Search PubMed⌕ Search

Biomedical subjects

C K Chan

Publications and source records attributed to C K Chan.

At least 145 records · Page 8Linked to original sources
PubMed1996

Lack of desensitization to aerosol pentamidine with long-term use.

OBJECTIVE: To assess whether long-term exposure to aerosol pentamidine (AP) results in desensitization. STUDY DESIGN: Phase I-A retrospective, two group comparative study. Phase II-A prospective intervention study. METHODS: Patients were selected from a 5-year database of 1200 individuals infected with the human immunodeficiency virus (HIV) who received AP as prophylaxis for Pneumocystis carinii pneumonia (PCP). In phase I, serial pre- and post-AP spirometry data of 33 subjects with significant bronchospasm on initial exposure to AP, who thus received aerosol salbutamol (AS) as regular pre-AP premedication for over 18 months, were compared to 33 matched controls who did not use AS. In phase II, 13 of the original group of 33 patients who required regular AS consented to a follow-up AP treatment without AS premedication to examine the effects of discontinuing AS premedication. RESULTS: Phase I: on their initial AP treatment without AS premedication, the drop in mean FVC, FEV1, and FEV1/FVC values post-AP therapy was significantly lower for the AS group compared to the control group. The mean FEV1/FVC value for the AS group was 84% pre-AP and dropped to 75% post-AP therapy. For the control group the corresponding FEV1/FVC values were 83% (pre-AP) and 79% (post-AP). After using AS as premedication for AP for 18 months, the AS group did not show any reduction in flow rates as the mean FEV1/FVC values were 77% (pre-AP) and 80% (post-AP). The values in the control group were 80 and 78%, respectively. In phase II, when the 13 subjects who needed regular AS premedication were exposed to AP without premedication with AS, the flow rates are reduced in the same magnitude as observed at initial exposure to AP. CONCLUSIONS: The results of this study show that the prevention of bronchospasm with AS premedication while receiving long-term AP administration is due to the bronchodilator effect of AS, as desensitization is not achieved after over 18 months of exposure. These findings support long-term regular premedication with AS in patients with documented AP-induced bronchospasm.

AIDS-Related Opportunistic Infections↗
PubMed1996

Acute pulmonary effects of three nebulizers for administering aerosol pentamidine: comparison of Parineb to Fisoneb and Respirgard II.

We conducted a prospective, unblinded, nonrandomized, multiple crossover study to assess the acute pulmonary effects of a new jet nebulizer-Parineb, comparing it to Respirgard II (jet nebulizer) and Fisoneb (ultrasonic nebulizer) for administering aerosol pentamidine (AP). Twenty-three HIV patients received AP at 60 mg dissolved in 3 ml sterile water with Parineb and Fisoneb and 300 mg dissolved in 5 ml sterile water with Respirgard II on three successive clinic visits. Twelve patients known to develop bronchospasm with AP received 200 micrograms of salbutamol as premedication for all three nebulizers. Eleven subjects received AP without bronchodilator premedication. All subjects had a reduction in flow rates with AP. No significant difference was noted in the reduction of flow rates between the three nebulizers in those patients without prior history of bronchospasm with AP. However, there was a significantly greater reduction in flow rates with Parineb in patients with known AP-induced bronchospasm despite premedication with bronchodilator. This decrease in flow rates with Parineb was not felt by patients based on the subjective rating of cough using a visual analog score when compared to the other two nebulizers. Parineb should be used cautiously in individuals with known AP-induced bronchospasm.

Administration, Inhalation↗
PubMed1996

Interactions between propofol and lipid mediator receptors: inhibition of lysophosphatidate signaling.

As a highly lipophilic drug, propofol may interact with lipophilic domains in addition to its likely primary site of action on the gamma-aminobutyrateA) (GABA(A)) receptor. Likely candidates for such interaction are the G protein-coupled membrane receptors for lipid intercellular mediators. The phospholipid lysophosphatidate (LP) has attracted attention as such a signaling molecule. It has a variety of biological actions, including vasoconstriction. We therefore studied the interaction between propofol and the LP receptor. Intracellular Ca2+ release in response to LP was assessed by measuring C1- flux through Ca(2+)-activated C1- channels in Xenopus oocytes. The average charge movement in response to LP 10(-7)M was 2.0 +/- 0.2 microCoulombs. Propofol in Intralipid (0.01%) dose-dependently inhibited LP signaling (50% inhibitory concentration [IC50] 5.38 microM). Propofol 28 microM inhibited LP signaling by 81%. Intralipid (0.01%) was without effect. To ascertain that intracellular signaling pathways and the Ca(2+)-activated C1- channel were not affected by propofol, we tested the effects of propofol (5.6 microM) on currents induced by methylcholine (10(-7)M) in oocytes expressing the m1 muscarinic acetylcholine receptor. No inhibition was observed. As both receptors share the same intracellular signaling pathway, we conclude that clinically relevant concentrations of propofol most likely inhibit the LP receptor or its G protein. Inhibition of LP signaling may explain some of propofol's vasodilating actions.

