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Biomedical subjects

M F Chiang

Publications and source records attributed to M F Chiang.

9 recordsLinked to original sources
PubMed2006

Remote image based retinopathy of prematurity diagnosis: a receiver operating characteristic analysis of accuracy.

BACKGROUND/AIMS: Telemedicine offers potential to improve the accessibility and quality of diagnosis of retinopathy of prematurity (ROP). The aim of this study was to measure accuracy of remote image based ROP diagnosis by three readers using receiver operating characteristic (ROC) analysis. METHODS: 64 hospitalised infants who met ROP examination criteria underwent two consecutive bedside procedures: dilated examination by an experienced paediatric ophthalmologist and digital retinal imaging with a commercially available wide angle camera. 410 images from 163 eyes were reviewed independently by three trained ophthalmologist readers, who classified each eye into one of four categories: no ROP, mild ROP, type 2 prethreshold ROP, or ROP requiring treatment. Sensitivity and specificity for detection of mild or worse ROP, type 2 prethreshold or worse ROP, and ROP requiring treatment were determined, compared to a reference standard of dilated ophthalmoscopy. ROC curves were generated by calculating values for each reader at three diagnostic cut-off levels: mild or worse ROP (that is, reader was asked whether image sets represented mild or worse ROP), type 2 prethreshold or worse ROP (that is, reader was asked whether image sets represented type 2 prethreshold or worse ROP), and ROP requiring treatment. RESULTS: Areas under ROC curves ranged from 0.747-0.896 for detection of mild or worse ROP, 0.905-0.946 for detection of type 2 prethreshold or worse ROP, and 0.941-0.968 for detection of ROP requiring treatment. CONCLUSIONS: Remote interpretation is highly accurate among multiple readers for the detection of ROP requiring treatment, but less so for detection of mild or worse ROP.

Diagnostic Techniques, Ophthalmological↗
PubMed2001

Treatment of childhood myopia with atropine eyedrops and bifocal spectacles.

BACKGROUND: Animal and human studies have suggested that muscarinic antagonists and bifocal spectacles may decrease the progression of myopia in children. The purpose of this study is to report the largest known series of patients treated simultaneously with bifocals and topical atropine. DESIGN: Retrospective, interventional, non-comparative case series. METHODS: 706 myopic children (296 boys and 410 girls, ages 6 to 16 years) were prescribed full cycloplegic spectacle corrections, with photochromic lenses and +2.25 diopter (D) reading adds in each eye. Both eyes were treated with atropine 1% drops once daily. OUTCOME MEASURES: Annual change in cycloplegic refractions of right eyes. Compliance with therapy was monitored by patient and parental report. RESULTS: 496 (70%) of the 706 patients reported full compliance with the treatment regimen, whereas the remaining 210 (30%) patients were partially compliant. The median interval of treatment was 3.62 years (range, 21 days-10.1 years). The mean rate of myopic progression was significantly less (P<0.001) in patients who were fully compliant with atropine therapy and bifocals (0.08 D/year) than in patients who were partially compliant with the treatment regimen (0.23 D/per year). No serious adverse effects were associated with atropine therapy. CONCLUSIONS: Full compliance with topical atropine therapy and bifocal spectacles was associated with decreased progression of myopia compared to partial compliance with treatment. For each of the treated groups, the mean rate of myopic progression was significantly less (P<0.05) than the mean annual rates of myopic progression published for the pediatric population.

Adolescent↗
PubMed1999

A novel mutation in the ABCR gene in four patients with autosomal recessive Stargardt disease.

