Efferent and afferent innervation of primate trabecular meshwork and scleral spur

PURPOSE: To determine the correlation between nerve terminals and cells or extracellular matrix (ECM) components in different portions of the primate trabecular meshwork (TM) and scleral spur (SS). METHODS: Serial sagittal and tangential sections through the anterior segments of 10 cynomolgus monkey eyes and 12 human eyes were investigated immunohistochemically with antibodies against the vesicular acetylcholine transporter (VACHT), vasoactive intestinal polypeptide (VIP), tyrosine-hydroxylase (TH), neuropeptide Y (NPY), substance P (SP), calcitonin gene-related peptide (CGRP), and galanin (GAL) and with a reduced nicotinamide adenine dinucleotide phosphate-diaphorase (NADPHd) reaction. The distribution of the terminals was compared with that of alpha-smooth-muscle actin (SMA) staining in TM and SS. The relationship between terminals and adjacent cells or ECM components was also studied in ultrathin sections through the TM and SS of 11 monkey eyes cut in sagittal, tangential, and frontal planes. RESULTS: NADPHd-positive nerve terminals were present, especially in the outer portion of both human and monkey TM and in the SS. VACHT-immunoreactive (IR) fibers were found in human but not in monkey SS and TM. The fibers were most numerous in the elongated SS and posterior TM where most cells also stained for SMA. SP- and CGRP-IR nerve endings were also more numerous in the outer TM and SS than in the inner TM. Ultrastructurally, staining for SP was seen in nerve endings containing mitochondria and dense core vesicles and was in contact with the cribriform elastic network. In the posterior SS of monkey eyes were large terminals similar to those previously described in human eyes. CONCLUSIONS: The results show for the first time that in the primate TM and SS, there are cholinergic and nitrergic nerve terminals that could induce contraction and relaxation of TM and SS cells. Terminals in contact with the elastic-like network of the TM and containing SP-IR resemble afferent mechanoreceptor-like terminals in other parts of the body. These findings raise the possibility that the TM may have some ability to self-regulate aqueous humor outflow.     

Characterization of nitrergic neurons in the porcine and human ciliary nerves

PURPOSE: To further characterize a subpopulation of choroidal ganglion cells associated with the ciliary nerves. METHODS: Isolated long ciliary nerves of porcine and human eyes containing ciliary nerve-associated ganglion cells (CNGCs) were embedded in Epon for ultrastructural investigation, or wholemounts were stained with antibodies against nitric oxide synthase (NOS), vasoactive intestinal polypeptide (VIP), vesicular acetylcholine transporter, neuropeptide Y (NPY), tyrosine hydroxylase (TH), calcitonin gene-related peptide (CGRP), substance P (SP), and synaptophysin. In addition, wholemount preparations of the choroid and of the anterior segment were stained for reduced nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-D). Serial sections through choroid and anterior segment were stained with the prior antibodies listed. RESULTS: In the porcine choroid only CNGCs were present. They stained for brain (b)NOS and VIP and were surrounded by SP and VIP-immunoreactive (IR) nerve terminals. The axonal processes of the CNGCs followed the ciliary nerves to the anterior eye segment, where they formed a nerve fiber plexus that terminated in the trabecular meshwork. None of the axons passed into the sparse NOS-IR nerve fiber plexus surrounding the choroidal vasculature. The CNGCs in the human choroid morphologically resembled those seen in the pig. CONCLUSIONS: The CNGC proportion of choroidal ganglion cells is presumably involved in the intrinsic (peripheral) innervation of the aqueous outflow tissues and of the choroid.     

Immunohistochemical classification and functional morphology of human choroidal ganglion cells

