Fine structure of the retinal pigment epithelium, Bruch's membrane and choriocapillaris in the horse

The fine structure of the retinal pigment epithelium (RPE), Bruch's membrane and choriocapillaris was investigated by light and transmission electron microscopy in both the tapetal and non-tapetal fundus of the horse eye. In all locations, the RPE consisted of a single layer of low cuboidal cells. The epithelial cells were joined laterally by apically located tight junctions. These cells displayed numerous basal infoldings and abundant thin apical processes which enclosed the rod outer segments. The epithelial cell nuclei were large and located basally. Within the epithelial cells, smooth endoplasmic reticulum was very abundant, while rough endoplasmic reticulum was scarce, polysomes and mitochondria, which often display a ring-shaped structure, were abundant. Melanosomes were abundant in the non-tapetal area but absent in the tapetal area. Bruch's membrane was pentalaminate throughout the retina. The endothelium of the choriocapillaris was heavily fenestrated.     

Fine structure of the retinal pigment epithelium, Bruch's membrane and choriocapillaris in the ostrich (Struthio camelus)

The fine structure of the retinal pigment epithelium (RPE), Bruch's membrane and choriocapillaris in the ostrich (Struthio camelus) was investigated by using light microscopy and transmission electron microscopy. In this species, the RPE consisted of a single layer of low columnar cells. The epithelial cells were joined laterally by two type junctions, zonulae occludentes and zonulae adherentes located in the midregion of the cells. These cells displayed numerous deep basal infoldings and thick extensive apical processes, which enclosed the outer segments of the rods. The epithelial cell nuclei were large, vesicular and located basally within the epithelial cells. Smooth endoplasmic reticulum was very abundant, while rough endoplasmic reticulum was scarce. Mitochondria of various shapes were abundant basally while polysomes were plentiful and widespread. In the light-adapted state melanosomes were located in the apical region and in apical processes of the epithelial cells. Myeloid bodies were large, numerous and often showed ribosomes on their outer surface. Bruch's membrane (complexus basalis) was typical pentalaminate throughout the retina, as noted in the majority of other vertebrates. The endothelium of the choriocapillaris facing Bruch's membrane was extremely thin but only moderately fenestrated. Some of the fenestrations displayed a double-layered diaphragm while the majority showed the more typical single-layered diaphragm noted in most species.     

Retinal Pigment Epithelial Fine Structure in the Great Blue Heron (Ardea herodias)

The fine structure of the retinal epithelium (RPE), choriocapillaris and Bruch's membrane (complexus basalis) has been studied by light and electron microscopy in the great blue heron (Ardea herodias). In this species the RPE consists of a single layer of cuboidal cells which display numerous basal (scleral) infoldings and plentiful apical (vitreal) processes which surround photoreceptor outer segments. These epithelial cells are joined laterally by a series of tight junctions located in the mid to basal region. Within the epithelial cells, smooth endoplasmic reticulum is very abundant while rough ER is not. Mitochondria (some of which are ring-shaped) and polysomes are abundant. In light-adaptation the RPE nuclei are large vesicular and basally located while the melanosomes of these cells are almost exclusively located within the apical processes. Myeloid bodies are large and numerous and often show ribosomes on their outer surface. Bruch's membrane (complexus basalis) shows the typical pentalaminate structure noted in the majority of vertebrates except teleosts. The choriocapillary endothelium is very thin facing Bruch's membrane but is only moderately fenestrated. The majority of these fenestrations show a single-layered diaphragm but double-layered diaphragms are also noted.     

Retinal Pigment Epithelial Fine Structure in the American Crow (Corvus brachyrhynchos)

The fine structure of the retinal epithelial (RPE) region has been investigated by light and electron microscopy in the American crow (Corvus brachyrhynchos). In this species the RPE consists of a single layer of cuboidal cells which display numerous deep basal (scleral) infoldings and plentiful apical (vitreai) microvillar processes which surround photoreceptor inner and outer segments. The RPE cells are joined laterally by a series of tight junctions (VERHOEFF'S membrane) located in the mid to basal region. Within the epithelial cells, smooth endoplasmic reticulum is very abundant while rough endoplasmic reticulum (RER) is scarce. Mitochondria of various shapes are abundant basally while polysomes are plentiful and widespread. In the light-adapted state RPE nuclei are large and vesicular and basally located while the melanosomes of these cells are predominantly located with the apical processes indicating photomechanical movements. Myeloid bodies are large and numerous and often have ribosomes on their outer surface. Bruch's membrane (complexus basalis) is typical of avian species in that it is pentalaminate and the lamina densa is displaced near the cho-riocapillaris. The endothelium of the choriocapillaris is thin facing Bruch's membrane but is only moderately fenestrated. Some of these fenestrations display a double-layered diaphragm while the majority show the more typical single-layered diaphragm noted in most species.     

