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David Ammar, Ph.D.


David Ammar, Ph.D.
Background
Dr. Ammar has a broad-based background in vision research combining biochemistry, cell biology, and cell physiology.  He has extensive experience with epithelial and endothelial cells, specialized cells that line the interior of the eye.  These cells perform critical functions that support the proper function of the retina, such as ion and metabolite transport, fluid production, tissue remodeling and fluid outflow. Dr. Ammar collaborates with other Department of Ophthalmology faculty in several research areas.  A current collaboration with Drs. Kahook and Masihzadeh involves using laser-assisted multiphoton microscopy to image regions of the eye involved in Glaucoma.  This work brings together a group of investigators with complementary skills and expertise, and our recent publication was one of the first to see fluid outflow structures in the intact human and mouse eyes. A second collaboration with Dr. Petrash involves understanding the mechanisms of diabetic eye diseases, cataract formation, and retinal degeneration.  Dr. Ammar also has fifteen years of experience in live-cell imaging and as well as knowledge of specialized microscopy, and currently collaborates with Dr. Petrash’s lab to image fluorescently-tagged proteins in live cells. Various other research projects include in vitro toxicity assays using various ocular cells to test the effects of various drugs, chemicals, and surgical devices.
 
As part of his departmental duties, Dr. Ammar heads the Department of Ophthalmology Research Histology Core. The eye is an organ containing several different tissue types that requires specialized histological expertise.  Dr. Ammar oversees the work of Pat Lenhart, our histologist, to provide assistance to researchers who require histological stains in paraffin sections and immunofluorescence stains in cryo-sections.
 
Glaucoma
Fluid Flow Pathway.  Image from The National Eye Institute.
Glaucoma is the second leading cause of blindness in the United States, affecting approximately more than 2 million adults. The risk of glaucoma increases with age, with an incident rate of ~1% at age 40 to increasing to >5% at age 70. Although glaucoma is a neurodegenerative disease of the retina, the primary cause of glaucoma is believed to be dysfunction of aqueous humor (AH) outflow resulting in increased intraocular pressure (IOP).
 
AH fluid is produced in the ciliary body, and most of the fluid exits the eye through the angle of the eye (a pocket formed at the junction of the iris and cornea).  The outflow structures consist of the trabecular meshwork, Schlemm’s canal, and collector channels. Dysfunction of these structures is believed to be directly linked to a reduction in fluid outflow, resulting in increased IOP.  However, these structures are hidden within the opaque scleral tissue and cannot be directly imaged. 
 
Therefore, current diagnosis of glaucoma depends on either detecting loss of visual function or detecting specific structural changes to the retina. However, small structural changes to the retina and visual field may not diagnostic glaucoma, while large changes suggest that the disease has already progressed.  Since nerve damage is irreversible, early diagnosis and detection is the most effective way to limit damage to the retina and prevent disease progression. Developing new technologies to accurately track structural and functional changes within the outflow structures of the eye would allow earlier diagnosis as well as enable us to monitor the effectiveness of medical intervention. This could potentially prevent premature blindness in millions of patients.
 
Our publications demonstrate the ability to utilize multi-photon microscopy (MPM) to obtain high-resolution (~1 µm) three-dimensional images of the intact mouse eye. MPM has been used to perform label-free measurements to quantify the structure of the extracellular collagen matrix, characterize the size and shape of Schlemm’s canal and collector channels, and measure the state of oxidative stress of epithelial cells located in the trabecular meshwork. Using a custom-built MPM imaging platform, we have successfully imaged the mouse eye in situ.

​Principal Investigator

Ammar 200.jpgDavid Ammar, Ph.D.
Assistant Research Professor
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Laboratory Staff

Lenhart 200.jpgPatricia Lenhart, HT(ASCP)
Professional Research Assistant
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Medical Students 

Nicole 200 (2).jpgNicole Nghiem
4th Year Medical Student
B.A., Biochemistry - University of Colorado at Boulder
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​Peer Reviewed Publications

