Conditional Loss of the Exocyst Component Exoc5 in Retinal Pigment Epithelium (RPE) Results in RPE Dysfunction, Photoreceptor Cell Degeneration, and Decreased Visual Function

To characterize the mechanisms by which the highly conserved exocyst trafficking complex regulates eye physiology in zebrafish and mice, we focused on Exoc5 (also known as sec10), a central exocyst component. We analyzed both exoc5 zebrafish mutants and retinal pigmented epithelium (RPE)-specific Exoc5 knockout mice. Exoc5 is present in both the non-pigmented epithelium of the ciliary body and in the RPE. In this study, we set out to establish an animal model to study the mechanisms underlying the ocular phenotype and to establish if loss of visual function is induced by postnatal RPE Exoc5-deficiency. Exoc5-/- zebrafish had smaller eyes, with decreased number of melanocytes in the RPE and shorter photoreceptor outer segments. At 3.5 days post-fertilization, loss of rod and cone opsins were observed in zebrafish exoc5 mutants. Mice with postnatal RPE-specific loss of Exoc5 showed retinal thinning associated with compromised visual function and loss of visual photoreceptor pigments. Abnormal levels of RPE65 together with a reduced c-wave amplitude indicate a dysfunctional RPE. The retinal phenotype in Exoc5-/- mice was present at 20 weeks, but was more pronounced at 27 weeks, indicating progressive disease phenotype. We previously showed that the exocyst is necessary for photoreceptor ciliogenesis and retinal development. Here, we report that exoc5 mutant zebrafish and mice with RPE-specific genetic ablation of Exoc5 develop abnormal RPE pigmentation, resulting in retinal cell dystrophy and loss of visual pigments associated with compromised vision. Together, these data suggest that exocyst-mediated signaling in the RPE is required for RPE structure and function, indirectly leading to photoreceptor degeneration.

Neuro-ophthalmologic complications of coronavirus disease 2019 (COVID-19)

Multiple neuro-ophthalmological manifestations have been described in association with COVID-19. These symptoms and signs may be the result of a range of pathophysiological mechanisms throughout the course from acute illness to recovery phase. Optic nerve dysfunction, eye movement abnormalities and visual field defects have been described.

Clinical, Hormonal, and Neuroradiological Characteristics and Therapeutic Outcomes of Prolactinomas in Children and Adolescents at a Single Center

Background/Purpose: A prolactinoma is the most common pituitary adenoma, but it is relatively rare in childhood and adolescence. There is only limited research about the clinical spectrum, treatment, and outcomes of prolactinomas in childhood and adolescence. In this single-center cohort study, we assessed the clinical, hormonal, and neuroradiological characteristics and therapeutic outcomes of children and adolescents with prolactinomas. Methods: This retrospective cohort study included 25 patients with prolactinomas diagnosed before 19 years of age, who presented at Samsung Medical Center during a 15-year period (March 2005 to August 2019). Results: The median age at diagnosis was 16.9 (range 10.1-18.5) years, and 80% of the patients were female. The common clinical manifestations at diagnosis were galactorrhea (10/20, 50%) and amenorrhea (9/20, 45%) among females and visual field defects (3/5, 60%) and headaches (2/5, 40%) among males. In our cohort, macroadenomas accounted for 56% of cases, and the rate of overall responsiveness to dopamine agonists (DAs) was 56% (10/18). Male gender, the prolactin (PRL) level at diagnosis, and the presence of panhypopituitarism were positively correlated with maximum tumor diameter (r = 0.443, P = 0.026; r = 0.710, P < 0.001; and r = 0.623, P = 0.001, respectively). After the trans-sphenoidal approach (TSA), 53% (8/15) of patients showed normalization of the PRL level. Three patients, who underwent gamma knife surgery (GKS) owing to either resistance or intolerance to DAs or recurrence after the TSA, achieved a normal PRL level accompanied with marked tumor reduction and symptom remission. Conclusions: A macroprolactinoma is more prevalent than a microprolactinoma in children and adolescents than in adults. Male gender, increased PRL levels, and the presence of panhypopituitarism at diagnosis are closely related to macroprolactinomas in children and adolescents.

Short-Wavelength Sensitive Cone (S-cone) Testing as an Outcome Measure for NR2E3 Clinical Treatment Trials

Recessively-inherited NR2E3 gene mutations cause an unusual retinopathy with abnormally-increased short-wavelength sensitive cone (S-cone) function, in addition to reduced rod and long/middle-wavelength sensitive cone (L/M-cone) function. Progress toward clinical trials to treat patients with this otherwise incurable retinal degeneration prompted the need to determine efficacy outcome measures. Comparisons were made between three computerized perimeters available in the clinic. These perimeters could deliver short-wavelength stimuli on longer-wavelength adapting backgrounds to measure whether S-cone vision can be quantified. Results from a cohort of normal subjects were compared across the three perimeters to determine S-cone isolation and test-retest variability. S-cone perimetry data from NR2E3-ESCS (enhanced S-cone syndrome) patients were examined and determined to have five stages of disease severity. Using these stages, strategies were proposed for monitoring efficacy of either a focal or retina-wide intervention. This work sets the stage for clinical trials.

An augmentation in histone dimethylation at lysine nine residues elicits vision impairment following traumatic brain injury

Traumatic Brain Injury (TBI) affects more than 1.7 million Americans each year and about 30% of TBI-patients having visual impairments. The loss of retinal ganglion cells (RGC) in the retina and axonal degeneration in the optic nerve have been attributed to vision impairment following TBI; however, the molecular mechanism has not been elucidated. Here we have shown that an increase in histone di-methylation at lysine 9 residue (H3K9Me2), synthesized by the catalytic activity of a histone methyltransferase, G9a is responsible for RGC loss and axonal degeneration in the optic nerve following TBI. To elucidate the molecular mechanism, we found that an increase in H3K9Me2 results in the induction of oxidative stress both in the RGC and optic nerve by decreasing the mRNA level of antioxidants such as Superoxide dismutase (sod) and catalase through impairing the transcriptional activity of Nuclear factor E2-related factor 2 (Nrf2) via direct interaction. The induction of oxidative stress is associated with death in RGC and oligodendrocyte precursor cells (OPCs). The death in OPCs is correlated with a reduction in myelination, and the expression of myelin binding protein (MBP) in association with degeneration of neurofilaments in the optic nerve. This event allied to an impairment of the retrograde transport of axons and loss of nerve fiber layer in the optic nerve following TBI. An administration of G9a inhibitor, UNC0638 attenuates the induction of H3K9Me2 both in RGC and optic nerve and subsequently activates Nrf2 to reduce oxidative stress. This event was concomitant with the rescue in the loss of retinal thickness, attenuation in optic nerve degeneration and improvement in the retrograde transport of axons following TBI.

