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1.
Abstract: Northern Italy is a habitat for many species of viper; Vipera aspis is responsible for most reported bites of humans and animals. Five dogs of different breeds and ages were presented by their owners to a veterinary clinic in northern Italy between September 2004 and August 2007 with a history of being bitten by a viper within the past 2 hours. On physical examination, all of the dogs were depressed, had pale mucous membranes, and had a painful area consistent with a recent viper bite wound on the nose (2), distal front leg (2), or lip (1). Hemoglobinemia and hemoglobinuria were observed in plasma and urine from all dogs. CBCs were done at the time of presentation, daily for 4 days, and 10 days after presentation in all dogs with the exception of one dog that died after 2 days. All dogs had an acute decrease in HCT within 24 hours of presentation; all dogs had neutrophilia, 3/5 had a mildly toxic left shift, and 4/5 had thrombocytopenia. On Diff‐Quik‐stained blood smears, moderate numbers of echinocytes, spherocytes, and erythrocyte ghosts were observed. In addition, moderate numbers of unusual erythrocyte membrane‐like structures (“erythroid loops”) were observed. The loops were annular in shape and sometimes disrupted, appearing as thin pale blue bands. Erythrocyte morphologic abnormalities decreased by day 3 and were no longer observed on day 10. The unique appearance of the erythroid loops together with evidence for intravascular hemolysis and other erythrocyte morphologic changes suggest they may be a consequence of erythrocyte lysis. Echinocytes, spherocytes, and erythrocyte ghosts are known to result from the action of phospholipase in viper venom; however, erythroid loops have not been reported previously and their exact mechanism of formation is unknown.  相似文献   

2.
对猪细小病毒(PPV)、牛疱疹病毒2型(BHV2)和犬腺病毒1型(CAV1)3种动物DNA病毒在宿主细胞内的增殖、释放方式以及所致细胞结构的变化,通过电镜进行了观察比较.(1)这3种动物DNA病毒的复制和装配过程均发生在细胞核内,以毒浆结构(Viroplast)或核内包涵体为增殖场所和物质基础,但并非都形成结晶样结构.(2)有囊膜的BHV2,其核壳体在细胞核内装配完成后,从核内膜上以出芽方式获得囊膜,然后进入核周池,聚集的病毒使核外膜向胞质方向隆起,形成病毒性包涵体而脱离核外膜,并逐渐向细胞膜的方向移动,最后从细胞膜的破损处以病毒包涵体形式释放到细胞间隙.而无囊膜的CAV1,核壳体在细胞核内装配完成后,从细胞核膜破损处或细胞核崩解后进入细胞质,待整个细胞崩解后才能释放出来.无囊膜的PPV,在核壳体装配完成后,成堆地以病毒流的方式,从扩张的核孔释放到细胞质中,待细胞崩解后再释放出来.(3)3种病毒增殖时,宿主细胞的固有细胞器,如线粒体、内质网以及溶酶体等均出现不同程度的超微结构变化,并能诱导宿主细胞出现一些新的结构,除毒浆结构外,还有管状结构、细纤维样结构、周期性结构和髓膜样结构等,其中周期性结构仅见于BHV2感染.  相似文献   

3.
The influence of free radicals generated by polymorphonuclear leukocytes from bronchopneumonic calves on lipid peroxidation in red blood cells was studied. Incubation of granulocytes with red blood cells causes a rise in malondialdehyde production in these cells in linear dependence on the granulocyte number. Incubation of red blood cells with malondialdehyde causes a generation of adduct moiety of this compound with phosphatidylserine and phosphatidylethanolamine. This adduct is also present in erythrocytes which have been incubated with neutrophils of bronchopneumonic calves. Cytochrome c loaded erythrocyte ghosts showed a high reduction rate of this compound during incubation of ghosts with neutrophils of diseased calves. It is suggested that neutrophils of bronchopneumonic calves are in an activated state in the blood-stream, and free radicals generated by these cells are capable of peroxidizing the red blood cell membrane lipids and causing cross-links between phospholipid moieties in erythrocyte membranes.  相似文献   