  1. Ammar DA, Eadie DM, Wong DJ, Ma YY, Kolakowski LF, Jr., Yang-Feng TL, and Thompson DA. (1996) Characterization of the human type 2 neuropeptide Y receptor gene (NPY2R) and localization to the chromosome 4q region containing the type 1 neuropeptide Y receptor gene, Genomics 38(3): 392-398.
  2. Ammar DA, Hughes BA, and Thompson DA. (1998) Neuropeptide Y and the retinal pigment epithelium: receptor subtypes, signaling, and bioelectrical responses, Invest Ophthalmol Vis Sci 39(10): 1870-1878.
  3. Ammar DA, Nguyen PN, and Forte JG. (2001) Functionally distinct pools of actin in secretory cells, Am J Physiol Cell Physiol 281(2): C407-417.
  4. Ammar DA, Zhou R, Forte JG, and Yao X. (2002) Syntaxin 3 is required for cAMP-induced acid secretion: streptolysin O-permeabilized gastric gland model, Am J Physiol Gastrointest Liver Physiol 282(1): G23-33.
  5. Lu M, Ammar D, Ives H, Albrecht F, and Gluck SL. (2007) Physical interaction between aldolase and vacuolar H+-ATPase is essential for the assembly and activity of the proton pump, J Biol Chem 282(34): 24495-24503.
  6. Kahook MY, Kimura AE, Wong LJ, Ammar DA, Maycotte MA, and Mandava N. (2009) Sustained elevation in intraocular pressure associated with intravitreal bevacizumab injections, Ophthalmic Surg Lasers Imaging 40(3): 293-295.
  7. Ammar DA, and Kahook MY. (2009) The effects of combination glaucoma medications on ocular surface epithelial cells, Adv Ther 26(10): 970-975.
  8. Ammar DA, Lei TC, Gibson EA, and Kahook MY. (2010) Two-photon imaging of the trabecular meshwork, Mol Vis 16: 935-944.
  9. Kahook MY, and Ammar DA. (2010) In vitro toxicity of topical ocular prostaglandin analogs and preservatives on corneal epithelial cells, J Ocul Pharmacol Ther 26(3): 259-263.
  10. Kahook MY, Liu L, Ruzycki P, Mandava N, Carpenter JF, Petrash JM, and Ammar DA. (2010) High-molecular-weight aggregates in repackaged bevacizumab, Retina 30(6): 887-892.
  11. Kahook MY, and Ammar DA. (2010) In vitro effects of antivascular endothelial growth factors on cultured human trabecular meshwork cells, J Glaucoma 19(7): 437-441.
  12. Ammar DA, Noecker RJ, and Kahook MY. (2010) Effects of benzalkonium chloride-preserved, polyquad-preserved, and sofZia-preserved topical glaucoma medications on human ocular epithelial cells, Adv Ther 27(11): 837-845.
  13. Gibson EA, Masihzadeh O, Lei TC, Ammar DA, and Kahook MY. (2011) Multi-photon microscopy for ophthalmic imaging, J Ophthalmol 2011: 870879.
  14. Ammar DA, Lei TC, Masihzadeh O, Gibson EA, and Kahook MY. (2011) Trans-scleral imaging of the human trabecular meshwork by two-photon microscopy, Mol Vis 17: 583-590.
  15. Liu L, Ammar DA, Ross LA, Mandava N, Kahook MY, and Carpenter JF. (2011) Silicone oil microdroplets and protein aggregates in repackaged bevacizumab and ranibizumab: effects of long-term storage and product mishandling, Invest Ophthalmol Vis Sci 52(2): 1023-1034.
  16. Ammar DA, Noecker RJ, and Kahook MY. (2011) Effects of benzalkonium chloride- and polyquad-preserved combination glaucoma medications on cultured human ocular surface cells, Adv Ther 28(6): 501-510.
  17. Johnson AW, Ammar DA, and Kahook MY. (2011) Two-photon imaging of the mouse eye, Invest Ophthalmol Vis Sci 52(7): 4098-4105.
  18. Ammar DA, and Kahook MY. (2011) Effects of benzalkonium chloride- or polyquad-preserved fixed combination glaucoma medications on human trabecular meshwork cells, Mol Vis 17: 1806-1813.
  19. Masihzadeh O*, Ammar DA*, Lei TC, Gibson EA, and Kahook MY. (2011) Real-time measurements of nicotinamide adenine dinucleotide in live human trabecular meshwork cells: effects of acute oxidative stress, Exp Eye Res 93(3): 316-320.
  20. Ammar DA, and Kahook MY. (2011) Effects of glaucoma medications and preservatives on cultured human trabecular meshwork and non-pigmented ciliary epithelial cell lines, Br J Ophthalmol 95(10): 1466-1469.
  21. Lei TC, Ammar DA, Masihzadeh O, Gibson EA, and Kahook MY. (2011) Label-free imaging of trabecular meshwork cells using Coherent Anti-Stokes Raman Scattering (CARS) microscopy, Mol Vis 17: 2628-2633.
  22. Kahook MY, Fechtner RD, Katz LJ, Noecker RJ, and Ammar DA. (2012) A comparison of active ingredients and preservatives between brand name and generic topical glaucoma medications using liquid chromatography-tandem mass spectrometry, Curr Eye Res 37(2): 101-108.
  23. Ammar DA, Hamweyah KM, and Kahook MY. (2012) Anti-oxidants protect trabecular meshwork cells from peroxide-induced cell death, Trans Vis Sci Tech, 1(1):4.
  24. Masihzadeh O, Lei TC, Ammar DA, Kahook MY, and Gibson EA. (2012) A multiphoton microscope platform for imaging the mouse eye. Mol Vis, 18:1840-8.
  25. Tewari-Singh N, Jain AK, Inturi S, Ammar DA, Agarwal C, Tyagi P, Kompella UB, Enzenauer RW, Petrash JM, and Agarwal R. (2012) Potential therapies for vesicant-inflicted ocular injuries. Toxicol Appl Pharmacol, 264(1):23-3.