Identification of unknown quaternary ammonium compounds in corneal epithelium and aqueous humor.

Bovine corneal epithelium and bovine aqueous humor are investigated for their content of quaternary ammonium compounds. In total, four compounds are found. Three of these are identified. For the fourth compound, a proposal for its structure is made on the basis of tandem mass spectrometry fragmentation spectra. The compounds investigated have m/z values of 146, 160, and 174. The compounds with m/z 146 are confirmed as acetylcholine (in corneal epithelium) and (3-carboxypropyl)-trimethylammonium (in both corneal epithelium and aqueous humor). The compound with m/z 174 is identified as butyrylcholine (in corneal epithelium). The compound with m/z 160 is probably acetyl-g-homocholine (in both corneal epithelium and aqueous humor). For both butyrylcholine and acetyl-g-homocholine, it is the first time the presence of these compounds in corneal epithelium or aqueous humor (or both) is described. Both acetylcholine and butyrylcholine are unstable compounds, which are probably susceptible to enzymatic degradation by acetylcholine-esterase and butytrylcholine- esterase, respectively.

UV absorption by uric acid in diurnal bird aqueous humor.

PURPOSE: To analyze the components responsible for the UV absorbance in diurnal bird aqueous humor. METHODS: The absorbance studies were carried out using a Hitachi spectrophotometer (U 2000). Uric acid was determined by high-performance liquid chromatography (LC-10 system; Shimadzu, Kyoto, Japan). Chicken and turkey eyes were examined. RESULTS: The UV absorbance in chicken aqueous was largely accounted for by the presence of protein, tryptophan, tyrosine, ascorbic acid, and uric acid. Ascorbic acid was low (23 micromol/l). Uric acid was, on the other hand, remarkably high (151 micromol/l) compared with that in mammals (cattle, 16 micromol/l). Principally the same results were obtained in chicken and turkey. CONCLUSIONS: Uric acid is a significant UV-absorbing substance in the aqueous humor of diurnal birds with its peak absorbance at 292 nm. The hypothesis that the aqueous humor acts as a UV filter seems to be valid also for the avian eye. However, in these eyes uric acid fulfills the role that ascorbic acid does in mammals.

Distribution of ascorbate in the anterior bovine eye.

PURPOSE: To analyze the ascorbate distribution in the anterior eye wall to better understand the functional significance of this compound in the eye. METHOD: Ascorbic acid was determined by high-performance liquid chromatography using an LC-10 system (Shimadzu, Kyoto, Japan). Bovine eye samples were used. RESULTS: The highest ascorbate concentration was observed in the corneal epithelium, with significantly higher values in the central (1.56 mg/g) than in the peripheral (1.39 mg/g) area. The ascorbate content was similar in the corneal stroma (0.22 mg/g), the Descemet's membrane (DM)/endothelium (0.22 mg/g), and the aqueous humor (0.21 mg/ml). By comparison, the sclera (0.15 mg/g) and the conjunctiva (0.11 mg/g) showed lower values, as did the lacrimal gland (0.09 mg/g) and the serum (0.0008 mg/ml). CONCLUSIONS: (1) Peak ascorbate concentration was observed in the central corneal epithelium covering the pupillary area. This is compatible with the idea that the ascorbate may act as an UV filter shielding internal eye structures from radiation damage. (2) The ascorbate concentration in the corneal stroma and DM/endothelium was as high as in the aqueous humor, and it is suggested that the aqueous humor plays a key role in the distribution of ascorbate to the anterior eye wall.

Ascorbate in the corneal epithelium of diurnal and nocturnal species.

