Susan M. Culican

Axon Withdrawal during Synapse Elimination at the Neuromuscular Junction Is Accompanied by Disassembly of the Postsynaptic Specialization and Withdrawal of Schwann Cell Processes

Nerve terminal withdrawal is accompanied by a loss of acetylcholine receptors (AChRs) at corresponding postsynaptic sites during the process of synapse elimination at developing (Balice-Gordon and Lichtman, 1993) and reinnervated adult (Rich and Lichtman, 1989a) neuromuscular junctions. Aside from AChR and nerve terminal loss, however, the molecular and cellular alterations that occur at sites of elimination are unknown. To gain a better understanding of the cascade of events that leads to the disassembly of synaptic sites during the synapse elimination process, we surveyed the distribution of molecular elements of the postsynaptic specialization, the basal lamina, and supporting Schwann cells during the process of synapse elimination that occurs after reinnervation. In addition, quantitative techniques were used to determine the temporal order of disappearance of molecules that were lost relative to the loss of postsynaptic AChRs. We found that the dismantling of the postsynaptic specialization was inhomogeneous, with evidence of rapid dissolution of some aspects of the postsynaptic apparatus and slower loss of others. We also observed a loss of Schwann cell processes from sites of synapse elimination, with a time course similar to that seen for nerve terminal retraction. In contrast, all of the extracellular markers that we examined were lost slowly from sites of synapse loss. We therefore conclude that the synapse elimination process is synapse-wide, removing not only nerve terminals but also Schwann cells and many aspects of the postsynaptic apparatus. The disassembly occurs in a stereotyped sequence with some synaptic elements appearing much more stable than others.

Spontaneous activity promotes synapse formation in a cell-type-dependent manner in the developing retina.

Spontaneous activity is thought to regulate synaptogenesis in many parts of the developing nervous system. In vivo evidence for this regulation, however, is scarce and comes almost exclusively from experiments in which normal activity was reduced or blocked completely. Thus, whether spontaneous activity itself promotes synaptogenesis or plays a purely permissive role remains uncertain. In addition, how activity influences synapse dynamics to shape connectivity and whether its effects among neurons are uniform or cell-type-dependent is unclear. In mice lacking the cone–rod homeobox gene (Crx), photoreceptors fail to establish normal connections with bipolar cells (BCs). Here, we find that retinal ganglion cells (RGCs) in Crx−/− mice become rhythmically hyperactive around the time of eye opening as a result of increased spontaneous glutamate release from BCs. This elevated neurotransmission enhances synaptogenesis between BCs and RGCs, without altering the overall circuit architecture. Using live imaging, we discover that spontaneous activity selectively regulates the rate of synapse formation, not elimination, in this circuit. Reconstructions of the connectivity patterns of three BC types with a shared RGC target further revealed that neurotransmission specifically promotes the formation of multisynaptic appositions from one BC type without affecting the maintenance or elimination of connections from the other two. Although hyperactivity in Crx−/− mice persists, synapse numbers do not increase beyond 4 weeks of age, suggesting closure of a critical period for synaptic refinement in the inner retina. Interestingly, despite their hyperactivity, RGC axons maintain normal eye-specific territories and cell-type-specific layers in the dorsal lateral geniculate nucleus.

Repair of cicatricial ectropion in an infant with harlequin ichthyosis using engineered human skin

PURPOSE To report the use of an Apligraf (Organogenesis, Inc., Canton, Massachusetts, USA) human skin equivalent for repair of cicatricial ectropion in a patient with harlequin ichthyosis. DESIGN Interventional case report. METHODS A 6-week-old male child with harlequin ichthyosis and severe bilateral upper eyelid cicatricial ectropion underwent repair with Apligraf grafts. RESULTS After the initial repair with Apligraf grafts, recurrent bilateral upper eyelid ectropion developed, requiring repeat Apligraf grafting at age 61 days. After the second graft, the eyelids remained well positioned until the childs sudden death from respiratory failure at age 6 months. CONCLUSION Apligraf human skin equivalent facilitated the repair of cicatricial ectropion in a child with harlequin ichthyosis.

A quantitative fluorescence-imaging technique for studying acetylcholine receptor turnover at neuromuscular junctions in living animals

We have developed a technique to measure changes in the amount of fluorescently labeled acetylcholine receptors in living muscles over long time periods. The measurements of fluorescence are made relative to a novel, photolytically stable fluorescence standard (Spectralon) which allows changes in fluorescence to be followed over days, even months. The method compensates for spatial and temporal variations in image brightness due to the light source, microscope, and camera. We use this approach to study the turnover of fluorescently labeled acetylcholine receptors at a single neuromuscular junction in a living mouse by re-imaging the same junction in situ over a period of 3 weeks. In addition we show that the SIT video camera, which is generally considered inadequate for quantitative imaging (in comparison to CCD cameras), is actually a very good quantitative device, especially in situations requiring both fast acquisition and high resolution.

Phr1 regulates retinogeniculate targeting independent of activity and ephrin-A signalling

Proper functioning of the mammalian visual system requires that connections between the eyes and their central targets develop precisely. At birth, axons from the two eyes project to broad, overlapping regions of the dorsal-lateral geniculate nucleus (dLGN). In the adult, retinal axons segregate into distinct monocular regions at stereotyped locations within the dLGN. This process is driven by both molecular cues and activity-dependent synaptic competition. Here we demonstrate that Phr1, an evolutionarily conserved regulator of synapse formation and axon guidance, defines a novel molecular pathway required for proper localization of retinogeniculate projections. Following conditional excision of Phr1 in the retina, eye-specific domains within the dLGN are severely disturbed, despite normal spontaneous retinal wave activity and monocular segregation. Although layer placement is dramatically altered, Phr1 mutant retinal axons respond to ephrin-A in vitro. These findings indicate that Phr1 is a key presynaptic regulator of retinogeniculate layer placement independent of activity, segregation, or ephrin-A signaling.

