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Biomedical subjects

D A Lee

Publications and source records attributed to D A Lee.

At least 127 records · Page 7Linked to original sources
PubMed1993

Aqueous and vitreous concentration of mitomycin C by topical administration after glaucoma filtration surgery in rabbits.

PURPOSE: The authors investigated the aqueous and vitreous pharmacokinetics of mitomycin after postoperative topical administration in rabbits. METHODS: Filtration surgery was performed in one eye of each rabbit. On the first postoperative day, mitomycin solution (0.4 mg/ml) was administered by either topical drop or cellulose sponge in both eyes of each rabbit. Aqueous and vitreous paracenteses were performed at 0.25, 0.5, 1, 2, 3, and 4 hours thereafter. Three rabbits were tested at each time interval for each type of administration. RESULTS: After topical drop administration, the peak aqueous concentration was 0.03 +/- 0.02 microgram/ml (mean +/- standard error) in surgical eyes and 0.06 +/- 0.03 microgram/ml in control eyes. After sponge administration, the peak aqueous concentration was 0.10 +/- 0.03 microgram/ml in surgical eyes and 0.08 +/- 0.04 microgram/ml in control eyes. Peak aqueous concentrations from drop and sponge applications were achieved at 1 to 2 hours after administration. Vitreous levels were well below the concentration known to cause retinal toxicity at all time intervals tested. CONCLUSION: Postoperative topical administration of mitomycin was successful in delivering mitomycin into the aqueous humor of rabbit eyes. Alternative methods of mitomycin application from the currently popular intraoperative administration may be beneficial in situations in which mitomycin delivery across intact conjunctiva may be desirable.

Administration, Topical↗
PubMed1993

The control of cell division in articular chondrocytes.

Our objective was to investigate the factors that control chondrocyte division, namely, (1) steric hindrance caused by the surrounding matrix, (2) growth factors and (3) cell shape. Bovine articular cartilage explants and isolated chondrocytes were cultured in medium containing [3H]-TdR to measure DNA synthesis. The effect of enzyme treatment, growth factors and cell shape was investigated. Proteoglycan (PG) depletion did not stimulate DNA synthesis whilst disruption of the collagen architecture promoted incorporation of [3H]-TdR into DNA. DNA synthesis was also stimulated by IGF-1 in flattened chondrocytes but not in rounded cells. It was found that the control of chondrocyte division depends on several variably related factors that may act singly or together to induce cell division and that PG depletion alone is insufficient to induce DNA synthesis, but division was noted when PG depletion was accompanied by matrix disruption and cell shape changes. Cell shape appears to alter the chondrocytes ability to respond to IGF-1 as a mitogen.

Animals↗
PubMed1993

Validation of chromosome painting as a biodosimeter in human peripheral lymphocytes following acute exposure to ionizing radiation in vitro.

Fluorescence in situ hybridization with chromosome-specific composite DNA probes ('chromosome painting') appears to be a useful tool for quantifying symmetrical cytogenetic damage. However, a thorough comparison between chromosome painting and the conventional methods of GTG-banding and dicentric analysis has not been performed. We have undertaken the validation of chromosome painting using human blood exposed in vitro to 137Cs gamma-rays at doses ranging from 0 to 400 cGy, then cultured according to standard procedures and harvested at 52 h. For painting, bound probes were detected either with fluoresceinated avidin and counterstained with propidium iodide, or with ChromoBlue WCP Probe and Giemsa. The first approach utilizes ultraviolet excitation in which painted chromosomes appear yellow and the remaining chromosomes appear red. The ChromoBlue labelling approach requires ordinary light microscopy in which painted chromosomes appear dark blue and the remaining chromosomes appear light blue. With each method, exchanges between painted and unpainted chromosomes appear bi-coloured. Because only a fraction of all possible exchanges are detected, the number of metaphases examined is adjusted according to the fraction of the genome painted. We have performed painting by several methods, including fluorescence with chromosome 4 probe alone, fluorescence with probes for chromosomes 1, 3 and 4 simultaneously, and chromogenic painting with chromosome 4 probe alone. The results obtained by the various painting methods were compared with GTG-banded cells which were examined for both translocations and dicentrics. In addition, unbanded metaphases stained with Giemsa were scored for dicentrics. Our data show that the frequency of chromosome exchanges detected by painting and banding agree with each other and with the number of dicentrics seen in unbanded cells, at least at doses of < or = 200 cGy.

Adult↗
PubMed1993

The effects of photofrin on human Tenon's capsule fibroblasts in vitro.