4.
The aim of the present study was to analyze the time-course of t-butyl hydroperoxide-induced changes in lipid peroxidation, fatty acid composition and chemiluminescence intensity in rat, caprine, equine and bovine erythrocyte ghosts. A relatively high content of arachidonic acid (C20:4 n6) and docosahexaenoic acid (C22:6 n3) was characteristic of the rat erythrocyte ghosts. The fatty acid composition of native erythrocyte ghosts obtained from caprine, equine and bovine was characterized by a high content of oleic acid (C18:1 n9) and a low content of the peroxidable polyunsaturated fatty acids (C20:4 n6 and C22:6 n3). The proportion of linoleic acid (C18:2 n6) was higher in equine and bovine compared to rat and caprine. Increase in lipid peroxidation in rat erythrocyte ghosts was maximal within 12 min of incubation, t-butyl hydroperoxide concentration dependent and was paralleled by a decrease in C18:2 n6, C20:4 n6 and C22:6 n3 and an increase in chemiluminescence formation. Polyunsaturated fatty acids (PUFAs) present in rat erythrocyte ghosts exhibit the highest sensitivity to oxidative damaged and their sensitivity increases as a power function of the number of double bonds per fatty acid molecule. Light emission in caprine, equine and bovine erythrocyte ghosts was very low, t-butyl hydroperoxide concentration-dependent but changes in fatty acid composition were not observed. The main conclusion of this work is that a low unsaturation degree of fatty acids in erythrocyte ghosts of caprine, equine and bovine prevent the lipid peroxidation on those membranes when they are incubated with t-butyl hydroperoxide.  相似文献   

5.
为研究鸭病毒性肠炎病毒(DEV)CH强毒株在感染鸭体内的分布和形态学发生规律，应用透射电镜和超薄切片技术对人工感染DEV的成年鸭各组织器官进行观察。结果表明：感染后12h在脾脏和法氏囊首先观察到少量的DEV出现，24h后在脾、胸腺和法氏囊以及死亡鸭的肝、肠和胰中均观察到具有典型的疱疹病毒粒子及其核衣壳形态的DEV。DEV病毒核衣壳有空心型、致密核心型、双环型和内壁附有颗粒型4种形态，存在胞核和胞浆两种装配方式。病毒成熟有两种方式：一为细胞核内核衣壳在核内获得皮层，通过核内膜获得囊膜成为成熟病毒；二为核内核衣壳通过内外核膜进入胞浆，核内和胞浆内的核衣壳在细胞浆中获得皮层，然后在各种质膜上获得囊膜，最后成熟病毒通过细胞破裂或其他方式释放到细胞外。伴随着病毒的复制、装配和成熟，细胞中出现多种核内和胞浆包涵体、核内致密颗粒、核内微管和中空短管、胞浆电子致密小体等结构。  相似文献   

6.
The objective of the present paper was to describe the topographic orientation of intramembraneous particles (IMP) in the membranes of freshly ejaculated boar spermatozoa applying the method of freeze fracturing. Disc clusters of IMP's could be distinguished in the acrosome-covering plasma membrane (PF). The border of the head to a distance of about 0.3 micron seemed to contain no IMP's (Figs. 1, 2). In the postacrosomal region in an anterior direction from the posterior ring the IMP's were found to be arranged in palissade slant rows. Statistical measurements of 20 spermatozoa (Tab. I) indicated that the slant rows extended to the greatest distance in the lateral part of the head, up to 0.67 micron (+/- 1.45-0.39) from the posterior ring. In the middle of the head the rows extended to a distance of 0.18 micron (+/- 0.10-0.42). The transition spot between the zone of sparse IMP's and the zone of densely arranged IMP's was at a distance of 1.63 microns (+/- 1.87-0.69) in an anterior direction from the posterior ring (Figs. 3, 4). In the flagellum in the plasma membrane (PF) the first spot of an ample occurrence of IMP's is located in the first mitochondrion in the spiral. The IMP clusters follow the cicumferential orientation of mitochondria in the mitochondrial spiral. The IMP's were missing in the spaces between the spiral coils (Fig. 5). The membranes of the mitochondria contain a large amount of IMP's. This activity is transferred to the clinging part of the plasma membrane (Fig. 6). A larger accumulation of IMP's can be seen at the spot where the plasma membrane covers the annulus (Fig. 7). In the plasma membrane of the main segment of the flagellum the IMP's are distributed irregularly in PF, and also in EF (Fig. 8). The EF surfaces of the plasma membrane had in general an indistinct structural organisation of IMP's. The distribution of IMP's in acrosomal membranes was found to be irregular. The postacrosomal lamina in the freeze fracturing did not look like a morphologically identifiable structure. In the nuclear envelope delimiting the posterior nuclear space, nuclear pores could be identified (Fig. 9). No nuclear pores could be seen in the nuclear envelope clinging to the posterior part of the nucleus. At this spot smaller IMP's were observed which could be a part of the proteins of the filaments connecting the concave surface of the head with the convex articular surface of the flagellum. These filaments connect the head and the flagellum (Fig. 10).(ABSTRACT TRUNCATED AT 400 WORDS)  相似文献   

