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Charlie R. Braekevelt - One of the best experts on this subject based on the ideXlab platform.
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Fine structure of the Pecten oculi of the barred owl (Strix varia).
Histology and histopathology, 1996Co-Authors: Bonnie J. Smith, Stephen A. Smith, Charlie R. BraekeveltAbstract:The Pecten oculi of the barred owl (Strix varia) has been examined by light and transmission electron microscopy. The Pecten in this species is of the pleated type and is small in comparison to the size of the ocular globe. The Pecten consists of 8-10 accordion-like folds that are linked apically by a pigmented tissue bridge. Each fold contains numerous capillaries, larger supply and drainage vessels, and abundant pleomorphic melanocytes. Most of these capillaries are extremely specialized vessels that possess plentiful microfolds on both the luminal and abluminal surfaces. Some capillaries however display only a few microfolds. The endothelial cell bodies are extremely attenuated, with most organelles located near the nucleus. All capillaries are surrounded by a very thick fibrillar basal lamina, which is thought to provide structural support to these small vessels. Pericytes are commonly found within these thickened basal laminae. Numerous melanocytes are also present, with processes that form an incomplete sheath around the capillaries. These processes are also presumed to provide structural support for the capillaries. As in other avian species, the morphology of the barred owl Pecten is indicative of extensive involvement in substance transport. When compared to the Pecten of more visually-oriented species, this Pecten is smaller, has fewer folds, and displays a reduced number of microfolds within the capillaries. In these and other features, the barred owl Pecten is similar to the Pecten of the great horned owl (Bubo virginianus).
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Fine structure of the Pecten oculi in the Australian galah (Eolophus roseicapillus) (Aves).
Histology and histopathology, 1996Co-Authors: Charlie R. Braekevelt, Kenneth C. RichardsonAbstract:The Pecten oculi of the Australian galah (Eolophus roseicapillus) has been examined by both light and electron microscopy. In this species the Pecten is large relative to the size of the eye and is of the pleated type. It consists of 20-25 accordion folds that are joined apically by a bridge of tissue which holds the Pecten in a fan-like shape widest at its base. Within each fold are many melanocytes, numerous capillaries as well as larger supply and drainage vessels. The capillaries are extremely specialized for transport functions and display extensive microfolds on both their luminal (inner) and abluminal (outer) borders. Except for the nuclear region which also contains most of the organelles, the endothelial cell bodies are extremely thin. These capillaries are surrounded by thick fibrillar basal laminae which are felt to be structurally important. Pericytes are a common feature within the basal lamina of capillaries. The numerous pleomorphic melanocytes which more or less surround the capillaries are also presumed to be important in structural support of the Pecten. The Pecten represents a supplementary retinal circulation and is comparable to the falciform process of some teleosts, the conus papillaris of reptiles, the supraretinal vessels of amphibians and some teleosts and the intraretinal vessels of mammals, all of which are felt to be alternative methods of bringing nutrients to the inner retina.
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Fine structure of the Pecten oculi in the American crow (Corvus brachyrhynchos).
Anatomia histologia embryologia, 1994Co-Authors: Charlie R. BraekeveltAbstract:The Pecten oculi of the American crow (Corvus brachyrhynchos) has been examined by both light and electron microscopy. In this species the Pecten is very large and of the pleated type. It consists of 22-25 accordion folds that are joined apically by a bridge of tissue which holds the Pecten in a fan-like shape widest at its base. Within each fold are numerous capillaries, larger supply and drainage vessels and many melanocytes. The capillaries are extremely specialized for transport functions and display extensive microfolds on both their luminal and abluminal borders. Except for the nuclear region which contains most of the organelles, the endothelial cell bodies are extremely thin. These capillaries are surrounded by thick fibrillar basal laminae which are conjectured to be structurally important. Pericytes are a common feature of these capillaries. The numerous pleomorphic melanocytes interspersed between the capillaries are also felt to be important in structural support of the Pecten. The Pecten is considered to be comparable to the falciform process of some teleosts, the conus papillaris of reptiles, the supraretinal vessels of amphibians and teleosts and the intraretinal vessels of mammals which are all felt to be alternative methods of bringing nutrients to the inner retina.
