Cytotoxic effects of antiproliferative agents on human retinal glial cells in vitro

Purpose: Proliferative vitreoretinopathy (PVR) is characterizedby the formation of cellular membranes on the detached retina and also in the vitreous. Glial cellscan be found in epiretinal and subretinal membranes from eyes with PVR, proliferative diabeticretinopathy (PDR), idiopathic macular pucker, uveitis and other diseases affecting theretina. Proliferation and contraction of glial cells appears to play a role in the pathogenesisof PVR. This study is designed to inspect the effectiveness of harringtonine, as well as colchicine,daunomycin and fluorouracil, against cellular proliferation of cultured human retinal glial cellsthat might be involved in the retinal and/or vitreous proliferation. Methods: Cultures of human retinal glial cells were preparedusing the enzyme digesting method. Cells that had been in culture for 2–5 passages were usedin this study. Harringtonine (0.063 g/ml 2.0 g/ml), colchicines(0.5 g/ml 16.0 g/ml), daunomycin (0.1 g/ml 3.2 g/ml) and 5-fluorouracil(0.5 g/ml 16.0 g/ml) were added to cultures of human retinal glial cellsand the proliferation rates of the cells were measured by the MTT method. Results: Harringtonine at the dosage of 0.063 g/mlinduced suppression of cellular growth, but the changes were not statistically significant (p > 0.05).At a dosage ranging from 0.125 g/ml to 2.0 g/ml, harringtonine significantly suppressedcellular growth according to the test (p < 0.01). Likewise, other antiproliferativeagents inhibited cellular growth significantly at a dosage from 1.0 g/ml to 16.0 g/ml(colchicine), 0.2 g/ml to 3.2 g/ml (daunomycin) and 1.0 g/ml to 16.0 g/ml(5-fluorouracil), but not at 0.5 g/ml (colchicine), 0.1 g/ml (daunomycin) and0.5 g/ml (5-fluorouracil). The ID₅₀ were 0.33 g/ml (harringtonine), 3.11 g/ml (colchicine), 0.79 g/ml (daunomycin) and 5.23 g/ml (5-fluorouracil), respectively.Conclusions: Harringtonine was extremely effective ininhibiting human retinal glial cell proliferation, like other antiproliferative drugs such as colchicine,daunomycin and 5-fluorouracil. Harringtonine, therefore, may be a candidate for further studies regardingthe treatment of experimental PVR.     

Effects of β-agonists on b- and c-waves implicit for adrenergic mechanisms in cat retina

Nylidrin (buphenine) is a -adrenergic agonist known to dilate peripheral vessels and used therapeutically in retinal degeneration and glaucoma. We studied retinal function under -agonists in arterially perfused cat eyes and observed a dose-dependent, reversible increase in b-wave amplitude and a decrease in c-wave amplitude in concentrations from 4.5 to 120M. A half maximal response was obtained at 40 to 50M. The optic nerve response to light showed dose-dependent reversible changes under nylidrin. Standing potential, light peak, intraocular pressure, vascular resistance, and diameter of or retinal vessels showed no consistent changes under nylidrin.The effects were inhibited by each of the -blocking agents propranolol, ICI 118, and oxprenolol (in sequence of decreasing potency).Another potent ₂-agonist, clenbuterol, was used to determine the extent to which the responses to nylidrin were due to -receptor-mediated action. Clenbuterol had similar effects on the b-wave and optic nerve response at slightly higher concentrations (30–200 M) but more variable effects on the c-wave.The data are interpreted as functional evidence that -adrenergic mechanisms are involved in retinal signal processing. This concept is corroborated by identification of -adrenergic binding sites in cat retina (Bruinink et al., 1986).     

Die Stereo-Ultrastruktur der Cornealoberfläche bei der Ratte

Zusammenfassung Die dreidimensionale Beschaffenheit der Cornealoberfläche der Ratte wurde mittels des Scanning Electron Microscope und anhand konventioneller elektronenmikroskopischer Schnittpräparate untersucht. Dabei konnte das Vorhandensein von Mikrovilli (0,15 breit, bis 1,0 hoch) und von Mikroplicae (0,1–0,2 breit, 0,3–0,4 hoch, 1–3 lang) nachgewiesen werden. Bei diesen Strukturen dürfte es sich um während der Desquamation entstandene Ausstülpungen der Epithelzellmembran im Bereiche der Desmosomen handeln.