Blood-retina barrier failure and vision loss in neuron-specific degeneration

Changes in neuronal activity alter blood flow to match energy demand with the supply of oxygen and nutrients. This functional hyperemia is maintained by interactions between neurons, vascular cells, and glia. However, how changing neuronal activity prevalent at the onset of neurodegenerative disease affects neurovascular elements is unclear. Here, in mice with photoreceptor degeneration, a model of neuron-specific dysfunction, we combined assessment of visual function, neurovascular unit structure, and the blood-retina barrier permeability. We found that the rod loss paralleled remodeling of the neurovascular unit, comprised of photoreceptors, retinal pigment epithelium, and Muller glia. When significant visual function was still present, blood flow became disrupted and blood-retina barrier began to fail, facilitating cone loss and vision decline. Thus, in contrast to the established view, vascular deficit in neuronal degeneration is not a late consequence of neuronal dysfunction, but is present early in the course of disease. These findings further establish the importance of vascular deficit and blood retina barrier function in neuron-specific loss, and highlight it as a target for early therapeutic intervention.

Visual Features in Alzheimer's Disease: From Basic Mechanisms to Clinical Overview

Alzheimer's disease (AD) is the leading cause of dementia worldwide. It compromises patients' daily activities owing to progressive cognitive deterioration, which has elevated direct and indirect costs. Although AD has several risk factors, aging is considered the most important. Unfortunately, clinical diagnosis is usually performed at an advanced disease stage when dementia is established, making implementation of successful therapeutic interventions difficult. Current biomarkers tend to be expensive, insufficient, or invasive, raising the need for novel, improved tools aimed at early disease detection. AD is characterized by brain atrophy due to neuronal and synaptic loss, extracellular amyloid plaques composed of amyloid-beta peptide (Aβ), and neurofibrillary tangles of hyperphosphorylated tau protein. The visual system and central nervous system share many functional components. Thus, it is plausible that damage induced by Aβ, tau, and neuroinflammation may be observed in visual components such as the retina, even at an early disease stage. This underscores the importance of implementing ophthalmological examinations, less invasive and expensive than other biomarkers, as useful measures to assess disease progression and severity in individuals with or at risk of AD. Here, we review functional and morphological changes of the retina and visual pathway in AD from pathophysiological and clinical perspectives.

Reduction of the ATPase inhibitory factor 1 (IF1) leads to visual impairment in vertebrates

In vertebrates, mitochondria are tightly preserved energy producing organelles, which sustain nervous system development and function. The understanding of proteins that regulate their homoeostasis in complex animals is therefore critical and doing so via means of systemic analysis pivotal to inform pathophysiological conditions associated with mitochondrial deficiency. With the goal to decipher the role of the ATPase inhibitory factor 1 (IF1) in brain development, we employed the zebrafish as elected model reporting that the Atpif1a-/- zebrafish mutant, pinotage (pnt tq209 ), which lacks one of the two IF1 paralogous, exhibits visual impairment alongside increased apoptotic bodies and neuroinflammation in both brain and retina. This associates with increased processing of the dynamin-like GTPase optic atrophy 1 (OPA1), whose ablation is a direct cause of inherited optic atrophy. Defects in vision associated with the processing of OPA1 are specular in Atpif1-/- mice thus confirming a regulatory axis, which interlinks IF1 and OPA1 in the definition of mitochondrial fitness and specialised brain functions. This study unveils a functional relay between IF1 and OPA1 in central nervous system besides representing an example of how the zebrafish model could be harnessed to infer the activity of mitochondrial proteins during development.

Diabetic brain or retina? Visual psychophysical performance in diabetic patients in relation to GABA levels in occipital cortex

Visual impairment is one of the most feared complications of Type 2 Diabetes Mellitus. Here, we aimed to investigate the role of occipital cortex γ-aminobutyric acid (GABA) as a predictor of visual performance in type 2 diabetes. 18 type 2 diabetes patients were included in a longitudinal prospective one-year study, as well as 22 healthy age-matched controls. We collected demographic data, HbA1C and used a novel set of visual psychophysical tests addressing color, achromatic luminance and speed discrimination in both groups. Psychophysical tests underwent dimension reduction with principle component analysis into three synthetic variables: speed, achromatic luminance and color discrimination. A MEGA-PRESS magnetic resonance brain spectroscopy sequence was used to measure occipital GABA levels in the type 2 diabetes group. Retinopathy grading and retinal microaneurysms counting were performed in the type 2 diabetes group for single-armed correlations. Speed discrimination thresholds were significantly higher in the type 2 diabetes group in both visits; mean difference (95% confidence interval), [0.86 (0.32-1.40) in the first visit, 0.74 (0.04-1.44) in the second visit]. GABA from the occipital cortex predicted speed and achromatic luminance discrimination thresholds within the same visit (r = 0.54 and 0.52; p = 0.02 and 0.03, respectively) in type 2 diabetes group. GABA from the occipital cortex also predicted speed discrimination thresholds one year later (r = 0.52; p = 0.03) in the type 2 diabetes group. Our results suggest that speed discrimination is impaired in type 2 diabetes and that occipital cortical GABA is a novel predictor of visual psychophysical performance independently from retinopathy grade, metabolic control or disease duration in the early stages of the disease.

Eyeing the Fountain of Youth

Stem cell-based disease modeling is an emerging technology for the mechanistic study and therapeutic screening of complex ocular pathologies. In this issue of Cell Stem Cell, Saini et al. (2017) show that iPSC-derived RPE cells from age-related macular degeneration patients express increased levels of pro-inflammatory factors that can be normalized by the anti-aging drug nicotinamide.

The Pharmacological Effects of Lutein and Zeaxanthin on Visual Disorders and Cognition Diseases

Lutein (L) and zeaxanthin (Z) are dietary carotenoids derived from dark green leafy vegetables, orange and yellow fruits that form the macular pigment of the human eyes. It was hypothesized that they protect against visual disorders and cognition diseases, such as age-related macular degeneration (AMD), age-related cataract (ARC), cognition diseases, ischemic/hypoxia induced retinopathy, light damage of the retina, retinitis pigmentosa, retinal detachment, uveitis and diabetic retinopathy. The mechanism by which they are involved in the prevention of eye diseases may be due their physical blue light filtration properties and local antioxidant activity. In addition to their protective roles against light-induced oxidative damage, there are increasing evidences that L and Z may also improve normal ocular function by enhancing contrast sensitivity and by reducing glare disability. Surveys about L and Z supplementation have indicated that moderate intakes of L and Z are associated with decreased AMD risk and less visual impairment. Furthermore, this review discusses the appropriate consumption quantities, the consumption safety of L, side effects and future research directions.