Anesthetics, Intravenous↗
PubMed1996

Relative importance of central imidazoline receptors for the antihypertensive effects of moxonidine and rilmenidine.

OBJECTIVE: To determine the involvement of central imidazoline receptors in the cardiovascular actions of the antihypertensive agents moxonidine, rilmenidine and clonidine administered systemically. DESIGN AND METHODS: We determined the relative potency of these drugs with respect to their effects on mean arterial pressure and heart rate by performing cumulative intravenous dose-response relationship studies in six conscious rabbits. In another eight rabbits with implanted fourth-ventricular catheters, we investigated the central effects of three cumulative doses of an l1-imidazoline/ alpha 2-adrenoceptor antagonist, efaroxan, and of an alpha 2-adrenoceptor antagonist, 2-methoxyidazoxan (2-Ml), on the hypotension and bradycardia elicited by a single intravenous dose of the above agents. The doses of antagonists were matched for an equal reversal of the hypotension induced by fourth-ventricular alpha-methyldopa (an alpha 2-adrenoceptor agonist) and hence for similar alpha 2-adrenoceptor blockade. RESULTS: Moxonidine and rilmenidine were sevenfold and eightfold less potent, respectively, than was clonidine in eliciting hypotension. By comparison, moxonidine and clonidine were more potent than was rilmenidine in producing bradycardia. Efaroxan and 2-Ml reversed the hypotension and bradycardia induced by a single dose of all three agents dose-dependently. However, efaroxan was more effective than was 2-Ml at reversing the effects of rilmenidine and moxonidine. Complete reversal of their hypotensive effect was observed with the highest dose of efaroxan but the highest dose of 2-Ml reversed approximately 50% of that effect. In contrast, the two antagonists were equally effective at reversing the responses to clonidine. CONCLUSIONS: These results suggest that the hypotension and bradycardia induced by intravenous administration of moxonidine and rilmenidine were mediated mainly by actions on central imidazoline receptors whereas clonidine appears to act predominantly on central alpha 2-adrenoceptors.

Adrenergic alpha-2 Receptor Antagonists↗
PubMed1996

Prefrontal neuropsychological impairment and illness duration in schizophrenia: a study of 204 patients in Hong Kong.

Previous studies investigating the progression of neuropsychological impairment in schizophrenia have yielded conflicting results. We compared prefrontal neuropsychological function and other cognitive performance in a larger sample of schizophrenic patients with different duration of illness. The inclusion of a normal control group also allowed the effect of age to be taken into account. Performance in the Wisconsin Card Sorting Test (WCST) and semantic fluency were both impaired at an early stage in the illness and did not significantly deteriorate as the illness duration increased. Against this background there was preliminary evidence for deterioration in verbal memory function. The data support a lack of progression in prefrontal dysfunction and in most other cognitive domains.

Adolescent↗
PubMed1996

Isolation and partial characterization of a high molecular weight anionic glycoconjugate from transforming growth factor-beta treated bovine articular chondrocyte cultures.

A high molecular weight anionic glycoconjugate was isolated from the media of the transforming growth factor-beta treated chondrocyte cultures by anion-exchange chromatography on DEAE-Sephacel and Mono Q columns and was partially characterized. This high molecular weight anionic glycoconjugate was not detected in the non-treated (control) cultures. Characterization studies showed that the glycoconjugate is a non-reducible, non-collagenous glycoprotein containing O-linked, N-linked, and sialic acid substituted carbohydrate units. The isolated glycoconjugate stained "blue" with Stains All and migrated as a single band on sodium dodecyl sulfate gradient gels (2.5-10% acrylamide - diallyl tartardiamide) at an estimated molecular weight of 540 000. Amino acid and amino sugar analyses showed that it is rich in aspartic acid--asparagine, glutamic acid--glutamine, alanine, proline, and glycine, and contains galactosamine and glucoasmine. This transforming growth factor-beta inducible glycoprotein may be involved in cell differentiation and in the cartilage repair process. It may also be used as a marker to localize the biological activity of transforming growth factor-beta in articular cartilage.