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The stereo ultrastructure of the corneal surface in rat

Summary Combined morphological examination of the corneal surface of rat both with the scanning and the transmission electron microscope reveals two kinds of protrusions covering the polygonal, regularly arranged epithelial cells: Mikrovilli and Mikroplicae; the former being approximatively 0.15 large and up to 1.0 high, the latter being 0.1–0.2 large, 0.3–0.4 high and 1–3 long. These formations are with high probability the remnants of desmosomes having been formed during desquamation.

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Diese Untersuchungen wurden mit Unterstützung des Fonds National suisse de la recherche scientifique (Nr. 5322.3) durchgeführt.     

Lamellar excimer laser keratoplasty: Reproducible photoablation of corneal tissue

We examined the depth of ablation of the recipient bed with different counts of oscillations of excimer laser beam, to determine the correlation between planned and real depth. The ablation rate per oscillation was tested preoperatively by blackened photographic paper of defined thickness and thus was calculated to be 5 m. Forty pig eyes were used for the first study. Each eight eyes were ablated in the planned depth 100 m, 200 m, 300 m, 400 m and 500 m. The corneal thickness was measured with an ultrasonic pachymeter before and after the procedure. The depth measured after the photoablation was 99.4 ± 36.4 m for 100 m planned depth, 186.7 ± 55.3 m for 200 m, 298.4 ± 68.5 m for 300 m, 373.9 ± 65.7 m for 400 m and 480.1 ± 59.3 m for 500 m. Comparing the depth measured after the photoablation to planned depth, there was a significant correlation (correlation coefficient: R = 0.93; p < 0.0001). Five other corneas trephinated from pig cadaver eyes were ablated from the endothelial side to the desired thickness (100 to 500 m) of lamellar graft. In a second step a donor mask was placed onto the cornea and a laser light spot was led until perforating on all sides. The lamellar keratoplasty was completed by suturing the corneal graft into the bed. Macroscopic and microscopic examination of sutured eyes after fixation showed a good fit of wound margins and stromal interface. These results indicate that excimer laser is useful for reproducible corneal photoablation in lamellar keratoplasty.     

Use of vancomycin in vitrectomy infusion solution and evaluation of retinal toxicity

The retinal toxicity of vancomycin in infusion solution used in vitrectomy and lensectomy was investigated in rabbit eyes by means of electroretinography and histologie study (light microscopy). Concentrations of 8g/ ml, 16g/ml, and 32g/ml of vancomycin in balanced salt solution caused no abnormal ERG or histologic changes. However, ERG amplitude depression and abnormal histologie changes occurred when the concentration of 100g/ml of vancomycin was used.Supported in part by U.S. Public Health Service grants EY07541 and EY02377 from the National Eye Institute, National Institutes of Health, Bethesda, MD.     

Eye references in the Homeric Epics

After a short introduction to the Homeric Epics, the name of Homer and the time and place where the poems were written, the authors refer to the terms of the eyes and to the verses where they are found. Among these terms, the most important is the term oaó, the first term for the eye in ophthalmology, which has remained throughout the years unchanged.Finally, they refer to the injuries of the eyes, the participation of the two sons of Asclepios in the Trojan campaign and to the verses including the classical paragraph ... a doctor is more capable than the other men ...Both Epics relating to the cardinal human values: prudence, temperance, fortitude and justice, contain the lofty ideal of human excellence, called by the Greeks a.     

Shiva-1: in vitro and in vivo tests of the effects of a novel,synthetic, lytic peptide on ocular cells

An investigation was undertaken to determine the toxicity of an intravitreal injection of a novel peptide drug, Shiva-1, in rabbits. The drug, a synthetic peptide modeled after lytic peptides secreted by certain insects, has antiproliferative and antibacterial properties. Initial in vitro experiments showed that the drug, at a concentration of 100 M, was toxic to both Y-79 retinoblastoma cells and human retinal pigment epithelial cells. A wide range of doses (6–1200 g) was injected into the rabbit vitreous in an attempt to determine the maximum tolerated dose. Retinal toxicity was evaluated clinically, by electroretinography, and by light microscopy. Some localized toxicity was evident at 200 g; all doses of 240 g and above were toxic. While the drug appears to exhibit a narrow range between effective and toxic doses, the results suggest that this and other peptides of similar design merit further investigation for the treatment of proliferative and infectious diseases of the eye.Supported in part by U.S. Public Health Service grants EY07541 and EY02377 from the National Eye Institute, the National Institutes of Health Services, Bethesda, MD, USA     

