家犬嗅球组织学结构的性别和年龄差异

用组织学方法研究家犬嗅球的结构,观察家犬嗅球内结构的性别和年龄差异,依据常规HE染色法及数理统计学原理对家犬嗅球各层宽度,主要细胞的数量进行比较统计学分析,探讨嗅球内部结构的发育过程以及性别差异对雌雄动物嗅觉差异的影响。结果表明：雌雄幼年家犬嗅球内各层结构差异不显著;成年家犬也表现出同样的结果,但是成年动物的僧帽细胞形态、数量差异极显著。分析发现,幼年家犬嗅球各层结构都已比较明显,成年家犬嗅球体积和重量明显增加,各层宽度明显变宽,各层细胞密度显著降低,说明嗅球也处在不断的发育完善过程之中。同时僧帽细胞的差异可能是造成雌雄动物嗅觉差别的原因之一。     

秦岭蝮嗅觉系统和犁鼻系统的显微结构观察

用光镜观察了秦岭蝮Gloydius qinlingensis嗅觉系统和犁鼻系统的组织结构.结果显示秦岭蝮嗅觉系统主要包括嗅器和嗅球,犁鼻系统主要包括犁鼻器和副嗅球,并且嗅器和犁鼻器已经完全分离形成两个独立的囊,犁鼻器位于嗅器的内侧.嗅器粘膜上皮进一步分化为嗅上皮和呼吸上皮,背侧嗅上皮下的固有层内有丰富的Bowmans腺,腹侧呼吸上皮内有大量的杯状细胞,其固有层未见有Bowmans腺.鼻腔的中段出现了发达的犁鼻器,犁鼻上皮明显比嗅上皮厚,其固有层内未见有犁鼻腺,在犁鼻腔内还有蘑菇体.     

嗅球成鞘细胞的分离培养与鉴定

目的:探讨一种获取高纯度嗅球成鞘细胞(olfactory ensheathing cells,OECs)的方法.方法:从新生SD大鼠(3d)嗅球中迅速分离嗅神经层和嗅颗粒层,采用酶消化法分离细胞,差速贴壁法纯化细胞,接种于多聚赖氨酸包被的培养板内培养2d,采用NGFRp75和S100蛋白双标免疫组化、以Hoechst33342复染鉴定OECs的纯度.结果:OECs的纯度为(95.64±2.76)%.结论:本法是一种相对简便易行且经济、稳定、有效的OECs分离方法.     

成年大鼠嗅鞘细胞与嗅觉神经成纤维细胞的原代培养及鉴定

目的 建立一种原代提取嗅鞘细胞与嗅觉神经成纤维细胞混合培养的方法.方法 自2.5月龄SD大鼠嗅球最外两层分离嗅鞘细胞和嗅觉神经成纤维细胞进行混合培养,并不进行纯化,分别于7 d、10 d、14 d行免疫细胞化学鉴定,并计算各个时间点嗅鞘细胞的纯度.结果 体外培养的嗅鞘细胞主要呈两极或多极状,而嗅觉神经成纤维细胞则成扁平的像成纤维细胞的形态,免疫细胞化学结果显示嗅鞘细胞呈p75 NGFR阳性,嗅觉神经成纤维细胞呈fibronectin阳性,两种细胞都呈vimentin阳性,在7 d、10 d、14 d各个时间点嗅鞘细胞分别占混合培养的34.1%、25.6%、8.6%.结论 从成年大鼠嗅球最外两层分离的培养中主要包含嗅鞘细胞和嗅觉神经成纤维细胞,嗅鞘细胞在混合培养中所占的比例随培养时间的延长而逐渐降低.     

