Biomedical subjects
Publications and source records attributed to R C Tripathi.
A family with total (internal and external) ophthalmoplegia had associated iris transillumination. No abnormal visual-evoked response brain lateralization indicative of albinism was found. On the basis of avian chimera experiments showing iris muscles to be derived from neural crest cells, we proposed a neurocristopathic theory to explain all clinical findings in this family.
We have correlated the clinical and histopathologic features of the eyes and central nervous system in a patient with Hallervorden-Spatz syndrome who died at age 11 years. The main ocular findings included degeneration of photoreceptors, marked thinning of the outer nuclear and outer plexiform layers, retinal gliosis, narrowing and obliteration of blood vessels with a perivascular cuffing of pigment cells, and degenerative changes in the retinal pigment epithelial cells with accumulation of melanolipofuscin. The positive findings in the brain included a symmetrical, partially destructive lesion of the globus pallidus, especially in its internal fibers and neurons; in addition, we noted gliosis, widely disseminated axonal spheroidal bodies, which were most numerous in the globus pallidus and pars reticulata, as well as deposits of iron. Our histopathologic findings implicate three possible mechanisms, namely, lipid peroxidation, a deficiency of fatty acid membrane components, and increased cGMP which, either singly or in combination, are responsible for a pathogenesis that is common to the eye and brain in Hallervorden-Spatz syndrome.
By using a highly specific and sensitive heterologous radioimmunoassay, we determined the content of basic fibroblast growth factor (bFGF) in fresh samples of aqueous humor obtained from human (n = 18), feline (n = 8), canine (n = 12), and porcine (n = 10) eyes by paracentesis. The content of bFGF in human aqueous humor ranged from 0.480 to 1.44 ng ml-1 (mean +/- S.D. = 1.074 +/- 0.297 ng ml-1); in feline samples, from 0.672 to 1.152 ng ml-1 (1.016 +/- 0.158 ng ml-1); in canine samples, from 0.640 to 1.232 ng ml-1 (1.026 +/- 0.171 ng ml-1); and in porcine samples, from 0.627 to 0.957 ng ml-1 (0.728 +/- 0.115 ng ml-1). These values were confirmed by means of a dot/slot-blot technique. For all species, the aqueous samples had normal protein levels that ranged from 5 to 19 mg dl-1. There was no correlation of the content of bFGF with the level of protein or with age of the human subjects. The similarity in the concentrations of bFGF in the aqueous humor as well as the stability of the blood-aqueous barriers of all four species indicate that cats, dogs, and pigs can serve as suitable animal models for the study of the role of bFGF in health and disease. We suggest the possible involvement of bFGF in the pathogenesis of anterior-segment disorders, such as neovascular glaucoma, and in the wound-healing response of limbal tissues after glaucoma filtration surgery.
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Intraocular pressure (IOP) was measured in 54 pediatric patients (aged 7-21 years) with inflammatory bowel disease (IBD) who were treated with oral prednisone for 1-104 months. The difference in mean IOP between the treated patients (mean +/- SD, 15.62 +/- 4.11 mm Hg) and 55 age-matched controls (13.83 +/- 2.42 mm Hg) was statistically significant (P = 0.007). The IBD patients were classified as group I, IOP less than or equal to 19 mm Hg in both eyes, and group II, IOP greater than or equal to 20 mm Hg in either eye. Twelve of the 54 patients (22.2%) and none of the controls had IOP greater than or equal to 20 mm Hg (P less than 0.001). Seventeen of the 54 patients (31.5%) were characterized as "steroid responders" (IOP of greater than or equal to 20 mm Hg, change in IOP of greater than or equal to 6 mm Hg between visits, or difference in IOP of greater than or equal to 6 mm Hg between the two eyes). When the dose of prednisone was reduced to 0-10 mg/day 30 days or more before measurement, 9 steroid responders showed a decrease in IOP to within 2 SD of the mean control IOP; 7 of the 9 showed a decrease in IOP of greater than or equal to 6 mm Hg. These observations indicate that while prednisone is a causative factor in increasing the IOP, susceptibility to average doses of prednisone is highly variable, and patients need to be monitored on an individual basis. Because IBD is a chronic disorder that requires prolonged corticosteroid treatment, these children are at risk of developing steroid-induced glaucoma. Careful ophthalmologic monitoring of pediatric IBD patients, as well as of other pediatric patients who receive corticosteroid therapy, is recommended.