Pharmacological agents that modulate the wound healing process by inhibiting fibroblast proliferation may improve the success of proliferative vitreoretinopathy and glaucoma filtration surgery and may have applications in other surgical fields. It is possible that light-absorbing chemicals can be used to cause photo reactions in proliferating fibroblasts as a means of controlling this wound healing process. We present the effects of photofrin porfimer sodium (serial tenfold dilutions 1000-0.00001 micrograms/ml) on human fibroblasts from Tenon's capsule in vitro, with and without photoactivation with Argon green laser (700 mW for 1 and 5 minutes) and with bright sunlight (for 1 and 5 min). The cell density was measured on day 2 by 3H-thymidine uptake and on day 9 by means of a coulter counter, and optical density was measured in terms of the activity of the enzyme hexosaminidase. Each experiment was performed three times in quadruplicate. The counts were averaged for each drug concentration and mean cell count with a standard error as well as the 50% inhibitory doses (ID50s) were calculated. Photofrin demonstrated an inhibitory dose response curve (dark toxicity) to human fibroblasts. Concentrations greater than 100 micrograms/ml of photofrin alone completely inhibited cell growth. Concentrations less than 0.01 micrograms/ml did not have any effect on fibroblast proliferation. There was no significant log dose shift of the inhibitory effect of photofrin with the exposure to either sunlight or Argon laser. Photofrin may be used as a cytotoxic agent alone but does not appear to be activated by light to modulate subconjunctival fibroblast proliferation within the laser parameters used.

Cell Count↗
PubMed1993

Iontophoresis of reactive black 5 for pulsed dye laser sclerostomy.

Ab interno pulsed dye laser sclerostomy uses a gonioscopic approach to form a limbal fistula for the treatment of glaucoma. This procedure requires a full thickness penetration of stain in sclera for adequate absorption of the visible light energy. Iontophoresis is a technique using an electrical current to noninvasively deliver Reactive Black 5 (RB5) stain into sclera. This project determined the stability of RB5 stain as well as the optimal parameters for iontophoresis (probe tip surface area, current, and duration) in a rabbit model. RB5 stain was stable over time (72 hr) as well as after exposure to extreme heat (120 degrees C), scleral constituents (namely collagen), high concentrations of oxidants (1.5% H2O2), and laser light energy. Ideal parameters for iontophoresis included a probe tip surface area between 0.1 and 0.7 mm2, a current of 0.5 mA, and a duration of 5 min. The maximum concentration of RB5 stain achieved in sclera was 0.15%. The threshold of ablation for RB5 using an energy of 250 mJ was 0.001%. Iontophoresis can effectively deliver RB5 stain into sclera and may be a viable adjunct to ab interno pulsed dye laser sclerostomy procedures in the eye.

Animals↗
PubMed1993

Iontophoresis of methylene blue for gonioscopic pulsed dye laser sclerostomy.

Iontophoresis of methylene blue using pipette tip probes is an effective means of scleral staining in preparation for gonioscopic pulsed dye laser sclerostomy. The effects of the surface area of the pipette tip and of the duration of iontophoresis on the concentration and distribution of stain were investigated in rabbit eyes. Iontophoresis of 1% methylene blue was done using currents from 0.2 to 2.0 mAmp, pipette tip probes with surface areas from 0.02 to 7.1 mm2, and durations of iontophoresis from 0.5 to 10 minutes. Optimum iontophoresis parameters for delivering methylene blue to the eye were a current of 0.4 mA, a probe tip surface area of 0.19 mm2, and a duration of five minutes. The maximal scleral stain concentration, approximately 0.4%, was achieved using these optimal parameters. Microscopic analysis of frozen tissue sections demonstrated the stain to have penetrated the full thickness of the sclera after five minutes. Tissue samples were analyzed for dye 0.5, 2, 5, 12, and 24 hours after iontophoresis was completed. Decreased dye concentration by over 50% within 2 hours and complete disappearance of dye within 24 hours were demonstrated. Methylene blue concentration thresholds for laser ablation were also examined; the threshold of ablation of methylene blue was 0.0625% when an energy level of 75 mJ was used. We propose that iontophoresis of methylene blue is a useful adjunct to pulsed dye laser sclerostomy formation.

Animals↗
PubMed1993

Management of concurrent corneal diseases and cataract.