Retinal Pigment Epithelial Fine Structure in the Red-Tailed Hawk (Buto jamaicensis)

As part of a comparative morphological study, the fine structure of the retinal epithelium (RPE), choriocapillaris and Bruch's membrane (complexus basalis) has been studied by electron microscopy in the red-tailed hawk (Buteo jamaicensis). In this species the RPE consists of a single layer of low cuboidal cells which display numerous basal (scleral) infoldings and extensive apical (vitreal) processes which interdigitate with photoreceptor outer segments. These epithelial cells are joined laterally by a series of basally located tight junctions. Internally SER is the most abundant cell organelle while only small amounts of RER are present. Polysomes are however abundant as are mitochondria. The RPE cell nucleus is large and vesicular. Melanosomes are mainly located in the apical processes of the RPE cells in light-adaptation. Myeloid bodies are large and numerous in light-adaptation and often show ribosomes on their outer border. Bruch's membrane (complexus basalis) shows the typical pentalaminate structure noted in most vertebrates but with only a poorly defined central elastic layer. The endothelium of the choriocapillaris is very thin facing the RPE but is only moderately fenestrated. The choriocapillaris in this species is unusual however in that many of the fenestrae show a double-layered diaphragm.     

Retinal Epithelial Fine Structure in the Domestic Cat (Felis catus)

The morphology of the retinal epithelium (RPE) and closely associated choriocapillaris and Bruch's membrane (complexus basalis) has been investigated in the eye of the domestic cat (felis catus) by light and electron microscopy. The RPE consists of a single layer of cuboidal cells joined laterally by apically-located junctional complexes. Basally (sclerally) these cells display numerous infoldings while apically (vitreally) two distinct types of processes enclose photoreceptor outer segments. Internally the large vesicular nucleus is centrally located. Smooth endoplasmic reticulum, mitochondria, polysomes and lysosome-like bodies are abundant. Rough endoplasmic reticulum while present is not plentiful. Over the tapetum lucidum, melanosomes are absent from the RPE cells while in non-tapetal locations melanosomes are large and plentiful. The endothelium of the choriocapillaris is highly fenestrated and these capillaries are deeply indented into the epithelial layer over the tapetum. Bruch's membrane (complexus basalis) is non-tapetal regions is the typical pentalaminate structure noted for most mammals. Over the tapetum however it is reduced to a trilaminate structure and when associated with the indented capillary profiles is further reduced to a single thickened basal lamina.     

Fine Structure of the Choriocapillaris, Bruch''s Membrane and Retinal Epithelium of the Cow

The fine structure of the choriocapillaris, Bruch's membrane and retinal epithelium was investigated in both the tapetal and non-tapetal fundus of the bovine eye. In ail locations the retinal epithelium consists of a single layer of cuboidal cells. The epithelial cells are joined laterally by apically located tight junctions and throughout the retina display numerous basal infoldings and fine apical processes which enclose rod outer segments. All retinal epithelial cells are rich in smooth endoplasmic reticulum and mitochondria and contain phagosomes. Although not as abundant, profiles of rough endoplasmic reticulum and polysomes are also noted in all locations. In non-tapetal areas, melano-somes are numerous whereas over the central tapetum fibrosum they are absent. The absence of melanosomes over a functional tapetum is to be expected. While lysosomes are present throughout the epithelial layer, over the tapetal region they appear to be more numerous. The apparent increase in lysosomal numbers in this location may indicate an enhanced shedding of outer segment material over the tapetum. Although some retinal epithelial cells are modified to accomodate a tapetum lucidum their morphology is basically similar throughout the retina and probably indicates that ail regions of the retinal epithelium are capable of the normal functions of this indispensible retinal layer. The choriocapillaris is heavily fenestrated on the border facing the retina and overlying the tapetum also displays fenestrae on its choroidal edge. Bruch's membrane ( complexus basalis ) is pentalaminate throughout the retina and is slightly thicker in the posterior fundus.     

Ultrastructural and ultracytochemical cyclic changes in the bovine uterine tube (oviduct) epithelium.

