Lecture 12 (Ocular Toxicology) Flashcards
structure of retina
consists of macula and fovea
cell types w/in retina:
- photoreceptors
- horizontal, bipolar, amacrine cells
- inner synaptic layer
- ganglion cells
optic nerve made of…
retinal ganglion cells
parts of the brain reached by retinal ganglion cells
suprachiasmatic nucleus
medial temporal lobe
lateral geniculate nucleus
stratum cellulare
why is retina part of the brain?
because developmental origin is in the forebrain
what are photoreceptors and what do they do
rods – night
cones – daytime, color
diseases affecting photoreceptors
retina pigmentosa
macular degeneration
symptoms of retina pigmentosa
loss of night vision
loss of side (peripheral) vision
sensitivity to bright light
loss of color vision
retinal ganglion cell (optic nerve) diseases
glaucoma
retina neuropathy
optic neuritis
what is retina neuropathy?
loss of nerve cells in retina
toxicants that affect photoreceptors
methyl mercury
lead
toluene
toxicants that affect bipolar cells
prenatal lead
toxicants that affect retinal ganglion cells
lead
pesticides
cyandie
toxicants that affect amacrine cells
prenatal lead
what epidemic happened in Cuba?
optic and peripheral neuropathy
what were the symptoms of optic and peripheral neuropathy epidemic?
blurry vision
loss of color vision
scotoma (blind spot)
blindness
peripheral neuropathy (damage to nerves outside brain and spinal cord)
neuropathy symptoms in men vs. women in cuba
optic neuropathy:
- men had much higher than women
peripheral neuropathy:
- women had slightly higher than men
likely cause of optic neuropathy epidemic in cuba
diet –> Vitamin-B deficiency
cyanide poisoning
increased physical activity –> drained B-vitamins
Vitamin B counteracts cyanide from disrupting cytochrome oxidase in Complex IV
if cyanide disrupts Compelx IV –> no nutrient and oxygen supply –> nerve tissue is damaged and lost –> vision loss
how does moonshine cause blindness?
corn fermentation –> methanol
methanol –> formic acid –> disrupts cytochrome oxidase in Complex IV –> oxygen and nutrient lost –> nerve tissue is damaged and lost –> vision loss
how does formic acid affect vision?
formic acid accumulates in the vitreous and disrupts retinal ganglion cells
which cell types are most susceptible to dysfunction and cell death?
retinal ganglion cells
photoreceptors
inadequate nutrition…
leaves humans vulnerable to toxic exposures
what do many toxicants target?
target the mitochondria to disrupt neuronal function and survival
how does retinoblastoma occur?
targets horizontal cells
over-proliferation of horizontal cells
diseases affecting photoreceptors
retina pigmentosa
macular degeneration