The half-life of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), the contaminant of Agent Orange, has been recently estimated in 36 members of Operation Ranch Hand, the Air Force unit responsible for the aerial spraying of Agent Orange in Vietnam, as 7.1 yr with a 95% [corrected] confidence interval of 5.8-9.6 yr. We investigated the variability of TCDD half-life with percent body fat in these 36 Ranch Hand veterans who have two TCDD assay results from serum drawn in 1982 and 1987. Using a repeated measures linear model, we found a marginally significant change in half-life with percentage of body fat (p = .09) and no statistically significant change in half-life with relative changes in percentage of body fat from 1982 to 1987 (p = .60).
Because the corneal epithelium invariably encounters the full concentration of the preservative that is contained in multi-dose topical ophthalmic preparations, we investigated the cytotoxicity of several of these agents by using a sensitive model of human corneal epithelial cells in vitro. Primary cultures of epithelial cells were prepared from freshly enucleated globes. At confluence, all experimental cultures received a single dose of preservative at the concentration present in marketed formulations. The serum in the culture medium simulated the possible neutralizing effect of proteins present in the tear film in vivo. The cells were observed continuously by phase-contrast microscopy and time-lapse videomicrography for 24 hrs. Benzalkonium chloride at a concentration of 0.01% and chlorobutanol at 0.5% caused immediate cell retraction, as well as cessation of normal cytokinesis, cell movement, and mitotic activity; the epithelial cells degenerated within 2 hrs and 8 hrs, respectively. Cultures treated with chlorobutanol developed conspicuous blebs on the cell surface after 3 to 5 hrs of exposure. Thimerosal (0.001%) caused cell retraction, cessation of mitotic activity, and total cell destruction within 9 hrs. Sorbic acid (0.1% and 0.2%) greatly reduced cell movement and suppressed mitotic activity, but no cell death occurred. At concentrations of 50 ppm and 30 ppm, H2O2 instantaneously caused a marked retraction of the cells, followed by cessation of cytokinesis, cell movement, and mitosis. Retraction and death of the epithelial cells occurred within 12-24 hrs after exposure to 1 ppm H2O2 in serum-free medium. Polyquaternium ammonium chloride (0.001%) and polyaminopropyl biguanide (0.00005%) had no discernible effects on cytokinetic movement or on the mitotic activity of the epithelial cells. We relate our findings in vitro to those reported in vivo and discuss the mechanism of cytotoxicity of the various preservatives.
We performed ocular examinations on 58 corticosteroid-treated pediatric patients with inflammatory bowel disease (IBD) and on 58 age-matched controls. Posterior subcapsular cataracts (PSC) were detected in 12 of the 58 treated patients (20.7%) and in none of the controls. The difference in mean intraocular pressure (IOP) between the treated patients (15.89 +/- 4.11 mm Hg) and control subjects (13.63 +/- 2.35 mm Hg) was significant statistically (P < 0.001). Twenty-one patients (36.2%) were characterized as "IOP responders" (IOP > or = 20 mm Hg, change in IOP > or = 6 mm Hg between visits, or a difference in IOP > or = 6 mm Hg between the two eyes). Formation of PSC was not correlated significantly (P > 0.05) with the total dose of prednisone, duration of treatment, average daily dose, or number of days on high doses (> or = 25 mg). Raised IOP was correlated (P = 0.005) only with average daily dose (12.4 +/- 10.9 mg/day; range, 0-47 mg/day) 30 days before examination. When the dose of corticosteroid was reduced to < 10 mg/day, 2 patients manifested regression of PSC, and 12 IOP responders showed a decrease in IOP to within 2 SD of the mean control IOP. Only 3 of the 58 treated patients (5.2%) manifested both PSC and raised IOP. A significant inverse correlation (P = 0.02) was established between IOP at first examination and formation of PSC. We propose that the mechanisms for steroid-induced lens opacities and raised IOP do not share the same genetic basis. Because 52% of these children developed either PSC or raised IOP with prednisone therapy, we advocate careful ophthalmologic monitoring of pediatric patients receiving corticosteroids for IBD or any other condition.
By using two specific receptor assays, we identified and partially characterized receptors for transforming growth factor-beta 1 (TGF-beta 1) on porcine trabecular cells in vitro. Cultured trabecular cells were incubated with labeled TGF-beta 1 and analyzed by flow cytometry. Pretreatment with trypsin or preincubation with cold TGF-beta 1 or a neutralizing antibody to TGF-beta 1 inhibited the binding of labeled TGF-beta 1. 125I-TGF-beta 1 was cross-linked covalently to cell surface receptors on the trabecular cells. By SDS-PAGE and autoradiography, we identified three labeled macromolecular species of receptors, two of which had apparent molecular weights greater than 212 kDa and one of which had an apparent molecular weight of approximately 80-90 kDa under reducing conditions. The low and high molecular weight species probably represent type II and type III TGF-beta 1 receptors, respectively. At concentrations of 0.5 and 1 ng/ml, activated TGF-beta 1 caused retraction and a marked decrease in the rate of proliferation and in the motility of trabecular cells in vitro. Our findings implicate TGF-beta 1 in the modulation of the functional homeostasis of trabecular cells and suggest that the aqueous humor contains a level of TGF-beta 1 which, once activated, is sufficient to exert a biologic effect on the trabecular meshwork.