PURPOSE: To identify additional mutations in the ABCR gene and describe the clinical features of four affected siblings with autosomal recessive Stargardt disease. METHODS: A cohort of eight siblings was identified for study. Four of these individuals were diagnosed with Stargardt disease based on clinical evaluation and fluorescein angiography. Blood samples were obtained from seven of eight siblings, including all those affected. All 50 exons of the ABCR gene were analyzed by single-stranded confirmation polymorphism analysis, followed by direct sequencing of observed variants, to identify mutations in the ABCR gene. RESULTS: We identified a previously unreported kindred of eight siblings, four of whom had mutations in both of their ABCR alleles. A previously described G-to-C transversion of nucleotide 2588, predicting a Gly863Ala amino acid substitution, and a novel G-to-A transition of nucleotide 161, resulting in a Cys54Tyr substitution, were identified. These mutations co-segregated with the affected members of this family. Three of the siblings demonstrated clinical features characteristic of classic Stargardt disease, with bilateral regions of macular atrophy associated with yellow-white "flavimaculatus" flecks in the posterior pole at the level of the retinal pigment epithelium. The fourth affected sibling showed features of early Stargardt disease, with a beaten-bronze appearance to both maculas, as well as perimacular flecks. In all four affected patients, fluorescein angiography showed a characteristic peripheral dark choroid. CONCLUSIONS: We have identified both a previously described and a novel mutation in the ABCR gene in four patients with autosomal recessive Stargardt disease. In-depth knowledge of the ABCR mutation spectrum in patients with Stargardt disease will provide for more efficient screening and may provide potential therapies for Stargardt disease and other retinal diseases.

ATP-Binding Cassette Transporters↗
PubMed1999

Clinical and genetic studies of an autosomal dominant cone-rod dystrophy with features of Stargardt disease.

Cone-rod dystrophy (CORD) and Stargardt disease (STGD) are two hereditary retinal dystrophies with similarities to age-related macular degeneration. Cone-rod dystrophies are a group of degenerative disorders resulting in decreased visual acuity and color vision, attenuated electroretinographic (ERG) responses, and atrophic macular lesions. Autosomal dominant, autosomal recessive, and X-linked forms of cone-rod dystrophy have been reported. Stargardt disease is characterized by reduced visual acuity, atrophic macular changes, prominent 'flavimaculatus flecks' in the pigment epithelium of the posterior retina, and a virtually pathognomic 'dark choroid' pattern on fluorescein angiography. Stargardt disease is classically inherited as an autosomal recessive trait, although numerous families have been described in which features of Stargardt disease are transmitted in an autosomal dominant manner. We have identified a new kindred with autosomal dominant cone-rod dystrophy with features of Stargardt-like disease. Detailed clinical evaluation, genotype analysis, and linkage analysis were performed. Fluorescein angiography revealed a 'dark choroid' pattern in three affected subjects. Electroretinography disclosed markedly reduced scotopic and photopic responses in three affected individuals. Genetic analysis revealed linkage to known loci for cone-rod dystrophy (CORD7) and Stargardt-like disease (STGD3) on chromosome 6q14. A peak lod score of 3.3 was obtained with the marker D6S280 at straight theta =0.010. A physical map was constructed by screening a YAC library with short tandem repeat markers in the region. Screening of a candidate gene, the rho1 subunit of the GABA receptor, failed to reveal any mutations.

Adult↗
PubMed1999

A new locus for autosomal dominant stargardt-like disease maps to chromosome 4.

Stargardt disease (STGD) is the most common hereditary macular dystrophy and is characterized by decreased central vision, atrophy of the macula and underlying retinal-pigment epithelium, and frequent presence of prominent flecks in the posterior pole of the retina. STGD is most commonly inherited as an autosomal recessive trait, but many families have been described in which features of the disease are transmitted in an autosomal dominant manner. A recessive locus has been identified on chromosome 1p (STGD1), and dominant loci have been mapped to both chromosome 13q (STGD2) and chromosome 6q (STGD3). In this study, we describe a kindred with an autosomal dominant Stargardt-like phenotype. A genomewide search demonstrated linkage to a locus on chromosome 4p, with a maximum LOD score of 5.12 at a recombination fraction of.00, for marker D4S403. Analysis of extended haplotypes localized the disease gene to an approximately 12-cM interval between loci D4S1582 and D4S2397. Therefore, this kindred establishes a new dominant Stargardt-like locus, STGD4.

Chromosome Mapping↗
PubMed1998

Nuclear multiparameter flow cytometric DNA analysis of human brain tumors: correlation of DNA content with tumor histology and clinical behavior.

