Light and electron microscopic studies on the pecten oculi showing blood–retina barrier properties in Turkey’s native Gerze chicken

The pecten oculi is a highly vascularized and pigmented organ that projects from the optic disc into the vitreous body in the avian eye. In this study, the pecten oculi of Turkey's native Gerze chicken was examined by light and scanning electron microscopy. Furthermore, the localization of some adherens junction components (E-cadherin and pan-cadherin) in intact vessels of the blood–retina barrier was investigated by immunohistochemistry. In the Gerze chicken, the pecten oculi was a thin structure, which was located over the head of the discus nervi optici and projected from the retina into the corpus vitreum. The pecten oculi consisted of 18–21 highly vascularized pleats, joined apically by a bridge and resembled an accordion in appearance. Hyalocytes and melanocytes were observed around the small and large vessels. The morphometric data of the pecten oculi showed that there were no statistical differences in terms of sex. The immunohistochemical analysis of the pecten oculi, which is used as a model for the investigation of the formation and maturation of the barrier properties in the central nervous system, revealed cytoplasmic E-cadherin and pan-cadherin immunoreactivity in the endothelial cells of the small, large and capillary vessels. These observations suggest that while the morphological and histological structure of the Gerze chicken's pecten oculi was generally similar to that of other diurnal domestic birds, the pecten oculi, a model system for vascular differentiation and the blood–retina barrier, expressed different cadherins.     

Fine Structure of the Pecten Oculi of the Red-Tailed Hawk (Buteo jamaicensis)

The pecten oculi of the red-tailed hawk (Buteo jamaicensis) has been examined by light and electron microscopy. In this species the pecten is very large and of the pleated type. It consists of 17-18 accordion folds which are joined apically by a heavily pigmented bridge of tissue which holds the pecten in a fan-like shape, widest at its base. It is situated over the optic nerve head and extends into the vitreous. Within each fold are numerous capillaries, larger supply and drainage vessels and melanocytes. The capillaries are specialized and display extensive microfolds on both the luminal and abluminal borders. The endothelial cell bodies are thin with most organelles present in a paranuclear location. The capillaries are surrounded by thick fibrillar basal laminae which are probably structurally important and which often enclose pericytes. The melanocytes which are most plentiful in the bridge region and peripherally in the pecten, form an incomplete sheath around the capillaries and other blood vessels. These melanocytes are also felt to be fulfilling a structural role within the pecten. The morphology of the pecten of the red-tailed hawk is indicative of a heavy involvement in the transport of materials to the avascular avian retina.     

The development of the pecten oculi in the chick

The development of the pecten oculi, a structure peculiar to the avian eye, was studied by scanning electron microscopy (SEM) correlated with light microscopy (LM) in embryonic and adult chickens. The development of the chick pecten was divided into 4 phases: (1) formation of the primordial pecten (Hamburger-Hamilton's stages 27 to 29), (2) formation of the plate-like pecten (stages 30 to 34), (3) pleat formation and pigmentation (stages 35 to 37), and (4) bridge formation and high-vascularization (stage 38 to adult). The primordial pecten is formed entirely from the ectoderm by fusion of the inwardly-projecting edges of the optic fissure. The primordial pecten grows into a tall, thin plate rising from a broad base. The pecten begins to fold slightly at stage 35. The number of pleats increases rapidly, from 7 at stage 35, to 16 at stage 36, 18 at stage 37, and 19 to 20 at stage 40. The bridge begins to form at stage 38 by a swelling of the apical edge of the pecten and completes its development by the twentieth post-hatch day. Blood vessels appear first in the broad base of the plate-like pecten, then become more numerous and gradually extend into the pleats. The pecten becomes more vascular than cellular at stage 43, and it is highly vascularized in the adult. The pleat surface becomes conspicuously irregular with increased vascularization. The peripectinate cells, located on the pecten, are already present at stage 27.     

Retinal vascular patterns in domestic animals

In this paper a morphological study of the retinal vascular patterns in various species of domestic animals is reported. A classification of these patterns into four well-defined groups is described. In the domestic ruminants, pigs and carnivores the retina contains a compact plexus of blood vessels located in the major part of the light-sensitive portion of the retina (euangiotic or holangiotic pattern). In other domestic animals blood vessels are present only in a smaller part of the retina. In the rabbit, vessels are confined to a broad horizontal band coincident with the area of dispersion of the myelinated nerve fibres. The larger of these vessels are readily visible macroscopically (merangiotic pattern). In the horse and the guinea pig the retinal blood vessels are minute and restricted to the direct neighbourhood of the optic disc (paurangiotic pattern). The avian retina is completely avascular (anangiotic pattern), but a densely vascularised pecten oculi is attached to the linear optic nerve head and protrudes far into the inferior part of the vitreous body.     