PURPOSE: To compare the amount of ascorbic acid in the corneal epithelium of various species to unveil possible differences between diurnal and nocturnal mammals. METHODS: Ascorbic acid was determined by high-performance liquid chromatography, using an LC-10 system (Shimadzu, Kyoto, Japan). RESULTS: Diurnal animals show a higher ascorbate concentration in the corneal epithelium than nocturnal animals. Ascorbate concentration is higher in the corneal epithelium than in the matching aqueous humor in diurnal and nocturnal species. The highest ascorbate concentration is found in the corneal epithelium of the reindeer. CONCLUSIONS: Ascorbate level in the corneal epithelium seems to vary in accordance with ambient radiation exposure of the respective species, just as in the aqueous humor. Both phenomena are regarded as environmental adaptations, and the ascorbic acid is suggested as protecting against photokeratitis and as acting as an ultraviolet filter for internal eye structures.

Dose response and duration of action of dorzolamide, a topical carbonic anhydrase inhibitor.

The multiple-dose, dose-response relationship and duration of action of the novel topical carbonic anhydrase inhibitor dorzolamide (previously known as MK-507) were investigated in a double-masked, randomized, placebo-controlled, parallel study in 73 patients with bilateral primary open angle glaucoma or ocular hypertension. Dorzolamide (0.7%, 1.4%, or 2%) or placebo was administered every 12 hours for 5 days and then every 8 hours for 7 days. Intraocular pressure was investigated with multiple 12-hour diurnal curves. All concentrations of dorzolamide demonstrated substantial lowering of intraocular pressure throughout the day when given twice daily (9% to 21%) or three times daily (14% to 24%). Although a dose-dependent response was observed immediately following the first dose, there were no significant differences between concentrations or dose response at either the twice or three times daily dosing regimen. Three times daily administration of 2% dorzolamide demonstrated a mean percent decrease in intraocular pressure of 18% to 22% throughout the day (mean decrease, 4.5 to 6.1 mm Hg). Dorzolamide appears to have substantial potential in the treatment of glaucoma and ocular hypertension.

Iris neovascularisation in eyes with pseudoexfoliation syndrome.

The iris vascular bed of eyes with pseudoexfoliation syndrome has been studied with electron microscopy. Two of the eyes suffered from painful glaucoma, whereas the third showed normal intraocular pressure. The following changes were observed: (1) deposits of pseudoexfoliation material lying adjacent to the endothelial wall; (2) thin vessel basement membrane, sometimes even interrupted; (3) extreme reduction of vessel lumina through increased volume of the endothelial cells; (4) fenestration of the endothelial wall. It is suggested that the iris neovascularisation in eyes with pseudoexfoliation syndrome is due to an obstruction of iris vessels causing tissue hypoxia.

Epidemiology of glaucoma in northern Europe.

PURPOSE: To survey glaucoma epidemiology in Northern Europe. RESULTS OF LITERATURE REVIEW: Open-angle glaucoma is defined here as the simple and capsular types taken together. On this basis open-angle glaucoma makes up by far the largest group of glaucoma in Northern Europe. These are the target groups of this study, and pigmentary glaucoma is excluded because of the small numbers. CONCLUSION: Open-angle glaucoma is less frequent in Southern Sweden and Denmark than in Finland, Middle Sweden, Norway, and iceland. This may to some extent be explained by the suggested low prevalence of pseudoexfoliation in the southern areas, but other factors are presumed to be of importance as well.

Sample preparation and determination of acetylcholine in corneal epithelium cells using liquid chromatography-tandem mass spectrometry.

A sample preparation method with subsequent liquid chromatography (LC)-mass spectrometry (MS)-MS analysis for acetylcholine in corneal epithelium is developed. The sample preparation is developed with a focus on compatibility with the LC-MS-MS system and the stability of acetylcholine because acetylcholine esterase is present in the tissue. It appears that both acetylcholine as well as the internal standard (IS) used (acetyl-beta-methylcholine) have fragments at m/z values in the tandem MS spectrum, which correspond with the m/z values of fragments of endogenous substances. Acetylcholine and (3-carboxypropyl)triethylammonium both have 146-->87 and 146-->60 transitions. Acetyl-beta-methylcholine and an unknown compound both have 160-->101 and 160-->60 transitions. This makes it necessary to use a chromatographic step, which has a baseline separation between these endogenous compounds, acetylcholine, and the IS. The analytical procedure has linearity from 1 ng/mL (30 pg/mg corneal epithelium tissue) to at least 250 ng/mL (7.55 ng/mg corneal epithelium tissue). The limits of detection and quantitation are 15 and 45 pg on column, respectively. Relative standard deviation and bias values are within the range of acceptance for all concentration levels.