PURPOSE: To characterize human choroidal ganglion cells (CGCs) further, regarding their immunohistochemical and ultrastructural appearance and their pre- and postsynaptic connections. METHODS:. Choroidal wholemounts and serial sections of human donor eyes were stained with antibodies against neuronal nitric oxide synthase (nNOS), vasoactive intestinal peptide (VIP), tyrosine hydroxylase (TH), vesicular monoaminergic transporter (VMAT)-2, vesicular acetylcholine transporter (VAChT), neuropeptide Y (NPY), substance P (SP), calcitonin gene-related peptide (CGRP), calretinin, galanin, synaptophysin, and alpha-smooth muscle actin. Ultrathin sections of glutaraldehyde-fixed eyes were studied with an electron microscope. RESULTS: All CGCs stained for nNOS, most for VIP, approximately 45% for calretinin, and only single neurons for NPY and galanin. Ultrastructurally, the CGCs showed an incomplete glial sheath and, in places, showed close contact to surrounding collagen fibrils. The CGCs were in close contact with numerous boutons staining for the different neuronal markers including synaptophysin, nNOS, VIP, NPY, TH, VMAT-2, VAChT, calretinin, and NPY. CONCLUSIONS: The data indicate a complex integrative function of CGCs. The immunohistochemical and ultrastructural characteristics also indicate that the CGCs may have mechanosensory properties. The complex synaptic information points to a specific regulative CGC function in parallel with ciliary muscle contraction (accommodation). Axons originating from CGCs mainly supply the choroidal vasculature, thus implicating the CGCs as vasodilative neurons, but single CGCs may also innervate other structures such as nonvascular choroidal smooth muscle cells.     

Peptidergic innervation of the retinal vasculature and optic nerve head.

Using immunocytochemistry, the authors studied the peptidergic innervation to the vasculature of the optic nerve and retina in the rhesus monkey and rat. In the monkey, beaded nerve fibers immunoreactive to the vasoactive peptides, calcitonin gene-related peptide (CGRP), neuropeptide Y (NPY), substance P (SP), and vasoactive intestinal peptide (VIP), are present in the adventitia and perivascular space along the course of the central retinal artery within the optic nerve. The CGRP and SP immunoreactivities fully co-localize. Perivascular peptidergic nerve fibers terminate as the blood vessel enters the globe and do not follow the branches of the central retinal artery inside the eye. Within the substance of the optic nerve behind the lamina cribrosa, small blood vessels occasionally are supplied with CGRP-, SP-, and sometimes NPY- or VIP-immunoreactive nerve fibers. Of special note, fine nerve fibers not clearly related to blood vessels are seen within the lamina cribrosa; their simultaneous immunoreactivity to CGRP and SP suggests a sensory function. In the rat as in the monkey, the retinal arterioles beyond the surface of the optic disc lack evident peptidergic innervation. Perhaps an explanation for the known physiologic reactivity of the retinal circulation to neurohumors in the absence of recognizable peripheral innervation can be based on comparison to the brain where intraparenchymal blood vessels may be regulated by local neurons. Since the inner plexiform layer has abundant amacrine-derived nerve processes containing classical neurotransmitters and/or neuropeptides, a local mechanism coupled to intrinsic retinal activity might contribute to the regulation of the circulation.     

Choroidal innervation in primate eyes

Arteries and arterioles of the choroid are surrounded by numerous nerve fibers staining for nitric oxide synthase (NOS) and vasoactive intestinal peptide (VIP). In most mammalian eyes these nerve fibers derive from the pterygopalatine ganglion via the facial nerve. Stimulation of the facial nerve causes vasodilation of the choroidal vasculature. In primates with a well developed fovea centralis there are ganglion cells in the choroidal stroma which in human eyes amount to around 2000. The postganglionic nerve fibers of these choroidal ganglion cells (CGC) join the perivascular nerve fiber plexus. The CGC stain for NOS and VIP like the nerve cells within the pterygopalatine ganglion. There are, however, differences between the two cell populations. Immunohistochemical and ultrastructural classification of the CGC show that in addition to NOS and VIP almost half of the cells stain for calretinin, single ones for neuropeptide Y (NPY) and galanin. A number of cells is in close contact with numerous boutons staining for nNOS, VIP, NPY, tyrosine hydroxylase (TH), vesicular monoaminergic transporter (VMAT)2, vesicular acetylcholine transporter (VACHT), calretinin, and NPY. These data indicate a more complex integrative function of CGCs e.g. volume regulation in parallel with ciliary muscle contraction during accommodation. Ultrastructural and immunohistochemical studies indicate, that CGCs in addition may have mechanosensory properties. Whether they are involved in volume-regulatory functions independent of accommodation is not yet known. In glaucoma disease the number of CGCs is significantly reduced. This holds true for eyes with primary open angle glaucoma, pseudoexfoliation glaucoma and experimentally induced monkey glaucoma indicating that elevated IOP is involved in the pathogenesis of glaucomatous CGC-degeneration.     

