Biomedical subjects

Shih-Jen Chen

Publications and source records attributed to Shih-Jen Chen.

28 records · Page 2Linked to original sources

PubMed2002

Syphilitic uveitis as the initial manifestation of HIV infection.

Syphilis is an uncommon cause of uveitis in HIV-infected patients. We report a case of bilateral panuveitis and describe its characteristics as the initial manifestation of HIV infection. A 74-year-old heterosexual male complained of blurred vision and floaters in both eyes for 40 days. Slit lamp examination showed diffuse keratic precipitates and cells in the anterior chamber of both eyes. Fundus examination revealed multiple small white dots and scattered retinal hemorrhage over the mid-equatorial retina with marked vitritis. Physical examination disclosed multiple erythematous papules over bilateral palms compatible with secondary syphilis. Serologic tests--the venereal disease research laboratory (VDRL) test, fluorescent treponemal antibody absorption (FTA-ABS) test, and Treponema pallidum hemagglutination (TPHA) test--were all positive. Aqueous fluid also showed positive FTA-ABS reaction. Under the impression of acquired secondary syphilis, enzyme-linked immunosorbent assay and Western blot test were performed and revealed concurrent HIV infection. After intravenous administration of penicillin-G, 18 million units daily for 2 weeks, the vitritis and retinochoroiditis improved. All patients with panuveitis of unknown cause should undergo VDRL and FTA-ABS screening. Subsequent testing for HIV antibody in leutic uveitis is also mandatory.

Aged↗

PubMedDate not supplied

Comparison of electrical stimulation thresholds in normal and retinal degenerated mouse retina.

PURPOSE: To compare the threshold for electrically elicited action potentials of retinal ganglion cells in normal mouse retina and photoreceptor degenerated (rd) mouse retina. METHODS: Microelectrode recordings were made from retinal ganglion cells of normal and rd mice. Mice with a genetically based retinal degeneration (rd mice) were grown to the age of 16 weeks, when light-evoked responses could no longer be recorded. A bare wire was placed in the vitreous to stimulate the retina with charge-balanced current pulses. The following pulse shapes were investigated: single, square biphasic pulse, single sine wave, and biphasic pulse trains. RESULTS: Normal mice had significantly lower stimulus thresholds than rd mice for all pulse shapes. In normal and rd mice, short pulses were more efficient with respect to total charge used, but required a higher current. In normal mice, sine wave stimulation was significantly more efficient than a biphasic pulse of the same duration. No difference was noted between sine wave and square wave stimulation in rd mice. Pulse trains offered little benefit over single pulses. CONCLUSION: The amount of electrical charge required to elicit an action potential is dependent on the condition of the retina and the shape of the stimulus pulse used to deliver the charge.

Action Potentials↗

PubMedDate not supplied

Population-based study of nonproliferative diabetic retinopathy among type 2 diabetic patients in Kinmen, Taiwan.

PURPOSE: This study was conducted to assess the prevalence and associated factors of nonproliferative diabetic retinopathy among type 2 diabetic patients in Kinmen, Taiwan. METHODS: From 1991 to 1993, 971 type 2 diabetic patients in Kinmen underwent diabetic retinopathy screening performed by a panel of ophthalmologists using indirect ophthalmoscopy and 45 degrees color fundus retinal photographs. RESULTS: Of the 971 patients screened in 1991-1993, 578 (59.5%) were examined for this study. Diabetic retinopathy was diagnosed in 127 patients (22.0%), including nonproliferative diabetic retinopathy in 13.3%, proliferative diabetic retinopathy in 1.4%, legal blindness in 1.4%, and ungradable diabetic retinopathy in 5.9%. Significant associated factors of nonproliferative diabetic retinopathy based on multiple logistic regression analysis were fasting plasma glucose (FPG) at baseline [> or =126 mg/dl vs. <126 mg/dl; odds ratio (OR) = 2.89; 95% confidence interval (CI), 1.01-9.09], 2-h postload at baseline (> or =200 vs. <200 mg/dl; OR = 1.48; 95% CI, 1.09-2.07); HbA1c at follow-up (> or =7% vs. <7%; OR = 6.54; 95% CI, 3.01-14.20), duration of diabetes (> or =15 years vs. <10 years; OR = 6.72; 95% CI, 2.13-21.18), and incremental systolic blood pressure between baseline and follow-up (OR = 1.02; 95% CI, 1.00-1.04). CONCLUSIONS: In addition to the longer duration of type 2 diabetes, FPG at baseline, poorly controlled glucose concentration, and altered blood pressure may increase the risk of nonproliferative diabetic retinopathy in type 2 diabetic patients.

Adult↗

PubMedDate not supplied

Significant variation of the elevated nitric oxide levels in aqueous humor from patients with different types of glaucoma.

