Eye Fluid Research Articles

Osmolality of the tear fluid in the contralateral eye during monocular contact lens wear

The effect of monocular hydrogel contact lens wear on the osmolality of the tear fluid in the ipsilateral and contralateral eyes was measured. The hydrogel contact lenses were of similar diameter and either 38% or 70% water content with thicknesses of 0.07 mm, 0.15 mm or 0.30 mm. The ipsilateral eye showed an initial 2 m.osm/kg decrease (hypo-osmotic) in tear fluid osmolality from baseline after lens insertion. After 5 min the osmolality increased (hyperosmotic) to 15 m.osm/kg greater than baseline, remaining around this level for the 60 min of lens wear. This hyperosmotic change was attributed to an increase in water evaporation due to disruption of the tear film by the contact lens. There was a similar pattern of change in the contralateral eye, but of smaller magnitude. All contact lenses produced a similar effect on tear fluid osmolality, except the combination of a 0.30 mm thick lens of 70% water content fitted with a flat bearing relationship which induced a greater hyperosmotic change after 5 min wear.

Lactoferrin and serum albumin in the conjunctival fluid of eyes operated for senile cataract

The concentrations of serum albumin (SA) in the conjunctival fluid were measured in 25 patients before surgery and in the post-operative period following cataract extraction. We found a significant increase in mean tear fluid SA concentration on the first post-operative day. The SA concentration remained high during the first 3 pre-operative levels. No correlation between the post-operative concentration profile of tear fluid SA and earlier findings of the tear lactoferrin (LF) profile of the same group of patients (Jensen et al. 1985) could be shown, although a trend towards an inverse relationship was apparent from the graphs. Pre-operatively, we found a significant positive correlation between age and concentration of SA in the conjunctival fluid (P less than 0.05) which might be interpreted as an increase in leakage from conjunctival vessels with age. This would, at least partly, explain the decreasing LF concentration with age (Jensen et al. 1986; McGill et al. 1984). It is concluded that transudate/exudate from the conjunctival vessels, represented by the change in the SA concentration in the conjunctival fluid, might be responsible for an initial post-operatively reduced concentration of LF and possibly other lacrimal gland proteins.

Inflammatory mediators in alkali-burned corneas: preliminary characterization.

Leukocyte chemotactic factors (LCF) are important inflammatory mediators which activate and recruit leukocytes from the circulation into sites of tissue damage. These factors were recently detected in the tear fluid of inflamed eyes induced by alkali burn. It remains unclear, however, whether the detected LCF are released from injured corneal tissues or leaked from the circulation. Using a corneal cup model developed in our laboratory, we began examining the capability of corneal tissues to produce LCF in response to alkali injury. We also evaluated the influence of citric acid on the production of LCF from corneas preinjured by the alkali sodium hydroxide (NaOH). For these studies, the epithelial surfaces of corneas isolated from bovine and human eyes were exposed to 1N NaOH for 35 seconds at room temperature. The NaOH was then removed and the epithelial surfaces washed once with buffer and incubated with culture medium for 1, 2, 4, and 6 hours at 37 degrees C/5% CO2 atmosphere. Our results showed that (1) NaOH2 induced corneal epithelial cell injury ranging from cell discoloration and moderate damage of the upper half of the epithelium (1-4 hrs) to total destruction of the epithelium (6 hrs); (2) NaOH-injured corneas (2 hr incubation post injury) produced significant levels of chemotactic activity (via checkerboard analysis) specific for neutrophils (115% maximum chemotactic response [MCR]) and mononuclear cells (94% MCR); (3) preliminary characterization of these factors revealed that they are protease and heat sensitive, extractable by organic solvents, and possess molecular weight values greater than 100,000 daltons; and (4) incubation of NaOH-pretreated corneas with 0.01% citric acid for 2 hours markedly inhibited the production of LCF for both neutrophils (98% inhibition) and mononuclear cells (91% inhibition). Results of these studies indicate that alkali-burned bovine and human corneas generate leukocyte chemoattractants which differ in their biochemical characteristics from previously known low molecular weight chemotactic factors such as C5a, interleukin-1, or leukotriene B4.

RETINAL TOXICITY OF GANCICLOVIR IN VITRECTOMY INFUSION SOLUTION

The authors investigated the retinal toxicity of the antiviral agent ganciclovir after its addition to vitrectomy infusion fluid in rabbit eyes. Intravitreal infusion of the drug in concentrations up to 30 micrograms/ml produced no electroretinographic or histologic changes suggestive of retinal toxicity. Ganciclovir in vitrectomy infusion fluid has potential therapeutic benefit in viral retinitis (particularly in cytomegalovirus retinitis) associated with vitreous traction or rhegmatogenous retinal detachment. Based on the median inhibitory doses of ganciclovir against various herpes group viruses and the results of this study, a concentration of 30 micrograms/ml or less of the drug is recommended for vitrectomy infusion solution.

