Protective effect of light emitting diode phototherapy on fluorescent light induced retinal damage in Wistar strain albino rats.

BACKGROUND: Artificial light at night alters retinal physiology. Several studies have shown that light emitting diode phototherapy protects the retina from the damaging effects of acute light exposure. OBJECTIVE: The aim of this study has been to elucidate the protective effects of 670 nm LED light on retinal damage induced by chronic fluorescent light in Wistar rats. METHODS: Male Wistar albino rats were divided into four groups: group 1 were control (CL), group 2, 3 and 4 were exposed to fluorescent light (FL), LED preexposure+fluorescent light exposure (LL) and only LED light exposure (OL) respectively. All animals were maintained in their specific exposure regime for 30 days. Fluorescent light of 1800 lx was exposed between 8 pm to 8 am. Rats were exposed to therapeutic LED light of 670 nm of 9 J/cm2 at 25 mW/cm2 for 6 min duration. Histopathological changes in the retina were studied. RESULTS: Animals of the FL group showed a significant reduction in the outer nuclear layer thickness and cell count in addition to the total thickness of the retina. LL group which were exposed to 670 nm LED prior to exposure to fluorescent light showed a significant decrease in the degree of damage. CONCLUSIONS: 670 nm LED light preexposure is protective to retinal cells against fluorescent light-induced damage.

Abnormal lateral geniculate nucleus and optic chiasm in human albinism.

Our objective was to measure how the misrouting of retinal ganglion cell (RGC) fibers affects the organization of the optic chiasm and lateral geniculate nuclei (LGN) in human albinism. We compared the chiasmal structures and the LGN in both pigmented controls and patients with albinism by using high-resolution structural magnetic resonance imaging (MRI). We studied 12 patients with oculocutaneous albinism and 12 age-matched pigmented controls. Using a 3T MRI scanner, we acquired a T1 -weighted three-dimensional magnetization-prepared rapid gradient-echo (MPRAGE) image of the whole brain, oriented so that the optic nerves, chiasm, and tracts were in the same plane. We acquired multiple proton density-weighted images centered on the thalamus and midbrain, and averaged them to increase the signal, enabling precise manual tracing of the anatomical boundaries of the LGN. Albinism patients exhibited significantly smaller diameters of the optic nerves, chiasm and tracts, and optic chiasm and LGN volume compared with controls (P < 0.001 for all). The reductions in chiasmal diameters in the albinism compared with the control group can be attributed to the abnormal crossing of optic fibers and the reduction of RGCs in the central retina. The volume of the LGN devoted to the center of the visual field may be reduced in albinism due to fewer RGCs representing the area where the fovea would normally lie. Our data may be clinically useful in addressing how genetic deficits compromise proper structural and functional development in the brain.

Abortifacient activity of Plumeria rubra (Linn) pod extract in female albino rats.

To evaluate the potential abortifacient activity of the aqueous, alcohol, ethyl acetate and chloroform extracts of P. rubra pod in female albino rats 50, 100 and 200 mg/kg body weight doses of each extract were administered from day 11 to 15 of pregnancy and animals were allowed to go full-term. The phytochemical screening revealed the presence of alkaloids, flavonoids, simple phenolics, steroids, tannins and saponins. Clinical toxicity symptoms such as respiratory distress, salivation, weight loss, dull eyes, diarrhea, and change in the appearance of fur as well as mortality were not observed in the animals at any period of the experiment. All the four extracts of P. rubra pods exhibited abortifacient activity (8-100%). The extracts significantly reduced the number of live fetuses, whereas the resorption index and post implantation losses increased significantly. The % of abortion was found to be highest (100%) with 200 mg/kg dose of alcoholic extract of P. rubra pods.

Ameliorative role of atorvastatin on methionine-induced hyperhomocysteinemia and hematological changes in albino rats.

Methionine (1g/kg, po) administration to pathogenic control rats for 30 days significantly increased the levels of homocysteine, total cholesterol (TC), low density lipoprotein (LDL-C), very low density lipoprotein (VLDL-C) and triglycerides (TGs) and decreased the levels of high density lipoprotein (HDL-C) in serum. Hematological observations of the peripheral blood smears of pathogenic rats fed with methionine also showed crenation of RBCs cell membrane and significant increase in total leukocyte count, differential leukocyte count and platelet counts with significant decrease in the mean hemoglobin levels as compared to vehicle control rats. Administration of atorvastatin (0.2 mg/kg/po) to hyperhomocysteinemic rats significantly decreased the levels of homocysteine, TC, TGs, LDL-C and VLDL-C and increased the levels of HDL-C in serum. The present results provide clear evidence that oral treatment with atorvastatin exhibit homocysteine and lipid lowering activity and also reversal of hematological changes induced by methionine in albino rats.

Organization of the visual cortex in human albinism.

In albinism there is an abnormal projection of part of the temporal retina to the visual cortex contralateral to the eye. This projection, together with the normally routed fibers from nasal retina, provides a cortical hemisphere with visual input from more than the normal hemifield of visual space. In many mammalian models of albinism, a possible sensory mismatch in the visual cortex is avoided either by reorganization of the thalamocortical connections to give the abnormal input an exclusive cortical representation, or by the abnormal input being substantially suppressed. In this study we examine, with fMRI, how the human visual cortex topographically maps its input in albinism. We find that the input from temporal retina is not substantially suppressed and forms a retinotopic mapping that is superimposed on the mapping of the nasal retina in striate and extrastriate areas. The abnormal routing of temporal fibers is not total, with the line of decussation shifting to between 6 and 14 degrees into temporal retina. Our results indicate that the abnormal input to visual cortex in human albinism does not undergo topographic reorganization between the thalamus and cortex. Furthermore, the abnormal input is not significantly suppressed in either striate or extrastriate areas. The topographic mapping that we report in human does not conform, therefore, to the commonly observed patterns in other mammals but takes the form of the "true albino" pattern that has been reported rarely in cat and in the only other individual primate studied.

Differences in the retinohypothalamic tract in albino Lewis versus brown Norway rat strains.

Differences in sleep-wake patterns in response to light-dark stimulation have been observed between albino Lewis and pigmented Brown Norway strains of rats, which may be associated with albinism. Since several anatomical differences have been demonstrated in the visual pathways of albino and pigmented mammals, the present study was undertaken to determine whether additional differences in visual pathways of these rat strains exist that might account for their behavioral differences. Using anterograde tracing techniques and image analysis, we have investigated the retinal projections of Lewis and Brown Norway rats. Our results demonstrate that the distribution of retinal terminals in the hypothalamic suprachiasmatic nucleus extends over a greater area in Lewis compared to Brown Norway rats. This zone of termination corresponds to a cytoarchitectonically definable ventrolateral subdivision of the suprachiasmatic nucleus (SCN), which is also greater in Lewis than in Brown Norway rats. These results may have implications for behaviors related to the SCN.