Though several studies have shown that the biochemical function of nitric oxide (NO) in the eye might play an important role in the regulation of intraocular pressure (IOP), local control of ocular blood flow and loss of retinal ganglion cells by apoptosis, it is unclear whether the role of NO is similar in the pathogenesis of different kinds of glaucoma: primary open-angle glaucoma (POAG), chronic closed-angle glaucoma (CCAG) and neovascular glaucoma (NVG). To further explore this issue, we measured the concentrations of NO in aqueous humor and plasma samples from patients with POAG (n = 31), CCAG (n = 76), NVG (n = 8) and cataract (n = 30). All of the NVG patients suffered from severe proliferative diabetic retinopathy, while other patients were free of any other systemic disease. The NO levels in both aqueous humor and plasma samples were assessed by chemiluminescence assay. We found that the NO levels in aqueous humor samples were greatly varied in patients with POAG (36.2 +/- 3.3 microM), CCAG (47.7 +/- 3.4 microM) and NVG (65.8 +/- 5.4 microM), and all of them were significantly higher than in cataract patients (27.0 +/- 2.9 microM p < 0.05). Except NVG patients whose NO levels in plasma samples were highest (24.1 +/- 3.5 microM) among all groups, the plasma NO levels were not significantly different between the other glaucoma patients and the cataract patients. We therefore concluded that significant variation of the elevated NO levels in aqueous humor samples from the patients with different types of glaucoma may reflect their differences in the pathogenesis.

Aged↗

PubMedDate not supplied

A feasible tool to detect mRNA expression of matrix metalloproteinases and their tissue inhibitors in human Tenon's capsule.

PURPOSE: To determine the mRNA expression of matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) in human specimens of Tenon's capsule. METHODS: Reverse transcription-polymerase chain reaction (RT-PCR) with specific primers for MMP-1, MMP-2, MMP-9, TIMP-1 and TIMP-2 was performed on tissue specimens obtained from patients with cataract, rhegmatogenous retinal detachment, glaucoma, or diabetes mellitus. RESULTS: Glyceraldehyde phosphate dehydrogenase (GAPDH) mRNA transcripts were detected in 26 (76.5%) of 34 specimens, with almost the same amount of expression in each of these samples. Messenger RNA expression of one or more of the MMPs/TIMPs could also be detected in all of these 26 samples, but not in any sample without GAPDH expression. MMP-2, TIMP-1 and TIMP-2 were detected in 25 (96.2%) of the 26 samples with GAPDH expression, while MMP-1 and MMP-9 were detected with a lower percentage (34.6 and 19.2%, respectively). CONCLUSION: The feasibility of RT- PCR with GAPDH as an internal standard to determine mRNA transcripts of the MMPs and TIMPs in the subconjunctival Tenon's capsule was demonstrated.

Conjunctiva↗

PubMedDate not supplied

Possible involvement of nitric oxide in the progression of diabetic retinopathy.

Abnormal nitric oxide (NO) synthesis has been implicated in the pathogenesis of diabetes mellitus. The aim of our study was to elucidate the relationship between the stages of diabetic retinopathy (DR) and the NO levels in aqueous humor and plasma. Using the chemiluminescence assay, we measured the concentrations of NO in aqueous humor and plasma samples obtained during intraocular surgery from 45 diabetic patients and 19 nondiabetic cataract patients. The patients with diabetes were classified into 4 groups: proliferative DR (PDR) with active neovascularization (active PDR; 9 cases), PDR with quiescent neovascularization (regressed PDR; 6 cases), background DR (BDR; 16 cases) and no DR (14 cases). We found that the aqueous NO levels (mean +/- SE) of the active PDR group (83.2 +/- 13.9 microM) were significantly higher than those of the BDR group (45.8 +/- 6.0 microM, p = 0.049) and the diabetics without DR (33.3 +/- 5.2 microM, p = 0.011), and, although not statistically significantly, they were also higher than those of the regressed PDR group (52.1 +/- 10.3 microM, p = 0.224). However, no significant differences were observed between any of the diabetic subgroups in the plasma NO levels (p = 0.345). We therefore concluded that NO present in the ocular tissues may play important roles in the progression of DR.

Aged↗

PubMedDate not supplied

The HIV RNA Levels of Plasma and Ocular Fluids in AIDS Patients with Ophthalmic Infections.

The aim of the present study was to evaluate the impact of highly active antiretroviral therapy (HAART) on HIV viral load of plasma and intraocular fluids in AIDS patients with ophthalmic opportunistic infections. We further compared the treatment effect of HAART on these patients. From June 1997 to July 2003, we examined and followed up the ophthalmic conditions of 49 patients receiving HAART with ophthalmic diseases during this period. The method of reverse-transcriptase polymerase chain reaction was used to detect and monitor HIV load in plasma and/or aqueous humor of AIDS patients. Before HAART, the HIV levels in the plasma and aqueous humor in 8 AIDS patients with ophthalmic opportunistic infections were significantly higher than those in 6 patients with HIV-related retinopathy (p < 0.05). Compared to the eye findings and clinical improvement, HIV loads of aqueous humor in 10 of 14 AIDS patients (6 with HIV-related retinopathy, 5 with cytomegalovirus retinitis, 2 with toxoplasmic retinitis and 1 with cryptococcal chorioretinitis) declined to undetectable levels (< 400 copies/ml) after 4-8 months of HAART. HIV virus levels in the plasma of AIDS patients were significantly decreased, and the CD4 counts of these patients were significantly increased (Wilcoxon test) after initiation of HAART.

