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Mauricio Maia

Publications and source records attributed to Mauricio Maia.

9 recordsLinked to original sources
PubMed2007

Effect of oxygenated intraocular irrigation solutions on the electroretinogram after vitrectomy.

PURPOSE: To investigate the effect of oxygenated intraocular irrigating solutions on electroretinograms (ERGs) for postvitrectomy rabbits. METHODS: Eight groups of five rabbits each underwent pars plana vitrectomy on the right eye; the left eye of each rabbit served as control. The intraocular irrigating solutions were balanced salt solution (BSS), BSS-plus, BSS + oxygen (BSS + O2), BSS-plus + O2, and combinations of each with the addition of endoillumination (L). All animals were evaluated by single-flash scotopic electroretinography on the operated and nonoperated eyes before surgery and at 1 hour, 1 day, 1 week, and 1 month after surgery by an unmasked observer. The main outcome measures were dark-adapted b-wave amplitudes of operated eye/nonoperated eye ratios. The results for the different groups were compared by analysis of variance. RESULTS: Mean dark-adapted b-wave amplitudes of operated eye/nonoperated eye ratios +/- SD for BSS-plus and BSS-plus + O2 before surgery and 1 hour, 1 day, 1 week, and 1 month after surgery were 1.01 +/- 0.09, 0.50 +/- 0.11, 0.95 +/- 0.11, 0.97 +/- 0.11, and 0.99 +/- 0.08 and 0.98 +/- 0.08, 0.59 +/- 0.10, 0.92 +/- 0.06, 0.97 +/- 0.08, and 0.97 +/- 0.10, respectively. At both 1 hour and 1 day after surgery, rabbits treated with BSS-plus + O2 had an earlier b-wave return to baseline findings, but the differences were not statistically significant (P > 0.05). Mean dark-adapted b-wave amplitudes of operated eye/nonoperated eye ratios +/- SD for BSS and BSS + O2 before surgery and 1 hour, 1 day, 1 week, and 1 month after surgery were 1.02 +/- 0.10, 0.47 +/- 0.09, 0.77 +/- 0.07, 0.89 +/- 0.07, and 0.89 +/- 0.07 and 1.02 +/- 0.06, 0.62 +/- 0.16, 0.94 +/- 0.09, 0.97 +/- 0.08, and 0.96 +/- 0.06, respectively. One hour and 1 day after surgery, ERG readings for rabbits treated with BSS + O2 exhibited a statistically significantly earlier return of ERG voltage to baseline values compared with both BSS and BSS + L (P = 0.05 and P = 0.02, respectively). One day after surgery, rabbits treated with BSS alone had the lowest ERG ratios. One week and 1 month after surgery, for all solutions tested other than BSS, ERG values were within normal limits. CONCLUSION: The use of oxygenated solutions appears to affect ERG readings after pars plana vitrectomy. Further studies to evaluate the role of oxygenated solutions in different vitreoretinal surgical procedures are warranted.

Acetates↗
PubMed2006

Electrical stimulation in normal and retinal degeneration (rd1) isolated mouse retina.

Stimulus threshold and response latencies were measured for electrically elicited retinal ganglion cell responses in retina isolated from the eyes of normal and retinal degenerate (rd1) mice. Stimulation of the ganglion cell-side in normal retina yielded a significantly lower mean threshold and shorter latency when compared with stimulation of the photoreceptor side in normal retina. The latency of the ganglion cell-side stimulation in normal retina also proved to be significantly shorter than the latency for stimulation of the ganglion cell side in rd1 retina. Thus both the electrode positioning as well as the health of the retinal tissue play a role in the stimulating current required to elicit a retinal response.

Animals↗
PubMed2006

Electrical stimulation in isolated rabbit retina.

Experiments were conducted to assess the effect of stimulating electrode parameters (size, position, and waveform shape) on electrically elicited ganglion cell action potentials from isolated rabbit retina. Thirty-eight isolated rabbit retinas were stimulated with bipolar stimulating electrodes (either 125 or 25 microm in diameter) positioned on either the ganglion or the photoreceptor side. Recording electrodes were placed between the optic disc and the stimulating electrodes. Cathodic-first, biphasic, current waveforms of varying pulse durations (0.1, 0.5, 1 ms) were used. For the four conditions tested (125-electrode and 25-microm electrode, ganglion cell, and photoreceptor positions) threshold currents ranged from 6.7 to 23.6 microA, depending on location and pulse duration. With 1-ms pulse duration, no statistically significant difference was seen between threshold currents when either size electrode was used to stimulate either the ganglion cell side or the photoreceptor side. For all groups, the threshold currents using the 1-ms pulse were lower than those using 0.1 ms, but the 0.1-ms pulses used less charge. These experiments provide a number of valuable insights into the relative effects of several stimulation parameters critical to the development of an implanted electronic retinal prosthesis.

