Reference #: ZIG-1016-122495
Submit Date: 03/14/2002 09:41:17-0500

Visual significance of yellow optical filters.

ABSTRACT:
In this study, optical lenses were formulated to remove wavelengths shorter than 450 nm from various environmental light sources. They were tested for their abillity to improve vision by preventing harmful and useless light from entering the eye, and to transmit nearly all visually useful wavelengths. A spectral colorimeter was used to determine the alterations of the transmission of mixed wavelengths of light caused by these yellow lenses. Further studies of how these lenses effect contrast vision in elderly and partially visually impaired human eyes were done. The results have shown that the yellow lenses adjusted the wavelengths of light reaching the spectral colorimeter from various environmental light sources. They removed short wavelength light (<450nm),but also transmitted from 500 to 600 n very efficiently. Studies of contrast vision in elderly subjects and those with early cataracts (primarily) suggested that the yellow lenses improved contrast vision appreciably. The findings show that an optical filter that can prevent short wavelength light from entering the eyes of elderly and visually compromised people has a positive influence on their vision

Keywords: contrast sensitivity, low vision, radiation damage, visual impairment

Reference #: HIR-1016-613325
Submit Date: 03/20/2002 02:17:44-0500

Effects of combined PDT and ionising radiation or hyperthermia on human glioma spheroids

ABSTRACT:
Although photodynamic therapy (PDT) has been used in the treatment of brain tumors since 1980, the results of clinical trials have been ambiguous due, in part, to the fact that, PDT has been given as single-shot, intraoperative treatment. Furthermore interactions with standard treatment modalities, such as ionizing radiation, or hyperthermia are poorly understood. In this study, a human glioma spheroid model was used to investigate the degree of interaction between these modalities.Spheroids were grown from a human grade IV GBM cell line. 5-Aminolevulinic acid (ALA) mediated PDT, radiation, hyperthermia, or combined treatments were carried out in bulk cultures. Following treatment, individual spheroids were placed into separate wells and monitored for growth.Gamma radiation and PDT interacted in a synergistic manner if both light and gamma radiation exceed threshold doses of approximately 25 J cm-2 and 8 Gy, respectively. Synergistic interactions were only observed below light dose rates of 25 mW cm-2. The degree of interaction appeared to be more pronounced if PDT was give prior to gamma irradiation but was independent of the time intervals investigated (1 and 24 h). Nuclear morphology changes consistent with both necrosis and apoptosis, following combined treatment was observed. Hyperthermia up to 47C gave no additional cytotoxic effects Interactions between necrotic and apoptotic pathways could play a role in the observed synergism. The decrease in hypoxic cell content in the spheroids following PDT could also enhance the cytotoxic effects of gamma irradiation.

Keywords: photodynamic therapy, brain tumors, ionizing radiation, apoptosis

Reference #: BER-1017-068747
Submit Date: 03/25/2002 08:03:51-0500

Mycosporine like amino acids as potential cosmetic UV agents?

ABSTRACT:
Mycosporine like amino acids (MAAs) e.g Mycosporine-glycine are thought to play an important role as UV screens in various organisms such as macroalgae, phytoplankton, cyanobacteria, corals and other primary and secondary consumers. For this reason MAAs or analogous structures appear to be potentially attractive as commercial UV agents to protect human skin. As only little is known about the stability of MAAs against light we investigated the photostability of two structural analogs, 2-Methoxy-5,5-dimethyl-3-piperidin-1-yl-cyclohex-2-enone (1) and 2-Methoxy-3-pentyl-cyclohex-2-enone (2). Photolysis of 1 or 2 in hexane led to complete decomposition of the MAA analogs. Isolation and characterization of the degradation products of 1 led to the unambiguous identification of six different photoproducts derived from Norrish type I and II reactions as well as reaction with singlet oxygen. The degradation of 2 upon irradiation was less specific. However we were still able to unambiguously identify three photoproducts.