Differential distribution of neuronal markers and neuropeptides in the human lacrimal gland

Background: The present study was untertaken in an attempt to broaden the spectrum of known neuronal markers and neuropeptides in the main lacrimal gland of the human by light-microscopic immunohistochemistry. Methods: Using antisera against the neuronal markers protein gene product (PGP) and S-100 protein (S-100), the distribution of nerve fibers in the human main lacrimal gland was studied. Vasoactive intestinal polypeptide (VIP), calcitonin gene-related peptide (CGRP), neuropeptide Y (NPY) and tyrosine hydroxylase (TH) were identified by their specific antisera. Results: The nerve fibers are distributed throughout the interstice between the glandular tubules. Associations were also found between nerve fibers and both the interlobular ductal system and blood vessels (mainly arterioles). Within the glandular lobules isolated groups of secretory cells stained positive for S-100 protein. Nerve fibers situated in the glandular interstice between the tubules showed predominantly positive immunoreactions for the neuropeptide VIP, while only very few fibers stained positive for CGRP, NPY and the catecholamine marker TH. Nerve fibers associated with interlobular blood vessels were mainly CGRP and NPY positive and stained only very rarely for VIP. The epithelia of interlobular ducts and excretory ducts were associated with CGRP-immunoreactive nerve fibers. Conclusion: The neuropeptides identified in the lacrimal gland indicate the complexity with which a variety of biologic signals regulate and modulate the lacrimal gland.Presented in part at the Joint European Research Meetings in Ophthalmology and Vision (JERMOV), 15–19 October 1994, Montpellier, France     

Immunocytochemical and ultrastructural evaluation of the distribution of nervous tissue and neuropeptides in the meibomian gland

Background: The ultrastructure of the meibomian gland, of its innervation and the localization of neuropeptides in the glandular tissue of the guinea pig and humans are incompletely known. Therefore they have been investigated in the present study. Methods: The ultrastructure of the tissue was examined using standard transmission electron microscopic techniques. Additional scanning electron microscopy was carried out on rabbit tissue. Antisera against the neuronal marker protein gene product were used to demonstrate the distribution pattern of the nerve fibers. The neuropeptides substance P (SP) and neuropeptide Y (NPY), vasoactive intestinal polypeptide (VIP) and calcitonin gene-related peptide (CGRP) and the neuronal enzyme tyrosine hydroxylase (TH) were identified by their specific antisera. Results: The glands were found to be composed of arrays of alveoli. The outer cells of the alveoli form a germinal layer. Toward the inside of the alveolus the cells are laden with a secretory substance. The cells disintegrate as they approach the excretory duct. Nerve fibers from a plexus around the alveoli. These nerve fibers form synapses à distance to the basal alveolar cells and enter the basal lamina of the capillaries. In guinea pigs many nerve fibers were positive for the neuropeptides SP and NPY and for VIP, and fewer for CGRP and TH; in humans only SP and CGRP were demonstrated. Conclusion: Both the density of nerve fibers and the presence of various neuropeptides suggest that the stimulation of the meibomian gland is subject to nervous control.Presented at the Joint European Research Meetings in Ophthalmology and Vision (JERMOV), October 1995, Montpellier, France     

Indocyanine green anterior segment angiography for studying conjunctival vascular changes after trabeculectomy

Background : The aim of the study was to evaluate the use of indocyanine green (ICG) for angiography of the anterior segment to characterize conjunctival and episcleral vasculature changes after trabeculectomy. Methods : This was a prospective evaluation of anterior segment ICG angiography in 10 eyes of 10 patients undergoing trabeculectomy for the first time. Trabeculectomy was performed with intraoperative sponge application of 5‐ fluorouracil (5 cases) or mitomycin C (5 cases). Anterior segment ICG angiography was performed prior to surgery, then at 2 weeks and 2 months after surgery. Results : With ICG, the anterior segment vessels were well delineated, including deep episcleral veins, which have not been clearly shown in previous angiographic techniques. Late phases of the angiogram could also be studied. The vascular alterations after trabeculectomy noted included loss of vascularity over the bleb area and vascular anastomoses along the perimeter of the avascular bleb. Conclusions : Angiography using ICG has potential as an investigative tool to study the conjunctival and episcleral vasculature changes after trabeculectomy.     

