Electron microscopic study of the occlusible tapetum lucidum of the southern fiddler ray (Trygonorhina fasciata).

The choroidally located tapetum lucidum of the southern fiddler ray (Trygonorhina fasciata) has been examined by light and electron microscopy in both light- and dark-adaptation. In this species, the tapetum consists of a single layer of overlapping cells oriented at an angle of about 30 degrees to the incoming light. These are situated immediately external to the choriocapillaris. These tapetal cells alternate with and are separated from one another by melanocytes which have an inner extension that curves and intervenes between the tapetal cells and the choriocapillaris. The tapetal cells and the melanocytes are flattened cells with their widest dimension facing the retina. Internally the tapetal cells display a peripherally-located, vesicular nucleus with most of the cell organelles in a paranuclear location. The bulk of the cell is packed with regularly-spaced crystals reported to be guanine. The size and spacing of these reflective crystals is commensurate with constructive interference. In light-adaptation the small melanosomes of the melanocytes are widely dispersed and fill the portion of the cell intervening between the tapetal cells and the incoming light. This effectively occludes the tapetum as light is unable to reach the reflective material. In dark-adaptation the melanosomes withdraw from this location, exposing the tapetum to light and allowing it to act as a reflective layer. The retinal epithelium overlying the tapetal area is totally unpigmented so as not to interfere with the passage of light.     

Guanine-type retinal tapetum and ganglion cell topography in the retina of a carangid fish, Kaiwarinus equula.

A guanine-type retinal tapetum was recorded in the eyes of a carangid fish Kaiwarinus equula (= Carangoides equula), spectrophotometric evidence of such being presented. The total amount of guanine in one eye was about 6.5 mg, the guanine density being ca. 1.3 mg cm(-2) over the retinal surface area. To examine the guanine distribution within the retina, the latter was divided into 21 regions. An area of high guanine density (more than 2.0 mg cm(-2)) was observed in the dorsal fundus of the retina, suggesting that the most sensitive vision was checked downward. Using whole-mount retinal preparations, the distribution of Nissl-stained cells within the retinal ganglion cell layer was examined. The greatest cell density area (area centralis) was observed only in the temporal retina. The visual acuity of the area centralis was 4.3 cycles deg(-1), suggesting that high resolution and binocular vision were directed frontally in this species. The eyes of a related carangid (Pseudocaranx dentex), lacking a tapetum, were also examined for comparison. The possible ecological advantage resulting from the tapetum is discussed in terms of visual threshold.     

獐牙菜小孢子发生及雄配子体发育(英文)

用石蜡切片法对獐牙菜小孢子发生及雄配子体发育过程进行首次观察研究。主要结果如下:花药四室,药壁发育为基本型;绒毡层异型起源,属于腺质型绒毡层,药室内具有的退化绒毡层核是早期该层细胞有丝分裂凸入药室中央并原位退化形成的;中层细胞2层;药室内壁同表皮同时宿存,细胞柱状伸长,纤维状加厚。小孢子母细胞减数分裂为同时型,四分体排列方式主要为四面体形,少数为左右对称形和十字交叉形;成熟花粉多为2-细胞类型,偶见3-细胞型,具三萌发孔。     

The fine structure of the adepidermal reticulum in the basal membrane of the skin of the newt,Triturus

The fine structure of the tapetum of the cat eye has been investigated by electron microscopy. The tapetum is made up of modified choroidal cells, seen as polygonal plates grouped around penetrating blood vessels which terminate in the anastomosing capillary network of the choriocapillaris. The tapetal cells are rectangular in cross-section, set in regular brick-like rows, and attain a depth of some thirty-five cell layers in the central region. This number is gradually reduced peripherally, and is replaced at the margin of the tapetum by normal choroidal tissue. The individual cells are packed with long slender rods 0.1 micro by 4 to 5 micro. The rods are packed in groups and with their long axes oriented roughly parallel to the plane of the retinal surface. Each cell contains several such groups. Cells at the periphery or in the outer layers of the tapetum are frequently seen to contain both tapetal rods and melanin granules, the latter typical of the choroidal melanocytes. Also melanocyte granules may have intermediate shapes. These observations plus the similar density of the two inclusions lead to the belief that the tapetal rods may be melanin derivatives. A fibrous connective tissue layer lies between the tapetum and the retina. The subretinal capillary network, the choriocapillaris, rests on this layer and is covered by the basement membrane of the retinal epithelium. The cytoplasm of the retinal epithelium exhibits marked absorptive modifications where it comes in contact with the vessels of the choriocapillaris. This fibrous layer and the basement membrane of the retinal epithelium apparently comprise the structural elements of Bruch's membrane.     