Fine Structure of the Pecten Oculi in the American Crow (Corvus brachyrhynchos)

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.     

A comparative ultrastructural study of the pecten oculi in adult,juvenile, and nestling yellow‐legged gulls,Larus michahellis (Naumann, 1840)

This study aimed at examining the histological structure of the pecten oculi in the adult yellow‐legged gull, Larus michahellis, and at two moments of postnatal development: during the posthatch (nestling) and juvenile periods. Particular attention was paid to differences in the diameter of vessels, the thickness of the basement membrane, and ultrastructural features of endothelial and pigmented stromal cells. Capillary endothelial cells displayed numerous microvillous‐like folds projecting from their internal and external surfaces. Intercellular spaces between capillaries were occupied by pigmented stromal cells. The ultrastructure of pecten oculi underwent noticeable changes during postnatal development. The examination of the capillaries in nestlings, juveniles, and adults revealed that the formation process of vessels and pigmented stromal cells did not complete itself in the posthaching phase. The prominent feature of endothelial cells of capillaries in nestlings was that the microvilli were longer than in juvenile and adult cells, and the capillary lumen was therefore reduced. In this sense, their pigmented stromal cells showed fewer melanosomes, lacked intercellular spaces, and cellular junctions could still be observed. These results provide evidence that the pecten oculi during the posthatching phase maintains immature morphological features consistent with a role of pigmented stromal cells in the blood‐retina barrier.     

Quantitative studies of the optic nerve fiber layer in the chicken retina.

The optic nerve fiber layer (NFL) of the chicken retina was studied quantitatively and morphologically at 17 positions along seven radially arranged bands from the dorsal tip of the pecten oculi using electron microscopy. The number of nerve fibers was counted in areas 6 microm in width x the full thickness of the NFL. Myelinated nerve fibers in the NFL were also identified immunohistochemically using anti-myelin basic protein serum. The dorsal area (dorsal, dorso-temporal and dorso-nasal bands) in the retina had thin NFL and contained the largest number of nerve fibers, which were mainly thin and unmyelinated. The ventral area (ventral and ventro-temporal bands) had a thick NFL and contained a relatively small number of nerve fibers, many of which were myelinated. The nasal band had the thickest NFL and contained as many nerve fibers as the dorsal area, with the temporal band showing a high ratio of myelinated fibers. The band had a thick NFL and contained many nerve fibers with a relatively low ratio of myelinated fibers. The relationship between the number and composition of nerve fibers in the NFL to the chicken visual characteristics was discussed. Although the myelin in the chicken retina was loose type, the myelin-forming cells were similar in appearance to dense oligodendrocytes. retina, morphometry, myelinated fiber, nerve fiber layer.     

Factors influencing the use of winter-burnt grassland by foraging bald ibises Geronticus calvus

Use of winter-burnt grassland by foraging bald ibises, Geronticus calvus, and the abundance of invertebrates in winter-burnt grassland were investigated in relation to the time elapsed after burning In Natal high grassland. Bald ibises were recorded feeding In dormant, winter-burnt grassland from less than 4 h after burning up to 35 days after burning. Insects and other potential prey items were significantly more abundant 0-7 days than 14-37 days after burning: most specimens consisted of fire-killed arthropods. Live Insects increased in abundance soon after the appearance of new growth 46 - 82 days after burning. Possible factors Influencing the use of winter-burnt grassland by foraging bald ibises are discussed with emphasis on changes In the relative abundance of living and dead arthropods in relation to the time elapsed after burning.     

山东半岛珍稀鸟类的研究

山东半岛位于太平洋西岸中部、我国东部沿海，地处温带，一面连陆，三面环海。境内生态环境多样，动植物资源丰富，是我国东部、东亚及环太平洋西海岸地区候鸟迁徙的必经之地和部分鸟类繁殖、越冬区域，鸟类资源十分丰富。有鸟类389种和亚种，其中属国际濒危种类63种；国家重点保护种类68种；有中、日候鸟保护协定所列种类198种；有中、澳双方保护鸟类61种；有候乌344种，占我国候乌60％；有部分特殊分布和大量繁殖、越冬的种群。     

ULTRASONOGRAPHIC AND COMPUTED TOMOGRAPHIC EXAMINATIONS OF THE AVIAN EYE: PHYSIOLOGIC APPEARANCE, PATHOLOGIC FINDINGS, AND COMPARATIVE BIOMETRIC MEASUREMENT

