-hatching Yangtze alligator, and the cerebellar histological structure and the distribution profiles of 5-hydroxytryptamine (5-HT) and dopamine (DA) neurons were investigated for the first time. The results of cerebellar histological structure showed that there was a ventriculus cerebelli in the cerebellum of the new-hatching Yangtze alligator, the surface of the cerebellar cortex was not very smooth, the cerebellar cortex could be divided into four layers, which include external granular layer, molecular layer, Purkinje cell layer and granular layer, Purkinje cell layer could be characterized specially by multilayer, two cerebellar nuclei termed as the nucleus cerebelli lateralis and the nucleus cerebelli medialis were found in the cerebellar medulla. 5-hydroxytryptamine-immunoreactive (5-HT-IR) and dopamine-immunoreactive (DA-IR) neurons and fibers distributed widely in the cerebellum. The structures and profiles of 5-HT-IR and DA-IR neurons and fibers in the cerebellum of the Yangtze alligator were similar to that reported in other reptiles, but also had some specific features. The abundance of 5-HT and DA in cerebellum suggested that these highly conserved neurotransmitters would play important roles in motor control. Anat Rec, 302:861–868, 2019. © 2018 Wiley Periodicals, Inc.