Fine structure of the retinal epithelium and tapetum lucidum of the ranch mink Mustela vison

The morphology of the retinal pigment epithelium (RPE), Bruch's membrane (complexus basalis), choriocapillaris and tapetum lucidum has been studied in the eye of the ranch mink (Mustela vison) by light and electron microscopy. The RPE is composed of a single layer of cells joined laterally by apically located junctional complexes. Basally (sclerally) these cells display numerous infoldings whereas apically (vitreally) two types of processes are associated with rod and cone outer segments. Smooth endoplasmic reticulum and mitochondria are abundant in these cells whereas rough endoplasmic reticulum and polysomes, although present, are not plentiful. An occasional wandering phagocyte is noted at the RPE-photoreceptor interface. In the posterosuperior part of the fundus, a degenerative tapetum lucidum is present. The presence of only a few layers of tapetal cells containing but little reflective material and the haphazard arrangement of this material makes it very unlikely that this area functions as an effective tapetum lucidum. The RPE over the aberrant tapetum, however, shows the morphology that is seen when a functioning tapetum cellulosum is present, namely the absence of melanosomes and an indented choriocapillaris. Bruch's membrane in non-tapetal areas is pentalaminate but, over the tapetum and where it is associated with capillary profiles, it is reduced to a single, thickened basal lamina. The choriocapillary endothelium is highly fenestrated and in nontapetal areas these capillaries are not indented into the epithelial layer.     

Fine structure of the tapetum cellulosum of the grey seal (Halichoerus grypus)

The morphology of the tapetum lucidum of the grey seal (Halichoerus grypus) has been studied by light and electron microscopy. The reflective layer in this species is a tapetum cellulosum situated in the choroid and covering the entire effective fundus. Posteriorly the tapetum is composed of 30-35 layers of flattened polygonal cells. This number gradually declines to 15-20 layers in the extreme periphery. Near the retinal epithelial layer the tapetal cells are larger and more regular (brick-like) in arrangement whereas further from the retina the tapetal cells become more irregular in outline and more widely separated by collagen fibrils and connective tissue cells. In this outer region the tapetal cells are gradually replaced by melanocytes of the choroid. Within the tapetal cells a few mitochondria and profiles of smooth endoplasmic reticulum are scattered peripherally while the majority of the cell organelles are clustered near the centrally located vesicular nucleus. The dominant feature of the tapetal cells is, however, an accumulation of numerous electron-dense rodlets of presumed zinc cysteine. These rodlets are the reflective material of the tapetum and are arranged with their long axes perpendicular to the incoming light. The orientation of these rodlets is usually uniform within each tapetal cell but varies between adjacent cells. The diameter (0.10 micron) and spacing (0.15 micron) of these rodlets is consistent with the principles of constructive interference. Blood vessels penetrate the tapetum at right angles to supply the choriocapillaris which is indented into the amelanotic retinal epithelium to give a flat reflective surface to the tapetum.     

Electron Microscopy of the Tapetum Lucidum of the Cat

The fine structure of the tapetum of the cat eye has been investigated by electron microscopy. The tapetum is made up of modified choroidal cells, seen as polygonal plates grouped around penetrating blood vessels which terminate in the anastomosing capillary network of the choriocapillaris. The tapetal cells are rectangular in cross-section, set in regular brick-like rows, and attain a depth of some thirty-five cell layers in the central region. This number is gradually reduced peripherally, and is replaced at the margin of the tapetum by normal choroidal tissue. The individual cells are packed with long slender rods 0.1 µ by 4 to 5 µ. The rods are packed in groups and with their long axes oriented roughly parallel to the plane of the retinal surface. Each cell contains several such groups. Cells at the periphery or in the outer layers of the tapetum are frequently seen to contain both tapetal rods and melanin granules, the latter typical of the choroidal melanocytes. Also melanocyte granules may have intermediate shapes. These observations plus the similar density of the two inclusions lead to the belief that the tapetal rods may be melanin derivatives. A fibrous connective tissue layer lies between the tapetum and the retina. The subretinal capillary network, the choriocapillaris, rests on this layer and is covered by the basement membrane of the retinal epithelium. The cytoplasm of the retinal epithelium exhibits marked absorptive modifications where it comes in contact with the vessels of the choriocapillaris. This fibrous layer and the basement membrane of the retinal epithelium apparently comprise the structural elements of Bruch's membrane.     