7.
Thyrocalcitonin cells (C cells) were predominantly demonstrated in the ultimobranchial (UB) structures of the thyroid gland of one‐humped camels. The UB population was observed as clear cells, either singly distributed or as groups of cells between the component cellular elements lining the UB structures. They displayed various shapes: oval, pear‐like, rounded, cubical, columnar and or ellipsoid. Those populating the cell nests or solid cellular masses were almost polygonal or ovoid in shape. The cytoplasm contained well‐developed golgi complexes, several mitochondria and characteristically presented rounded or oval membrane‐bound electron dense granules of different sizes. The latter granules were irregularly distributed within the cytoplasm especially at the vascular pole. The nucleus of C cells was relatively large, indented, occupying a more or less central position in the cytoplasm. It presented various chromatin contents; the heterochromatin variety was predominantly demonstrated at the marginal zone. However, the euchromatin occupied a more central position within the nucleus.  相似文献   

8.
This study was conducted to determine why Babesia gibsoni replicates well in reticulocytes. First, B. gibsoni was cultivated in resealed erythrocyte ghosts loaded with either erythrocyte or reticulocyte lysate, and in reticulocyte ghosts loaded with either erythrocyte or reticulocyte lysate. The parasites multiplied well in the erythrocyte or reticulocyte ghosts loaded with reticulocyte lysate compared to the other resealed cells loaded with erythrocyte lysate. Second, the parasites were cultivated in erythrocytes in culture medium supplemented with either erythrocyte or reticulocyte lysate. The parasites multiplied better in reticulocyte lysate-containing cultures than in erythrocyte lysate-containing cultures. Finally, the parasites were cultivated in erythrocytes in culture medium supplemented with glutamate, aspartate, asparagine, glycine, isoleucine, proline, taurine or GSH, which were present in higher concentrations in reticulocytes than in erythrocytes. Supplementation of the culture medium with glutamate and GSH resulted in enhancement of the multiplication of the parasites, while the other amino acids did not enhance the multiplication. These results indicated that the high levels of the multiplication of B. gibsoni in reticulocytes are partly due to the high concentrations of glutamate and GSH in reticulocytes.  相似文献   

9.
Recent studies have indicated that dogs with canine atopic dermatitis (CAD) may have a disorder of fatty acid metabolism: possibly low or absent activity of delta6-desaturase or delta5-desaturase, or both. To clarify this possibility, we examined the erythrocyte and plasma fatty acid patterns of 8 dogs with CAD and their 8 healthy housemates. Atopic dermatitis was diagnosed according to the criteria proposed by Willemse; other causes of dermatitis were excluded clinically and by appropriate tests. Erythrocyte ghosts were prepared from blood samples. Membrane lipids were extracted and separated by thin-layer chromatography. From plasma and lipid fractions, fatty acid content was determined by gas chromatography. In erythrocytes, but not in plasma, we observed significant differences in the fatty acid pattern that suggested a reduction in the n6 fatty acid products of the delta6- and delta5-desaturases in dogs with atopic dermatitis when compared with healthy housemates.  相似文献   

10.
In cases of lymphatic bovine leukemia, the nuclear pockets of the tumour cells in the lymph nodes contain part of cytoplasm and usually protrude above nucleus surface. A wall 60 to 90 nm thick forms the boundary between the nuclear pockets and cytoplasm. The wall consists of two complete nuclear membranes 25 nm thick with a 30-40 nm layer of heavily condensed heterochromatin in between. The nuclear membranes of the walls of the pockets have no nuclear pores. Extensive fusions, built from all the three layers, occur in the walls of the nuclear pockets. These pockets appear on nucleus surface when the plicae of the nuclear membrane are closed or when the apex of the plica merges with nucleus surface. Centriol is involved in the rise of the plicae of the nuclear membrane. The microtubuli inserted in the centriolar satellites on the one side merge with nucleus surface on the other side.  相似文献   