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Fine structure of the Pecten oculi in the great horned owl (Bubo virginianus).
Histology and histopathology, 1993Co-Authors: Charlie R. BraekeveltAbstract:The Pecten oculi of the great horned owl (Bubo virginianus) has been examined by light and electron microscopy. The Pecten in this species is of the pleated type and is small in comparison to the size of the eyeball. It consists of 7-8 accordion folds which are joined apically by a pigmented bridge of tissue. Within each fold are numerous capillaries, larger supply and drainage vessels and plentiful pleomorphic melanocytes. The capillaries are extremely specialized vessels, most of which display plentiful microfolds on both their luminal and abluminal surfaces although some capillaries show but a few microfolds. The endothelial cell bodies are extremely thin with most organelles located near the nucleus. All capillaries are surrounded by a thick fibrillar basal lamina which is felt to be structurally important. Pericytes are a common feature within these thickened basal laminae. The numerous melanocytes form an incomplete sheath around the capillaries and are also presumed to be fulfilling a structural role. While the morphology of the Pecten in the great horned owl is certainly indicative of a heavy involvement in transport, when compared to the Pecten in species that are more visually oriented it is smaller, displays fewer folds and a reduced number of microfolds within the capillaries.
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Electron microscopic observations on the Pecten of the great blue heron (Ardea herodias).
Histology and Histopathology, 1991Co-Authors: Charlie R. BraekeveltAbstract:: The Pecten oculi of the great blue heron (Ardea herodias) has been examined by both light and electron microscopy. In this species the Pecten is large and of the pleated type. It consists of 14-15 acordion folds that are joined apically by a more heavily pigmented bridge of tissue which holds the Pecten in a fan-like shape widest at its base. As in other species it is situated over the optic nerve head and projects out into the vitreous. Within each fold are numerous capillaries, larger supply and drainage vessels and many melanocytes. The capillaries are extremely specialized vessels which display extensive microfolds on both their luminal and abluminal borders. The endothelial cell bodies are extremely thin with most organelles present in a paranuclear location. The capillaries are surrounded by thick fibrillar basal laminae which are felt to be structurally useful. Pericytes are a common feature of these capillaries. The numerous pleomorphic melanocytes which form an incomplete sheath around the capillaries and other blood vessels are also felt to be important in structural support of the Pecten. The morphology of the Pecten of the great blue heron is indicative of a heavy involvement in the transport of materials.
S G Kiama - One of the best experts on this subject based on the ideXlab platform.
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functional morphology of the Pecten oculi in the nocturnal spotted eagle owl bubo bubo africanus and the diurnal black kite milvus migrans and domestic fowl gallus gallus var domesticus a comparative study
Journal of Zoology, 2001Co-Authors: J.n. Maina, J. Bhattacharjee, S G Kiama, K. D. WeyrauchAbstract:The Pecten oculi is a highly vascularized and pigmented organ that overlies the optic disc and projects into the vitreous body in the avian eye. First reported over 300 years ago, its function(s) remains a puzzle to ornithologists, ophthalmologists and anatomists. Morphometric study of this unique organ was undertaken in birds exhibiting apparently different visual acuities, namely two species of diurnal birds (the ground-dwelling domestic fowl Gallus gallus var. domesticus and a highly active predator bird, the black kite (Milvus migrans) and a nocturnal bird (the spotted-eagle owl Bubo bubo africanus). The volume of the owl's eye was 4.8 and 2.2 times larger than that of the fowl and the kite, respectively. However, the Pecten of the fowl consisted of more pleats (16–18) compared to the kite (12–13) and the owl (5–6). The volume of the Pecten of the kite was 1.4 and 2.7 times larger than that of the fowl and the owl, respectively (P < 0.05). Similarly, the surface area of the Pecten of the kite was 2.6 and 4 times larger than that of the fowl and owl, respectively (P < 0.05). The volume density of blood vessels (lumen and wall) in the Pecten of the kite, fowl and owl comprised 67.7%, 66.9% and 62.6%, respectively, the pigmented tissue constituting the rest. Both the volume density and the volume of the blood in the Pecten were higher in the diurnal birds (kite, fowl) than the owl (P < 0.05). The surface area of the capillary luminal surface was 1.7 and 5.3 times higher in the kite than in the fowl and the owl, respectively (P < 0.05). These results suggest that the functional morphology of the Pecten correlates with the life-style of the bird and with functional need, and lends further support to the nutritive role of the Pecten.