Ultrasonography (US) and computed tomography (CT) were performed after routine ophthalmologic and ophthalmoscopic examinations in 190 eyes of six various diurnal (common buzzard [Buteo buteo L., 1758], n = 20; common kestrel [Tinnunculus tinnunculus L., 1758], n = 20) and nocturnal raptor species (barn owl [Tyto alba L., 1758], n = 22; tawny owl [Strix aluco L., 1758], n = 8; long-eared owl [Asio otus L., 1758], n = 5; horned owl [Bubo bubo L., 1758], n = 1); and domestic pigeons (Columba livia, Gmel., 1789; n = 19), with a total of 95 individuals. Pathologic findings such as lens subluxation and luxation, intravitreal hemorrhage, detached retina, post-traumatic partial sequestration, or malformation of the pecten could be demonstrated with diagnostic imaging tools, while opacities of cornea or lens constrained direct ophthalmoscopic examination. The results proved US to be a quick noninvasive imaging technique for detailed ocular diagnoses. CT provided detailed information of the bony skull and bony scleral rings as well as adequate visualization of shape, size, and margination of the eye and lens. Nevertheless, CT was unable to differentiate subtle structures within the vitreous like the pecten oculi or hemorrhage. Biometric measurements were carried out to objectify imaging results. Results showed good correlation of depth and width of the anterior eye chamber, lens and vitreous, length of the bulbus, and the pecten but no correlation of cornea and posterior wall thickness was found.     

Effect of Newcastle disease virus on ocular and paraocular tissues in experimentally inoculated chickens

The effects of a mesogenic strain of Newcastle disease virus on ocular and paraocular structures were studied in 10-to-12-week-old chickens inoculated conjunctivally, intraocularly, intracerebrally, or intravenously. Paraffin-embedded tissues were examined by light and fluorescent microscopy using conventional staining and immunohistochemistry. Lesions were most severe in intraocularly inoculated chickens, where a marked iridocyclochoroiditis was evident from 8-12 hours up to 21 days postinfection. Viral antigens were detected in the iris, ciliary body, Schlemm's canal, and occasionally the lens, choroid, and base of the pecten. Although optic neuritis and iridocyclochoroiditis were found in intracerebrally inoculated birds, no viral antigens were detected in the optic nerve.     

Distribution of nitric oxide synthase (NOS) immunoreactivity in the chicken stomach

NOS-immunoactive nerve structures were studied in the domestic hen (Gallus domesticus) stomach using single-labelling immunofluorescence. The examined tissues were collected from 10-12 months old laying hens (n=11), Isabrown and Zielononózka races. The distribution and number of the nerve fibres was examined considering differences between the proventriculus and gizzard, and also between particular layers of the stomach wall. Large or moderate numbers of nerve fibres showing NOS-immunoreactivity (NOS-IR) were found in all major layers of both parts of the stomach. In the muscular layer of the gizzard, NOS-positive nerve cell bodies were also observed. Small or moderate numbers of nerve terminals were distributed around blood vessels. NOS-IR nerve fibres associated with blood vessels were slightly more numerous in the gizzard than in the proventriculus. The widespread occurrence of NOS in both parts of the hen stomach can prove its important role in the control of digestive processes. It seems that there is a reasonable necessity of further, more detailed studies on morphological characteristics of the nitrergic nerve structures the bird alimentary tract, their functional significance and plasticity in different physiological and pathological conditions.     

A preliminary analysis of the response of an avian community to silvicultural treatments in the southern Cumberland Plateau,Alabama, USA

We simulated a shelterwood forest regeneration treatment by reducing basal area, and monitored the response of an avian community in oak‐hickory forest on the southern Cumberland Plateau, northern Alabama, USA. We used five treatments: control (no removal), clear‐cut (100% removal), and 25, 50, and 75% removal of basal area. Territory mapping was used to quantify bird community between mid‐April and July of both 2002 and 2003. Microclimate variables were recorded at each plot. The residual basal area and canopy cover showed three distinct conditions after treatment: closed canopy, open forest, and clear‐cut. The microclimate varied among treatments: air temperature was highest in clear‐cut plots and lowest in control plots, whereas soil moisture had the opposite pattern. A total of 71 bird species were detected, with 36 of them defending territories. Territory density, species richness, and Shannon diversity index differed among the treatments; the relationship between these bird community indices and the level of basal area removal was quadratic, lowest in the clear‐cut plots and highest in the intermediate levels. Although species richness was similar among the control, 25, 50, and 75% removal treatments, species composition varied. The richness difference among treatments became smaller in the second year post‐treatment (2003) with an increase in bird density and richness occurring in the clear‐cut plots.     