棕色田鼠脑和行为不同发育阶段副嗅球和主嗅球的细胞活动

本文运用免疫组化显示Fos蛋白的方法首次研究了棕色田鼠脑和行为不同发育阶段副嗅球和主嗅球的细胞活动。当不同年龄阶段的幼鼠同时暴露于自己家庭的熟悉底物和另一家庭的陌生底物时 ,嗅闻和呆在自己熟悉底物上的时间较多 ,直到产后 15d、 2 0d和 2 5d时 ,幼鼠探究不同底物的行为显示出显著性差异。脑的大小随着日龄增加而增加 ,但从产后 1到 15d ,脑重、脑宽和嗅球大小随着日龄增加特别显著。当不同日龄幼鼠暴露于陌生底物或者暴露于自己的熟悉底物时 ,从产后 5到 15日龄 ,主嗅球僧帽细胞层、颗粒细胞层、副嗅球僧帽细胞层和颗粒细胞层Fos免疫阳性细胞随着日龄明显增加 ,但直到 15和 30日龄时 ,和对照组相比 ,陌生底物可引起幼鼠主嗅球Fos免疫阳性细胞明显增加 ,从 2 0日龄起 ,陌生底物可引起副嗅球Fos免疫阳性细胞明显增加。主嗅球颗粒细胞层Fos免疫阳性细胞随着日龄的增加从边缘到中心逐渐出现 ,而副嗅球Fos免疫阳性细胞随着日龄的增加从顶部到底部逐渐出现。以上结果说明产后第 1d到 15d左右可能是棕色田鼠脑结构发育的重要阶段 ,而从此以后棕色田鼠主嗅球和副嗅球就具有区别熟悉气味和陌生气味的能力 ,表明棕色田鼠行为、脑发育和细胞活动间有紧密关系     

棕色田鼠雄性幼体不同发育期犁鼻器和副嗅球的组织结构

通过对出生后不同发育时期雄性棕色田鼠犁鼻器和副嗅球进行组织学观察, 探讨棕色田鼠出生后犁鼻器和副嗅球的发育规律。实验以出生后当天(0 日龄) , 5 日龄, 15 日龄, 25 日龄以及成年棕色田鼠为研究对象,副嗅球采用Pischinger 氏染色法染色, 犁鼻器用H. E. 染色法染色后进行组织学观察。结果显示, 棕色田鼠出生时, 犁鼻器和副嗅球就已具有成体的基本结构, 随着动物个体的发育, 犁鼻上皮逐渐增厚, 犁鼻管变长, 犁鼻上皮中神经元密度增加; 腺体逐渐增大, 犁鼻管腔填充物增多, 犁鼻管背外侧的静脉血管逐日增大, 管腔周围出现越来越多的血管; 副嗅球长宽都增加, 僧帽细胞层和颗粒细胞层逐渐增长, 各层细胞密度变化稍有不同;出生后15 日内, 僧帽细胞层细胞密度增加, 15 日龄以后又开始降低, 25 日龄及成体的僧帽细胞层细胞密度与5日龄的相似; 颗粒细胞层细胞密度持续增高。实验结果提示, 棕色田鼠5 日龄时, 犁鼻器和副嗅球已具有了完整的结构, 到25 日龄时可能达到了功能上的成熟。     

达乌尔黄鼠犁鼻器和副嗅球的组织结构及嗅球c-Fos表达的季节变化

啮齿动物的犁鼻器和副嗅球与社会通讯和生殖行为有关,主嗅球影响其觅食行为。达乌尔黄鼠（Spermophilus dauricus）是一种具有较低社会行为的储脂类冬眠动物。本研究用组织学和免疫组织化学方法探究了其犁鼻器和副嗅球的结构特点及嗅球神经元活动对季节变化的适应。结果发现,达乌尔黄鼠犁鼻器具有较大的血管,犁鼻器管腔外侧为非感觉性的呼吸上皮（Respiratory epithelium,RE）,内侧为感觉上皮（Sensory epithelium,SE）,RE较SE薄,靠近管腔处为假复层柱状上皮。选取犁鼻器中间部位比较,发现SE的厚度、长度及感觉细胞密度均无性别差异。副嗅球位于主嗅球后方背内侧,由6层细胞构成。侧嗅束穿过副嗅球,位于颗粒细胞层之上。雄性达乌尔黄鼠较雌性有更长的僧帽细胞层和颗粒细胞层。春季（3月）和冬季（1月）达乌尔黄鼠主嗅球的嗅小球层、僧帽细胞层和颗粒细胞层的c-Fos-ir神经元密度显著低于夏季（7月）和秋季（10月）,且冬季外网织层的c-Fos-ir神经元密度显著低于夏季和秋季,说明达乌尔黄鼠在冬季和春季的嗅觉神经活动较弱,呈现出对冬眠的生理性适应。这些结果丰富了动物犁鼻器和副嗅球的形态学资料,并有助于理解冬眠动物嗅觉系统对季节变化和冬眠的适应。     

