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Biomedical subjects

C C Chan

Publications and source records attributed to C C Chan.

At least 361 records · Page 20Linked to original sources
PubMed1992

A new effective and non-harmful chemical adjuvant for the induction of experimental autoimmune uveoretinitis.

The induction of T cell mediated disease models in animals is usually dependent on the use of complete Freund's adjuvant (CFA). In order to avoid the painful side effects of CFA on the animals, we tested the capacity to induce experimental autoimmune uveoretinitis (EAU) with Hunter's adjuvant (HA). This new adjuvant makes use of nonionic copolymer surfactants, and does not cause deleterious effects to animals. We have found that EAU could be efficiently induced in rats with low doses of S-Ag (10 micrograms) in very small quantity of HA (10 microliters). The biologic parameters of EAU induction showed a potent stimulation of lymphocytes proliferation maximal 11 days after immunization, as well as high levels of antibody production.

Adjuvants, Immunologic↗
PubMed1992

The effect of chlorpromazine on endotoxin-induced uveitis in the Lewis rat.

Chlorpromazine (CPZ) has been used extensively in the treatment of psychiatric disorders, and has recently been shown to possess systemic anti-inflammatory properties as well. To investigate the potential effects of CPZ on ocular inflammation, we evaluated its action on endotoxin-induced uveitis (EIU) in Lewis rats. At three different dosage levels, CPZ produced highly significant reductions in the mean aqueous aspirate inflammatory cell counts and histological inflammatory scores as compared to controls treated with vehicle only. Analysis of aqueous fluid demonstrated a similar decrease in protein concentration and phospholipase A2 (PLA-2) activity in the treated animals. The ability of CPZ to inhibit the development of EIU may be related to its properties as a calcium channel blocker and inhibitor of the enzyme phospholipase A2.

Animals↗
PubMed1992

Immunopathology of experimental autoimmune uveoretinitis in primates.

The eyes and pineal glands from 10 monkeys immunized with S-antigen were studied using routine histopathological and immunohistochemical techniques. Seven out of 10 animals developed uveitis between 19 and 33 days after the initial immunization. Histopathology of the eyes harvested 70 days after immunization showed moderate to marked uveoretinitis, subretinal fibrosis, retinal necrosis and gliosis. The pineal glands demonstrated chronic pinealitis. The infiltrating cells were both CD3 and CD19/CD22 lymphocytes with a ratio of 1.4 in the eye and 2.2 in the pineal gland. The ratio of CD4 to CD8 lymphocytes was 1.5:1. MHC Class II antigens and adhesion molecule (ICAM-1) were observed on resident cells. The influx of B lymphocytes and the formation of subretinal fibrosis differentiate the disease in the monkey from that in the rat and mouse. These findings are similar to Vogt-Koyanagi-Harada syndrome and subretinal fibrosis with uveitis syndrome in human.

Animals↗
PubMed1992

The feasibility of castable ceramic material in dental bridge construction.

This study was to investigate the feasibility of dental bridges constructed with castable ceramic material (Dicor). A dental bridge model was designed similar to the clinical situation. The marginal fit of Dicor crown and a three-unit bridge was evaluated and no statistically significant differences in marginal openings between Dicor crowns and bridges were determined except the mesial and distal end surfaces of the bridge works. The fracture strengths of different thicknesses of Dicor test bars were measured with a three-point bending technique in a jig mounted in a universal testing machine. The results revealed that the bridge design with the thickest (6mm) connector and the shortest (8 mm) width of the pontic had the highest fracture resistance. In addition, pores with size up to 50 microns were disclosed in the fractured interface. The optimal design of Dicor bridge is determined according to the results of this study along with the clinical trial.

Animals↗
PubMed1992

Endothelial leukocyte adhesion molecule-1 in endotoxin-induced uveitis.

