29 - Ocular Photobiology, 2
Florida 1 10:00 - 12:00
|Chair(s): David Sliney|
10:00 What are the Spectral Limits of Visual Radiation? David H. Sliney*, Johns Hopkins Bloomberg School of Public Health
; David Sliney
Abstract: Historically, the concept of the nature of light has endured some controversies - from the ancient Greek concept that light originated in the eye, to Newton's corpuscular theory, on to wave-particle duality. However, the true extent of the visible spectrum has not been possible to standardize. The CIE defines infrared and ultraviolet photobiological spectral bands (e.g., UV-A and IR-B), but the CIE recognizes the variable spectral limits of vision. The limits of visibility really extend from about 310 nm in the ultraviolet (in youth) to about 1100 nm in the near-infrared, but depend very much on the radiance, that is, "˜brightness' of the light source. Recent suggestions that infrared vision occurs from two-photon isomerization are based only on non-linear effects from ultra-short pulses.
10:20 Identifying Novel Fluorophores in Human RPE Melanolipofuscin MC Vega*, Northern Illinois University
; ER Gaillard, Northern Illinois University
Abstract: Age related macular degeneration (AMD) is a debilitating and poorly understand retinal degenerative disease that causes progressive loss of central vision. The retinal pigment epithelium (RPE) cells are critical for maintaining the photoreceptors and retinal tissue. Auto-fluorescent pigment granules, known as melanolipofuscin, accumulate in RPE cells with age. The current study aims to identify novel fluorophores in human RPE melanolipofuscin which may lead to the development of new diagnostic techniques for the early detection of age related macular degeneration. Human RPE melanolipofuscin is extracted from human donor eyes as previously described by Feeney-Burns and subjected to a Folch extraction. The organic soluble portion of melanolipofuscin is collected, dried under argon gas, and reconstituted in HPLC grade methanol for analysis using high performance liquid chromatography tandem mass spectrometry (LC/MS/MS) coupled to a fluorescence detector (Surveyor LC with PDA, Thermo Finnigan LCQ Advantage MS, Surveyor FL). Fluorescence detection and tandem mass spectrometry data are analyzed for the identification and structure elucidation of the fluorescent components of human RPE melanolipofuscin. The fluorophore, A2E, has been observed as a component of human RPE melanolipofuscin. The presence of additional fluorophores has been confirmed. Tandem mass spectrometry analysis of these fluorophores has provided structural information for these vitamin A derivatives. Human RPE melanolipofuscin is observed to accumulate in the RPE with age and this accumulation has been suggested to closely correlate with the onset of AMD. Fluorescent components of melanolipofuscin have been identified in human melanolipofuscin extracts. These fluorophores may lead to the development of a new fluorescence based diagnostic technique for the early detection of AMD.
10:40 Photochemical/spectroscopic studies in turbid and scattering media KM Solntsev*, OLIS, Inc.
; P Boxrud, OLIS, Inc.; JA Lorenz, OLIS, Inc.; RJ DeSa, OLIS, Inc.
Abstract: The talk is dedicated to the scientific research in business environment. The research at OLIS involves the development and utilization of various state or the art optical spectrometers. This privately-held American company continues to serve the biophysical, biochemical, and bioenergetics fields with absorbance, fluorescence, and circular dichroism spectroscopy for sophisticated research and routine measurements. Our newest product line " the CLARiTY series " has eliminated the previously insurmountable barrier to accurate absorbance spectroscopy of live, whole, particulate, aggregated, turbid samples. Few sample cases will be discussed. They involve steady-state and time-resolved measurements of redox reaction in cell suspension, photoswitching of MOFs, monitoring vitamin A delivery & uptake in intact frog eye retina, and many more. Finally, an active CLARiTY spectrophotometer will be demonstrated and the audience will have to chance to take the absorbance spectra of their own samples. Bring your own turbid sample! OLIS website: http://olisweb.com/ Dr. Solntsev's website at GaTech: http://ww2.chemistry.gatech.edu/solntsev/
11:00 Evaluating the Influence of Melanin in Cytokine Secretion in Photo-stressed Retinal Pigment Epithelial Cells SM Yacout*, Northern Illinois University
; SF Elsawa, Northern Illinois University; ER Gaillard, Northern Illinois University
Abstract: The retinal pigment epithelium (RPE) is a monolayer of post-mitotic cells that maintain retinal health and preserve vision. It is well known that these cells regulate ocular immune response by expressing and secreting cytokines and by presenting antigens. A factor that may influence the role of RPE cells in immune response is pigmentation. While the function of RPE melanin is not fully understood, experimental evidence suggests the pigment behaves as a photo-protectant and antioxidant. Given the beneficial nature of RPE melanin, it is possible that this pigment also impacts retina immune response. Of particular interest is the photo-stress elicited immune response in the aged human retina. In this study tissue culturing was utilized and UV exposure to the retina with time was modeled by exposing human cell line ARPE-19 to UV-C radiation. Cells were pigmented by phagocytizing bovine melanin and unpigmented cells were used as a control. Secretion of the cytokine interleukin-6 (IL-6) was monitored using an enzyme-linked immunosorbent assay (ELISA) and gene expression was detected using PCR. Elevated IL-6 secretion was observed in pigmented cells under dark and photo-stress conditions compared to unpigmented dark control cells. Additionally, UV-C irradiation resulted in an increase in IL-6 secretion in pigmented cells compared to irradiated unpigmented cells. It is suggested that inflammation contributes to age-related atrophy of the retina and degradation of melanin with time may result in ocular disease such as age-related macular degeneration.