基质金属蛋白酶

基质金属蛋白酶是一类分解细胞外基质组分的锌蛋白酶⒚它们在有机体生长发育中的细胞外基质逆转与重塑以及疾病中的病理损害起着极为重要的作用⒚基质金属蛋白酶的表达和活性在不同细胞水平受到严密调控,如细胞因子、生长因子以及激素的调节⒚基质金属蛋白酶以酶原形式分泌,随后被其它蛋白酶如胞浆素或非蛋白酶类化学物质如有机汞所激活⒚所有基质金属蛋白酶都受到天然抑制剂 金属蛋白酶组织抑制剂所抑制⒚两者的不平衡导致许多疾病的发生,如肿瘤侵入及转移⒚合成基质金属蛋白酶组织抑制剂所抑制,如 Ｍ ａｒｉｍ ａｓｔａｔ 能控制肿瘤转移的发生及进一步扩散⒚本文将对基质金属蛋白酶的特征、分子区域结构、底物特性、激活机制、调控方式等方面进行最新概述⒚     

刺猬嗅球冬眠期与非冬眠期c-Fos 表达的差异

利用免疫组化法检测c-Fos 蛋白在不同季节刺猬嗅球各层次的表达差异,探讨c-Fos、嗅觉、冬眠三者的关系。分别选取春、夏、秋、冬四个季节各6 只野生健康刺猬,固定剥离嗅球,石蜡切片,免疫组化显色,拍片,载入Motic Images Advanced 3.2 软件,测量四个季节刺猬嗅球各层次c-Fos 的表达率,将结果载入GraphPadPrism4 软件分析,Microsoft Excel 作图。结果表明:c-Fos 蛋白在成年刺猬嗅球各层均有不同程度的表达,阴性对照不着色,且表现出明显的季节性差异。1)与秋季相比,冬眠期c-Fos 蛋白在刺猬嗅球各层次的表达均有极显著的降低(P <0.01);2)与夏季相比,冬眠期c-Fos 蛋白在外网丛层、僧帽细胞层、颗粒细胞层的表达有极显著降低(P < 0. 01),在嗅神经层、嗅小球层、室管膜层的表达也有显著降低(P < 0. 05);3)与冬眠期相比,春季c-Fos 蛋白在嗅小球层、僧帽细胞层、颗粒细胞层的表达有极显著的升高(P <0. 01),在嗅神经层、外网丛层、室管膜层的表达却没有显著变化(P ﹥ 0.05);4)嗅神经层c-Fos 的表达在春季显著低于秋季,夏季与秋季没有显著差异。颗粒细胞层夏季显著低于秋季(P < 0.05)。秋季c-Fos 在其余各层次的表达与春季、夏季相比都有极显著的提高(P <0.01)。结论:秋季刺猬嗅球神经元最活跃,嗅觉最灵敏,冬眠期刺猬嗅球活跃性大大降低,嗅觉系统最迟钝。c-Fos 在刺猬嗅球中的强表达表明其在嗅觉信息的传递中可能发挥一定作用,c-Fos 表达率的显著季节性差异揭示了刺猬嗅球的活跃性与其冬眠具有一定的相关性。     

幼龄红嘴相思鸟小脑皮层组织学结构

为了探讨不同日龄幼龄红嘴相思鸟（Leiothrix lutea）小脑皮质的组织学结构变化,本文分别以1、5、9日龄幼龄红嘴相思鸟为研究对象,通过H.E.和甲苯胺蓝法进行染色,光镜下观察红嘴相思鸟小脑冠状切面的显微结构。结果显示,1日龄时小脑皮层由外颗粒层（EGL）、浦肯野细胞层（PCL）和内颗粒层（IGL）3层构成,外颗粒层较厚且清晰,而浦肯野细胞层和内颗粒层界限不清楚;5日龄和9日龄时小脑皮质均可见外颗粒层、分子层（ML）、浦肯野细胞层和内颗粒层4层结构。对不同日龄红嘴相思鸟小脑皮质各层厚度进行单因素方差分析显示,随日龄增长,小脑皮质、分子层和内颗粒层厚度极显著增厚（P < 0.01）,浦肯野细胞体积也极显著增加（P < 0.01）;外颗粒层厚度变化不明显（P < 0.01）,呈现先增厚后变薄的趋势,与皮质厚度的比例逐渐减小。研究表明,幼龄红嘴相思鸟在出生后,随日龄增长,小脑皮质层逐渐发育成熟。内颗粒层与外颗粒层的相对变化规律表明内颗粒层细胞是由外颗粒层细胞迁移而来。     

