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Biomedical subjects

A S Chen

Publications and source records attributed to A S Chen.

6 recordsLinked to original sources
PubMed1995

Managing diabetic retinopathy: the partnership between ophthalmologist and primary care physician.

Diabetic retinopathy (DR), an ocular complication of diabetes mellitus, is the leading cause of blindness in Americans age 20 to 74 today. The more severe stage of the disease, proliferative diabetic retinopathy, affects an estimated 700,000 Americans. Based on clinical findings, the disease is generally classified as nonproliferative DR or proliferative DR. While the former often begins as a symptomatically silent disease, it nevertheless may be progressing to itself cause significant visual loss. Based principally on evidence from several studies sponsored by the National Eye Institute, current treatment consists of regular observation by an ophthalmologist, laser photocoagulation, and vitrectomy. In addition, preventive methods such as tight glycemic control and ophthalmic screening of diabetics appear beneficial. While the ophthalmologist can provide specialized services for the DR patient, prevention and control lie largely in the hands of the primary care physician. Thus, only when primary and specialized care have established a strong partnership can they save the sight of the thousands at risk for diabetic retinopathy.

Adult↗
PubMed1990

Transcription initiation sites and structural organization of the extreme 5' region of the rat neural cell adhesion molecule gene.

Through analysis of rat genomic cosmid clones, the 5'-most exon of the rat neural cell adhesion molecule (NCAM) gene was identified. This exon, here named exon 0, contained the entire 5' untranslated region and the N-terminal signal sequence of the polypeptide. Exon 0 was isolated from a 1.6-kilobase (kb) EcoRI-HindIII fragment of rat genomic cosmid clone 9 which was 35 kb in length. This fragment was sequenced and found to contain approximately 940 base pairs (bp) of 5'-flanking sequence, exon 0, which was approximately 245 bp in length, and approximately 400 bp of the following intron 0. By using information derived from this fragment and the pR18 rat NCAM cDNA, the transcription initiation sites were determined with two assays. Both primer extensions and nuclease S1 protection assays of postnatal day 7 rat brain RNA identified seven initiation sites within a single 10-bp region at positions -195 to -186 relative to the translation start site. An additional minor site was found at position -329. In the immediate 5' region, no consensus TATA or CCAAT sequences were found. Potential regulatory elements within this region include Sp1 consensus binding sites and also a 178-bp homopurine-homopyrimidine sequence containing several mirror repeats. NCAM has multiple transcripts which are regulated in a developmental and tissue-specific fashion. To determine whether these transcripts are initiated at the same sites, transcription initiation sites were analyzed in postnatal day 7 and adult rat brain and also in cultured cell lines of neuronal, glial, and muscle phenotypes. These tissues and cells exhibited distinct NCAM transcript populations in Northern (RNA) dot blot analysis. In all cases similar transcription start sites were found, suggesting that all major NCAM transcripts have similar or identical initiation sites. These results provide essential information to begin analysis of NCAM regulation in different tissues and during development.

Aging↗
PubMed1986

Hypochlorous acid-activated carbon: an oxidizing agent capable of producing hydroxylated polychlorinated biphenyls.

Granular activated carbon (GAC), in the presence of dilute aqueous hypochlorite solutions typical of those used in water treatment, was converted to a reagent capable of carrying out free-radical coupling reactions and other oxidations of dilute aqueous solutions of phenols. The products included biphenyls with chlorine and hydroxyl substitution (hydroxylated polychlorinated biphenyls). For example, 2,4-dichlorophenol, a common constituent of wastewaters and also natural waters treated with hypochlorite, was converted to 3,5,5'trichloro-2,4'-dihydroxybiphenyl and several related compounds in significant amounts. It is possible that these products pose more of a health hazard than either the starting phenols or the unhydroxylated polychlorinated biphenyl derivatives.

Carbon↗
PubMed1979

Patterns and intensity of autofluorescence and its relation to melanin in human epidermis and hair.

The skin of 41 patients including 16 blacks, 15 Caucasians, and 10 Hispanics, was observed using a fluorescent microscope. Three patterns of autofluorescence were observed: intercellular, cytoplasmic, and a combination of intercellular and cytoplasmic. The hair of 75 subjects, including 18 Negroes and 55 Caucasians, was observed. Two patterns were found: medullar and at the cortex. Skin form black patients was associated with the cytoplasmic pattern of autofluorescence. Compared to lighter skin, black skin was also significantly associated with increased intensity of autofluorescence, indicating that autofluorescence of the epidermis parallels the clinical degree of pigmentation. In the hair of 75 subjects, similar results were obtained: Negro hair exhibited more fluorescence than Caucasian hair, and darker hair (brown to black) exhibited more fluorescence than lighter hair (blond). This may be related to melanin and it breakdown products.

Black People↗