Keywords: mycosporine like amino acids, UV filter, Photochemistry

Reference #: POG-1016-488820
Submit Date: 03/18/2002 15:31:26-0500

Photodynamic therapy with verteporfin increases tumor pO2 and enhances the effect of radiation therapy in the RIF-1 tumor

ABSTRACT:
Photodynamic therapy or control treatment was applied to animals bearing the RIF-1 tumor, by the intraperitoneal injection of either verteporfin or saline (for control) at 3 hours prior to light. Some of the tumors were also previously injected with a 200 micron diameter piece of charcoal at a depth of 1-3 mm into the tumor to measure oxygen partial pressure (pO2) by electron paramagnetic resonance oximetry. The animals given PDT treatment showed a significant rise in tumor pO2 from 2.8 mmHg up to an average of 15.6 mmHg (n=5 animals, p-value = 0.04), indicating a significant rise in tumor oxygenation immediately following therapy. The pO2 decayed back down to pre-treatment levels after treatment. Combined radiation and PDT treatment was studies in a second section of animals, to examine the potential for this increased pO2 providing an enhanced effect of the radiation therapy because of the excess available oxygen. An optical irradiation of 100 J/cm2 was given over 12 minutes, with x-ray irradiation of 10 Gy dose using approximately 300 keV delivered in 3 minutes from a Pantak Therapax 300 Orthovoltage irradiator. The treatment effect was assayed by calculation of the tumor volume, and the average regrowth delay for the tumor to reach twice the treatment volume was calculated relative to the control group. The re-growth delay for radiation alone and PDT alone were 2.7 +/- 1.6 days (n=5 animals) and 3.2 +/- 1.7 days (n=6), respectively with their standard error values. The re-growth delay for the group given radiation followed by PDT was 5.4 +/- 1.4 days (n=7), and the value for the final group where PDT was given during the radiation therapy was 8.1 +/- 1.5 days (n=7). This latter increase in tumor regrowth delay indicates a potentially synergistic effect of radiation therapy, and indicates a statistically significant increase in treatment effect beyond the previous treatment group (p-value = 0.049).

Keywords: radiation, synergistic, epr, PDT

Reference #: KIM-1016-408400
Submit Date: 03/17/2002 15:21:09-0500

Monitoring tissue oxygenation and viability by non-invasive spectrally resolved reflectance imaging as applied to chlorin e₆-based photodynamic therapy

ABSTRACT:
Spectral imaging (SI) provides spectral and spatial information that enables monitoring hemoglobin profiles in living tissue. Balb/c mice with C26 colon carcinoma (5-7 mm diameter) implanted in the back were anesthetized. Dorsal skin (4x4 cm) was elevated as a lateral based fascial-cutaneous flap. Three hours after administration of chlorin e₆ (5 mg/kg), the tumor area in the skin flap was irradiated (at 650±20 nm, fluence rate 100 mW/cm², fluence 60-180 J/cm²) and photodynamic response (PDR) was measured. A novel spectral image-analysis system was used for in vivo reflectance imaging with ±0.1 mm spatial resolution. Each pixel of the CCD image collects an interferogram, which is Fourier transformed to give the spectrum of that pixel. Hemoglobin/oxyhemoglobin (Hb/HbO₂) spectra in vivo were acquired in the region 450-850 nm at a spectral resolution of 5 nm. False-color mapping (in the region 550-650 nm) was applied for visualization of tissue oxygenation. Vital microscopy of blood vessels and tumor oxygenation were investigated in the skin flap model. Dependent on the fluence, PDR was manifested by distinct hemodynamic and morphological alterations, starting with thrombi formation, proceeding through multiple embolization, constriction/dilation, to arteriolar occlusion and venous stasis. Below fluence threshold (<15 J/cm² when irradiating blood vessels and <60 J/cm² when irradiating tumors) PDR effects were transient: emboli disappeared from irradiated veins and blood flow recovered. Spectrally resolved images of tumors, and corresponding pixel spectra, showed that the HbO₂ absorption spectrum (with peaks at 572 and 579 nm) had changed due to PDT to that of Hb (with peaks at 576 and 760 nm), indicating acute hypoxia. Our results demonstrate, for the first time, that SI can serve as a diagnostic tool (not limited to PDR) for measuring non-invasively oxygen saturation in tissue and for real time monitoring of tissue viability.

Keywords: hemoglobin/oxyhemoglobin , hypoxia, microcirculation, photodynamic response