Multimodal Delivery of Isogenic Mesenchymal Stem Cells Yields Synergistic Protection from Retinal Degeneration and Vision Loss

We previously demonstrated that subretinal injection (SRI) of isogenic mesenchymal stem cells (MSCs) reduced the severity of retinal degeneration in Royal College of Surgeons rats in a focal manner. In contrast, intravenous MSC infusion (MSC^IV ) produced panoptic retinal rescue. By combining these treatments, we now show that MSC^IV supplementation potentiates the MSC^SRI -mediated rescue of photoreceptors and visual function. Electrophysiological recording from superior colliculi revealed 3.9-fold lower luminance threshold responses (LTRs) and 22% larger functional rescue area from combined treatment compared with MSC^SRI alone. MSC^IV supplementation of sham (saline) injection also improved LTRs 3.4-fold and enlarged rescue areas by 27% compared with saline alone. We confirmed the involvement of MSC chemotaxis for vision rescue by modulating C-X-C chemokine receptor 4 activity before MSC^IV but without increased retinal homing. Rather, circulating platelets and lymphocytes were reduced 3 and 7 days after MSC^IV , respectively. We demonstrated MSC^SRI -mediated paracrine support of vision rescue by SRI of concentrated MSC-conditioned medium and assessed function by electroretinography and optokinetic response. MSC-secreted peptides increased retinal pigment epithelium (RPE) metabolic activity and clearance of photoreceptor outer segments ex vivo, which was partially abrogated by antibody blockade of trophic factors in concentrated MSC-conditioned medium, or their cognate receptors on RPE. These data support multimodal mechanisms for MSC-mediated retinal protection that differ by administration route and synergize when combined. Thus, using MSC^IV as adjuvant therapy might improve cell therapies for retinal dystrophy and warrants further translational evaluation. Stem Cells Translational Medicine 2017;6:444-457.

Melanopsin retinal ganglion cell loss and circadian dysfunction in Alzheimer's disease (Review)

Alzheimer's disease affects 27 million individuals and is the most common cause of dementia worldwide. The pathology of Alzheimer's disease is primarily due to the β‑amyloid deposits and neurofibrillary tangles. These deposits exist largely in the cerebral blood vessels, but have also been shown to exist in retinal vessels. A new class of cells that were recently identified, known as melanopsin‑expressing retinal ganglion cells (mRGCs), are involved in the non‑image forming functions of the eye. These functions include circadian activities such as temperature rhythms, melatonin release and rest‑activity cycles. Circadian dysfunction has been investigated in many cases of Alzheimer's disease. In this review, we outline the current accepted Alzheimer's disease pathology, the role of mRCGs in optic neuropathies and the role of mRCGs, leading to circadian dysfunction, in Alzheimer's disease.

Collagens and proteoglycans of the cornea: importance in transparency and visual disorders

The cornea represents the external part of the eye and consists of an epithelium, a stroma and an endothelium. Due to its curvature and transparency this structure makes up approximately 70% of the total refractive power of the eye. This function is partly made possible by the particular organization of the collagen extracellular matrix contained in the corneal stroma that allows a constant refractive power. The maintenance of such an organization involves other molecules such as type V collagen, FACITs (fibril-associated collagens with interrupted triple helices) and SLRPs (small leucine-rich proteoglycans). These components play crucial roles in the preservation of the correct organization and function of the cornea since their absence or modification leads to abnormalities such as corneal opacities. Thus, the aim of this review is to describe the different corneal collagens and proteoglycans by highlighting their importance in corneal transparency as well as their implication in corneal visual disorders.

Vision deficits precede structural losses in a mouse model of mitochondrial dysfunction and progressive retinal degeneration

Current animal models of retinal disease often involve the rapid development of a retinal disease phenotype; however, this is at odds with age-related diseases that take many years to manifest clinical symptoms. The present study was performed to examine an apoptosis-inducing factor (Aif)-deficient model, the harlequin carrier mouse (X(hq)X), and determine how mitochondrial dysfunction and subsequent accelerated aging affect the function and structure of the mouse retina. Vision and eye structure for cohorts of 6 X(hq)X and 6 wild type mice at 3, 11, and 15 months of age were studied using in vivo electroretinography (ERG), and optical coherence tomography (OCT). Retinal superoxide levels were determined in situ using dihydroethidium (DHE) histochemistry. Retinal cell counts were quantified post mortem using hematoxylin and eosin (H&E) staining. ERG analysis of X(hq)X retinal function indicated a reduction in b-wave amplitude significant at 3 months of age (p < 0.05), declining further with age. However, retinal neuron counts demonstrated the absence of physical degeneration at 3 and 11 months of age despite significant reduction in ERG b-wave amplitude. Superoxide anion levels were elevated in the ganglion cell, inner nuclear and outer nuclear layers of the retina (p < 0.01, p < 0.01, and p < 0.001, respectively) of 11-month-old X(hq)X mice in comparison to wild type, preceding the structural losses observed at 15 mos. Early onset of retinal function deficits occurred independently of neuron loss. Changes in neurotransmitter localization in the stressed retina may account for the early and significant reduction in retinal function. This remodeling of retinal neurochemistry in response to stress may be a relevant mechanism in the progression of normal retinal aging and early stages of some retinal degenerative diseases.

Neuroaxonal dystrophy in Australian Merino lambs

Neuroaxonal dystrophy (NAD) is a morphological abnormality in man and animals that is characterized by the occurrence of numerous axonal swellings (spheroids) in the nervous system. NAD has been described in Suffolk lambs in the USA, Merino lambs in Australia and several breeds of sheep in New Zealand. This paper describes the clinicopathological changes of only the second occurrence of NAD reported in Merino lambs. There were some features (myelin loss, gliosis and visual impairment) in these Australian cases that have not been reported previously in ovine NAD. Application of immunohistochemical markers of axonal transport suggested that disruption of this transport mechanism contributed to spheroid development.

Mild systemic hypoxia and photopic visual field sensitivity

PURPOSE

Flickering stimuli increase the metabolic demand of the retina, making it a sensitive perimetric stimulus to the early onset of retinal disease. We determine whether flickering stimuli are a sensitive indicator of vision deficits resulting from acute, mild systemic hypoxia when compared to standard static perimetry.

