Search PubMed⌕ Search

Biomedical subjects

C C Chan

Publications and source records attributed to C C Chan.

At least 397 records · Page 22Linked to original sources
PubMed1990

Personal and indoor/outdoor nitrogen dioxide exposure assessments of 23 homes in Taiwan.

Indoor and outdoor nitrogen dioxide (NO2) concentrations of 23 homes from two areas in Taiwan, the city of Taipei and a rural village in central Taiwan, were measured concurrently from December 1987 to January 1988. NO2 measurements were carried out by Palmes tube for one week and filter badges for two days. In Taipei, the mean NO2 concentrations outdoors, in the kitchens, in the livingrooms, and in the bedrooms were 40.1 ppb, 34.4 ppb, 32.1 ppb, and 29.7 ppb for one week, and were 25.7 ppb, 25.6 ppb, 22.6 ppb, and 20.5 ppb for two days. In the village of central Taiwan, the corresponding concentrations were 23.5 ppb, 24.5 ppb, 20.4 ppb, and 17.5 ppb for one week, and 20.3 ppb, 24.7 ppb, 18.8 ppb, and 15.4 ppb for two days. The NO2 concentrations of all microenvironments in Taipei were significantly higher than those in the village of central Taiwan. The outdoor NO2 concentrations were significantly higher than the indoor NO2 concentrations in Taipei. The NO2 measurements in the kitchens were higher than all other measurements indoors and outdoors in the village of central Taiwan. The houses which used natural gas as cooking fuel had slightly higher indoor NO2 concentrations than the houses which used LPG as cooking fuel in Taipei city. Cement houses had slightly higher indoor NO2 concentrations than brick houses. The mean of housewives' exposures was 30.8 ppb in Taipei and 19.9 ppb in the village of central Taiwan. The explanation power of the housewife's exposure to NO2 was 72% by the time weighted-average model and 70% by the simple linear regression model.

Air Pollutants↗
PubMed1990

Endotoxin-induced uveitis in the rat: a hypothesis for preferential involvement of the anterior uvea.

Endotoxin-induced Uveitis (EIU) was produced in Lewis rats by footpad injection of Salmonella endotoxin. Protein and cells were measured both in the aqueous humor and in the cerebrospinal fluid (CSF) in order to examine if the inflammation was strictly limited to the anterior uvea. EIU was also induced in Fischer and Brown Norway rats and the inflammation was compared among the three strains. Although the function and structure of the choroid plexus is very similar to the ciliary body, no signs of inflammation were seen in the choroid plexus and the CSF. Among the 3 tested strains of rats, EIU was maximal in Lewis rats, less severe in Fischer rats and least pronounced in Brown Norway rats. It is thought that because of its specific microvascular structure, the ciliary body is specially prone to endotoxin induced inflammation. The amount of inflammation however depends on the genetic background of the animal.

Animals↗
PubMed1990

The mouse as a model of experimental autoimmune uveoretinitis (EAU).

An EAU model has been developed in the mouse using the retinal soluble antigen (SAg), and the interphotoreceptor retinoid-binding protein (IRBP). Immunogenetic studies indicate that sensitivity to disease is H-2 dependent, but some data suggest that non-MHC genes may also contribute to the regulation of EAU. IRBP was a more potent uveitogen than SAg. Ability to mount lymphocyte and antibody responses was exhibited both by EAU-susceptible and by EAU-resistant strains, and could not be used as a predictive parameter. Dependence of disease induction on variables of immunization was studied in B10.A mice (I-Ak) immunized with IRBP. Use of Bordetella pertussis as additional adjuvant was a prerequisite for successful disease induction. Use of purified pertussis toxin (PTX), rather than a suspension of pertussis bacteria, allowed reduction of the immunization protocol to a single dose of IRBP in CFA. Severity and incidence of disease, as well as its clinical course, were directly affected by the dose of antigen and PTX, and could be controlled by varying their respective doses. A spectrum of disease, from hyperacute to chronic, could be obtained. The chronic type of EAU tended to relapse, with lesions reappearing after a brief period of essential quiescence. The special advantages of the murine EAU model for the study of ocular autoimmunity are discussed.