Expression of endothelial leukocyte adhesion molecule-1 (ELAM-1) on endothelial cells leads to the attachment of polymorphonuclear leukocytes. The sequential expression of ELAM-1 and major histocompatibility complex (MHC) class II antigen was examined in the eyes of 59 Lewis rats with endotoxin-induced uveitis (EIU) after the injection of Salmonella typhimurium endotoxin. The eyes were enucleated at 2-hr intervals. Hematoxylin and eosin-stained paraffin-embedded sections and immunohistochemically stained cryostat sections were graded by two masked observers. The MHC class II antigen was expressed on cells in the iris and ciliary body 4 hr after injection of endotoxin and on the corneal endothelium, 8 hr postinjection. It was found that ELAM-1 was expressed first on cells of the ciliary body and iris 10 hr after the injection of endotoxin and on the corneal endothelium, 22 hr postinjection. Clinical and histopathologic disease developed 16 hr postinjection. Adherence of polymorphonuclear cells to the corneal endothelium was observed at the time of ELAM-1 expression. In conclusion, expression of ELAM-1 on ocular tissue occurred in EIU and appeared to promote polymorphonuclear cell accumulation in the anterior segment of the eye.

Animals↗
PubMed1991

Randomized, double-masked study of cyclosporine compared to prednisolone in the treatment of endogenous uveitis.

Fifty-six patients with bilateral sight-threatening noninfectious intermediate or posterior uveitis participated in a randomized double-masked study of the use of cyclosporine vs prednisolone in their treatment. Applying the end-point definitions, visual acuity or vitreal haze improved in only 13 of 28 (46%) patients in each group. The macular edema resolved in seven of 15 patients of the cyclosporine-treated group, and in ten of 16 patients of the prednisolone-treated group (P = .376). Patients whose therapies failed both cyclosporine and prednisolone trials were treated with both drugs, which resulted in additional patient improvements. Secondary effects were observed in both therapeutic alternatives, the most notable being alterations in serum creatinine concentration and hypertension with the dosage of cyclosporine used.

Adolescent↗
PubMed1991

Immunospecific suppression of encephalitogenic-activated T lymphocytes by chimeric cytotoxin IL-2-PE40.

We examined the action of a chimeric protein, IL-2-PE40, on the development of a T cell-mediated disease of the central nervous system with numerous similarities to multiple sclerosis, experimental autoimmune encephalomyelitis (EAE). EAE is caused by IL-2 receptor-bearing T cells specific for myelin basic protein (BP). We report here that the treatment of Lewis rats with IL-2-PE40 delayed and shortened the course of EAE induced by BP in adjuvant and dramatically prevented EAE mediated by anti-myelin basic protein T line cells. The absence of paralytic signs, the absence of cell infiltration in the central nervous system, and the abatement of cellular immunity to myelin basic protein in the treated rats are direct consequences of the specific mechanism of action of IL-2-PE40. Our data support the notion that IL-2-PE40 may be efficient as an immunosuppressive agent for those disorders in which activated T cells play a crucial role.

ADP Ribose Transferases↗
PubMed1991

Effects of antiflammins on endotoxin-induced uveitis in rats.

Antiflammins are phospholipase A2-inhibitory, anti-inflammatory, synthetic oligopeptides derived from the region of the highest amino-acid sequence similarity between uteroglobin and lipocortin I. Endotoxin-induced uveitis is a model for anterior uveitis of the eye, which has been suggested to be induced through phospholipase A2 activation. In a preliminary report we demonstrated that topical administration of antiflammins could inhibit endotoxin-induced uveitis in rats. In this study, the anti-inflammatory effects of antiflammins were compared with those of corticosteroids on endotoxin-induced uveitis as measured by phospholipase A2 enzyme activity, inflammatory cell counts in the aqueous humor, and histopathologic features. Antiflammins are as effective as corticosteroids in their ability to suppress endotoxin-induced uveitis.

Administration, Topical↗
PubMed1991

Immunohistochemistry of the inflammatory response in Propionibacterium acnes endophthalmitis.