METHODS

Static and flicker visual perimetry were performed in 14 healthy young participants while breathing 12% oxygen (hypoxia) under photopic illumination. The hypoxia visual field data were compared with the field data measured during normoxia. Absolute sensitivities (in dB) were analysed in seven concentric rings at 1°, 3°, 6°, 10°, 15°, 22° and 30° eccentricities as well as mean defect (MD) and pattern defect (PD) were calculated. Preliminary data are reported for mesopic light levels.

RESULTS

Under photopic illumination, flicker and static visual field sensitivities at all eccentricities were not significantly different between hypoxia and normoxia conditions. The mean defect and pattern defect were not significantly different for either test between the two oxygenation conditions.

CONCLUSION

Although flicker stimulation increases cellular metabolism, flicker photopic visual field impairment is not detected during mild hypoxia. These findings contrast with electrophysiological flicker tests in young participants that show impairment at photopic illumination during the same levels of mild hypoxia. Potential mechanisms contributing to the difference between the visual fields and electrophysiological flicker tests including variability in perimetric data, neuronal adaptation and vascular autoregulation are considered. The data have implications for the use of visual perimetry in the detection of ischaemic/hypoxic retinal disorders under photopic and mesopic light levels.

Lipid pathway alterations in Parkinson's disease primary visual cortex

BACKGROUND

We present a lipidomics analysis of human Parkinson's disease tissues. We have focused on the primary visual cortex, a region that is devoid of pathological changes and Lewy bodies; and two additional regions, the amygdala and anterior cingulate cortex which contain Lewy bodies at different disease stages but do not have as severe degeneration as the substantia nigra.

METHODOLOGY/PRINCIPAL FINDINGS

Using liquid chromatography mass spectrometry lipidomics techniques for an initial screen of 200 lipid species, significant changes in 79 sphingolipid, glycerophospholipid and cholesterol species were detected in the visual cortex of Parkinson's disease patients (n = 10) compared to controls (n = 10) as assessed by two-sided unpaired t-test (p-value <0.05). False discovery rate analysis confirmed that 73 of these 79 lipid species were significantly changed in the visual cortex (q-value <0.05). By contrast, changes in 17 and 12 lipid species were identified in the Parkinson's disease amygdala and anterior cingulate cortex, respectively, compared to controls; none of which remained significant after false discovery rate analysis. Using gas chromatography mass spectrometry techniques, 6 out of 7 oxysterols analysed from both non-enzymatic and enzymatic pathways were also selectively increased in the Parkinson's disease visual cortex. Many of these changes in visual cortex lipids were correlated with relevant changes in the expression of genes involved in lipid metabolism and an oxidative stress response as determined by quantitative polymerase chain reaction techniques.

CONCLUSIONS/SIGNIFICANCE

The data indicate that changes in lipid metabolism occur in the Parkinson's disease visual cortex in the absence of obvious pathology. This suggests that normalization of lipid metabolism and/or oxidative stress status in the visual cortex may represent a novel route for treatment of non-motor symptoms, such as visual hallucinations, that are experienced by a majority of Parkinson's disease patients.

Alzheimer's disease: visual system review

BACKGROUND

Ten million baby boomers in the United States will get Alzheimer's disease. Optometrists can benefit from understanding the impact the Alzheimer's disease process has on the visual system. This can result in more effective management of the condition and in more effective communication with members of the Alzheimer's disease multidisciplinary team.

METHODS

This is a review of the literature but by no means a completely exhaustive review. Alzheimer's disease is a complex disease. A rapidly expanding body of knowledge covers multiple disciplines.

RESULTS

The visual system shows deficits early in the degenerative process of Alzheimer's disease. Biomarkers through the visual system such as nerve fiber deficits, lens opacities, and functional losses in the magnocellular pathway, such as contrast sensitivity and temporal processing, may prove to not only help detect Alzheimer's disease early but also detect it before there are the classic cognitive and memory losses.

CONCLUSIONS

The effects of Alzheimer's disease are devastating. Optometrists, as primary care clinicians, can make critical contributions in the diagnosis, treatment, and management of this neurodegenerative disease.

[The changes of AMPA receptors subunit GluR2 and mEPSCs in visual cortex of monocular deprivation rats]

OBJECTIVE

To observe the change of expression in quantity of AMPA receptor subunit GluR2 and mEPSCs from monocular derivated rats. The preparative work was conducted for the further study on mechanism involved in regulation and control of the visual development plasticity.

METHODS

It was an experimental study. Forty 14 d healthy Wistar rats were divided into two groups randomly; twenty in each group which were divided into two groups (I, II) and derivated monocular in experiment group (group I), and then were killed at a week later. ForIA and IIA 5 microm thick section was cut from tissue of visual cortex in coronary side, then the expression of GluR2 was observed by microscope and image analyze of GluR2 was conducted after immunohistochemical staining; for IB and IIB, mEPSCs was investigated which was used Voltage-clamp technique with whole-cell mode.

RESULT

The level of GluR2 in visual cortex of normal rats was higher than experiment group. The mean amplitude and frequency of mEPSCs increased in the derivated monocular group.

CONCLUSIONS

The level of GluR2 has changed association with the visual stimulation, which suggests that GluR2 should have the important physiological function on the postnatal development of visual system of rats.

Aqueous humor sCD44 concentration and visual field loss in primary open-angle glaucoma

PURPOSE

To correlate aqueous humor soluble CD44 (sCD44) concentration, visual field loss, and glaucoma risk factors in primary open-angle glaucoma (POAG) patients.

METHODS

Aqueous samples were obtained by paracentesis from normal and glaucoma patients who were undergoing elective surgery and analyzed for sCD44 concentration by enzyme-linked immunosorbent assay.

RESULTS

In normal aqueous (n=124) the sCD44 concentration was 5.88+/-0.27 ng/mL, whereas in POAG aqueous (n=90) the sCD44 concentration was 12.76+/-0.66 ng/mL, a 2.2-fold increase (P<0.000001). In POAG patients with prior successful filtration surgery (n=13), the sCD44 concentration was decreased by 43% to 7.32+/-1.44 (P=0.001) in comparison with POAG patients without filtration surgery; however, the sCD44 concentration in the prior successful filtration subgroup with no medications and normal intraocular pressure was 12.62+/-3.81 (P=0.05) compared with normal. The sCD44 concentration of normal pressure glaucoma patients was 9.19+/-1.75 ng/mL, a 1.6-fold increase compared with normal (P=0.02). Race and intraocular pressure pulse amplitude were significant POAG risk factors in this cohort of patients. In both normal and POAG patients with mild and moderate visual field loss, sCD44 concentration was greater in African Americans than in whites (P=0.04).