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A scanning electron microscope study of the Pecten oculi of the black kite (Milvus migrans): possible involvement of melanosomes in protecting the Pecten against damage by ultraviolet light.
Journal of anatomy, 1994Co-Authors: S G Kiama, J.n. Maina, J. Bhattacharjee, K. D. WeyrauchAbstract:The Pecten oculi of the black kite (Milvus migrans), a diurnally active bird of prey, has been examined by scanning electron microscopy. In this species the Pecten consists of 12 highly vascularised pleats, held together apically by a heavily pigmented 'bridge' and projects freely into the vitreous body in the ventral part of the eye cup. Ascending and descending blood vessels of varying calibre, together with a profuse network of capillaries, essentially constitute the vascular framework of the Pecten. A distinct distribution of melanosomes is discernible on the Pecten, the concentration being highest at its apical end, moderate at the crest of the pleats and least at the basal and lateral margins. Overlying and within the vascular network, a close association between blood vessels and melanocytes is evident. It is conjectured that such an association may have evolved to augment the structural reinforcement of this nutritive organ in order to keep it firmly erectile within the gel-like vitreous. Such erectility may be an essential prerequisite for its optimal functioning, as well as in its overt use as a protective shield against the effects of ultraviolet light, which otherwise might lead to damage of the pectineal vessels.
K. D. Weyrauch - One of the best experts on this subject based on the ideXlab platform.
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The morphology of the Pecten oculi of the ostrich, Struthio camelus
Annals of anatomy = Anatomischer Anzeiger : official organ of the Anatomische Gesellschaft, 2006Co-Authors: Stephen G. Kiama, J.n. Maina, J. Bhattacharjee, D. K. Mwangi, R.g. Macharia, K. D. WeyrauchAbstract:Summary The Pecten oculi is a structure peculiar to the avian eye. Three morphological types of Pecten oculi are recognized: conical type, vaned type and pleated type. The pleated type has been well studied. However, there exists only scanty data on the morphology of the latter two types of Pectens. The structure of the vaned type of Pecten of the ostrich, Struthio camelus was investigated with light and electron microscope. The Pecten of this species consists of a vertical primary lamella that arises from the optic disc and supports 16–19 laterally located secondary lamellae, which run from the base and confluence at the apex. Some of the secondary lamellae give rise to 2 or 3 tertiary lamellae. The lamellae provide a wide surface, which supports 2–3 layers of blood capillaries. Pigmentation is highest at the distal ends of the secondary and tertiary lamella where blood capillaries are concentrated and very scanty on the primary and the proximal ends of the secondary lamella where the presence of capillaries is much reduced. In contrast to the capillaries of the pleated Pecten, the endothelium of the capillaries in the Pecten of the ostrich exhibits very few microvilli. These observations suggest that the morphology of the Pecten of the ostrich, a flightless ratite bird is unique to the pleated Pecten and is designed to meet the balance between optimal vision and large surface area for blood supply and yet ensuring it is kept firmly erect within the vitreous.