Amino Acids↗
PubMed1996

Role of reactive oxygen metabolites in murine peritoneal macrophage phagocytosis and phagocytic killing.

This study was designed to quantify the role of reactive oxygen metabolites (ROMs) in two distinct components of murine peritoneal macrophage activity, phagocytosis and killing, and to discriminate quantitatively the degree to which each component is dependent on NADPH oxidase and/or xanthine oxidase. A fluorochromatic vital staining technique was modified to simultaneously quantify phagocytosis and microbicidal activity of macrophages incubated with Candida parapsilosis targets. To determine the role of ROMs, macrophages were preincubated with free radical scavengers [superoxide dismutase (SOD) and/or catalase] or with selective inhibitors of xanthine oxidase (XO, e.g., allopurinol) or NADPH oxidase [diphenyleneiodonium (DPI)]. Phagocytosis was not affected by treatment of macrophages with SOD, catalase, allopurinol, or DPI. Candidacidal activity, however, was inhibited by SOD, allopurinol, or DPI. The inhibitory effects of DPI and allopurinol were additive. Histochemical and biochemical assays demonstrated substantial quantities of XO in murine peritoneal macrophages. The findings suggest that the generation of ROMs by XO- and NADPH oxidase-dependent pathways are each important for phagocytic killing by murine peritoneal macrophages.

Allopurinol↗
PubMed1996

Insight and general public attitude on psychotic experiences in Hong Kong.

Psychosis has been viewed with vastly different attitudes in different contexts. Medical professionals frequently assume that patients should have adequate insight into their abnormal experience. "Lack" of insight has been regarded as a characteristic feature of schizophrenic psychosis. However, these experiences have frequently been construed from a non-medically related perspective by the general public. We employed a case-vignette approach to study the opinion of a general public sample concerning attribution, intervention needs and concordance with medical professionals towards psychotic experience. Ninety eight healthy Chinese volunteers were recruited. Results showed that public opinion only agreed partly with the conventional medical model. Although most subjects agreed that the experience described in the case-vignette was psychological, they did not relate this to psychiatric treatment. Subjects having past contact with psychiatric patients showed a higher degree of agreement with the medical perspective than subjects without past contact. Potential implications of our results on management and health education are discussed.

Adolescent↗
PubMed1996

The safety of i.v. pentamidine administered in an ambulatory setting.

I.v. pentamidine is well known to cause severe multiorgan adverse effects and is usually given to hospitalized patients under close monitoring. The primary purpose of this retrospective quality assurance study is to assess the safety of administering i.v. pentamidine in the medical daycare unit (MDCU) for outpatients. Thirty-five outpatients infected with the HIV made 306 visits to the MDCU from January 1991 to December 1993. They received i.v. pentamidine in a dosage of either 300 mg once a month for prophylaxis or 4 mg/kg/d 5 days a week for treatment of Pneumocystis carinii pneumonia (PCP). BP was monitored every 15 to 30 min over 3 to 4 h and clinical side effects were noted. CBC count, BUN, creatinine, amylase, and blood glucose values were taken twice a week. The records were reviewed retrospectively and analyzed for clinical and biochemical derangement. GI side effects occurred in 59 of 306 (19%) visits; 43 (73%) of the side effects were nausea. Routine normal saline solution boluses before and after pentamidine infusion prevented the drop in BP and actually significantly elevated BP after i.v. pentamidine. The most common biochemical derangement was elevated BUN level in eight patients and creatinine in nine patients, but they were mild and required no intervention. Significant neutropenia occurred in three, anemia in two, hyponatremia in two, hyperamylasemia in two, and hyperglycemia in two patients. No palpitation or irregular pulse was encountered. No death was associated with the administration of i.v. pentamidine. Three patients required hospital admission. Only one hospital admission was definitely related to adverse drug effects. In conclusion, the side effects of i.v. pentamidine are common but minor. We conclude that it is safe to administer i.v. pentamidine in carefully selected patients with appropriate monitoring in an ambulatory setting. This has a major health economic implication, because ambulatory i.v. pentamidine can result in significant cost savings and can also enhance quality of life. Further studies regarding the feasibility of home administration of i.v. pentamidine is warranted as even further cost savings and improvement in the quality of life of HIV-infected patients may be achieved.