CONCLUSIONS

sCD44 concentration in the aqueous of POAG patients correlated with the severity of visual field loss in all stages in white patients and in mild to moderate stages in African American patients. sCD44 concentration in aqueous is a possible protein biomarker of visual field loss in POAG.

Visual field defect during therapy with valproic-acid

Visual field defect because of antiepileptic drug (AED) treatment has been widely reported during the clinical application of vigabatrin. But other gamma-aminobutyric acid (GABA)-ergic and non-GABA-ergic AEDs could also affect the visual field with different mechanisms of action. Here we report a case of a 22-year-old female patient, who suffered from bilateral concentric visual field defect during the long-term therapy with valproic-acid (VPA). A VPA-related metabolic dysfunction was found through blood and urine examination. Reduced B-waves were shown by electroretinography and a bilateral concentric visual field defect was confirmed by both manual and automated perimetry. In conclusion, the concentric visual field defect related to VPA treatment is rare but possible.

The blu Blur: mutation of a vesicular glutamate transporter reduces the resolution of zebrafish vision

Vesicular transporters mediate the packaging of neurotransmitters into synaptic vesicles and can therefore control the amount of neurotransmitter released into the synaptic cleft. In this issue of Neuron, Smear et al. demonstrate that mutation of a vesicular glutamate transporter (Vglut) found in the retinal ganglion cells (RGCs) of zebrafish alters both the synaptic transmission and connectivity between RGCs and their targets, limiting the transfer of visually evoked activity from RGCs and degrading behaviors that depend on high-acuity vision.

Vesicular glutamate transport at a central synapse limits the acuity of visual perception in zebrafish

The neural circuitry that constrains visual acuity in the CNS has not been experimentally identified. We show here that zebrafish blumenkohl (blu) mutants are impaired in resolving rapid movements and fine spatial detail. The blu gene encodes a vesicular glutamate transporter expressed by retinal ganglion cells. Mutant retinotectal synapses release less glutamate, per vesicle and per terminal, and fatigue more quickly than wild-type in response to high-frequency stimulation. In addition, mutant axons arborize more extensively, thus increasing the number of synaptic terminals and effectively normalizing the combined input to postsynaptic cells in the tectum. This presumably homeostatic response results in larger receptive fields of tectal cells and a degradation of the retinotopic map. As predicted, mutants have a selective deficit in the capture of small prey objects, a behavior dependent on the tectum. Our studies successfully link the disruption of a synaptic protein to complex changes in neural circuitry and behavior.

Visual impairment and circadian rhythm disorders

Many aspects of human physiology and behavior are dominated by 24-hour circadian rhythms that have a major impact on our health and well-being, including the sleep-wake cycle, alertness and performance patterns, and many daily hormone profiles. These rhythms are spontaneously generated by an internal "pacemaker" in the hypothalamus, and daily light exposure to the eyes is required to keep these circadian rhythms synchronized both internally and with the external environment. Sighted individuals take this daily synchronization process for granted, although they experience some of the consequences of circadian desynchrony when "jetlagged" or working night shifts. Most blind people with no perception of light, however, experience continual circadian desynchrony through a failure of light information to reach the hypothalamic circadian clock, resulting in cyclical episodes of poor sleep and daytime dysfunction. Daily melatonin administration, which provides a replacement synchronizing daily "time cue, " is a promising therapeutic strategy, although optimal treatment dose and timing remain to be determined.

Cortical Gene Expression in the Vitamin E-Deficient Rat: Possible Mechanisms for the Electrophysiological Abnormalities of Visual and Neural Function

In mammals, severe and chronic deficiency of vitamin E (alpha-tocopherol) is associated with a characteristic neurological syndrome. Previously, we have shown that this syndrome is accompanied by electrophysiological abnormalities of neural and visual function. To investigate the molecular basis of the observed abnormalities, we used microarrays to monitor the expression of approximately 14,000 genes in the cerebral cortex from rats which had received diets containing 0, 1.25 and 5.0 mg/kg diet of all-rac-alpha-tocopheryl acetate for 14 months. Compared to the groups receiving 1.25 and 5.0 mg/kg alpha-tocopheryl acetate, a total of 11 genes were statistically significantly upregulated (> or =1.3-fold) and 34 downregulated (< or =1.3-fold) in the vitamin E-deficient group. Increased expression was observed for the genes encoding the antioxidant enzyme catalase and the axon guidance molecule tenascin-R, while decreased expression was detected for genes encoding protein components of myelin and determinants of neuronal signal propagation. Thus our observations suggest that vitamin E deficiency results in transcriptional alterations in the cerebral cortex of the rat which are consistent with the observed neurological and electrophysiological alterations.

Distribution of calbindin-28kD and parvalbumin in V1 in normal adult Cebus apella monkeys and in monkeys with retinal lesions

Several proteins have their normal patterns of distributions altered by monocular visual deprivation. We studied the distribution of the calcium-binding proteins calbindin-28kD (Cb) and parvalbumin (Pv) in V1 in normal adult Cebus apella monkeys and in monkeys with monocular retinal lesions. In normal monkeys, the interblobs regions in layers 2/3 and the layer 4B are intensely labeled for Cb, while Pv reaction showed a complementary labeling pattern with a stronger staining in layers 4A, 4C and in the blob regions in layers 2/3. In monkeys with monocular retinal lesion, the laminar distribution of these proteins was differentially affected, although both reactions resulted in stronger labeling in non-deprived ocular dominance columns. While Cb reaction resulted in stronger labeling in layers 1 through 5, Pv labeling was heavier in layers 2/3, 4A and 4C. There was a clear reduction in the intensity of neuropil staining for both Pv and Cb in deprived ocular dominance columns with little or no reduction in number of labeled cells. This reduction could thus be attributed to activity-dependent changes at synapses level.

Semaphorins and their receptors in lamprey CNS: Cloning, phylogenetic analysis, and developmental changes during metamorphosis

The large, conserved semaphorin gene family encodes axon guidance molecules in both invertebrates and vertebrates. The primitive vertebrate lamprey diverged near the time of vertebrate origins and is useful for understanding the gene duplication events that led to the increased complexity of the vertebrate genome. We characterized the sequence and expression pattern of semaphorins and their receptors genes in the sea lamprey, Petromyzon marinus. We uncovered two members of the semaphorin family in sea lamprey. The first encodes a diffusible class 3 type semaphorin protein that is most similar to the human and mouse Sema3F (71% amino acid identity). The second encodes a transmembrane class 4 type semaphorin that is most similar to mouse Sema4D and human Sema4G, with 38% amino acid identity within the Sema domain. We also identified in lamprey two members of the semaphorin receptor family, lamprey Plexin A1 and Plexin A2. Phylogenetic analysis indicates that lamprey Sema3 and Sema4 represent precursor genes existing prior to the origin of the vertebrate Sema3A-G and Sema4A-G subfamilies. Therefore, the gene duplication event that gave rise to those subfamilies must have occurred after the divergence of jawed vertebrates from jawless fish. These semaphorins and plexins are expressed in unique and dynamic patterns in lamprey spinal cord and brain during development.