Action Potentials↗
PubMed2004

Recommendations for the design and optimization of immunoassays used in the detection of host antibodies against biotechnology products.

Most biopharmaceutical therapeutics elicit some level of antibody response against the product. This antibody response can, in some cases, lead to potentially serious side effects and/or loss of efficacy. Therefore, the immunogenicity of therapeutic proteins is a concern for clinicians, manufacturers and regulatory agencies. In order to assess immunogenicity of these molecules, appropriate detection, quantitation and characterization of antibody responses are necessary. Inadequately designed antibody assays have led to the hampering of product development or, during licensure, post-marketing commitments. This document provides scientific recommendations based on the experience of the authors for the development of anti-product antibody immunoassays intended for preclinical or clinical studies. While the main focus of this document is assay design considerations, we provide scientific focus and background to the various assay performance parameters necessary for developing a valid assay. Sections on assay performance parameters, including those that appear in regulatory guidances, are contained in this manuscript.

Antibodies↗
PubMed2004

Effects of intravitreal indocyanine green injection in rabbits.

PURPOSE: To report the clinical, electrophysiologic, and histologic findings of different concentrations of indocyanine green (ICG) injected into the vitreous cavity of rabbit eyes. METHODS: Forty-two rabbits underwent intravitreal injection of 0.1 mL of ICG in three different concentrations: 0.5 mg/mL (250 mOsm), 5 mg/mL (270 mOsm), and 25 mg/mL (170 mOsm). Fellow eyes were injected with 0.1 mL of balanced salt solution. Biomicroscopy, ophthalmoscopy, electroretinography, fluorescein angiography, and histologic evaluation were performed. RESULTS: Eyes injected with 0.5 mg/mL of ICG showed b-wave latency delay on the first day after injection. Eyes injected with 5 mg/mL of ICG showed b-wave latency delay and decreased b-wave amplitude on the first and seventh days after injection; delayed a-wave latency on the first day after injection was also observed. Eyes injected with 25 mg/mL of ICG showed b- and a-wave amplitude and latency abnormalities during the entire follow-up. Direct correlation of increasing retinal edema proportional to the progressively increasing ICG concentrations was shown on histologic evaluation. CONCLUSION: Intravitreal ICG injection in rabbit eyes may impair retinal function and morphology proportional to the progressively increasing ICG dosages.

Animals↗
PubMed2004

Effects of indocyanine green injection on the retinal surface and into the subretinal space in rabbits.

PURPOSE: To evaluate the effects of indocyanine green (ICG) injection on the retinal surface and into the subretinal space of rabbit eyes. METHODS: Twenty-two Dutch-belted rabbits underwent two-port vitrectomy followed by injection of ICG (5 mg/mL) on the retinal surface and into the subretinal space. Balanced salt solution (BSS) was also injected subretinally. The locations where ICG was delivered (both epiretinal and subretinal) were exposed to light from an endoilluminator for 7 minutes. The animals were examined at 1, 7, and 14 days after surgery. The eyes were studied by fluorescein angiography as well as light and electron microscopy. RESULTS: No damage was observed after epiretinal ICG injection, but subretinal ICG injection resulted in damage to the outer nuclear layer, photoreceptor inner and outer segments, and retinal pigment epithelium. This damage was more severe with longer follow-up. Control experiments without ICG, in which balanced salt solution was injected into the subretinal space or light was delivered on the epiretinal surface, demonstrated only damage to the photoreceptor outer segments. CONCLUSION: Subretinal delivery of ICG (5 mg/mL) in rabbits induces retinal pigment epithelium, photoreceptor inner and outer segment, and outer nuclear layer damage. These mechanisms of damage may explain the retinal pigment epithelium changes that are sometimes seen after ICG-assisted internal limiting membrane peeling in humans.

Animals↗
PubMedDate not supplied

Retinal prosthesis for the blind.

Most of current concepts for a visual prosthesis are based on neuronal electrical stimulation at different locations along the visual pathways within the central nervous system. The different designs of visual prostheses are named according to their locations (i.e., cortical, optic nerve, subretinal, and epiretinal). Visual loss caused by outer retinal degeneration in diseases such as retinitis pigmentosa or age-related macular degeneration can be reversed by electrical stimulation of the retina or the optic nerve (retinal or optic nerve prostheses, respectively). On the other hand, visual loss caused by inner or whole thickness retinal diseases, eye loss, optic nerve diseases (tumors, ischemia, inflammatory processes etc.), or diseases of the central nervous system (not including diseases of the primary and secondary visual cortices) can be reversed by a cortical visual prosthesis. The intent of this article is to provide an overview of current and future concepts of retinal and optic nerve prostheses. This article will begin with general considerations that are related to all or most of visual prostheses and then concentrate on the retinal and optic nerve designs. The authors believe that the field has grown beyond the scope of a single article so cortical prostheses will be described only because of their direct effect on the concept and technical development of the other prostheses, and this will be done in a more general and historic perspective.

Blindness↗