AIDS-Related Opportunistic Infections↗
PubMed1996

An effectiveness community-based clinical trial of Respirgard II and Fisoneb nebulizers for Pneumocystis carinii prophylaxis with aerosol pentamidine in HIV-infected individuals. Toronto Aerosol Pentamidine Study (TAPS) Group.

STUDY OBJECTIVE: To compare the effectiveness of a standard jet nebulizer, Respirgard II, and a standard ultrasonic nebulizer, Fisoneb, for the administration of aerosolized pentamidine (AP) as primary and secondary prophylaxis against Pneumocystis carinii pneumonia (PCP) in HIV-infected individuals. DESIGN: A retrospective, nonrandomized, parallel group comparative study. SETTING: Patients were enrolled in a community-based AP program (APP) between May 1989 and April 1992 in Ontario, Canada. They received AP in either (1) a centralized treatment facility ("clinic") or (2) their attending physician's office or regionalized centers ("nonclinic"). Clinic administration of pentamidine was via Fisomeb; nonclinic via Respirgard II. PATIENTS: The study group comprised of 1,762 HIV-infected individuals requiring AP for either primary (CD4 < 200/mm3) or secondary PCP prophylaxis. Of these, 1,151 used Fisoneb (clinic) and 611 used Respirgard II (nonclinic). RESULTS: In the primary prophylaxis group, 41 of the 892 patients using Fisoneb (4.6%; mean follow-up, 18 months) compared with 16 of 435 patients using Respirgard II (3.7%; mean follow-up, 14.6 months) developed PCP (p = 0.44). A total of 28 of 259 (10.8%; mean follow-up, 15.3 months) patients using Fisoneb for secondary prophylaxis compared with 11 of 176 (6.3%; mean follow-up, 14.4 months) patients using Respirgard II for secondary prophylaxis developed PCP (p = 0.1). CONCLUSIONS: Despite the difference in dosage (120 mg/mo vs 300 mg/mo), type of nebulizer (ultrasonic vs jet), and frequency of administration (twice vs once monthly), the results of this study indicate that both regimens of AP provide comparable protection against PCP. This study further supports the effectiveness of AP as a solid second-line prophylaxis for HIV-infected individuals who are intolerant to trimethoprim/sulfamethoxazole or dapsone.

AIDS-Related Opportunistic Infections↗
PubMed1996

Role of imidazoline receptors in the cardiovascular actions of moxonidine, rilmenidine and clonidine in conscious rabbits.

The present study in conscious rabbits with intracisternal (i.c.) catheters sought to determine the relative contribution of the I1 subtype of imidazoline receptors (IR) and alpha 2 adrenoceptors to the hypotensive effects of rilmenidine, clonidine and moxonidine with an I1-IR/alpha 2 adrenoceptor antagonist efaroxan and a specific alpha 2 adrenoceptor antagonist 2-methoxyidazoxan (2-MI). The alpha 2 adrenoceptor antagonist effect of efaroxan was compared with 2-MI by performing cumulative dose-response curves in the presence of alpha-methyldopa (400 micrograms/kg i.c.). 2-MI was 5.6 times more potent than efaroxan at reversing 75% of the hypotension elicited by alpha-methyldopa (P < .025). This dose ratio was used to match doses of efaroxan and 2-MI for similar alpha 2 adrenoceptor blockade. The effects of efaroxan (4.1, 13, 41 micrograms/kg i.c.) and 2-MI (0.74, 2.3, 7.4 micrograms/kg i.c.) were investigated on a single i.c. dose of rilmenidine (12 micrograms/kg), clonidine (0.75 microgram/kg) and moxonidine (0.51 microgram/kg). These doses of the antihypertensive agents, which were determined from cumulative dose-response curves, produce 90% of the maximum hypotension. Efaroxan was more effective at reversing the hypotension induced by moxonidine and rilmenidine than was 2-MI (P < .01). These findings suggest that rilmenidine and moxonidine act predominantly via IR. By contrast, 2-MI was more effective at reversing the clonidine-induced hypotension than was efaroxan (P < .001), suggesting that clonidine acts mainly via alpha 2 adrenoceptors in conscious normotensive rabbits. Thus, a higher selectivity of the second generation agents moxonidine and rilmenidine for I1-IR over alpha 2 adrenoceptors, compared with the first generation agent clonidine, appears to be necessary for this effect to be manifested in their hypotensive actions.