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functional morphology of the Pecten oculi in the nocturnal spotted eagle owl bubo bubo africanus and the diurnal black kite milvus migrans and domestic fowl gallus gallus var domesticus a comparative study
Journal of Zoology, 2001Co-Authors: J.n. Maina, J. Bhattacharjee, S G Kiama, K. D. WeyrauchAbstract:The Pecten oculi is a highly vascularized and pigmented organ that overlies the optic disc and projects into the vitreous body in the avian eye. First reported over 300 years ago, its function(s) remains a puzzle to ornithologists, ophthalmologists and anatomists. Morphometric study of this unique organ was undertaken in birds exhibiting apparently different visual acuities, namely two species of diurnal birds (the ground-dwelling domestic fowl Gallus gallus var. domesticus and a highly active predator bird, the black kite (Milvus migrans) and a nocturnal bird (the spotted-eagle owl Bubo bubo africanus). The volume of the owl's eye was 4.8 and 2.2 times larger than that of the fowl and the kite, respectively. However, the Pecten of the fowl consisted of more pleats (16–18) compared to the kite (12–13) and the owl (5–6). The volume of the Pecten of the kite was 1.4 and 2.7 times larger than that of the fowl and the owl, respectively (P < 0.05). Similarly, the surface area of the Pecten of the kite was 2.6 and 4 times larger than that of the fowl and owl, respectively (P < 0.05). The volume density of blood vessels (lumen and wall) in the Pecten of the kite, fowl and owl comprised 67.7%, 66.9% and 62.6%, respectively, the pigmented tissue constituting the rest. Both the volume density and the volume of the blood in the Pecten were higher in the diurnal birds (kite, fowl) than the owl (P < 0.05). The surface area of the capillary luminal surface was 1.7 and 5.3 times higher in the kite than in the fowl and the owl, respectively (P < 0.05). These results suggest that the functional morphology of the Pecten correlates with the life-style of the bird and with functional need, and lends further support to the nutritive role of the Pecten.
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A scanning electron microscope study of the Pecten oculi of the black kite (Milvus migrans): possible involvement of melanosomes in protecting the Pecten against damage by ultraviolet light.
Journal of anatomy, 1994Co-Authors: S G Kiama, J.n. Maina, J. Bhattacharjee, K. D. WeyrauchAbstract:The Pecten oculi of the black kite (Milvus migrans), a diurnally active bird of prey, has been examined by scanning electron microscopy. In this species the Pecten consists of 12 highly vascularised pleats, held together apically by a heavily pigmented 'bridge' and projects freely into the vitreous body in the ventral part of the eye cup. Ascending and descending blood vessels of varying calibre, together with a profuse network of capillaries, essentially constitute the vascular framework of the Pecten. A distinct distribution of melanosomes is discernible on the Pecten, the concentration being highest at its apical end, moderate at the crest of the pleats and least at the basal and lateral margins. Overlying and within the vascular network, a close association between blood vessels and melanocytes is evident. It is conjectured that such an association may have evolved to augment the structural reinforcement of this nutritive organ in order to keep it firmly erectile within the gel-like vitreous. Such erectility may be an essential prerequisite for its optimal functioning, as well as in its overt use as a protective shield against the effects of ultraviolet light, which otherwise might lead to damage of the pectineal vessels.
Pietro Renon - One of the best experts on this subject based on the ideXlab platform.
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A case of identification of pectinid scallop (Pecten jacobaeus, Pecten maximus) in a frozen and seasoned food product with PCR technique
Food Control, 2004Co-Authors: Fabio Colombo, Isabella Trezzi, Cristian Bernardi, Carlo Cantoni, Pietro RenonAbstract:Abstract Several parts of a frozen, cut and seasoned food product, labelled as pectinid scallop (mainly Pecten jacobaeus and Pecten maximus) and suspected to contain vertebrate fish were analysed with PCR: a specific primer pair was designed, tested and used. Moreover an “universal” vertebrate primer pair was applied. The sample was confirmed to be a scallop belonging to P. jacobaeus or P. maximus species.
J.n. Maina - One of the best experts on this subject based on the ideXlab platform.