The authors identified and quantified the receptor for transferrin on trabecular meshwork (TM) cells cultured from porcine eyes by using two receptor assays. Flow-cytometric analysis of TM cells that were incubated with a monoclonal antibody to the transferrin receptor revealed such receptors, which decreased in number as the cells passed from the pre- to the post-confluent phase. Quantitative characterization by radioligand binding of 125I-transferrin to trabecular cells followed by Scatchard analysis showed that pre-confluent cultures expressed 23,839 +/- 6746 high-affinity receptors/cell and post-confluent cultures expressed 5104 +/- 3639 receptors/cell. The expression of the receptor for transferrin reflects the index of mitotic activity and can be correlated with the proliferative state of the trabecular cells. Further characterization of the receptors for transferrin in the TM may open up the possibility of a pharmacologic approach that enhances the TM cell population, which is known to decrease with age and in glaucomatous states of the eye.
By using a highly sensitive and specific radioimmunoassay and the slot-blot technique, transferrin was quantified in fresh samples of aqueous humor from patients with primary open-angle glaucoma (POAG, n = 36) or secondary glaucoma (SG, n = 18). The levels were compared with those in aqueous humor obtained from age-matched patients without glaucoma (n = 33) and in primary and secondary aqueous humor from normal dogs (n = 10) in which breakdown of the blood-aqueous barrier was induced experimentally. The concentration of transferrin in the aqueous humor of human control subjects ranged from 0.3-3.4 mg/dl (mean +/- standard deviation, 1.36 +/- 0.66 mg/dl); in POAG samples, from 0.34 to greater than 10 mg/dl (2.07 +/- 1.90 mg/dl); and in SG samples, from 0.29 to greater than 10 mg/dl (2.79 +/- 2.24 mg/dl). The level of transferrin in secondary aqueous humor samples obtained from dogs was as much as ninefold greater than that in primary aqueous humor. The protein concentration in the human aqueous humor samples was 11.87 +/- 4.47 mg/dl for control subjects, 62.11 +/- 56.74 mg/dl for patients with POAG, and 124.53 +/- 152.67 mg/dl for those with SG. In dogs, the protein levels were 7.97 +/- 3.12 mg/dl for primary aqueous humor and 191.9 +/- 149.8 mg/dl for secondary aqueous humor. A significant correlation (r = 0.744, P less than 0.01) was found between total protein and transferrin contents in the samples of aqueous humor from patients with glaucoma but not in the samples from age-matched control subjects.(ABSTRACT TRUNCATED AT 250 WORDS)
By using gel electrophoresis, as well as Western blotting with specific antibodies or with the lectin concanavalin A, we characterized the types and amounts of proteins that are deposited on 58% ionic and 38% nonionic water-content disposable soft contact lenses (DSCLs) worn for 1 to 21 days by asymptomatic subjects with mild to moderate myopic refractive errors. The total amounts of protein eluted from the lenses ranged from 0.1 to 80 micrograms/lens. The amount of protein deposited on 58% water-content lenses was greater than that on 38% water-content DSCLs. We did not find a strict correlation between the amount of protein deposited and the duration of wear for either type of lens. The major polypeptide fractions detected had apparent molecular weights of 14, 17, 21, 30, and 60 kD. The fractions at 14 kD-bound antibodies specific for human lysozyme, and those at 17 kD corresponded to prealbumin. The 60 kD fraction included IgG heavy chains. The identity of the fractions at 21 kD and 30 kD is unknown. Because oligosaccharide side chains on the proteins attract microbes and facilitate their adherence, knowledge about the types of carbohydrate moieties in lens deposits can provide a rational approach to inhibiting or reversing microbial infection.
