Alain Proulx

Blocking gap junctional intercellular communication in myoblasts inhibits myogenin and MRF4 expression

Cells rely heavily on cues from their extracellular environment and other cells to coordinate normal physiological processes, and the exchange of molecules via gap junctions has been suggested as on important avenue for cell-cell communication. Gap junctions are found in virtually all mammalian tissues with the notable exception of adult skeletal muscle. However, since functional gap junctions have been detected during the early stages of muscle development, gap junctional intercellular communication (GJIC) may play on important role in myogenesis. In this study, GJIC in normal 16 myoblasts was inhibited using the known blockers l-octanol and beta-glycyrrhetinic acid (beta-GA). Under differentiation promoting conditions, 16 cells fused to form multinucleated myotubes, but when treated with either octanol or beta-GA, no fusion was observed. The expression of two muscle regulatory factors (MRFs), myogenin and MRF4, was examined in both the blocked and control cells. As expected, the activation of both the myogenin and MRF4 genes coincided with the onset of differentiation in the control 16 cells. Neither of these genes were turned on in the blocked cells, even when grown under low serum conditions. This inhibition of differentiation by octanol and beta-GA was reversible, since the activation of both MRF genes as well as myoblast fusion were observed when the blocking medium was replaced with normal differentiating medium. These results suggest that intercellular communication via gap junctions plays an important role in skeletal muscle development and perhaps in the cell signaling events that trigger the activation of muscle-specific MRF genes.

Comparison of the In vitro Safety of Intraocular Dyes Using Two Retinal Cell Lines: A Focus on Brilliant Blue G and Indocyanine Green

PURPOSE To compare the in vitro toxicity of brilliant blue G (BBG), indocyanine green (ICG), Trypan blue (TB), and Evans blue (EB) in a human retinal pigment epithelial cell line (ARPE-19) and a murine retinal ganglion/Muller glial (RGC) primary cell culture. DESIGN In vitro cell biology experimental study. METHODS The dose-dependent toxicity of the dyes was determined by exposing each dye at four different concentrations to the two cell cultures for a short exposure (three minutes) and a medium exposure (30 minutes). The time-dependent toxicity of the dyes was also determined. All four dyes, each diluted to 1/500th of stock concentration, were applied only to the ARPE-19 cells for a prolonged exposure of two, 24, 48, and 72 hours. Cell viability was measured via a mitochondrial dehydrogenase assay. RESULTS BBG was the only dye to cause toxicity in the ARPE-19 cell line at short exposure times. BBG and TB demonstrated toxicity at medium exposure times. BBG and ICG demonstrated toxicity at long exposure times and dilute concentrations. At short exposure times, none of the dyes caused toxicity in the RGC mixed primary cultures. In contrast, at medium exposure times, all dyes except ICG demonstrated toxicity that lessened with lower concentrations. CONCLUSIONS All dyes demonstrated relatively safe viability profiles in both cell lines at surgically relevant concentrations and times. Cell toxicity could be elicited at higher concentrations and longer exposure times. ICG had a favorable viability profile at almost all of the concentrations and times tested.

Creutzfeldt-Jakob disease presenting with visual manifestations

BACKGROUND Creutzfeldt-Jakob disease (CJD) is a rare and progressive degenerative disease of the central nervous system (CNS), characterized pathologically by spongiform changes in various CNS tissues. It most often presents with rapidly progressing dementia and cognitive decline, along with other neurologic findings that correspond to affected areas of the CNS. We present 5 sporadic cases of CJD presenting with visual manifestations, 2 of which were consistent with the Heidenhain variant, which predominantly affects the occipital lobe. METHODS Each of the cases demonstrated electroencephalographic changes suggestive of CJD. The neuro-ophthalmic findings included both sensory and motor manifestations, including cortical blindness, hemianopsia, dysmetria, visual hallucinations, hypometric saccades, and diplopia. RESULTS All patients died within 5 months after the onset of signs of the disease and pathologic specimens were obtained in 4 of the cases. INTERPRETATION Although CJD is not a commonly seen condition, its possibility should be entertained in any patient presenting with typical neurologic deterioration and complaining of visual symptoms.

Primary intraocular lymphoma arising during methotrexate treatment of temporal arteritis

CASE REPORT Primary intraocular lymphoma arose over a period of 9 months in the left eye of an 81-year-old woman who was blind in both eyes from temporal arteritis. During this period, she was treated with prednisone and methotrexate. Following a sudden total hyphema, the eye was enucleated. Examination revealed that, in addition to iris neovascularisation and central retinal artery occlusion, the neurosensory retina was replaced by atypical lymphocytes. COMMENTS Histological and immunohistochemical studies confirmed the presence of a lymphoma with features indicative of an immunosuppression-related disorder. The relationship of the lymphoma to the vascular changes within the eye is discussed.