Toxicity of 1-(β-d-arabinofuranosyl)cytosine after intravitreal injection in the rabbit eye

The retinal toxicity of intravitreally injected 1-(-d-arabinofuranosyl)cytosine (cytarabine) was examined in 7 chinchilla rabbits to determine if cytarabine can be used as local therapy for vitreoretinal non-Hodgkin's lymphoma. Fractionated dose of 600 g, 1500 g, and 2700 g cytarabine in stabilized saline were given intravitreally in one eye (2 × 300 g, 5 × 300 g, and 3 × 900 g, respectively, with an interval time of 24 h) and stabilized saline in the other eye as control. Toxic effects were evaluated with biomicroscopy, direct ophthalmoscopy, fluorophotometry, electroretinography, light, and electron microscopy. Toxic effects were found with the 1500 g and 2700 g doses only. They consisted of a temporary impairment of the blood retina barrier function for fluorescein as measured by fluorophotometry and an irreversible change of the b-wave in the electroretinograms. No histopathologic changes were seen under the light microscope. Electron microscopic examination showed aberrations in the synaptic pedicles of the photoreceptor cells at a dose of 1500 g cytarabine. The results suggest that the cytarabine dose that is expected to be therapeutic for vitreoretinal non-Hodgkin's lymphoma (about 90 g given in three doses of 30 g) is non-toxic for ocular structures.Correspondence to: J.A. van Best     

The effect of body temperature on the murine electroretinogram

Purpose: To study the effect of body temperature on the murine electroretinogram (ERG). Methods: The corneal ERG elicited by a strobe flash from dark-adapted mice was recorded using a saline wick electrode while measuring rectal temperature continuously. The mouse was placed within a cylindrical coil of tubing through which water circulated from a temperature controlled bath. The body temperature of the mouse was changed stepwise between 30 and 37°C. Results: ERGs of approximately normal configuration were recorded at body temperature ranging between 30 and 37°C. The maximum amplitude of the a- and b-waves varied linearly with temperature. The rate of change of b-wave amplitude was about 100 V/degree. At 30°C, maximum b-wave amplitude was about 400 V; at 37°C it was about 1000 V. A change in body temperature produced a rapid change in ERG amplitude. Conclusion: The murine ERG is very sensitive to changes in temperature. In order to monitor the ERG accurately over time, continuous recording of body temperature is essential.     

Inhibition of corneal allograft reaction by CTLA4-Ig

Background: Activation of T cells requires both the interaction of T-cell receptor with major histocompatibility complex on the antigen-presenting cell and costimulatory signals, for instance the B7 antigens expressed on antigen-presenting cells and the CD28 molecule expressed on T cells. A recombinant fusion protein, CTLA4-Ig, has been produced that contains the extracellular domain of human CTLA4 fused to IgGl constant region and that binds the B7 molecule with high affinity. Blocking the CD28/B7 interaction with CTLA4-Ig inhibits T cell activation in vitro and in vivo. Methods: We used CTLA4-Ig in a fully MHC-mismatched mouse keratoplasty model. The animals were divided into four groups: (1) no treatment, (2) intraperitoneal treatment with 130 g CTLA4-Ig, (3) intraperitoneal treatment with 300 g CTLA4-Ig, (4) subconjunctival treatment with 290 g CTLA4-Ig. Results: The allograft reaction occurred in untreated animals between days 12 and 16 (mean 13.5). While topical application of CTLA4-Ig seemed to shorten the graft survival (mean 11.6 days) and systemic application of 130 g had no influence (mean 14.0), only intraperitoneal injection of 300 g of CTLA4-Ig prolonged the survival of allografts (mean >20 days) (P<0.01). Conclusion: CTLA4-Ig prolonged significantly the survival of corneal allografts in a fully MHC-mismatched mouse keratoplasty model, but the small antigen load of the corneal transplant and the anterior chamber-associated immune deviation (ACAID) may have a disadvantage to induce tolerance in this model of CTLA4-Ig therapy.Presented at JERMOV 1996 in Montpellier     

Penetration of five beta-adrenergic antagonists into the rabbit eye after ocular instillation

