IgA antibodies to Toxoplasma gondii in human tears.
(41/947)
PURPOSE: To investigate whether mucosal immune responses directed against the ubiquitous parasite Toxoplasma gondii can be detected in tears of healthy humans. METHODS: Nonstimulated tears and blood were obtained from 62 healthy humans (mean age, 35 +/- 10 [SD] years). Serum anti-T. gondii immunoglobulin titers were determined by Sabin-Feldman (SF) dye test. Western blot analysis was used to compare the anti-T. gondii repertoire in tears and serum, and antibody avidity was determined by urea elution. Diluted tear and serum samples were incubated with the intact parasite to determine whether the antibodies found in tears and serum are capable of binding to surface exposed antigens of T. gondii. RESULTS: Eighty-one percent of the individuals tested had an anti-T. gondii IgA response in their tears, whereas only 23% had evidence of systemic immunity against the parasite. There was no apparent relation between chronic infection and presence of anti-T. gondii IgA in tears. Characteristically, the antigens recognized by the IgA antibodies in tears were often limited to at least one of four antigens with molecular weights of 74, 70, 49, and 34 kDa. The avidity of the anti-T. gondii IgA antibodies in tears was similar to the avidity of serum IgG antibodies. IgA antibodies directed against the 49- and 74-kDa antigens recognized epitopes exposed on the surface of the parasite. CONCLUSIONS: A major finding of this study is that tears of many individuals, chronically infected or not, contain IgA antibodies against T. gondii. It is not known whether these frequently observed antibody responses are the result of common mucosal immune responses against T. gondii or represent the natural antibody repertoire. (+info)
Ascorbic acid concentration and total antioxidant activity of human tear fluid measured using the FRASC assay.
(42/947)
PURPOSE: To evaluate a novel method (FRASC) for total ferric reducing (antioxidant) activity and ascorbic acid concentration applied to human tears, to investigate the stability of ascorbic acid, and to determine the antioxidant status of human reflex tears. METHODS: Linearity, sensitivity, and precision of FRASC and ascorbic acid loss during 7 days' storage were assessed; total antioxidant activity and ascorbic acid and uric acid concentrations of reflex tears from 47 healthy subjects were measured. RESULTS: FRASC has good precision, linearity, and sensitivity. Ascorbic acid is stable for at least 7 days at moderately acidic pH (pH 3.6) and low temperature. Total antioxidant activity and ascorbic acid and uric acid concentrations (mean +/- SD) in reflex tears were 409 +/- 162, 23 +/- 9.6, and 68 +/- 46 microM, respectively. Ascorbic acid and uric acid constituted around half the total antioxidant activity measured. There was a significant correlation between uric acid and total antioxidant activity (r = 0.754; P: < 0.0001). Men had significantly (P: = 0.0045) higher tear ascorbic acid concentrations than women. CONCLUSIONS: FRASC is suitable for measuring total antioxidant activity and ascorbic acid in human tears. Further clinical study is needed to investigate the male-female difference seen, to characterize the remaining 50% antioxidant activity, and to investigate the effects of environmental conditions, antioxidant supplementation, age, and ocular disease on tear antioxidant status. (+info)
The thickness of the human precorneal tear film: evidence from reflection spectra.