Morphology and neurochemistry of canine corneal innervation

PURPOSE: To determine the architectural pattern and neuropeptide content of canine corneal innervation. METHODS: Corneal nerve fibers in normal dog eyes were labeled immunohistochemically with antibodies against protein gene product (PGP)-9.5, calcitonin gene-related peptide (CGRP), substance P (SP), vasoactive intestinal polypeptide (VIP), and tyrosine hydroxylase (TH). Relative innervation densities and distribution patterns for each fiber population were assessed qualitatively by serial line-drawing reconstructions and quantitatively by computer-assisted analyses. RESULTS: More than 99% of all corneal PGP-9.5-immunoreactive (IR) nerves contained both CGRP and SP, approximately 30% contained TH, and none contained VIP. Distribution patterns of corneal PGP-9.5-, CGRP-, SP-, and TH-IR nerves were indistinguishable, except that TH-IR fibers were absent from the corneal epithelium. Morphologically, canine corneal innervation consisted of a rich anterior stromal plexus, divided on the basis of morphologic criteria into anterior and posterior levels, and a rich epithelial innervation, characterized by large numbers of horizontally oriented, basal epithelial "leash" formations. Leash axons in all quadrants of the corneal epithelium oriented preferentially toward a common locus in the perilimbal cornea. CONCLUSIONS: The results of this study demonstrate for the first time the detailed architectural features, distinctive basal epithelial leash orientations, and peptidergic content of canine corneal innervation. The normal innervation pattern described in this study will provide other investigators with essential baseline data for assessing corneal nerve alterations in canine patients with spontaneous chronic corneal epithelial defects (SCCED) and other ocular diseases or injuries.     

Anterior collateral circulation in the primate eye

Sequential microdissection and scanning electron microscopy of whole primate ocular lumenal methyl methacrylate corrosion castings were performed to determine the anatomic basis of collateral arterial blood flow to the anterior uvea. Collateral anastomoses were observed at three sites: (1) the episclera where the anterior ciliary arteries interconnect at the limbus to form the episcleral circle; (2) the ciliary muscle where anastomoses between the perforating anterior ciliary and long posterior ciliary arteries comprise the intramuscular circle, the most extensive of the three collateral arterial rings, and (3) the root of the iris where circumferentially oriented vessels derived from the intramuscular circle form the "major arterial circle". Of these, the "major arterial circle" is the most discontinuous. This multilevel collateral system probably accounts for the rarity of anterior segment ischemia following all but the most extensive extraocular muscle surgeries.     

Neuroanatomy and neurochemistry of rat cornea: Changes with age

PurposeTo characterize the entire rat corneal nerve architecture, the changes that occur with aging, and its sensory, sympathetic, and parasympathetic fiber distribution.MethodsSprague-Dawley rats (aged 1 day to 2 years old) of both sexes were euthanized, and the whole corneas were immunostained with protein gene product 9.5 (PGP9.5). The specimens were double-labeled with antibodies against calcitonin gene-related peptide (CGRP) and substance P (SP) as sensory nerve markers, vasoactive intestinal peptide (VIP) as a parasympathetic nerve marker, and neuropeptide Y (NPY) and tyrosine hydroxylase (TH) as markers of sympathetic fibers. Relative nerve density positive for each antibody was assessed by computer-assisted image analysis.ResultsThick nerve trunks enter the cornea in the middle of the stroma and run towards the anterior stroma, subsequently dividing into smaller branches that penetrate upwards into the epithelium to form the subbasal nerve bundles. There was no significant difference in corneal innervation between sexes. CGRP and SP were the major sensory neuropeptides with 47.6% ± 3.5% and 34.9% ± 5.1%, respectively, of the total nerves. VIP was 18.4% ± 5.7%, and NPY and TH positive fibers took up 6.92% ± 2.66% and 2.92% ± 1.52%, respectively. Epithelial nerve density increased with age, reached full development at 5 weeks, and decreased at 120 weeks.ConclusionThis study provides a complete nerve architecture and content of components of sensory, parasympathetic, and sympathetic nerves in the rat cornea. The normal innervation pattern described here will provide an essential baseline for investigators who use the rat model for assessing corneal pathologies that involve nerve alterations.     