川东獐牙菜小孢子发生和雄配子体形成

报道了川东獐牙菜（Swertia davidii Franch.）小孢子发生和雄配子体形成的过程。主要结果如下：花药四室,药壁发育为基本型;绒毡层异型起源,属于腺质型绒毡层,药室内具有的退化绒毡层核是早期该层细胞有丝分裂凸入药室中央并原位退化形成的;中层细胞3层;药室内壁退化;花药壁表皮宿存,细胞柱状伸长,纤维状加厚。小孢母细胞减数分裂为同时型,四分体排列方式主要为四面体形和左右对称型,少数为“T”形和十字交叉形;成熟花粉为2-细胞类型。     

Guanine and its retinal distribution in the tapetum of the bigeye tuna,thunnus obesus

The eye of the bigeye tuna (Thunnus obesus) contains a retinal tapetum composed of guanine. The total amount of the guanine in one eye of the fish (SL=120 cm) was about 88.6 mg. The mean guanine content of the tapetum was approximately 1.25 mg/cm² of the retinal surface. The highest content of guanine (2.15 mg/cm²) was observed only in the ventro-temporal part of the retina. To distinguish this area from the rest of the eye, we suggested the term ‘locus tapetalis’ for it. The visual accommodation system clearly indicated that the visual axis of the fish is upper-forward and the resulting retinal area for acute vision was suggested to be in the ventro-temporal retina. We discussed that the area centralis of the bigeye tuna may have two functions: to guarantee high visual acuity and to allow for high photo-sensitivity in dim light vision.     

Hereditary abnormality in tapetum lucidum of the Siamese cats

Summary Gross examination showed a weaker reflection (less shining) of the tapetum lucidum of the Siamese cats compared with common cats. Toluidine blue sections revealed that many tapetal cells were weakly stained and giving vacuolated appearance under high magnification. Further examination with electron microscope showed that those weakly stained cells were filled with disrupted tapetal rods. In these affected cells, the arrangement of the tapetal rods was no longer regular. The membranes of the tapetal rods were either enlarged or disrupted. Some of them appeared to be myelin-like structures. The cores of the tapetal rods were either empty or filled with electron-dense materials which may be the remnant of the original cores. The severity of this type of abnormality or degeneration in the tapetum varied from lavers to layers. Those layers closer to the retina showed a greater number of cells with degeneration. Quantitative analysis of histochemical detection of zinc showed a significantly smaller amount of zinc in tapetal rods of the Siamese cats as compared with common cats. Less zinc and disruption of the regular arrangement of the tapetal rods may result in weaker reflection of light by Siamese cat tapetum. In four of the nine Siamese cats studied, this type of abnormality was observed. It suggests that it is a hereditary disorder of relatively high frequency.     

侧柏小孢子囊壁绒毡层和中层细胞的发育

侧柏[Platycladus orientalis (L.)Franco]小孢子囊壁包括3层细胞：表皮、中层和绒毡层。中层细胞为1层扁平的细胞。绒毡尾细胞属于分泌型。成熟的绒毡层细胞除了有单核和双核细胞外,还有三核和四核等多核细胞,细胞核有圆形和长椭圆形2种形态。绒毡层细胞的洒色质伴随着小孢子母细胞减数分裂有一个浓缩和伸展的时期,这个时期影响营养物质向小孢子囊内部转运,绒毡层细胞发育的初期就为造孢细胞提供营养,后期解体时,分泌的乌氏体不是散乱地而是有组织地向花粉粒的表面转移。中层和绒毡层细胞最终作为营养被全部吸收利用。     