Aqueous humor and serum levels of five beta-adrenergic blockers were measured using gas Chromatographic techniques following ocular instillation of 1% solutions to rabbits. Octanol/buffer partition ratios were also determined. No apparent relationship was found betweeen the peak levels of the agents in aqueous humor and their octanol/buffer partition ratios. However, peak aqueous humor levels of timolol (461 ng/100 mg) and practolol (919 ng/100 mg), whose partition ratios were less than unity, occurred somewhat later (1 h) than the peaks of propranolol (859 ng/100 mg at 30 min), oxprenolol (1,771 ng/100 mg at 30 min) or alprenolol (1,004 ng/ 100 mg at 10 min) whose partition ratios exceeded unity. Peak levels in serum of timolol (8.0 ng/100 l), propranolol (4.2 ng/100 l), oxprenolol (11.5 ng/100 l), and alprenolol (4.5 ng/100 l) were achieved within 10 min and reduced to less than 15% within 4 h. Peak serum levels of practolol (9.9 ng/100 l) occurred somewhat later (2 h) and remained high (41%) 6 h later.     

Retinal toxicity and ocular kinetics of 1-β-D-arabinofuranosyl-E-5-(2-bromovinyl)uracil in rabbits

The intraocular penetration of 1--d-arabinofuranosyl-E-5-(2-bromovinyl)uracil (BV-araU), a new antiviral drug, after oral administration, the effects of non-toxic intravitreal doses of BV-araU, and the intraocular kinetics of BV-araU after intraocular injection were studied in rabbits. The intravitreal penetration of BV-araU after oral administration was very poor: 0.11 ± 0.13 g/ml and 0.20 ±0.02 g/ml respectively in albino and pigmented rabbits 2 h after 30 mg/kg. An intravitreal injection of 200 g BV-araU caused transient electroretinographic (ERG) changes, whereas a 100-g injection and intravitreal irrigation with 20 g/ml BV-araU caused no ERG and histologic changes over the 4-week follow-up period. The half-life of the intravitreal concentration of BV-araU after an intravitreal injection was short (2.4 h). The results suggest that an intravitreal injection of 100 g BV-araU or an intravitreal irrigating solution containing 20 g/ml BV-araU is nontoxic to the retina and may be used for treatment of retinitis caused by varicella-zoster virus or herpes simplex virus type 1.     

Contact diode laser: High power application through fiberoptic cutting tips

Diode laser energy has been applied through a fiberoptic probe using a power setting of 2.5 watts (W) in the continuous mode. In this study we employed high-power diode laser energy (4 to 12 W, continuous wave) to incise ocular tissue through a fiberoptic probe using 100m and 300m tips. The retina was photocoagulated with a 300m orb tip. No bleeding occurred at the incision sites. Histologic evaluation revealed coagulation into the healthy tissue ranging from 10 to 50m.     

Die fixation des menschlichen auges

Zusammenfassung Während der Fixation wird ein Fixationsfeld beansprucht im Ausmaße von 100 , d.i. das Bereich der dünnsten und höchsten Zapfen, von 1 Durchmesser. In diesem Fixationsfeld ist der Fixationspunkt der Willkür entzogen. Während der strengen Fixation macht das Auge bekanntlich dreierlei Bewegungen, von denen die schnellen ebenfalls in einem Feld von 100 Durchmesser liegen. Das maculopapilläre Bündel führt die Erregungen aus dem auch in Bezug auf das Ableitungssystem ausgezeichneten Fixationsfeld ab. Die Sehschärfe unterschreitet weit die Grenze von 1 , was auf die Synapsenfunktionen der Retina, des Corpus geniculatum laterale und auf die cortikalen Bezirke zurückgeführt wird.

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Summary During fixation a fixation-field of 100 diameter is required, corresponding to the area of the thinnest and longest cones of 1 diameter. Within this fixation-field the position of the fixation point is involuntary and at random. The fast component of the three eye movements during fixation also covers a field of 100 diameter. Impulses from this field are conducted via the maculo-papillary bundle. The visual acuity is far below the limit of 1 ; this is attributed to the synaptic function of the retina, the lateral geniculate body and the cortical areas.

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Résumé Pendant la fixation un champ de 100 se trouve occupé, c'est-à-dire la région des cônes les plus hauts et les plus minces, qui ont pour diamètre 1 . Dans le champ de fixation le point de fixation n'est plus soumis à la volonté. Pendant la fixation précise l'oeil fait trois sortes de mouvements; les plus rapides d'entre eux intéressent aussi un champ d'un diamètre de 100 . Le faisceau papillo-maculaire conduit les influx nerveux hors du champ de fixation. L'acuité visuelle descend bien en-dessous de 1 . Ce fait est attribué aux fonctions synaptiques de la rétine, du corps genouillé externe et des régions corticales.