Timentin--clinical and pharmacokinetic evaluation in otorhinolaryngology.

The efficacy and tolerance of Timentin was studied in 41 patients with various infections of the ears, nose and throat. The pharmacokinetics of Timentin were determined in pus, mucosa and polyps of the nose and paranasal sinuses, the tonsils and submandibular gland as well as in the interstitial fluid collected in Redon vacuum drainage. Experimental pharmacokinetic studies in the guinea pig were performed in the inner ear and eye fluids and in serum. Ticarcillin and clavulanic acid concentrations were determined by a microbiological micromethod. The clinical studies demonstrated that Timentin was very effective and well tolerated. The clinical and experimental pharmacokinetic studies provide a good explanation of this high degree of effectiveness.

Should corneas from donors receiving a high dose of salicylate be used as grafts: An animal experimentation

Rabbits were injected intravenously with a single dose of sodium salicylate (350 mg kg −1) in order to study the following in vivo: (i) the distribution of the drug in the various eye tissues and fluids, particularly the cornea and aqueous humour, and (ii) transfer of the drug from corneal grafts obtained from donors receiving sodium salicylate to the eye tissues of the recipient. In additional experiments, the in vitro effects of sodium salicylate on the growth and protein synthesis of corneal cells grown in tissue culture were also studied. In vivo experiments showed that the periods during which we observed the highest concentration of salicylate in the serum and in the eye tissues were within 30 min and 2 hr respectively following the injection. These experiments also showed that salicylate was transferred from the treated donor via corneal graft to the recipient's eye tissues where it could still be detected 48 hr after the operation. In vitro experiments showed that a 50% inhibition of cell growth was obtained at a concentration of about 1000 μg salicylate ml −1 while protein synthesis was decreased by 50% at a concentration of about 200 μg ml −1. A consideration of our data from the in vivo and in vitro experiments together suggests that ingestion by the donor of high concentrations of salicylate may have the potentiality of subjecting the corneal endothelial cells to cytotoxic concentrations of the drug thus jeopardizing the success rate of corneal graft operations.

Distribution of radiolabelled azelaic acid in eye membranes and fluids of rabbits

A direct cytotoxic effect of azelaic acid on melanocytes of human melanoma has been demonstrated. In view of a possible future therapeutic employment of this drug in the treatment of primary ocular melanoma, we investigated the route of choice of azelaic acid administration in rabbits. Our results evidenced a suden and direct blood absorption of topically (by retrobulbar injection) administered azelaic acid. This is in agreement with the high water solubility of azelaic acid sodium salt. These preliminary reports indicate that the elective route of azelaic administration in primitive eye melanoma is intravenously by continuous infusion.

Blood, bone marrow and eye fluid ethanol concentrations in putrefied rabbits

The effect of putrefaction on postmortem blood, bone marrow and eye fluid ethanol levels was evaluated in rabbits. Control and dosed animals were sacrificed and stored at either room temperature (approx. 19°C) or cold temperature (approx. 3.5°C) for as long as 28 days. Control animals stored at room temperature showed ethanol levels in the bone marrow that peaked at 7 days after sacrifice, followed by decreases to a non-detectable level at 21 days. Overall decreases were demonstrated in bone marrow of dosed rabbits stored at room temperature for all postmortem intervals. The control animals stored at low temperature showed no ethanol in the bone marrow and blood until 21 days after sacrifice. Dosed rabbits stored at low temperature showed no significant changes in blood and marrow ethanol until 21 days after sacrifice.

Experimental Perfusions Through the Anterior and Vitreous Chambers with Possible Relationships to Malignant Glaucoma

Enucleated eyes were perfused alternately via the anterior and vitreous chambers. At low intraocular pressure (IOP), vitreous humor presented considerable resistance to forward flow of perfusion fluid in calf eyes, but not in human eyes. In human eyes when the perfusion pressure was increased to 60 mm Hg, the resistance to flow forward from the vitreous body increased, but became practically nil again when the IOP was decreased. At high pressure the volume of the vitreous body apparently increases and the anterior hyaloid membrane probably presses against the ciliary body, reducing the area of hyaloid membrane through which fluid can flow. Whether increased perfusion pressure can in some other manner change the permeability of human vitreous to resemble that of the calf remains unanswered. Our results suggest that factors other than, or in addition to, simple diversion of aqeous humor must be important in malignant glaucoma.