Pilot study of efficacy of tongue and body acupuncture in children with visual impairment

We studied the efficacy of tongue and body acupuncture in affecting visual recovery in children with central and peripheral visual disorders. Twelve children (five boys, seven girls) (age range 18 months to 14.5 years) with visual disorder with static functional visual ability for at least 12 months were recruited for the study. The causes of cortical visual impairment (10) included severe perinatal asphyxia (4), postencephalitis (1), traumatic brain injury (1), hydrocephalus (1), and increased intracranial pressure (3). Peripheral causes (2) were due to congenital optic atrophy. We used the following assessment tools: clinical visual improvement, defined as improvement of vision by one grade in one or both eyes with measurement of visual acuity; the functional visual outcome scale of 0 to 5, with positive outcome defined as improvement in one level on a functional scale; visual evoked potential, with positive improvement defined as 10% improvement in P100 latency of one or both eyes; [18F]-fluorodeoxyglucose (FDG) positron emission tomography (PET) of the brain, with positive improvement defined as a 10% increase in glucose metabolism in one or both occipital lobes; and the Clinical Global Impression Scale (parental report). Tongue and body acupuncture consisted of 60 sessions, with 5 sessions per week. Four children showed clinical or functional improvement (33%). Of nine children with abnormal visual evoked potentials, five had improvement (56%). Of seven children who underwent PET, six had improvement in glucose metabolism in the visual cortex (86%). Seven parents (58%) reported improvement (three children had 75% improvement; four children had 25% improvement). There was a significant correlation between the interval of onset of visual impairment and starting treatment with clinical or functional outcome, with a longer interval resulting in a better outcome (P = .0282). However, there was no correlation between cause, severity, or clinical or functional visual outcome with improvement in the visual evoked potential or PET. We demonstrated that tongue and body acupuncture can improve the visual status of children with visual disorders, both peripheral and central in origin. As children with chronic visual impairment also showed some visual recovery, more studies should be done to assess the full potential of acupuncture as an adjunct to Western medicine in neuroplasticity.

The prognosis of hearing impairment complicating HIV-negative cryptococcal meningitis

Eight patients who had sensorineural hearing loss (SNHL) associated with cryptococcal meningitis were studied. After a minimum 3-year follow-up, one had died. Among the seven survivors, three had improved, two stabilized, and two progressed. Predictive factors included visual disturbance, meningeal enhancements on MRI, and a CSF cryptococcal antigen titer of >1:1,024. SNHL accounted for 30.8% (8/26) of cryptococcal meningitis patients in our study.

Near-infrared spectroscopy of the visual cortex in unilateral optic neuritis

PURPOSE

To examine the occipital-lobe activation of patients with optic neuritis using near-infrared spectroscopy.

DESIGN

Experimental study.

METHODS

NIRS was performed on five patients with acute unilateral optic neuritis during monocular visual stimulation. As controls, six normal subjects were also tested in the same manner.

RESULTS

In the patients with optic neuritis, the changes in the hemoglobin concentrations (oxyhemoglobin, deoxyhemoglobin, and total hemoglobin) in the occipital lobe were found to be markedly reduced when the clinically affected eyes were stimulated compared with the fellow eyes. The response induced by the stimulation of the affected eye was decreased, even when the patient's visual acuity improved to 20/20 in the recovery phase. There was no difference in the concentration changes between the two eyes in the control subjects.

CONCLUSIONS

NIRS may be useful in detecting visual dysfunction objectively and noninvasively in patients with visual disturbance, especially when used at the bedside.

An explanation of transient visual loss associated with leaking filtering bleb

PURPOSE

To report a presumed cause for the transient visual loss noted by a patient with a leaking bleb following trabeculectomy.

DESIGN

Case report.

METHODS

Description of an otherwise healthy woman who developed delayed-onset transient visual loss associated with a leaking filtering bleb.

RESULTS

A 62-year-old woman who underwent trabeculectomy with mitomycin C in her right eye 5 years earlier (Feb 23, 1999) presented with a 3-month history of transient decreased vision. The apparent cause was a periodic gush of aqueous flowing across the surface of the cornea.

CONCLUSIONS

One cause of bleb-associated transient visual loss can be aqueous leaking from the bleb on to the anterior surface of the cornea, disturbing vision as it flows past the visual axis. This is temporarily relieved by blinking.

Ophthalmic drug discovery

Millions of people suffer from a wide variety of ocular diseases, many of which lead to irreversible blindness. The leading causes of irreversible blindness in the elderly--age-related macular degeneration and glaucoma--will continue to effect more individuals as the worldwide population continues to age. Although there are therapies for treating glaucoma, as well as ongoing clinical trials of treatments for age-related macular degeneration, there still is a great need for more efficacious treatments that halt or even reverse ocular diseases. The eye has special attributes that allow local drug delivery and non-invasive clinical assessment of disease, but it is also a highly complex and unique organ, which makes understanding disease pathogenesis and ocular drug discovery challenging. As we learn more about the cellular mechanisms involved in age-related macular degeneration and glaucoma, potentially, new drug targets will emerge. This review provides insight into some of the new approaches to therapy.

Ocular surface, ocular adnexal, and lacrimal complications associated with the use of systemic 5-fluorouracil

PURPOSE

To determine the prevalence rates and associated characteristics of patients who have ocular surface, ocular adnexal, and lacrimal complications associated with the systemic use of the cancer chemotherapeutic agent 5-Fluorouracil (5-FU).

METHODS

An exposure-based cohort study was designed. Adult patients who had completed at least 3 months of systemic 5-FU therapy within the past 5 years were eligible for enrollment. Study subjects had a detailed medical history taken with emphasis on preexisting conditions known to be associated with the development of ocular surface, ocular adnexal, and lacrimal complications. An ocular examination was then performed. A complete nasolacrimal system evaluation was performed if symptoms or findings were identified. The prevalence was then determined for each ocular symptom and each ocular finding identified that was not present pretreatment. An exploratory analysis was then performed to identify patient characteristics that might influence the likelihood of developing any of the above complications.