     

Electrophysiologic characteristics of human and rat retinas in vitro

To promote studies on the human retina, we investigated the survival of function in postmortem specimens. Visual pigment has been regenerated in normal human retinas, 5 to 58 hours postmorten, by exposure to retinal isomers in the dark. Levels from 0.1 to 0.41 nmol/ mg protein were reached. Photoresponses were obtained in 9 of 13 retinas: P III maximum amplitudes ranged from 20–398 V and thresholds, taking the criterion amplitude as 3 V, ranged from 8.8–1340 quanta/m ². In three cases, the b-wave was also seen. The P III amplitude vs. log intensity curves gave values of n between 0.6 and 1.0, and (the stimulus intensity for a half maximal response) between 132–3700 quanta/m². Recovery of sensitivity did not always correspond to that of maximum response.     

Increased release of tenascin in tear fluid after photorefractive keratectomy

Background: Extracellular matrix protein tenascin (TN) is expressed in the anterior stroma during corneal wound healing. In this study we analysed TN release in tear fluid after photorefractive keratectomy (PRK). Methods: Tear fluid TN concentrations of ten PRK patients were measured with an immunoassay. Tear fluids were collected preoperatively and 1, 2 and 7 days after PRK. The tear fluid collection time and the volume of tears collected were registered. Because tear fluid flow was greatly increased postoperatively, tear fluid flow-corrected release (TN flux) was calculated. Results: The tear fluid flow was 4.50±0.94 l/min (mean±SEM) preoperatively, 55.48±16.70 l/min (P<0.01) on the 1st, 33.91±7.91 l/min (P<0.01) on the 2nd, and 13.79±5.49 l/min (P>0.05) on the 7th postoperative day. The preoperative TN concentration was 0.85±0.20 g/ml. On the 1st postoperative day it decreased to 0.37±0.17 g/ml (P>0.05), most likely due to the dilution effect caused by hypersecretion after PRK. The TN concentration was 0.67±0.12 g/ml (P>0.05) on the 2nd and 0.78±0.15 g/ml (P>0.05) on the 7th postoperative day. The preoperative TN flux was 5.23±1.88 ng/min. On the 1st and 2nd postoperative days the TN flux was 14.40±4.99 ng/min (P<0.05) and 22.66±6.I2 ng/min (P<0.05), respectively. On the 7th postoperative day a tendency towards decreased flux (14.00±6.02 ng/min, P>0.05) was observed. Conclusion: Although there is a minor decrease in TN concentration after PRK due to increased tear fluid flow, a significant increase in TN flux was observed. Complete reepithelialization of the ablated area was observed in all eyes at the follow-up visit on postoperative day 7.     

Influence of oxygen free radicals and free radical scavengers on the growth behaviour and oxidative tissue damage of bovine retinal pigment epithelium cells in vitro

Purpose: This investigation was carried out to ascertain whether oxygen free radicals can influence the growth behaviour and consecutive lipid peroxidation of retinal pigment epithelium (RPE) cells in vitro and whether scavengers can counteract these effects. Methods: The experimental model was based on calf RPE cells. Hypoxanthine/xanthine oxidase (HX/XO) and superoxide dismutase/catalase (SOD/CAT) served as the radical generating system and scavengers, respectively. The components were tested alone and in combination. Lipid peroxides were determined in culture supernatants by a thiobarbituric acid assay. Results: Concentrations of up to 100 mol/1 of HX alone and 500/1000 U of XO alone, as well as the application of the scavengers without the radical generating system (HX/XO), had no effect. Doserelated reduction of cell growth and increase of lipid peroxidation were found with HX/XO treatment (single dose of 500 and 1000 U/ml 24 h after seeding). After application of 500 or 1000 U/ml of XO, CAT, when given alone (1200 U/ ml), counteracted the effect of the radicals on cell growth and lipid peroxidation; SOD (300 U/ml) had no effect. A combination of SOD and CAT was no better than the effect of CAT alone. Conclusion: The prevention of radical-induced reduction of cell growth and lipid peroxidation by scavengers supports trials of therapy using antioxidants and/or free radical scavengers for various ocular syndromes with RPE involvement.     

