Biomedical subjects

G K Lang

Publications and source records attributed to G K Lang.

152 records · Page 9Linked to original sources

PubMedDate not supplied

Thalidomide and prednisolone inhibit growth factor-induced human retinal pigment epithelium cell proliferation in vitro.

Thalidomide and prednisolone were recently introduced as treatment modalities in age-related macular degeneration (AMD). Growth factor-induced activation of retinal pigment epithelial (RPE) cells is a crucial event in this disease. The purpose was to examine the effect of thalidomide and prednisolone on growth factor-preactivated RPE cells. Human RPE cells were stimulated with 10 ng/ml platelet-derived growth factor (PDGF), basic fibroblast growth factor (bFGF), or vascular endothelial growth factor (VEGF) for 24 h. Afterwards, thalidomide (50 microg/ml) or prednisolone (100 ng/ml) were added for 24 h. RPE cell proliferation was determined by [3H]-thymidine incorporation. PDGF and bFGF significantly stimulated human RPE cell proliferation (p < 0.005), the value for VEGF stimulation was not significant (p = 0.3). The effect of the growth factors was diminished after addition of thalidomide and prednisolone (p < 0.005). The current study shows that the inhibitory properties of thalidomide and prednisolone remain even after growth factor activation of the cells.

Angiogenesis Inducing Agents↗

PubMedDate not supplied

Effect of insulin-like growth factors 1 and 2, and glucose on the migration and proliferation of bovine retinal pigment epithelial cellsin vitro.

BACKGROUND: The retinal pigment epithelium (RPE) has been implicated in the development of diabetic retinopathy and it has been suggested that insulin-like growth factors (IGF) and glucose may be among those factors which are responsible for the RPE changes in diabetics. The purpose of this study was to investigate the effect of IGF-1, IGF-2, and glucose on the migration and proliferation of bovine RPE cells in vitro. METHODS: Primary cultures of bovine RPE cells were established from freshly enucleated eyes and passages 5-8 were used for these experiments. RPE cell migration was studied in confluent RPE cultures grown in multiwell plates. After inhibition of proliferation with mitomycin C (10 microg/ml) and partial denudation of the RPE in each well, the cells were incubated with IGF-1 (10 ng/ml), IGF-2 (10 ng/ml) or glucose (10 mM). Migration was measured as the number of cells that had entered the denuded area after 20 h. RPE cell proliferation was determined by [(3)H]-thymidine incorporation after incubation with IGF-1, IGF-2, and glucose for 24 h. Statistical analysis was performed with the paired Student's t test. RESULTS: Exposure of RPE cells to IGF-1, IGF-2, and glucose resulted in a significantly higher RPE cell migration as compared to the control medium (p < 0.008) with 21, 20, 17, and 9 cells/raster field, respectively. Additionally, IGF-1 (p = 0.004) and IGF-2 (p = 0.008) but not glucose caused a statistically significant stimulation of DNA synthesis with 761, 747, and 593 ccpm, respectively, as compared to the negative control (352 ccpm). CONCLUSION: This study indicates that IGF-1 and IGF-2 influence RPE cell migration and proliferation. This is further evidence that these factors are among those which have to be kept in mind when trying to modulate the development of diabetic eye diseases.

Animals↗

PubMedDate not supplied

Chemical and physical stability of perfluorocarbons with laser treatment.

Physical and toxicological aspects of different perfluorocarbons and semifluorinated compounds are discussed. The urgent need for ultrapurification of perfluorocarbons is demonstrated. In vitro laser treatment simulating physiological conditions of two ultrapurified perfluorocarbons used for temporary tamponade and mechanical fixation of unfolded retina in case of giant tears, and one semifluorinated diether resulted in no detectable chemical alteration. Cytotoxic examinations of both laser treated and untreated probes showed no difference in cell proliferation.

Cell Division↗

PubMedDate not supplied

Comparison of free-running vs. Q-switched Er:YAG laser photorefractive keratectomy (scanning mode) in swine eyes.

PURPOSE: To examine morphology in plane and incisional corneal ablation (in vitro) induced by an Er:YAG laser (2.94 microm) in two modes: free-running and q-switched. METHODS: Sequences of different fluences in each mode were applied to freshly enucleated pig eyes. Parameters of free-running mode were: pulse length 50 micros, fluences 1.21 to 4.77 J/cm2, frequency 80 Hz, spot size 500 microm FWHM, hexagonal spot shape. Parameters of q-switched mode were: pulse length 200 ns, fluences 0.79 to 2.33 J/cm2, frequency 20 Hz, spot size 500 microm FWHM, round spot shape. RESULTS: Histology showed thermal damage of 10 to 25 microm in depth caused by the free-running mode compared with 4.5 to 7.5 microm by the q-switched mode. In both gross photography and scanning electron microscopic examination, the surface was more homogeneous and smoother in the q-switched mode. CONCLUSIONS: Depending on the different application modes, both laser systems could be used for a defined corneal ablation in photorefractive keratectomy. At present, results using the Er:YAG laser are not as favorable as with the excimer laser.