Animals↗
PubMed1996

Zonal heterogeneity of hepatic injury following shock/resuscitation: relationship of xanthine oxidase activity to localization of neutrophil accumulation and central lobular necrosis.

Post-ischemic hepatic injury is characterized by zonal heterogeneity of injury (central lobular necrosis), sinusoidal neutrophil accumulation, and injury generated by reactive oxygen metabolites. We evaluated the role of the heterogeneous distribution of hepatic xanthine oxidase in the generation of neutrophil accumulation and consequent hepatocellular injury in rats subjected to shock [controlled hemorrhagic hypotension (mean arterial pressure = 37.5 + or - 2.5 mmHg for 120 min)], with or without subsequent resuscitation and hemodynamic stabilization, compared with sham-operated rats. Shock/resuscitation produced striking neutrophil accumulation (assayed by esterase histochemistry) in the pericentral sinusoids, associated with centrolobular necrosis. This paralleled the pericentral distribution of xanthine oxidase (determined by histochemical assay of frozen sections) and its release from the liver into the circulation at resuscitation. Pretreatment with allopurinol inhibited hepatic xanthine oxidase activity, neutrophil accumulation, and pericentral hepatocyte necrosis in shock/resuscitation in rats. These findings suggest that reactive oxygen metabolites generated by heterogeneously distributed xanthine oxidase may contribute to the heterogeneity of hepatocellular injury in "ischemic hepatitis."

Animals↗
PubMed1995

Signaling functions of L-selectin. Enhancement of tyrosine phosphorylation and activation of MAP kinase.

L-selectin is a leukocyte cell surface glycoprotein involved in carbohydrate-specific ligand binding which mediates rolling of leukocytes along endothelial surfaces. In addition to its role in adhesion, an intracellular signaling role for L-selectin has recently been recognized. In particular, cross-linking L-selectin leads to increased cytosolic Ca2+ levels and potentiation of the oxidative burst. As several cell surface glycoproteins have been shown to be linked to tyrosine kinases, we examined the hypothesis that L-selectin may be linked to pathways involving tyrosine phosphorylation in human neutrophils. Ligation of L-selectin by three different antibodies recognizing separate epitopes led to increased tyrosine phosphorylation of several cellular proteins as judged by anti-phosphotyrosine immunoblots of whole cell lysates with prominent bands at 40-42, 55-60, 70-72, and 105-120 kDa. The 42-kDa band comigrated with mitogen-activated protein (MAP) kinase as determined by immunoblotting with anti-MAP kinase antibody. This effect was specific for L-selectin, because antibodies against CD18, CD45, and CD10 did not increase tyrosine phosphorylation. Phosphorylation was not due to Fc binding, since F(ab')2 fragments of the anti-L-selectin antibodies were similarly effective, and the response was unaffected by Fc receptor blockade. Cross-linking of L-selectin was not required for enhanced tyrosine phosphorylation, because monovalent Fab fragments also increased tyrosine phosphorylation. The response to L-selectin antibodies was not inhibited by cytochalasin, suggesting that reorganization of the actin cytoskeleton was not required for this response. Sulfatides, sulfated glycolipids which may be natural ligands for L-selectin, also induced a rapid, dose-dependent increase in tyrosine phosphorylation. In addition, sulfatides, but not control glycolipids, resulted in enhanced tyrosine phosphorylation of MAP kinase. Both sulfatides and anti-L-selectin antibodies increased kinase activity of MAP kinase as determined by gel renaturation assay. The tyrosine kinase inhibitor, genistein, blocked the transient increase in intracellular Ca2+ and the oxidative burst induced by sulfatides, suggesting that this tyrosine phosphorylation is functionally important. We conclude that L-selectin is able to transmit intracellular signals, including increased tyrosine phosphorylation and activation of MAP kinase in neutrophils. We speculate that these events may contribute to the activation of neutrophils during adhesion.

Animals↗
PubMed1995

Energy transfer and trapping in photosystem I reaction centers from cyanobacteria.

