William S. Stark
SLU Biology Department Seminar
http://starklab.slu.edu/Seminar2007.htm
Fall, 2007
Recent Biology seminars:
Microscopy of Drosophila's
6 rhodopsins, Fall, 2002
Vision in the Ultraviolet,
Fall 2005
Funding (and conflict of interest disclosure)
Research
$350 Undergraduate Research Fund
College of Arts and Sciences
Neil Patel "The effect of zeaxanthin and other carotenoids
in the health of Drosophila eyes"
Travel to Association for Research in Vision and Ophthalmology
(ARVO) 2007 meeting
$2000 Dennis and Laura Gierhart (charitable giving account)
Grant ID 3676725
Background (Drosophila)
Fly food (the snotty term, Drosophila medium) usually contains
yellow corn meal.
Serendipity, trying white corn meal, and using a retinoid free
medium, started me on a lifelong interest in vitamin A deprivation
and replacement. This
picture shows Freeze fracture EM of rhabdomeric microvilli of
vitamin A replete and deprived Drosophila
Harris,
W.A., Ready, D.F., Lipson, E.D., Hudspeth, A.J. and Stark, W.S.
Vitamin A deprivation and Drosophila photopigments. Nature, 1977,
266, 648-650.
Decades later:
I had worked out the visualization
of all 6 Drosophila rhodopsins.
and
I had worked out GFP
reporter for vitamin A induced rhodopsin gene transcription
Stark, W. S., Thomas, C. F. Microscopy of multiple visual receptor
types in Drosophila, Molecular Vision, 2004, 2004; 10:943-955
Why is Lutein in your vitamin?
(that's a good question!)
Before she retired in 1990, Lynette
Feeney-Burns gave me several of her photographs including this
one of a monkey retina fed a chow rich in carotenoids. Note the
yellow pigmentation, the macular
pigments.
Beta-carotene is the best known carotenoid,
a dimer of vitamin A. The macular pigments were first identified
as lutein and zeaxanthin.
Many years ago, I met John
Landrum, a chemist from Florida International University,
and Richard
Bone (second from left), a physicist from Florida International
University. They gave me enough zeaxanthin and lutein for one
study:
Stark,
W.S., Schilly, D., Christianson, J.S., Bone, R.A. and Landrum,J.T.
Photoreceptor specific efficiencies of beta-carotene, zeaxanthin
and lutein for photopigment formation deduced from receptor mutant
Drosophila melanogaster.Journal of Comparative Physiology, 1990,
166, 429-436.
But that is beside the point.
They did psychophysical studies addressed to the macular pigments
and were the first to identify the macular pigments as lutein
and zeaxanthin. Eventually, in a bold experiment, they ate large
amounts and showed, by studying their own vision, that their macular
pigments increased.
Their work was far more elegant than mine, but I already have
mine on my web site, so I'll use mine (1987) to give you an idea:
A subject
reports what he sees, and the difference
between photopic spectral sensitivities on and off of fovea are
due mainly to absorbance by macular pigments.
Photopic
sensitivities to ultraviolet and visible wavelengths and the effects
of the macular pigments in human aphakic observers. Current Eye
Research, 1987, 6, 631-638.
By then, numerous studies had suggested that
(1) blue light damaged photoreceptors
(2) macular pigments decreased blue light to foveal cones
and
(3) these were the receptors lost in AMD (age-related macular
degeneration)
It was soon after I saw their study that I started to notice that
lutein was in vitamins.
The chromophore of Drosophila rhodopsin
Take a look again at the carotenoids.
Beta carotene is a dimer of vitamin A, retinol. The aldehyde,
retinal, is the chromophore of most vertebrate rhodopsins (some
fish rhodopsins are based on vitamin A2, dehydroretinol). Many
insect rhodopsins are based on 3-hydroxyretinol. Zeaxanthin is
a dimer of the 3-hydroxylated chromophore, and lutein is a dimer
half of which is this chromophore.
Going beyond my
laboratory's previous studies, we used these carotenoids in
the diet
(1) as precursors of the visual pigment's chromophore.
and
(2) to assay for activation of opsin's promoter
For 10 years, I have been going to this
dinner at the ARVO (Association for Research in Vision and Ophthalmology).