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The vertebrate eye is composed of a variety of tissues that, embryonically, have their derivation from surface ectoderm, neural ectoderm, neural crest, and mesodermal mesenchyme. During development, these different types of cells are subjected to complex processes of induction and suppressive interactions that bring about their final differentiation and arrangement in the fully formed eye. With the changing concept of ocular development, we present a new perspective on the control of morphogenesis at the cellular and molecular levels by growth factors that include fibroblast growth factors, epidermal growth factor, nerve growth factor, platelet-derived growth factor, transforming growth factors, mesodermal growth factors, transferrin, tumor necrosis factor, neuronotrophic factors, angiogenic factors, and antiangiogenic factors. Growth factors, especially transforming growth factor-beta, have a crucial role in directing the migration and developmental patterns of the cranial neural-crest cells that contribute extensively to the structures of the eye. Some growth factors also exert an effect on the developing ocular tissues by influencing the synthesis and degradation of the extracellular matrix. The mRNAs for the growth factors that are involved in the earliest aspects of the growth and differentiation of the fertilized egg are supplied from maternal sources until embryonic tissues are able to synthesize them. Subsequently, the developing eye tissues are exposed to both endogenous and exogenous growth factors that are derived from nonocular tissues as well as from embryonic fluids and the systemic circulation. The early interaction between the surface head ectoderm and the underlying chordamesoderm confers a lens-forming bias on the ectoderm; later, the optic vesicle elicits the final phase of determination and enhances differentiation by the lens. After the blood-ocular barrier is established, the internal milieu of the eye is controlled by the interactions among the intraocular tissues; only those growth factors that selectively cross the barrier or that are synthesized by the ocular tissues can influence further development and differentiation of the cells. An understanding of the tissue interactions that are regulated by growth factors could clarify the precise mechanism of normal and abnormal ocular development.
By using a highly specific and sensitive homologous radioimmunoassay, we found that the content of epidermal growth factor (EGF) in the lateral one-third of whole cataractous human lenses (age range 45-85 yr) extracted at elective intracapsular lens surgery, varied from undetectable to 106.25 pg mg-1 water soluble protein (WSP) (mean +/- S.D. = 39.70 +/- 38.90). When the lenses were grouped according to the stage of the cataract, i.e. immature (n = 3), mature (n = 4), and hypermature (n = 3), the means +/- S.D. were 92.56 +/- 26.23, 23.89 +/- 7.71, and 7.92 +/- 2.00 pg mg-1 WSP, respectively. In ten age-matched whole 'normal' lenses that we removed within 2-12 hr after death, the values in EGF of the lateral one-third of the lenses ranged from 2.91 to 36.40 pg mg-1 WSP (19.39 +/- 13.65). No correlation between the age of the lenses and the content of EGF could be demonstrated at the 95% confidence interval for the cataractous and 'normal' lenses. The quantity of endogenous EGF correlated significantly (P less than 0.01) with the clinical stage of the cataract and is probably related to the mitotic activity of the equatorial proliferative zone. We discuss the importance of EGF in normal and cataractous lenses and postulate that EGF in the lens is endogenous in origin.
By using an immunohistochemical technique, we detected a strong reaction product for Fc gamma receptors in the keratoconjunctival epithelium, uveal trabecular meshwork, optic nerve, and muscle walls of the retinal and ciliary vessels of infant human eyes; moderate staining was seen on the corneal endothelium, corneoscleral trabecular meshwork, non-pigmented ciliary epithelium, ciliary muscle fibers, endothelial lining of ocular blood vessels, as well as the anterior region of Muller cells, the outer nuclear layer, and pigment epithelium of the retina. In aged human and porcine eyes, the same structures stained somewhat less intensely than did those in infant human tissues. Primary cultures of porcine trabecular cells demonstrated a more intense immunoreaction product than did tertiary cultures. We discuss the possible role of Fc gamma receptors in various ocular inflammatory conditions and the implications of age-dependent expression by human trabecular cells in the pathogenesis of open-angle glaucoma.
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Fenoldopam mesylate stimulates adenyl cyclase in porcine ocular trabecular meshwork and raises intraocular pressure in humans. To clarify whether this results from direct activation of the dopamine-1 receptor or indirectly from baroreflex sympathetic stimulation after blood pressure reduction, intraocular pressure was measured in 14 patients with accelerated/malignant hypertension, randomized between intravenous fenoldopam or sodium nitroprusside. Intraocular pressure was measured with a Perkins tonometer, before and at the twentieth minute of each dose increment. In seven patients with a mean blood pressure of 232/131 mm Hg treated with fenoldopam, intraocular pressure increased in a dose-dependent fashion, from 16 +/- 1 to 20 +/- 2 mm Hg (p less than 0.005). In contrast, seven patients with a mean blood pressure of 225/134 mm Hg treated with sodium nitroprusside exhibited no change in intraocular pressure (15 +/- 1 versus 14 +/- 1 mm Hg) despite similar blood pressure reduction. Increases in heart rate were not significantly different. Rates of urinary excretion of norepinephrine plus epinephrine increased significantly relative to baseline (p less than 0.05) but were not different between groups. These data suggest that the increase in intraocular pressure with fenoldopam results from specific activation of the dopamine-1 receptor and is not caused by baroreflex sympathetic stimulation. Because dopamine-1 receptors may modulate intraocular pressure, dopamine-1 receptor blockers might be useful therapy for glaucoma.