Search PubMed⌕ Search

Biomedical subjects

D D Donaldson

Publications and source records attributed to D D Donaldson.

At least 37 records · Page 2Linked to original sources
PubMed1985

Characterization of two Phaseolus vulgaris phytohemagglutinin genes closely linked on the chromosome.

A lambda 1059 library of Phaseolus vulgaris cv. 'Tendergreen' DNA was screened with a cloned lectin-like cDNA. Among the phages selected was clone lambda B10 containing two complete lectin genes in the same orientation approximately 4 kb apart. The DNA sequences of the lectin genes and their flanking regions have been determined and their transcriptional initiation sites were located by S1 nuclease mapping. On the basis of the deduced amino acid sequences and compositions and the mol. wts. of their encoded glycoproteins, the genes, dlec1 and dlec2, are predicted to encode erythro- and leucoagglutinating phytohemagglutinins (PHA-E and PHA-L), respectively. The mRNA coding regions of dlec1 and dlec2 are 90% homologous, suggesting an origin involving duplication of an ancestral gene. Both lectin genes are intronless and have at least two ATG codons in a short (11-14 bp) 5'-untranslated region. Most of their 5'-untranslated regions consist of alternating pyrimidines and purines (RY repeats). Upstream sequences are also highly conserved between dlec1 and dlec2, including stretches of nine or more alternating R and Y residues. RY repeats of such length are not found within the protein coding portion of dlec1, dlec2 or a Phaseolus lectinlike gene previously described. Overlapping double (dlec1) or triple (dlec2) polyadenylation addition signals are found and there is an unusually high degree of homology (84%) between their 3'-untranslated regions.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1981

Solution hybridization using cloned, 5'-32P-labeled, double-stranded DNA to distinguish among closely related nucleic acids.

A rapid, sensitive, and specific solution-hybridization method is described that utilizes cloned, double-stranded DNA. The DNA is treated with restriction enzyme(s), and fragments are 32P-labeled at their 5' termini with polynucleotide kinase. A single fragment is partially purified by gel electrophoresis, denatured, and annealed with unlabeled RNA or DNA. The reaction mix is treated with S1 nuclease, precipitated with TCA, and the [32P]DNA counted. Hybridization is recognized only when the 32P label is associated with duplexes that are TCA-precipitable. The specificity of the method was analyzed by annealing experiments with cloned, human globin DNAs. Restriction fragments labeled in the 3' untranslated region of human beta globin clones formed S1-resistant, TCA-precipitable duplexes with beta globin DNA, but not with delta or gamma globin DNA. Thus, a major advantage of the method is that it can distinguish among homologous nucleic acids whose uniformly labeled cDNAs cross hybridize under moderately stringent conditions. This assay is as sensitive as the [3H]cDNA hybridization method, and it circumvents the requirement for purified mRNA as a template for [3H]cDNA synthesis. It also avoids a gel electrophoresis step, it is rapid and quantitative, and many samples can be simultaneously analyzed.

Cloning, Molecular↗
PubMed1980

Simultaneous stereoscopic fundus camera incorporating a single optical axis.

The method of stereoscopic fundus photography, where both photographs are taken simultaneously, yields the most consistent and reproducible record of depths in the fundus. However, all systems devised to date have had undesirable photographic aberrations. For the most part, this has resulted because the optical axis of each image is not the same as that of the objective lens. A single-axis system has now been devised to minimize distortions in the stereoscopic photographs, which therefore makes stereophotogrammetry relatively simple. This design also has other advantages such as simplified alignment procedures, the use of Barlow lenses for multiple magnifications, and various paired apertures for obtaining photographs especially adapted to unusual situations.

Fundus Oculi↗
PubMed1977

Comparative reproducibility of the digital photogrammetric procedure utilizing three methods of stereophotography.

The reproducibility of digital photogrammetry of optic nervehead photographs taken with the Zeiss fundus camera with Allen stereoseparator, the Donaldson fundus camera, and the Zeiss fundus camera with twin-prism separator were evaluated. Reproducibility of the various quantitative factors was significantly better when the two types of simultantic cups. Larger per cent errors were encountered with shallower optic cups. Substantial improvements in parameter reproducibility were obtained when finer sampling intervals were used during film digitization.

Computers↗
PubMed1976

Fleck (Mouchetée) dystrophy of the cornea.

Five families, four Caucasian and one Negro (14 patients) with fleck (speckled or Mouchetée) dystrophy of the cornea are presented. In each, the typical presentation of fine scattered fleck-like dystrophic lesions was found throughout all layers of the central and peripheral corneal stroma but not affecting the epithelium, Bowman's membrane, Descemet's membrane or the endothelium. Clear stroma was noted between each lesion. Visual acuity in all patients was normal or only slightly affected. Except for an occasional patient with minor photophobia, almost all patients found affected with this dystrophy were asymptomatic in regard to their corneal condition. There was no decrease in corneal sensitivity noted in any patient. All families displayed evidence of an autosomal dominant hereditary pattern and progression of the dystrophy is slow and benign in character. With the exception of one family with atopic disease, no systemic organic illness was noted by histroy in all of the families. Laboratory screening of 2 of the 5 families showed no abnormalities of any systemic metabolic disorders. The characteristic clinical picture and favorable prognosis of this condition enables one to easily differentiate this condition from other known parenchymatous corneal dystrophies. The incidence of this condition is probably much more common than the reported cases in the literature might indicate.

Adolescent↗