Blindness in a wild American black bear cub (Ursus americanus)

An approximately six‐month‐old wild American black bear (Ursus americanus) was found wandering in Saskatchewan and was presented to the Veterinary Medical Centre of the Western College of Veterinary Medicine for apparent blindness. Clinical examination confirmed an inability to navigate a photopic maze, bilateral tapetal hyper‐reflectivity, fundi devoid of retinal vessels, and small pale optic nerve papillae. Single‐flash electroretinography revealed A and B‐wave amplitudes of approximately 40 and 140 microvolts, respectively, in both eyes. Histologic abnormalities included bilateral optic papillary mineralization and bilateral segmental optic nerve degeneration, with occasional intralesional lymphocytes confirmed with immunohistochemistry for CD3+. There was also bilateral multifocal retinal dysplasia, gliosis, lymphocytic retinitis, a complete lack of retinal blood vessels, an intravitreal vascular membrane, and a mild lymphocytic–plasmacytic uveitis with small pre‐iridal cellular membranes. The presence of a positive ERG in a blind bear with numerous retinal ganglion cells and degenerative changes in the optic nerve are most consistent with vision loss due to optic nerve injury, which given the young age of the bear likely occurred during ocular development. The presence of ocular inflammation suggests this injury resulted from an inflammatory/infectious process. The etiology could not be determined. Hepatic concentrations of vitamin A were within the normal reference range for domestic species. Pan‐herpesvirus PCR and immunohistochemistry for canine distemper virus and Toxoplasma gondii were negative, although this does not rule out these or other infectious etiologies. This represents the first case report of neonatal or congenital ocular abnormalities in an ursid species.     

Comparative optic nerve physiology: implications for glaucoma, neuroprotection, and neuroregeneration

The axoplasm of optic nerve axons moves bidirectionally at various speeds along an intra-axonal pressure gradient from the retinal ganglion cell (RGC) somata toward its synapse, and from the synapse towards the RGC somata. The axoplasmic flow of optic nerve axons is precarious even at normal intraocular pressures (IOP) as it moves from the intraocular optic nerve through the scleral lamina cribrosa to the intraorbital optic nerve. The scleral lamina cribrosa is not simply a porous region of the sclera but a specialized extracellular matrix of the central nervous system whose movement during fluctuations in IOP can affect optic nerve axoplasmic flow. The abundant optic nerve blood supply maintains adequate optic nerve head perfusion through a process of vascular autoregulation. Glaucoma is associated with reduced optic nerve axoplasmic flow and compromised optic nerve circulation such that RGC death due to glutamate excitotoxicity and neurotrophin deprivation result.     

湖南屏风界候鸟种类与迁徙规律调查

2001-2006年，通过对湖南省屏风界候鸟种类及迁徙规律的调查，表明屏风界候乌资源较为丰富，共环志鸟类26科95种，其中国家Ⅱ级保护鸟类18种。同时摸清了该地区候乌迁徙的主要规律，对候鸟迁徙通道的形成原因进行了分析，为该地区鸟类资源的有效保护和管理提供了科学依据。     

雁荡山鸟类资源及保护利用意见

雁荡山有鸟类资源293种,隶属19目55科,其中夏候鸟43种,冬候鸟104种,留鸟99种,旅鸟47种,有27种属国家ⅠⅡ级保护鸟类。通过调查,本文对雁荡山鸟类资源特点和区系组成进行分析,提出保护和合理利用意见。     

MAGNETIC RESONANCE IMAGING OF THE CANINE OPTIC NERVE

We describe the magnetic resonance (MR) imaging aspects of normal canine optic nerve, the diameter of the optic nerve as measured on MR images, and optimal MR sequences for the evaluation of the optic nerve using a 0.2 T MR unit. Three millimeter contiguous slides of the normal canine orbital region were acquired in transverse and dorsal oblique planes using a variety of tissue weighting sequences. It was apparent that detailed anatomic assessment of the optic nerve can be performed with low‐field MR imaging, but none of the sequences provided unequivocal superior image quality of the optic nerve. The mean diameter of the optic nerve sheath complex was 3.7 mm and of the optic nerve 1.7 mm. The intraorbital and intracanalicular parts of the optic nerve are consistently visible and differentiation between the optic nerve and optic nerve sheath complex is possible using low‐field MR systems.     

山东鲁山自然保护区动物资源调查及保护初探

鲁山自然保护区,隶属山东省淄博市,地处博山区和沂源县境内。经调查,保护区内共记录野生动物13纲,55目,236科,1351种。其中国家Ⅰ级保护野生动物4种,国家Ⅱ级保护野生动物35种;山东省重点保护野生动物43种。列于《濒危野生动植物种国际贸易公约》中的保护动物45种,在《中国和日本国政府保护候鸟及其栖息环境协定》中保护的鸟类129种,在《中国与澳大利亚政府保护候鸟及其栖息环境协定》中保护的鸟类31种。通过对保护区动物资源的调查,提出了保护对策和建议。