Cataract surgery is the most common surgical procedure in the United States, and the likelihood of encountering complications from concurrent corneal disease and cataract surgery is great. The rise of pseudophakic bullous keratopathy as an indication for corneal transplantation reflects the current trend toward increasing corneal pathology arising from cataract surgery and intraocular lens complications. Attitudes regarding astigmatism have changed drastically. Cataract surgery, coupled with astigmatic procedures, is becoming the procedure of choice for visual rehabilitation. Congenital corneal conditions and systemic disease processes are also considered in this review.

Astigmatism↗
PubMed1993

Congenital rubella syndrome: ophthalmic manifestations and associated systemic disorders.

Congenital rubella syndrome has a wide variety of severe ophthalmic and systemic complications. A worldwide rubella epidemic from 1963 to 1965 affected thousands of infants. This is a 20 year follow up study of patients with congenital rubella syndrome analysing the prevalence of ophthalmic disorders, associated systemic problems, and correlations among these defects. The authors statistically analysed 125 cases of congenital rubella seen in the Mayo clinic ophthalmology department over a 32 year interval. Most patients were young adults. Ocular disease was the most commonly noted disorder (78%), followed by sensorineural hearing deficits (66%), psychomotor retardation (62%), cardiac abnormalities (58%), and mental retardation (42%). Multiorgan disease was typical (88%). Ocular disease and hearing loss were frequently associated (53% had both) but not significantly correlated. A similar association existed between ocular and cardiac disease. Cataracts and microphthalmia were significantly correlated with poor visual acuity (each p < 0.0001). Glaucoma was significantly correlated with cataracts (p = 0.0002) and microphthalmia (p = 0.0024) but not poor visual acuity. Four patients with microphthalmia developed late onset glaucoma. No significant association was found between gestational age at time of maternal infection and the incidence of individual ocular conditions. However, several cardiac disorders were significantly associated with gestational age. Although new cases of congenital rubella are rare, surviving victims continue to challenge the ophthalmic and medical communities with a wide range of ocular and systemic disorders.

Age Factors↗
PubMed1992

Reliability coefficients of three corneal pachymeters.

We compared the accuracy and reproducibility of a hand-held portable ultrasound pachymeter, the Pach-Pen (Bio-Rad, Ophthalmic Division, Santa Ana, California); another ultrasound pachymeter, the DGH 1000 (DGH Technology, Inc., Frazer, Pennsylvania); and the Pro-Cem 4 endothelial specular microscope (Alcon-Surgical, Inc., Irvine, California). Each eye of 18 healthy human subjects was examined to determine corneal thickness using the three different instruments. For each instrument, five repeated measurements were obtained at each of five corneal locations (one central, four peripheral), for a total of 25 measurements per eye. The accuracy of the two ultrasound pachymeters was tested by comparing measurements obtained on specially designed test blocks of known thickness. The Pach-Pen was the more accurate of the two ultrasound pachymeters, with measurements within the range of 0.003 to 0.065 mm from the true thickness. The three instruments were most consistent in mean thickness in the center of the cornea. All three instruments showed excellent intraobserver reproducibility, as measured by reliability coefficients over 90%. Overall, the Pach-Pen pachymeter had high reproducibility, and produced more accurate measurements than the DGH 1000 pachymeter.

Adult↗
PubMed1992

Use of collagen shields containing amphotericin B in the treatment of experimental Candida albicans-induced keratomycosis in rabbits.

We evaluated the effect of collagen shields presoaked with amphotericin B on the treatment of experimental Candida albicans-induced keratitis. Treatment results were compared to those of amphotericin B eyedrops instilled hourly. Forty-eight albino rabbits received intrastromal injections of 10(8) C. albicans organisms. Twenty-four hours later, eyes were treated for eight hours each day with hourly instillation of 0.15% amphotericin B drops, hourly instillation of saline drops, or application of a collagen shield presoaked in 0.5% amphotericin B for one hour. The rabbits were killed after one, three, or five days of treatment. Quantitation of fungi in the cornea was achieved by culturing homogenates and counting colony-forming units. Treatment with amphotericin B applied either as hourly instilled drops or absorbed in collagen shields significantly (P less than .05) reduced corneal fungal counts at all time points when compared to saline-treated control eyes. Rabbit eyes treated with amphotericin B-soaked collagen shields had significantly lower fungal counts compared with hourly instilled amphotericin B drops at Days 1 (P = .02) and 3 (P = .04), but not at Day 5. The collagen shields were as effective in reducing the number of colony-forming units as were amphotericin B drops at Day 5. These data suggest that collagen shields soaked in amphotericin B could be a useful and convenient treatment device in keratomycosis such as that caused by C. albicans.