Action of biologically active peptides on monkey iris sphincter and dilator muscles

Biologically active peptides modulate pupillary responsiveness in many non-primate mammals. We examined the action of seven different peptides on iris sphincter and dilator muscles of rhesus monkey. Iris sphincter and dilator muscle preparations from rhesus monkeys were mounted in an organ bath, and tension changes were recorded by an isometric transducer. Electrical field stimulation (100Hz, 0.3 msec, 10V) was applied through a pair of platinum plate electrodes. Monkey iris sphincter and dilator muscles produced simple cholinergic and adrenergic excitatory responses respectively to electrical field stimulation. Strong field stimulation did not elicit slow Substance P (SP) mediated contractions like those in rabbit iris sphincter. Exogenously applied pituitary adenylate cyclase-activating peptide (PACAP) enhanced in a concentration-dependent manner (0.3 nM-0.1 microm) the sphincter response to field stimulation, while neuropeptide Y (NPY) and somatostatin (SRIF) attenuated it. These three peptides did not affect sphincter contractions induced by acetylcholine, and therefore were acting at presynaptically. SP, calcitonin gene-related peptide (CGRP), vasoactive intestinal polypeptide (VIP) and galanin (GAL) had no effect (at 0.1 microm) on iris sphincter. None of seven exogenously applied peptides had an effect on monkey iris dilator muscle. The innervation of primate irises may be relatively simple compared to non-primates because each of the peptides in this study can modulate miosis or mydriasis in non-primate mammals. Future studies will be expected on the functional significance of species differences in iridial innervation.     

Intrinsic neurons in the duck choroid are contacted by CGRP-immunoreactive nerve fibres: evidence for a local pre-central reflex arc in the eye

Intrinsic choroidal neurons represent peripherally displaced autonomic nerve cells supposed to work as a local integrative network similar to the enteric nervous system, to control choroidal vasculature and stromal smooth muscle. A typical feature of such intramural neuronal networks is the innervation by primary afferent collaterals expressing peptides, e.g. CGRP. The present study was aimed at determining primary afferent contacts on nitrergic intrinsic choroidal neurons (ICN) in the duck eye. In addition, a sympathetic innervation of ICN was assessed. Choroids were immunohistochemically processed for the following markers: neuronal nitric oxide synthase (nNOS), galanin (GAL), calcitonin gene-related peptide (CGRP), and tyrosine hydroxylase (TH). For evaluation, fluorescence as well as confocal laser scanning microscopy were used. For electron microscopy, immunoperoxidase staining for CGRP in combination with NADPH-diaphorase histochemistry was applied. ICN immunoreactive for nNOS or GAL spread over the entire choroid, although they were concentrated in an equatorial zone passing obliquely from naso-cranial to temporo-caudal. About 40% of ICN showed close relationships with CGRP-immunoreactive nerve fibres, originating most likely in the trigeminal ganglion, as seen in the fluorescence and confocal laserscanning microscope. These appositions could be ultrastructurally defined as both synapses and close contacts without synaptic specialization. Some ICN endowed with CGRP-positive fibres also received TH-immunoreactive boutons. CGRP-immunoreactive profiles were also detected in close relationship to choroidal non-vascular smooth muscle cells and collagen fibres connected to them. In many instances, they were intercalated between smooth muscle cells and processes of ICN forming triads. These results suggest that ICN, similar to other intramural autonomic systems integrate signals from trigeminal primary afferent collaterals. The 'sensory' terminals of these primary afferents may be located in the anterior eye segment but also within the smooth muscle stroma of the choroid itself. Thus, ocular homeostasis may be regulated via intraocular pre-central reflexes which are probably subject to sympathetic modulation.     

Neuronal nitric oxide synthase and the autonomic innervation of the mouse lacrimal gland.