11:20 Syntonic Phototherapy - an Introduction R Gottlieb*, College of Syntonic Optometry
Abstract: Syntonic phototherapy uses low-level, non-coherent, non-polarized, broad-band filtered light delivered through the eyes. The eyes permit nearly direct, non-invasive application of light to the reservoir of blood circulating through the retina as well as to non-visual, retinal photoreceptor systems that signal circadian and other brain centers. This input is thought to rebalance and resynchronize poorly functioning homeostatic, autonomic and circadian causes of visual weakness. Syntonics is especially effective in treating brain injury, headache, strabismus, eyestrain, eye pathology, and attention and learning dysfunctions. Patients typically look at prescribed colors for 20-minute periods, several times a week for twenty sessions. Special visual field, pupil, and binocular vision tests, along with patient symptoms and medical history determine the syntonic prescription, progress and final outcome measures. Presentation will include discussion of kinetic and color visual fields, pupil fatigue, theoretical and historical background, and will review cases showing initial and post-treatment data and case resolution. Optometrists, ophthalmologists and psychologists in many countries currently practice this 85 year-old therapy.
11:40 Measuring Absorption Coefficients in Human Retinal Pigmented Epithelium Cells and Subcellular Fractions JC Wigle*, Air Force Research Laboratory
; MT Cone, Texas A&M University; JD Mason, Texas A&M University; E Figueroa, Texas A&M University; BH Hokr, Texas A&M University; JN Bixler, Texas A&M University; CC Gonzales, Air Force Research Laboratory; BA Rockwell, Air Force Research Laboratory; VV Yakovlev, Texas A&M University; ES Fry, Texas A&M University
Abstract: Retinal pigmented epithelium (RPE) is the tissue where most of the light entering the eye is absorbed and, therefore, the site of laser injury for wavelengths of 400-1200nm. An in vitro model of this interaction, using an immortalized human RPE cell line, was developed to study light-tissue interactions at these wavelengths. We have previously shown that an induced resistance to a lethal pulse of 2-µm laser radiation occurs in these cells when exposed to low levels of red light (photobiomodulation, PBM) 24h prior to the laser challenge (adaptive response). While "downstream" physiological effects have been extensively studied, little is known about the initiation of the cascade which is hypothesized to start with light absorption by the mitochondria. But true light absorption by the mitochondria has never been measured because cells and organelles in suspension have very large scattering cross sections compared to absorption cross sections. Because of this, "linear" absorption measurements (intensity of light before and after it passes through a sample) overestimate true absorption because these values include losses due to scattering, for which there is no correction. However, photon absorption is essential for PBM and, since light-tissue interaction models also use absorption coefficients to predict laser bioeffects, we measured absorption coefficients of human RPE cells and subcellular components. The technique we used is based on cavity ring-down spectroscopy (CRDS), but the traditional mirrored cavity is replaced with a high-reflectivity integrating cavity which prevents scattered light from escaping. So integrating cavity ring-down spectroscopy (ICRDS) provides a true, direct measurement of absorption. At wavelengths of 400-700 nm absorption coefficients are 7 to 85-fold lower than corresponding attenuation coefficients, as a function of increasing wavelength, and the mitochondria absorption coefficients are dependent upon their oxidation state.