An ultrastructural study of embryonic chick retinal neurons in culture

Summary The differentiation of cells and synapses in explants of 9-day-old chick embryo retina has been studied by light and electron microscopy over a period of 35 days in vitro, and samples of retina from the 9-day chick foetus were directly fixed and prepared for study.At the time of explantation the retinae were poorly differentiated and no lamination was apparent. From day 14 onwards, (i) outer and inner nuclear layers (ONL, INL) separated by a layer of neuropil corresponding to the outer plexiform layer (OPL) and (ii) a layer of scattered large ganglion cells separated from the INL by a zone of neuropil resembling the inner plexiform layer (IPL) were apparent, and (iii) a well-differentiated outer limiting membrane was established close to the surface of the explants. In the oldest cultures some development of photoreceptor outer segments occurred but a distinct optic nerve fibre layer did not form.Although cell identification presented problems even in the oldest cultures, the major retinal cell types described in vivo could be identified. Photoreceptor cells developed pedicles in the OPL which became filled with synaptic vesicles and synaptic ribbons and established ribbon synapses (including triads) with and were commonly invaginated by processes from horizontal and bipolar cells. Processes of bipolar cells in the IPL formed simple and dyad synapses. At least two types of presynaptic amacrine cells were also identified in the INL, one of which contained large numbers of dense-core vesicles. The ganglion cells, though sparse, were large and well differentiated.These findings show that all the major neuronal types of the retina are capable of developing and differentiating in vitro, lagging behind the time-table of development and differentiation in vivo by approximately 7 days, but resulting in a histotypically organised retina with synaptic neuropil showing many similarities to the corresponding neuropil in vivo.     

Pattern formation and the fine structure of the developing cell wall in colonies of Pediastrum boryanum

A single-layered disc of peripheral pronged cells and central prongless cells impart the typical gear shape to colonies of Pediastrum, while the walls of each cell have a characteristic reticulate triangular pattern. The two-layered wall forms in the cells during colony formation following zoospore aggregation and adhesion. The uniformly thin outer layer reflects contours resulting from differential thickening in the reticulate pattern of the inner, thicker, more fibrillar and granular wall layer. The reticulate pattern thus imparted to the outer wall layer persists in empty zoosporangia following the release of zoospores. Columns of electron-dense material extend through the outer wall layer except at the ridges and centers of the reticulum. Following mitosis and cleavage, the resulting zoospores are extruded within a vesicle membrane consisting of the inner wall layer. Separation of this membrane from the parent cell occurs in material of the inner layer adjacent to the outer wall. Vesicles containing swarming zoospores also contain a granular material which appears to become associated with the aggregating and adhering cells of new colonies. Microtubules occur in zoospores prior to adherence but are absent during wall deposition.     

Some horizontal cells of the bovine retina receive input synapses in the inner plexiform layer

Bovine retinae were stained immunocytochemically with antibodies against the calcium-binding protein, calbindin. Horizontal cells in the outer plexiform layer were heavily labelled. The processes of most horizontal cells were confined to the level of the outer plexiform layer, and the tips of their dendrites were positioned as the lateral elements of the cone triads, viz. the usual mammalian arrangement. However, some of the horizontal cells had additional thick processes descending to branch within the inner plexiform layer, where they were postsynaptic at bipolar cell dyads and where they also received input from amacrine cells. No output synapses of horizontal cells were observed in the inner plexiform layer.     