(43/947)
PURPOSE: Interferometric methods have considerable potential for studying the thickness of layers of the human tear film and cornea because of their ability to make noninvasive, accurate, and rapid measurements. However, previous interferometric studies by Prydal and Danjo yielded tear thickness values near 40 and 11 microm, respectively, considerably greater than estimates made by invasive methods of 4 to 8 microm. Using a modified version of Danjo's method, interference effects from the tear film and cornea were studied, with the aim of correlation with known structure and optical properties of the cornea and hence determining the most probable value of tear film thickness. METHODS: Reflectance spectra from the human cornea were measured at normal incidence. These spectra show oscillations whose maxima correspond to constructive interference between light reflected from the air surface and from some deeper surface. The frequency of these spectral oscillations is proportional to the thickness of the layer between the air surface and the second surface. Therefore, Fourier analysis of reflectance spectra can be used to determine the thickness of layers of the tear film and cornea. In the main experiment, 36 low-resolution spectra were obtained from six normal eyes for measuring thickness up to 100 microm. Control experiments included measurements of the time course of thickness changes and high-resolution spectra for measuring thickness up to 1000 microm. RESULTS: For the main experiment, in the thickness range 1 to 100 microm, the strongest peak in the Fourier transform was near 3 microm (range, 1.5-4.7 microm) beneath the air surface. In the range 20 to 100 microm, the strongest peak was near 55 microm (range, 50-59 microm) for all 36 spectra; none were in Prydal's range near 40 microm. This 55-microm peak is consistent with a reflection from the basement membrane of the epithelium. Time course measurements after a blink show that the 3-microm peak is not an artifact. High-resolution spectra gave a peak near 510 microm, corresponding to the complete thickness of the cornea (plus tear film). This peak had a contrast similar to that of the 3-microm peak. CONCLUSIONS: These studies did not confirm Prydal's estimate of approximately 40 microm. Nor were there prominent peaks near Danjo's value of approximately 11 microm, except in cases of probable reflex tears. Because the reflection at the aqueous-mucus boundary would be expected to be weaker than that from the epithelial surface, the 3-microm peak is unlikely to correspond to the aqueous layer (rather than the complete tear film). The proposal that the 3-microm peak corresponds to a reflection from the front of the cornea is supported by the demonstration of a peak of similar contrast from the back of the cornea. Thus, the current evidence consistently supports a value of approximately 3 microm for the thickness of the human precorneal tear film. (+info)
The instilled fluid dynamics and surface chemistry of polymers in the preocular tear film.
(44/947)
Using slit lamp fluorophotometry it was demonstrated that the rate of drainage of a vehicle placed in the eye increased with increasing volume and that polymer solutions increased the thickness of the precorneal tear film (PTF). By increasing the viscosity of the delivery vehicle, (e.g., a hydroxypropylmethylcellulose polymer solutions), the PTF retention of fluorescein could be increased. The increased retention was shown to be due to an increase in the tear reservoir volume provided by the more viscous solutions. The PTF retention of fluorescein in a polyvinyl alcohol (PVA) vehicle was not as viscosity dependent, although PVA did seem to produce greater initial PTF fluorescence. This suggested that PVA initially produced a thicker PTF. The PTF retention of fluorescein by five commercial solutions did not have any relation to their wetting properties. The only good correlation with fluorescein retention in the PTF measured, seemed to be the ability of different polymer solutions to stabilize a thick layer of water as measured by the spontaneous spreading of polymer molecules at the air/liquid interface on wet glass surfaces. This model was designed to simulate tear film spreading in vivo. The results suggest that different polymer solutions may produce thicker PTF's than normal by virtue of their ability to drag water with them as they spread over the ocular surface with each blink. Mechanisms by which polymer solutions may increase the thickness of the PTF are discussed. (+info)
Anti-inflammatory and antiallergic effects of ketorolac tromethamine in the conjunctival provocation model.
(45/947)
AIM: To study the effect of the topical anti-inflammatory drug, ketorolac, on (1) the clinical allergic reaction induced by the conjunctival provocation test (CPT); (2) the release of tryptase in tears; and (3) the expression of adhesion molecules on the conjunctival epithelium. METHODS: 10 allergic but non-active patients were challenged in both eyes with increasing doses of specific allergen to obtain a positive bilateral reaction and rechallenged, after 1 week, to confirm the allergic threshold dose response. After 2 weeks, a third CPT was then performed bilaterally 30 minutes after topical application of ketorolac in one eye and placebo in the contralateral eye in a double blind fashion. Clinical symptoms and signs were registered 5, 10, 15, and 20 minutes after challenge. The following objective tests were performed: tear tryptase measurement; tear cytology; and conjunctival impression cytology for immunohistochemical expression of ICAM-1 on epithelial cells. RESULTS: Compared with placebo, ketorolac significantly reduced the total clinical score and the itching score in the 20 minutes after challenge (p<0.0005). Tear levels of tryptase were significantly reduced in the ketorolac pretreated eyes compared with placebo (p<0.03). Eosinophils, neutrophils, and lymphocytes in tear cytology were significantly lower in ketorolac treated eyes compared with placebo. A significant difference in the epithelial expression of ICAM-1 was observed between placebo and ketorolac treated eyes (p<0.05). CONCLUSION: Ketorolac proved to be effective in reducing mast cell degranulation, as indicated by significantly decreased tryptase tear levels, as well as the clinical and cytological allergic reaction. (+info)
Changes in ocular surface caused by antiglaucomatous eyedrops: prospective, randomised study for the comparison of 0.5% timolol v 0. 12% unoprostone.