Animals↗

PubMedDate not supplied

Corneal morphology in vitro after superficial keratectomy with q-switched Er:YSGG and free-running Er:YAG lasers.

PURPOSE: Examination of morphology in corneal ablation induced by a q-switched Er:YSGG (2.79 microm) laser and a free-running Er:YAG laser (2.94 microm). METHODS: Defined ablation of 6-mm diameter and 15, 30, 55, 90, and 120-microm depth was performed on freshly enucleated swine eyes. Er:YSGG laser parameters: fluence 1.6 J/cm2, frequency 6 Hz, spot-size 465 microm FWHM, scanning-mode, pulse number 1520 to 6210. Er:YAG laser parameters: fluence 3 J/cm2, frequency 1.5 Hz, spotsize 6 mm, wide area ablation, pulse number 2 to 13. Corneal morphology was analyzed by gross photography, histology, scanning electron microscopy, and scanning nearfield acoustic microscopy. RESULTS: Histology showed thermal damage of 5 to 15 microm in depth caused by the Er:YSGG laser in comparison with 10 to 20 microm by the Er:YAG laser. Average roughness of the ablated surface measured with scanning nearfield acoustic microscopy was 20 to 40 microm for the Er:YSGG laser and 5 to 15 microm for the Er:YAG laser. These data confirm the subjective impression of images created by scanning electron microscopy and gross photography. CONCLUSIONS: Although the Er:YAG laser system appeared to demonstrate a smoother corneal surface than the q-switched Er:YSGG laser, the thermal damage in either case poses a potential limitation for clinical use in lamellar refractive surgery.

Animals↗

PubMedDate not supplied

Endothelial reaction to perforating and non-perforating excimer laser excisions in rabbits.

With an ArF excimer laser (193 nm, 750 mJ/cm2, 20 Hz) and a special slit-mask system, perforating and non-perforating linear keratectomies were performed in 55 rabbit corneas with a follow-up from 1 hour to 6 months. Varying the pulse number according to ablation rate (0.8 micron/pulse) and corneal thickness, four linear radial excisions (3 mm length, 70 microns width) of increasing depth (70%, 80%, 90%, 100% perforation) were produced. The corneas were processed for light microscopy, scanning and transmission electron microscopy, and vital staining of the endothelium. Except for mild cell contact alterations and discrete single cell damage in the 90% deep excisions, no endothelial damage could be detected after non-perforating keratectomies. Minute (less than 20 microns) and small (20 to 100 microns maximal diameter) perforations induced cell enlargement, formation of pseudopodia, rosette-like figures, multi-nucleated giant cells, and ultimately uniform reformation of the cell pattern (1 hour to 7 days postoperatively). Larger excimer laser defects of Descemet's membrane (greater than 100 microns) were overgrown by dedifferentiated endothelial cells producing a new PAS-positive basement membrane. Vital staining revealed the complete and stable reorganization of the endothelium over these lesions within 6 months. Our observations are similar to those reported on the endothelial repair process following other surgical manipulations (knife incisions, direct Nd:YAG-laser trauma) and support the applicability of excimer lasers for corneal trephination in patients.

Animals↗

PubMedDate not supplied

Ocular reticulum cell sarcoma. Clinicopathologic correlation of a case with multifocal lesions.

A 56-year-old man presented with recalcitrant uveitis with anterior chamber and vitreous cells. He developed small scattered lesions in the macular areas of both eyes, which disappeared in the right eye and evolved to multifocal, discrete, punched-out lesions resembling birdshot retinochoroidopathy in the left eye. Ocular reticulum cell sarcoma (RCS) was suspected but was not confirmed by diagnostic vitrectomy. The patient died 3 years later and was found to have RCS with central nervous system and ocular involvement. The occurrence of tumor cells under the retinal pigment was the apparent cause of the multifocal lesions that disappeared in the right eye and that led to discrete punched-out lesions with no scarring in the left eye.

Diagnosis, Differential↗

PubMedDate not supplied

Clinicopathologic studies of keratoplasty eyes obtained surgically.

Seventy-two keratoplasty eyes obtained surgically from 72 patients were examined histopathologically. The age at the time of enucleation ranged between 2 months and 91 years, with an average of 47.2 years. The 72 eyes were placed in five categories according to the surgical procedures performed: (a) 20 eyes with a penetrating keratoplasty as the only intraocular operation; (b) nine eyes with two or more penetrating keratoplasties; (c) 29 eyes with one or more keratoplasties with other procedures performed at the same time or another time; (d) nine eyes with lamellar keratoplasties; (e) five eyes with tectonic keratoplasties. The corneas were perforated at the time of keratoplasty in 15 eyes (20.8%). The average age at the first keratoplasty was 45.1 years. Overall, the most frequent causes of enucleation were secondary glaucoma (45.8%), melting of the graft (13.9%), exogenous endophthalmitis (12.5%), and trauma (8.3%). An expulsive hemorrhage occurred in 5.6% of eyes.

Adolescent↗