Comparison of the effectiveness and safety of transscleral cyclophotocoagulation and endoscopic cyclophotocoagulation in pediatric glaucoma.

PURPOSE Among the options for surgical management of pediatric glaucoma, destruction of the ciliary body reduces aqueous production and, consequently, intraocular pressure (IOP). Compared to more invasive filtering and shunt procedures, cyclodestruction is an attractive option for control of IOP in pediatric glaucomas. METHODS The relative reduction in IOP, duration of effect, and comparable safety and efficacy of transscleral cyclophotocoagulation (TSCP) and endoscopic cyclophotocoagulation (ECP) in pediatric patients with glaucoma was studied in this retrospective chart review. RESULTS A reduction in IOP of 28.6% and 33.2% with TSCP and ECP, respectively, was found. Eyes treated with ECP underwent an average of 3.24 cyclodestructive procedures; eyes treated with TSCP underwent an average of 2.29 cyclodestructive treatments. These differences were not statistically significant. A final success rate of 67.6% after TSCP and 62% after ECP failed to significantly differ between the two groups. Consequently, two-thirds of the patients were able to avoid penetrating surgery and the associated risks after one or more cyclodestructive procedures. CONCLUSIONS TSCP and ECP are safe, effective, and comparable treatments for pediatric glaucomas. The results suggest that TSCP and ECP may be considered first-line therapy to achieve control of IOP in all forms of pediatric glaucoma. [J Pediatr Ophthalmol Strabismus 2014;51(2):120-127.].

Nummular keratopathy in a patient with Hyper-IgD Syndrome

PurposeTo report a case of recurrent nummular keratitis in a pediatric patient with Hyperimmunoglobulinemia D syndrome.MethodsA retrospective chart review.ResultsA 14-year-old boy with Hyperimmunoglobulinemia D syndrome (HIDS) presented with photophobia and ocular irritation concomitant with disease exacerbation. He was found on exam to have significant nummular keratitis, which responded to a short course of topical steroids. Despite acute response to local immunosuppression, the patient had several recurrent attacks and eventually developed a large corneal scar and decreased vision. After initiation of infliximab therapy his ocular sequelae improved dramatically and his vision returned to 20/20.ConclusionOne possible form of end-organ damage associated with HIDS is vision threatening nummular keratopathy.

A Multicenter Analysis of the Ophthalmic Knowledge Assessment Program and American Board of Ophthalmology Written Qualifying Examination Performance

OBJECTIVE To compare the performance on the American Board of Ophthalmology Written Qualifying Examination (WQE) with the performance on step 1 of the United States Medical Licensing Examination (USMLE) and the Ophthalmic Knowledge Assessment Program (OKAP) examination for residents in multiple residency programs. DESIGN Comparative case series. PARTICIPANTS Fifteen residency programs with 339 total residents participated in this study. The data were extracted from the 5-year American Board of Ophthalmology report to each participating program in 2009 and included residency graduating classes from 2003 through 2007. Residents were included if data were available for the USMLE, OKAP examination in ophthalmology years 1 through 3, and the WQE score. Residents were excluded if one or more of the test scores were not available. METHODS Two-sample t tests, logistic regression analysis, and receiver operating characteristic (ROC) curves were used to examine the association of the various tests (USMLE, OKAP examination year 1, OKAP examination year 2, OKAP examination year 3, and maximum OKAP examination score) as a predictor for a passing or failing grade on the WQE. MAIN OUTCOME MEASURES The primary outcome measure of this study was first time pass rate for the WQE. RESULTS Using ROC analysis, the OKAP examination taken at the third year of ophthalmology residency best predicted performance on the WQE. For the OKAP examination taken during the third year of residency, the probability of passing the WQE was at least 80% for a score of 35 or higher and at least 95% for a score of 72 or higher. CONCLUSIONS The OKAP examination, especially in the third year of residency, can be useful to residents to predict the likelihood of success on the high-stakes WQE examination.

Phr1 is required for proper retinocollicular targeting of nasal-dorsal retinal ganglion cells

Precise targeting of retinal projections is required for the normal development of topographic maps in the mammalian primary visual system. During development, retinal axons project to and occupy topographically appropriate positions in the dorsal lateral geniculate nucleus (dLGN) and superior colliculus (SC). Phr1 retinal mutant mice, which display mislocalization of the ipsilateral retinogeniculate projection independent of activity and ephrin-A signaling, were found to have a more global disruption of topographic specificity of retinofugal inputs. The retinocollicular projection lacks local refinement of terminal zones and multiple ectopic termination zones originate from the dorsal-nasal (DN) retinal quadrant. Similarly, in the dLGN, the inputs originating from the contralateral DN retina are poorly refined in the Phr1 mutant. These results show that Phr1 is an essential regulator of retinal ganglion cell projection during both dLGN and SC topographic map development.

Use of Biologic Agents in Ocular Manifestations of Rheumatic Disease

Biologic agents have dramatically shifted the treatment paradigm for rheumatic disease. Use of these agents can decrease disease burden, allow the patient to be weaned from corticosteroids, and reduce the likelihood of relapse. Eye disease associated with rheumatic conditions may present with a wide range of signs and symptoms. This coexisting pathology should not be overlooked and should be considered a reason for initiation or continuation of biologic therapy. Additionally, many of the ocular manifestations of rheumatic disease respond preferentially to specific targeting molecules. This paper summarizes the available studies on the use, efficacy, and safety of biologic agents in the treatment of ocular manifestations of rheumatic disease.