Specimens were obtained from two patients with culture-proven Propionibacterium acnes endophthalmitis who had undergone vitrectomy. Wright's and Giemsa stains were performed using cytospin preparations of the dilute vitreous and revealed a predominance of polymorphonuclear leukocytes (80% to 90%). The remaining inflammatory cells in the vitreous were mostly macrophages (10% to 15%); very few lymphocytes were present (less than 5%). Immunohistochemical studies using monoclonal antibodies confirmed the paucity of lymphocytes. Most lymphocytes were CD4+ helper/inducer T cells. Almost no CD8+ suppressor/cytotoxic T lymphocytes or B lymphocytes were found. The inflammatory response in these two patients is most characteristic of acute inflammation and consistent with an underlying bacterial infection, despite a clinical picture of persistent, low-grade inflammation. Infection with P acnes has been shown to inhibit CD8+ T cells and may play a role in the persistent inflammation in cases of P acnes endophthalmitis.

Aged↗
PubMed1991

Immunohistochemistry of Terrien's and Mooren's corneal degeneration.

Lamellar keratoplasty specimens from a patient with Terrien's marginal degeneration and a patient with Mooren's ulcer were compared using routine histopathologic and immunohistochemical staining with an avidin-biotin-peroxidase complex. Less than 25% of the resident cells in the Terrien's marginal degeneration specimen expressed major histocompatibility class II antigens compared with 75% to 100% of the resident cells in the Mooren's ulcer specimen. The ratio of CD4 cells (T-helper/inducer) to CD8 cells (T-suppressor/cytotoxic cells) in the Terrien's marginal degeneration specimen was almost 1:1 compared with 24:1 in the Mooren's ulcer specimen. In addition, less than 5% of the infiltrating cells from the Terrien's marginal degeneration specimen stained positive for CD22 (B cells), compared with 25% to 50% from the Mooren's ulcer specimen. These data may help explain why Terrien's marginal degeneration runs a more benign course than does Mooren's ulcer and provides a rationale for the use of immunosuppressive drugs to treat Mooren's ulcer.

Adult↗
PubMed1991

Injury of Müller cells increases the incidence of experimental autoimmune uveoretinitis.

Müller cells have been shown to have a dual effect in vitro on autoimmune T helper lymphocytes. In a coculture system, Müller cells have a primary inhibitory effect on the proliferation of T lymphocytes. In conditions where their inhibitory action is suppressed, Müller cells can, however, stimulate T cells. In the present study we evaluated the in vivo effect of Müller cells on actively induced experimental autoimmune uveoretinitis (EAU). Ten millimoles of L-alpha-aminoadipic acid (L-AAA), a specific gliotoxic agent, was injected into the vitreous of one eye of Wistar-Furth (WF) rats (a low EAU responder) on the day of immunization. Control rats were injected similarly with phosphate-buffered saline alone. The rats were immunized with S-antigen in CFA or in CFA alone. The results demonstrate that the incidence of EAU increases twofold in the eyes receiving an intravitreal injection of L-AAA in comparison to the contralateral eyes not receiving an injection. No such difference in EAU incidence was observed in control animals. Some rats that had been immunized with CFA alone after an intravitreal injection of L-AAA demonstrated a small amount of retinal perivascular inflammatory cell infiltrate but did not develop typical EAU lesions. The retinal vasculature was normal on examination by fluorescein angiography after injection of L-AAA. These data suggest that Müller cells can influence the course of uveoretinitis through their interaction with T cells.

2-Aminoadipic Acid↗
PubMed1991

Inhibition of leukotriene B4 biosynthesis by disulfiram and A-64077 during carrageenan-induced pleurisy in the rat.