Studies on the Handling of Retinotoxic Doses of Iodate in Rabbits

Accumulation of iodate in eye tissues and fluids as a possible explanation of the retinotoxic effect of iodate has been studied by intravenous injection of NaIO3(30 mg/kg), 125IO-3 and 131I- in rabbits. 125IO-3 was determined in fluids and tissue extracts by precipitation with BaCl2 after addition of KIO3. 125IO-3 was rapidly broken down in blood (T 1/2 = 14 min.). 125IO-3 was not present in aqueous humour, vitreous or extracts from retina, choroid + pigmentary epithelium or liver. Concentrations of 125I were comparable in blood, choroid + pigmentary epithelium and liver tissue while in vitreous and aqueous humour low concentrations of 125I were found which, however, increased gradually during 5 hrs after injection to reach levels comparable with blood levels of 125I. Retina had a low concentration of 125I. The ratio 125I/131I (R) in blood decreases during the first 60 min. after injection followed by a slow rise. R in retina, choroid + pigmentary epithelium and liver was the same as in blood at the same time after injection. During the first 80 min. after injection R was higher in vitreous than in blood while it was lower in aqueous humour than in blood. At longer times after injection R was identical in the three fluids. The investigation has been supplemented with whole body scintigraphy of rabbits injected with NaIO3(30 mg/kg) and 131IO-3 or 131I-. The reduction kinetics of IO-3 to I- by some body fluids, tissues, cystein and glutathione was also studied. It is concluded that the retinotoxic effect of iodate is not due to accumulation of IO-3 in eye tissues, but more likely to damage to biochemical mechanisms involved in the reduction of IO-3 to I-.

Effects of cervical sympathetic ganglionectomy on cyclic-amp and prostaglandins in brain and eye tissues and fluids

Studies were conducted confirming supersensitivity to catecholamines on intraocular pressure and pupil size following bilateral superior cervical ganglionectomy in rabbits. At the termination of these studies we examined changes in cyclic adenylic acid and prostaglandin content in jugular vein effluent and various brain and ocular tissues and fluids of the sympathectomized versus control animals. In the blood effluent and various brain and ocular tissues and fluids of and significant lowering of prostaglandin F1 α in the sympathectomized animals. Although we found elevation of prostaglandin in certain tissues of the sympathectomized animals, there were no significant changes in cyclic adenylic acid levels between sympathectomized and control animals in the tissues examined. The findings of prostaglandin (blood and tissue) and cyclic adenylic acid (blood) changes in sympathectomized animals, associated with known changes in intraocular pressure and pupil size (due to catecholamine supersensitivity) must elicit further interest in the correlation and interpretation of various other central physiological and metabolic events in cervical sympathectomized animals.

Clinical blood values of the northern fur seal, Callorhinus ursinus. III. Comparison of eye fluid and serum values.

The levels of 13 components in the serum and eye fluids of the northern fur seal, Callorhinus ursinus, are compared. The wide variations observed would appear to limit the usefulness of eye fluid values as a substitute for serum values.

Regional Differences in Ocular Concentration of Gentamicin After Subconjunctival and Retrobulbar Injection in the Rabbit

We compared the penetration of radioactive carbon (14C) labeled-gentamicin into ocular tissues and fluids of albino rabbit eyes after subconjunctival (anterior subtenon's) and retrobulbar (posterior subtenon's) injections. In both normal and infected (Staphylococcus aureus endophthalmitis) eyes, higher levels of drug were produced with subconjunctival rather than with retrobullar admininistration in cornea, sclera, choroid and retina (as a unit), and iris; levels in the aqueous and vitreous humors of infected eyes were similar with the two routes of injection. Marked regional variations in the concentrations of gentamicin were noted in cornea, sclera, and choroid-retina after subconjunctival therapy. The pattern of these variations suggests that subconjunctival antibiotic penetrates the eye by direct diffusion. The low levels of drug after retrobulblar injection may be due to systemic absorption through the highly vascular orbital plexus of the rabbit.