RESULTS

Fifty-two patients were enrolled in the study. The prevalence rates of the following ocular abnormalities were calculated: ocular irritation, 5.8%; blepharitis, 3.8%; conjunctivitis, 3.8%; keratitis, 3.8%; eyelid dermatitis, 5.8%; cicatricial ectropion, 1.9%; tearing, 26.9%; punctal-canalicular stenosis, 5.8%; and blurred vision, 11.5%. Blacks had tearing at a significantly higher rate when compared with whites (P = 0.022, 2-sided Fisher exact test). Three patients had permanent complications that will require surgery for correction. Of the 7 patients who had a single abnormality, 6 had tearing and one had eyelid dermatitis. All of the 8 patients who had multiple findings had tearing as one of their abnormalities.

CONCLUSIONS

Ninety-three percent of the patients who had an ocular abnormality had tearing as one of the complications. Patients who are receiving systemic 5-FU and begin to tear should have an ocular examination, looking for ocular surface, ocular adnexal, and lacrimal complications.

Retinol-binding protein-deficient mice: biochemical basis for impaired vision

We reported previously that mice lacking plasma retinol-binding protein (RBP) are phenotypically normal except that they display impaired vision at the time of weaning. This visual defect is associated with greatly diminished eyecup levels of retinaldehyde and is reversible if the mutants are maintained for several months on a vitamin A-sufficient diet. Here we provide a biochemical basis for the visual phenotype of RBP-deficient mice. This phenotype does not result from inadequate milk total retinol levels since these are not different for RBP-deficient and wild-type mice. The eye, unlike all other tissues that have been examined, takes up dietary retinol very poorly. Moreover, compared to other tissues, the eye displays a strong preference for retinol uptake when retinol is delivered bound to RBP. The poor uptake of dietary retinol by the eye coupled with its marked ability to take up retinol from RBP, we propose, provides a basis for the impaired vision observed in weanling RBP-deficient mice. Further study of the mutants suggests that the impaired vision is reversible because the eyes of mutant mice slowly acquire sufficient retinol from the low levels of retinol present in their circulation either bound to albumin or present in lipoprotein fractions. Thus, the eye is unlike other tissues in the body in that it shows a very marked preference for acquiring retinol needed to support vision from the retinol-RBP complex and is unable to meet adequately its retinol need through uptake of recently absorbed dietary retinol. This provides an explanation for the impaired vision phenotype of RBP-deficient mice.

Neurotrophin-3 is required for appropriate establishment of thalamocortical connections

In the vertebrate brain, the thalamus serves as a relay and integration station for diverse neuronal information en route from the periphery to the cortex. Formation of the thalamocortical tract occurs during pre- and postnatal development, with distinct thalamic nuclei projecting to specific cortical regions. The molecular forces that underlie the invasion by axons into specific cortical layers followed by activity-dependent maturation of synapses are poorly understood. We show that genetic ablation of neurotrophin-3 (NT-3) in the mouse neocortex results in reduction of a set of anatomically distinct axonal bundles projecting from thalamus through cortical white matter. These bundles include thalamocortical axons that normally establish connections with retrosplenial and visual cortex, sites of early postnatal NT-3 expression. These results implicate neurotrophins in the critical stage of precise thalamocortical connections.

Diffuse metabolic abnormalities in reversible posterior leukoencephalopathy syndrome

Two cases of reversible posterior leukoencephalopathy syndrome were examined with proton MR spectroscopic imaging. Widespread metabolic abnormalities, consisting of increased choline and creatine levels and mildly decreased N-acetylaspartate, occurred in regions with both normal and abnormal MR imaging appearances. In one case for which proton MR spectroscopic imaging follow-up was available, all metabolite levels had returned to normal by 2 months. Proton MR spectroscopic imaging may be helpful for the diagnosis and investigation of the underlying pathophysiology of reversible posterior leukoencephalopathy syndrome.

[Clinical investigation of hyaluronidase and nerve growth factor (NGF) at the ocular level: detailed review of the international literature]

In this paper the authors analyse the international bibliography about clinic tests on hyaluronic acid and Nerve Growth Factor at ocular level. This study was performed on request of a private oculistic clinic in the centre of Rome about the clinic test of the drugs mentioned above. Therefore, this paper is a joint work of Public Health physicians and oculists.

[Postoperative opacification of 12 hydrogel foldable lenses (Hydroview(R))]

BACKGROUND

To evaluate postoperative lens opacifications in foldable hydrophilic intraocular lenses.

PATIENTS AND METHODS

12 patients (9 female; 3 male; mean age 77.5 +/- 3 years) were referred from one ophthalmologic surgeon because of opacification of IOLs and markedly decreased visual acuity. Time between implantation and explantation varied from 8 month to 3 years. IOL explantation was performed in all 12 patients and IOL were examined by light-, transmission- and scanning electron microscopy.

RESULTS

IOL-explantation was uneventful in all 12 patients. The explanted IOLs showed crystalline deposits 0.5 to 2 microm in diameter immediately beneath the surface of the lens. Eight of 12 patients had elevated serum levels for glucose (6 patients with manifest diabetes mellitus, 2 patients with pathological elevated levels for glucose).

CONCLUSIONS

Postoperative opacification of hydrogel foldable lenses (Hydroview(R)) are apperantly caused by formation of crystalline deposits beneath the lens surface. These deposits may be associated with metabolic disorders, e.g. diabetes mellitus.

Changes of contrast gain in cat dorsal lateral geniculate nucleus by dopamine receptor agonists

The modulatory effects of dopamine (DA) on the contrast gain of retino-geniculate transmission were tested with local micro-iontophoretical application of DA and the DA receptor agonists SKF38393 (SKF, D1/D5) and quinpirole (QUIN, D2/D3/D4) while recording visually induced spike activity of relay cells of the dorsal aspect of cat lateral geniculate nucleus (dLGN) in the anesthetised and paralyzed preparation. DA and QUIN could either facilitate or inhibit visual activity in a dose-dependent fashion: small amounts caused a facilitation while larger quantities resulted in a more (DA) or less (QUIN) strong inhibition. The effect of SKF was almost always suppressive and increased with the amount of drug applied. The absolute change in activity was depending on stimulus contrast and the strength of the elicited response: facilitation and inhibition of activity was proportional to stimulus contrast and response strength and thus resulted in a changed contrast gain. The results indicate that the visual deficits found in Parkinson's disease patients my be not solely related to retinal dysfunctions.

Rate of visual field loss and long-term visual outcome in primary open-angle glaucoma

PURPOSE

To evaluate long-term visual field outcome in primary open-angle glaucoma.