As you see, it is called the "Macula and nutrition group,"
but my first invitation referred to "investigators and students
interested in the role of carotenoids in the eye." You'll
be happy to note that there are many carotenoids
in the food served. Also, noting that these pix are on my server,
I am obviously the self-appointed photo-journalist for the event.
Here I met Wolfgang
Schalch (left) of a company (formerly Roche, now DSM "don't
spend money"), and, after the appropriate Material Transfer
Agreement, they gave me enough zeaxanthin and lutein for one study:
Stark,
W. S. Effects of lutein and zeaxanthin as chromophore precursors
and in regulating opsin gene expression in Drosophila. Association
for Research in Vision and Ophthalmology, 2006, Fort Lauderdale,
FL (*Investigative Ophthalmology and Visual Science, 2006, 47).
Here is Dennis Gierhart
(left), Chairman and Chief Scientific Officer of ZeaVision.
I've only known him for a few years, amazingly, since his company
is here in St. Louis and markets a nutritional supplement, EyePromise.
The formula
indicates that zeaxanthin. as well as lutein, is included.
Here are containers
and smears.
Here is Mark Sankoorikal,
an undergraduate who worked in my lab on the zeaxanthin-EyePromise
project. He's not always dressed like this, but I'm now on the
premed (oh, bite my tongue, pre health professional) committee
and have access to such embarrassing photos (and I always threaten
people with putting embarrassing pix on the internet). And, while
I'm on a roll, here is one of his partners in crime, Samir
Sharma. Also Nilay
Patel worked on this.
Enough family photos, here's some data they obtained:
This
photo shows that EyePromise serves as a precursor for R1-6 rhodopsin
and that it also activates the promoter of the gene for R7's rhodopsin.
This
photograph is a better demonstration that EyePromise serves as
a precursor for R1-6 rhodopsin.
Where do we go? (human studies)
People cherish their eyesight; understanding the causes and prevention
of blindness is so important for the quality of life -- I use
this site of
one of many possible links to state that a lot of funding (public
and private), information and publications, and marketing center
around preventing loss of vision.
Follow this reasoning:
(1) Many studies, including my own my
own, suggest that blue and ultraviolet light is especially
damaging to photoreceptors.
(2) Many studies, including my
own, demonsrtrate that macular pigments block blue light to
foveal cones.
(3) Many studies, starting with those of Bone and Landrum, show
that diet can increase macular pigment optical density (MPOD)
(4) Foveal cone-mediated vision is lost in age-related macular
degeneration (AMD)
Thus, testing MPOD is useful
My eye doctor (oh, bite my tongue, eye care professional), Dr. Susan Yang, is also the eye doctor of a few other people in this department. She, and her family, are close friends. So she did me the favor of carefully doing the refraction on my aphakic eye.
Here is a self-portrait, looking even goofier than ever (even goofier than my premed students), but hey, at least I still have both ears. The minus correction for my right eye is for myopia. The strong plus correction for the left eye is because I had cataract surgery in 1959. Since the lens blocks UV, human UV vision has always been one of my interests, one topic in my last seminar.
The life expectancy after cataract surgery is about 5 years since most people get surgery when they are old. Also, most people get intraocular lens implants that block UV. My retina is uniquely useful for study, exposed to UV for 48 years so far. The conventional wisdom is that UV is damaging.
Here is "quantifeye," a clinical psychophysical apparatus marketed for ophthalmologists and optometrists to quantify patient's macular pigments. They get a reading of 0.43 (optical density) for my right eye, much lower for my left eye.
Is that because of poor vision or low macular pigment optical
density?
Before I explain my method for demonstrating to subjects whether
they have healthy macular pigments, here's a reminder of what
everybody (hopefully) learned about polarized
light.
I posted this picture of macular
pigments on my BIOL 347 (General physiology lab) site in conjunction
with a demonstration for students of Haidinger's brushes. The
optics are shown here.
I see Haidinger's brushes clearly with both eyes.
Here's Maxwell's spot. Stare at the green. Then you'll se a dot in the middle of the blue.
There are thus several qualitative assays that do not rely on visual acuity. These could be refined into quantitative tests.
Am I losing macular pigments? Am I losing eyesight? If so, is it because I lack UV protection from the lens? Or because I lack macular pigments? Or both? These optics, shown here, can also be used to study sensitivity.
This page was last updated 9/6/07