百合花药壁层的发育及组织化学研究

对生长在陕西留坝的百合的花药壁层发育过程,特别是绒毡层的发育做了形态学观察。其结果是：百合花药壁层的发育方式为基本型。花药绒毡层属腺质绒毡层类型。在单细胞花粉阶段后期,部分花粉粒壁一侧凹陷时,绒毡层细胞内切向面上出现乌氏体。随着发育阶段的推移,乌氏体的数量有所增加。在光学显微镜下观察：每个乌氏体只有一个乌氏体芯。在乌氏体出现时,也可观察到花粉外壁外层的出现。到二细胞花粉时,花药开裂之前,绒毡层细胞     

Anther ontogeny in Campsis radicans (L.) Seem. (Bignoniaceae)

In this study anther ontogeny of Campsis radicans (L.) Seem. was investigated by transmission electron microscopy and light microscopy with special reference to the development of the anther wall. The anther wall formation follows the dicotyledonous type. The differentiation in anther starts with the appearance of archesporial cells which undergo periclinal divisions to give primary parietal layer to the epidermal site and the primary sporogenous cells to the inside. The primary parietal layer also divides to form two secondary parietal layers. Later, the outer secondary parietal layer (spl1) forms the endothecium and the middle layer by periclinal division whereas the inner one (spl2) directly develops into the outer tapetum forming the inner most layer of the anther wall. The sporogenous tissue is generally organized in two rows of cells with a horseshoe-shaped outline. The remainder of the tapetum lining the sporogenous mass is derived from the connective tissue. The tapetum thus has dual origin and dimorphic. Anthers are tetrasporangiate. The wall of the anther consists of an epidermis, endothecium, middle layer, and the secretory type tapetum. Tapetal cells are usually binucleated. Epidermis and Endothecium layers of anther wall remain intact until the end of anther and pollen development; however, middle layer and tapetum disappear during development.     

Guanine-Type retinal tapetum of three species of mormyrid fishes

The eye of mormyrid fishes (Marcusenius andGnathonenius) contains a retinal tapetum composed of guanine crystals. InMarcusenius, the quantity of guanine is about 2 mg cm^?2 of the retinal surface area. The retina is duplex, and the cones and rods are grouped in bundles. Each bundle is surrounded by pigment epithelial cell processes which contain numerous guanine reflectors. Two kinds of reflector are present: brick-shaped and rodlet. Mormyrids may use their high sensitivity for nocturnal activities. The retinal features of mormyrid fishes were compared with those of other fish species belonging to the Notopteroidei such as the Hiodontidae, Notopteridae and Gymnarchidae, and related to the chemical nature of notopterid and gymnarchid tapetum.     

STUDIES IN THE BIGNONIACEAE. I. ONTOGENY OF DIMORPHIC ANTHER TAPETUM IN PYROSTEGIA

Development of the anther wall was studied with special reference to the tapetum in Pyrostegia ignea. The archesporium in each microsporangium is horseshoe-shaped. The inner tapetum develops earlier from the vegetative cells of the connective region while the outer differentiates a little later from the parietal layers. Thus, the tapetum has a distinct dual origin. The two tapetal layers exhibit a pronounced structural dimorphism. Sometimes, sterile septae, partitioning the sporogenous tissue, develop in microsporangia. A prominent membrane with Ubisch granules (orbicules) is organised on the inner tangential surface of the tapetal protoplasts facing the uninucleate microspores.     

甜椒花药绒毡层的二型性及其组织化学研究

在甜椒（Capsicum annuum L.)中,靠近花粉中部的绒毡层自药隔产生,由较大的细胞组成,而花药外部区域的其余的绒毡层细胞较小,来自于初生壁层,前者的细胞具有大液泡和较大的细胞核,甲基绿－派罗宁和汞－溴酚蓝染色反应较后者弱,在造孢组织时期,二者液泡内都含有较大的球形的酸性磷酸酶颗粒,在以后的发育中,这种颗粒消失,在减数分裂时期,两种绒毡层的DNA,RNA和蛋白质合成活动增强,来自药隔的绒毡层积累了更多的DNA,绒毡层在解体时酸性磷本酶活性很高,两种不同的绒毡层退化过程相似,在全部发育过程中绒毡层内无淀粉粒。     