Animals↗
PubMed1990

FR900506 (FK506) and 15-deoxyspergualin (15-DSG) modulate the kinetics of infiltrating cells in eyes with experimental autoimmune uveoretinitis.

In order to evaluate two new immunosuppressive agents, FR900506 (FK 506) and 15-Deoxyspergualine (15-DSG), the kinetics of infiltrating cells in the eyes of Lewis rats with experimental autoimmune uveoretinitis (EAU) were studied. Rats were immunized with retinal S-antigen and treated with different doses of either FK 506 or 15-DSG. The inflammatory ocular tissues obtained at various intervals during the process of EAU were examined using an immunoperoxidase technique. The results were compared with those eyes developing EAU without treatment or with suboptimal doses or a suboptimal dose of Cyclosporine (CsA). Both FK 506 and 15-DSG, like CsA, delayed the cellular kinetics during the course of EAU. However, FK 506 had the greatest effect on the kinetics of T lymphocyte subsets by causing the greatest increase in the recruitment time of the T suppressor/cytotoxic population. FK506 treatment resulted not only in the highest inhibition of expression of IL-2 receptors on T cells, but also in the prevention of the expression of MHC class II antigens on ocular resident cells. Treatment with 15-DSG resulted in general immunosuppression on various infiltrating inflammatory cells.

Animals↗
PubMed1990

Serial adoptive transfer of experimental autoimmune uveoretinitis in rats.

Experimental autoimmune uveoretinitis (EAU) and pinealitis induced by an interphotoreceptor retinoid-binding protein (IRBP)-derived peptide (R4) was serially transferred into naive recipient rats, using spleen cells from recipients of previous "orders" of transfer. The cells initiating the disease in recipients of the first order were either lymph node cells from rats immunized against peptide R4, or lymphocytes of a cell line specific toward this peptide. The serial transfer was successfully carried out through as many as four orders of sequential recipients.

Amino Acid Sequence↗
PubMed1989

Selective immunosuppression of activated T cells with the chimeric toxin IL-2-PE40. Inhibition of experimental autoimmune uveoretinitis.

A characteristic of activated T lymphocytes is the expression of high affinity IL-2R. We studied a new method of selective immunosuppression directed against activated T cells by using a chimeric recombinant protein (IL-2-PE40) composed of IL-2 fused to a modified Pseudomonas exotoxin lacking its cell recognition domain. As a model of T cell-mediated disease, we used experimental autoimmune uveoretinitis (EAU) produced in Lewis rats by active immunization with the retinal S-Ag. The treatment protocol consisted of i.p. injection of IL-2-PE40 at 0.25 micrograms/g every 12 h. Controls were PBS, PE40, or IL-2-PE40asp553 a mutant form of the molecule with reduced activity. Treatment with IL-2-PE40 resulted in a significant reduction of the incidence and severity of EAU over controls. The analysis of the effect of i.p. injection of IL-2-PE40 on the popliteal draining lymph nodes of immunized animals showed a marked reduction in the lymphocytes content. Transfer experiments demonstrated that IL-2-PE40 prevented the development of EAU effector T cells. Interestingly, although activated B cells were reported to express IL-2R, there was no significant reduction of antibody production against the immunizing Ag under IL-2-PE40 treatment, suggesting sparing of the B cells.

ADP Ribose Transferases↗
PubMed1989

Endogenous bacterial retinitis in AIDS.

We studied two patients, one with histologically confirmed endogenous bacterial retinitis associated with the acquired immunodeficiency syndrome and a second with ophthalmoscopically identical findings who also responded to antibiotic treatment. Both patients had focal, discrete patches of retinitis that enlarged slowly over weeks and ultimately accumulated large amounts of subretinal fluid and retinal exudate. One patient underwent retinal biopsy after systemic and vitreous cultures were negative. Histopathologic sections showed necrotic retina infiltrated with multiple histiocytes containing intracytoplasmic, iodine-positive, pleomorphic, encapsulated bacterial forms. The organism was not grown from the retinal biopsy specimen. Treatment with antibiotics resulted in improved vision in both patients. Our results indicate that endogenous bacterial infection should be considered in the differential diagnosis of retinitis associated with the acquired immunodeficiency syndrome.