11.
日本七鳃鳗血细胞显微及亚显微结构   总被引：3，自引：0，他引：3  
用光镜和透射电镜技术对１０尾日本七鳃鳗的血细胞进行了观察。结果表明：红细胞为圆形或椭圆形,胞质不很均匀,电子密度较低,含有板状嵴线粒体,核呈圆形或椭圆形。中性粒细胞表面有伪足,形态各异,胞质内含有Ａ、Ｂ２种颗粒（Ａ型颗粒为圆形,电子密度较低;Ｂ型颗粒为长椭圆形,电子密度较高）。嗜酸粒细胞数量较少,胞质内含有Ａ、Ｂ、Ｃ３种形态各异的有膜颗粒（Ａ型颗粒为圆形,电子密度较高,均质;Ｂ型为长椭圆形,颗粒中央有电子密度较高的长椭圆形致密芯;Ｃ型内含有电子密度较高的杆状致密芯,位于颗粒一侧）。单核细胞表面有伪足,胞质内含有粗面内质网、板状嵴线粒体、溶酶体和液泡。淋巴细胞为圆形,核较大,胞质内含有板状嵴线粒体、粗面内质网和嗜天青颗粒。血栓细胞体积较小,形态各异,胞质内含有线粒体、粗面内质网和细小颗粒。  相似文献   

12.
Intracytoplasmic sperm injection (ICSI) is an assisted reproduction tool with several applications. Its effectiveness in bovines is lower than that in other species, mainly because of difficulties in the decondensation of the sperm nucleus after injection, and the presence of the acrosome and the plasma membrane which remain intact in this procedure. In this study, we assessed the effect of lysolecithin (LL) and Triton X‐100 (TX), in combination with glutathione (GSH) as sperm pretreatments prior to ICSI. The GSH‐LL and GSH‐TX groups showed 0% of spermatozoa with intact membrane (SYBR 14+/PI), in comparison with the control (63.3%) and GSH (65.7%) groups. The proportions of spermatozoa with damaged acrosome membrane in the GSH‐LL, GSH‐TX, GSH and control groups were 46%, 35.9%, 10.5% and 7.5%, respectively. Sperm chromatin decondensation analysis showed that the groups incubated for 3 hr with GSH presented greater decondensation (p < .05). Although fertilization was improved in all treatment groups evaluated, no differences were observed in the cleavage rate 72 hr after activation in the GSH (73.7%), GSH‐LL (80.2%) and GSH‐TX (77.8%) groups compared to the control (66.3%), neither in the blastocyst rate on day 8 (24.0%, 26.2%, 27.1% and 28.4% for the control, GSH, GSH‐LL and GSH‐TX groups, respectively). No differences were also observed in the total number of cells in all groups. In conclusion, although these sperm treatments promoted nuclear decondensation and induced plasma membrane disruption, these effects were not sufficient to improve bovine embryonic development after ICSI.  相似文献   

13.
1. Bacteria adhering to the ileal epithelial cells in broiler and White Leghorn (WL) chickens aged 1 to 60 d were observed with scanning (SEM) and transmission (TEM) electron microscopes. 2. In SEM observations, bacteria were not found on day 1 after hatching in either breed. In 10-d-old broilers many bacteria were observed around the apical area of villi. The number decreased with age and disappeared by 50 d. In WL chicks, the bacteria were first observed at 20 d. Numbers were much fewer than in broilers and none were seen after 30 d. 3. TEM investigations showed that bacteria had a cytoplasmic membrane, cell wall and nucleus but no nuclear membrane and organella, were compartmentalised and resembled Streptobacillus moniliformis. At the attachment zone to the epithelium, many mitochondria were observed in the epithelial cells; the bacterial membrane did not fuse to the epithelial cell membrane except at the apex of the attachment end where the bacterial membrane seemed to undergo lysis, suggesting a possibility that some bacterial components were transferred to the epithelial cells. 4. It is possible that the bacterial aid in the functioning of ileal epithelial cells. Possible functions are discussed in relation to the morphological features.  相似文献   