Anther Wall of Cymbidium Goeringii with Special Reference to the Tapetum

The structure of the anther wall in Cymhidum goeringii (Rchb. f.)Rchb.f, was followed through two developmental stages using light and electron microscope: The peculiar anatomical pattern of the anther wall and the cytological characteristics of its tissues are described. Tapetum is the most notable feature in the anther wall. The specialized characteristics of the tapetal cells may be summerized as followings: (1) The tapetum may be distinguished into outer and inner tapetum, but they constitute the continuous layers surrounding the pollinium. The inner tapetum is derived from the connective tissue. (2) The outer and inner tapetum are composed of 2--3 cell layers. They have the same ultrastructural features and functions. (3) There are many lipid-containg plastids in the tapetal cells during their developmental stage. This is the main source of lipid bodies in the tapetal cells during their final developmental stage. The lipid-containing plasmids are derived from the extension of the nuclear membrane. (4) After the formation of tetrads, the secretion and the autolysates from of the tapetal cells not only deposition the surface of the pollinium to form the film, but also flow into the inner region of the polinia between the retrads contributing to their adhesion. The results of this study provide some new data of the tapetal structure and function in the angiosperms.     

ABA and IAA control microsporogenesis in <Emphasis Type="Italic">Petunia hybrida</Emphasis> L.

The formation of fertile male gametophyte is known to require timely degeneration of polyfunctional tapetum tissue. The last process caused by the programmed cell death (PCD) is a part of the anther program maturation which leads to sequential anther tissue destruction coordinated with pollen differentiation. In the present work, distribution of abscisic acid (ABA) and indole-3-acetic acid (IAA) in developing anthers of male-fertile and male-sterile lines of petunia (Petunia hybrida L.) was analyzed by using the immunohistochemical method. It was established that the development of fertile male gametophyte was accompanied by monotonous elevation of ABA and IAA levels in reproductive cells and, in contrast, their monotonous lowering in tapetum cells and the middle layers. Abortion of microsporocytes in the meiosis prophase in the sterile line caused by premature tapetum degeneration along with complete maintenance of the middle layers was accompanied by dramatic, twofold elevation in the levels of both the phytohormones in reproductive cells. The data obtained allowed us to conclude that at the meiosis stage ABA and IAA are involved in the PCD of microsporocytes.     

Tapetum Dimorphism and Its Histochemical Study in Sweet Pepper (Capsicum annuum L. Var. grossum)

In sweet pepper, the portion of tapetum toward the interior of the anther comprising large cells is derived from cells of connective of anther whereas the remaining tapetum on the outside of the anther comprising comparatively small cells is derived from the parietal layer. Those ceils of the former prosessing large vacuoles and large nuclei are stained weaker than the cells of the latter by methyl green-pyronin and mercuric-bromophenol blue staining. Large spherical grains which contain acid phosphatase appear in the vacuoles in both kinds of tapetum at sporogenesis stage. During meiosis of pollen mother cells, DNA, RNA and protein sysntheses increase in tapetum. The tapetum derived from connective accumulates more DNA than that derived from parietal layer. The activity of acid phosphatase becomes higher in tapetum when it degenerates. The degeneration of two kinds of tapetum is similar. There are no starch grains in tapetum through its whole course of development.     

巨龙竹生殖器官形态结构及雌、雄配子体的发育

通过石蜡切片的方法对巨龙竹生殖器官结构、大小孢子的发生和雌、雄配子体的发育过程进行了观察研究。 巨龙竹为一心皮组成的单室单子房,子房内具有一个胚珠,倒生、双珠被、厚珠心。大孢子母细胞减数分裂形成线形排列的4个大孢子,合点端大孢子具功能。胚囊的发育为蓼型,具多个反足细胞。巨龙竹的花药壁由4层结构组成,包括表皮、药室内壁、中层、绒毡层;花药壁发育为单子叶型,绒毡层为腺质型。小孢子母细胞减数分裂中的胞质分裂为连续型,四分孢子为四面体型;成熟花粉粒为2细胞型,具1个萌发孔。小穗发育雌雄异熟,雌蕊的发育早于雄蕊的发育。