Acquired Immunodeficiency Syndrome↗
PubMed1989

Immunohistochemical staining of sebaceous cell carcinoma of the eyelid.

We characterized the inflammatory infiltrate of two sebaceous cell carcinomas of the eyelid with immunohistochemical staining to determine the functional class of the mononuclear cells associated with the tumor. The results were compared with the inflammatory infiltrate associated with basal cell carcinomas. The subepithelial spaces and the area immediately surrounding the sebaceous cell neoplasms were free of mononuclear inflammatory cells, in contrast to the basal cell tumors, which had large numbers of subepithelial inflammatory cells and inflammatory cells in intimate contact with the neoplastic cells as previously reported. Inflammatory reaction in the sebaceous cell tumor was limited to a T-cell infiltrate surrounding the vessels adjacent to the tumor. The predominant mononuclear inflammatory cell in both the sebaceous cell and the basal cell carcinomas was the T helper cell. The apparent difference in mononuclear cell infiltrate may be a significant factor in the clinical behavior of the tumors.

Adenocarcinoma↗
PubMed1989

Immunohistologic findings and results of treatment with cyclosporine in ligneous conjunctivitis.

Using immunohistochemical techniques, we studied ligneous conjunctival lesions from two patients. A significant immune reaction was detected that was characterized by activated T lymphocytes and focal accumulation of plasma cells and B lymphocytes. Immunofluorescent studies demonstrated that IgG was a prominent component of the amorphous hyaline material seen in these lesions. After previous treatment methods had failed, both patients were treated with excisional biopsy and topical cyclosporine. Patient 1 had a dramatic response, with complete resolution of the lesions. Patient 2 had a significant improvement resulting in small, slow-growing recurrences instead of the rapid and extensive recurrences that occurred before treatment with cyclosporine.

Adult↗
PubMed1989

Randomized trial comparing ciprofloxacin plus netilmicin versus piperacillin plus netilmicin for empiric treatment of fever in neutropenic patients.

To assess the efficacy of ciprofloxacin in neutropenic patients, we conducted a randomized prospective trial comparing the combination of ciprofloxacin and netilmicin against piperacillin plus netilmicin as an empiric treatment of fever in cancer patients with neutropenia. Of 214 evaluable episodes, 115 and 99 were randomly assigned to the ciprofloxacin and the piperacillin arms, respectively. The overall response rates were very similar (59 and 62% for the ciprofloxacin and piperacillin arms, respectively). The response for the gram-positive bacteremias was almost identical (around 40%); this low response was due in part to an outbreak of infection by a multiply resistant strain of Staphylococcus epidermidis (for which the ciprofloxacin MIC was greater than or equal to 128 micrograms/ml) which occurred during the second half of the trial. Among gram-negative bacteremias, 9 of 11 infections (82%) responded to the ciprofloxacin combination compared with 3 of 7 (43%) that responded to the piperacillin combination (P = 0.23). The incidences of persistent, profound neutropenia were comparable in both treatments, but the susceptibility of the gram-negative organism to ciprofloxacin and netilmicin was significantly higher than was susceptibility to the other combination. Ciprofloxacin was well tolerated, and patients were able to convert from intravenous to oral therapy in 64 of 115 episodes.

Administration, Oral↗
PubMed1989

Immediate hypersensitivity reactions in the guinea-pig conjunctiva: studies with a second-generation leukotriene D4 receptor antagonist, MK-571.

The role of leukotriene D4 (LTD4) as a mediator of immediate hypersensitivity reactions in the guinea-pig conjunctiva was examined using a potent, second-generation LTD4 receptor antagonist, MK-571 (also known as L-660,711). The microvascular permeability changes in the guinea-pig conjunctiva following challenge with either LTD4 or antigen were measured through accumulation of intravenously administered 99mtechnetium-labeled albumin. Topical application of MK-571 (up to 2 h pretreatment) significantly inhibited the conjunctival responses to LTD4 (ED50 of 18-60 ng/eye) but not to histamine. The responses to a single topical antigen challenge in ovalbumin-sensitized guinea pigs were significantly inhibited (44%) by topical treatment with MK-571, in contrast to the lack of effect previously observed with prototypic antagonists. The inhibitory effects of MK-571 did not involve an action on conversion of [3H]LTC4 to LTD4 and LTE4. Following a second antigen challenge (24 h after the first), MK-571 inhibited the resultant permeability changes by 78%. Specific histamine H1 and H2 antagonists similarly inhibited the responses to the first and second challenges (63 and 74%, respectively). The present study suggests that LTD4 is involved in conjunctival hypersensitivity reactions and that potent LTD4 receptor antagonists may be of therapeutic value in the treatment of allergic conjunctivitis.

