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Biomedical subjects

R A Bell

Publications and source records attributed to R A Bell.

At least 127 records · Page 7Linked to original sources
PubMed1984

Sympathetic ophthalmia. Histopathologic and fluorescein angiographic correlation.

Sympathetic ophthalmia was found 15 months after cataract extraction in a previously traumatized eye. Histopathologic examination disclosed numerous Dalen-Fuchs nodules with underlying choroidal granulomas causing obliteration of the choriocapillaris and disruption of Bruch's membrane. Prominent Dalen-Fuchs nodules were also observed clinically in the sympathizing eye, and the angiographic findings of initial hypofluorescence followed by late hyperfluorescence correlated with the pathologic findings in the sympathogenic eye. Only ten cases of sympathetic ophthalmia with fluorescein angiography have been reported previously. This is the fifth case accompanied by a histopathologic description of the exciting eye. The finding of breaks in Bruch's membrane has not been previously reported, to the best of our knowledge. This article compares the angiographic and pathologic appearances with those described in previous reports.

Aged↗
PubMed1984

Aicardi's syndrome. A clinicopathologic study.

A 9-week-old female infant was seen with typical clinical features of Aicardi's syndrome. At autopsy (at 21 months of age), examination of the brain disclosed polymicrogyria and agenesis of the corpus callosum. Histopathologic studies of the posterior segments showed areas of intact but attenuated and depigmented retinal pigment epithelium, and atypical colobomatous defect of both posterior segments, and ectatic scleral channels lined by a retinal pigment epithelial choriocapillarislike complex in the left eye. The pathogenesis of the ocular defects is discussed.

Abnormalities, Multiple↗
PubMed1984

1H-nuclear magnetic resonance of intercalators and rGCA: a potential mutagenicity probe.

Variable temperature 1H-nuclear magnetic resonance (NMR) has been used to study the interaction of the RNA trimer, GpCpA, with the intercalators ethidium bromide and the acridine derivatives; proflavin, 9-amino-acridine, acridine orange, acridine yellow and acriflavin. The complexes formed were studied at nucleic acid to drug ratios of 1:1 and 5:1, the latter being useful in defining the effects of structural variation in the acridine series and in determining the site of intercalation. All the intercalators greatly stabilized the oligonucleotide duplex, the average melting temperature (Tm) increasing by up to 30 degrees C. Significant changes in individual Tms and chemical shifts were observed for all the GpCpA protons. 9-Amino-acridine and acriflavin did not stabilize the GpCpA duplex as substantially as the other acridine derivatives. It is suggested that this intercalator:GpCpA system, and its associated NMR-derived Tm, is a useful physical probe for potential mutagens.

Acridine Orange↗
PubMed1983

Prediction of 1H NMR chemical shifts of DNA oligomers.

A set of parameters, devised for the prediction of 1H NMR chemical shifts of heterobase and anomeric protons in the high temperature (greater than 70 degrees C) spectra of RNA oligomers has been found to be applicable to the corresponding DNA oligomers. Fifteen examples of DNA oligomers that have had high temperature spectra recorded and assigned show a mean absolute difference between predicted and assigned shifts of 0.045 ppm. The parameters for uridine H-5 are applied to the calculation of thymidine methyl group shifts and give excellent agreement with experimental assigned shifts. The RNA parameter set is a practical means of assigning heterobase and anomeric protons in DNA oligomers. A programme using the RNA parameter set has been written which enables the sequence of short DNA oligomers to be predicted from their 1H NMR spectra.

DNA↗
PubMed1982

Effects of flanking G . C base pairs on internal Watson-Crick, G . U, and nonbonded base pairs within a short ribonucleic acid duplex.

A series of pentaribonucleotides, ApGpXpGpU (where X identical to A, G, C, or U), was synthesized to investigate the effects of flanking G . C pairs on internal Watson-Crick, G . U, and nonbonded base pairs. Sequences ApGpApCpU (Tm = 26 degrees C) and ApGpCpCpU (Tm = 25 degrees C) were each found to form a duplex with non-base-paired internal residues that stacked with the rest of the sequence but were not looped out. ApGpGpCpU also forms a duplex (Tm = 30 degrees C) but with dangling terminal nonbonded adenosines rather than internal nonbonded guanosines. ApGpUpCpU prefers a stacked single-strand conformation. In addition, contribution to duplex stability from an internal A . U or G . C base pair is enhanced by 6 degrees C when flanked by G . C base pairs as compared to A . U base pairs. G . C base pairs flanking an internal G . U base pair were found to be more tolerant to the altered conformation of a G . U pair and result in an increase to stability comparable with that found for an internal A . U base pair.

Base Composition↗
PubMed1982

Evaluating the mediating effects of social support upon life events and depressive symptoms.

Previous research has yielded inconsistent results regarding the mediating effects of social support upon psychiatric illness. Using data (N = 2029) gathered as part of a major epidemiologic study in the southeastern United States, the authors examine the relationships among depressive symptoms, social support, stressful life events, and socioeconomic status. As anticipated, direct effects were found for social support, stressful life events, and socioeconomic status upon depressive symptoms. However, when the data were analyzed via three-way analysis of variance and multiple regression (including all possible interaction terms) analysis, no statistically significant interactive effects were found. The authors conclude that these findings clearly demonstrate direct effects of social support and stressful life events upon depressive symptoms. Respondents in the lower social support groups experience the greatest impact of stressful life events; in contrast, persons in high social support groups, although evidencing increased symptom scores with increasing numbers of life events, experience the buffering effect of social support by showing less severe distress.

Adult↗
PubMed1982

Anterior segment necrosis following cyclocryotherapy.

A 74-year-old woman with secondary glaucoma underwent cyclocryotherapy. Ten weeks later anterior segment necrosis and dehiscence in the area of the cryotherapy lesions resulted in an expulsive choroidal hemorrhage. Anterior segment ischemia following cyclocryotherapy has previously been described, but this is the first reported case of anterior segment necrosis as a complication of this procedure.

Aged↗