A mutant strain of the cyanobacterium Synechocystis 6803, TolE4B, was constructed by genetic deletion of the protein that links phycobilisomes to thylakoid membranes and of the CP43 and CP47 proteins of photosystem II (PSII), leaving the photosystem I (PSI) center as the sole chromophore in the photosynthetic membranes. Both intact membrane and detergent-isolated samples of PSI were characterized by time-resolved and steady-state fluorescence methods. A decay component of approximately 25 ps dominates (99% of the amplitude) the fluorescence of the membrane sample. This result indicates that an intermediate lifetime is not associated with the intact membrane preparation and the charge separation in PSI is irreversible. The decay time of the detergent-isolated sample is similar. The 600-nm excited steady-state fluorescence spectrum displays a red fluorescence peak at approximately 703 nm at room temperature. The 450-nm excited steady-state fluorescence spectrum is dominated by a single peak around 700 nm without 680-nm "bulk" fluorescence. The experimental results were compared with several computer simulations. Assuming an antenna size of 130 chlorophyll molecules, an apparent charge separation time of approximately 1 ps is estimated. Alternatively, the kinetics could be modeled on the basis of a two-domain antenna for PSI, consistent with the available structural data, each containing approximately 65 chlorophyll a molecules. If excitation can migrate freely within each domain and communication between domains occurs only close to the reaction center, a charge separation time of 3-4 ps is obtained instead.

Cyanobacteria↗
PubMed1995

Volume regulation in leukocytes: requirement for an intact cytoskeleton.

Animal cells regulate their volume by controlling the flux of ions across their plasma membrane. Recent evidence suggests that ion channels and pumps are physically associated with, and may be regulated by components of the cytoskeleton. To elucidate the role of elements of the cytoskeleton in volume regulation, we studied the effects of cytoskeletal disrupting agents on regulatory volume decrease (RVD) in three different leukocyte types: Jurkat lymphoma cells, HL-60 cells, and human peripheral blood neutrophils. Cell volume was measured in two ways: (i) electronically with a Coulter counter and (ii) by forward light scattering in a flow cytometer. Exposure of all leukocyte types to hypotonic medium (200 mOsm) resulted in an immediate increase in cell volume followed by a regulatory decrease to baseline by 20 min. In the presence of the microtubule disrupting agents, colchicine and nocodazole, RVD was totally inhibited which corresponded to loss of microtubules as determined by immunofluorescence. Similarly, RVD was inhibited in Jurkat cells incubated with the actin binding agents, cytochalasin B (CB) or D (CD). In contrast, in HL-60 cells and human neutrophils, RVD was unaffected by treatment with either CB or CD. While cytochalasins are generally thought of as microfilament disrupting agents, their primary action is to prevent F-actin polymerization. The extent of ensuing microfilament disruption depends in part on the rate of filament turnover. In an attempt to understand the differential effects of the cytochalasins on RVD, the F-actin content of the different cells was determined by NBD-phallacidin staining and flow cytometry. Pretreatment with CB or CD resulted in profound actin disassembly in Jurkat cells (relative fluorescence index RFI: 1.0 control vs. 0.21 +/- 0.01 for CB and 0.48 +/- 0.02 for CD). However, the cytochalasins did not induce net disassembly in either HL-60 cells or human neutrophils. To study the effects of an increase in F-actin on volume regulation, neutrophils were treated with the chemoattractant f-Met-Leu-Phe or with an antibody (Ab) to beta 2 integrins followed by a cross-linking secondary Ab. Despite an increase in F-actin in both circumstances, RVD remained intact. Taken together, these results suggest that both microtubules and microfilaments are important in volume regulation.

Actins↗
PubMed1995

Subretinal fibrosis in central serous chorioretinopathy.

PURPOSE: To report unusual and heretofore unreported visually damaging manifestations of severe central serous chorioretinopathy. METHODS: Case studies. RESULTS: Each of six male patients (average age, 40 years) had a form of severe central serous chorioretinopathy with at least one eye containing fibrin in the subretinal space that then developed into a subretinal fibrotic scar. Scar formation was followed by a tenting up of the macula, vascularization of the fibrosis (subretinal neovascularization), or a retinal pigment epithelial rip. Four of the seven eyes with subretinal fibrosis had severe visual loss (20/400 or worse). CONCLUSION: Subretinal fibrin and other extracellular matrix molecules appear to stimulate the retinal pigment epithelium to undergo fibrous metaplasia, which results in subretinal fibrotic scar formation and other sequelae, all of which can lead to severe visual loss.

Adult↗