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Biomedical subjects

Timothy W Olsen

Publications and source records attributed to Timothy W Olsen.

8 recordsLinked to original sources
PubMed2005

Declines in arrestin and rhodopsin in the macula with progression of age-related macular degeneration.

PURPOSE: Biochemical analysis of age-related macular degeneration (AMD) at distinct stages of the disease will help further understanding of the molecular events associated with disease progression. This study was conducted to determine the ability of a new grading system for eye bank eyes, the Minnesota Grading System (MGS), to discern distinct stages of AMD so that retinal region-specific changes in rod photoreceptor protein expression from donors could be determined. METHODS: Donor eyes were assigned to a specific level of AMD by using the MGS. Expression of the rod photoreceptor proteins rhodopsin and arrestin was evaluated by Western immunoblot analysis in the macular and peripheral regions of the neurosensory retina from donors at different stages of AMD. RESULTS: A significant linear decline in both arrestin and rhodopsin content correlated with progressive MGS levels in the macula. In contrast, the peripheral region showed no significant correlation between MGS level and the content of either protein. CONCLUSIONS: The statistically significant relationship between decreasing macular rod photoreceptor proteins and progressive MGS levels of AMD demonstrates the utility of the clinically based MGS to correspond with specific protein changes found at known, progressive stages of degeneration. Future biochemical analysis of clinically characterized donor eyes will further understanding of the pathobiochemistry of AMD.

Adult↗
PubMed2004

Identification and localization of major soluble vitreous proteins in human ocular tissue.

PURPOSE: To identify the major soluble proteins from human vitreous, and to establish a baseline for comparison of vitreous samples from eyes with various diseases. DESIGN: Laboratory investigation. METHODS: Normal vitreous was obtained from eight human donor eyes and from eight eyes of patients undergoing diabetic vitrectomy. Vitreous specimens were subjected to SDS-PAGE and MALDI-TOF-MS analysis. Six specific antibodies were used to identify proteins using Western blot. Four proteins were localized within ocular tissue in a normal donor eyebank eye. RESULTS: We found eight distinct bands on SDS-PAGE in normal vitreous and two additional bands (hemoglobin) in eyes with diabetic retinopathy. Proteins were identified using MALDI-TOF-MS and confirmed by Western blot. We established a quantitative analysis of relative protein concentrations of undiluted vitreous. Immunohistochemistry localized selected proteins within the posterior segment layers. CONCLUSIONS: We present a normal human vitreous protein profile using current technologies and provide a baseline for comparison to ocular disease states. Tissue distribution of vitreous proteins may help to elucidate more specific protein function.

Amino Acid Sequence↗
PubMed2004

Fluorescein angiographic lesion type frequency in neovascular age-related macular degeneration.

OBJECTIVE: To assess the frequency of lesion types using fluorescein angiography (FA) in neovascular age-related macular degeneration (nAMD). DESIGN: Cross-sectional study. PARTICIPANTS: Two hundred cases of nAMD. METHODS: Fluorescein angiograms from 908 patients (university-based, tertiary retinal referral practice [UP] = 478; comprehensive, community-based eye clinic [CC] = 430) were reviewed to identify 200 cases of nAMD (100 from each center). Two graders evaluated the frequency of angiographic subtypes. MAIN OUTCOME MEASURES: Identifying (1) the frequency of subfoveal nAMD lesions that meet the definition of "predominantly classic," "minimally classic," "occult with no classic"; (2) lesion location, size, and subtype; and (3) the intergrader agreement (kappa). RESULTS: There was little difference in the frequency of lesion type between the UP and the CC. Most nAMD lesions were subfoveal (78.5%, 157 of 200), and of these, 20% (32 of 157) were predominantly classic; whereas 73% (114 of 157) were occult with no classic, and 7% (11 of 157) were minimally classic. Of the 200 angiograms, 33 (16.5%) were juxtafoveal, and 10 (5%) were extrafoveal. Twenty of the 43 juxtafoveal and extrafoveal lesions (47%) were predominantly classic. Classic with no occult subfoveal lesions were smaller than minimally classic or occult with no classic (1.7 vs. 3.7 and 2.8 mm; P = 0.001 and 0.01, respectively). Of 114 subfoveal occult with no classic lesions, 54 (47%) had both smaller lesion size <==4 disc areas (DA) and lower visual acuity <20/50, whereas 107 (94%) had a smaller lesion or lower visual acuity. CONCLUSIONS: Most angiographic lesions of patients who undergo FA for nAMD are subfoveal and occult. We estimate that 20% of subfoveal lesions are predominantly classic. Approximately half of the juxtafoveal and extrafoveal lesions are predominantly classic. Nearly 30% of all nAMD lesions have both small occult lesions (size <==4 DA) and a visual acuity less than 20/50. We found minimal difference in lesion type between a UP and a CC.

Aged↗
PubMed2004

The Minnesota Grading System of eye bank eyes for age-related macular degeneration.