Animals↗
PubMed1989

Immunopharmacological studies of qingkaining, a Chinese blended medicine: effects on experimental autoimmune uveoretinitis in the rat.

Qingkaining, a blended Chinese medicine, is reported to be effective in treating patients with uveitis in China. In this study, the immunomodulatory effectiveness of this drug was evaluated on experimental autoimmune uveoretinitis (EAU) induced by S-antigen (S-Ag). Rats treated with high (2.5 cc/kg/day) and low (1 cc/kg/day) doses of Qingkaining, high (10 mg/kg/day) and low (3 mg/kg/day) doses of Cyclosporine A (CsA) and a combination of high or low dose of Qingkaining and low dose CsA were compared by the following parameters: clinical manifestations, histopathology, skin delayed-type hypersensitivity (DTH) reactions, lymphocyte proliferative responses and serum anti-S-antigen antibody production. The incidences of clinically and histopathologically determined EAU were 14.29% and 28.57% respectively in the rats treated with high and low doses of Qingkaining in comparison to 57.14% and none in the rats treated with low and high doses of CsA. EAU did not develop in the rats treated with the combination of low dose CsA and low or high doses of Qingkaining. The skin DTH reaction showed a diminished response in the rats treated with either Qingkaining or CsA. However, the lymphocyte proliferative responses and anti-S-Ag antibody were not effected in the rats treated with Qingkaining alone. This study demonstrates that Qingkaining is a potent immunosuppressive agent in this model for human disease. The experimental data support the clinical effectiveness of Qingkaining in the treatment of patients with uveitis.

Animals↗
PubMed1989

Retinal glial cell proliferation and ion channels: a possible link.

Under a variety of pathological conditions, glial cells of the retina proliferate. Although glial cell proliferation may play a role in a number of important retinal disorders, the regulation of this proliferative response is understood poorly. We examined the possibility that the function of certain ion channels in retinal glial cells may be linked with the induction of proliferation. Experiments were performed on glial cells derived from the adult rat retina and maintained in culture. The cells stained positively by immunocytochemistry with antibodies specific for glial fibrillary acidic protein and for Muller cells. Patch clamp studies of these retinal glial cells demonstrated the presence of a large conductance, calcium-activated potassium channel that is sensitive to tetraethylammonium, a classical blocker of potassium channels. The activity of this type of potassium channel was monitored by patch clamp recordings in the cell-attached configuration before and after exposure of the glial cells to a mitogenic conditioned medium. Exposure to this conditioned medium was associated with a marked increase in the activity of the ion channel. A possible link between the activity of potassium channels and the action of mitogens was suggested further by the finding that tetraethylammonium significantly blocked the proliferative response of retinal glial cells to the conditioned medium. Our findings support the hypothesis that there is a link between the biophysical processes involved in ion channel activity and the proliferation of retinal glial cells.

Animals↗
PubMed1989

Expression of Ia antigen by ocular tissues of mice treated with interferon gamma.

Intraperitoneal injections of interferon gamma (IFN-gamma) induced or enhanced the expression of Ia antigen by selected murine ocular tissues. In contrast, topical application of this lymphokine had no effect. Ia antigen expression was noted in most cellular components of the conjunctiva, iris, ciliary body, choroid and sclera of treated mice. Intense staining was also found in stromal cells of the cornea, but no Ia reactivity was detected in the corneal epithelium. The lack of staining in the corneal epithelium is in contrast to the strong reactivity in the adjacent conjunctival epithelium, as well as in the skin epithelium. There was no increase in the number of Langerhans cells in the peripheral cornea and limbus, or in their intensity of staining with the anti Ia antibodies. The pattern of Ia expression in ocular tissues of mice treated with IFN-gamma is similar to that of rats with experimental autoimmune uveoretinitis (EAU) except that Ia is expressed more regularly and with higher intensity by the retinal vascular endothelium of rats with EAU than by that of IFN-gamma-treated mice. The findings in the current study thus support the notion that IFN-gamma may be involved in immune-mediated inflammation in the eye.