14.
The ultrastructure of Sertoli cell in the water buffalo (Bubalus bubalis) was observed in a transmission electron microscope. The nucleus had homogeneous nucleoplasm, scarce heterochromatin and multivesicular nuclear body (MNB). The MNB was composed of numerous vesicles and ribosome-like dense structures. The vesicles varied in size and number and contained a sparse and flocculent substance. In the indentation of the nucleus, aggregates of ribosomes were frequently observed. In the apical and middle region of the cell, long mitochondria and microtubules were distributed parallel to the long axis of the cell. Non-laminated smooth ER and some ribosomes were also recognizable throughout this region. In the basal region, widely-distributed laminated smooth ER was characteristic. Microfilament bundles at ectoplasmic specialization were irregularly arranged. Frequently-emerged nodular processes occasionally separated from basal lamina and formed round structures within Sertoli cytoplasm. Although these characteristics of buffalo Sertoli cell were very similar to those of the bovine studied, the aggregate of ribosomes was more developed in the buffalo.  相似文献   

15.
We focused on elucidating the toxic effects of water‐borne copper on the giant freshwater prawn Macrobrachium rosenbergii. After seven days of exposure to copper (Cu2+) at concentrations ranging from 0.01 mg L?1 to 0.5 mg L?1, three isozymes, malate dehydrogenase, alkaline phosphatase and esterase, were analyzed and compared using polyacrylamide electrophoresis (PAGE) and biochemical staining. The results indicated that the electrophoretic patterns of the isozymes showed a copper‐concentration‐related difference. Low doses of copper stimulated strong expression of the three isozymes. Electrophoretic patterns of malate dehydrogenase and alkaline phosphatase gradually became weaker or even lost as the level of copper increased. In contrast, esterase patterns exhibited an increased molecular heterogeneity at higher copper concentrations. A transmission electron microscope was used to study ultrastructure differences in the gills and hepatopancreas of M. rosenbergii, and the results showed significant structural damage at increased levels of copper compared with the control group. The basement membranes and mitochondira in the gills were seriously damaged, the cuticle electron density distribution was not homogeneous, and an infolded basement membrane, circularized nucleus, disintegrated nuclear membrane, and decreased mitochondria number and size were observed in the gills. Similarly, flowing out of karyoplasms, partly falling microvilli, decreased mitochondrion, partly disappeared mitochondrial cristae, and a thinned matrix were observed in the hepatopancreas. These findings indicate that exposure to elevated copper levels might damage the ultrastructure of the gills and hepatopancreas of M. rosenbergii and might further weaken their normal physical activities. Isozymes were quite sensitive to environmental stress and changes in isozyme elctrophoretic patterns might be effective biomarkers of environmental contamination.  相似文献   

16.
Cell secretion and membrane fusion   总被引：4，自引：0，他引：4  
Secretion occurs in all cells of multicellular organisms and involves the delivery of secretory products packaged in membrane-bound vesicles to the cell exterior. Specialized cells for neurotransmission, enzyme secretion or hormone release utilize a highly regulated secretory process. Secretory vesicles are transported to specific sites at the plasma membrane, where they dock and fuse to release their contents. Similar to other cellular processes, cell secretion is found to be highly regulated and a precisely orchestrated event. It has been demonstrated that membrane-bound secretory vesicles dock and fuse at porosomes, which are specialized supramolecular structures at the cell plasma membrane. Swelling of secretory vesicles results in a build-up of pressure, allowing expulsion of intravesicular contents. The extent of secretory vesicle swelling dictates the amount of intravesicular contents expelled during secretion. The discovery of the porosome, its isolation, its structure and dynamics at nm resolution and in real time, its biochemical composition and functional reconstitution into artificial lipid membrane, have been determined. The molecular mechanism of secretory vesicle fusion at the base of porosomes, and vesicle swelling, has also been resolved. These findings reveal the molecular mechanism of cell secretion.  相似文献   