Ultrastructural and ultracytochemical features of the uterine tube (oviduct) infundibulum were studied in 8 Hereford cows, which were slaughtered in pairs on days 1 (estrus), 3, 9 or 10, and 18 of the estrous cycle. Fibrous granules (60 to 80 nm), which are supposedly related to basal body replication, were observed in the apical cytoplasm of ciliated cells. Close association between basal bodies and fibrous granules was apparent, especially during the follicular phase. Cilia were observed throughout of estrous cycle, although degeneration of cilia was not observed at any phase of the cycle. Prominent, striated rootlets were observed during both the follicular and luteal phases of the cycle. Maximum secretory cell differentiation was apparent during the follicular phase, at which time these cells were characterized by having a well-developed, rough endoplasmic reticulum with dilated cisternae, numerous ribosomes, and secretory granules of varied size and density. A prominent feature of the secretory granules was their membranous structure, consisting of concentric lamellae of equal dimensions. During the luteal phase, cytoplasmic protrusions were prominent, and extruded nuclei along with other cytoplasmic organelles were present in the tubal lumen. The presence of a well-developed, rough endoplasmic reticulum and numerous secretory granules during the follicular phase indicates that secretory activity of the uterine tube infundibulum may be stimulated by estrogen. During estrus, the cytoplasm of the stromal cells displayed abundant, rough endoplasmic reticulum with dilated cisternae. The increased and extensively dilated rough endoplasmic reticulum at the time of estrus probably indicates increased protein synthesis by the stromal cells. The presence of adenosine triphosphatase activity on the membrane of cilia suggests that this enzyme is involved in energy-forming reactions related to the vigorous action of cilia. The presence of acid phosphatase activity on the cell membrane of the epithelium, microvilli, and secretory granules may indicate involvement in the secretory mechanism of the cell.     

Ultrastructural studies on the pancreatic acini in duck (Anas boscas) and pigeon (Columba livia)

The aim of this research work was to study the histological structure of the pancreatic acini by transmission electron microscope in two avian species, duck and pigeon. The specimens were collected and processed for electron microscopic study. The results showed that the acini of the two avian species were two types; the first one was an electron dense and the second one an electron lucent. The light acinar cells were larger in size than the dark cells. These cells contained centrally located ovoid nuclei with prominent nucleoli and abundant euchromatin. The cytoplasm was electron lucent, with many rough endoplasmic reticulum, polymorphic mitochondria. Numerous zymogen granules were distributed in the basal part and around the nucleus, so these cells considered active cells. The dark acinar cells were characterized by an electron dense cytoplasm. The most prominent cell organelle in these cells were the zymogen granules that appeared in different sizes while other organelles as mitochondria, and rough endoplasmic reticulum were inconspicuous or few, so these cells were considered as inactive cells. The nucleus with indented nuclear membrane located centrally with prominent nucleoli and abundant heterochromatin. Prominent intercellular spaces between the individual acinar cells, as well as well-developed basement membrane separating the electron dense cells and the lumen contained the secretion between acinar cells. It could be concluded that the acinar cells in ducks and pigeons were divided into two types, that is, light and dark acinar cells which mainly attributed to the activity of these cells.     

Structural and ultrastructural characteristics of interrenal gland and chromaffin cell of matrinxã, Brycon cephalus Gunther 1869 (Teleostei-Characidae)

This work presents the structure and ultrastructure of the interrenal gland and chromaffin cells, as well as the morphology of the head kidney of Brycon cephalus. The head kidney is composed of fused bilateral lobes located anterior to the swim bladder and ventrolateral to the spinal column. The parenchyma revealed lympho-haematopoietic tissue, melano-macrophage centres, interrenal gland and chromaffin cells. The interrenal gland consisted of cords or strands of cells grouped around the posterior cardinal vein and their branches. Chromaffin cells are found in small groups, closely associated with the interrenal gland and/or under the endothelium of the posterior cardinal vein. So far, the ultrastructural analysis has revealed only one interrenal cell type which contained abundant smooth endoplasmic reticulum and numerous mitochondria with tubulo-vesicular cristae, characteristic of steroid-producing cells. Two types of chromaffin cells were observed. The first type was characterized by the presence of vesicles with round, strongly electron-dense granules, which were eccentrically located. Such cells were interpreted as noradrenaline cells. Meanwhile, cells which contained smaller vesicles and electron-lucent granules, with a small halo separating the granule from the vesicular limiting membrane, were identified as adrenaline cells.     

Retinal Photoreceptor Fine Structure in the Red-Tailed Hawk (Buteo jamaicensis)

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.     