Submicroscopic Changes in Visual Cells of the Rabbit Induced by Iodoacetate

Alterations produced by iodoacetate in visual cells have been studied under the electron microscope. Lesions of the outer segments of the rods are visible as early as 3 hours after a single injection of 20 mg. iodoacetate per kg. body weight. After 6 hours the changes are more marked and consist then of disorganization, vesiculation, and lysis of the rod sacs. The inner segments of most rod cells show swelling and vacuolization of the matrix, the endoplasmic reticulum, and the Golgi complex. The mitochondria of the ellipsoid show a tendency to disintegrate. In some inner segments the changes consist primarily in an increase in density of the matrix and deposition of a granular material. The rod synapses are also affected, showing lysis of the synaptic vesicles and alterations of the synaptic membrane. With a second injection of 20 mg. iodoacetate per kg. body weight, all these changes become more marked and lead to complete destruction of the rod cells. The cones seem more resistant than the rods. A single injection produces no visible changes in the outer or inner segments of the cones. At cone synapses, however, there are changes consisting of fusion of synaptic vesicles and other membranous material to form large concentric membranes characteristic of myelin figures. A second dose of the drug causes complete destruction of the cone cells. All these, and other submicroscopic changes, are discussed in relation to various hypotheses put forward to explain the mode of action of iodoacetate on visual cells. The pronounced alterations of submicroscopic intracellular membranes suggest that the locus of action of iodoacetate may be a component widely dispersed throughout the visual cells and related, in some way, to the maintenance of these lipoprotein structures.     

THE DISTRIBUTION OF CHOLINE ACETYLTRANSFERASE ACTIVITY IN VERTEBRATE RETINA1

Abstract— Choline acetyltransferase (ChAc) activity was determined in retinal layers from 10 vertebrates. In all animals, the highest activity was in the inner plexiform layer, intermediate activity in the inner nuclear and ganglion cell layers, and very low activity in the photoreceptor and outer plexiform layers and optic nerve. The pattern of distribution of enzyme activity within the inner nuclear layer corresponds quantitatively to the distribution of amacrine cells within that layer. A species difference of almost 90-fold was found between the lowest and highest values for ChAc activity in inner plexiform layer. The variation in enzyme activity found among homeotherms in inner nuclear and inner plexiform layers is related to the number of amacrine cell synapses in the inner plexiform layer. But the differences in enzyme activity are generally greater than those which have been found in numbers of amacrine cell synapses between species. The data suggest that cholinergic neurons in retina are to be found predominantly among the amacrine cell types and that not all amacrine cells will be found to be cholinergic.     

Ciliary epithelia of the mammalian eye in cultured explants

The ultrastructural characteristics of ciliary epithelium from bovine, pigmented rabbit, and fetal albino rabbit were studied in cultured explants. The tips of ciliary processes were cultured in plastic dishes with Dulbecco Modified Eagle Medium (DMEM) containing 5% fetal bovine serum. More than half of the explants adhered to the plastic culture dish, and epithelial cells spread as monolayers within a few days. Initially the explant contains two layers, the outer (nonpigmented cells) and the inner (pigmented cells). Later the explant exhibits three layers: 1) outermost lightly pigmented flattened cells, 2) an outer layer of non-pigmented cells, and 3) an inner layer of densely pigmented cuboidal cells. The cells of the outermost layer are continuous with the cells of the inner layer. A narrow space lies between the outermost layer and the outer layer. The columnar cells in the outer layer contain well developed organelles but no pigment granules; they possess a basement membrane, lateral interdigitations, and junctional complexes near their apices. Numerous focal junctions and some ciliary channel-like structures were detected between the columnar cells of the outer layer and the cuboidal cells of the inner layer. The cuboidal cells of the inner layer are filled with pigment granules. These observations suggest that the columnar cells of the outer layer are nonpigmented epithelium, the cuboidal cells of the inner layer are pigmented epithelium, and the flattened cells in the outermost layer are derived from pigmented epithelium.     

Layer by layer analysis of synaptic organization in the optic tectum of the prog

The distribution of axo-axonal and axo-dendritic synapses, nerve endings, and bodies of neurons by depth in the optic tectum ofRana temporaria L. was investigated under normal conditions and 6–9, 60, and 134 days after removal of the contralateral eye. Counting was carried out on long oriented sections examined in the electron microscope. In outer plexiform layer 9 the density of synapses was greatest near the surface of the tectum and decreased in the direction away from it; no inner sublayers with differing density of synapses could be distinguished. In the outer zone of layer 9 (to a depth of about 30 ) many axo-axonal synpases were discovered. Endings of myelinated optic fibers of large diameter ("dark" terminal degeneration) were widely distributed in the same layer. The density of axo-dendritic synapses in deep plexiform layer 5 was similar to that in layer 9. Many nerve endings containing granular vesicles as well as pale synaptic vesicles were found in layer 5 and neighboring zones.A. N. Severtsov Institute of Evolutionary Morphology and Ecology of Animals, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 11, No. 2, pp. 130–136, March–April, 1979.     