BACKGROUND: Using fresh surgical specimens of brain tumors to investigate cellular DNA content is uncommon. The aim of this study is to elucidate the relationship among cellular nuclear DNA content, tumor histology, and tumor clinical behavior of various tumors of the central nervous system. METHODS: Multiparameter flow cytometry (FACStar, Becton-Dickinson, San Jose, CA) was randomly applied to analyze 40 fresh surgical specimens from brain tumors. Histologically, there were 19 cases of benign tumors and 21 cases of malignant tumors. RESULTS: DNA distribution profiles in the benign tumors revealed 15 cases of diploidy and four cases of aneuploidy, while the malignant tumors had eight cases of diploidy and 13 cases of aneuploidy (p < 0.01). The mean DNA index (DI) in benign tumors was 1.13 +/- 0.27 and in malignant tumors 1.43 +/- 0.48 (p < 0.05). The mean proliferative index (PI) in benign tumors was 10.27 +/- 5.46% and 18.44 +/- 8.98% in malignant tumors (p < 0.05). Clinically, 10 patients had postoperative recurrence. The PI in recurrent and nonrecurrent tumors was 17.83 +/- 11.13% and 13.20 +/- 7.19%, respectively (p < 0.05). The 1-year cumulative survival rate in benign tumors was 78.9%, and 57.1% in malignant tumors (p < 0.05). CONCLUSIONS: Malignant tumors had a significantly higher incidence of aneuploid DNA histograms, a higher DNA index, and a higher proliferative index. Tumors with a high PI had a higher incidence of recurrence and a lower survival rate. Multiparameter DNA analysis by flow cytometry provides a valuable diagnostic aid for the histopathologic differentiation of human brain tumors.

Adolescent↗
PubMed1993

Reversible heat stress-related loss of phosphorylated Alzheimer-type epitopes in Tau proteins of human neuroblastoma cells.

Human neuroblastoma cells, LAN, were used to study the phosphorylation and dephosphorylation of tau proteins. These cells contained mainly a form of tau comparable to fetal brain tau in molecular weight (55 kDa). Neuroblastoma tau reacted with antibodies that recognize epitopes spanning the whole tau molecule (E-1, Alz50, Tau-1, and Tau46), and antibodies (PHF-1, NP8, and T3P) that recognize hyperphosphorylated tau (PHF-tau) in Alzheimer's disease (AD) brains. Exposure of the cells to 45 degrees C heat stress resulted in dephosphorylation of the epitopes recognized by PHF-1, NP8, and T3P. Transfer of the heat-stressed cells to 37 degrees C led to rephosphorylation of the dephosphorylated epitopes. Cells that had been treated with okadaic acid (OA), regardless of whether they were subsequently subjected to heat stress or heat stress and recovery, all contained tau with a molecular weight similar to that of control cells. These tau proteins, similar to tau in control cells, also reacted with antibodies to phosphorylated epitopes. However, unlike the tau from control or heat-stressed cells, the OA-treated and heat-stressed tau had decreased reactivity with Tau-1. Alteration of Tau-1 immunoreactivity has been reported to be an early event in AD neurodegeneration. The reduction of Tau-1 immunoreactivity observed in OA-treated samples could be restored by incubation of electroblots of isolated tau with alkaline phosphatase, indicating an induction of the Tau-1 epitope phosphorylation by OA.(ABSTRACT TRUNCATED AT 250 WORDS)

Alzheimer Disease↗
PubMed1990

Pituitary metastases.

Over the past 12 years we encountered three histologically confirmed pituitary metastases. Primary cancer had been diagnosed and treated previously in only one patient. In the remaining two a transsphenoidal operation provided the initial diagnosis of metastasis, and the primary lesion was subsequently detected at autopsy in one. In two of the three patients symptoms and signs of pituitary dysfunction were the first manifestations of the malignant disease. The main symptoms and signs were impairment of visual acuity, visual field defect, headache, adenohypophyseal insufficency and diabetes insipidus. A sellar mass was demonstrated by CT or MRI in all patients. The tumours were all completely extirpated by subfrontal route in one case and transsphenoidally in the remaining two patients. Following surgery the presenting symptoms improved satisfactorily in all patients.

Adenocarcinoma↗