Retinal Photoreceptor Fine Structure in the Great Blue Heron (Ardea herodias)

The morphology of the retinal photoreceptors of the great blue heron (Ardea herodias) has been investigated by light and electron microscopy. They consist of rods, single cones and double (unequal) cones present in a ratio of about 2:1:1 respectively. The rods are slender elongated cells with outer segments that reach to the retinal epithelial (RPE) cells and are surrounded by pigment-rich apical processes of the RPE cells in the light-adapted state. The rod inner segment displays an ellipsoid of mitochondria, an hyperboloid of glycogen, much rough ER, numerous polysomes, Golgi zones and autophagic vacuoles. The rod nucleus is located deep in the outer nuclear layer and the rod synaptic pedicle displays both invaginated and superficial synaptic sites. Single cones display a slightly tapered outer segment, a large electron lucent oil droplet and an ellipsoid of mitochondria in the apex of the inner segment. Double cones consist of a long thin chief member which shows an electron dense oil droplet and a shorter, stouter accessory cone with no oil droplet but a paraboloid of glycogen below the ellipsoid. As in the single cone, polysomes, RER and Golgi zones are present in the myoid region of both members of the double cone. All photoreceptor types have a connecting cilium joining inner and outer segments. Near the external limiting membrane, the chief and accessory cones show intercellular junctions. All cone photoreceptors are relatively small in diameter and hence tightly packed. While rods are felt to undergo retinomotor movements, cones are felt to move minimally or not at all. Both single and double cones display several invaginated (ribbon) synapses as well as numerous superficial (conventional) synaptic sites.     

Dome epithelial M cells dissociated from rabbit gut-associated lymphoid tissues

Dome and dome epithelial cells were selectively dissociated from gut-associated lymphoid tissues of rabbits. Sequential tissue washes in dithiothreitol, EDTA, and collagenase removed the dome epithelium, without disrupting the follicles or villi, and provided a cell suspension containing 74 +/- 6% lymphocytes, 9 +/- 4% columnar epithelial cells, 10 +/- 7% tangible-body macrophages, and 4 +/- 2% M cells (follicle-associated epithelial cells). The last mentioned cells were characterized by transmission electron microscopy as large (20 to 55 microns diameter) cuboidal, round, or oval cells with eccentric nuclei and thin membranous processes surrounding empty vacuoles. The M cells were occasionally joined together by tight junctions. Histochemical and immunocytochemical analyses of M cells with the light microscope showed that they were devoid of immunoglobulins and negative for T-cell antigen and secretory component and had no detectable alkaline phosphatase or endogenous peroxidase activity. The M cells had few vacuoles with faint acid phosphatase activity; nonspecific neutral esterase was abundant. Possible uses for dome and dome epithelial cells are discussed.     

Ultrastructure of a feline extraskeletal giant cell tumor (malignant fibrous histiocytoma)

A subcutaneous extraskeletal giant cell tumor (malignant fibrous histiocytoma) was excised repeatedly from a 9-year-old Domestic Shorthair cat. Ultrastructurally, the mass was composed of fibroblast-like, histiocyte-like, and multinucleated giant cells, and some undifferentiated cells and mononuclear cells intermediate between the fibroblast-like and histiocyte-like cells. Fibroblast-like cells were characterized by abundant well-developed rough endoplasmic reticulum, relatively smooth cytoplasmic membranes, few lysosomal structures, and finely granular chromatin. Histiocyte-like cells resembled immature macrophages. The cell membranes had many villous projections. Rough endoplasmic reticulum varied in quantity. Lysosomes were numerous. Multinucleated giant cells had characteristics of both the fibroblast-like and histiocyte-like cells. No viral particles were seen.     

鹅胸腺APUD(样)细胞的超微结构

应用透射电镜在鹅胸腺内发现一种ＡＰＵＤ（样）细胞。这种细胞形态不规则,有突起伸入相邻细胞之间;胞核圆形,电子密度低,核仁明显;胞质内含有粗面内质网、线粒体等丰富的细胞器。其主要特征是含有大量的多分布于胞质一侧的膜包小分泌颗粒,呈圆形或椭圆形,大小不等,直径１１０～５５０ｎｍ,有些颗粒在界膜与内含物之间可见低电子密度的晕轮。根据其超微结构特征,可将颗粒分为３型：Ⅰ型颗粒为中等电子密度;Ⅱ型颗粒为均质状高电子密度;Ⅲ型颗粒在中等电子密度中含有一高电子密度的核芯。作者认为这种细胞属于内分泌细胞,并且很可能是分泌肽类激素的ＡＰＵＤ细胞。     