Quantitative evaluation of vision-related and health-related quality of life after endoscopic transsphenoidal surgery for pituitary adenoma

OBJECTIVE Endoscopic resection of pituitary adenomas has been reported to improve vision function in up to 80%-90% of patients with visual impairment due to these adenomas. It is unclear how these reported rates translate into improvement in visual outcomes and general health as perceived by the patients. The authors evaluated self-assessed health-related quality of life (HR-QOL) and vision-related QOL (VR-QOL) in patients before and after endoscopic resection of pituitary adenomas. METHODS The authors prospectively collected data from 50 patients who underwent endoscopic resection of pituitary adenomas. This cohort included 32 patients (64%) with visual impairment preoperatively. Twenty-seven patients (54%) had pituitary dysfunction, including 17 (34%) with hormone-producing tumors. Patients completed the National Eye Institute Visual Functioning Questionnaire and the 36-Item Short Form Health Survey preoperatively and 6 weeks and 6 months after surgery. RESULTS Patients with preoperative visual impairment reported a significant impact of this condition on VR-QOL preoperatively, including general vision, near activities, and peripheral vision; they also noted vision-specific impacts on mental health, role difficulties, dependency, and driving. After endoscopic resection of adenomas, patients reported improvement across all these categories 6 weeks postoperatively, and this improvement was maintained by 6 months postoperatively. Patients with preoperative pituitary dysfunction, including hormone-producing tumors, perceived their general health and physical function as poorer, with some of these patients reporting improvement in perceived general health after the endoscopic surgery. All patients noted that their ability to work or perform activities of daily living was transiently reduced 6 weeks postoperatively, followed by significant improvement by 6 months after the surgery. CONCLUSIONS Both VR-QOL and patients perceptions of their ability to do work and perform other daily activities as a result of their physical health significantly improved by 6 months after endoscopic resection of pituitary adenoma. The use of multidimensional QOL questionnaires provides a precise assessment of perceived outcomes after endoscopic surgery.

Remission of nonparaneoplastic autoimmune retinopathy after minimal steroid treatment.

PURPOSE To describe the clinical findings in a patient demonstrating recovery from nonparaneoplastic autoimmune retinopathy after a minimal course of steroid treatment. METHODS Clinical presentation was documented, and paraclinical tests were obtained using Humphrey automated perimetry for visual fields, Western blotting for antiretinal antibodies, and electroretinography for evaluation of rod and cone function. RESULTS Initial presentation revealed marked visual field deficits, electroretinographic dysfunction, and the presence of α-enolase autoantibodies. After a brief course of oral corticosteroids, the patient demonstrated improvement in visual fields, disappearance of α-enolase autoantibodies, partial recovery of the cone on-response, and complete recovery of the rod response. CONCLUSION This case is distinguished from previous reports by the rapidity and degree of recovery, the brevity of treatment required, and the unique electroretinographic recovery pattern with concomitant disappearance of α-enolase autoantibodies. These findings suggest a pathologic role for α-enolase autoantibodies in autoimmune rod bipolar cell dysfunction. Identification of other cases exhibiting such improvements and associated autoantibody activity may expand our understanding of nonparaneoplastic autoimmune retinopathy disease pathogenesis.

Retinotopic organization of the primary visual cortex before and after pharmacological treatment for a large prolactinoma with compression of the optic chiasm

Patients suffering from pituitary macroadenomas - pituitary tumors larger than 10mm - often have visual deficits, typically bilateral hemianopsia, because of chiasmal compression. Treatment of macroadenomas is usually successful, and thus such patients provide a unique opportunity for studying neuroplasticity in the human visual system and its consequences for vision. This case study focuses on patient BS, a 48-year-old man, who had a large prolactinoma, a common pituitary tumor, and, as a consequence, a severe visual field loss. We used functional magnetic resonance imaging (fMRI) to map the retinotopic organization of primary visual cortex (V1) of patient BS before and after successful treatment of his prolactinoma with cabergoline over the course of 13 months. In addition, we used the same fMRI protocol to examine the organization of V1 in a healthy age- and gender-matched control participant with normal vision. Humphreys perimetry was used to assess the integrity of the visual fields, before and after the completion of treatment for patient BS, and over two successive scans in the healthy control. The Humphrey field exam revealed significant visual improvement after treatment and this recovery was accompanied by substantial changes in V1 activation. Before the start of treatment, the amount of cortical tissue in V1 which was activated by the retinotopic stimuli was only 21% that of the healthy control participant. After treatment, the amount of activation normalized to approximately 90% of that of the control participant. The organization of retinotopic representations in V1 also normalized after treatment. These results illustrate that the visual system is capable of repair following conservative medical treatment, opening the door for assessing the effects of compression on different components of the optic nerve and tract. Meeting abstract presented at VSS 2015.

A comparison of hand- and foot-activated surgical tools in simulated ophthalmic surgery

A comparison of handand foot-activated surgical tools in simulated ophthalmic surgery In their article entitled “A comparison of handand footactivated tools in simulated ophthalmic surgery”, the authors suggest that handand foot-operated ophthalmic surgical skills can be practiced and assessed effectively using virtual reality surgical simulation. Surgical simulation training has developed into an extremely attractive teaching modality for training programs, as it allows for the development and practice of early surgical skills without risk of adverse patient outcomes. Although numerous surgical simulation modalities have been assessed and trialed, there is little in the ophthalmology literature to validate surgical simulation as a tool that directly leads to improved patient outcomes and safety. In recent years, a number of studies have been published showing improvements in basic ophthalmic surgical skill acquisition, but until recently there has been very little to demonstrate actual improvements in surgery outcomes in the operating room setting. In first reviewing the article, one might criticize the utility of its findings, given that the experimental protocol does not closely mimic real-life surgical scenarios. Having said that, the paper does in fact contribute to the ever-expanding knowledge base on ophthalmic surgical simulation and its use as a potentially valuable teaching tool. Proponents of surgical simulation do not suggest that it can replace actual surgery on human tissue, but rather offer it is a useful adjunct in surgical training, especially in the earlier formative years of surgical skill acquisition. Particularly with microsurgical techniques, time spent practicing basic techniques (for example: suturing