AIDS-Related Opportunistic Infections↗

PubMedDate not supplied

Detection of HIV RNA levels in intraocular and cerebrospinal fluids in patients with AIDS-related cryptococcosis.

The objective of the present study was to evaluate human immunodeficiency virus (HIV) levels in the aqueous humor and vitreous fluid in patients with and those without ocular involvement due to AIDS-related cryptococcosis. We also assessed whether cryptococcosis infection in the central nervous system (CNS) was associated with elevated HIV levels in the cerebrospinal fluid (CSF). From 1993 to 2003, we obtained 16 CSF samples from 9 AIDS patients with cryptococcal meningitis and 7 AIDS patients without CNS opportunistic infection. Samples of intraocular fluids were obtained from all 9 patients with cryptococcal meningitis. Five cases presented with ocular involvement in patients with meningitis. By using the method of reverse transcriptase-polymerase chain reaction, we detected higher HIV loads in aqueous humor (27,244+/-4,123 copies/ml) and vitreous fluid (84,930+/-5,071 copies/ml) in patients with concomitant CNS and ocular involvement due to AIDS-related cryptococcosis (p<0.05). HIV levels in the vitreous fluid were correlated with levels in CSF (r=0.77). Mean HIV level in the CSF (209,761+/-18,787 copies/ml) was significantly elevated in AIDS patients with cryptococcoal meningitis (p<0.05). To our knowledge, this is the first report to study the level of HIV loads in the CSF and intraocular fluid simultaneously in AIDS patients with cryptococcosis. Our results revealed the intrathecal and intraocular HIV replication in patients with cryptococcosis.

AIDS-Related Opportunistic Infections↗

PubMedDate not supplied

Comparison of the proliferation and differentiation ability between adult rat retinal stem cells and cerebral cortex-derived neural stem cells.

Recent studies have demonstrated that retinal stem cells (RSCs) and stem cells of the central nervous system both exhibited the abilities of self-renewal, proliferation and differentiation into multilineage. In the present study, we compared the proliferation and differentiation abilities between RSCs and cerebral corticex-derived neural stem cells (CNSCs) of adult rats. Stem cells isolated from pigmented ciliary margins of eyes and cerebral cortical tissues of adult rats were cultured in 96-well plates that contained serum-free medium with epidermal growth factor (EGF) and basic fibroblast growth factor (bFGF). In contrast to RSCs, which stopped proliferating after the 8th week, the total cell count of neurospheres in CNSCs increased twofold at the 5th week and more than fourfold at the 10th week after in vitro culture. In contrast, RSCs stopped proliferating after 8 weeks of culture. After adding 2% fetal calf serum and withdrawing EGF and bFGF from the culture medium, the percentages of nestin-positive cells(20.6 +/- 2.7%), microtubule-associated-protein-2-positive neurons (33.2 +/- 3.9%) and glial-fibrillary-acidic-protein-positive glial cells(51.3 +/- 6.2%) in the differentiated CNSCs were significantly higher than those in the differentiated RSCs (10.2 +/- 1.9, 22.3 +/- 1.3 and 44.6 +/- 5.1%, respectively; p < 0.05). We also found that the combination of transforming growth factor beta type III with retinoic acid played an important role in the induction of CNSCs to differentiate into opsin-positive cells. Our data demonstrated that CNSCs displayed a higher ability of proliferation and retinal lineage. This report also offers an alternative protocol of cell reproduction for producing retinal cells.

Animals↗

PubMedDate not supplied

Heat effects on the retina.

BACKGROUND AND OBJECTIVE: To study the heat and power dissipation effect of anintraocular electronic heater on the retina. The determination of thermal parameters that are nonharmful to the retina will aid in the development of an implantable intraocular electronic retinal prosthesis. MATERIALS AND METHODS: In dogs, five different retinal areas were touched with a custom intraocular heater probe (1.4 x 1.4 x 1.0 mm) for 1 second while the heater dissipated 0 (control), 10, 20, 50, or 100 mW. In a second protocol, the heater was mechanically held in the vitreous cavity while dissipating 500 mW for 2 hours while monitoring intraocular temperature. The animals were observed for 4 weeks with serial fundus photography and electroretinography. The procedure was then repeated in the fellow eye. The dogs were killed and both eyes were enucleated and submitted for histology. RESULTS: In experiments using protocol 1, heater settings of 50 mW or higher caused an immediate visible whitening of the retinal tissue. Histologically, this damage was evident only if the eyeswere immediately enucleated. Permanent damage was caused by heater settings of 100 mW or higher. Under protocol 2, no ophthalmologic, electroretinography, or histologic differences were noted between the groups. Temperature increases of 5 degrees C in the vitreous and 2 degrees C near the retina were noted. CONCLUSIONS: The liquid environment of the eye acts as a heat sink that is capable of dissipating a significant amount of power. An electronic chip positioned away from the retina can run at considerably higher powers than a chip positioned on the retinal surface.

Animals↗