Fasciola hepatica: a light and electron microscope study of sustentacular tissue and heterophagy in the testis

In order to investigate cytolytic activity in the testis of Fasciola hepatica, flukes belonging to several different triclabendazole (TCBZ)-sensitive and TCBZ-resistant isolates, and wild-type flukes from field infections, were studied by light and electron microscopy with a view to identifying sites of heterophagy and macromolecular hydrolysis. At the periphery of the testis tubules in all the flukes examined, large euchromatic nuclei, each bearing a prominent nucleolus, were seen. These were invested with a thin cytoplasmic layer, extensions of which partially enveloped and probably supported the neighbouring spermatogonia. No lateral cell boundaries were identified in this tissue, possibly indicating syncytial organisation. The tissue, considered to be analogous to Sertoli cells in vertebrate testis, was identified as sustentacular tissue. It displayed cytoplasmic features consistent with protein/glycoprotein synthesis (through a granular endoplasmic reticulum-Golgi mediated mechanism) and intracellular digestion/heterophagy (through a lysosomal system). The intracytoplasmic hydrolytic activity of the sustentacular tissue probably serves to scavenge effete cells and cytoplasmic debris, to recycle useful molecules, to promote spermatozoon maturation and possibly to aid osmoregulation within the tubules. Certain protein-containing macromolecules synthesised in the sustentacular tissue may contribute to the seminiferous fluid, or have pheromonal activity. The presence of numerous mitochondria and abundant smooth endoplasmic reticulum is consistent with facilitation of inward and outward movement of micromolecular nutrients, metabolites including excretory products and water. In the sustentacular tissue of certain flukes with dysfunctional spermiogenesis, there was increased heterophagic and cytolytic scavenging activity. The cytoplasmic residual vacuoles remaining after the release of spermatids were also identified as possible sites for lysosome-mediated intracellular digestion and osmoregulation in the testis tubules of F. hepatica.     

Ultrastructural pathology of Bordetella avium infection in turkeys

One-day-old turkeys were infected intranasally with Bordetella avium, and tracheas were examined by scanning and transmission electron microscopy at 1 to 5 weeks post-inoculation (PI). The predominant ultrastructural lesions were progressive loss of ciliated epithelium with replacement by nonciliated cells, bacterial colonization of ciliated cells, membrane-bound crystalline inclusions in cytoplasma of epithelial cells, depletion of mucous granules, and distortion of tracheal rings and the mucosal surface. Tracheal surface exudates consisted of mucus, necrotic cells, heterophils, and fibrin. Ciliated cells were replaced by immature cuboidal cells characterized by abundant rough endoplasmic reticulum with small numbers of electron-dense mucous granules in the apical cytoplasm. Bacterial surfaces were rough and contained numerous pleomorphic, knob-like structures, 20-50 nm in diameter. Other changes included enlarged mucosal gland openings, cell extrusion marks, pleomorphic microvilli, and cells with small numbers of short cilia.     

Pseudorabies virus infections in explants of porcine nasal mucosa.

The spread of infection and the morphogenesis of three pseudorabies virus strains were studied in explants of porcine nasal mucosa. Virulent NIA-3 virus was compared with a deletion mutant 2.4N3A, and with a non-virulent Bartha virus. All three virus strains infected nasal epithelial cells. NIA-3 virus particles were enveloped mainly at the inner nuclear membrane; the virus rapidly invaded the stroma, causing widespread necrosis. In contrast, 2.4N3A virus particles were enveloped mainly at the endoplasmic reticulum and the infection spread more slowly. Bartha virus particles were enveloped mainly at the endoplasmic reticulum; the infection spread slowly and remained restricted to the epithelial cells. In situ DNA hybridisation showed an accumulation of Bartha virus DNA in the nucleus 24 hours after inoculation. In nasal mucosa viral virulence seemed directly related to the speed of replication and release of virus from infected cells.     

Peritoneal biphasic mesothelioma in a dog

A 10-year-old German shepherd dog was presented with a severe abdominal distension. At necropsy, whitish and firm mass was observed in the mesentery with metastases in the pericardium and pleura. The intestinal serosa was thickened and stiff. Histologically, the tumours were composed of a biphasic population of cells, which reacted with cytokeratin, vimentin and Wilms' tumour 1 protein antibody. Ultrastructural examination revealed numerous microvilli, abundant rough endoplasmic reticulum, numerous desmosomes and bundles of microfilament. The tumour was classified as biphasic mesothelioma of peritoneal origin.