Animals↗
PubMed1989

The interrelationship between the root surface and alveolar bone of the replanted avulsed tooth after etching.

It has been suggested that removal of the damaged nonvital periodontal ligament (PDL) may result in slower destruction of tooth substance following replantation of teeth. It has also been suggested that citric acid conditioning of surgically exposed dentin may enhance connective tissue attachment on root surfaces. The aim of this study was to examine the interrelationship between the acid etched root surface of the replanted tooth and the alveolar bone. Forty-five available anterior teeth from six monkeys were divided into 3 groups in this experiment. All teeth were extracted and dried for 2 hrs. In the first group the teeth were replanted immediately after endodontic therapy. The teeth in the second group were replanted after immersion in 10% sodium hypochlorite and subsequently irrigation with normal saline. In the third group, the cementum and necrotic PDL were removed by grinding the root surfaces which were then treated with citric acid (PH = 1) for 3 minutes followed by normal saline irrigation. All teeth were replanted without splinting and were subjected to histological examination at 12 week post-replantation. Close apposition of collagen fibrils of the new connective tissue to the exposed root surface was observed in most cases in the second and third group, although bony ankylosis and inflammatory root resorptions were also found in some areas. Teeth in the first group, the control experiment, had much more replacement and inflammatory resorptions. Then the result suggested that demineralization with citric acid on the denuded avulsed tooth prior to replantation may decrease the chance of replacement resorption and result in fibrous adhesion to the alveolar bone.

Adhesiveness↗
PubMed1989

Cryopexy enhances experimental autoimmune uveoretinitis (EAU) in rats.

Treatment of rat eyes with cryopexy enhanced the development of experimental autoimmune uveitis (EAU) in these eyes. The enhancement of EAU by cryopexy was particularly pronounced when the disease was induced by active immunization in rats of a low responder strain (Wistar Furth), or by adoptive transfer with lymphocytes sensitized against S-antigen. The disease enhancement was expressed by earlier onset of clinical symptoms and by more severe inflammatory changes. Histological examination of cryopexy-treated eyes showed focal necrosis and inflammation, confined to the affected sites. Immunohistochemical analysis of the inflammatory infiltration revealed it consists mainly of macrophages and T-lymphocytes of the helper and suppressor subsets. In addition, increased expression of class II antigens was observed in affected areas, on both inflammatory and resident ocular cells. Using electron microscopy and Evans blue angiography we could show breakdown of the blood-retinal barrier at the treated sites. Histological examination of eyes with EAU following cryopexy showed localization of the early inflammation at the injured site. The data are interpreted to suggest that the enhanced EAU in cryopexy-treated eyes is mainly due to the breakdown of the blood-retinal barrier, the accumulation of lymphoid cells and the increased expression of class II antigens, which facilitates antigen presentation.

Animals↗
PubMed1989

Immunopathology of ocular onchocerciasis. I. Inflammatory cells infiltrating the anterior segment.

Ocular tissue (conjunctiva and iris) was obtained from 12 adult African men with active ocular onchocerciasis and from nine age-matched persons from the same endemic region but without onchocercal infection. These tissues were examined immunohistologically and two major findings were noted. First, mild-to-moderate chronic inflammatory cellular infiltration was present in the conjunctiva of the onchocerciasis patients. T lymphocytes (CD3+) were the major inflammatory cells, and the T suppressor/cytotoxic (CD8+) subset was significantly increased in the ocular onchocerciasis patients (P less than 0.03). Second, in the onchocerciasis patients, non-lymphoid cells of the conjunctiva and iris, such as vascular endothelium, pericytes and fibroblasts were in an activated state, as shown by increased expression of Class II MHC antigens (P less than 0.02, conjunctiva; P less than 0.05, iris). These concomitant findings of lymphocyte infiltration and resident cell activation indicate a dynamic state of localized host responsiveness presumably to the microfilarial parasites and their products in the anterior segments of the eyes of patients with ocular onchocerciasis.

Aged↗