(46/947)
AIM: To study changes induced in ocular surface epithelia and the tear film by antiglaucomatous eyedrops. A beta blocker (0.5% timolol) and a novel prostaglandin F(2alpha) metabolite related drug (0.12% unoprostone) were examined in a prospective, randomised fashion. METHODS: 40 patients were randomly assigned to use either 0. 5% timolol (timolol group) or 0.12% unoprostone eyedrops (unoprostone group) twice a day for 24 weeks. In addition to routine ocular examinations, corneal epithelial integrity (vital staining tests, tear film break up time (BUT), anterior fluorometry, specular microscopy) and tear function (Schirmer's test, cotton thread test, tear clearance test (TCT)) were examined before and after the treatment. RESULTS: Both eyedrops caused significant reduction in intraocular pressure from the baseline levels. No significant changes were noted in corneal integrity in both groups, except a decrease in BUT at 20 weeks in the timolol group. The timolol group demonstrated significant decreases in Schirmer's test, tear clearance test, and tear function index (Schirmer's test value multiplied by clearance test); however, no such changes were noted in the unoprostone group. CONCLUSION: While unoprostone eyedrops caused no adverse effects on the corneal epithelial integrity and tear function, timolol caused significant impairments in tear production and turnover. (+info)
Androgen influence on the meibomian gland.
(47/947)
PURPOSE: The hypothesis in the study was that androgens control meibomian gland function, regulate the quality and/or quantity of lipids produced by this tissue, and promote the formation of the tear film's lipid layer. To test this hypothesis, a study was conducted to determine whether androgen receptor protein exists in the epithelial cell nuclei of rat meibomian glands and, in addition, whether androgen deficiency and/or treatment influences the gross morphology, neutral lipid content, and fatty acid profile of the rabbit meibomian gland, as well as the appearance of the tear film lipid layer. METHODS: Rat lids were obtained and processed for immunohistochemistry. Meibomian glands from intact, androgen- and/or placebo-treated rabbits were analyzed by histology, and glandular lipids were evaluated by gas chromatography, high-performance liquid chromatography (HPLC), and mass spectrometry. The rabbit tear film lipid layer was assessed by interferometry. RESULTS: In the current study androgen receptor protein existed within acinar epithelial cell nuclei of rat meibomian glands; androgen deficiency was associated with alterations in the lipid content of the rabbit meibomian gland; 19-nortestosterone treatment modulated the fatty acid profile in the total and neutral lipid fractions of the rabbit meibomian gland; and androgens did not appear to influence the gross morphology of meibomian tissue or to exert a demonstrable effect on the rabbit tear film lipid layer. CONCLUSIONS: The findings show that the meibomian gland is an androgen target organ and that androgens influence the lipid profile within this tissue. However, the extent to which androgens regulate the production of these lipids and whether this action may impact tear film stability remain to be determined. (+info)
Plasminogen activator activity in tears after excimer laser photorefractive keratectomy.
(48/947)
PURPOSE: To quantify changes of plasminogen activator activity in tear fluid during corneal re-epithelialization after excimer laser photorefractive keratectomy (PRK). METHODS: Tear samples were collected with glass capillaries from 77 eyes of 42 patients immediately before and immediately after PRK treatment and on postoperative days 3 and 5. In 20 patients, the contralateral eye was similarly sampled to serve as control. Plasminogen activator activity in the tear samples was measured by a spectrophotometric method using human plasminogen and chromogenic peptide substrate, D-valyl-L-leucyl-L-lysine-p-nitroanilide (S-2251). RESULTS: In tears of all eyes that underwent PRK, the plasminogen activator activities were lower immediately after PRK than were the preoperative values. For patient eyes with normal wound healing, tear plasminogen activator activities were significantly elevated above the preoperative level on the third postoperative day and then returned to the preoperative level by the fifth postoperative day. In contrast, tear plasminogen activator activities remained low through the third postoperative day in all (six) eyes in which haze developed after 3 to 6 months. The contralateral control eyes showed no appreciable change in plasminogen activator activity over the 5-day period. CONCLUSIONS: Plasminogen activator activity levels measured in tears of excimer laser PRK-treated eyes may serve as a predictor of wound healing. Extended low levels of plasminogen activator activity through the third postoperative day correlate with the development of corneal healing abnormalities (haze). The low plasminogen activator activity could be not only an accompanying sign but also a cause of defective corneal wound healing. (+info)