Administration, Topical↗
PubMed1992

The effects of transferrin receptor antibody, transferrin receptor antibody bound to Pseudomonas exotoxin and transforming growth factor-alpha bound to Pseudomonas exotoxin on human tenon's capsule fibroblast proliferation.

Pharmacological agents which modulate the wound healing process by the inhibition of proliferation of fibroblasts may improve the success of glaucoma filtration surgery. Since cell proliferation is essential to the wound healing process, we targeted the surface receptors that are associated with proliferating cells. We present the effects of three such agents-purified mouse anti-human transferrin receptor monoclonal antibody 42/6 (anti-TfR-42/6), anti-transferrin monoclonal antibody bound to a Pseudomonas exotoxin (anti-TfR-PE40) and transforming growth factor-alpha Pseudomonas exotoxin (TGF-alpha-PE40)--on human fibroblasts from Tenon's capsule. The inhibition of human subconjunctival fibroblast proliferation by anti-TfR-42/6 (with a concentration up to 25 micrograms/ml) and by anti-TfR-PE40 and TGF-alpha-PE40 (both with a concentration range of 5000-0.00001 micrograms/ml) was determined by colorimetric (OD), and cell counting (CC) assays over a 9-day period. Neither anti-TfR-42/6 nor anti-TfR-PE40 had an antiproliferative effect on the fibroblasts. TGF-alpha-PE40 demonstrated an antiproliferative effect in a dose response manner. The mean 50% inhibitory dose (ID50) by OD was 32.91 micrograms/ml, while the ID50 by CC was 27.88 micrograms/ml. EGF was used as a negative control for TGF-alpha-PE40 toxin. The inhibitory effect of the toxin conjugate was completely blocked by the addition of 1000 micrograms/ml of EGF. These in vitro studies show that TGF-alpha-PE40 may be useful in modulating the proliferation of human ocular fibroblasts; they also give some indication of drug dosages for future in vivo testing.

ADP Ribose Transferases↗
PubMed1992

Effect of steroids and nonsteroidal antiinflammatory agents on human ocular fibroblast.

5-fluorouracil and steroids have been used to suppress excessive scar formation after glaucoma filtering surgery (GFS). Steroidal and nonsteroidal antiinflammatory drugs (NSAIDs), which are inhibitors of arachidonic acid (AA) pathway, both limit fibroblast activity and reduce inflammation. In this experiment, the ability of corticosteroid (dexamethasone sodium phosphate), cyclooxygenase inhibitor (piroxicam), lipoxygenase inhibitor (ferulic acid), and dual cyclo/lipoxygenase inhibitor (phenidone) to inhibit human Tenon's fibroblast proliferation was evaluated in culture. After human Tenon's fibroblast cell lines were established, a complete dose-response curve was done for the representative compounds for 8 days. Fibroblast attachment and proliferation were quantified by Coulter counter, hexosaminidase, and tritiated thymidine uptake assays. All four drugs inhibited attachment and proliferation at high concentrations. Phenidone was the most effective, with inhibition occurring within the 0.001-0.1 mmol/l range. It also was the only drug that showed inhibition at the antiinflammatory range in vivo. Dexamethasone, piroxicam, and ferulic acid did not inhibit fibroblast attachment and proliferation until doses well above those required to inhibit AA biosynthesis were attained. Only dexamethasone showed increased potency with incubation time. Overall, the NSAIDs showed antiproliferative activity comparable to or better than that of the steroids. Because the potency of steroids increases over time, these drugs may be more beneficial if given prior to initiation of inflammation. These results suggest that NSAIDs may be useful as both antiinflammatory and antiproliferative agents in preventing bleb failure after GFS.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed1992

Effects of timolol, betaxolol, and levobunolol on human tenon's fibroblasts in tissue culture.

Evidence has been found suggesting that long-term therapy with topical antiglaucoma medications may decrease the success of glaucoma filtering surgery. To investigate this question further, the antiproliferative effects of the preservative benzalkonium chloride and three pure and commercially available beta-adrenergic antagonist preparations (timolol, betaxolol, and levobunolol) were studied on tissue cultures of human Tenon's capsule fibroblasts. Each drug preparation was tested on three different cell lines. Fibroblast growth was measured with tritiated thymidine uptake and hexosaminidase assays. Trypan blue uptake was used to assess cell viability microscopically. The commercially available preparations containing benzalkonium chloride and those of betaxolol and levobunolol without the preservative had similar inhibitory doses for 50% of cells. The timolol preparation without preservative was significantly less toxic than its commercially available one. The three tested beta-adrenergic blockers did not stimulate fibroblast proliferation directly in this in vitro model. Even when the cultures were washed free of the drugs, growth continued to be suppressed, suggesting that the inhibition was not reversible. An increase in fibroblasts and inflammatory cells after long-term antiglaucoma medical therapy thus may be caused not by a direct stimulation of cell proliferation but by chronic inflammation from the irritating effects of antiglaucoma medications and/or their preservatives.