Reference #: GOD-1016-749184
Submit Date: 03/21/2002 15:30:49-0500

Childhood UV Doses: Reality versus Myth

ABSTRACT:
Since 1986, people were told they got about 80% of their lifetime UV dose by the age of 18. This myth originated from a paper that concluded diligent use of sunscreen (SPF 15 or higher) during the first 18 years of life could reduce the lifetime incidence of non-melanoma skin cancers by 78%. This conclusion, combined with the fact that squamous cell carcinoma (SCC) is dependent on the cumulative dose, mistakenly led others to believe people get about 80% of their lifetime UV dose by the age of 18. However, analysis of actual exposure data shows that people get less than 25% of their lifetime dose by the age of 18. Surprisingly, it is the older people, especially the men, who get the highest percent of their lifetime doses after the age of 40. This reality appears to be true worldwide because America, Australia, England and the Netherlands all find similar exposure patterns. Unfortunately, it is possible that this myth might have contributed toward increasing the incidence of skin cancers, which are now over 1 million cases/yr. in the US alone, possibly because adults assumed they no longer had to worry about getting exposed to UV radiation. However, it is known that SCC is dependent on the cumulative dose, and although childhood exposures appear to contribute more toward melanoma and basal cell carcinoma, these cancers are also somewhat dependent on the cumulative dose. Thus, fair-skinned people of all ages should protect themselves from getting too much UV radiation.

Keywords: Cancer, Children, Environment, Risk

Reference #: EL-1017-010103
Submit Date: 03/24/2002 16:29:50-0500

UV Visible Radiation Hazards To Lens And Aqueous Humour Protein of the Rabbits' Eye

ABSTRACT:
The international interest on the biological effects of artificial light on human eyes is increasing with the growing illumination technology and manufacture of television studios and theaters. In the present work, the effect of artificial light prolonged exposures on the eyes of New-Zealand rabbits (500, watt), for periods of 555, 1110 and 1666 hours respectively was studied. The animals were exposed to light at a rate of 15 hours daily with the average illumination 470 Lux/m2 at the centre of the cage-was studied .Total soluble protein content, refractive index, molecular weight distribution, electrophoretic mobility of lens protein and aqueous humour for normal and exposed animals were investigated. The results showed a marked decrease in total soluble protein content with increasing the exposure time for both lens and aqueous humour. Moreover, the molecular weight distribution showed mainly a shift towards low molecular weight. Also the electrophoretic mobility and the refractive index data showed a significant decrease which was a function of exposure time. In conclusion eye must be protected against such optical radiation as well as avoidance of prolonged exposure time.

Keywords: UV, aqueous humour, lens

Reference #: ZUC-1016-734306
Submit Date: 03/21/2002 10:53:04-0500

Near-UV/blue light - induced fluorescence in the human lens: potential veiling glare interference with visual function.

ABSTRACT:
Irradiation of the ocular lens of numerous species (including primates) by near-UV or short visible wavelengths induces a blue-green fluorescence which can be a source of intraocular veiling glare. Wavelengths longer than the ~365 nm lens absorption peak induce progressively weaker but also progressively more red-shifted fluorescence emission. The more red-shifted emission implies a higher luminous efficiency and, in fact, earlier studies in this laboratory have demonstrated that the lens fluorescence in the non-human primate yields an approximately constant luminous efficiency when excited by equal radiant exposures over the wavelength range from 360 to 430 nm. Now, with the recent development and projected widespread use of "blue" diode lasers, a concern arises for the potential for disruption of visual function during critical performance tasks (e.g., nighttime driving), especially during military engagements. The current study quantitates the fluorescence intensity induced in the human lens, both in terms of radiance and luminance, as a function of exciting light intensity, excitation wavelength and subject age. The data will be shown to imply that accidental or deliberate exposures to near-UV/blue wavelength sources at "safe" exposure levels (reference existing laser safety standards) can induce a veiling glare intense enough to degrade visual performance. In an ongoing study, measurements in human subjects are employing an adaptive procedure to determine changes in test stimuli detection thresholds in the presence of lens fluorescence veiling glare. Progress on this performance test study will also be summarized.