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The morphology of the Pecten oculi of the ostrich, Struthio camelus
Annals of anatomy = Anatomischer Anzeiger : official organ of the Anatomische Gesellschaft, 2006Co-Authors: Stephen G. Kiama, J.n. Maina, J. Bhattacharjee, D. K. Mwangi, R.g. Macharia, K. D. WeyrauchAbstract:Summary The Pecten oculi is a structure peculiar to the avian eye. Three morphological types of Pecten oculi are recognized: conical type, vaned type and pleated type. The pleated type has been well studied. However, there exists only scanty data on the morphology of the latter two types of Pectens. The structure of the vaned type of Pecten of the ostrich, Struthio camelus was investigated with light and electron microscope. The Pecten of this species consists of a vertical primary lamella that arises from the optic disc and supports 16–19 laterally located secondary lamellae, which run from the base and confluence at the apex. Some of the secondary lamellae give rise to 2 or 3 tertiary lamellae. The lamellae provide a wide surface, which supports 2–3 layers of blood capillaries. Pigmentation is highest at the distal ends of the secondary and tertiary lamella where blood capillaries are concentrated and very scanty on the primary and the proximal ends of the secondary lamella where the presence of capillaries is much reduced. In contrast to the capillaries of the pleated Pecten, the endothelium of the capillaries in the Pecten of the ostrich exhibits very few microvilli. These observations suggest that the morphology of the Pecten of the ostrich, a flightless ratite bird is unique to the pleated Pecten and is designed to meet the balance between optimal vision and large surface area for blood supply and yet ensuring it is kept firmly erect within the vitreous.
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functional morphology of the Pecten oculi in the nocturnal spotted eagle owl bubo bubo africanus and the diurnal black kite milvus migrans and domestic fowl gallus gallus var domesticus a comparative study
Journal of Zoology, 2001Co-Authors: J.n. Maina, J. Bhattacharjee, S G Kiama, K. D. WeyrauchAbstract:The Pecten oculi is a highly vascularized and pigmented organ that overlies the optic disc and projects into the vitreous body in the avian eye. First reported over 300 years ago, its function(s) remains a puzzle to ornithologists, ophthalmologists and anatomists. Morphometric study of this unique organ was undertaken in birds exhibiting apparently different visual acuities, namely two species of diurnal birds (the ground-dwelling domestic fowl Gallus gallus var. domesticus and a highly active predator bird, the black kite (Milvus migrans) and a nocturnal bird (the spotted-eagle owl Bubo bubo africanus). The volume of the owl's eye was 4.8 and 2.2 times larger than that of the fowl and the kite, respectively. However, the Pecten of the fowl consisted of more pleats (16–18) compared to the kite (12–13) and the owl (5–6). The volume of the Pecten of the kite was 1.4 and 2.7 times larger than that of the fowl and the owl, respectively (P < 0.05). Similarly, the surface area of the Pecten of the kite was 2.6 and 4 times larger than that of the fowl and owl, respectively (P < 0.05). The volume density of blood vessels (lumen and wall) in the Pecten of the kite, fowl and owl comprised 67.7%, 66.9% and 62.6%, respectively, the pigmented tissue constituting the rest. Both the volume density and the volume of the blood in the Pecten were higher in the diurnal birds (kite, fowl) than the owl (P < 0.05). The surface area of the capillary luminal surface was 1.7 and 5.3 times higher in the kite than in the fowl and the owl, respectively (P < 0.05). These results suggest that the functional morphology of the Pecten correlates with the life-style of the bird and with functional need, and lends further support to the nutritive role of the Pecten.
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A scanning electron microscope study of the Pecten oculi of the black kite (Milvus migrans): possible involvement of melanosomes in protecting the Pecten against damage by ultraviolet light.
Journal of anatomy, 1994Co-Authors: S G Kiama, J.n. Maina, J. Bhattacharjee, K. D. WeyrauchAbstract:The Pecten oculi of the black kite (Milvus migrans), a diurnally active bird of prey, has been examined by scanning electron microscopy. In this species the Pecten consists of 12 highly vascularised pleats, held together apically by a heavily pigmented 'bridge' and projects freely into the vitreous body in the ventral part of the eye cup. Ascending and descending blood vessels of varying calibre, together with a profuse network of capillaries, essentially constitute the vascular framework of the Pecten. A distinct distribution of melanosomes is discernible on the Pecten, the concentration being highest at its apical end, moderate at the crest of the pleats and least at the basal and lateral margins. Overlying and within the vascular network, a close association between blood vessels and melanocytes is evident. It is conjectured that such an association may have evolved to augment the structural reinforcement of this nutritive organ in order to keep it firmly erectile within the gel-like vitreous. Such erectility may be an essential prerequisite for its optimal functioning, as well as in its overt use as a protective shield against the effects of ultraviolet light, which otherwise might lead to damage of the pectineal vessels.