17.
哺乳动物精子线粒体是维持精子活力的关键细胞器，对精子超激活运动、获能、顶体反应及受精等过程起到重要的调节作用。哺乳动物精子线粒体特有的形态特征与特异性酶异构体使其具有独特动力学和调节特性。精子线粒体中发生的氧化磷酸化过程是维持精子运动的重要途径，该过程产生的活性氧对精子功能的维持具有重要作用，但过量可能导致精子损伤，加速精子凋亡。哺乳动物精子质膜磷脂酰丝氨酸外翻和相关半胱氨酸蛋白酶激活级联反应引起细胞凋亡。区别于体细胞线粒体，精子线粒体钙信号可能并未参与精子固有的凋亡途径，作为衡量线粒体功能的敏感指标，其对线粒体膜电位和耗氧量的检测研究至关重要。哺乳动物精子线粒体具有自身的遗传系统，线粒体基因拷贝数可能作为无创衡量精子质量和受精能力的标记。作者重点阐述了哺乳动物精子线粒体的结构、线粒体鞘的形成及其生物功能，包括发生在线粒体中的氧化磷酸化过程、活性氧对精子的利与弊、线粒体参与钙稳态与细胞凋亡过程；介绍了线粒体膜电位和耗氧量的检测，简述了线粒体基因组的研究进展，为进一步探讨线粒体所涉及的精子功能机制奠定基础。  相似文献   

18.
Herpes virions are complex particles that consist of more than 30 different virally encoded proteins. The molecular basis of how this complicated structure is assembled is only recently beginning to emerge. After replication in the host cell nucleus viral DNA is incorporated into preformed capsids which leave the nucleus by budding at the inner nuclear membrane resulting in the formation of primary enveloped virions in the perinuclear space. The primary envelope then fuses with the outer leaflet of the nuclear membrane, thereby releasing nucleocapsids into the cytoplasm. Final envelopment including the acquisition of more than 15 tegument and more than 10 envelope (glyco)proteins occurs by budding into Golgi-derived vesicles. Mature virions are released after fusion of the vesicle membrane with the plasma membrane of the cell. Thus, herpesvirus morphogenesis requires a sequence of envelopment--de-envelopment--re-envelopment processes which are distinct not only in the subcellular compartments in which they occur but also in the viral proteins involved. This review summarizes recent advances in our understanding of the complex protein-protein interactions involved in herpesvirus assembly and egress.  相似文献   

19.
Erythrocytes from pigs with experimental porcine eperythrozoonosis were examined using light microscopy and scanning and transmission electron microscopy. Three distinct forms of Eperythrozoon suis were attached to the plasma surface of erythrocyte membrane. Erythrocytes were initially parasitized by one or several immature forms. Immature forms enlarged and developed into juvenile and mature forms. The parasite replicated by budding of small immature forms from larger immature forms, juvenile forms, and mature forms. Small immature forms attached to adjacent membrane of the same erythrocyte or a nonparasitized erythrocyte. E. suis organisms were intimately associated with, but distinctly separated from erythrocyte membrane by a 30-nm electron lucent zone. Cell membrane in this area was denser than adjacent nonparasitized membrane. Early interaction between erythrocyte membrane and small immature forms resulted in no membrane deformation, but as this form enlarged, it later became embedded in a deep cup-like membrane invagination. As the immature form developed into the juvenile form a shallow, broad-based depression was observed in the membrane. A similar depression that covered a greater surface area was observed in the membrane parasitized by the mature form. The interaction between the parasitic forms and erythrocyte membrane resulted ultimately in severe membrane deformation. Parasite-membrane interactions may play an important role in the development of misdirected immune responses in experimental porcine eperythrozoonosis.  相似文献   

20.
The retinal photoreceptors of the red-tailed hawk (Buteo jamaicensis) consist of rods, single cones and double (unequal) cones present in a ratio of about 2: 11 5. In the light-adapted state, the rods are slender elongated cells with outer segments that reach to the retinal epithelial (RPE) cells. The inner segment displays an ellipsoid of mitochondria, plentiful polysomes, some rough ER and Golgi zones. The rod nucleus is located deep within the outer nuclear layer and the synaptic spherule displays both invaginated (ribbon) and superficial (conventional) synaptic sites. Single cones show a thin tapering outer segment, a large electron lucent oil droplet at the apex of the inner segment and an ellipsoid of mitochondria. Double cones consist of a larger chief member which displays a thin tapering outer segment and an electron dense oil droplet as well as a smaller accessory cone which shows no oil droplet, an ellipsoid and a paraboloid of glycogen. As in the single cone, polysomes, RER and Golgi zones are also noted in the inner segments of both members of the double cone. Near the external limiting membrane the chief and accessory cones show membrane specializations indicative of junctions on their contiguous surfaces. All cone photoreceptors are of a smaller diameter than is normally reported for avian species. Both single and double cones display several invaginated synapses as well as numerous superficial synaptic sites.  相似文献   

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