The functional morphology of the outflow systems of ocular and cerebrospinal fluids

The drainage pathway of aqueous hmnour of the eye and cerebrospinal fluid (CSF) of the brain has been investigated with and without experimental procedures; and the appropriate tissues have been analysed by light-, scanning- and transmission-electron microscopy to unravel the structural basis for the resistance to, and the precise mechanism of, the outflow of these fluids. The close similarities in the origin, circulation, dynamics and drainage of the humours of the eye and brain are emphasized. In both cases, controversy has centred upon whether or not there are pores in the mesothelial lining of the canal of Schlemm and arachnoid villi which mediate the final outflow of aqueous humour and CSF respectively. Morphometrically, as revealed by scanning electron microscopy, the mesothelial lining of Schlemm's canal and the arachnoid villi are closely comparable, both being constituted by spindle-shaped cells measuring some 40–120 µm in length and 4µ12µm in width in the central region corresponding to one or more apical bulges. Transmission electron microscopy showed that in both cases the mesothelial lining forms a continuous single-layered membrane with adjacent cells joined by junctional complexes offering a restraint to the passage of experimentally introduced colloidal molecules of 10 nm or smaller size. The cells contain an apically bulging nucleus and a moderate amount of the usual intracelhdar organelles including a system of well developed cytoplasmic microfilaments presumably associated with a contractile function. The special feature of many lining cells of both Schlemm's canal and arachnoid villi is the presence of giant vacuolar structures of several micrometers in size. Arguments are advanced that these unit membrane-bound configurations are a real morphological entity and not a product of postmortem or fixation artefact. Morphogenetically, they are considered as developing from surface infoldings or invaginations on the basal aspect of the lining cells, which, by gradually enlarging, eventually open on to the apical cell surface thus cleaving the cells to form wide vacuolar transcellular channels of heterogenous dimensions with basal openings up to 4µm and apical openings up to 2·5µm in size. Our correlative physiological and morphological studies using a variety of tracer substances have shown that the bulk outflow of aqueous humour and of CSF takes place down a pressure gradient via the vacuolar transcellular channels which constitute a dynamic system of pores and act as one-way valves allowing fluid to pass from basal to apical aspects far more easily than in the reverse direction. According to this hypothesis the process of vacuolation is cyclical, and it would now seem certain that this delicate and probably pressure-sensitive vacuolation cycle, in providing the requisite number of pores at any given time, is a controlling factor in the bulk outflow of aqueous humour and CSF, and consequently in the maintenance of normal fluid pressure in the eye and brain. The role of various factors, especially hydrostatic pressure gradient, in influencing the vacuolation cycle is discussed. In contrast to the open passage provided by the unique biological system of vacuolar transcellular channels, other processes, e.g. micropinocytosis, passage through intercellular clefts or small diaphragmed fenestrations, phagocytosis, etc., would normally appear to make a relatively minor contribution in the bulk clearance of the humours of the eye and brain. Our comparative morphological and physiological studies of the eyes of a wide variety of sub-primate vertebrates have further resolved the age-old controversy between morphologists and physiologists, the former concluding a fimdamental difference between primates and lower mammals and the latter contending the essential similarity. Despite gross morphological differences in the configuration of the angle of the anterior chamber, it is shown that, apart from minor variations, there exists throughout the vertebrates an angular aqueous plexus or sinus (analogous to the canal of Schlemm in primate eyes) and that the bulk outflow of aqueous humour takes place across the mesothelial barrier of these aqueous plexuses via vacuolar transcellular channels in a manner exactly comparable to primates. Although an extensive analysis of arachnoid villi in sub-primate species has not been completed, preliminary studies indicate that macrovacuolar configurations may similarly be involved in the bulk outflow of CSF in a wide variety of vertebrates.

Magnesium and other electrolytes in bovine eyeballs immersed in sea water and other fluids

Bovine eyeballs were immersed in fluids including sea water for variable intervals of time, and magnesium concentrations and those of other electrolytes were determined in the aqueous and vitreous humor. Magnesium values increased with time, but no final saturation was reached nor were the levels obtained as high as those previously reported. In human immersion fatalities, Mg ++ increased comparably to the most closely simulating experimental situation, that is, corneal exposure in an unstirred medium. At best, vitreous Mg ++ appears to be an imperfect marker in estimating the length of immersion, and then only if the sample remains unhemolyzed and the total post-mortem interval is considered. Establishing or excluding the diagnosis of drowning solely by this technique seems unlikely because of ion diffusion into the eye fluids.

Ocular lesions in sheep infected with Trypanosoma brucei

Sixteen out of 22 sheep inoculated intravenously with Trypanosoma brucei developed mild to severe eye lesions characterized clinically by oedema and inflammation of the eyelids, lacrimation, recurrent corneal opacity, hypopyon, amaurosis and blindness. Histologically, there was a non-purulent panophthalmitis characterized by a fibrinous and mononuclear exudate in the aqueous and vitreous humours, and mononuclear iridocyclitis, choroiditis, retinitis, optic neuritis and ocular myositis. The lesions were associated with the presence of extravascular trypomastigote trypanosomes in the eye fluid and in the interstitial tissue. These findings indicate that the ocular lesions often associated clinically with infections by the brucei group of trypanosomes are due to invasion of the eye by the parasites.