Aqueous humour and ultraviolet radiation.

Studies on the ultraviolet ray absorption in the aqueous humour of rabbit, cat, monkey, guinea pig, and rat showed marked species differences. In the rabbit aqueous the ascorbic acid, the proteins, and some amino acids (tyrosine, phenylalanine, cystine, and tryptophane) are together responsible for the total absorption, and a very great part of it refers to the ascorbic acid content. Accordingly, species with significant amounts of ascorbic acid in the aqueous (monkey, rabbit, guinea pig) have a greater absorption capacity towards ultraviolet radiation than species (cat, rat) lacking this substance. This effect of the ascorbic acid may contribute in protecting the lens against the most biotoxic ultraviolet rays. It seems that the ascorbic acid concentration is highest in the aqueous of typical day animals and lowest in species being active in the dark, indicating a correlation between the aqueous' ascorbic acid level and the quantity of incident light on the eye. The possible significance of changed aqueous ultraviolet ray absorption in the pathogenesis of human cataract development is discussed.

Cornea and ultraviolet radiation.

The absorption of ultraviolet radiation in the cornea of rabbit, cat, guinea pig, and rat has been studied. It turned out that about 80% of incident radiation is absorbed at the 290 nm wavelength limit in rabbit and cat, whereas the absorption is considerably lower in guinea pig and rat. In a model experiment based on conditions in the rabbit cornea epithelium, it is shown that the ascorbic acid in these cells is roughly responsible for ultraviolet ray absorption of the same order as proteins and nucleic acids in the 250-290 nm spectral range. This implies that for radiation below 290 nm wavelength also the ascorbic acid should be regarded as a potential target substance which may mediate photophthalmic damage to the tissue. The low absorption of the ascorbic acid compared to the other two components above 290 nm, indicates that the ascorbic acid contributes less in photophthalmic development due to solar radiation.

Evidence that hypotony in retinal detachment is due to subretinal juxtapapillary fluid drainage.

One case of aphakic retinal detachment with increased intraocular pressure is described. Overnight the intraocular pressure fell abruptly to non-measurable values, and simultaneously the detachment had advanced to the optic disc border. The hypothesis is formulated that decreased intraocular pressure in eyes with retinal detachment is brought about because intraocular fluid is leaking out of the eye through a subretinal route to the perioptic connective tissue. Additional support for this posterior aqueous outflow is obtained from clinical studies showing that maximum hypotony is reached when the detachment has advanced to the optic disc border.

[Acute eye problems]. / Akutte oyeproblemer.

The article reviews diagnostic and therapeutic problems in connection with patients with "acute eye". Usually the person visits the doctor for one of the following reasons: Sudden change in vision A red and perhaps painful eye Injury to the eye.

Quenching of UV-induced fluorescence by ascorbic acid in the aqueous humour.

Spectrophotometry and spectrofluorimetry of bovine aqueous humour have been performed. The question of whether mechanisms for fluorescence quenching exist in the eye media was evaluated. It turned out that the marked fluorescence of tryptophane and protein was considerably quenched by the ascorbic acid, an observation not shown before. Thus, the aqueous humour minimizes UV-radiation to the lens in diurnal animals through three different mechanisms: 1) Absorption. 2) Fluorescence-quenching. 3) Fluorescence-mediated ray transformation of energy-rich short wavelengths to less potent longer wave-lengths. The impact of each of them is significantly influenced by the ascorbate concentration in the aqueous humour. The phenomenon of fluorescence-mediated ray transformation is, of course, per se independent of ascorbate, but the transformational input is significantly reduced due to ascorbate.

In vitro evidence for UV-protection of the eye by the corneal epithelium mediated by the cytoplasmic protein, RNA, and ascorbate.