PURPOSE: The Minnesota Grading System (MGS) is a method to evaluate human eye bank eyes and determine the level of age-related macular degeneration (AMD), by using criteria and definitions from the Age-Related Eye Disease Study (AREDS). METHODS: Donor eyes (108 pairs) from the Minnesota Lions Eye Bank were cut circumferentially at the pars plana to remove the anterior segment. A 1000 +/- 2.5-microm ruby sphere was placed on the optic nerve as a size reference. A digital, high-resolution, color macular photograph was taken through a dissecting microscope. The neurosensory retina was removed from one globe of the pair. The underlying retinal pigment epithelium was rephotographed, localizing the fovea with a proportional triangle. A grid was superimposed in the macular photographs and images were graded according to AREDS criteria. Twenty pairs were dissected bilaterally and graded for symmetry. RESULTS: Eighty-eight globes were graded into one of four MGS categories. Nineteen (95%) of 20 globes had symmetric grades. CONCLUSIONS: The MGS provides a methodology to grade donor tissue from eye bank eyes to correspond to the AREDS classification system. Donor tissue may be used for subsequent molecular analysis, including genomics and proteomics.

Aged↗
PubMed2003

Stability of RNA from the retina and retinal pigment epithelium in a porcine model simulating human eye bank conditions.

PURPOSE: To assess RNA stability after death in a porcine model to simulate current human eye bank techniques. METHODS: Eye bank time interval data were collected from 191 donor specimens: death to refrigeration, enucleation, and tissue processing. A control porcine eye was enucleated, retina and RPE isolated, and specimens frozen (-80 degrees C). Fourteen porcine eyes remained at room temperature for 2 hours and then cooled to 4 degrees C. Retina and RPE were isolated and frozen (-80 degrees C) at 5, 12, 24, 29, 36, 48, and 72 hours. Four globes remained in a moist chamber, five whole and five sectioned globes were immersed in RNAlater (Ambion, Austin, TX) at 5, 12, 24, or 48 hours. RNA was isolated. The 28S and 18S rRNA peaks were analyzed by electrophoresis. RT-PCR was performed on each sample. Messenger RNA for GAPDH, beta-actin, mouse rhodopsin from retina (mRHO), and RPE-65 (from RPE) were analyzed with gel electrophoresis. RESULTS: The average time from death to refrigeration was 4.2 hours, to enucleation 6.4 hours, and to tissue processing 10.7 hours. RT-PCR gel electrophoresis patterns from retinal tissue had bands of similar intensity at each interval from beta-actin, GAPDH, and RHO. Band patterns from RPE demonstrated decay of the RT-PCR gene products after 5 hours. This decay was delayed by at least 24 hours with the use of RNAlater. The 28S rRNA decay was similar for retina and RPE. CONCLUSIONS: Retinal tissue RNA can be analyzed within the time constraints of current eye bank tissue processing, whereas analysis of RPE necessitates either rapid processing or use of RNAlater. These results should aid in future studies in which eye bank tissue is used for RNA analysis.

Actins↗
PubMed2002

Porcine sclera: thickness and surface area.

PURPOSE: To assess the thickness and surface area of porcine sclera. METHODS: One hundred twenty-eight porcine globes were sectioned from the center of the cornea to the region of the optic nerve. Photographs of the sectioned sclera including a millimeter scale were taken. Photographic slides were projected onto blank paper, and the scleral silhouette was traced. Perpendicular thickness measurements were taken at 1-mm intervals from the limbus to the optic nerve. The sclera of 18 porcine eyes were cut into small pieces, and the surface area was calculated with computerized digital tracing software. RESULTS: The scleral thickness near the corneal scleral limbus was 0.83 +/- 0.2, 0.91 +/- 0.17, and 1.12 +/- 0.23 mm in the small-, medium-, and large-sized pigs, respectively. Thickness decreased to minimum of 0.31 +/- 0.07, 0.35 +/- 0.1, and 0.43 +/- 0.16 mm at a distance of 5 mm from the limbus in the small- and medium-sized pigs and 6 mm in the large-sized pigs, respectively. The mean scleral surface area was 7.78 +/- 0.66, 9.66 +/- 0.75, and 11.92 +/- 1.57 cm(2) in the small-, medium-, and large-sized pigs, whereas the corneal surface area was 1.09 +/- 0.07, 1.15 +/- 0.09, and 1.40 +/- 0.19 cm(2), respectively. CONCLUSIONS: Porcine scleral thickness is very similar to human scleral thickness. The porcine model is an excellent model for studying transscleral drug delivery.

Animals↗
PubMedDate not supplied

Vitrectomy for dense vitreous hemorrhage in infancy.

PURPOSE: To report clinical data, including etiology and visual outcome, in newborns requiring vitrectomy for dense vitreous hemorrhage. METHODS: In this retrospective case series, we surveyed subscribers to the American Association for Pediatric Ophthalmology and Strabismus ListServe regarding patients under their care. RESULTS: A total of 28 eyes of 21 patients were included. Most common etiologies were thrombocytopenia, shaken baby syndrome, and birth trauma. In 9 cases (12 eyes), the vitreous hemorrhage was idiopathic. Mean time between diagnosis and surgery was 1.4 months. Complications included strabismus, cataract, glaucoma, high myopia, and retinal detachment. Recognition visual acuities were available for 8 eyes: 20/25 (2 eyes), 20/30, 20/40 (2 eyes), 20/60 (2 eyes), and 20/100. One eye had no light perception. CONCLUSIONS: The etiologies encountered in our patients were similar to those reported previously. Visual outcomes were much worse in cases with retinal complications. Other patients had better visual outcomes. Despite potential surgical and postoperative complications, this series demonstrates favorable visual outcomes can be achieved following early vitrectomy in this setting.

Birth Injuries↗