Penetration of Radioactive Sulphate and Glucose from Hydrophilic Gel Contact Lenses into the Eye of the Rabbit

Soft poly(hydroxyethylmethacrylate) gel contact lenses soaked with a solution containing either radioactive sulphate or D-glucose-14C were applied to the rabbit eyes for time intervals ranging from 10 min to 24 h. It was estimated that the radioactive substances were released very rapidly from the contact lens; about 90% within the first hour of application. Radioactivity was then detected in the cornea, aqueous humour, crystalline lens, and vitreous in amounts decreasing with the duration of the experiment. A stepwise accumulation of radioactivity in the eye tissues and fluids was observed with sulphate but not with glucose.

Competitive Inhibition of Drug–Protein Interaction in Eye Fluids and Tissues

Binding of drugs to proteins in fluids and tissues of the eye previously was shown to modify significantly the bioavailability of a number of drugs. This adverse effect is particularly important in the precorneal portion and anterior chamber of the eye, since tears and aqueous humor are turned over at relatively rapid rates, removing both free and bound forms of the drug. In addition, rapid drainage of instilled solutions also removes substantial drug quantities. The drug–protein interaction can be minimized through the use of competitive inhibitors of protein binding. These agents occupy binding sites normally bound by drug, increasing free drug concentration. In vitro experiments with eye fluids and tissues, as well as in vivo studies in rabbits, support the concept of competitive inhibition as a means of significantly improving drug bioavailability. These experiments are principally concerned with competitive inhibition in the precorneal portion of the eye. Pilocarpine nitrate, a miotic drug with low binding affinity for albumin, shows a 10-fold increase in biological activity in the presence of the competitive inhibitor cetylpyridinium chloride. This increase in response is suggested to be due, in part, to competitive inhibition of drug–protein interaction. Competitive inhibition of drug binding in tears and the precorneal portion of the eye can be applied successfully without the attendent problems when the concept is applied to blood proteins. Tear proteins have apparently less substrate carrier function as compared to blood proteins, there is less total protein in tears as compared to blood, and the amount of drug plus inhibitor applied to the eye is small. Thus, side effects due to undesired substrate displacement arc not present when rather nonspecific competitive inhibitors are used in ophthalmic systems. Extrapolation of the pilocarpine nitrate data to drugs with higher protein binding affinities suggests that substantial increases in drug activity can be expected through competitive inhibition of drug–protein interactions in eye fluids and tissues.

Effects of iodate on the blood-vitreous barrier

Abstract The effects of a single intravenous dose of Na iodate on the penetration of 24 Na, 131 I and thiourea into the aqueous humour and vitreous body of the rabbit have been measured. Within a few minutes there is a marked increase in rate of penetration into the vitreous body, the maximal effect being reached within 30–60 min after the injection. Penetration into the posterior segment of vitreous is increased to a much greater extent than into other regions. It is concluded that the site of attack is at the retinal pigment epithelium, increasing its passive permeability characteristics. For comparative purposes, the effects of perchlorate on penetration of 131 I into the eye fluids were measured, since this compound inhibits ciliary body activity. The pattern of altered permeability of the blood-vitreal barrier now conforms with the idea of an exclusive attack on the ciliary body.

Immunity to chlamydial infections of the eye. VI. Homologous neutralization of trachoma infectivity for the owl monkey conjuctivae by eye secretions from humans with trachoma.

Neutralization of trachoma infectivity for the owl monkey was demonstrated by use of two pools of eye secretions, with low or high titers of antibody, from children with trachoma. Type specificity of antibody to the strain used in the neutralization test (HAR-13, type 1) was found in all individual eye fluids comprising the pool with a high titer of antibody. No neutralization was found when eye fluids from normal adult subjects were used. Neutralization of trachoma infectivity by secretions from the human eye is described. Trachoma persists as the leading chronic disabling eye disease in the world. Efforts to unravel the defense mechanisms of the host that influence the course of infection have been underway for several years in research laboratories throughout the world. Much of the knowledge acquired was gained from experiments with animals, including primates; this knowledge now needs to be applied to the natural infection in man. Bernkopf first reported that eye secretions from humans with trachoma contained antibodies to