PURPOSE: (1) To evaluate the effect of ribonucleic acid (RNA) and ascorbate on UV-absorption and their impact on ultraviolet-induced (UV) fluorescence from various proteins, and (2) to compare RNA and DNA reduction of protein fluorescence. These informations will be useful for later work on the UV-filtering effect of the corneal epithelium. METHOD: Spectrophotometry and spectrofluorimetry. RESULTS: (1) RNA and ascorbate caused a significant UV-absorption and reduced the fluorescence from various water-soluble proteins, the degree of reduction varying independently from one protein to the other. (2) RNA and DNA showed protein fluorescence reduction of roughly the same order. CONCLUSION: The results are discussed both in the context of UV-protection of the cell nucleus in general, and the possible UV-filtering effect for the eye of bovine corneal epithelium.

The significance of ascorbate in the aqueous humour protection against UV-A and UV-B.

It has previously been suggested that the aqueous humour acts as a UV-filter protecting the structures behind. This hypothesis has here been further evaluated by use of spectrophotometry and spectrofluorimetry. Principally three different aspects of the protecting mechanism have been unveiled: absorption, fluorescence quenching and wavelength transformation. The extremely high ascorbate values obviously play a key role in all of them. Thus, aqueous ascorbate both increased absorption and suppressed fluorescence of radiation below roughly 310 nm wavelength. In addition, as a consequence of ascorbate quenching, fluorescence emission to the UV-A range (320-400 nm) is substantially reduced.

Actin filaments in trabecular endothelial cells in eyes of the vervet monkey. (Cercopithecus aethiops).

An electron microscopic study was performed on the trabecular meshwork of two monkeys (cercopithecus aethiops). Specimens from one animal revealed numerous cytoplasmic filaments of 45-65 A thickness in endothelial cells both on the trabeculae in the wall of Schlemm's canal after conventional glutaraldehyde and osmium fixation. Using a histochemical technique it was shown in specimens from the other animal that these filaments consist of actin material. This evidence of intracellular actin filaments in the trabecular endothelium indicates that these cells have contractile properties, and the possible significance of this finding for the regulation of outflow facility of aqueous humour is suggested.

Distribution of ascorbic acid in the ciliary body of albino rabbit, guinea pig and rat.

The distribution of ascorbic acid in the ciliary body has been demonstrated by means of a silver nitrate technique. It appeared that the basal cells in the pars plana region and in the valleys between the ciliary processes contain great amounts of ascorbic acid, in contrast to the basal cells over the processes proper which showed only traces. Rabbit and guinea pig revealed mainly the same findings, and quantitative differences occurred before and after intracardial injection of ascorbic acid. On the other hand, ascorbic acid was absent in the ciliary body of untreated rats, whereas only traces were found after intracardial injection of this substance. These species differences are in keeping with previous reports showing high concentration of ascorbic acid in the aqueous humour from rabbit/guinea pig, and no ascorbic acid at all in aqueous humour from rats.

Damage of the cornea epithelium caused by ultraviolet radiation. A scanning electron microscopic study in rabbit.

Rabbit cornea epithelium was exposed to UV-radiation for 15 min from a distance of 50 cm, and specimens were studied after 1/2, 1, and 3 h, respectively. The following changes occurred: 1) Reduced number of the large impressions or the full-thickness holes of the superficial cells. 2) Partly rejected cells. 3) Numerous small plasma membrane defects. This investigation shows plasma membrane defects at an early stage after the exposure, and this may be the locus for the initial damage.

Epidemiology of the pseudo-exfoliation syndrome.

1) Pseudo-exfoliation syndrome (PE syndrome) is a condition with worldwide distribution. 2) Marked geographical variations have been demonstrated. 3) Environmental factors may be of etiological significance for the development of PE syndrome. 4) The PE syndrome's ability to promote glaucoma may vary from one area to another. 5) There seems to be a trend towards lower debut age of PE syndrome at lower latitudes. 6) More prevalence studies from different parts of the world are needed. A standardized set-up of such works would facilitate comparison of the results, and so some guidelines have been proposed.