Distribution of calcium and sulphur in the blue-light-exposed rat retina

Background: Blue-light exposure inhibits cytochrome oxidase and may therefore inhibit retinal metabolism. The reduced metabolism decreases the extrusion of calcium from the photoreceptor cell. Overload of calcium is proposed as one of the factors that lead to photoreceptor degeneration after light exposure. The light-induced photoreceptor degeneration can be ameliorated by calcium overload blocker. In the present study the calcium concentration was measured in the inner and outer segment layer of the rat retina. Methods: Six eyes were exposed to blue (404 nm) light at a retinal dose of 380 kJ/m². Five eyes served as the control group. The calcium and sulphur distributions were measured with a nuclear microprobe in the freeze-dried rat retina. The proton beam size was 12 × 12 m and the energy of the protons was 2.55 MeV The calcium concentration was calculated using sulphur as a reference. Results: The level of calcium per milligram sulphur was 21 g (range 17–23 g) in the inner segment of the control retina. It increased to 62 g/mg sulphur (range 52–67 g) and 61 g/mg sulphur (range 58–66 g) 1 h and 12 h after blue-light exposure, respectively. Conclusion: The findings of the present study support the idea that accumulation of calcium in the inner segment layer is one of the factors that cause photoreceptor degeneration.     

Argon-Laser Coagulation der Kanincheniris

Zusammenfassung Beim Chinchilla-Kaninchen wurde das kammerwinkelnahe Drittel der Iris nach Ermittlung der Schwellenwerte mit Argon-Laser-Energien von 0,02–4,8 J und einem Brennfleckdurchmesser von 50 m coaguliert. Irisschädigungen, die mit einer Energie von 1,2 J erzielt werden konnten, untersuchten wir 30 min post coagulationem sowie 72 Std, 10 und 28 Tage nach der Exposition spaltlampen-, stereo- und rasterelektronenmikroskopisch. Nach 30 min findet sich ein zentraler Substanzdefekt von 50–80 m Durchmesser, der von einer intermediären Zone 30–60 m Breite stärkerer Zelldestruktion umgeben ist. Daran schließt sich eine periphere Zone abnehmender Zellstörung bis zu 200 m Breite an. Nach 72 Std lassen sich am Rand des zentralen Defektes entzündliche Zeichen nachweisen. Nach 10 bzw. 28 Tagen bleibt der zentrale Defekt erhalten, die oben genannten angrenzenden Zonen sind jedoch nicht mehr eindeutig abgrenzbar.

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Argon-laser coagulation in the rabbit irisDetermination of threshold dosis and respective scanning electron microscopic findings

Summary The lateral third of the iris near the chamber angle was photocoagulated after determination of the threshold dose with argon-laser energy of 0.02–4.8 J and spot diameters of 50 m. Iris lesions produced with energy levels of 1.2 J, were examined with slitlamp, dissecting microscope, and scanning electron microscope. After 30 minutes the following findings were recorded: central stromal defect 50–80 m in diameter, surrounded by an intermediary zone of 30–60 m with severe cell destruction; a peripheral zone up to 200 m in breadth with less cell fragmentation adjacent to the intermediary zone. After 72 hours the margin of the central defect showed inflammatory changes. After 10–28 days the central defect remained stable; the bordering zones described previously were no longer discernible.

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Auszugsweise vorgetragen auf der 45. Versammlung der Vereinigung Rhein-Mainischer Augenärzte am 14. und 15. Oktober 1972 in Mainz.

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Die Untersuchungen wurden in dankenswerter Weise unterstützt durch die Jung-Stiftung für Wissenschaft und Forschung und die Stiftung Volkswagen-Werk.     

Über das Vorkommen lichtempfindlicher,fluorescierender Substanzen in verschiedenen Geweben von Rinderaugen

Zusammenfassung und Ergebnisse Papierchromatographisch wurde aus Hornhäuten, Linsen und Netzhäuten von Rindern eine nach denR _f -Werten und UV-Spektren gleiche Substanz isoliert. Sie fluorescierte im alkalischem Medium leuchtend grün, im sauren leuchtend blau. Die Absorptionsmaxima lagen in n/10 Natronlauge bei 258–260 m und bei 400 m und in n/10 Salzsäure bei 258–260 m und bei 360 m. Auffallend war die starke Lichtempfindlichkeit dieser Verbindung. Eine Identifizierung der fluorescierenden Substanz gelang nicht. Auf Grund der gefundenen UV-Spektren und derR _f -Werte in Pteridinlaufmitteln kann vermutet werden, daß es sich um ein Pteridin handeln könnte.Mit 5 Textabbildungen