A new and unusual eimerian (protozoa: Eimeriidae) from the liver of the Gulf killifish, Fundulus grandis

Oocysts and sporocysts of Eimeria funduli sp. n. are described from the Gulf killifish, Fundulus grandis, on the basis of light microscopy, transmission and scanning electron miscroscopy, and location in the liver of infected hosts. The spherical sporulated oocysts of E. funduli isolated from liver tissue measure 20-31 (25) micrometer across with ovoid sporocysts 9-11 X 5-7 (10 X 6) micrometer. A micropyle, polar granule, and oocyst residuum are absent, but sporocysts have Stieda and substieda bodies, a few residual granules, and 10-25 (15) unique projecting structures with expanded distal portions that we term "sporopodia". Sporopodia 1-3 (2) micrometer high support a transparent membrane that completely surrounds the sporocyst. Sporozoites have one large posterior refractile body. Ultrastructurally, the oocyst wall consists of two thin layers of granular material: an electron-dense outer layer with a rough external surface and an electron-lucent inner one of approximately equal thickness. One or two unit membranes line the inner surface of the inner layer. Each layer is 40-60 (55) nm thick. The sporocyst wall, 78-130 (110) nm thick, consists of an electron-lucent material with the outer surface being more electron dense and giving rise to osmiophilic sporopodia; closely associated with these and the outer surface are one or two unit membranes. A thin osmiophilic layer of fine granular material lines the inner surface.     

Distribution of activities of aspartate aminotransferase isoenzymes and malate dehydrogenase in guinea pig retinal layers

Distributions of activity of the cytosolic (cAAT) and mitochondrial (mAAT) isoenzymes of aspartate aminotransferase and of malate dehydrogenase (MDH) were determined in guinea pig retinal layers. The distribution of total AAT activity (tAAT = cAAT + mAAT) and of mAAT activity correlated well (r = 0.88-0.91) with the distribution of MDH activity. mAAT activity was highest in the inner segments of the photoreceptors; there was a greater than twelve-fold difference between activity in that layer and in the inner retinal layers. cAAT activity was also highest in the inner segments, but the difference between the activity in the inner segments and the other layers was not nearly as great as with mAAT. cAAT activity was also relatively high in the outer nuclear layer, outer plexiform layer, and part of the inner plexiform layer. The high activity of cAAT, mAAT, and MDH in the inner segments indicates that all of these enzymes are involved in metabolic reactions related to energy production and/or to photoreceptive processes in the outer segments and, therefore, that the enzymes are probably involved in energy-related metabolism at synapses. However, other functions, including those related to neurotransmission, are not excluded.     

The pineal organ of Raja clavata: Opsin immunoreactivity and ultrastructure

Summary The pineal organ of Raja clavata was studied by light and electron microscopy, including the immunocytochemical antiopsin reaction. The pineal organ of the ray consists of three portions: (i) a large proximal pineal, (ii) a long tube-like connecting stalk, and (iii) a short distal terminal enlargement. This latter end-vesicle lies in the deep connective tissue layers of the braincase. All portions of the pineal are composed of pinealocytes, intrinsic neurons, ependymal/glial cells, and bundles of nerve fibers embedded in thin neuropil formations. The inner segments of the pinealocytes protrude into the lumen in all parts of the organ and usually contain basal bodies and numerous mitochondria. Often, two outer segments were found to arise from the basal bodies of a single inner segment. By means of light-microscopic immunocytochemistry the outer segments showed a strong antiopsin reaction.The axons of the pinealocytes form ribbon-containing synapses on dendritelike profiles, which appear to belong to the intrinsic pineal neurons. There are other axo-dendritic synapses established by presynaptic terminals lacking ribbons and containing granular and synaptic vesicles. Pineal neurons may contain granular vesicles approximately 60–100 nm in diameter; their processes contribute to the bundles of unmyelinated axons.The fine structural organization of the pineal organ and the opsin immunoreactivity of the outer segments of the pinealocytes indicate a photoreceptive capacity of the organ. The double outer segments represent a peculiar multiplication of the photoreceptor structures.This investigation was supported by grants from the Deutsche Forschungsgemeinschaft to A. Oksche (Ok 1/24; 1/25: Mechanismen biologischer Uhren)On leave from the 2nd Department of Anatomy, Semmelweis OTE, Budapest, Hungary