1. The effect of disulfiram and A-64077 on leukotriene B4 biosynthesis was investigated using human polymorphonuclear leukocyte preparations and an in vivo rat pleurisy assay. 2. Disulfiram inhibited the calcium ionophore-induced release of LTB4 by human leukocytes in vitro with an IC50 of 4.6 +/- 0.3 microM, a value similar to that observed with the 5-lipoxygenase inhibitor A-64077 (IC50 = 1.2 +/- 0.3 microM). These inhibitors were at least 100-fold more potent than diethyldithiocarbamate, the primary metabolite of disulfiram. 3. In a rat pleurisy model, the administration of A-64077 (p.o., 2 hr pretreatment) caused a marked decrease in LTB4 levels measureable after ionophore stimulation at doses of 3 and 10 mg kg (67 and 96% inhibition, respectively). Disulfiram was about a 100-fold less potent, inhibiting LTB4 release by 65% at 300 mg kg (p.o., 6 hr pretreatment). 4. In contrast to A-64077, the inhibitory effect of disulfiram on LTB4 production by isolated leukocytes from the pleural cavity was reduced by the addition of the cell-free pleural exudate, suggesting that protein binding or conversion of disulfiram to inactive species contributes to diminish the potency of the drug. 5. The results indicate that disulfiram, after oral administration in rats, causes an inhibition of leukotriene biosynthesis in the pleural cavity and further illustrate the limited specificity of this drug as an inhibitor of aldehyde dehydrogenase at doses generally used to inhibit this enzyme in vivo.

Aldehyde Dehydrogenase↗
PubMed1991

Inhibition of T lymphocyte proliferation by retinal glial Müller cells: reversal of inhibition by glucocorticoids.

Study of interactions between retinal glial Müller cells and T lymphocytes have revealed a wide array of reciprocal influences on the functions of these cells. In the present study we show that these interactions can be further modified by corticosteroid hormones. The primary effect of Müller cells on T lymphocytes is an inhibition of the T-cell proliferative response, and it is exerted via a membrane-bound factor. In this report we show that glucocorticoids can reverse the inhibition by suppressing the expression of the Müller cell inhibitory factor. This effect was independent of the action of glucocorticoids on arachidonic acid metabolism.

Animals↗
PubMed1991

Induction of oral tolerance to S-antigen induced experimental autoimmune uveitis by a uveitogenic 20mer peptide.

Experimental autoimmune uveitis (EAU) in Lewis rats is a T-cell dependent disease, which is induced by immunization with retinal S-Antigen (S-Ag) or its unveitogenic peptides. We have recently reported that the oral administration of S-Ag prior to the uveitogenic challenge results in suppression of the disease and of the cellular responses. We examined the effect of oral administration of a recently described uveitogenic peptide (Peptide 35) on the development of EAU induced with the whole protein. The severity of inflammation and retinal destruction, as well as the cellular proliferative responses, were suppressed compared to controls fed with Keyhole Limpet Hemocyanin (KLH). In addition, the levels of antigen-specific antibody isotypes in the serum of gavaged rats were determined. Although (IgA) levels were reduced in rats gavaged with S-Ag or the uveitogenic peptide, IgM and IgG levels were unaltered. Thus, the oral administration of Peptide 35 approaches the state of unresponsiveness seen in S-Ag feeding. In addition, the unresponsiveness can be demonstrated on both the cellular and humoral level.

Administration, Oral↗
PubMed1991

Role of chorioretinal biopsy in inflammatory eye disease.

Two patients who had similar clinical presentations of bilateral multiple chorioretinal lesions and needed a correct diagnosis underwent chorioretinal biopsy. The biopsy from one patient demonstrated mainly a B cell infiltrate in choroidal and subretinal nodules, while the biopsy from the second patient showed mainly macrophages in the retina. These findings directed the therapeutic approach taken in each patient. Although chorioretinal biopsy is an invasive procedure with the potential for serious complications, the resultant finding may aid in the diagnosis and guide the subsequent management of certain patients presenting with serious ocular findings of undefined etiology.

Biopsy↗