Benzalkonium Compounds↗
PubMed1991

The effects of Nd:YAG laser iridotomy on the corneal endothelium.

We studied 18 eyes of 18 patients undergoing Nd:YAG laser peripheral iridotomy for occludable anterior chamber angles. A Q-switched laser was used for all treatments. Preoperative and postoperative pachymetry and corneal endothelial cell counts were obtained centrally, in the nontreated superonasal quadrant, and in the treated superotemporal quadrant. No significant differences were found between preoperative and postoperative corneal thickness at any site. A small decrease in endothelial cell count (95 cells/mm2) at the treated site was statistically significant (P = .04).

Cell Count↗
PubMed1991

The ocular effects of gases when injected into the anterior chamber of rabbit eyes.

We studied the toxic effects of sulfur hexafluoride and perfluoropropane in comparison with air, balanced salt solution, hyaluronate sodium, and aqueous humor in a rabbit model. Sixty normal pigmented rabbits were studied during a period of 4 weeks. The variables studied were slit-lamp biomicroscopic examination of the anterior segment, intraocular pressure as measured by pneumotonometry, corneal thickness and endothelial cell count as measured by specular microscopy, lens opacity by Scheimpflug photography, and light and transmission electron microscopy. All three gases were more toxic to the cornea and lens than were balanced salt solution, hyaluronate, and aqueous humor. However, 15% perfluoropropane and 50% sulfur hexafluoride were no more toxic to the eye than air was. Therefore, this study suggests that nonexpansile mixtures of perfluoropropane and sulfur hexafluoride may be beneficial and relatively safe in re-forming persistently flat anterior chambers in situations where the use of air is being considered.

Air↗
PubMed1991

Use of bioerodible polymers impregnated with mitomycin in glaucoma filtration surgery in rabbits.

A prospective, randomized, double-masked, and placebo-controlled study was performed to evaluate the effects of a localized and sustained release of mitomycin on the success of glaucoma filtration surgery in rabbits. A bioerodible polymer was used as the drug carrier. Full-thickness filtration surgeries were performed and data from 22 rabbits were collected. One eye received a polymer impregnated with mitomycin (0.02 mg or 0.06 mg), while the fellow eye received a drug-free polymer. Intraocular pressure, bleb survival, and postoperative complications were investigated. Intraocular pressures remained lower for a longer period of time (P less than 0.004) and filtration blebs lasted longer (P less than 0.05) in experimental eyes than in control eyes. Conjunctivitis and sectorial corneal haze occurred more frequently in eyes treated with the higher dosage mitomycin compared with control eyes. The use of mitomycin-C in a polymer delivery system appeared to promote the success of glaucoma filtration surgery in rabbits. With the lower dosage of mitomycin, clinically significant ocular toxicity was not noted.

Animals↗
PubMed1991

The effects of topical mitomycin on glaucoma filtration surgery in rabbits.

A prospective, randomized, double-masked, and placebo controlled study was performed to examine the effects of topically applied mitomycin on the success of full thickness filtration surgery in 23 rabbits. Both eyes of each rabbit had surgery by the same surgeon. After surgery, the experimental eye received a single subconjunctival injection of mitomycin (0.2 mg), and 50 microliters of a 0.2 mg/cc solution of mitomycin topically four time daily. The fellow control eyes were treated with sterile water. The mean intraocular pressure reduction from baseline exhibited by the experimental eyes was greater than that observed for the control eyes. The difference in intraocular pressure reduction between the two groups was statistically significant from post-operative day three through day 21 (p less than .05). With survival analysis, fewer failures were noted in the experimental eyes compared to control eyes for each time period throughout the study (p less than .005). The experimental eyes also demonstrated a longer time to bleb failure although this difference did not achieve statistical significance (p less than .10). An additional five rabbits were treated with the experimental drop in one eye and sterile water in the fellow eye but underwent no surgery. No differences between eyes were noted with regard to intraocular pressure change or anterior segment pathology. These data demonstrated the efficacy of mitomycin in promoting filtration surgical success in rabbits.

Administration, Topical↗