PURPOSE: To determine the expression patterns of the vesicular acetylcholine transporter (VAChT), tyrosine hydroxylase (TH) and neuronal nitric oxide synthase (nNOS) in the pterygopalatine ganglion (PPG) and the exorbital lacrimal gland of normal mice. METHODS: Mouse PPG and lacrimal glands were processed for single- and double-labeled indirect immunofluorescence studies. Slides were examined with conventional fluorescence microscopy and confocal laser scanning microscopy. RESULTS: All the somata in the PPG expressed both VAChT and nNOS immunoreactivity (IR). The postganglionic axons within the ganglion showed less VAChT-immunoreactive intensity than that seen in the somata, whereas nNOS IR was almost undetectable. In the lacrimal gland, nNOS-positive nerve bundles and fibers were observed to be associated with tear-collecting ducts, blood vessels, and acini. Some nNOS-positive punctate elements appeared to be distributed among acini. Many nerve fibers were VAChT immunoreactive and a small number of fibers were TH immunoreactive in the gland. Most of the VAChT-positive fibers and some of the TH-positive nerves displayed nNOS IR. CONCLUSIONS: The expression of nNOS in cells of the PPG and in lacrimal gland nerves suggests that NO may play a role in modulating tear production. The site of action may include the PPG, ducts, blood vessels, acini, nerve fibers, and myoepithelial cells within the gland. NO may modulate parasympathetic and/or sympathetic synaptic transmission or by acting directly on lacrimal gland components. The interaction between NO-ergic and the conventional autonomic input illustrates the complexity of the innervation pattern of the mouse lacrimal gland.     

Corrosion casts and scanning electron microscopy of choroidal vasculature in rats with inherited hypercholesterolemia

PURPOSE: The purpose of the present study is to determine the specific morphological changes in choroidal vasculature due to hypercholesterolemia. METHODS: The choroidal vessels of rats with inherited hypercholesterolemia (RICO) were examined by the corrosion cast technique and electron microscopy. RESULTS: In 18-month-old RICO rats, corrosion casts and scanning electron microscopy showed severe tortuosity, caliber irregularity and generalized dilatation of the large choroidal arteries and veins. The branch arterioles and draining venules were also tortuous and dilated. The ampullae of the vortex veins were wide, but no arteriovenous anastomoses, crossing defects or obstruction were seen. However, there were many venular collateral channels and venulo-venular anastomoses. The choriocapillaries appeared normal. Transmission electron microscopy of the choroidal vessels showed hypertrophy of smooth muscle cells and irregular thickening of the basement membrane. The RPE and Bruch's membrane were intact. CONCLUSION: These findings indicate that the choroidal vascular changes are probably related to hypercholesterolemia. The results of the present study will be useful in the interpretation of the changes seen in hypertensive, diabetic and aged choroids.     

Increased Intraocular Pressure after Extensive Conjunctival Removal: A Case Report

A 50-year-old woman, who had undergone extensive removal of conjunctiva on the right eye for cosmetic purposes at a local clinic 8 months prior to presentation, was referred for uncontrolled intraocular pressure (IOP) elevation (up to 38 mmHg) despite maximal medical treatment. The superior and inferior conjunctival and episcleral vessels were severely engorged and the nasal and temporal bulbar conjunctival areas were covered with an avascular epithelium. Gonioscopic examination revealed an open angle with Schlemm''s canal filled with blood to 360 degrees in the right eye. Brain and orbital magnetic resonance imaging and angiography results were normal. With the maximum tolerable anti-glaucoma medications, the IOP gradually decreased to 25 mmHg over 4 months of treatment. Extensive removal of conjunctiva and Tenon''s capsule, leaving bare sclera, may lead to an elevation of the episcleral venous pressure because intrascleral and episcleral veins may no longer drain properly due to a lack of connection to Tenon''s capsule and the conjunctival vasculature. This rare case suggests one possible mechanism of secondary glaucoma following ocular surgery.     

Spontaneous remodeling of the peripheral retinal vasculature in sickling disorders.