METHODS

In this retrospective cohort study, 40 eyes of 40 patients with primary open-angle glaucoma with elevated intraocular pressure and a minimum of 8-year longitudinal series of visual fields were plotted with Goldmann perimeter. Eyes with any other ocular disease except cataract were excluded. Manual grid templates were used to quantify the visual fields. Linear regression was performed to estimate the rate of visual field decline. Pertinent clinical factors were evaluated for statistical association with the rate of decline. Long-term clinical outcome including visual acuity, rate of legal blindness, and rate of medical and surgical interventions was also measured.

RESULTS

In the 40 eyes studied, with a mean follow-up of 14 years, the visual field score decreased at the rate of -1.5% per year. Overall, 68% showed significant decrease, and the rate of decrease among these eyes was -2.1% per year. Five eyes became legally blind from glaucoma; the cumulative rate of blindness from glaucoma was 19% at 22 years. Higher intraocular pressure and greater number of antiglaucoma medications on initial presentation were associated with faster and slower deterioration of visual field (compared with the average), respectively.

CONCLUSIONS

With standard glaucoma therapy, the rate of visual field loss in primary open-angle glaucoma is slow. Lower intraocular pressure and more antiglaucoma medications are associated with slower visual field decline. Legal blindness from glaucoma is 19% over a follow-up of 22 years.

Optical and visual impact of tear break-up in human eyes

PURPOSE

The purpose of this study was to examine the optical and visual impact of tear break-up.

METHODS

Optical quality of the eye was assessed during periods of nonblinking by quantifying vessel contrast in the fundus image and by monitoring the psychophysical contrast sensitivity and the spatial distribution of tear thickness changes by retroillumination. All measures were obtained from three eyes either with or without a soft contact lens.

RESULTS

A noticeable decrease in retinal vessel contrast and contrast sensitivity were observed soon after a blink. Both of these measures of optical quality of the eye showed a similar pattern of image degradation both with and without a soft contact lens. Although trial-to-trial variability was considerable, sample means show that image contrast in the low spatial frequency range can drop to between 20% and 40% of initial values after 60 seconds of nonblinking. Retroillumination of the tear film showed local intensity fluctuations that progressively spread across the pupil with increasing time after the blink.

CONCLUSIONS

Optical aberrations created by tear break-up contribute to the decline in image quality observed objectively and psychophysically. The decline in image quality that accompanies tear break-up may be a direct cause of the blurry vision complaints commonly encountered in dry-eye patients.

Disturbances of spatial vision and object vision correlate differently with regional cerebral glucose metabolism in Alzheimer's disease

There is evidence of two neuronal systems for visual cognition which are referred to as spatial vision and object vision. We subjected 49 patients with mild-to-moderate probable Alzheimer's disease (AD) to tasks associated with these two types of visual cognition. Visual counting was employed as a task to assess visuospatial recognition. Identification of overlapping figures and discrimination of visual forms were used as visuoperceptual tasks that require an ability to recognize objects. Regional cerebral glucose metabolism (rCMRglc) of the subjects was also determined by positron emission tomography. Multivariate statistics controlling for the confounding factors assessed the correlation between the task performances and the rCMRglc. The visual counting score significantly correlated with the metabolic rate of the bilateral inferior parietal lobules. On the other hand, the scores of the visuoperceptual tasks significantly correlated with the metabolic rate of the right middle temporal gyrus and the right inferior parietal lobule. The present study showed that visuospatial disturbance was related to bilateral parietal metabolism, and that visuoperceptual disturbance was related to right temporo-parietal metabolism in patients with mild-to-moderate AD.

Visually significant calcification of hydrogel intraocular lenses necessitating explantation

PURPOSE

To report two cases of HydroviewR (Storz H60M) hydrogel intraocular lens (IOL) opacification necessitating explantation. To analyse the explanted lenses and compare them with a new lens in order to determine the cause of opacification.

METHODS

Two cases are presented. Both patients complained of subjective decreases in vision approximately 1 year following uneventful cataract extraction and implantation of hydrogel lenses by the same experienced surgeon in the same institution. The reduced contrast sensitivity was thought to be due to failure of the hydrogel lenses which appeared opacified at the slit-lamp. They were then exchanged for acrylic lenses. Pre- and postoperative contrast sensitivity testing was performed using the VectorvisionR CSV-1000E instrument. A detailed comparative analysis of the opacified explanted lenses and a new lens was undertaken. This included surface microscopy, infrared spectral analysis, X-ray elemental analysis, scanning electron microscopy, and electron microscopy of lens slices.

RESULTS

Lens exchange resulted in an improvement in subjective visual acuity (VA) and in objective contrast sensitivity testing. Analysis revealed deposits of calcium phosphate (hydroxyapatite) on the explanted lens' surfaces.

CONCLUSIONS

The surface of the HydroviewR H60M intraocular lens is subject to opacification as a result of calcium phosphate (hydroxyapatite) deposition, thereby limiting the patient's visual outcome, and in some cases necessitating explantation. The reason for surface calcification requires further study.

NMDAR-1 staining in the lateral geniculate nucleus of normal and visually deprived cats

In normal adult cats, a monoclonal antibody directed toward the NR-1 subunit of the N-methyl-D-aspartate (NMDA) receptor (Pharmingen, clone 54.1) produced dense cellular and neuropil labeling throughout all layers of the lateral geniculate nucleus (LGN) and adjacent thalamic nuclei, including the thalamic reticular, perigeniculate, medial intralaminar, and ventral lateral geniculate nuclei. Cellular staining revealed well-defined somata, and in some cases proximal dendrites. NMDAR-1 cell labeling was also evident in the LGN of early postnatal kittens, suggesting that developing LGN cells possess this receptor subunit at or before eye opening. Within the A-layers of the adult LGN, staining encompassed a wide range of soma sizes. Soma size comparisons of NMDAR-1 stained cells with those stained with an antibody directed toward a nonphosphorylated neurofilament protein (SMI-32), which selectively stains Y-relay cells (Bickford et al., 1998), or an antibody to glutamic acid decarboxylase (GAD), which stains for GABAergic interneurons, suggested that NMDA receptors are utilized by relay cells and interneurons. NMDAR-1 staining was also observed in the LGN of cats with early monocular lid suture. Although labeling was apparent in both deprived and nondeprived A-layers of LGN, the distribution of soma sizes was significantly different. In the deprived A-layers of LGN, staining was limited to small- and medium-sized cells. Cells with relatively large soma were lacking. However, cell density measurements as well as soma size comparisons with cells stained for Nissl substance suggested these differences were due to deprivation-induced cell shrinkage and not to a loss of NMDAR-1 staining in Y-cells. Taken together, these results suggest that NMDA receptors are utilized by both relay cells and interneurons in LGN and that alterations in early visual experience do not necessarily affect the expression of NMDA receptors in the LGN.