Keywords: lens fluorescence, blue diode laser, veiling glare, visual performance

Reference #: GOR-1016-647083
Submit Date: 03/20/2002 11:16:01-0500

UV radiation and the snow alga Chlamydomonas nivalis

ABSTRACT:
The snow alga Chlamydomonas nivalis lives at high altitude on persistent summer snow fields, at or below freezing and is exposed to high levels of both visible and UV radiation. The red carotenoid astaxanthin screens the centrally-located chloroplast, approximately halving the PAR reaching the photosynthetic apparatus and presumably reducing photodamage. The purposes of this investigation were to evaluate the UV environment of this alga in situ and to localize the organism's potentially protective UV-screening materials. Our field site was a persistent SSE-facing snow field at 3250 m in the Rocky Mountains west of Laramie, WY. We measured 300-420 nm radiation penetrating the snow using an Ocean Optics miniature spectrometer with a cosine-corrected sensor; we also measured visible irradiance (cosine-corrected sensor) and fluence rate (spherical sensor) to estimate how radiation might be amplified by scattering in the snow. We could detect UVB (300-320 nm) 2 cm deep in the snow and UVA (320-400 nm) at depths up to 8 cm. Transmittance for UVA was about 20% at 4 cm, and a few percent at 8 cm. UV fluence rate incident on an algal cell would probably be increased several-fold over measured irradiance levels because of light scattering. We used a microscope with a quartz condenser and objective lens to measure how much UV was transmitted through various cellular regions. Cells appeared to absorb almost all the visible light and UV radiation below 550 nm. Experiments with plasmolyzed cells and with broken cells showed that absorption within the UV occurred in the cytoplasm and not in the cell walls. Spectra of an acidified methanolic extract showed an absorbance maximum at 335 nm, that was not attributable to astaxanthin.

Keywords: Clamydomonas nivalis, ultraviolet, snow

Reference #: H-1015-945152
Submit Date: 03/12/2002 08:38:31-0500

Effects of solar radiation on photosynthesis in macroalgae

ABSTRACT:
Macroalgae are major biomass producers in marine aquatic ecosystems. Living in the intertidal zone, they are exposed to drastically changing irradiances. Since most of the species are sessile, they experience a complicated pattern of irradiances controlled by the diurnal changes and the superimposed tidal rhythm. The thalli can adapt to the widely changing irradiances by several protective mechanisms. One adaptation mechanism is photoinhition, which is a high light-induced reduction of the photosynthetic quantum yield. Photoinhibition can be monitored by measuring photosynthetic oxygen production or by following chlorophyll fluorescence parameters using a pulse amplitude modulated (PAM) fluorometer. During exposure to intense solar radiation photosynthetic pigment contents either decreases or increases. Another protective mechanism against excessive radiation is the xanthophyll cycle which relies on the thermal dissipation of excess excitation energy preventing the formation of singlet oxygen in the chloroplasts. A third mechanism is the production of UV absorbing pigments such as mycosporine-like amino acids (MAAs). The roles and mechanisms of these protective strategies are discussed for several macroalgae from different geographic locations.

Keywords: macroalgae, ecophysiology, solar radiation, mycosporine-like amino acids

Reference #: BLA-1014-664122
Submit Date: 02/25/2002 10:50:44-0500

Varying levels of dietary vitamins E and C does not ameliorate -carotene exacerbation of UV-carcinogenesis

ABSTRACT:
-Carotene is a strong singlet oxygen quencher and, under most conditions, exhibits strong antioxidant properties. Based on these properties, and a number of epidemiological studies, it was suggested that an above average intake of the carotenoid might reduce cancer risk. Earlier studies had found that -carotene, when added to commercial closed-formula rodent diets, provided significant photoprotection to UV-carcinogenesis. However, clinical trials found that -carotene supplementation evoked no change in incidence of nonmelanoma skin cancer and that smokers suffered a significant increase in lung cancer incidence. Further, recent studies, employing -carotene-supplemented semi-defined diets, not only failed to find a photoprotective effect, but significant exacerbation of UV-carcinogenic expression resulted. Based on the relative electron transfer rate constants for interactions between -carotene, -tocopherol, and vitamin C, a mechanism was proposed for the repair of -carotene radical cation, a strongly oxidizing radical resulting from -carotene interactions with many oxidizing species. It was theorized that vitamin C repaired the carotenoid radical cation. As mice have no nutritional requirement for vitamin C and smokers are known to exhibit low levels of the vitamin, it was suggested that differences in the relative levels of vitamin C in closed-formula rations (no vitamin C) in which photoprotection occurred, and semi-defined diets (containing vitamin C) in which exacerbation resulted, might account for the differences in response. Hairless mice were fed -carotene-supplemented semi-defined diets containing varied levels of -tocopherol and vitamin C (reflecting levels found in closed-formula rations) and subjected to a UV-carcinogenesis protocol. Increasing levels of -tocopherol and vitamin C did not ameliorate -carotene exacerbation of UV-carcinogenesis. Nor did elimination of vitamin C from the diet. It is concluded that the photoprotective, or non-injurious, effect of -carotene might depend on interaction with other dietary factors that are absent, or present in ineffectual concentrations, in the semi-defined diet. Those factors could be other carotenoids, their isomers, or some yet unidentified phytochemicals.

Keywords: -carotene, UV-carcinogenesis