Periodic photographic and angiographic surveys of patients with the earliest stages of sickle retinopathy showed a number of fundus findings. In seven cases (sickle cell anemia, four; sickle cell hemoglobin C, three), these findings included: (1) a variety of vascular abnormalities in the equatorial and post-equatorial retina such as segmented dilations of the vessel walls, hairpin-shaped vascular loops, hypertrophic, tortuous A-V anastomoses, intraluminal plugs, closure and loss of capillary bed, and terminal budding of capillaries; and (2) a continuous, spontaneous remodeling of the peripheral retinal vasculature due to successive closures and reopenings of equatorial retinal vessels. A centripetal recession of the peripheral retinal vasculature usually resulted. No correlation between the ophthalmoscopic and the systemic condition of the patients could be made.     

A light and electron microscopic study of the healing of pars plana incisions in the rhesus monkey

Pars plana incisions were made in 11 rhesus monkey eyes. Six animals had injections of 0.1 ml of blood into the vitreous cavity with a 25-gauge needle and five animals had vitrectomy through a 4-mm incision with a multifunction vitrectomy probe. Six to 13 years later the scars in the pars plana were found to consist of fibrous tissue and blood vessels which extended from the episclera into the vitreous. The intravitreous scar was shaped by the incarceration of vitreous strands in the internal aspect of the wounds. There were quantitative, but no qualitative differences between the two types of incision. The ultrastructural features were those of mature scar tissue: fibroblasts, adult collagen, uveal melanocytes, macrophages, myelinated and non-myelinated nerves, and capillaries with non-fenestrated endothelium. There were associated proliferative ciliary epithelial changes, but no evidence of ciliary epithelial metaplasia.     

The autonomic facial nerve pathway in birds: a tracing study in chickens

PURPOSE: In birds, the parasympathetic innervation of the choroid is via the ciliary (cranial nerve III) and pterygopalatine (cranial nerve VII) ganglia, the latter consisting of a chain of microganglia within the orbit. Because of the scattered nature of these microganglia, lesions of this nerve pathway in birds have not been attempted, making interpretation of the functional contribution of this parasympathetic input to the avian eye uncertain. The purpose of this study was to find an extraorbital approach to the preganglionic part of cranial nerve VII and to reveal its peripheral terminals and its site of origin in the brain stem. METHODS: The radix autonomica cranial nerve VII was accessed via the tympanic cavity and injected with dextran coupled to Texas red (DTxR). Orbital structures and the brain stem were prepared for tracer detection and immunohistochemistry for neuronal nitric oxide synthase (nNOS), choline acetyl transferase (ChAT), vasoactive intestinal polypeptide (VIP), calcitonin gene-related peptide (CGRP), galanin (GAL), and somatostatin (SOM). For documentation, fluorescence and confocal laser scanning microscopy were used. RESULTS: Anterogradely labeled DTxR-positive nerve fibers were detected within the orbital pterygopalatine microganglionic chain, forming boutons closely associated with nNOS-positive neurons. Retrogradely labeled DTxR-positive neurons with cell diameters of approximately 20 microm were found in the brain stem. These were positive for ChAT, but negative for nNOS, VIP, SOM, GAL, and CGRP. They most likely represent the preganglionic neurons of the superior salivatory nucleus. In close proximity, there were larger (40 microm) unlabeled neurons that were positive for ChAT and CGRP, but negative for GAL. These most likely represent motoneurons of the facial nerve. CONCLUSIONS: This surgical approach offers excellent opportunities for lesioning experiments for the study of the autonomic facial nerve pathway in birds in terms of both its anatomic organization and its function.     

Low dose fluorescein angiography of the conjunctiva and episclera.

By reducing the dose of injected fluorescein its leakage from conjunctival and episcleral capillaries has been minimised. These vessels have been demonstrated with great clarity, and the venous circulation, previously obscured by extravascular fluorescein, has also been revealed. The anatomy of the anterior segment vessels, and the blood flow within them, has been studied in eight normal subjects. The anterior ciliary arteries feed an anterior episcleral arterial circle that has superficial and deep components. This supplies the anterior conjunctival and episcleral circulations, the limbal arcades, and the iris arterioles. Where the superficial arterial circle is deficient, isolated vessels emerge from the deep segments of the circle to supply the episcleral plexus and conjunctival arterioles. Watershed zones between the anterior and posterior territories of the conjunctival and episcleral circulations overlap. They may fluoresce up to 30 seconds after the anterior ciliary arteries. The scope of this technique and the implications of these findings are discussed.